Root/
1 | /* |
2 | This is a maximally equidistributed combined Tausworthe generator |
3 | based on code from GNU Scientific Library 1.5 (30 Jun 2004) |
4 | |
5 | x_n = (s1_n ^ s2_n ^ s3_n) |
6 | |
7 | s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19)) |
8 | s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25)) |
9 | s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11)) |
10 | |
11 | The period of this generator is about 2^88. |
12 | |
13 | From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe |
14 | Generators", Mathematics of Computation, 65, 213 (1996), 203--213. |
15 | |
16 | This is available on the net from L'Ecuyer's home page, |
17 | |
18 | http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps |
19 | ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps |
20 | |
21 | There is an erratum in the paper "Tables of Maximally |
22 | Equidistributed Combined LFSR Generators", Mathematics of |
23 | Computation, 68, 225 (1999), 261--269: |
24 | http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps |
25 | |
26 | ... the k_j most significant bits of z_j must be non- |
27 | zero, for each j. (Note: this restriction also applies to the |
28 | computer code given in [4], but was mistakenly not mentioned in |
29 | that paper.) |
30 | |
31 | This affects the seeding procedure by imposing the requirement |
32 | s1 > 1, s2 > 7, s3 > 15. |
33 | |
34 | */ |
35 | |
36 | #include <linux/types.h> |
37 | #include <linux/percpu.h> |
38 | #include <linux/module.h> |
39 | #include <linux/jiffies.h> |
40 | #include <linux/random.h> |
41 | |
42 | struct rnd_state { |
43 | u32 s1, s2, s3; |
44 | }; |
45 | |
46 | static DEFINE_PER_CPU(struct rnd_state, net_rand_state); |
47 | |
48 | static u32 __random32(struct rnd_state *state) |
49 | { |
50 | #define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b) |
51 | |
52 | state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12); |
53 | state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4); |
54 | state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17); |
55 | |
56 | return (state->s1 ^ state->s2 ^ state->s3); |
57 | } |
58 | |
59 | /* |
60 | * Handle minimum values for seeds |
61 | */ |
62 | static inline u32 __seed(u32 x, u32 m) |
63 | { |
64 | return (x < m) ? x + m : x; |
65 | } |
66 | |
67 | /** |
68 | * random32 - pseudo random number generator |
69 | * |
70 | * A 32 bit pseudo-random number is generated using a fast |
71 | * algorithm suitable for simulation. This algorithm is NOT |
72 | * considered safe for cryptographic use. |
73 | */ |
74 | u32 random32(void) |
75 | { |
76 | unsigned long r; |
77 | struct rnd_state *state = &get_cpu_var(net_rand_state); |
78 | r = __random32(state); |
79 | put_cpu_var(state); |
80 | return r; |
81 | } |
82 | EXPORT_SYMBOL(random32); |
83 | |
84 | /** |
85 | * srandom32 - add entropy to pseudo random number generator |
86 | * @seed: seed value |
87 | * |
88 | * Add some additional seeding to the random32() pool. |
89 | */ |
90 | void srandom32(u32 entropy) |
91 | { |
92 | int i; |
93 | /* |
94 | * No locking on the CPUs, but then somewhat random results are, well, |
95 | * expected. |
96 | */ |
97 | for_each_possible_cpu (i) { |
98 | struct rnd_state *state = &per_cpu(net_rand_state, i); |
99 | state->s1 = __seed(state->s1 ^ entropy, 1); |
100 | } |
101 | } |
102 | EXPORT_SYMBOL(srandom32); |
103 | |
104 | /* |
105 | * Generate some initially weak seeding values to allow |
106 | * to start the random32() engine. |
107 | */ |
108 | static int __init random32_init(void) |
109 | { |
110 | int i; |
111 | |
112 | for_each_possible_cpu(i) { |
113 | struct rnd_state *state = &per_cpu(net_rand_state,i); |
114 | |
115 | #define LCG(x) ((x) * 69069) /* super-duper LCG */ |
116 | state->s1 = __seed(LCG(i + jiffies), 1); |
117 | state->s2 = __seed(LCG(state->s1), 7); |
118 | state->s3 = __seed(LCG(state->s2), 15); |
119 | |
120 | /* "warm it up" */ |
121 | __random32(state); |
122 | __random32(state); |
123 | __random32(state); |
124 | __random32(state); |
125 | __random32(state); |
126 | __random32(state); |
127 | } |
128 | return 0; |
129 | } |
130 | core_initcall(random32_init); |
131 | |
132 | /* |
133 | * Generate better values after random number generator |
134 | * is fully initalized. |
135 | */ |
136 | static int __init random32_reseed(void) |
137 | { |
138 | int i; |
139 | |
140 | for_each_possible_cpu(i) { |
141 | struct rnd_state *state = &per_cpu(net_rand_state,i); |
142 | u32 seeds[3]; |
143 | |
144 | get_random_bytes(&seeds, sizeof(seeds)); |
145 | state->s1 = __seed(seeds[0], 1); |
146 | state->s2 = __seed(seeds[1], 7); |
147 | state->s3 = __seed(seeds[2], 15); |
148 | |
149 | /* mix it in */ |
150 | __random32(state); |
151 | } |
152 | return 0; |
153 | } |
154 | late_initcall(random32_reseed); |
155 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9