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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> | |
13 | ||
14 | u32 prandom_u32(void); | |
15 | void prandom_bytes(void *buf, size_t nbytes); | |
16 | void prandom_seed(u32 seed); | |
17 | void prandom_reseed_late(void); | |
18 | ||
3744741a WT |
19 | DECLARE_PER_CPU(unsigned long, net_rand_noise); |
20 | ||
21 | #define PRANDOM_ADD_NOISE(a, b, c, d) \ | |
22 | prandom_u32_add_noise((unsigned long)(a), (unsigned long)(b), \ | |
23 | (unsigned long)(c), (unsigned long)(d)) | |
24 | ||
c51f8f88 GS |
25 | #if BITS_PER_LONG == 64 |
26 | /* | |
27 | * The core SipHash round function. Each line can be executed in | |
28 | * parallel given enough CPU resources. | |
29 | */ | |
30 | #define PRND_SIPROUND(v0, v1, v2, v3) ( \ | |
31 | v0 += v1, v1 = rol64(v1, 13), v2 += v3, v3 = rol64(v3, 16), \ | |
32 | v1 ^= v0, v0 = rol64(v0, 32), v3 ^= v2, \ | |
33 | v0 += v3, v3 = rol64(v3, 21), v2 += v1, v1 = rol64(v1, 17), \ | |
34 | v3 ^= v0, v1 ^= v2, v2 = rol64(v2, 32) \ | |
35 | ) | |
36 | ||
37 | #define PRND_K0 (0x736f6d6570736575 ^ 0x6c7967656e657261) | |
38 | #define PRND_K1 (0x646f72616e646f6d ^ 0x7465646279746573) | |
39 | ||
40 | #elif BITS_PER_LONG == 32 | |
41 | /* | |
42 | * On 32-bit machines, we use HSipHash, a reduced-width version of SipHash. | |
43 | * This is weaker, but 32-bit machines are not used for high-traffic | |
44 | * applications, so there is less output for an attacker to analyze. | |
45 | */ | |
46 | #define PRND_SIPROUND(v0, v1, v2, v3) ( \ | |
47 | v0 += v1, v1 = rol32(v1, 5), v2 += v3, v3 = rol32(v3, 8), \ | |
48 | v1 ^= v0, v0 = rol32(v0, 16), v3 ^= v2, \ | |
49 | v0 += v3, v3 = rol32(v3, 7), v2 += v1, v1 = rol32(v1, 13), \ | |
50 | v3 ^= v0, v1 ^= v2, v2 = rol32(v2, 16) \ | |
51 | ) | |
52 | #define PRND_K0 0x6c796765 | |
53 | #define PRND_K1 0x74656462 | |
54 | ||
55 | #else | |
56 | #error Unsupported BITS_PER_LONG | |
57 | #endif | |
58 | ||
3744741a WT |
59 | static inline void prandom_u32_add_noise(unsigned long a, unsigned long b, |
60 | unsigned long c, unsigned long d) | |
61 | { | |
62 | /* | |
63 | * This is not used cryptographically; it's just | |
64 | * a convenient 4-word hash function. (3 xor, 2 add, 2 rol) | |
65 | */ | |
66 | a ^= raw_cpu_read(net_rand_noise); | |
67 | PRND_SIPROUND(a, b, c, d); | |
68 | raw_cpu_write(net_rand_noise, d); | |
69 | } | |
70 | ||
c0842fbc LT |
71 | struct rnd_state { |
72 | __u32 s1, s2, s3, s4; | |
73 | }; | |
74 | ||
c0842fbc LT |
75 | u32 prandom_u32_state(struct rnd_state *state); |
76 | void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); | |
77 | void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); | |
78 | ||
79 | #define prandom_init_once(pcpu_state) \ | |
80 | DO_ONCE(prandom_seed_full_state, (pcpu_state)) | |
81 | ||
82 | /** | |
83 | * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro) | |
84 | * @ep_ro: right open interval endpoint | |
85 | * | |
86 | * Returns a pseudo-random number that is in interval [0, ep_ro). Note | |
87 | * that the result depends on PRNG being well distributed in [0, ~0U] | |
88 | * u32 space. Here we use maximally equidistributed combined Tausworthe | |
89 | * generator, that is, prandom_u32(). This is useful when requesting a | |
90 | * random index of an array containing ep_ro elements, for example. | |
91 | * | |
92 | * Returns: pseudo-random number in interval [0, ep_ro) | |
93 | */ | |
94 | static inline u32 prandom_u32_max(u32 ep_ro) | |
95 | { | |
96 | return (u32)(((u64) prandom_u32() * ep_ro) >> 32); | |
97 | } | |
98 | ||
99 | /* | |
100 | * Handle minimum values for seeds | |
101 | */ | |
102 | static inline u32 __seed(u32 x, u32 m) | |
103 | { | |
104 | return (x < m) ? x + m : x; | |
105 | } | |
106 | ||
107 | /** | |
108 | * prandom_seed_state - set seed for prandom_u32_state(). | |
109 | * @state: pointer to state structure to receive the seed. | |
110 | * @seed: arbitrary 64-bit value to use as a seed. | |
111 | */ | |
112 | static inline void prandom_seed_state(struct rnd_state *state, u64 seed) | |
113 | { | |
114 | u32 i = (seed >> 32) ^ (seed << 10) ^ seed; | |
115 | ||
116 | state->s1 = __seed(i, 2U); | |
117 | state->s2 = __seed(i, 8U); | |
118 | state->s3 = __seed(i, 16U); | |
119 | state->s4 = __seed(i, 128U); | |
3744741a | 120 | PRANDOM_ADD_NOISE(state, i, 0, 0); |
c0842fbc LT |
121 | } |
122 | ||
123 | /* Pseudo random number generator from numerical recipes. */ | |
124 | static inline u32 next_pseudo_random32(u32 seed) | |
125 | { | |
126 | return seed * 1664525 + 1013904223; | |
127 | } | |
128 | ||
129 | #endif |