[sanitizer] Implement NanoTime() on Darwin

[kubamracek]

Summary

Currently NanoTime() on Darwin is unimplemented and always returns 0. Looks like there's quite a few things broken because of that (TSan periodic memory flush, ASan allocator releasing pages back to the OS). Let's fix that.

[kubamracek]

lib/sanitizer_common/sanitizer_mac.cc

367

Actually, this is racy unless we guarantee NanoTime is called during initialization...

[alekseyshl]

FYI, D40679 adds MonotonicNanoTime() for that NanoTime() is too expensive for the allocator's purposes.

[kubamracek]

I've updated the patch to provide both NanoTime and MonotonicNanoTime.

[cryptoad]

Hey @kubamracek, checking in to see if you are planning on committing this, we could use the functions. Thanks!

[kubamracek]

Landed in r324847.

lib/sanitizer_common/sanitizer_mac.cc

 
 #include <asl.h>
 #include <dlfcn.h>  // for dladdr()
 #include <errno.h>
 #include <fcntl.h>
 #include <libkern/OSAtomic.h>
 #include <mach-o/dyld.h>
 #include <mach/mach.h>
+#include <mach/mach_time.h>
 #include <mach/vm_statistics.h>
 #include <pthread.h>
 #include <sched.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <sys/mman.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
void BlockingMutex::Unlock() {
   OSSpinLockUnlock((OSSpinLock*)&opaque_storage_);
 }
 
 void BlockingMutex::CheckLocked() {
   CHECK_NE(*(OSSpinLock*)&opaque_storage_, 0);
 }
 
 u64 NanoTime() {
-  return 0;
+  timeval tv;
+  internal_memset(&tv, 0, sizeof(tv));
+  gettimeofday(&tv, 0);
+  return (u64)tv.tv_sec * 1000*1000*1000 + tv.tv_usec * 1000;
 }
 
+// This needs to be called during initialization to avoid being racy.
 u64 MonotonicNanoTime() {
-  return 0;
+  static mach_timebase_info_data_t timebase_info;
+  if (timebase_info.denom == 0) mach_timebase_info(&timebase_info);
+  return (mach_absolute_time() * timebase_info.numer) / timebase_info.denom;
 }
 
 uptr GetTlsSize() {
   return 0;
 }
 
 void InitTlsSize() {
 }
bool DyldNeedsEnvVariable() {
   // DYLD_INSERT_LIBRARIES is not set. However, checking OS version via
   // GetMacosVersion() doesn't work for the simulator. Let's instead check
   // `dyldVersionNumber`, which is exported by dyld, against a known version
   // number from the first OS release where this appeared.
   return dyldVersionNumber < kMinDyldVersionWithAutoInterposition;
 }
 
 void MaybeReexec() {
+  // FIXME: This should really live in some "InitializePlatform" method.
+  MonotonicNanoTime();
+
   if (ReexecDisabled()) return;
 
   // Make sure the dynamic runtime library is preloaded so that the
   // wrappers work. If it is not, set DYLD_INSERT_LIBRARIES and re-exec
   // ourselves.
   Dl_info info;
   RAW_CHECK(dladdr((void*)((uptr)&__sanitizer_report_error_summary), &info));
   char *dyld_insert_libraries =