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// 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/memory/shared_memory.h"
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <limits>
#include "base/logging.h"
#include "base/memory/shared_memory_tracker.h"
namespace base {
SharedMemory::SharedMemory()
: mapped_size_(0), memory_(NULL), read_only_(false), requested_size_(0) {}
SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
: shm_(handle),
mapped_size_(0),
memory_(NULL),
read_only_(read_only),
requested_size_(0) {}
SharedMemory::~SharedMemory() {
Unmap();
Close();
}
// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
return handle.IsValid();
}
// static
void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
DCHECK(handle.IsValid());
handle.Close();
}
// static
SharedMemoryHandle SharedMemory::DuplicateHandle(
const SharedMemoryHandle& handle) {
return handle.Duplicate();
}
bool SharedMemory::CreateAndMapAnonymous(size_t size) {
// Untrusted code can't create descriptors or handles.
return false;
}
bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
// Untrusted code can't create descriptors or handles.
return false;
}
bool SharedMemory::Delete(const std::string& name) {
return false;
}
bool SharedMemory::Open(const std::string& name, bool read_only) {
return false;
}
bool SharedMemory::MapAt(off_t offset, size_t bytes) {
if (!shm_.IsValid())
return false;
if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
return false;
if (memory_)
return false;
memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
MAP_SHARED, shm_.GetHandle(), offset);
bool mmap_succeeded = memory_ != MAP_FAILED && memory_ != NULL;
if (mmap_succeeded) {
mapped_size_ = bytes;
DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
(SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
mapped_id_ = shm_.GetGUID();
SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
} else {
memory_ = NULL;
}
return mmap_succeeded;
}
bool SharedMemory::Unmap() {
if (memory_ == NULL)
return false;
SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
if (munmap(memory_, mapped_size_) < 0)
DPLOG(ERROR) << "munmap";
memory_ = NULL;
mapped_size_ = 0;
mapped_id_ = UnguessableToken();
return true;
}
SharedMemoryHandle SharedMemory::handle() const {
SharedMemoryHandle handle_copy = shm_;
handle_copy.SetOwnershipPassesToIPC(false);
return handle_copy;
}
SharedMemoryHandle SharedMemory::TakeHandle() {
SharedMemoryHandle handle_copy = shm_;
handle_copy.SetOwnershipPassesToIPC(true);
Unmap();
shm_ = SharedMemoryHandle();
return handle_copy;
}
void SharedMemory::Close() {
if (shm_.IsValid()) {
shm_.Close();
shm_ = SharedMemoryHandle();
}
}
SharedMemoryHandle SharedMemory::GetReadOnlyHandle() const {
// Untrusted code can't create descriptors or handles, which is needed to
// drop permissions.
return SharedMemoryHandle();
}
} // namespace base
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