Index: lib/tsan/rtl/tsan_interceptors.cc
===================================================================
--- lib/tsan/rtl/tsan_interceptors.cc
+++ lib/tsan/rtl/tsan_interceptors.cc
@@ -669,9 +669,12 @@
 }
 
 TSAN_INTERCEPTOR(void*, memcpy, void *dst, const void *src, uptr size) {
-  SCOPED_TSAN_INTERCEPTOR(memcpy, dst, src, size);
-  MemoryAccessRange(thr, pc, (uptr)dst, size, true);
-  MemoryAccessRange(thr, pc, (uptr)src, size, false);
+  // On FreeBSD we get here from libthr internals on thread initialization.
+  if (cur_thread()->shadow_stack_pos != 0) {
+    SCOPED_TSAN_INTERCEPTOR(memcpy, dst, src, size);
+    MemoryAccessRange(thr, pc, (uptr)dst, size, true);
+    MemoryAccessRange(thr, pc, (uptr)src, size, false);
+  }
   return internal_memcpy(dst, src, size);
 }