| 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 |