mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 19:00:25 +00:00
![Andi Kleen](/assets/img/avatar_default.png)
- Let it update the state of all CPUs. The network stack goes into pains to feed the current IP addresses in, but it is not very effective if that is only done for some random CPU instead of all. So change it to feed bits into all CPUs. I decided to do that lockless because well somewhat random results are ok. v2: Drop rename so that this patch doesn't depend on x86 maintainers Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: David S. Miller <davem@davemloft.net>
148 lines
3.7 KiB
C
148 lines
3.7 KiB
C
/*
|
|
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/jiffies.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.
|
|
*/
|
|
void srandom32(u32 entropy)
|
|
{
|
|
int i;
|
|
/*
|
|
* No locking on the CPUs, but then somewhat random results are, well,
|
|
* expected.
|
|
*/
|
|
for_each_possible_cpu (i) {
|
|
struct rnd_state *state = &per_cpu(net_rand_state, i);
|
|
__set_random32(state, state->s1 ^ entropy);
|
|
}
|
|
}
|
|
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);
|