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c0842fbc LT |
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> | |
d4150779 | 13 | #include <linux/random.h> |
c0842fbc | 14 | |
d4150779 JD |
15 | static inline u32 prandom_u32(void) |
16 | { | |
17 | return get_random_u32(); | |
18 | } | |
c51f8f88 | 19 | |
d4150779 | 20 | static inline void prandom_bytes(void *buf, size_t nbytes) |
3744741a | 21 | { |
d4150779 | 22 | return get_random_bytes(buf, nbytes); |
3744741a WT |
23 | } |
24 | ||
c0842fbc LT |
25 | struct rnd_state { |
26 | __u32 s1, s2, s3, s4; | |
27 | }; | |
28 | ||
c0842fbc LT |
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 | */ | |
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 | */ | |
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 | */ | |
66 | static inline void prandom_seed_state(struct rnd_state *state, u64 seed) | |
67 | { | |
d327ea15 | 68 | u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; |
c0842fbc LT |
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. */ | |
77 | static inline u32 next_pseudo_random32(u32 seed) | |
78 | { | |
79 | return seed * 1664525 + 1013904223; | |
80 | } | |
81 | ||
82 | #endif |