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
prandom_u32(void)15 static inline u32 prandom_u32(void)
16 {
17 return get_random_u32();
18 }
19
prandom_bytes(void * buf,size_t nbytes)20 static inline void prandom_bytes(void *buf, size_t nbytes)
21 {
22 return get_random_bytes(buf, nbytes);
23 }
24
25 struct rnd_state {
26 __u32 s1, s2, s3, s4;
27 };
28
29 u32 prandom_u32_state(struct rnd_state *state);
30 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
31 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
32
33 #define prandom_init_once(pcpu_state) \
34 DO_ONCE(prandom_seed_full_state, (pcpu_state))
35
36 /**
37 * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro)
38 * @ep_ro: right open interval endpoint
39 *
40 * Returns a pseudo-random number that is in interval [0, ep_ro). Note
41 * that the result depends on PRNG being well distributed in [0, ~0U]
42 * u32 space. Here we use maximally equidistributed combined Tausworthe
43 * generator, that is, prandom_u32(). This is useful when requesting a
44 * random index of an array containing ep_ro elements, for example.
45 *
46 * Returns: pseudo-random number in interval [0, ep_ro)
47 */
prandom_u32_max(u32 ep_ro)48 static inline u32 prandom_u32_max(u32 ep_ro)
49 {
50 return (u32)(((u64) prandom_u32() * ep_ro) >> 32);
51 }
52
53 /*
54 * Handle minimum values for seeds
55 */
__seed(u32 x,u32 m)56 static inline u32 __seed(u32 x, u32 m)
57 {
58 return (x < m) ? x + m : x;
59 }
60
61 /**
62 * prandom_seed_state - set seed for prandom_u32_state().
63 * @state: pointer to state structure to receive the seed.
64 * @seed: arbitrary 64-bit value to use as a seed.
65 */
prandom_seed_state(struct rnd_state * state,u64 seed)66 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
67 {
68 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
69
70 state->s1 = __seed(i, 2U);
71 state->s2 = __seed(i, 8U);
72 state->s3 = __seed(i, 16U);
73 state->s4 = __seed(i, 128U);
74 }
75
76 /* Pseudo random number generator from numerical recipes. */
next_pseudo_random32(u32 seed)77 static inline u32 next_pseudo_random32(u32 seed)
78 {
79 return seed * 1664525 + 1013904223;
80 }
81
82 #endif
83