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// 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 "mojo/embedder/simple_platform_shared_buffer.h"
#include <stdint.h>
#include <stdio.h> // For |fileno()|.
#include <sys/mman.h> // For |mmap()|/|munmap()|.
#include <sys/stat.h>
#include <sys/types.h> // For |off_t|.
#include <unistd.h>
#include <limits>
#include "base/files/file_path.h"
#include "base/files/file_util.h"
#include "base/files/scoped_file.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/posix/eintr_wrapper.h"
#include "base/sys_info.h"
#include "base/threading/thread_restrictions.h"
#include "mojo/embedder/platform_handle.h"
// We assume that |size_t| and |off_t| (type for |ftruncate()|) fits in a
// |uint64_t|.
static_assert(sizeof(size_t) <= sizeof(uint64_t), "size_t too big");
static_assert(sizeof(off_t) <= sizeof(uint64_t), "off_t too big");
namespace mojo {
namespace embedder {
// SimplePlatformSharedBuffer --------------------------------------------------
bool SimplePlatformSharedBuffer::Init() {
DCHECK(!handle_.is_valid());
base::ThreadRestrictions::ScopedAllowIO allow_io;
if (static_cast<uint64_t>(num_bytes_) >
static_cast<uint64_t>(std::numeric_limits<off_t>::max())) {
return false;
}
// TODO(vtl): This is stupid. The implementation of
// |CreateAndOpenTemporaryFileInDir()| starts with an FD, |fdopen()|s to get a
// |FILE*|, and then we have to |dup(fileno(fp))| to get back to an FD that we
// can own. (base/memory/shared_memory_posix.cc does this too, with more
// |fstat()|s thrown in for good measure.)
base::FilePath shared_buffer_dir;
if (!base::GetShmemTempDir(false, &shared_buffer_dir)) {
LOG(ERROR) << "Failed to get temporary directory for shared memory";
return false;
}
base::FilePath shared_buffer_file;
base::ScopedFILE fp(base::CreateAndOpenTemporaryFileInDir(
shared_buffer_dir, &shared_buffer_file));
if (!fp) {
LOG(ERROR) << "Failed to create/open temporary file for shared memory";
return false;
}
// Note: |unlink()| is not interruptible.
if (unlink(shared_buffer_file.value().c_str()) != 0) {
PLOG(WARNING) << "unlink";
// This isn't "fatal" (e.g., someone else may have unlinked the file first),
// so we may as well continue.
}
// Note: |dup()| is not interruptible (but |dup2()|/|dup3()| are).
base::ScopedFD fd(dup(fileno(fp.get())));
if (!fd.is_valid()) {
PLOG(ERROR) << "dup";
return false;
}
if (HANDLE_EINTR(ftruncate(fd.get(), static_cast<off_t>(num_bytes_))) != 0) {
PLOG(ERROR) << "ftruncate";
return false;
}
handle_.reset(PlatformHandle(fd.release()));
return true;
}
bool SimplePlatformSharedBuffer::InitFromPlatformHandle(
ScopedPlatformHandle platform_handle) {
DCHECK(!handle_.is_valid());
if (static_cast<uint64_t>(num_bytes_) >
static_cast<uint64_t>(std::numeric_limits<off_t>::max())) {
return false;
}
struct stat sb = {};
// Note: |fstat()| isn't interruptible.
if (fstat(platform_handle.get().fd, &sb) != 0) {
PLOG(ERROR) << "fstat";
return false;
}
if (!S_ISREG(sb.st_mode)) {
LOG(ERROR) << "Platform handle not to a regular file";
return false;
}
if (sb.st_size != static_cast<off_t>(num_bytes_)) {
LOG(ERROR) << "Shared memory file has the wrong size";
return false;
}
// TODO(vtl): More checks?
handle_ = platform_handle.Pass();
return true;
}
scoped_ptr<PlatformSharedBufferMapping> SimplePlatformSharedBuffer::MapImpl(
size_t offset,
size_t length) {
size_t offset_rounding = offset % base::SysInfo::VMAllocationGranularity();
size_t real_offset = offset - offset_rounding;
size_t real_length = length + offset_rounding;
// This should hold (since we checked |num_bytes| versus the maximum value of
// |off_t| on creation, but it never hurts to be paranoid.
DCHECK_LE(static_cast<uint64_t>(real_offset),
static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
void* real_base = mmap(nullptr,
real_length,
PROT_READ | PROT_WRITE,
MAP_SHARED,
handle_.get().fd,
static_cast<off_t>(real_offset));
// |mmap()| should return |MAP_FAILED| (a.k.a. -1) on error. But it shouldn't
// return null either.
if (real_base == MAP_FAILED || !real_base) {
PLOG(ERROR) << "mmap";
return nullptr;
}
void* base = static_cast<char*>(real_base) + offset_rounding;
return scoped_ptr<PlatformSharedBufferMapping>(
new SimplePlatformSharedBufferMapping(
base, length, real_base, real_length));
}
// SimplePlatformSharedBufferMapping -------------------------------------------
void SimplePlatformSharedBufferMapping::Unmap() {
int result = munmap(real_base_, real_length_);
PLOG_IF(ERROR, result != 0) << "munmap";
}
} // namespace embedder
} // namespace mojo
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