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
7 struct rnd_state {
8 __u32 s1, s2, s3, s4;
9 };
10
11 /*
12 * Handle minimum values for seeds
13 */
__seed(u32 x,u32 m)14 static 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 */
prandom_seed_state(struct rnd_state * state,u64 seed)24 static 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 */
prandom_u32_state(struct rnd_state * state)41 static 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
52