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prandom: introduce prandom_bytes() and prandom_bytes_state() 

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: Eilon Greenstein <eilong@broadcom.com>
Cc: David Laight <david.laight@aculab.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Robert Love <robert.w.love@intel.com>
Cc: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Akinobu Mita 2012-12-17 16:04:25 -08:00 committed by Linus Torvalds
parent 496f2f93b1
commit 6582c665d6
2 changed files with 51 additions and 0 deletions
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2
include/linux/random.h
View File

@ -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

49
lib/random32.c
View File

@ -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