Index: lib/sanitizer_common/sanitizer_allocator_primary64.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator_primary64.h
+++ lib/sanitizer_common/sanitizer_allocator_primary64.h
@@ -682,7 +682,7 @@
         // Do it only when the feature is turned on, to avoid a potentially
         // extraneous syscall.
         if (ReleaseToOSIntervalMs() >= 0)
-          region->rtoi.last_release_at_ns = NanoTime();
+          region->rtoi.last_release_at_ns = MonotonicNanoTime();
       }
       // Do the mmap for the user memory.
       uptr map_size = kUserMapSize;
@@ -819,7 +819,7 @@
         return;
 
       if (region->rtoi.last_release_at_ns + interval_ms * 1000000ULL >
-          NanoTime()) {
+          MonotonicNanoTime()) {
         return;  // Memory was returned recently.
       }
     }
@@ -836,6 +836,6 @@
       region->rtoi.num_releases += memory_mapper.GetReleasedRangesCount();
       region->rtoi.last_released_bytes = memory_mapper.GetReleasedBytes();
     }
-    region->rtoi.last_release_at_ns = NanoTime();
+    region->rtoi.last_release_at_ns = MonotonicNanoTime();
   }
 };
Index: lib/sanitizer_common/sanitizer_common.h
===================================================================
--- lib/sanitizer_common/sanitizer_common.h
+++ lib/sanitizer_common/sanitizer_common.h
@@ -295,6 +295,7 @@
 void SleepForSeconds(int seconds);
 void SleepForMillis(int millis);
 u64 NanoTime();
+u64 MonotonicNanoTime();
 int Atexit(void (*function)(void));
 void SortArray(uptr *array, uptr size);
 void SortArray(u32 *array, uptr size);
Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -2005,6 +2005,13 @@
   }
   return res;
 }
+namespace __sanitizer {
+extern "C" {
+int real_clock_gettime(u32 clk_id, void *tp) {
+  return REAL(clock_gettime)(clk_id, tp);
+}
+}  // extern "C"
+}  // namespace __sanitizer
 INTERCEPTOR(int, clock_settime, u32 clk_id, const void *tp) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, clock_settime, clk_id, tp);
Index: lib/sanitizer_common/sanitizer_fuchsia.cc
===================================================================
--- lib/sanitizer_common/sanitizer_fuchsia.cc
+++ lib/sanitizer_common/sanitizer_fuchsia.cc
@@ -51,6 +51,8 @@
 
 u64 NanoTime() { return _zx_time_get(ZX_CLOCK_UTC); }
 
+u64 MonotonicNanoTime() { return _zx_time_get(ZX_CLOCK_MONOTONIC); }
+
 uptr internal_getpid() {
   zx_info_handle_basic_t info;
   zx_status_t status =
Index: lib/sanitizer_common/sanitizer_linux.cc
===================================================================
--- lib/sanitizer_common/sanitizer_linux.cc
+++ lib/sanitizer_common/sanitizer_linux.cc
@@ -459,6 +459,40 @@
   return (u64)tv.tv_sec * 1000*1000*1000 + tv.tv_usec * 1000;
 }
 
+// glibc cannot use clock_gettime from a preinit_array function as the vDSO
+// function pointers haven't been initialized yet. To prevent a crash, we check
+// for the presence of the glibc symbol __vdso_clock_gettime, and verify that it
+// is not null (it can be mangled so we can't use it directly). Bionic's
+// clock_gettime actually falls back to the syscall in the same situation.
+extern "C" SANITIZER_WEAK_ATTRIBUTE
+int __vdso_clock_gettime(clockid_t clock, struct timespec* ts);
+bool CanUseVDSO() {
+  return !SANITIZER_FREEBSD && !SANITIZER_NETBSD &&
+      (SANITIZER_ANDROID || (&__vdso_clock_gettime && __vdso_clock_gettime));
+}
+
+// MonotonicNanoTime is a timing function that can leverage the vDSO by calling
+// clock_gettime. real_clock_gettime only exists if clock_gettime is
+// intercepted, so define it weakly and use it if available.
+extern "C" SANITIZER_WEAK_ATTRIBUTE
+int real_clock_gettime(u32 clk_id, void *tp);
+u64 MonotonicNanoTime() {
+  timespec ts;
+  if (CanUseVDSO()) {
+    if (&real_clock_gettime)
+      real_clock_gettime(CLOCK_MONOTONIC, &ts);
+    else
+      clock_gettime(CLOCK_MONOTONIC, &ts);
+  } else {
+#if SANITIZER_NETBSD
+    internal_syscall_ptr(SYSCALL(__clock_gettime50), CLOCK_MONOTONIC, &ts);
+#else
+    internal_syscall_ptr(SYSCALL(clock_gettime), CLOCK_MONOTONIC, &ts);
+#endif
+  }
+  return (u64)ts.tv_sec * (1000ULL * 1000 * 1000) + ts.tv_nsec;
+}
+
 // Like getenv, but reads env directly from /proc (on Linux) or parses the
 // 'environ' array (on FreeBSD) and does not use libc. This function should be
 // called first inside __asan_init.
Index: lib/sanitizer_common/sanitizer_win.cc
===================================================================
--- lib/sanitizer_common/sanitizer_win.cc
+++ lib/sanitizer_common/sanitizer_win.cc
@@ -505,6 +505,10 @@
   return 0;
 }
 
+u64 MonotonicNanoTime() {
+  return 0;
+}
+
 void Abort() {
   internal__exit(3);
 }
Index: lib/scudo/scudo_tsd.h
===================================================================
--- lib/scudo/scudo_tsd.h
+++ lib/scudo/scudo_tsd.h
@@ -37,7 +37,7 @@
       return true;
     }
     if (atomic_load_relaxed(&Precedence) == 0)
-      atomic_store_relaxed(&Precedence, NanoTime());
+      atomic_store_relaxed(&Precedence, MonotonicNanoTime());
     return false;
   }