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.

1 files changed, 2 insertions, 10 deletions

diff --git a/resolv/res_send.c b/resolv/res_send.c
index 0f6ec83a7b..ca441c4ce1 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;