hardware-support.cc

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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.
 
#include "src/sandbox/hardware-support.h"
 
#if V8_ENABLE_SANDBOX_HARDWARE_SUPPORT
#include "src/base/platform/memory-protection-key.h"
#endif
 
namespace v8 {
namespace internal {
 
#if V8_ENABLE_SANDBOX_HARDWARE_SUPPORT
 
int SandboxHardwareSupport::pkey_ =
    base::MemoryProtectionKey::kNoMemoryProtectionKey;
 
// static
bool SandboxHardwareSupport::TryEnable(Address addr, size_t size) {
  if (pkey_ != base::MemoryProtectionKey::kNoMemoryProtectionKey) {
    return base::MemoryProtectionKey::SetPermissionsAndKey(
        {addr, size}, v8::PageAllocator::Permission::kNoAccess, pkey_);
  }
  return false;
}
 
// static
void SandboxHardwareSupport::InitializeBeforeThreadCreation() {
  DCHECK_EQ(pkey_, base::MemoryProtectionKey::kNoMemoryProtectionKey);
  pkey_ = base::MemoryProtectionKey::AllocateKey();
}
 
// static
void SandboxHardwareSupport::SetDefaultPermissionsForSignalHandler() {
  if (pkey_ != base::MemoryProtectionKey::kNoMemoryProtectionKey) {
    base::MemoryProtectionKey::SetPermissionsForKey(
        pkey_, base::MemoryProtectionKey::Permission::kNoRestrictions);
  }
}
 
// static
void SandboxHardwareSupport::NotifyReadOnlyPageCreated(
    Address addr, size_t size, PageAllocator::Permission perm) {
  if (pkey_ != base::MemoryProtectionKey::kNoMemoryProtectionKey) {
    // Reset the pkey of the read-only page to the default pkey, since some
    // SBXCHECKs will safely read read-only data from the heap.
    base::MemoryProtectionKey::SetPermissionsAndKey(
        {addr, size}, perm, base::MemoryProtectionKey::kDefaultProtectionKey);
  }
}
 
// static
SandboxHardwareSupport::BlockAccessScope
SandboxHardwareSupport::MaybeBlockAccess() {
  return BlockAccessScope(pkey_);
}
 
SandboxHardwareSupport::BlockAccessScope::BlockAccessScope(int pkey)
    : pkey_(pkey) {
  if (pkey_ != base::MemoryProtectionKey::kNoMemoryProtectionKey) {
    base::MemoryProtectionKey::SetPermissionsForKey(
        pkey_, base::MemoryProtectionKey::Permission::kDisableAccess);
  }
}
 
SandboxHardwareSupport::BlockAccessScope::~BlockAccessScope() {
  if (pkey_ != base::MemoryProtectionKey::kNoMemoryProtectionKey) {
    base::MemoryProtectionKey::SetPermissionsForKey(
        pkey_, base::MemoryProtectionKey::Permission::kNoRestrictions);
  }
}
 
#else  // V8_ENABLE_SANDBOX_HARDWARE_SUPPORT
 
// static
bool SandboxHardwareSupport::TryEnable(Address addr, size_t size) {
  return false;
}
 
// static
void SandboxHardwareSupport::InitializeBeforeThreadCreation() {}
 
// static
void SandboxHardwareSupport::SetDefaultPermissionsForSignalHandler() {}
 
// static
void SandboxHardwareSupport::NotifyReadOnlyPageCreated(
    Address addr, size_t size, PageAllocator::Permission perm) {}
 
// static
SandboxHardwareSupport::BlockAccessScope
SandboxHardwareSupport::MaybeBlockAccess() {
  return BlockAccessScope();
}
 
#endif
 
}  // namespace internal
}  // namespace v8