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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __TOOLS_LINUX_PRANDOM_H
3#define __TOOLS_LINUX_PRANDOM_H
4
5#include <linux/types.h>
6
7struct rnd_state {
8 __u32 s1, s2, s3, s4;
9};
10
11/*
12 * Handle minimum values for seeds
13 */
14static inline u32 __seed(u32 x, u32 m)
15{
16 return (x < m) ? x + m : x;
17}
18
19/**
20 * prandom_seed_state - set seed for prandom_u32_state().
21 * @state: pointer to state structure to receive the seed.
22 * @seed: arbitrary 64-bit value to use as a seed.
23 */
24static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
25{
26 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
27
28 state->s1 = __seed(i, 2U);
29 state->s2 = __seed(i, 8U);
30 state->s3 = __seed(i, 16U);
31 state->s4 = __seed(i, 128U);
32}
33
34/**
35 * prandom_u32_state - seeded pseudo-random number generator.
36 * @state: pointer to state structure holding seeded state.
37 *
38 * This is used for pseudo-randomness with no outside seeding.
39 * For more random results, use get_random_u32().
40 */
41static inline u32 prandom_u32_state(struct rnd_state *state)
42{
43#define TAUSWORTHE(s, a, b, c, d) (((s & c) << d) ^ (((s << a) ^ s) >> b))
44 state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U);
45 state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U);
46 state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U);
47 state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U);
48
49 return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
50}
51#endif // __TOOLS_LINUX_PRANDOM_H