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

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