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