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1// SPDX-License-Identifier: GPL-2.02/*3 * This is a maximally equidistributed combined Tausworthe generator4 * 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 Tausworthe18 * Generators", Mathematics of Computation, 65, 213 (1996), 203--213:19 * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps20 * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps21 *22 * There is an erratum in the paper "Tables of Maximally Equidistributed23 * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999),24 * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps25 *26 * ... the k_j most significant bits of z_j must be non-zero,27 * for each j. (Note: this restriction also applies to the28 * computer code given in [4], but was mistakenly not mentioned29 * in that paper.)30 *31 * This affects the seeding procedure by imposing the requirement32 * 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 <linux/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 */52u32 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}62EXPORT_SYMBOL(prandom_u32_state);63 64/**65 * prandom_bytes_state - get the requested number of pseudo-random bytes66 *67 * @state: pointer to state structure holding seeded state.68 * @buf: where to copy the pseudo-random bytes to69 * @bytes: the requested number of bytes70 *71 * This is used for pseudo-randomness with no outside seeding.72 * For more random results, use get_random_bytes().73 */74void 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}93EXPORT_SYMBOL(prandom_bytes_state);94 95static 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 110void 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}127EXPORT_SYMBOL(prandom_seed_full_state);128 129#ifdef CONFIG_RANDOM32_SELFTEST130static 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 140static 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 248static 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 257static 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 else275 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 else296 pr_info("prandom: %d self tests passed\n", runs);297 return 0;298}299core_initcall(prandom_state_selftest);300#endif301