1 /* 2 * This is a maximally equidistributed combined Tausworthe generator 3 * based on code from GNU Scientific Library 1.5 (30 Jun 2004) 4 * 5 * lfsr113 version: 6 * 7 * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n) 8 * 9 * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13)) 10 * s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27)) 11 * s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21)) 12 * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12)) 13 * 14 * The period of this generator is about 2^113 (see erratum paper). 15 * 16 * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe 17 * Generators", Mathematics of Computation, 65, 213 (1996), 203--213: 18 * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps 19 * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps 20 * 21 * There is an erratum in the paper "Tables of Maximally Equidistributed 22 * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999), 23 * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps 24 * 25 * ... the k_j most significant bits of z_j must be non-zero, 26 * for each j. (Note: this restriction also applies to the 27 * computer code given in [4], but was mistakenly not mentioned 28 * in that paper.) 29 * 30 * This affects the seeding procedure by imposing the requirement 31 * s1 > 1, s2 > 7, s3 > 15, s4 > 127. 32 */ 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 41 #ifdef CONFIG_RANDOM32_SELFTEST 42 static void __init prandom_state_selftest(void); 43 #else 44 static inline void prandom_state_selftest(void) 45 { 46 } 47 #endif 48 49 static DEFINE_PER_CPU(struct rnd_state, net_rand_state); 50 51 /** 52 * prandom_u32_state - seeded pseudo-random number generator. 53 * @state: pointer to state structure holding seeded state. 54 * 55 * This is used for pseudo-randomness with no outside seeding. 56 * For more random results, use prandom_u32(). 57 */ 58 u32 prandom_u32_state(struct rnd_state *state) 59 { 60 #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) 61 state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); 62 state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); 63 state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); 64 state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); 65 66 return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); 67 } 68 EXPORT_SYMBOL(prandom_u32_state); 69 70 /** 71 * prandom_u32 - pseudo random number generator 72 * 73 * A 32 bit pseudo-random number is generated using a fast 74 * algorithm suitable for simulation. This algorithm is NOT 75 * considered safe for cryptographic use. 76 */ 77 u32 prandom_u32(void) 78 { 79 struct rnd_state *state = &get_cpu_var(net_rand_state); 80 u32 res; 81 82 res = prandom_u32_state(state); 83 put_cpu_var(state); 84 85 return res; 86 } 87 EXPORT_SYMBOL(prandom_u32); 88 89 /** 90 * prandom_bytes_state - get the requested number of pseudo-random bytes 91 * 92 * @state: pointer to state structure holding seeded state. 93 * @buf: where to copy the pseudo-random bytes to 94 * @bytes: the requested number of bytes 95 * 96 * This is used for pseudo-randomness with no outside seeding. 97 * For more random results, use prandom_bytes(). 98 */ 99 void prandom_bytes_state(struct rnd_state *state, void *buf, int bytes) 100 { 101 unsigned char *p = buf; 102 int i; 103 104 for (i = 0; i < round_down(bytes, sizeof(u32)); i += sizeof(u32)) { 105 u32 random = prandom_u32_state(state); 106 int j; 107 108 for (j = 0; j < sizeof(u32); j++) { 109 p[i + j] = random; 110 random >>= BITS_PER_BYTE; 111 } 112 } 113 if (i < bytes) { 114 u32 random = prandom_u32_state(state); 115 116 for (; i < bytes; i++) { 117 p[i] = random; 118 random >>= BITS_PER_BYTE; 119 } 120 } 121 } 122 EXPORT_SYMBOL(prandom_bytes_state); 123 124 /** 125 * prandom_bytes - get the requested number of pseudo-random bytes 126 * @buf: where to copy the pseudo-random bytes to 127 * @bytes: the requested number of bytes 128 */ 129 void prandom_bytes(void *buf, int bytes) 130 { 131 struct rnd_state *state = &get_cpu_var(net_rand_state); 132 133 prandom_bytes_state(state, buf, bytes); 134 put_cpu_var(state); 135 } 136 EXPORT_SYMBOL(prandom_bytes); 137 138 static void prandom_warmup(struct rnd_state *state) 139 { 140 /* Calling RNG ten times to satify recurrence condition */ 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 prandom_u32_state(state); 150 prandom_u32_state(state); 151 } 152 153 static u32 __extract_hwseed(void) 154 { 155 u32 val = 0; 156 157 (void)(arch_get_random_seed_int(&val) || 158 arch_get_random_int(&val)); 159 160 return val; 161 } 162 163 static void prandom_seed_early(struct rnd_state *state, u32 seed, 164 bool mix_with_hwseed) 165 { 166 #define LCG(x) ((x) * 69069U) /* super-duper LCG */ 167 #define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0) 168 state->s1 = __seed(HWSEED() ^ LCG(seed), 2U); 169 state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U); 170 state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U); 171 state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U); 172 } 173 174 /** 175 * prandom_seed - add entropy to pseudo random number generator 176 * @seed: seed value 177 * 178 * Add some additional seeding to the prandom pool. 179 */ 180 void prandom_seed(u32 entropy) 181 { 182 int i; 183 /* 184 * No locking on the CPUs, but then somewhat random results are, well, 185 * expected. 186 */ 187 for_each_possible_cpu (i) { 188 struct rnd_state *state = &per_cpu(net_rand_state, i); 189 190 state->s1 = __seed(state->s1 ^ entropy, 2U); 191 prandom_warmup(state); 192 } 193 } 194 EXPORT_SYMBOL(prandom_seed); 195 196 /* 197 * Generate some initially weak seeding values to allow 198 * to start the prandom_u32() engine. 199 */ 200 static int __init prandom_init(void) 201 { 202 int i; 203 204 prandom_state_selftest(); 205 206 for_each_possible_cpu(i) { 207 struct rnd_state *state = &per_cpu(net_rand_state,i); 208 u32 weak_seed = (i + jiffies) ^ random_get_entropy(); 209 210 prandom_seed_early(state, weak_seed, true); 211 prandom_warmup(state); 212 } 213 214 return 0; 215 } 216 core_initcall(prandom_init); 217 218 static void __prandom_timer(unsigned long dontcare); 219 220 static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0); 221 222 static void __prandom_timer(unsigned long dontcare) 223 { 224 u32 entropy; 225 unsigned long expires; 226 227 get_random_bytes(&entropy, sizeof(entropy)); 228 prandom_seed(entropy); 229 230 /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ 231 expires = 40 + (prandom_u32() % 40); 232 seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC); 233 234 add_timer(&seed_timer); 235 } 236 237 static void __init __prandom_start_seed_timer(void) 238 { 239 set_timer_slack(&seed_timer, HZ); 240 seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC); 241 add_timer(&seed_timer); 242 } 243 244 /* 245 * Generate better values after random number generator 246 * is fully initialized. 247 */ 248 static void __prandom_reseed(bool late) 249 { 250 int i; 251 unsigned long flags; 252 static bool latch = false; 253 static DEFINE_SPINLOCK(lock); 254 255 /* Asking for random bytes might result in bytes getting 256 * moved into the nonblocking pool and thus marking it 257 * as initialized. In this case we would double back into 258 * this function and attempt to do a late reseed. 259 * Ignore the pointless attempt to reseed again if we're 260 * already waiting for bytes when the nonblocking pool 261 * got initialized. 262 */ 263 264 /* only allow initial seeding (late == false) once */ 265 if (!spin_trylock_irqsave(&lock, flags)) 266 return; 267 268 if (latch && !late) 269 goto out; 270 271 latch = true; 272 273 for_each_possible_cpu(i) { 274 struct rnd_state *state = &per_cpu(net_rand_state,i); 275 u32 seeds[4]; 276 277 get_random_bytes(&seeds, sizeof(seeds)); 278 state->s1 = __seed(seeds[0], 2U); 279 state->s2 = __seed(seeds[1], 8U); 280 state->s3 = __seed(seeds[2], 16U); 281 state->s4 = __seed(seeds[3], 128U); 282 283 prandom_warmup(state); 284 } 285 out: 286 spin_unlock_irqrestore(&lock, flags); 287 } 288 289 void prandom_reseed_late(void) 290 { 291 __prandom_reseed(true); 292 } 293 294 static int __init prandom_reseed(void) 295 { 296 __prandom_reseed(false); 297 __prandom_start_seed_timer(); 298 return 0; 299 } 300 late_initcall(prandom_reseed); 301 302 #ifdef CONFIG_RANDOM32_SELFTEST 303 static struct prandom_test1 { 304 u32 seed; 305 u32 result; 306 } test1[] = { 307 { 1U, 3484351685U }, 308 { 2U, 2623130059U }, 309 { 3U, 3125133893U }, 310 { 4U, 984847254U }, 311 }; 312 313 static struct prandom_test2 { 314 u32 seed; 315 u32 iteration; 316 u32 result; 317 } test2[] = { 318 /* Test cases against taus113 from GSL library. */ 319 { 931557656U, 959U, 2975593782U }, 320 { 1339693295U, 876U, 3887776532U }, 321 { 1545556285U, 961U, 1615538833U }, 322 { 601730776U, 723U, 1776162651U }, 323 { 1027516047U, 687U, 511983079U }, 324 { 416526298U, 700U, 916156552U }, 325 { 1395522032U, 652U, 2222063676U }, 326 { 366221443U, 617U, 2992857763U }, 327 { 1539836965U, 714U, 3783265725U }, 328 { 556206671U, 994U, 799626459U }, 329 { 684907218U, 799U, 367789491U }, 330 { 2121230701U, 931U, 2115467001U }, 331 { 1668516451U, 644U, 3620590685U }, 332 { 768046066U, 883U, 2034077390U }, 333 { 1989159136U, 833U, 1195767305U }, 334 { 536585145U, 996U, 3577259204U }, 335 { 1008129373U, 642U, 1478080776U }, 336 { 1740775604U, 939U, 1264980372U }, 337 { 1967883163U, 508U, 10734624U }, 338 { 1923019697U, 730U, 3821419629U }, 339 { 442079932U, 560U, 3440032343U }, 340 { 1961302714U, 845U, 841962572U }, 341 { 2030205964U, 962U, 1325144227U }, 342 { 1160407529U, 507U, 240940858U }, 343 { 635482502U, 779U, 4200489746U }, 344 { 1252788931U, 699U, 867195434U }, 345 { 1961817131U, 719U, 668237657U }, 346 { 1071468216U, 983U, 917876630U }, 347 { 1281848367U, 932U, 1003100039U }, 348 { 582537119U, 780U, 1127273778U }, 349 { 1973672777U, 853U, 1071368872U }, 350 { 1896756996U, 762U, 1127851055U }, 351 { 847917054U, 500U, 1717499075U }, 352 { 1240520510U, 951U, 2849576657U }, 353 { 1685071682U, 567U, 1961810396U }, 354 { 1516232129U, 557U, 3173877U }, 355 { 1208118903U, 612U, 1613145022U }, 356 { 1817269927U, 693U, 4279122573U }, 357 { 1510091701U, 717U, 638191229U }, 358 { 365916850U, 807U, 600424314U }, 359 { 399324359U, 702U, 1803598116U }, 360 { 1318480274U, 779U, 2074237022U }, 361 { 697758115U, 840U, 1483639402U }, 362 { 1696507773U, 840U, 577415447U }, 363 { 2081979121U, 981U, 3041486449U }, 364 { 955646687U, 742U, 3846494357U }, 365 { 1250683506U, 749U, 836419859U }, 366 { 595003102U, 534U, 366794109U }, 367 { 47485338U, 558U, 3521120834U }, 368 { 619433479U, 610U, 3991783875U }, 369 { 704096520U, 518U, 4139493852U }, 370 { 1712224984U, 606U, 2393312003U }, 371 { 1318233152U, 922U, 3880361134U }, 372 { 855572992U, 761U, 1472974787U }, 373 { 64721421U, 703U, 683860550U }, 374 { 678931758U, 840U, 380616043U }, 375 { 692711973U, 778U, 1382361947U }, 376 { 677703619U, 530U, 2826914161U }, 377 { 92393223U, 586U, 1522128471U }, 378 { 1222592920U, 743U, 3466726667U }, 379 { 358288986U, 695U, 1091956998U }, 380 { 1935056945U, 958U, 514864477U }, 381 { 735675993U, 990U, 1294239989U }, 382 { 1560089402U, 897U, 2238551287U }, 383 { 70616361U, 829U, 22483098U }, 384 { 368234700U, 731U, 2913875084U }, 385 { 20221190U, 879U, 1564152970U }, 386 { 539444654U, 682U, 1835141259U }, 387 { 1314987297U, 840U, 1801114136U }, 388 { 2019295544U, 645U, 3286438930U }, 389 { 469023838U, 716U, 1637918202U }, 390 { 1843754496U, 653U, 2562092152U }, 391 { 400672036U, 809U, 4264212785U }, 392 { 404722249U, 965U, 2704116999U }, 393 { 600702209U, 758U, 584979986U }, 394 { 519953954U, 667U, 2574436237U }, 395 { 1658071126U, 694U, 2214569490U }, 396 { 420480037U, 749U, 3430010866U }, 397 { 690103647U, 969U, 3700758083U }, 398 { 1029424799U, 937U, 3787746841U }, 399 { 2012608669U, 506U, 3362628973U }, 400 { 1535432887U, 998U, 42610943U }, 401 { 1330635533U, 857U, 3040806504U }, 402 { 1223800550U, 539U, 3954229517U }, 403 { 1322411537U, 680U, 3223250324U }, 404 { 1877847898U, 945U, 2915147143U }, 405 { 1646356099U, 874U, 965988280U }, 406 { 805687536U, 744U, 4032277920U }, 407 { 1948093210U, 633U, 1346597684U }, 408 { 392609744U, 783U, 1636083295U }, 409 { 690241304U, 770U, 1201031298U }, 410 { 1360302965U, 696U, 1665394461U }, 411 { 1220090946U, 780U, 1316922812U }, 412 { 447092251U, 500U, 3438743375U }, 413 { 1613868791U, 592U, 828546883U }, 414 { 523430951U, 548U, 2552392304U }, 415 { 726692899U, 810U, 1656872867U }, 416 { 1364340021U, 836U, 3710513486U }, 417 { 1986257729U, 931U, 935013962U }, 418 { 407983964U, 921U, 728767059U }, 419 }; 420 421 static void __init prandom_state_selftest(void) 422 { 423 int i, j, errors = 0, runs = 0; 424 bool error = false; 425 426 for (i = 0; i < ARRAY_SIZE(test1); i++) { 427 struct rnd_state state; 428 429 prandom_seed_early(&state, test1[i].seed, false); 430 prandom_warmup(&state); 431 432 if (test1[i].result != prandom_u32_state(&state)) 433 error = true; 434 } 435 436 if (error) 437 pr_warn("prandom: seed boundary self test failed\n"); 438 else 439 pr_info("prandom: seed boundary self test passed\n"); 440 441 for (i = 0; i < ARRAY_SIZE(test2); i++) { 442 struct rnd_state state; 443 444 prandom_seed_early(&state, test2[i].seed, false); 445 prandom_warmup(&state); 446 447 for (j = 0; j < test2[i].iteration - 1; j++) 448 prandom_u32_state(&state); 449 450 if (test2[i].result != prandom_u32_state(&state)) 451 errors++; 452 453 runs++; 454 cond_resched(); 455 } 456 457 if (errors) 458 pr_warn("prandom: %d/%d self tests failed\n", errors, runs); 459 else 460 pr_info("prandom: %d self tests passed\n", runs); 461 } 462 #endif 463