1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * This is a maximally equidistributed combined Tausworthe generator |
4 | * based on code from GNU Scientific Library 1.5 (30 Jun 2004) |
5 | * |
6 | * lfsr113 version: |
7 | * |
8 | * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n) |
9 | * |
10 | * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13)) |
11 | * s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27)) |
12 | * s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21)) |
13 | * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12)) |
14 | * |
15 | * The period of this generator is about 2^113 (see erratum paper). |
16 | * |
17 | * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe |
18 | * Generators", Mathematics of Computation, 65, 213 (1996), 203--213: |
19 | * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps |
20 | * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps |
21 | * |
22 | * There is an erratum in the paper "Tables of Maximally Equidistributed |
23 | * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999), |
24 | * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps |
25 | * |
26 | * ... the k_j most significant bits of z_j must be non-zero, |
27 | * for each j. (Note: this restriction also applies to the |
28 | * computer code given in [4], but was mistakenly not mentioned |
29 | * in that paper.) |
30 | * |
31 | * This affects the seeding procedure by imposing the requirement |
32 | * s1 > 1, s2 > 7, s3 > 15, s4 > 127. |
33 | */ |
34 | |
35 | #include <linux/types.h> |
36 | #include <linux/percpu.h> |
37 | #include <linux/export.h> |
38 | #include <linux/jiffies.h> |
39 | #include <linux/random.h> |
40 | #include <linux/sched.h> |
41 | #include <linux/bitops.h> |
42 | #include <linux/slab.h> |
43 | #include <asm/unaligned.h> |
44 | |
45 | /** |
46 | * prandom_u32_state - seeded pseudo-random number generator. |
47 | * @state: pointer to state structure holding seeded state. |
48 | * |
49 | * This is used for pseudo-randomness with no outside seeding. |
50 | * For more random results, use get_random_u32(). |
51 | */ |
52 | u32 prandom_u32_state(struct rnd_state *state) |
53 | { |
54 | #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) |
55 | state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); |
56 | state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); |
57 | state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); |
58 | state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); |
59 | |
60 | return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); |
61 | } |
62 | EXPORT_SYMBOL(prandom_u32_state); |
63 | |
64 | /** |
65 | * prandom_bytes_state - get the requested number of pseudo-random bytes |
66 | * |
67 | * @state: pointer to state structure holding seeded state. |
68 | * @buf: where to copy the pseudo-random bytes to |
69 | * @bytes: the requested number of bytes |
70 | * |
71 | * This is used for pseudo-randomness with no outside seeding. |
72 | * For more random results, use get_random_bytes(). |
73 | */ |
74 | void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes) |
75 | { |
76 | u8 *ptr = buf; |
77 | |
78 | while (bytes >= sizeof(u32)) { |
79 | put_unaligned(prandom_u32_state(state), (u32 *) ptr); |
80 | ptr += sizeof(u32); |
81 | bytes -= sizeof(u32); |
82 | } |
83 | |
84 | if (bytes > 0) { |
85 | u32 rem = prandom_u32_state(state); |
86 | do { |
87 | *ptr++ = (u8) rem; |
88 | bytes--; |
89 | rem >>= BITS_PER_BYTE; |
90 | } while (bytes > 0); |
91 | } |
92 | } |
93 | EXPORT_SYMBOL(prandom_bytes_state); |
94 | |
95 | static void prandom_warmup(struct rnd_state *state) |
96 | { |
97 | /* Calling RNG ten times to satisfy recurrence condition */ |
98 | prandom_u32_state(state); |
99 | prandom_u32_state(state); |
100 | prandom_u32_state(state); |
101 | prandom_u32_state(state); |
102 | prandom_u32_state(state); |
103 | prandom_u32_state(state); |
104 | prandom_u32_state(state); |
105 | prandom_u32_state(state); |
106 | prandom_u32_state(state); |
107 | prandom_u32_state(state); |
108 | } |
109 | |
110 | void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state) |
111 | { |
112 | int i; |
113 | |
114 | for_each_possible_cpu(i) { |
115 | struct rnd_state *state = per_cpu_ptr(pcpu_state, i); |
116 | u32 seeds[4]; |
117 | |
118 | get_random_bytes(buf: &seeds, len: sizeof(seeds)); |
119 | state->s1 = __seed(x: seeds[0], m: 2U); |
120 | state->s2 = __seed(x: seeds[1], m: 8U); |
121 | state->s3 = __seed(x: seeds[2], m: 16U); |
122 | state->s4 = __seed(x: seeds[3], m: 128U); |
123 | |
124 | prandom_warmup(state); |
125 | } |
126 | } |
127 | EXPORT_SYMBOL(prandom_seed_full_state); |
128 | |
129 | #ifdef CONFIG_RANDOM32_SELFTEST |
130 | static struct prandom_test1 { |
131 | u32 seed; |
132 | u32 result; |
133 | } test1[] = { |
134 | { 1U, 3484351685U }, |
135 | { 2U, 2623130059U }, |
136 | { 3U, 3125133893U }, |
137 | { 4U, 984847254U }, |
138 | }; |
139 | |
140 | static struct prandom_test2 { |
141 | u32 seed; |
142 | u32 iteration; |
143 | u32 result; |
144 | } test2[] = { |
145 | /* Test cases against taus113 from GSL library. */ |
146 | { 931557656U, 959U, 2975593782U }, |
147 | { 1339693295U, 876U, 3887776532U }, |
148 | { 1545556285U, 961U, 1615538833U }, |
149 | { 601730776U, 723U, 1776162651U }, |
150 | { 1027516047U, 687U, 511983079U }, |
151 | { 416526298U, 700U, 916156552U }, |
152 | { 1395522032U, 652U, 2222063676U }, |
153 | { 366221443U, 617U, 2992857763U }, |
154 | { 1539836965U, 714U, 3783265725U }, |
155 | { 556206671U, 994U, 799626459U }, |
156 | { 684907218U, 799U, 367789491U }, |
157 | { 2121230701U, 931U, 2115467001U }, |
158 | { 1668516451U, 644U, 3620590685U }, |
159 | { 768046066U, 883U, 2034077390U }, |
160 | { 1989159136U, 833U, 1195767305U }, |
161 | { 536585145U, 996U, 3577259204U }, |
162 | { 1008129373U, 642U, 1478080776U }, |
163 | { 1740775604U, 939U, 1264980372U }, |
164 | { 1967883163U, 508U, 10734624U }, |
165 | { 1923019697U, 730U, 3821419629U }, |
166 | { 442079932U, 560U, 3440032343U }, |
167 | { 1961302714U, 845U, 841962572U }, |
168 | { 2030205964U, 962U, 1325144227U }, |
169 | { 1160407529U, 507U, 240940858U }, |
170 | { 635482502U, 779U, 4200489746U }, |
171 | { 1252788931U, 699U, 867195434U }, |
172 | { 1961817131U, 719U, 668237657U }, |
173 | { 1071468216U, 983U, 917876630U }, |
174 | { 1281848367U, 932U, 1003100039U }, |
175 | { 582537119U, 780U, 1127273778U }, |
176 | { 1973672777U, 853U, 1071368872U }, |
177 | { 1896756996U, 762U, 1127851055U }, |
178 | { 847917054U, 500U, 1717499075U }, |
179 | { 1240520510U, 951U, 2849576657U }, |
180 | { 1685071682U, 567U, 1961810396U }, |
181 | { 1516232129U, 557U, 3173877U }, |
182 | { 1208118903U, 612U, 1613145022U }, |
183 | { 1817269927U, 693U, 4279122573U }, |
184 | { 1510091701U, 717U, 638191229U }, |
185 | { 365916850U, 807U, 600424314U }, |
186 | { 399324359U, 702U, 1803598116U }, |
187 | { 1318480274U, 779U, 2074237022U }, |
188 | { 697758115U, 840U, 1483639402U }, |
189 | { 1696507773U, 840U, 577415447U }, |
190 | { 2081979121U, 981U, 3041486449U }, |
191 | { 955646687U, 742U, 3846494357U }, |
192 | { 1250683506U, 749U, 836419859U }, |
193 | { 595003102U, 534U, 366794109U }, |
194 | { 47485338U, 558U, 3521120834U }, |
195 | { 619433479U, 610U, 3991783875U }, |
196 | { 704096520U, 518U, 4139493852U }, |
197 | { 1712224984U, 606U, 2393312003U }, |
198 | { 1318233152U, 922U, 3880361134U }, |
199 | { 855572992U, 761U, 1472974787U }, |
200 | { 64721421U, 703U, 683860550U }, |
201 | { 678931758U, 840U, 380616043U }, |
202 | { 692711973U, 778U, 1382361947U }, |
203 | { 677703619U, 530U, 2826914161U }, |
204 | { 92393223U, 586U, 1522128471U }, |
205 | { 1222592920U, 743U, 3466726667U }, |
206 | { 358288986U, 695U, 1091956998U }, |
207 | { 1935056945U, 958U, 514864477U }, |
208 | { 735675993U, 990U, 1294239989U }, |
209 | { 1560089402U, 897U, 2238551287U }, |
210 | { 70616361U, 829U, 22483098U }, |
211 | { 368234700U, 731U, 2913875084U }, |
212 | { 20221190U, 879U, 1564152970U }, |
213 | { 539444654U, 682U, 1835141259U }, |
214 | { 1314987297U, 840U, 1801114136U }, |
215 | { 2019295544U, 645U, 3286438930U }, |
216 | { 469023838U, 716U, 1637918202U }, |
217 | { 1843754496U, 653U, 2562092152U }, |
218 | { 400672036U, 809U, 4264212785U }, |
219 | { 404722249U, 965U, 2704116999U }, |
220 | { 600702209U, 758U, 584979986U }, |
221 | { 519953954U, 667U, 2574436237U }, |
222 | { 1658071126U, 694U, 2214569490U }, |
223 | { 420480037U, 749U, 3430010866U }, |
224 | { 690103647U, 969U, 3700758083U }, |
225 | { 1029424799U, 937U, 3787746841U }, |
226 | { 2012608669U, 506U, 3362628973U }, |
227 | { 1535432887U, 998U, 42610943U }, |
228 | { 1330635533U, 857U, 3040806504U }, |
229 | { 1223800550U, 539U, 3954229517U }, |
230 | { 1322411537U, 680U, 3223250324U }, |
231 | { 1877847898U, 945U, 2915147143U }, |
232 | { 1646356099U, 874U, 965988280U }, |
233 | { 805687536U, 744U, 4032277920U }, |
234 | { 1948093210U, 633U, 1346597684U }, |
235 | { 392609744U, 783U, 1636083295U }, |
236 | { 690241304U, 770U, 1201031298U }, |
237 | { 1360302965U, 696U, 1665394461U }, |
238 | { 1220090946U, 780U, 1316922812U }, |
239 | { 447092251U, 500U, 3438743375U }, |
240 | { 1613868791U, 592U, 828546883U }, |
241 | { 523430951U, 548U, 2552392304U }, |
242 | { 726692899U, 810U, 1656872867U }, |
243 | { 1364340021U, 836U, 3710513486U }, |
244 | { 1986257729U, 931U, 935013962U }, |
245 | { 407983964U, 921U, 728767059U }, |
246 | }; |
247 | |
248 | static void prandom_state_selftest_seed(struct rnd_state *state, u32 seed) |
249 | { |
250 | #define LCG(x) ((x) * 69069U) /* super-duper LCG */ |
251 | state->s1 = __seed(LCG(seed), m: 2U); |
252 | state->s2 = __seed(LCG(state->s1), m: 8U); |
253 | state->s3 = __seed(LCG(state->s2), m: 16U); |
254 | state->s4 = __seed(LCG(state->s3), m: 128U); |
255 | } |
256 | |
257 | static int __init prandom_state_selftest(void) |
258 | { |
259 | int i, j, errors = 0, runs = 0; |
260 | bool error = false; |
261 | |
262 | for (i = 0; i < ARRAY_SIZE(test1); i++) { |
263 | struct rnd_state state; |
264 | |
265 | prandom_state_selftest_seed(state: &state, seed: test1[i].seed); |
266 | prandom_warmup(state: &state); |
267 | |
268 | if (test1[i].result != prandom_u32_state(&state)) |
269 | error = true; |
270 | } |
271 | |
272 | if (error) |
273 | pr_warn("prandom: seed boundary self test failed\n" ); |
274 | else |
275 | pr_info("prandom: seed boundary self test passed\n" ); |
276 | |
277 | for (i = 0; i < ARRAY_SIZE(test2); i++) { |
278 | struct rnd_state state; |
279 | |
280 | prandom_state_selftest_seed(state: &state, seed: test2[i].seed); |
281 | prandom_warmup(state: &state); |
282 | |
283 | for (j = 0; j < test2[i].iteration - 1; j++) |
284 | prandom_u32_state(&state); |
285 | |
286 | if (test2[i].result != prandom_u32_state(&state)) |
287 | errors++; |
288 | |
289 | runs++; |
290 | cond_resched(); |
291 | } |
292 | |
293 | if (errors) |
294 | pr_warn("prandom: %d/%d self tests failed\n" , errors, runs); |
295 | else |
296 | pr_info("prandom: %d self tests passed\n" , runs); |
297 | return 0; |
298 | } |
299 | core_initcall(prandom_state_selftest); |
300 | #endif |
301 | |