X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/f1da6683c88aa279a6350122d96856185d581925..15dfa998435a40ff3a7b1de4ec85541e8bac08dc:/rand/rand.c

diff --git a/rand/rand.c b/rand/rand.c
index aa3fb453..f9f16d5d 100644
--- a/rand/rand.c
+++ b/rand/rand.c
@@ -161,8 +161,26 @@ CPU_DISPATCH(static, return, int, quick, (rand_pool *r), (r),
 
 static int trivial_quick(rand_pool *r) { return (-1); }
 
+#if __GNUC__ && (CPUFAM_X86 || CPUFAM_AMD64)
+static int rdrand_quick(rand_pool *r)
+{
+  unsigned long rr;
+  int i = 16;
+
+  __asm__ ("0: rdrand %0; jc 9f; dec %1; jnz 0b; 9:"
+	   : "=r" (rr), "=r" (i) : "1" (i) : "cc");
+  if (!i) return (-1);
+  rand_add(r, &rr, sizeof(rr), 8*sizeof(rr));
+  return (0);
+}
+#endif
+
 static quick__functype *pick_quick(void)
 {
+#if __GNUC__ && (CPUFAM_X86 || CPUFAM_AMD64)
+  DISPATCH_PICK_COND(rand_quick, rdrand_quick,
+		     cpu_feature_p(CPUFEAT_X86_RDRAND));
+#endif
   DISPATCH_PICK_FALLBACK(rand_quick, trivial_quick);
 }