[Mesa-dev] [PATCH v2] util/rand_xor: seed with getentropy when available

[Jonathan Gray]

On Thu, Mar 23, 2017 at 03:24:16PM +1100, Jonathan Gray wrote:
> Instead of using using /dev/urandom on Linux and time(NULL) elsewhere
> for a seed first use getentropy() for systems that have a kernel
> interface to get a seed such as OpenBSD.  This interface is also
> present in other systems such as Solaris and even Linux with a recent
> version of glibc.
> 
> v2: check for/use the different header Solaris and glibc use
> 
> Signed-off-by: Jonathan Gray <jsg at jsg.id.au>

The functions should really be split for random and deterministic
as well, but that is hard to cleanup without being able to assume
arc4random or equivalent is present.

diff --git a/configure.ac b/configure.ac
index c27646ca4c..a1a62482d9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -792,6 +792,9 @@ AC_CHECK_FUNC([posix_memalign], [DEFINES="$DEFINES -DHAVE_POSIX_MEMALIGN"])
 dnl See if getentropy is available
 AC_CHECK_FUNC([getentropy], [DEFINES="$DEFINES -DHAVE_GETENTROPY"])
 
+dnl See if arc4random_buf is available
+AC_CHECK_FUNC([arc4random_buf], [DEFINES="$DEFINES -DHAVE_ARC4RANDOM_BUF"])
+
 dnl Check for zlib
 PKG_CHECK_MODULES([ZLIB], [zlib >= $ZLIB_REQUIRED])
 
diff --git a/src/gallium/drivers/radeon/r600_test_dma.c b/src/gallium/drivers/radeon/r600_test_dma.c
index 3c23b09329..0cdd24d1c0 100644
--- a/src/gallium/drivers/radeon/r600_test_dma.c
+++ b/src/gallium/drivers/radeon/r600_test_dma.c
@@ -77,7 +77,7 @@ static void set_random_pixels(struct pipe_context *ctx,
 
 			for (x = 0; x < size; x++) {
 				*ptr++ = *ptr_cpu++ =
-					rand_xorshift128plus(seed_xorshift128plus);
+					rand_xorshift128plus_deterministic(seed_xorshift128plus);
 			}
 		}
 	}
diff --git a/src/util/rand_xor.c b/src/util/rand_xor.c
index c613371f67..db642dae54 100644
--- a/src/util/rand_xor.c
+++ b/src/util/rand_xor.c
@@ -37,6 +37,10 @@
 #include <time.h>
 #endif
 
+#ifdef HAVE_ARC4RANDOM_BUF
+#include <stdlib.h>
+#endif
+
 #include "rand_xor.h"
 
 /* Super fast random number generator.
@@ -45,7 +49,7 @@
  * to the public domain.
  */
 uint64_t
-rand_xorshift128plus(uint64_t *seed)
+rand_xorshift128plus_deterministic(uint64_t *seed)
 {
    uint64_t *s = seed;
 
@@ -58,6 +62,18 @@ rand_xorshift128plus(uint64_t *seed)
    return s[1] + s0;
 }
 
+uint64_t
+rand_xorshift128plus(uint64_t *seed)
+{
+#ifdef HAVE_ARC4RANDOM_BUF
+  uint64_t buf;
+  arc4random_buf(&buf, sizeof(buf));
+  return buf;
+#else
+  return rand_xorshift128plus_deterministic(seed);
+#endif
+}
+
 void
 s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed)
 {
diff --git a/src/util/rand_xor.h b/src/util/rand_xor.h
index 532d549bcd..0fbf4d3a8a 100644
--- a/src/util/rand_xor.h
+++ b/src/util/rand_xor.h
@@ -31,6 +31,9 @@
 uint64_t
 rand_xorshift128plus(uint64_t *seed);
 
+uint64_t
+rand_xorshift128plus_deterministic(uint64_t *seed);
+
 void
 s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed);