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Stephen Hemmingeraaa248f2006-10-17 00:09:42 -07001/*
2 This is a maximally equidistributed combined Tausworthe generator
3 based on code from GNU Scientific Library 1.5 (30 Jun 2004)
4
Daniel Borkmanna98814c2013-11-11 12:20:36 +01005 lfsr113 version:
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -07006
Daniel Borkmanna98814c2013-11-11 12:20:36 +01007 x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -07008
Daniel Borkmanna98814c2013-11-11 12:20:36 +01009 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).
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070015
16 From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
Daniel Borkmanna98814c2013-11-11 12:20:36 +010017 Generators", Mathematics of Computation, 65, 213 (1996), 203--213:
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070018 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
22 Equidistributed Combined LFSR Generators", Mathematics of
23 Computation, 68, 225 (1999), 261--269:
24 http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
25
26 ... the k_j most significant bits of z_j must be non-
27 zero, for each j. (Note: this restriction also applies to the
28 computer code given in [4], but was mistakenly not mentioned in
29 that paper.)
30
31 This affects the seeding procedure by imposing the requirement
Daniel Borkmanna98814c2013-11-11 12:20:36 +010032 s1 > 1, s2 > 7, s3 > 15, s4 > 127.
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070033
34*/
35
36#include <linux/types.h>
37#include <linux/percpu.h>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050038#include <linux/export.h>
Al Virof6a57032006-10-18 01:47:25 -040039#include <linux/jiffies.h>
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070040#include <linux/random.h>
Daniel Borkmanna6a9c0f2013-11-11 12:20:37 +010041#include <linux/sched.h>
42
43#ifdef CONFIG_RANDOM32_SELFTEST
44static void __init prandom_state_selftest(void);
45#endif
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070046
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070047static DEFINE_PER_CPU(struct rnd_state, net_rand_state);
48
Joe Eykholt59601642010-05-26 14:44:13 -070049/**
Akinobu Mita496f2f92012-12-17 16:04:23 -080050 * prandom_u32_state - seeded pseudo-random number generator.
Joe Eykholt59601642010-05-26 14:44:13 -070051 * @state: pointer to state structure holding seeded state.
52 *
53 * This is used for pseudo-randomness with no outside seeding.
Akinobu Mita496f2f92012-12-17 16:04:23 -080054 * For more random results, use prandom_u32().
Joe Eykholt59601642010-05-26 14:44:13 -070055 */
Akinobu Mita496f2f92012-12-17 16:04:23 -080056u32 prandom_u32_state(struct rnd_state *state)
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070057{
58#define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b)
59
Daniel Borkmanna98814c2013-11-11 12:20:36 +010060 state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U);
61 state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U);
62 state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U);
63 state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070064
Daniel Borkmanna98814c2013-11-11 12:20:36 +010065 return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070066}
Akinobu Mita496f2f92012-12-17 16:04:23 -080067EXPORT_SYMBOL(prandom_u32_state);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070068
69/**
Akinobu Mita496f2f92012-12-17 16:04:23 -080070 * prandom_u32 - pseudo random number generator
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070071 *
72 * A 32 bit pseudo-random number is generated using a fast
73 * algorithm suitable for simulation. This algorithm is NOT
74 * considered safe for cryptographic use.
75 */
Akinobu Mita496f2f92012-12-17 16:04:23 -080076u32 prandom_u32(void)
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070077{
78 unsigned long r;
79 struct rnd_state *state = &get_cpu_var(net_rand_state);
Akinobu Mita496f2f92012-12-17 16:04:23 -080080 r = prandom_u32_state(state);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070081 put_cpu_var(state);
82 return r;
83}
Akinobu Mita496f2f92012-12-17 16:04:23 -080084EXPORT_SYMBOL(prandom_u32);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -070085
Akinobu Mita6582c662012-12-17 16:04:25 -080086/*
87 * prandom_bytes_state - get the requested number of pseudo-random bytes
88 *
89 * @state: pointer to state structure holding seeded state.
90 * @buf: where to copy the pseudo-random bytes to
91 * @bytes: the requested number of bytes
92 *
93 * This is used for pseudo-randomness with no outside seeding.
94 * For more random results, use prandom_bytes().
95 */
96void prandom_bytes_state(struct rnd_state *state, void *buf, int bytes)
97{
98 unsigned char *p = buf;
99 int i;
100
101 for (i = 0; i < round_down(bytes, sizeof(u32)); i += sizeof(u32)) {
102 u32 random = prandom_u32_state(state);
103 int j;
104
105 for (j = 0; j < sizeof(u32); j++) {
106 p[i + j] = random;
107 random >>= BITS_PER_BYTE;
108 }
109 }
110 if (i < bytes) {
111 u32 random = prandom_u32_state(state);
112
113 for (; i < bytes; i++) {
114 p[i] = random;
115 random >>= BITS_PER_BYTE;
116 }
117 }
118}
119EXPORT_SYMBOL(prandom_bytes_state);
120
121/**
122 * prandom_bytes - get the requested number of pseudo-random bytes
123 * @buf: where to copy the pseudo-random bytes to
124 * @bytes: the requested number of bytes
125 */
126void prandom_bytes(void *buf, int bytes)
127{
128 struct rnd_state *state = &get_cpu_var(net_rand_state);
129
130 prandom_bytes_state(state, buf, bytes);
131 put_cpu_var(state);
132}
133EXPORT_SYMBOL(prandom_bytes);
134
Daniel Borkmanna98814c2013-11-11 12:20:36 +0100135static void prandom_warmup(struct rnd_state *state)
136{
137 /* Calling RNG ten times to satify recurrence condition */
138 prandom_u32_state(state);
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}
149
Daniel Borkmanna6a9c0f2013-11-11 12:20:37 +0100150static void prandom_seed_very_weak(struct rnd_state *state, u32 seed)
151{
152 /* Note: This sort of seeding is ONLY used in test cases and
153 * during boot at the time from core_initcall until late_initcall
154 * as we don't have a stronger entropy source available yet.
155 * After late_initcall, we reseed entire state, we have to (!),
156 * otherwise an attacker just needs to search 32 bit space to
157 * probe for our internal 128 bit state if he knows a couple
158 * of prandom32 outputs!
159 */
160#define LCG(x) ((x) * 69069U) /* super-duper LCG */
161 state->s1 = __seed(LCG(seed), 2U);
162 state->s2 = __seed(LCG(state->s1), 8U);
163 state->s3 = __seed(LCG(state->s2), 16U);
164 state->s4 = __seed(LCG(state->s3), 128U);
165}
166
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700167/**
Akinobu Mita496f2f92012-12-17 16:04:23 -0800168 * prandom_seed - add entropy to pseudo random number generator
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700169 * @seed: seed value
170 *
Akinobu Mita496f2f92012-12-17 16:04:23 -0800171 * Add some additional seeding to the prandom pool.
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700172 */
Akinobu Mita496f2f92012-12-17 16:04:23 -0800173void prandom_seed(u32 entropy)
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700174{
Andi Kleen61407f82008-04-03 14:07:02 -0700175 int i;
176 /*
177 * No locking on the CPUs, but then somewhat random results are, well,
178 * expected.
179 */
180 for_each_possible_cpu (i) {
181 struct rnd_state *state = &per_cpu(net_rand_state, i);
Daniel Borkmanna98814c2013-11-11 12:20:36 +0100182
183 state->s1 = __seed(state->s1 ^ entropy, 2U);
184 prandom_warmup(state);
Andi Kleen61407f82008-04-03 14:07:02 -0700185 }
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700186}
Akinobu Mita496f2f92012-12-17 16:04:23 -0800187EXPORT_SYMBOL(prandom_seed);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700188
189/*
190 * Generate some initially weak seeding values to allow
Akinobu Mita496f2f92012-12-17 16:04:23 -0800191 * to start the prandom_u32() engine.
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700192 */
Akinobu Mita496f2f92012-12-17 16:04:23 -0800193static int __init prandom_init(void)
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700194{
195 int i;
196
Daniel Borkmanna6a9c0f2013-11-11 12:20:37 +0100197#ifdef CONFIG_RANDOM32_SELFTEST
198 prandom_state_selftest();
199#endif
200
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700201 for_each_possible_cpu(i) {
202 struct rnd_state *state = &per_cpu(net_rand_state,i);
Stephen Hemminger697f8d02008-07-30 16:29:19 -0700203
Daniel Borkmanna6a9c0f2013-11-11 12:20:37 +0100204 prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy());
Daniel Borkmanna98814c2013-11-11 12:20:36 +0100205 prandom_warmup(state);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700206 }
207 return 0;
208}
Akinobu Mita496f2f92012-12-17 16:04:23 -0800209core_initcall(prandom_init);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700210
Hannes Frederic Sowa6d319202013-11-11 12:20:33 +0100211static void __prandom_timer(unsigned long dontcare);
212static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0);
213
214static void __prandom_timer(unsigned long dontcare)
215{
216 u32 entropy;
Daniel Borkmann0125737a2013-11-12 23:45:42 +0100217 unsigned long expires;
Hannes Frederic Sowa6d319202013-11-11 12:20:33 +0100218
219 get_random_bytes(&entropy, sizeof(entropy));
220 prandom_seed(entropy);
Daniel Borkmann0125737a2013-11-12 23:45:42 +0100221
Hannes Frederic Sowa6d319202013-11-11 12:20:33 +0100222 /* reseed every ~60 seconds, in [40 .. 80) interval with slack */
Daniel Borkmann0125737a2013-11-12 23:45:42 +0100223 expires = 40 + (prandom_u32() % 40);
224 seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC);
225
Hannes Frederic Sowa6d319202013-11-11 12:20:33 +0100226 add_timer(&seed_timer);
227}
228
Daniel Borkmann66b25142013-11-12 23:45:41 +0100229static void __init __prandom_start_seed_timer(void)
Hannes Frederic Sowa6d319202013-11-11 12:20:33 +0100230{
231 set_timer_slack(&seed_timer, HZ);
Daniel Borkmann0125737a2013-11-12 23:45:42 +0100232 seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC);
Hannes Frederic Sowa6d319202013-11-11 12:20:33 +0100233 add_timer(&seed_timer);
234}
235
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700236/*
237 * Generate better values after random number generator
Uwe Kleine-König421f91d2010-06-11 12:17:00 +0200238 * is fully initialized.
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700239 */
Hannes Frederic Sowa4af712e2013-11-11 12:20:34 +0100240static void __prandom_reseed(bool late)
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700241{
242 int i;
Hannes Frederic Sowa4af712e2013-11-11 12:20:34 +0100243 unsigned long flags;
244 static bool latch = false;
245 static DEFINE_SPINLOCK(lock);
246
247 /* only allow initial seeding (late == false) once */
248 spin_lock_irqsave(&lock, flags);
249 if (latch && !late)
250 goto out;
251 latch = true;
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700252
253 for_each_possible_cpu(i) {
254 struct rnd_state *state = &per_cpu(net_rand_state,i);
Daniel Borkmanna98814c2013-11-11 12:20:36 +0100255 u32 seeds[4];
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700256
Stephen Hemminger697f8d02008-07-30 16:29:19 -0700257 get_random_bytes(&seeds, sizeof(seeds));
Daniel Borkmanna98814c2013-11-11 12:20:36 +0100258 state->s1 = __seed(seeds[0], 2U);
259 state->s2 = __seed(seeds[1], 8U);
260 state->s3 = __seed(seeds[2], 16U);
261 state->s4 = __seed(seeds[3], 128U);
Stephen Hemminger697f8d02008-07-30 16:29:19 -0700262
Daniel Borkmanna98814c2013-11-11 12:20:36 +0100263 prandom_warmup(state);
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700264 }
Hannes Frederic Sowa4af712e2013-11-11 12:20:34 +0100265out:
266 spin_unlock_irqrestore(&lock, flags);
267}
268
269void prandom_reseed_late(void)
270{
271 __prandom_reseed(true);
272}
273
274static int __init prandom_reseed(void)
275{
276 __prandom_reseed(false);
Daniel Borkmann66b25142013-11-12 23:45:41 +0100277 __prandom_start_seed_timer();
Stephen Hemmingeraaa248f2006-10-17 00:09:42 -0700278 return 0;
279}
Akinobu Mita496f2f92012-12-17 16:04:23 -0800280late_initcall(prandom_reseed);
Daniel Borkmanna6a9c0f2013-11-11 12:20:37 +0100281
282#ifdef CONFIG_RANDOM32_SELFTEST
283static struct prandom_test1 {
284 u32 seed;
285 u32 result;
286} test1[] = {
287 { 1U, 3484351685U },
288 { 2U, 2623130059U },
289 { 3U, 3125133893U },
290 { 4U, 984847254U },
291};
292
293static struct prandom_test2 {
294 u32 seed;
295 u32 iteration;
296 u32 result;
297} test2[] = {
298 /* Test cases against taus113 from GSL library. */
299 { 931557656U, 959U, 2975593782U },
300 { 1339693295U, 876U, 3887776532U },
301 { 1545556285U, 961U, 1615538833U },
302 { 601730776U, 723U, 1776162651U },
303 { 1027516047U, 687U, 511983079U },
304 { 416526298U, 700U, 916156552U },
305 { 1395522032U, 652U, 2222063676U },
306 { 366221443U, 617U, 2992857763U },
307 { 1539836965U, 714U, 3783265725U },
308 { 556206671U, 994U, 799626459U },
309 { 684907218U, 799U, 367789491U },
310 { 2121230701U, 931U, 2115467001U },
311 { 1668516451U, 644U, 3620590685U },
312 { 768046066U, 883U, 2034077390U },
313 { 1989159136U, 833U, 1195767305U },
314 { 536585145U, 996U, 3577259204U },
315 { 1008129373U, 642U, 1478080776U },
316 { 1740775604U, 939U, 1264980372U },
317 { 1967883163U, 508U, 10734624U },
318 { 1923019697U, 730U, 3821419629U },
319 { 442079932U, 560U, 3440032343U },
320 { 1961302714U, 845U, 841962572U },
321 { 2030205964U, 962U, 1325144227U },
322 { 1160407529U, 507U, 240940858U },
323 { 635482502U, 779U, 4200489746U },
324 { 1252788931U, 699U, 867195434U },
325 { 1961817131U, 719U, 668237657U },
326 { 1071468216U, 983U, 917876630U },
327 { 1281848367U, 932U, 1003100039U },
328 { 582537119U, 780U, 1127273778U },
329 { 1973672777U, 853U, 1071368872U },
330 { 1896756996U, 762U, 1127851055U },
331 { 847917054U, 500U, 1717499075U },
332 { 1240520510U, 951U, 2849576657U },
333 { 1685071682U, 567U, 1961810396U },
334 { 1516232129U, 557U, 3173877U },
335 { 1208118903U, 612U, 1613145022U },
336 { 1817269927U, 693U, 4279122573U },
337 { 1510091701U, 717U, 638191229U },
338 { 365916850U, 807U, 600424314U },
339 { 399324359U, 702U, 1803598116U },
340 { 1318480274U, 779U, 2074237022U },
341 { 697758115U, 840U, 1483639402U },
342 { 1696507773U, 840U, 577415447U },
343 { 2081979121U, 981U, 3041486449U },
344 { 955646687U, 742U, 3846494357U },
345 { 1250683506U, 749U, 836419859U },
346 { 595003102U, 534U, 366794109U },
347 { 47485338U, 558U, 3521120834U },
348 { 619433479U, 610U, 3991783875U },
349 { 704096520U, 518U, 4139493852U },
350 { 1712224984U, 606U, 2393312003U },
351 { 1318233152U, 922U, 3880361134U },
352 { 855572992U, 761U, 1472974787U },
353 { 64721421U, 703U, 683860550U },
354 { 678931758U, 840U, 380616043U },
355 { 692711973U, 778U, 1382361947U },
356 { 677703619U, 530U, 2826914161U },
357 { 92393223U, 586U, 1522128471U },
358 { 1222592920U, 743U, 3466726667U },
359 { 358288986U, 695U, 1091956998U },
360 { 1935056945U, 958U, 514864477U },
361 { 735675993U, 990U, 1294239989U },
362 { 1560089402U, 897U, 2238551287U },
363 { 70616361U, 829U, 22483098U },
364 { 368234700U, 731U, 2913875084U },
365 { 20221190U, 879U, 1564152970U },
366 { 539444654U, 682U, 1835141259U },
367 { 1314987297U, 840U, 1801114136U },
368 { 2019295544U, 645U, 3286438930U },
369 { 469023838U, 716U, 1637918202U },
370 { 1843754496U, 653U, 2562092152U },
371 { 400672036U, 809U, 4264212785U },
372 { 404722249U, 965U, 2704116999U },
373 { 600702209U, 758U, 584979986U },
374 { 519953954U, 667U, 2574436237U },
375 { 1658071126U, 694U, 2214569490U },
376 { 420480037U, 749U, 3430010866U },
377 { 690103647U, 969U, 3700758083U },
378 { 1029424799U, 937U, 3787746841U },
379 { 2012608669U, 506U, 3362628973U },
380 { 1535432887U, 998U, 42610943U },
381 { 1330635533U, 857U, 3040806504U },
382 { 1223800550U, 539U, 3954229517U },
383 { 1322411537U, 680U, 3223250324U },
384 { 1877847898U, 945U, 2915147143U },
385 { 1646356099U, 874U, 965988280U },
386 { 805687536U, 744U, 4032277920U },
387 { 1948093210U, 633U, 1346597684U },
388 { 392609744U, 783U, 1636083295U },
389 { 690241304U, 770U, 1201031298U },
390 { 1360302965U, 696U, 1665394461U },
391 { 1220090946U, 780U, 1316922812U },
392 { 447092251U, 500U, 3438743375U },
393 { 1613868791U, 592U, 828546883U },
394 { 523430951U, 548U, 2552392304U },
395 { 726692899U, 810U, 1656872867U },
396 { 1364340021U, 836U, 3710513486U },
397 { 1986257729U, 931U, 935013962U },
398 { 407983964U, 921U, 728767059U },
399};
400
401static void __init prandom_state_selftest(void)
402{
403 int i, j, errors = 0, runs = 0;
404 bool error = false;
405
406 for (i = 0; i < ARRAY_SIZE(test1); i++) {
407 struct rnd_state state;
408
409 prandom_seed_very_weak(&state, test1[i].seed);
410 prandom_warmup(&state);
411
412 if (test1[i].result != prandom_u32_state(&state))
413 error = true;
414 }
415
416 if (error)
417 pr_warn("prandom: seed boundary self test failed\n");
418 else
419 pr_info("prandom: seed boundary self test passed\n");
420
421 for (i = 0; i < ARRAY_SIZE(test2); i++) {
422 struct rnd_state state;
423
424 prandom_seed_very_weak(&state, test2[i].seed);
425 prandom_warmup(&state);
426
427 for (j = 0; j < test2[i].iteration - 1; j++)
428 prandom_u32_state(&state);
429
430 if (test2[i].result != prandom_u32_state(&state))
431 errors++;
432
433 runs++;
434 cond_resched();
435 }
436
437 if (errors)
438 pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
439 else
440 pr_info("prandom: %d self tests passed\n", runs);
441}
442#endif