// SPDX-License-Identifier: GPL-2.0/* * This is a maximally equidistributed combined Tausworthe generator * based on code from GNU Scientific Library 1.5 (30 Jun 2004) * * lfsr113 version: * * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n) * * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n <<  6) ^ s1_n) >> 13)) * s2_{n+1} = (((s2_n & 4294967288) <<  2) ^ (((s2_n <<  2) ^ s2_n) >> 27)) * s3_{n+1} = (((s3_n & 4294967280) <<  7) ^ (((s3_n << 13) ^ s3_n) >> 21)) * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n <<  3) ^ s4_n) >> 12)) * * The period of this generator is about 2^113 (see erratum paper). * * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe * Generators", Mathematics of Computation, 65, 213 (1996), 203--213: * 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, s4 > 127. */ #include <linux/types.h>#include <linux/percpu.h>#include <linux/export.h>#include <linux/jiffies.h>#include <linux/prandom.h>#include <linux/sched.h>#include <linux/bitops.h>#include <linux/slab.h>#include <linux/unaligned.h>#include <kunit/visibility.h> /** *	prandom_u32_state - seeded pseudo-random number generator. *	@state: pointer to state structure holding seeded state. * *	This is used for pseudo-randomness with no outside seeding. *	For more random results, use get_random_u32(). */u32 prandom_u32_state(struct rnd_state *state){#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)	state->s1 = TAUSWORTHE(state->s1,  6U, 13U, 4294967294U, 18U);	state->s2 = TAUSWORTHE(state->s2,  2U, 27U, 4294967288U,  2U);	state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U,  7U);	state->s4 = TAUSWORTHE(state->s4,  3U, 12U, 4294967168U, 13U); 	return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);}EXPORT_SYMBOL(prandom_u32_state); /** *	prandom_bytes_state - 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 get_random_bytes(). */void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes){	u8 *ptr = buf; 	while (bytes >= sizeof(u32)) {		put_unaligned(prandom_u32_state(state), (u32 *) ptr);		ptr += sizeof(u32);		bytes -= sizeof(u32);	} 	if (bytes > 0) {		u32 rem = prandom_u32_state(state);		do {			*ptr++ = (u8) rem;			bytes--;			rem >>= BITS_PER_BYTE;		} while (bytes > 0);	}}EXPORT_SYMBOL(prandom_bytes_state); /* * Only declared here so that it has a prototype when made * non-static for KUnit testing (avoids -Wmissing-prototypes). */#if IS_ENABLED(CONFIG_KUNIT)void prandom_warmup(struct rnd_state *state);#endifVISIBLE_IF_KUNIT void prandom_warmup(struct rnd_state *state){	/* Calling RNG ten times to satisfy recurrence condition */	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);	prandom_u32_state(state);}EXPORT_SYMBOL_IF_KUNIT(prandom_warmup); void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state){	int i; 	for_each_possible_cpu(i) {		struct rnd_state *state = per_cpu_ptr(pcpu_state, i);		u32 seeds[4]; 		get_random_bytes(&seeds, sizeof(seeds));		state->s1 = __seed(seeds[0],   2U);		state->s2 = __seed(seeds[1],   8U);		state->s3 = __seed(seeds[2],  16U);		state->s4 = __seed(seeds[3], 128U); 		prandom_warmup(state);	}}EXPORT_SYMBOL(prandom_seed_full_state);