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eal: improve entropy for initial PRNG seed

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Replace the use of rte_get_timer_cycles() with getentropy() for
seeding the pseudo-random number generator. getentropy() provides a
more truly random value.

getentropy() requires glibc 2.25 and Linux kernel 3.17. In case
getentropy() is not found at compile time, or the relevant syscall
fails in runtime, the rdseed machine instruction will be used as a
fallback.

rdseed is only available on x86 (Broadwell or later). In case it is
not present, rte_get_timer_cycles() will be used as a second fallback.

On non-Meson builds, getentropy() will not be used.

Suggested-by: Bruce Richardson <bruce.richardson@intel.com>
Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
This commit is contained in:
Mattias Rönnblom 2019-06-28 11:01:22 +02:00 committed by Thomas Monjalon
parent 3f002f0696
commit faf8fd2527
2 changed files with 38 additions and 1 deletions
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36
lib/librte_eal/common/rte_random.c
View File

@ -2,7 +2,11 @@
* Copyright(c) 2019 Ericsson AB
*/
#ifdef RTE_MACHINE_CPUFLAG_RDSEED
#include <x86intrin.h>
#endif
#include <stdlib.h>
#include <unistd.h>
#include <rte_branch_prediction.h>
#include <rte_cycles.h>
@ -133,7 +137,37 @@ rte_rand(void)
return __rte_rand_lfsr258(state);
}
static uint64_t
__rte_random_initial_seed(void)
{
#ifdef RTE_LIBEAL_USE_GETENTROPY
int ge_rc;
uint64_t ge_seed;
ge_rc = getentropy(&ge_seed, sizeof(ge_seed));
if (ge_rc == 0)
return ge_seed;
#endif
#ifdef RTE_MACHINE_CPUFLAG_RDSEED
unsigned int rdseed_rc;
unsigned long long rdseed_seed;
/* first fallback: rdseed instruction, if available */
rdseed_rc = _rdseed64_step(&rdseed_seed);
if (rdseed_rc == 1)
return (uint64_t)rdseed_seed;
#endif
/* second fallback: seed using rdtsc */
return rte_get_timer_cycles();
}
RTE_INIT(rte_rand_init)
{
rte_srand(rte_get_timer_cycles());
uint64_t seed;
seed = __rte_random_initial_seed();
rte_srand(seed);
}

3
lib/librte_eal/meson.build
View File

@ -18,6 +18,9 @@ deps += 'kvargs'
if dpdk_conf.has('RTE_USE_LIBBSD')
ext_deps += libbsd
endif
if cc.has_function('getentropy', prefix : '#include <unistd.h>')
cflags += '-DRTE_LIBEAL_USE_GETENTROPY'
endif
sources = common_sources + env_sources
objs = common_objs + env_objs
headers = common_headers + env_headers