projects/linux·blob v3.17 · refs

462 lines · 12.6 KiB

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
42static void __init prandom_state_selftest(void);
43#else
44static inline void prandom_state_selftest(void)
45{
46}
47#endif
48
49static 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 */
58u32 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}
68EXPORT_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 */
77u32 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}
87EXPORT_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 */
99void 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}
122EXPORT_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 */
129void 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}
136EXPORT_SYMBOL(prandom_bytes);
137
138static 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
153static 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
163static 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 */
180void 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}
194EXPORT_SYMBOL(prandom_seed);
195
196/*
197 * Generate some initially weak seeding values to allow
198 * to start the prandom_u32() engine.
199 */
200static 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}
216core_initcall(prandom_init);
217
218static void __prandom_timer(unsigned long dontcare);
219
220static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0);
221
222static 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
237static 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 */
248static 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 }
285out:
286 spin_unlock_irqrestore(&lock, flags);
287}
288
289void prandom_reseed_late(void)
290{
291 __prandom_reseed(true);
292}
293
294static int __init prandom_reseed(void)
295{
296 __prandom_reseed(false);
297 __prandom_start_seed_timer();
298 return 0;
299}
300late_initcall(prandom_reseed);
301
302#ifdef CONFIG_RANDOM32_SELFTEST
303static 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
313static 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
421static 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