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authorStephen Hemminger <shemminger@osdl.org>2006-10-17 00:09:42 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-17 08:18:43 -0700
commitaaa248f6c9c81b2683db7dbb0689cd5ed1c86d88 (patch)
tree106d9ce5ebac4175b0fb97ff80a92e399fcf2a33 /lib/random32.c
parent0187f879ee8d4b914e74ffa3cc5df268311fc2d2 (diff)
downloadlinux-linaro-precise-aaa248f6c9c81b2683db7dbb0689cd5ed1c86d88.tar.gz
[PATCH] rename net_random to random32
Make net_random() more widely available by calling it random32 akpm: hopefully this will permit the removal of carta_random32. That needs confirmation from Stephane - this code looks somewhat more computationally expensive, and has a different (ie: callee-stateful) interface. [akpm@osdl.org: lots of build fixes, cleanups] Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net> Cc: Stephane Eranian <eranian@hpl.hp.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'lib/random32.c')
-rw-r--r--lib/random32.c142
1 files changed, 142 insertions, 0 deletions
diff --git a/lib/random32.c b/lib/random32.c
new file mode 100644
index 00000000000..4a15ce51cea
--- /dev/null
+++ b/lib/random32.c
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+/*
+ This is a maximally equidistributed combined Tausworthe generator
+ based on code from GNU Scientific Library 1.5 (30 Jun 2004)
+
+ x_n = (s1_n ^ s2_n ^ s3_n)
+
+ s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19))
+ s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25))
+ s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11))
+
+ The period of this generator is about 2^88.
+
+ From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
+ Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
+
+ This is available on the net from L'Ecuyer's home page,
+
+ http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
+ ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
+
+ There is an erratum in the paper "Tables of Maximally
+ Equidistributed Combined LFSR Generators", Mathematics of
+ Computation, 68, 225 (1999), 261--269:
+ http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
+
+ ... the k_j most significant bits of z_j must be non-
+ zero, for each j. (Note: this restriction also applies to the
+ computer code given in [4], but was mistakenly not mentioned in
+ that paper.)
+
+ This affects the seeding procedure by imposing the requirement
+ s1 > 1, s2 > 7, s3 > 15.
+
+*/
+
+#include <linux/types.h>
+#include <linux/percpu.h>
+#include <linux/module.h>
+#include <linux/random.h>
+
+struct rnd_state {
+ u32 s1, s2, s3;
+};
+
+static DEFINE_PER_CPU(struct rnd_state, net_rand_state);
+
+static u32 __random32(struct rnd_state *state)
+{
+#define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b)
+
+ state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12);
+ state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4);
+ state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17);
+
+ return (state->s1 ^ state->s2 ^ state->s3);
+}
+
+static void __set_random32(struct rnd_state *state, unsigned long s)
+{
+ if (s == 0)
+ s = 1; /* default seed is 1 */
+
+#define LCG(n) (69069 * n)
+ state->s1 = LCG(s);
+ state->s2 = LCG(state->s1);
+ state->s3 = LCG(state->s2);
+
+ /* "warm it up" */
+ __random32(state);
+ __random32(state);
+ __random32(state);
+ __random32(state);
+ __random32(state);
+ __random32(state);
+}
+
+/**
+ * random32 - pseudo random number generator
+ *
+ * A 32 bit pseudo-random number is generated using a fast
+ * algorithm suitable for simulation. This algorithm is NOT
+ * considered safe for cryptographic use.
+ */
+u32 random32(void)
+{
+ unsigned long r;
+ struct rnd_state *state = &get_cpu_var(net_rand_state);
+ r = __random32(state);
+ put_cpu_var(state);
+ return r;
+}
+EXPORT_SYMBOL(random32);
+
+/**
+ * srandom32 - add entropy to pseudo random number generator
+ * @seed: seed value
+ *
+ * Add some additional seeding to the random32() pool.
+ * Note: this pool is per cpu so it only affects current CPU.
+ */
+void srandom32(u32 entropy)
+{
+ struct rnd_state *state = &get_cpu_var(net_rand_state);
+ __set_random32(state, state->s1 ^ entropy);
+ put_cpu_var(state);
+}
+EXPORT_SYMBOL(srandom32);
+
+/*
+ * Generate some initially weak seeding values to allow
+ * to start the random32() engine.
+ */
+static int __init random32_init(void)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ struct rnd_state *state = &per_cpu(net_rand_state,i);
+ __set_random32(state, i + jiffies);
+ }
+ return 0;
+}
+core_initcall(random32_init);
+
+/*
+ * Generate better values after random number generator
+ * is fully initalized.
+ */
+static int __init random32_reseed(void)
+{
+ int i;
+ unsigned long seed;
+
+ for_each_possible_cpu(i) {
+ struct rnd_state *state = &per_cpu(net_rand_state,i);
+
+ get_random_bytes(&seed, sizeof(seed));
+ __set_random32(state, seed);
+ }
+ return 0;
+}
+late_initcall(random32_reseed);