chromium/v8/include/v8-sandbox.h

// Copyright 2024 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 INCLUDE_V8_SANDBOX_H_
#define INCLUDE_V8_SANDBOX_H_

#include <cstdint>

#include "v8-internal.h"  // NOLINT(build/include_directory)
#include "v8config.h"     // NOLINT(build/include_directory)

namespace v8 {

/**
 * A pointer tag used for wrapping and unwrapping `CppHeap` pointers as used
 * with JS API wrapper objects that rely on `v8::Object::Wrap()` and
 * `v8::Object::Unwrap()`.
 *
 * The CppHeapPointers use a range-based type checking scheme, where on access
 * to a pointer, the actual type of the pointer is checked to be within a
 * specified range of types. This allows supporting type hierarchies, where a
 * type check for a supertype must succeed for any subtype.
 *
 * The tag is currently in practice limited to 15 bits since it needs to fit
 * together with a marking bit into the unused parts of a pointer (the top 16
 * bits).
 */
enum class CppHeapPointerTag : uint16_t { … };

// Convenience struct to represent tag ranges. This is used for type checks
// against supertypes, which cover a range of types (their subtypes).
// Both the lower- and the upper bound are inclusive. In other words, this
// struct represents the range [lower_bound, upper_bound].
struct CppHeapPointerTagRange { … };

constexpr CppHeapPointerTagRange kAnyCppHeapPointer(
    CppHeapPointerTag::kFirstTag, CppHeapPointerTag::kLastTag);

class SandboxHardwareSupport { … };

namespace internal {

#ifdef V8_COMPRESS_POINTERS
V8_INLINE static Address* GetCppHeapPointerTableBase(v8::Isolate* isolate) { … }
#endif  // V8_COMPRESS_POINTERS

template <typename T>
V8_INLINE static T* ReadCppHeapPointerField(v8::Isolate* isolate,
                                            Address heap_object_ptr, int offset,
                                            CppHeapPointerTagRange tag_range) { … }

}  // namespace internal
}  // namespace v8

#endif  // INCLUDE_V8_SANDBOX_H_