use a larger chunk for getentropy() and save some for next time.

coalesces some syscalls instead of one per random number.
ok deraadt

diff --git a/libexec/ld.so/util.c b/libexec/ld.so/util.c
index ebf33e0..c81cb53 100644 (file)
--- a/libexec/ld.so/util.c
+++ b/libexec/ld.so/util.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: util.c,v 1.41 2016/03/21 22:41:28 bluhm Exp $ */
+/*     $OpenBSD: util.c,v 1.42 2016/08/05 15:42:05 tedu Exp $  */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -74,16 +74,36 @@ _dl_strdup(const char *orig)
 void
 _dl_randombuf(void *v, size_t buflen)
 {
+       static char bytes[256];
+       static u_int reserve;
        char *buf = v;
        size_t chunk;
 
        while (buflen != 0) {
-               if (buflen > 256)
-                       chunk = 256;
+               if (reserve == 0) {
+                       if (_dl_getentropy(bytes, sizeof(bytes)) != 0)
+                               _dl_exit(8);
+                       reserve = sizeof(bytes);
+               }
+               if (buflen > reserve)
+                       chunk = reserve;
                else
                        chunk = buflen;
-               if (_dl_getentropy(buf, chunk) != 0)
-                       _dl_exit(8);
+#if 0
+               memcpy(buf, bytes + reserve - chunk, chunk);
+               memset(bytes + reserve - chunk, 0, chunk);
+#else
+               {
+                       char *d = buf;
+                       char *s = bytes + reserve - chunk;
+                       u_int l;
+                       for (l = chunk; l > 0; l--, s++, d++) {
+                               *d = *s;
+                               *s = 0;
+                       }
+               }
+#endif
+               reserve -= chunk;
                buflen -= chunk;
                buf += chunk;
        }