lib/asan/asan_mac.cc - platform/external/compiler-rt - Git at Google

 //===-- asan_mac.cc -------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of AddressSanitizer, an address sanity checker.
 //
 // Mac-specific details.
 //===----------------------------------------------------------------------===//

 #ifdef __APPLE__

 #include "asan_interceptors.h"
 #include "asan_internal.h"
 #include "asan_mac.h"
 #include "asan_mapping.h"
 #include "asan_stack.h"
 #include "asan_thread.h"
 #include "asan_thread_registry.h"
 #include "sanitizer_common/sanitizer_libc.h"

 #include <crt_externs.h>  // for _NSGetEnviron
 #include <mach-o/dyld.h>
 #include <mach-o/loader.h>
 #include <sys/mman.h>
 #include <sys/resource.h>
 #include <sys/sysctl.h>
 #include <sys/ucontext.h>
 #include <fcntl.h>
 #include <pthread.h>
 #include <stdlib.h>  // for free()
 #include <unistd.h>
 #include <libkern/OSAtomic.h>
 #include <CoreFoundation/CFString.h>

 namespace __asan {

 void GetPcSpBp(void *context, uptr *pc, uptr *sp, uptr *bp) {
   ucontext_t *ucontext = (ucontext_t*)context;
 # if __WORDSIZE == 64
   *pc = ucontext->uc_mcontext->__ss.__rip;
   *bp = ucontext->uc_mcontext->__ss.__rbp;
   *sp = ucontext->uc_mcontext->__ss.__rsp;
 # else
   *pc = ucontext->uc_mcontext->__ss.__eip;
   *bp = ucontext->uc_mcontext->__ss.__ebp;
   *sp = ucontext->uc_mcontext->__ss.__esp;
 # endif  // __WORDSIZE
 }

 int GetMacosVersion() {
   int mib[2] = { CTL_KERN, KERN_OSRELEASE };
   char version[100];
   uptr len = 0, maxlen = sizeof(version) / sizeof(version[0]);
   for (int i = 0; i < maxlen; i++) version[i] = '\0';
   // Get the version length.
   CHECK(sysctl(mib, 2, 0, &len, 0, 0) != -1);
   CHECK(len < maxlen);
   CHECK(sysctl(mib, 2, version, &len, 0, 0) != -1);
   switch (version[0]) {
     case '9': return MACOS_VERSION_LEOPARD;
     case '1': {
       switch (version[1]) {
         case '0': return MACOS_VERSION_SNOW_LEOPARD;
         case '1': return MACOS_VERSION_LION;
         default: return MACOS_VERSION_UNKNOWN;
       }
     }
     default: return MACOS_VERSION_UNKNOWN;
   }
 }

 bool PlatformHasDifferentMemcpyAndMemmove() {
   // On OS X 10.7 memcpy() and memmove() are both resolved
   // into memmove$VARIANT$sse42.
   // See also http://code.google.com/p/address-sanitizer/issues/detail?id=34.
   // TODO(glider): need to check dynamically that memcpy() and memmove() are
   // actually the same function.
   return GetMacosVersion() == MACOS_VERSION_SNOW_LEOPARD;
 }

 // No-op. Mac does not support static linkage anyway.
 void *AsanDoesNotSupportStaticLinkage() {
   return 0;
 }

 bool AsanInterceptsSignal(int signum) {
   return (signum == SIGSEGV || signum == SIGBUS) && FLAG_handle_segv;
 }

 AsanLock::AsanLock(LinkerInitialized) {
   // We assume that OS_SPINLOCK_INIT is zero
 }

 void AsanLock::Lock() {
   CHECK(sizeof(OSSpinLock) <= sizeof(opaque_storage_));
   CHECK(OS_SPINLOCK_INIT == 0);
   CHECK(owner_ != (uptr)pthread_self());
   OSSpinLockLock((OSSpinLock*)&opaque_storage_);
   CHECK(!owner_);
   owner_ = (uptr)pthread_self();
 }

 void AsanLock::Unlock() {
   CHECK(owner_ == (uptr)pthread_self());
   owner_ = 0;
   OSSpinLockUnlock((OSSpinLock*)&opaque_storage_);
 }

 void AsanStackTrace::GetStackTrace(uptr max_s, uptr pc, uptr bp) {
   size = 0;
   trace[0] = pc;
   if ((max_s) > 1) {
     max_size = max_s;
     FastUnwindStack(pc, bp);
   }
 }

 // The range of pages to be used for escape islands.
 // TODO(glider): instead of mapping a fixed range we must find a range of
 // unmapped pages in vmmap and take them.
 // These constants were chosen empirically and may not work if the shadow
 // memory layout changes. Unfortunately they do necessarily depend on
 // kHighMemBeg or kHighMemEnd.
 static void *island_allocator_pos = 0;

 #if __WORDSIZE == 32
 # define kIslandEnd (0xffdf0000 - kPageSize)
 # define kIslandBeg (kIslandEnd - 256 * kPageSize)
 #else
 # define kIslandEnd (0x7fffffdf0000 - kPageSize)
 # define kIslandBeg (kIslandEnd - 256 * kPageSize)
 #endif

 extern "C"
 mach_error_t __interception_allocate_island(void **ptr,
                                             uptr unused_size,
                                             void *unused_hint) {
   if (!island_allocator_pos) {
     island_allocator_pos =
         internal_mmap((void*)kIslandBeg, kIslandEnd - kIslandBeg,
                       PROT_READ | PROT_WRITE | PROT_EXEC,
                       MAP_PRIVATE | MAP_ANON | MAP_FIXED,
                       -1, 0);
     if (island_allocator_pos != (void*)kIslandBeg) {
       return KERN_NO_SPACE;
     }
     if (FLAG_v) {
       Report("Mapped pages %p--%p for branch islands.\n",
              (void*)kIslandBeg, (void*)kIslandEnd);
     }
     // Should not be very performance-critical.
     internal_memset(island_allocator_pos, 0xCC, kIslandEnd - kIslandBeg);
   };
   *ptr = island_allocator_pos;
   island_allocator_pos = (char*)island_allocator_pos + kPageSize;
   if (FLAG_v) {
     Report("Branch island allocated at %p\n", *ptr);
   }
   return err_none;
 }

 extern "C"
 mach_error_t __interception_deallocate_island(void *ptr) {
   // Do nothing.
   // TODO(glider): allow to free and reuse the island memory.
   return err_none;
 }

 // Support for the following functions from libdispatch on Mac OS:
 //   dispatch_async_f()
 //   dispatch_async()
 //   dispatch_sync_f()
 //   dispatch_sync()
 //   dispatch_after_f()
 //   dispatch_after()
 //   dispatch_group_async_f()
 //   dispatch_group_async()
 // TODO(glider): libdispatch API contains other functions that we don't support
 // yet.
 //
 // dispatch_sync() and dispatch_sync_f() are synchronous, although chances are
 // they can cause jobs to run on a thread different from the current one.
 // TODO(glider): if so, we need a test for this (otherwise we should remove
 // them).
 //
 // The following functions use dispatch_barrier_async_f() (which isn't a library
 // function but is exported) and are thus supported:
 //   dispatch_source_set_cancel_handler_f()
 //   dispatch_source_set_cancel_handler()
 //   dispatch_source_set_event_handler_f()
 //   dispatch_source_set_event_handler()
 //
 // The reference manual for Grand Central Dispatch is available at
 //   http://developer.apple.com/library/mac/#documentation/Performance/Reference/GCD_libdispatch_Ref/Reference/reference.html
 // The implementation details are at
 //   http://libdispatch.macosforge.org/trac/browser/trunk/src/queue.c

 typedef void* pthread_workqueue_t;
 typedef void* pthread_workitem_handle_t;

 typedef void* dispatch_group_t;
 typedef void* dispatch_queue_t;
 typedef u64 dispatch_time_t;
 typedef void (*dispatch_function_t)(void *block);
 typedef void* (*worker_t)(void *block);

 // A wrapper for the ObjC blocks used to support libdispatch.
 typedef struct {
   void *block;
   dispatch_function_t func;
   u32 parent_tid;
 } asan_block_context_t;

 // We use extern declarations of libdispatch functions here instead
 // of including <dispatch/dispatch.h>. This header is not present on
 // Mac OS X Leopard and eariler, and although we don't expect ASan to
 // work on legacy systems, it's bad to break the build of
 // LLVM compiler-rt there.
 extern "C" {
 void dispatch_async_f(dispatch_queue_t dq, void *ctxt,
                       dispatch_function_t func);
 void dispatch_sync_f(dispatch_queue_t dq, void *ctxt,
                      dispatch_function_t func);
 void dispatch_after_f(dispatch_time_t when, dispatch_queue_t dq, void *ctxt,
                       dispatch_function_t func);
 void dispatch_barrier_async_f(dispatch_queue_t dq, void *ctxt,
                               dispatch_function_t func);
 void dispatch_group_async_f(dispatch_group_t group, dispatch_queue_t dq,
                             void *ctxt, dispatch_function_t func);
 int pthread_workqueue_additem_np(pthread_workqueue_t workq,
     void *(*workitem_func)(void *), void * workitem_arg,
     pthread_workitem_handle_t * itemhandlep, unsigned int *gencountp);
 }  // extern "C"

 extern "C"
 void asan_dispatch_call_block_and_release(void *block) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *context = (asan_block_context_t*)block;
   if (FLAG_v >= 2) {
     Report("asan_dispatch_call_block_and_release(): "
            "context: %p, pthread_self: %p\n",
            block, pthread_self());
   }
   AsanThread *t = asanThreadRegistry().GetCurrent();
   if (!t) {
     t = AsanThread::Create(context->parent_tid, 0, 0, &stack);
     asanThreadRegistry().RegisterThread(t);
     t->Init();
     asanThreadRegistry().SetCurrent(t);
   }
   // Call the original dispatcher for the block.
   context->func(context->block);
   asan_free(context, &stack);
 }

 }  // namespace __asan

 using namespace __asan;  // NOLINT

 // Wrap |ctxt| and |func| into an asan_block_context_t.
 // The caller retains control of the allocated context.
 extern "C"
 asan_block_context_t *alloc_asan_context(void *ctxt, dispatch_function_t func,
                                          AsanStackTrace *stack) {
   asan_block_context_t *asan_ctxt =
       (asan_block_context_t*) asan_malloc(sizeof(asan_block_context_t), stack);
   asan_ctxt->block = ctxt;
   asan_ctxt->func = func;
   asan_ctxt->parent_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
   return asan_ctxt;
 }

 // TODO(glider): can we reduce code duplication by introducing a macro?
 INTERCEPTOR(void, dispatch_async_f, dispatch_queue_t dq, void *ctxt,
                                     dispatch_function_t func) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
   if (FLAG_v >= 2) {
     Report("dispatch_async_f(): context: %p, pthread_self: %p\n",
         asan_ctxt, pthread_self());
     PRINT_CURRENT_STACK();
   }
   return REAL(dispatch_async_f)(dq, (void*)asan_ctxt,
                                 asan_dispatch_call_block_and_release);
 }

 INTERCEPTOR(void, dispatch_sync_f, dispatch_queue_t dq, void *ctxt,
                                    dispatch_function_t func) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
   if (FLAG_v >= 2) {
     Report("dispatch_sync_f(): context: %p, pthread_self: %p\n",
         asan_ctxt, pthread_self());
     PRINT_CURRENT_STACK();
   }
   return REAL(dispatch_sync_f)(dq, (void*)asan_ctxt,
                                asan_dispatch_call_block_and_release);
 }

 INTERCEPTOR(void, dispatch_after_f, dispatch_time_t when,
                                     dispatch_queue_t dq, void *ctxt,
                                     dispatch_function_t func) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
   if (FLAG_v >= 2) {
     Report("dispatch_after_f: %p\n", asan_ctxt);
     PRINT_CURRENT_STACK();
   }
   return REAL(dispatch_after_f)(when, dq, (void*)asan_ctxt,
                                 asan_dispatch_call_block_and_release);
 }

 INTERCEPTOR(void, dispatch_barrier_async_f, dispatch_queue_t dq, void *ctxt,
                                             dispatch_function_t func) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
   if (FLAG_v >= 2) {
     Report("dispatch_barrier_async_f(): context: %p, pthread_self: %p\n",
            asan_ctxt, pthread_self());
     PRINT_CURRENT_STACK();
   }
   REAL(dispatch_barrier_async_f)(dq, (void*)asan_ctxt,
                                  asan_dispatch_call_block_and_release);
 }

 INTERCEPTOR(void, dispatch_group_async_f, dispatch_group_t group,
                                           dispatch_queue_t dq, void *ctxt,
                                           dispatch_function_t func) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
   if (FLAG_v >= 2) {
     Report("dispatch_group_async_f(): context: %p, pthread_self: %p\n",
            asan_ctxt, pthread_self());
     PRINT_CURRENT_STACK();
   }
   REAL(dispatch_group_async_f)(group, dq, (void*)asan_ctxt,
                                asan_dispatch_call_block_and_release);
 }

 // The following stuff has been extremely helpful while looking for the
 // unhandled functions that spawned jobs on Chromium shutdown. If the verbosity
 // level is 2 or greater, we wrap pthread_workqueue_additem_np() in order to
 // find the points of worker thread creation (each of such threads may be used
 // to run several tasks, that's why this is not enough to support the whole
 // libdispatch API.
 extern "C"
 void *wrap_workitem_func(void *arg) {
   if (FLAG_v >= 2) {
     Report("wrap_workitem_func: %p, pthread_self: %p\n", arg, pthread_self());
   }
   asan_block_context_t *ctxt = (asan_block_context_t*)arg;
   worker_t fn = (worker_t)(ctxt->func);
   void *result =  fn(ctxt->block);
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_free(arg, &stack);
   return result;
 }

 INTERCEPTOR(int, pthread_workqueue_additem_np, pthread_workqueue_t workq,
     void *(*workitem_func)(void *), void * workitem_arg,
     pthread_workitem_handle_t * itemhandlep, unsigned int *gencountp) {
   GET_STACK_TRACE_HERE(kStackTraceMax);
   asan_block_context_t *asan_ctxt =
       (asan_block_context_t*) asan_malloc(sizeof(asan_block_context_t), &stack);
   asan_ctxt->block = workitem_arg;
   asan_ctxt->func = (dispatch_function_t)workitem_func;
   asan_ctxt->parent_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
   if (FLAG_v >= 2) {
     Report("pthread_workqueue_additem_np: %p\n", asan_ctxt);
     PRINT_CURRENT_STACK();
   }
   return REAL(pthread_workqueue_additem_np)(workq, wrap_workitem_func,
                                             asan_ctxt, itemhandlep,
                                             gencountp);
 }

 // See http://opensource.apple.com/source/CF/CF-635.15/CFString.c
 int __CFStrIsConstant(CFStringRef str) {
   CFRuntimeBase *base = (CFRuntimeBase*)str;
 #if __LP64__
   return base->_rc == 0;
 #else
   return (base->_cfinfo[CF_RC_BITS]) == 0;
 #endif
 }

 INTERCEPTOR(CFStringRef, CFStringCreateCopy, CFAllocatorRef alloc,
                                              CFStringRef str) {
   if (__CFStrIsConstant(str)) {
     return str;
   } else {
     return REAL(CFStringCreateCopy)(alloc, str);
   }
 }

 DECLARE_REAL_AND_INTERCEPTOR(void, free, void *ptr)

 extern "C"
 void __CFInitialize();
 DECLARE_REAL_AND_INTERCEPTOR(void, __CFInitialize)

 namespace __asan {

 void InitializeMacInterceptors() {
   CHECK(INTERCEPT_FUNCTION(dispatch_async_f));
   CHECK(INTERCEPT_FUNCTION(dispatch_sync_f));
   CHECK(INTERCEPT_FUNCTION(dispatch_after_f));
   CHECK(INTERCEPT_FUNCTION(dispatch_barrier_async_f));
   CHECK(INTERCEPT_FUNCTION(dispatch_group_async_f));
   // We don't need to intercept pthread_workqueue_additem_np() to support the
   // libdispatch API, but it helps us to debug the unsupported functions. Let's
   // intercept it only during verbose runs.
   if (FLAG_v >= 2) {
     CHECK(INTERCEPT_FUNCTION(pthread_workqueue_additem_np));
   }
   // Normally CFStringCreateCopy should not copy constant CF strings.
   // Replacing the default CFAllocator causes constant strings to be copied
   // rather than just returned, which leads to bugs in big applications like
   // Chromium and WebKit, see
   // http://code.google.com/p/address-sanitizer/issues/detail?id=10
   // Until this problem is fixed we need to check that the string is
   // non-constant before calling CFStringCreateCopy.
   CHECK(INTERCEPT_FUNCTION(CFStringCreateCopy));
   // Some of the library functions call free() directly, so we have to
   // intercept it.
   CHECK(INTERCEPT_FUNCTION(free));
   if (FLAG_replace_cfallocator) {
     CHECK(INTERCEPT_FUNCTION(__CFInitialize));
   }
 }

 }  // namespace __asan

 #endif  // __APPLE__
	//===-- asan_mac.cc -------------------------------------------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file is a part of AddressSanitizer, an address sanity checker.
	//
	// Mac-specific details.
	//===----------------------------------------------------------------------===//

	#ifdef __APPLE__

	#include "asan_interceptors.h"
	#include "asan_internal.h"
	#include "asan_mac.h"
	#include "asan_mapping.h"
	#include "asan_stack.h"
	#include "asan_thread.h"
	#include "asan_thread_registry.h"
	#include "sanitizer_common/sanitizer_libc.h"

	#include <crt_externs.h> // for _NSGetEnviron
	#include <mach-o/dyld.h>
	#include <mach-o/loader.h>
	#include <sys/mman.h>
	#include <sys/resource.h>
	#include <sys/sysctl.h>
	#include <sys/ucontext.h>
	#include <fcntl.h>
	#include <pthread.h>
	#include <stdlib.h> // for free()
	#include <unistd.h>
	#include <libkern/OSAtomic.h>
	#include <CoreFoundation/CFString.h>

	namespace __asan {

	void GetPcSpBp(void context, uptr pc, uptr sp, uptr bp) {
	ucontext_t ucontext = (ucontext_t)context;
	# if __WORDSIZE == 64
	*pc = ucontext->uc_mcontext->__ss.__rip;
	*bp = ucontext->uc_mcontext->__ss.__rbp;
	*sp = ucontext->uc_mcontext->__ss.__rsp;
	# else
	*pc = ucontext->uc_mcontext->__ss.__eip;
	*bp = ucontext->uc_mcontext->__ss.__ebp;
	*sp = ucontext->uc_mcontext->__ss.__esp;
	# endif // __WORDSIZE
	}

	int GetMacosVersion() {
	int mib[2] = { CTL_KERN, KERN_OSRELEASE };
	char version[100];
	uptr len = 0, maxlen = sizeof(version) / sizeof(version[0]);
	for (int i = 0; i < maxlen; i++) version[i] = '\0';
	// Get the version length.
	CHECK(sysctl(mib, 2, 0, &len, 0, 0) != -1);
	CHECK(len < maxlen);
	CHECK(sysctl(mib, 2, version, &len, 0, 0) != -1);
	switch (version[0]) {
	case '9': return MACOS_VERSION_LEOPARD;
	case '1': {
	switch (version[1]) {
	case '0': return MACOS_VERSION_SNOW_LEOPARD;
	case '1': return MACOS_VERSION_LION;
	default: return MACOS_VERSION_UNKNOWN;
	}
	}
	default: return MACOS_VERSION_UNKNOWN;
	}
	}

	bool PlatformHasDifferentMemcpyAndMemmove() {
	// On OS X 10.7 memcpy() and memmove() are both resolved
	// into memmove$VARIANT$sse42.
	// See also http://code.google.com/p/address-sanitizer/issues/detail?id=34.
	// TODO(glider): need to check dynamically that memcpy() and memmove() are
	// actually the same function.
	return GetMacosVersion() == MACOS_VERSION_SNOW_LEOPARD;
	}

	// No-op. Mac does not support static linkage anyway.
	void *AsanDoesNotSupportStaticLinkage() {
	return 0;
	}

	bool AsanInterceptsSignal(int signum) {
	return (signum == SIGSEGV \|\| signum == SIGBUS) && FLAG_handle_segv;
	}

	AsanLock::AsanLock(LinkerInitialized) {
	// We assume that OS_SPINLOCK_INIT is zero
	}

	void AsanLock::Lock() {
	CHECK(sizeof(OSSpinLock) <= sizeof(opaque_storage_));
	CHECK(OS_SPINLOCK_INIT == 0);
	CHECK(owner_ != (uptr)pthread_self());
	OSSpinLockLock((OSSpinLock*)&opaque_storage_);
	CHECK(!owner_);
	owner_ = (uptr)pthread_self();
	}

	void AsanLock::Unlock() {
	CHECK(owner_ == (uptr)pthread_self());
	owner_ = 0;
	OSSpinLockUnlock((OSSpinLock*)&opaque_storage_);
	}

	void AsanStackTrace::GetStackTrace(uptr max_s, uptr pc, uptr bp) {
	size = 0;
	trace[0] = pc;
	if ((max_s) > 1) {
	max_size = max_s;
	FastUnwindStack(pc, bp);
	}
	}

	// The range of pages to be used for escape islands.
	// TODO(glider): instead of mapping a fixed range we must find a range of
	// unmapped pages in vmmap and take them.
	// These constants were chosen empirically and may not work if the shadow
	// memory layout changes. Unfortunately they do necessarily depend on
	// kHighMemBeg or kHighMemEnd.
	static void *island_allocator_pos = 0;

	#if __WORDSIZE == 32
	# define kIslandEnd (0xffdf0000 - kPageSize)
	# define kIslandBeg (kIslandEnd - 256 * kPageSize)
	#else
	# define kIslandEnd (0x7fffffdf0000 - kPageSize)
	# define kIslandBeg (kIslandEnd - 256 * kPageSize)
	#endif

	extern "C"
	mach_error_t __interception_allocate_island(void **ptr,
	uptr unused_size,
	void *unused_hint) {
	if (!island_allocator_pos) {
	island_allocator_pos =
	internal_mmap((void*)kIslandBeg, kIslandEnd - kIslandBeg,
	PROT_READ \| PROT_WRITE \| PROT_EXEC,
	MAP_PRIVATE \| MAP_ANON \| MAP_FIXED,
	-1, 0);
	if (island_allocator_pos != (void*)kIslandBeg) {
	return KERN_NO_SPACE;
	}
	if (FLAG_v) {
	Report("Mapped pages %p--%p for branch islands.\n",
	(void)kIslandBeg, (void)kIslandEnd);
	}
	// Should not be very performance-critical.
	internal_memset(island_allocator_pos, 0xCC, kIslandEnd - kIslandBeg);
	};
	*ptr = island_allocator_pos;
	island_allocator_pos = (char*)island_allocator_pos + kPageSize;
	if (FLAG_v) {
	Report("Branch island allocated at %p\n", *ptr);
	}
	return err_none;
	}

	extern "C"
	mach_error_t __interception_deallocate_island(void *ptr) {
	// Do nothing.
	// TODO(glider): allow to free and reuse the island memory.
	return err_none;
	}

	// Support for the following functions from libdispatch on Mac OS:
	// dispatch_async_f()
	// dispatch_async()
	// dispatch_sync_f()
	// dispatch_sync()
	// dispatch_after_f()
	// dispatch_after()
	// dispatch_group_async_f()
	// dispatch_group_async()
	// TODO(glider): libdispatch API contains other functions that we don't support
	// yet.
	//
	// dispatch_sync() and dispatch_sync_f() are synchronous, although chances are
	// they can cause jobs to run on a thread different from the current one.
	// TODO(glider): if so, we need a test for this (otherwise we should remove
	// them).
	//
	// The following functions use dispatch_barrier_async_f() (which isn't a library
	// function but is exported) and are thus supported:
	// dispatch_source_set_cancel_handler_f()
	// dispatch_source_set_cancel_handler()
	// dispatch_source_set_event_handler_f()
	// dispatch_source_set_event_handler()
	//
	// The reference manual for Grand Central Dispatch is available at
	// http://developer.apple.com/library/mac/#documentation/Performance/Reference/GCD_libdispatch_Ref/Reference/reference.html
	// The implementation details are at
	// http://libdispatch.macosforge.org/trac/browser/trunk/src/queue.c

	typedef void* pthread_workqueue_t;
	typedef void* pthread_workitem_handle_t;

	typedef void* dispatch_group_t;
	typedef void* dispatch_queue_t;
	typedef u64 dispatch_time_t;
	typedef void (dispatch_function_t)(void block);
	typedef void* (worker_t)(void block);

	// A wrapper for the ObjC blocks used to support libdispatch.
	typedef struct {
	void *block;
	dispatch_function_t func;
	u32 parent_tid;
	} asan_block_context_t;

	// We use extern declarations of libdispatch functions here instead
	// of including <dispatch/dispatch.h>. This header is not present on
	// Mac OS X Leopard and eariler, and although we don't expect ASan to
	// work on legacy systems, it's bad to break the build of
	// LLVM compiler-rt there.
	extern "C" {
	void dispatch_async_f(dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func);
	void dispatch_sync_f(dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func);
	void dispatch_after_f(dispatch_time_t when, dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func);
	void dispatch_barrier_async_f(dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func);
	void dispatch_group_async_f(dispatch_group_t group, dispatch_queue_t dq,
	void *ctxt, dispatch_function_t func);
	int pthread_workqueue_additem_np(pthread_workqueue_t workq,
	void (workitem_func)(void ), void workitem_arg,
	pthread_workitem_handle_t * itemhandlep, unsigned int *gencountp);
	} // extern "C"

	extern "C"
	void asan_dispatch_call_block_and_release(void *block) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t context = (asan_block_context_t)block;
	if (FLAG_v >= 2) {
	Report("asan_dispatch_call_block_and_release(): "
	"context: %p, pthread_self: %p\n",
	block, pthread_self());
	}
	AsanThread *t = asanThreadRegistry().GetCurrent();
	if (!t) {
	t = AsanThread::Create(context->parent_tid, 0, 0, &stack);
	asanThreadRegistry().RegisterThread(t);
	t->Init();
	asanThreadRegistry().SetCurrent(t);
	}
	// Call the original dispatcher for the block.
	context->func(context->block);
	asan_free(context, &stack);
	}

	} // namespace __asan

	using namespace __asan; // NOLINT

	// Wrap \|ctxt\| and \|func\| into an asan_block_context_t.
	// The caller retains control of the allocated context.
	extern "C"
	asan_block_context_t alloc_asan_context(void ctxt, dispatch_function_t func,
	AsanStackTrace *stack) {
	asan_block_context_t *asan_ctxt =
	(asan_block_context_t*) asan_malloc(sizeof(asan_block_context_t), stack);
	asan_ctxt->block = ctxt;
	asan_ctxt->func = func;
	asan_ctxt->parent_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
	return asan_ctxt;
	}

	// TODO(glider): can we reduce code duplication by introducing a macro?
	INTERCEPTOR(void, dispatch_async_f, dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
	if (FLAG_v >= 2) {
	Report("dispatch_async_f(): context: %p, pthread_self: %p\n",
	asan_ctxt, pthread_self());
	PRINT_CURRENT_STACK();
	}
	return REAL(dispatch_async_f)(dq, (void*)asan_ctxt,
	asan_dispatch_call_block_and_release);
	}

	INTERCEPTOR(void, dispatch_sync_f, dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
	if (FLAG_v >= 2) {
	Report("dispatch_sync_f(): context: %p, pthread_self: %p\n",
	asan_ctxt, pthread_self());
	PRINT_CURRENT_STACK();
	}
	return REAL(dispatch_sync_f)(dq, (void*)asan_ctxt,
	asan_dispatch_call_block_and_release);
	}

	INTERCEPTOR(void, dispatch_after_f, dispatch_time_t when,
	dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
	if (FLAG_v >= 2) {
	Report("dispatch_after_f: %p\n", asan_ctxt);
	PRINT_CURRENT_STACK();
	}
	return REAL(dispatch_after_f)(when, dq, (void*)asan_ctxt,
	asan_dispatch_call_block_and_release);
	}

	INTERCEPTOR(void, dispatch_barrier_async_f, dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
	if (FLAG_v >= 2) {
	Report("dispatch_barrier_async_f(): context: %p, pthread_self: %p\n",
	asan_ctxt, pthread_self());
	PRINT_CURRENT_STACK();
	}
	REAL(dispatch_barrier_async_f)(dq, (void*)asan_ctxt,
	asan_dispatch_call_block_and_release);
	}

	INTERCEPTOR(void, dispatch_group_async_f, dispatch_group_t group,
	dispatch_queue_t dq, void *ctxt,
	dispatch_function_t func) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t *asan_ctxt = alloc_asan_context(ctxt, func, &stack);
	if (FLAG_v >= 2) {
	Report("dispatch_group_async_f(): context: %p, pthread_self: %p\n",
	asan_ctxt, pthread_self());
	PRINT_CURRENT_STACK();
	}
	REAL(dispatch_group_async_f)(group, dq, (void*)asan_ctxt,
	asan_dispatch_call_block_and_release);
	}

	// The following stuff has been extremely helpful while looking for the
	// unhandled functions that spawned jobs on Chromium shutdown. If the verbosity
	// level is 2 or greater, we wrap pthread_workqueue_additem_np() in order to
	// find the points of worker thread creation (each of such threads may be used
	// to run several tasks, that's why this is not enough to support the whole
	// libdispatch API.
	extern "C"
	void wrap_workitem_func(void arg) {
	if (FLAG_v >= 2) {
	Report("wrap_workitem_func: %p, pthread_self: %p\n", arg, pthread_self());
	}
	asan_block_context_t ctxt = (asan_block_context_t)arg;
	worker_t fn = (worker_t)(ctxt->func);
	void *result = fn(ctxt->block);
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_free(arg, &stack);
	return result;
	}

	INTERCEPTOR(int, pthread_workqueue_additem_np, pthread_workqueue_t workq,
	void (workitem_func)(void ), void workitem_arg,
	pthread_workitem_handle_t * itemhandlep, unsigned int *gencountp) {
	GET_STACK_TRACE_HERE(kStackTraceMax);
	asan_block_context_t *asan_ctxt =
	(asan_block_context_t*) asan_malloc(sizeof(asan_block_context_t), &stack);
	asan_ctxt->block = workitem_arg;
	asan_ctxt->func = (dispatch_function_t)workitem_func;
	asan_ctxt->parent_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
	if (FLAG_v >= 2) {
	Report("pthread_workqueue_additem_np: %p\n", asan_ctxt);
	PRINT_CURRENT_STACK();
	}
	return REAL(pthread_workqueue_additem_np)(workq, wrap_workitem_func,
	asan_ctxt, itemhandlep,
	gencountp);
	}

	// See http://opensource.apple.com/source/CF/CF-635.15/CFString.c
	int __CFStrIsConstant(CFStringRef str) {
	CFRuntimeBase base = (CFRuntimeBase)str;
	#if __LP64__
	return base->_rc == 0;
	#else
	return (base->_cfinfo[CF_RC_BITS]) == 0;
	#endif
	}

	INTERCEPTOR(CFStringRef, CFStringCreateCopy, CFAllocatorRef alloc,
	CFStringRef str) {
	if (__CFStrIsConstant(str)) {
	return str;
	} else {
	return REAL(CFStringCreateCopy)(alloc, str);
	}
	}

	DECLARE_REAL_AND_INTERCEPTOR(void, free, void *ptr)

	extern "C"
	void __CFInitialize();
	DECLARE_REAL_AND_INTERCEPTOR(void, __CFInitialize)

	namespace __asan {

	void InitializeMacInterceptors() {
	CHECK(INTERCEPT_FUNCTION(dispatch_async_f));
	CHECK(INTERCEPT_FUNCTION(dispatch_sync_f));
	CHECK(INTERCEPT_FUNCTION(dispatch_after_f));
	CHECK(INTERCEPT_FUNCTION(dispatch_barrier_async_f));
	CHECK(INTERCEPT_FUNCTION(dispatch_group_async_f));
	// We don't need to intercept pthread_workqueue_additem_np() to support the
	// libdispatch API, but it helps us to debug the unsupported functions. Let's
	// intercept it only during verbose runs.
	if (FLAG_v >= 2) {
	CHECK(INTERCEPT_FUNCTION(pthread_workqueue_additem_np));
	}
	// Normally CFStringCreateCopy should not copy constant CF strings.
	// Replacing the default CFAllocator causes constant strings to be copied
	// rather than just returned, which leads to bugs in big applications like
	// Chromium and WebKit, see
	// http://code.google.com/p/address-sanitizer/issues/detail?id=10
	// Until this problem is fixed we need to check that the string is
	// non-constant before calling CFStringCreateCopy.
	CHECK(INTERCEPT_FUNCTION(CFStringCreateCopy));
	// Some of the library functions call free() directly, so we have to
	// intercept it.
	CHECK(INTERCEPT_FUNCTION(free));
	if (FLAG_replace_cfallocator) {
	CHECK(INTERCEPT_FUNCTION(__CFInitialize));
	}
	}

	} // namespace __asan

	#endif // __APPLE__