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76 lines
2.2 KiB
C++
76 lines
2.2 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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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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#include "base/memory/shared_memory.h"
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#include <stddef.h>
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#include <sys/mman.h>
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#include "base/logging.h"
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#include "third_party/ashmem/ashmem.h"
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namespace base {
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// For Android, we use ashmem to implement SharedMemory. ashmem_create_region
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// will automatically pin the region. We never explicitly call pin/unpin. When
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// all the file descriptors from different processes associated with the region
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// are closed, the memory buffer will go away.
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bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
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DCHECK(!shm_.IsValid());
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if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
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return false;
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// "name" is just a label in ashmem. It is visible in /proc/pid/maps.
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int fd = ashmem_create_region(
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options.name_deprecated ? options.name_deprecated->c_str() : "",
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options.size);
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shm_ = SharedMemoryHandle::ImportHandle(fd, options.size);
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if (!shm_.IsValid()) {
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DLOG(ERROR) << "Shared memory creation failed";
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return false;
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}
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int flags = PROT_READ | PROT_WRITE | (options.executable ? PROT_EXEC : 0);
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int err = ashmem_set_prot_region(shm_.GetHandle(), flags);
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if (err < 0) {
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DLOG(ERROR) << "Error " << err << " when setting protection of ashmem";
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return false;
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}
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requested_size_ = options.size;
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return true;
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}
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bool SharedMemory::Delete(const std::string& name) {
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// Like on Windows, this is intentionally returning true as ashmem will
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// automatically releases the resource when all FDs on it are closed.
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return true;
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}
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bool SharedMemory::Open(const std::string& name, bool read_only) {
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// ashmem doesn't support name mapping
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NOTIMPLEMENTED();
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return false;
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}
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void SharedMemory::Close() {
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if (shm_.IsValid()) {
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shm_.Close();
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shm_ = SharedMemoryHandle();
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}
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}
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SharedMemoryHandle SharedMemory::GetReadOnlyHandle() const {
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// There are no read-only Ashmem descriptors on Android.
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// Instead, the protection mask is a property of the region itself.
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SharedMemoryHandle handle = shm_.Duplicate();
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handle.SetReadOnly();
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return handle;
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}
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} // namespace base
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