[Mesa-dev] [PATCH 2/3] util/rand_xor: add function to seed rand

[Timothy Arceri]

---
 src/gallium/drivers/radeon/r600_test_dma.c |  3 +-
 src/util/rand_xor.c                        | 62 ++++++++++++++++++++++++++++--
 src/util/rand_xor.h                        |  6 ++-
 3 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/src/gallium/drivers/radeon/r600_test_dma.c b/src/gallium/drivers/radeon/r600_test_dma.c
index 7d636b9..abef8ed 100644
--- a/src/gallium/drivers/radeon/r600_test_dma.c
+++ b/src/gallium/drivers/radeon/r600_test_dma.c
@@ -172,22 +172,21 @@ void r600_test_dma(struct r600_common_screen *rscreen)
 
 	max_levels = screen->get_param(screen, PIPE_CAP_MAX_TEXTURE_2D_LEVELS);
 	max_tex_side = 1 << (max_levels - 1);
 
 	/* Max 128 MB allowed for both textures. */
 	max_alloc_size = 128 * 1024 * 1024;
 
 	/* the seed for random test parameters */
 	srand(0x9b47d95b);
 	/* the seed for random pixel data */
-	seed_xorshift128plus[0] = 0x3bffb83978e24f88;
-	seed_xorshift128plus[1] = 0x9238d5d56c71cd35;
+	s_rand_xorshift128plus(false);
 
 	iterations = 1000000000; /* just kill it when you are bored */
 	num_partial_copies = 30;
 
 	/* These parameters are randomly generated per test:
 	 * - whether to do one whole-surface copy or N partial copies per test
 	 * - which tiling modes to use (LINEAR_ALIGNED, 1D, 2D)
 	 * - which texture dimensions to use
 	 * - whether to use VRAM (all tiling modes) and GTT (staging, linear
 	 *   only) allocations
diff --git a/src/util/rand_xor.c b/src/util/rand_xor.c
index adb799d..cc834fa 100644
--- a/src/util/rand_xor.c
+++ b/src/util/rand_xor.c
@@ -1,21 +1,77 @@
-/* Super fast random number generator.
+/*
+ * Copyright 2017 Timothy Arceri
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
  *
- * This rand_xorshift128plus function by Sebastiano Vigna belongs
- * to the public domain.
  */
 
+#if defined(__linux__)
+#include <sys/file.h>
+#include <unistd.h>
+#endif
+
 #include "rand_xor.h"
 
+static uint64_t seed_xorshift128plus[2];
+
+/* Super fast random number generator.
+ *
+ * This rand_xorshift128plus function by Sebastiano Vigna belongs
+ * to the public domain.
+ */
 uint64_t
 rand_xorshift128plus(void)
 {
    uint64_t *s = seed_xorshift128plus;
 
    uint64_t s1 = s[0];
    const uint64_t s0 = s[1];
    s[0] = s0;
    s1 ^= s1 << 23;
    s[1] = s1 ^ s0 ^ (s1 >> 18) ^ (s0 >> 5);
 
    return s[1] + s0;
 }
+
+void
+s_rand_xorshift128plus(bool randomised_seed)
+{
+#if defined(__linux__)
+   if (!randomised_seed)
+      goto fixed_seed;
+
+   int fd = open("/dev/urandom", O_RDONLY);
+   if (fd < 0)
+      goto fixed_seed;
+
+   size_t seed_size = sizeof(uint64_t) * 2;
+   if (read(fd, &seed_xorshift128plus, seed_size) != seed_size)
+      goto fixed_seed;
+
+   close(fd);
+   return;
+
+fixed_seed:
+#endif
+
+   /* Fallback to a fixed seed */
+   seed_xorshift128plus[0] = 0x3bffb83978e24f88;
+   seed_xorshift128plus[1] = 0x9238d5d56c71cd35;
+}
diff --git a/src/util/rand_xor.h b/src/util/rand_xor.h
index c7667e4..8a48d63 100644
--- a/src/util/rand_xor.h
+++ b/src/util/rand_xor.h
@@ -19,17 +19,19 @@
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
  */
 
 #ifndef RAND_XOR_H
 #define RAND_XOR_H
 
 #include <stdint.h>
-
-static uint64_t seed_xorshift128plus[2];
+#include <stdbool.h>
 
 uint64_t
 rand_xorshift128plus(void);
 
+void
+s_rand_xorshift128plus(bool randomised_seed);
+
 #endif /* RAND_XOR_H */
-- 
2.9.3