the-tree/lib/random32.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * This is a maximally equidistributed combined Tausworthe generator
0004  * based on code from GNU Scientific Library 1.5 (30 Jun 2004)
0005  *
0006  * lfsr113 version:
0007  *
0008  * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)
0009  *
0010  * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n <<  6) ^ s1_n) >> 13))
0011  * s2_{n+1} = (((s2_n & 4294967288) <<  2) ^ (((s2_n <<  2) ^ s2_n) >> 27))
0012  * s3_{n+1} = (((s3_n & 4294967280) <<  7) ^ (((s3_n << 13) ^ s3_n) >> 21))
0013  * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n <<  3) ^ s4_n) >> 12))
0014  *
0015  * The period of this generator is about 2^113 (see erratum paper).
0016  *
0017  * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
0018  * Generators", Mathematics of Computation, 65, 213 (1996), 203--213:
0019  * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
0020  * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
0021  *
0022  * There is an erratum in the paper "Tables of Maximally Equidistributed
0023  * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999),
0024  * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
0025  *
0026  *      ... the k_j most significant bits of z_j must be non-zero,
0027  *      for each j. (Note: this restriction also applies to the
0028  *      computer code given in [4], but was mistakenly not mentioned
0029  *      in that paper.)
0030  *
0031  * This affects the seeding procedure by imposing the requirement
0032  * s1 > 1, s2 > 7, s3 > 15, s4 > 127.
0033  */
0034
0035 #include <linux/types.h>
0036 #include <linux/percpu.h>
0037 #include <linux/export.h>
0038 #include <linux/jiffies.h>
0039 #include <linux/random.h>
0040 #include <linux/sched.h>
0041 #include <linux/bitops.h>
0042 #include <linux/slab.h>
0043 #include <asm/unaligned.h>
0044
0045 /**
0046  *  prandom_u32_state - seeded pseudo-random number generator.
0047  *  @state: pointer to state structure holding seeded state.
0048  *
0049  *  This is used for pseudo-randomness with no outside seeding.
0050  *  For more random results, use prandom_u32().
0051  */
0052 u32 prandom_u32_state(struct rnd_state *state)
0053 {
0054 #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)
0055     state->s1 = TAUSWORTHE(state->s1,  6U, 13U, 4294967294U, 18U);
0056     state->s2 = TAUSWORTHE(state->s2,  2U, 27U, 4294967288U,  2U);
0057     state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U,  7U);
0058     state->s4 = TAUSWORTHE(state->s4,  3U, 12U, 4294967168U, 13U);
0059
0060     return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
0061 }
0062 EXPORT_SYMBOL(prandom_u32_state);
0063
0064 /**
0065  *  prandom_bytes_state - get the requested number of pseudo-random bytes
0066  *
0067  *  @state: pointer to state structure holding seeded state.
0068  *  @buf: where to copy the pseudo-random bytes to
0069  *  @bytes: the requested number of bytes
0070  *
0071  *  This is used for pseudo-randomness with no outside seeding.
0072  *  For more random results, use prandom_bytes().
0073  */
0074 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes)
0075 {
0076     u8 *ptr = buf;
0077
0078     while (bytes >= sizeof(u32)) {
0079         put_unaligned(prandom_u32_state(state), (u32 *) ptr);
0080         ptr += sizeof(u32);
0081         bytes -= sizeof(u32);
0082     }
0083
0084     if (bytes > 0) {
0085         u32 rem = prandom_u32_state(state);
0086         do {
0087             *ptr++ = (u8) rem;
0088             bytes--;
0089             rem >>= BITS_PER_BYTE;
0090         } while (bytes > 0);
0091     }
0092 }
0093 EXPORT_SYMBOL(prandom_bytes_state);
0094
0095 static void prandom_warmup(struct rnd_state *state)
0096 {
0097     /* Calling RNG ten times to satisfy recurrence condition */
0098     prandom_u32_state(state);
0099     prandom_u32_state(state);
0100     prandom_u32_state(state);
0101     prandom_u32_state(state);
0102     prandom_u32_state(state);
0103     prandom_u32_state(state);
0104     prandom_u32_state(state);
0105     prandom_u32_state(state);
0106     prandom_u32_state(state);
0107     prandom_u32_state(state);
0108 }
0109
0110 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
0111 {
0112     int i;
0113
0114     for_each_possible_cpu(i) {
0115         struct rnd_state *state = per_cpu_ptr(pcpu_state, i);
0116         u32 seeds[4];
0117
0118         get_random_bytes(&seeds, sizeof(seeds));
0119         state->s1 = __seed(seeds[0],   2U);
0120         state->s2 = __seed(seeds[1],   8U);
0121         state->s3 = __seed(seeds[2],  16U);
0122         state->s4 = __seed(seeds[3], 128U);
0123
0124         prandom_warmup(state);
0125     }
0126 }
0127 EXPORT_SYMBOL(prandom_seed_full_state);
0128
0129 #ifdef CONFIG_RANDOM32_SELFTEST
0130 static struct prandom_test1 {
0131     u32 seed;
0132     u32 result;
0133 } test1[] = {
0134     { 1U, 3484351685U },
0135     { 2U, 2623130059U },
0136     { 3U, 3125133893U },
0137     { 4U,  984847254U },
0138 };
0139
0140 static struct prandom_test2 {
0141     u32 seed;
0142     u32 iteration;
0143     u32 result;
0144 } test2[] = {
0145     /* Test cases against taus113 from GSL library. */
0146     {  931557656U, 959U, 2975593782U },
0147     { 1339693295U, 876U, 3887776532U },
0148     { 1545556285U, 961U, 1615538833U },
0149     {  601730776U, 723U, 1776162651U },
0150     { 1027516047U, 687U,  511983079U },
0151     {  416526298U, 700U,  916156552U },
0152     { 1395522032U, 652U, 2222063676U },
0153     {  366221443U, 617U, 2992857763U },
0154     { 1539836965U, 714U, 3783265725U },
0155     {  556206671U, 994U,  799626459U },
0156     {  684907218U, 799U,  367789491U },
0157     { 2121230701U, 931U, 2115467001U },
0158     { 1668516451U, 644U, 3620590685U },
0159     {  768046066U, 883U, 2034077390U },
0160     { 1989159136U, 833U, 1195767305U },
0161     {  536585145U, 996U, 3577259204U },
0162     { 1008129373U, 642U, 1478080776U },
0163     { 1740775604U, 939U, 1264980372U },
0164     { 1967883163U, 508U,   10734624U },
0165     { 1923019697U, 730U, 3821419629U },
0166     {  442079932U, 560U, 3440032343U },
0167     { 1961302714U, 845U,  841962572U },
0168     { 2030205964U, 962U, 1325144227U },
0169     { 1160407529U, 507U,  240940858U },
0170     {  635482502U, 779U, 4200489746U },
0171     { 1252788931U, 699U,  867195434U },
0172     { 1961817131U, 719U,  668237657U },
0173     { 1071468216U, 983U,  917876630U },
0174     { 1281848367U, 932U, 1003100039U },
0175     {  582537119U, 780U, 1127273778U },
0176     { 1973672777U, 853U, 1071368872U },
0177     { 1896756996U, 762U, 1127851055U },
0178     {  847917054U, 500U, 1717499075U },
0179     { 1240520510U, 951U, 2849576657U },
0180     { 1685071682U, 567U, 1961810396U },
0181     { 1516232129U, 557U,    3173877U },
0182     { 1208118903U, 612U, 1613145022U },
0183     { 1817269927U, 693U, 4279122573U },
0184     { 1510091701U, 717U,  638191229U },
0185     {  365916850U, 807U,  600424314U },
0186     {  399324359U, 702U, 1803598116U },
0187     { 1318480274U, 779U, 2074237022U },
0188     {  697758115U, 840U, 1483639402U },
0189     { 1696507773U, 840U,  577415447U },
0190     { 2081979121U, 981U, 3041486449U },
0191     {  955646687U, 742U, 3846494357U },
0192     { 1250683506U, 749U,  836419859U },
0193     {  595003102U, 534U,  366794109U },
0194     {   47485338U, 558U, 3521120834U },
0195     {  619433479U, 610U, 3991783875U },
0196     {  704096520U, 518U, 4139493852U },
0197     { 1712224984U, 606U, 2393312003U },
0198     { 1318233152U, 922U, 3880361134U },
0199     {  855572992U, 761U, 1472974787U },
0200     {   64721421U, 703U,  683860550U },
0201     {  678931758U, 840U,  380616043U },
0202     {  692711973U, 778U, 1382361947U },
0203     {  677703619U, 530U, 2826914161U },
0204     {   92393223U, 586U, 1522128471U },
0205     { 1222592920U, 743U, 3466726667U },
0206     {  358288986U, 695U, 1091956998U },
0207     { 1935056945U, 958U,  514864477U },
0208     {  735675993U, 990U, 1294239989U },
0209     { 1560089402U, 897U, 2238551287U },
0210     {   70616361U, 829U,   22483098U },
0211     {  368234700U, 731U, 2913875084U },
0212     {   20221190U, 879U, 1564152970U },
0213     {  539444654U, 682U, 1835141259U },
0214     { 1314987297U, 840U, 1801114136U },
0215     { 2019295544U, 645U, 3286438930U },
0216     {  469023838U, 716U, 1637918202U },
0217     { 1843754496U, 653U, 2562092152U },
0218     {  400672036U, 809U, 4264212785U },
0219     {  404722249U, 965U, 2704116999U },
0220     {  600702209U, 758U,  584979986U },
0221     {  519953954U, 667U, 2574436237U },
0222     { 1658071126U, 694U, 2214569490U },
0223     {  420480037U, 749U, 3430010866U },
0224     {  690103647U, 969U, 3700758083U },
0225     { 1029424799U, 937U, 3787746841U },
0226     { 2012608669U, 506U, 3362628973U },
0227     { 1535432887U, 998U,   42610943U },
0228     { 1330635533U, 857U, 3040806504U },
0229     { 1223800550U, 539U, 3954229517U },
0230     { 1322411537U, 680U, 3223250324U },
0231     { 1877847898U, 945U, 2915147143U },
0232     { 1646356099U, 874U,  965988280U },
0233     {  805687536U, 744U, 4032277920U },
0234     { 1948093210U, 633U, 1346597684U },
0235     {  392609744U, 783U, 1636083295U },
0236     {  690241304U, 770U, 1201031298U },
0237     { 1360302965U, 696U, 1665394461U },
0238     { 1220090946U, 780U, 1316922812U },
0239     {  447092251U, 500U, 3438743375U },
0240     { 1613868791U, 592U,  828546883U },
0241     {  523430951U, 548U, 2552392304U },
0242     {  726692899U, 810U, 1656872867U },
0243     { 1364340021U, 836U, 3710513486U },
0244     { 1986257729U, 931U,  935013962U },
0245     {  407983964U, 921U,  728767059U },
0246 };
0247
0248 static void prandom_state_selftest_seed(struct rnd_state *state, u32 seed)
0249 {
0250 #define LCG(x)   ((x) * 69069U) /* super-duper LCG */
0251     state->s1 = __seed(LCG(seed),        2U);
0252     state->s2 = __seed(LCG(state->s1),   8U);
0253     state->s3 = __seed(LCG(state->s2),  16U);
0254     state->s4 = __seed(LCG(state->s3), 128U);
0255 }
0256
0257 static int __init prandom_state_selftest(void)
0258 {
0259     int i, j, errors = 0, runs = 0;
0260     bool error = false;
0261
0262     for (i = 0; i < ARRAY_SIZE(test1); i++) {
0263         struct rnd_state state;
0264
0265         prandom_state_selftest_seed(&state, test1[i].seed);
0266         prandom_warmup(&state);
0267
0268         if (test1[i].result != prandom_u32_state(&state))
0269             error = true;
0270     }
0271
0272     if (error)
0273         pr_warn("prandom: seed boundary self test failed\n");
0274     else
0275         pr_info("prandom: seed boundary self test passed\n");
0276
0277     for (i = 0; i < ARRAY_SIZE(test2); i++) {
0278         struct rnd_state state;
0279
0280         prandom_state_selftest_seed(&state, test2[i].seed);
0281         prandom_warmup(&state);
0282
0283         for (j = 0; j < test2[i].iteration - 1; j++)
0284             prandom_u32_state(&state);
0285
0286         if (test2[i].result != prandom_u32_state(&state))
0287             errors++;
0288
0289         runs++;
0290         cond_resched();
0291     }
0292
0293     if (errors)
0294         pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
0295     else
0296         pr_info("prandom: %d self tests passed\n", runs);
0297     return 0;
0298 }
0299 core_initcall(prandom_state_selftest);
0300 #endif