[Tsan] Do not sanitize memcpy() during thread initialization on FreeBSD

[dvyukov]

lib/tsan/rtl/tsan_interceptors.cc

673

please add is_inited flag to ThreadState, similar to is_dead
and set it in ThreadContext::OnStarted
shadow_stack_pos check looks confusing

[kutuzov.viktor.84]

Updated.

[dvyukov]

LGTM

lib/tsan/rtl/tsan_interceptors.cc

 
 TSAN_INTERCEPTOR(void*, memset, void *dst, int v, uptr size) {
   SCOPED_TSAN_INTERCEPTOR(memset, dst, v, size);
   MemoryAccessRange(thr, pc, (uptr)dst, size, true);
   return internal_memset(dst, v, size);
 }
 
 TSAN_INTERCEPTOR(void*, memcpy, void *dst, const void *src, uptr size) {
+  // 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);
 }
 
 TSAN_INTERCEPTOR(int, memcmp, const void *s1, const void *s2, uptr n) {
   SCOPED_TSAN_INTERCEPTOR(memcmp, s1, s2, n);
   int res = 0;
   uptr len = 0;
   for (; len < n; len++) {