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 prandom_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 prandom_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(&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 }; 247 248 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 } 256 257 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