# Copyright 2015 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/chrome_build.gni")
import("//build/config/chromecast_build.gni")
import("//build/toolchain/toolchain.gni")

declare_args() {
  # Compile for Address Sanitizer to find memory bugs.
  is_asan = false

  # Compile for Leak Sanitizer to find leaks.
  is_lsan = false

  # Compile for Memory Sanitizer to find uninitialized reads.
  is_msan = false

  # Compile for Thread Sanitizer to find threading bugs.
  is_tsan = false

  # Compile for Undefined Behaviour Sanitizer to find various types of
  # undefined behaviour (excludes vptr checks).
  is_ubsan = false

  # Halt the program if a problem is detected.
  is_ubsan_no_recover = false

  # Compile for Undefined Behaviour Sanitizer's null pointer checks.
  is_ubsan_null = false

  # Compile for Undefined Behaviour Sanitizer's vptr checks.
  is_ubsan_vptr = false

  # Track where uninitialized memory originates from. From fastest to slowest:
  # 0 - no tracking, 1 - track only the initial allocation site, 2 - track the
  # chain of stores leading from allocation site to use site.
  msan_track_origins = 2

  # Use dynamic libraries instrumented by one of the sanitizers instead of the
  # standard system libraries. Set this flag to download prebuilt binaries from
  # GCS.
  use_prebuilt_instrumented_libraries = false

  # Use dynamic libraries instrumented by one of the sanitizers instead of the
  # standard system libraries. Set this flag to build the libraries from source.
  use_locally_built_instrumented_libraries = false

  # Enable building with SyzyAsan which can find certain types of memory
  # errors. Only works on Windows. See
  # https://github.com/google/syzygy/wiki/SyzyASanHowTo
  is_syzyasan = false

  # Compile with Control Flow Integrity to protect virtual calls and casts.
  # See http://clang.llvm.org/docs/ControlFlowIntegrity.html
  #
  # TODO(pcc): Remove this flag if/when CFI is enabled in all official builds.
  is_cfi = target_os == "linux" && !is_chromeos && target_cpu == "x64" &&
           is_official_build

  # Enable checks for bad casts: derived cast and unrelated cast.
  # TODO(krasin): remove this, when we're ready to add these checks by default.
  # https://crbug.com/626794
  use_cfi_cast = false

  # Enable checks for indirect function calls via a function pointer.
  # TODO(pcc): remove this when we're ready to add these checks by default.
  # https://crbug.com/701919
  use_cfi_icall = false

  # Print detailed diagnostics when Control Flow Integrity detects a violation.
  use_cfi_diag = false

  # Let Control Flow Integrity continue execution instead of crashing when
  # printing diagnostics (use_cfi_diag = true).
  use_cfi_recover = false

  # Compile for fuzzing with LLVM LibFuzzer.
  # See http://www.chromium.org/developers/testing/libfuzzer
  use_libfuzzer = false

  # Compile for fuzzing with AFL.
  use_afl = false

  # Enables core ubsan security features. Will later be removed once it matches
  # is_ubsan.
  is_ubsan_security = false

  # Compile for fuzzing with Dr. Fuzz
  # See http://www.chromium.org/developers/testing/dr-fuzz
  use_drfuzz = false

  # Helper variable for testing builds with disabled libfuzzer.
  # Not for client use.
  disable_libfuzzer = false

  # Value for -fsanitize-coverage flag. Setting this causes
  # use_sanitizer_coverage to be enabled.
  # Default value when unset and use_afl=true or use_libfuzzer=true:
  #     trace-pc-guard
  # Default value when unset and use_sanitizer_coverage=true:
  #     trace-pc-guard,indirect-calls
  sanitizer_coverage_flags = ""

  # Keep symbol level when building with sanitizers. When sanitizers are
  # enabled, the default is to compile with the minimum debug info level
  # necessary, overriding any other symbol level arguments that may be set.
  # Setting this to true prevents this.
  sanitizer_keep_symbols = false
}

# Disable sanitizers for non-default toolchains.
if (current_toolchain != default_toolchain) {
  is_asan = false
  is_cfi = false
  is_lsan = false
  is_msan = false
  is_syzyasan = false
  is_tsan = false
  is_ubsan = false
  is_ubsan_null = false
  is_ubsan_no_recover = false
  is_ubsan_security = false
  is_ubsan_vptr = false
  msan_track_origins = 0
  sanitizer_coverage_flags = ""
  use_afl = false
  use_cfi_diag = false
  use_cfi_recover = false
  use_drfuzz = false
  use_libfuzzer = false
  use_prebuilt_instrumented_libraries = false
  use_locally_built_instrumented_libraries = false
  use_sanitizer_coverage = false
}

# Args that are in turn dependent on other args must be in a separate
# declare_args block. User overrides are only applied at the end of a
# declare_args block.
declare_args() {
  # Enable -fsanitize-coverage.
  use_sanitizer_coverage =
      use_libfuzzer || use_afl || sanitizer_coverage_flags != ""

  # Detect overflow/underflow for global objects.
  #
  # Mac: http://crbug.com/352073
  asan_globals = !is_mac
}

if ((use_afl || use_libfuzzer) && sanitizer_coverage_flags == "") {
  sanitizer_coverage_flags = "trace-pc-guard"
} else if (use_sanitizer_coverage && sanitizer_coverage_flags == "") {
  sanitizer_coverage_flags = "trace-pc-guard,indirect-calls"
}

# Whether we are linking against a sanitizer runtime library. Among other
# things, this changes the default symbol level and other settings in order to
# prepare to create stack traces "live" using the sanitizer runtime.
using_sanitizer =
    is_asan || is_lsan || is_tsan || is_msan || is_ubsan || is_ubsan_null ||
    is_ubsan_vptr || is_ubsan_security || use_sanitizer_coverage || use_cfi_diag

# Whether we are doing a fuzzer build. Normally this should be checked instead
# of checking "use_libfuzzer || use_afl" because often developers forget to
# check for "use_afl".
use_fuzzing_engine = use_libfuzzer || use_afl

assert(!using_sanitizer || is_clang,
       "Sanitizers (is_*san) require setting is_clang = true in 'gn args'")

assert(!is_cfi || is_clang,
       "is_cfi requires setting is_clang = true in 'gn args'")

prebuilt_instrumented_libraries_available =
    is_msan && (msan_track_origins == 0 || msan_track_origins == 2)

if (use_libfuzzer && is_linux) {
  if (is_asan) {
    # We do leak checking with libFuzzer on Linux. Set is_lsan for code that
    # relies on LEAK_SANITIZER define to avoid false positives.
    is_lsan = true
  }
  if (is_msan) {
    use_prebuilt_instrumented_libraries = true
  }
}

# MSan only links Chrome properly in release builds (brettw -- 9/1/2015). The
# same is possibly true for the other non-ASan sanitizers. But regardless of
# whether it links, one would normally never run a sanitizer in debug mode.
# Running in debug mode probably indicates you forgot to set the "is_debug =
# false" flag in the build args. ASan seems to run fine in debug mode.
#
# If you find a use-case where you want to compile a sanitizer in debug mode
# and have verified it works, ask brettw and we can consider removing it from
# this condition. We may also be able to find another way to enable your case
# without having people accidentally get broken builds by compiling an
# unsupported or unadvisable configurations.
#
# For one-off testing, just comment this assertion out.
assert(!is_debug || !(is_msan || is_ubsan || is_ubsan_null || is_ubsan_vptr),
       "Sanitizers should generally be used in release (set is_debug=false).")

assert(!is_msan || (is_linux && current_cpu == "x64"),
       "MSan currently only works on 64-bit Linux and ChromeOS builds.")

# ASAN build on Windows is not working in debug mode. Intercepting memory
# allocation functions is hard on Windows and not yet implemented in LLVM.
assert(!is_win || !is_debug || !is_asan,
       "ASan on Windows doesn't work in debug (set is_debug=false).")

# Make sure that if we recover on detection (i.e. not crash), diagnostics are
# printed.
assert(!use_cfi_recover || use_cfi_diag,
       "Only use CFI recovery together with diagnostics.")

# TODO(crbug.com/753445): the use_sanitizer_coverage arg is currently
# not supported by the Chromium mac_clang_x64 toolchain on iOS distribution.
# The coverage works with iOS toolchain but it is broken when the mac
# toolchain is used as a secondary one on iOS distribution. E.g., it should be
# possible to build the "net" target for iOS with the sanitizer coverage
# enabled.
assert(
    !(use_sanitizer_coverage && is_mac && target_os == "ios"),
    "crbug.com/753445: use_sanitizer_coverage=true is not supported by the " +
        "Chromium mac_clang_x64 toolchain on iOS distribution. Please set " +
        "the argument value to false.")

# Use these lists of configs to disable instrumenting code that is part of a
# fuzzer, but which isn't being targeted (such as libprotobuf-mutator, *.pb.cc
# and libprotobuf when they are built as part of a proto fuzzer). Adding or
# removing these lists does not have any effect if use_libfuzzer or use_afl are
# not passed as arguments to gn.
not_fuzzed_remove_configs = []
not_fuzzed_remove_nonasan_configs = []

if (use_fuzzing_engine) {
  # Removing coverage should always just work.
  not_fuzzed_remove_configs += [ "//build/config/coverage:default_coverage" ]
  not_fuzzed_remove_nonasan_configs +=
      [ "//build/config/coverage:default_coverage" ]

  if (!is_msan) {
    # Allow sanitizer instrumentation to be removed if we are not using MSan
    # since binaries cannot be partially instrumented with MSan.
    not_fuzzed_remove_configs +=
        [ "//build/config/sanitizers:default_sanitizer_flags" ]

    # Certain parts of binaries must be instrumented with ASan if the rest of
    # the binary is. For these, only remove non-ASan sanitizer instrumentation.
    if (!is_asan) {
      not_fuzzed_remove_nonasan_configs +=
          [ "//build/config/sanitizers:default_sanitizer_flags" ]

      assert(not_fuzzed_remove_nonasan_configs == not_fuzzed_remove_configs)
    }
  }
}