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 <asm/unaligned.h> 42 43 #ifdef CONFIG_RANDOM32_SELFTEST 44 static void __init prandom_state_selftest(void); 45 #else 46 static inline void prandom_state_selftest(void) 47 { 48 } 49 #endif 50 51 static DEFINE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy; 52 53 /** 54 * prandom_u32_state - seeded pseudo-random number generator. 55 * @state: pointer to state structure holding seeded state. 56 * 57 * This is used for pseudo-randomness with no outside seeding. 58 * For more random results, use prandom_u32(). 59 */ 60 u32 prandom_u32_state(struct rnd_state *state) 61 { 62 #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) 63 state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); 64 state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); 65 state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); 66 state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); 67 68 return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); 69 } 70 EXPORT_SYMBOL(prandom_u32_state); 71 72 /** 73 * prandom_u32 - pseudo random number generator 74 * 75 * A 32 bit pseudo-random number is generated using a fast 76 * algorithm suitable for simulation. This algorithm is NOT 77 * considered safe for cryptographic use. 78 */ 79 u32 prandom_u32(void) 80 { 81 struct rnd_state *state = &get_cpu_var(net_rand_state); 82 u32 res; 83 84 res = prandom_u32_state(state); 85 put_cpu_var(net_rand_state); 86 87 return res; 88 } 89 EXPORT_SYMBOL(prandom_u32); 90 91 /** 92 * prandom_bytes_state - get the requested number of pseudo-random bytes 93 * 94 * @state: pointer to state structure holding seeded state. 95 * @buf: where to copy the pseudo-random bytes to 96 * @bytes: the requested number of bytes 97 * 98 * This is used for pseudo-randomness with no outside seeding. 99 * For more random results, use prandom_bytes(). 100 */ 101 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes) 102 { 103 u8 *ptr = buf; 104 105 while (bytes >= sizeof(u32)) { 106 put_unaligned(prandom_u32_state(state), (u32 *) ptr); 107 ptr += sizeof(u32); 108 bytes -= sizeof(u32); 109 } 110 111 if (bytes > 0) { 112 u32 rem = prandom_u32_state(state); 113 do { 114 *ptr++ = (u8) rem; 115 bytes--; 116 rem >>= BITS_PER_BYTE; 117 } while (bytes > 0); 118 } 119 } 120 EXPORT_SYMBOL(prandom_bytes_state); 121 122 /** 123 * prandom_bytes - get the requested number of pseudo-random bytes 124 * @buf: where to copy the pseudo-random bytes to 125 * @bytes: the requested number of bytes 126 */ 127 void prandom_bytes(void *buf, size_t bytes) 128 { 129 struct rnd_state *state = &get_cpu_var(net_rand_state); 130 131 prandom_bytes_state(state, buf, bytes); 132 put_cpu_var(net_rand_state); 133 } 134 EXPORT_SYMBOL(prandom_bytes); 135 136 static void prandom_warmup(struct rnd_state *state) 137 { 138 /* Calling RNG ten times to satisfy recurrence condition */ 139 prandom_u32_state(state); 140 prandom_u32_state(state); 141 prandom_u32_state(state); 142 prandom_u32_state(state); 143 prandom_u32_state(state); 144 prandom_u32_state(state); 145 prandom_u32_state(state); 146 prandom_u32_state(state); 147 prandom_u32_state(state); 148 prandom_u32_state(state); 149 } 150 151 static u32 __extract_hwseed(void) 152 { 153 unsigned int val = 0; 154 155 (void)(arch_get_random_seed_int(&val) || 156 arch_get_random_int(&val)); 157 158 return val; 159 } 160 161 static void prandom_seed_early(struct rnd_state *state, u32 seed, 162 bool mix_with_hwseed) 163 { 164 #define LCG(x) ((x) * 69069U) /* super-duper LCG */ 165 #define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0) 166 state->s1 = __seed(HWSEED() ^ LCG(seed), 2U); 167 state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U); 168 state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U); 169 state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U); 170 } 171 172 /** 173 * prandom_seed - add entropy to pseudo random number generator 174 * @seed: seed value 175 * 176 * Add some additional seeding to the prandom pool. 177 */ 178 void prandom_seed(u32 entropy) 179 { 180 int i; 181 /* 182 * No locking on the CPUs, but then somewhat random results are, well, 183 * expected. 184 */ 185 for_each_possible_cpu(i) { 186 struct rnd_state *state = &per_cpu(net_rand_state, i); 187 188 state->s1 = __seed(state->s1 ^ entropy, 2U); 189 prandom_warmup(state); 190 } 191 } 192 EXPORT_SYMBOL(prandom_seed); 193 194 /* 195 * Generate some initially weak seeding values to allow 196 * to start the prandom_u32() engine. 197 */ 198 static int __init prandom_init(void) 199 { 200 int i; 201 202 prandom_state_selftest(); 203 204 for_each_possible_cpu(i) { 205 struct rnd_state *state = &per_cpu(net_rand_state, i); 206 u32 weak_seed = (i + jiffies) ^ random_get_entropy(); 207 208 prandom_seed_early(state, weak_seed, true); 209 prandom_warmup(state); 210 } 211 212 return 0; 213 } 214 core_initcall(prandom_init); 215 216 static void __prandom_timer(struct timer_list *unused); 217 218 static DEFINE_TIMER(seed_timer, __prandom_timer); 219 220 static void __prandom_timer(struct timer_list *unused) 221 { 222 u32 entropy; 223 unsigned long expires; 224 225 get_random_bytes(&entropy, sizeof(entropy)); 226 prandom_seed(entropy); 227 228 /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ 229 expires = 40 + prandom_u32_max(40); 230 seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC); 231 232 add_timer(&seed_timer); 233 } 234 235 static void __init __prandom_start_seed_timer(void) 236 { 237 seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC); 238 add_timer(&seed_timer); 239 } 240 241 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state) 242 { 243 int i; 244 245 for_each_possible_cpu(i) { 246 struct rnd_state *state = per_cpu_ptr(pcpu_state, i); 247 u32 seeds[4]; 248 249 get_random_bytes(&seeds, sizeof(seeds)); 250 state->s1 = __seed(seeds[0], 2U); 251 state->s2 = __seed(seeds[1], 8U); 252 state->s3 = __seed(seeds[2], 16U); 253 state->s4 = __seed(seeds[3], 128U); 254 255 prandom_warmup(state); 256 } 257 } 258 EXPORT_SYMBOL(prandom_seed_full_state); 259 260 /* 261 * Generate better values after random number generator 262 * is fully initialized. 263 */ 264 static void __prandom_reseed(bool late) 265 { 266 unsigned long flags; 267 static bool latch = false; 268 static DEFINE_SPINLOCK(lock); 269 270 /* Asking for random bytes might result in bytes getting 271 * moved into the nonblocking pool and thus marking it 272 * as initialized. In this case we would double back into 273 * this function and attempt to do a late reseed. 274 * Ignore the pointless attempt to reseed again if we're 275 * already waiting for bytes when the nonblocking pool 276 * got initialized. 277 */ 278 279 /* only allow initial seeding (late == false) once */ 280 if (!spin_trylock_irqsave(&lock, flags)) 281 return; 282 283 if (latch && !late) 284 goto out; 285 286 latch = true; 287 prandom_seed_full_state(&net_rand_state); 288 out: 289 spin_unlock_irqrestore(&lock, flags); 290 } 291 292 void prandom_reseed_late(void) 293 { 294 __prandom_reseed(true); 295 } 296 297 static int __init prandom_reseed(void) 298 { 299 __prandom_reseed(false); 300 __prandom_start_seed_timer(); 301 return 0; 302 } 303 late_initcall(prandom_reseed); 304 305 #ifdef CONFIG_RANDOM32_SELFTEST 306 static struct prandom_test1 { 307 u32 seed; 308 u32 result; 309 } test1[] = { 310 { 1U, 3484351685U }, 311 { 2U, 2623130059U }, 312 { 3U, 3125133893U }, 313 { 4U, 984847254U }, 314 }; 315 316 static struct prandom_test2 { 317 u32 seed; 318 u32 iteration; 319 u32 result; 320 } test2[] = { 321 /* Test cases against taus113 from GSL library. */ 322 { 931557656U, 959U, 2975593782U }, 323 { 1339693295U, 876U, 3887776532U }, 324 { 1545556285U, 961U, 1615538833U }, 325 { 601730776U, 723U, 1776162651U }, 326 { 1027516047U, 687U, 511983079U }, 327 { 416526298U, 700U, 916156552U }, 328 { 1395522032U, 652U, 2222063676U }, 329 { 366221443U, 617U, 2992857763U }, 330 { 1539836965U, 714U, 3783265725U }, 331 { 556206671U, 994U, 799626459U }, 332 { 684907218U, 799U, 367789491U }, 333 { 2121230701U, 931U, 2115467001U }, 334 { 1668516451U, 644U, 3620590685U }, 335 { 768046066U, 883U, 2034077390U }, 336 { 1989159136U, 833U, 1195767305U }, 337 { 536585145U, 996U, 3577259204U }, 338 { 1008129373U, 642U, 1478080776U }, 339 { 1740775604U, 939U, 1264980372U }, 340 { 1967883163U, 508U, 10734624U }, 341 { 1923019697U, 730U, 3821419629U }, 342 { 442079932U, 560U, 3440032343U }, 343 { 1961302714U, 845U, 841962572U }, 344 { 2030205964U, 962U, 1325144227U }, 345 { 1160407529U, 507U, 240940858U }, 346 { 635482502U, 779U, 4200489746U }, 347 { 1252788931U, 699U, 867195434U }, 348 { 1961817131U, 719U, 668237657U }, 349 { 1071468216U, 983U, 917876630U }, 350 { 1281848367U, 932U, 1003100039U }, 351 { 582537119U, 780U, 1127273778U }, 352 { 1973672777U, 853U, 1071368872U }, 353 { 1896756996U, 762U, 1127851055U }, 354 { 847917054U, 500U, 1717499075U }, 355 { 1240520510U, 951U, 2849576657U }, 356 { 1685071682U, 567U, 1961810396U }, 357 { 1516232129U, 557U, 3173877U }, 358 { 1208118903U, 612U, 1613145022U }, 359 { 1817269927U, 693U, 4279122573U }, 360 { 1510091701U, 717U, 638191229U }, 361 { 365916850U, 807U, 600424314U }, 362 { 399324359U, 702U, 1803598116U }, 363 { 1318480274U, 779U, 2074237022U }, 364 { 697758115U, 840U, 1483639402U }, 365 { 1696507773U, 840U, 577415447U }, 366 { 2081979121U, 981U, 3041486449U }, 367 { 955646687U, 742U, 3846494357U }, 368 { 1250683506U, 749U, 836419859U }, 369 { 595003102U, 534U, 366794109U }, 370 { 47485338U, 558U, 3521120834U }, 371 { 619433479U, 610U, 3991783875U }, 372 { 704096520U, 518U, 4139493852U }, 373 { 1712224984U, 606U, 2393312003U }, 374 { 1318233152U, 922U, 3880361134U }, 375 { 855572992U, 761U, 1472974787U }, 376 { 64721421U, 703U, 683860550U }, 377 { 678931758U, 840U, 380616043U }, 378 { 692711973U, 778U, 1382361947U }, 379 { 677703619U, 530U, 2826914161U }, 380 { 92393223U, 586U, 1522128471U }, 381 { 1222592920U, 743U, 3466726667U }, 382 { 358288986U, 695U, 1091956998U }, 383 { 1935056945U, 958U, 514864477U }, 384 { 735675993U, 990U, 1294239989U }, 385 { 1560089402U, 897U, 2238551287U }, 386 { 70616361U, 829U, 22483098U }, 387 { 368234700U, 731U, 2913875084U }, 388 { 20221190U, 879U, 1564152970U }, 389 { 539444654U, 682U, 1835141259U }, 390 { 1314987297U, 840U, 1801114136U }, 391 { 2019295544U, 645U, 3286438930U }, 392 { 469023838U, 716U, 1637918202U }, 393 { 1843754496U, 653U, 2562092152U }, 394 { 400672036U, 809U, 4264212785U }, 395 { 404722249U, 965U, 2704116999U }, 396 { 600702209U, 758U, 584979986U }, 397 { 519953954U, 667U, 2574436237U }, 398 { 1658071126U, 694U, 2214569490U }, 399 { 420480037U, 749U, 3430010866U }, 400 { 690103647U, 969U, 3700758083U }, 401 { 1029424799U, 937U, 3787746841U }, 402 { 2012608669U, 506U, 3362628973U }, 403 { 1535432887U, 998U, 42610943U }, 404 { 1330635533U, 857U, 3040806504U }, 405 { 1223800550U, 539U, 3954229517U }, 406 { 1322411537U, 680U, 3223250324U }, 407 { 1877847898U, 945U, 2915147143U }, 408 { 1646356099U, 874U, 965988280U }, 409 { 805687536U, 744U, 4032277920U }, 410 { 1948093210U, 633U, 1346597684U }, 411 { 392609744U, 783U, 1636083295U }, 412 { 690241304U, 770U, 1201031298U }, 413 { 1360302965U, 696U, 1665394461U }, 414 { 1220090946U, 780U, 1316922812U }, 415 { 447092251U, 500U, 3438743375U }, 416 { 1613868791U, 592U, 828546883U }, 417 { 523430951U, 548U, 2552392304U }, 418 { 726692899U, 810U, 1656872867U }, 419 { 1364340021U, 836U, 3710513486U }, 420 { 1986257729U, 931U, 935013962U }, 421 { 407983964U, 921U, 728767059U }, 422 }; 423 424 static void __init prandom_state_selftest(void) 425 { 426 int i, j, errors = 0, runs = 0; 427 bool error = false; 428 429 for (i = 0; i < ARRAY_SIZE(test1); i++) { 430 struct rnd_state state; 431 432 prandom_seed_early(&state, test1[i].seed, false); 433 prandom_warmup(&state); 434 435 if (test1[i].result != prandom_u32_state(&state)) 436 error = true; 437 } 438 439 if (error) 440 pr_warn("prandom: seed boundary self test failed\n"); 441 else 442 pr_info("prandom: seed boundary self test passed\n"); 443 444 for (i = 0; i < ARRAY_SIZE(test2); i++) { 445 struct rnd_state state; 446 447 prandom_seed_early(&state, test2[i].seed, false); 448 prandom_warmup(&state); 449 450 for (j = 0; j < test2[i].iteration - 1; j++) 451 prandom_u32_state(&state); 452 453 if (test2[i].result != prandom_u32_state(&state)) 454 errors++; 455 456 runs++; 457 cond_resched(); 458 } 459 460 if (errors) 461 pr_warn("prandom: %d/%d self tests failed\n", errors, runs); 462 else 463 pr_info("prandom: %d self tests passed\n", runs); 464 } 465 #endif 466