/*  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);}/* * Handle minimum values for seeds */static inline u32 __seed(u32 x, u32 m){	return (x < m) ? x + m : x;}/** *	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);		state->s1 = __seed(state->s1 ^ entropy, 1);	}}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);#define LCG(x)	((x) * 69069)	/* super-duper LCG */		state->s1 = __seed(LCG(i + jiffies), 1);		state->s2 = __seed(LCG(state->s1), 7);		state->s3 = __seed(LCG(state->s2), 15);		/* "warm it up" */		__random32(state);		__random32(state);		__random32(state);		__random32(state);		__random32(state);		__random32(state);	}	return 0;}core_initcall(random32_init);/* *	Generate better values after random number generator *	is fully initalized. */static int __init random32_reseed(void){	int i;	for_each_possible_cpu(i) {		struct rnd_state *state = &per_cpu(net_rand_state,i);		u32 seeds[3];		get_random_bytes(&seeds, sizeof(seeds));		state->s1 = __seed(seeds[0], 1);		state->s2 = __seed(seeds[1], 7);		state->s3 = __seed(seeds[2], 15);		/* mix it in */		__random32(state);	}	return 0;}late_initcall(random32_reseed);