Import chromium-92.0.4515.107

src/.clang-format

@@ -0,0 +1,39 @@
+# Defines the Chromium style for automatic reformatting.
+# http://clang.llvm.org/docs/ClangFormatStyleOptions.html
+BasedOnStyle: Chromium
+# This defaults to 'Auto'. Explicitly set it for a while, so that
+# 'vector<vector<int> >' in existing files gets formatted to
+# 'vector<vector<int>>'. ('Auto' means that clang-format will only use
+# 'int>>' if the file already contains at least one such instance.)
+Standard: Cpp11
+
+# Make sure code like:
+# IPC_BEGIN_MESSAGE_MAP()
+#   IPC_MESSAGE_HANDLER(WidgetHostViewHost_Update, OnUpdate)
+# IPC_END_MESSAGE_MAP()
+# gets correctly indented.
+MacroBlockBegin: "^\
+BEGIN_MSG_MAP|\
+BEGIN_MSG_MAP_EX|\
+BEGIN_SAFE_MSG_MAP_EX|\
+CR_BEGIN_MSG_MAP_EX|\
+IPC_BEGIN_MESSAGE_MAP|\
+IPC_BEGIN_MESSAGE_MAP_WITH_PARAM|\
+IPC_PROTOBUF_MESSAGE_TRAITS_BEGIN|\
+IPC_STRUCT_BEGIN|\
+IPC_STRUCT_BEGIN_WITH_PARENT|\
+IPC_STRUCT_TRAITS_BEGIN|\
+POLPARAMS_BEGIN|\
+PPAPI_BEGIN_MESSAGE_MAP$"
+MacroBlockEnd: "^\
+CR_END_MSG_MAP|\
+END_MSG_MAP|\
+IPC_END_MESSAGE_MAP|\
+IPC_PROTOBUF_MESSAGE_TRAITS_END|\
+IPC_STRUCT_END|\
+IPC_STRUCT_TRAITS_END|\
+POLPARAMS_END|\
+PPAPI_END_MESSAGE_MAP$"
+
+# TODO: Remove this once clang-format r357700 is rolled in.
+JavaImportGroups: ['android', 'androidx', 'com', 'dalvik', 'junit', 'org', 'com.google.android.apps.chrome', 'org.chromium', 'java', 'javax']

src/.gitattributes

@@ -0,0 +1,56 @@
+# Stop Windows python license check presubmit errors by forcing LF checkout.
+*.py  text eol=lf
+
+# Force LF checkout of the pins files to avoid transport_security_state_generator errors.
+/net/http/*.pins  text eol=lf
+
+# Force LF checkout for all source files
+*.bin binary
+*.c text eol=lf
+*.cc text eol=lf
+*.cpp text eol=lf
+*.csv text eol=lf
+*.grd   text eol=lf
+*.grdp   text eol=lf
+*.gn text eol=lf
+*.gni text eol=lf
+*.h text eol=lf
+*.html   text eol=lf
+*.idl text eol=lf
+*.in   text eol=lf
+*.inc   text eol=lf
+*.java   text eol=lf
+*.js   text eol=lf
+*.json   text eol=lf
+*.json5 text eol=lf
+*.md text eol=lf
+*.mm text eol=lf
+*.mojom text eol=lf
+*.pdf -diff
+*.proto text eol=lf
+*.sh text eol=lf
+*.sql   text eol=lf
+*.txt   text eol=lf
+*.xml   text eol=lf
+*.xslt   text eol=lf
+.clang-format   text eol=lf
+.eslintrc.js   text eol=lf
+.git-blame-ignore-revs   text eol=lf
+.gitattributes   text eol=lf
+.gitignore   text eol=lf
+.vpython   text eol=lf
+codereview.settings   text eol=lf
+DEPS   text eol=lf
+ENG_REVIEW_OWNERS   text eol=lf
+LICENSE text eol=lf
+LICENSE.* text eol=lf
+MAJOR_BRANCH_DATE   text eol=lf
+OWNERS   text eol=lf
+README   text eol=lf
+README.*   text eol=lf
+WATCHLISTS   text eol=lf
+VERSION   text eol=lf
+DIR_METADATA   text eol=lf
+
+# Skip Tricium by default on files in third_party.
+third_party/** -tricium

src/.gn

@@ -0,0 +1,193 @@
+# This file is used by the GN meta build system to find the root of the source
+# tree and to set startup options. For documentation on the values set in this
+# file, run "gn help dotfile" at the command line.
+
+import("//build/dotfile_settings.gni")
+import("//third_party/angle/dotfile_settings.gni")
+
+# The location of the build configuration file.
+buildconfig = "//build/config/BUILDCONFIG.gn"
+
+# The python interpreter to use by default. On Windows, this will look
+# for python3.exe and python3.bat.
+script_executable = "python3"
+
+# These arguments override the default values for items in a declare_args
+# block. "gn args" in turn can override these.
+#
+# In general the value for a build arg in the declare_args block should be the
+# default. In some cases, a DEPS-ed in project will want different defaults for
+# being built as part of Chrome vs. being built standalone. In this case, the
+# Chrome defaults should go here. There should be no overrides here for
+# values declared in the main Chrome repository.
+#
+# Important note for defining defaults: This file is executed before the
+# BUILDCONFIG.gn file. That file sets up the global variables like "is_ios".
+# This means that the default_args can not depend on the platform,
+# architecture, or other build parameters. If you really need that, the other
+# repo should define a flag that toggles on a behavior that implements the
+# additional logic required by Chrome to set the variables.
+default_args = {
+  # TODO(brettw) bug 684096: Chrome on iOS does not build v8, so "gn gen" prints
+  # a warning that "Build argument has no effect". When adding a v8 variable, it
+  # also needs to be defined to src/ios/BUILD.gn (respectively removed from both
+  # location when it is removed).
+
+  v8_extra_library_files = []
+  v8_experimental_extra_library_files = []
+  v8_enable_gdbjit = false
+  v8_imminent_deprecation_warnings = false
+
+  # Don't include webrtc's builtin task queue implementation.
+  rtc_link_task_queue_impl = false
+
+  # Don't include the iLBC audio codec.
+  # TODO(bugs.webrtc.org/8396): Once WebRTC gets rid of its internal
+  # deps on codecs, we can remove this.
+  rtc_include_ilbc = false
+
+  # Changes some setup for the Crashpad build to set them to build against
+  # Chromium's zlib, base, etc.
+  crashpad_dependencies = "chromium"
+
+  # Override ANGLE's Vulkan dependencies.
+  angle_vulkan_headers_dir = "//third_party/vulkan-deps/vulkan-headers/src"
+  angle_vulkan_loader_dir = "//third_party/vulkan-deps/vulkan-loader/src"
+  angle_vulkan_tools_dir = "//third_party/vulkan-deps/vulkan-tools/src"
+  angle_vulkan_validation_layers_dir =
+      "//third_party/vulkan-deps/vulkan-validation-layers/src"
+}
+
+# These are the targets to skip header checking by default. The files in targets
+# matching these patterns (see "gn help label_pattern" for format) will not have
+# their includes checked for proper dependencies when you run either
+# "gn check" or "gn gen --check".
+no_check_targets = [
+  "//chrome/test:browser_tests",
+  "//chrome/test:browser_tests_runner",
+  "//chrome/test:interactive_ui_tests",
+  "//chrome/test:unit_tests",
+  "//chrome/test:unit_tests__library",
+  "//chrome/test:usage_time_limit_unittests",
+  "//chrome/test:xr_browser_tests_common",
+  "//extensions/browser/api:*",  # 7 errors
+  "//extensions/browser:*",  # 20 errors
+  "//extensions:*",  # 75 errors
+  "//headless:*",  # 167 errors
+  "//native_client/src/trusted/service_runtime:*",  # 2 errors
+  "//ppapi/cpp/private:*",  # 1 error
+  "//ppapi/host:*",  # 1 error
+  "//ppapi/native_client/src/untrusted/pnacl_irt_shim:*",  # 197 errors
+  "//ppapi/proxy:*",  # 31 errors
+  "//ppapi/thunk:*",  # 1071 errors
+  "//ppapi:*",  # 3 errors
+  "//remoting/host/file_transfer:*",  # 43 errors
+  "//remoting/host/installer/mac:*",  # 1 error
+  "//remoting/host/mac:*",  # 49 errors
+  "//remoting/host/security_key:*",  # 68 errors
+  "//remoting/host/win:*",  # 43 errors
+  "//remoting/ios/app/settings:*",  # 6 errors
+  "//remoting/ios/app:*",  # 9 errors
+  "//remoting/ios/audio:*",  # 5 errors
+  "//remoting/ios/domain:*",  # 2 errors
+  "//remoting/ios/facade:*",  # 8 errors
+  "//remoting/ios/persistence:*",  # 10 errors
+  "//remoting/ios/session:*",  # 7 errors
+  "//remoting/ios:*",  # 2 errors
+  "//remoting/protocol:*",  # 3 errors
+  "//remoting/test:*",  # 2 error
+  "//sandbox/win:*",  # 7 errors
+
+  "//third_party/icu/*",
+  "//third_party/libwebp:*",  # 80 errors, https://crbug.com/800762
+
+  # //v8, https://crbug.com/v8/7330
+  "//v8/src/inspector:inspector",  # 20 errors
+  "//v8/test/cctest:cctest_sources",  # 2 errors
+  "//v8:cppgc_base",  # 1 error
+  "//v8:v8_internal_headers",  # 11 errors
+  "//v8:v8_libplatform",  # 2 errors
+]
+
+# These are the list of GN files that run exec_script. This whitelist exists
+# to force additional review for new uses of exec_script, which is strongly
+# discouraged.
+#
+# PLEASE READ
+#
+# You should almost never need to add new exec_script calls. exec_script is
+# slow, especially on Windows, and can cause confusing effects. Although
+# individually each call isn't slow or necessarily very confusing, at the scale
+# of our repo things get out of hand quickly. By strongly pushing back on all
+# additions, we keep the build fast and clean. If you think you need to add a
+# new call, please consider:
+#
+# - Do not use a script to check for the existence of a file or directory to
+#   enable a different mode. Instead, use GN build args to enable or disable
+#   functionality and set options. An example is checking for a file in the
+#   src-internal repo to see if the corresponding src-internal feature should
+#   be enabled. There are several things that can go wrong with this:
+#
+#    - It's mysterious what causes some things to happen. Although in many cases
+#      such behavior can be conveniently automatic, GN optimizes for explicit
+#      and obvious behavior so people can more easily diagnose problems.
+#
+#    - The user can't enable a mode for one build and not another. With GN build
+#      args, the user can choose the exact configuration of multiple builds
+#      using one checkout. But implicitly basing flags on the state of the
+#      checkout, this functionality is broken.
+#
+#    - It's easy to get stale files. If for example the user edits the gclient
+#      to stop checking out src-internal (or any other optional thing), it's
+#      easy to end up with stale files still mysteriously triggering build
+#      conditions that are no longer appropriate (yes, this happens in real
+#      life).
+#
+# - Do not use a script to iterate files in a directory (glob):
+#
+#    - This has the same "stale file" problem as the above discussion. Various
+#      operations can leave untracked files in the source tree which can cause
+#      surprising effects.
+#
+#    - It becomes impossible to use "git grep" to find where a certain file is
+#      referenced. This operation is very common and people really do get
+#      confused when things aren't listed.
+#
+#    - It's easy to screw up. One common case is a build-time script that packs
+#      up a directory. The author notices that the script isn't re-run when the
+#      directory is updated, so adds a glob so all the files are listed as
+#      inputs. This seems to work great... until a file is deleted. When a
+#      file is deleted, all the inputs the glob lists will still be up to date
+#      and no command-lines will have been changed. The action will not be
+#      re-run and the build will be broken. It is possible to get this correct
+#      using glob, and it's possible to mess it up without glob, but globs make
+#      this situation much easier to create. if the build always lists the
+#      files and passes them to a script, it will always be correct.
+
+exec_script_whitelist =
+    build_dotfile_settings.exec_script_whitelist +
+    angle_dotfile_settings.exec_script_whitelist +
+    [
+      # Whitelist entries for //build should go into
+      # //build/dotfile_settings.gni instead, so that they can be shared
+      # with other repos. The entries in this list should be only for files
+      # in the Chromium repo outside of //build.
+      "//build_overrides/build.gni",
+
+      "//chrome/android/webapk/shell_apk/prepare_upload_dir/BUILD.gn",
+
+      # TODO(dgn): Layer violation but breaks the build otherwise, see
+      # https://crbug.com/474506.
+      "//clank/java/BUILD.gn",
+      "//clank/native/BUILD.gn",
+
+      "//google_apis/BUILD.gn",
+      "//printing/BUILD.gn",
+
+      "//remoting/host/installer/linux/BUILD.gn",
+      "//remoting/remoting_version.gni",
+      "//remoting/host/installer/win/generate_clsids.gni",
+
+      "//tools/grit/grit_rule.gni",
+      "//tools/gritsettings/BUILD.gn",
+    ]

src/LICENSE

@@ -0,0 +1,27 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

src/base/DEPS

@@ -0,0 +1,22 @@
+include_rules = [
+  "+third_party/ashmem",
+  "+third_party/apple_apsl",
+  "+third_party/boringssl/src/include",
+  "+third_party/ced",
+  "+third_party/libunwindstack/src/libunwindstack/include",
+  "+third_party/lss",
+  "+third_party/modp_b64",
+  "+third_party/perfetto/include",
+  "+third_party/perfetto/protos/perfetto",
+  "+third_party/tcmalloc",
+
+  # These are implicitly brought in from the root, and we don't want them.
+  "-ipc",
+  "-url",
+
+  # ICU dependendencies must be separate from the rest of base.
+  "-i18n",
+
+  # //base/util can use //base but not vice versa.
+  "-util",
+]

src/base/DIR_METADATA

@@ -0,0 +1,3 @@
+monorail {
+  component: "Internals>Core"
+}

src/base/OWNERS

@@ -0,0 +1,44 @@
+# See //base/README.md to find qualification for being an owner.
+
+set noparent
+# NOTE: keep this in sync with lsc-owners-override@chromium.org owners
+ajwong@chromium.org
+danakj@chromium.org
+dcheng@chromium.org
+fdoray@chromium.org
+gab@chromium.org
+jdoerrie@chromium.org
+kylechar@chromium.org
+mark@chromium.org
+thakis@chromium.org
+thestig@chromium.org
+wez@chromium.org
+# NOTE: keep this in sync with lsc-owners-override@chromium.org owners
+
+# per-file rules:
+# These are for the common case of adding or renaming files. If you're doing
+# structural changes, please get a review from a reviewer in this file.
+per-file BUILD.gn=*
+
+# For Android-specific changes:
+per-file *android*=file://base/android/OWNERS
+per-file BUILD.gn=file://base/android/OWNERS
+
+# For Fuchsia-specific changes:
+per-file *_fuchsia*=file://build/fuchsia/OWNERS
+
+# For Windows-specific changes:
+per-file *_win*=file://base/win/OWNERS
+
+per-file callback_list*=pkasting@chromium.org
+per-file feature_list*=asvitkine@chromium.org
+per-file feature_list*=isherman@chromium.org
+
+# Restricted since rand_util.h also backs the cryptographically secure RNG.
+per-file rand_util*=set noparent
+per-file rand_util*=file://ipc/SECURITY_OWNERS
+
+per-file safe_numerics_unittest.cc=file://base/numerics/OWNERS
+
+# For TCMalloc tests:
+per-file security_unittest.cc=jln@chromium.org

src/base/PRESUBMIT.py

@@ -0,0 +1,140 @@
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Chromium presubmit script for src/base.
+
+See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
+for more details on the presubmit API built into depot_tools.
+"""
+
+def _CheckNoInterfacesInBase(input_api, output_api):
+  """Checks to make sure no files in libbase.a have |@interface|."""
+  pattern = input_api.re.compile(r'^\s*@interface', input_api.re.MULTILINE)
+  files = []
+  for f in input_api.AffectedSourceFiles(input_api.FilterSourceFile):
+    if (f.LocalPath().startswith('base/') and
+        not "/ios/" in f.LocalPath() and
+        not "/test/" in f.LocalPath() and
+        not f.LocalPath().endswith('.java') and
+        not f.LocalPath().endswith('_unittest.mm') and
+        not f.LocalPath().endswith('mac/sdk_forward_declarations.h')):
+      contents = input_api.ReadFile(f)
+      if pattern.search(contents):
+        files.append(f)
+
+  if len(files):
+    return [ output_api.PresubmitError(
+        'Objective-C interfaces or categories are forbidden in libbase. ' +
+        'See http://groups.google.com/a/chromium.org/group/chromium-dev/' +
+        'browse_thread/thread/efb28c10435987fd',
+        files) ]
+  return []
+
+
+def _FindLocations(input_api, search_regexes, files_to_check, files_to_skip):
+  """Returns locations matching one of the search_regexes."""
+  def FilterFile(affected_file):
+    return input_api.FilterSourceFile(
+      affected_file,
+      files_to_check=files_to_check,
+      files_to_skip=files_to_skip)
+
+  no_presubmit = r"// no-presubmit-check"
+  locations = []
+  for f in input_api.AffectedSourceFiles(FilterFile):
+    for line_num, line in f.ChangedContents():
+      for search_regex in search_regexes:
+        if (input_api.re.search(search_regex, line) and
+            not input_api.re.search(no_presubmit, line)):
+          locations.append("    %s:%d" % (f.LocalPath(), line_num))
+          break
+  return locations
+
+
+def _CheckNoTraceEventInclude(input_api, output_api):
+  """Verify that //base includes base_tracing.h instead of trace event headers.
+
+  Checks that files outside trace event implementation include the
+  base_tracing.h header instead of specific trace event implementation headers
+  to maintain compatibility with the gn flag "enable_base_tracing = false".
+  """
+  discouraged_includes = [
+    r'^#include "base/trace_event/(?!base_tracing\.h|base_tracing_forward\.h)',
+    r'^#include "third_party/perfetto/include/',
+  ]
+
+  files_to_check = [
+    r".*\.(h|cc|mm)$",
+  ]
+  files_to_skip = [
+    r".*[\\/]test[\\/].*",
+    r".*[\\/]trace_event[\\/].*",
+    r".*[\\/]tracing[\\/].*",
+  ]
+
+  locations = _FindLocations(input_api, discouraged_includes, files_to_check,
+                             files_to_skip)
+  if locations:
+    return [ output_api.PresubmitError(
+        'Base code should include "base/trace_event/base_tracing.h" instead\n' +
+        'of trace_event implementation headers. If you need to include an\n' +
+        'implementation header, verify that "gn check" and base_unittests\n' +
+        'still pass with gn arg "enable_base_tracing = false" and add\n' +
+        '"// no-presubmit-check" after the include. \n' +
+        '\n'.join(locations)) ]
+  return []
+
+
+def _WarnPbzeroIncludes(input_api, output_api):
+  """Warn to check enable_base_tracing=false when including a pbzero header.
+
+  Emits a warning when including a perfetto pbzero header, encouraging the
+  user to verify that //base still builds with enable_base_tracing=false.
+  """
+  warn_includes = [
+    r'^#include "third_party/perfetto/protos/',
+    r'^#include "base/tracing/protos/',
+  ]
+
+  files_to_check = [
+    r".*\.(h|cc|mm)$",
+  ]
+  files_to_skip = [
+    r".*[\\/]test[\\/].*",
+    r".*[\\/]trace_event[\\/].*",
+    r".*[\\/]tracing[\\/].*",
+  ]
+
+  locations = _FindLocations(input_api, warn_includes, files_to_check,
+                             files_to_skip)
+  if locations:
+    return [ output_api.PresubmitPromptWarning(
+        'Please verify that "gn check" and base_unittests still pass with\n' +
+        'gn arg "enable_base_tracing = false" when adding typed trace\n' +
+        'events to //base. You can use "#if BUILDFLAG(ENABLE_BASE_TRACING)"\n' +
+        'to exclude pbzero headers and anything not supported by\n' +
+        '//base/trace_event/trace_event_stub.h.\n' +
+        '\n'.join(locations)) ]
+  return []
+
+
+def _CommonChecks(input_api, output_api):
+  """Checks common to both upload and commit."""
+  results = []
+  results.extend(_CheckNoInterfacesInBase(input_api, output_api))
+  results.extend(_CheckNoTraceEventInclude(input_api, output_api))
+  results.extend(_WarnPbzeroIncludes(input_api, output_api))
+  return results
+
+
+def CheckChangeOnUpload(input_api, output_api):
+  results = []
+  results.extend(_CommonChecks(input_api, output_api))
+  return results
+
+
+def CheckChangeOnCommit(input_api, output_api):
+  results = []
+  results.extend(_CommonChecks(input_api, output_api))
+  return results

src/base/README.md

@@ -0,0 +1,81 @@
+# What is this
+Contains a written down set of principles and other information on //base.
+Please add to it!
+
+## About //base:
+
+Chromium is a very mature project. Most things that are generally useful are
+already here and things not here aren't generally useful.
+
+The bar for adding stuff to base is that it must have demonstrated wide
+applicability. Prefer to add things closer to where they're used (i.e. "not
+base"), and pull into base only when needed. In a project our size,
+sometimes even duplication is OK and inevitable.
+
+Adding a new logging macro `DPVELOG_NE` is not more clear than just
+writing the stuff you want to log in a regular logging statement, even
+if it makes your calling code longer. Just add it to your own code.
+
+If the code in question does not need to be used inside base, but will have
+multiple consumers across the codebase, consider placing it in a new directory
+under components/ instead.
+
+base is written for the Chromium project and is not intended to be used
+outside it.  Using base outside of src.git is explicitly not supported,
+and base makes no guarantees about API (or even ABI) stability (like all
+other code in Chromium).  New code that depends on base/ must be in
+src.git. Code that's not in src.git but pulled in through DEPS (for
+example, v8) cannot use base.
+
+## Qualifications for being in //base OWNERS
+  * interest and ability to learn low level/high detail/complex c++ stuff
+  * inclination to always ask why and understand everything (including external
+    interactions like win32) rather than just hoping the author did it right
+  * mentorship/experience
+  * demonstrated good judgement (esp with regards to public APIs) over a length
+    of time
+
+Owners are added when a contributor has shown the above qualifications and
+when they express interest. There isn't an upper bound on the number of OWNERS.
+
+## Design and naming
+  * Be sure to use the base namespace.
+  * STL-like constructs should adhere as closely to STL as possible. Functions
+    and behaviors not present in STL should only be added when they are related
+    to the specific data structure implemented by the container.
+  * For STL-like constructs our policy is that they should use STL-like naming
+    even when it may conflict with the style guide. So functions and class names
+    should be lower case with underscores. Non-STL-like classes and functions
+    should use Google naming.
+
+## Performance testing
+
+Since the primitives provided by //base are used very widely, it is important to
+ensure they scale to the necessary workloads and perform well under all
+supported platforms. The `base_perftests` target is a suite of
+synthetic microbenchmarks that measure performance in various scenarios:
+
+  * BasicPostTaskPerfTest: Exercises MessageLoopTaskRunner's multi-threaded
+    queue in isolation.
+  * ConditionVariablePerfTest: Measures thread switching cost of condition
+    variables.
+  * IntegratedPostTaskPerfTest: Exercises the full MessageLoop/RunLoop
+    machinery.
+  * JSONPerfTest: Tests JSONWriter and JSONReader performance.
+  * MessageLoopPerfTest: Measures the speed of task posting in various
+    configurations.
+  * ObserverListPerfTest: Exercises adding, removing and signalling observers.
+  * PthreadEventPerfTest: Establishes the baseline thread switching cost using
+    pthreads.
+  * ScheduleWorkTest: Measures the overhead of MessagePump::ScheduleWork.
+  * SequenceManagerPerfTest: Benchmarks SequenceManager scheduling with various
+    underlying task runners.
+  * TaskObserverPerfTest: Measures the incremental cost of adding task
+    observers.
+  * TaskPerfTest: Checks the cost of posting tasks between threads.
+  * WaitableEvent{Thread,}PerfTest: Measures waitable events in single and
+    multithreaded scenarios.
+
+Regressions in these benchmarks can generally by caused by 1) operating system
+changes, 2) compiler version or flag changes or 3) changes in //base code
+itself.

src/base/SECURITY_OWNERS

@@ -0,0 +1,14 @@
+# Changes to code that runs at high privilege and which has a high risk of
+# memory corruption, such as parsers for complex inputs, require a security
+# review to avoid introducing sandbox escapes.
+#
+# Although this file is in base/, it may apply to more than just base, OWNERS
+# files outside of base may also include this file.
+#
+# Security team: If you are uncomfortable reviewing a particular bit of code
+# yourself, don't hesitate to seek help from another security team member!
+# Nobody knows everything, and the only way to learn is from experience.
+dcheng@chromium.org
+palmer@chromium.org
+rsesek@chromium.org
+tsepez@chromium.org

src/base/allocator/BUILD.gn

@@ -0,0 +1,328 @@
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//base/allocator/allocator.gni")
+import("//build/buildflag_header.gni")
+import("//build/config/compiler/compiler.gni")
+
+declare_args() {
+  # Provide a way to force disable debugallocation in Debug builds,
+  # e.g. for profiling (it's more rare to profile Debug builds,
+  # but people sometimes need to do that).
+  enable_debugallocation = is_debug
+
+  # Provide a way to build tcmalloc with a low memory footprint.
+  use_tcmalloc_small_but_slow = false
+}
+
+# This "allocator" meta-target will forward to the default allocator according
+# to the build settings.
+group("allocator") {
+  public_deps = []
+  deps = []
+
+  if (use_allocator == "tcmalloc") {
+    deps += [ ":tcmalloc" ]
+  }
+}
+
+config("tcmalloc_flags") {
+  defines = [
+    "TCMALLOC_USE_DOUBLYLINKED_FREELIST",
+    "TCMALLOC_DISABLE_HUGE_ALLOCATIONS",
+  ]
+  if (enable_debugallocation) {
+    defines += [
+      # Use debugallocation for Debug builds to catch problems early
+      # and cleanly, http://crbug.com/30715 .
+      "TCMALLOC_FOR_DEBUGALLOCATION",
+    ]
+  }
+  if (use_allocator_shim) {
+    defines += [ "TCMALLOC_DONT_REPLACE_SYSTEM_ALLOC" ]
+  }
+  if (use_tcmalloc_small_but_slow) {
+    defines += [ "TCMALLOC_SMALL_BUT_SLOW" ]
+  }
+  if (is_clang) {
+    cflags = [
+      # tcmalloc initializes some fields in the wrong order.
+      "-Wno-reorder",
+
+      # tcmalloc contains some unused local template specializations.
+      "-Wno-unused-function",
+
+      # tcmalloc uses COMPILE_ASSERT without static_assert but with typedefs.
+      "-Wno-unused-local-typedefs",
+
+      # for magic2_ in debugallocation.cc (only built in Debug builds) typedefs.
+      "-Wno-unused-private-field",
+    ]
+  } else {
+    cflags = []
+  }
+
+  if (is_linux || is_chromeos || is_android) {
+    # We enable all warnings by default, but upstream disables a few.
+    # Keep "-Wno-*" flags in sync with upstream by comparing against:
+    # http://code.google.com/p/google-perftools/source/browse/trunk/Makefile.am
+    cflags += [
+      "-Wno-sign-compare",
+      "-Wno-unused-result",
+    ]
+  }
+}
+
+if (use_allocator == "tcmalloc") {
+  # tcmalloc currently won't compile on Android.
+  source_set("tcmalloc") {
+    tcmalloc_dir = "//third_party/tcmalloc/chromium"
+
+    # Don't check tcmalloc's includes. These files include various files like
+    # base/foo.h and they actually refer to tcmalloc's forked copy of base
+    # rather than the regular one, which confuses the header checker.
+    check_includes = false
+
+    sources = [
+      # Generated for our configuration from tcmalloc's build
+      # and checked in.
+      "$tcmalloc_dir/src/config.h",
+
+      # tcmalloc native and forked files.
+      "$tcmalloc_dir/src/base/abort.cc",
+      "$tcmalloc_dir/src/base/abort.h",
+      "$tcmalloc_dir/src/base/arm_instruction_set_select.h",
+      "$tcmalloc_dir/src/base/atomicops-internals-arm-generic.h",
+      "$tcmalloc_dir/src/base/atomicops-internals-arm-v6plus.h",
+      "$tcmalloc_dir/src/base/atomicops-internals-linuxppc.h",
+      "$tcmalloc_dir/src/base/atomicops-internals-macosx.h",
+      "$tcmalloc_dir/src/base/atomicops-internals-windows.h",
+      "$tcmalloc_dir/src/base/atomicops-internals-x86.cc",
+      "$tcmalloc_dir/src/base/atomicops-internals-x86.h",
+      "$tcmalloc_dir/src/base/atomicops.h",
+      "$tcmalloc_dir/src/base/commandlineflags.h",
+
+      # We don't list dynamic_annotations.c since its copy is already
+      # present in the dynamic_annotations target.
+      "$tcmalloc_dir/src/base/elf_mem_image.cc",
+      "$tcmalloc_dir/src/base/elf_mem_image.h",
+      "$tcmalloc_dir/src/base/linuxthreads.cc",
+      "$tcmalloc_dir/src/base/linuxthreads.h",
+      "$tcmalloc_dir/src/base/logging.cc",
+      "$tcmalloc_dir/src/base/logging.h",
+      "$tcmalloc_dir/src/base/low_level_alloc.cc",
+      "$tcmalloc_dir/src/base/low_level_alloc.h",
+      "$tcmalloc_dir/src/base/spinlock.cc",
+      "$tcmalloc_dir/src/base/spinlock.h",
+      "$tcmalloc_dir/src/base/spinlock_internal.cc",
+      "$tcmalloc_dir/src/base/spinlock_internal.h",
+      "$tcmalloc_dir/src/base/sysinfo.cc",
+      "$tcmalloc_dir/src/base/sysinfo.h",
+      "$tcmalloc_dir/src/base/vdso_support.cc",
+      "$tcmalloc_dir/src/base/vdso_support.h",
+      "$tcmalloc_dir/src/central_freelist.cc",
+      "$tcmalloc_dir/src/central_freelist.h",
+      "$tcmalloc_dir/src/common.cc",
+      "$tcmalloc_dir/src/common.h",
+
+      # #included by debugallocation_shim.cc
+      #"$tcmalloc_dir/src/debugallocation.cc",
+      "$tcmalloc_dir/src/fake_stacktrace_scope.cc",
+      "$tcmalloc_dir/src/free_list.cc",
+      "$tcmalloc_dir/src/free_list.h",
+      "$tcmalloc_dir/src/gperftools/heap-profiler.h",
+      "$tcmalloc_dir/src/gperftools/malloc_extension.h",
+      "$tcmalloc_dir/src/gperftools/malloc_hook.h",
+      "$tcmalloc_dir/src/gperftools/stacktrace.h",
+      "$tcmalloc_dir/src/internal_logging.cc",
+      "$tcmalloc_dir/src/internal_logging.h",
+      "$tcmalloc_dir/src/linked_list.h",
+      "$tcmalloc_dir/src/malloc_extension.cc",
+      "$tcmalloc_dir/src/malloc_hook-inl.h",
+      "$tcmalloc_dir/src/malloc_hook.cc",
+      "$tcmalloc_dir/src/maybe_emergency_malloc.h",
+      "$tcmalloc_dir/src/maybe_threads.cc",
+      "$tcmalloc_dir/src/maybe_threads.h",
+      "$tcmalloc_dir/src/page_heap.cc",
+      "$tcmalloc_dir/src/page_heap.h",
+      "$tcmalloc_dir/src/raw_printer.cc",
+      "$tcmalloc_dir/src/raw_printer.h",
+      "$tcmalloc_dir/src/sampler.cc",
+      "$tcmalloc_dir/src/sampler.h",
+      "$tcmalloc_dir/src/span.cc",
+      "$tcmalloc_dir/src/span.h",
+      "$tcmalloc_dir/src/stack_trace_table.cc",
+      "$tcmalloc_dir/src/stack_trace_table.h",
+      "$tcmalloc_dir/src/stacktrace.cc",
+      "$tcmalloc_dir/src/static_vars.cc",
+      "$tcmalloc_dir/src/static_vars.h",
+      "$tcmalloc_dir/src/symbolize.cc",
+      "$tcmalloc_dir/src/symbolize.h",
+      "$tcmalloc_dir/src/system-alloc.cc",
+      "$tcmalloc_dir/src/system-alloc.h",
+
+      # #included by debugallocation_shim.cc
+      #"$tcmalloc_dir/src/tcmalloc.cc",
+      #"$tcmalloc_dir/src/tcmalloc.h",
+      "$tcmalloc_dir/src/thread_cache.cc",
+      "$tcmalloc_dir/src/thread_cache.h",
+      "$tcmalloc_dir/src/windows/port.cc",
+      "$tcmalloc_dir/src/windows/port.h",
+      "debugallocation_shim.cc",
+
+      # These are both #included by allocator_shim for maximal linking.
+      #"generic_allocators.cc",
+      #"win_allocator.cc",
+    ]
+
+    if (is_android) {
+      sources += [ "$tcmalloc_dir/src/config_android.h" ]
+    }
+
+    if (is_linux || is_chromeos) {
+      sources += [ "$tcmalloc_dir/src/config_linux.h" ]
+    }
+
+    if (is_win) {
+      sources += [ "$tcmalloc_dir/src/config_win.h" ]
+    }
+
+    # Not included on mips64el.
+    if (current_cpu == "mips64el") {
+      sources -= [
+        "$tcmalloc_dir/src/base/linuxthreads.cc",
+        "$tcmalloc_dir/src/base/linuxthreads.h",
+      ]
+    }
+
+    # Disable the heap checker in tcmalloc.
+    defines = [ "NO_HEAP_CHECK" ]
+
+    include_dirs = [
+      ".",
+      "$tcmalloc_dir/src/base",
+      "$tcmalloc_dir/src",
+    ]
+
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [
+      "//build/config/compiler:no_chromium_code",
+      ":tcmalloc_flags",
+    ]
+
+    # Thumb mode disabled due to bug in clang integrated assembler
+    # TODO(https://llvm.org/bugs/show_bug.cgi?id=31058)
+    configs -= [ "//build/config/compiler:compiler_arm_thumb" ]
+    configs += [ "//build/config/compiler:compiler_arm" ]
+
+    # TODO(crbug.com/633719) Make tcmalloc work with AFDO on GCC if possible.
+    if (!is_clang) {
+      configs -= [ "//build/config/compiler:afdo" ]
+    }
+
+    deps = [
+      ":buildflags",
+      "//build:chromeos_buildflags",
+    ]
+
+    if (enable_profiling) {
+      sources += [
+        "$tcmalloc_dir/src/base/thread_lister.c",
+        "$tcmalloc_dir/src/base/thread_lister.h",
+        "$tcmalloc_dir/src/heap-profile-table.cc",
+        "$tcmalloc_dir/src/heap-profile-table.h",
+        "$tcmalloc_dir/src/heap-profiler.cc",
+        "$tcmalloc_dir/src/memory_region_map.cc",
+        "$tcmalloc_dir/src/memory_region_map.h",
+        "$tcmalloc_dir/src/profile-handler.cc",
+        "$tcmalloc_dir/src/profile-handler.h",
+        "$tcmalloc_dir/src/profiledata.cc",
+        "$tcmalloc_dir/src/profiledata.h",
+        "$tcmalloc_dir/src/profiler.cc",
+      ]
+      defines += [ "ENABLE_PROFILING=1" ]
+    }
+
+    if (is_linux || is_chromeos || is_android) {
+      sources -= [
+        "$tcmalloc_dir/src/system-alloc.h",
+        "$tcmalloc_dir/src/windows/port.cc",
+        "$tcmalloc_dir/src/windows/port.h",
+      ]
+
+      # Compiling tcmalloc with -fvisibility=default is only necessary when
+      # not using the allocator shim, which provides the correct visibility
+      # annotations for those symbols which need to be exported (see
+      # //base/allocator/allocator_shim_override_glibc_weak_symbols.h and
+      # //base/allocator/allocator_shim_internals.h for the definition of
+      # SHIM_ALWAYS_EXPORT).
+      if (!use_allocator_shim) {
+        configs -= [ "//build/config/gcc:symbol_visibility_hidden" ]
+        configs += [ "//build/config/gcc:symbol_visibility_default" ]
+      }
+
+      ldflags = [
+        # Don't let linker rip this symbol out, otherwise the heap&cpu
+        # profilers will not initialize properly on startup.
+        "-Wl,-uIsHeapProfilerRunning,-uProfilerStart",
+
+        # Do the same for heap leak checker.
+        "-Wl,-u_Z21InitialMallocHook_NewPKvj,-u_Z22InitialMallocHook_MMapPKvS0_jiiix,-u_Z22InitialMallocHook_SbrkPKvi",
+        "-Wl,-u_Z21InitialMallocHook_NewPKvm,-u_Z22InitialMallocHook_MMapPKvS0_miiil,-u_Z22InitialMallocHook_SbrkPKvl",
+        "-Wl,-u_ZN15HeapLeakChecker12IgnoreObjectEPKv,-u_ZN15HeapLeakChecker14UnIgnoreObjectEPKv",
+      ]
+    }
+
+    # Make sure the allocation library is optimized as much as possible when
+    # we"re in release mode.
+    if (!is_debug) {
+      configs -= [ "//build/config/compiler:default_optimization" ]
+      configs += [ "//build/config/compiler:optimize_max" ]
+    }
+
+    deps += [ "//base/third_party/dynamic_annotations" ]
+  }
+}  # use_allocator == "tcmalloc"
+
+buildflag_header("buildflags") {
+  header = "buildflags.h"
+  _use_partition_alloc = use_allocator == "partition"
+  _use_tcmalloc = use_allocator == "tcmalloc"
+  assert(use_allocator_shim || !_use_partition_alloc,
+         "Partition alloc requires the allocator shim")
+
+  flags = [
+    "USE_ALLOCATOR_SHIM=$use_allocator_shim",
+    "USE_TCMALLOC=$_use_tcmalloc",
+    "USE_PARTITION_ALLOC_AS_MALLOC=$_use_partition_alloc",
+  ]
+}
+
+# Used to shim malloc symbols on Android. see //base/allocator/README.md.
+config("wrap_malloc_symbols") {
+  ldflags = [
+    "-Wl,-wrap,calloc",
+    "-Wl,-wrap,free",
+    "-Wl,-wrap,malloc",
+    "-Wl,-wrap,memalign",
+    "-Wl,-wrap,posix_memalign",
+    "-Wl,-wrap,pvalloc",
+    "-Wl,-wrap,realloc",
+    "-Wl,-wrap,valloc",
+
+    # <stdlib.h> functions
+    "-Wl,-wrap,realpath",
+
+    # <string.h> functions
+    "-Wl,-wrap,strdup",
+    "-Wl,-wrap,strndup",
+
+    # <unistd.h> functions
+    "-Wl,-wrap,getcwd",
+
+    # <stdio.h> functions
+    "-Wl,-wrap,asprintf",
+    "-Wl,-wrap,vasprintf",
+  ]
+}

src/base/allocator/DIR_METADATA

@@ -0,0 +1,3 @@
+monorail {
+  component: "Internals"
+}

src/base/allocator/OWNERS

@@ -0,0 +1,3 @@
+lizeb@chromium.org
+primiano@chromium.org
+wfh@chromium.org

src/base/allocator/README.md

@@ -0,0 +1,188 @@
+This document describes how malloc / new calls are routed in the various Chrome
+platforms.
+
+Bare in mind that the chromium codebase does not always just use `malloc()`.
+Some examples:
+ - Large parts of the renderer (Blink) use two home-brewed allocators,
+   PartitionAlloc and BlinkGC (Oilpan).
+ - Some subsystems, such as the V8 JavaScript engine, handle memory management
+   autonomously.
+ - Various parts of the codebase use abstractions such as `SharedMemory` or
+   `DiscardableMemory` which, similarly to the above, have their own page-level
+   memory management.
+
+Background
+----------
+The `allocator` target defines at compile-time the platform-specific choice of
+the allocator and extra-hooks which services calls to malloc/new. The relevant
+build-time flags involved are `use_allocator` and `use_allocator_shim`.
+
+The default choices are as follows:
+
+**Windows**
+`use_allocator: winheap`, the default Windows heap.
+Additionally, `static_library` (i.e. non-component) builds have a shim
+layer wrapping malloc/new, which is controlled by `use_allocator_shim`.
+The shim layer provides extra security features, such as preventing large
+allocations that can hit signed vs. unsigned bugs in third_party code.
+
+**Linux Desktop / CrOS**
+`use_allocator: tcmalloc`, a forked copy of tcmalloc which resides in
+`third_party/tcmalloc/chromium`. Setting `use_allocator: none` causes the build
+to fall back to the system (Glibc) symbols.
+
+**Android**
+`use_allocator: none`, always use the allocator symbols coming from Android's
+libc (Bionic). As it is developed as part of the OS, it is considered to be
+optimized for small devices and more memory-efficient than other choices.
+The actual implementation backing malloc symbols in Bionic is up to the board
+config and can vary (typically *dlmalloc* or *jemalloc* on most Nexus devices).
+
+**Mac/iOS**
+`use_allocator: none`, we always use the system's allocator implementation.
+
+In addition, when building for `asan` / `msan` both the allocator and the shim
+layer are disabled.
+
+Layering and build deps
+-----------------------
+The `allocator` target provides both the source files for tcmalloc (where
+applicable) and the linker flags required for the Windows shim layer.
+The `base` target is (almost) the only one depending on `allocator`. No other
+targets should depend on it, with the exception of the very few executables /
+dynamic libraries that don't depend, either directly or indirectly, on `base`
+within the scope of a linker unit.
+
+More importantly, **no other place outside of `/base` should depend on the
+specific allocator** (e.g., directly include `third_party/tcmalloc`).
+If such a functional dependency is required that should be achieved using
+abstractions in `base` (see `/base/allocator/allocator_extension.h` and
+`/base/memory/`)
+
+**Why `base` depends on `allocator`?**
+Because it needs to provide services that depend on the actual allocator
+implementation. In the past `base` used to pretend to be allocator-agnostic
+and get the dependencies injected by other layers. This ended up being an
+inconsistent mess.
+See the [allocator cleanup doc][url-allocator-cleanup] for more context.
+
+Linker unit targets (executables and shared libraries) that depend in some way
+on `base` (most of the targets in the codebase) get automatically the correct
+set of linker flags to pull in tcmalloc or the Windows shim-layer.
+
+
+Source code
+-----------
+This directory contains just the allocator (i.e. shim) layer that switches
+between the different underlying memory allocation implementations.
+
+The tcmalloc library originates outside of Chromium and exists in
+`../../third_party/tcmalloc` (currently, the actual location is defined in the
+allocator.gyp file). The third party sources use a vendor-branch SCM pattern to
+track Chromium-specific changes independently from upstream changes.
+
+The general intent is to push local changes upstream so that over
+time we no longer need any forked files.
+
+
+Unified allocator shim
+----------------------
+On most platforms, Chrome overrides the malloc / operator new symbols (and
+corresponding free / delete and other variants). This is to enforce security
+checks and lately to enable the
+[memory-infra heap profiler][url-memory-infra-heap-profiler].
+Historically each platform had its special logic for defining the allocator
+symbols in different places of the codebase. The unified allocator shim is
+a project aimed to unify the symbol definition and allocator routing logic in
+a central place.
+
+ - Full documentation: [Allocator shim design doc][url-allocator-shim].
+ - Current state: Available and enabled by default on Android, CrOS, Linux,
+   Mac OS and Windows.
+ - Tracking bug: [https://crbug.com/550886][crbug.com/550886].
+ - Build-time flag: `use_allocator_shim`.
+
+**Overview of the unified allocator shim**
+The allocator shim consists of three stages:
+```
++-------------------------+    +-----------------------+    +----------------+
+|     malloc & friends    | -> |       shim layer      | -> |   Routing to   |
+|    symbols definition   |    |     implementation    |    |    allocator   |
++-------------------------+    +-----------------------+    +----------------+
+| - libc symbols (malloc, |    | - Security checks     |    | - tcmalloc     |
+|   calloc, free, ...)    |    | - Chain of dispatchers|    | - glibc        |
+| - C++ symbols (operator |    |   that can intercept  |    | - Android      |
+|   new, delete, ...)     |    |   and override        |    |   bionic       |
+| - glibc weak symbols    |    |   allocations         |    | - WinHeap      |
+|   (__libc_malloc, ...)  |    +-----------------------+    +----------------+
++-------------------------+
+```
+
+**1. malloc symbols definition**
+This stage takes care of overriding the symbols `malloc`, `free`,
+`operator new`, `operator delete` and friends and routing those calls inside the
+allocator shim (next point).
+This is taken care of by the headers in `allocator_shim_override_*`.
+
+*On Windows*: Windows' UCRT (Universal C Runtime) exports weak symbols, that we
+can override in `allocator_shim_override_ucr_symbols_win.h`.
+
+*On Linux/CrOS*: the allocator symbols are defined as exported global symbols
+in `allocator_shim_override_libc_symbols.h` (for `malloc`, `free` and friends)
+and in `allocator_shim_override_cpp_symbols.h` (for `operator new`,
+`operator delete` and friends).
+This enables proper interposition of malloc symbols referenced by the main
+executable and any third party libraries. Symbol resolution on Linux is a breadth first search that starts from the root link unit, that is the executable
+(see EXECUTABLE AND LINKABLE FORMAT (ELF) - Portable Formats Specification).
+Additionally, when tcmalloc is the default allocator, some extra glibc symbols
+are also defined in `allocator_shim_override_glibc_weak_symbols.h`, for subtle
+reasons explained in that file.
+The Linux/CrOS shim was introduced by
+[crrev.com/1675143004](https://crrev.com/1675143004).
+
+*On Android*: load-time symbol interposition (unlike the Linux/CrOS case) is not
+possible. This is because Android processes are `fork()`-ed from the Android
+zygote, which pre-loads libc.so and only later native code gets loaded via
+`dlopen()` (symbols from `dlopen()`-ed libraries get a different resolution
+scope).
+In this case, the approach instead of wrapping symbol resolution at link time
+(i.e. during the build), via the `--Wl,-wrap,malloc` linker flag.
+The use of this wrapping flag causes:
+ - All references to allocator symbols in the Chrome codebase to be rewritten as
+   references to `__wrap_malloc` and friends. The `__wrap_malloc` symbols are
+   defined in the `allocator_shim_override_linker_wrapped_symbols.h` and
+   route allocator calls inside the shim layer.
+ - The reference to the original `malloc` symbols (which typically is defined by
+   the system's libc.so) are accessible via the special `__real_malloc` and
+   friends symbols (which will be relocated, at load time, against `malloc`).
+
+In summary, this approach is transparent to the dynamic loader, which still sees
+undefined symbol references to malloc symbols.
+These symbols will be resolved against libc.so as usual.
+More details in [crrev.com/1719433002](https://crrev.com/1719433002).
+
+**2. Shim layer implementation**
+This stage contains the actual shim implementation. This consists of:
+- A singly linked list of dispatchers (structs with function pointers to `malloc`-like functions). Dispatchers can be dynamically inserted at runtime
+(using the `InsertAllocatorDispatch` API). They can intercept and override
+allocator calls.
+- The security checks (suicide on malloc-failure via `std::new_handler`, etc).
+This happens inside `allocator_shim.cc`
+
+**3. Final allocator routing**
+The final element of the aforementioned dispatcher chain is statically defined
+at build time and ultimately routes the allocator calls to the actual allocator
+(as described in the *Background* section above). This is taken care of by the
+headers in `allocator_shim_default_dispatch_to_*` files.
+
+
+Related links
+-------------
+- [Unified allocator shim doc - Feb 2016][url-allocator-shim]
+- [Allocator cleanup doc - Jan 2016][url-allocator-cleanup]
+- [Proposal to use PartitionAlloc as default allocator](https://crbug.com/339604)
+- [Memory-Infra: Tools to profile memory usage in Chrome](/docs/memory-infra/README.md)
+
+[url-allocator-cleanup]: https://docs.google.com/document/d/1V77Kgp_4tfaaWPEZVxNevoD02wXiatnAv7Ssgr0hmjg/edit?usp=sharing
+[url-memory-infra-heap-profiler]: /docs/memory-infra/heap_profiler.md
+[url-allocator-shim]: https://docs.google.com/document/d/1yKlO1AO4XjpDad9rjcBOI15EKdAGsuGO_IeZy0g0kxo/edit?usp=sharing

src/base/allocator/allocator.gni

@@ -0,0 +1,89 @@
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/chromecast_build.gni")
+import("//build/config/sanitizers/sanitizers.gni")
+
+# Sanitizers replace the allocator, don't use our own.
+_is_using_sanitizers = is_asan || is_hwasan || is_lsan || is_tsan || is_msan
+
+# - Windows: shims don't work for component builds and debug CRT is not
+# compatible, see below.
+# - Android: symbol wrapping is not universal for component builds.
+# - Chromecast on Android: causes issues with crash reporting, see b/178423326.
+_disable_partition_alloc =
+    (is_win && (is_component_build || is_debug)) ||
+    (is_android && is_component_build) || (is_android && is_chromecast) ||
+    (is_linux && is_component_build)
+_is_partition_alloc_platform = is_android || is_win || is_linux
+
+# The debug CRT on Windows has some debug features that are incompatible with
+# the shim. NaCl in particular does seem to link some binaries statically
+# against the debug CRT with "is_nacl=false".
+if ((is_linux || is_chromeos || is_android || is_apple ||
+     (is_win && !is_component_build && !is_debug)) && !_is_using_sanitizers) {
+  _default_use_allocator_shim = true
+} else {
+  _default_use_allocator_shim = false
+}
+
+if (_default_use_allocator_shim && _is_partition_alloc_platform &&
+    !_disable_partition_alloc) {
+  _default_allocator = "partition"
+} else if (is_android || is_apple || _is_using_sanitizers || is_win ||
+           is_fuchsia || ((is_linux || is_chromeos) && target_cpu == "arm64") ||
+           (is_cast_audio_only && target_cpu == "arm")) {
+  # Temporarily disable tcmalloc on arm64 linux to get rid of compilation
+  # errors.
+  _default_allocator = "none"
+} else {
+  _default_allocator = "tcmalloc"
+}
+
+declare_args() {
+  # Memory allocator to use. Set to "none" to use default allocator.
+  use_allocator = _default_allocator
+
+  # Causes all the allocations to be routed via allocator_shim.cc.
+  use_allocator_shim = _default_use_allocator_shim
+
+  # Whether PartitionAlloc should be available for use or not.
+  # true makes PartitionAlloc linked to the executable or shared library and
+  # makes it available for use, but it doesn't mean that the default allocator
+  # is PartitionAlloc.  PartitionAlloc may or may not be the default allocator.
+  #
+  # |use_allocator = "partition"| makes PartitionAlloc the default allocator
+  # but it's effective only when |use_partition_alloc = true|.
+  #
+  # TODO(lizeb, yukishiino): Determine if |use_partition_alloc| is necessary or
+  # not, and redesign or remove the flag accordingly.  We may want to assert a
+  # possible conflict between |use_allocator = "partition"| and
+  # |use_partition_alloc = true| rather than prioritizing use_partition_alloc.
+  use_partition_alloc = !is_ios  # Never use PartitionAlloc on iOS.
+}
+
+if (!use_partition_alloc && use_allocator == "partition") {
+  # If there is a conflict, prioritize |use_partition_alloc| over
+  # |use_allocator|.
+  use_allocator = "none"
+}
+
+assert(use_allocator == "none" || use_allocator == "tcmalloc" ||
+       use_allocator == "partition")
+
+assert(!is_win || use_allocator != "tcmalloc",
+       "Tcmalloc doesn't work on Windows.")
+assert(!is_mac || use_allocator != "tcmalloc",
+       "Tcmalloc doesn't work on macOS.")
+assert(!is_ios || use_allocator != "tcmalloc", "Tcmalloc doesn't work on iOS.")
+
+assert(
+    !use_allocator_shim || is_linux || is_chromeos || is_android || is_win ||
+        is_apple,
+    "use_allocator_shim works only on Android, iOS, Linux, macOS, and Windows.")
+
+if (is_win && use_allocator_shim) {
+  assert(!is_component_build,
+         "The allocator shim doesn't work for the component build on Windows.")
+}

src/base/allocator/allocator_check.cc

@@ -0,0 +1,46 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_check.h"
+
+#include "base/allocator/buildflags.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include "base/allocator/winheap_stubs_win.h"
+#endif
+
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+#include <malloc.h>
+#endif
+
+#if defined(OS_APPLE)
+#include "base/allocator/allocator_interception_mac.h"
+#endif
+
+namespace base {
+namespace allocator {
+
+bool IsAllocatorInitialized() {
+#if defined(OS_WIN) && BUILDFLAG(USE_ALLOCATOR_SHIM)
+  // Set by allocator_shim_override_ucrt_symbols_win.h when the
+  // shimmed _set_new_mode() is called.
+  return g_is_win_shim_layer_initialized;
+#elif (defined(OS_LINUX) || defined(OS_CHROMEOS)) && \
+    BUILDFLAG(USE_TCMALLOC) && !defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+// From third_party/tcmalloc/chromium/src/gperftools/tcmalloc.h.
+// TODO(primiano): replace with an include once base can depend on allocator.
+#define TC_MALLOPT_IS_OVERRIDDEN_BY_TCMALLOC 0xbeef42
+  return (mallopt(TC_MALLOPT_IS_OVERRIDDEN_BY_TCMALLOC, 0) ==
+          TC_MALLOPT_IS_OVERRIDDEN_BY_TCMALLOC);
+#elif defined(OS_APPLE) && !defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+  // From allocator_interception_mac.mm.
+  return base::allocator::g_replaced_default_zone;
+#else
+  return true;
+#endif
+}
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/allocator_check.h

@@ -0,0 +1,18 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_CHECK_H_
+#define BASE_ALLOCATOR_ALLOCATOR_CHECK_H_
+
+#include "base/base_export.h"
+
+namespace base {
+namespace allocator {
+
+BASE_EXPORT bool IsAllocatorInitialized();
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_CHECK_H_

src/base/allocator/allocator_extension.cc

@@ -0,0 +1,77 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_extension.h"
+#include "base/allocator/buildflags.h"
+#include "base/check.h"
+
+#if BUILDFLAG(USE_TCMALLOC)
+#include "third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h"
+#include "third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h"
+#include "third_party/tcmalloc/chromium/src/gperftools/malloc_hook.h"
+#endif
+
+namespace base {
+namespace allocator {
+
+void ReleaseFreeMemory() {
+#if BUILDFLAG(USE_TCMALLOC)
+  ::MallocExtension::instance()->ReleaseFreeMemory();
+#endif
+}
+
+bool GetNumericProperty(const char* name, size_t* value) {
+#if BUILDFLAG(USE_TCMALLOC)
+  return ::MallocExtension::instance()->GetNumericProperty(name, value);
+#else
+  return false;
+#endif
+}
+
+bool SetNumericProperty(const char* name, size_t value) {
+#if BUILDFLAG(USE_TCMALLOC)
+  return ::MallocExtension::instance()->SetNumericProperty(name, value);
+#else
+  return false;
+#endif
+}
+
+void GetHeapSample(std::string* writer) {
+#if BUILDFLAG(USE_TCMALLOC)
+  ::MallocExtension::instance()->GetHeapSample(writer);
+#endif
+}
+
+bool IsHeapProfilerRunning() {
+#if BUILDFLAG(USE_TCMALLOC) && defined(ENABLE_PROFILING)
+  return ::IsHeapProfilerRunning();
+#else
+  return false;
+#endif
+}
+
+void SetHooks(AllocHookFunc alloc_hook, FreeHookFunc free_hook) {
+// TODO(sque): Use allocator shim layer instead.
+#if BUILDFLAG(USE_TCMALLOC)
+  // Make sure no hooks get overwritten.
+  auto prev_alloc_hook = MallocHook::SetNewHook(alloc_hook);
+  if (alloc_hook)
+    DCHECK(!prev_alloc_hook);
+
+  auto prev_free_hook = MallocHook::SetDeleteHook(free_hook);
+  if (free_hook)
+    DCHECK(!prev_free_hook);
+#endif
+}
+
+int GetCallStack(void** stack, int max_stack_size) {
+#if BUILDFLAG(USE_TCMALLOC)
+  return MallocHook::GetCallerStackTrace(stack, max_stack_size, 0);
+#else
+  return 0;
+#endif
+}
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/allocator_extension.h

@@ -0,0 +1,67 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_EXTENSION_H_
+#define BASE_ALLOCATOR_ALLOCATOR_EXTENSION_H_
+
+#include <stddef.h> // for size_t
+#include <string>
+
+#include "base/base_export.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace allocator {
+
+// Callback types for alloc and free.
+using AllocHookFunc = void (*)(const void*, size_t);
+using FreeHookFunc = void (*)(const void*);
+
+// Request that the allocator release any free memory it knows about to the
+// system.
+BASE_EXPORT void ReleaseFreeMemory();
+
+// Get the named property's |value|. Returns true if the property is known.
+// Returns false if the property is not a valid property name for the current
+// allocator implementation.
+// |name| or |value| cannot be NULL
+BASE_EXPORT bool GetNumericProperty(const char* name, size_t* value);
+
+// Set the named property's |value|. Returns true if the property is known and
+// writable. Returns false if the property is not a valid property name for the
+// current allocator implementation, or is not writable. |name| cannot be NULL.
+BASE_EXPORT bool SetNumericProperty(const char* name, size_t value);
+
+// Outputs to |writer| a sample of live objects and the stack traces
+// that allocated these objects.  The format of the returned output
+// is equivalent to the output of the heap profiler and can
+// therefore be passed to "pprof".
+// NOTE: by default, the allocator does not do any heap sampling, and this
+//       function will always return an empty sample.  To get useful
+//       data from GetHeapSample, you must also set the numeric property
+//       "tcmalloc.sampling_period_bytes" to a value such as 524288.
+BASE_EXPORT void GetHeapSample(std::string* writer);
+
+BASE_EXPORT bool IsHeapProfilerRunning();
+
+// Register callbacks for alloc and free. Can only store one callback at a time
+// for each of alloc and free.
+BASE_EXPORT void SetHooks(AllocHookFunc alloc_hook, FreeHookFunc free_hook);
+
+// Attempts to unwind the call stack from the current location where this
+// function is being called from. Must be called from a hook function registered
+// by calling SetSingle{Alloc,Free}Hook, directly or indirectly.
+//
+// Arguments:
+//   stack:          pointer to a pre-allocated array of void*'s.
+//   max_stack_size: indicates the size of the array in |stack|.
+//
+// Returns the number of call stack frames stored in |stack|, or 0 if no call
+// stack information is available.
+BASE_EXPORT int GetCallStack(void** stack, int max_stack_size);
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_EXTENSION_H_

src/base/allocator/allocator_interception_mac.h

@@ -0,0 +1,65 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_INTERCEPTION_MAC_H_
+#define BASE_ALLOCATOR_ALLOCATOR_INTERCEPTION_MAC_H_
+
+#include <stddef.h>
+
+#include "base/base_export.h"
+#include "third_party/apple_apsl/malloc.h"
+
+namespace base {
+namespace allocator {
+
+struct MallocZoneFunctions;
+
+// This initializes AllocatorDispatch::default_dispatch by saving pointers to
+// the functions in the current default malloc zone. This must be called before
+// the default malloc zone is changed to have its intended effect.
+void InitializeDefaultDispatchToMacAllocator();
+
+// Saves the function pointers currently used by the default zone.
+void StoreFunctionsForDefaultZone();
+
+// Same as StoreFunctionsForDefaultZone, but for all malloc zones.
+void StoreFunctionsForAllZones();
+
+// For all malloc zones that have been stored, replace their functions with
+// |functions|.
+void ReplaceFunctionsForStoredZones(const MallocZoneFunctions* functions);
+
+extern bool g_replaced_default_zone;
+
+// Calls the original implementation of malloc/calloc prior to interception.
+bool UncheckedMallocMac(size_t size, void** result);
+bool UncheckedCallocMac(size_t num_items, size_t size, void** result);
+
+// Intercepts calls to default and purgeable malloc zones. Intercepts Core
+// Foundation and Objective-C allocations.
+// Has no effect on the default malloc zone if the allocator shim already
+// performs that interception.
+BASE_EXPORT void InterceptAllocationsMac();
+
+// Updates all malloc zones to use their original functions.
+// Also calls ClearAllMallocZonesForTesting.
+BASE_EXPORT void UninterceptMallocZonesForTesting();
+
+// Returns true if allocations are successfully being intercepted for all malloc
+// zones.
+bool AreMallocZonesIntercepted();
+
+// Periodically checks for, and shims new malloc zones. Stops checking after 1
+// minute.
+BASE_EXPORT void PeriodicallyShimNewMallocZones();
+
+// Exposed for testing.
+BASE_EXPORT void ShimNewMallocZones();
+BASE_EXPORT void ReplaceZoneFunctions(ChromeMallocZone* zone,
+                                      const MallocZoneFunctions* functions);
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_INTERCEPTION_MAC_H_

src/base/allocator/allocator_interception_mac.mm

@@ -0,0 +1,604 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file contains all the logic necessary to intercept allocations on
+// macOS. "malloc zones" are an abstraction that allows the process to intercept
+// all malloc-related functions.  There is no good mechanism [short of
+// interposition] to determine new malloc zones are added, so there's no clean
+// mechanism to intercept all malloc zones. This file contains logic to
+// intercept the default and purgeable zones, which always exist. A cursory
+// review of Chrome seems to imply that non-default zones are almost never used.
+//
+// This file also contains logic to intercept Core Foundation and Objective-C
+// allocations. The implementations forward to the default malloc zone, so the
+// only reason to intercept these calls is to re-label OOM crashes with slightly
+// more details.
+
+#include "base/allocator/allocator_interception_mac.h"
+
+#include <CoreFoundation/CoreFoundation.h>
+#import <Foundation/Foundation.h>
+#include <errno.h>
+#include <mach/mach.h>
+#import <objc/runtime.h>
+#include <stddef.h>
+
+#include <new>
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/malloc_zone_functions_mac.h"
+#include "base/bind.h"
+#include "base/bits.h"
+#include "base/logging.h"
+#include "base/mac/mach_logging.h"
+#include "base/process/memory.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "build/build_config.h"
+#include "third_party/apple_apsl/CFBase.h"
+
+#if defined(OS_IOS)
+#include "base/ios/ios_util.h"
+#else
+#include "base/mac/mac_util.h"
+#endif
+
+namespace base {
+namespace allocator {
+
+bool g_replaced_default_zone = false;
+
+namespace {
+
+bool g_oom_killer_enabled;
+bool g_allocator_shims_failed_to_install;
+
+// Starting with Mac OS X 10.7, the zone allocators set up by the system are
+// read-only, to prevent them from being overwritten in an attack. However,
+// blindly unprotecting and reprotecting the zone allocators fails with
+// GuardMalloc because GuardMalloc sets up its zone allocator using a block of
+// memory in its bss. Explicit saving/restoring of the protection is required.
+//
+// This function takes a pointer to a malloc zone, de-protects it if necessary,
+// and returns (in the out parameters) a region of memory (if any) to be
+// re-protected when modifications are complete. This approach assumes that
+// there is no contention for the protection of this memory.
+//
+// Returns true if the malloc zone was properly de-protected, or false
+// otherwise. If this function returns false, the out parameters are invalid and
+// the region does not need to be re-protected.
+bool DeprotectMallocZone(ChromeMallocZone* default_zone,
+                         vm_address_t* reprotection_start,
+                         vm_size_t* reprotection_length,
+                         vm_prot_t* reprotection_value) {
+  mach_port_t unused;
+  *reprotection_start = reinterpret_cast<vm_address_t>(default_zone);
+  struct vm_region_basic_info_64 info;
+  mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
+  kern_return_t result =
+      vm_region_64(mach_task_self(), reprotection_start, reprotection_length,
+                   VM_REGION_BASIC_INFO_64,
+                   reinterpret_cast<vm_region_info_t>(&info), &count, &unused);
+  if (result != KERN_SUCCESS) {
+    MACH_LOG(ERROR, result) << "vm_region_64";
+    return false;
+  }
+
+  // The kernel always returns a null object for VM_REGION_BASIC_INFO_64, but
+  // balance it with a deallocate in case this ever changes. See
+  // the VM_REGION_BASIC_INFO_64 case in vm_map_region() in 10.15's
+  // https://opensource.apple.com/source/xnu/xnu-6153.11.26/osfmk/vm/vm_map.c .
+  mach_port_deallocate(mach_task_self(), unused);
+
+  if (!(info.max_protection & VM_PROT_WRITE)) {
+    LOG(ERROR) << "Invalid max_protection " << info.max_protection;
+    return false;
+  }
+
+  // Does the region fully enclose the zone pointers? Possibly unwarranted
+  // simplification used: using the size of a full version 10 malloc zone rather
+  // than the actual smaller size if the passed-in zone is not version 10.
+  DCHECK(*reprotection_start <= reinterpret_cast<vm_address_t>(default_zone));
+  vm_size_t zone_offset = reinterpret_cast<vm_address_t>(default_zone) -
+                          reinterpret_cast<vm_address_t>(*reprotection_start);
+  DCHECK(zone_offset + sizeof(ChromeMallocZone) <= *reprotection_length);
+
+  if (info.protection & VM_PROT_WRITE) {
+    // No change needed; the zone is already writable.
+    *reprotection_start = 0;
+    *reprotection_length = 0;
+    *reprotection_value = VM_PROT_NONE;
+  } else {
+    *reprotection_value = info.protection;
+    result =
+        vm_protect(mach_task_self(), *reprotection_start, *reprotection_length,
+                   false, info.protection | VM_PROT_WRITE);
+    if (result != KERN_SUCCESS) {
+      MACH_LOG(ERROR, result) << "vm_protect";
+      return false;
+    }
+  }
+  return true;
+}
+
+#if !defined(ADDRESS_SANITIZER)
+
+MallocZoneFunctions g_old_zone;
+MallocZoneFunctions g_old_purgeable_zone;
+
+void* oom_killer_malloc(struct _malloc_zone_t* zone, size_t size) {
+  void* result = g_old_zone.malloc(zone, size);
+  if (!result && size)
+    TerminateBecauseOutOfMemory(size);
+  return result;
+}
+
+void* oom_killer_calloc(struct _malloc_zone_t* zone,
+                        size_t num_items,
+                        size_t size) {
+  void* result = g_old_zone.calloc(zone, num_items, size);
+  if (!result && num_items && size)
+    TerminateBecauseOutOfMemory(num_items * size);
+  return result;
+}
+
+void* oom_killer_valloc(struct _malloc_zone_t* zone, size_t size) {
+  void* result = g_old_zone.valloc(zone, size);
+  if (!result && size)
+    TerminateBecauseOutOfMemory(size);
+  return result;
+}
+
+void oom_killer_free(struct _malloc_zone_t* zone, void* ptr) {
+  g_old_zone.free(zone, ptr);
+}
+
+void* oom_killer_realloc(struct _malloc_zone_t* zone, void* ptr, size_t size) {
+  void* result = g_old_zone.realloc(zone, ptr, size);
+  if (!result && size)
+    TerminateBecauseOutOfMemory(size);
+  return result;
+}
+
+void* oom_killer_memalign(struct _malloc_zone_t* zone,
+                          size_t alignment,
+                          size_t size) {
+  void* result = g_old_zone.memalign(zone, alignment, size);
+  // Only die if posix_memalign would have returned ENOMEM, since there are
+  // other reasons why null might be returned. See posix_memalign() in 10.15's
+  // https://opensource.apple.com/source/libmalloc/libmalloc-283/src/malloc.c .
+  if (!result && size && alignment >= sizeof(void*) &&
+      base::bits::IsPowerOfTwo(alignment)) {
+    TerminateBecauseOutOfMemory(size);
+  }
+  return result;
+}
+
+void* oom_killer_malloc_purgeable(struct _malloc_zone_t* zone, size_t size) {
+  void* result = g_old_purgeable_zone.malloc(zone, size);
+  if (!result && size)
+    TerminateBecauseOutOfMemory(size);
+  return result;
+}
+
+void* oom_killer_calloc_purgeable(struct _malloc_zone_t* zone,
+                                  size_t num_items,
+                                  size_t size) {
+  void* result = g_old_purgeable_zone.calloc(zone, num_items, size);
+  if (!result && num_items && size)
+    TerminateBecauseOutOfMemory(num_items * size);
+  return result;
+}
+
+void* oom_killer_valloc_purgeable(struct _malloc_zone_t* zone, size_t size) {
+  void* result = g_old_purgeable_zone.valloc(zone, size);
+  if (!result && size)
+    TerminateBecauseOutOfMemory(size);
+  return result;
+}
+
+void oom_killer_free_purgeable(struct _malloc_zone_t* zone, void* ptr) {
+  g_old_purgeable_zone.free(zone, ptr);
+}
+
+void* oom_killer_realloc_purgeable(struct _malloc_zone_t* zone,
+                                   void* ptr,
+                                   size_t size) {
+  void* result = g_old_purgeable_zone.realloc(zone, ptr, size);
+  if (!result && size)
+    TerminateBecauseOutOfMemory(size);
+  return result;
+}
+
+void* oom_killer_memalign_purgeable(struct _malloc_zone_t* zone,
+                                    size_t alignment,
+                                    size_t size) {
+  void* result = g_old_purgeable_zone.memalign(zone, alignment, size);
+  // Only die if posix_memalign would have returned ENOMEM, since there are
+  // other reasons why null might be returned. See posix_memalign() in 10.15's
+  // https://opensource.apple.com/source/libmalloc/libmalloc-283/src/malloc.c .
+  if (!result && size && alignment >= sizeof(void*) &&
+      base::bits::IsPowerOfTwo(alignment)) {
+    TerminateBecauseOutOfMemory(size);
+  }
+  return result;
+}
+
+#endif  // !defined(ADDRESS_SANITIZER)
+
+#if !defined(ADDRESS_SANITIZER)
+
+// === Core Foundation CFAllocators ===
+
+bool CanGetContextForCFAllocator() {
+#if defined(OS_IOS)
+  return !base::ios::IsRunningOnOrLater(14, 0, 0);
+#else
+  return !base::mac::IsOSLaterThan11_DontCallThis();
+#endif
+}
+
+CFAllocatorContext* ContextForCFAllocator(CFAllocatorRef allocator) {
+  ChromeCFAllocatorLions* our_allocator = const_cast<ChromeCFAllocatorLions*>(
+      reinterpret_cast<const ChromeCFAllocatorLions*>(allocator));
+  return &our_allocator->_context;
+}
+
+CFAllocatorAllocateCallBack g_old_cfallocator_system_default;
+CFAllocatorAllocateCallBack g_old_cfallocator_malloc;
+CFAllocatorAllocateCallBack g_old_cfallocator_malloc_zone;
+
+void* oom_killer_cfallocator_system_default(CFIndex alloc_size,
+                                            CFOptionFlags hint,
+                                            void* info) {
+  void* result = g_old_cfallocator_system_default(alloc_size, hint, info);
+  if (!result)
+    TerminateBecauseOutOfMemory(alloc_size);
+  return result;
+}
+
+void* oom_killer_cfallocator_malloc(CFIndex alloc_size,
+                                    CFOptionFlags hint,
+                                    void* info) {
+  void* result = g_old_cfallocator_malloc(alloc_size, hint, info);
+  if (!result)
+    TerminateBecauseOutOfMemory(alloc_size);
+  return result;
+}
+
+void* oom_killer_cfallocator_malloc_zone(CFIndex alloc_size,
+                                         CFOptionFlags hint,
+                                         void* info) {
+  void* result = g_old_cfallocator_malloc_zone(alloc_size, hint, info);
+  if (!result)
+    TerminateBecauseOutOfMemory(alloc_size);
+  return result;
+}
+
+#endif  // !defined(ADDRESS_SANITIZER)
+
+// === Cocoa NSObject allocation ===
+
+typedef id (*allocWithZone_t)(id, SEL, NSZone*);
+allocWithZone_t g_old_allocWithZone;
+
+id oom_killer_allocWithZone(id self, SEL _cmd, NSZone* zone) {
+  id result = g_old_allocWithZone(self, _cmd, zone);
+  if (!result)
+    TerminateBecauseOutOfMemory(0);
+  return result;
+}
+
+void UninterceptMallocZoneForTesting(struct _malloc_zone_t* zone) {
+  ChromeMallocZone* chrome_zone = reinterpret_cast<ChromeMallocZone*>(zone);
+  if (!IsMallocZoneAlreadyStored(chrome_zone))
+    return;
+  MallocZoneFunctions& functions = GetFunctionsForZone(zone);
+  ReplaceZoneFunctions(chrome_zone, &functions);
+}
+
+}  // namespace
+
+bool UncheckedMallocMac(size_t size, void** result) {
+#if defined(ADDRESS_SANITIZER)
+  *result = malloc(size);
+#else
+  if (g_old_zone.malloc) {
+    *result = g_old_zone.malloc(malloc_default_zone(), size);
+  } else {
+    *result = malloc(size);
+  }
+#endif  // defined(ADDRESS_SANITIZER)
+
+  return *result != NULL;
+}
+
+bool UncheckedCallocMac(size_t num_items, size_t size, void** result) {
+#if defined(ADDRESS_SANITIZER)
+  *result = calloc(num_items, size);
+#else
+  if (g_old_zone.calloc) {
+    *result = g_old_zone.calloc(malloc_default_zone(), num_items, size);
+  } else {
+    *result = calloc(num_items, size);
+  }
+#endif  // defined(ADDRESS_SANITIZER)
+
+  return *result != NULL;
+}
+
+void InitializeDefaultDispatchToMacAllocator() {
+  StoreFunctionsForAllZones();
+}
+
+void StoreFunctionsForDefaultZone() {
+  ChromeMallocZone* default_zone = reinterpret_cast<ChromeMallocZone*>(
+      malloc_default_zone());
+  StoreMallocZone(default_zone);
+}
+
+void StoreFunctionsForAllZones() {
+  // This ensures that the default zone is always at the front of the array,
+  // which is important for performance.
+  StoreFunctionsForDefaultZone();
+
+  vm_address_t* zones;
+  unsigned int count;
+  kern_return_t kr = malloc_get_all_zones(mach_task_self(), 0, &zones, &count);
+  if (kr != KERN_SUCCESS)
+    return;
+  for (unsigned int i = 0; i < count; ++i) {
+    ChromeMallocZone* zone = reinterpret_cast<ChromeMallocZone*>(zones[i]);
+    StoreMallocZone(zone);
+  }
+}
+
+void ReplaceFunctionsForStoredZones(const MallocZoneFunctions* functions) {
+  // The default zone does not get returned in malloc_get_all_zones().
+  ChromeMallocZone* default_zone =
+      reinterpret_cast<ChromeMallocZone*>(malloc_default_zone());
+  if (DoesMallocZoneNeedReplacing(default_zone, functions)) {
+    ReplaceZoneFunctions(default_zone, functions);
+  }
+
+  vm_address_t* zones;
+  unsigned int count;
+  kern_return_t kr =
+      malloc_get_all_zones(mach_task_self(), nullptr, &zones, &count);
+  if (kr != KERN_SUCCESS)
+    return;
+  for (unsigned int i = 0; i < count; ++i) {
+    ChromeMallocZone* zone = reinterpret_cast<ChromeMallocZone*>(zones[i]);
+    if (DoesMallocZoneNeedReplacing(zone, functions)) {
+      ReplaceZoneFunctions(zone, functions);
+    }
+  }
+  g_replaced_default_zone = true;
+}
+
+void InterceptAllocationsMac() {
+  if (g_oom_killer_enabled)
+    return;
+
+  g_oom_killer_enabled = true;
+
+// === C malloc/calloc/valloc/realloc/posix_memalign ===
+
+// This approach is not perfect, as requests for amounts of memory larger than
+// MALLOC_ABSOLUTE_MAX_SIZE (currently SIZE_T_MAX - (2 * PAGE_SIZE)) will still
+// fail with a NULL rather than dying (see malloc_zone_malloc() in
+// https://opensource.apple.com/source/libmalloc/libmalloc-283/src/malloc.c for
+// details). Unfortunately, it's the best we can do. Also note that this does
+// not affect allocations from non-default zones.
+
+#if !defined(ADDRESS_SANITIZER)
+  // Don't do anything special on OOM for the malloc zones replaced by
+  // AddressSanitizer, as modifying or protecting them may not work correctly.
+  ChromeMallocZone* default_zone =
+      reinterpret_cast<ChromeMallocZone*>(malloc_default_zone());
+  if (!IsMallocZoneAlreadyStored(default_zone)) {
+    StoreZoneFunctions(default_zone, &g_old_zone);
+    MallocZoneFunctions new_functions = {};
+    new_functions.malloc = oom_killer_malloc;
+    new_functions.calloc = oom_killer_calloc;
+    new_functions.valloc = oom_killer_valloc;
+    new_functions.free = oom_killer_free;
+    new_functions.realloc = oom_killer_realloc;
+    new_functions.memalign = oom_killer_memalign;
+
+    ReplaceZoneFunctions(default_zone, &new_functions);
+    g_replaced_default_zone = true;
+  }
+
+  ChromeMallocZone* purgeable_zone =
+      reinterpret_cast<ChromeMallocZone*>(malloc_default_purgeable_zone());
+  if (purgeable_zone && !IsMallocZoneAlreadyStored(purgeable_zone)) {
+    StoreZoneFunctions(purgeable_zone, &g_old_purgeable_zone);
+    MallocZoneFunctions new_functions = {};
+    new_functions.malloc = oom_killer_malloc_purgeable;
+    new_functions.calloc = oom_killer_calloc_purgeable;
+    new_functions.valloc = oom_killer_valloc_purgeable;
+    new_functions.free = oom_killer_free_purgeable;
+    new_functions.realloc = oom_killer_realloc_purgeable;
+    new_functions.memalign = oom_killer_memalign_purgeable;
+    ReplaceZoneFunctions(purgeable_zone, &new_functions);
+  }
+#endif
+
+  // === C malloc_zone_batch_malloc ===
+
+  // batch_malloc is omitted because the default malloc zone's implementation
+  // only supports batch_malloc for "tiny" allocations from the free list. It
+  // will fail for allocations larger than "tiny", and will only allocate as
+  // many blocks as it's able to from the free list. These factors mean that it
+  // can return less than the requested memory even in a non-out-of-memory
+  // situation. There's no good way to detect whether a batch_malloc failure is
+  // due to these other factors, or due to genuine memory or address space
+  // exhaustion. The fact that it only allocates space from the "tiny" free list
+  // means that it's likely that a failure will not be due to memory exhaustion.
+  // Similarly, these constraints on batch_malloc mean that callers must always
+  // be expecting to receive less memory than was requested, even in situations
+  // where memory pressure is not a concern. Finally, the only public interface
+  // to batch_malloc is malloc_zone_batch_malloc, which is specific to the
+  // system's malloc implementation. It's unlikely that anyone's even heard of
+  // it.
+
+#ifndef ADDRESS_SANITIZER
+  // === Core Foundation CFAllocators ===
+
+  // This will not catch allocation done by custom allocators, but will catch
+  // all allocation done by system-provided ones.
+
+  CHECK(!g_old_cfallocator_system_default && !g_old_cfallocator_malloc &&
+        !g_old_cfallocator_malloc_zone)
+      << "Old allocators unexpectedly non-null";
+
+  bool cf_allocator_internals_known = CanGetContextForCFAllocator();
+
+  if (cf_allocator_internals_known) {
+    CFAllocatorContext* context =
+        ContextForCFAllocator(kCFAllocatorSystemDefault);
+    CHECK(context) << "Failed to get context for kCFAllocatorSystemDefault.";
+    g_old_cfallocator_system_default = context->allocate;
+    CHECK(g_old_cfallocator_system_default)
+        << "Failed to get kCFAllocatorSystemDefault allocation function.";
+    context->allocate = oom_killer_cfallocator_system_default;
+
+    context = ContextForCFAllocator(kCFAllocatorMalloc);
+    CHECK(context) << "Failed to get context for kCFAllocatorMalloc.";
+    g_old_cfallocator_malloc = context->allocate;
+    CHECK(g_old_cfallocator_malloc)
+        << "Failed to get kCFAllocatorMalloc allocation function.";
+    context->allocate = oom_killer_cfallocator_malloc;
+
+    context = ContextForCFAllocator(kCFAllocatorMallocZone);
+    CHECK(context) << "Failed to get context for kCFAllocatorMallocZone.";
+    g_old_cfallocator_malloc_zone = context->allocate;
+    CHECK(g_old_cfallocator_malloc_zone)
+        << "Failed to get kCFAllocatorMallocZone allocation function.";
+    context->allocate = oom_killer_cfallocator_malloc_zone;
+  } else {
+    DLOG(WARNING) << "Internals of CFAllocator not known; out-of-memory "
+                     "failures via CFAllocator will not result in termination. "
+                     "http://crbug.com/45650";
+  }
+#endif
+
+  // === Cocoa NSObject allocation ===
+
+  // Note that both +[NSObject new] and +[NSObject alloc] call through to
+  // +[NSObject allocWithZone:].
+
+  CHECK(!g_old_allocWithZone) << "Old allocator unexpectedly non-null";
+
+  Class nsobject_class = [NSObject class];
+  Method orig_method =
+      class_getClassMethod(nsobject_class, @selector(allocWithZone:));
+  g_old_allocWithZone =
+      reinterpret_cast<allocWithZone_t>(method_getImplementation(orig_method));
+  CHECK(g_old_allocWithZone)
+      << "Failed to get allocWithZone allocation function.";
+  method_setImplementation(orig_method,
+                           reinterpret_cast<IMP>(oom_killer_allocWithZone));
+}
+
+void UninterceptMallocZonesForTesting() {
+  UninterceptMallocZoneForTesting(malloc_default_zone());
+  vm_address_t* zones;
+  unsigned int count;
+  kern_return_t kr = malloc_get_all_zones(mach_task_self(), 0, &zones, &count);
+  CHECK(kr == KERN_SUCCESS);
+  for (unsigned int i = 0; i < count; ++i) {
+    UninterceptMallocZoneForTesting(
+        reinterpret_cast<struct _malloc_zone_t*>(zones[i]));
+  }
+
+  ClearAllMallocZonesForTesting();
+}
+
+bool AreMallocZonesIntercepted() {
+  return !g_allocator_shims_failed_to_install;
+}
+
+namespace {
+
+void ShimNewMallocZonesAndReschedule(base::Time end_time,
+                                     base::TimeDelta delay) {
+  ShimNewMallocZones();
+
+  if (base::Time::Now() > end_time)
+    return;
+
+  base::TimeDelta next_delay = delay * 2;
+  SequencedTaskRunnerHandle::Get()->PostDelayedTask(
+      FROM_HERE,
+      base::BindOnce(&ShimNewMallocZonesAndReschedule, end_time, next_delay),
+      delay);
+}
+
+}  // namespace
+
+void PeriodicallyShimNewMallocZones() {
+  base::Time end_time = base::Time::Now() + base::TimeDelta::FromMinutes(1);
+  base::TimeDelta initial_delay = base::TimeDelta::FromSeconds(1);
+  ShimNewMallocZonesAndReschedule(end_time, initial_delay);
+}
+
+void ShimNewMallocZones() {
+  StoreFunctionsForAllZones();
+
+  // Use the functions for the default zone as a template to replace those
+  // new zones.
+  ChromeMallocZone* default_zone =
+      reinterpret_cast<ChromeMallocZone*>(malloc_default_zone());
+  DCHECK(IsMallocZoneAlreadyStored(default_zone));
+
+  MallocZoneFunctions new_functions;
+  StoreZoneFunctions(default_zone, &new_functions);
+  ReplaceFunctionsForStoredZones(&new_functions);
+}
+
+void ReplaceZoneFunctions(ChromeMallocZone* zone,
+                          const MallocZoneFunctions* functions) {
+  // Remove protection.
+  vm_address_t reprotection_start = 0;
+  vm_size_t reprotection_length = 0;
+  vm_prot_t reprotection_value = VM_PROT_NONE;
+  bool success = DeprotectMallocZone(zone, &reprotection_start,
+                                     &reprotection_length, &reprotection_value);
+  if (!success) {
+    g_allocator_shims_failed_to_install = true;
+    return;
+  }
+
+  CHECK(functions->malloc && functions->calloc && functions->valloc &&
+        functions->free && functions->realloc);
+  zone->malloc = functions->malloc;
+  zone->calloc = functions->calloc;
+  zone->valloc = functions->valloc;
+  zone->free = functions->free;
+  zone->realloc = functions->realloc;
+  if (functions->batch_malloc)
+    zone->batch_malloc = functions->batch_malloc;
+  if (functions->batch_free)
+    zone->batch_free = functions->batch_free;
+  if (functions->size)
+    zone->size = functions->size;
+  if (zone->version >= 5 && functions->memalign) {
+    zone->memalign = functions->memalign;
+  }
+  if (zone->version >= 6 && functions->free_definite_size) {
+    zone->free_definite_size = functions->free_definite_size;
+  }
+
+  // Restore protection if it was active.
+  if (reprotection_start) {
+    kern_return_t result =
+        vm_protect(mach_task_self(), reprotection_start, reprotection_length,
+                   false, reprotection_value);
+    MACH_DCHECK(result == KERN_SUCCESS, result) << "vm_protect";
+  }
+}
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/allocator_shim.cc

@@ -0,0 +1,407 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_shim.h"
+
+#include <errno.h>
+
+#include <atomic>
+#include <new>
+
+#include "base/allocator/buildflags.h"
+#include "base/bits.h"
+#include "base/check_op.h"
+#include "base/macros.h"
+#include "base/memory/page_size.h"
+#include "base/threading/platform_thread.h"
+#include "build/build_config.h"
+
+#if !defined(OS_WIN)
+#include <unistd.h>
+#else
+#include "base/allocator/winheap_stubs_win.h"
+#endif
+
+#if defined(OS_APPLE)
+#include <malloc/malloc.h>
+
+#include "base/allocator/allocator_interception_mac.h"
+#include "base/mac/mach_logging.h"
+#endif
+
+// No calls to malloc / new in this file. They would would cause re-entrancy of
+// the shim, which is hard to deal with. Keep this code as simple as possible
+// and don't use any external C++ object here, not even //base ones. Even if
+// they are safe to use today, in future they might be refactored.
+
+namespace {
+
+std::atomic<const base::allocator::AllocatorDispatch*> g_chain_head{
+    &base::allocator::AllocatorDispatch::default_dispatch};
+
+bool g_call_new_handler_on_malloc_failure = false;
+
+ALWAYS_INLINE size_t GetCachedPageSize() {
+  static size_t pagesize = 0;
+  if (!pagesize)
+    pagesize = base::GetPageSize();
+  return pagesize;
+}
+
+// Calls the std::new handler thread-safely. Returns true if a new_handler was
+// set and called, false if no new_handler was set.
+bool CallNewHandler(size_t size) {
+#if defined(OS_WIN)
+  return base::allocator::WinCallNewHandler(size);
+#else
+  std::new_handler nh = std::get_new_handler();
+  if (!nh)
+    return false;
+  (*nh)();
+  // Assume the new_handler will abort if it fails. Exception are disabled and
+  // we don't support the case of a new_handler throwing std::bad_balloc.
+  return true;
+#endif
+}
+
+ALWAYS_INLINE const base::allocator::AllocatorDispatch* GetChainHead() {
+  return g_chain_head.load(std::memory_order_relaxed);
+}
+
+}  // namespace
+
+namespace base {
+namespace allocator {
+
+void SetCallNewHandlerOnMallocFailure(bool value) {
+  g_call_new_handler_on_malloc_failure = value;
+}
+
+void* UncheckedAlloc(size_t size) {
+  const allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->alloc_unchecked_function(chain_head, size, nullptr);
+}
+
+void InsertAllocatorDispatch(AllocatorDispatch* dispatch) {
+  // Loop in case of (an unlikely) race on setting the list head.
+  size_t kMaxRetries = 7;
+  for (size_t i = 0; i < kMaxRetries; ++i) {
+    const AllocatorDispatch* chain_head = GetChainHead();
+    dispatch->next = chain_head;
+
+    // This function guarantees to be thread-safe w.r.t. concurrent
+    // insertions. It also has to guarantee that all the threads always
+    // see a consistent chain, hence the atomic_thread_fence() below.
+    // InsertAllocatorDispatch() is NOT a fastpath, as opposite to malloc(), so
+    // we don't really want this to be a release-store with a corresponding
+    // acquire-load during malloc().
+    std::atomic_thread_fence(std::memory_order_seq_cst);
+    // Set the chain head to the new dispatch atomically. If we lose the race,
+    // retry.
+    if (g_chain_head.compare_exchange_strong(chain_head, dispatch,
+                                             std::memory_order_relaxed,
+                                             std::memory_order_relaxed)) {
+      // Success.
+      return;
+    }
+  }
+
+  CHECK(false);  // Too many retries, this shouldn't happen.
+}
+
+void RemoveAllocatorDispatchForTesting(AllocatorDispatch* dispatch) {
+  DCHECK_EQ(GetChainHead(), dispatch);
+  g_chain_head.store(dispatch->next, std::memory_order_relaxed);
+}
+
+}  // namespace allocator
+}  // namespace base
+
+// The Shim* functions below are the entry-points into the shim-layer and
+// are supposed to be invoked by the allocator_shim_override_*
+// headers to route the malloc / new symbols through the shim layer.
+// They are defined as ALWAYS_INLINE in order to remove a level of indirection
+// between the system-defined entry points and the shim implementations.
+extern "C" {
+
+// The general pattern for allocations is:
+// - Try to allocate, if succeded return the pointer.
+// - If the allocation failed:
+//   - Call the std::new_handler if it was a C++ allocation.
+//   - Call the std::new_handler if it was a malloc() (or calloc() or similar)
+//     AND SetCallNewHandlerOnMallocFailure(true).
+//   - If the std::new_handler is NOT set just return nullptr.
+//   - If the std::new_handler is set:
+//     - Assume it will abort() if it fails (very likely the new_handler will
+//       just suicide printing a message).
+//     - Assume it did succeed if it returns, in which case reattempt the alloc.
+
+ALWAYS_INLINE void* ShimCppNew(size_t size) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr;
+  do {
+    void* context = nullptr;
+#if defined(OS_APPLE)
+    context = malloc_default_zone();
+#endif
+    ptr = chain_head->alloc_function(chain_head, size, context);
+  } while (!ptr && CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void* ShimCppNewNoThrow(size_t size) {
+  void* context = nullptr;
+#if defined(OS_APPLE)
+  context = malloc_default_zone();
+#endif
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->alloc_unchecked_function(chain_head, size, context);
+}
+
+ALWAYS_INLINE void* ShimCppAlignedNew(size_t size, size_t alignment) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr;
+  do {
+    void* context = nullptr;
+#if defined(OS_APPLE)
+    context = malloc_default_zone();
+#endif
+    ptr = chain_head->alloc_aligned_function(chain_head, alignment, size,
+                                             context);
+  } while (!ptr && CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void ShimCppDelete(void* address) {
+  void* context = nullptr;
+#if defined(OS_APPLE)
+  context = malloc_default_zone();
+#endif
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->free_function(chain_head, address, context);
+}
+
+ALWAYS_INLINE void* ShimMalloc(size_t size, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr;
+  do {
+    ptr = chain_head->alloc_function(chain_head, size, context);
+  } while (!ptr && g_call_new_handler_on_malloc_failure &&
+           CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void* ShimCalloc(size_t n, size_t size, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr;
+  do {
+    ptr = chain_head->alloc_zero_initialized_function(chain_head, n, size,
+                                                      context);
+  } while (!ptr && g_call_new_handler_on_malloc_failure &&
+           CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void* ShimRealloc(void* address, size_t size, void* context) {
+  // realloc(size == 0) means free() and might return a nullptr. We should
+  // not call the std::new_handler in that case, though.
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr;
+  do {
+    ptr = chain_head->realloc_function(chain_head, address, size, context);
+  } while (!ptr && size && g_call_new_handler_on_malloc_failure &&
+           CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void* ShimMemalign(size_t alignment, size_t size, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr;
+  do {
+    ptr = chain_head->alloc_aligned_function(chain_head, alignment, size,
+                                             context);
+  } while (!ptr && g_call_new_handler_on_malloc_failure &&
+           CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE int ShimPosixMemalign(void** res, size_t alignment, size_t size) {
+  // posix_memalign is supposed to check the arguments. See tc_posix_memalign()
+  // in tc_malloc.cc.
+  if (((alignment % sizeof(void*)) != 0) ||
+      !base::bits::IsPowerOfTwo(alignment)) {
+    return EINVAL;
+  }
+  void* ptr = ShimMemalign(alignment, size, nullptr);
+  *res = ptr;
+  return ptr ? 0 : ENOMEM;
+}
+
+ALWAYS_INLINE void* ShimValloc(size_t size, void* context) {
+  return ShimMemalign(GetCachedPageSize(), size, context);
+}
+
+ALWAYS_INLINE void* ShimPvalloc(size_t size) {
+  // pvalloc(0) should allocate one page, according to its man page.
+  if (size == 0) {
+    size = GetCachedPageSize();
+  } else {
+    size = (size + GetCachedPageSize() - 1) & ~(GetCachedPageSize() - 1);
+  }
+  // The third argument is nullptr because pvalloc is glibc only and does not
+  // exist on OSX/BSD systems.
+  return ShimMemalign(GetCachedPageSize(), size, nullptr);
+}
+
+ALWAYS_INLINE void ShimFree(void* address, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->free_function(chain_head, address, context);
+}
+
+ALWAYS_INLINE size_t ShimGetSizeEstimate(const void* address, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->get_size_estimate_function(
+      chain_head, const_cast<void*>(address), context);
+}
+
+ALWAYS_INLINE unsigned ShimBatchMalloc(size_t size,
+                                       void** results,
+                                       unsigned num_requested,
+                                       void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->batch_malloc_function(chain_head, size, results,
+                                           num_requested, context);
+}
+
+ALWAYS_INLINE void ShimBatchFree(void** to_be_freed,
+                                 unsigned num_to_be_freed,
+                                 void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->batch_free_function(chain_head, to_be_freed,
+                                         num_to_be_freed, context);
+}
+
+ALWAYS_INLINE void ShimFreeDefiniteSize(void* ptr, size_t size, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->free_definite_size_function(chain_head, ptr, size,
+                                                 context);
+}
+
+ALWAYS_INLINE void* ShimAlignedMalloc(size_t size,
+                                      size_t alignment,
+                                      void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr = nullptr;
+  do {
+    ptr = chain_head->aligned_malloc_function(chain_head, size, alignment,
+                                              context);
+  } while (!ptr && g_call_new_handler_on_malloc_failure &&
+           CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void* ShimAlignedRealloc(void* address,
+                                       size_t size,
+                                       size_t alignment,
+                                       void* context) {
+  // _aligned_realloc(size == 0) means _aligned_free() and might return a
+  // nullptr. We should not call the std::new_handler in that case, though.
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  void* ptr = nullptr;
+  do {
+    ptr = chain_head->aligned_realloc_function(chain_head, address, size,
+                                               alignment, context);
+  } while (!ptr && size && g_call_new_handler_on_malloc_failure &&
+           CallNewHandler(size));
+  return ptr;
+}
+
+ALWAYS_INLINE void ShimAlignedFree(void* address, void* context) {
+  const base::allocator::AllocatorDispatch* const chain_head = GetChainHead();
+  return chain_head->aligned_free_function(chain_head, address, context);
+}
+
+}  // extern "C"
+
+#if !defined(OS_WIN) && !defined(OS_APPLE)
+// Cpp symbols (new / delete) should always be routed through the shim layer
+// except on Windows and macOS where the malloc intercept is deep enough that it
+// also catches the cpp calls.
+#include "base/allocator/allocator_shim_override_cpp_symbols.h"
+#endif
+
+#if defined(OS_ANDROID)
+// Android does not support symbol interposition. The way malloc symbols are
+// intercepted on Android is by using link-time -wrap flags.
+#include "base/allocator/allocator_shim_override_linker_wrapped_symbols.h"
+#elif defined(OS_WIN)
+// On Windows we use plain link-time overriding of the CRT symbols.
+#include "base/allocator/allocator_shim_override_ucrt_symbols_win.h"
+#elif defined(OS_APPLE)
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+#include "base/allocator/allocator_shim_override_mac_default_zone.h"
+#else  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+#include "base/allocator/allocator_shim_override_mac_symbols.h"
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+#else
+#include "base/allocator/allocator_shim_override_libc_symbols.h"
+#endif
+
+// In the case of tcmalloc we also want to plumb into the glibc hooks
+// to avoid that allocations made in glibc itself (e.g., strdup()) get
+// accidentally performed on the glibc heap.
+//
+// More details:
+// Some glibc versions (until commit 6c444ad6e953dbdf9c7be065308a0a777)
+// incorrectly call __libc_memalign() to allocate memory (see elf/dl-tls.c in
+// glibc 2.23 for instance), and free() to free it. This causes issues for us,
+// as we are then asked to free memory we didn't allocate.
+//
+// This only happened in glibc to allocate TLS storage metadata, and there are
+// no other callers of __libc_memalign() there as of September 2020. To work
+// around this issue, intercept this internal libc symbol to make sure that both
+// the allocation and the free() are caught by the shim.
+//
+// This seems fragile, and is, but there is ample precedent for it, making it
+// quite likely to keep working in the future. For instance, both tcmalloc (in
+// libc_override_glibc.h, see in third_party/tcmalloc) and LLVM for LSAN use the
+// same mechanism.
+
+#if defined(LIBC_GLIBC) && \
+    (BUILDFLAG(USE_TCMALLOC) || BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC))
+#include "base/allocator/allocator_shim_override_glibc_weak_symbols.h"
+#endif
+
+#if defined(OS_APPLE)
+namespace base {
+namespace allocator {
+
+void InitializeAllocatorShim() {
+#if !BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+  // Prepares the default dispatch. After the intercepted malloc calls have
+  // traversed the shim this will route them to the default malloc zone.
+  InitializeDefaultDispatchToMacAllocator();
+
+  MallocZoneFunctions functions = MallocZoneFunctionsToReplaceDefault();
+
+  // This replaces the default malloc zone, causing calls to malloc & friends
+  // from the codebase to be routed to ShimMalloc() above.
+  base::allocator::ReplaceFunctionsForStoredZones(&functions);
+#endif  // !BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+}
+
+}  // namespace allocator
+}  // namespace base
+#endif
+
+// Cross-checks.
+
+#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+#error The allocator shim should not be compiled when building for memory tools.
+#endif
+
+#if (defined(__GNUC__) && defined(__EXCEPTIONS)) || \
+    (defined(_MSC_VER) && defined(_CPPUNWIND))
+#error This code cannot be used when exceptions are turned on.
+#endif

src/base/allocator/allocator_shim.h

@@ -0,0 +1,176 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_H_
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_H_
+
+#include <stddef.h>
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+#include "base/base_export.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace allocator {
+
+// Allocator Shim API. Allows to:
+//  - Configure the behavior of the allocator (what to do on OOM failures).
+//  - Install new hooks (AllocatorDispatch) in the allocator chain.
+
+// When this shim layer is enabled, the route of an allocation is as-follows:
+//
+// [allocator_shim_override_*.h] Intercept malloc() / operator new calls:
+//   The override_* headers define the symbols required to intercept calls to
+//   malloc() and operator new (if not overridden by specific C++ classes).
+//
+// [allocator_shim.cc] Routing allocation calls to the shim:
+//   The headers above route the calls to the internal ShimMalloc(), ShimFree(),
+//   ShimCppNew() etc. methods defined in allocator_shim.cc.
+//   These methods will: (1) forward the allocation call to the front of the
+//   AllocatorDispatch chain. (2) perform security hardenings (e.g., might
+//   call std::new_handler on OOM failure).
+//
+// [allocator_shim_default_dispatch_to_*.cc] The AllocatorDispatch chain:
+//   It is a singly linked list where each element is a struct with function
+//   pointers (|malloc_function|, |free_function|, etc). Normally the chain
+//   consists of a single AllocatorDispatch element, herein called
+//   the "default dispatch", which is statically defined at build time and
+//   ultimately routes the calls to the actual allocator defined by the build
+//   config (tcmalloc, glibc, ...).
+//
+// It is possible to dynamically insert further AllocatorDispatch stages
+// to the front of the chain, for debugging / profiling purposes.
+//
+// All the functions must be thread safe. The shim does not enforce any
+// serialization. This is to route to thread-aware allocators (e.g, tcmalloc)
+// wihout introducing unnecessary perf hits.
+
+struct AllocatorDispatch {
+  using AllocFn = void*(const AllocatorDispatch* self,
+                        size_t size,
+                        void* context);
+  using AllocUncheckedFn = void*(const AllocatorDispatch* self,
+                                 size_t size,
+                                 void* context);
+  using AllocZeroInitializedFn = void*(const AllocatorDispatch* self,
+                                       size_t n,
+                                       size_t size,
+                                       void* context);
+  using AllocAlignedFn = void*(const AllocatorDispatch* self,
+                               size_t alignment,
+                               size_t size,
+                               void* context);
+  using ReallocFn = void*(const AllocatorDispatch* self,
+                          void* address,
+                          size_t size,
+                          void* context);
+  using FreeFn = void(const AllocatorDispatch* self,
+                      void* address,
+                      void* context);
+  // Returns the allocated size of user data (not including heap overhead).
+  // Can be larger than the requested size.
+  using GetSizeEstimateFn = size_t(const AllocatorDispatch* self,
+                                   void* address,
+                                   void* context);
+  using BatchMallocFn = unsigned(const AllocatorDispatch* self,
+                                 size_t size,
+                                 void** results,
+                                 unsigned num_requested,
+                                 void* context);
+  using BatchFreeFn = void(const AllocatorDispatch* self,
+                           void** to_be_freed,
+                           unsigned num_to_be_freed,
+                           void* context);
+  using FreeDefiniteSizeFn = void(const AllocatorDispatch* self,
+                                  void* ptr,
+                                  size_t size,
+                                  void* context);
+  using AlignedMallocFn = void*(const AllocatorDispatch* self,
+                                size_t size,
+                                size_t alignment,
+                                void* context);
+  using AlignedReallocFn = void*(const AllocatorDispatch* self,
+                                 void* address,
+                                 size_t size,
+                                 size_t alignment,
+                                 void* context);
+  using AlignedFreeFn = void(const AllocatorDispatch* self,
+                             void* address,
+                             void* context);
+
+  AllocFn* const alloc_function;
+  AllocUncheckedFn* const alloc_unchecked_function;
+  AllocZeroInitializedFn* const alloc_zero_initialized_function;
+  AllocAlignedFn* const alloc_aligned_function;
+  ReallocFn* const realloc_function;
+  FreeFn* const free_function;
+  GetSizeEstimateFn* const get_size_estimate_function;
+  // batch_malloc, batch_free, and free_definite_size are specific to the OSX
+  // and iOS allocators.
+  BatchMallocFn* const batch_malloc_function;
+  BatchFreeFn* const batch_free_function;
+  FreeDefiniteSizeFn* const free_definite_size_function;
+  // _aligned_malloc, _aligned_realloc, and _aligned_free are specific to the
+  // Windows allocator.
+  AlignedMallocFn* const aligned_malloc_function;
+  AlignedReallocFn* const aligned_realloc_function;
+  AlignedFreeFn* const aligned_free_function;
+
+  const AllocatorDispatch* next;
+
+  // |default_dispatch| is statically defined by one (and only one) of the
+  // allocator_shim_default_dispatch_to_*.cc files, depending on the build
+  // configuration.
+  static const AllocatorDispatch default_dispatch;
+};
+
+// When true makes malloc behave like new, w.r.t calling the new_handler if
+// the allocation fails (see set_new_mode() in Windows).
+BASE_EXPORT void SetCallNewHandlerOnMallocFailure(bool value);
+
+// Allocates |size| bytes or returns nullptr. It does NOT call the new_handler,
+// regardless of SetCallNewHandlerOnMallocFailure().
+BASE_EXPORT void* UncheckedAlloc(size_t size);
+
+// Inserts |dispatch| in front of the allocator chain. This method is
+// thread-safe w.r.t concurrent invocations of InsertAllocatorDispatch().
+// The callers have responsibility for inserting a single dispatch no more
+// than once.
+BASE_EXPORT void InsertAllocatorDispatch(AllocatorDispatch* dispatch);
+
+// Test-only. Rationale: (1) lack of use cases; (2) dealing safely with a
+// removal of arbitrary elements from a singly linked list would require a lock
+// in malloc(), which we really don't want.
+BASE_EXPORT void RemoveAllocatorDispatchForTesting(AllocatorDispatch* dispatch);
+
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && defined(OS_WIN)
+// Configures the allocator for the caller's allocation domain. Allocations that
+// take place prior to this configuration step will succeed, but will not
+// benefit from its one-time mitigations. As such, this function must be called
+// as early as possible during startup.
+BASE_EXPORT void ConfigurePartitionAlloc();
+#endif  // defined(OS_WIN)
+
+#if defined(OS_APPLE)
+// On macOS, the allocator shim needs to be turned on during runtime.
+BASE_EXPORT void InitializeAllocatorShim();
+#endif  // defined(OS_APPLE)
+
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+BASE_EXPORT void EnablePartitionAllocMemoryReclaimer();
+
+BASE_EXPORT void ReconfigurePartitionAllocLazyCommit();
+
+BASE_EXPORT void ConfigurePartitionRefCountSupport(bool enable_ref_count);
+#endif
+
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && PA_ALLOW_PCSCAN
+BASE_EXPORT void EnablePCScan(bool dcscan);
+#endif
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_SHIM_H_

src/base/allocator/allocator_shim_default_dispatch_to_glibc.cc

@@ -0,0 +1,89 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_shim.h"
+#include "base/compiler_specific.h"
+
+#include <dlfcn.h>
+#include <malloc.h>
+
+// This translation unit defines a default dispatch for the allocator shim which
+// routes allocations to libc functions.
+// The code here is strongly inspired from tcmalloc's libc_override_glibc.h.
+
+extern "C" {
+void* __libc_malloc(size_t size);
+void* __libc_calloc(size_t n, size_t size);
+void* __libc_realloc(void* address, size_t size);
+void* __libc_memalign(size_t alignment, size_t size);
+void __libc_free(void* ptr);
+}  // extern "C"
+
+namespace {
+
+using base::allocator::AllocatorDispatch;
+
+void* GlibcMalloc(const AllocatorDispatch*, size_t size, void* context) {
+  return __libc_malloc(size);
+}
+
+void* GlibcCalloc(const AllocatorDispatch*,
+                  size_t n,
+                  size_t size,
+                  void* context) {
+  return __libc_calloc(n, size);
+}
+
+void* GlibcRealloc(const AllocatorDispatch*,
+                   void* address,
+                   size_t size,
+                   void* context) {
+  return __libc_realloc(address, size);
+}
+
+void* GlibcMemalign(const AllocatorDispatch*,
+                    size_t alignment,
+                    size_t size,
+                    void* context) {
+  return __libc_memalign(alignment, size);
+}
+
+void GlibcFree(const AllocatorDispatch*, void* address, void* context) {
+  __libc_free(address);
+}
+
+NO_SANITIZE("cfi-icall")
+size_t GlibcGetSizeEstimate(const AllocatorDispatch*,
+                            void* address,
+                            void* context) {
+  // glibc does not expose an alias to resolve malloc_usable_size. Dynamically
+  // resolve it instead. This should be safe because glibc (and hence dlfcn)
+  // does not use malloc_size internally and so there should not be a risk of
+  // recursion.
+  using MallocUsableSizeFunction = decltype(malloc_usable_size)*;
+  static MallocUsableSizeFunction fn_ptr =
+      reinterpret_cast<MallocUsableSizeFunction>(
+          dlsym(RTLD_NEXT, "malloc_usable_size"));
+
+  return fn_ptr(address);
+}
+
+}  // namespace
+
+const AllocatorDispatch AllocatorDispatch::default_dispatch = {
+    &GlibcMalloc,          /* alloc_function */
+    &GlibcMalloc,          /* alloc_unchecked_function */
+    &GlibcCalloc,          /* alloc_zero_initialized_function */
+    &GlibcMemalign,        /* alloc_aligned_function */
+    &GlibcRealloc,         /* realloc_function */
+    &GlibcFree,            /* free_function */
+    &GlibcGetSizeEstimate, /* get_size_estimate_function */
+    nullptr,               /* batch_malloc_function */
+    nullptr,               /* batch_free_function */
+    nullptr,               /* free_definite_size_function */
+    nullptr,               /* aligned_malloc_function */
+    nullptr,               /* aligned_realloc_function */
+    nullptr,               /* aligned_free_function */
+    nullptr,               /* next */
+};

src/base/allocator/allocator_shim_default_dispatch_to_linker_wrapped_symbols.cc

@@ -0,0 +1,77 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <malloc.h>
+
+#include "base/allocator/allocator_shim.h"
+#include "build/build_config.h"
+
+// This translation unit defines a default dispatch for the allocator shim which
+// routes allocations to the original libc functions when using the link-time
+// -Wl,-wrap,malloc approach (see README.md).
+// The __real_X functions here are special symbols that the linker will relocate
+// against the real "X" undefined symbol, so that __real_malloc becomes the
+// equivalent of what an undefined malloc symbol reference would have been.
+// This is the counterpart of allocator_shim_override_linker_wrapped_symbols.h,
+// which routes the __wrap_X functions into the shim.
+
+extern "C" {
+void* __real_malloc(size_t);
+void* __real_calloc(size_t, size_t);
+void* __real_realloc(void*, size_t);
+void* __real_memalign(size_t, size_t);
+void* __real_free(void*);
+}  // extern "C"
+
+namespace {
+
+using base::allocator::AllocatorDispatch;
+
+void* RealMalloc(const AllocatorDispatch*, size_t size, void* context) {
+  return __real_malloc(size);
+}
+
+void* RealCalloc(const AllocatorDispatch*,
+                 size_t n,
+                 size_t size,
+                 void* context) {
+  return __real_calloc(n, size);
+}
+
+void* RealRealloc(const AllocatorDispatch*,
+                  void* address,
+                  size_t size,
+                  void* context) {
+  return __real_realloc(address, size);
+}
+
+void* RealMemalign(const AllocatorDispatch*,
+                   size_t alignment,
+                   size_t size,
+                   void* context) {
+  return __real_memalign(alignment, size);
+}
+
+void RealFree(const AllocatorDispatch*, void* address, void* context) {
+  __real_free(address);
+}
+
+}  // namespace
+
+const AllocatorDispatch AllocatorDispatch::default_dispatch = {
+    &RealMalloc,   /* alloc_function */
+    &RealMalloc,   /* alloc_unchecked_function */
+    &RealCalloc,   /* alloc_zero_initialized_function */
+    &RealMemalign, /* alloc_aligned_function */
+    &RealRealloc,  /* realloc_function */
+    &RealFree,     /* free_function */
+    nullptr,       /* get_size_estimate_function */
+    nullptr,       /* batch_malloc_function */
+    nullptr,       /* batch_free_function */
+    nullptr,       /* free_definite_size_function */
+    nullptr,       /* aligned_malloc_function */
+    nullptr,       /* aligned_realloc_function */
+    nullptr,       /* aligned_free_function */
+    nullptr,       /* next */
+};

src/base/allocator/allocator_shim_default_dispatch_to_mac_zoned_malloc.cc

@@ -0,0 +1,107 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <utility>
+
+#include "base/allocator/allocator_interception_mac.h"
+#include "base/allocator/allocator_shim.h"
+#include "base/allocator/malloc_zone_functions_mac.h"
+
+namespace base {
+namespace allocator {
+namespace {
+
+void* MallocImpl(const AllocatorDispatch*, size_t size, void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  return functions.malloc(reinterpret_cast<struct _malloc_zone_t*>(context),
+                          size);
+}
+
+void* CallocImpl(const AllocatorDispatch*,
+                 size_t n,
+                 size_t size,
+                 void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  return functions.calloc(reinterpret_cast<struct _malloc_zone_t*>(context), n,
+                          size);
+}
+
+void* MemalignImpl(const AllocatorDispatch*,
+                   size_t alignment,
+                   size_t size,
+                   void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  return functions.memalign(reinterpret_cast<struct _malloc_zone_t*>(context),
+                            alignment, size);
+}
+
+void* ReallocImpl(const AllocatorDispatch*,
+                  void* ptr,
+                  size_t size,
+                  void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  return functions.realloc(reinterpret_cast<struct _malloc_zone_t*>(context),
+                           ptr, size);
+}
+
+void FreeImpl(const AllocatorDispatch*, void* ptr, void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  functions.free(reinterpret_cast<struct _malloc_zone_t*>(context), ptr);
+}
+
+size_t GetSizeEstimateImpl(const AllocatorDispatch*, void* ptr, void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  return functions.size(reinterpret_cast<struct _malloc_zone_t*>(context), ptr);
+}
+
+unsigned BatchMallocImpl(const AllocatorDispatch* self,
+                         size_t size,
+                         void** results,
+                         unsigned num_requested,
+                         void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  return functions.batch_malloc(
+      reinterpret_cast<struct _malloc_zone_t*>(context), size, results,
+      num_requested);
+}
+
+void BatchFreeImpl(const AllocatorDispatch* self,
+                   void** to_be_freed,
+                   unsigned num_to_be_freed,
+                   void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  functions.batch_free(reinterpret_cast<struct _malloc_zone_t*>(context),
+                       to_be_freed, num_to_be_freed);
+}
+
+void FreeDefiniteSizeImpl(const AllocatorDispatch* self,
+                          void* ptr,
+                          size_t size,
+                          void* context) {
+  MallocZoneFunctions& functions = GetFunctionsForZone(context);
+  functions.free_definite_size(
+      reinterpret_cast<struct _malloc_zone_t*>(context), ptr, size);
+}
+
+}  // namespace
+
+const AllocatorDispatch AllocatorDispatch::default_dispatch = {
+    &MallocImpl,           /* alloc_function */
+    &MallocImpl,           /* alloc_unchecked_function */
+    &CallocImpl,           /* alloc_zero_initialized_function */
+    &MemalignImpl,         /* alloc_aligned_function */
+    &ReallocImpl,          /* realloc_function */
+    &FreeImpl,             /* free_function */
+    &GetSizeEstimateImpl,  /* get_size_estimate_function */
+    &BatchMallocImpl,      /* batch_malloc_function */
+    &BatchFreeImpl,        /* batch_free_function */
+    &FreeDefiniteSizeImpl, /* free_definite_size_function */
+    nullptr,               /* aligned_malloc_function */
+    nullptr,               /* aligned_realloc_function */
+    nullptr,               /* aligned_free_function */
+    nullptr,               /* next */
+};
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/allocator_shim_default_dispatch_to_partition_alloc.cc

@@ -0,0 +1,604 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_shim_default_dispatch_to_partition_alloc.h"
+
+#include <atomic>
+#include <cstddef>
+
+#include "base/allocator/allocator_shim_internals.h"
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/memory_reclaimer.h"
+#include "base/allocator/partition_allocator/partition_alloc.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+#include "base/allocator/partition_allocator/partition_root.h"
+#include "base/allocator/partition_allocator/partition_stats.h"
+#include "base/bits.h"
+#include "base/compiler_specific.h"
+#include "base/memory/nonscannable_memory.h"
+#include "base/no_destructor.h"
+#include "base/numerics/checked_math.h"
+#include "base/partition_alloc_buildflags.h"
+#include "build/build_config.h"
+
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+#include <malloc.h>
+#endif
+
+using base::allocator::AllocatorDispatch;
+
+namespace {
+
+// We can't use a "static local" or a base::LazyInstance, as:
+// - static local variables call into the runtime on Windows, which is not
+//   prepared to handle it, as the first allocation happens during CRT init.
+// - We don't want to depend on base::LazyInstance, which may be converted to
+//   static locals one day.
+//
+// Nevertheless, this provides essentially the same thing.
+template <typename T, typename Constructor>
+class LeakySingleton {
+ public:
+  constexpr LeakySingleton() = default;
+
+  ALWAYS_INLINE T* Get() {
+    auto* instance = instance_.load(std::memory_order_acquire);
+    if (LIKELY(instance))
+      return instance;
+
+    return GetSlowPath();
+  }
+
+  // Replaces the instance pointer with a new one.
+  void Replace(T* new_instance) {
+    instance_.store(new_instance, std::memory_order_release);
+  }
+
+ private:
+  T* GetSlowPath();
+
+  std::atomic<T*> instance_;
+  alignas(T) uint8_t instance_buffer_[sizeof(T)];
+  std::atomic<bool> initialization_lock_;
+};
+
+template <typename T, typename Constructor>
+T* LeakySingleton<T, Constructor>::GetSlowPath() {
+  // The instance has not been set, the proper way to proceed (correct
+  // double-checked locking) is:
+  //
+  // auto* instance = instance_.load(std::memory_order_acquire);
+  // if (!instance) {
+  //   ScopedLock initialization_lock;
+  //   root = instance_.load(std::memory_order_relaxed);
+  //   if (root)
+  //     return root;
+  //   instance = Create new root;
+  //   instance_.store(instance, std::memory_order_release);
+  //   return instance;
+  // }
+  //
+  // However, we don't want to use a base::Lock here, so instead we use
+  // compare-and-exchange on a lock variable, which provides the same
+  // guarantees.
+  //
+  // Lock.
+  bool expected = false;
+  // Semantically equivalent to base::Lock::Acquire().
+  while (!initialization_lock_.compare_exchange_strong(
+      expected, true, std::memory_order_acquire, std::memory_order_acquire)) {
+    expected = false;
+  }
+
+  T* instance = instance_.load(std::memory_order_relaxed);
+  // Someone beat us.
+  if (instance) {
+    // Unlock.
+    initialization_lock_.store(false, std::memory_order_release);
+    return instance;
+  }
+
+  instance = Constructor::New(reinterpret_cast<void*>(instance_buffer_));
+  instance_.store(instance, std::memory_order_release);
+
+  // Unlock.
+  initialization_lock_.store(false, std::memory_order_release);
+
+  return instance;
+}
+
+class MainPartitionConstructor {
+ public:
+  static base::ThreadSafePartitionRoot* New(void* buffer) {
+    auto* new_root = new (buffer) base::ThreadSafePartitionRoot({
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+      base::PartitionOptions::AlignedAlloc::kDisallowed,
+#else
+      base::PartitionOptions::AlignedAlloc::kAllowed,
+#endif
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && \
+    !BUILDFLAG(ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL)
+          base::PartitionOptions::ThreadCache::kEnabled,
+#elif BUILDFLAG(ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL)
+          // With ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL, this partition is only
+          // temporary until BackupRefPtr is re-configured at run-time. Leave
+          // the ability to have a thread cache to the main partition. (Note
+          // that ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL implies that
+          // USE_BACKUP_REF_PTR is true.)
+          base::PartitionOptions::ThreadCache::kDisabled,
+#else
+      // Other tests, such as the ThreadCache tests create a thread cache, and
+      // only one is supported at a time.
+      base::PartitionOptions::ThreadCache::kDisabled,
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) &&
+        // !BUILDFLAG(ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL)
+          base::PartitionOptions::Quarantine::kAllowed,
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+          base::PartitionOptions::Cookies::kAllowed,
+#else
+          base::PartitionOptions::Cookies::kDisallowed,
+#endif
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC) || \
+    BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+          base::PartitionOptions::RefCount::kAllowed,
+#else
+          base::PartitionOptions::RefCount::kDisallowed,
+#endif
+    });
+
+    return new_root;
+  }
+};
+
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+class AlignedPartitionConstructor {
+ public:
+  static base::ThreadSafePartitionRoot* New(void* buffer) {
+    // Since the general-purpose allocator uses the thread cache, this one
+    // cannot.
+    auto* new_root =
+        new (buffer) base::ThreadSafePartitionRoot(base::PartitionOptions {
+          base::PartitionOptions::AlignedAlloc::kAllowed,
+              base::PartitionOptions::ThreadCache::kDisabled,
+              base::PartitionOptions::Quarantine::kAllowed,
+              base::PartitionOptions::Cookies::kDisallowed,
+#if BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+              // Given the outer #if, this is possible only when DCHECK_IS_ON().
+              base::PartitionOptions::RefCount::kAllowed,
+#else
+            base::PartitionOptions::RefCount::kDisallowed,
+#endif
+        });
+    return new_root;
+  }
+};
+
+LeakySingleton<base::ThreadSafePartitionRoot, AlignedPartitionConstructor>
+    g_aligned_root CONSTINIT = {};
+#endif  // BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+
+// Original g_root_ if it was replaced by ConfigurePartitionRefCountSupport().
+std::atomic<base::ThreadSafePartitionRoot*> g_original_root_(nullptr);
+
+LeakySingleton<base::ThreadSafePartitionRoot, MainPartitionConstructor> g_root
+    CONSTINIT = {};
+base::ThreadSafePartitionRoot* Allocator() {
+  return g_root.Get();
+}
+
+base::ThreadSafePartitionRoot* OriginalAllocator() {
+  return g_original_root_.load(std::memory_order_relaxed);
+}
+
+base::ThreadSafePartitionRoot* AlignedAllocator() {
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+  return g_aligned_root.Get();
+#else   // BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+  return Allocator();
+#endif  // BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+}
+
+#if defined(OS_WIN) && defined(ARCH_CPU_X86)
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+bool IsRunning32bitEmulatedOnArm64() {
+  using IsWow64Process2Function = decltype(&IsWow64Process2);
+
+  IsWow64Process2Function is_wow64_process2 =
+      reinterpret_cast<IsWow64Process2Function>(::GetProcAddress(
+          ::GetModuleHandleA("kernel32.dll"), "IsWow64Process2"));
+  if (!is_wow64_process2)
+    return false;
+  USHORT process_machine;
+  USHORT native_machine;
+  bool retval = is_wow64_process2(::GetCurrentProcess(), &process_machine,
+                                  &native_machine);
+  if (!retval)
+    return false;
+  if (native_machine == IMAGE_FILE_MACHINE_ARM64)
+    return true;
+  return false;
+}
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+// The number of bytes to add to every allocation. Ordinarily zero, but set to 8
+// when emulating an x86 on ARM64 to avoid a bug in the Windows x86 emulator.
+size_t g_extra_bytes;
+#endif  // defined(OS_WIN) && defined(ARCH_CPU_X86)
+
+// TODO(brucedawson): Remove this when https://crbug.com/1151455 is fixed.
+ALWAYS_INLINE size_t MaybeAdjustSize(size_t size) {
+#if defined(OS_WIN) && defined(ARCH_CPU_X86)
+  return base::CheckAdd(size, g_extra_bytes).ValueOrDie();
+#else   // defined(OS_WIN) && defined(ARCH_CPU_X86)
+  return size;
+#endif  // defined(OS_WIN) && defined(ARCH_CPU_X86)
+}
+
+void* AllocateAlignedMemory(size_t alignment, size_t size) {
+  // Memory returned by the regular allocator *always* respects |kAlignment|,
+  // which is a power of two, and any valid alignment is also a power of two. So
+  // we can directly fulfill these requests with the main allocator.
+  //
+  // This has several advantages:
+  // - The thread cache is supported on the main partition
+  // - Reduced fragmentation
+  // - Better coverage for MiraclePtr variants requiring extras
+  //
+  // There are several call sites in Chromium where base::AlignedAlloc is called
+  // with a small alignment. Some may be due to overly-careful code, some are
+  // because the client code doesn't know the required alignment at compile
+  // time.
+  //
+  // Note that all "AlignedFree()" variants (_aligned_free() on Windows for
+  // instance) directly call PartitionFree(), so there is no risk of
+  // mismatch. (see below the default_dispatch definition).
+  if (alignment <= base::kAlignment) {
+    // This is mandated by |posix_memalign()| and friends, so should never fire.
+    PA_CHECK(base::bits::IsPowerOfTwo(alignment));
+    // TODO(bartekn): See if the compiler optimizes branches down the stack on
+    // Mac, where PartitionPageSize() isn't constexpr.
+    return Allocator()->AllocFlagsNoHooks(0, size, base::PartitionPageSize());
+  }
+
+  return AlignedAllocator()->AlignedAllocFlags(base::PartitionAllocNoHooks,
+                                               alignment, size);
+}
+
+}  // namespace
+
+namespace base {
+namespace internal {
+
+void* PartitionMalloc(const AllocatorDispatch*, size_t size, void* context) {
+  return Allocator()->AllocFlagsNoHooks(0, MaybeAdjustSize(size),
+                                        PartitionPageSize());
+}
+
+void* PartitionMallocUnchecked(const AllocatorDispatch*,
+                               size_t size,
+                               void* context) {
+  return Allocator()->AllocFlagsNoHooks(base::PartitionAllocReturnNull,
+                                        MaybeAdjustSize(size),
+                                        PartitionPageSize());
+}
+
+void* PartitionCalloc(const AllocatorDispatch*,
+                      size_t n,
+                      size_t size,
+                      void* context) {
+  const size_t total = base::CheckMul(n, MaybeAdjustSize(size)).ValueOrDie();
+  return Allocator()->AllocFlagsNoHooks(base::PartitionAllocZeroFill, total,
+                                        PartitionPageSize());
+}
+
+void* PartitionMemalign(const AllocatorDispatch*,
+                        size_t alignment,
+                        size_t size,
+                        void* context) {
+  return AllocateAlignedMemory(alignment, size);
+}
+
+void* PartitionAlignedAlloc(const AllocatorDispatch* dispatch,
+                            size_t size,
+                            size_t alignment,
+                            void* context) {
+  return AllocateAlignedMemory(alignment, size);
+}
+
+// aligned_realloc documentation is
+// https://docs.microsoft.com/ja-jp/cpp/c-runtime-library/reference/aligned-realloc
+// TODO(tasak): Expand the given memory block to the given size if possible.
+// This realloc always free the original memory block and allocates a new memory
+// block.
+// TODO(tasak): Implement PartitionRoot<thread_safe>::AlignedReallocFlags and
+// use it.
+void* PartitionAlignedRealloc(const AllocatorDispatch* dispatch,
+                              void* address,
+                              size_t size,
+                              size_t alignment,
+                              void* context) {
+  void* new_ptr = nullptr;
+  if (size > 0) {
+    size = MaybeAdjustSize(size);
+    new_ptr = AllocateAlignedMemory(alignment, size);
+  } else {
+    // size == 0 and address != null means just "free(address)".
+    if (address)
+      base::ThreadSafePartitionRoot::FreeNoHooks(address);
+  }
+  // The original memory block (specified by address) is unchanged if ENOMEM.
+  if (!new_ptr)
+    return nullptr;
+  // TODO(tasak): Need to compare the new alignment with the address' alignment.
+  // If the two alignments are not the same, need to return nullptr with EINVAL.
+  if (address) {
+    size_t usage = base::ThreadSafePartitionRoot::GetUsableSize(address);
+    size_t copy_size = usage > size ? size : usage;
+    memcpy(new_ptr, address, copy_size);
+
+    base::ThreadSafePartitionRoot::FreeNoHooks(address);
+  }
+  return new_ptr;
+}
+
+void* PartitionRealloc(const AllocatorDispatch*,
+                       void* address,
+                       size_t size,
+                       void* context) {
+#if defined(OS_APPLE)
+  if (!base::IsManagedByPartitionAlloc(address)) {
+    // A memory region allocated by the system allocator is passed in this
+    // function.  Forward the request to `realloc` which supports zone-
+    // dispatching so that it appropriately selects the right zone.
+    return realloc(address, size);
+  }
+#endif  // defined(OS_APPLE)
+
+  return Allocator()->ReallocFlags(base::PartitionAllocNoHooks, address,
+                                   MaybeAdjustSize(size), "");
+}
+
+void PartitionFree(const AllocatorDispatch*, void* address, void* context) {
+#if defined(OS_APPLE)
+  if (!base::IsManagedByPartitionAlloc(address)) {
+    // A memory region allocated by the system allocator is passed in this
+    // function.  Forward the request to `free` which supports zone-
+    // dispatching so that it appropriately selects the right zone.
+    return free(address);
+  }
+#endif  // defined(OS_APPLE)
+
+  base::ThreadSafePartitionRoot::FreeNoHooks(address);
+}
+
+size_t PartitionGetSizeEstimate(const AllocatorDispatch*,
+                                void* address,
+                                void* context) {
+#if defined(OS_APPLE)
+  if (!base::IsManagedByPartitionAlloc(address)) {
+    // The object pointed to by `address` is not allocated by the
+    // PartitionAlloc.  The return value `0` means that the pointer does not
+    // belong to this malloc zone.
+    return 0;
+  }
+#endif  // defined(OS_APPLE)
+
+  // TODO(lizeb): Returns incorrect values for aligned allocations.
+  const size_t size = base::ThreadSafePartitionRoot::GetUsableSize(address);
+#if defined(OS_APPLE)
+  // The object pointed to by `address` is allocated by the PartitionAlloc.
+  // So, this function must not return zero so that the malloc zone dispatcher
+  // finds the appropriate malloc zone.
+  PA_DCHECK(size);
+#endif  // defined(OS_APPLE)
+  return size;
+}
+
+// static
+ThreadSafePartitionRoot* PartitionAllocMalloc::Allocator() {
+  return ::Allocator();
+}
+
+// static
+ThreadSafePartitionRoot* PartitionAllocMalloc::OriginalAllocator() {
+  return ::OriginalAllocator();
+}
+
+// static
+ThreadSafePartitionRoot* PartitionAllocMalloc::AlignedAllocator() {
+  return ::AlignedAllocator();
+}
+
+}  // namespace internal
+}  // namespace base
+
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+namespace base {
+namespace allocator {
+
+void EnablePartitionAllocMemoryReclaimer() {
+  // Unlike other partitions, Allocator() and AlignedAllocator() do not register
+  // their PartitionRoots to the memory reclaimer, because doing so may allocate
+  // memory. Thus, the registration to the memory reclaimer has to be done
+  // some time later, when the main root is fully configured.
+  // TODO(bartekn): Aligned allocator can use the regular initialization path.
+  PartitionAllocMemoryReclaimer::Instance()->RegisterPartition(Allocator());
+  auto* original_root = OriginalAllocator();
+  if (original_root)
+    PartitionAllocMemoryReclaimer::Instance()->RegisterPartition(original_root);
+  if (AlignedAllocator() != Allocator()) {
+    PartitionAllocMemoryReclaimer::Instance()->RegisterPartition(
+        AlignedAllocator());
+  }
+}
+
+void ReconfigurePartitionAllocLazyCommit() {
+  // Unlike other partitions, Allocator() and AlignedAllocator() do not
+  // configure lazy commit upfront, because it uses base::Feature, which in turn
+  // allocates memory. Thus, lazy commit configuration has to be done after
+  // base::FeatureList is initialized.
+  // TODO(bartekn): Aligned allocator can use the regular initialization path.
+  Allocator()->ConfigureLazyCommit();
+  auto* original_root = OriginalAllocator();
+  if (original_root)
+    original_root->ConfigureLazyCommit();
+  AlignedAllocator()->ConfigureLazyCommit();
+}
+
+// Note that ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL implies that
+// USE_BACKUP_REF_PTR is true.
+#if BUILDFLAG(ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL)
+alignas(base::ThreadSafePartitionRoot) uint8_t
+    g_allocator_buffer_for_ref_count_config[sizeof(
+        base::ThreadSafePartitionRoot)];
+
+void ConfigurePartitionRefCountSupport(bool enable_ref_count) {
+  auto* current_root = g_root.Get();
+  current_root->PurgeMemory(PartitionPurgeDecommitEmptySlotSpans |
+                            PartitionPurgeDiscardUnusedSystemPages);
+
+  auto* new_root = new (g_allocator_buffer_for_ref_count_config)
+      base::ThreadSafePartitionRoot({
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+        base::PartitionOptions::AlignedAlloc::kDisallowed,
+#else
+        base::PartitionOptions::AlignedAlloc::kAllowed,
+#endif
+            base::PartitionOptions::ThreadCache::kEnabled,
+            base::PartitionOptions::Quarantine::kAllowed,
+#if BUILDFLAG(USE_DEDICATED_PARTITION_FOR_ALIGNED_ALLOC)
+            base::PartitionOptions::Cookies::kAllowed,
+#else
+            base::PartitionOptions::Cookies::kDisallowed,
+#endif
+            enable_ref_count ? base::PartitionOptions::RefCount::kAllowed
+                             : base::PartitionOptions::RefCount::kDisallowed,
+      });
+  g_root.Replace(new_root);
+  g_original_root_ = current_root;
+}
+#endif  // BUILDFLAG(ENABLE_RUNTIME_BACKUP_REF_PTR_CONTROL)
+
+#if PA_ALLOW_PCSCAN
+void EnablePCScan(bool dcscan) {
+  internal::PCScan::Initialize(
+      dcscan ? internal::PCScan::WantedWriteProtectionMode::kEnabled
+             : internal::PCScan::WantedWriteProtectionMode::kDisabled);
+  internal::PCScan::RegisterScannableRoot(Allocator());
+  if (Allocator() != AlignedAllocator())
+    internal::PCScan::RegisterScannableRoot(AlignedAllocator());
+  internal::NonScannableAllocator::Instance().EnablePCScan();
+}
+#endif
+
+#if defined(OS_WIN)
+// Call this as soon as possible during startup.
+void ConfigurePartitionAlloc() {
+#if defined(ARCH_CPU_X86)
+  if (IsRunning32bitEmulatedOnArm64())
+    g_extra_bytes = 8;
+#endif  // defined(ARCH_CPU_X86)
+}
+#endif  // defined(OS_WIN)
+}  // namespace allocator
+}  // namespace base
+
+constexpr AllocatorDispatch AllocatorDispatch::default_dispatch = {
+    &base::internal::PartitionMalloc,           // alloc_function
+    &base::internal::PartitionMallocUnchecked,  // alloc_unchecked_function
+    &base::internal::PartitionCalloc,    // alloc_zero_initialized_function
+    &base::internal::PartitionMemalign,  // alloc_aligned_function
+    &base::internal::PartitionRealloc,   // realloc_function
+    &base::internal::PartitionFree,      // free_function
+    &base::internal::PartitionGetSizeEstimate,  // get_size_estimate_function
+    nullptr,                                    // batch_malloc_function
+    nullptr,                                    // batch_free_function
+    nullptr,                                    // free_definite_size_function
+    &base::internal::PartitionAlignedAlloc,     // aligned_malloc_function
+    &base::internal::PartitionAlignedRealloc,   // aligned_realloc_function
+    &base::internal::PartitionFree,             // aligned_free_function
+    nullptr,                                    // next
+};
+
+// Intercept diagnostics symbols as well, even though they are not part of the
+// unified shim layer.
+//
+// TODO(lizeb): Implement the ones that doable.
+
+extern "C" {
+
+#if !defined(OS_APPLE)
+
+SHIM_ALWAYS_EXPORT void malloc_stats(void) __THROW {}
+
+SHIM_ALWAYS_EXPORT int mallopt(int cmd, int value) __THROW {
+  return 0;
+}
+
+#endif  // !defined(OS_APPLE)
+
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+SHIM_ALWAYS_EXPORT struct mallinfo mallinfo(void) __THROW {
+  base::SimplePartitionStatsDumper allocator_dumper;
+  Allocator()->DumpStats("malloc", true, &allocator_dumper);
+  // TODO(bartekn): Dump OriginalAllocator() into "malloc" as well.
+
+  base::SimplePartitionStatsDumper aligned_allocator_dumper;
+  if (AlignedAllocator() != Allocator()) {
+    AlignedAllocator()->DumpStats("posix_memalign", true,
+                                  &aligned_allocator_dumper);
+  }
+
+  // Dump stats for nonscannable allocators.
+  auto& nonscannable_allocator =
+      base::internal::NonScannableAllocator::Instance();
+  base::SimplePartitionStatsDumper nonscannable_allocator_dumper;
+  if (auto* nonscannable_root = nonscannable_allocator.root())
+    nonscannable_root->DumpStats("malloc", true,
+                                 &nonscannable_allocator_dumper);
+
+  struct mallinfo info = {0};
+  info.arena = 0;  // Memory *not* allocated with mmap().
+
+  // Memory allocated with mmap(), aka virtual size.
+  info.hblks = allocator_dumper.stats().total_mmapped_bytes +
+               aligned_allocator_dumper.stats().total_mmapped_bytes +
+               nonscannable_allocator_dumper.stats().total_mmapped_bytes;
+  // Resident bytes.
+  info.hblkhd = allocator_dumper.stats().total_resident_bytes +
+                aligned_allocator_dumper.stats().total_resident_bytes +
+                nonscannable_allocator_dumper.stats().total_resident_bytes;
+  // Allocated bytes.
+  info.uordblks = allocator_dumper.stats().total_active_bytes +
+                  aligned_allocator_dumper.stats().total_active_bytes +
+                  nonscannable_allocator_dumper.stats().total_active_bytes;
+
+  return info;
+}
+#endif  // defined(OS_LINUX) || defined(OS_CHROMEOS)
+
+}  // extern "C"
+
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+#if defined(OS_APPLE)
+
+namespace base {
+namespace allocator {
+
+void InitializeDefaultAllocatorPartitionRoot() {
+  // On OS_APPLE, the initialization of PartitionRoot uses memory allocations
+  // internally, e.g. __builtin_available, and it's not easy to avoid it.
+  // Thus, we initialize the PartitionRoot with using the system default
+  // allocator before we intercept the system default allocator.
+  ignore_result(Allocator());
+}
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // defined(OS_APPLE)

src/base/allocator/allocator_shim_default_dispatch_to_partition_alloc.h

@@ -0,0 +1,73 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_DEFAULT_DISPATCH_TO_PARTITION_ALLOC_H_
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_DEFAULT_DISPATCH_TO_PARTITION_ALLOC_H_
+
+#include "base/allocator/allocator_shim.h"
+#include "base/allocator/partition_allocator/partition_alloc.h"
+#include "base/base_export.h"
+
+namespace base {
+namespace internal {
+
+class BASE_EXPORT PartitionAllocMalloc {
+ public:
+  static ThreadSafePartitionRoot* Allocator();
+  // May return |nullptr|, will never return the same pointer as |Allocator()|.
+  static ThreadSafePartitionRoot* OriginalAllocator();
+  // May return the same pointer as |Allocator()|.
+  static ThreadSafePartitionRoot* AlignedAllocator();
+};
+
+BASE_EXPORT void* PartitionMalloc(const base::allocator::AllocatorDispatch*,
+                                  size_t size,
+                                  void* context);
+
+BASE_EXPORT void* PartitionMallocUnchecked(
+    const base::allocator::AllocatorDispatch*,
+    size_t size,
+    void* context);
+
+BASE_EXPORT void* PartitionCalloc(const base::allocator::AllocatorDispatch*,
+                                  size_t n,
+                                  size_t size,
+                                  void* context);
+
+BASE_EXPORT void* PartitionMemalign(const base::allocator::AllocatorDispatch*,
+                                    size_t alignment,
+                                    size_t size,
+                                    void* context);
+
+BASE_EXPORT void* PartitionAlignedAlloc(
+    const base::allocator::AllocatorDispatch* dispatch,
+    size_t size,
+    size_t alignment,
+    void* context);
+
+BASE_EXPORT void* PartitionAlignedRealloc(
+    const base::allocator::AllocatorDispatch* dispatch,
+    void* address,
+    size_t size,
+    size_t alignment,
+    void* context);
+
+BASE_EXPORT void* PartitionRealloc(const base::allocator::AllocatorDispatch*,
+                                   void* address,
+                                   size_t size,
+                                   void* context);
+
+BASE_EXPORT void PartitionFree(const base::allocator::AllocatorDispatch*,
+                               void* address,
+                               void* context);
+
+BASE_EXPORT size_t
+PartitionGetSizeEstimate(const base::allocator::AllocatorDispatch*,
+                         void* address,
+                         void* context);
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_SHIM_DEFAULT_DISPATCH_TO_PARTITION_ALLOC_H_

src/base/allocator/allocator_shim_default_dispatch_to_tcmalloc.cc

@@ -0,0 +1,89 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_shim.h"
+#include "base/allocator/allocator_shim_internals.h"
+
+#include "third_party/tcmalloc/chromium/src/config.h"
+#include "third_party/tcmalloc/chromium/src/gperftools/tcmalloc.h"
+
+namespace {
+
+using base::allocator::AllocatorDispatch;
+
+void* TCMalloc(const AllocatorDispatch*, size_t size, void* context) {
+  return tc_malloc(size);
+}
+
+void* TCMallocUnchecked(const AllocatorDispatch*, size_t size, void* context) {
+  return tc_malloc_skip_new_handler(size);
+}
+
+void* TCCalloc(const AllocatorDispatch*, size_t n, size_t size, void* context) {
+  return tc_calloc(n, size);
+}
+
+void* TCMemalign(const AllocatorDispatch*,
+                 size_t alignment,
+                 size_t size,
+                 void* context) {
+  return tc_memalign(alignment, size);
+}
+
+void* TCRealloc(const AllocatorDispatch*,
+                void* address,
+                size_t size,
+                void* context) {
+  return tc_realloc(address, size);
+}
+
+void TCFree(const AllocatorDispatch*, void* address, void* context) {
+  tc_free(address);
+}
+
+size_t TCGetSizeEstimate(const AllocatorDispatch*,
+                         void* address,
+                         void* context) {
+  return tc_malloc_size(address);
+}
+
+}  // namespace
+
+const AllocatorDispatch AllocatorDispatch::default_dispatch = {
+    &TCMalloc,          /* alloc_function */
+    &TCMallocUnchecked, /* alloc_unchecked_function */
+    &TCCalloc,          /* alloc_zero_initialized_function */
+    &TCMemalign,        /* alloc_aligned_function */
+    &TCRealloc,         /* realloc_function */
+    &TCFree,            /* free_function */
+    &TCGetSizeEstimate, /* get_size_estimate_function */
+    nullptr,            /* batch_malloc_function */
+    nullptr,            /* batch_free_function */
+    nullptr,            /* free_definite_size_function */
+    nullptr,            /* aligned_malloc_function */
+    nullptr,            /* aligned_realloc_function */
+    nullptr,            /* aligned_free_function */
+    nullptr,            /* next */
+};
+
+// In the case of tcmalloc we have also to route the diagnostic symbols,
+// which are not part of the unified shim layer, to tcmalloc for consistency.
+
+extern "C" {
+
+SHIM_ALWAYS_EXPORT void malloc_stats(void) __THROW {
+  return tc_malloc_stats();
+}
+
+SHIM_ALWAYS_EXPORT int mallopt(int cmd, int value) __THROW {
+  return tc_mallopt(cmd, value);
+}
+
+#ifdef HAVE_STRUCT_MALLINFO
+SHIM_ALWAYS_EXPORT struct mallinfo mallinfo(void) __THROW {
+  return tc_mallinfo();
+}
+#endif
+
+}  // extern "C"

src/base/allocator/allocator_shim_default_dispatch_to_winheap.cc

@@ -0,0 +1,106 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/allocator_shim.h"
+
+#include <ostream>
+
+#include "base/allocator/winheap_stubs_win.h"
+#include "base/check.h"
+
+namespace {
+
+using base::allocator::AllocatorDispatch;
+
+void* DefaultWinHeapMallocImpl(const AllocatorDispatch*,
+                               size_t size,
+                               void* context) {
+  return base::allocator::WinHeapMalloc(size);
+}
+
+void* DefaultWinHeapCallocImpl(const AllocatorDispatch* self,
+                               size_t n,
+                               size_t elem_size,
+                               void* context) {
+  // Overflow check.
+  const size_t size = n * elem_size;
+  if (elem_size != 0 && size / elem_size != n)
+    return nullptr;
+
+  void* result = DefaultWinHeapMallocImpl(self, size, context);
+  if (result) {
+    memset(result, 0, size);
+  }
+  return result;
+}
+
+void* DefaultWinHeapMemalignImpl(const AllocatorDispatch* self,
+                                 size_t alignment,
+                                 size_t size,
+                                 void* context) {
+  CHECK(false) << "The windows heap does not support memalign.";
+  return nullptr;
+}
+
+void* DefaultWinHeapReallocImpl(const AllocatorDispatch* self,
+                                void* address,
+                                size_t size,
+                                void* context) {
+  return base::allocator::WinHeapRealloc(address, size);
+}
+
+void DefaultWinHeapFreeImpl(const AllocatorDispatch*,
+                            void* address,
+                            void* context) {
+  base::allocator::WinHeapFree(address);
+}
+
+size_t DefaultWinHeapGetSizeEstimateImpl(const AllocatorDispatch*,
+                                         void* address,
+                                         void* context) {
+  return base::allocator::WinHeapGetSizeEstimate(address);
+}
+
+void* DefaultWinHeapAlignedMallocImpl(const AllocatorDispatch*,
+                                      size_t size,
+                                      size_t alignment,
+                                      void* context) {
+  return base::allocator::WinHeapAlignedMalloc(size, alignment);
+}
+
+void* DefaultWinHeapAlignedReallocImpl(const AllocatorDispatch*,
+                                       void* ptr,
+                                       size_t size,
+                                       size_t alignment,
+                                       void* context) {
+  return base::allocator::WinHeapAlignedRealloc(ptr, size, alignment);
+}
+
+void DefaultWinHeapAlignedFreeImpl(const AllocatorDispatch*,
+                                   void* ptr,
+                                   void* context) {
+  base::allocator::WinHeapAlignedFree(ptr);
+}
+
+}  // namespace
+
+// Guarantee that default_dispatch is compile-time initialized to avoid using
+// it before initialization (allocations before main in release builds with
+// optimizations disabled).
+constexpr AllocatorDispatch AllocatorDispatch::default_dispatch = {
+    &DefaultWinHeapMallocImpl,
+    &DefaultWinHeapMallocImpl, /* alloc_unchecked_function */
+    &DefaultWinHeapCallocImpl,
+    &DefaultWinHeapMemalignImpl,
+    &DefaultWinHeapReallocImpl,
+    &DefaultWinHeapFreeImpl,
+    &DefaultWinHeapGetSizeEstimateImpl,
+    nullptr, /* batch_malloc_function */
+    nullptr, /* batch_free_function */
+    nullptr, /* free_definite_size_function */
+    &DefaultWinHeapAlignedMallocImpl,
+    &DefaultWinHeapAlignedReallocImpl,
+    &DefaultWinHeapAlignedFreeImpl,
+    nullptr, /* next */
+};

src/base/allocator/allocator_shim_internals.h

@@ -0,0 +1,51 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_INTERNALS_H_
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_INTERNALS_H_
+
+#include "build/build_config.h"
+
+#if defined(__GNUC__)
+
+#include <sys/cdefs.h>  // for __THROW
+
+#ifndef __THROW  // Not a glibc system
+#ifdef _NOEXCEPT  // LLVM libc++ uses noexcept instead
+#define __THROW _NOEXCEPT
+#else
+#define __THROW
+#endif  // !_NOEXCEPT
+#endif
+
+// Shim layer symbols need to be ALWAYS exported, regardless of component build.
+//
+// If an exported symbol is linked into a DSO, it may be preempted by a
+// definition in the main executable. If this happens to an allocator symbol, it
+// will mean that the DSO will use the main executable's allocator. This is
+// normally relatively harmless -- regular allocations should all use the same
+// allocator, but if the DSO tries to hook the allocator it will not see any
+// allocations.
+//
+// However, if LLVM LTO is enabled, the compiler may inline the shim layer
+// symbols into callers. The end result is that allocator calls in DSOs may use
+// either the main executable's allocator or the DSO's allocator, depending on
+// whether the call was inlined. This is arguably a bug in LLVM caused by its
+// somewhat irregular handling of symbol interposition (see llvm.org/PR23501).
+// To work around the bug we use noinline to prevent the symbols from being
+// inlined.
+//
+// In the long run we probably want to avoid linking the allocator bits into
+// DSOs altogether. This will save a little space and stop giving DSOs the false
+// impression that they can hook the allocator.
+#define SHIM_ALWAYS_EXPORT __attribute__((visibility("default"), noinline))
+
+#elif defined(OS_WIN)  // __GNUC__
+
+#define __THROW
+#define SHIM_ALWAYS_EXPORT __declspec(noinline)
+
+#endif  // __GNUC__
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_SHIM_INTERNALS_H_

src/base/allocator/allocator_shim_override_cpp_symbols.h

@@ -0,0 +1,152 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_CPP_SYMBOLS_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_CPP_SYMBOLS_H_
+
+// Preempt the default new/delete C++ symbols so they call the shim entry
+// points. This file is strongly inspired by tcmalloc's
+// libc_override_redefine.h.
+
+#include <new>
+
+#include "base/allocator/allocator_shim_internals.h"
+#include "build/build_config.h"
+
+// std::align_val_t isn't available until C++17, but we want to override aligned
+// new/delete anyway to prevent a possible situation where a library gets loaded
+// in that uses the aligned operators.  We want to avoid a situation where
+// separate heaps are used.
+// TODO(thomasanderson): Remove this once building with C++17 or later.
+#if defined(__cpp_aligned_new) && __cpp_aligned_new >= 201606
+#define ALIGN_VAL_T std::align_val_t
+#define ALIGN_LINKAGE
+#define ALIGN_NEW operator new
+#define ALIGN_NEW_NOTHROW operator new
+#define ALIGN_DEL operator delete
+#define ALIGN_DEL_SIZED operator delete
+#define ALIGN_DEL_NOTHROW operator delete
+#define ALIGN_NEW_ARR operator new[]
+#define ALIGN_NEW_ARR_NOTHROW operator new[]
+#define ALIGN_DEL_ARR operator delete[]
+#define ALIGN_DEL_ARR_SIZED operator delete[]
+#define ALIGN_DEL_ARR_NOTHROW operator delete[]
+#else
+#define ALIGN_VAL_T size_t
+#define ALIGN_LINKAGE extern "C"
+#if defined(OS_APPLE) || defined(OS_WIN)
+#error "Mangling is different on these platforms."
+#else
+#define ALIGN_NEW _ZnwmSt11align_val_t
+#define ALIGN_NEW_NOTHROW _ZnwmSt11align_val_tRKSt9nothrow_t
+#define ALIGN_DEL _ZdlPvSt11align_val_t
+#define ALIGN_DEL_SIZED _ZdlPvmSt11align_val_t
+#define ALIGN_DEL_NOTHROW _ZdlPvSt11align_val_tRKSt9nothrow_t
+#define ALIGN_NEW_ARR _ZnamSt11align_val_t
+#define ALIGN_NEW_ARR_NOTHROW _ZnamSt11align_val_tRKSt9nothrow_t
+#define ALIGN_DEL_ARR _ZdaPvSt11align_val_t
+#define ALIGN_DEL_ARR_SIZED _ZdaPvmSt11align_val_t
+#define ALIGN_DEL_ARR_NOTHROW _ZdaPvSt11align_val_tRKSt9nothrow_t
+#endif
+#endif
+
+SHIM_ALWAYS_EXPORT void* operator new(size_t size) {
+  return ShimCppNew(size);
+}
+
+SHIM_ALWAYS_EXPORT void operator delete(void* p) __THROW {
+  ShimCppDelete(p);
+}
+
+SHIM_ALWAYS_EXPORT void* operator new[](size_t size) {
+  return ShimCppNew(size);
+}
+
+SHIM_ALWAYS_EXPORT void operator delete[](void* p) __THROW {
+  ShimCppDelete(p);
+}
+
+SHIM_ALWAYS_EXPORT void* operator new(size_t size,
+                                      const std::nothrow_t&) __THROW {
+  return ShimCppNewNoThrow(size);
+}
+
+SHIM_ALWAYS_EXPORT void* operator new[](size_t size,
+                                        const std::nothrow_t&) __THROW {
+  return ShimCppNewNoThrow(size);
+}
+
+SHIM_ALWAYS_EXPORT void operator delete(void* p, const std::nothrow_t&) __THROW {
+  ShimCppDelete(p);
+}
+
+SHIM_ALWAYS_EXPORT void operator delete[](void* p,
+                                          const std::nothrow_t&) __THROW {
+  ShimCppDelete(p);
+}
+
+SHIM_ALWAYS_EXPORT void operator delete(void* p, size_t) __THROW {
+  ShimCppDelete(p);
+}
+
+SHIM_ALWAYS_EXPORT void operator delete[](void* p, size_t) __THROW {
+  ShimCppDelete(p);
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void* ALIGN_NEW(std::size_t size,
+                                                 ALIGN_VAL_T alignment) {
+  return ShimCppAlignedNew(size, static_cast<size_t>(alignment));
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void* ALIGN_NEW_NOTHROW(
+    std::size_t size,
+    ALIGN_VAL_T alignment,
+    const std::nothrow_t&) __THROW {
+  return ShimCppAlignedNew(size, static_cast<size_t>(alignment));
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void ALIGN_DEL(void* p, ALIGN_VAL_T) __THROW {
+  ShimCppDelete(p);
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void ALIGN_DEL_SIZED(void* p,
+                                                      std::size_t size,
+                                                      ALIGN_VAL_T) __THROW {
+  ShimCppDelete(p);
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void
+ALIGN_DEL_NOTHROW(void* p, ALIGN_VAL_T, const std::nothrow_t&) __THROW {
+  ShimCppDelete(p);
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void* ALIGN_NEW_ARR(std::size_t size,
+                                                     ALIGN_VAL_T alignment) {
+  return ShimCppAlignedNew(size, static_cast<size_t>(alignment));
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void* ALIGN_NEW_ARR_NOTHROW(
+    std::size_t size,
+    ALIGN_VAL_T alignment,
+    const std::nothrow_t&) __THROW {
+  return ShimCppAlignedNew(size, static_cast<size_t>(alignment));
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void ALIGN_DEL_ARR(void* p,
+                                                    ALIGN_VAL_T) __THROW {
+  ShimCppDelete(p);
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void ALIGN_DEL_ARR_SIZED(void* p,
+                                                          std::size_t size,
+                                                          ALIGN_VAL_T) __THROW {
+  ShimCppDelete(p);
+}
+
+ALIGN_LINKAGE SHIM_ALWAYS_EXPORT void
+ALIGN_DEL_ARR_NOTHROW(void* p, ALIGN_VAL_T, const std::nothrow_t&) __THROW {
+  ShimCppDelete(p);
+}

src/base/allocator/allocator_shim_override_glibc_weak_symbols.h

@@ -0,0 +1,119 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_GLIBC_WEAK_SYMBOLS_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_GLIBC_WEAK_SYMBOLS_H_
+
+// Alias the internal Glibc symbols to the shim entry points.
+// This file is strongly inspired by tcmalloc's libc_override_glibc.h.
+// Effectively this file does two things:
+//  1) Re-define the  __malloc_hook & co symbols. Those symbols are defined as
+//     weak in glibc and are meant to be defined strongly by client processes
+//     to hook calls initiated from within glibc.
+//  2) Re-define Glibc-specific symbols (__libc_malloc). The historical reason
+//     is that in the past (in RedHat 9) we had instances of libraries that were
+//     allocating via malloc() and freeing using __libc_free().
+//     See tcmalloc's libc_override_glibc.h for more context.
+
+#include <features.h>  // for __GLIBC__
+#include <malloc.h>
+#include <unistd.h>
+
+#include <new>
+
+#include "base/allocator/allocator_shim_internals.h"
+
+// __MALLOC_HOOK_VOLATILE not defined in all Glibc headers.
+#if !defined(__MALLOC_HOOK_VOLATILE)
+#define MALLOC_HOOK_MAYBE_VOLATILE /**/
+#else
+#define MALLOC_HOOK_MAYBE_VOLATILE __MALLOC_HOOK_VOLATILE
+#endif
+
+extern "C" {
+
+// 1) Re-define malloc_hook weak symbols.
+namespace {
+
+void* GlibcMallocHook(size_t size, const void* caller) {
+  return ShimMalloc(size, nullptr);
+}
+
+void* GlibcReallocHook(void* ptr, size_t size, const void* caller) {
+  return ShimRealloc(ptr, size, nullptr);
+}
+
+void GlibcFreeHook(void* ptr, const void* caller) {
+  return ShimFree(ptr, nullptr);
+}
+
+void* GlibcMemalignHook(size_t align, size_t size, const void* caller) {
+  return ShimMemalign(align, size, nullptr);
+}
+
+}  // namespace
+
+__attribute__((visibility("default"))) void* (
+    *MALLOC_HOOK_MAYBE_VOLATILE __malloc_hook)(size_t,
+                                               const void*) = &GlibcMallocHook;
+
+__attribute__((visibility("default"))) void* (
+    *MALLOC_HOOK_MAYBE_VOLATILE __realloc_hook)(void*, size_t, const void*) =
+    &GlibcReallocHook;
+
+__attribute__((visibility("default"))) void (
+    *MALLOC_HOOK_MAYBE_VOLATILE __free_hook)(void*,
+                                             const void*) = &GlibcFreeHook;
+
+__attribute__((visibility("default"))) void* (
+    *MALLOC_HOOK_MAYBE_VOLATILE __memalign_hook)(size_t, size_t, const void*) =
+    &GlibcMemalignHook;
+
+// 2) Redefine libc symbols themselves.
+
+SHIM_ALWAYS_EXPORT void* __libc_malloc(size_t size) {
+  return ShimMalloc(size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void __libc_free(void* ptr) {
+  ShimFree(ptr, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __libc_realloc(void* ptr, size_t size) {
+  return ShimRealloc(ptr, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __libc_calloc(size_t n, size_t size) {
+  return ShimCalloc(n, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void __libc_cfree(void* ptr) {
+  return ShimFree(ptr, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __libc_memalign(size_t align, size_t s) {
+  return ShimMemalign(align, s, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __libc_valloc(size_t size) {
+  return ShimValloc(size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __libc_pvalloc(size_t size) {
+  return ShimPvalloc(size);
+}
+
+SHIM_ALWAYS_EXPORT int __posix_memalign(void** r, size_t a, size_t s) {
+  return ShimPosixMemalign(r, a, s);
+}
+
+}  // extern "C"
+
+// Safety check.
+#if !defined(__GLIBC__)
+#error The target platform does not seem to use Glibc. Disable the allocator \
+shim by setting use_allocator_shim=false in GN args.
+#endif

src/base/allocator/allocator_shim_override_libc_symbols.h

@@ -0,0 +1,77 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Its purpose is to preempt the Libc symbols for malloc/new so they call the
+// shim layer entry points.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_LIBC_SYMBOLS_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_LIBC_SYMBOLS_H_
+
+#if defined(OS_APPLE)
+#include <malloc/malloc.h>
+#else
+#include <malloc.h>
+#endif
+
+#include "base/allocator/allocator_shim_internals.h"
+
+extern "C" {
+
+SHIM_ALWAYS_EXPORT void* malloc(size_t size) __THROW {
+  return ShimMalloc(size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void free(void* ptr) __THROW {
+  ShimFree(ptr, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* realloc(void* ptr, size_t size) __THROW {
+  return ShimRealloc(ptr, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* calloc(size_t n, size_t size) __THROW {
+  return ShimCalloc(n, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void cfree(void* ptr) __THROW {
+  ShimFree(ptr, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* memalign(size_t align, size_t s) __THROW {
+  return ShimMemalign(align, s, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* aligned_alloc(size_t align, size_t s) __THROW {
+  return ShimMemalign(align, s, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* valloc(size_t size) __THROW {
+  return ShimValloc(size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* pvalloc(size_t size) __THROW {
+  return ShimPvalloc(size);
+}
+
+SHIM_ALWAYS_EXPORT int posix_memalign(void** r, size_t a, size_t s) __THROW {
+  return ShimPosixMemalign(r, a, s);
+}
+
+SHIM_ALWAYS_EXPORT size_t malloc_size(const void* address) __THROW {
+  return ShimGetSizeEstimate(address, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT size_t malloc_usable_size(void* address) __THROW {
+  return ShimGetSizeEstimate(address, nullptr);
+}
+
+// The default dispatch translation unit has to define also the following
+// symbols (unless they are ultimately routed to the system symbols):
+//   void malloc_stats(void);
+//   int mallopt(int, int);
+//   struct mallinfo mallinfo(void);
+
+}  // extern "C"

src/base/allocator/allocator_shim_override_linker_wrapped_symbols.h

@@ -0,0 +1,147 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_LINKER_WRAPPED_SYMBOLS_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_LINKER_WRAPPED_SYMBOLS_H_
+
+// This header overrides the __wrap_X symbols when using the link-time
+// -Wl,-wrap,malloc shim-layer approach (see README.md).
+// All references to malloc, free, etc. within the linker unit that gets the
+// -wrap linker flags (e.g., libchrome.so) will be rewritten to the
+// linker as references to __wrap_malloc, __wrap_free, which are defined here.
+
+#include <algorithm>
+#include <cstring>
+
+#include "base/allocator/allocator_shim_internals.h"
+
+extern "C" {
+
+SHIM_ALWAYS_EXPORT void* __wrap_calloc(size_t n, size_t size) {
+  return ShimCalloc(n, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void __wrap_free(void* ptr) {
+  ShimFree(ptr, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __wrap_malloc(size_t size) {
+  return ShimMalloc(size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __wrap_memalign(size_t align, size_t size) {
+  return ShimMemalign(align, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT int __wrap_posix_memalign(void** res,
+                                             size_t align,
+                                             size_t size) {
+  return ShimPosixMemalign(res, align, size);
+}
+
+SHIM_ALWAYS_EXPORT void* __wrap_pvalloc(size_t size) {
+  return ShimPvalloc(size);
+}
+
+SHIM_ALWAYS_EXPORT void* __wrap_realloc(void* address, size_t size) {
+  return ShimRealloc(address, size, nullptr);
+}
+
+SHIM_ALWAYS_EXPORT void* __wrap_valloc(size_t size) {
+  return ShimValloc(size, nullptr);
+}
+
+const size_t kPathMaxSize = 8192;
+static_assert(kPathMaxSize >= PATH_MAX, "");
+
+extern char* __wrap_strdup(const char* str);
+
+// Override <stdlib.h>
+
+extern char* __real_realpath(const char* path, char* resolved_path);
+
+SHIM_ALWAYS_EXPORT char* __wrap_realpath(const char* path,
+                                         char* resolved_path) {
+  if (resolved_path)
+    return __real_realpath(path, resolved_path);
+
+  char buffer[kPathMaxSize];
+  if (!__real_realpath(path, buffer))
+    return nullptr;
+  return __wrap_strdup(buffer);
+}
+
+// Override <string.h> functions
+
+SHIM_ALWAYS_EXPORT char* __wrap_strdup(const char* str) {
+  std::size_t length = std::strlen(str) + 1;
+  void* buffer = ShimMalloc(length, nullptr);
+  if (!buffer)
+    return nullptr;
+  return reinterpret_cast<char*>(std::memcpy(buffer, str, length));
+}
+
+SHIM_ALWAYS_EXPORT char* __wrap_strndup(const char* str, size_t n) {
+  std::size_t length = std::min(std::strlen(str), n);
+  char* buffer = reinterpret_cast<char*>(ShimMalloc(length + 1, nullptr));
+  if (!buffer)
+    return nullptr;
+  std::memcpy(buffer, str, length);
+  buffer[length] = '\0';
+  return buffer;
+}
+
+// Override <unistd.h>
+
+extern char* __real_getcwd(char* buffer, size_t size);
+
+SHIM_ALWAYS_EXPORT char* __wrap_getcwd(char* buffer, size_t size) {
+  if (buffer)
+    return __real_getcwd(buffer, size);
+
+  if (!size)
+    size = kPathMaxSize;
+  char local_buffer[size];
+  if (!__real_getcwd(local_buffer, size))
+    return nullptr;
+  return __wrap_strdup(local_buffer);
+}
+
+// Override stdio.h
+
+// This is non-standard (_GNU_SOURCE only), but implemented by Bionic on
+// Android, and used by libc++.
+SHIM_ALWAYS_EXPORT int __wrap_vasprintf(char** strp,
+                                        const char* fmt,
+                                        va_list va_args) {
+  constexpr int kInitialSize = 128;
+  *strp = static_cast<char*>(
+      malloc(kInitialSize));  // Our malloc() doesn't return nullptr.
+
+  int actual_size = vsnprintf(*strp, kInitialSize, fmt, va_args);
+  *strp = static_cast<char*>(realloc(*strp, actual_size + 1));
+
+  // Now we know the size. This is not very efficient, but we cannot really do
+  // better without accessing internal libc functions, or reimplementing
+  // *printf().
+  //
+  // This is very lightly used in Chromium in practice, see crbug.com/116558 for
+  // details.
+  if (actual_size >= kInitialSize)
+    return vsnprintf(*strp, actual_size + 1, fmt, va_args);
+
+  return actual_size;
+}
+
+SHIM_ALWAYS_EXPORT int __wrap_asprintf(char** strp, const char* fmt, ...) {
+  va_list va_args;
+  va_start(va_args, fmt);
+  int retval = vasprintf(strp, fmt, va_args);
+  va_end(va_args);
+  return retval;
+}
+
+}  // extern "C"

src/base/allocator/allocator_shim_override_mac_default_zone.h

@@ -0,0 +1,242 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_MAC_DEFAULT_ZONE_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_MAC_DEFAULT_ZONE_H_
+
+#if !BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+#error This header must be included iff PartitionAlloc-Everywhere is enabled.
+#endif
+
+#include "base/notreached.h"
+
+namespace base {
+namespace allocator {
+
+void InitializeDefaultAllocatorPartitionRoot();
+
+namespace {
+
+// malloc_introspection_t's callback functions for our own zone
+
+kern_return_t MallocIntrospectionEnumerator(task_t task,
+                                            void*,
+                                            unsigned type_mask,
+                                            vm_address_t zone_address,
+                                            memory_reader_t reader,
+                                            vm_range_recorder_t recorder) {
+  NOTREACHED();
+  return KERN_FAILURE;
+}
+
+size_t MallocIntrospectionGoodSize(malloc_zone_t* zone, size_t size) {
+  return size;
+}
+
+boolean_t MallocIntrospectionCheck(malloc_zone_t* zone) {
+  NOTREACHED();
+  return true;
+}
+
+void MallocIntrospectionPrint(malloc_zone_t* zone, boolean_t verbose) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionLog(malloc_zone_t* zone, void* address) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionForceLock(malloc_zone_t* zone) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionForceUnlock(malloc_zone_t* zone) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionStatistics(malloc_zone_t* zone,
+                                   malloc_statistics_t* stats) {
+  NOTREACHED();
+}
+
+boolean_t MallocIntrospectionZoneLocked(malloc_zone_t* zone) {
+  NOTREACHED();
+  return false;
+}
+
+boolean_t MallocIntrospectionEnableDischargeChecking(malloc_zone_t* zone) {
+  NOTREACHED();
+  return false;
+}
+
+void MallocIntrospectionDisableDischargeChecking(malloc_zone_t* zone) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionDischarge(malloc_zone_t* zone, void* memory) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionEnumerateDischargedPointers(
+    malloc_zone_t* zone,
+    void (^report_discharged)(void* memory, void* info)) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionReinitLock(malloc_zone_t* zone) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionPrintTask(task_t task,
+                                  unsigned level,
+                                  vm_address_t zone_address,
+                                  memory_reader_t reader,
+                                  print_task_printer_t printer) {
+  NOTREACHED();
+}
+
+void MallocIntrospectionTaskStatistics(task_t task,
+                                       vm_address_t zone_address,
+                                       memory_reader_t reader,
+                                       malloc_statistics_t* stats) {
+  NOTREACHED();
+}
+
+// malloc_zone_t's callback functions for our own zone
+
+size_t MallocZoneSize(malloc_zone_t* zone, const void* ptr) {
+  return ShimGetSizeEstimate(ptr, nullptr);
+}
+
+void* MallocZoneMalloc(malloc_zone_t* zone, size_t size) {
+  return ShimMalloc(size, nullptr);
+}
+
+void* MallocZoneCalloc(malloc_zone_t* zone, size_t n, size_t size) {
+  return ShimCalloc(n, size, nullptr);
+}
+
+void* MallocZoneValloc(malloc_zone_t* zone, size_t size) {
+  return ShimValloc(size, nullptr);
+}
+
+void MallocZoneFree(malloc_zone_t* zone, void* ptr) {
+  return ShimFree(ptr, nullptr);
+}
+
+void* MallocZoneRealloc(malloc_zone_t* zone, void* ptr, size_t size) {
+  return ShimRealloc(ptr, size, nullptr);
+}
+
+void MallocZoneDestroy(malloc_zone_t* zone) {
+  NOTREACHED();
+  IMMEDIATE_CRASH();
+}
+
+void* MallocZoneMemalign(malloc_zone_t* zone, size_t alignment, size_t size) {
+  return ShimMemalign(alignment, size, nullptr);
+}
+
+void MallocZoneFreeDefiniteSize(malloc_zone_t* zone, void* ptr, size_t size) {
+  return ShimFree(ptr, nullptr);
+}
+
+malloc_introspection_t g_mac_malloc_introspection{};
+malloc_zone_t g_mac_malloc_zone{};
+
+// Replaces the default malloc zone with our own malloc zone backed by
+// PartitionAlloc.  Since we'd like to make as much code as possible to use our
+// own memory allocator (and reduce bugs caused by mixed use of the system
+// allocator and our own allocator), run the following function
+// `InitializeDefaultAllocatorPartitionRoot` with the highest priority.
+//
+// Note that, despite of the highest priority of the initialization order,
+// [NSThread init] runs before InitializeDefaultMallocZoneWithPartitionAlloc
+// unfortunately and allocates memory with the system allocator.  Plus, the
+// allocated memory will be deallocated with the default zone's `free` at that
+// moment without using a zone dispatcher.  Hence, our own `free` function
+// receives an address allocated by the system allocator.
+__attribute__((constructor(0))) void
+InitializeDefaultMallocZoneWithPartitionAlloc() {
+  // Instantiate the existing regular and purgeable zones in order to make the
+  // existing purgeable zone use the existing regular zone since PartitionAlloc
+  // doesn't support a purgeable zone.
+  ignore_result(malloc_default_zone());
+  ignore_result(malloc_default_purgeable_zone());
+
+  // Initialize the default allocator's PartitionRoot with the existing zone.
+  InitializeDefaultAllocatorPartitionRoot();
+
+  // Create our own malloc zone.
+  g_mac_malloc_introspection.enumerator = MallocIntrospectionEnumerator;
+  g_mac_malloc_introspection.good_size = MallocIntrospectionGoodSize;
+  g_mac_malloc_introspection.check = MallocIntrospectionCheck;
+  g_mac_malloc_introspection.print = MallocIntrospectionPrint;
+  g_mac_malloc_introspection.log = MallocIntrospectionLog;
+  g_mac_malloc_introspection.force_lock = MallocIntrospectionForceLock;
+  g_mac_malloc_introspection.force_unlock = MallocIntrospectionForceUnlock;
+  g_mac_malloc_introspection.statistics = MallocIntrospectionStatistics;
+  g_mac_malloc_introspection.zone_locked = MallocIntrospectionZoneLocked;
+  g_mac_malloc_introspection.enable_discharge_checking =
+      MallocIntrospectionEnableDischargeChecking;
+  g_mac_malloc_introspection.disable_discharge_checking =
+      MallocIntrospectionDisableDischargeChecking;
+  g_mac_malloc_introspection.discharge = MallocIntrospectionDischarge;
+  g_mac_malloc_introspection.enumerate_discharged_pointers =
+      MallocIntrospectionEnumerateDischargedPointers;
+  g_mac_malloc_introspection.reinit_lock = MallocIntrospectionReinitLock;
+  g_mac_malloc_introspection.print_task = MallocIntrospectionPrintTask;
+  g_mac_malloc_introspection.task_statistics =
+      MallocIntrospectionTaskStatistics;
+  // `version` member indicates which APIs are supported in this zone.
+  //   version >= 5: memalign is supported
+  //   version >= 6: free_definite_size is supported
+  //   version >= 8: pressure_relief is supported
+  //   version >= 10: claimed_address is supported
+  g_mac_malloc_zone.version = 6;
+  g_mac_malloc_zone.zone_name = "PartitionAlloc";
+  g_mac_malloc_zone.introspect = &g_mac_malloc_introspection;
+  g_mac_malloc_zone.size = MallocZoneSize;
+  g_mac_malloc_zone.malloc = MallocZoneMalloc;
+  g_mac_malloc_zone.calloc = MallocZoneCalloc;
+  g_mac_malloc_zone.valloc = MallocZoneValloc;
+  g_mac_malloc_zone.free = MallocZoneFree;
+  g_mac_malloc_zone.realloc = MallocZoneRealloc;
+  g_mac_malloc_zone.destroy = MallocZoneDestroy;
+  g_mac_malloc_zone.batch_malloc = nullptr;
+  g_mac_malloc_zone.batch_free = nullptr;
+  g_mac_malloc_zone.memalign = MallocZoneMemalign;
+  g_mac_malloc_zone.free_definite_size = MallocZoneFreeDefiniteSize;
+  g_mac_malloc_zone.pressure_relief = nullptr;
+  g_mac_malloc_zone.claimed_address = nullptr;
+
+  // Install our own malloc zone.
+  malloc_zone_register(&g_mac_malloc_zone);
+
+  // Make our own zone the default zone.
+  for (unsigned int retry_count = 0;; ++retry_count) {
+    vm_address_t* zones = nullptr;
+    unsigned int zone_count = 0;
+    kern_return_t result =
+        malloc_get_all_zones(mach_task_self(), nullptr, &zones, &zone_count);
+    MACH_CHECK(result == KERN_SUCCESS, result) << "malloc_get_all_zones";
+
+    malloc_zone_t* top_zone = reinterpret_cast<malloc_zone_t*>(zones[0]);
+    if (top_zone == &g_mac_malloc_zone) {
+      break;  // Our own malloc zone is now the default zone.
+    }
+    CHECK_LE(retry_count, zone_count);
+
+    // Reorder malloc zones so that our own zone becomes the default one.
+    malloc_zone_unregister(top_zone);
+    malloc_zone_register(top_zone);
+  }
+}
+
+}  // namespace
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/allocator_shim_override_mac_symbols.h

@@ -0,0 +1,60 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifdef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_MAC_SYMBOLS_H_
+#error This header is meant to be included only once by allocator_shim.cc
+#endif
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_MAC_SYMBOLS_H_
+
+#include "base/allocator/malloc_zone_functions_mac.h"
+#include "third_party/apple_apsl/malloc.h"
+
+namespace base {
+namespace allocator {
+
+MallocZoneFunctions MallocZoneFunctionsToReplaceDefault() {
+  MallocZoneFunctions new_functions;
+  memset(&new_functions, 0, sizeof(MallocZoneFunctions));
+  new_functions.size = [](malloc_zone_t* zone, const void* ptr) -> size_t {
+    return ShimGetSizeEstimate(ptr, zone);
+  };
+  new_functions.malloc = [](malloc_zone_t* zone, size_t size) -> void* {
+    return ShimMalloc(size, zone);
+  };
+  new_functions.calloc = [](malloc_zone_t* zone, size_t n,
+                            size_t size) -> void* {
+    return ShimCalloc(n, size, zone);
+  };
+  new_functions.valloc = [](malloc_zone_t* zone, size_t size) -> void* {
+    return ShimValloc(size, zone);
+  };
+  new_functions.free = [](malloc_zone_t* zone, void* ptr) {
+    ShimFree(ptr, zone);
+  };
+  new_functions.realloc = [](malloc_zone_t* zone, void* ptr,
+                             size_t size) -> void* {
+    return ShimRealloc(ptr, size, zone);
+  };
+  new_functions.batch_malloc = [](struct _malloc_zone_t* zone, size_t size,
+                                  void** results,
+                                  unsigned num_requested) -> unsigned {
+    return ShimBatchMalloc(size, results, num_requested, zone);
+  };
+  new_functions.batch_free = [](struct _malloc_zone_t* zone, void** to_be_freed,
+                                unsigned num_to_be_freed) -> void {
+    ShimBatchFree(to_be_freed, num_to_be_freed, zone);
+  };
+  new_functions.memalign = [](malloc_zone_t* zone, size_t alignment,
+                              size_t size) -> void* {
+    return ShimMemalign(alignment, size, zone);
+  };
+  new_functions.free_definite_size = [](malloc_zone_t* zone, void* ptr,
+                                        size_t size) {
+    ShimFreeDefiniteSize(ptr, size, zone);
+  };
+  return new_functions;
+}
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/allocator_shim_override_ucrt_symbols_win.h

@@ -0,0 +1,178 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This header defines symbols to override the same functions in the Visual C++
+// CRT implementation.
+
+#ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_UCRT_SYMBOLS_WIN_H_
+#define BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_UCRT_SYMBOLS_WIN_H_
+
+#include <malloc.h>
+
+#include <windows.h>
+
+#include "base/allocator/allocator_shim_internals.h"
+
+// Even though most C++ allocation operators can be left alone since the
+// interception works at a lower level, these ones should be
+// overridden. Otherwise they redirect to malloc(), which is configured to crash
+// with an OOM in failure cases, such as allocation requests that are too large.
+SHIM_ALWAYS_EXPORT void* operator new(size_t size,
+                                      const std::nothrow_t&) __THROW {
+  return ShimCppNewNoThrow(size);
+}
+
+SHIM_ALWAYS_EXPORT void* operator new[](size_t size,
+                                        const std::nothrow_t&) __THROW {
+  return ShimCppNewNoThrow(size);
+}
+
+extern "C" {
+
+void* (*malloc_unchecked)(size_t) = &base::allocator::UncheckedAlloc;
+
+namespace {
+
+int win_new_mode = 0;
+
+}  // namespace
+
+// This function behaves similarly to MSVC's _set_new_mode.
+// If flag is 0 (default), calls to malloc will behave normally.
+// If flag is 1, calls to malloc will behave like calls to new,
+// and the std_new_handler will be invoked on failure.
+// Returns the previous mode.
+//
+// Replaces _set_new_mode in ucrt\heap\new_mode.cpp
+int _set_new_mode(int flag) {
+  // The MS CRT calls this function early on in startup, so this serves as a low
+  // overhead proof that the allocator shim is in place for this process.
+  base::allocator::g_is_win_shim_layer_initialized = true;
+  int old_mode = win_new_mode;
+  win_new_mode = flag;
+
+  base::allocator::SetCallNewHandlerOnMallocFailure(win_new_mode != 0);
+
+  return old_mode;
+}
+
+// Replaces _query_new_mode in ucrt\heap\new_mode.cpp
+int _query_new_mode() {
+  return win_new_mode;
+}
+
+// These symbols override the CRT's implementation of the same functions.
+__declspec(restrict) void* malloc(size_t size) {
+  return ShimMalloc(size, nullptr);
+}
+
+void free(void* ptr) {
+  ShimFree(ptr, nullptr);
+}
+
+__declspec(restrict) void* realloc(void* ptr, size_t size) {
+  return ShimRealloc(ptr, size, nullptr);
+}
+
+__declspec(restrict) void* calloc(size_t n, size_t size) {
+  return ShimCalloc(n, size, nullptr);
+}
+
+// _msize() is the Windows equivalent of malloc_size().
+size_t _msize(void* memblock) {
+  return ShimGetSizeEstimate(memblock, nullptr);
+}
+
+__declspec(restrict) void* _aligned_malloc(size_t size, size_t alignment) {
+  return ShimAlignedMalloc(size, alignment, nullptr);
+}
+
+__declspec(restrict) void* _aligned_realloc(void* address,
+                                            size_t size,
+                                            size_t alignment) {
+  return ShimAlignedRealloc(address, size, alignment, nullptr);
+}
+
+void _aligned_free(void* address) {
+  ShimAlignedFree(address, nullptr);
+}
+
+// _recalloc_base is called by CRT internally.
+__declspec(restrict) void* _recalloc_base(void* block,
+                                          size_t count,
+                                          size_t size) {
+  const size_t old_block_size = (block != nullptr) ? _msize(block) : 0;
+  base::CheckedNumeric<size_t> new_block_size_checked = count;
+  new_block_size_checked *= size;
+  const size_t new_block_size = new_block_size_checked.ValueOrDie();
+
+  void* const new_block = realloc(block, new_block_size);
+
+  if (new_block != nullptr && old_block_size < new_block_size) {
+    memset(static_cast<char*>(new_block) + old_block_size, 0,
+           new_block_size - old_block_size);
+  }
+
+  return new_block;
+}
+
+__declspec(restrict) void* _malloc_base(size_t size) {
+  return malloc(size);
+}
+
+__declspec(restrict) void* _calloc_base(size_t n, size_t size) {
+  return calloc(n, size);
+}
+
+void _free_base(void* block) {
+  free(block);
+}
+
+__declspec(restrict) void* _recalloc(void* block, size_t count, size_t size) {
+  return _recalloc_base(block, count, size);
+}
+
+// The following uncommon _aligned_* routines are not used in Chromium and have
+// been shimmed to immediately crash to ensure that implementations are added if
+// uses are introduced.
+__declspec(restrict) void* _aligned_recalloc(void* address,
+                                             size_t num,
+                                             size_t size,
+                                             size_t alignment) {
+  CHECK(false) << "This routine has not been implemented";
+  __builtin_unreachable();
+}
+
+size_t _aligned_msize(void* address, size_t alignment, size_t offset) {
+  CHECK(false) << "This routine has not been implemented";
+  __builtin_unreachable();
+}
+
+__declspec(restrict) void* _aligned_offset_malloc(size_t size,
+                                                  size_t alignment,
+                                                  size_t offset) {
+  CHECK(false) << "This routine has not been implemented";
+  __builtin_unreachable();
+}
+
+__declspec(restrict) void* _aligned_offset_realloc(void* address,
+                                                   size_t size,
+                                                   size_t alignment,
+                                                   size_t offset) {
+  CHECK(false) << "This routine has not been implemented";
+  __builtin_unreachable();
+}
+
+__declspec(restrict) void* _aligned_offset_recalloc(void* address,
+                                                    size_t num,
+                                                    size_t size,
+                                                    size_t alignment,
+                                                    size_t offset) {
+  CHECK(false) << "This routine has not been implemented";
+  __builtin_unreachable();
+}
+
+}  // extern "C"
+
+#endif  // BASE_ALLOCATOR_ALLOCATOR_SHIM_OVERRIDE_UCRT_SYMBOLS_WIN_H_

src/base/allocator/debugallocation_shim.cc

@@ -0,0 +1,23 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Workaround for crosbug:629593.  Using AFDO on the tcmalloc files is
+// causing problems. The tcmalloc files depend on stack layouts and
+// AFDO can mess with them. Better not to use AFDO there.  This is a
+// temporary hack. We will add a mechanism in the build system to
+// avoid using -fauto-profile for tcmalloc files.
+#include "build/chromeos_buildflags.h"
+
+#if !defined(__clang__) && \
+    (BUILDFLAG(IS_CHROMEOS_ASH) || (__GNUC__ > 5 && __GNUC__ < 7))
+// Note that this option only seems to be available in the chromeos GCC 4.9
+// toolchain, and stock GCC 5 upto 7.
+#pragma GCC optimize ("no-auto-profile")
+#endif
+
+#if defined(TCMALLOC_FOR_DEBUGALLOCATION)
+#include "third_party/tcmalloc/chromium/src/debugallocation.cc"
+#else
+#include "third_party/tcmalloc/chromium/src/tcmalloc.cc"
+#endif

src/base/allocator/malloc_zone_functions_mac.cc

@@ -0,0 +1,119 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/malloc_zone_functions_mac.h"
+
+#include <atomic>
+
+#include "base/synchronization/lock.h"
+
+namespace base {
+namespace allocator {
+
+MallocZoneFunctions g_malloc_zones[kMaxZoneCount];
+static_assert(std::is_pod<MallocZoneFunctions>::value,
+              "MallocZoneFunctions must be POD");
+
+void StoreZoneFunctions(const ChromeMallocZone* zone,
+                        MallocZoneFunctions* functions) {
+  memset(functions, 0, sizeof(MallocZoneFunctions));
+  functions->malloc = zone->malloc;
+  functions->calloc = zone->calloc;
+  functions->valloc = zone->valloc;
+  functions->free = zone->free;
+  functions->realloc = zone->realloc;
+  functions->size = zone->size;
+  CHECK(functions->malloc && functions->calloc && functions->valloc &&
+        functions->free && functions->realloc && functions->size);
+
+  // These functions might be nullptr.
+  functions->batch_malloc = zone->batch_malloc;
+  functions->batch_free = zone->batch_free;
+
+  if (zone->version >= 5) {
+    // Not all custom malloc zones have a memalign.
+    functions->memalign = zone->memalign;
+  }
+  if (zone->version >= 6) {
+    // This may be nullptr.
+    functions->free_definite_size = zone->free_definite_size;
+  }
+
+  // Note that zone version 8 introduced a pressure relief callback, and version
+  // 10 introduced a claimed address callback, but neither are allocation or
+  // deallocation callbacks and so aren't important to intercept.
+
+  functions->context = zone;
+}
+
+namespace {
+
+// All modifications to g_malloc_zones are gated behind this lock.
+// Dispatch to a malloc zone does not need to acquire this lock.
+base::Lock& GetLock() {
+  static base::Lock* g_lock = new base::Lock;
+  return *g_lock;
+}
+
+void EnsureMallocZonesInitializedLocked() {
+  GetLock().AssertAcquired();
+}
+
+int g_zone_count = 0;
+
+bool IsMallocZoneAlreadyStoredLocked(ChromeMallocZone* zone) {
+  EnsureMallocZonesInitializedLocked();
+  GetLock().AssertAcquired();
+  for (int i = 0; i < g_zone_count; ++i) {
+    if (g_malloc_zones[i].context == reinterpret_cast<void*>(zone))
+      return true;
+  }
+  return false;
+}
+
+}  // namespace
+
+bool StoreMallocZone(ChromeMallocZone* zone) {
+  base::AutoLock l(GetLock());
+  EnsureMallocZonesInitializedLocked();
+  if (IsMallocZoneAlreadyStoredLocked(zone))
+    return false;
+
+  if (g_zone_count == kMaxZoneCount)
+    return false;
+
+  StoreZoneFunctions(zone, &g_malloc_zones[g_zone_count]);
+  ++g_zone_count;
+
+  // No other thread can possibly see these stores at this point. The code that
+  // reads these values is triggered after this function returns. so we want to
+  // guarantee that they are committed at this stage"
+  std::atomic_thread_fence(std::memory_order_seq_cst);
+  return true;
+}
+
+bool IsMallocZoneAlreadyStored(ChromeMallocZone* zone) {
+  base::AutoLock l(GetLock());
+  return IsMallocZoneAlreadyStoredLocked(zone);
+}
+
+bool DoesMallocZoneNeedReplacing(ChromeMallocZone* zone,
+                                 const MallocZoneFunctions* functions) {
+  return IsMallocZoneAlreadyStored(zone) && zone->malloc != functions->malloc;
+}
+
+int GetMallocZoneCountForTesting() {
+  base::AutoLock l(GetLock());
+  return g_zone_count;
+}
+
+void ClearAllMallocZonesForTesting() {
+  base::AutoLock l(GetLock());
+  EnsureMallocZonesInitializedLocked();
+  memset(g_malloc_zones, 0, kMaxZoneCount * sizeof(MallocZoneFunctions));
+  g_zone_count = 0;
+}
+
+}  // namespace allocator
+}  // namespace base

src/base/allocator/malloc_zone_functions_mac.h

@@ -0,0 +1,103 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_MALLOC_ZONE_FUNCTIONS_MAC_H_
+#define BASE_ALLOCATOR_MALLOC_ZONE_FUNCTIONS_MAC_H_
+
+#include <malloc/malloc.h>
+#include <stddef.h>
+
+#include "base/base_export.h"
+#include "base/immediate_crash.h"
+#include "third_party/apple_apsl/malloc.h"
+
+namespace base {
+namespace allocator {
+
+typedef void* (*malloc_type)(struct _malloc_zone_t* zone, size_t size);
+typedef void* (*calloc_type)(struct _malloc_zone_t* zone,
+                             size_t num_items,
+                             size_t size);
+typedef void* (*valloc_type)(struct _malloc_zone_t* zone, size_t size);
+typedef void (*free_type)(struct _malloc_zone_t* zone, void* ptr);
+typedef void* (*realloc_type)(struct _malloc_zone_t* zone,
+                              void* ptr,
+                              size_t size);
+typedef void* (*memalign_type)(struct _malloc_zone_t* zone,
+                               size_t alignment,
+                               size_t size);
+typedef unsigned (*batch_malloc_type)(struct _malloc_zone_t* zone,
+                                      size_t size,
+                                      void** results,
+                                      unsigned num_requested);
+typedef void (*batch_free_type)(struct _malloc_zone_t* zone,
+                                void** to_be_freed,
+                                unsigned num_to_be_freed);
+typedef void (*free_definite_size_type)(struct _malloc_zone_t* zone,
+                                        void* ptr,
+                                        size_t size);
+typedef size_t (*size_fn_type)(struct _malloc_zone_t* zone, const void* ptr);
+
+struct MallocZoneFunctions {
+  malloc_type malloc;
+  calloc_type calloc;
+  valloc_type valloc;
+  free_type free;
+  realloc_type realloc;
+  memalign_type memalign;
+  batch_malloc_type batch_malloc;
+  batch_free_type batch_free;
+  free_definite_size_type free_definite_size;
+  size_fn_type size;
+  const ChromeMallocZone* context;
+};
+
+BASE_EXPORT void StoreZoneFunctions(const ChromeMallocZone* zone,
+                                    MallocZoneFunctions* functions);
+static constexpr int kMaxZoneCount = 30;
+BASE_EXPORT extern MallocZoneFunctions g_malloc_zones[kMaxZoneCount];
+
+// The array g_malloc_zones stores all information about malloc zones before
+// they are shimmed. This information needs to be accessed during dispatch back
+// into the zone, and additional zones may be added later in the execution fo
+// the program, so the array needs to be both thread-safe and high-performance.
+//
+// We begin by creating an array of MallocZoneFunctions of fixed size. We will
+// never modify the container, which provides thread-safety to iterators.  When
+// we want to add a MallocZoneFunctions to the container, we:
+//   1. Fill in all the fields.
+//   2. Update the total zone count.
+//   3. Insert a memory barrier.
+//   4. Insert our shim.
+//
+// Each MallocZoneFunctions is uniquely identified by |context|, which is a
+// pointer to the original malloc zone. When we wish to dispatch back to the
+// original malloc zones, we iterate through the array, looking for a matching
+// |context|.
+//
+// Most allocations go through the default allocator. We will ensure that the
+// default allocator is stored as the first MallocZoneFunctions.
+//
+// Returns whether the zone was successfully stored.
+BASE_EXPORT bool StoreMallocZone(ChromeMallocZone* zone);
+BASE_EXPORT bool IsMallocZoneAlreadyStored(ChromeMallocZone* zone);
+BASE_EXPORT bool DoesMallocZoneNeedReplacing(
+    ChromeMallocZone* zone,
+    const MallocZoneFunctions* functions);
+
+BASE_EXPORT int GetMallocZoneCountForTesting();
+BASE_EXPORT void ClearAllMallocZonesForTesting();
+
+inline MallocZoneFunctions& GetFunctionsForZone(void* zone) {
+  for (unsigned int i = 0; i < kMaxZoneCount; ++i) {
+    if (g_malloc_zones[i].context == zone)
+      return g_malloc_zones[i];
+  }
+  IMMEDIATE_CRASH();
+}
+
+}  // namespace allocator
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_MALLOC_ZONE_FUNCTIONS_MAC_H_

src/base/allocator/partition_allocator/DIR_METADATA

@@ -0,0 +1,6 @@
+monorail {
+  component: "Blink>MemoryAllocator>Partition"
+}
+
+# Also security-dev@chromium.org
+team_email: "platform-architecture-dev@chromium.org"

src/base/allocator/partition_allocator/OWNERS

@@ -0,0 +1,5 @@
+ajwong@chromium.org
+bartekn@chromium.org
+haraken@chromium.org
+lizeb@chromium.org
+palmer@chromium.org

src/base/allocator/partition_allocator/PartitionAlloc.md

@@ -0,0 +1,247 @@
+# PartitionAlloc Design
+
+This document describes PartitionAlloc at a high level, with some architectural
+details. For implementation details, see the comments in
+`partition_alloc_constants.h`.
+
+## Overview
+
+PartitionAlloc is a memory allocator optimized for space efficiency,
+allocation latency, and security.
+
+### Core terms
+
+A *partition* is a heap that is separated and protected from any other
+partitions, as well as from non-PartitionAlloc memory. The most typical use of
+partitions is to isolate certain object types. However, one can also isolate
+objects of certain sizes, or objects of a certain lifetime (as the caller
+prefers). Callers can create as many partitions as they need. The direct
+memory cost of partitions is minimal, but the implicit cost resulting from
+fragmentation is not to be underestimated.
+
+Each partition holds multiple buckets. A *bucket* is a series of regions in a
+partition that contains similar-sized objects, e.g. one bucket holds sizes
+(240, 256], another (256, 288], and so on. Bucket sizes are
+geometrically-spaced, and go all the way up to `kMaxBucketed=960KiB`
+(so called *normal buckets*). There are 8 buckets between each power of two.
+Note that buckets that aren't a multiple of `base::kAlignment` can't be used.
+
+Larger allocations (>`kMaxBucketed`) are realized by direct memory mapping
+(*direct map*).
+
+### Performance
+
+PartitionAlloc is designed to be extremely fast in its fast paths. The fast
+paths of allocation and deallocation require very few (reasonably predictable)
+branches. The number of operations in the fast paths is minimal, leading to the
+possibility of inlining.
+
+However, even the fast path isn't the fastest, because it requires taking
+a per-partition lock. Although we optimized the lock, there was still room for
+improvement. Therefore we introduced the *thread cache*, which holds a small
+amount of not-too-large memory chunks, ready to be allocated. Because these
+chunks are stored per-thread, they can be allocated without a lock, only
+requiring a faster thread-local storage (TLS) lookup, improving cache locality
+in the process.
+The thread cache has been tailored to satisfy a vast majority of requests by
+allocating from and releasing memory to the main allocator in batches,
+amortizing lock acquisition and further improving locality while not trapping
+excess memory.
+
+### Security
+
+Security is one of the important goals of PartitionAlloc.
+
+PartitionAlloc guarantees that different partitions exist in different regions
+of the process's address space. When the caller has freed all objects contained
+in a page in a partition, PartitionAlloc returns the physical memory to the
+operating system, but continues to reserve the region of address space.
+PartitionAlloc will only reuse an address space region for the same partition.
+
+Similarly, one page can contain only objects from the same bucket.
+When freed, PartitionAlloc returns the physical memory, but continues to reserve
+the region for this very bucket.
+
+The above techniques help avoid type confusion attacks. Note, however, these
+apply only to normal buckets and not to direct map, as it'd waste too much
+address space.
+
+PartitionAlloc also guarantees that:
+
+* Linear overflows/underflows cannot corrupt into, out of, or between
+  partitions. There are guard pages at the beginning and the end of each memory
+  region owned by a partition.
+
+* Linear overflows/underflows cannot corrupt the allocation metadata.
+  PartitionAlloc records metadata in a dedicated, out-of-line region (not
+  adjacent to objects), surrounded by guard pages. (Freelist pointers are an
+  exception.)
+
+* Partial pointer overwrite of freelist pointer should fault.
+
+* Direct map allocations have guard pages at the beginning and the end.
+
+### Alignment
+
+PartitionAlloc guarantees that returned pointers are aligned on
+`base::kAlignment` boundary (typically 16B on 64-bit systems, and 8B on 32-bit).
+
+PartitionAlloc also supports higher levels of alignment, that can be requested
+via `PartitionAlloc::AlignedAllocFlags()` or platform-specific APIs (such as
+`posix_memalign()`). The requested
+alignment has to be a power of two. PartitionAlloc reserves the right to round
+up the requested size to the nearest power of two, greater than or equal to the
+requested alignment. This may be wasteful, but allows taking advantage of
+natural PartitionAlloc alignment guarantees. Allocations with an alignment
+requirement greater than `base::kAlignment` are expected to be very rare.
+
+## PartitionAlloc-Everywhere
+
+Originally, PartitionAlloc was used only in Blink (Chromium’s rendering engine).
+It was invoked explicitly, by calling PartitionAlloc APIs directly.
+
+PartitionAlloc-Everywhere is the name of the project that brought PartitionAlloc
+to the entire-ish codebase (exclusions apply). This was done by intercepting
+`malloc()`, `free()`, `realloc()`, aforementioned `posix_memalign()`, etc. and
+routing them into PartitionAlloc. The shim located in
+`base/allocator/allocator_shim_default_dispatch_to_partition_alloc.h` is
+responsible for intercepting. For more details, see
+[base/allocator/README.md](../../../base/allocator/README.md).
+
+A special, catch-it-all *Malloc* partition has been created for the intercepted
+`malloc()` et al. This is to isolate from already existing Blink partitions.
+The only exception from that is Blink's *FastMalloc* partition, which was also
+catch-it-all in nature, so it's perfectly fine to merge these together, to
+minimize fragmentation.
+
+PartitionAlloc-Everywhere was launched in M89 for Windows 64-bit and Android.
+Windows 32-bit and Linux followed it shortly after, in M90.
+
+## Architecture
+
+### Many Different Flavors of Pages
+
+In PartitionAlloc, by *system page* we mean a memory page as defined by CPU/OS
+(often referred to as "virtual page" out there). It is most commonly 4KiB in
+size, but depending on CPU it can be larger (PartitionAlloc supports up to
+64KiB).
+
+The reason why we use the term "system page" is to disambiguate from
+*partition page*, which is the most common granularity used by PartitionAlloc.
+Each partition page consists of exactly 4 system pages.
+
+A *super page* is a 2MiB region, aligned on a 2MiB boundary.
+Don't confuse it with CPU/OS terms like "large page" or "huge page", which are
+also commonly 2MiB in size. These have to be fully committed/uncommitted in
+memory, whereas super pages can be partially committed, with system page
+granularity.
+
+### Slots and Spans
+
+A *slot* is an indivisible allocation unit. Slot sizes are tied to buckets.
+For example each allocation that falls into the bucket (240; 256] would
+be satisfied with a slot of size 256. This applies only to normal buckets, not
+to direct map.
+
+A *slot span* is just a grouping of slots of the same size next to each other
+in memory. Slot span size is a multiple of a partition page.
+
+A bucket is a collection of slot spans containing slots of the same size,
+organized as linked-lists.
+
+Allocations up to 4 partition pages are referred to as *small buckets*.
+In these cases, slot spans are always between 1 and 4 partition pages in size.
+The size is chosen based on the slot size, such that the rounding waste is
+minimized. For example, if the slot size was 96B and slot span was 1 partition
+page of 16KiB, 64B would be wasted at the end, but nothing is wasted if 3
+partition pages totalling 48KiB are used. Furthermore, PartitionAlloc may avoid
+waste by lowering the number of committed system pages compared to the number of
+reserved pages. For example, for the slot size of 80B we'd use a slot span of 4
+partition pages of 16KiB, i.e. 16 system pages of 4KiB, but commit only up to
+15, thus resulting in perfect packing.
+
+Allocations above 4 partition pages (but ≤`kMaxBucketed`) are referred to as
+*single slot spans*. That's because each slot span is guaranteed to hold exactly
+one slot. Fun fact: there are sizes ≤4 partition pages that result in a slot
+span having exactly 1 slot, but nonetheless they're still classified as small
+buckets. The reason is that single slot spans are often handled by a different
+code path, and that distinction is made purely based on slot size, for
+simplicity and efficiency.
+
+### Layout in Memory
+
+PartitionAlloc handles normal buckets by reserving (not committing) 2MiB super
+pages. Each super page is split into partition pages.
+The first and the last partition page are permanently inaccessible and serve
+as guard pages, with the exception of one system page in the middle of the first
+partition page that holds metadata (32B struct per partition page).
+
+As allocation requests arrive, there is eventually a need to allocate a new slot
+span.
+Address space for such a slot span is carved out from the last super page. If
+not enough space, a new super page is allocated. Due to varying sizes of slot
+span, this may lead to leaving space unused (we never go back to fill previous
+super pages), which is fine because this memory is merely reserved, which is far
+less precious than committed memory. Note also that address space reserved for a
+slot span is never released, even if the slot span isn't used for a long time.
+
+All slots in a newly allocated slot span are *free*, i.e. available for
+allocation.
+
+### Freelist Pointers
+
+All free slots within a slot span are chained into a singly-linked free-list,
+by writing the *next* pointer at the beginning of each slot, and the head of the
+list is written in the metadata struct.
+
+However, writing a pointer in each free slot of a newly allocated span would
+require committing and faulting in physical pages upfront, which would be
+unacceptable. Therefore, PartitionAlloc has a concept of *provisioning slots*.
+Only provisioned slots are chained into the free-list.
+Once provisioned slots in a span are depleted, then another page worth of slots
+is provisioned (note, a slot that crosses a page boundary only gets
+provisioned with slots of the next page). See
+`PartitionBucket::ProvisionMoreSlotsAndAllocOne()` for more details.
+
+Freelist pointers are stored at the beginning of each free slot. As such, they
+are the only metadata that is inline, i.e. stored among the
+objects. This makes them prone to overruns. On little-endian systems, the
+pointers are encoded by reversing byte order, so that partial overruns will very
+likely result in destroying the pointer, as opposed to forming a valid pointer
+to a nearby location.
+
+Furthermore, a shadow of a freelist pointer is stored next to it, encoded in a
+different manner. This helps PartitionAlloc detect corruptions.
+
+### Slot Span States
+
+A slot span can be in any of 4 states:
+* *Full*. A full span has no free slots.
+* *Free*. A free span has no allocated slots, only free slots.
+* *Active*. An active span is anything in between the above two.
+* *Decommitted*. A decommitted span is a special case of a free span, where all
+  pages are decommitted from memory.
+
+PartitionAlloc prioritizes getting an available slot from an active span, over
+a free one, in hope that the latter can be soon transitioned into a decommitted
+state, thus releasing memory. There is no mechanism, however, to prioritize
+selection of a slot span based on the number of already allocated slots.
+
+A free span becomes decommitted if there are too many free spans (FIFO), or when
+`PartitionRoot::PurgeMemory()` gets invoked periodically (or in low memory
+pressure conditions). An allocation can be satisfied from
+a decommitted span if there are no active or free spans available. The slot
+provisioning mechanism kicks back in, committing the pages gradually as needed,
+and the span becomes active. (There is currently no other way
+to unprovision slots than decommitting the entire span).
+
+As mentioned above, a bucket is a collection of slot spans containing slots of
+the same size. In fact, each bucket has 3 linked-lists, chaining active, free
+and decommitted spans (see `PartitionBucket::*_slot_spans_head`).
+There is no need for a full span list. The lists are updated lazily. A free,
+decommitted or full span may stay on the active list for some time, until
+`PartitionBucket::SetNewActiveSlotSpan()` encounters it.
+A decommitted span may stay on the free list for some time,
+until `PartitionBucket<thread_safe>::SlowPathAlloc()` encounters it. However,
+the inaccuracy can't happen in the other direction, i.e. an active span can only
+be on the active list, and a free span can only be on the active or free list.

src/base/allocator/partition_allocator/address_pool_manager.cc

@@ -0,0 +1,392 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/address_pool_manager.h"
+
+#if defined(OS_APPLE)
+#include <sys/mman.h>
+#endif
+
+#include <algorithm>
+#include <limits>
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/allocator/partition_allocator/page_allocator_constants.h"
+#include "base/allocator/partition_allocator/page_allocator_internal.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/lazy_instance.h"
+#include "base/notreached.h"
+#include "base/stl_util.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+base::LazyInstance<AddressPoolManager>::Leaky g_address_pool_manager =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+// static
+AddressPoolManager* AddressPoolManager::GetInstance() {
+  return g_address_pool_manager.Pointer();
+}
+
+#if defined(PA_HAS_64_BITS_POINTERS)
+
+namespace {
+
+// This will crash if the range cannot be decommitted.
+void DecommitPages(void* address, size_t size) {
+#if defined(OS_APPLE)
+  // MAP_FIXED replaces an existing mapping with a new one, when the address is
+  // already part of a mapping. Since newly-created mappings are guaranteed to
+  // be zero-filled, this has the desired effect. It is only required on macOS,
+  // as on other operating systems, |DecommitSystemPages()| provides the same
+  // behavior.
+  void* ptr = mmap(address, size, PROT_NONE,
+                   MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  PA_CHECK(ptr == address);
+#else
+  static_assert(DecommittedMemoryIsAlwaysZeroed(), "");
+  DecommitSystemPages(address, size, PageUpdatePermissions);
+#endif
+}
+
+}  // namespace
+
+constexpr size_t AddressPoolManager::Pool::kMaxBits;
+
+pool_handle AddressPoolManager::Add(uintptr_t ptr, size_t length) {
+  PA_DCHECK(!(ptr & kSuperPageOffsetMask));
+  PA_DCHECK(!((ptr + length) & kSuperPageOffsetMask));
+
+  for (pool_handle i = 0; i < base::size(pools_); ++i) {
+    if (!pools_[i].IsInitialized()) {
+      pools_[i].Initialize(ptr, length);
+      return i + 1;
+    }
+  }
+  NOTREACHED();
+  return 0;
+}
+
+void AddressPoolManager::ResetForTesting() {
+  for (pool_handle i = 0; i < base::size(pools_); ++i)
+    pools_[i].Reset();
+}
+
+void AddressPoolManager::Remove(pool_handle handle) {
+  Pool* pool = GetPool(handle);
+  PA_DCHECK(pool->IsInitialized());
+  pool->Reset();
+}
+
+char* AddressPoolManager::Reserve(pool_handle handle,
+                                  void* requested_address,
+                                  size_t length) {
+  Pool* pool = GetPool(handle);
+  if (!requested_address)
+    return reinterpret_cast<char*>(pool->FindChunk(length));
+  const bool is_available = pool->TryReserveChunk(
+      reinterpret_cast<uintptr_t>(requested_address), length);
+  if (is_available)
+    return static_cast<char*>(requested_address);
+  return reinterpret_cast<char*>(pool->FindChunk(length));
+}
+
+void AddressPoolManager::UnreserveAndDecommit(pool_handle handle,
+                                              void* ptr,
+                                              size_t length) {
+  PA_DCHECK(0 < handle && handle <= kNumPools);
+  Pool* pool = GetPool(handle);
+  PA_DCHECK(pool->IsInitialized());
+  DecommitPages(ptr, length);
+  pool->FreeChunk(reinterpret_cast<uintptr_t>(ptr), length);
+}
+
+void AddressPoolManager::Pool::Initialize(uintptr_t ptr, size_t length) {
+  PA_CHECK(ptr != 0);
+  PA_CHECK(!(ptr & kSuperPageOffsetMask));
+  PA_CHECK(!(length & kSuperPageOffsetMask));
+  address_begin_ = ptr;
+#if DCHECK_IS_ON()
+  address_end_ = ptr + length;
+  PA_DCHECK(address_begin_ < address_end_);
+#endif
+
+  total_bits_ = length / kSuperPageSize;
+  PA_CHECK(total_bits_ <= kMaxBits);
+
+  base::AutoLock scoped_lock(lock_);
+  alloc_bitset_.reset();
+  bit_hint_ = 0;
+}
+
+bool AddressPoolManager::Pool::IsInitialized() {
+  return address_begin_ != 0;
+}
+
+void AddressPoolManager::Pool::Reset() {
+  address_begin_ = 0;
+}
+
+uintptr_t AddressPoolManager::Pool::FindChunk(size_t requested_size) {
+  base::AutoLock scoped_lock(lock_);
+
+  PA_DCHECK(!(requested_size & kSuperPageOffsetMask));
+  const size_t need_bits = requested_size >> kSuperPageShift;
+
+  // Use first-fit policy to find an available chunk from free chunks. Start
+  // from |bit_hint_|, because we know there are no free chunks before.
+  size_t beg_bit = bit_hint_;
+  size_t curr_bit = bit_hint_;
+  while (true) {
+    // |end_bit| points 1 past the last bit that needs to be 0. If it goes past
+    // |total_bits_|, return |nullptr| to signal no free chunk was found.
+    size_t end_bit = beg_bit + need_bits;
+    if (end_bit > total_bits_)
+      return 0;
+
+    bool found = true;
+    for (; curr_bit < end_bit; ++curr_bit) {
+      if (alloc_bitset_.test(curr_bit)) {
+        // The bit was set, so this chunk isn't entirely free. Set |found=false|
+        // to ensure the outer loop continues. However, continue the inner loop
+        // to set |beg_bit| just past the last set bit in the investigated
+        // chunk. |curr_bit| is advanced all the way to |end_bit| to prevent the
+        // next outer loop pass from checking the same bits.
+        beg_bit = curr_bit + 1;
+        found = false;
+        if (bit_hint_ == curr_bit)
+          ++bit_hint_;
+      }
+    }
+
+    // An entire [beg_bit;end_bit) region of 0s was found. Fill them with 1s (to
+    // mark as allocated) and return the allocated address.
+    if (found) {
+      for (size_t i = beg_bit; i < end_bit; ++i) {
+        PA_DCHECK(!alloc_bitset_.test(i));
+        alloc_bitset_.set(i);
+      }
+      if (bit_hint_ == beg_bit) {
+        bit_hint_ = end_bit;
+      }
+      uintptr_t address = address_begin_ + beg_bit * kSuperPageSize;
+#if DCHECK_IS_ON()
+      PA_DCHECK(address + requested_size <= address_end_);
+#endif
+      return address;
+    }
+  }
+
+  NOTREACHED();
+  return 0;
+}
+
+bool AddressPoolManager::Pool::TryReserveChunk(uintptr_t address,
+                                               size_t requested_size) {
+  base::AutoLock scoped_lock(lock_);
+  PA_DCHECK(!(address & kSuperPageOffsetMask));
+  PA_DCHECK(!(requested_size & kSuperPageOffsetMask));
+  const size_t begin_bit = (address - address_begin_) / kSuperPageSize;
+  const size_t need_bits = requested_size / kSuperPageSize;
+  const size_t end_bit = begin_bit + need_bits;
+  // Check that requested address is not too high.
+  if (end_bit > total_bits_)
+    return false;
+  // Check if any bit of the requested region is set already.
+  for (size_t i = begin_bit; i < end_bit; ++i) {
+    if (alloc_bitset_.test(i))
+      return false;
+  }
+  // Otherwise, set the bits.
+  for (size_t i = begin_bit; i < end_bit; ++i) {
+    alloc_bitset_.set(i);
+  }
+  return true;
+}
+
+void AddressPoolManager::Pool::FreeChunk(uintptr_t address, size_t free_size) {
+  base::AutoLock scoped_lock(lock_);
+
+  PA_DCHECK(!(address & kSuperPageOffsetMask));
+  PA_DCHECK(!(free_size & kSuperPageOffsetMask));
+
+  PA_DCHECK(address_begin_ <= address);
+#if DCHECK_IS_ON()
+  PA_DCHECK(address + free_size <= address_end_);
+#endif
+
+  const size_t beg_bit = (address - address_begin_) / kSuperPageSize;
+  const size_t end_bit = beg_bit + free_size / kSuperPageSize;
+  for (size_t i = beg_bit; i < end_bit; ++i) {
+    PA_DCHECK(alloc_bitset_.test(i));
+    alloc_bitset_.reset(i);
+  }
+  bit_hint_ = std::min(bit_hint_, beg_bit);
+}
+
+AddressPoolManager::Pool::Pool() = default;
+AddressPoolManager::Pool::~Pool() = default;
+
+#else  // defined(PA_HAS_64_BITS_POINTERS)
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+uint16_t AddressPoolManager::reservation_offset_table_
+    [AddressPoolManager::kReservationOffsetTableSize] = {};
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+
+static_assert(
+    kSuperPageSize % AddressPoolManagerBitmap::kBytesPer1BitOfBRPPoolBitmap ==
+        0,
+    "kSuperPageSize must be a multiple of kBytesPer1BitOfBRPPoolBitmap.");
+static_assert(
+    kSuperPageSize / AddressPoolManagerBitmap::kBytesPer1BitOfBRPPoolBitmap > 0,
+    "kSuperPageSize must be larger than kBytesPer1BitOfBRPPoolBitmap.");
+static_assert(AddressPoolManagerBitmap::kGuardBitsOfBRPPoolBitmap >=
+                  AddressPoolManagerBitmap::kGuardOffsetOfBRPPoolBitmap,
+              "kGuardBitsOfBRPPoolBitmap must be larger than or equal to "
+              "kGuardOffsetOfBRPPoolBitmap.");
+
+template <size_t bitsize>
+void SetBitmap(std::bitset<bitsize>& bitmap,
+               size_t start_bit,
+               size_t bit_length) {
+  const size_t end_bit = start_bit + bit_length;
+  PA_DCHECK(start_bit <= bitsize);
+  PA_DCHECK(end_bit <= bitsize);
+
+  for (size_t i = start_bit; i < end_bit; ++i) {
+    PA_DCHECK(!bitmap.test(i));
+    bitmap.set(i);
+  }
+}
+
+template <size_t bitsize>
+void ResetBitmap(std::bitset<bitsize>& bitmap,
+                 size_t start_bit,
+                 size_t bit_length) {
+  const size_t end_bit = start_bit + bit_length;
+  PA_DCHECK(start_bit <= bitsize);
+  PA_DCHECK(end_bit <= bitsize);
+
+  for (size_t i = start_bit; i < end_bit; ++i) {
+    PA_DCHECK(bitmap.test(i));
+    bitmap.reset(i);
+  }
+}
+
+char* AddressPoolManager::Reserve(pool_handle handle,
+                                  void* requested_address,
+                                  size_t length) {
+  PA_DCHECK(!(length & DirectMapAllocationGranularityOffsetMask()));
+  char* ptr = reinterpret_cast<char*>(
+      AllocPages(requested_address, length, kSuperPageSize, PageInaccessible,
+                 PageTag::kPartitionAlloc));
+  if (UNLIKELY(!ptr))
+    return nullptr;
+
+  MarkUsed(handle, ptr, length);
+  return ptr;
+}
+
+void AddressPoolManager::UnreserveAndDecommit(pool_handle handle,
+                                              void* ptr,
+                                              size_t length) {
+  uintptr_t ptr_as_uintptr = reinterpret_cast<uintptr_t>(ptr);
+  PA_DCHECK(!(ptr_as_uintptr & kSuperPageOffsetMask));
+  PA_DCHECK(!(length & DirectMapAllocationGranularityOffsetMask()));
+  MarkUnused(handle, ptr_as_uintptr, length);
+  FreePages(ptr, length);
+}
+
+void AddressPoolManager::MarkUsed(pool_handle handle,
+                                  const char* address,
+                                  size_t length) {
+  uintptr_t ptr_as_uintptr = reinterpret_cast<uintptr_t>(address);
+  AutoLock guard(AddressPoolManagerBitmap::GetLock());
+  if (handle == kNonBRPPoolHandle) {
+    SetBitmap(AddressPoolManagerBitmap::non_brp_pool_bits_,
+              ptr_as_uintptr / DirectMapAllocationGranularity(),
+              length / DirectMapAllocationGranularity());
+  } else {
+    PA_DCHECK(handle == kBRPPoolHandle);
+    PA_DCHECK(
+        (length % AddressPoolManagerBitmap::kBytesPer1BitOfBRPPoolBitmap) == 0);
+
+    // Make IsManagedByBRPPoolPool() return false when an address inside the
+    // first or the last PartitionPageSize()-bytes block is given:
+    //
+    //          ------+---+---------------+---+----
+    // memory   ..... | B | managed by PA | B | ...
+    // regions  ------+---+---------------+---+----
+    //
+    // B: PartitionPageSize()-bytes block. This is used internally by the
+    // allocator and is not available for callers.
+    //
+    // This is required to avoid crash caused by the following code:
+    //   {
+    //     // Assume this allocation happens outside of PartitionAlloc.
+    //     CheckedPtr<T> ptr = new T[20];
+    //     for (size_t i = 0; i < 20; i ++) { ptr++; }
+    //     // |ptr| may point to an address inside 'B'.
+    //   }
+    //
+    // Suppose that |ptr| points to an address inside B after the loop. If
+    // IsManagedByBRPPoolPool(ptr) were to return true, ~CheckedPtr would crash,
+    // since the memory is not allocated by Partition.
+    SetBitmap(
+        AddressPoolManagerBitmap::brp_pool_bits_,
+        (ptr_as_uintptr >> AddressPoolManagerBitmap::kBitShiftOfBRPPoolBitmap) +
+            AddressPoolManagerBitmap::kGuardOffsetOfBRPPoolBitmap,
+        (length >> AddressPoolManagerBitmap::kBitShiftOfBRPPoolBitmap) -
+            AddressPoolManagerBitmap::kGuardBitsOfBRPPoolBitmap);
+  }
+}
+
+void AddressPoolManager::MarkUnused(pool_handle handle,
+                                    uintptr_t address,
+                                    size_t length) {
+  AutoLock guard(AddressPoolManagerBitmap::GetLock());
+  // Currently, address regions allocated by kBRPPoolHandle are never freed
+  // in PartitionAlloc, except on error paths, because only normal buckets are
+  // allocated from there. Thus LIKELY is used.
+  if (LIKELY(handle == kNonBRPPoolHandle)) {
+    ResetBitmap(AddressPoolManagerBitmap::non_brp_pool_bits_,
+                address / DirectMapAllocationGranularity(),
+                length / DirectMapAllocationGranularity());
+  } else {
+    PA_DCHECK(handle == kBRPPoolHandle);
+    PA_DCHECK(
+        (length % AddressPoolManagerBitmap::kBytesPer1BitOfBRPPoolBitmap) == 0);
+
+    // Make IsManagedByBRPPoolPool() return false when an address inside the
+    // first or the last PartitionPageSize()-bytes block is given.
+    // (See MarkUsed comment)
+    ResetBitmap(
+        AddressPoolManagerBitmap::brp_pool_bits_,
+        (address >> AddressPoolManagerBitmap::kBitShiftOfBRPPoolBitmap) +
+            AddressPoolManagerBitmap::kGuardOffsetOfBRPPoolBitmap,
+        (length >> AddressPoolManagerBitmap::kBitShiftOfBRPPoolBitmap) -
+            AddressPoolManagerBitmap::kGuardBitsOfBRPPoolBitmap);
+  }
+}
+
+void AddressPoolManager::ResetForTesting() {
+  AutoLock guard(AddressPoolManagerBitmap::GetLock());
+  AddressPoolManagerBitmap::non_brp_pool_bits_.reset();
+  AddressPoolManagerBitmap::brp_pool_bits_.reset();
+}
+
+#endif  // defined(PA_HAS_64_BITS_POINTERS)
+
+AddressPoolManager::AddressPoolManager() = default;
+AddressPoolManager::~AddressPoolManager() = default;
+
+}  // namespace internal
+}  // namespace base

src/base/allocator/partition_allocator/address_pool_manager.h

@@ -0,0 +1,256 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_H_
+
+#include <bitset>
+#include <limits>
+
+#include "base/allocator/partition_allocator/address_pool_manager_bitmap.h"
+#include "base/allocator/partition_allocator/address_pool_manager_types.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/synchronization/lock.h"
+#include "base/thread_annotations.h"
+#include "build/build_config.h"
+
+namespace base {
+
+template <typename Type>
+struct LazyInstanceTraitsBase;
+
+namespace internal {
+
+// (64bit version)
+// AddressPoolManager takes a reserved virtual address space and manages address
+// space allocation.
+//
+// AddressPoolManager (currently) supports up to 2 pools. Each pool manages a
+// contiguous reserved address space. Alloc() takes a pool_handle and returns
+// address regions from the specified pool. Free() also takes a pool_handle and
+// returns the address region back to the manager.
+//
+// (32bit version)
+// AddressPoolManager wraps AllocPages and FreePages and remembers allocated
+// address regions using bitmaps. IsManagedByPartitionAllocBRPPool and
+// IsManagedByPartitionAllocNonBRPPool use the bitmaps to judge whether a given
+// address is in a pool that supports BackupRefPtr or in a pool that doesn't.
+// All PartitionAlloc allocations must be in either of the pools.
+class BASE_EXPORT AddressPoolManager {
+  static constexpr uint64_t kGiB = 1024 * 1024 * 1024ull;
+
+ public:
+  static constexpr uint64_t kBRPPoolMaxSize =
+#if defined(PA_HAS_64_BITS_POINTERS)
+      // TODO(bartekn): Use kBRPPoolSize from partition_address_space.h
+      8 * kGiB;
+#else
+      4 * kGiB;
+#endif
+
+  static AddressPoolManager* GetInstance();
+
+#if defined(PA_HAS_64_BITS_POINTERS)
+  pool_handle Add(uintptr_t address, size_t length);
+  void Remove(pool_handle handle);
+#endif
+  // Reserves address space from GigaCage.
+  char* Reserve(pool_handle handle, void* requested_address, size_t length);
+  // Frees address space back to GigaCage and decommits underlying system pages.
+  void UnreserveAndDecommit(pool_handle handle, void* ptr, size_t length);
+  void ResetForTesting();
+
+#if !defined(PA_HAS_64_BITS_POINTERS)
+  static bool IsManagedByNonBRPPool(const void* address) {
+    return AddressPoolManagerBitmap::IsManagedByNonBRPPool(address);
+  }
+
+  static bool IsManagedByBRPPool(const void* address) {
+    return AddressPoolManagerBitmap::IsManagedByBRPPool(address);
+  }
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  static constexpr uint16_t kNotInDirectMap =
+      std::numeric_limits<uint16_t>::max();
+
+  // (For !defined(PA_HAS_64_BITS_POINTERS))
+  // reservation_offset_table_ is used to get the reservation start address
+  // when an address is given. Each entry of the table is prepared for each
+  // super page. When PartitionAlloc reserves an address space (its required
+  // alignment is SuperPageSize but its required size is not
+  // SuperPageSize-aligned),
+  //
+  // |<---------- SuperPage-aligned reserved size -------->|
+  // |<---------- Reserved size ------------------>|
+  // +----------+----------+-----+-----------+-----+ - - - +
+  // |SuperPage0|SuperPage1| ... |SuperPage K|SuperPage K+1|
+  // +----------+----------+-----+-----------+-----+ - - -.+
+  //                                         |<-X->|<--Y-->|
+  //
+  // the table entries for reserved SuperPages have the numbers of SuperPages
+  // between the reservation start and each reserved SuperPage:
+  // +----------+----------+-----+-----------+-------------+
+  // |Entry for |Entry for | ... |Entry for  |Entry for    |
+  // |SuperPage0|SuperPage1|     |SuperPage K|SuperPage K+1|
+  // +----------+----------+-----+-----------+-------------+
+  // |     0    |    1     | ... |     K     |   K + 1     |
+  // +----------+----------+-----+-----------+-------------+
+  // 65535 is used as a special number: "not used for direct-map allocation".
+  //
+  // So when we have an address Z, ((Z >> SuperPageShift) - (the entry for Z))
+  // << SuperPageShift is the reservation start when allocating an address space
+  // which contains Z.
+  //
+  // (*) Y is not used by PartitionAlloc until X is unreserved, because
+  // PartitionAlloc always uses SuperPageSize alignment when reserving address
+  // spaces. So we don't need to keep any offset for Y. GigaCage helps us to see
+  // whether the given address space is used by PA or not.
+  static uint16_t* ReservationOffsetTable() {
+    return reservation_offset_table_;
+  }
+
+  static const uint16_t* EndOfReservationOffsetTable() {
+    return reservation_offset_table_ + kReservationOffsetTableSize;
+  }
+
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+#endif  // !defined(PA_HAS_64_BITS_POINTERS)
+
+ private:
+  friend class AddressPoolManagerForTesting;
+
+  AddressPoolManager();
+  ~AddressPoolManager();
+
+#if defined(PA_HAS_64_BITS_POINTERS)
+  class Pool {
+   public:
+    Pool();
+    ~Pool();
+
+    void Initialize(uintptr_t ptr, size_t length);
+    bool IsInitialized();
+    void Reset();
+
+    uintptr_t FindChunk(size_t size);
+    void FreeChunk(uintptr_t address, size_t size);
+
+    bool TryReserveChunk(uintptr_t address, size_t size);
+
+   private:
+    // The bitset stores the allocation state of the address pool. 1 bit per
+    // super-page: 1 = allocated, 0 = free.
+    static constexpr size_t kMaxBits = kBRPPoolMaxSize / kSuperPageSize;
+
+    base::Lock lock_;
+    std::bitset<kMaxBits> alloc_bitset_ GUARDED_BY(lock_);
+    // An index of a bit in the bitset before which we know for sure there all
+    // 1s. This is a best-effort hint in the sense that there still may be lots
+    // of 1s after this index, but at least we know there is no point in
+    // starting the search before it.
+    size_t bit_hint_ GUARDED_BY(lock_);
+
+    size_t total_bits_ = 0;
+    uintptr_t address_begin_ = 0;
+#if DCHECK_IS_ON()
+    uintptr_t address_end_ = 0;
+#endif
+  };
+
+  ALWAYS_INLINE Pool* GetPool(pool_handle handle) {
+    PA_DCHECK(0 < handle && handle <= kNumPools);
+    return &pools_[handle - 1];
+  }
+
+  static constexpr size_t kNumPools = 2;
+  Pool pools_[kNumPools];
+
+#else   // defined(PA_HAS_64_BITS_POINTERS)
+
+  void MarkUsed(pool_handle handle, const char* address, size_t size);
+  void MarkUnused(pool_handle handle, uintptr_t address, size_t size);
+
+  // BRP stands for BackupRefPtr. GigaCage is split into pools, one which
+  // supports BackupRefPtr and one that doesn't.
+  static constexpr pool_handle kNonBRPPoolHandle = 1;
+  static constexpr pool_handle kBRPPoolHandle = 2;
+  friend internal::pool_handle GetNonBRPPool();
+  friend internal::pool_handle GetBRPPool();
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  // Allocation size is a multiple of DirectMapAllocationGranularity(), but
+  // alignment is kSuperPageSize.
+  static constexpr size_t kReservationOffsetTableSize =
+      4 * kGiB / kSuperPageSize;
+
+  static_assert(kReservationOffsetTableSize <
+                    std::numeric_limits<uint16_t>::max(),
+                "kReservationOffsetTableSize should be smaller than 65536.");
+
+  static uint16_t reservation_offset_table_[kReservationOffsetTableSize];
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+
+#endif  // defined(PA_HAS_64_BITS_POINTERS)
+
+  friend struct base::LazyInstanceTraitsBase<AddressPoolManager>;
+  DISALLOW_COPY_AND_ASSIGN(AddressPoolManager);
+};
+
+#if !defined(PA_HAS_64_BITS_POINTERS)
+ALWAYS_INLINE internal::pool_handle GetNonBRPPool() {
+  return AddressPoolManager::kNonBRPPoolHandle;
+}
+
+ALWAYS_INLINE internal::pool_handle GetBRPPool() {
+  return AddressPoolManager::kBRPPoolHandle;
+}
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+ALWAYS_INLINE constexpr uint16_t NotInDirectMapOffsetTag() {
+  return internal::AddressPoolManager::kNotInDirectMap;
+}
+
+ALWAYS_INLINE uint16_t* ReservationOffsetPointer(uintptr_t address) {
+  unsigned table_offset = address >> kSuperPageShift;
+  return internal::AddressPoolManager::ReservationOffsetTable() + table_offset;
+}
+
+ALWAYS_INLINE const uint16_t* EndOfReservationOffsetTable() {
+  return internal::AddressPoolManager::EndOfReservationOffsetTable();
+}
+
+ALWAYS_INLINE uintptr_t GetReservationStart(void* address) {
+  PA_DCHECK(internal::AddressPoolManager::IsManagedByBRPPool(address));
+  uintptr_t ptr_as_uintptr = reinterpret_cast<uintptr_t>(address);
+  uint16_t* offset_ptr = internal::ReservationOffsetPointer(ptr_as_uintptr);
+  PA_DCHECK(*offset_ptr != internal::NotInDirectMapOffsetTag());
+  uintptr_t reservation_start =
+      (ptr_as_uintptr & kSuperPageBaseMask) -
+      (static_cast<size_t>(*offset_ptr) << kSuperPageShift);
+  // Because the first
+  // internal::AddressPoolManagerBitmap::kBytesPer1BitOfBRPPoolBitmap *
+  // internal::AddressPoolManagerBitmap::kGuardOffsetOfBRPPoolBitmap bytes
+  // of each reserved memory are used as guard pages,
+  // IsManagedByBRPPool(reservation_start) returns false. Need to use
+  // reservation_start + kBytesPer1BitOfBRPPoolBitmap *
+  // kGuardOffsetOfBRPPoolBitmap.
+  PA_DCHECK(internal::AddressPoolManager::IsManagedByBRPPool(reinterpret_cast<
+                                                             void*>(
+      reservation_start +
+      internal::AddressPoolManagerBitmap::kBytesPer1BitOfBRPPoolBitmap *
+          internal::AddressPoolManagerBitmap::kGuardOffsetOfBRPPoolBitmap)));
+  PA_DCHECK(*internal::ReservationOffsetPointer(reservation_start) == 0);
+  return reservation_start;
+}
+
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+#endif  // !defined(PA_HAS_64_BITS_POINTERS)
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_H_

src/base/allocator/partition_allocator/address_pool_manager_bitmap.cc

@@ -0,0 +1,42 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/address_pool_manager_bitmap.h"
+
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/lazy_instance.h"
+
+#if !defined(PA_HAS_64_BITS_POINTERS)
+
+namespace base {
+namespace internal {
+
+namespace {
+
+LazyInstance<Lock>::Leaky g_lock = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+Lock& AddressPoolManagerBitmap::GetLock() {
+  return g_lock.Get();
+}
+
+std::bitset<AddressPoolManagerBitmap::kNonBRPPoolBits>
+    AddressPoolManagerBitmap::non_brp_pool_bits_;  // GUARDED_BY(GetLock())
+std::bitset<AddressPoolManagerBitmap::kBRPPoolBits>
+    AddressPoolManagerBitmap::brp_pool_bits_;  // GUARDED_BY(GetLock())
+#if BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+#if BUILDFLAG(NEVER_REMOVE_FROM_BRP_POOL_BLOCKLIST)
+std::array<std::atomic_bool,
+           AddressPoolManagerBitmap::kAddressSpaceSize / kSuperPageSize>
+    AddressPoolManagerBitmap::brp_forbidden_super_page_map_;
+#endif
+std::array<std::atomic_uint32_t,
+           AddressPoolManagerBitmap::kAddressSpaceSize / kSuperPageSize>
+    AddressPoolManagerBitmap::super_page_refcount_map_;
+#endif  // BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+}  // namespace internal
+}  // namespace base
+
+#endif  // !defined(PA_HAS_64_BITS_POINTERS)

src/base/allocator/partition_allocator/address_pool_manager_bitmap.h

@@ -0,0 +1,185 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_BITMAP_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_BITMAP_H_
+
+#include <array>
+#include <atomic>
+#include <bitset>
+#include <limits>
+
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/partition_alloc_buildflags.h"
+#include "base/synchronization/lock.h"
+
+#if !defined(PA_HAS_64_BITS_POINTERS)
+
+namespace base {
+
+namespace internal {
+
+// AddressPoolManagerBitmap is a set of bitmaps that track whether a given
+// address is in a pool that supports BackupRefPtr, or in a pool that doesn't
+// support it. All PartitionAlloc allocations must be in either of the pools.
+//
+// This code is specific to 32-bit systems.
+class BASE_EXPORT AddressPoolManagerBitmap {
+ public:
+  static constexpr uint64_t kGiB = 1024 * 1024 * 1024ull;
+  static constexpr uint64_t kAddressSpaceSize = 4ull * kGiB;
+
+  // If !BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT),
+  // BRP pool includes only normal buckets. Despite normal buckets operate at
+  // the 2MB super page granularity, we need to lower granularity down to
+  // partition page level to eliminate the guard pages at the ends. This is
+  // needed so that pointers immediately past an allocation that immediately
+  // precede a super page in BRP pool don't accidentally fall into that pool.
+  // If BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT), BRP pool includes both normal
+  // buckets and direct-maps. Because of the guard pages, we still need to use
+  // PartitionPageSize(). c.f. GetDirectMapMetadataAndGuardPagesSize().
+  // As long as DirectMapAllocationGranularity() is no smaller than
+  // PageAllocationGranularity(), which it is, we don't need to decrease
+  // the bitmap granularity any further.
+  static constexpr size_t kBitShiftOfBRPPoolBitmap = PartitionPageShift();
+  static constexpr size_t kBytesPer1BitOfBRPPoolBitmap = PartitionPageSize();
+  static constexpr size_t kGuardOffsetOfBRPPoolBitmap = 1;
+  static constexpr size_t kGuardBitsOfBRPPoolBitmap = 2;
+  static constexpr size_t kBRPPoolBits =
+      kAddressSpaceSize / kBytesPer1BitOfBRPPoolBitmap;
+
+  // Non-BRP pool includes both normal bucket and direct map allocations, so
+  // DirectMapAllocationGranularity() has to be used. No need to eliminate guard
+  // pages at the ends, as this is a BackupRefPtr-specific concern.
+  static constexpr size_t kNonBRPPoolBits =
+      kAddressSpaceSize / DirectMapAllocationGranularity();
+
+  // Returns false for nullptr.
+  static bool IsManagedByNonBRPPool(const void* address) {
+    uintptr_t address_as_uintptr = reinterpret_cast<uintptr_t>(address);
+    static_assert(
+        std::numeric_limits<uintptr_t>::max() /
+                DirectMapAllocationGranularity() <
+            non_brp_pool_bits_.size(),
+        "The bitmap is too small, will result in unchecked out of bounds "
+        "accesses.");
+    // It is safe to read |non_brp_pool_bits_| without a lock since the caller
+    // is responsible for guaranteeing that the address is inside a valid
+    // allocation and the deallocation call won't race with this call.
+    return TS_UNCHECKED_READ(
+        non_brp_pool_bits_)[address_as_uintptr /
+                            DirectMapAllocationGranularity()];
+  }
+
+  // Returns false for nullptr.
+  static bool IsManagedByBRPPool(const void* address) {
+    uintptr_t address_as_uintptr = reinterpret_cast<uintptr_t>(address);
+    static_assert(std::numeric_limits<uintptr_t>::max() >>
+                      kBitShiftOfBRPPoolBitmap < brp_pool_bits_.size(),
+                  "The bitmap is too small, will result in unchecked out of "
+                  "bounds accesses.");
+    // It is safe to read |brp_pool_bits_| without a lock since the caller
+    // is responsible for guaranteeing that the address is inside a valid
+    // allocation and the deallocation call won't race with this call.
+    return TS_UNCHECKED_READ(
+        brp_pool_bits_)[address_as_uintptr >> kBitShiftOfBRPPoolBitmap];
+  }
+
+#if BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+  static void IncrementOutsideOfBRPPoolPtrRefCount(const void* address) {
+    uintptr_t address_as_uintptr = reinterpret_cast<uintptr_t>(address);
+
+#if BUILDFLAG(NEVER_REMOVE_FROM_BRP_POOL_BLOCKLIST)
+    brp_forbidden_super_page_map_[address_as_uintptr >> kSuperPageShift].store(
+        true, std::memory_order_relaxed);
+#else
+    super_page_refcount_map_[address_as_uintptr >> kSuperPageShift].fetch_add(
+        1, std::memory_order_relaxed);
+#endif
+  }
+
+  static void DecrementOutsideOfBRPPoolPtrRefCount(const void* address) {
+#if BUILDFLAG(NEVER_REMOVE_FROM_BRP_POOL_BLOCKLIST)
+    // No-op. In this mode, we only use one bit per super-page and, therefore,
+    // can't tell if there's more than one associated CheckedPtr at a given
+    // time. There's a small risk is that we may exhaust the entire address
+    // space. On the other hand, a single relaxed store (in the above function)
+    // is much less expensive than two CAS operations.
+#else
+    uintptr_t address_as_uintptr = reinterpret_cast<uintptr_t>(address);
+
+    super_page_refcount_map_[address_as_uintptr >> kSuperPageShift].fetch_sub(
+        1, std::memory_order_relaxed);
+#endif
+  }
+
+  static bool IsAllowedSuperPageForBRPPool(const void* address) {
+    uintptr_t address_as_uintptr = reinterpret_cast<uintptr_t>(address);
+
+    // The only potentially dangerous scenario, in which this check is used, is
+    // when the assignment of the first |CheckedPtr| object for a non-GigaCage
+    // address is racing with the allocation of a new GigCage super-page at the
+    // same address. We assume that if |CheckedPtr| is being initialized with a
+    // raw pointer, the associated allocation is "alive"; otherwise, the issue
+    // should be fixed by rewriting the raw pointer variable as |CheckedPtr|.
+    // In the worst case, when such a fix is impossible, we should just undo the
+    // |raw pointer -> CheckedPtr| rewrite of the problematic field. If the
+    // above assumption holds, the existing allocation will prevent us from
+    // reserving the super-page region and, thus, having the race condition.
+    // Since we rely on that external synchronization, the relaxed memory
+    // ordering should be sufficient.
+#if BUILDFLAG(NEVER_REMOVE_FROM_BRP_POOL_BLOCKLIST)
+    return !brp_forbidden_super_page_map_[address_as_uintptr >> kSuperPageShift]
+                .load(std::memory_order_relaxed);
+#else
+    return super_page_refcount_map_[address_as_uintptr >> kSuperPageShift].load(
+               std::memory_order_relaxed) == 0;
+#endif
+  }
+#endif  // BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+
+ private:
+  friend class AddressPoolManager;
+
+  static Lock& GetLock();
+
+  static std::bitset<kNonBRPPoolBits> non_brp_pool_bits_ GUARDED_BY(GetLock());
+  static std::bitset<kBRPPoolBits> brp_pool_bits_ GUARDED_BY(GetLock());
+#if BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+#if BUILDFLAG(NEVER_REMOVE_FROM_BRP_POOL_BLOCKLIST)
+  static std::array<std::atomic_bool, kAddressSpaceSize / kSuperPageSize>
+      brp_forbidden_super_page_map_;
+#endif
+  static std::array<std::atomic_uint32_t, kAddressSpaceSize / kSuperPageSize>
+      super_page_refcount_map_;
+#endif  // BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+};
+
+}  // namespace internal
+
+// Returns false for nullptr.
+ALWAYS_INLINE bool IsManagedByPartitionAlloc(const void* address) {
+  // Currently even when BUILDFLAG(USE_BACKUP_REF_PTR) is off, BRP pool is used
+  // for non-BRP allocations, so we have to check both pools regardless of
+  // BUILDFLAG(USE_BACKUP_REF_PTR).
+  return internal::AddressPoolManagerBitmap::IsManagedByNonBRPPool(address) ||
+         internal::AddressPoolManagerBitmap::IsManagedByBRPPool(address);
+}
+
+// Returns false for nullptr.
+ALWAYS_INLINE bool IsManagedByPartitionAllocNonBRPPool(const void* address) {
+  return internal::AddressPoolManagerBitmap::IsManagedByNonBRPPool(address);
+}
+
+// Returns false for nullptr.
+ALWAYS_INLINE bool IsManagedByPartitionAllocBRPPool(const void* address) {
+  return internal::AddressPoolManagerBitmap::IsManagedByBRPPool(address);
+}
+
+}  // namespace base
+
+#endif  // !defined(PA_HAS_64_BITS_POINTERS)
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_BITMAP_H_

src/base/allocator/partition_allocator/address_pool_manager_types.h

@@ -0,0 +1,17 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_TYPES_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_TYPES_H_
+
+namespace base {
+
+namespace internal {
+
+using pool_handle = unsigned;
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_POOL_MANAGER_TYPES_H_

src/base/allocator/partition_allocator/address_space_randomization.cc

@@ -0,0 +1,68 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/address_space_randomization.h"
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/random.h"
+#include "base/check_op.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>  // Must be in front of other Windows header files.
+
+#include <VersionHelpers.h>
+#endif
+
+namespace base {
+
+void* GetRandomPageBase() {
+  uintptr_t random = static_cast<uintptr_t>(RandomValue());
+
+#if defined(ARCH_CPU_64_BITS)
+  random <<= 32ULL;
+  random |= static_cast<uintptr_t>(RandomValue());
+
+// The ASLRMask() and ASLROffset() constants will be suitable for the
+// OS and build configuration.
+#if defined(OS_WIN) && !defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+  // Windows >= 8.1 has the full 47 bits. Use them where available.
+  static bool windows_81 = false;
+  static bool windows_81_initialized = false;
+  if (!windows_81_initialized) {
+    windows_81 = IsWindows8Point1OrGreater();
+    windows_81_initialized = true;
+  }
+  if (!windows_81) {
+    random &= internal::ASLRMaskBefore8_10();
+  } else {
+    random &= internal::ASLRMask();
+  }
+  random += internal::ASLROffset();
+#else
+  random &= internal::ASLRMask();
+  random += internal::ASLROffset();
+#endif  // defined(OS_WIN) && !defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+#else   // defined(ARCH_CPU_32_BITS)
+#if defined(OS_WIN)
+  // On win32 host systems the randomization plus huge alignment causes
+  // excessive fragmentation. Plus most of these systems lack ASLR, so the
+  // randomization isn't buying anything. In that case we just skip it.
+  // TODO(palmer): Just dump the randomization when HE-ASLR is present.
+  static BOOL is_wow64 = -1;
+  if (is_wow64 == -1 && !IsWow64Process(GetCurrentProcess(), &is_wow64))
+    is_wow64 = FALSE;
+  if (!is_wow64)
+    return nullptr;
+#endif  // defined(OS_WIN)
+  random &= internal::ASLRMask();
+  random += internal::ASLROffset();
+#endif  // defined(ARCH_CPU_32_BITS)
+
+  PA_DCHECK(!(random & PageAllocationGranularityOffsetMask()));
+  return reinterpret_cast<void*>(random);
+}
+
+}  // namespace base

src/base/allocator/partition_allocator/address_space_randomization.h

@@ -0,0 +1,266 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_SPACE_RANDOMIZATION_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_SPACE_RANDOMIZATION_H_
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "build/build_config.h"
+
+namespace base {
+
+// Calculates a random preferred mapping address. In calculating an address, we
+// balance good ASLR against not fragmenting the address space too badly.
+BASE_EXPORT void* GetRandomPageBase();
+
+namespace internal {
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+AslrAddress(uintptr_t mask) {
+  return mask & PageAllocationGranularityBaseMask();
+}
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+AslrMask(uintptr_t bits) {
+  return AslrAddress((1ULL << bits) - 1ULL);
+}
+
+// Turn off formatting, because the thicket of nested ifdefs below is
+// incomprehensible without indentation. It is also incomprehensible with
+// indentation, but the only other option is a combinatorial explosion of
+// *_{win,linux,mac,foo}_{32,64}.h files.
+//
+// clang-format off
+
+#if defined(ARCH_CPU_64_BITS)
+
+  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+
+    // We shouldn't allocate system pages at all for sanitizer builds. However,
+    // we do, and if random hint addresses interfere with address ranges
+    // hard-coded in those tools, bad things happen. This address range is
+    // copied from TSAN source but works with all tools. See
+    // https://crbug.com/539863.
+    PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+    ASLRMask() {
+      return AslrAddress(0x007fffffffffULL);
+    }
+    PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+    ASLROffset() {
+      return AslrAddress(0x7e8000000000ULL);
+    }
+
+  #elif defined(OS_WIN)
+
+    // Windows 8.10 and newer support the full 48 bit address range. Older
+    // versions of Windows only support 44 bits. Since ASLROffset() is non-zero
+    // and may cause a carry, use 47 and 43 bit masks. See
+    // http://www.alex-ionescu.com/?p=246
+    constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+      return AslrMask(47);
+    }
+    constexpr ALWAYS_INLINE uintptr_t ASLRMaskBefore8_10() {
+      return AslrMask(43);
+    }
+    // Try not to map pages into the range where Windows loads DLLs by default.
+    constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+      return 0x80000000ULL;
+    }
+
+  #elif defined(OS_APPLE)
+
+    // macOS as of 10.12.5 does not clean up entries in page map levels 3/4
+    // [PDP/PML4] created from mmap or mach_vm_allocate, even after the region
+    // is destroyed. Using a virtual address space that is too large causes a
+    // leak of about 1 wired [can never be paged out] page per call to mmap. The
+    // page is only reclaimed when the process is killed. Confine the hint to a
+    // 39-bit section of the virtual address space.
+    //
+    // This implementation adapted from
+    // https://chromium-review.googlesource.com/c/v8/v8/+/557958. The difference
+    // is that here we clamp to 39 bits, not 32.
+    //
+    // TODO(crbug.com/738925): Remove this limitation if/when the macOS behavior
+    // changes.
+    PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+    ASLRMask() {
+      return AslrMask(38);
+    }
+    PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+    ASLROffset() {
+      return AslrAddress(0x1000000000ULL);
+    }
+
+  #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
+
+    #if defined(ARCH_CPU_X86_64)
+
+      // Linux (and macOS) support the full 47-bit user space of x64 processors.
+      // Use only 46 to allow the kernel a chance to fulfill the request.
+      constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+        return AslrMask(46);
+      }
+      constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+        return AslrAddress(0);
+      }
+
+    #elif defined(ARCH_CPU_ARM64)
+
+      #if defined(OS_ANDROID)
+
+      // Restrict the address range on Android to avoid a large performance
+      // regression in single-process WebViews. See https://crbug.com/837640.
+      constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+        return AslrMask(30);
+      }
+      constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+        return AslrAddress(0x20000000ULL);
+      }
+
+      #else
+
+      // ARM64 on Linux has 39-bit user space. Use 38 bits since ASLROffset()
+      // could cause a carry.
+      constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+        return AslrMask(38);
+      }
+      constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+        return AslrAddress(0x1000000000ULL);
+      }
+
+      #endif
+
+    #elif defined(ARCH_CPU_PPC64)
+
+      #if defined(OS_AIX)
+
+        // AIX has 64 bits of virtual addressing, but we limit the address range
+        // to (a) minimize segment lookaside buffer (SLB) misses; and (b) use
+        // extra address space to isolate the mmap regions.
+        constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+          return AslrMask(30);
+        }
+        constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+          return AslrAddress(0x400000000000ULL);
+        }
+
+      #elif defined(ARCH_CPU_BIG_ENDIAN)
+
+        // Big-endian Linux PPC has 44 bits of virtual addressing. Use 42.
+        constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+          return AslrMask(42);
+        }
+        constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+          return AslrAddress(0);
+        }
+
+      #else  // !defined(OS_AIX) && !defined(ARCH_CPU_BIG_ENDIAN)
+
+        // Little-endian Linux PPC has 48 bits of virtual addressing. Use 46.
+        constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+          return AslrMask(46);
+        }
+        constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+          return AslrAddress(0);
+        }
+
+      #endif  // !defined(OS_AIX) && !defined(ARCH_CPU_BIG_ENDIAN)
+
+    #elif defined(ARCH_CPU_S390X)
+
+      // Linux on Z uses bits 22 - 32 for Region Indexing, which translates to
+      // 42 bits of virtual addressing. Truncate to 40 bits to allow kernel a
+      // chance to fulfill the request.
+      constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+        return AslrMask(40);
+      }
+      constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+        return AslrAddress(0);
+      }
+
+    #elif defined(ARCH_CPU_S390)
+
+      // 31 bits of virtual addressing. Truncate to 29 bits to allow the kernel
+      // a chance to fulfill the request.
+      constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+        return AslrMask(29);
+      }
+      constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+        return AslrAddress(0);
+      }
+
+    #else  // !defined(ARCH_CPU_X86_64) && !defined(ARCH_CPU_PPC64) &&
+           // !defined(ARCH_CPU_S390X) && !defined(ARCH_CPU_S390)
+
+      // For all other POSIX variants, use 30 bits.
+      constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+        return AslrMask(30);
+      }
+
+      #if defined(OS_SOLARIS)
+
+        // For our Solaris/illumos mmap hint, we pick a random address in the
+        // bottom half of the top half of the address space (that is, the third
+        // quarter). Because we do not MAP_FIXED, this will be treated only as a
+        // hint -- the system will not fail to mmap because something else
+        // happens to already be mapped at our random address. We deliberately
+        // set the hint high enough to get well above the system's break (that
+        // is, the heap); Solaris and illumos will try the hint and if that
+        // fails allocate as if there were no hint at all. The high hint
+        // prevents the break from getting hemmed in at low values, ceding half
+        // of the address space to the system heap.
+        constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+          return AslrAddress(0x80000000ULL);
+        }
+
+      #elif defined(OS_AIX)
+
+        // The range 0x30000000 - 0xD0000000 is available on AIX; choose the
+        // upper range.
+        constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+          return AslrAddress(0x90000000ULL);
+        }
+
+      #else  // !defined(OS_SOLARIS) && !defined(OS_AIX)
+
+        // The range 0x20000000 - 0x60000000 is relatively unpopulated across a
+        // variety of ASLR modes (PAE kernel, NX compat mode, etc) and on macOS
+        // 10.6 and 10.7.
+        constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+          return AslrAddress(0x20000000ULL);
+        }
+
+      #endif  // !defined(OS_SOLARIS) && !defined(OS_AIX)
+
+    #endif  // !defined(ARCH_CPU_X86_64) && !defined(ARCH_CPU_PPC64) &&
+            // !defined(ARCH_CPU_S390X) && !defined(ARCH_CPU_S390)
+
+  #endif  // defined(OS_POSIX)
+
+#elif defined(ARCH_CPU_32_BITS)
+
+  // This is a good range on 32-bit Windows and Android (the only platforms on
+  // which we support 32-bitness). Allocates in the 0.5 - 1.5 GiB region. There
+  // is no issue with carries here.
+  constexpr ALWAYS_INLINE uintptr_t ASLRMask() {
+    return AslrMask(30);
+  }
+  constexpr ALWAYS_INLINE uintptr_t ASLROffset() {
+    return AslrAddress(0x20000000ULL);
+  }
+
+#else
+
+  #error Please tell us about your exotic hardware! Sounds interesting.
+
+#endif  // defined(ARCH_CPU_32_BITS)
+
+// clang-format on
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_ADDRESS_SPACE_RANDOMIZATION_H_

src/base/allocator/partition_allocator/arm_bti_test_functions.S

@@ -0,0 +1,47 @@
+# Copyright (c) 2021 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This file contains a test function for checking Arm's branch target
+# identification (BTI) feature, which helps mitigate jump-oriented
+# programming. To get it working, BTI instructions must be executed
+# on a compatible core, and the executable pages must be mapped with
+# PROT_BTI. To validate that pages mapped with PROT_BTI are working
+# correctly:
+# 1) Allocate a read-write page.
+# 2) Copy between the start and end symbols into that page.
+# 3) Set the page to read-execute with PROT_BTI.
+# 4) Call the first offset of the page, verify the result.
+# 5) Call the second offset of the page (skipping the landing pad).
+#    Verify that it crashes as expected.
+# This test works irrespective of whether BTI is enabled for C/C++
+# objects via -mbranch-protection=standard.
+
+.text
+.global arm_bti_test_function
+.global arm_bti_test_function_invalid_offset
+.global arm_bti_test_function_end
+arm_bti_test_function:
+    # Mark the start of this function as a valid call target.
+    bti jc
+    add x0, x0, #1
+arm_bti_test_function_invalid_offset:
+    # This label simulates calling an incomplete function.
+    # Jumping here should crash systems which support BTI.
+    add x0, x0, #2
+    ret
+arm_bti_test_function_end:
+    nop
+
+.pushsection .note.gnu.property, "a";
+.balign 8;
+.long 4;
+.long 0x10;
+.long 0x5;
+.asciz "GNU";
+.long 0xc0000000; /* GNU_PROPERTY_AARCH64_FEATURE_1_AND */
+.long 4;
+.long 1;           /* GNU_PROPERTY_AARCH64_BTI */;
+.long 0;
+.popsection
+

src/base/allocator/partition_allocator/arm_bti_test_functions.h

@@ -0,0 +1,17 @@
+// Copyright (c) 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_ARM_BTI_TEST_FUNCTIONS_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_ARM_BTI_TEST_FUNCTIONS_H_
+
+#include "build/build_config.h"
+#if defined(ARCH_CPU_ARM64)
+extern "C" {
+int64_t arm_bti_test_function(int64_t);
+int64_t arm_bti_test_function_invalid_offset(int64_t);
+void arm_bti_test_function_end(void);
+}
+#endif  // defined(ARCH_CPU_ARM64)
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_ARM_BTI_TEST_FUNCTIONS_H_

src/base/allocator/partition_allocator/extended_api.cc

@@ -0,0 +1,46 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/extended_api.h"
+
+#include "base/allocator/allocator_shim_default_dispatch_to_partition_alloc.h"
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/partition_root.h"
+#include "base/allocator/partition_allocator/thread_cache.h"
+
+namespace base {
+
+namespace internal {
+
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+void DisableThreadCacheForRootIfEnabled(ThreadSafePartitionRoot* root) {
+  // Some platforms don't have a thread cache, or it could already have been
+  // disabled.
+  if (!root || !root->with_thread_cache)
+    return;
+
+  internal::ThreadCacheRegistry::Instance().PurgeAll();
+  root->with_thread_cache = false;
+  // Doesn't destroy the thread cache object(s). For background threads, they
+  // will be collected (and free cached memory) at thread destruction
+  // time. For the main thread, we leak it.
+}
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+}  // namespace internal
+
+void DisablePartitionAllocThreadCacheForProcess() {
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+  auto* regular_allocator = base::internal::PartitionAllocMalloc::Allocator();
+  auto* aligned_allocator =
+      base::internal::PartitionAllocMalloc::AlignedAllocator();
+  internal::DisableThreadCacheForRootIfEnabled(regular_allocator);
+  if (aligned_allocator != regular_allocator)
+    internal::DisableThreadCacheForRootIfEnabled(aligned_allocator);
+  internal::DisableThreadCacheForRootIfEnabled(
+      base::internal::PartitionAllocMalloc::OriginalAllocator());
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+}
+
+}  // namespace base

src/base/allocator/partition_allocator/extended_api.h

@@ -0,0 +1,31 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_EXTENDED_API_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_EXTENDED_API_H_
+
+#include "base/base_export.h"
+
+namespace base {
+// Disables the thread cache for the entire process.
+//
+// Saves memory but slows down the allocator *significantly*. Only use for
+// configurations that are very memory-constrained or performance-insensitive
+// processes.
+//
+// Must preferably be called from the main thread, when no/few threads have
+// been started.
+//
+// Otherwise, there are several things that can happen:
+// 1. Another thread is currently temporarily disabling the thread cache, and
+//    will re-enable it, negating this call's effect.
+// 2. Other threads' caches cannot be purged from here, and would retain their
+//    cached memory until thread destruction (where it is reclaimed).
+//
+// These are not correctness issues, at worst in the first case, memory is not
+// saved, and in the second one, *some* of the memory is leaked.
+BASE_EXPORT void DisablePartitionAllocThreadCacheForProcess();
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_EXTENDED_API_H_

src/base/allocator/partition_allocator/memory_reclaimer.cc

@@ -0,0 +1,163 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/memory_reclaimer.h"
+
+#include "base/allocator/partition_allocator/partition_alloc.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "base/allocator/partition_allocator/starscan/pcscan.h"
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/metrics/histogram_functions.h"
+#include "base/trace_event/base_tracing.h"
+
+namespace base {
+
+namespace {
+
+template <bool thread_safe>
+void Insert(std::set<PartitionRoot<thread_safe>*>* partitions,
+            PartitionRoot<thread_safe>* partition) {
+  PA_DCHECK(partition);
+  auto it_and_whether_inserted = partitions->insert(partition);
+  PA_DCHECK(it_and_whether_inserted.second);
+}
+
+template <bool thread_safe>
+void Remove(std::set<PartitionRoot<thread_safe>*>* partitions,
+            PartitionRoot<thread_safe>* partition) {
+  PA_DCHECK(partition);
+  size_t erased_count = partitions->erase(partition);
+  PA_DCHECK(erased_count == 1u);
+}
+
+}  // namespace
+
+// static
+PartitionAllocMemoryReclaimer* PartitionAllocMemoryReclaimer::Instance() {
+  static NoDestructor<PartitionAllocMemoryReclaimer> instance;
+  return instance.get();
+}
+
+void PartitionAllocMemoryReclaimer::RegisterPartition(
+    PartitionRoot<internal::ThreadSafe>* partition) {
+  AutoLock lock(lock_);
+  Insert(&thread_safe_partitions_, partition);
+}
+
+void PartitionAllocMemoryReclaimer::RegisterPartition(
+    PartitionRoot<internal::NotThreadSafe>* partition) {
+  AutoLock lock(lock_);
+  Insert(&thread_unsafe_partitions_, partition);
+}
+
+void PartitionAllocMemoryReclaimer::UnregisterPartition(
+    PartitionRoot<internal::ThreadSafe>* partition) {
+  AutoLock lock(lock_);
+  Remove(&thread_safe_partitions_, partition);
+}
+
+void PartitionAllocMemoryReclaimer::UnregisterPartition(
+    PartitionRoot<internal::NotThreadSafe>* partition) {
+  AutoLock lock(lock_);
+  Remove(&thread_unsafe_partitions_, partition);
+}
+
+void PartitionAllocMemoryReclaimer::Start(
+    scoped_refptr<SequencedTaskRunner> task_runner) {
+  PA_DCHECK(!timer_);
+  PA_DCHECK(task_runner);
+
+  {
+    AutoLock lock(lock_);
+    PA_DCHECK(!thread_safe_partitions_.empty());
+  }
+
+  // This does not need to run on the main thread, however there are a few
+  // reasons to do it there:
+  // - Most of PartitionAlloc's usage is on the main thread, hence PA's metadata
+  //   is more likely in cache when executing on the main thread.
+  // - Memory reclaim takes the partition lock for each partition. As a
+  //   consequence, while reclaim is running, the main thread is unlikely to be
+  //   able to make progress, as it would be waiting on the lock.
+  // - Finally, this runs in idle time only, so there should be no visible
+  //   impact.
+  //
+  // From local testing, time to reclaim is 100us-1ms, and reclaiming every few
+  // seconds is useful. Since this is meant to run during idle time only, it is
+  // a reasonable starting point balancing effectivenes vs cost. See
+  // crbug.com/942512 for details and experimental results.
+  constexpr TimeDelta kInterval = TimeDelta::FromSeconds(4);
+
+  timer_ = std::make_unique<RepeatingTimer>();
+  timer_->SetTaskRunner(task_runner);
+  // Here and below, |Unretained(this)| is fine as |this| lives forever, as a
+  // singleton.
+  timer_->Start(
+      FROM_HERE, kInterval,
+      BindRepeating(&PartitionAllocMemoryReclaimer::ReclaimPeriodically,
+                    Unretained(this)));
+}
+
+PartitionAllocMemoryReclaimer::PartitionAllocMemoryReclaimer() = default;
+PartitionAllocMemoryReclaimer::~PartitionAllocMemoryReclaimer() = default;
+
+void PartitionAllocMemoryReclaimer::ReclaimAll() {
+  constexpr int kFlags = PartitionPurgeDecommitEmptySlotSpans |
+                         PartitionPurgeDiscardUnusedSystemPages |
+                         PartitionPurgeAggressiveReclaim;
+  Reclaim(kFlags);
+}
+
+void PartitionAllocMemoryReclaimer::ReclaimPeriodically() {
+  constexpr int kFlags = PartitionPurgeDecommitEmptySlotSpans |
+                         PartitionPurgeDiscardUnusedSystemPages;
+  Reclaim(kFlags);
+}
+
+void PartitionAllocMemoryReclaimer::Reclaim(int flags) {
+  AutoLock lock(lock_);  // Has to protect from concurrent (Un)Register calls.
+  TRACE_EVENT0("base", "PartitionAllocMemoryReclaimer::Reclaim()");
+
+  // PCScan quarantines freed slots. Trigger the scan first to let it call
+  // FreeNoHooksImmediate on slots that pass the quarantine.
+  //
+  // In turn, FreeNoHooksImmediate may add slots to thread cache. Purge it next
+  // so that the slots are actually freed. (This is done synchronously only for
+  // the current thread.)
+  //
+  // Lastly decommit empty slot spans and lastly try to discard unused pages at
+  // the end of the remaining active slots.
+  {
+    using PCScan = internal::PCScan;
+    const auto invocation_mode = flags & PartitionPurgeAggressiveReclaim
+                                     ? PCScan::InvocationMode::kForcedBlocking
+                                     : PCScan::InvocationMode::kBlocking;
+    PCScan::PerformScanIfNeeded(invocation_mode);
+  }
+
+#if defined(PA_THREAD_CACHE_SUPPORTED)
+  // Don't completely empty the thread cache outside of low memory situations,
+  // as there is periodic purge which makes sure that it doesn't take too much
+  // space.
+  if (flags & PartitionPurgeAggressiveReclaim)
+    internal::ThreadCacheRegistry::Instance().PurgeAll();
+#endif
+
+  for (auto* partition : thread_safe_partitions_)
+    partition->PurgeMemory(flags);
+  for (auto* partition : thread_unsafe_partitions_)
+    partition->PurgeMemory(flags);
+}
+
+void PartitionAllocMemoryReclaimer::ResetForTesting() {
+  AutoLock lock(lock_);
+
+  timer_ = nullptr;
+  thread_safe_partitions_.clear();
+  thread_unsafe_partitions_.clear();
+}
+
+}  // namespace base

src/base/allocator/partition_allocator/memory_reclaimer.h

@@ -0,0 +1,72 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_MEMORY_RECLAIMER_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_MEMORY_RECLAIMER_H_
+
+#include <memory>
+#include <set>
+
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/no_destructor.h"
+#include "base/sequenced_task_runner.h"
+#include "base/thread_annotations.h"
+#include "base/timer/timer.h"
+
+namespace base {
+
+// Posts and handles memory reclaim tasks for PartitionAlloc.
+//
+// Thread safety: |RegisterPartition()| and |UnregisterPartition()| can be
+// called from any thread, concurrently with reclaim. Reclaim itself runs in the
+// context of the provided |SequencedTaskRunner|, meaning that the caller must
+// take care of this runner being compatible with the various partitions.
+//
+// Singleton as this runs as long as the process is alive, and
+// having multiple instances would be wasteful.
+class BASE_EXPORT PartitionAllocMemoryReclaimer {
+ public:
+  static PartitionAllocMemoryReclaimer* Instance();
+
+  // Internal. Do not use.
+  // Registers a partition to be tracked by the reclaimer.
+  void RegisterPartition(PartitionRoot<internal::ThreadSafe>* partition);
+  void RegisterPartition(PartitionRoot<internal::NotThreadSafe>* partition);
+  // Internal. Do not use.
+  // Unregisters a partition to be tracked by the reclaimer.
+  void UnregisterPartition(PartitionRoot<internal::ThreadSafe>* partition);
+  void UnregisterPartition(PartitionRoot<internal::NotThreadSafe>* partition);
+  // Starts the periodic reclaim. Should be called once.
+  void Start(scoped_refptr<SequencedTaskRunner> task_runner);
+  // Triggers an explicit reclaim now reclaiming all free memory
+  void ReclaimAll();
+  // Triggers an explicit reclaim now to reclaim as much free memory as
+  // possible.
+  void ReclaimPeriodically();
+
+ private:
+  PartitionAllocMemoryReclaimer();
+  ~PartitionAllocMemoryReclaimer();
+  // |flags| is an OR of base::PartitionPurgeFlags
+  void Reclaim(int flags);
+  void ReclaimAndReschedule();
+  void ResetForTesting();
+
+  // Schedules periodic |Reclaim()|.
+  std::unique_ptr<RepeatingTimer> timer_;
+
+  Lock lock_;
+  std::set<PartitionRoot<internal::ThreadSafe>*> thread_safe_partitions_
+      GUARDED_BY(lock_);
+  std::set<PartitionRoot<internal::NotThreadSafe>*> thread_unsafe_partitions_
+      GUARDED_BY(lock_);
+
+  friend class NoDestructor<PartitionAllocMemoryReclaimer>;
+  friend class PartitionAllocMemoryReclaimerTest;
+  DISALLOW_COPY_AND_ASSIGN(PartitionAllocMemoryReclaimer);
+};
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_MEMORY_RECLAIMER_H_

src/base/allocator/partition_allocator/oom.h

@@ -0,0 +1,38 @@
+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_OOM_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_OOM_H_
+
+#include "base/allocator/partition_allocator/oom_callback.h"
+#include "base/compiler_specific.h"
+#include "base/immediate_crash.h"
+#include "base/process/memory.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
+namespace {
+// The crash is generated in a NOINLINE function so that we can classify the
+// crash as an OOM solely by analyzing the stack trace. It is tagged as
+// NOT_TAIL_CALLED to ensure that its parent function stays on the stack.
+[[noreturn]] NOINLINE void NOT_TAIL_CALLED OnNoMemory(size_t size) {
+  base::internal::RunPartitionAllocOomCallback();
+  base::TerminateBecauseOutOfMemory(size);
+  IMMEDIATE_CRASH();
+}
+}  // namespace
+
+// OOM_CRASH(size) - Specialization of IMMEDIATE_CRASH which will raise a custom
+// exception on Windows to signal this is OOM and not a normal assert.
+// OOM_CRASH(size) is called by users of PageAllocator (including
+// PartitionAlloc) to signify an allocation failure from the platform.
+#define OOM_CRASH(size) \
+  do {                  \
+    OnNoMemory(size);   \
+  } while (0)
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_OOM_H_

src/base/allocator/partition_allocator/oom_callback.cc

@@ -0,0 +1,27 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/oom_callback.h"
+
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+
+namespace base {
+
+namespace {
+PartitionAllocOomCallback g_oom_callback;
+}  // namespace
+
+void SetPartitionAllocOomCallback(PartitionAllocOomCallback callback) {
+  PA_DCHECK(!g_oom_callback);
+  g_oom_callback = callback;
+}
+
+namespace internal {
+void RunPartitionAllocOomCallback() {
+  if (g_oom_callback)
+    g_oom_callback();
+}
+}  // namespace internal
+
+}  // namespace base

src/base/allocator/partition_allocator/oom_callback.h

@@ -0,0 +1,24 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_OOM_CALLBACK_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_OOM_CALLBACK_H_
+
+#include "base/base_export.h"
+
+namespace base {
+typedef void (*PartitionAllocOomCallback)();
+// Registers a callback to be invoked during an OOM_CRASH(). OOM_CRASH is
+// invoked by users of PageAllocator (including PartitionAlloc) to signify an
+// allocation failure from the platform.
+BASE_EXPORT void SetPartitionAllocOomCallback(
+    PartitionAllocOomCallback callback);
+
+namespace internal {
+BASE_EXPORT void RunPartitionAllocOomCallback();
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_OOM_CALLBACK_H_

src/base/allocator/partition_allocator/page_allocator.cc

@@ -0,0 +1,343 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+
+#include <limits.h>
+
+#include <atomic>
+
+#include "base/allocator/partition_allocator/address_space_randomization.h"
+#include "base/allocator/partition_allocator/page_allocator_internal.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/bits.h"
+#include "base/lazy_instance.h"
+#include "base/no_destructor.h"
+#include "base/synchronization/lock.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
+#if defined(OS_WIN)
+#include "base/allocator/partition_allocator/page_allocator_internals_win.h"
+#elif defined(OS_POSIX)
+#include "base/allocator/partition_allocator/page_allocator_internals_posix.h"
+#elif defined(OS_FUCHSIA)
+#include "base/allocator/partition_allocator/page_allocator_internals_fuchsia.h"
+#else
+#error Platform not supported.
+#endif
+
+namespace base {
+
+namespace {
+
+LazyInstance<Lock>::Leaky g_reserve_lock = LAZY_INSTANCE_INITIALIZER;
+
+// We may reserve/release address space on different threads.
+Lock& GetReserveLock() {
+  return g_reserve_lock.Get();
+}
+
+std::atomic<size_t> g_total_mapped_address_space;
+
+// We only support a single block of reserved address space.
+void* s_reservation_address GUARDED_BY(GetReserveLock()) = nullptr;
+size_t s_reservation_size GUARDED_BY(GetReserveLock()) = 0;
+
+void* AllocPagesIncludingReserved(void* address,
+                                  size_t length,
+                                  PageAccessibilityConfiguration accessibility,
+                                  PageTag page_tag) {
+  void* ret = SystemAllocPages(address, length, accessibility, page_tag);
+  if (ret == nullptr) {
+    const bool cant_alloc_length = kHintIsAdvisory || address == nullptr;
+    if (cant_alloc_length) {
+      // The system cannot allocate |length| bytes. Release any reserved address
+      // space and try once more.
+      ReleaseReservation();
+      ret = SystemAllocPages(address, length, accessibility, page_tag);
+    }
+  }
+  return ret;
+}
+
+// Trims |base| to given |trim_length| and |alignment|.
+//
+// On failure, on Windows, this function returns nullptr and frees |base|.
+void* TrimMapping(void* base,
+                  size_t base_length,
+                  size_t trim_length,
+                  uintptr_t alignment,
+                  uintptr_t alignment_offset,
+                  PageAccessibilityConfiguration accessibility) {
+  PA_DCHECK(base_length >= trim_length);
+  PA_DCHECK(bits::IsPowerOfTwo(alignment));
+  PA_DCHECK(alignment_offset < alignment);
+  uintptr_t base_as_uintptr = reinterpret_cast<uintptr_t>(base);
+  uintptr_t new_base =
+      NextAlignedWithOffset(base_as_uintptr, alignment, alignment_offset);
+  PA_DCHECK(new_base >= base_as_uintptr);
+  size_t pre_slack = new_base - base_as_uintptr;
+  size_t post_slack = base_length - pre_slack - trim_length;
+  PA_DCHECK(base_length == trim_length || pre_slack || post_slack);
+  PA_DCHECK(pre_slack < base_length);
+  PA_DCHECK(post_slack < base_length);
+  return TrimMappingInternal(base, base_length, trim_length, accessibility,
+                             pre_slack, post_slack);
+}
+
+}  // namespace
+
+// Align |address| up to the closest, non-smaller address, that gives
+// |requested_offset| remainder modulo |alignment|.
+//
+// Examples for alignment=1024 and requested_offset=64:
+//   64 -> 64
+//   65 -> 1088
+//   1024 -> 1088
+//   1088 -> 1088
+//   1089 -> 2112
+//   2048 -> 2112
+uintptr_t NextAlignedWithOffset(uintptr_t address,
+                                uintptr_t alignment,
+                                uintptr_t requested_offset) {
+  PA_DCHECK(bits::IsPowerOfTwo(alignment));
+  PA_DCHECK(requested_offset < alignment);
+
+  uintptr_t actual_offset = address & (alignment - 1);
+  uintptr_t new_address;
+  if (actual_offset <= requested_offset)
+    new_address = address + requested_offset - actual_offset;
+  else
+    new_address = address + alignment + requested_offset - actual_offset;
+  PA_DCHECK(new_address >= address);
+  PA_DCHECK(new_address - address < alignment);
+  PA_DCHECK(new_address % alignment == requested_offset);
+
+  return new_address;
+}
+
+void* SystemAllocPages(void* hint,
+                       size_t length,
+                       PageAccessibilityConfiguration accessibility,
+                       PageTag page_tag) {
+  PA_DCHECK(!(length & PageAllocationGranularityOffsetMask()));
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(hint) &
+              PageAllocationGranularityOffsetMask()));
+  void* ptr = SystemAllocPagesInternal(hint, length, accessibility, page_tag);
+  if (ptr)
+    g_total_mapped_address_space.fetch_add(length, std::memory_order_relaxed);
+
+  return ptr;
+}
+
+void* AllocPages(void* address,
+                 size_t length,
+                 size_t align,
+                 PageAccessibilityConfiguration accessibility,
+                 PageTag page_tag) {
+  return AllocPagesWithAlignOffset(address, length, align, 0, accessibility,
+                                   page_tag);
+}
+
+void* AllocPagesWithAlignOffset(void* address,
+                                size_t length,
+                                size_t align,
+                                size_t align_offset,
+                                PageAccessibilityConfiguration accessibility,
+                                PageTag page_tag) {
+  PA_DCHECK(length >= PageAllocationGranularity());
+  PA_DCHECK(!(length & PageAllocationGranularityOffsetMask()));
+  PA_DCHECK(align >= PageAllocationGranularity());
+  // Alignment must be power of 2 for masking math to work.
+  PA_DCHECK(base::bits::IsPowerOfTwo(align));
+  PA_DCHECK(align_offset < align);
+  PA_DCHECK(!(align_offset & PageAllocationGranularityOffsetMask()));
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(address) &
+              PageAllocationGranularityOffsetMask()));
+  uintptr_t align_offset_mask = align - 1;
+  uintptr_t align_base_mask = ~align_offset_mask;
+  PA_DCHECK(address == nullptr || (reinterpret_cast<uintptr_t>(address) &
+                                   align_offset_mask) == align_offset);
+
+  // If the client passed null as the address, choose a good one.
+  if (address == nullptr) {
+    address = GetRandomPageBase();
+    address = reinterpret_cast<void*>(
+        (reinterpret_cast<uintptr_t>(address) & align_base_mask) +
+        align_offset);
+  }
+
+  // First try to force an exact-size, aligned allocation from our random base.
+#if defined(ARCH_CPU_32_BITS)
+  // On 32 bit systems, first try one random aligned address, and then try an
+  // aligned address derived from the value of |ret|.
+  constexpr int kExactSizeTries = 2;
+#else
+  // On 64 bit systems, try 3 random aligned addresses.
+  constexpr int kExactSizeTries = 3;
+#endif
+
+  for (int i = 0; i < kExactSizeTries; ++i) {
+    void* ret =
+        AllocPagesIncludingReserved(address, length, accessibility, page_tag);
+    if (ret != nullptr) {
+      // If the alignment is to our liking, we're done.
+      if ((reinterpret_cast<uintptr_t>(ret) & align_offset_mask) ==
+          align_offset)
+        return ret;
+      // Free the memory and try again.
+      FreePages(ret, length);
+    } else {
+      // |ret| is null; if this try was unhinted, we're OOM.
+      if (kHintIsAdvisory || address == nullptr)
+        return nullptr;
+    }
+
+#if defined(ARCH_CPU_32_BITS)
+    // For small address spaces, try the first aligned address >= |ret|. Note
+    // |ret| may be null, in which case |address| becomes null. If
+    // |align_offset| is non-zero, this calculation may get us not the first,
+    // but the next matching address.
+    address = reinterpret_cast<void*>(
+        ((reinterpret_cast<uintptr_t>(ret) + align_offset_mask) &
+         align_base_mask) +
+        align_offset);
+#else  // defined(ARCH_CPU_64_BITS)
+    // Keep trying random addresses on systems that have a large address space.
+    address = GetRandomPageBase();
+    address = reinterpret_cast<void*>(NextAlignedWithOffset(
+        reinterpret_cast<uintptr_t>(address), align, align_offset));
+#endif
+  }
+
+  // Make a larger allocation so we can force alignment.
+  size_t try_length = length + (align - PageAllocationGranularity());
+  PA_CHECK(try_length >= length);
+  void* ret;
+
+  do {
+    // Continue randomizing only on POSIX.
+    address = kHintIsAdvisory ? GetRandomPageBase() : nullptr;
+    ret = AllocPagesIncludingReserved(address, try_length, accessibility,
+                                      page_tag);
+    // The retries are for Windows, where a race can steal our mapping on
+    // resize.
+  } while (ret != nullptr &&
+           (ret = TrimMapping(ret, try_length, length, align, align_offset,
+                              accessibility)) == nullptr);
+
+  return ret;
+}
+
+void FreePages(void* address, size_t length) {
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(address) &
+              PageAllocationGranularityOffsetMask()));
+  PA_DCHECK(!(length & PageAllocationGranularityOffsetMask()));
+  FreePagesInternal(address, length);
+  PA_DCHECK(g_total_mapped_address_space.load(std::memory_order_relaxed) > 0);
+  g_total_mapped_address_space.fetch_sub(length, std::memory_order_relaxed);
+}
+
+bool TrySetSystemPagesAccess(void* address,
+                             size_t length,
+                             PageAccessibilityConfiguration accessibility) {
+  PA_DCHECK(!(length & SystemPageOffsetMask()));
+  return TrySetSystemPagesAccessInternal(address, length, accessibility);
+}
+
+void SetSystemPagesAccess(void* address,
+                          size_t length,
+                          PageAccessibilityConfiguration accessibility) {
+  PA_DCHECK(!(length & SystemPageOffsetMask()));
+  SetSystemPagesAccessInternal(address, length, accessibility);
+}
+
+void DecommitSystemPages(
+    void* address,
+    size_t length,
+    PageAccessibilityDisposition accessibility_disposition) {
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(address) & SystemPageOffsetMask()));
+  PA_DCHECK(!(length & SystemPageOffsetMask()));
+  DecommitSystemPagesInternal(address, length, accessibility_disposition);
+}
+
+void RecommitSystemPages(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(address) & SystemPageOffsetMask()));
+  PA_DCHECK(!(length & SystemPageOffsetMask()));
+  PA_DCHECK(accessibility != PageInaccessible);
+  RecommitSystemPagesInternal(address, length, accessibility,
+                              accessibility_disposition);
+}
+
+bool TryRecommitSystemPages(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // Duplicated because we want errors to be reported at a lower level in the
+  // crashing case.
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(address) & SystemPageOffsetMask()));
+  PA_DCHECK(!(length & SystemPageOffsetMask()));
+  PA_DCHECK(accessibility != PageInaccessible);
+  return TryRecommitSystemPagesInternal(address, length, accessibility,
+                                        accessibility_disposition);
+}
+
+void DiscardSystemPages(void* address, size_t length) {
+  PA_DCHECK(!(length & SystemPageOffsetMask()));
+  DiscardSystemPagesInternal(address, length);
+}
+
+bool ReserveAddressSpace(size_t size) {
+  // To avoid deadlock, call only SystemAllocPages.
+  AutoLock guard(GetReserveLock());
+  if (s_reservation_address == nullptr) {
+    void* mem =
+        SystemAllocPages(nullptr, size, PageInaccessible, PageTag::kChromium);
+    if (mem != nullptr) {
+      // We guarantee this alignment when reserving address space.
+      PA_DCHECK(!(reinterpret_cast<uintptr_t>(mem) &
+                  PageAllocationGranularityOffsetMask()));
+      s_reservation_address = mem;
+      s_reservation_size = size;
+      return true;
+    }
+  }
+  return false;
+}
+
+bool ReleaseReservation() {
+  // To avoid deadlock, call only FreePages.
+  AutoLock guard(GetReserveLock());
+  if (!s_reservation_address)
+    return false;
+
+  FreePages(s_reservation_address, s_reservation_size);
+  s_reservation_address = nullptr;
+  s_reservation_size = 0;
+  return true;
+}
+
+bool HasReservationForTesting() {
+  AutoLock guard(GetReserveLock());
+  return s_reservation_address != nullptr;
+}
+
+uint32_t GetAllocPageErrorCode() {
+  return s_allocPageErrorCode;
+}
+
+size_t GetTotalMappedSize() {
+  return g_total_mapped_address_space;
+}
+
+}  // namespace base

src/base/allocator/partition_allocator/page_allocator.h

@@ -0,0 +1,276 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_H_
+
+#include <stdint.h>
+
+#include <cstddef>
+
+#include "base/allocator/partition_allocator/page_allocator_constants.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "build/build_config.h"
+
+namespace base {
+
+enum PageAccessibilityConfiguration {
+  PageInaccessible,
+  PageRead,
+  PageReadWrite,
+  // This flag is mapped to PageReadWrite on systems that
+  // don't support MTE.
+  PageReadWriteTagged,
+  // This flag is mapped to PageReadExecute on systems
+  // that don't support Arm's BTI.
+  PageReadExecuteProtected,
+  PageReadExecute,
+  // This flag is deprecated and will go away soon.
+  // TODO(bbudge) Remove this as soon as V8 doesn't need RWX pages.
+  PageReadWriteExecute,
+};
+
+// Use for De/RecommitSystemPages API.
+enum PageAccessibilityDisposition {
+  // Enforces permission update (Decommit will set to PageInaccessible;
+  // Recommit will set to whatever was requested, other than PageInaccessible).
+  PageUpdatePermissions,
+  // Will not update permissions, if the platform supports that (POSIX & Fuchsia
+  // only).
+  PageKeepPermissionsIfPossible,
+};
+
+// macOS supports tagged memory regions, to help in debugging. On Android,
+// these tags are used to name anonymous mappings.
+enum class PageTag {
+  kFirst = 240,           // Minimum tag value.
+  kBlinkGC = 252,         // Blink GC pages.
+  kPartitionAlloc = 253,  // PartitionAlloc, no matter the partition.
+  kChromium = 254,        // Chromium page.
+  kV8 = 255,              // V8 heap pages.
+  kLast = kV8             // Maximum tag value.
+};
+
+BASE_EXPORT uintptr_t NextAlignedWithOffset(uintptr_t ptr,
+                                            uintptr_t alignment,
+                                            uintptr_t requested_offset);
+
+// Allocate one or more pages.
+//
+// The requested |address| is just a hint; the actual address returned may
+// differ. The returned address will be aligned to |align_offset| modulo |align|
+// bytes.
+//
+// |length|, |align| and |align_offset| are in bytes, and must be a multiple of
+// |PageAllocationGranularity()|. |length| and |align| must be non-zero.
+// |align_offset| must be less than |align|. |align| must be a power of two.
+//
+// If |address| is null, then a suitable and randomized address will be chosen
+// automatically.
+//
+// |accessibility| controls the permission of the allocated pages.
+// PageInaccessible means uncommitted.
+//
+// |page_tag| is used on some platforms to identify the source of the
+// allocation. Use PageTag::kChromium as a catch-all category.
+//
+// This call will return null if the allocation cannot be satisfied.
+BASE_EXPORT void* AllocPages(void* address,
+                             size_t length,
+                             size_t align,
+                             PageAccessibilityConfiguration accessibility,
+                             PageTag page_tag);
+BASE_EXPORT void* AllocPagesWithAlignOffset(
+    void* address,
+    size_t length,
+    size_t align,
+    size_t align_offset,
+    PageAccessibilityConfiguration page_accessibility,
+    PageTag page_tag);
+
+// Free one or more pages starting at |address| and continuing for |length|
+// bytes.
+//
+// |address| and |length| must match a previous call to |AllocPages|. Therefore,
+// |address| must be aligned to |PageAllocationGranularity()| bytes, and
+// |length| must be a multiple of |PageAllocationGranularity()|.
+BASE_EXPORT void FreePages(void* address, size_t length);
+
+// Mark one or more system pages, starting at |address| with the given
+// |page_accessibility|. |length| must be a multiple of |SystemPageSize()|
+// bytes.
+//
+// Returns true if the permission change succeeded. In most cases you must
+// |CHECK| the result.
+BASE_EXPORT WARN_UNUSED_RESULT bool TrySetSystemPagesAccess(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration page_accessibility);
+
+// Mark one or more system pages, starting at |address| with the given
+// |page_accessibility|. |length| must be a multiple of |SystemPageSize()|
+// bytes.
+//
+// Performs a CHECK that the operation succeeds.
+BASE_EXPORT void SetSystemPagesAccess(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration page_accessibility);
+
+// Decommit one or more system pages starting at |address| and continuing for
+// |length| bytes. |address| and |length| must be aligned to a system page
+// boundary.
+//
+// |accessibility_disposition| allows to specify whether the pages should be
+// made inaccessible (PageUpdatePermissions), or left as is
+// (PageKeepPermissionsIfPossible, POSIX & Fuchsia only). The latter should only
+// be used as an optimization if you really know what you're doing.
+// TODO(bartekn): Ideally, all callers should use PageUpdatePermissions,
+// for better security, but that may lead to a perf regression. Tracked at
+// http://crbug.com/766882.
+//
+// Decommitted means that physical resources (RAM or swap) backing the allocated
+// virtual address range may be released back to the system, but the address
+// space is still allocated to the process (possibly using up page table entries
+// or other accounting resources). There is no guarantee that the pages are
+// zeroed, see |DecommittedMemoryIsAlwaysZeroed()| for such a guarantee. Unless
+// PageKeepPermissionsIfPossible disposition is used, any access to a
+// decommitted region of memory is an error and will generate a fault.
+//
+// This operation is not atomic on all platforms.
+//
+// Note: "Committed memory" is a Windows Memory Subsystem concept that ensures
+// processes will not fault when touching a committed memory region. There is
+// no analogue in the POSIX & Fuchsia memory API where virtual memory pages are
+// best-effort allocated resources on the first touch. If PageUpdatePermissions
+// disposition is used, this API behaves in a platform-agnostic way by
+// simulating the Windows "decommit" state by both discarding the region
+// (allowing the OS to avoid swap operations) *and* changing the page
+// protections so accesses fault.
+//
+// This API will crash if the operation cannot be performed.
+BASE_EXPORT void DecommitSystemPages(
+    void* address,
+    size_t length,
+    PageAccessibilityDisposition accessibility_disposition);
+
+// Whether decommitted memory is guaranteed to be zeroed when it is
+// recommitted. Do not assume that this will not change over time.
+constexpr BASE_EXPORT bool DecommittedMemoryIsAlwaysZeroed() {
+#if defined(OS_APPLE)
+  return false;
+#else
+  return true;
+#endif
+}
+
+// Recommit one or more system pages, starting at |address| and continuing for
+// |length| bytes with the given |page_accessibility| (must not be
+// PageInaccsessible). |address| and |length| must be aligned to a system page
+// boundary.
+//
+// |accessibility_disposition| allows to specify whether the page permissions
+// should be set to |page_accessibility| (PageUpdatePermissions), or left as is
+// (PageKeepPermissionsIfPossible, POSIX & Fuchsia only). The latter can only be
+// used if the pages were previously accessible and decommitted with
+// PageKeepPermissionsIfPossible. It is ok, however, to recommit with
+// PageUpdatePermissions even if pages were decommitted with
+// PageKeepPermissionsIfPossible (merely losing an optimization).
+//
+// This operation is not atomic on all platforms.
+//
+// This API will crash if the operation cannot be performed.
+BASE_EXPORT void RecommitSystemPages(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration page_accessibility,
+    PageAccessibilityDisposition accessibility_disposition);
+
+// Like RecommitSystemPages(), but returns false instead of crashing.
+BASE_EXPORT bool TryRecommitSystemPages(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration page_accessibility,
+    PageAccessibilityDisposition accessibility_disposition) WARN_UNUSED_RESULT;
+
+// Discard one or more system pages starting at |address| and continuing for
+// |length| bytes. |length| must be a multiple of |SystemPageSize()|.
+//
+// Discarding is a hint to the system that the page is no longer required. The
+// hint may:
+//   - Do nothing.
+//   - Discard the page immediately, freeing up physical pages.
+//   - Discard the page at some time in the future in response to memory
+//   pressure.
+//
+// Only committed pages should be discarded. Discarding a page does not decommit
+// it, and it is valid to discard an already-discarded page. A read or write to
+// a discarded page will not fault.
+//
+// Reading from a discarded page may return the original page content, or a page
+// full of zeroes.
+//
+// Writing to a discarded page is the only guaranteed way to tell the system
+// that the page is required again. Once written to, the content of the page is
+// guaranteed stable once more. After being written to, the page content may be
+// based on the original page content, or a page of zeroes.
+BASE_EXPORT void DiscardSystemPages(void* address, size_t length);
+
+// Rounds up |address| to the next multiple of |SystemPageSize()|. Returns
+// 0 for an |address| of 0.
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+RoundUpToSystemPage(uintptr_t address) {
+  return (address + SystemPageOffsetMask()) & SystemPageBaseMask();
+}
+
+// Rounds down |address| to the previous multiple of |SystemPageSize()|. Returns
+// 0 for an |address| of 0.
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+RoundDownToSystemPage(uintptr_t address) {
+  return address & SystemPageBaseMask();
+}
+
+// Rounds up |address| to the next multiple of |PageAllocationGranularity()|.
+// Returns 0 for an |address| of 0.
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+RoundUpToPageAllocationGranularity(uintptr_t address) {
+  return (address + PageAllocationGranularityOffsetMask()) &
+         PageAllocationGranularityBaseMask();
+}
+
+// Rounds down |address| to the previous multiple of
+// |PageAllocationGranularity()|. Returns 0 for an |address| of 0.
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE uintptr_t
+RoundDownToPageAllocationGranularity(uintptr_t address) {
+  return address & PageAllocationGranularityBaseMask();
+}
+
+// Reserves (at least) |size| bytes of address space, aligned to
+// |PageAllocationGranularity()|. This can be called early on to make it more
+// likely that large allocations will succeed. Returns true if the reservation
+// succeeded, false if the reservation failed or a reservation was already made.
+BASE_EXPORT bool ReserveAddressSpace(size_t size);
+
+// Releases any reserved address space. |AllocPages| calls this automatically on
+// an allocation failure. External allocators may also call this on failure.
+//
+// Returns true when an existing reservation was released.
+BASE_EXPORT bool ReleaseReservation();
+
+// Returns true if there is currently an address space reservation.
+BASE_EXPORT bool HasReservationForTesting();
+
+// Returns |errno| (POSIX) or the result of |GetLastError| (Windows) when |mmap|
+// (POSIX) or |VirtualAlloc| (Windows) fails.
+BASE_EXPORT uint32_t GetAllocPageErrorCode();
+
+// Returns the total amount of mapped pages from all clients of
+// PageAllocator. These pages may or may not be committed. This is mostly useful
+// to assess address space pressure.
+BASE_EXPORT size_t GetTotalMappedSize();
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_H_

src/base/allocator/partition_allocator/page_allocator_constants.h

@@ -0,0 +1,117 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_CONSTANTS_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_CONSTANTS_H_
+
+#include <stddef.h>
+
+#include "base/compiler_specific.h"
+#include "build/build_config.h"
+
+#if defined(OS_APPLE)
+
+#include <mach/vm_page_size.h>
+
+// Although page allocator constants are not constexpr, they are run-time
+// constant. Because the underlying variables they access, such as vm_page_size,
+// are not marked const, the compiler normally has no way to know that they
+// don’t change and must obtain their values whenever it can't prove that they
+// haven't been modified, even if they had already been obtained previously.
+// Attaching __attribute__((const)) to these declarations allows these redundant
+// accesses to be omitted under optimization such as common subexpression
+// elimination.
+#define PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR __attribute__((const))
+
+#else
+
+// When defined, page size constants are fixed at compile time. When not
+// defined, they may vary at run time.
+#define PAGE_ALLOCATOR_CONSTANTS_ARE_CONSTEXPR 1
+
+// Use this macro to declare a function as constexpr or not based on whether
+// PAGE_ALLOCATOR_CONSTANTS_ARE_CONSTEXPR is defined.
+#define PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR constexpr
+
+#endif
+
+namespace {
+
+#if !defined(OS_APPLE)
+
+constexpr ALWAYS_INLINE int PageAllocationGranularityShift() {
+#if defined(OS_WIN) || defined(ARCH_CPU_PPC64)
+  // Modern ppc64 systems support 4kB (shift = 12) and 64kB (shift = 16) page
+  // sizes.  Since 64kB is the de facto standard on the platform and binaries
+  // compiled for 64kB are likely to work on 4kB systems, 64kB is a good choice
+  // here.
+  return 16;  // 64kB
+#elif defined(_MIPS_ARCH_LOONGSON)
+  return 14;  // 16kB
+#else
+  return 12;  // 4kB
+#endif
+}
+
+#endif
+
+}  // namespace
+
+namespace base {
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+PageAllocationGranularity() {
+#if defined(OS_APPLE)
+  return vm_page_size;
+#else
+  return 1 << PageAllocationGranularityShift();
+#endif
+}
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+PageAllocationGranularityOffsetMask() {
+  return PageAllocationGranularity() - 1;
+}
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+PageAllocationGranularityBaseMask() {
+  return ~PageAllocationGranularityOffsetMask();
+}
+
+#if !defined(OS_APPLE)
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+SystemPageShift() {
+#if defined(OS_WIN)
+  return 12;  // 4096=1<<12
+#else
+  return PageAllocationGranularityShift();
+#endif
+}
+#endif
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+SystemPageSize() {
+#if !defined(OS_APPLE)
+  return 1 << SystemPageShift();
+#else
+  return PageAllocationGranularity();
+#endif
+}
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+SystemPageOffsetMask() {
+  return SystemPageSize() - 1;
+}
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+SystemPageBaseMask() {
+  return ~SystemPageOffsetMask();
+}
+
+static constexpr size_t kPageMetadataShift = 5;  // 32 bytes per partition page.
+static constexpr size_t kPageMetadataSize = 1 << kPageMetadataShift;
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_CONSTANTS_H_

src/base/allocator/partition_allocator/page_allocator_internal.h

@@ -0,0 +1,17 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNAL_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNAL_H_
+
+namespace base {
+
+void* SystemAllocPages(void* hint,
+                       size_t length,
+                       PageAccessibilityConfiguration accessibility,
+                       PageTag page_tag);
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNAL_H_

src/base/allocator/partition_allocator/page_allocator_internals_fuchsia.h

@@ -0,0 +1,228 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// This file implements memory allocation primitives for PageAllocator using
+// Fuchsia's VMOs (Virtual Memory Objects). VMO API is documented in
+// https://fuchsia.dev/fuchsia-src/zircon/objects/vm_object . A VMO is a kernel
+// object that corresponds to a set of memory pages. VMO pages may be mapped
+// to an address space. The code below creates VMOs for each memory allocations
+// and maps them to the default address space of the current process.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_
+
+#include <lib/zx/vmar.h>
+#include <lib/zx/vmo.h>
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/fuchsia/fuchsia_logging.h"
+#include "base/notreached.h"
+
+namespace base {
+
+namespace {
+
+// Returns VMO name for a PageTag.
+const char* PageTagToName(PageTag tag) {
+  switch (tag) {
+    case PageTag::kBlinkGC:
+      return "cr_blink_gc";
+    case PageTag::kPartitionAlloc:
+      return "cr_partition_alloc";
+    case PageTag::kChromium:
+      return "cr_chromium";
+    case PageTag::kV8:
+      return "cr_v8";
+    default:
+      PA_DCHECK(false);
+      return "";
+  }
+}
+
+zx_vm_option_t PageAccessibilityToZxVmOptions(
+    PageAccessibilityConfiguration accessibility) {
+  switch (accessibility) {
+    case PageRead:
+      return ZX_VM_PERM_READ;
+    case PageReadWrite:
+    case PageReadWriteTagged:
+      return ZX_VM_PERM_READ | ZX_VM_PERM_WRITE;
+    case PageReadExecuteProtected:
+    case PageReadExecute:
+      return ZX_VM_PERM_READ | ZX_VM_PERM_EXECUTE;
+    case PageReadWriteExecute:
+      return ZX_VM_PERM_READ | ZX_VM_PERM_WRITE | ZX_VM_PERM_EXECUTE;
+    default:
+      NOTREACHED();
+      FALLTHROUGH;
+    case PageInaccessible:
+      return 0;
+  }
+}
+
+}  // namespace
+
+// zx_vmar_map() will fail if the VMO cannot be mapped at |vmar_offset|, i.e.
+// |hint| is not advisory.
+constexpr bool kHintIsAdvisory = false;
+
+std::atomic<int32_t> s_allocPageErrorCode{0};
+
+void* SystemAllocPagesInternal(void* hint,
+                               size_t length,
+                               PageAccessibilityConfiguration accessibility,
+                               PageTag page_tag) {
+  zx::vmo vmo;
+  zx_status_t status = zx::vmo::create(length, 0, &vmo);
+  if (status != ZX_OK) {
+    ZX_DLOG(INFO, status) << "zx_vmo_create";
+    return nullptr;
+  }
+
+  const char* vmo_name = PageTagToName(page_tag);
+  status = vmo.set_property(ZX_PROP_NAME, vmo_name, strlen(vmo_name));
+
+  // VMO names are used only for debugging, so failure to set a name is not
+  // fatal.
+  ZX_DCHECK(status == ZX_OK, status);
+
+  if (page_tag == PageTag::kV8) {
+    // V8 uses JIT. Call zx_vmo_replace_as_executable() to allow code execution
+    // in the new VMO.
+    status = vmo.replace_as_executable(zx::resource(), &vmo);
+    if (status != ZX_OK) {
+      ZX_DLOG(INFO, status) << "zx_vmo_replace_as_executable";
+      return nullptr;
+    }
+  }
+
+  zx_vm_option_t options = PageAccessibilityToZxVmOptions(accessibility);
+
+  uint64_t vmar_offset = 0;
+  if (hint) {
+    vmar_offset = reinterpret_cast<uint64_t>(hint);
+    options |= ZX_VM_SPECIFIC;
+  }
+
+  uint64_t address;
+  status =
+      zx::vmar::root_self()->map(options, vmar_offset, vmo,
+                                 /*vmo_offset=*/0, length, &address);
+  if (status != ZX_OK) {
+    // map() is expected to fail if |hint| is set to an already-in-use location.
+    if (!hint) {
+      ZX_DLOG(ERROR, status) << "zx_vmar_map";
+    }
+    return nullptr;
+  }
+
+  return reinterpret_cast<void*>(address);
+}
+
+void* TrimMappingInternal(void* base,
+                          size_t base_length,
+                          size_t trim_length,
+                          PageAccessibilityConfiguration accessibility,
+                          size_t pre_slack,
+                          size_t post_slack) {
+  PA_DCHECK(base_length == trim_length + pre_slack + post_slack);
+
+  uint64_t base_address = reinterpret_cast<uint64_t>(base);
+
+  // Unmap head if necessary.
+  if (pre_slack) {
+    zx_status_t status = zx::vmar::root_self()->unmap(base_address, pre_slack);
+    ZX_CHECK(status == ZX_OK, status);
+  }
+
+  // Unmap tail if necessary.
+  if (post_slack) {
+    zx_status_t status = zx::vmar::root_self()->unmap(
+        base_address + pre_slack + trim_length, post_slack);
+    ZX_CHECK(status == ZX_OK, status);
+  }
+
+  return reinterpret_cast<void*>(base_address + pre_slack);
+}
+
+bool TrySetSystemPagesAccessInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility) {
+  zx_status_t status = zx::vmar::root_self()->protect(
+      PageAccessibilityToZxVmOptions(accessibility),
+      reinterpret_cast<uint64_t>(address), length);
+  return status == ZX_OK;
+}
+
+void SetSystemPagesAccessInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility) {
+  zx_status_t status = zx::vmar::root_self()->protect(
+      PageAccessibilityToZxVmOptions(accessibility),
+      reinterpret_cast<uint64_t>(address), length);
+  ZX_CHECK(status == ZX_OK, status);
+}
+
+void FreePagesInternal(void* address, size_t length) {
+  uint64_t address_int = reinterpret_cast<uint64_t>(address);
+  zx_status_t status = zx::vmar::root_self()->unmap(address_int, length);
+  ZX_CHECK(status == ZX_OK, status);
+}
+
+void DiscardSystemPagesInternal(void* address, size_t length) {
+  // TODO(https://crbug.com/1022062): Mark pages as discardable, rather than
+  // forcibly de-committing them immediately, when Fuchsia supports it.
+  uint64_t address_int = reinterpret_cast<uint64_t>(address);
+  zx_status_t status = zx::vmar::root_self()->op_range(
+      ZX_VMO_OP_DECOMMIT, address_int, length, nullptr, 0);
+  ZX_CHECK(status == ZX_OK, status);
+}
+
+void DecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityDisposition accessibility_disposition) {
+  if (accessibility_disposition == PageUpdatePermissions) {
+    SetSystemPagesAccess(address, length, PageInaccessible);
+  }
+
+  // TODO(https://crbug.com/1022062): Review whether this implementation is
+  // still appropriate once DiscardSystemPagesInternal() migrates to a "lazy"
+  // discardable API.
+  DiscardSystemPagesInternal(address, length);
+}
+
+void RecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // On Fuchsia systems, the caller needs to simply read the memory to recommit
+  // it. However, if decommit changed the permissions, recommit has to change
+  // them back.
+  if (accessibility_disposition == PageUpdatePermissions) {
+    SetSystemPagesAccess(address, length, accessibility);
+  }
+}
+
+bool TryRecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // On Fuchsia systems, the caller needs to simply read the memory to recommit
+  // it. However, if decommit changed the permissions, recommit has to change
+  // them back.
+  if (accessibility_disposition == PageUpdatePermissions) {
+    return TrySetSystemPagesAccess(address, length, accessibility);
+  }
+  return true;
+}
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_FUCHSIA_H_

src/base/allocator/partition_allocator/page_allocator_internals_posix.cc

@@ -0,0 +1,62 @@
+// Copyright (c) 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/cpu.h"
+#include "base/notreached.h"
+
+#include <sys/mman.h>
+
+// PROT_BTI requests a page that supports BTI landing pads.
+#define PROT_BTI 0x10
+// PROT_MTE requests a page that's suitable for memory tagging.
+#define PROT_MTE 0x20
+
+namespace base {
+
+// Two helper functions to detect whether we can safely use PROT_BTI
+// and PROT_MTE (static CPU triggers a -Wexit-time-destructors warning.)
+static bool HasCPUBranchIdentification() {
+#if defined(ARCH_CPU_ARM_FAMILY)
+  CPU cpu = CPU::CreateNoAllocation();
+  return cpu.has_bti();
+#else
+  return false;
+#endif
+}
+
+static bool HasCPUMemoryTaggingExtension() {
+#if defined(ARCH_CPU_ARM_FAMILY)
+  CPU cpu = CPU::CreateNoAllocation();
+  return cpu.has_mte();
+#else
+  return false;
+#endif
+}
+
+int GetAccessFlags(PageAccessibilityConfiguration accessibility) {
+  static const bool has_bti = HasCPUBranchIdentification();
+  static const bool has_mte = HasCPUMemoryTaggingExtension();
+  switch (accessibility) {
+    case PageRead:
+      return PROT_READ;
+    case PageReadWrite:
+      return PROT_READ | PROT_WRITE;
+    case PageReadWriteTagged:
+      return PROT_READ | PROT_WRITE | (has_mte ? PROT_MTE : 0u);
+    case PageReadExecuteProtected:
+      return PROT_READ | PROT_EXEC | (has_bti ? PROT_BTI : 0u);
+    case PageReadExecute:
+      return PROT_READ | PROT_EXEC;
+    case PageReadWriteExecute:
+      return PROT_READ | PROT_WRITE | PROT_EXEC;
+    default:
+      NOTREACHED();
+      FALLTHROUGH;
+    case PageInaccessible:
+      return PROT_NONE;
+  }
+}
+
+}  // namespace base

src/base/allocator/partition_allocator/page_allocator_internals_posix.h

@@ -0,0 +1,350 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_POSIX_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_POSIX_H_
+
+#include <errno.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <algorithm>
+
+#include "base/allocator/partition_allocator/oom.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/dcheck_is_on.h"
+#include "base/posix/eintr_wrapper.h"
+#include "build/build_config.h"
+
+#if defined(OS_APPLE)
+#include "base/mac/foundation_util.h"
+#include "base/mac/mac_util.h"
+#include "base/mac/scoped_cftyperef.h"
+
+#include <Availability.h>
+#include <Security/Security.h>
+#include <mach/mach.h>
+#endif
+#if defined(OS_ANDROID)
+#include <sys/prctl.h>
+#endif
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
+#include <sys/resource.h>
+#endif
+
+#include "base/allocator/partition_allocator/page_allocator.h"
+
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+#if defined(OS_APPLE)
+
+// SecTaskGetCodeSignStatus is marked as unavailable on macOS, although it’s
+// available on iOS and other Apple operating systems. It is, in fact, present
+// on the system since macOS 10.12.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wavailability"
+uint32_t SecTaskGetCodeSignStatus(SecTaskRef task)
+#if __MAC_OS_X_VERSION_MIN_REQUIRED < __MAC_10_12
+    // When redeclaring something previously declared as unavailable, the
+    // weak_import attribute won’t be applied unless manually set.
+    __attribute__((weak_import))
+#endif  // DT < 10.12
+    API_AVAILABLE(macos(10.12));
+#pragma clang diagnostic pop
+
+#endif  // OS_APPLE
+
+namespace base {
+
+namespace {
+
+#if defined(OS_ANDROID)
+const char* PageTagToName(PageTag tag) {
+  // Important: All the names should be string literals. As per prctl.h in
+  // //third_party/android_ndk the kernel keeps a pointer to the name instead
+  // of copying it.
+  //
+  // Having the name in .rodata ensures that the pointer remains valid as
+  // long as the mapping is alive.
+  switch (tag) {
+    case PageTag::kBlinkGC:
+      return "blink_gc";
+    case PageTag::kPartitionAlloc:
+      return "partition_alloc";
+    case PageTag::kChromium:
+      return "chromium";
+    case PageTag::kV8:
+      return "v8";
+    default:
+      PA_DCHECK(false);
+      return "";
+  }
+}
+#endif  // defined(OS_ANDROID)
+
+#if defined(OS_APPLE)
+// Tests whether the version of macOS supports the MAP_JIT flag and if the
+// current process is signed with the hardened runtime and the allow-jit
+// entitlement, returning whether MAP_JIT should be used to allocate regions
+// that will contain JIT-compiled executable code.
+bool UseMapJit() {
+  if (!mac::IsAtLeastOS10_14()) {
+    // MAP_JIT existed before macOS 10.14, but had somewhat different semantics.
+    // Only one MAP_JIT region was permitted per process, but calling code here
+    // will very likely require more than one such region. Since MAP_JIT is not
+    // strictly necessary to write code to a region and then execute it on these
+    // older OSes, don’t use it at all.
+    return false;
+  }
+
+  // Until determining that the hardened runtime is enabled, early returns will
+  // return true, so that MAP_JIT will be used. This is important on arm64,
+  // which only allows pages to be simultaneously writable and executable when
+  // in a region allocated with MAP_JIT, regardless of code signing options. On
+  // arm64, an attempt to set a non-MAP_JIT page as simultaneously writable and
+  // executable fails with EPERM. Although this is not enforced on x86_64,
+  // MAP_JIT is harmless in that case.
+
+  ScopedCFTypeRef<SecTaskRef> task(SecTaskCreateFromSelf(kCFAllocatorDefault));
+  if (!task) {
+    return true;
+  }
+
+  uint32_t flags = SecTaskGetCodeSignStatus(task);
+  if (!(flags & kSecCodeSignatureRuntime)) {
+    // The hardened runtime is not enabled. Note that kSecCodeSignatureRuntime
+    // == CS_RUNTIME.
+    return true;
+  }
+
+  // The hardened runtime is enabled. From this point on, early returns must
+  // return false, indicating that MAP_JIT is not to be used. It’s an error
+  // (EINVAL) to use MAP_JIT with the hardened runtime unless the JIT
+  // entitlement is specified.
+
+  ScopedCFTypeRef<CFTypeRef> jit_entitlement(SecTaskCopyValueForEntitlement(
+      task.get(), CFSTR("com.apple.security.cs.allow-jit"), nullptr));
+  if (!jit_entitlement)
+    return false;
+
+  return mac::CFCast<CFBooleanRef>(jit_entitlement.get()) == kCFBooleanTrue;
+}
+#endif  // defined(OS_APPLE)
+
+}  // namespace
+
+// |mmap| uses a nearby address if the hint address is blocked.
+constexpr bool kHintIsAdvisory = true;
+std::atomic<int32_t> s_allocPageErrorCode{0};
+
+int GetAccessFlags(PageAccessibilityConfiguration accessibility);
+
+void* SystemAllocPagesInternal(void* hint,
+                               size_t length,
+                               PageAccessibilityConfiguration accessibility,
+                               PageTag page_tag) {
+#if defined(OS_APPLE)
+  // Use a custom tag to make it easier to distinguish Partition Alloc regions
+  // in vmmap(1). Tags between 240-255 are supported.
+  PA_DCHECK(PageTag::kFirst <= page_tag);
+  PA_DCHECK(PageTag::kLast >= page_tag);
+  int fd = VM_MAKE_TAG(static_cast<int>(page_tag));
+#else
+  int fd = -1;
+#endif
+
+  int access_flag = GetAccessFlags(accessibility);
+  int map_flags = MAP_ANONYMOUS | MAP_PRIVATE;
+
+#if defined(OS_APPLE)
+  // On macOS 10.14 and higher, executables that are code signed with the
+  // "runtime" option cannot execute writable memory by default. They can opt
+  // into this capability by specifying the "com.apple.security.cs.allow-jit"
+  // code signing entitlement and allocating the region with the MAP_JIT flag.
+  static const bool kUseMapJit = UseMapJit();
+  if (page_tag == PageTag::kV8 && kUseMapJit) {
+    map_flags |= MAP_JIT;
+  }
+#endif
+
+  void* ret = mmap(hint, length, access_flag, map_flags, fd, 0);
+  if (ret == MAP_FAILED) {
+    s_allocPageErrorCode = errno;
+    ret = nullptr;
+  }
+
+#if defined(OS_ANDROID)
+  // On Android, anonymous mappings can have a name attached to them. This is
+  // useful for debugging, and double-checking memory attribution.
+  if (ret) {
+    // No error checking on purpose, testing only.
+    prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ret, length,
+          PageTagToName(page_tag));
+  }
+#endif
+
+  return ret;
+}
+
+bool TrySetSystemPagesAccessInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility) {
+  return 0 ==
+         HANDLE_EINTR(mprotect(address, length, GetAccessFlags(accessibility)));
+}
+
+void SetSystemPagesAccessInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility) {
+  int access_flags = GetAccessFlags(accessibility);
+  const int ret = HANDLE_EINTR(mprotect(address, length, access_flags));
+
+  // On Linux, man mprotect(2) states that ENOMEM is returned when (1) internal
+  // kernel data structures cannot be allocated, (2) the address range is
+  // invalid, or (3) this would split an existing mapping in a way that would
+  // exceed the maximum number of allowed mappings.
+  //
+  // Neither are very likely, but we still get a lot of crashes here. This is
+  // because setrlimit(RLIMIT_DATA)'s limit is checked and enforced here, if the
+  // access flags match a "data" mapping, which in our case would be MAP_PRIVATE
+  // | MAP_ANONYMOUS, and PROT_WRITE. see the call to may_expand_vm() in
+  // mm/mprotect.c in the kernel for details.
+  //
+  // In this case, we are almost certainly bumping into the sandbox limit, mark
+  // the crash as OOM. See SandboxLinux::LimitAddressSpace() for details.
+  if (ret == -1 && errno == ENOMEM && (access_flags & PROT_WRITE))
+    OOM_CRASH(length);
+
+  PA_PCHECK(0 == ret);
+}
+
+void FreePagesInternal(void* address, size_t length) {
+  PA_PCHECK(0 == munmap(address, length));
+}
+
+void* TrimMappingInternal(void* base,
+                          size_t base_length,
+                          size_t trim_length,
+                          PageAccessibilityConfiguration accessibility,
+                          size_t pre_slack,
+                          size_t post_slack) {
+  void* ret = base;
+  // We can resize the allocation run. Release unneeded memory before and after
+  // the aligned range.
+  if (pre_slack) {
+    FreePages(base, pre_slack);
+    ret = reinterpret_cast<char*>(base) + pre_slack;
+  }
+  if (post_slack) {
+    FreePages(reinterpret_cast<char*>(ret) + trim_length, post_slack);
+  }
+  return ret;
+}
+
+void DecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // In POSIX, there is no decommit concept. Discarding is an effective way of
+  // implementing the Windows semantics where the OS is allowed to not swap the
+  // pages in the region.
+  DiscardSystemPages(address, length);
+
+  bool change_permissions = accessibility_disposition == PageUpdatePermissions;
+#if DCHECK_IS_ON()
+  // This is not guaranteed, show that we're serious.
+  //
+  // More specifically, several callers have had issues with assuming that
+  // memory is zeroed, this would hopefully make these bugs more visible.  We
+  // don't memset() everything, because ranges can be very large, and doing it
+  // over the entire range could make Chrome unusable with DCHECK_IS_ON().
+  //
+  // Only do it when we are about to change the permissions, since we don't know
+  // the previous permissions, and cannot restore them.
+  if (!DecommittedMemoryIsAlwaysZeroed() && change_permissions) {
+    // Memory may not be writable.
+    size_t size = std::min(length, 2 * SystemPageSize());
+    PA_CHECK(mprotect(address, size, PROT_WRITE) == 0);
+    memset(address, 0xcc, size);
+  }
+#endif
+
+  // Make pages inaccessible, unless the caller requested to keep permissions.
+  //
+  // Note, there is a small window between these calls when the pages can be
+  // incorrectly touched and brought back to memory. Not ideal, but doing those
+  // operations in the opposite order resulted in PMF regression on Mac (see
+  // crbug.com/1153021).
+  if (change_permissions) {
+    SetSystemPagesAccess(address, length, PageInaccessible);
+  }
+}
+
+void RecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // On POSIX systems, the caller needs to simply read the memory to recommit
+  // it. However, if decommit changed the permissions, recommit has to change
+  // them back.
+  if (accessibility_disposition == PageUpdatePermissions) {
+    SetSystemPagesAccess(address, length, accessibility);
+  }
+
+#if defined(OS_APPLE)
+  // On macOS, to update accounting, we need to make another syscall. For more
+  // details, see https://crbug.com/823915.
+  madvise(address, length, MADV_FREE_REUSE);
+#endif
+}
+
+bool TryRecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // On POSIX systems, the caller needs to simply read the memory to recommit
+  // it. However, if decommit changed the permissions, recommit has to change
+  // them back.
+  if (accessibility_disposition == PageUpdatePermissions) {
+    bool ok = TrySetSystemPagesAccess(address, length, accessibility);
+    if (!ok)
+      return false;
+  }
+
+#if defined(OS_APPLE)
+  // On macOS, to update accounting, we need to make another syscall. For more
+  // details, see https://crbug.com/823915.
+  madvise(address, length, MADV_FREE_REUSE);
+#endif
+
+  return true;
+}
+
+void DiscardSystemPagesInternal(void* address, size_t length) {
+#if defined(OS_APPLE)
+  int ret = madvise(address, length, MADV_FREE_REUSABLE);
+  if (ret) {
+    // MADV_FREE_REUSABLE sometimes fails, so fall back to MADV_DONTNEED.
+    ret = madvise(address, length, MADV_DONTNEED);
+  }
+  PA_PCHECK(ret == 0);
+#else
+  // We have experimented with other flags, but with suboptimal results.
+  //
+  // MADV_FREE (Linux): Makes our memory measurements less predictable;
+  // performance benefits unclear.
+  //
+  // Therefore, we just do the simple thing: MADV_DONTNEED.
+  PA_PCHECK(0 == madvise(address, length, MADV_DONTNEED));
+#endif
+}
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_POSIX_H_

src/base/allocator/partition_allocator/page_allocator_internals_win.h

@@ -0,0 +1,165 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_WIN_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_WIN_H_
+
+#include "base/allocator/partition_allocator/oom.h"
+#include "base/allocator/partition_allocator/page_allocator_internal.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/notreached.h"
+
+namespace base {
+
+// |VirtualAlloc| will fail if allocation at the hint address is blocked.
+constexpr bool kHintIsAdvisory = false;
+std::atomic<int32_t> s_allocPageErrorCode{ERROR_SUCCESS};
+
+int GetAccessFlags(PageAccessibilityConfiguration accessibility) {
+  switch (accessibility) {
+    case PageRead:
+      return PAGE_READONLY;
+    case PageReadWrite:
+    case PageReadWriteTagged:
+      return PAGE_READWRITE;
+    case PageReadExecute:
+    case PageReadExecuteProtected:
+      return PAGE_EXECUTE_READ;
+    case PageReadWriteExecute:
+      return PAGE_EXECUTE_READWRITE;
+    default:
+      NOTREACHED();
+      FALLTHROUGH;
+    case PageInaccessible:
+      return PAGE_NOACCESS;
+  }
+}
+
+void* SystemAllocPagesInternal(void* hint,
+                               size_t length,
+                               PageAccessibilityConfiguration accessibility,
+                               PageTag page_tag) {
+  DWORD access_flag = GetAccessFlags(accessibility);
+  const DWORD type_flags = (accessibility != PageInaccessible)
+                               ? (MEM_RESERVE | MEM_COMMIT)
+                               : MEM_RESERVE;
+  void* ret = VirtualAlloc(hint, length, type_flags, access_flag);
+  if (ret == nullptr) {
+    s_allocPageErrorCode = GetLastError();
+  }
+  return ret;
+}
+
+void* TrimMappingInternal(void* base,
+                          size_t base_length,
+                          size_t trim_length,
+                          PageAccessibilityConfiguration accessibility,
+                          size_t pre_slack,
+                          size_t post_slack) {
+  void* ret = base;
+  if (pre_slack || post_slack) {
+    // We cannot resize the allocation run. Free it and retry at the aligned
+    // address within the freed range.
+    ret = reinterpret_cast<char*>(base) + pre_slack;
+    FreePages(base, base_length);
+    ret = SystemAllocPages(ret, trim_length, accessibility, PageTag::kChromium);
+  }
+  return ret;
+}
+
+bool TrySetSystemPagesAccessInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility) {
+  if (accessibility == PageInaccessible)
+    return VirtualFree(address, length, MEM_DECOMMIT) != 0;
+  return nullptr != VirtualAlloc(address, length, MEM_COMMIT,
+                                 GetAccessFlags(accessibility));
+}
+
+void SetSystemPagesAccessInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility) {
+  if (accessibility == PageInaccessible) {
+    if (!VirtualFree(address, length, MEM_DECOMMIT)) {
+      // We check `GetLastError` for `ERROR_SUCCESS` here so that in a crash
+      // report we get the error number.
+      PA_CHECK(static_cast<uint32_t>(ERROR_SUCCESS) == GetLastError());
+    }
+  } else {
+    if (!VirtualAlloc(address, length, MEM_COMMIT,
+                      GetAccessFlags(accessibility))) {
+      int32_t error = GetLastError();
+      if (error == ERROR_COMMITMENT_LIMIT)
+        OOM_CRASH(length);
+      // We check `GetLastError` for `ERROR_SUCCESS` here so that in a crash
+      // report we get the error number.
+      PA_CHECK(ERROR_SUCCESS == error);
+    }
+  }
+}
+
+void FreePagesInternal(void* address, size_t length) {
+  PA_CHECK(VirtualFree(address, 0, MEM_RELEASE));
+}
+
+void DecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // Ignore accessibility_disposition, because decommitting is equivalent to
+  // making pages inaccessible.
+  SetSystemPagesAccess(address, length, PageInaccessible);
+}
+
+void RecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // Ignore accessibility_disposition, because decommitting is equivalent to
+  // making pages inaccessible.
+  SetSystemPagesAccess(address, length, accessibility);
+}
+
+bool TryRecommitSystemPagesInternal(
+    void* address,
+    size_t length,
+    PageAccessibilityConfiguration accessibility,
+    PageAccessibilityDisposition accessibility_disposition) {
+  // Ignore accessibility_disposition, because decommitting is equivalent to
+  // making pages inaccessible.
+  return TrySetSystemPagesAccess(address, length, accessibility);
+}
+
+void DiscardSystemPagesInternal(void* address, size_t length) {
+  // On Windows, discarded pages are not returned to the system immediately and
+  // not guaranteed to be zeroed when returned to the application.
+  using DiscardVirtualMemoryFunction =
+      DWORD(WINAPI*)(PVOID virtualAddress, SIZE_T size);
+  static DiscardVirtualMemoryFunction discard_virtual_memory =
+      reinterpret_cast<DiscardVirtualMemoryFunction>(-1);
+  if (discard_virtual_memory ==
+      reinterpret_cast<DiscardVirtualMemoryFunction>(-1))
+    discard_virtual_memory =
+        reinterpret_cast<DiscardVirtualMemoryFunction>(GetProcAddress(
+            GetModuleHandle(L"Kernel32.dll"), "DiscardVirtualMemory"));
+  // Use DiscardVirtualMemory when available because it releases faster than
+  // MEM_RESET.
+  DWORD ret = 1;
+  if (discard_virtual_memory) {
+    ret = discard_virtual_memory(address, length);
+  }
+  // DiscardVirtualMemory is buggy in Win10 SP0, so fall back to MEM_RESET on
+  // failure.
+  if (ret) {
+    void* ptr = VirtualAlloc(address, length, MEM_RESET, PAGE_READWRITE);
+    PA_CHECK(ptr);
+  }
+}
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_INTERNALS_WIN_H_

src/base/allocator/partition_allocator/partition_address_space.cc

@@ -0,0 +1,118 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_address_space.h"
+
+#include <array>
+
+#include "base/allocator/partition_allocator/address_pool_manager.h"
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/allocator/partition_allocator/page_allocator_internal.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+#include "base/bits.h"
+
+namespace base {
+
+namespace internal {
+
+#if defined(PA_HAS_64_BITS_POINTERS)
+
+constexpr std::array<size_t, 2> PartitionAddressSpace::kPoolSizes;
+
+uintptr_t PartitionAddressSpace::reserved_base_address_ = 0;
+// Before PartitionAddressSpace::Init(), no allocation are allocated from a
+// reserved address space. Therefore, set *_pool_base_address_ initially to
+// k*PoolOffsetMask, so that PartitionAddressSpace::IsIn*Pool() always returns
+// false.
+uintptr_t PartitionAddressSpace::non_brp_pool_base_address_ =
+    kNonBRPPoolOffsetMask;
+uintptr_t PartitionAddressSpace::brp_pool_base_address_ = kBRPPoolOffsetMask;
+
+pool_handle PartitionAddressSpace::non_brp_pool_ = 0;
+pool_handle PartitionAddressSpace::brp_pool_ = 0;
+
+void PartitionAddressSpace::Init() {
+  if (IsInitialized())
+    return;
+
+  GigaCageProperties properties = CalculateGigaCageProperties(kPoolSizes);
+
+  reserved_base_address_ =
+      reinterpret_cast<uintptr_t>(AllocPagesWithAlignOffset(
+          nullptr, properties.size, properties.alignment,
+          properties.alignment_offset, base::PageInaccessible,
+          PageTag::kPartitionAlloc));
+  PA_CHECK(reserved_base_address_);
+
+  uintptr_t current = reserved_base_address_;
+
+  non_brp_pool_base_address_ = current;
+  PA_DCHECK(!(non_brp_pool_base_address_ & (kNonBRPPoolSize - 1)));
+  non_brp_pool_ = internal::AddressPoolManager::GetInstance()->Add(
+      current, kNonBRPPoolSize);
+  PA_DCHECK(non_brp_pool_);
+  PA_DCHECK(!IsInNonBRPPool(reinterpret_cast<void*>(current - 1)));
+  PA_DCHECK(IsInNonBRPPool(reinterpret_cast<void*>(current)));
+  current += kNonBRPPoolSize;
+  PA_DCHECK(IsInNonBRPPool(reinterpret_cast<void*>(current - 1)));
+  PA_DCHECK(!IsInNonBRPPool(reinterpret_cast<void*>(current)));
+
+  brp_pool_base_address_ = current;
+  PA_DCHECK(!(brp_pool_base_address_ & (kBRPPoolSize - 1)));
+  brp_pool_ =
+      internal::AddressPoolManager::GetInstance()->Add(current, kBRPPoolSize);
+  PA_DCHECK(brp_pool_);
+  PA_DCHECK(!IsInBRPPool(reinterpret_cast<void*>(current - 1)));
+  PA_DCHECK(IsInBRPPool(reinterpret_cast<void*>(current)));
+  current += kBRPPoolSize;
+  PA_DCHECK(IsInBRPPool(reinterpret_cast<void*>(current - 1)));
+  PA_DCHECK(!IsInBRPPool(reinterpret_cast<void*>(current)));
+
+#if PA_ALLOW_PCSCAN
+  // Reserve memory for PCScan quarantine card table.
+  void* requested_address = reinterpret_cast<void*>(brp_pool_base_address_);
+  char* actual_address = internal::AddressPoolManager::GetInstance()->Reserve(
+      brp_pool_, requested_address, kSuperPageSize);
+  PA_CHECK(requested_address == actual_address)
+      << "QuarantineCardTable is required to be allocated in the beginning of "
+         "the BRPPool";
+  SetSystemPagesAccess(actual_address, kSuperPageSize, PageInaccessible);
+#endif
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  // Allocate the BRP pool offset table in the BRP pool.
+  void* requested_offset_table_address = reinterpret_cast<void*>(
+      brp_pool_base_address_ + kBRPPoolSize - kBRPPoolOffsetTableSize);
+  void* actual_offset_table_address =
+      internal::AddressPoolManager::GetInstance()->Reserve(
+          brp_pool_, requested_offset_table_address, kBRPPoolOffsetTableSize);
+  PA_CHECK(requested_offset_table_address == actual_offset_table_address)
+      << "ReservationStartOffsetTable is required to be allocated in the end "
+         "of the BRPPool";
+  RecommitSystemPages(actual_offset_table_address, kBRPPoolOffsetTableSize,
+                      PageReadWrite, PageUpdatePermissions);
+#endif
+
+  PA_DCHECK(reserved_base_address_ + properties.size == current);
+}
+
+void PartitionAddressSpace::UninitForTesting() {
+  GigaCageProperties properties = CalculateGigaCageProperties(kPoolSizes);
+
+  FreePages(reinterpret_cast<void*>(reserved_base_address_), properties.size);
+  reserved_base_address_ = 0;
+  non_brp_pool_base_address_ = kNonBRPPoolOffsetMask;
+  brp_pool_base_address_ = kBRPPoolOffsetMask;
+  non_brp_pool_ = 0;
+  brp_pool_ = 0;
+  internal::AddressPoolManager::GetInstance()->ResetForTesting();
+}
+
+#endif  // defined(PA_HAS_64_BITS_POINTERS)
+
+}  // namespace internal
+
+}  // namespace base

src/base/allocator/partition_allocator/partition_address_space.h

@@ -0,0 +1,325 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ADDRESS_SPACE_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ADDRESS_SPACE_H_
+
+#include <algorithm>
+#include <array>
+#include <limits>
+
+#include "base/allocator/partition_allocator/address_pool_manager_types.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/base_export.h"
+#include "base/bits.h"
+#include "base/notreached.h"
+#include "base/partition_alloc_buildflags.h"
+#include "build/build_config.h"
+#include "build/buildflag.h"
+
+namespace base {
+
+namespace internal {
+
+// The feature is not applicable to 32-bit address space.
+#if defined(PA_HAS_64_BITS_POINTERS)
+
+struct GigaCageProperties {
+  size_t size;
+  size_t alignment;
+  size_t alignment_offset;
+};
+
+template <size_t N>
+GigaCageProperties CalculateGigaCageProperties(
+    const std::array<size_t, N>& pool_sizes) {
+  size_t size_sum = 0;
+  size_t alignment = 0;
+  size_t alignment_offset;
+  // The goal is to find properties such that each pool's start address is
+  // aligned to its own size. To achieve that, the largest pool will serve
+  // as an anchor (the first one, if there are more) and it'll be used to
+  // determine the core alignment. The sizes of pools before the anchor will
+  // determine the offset within the core alignment at which the GigaCage will
+  // start.
+  // If this algorithm doesn't find the proper alignment, it means such an
+  // alignment doesn't exist.
+  for (size_t pool_size : pool_sizes) {
+    PA_CHECK(bits::IsPowerOfTwo(pool_size));
+    if (pool_size > alignment) {
+      alignment = pool_size;
+      // This may underflow, leading to a very high value, so use modulo
+      // |alignment| to bring it down.
+      alignment_offset = (alignment - size_sum) & (alignment - 1);
+    }
+    size_sum += pool_size;
+  }
+  // Use PA_CHECK because we can't correctly proceed if any pool's start address
+  // isn't aligned to its own size. Exact initial value of |sample_address|
+  // doesn't matter as long as |address % alignment == alignment_offset|.
+  uintptr_t sample_address = alignment_offset + 7 * alignment;
+  for (size_t pool_size : pool_sizes) {
+    PA_CHECK(!(sample_address & (pool_size - 1)));
+    sample_address += pool_size;
+  }
+  return GigaCageProperties{size_sum, alignment, alignment_offset};
+}
+
+// Reserves address space for PartitionAllocator.
+class BASE_EXPORT PartitionAddressSpace {
+ public:
+  // BRP stands for BackupRefPtr. GigaCage is split into pools, one which
+  // supports BackupRefPtr and one that doesn't.
+  static ALWAYS_INLINE internal::pool_handle GetNonBRPPool() {
+    return non_brp_pool_;
+  }
+  static ALWAYS_INLINE internal::pool_handle GetBRPPool() { return brp_pool_; }
+
+  static ALWAYS_INLINE constexpr uintptr_t BRPPoolBaseMask() {
+    return kBRPPoolBaseMask;
+  }
+
+  static void Init();
+  static void UninitForTesting();
+
+  static ALWAYS_INLINE bool IsInitialized() {
+    if (reserved_base_address_) {
+      PA_DCHECK(non_brp_pool_ != 0);
+      PA_DCHECK(brp_pool_ != 0);
+      return true;
+    }
+
+    PA_DCHECK(non_brp_pool_ == 0);
+    PA_DCHECK(brp_pool_ == 0);
+    return false;
+  }
+
+  // Returns false for nullptr.
+  static ALWAYS_INLINE bool IsInNonBRPPool(const void* address) {
+    return (reinterpret_cast<uintptr_t>(address) & kNonBRPPoolBaseMask) ==
+           non_brp_pool_base_address_;
+  }
+  // Returns false for nullptr.
+  static ALWAYS_INLINE bool IsInBRPPool(const void* address) {
+    return (reinterpret_cast<uintptr_t>(address) & kBRPPoolBaseMask) ==
+           brp_pool_base_address_;
+  }
+
+  static ALWAYS_INLINE uintptr_t BRPPoolBase() {
+    return brp_pool_base_address_;
+  }
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  static ALWAYS_INLINE uintptr_t BRPPoolEnd() {
+    return brp_pool_base_address_ + kBRPPoolSize;
+  }
+
+  static ALWAYS_INLINE uintptr_t BRPPoolOffset(uintptr_t address) {
+    return address & kBRPPoolOffsetMask;
+  }
+
+  static uint16_t* ReservationOffsetTable() {
+    return reinterpret_cast<uint16_t*>(BRPPoolEnd() - kBRPPoolOffsetTableSize);
+  }
+
+  static uint16_t* ReservationOffsetPointer(uintptr_t address) {
+    PA_DCHECK(IsInBRPPool(reinterpret_cast<const void*>(address)));
+    size_t table_index = BRPPoolOffset(address) >> kSuperPageShift;
+    PA_DCHECK(table_index < (kBRPPoolSize >> kSuperPageShift));
+    return ReservationOffsetTable() + table_index;
+  }
+
+  static const uint16_t* EndOfReservationOffsetTable() {
+    return reinterpret_cast<uint16_t*>(reinterpret_cast<uintptr_t>(
+        ReservationOffsetTable() +
+        internal::PartitionAddressSpace::kBRPPoolOffsetTableActualSize));
+  }
+
+  static constexpr uint16_t kNotInDirectMap =
+      std::numeric_limits<uint16_t>::max();
+
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+
+  // PartitionAddressSpace is static_only class.
+  PartitionAddressSpace() = delete;
+  PartitionAddressSpace(const PartitionAddressSpace&) = delete;
+  void* operator new(size_t) = delete;
+  void* operator new(size_t, void*) = delete;
+
+ private:
+  // Partition Alloc Address Space
+  // Reserves 16GiB address space for one pool that supports BackupRefPtr and
+  // one that doesn't, 8GiB each.
+  // TODO(bartekn): Look into devices with 39-bit address space that have 256GiB
+  // user-mode space (most ARM64 Android devices as of 2021). Libraries loaded
+  // at random addresses may stand in the way of reserving a contiguous 24GiB
+  // region (even though we're requesting only 16GiB, AllocPages may under the
+  // covers reserve extra 8GiB to satisfy the alignment requirements).
+  //
+  // +----------------+ reserved_base_address_ (8GiB aligned)
+  // |    non-BRP     |     == non_brp_pool_base_address_
+  // |      pool      |
+  // +----------------+ reserved_base_address_ + 8GiB
+  // |      BRP       |     == brp_pool_base_address_
+  // |      pool      |
+  // +----------------+ reserved_base_address_ + 16GiB
+  //
+  // NOTE! On 64-bit systems with BackupRefPtr enabled, the non-BRP pool must
+  // precede the BRP pool. This is to prevent a pointer immediately past a
+  // non-GigaCage allocation from falling into the BRP pool, thus triggering
+  // BackupRefPtr mechanism and likely crashing.
+
+  static constexpr size_t kGigaBytes = 1024 * 1024 * 1024;
+
+  // Pool sizes have to be the power of two. Each pool will be aligned at its
+  // own size boundary.
+  //
+  // In theory, pools can be allocated separately in the address space. However,
+  // due to the above restriction to have BRP pool be preceded by another pool,
+  // better to have them occupy contiguous addresses. Therefore, care has to be
+  // taken when choosing sizes, if more than 2 pools are needed. For example,
+  // with sizes [8GiB,4GiB,8GiB], it'd be impossible to align each pool at its
+  // own size boundary while keeping them next to each other.
+  // CalculateGigaCageProperties() has non-debug run-time checks to ensure that.
+  static constexpr size_t kNonBRPPoolSize = 8 * kGigaBytes;
+  static constexpr size_t kBRPPoolSize = 8 * kGigaBytes;
+  static constexpr std::array<size_t, 2> kPoolSizes = {kNonBRPPoolSize,
+                                                       kBRPPoolSize};
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  // (For defined(PA_HAS_64_BITS_POINTERS))
+  // The last SuperPage inside NonBRPPool is used as a table to get the
+  // reservation start address when an address inside of BRP pool is given. Each
+  // entry of the table is prepared for each super page (inside BRP pool):
+  //
+  //  |<------ reserved size (SuperPageSize-aligned) ------>|
+  //  +----------+----------+-------------------+-----------+
+  //  |SuperPage0|SuperPage1|        ...        |SuperPage K|
+  //  +----------+----------+-------------------+-----------+
+  //
+  // the table entries for reserved SuperPages have the numbers of SuperPages
+  // between the reservation start and each reserved SuperPage:
+  // +----------+----------+--------------------+-----------+
+  // |Entry for |Entry for |         ...        |Entry for  |
+  // |SuperPage0|SuperPage1|                    |SuperPage K|
+  // +----------+----------+--------------------+-----------+
+  // |     0    |    1     |         ...        |      K    |
+  // +----------+----------+--------------------+-----------+
+  // 65535 is used as a special number: "not used for direct-map allocation".
+  //
+  // So when we have an address Z, ((Z >> SuperPageShift) - (the entry for Z))
+  // << SuperPageShift is the reservation start when allocating an address space
+  // which contains Z.
+
+  // The size of the table is (kBRPPoolSize / kSuperPageSize) * sizeof(each
+  // table entry). Since kBRPPoolSize / kSuperPageSize < MAX_UINT16, each
+  // table entry is uint16_t. So the size is AlignUp((kBRPPoolSize /
+  // kSuperPageSize) * sizeof(uint16_t), kSuperPageSize).
+  static constexpr size_t kBRPPoolOffsetTableActualSize =
+      (kBRPPoolSize >> kSuperPageShift) * sizeof(uint16_t);
+  // TODO(tasak): Use bits::AlignUp after making the function support constexpr.
+  static constexpr size_t kBRPPoolOffsetTableSize =
+      (kBRPPoolOffsetTableActualSize + kSuperPageSize - 1) & kSuperPageBaseMask;
+
+  static_assert(kBRPPoolOffsetTableSize == kSuperPageSize,
+                "kBRPPoolOffsetTableSize should be equal to kSuperPageSize, "
+                "because the table should be as small as possible.");
+  static_assert((kBRPPoolSize >> kSuperPageShift) < kNotInDirectMap,
+                "Offsets should be smaller than kNotInDirectMap.");
+#else
+  static constexpr size_t kBRPPoolOffsetTableSize = 0;
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+
+  static_assert(bits::IsPowerOfTwo(kNonBRPPoolSize) &&
+                    bits::IsPowerOfTwo(kBRPPoolSize),
+                "Each pool size should be a power of two.");
+
+  // Masks used to easy determine belonging to a pool.
+  static constexpr uintptr_t kNonBRPPoolOffsetMask =
+      static_cast<uintptr_t>(kNonBRPPoolSize) - 1;
+  static constexpr uintptr_t kNonBRPPoolBaseMask = ~kNonBRPPoolOffsetMask;
+  static constexpr uintptr_t kBRPPoolOffsetMask =
+      static_cast<uintptr_t>(kBRPPoolSize) - 1;
+  static constexpr uintptr_t kBRPPoolBaseMask = ~kBRPPoolOffsetMask;
+
+  // See the comment describing the address layout above.
+  static uintptr_t reserved_base_address_;
+  static uintptr_t non_brp_pool_base_address_;
+  static uintptr_t brp_pool_base_address_;
+
+  static internal::pool_handle non_brp_pool_;
+  static internal::pool_handle brp_pool_;
+};
+
+ALWAYS_INLINE internal::pool_handle GetNonBRPPool() {
+  return PartitionAddressSpace::GetNonBRPPool();
+}
+
+ALWAYS_INLINE internal::pool_handle GetBRPPool() {
+  return PartitionAddressSpace::GetBRPPool();
+}
+
+#endif  // defined(PA_HAS_64_BITS_POINTERS)
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT) && defined(PA_HAS_64_BITS_POINTERS)
+ALWAYS_INLINE constexpr uint16_t NotInDirectMapOffsetTag() {
+  return internal::PartitionAddressSpace::kNotInDirectMap;
+}
+
+ALWAYS_INLINE uint16_t* ReservationOffsetPointer(uintptr_t address) {
+  return internal::PartitionAddressSpace::ReservationOffsetPointer(address);
+}
+
+ALWAYS_INLINE const uint16_t* EndOfReservationOffsetTable() {
+  return internal::PartitionAddressSpace::EndOfReservationOffsetTable();
+}
+
+ALWAYS_INLINE uintptr_t GetReservationStart(void* address) {
+  PA_DCHECK(internal::PartitionAddressSpace::IsInBRPPool(address));
+  uintptr_t ptr_as_uintptr = reinterpret_cast<uintptr_t>(address);
+  uint16_t* offset_ptr =
+      internal::PartitionAddressSpace::ReservationOffsetPointer(ptr_as_uintptr);
+  PA_DCHECK(*offset_ptr != internal::NotInDirectMapOffsetTag());
+  uintptr_t reservation_start =
+      (ptr_as_uintptr & kSuperPageBaseMask) -
+      (static_cast<size_t>(*offset_ptr) << kSuperPageShift);
+  PA_DCHECK(internal::PartitionAddressSpace::IsInBRPPool(
+      reinterpret_cast<void*>(reservation_start)));
+  PA_DCHECK(*internal::PartitionAddressSpace::ReservationOffsetPointer(
+                reservation_start) == 0);
+  return reservation_start;
+}
+
+#endif  //  BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT) &&
+        //  defined(PA_HAS_64_BITS_POINTERS)
+
+}  // namespace internal
+
+#if defined(PA_HAS_64_BITS_POINTERS)
+// Returns false for nullptr.
+ALWAYS_INLINE bool IsManagedByPartitionAlloc(const void* address) {
+  // Currently even when BUILDFLAG(USE_BACKUP_REF_PTR) is off, BRP pool is used
+  // for non-BRP allocations, so we have to check both pools regardless of
+  // BUILDFLAG(USE_BACKUP_REF_PTR).
+  return internal::PartitionAddressSpace::IsInNonBRPPool(address) ||
+         internal::PartitionAddressSpace::IsInBRPPool(address);
+}
+
+// Returns false for nullptr.
+ALWAYS_INLINE bool IsManagedByPartitionAllocNonBRPPool(const void* address) {
+  return internal::PartitionAddressSpace::IsInNonBRPPool(address);
+}
+
+// Returns false for nullptr.
+ALWAYS_INLINE bool IsManagedByPartitionAllocBRPPool(const void* address) {
+  return internal::PartitionAddressSpace::IsInBRPPool(address);
+}
+#endif
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ADDRESS_SPACE_H_

src/base/allocator/partition_allocator/partition_alloc-inl.h

@@ -0,0 +1,68 @@
+// Copyright (c) 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_INL_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_INL_H_
+
+#include <cstring>
+
+#include "base/allocator/partition_allocator/partition_cookie.h"
+#include "base/allocator/partition_allocator/partition_ref_count.h"
+#include "base/allocator/partition_allocator/random.h"
+#include "base/partition_alloc_buildflags.h"
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
+// Prefetch *x into memory.
+#if defined(__clang__) || defined(COMPILER_GCC)
+#define PA_PREFETCH(x) __builtin_prefetch(x)
+#else
+#define PA_PREFETCH(x)
+#endif
+
+namespace base {
+
+namespace internal {
+// This is a `memset` that resists being optimized away. Adapted from
+// boringssl/src/crypto/mem.c. (Copying and pasting is bad, but //base can't
+// depend on //third_party, and this is small enough.)
+ALWAYS_INLINE void SecureMemset(void* ptr, uint8_t value, size_t size) {
+#if defined(OS_WIN)
+  if (value == 0) {
+    SecureZeroMemory(ptr, size);
+    return;
+  }
+#endif  // defined(OS_WIN)
+  memset(ptr, value, size);
+
+  // As best as we can tell, this is sufficient to break any optimisations that
+  // might try to eliminate "superfluous" memsets. If there's an easy way to
+  // detect memset_s, it would be better to use that.
+  __asm__ __volatile__("" : : "r"(ptr) : "memory");
+}
+
+// Returns true if we've hit the end of a random-length period. We don't want to
+// invoke `RandomValue` too often, because we call this function in a hot spot
+// (`Free`), and `RandomValue` incurs the cost of atomics.
+#if !DCHECK_IS_ON()
+ALWAYS_INLINE bool RandomPeriod() {
+  static thread_local uint8_t counter = 0;
+  if (UNLIKELY(counter == 0)) {
+    // It's OK to truncate this value.
+    counter = static_cast<uint8_t>(base::RandomValue());
+  }
+  // If `counter` is 0, this will wrap. That is intentional and OK.
+  counter--;
+  return counter == 0;
+}
+#endif
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_INL_H_

src/base/allocator/partition_allocator/partition_alloc.cc

@@ -0,0 +1,119 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_alloc.h"
+
+#include <string.h>
+
+#include <memory>
+
+#include "base/allocator/partition_allocator/address_pool_manager.h"
+#include "base/allocator/partition_allocator/memory_reclaimer.h"
+#include "base/allocator/partition_allocator/page_allocator_internal.h"
+#include "base/allocator/partition_allocator/partition_address_space.h"
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+#include "base/allocator/partition_allocator/partition_alloc_hooks.h"
+#include "base/allocator/partition_allocator/partition_direct_map_extent.h"
+#include "base/allocator/partition_allocator/partition_oom.h"
+#include "base/allocator/partition_allocator/partition_page.h"
+#include "base/allocator/partition_allocator/partition_root.h"
+#include "base/allocator/partition_allocator/partition_stats.h"
+#include "base/allocator/partition_allocator/starscan/pcscan.h"
+#include "base/partition_alloc_buildflags.h"
+
+namespace base {
+
+void PartitionAllocGlobalInit(OomFunction on_out_of_memory) {
+  // This is from page_allocator_constants.h and doesn't really fit here, but
+  // there isn't a centralized initialization function in page_allocator.cc, so
+  // there's no good place in that file to do a STATIC_ASSERT_OR_PA_CHECK.
+  STATIC_ASSERT_OR_PA_CHECK((SystemPageSize() & (SystemPageSize() - 1)) == 0,
+                            "SystemPageSize() must be power of 2");
+
+  // Two partition pages are used as guard / metadata page so make sure the
+  // super page size is bigger.
+  STATIC_ASSERT_OR_PA_CHECK(PartitionPageSize() * 4 <= kSuperPageSize,
+                            "ok super page size");
+  STATIC_ASSERT_OR_PA_CHECK(!(kSuperPageSize % PartitionPageSize()),
+                            "ok super page multiple");
+  // Four system pages gives us room to hack out a still-guard-paged piece
+  // of metadata in the middle of a guard partition page.
+  STATIC_ASSERT_OR_PA_CHECK(SystemPageSize() * 4 <= PartitionPageSize(),
+                            "ok partition page size");
+  STATIC_ASSERT_OR_PA_CHECK(!(PartitionPageSize() % SystemPageSize()),
+                            "ok partition page multiple");
+  static_assert(sizeof(internal::PartitionPage<internal::ThreadSafe>) <=
+                    kPageMetadataSize,
+                "PartitionPage should not be too big");
+  STATIC_ASSERT_OR_PA_CHECK(
+      kPageMetadataSize * NumPartitionPagesPerSuperPage() <= SystemPageSize(),
+      "page metadata fits in hole");
+
+  // Limit to prevent callers accidentally overflowing an int size.
+  STATIC_ASSERT_OR_PA_CHECK(
+      MaxDirectMapped() <= (1UL << 31) + DirectMapAllocationGranularity(),
+      "maximum direct mapped allocation");
+
+  // Check that some of our zanier calculations worked out as expected.
+  static_assert(kSmallestBucket == kAlignment, "generic smallest bucket");
+  static_assert(kMaxBucketed == 983040, "generic max bucketed");
+  STATIC_ASSERT_OR_PA_CHECK(
+      MaxSystemPagesPerSlotSpan() < (1 << 8),
+      "System pages per slot span must be less than 128.");
+
+  PA_DCHECK(on_out_of_memory);
+  internal::g_oom_handling_function = on_out_of_memory;
+}
+
+void PartitionAllocGlobalUninitForTesting() {
+  internal::PCScan::UninitForTesting();  // IN-TEST
+#if !BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+#if defined(PA_HAS_64_BITS_POINTERS)
+  internal::PartitionAddressSpace::UninitForTesting();
+#else
+  internal::AddressPoolManager::GetInstance()->ResetForTesting();
+#endif  // defined(PA_HAS_64_BITS_POINTERS)
+#endif  // !BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+  internal::g_oom_handling_function = nullptr;
+}
+
+namespace internal {
+
+template <bool thread_safe>
+PartitionAllocator<thread_safe>::~PartitionAllocator() {
+  PartitionAllocMemoryReclaimer::Instance()->UnregisterPartition(
+      &partition_root_);
+}
+
+template <bool thread_safe>
+void PartitionAllocator<thread_safe>::init(PartitionOptions opts) {
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+  PA_CHECK(opts.thread_cache == PartitionOptions::ThreadCache::kDisabled)
+      << "Cannot use a thread cache when PartitionAlloc is malloc().";
+#endif
+  partition_root_.Init(opts);
+  partition_root_.ConfigureLazyCommit();
+  PartitionAllocMemoryReclaimer::Instance()->RegisterPartition(
+      &partition_root_);
+}
+
+template PartitionAllocator<internal::ThreadSafe>::~PartitionAllocator();
+template void PartitionAllocator<internal::ThreadSafe>::init(PartitionOptions);
+template PartitionAllocator<internal::NotThreadSafe>::~PartitionAllocator();
+template void PartitionAllocator<internal::NotThreadSafe>::init(
+    PartitionOptions);
+
+#if DCHECK_IS_ON() && BUILDFLAG(USE_BACKUP_REF_PTR)
+void DCheckGetSlotOffsetIsZero(void* ptr) {
+  // Add kPartitionPastAllocationAdjustment, because PartitionAllocGetSlotStart
+  // will subtract it.
+  PA_DCHECK(PartitionAllocGetSlotStart(reinterpret_cast<char*>(ptr) +
+                                       kPartitionPastAllocationAdjustment) ==
+            ptr);
+}
+#endif
+
+}  // namespace internal
+
+}  // namespace base

src/base/allocator/partition_allocator/partition_alloc.h

@@ -0,0 +1,44 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_H_
+
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/allocator/partition_allocator/partition_oom.h"
+#include "base/allocator/partition_allocator/partition_root.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+
+namespace base {
+
+BASE_EXPORT void PartitionAllocGlobalInit(OomFunction on_out_of_memory);
+BASE_EXPORT void PartitionAllocGlobalUninitForTesting();
+
+namespace internal {
+template <bool thread_safe>
+struct BASE_EXPORT PartitionAllocator {
+  PartitionAllocator() = default;
+  ~PartitionAllocator();
+
+  void init(PartitionOptions);
+
+  ALWAYS_INLINE PartitionRoot<thread_safe>* root() { return &partition_root_; }
+  ALWAYS_INLINE const PartitionRoot<thread_safe>* root() const {
+    return &partition_root_;
+  }
+
+ private:
+  PartitionRoot<thread_safe> partition_root_;
+};
+
+}  // namespace internal
+
+using PartitionAllocator = internal::PartitionAllocator<internal::ThreadSafe>;
+using ThreadUnsafePartitionAllocator =
+    internal::PartitionAllocator<internal::NotThreadSafe>;
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_H_

src/base/allocator/partition_allocator/partition_alloc_check.h

@@ -0,0 +1,83 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CHECK_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CHECK_H_
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/page_allocator_constants.h"
+#include "base/check.h"
+#include "base/debug/alias.h"
+#include "base/immediate_crash.h"
+
+#define PA_STRINGIFY_IMPL(s) #s
+#define PA_STRINGIFY(s) PA_STRINGIFY_IMPL(s)
+
+// When PartitionAlloc is used as the default allocator, we cannot use the
+// regular (D)CHECK() macros, as they allocate internally. When an assertion is
+// triggered, they format strings, leading to reentrancy in the code, which none
+// of PartitionAlloc is designed to support (and especially not for error
+// paths).
+//
+// As a consequence:
+// - When PartitionAlloc is not malloc(), use the regular macros
+// - Otherwise, crash immediately. This provides worse error messages though.
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+// For official build discard log strings to reduce binary bloat.
+#if defined(OFFICIAL_BUILD) && defined(NDEBUG)
+// See base/check.h for implementation details.
+#define PA_CHECK(condition) \
+  UNLIKELY(!(condition)) ? IMMEDIATE_CRASH() : EAT_CHECK_STREAM_PARAMS()
+#else
+// PartitionAlloc uses async-signal-safe RawCheck() for error reporting.
+// Async-signal-safe functions are guaranteed to not allocate as otherwise they
+// could operate with inconsistent allocator state.
+#define PA_CHECK(condition)                                                \
+  UNLIKELY(!(condition))                                                   \
+  ? logging::RawCheck(                                                     \
+        __FILE__ "(" PA_STRINGIFY(__LINE__) ") Check failed: " #condition) \
+  : EAT_CHECK_STREAM_PARAMS()
+#endif  // defined(OFFICIAL_BUILD) && defined(NDEBUG)
+
+#if DCHECK_IS_ON()
+#define PA_DCHECK(condition) PA_CHECK(condition)
+#else
+#define PA_DCHECK(condition) EAT_CHECK_STREAM_PARAMS(!(condition))
+#endif  // DCHECK_IS_ON()
+
+#define PA_PCHECK(condition)    \
+  if (!(condition)) {           \
+    int error = errno;          \
+    base::debug::Alias(&error); \
+    IMMEDIATE_CRASH();          \
+  }
+
+#else
+#define PA_CHECK(condition) CHECK(condition)
+#define PA_DCHECK(condition) DCHECK(condition)
+#define PA_PCHECK(condition) PCHECK(condition)
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+#if defined(PAGE_ALLOCATOR_CONSTANTS_ARE_CONSTEXPR)
+
+// Use this macro to assert on things that are conditionally constexpr as
+// determined by PAGE_ALLOCATOR_CONSTANTS_ARE_CONSTEXPR or
+// PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR. Where fixed at compile time, this
+// is a static_assert. Where determined at run time, this is a PA_CHECK.
+// Therefore, this macro must only be used where both a static_assert and a
+// PA_CHECK would be viable, that is, within a function, and ideally a function
+// that executes only once, early in the program, such as during initialization.
+#define STATIC_ASSERT_OR_PA_CHECK(condition, message) \
+  static_assert(condition, message)
+
+#else
+
+#define STATIC_ASSERT_OR_PA_CHECK(condition, message) \
+  do {                                                \
+    PA_CHECK(condition) << (message);                 \
+  } while (false)
+
+#endif
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CHECK_H_

src/base/allocator/partition_allocator/partition_alloc_config.h

@@ -0,0 +1,93 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CONFIG_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CONFIG_H_
+
+#include "base/allocator/buildflags.h"
+#include "base/dcheck_is_on.h"
+#include "base/partition_alloc_buildflags.h"
+#include "build/build_config.h"
+
+// ARCH_CPU_64_BITS implies 64-bit instruction set, but not necessarily 64-bit
+// address space. The only known case where address space is 32-bit is NaCl, so
+// eliminate it explicitly. static_assert below ensures that others won't slip
+// through.
+#if defined(ARCH_CPU_64_BITS) && !defined(OS_NACL)
+#define PA_HAS_64_BITS_POINTERS
+static_assert(sizeof(void*) == 8, "");
+#else
+static_assert(sizeof(void*) != 8, "");
+#endif
+
+// BackupRefPtr and PCScan are incompatible, and due to its conservative nature,
+// it is 64 bits only.
+#if defined(PA_HAS_64_BITS_POINTERS) && !BUILDFLAG(USE_BACKUP_REF_PTR)
+#define PA_ALLOW_PCSCAN 1
+#else
+#define PA_ALLOW_PCSCAN 0
+#endif
+
+#if defined(PA_HAS_64_BITS_POINTERS) && \
+    (defined(__ARM_NEON) || defined(__ARM_NEON__)) && defined(__ARM_FP)
+#define PA_STARSCAN_NEON_SUPPORTED
+#endif
+
+#if defined(PA_HAS_64_BITS_POINTERS) && \
+    (defined(OS_LINUX) || defined(OS_ANDROID))
+// TODO(bikineev): Enable for ChromeOS.
+#define PA_STARSCAN_UFFD_WRITE_PROTECTOR_SUPPORTED
+#endif
+
+// POSIX is not only UNIX, e.g. macOS and other OSes. We do use Linux-specific
+// features such as futex(2).
+#if defined(OS_LINUX) || defined(OS_CHROMEOS) || defined(OS_ANDROID)
+#define PA_HAS_LINUX_KERNEL
+#endif
+
+// SpinningMutex uses either futex(2) on Linux, or a fast userspace "try"
+// operation, which is available on Windows.
+#if defined(PA_HAS_LINUX_KERNEL) || defined(OS_WIN)
+#define PA_HAS_SPINNING_MUTEX
+#endif
+
+// If set to 1, enables zeroing memory on Free() with roughly 1% probability.
+// This applies only to normal buckets, as direct-map allocations are always
+// decommitted.
+// TODO(bartekn): Re-enable once PartitionAlloc-Everywhere evaluation is done.
+#define PA_ZERO_RANDOMLY_ON_FREE 0
+
+// Need TLS support.
+#if defined(OS_POSIX) || defined(OS_WIN)
+#define PA_THREAD_CACHE_SUPPORTED
+#endif
+
+// Too expensive for official builds, as it adds cache misses to all
+// allocations. On the other hand, we want wide metrics coverage to get
+// realistic profiles.
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && !defined(OFFICIAL_BUILD)
+#define PA_THREAD_CACHE_ALLOC_STATS
+#endif
+
+// Optional statistics collection. Lightweight, contrary to the ones above,
+// hence enabled by default.
+#define PA_THREAD_CACHE_ENABLE_STATISTICS
+
+// Enable free list hardening as much as possible.
+//
+// Disabled on ARM64 Macs, as this crashes very early (crbug.com/1172236).
+// TODO(lizeb): Enable in as many configurations as possible.
+//
+// Disabled when putting refcount in the previous slot, which is what
+// PUT_REF_COUNT_IN_PREVIOUS_SLOT does. In this case the refcount overlaps with
+// the next pointer shadow for the smallest bucket.
+#if !(defined(OS_MAC) && defined(ARCH_CPU_ARM64)) && \
+    !BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+#define PA_HAS_FREELIST_HARDENING
+#endif
+
+// Specifies whether allocation extras need to be added.
+#define PA_EXTRAS_REQUIRED (DCHECK_IS_ON() || BUILDFLAG(USE_BACKUP_REF_PTR))
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CONFIG_H_

src/base/allocator/partition_allocator/partition_alloc_constants.h

@@ -0,0 +1,318 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CONSTANTS_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CONSTANTS_H_
+
+#include <limits.h>
+#include <cstddef>
+
+#include <algorithm>
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/page_allocator_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "build/build_config.h"
+
+#if defined(OS_APPLE)
+#include <mach/vm_page_size.h>
+#endif
+
+namespace base {
+
+// Underlying partition storage pages (`PartitionPage`s) are a power-of-2 size.
+// It is typical for a `PartitionPage` to be based on multiple system pages.
+// Most references to "page" refer to `PartitionPage`s.
+//
+// *Super pages* are the underlying system allocations we make. Super pages
+// contain multiple partition pages and include space for a small amount of
+// metadata per partition page.
+//
+// Inside super pages, we store *slot spans*. A slot span is a continguous range
+// of one or more `PartitionPage`s that stores allocations of the same size.
+// Slot span sizes are adjusted depending on the allocation size, to make sure
+// the packing does not lead to unused (wasted) space at the end of the last
+// system page of the span. For our current maximum slot span size of 64 KiB and
+// other constant values, we pack _all_ `PartitionRoot::Alloc` sizes perfectly
+// up against the end of a system page.
+
+#if defined(_MIPS_ARCH_LOONGSON)
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE int
+PartitionPageShift() {
+  return 16;  // 64 KiB
+}
+#elif defined(ARCH_CPU_PPC64)
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE int
+PartitionPageShift() {
+  return 18;  // 256 KiB
+}
+#elif defined(OS_APPLE)
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE int
+PartitionPageShift() {
+  return vm_page_shift + 2;
+}
+#else
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE int
+PartitionPageShift() {
+  return 14;  // 16 KiB
+}
+#endif
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+PartitionPageSize() {
+  return 1 << PartitionPageShift();
+}
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+PartitionPageOffsetMask() {
+  return PartitionPageSize() - 1;
+}
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+PartitionPageBaseMask() {
+  return ~PartitionPageOffsetMask();
+}
+// TODO: Should this be 1 if defined(_MIPS_ARCH_LOONGSON)?
+static const size_t kMaxPartitionPagesPerSlotSpan = 4;
+
+// To avoid fragmentation via never-used freelist entries, we hand out partition
+// freelist sections gradually, in units of the dominant system page size. What
+// we're actually doing is avoiding filling the full `PartitionPage` (16 KiB)
+// with freelist pointers right away. Writing freelist pointers will fault and
+// dirty a private page, which is very wasteful if we never actually store
+// objects there.
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+NumSystemPagesPerPartitionPage() {
+  return PartitionPageSize() / SystemPageSize();
+}
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+MaxSystemPagesPerSlotSpan() {
+  return NumSystemPagesPerPartitionPage() * kMaxPartitionPagesPerSlotSpan;
+}
+
+// We reserve virtual address space in 2 MiB chunks (aligned to 2 MiB as well).
+// These chunks are called *super pages*. We do this so that we can store
+// metadata in the first few pages of each 2 MiB-aligned section. This makes
+// freeing memory very fast. 2 MiB size & alignment were chosen, because this
+// virtual address block represents a full but single page table allocation on
+// ARM, ia32 and x64, which may be slightly more performance&memory efficient.
+// (Note, these super pages are backed by 4 KiB system pages and have nothing to
+// do with OS concept of "huge pages"/"large pages", even though the size
+// coincides.)
+//
+// The layout of the super page is as follows. The sizes below are the same for
+// 32- and 64-bit platforms.
+//
+//     +-----------------------+
+//     | Guard page (4 KiB)    |
+//     | Metadata page (4 KiB) |
+//     | Guard pages (8 KiB)   |
+//     | QuarantineBitmaps     |
+//     | Slot span             |
+//     | Slot span             |
+//     | ...                   |
+//     | Slot span             |
+//     | Guard pages (16 KiB)  |
+//     +-----------------------+
+//
+// QuarantineBitmaps are inserted for partitions that may have PCScan enabled.
+//
+// If refcount_at_end_allocation is enabled, RefcountBitmap(4KiB) is inserted
+// after the Metadata page for BackupRefPtr. The guard pages after the bitmap
+// will be 4KiB.
+//
+//...
+//     | Metadata page (4 KiB) |
+//     | RefcountBitmap (4 KiB)|
+//     | Guard pages (4 KiB)   |
+//...
+//
+// Each slot span is a contiguous range of one or more `PartitionPage`s. Note
+// that slot spans of different sizes may co-exist with one super page. Even
+// slot spans of the same size may support different slot sizes. However, all
+// slots within a span have to be of the same size.
+//
+// The metadata page has the following format. Note that the `PartitionPage`
+// that is not at the head of a slot span is "unused" (by most part, it only
+// stores the offset from the head page). In other words, the metadata for the
+// slot span is stored only in the first `PartitionPage` of the slot span.
+// Metadata accesses to other `PartitionPage`s are redirected to the first
+// `PartitionPage`.
+//
+//     +---------------------------------------------+
+//     | SuperPageExtentEntry (32 B)                 |
+//     | PartitionPage of slot span 1 (32 B, used)   |
+//     | PartitionPage of slot span 1 (32 B, unused) |
+//     | PartitionPage of slot span 1 (32 B, unused) |
+//     | PartitionPage of slot span 2 (32 B, used)   |
+//     | PartitionPage of slot span 3 (32 B, used)   |
+//     | ...                                         |
+//     | PartitionPage of slot span N (32 B, used)   |
+//     | PartitionPage of slot span N (32 B, unused) |
+//     | PartitionPage of slot span N (32 B, unused) |
+//     +---------------------------------------------+
+//
+// A direct-mapped page has an identical layout at the beginning to fake it
+// looking like a super page:
+//
+//     +---------------------------------+
+//     | Guard page (4 KiB)              |
+//     | Metadata page (4 KiB)           |
+//     | Guard pages (8 KiB)             |
+//     | Direct mapped object            |
+//     | Guard page (4 KiB, 32-bit only) |
+//     +---------------------------------+
+//
+// A direct-mapped page's metadata page has the following layout (on 64 bit
+// architectures. On 32 bit ones, the layout is identical, some sizes are
+// different due to smaller pointers.):
+//
+//     +----------------------------------+
+//     | SuperPageExtentEntry (32 B)      |
+//     | PartitionPage (32 B)             |
+//     | PartitionBucket (40 B)           |
+//     | PartitionDirectMapExtent (32 B)  |
+//     +----------------------------------+
+//
+// See |PartitionDirectMapMetadata| for details.
+
+static const size_t kSuperPageShift = 21;  // 2 MiB
+static const size_t kSuperPageSize = 1 << kSuperPageShift;
+static const size_t kSuperPageAlignment = kSuperPageSize;
+static const size_t kSuperPageOffsetMask = kSuperPageAlignment - 1;
+static const size_t kSuperPageBaseMask = ~kSuperPageOffsetMask;
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+NumPartitionPagesPerSuperPage() {
+  return kSuperPageSize / PartitionPageSize();
+}
+
+#if defined(PA_HAS_64_BITS_POINTERS)
+// In 64-bit mode, the direct map allocation granularity is super page size,
+// because this is the reservation granularit of the GigaCage.
+constexpr ALWAYS_INLINE size_t DirectMapAllocationGranularity() {
+  return kSuperPageSize;
+}
+#else
+// In 32-bit mode, address space is space is a scarce resource. Use the system
+// allocation granularity, which is the lowest possible address space allocation
+// unit. However, don't go below partition page size, so that GigaCage bitmaps
+// don't get too large. See kBytesPer1BitOfBRPPoolBitmap.
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+DirectMapAllocationGranularity() {
+  return std::max(PageAllocationGranularity(), PartitionPageSize());
+}
+#endif  // defined(PA_HAS_64_BITS_POINTERS)
+
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+DirectMapAllocationGranularityOffsetMask() {
+  return DirectMapAllocationGranularity() - 1;
+}
+
+// Alignment has two constraints:
+// - Alignment requirement for scalar types: alignof(std::max_align_t)
+// - Alignment requirement for operator new().
+//
+// The two are separate on Windows 64 bits, where the first one is 8 bytes, and
+// the second one 16. We could technically return something different for
+// malloc() and operator new(), but this would complicate things, and most of
+// our allocations are presumably coming from operator new() anyway.
+//
+// __STDCPP_DEFAULT_NEW_ALIGNMENT__ is C++17. As such, it is not defined on all
+// platforms, as Chrome's requirement is C++14 as of 2020.
+#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
+static constexpr size_t kAlignment =
+    std::max(alignof(max_align_t), __STDCPP_DEFAULT_NEW_ALIGNMENT__);
+#else
+static constexpr size_t kAlignment = alignof(max_align_t);
+#endif
+static_assert(kAlignment <= 16,
+              "PartitionAlloc doesn't support a fundamental alignment larger "
+              "than 16 bytes.");
+
+// The "order" of an allocation is closely related to the power-of-1 size of the
+// allocation. More precisely, the order is the bit index of the
+// most-significant-bit in the allocation size, where the bit numbers starts at
+// index 1 for the least-significant-bit.
+//
+// In terms of allocation sizes, order 0 covers 0, order 1 covers 1, order 2
+// covers 2->3, order 3 covers 4->7, order 4 covers 8->15.
+
+// PartitionAlloc should return memory properly aligned for any type, to behave
+// properly as a generic allocator. This is not strictly required as long as
+// types are explicitly allocated with PartitionAlloc, but is to use it as a
+// malloc() implementation, and generally to match malloc()'s behavior.
+//
+// In practice, this means 8 bytes alignment on 32 bit architectures, and 16
+// bytes on 64 bit ones.
+static const size_t kMinBucketedOrder =
+    kAlignment == 16 ? 5 : 4;  // 2^(order - 1), that is 16 or 8.
+// The largest bucketed order is 1 << (20 - 1), storing [512 KiB, 1 MiB):
+static const size_t kMaxBucketedOrder = 20;
+static const size_t kNumBucketedOrders =
+    (kMaxBucketedOrder - kMinBucketedOrder) + 1;
+// Eight buckets per order (for the higher orders), e.g. order 8 is 128, 144,
+// 160, ..., 240:
+static const size_t kNumBucketsPerOrderBits = 3;
+static const size_t kNumBucketsPerOrder = 1 << kNumBucketsPerOrderBits;
+static const size_t kNumBuckets = kNumBucketedOrders * kNumBucketsPerOrder;
+static const size_t kSmallestBucket = 1 << (kMinBucketedOrder - 1);
+static const size_t kMaxBucketSpacing =
+    1 << ((kMaxBucketedOrder - 1) - kNumBucketsPerOrderBits);
+static const size_t kMaxBucketed =
+    (1 << (kMaxBucketedOrder - 1)) +
+    ((kNumBucketsPerOrder - 1) * kMaxBucketSpacing);
+// Limit when downsizing a direct mapping using `realloc`:
+static const size_t kMinDirectMappedDownsize = kMaxBucketed + 1;
+// Intentionally set to less than 2GiB to make sure that a 2GiB allocation
+// fails. This is a security choice in Chrome, to help making size_t vs int bugs
+// harder to exploit.
+//
+// There are matching limits in other allocators, such as tcmalloc. See
+// crbug.com/998048 for details.
+PAGE_ALLOCATOR_CONSTANTS_DECLARE_CONSTEXPR ALWAYS_INLINE size_t
+MaxDirectMapped() {
+  // Subtract kSuperPageSize to accommodate for granularity inside
+  // PartitionRoot::GetDirectMapReservedSize.
+  return (1UL << 31) - kSuperPageSize;
+}
+
+// Max alignment supported by AlignedAllocFlags().
+// kSuperPageSize alignment can't be easily supported, because each super page
+// starts with guard pages & metadata.
+static const size_t kMaxSupportedAlignment = kSuperPageSize / 2;
+
+static const size_t kBitsPerSizeT = sizeof(void*) * CHAR_BIT;
+
+// Constant for the memory reclaim logic.
+static const size_t kMaxFreeableSpans = 16;
+
+// If the total size in bytes of allocated but not committed pages exceeds this
+// value (probably it is a "out of virtual address space" crash), a special
+// crash stack trace is generated at
+// `PartitionOutOfMemoryWithLotsOfUncommitedPages`. This is to distinguish "out
+// of virtual address space" from "out of physical memory" in crash reports.
+static const size_t kReasonableSizeOfUnusedPages = 1024 * 1024 * 1024;  // 1 GiB
+
+// These byte values match tcmalloc.
+static const unsigned char kUninitializedByte = 0xAB;
+static const unsigned char kFreedByte = 0xCD;
+
+static const unsigned char kQuarantinedByte = 0xEF;
+
+// Flags for `PartitionAllocFlags`.
+enum PartitionAllocFlags {
+  PartitionAllocReturnNull = 1 << 0,
+  PartitionAllocZeroFill = 1 << 1,
+  PartitionAllocNoHooks = 1 << 2,  // Internal only.
+  // If the allocation requires a "slow path" (such as allocating/committing a
+  // new slot span), return nullptr instead. Note this makes all large
+  // allocations return nullptr, such as direct-mapped ones, and even for
+  // smaller ones, a nullptr value is common.
+  PartitionAllocFastPathOrReturnNull = 1 << 3,  // Internal only.
+
+  PartitionAllocLastFlag = PartitionAllocFastPathOrReturnNull
+};
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_CONSTANTS_H_

src/base/allocator/partition_allocator/partition_alloc_features.cc

@@ -0,0 +1,61 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+
+#include "base/feature_list.h"
+
+namespace base {
+namespace features {
+
+#if PA_ALLOW_PCSCAN
+// If enabled, PCScan is turned on by default for all partitions that don't
+// disable it explicitly.
+const Feature kPartitionAllocPCScan{"PartitionAllocPCScan",
+                                    FEATURE_DISABLED_BY_DEFAULT};
+#endif  // PA_ALLOW_PCSCAN
+
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+// If enabled, PCScan is turned on only for the browser's malloc partition.
+const Feature kPartitionAllocPCScanBrowserOnly{
+    "PartitionAllocPCScanBrowserOnly", FEATURE_DISABLED_BY_DEFAULT};
+
+// If enabled, this instance belongs to the Control group of the BackupRefPtr
+// binary experiment.
+const Feature kPartitionAllocBackupRefPtrControl{
+    "PartitionAllocBackupRefPtrControl", FEATURE_DISABLED_BY_DEFAULT};
+
+// If enabled, the thread cache will be periodically purged.
+const Feature kPartitionAllocThreadCachePeriodicPurge{
+    "PartitionAllocThreadCachePeriodicPurge", FEATURE_ENABLED_BY_DEFAULT};
+
+// Use a larger maximum thread cache cacheable bucket size.
+const Feature kPartitionAllocLargeThreadCacheSize{
+    "PartitionAllocLargeThreadCacheSize", FEATURE_DISABLED_BY_DEFAULT};
+
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+const Feature kPartitionAllocLazyCommit{"PartitionAllocLazyCommit",
+                                        FEATURE_ENABLED_BY_DEFAULT};
+
+// If enabled, switches PCScan scheduling to a mutator-aware scheduler. Does not
+// affect whether PCScan is enabled itself.
+const Feature kPartitionAllocPCScanMUAwareScheduler{
+    "PartitionAllocPCScanMUAwareScheduler", FEATURE_ENABLED_BY_DEFAULT};
+
+// In addition to heap, scan also the stack of the current mutator.
+const Feature kPartitionAllocPCScanStackScanning {
+  "PartitionAllocPCScanStackScanning",
+#if defined(PA_PCSCAN_STACK_SUPPORTED)
+      FEATURE_ENABLED_BY_DEFAULT
+#else
+      FEATURE_DISABLED_BY_DEFAULT
+#endif  // defined(PA_PCSCAN_STACK_SUPPORTED)
+};
+
+const Feature kPartitionAllocDCScan{"PartitionAllocDCScan",
+                                    FEATURE_DISABLED_BY_DEFAULT};
+
+}  // namespace features
+}  // namespace base

src/base/allocator/partition_allocator/partition_alloc_features.h

@@ -0,0 +1,38 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FEATURES_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FEATURES_H_
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+
+namespace base {
+
+struct Feature;
+
+namespace features {
+
+#if PA_ALLOW_PCSCAN
+extern const BASE_EXPORT Feature kPartitionAllocPCScan;
+#endif  // PA_ALLOW_PCSCAN
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+extern const BASE_EXPORT Feature kPartitionAllocPCScanBrowserOnly;
+extern const BASE_EXPORT Feature kPartitionAllocBackupRefPtrControl;
+extern const BASE_EXPORT Feature kPartitionAllocThreadCachePeriodicPurge;
+extern const BASE_EXPORT Feature kPartitionAllocLargeThreadCacheSize;
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+
+extern const BASE_EXPORT Feature kPartitionAllocPCScanMUAwareScheduler;
+extern const BASE_EXPORT Feature kPartitionAllocPCScanStackScanning;
+extern const BASE_EXPORT Feature kPartitionAllocDCScan;
+
+extern const BASE_EXPORT Feature kPartitionAllocLazyCommit;
+
+}  // namespace features
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FEATURES_H_

src/base/allocator/partition_allocator/partition_alloc_forward.h

@@ -0,0 +1,36 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FORWARD_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FORWARD_H_
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/dcheck_is_on.h"
+#include "base/partition_alloc_buildflags.h"
+
+namespace base {
+namespace internal {
+
+template <bool thread_safe>
+struct SlotSpanMetadata;
+
+constexpr bool ThreadSafe = true;
+constexpr bool NotThreadSafe = false;
+
+#if BUILDFLAG(USE_BACKUP_REF_PTR)
+#if DCHECK_IS_ON()
+BASE_EXPORT void DCheckGetSlotOffsetIsZero(void*);
+#else
+ALWAYS_INLINE void DCheckGetSlotOffsetIsZero(void*) {}
+#endif
+#endif  // BUILDFLAG(USE_BACKUP_REF_PTR)
+}  // namespace internal
+
+template <bool thread_safe>
+struct PartitionRoot;
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FORWARD_H_

src/base/allocator/partition_allocator/partition_alloc_hooks.cc

@@ -0,0 +1,115 @@
+// Copyright (c) 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_alloc_hooks.h"
+
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/no_destructor.h"
+#include "base/synchronization/lock.h"
+
+namespace base {
+
+Lock& GetHooksLock() {
+  static NoDestructor<Lock> lock;
+  return *lock;
+}
+
+std::atomic<bool> PartitionAllocHooks::hooks_enabled_(false);
+std::atomic<PartitionAllocHooks::AllocationObserverHook*>
+    PartitionAllocHooks::allocation_observer_hook_(nullptr);
+std::atomic<PartitionAllocHooks::FreeObserverHook*>
+    PartitionAllocHooks::free_observer_hook_(nullptr);
+std::atomic<PartitionAllocHooks::AllocationOverrideHook*>
+    PartitionAllocHooks::allocation_override_hook_(nullptr);
+std::atomic<PartitionAllocHooks::FreeOverrideHook*>
+    PartitionAllocHooks::free_override_hook_(nullptr);
+std::atomic<PartitionAllocHooks::ReallocOverrideHook*>
+    PartitionAllocHooks::realloc_override_hook_(nullptr);
+
+void PartitionAllocHooks::SetObserverHooks(AllocationObserverHook* alloc_hook,
+                                           FreeObserverHook* free_hook) {
+  AutoLock guard(GetHooksLock());
+
+  // Chained hooks are not supported. Registering a non-null hook when a
+  // non-null hook is already registered indicates somebody is trying to
+  // overwrite a hook.
+  PA_CHECK((!allocation_observer_hook_ && !free_observer_hook_) ||
+           (!alloc_hook && !free_hook))
+      << "Overwriting already set observer hooks";
+  allocation_observer_hook_ = alloc_hook;
+  free_observer_hook_ = free_hook;
+
+  hooks_enabled_ = allocation_observer_hook_ || allocation_override_hook_;
+}
+
+void PartitionAllocHooks::SetOverrideHooks(AllocationOverrideHook* alloc_hook,
+                                           FreeOverrideHook* free_hook,
+                                           ReallocOverrideHook realloc_hook) {
+  AutoLock guard(GetHooksLock());
+
+  PA_CHECK((!allocation_override_hook_ && !free_override_hook_ &&
+            !realloc_override_hook_) ||
+           (!alloc_hook && !free_hook && !realloc_hook))
+      << "Overwriting already set override hooks";
+  allocation_override_hook_ = alloc_hook;
+  free_override_hook_ = free_hook;
+  realloc_override_hook_ = realloc_hook;
+
+  hooks_enabled_ = allocation_observer_hook_ || allocation_override_hook_;
+}
+
+void PartitionAllocHooks::AllocationObserverHookIfEnabled(
+    void* address,
+    size_t size,
+    const char* type_name) {
+  if (auto* hook = allocation_observer_hook_.load(std::memory_order_relaxed))
+    hook(address, size, type_name);
+}
+
+bool PartitionAllocHooks::AllocationOverrideHookIfEnabled(
+    void** out,
+    int flags,
+    size_t size,
+    const char* type_name) {
+  if (auto* hook = allocation_override_hook_.load(std::memory_order_relaxed))
+    return hook(out, flags, size, type_name);
+  return false;
+}
+
+void PartitionAllocHooks::FreeObserverHookIfEnabled(void* address) {
+  if (auto* hook = free_observer_hook_.load(std::memory_order_relaxed))
+    hook(address);
+}
+
+bool PartitionAllocHooks::FreeOverrideHookIfEnabled(void* address) {
+  if (auto* hook = free_override_hook_.load(std::memory_order_relaxed))
+    return hook(address);
+  return false;
+}
+
+void PartitionAllocHooks::ReallocObserverHookIfEnabled(void* old_address,
+                                                       void* new_address,
+                                                       size_t size,
+                                                       const char* type_name) {
+  // Report a reallocation as a free followed by an allocation.
+  AllocationObserverHook* allocation_hook =
+      allocation_observer_hook_.load(std::memory_order_relaxed);
+  FreeObserverHook* free_hook =
+      free_observer_hook_.load(std::memory_order_relaxed);
+  if (allocation_hook && free_hook) {
+    free_hook(old_address);
+    allocation_hook(new_address, size, type_name);
+  }
+}
+
+bool PartitionAllocHooks::ReallocOverrideHookIfEnabled(size_t* out,
+                                                       void* address) {
+  if (ReallocOverrideHook* hook =
+          realloc_override_hook_.load(std::memory_order_relaxed)) {
+    return hook(out, address);
+  }
+  return false;
+}
+
+}  // namespace base

src/base/allocator/partition_allocator/partition_alloc_hooks.h

@@ -0,0 +1,85 @@
+// Copyright (c) 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_HOOKS_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_HOOKS_H_
+
+#include <atomic>
+#include <cstddef>
+
+#include "base/base_export.h"
+
+namespace base {
+
+// PartitionAlloc supports setting hooks to observe allocations/frees as they
+// occur as well as 'override' hooks that allow overriding those operations.
+class BASE_EXPORT PartitionAllocHooks {
+ public:
+  // Log allocation and free events.
+  typedef void AllocationObserverHook(void* address,
+                                      size_t size,
+                                      const char* type_name);
+  typedef void FreeObserverHook(void* address);
+
+  // If it returns true, the allocation has been overridden with the pointer in
+  // *out.
+  typedef bool AllocationOverrideHook(void** out,
+                                      int flags,
+                                      size_t size,
+                                      const char* type_name);
+  // If it returns true, then the allocation was overridden and has been freed.
+  typedef bool FreeOverrideHook(void* address);
+  // If it returns true, the underlying allocation is overridden and *out holds
+  // the size of the underlying allocation.
+  typedef bool ReallocOverrideHook(size_t* out, void* address);
+
+  // To unhook, call Set*Hooks with nullptrs.
+  static void SetObserverHooks(AllocationObserverHook* alloc_hook,
+                               FreeObserverHook* free_hook);
+  static void SetOverrideHooks(AllocationOverrideHook* alloc_hook,
+                               FreeOverrideHook* free_hook,
+                               ReallocOverrideHook realloc_hook);
+
+  // Helper method to check whether hooks are enabled. This is an optimization
+  // so that if a function needs to call observer and override hooks in two
+  // different places this value can be cached and only loaded once.
+  static bool AreHooksEnabled() {
+    return hooks_enabled_.load(std::memory_order_relaxed);
+  }
+
+  static void AllocationObserverHookIfEnabled(void* address,
+                                              size_t size,
+                                              const char* type_name);
+  static bool AllocationOverrideHookIfEnabled(void** out,
+                                              int flags,
+                                              size_t size,
+                                              const char* type_name);
+
+  static void FreeObserverHookIfEnabled(void* address);
+  static bool FreeOverrideHookIfEnabled(void* address);
+
+  static void ReallocObserverHookIfEnabled(void* old_address,
+                                           void* new_address,
+                                           size_t size,
+                                           const char* type_name);
+  static bool ReallocOverrideHookIfEnabled(size_t* out, void* address);
+
+ private:
+  // Single bool that is used to indicate whether observer or allocation hooks
+  // are set to reduce the numbers of loads required to check whether hooking is
+  // enabled.
+  static std::atomic<bool> hooks_enabled_;
+
+  // Lock used to synchronize Set*Hooks calls.
+  static std::atomic<AllocationObserverHook*> allocation_observer_hook_;
+  static std::atomic<FreeObserverHook*> free_observer_hook_;
+
+  static std::atomic<AllocationOverrideHook*> allocation_override_hook_;
+  static std::atomic<FreeOverrideHook*> free_override_hook_;
+  static std::atomic<ReallocOverrideHook*> realloc_override_hook_;
+};
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_HOOKS_H_

src/base/allocator/partition_allocator/partition_bucket.cc

@@ -0,0 +1,922 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_bucket.h"
+
+#include "base/allocator/partition_allocator/address_pool_manager.h"
+#include "base/allocator/partition_allocator/oom.h"
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/allocator/partition_allocator/page_allocator_constants.h"
+#include "base/allocator/partition_allocator/partition_address_space.h"
+#include "base/allocator/partition_allocator/partition_alloc.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+#include "base/allocator/partition_allocator/partition_direct_map_extent.h"
+#include "base/allocator/partition_allocator/partition_oom.h"
+#include "base/allocator/partition_allocator/partition_page.h"
+#include "base/allocator/partition_allocator/starscan/object_bitmap.h"
+#include "base/bits.h"
+#include "base/check.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT) && \
+    !defined(PA_HAS_64_BITS_POINTERS) && BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+bool IsAllowedSuperPagesForBRPPool(const char* super_page,
+                                   const char* super_page_end) {
+  while (super_page < super_page_end) {
+    // If any blocked superpage is found inside the given memory region,
+    // the memory region is blocked.
+    if (!AddressPoolManagerBitmap::IsAllowedSuperPageForBRPPool(super_page))
+      return false;
+    super_page += kSuperPageSize;
+  }
+  return true;
+}
+
+char* ReserveSuperPagesAllowedForBRPPool(size_t requested_size) {
+  char* super_page = internal::AddressPoolManager::GetInstance()->Reserve(
+      GetBRPPool(), nullptr, requested_size);
+
+  constexpr int kMaxRandomAddressTries = 10;
+  for (int i = 0; i < kMaxRandomAddressTries; ++i) {
+    if (!super_page ||
+        IsAllowedSuperPagesForBRPPool(super_page, super_page + requested_size))
+      break;
+    AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+        GetBRPPool(), super_page, requested_size);
+    super_page = AddressPoolManager::GetInstance()->Reserve(
+        GetBRPPool(), nullptr, requested_size);
+  }
+
+  // If the allocation attempt succeeds, we will break out of the following
+  // loop immediately.
+  //
+  // Last resort: sequentially scan the whole 32-bit address space. The number
+  // of blocked super-pages should be very small, so we expect to practically
+  // never need to run the following code. Note that it may fail to find an
+  // available page, e.g., when it becomes available after the scan passes
+  // through it, but we accept the risk.
+  for (uintptr_t ptr = kSuperPageSize; ptr != 0; ptr += kSuperPageSize) {
+    if (!super_page ||
+        IsAllowedSuperPagesForBRPPool(super_page, super_page + requested_size))
+      break;
+    AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+        GetBRPPool(), super_page, requested_size);
+    super_page = AddressPoolManager::GetInstance()->Reserve(
+        GetBRPPool(), reinterpret_cast<void*>(ptr), requested_size);
+  }
+
+  if (super_page &&
+      !IsAllowedSuperPagesForBRPPool(super_page, super_page + requested_size)) {
+    AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+        GetBRPPool(), super_page, requested_size);
+    super_page = nullptr;
+  }
+  return super_page;
+}
+#endif
+
+template <bool thread_safe>
+SlotSpanMetadata<thread_safe>* PartitionDirectMap(
+    PartitionRoot<thread_safe>* root,
+    int flags,
+    size_t raw_size) {
+  // No static EXCLUSIVE_LOCKS_REQUIRED(), as the checker doesn't understand
+  // scoped unlocking.
+  root->lock_.AssertAcquired();
+
+  const bool return_null = flags & PartitionAllocReturnNull;
+  if (UNLIKELY(raw_size > MaxDirectMapped())) {
+    if (return_null)
+      return nullptr;
+
+    // The lock is here to protect PA from:
+    // 1. Concurrent calls
+    // 2. Reentrant calls
+    //
+    // This is fine here however, as:
+    // 1. Concurrency: |PartitionRoot::OutOfMemory()| never returns, so the lock
+    //    will not be re-acquired, which would lead to acting on inconsistent
+    //    data that could have been modified in-between releasing and acquiring
+    //    it.
+    // 2. Reentrancy: This is why we release the lock. On some platforms,
+    //    terminating the process may free() memory, or even possibly try to
+    //    allocate some. Calling free() is fine, but will deadlock since
+    //    |PartitionRoot::lock_| is not recursive.
+    //
+    // Supporting reentrant calls properly is hard, and not a requirement for
+    // PA. However up to that point, we've only *read* data, not *written* to
+    // any state. Reentrant calls are then fine, especially as we don't continue
+    // on this path. The only downside is possibly endless recursion if the OOM
+    // handler allocates and fails to use UncheckedMalloc() or equivalent, but
+    // that's violating the contract of base::TerminateBecauseOutOfMemory().
+    ScopedUnlockGuard<thread_safe> unlock{root->lock_};
+    PartitionExcessiveAllocationSize(raw_size);
+    IMMEDIATE_CRASH();  // Not required, kept as documentation.
+  }
+
+  PartitionDirectMapExtent<thread_safe>* map_extent = nullptr;
+  PartitionPage<thread_safe>* page = nullptr;
+
+  char* ptr = nullptr;
+  const size_t reserved_size =
+      PartitionRoot<thread_safe>::GetDirectMapReservedSize(raw_size);
+
+  {
+    // Getting memory for direct-mapped allocations doesn't interact with the
+    // rest of the allocator, but takes a long time, as it involves several
+    // system calls. With GigaCage, no mmap() (or equivalent) call is made on 64
+    // bit systems, but page permissions are changed with mprotect(), which is a
+    // syscall.
+    //
+    // These calls are almost always slow (at least a couple us per syscall on a
+    // desktop Linux machine), and they also have a very long latency tail,
+    // possibly from getting descheduled. As a consequence, we should not hold
+    // the lock when performing a syscall. This is not the only problematic
+    // location, but since this one doesn't interact with the rest of the
+    // allocator, we can safely drop and then re-acquire the lock.
+    //
+    // Note that this only affects allocations that are not served out of the
+    // thread cache, but as a simple example the buffer partition in blink is
+    // frequently used for large allocations (e.g. ArrayBuffer), and frequent,
+    // small ones (e.g. WTF::String), and does not have a thread cache.
+    ScopedUnlockGuard<thread_safe> scoped_unlock{root->lock_};
+
+    const size_t slot_size =
+        PartitionRoot<thread_safe>::GetDirectMapSlotSize(raw_size);
+    const size_t map_size =
+        reserved_size -
+        PartitionRoot<thread_safe>::GetDirectMapMetadataAndGuardPagesSize();
+    PA_DCHECK(slot_size <= map_size);
+
+    pool_handle pool;
+    // Allocate from GigaCage, from the non-BRP pool, because BackupRefPtr isn't
+    // supported in direct maps.
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT) && \
+    !defined(PA_HAS_64_BITS_POINTERS) && BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+    if (root->UseBRPPool()) {
+      ptr = ReserveSuperPagesAllowedForBRPPool(reserved_size);
+      pool = GetBRPPool();
+    } else {
+      ptr = internal::AddressPoolManager::GetInstance()->Reserve(
+          GetNonBRPPool(), nullptr, reserved_size);
+      pool = GetNonBRPPool();
+    }
+#else  // !BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT) ||
+       // defined(PA_HAS_64_BITS_POINTERS) || !BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+    pool = root->UseBRPPool() ? GetBRPPool() : GetNonBRPPool();
+#else
+    pool = GetNonBRPPool();
+#endif
+    ptr = internal::AddressPoolManager::GetInstance()->Reserve(pool, nullptr,
+                                                               reserved_size);
+#endif  // !BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT) ||
+        // defined(PA_HAS_64_BITS_POINTERS) ||
+        // !BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+
+    if (UNLIKELY(!ptr)) {
+      if (return_null)
+        return nullptr;
+
+      // Crash handling is split on purpose in this function:
+      // - Crashing here likely means that Chrome is out of address space (on 32
+      //   bit platforms), or out of GigaCage space (on 64 bit ones).
+      // - Crashing below would likely mean out of commit charge.
+      root->OutOfMemory(raw_size);
+      IMMEDIATE_CRASH();  // Not required, kept as documentation.
+    }
+
+    root->total_size_of_direct_mapped_pages.fetch_add(
+        reserved_size, std::memory_order_relaxed);
+
+    char* const slot = ptr + PartitionPageSize();
+    RecommitSystemPages(
+        ptr + SystemPageSize(),
+#if BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT) && \
+    BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+        // Allocate 2 SystemPages, one for SuperPage metadata
+        // and the other for RefCount.
+        root->UseBRPPool() ? SystemPageSize() * 2 : SystemPageSize(),
+#else
+        SystemPageSize(),
+#endif
+        PageReadWrite, PageUpdatePermissions);
+    // It is typically possible to map a large range of inaccessible pages, and
+    // this is leveraged in multiple places, including the GigaCage. However,
+    // this doesn't mean that we can commit all this memory.  For the vast
+    // majority of allocations, this just means that we crash in a slightly
+    // different place, but for callers ready to handle failures, we have to
+    // return nullptr. See crbug.com/1187404.
+    //
+    // Note that we didn't check above, because if we cannot even commit a
+    // single page, then this is likely hopeless anyway, and we will crash very
+    // soon.
+    const bool ok = root->TryRecommitSystemPagesForData(slot, slot_size,
+                                                        PageUpdatePermissions);
+    if (!ok) {
+      if (!return_null) {
+        root->OutOfMemory(raw_size);
+        IMMEDIATE_CRASH();  // Not required, kept as documentation.
+      }
+
+      internal::AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+          pool, ptr, reserved_size);
+      return nullptr;
+    }
+
+    auto* metadata = reinterpret_cast<PartitionDirectMapMetadata<thread_safe>*>(
+        PartitionSuperPageToMetadataArea(ptr));
+    metadata->extent.root = root;
+    // The new structures are all located inside a fresh system page so they
+    // will all be zeroed out. These DCHECKs are for documentation and to assert
+    // our expectations of the kernel.
+    PA_DCHECK(!metadata->extent.super_page_base);
+    PA_DCHECK(!metadata->extent.super_pages_end);
+    PA_DCHECK(!metadata->extent.next);
+    PA_DCHECK(PartitionPage<thread_safe>::FromPtr(slot) == &metadata->page);
+
+    page = &metadata->page;
+    page->is_valid = true;
+    PA_DCHECK(!page->has_valid_span_after_this);
+    PA_DCHECK(!page->slot_span_metadata_offset);
+    PA_DCHECK(!page->slot_span_metadata.next_slot_span);
+    PA_DCHECK(!page->slot_span_metadata.num_allocated_slots);
+    PA_DCHECK(!page->slot_span_metadata.num_unprovisioned_slots);
+    PA_DCHECK(!page->slot_span_metadata.empty_cache_index);
+
+    PA_DCHECK(!metadata->bucket.active_slot_spans_head);
+    PA_DCHECK(!metadata->bucket.empty_slot_spans_head);
+    PA_DCHECK(!metadata->bucket.decommitted_slot_spans_head);
+    PA_DCHECK(!metadata->bucket.num_system_pages_per_slot_span);
+    PA_DCHECK(!metadata->bucket.num_full_slot_spans);
+    metadata->bucket.slot_size = slot_size;
+
+    new (&page->slot_span_metadata)
+        SlotSpanMetadata<thread_safe>(&metadata->bucket);
+    auto* next_entry = new (slot) PartitionFreelistEntry();
+    page->slot_span_metadata.SetFreelistHead(next_entry);
+
+    map_extent = &metadata->direct_map_extent;
+    map_extent->map_size = map_size;
+    map_extent->bucket = &metadata->bucket;
+  }
+
+  root->lock_.AssertAcquired();
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  // TODO(tasak): If no lock is required, move the code inside
+  // ScopedUnlockGuard.
+  if (root->UseBRPPool()) {
+    uintptr_t ptr_start = reinterpret_cast<uintptr_t>(ptr);
+    uintptr_t ptr_end = ptr_start + reserved_size;
+    auto* offset_ptr = base::internal::ReservationOffsetPointer(ptr_start);
+    int offset = 0;
+    while (ptr_start < ptr_end) {
+      PA_DCHECK(offset_ptr < internal::EndOfReservationOffsetTable());
+      PA_DCHECK(offset < internal::NotInDirectMapOffsetTag());
+      *offset_ptr++ = offset++;
+      ptr_start += kSuperPageSize;
+    }
+  }
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+
+  // Maintain the doubly-linked list of all direct mappings.
+  map_extent->next_extent = root->direct_map_list;
+  if (map_extent->next_extent)
+    map_extent->next_extent->prev_extent = map_extent;
+  map_extent->prev_extent = nullptr;
+  root->direct_map_list = map_extent;
+
+  return &page->slot_span_metadata;
+}
+
+}  // namespace
+
+// TODO(ajwong): This seems to interact badly with
+// get_pages_per_slot_span() which rounds the value from this up to a
+// multiple of NumSystemPagesPerPartitionPage() (aka 4) anyways.
+// http://crbug.com/776537
+//
+// TODO(ajwong): The waste calculation seems wrong. The PTE usage should cover
+// both used and unsed pages.
+// http://crbug.com/776537
+template <bool thread_safe>
+uint8_t PartitionBucket<thread_safe>::get_system_pages_per_slot_span() {
+  // This works out reasonably for the current bucket sizes of the generic
+  // allocator, and the current values of partition page size and constants.
+  // Specifically, we have enough room to always pack the slots perfectly into
+  // some number of system pages. The only waste is the waste associated with
+  // unfaulted pages (i.e. wasted address space).
+  // TODO: we end up using a lot of system pages for very small sizes. For
+  // example, we'll use 12 system pages for slot size 24. The slot size is
+  // so small that the waste would be tiny with just 4, or 1, system pages.
+  // Later, we can investigate whether there are anti-fragmentation benefits
+  // to using fewer system pages.
+  double best_waste_ratio = 1.0f;
+  uint16_t best_pages = 0;
+  if (slot_size > MaxSystemPagesPerSlotSpan() * SystemPageSize()) {
+    // TODO(ajwong): Why is there a DCHECK here for this?
+    // http://crbug.com/776537
+    PA_DCHECK(!(slot_size % SystemPageSize()));
+    best_pages = static_cast<uint16_t>(slot_size / SystemPageSize());
+    // TODO(ajwong): Should this be checking against
+    // MaxSystemPagesPerSlotSpan() or numeric_limits<uint8_t>::max?
+    // http://crbug.com/776537
+    PA_CHECK(best_pages < (1 << 8));
+    return static_cast<uint8_t>(best_pages);
+  }
+  PA_DCHECK(slot_size <= MaxSystemPagesPerSlotSpan() * SystemPageSize());
+  for (uint16_t i = NumSystemPagesPerPartitionPage() - 1;
+       i <= MaxSystemPagesPerSlotSpan(); ++i) {
+    size_t page_size = SystemPageSize() * i;
+    size_t num_slots = page_size / slot_size;
+    size_t waste = page_size - (num_slots * slot_size);
+    // Leaving a page unfaulted is not free; the page will occupy an empty page
+    // table entry.  Make a simple attempt to account for that.
+    //
+    // TODO(ajwong): This looks wrong. PTEs are allocated for all pages
+    // regardless of whether or not they are wasted. Should it just
+    // be waste += i * sizeof(void*)?
+    // http://crbug.com/776537
+    size_t num_remainder_pages = i & (NumSystemPagesPerPartitionPage() - 1);
+    size_t num_unfaulted_pages =
+        num_remainder_pages
+            ? (NumSystemPagesPerPartitionPage() - num_remainder_pages)
+            : 0;
+    waste += sizeof(void*) * num_unfaulted_pages;
+    double waste_ratio =
+        static_cast<double>(waste) / static_cast<double>(page_size);
+    if (waste_ratio < best_waste_ratio) {
+      best_waste_ratio = waste_ratio;
+      best_pages = i;
+    }
+  }
+  PA_DCHECK(best_pages > 0);
+  PA_CHECK(best_pages <= MaxSystemPagesPerSlotSpan());
+  return static_cast<uint8_t>(best_pages);
+}
+
+template <bool thread_safe>
+void PartitionBucket<thread_safe>::Init(uint32_t new_slot_size) {
+  slot_size = new_slot_size;
+  slot_size_reciprocal = kReciprocalMask / new_slot_size + 1;
+  active_slot_spans_head =
+      SlotSpanMetadata<thread_safe>::get_sentinel_slot_span();
+  empty_slot_spans_head = nullptr;
+  decommitted_slot_spans_head = nullptr;
+  num_full_slot_spans = 0;
+  num_system_pages_per_slot_span = get_system_pages_per_slot_span();
+}
+
+template <bool thread_safe>
+NOINLINE void PartitionBucket<thread_safe>::OnFull() {
+  OOM_CRASH(0);
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE SlotSpanMetadata<thread_safe>*
+PartitionBucket<thread_safe>::AllocNewSlotSpan(PartitionRoot<thread_safe>* root,
+                                               int flags,
+                                               size_t slot_span_alignment) {
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(root->next_partition_page) %
+              PartitionPageSize()));
+  PA_DCHECK(!(reinterpret_cast<uintptr_t>(root->next_partition_page_end) %
+              PartitionPageSize()));
+
+  size_t num_partition_pages = get_pages_per_slot_span();
+  size_t slot_span_reserved_size = PartitionPageSize() * num_partition_pages;
+  size_t slot_span_committed_size = get_bytes_per_span();
+  PA_DCHECK(num_partition_pages <= NumPartitionPagesPerSuperPage());
+  PA_DCHECK(slot_span_committed_size % SystemPageSize() == 0);
+  PA_DCHECK(slot_span_committed_size <= slot_span_reserved_size);
+
+  auto adjusted_next_partition_page =
+      bits::AlignUp(root->next_partition_page, slot_span_alignment);
+  if (UNLIKELY(adjusted_next_partition_page + slot_span_reserved_size >
+               root->next_partition_page_end)) {
+    // In this case, we can no longer hand out pages from the current super page
+    // allocation. Get a new super page.
+    if (!AllocNewSuperPage(root)) {
+      return nullptr;
+    }
+    // AllocNewSuperPage() updates root->next_partition_page, re-query.
+    adjusted_next_partition_page =
+        bits::AlignUp(root->next_partition_page, slot_span_alignment);
+    PA_CHECK(adjusted_next_partition_page + slot_span_reserved_size <=
+             root->next_partition_page_end);
+  }
+
+  auto* gap_start_page =
+      PartitionPage<thread_safe>::FromPtr(root->next_partition_page);
+  auto* gap_end_page =
+      PartitionPage<thread_safe>::FromPtr(adjusted_next_partition_page);
+  for (auto* page = gap_start_page; page < gap_end_page; ++page) {
+    PA_DCHECK(!page->is_valid);
+    page->has_valid_span_after_this = 1;
+  }
+  root->next_partition_page =
+      adjusted_next_partition_page + slot_span_reserved_size;
+
+  void* slot_span_start = adjusted_next_partition_page;
+  auto* slot_span = &gap_end_page->slot_span_metadata;
+  InitializeSlotSpan(slot_span);
+  // Now that slot span is initialized, it's safe to call FromSlotStartPtr.
+  PA_DCHECK(slot_span ==
+            SlotSpanMetadata<thread_safe>::FromSlotStartPtr(slot_span_start));
+
+  // System pages in the super page come in a decommited state. Commit them
+  // before vending them back.
+  // If lazy commit is enabled, pages will be committed when provisioning slots,
+  // in ProvisionMoreSlotsAndAllocOne(), not here.
+  if (!root->use_lazy_commit) {
+    root->RecommitSystemPagesForData(slot_span_start, slot_span_committed_size,
+                                     PageUpdatePermissions);
+  }
+
+  // Double check that we had enough space in the super page for the new slot
+  // span.
+  PA_DCHECK(root->next_partition_page <= root->next_partition_page_end);
+  return slot_span;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE void* PartitionBucket<thread_safe>::AllocNewSuperPage(
+    PartitionRoot<thread_safe>* root) {
+  // Need a new super page. We want to allocate super pages in a contiguous
+  // address region as much as possible. This is important for not causing
+  // page table bloat and not fragmenting address spaces in 32 bit
+  // architectures.
+  char* requested_address = root->next_super_page;
+  char* super_page = nullptr;
+  // Allocate from GigaCage. Route to the appropriate GigaCage pool based on
+  // BackupRefPtr support.
+  super_page = AddressPoolManager::GetInstance()->Reserve(
+      root->UseBRPPool() ? GetBRPPool() : GetNonBRPPool(), requested_address,
+      kSuperPageSize);
+
+#if !defined(PA_HAS_64_BITS_POINTERS) && BUILDFLAG(USE_BRP_POOL_BLOCKLIST)
+  if (root->UseBRPPool()) {
+    constexpr int kMaxRandomAddressTries = 10;
+    for (int i = 0; i < kMaxRandomAddressTries; ++i) {
+      if (!super_page ||
+          AddressPoolManagerBitmap::IsAllowedSuperPageForBRPPool(super_page))
+        break;
+      AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+          GetBRPPool(), super_page, kSuperPageSize);
+      super_page = AddressPoolManager::GetInstance()->Reserve(
+          GetBRPPool(), nullptr, kSuperPageSize);
+    }
+
+    // If the allocation attempt succeeds, we will break out of the following
+    // loop immediately.
+    //
+    // Last resort: sequentially scan the whole 32-bit address space. The number
+    // of blocked super-pages should be very small, so we expect to practically
+    // never need to run the following code. Note that it may fail to find an
+    // available page, e.g., when it becomes available after the scan passes
+    // through it, but we accept the risk.
+    for (uintptr_t ptr = kSuperPageSize; ptr != 0; ptr += kSuperPageSize) {
+      if (!super_page ||
+          AddressPoolManagerBitmap::IsAllowedSuperPageForBRPPool(super_page))
+        break;
+      AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+          GetBRPPool(), super_page, kSuperPageSize);
+      super_page = AddressPoolManager::GetInstance()->Reserve(
+          GetBRPPool(), reinterpret_cast<void*>(ptr), kSuperPageSize);
+    }
+
+    if (super_page &&
+        !AddressPoolManagerBitmap::IsAllowedSuperPageForBRPPool(super_page)) {
+      AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+          GetBRPPool(), super_page, kSuperPageSize);
+      super_page = nullptr;
+    }
+  }
+#endif
+  if (UNLIKELY(!super_page))
+    return nullptr;
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  if (root->UseBRPPool()) {
+    // The reservation offset table is used to see whether the given SuperPage
+    // is DirectMap allocated or not by comparing the table entry with
+    // NotInDirectMapOffsetTag (!=0). Since the SuperPage is not DirectMap
+    // allocated, the table entry must be NotInDirectMapOffsetTag.
+    *base::internal::ReservationOffsetPointer(reinterpret_cast<uintptr_t>(
+        super_page)) = base::internal::NotInDirectMapOffsetTag();
+  }
+#endif
+
+  root->total_size_of_super_pages.fetch_add(kSuperPageSize,
+                                            std::memory_order_relaxed);
+
+  root->next_super_page = super_page + kSuperPageSize;
+  char* quarantine_bitmaps = super_page + PartitionPageSize();
+  const size_t quarantine_bitmaps_reserved_size =
+      root->IsQuarantineAllowed() ? ReservedQuarantineBitmapsSize() : 0;
+  const size_t quarantine_bitmaps_size_to_commit =
+      root->IsQuarantineAllowed() ? CommittedQuarantineBitmapsSize() : 0;
+  PA_DCHECK(quarantine_bitmaps_reserved_size % PartitionPageSize() == 0);
+  PA_DCHECK(quarantine_bitmaps_size_to_commit % SystemPageSize() == 0);
+  PA_DCHECK(quarantine_bitmaps_size_to_commit <=
+            quarantine_bitmaps_reserved_size);
+  char* ret = quarantine_bitmaps + quarantine_bitmaps_reserved_size;
+  root->next_partition_page = ret;
+  root->next_partition_page_end = root->next_super_page - PartitionPageSize();
+  PA_DCHECK(ret ==
+            SuperPagePayloadBegin(super_page, root->IsQuarantineAllowed()));
+  PA_DCHECK(root->next_partition_page_end == SuperPagePayloadEnd(super_page));
+
+  // Keep the first partition page in the super page inaccessible to serve as a
+  // guard page, except an "island" in the middle where we put page metadata and
+  // also a tiny amount of extent metadata.
+  RecommitSystemPages(super_page + SystemPageSize(),
+#if BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+                      // Allocate 2 SystemPages, one for SuperPage metadata and
+                      // the other for RefCount bitmap.
+                      SystemPageSize() * 2,
+#else
+                      SystemPageSize(),
+#endif
+                      PageReadWrite, PageUpdatePermissions);
+
+  // If PCScan is used, commit the quarantine bitmap. Otherwise, leave it
+  // uncommitted and let PartitionRoot::EnablePCScan commit it when needed.
+  if (root->IsQuarantineEnabled()) {
+    RecommitSystemPages(quarantine_bitmaps, quarantine_bitmaps_size_to_commit,
+                        PageReadWrite, PageUpdatePermissions);
+  }
+
+  // If we were after a specific address, but didn't get it, assume that
+  // the system chose a lousy address. Here most OS'es have a default
+  // algorithm that isn't randomized. For example, most Linux
+  // distributions will allocate the mapping directly before the last
+  // successful mapping, which is far from random. So we just get fresh
+  // randomness for the next mapping attempt.
+  if (requested_address && requested_address != super_page)
+    root->next_super_page = nullptr;
+
+  // We allocated a new super page so update super page metadata.
+  // First check if this is a new extent or not.
+  auto* latest_extent =
+      reinterpret_cast<PartitionSuperPageExtentEntry<thread_safe>*>(
+          PartitionSuperPageToMetadataArea(super_page));
+  // By storing the root in every extent metadata object, we have a fast way
+  // to go from a pointer within the partition to the root object.
+  latest_extent->root = root;
+  // Most new extents will be part of a larger extent, and these three fields
+  // are unused, but we initialize them to 0 so that we get a clear signal
+  // in case they are accidentally used.
+  latest_extent->super_page_base = nullptr;
+  latest_extent->super_pages_end = nullptr;
+  latest_extent->next = nullptr;
+
+  PartitionSuperPageExtentEntry<thread_safe>* current_extent =
+      root->current_extent;
+  const bool is_new_extent = super_page != requested_address;
+  if (UNLIKELY(is_new_extent)) {
+    if (UNLIKELY(!current_extent)) {
+      PA_DCHECK(!root->first_extent);
+      root->first_extent = latest_extent;
+    } else {
+      PA_DCHECK(current_extent->super_page_base);
+      current_extent->next = latest_extent;
+    }
+    root->current_extent = latest_extent;
+    latest_extent->super_page_base = super_page;
+    latest_extent->super_pages_end = super_page + kSuperPageSize;
+  } else {
+    // We allocated next to an existing extent so just nudge the size up a
+    // little.
+    PA_DCHECK(current_extent->super_pages_end);
+    current_extent->super_pages_end += kSuperPageSize;
+    PA_DCHECK(ret >= current_extent->super_page_base &&
+              ret < current_extent->super_pages_end);
+  }
+  return ret;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE void PartitionBucket<thread_safe>::InitializeSlotSpan(
+    SlotSpanMetadata<thread_safe>* slot_span) {
+  new (slot_span) SlotSpanMetadata<thread_safe>(this);
+  slot_span->empty_cache_index = -1;
+
+  slot_span->Reset();
+
+  uint16_t num_partition_pages = get_pages_per_slot_span();
+  auto* page = reinterpret_cast<PartitionPage<thread_safe>*>(slot_span);
+  for (uint16_t i = 0; i < num_partition_pages; ++i, ++page) {
+    PA_DCHECK(i <= PartitionPage<thread_safe>::kMaxSlotSpanMetadataOffset);
+    page->slot_span_metadata_offset = i;
+    page->is_valid = true;
+  }
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE char* PartitionBucket<thread_safe>::ProvisionMoreSlotsAndAllocOne(
+    PartitionRoot<thread_safe>* root,
+    SlotSpanMetadata<thread_safe>* slot_span) {
+  PA_DCHECK(slot_span !=
+            SlotSpanMetadata<thread_safe>::get_sentinel_slot_span());
+  uint16_t num_slots = slot_span->num_unprovisioned_slots;
+  PA_DCHECK(num_slots);
+  // We should only get here when _every_ slot is either used or unprovisioned.
+  // (The third state is "on the freelist". If we have a non-empty freelist, we
+  // should not get here.)
+  PA_DCHECK(num_slots + slot_span->num_allocated_slots == get_slots_per_span());
+  // Similarly, make explicitly sure that the freelist is empty.
+  PA_DCHECK(!slot_span->freelist_head);
+  PA_DCHECK(slot_span->num_allocated_slots >= 0);
+
+  size_t size = slot_size;
+  char* base = reinterpret_cast<char*>(
+      SlotSpanMetadata<thread_safe>::ToSlotSpanStartPtr(slot_span));
+  // If we got here, the first unallocated slot is either partially or fully on
+  // an uncommitted page. If the latter, it must be at the start of that page.
+  char* return_slot = base + (size * slot_span->num_allocated_slots);
+  char* next_slot = return_slot + size;
+  char* commit_start = bits::AlignUp(return_slot, SystemPageSize());
+  PA_DCHECK(next_slot > commit_start);
+  char* commit_end = bits::AlignUp(next_slot, SystemPageSize());
+  // If the slot was partially committed, |return_slot| and |next_slot| fall
+  // in different pages. If the slot was fully uncommitted, |return_slot| points
+  // to the page start and |next_slot| doesn't, thus only the latter gets
+  // rounded up.
+  PA_DCHECK(commit_end > commit_start);
+
+  // The slot being returned is considered allocated.
+  slot_span->num_allocated_slots++;
+  // Round down, because a slot that doesn't fully fit in the new page(s) isn't
+  // provisioned.
+  uint16_t slots_to_provision = (commit_end - return_slot) / size;
+  slot_span->num_unprovisioned_slots -= slots_to_provision;
+  PA_DCHECK(slot_span->num_allocated_slots +
+                slot_span->num_unprovisioned_slots <=
+            get_slots_per_span());
+
+  // If lazy commit is enabled, meaning system pages in the slot span come
+  // in an initially decommitted state, commit them here.
+  // Note, we can't use PageKeepPermissionsIfPossible, because we have no
+  // knowledge which pages have been committed before (it doesn't matter on
+  // Windows anyway).
+  if (root->use_lazy_commit) {
+    // TODO(lizeb): Handle commit failure.
+    root->RecommitSystemPagesForData(commit_start, commit_end - commit_start,
+                                     PageUpdatePermissions);
+  }
+
+  // Add all slots that fit within so far committed pages to the free list.
+  PartitionFreelistEntry* prev_entry = nullptr;
+  char* next_slot_end = next_slot + size;
+  size_t free_list_entries_added = 0;
+  while (next_slot_end <= commit_end) {
+    auto* entry = new (next_slot) PartitionFreelistEntry();
+    if (!slot_span->freelist_head) {
+      PA_DCHECK(!prev_entry);
+      PA_DCHECK(!free_list_entries_added);
+      slot_span->SetFreelistHead(entry);
+    } else {
+      PA_DCHECK(free_list_entries_added);
+      prev_entry->SetNext(entry);
+    }
+    next_slot = next_slot_end;
+    next_slot_end = next_slot + size;
+    prev_entry = entry;
+#if DCHECK_IS_ON()
+    free_list_entries_added++;
+#endif
+  }
+
+#if DCHECK_IS_ON()
+  // The only provisioned slot not added to the free list is the one being
+  // returned.
+  PA_DCHECK(slots_to_provision == free_list_entries_added + 1);
+  // We didn't necessarily provision more than one slot (e.g. if |slot_size|
+  // is large), meaning that |slot_span->freelist_head| can be nullptr.
+  if (slot_span->freelist_head) {
+    PA_DCHECK(free_list_entries_added);
+    slot_span->freelist_head->CheckFreeList();
+  }
+#endif
+
+  return return_slot;
+}
+
+template <bool thread_safe>
+bool PartitionBucket<thread_safe>::SetNewActiveSlotSpan() {
+  SlotSpanMetadata<thread_safe>* slot_span = active_slot_spans_head;
+  if (slot_span == SlotSpanMetadata<thread_safe>::get_sentinel_slot_span())
+    return false;
+
+  SlotSpanMetadata<thread_safe>* next_slot_span;
+
+  for (; slot_span; slot_span = next_slot_span) {
+    next_slot_span = slot_span->next_slot_span;
+    PA_DCHECK(slot_span->bucket == this);
+    PA_DCHECK(slot_span != empty_slot_spans_head);
+    PA_DCHECK(slot_span != decommitted_slot_spans_head);
+
+    if (LIKELY(slot_span->is_active())) {
+      // This slot span is usable because it has freelist entries, or has
+      // unprovisioned slots we can create freelist entries from.
+      active_slot_spans_head = slot_span;
+      return true;
+    }
+
+    // Deal with empty and decommitted slot spans.
+    if (LIKELY(slot_span->is_empty())) {
+      slot_span->next_slot_span = empty_slot_spans_head;
+      empty_slot_spans_head = slot_span;
+    } else if (LIKELY(slot_span->is_decommitted())) {
+      slot_span->next_slot_span = decommitted_slot_spans_head;
+      decommitted_slot_spans_head = slot_span;
+    } else {
+      PA_DCHECK(slot_span->is_full());
+      // If we get here, we found a full slot span. Skip over it too, and also
+      // mark it as full (via a negative value). We need it marked so that
+      // free'ing can tell, and move it back into the active list.
+      slot_span->num_allocated_slots = -slot_span->num_allocated_slots;
+      ++num_full_slot_spans;
+      // num_full_slot_spans is a uint16_t for efficient packing so guard
+      // against overflow to be safe.
+      if (UNLIKELY(!num_full_slot_spans))
+        OnFull();
+      // Not necessary but might help stop accidents.
+      slot_span->next_slot_span = nullptr;
+    }
+  }
+
+  active_slot_spans_head =
+      SlotSpanMetadata<thread_safe>::get_sentinel_slot_span();
+  return false;
+}
+
+template <bool thread_safe>
+void* PartitionBucket<thread_safe>::SlowPathAlloc(
+    PartitionRoot<thread_safe>* root,
+    int flags,
+    size_t raw_size,
+    size_t slot_span_alignment,
+    bool* is_already_zeroed) {
+  PA_DCHECK(slot_span_alignment &&
+            !(slot_span_alignment & PartitionPageOffsetMask()));
+
+  // The slow path is called when the freelist is empty. The only exception is
+  // when a higher-order alignment is requested, in which case the freelist
+  // logic is bypassed and we go directly for slot span allocation.
+  bool allocate_aligned_slot_span = slot_span_alignment > PartitionPageSize();
+  PA_DCHECK(!active_slot_spans_head->freelist_head ||
+            allocate_aligned_slot_span);
+
+  SlotSpanMetadata<thread_safe>* new_slot_span = nullptr;
+  // |new_slot_span->bucket| will always be |this|, except when |this| is the
+  // sentinel bucket, which is used to signal a direct mapped allocation.  In
+  // this case |new_bucket| will be set properly later. This avoids a read for
+  // most allocations.
+  PartitionBucket* new_bucket = this;
+  *is_already_zeroed = false;
+
+  // For the PartitionRoot::Alloc() API, we have a bunch of buckets
+  // marked as special cases. We bounce them through to the slow path so that
+  // we can still have a blazing fast hot path due to lack of corner-case
+  // branches.
+  //
+  // Note: The ordering of the conditionals matter! In particular,
+  // SetNewActiveSlotSpan() has a side-effect even when returning
+  // false where it sweeps the active list and may move things into the empty or
+  // decommitted lists which affects the subsequent conditional.
+  if (UNLIKELY(is_direct_mapped())) {
+    PA_DCHECK(raw_size > kMaxBucketed);
+    PA_DCHECK(this == &root->sentinel_bucket);
+    PA_DCHECK(active_slot_spans_head ==
+              SlotSpanMetadata<thread_safe>::get_sentinel_slot_span());
+    PA_DCHECK(!allocate_aligned_slot_span);  // not supported for direct map
+
+    // No fast path for direct-mapped allocations.
+    if (flags & PartitionAllocFastPathOrReturnNull)
+      return nullptr;
+
+    new_slot_span = PartitionDirectMap(root, flags, raw_size);
+    if (new_slot_span)
+      new_bucket = new_slot_span->bucket;
+    // Memory from PageAllocator is always zeroed.
+    *is_already_zeroed = true;
+  } else if (LIKELY(!allocate_aligned_slot_span && SetNewActiveSlotSpan())) {
+    // First, did we find an active slot span in the active list?
+    new_slot_span = active_slot_spans_head;
+    PA_DCHECK(new_slot_span->is_active());
+  } else if (LIKELY(!allocate_aligned_slot_span &&
+                    (empty_slot_spans_head != nullptr ||
+                     decommitted_slot_spans_head != nullptr))) {
+    // Second, look in our lists of empty and decommitted slot spans.
+    // Check empty slot spans first, which are preferred, but beware that an
+    // empty slot span might have been decommitted.
+    while (LIKELY((new_slot_span = empty_slot_spans_head) != nullptr)) {
+      PA_DCHECK(new_slot_span->bucket == this);
+      PA_DCHECK(new_slot_span->is_empty() || new_slot_span->is_decommitted());
+      empty_slot_spans_head = new_slot_span->next_slot_span;
+      // Accept the empty slot span unless it got decommitted.
+      if (new_slot_span->freelist_head) {
+        new_slot_span->next_slot_span = nullptr;
+        break;
+      }
+      PA_DCHECK(new_slot_span->is_decommitted());
+      new_slot_span->next_slot_span = decommitted_slot_spans_head;
+      decommitted_slot_spans_head = new_slot_span;
+    }
+    if (UNLIKELY(!new_slot_span) &&
+        LIKELY(decommitted_slot_spans_head != nullptr)) {
+      // Commit can be expensive, don't do it.
+      if (flags & PartitionAllocFastPathOrReturnNull)
+        return nullptr;
+
+      new_slot_span = decommitted_slot_spans_head;
+      PA_DCHECK(new_slot_span->bucket == this);
+      PA_DCHECK(new_slot_span->is_decommitted());
+      decommitted_slot_spans_head = new_slot_span->next_slot_span;
+
+      // If lazy commit is enabled, pages will be recommitted when provisioning
+      // slots, in ProvisionMoreSlotsAndAllocOne(), not here.
+      if (!root->use_lazy_commit) {
+        void* addr =
+            SlotSpanMetadata<thread_safe>::ToSlotSpanStartPtr(new_slot_span);
+        // If lazy commit was never used, we have a guarantee that all slot span
+        // pages have been previously committed, and then decommitted using
+        // PageKeepPermissionsIfPossible, so use the same option as an
+        // optimization. Otherwise fall back to PageUpdatePermissions (slower).
+        // (Insider knowledge: as of writing this comment, lazy commit is only
+        // used on Windows and this flag is ignored there, thus no perf impact.)
+        // TODO(lizeb): Handle commit failure.
+        root->RecommitSystemPagesForData(
+            addr, new_slot_span->bucket->get_bytes_per_span(),
+            root->never_used_lazy_commit ? PageKeepPermissionsIfPossible
+                                         : PageUpdatePermissions);
+      }
+
+      new_slot_span->Reset();
+      *is_already_zeroed = DecommittedMemoryIsAlwaysZeroed();
+    }
+    PA_DCHECK(new_slot_span);
+  } else {
+    // Getting a new slot span is expensive, don't do it.
+    if (flags & PartitionAllocFastPathOrReturnNull)
+      return nullptr;
+
+    // Third. If we get here, we need a brand new slot span.
+    // TODO(bartekn): For single-slot slot spans, we can use rounded raw_size
+    // as slot_span_committed_size.
+    new_slot_span = AllocNewSlotSpan(root, flags, slot_span_alignment);
+    // New memory from PageAllocator is always zeroed.
+    *is_already_zeroed = true;
+  }
+
+  // Bail if we had a memory allocation failure.
+  if (UNLIKELY(!new_slot_span)) {
+    PA_DCHECK(active_slot_spans_head ==
+              SlotSpanMetadata<thread_safe>::get_sentinel_slot_span());
+    if (flags & PartitionAllocReturnNull)
+      return nullptr;
+    // See comment in PartitionDirectMap() for unlocking.
+    ScopedUnlockGuard<thread_safe> unlock{root->lock_};
+    root->OutOfMemory(raw_size);
+    IMMEDIATE_CRASH();  // Not required, kept as documentation.
+  }
+
+  PA_DCHECK(new_bucket != &root->sentinel_bucket);
+  new_bucket->active_slot_spans_head = new_slot_span;
+  if (new_slot_span->CanStoreRawSize())
+    new_slot_span->SetRawSize(raw_size);
+
+  // If we found an active slot span with free slots, or an empty slot span, we
+  // have a usable freelist head.
+  if (LIKELY(new_slot_span->freelist_head != nullptr)) {
+    PartitionFreelistEntry* entry = new_slot_span->freelist_head;
+    PartitionFreelistEntry* new_head = entry->GetNext();
+    new_slot_span->SetFreelistHead(new_head);
+    new_slot_span->num_allocated_slots++;
+
+    // We likely set *is_already_zeroed to true above, make sure that the
+    // freelist entry doesn't contain data.
+    return entry->ClearForAllocation();
+  }
+
+  // Otherwise, we need to provision more slots by committing more pages. Build
+  // the free list for the newly provisioned slots.
+  PA_DCHECK(new_slot_span->num_unprovisioned_slots);
+  return ProvisionMoreSlotsAndAllocOne(root, new_slot_span);
+}
+
+template struct PartitionBucket<ThreadSafe>;
+template struct PartitionBucket<NotThreadSafe>;
+
+}  // namespace internal
+}  // namespace base

src/base/allocator/partition_allocator/partition_bucket.h

@@ -0,0 +1,187 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_BUCKET_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_BUCKET_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/thread_annotations.h"
+
+namespace base {
+namespace internal {
+
+template <bool thread_safe>
+struct PartitionBucket {
+  // Accessed most in hot path => goes first. Only nullptr for invalid buckets,
+  // may be pointing to the sentinel.
+  SlotSpanMetadata<thread_safe>* active_slot_spans_head;
+
+  SlotSpanMetadata<thread_safe>* empty_slot_spans_head;
+  SlotSpanMetadata<thread_safe>* decommitted_slot_spans_head;
+  uint32_t slot_size;
+  uint32_t num_system_pages_per_slot_span : 8;
+  uint32_t num_full_slot_spans : 24;
+
+  // `slot_size_reciprocal` is used to improve the performance of
+  // `GetSlotOffset`. It is computed as `(1 / size) * (2 ** M)` where M is
+  // chosen to provide the desired accuracy. As a result, we can replace a slow
+  // integer division (or modulo) operation with a pair of multiplication and a
+  // bit shift, i.e. `value / size` becomes `(value * size_reciprocal) >> M`.
+  uint64_t slot_size_reciprocal;
+
+  // This is `M` from the formula above. For accurate results, both `value` and
+  // `size`, which are bound by `kMaxBucketed` for our purposes, must be less
+  // than `2 ** (M / 2)`. On the other hand, the result of the expression
+  // `3 * M / 2` must be less than 64, otherwise integer overflow can occur.
+  static constexpr uint64_t kReciprocalShift = 42;
+  static constexpr uint64_t kReciprocalMask = (1ull << kReciprocalShift) - 1;
+  static_assert(
+      kMaxBucketed < (1 << (kReciprocalShift / 2)),
+      "GetSlotOffset may produce an incorrect result when kMaxBucketed is too "
+      "large.");
+
+  // Public API.
+  void Init(uint32_t new_slot_size);
+
+  // Sets |is_already_zeroed| to true if the allocation was satisfied by
+  // requesting (a) new page(s) from the operating system, or false otherwise.
+  // This enables an optimization for when callers use |PartitionAllocZeroFill|:
+  // there is no need to call memset on fresh pages; the OS has already zeroed
+  // them. (See |PartitionRoot::AllocFromBucket|.)
+  //
+  // Note the matching Free() functions are in SlotSpanMetadata.
+  BASE_EXPORT NOINLINE void* SlowPathAlloc(PartitionRoot<thread_safe>* root,
+                                           int flags,
+                                           size_t raw_size,
+                                           size_t slot_span_alignment,
+                                           bool* is_already_zeroed)
+      EXCLUSIVE_LOCKS_REQUIRED(root->lock_);
+
+  ALWAYS_INLINE bool CanStoreRawSize() const {
+    // For direct-map as well as single-slot slot spans (recognized by checking
+    // against |MaxSystemPagesPerSlotSpan()|), we have some spare metadata
+    // space in subsequent PartitionPage to store the raw size. It isn't only
+    // metadata space though, slot spans that have more than one slot can't have
+    // raw size stored, because we wouldn't know which slot it applies to.
+    if (LIKELY(slot_size <= MaxSystemPagesPerSlotSpan() * SystemPageSize()))
+      return false;
+
+    PA_DCHECK((slot_size % SystemPageSize()) == 0);
+    PA_DCHECK(is_direct_mapped() || get_slots_per_span() == 1);
+
+    return true;
+  }
+
+  // Some buckets are pseudo-buckets, which are disabled because they would
+  // otherwise not fulfill alignment constraints.
+  ALWAYS_INLINE bool is_valid() const {
+    return active_slot_spans_head != nullptr;
+  }
+  ALWAYS_INLINE bool is_direct_mapped() const {
+    return !num_system_pages_per_slot_span;
+  }
+  ALWAYS_INLINE size_t get_bytes_per_span() const {
+    // TODO(ajwong): Change to CheckedMul. https://crbug.com/787153
+    // https://crbug.com/680657
+    return num_system_pages_per_slot_span * SystemPageSize();
+  }
+  ALWAYS_INLINE uint16_t get_slots_per_span() const {
+    // TODO(ajwong): Change to CheckedMul. https://crbug.com/787153
+    // https://crbug.com/680657
+    return static_cast<uint16_t>(get_bytes_per_span() / slot_size);
+  }
+  // Returns a natural number of partition pages (calculated by
+  // get_system_pages_per_slot_span()) to allocate from the current
+  // super page when the bucket runs out of slots.
+  ALWAYS_INLINE uint16_t get_pages_per_slot_span() const {
+    // Rounds up to nearest multiple of NumSystemPagesPerPartitionPage().
+    return (num_system_pages_per_slot_span +
+            (NumSystemPagesPerPartitionPage() - 1)) /
+           NumSystemPagesPerPartitionPage();
+  }
+
+  // This helper function scans a bucket's active slot span list for a suitable
+  // new active slot span.  When it finds a suitable new active slot span (one
+  // that has free slots and is not empty), it is set as the new active slot
+  // span. If there is no suitable new active slot span, the current active slot
+  // span is set to SlotSpanMetadata::get_sentinel_slot_span(). As potential
+  // slot spans are scanned, they are tidied up according to their state. Empty
+  // slot spans are swept on to the empty list, decommitted slot spans on to the
+  // decommitted list and full slot spans are unlinked from any list.
+  //
+  // This is where the guts of the bucket maintenance is done!
+  bool SetNewActiveSlotSpan();
+
+  // Returns a slot number starting from the beginning of the slot span.
+  ALWAYS_INLINE size_t GetSlotNumber(size_t offset_in_slot_span) {
+    // See the static assertion for `kReciprocalShift` above.
+    PA_DCHECK(offset_in_slot_span <= kMaxBucketed);
+    PA_DCHECK(slot_size <= kMaxBucketed);
+
+    const size_t offset_in_slot =
+        ((offset_in_slot_span * slot_size_reciprocal) >> kReciprocalShift);
+    PA_DCHECK(offset_in_slot_span / slot_size == offset_in_slot);
+
+    return offset_in_slot;
+  }
+
+ private:
+  static NOINLINE void OnFull();
+
+  // Returns the number of system pages in a slot span.
+  //
+  // The calculation attempts to find the best number of system pages to
+  // allocate for the given slot_size to minimize wasted space. It uses a
+  // heuristic that looks at number of bytes wasted after the last slot and
+  // attempts to account for the PTE usage of each system page.
+  uint8_t get_system_pages_per_slot_span();
+
+  // Allocates a new slot span with size |num_partition_pages| from the
+  // current extent. Metadata within this slot span will be initialized.
+  // Returns nullptr on error.
+  ALWAYS_INLINE SlotSpanMetadata<thread_safe>* AllocNewSlotSpan(
+      PartitionRoot<thread_safe>* root,
+      int flags,
+      size_t slot_span_alignment) EXCLUSIVE_LOCKS_REQUIRED(root->lock_);
+
+  // Allocates a new super page from the current extent. All slot-spans will be
+  // in the decommitted state. Returns nullptr on error.
+  ALWAYS_INLINE void* AllocNewSuperPage(PartitionRoot<thread_safe>* root)
+      EXCLUSIVE_LOCKS_REQUIRED(root->lock_);
+
+  // Each bucket allocates a slot span when it runs out of slots.
+  // A slot span's size is equal to get_pages_per_slot_span() number of
+  // partition pages. This function initializes all PartitionPage within the
+  // span to point to the first PartitionPage which holds all the metadata
+  // for the span (in PartitionPage::SlotSpanMetadata) and registers this bucket
+  // as the owner of the span. It does NOT put the slots into the bucket's
+  // freelist.
+  ALWAYS_INLINE void InitializeSlotSpan(
+      SlotSpanMetadata<thread_safe>* slot_span);
+
+  // Commit 1 or more pages in |slot_span|, enough to get the next slot, which
+  // is returned by this function. If more slots fit into the committed pages,
+  // they'll be added to the free list of the slot span (note that next pointers
+  // are stored inside the slots).
+  // The free list must be empty when calling this function.
+  //
+  // If |slot_span| was freshly allocated, it must have been passed through
+  // InitializeSlotSpan() first.
+  ALWAYS_INLINE char* ProvisionMoreSlotsAndAllocOne(
+      PartitionRoot<thread_safe>* root,
+      SlotSpanMetadata<thread_safe>* slot_span)
+      EXCLUSIVE_LOCKS_REQUIRED(root->lock_);
+};
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_BUCKET_H_

src/base/allocator/partition_allocator/partition_cookie.h

@@ -0,0 +1,53 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_COOKIE_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_COOKIE_H_
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/compiler_specific.h"
+
+namespace base {
+namespace internal {
+
+// Handles alignment up to XMM instructions on Intel.
+static constexpr size_t kCookieSize = 16;
+
+// Cookies are enabled for debug builds.
+#if DCHECK_IS_ON()
+
+static constexpr unsigned char kCookieValue[kCookieSize] = {
+    0xDE, 0xAD, 0xBE, 0xEF, 0xCA, 0xFE, 0xD0, 0x0D,
+    0x13, 0x37, 0xF0, 0x05, 0xBA, 0x11, 0xAB, 0x1E};
+
+constexpr size_t kPartitionCookieSizeAdjustment = 2 * kCookieSize;
+constexpr size_t kPartitionCookieOffsetAdjustment = kCookieSize;
+
+ALWAYS_INLINE void PartitionCookieCheckValue(void* ptr) {
+  unsigned char* cookie_ptr = reinterpret_cast<unsigned char*>(ptr);
+  for (size_t i = 0; i < kCookieSize; ++i, ++cookie_ptr)
+    PA_DCHECK(*cookie_ptr == kCookieValue[i]);
+}
+
+ALWAYS_INLINE void PartitionCookieWriteValue(void* ptr) {
+  unsigned char* cookie_ptr = reinterpret_cast<unsigned char*>(ptr);
+  for (size_t i = 0; i < kCookieSize; ++i, ++cookie_ptr)
+    *cookie_ptr = kCookieValue[i];
+}
+
+#else
+
+constexpr size_t kPartitionCookieSizeAdjustment = 0;
+constexpr size_t kPartitionCookieOffsetAdjustment = 0;
+
+ALWAYS_INLINE void PartitionCookieCheckValue(void* ptr) {}
+
+ALWAYS_INLINE void PartitionCookieWriteValue(void* ptr) {}
+#endif  // DCHECK_IS_ON()
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_COOKIE_H_

src/base/allocator/partition_allocator/partition_direct_map_extent.h

@@ -0,0 +1,56 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_DIRECT_MAP_EXTENT_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_DIRECT_MAP_EXTENT_H_
+
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_bucket.h"
+#include "base/allocator/partition_allocator/partition_page.h"
+
+namespace base {
+namespace internal {
+
+template <bool thread_safe>
+struct PartitionDirectMapExtent {
+  PartitionDirectMapExtent<thread_safe>* next_extent;
+  PartitionDirectMapExtent<thread_safe>* prev_extent;
+  PartitionBucket<thread_safe>* bucket;
+  size_t map_size;  // Mapped size, not including guard pages and meta-data.
+
+  ALWAYS_INLINE static PartitionDirectMapExtent<thread_safe>* FromSlotSpan(
+      SlotSpanMetadata<thread_safe>* slot_span);
+};
+
+// Metadata page for direct-mapped allocations.
+template <bool thread_safe>
+struct PartitionDirectMapMetadata {
+  union {
+    PartitionSuperPageExtentEntry<thread_safe> extent;
+    // Never used, but must have the same size as a real PartitionPage.
+    PartitionPage<thread_safe> first_invalid_page;
+  };
+  PartitionPage<thread_safe> page;
+  PartitionBucket<thread_safe> bucket;
+  PartitionDirectMapExtent<thread_safe> direct_map_extent;
+};
+
+template <bool thread_safe>
+ALWAYS_INLINE PartitionDirectMapExtent<thread_safe>*
+PartitionDirectMapExtent<thread_safe>::FromSlotSpan(
+    SlotSpanMetadata<thread_safe>* slot_span) {
+  PA_DCHECK(slot_span->bucket->is_direct_mapped());
+  auto* page = reinterpret_cast<PartitionPage<thread_safe>*>(slot_span);
+  // The page passed here is always |page| in |PartitionDirectMapMetadata|
+  // above. To get the metadata structure, need to get the invalid page address.
+  auto* first_invalid_page = page - 1;
+  auto* metadata = reinterpret_cast<PartitionDirectMapMetadata<thread_safe>*>(
+      first_invalid_page);
+  return &metadata->direct_map_extent;
+}
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_DIRECT_MAP_EXTENT_H_

src/base/allocator/partition_allocator/partition_freelist_entry.h

@@ -0,0 +1,196 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_FREELIST_ENTRY_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_FREELIST_ENTRY_H_
+
+#include <stdint.h>
+
+#include "base/allocator/partition_allocator/partition_alloc-inl.h"
+#include "base/allocator/partition_allocator/partition_alloc_config.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_ref_count.h"
+#include "base/compiler_specific.h"
+#include "base/dcheck_is_on.h"
+#include "base/immediate_crash.h"
+#include "base/partition_alloc_buildflags.h"
+#include "base/sys_byteorder.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+#if defined(PA_HAS_FREELIST_HARDENING) || DCHECK_IS_ON()
+[[noreturn]] NOINLINE void FreelistCorruptionDetected() {
+  IMMEDIATE_CRASH();
+}
+#endif  // defined(PA_HAS_FREELIST_HARDENING) || DCHECK_IS_ON()
+
+}  // namespace
+
+struct EncodedPartitionFreelistEntry;
+
+#if defined(PA_HAS_FREELIST_HARDENING)
+static_assert(kSmallestBucket >= 2 * sizeof(void*),
+              "Need enough space for two pointers in freelist entries");
+#endif
+
+#if BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+constexpr size_t kMinimalBucketSizeWithRefCount =
+    (1 + sizeof(PartitionRefCount) + kSmallestBucket - 1) &
+    ~(kSmallestBucket - 1);
+#if defined(PA_HAS_FREELIST_HARDENING)
+static_assert(
+    kMinimalBucketSizeWithRefCount >=
+        sizeof(PartitionRefCount) + 2 * sizeof(void*),
+    "Need enough space for two pointer and one refcount in freelist entries");
+#else
+static_assert(
+    kMinimalBucketSizeWithRefCount >= sizeof(PartitionRefCount) + sizeof(void*),
+    "Need enough space for one pointer and one refcount in freelist entries");
+#endif
+#endif
+
+// Freelist entries are encoded for security reasons. See
+// //base/allocator/partition_allocator/PartitionAlloc.md and |Transform()| for
+// the rationale and mechanism, respectively.
+class PartitionFreelistEntry {
+ public:
+  PartitionFreelistEntry() { SetNext(nullptr); }
+  ~PartitionFreelistEntry() = delete;
+
+  // Creates a new entry, with |next| following it.
+  static ALWAYS_INLINE PartitionFreelistEntry* InitForThreadCache(
+      void* slot_start,
+      PartitionFreelistEntry* next) {
+    auto* entry = reinterpret_cast<PartitionFreelistEntry*>(slot_start);
+    // ThreadCache freelists can point to entries across superpage boundaries,
+    // no check contrary to |SetNext()|.
+    entry->SetNextInternal(next);
+    return entry;
+  }
+
+  // Placement new only.
+  void* operator new(size_t) = delete;
+  void operator delete(void* ptr) = delete;
+  void* operator new(size_t, void* buffer) { return buffer; }
+
+  ALWAYS_INLINE static EncodedPartitionFreelistEntry* Encode(
+      PartitionFreelistEntry* ptr) {
+    return reinterpret_cast<EncodedPartitionFreelistEntry*>(Transform(ptr));
+  }
+
+  ALWAYS_INLINE PartitionFreelistEntry* GetNext() const;
+  NOINLINE void CheckFreeList() const {
+#if defined(PA_HAS_FREELIST_HARDENING)
+    for (auto* entry = this; entry; entry = entry->GetNext()) {
+      // |GetNext()| checks freelist integrity.
+    }
+#endif
+  }
+
+  ALWAYS_INLINE void SetNext(PartitionFreelistEntry* ptr) {
+#if DCHECK_IS_ON()
+    // Regular freelists always point to an entry within the same super page.
+    if (UNLIKELY(ptr &&
+                 (reinterpret_cast<uintptr_t>(this) & kSuperPageBaseMask) !=
+                     (reinterpret_cast<uintptr_t>(ptr) & kSuperPageBaseMask))) {
+      FreelistCorruptionDetected();
+    }
+#endif  // DCHECK_IS_ON()
+    SetNextInternal(ptr);
+  }
+
+  // Zeroes out |this| before returning it.
+  ALWAYS_INLINE void* ClearForAllocation() {
+    next_ = nullptr;
+#if defined(PA_HAS_FREELIST_HARDENING)
+    inverted_next_ = 0;
+#endif
+    return reinterpret_cast<void*>(this);
+  }
+
+ private:
+  friend struct EncodedPartitionFreelistEntry;
+  ALWAYS_INLINE static void* Transform(void* ptr) {
+    // We use bswap on little endian as a fast mask for two reasons:
+    // 1) If an object is freed and its vtable used where the attacker doesn't
+    // get the chance to run allocations between the free and use, the vtable
+    // dereference is likely to fault.
+    // 2) If the attacker has a linear buffer overflow and elects to try and
+    // corrupt a freelist pointer, partial pointer overwrite attacks are
+    // thwarted.
+    // For big endian, similar guarantees are arrived at with a negation.
+#if defined(ARCH_CPU_BIG_ENDIAN)
+    uintptr_t masked = ~reinterpret_cast<uintptr_t>(ptr);
+#else
+    uintptr_t masked = ByteSwapUintPtrT(reinterpret_cast<uintptr_t>(ptr));
+#endif
+    return reinterpret_cast<void*>(masked);
+  }
+
+  ALWAYS_INLINE void SetNextInternal(PartitionFreelistEntry* ptr) {
+    next_ = Encode(ptr);
+#if defined(PA_HAS_FREELIST_HARDENING)
+    inverted_next_ = ~reinterpret_cast<uintptr_t>(next_);
+#endif
+  }
+
+  EncodedPartitionFreelistEntry* next_;
+  // This is intended to detect unintentional corruptions of the freelist.
+  // These can happen due to a Use-after-Free, or overflow of the previous
+  // allocation in the slot span.
+#if defined(PA_HAS_FREELIST_HARDENING)
+  uintptr_t inverted_next_;
+#endif
+};
+
+struct EncodedPartitionFreelistEntry {
+  char scrambled[sizeof(PartitionFreelistEntry*)];
+#if defined(PA_HAS_FREELIST_HARDENING)
+  char copy_of_scrambled[sizeof(PartitionFreelistEntry*)];
+#endif
+
+  EncodedPartitionFreelistEntry() = delete;
+  ~EncodedPartitionFreelistEntry() = delete;
+
+  ALWAYS_INLINE static PartitionFreelistEntry* Decode(
+      EncodedPartitionFreelistEntry* ptr) {
+    return reinterpret_cast<PartitionFreelistEntry*>(
+        PartitionFreelistEntry::Transform(ptr));
+  }
+};
+
+static_assert(sizeof(PartitionFreelistEntry) ==
+                  sizeof(EncodedPartitionFreelistEntry),
+              "Should not have padding");
+
+ALWAYS_INLINE PartitionFreelistEntry* PartitionFreelistEntry::GetNext() const {
+#if defined(PA_HAS_FREELIST_HARDENING)
+  // GetNext() can be called on decommitted memory, which is full of
+  // zeroes. This is not a corruption issue, so only check integrity when we
+  // have a non-nullptr |next_| pointer.
+  if (UNLIKELY(next_ && ~reinterpret_cast<uintptr_t>(next_) != inverted_next_))
+    FreelistCorruptionDetected();
+#endif  // defined(PA_HAS_FREELIST_HARDENING)
+  auto* ret = EncodedPartitionFreelistEntry::Decode(next_);
+  // In real-world profiles, the load of |next_| above is responsible for a
+  // large fraction of the allocation cost. However, we cannot anticipate it
+  // enough since it is accessed right after we know its address.
+  //
+  // In the case of repeated allocations, we can prefetch the access that will
+  // be done at the *next* allocation, which will touch *ret, prefetch it. There
+  // is no harm in prefetching nullptr, but on some architectures, it causes a
+  // needless dTLB miss.
+  if (ret)
+    PA_PREFETCH(ret);
+  return ret;
+}
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_FREELIST_ENTRY_H_

src/base/allocator/partition_allocator/partition_lock.cc

@@ -0,0 +1,62 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_lock.h"
+
+#include "base/allocator/partition_allocator/yield_processor.h"
+#include "base/threading/platform_thread.h"
+
+#if !defined(PA_HAS_SPINNING_MUTEX)
+
+#if defined(OS_POSIX) || defined(OS_FUCHSIA)
+#include <sched.h>
+
+#define YIELD_THREAD sched_yield()
+
+#else  // Other OS
+
+#warning "Thread yield not supported on this OS."
+#define YIELD_THREAD ((void)0)
+
+#endif  // defined(OS_POSIX) || defined(OS_FUCHSIA)
+
+namespace base {
+namespace internal {
+
+void SpinLock::AcquireSlow() {
+  // The value of |kYieldProcessorTries| is cargo culted from TCMalloc, Windows
+  // critical section defaults, and various other recommendations.
+  static const int kYieldProcessorTries = 1000;
+  // The value of |kYieldThreadTries| is completely made up.
+  static const int kYieldThreadTries = 10;
+  int yield_thread_count = 0;
+  do {
+    do {
+      for (int count = 0; count < kYieldProcessorTries; ++count) {
+        // Let the processor know we're spinning.
+        YIELD_PROCESSOR;
+        if (!lock_.load(std::memory_order_relaxed) &&
+            LIKELY(!lock_.exchange(true, std::memory_order_acquire)))
+          return;
+      }
+
+      if (yield_thread_count < kYieldThreadTries) {
+        ++yield_thread_count;
+        // Give the OS a chance to schedule something on this core.
+        YIELD_THREAD;
+      } else {
+        // At this point, it's likely that the lock is held by a lower priority
+        // thread that is unavailable to finish its work because of higher
+        // priority threads spinning here. Sleeping should ensure that they make
+        // progress.
+        PlatformThread::Sleep(TimeDelta::FromMilliseconds(1));
+      }
+    } while (lock_.load(std::memory_order_relaxed));
+  } while (UNLIKELY(lock_.exchange(true, std::memory_order_acquire)));
+}
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // !defined(PA_HAS_SPINNING_MUTEX)

src/base/allocator/partition_allocator/partition_lock.h

@@ -0,0 +1,185 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_LOCK_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_LOCK_H_
+
+#include <atomic>
+#include <type_traits>
+
+#include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/spinning_mutex.h"
+#include "base/thread_annotations.h"
+#include "base/threading/platform_thread.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace internal {
+
+template <bool thread_safe>
+class LOCKABLE MaybeSpinLock {
+ public:
+  void Lock() EXCLUSIVE_LOCK_FUNCTION() {}
+  void Unlock() UNLOCK_FUNCTION() {}
+  void AssertAcquired() const ASSERT_EXCLUSIVE_LOCK() {}
+};
+
+template <bool thread_safe>
+class SCOPED_LOCKABLE ScopedGuard {
+ public:
+  explicit ScopedGuard(MaybeSpinLock<thread_safe>& lock)
+      EXCLUSIVE_LOCK_FUNCTION(lock)
+      : lock_(lock) {
+    lock_.Lock();
+  }
+  ~ScopedGuard() UNLOCK_FUNCTION() { lock_.Unlock(); }
+
+ private:
+  MaybeSpinLock<thread_safe>& lock_;
+};
+
+template <bool thread_safe>
+class SCOPED_LOCKABLE ScopedUnlockGuard {
+ public:
+  explicit ScopedUnlockGuard(MaybeSpinLock<thread_safe>& lock)
+      UNLOCK_FUNCTION(lock)
+      : lock_(lock) {
+    lock_.Unlock();
+  }
+  ~ScopedUnlockGuard() EXCLUSIVE_LOCK_FUNCTION() { lock_.Lock(); }
+
+ private:
+  MaybeSpinLock<thread_safe>& lock_;
+};
+
+#if !defined(PA_HAS_SPINNING_MUTEX)
+// Spinlock. Do not use, to be removed. crbug.com/1061437.
+class LOCKABLE BASE_EXPORT SpinLock {
+ public:
+  constexpr SpinLock() = default;
+  ~SpinLock() = default;
+
+  ALWAYS_INLINE void Acquire() EXCLUSIVE_LOCK_FUNCTION() {
+    if (LIKELY(!lock_.exchange(true, std::memory_order_acquire)))
+      return;
+    AcquireSlow();
+  }
+
+  ALWAYS_INLINE bool Try() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
+    // Faster than simple CAS.
+    return !lock_.load(std::memory_order_relaxed) &&
+           !lock_.exchange(true, std::memory_order_acquire);
+  }
+
+  ALWAYS_INLINE void Release() UNLOCK_FUNCTION() {
+    lock_.store(false, std::memory_order_release);
+  }
+
+  // Not supported.
+  void AssertAcquired() const {}
+
+ private:
+  // This is called if the initial attempt to acquire the lock fails. It's
+  // slower, but has a much better scheduling and power consumption behavior.
+  void AcquireSlow();
+
+  std::atomic_int lock_{0};
+};
+#endif  // !defined(PA_HAS_SPINNING_MUTEX)
+
+template <>
+class LOCKABLE MaybeSpinLock<true> {
+ public:
+  constexpr MaybeSpinLock() : lock_() {}
+  void Lock() EXCLUSIVE_LOCK_FUNCTION() {
+#if DCHECK_IS_ON()
+    // When PartitionAlloc is malloc(), it can easily become reentrant. For
+    // instance, a DCHECK() triggers in external code (such as
+    // base::Lock). DCHECK() error message formatting allocates, which triggers
+    // PartitionAlloc, and then we get reentrancy, and in this case infinite
+    // recursion.
+    //
+    // To avoid that, crash quickly when the code becomes reentrant.
+    PlatformThreadRef current_thread = PlatformThread::CurrentRef();
+    if (!lock_.Try()) {
+      // The lock wasn't free when we tried to acquire it. This can be because
+      // another thread or *this* thread was holding it.
+      //
+      // If it's this thread holding it, then it cannot have become free in the
+      // meantime, and the current value of |owning_thread_ref_| is valid, as it
+      // was set by this thread. Assuming that writes to |owning_thread_ref_|
+      // are atomic, then if it's us, we are trying to recursively acquire a
+      // non-recursive lock.
+      //
+      // Note that we don't rely on a DCHECK() in base::Lock(), as it would
+      // itself allocate. Meaning that without this code, a reentrancy issue
+      // hangs on Linux.
+      if (UNLIKELY(owning_thread_ref_.load(std::memory_order_acquire) ==
+                   current_thread)) {
+        // Trying to acquire lock while it's held by this thread: reentrancy
+        // issue.
+        IMMEDIATE_CRASH();
+      }
+      lock_.Acquire();
+    }
+    owning_thread_ref_.store(current_thread, std::memory_order_release);
+#else
+    lock_.Acquire();
+#endif
+  }
+
+  void Unlock() UNLOCK_FUNCTION() {
+#if DCHECK_IS_ON()
+    owning_thread_ref_.store(PlatformThreadRef(), std::memory_order_release);
+#endif
+    lock_.Release();
+  }
+  void AssertAcquired() const ASSERT_EXCLUSIVE_LOCK() {
+    lock_.AssertAcquired();
+#if DCHECK_IS_ON()
+    PA_DCHECK(owning_thread_ref_.load(std ::memory_order_acquire) ==
+              PlatformThread::CurrentRef());
+#endif
+  }
+
+ private:
+#if defined(PA_HAS_SPINNING_MUTEX)
+  SpinningMutex lock_;
+#else
+  // base::Lock is slower on the fast path than SpinLock, hence we still use
+  // SpinLock. crbug.com/1125999
+  SpinLock lock_;
+#endif  // defined(PA_HAS_SPINNING_MUTEX)
+
+#if DCHECK_IS_ON()
+  // Should in theory be protected by |lock_|, but we need to read it to detect
+  // recursive lock acquisition (and thus, the allocator becoming reentrant).
+  std::atomic<PlatformThreadRef> owning_thread_ref_{};
+#endif
+};
+// We want PartitionRoot to not have a global destructor, so this should not
+// have one.
+static_assert(std::is_trivially_destructible<MaybeSpinLock<true>>::value, "");
+
+template <>
+class LOCKABLE MaybeSpinLock<false> {
+ public:
+  void Lock() EXCLUSIVE_LOCK_FUNCTION() {}
+  void Unlock() UNLOCK_FUNCTION() {}
+  void AssertAcquired() const ASSERT_EXCLUSIVE_LOCK() {}
+
+  char padding_[sizeof(MaybeSpinLock<true>)];
+};
+
+static_assert(
+    sizeof(MaybeSpinLock<true>) == sizeof(MaybeSpinLock<false>),
+    "Sizes should be equal to ensure identical layout of PartitionRoot");
+
+using PartitionLock = MaybeSpinLock<true>;
+using PartitionAutoLock = ScopedGuard<true>;
+
+}  // namespace internal
+}  // namespace base
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_LOCK_H_

src/base/allocator/partition_allocator/partition_oom.cc

@@ -0,0 +1,38 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_oom.h"
+
+#include "base/allocator/partition_allocator/oom.h"
+#include "base/compiler_specific.h"
+#include "base/debug/alias.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace internal {
+
+OomFunction g_oom_handling_function = nullptr;
+
+NOINLINE void NOT_TAIL_CALLED PartitionExcessiveAllocationSize(size_t size) {
+  NO_CODE_FOLDING();
+  OOM_CRASH(size);
+}
+
+#if !defined(ARCH_CPU_64_BITS)
+NOINLINE void NOT_TAIL_CALLED
+PartitionOutOfMemoryWithLotsOfUncommitedPages(size_t size) {
+  NO_CODE_FOLDING();
+  OOM_CRASH(size);
+}
+
+[[noreturn]] NOINLINE void NOT_TAIL_CALLED
+PartitionOutOfMemoryWithLargeVirtualSize(size_t virtual_size) {
+  NO_CODE_FOLDING();
+  OOM_CRASH(virtual_size);
+}
+
+#endif  // !defined(ARCH_CPU_64_BITS)
+
+}  // namespace internal
+}  // namespace base

src/base/allocator/partition_allocator/partition_oom.h

@@ -0,0 +1,40 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Holds functions for generating OOM errors from PartitionAlloc. This is
+// distinct from oom.h in that it is meant only for use in PartitionAlloc.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_OOM_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_OOM_H_
+
+#include <stddef.h>
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "build/build_config.h"
+
+namespace base {
+
+typedef void (*OomFunction)(size_t);
+
+namespace internal {
+
+// g_oom_handling_function is invoked when PartitionAlloc hits OutOfMemory.
+extern OomFunction g_oom_handling_function;
+
+[[noreturn]] BASE_EXPORT NOINLINE void PartitionExcessiveAllocationSize(
+    size_t size);
+
+#if !defined(ARCH_CPU_64_BITS)
+[[noreturn]] NOINLINE void PartitionOutOfMemoryWithLotsOfUncommitedPages(
+    size_t size);
+[[noreturn]] NOINLINE void PartitionOutOfMemoryWithLargeVirtualSize(
+    size_t virtual_size);
+#endif
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_OOM_H_

src/base/allocator/partition_allocator/partition_page.cc

@@ -0,0 +1,245 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/allocator/partition_allocator/partition_page.h"
+
+#include "base/allocator/partition_allocator/address_pool_manager.h"
+#include "base/allocator/partition_allocator/page_allocator.h"
+#include "base/allocator/partition_allocator/page_allocator_constants.h"
+#include "base/allocator/partition_allocator/partition_address_space.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_features.h"
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/allocator/partition_allocator/partition_direct_map_extent.h"
+#include "base/allocator/partition_allocator/partition_root.h"
+#include "base/bits.h"
+#include "base/dcheck_is_on.h"
+#include "base/feature_list.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+template <bool thread_safe>
+ALWAYS_INLINE DeferredUnmap
+PartitionDirectUnmap(SlotSpanMetadata<thread_safe>* slot_span) {
+  auto* root = PartitionRoot<thread_safe>::FromSlotSpan(slot_span);
+  root->lock_.AssertAcquired();
+  auto* extent = PartitionDirectMapExtent<thread_safe>::FromSlotSpan(slot_span);
+
+  // Maintain the doubly-linked list of all direct mappings.
+  if (extent->prev_extent) {
+    PA_DCHECK(extent->prev_extent->next_extent == extent);
+    extent->prev_extent->next_extent = extent->next_extent;
+  } else {
+    root->direct_map_list = extent->next_extent;
+  }
+  if (extent->next_extent) {
+    PA_DCHECK(extent->next_extent->prev_extent == extent);
+    extent->next_extent->prev_extent = extent->prev_extent;
+  }
+
+  // The actual decommit is deferred, when releasing the reserved memory region.
+  root->DecreaseCommittedPages(slot_span->bucket->slot_size);
+
+  size_t reserved_size =
+      extent->map_size +
+      PartitionRoot<thread_safe>::GetDirectMapMetadataAndGuardPagesSize();
+  PA_DCHECK(!(reserved_size & DirectMapAllocationGranularityOffsetMask()));
+  PA_DCHECK(root->total_size_of_direct_mapped_pages >= reserved_size);
+  root->total_size_of_direct_mapped_pages -= reserved_size;
+  PA_DCHECK(!(reserved_size & DirectMapAllocationGranularityOffsetMask()));
+
+  char* ptr = reinterpret_cast<char*>(
+      SlotSpanMetadata<thread_safe>::ToSlotSpanStartPtr(slot_span));
+  // Account for the mapping starting a partition page before the actual
+  // allocation address.
+  ptr -= PartitionPageSize();
+
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  if (root->UseBRPPool()) {
+    uintptr_t ptr_as_uintptr = reinterpret_cast<uintptr_t>(ptr);
+    uintptr_t ptr_end = ptr_as_uintptr + reserved_size;
+    auto* offset_ptr = internal::ReservationOffsetPointer(ptr_as_uintptr);
+    while (ptr_as_uintptr < ptr_end) {
+      PA_DCHECK(offset_ptr < internal::EndOfReservationOffsetTable());
+      *offset_ptr++ = internal::NotInDirectMapOffsetTag();
+      ptr_as_uintptr += kSuperPageSize;
+    }
+  }
+  return {ptr, reserved_size, root->UseBRPPool()};
+#else
+  return {ptr, reserved_size};
+#endif
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE void PartitionRegisterEmptySlotSpan(
+    SlotSpanMetadata<thread_safe>* slot_span) {
+  PA_DCHECK(slot_span->is_empty());
+  PartitionRoot<thread_safe>* root =
+      PartitionRoot<thread_safe>::FromSlotSpan(slot_span);
+  root->lock_.AssertAcquired();
+
+  // If the slot span is already registered as empty, give it another life.
+  if (slot_span->empty_cache_index != -1) {
+    PA_DCHECK(slot_span->empty_cache_index >= 0);
+    PA_DCHECK(static_cast<unsigned>(slot_span->empty_cache_index) <
+              kMaxFreeableSpans);
+    PA_DCHECK(root->global_empty_slot_span_ring[slot_span->empty_cache_index] ==
+              slot_span);
+    root->global_empty_slot_span_ring[slot_span->empty_cache_index] = nullptr;
+  }
+
+  int16_t current_index = root->global_empty_slot_span_ring_index;
+  SlotSpanMetadata<thread_safe>* slot_span_to_decommit =
+      root->global_empty_slot_span_ring[current_index];
+  // The slot span might well have been re-activated, filled up, etc. before we
+  // get around to looking at it here.
+  if (slot_span_to_decommit)
+    slot_span_to_decommit->DecommitIfPossible(root);
+
+  // We put the empty slot span on our global list of "slot spans that were once
+  // empty". thus providing it a bit of breathing room to get re-used before
+  // we really free it. This improves performance, particularly on Mac OS X
+  // which has subpar memory management performance.
+  root->global_empty_slot_span_ring[current_index] = slot_span;
+  slot_span->empty_cache_index = current_index;
+  ++current_index;
+  if (current_index == kMaxFreeableSpans)
+    current_index = 0;
+  root->global_empty_slot_span_ring_index = current_index;
+}
+
+}  // namespace
+
+// static
+template <bool thread_safe>
+SlotSpanMetadata<thread_safe>
+    SlotSpanMetadata<thread_safe>::sentinel_slot_span_;
+
+// static
+template <bool thread_safe>
+SlotSpanMetadata<thread_safe>*
+SlotSpanMetadata<thread_safe>::get_sentinel_slot_span() {
+  return &sentinel_slot_span_;
+}
+
+template <bool thread_safe>
+SlotSpanMetadata<thread_safe>::SlotSpanMetadata(
+    PartitionBucket<thread_safe>* bucket)
+    : bucket(bucket), can_store_raw_size(bucket->CanStoreRawSize()) {}
+
+template <bool thread_safe>
+DeferredUnmap SlotSpanMetadata<thread_safe>::FreeSlowPath() {
+#if DCHECK_IS_ON()
+  auto* root = PartitionRoot<thread_safe>::FromSlotSpan(this);
+  root->lock_.AssertAcquired();
+#endif
+  PA_DCHECK(this != get_sentinel_slot_span());
+  if (LIKELY(num_allocated_slots == 0)) {
+    // Slot span became fully unused.
+    if (UNLIKELY(bucket->is_direct_mapped())) {
+      return PartitionDirectUnmap(this);
+    }
+#if DCHECK_IS_ON()
+    freelist_head->CheckFreeList();
+#endif
+    // If it's the current active slot span, change it. We bounce the slot span
+    // to the empty list as a force towards defragmentation.
+    if (LIKELY(this == bucket->active_slot_spans_head))
+      bucket->SetNewActiveSlotSpan();
+    PA_DCHECK(bucket->active_slot_spans_head != this);
+
+    if (CanStoreRawSize())
+      SetRawSize(0);
+
+    PartitionRegisterEmptySlotSpan(this);
+  } else {
+    PA_DCHECK(!bucket->is_direct_mapped());
+    // Ensure that the slot span is full. That's the only valid case if we
+    // arrive here.
+    PA_DCHECK(num_allocated_slots < 0);
+    // A transition of num_allocated_slots from 0 to -1 is not legal, and
+    // likely indicates a double-free.
+    PA_CHECK(num_allocated_slots != -1);
+    num_allocated_slots = -num_allocated_slots - 2;
+    PA_DCHECK(num_allocated_slots == bucket->get_slots_per_span() - 1);
+    // Fully used slot span became partially used. It must be put back on the
+    // non-full list. Also make it the current slot span to increase the
+    // chances of it being filled up again. The old current slot span will be
+    // the next slot span.
+    PA_DCHECK(!next_slot_span);
+    if (LIKELY(bucket->active_slot_spans_head != get_sentinel_slot_span()))
+      next_slot_span = bucket->active_slot_spans_head;
+    bucket->active_slot_spans_head = this;
+    --bucket->num_full_slot_spans;
+    // Special case: for a partition slot span with just a single slot, it may
+    // now be empty and we want to run it through the empty logic.
+    if (UNLIKELY(num_allocated_slots == 0))
+      return FreeSlowPath();
+  }
+  return {};
+}
+
+template <bool thread_safe>
+void SlotSpanMetadata<thread_safe>::Decommit(PartitionRoot<thread_safe>* root) {
+  root->lock_.AssertAcquired();
+  PA_DCHECK(is_empty());
+  PA_DCHECK(!bucket->is_direct_mapped());
+  void* slot_span_start = SlotSpanMetadata::ToSlotSpanStartPtr(this);
+  // If lazy commit is enabled, only provisioned slots are committed.
+  size_t size_to_decommit =
+      root->use_lazy_commit
+          ? bits::AlignUp(GetProvisionedSize(), SystemPageSize())
+          : bucket->get_bytes_per_span();
+
+  // Not decommitted slot span must've had at least 1 allocation.
+  PA_DCHECK(size_to_decommit > 0);
+  root->DecommitSystemPagesForData(slot_span_start, size_to_decommit,
+                                   PageKeepPermissionsIfPossible);
+
+  // We actually leave the decommitted slot span in the active list. We'll sweep
+  // it on to the decommitted list when we next walk the active list.
+  // Pulling this trick enables us to use a singly-linked list for all
+  // cases, which is critical in keeping the slot span metadata structure down
+  // to 32 bytes in size.
+  SetFreelistHead(nullptr);
+  num_unprovisioned_slots = 0;
+  PA_DCHECK(is_decommitted());
+  PA_DCHECK(bucket);
+}
+
+template <bool thread_safe>
+void SlotSpanMetadata<thread_safe>::DecommitIfPossible(
+    PartitionRoot<thread_safe>* root) {
+  root->lock_.AssertAcquired();
+  PA_DCHECK(empty_cache_index >= 0);
+  PA_DCHECK(static_cast<unsigned>(empty_cache_index) < kMaxFreeableSpans);
+  PA_DCHECK(this == root->global_empty_slot_span_ring[empty_cache_index]);
+  empty_cache_index = -1;
+  if (is_empty())
+    Decommit(root);
+}
+
+void DeferredUnmap::Unmap() {
+  PA_DCHECK(ptr && size > 0);
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  if (use_brp_pool) {
+    internal::AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+        internal::GetBRPPool(), ptr, size);
+    return;
+  }
+#endif  // BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  PA_DCHECK(IsManagedByPartitionAllocNonBRPPool(ptr));
+  internal::AddressPoolManager::GetInstance()->UnreserveAndDecommit(
+      internal::GetNonBRPPool(), ptr, size);
+}
+
+template struct SlotSpanMetadata<ThreadSafe>;
+template struct SlotSpanMetadata<NotThreadSafe>;
+
+}  // namespace internal
+}  // namespace base

src/base/allocator/partition_allocator/partition_page.h

@@ -0,0 +1,692 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_PAGE_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_PAGE_H_
+
+#include <string.h>
+#include <cstdint>
+#include <limits>
+
+#include "base/allocator/partition_allocator/address_pool_manager.h"
+#include "base/allocator/partition_allocator/partition_address_space.h"
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/allocator/partition_allocator/partition_bucket.h"
+#include "base/allocator/partition_allocator/partition_freelist_entry.h"
+#include "base/allocator/partition_allocator/starscan/object_bitmap.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/dcheck_is_on.h"
+#include "base/thread_annotations.h"
+
+#if BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+#include "base/allocator/partition_allocator/partition_ref_count.h"
+#endif
+
+namespace base {
+namespace internal {
+
+// An "extent" is a span of consecutive superpages. We link the partition's next
+// extent (if there is one) to the very start of a superpage's metadata area.
+template <bool thread_safe>
+struct PartitionSuperPageExtentEntry {
+  PartitionRoot<thread_safe>* root;
+  char* super_page_base;
+  char* super_pages_end;
+  PartitionSuperPageExtentEntry<thread_safe>* next;
+};
+static_assert(
+    sizeof(PartitionSuperPageExtentEntry<ThreadSafe>) <= kPageMetadataSize,
+    "PartitionSuperPageExtentEntry must be able to fit in a metadata slot");
+
+// SlotSpanMetadata::Free() defers unmapping a large page until the lock is
+// released. Callers of SlotSpanMetadata::Free() must invoke Run().
+// TODO(1061437): Reconsider once the new locking mechanism is implemented.
+struct DeferredUnmap {
+  void* ptr = nullptr;
+  size_t size = 0;
+#if BUILDFLAG(ENABLE_BRP_DIRECTMAP_SUPPORT)
+  bool use_brp_pool = false;
+#endif
+
+  // In most cases there is no page to unmap and ptr == nullptr. This function
+  // is inlined to avoid the overhead of a function call in the common case.
+  ALWAYS_INLINE void Run();
+
+ private:
+  BASE_EXPORT NOINLINE void Unmap();
+};
+
+using QuarantineBitmap =
+    ObjectBitmap<kSuperPageSize, kSuperPageAlignment, kAlignment>;
+
+// Metadata of the slot span.
+//
+// Some notes on slot span states. It can be in one of four major states:
+// 1) Active.
+// 2) Full.
+// 3) Empty.
+// 4) Decommitted.
+// An active slot span has available free slots, as well as allocated ones.
+// A full slot span has no free slots. An empty slot span has no allocated
+// slots, and a decommitted slot span is an empty one that had its backing
+// memory released back to the system.
+//
+// There are three linked lists tracking slot spans. The "active" list is an
+// approximation of a list of active slot spans. It is an approximation because
+// full, empty and decommitted slot spans may briefly be present in the list
+// until we next do a scan over it. The "empty" list holds mostly empty slot
+// spans, but may briefly hold decommitted ones too. The "decommitted" list
+// holds only decommitted slot spans.
+//
+// The significant slot span transitions are:
+// - Free() will detect when a full slot span has a slot freed and immediately
+//   return the slot span to the head of the active list.
+// - Free() will detect when a slot span is fully emptied. It _may_ add it to
+//   the empty list or it _may_ leave it on the active list until a future
+//   list scan.
+// - Alloc() _may_ scan the active page list in order to fulfil the request.
+//   If it does this, full, empty and decommitted slot spans encountered will be
+//   booted out of the active list. If there are no suitable active slot spans
+//   found, an empty or decommitted slot spans (if one exists) will be pulled
+//   from the empty/decommitted list on to the active list.
+template <bool thread_safe>
+struct __attribute__((packed)) SlotSpanMetadata {
+  PartitionFreelistEntry* freelist_head = nullptr;
+  SlotSpanMetadata<thread_safe>* next_slot_span = nullptr;
+  PartitionBucket<thread_safe>* const bucket;
+
+  // Deliberately signed, 0 for empty or decommitted slot spans, -n for full
+  // slot spans:
+  int16_t num_allocated_slots = 0;
+  uint16_t num_unprovisioned_slots = 0;
+  int8_t empty_cache_index = 0;  // -1 if not in the empty cache.
+                                 // < kMaxFreeableSpans.
+  static_assert(kMaxFreeableSpans < std::numeric_limits<int8_t>::max(), "");
+  const bool can_store_raw_size;
+
+  explicit SlotSpanMetadata(PartitionBucket<thread_safe>* bucket);
+
+  // Public API
+  // Note the matching Alloc() functions are in PartitionPage.
+  // Callers must invoke DeferredUnmap::Run() after releasing the lock.
+  BASE_EXPORT NOINLINE DeferredUnmap FreeSlowPath() WARN_UNUSED_RESULT;
+  ALWAYS_INLINE DeferredUnmap Free(void* ptr) WARN_UNUSED_RESULT;
+
+  void Decommit(PartitionRoot<thread_safe>* root);
+  void DecommitIfPossible(PartitionRoot<thread_safe>* root);
+
+  // Pointer manipulation functions. These must be static as the input
+  // |slot_span| pointer may be the result of an offset calculation and
+  // therefore cannot be trusted. The objective of these functions is to
+  // sanitize this input.
+  ALWAYS_INLINE static void* ToSlotSpanStartPtr(
+      const SlotSpanMetadata* slot_span);
+  ALWAYS_INLINE static SlotSpanMetadata* FromSlotStartPtr(void* slot_start);
+  ALWAYS_INLINE static SlotSpanMetadata* FromSlotInnerPtr(void* ptr);
+
+  // Checks if it is feasible to store raw_size.
+  ALWAYS_INLINE bool CanStoreRawSize() const { return can_store_raw_size; }
+  // The caller is responsible for ensuring that raw_size can be stored before
+  // calling Set/GetRawSize.
+  ALWAYS_INLINE void SetRawSize(size_t raw_size);
+  ALWAYS_INLINE size_t GetRawSize() const;
+
+  ALWAYS_INLINE void SetFreelistHead(PartitionFreelistEntry* new_head);
+
+  // Returns size of the region used within a slot. The used region comprises
+  // of actual allocated data, extras and possibly empty space in the middle.
+  ALWAYS_INLINE size_t GetUtilizedSlotSize() const {
+    // The returned size can be:
+    // - The slot size for small buckets.
+    // - Exact size needed to satisfy allocation (incl. extras), for large
+    //   buckets and direct-mapped allocations (see also the comment in
+    //   CanStoreRawSize() for more info).
+    if (LIKELY(!CanStoreRawSize())) {
+      return bucket->slot_size;
+    }
+    return GetRawSize();
+  }
+
+  // Returns the size available to the app. It can be equal or higher than the
+  // requested size. If higher, the overage won't exceed what's actually usable
+  // by the app without a risk of running out of an allocated region or into
+  // PartitionAlloc's internal data (like extras).
+  ALWAYS_INLINE size_t GetUsableSize(PartitionRoot<thread_safe>* root) const {
+    // The returned size can be:
+    // - The slot size minus extras, for small buckets. This could be more than
+    //   requested size.
+    // - Raw size minus extras, for large buckets and direct-mapped allocations
+    //   (see also the comment in CanStoreRawSize() for more info). This is
+    //   equal to requested size.
+    size_t size_to_ajdust;
+    if (LIKELY(!CanStoreRawSize())) {
+      size_to_ajdust = bucket->slot_size;
+    } else {
+      size_to_ajdust = GetRawSize();
+    }
+    return root->AdjustSizeForExtrasSubtract(size_to_ajdust);
+  }
+
+  // Returns the total size of the slots that are currently provisioned.
+  ALWAYS_INLINE size_t GetProvisionedSize() const {
+    size_t num_provisioned_slots =
+        bucket->get_slots_per_span() - num_unprovisioned_slots;
+    size_t provisioned_size = num_provisioned_slots * bucket->slot_size;
+    PA_DCHECK(provisioned_size <= bucket->get_bytes_per_span());
+    return provisioned_size;
+  }
+
+  ALWAYS_INLINE void Reset();
+
+  // TODO(ajwong): Can this be made private?  https://crbug.com/787153
+  BASE_EXPORT static SlotSpanMetadata* get_sentinel_slot_span();
+
+  // Page State accessors.
+  // Note that it's only valid to call these functions on pages found on one of
+  // the page lists. Specifically, you can't call these functions on full pages
+  // that were detached from the active list.
+  //
+  // This restriction provides the flexibity for some of the status fields to
+  // be repurposed when a page is taken off a list. See the negation of
+  // |num_allocated_slots| when a full page is removed from the active list
+  // for an example of such repurposing.
+  ALWAYS_INLINE bool is_active() const;
+  ALWAYS_INLINE bool is_full() const;
+  ALWAYS_INLINE bool is_empty() const;
+  ALWAYS_INLINE bool is_decommitted() const;
+
+ private:
+  // sentinel_slot_span_ is used as a sentinel to indicate that there is no slot
+  // span in the active list. We could use nullptr, but in that case we need to
+  // add a null-check branch to the hot allocation path. We want to avoid that.
+  //
+  // Note, this declaration is kept in the header as opposed to an anonymous
+  // namespace so the getter can be fully inlined.
+  static SlotSpanMetadata sentinel_slot_span_;
+  // For the sentinel.
+  constexpr SlotSpanMetadata() noexcept
+      : bucket(nullptr), can_store_raw_size(false) {}
+};
+static_assert(sizeof(SlotSpanMetadata<ThreadSafe>) <= kPageMetadataSize,
+              "SlotSpanMetadata must fit into a Page Metadata slot.");
+
+// Metadata of a non-first partition page in a slot span.
+struct SubsequentPageMetadata {
+  // Raw size is the size needed to satisfy the allocation (requested size +
+  // extras). If available, it can be used to report better statistics or to
+  // bring protective cookie closer to the allocated memory.
+  //
+  // It can be used only if:
+  // - there is no more than one slot in the slot span (otherwise we wouldn't
+  //   know which slot the raw size applies to)
+  // - there is more than one partition page in the slot span (the metadata of
+  //   the first one is used to store slot information, but the second one is
+  //   available for extra information)
+  size_t raw_size;
+};
+
+// Each partition page has metadata associated with it. The metadata of the
+// first page of a slot span, describes that slot span. If a slot span spans
+// more than 1 page, the page metadata may contain rudimentary additional
+// information.
+template <bool thread_safe>
+struct PartitionPage {
+  // "Pack" the union so that common page metadata still fits within
+  // kPageMetadataSize. (SlotSpanMetadata is also "packed".)
+  union __attribute__((packed)) {
+    SlotSpanMetadata<thread_safe> slot_span_metadata;
+
+    SubsequentPageMetadata subsequent_page_metadata;
+
+    // sizeof(PartitionPageMetadata) must always be:
+    // - a power of 2 (for fast modulo operations)
+    // - below kPageMetadataSize
+    //
+    // This makes sure that this is respected no matter the architecture.
+    char optional_padding[kPageMetadataSize - sizeof(uint8_t) - sizeof(bool)];
+  };
+
+  // The first PartitionPage of the slot span holds its metadata. This offset
+  // tells how many pages in from that first page we are.
+  // 6 bits is enough to represent all possible offsets, given that the smallest
+  // partition page is 16kiB and normal buckets won't exceed 1MiB.
+  static constexpr uint16_t kMaxSlotSpanMetadataBits = 6;
+  static constexpr uint16_t kMaxSlotSpanMetadataOffset =
+      (1 << kMaxSlotSpanMetadataBits) - 1;
+  uint8_t slot_span_metadata_offset;
+
+  // |is_valid| tells whether the page is part of a slot span. If |false|,
+  // |has_valid_span_after_this| tells whether it's an unused region in between
+  // slot spans within the super page.
+  // Note, |is_valid| has been added for clarity, but if we ever need to save
+  // this bit, it can be inferred from:
+  //   |!slot_span_metadata_offset && slot_span_metadata->bucket|.
+  bool is_valid : 1;
+  bool has_valid_span_after_this : 1;
+
+  ALWAYS_INLINE static PartitionPage* FromPtr(void* slot_start);
+
+ private:
+  ALWAYS_INLINE static void* ToSlotSpanStartPtr(const PartitionPage* page);
+};
+
+static_assert(sizeof(PartitionPage<ThreadSafe>) == kPageMetadataSize,
+              "PartitionPage must be able to fit in a metadata slot");
+static_assert(sizeof(PartitionPage<NotThreadSafe>) == kPageMetadataSize,
+              "PartitionPage must be able to fit in a metadata slot");
+
+// Certain functions rely on PartitionPage being either SlotSpanMetadata or
+// SubsequentPageMetadata, and therefore freely casting between each other.
+static_assert(offsetof(PartitionPage<ThreadSafe>, slot_span_metadata) == 0, "");
+static_assert(offsetof(PartitionPage<ThreadSafe>, subsequent_page_metadata) ==
+                  0,
+              "");
+static_assert(offsetof(PartitionPage<NotThreadSafe>, slot_span_metadata) == 0,
+              "");
+static_assert(offsetof(PartitionPage<NotThreadSafe>,
+                       subsequent_page_metadata) == 0,
+              "");
+
+// CAUTION! Use only for normal buckets. Using on direct-mapped allocations may
+// lead to undefined behavior.
+ALWAYS_INLINE char* PartitionSuperPageToMetadataArea(char* ptr) {
+  // TODO(bartekn): Add a "is in normal buckets" DCHECK.
+  uintptr_t pointer_as_uint = reinterpret_cast<uintptr_t>(ptr);
+  PA_DCHECK(!(pointer_as_uint & kSuperPageOffsetMask));
+  // The metadata area is exactly one system page (the guard page) into the
+  // super page.
+  return reinterpret_cast<char*>(pointer_as_uint + SystemPageSize());
+}
+
+// Size that should be reserved for 2 back-to-back quarantine bitmaps (if
+// present) inside a super page. Elements of a super page are
+// partition-page-aligned, hence the returned size is a multiple of partition
+// page size.
+ALWAYS_INLINE size_t ReservedQuarantineBitmapsSize() {
+  return (2 * sizeof(QuarantineBitmap) + PartitionPageSize() - 1) &
+         PartitionPageBaseMask();
+}
+
+// Size that should be committed for 2 back-to-back quarantine bitmaps (if
+// present) inside a super page. It is a multiple of system page size.
+ALWAYS_INLINE size_t CommittedQuarantineBitmapsSize() {
+  return (2 * sizeof(QuarantineBitmap) + SystemPageSize() - 1) &
+         SystemPageBaseMask();
+}
+
+// Returns the pointer to the first, of two, quarantine bitmap in the super
+// page. It's the caller's responsibility to ensure that the bitmaps even exist.
+ALWAYS_INLINE QuarantineBitmap* SuperPageQuarantineBitmaps(
+    char* super_page_base) {
+  PA_DCHECK(
+      !(reinterpret_cast<uintptr_t>(super_page_base) % kSuperPageAlignment));
+  return reinterpret_cast<QuarantineBitmap*>(super_page_base +
+                                             PartitionPageSize());
+}
+
+ALWAYS_INLINE char* SuperPagePayloadBegin(char* super_page_base,
+                                          bool with_quarantine) {
+  PA_DCHECK(
+      !(reinterpret_cast<uintptr_t>(super_page_base) % kSuperPageAlignment));
+  return super_page_base + PartitionPageSize() +
+         (with_quarantine ? ReservedQuarantineBitmapsSize() : 0);
+}
+
+ALWAYS_INLINE char* SuperPagePayloadEnd(char* super_page_base) {
+  PA_DCHECK(
+      !(reinterpret_cast<uintptr_t>(super_page_base) % kSuperPageAlignment));
+  return super_page_base + kSuperPageSize - PartitionPageSize();
+}
+
+// CAUTION! Use only for normal buckets. Using on direct-mapped allocations may
+// lead to undefined behavior.
+ALWAYS_INLINE bool IsWithinSuperPagePayload(void* ptr, bool with_quarantine) {
+  // TODO(bartekn): Add a "is in normal buckets" DCHECK.
+  char* super_page_base = reinterpret_cast<char*>(
+      reinterpret_cast<uintptr_t>(ptr) & kSuperPageBaseMask);
+  void* payload_start = SuperPagePayloadBegin(super_page_base, with_quarantine);
+  void* payload_end = SuperPagePayloadEnd(super_page_base);
+  return ptr >= payload_start && ptr < payload_end;
+}
+
+// Returns the start of a slot or nullptr if |maybe_inner_ptr| is not inside of
+// an existing slot span. The function may return a pointer even inside a
+// decommitted or free slot span, it's the caller responsibility to check if
+// memory is actually allocated.
+//
+// Furthermore, |maybe_inner_ptr| must point to payload of a valid super page.
+//
+// CAUTION! Use only for normal buckets. Using on direct-mapped allocations may
+// lead to undefined behavior.
+template <bool thread_safe>
+ALWAYS_INLINE char* GetSlotStartInSuperPage(char* maybe_inner_ptr) {
+#if DCHECK_IS_ON()
+  // TODO(bartekn): Add a "is in normal buckets" DCHECK.
+  char* super_page_ptr = reinterpret_cast<char*>(
+      reinterpret_cast<uintptr_t>(maybe_inner_ptr) & kSuperPageBaseMask);
+  auto* extent = reinterpret_cast<PartitionSuperPageExtentEntry<thread_safe>*>(
+      PartitionSuperPageToMetadataArea(super_page_ptr));
+  PA_DCHECK(IsWithinSuperPagePayload(maybe_inner_ptr,
+                                     extent->root->IsQuarantineAllowed()));
+#endif
+  auto* slot_span =
+      SlotSpanMetadata<thread_safe>::FromSlotInnerPtr(maybe_inner_ptr);
+  // Check if the slot span is actually used and valid.
+  if (!slot_span->bucket)
+    return nullptr;
+#if DCHECK_IS_ON()
+  PA_DCHECK(PartitionRoot<thread_safe>::IsValidSlotSpan(slot_span));
+#endif
+  char* const slot_span_begin = static_cast<char*>(
+      SlotSpanMetadata<thread_safe>::ToSlotSpanStartPtr(slot_span));
+  const ptrdiff_t ptr_offset = maybe_inner_ptr - slot_span_begin;
+#if DCHECK_IS_ON()
+  PA_DCHECK(0 <= ptr_offset &&
+            ptr_offset < static_cast<ptrdiff_t>(
+                             slot_span->bucket->get_pages_per_slot_span() *
+                             PartitionPageSize()));
+#endif
+  // Slot span size in bytes is not necessarily multiple of partition page.
+  if (ptr_offset >=
+      static_cast<ptrdiff_t>(slot_span->bucket->get_bytes_per_span()))
+    return nullptr;
+  const size_t slot_size = slot_span->bucket->slot_size;
+  const size_t slot_number = slot_span->bucket->GetSlotNumber(ptr_offset);
+  char* const result = slot_span_begin + (slot_number * slot_size);
+  PA_DCHECK(result <= maybe_inner_ptr && maybe_inner_ptr < result + slot_size);
+  return result;
+}
+
+// Converts from a pointer to the PartitionPage object (within super pages's
+// metadata) into a pointer to the beginning of the slot span.
+// |page| must be the first PartitionPage of the slot span.
+template <bool thread_safe>
+ALWAYS_INLINE void* PartitionPage<thread_safe>::ToSlotSpanStartPtr(
+    const PartitionPage* page) {
+  PA_DCHECK(page->is_valid);
+  PA_DCHECK(!page->slot_span_metadata_offset);
+  return SlotSpanMetadata<thread_safe>::ToSlotSpanStartPtr(
+      &page->slot_span_metadata);
+}
+
+// Converts from a pointer inside a super page into a pointer to the
+// PartitionPage object (within super pages's metadata) that describes the
+// partition page where |ptr| is located. |ptr| doesn't have to be a located
+// within a valid (i.e. allocated) slot span, but must be within the super
+// page's payload (i.e. region devoted to slot spans).
+//
+// While it is generally valid for |ptr| to be in the middle of an allocation,
+// care has to be taken with direct maps that span multiple super pages. This
+// function's behavior is undefined if |ptr| lies in a subsequent super page.
+template <bool thread_safe>
+ALWAYS_INLINE PartitionPage<thread_safe>* PartitionPage<thread_safe>::FromPtr(
+    void* ptr) {
+  // Force |with_quarantine=false|, because we don't know whether its direct map
+  // and direct map allocations don't have quarantine bitmaps.
+  PA_DCHECK(IsWithinSuperPagePayload(ptr, /* with_quarantine= */ false));
+
+  uintptr_t pointer_as_uint = reinterpret_cast<uintptr_t>(ptr);
+  char* super_page_ptr =
+      reinterpret_cast<char*>(pointer_as_uint & kSuperPageBaseMask);
+  uintptr_t partition_page_index =
+      (pointer_as_uint & kSuperPageOffsetMask) >> PartitionPageShift();
+  // Index 0 is invalid because it is the super page extent metadata and the
+  // last index is invalid because the whole PartitionPage is set as guard
+  // pages. This repeats part of the payload PA_DCHECK above, which may check
+  // for other exclusions.
+  PA_DCHECK(partition_page_index);
+  PA_DCHECK(partition_page_index < NumPartitionPagesPerSuperPage() - 1);
+  return reinterpret_cast<PartitionPage<thread_safe>*>(
+      PartitionSuperPageToMetadataArea(super_page_ptr) +
+      (partition_page_index << kPageMetadataShift));
+}
+
+// Converts from a pointer to the SlotSpanMetadata object (within super pages's
+// metadata) into a pointer to the beginning of the slot span.
+//
+// CAUTION! Use only for normal buckets. Using on direct-mapped allocations may
+// lead to undefined behavior.
+template <bool thread_safe>
+ALWAYS_INLINE void* SlotSpanMetadata<thread_safe>::ToSlotSpanStartPtr(
+    const SlotSpanMetadata* slot_span) {
+  // TODO(bartekn): Add a "is in normal buckets" DCHECK.
+  uintptr_t pointer_as_uint = reinterpret_cast<uintptr_t>(slot_span);
+  uintptr_t super_page_offset = (pointer_as_uint & kSuperPageOffsetMask);
+
+  // A valid |page| must be past the first guard System page and within
+  // the following metadata region.
+  PA_DCHECK(super_page_offset > SystemPageSize());
+  // Must be less than total metadata region.
+  PA_DCHECK(super_page_offset <
+            SystemPageSize() +
+                (NumPartitionPagesPerSuperPage() * kPageMetadataSize));
+  uintptr_t partition_page_index =
+      (super_page_offset - SystemPageSize()) >> kPageMetadataShift;
+  // Index 0 is invalid because it is the super page extent metadata and the
+  // last index is invalid because the whole PartitionPage is set as guard
+  // pages.
+  PA_DCHECK(partition_page_index);
+  PA_DCHECK(partition_page_index < NumPartitionPagesPerSuperPage() - 1);
+  uintptr_t super_page_base = (pointer_as_uint & kSuperPageBaseMask);
+  void* ret = reinterpret_cast<void*>(
+      super_page_base + (partition_page_index << PartitionPageShift()));
+  return ret;
+}
+
+// Converts from a pointer inside a slot into a pointer to the SlotSpanMetadata
+// object (within super pages's metadata) that describes the slot span
+// containing that slot.
+//
+// CAUTION! Use only for normal buckets. Using on direct-mapped allocations may
+// lead to undefined behavior.
+template <bool thread_safe>
+ALWAYS_INLINE SlotSpanMetadata<thread_safe>*
+SlotSpanMetadata<thread_safe>::FromSlotInnerPtr(void* ptr) {
+  // TODO(bartekn): Add a "is in normal buckets" DCHECK.
+  auto* page = PartitionPage<thread_safe>::FromPtr(ptr);
+  PA_DCHECK(page->is_valid);
+  // Partition pages in the same slot span share the same slot span metadata
+  // object (located in the first PartitionPage object of that span). Adjust
+  // for that.
+  page -= page->slot_span_metadata_offset;
+  PA_DCHECK(page->is_valid);
+  PA_DCHECK(!page->slot_span_metadata_offset);
+  return &page->slot_span_metadata;
+}
+
+// Like |FromSlotInnerPtr|, but asserts that pointer points to the beginning of
+// the slot.
+template <bool thread_safe>
+ALWAYS_INLINE SlotSpanMetadata<thread_safe>*
+SlotSpanMetadata<thread_safe>::FromSlotStartPtr(void* slot_start) {
+  auto* slot_span = FromSlotInnerPtr(slot_start);
+  // Checks that the pointer is a multiple of slot size.
+  auto* slot_span_start = ToSlotSpanStartPtr(slot_span);
+  PA_DCHECK(!((reinterpret_cast<uintptr_t>(slot_start) -
+               reinterpret_cast<uintptr_t>(slot_span_start)) %
+              slot_span->bucket->slot_size));
+  return slot_span;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE void SlotSpanMetadata<thread_safe>::SetRawSize(size_t raw_size) {
+  PA_DCHECK(CanStoreRawSize());
+  auto* the_next_page = reinterpret_cast<PartitionPage<thread_safe>*>(this) + 1;
+  the_next_page->subsequent_page_metadata.raw_size = raw_size;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE size_t SlotSpanMetadata<thread_safe>::GetRawSize() const {
+  PA_DCHECK(CanStoreRawSize());
+  auto* the_next_page =
+      reinterpret_cast<const PartitionPage<thread_safe>*>(this) + 1;
+  return the_next_page->subsequent_page_metadata.raw_size;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE void SlotSpanMetadata<thread_safe>::SetFreelistHead(
+    PartitionFreelistEntry* new_head) {
+  PA_DCHECK(!new_head ||
+            (reinterpret_cast<uintptr_t>(this) & kSuperPageBaseMask) ==
+                (reinterpret_cast<uintptr_t>(new_head) & kSuperPageBaseMask));
+  freelist_head = new_head;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE DeferredUnmap
+SlotSpanMetadata<thread_safe>::Free(void* slot_start) {
+#if DCHECK_IS_ON()
+  auto* root = PartitionRoot<thread_safe>::FromSlotSpan(this);
+  root->lock_.AssertAcquired();
+#endif
+
+  PA_DCHECK(num_allocated_slots);
+  // Catches an immediate double free.
+  PA_CHECK(slot_start != freelist_head);
+  // Look for double free one level deeper in debug.
+  PA_DCHECK(!freelist_head || slot_start != freelist_head->GetNext());
+  auto* entry = static_cast<internal::PartitionFreelistEntry*>(slot_start);
+  entry->SetNext(freelist_head);
+  SetFreelistHead(entry);
+  --num_allocated_slots;
+  if (UNLIKELY(num_allocated_slots <= 0)) {
+    return FreeSlowPath();
+  } else {
+    // All single-slot allocations must go through the slow path to
+    // correctly update the raw size.
+    PA_DCHECK(!CanStoreRawSize());
+  }
+  return {};
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE bool SlotSpanMetadata<thread_safe>::is_active() const {
+  PA_DCHECK(this != get_sentinel_slot_span());
+  return (num_allocated_slots > 0 &&
+          (freelist_head || num_unprovisioned_slots));
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE bool SlotSpanMetadata<thread_safe>::is_full() const {
+  PA_DCHECK(this != get_sentinel_slot_span());
+  bool ret = (num_allocated_slots == bucket->get_slots_per_span());
+  if (ret) {
+    PA_DCHECK(!freelist_head);
+    PA_DCHECK(!num_unprovisioned_slots);
+  }
+  return ret;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE bool SlotSpanMetadata<thread_safe>::is_empty() const {
+  PA_DCHECK(this != get_sentinel_slot_span());
+  return (!num_allocated_slots && freelist_head);
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE bool SlotSpanMetadata<thread_safe>::is_decommitted() const {
+  PA_DCHECK(this != get_sentinel_slot_span());
+  bool ret = (!num_allocated_slots && !freelist_head);
+  if (ret) {
+    PA_DCHECK(!num_unprovisioned_slots);
+    PA_DCHECK(empty_cache_index == -1);
+  }
+  return ret;
+}
+
+template <bool thread_safe>
+ALWAYS_INLINE void SlotSpanMetadata<thread_safe>::Reset() {
+  PA_DCHECK(is_decommitted());
+
+  num_unprovisioned_slots = bucket->get_slots_per_span();
+  PA_DCHECK(num_unprovisioned_slots);
+
+  next_slot_span = nullptr;
+}
+
+ALWAYS_INLINE void DeferredUnmap::Run() {
+  if (UNLIKELY(ptr)) {
+    Unmap();
+  }
+}
+
+enum class QuarantineBitmapType { kMutator, kScanner };
+
+// CAUTION! Use only for normal buckets. Using on direct-mapped allocations may
+// lead to undefined behavior.
+ALWAYS_INLINE QuarantineBitmap* QuarantineBitmapFromPointer(
+    QuarantineBitmapType type,
+    size_t pcscan_epoch,
+    void* ptr) {
+  // TODO(bartekn): Add a "is in normal buckets" DCHECK.
+  auto* super_page_base = reinterpret_cast<char*>(
+      reinterpret_cast<uintptr_t>(ptr) & kSuperPageBaseMask);
+  auto* first_bitmap = SuperPageQuarantineBitmaps(super_page_base);
+  auto* second_bitmap = first_bitmap + 1;
+
+  if (type == QuarantineBitmapType::kScanner)
+    std::swap(first_bitmap, second_bitmap);
+
+  return (pcscan_epoch & 1) ? second_bitmap : first_bitmap;
+}
+
+// Iterates over all active and full slot spans in a super-page. Returns number
+// of the visited slot spans. |Callback| must return a bool indicating whether
+// the slot was visited (true) or skipped (false).
+template <bool thread_safe, typename Callback>
+size_t IterateSlotSpans(char* super_page_base,
+                        bool with_quarantine,
+                        Callback callback) {
+#if DCHECK_IS_ON()
+  PA_DCHECK(
+      !(reinterpret_cast<uintptr_t>(super_page_base) % kSuperPageAlignment));
+  auto* extent_entry =
+      reinterpret_cast<PartitionSuperPageExtentEntry<thread_safe>*>(
+          PartitionSuperPageToMetadataArea(super_page_base));
+  extent_entry->root->lock_.AssertAcquired();
+#endif
+
+  using Page = PartitionPage<thread_safe>;
+  using SlotSpan = SlotSpanMetadata<thread_safe>;
+  auto* const first_page =
+      Page::FromPtr(SuperPagePayloadBegin(super_page_base, with_quarantine));
+  auto* const last_page =
+      Page::FromPtr(SuperPagePayloadEnd(super_page_base) - PartitionPageSize());
+  size_t visited = 0;
+  Page* page;
+  SlotSpan* slot_span;
+  for (page = first_page; page <= last_page;) {
+    PA_DCHECK(!page->slot_span_metadata_offset);  // Ensure slot span beginning.
+    if (!page->is_valid) {
+      if (page->has_valid_span_after_this) {
+        // The page doesn't represent a valid slot span, but there is another
+        // one somewhere after this. Keep iterating to find it.
+        ++page;
+        continue;
+      }
+      // There are currently no valid spans from here on. No need to iterate
+      // the rest of the super page.
+      break;
+    }
+    slot_span = &page->slot_span_metadata;
+    if (callback(slot_span))
+      ++visited;
+    page += slot_span->bucket->get_pages_per_slot_span();
+  }
+  // Each super page must have at least one valid slot span.
+  PA_DCHECK(page > first_page);
+  // Just a quick check that the search ended at a valid slot span and there
+  // was no unnecessary iteration over gaps afterwards.
+  PA_DCHECK(page == reinterpret_cast<Page*>(slot_span) +
+                        slot_span->bucket->get_pages_per_slot_span());
+  return visited;
+}
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_PAGE_H_

src/base/allocator/partition_allocator/partition_ref_count.h

@@ -0,0 +1,229 @@
+// Copyright (c) 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_REF_COUNT_H_
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_REF_COUNT_H_
+
+#include <atomic>
+#include <cstdint>
+
+#include "base/allocator/partition_allocator/partition_alloc_check.h"
+#include "base/allocator/partition_allocator/partition_alloc_constants.h"
+#include "base/allocator/partition_allocator/partition_alloc_forward.h"
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/dcheck_is_on.h"
+#include "base/partition_alloc_buildflags.h"
+#include "build/build_config.h"
+
+namespace base {
+
+namespace internal {
+
+#if BUILDFLAG(USE_BACKUP_REF_PTR)
+
+// Special-purpose atomic reference count class used by BackupRefPtrImpl.
+// The least significant bit of the count is reserved for tracking the liveness
+// state of an allocation: it's set when the allocation is created and cleared
+// on free(). So the count can be:
+//
+// 1 for an allocation that is just returned from Alloc()
+// 2 * k + 1 for a "live" allocation with k references
+// 2 * k for an allocation with k dangling references after Free()
+//
+// This protects against double-free's, as we check whether the reference count
+// is odd in |ReleaseFromAllocator()|, and if not we have a double-free.
+class BASE_EXPORT PartitionRefCount {
+ public:
+  PartitionRefCount();
+
+  // Incrementing the counter doesn't imply any visibility about modified
+  // memory, hence relaxed atomics. For decrement, visibility is required before
+  // the memory gets freed, necessitating an acquire/release barrier before
+  // freeing the memory.
+
+  // For details, see base::AtomicRefCount, which has the same constraints and
+  // characteristics.
+  ALWAYS_INLINE void Acquire() {
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+    CheckCookie();
+#endif
+
+    PA_CHECK(count_.fetch_add(2, std::memory_order_relaxed) > 0);
+  }
+
+  // Returns true if the allocation should be reclaimed.
+  ALWAYS_INLINE bool Release() {
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+    CheckCookie();
+#endif
+
+    if (count_.fetch_sub(2, std::memory_order_release) == 2) {
+      // In most thread-safe reference count implementations, an acquire
+      // barrier is required so that all changes made to an object from other
+      // threads are visible to its destructor. In our case, the destructor
+      // finishes before the final `Release` call, so it shouldn't be a problem.
+      // However, we will keep it as a precautionary measure.
+      std::atomic_thread_fence(std::memory_order_acquire);
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+      // The allocation is about to get freed, so clear the cookie.
+      brp_cookie_ = 0;
+#endif
+      return true;
+    }
+
+    return false;
+  }
+
+  // Returns true if the allocation should be reclaimed.
+  // This function should be called by the allocator during Free().
+  ALWAYS_INLINE bool ReleaseFromAllocator() {
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+    CheckCookie();
+#endif
+
+    int32_t old_count = count_.fetch_sub(1, std::memory_order_release);
+    PA_CHECK(old_count & 1);  // double-free detection
+    if (old_count == 1) {
+      std::atomic_thread_fence(std::memory_order_acquire);
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+      // The allocation is about to get freed, so clear the cookie.
+      brp_cookie_ = 0;
+#endif
+      return true;
+    }
+
+    return false;
+  }
+
+  // "IsAlive" means is allocated and not freed. "KnownRefs" refers to
+  // CheckedPtr references. There may be other references from raw pointers or
+  // unique_ptr, but we have no way of tracking them, so we hope for the best.
+  // To summarize, the function returns whether we believe the allocation can be
+  // safely freed.
+  ALWAYS_INLINE bool IsAliveWithNoKnownRefs() {
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+    CheckCookie();
+#endif
+
+    return count_.load(std::memory_order_acquire) == 1;
+  }
+
+  ALWAYS_INLINE bool IsAlive() {
+    bool alive = count_.load(std::memory_order_relaxed) & 1;
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+    if (alive)
+      CheckCookie();
+#endif
+    return alive;
+  }
+
+ private:
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+  // The cookie helps us ensure that:
+  // 1) The reference count pointer calculation is correct.
+  // 2) The returned allocation slot is not freed.
+  ALWAYS_INLINE void CheckCookie() {
+    PA_CHECK(brp_cookie_ == CalculateCookie());
+  }
+
+  ALWAYS_INLINE uint32_t CalculateCookie() {
+    return static_cast<uint32_t>(reinterpret_cast<uintptr_t>(this)) ^
+           kCookieSalt;
+  }
+
+  static constexpr uint32_t kCookieSalt = 0xc01dbeef;
+  volatile uint32_t brp_cookie_;
+#endif  // DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+
+  std::atomic<int32_t> count_{1};
+};
+
+ALWAYS_INLINE PartitionRefCount::PartitionRefCount()
+#if DCHECK_IS_ON() || BUILDFLAG(ENABLE_BACKUP_REF_PTR_SLOW_CHECKS)
+    : brp_cookie_(CalculateCookie())
+#endif
+{
+}
+
+#if BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+
+static_assert(base::kAlignment % alignof(PartitionRefCount) == 0,
+              "kAlignment must be multiples of alignof(PartitionRefCount).");
+
+// Allocate extra space for the reference count to satisfy the alignment
+// requirement.
+static constexpr size_t kInSlotRefCountBufferSize = sizeof(PartitionRefCount);
+constexpr size_t kPartitionRefCountOffsetAdjustment = 0;
+constexpr size_t kPartitionPastAllocationAdjustment = 0;
+
+constexpr size_t kPartitionRefCountIndexMultiplier =
+    SystemPageSize() /
+    (sizeof(PartitionRefCount) * (kSuperPageSize / SystemPageSize()));
+
+static_assert((sizeof(PartitionRefCount) * (kSuperPageSize / SystemPageSize()) *
+                   kPartitionRefCountIndexMultiplier <=
+               SystemPageSize()),
+              "PartitionRefCount Bitmap size must be smaller than or equal to "
+              "<= SystemPageSize().");
+
+ALWAYS_INLINE PartitionRefCount* PartitionRefCountPointer(void* slot_start) {
+  DCheckGetSlotOffsetIsZero(slot_start);
+  uintptr_t slot_start_as_uintptr = reinterpret_cast<uintptr_t>(slot_start);
+  if (LIKELY(slot_start_as_uintptr & SystemPageOffsetMask())) {
+    uintptr_t refcount_ptr_as_uintptr =
+        slot_start_as_uintptr - sizeof(PartitionRefCount);
+    PA_DCHECK(refcount_ptr_as_uintptr % alignof(PartitionRefCount) == 0);
+    return reinterpret_cast<PartitionRefCount*>(refcount_ptr_as_uintptr);
+  } else {
+    PartitionRefCount* bitmap_base = reinterpret_cast<PartitionRefCount*>(
+        (slot_start_as_uintptr & kSuperPageBaseMask) + SystemPageSize() * 2);
+    size_t index = ((slot_start_as_uintptr & kSuperPageOffsetMask)
+#if !defined(OS_APPLE)
+                    >> SystemPageShift()
+#else
+                    / SystemPageSize()
+#endif
+                        ) *
+                   kPartitionRefCountIndexMultiplier;
+    PA_DCHECK(sizeof(PartitionRefCount) * index <= SystemPageSize());
+    return bitmap_base + index;
+  }
+}
+
+#else  // BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+
+// Allocate extra space for the reference count to satisfy the alignment
+// requirement.
+static constexpr size_t kInSlotRefCountBufferSize = base::kAlignment;
+constexpr size_t kPartitionRefCountOffsetAdjustment = kInSlotRefCountBufferSize;
+
+// This is for adjustment of pointers right past the allocation, which may point
+// to the next slot. First subtract 1 to bring them to the intended slot, and
+// only then we'll be able to find ref-count in that slot.
+constexpr size_t kPartitionPastAllocationAdjustment = 1;
+
+ALWAYS_INLINE PartitionRefCount* PartitionRefCountPointer(void* slot_start) {
+  DCheckGetSlotOffsetIsZero(slot_start);
+  return reinterpret_cast<PartitionRefCount*>(slot_start);
+}
+
+#endif  // BUILDFLAG(PUT_REF_COUNT_IN_PREVIOUS_SLOT)
+
+static_assert(sizeof(PartitionRefCount) <= kInSlotRefCountBufferSize,
+              "PartitionRefCount should fit into the in-slot buffer.");
+
+#else  // BUILDFLAG(USE_BACKUP_REF_PTR)
+
+static constexpr size_t kInSlotRefCountBufferSize = 0;
+constexpr size_t kPartitionRefCountOffsetAdjustment = 0;
+
+#endif  // BUILDFLAG(USE_BACKUP_REF_PTR)
+
+constexpr size_t kPartitionRefCountSizeAdjustment = kInSlotRefCountBufferSize;
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_REF_COUNT_H_

src/base/allocator/partition_allocator/partition_stats.cc

@@ -0,0 +1,21 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <cstring>
+
+#include "base/allocator/partition_allocator/partition_stats.h"
+
+namespace base {
+
+SimplePartitionStatsDumper::SimplePartitionStatsDumper() {
+  memset(&stats_, 0, sizeof(stats_));
+}
+
+void SimplePartitionStatsDumper::PartitionDumpTotals(
+    const char* partition_name,
+    const PartitionMemoryStats* memory_stats) {
+  stats_ = *memory_stats;
+}
+
+}  // namespace base