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 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 Create(const SharedMemoryCreateOptions & options)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 == NULL ? "" : options.name->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 Delete(const std::string & name)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 Open(const std::string & name,bool read_only)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