chromium/v8/src/heap/code-range.h

// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_HEAP_CODE_RANGE_H_
#define V8_HEAP_CODE_RANGE_H_

#include <unordered_map>
#include <vector>

#include "src/base/platform/mutex.h"
#include "src/common/globals.h"
#include "src/utils/allocation.h"
#include "v8-internal.h"

namespace v8 {
namespace internal {

// The process-wide singleton that keeps track of code range regions with the
// intention to reuse free code range regions as a workaround for CFG memory
// leaks (see crbug.com/870054).
class CodeRangeAddressHint { … };

// A code range is a virtual memory cage that may contain executable code. It
// has the following layout.
//
// +---------+-----+-----------------  ~~~  -+
// |   RW    | ... |     ...                 |
// +---------+-----+------------------ ~~~  -+
// ^               ^
// base            allocatable base
//
// <-------->      <------------------------->
//  reserved            allocatable region
// <----------------------------------------->
//                 CodeRange
//
// The start of the reservation may include reserved page with read-write access
// as required by some platforms (Win64) followed by an unmapped region which
// make allocatable base MemoryChunk::kAlignment-aligned. The cage's page
// allocator explicitly marks the optional reserved page as occupied, so it's
// excluded from further allocations.
//
// The following conditions hold:
// 1) |reservation()->region()| == [base(), base() + size()[,
// 2) if optional RW pages are not necessary, then |base| == |allocatable base|,
// 3) both |base| and |allocatable base| are MemoryChunk::kAlignment-aligned.
class CodeRange final : public VirtualMemoryCage { … };

}  // namespace internal
}  // namespace v8

#endif  // V8_HEAP_CODE_RANGE_H_