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Linux/drivers/char/random.c

  1 /*
  2  * random.c -- A strong random number generator
  3  *
  4  * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
  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  *
128  *      void add_device_randomness(const void *buf, unsigned int size);
129  *      void add_input_randomness(unsigned int type, unsigned int code,
130  *                                unsigned int value);
131  *      void add_interrupt_randomness(int irq, int irq_flags);
132  *      void add_disk_randomness(struct gendisk *disk);
133  *
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  *
142  * add_input_randomness() uses the input layer interrupt timing, as well as
143  * the event type information from the hardware.
144  *
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.
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.
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>
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>
251 #include <linux/mm.h>
252 #include <linux/nodemask.h>
253 #include <linux/spinlock.h>
254 #include <linux/kthread.h>
255 #include <linux/percpu.h>
256 #include <linux/cryptohash.h>
257 #include <linux/fips.h>
258 #include <linux/ptrace.h>
259 #include <linux/kmemcheck.h>
260 #include <linux/workqueue.h>
261 #include <linux/irq.h>
262 #include <linux/syscalls.h>
263 #include <linux/completion.h>
264 #include <linux/uuid.h>
265 #include <crypto/chacha20.h>
266 
267 #include <asm/processor.h>
268 #include <asm/uaccess.h>
269 #include <asm/irq.h>
270 #include <asm/irq_regs.h>
271 #include <asm/io.h>
272 
273 #define CREATE_TRACE_POINTS
274 #include <trace/events/random.h>
275 
276 /* #define ADD_INTERRUPT_BENCH */
277 
278 /*
279  * Configuration information
280  */
281 #define INPUT_POOL_SHIFT        12
282 #define INPUT_POOL_WORDS        (1 << (INPUT_POOL_SHIFT-5))
283 #define OUTPUT_POOL_SHIFT       10
284 #define OUTPUT_POOL_WORDS       (1 << (OUTPUT_POOL_SHIFT-5))
285 #define SEC_XFER_SIZE           512
286 #define EXTRACT_SIZE            10
287 
288 #define DEBUG_RANDOM_BOOT 0
289 
290 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
291 
292 /*
293  * To allow fractional bits to be tracked, the entropy_count field is
294  * denominated in units of 1/8th bits.
295  *
296  * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
297  * credit_entropy_bits() needs to be 64 bits wide.
298  */
299 #define ENTROPY_SHIFT 3
300 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
301 
302 /*
303  * The minimum number of bits of entropy before we wake up a read on
304  * /dev/random.  Should be enough to do a significant reseed.
305  */
306 static int random_read_wakeup_bits = 64;
307 
308 /*
309  * If the entropy count falls under this number of bits, then we
310  * should wake up processes which are selecting or polling on write
311  * access to /dev/random.
312  */
313 static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
314 
315 /*
316  * The minimum number of seconds between urandom pool reseeding.  We
317  * do this to limit the amount of entropy that can be drained from the
318  * input pool even if there are heavy demands on /dev/urandom.
319  */
320 static int random_min_urandom_seed = 60;
321 
322 /*
323  * Originally, we used a primitive polynomial of degree .poolwords
324  * over GF(2).  The taps for various sizes are defined below.  They
325  * were chosen to be evenly spaced except for the last tap, which is 1
326  * to get the twisting happening as fast as possible.
327  *
328  * For the purposes of better mixing, we use the CRC-32 polynomial as
329  * well to make a (modified) twisted Generalized Feedback Shift
330  * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
331  * generators.  ACM Transactions on Modeling and Computer Simulation
332  * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
333  * GFSR generators II.  ACM Transactions on Modeling and Computer
334  * Simulation 4:254-266)
335  *
336  * Thanks to Colin Plumb for suggesting this.
337  *
338  * The mixing operation is much less sensitive than the output hash,
339  * where we use SHA-1.  All that we want of mixing operation is that
340  * it be a good non-cryptographic hash; i.e. it not produce collisions
341  * when fed "random" data of the sort we expect to see.  As long as
342  * the pool state differs for different inputs, we have preserved the
343  * input entropy and done a good job.  The fact that an intelligent
344  * attacker can construct inputs that will produce controlled
345  * alterations to the pool's state is not important because we don't
346  * consider such inputs to contribute any randomness.  The only
347  * property we need with respect to them is that the attacker can't
348  * increase his/her knowledge of the pool's state.  Since all
349  * additions are reversible (knowing the final state and the input,
350  * you can reconstruct the initial state), if an attacker has any
351  * uncertainty about the initial state, he/she can only shuffle that
352  * uncertainty about, but never cause any collisions (which would
353  * decrease the uncertainty).
354  *
355  * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
356  * Videau in their paper, "The Linux Pseudorandom Number Generator
357  * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
358  * paper, they point out that we are not using a true Twisted GFSR,
359  * since Matsumoto & Kurita used a trinomial feedback polynomial (that
360  * is, with only three taps, instead of the six that we are using).
361  * As a result, the resulting polynomial is neither primitive nor
362  * irreducible, and hence does not have a maximal period over
363  * GF(2**32).  They suggest a slight change to the generator
364  * polynomial which improves the resulting TGFSR polynomial to be
365  * irreducible, which we have made here.
366  */
367 static struct poolinfo {
368         int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
369 #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
370         int tap1, tap2, tap3, tap4, tap5;
371 } poolinfo_table[] = {
372         /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
373         /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
374         { S(128),       104,    76,     51,     25,     1 },
375         /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
376         /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
377         { S(32),        26,     19,     14,     7,      1 },
378 #if 0
379         /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
380         { S(2048),      1638,   1231,   819,    411,    1 },
381 
382         /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
383         { S(1024),      817,    615,    412,    204,    1 },
384 
385         /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
386         { S(1024),      819,    616,    410,    207,    2 },
387 
388         /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
389         { S(512),       411,    308,    208,    104,    1 },
390 
391         /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
392         { S(512),       409,    307,    206,    102,    2 },
393         /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
394         { S(512),       409,    309,    205,    103,    2 },
395 
396         /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
397         { S(256),       205,    155,    101,    52,     1 },
398 
399         /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
400         { S(128),       103,    78,     51,     27,     2 },
401 
402         /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
403         { S(64),        52,     39,     26,     14,     1 },
404 #endif
405 };
406 
407 /*
408  * Static global variables
409  */
410 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
411 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
412 static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
413 static struct fasync_struct *fasync;
414 
415 static DEFINE_SPINLOCK(random_ready_list_lock);
416 static LIST_HEAD(random_ready_list);
417 
418 struct crng_state {
419         __u32           state[16];
420         unsigned long   init_time;
421         spinlock_t      lock;
422 };
423 
424 struct crng_state primary_crng = {
425         .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
426 };
427 
428 /*
429  * crng_init =  0 --> Uninitialized
430  *              1 --> Initialized
431  *              2 --> Initialized from input_pool
432  *
433  * crng_init is protected by primary_crng->lock, and only increases
434  * its value (from 0->1->2).
435  */
436 static int crng_init = 0;
437 #define crng_ready() (likely(crng_init > 0))
438 static int crng_init_cnt = 0;
439 #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
440 static void _extract_crng(struct crng_state *crng,
441                           __u8 out[CHACHA20_BLOCK_SIZE]);
442 static void _crng_backtrack_protect(struct crng_state *crng,
443                                     __u8 tmp[CHACHA20_BLOCK_SIZE], int used);
444 static void process_random_ready_list(void);
445 
446 /**********************************************************************
447  *
448  * OS independent entropy store.   Here are the functions which handle
449  * storing entropy in an entropy pool.
450  *
451  **********************************************************************/
452 
453 struct entropy_store;
454 struct entropy_store {
455         /* read-only data: */
456         const struct poolinfo *poolinfo;
457         __u32 *pool;
458         const char *name;
459         struct entropy_store *pull;
460         struct work_struct push_work;
461 
462         /* read-write data: */
463         unsigned long last_pulled;
464         spinlock_t lock;
465         unsigned short add_ptr;
466         unsigned short input_rotate;
467         int entropy_count;
468         int entropy_total;
469         unsigned int initialized:1;
470         unsigned int limit:1;
471         unsigned int last_data_init:1;
472         __u8 last_data[EXTRACT_SIZE];
473 };
474 
475 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
476                                size_t nbytes, int min, int rsvd);
477 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
478                                 size_t nbytes, int fips);
479 
480 static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
481 static void push_to_pool(struct work_struct *work);
482 static __u32 input_pool_data[INPUT_POOL_WORDS];
483 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
484 
485 static struct entropy_store input_pool = {
486         .poolinfo = &poolinfo_table[0],
487         .name = "input",
488         .limit = 1,
489         .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
490         .pool = input_pool_data
491 };
492 
493 static struct entropy_store blocking_pool = {
494         .poolinfo = &poolinfo_table[1],
495         .name = "blocking",
496         .limit = 1,
497         .pull = &input_pool,
498         .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
499         .pool = blocking_pool_data,
500         .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
501                                         push_to_pool),
502 };
503 
504 static __u32 const twist_table[8] = {
505         0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
506         0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
507 
508 /*
509  * This function adds bytes into the entropy "pool".  It does not
510  * update the entropy estimate.  The caller should call
511  * credit_entropy_bits if this is appropriate.
512  *
513  * The pool is stirred with a primitive polynomial of the appropriate
514  * degree, and then twisted.  We twist by three bits at a time because
515  * it's cheap to do so and helps slightly in the expected case where
516  * the entropy is concentrated in the low-order bits.
517  */
518 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
519                             int nbytes)
520 {
521         unsigned long i, tap1, tap2, tap3, tap4, tap5;
522         int input_rotate;
523         int wordmask = r->poolinfo->poolwords - 1;
524         const char *bytes = in;
525         __u32 w;
526 
527         tap1 = r->poolinfo->tap1;
528         tap2 = r->poolinfo->tap2;
529         tap3 = r->poolinfo->tap3;
530         tap4 = r->poolinfo->tap4;
531         tap5 = r->poolinfo->tap5;
532 
533         input_rotate = r->input_rotate;
534         i = r->add_ptr;
535 
536         /* mix one byte at a time to simplify size handling and churn faster */
537         while (nbytes--) {
538                 w = rol32(*bytes++, input_rotate);
539                 i = (i - 1) & wordmask;
540 
541                 /* XOR in the various taps */
542                 w ^= r->pool[i];
543                 w ^= r->pool[(i + tap1) & wordmask];
544                 w ^= r->pool[(i + tap2) & wordmask];
545                 w ^= r->pool[(i + tap3) & wordmask];
546                 w ^= r->pool[(i + tap4) & wordmask];
547                 w ^= r->pool[(i + tap5) & wordmask];
548 
549                 /* Mix the result back in with a twist */
550                 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
551 
552                 /*
553                  * Normally, we add 7 bits of rotation to the pool.
554                  * At the beginning of the pool, add an extra 7 bits
555                  * rotation, so that successive passes spread the
556                  * input bits across the pool evenly.
557                  */
558                 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
559         }
560 
561         r->input_rotate = input_rotate;
562         r->add_ptr = i;
563 }
564 
565 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
566                              int nbytes)
567 {
568         trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
569         _mix_pool_bytes(r, in, nbytes);
570 }
571 
572 static void mix_pool_bytes(struct entropy_store *r, const void *in,
573                            int nbytes)
574 {
575         unsigned long flags;
576 
577         trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
578         spin_lock_irqsave(&r->lock, flags);
579         _mix_pool_bytes(r, in, nbytes);
580         spin_unlock_irqrestore(&r->lock, flags);
581 }
582 
583 struct fast_pool {
584         __u32           pool[4];
585         unsigned long   last;
586         unsigned short  reg_idx;
587         unsigned char   count;
588 };
589 
590 /*
591  * This is a fast mixing routine used by the interrupt randomness
592  * collector.  It's hardcoded for an 128 bit pool and assumes that any
593  * locks that might be needed are taken by the caller.
594  */
595 static void fast_mix(struct fast_pool *f)
596 {
597         __u32 a = f->pool[0],   b = f->pool[1];
598         __u32 c = f->pool[2],   d = f->pool[3];
599 
600         a += b;                 c += d;
601         b = rol32(b, 6);        d = rol32(d, 27);
602         d ^= a;                 b ^= c;
603 
604         a += b;                 c += d;
605         b = rol32(b, 16);       d = rol32(d, 14);
606         d ^= a;                 b ^= c;
607 
608         a += b;                 c += d;
609         b = rol32(b, 6);        d = rol32(d, 27);
610         d ^= a;                 b ^= c;
611 
612         a += b;                 c += d;
613         b = rol32(b, 16);       d = rol32(d, 14);
614         d ^= a;                 b ^= c;
615 
616         f->pool[0] = a;  f->pool[1] = b;
617         f->pool[2] = c;  f->pool[3] = d;
618         f->count++;
619 }
620 
621 static void process_random_ready_list(void)
622 {
623         unsigned long flags;
624         struct random_ready_callback *rdy, *tmp;
625 
626         spin_lock_irqsave(&random_ready_list_lock, flags);
627         list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
628                 struct module *owner = rdy->owner;
629 
630                 list_del_init(&rdy->list);
631                 rdy->func(rdy);
632                 module_put(owner);
633         }
634         spin_unlock_irqrestore(&random_ready_list_lock, flags);
635 }
636 
637 /*
638  * Credit (or debit) the entropy store with n bits of entropy.
639  * Use credit_entropy_bits_safe() if the value comes from userspace
640  * or otherwise should be checked for extreme values.
641  */
642 static void credit_entropy_bits(struct entropy_store *r, int nbits)
643 {
644         int entropy_count, orig;
645         const int pool_size = r->poolinfo->poolfracbits;
646         int nfrac = nbits << ENTROPY_SHIFT;
647 
648         if (!nbits)
649                 return;
650 
651 retry:
652         entropy_count = orig = ACCESS_ONCE(r->entropy_count);
653         if (nfrac < 0) {
654                 /* Debit */
655                 entropy_count += nfrac;
656         } else {
657                 /*
658                  * Credit: we have to account for the possibility of
659                  * overwriting already present entropy.  Even in the
660                  * ideal case of pure Shannon entropy, new contributions
661                  * approach the full value asymptotically:
662                  *
663                  * entropy <- entropy + (pool_size - entropy) *
664                  *      (1 - exp(-add_entropy/pool_size))
665                  *
666                  * For add_entropy <= pool_size/2 then
667                  * (1 - exp(-add_entropy/pool_size)) >=
668                  *    (add_entropy/pool_size)*0.7869...
669                  * so we can approximate the exponential with
670                  * 3/4*add_entropy/pool_size and still be on the
671                  * safe side by adding at most pool_size/2 at a time.
672                  *
673                  * The use of pool_size-2 in the while statement is to
674                  * prevent rounding artifacts from making the loop
675                  * arbitrarily long; this limits the loop to log2(pool_size)*2
676                  * turns no matter how large nbits is.
677                  */
678                 int pnfrac = nfrac;
679                 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
680                 /* The +2 corresponds to the /4 in the denominator */
681 
682                 do {
683                         unsigned int anfrac = min(pnfrac, pool_size/2);
684                         unsigned int add =
685                                 ((pool_size - entropy_count)*anfrac*3) >> s;
686 
687                         entropy_count += add;
688                         pnfrac -= anfrac;
689                 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
690         }
691 
692         if (unlikely(entropy_count < 0)) {
693                 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
694                         r->name, entropy_count);
695                 WARN_ON(1);
696                 entropy_count = 0;
697         } else if (entropy_count > pool_size)
698                 entropy_count = pool_size;
699         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
700                 goto retry;
701 
702         r->entropy_total += nbits;
703         if (!r->initialized && r->entropy_total > 128) {
704                 r->initialized = 1;
705                 r->entropy_total = 0;
706         }
707 
708         trace_credit_entropy_bits(r->name, nbits,
709                                   entropy_count >> ENTROPY_SHIFT,
710                                   r->entropy_total, _RET_IP_);
711 
712         if (r == &input_pool) {
713                 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
714 
715                 if (crng_init < 2 && entropy_bits >= 128) {
716                         crng_reseed(&primary_crng, r);
717                         entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
718                 }
719 
720                 /* should we wake readers? */
721                 if (entropy_bits >= random_read_wakeup_bits) {
722                         wake_up_interruptible(&random_read_wait);
723                         kill_fasync(&fasync, SIGIO, POLL_IN);
724                 }
725                 /* If the input pool is getting full, send some
726                  * entropy to the blocking pool until it is 75% full.
727                  */
728                 if (entropy_bits > random_write_wakeup_bits &&
729                     r->initialized &&
730                     r->entropy_total >= 2*random_read_wakeup_bits) {
731                         struct entropy_store *other = &blocking_pool;
732 
733                         if (other->entropy_count <=
734                             3 * other->poolinfo->poolfracbits / 4) {
735                                 schedule_work(&other->push_work);
736                                 r->entropy_total = 0;
737                         }
738                 }
739         }
740 }
741 
742 static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
743 {
744         const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
745 
746         if (nbits < 0)
747                 return -EINVAL;
748 
749         /* Cap the value to avoid overflows */
750         nbits = min(nbits,  nbits_max);
751 
752         credit_entropy_bits(r, nbits);
753         return 0;
754 }
755 
756 /*********************************************************************
757  *
758  * CRNG using CHACHA20
759  *
760  *********************************************************************/
761 
762 #define CRNG_RESEED_INTERVAL (300*HZ)
763 
764 static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
765 
766 #ifdef CONFIG_NUMA
767 /*
768  * Hack to deal with crazy userspace progams when they are all trying
769  * to access /dev/urandom in parallel.  The programs are almost
770  * certainly doing something terribly wrong, but we'll work around
771  * their brain damage.
772  */
773 static struct crng_state **crng_node_pool __read_mostly;
774 #endif
775 
776 static void crng_initialize(struct crng_state *crng)
777 {
778         int             i;
779         unsigned long   rv;
780 
781         memcpy(&crng->state[0], "expand 32-byte k", 16);
782         if (crng == &primary_crng)
783                 _extract_entropy(&input_pool, &crng->state[4],
784                                  sizeof(__u32) * 12, 0);
785         else
786                 get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
787         for (i = 4; i < 16; i++) {
788                 if (!arch_get_random_seed_long(&rv) &&
789                     !arch_get_random_long(&rv))
790                         rv = random_get_entropy();
791                 crng->state[i] ^= rv;
792         }
793         crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
794 }
795 
796 static int crng_fast_load(const char *cp, size_t len)
797 {
798         unsigned long flags;
799         char *p;
800 
801         if (!spin_trylock_irqsave(&primary_crng.lock, flags))
802                 return 0;
803         if (crng_ready()) {
804                 spin_unlock_irqrestore(&primary_crng.lock, flags);
805                 return 0;
806         }
807         p = (unsigned char *) &primary_crng.state[4];
808         while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
809                 p[crng_init_cnt % CHACHA20_KEY_SIZE] ^= *cp;
810                 cp++; crng_init_cnt++; len--;
811         }
812         if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
813                 crng_init = 1;
814                 wake_up_interruptible(&crng_init_wait);
815                 pr_notice("random: fast init done\n");
816         }
817         spin_unlock_irqrestore(&primary_crng.lock, flags);
818         return 1;
819 }
820 
821 static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
822 {
823         unsigned long   flags;
824         int             i, num;
825         union {
826                 __u8    block[CHACHA20_BLOCK_SIZE];
827                 __u32   key[8];
828         } buf;
829 
830         if (r) {
831                 num = extract_entropy(r, &buf, 32, 16, 0);
832                 if (num == 0)
833                         return;
834         } else {
835                 _extract_crng(&primary_crng, buf.block);
836                 _crng_backtrack_protect(&primary_crng, buf.block,
837                                         CHACHA20_KEY_SIZE);
838         }
839         spin_lock_irqsave(&primary_crng.lock, flags);
840         for (i = 0; i < 8; i++) {
841                 unsigned long   rv;
842                 if (!arch_get_random_seed_long(&rv) &&
843                     !arch_get_random_long(&rv))
844                         rv = random_get_entropy();
845                 crng->state[i+4] ^= buf.key[i] ^ rv;
846         }
847         memzero_explicit(&buf, sizeof(buf));
848         crng->init_time = jiffies;
849         if (crng == &primary_crng && crng_init < 2) {
850                 crng_init = 2;
851                 process_random_ready_list();
852                 wake_up_interruptible(&crng_init_wait);
853                 pr_notice("random: crng init done\n");
854         }
855         spin_unlock_irqrestore(&primary_crng.lock, flags);
856 }
857 
858 static inline void maybe_reseed_primary_crng(void)
859 {
860         if (crng_init > 2 &&
861             time_after(jiffies, primary_crng.init_time + CRNG_RESEED_INTERVAL))
862                 crng_reseed(&primary_crng, &input_pool);
863 }
864 
865 static inline void crng_wait_ready(void)
866 {
867         wait_event_interruptible(crng_init_wait, crng_ready());
868 }
869 
870 static void _extract_crng(struct crng_state *crng,
871                           __u8 out[CHACHA20_BLOCK_SIZE])
872 {
873         unsigned long v, flags;
874 
875         if (crng_init > 1 &&
876             time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))
877                 crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
878         spin_lock_irqsave(&crng->lock, flags);
879         if (arch_get_random_long(&v))
880                 crng->state[14] ^= v;
881         chacha20_block(&crng->state[0], out);
882         if (crng->state[12] == 0)
883                 crng->state[13]++;
884         spin_unlock_irqrestore(&crng->lock, flags);
885 }
886 
887 static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE])
888 {
889         struct crng_state *crng = NULL;
890 
891 #ifdef CONFIG_NUMA
892         if (crng_node_pool)
893                 crng = crng_node_pool[numa_node_id()];
894         if (crng == NULL)
895 #endif
896                 crng = &primary_crng;
897         _extract_crng(crng, out);
898 }
899 
900 /*
901  * Use the leftover bytes from the CRNG block output (if there is
902  * enough) to mutate the CRNG key to provide backtracking protection.
903  */
904 static void _crng_backtrack_protect(struct crng_state *crng,
905                                     __u8 tmp[CHACHA20_BLOCK_SIZE], int used)
906 {
907         unsigned long   flags;
908         __u32           *s, *d;
909         int             i;
910 
911         used = round_up(used, sizeof(__u32));
912         if (used + CHACHA20_KEY_SIZE > CHACHA20_BLOCK_SIZE) {
913                 extract_crng(tmp);
914                 used = 0;
915         }
916         spin_lock_irqsave(&crng->lock, flags);
917         s = (__u32 *) &tmp[used];
918         d = &crng->state[4];
919         for (i=0; i < 8; i++)
920                 *d++ ^= *s++;
921         spin_unlock_irqrestore(&crng->lock, flags);
922 }
923 
924 static void crng_backtrack_protect(__u8 tmp[CHACHA20_BLOCK_SIZE], int used)
925 {
926         struct crng_state *crng = NULL;
927 
928 #ifdef CONFIG_NUMA
929         if (crng_node_pool)
930                 crng = crng_node_pool[numa_node_id()];
931         if (crng == NULL)
932 #endif
933                 crng = &primary_crng;
934         _crng_backtrack_protect(crng, tmp, used);
935 }
936 
937 static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
938 {
939         ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
940         __u8 tmp[CHACHA20_BLOCK_SIZE];
941         int large_request = (nbytes > 256);
942 
943         while (nbytes) {
944                 if (large_request && need_resched()) {
945                         if (signal_pending(current)) {
946                                 if (ret == 0)
947                                         ret = -ERESTARTSYS;
948                                 break;
949                         }
950                         schedule();
951                 }
952 
953                 extract_crng(tmp);
954                 i = min_t(int, nbytes, CHACHA20_BLOCK_SIZE);
955                 if (copy_to_user(buf, tmp, i)) {
956                         ret = -EFAULT;
957                         break;
958                 }
959 
960                 nbytes -= i;
961                 buf += i;
962                 ret += i;
963         }
964         crng_backtrack_protect(tmp, i);
965 
966         /* Wipe data just written to memory */
967         memzero_explicit(tmp, sizeof(tmp));
968 
969         return ret;
970 }
971 
972 
973 /*********************************************************************
974  *
975  * Entropy input management
976  *
977  *********************************************************************/
978 
979 /* There is one of these per entropy source */
980 struct timer_rand_state {
981         cycles_t last_time;
982         long last_delta, last_delta2;
983         unsigned dont_count_entropy:1;
984 };
985 
986 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
987 
988 /*
989  * Add device- or boot-specific data to the input pool to help
990  * initialize it.
991  *
992  * None of this adds any entropy; it is meant to avoid the problem of
993  * the entropy pool having similar initial state across largely
994  * identical devices.
995  */
996 void add_device_randomness(const void *buf, unsigned int size)
997 {
998         unsigned long time = random_get_entropy() ^ jiffies;
999         unsigned long flags;
1000 
1001         trace_add_device_randomness(size, _RET_IP_);
1002         spin_lock_irqsave(&input_pool.lock, flags);
1003         _mix_pool_bytes(&input_pool, buf, size);
1004         _mix_pool_bytes(&input_pool, &time, sizeof(time));
1005         spin_unlock_irqrestore(&input_pool.lock, flags);
1006 }
1007 EXPORT_SYMBOL(add_device_randomness);
1008 
1009 static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1010 
1011 /*
1012  * This function adds entropy to the entropy "pool" by using timing
1013  * delays.  It uses the timer_rand_state structure to make an estimate
1014  * of how many bits of entropy this call has added to the pool.
1015  *
1016  * The number "num" is also added to the pool - it should somehow describe
1017  * the type of event which just happened.  This is currently 0-255 for
1018  * keyboard scan codes, and 256 upwards for interrupts.
1019  *
1020  */
1021 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1022 {
1023         struct entropy_store    *r;
1024         struct {
1025                 long jiffies;
1026                 unsigned cycles;
1027                 unsigned num;
1028         } sample;
1029         long delta, delta2, delta3;
1030 
1031         preempt_disable();
1032 
1033         sample.jiffies = jiffies;
1034         sample.cycles = random_get_entropy();
1035         sample.num = num;
1036         r = &input_pool;
1037         mix_pool_bytes(r, &sample, sizeof(sample));
1038 
1039         /*
1040          * Calculate number of bits of randomness we probably added.
1041          * We take into account the first, second and third-order deltas
1042          * in order to make our estimate.
1043          */
1044 
1045         if (!state->dont_count_entropy) {
1046                 delta = sample.jiffies - state->last_time;
1047                 state->last_time = sample.jiffies;
1048 
1049                 delta2 = delta - state->last_delta;
1050                 state->last_delta = delta;
1051 
1052                 delta3 = delta2 - state->last_delta2;
1053                 state->last_delta2 = delta2;
1054 
1055                 if (delta < 0)
1056                         delta = -delta;
1057                 if (delta2 < 0)
1058                         delta2 = -delta2;
1059                 if (delta3 < 0)
1060                         delta3 = -delta3;
1061                 if (delta > delta2)
1062                         delta = delta2;
1063                 if (delta > delta3)
1064                         delta = delta3;
1065 
1066                 /*
1067                  * delta is now minimum absolute delta.
1068                  * Round down by 1 bit on general principles,
1069                  * and limit entropy entimate to 12 bits.
1070                  */
1071                 credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1072         }
1073         preempt_enable();
1074 }
1075 
1076 void add_input_randomness(unsigned int type, unsigned int code,
1077                                  unsigned int value)
1078 {
1079         static unsigned char last_value;
1080 
1081         /* ignore autorepeat and the like */
1082         if (value == last_value)
1083                 return;
1084 
1085         last_value = value;
1086         add_timer_randomness(&input_timer_state,
1087                              (type << 4) ^ code ^ (code >> 4) ^ value);
1088         trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1089 }
1090 EXPORT_SYMBOL_GPL(add_input_randomness);
1091 
1092 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1093 
1094 #ifdef ADD_INTERRUPT_BENCH
1095 static unsigned long avg_cycles, avg_deviation;
1096 
1097 #define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
1098 #define FIXED_1_2 (1 << (AVG_SHIFT-1))
1099 
1100 static void add_interrupt_bench(cycles_t start)
1101 {
1102         long delta = random_get_entropy() - start;
1103 
1104         /* Use a weighted moving average */
1105         delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1106         avg_cycles += delta;
1107         /* And average deviation */
1108         delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1109         avg_deviation += delta;
1110 }
1111 #else
1112 #define add_interrupt_bench(x)
1113 #endif
1114 
1115 static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1116 {
1117         __u32 *ptr = (__u32 *) regs;
1118 
1119         if (regs == NULL)
1120                 return 0;
1121         if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
1122                 f->reg_idx = 0;
1123         return *(ptr + f->reg_idx++);
1124 }
1125 
1126 void add_interrupt_randomness(int irq, int irq_flags)
1127 {
1128         struct entropy_store    *r;
1129         struct fast_pool        *fast_pool = this_cpu_ptr(&irq_randomness);
1130         struct pt_regs          *regs = get_irq_regs();
1131         unsigned long           now = jiffies;
1132         cycles_t                cycles = random_get_entropy();
1133         __u32                   c_high, j_high;
1134         __u64                   ip;
1135         unsigned long           seed;
1136         int                     credit = 0;
1137 
1138         if (cycles == 0)
1139                 cycles = get_reg(fast_pool, regs);
1140         c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1141         j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1142         fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1143         fast_pool->pool[1] ^= now ^ c_high;
1144         ip = regs ? instruction_pointer(regs) : _RET_IP_;
1145         fast_pool->pool[2] ^= ip;
1146         fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1147                 get_reg(fast_pool, regs);
1148 
1149         fast_mix(fast_pool);
1150         add_interrupt_bench(cycles);
1151 
1152         if (!crng_ready()) {
1153                 if ((fast_pool->count >= 64) &&
1154                     crng_fast_load((char *) fast_pool->pool,
1155                                    sizeof(fast_pool->pool))) {
1156                         fast_pool->count = 0;
1157                         fast_pool->last = now;
1158                 }
1159                 return;
1160         }
1161 
1162         if ((fast_pool->count < 64) &&
1163             !time_after(now, fast_pool->last + HZ))
1164                 return;
1165 
1166         r = &input_pool;
1167         if (!spin_trylock(&r->lock))
1168                 return;
1169 
1170         fast_pool->last = now;
1171         __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1172 
1173         /*
1174          * If we have architectural seed generator, produce a seed and
1175          * add it to the pool.  For the sake of paranoia don't let the
1176          * architectural seed generator dominate the input from the
1177          * interrupt noise.
1178          */
1179         if (arch_get_random_seed_long(&seed)) {
1180                 __mix_pool_bytes(r, &seed, sizeof(seed));
1181                 credit = 1;
1182         }
1183         spin_unlock(&r->lock);
1184 
1185         fast_pool->count = 0;
1186 
1187         /* award one bit for the contents of the fast pool */
1188         credit_entropy_bits(r, credit + 1);
1189 }
1190 EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1191 
1192 #ifdef CONFIG_BLOCK
1193 void add_disk_randomness(struct gendisk *disk)
1194 {
1195         if (!disk || !disk->random)
1196                 return;
1197         /* first major is 1, so we get >= 0x200 here */
1198         add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1199         trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1200 }
1201 EXPORT_SYMBOL_GPL(add_disk_randomness);
1202 #endif
1203 
1204 /*********************************************************************
1205  *
1206  * Entropy extraction routines
1207  *
1208  *********************************************************************/
1209 
1210 /*
1211  * This utility inline function is responsible for transferring entropy
1212  * from the primary pool to the secondary extraction pool. We make
1213  * sure we pull enough for a 'catastrophic reseed'.
1214  */
1215 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1216 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1217 {
1218         if (!r->pull ||
1219             r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
1220             r->entropy_count > r->poolinfo->poolfracbits)
1221                 return;
1222 
1223         if (r->limit == 0 && random_min_urandom_seed) {
1224                 unsigned long now = jiffies;
1225 
1226                 if (time_before(now,
1227                                 r->last_pulled + random_min_urandom_seed * HZ))
1228                         return;
1229                 r->last_pulled = now;
1230         }
1231 
1232         _xfer_secondary_pool(r, nbytes);
1233 }
1234 
1235 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1236 {
1237         __u32   tmp[OUTPUT_POOL_WORDS];
1238 
1239         /* For /dev/random's pool, always leave two wakeups' worth */
1240         int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
1241         int bytes = nbytes;
1242 
1243         /* pull at least as much as a wakeup */
1244         bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1245         /* but never more than the buffer size */
1246         bytes = min_t(int, bytes, sizeof(tmp));
1247 
1248         trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1249                                   ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1250         bytes = extract_entropy(r->pull, tmp, bytes,
1251                                 random_read_wakeup_bits / 8, rsvd_bytes);
1252         mix_pool_bytes(r, tmp, bytes);
1253         credit_entropy_bits(r, bytes*8);
1254 }
1255 
1256 /*
1257  * Used as a workqueue function so that when the input pool is getting
1258  * full, we can "spill over" some entropy to the output pools.  That
1259  * way the output pools can store some of the excess entropy instead
1260  * of letting it go to waste.
1261  */
1262 static void push_to_pool(struct work_struct *work)
1263 {
1264         struct entropy_store *r = container_of(work, struct entropy_store,
1265                                               push_work);
1266         BUG_ON(!r);
1267         _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1268         trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1269                            r->pull->entropy_count >> ENTROPY_SHIFT);
1270 }
1271 
1272 /*
1273  * This function decides how many bytes to actually take from the
1274  * given pool, and also debits the entropy count accordingly.
1275  */
1276 static size_t account(struct entropy_store *r, size_t nbytes, int min,
1277                       int reserved)
1278 {
1279         int entropy_count, orig;
1280         size_t ibytes, nfrac;
1281 
1282         BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1283 
1284         /* Can we pull enough? */
1285 retry:
1286         entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1287         ibytes = nbytes;
1288         /* If limited, never pull more than available */
1289         if (r->limit) {
1290                 int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1291 
1292                 if ((have_bytes -= reserved) < 0)
1293                         have_bytes = 0;
1294                 ibytes = min_t(size_t, ibytes, have_bytes);
1295         }
1296         if (ibytes < min)
1297                 ibytes = 0;
1298 
1299         if (unlikely(entropy_count < 0)) {
1300                 pr_warn("random: negative entropy count: pool %s count %d\n",
1301                         r->name, entropy_count);
1302                 WARN_ON(1);
1303                 entropy_count = 0;
1304         }
1305         nfrac = ibytes << (ENTROPY_SHIFT + 3);
1306         if ((size_t) entropy_count > nfrac)
1307                 entropy_count -= nfrac;
1308         else
1309                 entropy_count = 0;
1310 
1311         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1312                 goto retry;
1313 
1314         trace_debit_entropy(r->name, 8 * ibytes);
1315         if (ibytes &&
1316             (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1317                 wake_up_interruptible(&random_write_wait);
1318                 kill_fasync(&fasync, SIGIO, POLL_OUT);
1319         }
1320 
1321         return ibytes;
1322 }
1323 
1324 /*
1325  * This function does the actual extraction for extract_entropy and
1326  * extract_entropy_user.
1327  *
1328  * Note: we assume that .poolwords is a multiple of 16 words.
1329  */
1330 static void extract_buf(struct entropy_store *r, __u8 *out)
1331 {
1332         int i;
1333         union {
1334                 __u32 w[5];
1335                 unsigned long l[LONGS(20)];
1336         } hash;
1337         __u32 workspace[SHA_WORKSPACE_WORDS];
1338         unsigned long flags;
1339 
1340         /*
1341          * If we have an architectural hardware random number
1342          * generator, use it for SHA's initial vector
1343          */
1344         sha_init(hash.w);
1345         for (i = 0; i < LONGS(20); i++) {
1346                 unsigned long v;
1347                 if (!arch_get_random_long(&v))
1348                         break;
1349                 hash.l[i] = v;
1350         }
1351 
1352         /* Generate a hash across the pool, 16 words (512 bits) at a time */
1353         spin_lock_irqsave(&r->lock, flags);
1354         for (i = 0; i < r->poolinfo->poolwords; i += 16)
1355                 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1356 
1357         /*
1358          * We mix the hash back into the pool to prevent backtracking
1359          * attacks (where the attacker knows the state of the pool
1360          * plus the current outputs, and attempts to find previous
1361          * ouputs), unless the hash function can be inverted. By
1362          * mixing at least a SHA1 worth of hash data back, we make
1363          * brute-forcing the feedback as hard as brute-forcing the
1364          * hash.
1365          */
1366         __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1367         spin_unlock_irqrestore(&r->lock, flags);
1368 
1369         memzero_explicit(workspace, sizeof(workspace));
1370 
1371         /*
1372          * In case the hash function has some recognizable output
1373          * pattern, we fold it in half. Thus, we always feed back
1374          * twice as much data as we output.
1375          */
1376         hash.w[0] ^= hash.w[3];
1377         hash.w[1] ^= hash.w[4];
1378         hash.w[2] ^= rol32(hash.w[2], 16);
1379 
1380         memcpy(out, &hash, EXTRACT_SIZE);
1381         memzero_explicit(&hash, sizeof(hash));
1382 }
1383 
1384 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1385                                 size_t nbytes, int fips)
1386 {
1387         ssize_t ret = 0, i;
1388         __u8 tmp[EXTRACT_SIZE];
1389         unsigned long flags;
1390 
1391         while (nbytes) {
1392                 extract_buf(r, tmp);
1393 
1394                 if (fips) {
1395                         spin_lock_irqsave(&r->lock, flags);
1396                         if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1397                                 panic("Hardware RNG duplicated output!\n");
1398                         memcpy(r->last_data, tmp, EXTRACT_SIZE);
1399                         spin_unlock_irqrestore(&r->lock, flags);
1400                 }
1401                 i = min_t(int, nbytes, EXTRACT_SIZE);
1402                 memcpy(buf, tmp, i);
1403                 nbytes -= i;
1404                 buf += i;
1405                 ret += i;
1406         }
1407 
1408         /* Wipe data just returned from memory */
1409         memzero_explicit(tmp, sizeof(tmp));
1410 
1411         return ret;
1412 }
1413 
1414 /*
1415  * This function extracts randomness from the "entropy pool", and
1416  * returns it in a buffer.
1417  *
1418  * The min parameter specifies the minimum amount we can pull before
1419  * failing to avoid races that defeat catastrophic reseeding while the
1420  * reserved parameter indicates how much entropy we must leave in the
1421  * pool after each pull to avoid starving other readers.
1422  */
1423 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1424                                  size_t nbytes, int min, int reserved)
1425 {
1426         __u8 tmp[EXTRACT_SIZE];
1427         unsigned long flags;
1428 
1429         /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1430         if (fips_enabled) {
1431                 spin_lock_irqsave(&r->lock, flags);
1432                 if (!r->last_data_init) {
1433                         r->last_data_init = 1;
1434                         spin_unlock_irqrestore(&r->lock, flags);
1435                         trace_extract_entropy(r->name, EXTRACT_SIZE,
1436                                               ENTROPY_BITS(r), _RET_IP_);
1437                         xfer_secondary_pool(r, EXTRACT_SIZE);
1438                         extract_buf(r, tmp);
1439                         spin_lock_irqsave(&r->lock, flags);
1440                         memcpy(r->last_data, tmp, EXTRACT_SIZE);
1441                 }
1442                 spin_unlock_irqrestore(&r->lock, flags);
1443         }
1444 
1445         trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1446         xfer_secondary_pool(r, nbytes);
1447         nbytes = account(r, nbytes, min, reserved);
1448 
1449         return _extract_entropy(r, buf, nbytes, fips_enabled);
1450 }
1451 
1452 /*
1453  * This function extracts randomness from the "entropy pool", and
1454  * returns it in a userspace buffer.
1455  */
1456 static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1457                                     size_t nbytes)
1458 {
1459         ssize_t ret = 0, i;
1460         __u8 tmp[EXTRACT_SIZE];
1461         int large_request = (nbytes > 256);
1462 
1463         trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1464         xfer_secondary_pool(r, nbytes);
1465         nbytes = account(r, nbytes, 0, 0);
1466 
1467         while (nbytes) {
1468                 if (large_request && need_resched()) {
1469                         if (signal_pending(current)) {
1470                                 if (ret == 0)
1471                                         ret = -ERESTARTSYS;
1472                                 break;
1473                         }
1474                         schedule();
1475                 }
1476 
1477                 extract_buf(r, tmp);
1478                 i = min_t(int, nbytes, EXTRACT_SIZE);
1479                 if (copy_to_user(buf, tmp, i)) {
1480                         ret = -EFAULT;
1481                         break;
1482                 }
1483 
1484                 nbytes -= i;
1485                 buf += i;
1486                 ret += i;
1487         }
1488 
1489         /* Wipe data just returned from memory */
1490         memzero_explicit(tmp, sizeof(tmp));
1491 
1492         return ret;
1493 }
1494 
1495 /*
1496  * This function is the exported kernel interface.  It returns some
1497  * number of good random numbers, suitable for key generation, seeding
1498  * TCP sequence numbers, etc.  It does not rely on the hardware random
1499  * number generator.  For random bytes direct from the hardware RNG
1500  * (when available), use get_random_bytes_arch().
1501  */
1502 void get_random_bytes(void *buf, int nbytes)
1503 {
1504         __u8 tmp[CHACHA20_BLOCK_SIZE];
1505 
1506 #if DEBUG_RANDOM_BOOT > 0
1507         if (!crng_ready())
1508                 printk(KERN_NOTICE "random: %pF get_random_bytes called "
1509                        "with crng_init = %d\n", (void *) _RET_IP_, crng_init);
1510 #endif
1511         trace_get_random_bytes(nbytes, _RET_IP_);
1512 
1513         while (nbytes >= CHACHA20_BLOCK_SIZE) {
1514                 extract_crng(buf);
1515                 buf += CHACHA20_BLOCK_SIZE;
1516                 nbytes -= CHACHA20_BLOCK_SIZE;
1517         }
1518 
1519         if (nbytes > 0) {
1520                 extract_crng(tmp);
1521                 memcpy(buf, tmp, nbytes);
1522                 crng_backtrack_protect(tmp, nbytes);
1523         } else
1524                 crng_backtrack_protect(tmp, CHACHA20_BLOCK_SIZE);
1525         memzero_explicit(tmp, sizeof(tmp));
1526 }
1527 EXPORT_SYMBOL(get_random_bytes);
1528 
1529 /*
1530  * Add a callback function that will be invoked when the nonblocking
1531  * pool is initialised.
1532  *
1533  * returns: 0 if callback is successfully added
1534  *          -EALREADY if pool is already initialised (callback not called)
1535  *          -ENOENT if module for callback is not alive
1536  */
1537 int add_random_ready_callback(struct random_ready_callback *rdy)
1538 {
1539         struct module *owner;
1540         unsigned long flags;
1541         int err = -EALREADY;
1542 
1543         if (crng_ready())
1544                 return err;
1545 
1546         owner = rdy->owner;
1547         if (!try_module_get(owner))
1548                 return -ENOENT;
1549 
1550         spin_lock_irqsave(&random_ready_list_lock, flags);
1551         if (crng_ready())
1552                 goto out;
1553 
1554         owner = NULL;
1555 
1556         list_add(&rdy->list, &random_ready_list);
1557         err = 0;
1558 
1559 out:
1560         spin_unlock_irqrestore(&random_ready_list_lock, flags);
1561 
1562         module_put(owner);
1563 
1564         return err;
1565 }
1566 EXPORT_SYMBOL(add_random_ready_callback);
1567 
1568 /*
1569  * Delete a previously registered readiness callback function.
1570  */
1571 void del_random_ready_callback(struct random_ready_callback *rdy)
1572 {
1573         unsigned long flags;
1574         struct module *owner = NULL;
1575 
1576         spin_lock_irqsave(&random_ready_list_lock, flags);
1577         if (!list_empty(&rdy->list)) {
1578                 list_del_init(&rdy->list);
1579                 owner = rdy->owner;
1580         }
1581         spin_unlock_irqrestore(&random_ready_list_lock, flags);
1582 
1583         module_put(owner);
1584 }
1585 EXPORT_SYMBOL(del_random_ready_callback);
1586 
1587 /*
1588  * This function will use the architecture-specific hardware random
1589  * number generator if it is available.  The arch-specific hw RNG will
1590  * almost certainly be faster than what we can do in software, but it
1591  * is impossible to verify that it is implemented securely (as
1592  * opposed, to, say, the AES encryption of a sequence number using a
1593  * key known by the NSA).  So it's useful if we need the speed, but
1594  * only if we're willing to trust the hardware manufacturer not to
1595  * have put in a back door.
1596  */
1597 void get_random_bytes_arch(void *buf, int nbytes)
1598 {
1599         char *p = buf;
1600 
1601         trace_get_random_bytes_arch(nbytes, _RET_IP_);
1602         while (nbytes) {
1603                 unsigned long v;
1604                 int chunk = min(nbytes, (int)sizeof(unsigned long));
1605 
1606                 if (!arch_get_random_long(&v))
1607                         break;
1608                 
1609                 memcpy(p, &v, chunk);
1610                 p += chunk;
1611                 nbytes -= chunk;
1612         }
1613 
1614         if (nbytes)
1615                 get_random_bytes(p, nbytes);
1616 }
1617 EXPORT_SYMBOL(get_random_bytes_arch);
1618 
1619 
1620 /*
1621  * init_std_data - initialize pool with system data
1622  *
1623  * @r: pool to initialize
1624  *
1625  * This function clears the pool's entropy count and mixes some system
1626  * data into the pool to prepare it for use. The pool is not cleared
1627  * as that can only decrease the entropy in the pool.
1628  */
1629 static void init_std_data(struct entropy_store *r)
1630 {
1631         int i;
1632         ktime_t now = ktime_get_real();
1633         unsigned long rv;
1634 
1635         r->last_pulled = jiffies;
1636         mix_pool_bytes(r, &now, sizeof(now));
1637         for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1638                 if (!arch_get_random_seed_long(&rv) &&
1639                     !arch_get_random_long(&rv))
1640                         rv = random_get_entropy();
1641                 mix_pool_bytes(r, &rv, sizeof(rv));
1642         }
1643         mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1644 }
1645 
1646 /*
1647  * Note that setup_arch() may call add_device_randomness()
1648  * long before we get here. This allows seeding of the pools
1649  * with some platform dependent data very early in the boot
1650  * process. But it limits our options here. We must use
1651  * statically allocated structures that already have all
1652  * initializations complete at compile time. We should also
1653  * take care not to overwrite the precious per platform data
1654  * we were given.
1655  */
1656 static int rand_initialize(void)
1657 {
1658 #ifdef CONFIG_NUMA
1659         int i;
1660         struct crng_state *crng;
1661         struct crng_state **pool;
1662 #endif
1663 
1664         init_std_data(&input_pool);
1665         init_std_data(&blocking_pool);
1666         crng_initialize(&primary_crng);
1667 
1668 #ifdef CONFIG_NUMA
1669         pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
1670         for_each_online_node(i) {
1671                 crng = kmalloc_node(sizeof(struct crng_state),
1672                                     GFP_KERNEL | __GFP_NOFAIL, i);
1673                 spin_lock_init(&crng->lock);
1674                 crng_initialize(crng);
1675                 pool[i] = crng;
1676         }
1677         mb();
1678         crng_node_pool = pool;
1679 #endif
1680         return 0;
1681 }
1682 early_initcall(rand_initialize);
1683 
1684 #ifdef CONFIG_BLOCK
1685 void rand_initialize_disk(struct gendisk *disk)
1686 {
1687         struct timer_rand_state *state;
1688 
1689         /*
1690          * If kzalloc returns null, we just won't use that entropy
1691          * source.
1692          */
1693         state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1694         if (state) {
1695                 state->last_time = INITIAL_JIFFIES;
1696                 disk->random = state;
1697         }
1698 }
1699 #endif
1700 
1701 static ssize_t
1702 _random_read(int nonblock, char __user *buf, size_t nbytes)
1703 {
1704         ssize_t n;
1705 
1706         if (nbytes == 0)
1707                 return 0;
1708 
1709         nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1710         while (1) {
1711                 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1712                 if (n < 0)
1713                         return n;
1714                 trace_random_read(n*8, (nbytes-n)*8,
1715                                   ENTROPY_BITS(&blocking_pool),
1716                                   ENTROPY_BITS(&input_pool));
1717                 if (n > 0)
1718                         return n;
1719 
1720                 /* Pool is (near) empty.  Maybe wait and retry. */
1721                 if (nonblock)
1722                         return -EAGAIN;
1723 
1724                 wait_event_interruptible(random_read_wait,
1725                         ENTROPY_BITS(&input_pool) >=
1726                         random_read_wakeup_bits);
1727                 if (signal_pending(current))
1728                         return -ERESTARTSYS;
1729         }
1730 }
1731 
1732 static ssize_t
1733 random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1734 {
1735         return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1736 }
1737 
1738 static ssize_t
1739 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1740 {
1741         unsigned long flags;
1742         static int maxwarn = 10;
1743         int ret;
1744 
1745         if (!crng_ready() && maxwarn > 0) {
1746                 maxwarn--;
1747                 printk(KERN_NOTICE "random: %s: uninitialized urandom read "
1748                        "(%zd bytes read)\n",
1749                        current->comm, nbytes);
1750                 spin_lock_irqsave(&primary_crng.lock, flags);
1751                 crng_init_cnt = 0;
1752                 spin_unlock_irqrestore(&primary_crng.lock, flags);
1753         }
1754         nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1755         ret = extract_crng_user(buf, nbytes);
1756         trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
1757         return ret;
1758 }
1759 
1760 static unsigned int
1761 random_poll(struct file *file, poll_table * wait)
1762 {
1763         unsigned int mask;
1764 
1765         poll_wait(file, &random_read_wait, wait);
1766         poll_wait(file, &random_write_wait, wait);
1767         mask = 0;
1768         if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1769                 mask |= POLLIN | POLLRDNORM;
1770         if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1771                 mask |= POLLOUT | POLLWRNORM;
1772         return mask;
1773 }
1774 
1775 static int
1776 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1777 {
1778         size_t bytes;
1779         __u32 buf[16];
1780         const char __user *p = buffer;
1781 
1782         while (count > 0) {
1783                 bytes = min(count, sizeof(buf));
1784                 if (copy_from_user(&buf, p, bytes))
1785                         return -EFAULT;
1786 
1787                 count -= bytes;
1788                 p += bytes;
1789 
1790                 mix_pool_bytes(r, buf, bytes);
1791                 cond_resched();
1792         }
1793 
1794         return 0;
1795 }
1796 
1797 static ssize_t random_write(struct file *file, const char __user *buffer,
1798                             size_t count, loff_t *ppos)
1799 {
1800         size_t ret;
1801 
1802         ret = write_pool(&input_pool, buffer, count);
1803         if (ret)
1804                 return ret;
1805 
1806         return (ssize_t)count;
1807 }
1808 
1809 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1810 {
1811         int size, ent_count;
1812         int __user *p = (int __user *)arg;
1813         int retval;
1814 
1815         switch (cmd) {
1816         case RNDGETENTCNT:
1817                 /* inherently racy, no point locking */
1818                 ent_count = ENTROPY_BITS(&input_pool);
1819                 if (put_user(ent_count, p))
1820                         return -EFAULT;
1821                 return 0;
1822         case RNDADDTOENTCNT:
1823                 if (!capable(CAP_SYS_ADMIN))
1824                         return -EPERM;
1825                 if (get_user(ent_count, p))
1826                         return -EFAULT;
1827                 return credit_entropy_bits_safe(&input_pool, ent_count);
1828         case RNDADDENTROPY:
1829                 if (!capable(CAP_SYS_ADMIN))
1830                         return -EPERM;
1831                 if (get_user(ent_count, p++))
1832                         return -EFAULT;
1833                 if (ent_count < 0)
1834                         return -EINVAL;
1835                 if (get_user(size, p++))
1836                         return -EFAULT;
1837                 retval = write_pool(&input_pool, (const char __user *)p,
1838                                     size);
1839                 if (retval < 0)
1840                         return retval;
1841                 return credit_entropy_bits_safe(&input_pool, ent_count);
1842         case RNDZAPENTCNT:
1843         case RNDCLEARPOOL:
1844                 /*
1845                  * Clear the entropy pool counters. We no longer clear
1846                  * the entropy pool, as that's silly.
1847                  */
1848                 if (!capable(CAP_SYS_ADMIN))
1849                         return -EPERM;
1850                 input_pool.entropy_count = 0;
1851                 blocking_pool.entropy_count = 0;
1852                 return 0;
1853         default:
1854                 return -EINVAL;
1855         }
1856 }
1857 
1858 static int random_fasync(int fd, struct file *filp, int on)
1859 {
1860         return fasync_helper(fd, filp, on, &fasync);
1861 }
1862 
1863 const struct file_operations random_fops = {
1864         .read  = random_read,
1865         .write = random_write,
1866         .poll  = random_poll,
1867         .unlocked_ioctl = random_ioctl,
1868         .fasync = random_fasync,
1869         .llseek = noop_llseek,
1870 };
1871 
1872 const struct file_operations urandom_fops = {
1873         .read  = urandom_read,
1874         .write = random_write,
1875         .unlocked_ioctl = random_ioctl,
1876         .fasync = random_fasync,
1877         .llseek = noop_llseek,
1878 };
1879 
1880 SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1881                 unsigned int, flags)
1882 {
1883         if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1884                 return -EINVAL;
1885 
1886         if (count > INT_MAX)
1887                 count = INT_MAX;
1888 
1889         if (flags & GRND_RANDOM)
1890                 return _random_read(flags & GRND_NONBLOCK, buf, count);
1891 
1892         if (!crng_ready()) {
1893                 if (flags & GRND_NONBLOCK)
1894                         return -EAGAIN;
1895                 crng_wait_ready();
1896                 if (signal_pending(current))
1897                         return -ERESTARTSYS;
1898         }
1899         return urandom_read(NULL, buf, count, NULL);
1900 }
1901 
1902 /********************************************************************
1903  *
1904  * Sysctl interface
1905  *
1906  ********************************************************************/
1907 
1908 #ifdef CONFIG_SYSCTL
1909 
1910 #include <linux/sysctl.h>
1911 
1912 static int min_read_thresh = 8, min_write_thresh;
1913 static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1914 static int max_write_thresh = INPUT_POOL_WORDS * 32;
1915 static char sysctl_bootid[16];
1916 
1917 /*
1918  * This function is used to return both the bootid UUID, and random
1919  * UUID.  The difference is in whether table->data is NULL; if it is,
1920  * then a new UUID is generated and returned to the user.
1921  *
1922  * If the user accesses this via the proc interface, the UUID will be
1923  * returned as an ASCII string in the standard UUID format; if via the
1924  * sysctl system call, as 16 bytes of binary data.
1925  */
1926 static int proc_do_uuid(struct ctl_table *table, int write,
1927                         void __user *buffer, size_t *lenp, loff_t *ppos)
1928 {
1929         struct ctl_table fake_table;
1930         unsigned char buf[64], tmp_uuid[16], *uuid;
1931 
1932         uuid = table->data;
1933         if (!uuid) {
1934                 uuid = tmp_uuid;
1935                 generate_random_uuid(uuid);
1936         } else {
1937                 static DEFINE_SPINLOCK(bootid_spinlock);
1938 
1939                 spin_lock(&bootid_spinlock);
1940                 if (!uuid[8])
1941                         generate_random_uuid(uuid);
1942                 spin_unlock(&bootid_spinlock);
1943         }
1944 
1945         sprintf(buf, "%pU", uuid);
1946 
1947         fake_table.data = buf;
1948         fake_table.maxlen = sizeof(buf);
1949 
1950         return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1951 }
1952 
1953 /*
1954  * Return entropy available scaled to integral bits
1955  */
1956 static int proc_do_entropy(struct ctl_table *table, int write,
1957                            void __user *buffer, size_t *lenp, loff_t *ppos)
1958 {
1959         struct ctl_table fake_table;
1960         int entropy_count;
1961 
1962         entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1963 
1964         fake_table.data = &entropy_count;
1965         fake_table.maxlen = sizeof(entropy_count);
1966 
1967         return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1968 }
1969 
1970 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1971 extern struct ctl_table random_table[];
1972 struct ctl_table random_table[] = {
1973         {
1974                 .procname       = "poolsize",
1975                 .data           = &sysctl_poolsize,
1976                 .maxlen         = sizeof(int),
1977                 .mode           = 0444,
1978                 .proc_handler   = proc_dointvec,
1979         },
1980         {
1981                 .procname       = "entropy_avail",
1982                 .maxlen         = sizeof(int),
1983                 .mode           = 0444,
1984                 .proc_handler   = proc_do_entropy,
1985                 .data           = &input_pool.entropy_count,
1986         },
1987         {
1988                 .procname       = "read_wakeup_threshold",
1989                 .data           = &random_read_wakeup_bits,
1990                 .maxlen         = sizeof(int),
1991                 .mode           = 0644,
1992                 .proc_handler   = proc_dointvec_minmax,
1993                 .extra1         = &min_read_thresh,
1994                 .extra2         = &max_read_thresh,
1995         },
1996         {
1997                 .procname       = "write_wakeup_threshold",
1998                 .data           = &random_write_wakeup_bits,
1999                 .maxlen         = sizeof(int),
2000                 .mode           = 0644,
2001                 .proc_handler   = proc_dointvec_minmax,
2002                 .extra1         = &min_write_thresh,
2003                 .extra2         = &max_write_thresh,
2004         },
2005         {
2006                 .procname       = "urandom_min_reseed_secs",
2007                 .data           = &random_min_urandom_seed,
2008                 .maxlen         = sizeof(int),
2009                 .mode           = 0644,
2010                 .proc_handler   = proc_dointvec,
2011         },
2012         {
2013                 .procname       = "boot_id",
2014                 .data           = &sysctl_bootid,
2015                 .maxlen         = 16,
2016                 .mode           = 0444,
2017                 .proc_handler   = proc_do_uuid,
2018         },
2019         {
2020                 .procname       = "uuid",
2021                 .maxlen         = 16,
2022                 .mode           = 0444,
2023                 .proc_handler   = proc_do_uuid,
2024         },
2025 #ifdef ADD_INTERRUPT_BENCH
2026         {
2027                 .procname       = "add_interrupt_avg_cycles",
2028                 .data           = &avg_cycles,
2029                 .maxlen         = sizeof(avg_cycles),
2030                 .mode           = 0444,
2031                 .proc_handler   = proc_doulongvec_minmax,
2032         },
2033         {
2034                 .procname       = "add_interrupt_avg_deviation",
2035                 .data           = &avg_deviation,
2036                 .maxlen         = sizeof(avg_deviation),
2037                 .mode           = 0444,
2038                 .proc_handler   = proc_doulongvec_minmax,
2039         },
2040 #endif
2041         { }
2042 };
2043 #endif  /* CONFIG_SYSCTL */
2044 
2045 static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
2046 
2047 int random_int_secret_init(void)
2048 {
2049         get_random_bytes(random_int_secret, sizeof(random_int_secret));
2050         return 0;
2051 }
2052 
2053 static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash)
2054                 __aligned(sizeof(unsigned long));
2055 
2056 /*
2057  * Get a random word for internal kernel use only. Similar to urandom but
2058  * with the goal of minimal entropy pool depletion. As a result, the random
2059  * value is not cryptographically secure but for several uses the cost of
2060  * depleting entropy is too high
2061  */
2062 unsigned int get_random_int(void)
2063 {
2064         __u32 *hash;
2065         unsigned int ret;
2066 
2067         if (arch_get_random_int(&ret))
2068                 return ret;
2069 
2070         hash = get_cpu_var(get_random_int_hash);
2071 
2072         hash[0] += current->pid + jiffies + random_get_entropy();
2073         md5_transform(hash, random_int_secret);
2074         ret = hash[0];
2075         put_cpu_var(get_random_int_hash);
2076 
2077         return ret;
2078 }
2079 EXPORT_SYMBOL(get_random_int);
2080 
2081 /*
2082  * Same as get_random_int(), but returns unsigned long.
2083  */
2084 unsigned long get_random_long(void)
2085 {
2086         __u32 *hash;
2087         unsigned long ret;
2088 
2089         if (arch_get_random_long(&ret))
2090                 return ret;
2091 
2092         hash = get_cpu_var(get_random_int_hash);
2093 
2094         hash[0] += current->pid + jiffies + random_get_entropy();
2095         md5_transform(hash, random_int_secret);
2096         ret = *(unsigned long *)hash;
2097         put_cpu_var(get_random_int_hash);
2098 
2099         return ret;
2100 }
2101 EXPORT_SYMBOL(get_random_long);
2102 
2103 /*
2104  * randomize_range() returns a start address such that
2105  *
2106  *    [...... <range> .....]
2107  *  start                  end
2108  *
2109  * a <range> with size "len" starting at the return value is inside in the
2110  * area defined by [start, end], but is otherwise randomized.
2111  */
2112 unsigned long
2113 randomize_range(unsigned long start, unsigned long end, unsigned long len)
2114 {
2115         unsigned long range = end - len - start;
2116 
2117         if (end <= start + len)
2118                 return 0;
2119         return PAGE_ALIGN(get_random_int() % range + start);
2120 }
2121 
2122 /* Interface for in-kernel drivers of true hardware RNGs.
2123  * Those devices may produce endless random bits and will be throttled
2124  * when our pool is full.
2125  */
2126 void add_hwgenerator_randomness(const char *buffer, size_t count,
2127                                 size_t entropy)
2128 {
2129         struct entropy_store *poolp = &input_pool;
2130 
2131         if (!crng_ready()) {
2132                 crng_fast_load(buffer, count);
2133                 return;
2134         }
2135 
2136         /* Suspend writing if we're above the trickle threshold.
2137          * We'll be woken up again once below random_write_wakeup_thresh,
2138          * or when the calling thread is about to terminate.
2139          */
2140         wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2141                         ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2142         mix_pool_bytes(poolp, buffer, count);
2143         credit_entropy_bits(poolp, entropy);
2144 }
2145 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2146 

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