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