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/percpu.h> 13 #include <linux/random.h> 14 15 static inline u32 prandom_u32(void) 16 { 17 return get_random_u32(); 18 } 19 20 static inline void prandom_bytes(void *buf, size_t nbytes) 21 { 22 return get_random_bytes(buf, nbytes); 23 } 24 25 struct rnd_state { 26 __u32 s1, s2, s3, s4; 27 }; 28 29 u32 prandom_u32_state(struct rnd_state *state); 30 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); 31 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); 32 33 #define prandom_init_once(pcpu_state) \ 34 DO_ONCE(prandom_seed_full_state, (pcpu_state)) 35 36 /** 37 * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro) 38 * @ep_ro: right open interval endpoint 39 * 40 * Returns a pseudo-random number that is in interval [0, ep_ro). Note 41 * that the result depends on PRNG being well distributed in [0, ~0U] 42 * u32 space. Here we use maximally equidistributed combined Tausworthe 43 * generator, that is, prandom_u32(). This is useful when requesting a 44 * random index of an array containing ep_ro elements, for example. 45 * 46 * Returns: pseudo-random number in interval [0, ep_ro) 47 */ 48 static inline u32 prandom_u32_max(u32 ep_ro) 49 { 50 return (u32)(((u64) prandom_u32() * ep_ro) >> 32); 51 } 52 53 /* 54 * Handle minimum values for seeds 55 */ 56 static inline u32 __seed(u32 x, u32 m) 57 { 58 return (x < m) ? x + m : x; 59 } 60 61 /** 62 * prandom_seed_state - set seed for prandom_u32_state(). 63 * @state: pointer to state structure to receive the seed. 64 * @seed: arbitrary 64-bit value to use as a seed. 65 */ 66 static inline void prandom_seed_state(struct rnd_state *state, u64 seed) 67 { 68 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; 69 70 state->s1 = __seed(i, 2U); 71 state->s2 = __seed(i, 8U); 72 state->s3 = __seed(i, 16U); 73 state->s4 = __seed(i, 128U); 74 } 75 76 /* Pseudo random number generator from numerical recipes. */ 77 static inline u32 next_pseudo_random32(u32 seed) 78 { 79 return seed * 1664525 + 1013904223; 80 } 81 82 #endif 83