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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#endif
44
45static DEFINE_PER_CPU(struct rnd_state, net_rand_state);
46
47/**
48 * prandom_u32_state - seeded pseudo-random number generator.
49 * @state: pointer to state structure holding seeded state.
50 *
51 * This is used for pseudo-randomness with no outside seeding.
52 * For more random results, use prandom_u32().
53 */
54u32 prandom_u32_state(struct rnd_state *state)
55{
56#define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b)
57
58 state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U);
59 state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U);
60 state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U);
61 state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U);
62
63 return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
64}
65EXPORT_SYMBOL(prandom_u32_state);
66
67/**
68 * prandom_u32 - pseudo random number generator
69 *
70 * A 32 bit pseudo-random number is generated using a fast
71 * algorithm suitable for simulation. This algorithm is NOT
72 * considered safe for cryptographic use.
73 */
74u32 prandom_u32(void)
75{
76 struct rnd_state *state = &get_cpu_var(net_rand_state);
77 u32 res;
78
79 res = prandom_u32_state(state);
80 put_cpu_var(state);
81
82 return res;
83}
84EXPORT_SYMBOL(prandom_u32);
85
86/**
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
135static 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
150static 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
167/**
168 * prandom_seed - add entropy to pseudo random number generator
169 * @seed: seed value
170 *
171 * Add some additional seeding to the prandom pool.
172 */
173void prandom_seed(u32 entropy)
174{
175 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);
182
183 state->s1 = __seed(state->s1 ^ entropy, 2U);
184 prandom_warmup(state);
185 }
186}
187EXPORT_SYMBOL(prandom_seed);
188
189/*
190 * Generate some initially weak seeding values to allow
191 * to start the prandom_u32() engine.
192 */
193static int __init prandom_init(void)
194{
195 int i;
196
197#ifdef CONFIG_RANDOM32_SELFTEST
198 prandom_state_selftest();
199#endif
200
201 for_each_possible_cpu(i) {
202 struct rnd_state *state = &per_cpu(net_rand_state,i);
203
204 prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy());
205 prandom_warmup(state);
206 }
207
208 return 0;
209}
210core_initcall(prandom_init);
211
212static void __prandom_timer(unsigned long dontcare);
213static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0);
214
215static void __prandom_timer(unsigned long dontcare)
216{
217 u32 entropy;
218 unsigned long expires;
219
220 get_random_bytes(&entropy, sizeof(entropy));
221 prandom_seed(entropy);
222
223 /* reseed every ~60 seconds, in [40 .. 80) interval with slack */
224 expires = 40 + (prandom_u32() % 40);
225 seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC);
226
227 add_timer(&seed_timer);
228}
229
230static void __init __prandom_start_seed_timer(void)
231{
232 set_timer_slack(&seed_timer, HZ);
233 seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC);
234 add_timer(&seed_timer);
235}
236
237/*
238 * Generate better values after random number generator
239 * is fully initialized.
240 */
241static void __prandom_reseed(bool late)
242{
243 int i;
244 unsigned long flags;
245 static bool latch = false;
246 static DEFINE_SPINLOCK(lock);
247
248 /* Asking for random bytes might result in bytes getting
249 * moved into the nonblocking pool and thus marking it
250 * as initialized. In this case we would double back into
251 * this function and attempt to do a late reseed.
252 * Ignore the pointless attempt to reseed again if we're
253 * already waiting for bytes when the nonblocking pool
254 * got initialized.
255 */
256
257 /* only allow initial seeding (late == false) once */
258 if (!spin_trylock_irqsave(&lock, flags))
259 return;
260
261 if (latch && !late)
262 goto out;
263
264 latch = true;
265
266 for_each_possible_cpu(i) {
267 struct rnd_state *state = &per_cpu(net_rand_state,i);
268 u32 seeds[4];
269
270 get_random_bytes(&seeds, sizeof(seeds));
271 state->s1 = __seed(seeds[0], 2U);
272 state->s2 = __seed(seeds[1], 8U);
273 state->s3 = __seed(seeds[2], 16U);
274 state->s4 = __seed(seeds[3], 128U);
275
276 prandom_warmup(state);
277 }
278out:
279 spin_unlock_irqrestore(&lock, flags);
280}
281
282void prandom_reseed_late(void)
283{
284 __prandom_reseed(true);
285}
286
287static int __init prandom_reseed(void)
288{
289 __prandom_reseed(false);
290 __prandom_start_seed_timer();
291 return 0;
292}
293late_initcall(prandom_reseed);
294
295#ifdef CONFIG_RANDOM32_SELFTEST
296static struct prandom_test1 {
297 u32 seed;
298 u32 result;
299} test1[] = {
300 { 1U, 3484351685U },
301 { 2U, 2623130059U },
302 { 3U, 3125133893U },
303 { 4U, 984847254U },
304};
305
306static struct prandom_test2 {
307 u32 seed;
308 u32 iteration;
309 u32 result;
310} test2[] = {
311 /* Test cases against taus113 from GSL library. */
312 { 931557656U, 959U, 2975593782U },
313 { 1339693295U, 876U, 3887776532U },
314 { 1545556285U, 961U, 1615538833U },
315 { 601730776U, 723U, 1776162651U },
316 { 1027516047U, 687U, 511983079U },
317 { 416526298U, 700U, 916156552U },
318 { 1395522032U, 652U, 2222063676U },
319 { 366221443U, 617U, 2992857763U },
320 { 1539836965U, 714U, 3783265725U },
321 { 556206671U, 994U, 799626459U },
322 { 684907218U, 799U, 367789491U },
323 { 2121230701U, 931U, 2115467001U },
324 { 1668516451U, 644U, 3620590685U },
325 { 768046066U, 883U, 2034077390U },
326 { 1989159136U, 833U, 1195767305U },
327 { 536585145U, 996U, 3577259204U },
328 { 1008129373U, 642U, 1478080776U },
329 { 1740775604U, 939U, 1264980372U },
330 { 1967883163U, 508U, 10734624U },
331 { 1923019697U, 730U, 3821419629U },
332 { 442079932U, 560U, 3440032343U },
333 { 1961302714U, 845U, 841962572U },
334 { 2030205964U, 962U, 1325144227U },
335 { 1160407529U, 507U, 240940858U },
336 { 635482502U, 779U, 4200489746U },
337 { 1252788931U, 699U, 867195434U },
338 { 1961817131U, 719U, 668237657U },
339 { 1071468216U, 983U, 917876630U },
340 { 1281848367U, 932U, 1003100039U },
341 { 582537119U, 780U, 1127273778U },
342 { 1973672777U, 853U, 1071368872U },
343 { 1896756996U, 762U, 1127851055U },
344 { 847917054U, 500U, 1717499075U },
345 { 1240520510U, 951U, 2849576657U },
346 { 1685071682U, 567U, 1961810396U },
347 { 1516232129U, 557U, 3173877U },
348 { 1208118903U, 612U, 1613145022U },
349 { 1817269927U, 693U, 4279122573U },
350 { 1510091701U, 717U, 638191229U },
351 { 365916850U, 807U, 600424314U },
352 { 399324359U, 702U, 1803598116U },
353 { 1318480274U, 779U, 2074237022U },
354 { 697758115U, 840U, 1483639402U },
355 { 1696507773U, 840U, 577415447U },
356 { 2081979121U, 981U, 3041486449U },
357 { 955646687U, 742U, 3846494357U },
358 { 1250683506U, 749U, 836419859U },
359 { 595003102U, 534U, 366794109U },
360 { 47485338U, 558U, 3521120834U },
361 { 619433479U, 610U, 3991783875U },
362 { 704096520U, 518U, 4139493852U },
363 { 1712224984U, 606U, 2393312003U },
364 { 1318233152U, 922U, 3880361134U },
365 { 855572992U, 761U, 1472974787U },
366 { 64721421U, 703U, 683860550U },
367 { 678931758U, 840U, 380616043U },
368 { 692711973U, 778U, 1382361947U },
369 { 677703619U, 530U, 2826914161U },
370 { 92393223U, 586U, 1522128471U },
371 { 1222592920U, 743U, 3466726667U },
372 { 358288986U, 695U, 1091956998U },
373 { 1935056945U, 958U, 514864477U },
374 { 735675993U, 990U, 1294239989U },
375 { 1560089402U, 897U, 2238551287U },
376 { 70616361U, 829U, 22483098U },
377 { 368234700U, 731U, 2913875084U },
378 { 20221190U, 879U, 1564152970U },
379 { 539444654U, 682U, 1835141259U },
380 { 1314987297U, 840U, 1801114136U },
381 { 2019295544U, 645U, 3286438930U },
382 { 469023838U, 716U, 1637918202U },
383 { 1843754496U, 653U, 2562092152U },
384 { 400672036U, 809U, 4264212785U },
385 { 404722249U, 965U, 2704116999U },
386 { 600702209U, 758U, 584979986U },
387 { 519953954U, 667U, 2574436237U },
388 { 1658071126U, 694U, 2214569490U },
389 { 420480037U, 749U, 3430010866U },
390 { 690103647U, 969U, 3700758083U },
391 { 1029424799U, 937U, 3787746841U },
392 { 2012608669U, 506U, 3362628973U },
393 { 1535432887U, 998U, 42610943U },
394 { 1330635533U, 857U, 3040806504U },
395 { 1223800550U, 539U, 3954229517U },
396 { 1322411537U, 680U, 3223250324U },
397 { 1877847898U, 945U, 2915147143U },
398 { 1646356099U, 874U, 965988280U },
399 { 805687536U, 744U, 4032277920U },
400 { 1948093210U, 633U, 1346597684U },
401 { 392609744U, 783U, 1636083295U },
402 { 690241304U, 770U, 1201031298U },
403 { 1360302965U, 696U, 1665394461U },
404 { 1220090946U, 780U, 1316922812U },
405 { 447092251U, 500U, 3438743375U },
406 { 1613868791U, 592U, 828546883U },
407 { 523430951U, 548U, 2552392304U },
408 { 726692899U, 810U, 1656872867U },
409 { 1364340021U, 836U, 3710513486U },
410 { 1986257729U, 931U, 935013962U },
411 { 407983964U, 921U, 728767059U },
412};
413
414static void __init prandom_state_selftest(void)
415{
416 int i, j, errors = 0, runs = 0;
417 bool error = false;
418
419 for (i = 0; i < ARRAY_SIZE(test1); i++) {
420 struct rnd_state state;
421
422 prandom_seed_very_weak(&state, test1[i].seed);
423 prandom_warmup(&state);
424
425 if (test1[i].result != prandom_u32_state(&state))
426 error = true;
427 }
428
429 if (error)
430 pr_warn("prandom: seed boundary self test failed\n");
431 else
432 pr_info("prandom: seed boundary self test passed\n");
433
434 for (i = 0; i < ARRAY_SIZE(test2); i++) {
435 struct rnd_state state;
436
437 prandom_seed_very_weak(&state, test2[i].seed);
438 prandom_warmup(&state);
439
440 for (j = 0; j < test2[i].iteration - 1; j++)
441 prandom_u32_state(&state);
442
443 if (test2[i].result != prandom_u32_state(&state))
444 errors++;
445
446 runs++;
447 cond_resched();
448 }
449
450 if (errors)
451 pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
452 else
453 pr_info("prandom: %d self tests passed\n", runs);
454}
455#endif
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 x_n = (s1_n ^ s2_n ^ s3_n)
6
7 s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19))
8 s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25))
9 s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11))
10
11 The period of this generator is about 2^88.
12
13 From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
14 Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
15
16 This is available on the net from L'Ecuyer's home page,
17
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
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
32 s1 > 1, s2 > 7, s3 > 15.
33
34*/
35
36#include <linux/types.h>
37#include <linux/percpu.h>
38#include <linux/module.h>
39#include <linux/jiffies.h>
40#include <linux/random.h>
41
42static DEFINE_PER_CPU(struct rnd_state, net_rand_state);
43
44/**
45 * prandom32 - seeded pseudo-random number generator.
46 * @state: pointer to state structure holding seeded state.
47 *
48 * This is used for pseudo-randomness with no outside seeding.
49 * For more random results, use random32().
50 */
51u32 prandom32(struct rnd_state *state)
52{
53#define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b)
54
55 state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12);
56 state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4);
57 state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17);
58
59 return (state->s1 ^ state->s2 ^ state->s3);
60}
61EXPORT_SYMBOL(prandom32);
62
63/**
64 * random32 - pseudo random number generator
65 *
66 * A 32 bit pseudo-random number is generated using a fast
67 * algorithm suitable for simulation. This algorithm is NOT
68 * considered safe for cryptographic use.
69 */
70u32 random32(void)
71{
72 unsigned long r;
73 struct rnd_state *state = &get_cpu_var(net_rand_state);
74 r = prandom32(state);
75 put_cpu_var(state);
76 return r;
77}
78EXPORT_SYMBOL(random32);
79
80/**
81 * srandom32 - add entropy to pseudo random number generator
82 * @seed: seed value
83 *
84 * Add some additional seeding to the random32() pool.
85 */
86void srandom32(u32 entropy)
87{
88 int i;
89 /*
90 * No locking on the CPUs, but then somewhat random results are, well,
91 * expected.
92 */
93 for_each_possible_cpu (i) {
94 struct rnd_state *state = &per_cpu(net_rand_state, i);
95 state->s1 = __seed(state->s1 ^ entropy, 1);
96 }
97}
98EXPORT_SYMBOL(srandom32);
99
100/*
101 * Generate some initially weak seeding values to allow
102 * to start the random32() engine.
103 */
104static int __init random32_init(void)
105{
106 int i;
107
108 for_each_possible_cpu(i) {
109 struct rnd_state *state = &per_cpu(net_rand_state,i);
110
111#define LCG(x) ((x) * 69069) /* super-duper LCG */
112 state->s1 = __seed(LCG(i + jiffies), 1);
113 state->s2 = __seed(LCG(state->s1), 7);
114 state->s3 = __seed(LCG(state->s2), 15);
115
116 /* "warm it up" */
117 prandom32(state);
118 prandom32(state);
119 prandom32(state);
120 prandom32(state);
121 prandom32(state);
122 prandom32(state);
123 }
124 return 0;
125}
126core_initcall(random32_init);
127
128/*
129 * Generate better values after random number generator
130 * is fully initialized.
131 */
132static int __init random32_reseed(void)
133{
134 int i;
135
136 for_each_possible_cpu(i) {
137 struct rnd_state *state = &per_cpu(net_rand_state,i);
138 u32 seeds[3];
139
140 get_random_bytes(&seeds, sizeof(seeds));
141 state->s1 = __seed(seeds[0], 1);
142 state->s2 = __seed(seeds[1], 7);
143 state->s3 = __seed(seeds[2], 15);
144
145 /* mix it in */
146 prandom32(state);
147 }
148 return 0;
149}
150late_initcall(random32_reseed);