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 <asm/unaligned.h> 43 #include <trace/events/random.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 u32 __extract_hwseed(void) 249 { 250 unsigned int val = 0; 251 252 (void)(arch_get_random_seed_int(&val) || 253 arch_get_random_int(&val)); 254 255 return val; 256 } 257 258 static void prandom_seed_early(struct rnd_state *state, u32 seed, 259 bool mix_with_hwseed) 260 { 261 #define LCG(x) ((x) * 69069U) /* super-duper LCG */ 262 #define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0) 263 state->s1 = __seed(HWSEED() ^ LCG(seed), 2U); 264 state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U); 265 state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U); 266 state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U); 267 } 268 269 static int __init prandom_state_selftest(void) 270 { 271 int i, j, errors = 0, runs = 0; 272 bool error = false; 273 274 for (i = 0; i < ARRAY_SIZE(test1); i++) { 275 struct rnd_state state; 276 277 prandom_seed_early(&state, test1[i].seed, false); 278 prandom_warmup(&state); 279 280 if (test1[i].result != prandom_u32_state(&state)) 281 error = true; 282 } 283 284 if (error) 285 pr_warn("prandom: seed boundary self test failed\n"); 286 else 287 pr_info("prandom: seed boundary self test passed\n"); 288 289 for (i = 0; i < ARRAY_SIZE(test2); i++) { 290 struct rnd_state state; 291 292 prandom_seed_early(&state, test2[i].seed, false); 293 prandom_warmup(&state); 294 295 for (j = 0; j < test2[i].iteration - 1; j++) 296 prandom_u32_state(&state); 297 298 if (test2[i].result != prandom_u32_state(&state)) 299 errors++; 300 301 runs++; 302 cond_resched(); 303 } 304 305 if (errors) 306 pr_warn("prandom: %d/%d self tests failed\n", errors, runs); 307 else 308 pr_info("prandom: %d self tests passed\n", runs); 309 return 0; 310 } 311 core_initcall(prandom_state_selftest); 312 #endif 313 314 /* 315 * The prandom_u32() implementation is now completely separate from the 316 * prandom_state() functions, which are retained (for now) for compatibility. 317 * 318 * Because of (ab)use in the networking code for choosing random TCP/UDP port 319 * numbers, which open DoS possibilities if guessable, we want something 320 * stronger than a standard PRNG. But the performance requirements of 321 * the network code do not allow robust crypto for this application. 322 * 323 * So this is a homebrew Junior Spaceman implementation, based on the 324 * lowest-latency trustworthy crypto primitive available, SipHash. 325 * (The authors of SipHash have not been consulted about this abuse of 326 * their work.) 327 * 328 * Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to 329 * one word of output. This abbreviated version uses 2 rounds per word 330 * of output. 331 */ 332 333 struct siprand_state { 334 unsigned long v0; 335 unsigned long v1; 336 unsigned long v2; 337 unsigned long v3; 338 }; 339 340 static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy; 341 DEFINE_PER_CPU(unsigned long, net_rand_noise); 342 EXPORT_PER_CPU_SYMBOL(net_rand_noise); 343 344 /* 345 * This is the core CPRNG function. As "pseudorandom", this is not used 346 * for truly valuable things, just intended to be a PITA to guess. 347 * For maximum speed, we do just two SipHash rounds per word. This is 348 * the same rate as 4 rounds per 64 bits that SipHash normally uses, 349 * so hopefully it's reasonably secure. 350 * 351 * There are two changes from the official SipHash finalization: 352 * - We omit some constants XORed with v2 in the SipHash spec as irrelevant; 353 * they are there only to make the output rounds distinct from the input 354 * rounds, and this application has no input rounds. 355 * - Rather than returning v0^v1^v2^v3, return v1+v3. 356 * If you look at the SipHash round, the last operation on v3 is 357 * "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time. 358 * Likewise "v1 ^= v2". (The rotate of v2 makes a difference, but 359 * it still cancels out half of the bits in v2 for no benefit.) 360 * Second, since the last combining operation was xor, continue the 361 * pattern of alternating xor/add for a tiny bit of extra non-linearity. 362 */ 363 static inline u32 siprand_u32(struct siprand_state *s) 364 { 365 unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3; 366 unsigned long n = raw_cpu_read(net_rand_noise); 367 368 v3 ^= n; 369 PRND_SIPROUND(v0, v1, v2, v3); 370 PRND_SIPROUND(v0, v1, v2, v3); 371 v0 ^= n; 372 s->v0 = v0; s->v1 = v1; s->v2 = v2; s->v3 = v3; 373 return v1 + v3; 374 } 375 376 377 /** 378 * prandom_u32 - pseudo random number generator 379 * 380 * A 32 bit pseudo-random number is generated using a fast 381 * algorithm suitable for simulation. This algorithm is NOT 382 * considered safe for cryptographic use. 383 */ 384 u32 prandom_u32(void) 385 { 386 struct siprand_state *state = get_cpu_ptr(&net_rand_state); 387 u32 res = siprand_u32(state); 388 389 trace_prandom_u32(res); 390 put_cpu_ptr(&net_rand_state); 391 return res; 392 } 393 EXPORT_SYMBOL(prandom_u32); 394 395 /** 396 * prandom_bytes - get the requested number of pseudo-random bytes 397 * @buf: where to copy the pseudo-random bytes to 398 * @bytes: the requested number of bytes 399 */ 400 void prandom_bytes(void *buf, size_t bytes) 401 { 402 struct siprand_state *state = get_cpu_ptr(&net_rand_state); 403 u8 *ptr = buf; 404 405 while (bytes >= sizeof(u32)) { 406 put_unaligned(siprand_u32(state), (u32 *)ptr); 407 ptr += sizeof(u32); 408 bytes -= sizeof(u32); 409 } 410 411 if (bytes > 0) { 412 u32 rem = siprand_u32(state); 413 414 do { 415 *ptr++ = (u8)rem; 416 rem >>= BITS_PER_BYTE; 417 } while (--bytes > 0); 418 } 419 put_cpu_ptr(&net_rand_state); 420 } 421 EXPORT_SYMBOL(prandom_bytes); 422 423 /** 424 * prandom_seed - add entropy to pseudo random number generator 425 * @entropy: entropy value 426 * 427 * Add some additional seed material to the prandom pool. 428 * The "entropy" is actually our IP address (the only caller is 429 * the network code), not for unpredictability, but to ensure that 430 * different machines are initialized differently. 431 */ 432 void prandom_seed(u32 entropy) 433 { 434 int i; 435 436 add_device_randomness(&entropy, sizeof(entropy)); 437 438 for_each_possible_cpu(i) { 439 struct siprand_state *state = per_cpu_ptr(&net_rand_state, i); 440 unsigned long v0 = state->v0, v1 = state->v1; 441 unsigned long v2 = state->v2, v3 = state->v3; 442 443 do { 444 v3 ^= entropy; 445 PRND_SIPROUND(v0, v1, v2, v3); 446 PRND_SIPROUND(v0, v1, v2, v3); 447 v0 ^= entropy; 448 } while (unlikely(!v0 || !v1 || !v2 || !v3)); 449 450 WRITE_ONCE(state->v0, v0); 451 WRITE_ONCE(state->v1, v1); 452 WRITE_ONCE(state->v2, v2); 453 WRITE_ONCE(state->v3, v3); 454 } 455 } 456 EXPORT_SYMBOL(prandom_seed); 457 458 /* 459 * Generate some initially weak seeding values to allow 460 * the prandom_u32() engine to be started. 461 */ 462 static int __init prandom_init_early(void) 463 { 464 int i; 465 unsigned long v0, v1, v2, v3; 466 467 if (!arch_get_random_long(&v0)) 468 v0 = jiffies; 469 if (!arch_get_random_long(&v1)) 470 v1 = random_get_entropy(); 471 v2 = v0 ^ PRND_K0; 472 v3 = v1 ^ PRND_K1; 473 474 for_each_possible_cpu(i) { 475 struct siprand_state *state; 476 477 v3 ^= i; 478 PRND_SIPROUND(v0, v1, v2, v3); 479 PRND_SIPROUND(v0, v1, v2, v3); 480 v0 ^= i; 481 482 state = per_cpu_ptr(&net_rand_state, i); 483 state->v0 = v0; state->v1 = v1; 484 state->v2 = v2; state->v3 = v3; 485 } 486 487 return 0; 488 } 489 core_initcall(prandom_init_early); 490 491 492 /* Stronger reseeding when available, and periodically thereafter. */ 493 static void prandom_reseed(struct timer_list *unused); 494 495 static DEFINE_TIMER(seed_timer, prandom_reseed); 496 497 static void prandom_reseed(struct timer_list *unused) 498 { 499 unsigned long expires; 500 int i; 501 502 /* 503 * Reinitialize each CPU's PRNG with 128 bits of key. 504 * No locking on the CPUs, but then somewhat random results are, 505 * well, expected. 506 */ 507 for_each_possible_cpu(i) { 508 struct siprand_state *state; 509 unsigned long v0 = get_random_long(), v2 = v0 ^ PRND_K0; 510 unsigned long v1 = get_random_long(), v3 = v1 ^ PRND_K1; 511 #if BITS_PER_LONG == 32 512 int j; 513 514 /* 515 * On 32-bit machines, hash in two extra words to 516 * approximate 128-bit key length. Not that the hash 517 * has that much security, but this prevents a trivial 518 * 64-bit brute force. 519 */ 520 for (j = 0; j < 2; j++) { 521 unsigned long m = get_random_long(); 522 523 v3 ^= m; 524 PRND_SIPROUND(v0, v1, v2, v3); 525 PRND_SIPROUND(v0, v1, v2, v3); 526 v0 ^= m; 527 } 528 #endif 529 /* 530 * Probably impossible in practice, but there is a 531 * theoretical risk that a race between this reseeding 532 * and the target CPU writing its state back could 533 * create the all-zero SipHash fixed point. 534 * 535 * To ensure that never happens, ensure the state 536 * we write contains no zero words. 537 */ 538 state = per_cpu_ptr(&net_rand_state, i); 539 WRITE_ONCE(state->v0, v0 ? v0 : -1ul); 540 WRITE_ONCE(state->v1, v1 ? v1 : -1ul); 541 WRITE_ONCE(state->v2, v2 ? v2 : -1ul); 542 WRITE_ONCE(state->v3, v3 ? v3 : -1ul); 543 } 544 545 /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ 546 expires = round_jiffies(jiffies + 40 * HZ + prandom_u32_max(40 * HZ)); 547 mod_timer(&seed_timer, expires); 548 } 549 550 /* 551 * The random ready callback can be called from almost any interrupt. 552 * To avoid worrying about whether it's safe to delay that interrupt 553 * long enough to seed all CPUs, just schedule an immediate timer event. 554 */ 555 static void prandom_timer_start(struct random_ready_callback *unused) 556 { 557 mod_timer(&seed_timer, jiffies); 558 } 559 560 #ifdef CONFIG_RANDOM32_SELFTEST 561 /* Principle: True 32-bit random numbers will all have 16 differing bits on 562 * average. For each 32-bit number, there are 601M numbers differing by 16 563 * bits, and 89% of the numbers differ by at least 12 bits. Note that more 564 * than 16 differing bits also implies a correlation with inverted bits. Thus 565 * we take 1024 random numbers and compare each of them to the other ones, 566 * counting the deviation of correlated bits to 16. Constants report 32, 567 * counters 32-log2(TEST_SIZE), and pure randoms, around 6 or lower. With the 568 * u32 total, TEST_SIZE may be as large as 4096 samples. 569 */ 570 #define TEST_SIZE 1024 571 static int __init prandom32_state_selftest(void) 572 { 573 unsigned int x, y, bits, samples; 574 u32 xor, flip; 575 u32 total; 576 u32 *data; 577 578 data = kmalloc(sizeof(*data) * TEST_SIZE, GFP_KERNEL); 579 if (!data) 580 return 0; 581 582 for (samples = 0; samples < TEST_SIZE; samples++) 583 data[samples] = prandom_u32(); 584 585 flip = total = 0; 586 for (x = 0; x < samples; x++) { 587 for (y = 0; y < samples; y++) { 588 if (x == y) 589 continue; 590 xor = data[x] ^ data[y]; 591 flip |= xor; 592 bits = hweight32(xor); 593 total += (bits - 16) * (bits - 16); 594 } 595 } 596 597 /* We'll return the average deviation as 2*sqrt(corr/samples), which 598 * is also sqrt(4*corr/samples) which provides a better resolution. 599 */ 600 bits = int_sqrt(total / (samples * (samples - 1)) * 4); 601 if (bits > 6) 602 pr_warn("prandom32: self test failed (at least %u bits" 603 " correlated, fixed_mask=%#x fixed_value=%#x\n", 604 bits, ~flip, data[0] & ~flip); 605 else 606 pr_info("prandom32: self test passed (less than %u bits" 607 " correlated)\n", 608 bits+1); 609 kfree(data); 610 return 0; 611 } 612 core_initcall(prandom32_state_selftest); 613 #endif /* CONFIG_RANDOM32_SELFTEST */ 614 615 /* 616 * Start periodic full reseeding as soon as strong 617 * random numbers are available. 618 */ 619 static int __init prandom_init_late(void) 620 { 621 static struct random_ready_callback random_ready = { 622 .func = prandom_timer_start 623 }; 624 int ret = add_random_ready_callback(&random_ready); 625 626 if (ret == -EALREADY) { 627 prandom_timer_start(&random_ready); 628 ret = 0; 629 } 630 return ret; 631 } 632 late_initcall(prandom_init_late); 633