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 /* Deprecated: use get_random_u32 instead. */ 16 static inline u32 prandom_u32(void) 17 { 18 return get_random_u32(); 19 } 20 21 /* Deprecated: use get_random_bytes instead. */ 22 static inline void prandom_bytes(void *buf, size_t nbytes) 23 { 24 return get_random_bytes(buf, nbytes); 25 } 26 27 struct rnd_state { 28 __u32 s1, s2, s3, s4; 29 }; 30 31 u32 prandom_u32_state(struct rnd_state *state); 32 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); 33 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); 34 35 #define prandom_init_once(pcpu_state) \ 36 DO_ONCE(prandom_seed_full_state, (pcpu_state)) 37 38 /** 39 * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro) 40 * @ep_ro: right open interval endpoint 41 * 42 * Returns a pseudo-random number that is in interval [0, ep_ro). This is 43 * useful when requesting a random index of an array containing ep_ro elements, 44 * for example. The result is somewhat biased when ep_ro is not a power of 2, 45 * so do not use this for cryptographic purposes. 46 * 47 * Returns: pseudo-random number in interval [0, ep_ro) 48 */ 49 static inline u32 prandom_u32_max(u32 ep_ro) 50 { 51 if (__builtin_constant_p(ep_ro <= 1U << 8) && ep_ro <= 1U << 8) 52 return (get_random_u8() * ep_ro) >> 8; 53 if (__builtin_constant_p(ep_ro <= 1U << 16) && ep_ro <= 1U << 16) 54 return (get_random_u16() * ep_ro) >> 16; 55 return ((u64)get_random_u32() * ep_ro) >> 32; 56 } 57 58 /* 59 * Handle minimum values for seeds 60 */ 61 static inline u32 __seed(u32 x, u32 m) 62 { 63 return (x < m) ? x + m : x; 64 } 65 66 /** 67 * prandom_seed_state - set seed for prandom_u32_state(). 68 * @state: pointer to state structure to receive the seed. 69 * @seed: arbitrary 64-bit value to use as a seed. 70 */ 71 static inline void prandom_seed_state(struct rnd_state *state, u64 seed) 72 { 73 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; 74 75 state->s1 = __seed(i, 2U); 76 state->s2 = __seed(i, 8U); 77 state->s3 = __seed(i, 16U); 78 state->s4 = __seed(i, 128U); 79 } 80 81 /* Pseudo random number generator from numerical recipes. */ 82 static inline u32 next_pseudo_random32(u32 seed) 83 { 84 return seed * 1664525 + 1013904223; 85 } 86 87 #endif 88