base/shared_memory_android.cc

   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/shared_memory.h"
   6
   7 #include <sys/mman.h>
   8
   9 #include "base/logging.h"
  10 #include "third_party/ashmem/ashmem.h"
  11
  12 namespace 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
  19 bool SharedMemory::CreateNamed(const std::string& name,
  20                                bool open_existing, uint32 size) {
  21   DCHECK_EQ(-1, mapped_file_ );
  22
  23   // "name" is just a label in ashmem. It is visible in /proc/pid/maps.
  24   mapped_file_ = ashmem_create_region(name.c_str(), size);
  25   if (-1 == mapped_file_) {
  26     DLOG(ERROR) << "Shared memory creation failed";
  27     return false;
  28   }
  29
  30   int err = ashmem_set_prot_region(mapped_file_,
  31                                    PROT_READ | PROT_WRITE | PROT_EXEC);
  32   if (err < 0) {
  33     DLOG(ERROR) << "Error " << err << " when setting protection of ashmem";
  34     return false;
  35   }
  36   created_size_ = size;
  37
  38   return true;
  39 }
  40
  41 bool SharedMemory::Delete(const std::string& name) {
  42   // Like on Windows, this is intentionally returning true as ashmem will
  43   // automatically releases the resource when all FDs on it are closed.
  44   return true;
  45 }
  46
  47 bool SharedMemory::Open(const std::string& name, bool read_only) {
  48   // ashmem doesn't support name mapping
  49   NOTIMPLEMENTED();
  50   return false;
  51 }
  52
  53 }  // namespace base