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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/memory/platform_shared_memory_region.h"
#include <mach/vm_map.h>
#include "base/apple/mach_logging.h"
#include "base/apple/scoped_mach_vm.h"
namespace base::subtle {
// static
PlatformSharedMemoryRegion PlatformSharedMemoryRegion::Take(
apple::ScopedMachSendRight handle,
Mode mode,
size_t size,
const UnguessableToken& guid) {
if (!handle.is_valid()) {
return {};
}
if (size == 0) {
return {};
}
if (size > static_cast<size_t>(std::numeric_limits<int>::max())) {
return {};
}
CHECK(
CheckPlatformHandlePermissionsCorrespondToMode(handle.get(), mode, size));
return PlatformSharedMemoryRegion(std::move(handle), mode, size, guid);
}
mach_port_t PlatformSharedMemoryRegion::GetPlatformHandle() const {
return handle_.get();
}
bool PlatformSharedMemoryRegion::IsValid() const {
return handle_.is_valid();
}
PlatformSharedMemoryRegion PlatformSharedMemoryRegion::Duplicate() const {
if (!IsValid()) {
return {};
}
CHECK_NE(mode_, Mode::kWritable)
<< "Duplicating a writable shared memory region is prohibited";
// Increment the ref count.
kern_return_t kr = mach_port_mod_refs(mach_task_self(), handle_.get(),
MACH_PORT_RIGHT_SEND, 1);
if (kr != KERN_SUCCESS) {
MACH_DLOG(ERROR, kr) << "mach_port_mod_refs";
return {};
}
return PlatformSharedMemoryRegion(apple::ScopedMachSendRight(handle_.get()),
mode_, size_, guid_);
}
bool PlatformSharedMemoryRegion::ConvertToReadOnly() {
return ConvertToReadOnly(nullptr);
}
bool PlatformSharedMemoryRegion::ConvertToReadOnly(void* mapped_addr) {
if (!IsValid()) {
return false;
}
CHECK_EQ(mode_, Mode::kWritable)
<< "Only writable shared memory region can be converted to read-only";
apple::ScopedMachSendRight handle_copy(handle_.release());
void* temp_addr = mapped_addr;
apple::ScopedMachVM scoped_memory;
if (!temp_addr) {
// Intentionally lower current prot and max prot to |VM_PROT_READ|.
kern_return_t kr =
vm_map(mach_task_self(), reinterpret_cast<vm_address_t*>(&temp_addr),
size_, 0, VM_FLAGS_ANYWHERE, handle_copy.get(), 0, FALSE,
VM_PROT_READ, VM_PROT_READ, VM_INHERIT_NONE);
if (kr != KERN_SUCCESS) {
MACH_DLOG(ERROR, kr) << "vm_map";
return false;
}
scoped_memory.reset(reinterpret_cast<vm_address_t>(temp_addr),
mach_vm_round_page(size_));
}
// Make new memory object.
memory_object_size_t allocation_size = size_;
apple::ScopedMachSendRight named_right;
kern_return_t kr = mach_make_memory_entry_64(
mach_task_self(), &allocation_size,
reinterpret_cast<memory_object_offset_t>(temp_addr), VM_PROT_READ,
apple::ScopedMachSendRight::Receiver(named_right).get(), MACH_PORT_NULL);
if (kr != KERN_SUCCESS) {
MACH_DLOG(ERROR, kr) << "mach_make_memory_entry_64";
return false;
}
DCHECK_GE(allocation_size, size_);
handle_ = std::move(named_right);
mode_ = Mode::kReadOnly;
return true;
}
bool PlatformSharedMemoryRegion::ConvertToUnsafe() {
if (!IsValid()) {
return false;
}
CHECK_EQ(mode_, Mode::kWritable)
<< "Only writable shared memory region can be converted to unsafe";
mode_ = Mode::kUnsafe;
return true;
}
// static
PlatformSharedMemoryRegion PlatformSharedMemoryRegion::Create(Mode mode,
size_t size) {
if (size == 0) {
return {};
}
if (size > static_cast<size_t>(std::numeric_limits<int>::max())) {
return {};
}
CHECK_NE(mode, Mode::kReadOnly) << "Creating a region in read-only mode will "
"lead to this region being non-modifiable";
memory_object_size_t vm_size = size;
apple::ScopedMachSendRight named_right;
kern_return_t kr = mach_make_memory_entry_64(
mach_task_self(), &vm_size,
0, // Address.
MAP_MEM_NAMED_CREATE | VM_PROT_READ | VM_PROT_WRITE,
apple::ScopedMachSendRight::Receiver(named_right).get(),
MACH_PORT_NULL); // Parent handle.
// Crash as soon as shm allocation fails to debug the issue
// https://crbug.com/872237.
MACH_CHECK(kr == KERN_SUCCESS, kr) << "mach_make_memory_entry_64";
DCHECK_GE(vm_size, size);
return PlatformSharedMemoryRegion(std::move(named_right), mode, size,
UnguessableToken::Create());
}
// static
bool PlatformSharedMemoryRegion::CheckPlatformHandlePermissionsCorrespondToMode(
PlatformSharedMemoryHandle handle,
Mode mode,
size_t size) {
vm_address_t temp_addr = 0;
kern_return_t kr =
vm_map(mach_task_self(), &temp_addr, size, 0, VM_FLAGS_ANYWHERE, handle,
0, FALSE, VM_PROT_READ | VM_PROT_WRITE,
VM_PROT_READ | VM_PROT_WRITE, VM_INHERIT_NONE);
if (kr == KERN_SUCCESS) {
kern_return_t kr_deallocate =
vm_deallocate(mach_task_self(), temp_addr, size);
// TODO(https://crbug.com/838365): convert to DLOG when bug fixed.
MACH_LOG_IF(ERROR, kr_deallocate != KERN_SUCCESS, kr_deallocate)
<< "vm_deallocate";
} else if (kr != KERN_INVALID_RIGHT) {
MACH_LOG(ERROR, kr) << "vm_map";
return false;
}
bool is_read_only = kr == KERN_INVALID_RIGHT;
bool expected_read_only = mode == Mode::kReadOnly;
if (is_read_only != expected_read_only) {
// TODO(https://crbug.com/838365): convert to DLOG when bug fixed.
LOG(ERROR) << "VM region has a wrong protection mask: it is"
<< (is_read_only ? " " : " not ") << "read-only but it should"
<< (expected_read_only ? " " : " not ") << "be";
return false;
}
return true;
}
PlatformSharedMemoryRegion::PlatformSharedMemoryRegion(
apple::ScopedMachSendRight handle,
Mode mode,
size_t size,
const UnguessableToken& guid)
: handle_(std::move(handle)), mode_(mode), size_(size), guid_(guid) {}
} // namespace base::subtle
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