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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 <mach/mach.h>
#include <sys/mman.h>
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
namespace base {
namespace {
// The VM subsystem allows tagging of memory and 240-255 is reserved for
// application use (see mach/vm_statistics.h). Pick 252 (after chromium's atomic
// weight of ~52).
const int kDiscardableMemoryTag = VM_MAKE_TAG(252);
class DiscardableMemoryMac : public DiscardableMemory {
public:
DiscardableMemoryMac(void* memory, size_t size)
: memory_(memory),
size_(size) {
DCHECK(memory_);
}
virtual ~DiscardableMemoryMac() {
vm_deallocate(mach_task_self(),
reinterpret_cast<vm_address_t>(memory_),
size_);
}
virtual LockDiscardableMemoryStatus Lock() OVERRIDE {
DCHECK_EQ(0, mprotect(memory_, size_, PROT_READ | PROT_WRITE));
int state = VM_PURGABLE_NONVOLATILE;
kern_return_t ret = vm_purgable_control(
mach_task_self(),
reinterpret_cast<vm_address_t>(memory_),
VM_PURGABLE_SET_STATE,
&state);
if (ret != KERN_SUCCESS)
return DISCARDABLE_MEMORY_FAILED;
return state & VM_PURGABLE_EMPTY ? DISCARDABLE_MEMORY_PURGED
: DISCARDABLE_MEMORY_SUCCESS;
}
virtual void Unlock() OVERRIDE {
int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
kern_return_t ret = vm_purgable_control(
mach_task_self(),
reinterpret_cast<vm_address_t>(memory_),
VM_PURGABLE_SET_STATE,
&state);
DCHECK_EQ(0, mprotect(memory_, size_, PROT_NONE));
if (ret != KERN_SUCCESS)
DLOG(ERROR) << "Failed to unlock memory.";
}
virtual void* Memory() const OVERRIDE {
return memory_;
}
private:
void* const memory_;
const size_t size_;
DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMac);
};
} // namespace
// static
bool DiscardableMemory::SupportedNatively() {
return true;
}
// static
scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
size_t size) {
vm_address_t buffer = 0;
kern_return_t ret = vm_allocate(mach_task_self(),
&buffer,
size,
VM_FLAGS_PURGABLE |
VM_FLAGS_ANYWHERE |
kDiscardableMemoryTag);
if (ret != KERN_SUCCESS) {
DLOG(ERROR) << "vm_allocate() failed";
return scoped_ptr<DiscardableMemory>();
}
return scoped_ptr<DiscardableMemory>(
new DiscardableMemoryMac(reinterpret_cast<void*>(buffer), size));
}
// static
bool DiscardableMemory::PurgeForTestingSupported() {
return true;
}
// static
void DiscardableMemory::PurgeForTesting() {
int state = 0;
vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
}
} // namespace base
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