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116 lines
4.0 KiB
C++
116 lines
4.0 KiB
C++
// Copyright 2014 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_FILES_SCOPED_FILE_H_
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#define BASE_FILES_SCOPED_FILE_H_
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#include <stdio.h>
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#include <memory>
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#include "base/base_export.h"
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#include "base/scoped_generic.h"
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#include "build/build_config.h"
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namespace base {
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namespace internal {
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#if BUILDFLAG(IS_ANDROID)
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// Use fdsan on android.
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struct BASE_EXPORT ScopedFDCloseTraits : public ScopedGenericOwnershipTracking {
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static int InvalidValue() { return -1; }
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static void Free(int);
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static void Acquire(const ScopedGeneric<int, ScopedFDCloseTraits>&, int);
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static void Release(const ScopedGeneric<int, ScopedFDCloseTraits>&, int);
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};
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#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
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#if BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_LINUX)
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// On ChromeOS and Linux we guard FD lifetime with a global table and hook into
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// libc close() to perform checks.
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struct BASE_EXPORT ScopedFDCloseTraits : public ScopedGenericOwnershipTracking {
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#else
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struct BASE_EXPORT ScopedFDCloseTraits {
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#endif
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static int InvalidValue() {
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return -1;
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}
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static void Free(int fd);
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#if BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_LINUX)
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static void Acquire(const ScopedGeneric<int, ScopedFDCloseTraits>&, int);
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static void Release(const ScopedGeneric<int, ScopedFDCloseTraits>&, int);
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#endif
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};
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#endif
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// Functor for |ScopedFILE| (below).
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struct ScopedFILECloser {
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inline void operator()(FILE* x) const {
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if (x)
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fclose(x);
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}
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};
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} // namespace internal
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#if BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_LINUX)
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namespace subtle {
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// Enables or disables enforcement of FD ownership as tracked by ScopedFD
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// objects. Enforcement is disabled by default since it proves unwieldy in some
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// test environments, but tracking is always done. It's best to enable this as
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// early as possible in a process's lifetime.
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void BASE_EXPORT EnableFDOwnershipEnforcement(bool enabled);
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// Resets ownership state of all FDs. The only permissible use of this API is
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// in a forked child process between the fork() and a subsequent exec() call.
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//
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// For one issue, it is common to mass-close most open FDs before calling
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// exec(), to avoid leaking FDs into the new executable's environment. For
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// processes which have enabled FD ownership enforcement, this reset operation
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// is necessary before performing such closures.
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//
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// Furthermore, fork()+exec() may be used in a multithreaded context, and
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// because fork() is not atomic, the FD ownership state in the child process may
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// be inconsistent with the actual set of opened file descriptors once fork()
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// returns in the child process.
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//
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// It is therefore especially important to call this ASAP after fork() in the
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// child process if any FD manipulation will be done prior to the subsequent
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// exec call.
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void BASE_EXPORT ResetFDOwnership();
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} // namespace subtle
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#endif
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// -----------------------------------------------------------------------------
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#if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
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// A low-level Posix file descriptor closer class. Use this when writing
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// platform-specific code, especially that does non-file-like things with the
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// FD (like sockets).
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//
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// If you're writing low-level Windows code, see base/win/scoped_handle.h
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// which provides some additional functionality.
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//
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// If you're writing cross-platform code that deals with actual files, you
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// should generally use base::File instead which can be constructed with a
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// handle, and in addition to handling ownership, has convenient cross-platform
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// file manipulation functions on it.
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typedef ScopedGeneric<int, internal::ScopedFDCloseTraits> ScopedFD;
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#endif
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// Automatically closes |FILE*|s.
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typedef std::unique_ptr<FILE, internal::ScopedFILECloser> ScopedFILE;
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#if BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_LINUX)
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// Queries the ownership status of an FD, i.e. whether it is currently owned by
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// a ScopedFD in the calling process.
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bool BASE_EXPORT IsFDOwned(int fd);
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#endif // BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_LINUX)
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} // namespace base
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#endif // BASE_FILES_SCOPED_FILE_H_
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