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 */
prandom_u32_state(struct rnd_state * state)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 */
prandom_bytes_state(struct rnd_state * state,void * buf,size_t bytes)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
prandom_warmup(struct rnd_state * state)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
prandom_seed_full_state(struct rnd_state __percpu * pcpu_state)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(&seeds, sizeof(seeds));
119 state->s1 = __seed(seeds[0], 2U);
120 state->s2 = __seed(seeds[1], 8U);
121 state->s3 = __seed(seeds[2], 16U);
122 state->s4 = __seed(seeds[3], 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
prandom_state_selftest_seed(struct rnd_state * state,u32 seed)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), 2U);
252 state->s2 = __seed(LCG(state->s1), 8U);
253 state->s3 = __seed(LCG(state->s2), 16U);
254 state->s4 = __seed(LCG(state->s3), 128U);
255 }
256
prandom_state_selftest(void)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, test1[i].seed);
266 prandom_warmup(&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, test2[i].seed);
281 prandom_warmup(&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