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#include <asm/unaligned.h>
41
42#ifdef CONFIG_RANDOM32_SELFTEST
43static void __init prandom_state_selftest(void);
44#else
45static inline void prandom_state_selftest(void)
46{
47}
48#endif
49
50static DEFINE_PER_CPU(struct rnd_state, net_rand_state);
51
52/**
53 *	prandom_u32_state - seeded pseudo-random number generator.
54 *	@state: pointer to state structure holding seeded state.
55 *
56 *	This is used for pseudo-randomness with no outside seeding.
57 *	For more random results, use prandom_u32().
58 */
59u32 prandom_u32_state(struct rnd_state *state)
60{
61#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)
62	state->s1 = TAUSWORTHE(state->s1,  6U, 13U, 4294967294U, 18U);
63	state->s2 = TAUSWORTHE(state->s2,  2U, 27U, 4294967288U,  2U);
64	state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U,  7U);
65	state->s4 = TAUSWORTHE(state->s4,  3U, 12U, 4294967168U, 13U);
66
67	return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
68}
69EXPORT_SYMBOL(prandom_u32_state);
70
71/**
72 *	prandom_u32 - pseudo random number generator
73 *
74 *	A 32 bit pseudo-random number is generated using a fast
75 *	algorithm suitable for simulation. This algorithm is NOT
76 *	considered safe for cryptographic use.
77 */
78u32 prandom_u32(void)
79{
80	struct rnd_state *state = &get_cpu_var(net_rand_state);
81	u32 res;
82
83	res = prandom_u32_state(state);
84	put_cpu_var(state);
85
86	return res;
87}
88EXPORT_SYMBOL(prandom_u32);
89
90/**
91 *	prandom_bytes_state - get the requested number of pseudo-random bytes
92 *
93 *	@state: pointer to state structure holding seeded state.
94 *	@buf: where to copy the pseudo-random bytes to
95 *	@bytes: the requested number of bytes
96 *
97 *	This is used for pseudo-randomness with no outside seeding.
98 *	For more random results, use prandom_bytes().
99 */
100void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes)
101{
102	u8 *ptr = buf;
103
104	while (bytes >= sizeof(u32)) {
105		put_unaligned(prandom_u32_state(state), (u32 *) ptr);
106		ptr += sizeof(u32);
107		bytes -= sizeof(u32);
108	}
109
110	if (bytes > 0) {
111		u32 rem = prandom_u32_state(state);
112		do {
113			*ptr++ = (u8) rem;
114			bytes--;
115			rem >>= BITS_PER_BYTE;
116		} while (bytes > 0);
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, size_t 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 satisfy 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 u32 __extract_hwseed(void)
151{
152	unsigned int val = 0;
153
154	(void)(arch_get_random_seed_int(&val) ||
155	       arch_get_random_int(&val));
156
157	return val;
158}
159
160static void prandom_seed_early(struct rnd_state *state, u32 seed,
161			       bool mix_with_hwseed)
162{
163#define LCG(x)	 ((x) * 69069U)	/* super-duper LCG */
164#define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0)
165	state->s1 = __seed(HWSEED() ^ LCG(seed),        2U);
166	state->s2 = __seed(HWSEED() ^ LCG(state->s1),   8U);
167	state->s3 = __seed(HWSEED() ^ LCG(state->s2),  16U);
168	state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U);
169}
170
171/**
172 *	prandom_seed - add entropy to pseudo random number generator
173 *	@seed: seed value
174 *
175 *	Add some additional seeding to the prandom pool.
176 */
177void prandom_seed(u32 entropy)
178{
179	int i;
180	/*
181	 * No locking on the CPUs, but then somewhat random results are, well,
182	 * expected.
183	 */
184	for_each_possible_cpu (i) {
185		struct rnd_state *state = &per_cpu(net_rand_state, i);
186
187		state->s1 = __seed(state->s1 ^ entropy, 2U);
188		prandom_warmup(state);
189	}
190}
191EXPORT_SYMBOL(prandom_seed);
192
193/*
194 *	Generate some initially weak seeding values to allow
195 *	to start the prandom_u32() engine.
196 */
197static int __init prandom_init(void)
198{
199	int i;
200
201	prandom_state_selftest();
202
203	for_each_possible_cpu(i) {
204		struct rnd_state *state = &per_cpu(net_rand_state,i);
205		u32 weak_seed = (i + jiffies) ^ random_get_entropy();
206
207		prandom_seed_early(state, weak_seed, true);
208		prandom_warmup(state);
209	}
210
211	return 0;
212}
213core_initcall(prandom_init);
214
215static void __prandom_timer(unsigned long dontcare);
216
217static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0);
218
219static void __prandom_timer(unsigned long dontcare)
220{
221	u32 entropy;
222	unsigned long expires;
223
224	get_random_bytes(&entropy, sizeof(entropy));
225	prandom_seed(entropy);
226
227	/* reseed every ~60 seconds, in [40 .. 80) interval with slack */
228	expires = 40 + prandom_u32_max(40);
229	seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC);
230
231	add_timer(&seed_timer);
232}
233
234static void __init __prandom_start_seed_timer(void)
235{
236	set_timer_slack(&seed_timer, HZ);
237	seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC);
238	add_timer(&seed_timer);
239}
240
241/*
242 *	Generate better values after random number generator
243 *	is fully initialized.
244 */
245static void __prandom_reseed(bool late)
246{
247	int i;
248	unsigned long flags;
249	static bool latch = false;
250	static DEFINE_SPINLOCK(lock);
251
252	/* Asking for random bytes might result in bytes getting
253	 * moved into the nonblocking pool and thus marking it
254	 * as initialized. In this case we would double back into
255	 * this function and attempt to do a late reseed.
256	 * Ignore the pointless attempt to reseed again if we're
257	 * already waiting for bytes when the nonblocking pool
258	 * got initialized.
259	 */
260
261	/* only allow initial seeding (late == false) once */
262	if (!spin_trylock_irqsave(&lock, flags))
263		return;
264
265	if (latch && !late)
266		goto out;
267
268	latch = true;
269
270	for_each_possible_cpu(i) {
271		struct rnd_state *state = &per_cpu(net_rand_state,i);
272		u32 seeds[4];
273
274		get_random_bytes(&seeds, sizeof(seeds));
275		state->s1 = __seed(seeds[0],   2U);
276		state->s2 = __seed(seeds[1],   8U);
277		state->s3 = __seed(seeds[2],  16U);
278		state->s4 = __seed(seeds[3], 128U);
279
280		prandom_warmup(state);
281	}
282out:
283	spin_unlock_irqrestore(&lock, flags);
284}
285
286void prandom_reseed_late(void)
287{
288	__prandom_reseed(true);
289}
290
291static int __init prandom_reseed(void)
292{
293	__prandom_reseed(false);
294	__prandom_start_seed_timer();
295	return 0;
296}
297late_initcall(prandom_reseed);
298
299#ifdef CONFIG_RANDOM32_SELFTEST
300static struct prandom_test1 {
301	u32 seed;
302	u32 result;
303} test1[] = {
304	{ 1U, 3484351685U },
305	{ 2U, 2623130059U },
306	{ 3U, 3125133893U },
307	{ 4U,  984847254U },
308};
309
310static struct prandom_test2 {
311	u32 seed;
312	u32 iteration;
313	u32 result;
314} test2[] = {
315	/* Test cases against taus113 from GSL library. */
316	{  931557656U, 959U, 2975593782U },
317	{ 1339693295U, 876U, 3887776532U },
318	{ 1545556285U, 961U, 1615538833U },
319	{  601730776U, 723U, 1776162651U },
320	{ 1027516047U, 687U,  511983079U },
321	{  416526298U, 700U,  916156552U },
322	{ 1395522032U, 652U, 2222063676U },
323	{  366221443U, 617U, 2992857763U },
324	{ 1539836965U, 714U, 3783265725U },
325	{  556206671U, 994U,  799626459U },
326	{  684907218U, 799U,  367789491U },
327	{ 2121230701U, 931U, 2115467001U },
328	{ 1668516451U, 644U, 3620590685U },
329	{  768046066U, 883U, 2034077390U },
330	{ 1989159136U, 833U, 1195767305U },
331	{  536585145U, 996U, 3577259204U },
332	{ 1008129373U, 642U, 1478080776U },
333	{ 1740775604U, 939U, 1264980372U },
334	{ 1967883163U, 508U,   10734624U },
335	{ 1923019697U, 730U, 3821419629U },
336	{  442079932U, 560U, 3440032343U },
337	{ 1961302714U, 845U,  841962572U },
338	{ 2030205964U, 962U, 1325144227U },
339	{ 1160407529U, 507U,  240940858U },
340	{  635482502U, 779U, 4200489746U },
341	{ 1252788931U, 699U,  867195434U },
342	{ 1961817131U, 719U,  668237657U },
343	{ 1071468216U, 983U,  917876630U },
344	{ 1281848367U, 932U, 1003100039U },
345	{  582537119U, 780U, 1127273778U },
346	{ 1973672777U, 853U, 1071368872U },
347	{ 1896756996U, 762U, 1127851055U },
348	{  847917054U, 500U, 1717499075U },
349	{ 1240520510U, 951U, 2849576657U },
350	{ 1685071682U, 567U, 1961810396U },
351	{ 1516232129U, 557U,    3173877U },
352	{ 1208118903U, 612U, 1613145022U },
353	{ 1817269927U, 693U, 4279122573U },
354	{ 1510091701U, 717U,  638191229U },
355	{  365916850U, 807U,  600424314U },
356	{  399324359U, 702U, 1803598116U },
357	{ 1318480274U, 779U, 2074237022U },
358	{  697758115U, 840U, 1483639402U },
359	{ 1696507773U, 840U,  577415447U },
360	{ 2081979121U, 981U, 3041486449U },
361	{  955646687U, 742U, 3846494357U },
362	{ 1250683506U, 749U,  836419859U },
363	{  595003102U, 534U,  366794109U },
364	{   47485338U, 558U, 3521120834U },
365	{  619433479U, 610U, 3991783875U },
366	{  704096520U, 518U, 4139493852U },
367	{ 1712224984U, 606U, 2393312003U },
368	{ 1318233152U, 922U, 3880361134U },
369	{  855572992U, 761U, 1472974787U },
370	{   64721421U, 703U,  683860550U },
371	{  678931758U, 840U,  380616043U },
372	{  692711973U, 778U, 1382361947U },
373	{  677703619U, 530U, 2826914161U },
374	{   92393223U, 586U, 1522128471U },
375	{ 1222592920U, 743U, 3466726667U },
376	{  358288986U, 695U, 1091956998U },
377	{ 1935056945U, 958U,  514864477U },
378	{  735675993U, 990U, 1294239989U },
379	{ 1560089402U, 897U, 2238551287U },
380	{   70616361U, 829U,   22483098U },
381	{  368234700U, 731U, 2913875084U },
382	{   20221190U, 879U, 1564152970U },
383	{  539444654U, 682U, 1835141259U },
384	{ 1314987297U, 840U, 1801114136U },
385	{ 2019295544U, 645U, 3286438930U },
386	{  469023838U, 716U, 1637918202U },
387	{ 1843754496U, 653U, 2562092152U },
388	{  400672036U, 809U, 4264212785U },
389	{  404722249U, 965U, 2704116999U },
390	{  600702209U, 758U,  584979986U },
391	{  519953954U, 667U, 2574436237U },
392	{ 1658071126U, 694U, 2214569490U },
393	{  420480037U, 749U, 3430010866U },
394	{  690103647U, 969U, 3700758083U },
395	{ 1029424799U, 937U, 3787746841U },
396	{ 2012608669U, 506U, 3362628973U },
397	{ 1535432887U, 998U,   42610943U },
398	{ 1330635533U, 857U, 3040806504U },
399	{ 1223800550U, 539U, 3954229517U },
400	{ 1322411537U, 680U, 3223250324U },
401	{ 1877847898U, 945U, 2915147143U },
402	{ 1646356099U, 874U,  965988280U },
403	{  805687536U, 744U, 4032277920U },
404	{ 1948093210U, 633U, 1346597684U },
405	{  392609744U, 783U, 1636083295U },
406	{  690241304U, 770U, 1201031298U },
407	{ 1360302965U, 696U, 1665394461U },
408	{ 1220090946U, 780U, 1316922812U },
409	{  447092251U, 500U, 3438743375U },
410	{ 1613868791U, 592U,  828546883U },
411	{  523430951U, 548U, 2552392304U },
412	{  726692899U, 810U, 1656872867U },
413	{ 1364340021U, 836U, 3710513486U },
414	{ 1986257729U, 931U,  935013962U },
415	{  407983964U, 921U,  728767059U },
416};
417
418static void __init prandom_state_selftest(void)
419{
420	int i, j, errors = 0, runs = 0;
421	bool error = false;
422
423	for (i = 0; i < ARRAY_SIZE(test1); i++) {
424		struct rnd_state state;
425
426		prandom_seed_early(&state, test1[i].seed, false);
427		prandom_warmup(&state);
428
429		if (test1[i].result != prandom_u32_state(&state))
430			error = true;
431	}
432
433	if (error)
434		pr_warn("prandom: seed boundary self test failed\n");
435	else
436		pr_info("prandom: seed boundary self test passed\n");
437
438	for (i = 0; i < ARRAY_SIZE(test2); i++) {
439		struct rnd_state state;
440
441		prandom_seed_early(&state, test2[i].seed, false);
442		prandom_warmup(&state);
443
444		for (j = 0; j < test2[i].iteration - 1; j++)
445			prandom_u32_state(&state);
446
447		if (test2[i].result != prandom_u32_state(&state))
448			errors++;
449
450		runs++;
451		cond_resched();
452	}
453
454	if (errors)
455		pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
456	else
457		pr_info("prandom: %d self tests passed\n", runs);
458}
459#endif
460