[PATCH v2 02/11] random32: introduce random32_get_bytes() and random32_get_bytes_state()

Akinobu Mita
2012-11-03T15:44:23Z

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 random32(). It is fast, suitable for generating random bytes
for testing, and reproducible if random32_get_bytes_state() is used.

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
---
* v2
- rename prandom32_get_bytes to random32_get_bytes_state

include/linux/random.h | 2 ++
lib/random32.c | 38 ++++++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+)

diff --git a/include/linux/random.h b/include/linux/random.h
index bb96f79..4176762 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -27,8 +27,10 @@ unsigned long randomize_range(unsigned long start, unsigned long end, unsigned l

u32 random32(void);
void srandom32(u32 seed);
+void random32_get_bytes(void *buf, int nbytes);

u32 random32_state(struct rnd_state *);
+void random32_get_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 7a3e0c7..9557417 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -61,6 +61,44 @@ u32 random32_state(struct rnd_state *state)
EXPORT_SYMBOL(random32_state);

/**
+ * random32_get_bytes_state - get the 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 random32_get_bytes().
+ */
+void random32_get_bytes_state(struct rnd_state *state, void *buf, int bytes)
+{
+ unsigned char *p = buf;
+
+ for (; bytes > 0 && ((unsigned long)p) % sizeof(u32); bytes--, p++)
+ *p = random32_state(state);
+
+ for (; bytes > sizeof(u32) - 1; bytes -= sizeof(u32), p += sizeof(u32))
+ *(u32 *)p = random32_state(state);
+
+ for (; bytes > 0; bytes--, p++)
+ *p = random32_state(state);
+}
+EXPORT_SYMBOL(random32_get_bytes_state);
+
+/**
+ * random32_get_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 random32_get_bytes(void *buf, int bytes)
+{
+ struct rnd_state *state = &get_cpu_var(net_rand_state);
+
+ random32_get_bytes_state(state, buf, bytes);
+ put_cpu_var(state);
+}
+EXPORT_SYMBOL(random32_get_bytes);
+
+/**
* random32 - pseudo random number generator
*
* A 32 bit pseudo-random number is generated using a fast
--
1.7.11.7