rpms
/
glibc
7
0
Fork 1
Code Issues Pull Requests Releases Activity
glibc/SOURCES/glibc-rh1817513-23.patch

212 lines
7.1 KiB
Diff
Raw Permalink Blame History

commit 359653aaacad463d916323f03c0ac3c47405aafa
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Wed Jan 16 18:10:56 2019 +0000
Do not use HP_TIMING_NOW for random bits
This patch removes the HP_TIMING_BITS usage for fast random bits and replace
with clock_gettime (CLOCK_MONOTONIC). It has unspecified starting time and
nano-second accuracy, so its randomness is significantly better than
gettimeofday.
Althoug it should incur in more overhead (specially for architecture that
support hp-timing), the symbol is also common implemented as a vDSO.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu. I also
checked on a i686-gnu build.
* include/random-bits.h: New file.
* resolv/res_mkquery.c [HP_TIMING_AVAIL] (RANDOM_BITS,
(__res_context_mkquery): Remove usage hp-timing usage and replace with
random_bits.
* resolv/res_send.c [HP_TIMING_AVAIL] (nameserver_offset): Likewise.
* sysdeps/posix/tempname.c [HP_TIMING_AVAIL] (__gen_tempname):
Likewise.
diff --git a/include/random-bits.h b/include/random-bits.h
new file mode 100644
index 0000000000000000..a0651a5a34f80a8d
--- /dev/null
+++ b/include/random-bits.h
@@ -0,0 +1,41 @@
+/* Fast pseudo-random bits based on clock_gettime.
+ Copyright (C) 2019 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _RANDOM_BITS_H
+# define _RANDOM_BITS_H
+
+#include <time.h>
+#include <stdint.h>
+
+/* Provides fast pseudo-random bits through clock_gettime. It has unspecified
+ starting time, nano-second accuracy, its randomness is significantly better
+ than gettimeofday, and for mostly architectures it is implemented through
+ vDSO instead of a syscall. Since the source is a system clock, the upper
+ bits will have less entropy. */
+static inline uint32_t
+random_bits (void)
+{
+ struct timespec tv;
+ __clock_gettime (CLOCK_MONOTONIC, &tv);
+ /* Shuffle the lower bits to minimize the clock bias. */
+ uint32_t ret = tv.tv_nsec ^ tv.tv_sec;
+ ret ^= (ret << 24) | (ret >> 8);
+ return ret;
+}
+
+#endif
diff --git a/resolv/res_mkquery.c b/resolv/res_mkquery.c
index 213abeefadf7ece5..4471a8838b1de7ee 100644
--- a/resolv/res_mkquery.c
+++ b/resolv/res_mkquery.c
@@ -82,6 +82,7 @@
* SOFTWARE.
*/
+#include <stdint.h>
#include <sys/types.h>
#include <sys/param.h>
#include <netinet/in.h>
@@ -92,12 +93,7 @@
#include <string.h>
#include <sys/time.h>
#include <shlib-compat.h>
-
-#include <hp-timing.h>
-#include <stdint.h>
-#if HP_TIMING_AVAIL
-# define RANDOM_BITS(Var) { uint64_t v64; HP_TIMING_NOW (v64); Var = v64; }
-#endif
+#include <random-bits.h>
int
__res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
@@ -120,16 +116,7 @@ __res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
/* We randomize the IDs every time. The old code just incremented
by one after the initial randomization which still predictable if
the application does multiple requests. */
- int randombits;
-#ifdef RANDOM_BITS
- RANDOM_BITS (randombits);
-#else
- struct timeval tv;
- __gettimeofday (&tv, NULL);
- randombits = (tv.tv_sec << 8) ^ tv.tv_usec;
-#endif
-
- hp->id = randombits;
+ hp->id = random_bits ();
hp->opcode = op;
hp->rd = (ctx->resp->options & RES_RECURSE) != 0;
hp->rcode = NOERROR;
diff --git a/resolv/res_send.c b/resolv/res_send.c
index ac19627634281c2f..55e7fa438e7baac1 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -109,7 +109,7 @@
#include <unistd.h>
#include <kernel-features.h>
#include <libc-diag.h>
-#include <hp-timing.h>
+#include <random-bits.h>
#if PACKETSZ > 65536
#define MAXPACKET PACKETSZ
@@ -309,15 +309,7 @@ nameserver_offset (struct __res_state *statp)
if ((offset & 1) == 0)
{
/* Initialization is required. */
-#if HP_TIMING_AVAIL
- uint64_t ticks;
- HP_TIMING_NOW (ticks);
- offset = ticks;
-#else
- struct timeval tv;
- __gettimeofday (&tv, NULL);
- offset = ((tv.tv_sec << 8) ^ tv.tv_usec);
-#endif
+ offset = random_bits ();
/* The lowest bit is the most random. Preserve it. */
offset <<= 1;
diff --git a/sysdeps/posix/tempname.c b/sysdeps/posix/tempname.c
index 432262a03b6ecc23..3d26f378021680ae 100644
--- a/sysdeps/posix/tempname.c
+++ b/sysdeps/posix/tempname.c
@@ -71,22 +71,15 @@
#endif
#ifdef _LIBC
-# include <hp-timing.h>
-# if HP_TIMING_AVAIL
-# define RANDOM_BITS(Var) \
- if (__glibc_unlikely (value == UINT64_C (0))) \
- { \
- /* If this is the first time this function is used initialize \
- the variable we accumulate the value in to some somewhat \
- random value. If we'd not do this programs at startup time \
- might have a reduced set of possible names, at least on slow \
- machines. */ \
- struct timeval tv; \
- __gettimeofday (&tv, NULL); \
- value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
- } \
- HP_TIMING_NOW (Var)
-# endif
+# include <random-bits.h>
+# define RANDOM_BITS(Var) ((Var) = random_bits ())
+# else
+# define RANDOM_BITS(Var) \
+ { \
+ struct timeval tv; \
+ __gettimeofday (&tv, NULL); \
+ (Var) = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \
+ }
#endif
/* Use the widest available unsigned type if uint64_t is not
@@ -193,8 +186,7 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
{
int len;
char *XXXXXX;
- static uint64_t value;
- uint64_t random_time_bits;
+ uint64_t value;
unsigned int count;
int fd = -1;
int save_errno = errno;
@@ -227,16 +219,8 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
XXXXXX = &tmpl[len - 6 - suffixlen];
/* Get some more or less random data. */
-#ifdef RANDOM_BITS
- RANDOM_BITS (random_time_bits);
-#else
- {
- struct timeval tv;
- __gettimeofday (&tv, NULL);
- random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
- }
-#endif
- value += random_time_bits ^ __getpid ();
+ RANDOM_BITS (value);
+ value ^= (uint64_t)__getpid () << 32;
for (count = 0; count < attempts; value += 7777, ++count)
{
Reference in New Issue View Git Blame Copy Permalink