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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/shared_memory_mapping.h"
#include <cstdint>
#include <utility>
#include "base/bits.h"
#include "base/compiler_specific.h"
#include "base/logging.h"
#include "base/memory/shared_memory_security_policy.h"
#include "base/memory/shared_memory_tracker.h"
#include "base/system/sys_info.h"
#include "base/unguessable_token.h"
#include "build/build_config.h"
namespace base {
SharedMemoryMapping::SharedMemoryMapping() = default;
SharedMemoryMapping::SharedMemoryMapping(SharedMemoryMapping&& mapping) noexcept
: mapped_span_(std::exchange(mapping.mapped_span_, span<uint8_t>())),
size_(mapping.size_),
guid_(mapping.guid_),
mapper_(mapping.mapper_) {}
SharedMemoryMapping& SharedMemoryMapping::operator=(
SharedMemoryMapping&& mapping) noexcept {
Unmap();
mapped_span_ = std::exchange(mapping.mapped_span_, span<uint8_t>());
size_ = mapping.size_;
guid_ = mapping.guid_;
mapper_ = mapping.mapper_;
return *this;
}
SharedMemoryMapping::~SharedMemoryMapping() {
Unmap();
}
SharedMemoryMapping::SharedMemoryMapping(span<uint8_t> mapped_span,
size_t size,
const UnguessableToken& guid,
SharedMemoryMapper* mapper)
: mapped_span_(mapped_span), size_(size), guid_(guid), mapper_(mapper) {
CHECK_LE(size_, mapped_span_.size());
// Note: except on Windows, `mapped_span_.size() == size_`.
SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
}
void SharedMemoryMapping::Unmap() {
if (!IsValid()) {
return;
}
SharedMemorySecurityPolicy::ReleaseReservationForMapping(size_);
SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
SharedMemoryMapper* mapper = mapper_;
if (!mapper) {
mapper = SharedMemoryMapper::GetDefaultInstance();
}
// The backing mapper expects offset to be aligned to
// `SysInfo::VMAllocationGranularity()`, so replicate the alignment that was
// done when originally mapping in the region.
uint8_t* aligned_data =
bits::AlignDown(mapped_span_.data(), SysInfo::VMAllocationGranularity());
size_t adjusted_size =
mapped_span_.size() +
static_cast<size_t>(mapped_span_.data() - aligned_data);
mapper->Unmap(UNSAFE_TODO(span(aligned_data, adjusted_size)));
}
ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping() = default;
ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping(
ReadOnlySharedMemoryMapping&&) noexcept = default;
ReadOnlySharedMemoryMapping& ReadOnlySharedMemoryMapping::operator=(
ReadOnlySharedMemoryMapping&&) noexcept = default;
ReadOnlySharedMemoryMapping::ReadOnlySharedMemoryMapping(
span<uint8_t> mapped_span,
size_t size,
const UnguessableToken& guid,
SharedMemoryMapper* mapper)
: SharedMemoryMapping(mapped_span, size, guid, mapper) {}
WritableSharedMemoryMapping::WritableSharedMemoryMapping() = default;
WritableSharedMemoryMapping::WritableSharedMemoryMapping(
WritableSharedMemoryMapping&&) noexcept = default;
WritableSharedMemoryMapping& WritableSharedMemoryMapping::operator=(
WritableSharedMemoryMapping&&) noexcept = default;
WritableSharedMemoryMapping::WritableSharedMemoryMapping(
span<uint8_t> mapped_span,
size_t size,
const UnguessableToken& guid,
SharedMemoryMapper* mapper)
: SharedMemoryMapping(mapped_span, size, guid, mapper) {}
} // namespace base
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