chromium/base/memory/shared_memory_security_policy.cc

// Copyright 2020 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_security_policy.h"

#include <algorithm>
#include <atomic>
#include <limits>
#include <optional>

#include "base/bits.h"
#include "base/memory/page_size.h"
#include "base/numerics/checked_math.h"
#include "build/build_config.h"

namespace base {

namespace {

// Note: pointers are 32 bits on all architectures in NaCl. See
// https://bugs.chromium.org/p/nativeclient/issues/detail?id=1162
#if defined(ARCH_CPU_32_BITS) || BUILDFLAG(IS_NACL)
// No effective limit on 32-bit, since there simply isn't enough address space
// for ASLR to be particularly effective.
constexpr size_t kTotalMappedSizeLimit = std::numeric_limits<size_t>::max();
#elif defined(ARCH_CPU_64_BITS)
// 32 GB of mappings ought to be enough for anybody.
constexpr size_t kTotalMappedSizeLimit = …;
#endif

static std::atomic_size_t total_mapped_size_;

std::optional<size_t> AlignWithPageSize(size_t size) { … }

}  // namespace

// static
bool SharedMemorySecurityPolicy::AcquireReservationForMapping(size_t size) { … }

// static
void SharedMemorySecurityPolicy::ReleaseReservationForMapping(size_t size) { … }

}  // namespace base