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/*
* Generic address resultion entity
*
* Authors:
* net_random Alan Cox
* net_ratelimit Andy Kleen
*
* Created by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/random.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <asm/system.h>
#include <asm/uaccess.h>
/*
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.
*/
struct nrnd_state {
u32 s1, s2, s3;
};
static DEFINE_PER_CPU(struct nrnd_state, net_rand_state);
static u32 __net_random(struct nrnd_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 __net_srandom(struct nrnd_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" */
__net_random(state);
__net_random(state);
__net_random(state);
__net_random(state);
__net_random(state);
__net_random(state);
}
unsigned long net_random(void)
{
unsigned long r;
struct nrnd_state *state = &get_cpu_var(net_rand_state);
r = __net_random(state);
put_cpu_var(state);
return r;
}
void net_srandom(unsigned long entropy)
{
struct nrnd_state *state = &get_cpu_var(net_rand_state);
__net_srandom(state, state->s1^entropy);
put_cpu_var(state);
}
void __init net_random_init(void)
{
int i;
for (i = 0; i < NR_CPUS; i++) {
struct nrnd_state *state = &per_cpu(net_rand_state,i);
__net_srandom(state, i+jiffies);
}
}
static int net_random_reseed(void)
{
int i;
unsigned long seed[NR_CPUS];
get_random_bytes(seed, sizeof(seed));
for (i = 0; i < NR_CPUS; i++) {
struct nrnd_state *state = &per_cpu(net_rand_state,i);
__net_srandom(state, seed[i]);
}
return 0;
}
late_initcall(net_random_reseed);
int net_msg_cost = 5*HZ;
int net_msg_burst = 10;
/*
* All net warning printk()s should be guarded by this function.
*/
int net_ratelimit(void)
{
return __printk_ratelimit(net_msg_cost, net_msg_burst);
}
EXPORT_SYMBOL(net_random);
EXPORT_SYMBOL(net_ratelimit);
EXPORT_SYMBOL(net_srandom);
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