[Mesa-dev] [PATCH V2 2/3] util/rand_xor: add function to seed rand
Nicolai Hähnle
nhaehnle at gmail.com
Wed Mar 22 07:10:39 UTC 2017
On 22.03.2017 05:52, Jonathan Gray wrote:
> If a proper PRNG like arc4random backed by a syscall like getentropy
> were used this would already handle reseeding on fork and fd exhaustion.
>
> And look people have already gone out of their way to provide fallbacks
> for these interfaces.
>
> https://github.com/libressl-portable/openbsd/tree/master/src/lib/libcrypto/arc4random
Yeah, but then you have the headache of juggling those additional build
dependencies. I think the approach is fine as is.
Nicolai
>
> On Wed, Mar 22, 2017 at 10:59:47AM +1100, Timothy Arceri wrote:
>> V2: pass the seed to the seed function so that we can isolate
>> its uses. Stop leaking fd when urandom couldn't be read.
>> ---
>> src/gallium/drivers/radeon/r600_test_dma.c | 3 +-
>> src/util/rand_xor.c | 57 ++++++++++++++++++++++++++++++
>> src/util/rand_xor.h | 4 +++
>> 3 files changed, 62 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeon/r600_test_dma.c b/src/gallium/drivers/radeon/r600_test_dma.c
>> index 8b4149a..3c23b09 100644
>> --- a/src/gallium/drivers/radeon/r600_test_dma.c
>> +++ b/src/gallium/drivers/radeon/r600_test_dma.c
>> @@ -176,22 +176,21 @@ 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(seed_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 07b4c22..ee506a2 100644
>> --- a/src/util/rand_xor.c
>> +++ b/src/util/rand_xor.c
>> @@ -1,20 +1,77 @@
>> +/*
>> + * 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.
>> + *
>> + */
>> +
>> +#if defined(__linux__)
>> +#include <sys/file.h>
>> +#include <unistd.h>
>> +#endif
>> +
>> #include "rand_xor.h"
>>
>> /* Super fast random number generator.
>> *
>> * This rand_xorshift128plus function by Sebastiano Vigna belongs
>> * to the public domain.
>> */
>> uint64_t
>> rand_xorshift128plus(uint64_t *seed)
>> {
>> uint64_t *s = seed;
>>
>> 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(uint64_t *seed, 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, seed_size) != seed_size) {
>> + close(fd);
>> + goto fixed_seed;
>> + }
>> +
>> + close(fd);
>> + return;
>> +
>> +fixed_seed:
>> +#endif
>> +
>> + /* Fallback to a fixed seed */
>> + seed[0] = 0x3bffb83978e24f88;
>> + seed[1] = 0x9238d5d56c71cd35;
>> +}
>> diff --git a/src/util/rand_xor.h b/src/util/rand_xor.h
>> index d5144e9..532d549 100644
>> --- a/src/util/rand_xor.h
>> +++ b/src/util/rand_xor.h
>> @@ -19,15 +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>
>> +#include <stdbool.h>
>>
>> uint64_t
>> rand_xorshift128plus(uint64_t *seed);
>>
>> +void
>> +s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed);
>> +
>> #endif /* RAND_XOR_H */
>> --
>> 2.9.3
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
More information about the mesa-dev
mailing list