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/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 /*
27 * Handle minimum values for seeds
28 */
29 static inline u32 __seed(u32 x, u32 m)
30 {
31 return (x < m) ? x + m : x;
32 }
33
34 /**
35 * prandom_seed_state - set seed for prandom_u32_state().
36 * @state: pointer to state structure to receive the seed.
37 * @seed: arbitrary 64-bit value to use as a seed.
38 */
39 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
40 {
41 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
42
43 state->s1 = __seed(i, 2U);
44 state->s2 = __seed(i, 8U);
45 state->s3 = __seed(i, 16U);
46 state->s4 = __seed(i, 128U);
47 }
48
49 /* Pseudo random number generator from numerical recipes. */
50 static inline u32 next_pseudo_random32(u32 seed)
51 {
52 return seed * 1664525 + 1013904223;
53 }
54
55 #endif
56
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