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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
aaa248f6 | 2 | /* |
d3d47eb2 DB |
3 | * This is a maximally equidistributed combined Tausworthe generator |
4 | * based on code from GNU Scientific Library 1.5 (30 Jun 2004) | |
5 | * | |
6 | * lfsr113 version: | |
7 | * | |
8 | * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n) | |
9 | * | |
10 | * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13)) | |
11 | * s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27)) | |
12 | * s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21)) | |
13 | * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12)) | |
14 | * | |
15 | * The period of this generator is about 2^113 (see erratum paper). | |
16 | * | |
17 | * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe | |
18 | * Generators", Mathematics of Computation, 65, 213 (1996), 203--213: | |
19 | * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps | |
20 | * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps | |
21 | * | |
22 | * There is an erratum in the paper "Tables of Maximally Equidistributed | |
23 | * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999), | |
24 | * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps | |
25 | * | |
26 | * ... the k_j most significant bits of z_j must be non-zero, | |
27 | * for each j. (Note: this restriction also applies to the | |
28 | * computer code given in [4], but was mistakenly not mentioned | |
29 | * in that paper.) | |
30 | * | |
31 | * This affects the seeding procedure by imposing the requirement | |
32 | * s1 > 1, s2 > 7, s3 > 15, s4 > 127. | |
33 | */ | |
aaa248f6 SH |
34 | |
35 | #include <linux/types.h> | |
36 | #include <linux/percpu.h> | |
8bc3bcc9 | 37 | #include <linux/export.h> |
f6a57033 | 38 | #include <linux/jiffies.h> |
aaa248f6 | 39 | #include <linux/random.h> |
a6a9c0f1 | 40 | #include <linux/sched.h> |
a98406e2 | 41 | #include <asm/unaligned.h> |
a6a9c0f1 | 42 | |
5960164f | 43 | /** |
496f2f93 | 44 | * prandom_u32_state - seeded pseudo-random number generator. |
5960164f JE |
45 | * @state: pointer to state structure holding seeded state. |
46 | * | |
47 | * This is used for pseudo-randomness with no outside seeding. | |
496f2f93 | 48 | * For more random results, use prandom_u32(). |
5960164f | 49 | */ |
496f2f93 | 50 | u32 prandom_u32_state(struct rnd_state *state) |
aaa248f6 | 51 | { |
4ada97ab | 52 | #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) |
a98814ce DB |
53 | state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); |
54 | state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); | |
55 | state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); | |
56 | state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); | |
aaa248f6 | 57 | |
a98814ce | 58 | return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); |
aaa248f6 | 59 | } |
496f2f93 | 60 | EXPORT_SYMBOL(prandom_u32_state); |
aaa248f6 | 61 | |
d3d47eb2 | 62 | /** |
6582c665 AM |
63 | * prandom_bytes_state - get the requested number of pseudo-random bytes |
64 | * | |
65 | * @state: pointer to state structure holding seeded state. | |
66 | * @buf: where to copy the pseudo-random bytes to | |
67 | * @bytes: the requested number of bytes | |
68 | * | |
69 | * This is used for pseudo-randomness with no outside seeding. | |
70 | * For more random results, use prandom_bytes(). | |
71 | */ | |
a98406e2 | 72 | void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes) |
6582c665 | 73 | { |
a98406e2 | 74 | u8 *ptr = buf; |
6582c665 | 75 | |
a98406e2 DB |
76 | while (bytes >= sizeof(u32)) { |
77 | put_unaligned(prandom_u32_state(state), (u32 *) ptr); | |
78 | ptr += sizeof(u32); | |
79 | bytes -= sizeof(u32); | |
6582c665 | 80 | } |
6582c665 | 81 | |
a98406e2 DB |
82 | if (bytes > 0) { |
83 | u32 rem = prandom_u32_state(state); | |
84 | do { | |
85 | *ptr++ = (u8) rem; | |
86 | bytes--; | |
87 | rem >>= BITS_PER_BYTE; | |
88 | } while (bytes > 0); | |
6582c665 AM |
89 | } |
90 | } | |
91 | EXPORT_SYMBOL(prandom_bytes_state); | |
92 | ||
a98814ce DB |
93 | static void prandom_warmup(struct rnd_state *state) |
94 | { | |
a98406e2 | 95 | /* Calling RNG ten times to satisfy recurrence condition */ |
a98814ce DB |
96 | prandom_u32_state(state); |
97 | prandom_u32_state(state); | |
98 | prandom_u32_state(state); | |
99 | prandom_u32_state(state); | |
100 | prandom_u32_state(state); | |
101 | prandom_u32_state(state); | |
102 | prandom_u32_state(state); | |
103 | prandom_u32_state(state); | |
104 | prandom_u32_state(state); | |
105 | prandom_u32_state(state); | |
106 | } | |
107 | ||
897ece56 | 108 | void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state) |
0dd50d1b DB |
109 | { |
110 | int i; | |
111 | ||
112 | for_each_possible_cpu(i) { | |
113 | struct rnd_state *state = per_cpu_ptr(pcpu_state, i); | |
114 | u32 seeds[4]; | |
115 | ||
116 | get_random_bytes(&seeds, sizeof(seeds)); | |
117 | state->s1 = __seed(seeds[0], 2U); | |
118 | state->s2 = __seed(seeds[1], 8U); | |
119 | state->s3 = __seed(seeds[2], 16U); | |
120 | state->s4 = __seed(seeds[3], 128U); | |
121 | ||
122 | prandom_warmup(state); | |
123 | } | |
124 | } | |
b07edbe1 | 125 | EXPORT_SYMBOL(prandom_seed_full_state); |
0dd50d1b | 126 | |
a6a9c0f1 DB |
127 | #ifdef CONFIG_RANDOM32_SELFTEST |
128 | static struct prandom_test1 { | |
129 | u32 seed; | |
130 | u32 result; | |
131 | } test1[] = { | |
132 | { 1U, 3484351685U }, | |
133 | { 2U, 2623130059U }, | |
134 | { 3U, 3125133893U }, | |
135 | { 4U, 984847254U }, | |
136 | }; | |
137 | ||
138 | static struct prandom_test2 { | |
139 | u32 seed; | |
140 | u32 iteration; | |
141 | u32 result; | |
142 | } test2[] = { | |
143 | /* Test cases against taus113 from GSL library. */ | |
144 | { 931557656U, 959U, 2975593782U }, | |
145 | { 1339693295U, 876U, 3887776532U }, | |
146 | { 1545556285U, 961U, 1615538833U }, | |
147 | { 601730776U, 723U, 1776162651U }, | |
148 | { 1027516047U, 687U, 511983079U }, | |
149 | { 416526298U, 700U, 916156552U }, | |
150 | { 1395522032U, 652U, 2222063676U }, | |
151 | { 366221443U, 617U, 2992857763U }, | |
152 | { 1539836965U, 714U, 3783265725U }, | |
153 | { 556206671U, 994U, 799626459U }, | |
154 | { 684907218U, 799U, 367789491U }, | |
155 | { 2121230701U, 931U, 2115467001U }, | |
156 | { 1668516451U, 644U, 3620590685U }, | |
157 | { 768046066U, 883U, 2034077390U }, | |
158 | { 1989159136U, 833U, 1195767305U }, | |
159 | { 536585145U, 996U, 3577259204U }, | |
160 | { 1008129373U, 642U, 1478080776U }, | |
161 | { 1740775604U, 939U, 1264980372U }, | |
162 | { 1967883163U, 508U, 10734624U }, | |
163 | { 1923019697U, 730U, 3821419629U }, | |
164 | { 442079932U, 560U, 3440032343U }, | |
165 | { 1961302714U, 845U, 841962572U }, | |
166 | { 2030205964U, 962U, 1325144227U }, | |
167 | { 1160407529U, 507U, 240940858U }, | |
168 | { 635482502U, 779U, 4200489746U }, | |
169 | { 1252788931U, 699U, 867195434U }, | |
170 | { 1961817131U, 719U, 668237657U }, | |
171 | { 1071468216U, 983U, 917876630U }, | |
172 | { 1281848367U, 932U, 1003100039U }, | |
173 | { 582537119U, 780U, 1127273778U }, | |
174 | { 1973672777U, 853U, 1071368872U }, | |
175 | { 1896756996U, 762U, 1127851055U }, | |
176 | { 847917054U, 500U, 1717499075U }, | |
177 | { 1240520510U, 951U, 2849576657U }, | |
178 | { 1685071682U, 567U, 1961810396U }, | |
179 | { 1516232129U, 557U, 3173877U }, | |
180 | { 1208118903U, 612U, 1613145022U }, | |
181 | { 1817269927U, 693U, 4279122573U }, | |
182 | { 1510091701U, 717U, 638191229U }, | |
183 | { 365916850U, 807U, 600424314U }, | |
184 | { 399324359U, 702U, 1803598116U }, | |
185 | { 1318480274U, 779U, 2074237022U }, | |
186 | { 697758115U, 840U, 1483639402U }, | |
187 | { 1696507773U, 840U, 577415447U }, | |
188 | { 2081979121U, 981U, 3041486449U }, | |
189 | { 955646687U, 742U, 3846494357U }, | |
190 | { 1250683506U, 749U, 836419859U }, | |
191 | { 595003102U, 534U, 366794109U }, | |
192 | { 47485338U, 558U, 3521120834U }, | |
193 | { 619433479U, 610U, 3991783875U }, | |
194 | { 704096520U, 518U, 4139493852U }, | |
195 | { 1712224984U, 606U, 2393312003U }, | |
196 | { 1318233152U, 922U, 3880361134U }, | |
197 | { 855572992U, 761U, 1472974787U }, | |
198 | { 64721421U, 703U, 683860550U }, | |
199 | { 678931758U, 840U, 380616043U }, | |
200 | { 692711973U, 778U, 1382361947U }, | |
201 | { 677703619U, 530U, 2826914161U }, | |
202 | { 92393223U, 586U, 1522128471U }, | |
203 | { 1222592920U, 743U, 3466726667U }, | |
204 | { 358288986U, 695U, 1091956998U }, | |
205 | { 1935056945U, 958U, 514864477U }, | |
206 | { 735675993U, 990U, 1294239989U }, | |
207 | { 1560089402U, 897U, 2238551287U }, | |
208 | { 70616361U, 829U, 22483098U }, | |
209 | { 368234700U, 731U, 2913875084U }, | |
210 | { 20221190U, 879U, 1564152970U }, | |
211 | { 539444654U, 682U, 1835141259U }, | |
212 | { 1314987297U, 840U, 1801114136U }, | |
213 | { 2019295544U, 645U, 3286438930U }, | |
214 | { 469023838U, 716U, 1637918202U }, | |
215 | { 1843754496U, 653U, 2562092152U }, | |
216 | { 400672036U, 809U, 4264212785U }, | |
217 | { 404722249U, 965U, 2704116999U }, | |
218 | { 600702209U, 758U, 584979986U }, | |
219 | { 519953954U, 667U, 2574436237U }, | |
220 | { 1658071126U, 694U, 2214569490U }, | |
221 | { 420480037U, 749U, 3430010866U }, | |
222 | { 690103647U, 969U, 3700758083U }, | |
223 | { 1029424799U, 937U, 3787746841U }, | |
224 | { 2012608669U, 506U, 3362628973U }, | |
225 | { 1535432887U, 998U, 42610943U }, | |
226 | { 1330635533U, 857U, 3040806504U }, | |
227 | { 1223800550U, 539U, 3954229517U }, | |
228 | { 1322411537U, 680U, 3223250324U }, | |
229 | { 1877847898U, 945U, 2915147143U }, | |
230 | { 1646356099U, 874U, 965988280U }, | |
231 | { 805687536U, 744U, 4032277920U }, | |
232 | { 1948093210U, 633U, 1346597684U }, | |
233 | { 392609744U, 783U, 1636083295U }, | |
234 | { 690241304U, 770U, 1201031298U }, | |
235 | { 1360302965U, 696U, 1665394461U }, | |
236 | { 1220090946U, 780U, 1316922812U }, | |
237 | { 447092251U, 500U, 3438743375U }, | |
238 | { 1613868791U, 592U, 828546883U }, | |
239 | { 523430951U, 548U, 2552392304U }, | |
240 | { 726692899U, 810U, 1656872867U }, | |
241 | { 1364340021U, 836U, 3710513486U }, | |
242 | { 1986257729U, 931U, 935013962U }, | |
243 | { 407983964U, 921U, 728767059U }, | |
244 | }; | |
245 | ||
f88612b6 GS |
246 | static u32 __extract_hwseed(void) |
247 | { | |
248 | unsigned int val = 0; | |
249 | ||
250 | (void)(arch_get_random_seed_int(&val) || | |
251 | arch_get_random_int(&val)); | |
252 | ||
253 | return val; | |
254 | } | |
255 | ||
256 | static void prandom_seed_early(struct rnd_state *state, u32 seed, | |
257 | bool mix_with_hwseed) | |
258 | { | |
259 | #define LCG(x) ((x) * 69069U) /* super-duper LCG */ | |
260 | #define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0) | |
261 | state->s1 = __seed(HWSEED() ^ LCG(seed), 2U); | |
262 | state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U); | |
263 | state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U); | |
264 | state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U); | |
265 | } | |
266 | ||
267 | static int __init prandom_state_selftest(void) | |
a6a9c0f1 DB |
268 | { |
269 | int i, j, errors = 0, runs = 0; | |
270 | bool error = false; | |
271 | ||
272 | for (i = 0; i < ARRAY_SIZE(test1); i++) { | |
273 | struct rnd_state state; | |
274 | ||
4ada97ab | 275 | prandom_seed_early(&state, test1[i].seed, false); |
a6a9c0f1 DB |
276 | prandom_warmup(&state); |
277 | ||
278 | if (test1[i].result != prandom_u32_state(&state)) | |
279 | error = true; | |
280 | } | |
281 | ||
282 | if (error) | |
283 | pr_warn("prandom: seed boundary self test failed\n"); | |
284 | else | |
285 | pr_info("prandom: seed boundary self test passed\n"); | |
286 | ||
287 | for (i = 0; i < ARRAY_SIZE(test2); i++) { | |
288 | struct rnd_state state; | |
289 | ||
4ada97ab | 290 | prandom_seed_early(&state, test2[i].seed, false); |
a6a9c0f1 DB |
291 | prandom_warmup(&state); |
292 | ||
293 | for (j = 0; j < test2[i].iteration - 1; j++) | |
294 | prandom_u32_state(&state); | |
295 | ||
296 | if (test2[i].result != prandom_u32_state(&state)) | |
297 | errors++; | |
298 | ||
299 | runs++; | |
300 | cond_resched(); | |
301 | } | |
302 | ||
303 | if (errors) | |
304 | pr_warn("prandom: %d/%d self tests failed\n", errors, runs); | |
305 | else | |
306 | pr_info("prandom: %d self tests passed\n", runs); | |
f88612b6 GS |
307 | return 0; |
308 | } | |
309 | core_initcall(prandom_state_selftest); | |
310 | #endif | |
311 | ||
312 | /* | |
313 | * The prandom_u32() implementation is now completely separate from the | |
314 | * prandom_state() functions, which are retained (for now) for compatibility. | |
315 | * | |
316 | * Because of (ab)use in the networking code for choosing random TCP/UDP port | |
317 | * numbers, which open DoS possibilities if guessable, we want something | |
318 | * stronger than a standard PRNG. But the performance requirements of | |
319 | * the network code do not allow robust crypto for this application. | |
320 | * | |
321 | * So this is a homebrew Junior Spaceman implementation, based on the | |
322 | * lowest-latency trustworthy crypto primitive available, SipHash. | |
323 | * (The authors of SipHash have not been consulted about this abuse of | |
324 | * their work.) | |
325 | * | |
326 | * Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to | |
327 | * one word of output. This abbreviated version uses 2 rounds per word | |
328 | * of output. | |
329 | */ | |
330 | ||
331 | struct siprand_state { | |
332 | unsigned long v0; | |
333 | unsigned long v1; | |
334 | unsigned long v2; | |
335 | unsigned long v3; | |
336 | }; | |
337 | ||
338 | static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy; | |
339 | ||
340 | /* | |
341 | * This is the core CPRNG function. As "pseudorandom", this is not used | |
342 | * for truly valuable things, just intended to be a PITA to guess. | |
343 | * For maximum speed, we do just two SipHash rounds per word. This is | |
344 | * the same rate as 4 rounds per 64 bits that SipHash normally uses, | |
345 | * so hopefully it's reasonably secure. | |
346 | * | |
347 | * There are two changes from the official SipHash finalization: | |
348 | * - We omit some constants XORed with v2 in the SipHash spec as irrelevant; | |
349 | * they are there only to make the output rounds distinct from the input | |
350 | * rounds, and this application has no input rounds. | |
351 | * - Rather than returning v0^v1^v2^v3, return v1+v3. | |
352 | * If you look at the SipHash round, the last operation on v3 is | |
353 | * "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time. | |
354 | * Likewise "v1 ^= v2". (The rotate of v2 makes a difference, but | |
355 | * it still cancels out half of the bits in v2 for no benefit.) | |
356 | * Second, since the last combining operation was xor, continue the | |
357 | * pattern of alternating xor/add for a tiny bit of extra non-linearity. | |
358 | */ | |
359 | static inline u32 siprand_u32(struct siprand_state *s) | |
360 | { | |
361 | unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3; | |
362 | ||
363 | PRND_SIPROUND(v0, v1, v2, v3); | |
364 | PRND_SIPROUND(v0, v1, v2, v3); | |
365 | s->v0 = v0; s->v1 = v1; s->v2 = v2; s->v3 = v3; | |
366 | return v1 + v3; | |
367 | } | |
368 | ||
369 | ||
370 | /** | |
371 | * prandom_u32 - pseudo random number generator | |
372 | * | |
373 | * A 32 bit pseudo-random number is generated using a fast | |
374 | * algorithm suitable for simulation. This algorithm is NOT | |
375 | * considered safe for cryptographic use. | |
376 | */ | |
377 | u32 prandom_u32(void) | |
378 | { | |
379 | struct siprand_state *state = get_cpu_ptr(&net_rand_state); | |
380 | u32 res = siprand_u32(state); | |
381 | ||
382 | put_cpu_ptr(&net_rand_state); | |
383 | return res; | |
384 | } | |
385 | EXPORT_SYMBOL(prandom_u32); | |
386 | ||
387 | /** | |
388 | * prandom_bytes - get the requested number of pseudo-random bytes | |
389 | * @buf: where to copy the pseudo-random bytes to | |
390 | * @bytes: the requested number of bytes | |
391 | */ | |
392 | void prandom_bytes(void *buf, size_t bytes) | |
393 | { | |
394 | struct siprand_state *state = get_cpu_ptr(&net_rand_state); | |
395 | u8 *ptr = buf; | |
396 | ||
397 | while (bytes >= sizeof(u32)) { | |
398 | put_unaligned(siprand_u32(state), (u32 *)ptr); | |
399 | ptr += sizeof(u32); | |
400 | bytes -= sizeof(u32); | |
401 | } | |
402 | ||
403 | if (bytes > 0) { | |
404 | u32 rem = siprand_u32(state); | |
405 | ||
406 | do { | |
407 | *ptr++ = (u8)rem; | |
408 | rem >>= BITS_PER_BYTE; | |
409 | } while (--bytes > 0); | |
410 | } | |
411 | put_cpu_ptr(&net_rand_state); | |
412 | } | |
413 | EXPORT_SYMBOL(prandom_bytes); | |
414 | ||
415 | /** | |
416 | * prandom_seed - add entropy to pseudo random number generator | |
417 | * @entropy: entropy value | |
418 | * | |
419 | * Add some additional seed material to the prandom pool. | |
420 | * The "entropy" is actually our IP address (the only caller is | |
421 | * the network code), not for unpredictability, but to ensure that | |
422 | * different machines are initialized differently. | |
423 | */ | |
424 | void prandom_seed(u32 entropy) | |
425 | { | |
426 | int i; | |
427 | ||
428 | add_device_randomness(&entropy, sizeof(entropy)); | |
429 | ||
430 | for_each_possible_cpu(i) { | |
431 | struct siprand_state *state = per_cpu_ptr(&net_rand_state, i); | |
432 | unsigned long v0 = state->v0, v1 = state->v1; | |
433 | unsigned long v2 = state->v2, v3 = state->v3; | |
434 | ||
435 | do { | |
436 | v3 ^= entropy; | |
437 | PRND_SIPROUND(v0, v1, v2, v3); | |
438 | PRND_SIPROUND(v0, v1, v2, v3); | |
439 | v0 ^= entropy; | |
440 | } while (unlikely(!v0 || !v1 || !v2 || !v3)); | |
441 | ||
442 | WRITE_ONCE(state->v0, v0); | |
443 | WRITE_ONCE(state->v1, v1); | |
444 | WRITE_ONCE(state->v2, v2); | |
445 | WRITE_ONCE(state->v3, v3); | |
446 | } | |
447 | } | |
448 | EXPORT_SYMBOL(prandom_seed); | |
449 | ||
450 | /* | |
451 | * Generate some initially weak seeding values to allow | |
452 | * the prandom_u32() engine to be started. | |
453 | */ | |
454 | static int __init prandom_init_early(void) | |
455 | { | |
456 | int i; | |
457 | unsigned long v0, v1, v2, v3; | |
458 | ||
459 | if (!arch_get_random_long(&v0)) | |
460 | v0 = jiffies; | |
461 | if (!arch_get_random_long(&v1)) | |
462 | v1 = random_get_entropy(); | |
463 | v2 = v0 ^ PRND_K0; | |
464 | v3 = v1 ^ PRND_K1; | |
465 | ||
466 | for_each_possible_cpu(i) { | |
467 | struct siprand_state *state; | |
468 | ||
469 | v3 ^= i; | |
470 | PRND_SIPROUND(v0, v1, v2, v3); | |
471 | PRND_SIPROUND(v0, v1, v2, v3); | |
472 | v0 ^= i; | |
473 | ||
474 | state = per_cpu_ptr(&net_rand_state, i); | |
475 | state->v0 = v0; state->v1 = v1; | |
476 | state->v2 = v2; state->v3 = v3; | |
477 | } | |
478 | ||
479 | return 0; | |
a6a9c0f1 | 480 | } |
f88612b6 GS |
481 | core_initcall(prandom_init_early); |
482 | ||
483 | ||
484 | /* Stronger reseeding when available, and periodically thereafter. */ | |
485 | static void prandom_reseed(struct timer_list *unused); | |
486 | ||
487 | static DEFINE_TIMER(seed_timer, prandom_reseed); | |
488 | ||
489 | static void prandom_reseed(struct timer_list *unused) | |
490 | { | |
491 | unsigned long expires; | |
492 | int i; | |
493 | ||
494 | /* | |
495 | * Reinitialize each CPU's PRNG with 128 bits of key. | |
496 | * No locking on the CPUs, but then somewhat random results are, | |
497 | * well, expected. | |
498 | */ | |
499 | for_each_possible_cpu(i) { | |
500 | struct siprand_state *state; | |
501 | unsigned long v0 = get_random_long(), v2 = v0 ^ PRND_K0; | |
502 | unsigned long v1 = get_random_long(), v3 = v1 ^ PRND_K1; | |
503 | #if BITS_PER_LONG == 32 | |
504 | int j; | |
505 | ||
506 | /* | |
507 | * On 32-bit machines, hash in two extra words to | |
508 | * approximate 128-bit key length. Not that the hash | |
509 | * has that much security, but this prevents a trivial | |
510 | * 64-bit brute force. | |
511 | */ | |
512 | for (j = 0; j < 2; j++) { | |
513 | unsigned long m = get_random_long(); | |
514 | ||
515 | v3 ^= m; | |
516 | PRND_SIPROUND(v0, v1, v2, v3); | |
517 | PRND_SIPROUND(v0, v1, v2, v3); | |
518 | v0 ^= m; | |
519 | } | |
a6a9c0f1 | 520 | #endif |
f88612b6 GS |
521 | /* |
522 | * Probably impossible in practice, but there is a | |
523 | * theoretical risk that a race between this reseeding | |
524 | * and the target CPU writing its state back could | |
525 | * create the all-zero SipHash fixed point. | |
526 | * | |
527 | * To ensure that never happens, ensure the state | |
528 | * we write contains no zero words. | |
529 | */ | |
530 | state = per_cpu_ptr(&net_rand_state, i); | |
531 | WRITE_ONCE(state->v0, v0 ? v0 : -1ul); | |
532 | WRITE_ONCE(state->v1, v1 ? v1 : -1ul); | |
533 | WRITE_ONCE(state->v2, v2 ? v2 : -1ul); | |
534 | WRITE_ONCE(state->v3, v3 ? v3 : -1ul); | |
535 | } | |
536 | ||
537 | /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ | |
538 | expires = round_jiffies(jiffies + 40 * HZ + prandom_u32_max(40 * HZ)); | |
539 | mod_timer(&seed_timer, expires); | |
540 | } | |
541 | ||
542 | /* | |
543 | * The random ready callback can be called from almost any interrupt. | |
544 | * To avoid worrying about whether it's safe to delay that interrupt | |
545 | * long enough to seed all CPUs, just schedule an immediate timer event. | |
546 | */ | |
547 | static void prandom_timer_start(struct random_ready_callback *unused) | |
548 | { | |
549 | mod_timer(&seed_timer, jiffies); | |
550 | } | |
551 | ||
552 | /* | |
553 | * Start periodic full reseeding as soon as strong | |
554 | * random numbers are available. | |
555 | */ | |
556 | static int __init prandom_init_late(void) | |
557 | { | |
558 | static struct random_ready_callback random_ready = { | |
559 | .func = prandom_timer_start | |
560 | }; | |
561 | int ret = add_random_ready_callback(&random_ready); | |
562 | ||
563 | if (ret == -EALREADY) { | |
564 | prandom_timer_start(&random_ready); | |
565 | ret = 0; | |
566 | } | |
567 | return ret; | |
568 | } | |
569 | late_initcall(prandom_init_late); |