random32.c 9.1 KB

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  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. #include <linux/types.h>
  35. #include <linux/percpu.h>
  36. #include <linux/export.h>
  37. #include <linux/jiffies.h>
  38. #include <linux/random.h>
  39. #include <linux/sched.h>
  40. #include <linux/bitops.h>
  41. #include <linux/slab.h>
  42. #include <asm/unaligned.h>
  43. /**
  44. * prandom_u32_state - seeded pseudo-random number generator.
  45. * @state: pointer to state structure holding seeded state.
  46. *
  47. * This is used for pseudo-randomness with no outside seeding.
  48. * For more random results, use get_random_u32().
  49. */
  50. u32 prandom_u32_state(struct rnd_state *state)
  51. {
  52. #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)
  53. state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U);
  54. state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U);
  55. state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U);
  56. state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U);
  57. return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
  58. }
  59. EXPORT_SYMBOL(prandom_u32_state);
  60. /**
  61. * prandom_bytes_state - get the requested number of pseudo-random bytes
  62. *
  63. * @state: pointer to state structure holding seeded state.
  64. * @buf: where to copy the pseudo-random bytes to
  65. * @bytes: the requested number of bytes
  66. *
  67. * This is used for pseudo-randomness with no outside seeding.
  68. * For more random results, use get_random_bytes().
  69. */
  70. void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes)
  71. {
  72. u8 *ptr = buf;
  73. while (bytes >= sizeof(u32)) {
  74. put_unaligned(prandom_u32_state(state), (u32 *) ptr);
  75. ptr += sizeof(u32);
  76. bytes -= sizeof(u32);
  77. }
  78. if (bytes > 0) {
  79. u32 rem = prandom_u32_state(state);
  80. do {
  81. *ptr++ = (u8) rem;
  82. bytes--;
  83. rem >>= BITS_PER_BYTE;
  84. } while (bytes > 0);
  85. }
  86. }
  87. EXPORT_SYMBOL(prandom_bytes_state);
  88. static void prandom_warmup(struct rnd_state *state)
  89. {
  90. /* Calling RNG ten times to satisfy recurrence condition */
  91. prandom_u32_state(state);
  92. prandom_u32_state(state);
  93. prandom_u32_state(state);
  94. prandom_u32_state(state);
  95. prandom_u32_state(state);
  96. prandom_u32_state(state);
  97. prandom_u32_state(state);
  98. prandom_u32_state(state);
  99. prandom_u32_state(state);
  100. prandom_u32_state(state);
  101. }
  102. void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
  103. {
  104. int i;
  105. for_each_possible_cpu(i) {
  106. struct rnd_state *state = per_cpu_ptr(pcpu_state, i);
  107. u32 seeds[4];
  108. get_random_bytes(&seeds, sizeof(seeds));
  109. state->s1 = __seed(seeds[0], 2U);
  110. state->s2 = __seed(seeds[1], 8U);
  111. state->s3 = __seed(seeds[2], 16U);
  112. state->s4 = __seed(seeds[3], 128U);
  113. prandom_warmup(state);
  114. }
  115. }
  116. EXPORT_SYMBOL(prandom_seed_full_state);
  117. #ifdef CONFIG_RANDOM32_SELFTEST
  118. static struct prandom_test1 {
  119. u32 seed;
  120. u32 result;
  121. } test1[] = {
  122. { 1U, 3484351685U },
  123. { 2U, 2623130059U },
  124. { 3U, 3125133893U },
  125. { 4U, 984847254U },
  126. };
  127. static struct prandom_test2 {
  128. u32 seed;
  129. u32 iteration;
  130. u32 result;
  131. } test2[] = {
  132. /* Test cases against taus113 from GSL library. */
  133. { 931557656U, 959U, 2975593782U },
  134. { 1339693295U, 876U, 3887776532U },
  135. { 1545556285U, 961U, 1615538833U },
  136. { 601730776U, 723U, 1776162651U },
  137. { 1027516047U, 687U, 511983079U },
  138. { 416526298U, 700U, 916156552U },
  139. { 1395522032U, 652U, 2222063676U },
  140. { 366221443U, 617U, 2992857763U },
  141. { 1539836965U, 714U, 3783265725U },
  142. { 556206671U, 994U, 799626459U },
  143. { 684907218U, 799U, 367789491U },
  144. { 2121230701U, 931U, 2115467001U },
  145. { 1668516451U, 644U, 3620590685U },
  146. { 768046066U, 883U, 2034077390U },
  147. { 1989159136U, 833U, 1195767305U },
  148. { 536585145U, 996U, 3577259204U },
  149. { 1008129373U, 642U, 1478080776U },
  150. { 1740775604U, 939U, 1264980372U },
  151. { 1967883163U, 508U, 10734624U },
  152. { 1923019697U, 730U, 3821419629U },
  153. { 442079932U, 560U, 3440032343U },
  154. { 1961302714U, 845U, 841962572U },
  155. { 2030205964U, 962U, 1325144227U },
  156. { 1160407529U, 507U, 240940858U },
  157. { 635482502U, 779U, 4200489746U },
  158. { 1252788931U, 699U, 867195434U },
  159. { 1961817131U, 719U, 668237657U },
  160. { 1071468216U, 983U, 917876630U },
  161. { 1281848367U, 932U, 1003100039U },
  162. { 582537119U, 780U, 1127273778U },
  163. { 1973672777U, 853U, 1071368872U },
  164. { 1896756996U, 762U, 1127851055U },
  165. { 847917054U, 500U, 1717499075U },
  166. { 1240520510U, 951U, 2849576657U },
  167. { 1685071682U, 567U, 1961810396U },
  168. { 1516232129U, 557U, 3173877U },
  169. { 1208118903U, 612U, 1613145022U },
  170. { 1817269927U, 693U, 4279122573U },
  171. { 1510091701U, 717U, 638191229U },
  172. { 365916850U, 807U, 600424314U },
  173. { 399324359U, 702U, 1803598116U },
  174. { 1318480274U, 779U, 2074237022U },
  175. { 697758115U, 840U, 1483639402U },
  176. { 1696507773U, 840U, 577415447U },
  177. { 2081979121U, 981U, 3041486449U },
  178. { 955646687U, 742U, 3846494357U },
  179. { 1250683506U, 749U, 836419859U },
  180. { 595003102U, 534U, 366794109U },
  181. { 47485338U, 558U, 3521120834U },
  182. { 619433479U, 610U, 3991783875U },
  183. { 704096520U, 518U, 4139493852U },
  184. { 1712224984U, 606U, 2393312003U },
  185. { 1318233152U, 922U, 3880361134U },
  186. { 855572992U, 761U, 1472974787U },
  187. { 64721421U, 703U, 683860550U },
  188. { 678931758U, 840U, 380616043U },
  189. { 692711973U, 778U, 1382361947U },
  190. { 677703619U, 530U, 2826914161U },
  191. { 92393223U, 586U, 1522128471U },
  192. { 1222592920U, 743U, 3466726667U },
  193. { 358288986U, 695U, 1091956998U },
  194. { 1935056945U, 958U, 514864477U },
  195. { 735675993U, 990U, 1294239989U },
  196. { 1560089402U, 897U, 2238551287U },
  197. { 70616361U, 829U, 22483098U },
  198. { 368234700U, 731U, 2913875084U },
  199. { 20221190U, 879U, 1564152970U },
  200. { 539444654U, 682U, 1835141259U },
  201. { 1314987297U, 840U, 1801114136U },
  202. { 2019295544U, 645U, 3286438930U },
  203. { 469023838U, 716U, 1637918202U },
  204. { 1843754496U, 653U, 2562092152U },
  205. { 400672036U, 809U, 4264212785U },
  206. { 404722249U, 965U, 2704116999U },
  207. { 600702209U, 758U, 584979986U },
  208. { 519953954U, 667U, 2574436237U },
  209. { 1658071126U, 694U, 2214569490U },
  210. { 420480037U, 749U, 3430010866U },
  211. { 690103647U, 969U, 3700758083U },
  212. { 1029424799U, 937U, 3787746841U },
  213. { 2012608669U, 506U, 3362628973U },
  214. { 1535432887U, 998U, 42610943U },
  215. { 1330635533U, 857U, 3040806504U },
  216. { 1223800550U, 539U, 3954229517U },
  217. { 1322411537U, 680U, 3223250324U },
  218. { 1877847898U, 945U, 2915147143U },
  219. { 1646356099U, 874U, 965988280U },
  220. { 805687536U, 744U, 4032277920U },
  221. { 1948093210U, 633U, 1346597684U },
  222. { 392609744U, 783U, 1636083295U },
  223. { 690241304U, 770U, 1201031298U },
  224. { 1360302965U, 696U, 1665394461U },
  225. { 1220090946U, 780U, 1316922812U },
  226. { 447092251U, 500U, 3438743375U },
  227. { 1613868791U, 592U, 828546883U },
  228. { 523430951U, 548U, 2552392304U },
  229. { 726692899U, 810U, 1656872867U },
  230. { 1364340021U, 836U, 3710513486U },
  231. { 1986257729U, 931U, 935013962U },
  232. { 407983964U, 921U, 728767059U },
  233. };
  234. static void prandom_state_selftest_seed(struct rnd_state *state, u32 seed)
  235. {
  236. #define LCG(x) ((x) * 69069U) /* super-duper LCG */
  237. state->s1 = __seed(LCG(seed), 2U);
  238. state->s2 = __seed(LCG(state->s1), 8U);
  239. state->s3 = __seed(LCG(state->s2), 16U);
  240. state->s4 = __seed(LCG(state->s3), 128U);
  241. }
  242. static int __init prandom_state_selftest(void)
  243. {
  244. int i, j, errors = 0, runs = 0;
  245. bool error = false;
  246. for (i = 0; i < ARRAY_SIZE(test1); i++) {
  247. struct rnd_state state;
  248. prandom_state_selftest_seed(&state, test1[i].seed);
  249. prandom_warmup(&state);
  250. if (test1[i].result != prandom_u32_state(&state))
  251. error = true;
  252. }
  253. if (error)
  254. pr_warn("prandom: seed boundary self test failed\n");
  255. else
  256. pr_info("prandom: seed boundary self test passed\n");
  257. for (i = 0; i < ARRAY_SIZE(test2); i++) {
  258. struct rnd_state state;
  259. prandom_state_selftest_seed(&state, test2[i].seed);
  260. prandom_warmup(&state);
  261. for (j = 0; j < test2[i].iteration - 1; j++)
  262. prandom_u32_state(&state);
  263. if (test2[i].result != prandom_u32_state(&state))
  264. errors++;
  265. runs++;
  266. cond_resched();
  267. }
  268. if (errors)
  269. pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
  270. else
  271. pr_info("prandom: %d self tests passed\n", runs);
  272. return 0;
  273. }
  274. core_initcall(prandom_state_selftest);
  275. #endif