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// Copyright (c) 2012 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/shared_memory.h"
#include <errno.h>
#include <mach/mach_vm.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include "base/files/file_util.h"
#include "base/files/scoped_file.h"
#include "base/logging.h"
#include "base/mac/foundation_util.h"
#include "base/mac/mac_util.h"
#include "base/mac/scoped_mach_vm.h"
#include "base/memory/shared_memory_helper.h"
#include "base/memory/shared_memory_tracker.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/histogram_macros.h"
#include "base/posix/eintr_wrapper.h"
#include "base/posix/safe_strerror.h"
#include "base/process/process_metrics.h"
#include "base/scoped_generic.h"
#include "base/strings/utf_string_conversions.h"
#include "base/threading/thread_restrictions.h"
#include "base/unguessable_token.h"
#include "build/build_config.h"
#include "starboard/types.h"
#if defined(OS_IOS)
#error "MacOS only - iOS uses shared_memory_posix.cc"
#endif
namespace base {
namespace {
// Returns whether the operation succeeded.
// |new_handle| is an output variable, populated on success. The caller takes
// ownership of the underlying memory object.
// |handle| is the handle to copy.
// If |handle| is already mapped, |mapped_addr| is its mapped location.
// Otherwise, |mapped_addr| should be |nullptr|.
bool MakeMachSharedMemoryHandleReadOnly(SharedMemoryHandle* new_handle,
SharedMemoryHandle handle,
void* mapped_addr) {
if (!handle.IsValid())
return false;
size_t size = handle.GetSize();
// Map if necessary.
void* temp_addr = mapped_addr;
base::mac::ScopedMachVM scoper;
if (!temp_addr) {
// Intentionally lower current prot and max prot to |VM_PROT_READ|.
kern_return_t kr = mach_vm_map(
mach_task_self(), reinterpret_cast<mach_vm_address_t*>(&temp_addr),
size, 0, VM_FLAGS_ANYWHERE, handle.GetMemoryObject(), 0, FALSE,
VM_PROT_READ, VM_PROT_READ, VM_INHERIT_NONE);
if (kr != KERN_SUCCESS)
return false;
scoper.reset(reinterpret_cast<vm_address_t>(temp_addr),
mach_vm_round_page(size));
}
// Make new memory object.
mach_port_t named_right;
kern_return_t kr = mach_make_memory_entry_64(
mach_task_self(), reinterpret_cast<memory_object_size_t*>(&size),
reinterpret_cast<memory_object_offset_t>(temp_addr), VM_PROT_READ,
&named_right, MACH_PORT_NULL);
if (kr != KERN_SUCCESS)
return false;
*new_handle = SharedMemoryHandle(named_right, size, handle.GetGUID());
return true;
}
} // namespace
SharedMemory::SharedMemory() {}
SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
: mapped_memory_mechanism_(SharedMemoryHandle::POSIX),
shm_(handle),
read_only_(read_only) {}
SharedMemory::~SharedMemory() {
Unmap();
Close();
}
// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
return handle.IsValid();
}
// static
void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
handle.Close();
}
// static
size_t SharedMemory::GetHandleLimit() {
return GetMaxFds();
}
// static
SharedMemoryHandle SharedMemory::DuplicateHandle(
const SharedMemoryHandle& handle) {
return handle.Duplicate();
}
// static
int SharedMemory::GetFdFromSharedMemoryHandle(
const SharedMemoryHandle& handle) {
return handle.file_descriptor_.fd;
}
bool SharedMemory::CreateAndMapAnonymous(size_t size) {
return CreateAnonymous(size) && Map(size);
}
// Chromium mostly only uses the unique/private shmem as specified by
// "name == L"". The exception is in the StatsTable.
bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
DCHECK(!shm_.IsValid());
if (options.size == 0)
return false;
if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
return false;
if (options.type == SharedMemoryHandle::MACH) {
shm_ = SharedMemoryHandle(options.size, UnguessableToken::Create());
requested_size_ = options.size;
return shm_.IsValid();
}
// This function theoretically can block on the disk. Both profiling of real
// users and local instrumentation shows that this is a real problem.
// https://code.google.com/p/chromium/issues/detail?id=466437
ThreadRestrictions::ScopedAllowIO allow_io;
ScopedFD fd;
ScopedFD readonly_fd;
FilePath path;
bool result = CreateAnonymousSharedMemory(options, &fd, &readonly_fd, &path);
if (!result)
return false;
// Should be guaranteed by CreateAnonymousSharedMemory().
DCHECK(fd.is_valid());
// Get current size.
struct stat stat;
if (fstat(fd.get(), &stat) != 0)
return false;
const size_t current_size = stat.st_size;
if (current_size != options.size) {
if (HANDLE_EINTR(ftruncate(fd.get(), options.size)) != 0)
return false;
}
requested_size_ = options.size;
int mapped_file = -1;
int readonly_mapped_file = -1;
result = PrepareMapFile(std::move(fd), std::move(readonly_fd), &mapped_file,
&readonly_mapped_file);
shm_ = SharedMemoryHandle(FileDescriptor(mapped_file, false), options.size,
UnguessableToken::Create());
readonly_shm_ =
SharedMemoryHandle(FileDescriptor(readonly_mapped_file, false),
options.size, shm_.GetGUID());
return result;
}
bool SharedMemory::MapAt(off_t offset, size_t bytes) {
if (!shm_.IsValid())
return false;
if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
return false;
if (memory_)
return false;
bool success = shm_.MapAt(offset, bytes, &memory_, read_only_);
if (success) {
mapped_size_ = bytes;
DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
(SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
mapped_memory_mechanism_ = shm_.type_;
mapped_id_ = shm_.GetGUID();
SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
} else {
memory_ = nullptr;
}
return success;
}
bool SharedMemory::Unmap() {
if (!memory_)
return false;
SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
switch (mapped_memory_mechanism_) {
case SharedMemoryHandle::POSIX:
munmap(memory_, mapped_size_);
break;
case SharedMemoryHandle::MACH:
mach_vm_deallocate(mach_task_self(),
reinterpret_cast<mach_vm_address_t>(memory_),
mapped_size_);
break;
}
memory_ = nullptr;
mapped_size_ = 0;
mapped_id_ = UnguessableToken();
return true;
}
SharedMemoryHandle SharedMemory::handle() const {
return shm_;
}
SharedMemoryHandle SharedMemory::TakeHandle() {
SharedMemoryHandle dup = DuplicateHandle(handle());
Unmap();
Close();
return dup;
}
void SharedMemory::Close() {
shm_.Close();
shm_ = SharedMemoryHandle();
if (shm_.type_ == SharedMemoryHandle::POSIX) {
if (readonly_shm_.IsValid()) {
readonly_shm_.Close();
readonly_shm_ = SharedMemoryHandle();
}
}
}
SharedMemoryHandle SharedMemory::GetReadOnlyHandle() const {
if (shm_.type_ == SharedMemoryHandle::POSIX) {
// We could imagine re-opening the file from /dev/fd, but that can't make it
// readonly on Mac: https://codereview.chromium.org/27265002/#msg10.
CHECK(readonly_shm_.IsValid());
return readonly_shm_.Duplicate();
}
DCHECK(shm_.IsValid());
SharedMemoryHandle new_handle;
bool success = MakeMachSharedMemoryHandleReadOnly(&new_handle, shm_, memory_);
if (success)
new_handle.SetOwnershipPassesToIPC(true);
return new_handle;
}
} // namespace base