]> git.proxmox.com Git - mirror_ubuntu-hirsute-kernel.git/blame - drivers/char/random.c
random: use an improved fast_mix() function
[mirror_ubuntu-hirsute-kernel.git] / drivers / char / random.c
CommitLineData
1da177e4
LT
1/*
2 * random.c -- A strong random number generator
3 *
9e95ce27 4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
1da177e4
LT
5 *
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
7 * rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, and the entire permission notice in its entirety,
14 * including the disclaimer of warranties.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior
20 * written permission.
21 *
22 * ALTERNATIVELY, this product may be distributed under the terms of
23 * the GNU General Public License, in which case the provisions of the GPL are
24 * required INSTEAD OF the above restrictions. (This clause is
25 * necessary due to a potential bad interaction between the GPL and
26 * the restrictions contained in a BSD-style copyright.)
27 *
28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
31 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
39 * DAMAGE.
40 */
41
42/*
43 * (now, with legal B.S. out of the way.....)
44 *
45 * This routine gathers environmental noise from device drivers, etc.,
46 * and returns good random numbers, suitable for cryptographic use.
47 * Besides the obvious cryptographic uses, these numbers are also good
48 * for seeding TCP sequence numbers, and other places where it is
49 * desirable to have numbers which are not only random, but hard to
50 * predict by an attacker.
51 *
52 * Theory of operation
53 * ===================
54 *
55 * Computers are very predictable devices. Hence it is extremely hard
56 * to produce truly random numbers on a computer --- as opposed to
57 * pseudo-random numbers, which can easily generated by using a
58 * algorithm. Unfortunately, it is very easy for attackers to guess
59 * the sequence of pseudo-random number generators, and for some
60 * applications this is not acceptable. So instead, we must try to
61 * gather "environmental noise" from the computer's environment, which
62 * must be hard for outside attackers to observe, and use that to
63 * generate random numbers. In a Unix environment, this is best done
64 * from inside the kernel.
65 *
66 * Sources of randomness from the environment include inter-keyboard
67 * timings, inter-interrupt timings from some interrupts, and other
68 * events which are both (a) non-deterministic and (b) hard for an
69 * outside observer to measure. Randomness from these sources are
70 * added to an "entropy pool", which is mixed using a CRC-like function.
71 * This is not cryptographically strong, but it is adequate assuming
72 * the randomness is not chosen maliciously, and it is fast enough that
73 * the overhead of doing it on every interrupt is very reasonable.
74 * As random bytes are mixed into the entropy pool, the routines keep
75 * an *estimate* of how many bits of randomness have been stored into
76 * the random number generator's internal state.
77 *
78 * When random bytes are desired, they are obtained by taking the SHA
79 * hash of the contents of the "entropy pool". The SHA hash avoids
80 * exposing the internal state of the entropy pool. It is believed to
81 * be computationally infeasible to derive any useful information
82 * about the input of SHA from its output. Even if it is possible to
83 * analyze SHA in some clever way, as long as the amount of data
84 * returned from the generator is less than the inherent entropy in
85 * the pool, the output data is totally unpredictable. For this
86 * reason, the routine decreases its internal estimate of how many
87 * bits of "true randomness" are contained in the entropy pool as it
88 * outputs random numbers.
89 *
90 * If this estimate goes to zero, the routine can still generate
91 * random numbers; however, an attacker may (at least in theory) be
92 * able to infer the future output of the generator from prior
93 * outputs. This requires successful cryptanalysis of SHA, which is
94 * not believed to be feasible, but there is a remote possibility.
95 * Nonetheless, these numbers should be useful for the vast majority
96 * of purposes.
97 *
98 * Exported interfaces ---- output
99 * ===============================
100 *
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
103 *
104 * void get_random_bytes(void *buf, int nbytes);
105 *
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
108 *
109 * The two other interfaces are two character devices /dev/random and
110 * /dev/urandom. /dev/random is suitable for use when very high
111 * quality randomness is desired (for example, for key generation or
112 * one-time pads), as it will only return a maximum of the number of
113 * bits of randomness (as estimated by the random number generator)
114 * contained in the entropy pool.
115 *
116 * The /dev/urandom device does not have this limit, and will return
117 * as many bytes as are requested. As more and more random bytes are
118 * requested without giving time for the entropy pool to recharge,
119 * this will result in random numbers that are merely cryptographically
120 * strong. For many applications, however, this is acceptable.
121 *
122 * Exported interfaces ---- input
123 * ==============================
124 *
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
127 *
a2080a67 128 * void add_device_randomness(const void *buf, unsigned int size);
1da177e4
LT
129 * void add_input_randomness(unsigned int type, unsigned int code,
130 * unsigned int value);
775f4b29 131 * void add_interrupt_randomness(int irq, int irq_flags);
442a4fff 132 * void add_disk_randomness(struct gendisk *disk);
1da177e4 133 *
a2080a67
LT
134 * add_device_randomness() is for adding data to the random pool that
135 * is likely to differ between two devices (or possibly even per boot).
136 * This would be things like MAC addresses or serial numbers, or the
137 * read-out of the RTC. This does *not* add any actual entropy to the
138 * pool, but it initializes the pool to different values for devices
139 * that might otherwise be identical and have very little entropy
140 * available to them (particularly common in the embedded world).
141 *
1da177e4
LT
142 * add_input_randomness() uses the input layer interrupt timing, as well as
143 * the event type information from the hardware.
144 *
775f4b29
TT
145 * add_interrupt_randomness() uses the interrupt timing as random
146 * inputs to the entropy pool. Using the cycle counters and the irq source
147 * as inputs, it feeds the randomness roughly once a second.
442a4fff
JW
148 *
149 * add_disk_randomness() uses what amounts to the seek time of block
150 * layer request events, on a per-disk_devt basis, as input to the
151 * entropy pool. Note that high-speed solid state drives with very low
152 * seek times do not make for good sources of entropy, as their seek
153 * times are usually fairly consistent.
1da177e4
LT
154 *
155 * All of these routines try to estimate how many bits of randomness a
156 * particular randomness source. They do this by keeping track of the
157 * first and second order deltas of the event timings.
158 *
159 * Ensuring unpredictability at system startup
160 * ============================================
161 *
162 * When any operating system starts up, it will go through a sequence
163 * of actions that are fairly predictable by an adversary, especially
164 * if the start-up does not involve interaction with a human operator.
165 * This reduces the actual number of bits of unpredictability in the
166 * entropy pool below the value in entropy_count. In order to
167 * counteract this effect, it helps to carry information in the
168 * entropy pool across shut-downs and start-ups. To do this, put the
169 * following lines an appropriate script which is run during the boot
170 * sequence:
171 *
172 * echo "Initializing random number generator..."
173 * random_seed=/var/run/random-seed
174 * # Carry a random seed from start-up to start-up
175 * # Load and then save the whole entropy pool
176 * if [ -f $random_seed ]; then
177 * cat $random_seed >/dev/urandom
178 * else
179 * touch $random_seed
180 * fi
181 * chmod 600 $random_seed
182 * dd if=/dev/urandom of=$random_seed count=1 bs=512
183 *
184 * and the following lines in an appropriate script which is run as
185 * the system is shutdown:
186 *
187 * # Carry a random seed from shut-down to start-up
188 * # Save the whole entropy pool
189 * echo "Saving random seed..."
190 * random_seed=/var/run/random-seed
191 * touch $random_seed
192 * chmod 600 $random_seed
193 * dd if=/dev/urandom of=$random_seed count=1 bs=512
194 *
195 * For example, on most modern systems using the System V init
196 * scripts, such code fragments would be found in
197 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
198 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
199 *
200 * Effectively, these commands cause the contents of the entropy pool
201 * to be saved at shut-down time and reloaded into the entropy pool at
202 * start-up. (The 'dd' in the addition to the bootup script is to
203 * make sure that /etc/random-seed is different for every start-up,
204 * even if the system crashes without executing rc.0.) Even with
205 * complete knowledge of the start-up activities, predicting the state
206 * of the entropy pool requires knowledge of the previous history of
207 * the system.
208 *
209 * Configuring the /dev/random driver under Linux
210 * ==============================================
211 *
212 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
213 * the /dev/mem major number (#1). So if your system does not have
214 * /dev/random and /dev/urandom created already, they can be created
215 * by using the commands:
216 *
217 * mknod /dev/random c 1 8
218 * mknod /dev/urandom c 1 9
219 *
220 * Acknowledgements:
221 * =================
222 *
223 * Ideas for constructing this random number generator were derived
224 * from Pretty Good Privacy's random number generator, and from private
225 * discussions with Phil Karn. Colin Plumb provided a faster random
226 * number generator, which speed up the mixing function of the entropy
227 * pool, taken from PGPfone. Dale Worley has also contributed many
228 * useful ideas and suggestions to improve this driver.
229 *
230 * Any flaws in the design are solely my responsibility, and should
231 * not be attributed to the Phil, Colin, or any of authors of PGP.
232 *
233 * Further background information on this topic may be obtained from
234 * RFC 1750, "Randomness Recommendations for Security", by Donald
235 * Eastlake, Steve Crocker, and Jeff Schiller.
236 */
237
238#include <linux/utsname.h>
1da177e4
LT
239#include <linux/module.h>
240#include <linux/kernel.h>
241#include <linux/major.h>
242#include <linux/string.h>
243#include <linux/fcntl.h>
244#include <linux/slab.h>
245#include <linux/random.h>
246#include <linux/poll.h>
247#include <linux/init.h>
248#include <linux/fs.h>
249#include <linux/genhd.h>
250#include <linux/interrupt.h>
27ac792c 251#include <linux/mm.h>
1da177e4
LT
252#include <linux/spinlock.h>
253#include <linux/percpu.h>
254#include <linux/cryptohash.h>
5b739ef8 255#include <linux/fips.h>
775f4b29 256#include <linux/ptrace.h>
e6d4947b 257#include <linux/kmemcheck.h>
6265e169 258#include <linux/workqueue.h>
0244ad00 259#include <linux/irq.h>
d178a1eb 260
1da177e4
LT
261#include <asm/processor.h>
262#include <asm/uaccess.h>
263#include <asm/irq.h>
775f4b29 264#include <asm/irq_regs.h>
1da177e4
LT
265#include <asm/io.h>
266
00ce1db1
TT
267#define CREATE_TRACE_POINTS
268#include <trace/events/random.h>
269
43759d4f
TT
270/* #define ADD_INTERRUPT_BENCH */
271
1da177e4
LT
272/*
273 * Configuration information
274 */
30e37ec5
PA
275#define INPUT_POOL_SHIFT 12
276#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
277#define OUTPUT_POOL_SHIFT 10
278#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
279#define SEC_XFER_SIZE 512
280#define EXTRACT_SIZE 10
1da177e4 281
392a546d 282#define DEBUG_RANDOM_BOOT 0
1da177e4 283
d2e7c96a
PA
284#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
285
a283b5c4 286/*
95b709b6
TT
287 * To allow fractional bits to be tracked, the entropy_count field is
288 * denominated in units of 1/8th bits.
30e37ec5
PA
289 *
290 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
291 * credit_entropy_bits() needs to be 64 bits wide.
a283b5c4
PA
292 */
293#define ENTROPY_SHIFT 3
294#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
295
1da177e4
LT
296/*
297 * The minimum number of bits of entropy before we wake up a read on
298 * /dev/random. Should be enough to do a significant reseed.
299 */
2132a96f 300static int random_read_wakeup_bits = 64;
1da177e4
LT
301
302/*
303 * If the entropy count falls under this number of bits, then we
304 * should wake up processes which are selecting or polling on write
305 * access to /dev/random.
306 */
2132a96f 307static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
1da177e4
LT
308
309/*
dfd38750 310 * The minimum number of seconds between urandom pool reseeding. We
f5c2742c
TT
311 * do this to limit the amount of entropy that can be drained from the
312 * input pool even if there are heavy demands on /dev/urandom.
1da177e4 313 */
f5c2742c 314static int random_min_urandom_seed = 60;
1da177e4
LT
315
316/*
6e9fa2c8
TT
317 * Originally, we used a primitive polynomial of degree .poolwords
318 * over GF(2). The taps for various sizes are defined below. They
319 * were chosen to be evenly spaced except for the last tap, which is 1
320 * to get the twisting happening as fast as possible.
321 *
322 * For the purposes of better mixing, we use the CRC-32 polynomial as
323 * well to make a (modified) twisted Generalized Feedback Shift
324 * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
325 * generators. ACM Transactions on Modeling and Computer Simulation
326 * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
dfd38750 327 * GFSR generators II. ACM Transactions on Modeling and Computer
6e9fa2c8
TT
328 * Simulation 4:254-266)
329 *
330 * Thanks to Colin Plumb for suggesting this.
331 *
332 * The mixing operation is much less sensitive than the output hash,
333 * where we use SHA-1. All that we want of mixing operation is that
334 * it be a good non-cryptographic hash; i.e. it not produce collisions
335 * when fed "random" data of the sort we expect to see. As long as
336 * the pool state differs for different inputs, we have preserved the
337 * input entropy and done a good job. The fact that an intelligent
338 * attacker can construct inputs that will produce controlled
339 * alterations to the pool's state is not important because we don't
340 * consider such inputs to contribute any randomness. The only
341 * property we need with respect to them is that the attacker can't
342 * increase his/her knowledge of the pool's state. Since all
343 * additions are reversible (knowing the final state and the input,
344 * you can reconstruct the initial state), if an attacker has any
345 * uncertainty about the initial state, he/she can only shuffle that
346 * uncertainty about, but never cause any collisions (which would
347 * decrease the uncertainty).
348 *
349 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
350 * Videau in their paper, "The Linux Pseudorandom Number Generator
351 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
352 * paper, they point out that we are not using a true Twisted GFSR,
353 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
354 * is, with only three taps, instead of the six that we are using).
355 * As a result, the resulting polynomial is neither primitive nor
356 * irreducible, and hence does not have a maximal period over
357 * GF(2**32). They suggest a slight change to the generator
358 * polynomial which improves the resulting TGFSR polynomial to be
359 * irreducible, which we have made here.
1da177e4
LT
360 */
361static struct poolinfo {
a283b5c4
PA
362 int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
363#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
1da177e4
LT
364 int tap1, tap2, tap3, tap4, tap5;
365} poolinfo_table[] = {
6e9fa2c8
TT
366 /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
367 /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
368 { S(128), 104, 76, 51, 25, 1 },
369 /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
370 /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
371 { S(32), 26, 19, 14, 7, 1 },
1da177e4
LT
372#if 0
373 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
9ed17b70 374 { S(2048), 1638, 1231, 819, 411, 1 },
1da177e4
LT
375
376 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
9ed17b70 377 { S(1024), 817, 615, 412, 204, 1 },
1da177e4
LT
378
379 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
9ed17b70 380 { S(1024), 819, 616, 410, 207, 2 },
1da177e4
LT
381
382 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
9ed17b70 383 { S(512), 411, 308, 208, 104, 1 },
1da177e4
LT
384
385 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
9ed17b70 386 { S(512), 409, 307, 206, 102, 2 },
1da177e4 387 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
9ed17b70 388 { S(512), 409, 309, 205, 103, 2 },
1da177e4
LT
389
390 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
9ed17b70 391 { S(256), 205, 155, 101, 52, 1 },
1da177e4
LT
392
393 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
9ed17b70 394 { S(128), 103, 78, 51, 27, 2 },
1da177e4
LT
395
396 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
9ed17b70 397 { S(64), 52, 39, 26, 14, 1 },
1da177e4
LT
398#endif
399};
400
1da177e4
LT
401/*
402 * Static global variables
403 */
404static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
405static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
9a6f70bb 406static struct fasync_struct *fasync;
1da177e4 407
1da177e4
LT
408/**********************************************************************
409 *
410 * OS independent entropy store. Here are the functions which handle
411 * storing entropy in an entropy pool.
412 *
413 **********************************************************************/
414
415struct entropy_store;
416struct entropy_store {
43358209 417 /* read-only data: */
30e37ec5 418 const struct poolinfo *poolinfo;
1da177e4
LT
419 __u32 *pool;
420 const char *name;
1da177e4 421 struct entropy_store *pull;
6265e169 422 struct work_struct push_work;
1da177e4
LT
423
424 /* read-write data: */
f5c2742c 425 unsigned long last_pulled;
43358209 426 spinlock_t lock;
c59974ae
TT
427 unsigned short add_ptr;
428 unsigned short input_rotate;
cda796a3 429 int entropy_count;
775f4b29 430 int entropy_total;
775f4b29 431 unsigned int initialized:1;
c59974ae
TT
432 unsigned int limit:1;
433 unsigned int last_data_init:1;
e954bc91 434 __u8 last_data[EXTRACT_SIZE];
1da177e4
LT
435};
436
6265e169 437static void push_to_pool(struct work_struct *work);
1da177e4
LT
438static __u32 input_pool_data[INPUT_POOL_WORDS];
439static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
440static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
441
442static struct entropy_store input_pool = {
443 .poolinfo = &poolinfo_table[0],
444 .name = "input",
445 .limit = 1,
eece09ec 446 .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
1da177e4
LT
447 .pool = input_pool_data
448};
449
450static struct entropy_store blocking_pool = {
451 .poolinfo = &poolinfo_table[1],
452 .name = "blocking",
453 .limit = 1,
454 .pull = &input_pool,
eece09ec 455 .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
6265e169
TT
456 .pool = blocking_pool_data,
457 .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
458 push_to_pool),
1da177e4
LT
459};
460
461static struct entropy_store nonblocking_pool = {
462 .poolinfo = &poolinfo_table[1],
463 .name = "nonblocking",
464 .pull = &input_pool,
eece09ec 465 .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
6265e169
TT
466 .pool = nonblocking_pool_data,
467 .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
468 push_to_pool),
1da177e4
LT
469};
470
775f4b29
TT
471static __u32 const twist_table[8] = {
472 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
473 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
474
1da177e4 475/*
e68e5b66 476 * This function adds bytes into the entropy "pool". It does not
1da177e4 477 * update the entropy estimate. The caller should call
adc782da 478 * credit_entropy_bits if this is appropriate.
1da177e4
LT
479 *
480 * The pool is stirred with a primitive polynomial of the appropriate
481 * degree, and then twisted. We twist by three bits at a time because
482 * it's cheap to do so and helps slightly in the expected case where
483 * the entropy is concentrated in the low-order bits.
484 */
00ce1db1 485static void _mix_pool_bytes(struct entropy_store *r, const void *in,
85608f8e 486 int nbytes)
1da177e4 487{
85608f8e 488 unsigned long i, tap1, tap2, tap3, tap4, tap5;
feee7697 489 int input_rotate;
1da177e4 490 int wordmask = r->poolinfo->poolwords - 1;
e68e5b66 491 const char *bytes = in;
6d38b827 492 __u32 w;
1da177e4 493
1da177e4
LT
494 tap1 = r->poolinfo->tap1;
495 tap2 = r->poolinfo->tap2;
496 tap3 = r->poolinfo->tap3;
497 tap4 = r->poolinfo->tap4;
498 tap5 = r->poolinfo->tap5;
1da177e4 499
91fcb532
TT
500 input_rotate = r->input_rotate;
501 i = r->add_ptr;
1da177e4 502
e68e5b66
MM
503 /* mix one byte at a time to simplify size handling and churn faster */
504 while (nbytes--) {
c59974ae 505 w = rol32(*bytes++, input_rotate);
993ba211 506 i = (i - 1) & wordmask;
1da177e4
LT
507
508 /* XOR in the various taps */
993ba211 509 w ^= r->pool[i];
1da177e4
LT
510 w ^= r->pool[(i + tap1) & wordmask];
511 w ^= r->pool[(i + tap2) & wordmask];
512 w ^= r->pool[(i + tap3) & wordmask];
513 w ^= r->pool[(i + tap4) & wordmask];
514 w ^= r->pool[(i + tap5) & wordmask];
993ba211
MM
515
516 /* Mix the result back in with a twist */
1da177e4 517 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
feee7697
MM
518
519 /*
520 * Normally, we add 7 bits of rotation to the pool.
521 * At the beginning of the pool, add an extra 7 bits
522 * rotation, so that successive passes spread the
523 * input bits across the pool evenly.
524 */
c59974ae 525 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
1da177e4
LT
526 }
527
91fcb532
TT
528 r->input_rotate = input_rotate;
529 r->add_ptr = i;
1da177e4
LT
530}
531
00ce1db1 532static void __mix_pool_bytes(struct entropy_store *r, const void *in,
85608f8e 533 int nbytes)
00ce1db1
TT
534{
535 trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
85608f8e 536 _mix_pool_bytes(r, in, nbytes);
00ce1db1
TT
537}
538
539static void mix_pool_bytes(struct entropy_store *r, const void *in,
85608f8e 540 int nbytes)
1da177e4 541{
902c098a
TT
542 unsigned long flags;
543
00ce1db1 544 trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
902c098a 545 spin_lock_irqsave(&r->lock, flags);
85608f8e 546 _mix_pool_bytes(r, in, nbytes);
902c098a 547 spin_unlock_irqrestore(&r->lock, flags);
1da177e4
LT
548}
549
775f4b29
TT
550struct fast_pool {
551 __u32 pool[4];
552 unsigned long last;
840f9507
TT
553 unsigned char count;
554 unsigned char notimer_count;
775f4b29 555 unsigned char rotate;
775f4b29
TT
556};
557
558/*
559 * This is a fast mixing routine used by the interrupt randomness
560 * collector. It's hardcoded for an 128 bit pool and assumes that any
561 * locks that might be needed are taken by the caller.
562 */
43759d4f 563static void fast_mix(struct fast_pool *f)
775f4b29 564{
43759d4f
TT
565 __u32 a = f->pool[0], b = f->pool[1];
566 __u32 c = f->pool[2], d = f->pool[3];
567
568 a += b; c += d;
569 b = rol32(a, 6); d = rol32(c, 27);
570 d ^= a; b ^= c;
571
572 a += b; c += d;
573 b = rol32(a, 16); d = rol32(c, 14);
574 d ^= a; b ^= c;
575
576 a += b; c += d;
577 b = rol32(a, 6); d = rol32(c, 27);
578 d ^= a; b ^= c;
579
580 a += b; c += d;
581 b = rol32(a, 16); d = rol32(c, 14);
582 d ^= a; b ^= c;
583
584 f->pool[0] = a; f->pool[1] = b;
585 f->pool[2] = c; f->pool[3] = d;
655b2264 586 f->count++;
775f4b29
TT
587}
588
1da177e4 589/*
a283b5c4
PA
590 * Credit (or debit) the entropy store with n bits of entropy.
591 * Use credit_entropy_bits_safe() if the value comes from userspace
592 * or otherwise should be checked for extreme values.
1da177e4 593 */
adc782da 594static void credit_entropy_bits(struct entropy_store *r, int nbits)
1da177e4 595{
902c098a 596 int entropy_count, orig;
30e37ec5
PA
597 const int pool_size = r->poolinfo->poolfracbits;
598 int nfrac = nbits << ENTROPY_SHIFT;
1da177e4 599
adc782da
MM
600 if (!nbits)
601 return;
602
902c098a
TT
603retry:
604 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
30e37ec5
PA
605 if (nfrac < 0) {
606 /* Debit */
607 entropy_count += nfrac;
608 } else {
609 /*
610 * Credit: we have to account for the possibility of
611 * overwriting already present entropy. Even in the
612 * ideal case of pure Shannon entropy, new contributions
613 * approach the full value asymptotically:
614 *
615 * entropy <- entropy + (pool_size - entropy) *
616 * (1 - exp(-add_entropy/pool_size))
617 *
618 * For add_entropy <= pool_size/2 then
619 * (1 - exp(-add_entropy/pool_size)) >=
620 * (add_entropy/pool_size)*0.7869...
621 * so we can approximate the exponential with
622 * 3/4*add_entropy/pool_size and still be on the
623 * safe side by adding at most pool_size/2 at a time.
624 *
625 * The use of pool_size-2 in the while statement is to
626 * prevent rounding artifacts from making the loop
627 * arbitrarily long; this limits the loop to log2(pool_size)*2
628 * turns no matter how large nbits is.
629 */
630 int pnfrac = nfrac;
631 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
632 /* The +2 corresponds to the /4 in the denominator */
633
634 do {
635 unsigned int anfrac = min(pnfrac, pool_size/2);
636 unsigned int add =
637 ((pool_size - entropy_count)*anfrac*3) >> s;
638
639 entropy_count += add;
640 pnfrac -= anfrac;
641 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
642 }
00ce1db1 643
8b76f46a 644 if (entropy_count < 0) {
f80bbd8b
TT
645 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
646 r->name, entropy_count);
647 WARN_ON(1);
8b76f46a 648 entropy_count = 0;
30e37ec5
PA
649 } else if (entropy_count > pool_size)
650 entropy_count = pool_size;
902c098a
TT
651 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
652 goto retry;
1da177e4 653
6265e169 654 r->entropy_total += nbits;
0891ad82
LT
655 if (!r->initialized && r->entropy_total > 128) {
656 r->initialized = 1;
657 r->entropy_total = 0;
658 if (r == &nonblocking_pool) {
659 prandom_reseed_late();
660 pr_notice("random: %s pool is initialized\n", r->name);
4af712e8 661 }
775f4b29
TT
662 }
663
a283b5c4
PA
664 trace_credit_entropy_bits(r->name, nbits,
665 entropy_count >> ENTROPY_SHIFT,
00ce1db1
TT
666 r->entropy_total, _RET_IP_);
667
6265e169 668 if (r == &input_pool) {
7d1b08c4 669 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
6265e169
TT
670
671 /* should we wake readers? */
2132a96f 672 if (entropy_bits >= random_read_wakeup_bits) {
6265e169
TT
673 wake_up_interruptible(&random_read_wait);
674 kill_fasync(&fasync, SIGIO, POLL_IN);
675 }
676 /* If the input pool is getting full, send some
677 * entropy to the two output pools, flipping back and
678 * forth between them, until the output pools are 75%
679 * full.
680 */
2132a96f 681 if (entropy_bits > random_write_wakeup_bits &&
6265e169 682 r->initialized &&
2132a96f 683 r->entropy_total >= 2*random_read_wakeup_bits) {
6265e169
TT
684 static struct entropy_store *last = &blocking_pool;
685 struct entropy_store *other = &blocking_pool;
686
687 if (last == &blocking_pool)
688 other = &nonblocking_pool;
689 if (other->entropy_count <=
690 3 * other->poolinfo->poolfracbits / 4)
691 last = other;
692 if (last->entropy_count <=
693 3 * last->poolinfo->poolfracbits / 4) {
694 schedule_work(&last->push_work);
695 r->entropy_total = 0;
696 }
697 }
9a6f70bb 698 }
1da177e4
LT
699}
700
a283b5c4
PA
701static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
702{
703 const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
704
705 /* Cap the value to avoid overflows */
706 nbits = min(nbits, nbits_max);
707 nbits = max(nbits, -nbits_max);
708
709 credit_entropy_bits(r, nbits);
710}
711
1da177e4
LT
712/*********************************************************************
713 *
714 * Entropy input management
715 *
716 *********************************************************************/
717
718/* There is one of these per entropy source */
719struct timer_rand_state {
720 cycles_t last_time;
90b75ee5 721 long last_delta, last_delta2;
1da177e4
LT
722 unsigned dont_count_entropy:1;
723};
724
644008df
TT
725#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
726
a2080a67
LT
727/*
728 * Add device- or boot-specific data to the input and nonblocking
729 * pools to help initialize them to unique values.
730 *
731 * None of this adds any entropy, it is meant to avoid the
732 * problem of the nonblocking pool having similar initial state
733 * across largely identical devices.
734 */
735void add_device_randomness(const void *buf, unsigned int size)
736{
61875f30 737 unsigned long time = random_get_entropy() ^ jiffies;
3ef4cb2d 738 unsigned long flags;
a2080a67 739
5910895f 740 trace_add_device_randomness(size, _RET_IP_);
3ef4cb2d 741 spin_lock_irqsave(&input_pool.lock, flags);
85608f8e
TT
742 _mix_pool_bytes(&input_pool, buf, size);
743 _mix_pool_bytes(&input_pool, &time, sizeof(time));
3ef4cb2d
TT
744 spin_unlock_irqrestore(&input_pool.lock, flags);
745
746 spin_lock_irqsave(&nonblocking_pool.lock, flags);
85608f8e
TT
747 _mix_pool_bytes(&nonblocking_pool, buf, size);
748 _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
3ef4cb2d 749 spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
a2080a67
LT
750}
751EXPORT_SYMBOL(add_device_randomness);
752
644008df 753static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
3060d6fe 754
1da177e4
LT
755/*
756 * This function adds entropy to the entropy "pool" by using timing
757 * delays. It uses the timer_rand_state structure to make an estimate
758 * of how many bits of entropy this call has added to the pool.
759 *
760 * The number "num" is also added to the pool - it should somehow describe
761 * the type of event which just happened. This is currently 0-255 for
762 * keyboard scan codes, and 256 upwards for interrupts.
763 *
764 */
765static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
766{
40db23e5 767 struct entropy_store *r;
1da177e4 768 struct {
1da177e4 769 long jiffies;
cf833d0b 770 unsigned cycles;
1da177e4
LT
771 unsigned num;
772 } sample;
773 long delta, delta2, delta3;
774
775 preempt_disable();
1da177e4
LT
776
777 sample.jiffies = jiffies;
61875f30 778 sample.cycles = random_get_entropy();
1da177e4 779 sample.num = num;
40db23e5 780 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
85608f8e 781 mix_pool_bytes(r, &sample, sizeof(sample));
1da177e4
LT
782
783 /*
784 * Calculate number of bits of randomness we probably added.
785 * We take into account the first, second and third-order deltas
786 * in order to make our estimate.
787 */
788
789 if (!state->dont_count_entropy) {
790 delta = sample.jiffies - state->last_time;
791 state->last_time = sample.jiffies;
792
793 delta2 = delta - state->last_delta;
794 state->last_delta = delta;
795
796 delta3 = delta2 - state->last_delta2;
797 state->last_delta2 = delta2;
798
799 if (delta < 0)
800 delta = -delta;
801 if (delta2 < 0)
802 delta2 = -delta2;
803 if (delta3 < 0)
804 delta3 = -delta3;
805 if (delta > delta2)
806 delta = delta2;
807 if (delta > delta3)
808 delta = delta3;
809
810 /*
811 * delta is now minimum absolute delta.
812 * Round down by 1 bit on general principles,
813 * and limit entropy entimate to 12 bits.
814 */
40db23e5 815 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1da177e4 816 }
1da177e4
LT
817 preempt_enable();
818}
819
d251575a 820void add_input_randomness(unsigned int type, unsigned int code,
1da177e4
LT
821 unsigned int value)
822{
823 static unsigned char last_value;
824
825 /* ignore autorepeat and the like */
826 if (value == last_value)
827 return;
828
1da177e4
LT
829 last_value = value;
830 add_timer_randomness(&input_timer_state,
831 (type << 4) ^ code ^ (code >> 4) ^ value);
f80bbd8b 832 trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1da177e4 833}
80fc9f53 834EXPORT_SYMBOL_GPL(add_input_randomness);
1da177e4 835
775f4b29
TT
836static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
837
43759d4f
TT
838#ifdef ADD_INTERRUPT_BENCH
839static unsigned long avg_cycles, avg_deviation;
840
841#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
842#define FIXED_1_2 (1 << (AVG_SHIFT-1))
843
844static void add_interrupt_bench(cycles_t start)
845{
846 long delta = random_get_entropy() - start;
847
848 /* Use a weighted moving average */
849 delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
850 avg_cycles += delta;
851 /* And average deviation */
852 delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
853 avg_deviation += delta;
854}
855#else
856#define add_interrupt_bench(x)
857#endif
858
775f4b29 859void add_interrupt_randomness(int irq, int irq_flags)
1da177e4 860{
775f4b29
TT
861 struct entropy_store *r;
862 struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
863 struct pt_regs *regs = get_irq_regs();
864 unsigned long now = jiffies;
655b2264 865 cycles_t cycles = random_get_entropy();
43759d4f 866 __u32 c_high, j_high;
655b2264 867 __u64 ip;
83664a69 868 unsigned long seed;
91fcb532 869 int credit = 0;
3060d6fe 870
655b2264
TT
871 c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
872 j_high = (sizeof(now) > 4) ? now >> 32 : 0;
43759d4f
TT
873 fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
874 fast_pool->pool[1] ^= now ^ c_high;
655b2264 875 ip = regs ? instruction_pointer(regs) : _RET_IP_;
43759d4f
TT
876 fast_pool->pool[2] ^= ip;
877 fast_pool->pool[3] ^= ip >> 32;
3060d6fe 878
43759d4f 879 fast_mix(fast_pool);
840f9507
TT
880 if ((irq_flags & __IRQF_TIMER) == 0)
881 fast_pool->notimer_count++;
43759d4f 882 add_interrupt_bench(cycles);
3060d6fe 883
840f9507
TT
884 if (cycles) {
885 if ((fast_pool->count < 64) &&
886 !time_after(now, fast_pool->last + HZ))
887 return;
888 } else {
889 /* CPU does not have a cycle counting register :-( */
890 if (fast_pool->count < 64)
891 return;
892 }
1da177e4 893
775f4b29 894 r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
840f9507 895 if (!spin_trylock(&r->lock))
91fcb532 896 return;
840f9507 897
91fcb532 898 fast_pool->last = now;
85608f8e 899 __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
83664a69 900
91fcb532
TT
901 /*
902 * If we have architectural seed generator, produce a seed and
903 * add it to the pool. For the sake of paranoia count it as
904 * 50% entropic.
905 */
906 if (arch_get_random_seed_long(&seed)) {
85608f8e 907 __mix_pool_bytes(r, &seed, sizeof(seed));
91fcb532
TT
908 credit += sizeof(seed) * 4;
909 }
910 spin_unlock(&r->lock);
911
775f4b29 912 /*
840f9507
TT
913 * If we have a valid cycle counter or if the majority of
914 * interrupts collected were non-timer interrupts, then give
915 * an entropy credit of 1 bit. Yes, this is being very
916 * conservative.
775f4b29 917 */
840f9507
TT
918 if (cycles || (fast_pool->notimer_count >= 32))
919 credit++;
920
921 fast_pool->count = fast_pool->notimer_count = 0;
83664a69 922
83664a69 923 credit_entropy_bits(r, credit);
1da177e4
LT
924}
925
9361401e 926#ifdef CONFIG_BLOCK
1da177e4
LT
927void add_disk_randomness(struct gendisk *disk)
928{
929 if (!disk || !disk->random)
930 return;
931 /* first major is 1, so we get >= 0x200 here */
f331c029 932 add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
f80bbd8b 933 trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1da177e4 934}
bdcfa3e5 935EXPORT_SYMBOL_GPL(add_disk_randomness);
9361401e 936#endif
1da177e4 937
1da177e4
LT
938/*********************************************************************
939 *
940 * Entropy extraction routines
941 *
942 *********************************************************************/
943
90b75ee5 944static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1da177e4
LT
945 size_t nbytes, int min, int rsvd);
946
947/*
25985edc 948 * This utility inline function is responsible for transferring entropy
1da177e4
LT
949 * from the primary pool to the secondary extraction pool. We make
950 * sure we pull enough for a 'catastrophic reseed'.
951 */
6265e169 952static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1da177e4
LT
953static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
954{
cff85031
TT
955 if (!r->pull ||
956 r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
957 r->entropy_count > r->poolinfo->poolfracbits)
958 return;
959
f5c2742c
TT
960 if (r->limit == 0 && random_min_urandom_seed) {
961 unsigned long now = jiffies;
1da177e4 962
f5c2742c
TT
963 if (time_before(now,
964 r->last_pulled + random_min_urandom_seed * HZ))
965 return;
966 r->last_pulled = now;
1da177e4 967 }
cff85031
TT
968
969 _xfer_secondary_pool(r, nbytes);
6265e169
TT
970}
971
972static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
973{
974 __u32 tmp[OUTPUT_POOL_WORDS];
975
2132a96f
GP
976 /* For /dev/random's pool, always leave two wakeups' worth */
977 int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
6265e169
TT
978 int bytes = nbytes;
979
2132a96f
GP
980 /* pull at least as much as a wakeup */
981 bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
6265e169
TT
982 /* but never more than the buffer size */
983 bytes = min_t(int, bytes, sizeof(tmp));
984
f80bbd8b
TT
985 trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
986 ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
6265e169 987 bytes = extract_entropy(r->pull, tmp, bytes,
2132a96f 988 random_read_wakeup_bits / 8, rsvd_bytes);
85608f8e 989 mix_pool_bytes(r, tmp, bytes);
6265e169
TT
990 credit_entropy_bits(r, bytes*8);
991}
992
993/*
994 * Used as a workqueue function so that when the input pool is getting
995 * full, we can "spill over" some entropy to the output pools. That
996 * way the output pools can store some of the excess entropy instead
997 * of letting it go to waste.
998 */
999static void push_to_pool(struct work_struct *work)
1000{
1001 struct entropy_store *r = container_of(work, struct entropy_store,
1002 push_work);
1003 BUG_ON(!r);
2132a96f 1004 _xfer_secondary_pool(r, random_read_wakeup_bits/8);
6265e169
TT
1005 trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1006 r->pull->entropy_count >> ENTROPY_SHIFT);
1da177e4
LT
1007}
1008
1009/*
19fa5be1
GP
1010 * This function decides how many bytes to actually take from the
1011 * given pool, and also debits the entropy count accordingly.
1da177e4 1012 */
1da177e4
LT
1013static size_t account(struct entropy_store *r, size_t nbytes, int min,
1014 int reserved)
1015{
a283b5c4
PA
1016 int entropy_count, orig;
1017 size_t ibytes;
1da177e4 1018
a283b5c4 1019 BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1da177e4
LT
1020
1021 /* Can we pull enough? */
10b3a32d 1022retry:
a283b5c4 1023 entropy_count = orig = ACCESS_ONCE(r->entropy_count);
a283b5c4 1024 ibytes = nbytes;
0fb7a01a 1025 /* If limited, never pull more than available */
e33ba5fa
TT
1026 if (r->limit) {
1027 int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1028
1029 if ((have_bytes -= reserved) < 0)
1030 have_bytes = 0;
1031 ibytes = min_t(size_t, ibytes, have_bytes);
1032 }
0fb7a01a 1033 if (ibytes < min)
a283b5c4 1034 ibytes = 0;
e33ba5fa
TT
1035 if ((entropy_count -= ibytes << (ENTROPY_SHIFT + 3)) < 0)
1036 entropy_count = 0;
f9c6d498 1037
0fb7a01a
GP
1038 if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1039 goto retry;
1da177e4 1040
f80bbd8b 1041 trace_debit_entropy(r->name, 8 * ibytes);
0fb7a01a 1042 if (ibytes &&
2132a96f 1043 (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
b9809552
TT
1044 wake_up_interruptible(&random_write_wait);
1045 kill_fasync(&fasync, SIGIO, POLL_OUT);
1046 }
1047
a283b5c4 1048 return ibytes;
1da177e4
LT
1049}
1050
19fa5be1
GP
1051/*
1052 * This function does the actual extraction for extract_entropy and
1053 * extract_entropy_user.
1054 *
1055 * Note: we assume that .poolwords is a multiple of 16 words.
1056 */
1da177e4
LT
1057static void extract_buf(struct entropy_store *r, __u8 *out)
1058{
602b6aee 1059 int i;
d2e7c96a
PA
1060 union {
1061 __u32 w[5];
85a1f777 1062 unsigned long l[LONGS(20)];
d2e7c96a
PA
1063 } hash;
1064 __u32 workspace[SHA_WORKSPACE_WORDS];
902c098a 1065 unsigned long flags;
1da177e4 1066
85a1f777 1067 /*
dfd38750 1068 * If we have an architectural hardware random number
46884442 1069 * generator, use it for SHA's initial vector
85a1f777 1070 */
46884442 1071 sha_init(hash.w);
85a1f777
TT
1072 for (i = 0; i < LONGS(20); i++) {
1073 unsigned long v;
1074 if (!arch_get_random_long(&v))
1075 break;
46884442 1076 hash.l[i] = v;
85a1f777
TT
1077 }
1078
46884442
TT
1079 /* Generate a hash across the pool, 16 words (512 bits) at a time */
1080 spin_lock_irqsave(&r->lock, flags);
1081 for (i = 0; i < r->poolinfo->poolwords; i += 16)
1082 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1083
1da177e4 1084 /*
1c0ad3d4
MM
1085 * We mix the hash back into the pool to prevent backtracking
1086 * attacks (where the attacker knows the state of the pool
1087 * plus the current outputs, and attempts to find previous
1088 * ouputs), unless the hash function can be inverted. By
1089 * mixing at least a SHA1 worth of hash data back, we make
1090 * brute-forcing the feedback as hard as brute-forcing the
1091 * hash.
1da177e4 1092 */
85608f8e 1093 __mix_pool_bytes(r, hash.w, sizeof(hash.w));
902c098a 1094 spin_unlock_irqrestore(&r->lock, flags);
1da177e4 1095
ffd8d3fa 1096 memset(workspace, 0, sizeof(workspace));
1da177e4
LT
1097
1098 /*
1c0ad3d4
MM
1099 * In case the hash function has some recognizable output
1100 * pattern, we fold it in half. Thus, we always feed back
1101 * twice as much data as we output.
1da177e4 1102 */
d2e7c96a
PA
1103 hash.w[0] ^= hash.w[3];
1104 hash.w[1] ^= hash.w[4];
1105 hash.w[2] ^= rol32(hash.w[2], 16);
1106
d2e7c96a
PA
1107 memcpy(out, &hash, EXTRACT_SIZE);
1108 memset(&hash, 0, sizeof(hash));
1da177e4
LT
1109}
1110
19fa5be1
GP
1111/*
1112 * This function extracts randomness from the "entropy pool", and
1113 * returns it in a buffer.
1114 *
1115 * The min parameter specifies the minimum amount we can pull before
1116 * failing to avoid races that defeat catastrophic reseeding while the
1117 * reserved parameter indicates how much entropy we must leave in the
1118 * pool after each pull to avoid starving other readers.
1119 */
90b75ee5 1120static ssize_t extract_entropy(struct entropy_store *r, void *buf,
902c098a 1121 size_t nbytes, int min, int reserved)
1da177e4
LT
1122{
1123 ssize_t ret = 0, i;
1124 __u8 tmp[EXTRACT_SIZE];
1e7e2e05 1125 unsigned long flags;
1da177e4 1126
ec8f02da 1127 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1e7e2e05
JW
1128 if (fips_enabled) {
1129 spin_lock_irqsave(&r->lock, flags);
1130 if (!r->last_data_init) {
c59974ae 1131 r->last_data_init = 1;
1e7e2e05
JW
1132 spin_unlock_irqrestore(&r->lock, flags);
1133 trace_extract_entropy(r->name, EXTRACT_SIZE,
a283b5c4 1134 ENTROPY_BITS(r), _RET_IP_);
1e7e2e05
JW
1135 xfer_secondary_pool(r, EXTRACT_SIZE);
1136 extract_buf(r, tmp);
1137 spin_lock_irqsave(&r->lock, flags);
1138 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1139 }
1140 spin_unlock_irqrestore(&r->lock, flags);
1141 }
ec8f02da 1142
a283b5c4 1143 trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1da177e4
LT
1144 xfer_secondary_pool(r, nbytes);
1145 nbytes = account(r, nbytes, min, reserved);
1146
1147 while (nbytes) {
1148 extract_buf(r, tmp);
5b739ef8 1149
e954bc91 1150 if (fips_enabled) {
5b739ef8
NH
1151 spin_lock_irqsave(&r->lock, flags);
1152 if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1153 panic("Hardware RNG duplicated output!\n");
1154 memcpy(r->last_data, tmp, EXTRACT_SIZE);
1155 spin_unlock_irqrestore(&r->lock, flags);
1156 }
1da177e4
LT
1157 i = min_t(int, nbytes, EXTRACT_SIZE);
1158 memcpy(buf, tmp, i);
1159 nbytes -= i;
1160 buf += i;
1161 ret += i;
1162 }
1163
1164 /* Wipe data just returned from memory */
1165 memset(tmp, 0, sizeof(tmp));
1166
1167 return ret;
1168}
1169
19fa5be1
GP
1170/*
1171 * This function extracts randomness from the "entropy pool", and
1172 * returns it in a userspace buffer.
1173 */
1da177e4
LT
1174static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1175 size_t nbytes)
1176{
1177 ssize_t ret = 0, i;
1178 __u8 tmp[EXTRACT_SIZE];
1179
a283b5c4 1180 trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1da177e4
LT
1181 xfer_secondary_pool(r, nbytes);
1182 nbytes = account(r, nbytes, 0, 0);
1183
1184 while (nbytes) {
1185 if (need_resched()) {
1186 if (signal_pending(current)) {
1187 if (ret == 0)
1188 ret = -ERESTARTSYS;
1189 break;
1190 }
1191 schedule();
1192 }
1193
1194 extract_buf(r, tmp);
1195 i = min_t(int, nbytes, EXTRACT_SIZE);
1196 if (copy_to_user(buf, tmp, i)) {
1197 ret = -EFAULT;
1198 break;
1199 }
1200
1201 nbytes -= i;
1202 buf += i;
1203 ret += i;
1204 }
1205
1206 /* Wipe data just returned from memory */
1207 memset(tmp, 0, sizeof(tmp));
1208
1209 return ret;
1210}
1211
1212/*
1213 * This function is the exported kernel interface. It returns some
c2557a30 1214 * number of good random numbers, suitable for key generation, seeding
18e9cea7
GP
1215 * TCP sequence numbers, etc. It does not rely on the hardware random
1216 * number generator. For random bytes direct from the hardware RNG
1217 * (when available), use get_random_bytes_arch().
1da177e4
LT
1218 */
1219void get_random_bytes(void *buf, int nbytes)
c2557a30 1220{
392a546d
TT
1221#if DEBUG_RANDOM_BOOT > 0
1222 if (unlikely(nonblocking_pool.initialized == 0))
1223 printk(KERN_NOTICE "random: %pF get_random_bytes called "
1224 "with %d bits of entropy available\n",
1225 (void *) _RET_IP_,
1226 nonblocking_pool.entropy_total);
1227#endif
5910895f 1228 trace_get_random_bytes(nbytes, _RET_IP_);
c2557a30
TT
1229 extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1230}
1231EXPORT_SYMBOL(get_random_bytes);
1232
1233/*
1234 * This function will use the architecture-specific hardware random
1235 * number generator if it is available. The arch-specific hw RNG will
1236 * almost certainly be faster than what we can do in software, but it
1237 * is impossible to verify that it is implemented securely (as
1238 * opposed, to, say, the AES encryption of a sequence number using a
1239 * key known by the NSA). So it's useful if we need the speed, but
1240 * only if we're willing to trust the hardware manufacturer not to
1241 * have put in a back door.
1242 */
1243void get_random_bytes_arch(void *buf, int nbytes)
1da177e4 1244{
63d77173
PA
1245 char *p = buf;
1246
5910895f 1247 trace_get_random_bytes_arch(nbytes, _RET_IP_);
63d77173
PA
1248 while (nbytes) {
1249 unsigned long v;
1250 int chunk = min(nbytes, (int)sizeof(unsigned long));
c2557a30 1251
63d77173
PA
1252 if (!arch_get_random_long(&v))
1253 break;
1254
bd29e568 1255 memcpy(p, &v, chunk);
63d77173
PA
1256 p += chunk;
1257 nbytes -= chunk;
1258 }
1259
c2557a30
TT
1260 if (nbytes)
1261 extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1da177e4 1262}
c2557a30
TT
1263EXPORT_SYMBOL(get_random_bytes_arch);
1264
1da177e4
LT
1265
1266/*
1267 * init_std_data - initialize pool with system data
1268 *
1269 * @r: pool to initialize
1270 *
1271 * This function clears the pool's entropy count and mixes some system
1272 * data into the pool to prepare it for use. The pool is not cleared
1273 * as that can only decrease the entropy in the pool.
1274 */
1275static void init_std_data(struct entropy_store *r)
1276{
3e88bdff 1277 int i;
902c098a
TT
1278 ktime_t now = ktime_get_real();
1279 unsigned long rv;
1da177e4 1280
f5c2742c 1281 r->last_pulled = jiffies;
85608f8e 1282 mix_pool_bytes(r, &now, sizeof(now));
9ed17b70 1283 for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
83664a69
PA
1284 if (!arch_get_random_seed_long(&rv) &&
1285 !arch_get_random_long(&rv))
ae9ecd92 1286 rv = random_get_entropy();
85608f8e 1287 mix_pool_bytes(r, &rv, sizeof(rv));
3e88bdff 1288 }
85608f8e 1289 mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1da177e4
LT
1290}
1291
cbc96b75
TL
1292/*
1293 * Note that setup_arch() may call add_device_randomness()
1294 * long before we get here. This allows seeding of the pools
1295 * with some platform dependent data very early in the boot
1296 * process. But it limits our options here. We must use
1297 * statically allocated structures that already have all
1298 * initializations complete at compile time. We should also
1299 * take care not to overwrite the precious per platform data
1300 * we were given.
1301 */
53c3f63e 1302static int rand_initialize(void)
1da177e4
LT
1303{
1304 init_std_data(&input_pool);
1305 init_std_data(&blocking_pool);
1306 init_std_data(&nonblocking_pool);
1307 return 0;
1308}
ae9ecd92 1309early_initcall(rand_initialize);
1da177e4 1310
9361401e 1311#ifdef CONFIG_BLOCK
1da177e4
LT
1312void rand_initialize_disk(struct gendisk *disk)
1313{
1314 struct timer_rand_state *state;
1315
1316 /*
f8595815 1317 * If kzalloc returns null, we just won't use that entropy
1da177e4
LT
1318 * source.
1319 */
f8595815 1320 state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
644008df
TT
1321 if (state) {
1322 state->last_time = INITIAL_JIFFIES;
1da177e4 1323 disk->random = state;
644008df 1324 }
1da177e4 1325}
9361401e 1326#endif
1da177e4 1327
331c6490
PA
1328/*
1329 * Attempt an emergency refill using arch_get_random_seed_long().
1330 *
1331 * As with add_interrupt_randomness() be paranoid and only
1332 * credit the output as 50% entropic.
1333 */
1334static int arch_random_refill(void)
1335{
1336 const unsigned int nlongs = 64; /* Arbitrary number */
1337 unsigned int n = 0;
1338 unsigned int i;
1339 unsigned long buf[nlongs];
1340
7b878d4b
PA
1341 if (!arch_has_random_seed())
1342 return 0;
1343
331c6490
PA
1344 for (i = 0; i < nlongs; i++) {
1345 if (arch_get_random_seed_long(&buf[n]))
1346 n++;
1347 }
1348
1349 if (n) {
1350 unsigned int rand_bytes = n * sizeof(unsigned long);
1351
85608f8e 1352 mix_pool_bytes(&input_pool, buf, rand_bytes);
331c6490
PA
1353 credit_entropy_bits(&input_pool, rand_bytes*4);
1354 }
1355
1356 return n;
1357}
1358
1da177e4 1359static ssize_t
90b75ee5 1360random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4 1361{
12ff3a51 1362 ssize_t n;
1da177e4
LT
1363
1364 if (nbytes == 0)
1365 return 0;
1366
12ff3a51
GP
1367 nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1368 while (1) {
1369 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1370 if (n < 0)
1371 return n;
f80bbd8b
TT
1372 trace_random_read(n*8, (nbytes-n)*8,
1373 ENTROPY_BITS(&blocking_pool),
1374 ENTROPY_BITS(&input_pool));
12ff3a51
GP
1375 if (n > 0)
1376 return n;
331c6490 1377
12ff3a51
GP
1378 /* Pool is (near) empty. Maybe wait and retry. */
1379
331c6490
PA
1380 /* First try an emergency refill */
1381 if (arch_random_refill())
1382 continue;
1383
12ff3a51
GP
1384 if (file->f_flags & O_NONBLOCK)
1385 return -EAGAIN;
1386
1387 wait_event_interruptible(random_read_wait,
1388 ENTROPY_BITS(&input_pool) >=
2132a96f 1389 random_read_wakeup_bits);
12ff3a51
GP
1390 if (signal_pending(current))
1391 return -ERESTARTSYS;
1da177e4 1392 }
1da177e4
LT
1393}
1394
1395static ssize_t
90b75ee5 1396urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1da177e4 1397{
301f0595
TT
1398 int ret;
1399
1400 if (unlikely(nonblocking_pool.initialized == 0))
1401 printk_once(KERN_NOTICE "random: %s urandom read "
1402 "with %d bits of entropy available\n",
1403 current->comm, nonblocking_pool.entropy_total);
1404
1405 ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
f80bbd8b
TT
1406
1407 trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1408 ENTROPY_BITS(&input_pool));
1409 return ret;
1da177e4
LT
1410}
1411
1412static unsigned int
1413random_poll(struct file *file, poll_table * wait)
1414{
1415 unsigned int mask;
1416
1417 poll_wait(file, &random_read_wait, wait);
1418 poll_wait(file, &random_write_wait, wait);
1419 mask = 0;
2132a96f 1420 if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1da177e4 1421 mask |= POLLIN | POLLRDNORM;
2132a96f 1422 if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1da177e4
LT
1423 mask |= POLLOUT | POLLWRNORM;
1424 return mask;
1425}
1426
7f397dcd
MM
1427static int
1428write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1da177e4 1429{
1da177e4
LT
1430 size_t bytes;
1431 __u32 buf[16];
1432 const char __user *p = buffer;
1da177e4 1433
7f397dcd
MM
1434 while (count > 0) {
1435 bytes = min(count, sizeof(buf));
1436 if (copy_from_user(&buf, p, bytes))
1437 return -EFAULT;
1da177e4 1438
7f397dcd 1439 count -= bytes;
1da177e4
LT
1440 p += bytes;
1441
85608f8e 1442 mix_pool_bytes(r, buf, bytes);
91f3f1e3 1443 cond_resched();
1da177e4 1444 }
7f397dcd
MM
1445
1446 return 0;
1447}
1448
90b75ee5
MM
1449static ssize_t random_write(struct file *file, const char __user *buffer,
1450 size_t count, loff_t *ppos)
7f397dcd
MM
1451{
1452 size_t ret;
7f397dcd
MM
1453
1454 ret = write_pool(&blocking_pool, buffer, count);
1455 if (ret)
1456 return ret;
1457 ret = write_pool(&nonblocking_pool, buffer, count);
1458 if (ret)
1459 return ret;
1460
7f397dcd 1461 return (ssize_t)count;
1da177e4
LT
1462}
1463
43ae4860 1464static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1da177e4
LT
1465{
1466 int size, ent_count;
1467 int __user *p = (int __user *)arg;
1468 int retval;
1469
1470 switch (cmd) {
1471 case RNDGETENTCNT:
43ae4860 1472 /* inherently racy, no point locking */
a283b5c4
PA
1473 ent_count = ENTROPY_BITS(&input_pool);
1474 if (put_user(ent_count, p))
1da177e4
LT
1475 return -EFAULT;
1476 return 0;
1477 case RNDADDTOENTCNT:
1478 if (!capable(CAP_SYS_ADMIN))
1479 return -EPERM;
1480 if (get_user(ent_count, p))
1481 return -EFAULT;
a283b5c4 1482 credit_entropy_bits_safe(&input_pool, ent_count);
1da177e4
LT
1483 return 0;
1484 case RNDADDENTROPY:
1485 if (!capable(CAP_SYS_ADMIN))
1486 return -EPERM;
1487 if (get_user(ent_count, p++))
1488 return -EFAULT;
1489 if (ent_count < 0)
1490 return -EINVAL;
1491 if (get_user(size, p++))
1492 return -EFAULT;
7f397dcd
MM
1493 retval = write_pool(&input_pool, (const char __user *)p,
1494 size);
1da177e4
LT
1495 if (retval < 0)
1496 return retval;
a283b5c4 1497 credit_entropy_bits_safe(&input_pool, ent_count);
1da177e4
LT
1498 return 0;
1499 case RNDZAPENTCNT:
1500 case RNDCLEARPOOL:
ae9ecd92
TT
1501 /*
1502 * Clear the entropy pool counters. We no longer clear
1503 * the entropy pool, as that's silly.
1504 */
1da177e4
LT
1505 if (!capable(CAP_SYS_ADMIN))
1506 return -EPERM;
ae9ecd92
TT
1507 input_pool.entropy_count = 0;
1508 nonblocking_pool.entropy_count = 0;
1509 blocking_pool.entropy_count = 0;
1da177e4
LT
1510 return 0;
1511 default:
1512 return -EINVAL;
1513 }
1514}
1515
9a6f70bb
JD
1516static int random_fasync(int fd, struct file *filp, int on)
1517{
1518 return fasync_helper(fd, filp, on, &fasync);
1519}
1520
2b8693c0 1521const struct file_operations random_fops = {
1da177e4
LT
1522 .read = random_read,
1523 .write = random_write,
1524 .poll = random_poll,
43ae4860 1525 .unlocked_ioctl = random_ioctl,
9a6f70bb 1526 .fasync = random_fasync,
6038f373 1527 .llseek = noop_llseek,
1da177e4
LT
1528};
1529
2b8693c0 1530const struct file_operations urandom_fops = {
1da177e4
LT
1531 .read = urandom_read,
1532 .write = random_write,
43ae4860 1533 .unlocked_ioctl = random_ioctl,
9a6f70bb 1534 .fasync = random_fasync,
6038f373 1535 .llseek = noop_llseek,
1da177e4
LT
1536};
1537
1538/***************************************************************
1539 * Random UUID interface
1540 *
1541 * Used here for a Boot ID, but can be useful for other kernel
1542 * drivers.
1543 ***************************************************************/
1544
1545/*
1546 * Generate random UUID
1547 */
1548void generate_random_uuid(unsigned char uuid_out[16])
1549{
1550 get_random_bytes(uuid_out, 16);
c41b20e7 1551 /* Set UUID version to 4 --- truly random generation */
1da177e4
LT
1552 uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1553 /* Set the UUID variant to DCE */
1554 uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1555}
1da177e4
LT
1556EXPORT_SYMBOL(generate_random_uuid);
1557
1558/********************************************************************
1559 *
1560 * Sysctl interface
1561 *
1562 ********************************************************************/
1563
1564#ifdef CONFIG_SYSCTL
1565
1566#include <linux/sysctl.h>
1567
1568static int min_read_thresh = 8, min_write_thresh;
8c2aa339 1569static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1da177e4
LT
1570static int max_write_thresh = INPUT_POOL_WORDS * 32;
1571static char sysctl_bootid[16];
1572
1573/*
f22052b2 1574 * This function is used to return both the bootid UUID, and random
1da177e4
LT
1575 * UUID. The difference is in whether table->data is NULL; if it is,
1576 * then a new UUID is generated and returned to the user.
1577 *
f22052b2
GP
1578 * If the user accesses this via the proc interface, the UUID will be
1579 * returned as an ASCII string in the standard UUID format; if via the
1580 * sysctl system call, as 16 bytes of binary data.
1da177e4 1581 */
a151427e 1582static int proc_do_uuid(struct ctl_table *table, int write,
1da177e4
LT
1583 void __user *buffer, size_t *lenp, loff_t *ppos)
1584{
a151427e 1585 struct ctl_table fake_table;
1da177e4
LT
1586 unsigned char buf[64], tmp_uuid[16], *uuid;
1587
1588 uuid = table->data;
1589 if (!uuid) {
1590 uuid = tmp_uuid;
1da177e4 1591 generate_random_uuid(uuid);
44e4360f
MD
1592 } else {
1593 static DEFINE_SPINLOCK(bootid_spinlock);
1594
1595 spin_lock(&bootid_spinlock);
1596 if (!uuid[8])
1597 generate_random_uuid(uuid);
1598 spin_unlock(&bootid_spinlock);
1599 }
1da177e4 1600
35900771
JP
1601 sprintf(buf, "%pU", uuid);
1602
1da177e4
LT
1603 fake_table.data = buf;
1604 fake_table.maxlen = sizeof(buf);
1605
8d65af78 1606 return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1da177e4
LT
1607}
1608
a283b5c4
PA
1609/*
1610 * Return entropy available scaled to integral bits
1611 */
5eb10d91 1612static int proc_do_entropy(struct ctl_table *table, int write,
a283b5c4
PA
1613 void __user *buffer, size_t *lenp, loff_t *ppos)
1614{
5eb10d91 1615 struct ctl_table fake_table;
a283b5c4
PA
1616 int entropy_count;
1617
1618 entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1619
1620 fake_table.data = &entropy_count;
1621 fake_table.maxlen = sizeof(entropy_count);
1622
1623 return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1624}
1625
1da177e4 1626static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
a151427e
JP
1627extern struct ctl_table random_table[];
1628struct ctl_table random_table[] = {
1da177e4 1629 {
1da177e4
LT
1630 .procname = "poolsize",
1631 .data = &sysctl_poolsize,
1632 .maxlen = sizeof(int),
1633 .mode = 0444,
6d456111 1634 .proc_handler = proc_dointvec,
1da177e4
LT
1635 },
1636 {
1da177e4
LT
1637 .procname = "entropy_avail",
1638 .maxlen = sizeof(int),
1639 .mode = 0444,
a283b5c4 1640 .proc_handler = proc_do_entropy,
1da177e4
LT
1641 .data = &input_pool.entropy_count,
1642 },
1643 {
1da177e4 1644 .procname = "read_wakeup_threshold",
2132a96f 1645 .data = &random_read_wakeup_bits,
1da177e4
LT
1646 .maxlen = sizeof(int),
1647 .mode = 0644,
6d456111 1648 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1649 .extra1 = &min_read_thresh,
1650 .extra2 = &max_read_thresh,
1651 },
1652 {
1da177e4 1653 .procname = "write_wakeup_threshold",
2132a96f 1654 .data = &random_write_wakeup_bits,
1da177e4
LT
1655 .maxlen = sizeof(int),
1656 .mode = 0644,
6d456111 1657 .proc_handler = proc_dointvec_minmax,
1da177e4
LT
1658 .extra1 = &min_write_thresh,
1659 .extra2 = &max_write_thresh,
1660 },
f5c2742c
TT
1661 {
1662 .procname = "urandom_min_reseed_secs",
1663 .data = &random_min_urandom_seed,
1664 .maxlen = sizeof(int),
1665 .mode = 0644,
1666 .proc_handler = proc_dointvec,
1667 },
1da177e4 1668 {
1da177e4
LT
1669 .procname = "boot_id",
1670 .data = &sysctl_bootid,
1671 .maxlen = 16,
1672 .mode = 0444,
6d456111 1673 .proc_handler = proc_do_uuid,
1da177e4
LT
1674 },
1675 {
1da177e4
LT
1676 .procname = "uuid",
1677 .maxlen = 16,
1678 .mode = 0444,
6d456111 1679 .proc_handler = proc_do_uuid,
1da177e4 1680 },
43759d4f
TT
1681#ifdef ADD_INTERRUPT_BENCH
1682 {
1683 .procname = "add_interrupt_avg_cycles",
1684 .data = &avg_cycles,
1685 .maxlen = sizeof(avg_cycles),
1686 .mode = 0444,
1687 .proc_handler = proc_doulongvec_minmax,
1688 },
1689 {
1690 .procname = "add_interrupt_avg_deviation",
1691 .data = &avg_deviation,
1692 .maxlen = sizeof(avg_deviation),
1693 .mode = 0444,
1694 .proc_handler = proc_doulongvec_minmax,
1695 },
1696#endif
894d2491 1697 { }
1da177e4
LT
1698};
1699#endif /* CONFIG_SYSCTL */
1700
6e5714ea 1701static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1da177e4 1702
47d06e53 1703int random_int_secret_init(void)
1da177e4 1704{
6e5714ea 1705 get_random_bytes(random_int_secret, sizeof(random_int_secret));
1da177e4
LT
1706 return 0;
1707}
1da177e4
LT
1708
1709/*
1710 * Get a random word for internal kernel use only. Similar to urandom but
1711 * with the goal of minimal entropy pool depletion. As a result, the random
1712 * value is not cryptographically secure but for several uses the cost of
1713 * depleting entropy is too high
1714 */
74feec5d 1715static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1da177e4
LT
1716unsigned int get_random_int(void)
1717{
63d77173 1718 __u32 *hash;
6e5714ea 1719 unsigned int ret;
8a0a9bd4 1720
63d77173
PA
1721 if (arch_get_random_int(&ret))
1722 return ret;
1723
1724 hash = get_cpu_var(get_random_int_hash);
8a0a9bd4 1725
61875f30 1726 hash[0] += current->pid + jiffies + random_get_entropy();
6e5714ea
DM
1727 md5_transform(hash, random_int_secret);
1728 ret = hash[0];
8a0a9bd4
LT
1729 put_cpu_var(get_random_int_hash);
1730
1731 return ret;
1da177e4 1732}
16c7fa05 1733EXPORT_SYMBOL(get_random_int);
1da177e4
LT
1734
1735/*
1736 * randomize_range() returns a start address such that
1737 *
1738 * [...... <range> .....]
1739 * start end
1740 *
1741 * a <range> with size "len" starting at the return value is inside in the
1742 * area defined by [start, end], but is otherwise randomized.
1743 */
1744unsigned long
1745randomize_range(unsigned long start, unsigned long end, unsigned long len)
1746{
1747 unsigned long range = end - len - start;
1748
1749 if (end <= start + len)
1750 return 0;
1751 return PAGE_ALIGN(get_random_int() % range + start);
1752}