1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * include/linux/prandom.h 4 * 5 * Include file for the fast pseudo-random 32-bit 6 * generation. 7 */ 8 #ifndef _LINUX_PRANDOM_H 9 #define _LINUX_PRANDOM_H 10 11 #include <linux/types.h> 12 #include <linux/once.h> 13 #include <linux/percpu.h> 14 #include <linux/random.h> 15 16 struct rnd_state { 17 __u32 s1, s2, s3, s4; 18 }; 19 20 u32 prandom_u32_state(struct rnd_state *state); 21 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); 22 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); 23 24 #define prandom_init_once(pcpu_state) \ 25 DO_ONCE(prandom_seed_full_state, (pcpu_state)) 26 27 /* 28 * Handle minimum values for seeds 29 */ 30 static inline u32 __seed(u32 x, u32 m) 31 { 32 return (x < m) ? x + m : x; 33 } 34 35 /** 36 * prandom_seed_state - set seed for prandom_u32_state(). 37 * @state: pointer to state structure to receive the seed. 38 * @seed: arbitrary 64-bit value to use as a seed. 39 */ 40 static inline void prandom_seed_state(struct rnd_state *state, u64 seed) 41 { 42 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; 43 44 state->s1 = __seed(i, 2U); 45 state->s2 = __seed(i, 8U); 46 state->s3 = __seed(i, 16U); 47 state->s4 = __seed(i, 128U); 48 } 49 50 /* Pseudo random number generator from numerical recipes. */ 51 static inline u32 next_pseudo_random32(u32 seed) 52 { 53 return seed * 1664525 + 1013904223; 54 } 55 56 #endif 57