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 */
__seed(u32 x,u32 m)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 */
prandom_seed_state(struct rnd_state * state,u64 seed)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. */
next_pseudo_random32(u32 seed)51 static inline u32 next_pseudo_random32(u32 seed)
52 {
53 return seed * 1664525 + 1013904223;
54 }
55
56 #endif
57