tor-browser

scoped_handle.h (6765B)

---

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_WIN_SCOPED_HANDLE_H_
#define BASE_WIN_SCOPED_HANDLE_H_

#include <ostream>

#include "base/base_export.h"
#include "base/check_op.h"
#include "base/dcheck_is_on.h"
#include "base/gtest_prod_util.h"
#include "base/location.h"
#include "base/win/windows_types.h"
#include "build/build_config.h"

// TODO(rvargas): remove this with the rest of the verifier.
#if defined(COMPILER_MSVC)
#include <intrin.h>
#define BASE_WIN_GET_CALLER _ReturnAddress()
#elif defined(COMPILER_GCC)
#define BASE_WIN_GET_CALLER \
 __builtin_extract_return_addr(__builtin_return_address(0))
#endif

namespace base {
namespace win {

enum class HandleOperation {
 kHandleAlreadyTracked,
 kCloseHandleNotTracked,
 kCloseHandleNotOwner,
 kCloseHandleHook,
 kDuplicateHandleHook
};

std::ostream& operator<<(std::ostream& os, HandleOperation operation);

// Generic wrapper for raw handles that takes care of closing handles
// automatically. The class interface follows the style of
// the ScopedFILE class with two additions:
//   - IsValid() method can tolerate multiple invalid handle values such as NULL
//     and INVALID_HANDLE_VALUE (-1) for Win32 handles.
//   - Set() (and the constructors and assignment operators that call it)
//     preserve the Windows LastError code. This ensures that GetLastError() can
//     be called after stashing a handle in a GenericScopedHandle object. Doing
//     this explicitly is necessary because of bug 528394 and VC++ 2015.
template <class Traits, class Verifier>
class GenericScopedHandle {
public:
 using Handle = typename Traits::Handle;

 GenericScopedHandle() : handle_(Traits::NullHandle()) {}

 explicit GenericScopedHandle(Handle handle) : handle_(Traits::NullHandle()) {
   Set(handle);
 }

 GenericScopedHandle(GenericScopedHandle&& other)
     : handle_(Traits::NullHandle()) {
   Set(other.Take());
 }

 GenericScopedHandle(const GenericScopedHandle&) = delete;
 GenericScopedHandle& operator=(const GenericScopedHandle&) = delete;

 ~GenericScopedHandle() { Close(); }

 bool is_valid() const { return Traits::IsHandleValid(handle_); }

 // TODO(crbug.com/1291793): Migrate callers to is_valid().
 bool IsValid() const { return is_valid(); }

 GenericScopedHandle& operator=(GenericScopedHandle&& other) {
   DCHECK_NE(this, &other);
   Set(other.Take());
   return *this;
 }

 void Set(Handle handle) {
   if (handle_ != handle) {
     // Preserve old LastError to avoid bug 528394.
     auto last_error = ::GetLastError();
     Close();

     if (Traits::IsHandleValid(handle)) {
       handle_ = handle;
       Verifier::StartTracking(handle, this, BASE_WIN_GET_CALLER,
                               GetProgramCounter());
     }
     ::SetLastError(last_error);
   }
 }

 Handle get() const { return handle_; }

 // TODO(crbug.com/1291793): Migrate callers to get().
 Handle Get() const { return get(); }

 // Transfers ownership away from this object.
 [[nodiscard]] Handle release() {
   Handle temp = handle_;
   handle_ = Traits::NullHandle();
   if (Traits::IsHandleValid(temp)) {
     Verifier::StopTracking(temp, this, BASE_WIN_GET_CALLER,
                            GetProgramCounter());
   }
   return temp;
 }

 // TODO(crbug.com/1291793): Migrate callers to release().
 [[nodiscard]] Handle Take() { return release(); }

 // Explicitly closes the owned handle.
 void Close() {
   if (Traits::IsHandleValid(handle_)) {
     Verifier::StopTracking(handle_, this, BASE_WIN_GET_CALLER,
                            GetProgramCounter());

     Traits::CloseHandle(handle_);
     handle_ = Traits::NullHandle();
   }
 }

private:
 FRIEND_TEST_ALL_PREFIXES(ScopedHandleDeathTest, HandleVerifierWrongOwner);
 FRIEND_TEST_ALL_PREFIXES(ScopedHandleDeathTest,
                          HandleVerifierUntrackedHandle);
 Handle handle_;
};

#undef BASE_WIN_GET_CALLER

// The traits class for Win32 handles that can be closed via CloseHandle() API.
class HandleTraits {
public:
 using Handle = HANDLE;

 HandleTraits() = delete;
 HandleTraits(const HandleTraits&) = delete;
 HandleTraits& operator=(const HandleTraits&) = delete;

 // Closes the handle.
 static bool BASE_EXPORT CloseHandle(HANDLE handle);

 // Returns true if the handle value is valid.
 static bool IsHandleValid(HANDLE handle) {
   return handle != nullptr && handle != INVALID_HANDLE_VALUE;
 }

 // Returns NULL handle value.
 static HANDLE NullHandle() { return nullptr; }
};

// Do-nothing verifier.
class DummyVerifierTraits {
public:
 using Handle = HANDLE;

 DummyVerifierTraits() = delete;
 DummyVerifierTraits(const DummyVerifierTraits&) = delete;
 DummyVerifierTraits& operator=(const DummyVerifierTraits&) = delete;

 static void StartTracking(HANDLE handle,
                           const void* owner,
                           const void* pc1,
                           const void* pc2) {}
 static void StopTracking(HANDLE handle,
                          const void* owner,
                          const void* pc1,
                          const void* pc2) {}
};

// Performs actual run-time tracking.
class BASE_EXPORT VerifierTraits {
public:
 using Handle = HANDLE;

 VerifierTraits() = delete;
 VerifierTraits(const VerifierTraits&) = delete;
 VerifierTraits& operator=(const VerifierTraits&) = delete;

 static void StartTracking(HANDLE handle,
                           const void* owner,
                           const void* pc1,
                           const void* pc2);
 static void StopTracking(HANDLE handle,
                          const void* owner,
                          const void* pc1,
                          const void* pc2);
};

using UncheckedScopedHandle =
   GenericScopedHandle<HandleTraits, DummyVerifierTraits>;
using CheckedScopedHandle = GenericScopedHandle<HandleTraits, VerifierTraits>;

#if DCHECK_IS_ON()
using ScopedHandle = CheckedScopedHandle;
#else
using ScopedHandle = UncheckedScopedHandle;
#endif

// This function may be called by the embedder to disable the use of
// VerifierTraits at runtime. It has no effect if DummyVerifierTraits is used
// for ScopedHandle.
BASE_EXPORT void DisableHandleVerifier();

// This should be called whenever the OS is closing a handle, if extended
// verification of improper handle closing is desired. If |handle| is being
// tracked by the handle verifier and ScopedHandle is not the one closing it,
// a CHECK is generated.
BASE_EXPORT void OnHandleBeingClosed(HANDLE handle, HandleOperation operation);

}  // namespace win
}  // namespace base

#endif  // BASE_WIN_SCOPED_HANDLE_H_