Index: lib/sanitizer_common/sanitizer_stoptheworld_mac.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stoptheworld_mac.cc
+++ lib/sanitizer_common/sanitizer_stoptheworld_mac.cc
@@ -170,6 +170,11 @@
   internal_memcpy(buffer, &regs, sizeof(regs));
   *sp = regs.SP_REG;
 
+// On x86_64, we must account for the stack redzone, which is 128 bytes.
+#if defined(__x86_64__)
+  *sp -= 128;
+#endif
+
   return REGISTERS_AVAILABLE;
 }