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// Copyright (c) 2011 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 UI_GL_SAFE_SHARED_MEMORY_POOL_H_
#define UI_GL_SAFE_SHARED_MEMORY_POOL_H_
#include <map>
#include "base/basictypes.h"
#include "base/shared_memory.h"
#include "base/synchronization/lock.h"
#include "build/build_config.h"
namespace base {
class SharedMemory;
}
namespace gfx {
class SafeSharedMemoryPool;
class ScopedSafeSharedMemory;
}
namespace gfx {
// These classes exist to help protect against deletion of shared
// memory that is being used on a worker thread. It's mainly a
// security measure to prevent use-after-free in the browser, due
// to a misbehaving client. That said, this should be removed
// in favor of higher-level reference counting of an appropriate
// opaque 'memory blob' data-structure.
class ScopedSafeSharedMemory {
public:
base::SharedMemory* shared_memory();
ScopedSafeSharedMemory(SafeSharedMemoryPool* pool,
base::SharedMemory* memory,
size_t shm_size);
~ScopedSafeSharedMemory();
private:
base::SharedMemory* safe_shared_memory_;
base::SharedMemoryHandle original_handle_;
SafeSharedMemoryPool* pool_;
DISALLOW_COPY_AND_ASSIGN(ScopedSafeSharedMemory);
};
class SafeSharedMemoryPool {
public:
SafeSharedMemoryPool();
virtual ~SafeSharedMemoryPool();
private:
friend class ScopedSafeSharedMemory;
// Acquires and release shared memory. The acquired shared memory
// is guaranteed to live until it is released.
base::SharedMemory* AcquireSafeSharedMemory(base::SharedMemory*, size_t size);
void ReleaseSafeSharedMemory(const base::SharedMemoryHandle&);
// Utility function to duplicate shared memory.
base::SharedMemory* DuplicateSharedMemory(base::SharedMemory*, size_t size);
// Track all SharedMemory's that we have already duplicated.
struct TrackedMemory {
base::SharedMemory* safe_shared_memory;
size_t shm_size;
int reference_count;
};
typedef std::map<base::SharedMemoryHandle, TrackedMemory> MemoryMap;
MemoryMap memory_;
// Track usage to diagnose crashes.
int handles_acquired_;
int handles_consumed_;
size_t address_space_consumed_;
int max_handles_acquired_;
int max_handles_consumed_;
size_t max_address_space_consumed_;
base::Lock lock_;
DISALLOW_COPY_AND_ASSIGN(SafeSharedMemoryPool);
};
} // namespace gfx
#endif // UI_GL_ASYNC_TASK_DELEGATE_H_
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