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
16struct rnd_state {
17 __u32 s1, s2, s3, s4;
18};
19
20u32 prandom_u32_state(struct rnd_state *state);
21void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
22void 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 */
30static 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 */
40static 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(x: i, m: 2U);
45 state->s2 = __seed(x: i, m: 8U);
46 state->s3 = __seed(x: i, m: 16U);
47 state->s4 = __seed(x: i, m: 128U);
48}
49
50/* Pseudo random number generator from numerical recipes. */
51static inline u32 next_pseudo_random32(u32 seed)
52{
53 return seed * 1664525 + 1013904223;
54}
55
56#endif
57