2 * random.c -- A strong random number generator
4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
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
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.)
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
43 * (now, with legal B.S. out of the way.....)
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.
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.
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.
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.
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
98 * Exported interfaces ---- output
99 * ===============================
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
104 * void get_random_bytes(void *buf, int nbytes);
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
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.
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.
122 * Exported interfaces ---- input
123 * ==============================
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
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);
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).
142 * add_input_randomness() uses the input layer interrupt timing, as well as
143 * the event type information from the hardware.
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.
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.
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.
159 * Ensuring unpredictability at system startup
160 * ============================================
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
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
181 * chmod 600 $random_seed
182 * dd if=/dev/urandom of=$random_seed count=1 bs=512
184 * and the following lines in an appropriate script which is run as
185 * the system is shutdown:
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
192 * chmod 600 $random_seed
193 * dd if=/dev/urandom of=$random_seed count=1 bs=512
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.
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
209 * Configuring the /dev/random driver under Linux
210 * ==============================================
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:
217 * mknod /dev/random c 1 8
218 * mknod /dev/urandom c 1 9
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.
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.
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.
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/percpu.h>
254 #include <linux/cryptohash.h>
255 #include <linux/fips.h>
256 #include <linux/ptrace.h>
257 #include <linux/kmemcheck.h>
259 #ifdef CONFIG_GENERIC_HARDIRQS
260 # include <linux/irq.h>
263 #include <asm/processor.h>
264 #include <asm/uaccess.h>
266 #include <asm/irq_regs.h>
269 #define CREATE_TRACE_POINTS
270 #include <trace/events/random.h>
273 * Configuration information
275 #define INPUT_POOL_SHIFT 12
276 #define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
277 #define OUTPUT_POOL_SHIFT 10
278 #define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
279 #define SEC_XFER_SIZE 512
280 #define EXTRACT_SIZE 10
282 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
285 * To allow fractional bits to be tracked, the following fields contain
286 * this many fractional bits:
288 * entropy_count, trickle_thresh
290 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
291 * credit_entropy_bits() needs to be 64 bits wide.
293 #define ENTROPY_SHIFT 3
294 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
297 * The minimum number of bits of entropy before we wake up a read on
298 * /dev/random. Should be enough to do a significant reseed.
300 static int random_read_wakeup_thresh
= 64;
303 * If the entropy count falls under this number of bits, then we
304 * should wake up processes which are selecting or polling on write
305 * access to /dev/random.
307 static int random_write_wakeup_thresh
= 128;
310 * When the input pool goes over trickle_thresh, start dropping most
311 * samples to avoid wasting CPU time and reduce lock contention.
313 static const int trickle_thresh
= (INPUT_POOL_WORDS
* 28) << ENTROPY_SHIFT
;
315 static DEFINE_PER_CPU(int, trickle_count
);
318 * A pool of size .poolwords is stirred with a primitive polynomial
319 * of degree .poolwords over GF(2). The taps for various sizes are
320 * defined below. They are chosen to be evenly spaced (minimum RMS
321 * distance from evenly spaced; the numbers in the comments are a
322 * scaled squared error sum) except for the last tap, which is 1 to
323 * get the twisting happening as fast as possible.
326 static struct poolinfo
{
327 int poolbitshift
, poolwords
, poolbytes
, poolbits
, poolfracbits
;
328 #define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
329 int tap1
, tap2
, tap3
, tap4
, tap5
;
330 } poolinfo_table
[] = {
331 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
332 { S(128), 103, 76, 51, 25, 1 },
333 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
334 { S(32), 26, 20, 14, 7, 1 },
336 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
337 { S(2048), 1638, 1231, 819, 411, 1 },
339 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
340 { S(1024), 817, 615, 412, 204, 1 },
342 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
343 { S(1024), 819, 616, 410, 207, 2 },
345 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
346 { S(512), 411, 308, 208, 104, 1 },
348 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
349 { S(512), 409, 307, 206, 102, 2 },
350 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
351 { S(512), 409, 309, 205, 103, 2 },
353 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
354 { S(256), 205, 155, 101, 52, 1 },
356 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
357 { S(128), 103, 78, 51, 27, 2 },
359 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
360 { S(64), 52, 39, 26, 14, 1 },
365 * For the purposes of better mixing, we use the CRC-32 polynomial as
366 * well to make a twisted Generalized Feedback Shift Reigster
368 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
369 * Transactions on Modeling and Computer Simulation 2(3):179-194.
370 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
371 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
373 * Thanks to Colin Plumb for suggesting this.
375 * We have not analyzed the resultant polynomial to prove it primitive;
376 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
377 * of a random large-degree polynomial over GF(2) are more than large enough
378 * that periodicity is not a concern.
380 * The input hash is much less sensitive than the output hash. All
381 * that we want of it is that it be a good non-cryptographic hash;
382 * i.e. it not produce collisions when fed "random" data of the sort
383 * we expect to see. As long as the pool state differs for different
384 * inputs, we have preserved the input entropy and done a good job.
385 * The fact that an intelligent attacker can construct inputs that
386 * will produce controlled alterations to the pool's state is not
387 * important because we don't consider such inputs to contribute any
388 * randomness. The only property we need with respect to them is that
389 * the attacker can't increase his/her knowledge of the pool's state.
390 * Since all additions are reversible (knowing the final state and the
391 * input, you can reconstruct the initial state), if an attacker has
392 * any uncertainty about the initial state, he/she can only shuffle
393 * that uncertainty about, but never cause any collisions (which would
394 * decrease the uncertainty).
396 * The chosen system lets the state of the pool be (essentially) the input
397 * modulo the generator polymnomial. Now, for random primitive polynomials,
398 * this is a universal class of hash functions, meaning that the chance
399 * of a collision is limited by the attacker's knowledge of the generator
400 * polynomail, so if it is chosen at random, an attacker can never force
401 * a collision. Here, we use a fixed polynomial, but we *can* assume that
402 * ###--> it is unknown to the processes generating the input entropy. <-###
403 * Because of this important property, this is a good, collision-resistant
404 * hash; hash collisions will occur no more often than chance.
408 * Static global variables
410 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait
);
411 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait
);
412 static struct fasync_struct
*fasync
;
415 module_param(debug
, bool, 0644);
416 #define DEBUG_ENT(fmt, arg...) do { \
418 printk(KERN_DEBUG "random %04d %04d %04d: " \
420 input_pool.entropy_count,\
421 blocking_pool.entropy_count,\
422 nonblocking_pool.entropy_count,\
425 /**********************************************************************
427 * OS independent entropy store. Here are the functions which handle
428 * storing entropy in an entropy pool.
430 **********************************************************************/
432 struct entropy_store
;
433 struct entropy_store
{
434 /* read-only data: */
435 const struct poolinfo
*poolinfo
;
438 struct entropy_store
*pull
;
441 /* read-write data: */
444 unsigned input_rotate
;
447 unsigned int initialized
:1;
449 __u8 last_data
[EXTRACT_SIZE
];
452 static __u32 input_pool_data
[INPUT_POOL_WORDS
];
453 static __u32 blocking_pool_data
[OUTPUT_POOL_WORDS
];
454 static __u32 nonblocking_pool_data
[OUTPUT_POOL_WORDS
];
456 static struct entropy_store input_pool
= {
457 .poolinfo
= &poolinfo_table
[0],
460 .lock
= __SPIN_LOCK_UNLOCKED(input_pool
.lock
),
461 .pool
= input_pool_data
464 static struct entropy_store blocking_pool
= {
465 .poolinfo
= &poolinfo_table
[1],
469 .lock
= __SPIN_LOCK_UNLOCKED(blocking_pool
.lock
),
470 .pool
= blocking_pool_data
473 static struct entropy_store nonblocking_pool
= {
474 .poolinfo
= &poolinfo_table
[1],
475 .name
= "nonblocking",
477 .lock
= __SPIN_LOCK_UNLOCKED(nonblocking_pool
.lock
),
478 .pool
= nonblocking_pool_data
481 static __u32
const twist_table
[8] = {
482 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
483 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
486 * This function adds bytes into the entropy "pool". It does not
487 * update the entropy estimate. The caller should call
488 * credit_entropy_bits if this is appropriate.
490 * The pool is stirred with a primitive polynomial of the appropriate
491 * degree, and then twisted. We twist by three bits at a time because
492 * it's cheap to do so and helps slightly in the expected case where
493 * the entropy is concentrated in the low-order bits.
495 static void _mix_pool_bytes(struct entropy_store
*r
, const void *in
,
496 int nbytes
, __u8 out
[64])
498 unsigned long i
, j
, tap1
, tap2
, tap3
, tap4
, tap5
;
500 int wordmask
= r
->poolinfo
->poolwords
- 1;
501 const char *bytes
= in
;
504 tap1
= r
->poolinfo
->tap1
;
505 tap2
= r
->poolinfo
->tap2
;
506 tap3
= r
->poolinfo
->tap3
;
507 tap4
= r
->poolinfo
->tap4
;
508 tap5
= r
->poolinfo
->tap5
;
511 input_rotate
= ACCESS_ONCE(r
->input_rotate
);
512 i
= ACCESS_ONCE(r
->add_ptr
);
514 /* mix one byte at a time to simplify size handling and churn faster */
516 w
= rol32(*bytes
++, input_rotate
& 31);
517 i
= (i
- 1) & wordmask
;
519 /* XOR in the various taps */
521 w
^= r
->pool
[(i
+ tap1
) & wordmask
];
522 w
^= r
->pool
[(i
+ tap2
) & wordmask
];
523 w
^= r
->pool
[(i
+ tap3
) & wordmask
];
524 w
^= r
->pool
[(i
+ tap4
) & wordmask
];
525 w
^= r
->pool
[(i
+ tap5
) & wordmask
];
527 /* Mix the result back in with a twist */
528 r
->pool
[i
] = (w
>> 3) ^ twist_table
[w
& 7];
531 * Normally, we add 7 bits of rotation to the pool.
532 * At the beginning of the pool, add an extra 7 bits
533 * rotation, so that successive passes spread the
534 * input bits across the pool evenly.
536 input_rotate
+= i
? 7 : 14;
539 ACCESS_ONCE(r
->input_rotate
) = input_rotate
;
540 ACCESS_ONCE(r
->add_ptr
) = i
;
544 for (j
= 0; j
< 16; j
++)
545 ((__u32
*)out
)[j
] = r
->pool
[(i
- j
) & wordmask
];
548 static void __mix_pool_bytes(struct entropy_store
*r
, const void *in
,
549 int nbytes
, __u8 out
[64])
551 trace_mix_pool_bytes_nolock(r
->name
, nbytes
, _RET_IP_
);
552 _mix_pool_bytes(r
, in
, nbytes
, out
);
555 static void mix_pool_bytes(struct entropy_store
*r
, const void *in
,
556 int nbytes
, __u8 out
[64])
560 trace_mix_pool_bytes(r
->name
, nbytes
, _RET_IP_
);
561 spin_lock_irqsave(&r
->lock
, flags
);
562 _mix_pool_bytes(r
, in
, nbytes
, out
);
563 spin_unlock_irqrestore(&r
->lock
, flags
);
569 unsigned short count
;
570 unsigned char rotate
;
571 unsigned char last_timer_intr
;
575 * This is a fast mixing routine used by the interrupt randomness
576 * collector. It's hardcoded for an 128 bit pool and assumes that any
577 * locks that might be needed are taken by the caller.
579 static void fast_mix(struct fast_pool
*f
, const void *in
, int nbytes
)
581 const char *bytes
= in
;
583 unsigned i
= f
->count
;
584 unsigned input_rotate
= f
->rotate
;
587 w
= rol32(*bytes
++, input_rotate
& 31) ^ f
->pool
[i
& 3] ^
588 f
->pool
[(i
+ 1) & 3];
589 f
->pool
[i
& 3] = (w
>> 3) ^ twist_table
[w
& 7];
590 input_rotate
+= (i
++ & 3) ? 7 : 14;
593 f
->rotate
= input_rotate
;
597 * Credit (or debit) the entropy store with n bits of entropy.
598 * Use credit_entropy_bits_safe() if the value comes from userspace
599 * or otherwise should be checked for extreme values.
601 static void credit_entropy_bits(struct entropy_store
*r
, int nbits
)
603 int entropy_count
, orig
;
604 const int pool_size
= r
->poolinfo
->poolfracbits
;
605 int nfrac
= nbits
<< ENTROPY_SHIFT
;
610 DEBUG_ENT("added %d entropy credits to %s\n", nbits
, r
->name
);
612 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
615 entropy_count
+= nfrac
;
618 * Credit: we have to account for the possibility of
619 * overwriting already present entropy. Even in the
620 * ideal case of pure Shannon entropy, new contributions
621 * approach the full value asymptotically:
623 * entropy <- entropy + (pool_size - entropy) *
624 * (1 - exp(-add_entropy/pool_size))
626 * For add_entropy <= pool_size/2 then
627 * (1 - exp(-add_entropy/pool_size)) >=
628 * (add_entropy/pool_size)*0.7869...
629 * so we can approximate the exponential with
630 * 3/4*add_entropy/pool_size and still be on the
631 * safe side by adding at most pool_size/2 at a time.
633 * The use of pool_size-2 in the while statement is to
634 * prevent rounding artifacts from making the loop
635 * arbitrarily long; this limits the loop to log2(pool_size)*2
636 * turns no matter how large nbits is.
639 const int s
= r
->poolinfo
->poolbitshift
+ ENTROPY_SHIFT
+ 2;
640 /* The +2 corresponds to the /4 in the denominator */
643 unsigned int anfrac
= min(pnfrac
, pool_size
/2);
645 ((pool_size
- entropy_count
)*anfrac
*3) >> s
;
647 entropy_count
+= add
;
649 } while (unlikely(entropy_count
< pool_size
-2 && pnfrac
));
652 if (entropy_count
< 0) {
653 DEBUG_ENT("negative entropy/overflow\n");
655 } else if (entropy_count
> pool_size
)
656 entropy_count
= pool_size
;
657 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
660 if (!r
->initialized
&& nbits
> 0) {
661 r
->entropy_total
+= nbits
;
662 if (r
->entropy_total
> 128)
666 trace_credit_entropy_bits(r
->name
, nbits
,
667 entropy_count
>> ENTROPY_SHIFT
,
668 r
->entropy_total
, _RET_IP_
);
670 /* should we wake readers? */
671 if (r
== &input_pool
&&
672 (entropy_count
>> ENTROPY_SHIFT
) >= random_read_wakeup_thresh
) {
673 wake_up_interruptible(&random_read_wait
);
674 kill_fasync(&fasync
, SIGIO
, POLL_IN
);
678 static void credit_entropy_bits_safe(struct entropy_store
*r
, int nbits
)
680 const int nbits_max
= (int)(~0U >> (ENTROPY_SHIFT
+ 1));
682 /* Cap the value to avoid overflows */
683 nbits
= min(nbits
, nbits_max
);
684 nbits
= max(nbits
, -nbits_max
);
686 credit_entropy_bits(r
, nbits
);
689 /*********************************************************************
691 * Entropy input management
693 *********************************************************************/
695 /* There is one of these per entropy source */
696 struct timer_rand_state
{
698 long last_delta
, last_delta2
;
699 unsigned dont_count_entropy
:1;
703 * Add device- or boot-specific data to the input and nonblocking
704 * pools to help initialize them to unique values.
706 * None of this adds any entropy, it is meant to avoid the
707 * problem of the nonblocking pool having similar initial state
708 * across largely identical devices.
710 void add_device_randomness(const void *buf
, unsigned int size
)
712 unsigned long time
= random_get_entropy() ^ jiffies
;
715 trace_add_device_randomness(size
, _RET_IP_
);
716 spin_lock_irqsave(&input_pool
.lock
, flags
);
717 _mix_pool_bytes(&input_pool
, buf
, size
, NULL
);
718 _mix_pool_bytes(&input_pool
, &time
, sizeof(time
), NULL
);
719 spin_unlock_irqrestore(&input_pool
.lock
, flags
);
721 spin_lock_irqsave(&nonblocking_pool
.lock
, flags
);
722 _mix_pool_bytes(&nonblocking_pool
, buf
, size
, NULL
);
723 _mix_pool_bytes(&nonblocking_pool
, &time
, sizeof(time
), NULL
);
724 spin_unlock_irqrestore(&nonblocking_pool
.lock
, flags
);
726 EXPORT_SYMBOL(add_device_randomness
);
728 static struct timer_rand_state input_timer_state
;
731 * This function adds entropy to the entropy "pool" by using timing
732 * delays. It uses the timer_rand_state structure to make an estimate
733 * of how many bits of entropy this call has added to the pool.
735 * The number "num" is also added to the pool - it should somehow describe
736 * the type of event which just happened. This is currently 0-255 for
737 * keyboard scan codes, and 256 upwards for interrupts.
740 static void add_timer_randomness(struct timer_rand_state
*state
, unsigned num
)
747 long delta
, delta2
, delta3
;
750 /* if over the trickle threshold, use only 1 in 4096 samples */
751 if (ENTROPY_BITS(&input_pool
) > trickle_thresh
&&
752 ((__this_cpu_inc_return(trickle_count
) - 1) & 0xfff))
755 sample
.jiffies
= jiffies
;
756 sample
.cycles
= random_get_entropy();
758 mix_pool_bytes(&input_pool
, &sample
, sizeof(sample
), NULL
);
761 * Calculate number of bits of randomness we probably added.
762 * We take into account the first, second and third-order deltas
763 * in order to make our estimate.
766 if (!state
->dont_count_entropy
) {
767 delta
= sample
.jiffies
- state
->last_time
;
768 state
->last_time
= sample
.jiffies
;
770 delta2
= delta
- state
->last_delta
;
771 state
->last_delta
= delta
;
773 delta3
= delta2
- state
->last_delta2
;
774 state
->last_delta2
= delta2
;
788 * delta is now minimum absolute delta.
789 * Round down by 1 bit on general principles,
790 * and limit entropy entimate to 12 bits.
792 credit_entropy_bits(&input_pool
,
793 min_t(int, fls(delta
>>1), 11));
799 void add_input_randomness(unsigned int type
, unsigned int code
,
802 static unsigned char last_value
;
804 /* ignore autorepeat and the like */
805 if (value
== last_value
)
808 DEBUG_ENT("input event\n");
810 add_timer_randomness(&input_timer_state
,
811 (type
<< 4) ^ code
^ (code
>> 4) ^ value
);
813 EXPORT_SYMBOL_GPL(add_input_randomness
);
815 static DEFINE_PER_CPU(struct fast_pool
, irq_randomness
);
817 void add_interrupt_randomness(int irq
, int irq_flags
)
819 struct entropy_store
*r
;
820 struct fast_pool
*fast_pool
= &__get_cpu_var(irq_randomness
);
821 struct pt_regs
*regs
= get_irq_regs();
822 unsigned long now
= jiffies
;
823 __u32 input
[4], cycles
= random_get_entropy();
825 input
[0] = cycles
^ jiffies
;
828 __u64 ip
= instruction_pointer(regs
);
833 fast_mix(fast_pool
, input
, sizeof(input
));
835 if ((fast_pool
->count
& 1023) &&
836 !time_after(now
, fast_pool
->last
+ HZ
))
839 fast_pool
->last
= now
;
841 r
= nonblocking_pool
.initialized
? &input_pool
: &nonblocking_pool
;
842 __mix_pool_bytes(r
, &fast_pool
->pool
, sizeof(fast_pool
->pool
), NULL
);
844 * If we don't have a valid cycle counter, and we see
845 * back-to-back timer interrupts, then skip giving credit for
849 if (irq_flags
& __IRQF_TIMER
) {
850 if (fast_pool
->last_timer_intr
)
852 fast_pool
->last_timer_intr
= 1;
854 fast_pool
->last_timer_intr
= 0;
856 credit_entropy_bits(r
, 1);
860 void add_disk_randomness(struct gendisk
*disk
)
862 if (!disk
|| !disk
->random
)
864 /* first major is 1, so we get >= 0x200 here */
865 DEBUG_ENT("disk event %d:%d\n",
866 MAJOR(disk_devt(disk
)), MINOR(disk_devt(disk
)));
868 add_timer_randomness(disk
->random
, 0x100 + disk_devt(disk
));
872 /*********************************************************************
874 * Entropy extraction routines
876 *********************************************************************/
878 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
879 size_t nbytes
, int min
, int rsvd
);
882 * This utility inline function is responsible for transferring entropy
883 * from the primary pool to the secondary extraction pool. We make
884 * sure we pull enough for a 'catastrophic reseed'.
886 static void xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
888 __u32 tmp
[OUTPUT_POOL_WORDS
];
891 r
->entropy_count
< (nbytes
<< (ENTROPY_SHIFT
+ 3)) &&
892 r
->entropy_count
< r
->poolinfo
->poolfracbits
) {
893 /* If we're limited, always leave two wakeup worth's BITS */
894 int rsvd
= r
->limit
? 0 : random_read_wakeup_thresh
/4;
897 /* pull at least as many as BYTES as wakeup BITS */
898 bytes
= max_t(int, bytes
, random_read_wakeup_thresh
/ 8);
899 /* but never more than the buffer size */
900 bytes
= min_t(int, bytes
, sizeof(tmp
));
902 DEBUG_ENT("going to reseed %s with %d bits "
903 "(%zu of %d requested)\n",
904 r
->name
, bytes
* 8, nbytes
* 8,
905 r
->entropy_count
>> ENTROPY_SHIFT
);
907 bytes
= extract_entropy(r
->pull
, tmp
, bytes
,
908 random_read_wakeup_thresh
/ 8, rsvd
);
909 mix_pool_bytes(r
, tmp
, bytes
, NULL
);
910 credit_entropy_bits(r
, bytes
*8);
915 * These functions extracts randomness from the "entropy pool", and
916 * returns it in a buffer.
918 * The min parameter specifies the minimum amount we can pull before
919 * failing to avoid races that defeat catastrophic reseeding while the
920 * reserved parameter indicates how much entropy we must leave in the
921 * pool after each pull to avoid starving other readers.
923 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
926 static size_t account(struct entropy_store
*r
, size_t nbytes
, int min
,
930 int wakeup_write
= 0;
932 int entropy_count
, orig
;
935 /* Hold lock while accounting */
936 spin_lock_irqsave(&r
->lock
, flags
);
938 BUG_ON(r
->entropy_count
> r
->poolinfo
->poolfracbits
);
939 DEBUG_ENT("trying to extract %zu bits from %s\n",
940 nbytes
* 8, r
->name
);
942 /* Can we pull enough? */
944 entropy_count
= orig
= ACCESS_ONCE(r
->entropy_count
);
945 have_bytes
= entropy_count
>> (ENTROPY_SHIFT
+ 3);
947 if (have_bytes
< min
+ reserved
) {
950 /* If limited, never pull more than available */
951 if (r
->limit
&& ibytes
+ reserved
>= have_bytes
)
952 ibytes
= have_bytes
- reserved
;
954 if (have_bytes
>= ibytes
+ reserved
)
955 entropy_count
-= ibytes
<< (ENTROPY_SHIFT
+ 3);
957 entropy_count
= reserved
<< (ENTROPY_SHIFT
+ 3);
959 if (cmpxchg(&r
->entropy_count
, orig
, entropy_count
) != orig
)
962 if ((r
->entropy_count
>> ENTROPY_SHIFT
)
963 < random_write_wakeup_thresh
)
967 DEBUG_ENT("debiting %zu entropy credits from %s%s\n",
968 ibytes
* 8, r
->name
, r
->limit
? "" : " (unlimited)");
970 spin_unlock_irqrestore(&r
->lock
, flags
);
973 wake_up_interruptible(&random_write_wait
);
974 kill_fasync(&fasync
, SIGIO
, POLL_OUT
);
980 static void extract_buf(struct entropy_store
*r
, __u8
*out
)
985 unsigned long l
[LONGS(20)];
987 __u32 workspace
[SHA_WORKSPACE_WORDS
];
991 /* Generate a hash across the pool, 16 words (512 bits) at a time */
993 spin_lock_irqsave(&r
->lock
, flags
);
994 for (i
= 0; i
< r
->poolinfo
->poolwords
; i
+= 16)
995 sha_transform(hash
.w
, (__u8
*)(r
->pool
+ i
), workspace
);
998 * If we have a architectural hardware random number
999 * generator, mix that in, too.
1001 for (i
= 0; i
< LONGS(20); i
++) {
1003 if (!arch_get_random_long(&v
))
1009 * We mix the hash back into the pool to prevent backtracking
1010 * attacks (where the attacker knows the state of the pool
1011 * plus the current outputs, and attempts to find previous
1012 * ouputs), unless the hash function can be inverted. By
1013 * mixing at least a SHA1 worth of hash data back, we make
1014 * brute-forcing the feedback as hard as brute-forcing the
1017 __mix_pool_bytes(r
, hash
.w
, sizeof(hash
.w
), extract
);
1018 spin_unlock_irqrestore(&r
->lock
, flags
);
1021 * To avoid duplicates, we atomically extract a portion of the
1022 * pool while mixing, and hash one final time.
1024 sha_transform(hash
.w
, extract
, workspace
);
1025 memset(extract
, 0, sizeof(extract
));
1026 memset(workspace
, 0, sizeof(workspace
));
1029 * In case the hash function has some recognizable output
1030 * pattern, we fold it in half. Thus, we always feed back
1031 * twice as much data as we output.
1033 hash
.w
[0] ^= hash
.w
[3];
1034 hash
.w
[1] ^= hash
.w
[4];
1035 hash
.w
[2] ^= rol32(hash
.w
[2], 16);
1037 memcpy(out
, &hash
, EXTRACT_SIZE
);
1038 memset(&hash
, 0, sizeof(hash
));
1041 static ssize_t
extract_entropy(struct entropy_store
*r
, void *buf
,
1042 size_t nbytes
, int min
, int reserved
)
1045 __u8 tmp
[EXTRACT_SIZE
];
1046 unsigned long flags
;
1048 /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1050 spin_lock_irqsave(&r
->lock
, flags
);
1051 if (!r
->last_data_init
) {
1052 r
->last_data_init
= true;
1053 spin_unlock_irqrestore(&r
->lock
, flags
);
1054 trace_extract_entropy(r
->name
, EXTRACT_SIZE
,
1055 ENTROPY_BITS(r
), _RET_IP_
);
1056 xfer_secondary_pool(r
, EXTRACT_SIZE
);
1057 extract_buf(r
, tmp
);
1058 spin_lock_irqsave(&r
->lock
, flags
);
1059 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1061 spin_unlock_irqrestore(&r
->lock
, flags
);
1064 trace_extract_entropy(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1065 xfer_secondary_pool(r
, nbytes
);
1066 nbytes
= account(r
, nbytes
, min
, reserved
);
1069 extract_buf(r
, tmp
);
1072 spin_lock_irqsave(&r
->lock
, flags
);
1073 if (!memcmp(tmp
, r
->last_data
, EXTRACT_SIZE
))
1074 panic("Hardware RNG duplicated output!\n");
1075 memcpy(r
->last_data
, tmp
, EXTRACT_SIZE
);
1076 spin_unlock_irqrestore(&r
->lock
, flags
);
1078 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1079 memcpy(buf
, tmp
, i
);
1085 /* Wipe data just returned from memory */
1086 memset(tmp
, 0, sizeof(tmp
));
1091 static ssize_t
extract_entropy_user(struct entropy_store
*r
, void __user
*buf
,
1095 __u8 tmp
[EXTRACT_SIZE
];
1097 trace_extract_entropy_user(r
->name
, nbytes
, ENTROPY_BITS(r
), _RET_IP_
);
1098 xfer_secondary_pool(r
, nbytes
);
1099 nbytes
= account(r
, nbytes
, 0, 0);
1102 if (need_resched()) {
1103 if (signal_pending(current
)) {
1111 extract_buf(r
, tmp
);
1112 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
1113 if (copy_to_user(buf
, tmp
, i
)) {
1123 /* Wipe data just returned from memory */
1124 memset(tmp
, 0, sizeof(tmp
));
1130 * This function is the exported kernel interface. It returns some
1131 * number of good random numbers, suitable for key generation, seeding
1132 * TCP sequence numbers, etc. It does not use the hw random number
1133 * generator, if available; use get_random_bytes_arch() for that.
1135 void get_random_bytes(void *buf
, int nbytes
)
1137 trace_get_random_bytes(nbytes
, _RET_IP_
);
1138 extract_entropy(&nonblocking_pool
, buf
, nbytes
, 0, 0);
1140 EXPORT_SYMBOL(get_random_bytes
);
1143 * This function will use the architecture-specific hardware random
1144 * number generator if it is available. The arch-specific hw RNG will
1145 * almost certainly be faster than what we can do in software, but it
1146 * is impossible to verify that it is implemented securely (as
1147 * opposed, to, say, the AES encryption of a sequence number using a
1148 * key known by the NSA). So it's useful if we need the speed, but
1149 * only if we're willing to trust the hardware manufacturer not to
1150 * have put in a back door.
1152 void get_random_bytes_arch(void *buf
, int nbytes
)
1156 trace_get_random_bytes_arch(nbytes
, _RET_IP_
);
1159 int chunk
= min(nbytes
, (int)sizeof(unsigned long));
1161 if (!arch_get_random_long(&v
))
1164 memcpy(p
, &v
, chunk
);
1170 extract_entropy(&nonblocking_pool
, p
, nbytes
, 0, 0);
1172 EXPORT_SYMBOL(get_random_bytes_arch
);
1176 * init_std_data - initialize pool with system data
1178 * @r: pool to initialize
1180 * This function clears the pool's entropy count and mixes some system
1181 * data into the pool to prepare it for use. The pool is not cleared
1182 * as that can only decrease the entropy in the pool.
1184 static void init_std_data(struct entropy_store
*r
)
1187 ktime_t now
= ktime_get_real();
1190 r
->entropy_count
= 0;
1191 r
->entropy_total
= 0;
1192 r
->last_data_init
= false;
1193 mix_pool_bytes(r
, &now
, sizeof(now
), NULL
);
1194 for (i
= r
->poolinfo
->poolbytes
; i
> 0; i
-= sizeof(rv
)) {
1195 if (!arch_get_random_long(&rv
))
1197 mix_pool_bytes(r
, &rv
, sizeof(rv
), NULL
);
1199 mix_pool_bytes(r
, utsname(), sizeof(*(utsname())), NULL
);
1203 * Note that setup_arch() may call add_device_randomness()
1204 * long before we get here. This allows seeding of the pools
1205 * with some platform dependent data very early in the boot
1206 * process. But it limits our options here. We must use
1207 * statically allocated structures that already have all
1208 * initializations complete at compile time. We should also
1209 * take care not to overwrite the precious per platform data
1212 static int rand_initialize(void)
1214 init_std_data(&input_pool
);
1215 init_std_data(&blocking_pool
);
1216 init_std_data(&nonblocking_pool
);
1219 module_init(rand_initialize
);
1222 void rand_initialize_disk(struct gendisk
*disk
)
1224 struct timer_rand_state
*state
;
1227 * If kzalloc returns null, we just won't use that entropy
1230 state
= kzalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
1232 disk
->random
= state
;
1237 random_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1239 ssize_t n
, retval
= 0, count
= 0;
1244 while (nbytes
> 0) {
1246 if (n
> SEC_XFER_SIZE
)
1249 DEBUG_ENT("reading %zu bits\n", n
*8);
1251 n
= extract_entropy_user(&blocking_pool
, buf
, n
);
1258 DEBUG_ENT("read got %zd bits (%zd still needed)\n",
1262 if (file
->f_flags
& O_NONBLOCK
) {
1267 DEBUG_ENT("sleeping?\n");
1269 wait_event_interruptible(random_read_wait
,
1270 ENTROPY_BITS(&input_pool
) >=
1271 random_read_wakeup_thresh
);
1273 DEBUG_ENT("awake\n");
1275 if (signal_pending(current
)) {
1276 retval
= -ERESTARTSYS
;
1286 break; /* This break makes the device work */
1287 /* like a named pipe */
1290 return (count
? count
: retval
);
1294 urandom_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
1296 return extract_entropy_user(&nonblocking_pool
, buf
, nbytes
);
1300 random_poll(struct file
*file
, poll_table
* wait
)
1304 poll_wait(file
, &random_read_wait
, wait
);
1305 poll_wait(file
, &random_write_wait
, wait
);
1307 if (ENTROPY_BITS(&input_pool
) >= random_read_wakeup_thresh
)
1308 mask
|= POLLIN
| POLLRDNORM
;
1309 if (ENTROPY_BITS(&input_pool
) < random_write_wakeup_thresh
)
1310 mask
|= POLLOUT
| POLLWRNORM
;
1315 write_pool(struct entropy_store
*r
, const char __user
*buffer
, size_t count
)
1319 const char __user
*p
= buffer
;
1322 bytes
= min(count
, sizeof(buf
));
1323 if (copy_from_user(&buf
, p
, bytes
))
1329 mix_pool_bytes(r
, buf
, bytes
, NULL
);
1336 static ssize_t
random_write(struct file
*file
, const char __user
*buffer
,
1337 size_t count
, loff_t
*ppos
)
1341 ret
= write_pool(&blocking_pool
, buffer
, count
);
1344 ret
= write_pool(&nonblocking_pool
, buffer
, count
);
1348 return (ssize_t
)count
;
1351 static long random_ioctl(struct file
*f
, unsigned int cmd
, unsigned long arg
)
1353 int size
, ent_count
;
1354 int __user
*p
= (int __user
*)arg
;
1359 /* inherently racy, no point locking */
1360 ent_count
= ENTROPY_BITS(&input_pool
);
1361 if (put_user(ent_count
, p
))
1364 case RNDADDTOENTCNT
:
1365 if (!capable(CAP_SYS_ADMIN
))
1367 if (get_user(ent_count
, p
))
1369 credit_entropy_bits_safe(&input_pool
, ent_count
);
1372 if (!capable(CAP_SYS_ADMIN
))
1374 if (get_user(ent_count
, p
++))
1378 if (get_user(size
, p
++))
1380 retval
= write_pool(&input_pool
, (const char __user
*)p
,
1384 credit_entropy_bits_safe(&input_pool
, ent_count
);
1388 /* Clear the entropy pool counters. */
1389 if (!capable(CAP_SYS_ADMIN
))
1398 static int random_fasync(int fd
, struct file
*filp
, int on
)
1400 return fasync_helper(fd
, filp
, on
, &fasync
);
1403 const struct file_operations random_fops
= {
1404 .read
= random_read
,
1405 .write
= random_write
,
1406 .poll
= random_poll
,
1407 .unlocked_ioctl
= random_ioctl
,
1408 .fasync
= random_fasync
,
1409 .llseek
= noop_llseek
,
1412 const struct file_operations urandom_fops
= {
1413 .read
= urandom_read
,
1414 .write
= random_write
,
1415 .unlocked_ioctl
= random_ioctl
,
1416 .fasync
= random_fasync
,
1417 .llseek
= noop_llseek
,
1420 /***************************************************************
1421 * Random UUID interface
1423 * Used here for a Boot ID, but can be useful for other kernel
1425 ***************************************************************/
1428 * Generate random UUID
1430 void generate_random_uuid(unsigned char uuid_out
[16])
1432 get_random_bytes(uuid_out
, 16);
1433 /* Set UUID version to 4 --- truly random generation */
1434 uuid_out
[6] = (uuid_out
[6] & 0x0F) | 0x40;
1435 /* Set the UUID variant to DCE */
1436 uuid_out
[8] = (uuid_out
[8] & 0x3F) | 0x80;
1438 EXPORT_SYMBOL(generate_random_uuid
);
1440 /********************************************************************
1444 ********************************************************************/
1446 #ifdef CONFIG_SYSCTL
1448 #include <linux/sysctl.h>
1450 static int min_read_thresh
= 8, min_write_thresh
;
1451 static int max_read_thresh
= INPUT_POOL_WORDS
* 32;
1452 static int max_write_thresh
= INPUT_POOL_WORDS
* 32;
1453 static char sysctl_bootid
[16];
1456 * These functions is used to return both the bootid UUID, and random
1457 * UUID. The difference is in whether table->data is NULL; if it is,
1458 * then a new UUID is generated and returned to the user.
1460 * If the user accesses this via the proc interface, it will be returned
1461 * as an ASCII string in the standard UUID format. If accesses via the
1462 * sysctl system call, it is returned as 16 bytes of binary data.
1464 static int proc_do_uuid(struct ctl_table
*table
, int write
,
1465 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1467 struct ctl_table fake_table
;
1468 unsigned char buf
[64], tmp_uuid
[16], *uuid
;
1473 generate_random_uuid(uuid
);
1475 static DEFINE_SPINLOCK(bootid_spinlock
);
1477 spin_lock(&bootid_spinlock
);
1479 generate_random_uuid(uuid
);
1480 spin_unlock(&bootid_spinlock
);
1483 sprintf(buf
, "%pU", uuid
);
1485 fake_table
.data
= buf
;
1486 fake_table
.maxlen
= sizeof(buf
);
1488 return proc_dostring(&fake_table
, write
, buffer
, lenp
, ppos
);
1492 * Return entropy available scaled to integral bits
1494 static int proc_do_entropy(ctl_table
*table
, int write
,
1495 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1497 ctl_table fake_table
;
1500 entropy_count
= *(int *)table
->data
>> ENTROPY_SHIFT
;
1502 fake_table
.data
= &entropy_count
;
1503 fake_table
.maxlen
= sizeof(entropy_count
);
1505 return proc_dointvec(&fake_table
, write
, buffer
, lenp
, ppos
);
1508 static int sysctl_poolsize
= INPUT_POOL_WORDS
* 32;
1509 extern struct ctl_table random_table
[];
1510 struct ctl_table random_table
[] = {
1512 .procname
= "poolsize",
1513 .data
= &sysctl_poolsize
,
1514 .maxlen
= sizeof(int),
1516 .proc_handler
= proc_dointvec
,
1519 .procname
= "entropy_avail",
1520 .maxlen
= sizeof(int),
1522 .proc_handler
= proc_do_entropy
,
1523 .data
= &input_pool
.entropy_count
,
1526 .procname
= "read_wakeup_threshold",
1527 .data
= &random_read_wakeup_thresh
,
1528 .maxlen
= sizeof(int),
1530 .proc_handler
= proc_dointvec_minmax
,
1531 .extra1
= &min_read_thresh
,
1532 .extra2
= &max_read_thresh
,
1535 .procname
= "write_wakeup_threshold",
1536 .data
= &random_write_wakeup_thresh
,
1537 .maxlen
= sizeof(int),
1539 .proc_handler
= proc_dointvec_minmax
,
1540 .extra1
= &min_write_thresh
,
1541 .extra2
= &max_write_thresh
,
1544 .procname
= "boot_id",
1545 .data
= &sysctl_bootid
,
1548 .proc_handler
= proc_do_uuid
,
1554 .proc_handler
= proc_do_uuid
,
1558 #endif /* CONFIG_SYSCTL */
1560 static u32 random_int_secret
[MD5_MESSAGE_BYTES
/ 4] ____cacheline_aligned
;
1562 int random_int_secret_init(void)
1564 get_random_bytes(random_int_secret
, sizeof(random_int_secret
));
1569 * Get a random word for internal kernel use only. Similar to urandom but
1570 * with the goal of minimal entropy pool depletion. As a result, the random
1571 * value is not cryptographically secure but for several uses the cost of
1572 * depleting entropy is too high
1574 static DEFINE_PER_CPU(__u32
[MD5_DIGEST_WORDS
], get_random_int_hash
);
1575 unsigned int get_random_int(void)
1580 if (arch_get_random_int(&ret
))
1583 hash
= get_cpu_var(get_random_int_hash
);
1585 hash
[0] += current
->pid
+ jiffies
+ random_get_entropy();
1586 md5_transform(hash
, random_int_secret
);
1588 put_cpu_var(get_random_int_hash
);
1592 EXPORT_SYMBOL(get_random_int
);
1595 * randomize_range() returns a start address such that
1597 * [...... <range> .....]
1600 * a <range> with size "len" starting at the return value is inside in the
1601 * area defined by [start, end], but is otherwise randomized.
1604 randomize_range(unsigned long start
, unsigned long end
, unsigned long len
)
1606 unsigned long range
= end
- len
- start
;
1608 if (end
<= start
+ len
)
1610 return PAGE_ALIGN(get_random_int() % range
+ start
);