[compiler-rt] making getrandom call blocking. (llvm#78340)

except when `GRND_NONBLOCK` is present in the flags.

Author: devnexen

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

@@ -9965,7 +9965,13 @@ INTERCEPTOR(void, sl_free, void *sl, int freeall) {
 INTERCEPTOR(SSIZE_T, getrandom, void *buf, SIZE_T buflen, unsigned int flags) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, getrandom, buf, buflen, flags);
-  SSIZE_T n = REAL(getrandom)(buf, buflen, flags);
+  // If GRND_NONBLOCK is set in the flags, it is non blocking.
+  static const int grnd_nonblock = 1; 
+  SSIZE_T n;
+  if ((flags & grnd_nonblock))
+    n = REAL(getrandom)(buf, buflen, flags);
+  else
+    n = COMMON_INTERCEPTOR_BLOCK_REAL(getrandom)(buf, buflen, flags);
   if (n > 0) {
     COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, n);
   }