diff options
Diffstat (limited to 'crypto/jitterentropy-kcapi.c')
| -rw-r--r-- | crypto/jitterentropy-kcapi.c | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c index 597cedd3531c..c4938497eedb 100644 --- a/crypto/jitterentropy-kcapi.c +++ b/crypto/jitterentropy-kcapi.c @@ -87,24 +87,28 @@ void jent_memcpy(void *dest, const void *src, unsigned int n) memcpy(dest, src, n); } +/* + * Obtain a high-resolution time stamp value. The time stamp is used to measure + * the execution time of a given code path and its variations. Hence, the time + * stamp must have a sufficiently high resolution. + * + * Note, if the function returns zero because a given architecture does not + * implement a high-resolution time stamp, the RNG code's runtime test + * will detect it and will not produce output. + */ void jent_get_nstime(__u64 *out) { - struct timespec ts; __u64 tmp = 0; tmp = random_get_entropy(); /* - * If random_get_entropy does not return a value (which is possible on, - * for example, MIPS), invoke __getnstimeofday + * If random_get_entropy does not return a value, i.e. it is not + * implemented for a given architecture, use a clock source. * hoping that there are timers we can work with. */ - if ((0 == tmp) && - (0 == __getnstimeofday(&ts))) { - tmp = ts.tv_sec; - tmp = tmp << 32; - tmp = tmp | ts.tv_nsec; - } + if (tmp == 0) + tmp = ktime_get_ns(); *out = tmp; } |