xref: /linux/drivers/char/random.c (revision bfd5bb6f90af092aa345b15cd78143956a13c2a8)
1 /*
2  * random.c -- A strong random number generator
3  *
4  * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All
5  * Rights Reserved.
6  *
7  * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
8  *
9  * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
10  * rights reserved.
11  *
12  * Redistribution and use in source and binary forms, with or without
13  * modification, are permitted provided that the following conditions
14  * are met:
15  * 1. Redistributions of source code must retain the above copyright
16  *    notice, and the entire permission notice in its entirety,
17  *    including the disclaimer of warranties.
18  * 2. Redistributions in binary form must reproduce the above copyright
19  *    notice, this list of conditions and the following disclaimer in the
20  *    documentation and/or other materials provided with the distribution.
21  * 3. The name of the author may not be used to endorse or promote
22  *    products derived from this software without specific prior
23  *    written permission.
24  *
25  * ALTERNATIVELY, this product may be distributed under the terms of
26  * the GNU General Public License, in which case the provisions of the GPL are
27  * required INSTEAD OF the above restrictions.  (This clause is
28  * necessary due to a potential bad interaction between the GPL and
29  * the restrictions contained in a BSD-style copyright.)
30  *
31  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
32  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
33  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
34  * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
35  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
36  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
37  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
38  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
39  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
41  * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
42  * DAMAGE.
43  */
44 
45 /*
46  * (now, with legal B.S. out of the way.....)
47  *
48  * This routine gathers environmental noise from device drivers, etc.,
49  * and returns good random numbers, suitable for cryptographic use.
50  * Besides the obvious cryptographic uses, these numbers are also good
51  * for seeding TCP sequence numbers, and other places where it is
52  * desirable to have numbers which are not only random, but hard to
53  * predict by an attacker.
54  *
55  * Theory of operation
56  * ===================
57  *
58  * Computers are very predictable devices.  Hence it is extremely hard
59  * to produce truly random numbers on a computer --- as opposed to
60  * pseudo-random numbers, which can easily generated by using a
61  * algorithm.  Unfortunately, it is very easy for attackers to guess
62  * the sequence of pseudo-random number generators, and for some
63  * applications this is not acceptable.  So instead, we must try to
64  * gather "environmental noise" from the computer's environment, which
65  * must be hard for outside attackers to observe, and use that to
66  * generate random numbers.  In a Unix environment, this is best done
67  * from inside the kernel.
68  *
69  * Sources of randomness from the environment include inter-keyboard
70  * timings, inter-interrupt timings from some interrupts, and other
71  * events which are both (a) non-deterministic and (b) hard for an
72  * outside observer to measure.  Randomness from these sources are
73  * added to an "entropy pool", which is mixed using a CRC-like function.
74  * This is not cryptographically strong, but it is adequate assuming
75  * the randomness is not chosen maliciously, and it is fast enough that
76  * the overhead of doing it on every interrupt is very reasonable.
77  * As random bytes are mixed into the entropy pool, the routines keep
78  * an *estimate* of how many bits of randomness have been stored into
79  * the random number generator's internal state.
80  *
81  * When random bytes are desired, they are obtained by taking the SHA
82  * hash of the contents of the "entropy pool".  The SHA hash avoids
83  * exposing the internal state of the entropy pool.  It is believed to
84  * be computationally infeasible to derive any useful information
85  * about the input of SHA from its output.  Even if it is possible to
86  * analyze SHA in some clever way, as long as the amount of data
87  * returned from the generator is less than the inherent entropy in
88  * the pool, the output data is totally unpredictable.  For this
89  * reason, the routine decreases its internal estimate of how many
90  * bits of "true randomness" are contained in the entropy pool as it
91  * outputs random numbers.
92  *
93  * If this estimate goes to zero, the routine can still generate
94  * random numbers; however, an attacker may (at least in theory) be
95  * able to infer the future output of the generator from prior
96  * outputs.  This requires successful cryptanalysis of SHA, which is
97  * not believed to be feasible, but there is a remote possibility.
98  * Nonetheless, these numbers should be useful for the vast majority
99  * of purposes.
100  *
101  * Exported interfaces ---- output
102  * ===============================
103  *
104  * There are three exported interfaces; the first is one designed to
105  * be used from within the kernel:
106  *
107  * 	void get_random_bytes(void *buf, int nbytes);
108  *
109  * This interface will return the requested number of random bytes,
110  * and place it in the requested buffer.
111  *
112  * The two other interfaces are two character devices /dev/random and
113  * /dev/urandom.  /dev/random is suitable for use when very high
114  * quality randomness is desired (for example, for key generation or
115  * one-time pads), as it will only return a maximum of the number of
116  * bits of randomness (as estimated by the random number generator)
117  * contained in the entropy pool.
118  *
119  * The /dev/urandom device does not have this limit, and will return
120  * as many bytes as are requested.  As more and more random bytes are
121  * requested without giving time for the entropy pool to recharge,
122  * this will result in random numbers that are merely cryptographically
123  * strong.  For many applications, however, this is acceptable.
124  *
125  * Exported interfaces ---- input
126  * ==============================
127  *
128  * The current exported interfaces for gathering environmental noise
129  * from the devices are:
130  *
131  *	void add_device_randomness(const void *buf, unsigned int size);
132  * 	void add_input_randomness(unsigned int type, unsigned int code,
133  *                                unsigned int value);
134  *	void add_interrupt_randomness(int irq, int irq_flags);
135  * 	void add_disk_randomness(struct gendisk *disk);
136  *
137  * add_device_randomness() is for adding data to the random pool that
138  * is likely to differ between two devices (or possibly even per boot).
139  * This would be things like MAC addresses or serial numbers, or the
140  * read-out of the RTC. This does *not* add any actual entropy to the
141  * pool, but it initializes the pool to different values for devices
142  * that might otherwise be identical and have very little entropy
143  * available to them (particularly common in the embedded world).
144  *
145  * add_input_randomness() uses the input layer interrupt timing, as well as
146  * the event type information from the hardware.
147  *
148  * add_interrupt_randomness() uses the interrupt timing as random
149  * inputs to the entropy pool. Using the cycle counters and the irq source
150  * as inputs, it feeds the randomness roughly once a second.
151  *
152  * add_disk_randomness() uses what amounts to the seek time of block
153  * layer request events, on a per-disk_devt basis, as input to the
154  * entropy pool. Note that high-speed solid state drives with very low
155  * seek times do not make for good sources of entropy, as their seek
156  * times are usually fairly consistent.
157  *
158  * All of these routines try to estimate how many bits of randomness a
159  * particular randomness source.  They do this by keeping track of the
160  * first and second order deltas of the event timings.
161  *
162  * Ensuring unpredictability at system startup
163  * ============================================
164  *
165  * When any operating system starts up, it will go through a sequence
166  * of actions that are fairly predictable by an adversary, especially
167  * if the start-up does not involve interaction with a human operator.
168  * This reduces the actual number of bits of unpredictability in the
169  * entropy pool below the value in entropy_count.  In order to
170  * counteract this effect, it helps to carry information in the
171  * entropy pool across shut-downs and start-ups.  To do this, put the
172  * following lines an appropriate script which is run during the boot
173  * sequence:
174  *
175  *	echo "Initializing random number generator..."
176  *	random_seed=/var/run/random-seed
177  *	# Carry a random seed from start-up to start-up
178  *	# Load and then save the whole entropy pool
179  *	if [ -f $random_seed ]; then
180  *		cat $random_seed >/dev/urandom
181  *	else
182  *		touch $random_seed
183  *	fi
184  *	chmod 600 $random_seed
185  *	dd if=/dev/urandom of=$random_seed count=1 bs=512
186  *
187  * and the following lines in an appropriate script which is run as
188  * the system is shutdown:
189  *
190  *	# Carry a random seed from shut-down to start-up
191  *	# Save the whole entropy pool
192  *	echo "Saving random seed..."
193  *	random_seed=/var/run/random-seed
194  *	touch $random_seed
195  *	chmod 600 $random_seed
196  *	dd if=/dev/urandom of=$random_seed count=1 bs=512
197  *
198  * For example, on most modern systems using the System V init
199  * scripts, such code fragments would be found in
200  * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
201  * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
202  *
203  * Effectively, these commands cause the contents of the entropy pool
204  * to be saved at shut-down time and reloaded into the entropy pool at
205  * start-up.  (The 'dd' in the addition to the bootup script is to
206  * make sure that /etc/random-seed is different for every start-up,
207  * even if the system crashes without executing rc.0.)  Even with
208  * complete knowledge of the start-up activities, predicting the state
209  * of the entropy pool requires knowledge of the previous history of
210  * the system.
211  *
212  * Configuring the /dev/random driver under Linux
213  * ==============================================
214  *
215  * The /dev/random driver under Linux uses minor numbers 8 and 9 of
216  * the /dev/mem major number (#1).  So if your system does not have
217  * /dev/random and /dev/urandom created already, they can be created
218  * by using the commands:
219  *
220  * 	mknod /dev/random c 1 8
221  * 	mknod /dev/urandom c 1 9
222  *
223  * Acknowledgements:
224  * =================
225  *
226  * Ideas for constructing this random number generator were derived
227  * from Pretty Good Privacy's random number generator, and from private
228  * discussions with Phil Karn.  Colin Plumb provided a faster random
229  * number generator, which speed up the mixing function of the entropy
230  * pool, taken from PGPfone.  Dale Worley has also contributed many
231  * useful ideas and suggestions to improve this driver.
232  *
233  * Any flaws in the design are solely my responsibility, and should
234  * not be attributed to the Phil, Colin, or any of authors of PGP.
235  *
236  * Further background information on this topic may be obtained from
237  * RFC 1750, "Randomness Recommendations for Security", by Donald
238  * Eastlake, Steve Crocker, and Jeff Schiller.
239  */
240 
241 #include <linux/utsname.h>
242 #include <linux/module.h>
243 #include <linux/kernel.h>
244 #include <linux/major.h>
245 #include <linux/string.h>
246 #include <linux/fcntl.h>
247 #include <linux/slab.h>
248 #include <linux/random.h>
249 #include <linux/poll.h>
250 #include <linux/init.h>
251 #include <linux/fs.h>
252 #include <linux/genhd.h>
253 #include <linux/interrupt.h>
254 #include <linux/mm.h>
255 #include <linux/nodemask.h>
256 #include <linux/spinlock.h>
257 #include <linux/kthread.h>
258 #include <linux/percpu.h>
259 #include <linux/cryptohash.h>
260 #include <linux/fips.h>
261 #include <linux/ptrace.h>
262 #include <linux/workqueue.h>
263 #include <linux/irq.h>
264 #include <linux/ratelimit.h>
265 #include <linux/syscalls.h>
266 #include <linux/completion.h>
267 #include <linux/uuid.h>
268 #include <crypto/chacha20.h>
269 
270 #include <asm/processor.h>
271 #include <linux/uaccess.h>
272 #include <asm/irq.h>
273 #include <asm/irq_regs.h>
274 #include <asm/io.h>
275 
276 #define CREATE_TRACE_POINTS
277 #include <trace/events/random.h>
278 
279 /* #define ADD_INTERRUPT_BENCH */
280 
281 /*
282  * Configuration information
283  */
284 #define INPUT_POOL_SHIFT	12
285 #define INPUT_POOL_WORDS	(1 << (INPUT_POOL_SHIFT-5))
286 #define OUTPUT_POOL_SHIFT	10
287 #define OUTPUT_POOL_WORDS	(1 << (OUTPUT_POOL_SHIFT-5))
288 #define SEC_XFER_SIZE		512
289 #define EXTRACT_SIZE		10
290 
291 
292 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
293 
294 /*
295  * To allow fractional bits to be tracked, the entropy_count field is
296  * denominated in units of 1/8th bits.
297  *
298  * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
299  * credit_entropy_bits() needs to be 64 bits wide.
300  */
301 #define ENTROPY_SHIFT 3
302 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
303 
304 /*
305  * The minimum number of bits of entropy before we wake up a read on
306  * /dev/random.  Should be enough to do a significant reseed.
307  */
308 static int random_read_wakeup_bits = 64;
309 
310 /*
311  * If the entropy count falls under this number of bits, then we
312  * should wake up processes which are selecting or polling on write
313  * access to /dev/random.
314  */
315 static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
316 
317 /*
318  * Originally, we used a primitive polynomial of degree .poolwords
319  * over GF(2).  The taps for various sizes are defined below.  They
320  * were chosen to be evenly spaced except for the last tap, which is 1
321  * to get the twisting happening as fast as possible.
322  *
323  * For the purposes of better mixing, we use the CRC-32 polynomial as
324  * well to make a (modified) twisted Generalized Feedback Shift
325  * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
326  * generators.  ACM Transactions on Modeling and Computer Simulation
327  * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
328  * GFSR generators II.  ACM Transactions on Modeling and Computer
329  * Simulation 4:254-266)
330  *
331  * Thanks to Colin Plumb for suggesting this.
332  *
333  * The mixing operation is much less sensitive than the output hash,
334  * where we use SHA-1.  All that we want of mixing operation is that
335  * it be a good non-cryptographic hash; i.e. it not produce collisions
336  * when fed "random" data of the sort we expect to see.  As long as
337  * the pool state differs for different inputs, we have preserved the
338  * input entropy and done a good job.  The fact that an intelligent
339  * attacker can construct inputs that will produce controlled
340  * alterations to the pool's state is not important because we don't
341  * consider such inputs to contribute any randomness.  The only
342  * property we need with respect to them is that the attacker can't
343  * increase his/her knowledge of the pool's state.  Since all
344  * additions are reversible (knowing the final state and the input,
345  * you can reconstruct the initial state), if an attacker has any
346  * uncertainty about the initial state, he/she can only shuffle that
347  * uncertainty about, but never cause any collisions (which would
348  * decrease the uncertainty).
349  *
350  * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
351  * Videau in their paper, "The Linux Pseudorandom Number Generator
352  * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
353  * paper, they point out that we are not using a true Twisted GFSR,
354  * since Matsumoto & Kurita used a trinomial feedback polynomial (that
355  * is, with only three taps, instead of the six that we are using).
356  * As a result, the resulting polynomial is neither primitive nor
357  * irreducible, and hence does not have a maximal period over
358  * GF(2**32).  They suggest a slight change to the generator
359  * polynomial which improves the resulting TGFSR polynomial to be
360  * irreducible, which we have made here.
361  */
362 static struct poolinfo {
363 	int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
364 #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
365 	int tap1, tap2, tap3, tap4, tap5;
366 } poolinfo_table[] = {
367 	/* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
368 	/* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
369 	{ S(128),	104,	76,	51,	25,	1 },
370 	/* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
371 	/* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
372 	{ S(32),	26,	19,	14,	7,	1 },
373 #if 0
374 	/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
375 	{ S(2048),	1638,	1231,	819,	411,	1 },
376 
377 	/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
378 	{ S(1024),	817,	615,	412,	204,	1 },
379 
380 	/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
381 	{ S(1024),	819,	616,	410,	207,	2 },
382 
383 	/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
384 	{ S(512),	411,	308,	208,	104,	1 },
385 
386 	/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
387 	{ S(512),	409,	307,	206,	102,	2 },
388 	/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
389 	{ S(512),	409,	309,	205,	103,	2 },
390 
391 	/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
392 	{ S(256),	205,	155,	101,	52,	1 },
393 
394 	/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
395 	{ S(128),	103,	78,	51,	27,	2 },
396 
397 	/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
398 	{ S(64),	52,	39,	26,	14,	1 },
399 #endif
400 };
401 
402 /*
403  * Static global variables
404  */
405 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
406 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
407 static struct fasync_struct *fasync;
408 
409 static DEFINE_SPINLOCK(random_ready_list_lock);
410 static LIST_HEAD(random_ready_list);
411 
412 struct crng_state {
413 	__u32		state[16];
414 	unsigned long	init_time;
415 	spinlock_t	lock;
416 };
417 
418 struct crng_state primary_crng = {
419 	.lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
420 };
421 
422 /*
423  * crng_init =  0 --> Uninitialized
424  *		1 --> Initialized
425  *		2 --> Initialized from input_pool
426  *
427  * crng_init is protected by primary_crng->lock, and only increases
428  * its value (from 0->1->2).
429  */
430 static int crng_init = 0;
431 #define crng_ready() (likely(crng_init > 1))
432 static int crng_init_cnt = 0;
433 static unsigned long crng_global_init_time = 0;
434 #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
435 static void _extract_crng(struct crng_state *crng,
436 			  __u32 out[CHACHA20_BLOCK_WORDS]);
437 static void _crng_backtrack_protect(struct crng_state *crng,
438 				    __u32 tmp[CHACHA20_BLOCK_WORDS], int used);
439 static void process_random_ready_list(void);
440 static void _get_random_bytes(void *buf, int nbytes);
441 
442 static struct ratelimit_state unseeded_warning =
443 	RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
444 static struct ratelimit_state urandom_warning =
445 	RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
446 
447 static int ratelimit_disable __read_mostly;
448 
449 module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
450 MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
451 
452 /**********************************************************************
453  *
454  * OS independent entropy store.   Here are the functions which handle
455  * storing entropy in an entropy pool.
456  *
457  **********************************************************************/
458 
459 struct entropy_store;
460 struct entropy_store {
461 	/* read-only data: */
462 	const struct poolinfo *poolinfo;
463 	__u32 *pool;
464 	const char *name;
465 	struct entropy_store *pull;
466 	struct work_struct push_work;
467 
468 	/* read-write data: */
469 	unsigned long last_pulled;
470 	spinlock_t lock;
471 	unsigned short add_ptr;
472 	unsigned short input_rotate;
473 	int entropy_count;
474 	int entropy_total;
475 	unsigned int initialized:1;
476 	unsigned int last_data_init:1;
477 	__u8 last_data[EXTRACT_SIZE];
478 };
479 
480 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
481 			       size_t nbytes, int min, int rsvd);
482 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
483 				size_t nbytes, int fips);
484 
485 static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
486 static void push_to_pool(struct work_struct *work);
487 static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
488 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
489 
490 static struct entropy_store input_pool = {
491 	.poolinfo = &poolinfo_table[0],
492 	.name = "input",
493 	.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
494 	.pool = input_pool_data
495 };
496 
497 static struct entropy_store blocking_pool = {
498 	.poolinfo = &poolinfo_table[1],
499 	.name = "blocking",
500 	.pull = &input_pool,
501 	.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
502 	.pool = blocking_pool_data,
503 	.push_work = __WORK_INITIALIZER(blocking_pool.push_work,
504 					push_to_pool),
505 };
506 
507 static __u32 const twist_table[8] = {
508 	0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
509 	0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
510 
511 /*
512  * This function adds bytes into the entropy "pool".  It does not
513  * update the entropy estimate.  The caller should call
514  * credit_entropy_bits if this is appropriate.
515  *
516  * The pool is stirred with a primitive polynomial of the appropriate
517  * degree, and then twisted.  We twist by three bits at a time because
518  * it's cheap to do so and helps slightly in the expected case where
519  * the entropy is concentrated in the low-order bits.
520  */
521 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
522 			    int nbytes)
523 {
524 	unsigned long i, tap1, tap2, tap3, tap4, tap5;
525 	int input_rotate;
526 	int wordmask = r->poolinfo->poolwords - 1;
527 	const char *bytes = in;
528 	__u32 w;
529 
530 	tap1 = r->poolinfo->tap1;
531 	tap2 = r->poolinfo->tap2;
532 	tap3 = r->poolinfo->tap3;
533 	tap4 = r->poolinfo->tap4;
534 	tap5 = r->poolinfo->tap5;
535 
536 	input_rotate = r->input_rotate;
537 	i = r->add_ptr;
538 
539 	/* mix one byte at a time to simplify size handling and churn faster */
540 	while (nbytes--) {
541 		w = rol32(*bytes++, input_rotate);
542 		i = (i - 1) & wordmask;
543 
544 		/* XOR in the various taps */
545 		w ^= r->pool[i];
546 		w ^= r->pool[(i + tap1) & wordmask];
547 		w ^= r->pool[(i + tap2) & wordmask];
548 		w ^= r->pool[(i + tap3) & wordmask];
549 		w ^= r->pool[(i + tap4) & wordmask];
550 		w ^= r->pool[(i + tap5) & wordmask];
551 
552 		/* Mix the result back in with a twist */
553 		r->pool[i] = (w >> 3) ^ twist_table[w & 7];
554 
555 		/*
556 		 * Normally, we add 7 bits of rotation to the pool.
557 		 * At the beginning of the pool, add an extra 7 bits
558 		 * rotation, so that successive passes spread the
559 		 * input bits across the pool evenly.
560 		 */
561 		input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
562 	}
563 
564 	r->input_rotate = input_rotate;
565 	r->add_ptr = i;
566 }
567 
568 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
569 			     int nbytes)
570 {
571 	trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
572 	_mix_pool_bytes(r, in, nbytes);
573 }
574 
575 static void mix_pool_bytes(struct entropy_store *r, const void *in,
576 			   int nbytes)
577 {
578 	unsigned long flags;
579 
580 	trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
581 	spin_lock_irqsave(&r->lock, flags);
582 	_mix_pool_bytes(r, in, nbytes);
583 	spin_unlock_irqrestore(&r->lock, flags);
584 }
585 
586 struct fast_pool {
587 	__u32		pool[4];
588 	unsigned long	last;
589 	unsigned short	reg_idx;
590 	unsigned char	count;
591 };
592 
593 /*
594  * This is a fast mixing routine used by the interrupt randomness
595  * collector.  It's hardcoded for an 128 bit pool and assumes that any
596  * locks that might be needed are taken by the caller.
597  */
598 static void fast_mix(struct fast_pool *f)
599 {
600 	__u32 a = f->pool[0],	b = f->pool[1];
601 	__u32 c = f->pool[2],	d = f->pool[3];
602 
603 	a += b;			c += d;
604 	b = rol32(b, 6);	d = rol32(d, 27);
605 	d ^= a;			b ^= c;
606 
607 	a += b;			c += d;
608 	b = rol32(b, 16);	d = rol32(d, 14);
609 	d ^= a;			b ^= c;
610 
611 	a += b;			c += d;
612 	b = rol32(b, 6);	d = rol32(d, 27);
613 	d ^= a;			b ^= c;
614 
615 	a += b;			c += d;
616 	b = rol32(b, 16);	d = rol32(d, 14);
617 	d ^= a;			b ^= c;
618 
619 	f->pool[0] = a;  f->pool[1] = b;
620 	f->pool[2] = c;  f->pool[3] = d;
621 	f->count++;
622 }
623 
624 static void process_random_ready_list(void)
625 {
626 	unsigned long flags;
627 	struct random_ready_callback *rdy, *tmp;
628 
629 	spin_lock_irqsave(&random_ready_list_lock, flags);
630 	list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
631 		struct module *owner = rdy->owner;
632 
633 		list_del_init(&rdy->list);
634 		rdy->func(rdy);
635 		module_put(owner);
636 	}
637 	spin_unlock_irqrestore(&random_ready_list_lock, flags);
638 }
639 
640 /*
641  * Credit (or debit) the entropy store with n bits of entropy.
642  * Use credit_entropy_bits_safe() if the value comes from userspace
643  * or otherwise should be checked for extreme values.
644  */
645 static void credit_entropy_bits(struct entropy_store *r, int nbits)
646 {
647 	int entropy_count, orig;
648 	const int pool_size = r->poolinfo->poolfracbits;
649 	int nfrac = nbits << ENTROPY_SHIFT;
650 
651 	if (!nbits)
652 		return;
653 
654 retry:
655 	entropy_count = orig = READ_ONCE(r->entropy_count);
656 	if (nfrac < 0) {
657 		/* Debit */
658 		entropy_count += nfrac;
659 	} else {
660 		/*
661 		 * Credit: we have to account for the possibility of
662 		 * overwriting already present entropy.	 Even in the
663 		 * ideal case of pure Shannon entropy, new contributions
664 		 * approach the full value asymptotically:
665 		 *
666 		 * entropy <- entropy + (pool_size - entropy) *
667 		 *	(1 - exp(-add_entropy/pool_size))
668 		 *
669 		 * For add_entropy <= pool_size/2 then
670 		 * (1 - exp(-add_entropy/pool_size)) >=
671 		 *    (add_entropy/pool_size)*0.7869...
672 		 * so we can approximate the exponential with
673 		 * 3/4*add_entropy/pool_size and still be on the
674 		 * safe side by adding at most pool_size/2 at a time.
675 		 *
676 		 * The use of pool_size-2 in the while statement is to
677 		 * prevent rounding artifacts from making the loop
678 		 * arbitrarily long; this limits the loop to log2(pool_size)*2
679 		 * turns no matter how large nbits is.
680 		 */
681 		int pnfrac = nfrac;
682 		const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
683 		/* The +2 corresponds to the /4 in the denominator */
684 
685 		do {
686 			unsigned int anfrac = min(pnfrac, pool_size/2);
687 			unsigned int add =
688 				((pool_size - entropy_count)*anfrac*3) >> s;
689 
690 			entropy_count += add;
691 			pnfrac -= anfrac;
692 		} while (unlikely(entropy_count < pool_size-2 && pnfrac));
693 	}
694 
695 	if (unlikely(entropy_count < 0)) {
696 		pr_warn("random: negative entropy/overflow: pool %s count %d\n",
697 			r->name, entropy_count);
698 		WARN_ON(1);
699 		entropy_count = 0;
700 	} else if (entropy_count > pool_size)
701 		entropy_count = pool_size;
702 	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
703 		goto retry;
704 
705 	r->entropy_total += nbits;
706 	if (!r->initialized && r->entropy_total > 128) {
707 		r->initialized = 1;
708 		r->entropy_total = 0;
709 	}
710 
711 	trace_credit_entropy_bits(r->name, nbits,
712 				  entropy_count >> ENTROPY_SHIFT,
713 				  r->entropy_total, _RET_IP_);
714 
715 	if (r == &input_pool) {
716 		int entropy_bits = entropy_count >> ENTROPY_SHIFT;
717 
718 		if (crng_init < 2 && entropy_bits >= 128) {
719 			crng_reseed(&primary_crng, r);
720 			entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
721 		}
722 
723 		/* should we wake readers? */
724 		if (entropy_bits >= random_read_wakeup_bits &&
725 		    wq_has_sleeper(&random_read_wait)) {
726 			wake_up_interruptible(&random_read_wait);
727 			kill_fasync(&fasync, SIGIO, POLL_IN);
728 		}
729 		/* If the input pool is getting full, send some
730 		 * entropy to the blocking pool until it is 75% full.
731 		 */
732 		if (entropy_bits > random_write_wakeup_bits &&
733 		    r->initialized &&
734 		    r->entropy_total >= 2*random_read_wakeup_bits) {
735 			struct entropy_store *other = &blocking_pool;
736 
737 			if (other->entropy_count <=
738 			    3 * other->poolinfo->poolfracbits / 4) {
739 				schedule_work(&other->push_work);
740 				r->entropy_total = 0;
741 			}
742 		}
743 	}
744 }
745 
746 static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
747 {
748 	const int nbits_max = r->poolinfo->poolwords * 32;
749 
750 	if (nbits < 0)
751 		return -EINVAL;
752 
753 	/* Cap the value to avoid overflows */
754 	nbits = min(nbits,  nbits_max);
755 
756 	credit_entropy_bits(r, nbits);
757 	return 0;
758 }
759 
760 /*********************************************************************
761  *
762  * CRNG using CHACHA20
763  *
764  *********************************************************************/
765 
766 #define CRNG_RESEED_INTERVAL (300*HZ)
767 
768 static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
769 
770 #ifdef CONFIG_NUMA
771 /*
772  * Hack to deal with crazy userspace progams when they are all trying
773  * to access /dev/urandom in parallel.  The programs are almost
774  * certainly doing something terribly wrong, but we'll work around
775  * their brain damage.
776  */
777 static struct crng_state **crng_node_pool __read_mostly;
778 #endif
779 
780 static void invalidate_batched_entropy(void);
781 
782 static void crng_initialize(struct crng_state *crng)
783 {
784 	int		i;
785 	unsigned long	rv;
786 
787 	memcpy(&crng->state[0], "expand 32-byte k", 16);
788 	if (crng == &primary_crng)
789 		_extract_entropy(&input_pool, &crng->state[4],
790 				 sizeof(__u32) * 12, 0);
791 	else
792 		_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
793 	for (i = 4; i < 16; i++) {
794 		if (!arch_get_random_seed_long(&rv) &&
795 		    !arch_get_random_long(&rv))
796 			rv = random_get_entropy();
797 		crng->state[i] ^= rv;
798 	}
799 	crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
800 }
801 
802 #ifdef CONFIG_NUMA
803 static void do_numa_crng_init(struct work_struct *work)
804 {
805 	int i;
806 	struct crng_state *crng;
807 	struct crng_state **pool;
808 
809 	pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
810 	for_each_online_node(i) {
811 		crng = kmalloc_node(sizeof(struct crng_state),
812 				    GFP_KERNEL | __GFP_NOFAIL, i);
813 		spin_lock_init(&crng->lock);
814 		crng_initialize(crng);
815 		pool[i] = crng;
816 	}
817 	mb();
818 	if (cmpxchg(&crng_node_pool, NULL, pool)) {
819 		for_each_node(i)
820 			kfree(pool[i]);
821 		kfree(pool);
822 	}
823 }
824 
825 static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
826 
827 static void numa_crng_init(void)
828 {
829 	schedule_work(&numa_crng_init_work);
830 }
831 #else
832 static void numa_crng_init(void) {}
833 #endif
834 
835 /*
836  * crng_fast_load() can be called by code in the interrupt service
837  * path.  So we can't afford to dilly-dally.
838  */
839 static int crng_fast_load(const char *cp, size_t len)
840 {
841 	unsigned long flags;
842 	char *p;
843 
844 	if (!spin_trylock_irqsave(&primary_crng.lock, flags))
845 		return 0;
846 	if (crng_init != 0) {
847 		spin_unlock_irqrestore(&primary_crng.lock, flags);
848 		return 0;
849 	}
850 	p = (unsigned char *) &primary_crng.state[4];
851 	while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
852 		p[crng_init_cnt % CHACHA20_KEY_SIZE] ^= *cp;
853 		cp++; crng_init_cnt++; len--;
854 	}
855 	spin_unlock_irqrestore(&primary_crng.lock, flags);
856 	if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
857 		invalidate_batched_entropy();
858 		crng_init = 1;
859 		wake_up_interruptible(&crng_init_wait);
860 		pr_notice("random: fast init done\n");
861 	}
862 	return 1;
863 }
864 
865 /*
866  * crng_slow_load() is called by add_device_randomness, which has two
867  * attributes.  (1) We can't trust the buffer passed to it is
868  * guaranteed to be unpredictable (so it might not have any entropy at
869  * all), and (2) it doesn't have the performance constraints of
870  * crng_fast_load().
871  *
872  * So we do something more comprehensive which is guaranteed to touch
873  * all of the primary_crng's state, and which uses a LFSR with a
874  * period of 255 as part of the mixing algorithm.  Finally, we do
875  * *not* advance crng_init_cnt since buffer we may get may be something
876  * like a fixed DMI table (for example), which might very well be
877  * unique to the machine, but is otherwise unvarying.
878  */
879 static int crng_slow_load(const char *cp, size_t len)
880 {
881 	unsigned long		flags;
882 	static unsigned char	lfsr = 1;
883 	unsigned char		tmp;
884 	unsigned		i, max = CHACHA20_KEY_SIZE;
885 	const char *		src_buf = cp;
886 	char *			dest_buf = (char *) &primary_crng.state[4];
887 
888 	if (!spin_trylock_irqsave(&primary_crng.lock, flags))
889 		return 0;
890 	if (crng_init != 0) {
891 		spin_unlock_irqrestore(&primary_crng.lock, flags);
892 		return 0;
893 	}
894 	if (len > max)
895 		max = len;
896 
897 	for (i = 0; i < max ; i++) {
898 		tmp = lfsr;
899 		lfsr >>= 1;
900 		if (tmp & 1)
901 			lfsr ^= 0xE1;
902 		tmp = dest_buf[i % CHACHA20_KEY_SIZE];
903 		dest_buf[i % CHACHA20_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
904 		lfsr += (tmp << 3) | (tmp >> 5);
905 	}
906 	spin_unlock_irqrestore(&primary_crng.lock, flags);
907 	return 1;
908 }
909 
910 static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
911 {
912 	unsigned long	flags;
913 	int		i, num;
914 	union {
915 		__u32	block[CHACHA20_BLOCK_WORDS];
916 		__u32	key[8];
917 	} buf;
918 
919 	if (r) {
920 		num = extract_entropy(r, &buf, 32, 16, 0);
921 		if (num == 0)
922 			return;
923 	} else {
924 		_extract_crng(&primary_crng, buf.block);
925 		_crng_backtrack_protect(&primary_crng, buf.block,
926 					CHACHA20_KEY_SIZE);
927 	}
928 	spin_lock_irqsave(&crng->lock, flags);
929 	for (i = 0; i < 8; i++) {
930 		unsigned long	rv;
931 		if (!arch_get_random_seed_long(&rv) &&
932 		    !arch_get_random_long(&rv))
933 			rv = random_get_entropy();
934 		crng->state[i+4] ^= buf.key[i] ^ rv;
935 	}
936 	memzero_explicit(&buf, sizeof(buf));
937 	crng->init_time = jiffies;
938 	spin_unlock_irqrestore(&crng->lock, flags);
939 	if (crng == &primary_crng && crng_init < 2) {
940 		invalidate_batched_entropy();
941 		numa_crng_init();
942 		crng_init = 2;
943 		process_random_ready_list();
944 		wake_up_interruptible(&crng_init_wait);
945 		pr_notice("random: crng init done\n");
946 		if (unseeded_warning.missed) {
947 			pr_notice("random: %d get_random_xx warning(s) missed "
948 				  "due to ratelimiting\n",
949 				  unseeded_warning.missed);
950 			unseeded_warning.missed = 0;
951 		}
952 		if (urandom_warning.missed) {
953 			pr_notice("random: %d urandom warning(s) missed "
954 				  "due to ratelimiting\n",
955 				  urandom_warning.missed);
956 			urandom_warning.missed = 0;
957 		}
958 	}
959 }
960 
961 static void _extract_crng(struct crng_state *crng,
962 			  __u32 out[CHACHA20_BLOCK_WORDS])
963 {
964 	unsigned long v, flags;
965 
966 	if (crng_ready() &&
967 	    (time_after(crng_global_init_time, crng->init_time) ||
968 	     time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
969 		crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
970 	spin_lock_irqsave(&crng->lock, flags);
971 	if (arch_get_random_long(&v))
972 		crng->state[14] ^= v;
973 	chacha20_block(&crng->state[0], out);
974 	if (crng->state[12] == 0)
975 		crng->state[13]++;
976 	spin_unlock_irqrestore(&crng->lock, flags);
977 }
978 
979 static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
980 {
981 	struct crng_state *crng = NULL;
982 
983 #ifdef CONFIG_NUMA
984 	if (crng_node_pool)
985 		crng = crng_node_pool[numa_node_id()];
986 	if (crng == NULL)
987 #endif
988 		crng = &primary_crng;
989 	_extract_crng(crng, out);
990 }
991 
992 /*
993  * Use the leftover bytes from the CRNG block output (if there is
994  * enough) to mutate the CRNG key to provide backtracking protection.
995  */
996 static void _crng_backtrack_protect(struct crng_state *crng,
997 				    __u32 tmp[CHACHA20_BLOCK_WORDS], int used)
998 {
999 	unsigned long	flags;
1000 	__u32		*s, *d;
1001 	int		i;
1002 
1003 	used = round_up(used, sizeof(__u32));
1004 	if (used + CHACHA20_KEY_SIZE > CHACHA20_BLOCK_SIZE) {
1005 		extract_crng(tmp);
1006 		used = 0;
1007 	}
1008 	spin_lock_irqsave(&crng->lock, flags);
1009 	s = &tmp[used / sizeof(__u32)];
1010 	d = &crng->state[4];
1011 	for (i=0; i < 8; i++)
1012 		*d++ ^= *s++;
1013 	spin_unlock_irqrestore(&crng->lock, flags);
1014 }
1015 
1016 static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
1017 {
1018 	struct crng_state *crng = NULL;
1019 
1020 #ifdef CONFIG_NUMA
1021 	if (crng_node_pool)
1022 		crng = crng_node_pool[numa_node_id()];
1023 	if (crng == NULL)
1024 #endif
1025 		crng = &primary_crng;
1026 	_crng_backtrack_protect(crng, tmp, used);
1027 }
1028 
1029 static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1030 {
1031 	ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
1032 	__u32 tmp[CHACHA20_BLOCK_WORDS];
1033 	int large_request = (nbytes > 256);
1034 
1035 	while (nbytes) {
1036 		if (large_request && need_resched()) {
1037 			if (signal_pending(current)) {
1038 				if (ret == 0)
1039 					ret = -ERESTARTSYS;
1040 				break;
1041 			}
1042 			schedule();
1043 		}
1044 
1045 		extract_crng(tmp);
1046 		i = min_t(int, nbytes, CHACHA20_BLOCK_SIZE);
1047 		if (copy_to_user(buf, tmp, i)) {
1048 			ret = -EFAULT;
1049 			break;
1050 		}
1051 
1052 		nbytes -= i;
1053 		buf += i;
1054 		ret += i;
1055 	}
1056 	crng_backtrack_protect(tmp, i);
1057 
1058 	/* Wipe data just written to memory */
1059 	memzero_explicit(tmp, sizeof(tmp));
1060 
1061 	return ret;
1062 }
1063 
1064 
1065 /*********************************************************************
1066  *
1067  * Entropy input management
1068  *
1069  *********************************************************************/
1070 
1071 /* There is one of these per entropy source */
1072 struct timer_rand_state {
1073 	cycles_t last_time;
1074 	long last_delta, last_delta2;
1075 };
1076 
1077 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1078 
1079 /*
1080  * Add device- or boot-specific data to the input pool to help
1081  * initialize it.
1082  *
1083  * None of this adds any entropy; it is meant to avoid the problem of
1084  * the entropy pool having similar initial state across largely
1085  * identical devices.
1086  */
1087 void add_device_randomness(const void *buf, unsigned int size)
1088 {
1089 	unsigned long time = random_get_entropy() ^ jiffies;
1090 	unsigned long flags;
1091 
1092 	if (!crng_ready() && size)
1093 		crng_slow_load(buf, size);
1094 
1095 	trace_add_device_randomness(size, _RET_IP_);
1096 	spin_lock_irqsave(&input_pool.lock, flags);
1097 	_mix_pool_bytes(&input_pool, buf, size);
1098 	_mix_pool_bytes(&input_pool, &time, sizeof(time));
1099 	spin_unlock_irqrestore(&input_pool.lock, flags);
1100 }
1101 EXPORT_SYMBOL(add_device_randomness);
1102 
1103 static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1104 
1105 /*
1106  * This function adds entropy to the entropy "pool" by using timing
1107  * delays.  It uses the timer_rand_state structure to make an estimate
1108  * of how many bits of entropy this call has added to the pool.
1109  *
1110  * The number "num" is also added to the pool - it should somehow describe
1111  * the type of event which just happened.  This is currently 0-255 for
1112  * keyboard scan codes, and 256 upwards for interrupts.
1113  *
1114  */
1115 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1116 {
1117 	struct entropy_store	*r;
1118 	struct {
1119 		long jiffies;
1120 		unsigned cycles;
1121 		unsigned num;
1122 	} sample;
1123 	long delta, delta2, delta3;
1124 
1125 	preempt_disable();
1126 
1127 	sample.jiffies = jiffies;
1128 	sample.cycles = random_get_entropy();
1129 	sample.num = num;
1130 	r = &input_pool;
1131 	mix_pool_bytes(r, &sample, sizeof(sample));
1132 
1133 	/*
1134 	 * Calculate number of bits of randomness we probably added.
1135 	 * We take into account the first, second and third-order deltas
1136 	 * in order to make our estimate.
1137 	 */
1138 	delta = sample.jiffies - state->last_time;
1139 	state->last_time = sample.jiffies;
1140 
1141 	delta2 = delta - state->last_delta;
1142 	state->last_delta = delta;
1143 
1144 	delta3 = delta2 - state->last_delta2;
1145 	state->last_delta2 = delta2;
1146 
1147 	if (delta < 0)
1148 		delta = -delta;
1149 	if (delta2 < 0)
1150 		delta2 = -delta2;
1151 	if (delta3 < 0)
1152 		delta3 = -delta3;
1153 	if (delta > delta2)
1154 		delta = delta2;
1155 	if (delta > delta3)
1156 		delta = delta3;
1157 
1158 	/*
1159 	 * delta is now minimum absolute delta.
1160 	 * Round down by 1 bit on general principles,
1161 	 * and limit entropy entimate to 12 bits.
1162 	 */
1163 	credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1164 
1165 	preempt_enable();
1166 }
1167 
1168 void add_input_randomness(unsigned int type, unsigned int code,
1169 				 unsigned int value)
1170 {
1171 	static unsigned char last_value;
1172 
1173 	/* ignore autorepeat and the like */
1174 	if (value == last_value)
1175 		return;
1176 
1177 	last_value = value;
1178 	add_timer_randomness(&input_timer_state,
1179 			     (type << 4) ^ code ^ (code >> 4) ^ value);
1180 	trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1181 }
1182 EXPORT_SYMBOL_GPL(add_input_randomness);
1183 
1184 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1185 
1186 #ifdef ADD_INTERRUPT_BENCH
1187 static unsigned long avg_cycles, avg_deviation;
1188 
1189 #define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
1190 #define FIXED_1_2 (1 << (AVG_SHIFT-1))
1191 
1192 static void add_interrupt_bench(cycles_t start)
1193 {
1194         long delta = random_get_entropy() - start;
1195 
1196         /* Use a weighted moving average */
1197         delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1198         avg_cycles += delta;
1199         /* And average deviation */
1200         delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1201         avg_deviation += delta;
1202 }
1203 #else
1204 #define add_interrupt_bench(x)
1205 #endif
1206 
1207 static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1208 {
1209 	__u32 *ptr = (__u32 *) regs;
1210 	unsigned int idx;
1211 
1212 	if (regs == NULL)
1213 		return 0;
1214 	idx = READ_ONCE(f->reg_idx);
1215 	if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1216 		idx = 0;
1217 	ptr += idx++;
1218 	WRITE_ONCE(f->reg_idx, idx);
1219 	return *ptr;
1220 }
1221 
1222 void add_interrupt_randomness(int irq, int irq_flags)
1223 {
1224 	struct entropy_store	*r;
1225 	struct fast_pool	*fast_pool = this_cpu_ptr(&irq_randomness);
1226 	struct pt_regs		*regs = get_irq_regs();
1227 	unsigned long		now = jiffies;
1228 	cycles_t		cycles = random_get_entropy();
1229 	__u32			c_high, j_high;
1230 	__u64			ip;
1231 	unsigned long		seed;
1232 	int			credit = 0;
1233 
1234 	if (cycles == 0)
1235 		cycles = get_reg(fast_pool, regs);
1236 	c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1237 	j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1238 	fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1239 	fast_pool->pool[1] ^= now ^ c_high;
1240 	ip = regs ? instruction_pointer(regs) : _RET_IP_;
1241 	fast_pool->pool[2] ^= ip;
1242 	fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1243 		get_reg(fast_pool, regs);
1244 
1245 	fast_mix(fast_pool);
1246 	add_interrupt_bench(cycles);
1247 
1248 	if (unlikely(crng_init == 0)) {
1249 		if ((fast_pool->count >= 64) &&
1250 		    crng_fast_load((char *) fast_pool->pool,
1251 				   sizeof(fast_pool->pool))) {
1252 			fast_pool->count = 0;
1253 			fast_pool->last = now;
1254 		}
1255 		return;
1256 	}
1257 
1258 	if ((fast_pool->count < 64) &&
1259 	    !time_after(now, fast_pool->last + HZ))
1260 		return;
1261 
1262 	r = &input_pool;
1263 	if (!spin_trylock(&r->lock))
1264 		return;
1265 
1266 	fast_pool->last = now;
1267 	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1268 
1269 	/*
1270 	 * If we have architectural seed generator, produce a seed and
1271 	 * add it to the pool.  For the sake of paranoia don't let the
1272 	 * architectural seed generator dominate the input from the
1273 	 * interrupt noise.
1274 	 */
1275 	if (arch_get_random_seed_long(&seed)) {
1276 		__mix_pool_bytes(r, &seed, sizeof(seed));
1277 		credit = 1;
1278 	}
1279 	spin_unlock(&r->lock);
1280 
1281 	fast_pool->count = 0;
1282 
1283 	/* award one bit for the contents of the fast pool */
1284 	credit_entropy_bits(r, credit + 1);
1285 }
1286 EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1287 
1288 #ifdef CONFIG_BLOCK
1289 void add_disk_randomness(struct gendisk *disk)
1290 {
1291 	if (!disk || !disk->random)
1292 		return;
1293 	/* first major is 1, so we get >= 0x200 here */
1294 	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1295 	trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1296 }
1297 EXPORT_SYMBOL_GPL(add_disk_randomness);
1298 #endif
1299 
1300 /*********************************************************************
1301  *
1302  * Entropy extraction routines
1303  *
1304  *********************************************************************/
1305 
1306 /*
1307  * This utility inline function is responsible for transferring entropy
1308  * from the primary pool to the secondary extraction pool. We make
1309  * sure we pull enough for a 'catastrophic reseed'.
1310  */
1311 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1312 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1313 {
1314 	if (!r->pull ||
1315 	    r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
1316 	    r->entropy_count > r->poolinfo->poolfracbits)
1317 		return;
1318 
1319 	_xfer_secondary_pool(r, nbytes);
1320 }
1321 
1322 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1323 {
1324 	__u32	tmp[OUTPUT_POOL_WORDS];
1325 
1326 	int bytes = nbytes;
1327 
1328 	/* pull at least as much as a wakeup */
1329 	bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1330 	/* but never more than the buffer size */
1331 	bytes = min_t(int, bytes, sizeof(tmp));
1332 
1333 	trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1334 				  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1335 	bytes = extract_entropy(r->pull, tmp, bytes,
1336 				random_read_wakeup_bits / 8, 0);
1337 	mix_pool_bytes(r, tmp, bytes);
1338 	credit_entropy_bits(r, bytes*8);
1339 }
1340 
1341 /*
1342  * Used as a workqueue function so that when the input pool is getting
1343  * full, we can "spill over" some entropy to the output pools.  That
1344  * way the output pools can store some of the excess entropy instead
1345  * of letting it go to waste.
1346  */
1347 static void push_to_pool(struct work_struct *work)
1348 {
1349 	struct entropy_store *r = container_of(work, struct entropy_store,
1350 					      push_work);
1351 	BUG_ON(!r);
1352 	_xfer_secondary_pool(r, random_read_wakeup_bits/8);
1353 	trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1354 			   r->pull->entropy_count >> ENTROPY_SHIFT);
1355 }
1356 
1357 /*
1358  * This function decides how many bytes to actually take from the
1359  * given pool, and also debits the entropy count accordingly.
1360  */
1361 static size_t account(struct entropy_store *r, size_t nbytes, int min,
1362 		      int reserved)
1363 {
1364 	int entropy_count, orig, have_bytes;
1365 	size_t ibytes, nfrac;
1366 
1367 	BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1368 
1369 	/* Can we pull enough? */
1370 retry:
1371 	entropy_count = orig = READ_ONCE(r->entropy_count);
1372 	ibytes = nbytes;
1373 	/* never pull more than available */
1374 	have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1375 
1376 	if ((have_bytes -= reserved) < 0)
1377 		have_bytes = 0;
1378 	ibytes = min_t(size_t, ibytes, have_bytes);
1379 	if (ibytes < min)
1380 		ibytes = 0;
1381 
1382 	if (unlikely(entropy_count < 0)) {
1383 		pr_warn("random: negative entropy count: pool %s count %d\n",
1384 			r->name, entropy_count);
1385 		WARN_ON(1);
1386 		entropy_count = 0;
1387 	}
1388 	nfrac = ibytes << (ENTROPY_SHIFT + 3);
1389 	if ((size_t) entropy_count > nfrac)
1390 		entropy_count -= nfrac;
1391 	else
1392 		entropy_count = 0;
1393 
1394 	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1395 		goto retry;
1396 
1397 	trace_debit_entropy(r->name, 8 * ibytes);
1398 	if (ibytes &&
1399 	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1400 		wake_up_interruptible(&random_write_wait);
1401 		kill_fasync(&fasync, SIGIO, POLL_OUT);
1402 	}
1403 
1404 	return ibytes;
1405 }
1406 
1407 /*
1408  * This function does the actual extraction for extract_entropy and
1409  * extract_entropy_user.
1410  *
1411  * Note: we assume that .poolwords is a multiple of 16 words.
1412  */
1413 static void extract_buf(struct entropy_store *r, __u8 *out)
1414 {
1415 	int i;
1416 	union {
1417 		__u32 w[5];
1418 		unsigned long l[LONGS(20)];
1419 	} hash;
1420 	__u32 workspace[SHA_WORKSPACE_WORDS];
1421 	unsigned long flags;
1422 
1423 	/*
1424 	 * If we have an architectural hardware random number
1425 	 * generator, use it for SHA's initial vector
1426 	 */
1427 	sha_init(hash.w);
1428 	for (i = 0; i < LONGS(20); i++) {
1429 		unsigned long v;
1430 		if (!arch_get_random_long(&v))
1431 			break;
1432 		hash.l[i] = v;
1433 	}
1434 
1435 	/* Generate a hash across the pool, 16 words (512 bits) at a time */
1436 	spin_lock_irqsave(&r->lock, flags);
1437 	for (i = 0; i < r->poolinfo->poolwords; i += 16)
1438 		sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1439 
1440 	/*
1441 	 * We mix the hash back into the pool to prevent backtracking
1442 	 * attacks (where the attacker knows the state of the pool
1443 	 * plus the current outputs, and attempts to find previous
1444 	 * ouputs), unless the hash function can be inverted. By
1445 	 * mixing at least a SHA1 worth of hash data back, we make
1446 	 * brute-forcing the feedback as hard as brute-forcing the
1447 	 * hash.
1448 	 */
1449 	__mix_pool_bytes(r, hash.w, sizeof(hash.w));
1450 	spin_unlock_irqrestore(&r->lock, flags);
1451 
1452 	memzero_explicit(workspace, sizeof(workspace));
1453 
1454 	/*
1455 	 * In case the hash function has some recognizable output
1456 	 * pattern, we fold it in half. Thus, we always feed back
1457 	 * twice as much data as we output.
1458 	 */
1459 	hash.w[0] ^= hash.w[3];
1460 	hash.w[1] ^= hash.w[4];
1461 	hash.w[2] ^= rol32(hash.w[2], 16);
1462 
1463 	memcpy(out, &hash, EXTRACT_SIZE);
1464 	memzero_explicit(&hash, sizeof(hash));
1465 }
1466 
1467 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1468 				size_t nbytes, int fips)
1469 {
1470 	ssize_t ret = 0, i;
1471 	__u8 tmp[EXTRACT_SIZE];
1472 	unsigned long flags;
1473 
1474 	while (nbytes) {
1475 		extract_buf(r, tmp);
1476 
1477 		if (fips) {
1478 			spin_lock_irqsave(&r->lock, flags);
1479 			if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1480 				panic("Hardware RNG duplicated output!\n");
1481 			memcpy(r->last_data, tmp, EXTRACT_SIZE);
1482 			spin_unlock_irqrestore(&r->lock, flags);
1483 		}
1484 		i = min_t(int, nbytes, EXTRACT_SIZE);
1485 		memcpy(buf, tmp, i);
1486 		nbytes -= i;
1487 		buf += i;
1488 		ret += i;
1489 	}
1490 
1491 	/* Wipe data just returned from memory */
1492 	memzero_explicit(tmp, sizeof(tmp));
1493 
1494 	return ret;
1495 }
1496 
1497 /*
1498  * This function extracts randomness from the "entropy pool", and
1499  * returns it in a buffer.
1500  *
1501  * The min parameter specifies the minimum amount we can pull before
1502  * failing to avoid races that defeat catastrophic reseeding while the
1503  * reserved parameter indicates how much entropy we must leave in the
1504  * pool after each pull to avoid starving other readers.
1505  */
1506 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1507 				 size_t nbytes, int min, int reserved)
1508 {
1509 	__u8 tmp[EXTRACT_SIZE];
1510 	unsigned long flags;
1511 
1512 	/* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1513 	if (fips_enabled) {
1514 		spin_lock_irqsave(&r->lock, flags);
1515 		if (!r->last_data_init) {
1516 			r->last_data_init = 1;
1517 			spin_unlock_irqrestore(&r->lock, flags);
1518 			trace_extract_entropy(r->name, EXTRACT_SIZE,
1519 					      ENTROPY_BITS(r), _RET_IP_);
1520 			xfer_secondary_pool(r, EXTRACT_SIZE);
1521 			extract_buf(r, tmp);
1522 			spin_lock_irqsave(&r->lock, flags);
1523 			memcpy(r->last_data, tmp, EXTRACT_SIZE);
1524 		}
1525 		spin_unlock_irqrestore(&r->lock, flags);
1526 	}
1527 
1528 	trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1529 	xfer_secondary_pool(r, nbytes);
1530 	nbytes = account(r, nbytes, min, reserved);
1531 
1532 	return _extract_entropy(r, buf, nbytes, fips_enabled);
1533 }
1534 
1535 /*
1536  * This function extracts randomness from the "entropy pool", and
1537  * returns it in a userspace buffer.
1538  */
1539 static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1540 				    size_t nbytes)
1541 {
1542 	ssize_t ret = 0, i;
1543 	__u8 tmp[EXTRACT_SIZE];
1544 	int large_request = (nbytes > 256);
1545 
1546 	trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1547 	xfer_secondary_pool(r, nbytes);
1548 	nbytes = account(r, nbytes, 0, 0);
1549 
1550 	while (nbytes) {
1551 		if (large_request && need_resched()) {
1552 			if (signal_pending(current)) {
1553 				if (ret == 0)
1554 					ret = -ERESTARTSYS;
1555 				break;
1556 			}
1557 			schedule();
1558 		}
1559 
1560 		extract_buf(r, tmp);
1561 		i = min_t(int, nbytes, EXTRACT_SIZE);
1562 		if (copy_to_user(buf, tmp, i)) {
1563 			ret = -EFAULT;
1564 			break;
1565 		}
1566 
1567 		nbytes -= i;
1568 		buf += i;
1569 		ret += i;
1570 	}
1571 
1572 	/* Wipe data just returned from memory */
1573 	memzero_explicit(tmp, sizeof(tmp));
1574 
1575 	return ret;
1576 }
1577 
1578 #define warn_unseeded_randomness(previous) \
1579 	_warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1580 
1581 static void _warn_unseeded_randomness(const char *func_name, void *caller,
1582 				      void **previous)
1583 {
1584 #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1585 	const bool print_once = false;
1586 #else
1587 	static bool print_once __read_mostly;
1588 #endif
1589 
1590 	if (print_once ||
1591 	    crng_ready() ||
1592 	    (previous && (caller == READ_ONCE(*previous))))
1593 		return;
1594 	WRITE_ONCE(*previous, caller);
1595 #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1596 	print_once = true;
1597 #endif
1598 	if (__ratelimit(&unseeded_warning))
1599 		pr_notice("random: %s called from %pS with crng_init=%d\n",
1600 			  func_name, caller, crng_init);
1601 }
1602 
1603 /*
1604  * This function is the exported kernel interface.  It returns some
1605  * number of good random numbers, suitable for key generation, seeding
1606  * TCP sequence numbers, etc.  It does not rely on the hardware random
1607  * number generator.  For random bytes direct from the hardware RNG
1608  * (when available), use get_random_bytes_arch(). In order to ensure
1609  * that the randomness provided by this function is okay, the function
1610  * wait_for_random_bytes() should be called and return 0 at least once
1611  * at any point prior.
1612  */
1613 static void _get_random_bytes(void *buf, int nbytes)
1614 {
1615 	__u32 tmp[CHACHA20_BLOCK_WORDS];
1616 
1617 	trace_get_random_bytes(nbytes, _RET_IP_);
1618 
1619 	while (nbytes >= CHACHA20_BLOCK_SIZE) {
1620 		extract_crng(buf);
1621 		buf += CHACHA20_BLOCK_SIZE;
1622 		nbytes -= CHACHA20_BLOCK_SIZE;
1623 	}
1624 
1625 	if (nbytes > 0) {
1626 		extract_crng(tmp);
1627 		memcpy(buf, tmp, nbytes);
1628 		crng_backtrack_protect(tmp, nbytes);
1629 	} else
1630 		crng_backtrack_protect(tmp, CHACHA20_BLOCK_SIZE);
1631 	memzero_explicit(tmp, sizeof(tmp));
1632 }
1633 
1634 void get_random_bytes(void *buf, int nbytes)
1635 {
1636 	static void *previous;
1637 
1638 	warn_unseeded_randomness(&previous);
1639 	_get_random_bytes(buf, nbytes);
1640 }
1641 EXPORT_SYMBOL(get_random_bytes);
1642 
1643 /*
1644  * Wait for the urandom pool to be seeded and thus guaranteed to supply
1645  * cryptographically secure random numbers. This applies to: the /dev/urandom
1646  * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1647  * family of functions. Using any of these functions without first calling
1648  * this function forfeits the guarantee of security.
1649  *
1650  * Returns: 0 if the urandom pool has been seeded.
1651  *          -ERESTARTSYS if the function was interrupted by a signal.
1652  */
1653 int wait_for_random_bytes(void)
1654 {
1655 	if (likely(crng_ready()))
1656 		return 0;
1657 	return wait_event_interruptible(crng_init_wait, crng_ready());
1658 }
1659 EXPORT_SYMBOL(wait_for_random_bytes);
1660 
1661 /*
1662  * Add a callback function that will be invoked when the nonblocking
1663  * pool is initialised.
1664  *
1665  * returns: 0 if callback is successfully added
1666  *	    -EALREADY if pool is already initialised (callback not called)
1667  *	    -ENOENT if module for callback is not alive
1668  */
1669 int add_random_ready_callback(struct random_ready_callback *rdy)
1670 {
1671 	struct module *owner;
1672 	unsigned long flags;
1673 	int err = -EALREADY;
1674 
1675 	if (crng_ready())
1676 		return err;
1677 
1678 	owner = rdy->owner;
1679 	if (!try_module_get(owner))
1680 		return -ENOENT;
1681 
1682 	spin_lock_irqsave(&random_ready_list_lock, flags);
1683 	if (crng_ready())
1684 		goto out;
1685 
1686 	owner = NULL;
1687 
1688 	list_add(&rdy->list, &random_ready_list);
1689 	err = 0;
1690 
1691 out:
1692 	spin_unlock_irqrestore(&random_ready_list_lock, flags);
1693 
1694 	module_put(owner);
1695 
1696 	return err;
1697 }
1698 EXPORT_SYMBOL(add_random_ready_callback);
1699 
1700 /*
1701  * Delete a previously registered readiness callback function.
1702  */
1703 void del_random_ready_callback(struct random_ready_callback *rdy)
1704 {
1705 	unsigned long flags;
1706 	struct module *owner = NULL;
1707 
1708 	spin_lock_irqsave(&random_ready_list_lock, flags);
1709 	if (!list_empty(&rdy->list)) {
1710 		list_del_init(&rdy->list);
1711 		owner = rdy->owner;
1712 	}
1713 	spin_unlock_irqrestore(&random_ready_list_lock, flags);
1714 
1715 	module_put(owner);
1716 }
1717 EXPORT_SYMBOL(del_random_ready_callback);
1718 
1719 /*
1720  * This function will use the architecture-specific hardware random
1721  * number generator if it is available.  The arch-specific hw RNG will
1722  * almost certainly be faster than what we can do in software, but it
1723  * is impossible to verify that it is implemented securely (as
1724  * opposed, to, say, the AES encryption of a sequence number using a
1725  * key known by the NSA).  So it's useful if we need the speed, but
1726  * only if we're willing to trust the hardware manufacturer not to
1727  * have put in a back door.
1728  */
1729 void get_random_bytes_arch(void *buf, int nbytes)
1730 {
1731 	char *p = buf;
1732 
1733 	trace_get_random_bytes_arch(nbytes, _RET_IP_);
1734 	while (nbytes) {
1735 		unsigned long v;
1736 		int chunk = min(nbytes, (int)sizeof(unsigned long));
1737 
1738 		if (!arch_get_random_long(&v))
1739 			break;
1740 
1741 		memcpy(p, &v, chunk);
1742 		p += chunk;
1743 		nbytes -= chunk;
1744 	}
1745 
1746 	if (nbytes)
1747 		get_random_bytes(p, nbytes);
1748 }
1749 EXPORT_SYMBOL(get_random_bytes_arch);
1750 
1751 
1752 /*
1753  * init_std_data - initialize pool with system data
1754  *
1755  * @r: pool to initialize
1756  *
1757  * This function clears the pool's entropy count and mixes some system
1758  * data into the pool to prepare it for use. The pool is not cleared
1759  * as that can only decrease the entropy in the pool.
1760  */
1761 static void init_std_data(struct entropy_store *r)
1762 {
1763 	int i;
1764 	ktime_t now = ktime_get_real();
1765 	unsigned long rv;
1766 
1767 	r->last_pulled = jiffies;
1768 	mix_pool_bytes(r, &now, sizeof(now));
1769 	for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1770 		if (!arch_get_random_seed_long(&rv) &&
1771 		    !arch_get_random_long(&rv))
1772 			rv = random_get_entropy();
1773 		mix_pool_bytes(r, &rv, sizeof(rv));
1774 	}
1775 	mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1776 }
1777 
1778 /*
1779  * Note that setup_arch() may call add_device_randomness()
1780  * long before we get here. This allows seeding of the pools
1781  * with some platform dependent data very early in the boot
1782  * process. But it limits our options here. We must use
1783  * statically allocated structures that already have all
1784  * initializations complete at compile time. We should also
1785  * take care not to overwrite the precious per platform data
1786  * we were given.
1787  */
1788 static int rand_initialize(void)
1789 {
1790 	init_std_data(&input_pool);
1791 	init_std_data(&blocking_pool);
1792 	crng_initialize(&primary_crng);
1793 	crng_global_init_time = jiffies;
1794 	if (ratelimit_disable) {
1795 		urandom_warning.interval = 0;
1796 		unseeded_warning.interval = 0;
1797 	}
1798 	return 0;
1799 }
1800 early_initcall(rand_initialize);
1801 
1802 #ifdef CONFIG_BLOCK
1803 void rand_initialize_disk(struct gendisk *disk)
1804 {
1805 	struct timer_rand_state *state;
1806 
1807 	/*
1808 	 * If kzalloc returns null, we just won't use that entropy
1809 	 * source.
1810 	 */
1811 	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1812 	if (state) {
1813 		state->last_time = INITIAL_JIFFIES;
1814 		disk->random = state;
1815 	}
1816 }
1817 #endif
1818 
1819 static ssize_t
1820 _random_read(int nonblock, char __user *buf, size_t nbytes)
1821 {
1822 	ssize_t n;
1823 
1824 	if (nbytes == 0)
1825 		return 0;
1826 
1827 	nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1828 	while (1) {
1829 		n = extract_entropy_user(&blocking_pool, buf, nbytes);
1830 		if (n < 0)
1831 			return n;
1832 		trace_random_read(n*8, (nbytes-n)*8,
1833 				  ENTROPY_BITS(&blocking_pool),
1834 				  ENTROPY_BITS(&input_pool));
1835 		if (n > 0)
1836 			return n;
1837 
1838 		/* Pool is (near) empty.  Maybe wait and retry. */
1839 		if (nonblock)
1840 			return -EAGAIN;
1841 
1842 		wait_event_interruptible(random_read_wait,
1843 			ENTROPY_BITS(&input_pool) >=
1844 			random_read_wakeup_bits);
1845 		if (signal_pending(current))
1846 			return -ERESTARTSYS;
1847 	}
1848 }
1849 
1850 static ssize_t
1851 random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1852 {
1853 	return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1854 }
1855 
1856 static ssize_t
1857 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1858 {
1859 	unsigned long flags;
1860 	static int maxwarn = 10;
1861 	int ret;
1862 
1863 	if (!crng_ready() && maxwarn > 0) {
1864 		maxwarn--;
1865 		if (__ratelimit(&urandom_warning))
1866 			printk(KERN_NOTICE "random: %s: uninitialized "
1867 			       "urandom read (%zd bytes read)\n",
1868 			       current->comm, nbytes);
1869 		spin_lock_irqsave(&primary_crng.lock, flags);
1870 		crng_init_cnt = 0;
1871 		spin_unlock_irqrestore(&primary_crng.lock, flags);
1872 	}
1873 	nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1874 	ret = extract_crng_user(buf, nbytes);
1875 	trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1876 	return ret;
1877 }
1878 
1879 static __poll_t
1880 random_poll(struct file *file, poll_table * wait)
1881 {
1882 	__poll_t mask;
1883 
1884 	poll_wait(file, &random_read_wait, wait);
1885 	poll_wait(file, &random_write_wait, wait);
1886 	mask = 0;
1887 	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1888 		mask |= EPOLLIN | EPOLLRDNORM;
1889 	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1890 		mask |= EPOLLOUT | EPOLLWRNORM;
1891 	return mask;
1892 }
1893 
1894 static int
1895 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1896 {
1897 	size_t bytes;
1898 	__u32 t, buf[16];
1899 	const char __user *p = buffer;
1900 
1901 	while (count > 0) {
1902 		int b, i = 0;
1903 
1904 		bytes = min(count, sizeof(buf));
1905 		if (copy_from_user(&buf, p, bytes))
1906 			return -EFAULT;
1907 
1908 		for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
1909 			if (!arch_get_random_int(&t))
1910 				break;
1911 			buf[i] ^= t;
1912 		}
1913 
1914 		count -= bytes;
1915 		p += bytes;
1916 
1917 		mix_pool_bytes(r, buf, bytes);
1918 		cond_resched();
1919 	}
1920 
1921 	return 0;
1922 }
1923 
1924 static ssize_t random_write(struct file *file, const char __user *buffer,
1925 			    size_t count, loff_t *ppos)
1926 {
1927 	size_t ret;
1928 
1929 	ret = write_pool(&input_pool, buffer, count);
1930 	if (ret)
1931 		return ret;
1932 
1933 	return (ssize_t)count;
1934 }
1935 
1936 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1937 {
1938 	int size, ent_count;
1939 	int __user *p = (int __user *)arg;
1940 	int retval;
1941 
1942 	switch (cmd) {
1943 	case RNDGETENTCNT:
1944 		/* inherently racy, no point locking */
1945 		ent_count = ENTROPY_BITS(&input_pool);
1946 		if (put_user(ent_count, p))
1947 			return -EFAULT;
1948 		return 0;
1949 	case RNDADDTOENTCNT:
1950 		if (!capable(CAP_SYS_ADMIN))
1951 			return -EPERM;
1952 		if (get_user(ent_count, p))
1953 			return -EFAULT;
1954 		return credit_entropy_bits_safe(&input_pool, ent_count);
1955 	case RNDADDENTROPY:
1956 		if (!capable(CAP_SYS_ADMIN))
1957 			return -EPERM;
1958 		if (get_user(ent_count, p++))
1959 			return -EFAULT;
1960 		if (ent_count < 0)
1961 			return -EINVAL;
1962 		if (get_user(size, p++))
1963 			return -EFAULT;
1964 		retval = write_pool(&input_pool, (const char __user *)p,
1965 				    size);
1966 		if (retval < 0)
1967 			return retval;
1968 		return credit_entropy_bits_safe(&input_pool, ent_count);
1969 	case RNDZAPENTCNT:
1970 	case RNDCLEARPOOL:
1971 		/*
1972 		 * Clear the entropy pool counters. We no longer clear
1973 		 * the entropy pool, as that's silly.
1974 		 */
1975 		if (!capable(CAP_SYS_ADMIN))
1976 			return -EPERM;
1977 		input_pool.entropy_count = 0;
1978 		blocking_pool.entropy_count = 0;
1979 		return 0;
1980 	case RNDRESEEDCRNG:
1981 		if (!capable(CAP_SYS_ADMIN))
1982 			return -EPERM;
1983 		if (crng_init < 2)
1984 			return -ENODATA;
1985 		crng_reseed(&primary_crng, NULL);
1986 		crng_global_init_time = jiffies - 1;
1987 		return 0;
1988 	default:
1989 		return -EINVAL;
1990 	}
1991 }
1992 
1993 static int random_fasync(int fd, struct file *filp, int on)
1994 {
1995 	return fasync_helper(fd, filp, on, &fasync);
1996 }
1997 
1998 const struct file_operations random_fops = {
1999 	.read  = random_read,
2000 	.write = random_write,
2001 	.poll  = random_poll,
2002 	.unlocked_ioctl = random_ioctl,
2003 	.fasync = random_fasync,
2004 	.llseek = noop_llseek,
2005 };
2006 
2007 const struct file_operations urandom_fops = {
2008 	.read  = urandom_read,
2009 	.write = random_write,
2010 	.unlocked_ioctl = random_ioctl,
2011 	.fasync = random_fasync,
2012 	.llseek = noop_llseek,
2013 };
2014 
2015 SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
2016 		unsigned int, flags)
2017 {
2018 	int ret;
2019 
2020 	if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
2021 		return -EINVAL;
2022 
2023 	if (count > INT_MAX)
2024 		count = INT_MAX;
2025 
2026 	if (flags & GRND_RANDOM)
2027 		return _random_read(flags & GRND_NONBLOCK, buf, count);
2028 
2029 	if (!crng_ready()) {
2030 		if (flags & GRND_NONBLOCK)
2031 			return -EAGAIN;
2032 		ret = wait_for_random_bytes();
2033 		if (unlikely(ret))
2034 			return ret;
2035 	}
2036 	return urandom_read(NULL, buf, count, NULL);
2037 }
2038 
2039 /********************************************************************
2040  *
2041  * Sysctl interface
2042  *
2043  ********************************************************************/
2044 
2045 #ifdef CONFIG_SYSCTL
2046 
2047 #include <linux/sysctl.h>
2048 
2049 static int min_read_thresh = 8, min_write_thresh;
2050 static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
2051 static int max_write_thresh = INPUT_POOL_WORDS * 32;
2052 static int random_min_urandom_seed = 60;
2053 static char sysctl_bootid[16];
2054 
2055 /*
2056  * This function is used to return both the bootid UUID, and random
2057  * UUID.  The difference is in whether table->data is NULL; if it is,
2058  * then a new UUID is generated and returned to the user.
2059  *
2060  * If the user accesses this via the proc interface, the UUID will be
2061  * returned as an ASCII string in the standard UUID format; if via the
2062  * sysctl system call, as 16 bytes of binary data.
2063  */
2064 static int proc_do_uuid(struct ctl_table *table, int write,
2065 			void __user *buffer, size_t *lenp, loff_t *ppos)
2066 {
2067 	struct ctl_table fake_table;
2068 	unsigned char buf[64], tmp_uuid[16], *uuid;
2069 
2070 	uuid = table->data;
2071 	if (!uuid) {
2072 		uuid = tmp_uuid;
2073 		generate_random_uuid(uuid);
2074 	} else {
2075 		static DEFINE_SPINLOCK(bootid_spinlock);
2076 
2077 		spin_lock(&bootid_spinlock);
2078 		if (!uuid[8])
2079 			generate_random_uuid(uuid);
2080 		spin_unlock(&bootid_spinlock);
2081 	}
2082 
2083 	sprintf(buf, "%pU", uuid);
2084 
2085 	fake_table.data = buf;
2086 	fake_table.maxlen = sizeof(buf);
2087 
2088 	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2089 }
2090 
2091 /*
2092  * Return entropy available scaled to integral bits
2093  */
2094 static int proc_do_entropy(struct ctl_table *table, int write,
2095 			   void __user *buffer, size_t *lenp, loff_t *ppos)
2096 {
2097 	struct ctl_table fake_table;
2098 	int entropy_count;
2099 
2100 	entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2101 
2102 	fake_table.data = &entropy_count;
2103 	fake_table.maxlen = sizeof(entropy_count);
2104 
2105 	return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2106 }
2107 
2108 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2109 extern struct ctl_table random_table[];
2110 struct ctl_table random_table[] = {
2111 	{
2112 		.procname	= "poolsize",
2113 		.data		= &sysctl_poolsize,
2114 		.maxlen		= sizeof(int),
2115 		.mode		= 0444,
2116 		.proc_handler	= proc_dointvec,
2117 	},
2118 	{
2119 		.procname	= "entropy_avail",
2120 		.maxlen		= sizeof(int),
2121 		.mode		= 0444,
2122 		.proc_handler	= proc_do_entropy,
2123 		.data		= &input_pool.entropy_count,
2124 	},
2125 	{
2126 		.procname	= "read_wakeup_threshold",
2127 		.data		= &random_read_wakeup_bits,
2128 		.maxlen		= sizeof(int),
2129 		.mode		= 0644,
2130 		.proc_handler	= proc_dointvec_minmax,
2131 		.extra1		= &min_read_thresh,
2132 		.extra2		= &max_read_thresh,
2133 	},
2134 	{
2135 		.procname	= "write_wakeup_threshold",
2136 		.data		= &random_write_wakeup_bits,
2137 		.maxlen		= sizeof(int),
2138 		.mode		= 0644,
2139 		.proc_handler	= proc_dointvec_minmax,
2140 		.extra1		= &min_write_thresh,
2141 		.extra2		= &max_write_thresh,
2142 	},
2143 	{
2144 		.procname	= "urandom_min_reseed_secs",
2145 		.data		= &random_min_urandom_seed,
2146 		.maxlen		= sizeof(int),
2147 		.mode		= 0644,
2148 		.proc_handler	= proc_dointvec,
2149 	},
2150 	{
2151 		.procname	= "boot_id",
2152 		.data		= &sysctl_bootid,
2153 		.maxlen		= 16,
2154 		.mode		= 0444,
2155 		.proc_handler	= proc_do_uuid,
2156 	},
2157 	{
2158 		.procname	= "uuid",
2159 		.maxlen		= 16,
2160 		.mode		= 0444,
2161 		.proc_handler	= proc_do_uuid,
2162 	},
2163 #ifdef ADD_INTERRUPT_BENCH
2164 	{
2165 		.procname	= "add_interrupt_avg_cycles",
2166 		.data		= &avg_cycles,
2167 		.maxlen		= sizeof(avg_cycles),
2168 		.mode		= 0444,
2169 		.proc_handler	= proc_doulongvec_minmax,
2170 	},
2171 	{
2172 		.procname	= "add_interrupt_avg_deviation",
2173 		.data		= &avg_deviation,
2174 		.maxlen		= sizeof(avg_deviation),
2175 		.mode		= 0444,
2176 		.proc_handler	= proc_doulongvec_minmax,
2177 	},
2178 #endif
2179 	{ }
2180 };
2181 #endif 	/* CONFIG_SYSCTL */
2182 
2183 struct batched_entropy {
2184 	union {
2185 		u64 entropy_u64[CHACHA20_BLOCK_SIZE / sizeof(u64)];
2186 		u32 entropy_u32[CHACHA20_BLOCK_SIZE / sizeof(u32)];
2187 	};
2188 	unsigned int position;
2189 };
2190 static rwlock_t batched_entropy_reset_lock = __RW_LOCK_UNLOCKED(batched_entropy_reset_lock);
2191 
2192 /*
2193  * Get a random word for internal kernel use only. The quality of the random
2194  * number is either as good as RDRAND or as good as /dev/urandom, with the
2195  * goal of being quite fast and not depleting entropy. In order to ensure
2196  * that the randomness provided by this function is okay, the function
2197  * wait_for_random_bytes() should be called and return 0 at least once
2198  * at any point prior.
2199  */
2200 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64);
2201 u64 get_random_u64(void)
2202 {
2203 	u64 ret;
2204 	bool use_lock;
2205 	unsigned long flags = 0;
2206 	struct batched_entropy *batch;
2207 	static void *previous;
2208 
2209 #if BITS_PER_LONG == 64
2210 	if (arch_get_random_long((unsigned long *)&ret))
2211 		return ret;
2212 #else
2213 	if (arch_get_random_long((unsigned long *)&ret) &&
2214 	    arch_get_random_long((unsigned long *)&ret + 1))
2215 	    return ret;
2216 #endif
2217 
2218 	warn_unseeded_randomness(&previous);
2219 
2220 	use_lock = READ_ONCE(crng_init) < 2;
2221 	batch = &get_cpu_var(batched_entropy_u64);
2222 	if (use_lock)
2223 		read_lock_irqsave(&batched_entropy_reset_lock, flags);
2224 	if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2225 		extract_crng((__u32 *)batch->entropy_u64);
2226 		batch->position = 0;
2227 	}
2228 	ret = batch->entropy_u64[batch->position++];
2229 	if (use_lock)
2230 		read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2231 	put_cpu_var(batched_entropy_u64);
2232 	return ret;
2233 }
2234 EXPORT_SYMBOL(get_random_u64);
2235 
2236 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32);
2237 u32 get_random_u32(void)
2238 {
2239 	u32 ret;
2240 	bool use_lock;
2241 	unsigned long flags = 0;
2242 	struct batched_entropy *batch;
2243 	static void *previous;
2244 
2245 	if (arch_get_random_int(&ret))
2246 		return ret;
2247 
2248 	warn_unseeded_randomness(&previous);
2249 
2250 	use_lock = READ_ONCE(crng_init) < 2;
2251 	batch = &get_cpu_var(batched_entropy_u32);
2252 	if (use_lock)
2253 		read_lock_irqsave(&batched_entropy_reset_lock, flags);
2254 	if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2255 		extract_crng(batch->entropy_u32);
2256 		batch->position = 0;
2257 	}
2258 	ret = batch->entropy_u32[batch->position++];
2259 	if (use_lock)
2260 		read_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2261 	put_cpu_var(batched_entropy_u32);
2262 	return ret;
2263 }
2264 EXPORT_SYMBOL(get_random_u32);
2265 
2266 /* It's important to invalidate all potential batched entropy that might
2267  * be stored before the crng is initialized, which we can do lazily by
2268  * simply resetting the counter to zero so that it's re-extracted on the
2269  * next usage. */
2270 static void invalidate_batched_entropy(void)
2271 {
2272 	int cpu;
2273 	unsigned long flags;
2274 
2275 	write_lock_irqsave(&batched_entropy_reset_lock, flags);
2276 	for_each_possible_cpu (cpu) {
2277 		per_cpu_ptr(&batched_entropy_u32, cpu)->position = 0;
2278 		per_cpu_ptr(&batched_entropy_u64, cpu)->position = 0;
2279 	}
2280 	write_unlock_irqrestore(&batched_entropy_reset_lock, flags);
2281 }
2282 
2283 /**
2284  * randomize_page - Generate a random, page aligned address
2285  * @start:	The smallest acceptable address the caller will take.
2286  * @range:	The size of the area, starting at @start, within which the
2287  *		random address must fall.
2288  *
2289  * If @start + @range would overflow, @range is capped.
2290  *
2291  * NOTE: Historical use of randomize_range, which this replaces, presumed that
2292  * @start was already page aligned.  We now align it regardless.
2293  *
2294  * Return: A page aligned address within [start, start + range).  On error,
2295  * @start is returned.
2296  */
2297 unsigned long
2298 randomize_page(unsigned long start, unsigned long range)
2299 {
2300 	if (!PAGE_ALIGNED(start)) {
2301 		range -= PAGE_ALIGN(start) - start;
2302 		start = PAGE_ALIGN(start);
2303 	}
2304 
2305 	if (start > ULONG_MAX - range)
2306 		range = ULONG_MAX - start;
2307 
2308 	range >>= PAGE_SHIFT;
2309 
2310 	if (range == 0)
2311 		return start;
2312 
2313 	return start + (get_random_long() % range << PAGE_SHIFT);
2314 }
2315 
2316 /* Interface for in-kernel drivers of true hardware RNGs.
2317  * Those devices may produce endless random bits and will be throttled
2318  * when our pool is full.
2319  */
2320 void add_hwgenerator_randomness(const char *buffer, size_t count,
2321 				size_t entropy)
2322 {
2323 	struct entropy_store *poolp = &input_pool;
2324 
2325 	if (unlikely(crng_init == 0)) {
2326 		crng_fast_load(buffer, count);
2327 		return;
2328 	}
2329 
2330 	/* Suspend writing if we're above the trickle threshold.
2331 	 * We'll be woken up again once below random_write_wakeup_thresh,
2332 	 * or when the calling thread is about to terminate.
2333 	 */
2334 	wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2335 			ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2336 	mix_pool_bytes(poolp, buffer, count);
2337 	credit_entropy_bits(poolp, entropy);
2338 }
2339 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2340