1 /* SPDX-License-Identifier: GPL-2.0 */ 1 /* SPDX-License-Identifier: GPL-2.0 */
2 /* 2 /*
3 * include/linux/prandom.h 3 * include/linux/prandom.h
4 * 4 *
5 * Include file for the fast pseudo-random 32- 5 * Include file for the fast pseudo-random 32-bit
6 * generation. 6 * generation.
7 */ 7 */
8 #ifndef _LINUX_PRANDOM_H 8 #ifndef _LINUX_PRANDOM_H
9 #define _LINUX_PRANDOM_H 9 #define _LINUX_PRANDOM_H
10 10
11 #include <linux/types.h> 11 #include <linux/types.h>
12 #include <linux/once.h> !! 12 #include <linux/percpu.h>
13 #include <linux/random.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
>> 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
>> 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
>> 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 }
14 70
15 struct rnd_state { 71 struct rnd_state {
16 __u32 s1, s2, s3, s4; 72 __u32 s1, s2, s3, s4;
17 }; 73 };
18 74
19 u32 prandom_u32_state(struct rnd_state *state) 75 u32 prandom_u32_state(struct rnd_state *state);
20 void prandom_bytes_state(struct rnd_state *sta 76 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
21 void prandom_seed_full_state(struct rnd_state 77 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
22 78
23 #define prandom_init_once(pcpu_state) 79 #define prandom_init_once(pcpu_state) \
24 DO_ONCE(prandom_seed_full_state, (pcpu 80 DO_ONCE(prandom_seed_full_state, (pcpu_state))
25 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
26 /* 99 /*
27 * Handle minimum values for seeds 100 * Handle minimum values for seeds
28 */ 101 */
29 static inline u32 __seed(u32 x, u32 m) 102 static inline u32 __seed(u32 x, u32 m)
30 { 103 {
31 return (x < m) ? x + m : x; 104 return (x < m) ? x + m : x;
32 } 105 }
33 106
34 /** 107 /**
35 * prandom_seed_state - set seed for prandom_u 108 * prandom_seed_state - set seed for prandom_u32_state().
36 * @state: pointer to state structure to recei 109 * @state: pointer to state structure to receive the seed.
37 * @seed: arbitrary 64-bit value to use as a s 110 * @seed: arbitrary 64-bit value to use as a seed.
38 */ 111 */
39 static inline void prandom_seed_state(struct r 112 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
40 { 113 {
41 u32 i = ((seed >> 32) ^ (seed << 10) ^ 114 u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
42 115
43 state->s1 = __seed(i, 2U); 116 state->s1 = __seed(i, 2U);
44 state->s2 = __seed(i, 8U); 117 state->s2 = __seed(i, 8U);
45 state->s3 = __seed(i, 16U); 118 state->s3 = __seed(i, 16U);
46 state->s4 = __seed(i, 128U); 119 state->s4 = __seed(i, 128U);
>> 120 PRANDOM_ADD_NOISE(state, i, 0, 0);
47 } 121 }
48 122
49 /* Pseudo random number generator from numeric 123 /* Pseudo random number generator from numerical recipes. */
50 static inline u32 next_pseudo_random32(u32 see 124 static inline u32 next_pseudo_random32(u32 seed)
51 { 125 {
52 return seed * 1664525 + 1013904223; 126 return seed * 1664525 + 1013904223;
53 } 127 }
54 128
55 #endif 129 #endif
56 130
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