root/drivers/char/random.c

DEFINITIONS

1. _mix_pool_bytes
2. __mix_pool_bytes
3. mix_pool_bytes
4. fast_mix
5. process_random_ready_list
6. credit_entropy_bits
7. credit_entropy_bits_safe
8. parse_trust_cpu
9. crng_initialize
10. do_numa_crng_init
11. numa_crng_init
12. numa_crng_init
13. crng_fast_load
14. crng_slow_load
15. crng_reseed
16. _extract_crng
17. extract_crng
18. _crng_backtrack_protect
19. crng_backtrack_protect
20. extract_crng_user
21. add_device_randomness
22. add_timer_randomness
23. add_input_randomness
24. add_interrupt_bench
25. get_reg
26. add_interrupt_randomness
27. add_disk_randomness
28. xfer_secondary_pool
29. _xfer_secondary_pool
30. push_to_pool
31. account
32. extract_buf
33. _extract_entropy
34. extract_entropy
35. extract_entropy_user
36. _warn_unseeded_randomness
37. _get_random_bytes
38. get_random_bytes
39. entropy_timer
40. try_to_generate_entropy
41. wait_for_random_bytes
42. rng_is_initialized
43. add_random_ready_callback
44. del_random_ready_callback
45. get_random_bytes_arch
46. init_std_data
47. rand_initialize
48. rand_initialize_disk
49. _random_read
50. random_read
51. urandom_read
52. random_poll
53. write_pool
54. random_write
55. random_ioctl
56. random_fasync
57. SYSCALL_DEFINE3
58. proc_do_uuid
59. proc_do_entropy
60. get_random_u64
61. get_random_u32
62. invalidate_batched_entropy
63. randomize_page
64. add_hwgenerator_randomness
65. add_bootloader_randomness

   1 /*
   2  * random.c -- A strong random number generator
   3  *
   4  * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All
   5  * Rights Reserved.
   6  *
   7  * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
   8  *
   9  * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
  10  * rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, and the entire permission notice in its entirety,
  17  *    including the disclaimer of warranties.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. The name of the author may not be used to endorse or promote
  22  *    products derived from this software without specific prior
  23  *    written permission.
  24  *
  25  * ALTERNATIVELY, this product may be distributed under the terms of
  26  * the GNU General Public License, in which case the provisions of the GPL are
  27  * required INSTEAD OF the above restrictions.  (This clause is
  28  * necessary due to a potential bad interaction between the GPL and
  29  * the restrictions contained in a BSD-style copyright.)
  30  *
  31  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  32  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  33  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  34  * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  35  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  36  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  37  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  38  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  39  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  40  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  41  * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
  42  * DAMAGE.
  43  */
  44 
  45 /*
  46  * (now, with legal B.S. out of the way.....)
  47  *
  48  * This routine gathers environmental noise from device drivers, etc.,
  49  * and returns good random numbers, suitable for cryptographic use.
  50  * Besides the obvious cryptographic uses, these numbers are also good
  51  * for seeding TCP sequence numbers, and other places where it is
  52  * desirable to have numbers which are not only random, but hard to
  53  * predict by an attacker.
  54  *
  55  * Theory of operation
  56  * ===================
  57  *
  58  * Computers are very predictable devices.  Hence it is extremely hard
  59  * to produce truly random numbers on a computer --- as opposed to
  60  * pseudo-random numbers, which can easily generated by using a
  61  * algorithm.  Unfortunately, it is very easy for attackers to guess
  62  * the sequence of pseudo-random number generators, and for some
  63  * applications this is not acceptable.  So instead, we must try to
  64  * gather "environmental noise" from the computer's environment, which
  65  * must be hard for outside attackers to observe, and use that to
  66  * generate random numbers.  In a Unix environment, this is best done
  67  * from inside the kernel.
  68  *
  69  * Sources of randomness from the environment include inter-keyboard
  70  * timings, inter-interrupt timings from some interrupts, and other
  71  * events which are both (a) non-deterministic and (b) hard for an
  72  * outside observer to measure.  Randomness from these sources are
  73  * added to an "entropy pool", which is mixed using a CRC-like function.
  74  * This is not cryptographically strong, but it is adequate assuming
  75  * the randomness is not chosen maliciously, and it is fast enough that
  76  * the overhead of doing it on every interrupt is very reasonable.
  77  * As random bytes are mixed into the entropy pool, the routines keep
  78  * an *estimate* of how many bits of randomness have been stored into
  79  * the random number generator's internal state.
  80  *
  81  * When random bytes are desired, they are obtained by taking the SHA
  82  * hash of the contents of the "entropy pool".  The SHA hash avoids
  83  * exposing the internal state of the entropy pool.  It is believed to
  84  * be computationally infeasible to derive any useful information
  85  * about the input of SHA from its output.  Even if it is possible to
  86  * analyze SHA in some clever way, as long as the amount of data
  87  * returned from the generator is less than the inherent entropy in
  88  * the pool, the output data is totally unpredictable.  For this
  89  * reason, the routine decreases its internal estimate of how many
  90  * bits of "true randomness" are contained in the entropy pool as it
  91  * outputs random numbers.
  92  *
  93  * If this estimate goes to zero, the routine can still generate
  94  * random numbers; however, an attacker may (at least in theory) be
  95  * able to infer the future output of the generator from prior
  96  * outputs.  This requires successful cryptanalysis of SHA, which is
  97  * not believed to be feasible, but there is a remote possibility.
  98  * Nonetheless, these numbers should be useful for the vast majority
  99  * of purposes.
 100  *
 101  * Exported interfaces ---- output
 102  * ===============================
 103  *
 104  * There are four exported interfaces; two for use within the kernel,
 105  * and two or use from userspace.
 106  *
 107  * Exported interfaces ---- userspace output
 108  * -----------------------------------------
 109  *
 110  * The userspace interfaces are two character devices /dev/random and
 111  * /dev/urandom.  /dev/random is suitable for use when very high
 112  * quality randomness is desired (for example, for key generation or
 113  * one-time pads), as it will only return a maximum of the number of
 114  * bits of randomness (as estimated by the random number generator)
 115  * contained in the entropy pool.
 116  *
 117  * The /dev/urandom device does not have this limit, and will return
 118  * as many bytes as are requested.  As more and more random bytes are
 119  * requested without giving time for the entropy pool to recharge,
 120  * this will result in random numbers that are merely cryptographically
 121  * strong.  For many applications, however, this is acceptable.
 122  *
 123  * Exported interfaces ---- kernel output
 124  * --------------------------------------
 125  *
 126  * The primary kernel interface is
 127  *
 128  *      void get_random_bytes(void *buf, int nbytes);
 129  *
 130  * This interface will return the requested number of random bytes,
 131  * and place it in the requested buffer.  This is equivalent to a
 132  * read from /dev/urandom.
 133  *
 134  * For less critical applications, there are the functions:
 135  *
 136  *      u32 get_random_u32()
 137  *      u64 get_random_u64()
 138  *      unsigned int get_random_int()
 139  *      unsigned long get_random_long()
 140  *
 141  * These are produced by a cryptographic RNG seeded from get_random_bytes,
 142  * and so do not deplete the entropy pool as much.  These are recommended
 143  * for most in-kernel operations *if the result is going to be stored in
 144  * the kernel*.
 145  *
 146  * Specifically, the get_random_int() family do not attempt to do
 147  * "anti-backtracking".  If you capture the state of the kernel (e.g.
 148  * by snapshotting the VM), you can figure out previous get_random_int()
 149  * return values.  But if the value is stored in the kernel anyway,
 150  * this is not a problem.
 151  *
 152  * It *is* safe to expose get_random_int() output to attackers (e.g. as
 153  * network cookies); given outputs 1..n, it's not feasible to predict
 154  * outputs 0 or n+1.  The only concern is an attacker who breaks into
 155  * the kernel later; the get_random_int() engine is not reseeded as
 156  * often as the get_random_bytes() one.
 157  *
 158  * get_random_bytes() is needed for keys that need to stay secret after
 159  * they are erased from the kernel.  For example, any key that will
 160  * be wrapped and stored encrypted.  And session encryption keys: we'd
 161  * like to know that after the session is closed and the keys erased,
 162  * the plaintext is unrecoverable to someone who recorded the ciphertext.
 163  *
 164  * But for network ports/cookies, stack canaries, PRNG seeds, address
 165  * space layout randomization, session *authentication* keys, or other
 166  * applications where the sensitive data is stored in the kernel in
 167  * plaintext for as long as it's sensitive, the get_random_int() family
 168  * is just fine.
 169  *
 170  * Consider ASLR.  We want to keep the address space secret from an
 171  * outside attacker while the process is running, but once the address
 172  * space is torn down, it's of no use to an attacker any more.  And it's
 173  * stored in kernel data structures as long as it's alive, so worrying
 174  * about an attacker's ability to extrapolate it from the get_random_int()
 175  * CRNG is silly.
 176  *
 177  * Even some cryptographic keys are safe to generate with get_random_int().
 178  * In particular, keys for SipHash are generally fine.  Here, knowledge
 179  * of the key authorizes you to do something to a kernel object (inject
 180  * packets to a network connection, or flood a hash table), and the
 181  * key is stored with the object being protected.  Once it goes away,
 182  * we no longer care if anyone knows the key.
 183  *
 184  * prandom_u32()
 185  * -------------
 186  *
 187  * For even weaker applications, see the pseudorandom generator
 188  * prandom_u32(), prandom_max(), and prandom_bytes().  If the random
 189  * numbers aren't security-critical at all, these are *far* cheaper.
 190  * Useful for self-tests, random error simulation, randomized backoffs,
 191  * and any other application where you trust that nobody is trying to
 192  * maliciously mess with you by guessing the "random" numbers.
 193  *
 194  * Exported interfaces ---- input
 195  * ==============================
 196  *
 197  * The current exported interfaces for gathering environmental noise
 198  * from the devices are:
 199  *
 200  *      void add_device_randomness(const void *buf, unsigned int size);
 201  *      void add_input_randomness(unsigned int type, unsigned int code,
 202  *                                unsigned int value);
 203  *      void add_interrupt_randomness(int irq, int irq_flags);
 204  *      void add_disk_randomness(struct gendisk *disk);
 205  *
 206  * add_device_randomness() is for adding data to the random pool that
 207  * is likely to differ between two devices (or possibly even per boot).
 208  * This would be things like MAC addresses or serial numbers, or the
 209  * read-out of the RTC. This does *not* add any actual entropy to the
 210  * pool, but it initializes the pool to different values for devices
 211  * that might otherwise be identical and have very little entropy
 212  * available to them (particularly common in the embedded world).
 213  *
 214  * add_input_randomness() uses the input layer interrupt timing, as well as
 215  * the event type information from the hardware.
 216  *
 217  * add_interrupt_randomness() uses the interrupt timing as random
 218  * inputs to the entropy pool. Using the cycle counters and the irq source
 219  * as inputs, it feeds the randomness roughly once a second.
 220  *
 221  * add_disk_randomness() uses what amounts to the seek time of block
 222  * layer request events, on a per-disk_devt basis, as input to the
 223  * entropy pool. Note that high-speed solid state drives with very low
 224  * seek times do not make for good sources of entropy, as their seek
 225  * times are usually fairly consistent.
 226  *
 227  * All of these routines try to estimate how many bits of randomness a
 228  * particular randomness source.  They do this by keeping track of the
 229  * first and second order deltas of the event timings.
 230  *
 231  * Ensuring unpredictability at system startup
 232  * ============================================
 233  *
 234  * When any operating system starts up, it will go through a sequence
 235  * of actions that are fairly predictable by an adversary, especially
 236  * if the start-up does not involve interaction with a human operator.
 237  * This reduces the actual number of bits of unpredictability in the
 238  * entropy pool below the value in entropy_count.  In order to
 239  * counteract this effect, it helps to carry information in the
 240  * entropy pool across shut-downs and start-ups.  To do this, put the
 241  * following lines an appropriate script which is run during the boot
 242  * sequence:
 243  *
 244  *      echo "Initializing random number generator..."
 245  *      random_seed=/var/run/random-seed
 246  *      # Carry a random seed from start-up to start-up
 247  *      # Load and then save the whole entropy pool
 248  *      if [ -f $random_seed ]; then
 249  *              cat $random_seed >/dev/urandom
 250  *      else
 251  *              touch $random_seed
 252  *      fi
 253  *      chmod 600 $random_seed
 254  *      dd if=/dev/urandom of=$random_seed count=1 bs=512
 255  *
 256  * and the following lines in an appropriate script which is run as
 257  * the system is shutdown:
 258  *
 259  *      # Carry a random seed from shut-down to start-up
 260  *      # Save the whole entropy pool
 261  *      echo "Saving random seed..."
 262  *      random_seed=/var/run/random-seed
 263  *      touch $random_seed
 264  *      chmod 600 $random_seed
 265  *      dd if=/dev/urandom of=$random_seed count=1 bs=512
 266  *
 267  * For example, on most modern systems using the System V init
 268  * scripts, such code fragments would be found in
 269  * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
 270  * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
 271  *
 272  * Effectively, these commands cause the contents of the entropy pool
 273  * to be saved at shut-down time and reloaded into the entropy pool at
 274  * start-up.  (The 'dd' in the addition to the bootup script is to
 275  * make sure that /etc/random-seed is different for every start-up,
 276  * even if the system crashes without executing rc.0.)  Even with
 277  * complete knowledge of the start-up activities, predicting the state
 278  * of the entropy pool requires knowledge of the previous history of
 279  * the system.
 280  *
 281  * Configuring the /dev/random driver under Linux
 282  * ==============================================
 283  *
 284  * The /dev/random driver under Linux uses minor numbers 8 and 9 of
 285  * the /dev/mem major number (#1).  So if your system does not have
 286  * /dev/random and /dev/urandom created already, they can be created
 287  * by using the commands:
 288  *
 289  *      mknod /dev/random c 1 8
 290  *      mknod /dev/urandom c 1 9
 291  *
 292  * Acknowledgements:
 293  * =================
 294  *
 295  * Ideas for constructing this random number generator were derived
 296  * from Pretty Good Privacy's random number generator, and from private
 297  * discussions with Phil Karn.  Colin Plumb provided a faster random
 298  * number generator, which speed up the mixing function of the entropy
 299  * pool, taken from PGPfone.  Dale Worley has also contributed many
 300  * useful ideas and suggestions to improve this driver.
 301  *
 302  * Any flaws in the design are solely my responsibility, and should
 303  * not be attributed to the Phil, Colin, or any of authors of PGP.
 304  *
 305  * Further background information on this topic may be obtained from
 306  * RFC 1750, "Randomness Recommendations for Security", by Donald
 307  * Eastlake, Steve Crocker, and Jeff Schiller.
 308  */
 309 
 310 #include <linux/utsname.h>
 311 #include <linux/module.h>
 312 #include <linux/kernel.h>
 313 #include <linux/major.h>
 314 #include <linux/string.h>
 315 #include <linux/fcntl.h>
 316 #include <linux/slab.h>
 317 #include <linux/random.h>
 318 #include <linux/poll.h>
 319 #include <linux/init.h>
 320 #include <linux/fs.h>
 321 #include <linux/genhd.h>
 322 #include <linux/interrupt.h>
 323 #include <linux/mm.h>
 324 #include <linux/nodemask.h>
 325 #include <linux/spinlock.h>
 326 #include <linux/kthread.h>
 327 #include <linux/percpu.h>
 328 #include <linux/cryptohash.h>
 329 #include <linux/fips.h>
 330 #include <linux/ptrace.h>
 331 #include <linux/workqueue.h>
 332 #include <linux/irq.h>
 333 #include <linux/ratelimit.h>
 334 #include <linux/syscalls.h>
 335 #include <linux/completion.h>
 336 #include <linux/uuid.h>
 337 #include <crypto/chacha.h>
 338 
 339 #include <asm/processor.h>
 340 #include <linux/uaccess.h>
 341 #include <asm/irq.h>
 342 #include <asm/irq_regs.h>
 343 #include <asm/io.h>
 344 
 345 #define CREATE_TRACE_POINTS
 346 #include <trace/events/random.h>
 347 
 348 /* #define ADD_INTERRUPT_BENCH */
 349 
 350 /*
 351  * Configuration information
 352  */
 353 #define INPUT_POOL_SHIFT        12
 354 #define INPUT_POOL_WORDS        (1 << (INPUT_POOL_SHIFT-5))
 355 #define OUTPUT_POOL_SHIFT       10
 356 #define OUTPUT_POOL_WORDS       (1 << (OUTPUT_POOL_SHIFT-5))
 357 #define SEC_XFER_SIZE           512
 358 #define EXTRACT_SIZE            10
 359 
 360 
 361 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 362 
 363 /*
 364  * To allow fractional bits to be tracked, the entropy_count field is
 365  * denominated in units of 1/8th bits.
 366  *
 367  * 2*(ENTROPY_SHIFT + poolbitshift) must <= 31, or the multiply in
 368  * credit_entropy_bits() needs to be 64 bits wide.
 369  */
 370 #define ENTROPY_SHIFT 3
 371 #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 372 
 373 /*
 374  * The minimum number of bits of entropy before we wake up a read on
 375  * /dev/random.  Should be enough to do a significant reseed.
 376  */
 377 static int random_read_wakeup_bits = 64;
 378 
 379 /*
 380  * If the entropy count falls under this number of bits, then we
 381  * should wake up processes which are selecting or polling on write
 382  * access to /dev/random.
 383  */
 384 static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
 385 
 386 /*
 387  * Originally, we used a primitive polynomial of degree .poolwords
 388  * over GF(2).  The taps for various sizes are defined below.  They
 389  * were chosen to be evenly spaced except for the last tap, which is 1
 390  * to get the twisting happening as fast as possible.
 391  *
 392  * For the purposes of better mixing, we use the CRC-32 polynomial as
 393  * well to make a (modified) twisted Generalized Feedback Shift
 394  * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
 395  * generators.  ACM Transactions on Modeling and Computer Simulation
 396  * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
 397  * GFSR generators II.  ACM Transactions on Modeling and Computer
 398  * Simulation 4:254-266)
 399  *
 400  * Thanks to Colin Plumb for suggesting this.
 401  *
 402  * The mixing operation is much less sensitive than the output hash,
 403  * where we use SHA-1.  All that we want of mixing operation is that
 404  * it be a good non-cryptographic hash; i.e. it not produce collisions
 405  * when fed "random" data of the sort we expect to see.  As long as
 406  * the pool state differs for different inputs, we have preserved the
 407  * input entropy and done a good job.  The fact that an intelligent
 408  * attacker can construct inputs that will produce controlled
 409  * alterations to the pool's state is not important because we don't
 410  * consider such inputs to contribute any randomness.  The only
 411  * property we need with respect to them is that the attacker can't
 412  * increase his/her knowledge of the pool's state.  Since all
 413  * additions are reversible (knowing the final state and the input,
 414  * you can reconstruct the initial state), if an attacker has any
 415  * uncertainty about the initial state, he/she can only shuffle that
 416  * uncertainty about, but never cause any collisions (which would
 417  * decrease the uncertainty).
 418  *
 419  * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
 420  * Videau in their paper, "The Linux Pseudorandom Number Generator
 421  * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
 422  * paper, they point out that we are not using a true Twisted GFSR,
 423  * since Matsumoto & Kurita used a trinomial feedback polynomial (that
 424  * is, with only three taps, instead of the six that we are using).
 425  * As a result, the resulting polynomial is neither primitive nor
 426  * irreducible, and hence does not have a maximal period over
 427  * GF(2**32).  They suggest a slight change to the generator
 428  * polynomial which improves the resulting TGFSR polynomial to be
 429  * irreducible, which we have made here.
 430  */
 431 static const struct poolinfo {
 432         int poolbitshift, poolwords, poolbytes, poolfracbits;
 433 #define S(x) ilog2(x)+5, (x), (x)*4, (x) << (ENTROPY_SHIFT+5)
 434         int tap1, tap2, tap3, tap4, tap5;
 435 } poolinfo_table[] = {
 436         /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
 437         /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
 438         { S(128),       104,    76,     51,     25,     1 },
 439         /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
 440         /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
 441         { S(32),        26,     19,     14,     7,      1 },
 442 #if 0
 443         /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 444         { S(2048),      1638,   1231,   819,    411,    1 },
 445 
 446         /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 447         { S(1024),      817,    615,    412,    204,    1 },
 448 
 449         /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 450         { S(1024),      819,    616,    410,    207,    2 },
 451 
 452         /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 453         { S(512),       411,    308,    208,    104,    1 },
 454 
 455         /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 456         { S(512),       409,    307,    206,    102,    2 },
 457         /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 458         { S(512),       409,    309,    205,    103,    2 },
 459 
 460         /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 461         { S(256),       205,    155,    101,    52,     1 },
 462 
 463         /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 464         { S(128),       103,    78,     51,     27,     2 },
 465 
 466         /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 467         { S(64),        52,     39,     26,     14,     1 },
 468 #endif
 469 };
 470 
 471 /*
 472  * Static global variables
 473  */
 474 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 475 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 476 static struct fasync_struct *fasync;
 477 
 478 static DEFINE_SPINLOCK(random_ready_list_lock);
 479 static LIST_HEAD(random_ready_list);
 480 
 481 struct crng_state {
 482         __u32           state[16];
 483         unsigned long   init_time;
 484         spinlock_t      lock;
 485 };
 486 
 487 static struct crng_state primary_crng = {
 488         .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
 489 };
 490 
 491 /*
 492  * crng_init =  0 --> Uninitialized
 493  *              1 --> Initialized
 494  *              2 --> Initialized from input_pool
 495  *
 496  * crng_init is protected by primary_crng->lock, and only increases
 497  * its value (from 0->1->2).
 498  */
 499 static int crng_init = 0;
 500 #define crng_ready() (likely(crng_init > 1))
 501 static int crng_init_cnt = 0;
 502 static unsigned long crng_global_init_time = 0;
 503 #define CRNG_INIT_CNT_THRESH (2*CHACHA_KEY_SIZE)
 504 static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA_BLOCK_SIZE]);
 505 static void _crng_backtrack_protect(struct crng_state *crng,
 506                                     __u8 tmp[CHACHA_BLOCK_SIZE], int used);
 507 static void process_random_ready_list(void);
 508 static void _get_random_bytes(void *buf, int nbytes);
 509 
 510 static struct ratelimit_state unseeded_warning =
 511         RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
 512 static struct ratelimit_state urandom_warning =
 513         RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
 514 
 515 static int ratelimit_disable __read_mostly;
 516 
 517 module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
 518 MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
 519 
 520 /**********************************************************************
 521  *
 522  * OS independent entropy store.   Here are the functions which handle
 523  * storing entropy in an entropy pool.
 524  *
 525  **********************************************************************/
 526 
 527 struct entropy_store;
 528 struct entropy_store {
 529         /* read-only data: */
 530         const struct poolinfo *poolinfo;
 531         __u32 *pool;
 532         const char *name;
 533         struct entropy_store *pull;
 534         struct work_struct push_work;
 535 
 536         /* read-write data: */
 537         unsigned long last_pulled;
 538         spinlock_t lock;
 539         unsigned short add_ptr;
 540         unsigned short input_rotate;
 541         int entropy_count;
 542         unsigned int initialized:1;
 543         unsigned int last_data_init:1;
 544         __u8 last_data[EXTRACT_SIZE];
 545 };
 546 
 547 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 548                                size_t nbytes, int min, int rsvd);
 549 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
 550                                 size_t nbytes, int fips);
 551 
 552 static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
 553 static void push_to_pool(struct work_struct *work);
 554 static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
 555 static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
 556 
 557 static struct entropy_store input_pool = {
 558         .poolinfo = &poolinfo_table[0],
 559         .name = "input",
 560         .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 561         .pool = input_pool_data
 562 };
 563 
 564 static struct entropy_store blocking_pool = {
 565         .poolinfo = &poolinfo_table[1],
 566         .name = "blocking",
 567         .pull = &input_pool,
 568         .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 569         .pool = blocking_pool_data,
 570         .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
 571                                         push_to_pool),
 572 };
 573 
 574 static __u32 const twist_table[8] = {
 575         0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 576         0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 577 
 578 /*
 579  * This function adds bytes into the entropy "pool".  It does not
 580  * update the entropy estimate.  The caller should call
 581  * credit_entropy_bits if this is appropriate.
 582  *
 583  * The pool is stirred with a primitive polynomial of the appropriate
 584  * degree, and then twisted.  We twist by three bits at a time because
 585  * it's cheap to do so and helps slightly in the expected case where
 586  * the entropy is concentrated in the low-order bits.
 587  */
 588 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 589                             int nbytes)
 590 {
 591         unsigned long i, tap1, tap2, tap3, tap4, tap5;
 592         int input_rotate;
 593         int wordmask = r->poolinfo->poolwords - 1;
 594         const char *bytes = in;
 595         __u32 w;
 596 
 597         tap1 = r->poolinfo->tap1;
 598         tap2 = r->poolinfo->tap2;
 599         tap3 = r->poolinfo->tap3;
 600         tap4 = r->poolinfo->tap4;
 601         tap5 = r->poolinfo->tap5;
 602 
 603         input_rotate = r->input_rotate;
 604         i = r->add_ptr;
 605 
 606         /* mix one byte at a time to simplify size handling and churn faster */
 607         while (nbytes--) {
 608                 w = rol32(*bytes++, input_rotate);
 609                 i = (i - 1) & wordmask;
 610 
 611                 /* XOR in the various taps */
 612                 w ^= r->pool[i];
 613                 w ^= r->pool[(i + tap1) & wordmask];
 614                 w ^= r->pool[(i + tap2) & wordmask];
 615                 w ^= r->pool[(i + tap3) & wordmask];
 616                 w ^= r->pool[(i + tap4) & wordmask];
 617                 w ^= r->pool[(i + tap5) & wordmask];
 618 
 619                 /* Mix the result back in with a twist */
 620                 r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 621 
 622                 /*
 623                  * Normally, we add 7 bits of rotation to the pool.
 624                  * At the beginning of the pool, add an extra 7 bits
 625                  * rotation, so that successive passes spread the
 626                  * input bits across the pool evenly.
 627                  */
 628                 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
 629         }
 630 
 631         r->input_rotate = input_rotate;
 632         r->add_ptr = i;
 633 }
 634 
 635 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 636                              int nbytes)
 637 {
 638         trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 639         _mix_pool_bytes(r, in, nbytes);
 640 }
 641 
 642 static void mix_pool_bytes(struct entropy_store *r, const void *in,
 643                            int nbytes)
 644 {
 645         unsigned long flags;
 646 
 647         trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
 648         spin_lock_irqsave(&r->lock, flags);
 649         _mix_pool_bytes(r, in, nbytes);
 650         spin_unlock_irqrestore(&r->lock, flags);
 651 }
 652 
 653 struct fast_pool {
 654         __u32           pool[4];
 655         unsigned long   last;
 656         unsigned short  reg_idx;
 657         unsigned char   count;
 658 };
 659 
 660 /*
 661  * This is a fast mixing routine used by the interrupt randomness
 662  * collector.  It's hardcoded for an 128 bit pool and assumes that any
 663  * locks that might be needed are taken by the caller.
 664  */
 665 static void fast_mix(struct fast_pool *f)
 666 {
 667         __u32 a = f->pool[0],   b = f->pool[1];
 668         __u32 c = f->pool[2],   d = f->pool[3];
 669 
 670         a += b;                 c += d;
 671         b = rol32(b, 6);        d = rol32(d, 27);
 672         d ^= a;                 b ^= c;
 673 
 674         a += b;                 c += d;
 675         b = rol32(b, 16);       d = rol32(d, 14);
 676         d ^= a;                 b ^= c;
 677 
 678         a += b;                 c += d;
 679         b = rol32(b, 6);        d = rol32(d, 27);
 680         d ^= a;                 b ^= c;
 681 
 682         a += b;                 c += d;
 683         b = rol32(b, 16);       d = rol32(d, 14);
 684         d ^= a;                 b ^= c;
 685 
 686         f->pool[0] = a;  f->pool[1] = b;
 687         f->pool[2] = c;  f->pool[3] = d;
 688         f->count++;
 689 }
 690 
 691 static void process_random_ready_list(void)
 692 {
 693         unsigned long flags;
 694         struct random_ready_callback *rdy, *tmp;
 695 
 696         spin_lock_irqsave(&random_ready_list_lock, flags);
 697         list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
 698                 struct module *owner = rdy->owner;
 699 
 700                 list_del_init(&rdy->list);
 701                 rdy->func(rdy);
 702                 module_put(owner);
 703         }
 704         spin_unlock_irqrestore(&random_ready_list_lock, flags);
 705 }
 706 
 707 /*
 708  * Credit (or debit) the entropy store with n bits of entropy.
 709  * Use credit_entropy_bits_safe() if the value comes from userspace
 710  * or otherwise should be checked for extreme values.
 711  */
 712 static void credit_entropy_bits(struct entropy_store *r, int nbits)
 713 {
 714         int entropy_count, orig, has_initialized = 0;
 715         const int pool_size = r->poolinfo->poolfracbits;
 716         int nfrac = nbits << ENTROPY_SHIFT;
 717 
 718         if (!nbits)
 719                 return;
 720 
 721 retry:
 722         entropy_count = orig = READ_ONCE(r->entropy_count);
 723         if (nfrac < 0) {
 724                 /* Debit */
 725                 entropy_count += nfrac;
 726         } else {
 727                 /*
 728                  * Credit: we have to account for the possibility of
 729                  * overwriting already present entropy.  Even in the
 730                  * ideal case of pure Shannon entropy, new contributions
 731                  * approach the full value asymptotically:
 732                  *
 733                  * entropy <- entropy + (pool_size - entropy) *
 734                  *      (1 - exp(-add_entropy/pool_size))
 735                  *
 736                  * For add_entropy <= pool_size/2 then
 737                  * (1 - exp(-add_entropy/pool_size)) >=
 738                  *    (add_entropy/pool_size)*0.7869...
 739                  * so we can approximate the exponential with
 740                  * 3/4*add_entropy/pool_size and still be on the
 741                  * safe side by adding at most pool_size/2 at a time.
 742                  *
 743                  * The use of pool_size-2 in the while statement is to
 744                  * prevent rounding artifacts from making the loop
 745                  * arbitrarily long; this limits the loop to log2(pool_size)*2
 746                  * turns no matter how large nbits is.
 747                  */
 748                 int pnfrac = nfrac;
 749                 const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
 750                 /* The +2 corresponds to the /4 in the denominator */
 751 
 752                 do {
 753                         unsigned int anfrac = min(pnfrac, pool_size/2);
 754                         unsigned int add =
 755                                 ((pool_size - entropy_count)*anfrac*3) >> s;
 756 
 757                         entropy_count += add;
 758                         pnfrac -= anfrac;
 759                 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
 760         }
 761 
 762         if (unlikely(entropy_count < 0)) {
 763                 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
 764                         r->name, entropy_count);
 765                 WARN_ON(1);
 766                 entropy_count = 0;
 767         } else if (entropy_count > pool_size)
 768                 entropy_count = pool_size;
 769         if ((r == &blocking_pool) && !r->initialized &&
 770             (entropy_count >> ENTROPY_SHIFT) > 128)
 771                 has_initialized = 1;
 772         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 773                 goto retry;
 774 
 775         if (has_initialized) {
 776                 r->initialized = 1;
 777                 wake_up_interruptible(&random_read_wait);
 778                 kill_fasync(&fasync, SIGIO, POLL_IN);
 779         }
 780 
 781         trace_credit_entropy_bits(r->name, nbits,
 782                                   entropy_count >> ENTROPY_SHIFT, _RET_IP_);
 783 
 784         if (r == &input_pool) {
 785                 int entropy_bits = entropy_count >> ENTROPY_SHIFT;
 786                 struct entropy_store *other = &blocking_pool;
 787 
 788                 if (crng_init < 2) {
 789                         if (entropy_bits < 128)
 790                                 return;
 791                         crng_reseed(&primary_crng, r);
 792                         entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
 793                 }
 794 
 795                 /* initialize the blocking pool if necessary */
 796                 if (entropy_bits >= random_read_wakeup_bits &&
 797                     !other->initialized) {
 798                         schedule_work(&other->push_work);
 799                         return;
 800                 }
 801 
 802                 /* should we wake readers? */
 803                 if (entropy_bits >= random_read_wakeup_bits &&
 804                     wq_has_sleeper(&random_read_wait)) {
 805                         wake_up_interruptible(&random_read_wait);
 806                         kill_fasync(&fasync, SIGIO, POLL_IN);
 807                 }
 808                 /* If the input pool is getting full, and the blocking
 809                  * pool has room, send some entropy to the blocking
 810                  * pool.
 811                  */
 812                 if (!work_pending(&other->push_work) &&
 813                     (ENTROPY_BITS(r) > 6 * r->poolinfo->poolbytes) &&
 814                     (ENTROPY_BITS(other) <= 6 * other->poolinfo->poolbytes))
 815                         schedule_work(&other->push_work);
 816         }
 817 }
 818 
 819 static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
 820 {
 821         const int nbits_max = r->poolinfo->poolwords * 32;
 822 
 823         if (nbits < 0)
 824                 return -EINVAL;
 825 
 826         /* Cap the value to avoid overflows */
 827         nbits = min(nbits,  nbits_max);
 828 
 829         credit_entropy_bits(r, nbits);
 830         return 0;
 831 }
 832 
 833 /*********************************************************************
 834  *
 835  * CRNG using CHACHA20
 836  *
 837  *********************************************************************/
 838 
 839 #define CRNG_RESEED_INTERVAL (300*HZ)
 840 
 841 static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
 842 
 843 #ifdef CONFIG_NUMA
 844 /*
 845  * Hack to deal with crazy userspace progams when they are all trying
 846  * to access /dev/urandom in parallel.  The programs are almost
 847  * certainly doing something terribly wrong, but we'll work around
 848  * their brain damage.
 849  */
 850 static struct crng_state **crng_node_pool __read_mostly;
 851 #endif
 852 
 853 static void invalidate_batched_entropy(void);
 854 static void numa_crng_init(void);
 855 
 856 static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
 857 static int __init parse_trust_cpu(char *arg)
 858 {
 859         return kstrtobool(arg, &trust_cpu);
 860 }
 861 early_param("random.trust_cpu", parse_trust_cpu);
 862 
 863 static void crng_initialize(struct crng_state *crng)
 864 {
 865         int             i;
 866         int             arch_init = 1;
 867         unsigned long   rv;
 868 
 869         memcpy(&crng->state[0], "expand 32-byte k", 16);
 870         if (crng == &primary_crng)
 871                 _extract_entropy(&input_pool, &crng->state[4],
 872                                  sizeof(__u32) * 12, 0);
 873         else
 874                 _get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
 875         for (i = 4; i < 16; i++) {
 876                 if (!arch_get_random_seed_long(&rv) &&
 877                     !arch_get_random_long(&rv)) {
 878                         rv = random_get_entropy();
 879                         arch_init = 0;
 880                 }
 881                 crng->state[i] ^= rv;
 882         }
 883         if (trust_cpu && arch_init && crng == &primary_crng) {
 884                 invalidate_batched_entropy();
 885                 numa_crng_init();
 886                 crng_init = 2;
 887                 pr_notice("random: crng done (trusting CPU's manufacturer)\n");
 888         }
 889         crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
 890 }
 891 
 892 #ifdef CONFIG_NUMA
 893 static void do_numa_crng_init(struct work_struct *work)
 894 {
 895         int i;
 896         struct crng_state *crng;
 897         struct crng_state **pool;
 898 
 899         pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
 900         for_each_online_node(i) {
 901                 crng = kmalloc_node(sizeof(struct crng_state),
 902                                     GFP_KERNEL | __GFP_NOFAIL, i);
 903                 spin_lock_init(&crng->lock);
 904                 crng_initialize(crng);
 905                 pool[i] = crng;
 906         }
 907         mb();
 908         if (cmpxchg(&crng_node_pool, NULL, pool)) {
 909                 for_each_node(i)
 910                         kfree(pool[i]);
 911                 kfree(pool);
 912         }
 913 }
 914 
 915 static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
 916 
 917 static void numa_crng_init(void)
 918 {
 919         schedule_work(&numa_crng_init_work);
 920 }
 921 #else
 922 static void numa_crng_init(void) {}
 923 #endif
 924 
 925 /*
 926  * crng_fast_load() can be called by code in the interrupt service
 927  * path.  So we can't afford to dilly-dally.
 928  */
 929 static int crng_fast_load(const char *cp, size_t len)
 930 {
 931         unsigned long flags;
 932         char *p;
 933 
 934         if (!spin_trylock_irqsave(&primary_crng.lock, flags))
 935                 return 0;
 936         if (crng_init != 0) {
 937                 spin_unlock_irqrestore(&primary_crng.lock, flags);
 938                 return 0;
 939         }
 940         p = (unsigned char *) &primary_crng.state[4];
 941         while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
 942                 p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp;
 943                 cp++; crng_init_cnt++; len--;
 944         }
 945         spin_unlock_irqrestore(&primary_crng.lock, flags);
 946         if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
 947                 invalidate_batched_entropy();
 948                 crng_init = 1;
 949                 wake_up_interruptible(&crng_init_wait);
 950                 pr_notice("random: fast init done\n");
 951         }
 952         return 1;
 953 }
 954 
 955 /*
 956  * crng_slow_load() is called by add_device_randomness, which has two
 957  * attributes.  (1) We can't trust the buffer passed to it is
 958  * guaranteed to be unpredictable (so it might not have any entropy at
 959  * all), and (2) it doesn't have the performance constraints of
 960  * crng_fast_load().
 961  *
 962  * So we do something more comprehensive which is guaranteed to touch
 963  * all of the primary_crng's state, and which uses a LFSR with a
 964  * period of 255 as part of the mixing algorithm.  Finally, we do
 965  * *not* advance crng_init_cnt since buffer we may get may be something
 966  * like a fixed DMI table (for example), which might very well be
 967  * unique to the machine, but is otherwise unvarying.
 968  */
 969 static int crng_slow_load(const char *cp, size_t len)
 970 {
 971         unsigned long           flags;
 972         static unsigned char    lfsr = 1;
 973         unsigned char           tmp;
 974         unsigned                i, max = CHACHA_KEY_SIZE;
 975         const char *            src_buf = cp;
 976         char *                  dest_buf = (char *) &primary_crng.state[4];
 977 
 978         if (!spin_trylock_irqsave(&primary_crng.lock, flags))
 979                 return 0;
 980         if (crng_init != 0) {
 981                 spin_unlock_irqrestore(&primary_crng.lock, flags);
 982                 return 0;
 983         }
 984         if (len > max)
 985                 max = len;
 986 
 987         for (i = 0; i < max ; i++) {
 988                 tmp = lfsr;
 989                 lfsr >>= 1;
 990                 if (tmp & 1)
 991                         lfsr ^= 0xE1;
 992                 tmp = dest_buf[i % CHACHA_KEY_SIZE];
 993                 dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
 994                 lfsr += (tmp << 3) | (tmp >> 5);
 995         }
 996         spin_unlock_irqrestore(&primary_crng.lock, flags);
 997         return 1;
 998 }
 999 
1000 static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
1001 {
1002         unsigned long   flags;
1003         int             i, num;
1004         union {
1005                 __u8    block[CHACHA_BLOCK_SIZE];
1006                 __u32   key[8];
1007         } buf;
1008 
1009         if (r) {
1010                 num = extract_entropy(r, &buf, 32, 16, 0);
1011                 if (num == 0)
1012                         return;
1013         } else {
1014                 _extract_crng(&primary_crng, buf.block);
1015                 _crng_backtrack_protect(&primary_crng, buf.block,
1016                                         CHACHA_KEY_SIZE);
1017         }
1018         spin_lock_irqsave(&crng->lock, flags);
1019         for (i = 0; i < 8; i++) {
1020                 unsigned long   rv;
1021                 if (!arch_get_random_seed_long(&rv) &&
1022                     !arch_get_random_long(&rv))
1023                         rv = random_get_entropy();
1024                 crng->state[i+4] ^= buf.key[i] ^ rv;
1025         }
1026         memzero_explicit(&buf, sizeof(buf));
1027         crng->init_time = jiffies;
1028         spin_unlock_irqrestore(&crng->lock, flags);
1029         if (crng == &primary_crng && crng_init < 2) {
1030                 invalidate_batched_entropy();
1031                 numa_crng_init();
1032                 crng_init = 2;
1033                 process_random_ready_list();
1034                 wake_up_interruptible(&crng_init_wait);
1035                 pr_notice("random: crng init done\n");
1036                 if (unseeded_warning.missed) {
1037                         pr_notice("random: %d get_random_xx warning(s) missed "
1038                                   "due to ratelimiting\n",
1039                                   unseeded_warning.missed);
1040                         unseeded_warning.missed = 0;
1041                 }
1042                 if (urandom_warning.missed) {
1043                         pr_notice("random: %d urandom warning(s) missed "
1044                                   "due to ratelimiting\n",
1045                                   urandom_warning.missed);
1046                         urandom_warning.missed = 0;
1047                 }
1048         }
1049 }
1050 
1051 static void _extract_crng(struct crng_state *crng,
1052                           __u8 out[CHACHA_BLOCK_SIZE])
1053 {
1054         unsigned long v, flags;
1055 
1056         if (crng_ready() &&
1057             (time_after(crng_global_init_time, crng->init_time) ||
1058              time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
1059                 crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
1060         spin_lock_irqsave(&crng->lock, flags);
1061         if (arch_get_random_long(&v))
1062                 crng->state[14] ^= v;
1063         chacha20_block(&crng->state[0], out);
1064         if (crng->state[12] == 0)
1065                 crng->state[13]++;
1066         spin_unlock_irqrestore(&crng->lock, flags);
1067 }
1068 
1069 static void extract_crng(__u8 out[CHACHA_BLOCK_SIZE])
1070 {
1071         struct crng_state *crng = NULL;
1072 
1073 #ifdef CONFIG_NUMA
1074         if (crng_node_pool)
1075                 crng = crng_node_pool[numa_node_id()];
1076         if (crng == NULL)
1077 #endif
1078                 crng = &primary_crng;
1079         _extract_crng(crng, out);
1080 }
1081 
1082 /*
1083  * Use the leftover bytes from the CRNG block output (if there is
1084  * enough) to mutate the CRNG key to provide backtracking protection.
1085  */
1086 static void _crng_backtrack_protect(struct crng_state *crng,
1087                                     __u8 tmp[CHACHA_BLOCK_SIZE], int used)
1088 {
1089         unsigned long   flags;
1090         __u32           *s, *d;
1091         int             i;
1092 
1093         used = round_up(used, sizeof(__u32));
1094         if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) {
1095                 extract_crng(tmp);
1096                 used = 0;
1097         }
1098         spin_lock_irqsave(&crng->lock, flags);
1099         s = (__u32 *) &tmp[used];
1100         d = &crng->state[4];
1101         for (i=0; i < 8; i++)
1102                 *d++ ^= *s++;
1103         spin_unlock_irqrestore(&crng->lock, flags);
1104 }
1105 
1106 static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used)
1107 {
1108         struct crng_state *crng = NULL;
1109 
1110 #ifdef CONFIG_NUMA
1111         if (crng_node_pool)
1112                 crng = crng_node_pool[numa_node_id()];
1113         if (crng == NULL)
1114 #endif
1115                 crng = &primary_crng;
1116         _crng_backtrack_protect(crng, tmp, used);
1117 }
1118 
1119 static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
1120 {
1121         ssize_t ret = 0, i = CHACHA_BLOCK_SIZE;
1122         __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1123         int large_request = (nbytes > 256);
1124 
1125         while (nbytes) {
1126                 if (large_request && need_resched()) {
1127                         if (signal_pending(current)) {
1128                                 if (ret == 0)
1129                                         ret = -ERESTARTSYS;
1130                                 break;
1131                         }
1132                         schedule();
1133                 }
1134 
1135                 extract_crng(tmp);
1136                 i = min_t(int, nbytes, CHACHA_BLOCK_SIZE);
1137                 if (copy_to_user(buf, tmp, i)) {
1138                         ret = -EFAULT;
1139                         break;
1140                 }
1141 
1142                 nbytes -= i;
1143                 buf += i;
1144                 ret += i;
1145         }
1146         crng_backtrack_protect(tmp, i);
1147 
1148         /* Wipe data just written to memory */
1149         memzero_explicit(tmp, sizeof(tmp));
1150 
1151         return ret;
1152 }
1153 
1154 
1155 /*********************************************************************
1156  *
1157  * Entropy input management
1158  *
1159  *********************************************************************/
1160 
1161 /* There is one of these per entropy source */
1162 struct timer_rand_state {
1163         cycles_t last_time;
1164         long last_delta, last_delta2;
1165 };
1166 
1167 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
1168 
1169 /*
1170  * Add device- or boot-specific data to the input pool to help
1171  * initialize it.
1172  *
1173  * None of this adds any entropy; it is meant to avoid the problem of
1174  * the entropy pool having similar initial state across largely
1175  * identical devices.
1176  */
1177 void add_device_randomness(const void *buf, unsigned int size)
1178 {
1179         unsigned long time = random_get_entropy() ^ jiffies;
1180         unsigned long flags;
1181 
1182         if (!crng_ready() && size)
1183                 crng_slow_load(buf, size);
1184 
1185         trace_add_device_randomness(size, _RET_IP_);
1186         spin_lock_irqsave(&input_pool.lock, flags);
1187         _mix_pool_bytes(&input_pool, buf, size);
1188         _mix_pool_bytes(&input_pool, &time, sizeof(time));
1189         spin_unlock_irqrestore(&input_pool.lock, flags);
1190 }
1191 EXPORT_SYMBOL(add_device_randomness);
1192 
1193 static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
1194 
1195 /*
1196  * This function adds entropy to the entropy "pool" by using timing
1197  * delays.  It uses the timer_rand_state structure to make an estimate
1198  * of how many bits of entropy this call has added to the pool.
1199  *
1200  * The number "num" is also added to the pool - it should somehow describe
1201  * the type of event which just happened.  This is currently 0-255 for
1202  * keyboard scan codes, and 256 upwards for interrupts.
1203  *
1204  */
1205 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
1206 {
1207         struct entropy_store    *r;
1208         struct {
1209                 long jiffies;
1210                 unsigned cycles;
1211                 unsigned num;
1212         } sample;
1213         long delta, delta2, delta3;
1214 
1215         sample.jiffies = jiffies;
1216         sample.cycles = random_get_entropy();
1217         sample.num = num;
1218         r = &input_pool;
1219         mix_pool_bytes(r, &sample, sizeof(sample));
1220 
1221         /*
1222          * Calculate number of bits of randomness we probably added.
1223          * We take into account the first, second and third-order deltas
1224          * in order to make our estimate.
1225          */
1226         delta = sample.jiffies - state->last_time;
1227         state->last_time = sample.jiffies;
1228 
1229         delta2 = delta - state->last_delta;
1230         state->last_delta = delta;
1231 
1232         delta3 = delta2 - state->last_delta2;
1233         state->last_delta2 = delta2;
1234 
1235         if (delta < 0)
1236                 delta = -delta;
1237         if (delta2 < 0)
1238                 delta2 = -delta2;
1239         if (delta3 < 0)
1240                 delta3 = -delta3;
1241         if (delta > delta2)
1242                 delta = delta2;
1243         if (delta > delta3)
1244                 delta = delta3;
1245 
1246         /*
1247          * delta is now minimum absolute delta.
1248          * Round down by 1 bit on general principles,
1249          * and limit entropy entimate to 12 bits.
1250          */
1251         credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
1252 }
1253 
1254 void add_input_randomness(unsigned int type, unsigned int code,
1255                                  unsigned int value)
1256 {
1257         static unsigned char last_value;
1258 
1259         /* ignore autorepeat and the like */
1260         if (value == last_value)
1261                 return;
1262 
1263         last_value = value;
1264         add_timer_randomness(&input_timer_state,
1265                              (type << 4) ^ code ^ (code >> 4) ^ value);
1266         trace_add_input_randomness(ENTROPY_BITS(&input_pool));
1267 }
1268 EXPORT_SYMBOL_GPL(add_input_randomness);
1269 
1270 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
1271 
1272 #ifdef ADD_INTERRUPT_BENCH
1273 static unsigned long avg_cycles, avg_deviation;
1274 
1275 #define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
1276 #define FIXED_1_2 (1 << (AVG_SHIFT-1))
1277 
1278 static void add_interrupt_bench(cycles_t start)
1279 {
1280         long delta = random_get_entropy() - start;
1281 
1282         /* Use a weighted moving average */
1283         delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
1284         avg_cycles += delta;
1285         /* And average deviation */
1286         delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
1287         avg_deviation += delta;
1288 }
1289 #else
1290 #define add_interrupt_bench(x)
1291 #endif
1292 
1293 static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
1294 {
1295         __u32 *ptr = (__u32 *) regs;
1296         unsigned int idx;
1297 
1298         if (regs == NULL)
1299                 return 0;
1300         idx = READ_ONCE(f->reg_idx);
1301         if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
1302                 idx = 0;
1303         ptr += idx++;
1304         WRITE_ONCE(f->reg_idx, idx);
1305         return *ptr;
1306 }
1307 
1308 void add_interrupt_randomness(int irq, int irq_flags)
1309 {
1310         struct entropy_store    *r;
1311         struct fast_pool        *fast_pool = this_cpu_ptr(&irq_randomness);
1312         struct pt_regs          *regs = get_irq_regs();
1313         unsigned long           now = jiffies;
1314         cycles_t                cycles = random_get_entropy();
1315         __u32                   c_high, j_high;
1316         __u64                   ip;
1317         unsigned long           seed;
1318         int                     credit = 0;
1319 
1320         if (cycles == 0)
1321                 cycles = get_reg(fast_pool, regs);
1322         c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
1323         j_high = (sizeof(now) > 4) ? now >> 32 : 0;
1324         fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
1325         fast_pool->pool[1] ^= now ^ c_high;
1326         ip = regs ? instruction_pointer(regs) : _RET_IP_;
1327         fast_pool->pool[2] ^= ip;
1328         fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
1329                 get_reg(fast_pool, regs);
1330 
1331         fast_mix(fast_pool);
1332         add_interrupt_bench(cycles);
1333 
1334         if (unlikely(crng_init == 0)) {
1335                 if ((fast_pool->count >= 64) &&
1336                     crng_fast_load((char *) fast_pool->pool,
1337                                    sizeof(fast_pool->pool))) {
1338                         fast_pool->count = 0;
1339                         fast_pool->last = now;
1340                 }
1341                 return;
1342         }
1343 
1344         if ((fast_pool->count < 64) &&
1345             !time_after(now, fast_pool->last + HZ))
1346                 return;
1347 
1348         r = &input_pool;
1349         if (!spin_trylock(&r->lock))
1350                 return;
1351 
1352         fast_pool->last = now;
1353         __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
1354 
1355         /*
1356          * If we have architectural seed generator, produce a seed and
1357          * add it to the pool.  For the sake of paranoia don't let the
1358          * architectural seed generator dominate the input from the
1359          * interrupt noise.
1360          */
1361         if (arch_get_random_seed_long(&seed)) {
1362                 __mix_pool_bytes(r, &seed, sizeof(seed));
1363                 credit = 1;
1364         }
1365         spin_unlock(&r->lock);
1366 
1367         fast_pool->count = 0;
1368 
1369         /* award one bit for the contents of the fast pool */
1370         credit_entropy_bits(r, credit + 1);
1371 }
1372 EXPORT_SYMBOL_GPL(add_interrupt_randomness);
1373 
1374 #ifdef CONFIG_BLOCK
1375 void add_disk_randomness(struct gendisk *disk)
1376 {
1377         if (!disk || !disk->random)
1378                 return;
1379         /* first major is 1, so we get >= 0x200 here */
1380         add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
1381         trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
1382 }
1383 EXPORT_SYMBOL_GPL(add_disk_randomness);
1384 #endif
1385 
1386 /*********************************************************************
1387  *
1388  * Entropy extraction routines
1389  *
1390  *********************************************************************/
1391 
1392 /*
1393  * This utility inline function is responsible for transferring entropy
1394  * from the primary pool to the secondary extraction pool. We make
1395  * sure we pull enough for a 'catastrophic reseed'.
1396  */
1397 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
1398 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1399 {
1400         if (!r->pull ||
1401             r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
1402             r->entropy_count > r->poolinfo->poolfracbits)
1403                 return;
1404 
1405         _xfer_secondary_pool(r, nbytes);
1406 }
1407 
1408 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
1409 {
1410         __u32   tmp[OUTPUT_POOL_WORDS];
1411 
1412         int bytes = nbytes;
1413 
1414         /* pull at least as much as a wakeup */
1415         bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1416         /* but never more than the buffer size */
1417         bytes = min_t(int, bytes, sizeof(tmp));
1418 
1419         trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1420                                   ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1421         bytes = extract_entropy(r->pull, tmp, bytes,
1422                                 random_read_wakeup_bits / 8, 0);
1423         mix_pool_bytes(r, tmp, bytes);
1424         credit_entropy_bits(r, bytes*8);
1425 }
1426 
1427 /*
1428  * Used as a workqueue function so that when the input pool is getting
1429  * full, we can "spill over" some entropy to the output pools.  That
1430  * way the output pools can store some of the excess entropy instead
1431  * of letting it go to waste.
1432  */
1433 static void push_to_pool(struct work_struct *work)
1434 {
1435         struct entropy_store *r = container_of(work, struct entropy_store,
1436                                               push_work);
1437         BUG_ON(!r);
1438         _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1439         trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1440                            r->pull->entropy_count >> ENTROPY_SHIFT);
1441 }
1442 
1443 /*
1444  * This function decides how many bytes to actually take from the
1445  * given pool, and also debits the entropy count accordingly.
1446  */
1447 static size_t account(struct entropy_store *r, size_t nbytes, int min,
1448                       int reserved)
1449 {
1450         int entropy_count, orig, have_bytes;
1451         size_t ibytes, nfrac;
1452 
1453         BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1454 
1455         /* Can we pull enough? */
1456 retry:
1457         entropy_count = orig = READ_ONCE(r->entropy_count);
1458         ibytes = nbytes;
1459         /* never pull more than available */
1460         have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1461 
1462         if ((have_bytes -= reserved) < 0)
1463                 have_bytes = 0;
1464         ibytes = min_t(size_t, ibytes, have_bytes);
1465         if (ibytes < min)
1466                 ibytes = 0;
1467 
1468         if (unlikely(entropy_count < 0)) {
1469                 pr_warn("random: negative entropy count: pool %s count %d\n",
1470                         r->name, entropy_count);
1471                 WARN_ON(1);
1472                 entropy_count = 0;
1473         }
1474         nfrac = ibytes << (ENTROPY_SHIFT + 3);
1475         if ((size_t) entropy_count > nfrac)
1476                 entropy_count -= nfrac;
1477         else
1478                 entropy_count = 0;
1479 
1480         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1481                 goto retry;
1482 
1483         trace_debit_entropy(r->name, 8 * ibytes);
1484         if (ibytes &&
1485             (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1486                 wake_up_interruptible(&random_write_wait);
1487                 kill_fasync(&fasync, SIGIO, POLL_OUT);
1488         }
1489 
1490         return ibytes;
1491 }
1492 
1493 /*
1494  * This function does the actual extraction for extract_entropy and
1495  * extract_entropy_user.
1496  *
1497  * Note: we assume that .poolwords is a multiple of 16 words.
1498  */
1499 static void extract_buf(struct entropy_store *r, __u8 *out)
1500 {
1501         int i;
1502         union {
1503                 __u32 w[5];
1504                 unsigned long l[LONGS(20)];
1505         } hash;
1506         __u32 workspace[SHA_WORKSPACE_WORDS];
1507         unsigned long flags;
1508 
1509         /*
1510          * If we have an architectural hardware random number
1511          * generator, use it for SHA's initial vector
1512          */
1513         sha_init(hash.w);
1514         for (i = 0; i < LONGS(20); i++) {
1515                 unsigned long v;
1516                 if (!arch_get_random_long(&v))
1517                         break;
1518                 hash.l[i] = v;
1519         }
1520 
1521         /* Generate a hash across the pool, 16 words (512 bits) at a time */
1522         spin_lock_irqsave(&r->lock, flags);
1523         for (i = 0; i < r->poolinfo->poolwords; i += 16)
1524                 sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1525 
1526         /*
1527          * We mix the hash back into the pool to prevent backtracking
1528          * attacks (where the attacker knows the state of the pool
1529          * plus the current outputs, and attempts to find previous
1530          * ouputs), unless the hash function can be inverted. By
1531          * mixing at least a SHA1 worth of hash data back, we make
1532          * brute-forcing the feedback as hard as brute-forcing the
1533          * hash.
1534          */
1535         __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1536         spin_unlock_irqrestore(&r->lock, flags);
1537 
1538         memzero_explicit(workspace, sizeof(workspace));
1539 
1540         /*
1541          * In case the hash function has some recognizable output
1542          * pattern, we fold it in half. Thus, we always feed back
1543          * twice as much data as we output.
1544          */
1545         hash.w[0] ^= hash.w[3];
1546         hash.w[1] ^= hash.w[4];
1547         hash.w[2] ^= rol32(hash.w[2], 16);
1548 
1549         memcpy(out, &hash, EXTRACT_SIZE);
1550         memzero_explicit(&hash, sizeof(hash));
1551 }
1552 
1553 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
1554                                 size_t nbytes, int fips)
1555 {
1556         ssize_t ret = 0, i;
1557         __u8 tmp[EXTRACT_SIZE];
1558         unsigned long flags;
1559 
1560         while (nbytes) {
1561                 extract_buf(r, tmp);
1562 
1563                 if (fips) {
1564                         spin_lock_irqsave(&r->lock, flags);
1565                         if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1566                                 panic("Hardware RNG duplicated output!\n");
1567                         memcpy(r->last_data, tmp, EXTRACT_SIZE);
1568                         spin_unlock_irqrestore(&r->lock, flags);
1569                 }
1570                 i = min_t(int, nbytes, EXTRACT_SIZE);
1571                 memcpy(buf, tmp, i);
1572                 nbytes -= i;
1573                 buf += i;
1574                 ret += i;
1575         }
1576 
1577         /* Wipe data just returned from memory */
1578         memzero_explicit(tmp, sizeof(tmp));
1579 
1580         return ret;
1581 }
1582 
1583 /*
1584  * This function extracts randomness from the "entropy pool", and
1585  * returns it in a buffer.
1586  *
1587  * The min parameter specifies the minimum amount we can pull before
1588  * failing to avoid races that defeat catastrophic reseeding while the
1589  * reserved parameter indicates how much entropy we must leave in the
1590  * pool after each pull to avoid starving other readers.
1591  */
1592 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1593                                  size_t nbytes, int min, int reserved)
1594 {
1595         __u8 tmp[EXTRACT_SIZE];
1596         unsigned long flags;
1597 
1598         /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1599         if (fips_enabled) {
1600                 spin_lock_irqsave(&r->lock, flags);
1601                 if (!r->last_data_init) {
1602                         r->last_data_init = 1;
1603                         spin_unlock_irqrestore(&r->lock, flags);
1604                         trace_extract_entropy(r->name, EXTRACT_SIZE,
1605                                               ENTROPY_BITS(r), _RET_IP_);
1606                         xfer_secondary_pool(r, EXTRACT_SIZE);
1607                         extract_buf(r, tmp);
1608                         spin_lock_irqsave(&r->lock, flags);
1609                         memcpy(r->last_data, tmp, EXTRACT_SIZE);
1610                 }
1611                 spin_unlock_irqrestore(&r->lock, flags);
1612         }
1613 
1614         trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1615         xfer_secondary_pool(r, nbytes);
1616         nbytes = account(r, nbytes, min, reserved);
1617 
1618         return _extract_entropy(r, buf, nbytes, fips_enabled);
1619 }
1620 
1621 /*
1622  * This function extracts randomness from the "entropy pool", and
1623  * returns it in a userspace buffer.
1624  */
1625 static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1626                                     size_t nbytes)
1627 {
1628         ssize_t ret = 0, i;
1629         __u8 tmp[EXTRACT_SIZE];
1630         int large_request = (nbytes > 256);
1631 
1632         trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1633         if (!r->initialized && r->pull) {
1634                 xfer_secondary_pool(r, ENTROPY_BITS(r->pull)/8);
1635                 if (!r->initialized)
1636                         return 0;
1637         }
1638         xfer_secondary_pool(r, nbytes);
1639         nbytes = account(r, nbytes, 0, 0);
1640 
1641         while (nbytes) {
1642                 if (large_request && need_resched()) {
1643                         if (signal_pending(current)) {
1644                                 if (ret == 0)
1645                                         ret = -ERESTARTSYS;
1646                                 break;
1647                         }
1648                         schedule();
1649                 }
1650 
1651                 extract_buf(r, tmp);
1652                 i = min_t(int, nbytes, EXTRACT_SIZE);
1653                 if (copy_to_user(buf, tmp, i)) {
1654                         ret = -EFAULT;
1655                         break;
1656                 }
1657 
1658                 nbytes -= i;
1659                 buf += i;
1660                 ret += i;
1661         }
1662 
1663         /* Wipe data just returned from memory */
1664         memzero_explicit(tmp, sizeof(tmp));
1665 
1666         return ret;
1667 }
1668 
1669 #define warn_unseeded_randomness(previous) \
1670         _warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
1671 
1672 static void _warn_unseeded_randomness(const char *func_name, void *caller,
1673                                       void **previous)
1674 {
1675 #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1676         const bool print_once = false;
1677 #else
1678         static bool print_once __read_mostly;
1679 #endif
1680 
1681         if (print_once ||
1682             crng_ready() ||
1683             (previous && (caller == READ_ONCE(*previous))))
1684                 return;
1685         WRITE_ONCE(*previous, caller);
1686 #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
1687         print_once = true;
1688 #endif
1689         if (__ratelimit(&unseeded_warning))
1690                 printk_deferred(KERN_NOTICE "random: %s called from %pS "
1691                                 "with crng_init=%d\n", func_name, caller,
1692                                 crng_init);
1693 }
1694 
1695 /*
1696  * This function is the exported kernel interface.  It returns some
1697  * number of good random numbers, suitable for key generation, seeding
1698  * TCP sequence numbers, etc.  It does not rely on the hardware random
1699  * number generator.  For random bytes direct from the hardware RNG
1700  * (when available), use get_random_bytes_arch(). In order to ensure
1701  * that the randomness provided by this function is okay, the function
1702  * wait_for_random_bytes() should be called and return 0 at least once
1703  * at any point prior.
1704  */
1705 static void _get_random_bytes(void *buf, int nbytes)
1706 {
1707         __u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
1708 
1709         trace_get_random_bytes(nbytes, _RET_IP_);
1710 
1711         while (nbytes >= CHACHA_BLOCK_SIZE) {
1712                 extract_crng(buf);
1713                 buf += CHACHA_BLOCK_SIZE;
1714                 nbytes -= CHACHA_BLOCK_SIZE;
1715         }
1716 
1717         if (nbytes > 0) {
1718                 extract_crng(tmp);
1719                 memcpy(buf, tmp, nbytes);
1720                 crng_backtrack_protect(tmp, nbytes);
1721         } else
1722                 crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE);
1723         memzero_explicit(tmp, sizeof(tmp));
1724 }
1725 
1726 void get_random_bytes(void *buf, int nbytes)
1727 {
1728         static void *previous;
1729 
1730         warn_unseeded_randomness(&previous);
1731         _get_random_bytes(buf, nbytes);
1732 }
1733 EXPORT_SYMBOL(get_random_bytes);
1734 
1735 
1736 /*
1737  * Each time the timer fires, we expect that we got an unpredictable
1738  * jump in the cycle counter. Even if the timer is running on another
1739  * CPU, the timer activity will be touching the stack of the CPU that is
1740  * generating entropy..
1741  *
1742  * Note that we don't re-arm the timer in the timer itself - we are
1743  * happy to be scheduled away, since that just makes the load more
1744  * complex, but we do not want the timer to keep ticking unless the
1745  * entropy loop is running.
1746  *
1747  * So the re-arming always happens in the entropy loop itself.
1748  */
1749 static void entropy_timer(struct timer_list *t)
1750 {
1751         credit_entropy_bits(&input_pool, 1);
1752 }
1753 
1754 /*
1755  * If we have an actual cycle counter, see if we can
1756  * generate enough entropy with timing noise
1757  */
1758 static void try_to_generate_entropy(void)
1759 {
1760         struct {
1761                 unsigned long now;
1762                 struct timer_list timer;
1763         } stack;
1764 
1765         stack.now = random_get_entropy();
1766 
1767         /* Slow counter - or none. Don't even bother */
1768         if (stack.now == random_get_entropy())
1769                 return;
1770 
1771         timer_setup_on_stack(&stack.timer, entropy_timer, 0);
1772         while (!crng_ready()) {
1773                 if (!timer_pending(&stack.timer))
1774                         mod_timer(&stack.timer, jiffies+1);
1775                 mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1776                 schedule();
1777                 stack.now = random_get_entropy();
1778         }
1779 
1780         del_timer_sync(&stack.timer);
1781         destroy_timer_on_stack(&stack.timer);
1782         mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
1783 }
1784 
1785 /*
1786  * Wait for the urandom pool to be seeded and thus guaranteed to supply
1787  * cryptographically secure random numbers. This applies to: the /dev/urandom
1788  * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
1789  * family of functions. Using any of these functions without first calling
1790  * this function forfeits the guarantee of security.
1791  *
1792  * Returns: 0 if the urandom pool has been seeded.
1793  *          -ERESTARTSYS if the function was interrupted by a signal.
1794  */
1795 int wait_for_random_bytes(void)
1796 {
1797         if (likely(crng_ready()))
1798                 return 0;
1799 
1800         do {
1801                 int ret;
1802                 ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
1803                 if (ret)
1804                         return ret > 0 ? 0 : ret;
1805 
1806                 try_to_generate_entropy();
1807         } while (!crng_ready());
1808 
1809         return 0;
1810 }
1811 EXPORT_SYMBOL(wait_for_random_bytes);
1812 
1813 /*
1814  * Returns whether or not the urandom pool has been seeded and thus guaranteed
1815  * to supply cryptographically secure random numbers. This applies to: the
1816  * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
1817  * ,u64,int,long} family of functions.
1818  *
1819  * Returns: true if the urandom pool has been seeded.
1820  *          false if the urandom pool has not been seeded.
1821  */
1822 bool rng_is_initialized(void)
1823 {
1824         return crng_ready();
1825 }
1826 EXPORT_SYMBOL(rng_is_initialized);
1827 
1828 /*
1829  * Add a callback function that will be invoked when the nonblocking
1830  * pool is initialised.
1831  *
1832  * returns: 0 if callback is successfully added
1833  *          -EALREADY if pool is already initialised (callback not called)
1834  *          -ENOENT if module for callback is not alive
1835  */
1836 int add_random_ready_callback(struct random_ready_callback *rdy)
1837 {
1838         struct module *owner;
1839         unsigned long flags;
1840         int err = -EALREADY;
1841 
1842         if (crng_ready())
1843                 return err;
1844 
1845         owner = rdy->owner;
1846         if (!try_module_get(owner))
1847                 return -ENOENT;
1848 
1849         spin_lock_irqsave(&random_ready_list_lock, flags);
1850         if (crng_ready())
1851                 goto out;
1852 
1853         owner = NULL;
1854 
1855         list_add(&rdy->list, &random_ready_list);
1856         err = 0;
1857 
1858 out:
1859         spin_unlock_irqrestore(&random_ready_list_lock, flags);
1860 
1861         module_put(owner);
1862 
1863         return err;
1864 }
1865 EXPORT_SYMBOL(add_random_ready_callback);
1866 
1867 /*
1868  * Delete a previously registered readiness callback function.
1869  */
1870 void del_random_ready_callback(struct random_ready_callback *rdy)
1871 {
1872         unsigned long flags;
1873         struct module *owner = NULL;
1874 
1875         spin_lock_irqsave(&random_ready_list_lock, flags);
1876         if (!list_empty(&rdy->list)) {
1877                 list_del_init(&rdy->list);
1878                 owner = rdy->owner;
1879         }
1880         spin_unlock_irqrestore(&random_ready_list_lock, flags);
1881 
1882         module_put(owner);
1883 }
1884 EXPORT_SYMBOL(del_random_ready_callback);
1885 
1886 /*
1887  * This function will use the architecture-specific hardware random
1888  * number generator if it is available.  The arch-specific hw RNG will
1889  * almost certainly be faster than what we can do in software, but it
1890  * is impossible to verify that it is implemented securely (as
1891  * opposed, to, say, the AES encryption of a sequence number using a
1892  * key known by the NSA).  So it's useful if we need the speed, but
1893  * only if we're willing to trust the hardware manufacturer not to
1894  * have put in a back door.
1895  *
1896  * Return number of bytes filled in.
1897  */
1898 int __must_check get_random_bytes_arch(void *buf, int nbytes)
1899 {
1900         int left = nbytes;
1901         char *p = buf;
1902 
1903         trace_get_random_bytes_arch(left, _RET_IP_);
1904         while (left) {
1905                 unsigned long v;
1906                 int chunk = min_t(int, left, sizeof(unsigned long));
1907 
1908                 if (!arch_get_random_long(&v))
1909                         break;
1910 
1911                 memcpy(p, &v, chunk);
1912                 p += chunk;
1913                 left -= chunk;
1914         }
1915 
1916         return nbytes - left;
1917 }
1918 EXPORT_SYMBOL(get_random_bytes_arch);
1919 
1920 /*
1921  * init_std_data - initialize pool with system data
1922  *
1923  * @r: pool to initialize
1924  *
1925  * This function clears the pool's entropy count and mixes some system
1926  * data into the pool to prepare it for use. The pool is not cleared
1927  * as that can only decrease the entropy in the pool.
1928  */
1929 static void __init init_std_data(struct entropy_store *r)
1930 {
1931         int i;
1932         ktime_t now = ktime_get_real();
1933         unsigned long rv;
1934 
1935         r->last_pulled = jiffies;
1936         mix_pool_bytes(r, &now, sizeof(now));
1937         for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1938                 if (!arch_get_random_seed_long(&rv) &&
1939                     !arch_get_random_long(&rv))
1940                         rv = random_get_entropy();
1941                 mix_pool_bytes(r, &rv, sizeof(rv));
1942         }
1943         mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1944 }
1945 
1946 /*
1947  * Note that setup_arch() may call add_device_randomness()
1948  * long before we get here. This allows seeding of the pools
1949  * with some platform dependent data very early in the boot
1950  * process. But it limits our options here. We must use
1951  * statically allocated structures that already have all
1952  * initializations complete at compile time. We should also
1953  * take care not to overwrite the precious per platform data
1954  * we were given.
1955  */
1956 int __init rand_initialize(void)
1957 {
1958         init_std_data(&input_pool);
1959         init_std_data(&blocking_pool);
1960         crng_initialize(&primary_crng);
1961         crng_global_init_time = jiffies;
1962         if (ratelimit_disable) {
1963                 urandom_warning.interval = 0;
1964                 unseeded_warning.interval = 0;
1965         }
1966         return 0;
1967 }
1968 
1969 #ifdef CONFIG_BLOCK
1970 void rand_initialize_disk(struct gendisk *disk)
1971 {
1972         struct timer_rand_state *state;
1973 
1974         /*
1975          * If kzalloc returns null, we just won't use that entropy
1976          * source.
1977          */
1978         state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1979         if (state) {
1980                 state->last_time = INITIAL_JIFFIES;
1981                 disk->random = state;
1982         }
1983 }
1984 #endif
1985 
1986 static ssize_t
1987 _random_read(int nonblock, char __user *buf, size_t nbytes)
1988 {
1989         ssize_t n;
1990 
1991         if (nbytes == 0)
1992                 return 0;
1993 
1994         nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1995         while (1) {
1996                 n = extract_entropy_user(&blocking_pool, buf, nbytes);
1997                 if (n < 0)
1998                         return n;
1999                 trace_random_read(n*8, (nbytes-n)*8,
2000                                   ENTROPY_BITS(&blocking_pool),
2001                                   ENTROPY_BITS(&input_pool));
2002                 if (n > 0)
2003                         return n;
2004 
2005                 /* Pool is (near) empty.  Maybe wait and retry. */
2006                 if (nonblock)
2007                         return -EAGAIN;
2008 
2009                 wait_event_interruptible(random_read_wait,
2010                     blocking_pool.initialized &&
2011                     (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits));
2012                 if (signal_pending(current))
2013                         return -ERESTARTSYS;
2014         }
2015 }
2016 
2017 static ssize_t
2018 random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
2019 {
2020         return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
2021 }
2022 
2023 static ssize_t
2024 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
2025 {
2026         unsigned long flags;
2027         static int maxwarn = 10;
2028         int ret;
2029 
2030         if (!crng_ready() && maxwarn > 0) {
2031                 maxwarn--;
2032                 if (__ratelimit(&urandom_warning))
2033                         printk(KERN_NOTICE "random: %s: uninitialized "
2034                                "urandom read (%zd bytes read)\n",
2035                                current->comm, nbytes);
2036                 spin_lock_irqsave(&primary_crng.lock, flags);
2037                 crng_init_cnt = 0;
2038                 spin_unlock_irqrestore(&primary_crng.lock, flags);
2039         }
2040         nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
2041         ret = extract_crng_user(buf, nbytes);
2042         trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
2043         return ret;
2044 }
2045 
2046 static __poll_t
2047 random_poll(struct file *file, poll_table * wait)
2048 {
2049         __poll_t mask;
2050 
2051         poll_wait(file, &random_read_wait, wait);
2052         poll_wait(file, &random_write_wait, wait);
2053         mask = 0;
2054         if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
2055                 mask |= EPOLLIN | EPOLLRDNORM;
2056         if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
2057                 mask |= EPOLLOUT | EPOLLWRNORM;
2058         return mask;
2059 }
2060 
2061 static int
2062 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
2063 {
2064         size_t bytes;
2065         __u32 t, buf[16];
2066         const char __user *p = buffer;
2067 
2068         while (count > 0) {
2069                 int b, i = 0;
2070 
2071                 bytes = min(count, sizeof(buf));
2072                 if (copy_from_user(&buf, p, bytes))
2073                         return -EFAULT;
2074 
2075                 for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
2076                         if (!arch_get_random_int(&t))
2077                                 break;
2078                         buf[i] ^= t;
2079                 }
2080 
2081                 count -= bytes;
2082                 p += bytes;
2083 
2084                 mix_pool_bytes(r, buf, bytes);
2085                 cond_resched();
2086         }
2087 
2088         return 0;
2089 }
2090 
2091 static ssize_t random_write(struct file *file, const char __user *buffer,
2092                             size_t count, loff_t *ppos)
2093 {
2094         size_t ret;
2095 
2096         ret = write_pool(&input_pool, buffer, count);
2097         if (ret)
2098                 return ret;
2099 
2100         return (ssize_t)count;
2101 }
2102 
2103 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
2104 {
2105         int size, ent_count;
2106         int __user *p = (int __user *)arg;
2107         int retval;
2108 
2109         switch (cmd) {
2110         case RNDGETENTCNT:
2111                 /* inherently racy, no point locking */
2112                 ent_count = ENTROPY_BITS(&input_pool);
2113                 if (put_user(ent_count, p))
2114                         return -EFAULT;
2115                 return 0;
2116         case RNDADDTOENTCNT:
2117                 if (!capable(CAP_SYS_ADMIN))
2118                         return -EPERM;
2119                 if (get_user(ent_count, p))
2120                         return -EFAULT;
2121                 return credit_entropy_bits_safe(&input_pool, ent_count);
2122         case RNDADDENTROPY:
2123                 if (!capable(CAP_SYS_ADMIN))
2124                         return -EPERM;
2125                 if (get_user(ent_count, p++))
2126                         return -EFAULT;
2127                 if (ent_count < 0)
2128                         return -EINVAL;
2129                 if (get_user(size, p++))
2130                         return -EFAULT;
2131                 retval = write_pool(&input_pool, (const char __user *)p,
2132                                     size);
2133                 if (retval < 0)
2134                         return retval;
2135                 return credit_entropy_bits_safe(&input_pool, ent_count);
2136         case RNDZAPENTCNT:
2137         case RNDCLEARPOOL:
2138                 /*
2139                  * Clear the entropy pool counters. We no longer clear
2140                  * the entropy pool, as that's silly.
2141                  */
2142                 if (!capable(CAP_SYS_ADMIN))
2143                         return -EPERM;
2144                 input_pool.entropy_count = 0;
2145                 blocking_pool.entropy_count = 0;
2146                 return 0;
2147         case RNDRESEEDCRNG:
2148                 if (!capable(CAP_SYS_ADMIN))
2149                         return -EPERM;
2150                 if (crng_init < 2)
2151                         return -ENODATA;
2152                 crng_reseed(&primary_crng, NULL);
2153                 crng_global_init_time = jiffies - 1;
2154                 return 0;
2155         default:
2156                 return -EINVAL;
2157         }
2158 }
2159 
2160 static int random_fasync(int fd, struct file *filp, int on)
2161 {
2162         return fasync_helper(fd, filp, on, &fasync);
2163 }
2164 
2165 const struct file_operations random_fops = {
2166         .read  = random_read,
2167         .write = random_write,
2168         .poll  = random_poll,
2169         .unlocked_ioctl = random_ioctl,
2170         .fasync = random_fasync,
2171         .llseek = noop_llseek,
2172 };
2173 
2174 const struct file_operations urandom_fops = {
2175         .read  = urandom_read,
2176         .write = random_write,
2177         .unlocked_ioctl = random_ioctl,
2178         .fasync = random_fasync,
2179         .llseek = noop_llseek,
2180 };
2181 
2182 SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
2183                 unsigned int, flags)
2184 {
2185         int ret;
2186 
2187         if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
2188                 return -EINVAL;
2189 
2190         if (count > INT_MAX)
2191                 count = INT_MAX;
2192 
2193         if (flags & GRND_RANDOM)
2194                 return _random_read(flags & GRND_NONBLOCK, buf, count);
2195 
2196         if (!crng_ready()) {
2197                 if (flags & GRND_NONBLOCK)
2198                         return -EAGAIN;
2199                 ret = wait_for_random_bytes();
2200                 if (unlikely(ret))
2201                         return ret;
2202         }
2203         return urandom_read(NULL, buf, count, NULL);
2204 }
2205 
2206 /********************************************************************
2207  *
2208  * Sysctl interface
2209  *
2210  ********************************************************************/
2211 
2212 #ifdef CONFIG_SYSCTL
2213 
2214 #include <linux/sysctl.h>
2215 
2216 static int min_read_thresh = 8, min_write_thresh;
2217 static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
2218 static int max_write_thresh = INPUT_POOL_WORDS * 32;
2219 static int random_min_urandom_seed = 60;
2220 static char sysctl_bootid[16];
2221 
2222 /*
2223  * This function is used to return both the bootid UUID, and random
2224  * UUID.  The difference is in whether table->data is NULL; if it is,
2225  * then a new UUID is generated and returned to the user.
2226  *
2227  * If the user accesses this via the proc interface, the UUID will be
2228  * returned as an ASCII string in the standard UUID format; if via the
2229  * sysctl system call, as 16 bytes of binary data.
2230  */
2231 static int proc_do_uuid(struct ctl_table *table, int write,
2232                         void __user *buffer, size_t *lenp, loff_t *ppos)
2233 {
2234         struct ctl_table fake_table;
2235         unsigned char buf[64], tmp_uuid[16], *uuid;
2236 
2237         uuid = table->data;
2238         if (!uuid) {
2239                 uuid = tmp_uuid;
2240                 generate_random_uuid(uuid);
2241         } else {
2242                 static DEFINE_SPINLOCK(bootid_spinlock);
2243 
2244                 spin_lock(&bootid_spinlock);
2245                 if (!uuid[8])
2246                         generate_random_uuid(uuid);
2247                 spin_unlock(&bootid_spinlock);
2248         }
2249 
2250         sprintf(buf, "%pU", uuid);
2251 
2252         fake_table.data = buf;
2253         fake_table.maxlen = sizeof(buf);
2254 
2255         return proc_dostring(&fake_table, write, buffer, lenp, ppos);
2256 }
2257 
2258 /*
2259  * Return entropy available scaled to integral bits
2260  */
2261 static int proc_do_entropy(struct ctl_table *table, int write,
2262                            void __user *buffer, size_t *lenp, loff_t *ppos)
2263 {
2264         struct ctl_table fake_table;
2265         int entropy_count;
2266 
2267         entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
2268 
2269         fake_table.data = &entropy_count;
2270         fake_table.maxlen = sizeof(entropy_count);
2271 
2272         return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
2273 }
2274 
2275 static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
2276 extern struct ctl_table random_table[];
2277 struct ctl_table random_table[] = {
2278         {
2279                 .procname       = "poolsize",
2280                 .data           = &sysctl_poolsize,
2281                 .maxlen         = sizeof(int),
2282                 .mode           = 0444,
2283                 .proc_handler   = proc_dointvec,
2284         },
2285         {
2286                 .procname       = "entropy_avail",
2287                 .maxlen         = sizeof(int),
2288                 .mode           = 0444,
2289                 .proc_handler   = proc_do_entropy,
2290                 .data           = &input_pool.entropy_count,
2291         },
2292         {
2293                 .procname       = "read_wakeup_threshold",
2294                 .data           = &random_read_wakeup_bits,
2295                 .maxlen         = sizeof(int),
2296                 .mode           = 0644,
2297                 .proc_handler   = proc_dointvec_minmax,
2298                 .extra1         = &min_read_thresh,
2299                 .extra2         = &max_read_thresh,
2300         },
2301         {
2302                 .procname       = "write_wakeup_threshold",
2303                 .data           = &random_write_wakeup_bits,
2304                 .maxlen         = sizeof(int),
2305                 .mode           = 0644,
2306                 .proc_handler   = proc_dointvec_minmax,
2307                 .extra1         = &min_write_thresh,
2308                 .extra2         = &max_write_thresh,
2309         },
2310         {
2311                 .procname       = "urandom_min_reseed_secs",
2312                 .data           = &random_min_urandom_seed,
2313                 .maxlen         = sizeof(int),
2314                 .mode           = 0644,
2315                 .proc_handler   = proc_dointvec,
2316         },
2317         {
2318                 .procname       = "boot_id",
2319                 .data           = &sysctl_bootid,
2320                 .maxlen         = 16,
2321                 .mode           = 0444,
2322                 .proc_handler   = proc_do_uuid,
2323         },
2324         {
2325                 .procname       = "uuid",
2326                 .maxlen         = 16,
2327                 .mode           = 0444,
2328                 .proc_handler   = proc_do_uuid,
2329         },
2330 #ifdef ADD_INTERRUPT_BENCH
2331         {
2332                 .procname       = "add_interrupt_avg_cycles",
2333                 .data           = &avg_cycles,
2334                 .maxlen         = sizeof(avg_cycles),
2335                 .mode           = 0444,
2336                 .proc_handler   = proc_doulongvec_minmax,
2337         },
2338         {
2339                 .procname       = "add_interrupt_avg_deviation",
2340                 .data           = &avg_deviation,
2341                 .maxlen         = sizeof(avg_deviation),
2342                 .mode           = 0444,
2343                 .proc_handler   = proc_doulongvec_minmax,
2344         },
2345 #endif
2346         { }
2347 };
2348 #endif  /* CONFIG_SYSCTL */
2349 
2350 struct batched_entropy {
2351         union {
2352                 u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)];
2353                 u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)];
2354         };
2355         unsigned int position;
2356         spinlock_t batch_lock;
2357 };
2358 
2359 /*
2360  * Get a random word for internal kernel use only. The quality of the random
2361  * number is good as /dev/urandom, but there is no backtrack protection, with
2362  * the goal of being quite fast and not depleting entropy. In order to ensure
2363  * that the randomness provided by this function is okay, the function
2364  * wait_for_random_bytes() should be called and return 0 at least once at any
2365  * point prior.
2366  */
2367 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
2368         .batch_lock     = __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock),
2369 };
2370 
2371 u64 get_random_u64(void)
2372 {
2373         u64 ret;
2374         unsigned long flags;
2375         struct batched_entropy *batch;
2376         static void *previous;
2377 
2378         warn_unseeded_randomness(&previous);
2379 
2380         batch = raw_cpu_ptr(&batched_entropy_u64);
2381         spin_lock_irqsave(&batch->batch_lock, flags);
2382         if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
2383                 extract_crng((u8 *)batch->entropy_u64);
2384                 batch->position = 0;
2385         }
2386         ret = batch->entropy_u64[batch->position++];
2387         spin_unlock_irqrestore(&batch->batch_lock, flags);
2388         return ret;
2389 }
2390 EXPORT_SYMBOL(get_random_u64);
2391 
2392 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = {
2393         .batch_lock     = __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock),
2394 };
2395 u32 get_random_u32(void)
2396 {
2397         u32 ret;
2398         unsigned long flags;
2399         struct batched_entropy *batch;
2400         static void *previous;
2401 
2402         warn_unseeded_randomness(&previous);
2403 
2404         batch = raw_cpu_ptr(&batched_entropy_u32);
2405         spin_lock_irqsave(&batch->batch_lock, flags);
2406         if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
2407                 extract_crng((u8 *)batch->entropy_u32);
2408                 batch->position = 0;
2409         }
2410         ret = batch->entropy_u32[batch->position++];
2411         spin_unlock_irqrestore(&batch->batch_lock, flags);
2412         return ret;
2413 }
2414 EXPORT_SYMBOL(get_random_u32);
2415 
2416 /* It's important to invalidate all potential batched entropy that might
2417  * be stored before the crng is initialized, which we can do lazily by
2418  * simply resetting the counter to zero so that it's re-extracted on the
2419  * next usage. */
2420 static void invalidate_batched_entropy(void)
2421 {
2422         int cpu;
2423         unsigned long flags;
2424 
2425         for_each_possible_cpu (cpu) {
2426                 struct batched_entropy *batched_entropy;
2427 
2428                 batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu);
2429                 spin_lock_irqsave(&batched_entropy->batch_lock, flags);
2430                 batched_entropy->position = 0;
2431                 spin_unlock(&batched_entropy->batch_lock);
2432 
2433                 batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu);
2434                 spin_lock(&batched_entropy->batch_lock);
2435                 batched_entropy->position = 0;
2436                 spin_unlock_irqrestore(&batched_entropy->batch_lock, flags);
2437         }
2438 }
2439 
2440 /**
2441  * randomize_page - Generate a random, page aligned address
2442  * @start:      The smallest acceptable address the caller will take.
2443  * @range:      The size of the area, starting at @start, within which the
2444  *              random address must fall.
2445  *
2446  * If @start + @range would overflow, @range is capped.
2447  *
2448  * NOTE: Historical use of randomize_range, which this replaces, presumed that
2449  * @start was already page aligned.  We now align it regardless.
2450  *
2451  * Return: A page aligned address within [start, start + range).  On error,
2452  * @start is returned.
2453  */
2454 unsigned long
2455 randomize_page(unsigned long start, unsigned long range)
2456 {
2457         if (!PAGE_ALIGNED(start)) {
2458                 range -= PAGE_ALIGN(start) - start;
2459                 start = PAGE_ALIGN(start);
2460         }
2461 
2462         if (start > ULONG_MAX - range)
2463                 range = ULONG_MAX - start;
2464 
2465         range >>= PAGE_SHIFT;
2466 
2467         if (range == 0)
2468                 return start;
2469 
2470         return start + (get_random_long() % range << PAGE_SHIFT);
2471 }
2472 
2473 /* Interface for in-kernel drivers of true hardware RNGs.
2474  * Those devices may produce endless random bits and will be throttled
2475  * when our pool is full.
2476  */
2477 void add_hwgenerator_randomness(const char *buffer, size_t count,
2478                                 size_t entropy)
2479 {
2480         struct entropy_store *poolp = &input_pool;
2481 
2482         if (unlikely(crng_init == 0)) {
2483                 crng_fast_load(buffer, count);
2484                 return;
2485         }
2486 
2487         /* Suspend writing if we're above the trickle threshold.
2488          * We'll be woken up again once below random_write_wakeup_thresh,
2489          * or when the calling thread is about to terminate.
2490          */
2491         wait_event_interruptible(random_write_wait, kthread_should_stop() ||
2492                         ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
2493         mix_pool_bytes(poolp, buffer, count);
2494         credit_entropy_bits(poolp, entropy);
2495 }
2496 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
2497 
2498 /* Handle random seed passed by bootloader.
2499  * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
2500  * it would be regarded as device data.
2501  * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
2502  */
2503 void add_bootloader_randomness(const void *buf, unsigned int size)
2504 {
2505         if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
2506                 add_hwgenerator_randomness(buf, size, size * 8);
2507         else
2508                 add_device_randomness(buf, size);
2509 }
2510 EXPORT_SYMBOL_GPL(add_bootloader_randomness);