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1da177e4 LT |
1 | /* |
2 | * Generic address resultion entity | |
3 | * | |
4 | * Authors: | |
5 | * net_random Alan Cox | |
6 | * net_ratelimit Andy Kleen | |
7 | * | |
8 | * Created by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> | |
9 | * | |
10 | * This program is free software; you can redistribute it and/or | |
11 | * modify it under the terms of the GNU General Public License | |
12 | * as published by the Free Software Foundation; either version | |
13 | * 2 of the License, or (at your option) any later version. | |
14 | */ | |
15 | ||
16 | #include <linux/module.h> | |
17 | #include <linux/jiffies.h> | |
18 | #include <linux/kernel.h> | |
19 | #include <linux/mm.h> | |
20 | #include <linux/string.h> | |
21 | #include <linux/types.h> | |
22 | #include <linux/random.h> | |
23 | #include <linux/percpu.h> | |
24 | #include <linux/init.h> | |
25 | ||
26 | #include <asm/system.h> | |
27 | #include <asm/uaccess.h> | |
28 | ||
29 | ||
30 | /* | |
31 | This is a maximally equidistributed combined Tausworthe generator | |
32 | based on code from GNU Scientific Library 1.5 (30 Jun 2004) | |
33 | ||
34 | x_n = (s1_n ^ s2_n ^ s3_n) | |
35 | ||
36 | s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19)) | |
37 | s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25)) | |
38 | s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11)) | |
39 | ||
40 | The period of this generator is about 2^88. | |
41 | ||
42 | From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe | |
43 | Generators", Mathematics of Computation, 65, 213 (1996), 203--213. | |
44 | ||
45 | This is available on the net from L'Ecuyer's home page, | |
46 | ||
47 | http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps | |
48 | ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps | |
49 | ||
50 | There is an erratum in the paper "Tables of Maximally | |
51 | Equidistributed Combined LFSR Generators", Mathematics of | |
52 | Computation, 68, 225 (1999), 261--269: | |
53 | http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps | |
54 | ||
55 | ... the k_j most significant bits of z_j must be non- | |
56 | zero, for each j. (Note: this restriction also applies to the | |
57 | computer code given in [4], but was mistakenly not mentioned in | |
58 | that paper.) | |
59 | ||
60 | This affects the seeding procedure by imposing the requirement | |
61 | s1 > 1, s2 > 7, s3 > 15. | |
62 | ||
63 | */ | |
64 | struct nrnd_state { | |
65 | u32 s1, s2, s3; | |
66 | }; | |
67 | ||
68 | static DEFINE_PER_CPU(struct nrnd_state, net_rand_state); | |
69 | ||
70 | static u32 __net_random(struct nrnd_state *state) | |
71 | { | |
72 | #define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b) | |
73 | ||
74 | state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12); | |
75 | state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4); | |
76 | state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17); | |
77 | ||
78 | return (state->s1 ^ state->s2 ^ state->s3); | |
79 | } | |
80 | ||
81 | static void __net_srandom(struct nrnd_state *state, unsigned long s) | |
82 | { | |
83 | if (s == 0) | |
84 | s = 1; /* default seed is 1 */ | |
85 | ||
86 | #define LCG(n) (69069 * n) | |
87 | state->s1 = LCG(s); | |
88 | state->s2 = LCG(state->s1); | |
89 | state->s3 = LCG(state->s2); | |
90 | ||
91 | /* "warm it up" */ | |
92 | __net_random(state); | |
93 | __net_random(state); | |
94 | __net_random(state); | |
95 | __net_random(state); | |
96 | __net_random(state); | |
97 | __net_random(state); | |
98 | } | |
99 | ||
100 | ||
101 | unsigned long net_random(void) | |
102 | { | |
103 | unsigned long r; | |
104 | struct nrnd_state *state = &get_cpu_var(net_rand_state); | |
105 | r = __net_random(state); | |
106 | put_cpu_var(state); | |
107 | return r; | |
108 | } | |
109 | ||
110 | ||
111 | void net_srandom(unsigned long entropy) | |
112 | { | |
113 | struct nrnd_state *state = &get_cpu_var(net_rand_state); | |
114 | __net_srandom(state, state->s1^entropy); | |
115 | put_cpu_var(state); | |
116 | } | |
117 | ||
118 | void __init net_random_init(void) | |
119 | { | |
120 | int i; | |
121 | ||
122 | for (i = 0; i < NR_CPUS; i++) { | |
123 | struct nrnd_state *state = &per_cpu(net_rand_state,i); | |
124 | __net_srandom(state, i+jiffies); | |
125 | } | |
126 | } | |
127 | ||
128 | static int net_random_reseed(void) | |
129 | { | |
130 | int i; | |
131 | unsigned long seed[NR_CPUS]; | |
132 | ||
133 | get_random_bytes(seed, sizeof(seed)); | |
134 | for (i = 0; i < NR_CPUS; i++) { | |
135 | struct nrnd_state *state = &per_cpu(net_rand_state,i); | |
136 | __net_srandom(state, seed[i]); | |
137 | } | |
138 | return 0; | |
139 | } | |
140 | late_initcall(net_random_reseed); | |
141 | ||
142 | int net_msg_cost = 5*HZ; | |
143 | int net_msg_burst = 10; | |
144 | ||
145 | /* | |
146 | * All net warning printk()s should be guarded by this function. | |
147 | */ | |
148 | int net_ratelimit(void) | |
149 | { | |
150 | return __printk_ratelimit(net_msg_cost, net_msg_burst); | |
151 | } | |
152 | ||
153 | EXPORT_SYMBOL(net_random); | |
154 | EXPORT_SYMBOL(net_ratelimit); | |
155 | EXPORT_SYMBOL(net_srandom); |