[GWP-ASan] Add mutexes for Fuchsia

[cryptoad]

Summary

Mitch expressed a preference to not have #ifdefs in platform agnostic
code, this change tries to accomodate this.

I am not attached to the method this CL proposes, so if anyone has a
suggestion, I am open.

We move the platform specific member of the mutex into its own platform
specific class that the main Mutex class inherits from. Functions are
implemented in their respective platform specific compilation units.

For Fuchsia, we use the sync APIs, as those are also the ones being
used in Scudo.

[mcgrathr]

lgtm

[hctim]

LGTM w/ nits.

compiler-rt/lib/gwp_asan/platform_specific/mutex_fuchsia.cpp

12

Nit: Remove #ifdefs from platform-specific code. Should only be built on that platform, so this should be unnecessary.

12

(of course i mean platform-specific cpp's here, headers obviously need the guards)

15

Nit: IWYU - please include lib/sync/mutex.h in the cpp as well.

compiler-rt/lib/gwp_asan/platform_specific/mutex_posix.h

13

Tiny nit just to be clear that "this whole file should be a nop if this isn't posix", can you move the #if defined(__unix__) into the same block as the header guards, move the endif down into the same block as the endif for the header guards, and do the same in the fuchsia header?

Like:

#if defined(__unix__)
#ifndef GWP_ASAN_MUTEX_POSIX_H_
#define GWP_ASAN_MUTEX_POSIX_H_

#include <pthread.h>

namespace ...

} // namespace ...

#endif // GWP_ASAN_MUTEX_POSIX_H_
#endif // defined(__unix__)

[cryptoad]

Addressing review comments.

compiler-rt/lib/gwp_asan/CMakeLists.txt

set(GWP_ASAN_HEADERS
   common.h
   crash_handler.h
   definitions.h
   guarded_pool_allocator.h
   mutex.h
   options.h
   options.inc
   platform_specific/guarded_pool_allocator_tls.h
+  platform_specific/mutex_fuchsia.h
+  platform_specific/mutex_posix.h
   stack_trace_compressor.h
   utilities.h
 )
 
 # Ensure that GWP-ASan meets the delegated requirements of some supporting
 # allocators. Some supporting allocators (e.g. scudo standalone) cannot use any
 # parts of the C++ standard library.
 set(GWP_ASAN_CFLAGS ${SANITIZER_COMMON_CFLAGS} -fno-rtti -fno-exceptions

compiler-rt/lib/gwp_asan/mutex.h

 //===-- mutex.h -------------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef GWP_ASAN_MUTEX_H_
 #define GWP_ASAN_MUTEX_H_
 
-#ifdef __unix__
-#include <pthread.h>
-#else
-#error "GWP-ASan is not supported on this platform."
-#endif
+#include "gwp_asan/platform_specific/mutex_fuchsia.h"
+#include "gwp_asan/platform_specific/mutex_posix.h"
 
 namespace gwp_asan {
-class Mutex {
+class Mutex final : PlatformMutex {
 public:
   constexpr Mutex() = default;
   ~Mutex() = default;
   Mutex(const Mutex &) = delete;
   Mutex &operator=(const Mutex &) = delete;
   // Lock the mutex.
   void lock();
   // Nonblocking trylock of the mutex. Returns true if the lock was acquired.
   bool tryLock();
   // Unlock the mutex.
   void unlock();
-
-private:
-#ifdef __unix__
-  pthread_mutex_t Mu = PTHREAD_MUTEX_INITIALIZER;
-#endif // defined(__unix__)
 };
 
 class ScopedLock {
 public:
   explicit ScopedLock(Mutex &Mx) : Mu(Mx) { Mu.lock(); }
   ~ScopedLock() { Mu.unlock(); }
   ScopedLock(const ScopedLock &) = delete;
   ScopedLock &operator=(const ScopedLock &) = delete;
 
 private:
   Mutex &Mu;
 };
 } // namespace gwp_asan
 
 #endif // GWP_ASAN_MUTEX_H_

compiler-rt/lib/gwp_asan/platform_specific/mutex_fuchsia.h

+//===-- mutex_fuchsia.h -----------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#if defined(__Fuchsia__)
+#ifndef GWP_ASAN_MUTEX_FUCHSIA_H_
+#define GWP_ASAN_MUTEX_FUCHSIA_H_
+
+#include <lib/sync/mutex.h>
+
+namespace gwp_asan {
+class PlatformMutex {
+protected:
+  sync_mutex_t Mu = {};
+};
+} // namespace gwp_asan
+
+#endif // GWP_ASAN_MUTEX_FUCHSIA_H_
+#endif // defined(__Fuchsia__)

compiler-rt/lib/gwp_asan/platform_specific/mutex_fuchsia.cpp

+//===-- mutex_fuchsia.cpp ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "gwp_asan/mutex.h"
+
+#include <lib/sync/mutex.h>
+
+namespace gwp_asan {
+void Mutex::lock() __TA_NO_THREAD_SAFETY_ANALYSIS { sync_mutex_lock(&Mu); }
+
+bool Mutex::tryLock() __TA_NO_THREAD_SAFETY_ANALYSIS {
+  return sync_mutex_trylock(&Mu) == ZX_OK;
+}
+
+void Mutex::unlock() __TA_NO_THREAD_SAFETY_ANALYSIS { sync_mutex_unlock(&Mu); }
+} // namespace gwp_asan

compiler-rt/lib/gwp_asan/platform_specific/mutex_posix.h

+//===-- mutex_posix.h -------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#if defined(__unix__)
+#ifndef GWP_ASAN_MUTEX_POSIX_H_
+#define GWP_ASAN_MUTEX_POSIX_H_
+
+#include <pthread.h>
+
+namespace gwp_asan {
+class PlatformMutex {
+protected:
+  pthread_mutex_t Mu = PTHREAD_MUTEX_INITIALIZER;
+};
+} // namespace gwp_asan
+
+#endif // GWP_ASAN_MUTEX_POSIX_H_
+#endif // defined(__unix__)