repeat calls to getentrypy() with the same pid likely indicate reseeds.

Since we assume the PRNG above is doing "something old, something new"
folding, shortcut and do fewer repeats through the timing loop.
ok beck

src/lib/libcrypto/arc4random/getentropy_linux.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_linux.c,v 1.14 2014/06/26 13:48:11 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_linux.c,v 1.15 2014/07/08 08:33:43 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -288,7 +288,7 @@ static int
 getentropy_fallback(void *buf, size_t len)
 {
 	uint8_t results[SHA512_DIGEST_LENGTH];
-	int save_errno = errno, e, m, pgs = getpagesize(), repeat;
+	int save_errno = errno, e, m, pgs = getpagesize(), repeat = 0;
 	static int cnt;
 	struct timespec ts;
 	struct timeval tv;
@@ -296,13 +296,20 @@ getentropy_fallback(void *buf, size_t len)
 	sigset_t sigset;
 	struct stat st;
 	SHA512_CTX ctx;
+	static pid_t lastpid;
 	pid_t pid;
 	size_t i, ii;
 	char *p;
 
+	pid = getpid();
+	if (lastpid == getpid())
+		repeat = REPEAT - 1;
+	else
+		lastpid = pid;
+
 	for (i = 0; i < len; ) {
 		SHA512_Init(&ctx);
-		for (repeat = 0; repeat < REPEAT; repeat++) {
+		for (; repeat < REPEAT; repeat++) {
 
 			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 			if (e != -1) {

src/lib/libcrypto/crypto/getentropy_linux.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_linux.c,v 1.14 2014/06/26 13:48:11 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_linux.c,v 1.15 2014/07/08 08:33:43 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -288,7 +288,7 @@ static int
 getentropy_fallback(void *buf, size_t len)
 {
 	uint8_t results[SHA512_DIGEST_LENGTH];
-	int save_errno = errno, e, m, pgs = getpagesize(), repeat;
+	int save_errno = errno, e, m, pgs = getpagesize(), repeat = 0;
 	static int cnt;
 	struct timespec ts;
 	struct timeval tv;
@@ -296,13 +296,20 @@ getentropy_fallback(void *buf, size_t len)
 	sigset_t sigset;
 	struct stat st;
 	SHA512_CTX ctx;
+	static pid_t lastpid;
 	pid_t pid;
 	size_t i, ii;
 	char *p;
 
+	pid = getpid();
+	if (lastpid == getpid())
+		repeat = REPEAT - 1;
+	else
+		lastpid = pid;
+
 	for (i = 0; i < len; ) {
 		SHA512_Init(&ctx);
-		for (repeat = 0; repeat < REPEAT; repeat++) {
+		for (; repeat < REPEAT; repeat++) {
 
 			HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 			if (e != -1) {