linux-kernel - [PATCH 1/9] random32: introduce random32_get_bytes() and prandom32_get

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Date:	Sun, 28 Oct 2012 16:18:58 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Cc:	Akinobu Mita <akinobu.mita@...il.com>,
	"Theodore Ts'o" <tytso@....edu>,
	Artem Bityutskiy <dedekind1@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org
Subject: [PATCH 1/9] random32: introduce random32_get_bytes() and prandom32_get_bytes()

Add functions to get the requested number of pseudo-random bytes.

The difference from get_random_bytes() is that it uses pseudo-random
numbers generated by random32.  It is fast, suitable for generating
random bytes for testing, and reproducible if prandom32 interface is used.

Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Artem Bityutskiy <dedekind1@...il.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: linux-mtd@...ts.infradead.org
---
 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 6330ed4..eedf429b 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 prandom32(struct rnd_state *);
+void prandom32_get_bytes(struct rnd_state *state, void *buf, int nbytes);
 
 /*
  * Handle minimum values for seeds
diff --git a/lib/random32.c b/lib/random32.c
index 938bde5..aee87dd 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -61,6 +61,44 @@ u32 prandom32(struct rnd_state *state)
 EXPORT_SYMBOL(prandom32);
 
 /**
+ *	prandom32_get_bytes - 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 random32_get_bytes().
+ */
+void prandom32_get_bytes(struct rnd_state *state, void *buf, int bytes)
+{
+	unsigned char *p = buf;
+
+	for (; bytes > 0 && ((unsigned long)p) % sizeof(u32); bytes--, p++)
+		*p = prandom32(state);
+
+	for (; bytes > sizeof(u32) - 1; bytes -= sizeof(u32), p += sizeof(u32))
+		*(u32 *)p = prandom32(state);
+
+	for (; bytes > 0; bytes--, p++)
+		*p = prandom32(state);
+}
+EXPORT_SYMBOL(prandom32_get_bytes);
+
+/**
+ *	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);
+
+	prandom32_get_bytes(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

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