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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/memory/discardable_memory.h"
#include <sys/mman.h>
#include <unistd.h>
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/file_util.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/posix/eintr_wrapper.h"
#include "base/synchronization/lock.h"
#include "third_party/ashmem/ashmem.h"
namespace base {
namespace {
// Protects |g_num_discardable_memory| below.
base::LazyInstance<base::Lock>::Leaky g_discardable_memory_lock =
LAZY_INSTANCE_INITIALIZER;
// Total number of discardable memory in the process.
int g_num_discardable_memory = 0;
// Upper limit on the number of discardable memory to avoid hitting file
// descriptor limit.
const int kDiscardableMemoryNumLimit = 128;
bool CreateAshmemRegion(const char* name,
size_t size,
int* out_fd,
void** out_address) {
base::AutoLock lock(g_discardable_memory_lock.Get());
if (g_num_discardable_memory + 1 > kDiscardableMemoryNumLimit)
return false;
int fd = ashmem_create_region(name, size);
if (fd < 0) {
DLOG(ERROR) << "ashmem_create_region() failed";
return false;
}
file_util::ScopedFD fd_closer(&fd);
const int err = ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE);
if (err < 0) {
DLOG(ERROR) << "Error " << err << " when setting protection of ashmem";
return false;
}
// There is a problem using MAP_PRIVATE here. As we are constantly calling
// Lock() and Unlock(), data could get lost if they are not written to the
// underlying file when Unlock() gets called.
void* const address = mmap(
NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (address == MAP_FAILED) {
DPLOG(ERROR) << "Failed to map memory.";
return false;
}
ignore_result(fd_closer.release());
++g_num_discardable_memory;
*out_fd = fd;
*out_address = address;
return true;
}
bool DeleteAshmemRegion(int fd, size_t size, void* address) {
base::AutoLock lock(g_discardable_memory_lock.Get());
--g_num_discardable_memory;
if (munmap(address, size) == -1) {
DPLOG(ERROR) << "Failed to unmap memory.";
close(fd);
return false;
}
return close(fd) == 0;
}
LockDiscardableMemoryStatus LockAshmemRegion(int fd,
size_t off,
size_t size,
const void* address) {
const int result = ashmem_pin_region(fd, off, size);
return result == ASHMEM_WAS_PURGED ?
DISCARDABLE_MEMORY_PURGED : DISCARDABLE_MEMORY_SUCCESS;
}
bool UnlockAshmemRegion(int fd, size_t off, size_t size, const void* address) {
const int failed = ashmem_unpin_region(fd, off, size);
if (failed)
DLOG(ERROR) << "Failed to unpin memory.";
return !failed;
}
class DiscardableMemoryAndroid : public DiscardableMemory {
public:
DiscardableMemoryAndroid(int fd, void* address, size_t size)
: fd_(fd),
memory_(address),
size_(size) {
DCHECK_GE(fd_, 0);
DCHECK(memory_);
}
virtual ~DiscardableMemoryAndroid() {
DeleteAshmemRegion(fd_, size_, memory_);
}
// DiscardableMemory:
virtual LockDiscardableMemoryStatus Lock() OVERRIDE {
if (!memory_ && !MapRegion())
return DISCARDABLE_MEMORY_FAILED;
return LockAshmemRegion(fd_, 0, size_, memory_);
}
virtual void Unlock() OVERRIDE {
UnmapRegion();
UnlockAshmemRegion(fd_, 0, size_, memory_);
}
virtual void* Memory() const OVERRIDE {
DCHECK(memory_) << "Trying to access unmapped memory";
return memory_;
}
private:
// TODO(pliard): http://crbug.com/311633. Remove the two methods below once
// memory measurement infrastructure supports unpinned ashmem purging.
bool MapRegion() {
DCHECK(!memory_) << "Region already mapped";
void* const address = mmap(
NULL, size_, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0);
if (address == MAP_FAILED) {
DPLOG(ERROR) << "Failed to map memory.";
return false;
}
memory_ = address;
return true;
}
void UnmapRegion() {
DCHECK(memory_) << "Region already unmapped";
if (munmap(memory_, size_) == -1)
DPLOG(ERROR) << "Failed to unmap memory.";
memory_ = NULL;
}
const int fd_;
void* memory_;
const size_t size_;
DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAndroid);
};
} // namespace
// static
bool DiscardableMemory::SupportedNatively() {
return true;
}
// static
scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
size_t size) {
// Pinning & unpinning works with page granularity therefore align the size
// upfront.
const size_t kPageSize = 4096;
const size_t mask = ~(kPageSize - 1);
size = (size + kPageSize - 1) & mask;
int fd;
void* address;
if (!CreateAshmemRegion("", size, &fd, &address))
return scoped_ptr<DiscardableMemory>();
return scoped_ptr<DiscardableMemory>(
new DiscardableMemoryAndroid(fd, address, size));
}
// static
bool DiscardableMemory::PurgeForTestingSupported() {
return false;
}
// static
void DiscardableMemory::PurgeForTesting() {
NOTIMPLEMENTED();
}
} // namespace base
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