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>

diff --git a/include/linux/random.h b/include/linux/random.h
index db6debc6649e2c35ab00a6fe2e33f7ac1267c1d1..d9846088c2c5fe63ed7b97c0c1a19a5bf23f31dc 100644 (file)
--- 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 d1830fade91530fccb5698645e4d664c8b8f46b0..52280d5526be7e8e021dd204c662d3103e6d6726 100644 (file)
--- 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