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 <stddef.h> 8 #include <sys/mman.h> 9 10 #include "base/logging.h" 11 #include "third_party/ashmem/ashmem.h" 12 13 namespace base { 14 15 // For Android, we use ashmem to implement SharedMemory. ashmem_create_region 16 // will automatically pin the region. We never explicitly call pin/unpin. When 17 // all the file descriptors from different processes associated with the region 18 // are closed, the memory buffer will go away. 19 20 bool SharedMemory::Create(const SharedMemoryCreateOptions& options) { 21 DCHECK_EQ(-1, mapped_file_ ); 22 23 if (options.size > static_cast<size_t>(std::numeric_limits<int>::max())) 24 return false; 25 26 // "name" is just a label in ashmem. It is visible in /proc/pid/maps. 27 mapped_file_ = ashmem_create_region( 28 options.name_deprecated == NULL ? "" : options.name_deprecated->c_str(), 29 options.size); 30 if (-1 == mapped_file_) { 31 DLOG(ERROR) << "Shared memory creation failed"; 32 return false; 33 } 34 35 int err = ashmem_set_prot_region(mapped_file_, 36 PROT_READ | PROT_WRITE | PROT_EXEC); 37 if (err < 0) { 38 DLOG(ERROR) << "Error " << err << " when setting protection of ashmem"; 39 return false; 40 } 41 42 // Android doesn't appear to have a way to drop write access on an ashmem 43 // segment for a single descriptor. http://crbug.com/320865 44 readonly_mapped_file_ = dup(mapped_file_); 45 if (-1 == readonly_mapped_file_) { 46 DPLOG(ERROR) << "dup() failed"; 47 return false; 48 } 49 50 requested_size_ = options.size; 51 52 return true; 53 } 54 55 bool SharedMemory::Delete(const std::string& name) { 56 // Like on Windows, this is intentionally returning true as ashmem will 57 // automatically releases the resource when all FDs on it are closed. 58 return true; 59 } 60 61 bool SharedMemory::Open(const std::string& name, bool read_only) { 62 // ashmem doesn't support name mapping 63 NOTIMPLEMENTED(); 64 return false; 65 } 66 67 } // namespace base 68
