Module Name: src
Committed By: dsl
Date: Sat Aug 18 15:04:53 UTC 2012
Modified Files:
src/lib/libc/gen: arc4random.c
Log Message:
Change the logic used for thread locking to make the code more readable.
The effect on the object code is to replace a function call with a
branch that will predict correctly in the non-threaded case.
Minor optimise of some other paths.
To generate a diff of this commit:
cvs rdiff -u -r1.15 -r1.16 src/lib/libc/gen/arc4random.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/libc/gen/arc4random.c
diff -u src/lib/libc/gen/arc4random.c:1.15 src/lib/libc/gen/arc4random.c:1.16
--- src/lib/libc/gen/arc4random.c:1.15 Sat Aug 18 14:42:46 2012
+++ src/lib/libc/gen/arc4random.c Sat Aug 18 15:04:53 2012
@@ -1,4 +1,4 @@
-/* $NetBSD: arc4random.c,v 1.15 2012/08/18 14:42:46 dsl Exp $ */
+/* $NetBSD: arc4random.c,v 1.16 2012/08/18 15:04:53 dsl Exp $ */
/* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */
/*
@@ -27,7 +27,7 @@
#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
-__RCSID("$NetBSD: arc4random.c,v 1.15 2012/08/18 14:42:46 dsl Exp $");
+__RCSID("$NetBSD: arc4random.c,v 1.16 2012/08/18 15:04:53 dsl Exp $");
#endif /* LIBC_SCCS and not lint */
#include "namespace.h"
@@ -53,6 +53,21 @@ struct arc4_stream {
uint8_t s[RSIZE];
};
+#ifdef _REENTRANT
+#define LOCK(rs) { \
+ int isthreaded = __isthreaded; \
+ if (isthreaded) \
+ mutex_lock(&(rs)->mtx);
+#define UNLOCK(rs) \
+ if (isthreaded) \
+ mutex_unlock(&(rs)->mtx); \
+ }
+#else
+#define LOCK(rs)
+#define UNLOCK(rs)
+#endif
+
+
/* XXX lint explodes with an internal error if only mtx is initialized! */
static struct arc4_stream rs = { .i = 0, .mtx = MUTEX_INITIALIZER };
@@ -160,99 +175,53 @@ arc4_getword(struct arc4_stream *as)
return val;
}
-static inline void
-_arc4random_stir_unlocked(void)
-{
- if (__predict_false(!arc4_check_init(&rs))) /* init() stirs */
- arc4_stir(&rs);
-}
-
void
arc4random_stir(void)
{
-#ifdef _REENTRANT
- if (__isthreaded) {
- mutex_lock(&rs.mtx);
- _arc4random_stir_unlocked();
- mutex_unlock(&rs.mtx);
- return;
- }
-#endif
- _arc4random_stir_unlocked();
-}
-
-static inline void
-_arc4random_addrandom_unlocked(u_char *dat, int datlen)
-{
- arc4_check_init(&rs);
- arc4_addrandom(&rs, dat, datlen);
+ LOCK(&rs);
+ if (__predict_false(!arc4_check_init(&rs))) /* init() stirs */
+ arc4_stir(&rs);
+ UNLOCK(&rs);
}
void
arc4random_addrandom(u_char *dat, int datlen)
{
-#ifdef _REENTRANT
- if (__isthreaded) {
- mutex_lock(&rs.mtx);
- _arc4random_addrandom_unlocked(dat, datlen);
- mutex_unlock(&rs.mtx);
- return;
- }
-#endif
- _arc4random_addrandom_unlocked(dat, datlen);
-}
-
-static inline uint32_t
-_arc4random_unlocked(void)
-{
+ LOCK(&rs);
arc4_check_init(&rs);
- return arc4_getword(&rs);
+ arc4_addrandom(&rs, dat, datlen);
+ UNLOCK(&rs);
}
uint32_t
arc4random(void)
{
uint32_t v;
-#ifdef _REENTRANT
- if (__isthreaded) {
- mutex_lock(&rs.mtx);
- v = _arc4random_unlocked();
- mutex_unlock(&rs.mtx);
- return v;
- }
-#endif
- v = _arc4random_unlocked();
+
+ LOCK(&rs);
+ arc4_check_init(&rs);
+ v = arc4_getword(&rs);
+ UNLOCK(&rs);
return v;
}
-static void
-_arc4random_buf_unlocked(void *buf, size_t len)
+void
+arc4random_buf(void *buf, size_t len)
{
uint8_t *bp = buf;
uint8_t *ep = bp + len;
+ int skip;
+ LOCK(&rs);
arc4_check_init(&rs);
- bp[0] = arc4_getbyte(&rs) % 3;
- while (bp[0]--)
+ skip = arc4_getbyte(&rs) % 3;
+ while (skip--)
(void)arc4_getbyte(&rs);
while (bp < ep)
*bp++ = arc4_getbyte(&rs);
-}
-
-void
-arc4random_buf(void *buf, size_t len)
-{
-#ifdef _REENTRANT
- if (__isthreaded) {
- mutex_lock(&rs.mtx);
- _arc4random_buf_unlocked(buf, len);
- mutex_unlock(&rs.mtx);
- return;
- } else
-#endif
- _arc4random_buf_unlocked(buf, len);
+ UNLOCK(&rs);
}
/*-
@@ -271,25 +240,23 @@ arc4random_buf(void *buf, size_t len)
* [2^32 % upper_bound, 2^32[ which maps back to
* [0, upper_bound[ after reduction modulo upper_bound.
*/
-static uint32_t
-_arc4random_uniform_unlocked(uint32_t upper_bound)
+uint32_t
+arc4random_uniform(uint32_t upper_bound)
{
uint32_t r, min;
if (upper_bound < 2)
return 0;
-#if defined(ULONG_MAX) && (ULONG_MAX > 0xFFFFFFFFUL)
- min = (uint32_t)(0x100000000U % upper_bound);
-#else
/* calculate (2^32 % upper_bound) avoiding 64-bit math */
- if (upper_bound > 0x80000000U)
- /* 2^32 - upper_bound (only one "value area") */
- min = 1 + ~upper_bound;
- else
- /* ((2^32 - x) % x) == (2^32 % x) when x <= 2^31 */
- min = (0xFFFFFFFFU - upper_bound + 1) % upper_bound;
-#endif
+ /* ((2^32 - x) % x) == (2^32 % x) when x <= 2^31 */
+ min = (0xFFFFFFFFU - upper_bound + 1) % upper_bound;
+
+ LOCK(&rs);
+ arc4_check_init(&rs);
+
+ if (arc4_getbyte(&rs) & 1)
+ (void)arc4_getbyte(&rs);
/*
* This could theoretically loop forever but each retry has
@@ -297,28 +264,10 @@ _arc4random_uniform_unlocked(uint32_t up
* number inside the range we need, so it should rarely need
* to re-roll (at all).
*/
- arc4_check_init(&rs);
- if (arc4_getbyte(&rs) & 1)
- (void)arc4_getbyte(&rs);
do
r = arc4_getword(&rs);
while (r < min);
+ UNLOCK(&rs);
return r % upper_bound;
}
-
-uint32_t
-arc4random_uniform(uint32_t upper_bound)
-{
- uint32_t v;
-#ifdef _REENTRANT
- if (__isthreaded) {
- mutex_lock(&rs.mtx);
- v = _arc4random_uniform_unlocked(upper_bound);
- mutex_unlock(&rs.mtx);
- return v;
- }
-#endif
- v = _arc4random_uniform_unlocked(upper_bound);
- return v;
-}
