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 struct rnd_state {
16 __u32 s1, s2, s3, s4;
17 };
18
19 u32 prandom_u32_state(struct rnd_state *state);
20 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
21 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
22
23 #define prandom_init_once(pcpu_state) \
24 DO_ONCE(prandom_seed_full_state, (pcpu_state))
25
26 /* Deprecated: use get_random_u32_below() instead. */
prandom_u32_max(u32 ep_ro)27 static inline u32 prandom_u32_max(u32 ep_ro)
28 {
29 return get_random_u32_below(ep_ro);
30 }
31
32 /*
33 * Handle minimum values for seeds
34 */
__seed(u32 x,u32 m)35 static inline u32 __seed(u32 x, u32 m)
36 {
37 return (x < m) ? x + m : x;
38 }
39
40 /**
41 * prandom_seed_state - set seed for prandom_u32_state().
42 * @state: pointer to state structure to receive the seed.
43 * @seed: arbitrary 64-bit value to use as a seed.
44 */
prandom_seed_state(struct rnd_state * state,u64 seed)45 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
46 {
47 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
48
49 state->s1 = __seed(i, 2U);
50 state->s2 = __seed(i, 8U);
51 state->s3 = __seed(i, 16U);
52 state->s4 = __seed(i, 128U);
53 }
54
55 /* Pseudo random number generator from numerical recipes. */
next_pseudo_random32(u32 seed)56 static inline u32 next_pseudo_random32(u32 seed)
57 {
58 return seed * 1664525 + 1013904223;
59 }
60
61 #endif
62