hardware-support.h

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// 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 V8_SANDBOX_HARDWARE_SUPPORT_H_
#define V8_SANDBOX_HARDWARE_SUPPORT_H_
 
#include "include/v8-platform.h"
#include "src/common/globals.h"
 
namespace v8 {
namespace internal {
 
class V8_EXPORT_PRIVATE SandboxHardwareSupport {
 public:
  // Allocates a pkey that will be used to optionally block sandbox access. This
  // function should be called once before any threads are created so that new
  // threads inherit access to the new pkey.
  static void InitializeBeforeThreadCreation();
 
  // Try to set up hardware permissions to the sandbox address space. If
  // successful, future calls to MaybeBlockAccess will block the current thread
  // from accessing the memory.
  static bool TryEnable(Address addr, size_t size);
 
  class V8_NODISCARD V8_ALLOW_UNUSED BlockAccessScope {
   public:
#if V8_ENABLE_SANDBOX_HARDWARE_SUPPORT
    explicit BlockAccessScope(int pkey);
    ~BlockAccessScope();
 
   private:
    int pkey_;
#else
    BlockAccessScope() = default;
#endif
  };
 
  // If V8_ENABLE_SANDBOX_HARDWARE_SUPPORT is enabled, this function will
  // prevent any access (read or write) to all sandbox memory on the current
  // thread, as long as the returned Scope object is valid. The only exception
  // are read-only pages, which will still be readable.
  static BlockAccessScope MaybeBlockAccess();
 
  // Removes the pkey from read only pages, so that MaybeBlockAccess will still
  // allow read access.
  static void NotifyReadOnlyPageCreated(
      Address addr, size_t size, PageAllocator::Permission current_permissions);
 
  // This function should only be called by
  // `ThreadIsolatedAllocator::SetDefaultPermissionsForSignalHandler`.
  static void SetDefaultPermissionsForSignalHandler();
 
 private:
#if V8_ENABLE_SANDBOX_HARDWARE_SUPPORT
  static int pkey_;
#endif
};
 
}  // namespace internal
}  // namespace v8
 
#endif  // V8_SANDBOX_HARDWARE_SUPPORT_H_