Messages in this thread Patch in this message | | | From | Akinobu Mita <> | Subject | [PATCH v3 02/11] prandom: introduce prandom_bytes() and prandom_bytes_state() | Date | Tue, 13 Nov 2012 22:37:01 +0900 |
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Add functions to get the requested number of pseudo-random bytes.
The difference from get_random_bytes() is that it generates pseudo-random numbers by prandom_u32(). It doesn't consume the entropy pool, and the sequence is reproducible if the same rnd_state is used. So it is suitable for generating random bytes for testing.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: linux-mtd@lists.infradead.org Cc: Eilon Greenstein <eilong@broadcom.com> Cc: netdev@vger.kernel.org --- * v3 - rename random32_get_bytes_state to prandom_bytes_state - ensure prandom_bytes_state() generates same bytes with same rnd_state
* v2 - rename prandom32_get_bytes to random32_get_bytes_state
include/linux/random.h | 2 ++ lib/random32.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 51 insertions(+)
diff --git a/include/linux/random.h b/include/linux/random.h index db6debc..d984608 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -26,6 +26,7 @@ unsigned int get_random_int(void); unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len); u32 prandom_u32(void); +void prandom_bytes(void *buf, int nbytes); void prandom_seed(u32 seed); /* @@ -36,6 +37,7 @@ void prandom_seed(u32 seed); #define srandom32(seed) prandom_seed(seed) u32 prandom_u32_state(struct rnd_state *); +void prandom_bytes_state(struct rnd_state *state, void *buf, int nbytes); /* * Handle minimum values for seeds diff --git a/lib/random32.c b/lib/random32.c index d1830fa..52280d5 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -77,6 +77,55 @@ u32 prandom_u32(void) } EXPORT_SYMBOL(prandom_u32); +/* + * prandom_bytes_state - get the requested number of pseudo-random bytes + * + * @state: pointer to state structure holding seeded state. + * @buf: where to copy the pseudo-random bytes to + * @bytes: the requested number of bytes + * + * This is used for pseudo-randomness with no outside seeding. + * For more random results, use prandom_bytes(). + */ +void prandom_bytes_state(struct rnd_state *state, void *buf, int bytes) +{ + unsigned char *p = buf; + int i; + + for (i = 0; i < round_down(bytes, sizeof(u32)); i += sizeof(u32)) { + u32 random = prandom_u32_state(state); + int j; + + for (j = 0; j < sizeof(u32); j++) { + p[i + j] = random; + random >>= BITS_PER_BYTE; + } + } + if (i < bytes) { + u32 random = prandom_u32_state(state); + + for (; i < bytes; i++) { + p[i] = random; + random >>= BITS_PER_BYTE; + } + } +} +EXPORT_SYMBOL(prandom_bytes_state); + +/** + * prandom_bytes - get the requested number of pseudo-random bytes + * @buf: where to copy the pseudo-random bytes to + * @bytes: the requested number of bytes + */ +void prandom_bytes(void *buf, int bytes) +{ + struct rnd_state *state = &get_cpu_var(net_rand_state); + + prandom_bytes_state(state, buf, bytes); + put_cpu_var(state); +} +EXPORT_SYMBOL(prandom_bytes); + /** * prandom_seed - add entropy to pseudo random number generator * @seed: seed value -- 1.7.11.7
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