1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/memory/shared_memory.h"
6
7#include <sys/mman.h>
8
9#include "base/logging.h"
10#include "third_party/ashmem/ashmem.h"
11
12namespace base {
13
14// For Android, we use ashmem to implement SharedMemory. ashmem_create_region
15// will automatically pin the region. We never explicitly call pin/unpin. When
16// all the file descriptors from different processes associated with the region
17// are closed, the memory buffer will go away.
18
19bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
20  DCHECK_EQ(-1, mapped_file_ );
21
22  if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
23    return false;
24
25  // "name" is just a label in ashmem. It is visible in /proc/pid/maps.
26  mapped_file_ = ashmem_create_region(
27      options.name_deprecated == NULL ? "" : options.name_deprecated->c_str(),
28      options.size);
29  if (-1 == mapped_file_) {
30    DLOG(ERROR) << "Shared memory creation failed";
31    return false;
32  }
33
34  int err = ashmem_set_prot_region(mapped_file_,
35                                   PROT_READ | PROT_WRITE | PROT_EXEC);
36  if (err < 0) {
37    DLOG(ERROR) << "Error " << err << " when setting protection of ashmem";
38    return false;
39  }
40
41  // Android doesn't appear to have a way to drop write access on an ashmem
42  // segment for a single descriptor.  http://crbug.com/320865
43  readonly_mapped_file_ = dup(mapped_file_);
44  if (-1 == readonly_mapped_file_) {
45    DPLOG(ERROR) << "dup() failed";
46    return false;
47  }
48
49  requested_size_ = options.size;
50
51  return true;
52}
53
54bool SharedMemory::Delete(const std::string& name) {
55  // Like on Windows, this is intentionally returning true as ashmem will
56  // automatically releases the resource when all FDs on it are closed.
57  return true;
58}
59
60bool SharedMemory::Open(const std::string& name, bool read_only) {
61  // ashmem doesn't support name mapping
62  NOTIMPLEMENTED();
63  return false;
64}
65
66}  // namespace base
67