linux/drivers/char/random.c
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   1/*
   2 * random.c -- A strong random number generator
   3 *
   4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
   5 *
   6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
   7 * rights reserved.
   8 *
   9 * Redistribution and use in source and binary forms, with or without
  10 * modification, are permitted provided that the following conditions
  11 * are met:
  12 * 1. Redistributions of source code must retain the above copyright
  13 *    notice, and the entire permission notice in its entirety,
  14 *    including the disclaimer of warranties.
  15 * 2. Redistributions in binary form must reproduce the above copyright
  16 *    notice, this list of conditions and the following disclaimer in the
  17 *    documentation and/or other materials provided with the distribution.
  18 * 3. The name of the author may not be used to endorse or promote
  19 *    products derived from this software without specific prior
  20 *    written permission.
  21 *
  22 * ALTERNATIVELY, this product may be distributed under the terms of
  23 * the GNU General Public License, in which case the provisions of the GPL are
  24 * required INSTEAD OF the above restrictions.  (This clause is
  25 * necessary due to a potential bad interaction between the GPL and
  26 * the restrictions contained in a BSD-style copyright.)
  27 *
  28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  31 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
  39 * DAMAGE.
  40 */
  41
  42/*
  43 * (now, with legal B.S. out of the way.....)
  44 *
  45 * This routine gathers environmental noise from device drivers, etc.,
  46 * and returns good random numbers, suitable for cryptographic use.
  47 * Besides the obvious cryptographic uses, these numbers are also good
  48 * for seeding TCP sequence numbers, and other places where it is
  49 * desirable to have numbers which are not only random, but hard to
  50 * predict by an attacker.
  51 *
  52 * Theory of operation
  53 * ===================
  54 *
  55 * Computers are very predictable devices.  Hence it is extremely hard
  56 * to produce truly random numbers on a computer --- as opposed to
  57 * pseudo-random numbers, which can easily generated by using a
  58 * algorithm.  Unfortunately, it is very easy for attackers to guess
  59 * the sequence of pseudo-random number generators, and for some
  60 * applications this is not acceptable.  So instead, we must try to
  61 * gather "environmental noise" from the computer's environment, which
  62 * must be hard for outside attackers to observe, and use that to
  63 * generate random numbers.  In a Unix environment, this is best done
  64 * from inside the kernel.
  65 *
  66 * Sources of randomness from the environment include inter-keyboard
  67 * timings, inter-interrupt timings from some interrupts, and other
  68 * events which are both (a) non-deterministic and (b) hard for an
  69 * outside observer to measure.  Randomness from these sources are
  70 * added to an "entropy pool", which is mixed using a CRC-like function.
  71 * This is not cryptographically strong, but it is adequate assuming
  72 * the randomness is not chosen maliciously, and it is fast enough that
  73 * the overhead of doing it on every interrupt is very reasonable.
  74 * As random bytes are mixed into the entropy pool, the routines keep
  75 * an *estimate* of how many bits of randomness have been stored into
  76 * the random number generator's internal state.
  77 *
  78 * When random bytes are desired, they are obtained by taking the SHA
  79 * hash of the contents of the "entropy pool".  The SHA hash avoids
  80 * exposing the internal state of the entropy pool.  It is believed to
  81 * be computationally infeasible to derive any useful information
  82 * about the input of SHA from its output.  Even if it is possible to
  83 * analyze SHA in some clever way, as long as the amount of data
  84 * returned from the generator is less than the inherent entropy in
  85 * the pool, the output data is totally unpredictable.  For this
  86 * reason, the routine decreases its internal estimate of how many
  87 * bits of "true randomness" are contained in the entropy pool as it
  88 * outputs random numbers.
  89 *
  90 * If this estimate goes to zero, the routine can still generate
  91 * random numbers; however, an attacker may (at least in theory) be
  92 * able to infer the future output of the generator from prior
  93 * outputs.  This requires successful cryptanalysis of SHA, which is
  94 * not believed to be feasible, but there is a remote possibility.
  95 * Nonetheless, these numbers should be useful for the vast majority
  96 * of purposes.
  97 *
  98 * Exported interfaces ---- output
  99 * ===============================
 100 *
 101 * There are three exported interfaces; the first is one designed to
 102 * be used from within the kernel:
 103 *
 104 *      void get_random_bytes(void *buf, int nbytes);
 105 *
 106 * This interface will return the requested number of random bytes,
 107 * and place it in the requested buffer.
 108 *
 109 * The two other interfaces are two character devices /dev/random and
 110 * /dev/urandom.  /dev/random is suitable for use when very high
 111 * quality randomness is desired (for example, for key generation or
 112 * one-time pads), as it will only return a maximum of the number of
 113 * bits of randomness (as estimated by the random number generator)
 114 * contained in the entropy pool.
 115 *
 116 * The /dev/urandom device does not have this limit, and will return
 117 * as many bytes as are requested.  As more and more random bytes are
 118 * requested without giving time for the entropy pool to recharge,
 119 * this will result in random numbers that are merely cryptographically
 120 * strong.  For many applications, however, this is acceptable.
 121 *
 122 * Exported interfaces ---- input
 123 * ==============================
 124 *
 125 * The current exported interfaces for gathering environmental noise
 126 * from the devices are:
 127 *
 128 *      void add_device_randomness(const void *buf, unsigned int size);
 129 *      void add_input_randomness(unsigned int type, unsigned int code,
 130 *                                unsigned int value);
 131 *      void add_interrupt_randomness(int irq, int irq_flags);
 132 *      void add_disk_randomness(struct gendisk *disk);
 133 *
 134 * add_device_randomness() is for adding data to the random pool that
 135 * is likely to differ between two devices (or possibly even per boot).
 136 * This would be things like MAC addresses or serial numbers, or the
 137 * read-out of the RTC. This does *not* add any actual entropy to the
 138 * pool, but it initializes the pool to different values for devices
 139 * that might otherwise be identical and have very little entropy
 140 * available to them (particularly common in the embedded world).
 141 *
 142 * add_input_randomness() uses the input layer interrupt timing, as well as
 143 * the event type information from the hardware.
 144 *
 145 * add_interrupt_randomness() uses the interrupt timing as random
 146 * inputs to the entropy pool. Using the cycle counters and the irq source
 147 * as inputs, it feeds the randomness roughly once a second.
 148 *
 149 * add_disk_randomness() uses what amounts to the seek time of block
 150 * layer request events, on a per-disk_devt basis, as input to the
 151 * entropy pool. Note that high-speed solid state drives with very low
 152 * seek times do not make for good sources of entropy, as their seek
 153 * times are usually fairly consistent.
 154 *
 155 * All of these routines try to estimate how many bits of randomness a
 156 * particular randomness source.  They do this by keeping track of the
 157 * first and second order deltas of the event timings.
 158 *
 159 * Ensuring unpredictability at system startup
 160 * ============================================
 161 *
 162 * When any operating system starts up, it will go through a sequence
 163 * of actions that are fairly predictable by an adversary, especially
 164 * if the start-up does not involve interaction with a human operator.
 165 * This reduces the actual number of bits of unpredictability in the
 166 * entropy pool below the value in entropy_count.  In order to
 167 * counteract this effect, it helps to carry information in the
 168 * entropy pool across shut-downs and start-ups.  To do this, put the
 169 * following lines an appropriate script which is run during the boot
 170 * sequence:
 171 *
 172 *      echo "Initializing random number generator..."
 173 *      random_seed=/var/run/random-seed
 174 *      # Carry a random seed from start-up to start-up
 175 *      # Load and then save the whole entropy pool
 176 *      if [ -f $random_seed ]; then
 177 *              cat $random_seed >/dev/urandom
 178 *      else
 179 *              touch $random_seed
 180 *      fi
 181 *      chmod 600 $random_seed
 182 *      dd if=/dev/urandom of=$random_seed count=1 bs=512
 183 *
 184 * and the following lines in an appropriate script which is run as
 185 * the system is shutdown:
 186 *
 187 *      # Carry a random seed from shut-down to start-up
 188 *      # Save the whole entropy pool
 189 *      echo "Saving random seed..."
 190 *      random_seed=/var/run/random-seed
 191 *      touch $random_seed
 192 *      chmod 600 $random_seed
 193 *      dd if=/dev/urandom of=$random_seed count=1 bs=512
 194 *
 195 * For example, on most modern systems using the System V init
 196 * scripts, such code fragments would be found in
 197 * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
 198 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
 199 *
 200 * Effectively, these commands cause the contents of the entropy pool
 201 * to be saved at shut-down time and reloaded into the entropy pool at
 202 * start-up.  (The 'dd' in the addition to the bootup script is to
 203 * make sure that /etc/random-seed is different for every start-up,
 204 * even if the system crashes without executing rc.0.)  Even with
 205 * complete knowledge of the start-up activities, predicting the state
 206 * of the entropy pool requires knowledge of the previous history of
 207 * the system.
 208 *
 209 * Configuring the /dev/random driver under Linux
 210 * ==============================================
 211 *
 212 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
 213 * the /dev/mem major number (#1).  So if your system does not have
 214 * /dev/random and /dev/urandom created already, they can be created
 215 * by using the commands:
 216 *
 217 *      mknod /dev/random c 1 8
 218 *      mknod /dev/urandom c 1 9
 219 *
 220 * Acknowledgements:
 221 * =================
 222 *
 223 * Ideas for constructing this random number generator were derived
 224 * from Pretty Good Privacy's random number generator, and from private
 225 * discussions with Phil Karn.  Colin Plumb provided a faster random
 226 * number generator, which speed up the mixing function of the entropy
 227 * pool, taken from PGPfone.  Dale Worley has also contributed many
 228 * useful ideas and suggestions to improve this driver.
 229 *
 230 * Any flaws in the design are solely my responsibility, and should
 231 * not be attributed to the Phil, Colin, or any of authors of PGP.
 232 *
 233 * Further background information on this topic may be obtained from
 234 * RFC 1750, "Randomness Recommendations for Security", by Donald
 235 * Eastlake, Steve Crocker, and Jeff Schiller.
 236 */
 237
 238#include <linux/utsname.h>
 239#include <linux/module.h>
 240#include <linux/kernel.h>
 241#include <linux/major.h>
 242#include <linux/string.h>
 243#include <linux/fcntl.h>
 244#include <linux/slab.h>
 245#include <linux/random.h>
 246#include <linux/poll.h>
 247#include <linux/init.h>
 248#include <linux/fs.h>
 249#include <linux/genhd.h>
 250#include <linux/interrupt.h>
 251#include <linux/mm.h>
 252#include <linux/spinlock.h>
 253#include <linux/kthread.h>
 254#include <linux/percpu.h>
 255#include <linux/cryptohash.h>
 256#include <linux/fips.h>
 257#include <linux/ptrace.h>
 258#include <linux/kmemcheck.h>
 259#include <linux/workqueue.h>
 260#include <linux/irq.h>
 261#include <linux/syscalls.h>
 262#include <linux/completion.h>
 263#include <linux/uuid.h>
 264
 265#include <asm/processor.h>
 266#include <asm/uaccess.h>
 267#include <asm/irq.h>
 268#include <asm/irq_regs.h>
 269#include <asm/io.h>
 270
 271#define CREATE_TRACE_POINTS
 272#include <trace/events/random.h>
 273
 274/* #define ADD_INTERRUPT_BENCH */
 275
 276/*
 277 * Configuration information
 278 */
 279#define INPUT_POOL_SHIFT        12
 280#define INPUT_POOL_WORDS        (1 << (INPUT_POOL_SHIFT-5))
 281#define OUTPUT_POOL_SHIFT       10
 282#define OUTPUT_POOL_WORDS       (1 << (OUTPUT_POOL_SHIFT-5))
 283#define SEC_XFER_SIZE           512
 284#define EXTRACT_SIZE            10
 285
 286#define DEBUG_RANDOM_BOOT 0
 287
 288#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 289
 290/*
 291 * To allow fractional bits to be tracked, the entropy_count field is
 292 * denominated in units of 1/8th bits.
 293 *
 294 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
 295 * credit_entropy_bits() needs to be 64 bits wide.
 296 */
 297#define ENTROPY_SHIFT 3
 298#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 299
 300/*
 301 * The minimum number of bits of entropy before we wake up a read on
 302 * /dev/random.  Should be enough to do a significant reseed.
 303 */
 304static int random_read_wakeup_bits = 64;
 305
 306/*
 307 * If the entropy count falls under this number of bits, then we
 308 * should wake up processes which are selecting or polling on write
 309 * access to /dev/random.
 310 */
 311static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
 312
 313/*
 314 * The minimum number of seconds between urandom pool reseeding.  We
 315 * do this to limit the amount of entropy that can be drained from the
 316 * input pool even if there are heavy demands on /dev/urandom.
 317 */
 318static int random_min_urandom_seed = 60;
 319
 320/*
 321 * Originally, we used a primitive polynomial of degree .poolwords
 322 * over GF(2).  The taps for various sizes are defined below.  They
 323 * were chosen to be evenly spaced except for the last tap, which is 1
 324 * to get the twisting happening as fast as possible.
 325 *
 326 * For the purposes of better mixing, we use the CRC-32 polynomial as
 327 * well to make a (modified) twisted Generalized Feedback Shift
 328 * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
 329 * generators.  ACM Transactions on Modeling and Computer Simulation
 330 * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
 331 * GFSR generators II.  ACM Transactions on Modeling and Computer
 332 * Simulation 4:254-266)
 333 *
 334 * Thanks to Colin Plumb for suggesting this.
 335 *
 336 * The mixing operation is much less sensitive than the output hash,
 337 * where we use SHA-1.  All that we want of mixing operation is that
 338 * it be a good non-cryptographic hash; i.e. it not produce collisions
 339 * when fed "random" data of the sort we expect to see.  As long as
 340 * the pool state differs for different inputs, we have preserved the
 341 * input entropy and done a good job.  The fact that an intelligent
 342 * attacker can construct inputs that will produce controlled
 343 * alterations to the pool's state is not important because we don't
 344 * consider such inputs to contribute any randomness.  The only
 345 * property we need with respect to them is that the attacker can't
 346 * increase his/her knowledge of the pool's state.  Since all
 347 * additions are reversible (knowing the final state and the input,
 348 * you can reconstruct the initial state), if an attacker has any
 349 * uncertainty about the initial state, he/she can only shuffle that
 350 * uncertainty about, but never cause any collisions (which would
 351 * decrease the uncertainty).
 352 *
 353 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
 354 * Videau in their paper, "The Linux Pseudorandom Number Generator
 355 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
 356 * paper, they point out that we are not using a true Twisted GFSR,
 357 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
 358 * is, with only three taps, instead of the six that we are using).
 359 * As a result, the resulting polynomial is neither primitive nor
 360 * irreducible, and hence does not have a maximal period over
 361 * GF(2**32).  They suggest a slight change to the generator
 362 * polynomial which improves the resulting TGFSR polynomial to be
 363 * irreducible, which we have made here.
 364 */
 365static struct poolinfo {
 366        int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
 367#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
 368        int tap1, tap2, tap3, tap4, tap5;
 369} poolinfo_table[] = {
 370        /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
 371        /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
 372        { S(128),       104,    76,     51,     25,     1 },
 373        /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
 374        /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
 375        { S(32),        26,     19,     14,     7,      1 },
 376#if 0
 377        /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 378        { S(2048),      1638,   1231,   819,    411,    1 },
 379
 380        /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 381        { S(1024),      817,    615,    412,    204,    1 },
 382
 383        /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 384        { S(1024),      819,    616,    410,    207,    2 },
 385
 386        /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 387        { S(512),       411,    308,    208,    104,    1 },
 388
 389        /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 390        { S(512),       409,    307,    206,    102,    2 },
 391        /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 392        { S(512),       409,    309,    205,    103,    2 },
 393
 394        /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 395        { S(256),       205,    155,    101,    52,     1 },
 396
 397        /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 398        { S(128),       103,    78,     51,     27,     2 },
 399
 400        /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 401        { S(64),        52,     39,     26,     14,     1 },
 402#endif
 403};
 404
 405/*
 406 * Static global variables
 407 */
 408static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 409static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 410static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
 411static struct fasync_struct *fasync;
 412
 413static DEFINE_SPINLOCK(random_ready_list_lock);
 414static LIST_HEAD(random_ready_list);
 415
 416/**********************************************************************
 417 *
 418 * OS independent entropy store.   Here are the functions which handle
 419 * storing entropy in an entropy pool.
 420 *
 421 **********************************************************************/
 422
 423struct entropy_store;
 424struct entropy_store {
 425        /* read-only data: */
 426        const struct poolinfo *poolinfo;
 427        __u32 *pool;
 428        const char *name;
 429        struct entropy_store *pull;
 430        struct work_struct push_work;
 431
 432        /* read-write data: */
 433        unsigned long last_pulled;
 434        spinlock_t lock;
 435        unsigned short add_ptr;
 436        unsigned short input_rotate;
 437        int entropy_count;
 438        int entropy_total;
 439        unsigned int initialized:1;
 440        unsigned int limit:1;
 441        unsigned int last_data_init:1;
 442        __u8 last_data[EXTRACT_SIZE];
 443};
 444
 445static void push_to_pool(struct work_struct *work);
 446static __u32 input_pool_data[INPUT_POOL_WORDS];
 447static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
 448static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
 449
 450static struct entropy_store input_pool = {
 451        .poolinfo = &poolinfo_table[0],
 452        .name = "input",
 453        .limit = 1,
 454        .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 455        .pool = input_pool_data
 456};
 457
 458static struct entropy_store blocking_pool = {
 459        .poolinfo = &poolinfo_table[1],
 460        .name = "blocking",
 461        .limit = 1,
 462        .pull = &input_pool,
 463        .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 464        .pool = blocking_pool_data,
 465        .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
 466                                        push_to_pool),
 467};
 468
 469static struct entropy_store nonblocking_pool = {
 470        .poolinfo = &poolinfo_table[1],
 471        .name = "nonblocking",
 472        .pull = &input_pool,
 473        .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
 474        .pool = nonblocking_pool_data,
 475        .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
 476                                        push_to_pool),
 477};
 478
 479static __u32 const twist_table[8] = {
 480        0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 481        0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 482
 483/*
 484 * This function adds bytes into the entropy "pool".  It does not
 485 * update the entropy estimate.  The caller should call
 486 * credit_entropy_bits if this is appropriate.
 487 *
 488 * The pool is stirred with a primitive polynomial of the appropriate
 489 * degree, and then twisted.  We twist by three bits at a time because
 490 * it's cheap to do so and helps slightly in the expected case where
 491 * the entropy is concentrated in the low-order bits.
 492 */
 493static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 494                            int nbytes)
 495{
 496        unsigned long i, tap1, tap2, tap3, tap4, tap5;
 497        int input_rotate;
 498        int wordmask = r->poolinfo->poolwords - 1;
 499        const char *bytes = in;
 500        __u32 w;
 501
 502        tap1 = r->poolinfo->tap1;
 503        tap2 = r->poolinfo->tap2;
 504        tap3 = r->poolinfo->tap3;
 505        tap4 = r->poolinfo->tap4;
 506        tap5 = r->poolinfo->tap5;
 507
 508        input_rotate = r->input_rotate;
 509        i = r->add_ptr;
 510
 511        /* mix one byte at a time to simplify size handling and churn faster */
 512        while (nbytes--) {
 513                w = rol32(*bytes++, input_rotate);
 514                i = (i - 1) & wordmask;
 515
 516                /* XOR in the various taps */
 517                w ^= r->pool[i];
 518                w ^= r->pool[(i + tap1) & wordmask];
 519                w ^= r->pool[(i + tap2) & wordmask];
 520                w ^= r->pool[(i + tap3) & wordmask];
 521                w ^= r->pool[(i + tap4) & wordmask];
 522                w ^= r->pool[(i + tap5) & wordmask];
 523
 524                /* Mix the result back in with a twist */
 525                r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 526
 527                /*
 528                 * Normally, we add 7 bits of rotation to the pool.
 529                 * At the beginning of the pool, add an extra 7 bits
 530                 * rotation, so that successive passes spread the
 531                 * input bits across the pool evenly.
 532                 */
 533                input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
 534        }
 535
 536        r->input_rotate = input_rotate;
 537        r->add_ptr = i;
 538}
 539
 540static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 541                             int nbytes)
 542{
 543        trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 544        _mix_pool_bytes(r, in, nbytes);
 545}
 546
 547static void mix_pool_bytes(struct entropy_store *r, const void *in,
 548                           int nbytes)
 549{
 550        unsigned long flags;
 551
 552        trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
 553        spin_lock_irqsave(&r->lock, flags);
 554        _mix_pool_bytes(r, in, nbytes);
 555        spin_unlock_irqrestore(&r->lock, flags);
 556}
 557
 558struct fast_pool {
 559        __u32           pool[4];
 560        unsigned long   last;
 561        unsigned short  reg_idx;
 562        unsigned char   count;
 563};
 564
 565/*
 566 * This is a fast mixing routine used by the interrupt randomness
 567 * collector.  It's hardcoded for an 128 bit pool and assumes that any
 568 * locks that might be needed are taken by the caller.
 569 */
 570static void fast_mix(struct fast_pool *f)
 571{
 572        __u32 a = f->pool[0],   b = f->pool[1];
 573        __u32 c = f->pool[2],   d = f->pool[3];
 574
 575        a += b;                 c += d;
 576        b = rol32(b, 6);        d = rol32(d, 27);
 577        d ^= a;                 b ^= c;
 578
 579        a += b;                 c += d;
 580        b = rol32(b, 16);       d = rol32(d, 14);
 581        d ^= a;                 b ^= c;
 582
 583        a += b;                 c += d;
 584        b = rol32(b, 6);        d = rol32(d, 27);
 585        d ^= a;                 b ^= c;
 586
 587        a += b;                 c += d;
 588        b = rol32(b, 16);       d = rol32(d, 14);
 589        d ^= a;                 b ^= c;
 590
 591        f->pool[0] = a;  f->pool[1] = b;
 592        f->pool[2] = c;  f->pool[3] = d;
 593        f->count++;
 594}
 595
 596static void process_random_ready_list(void)
 597{
 598        unsigned long flags;
 599        struct random_ready_callback *rdy, *tmp;
 600
 601        spin_lock_irqsave(&random_ready_list_lock, flags);
 602        list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
 603                struct module *owner = rdy->owner;
 604
 605                list_del_init(&rdy->list);
 606                rdy->func(rdy);
 607                module_put(owner);
 608        }
 609        spin_unlock_irqrestore(&random_ready_list_lock, flags);
 610}
 611
 612/*
 613 * Credit (or debit) the entropy store with n bits of entropy.
 614 * Use credit_entropy_bits_safe() if the value comes from userspace
 615 * or otherwise should be checked for extreme values.
 616 */
 617static void credit_entropy_bits(struct entropy_store *r, int nbits)
 618{
 619        int entropy_count, orig;
 620        const int pool_size = r->poolinfo->poolfracbits;
 621        int nfrac = nbits << ENTROPY_SHIFT;
 622
 623        if (!nbits)
 624                return;
 625
 626retry:
 627        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 628        if (nfrac < 0) {
 629                /* Debit */
 630                entropy_count += nfrac;
 631        } else {
 632                /*
 633                 * Credit: we have to account for the possibility of
 634                 * overwriting already present entropy.  Even in the
 635                 * ideal case of pure Shannon entropy, new contributions
 636                 * approach the full value asymptotically:
 637                 *
 638                 * entropy <- entropy + (pool_size - entropy) *
 639                 *      (1 - exp(-add_entropy/pool_size))
 640                 *
 641                 * For add_entropy <= pool_size/2 then
 642                 * (1 - exp(-add_entropy/pool_size)) >=
 643                 *    (add_entropy/pool_size)*0.7869...
 644                 * so we can approximate the exponential with
 645                 * 3/4*add_entropy/pool_size and still be on the
 646                 * safe side by adding at most pool_size/2 at a time.
 647                 *
 648                 * The use of pool_size-2 in the while statement is to
 649                 * prevent rounding artifacts from making the loop
 650                 * arbitrarily long; this limits the loop to log2(pool_size)*2
 651                 * turns no matter how large nbits is.
 652                 */
 653                int pnfrac = nfrac;
 654                const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
 655                /* The +2 corresponds to the /4 in the denominator */
 656
 657                do {
 658                        unsigned int anfrac = min(pnfrac, pool_size/2);
 659                        unsigned int add =
 660                                ((pool_size - entropy_count)*anfrac*3) >> s;
 661
 662                        entropy_count += add;
 663                        pnfrac -= anfrac;
 664                } while (unlikely(entropy_count < pool_size-2 && pnfrac));
 665        }
 666
 667        if (unlikely(entropy_count < 0)) {
 668                pr_warn("random: negative entropy/overflow: pool %s count %d\n",
 669                        r->name, entropy_count);
 670                WARN_ON(1);
 671                entropy_count = 0;
 672        } else if (entropy_count > pool_size)
 673                entropy_count = pool_size;
 674        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 675                goto retry;
 676
 677        r->entropy_total += nbits;
 678        if (!r->initialized && r->entropy_total > 128) {
 679                r->initialized = 1;
 680                r->entropy_total = 0;
 681                if (r == &nonblocking_pool) {
 682                        prandom_reseed_late();
 683                        process_random_ready_list();
 684                        wake_up_all(&urandom_init_wait);
 685                        pr_notice("random: %s pool is initialized\n", r->name);
 686                }
 687        }
 688
 689        trace_credit_entropy_bits(r->name, nbits,
 690                                  entropy_count >> ENTROPY_SHIFT,
 691                                  r->entropy_total, _RET_IP_);
 692
 693        if (r == &input_pool) {
 694                int entropy_bits = entropy_count >> ENTROPY_SHIFT;
 695
 696                /* should we wake readers? */
 697                if (entropy_bits >= random_read_wakeup_bits) {
 698                        wake_up_interruptible(&random_read_wait);
 699                        kill_fasync(&fasync, SIGIO, POLL_IN);
 700                }
 701                /* If the input pool is getting full, send some
 702                 * entropy to the two output pools, flipping back and
 703                 * forth between them, until the output pools are 75%
 704                 * full.
 705                 */
 706                if (entropy_bits > random_write_wakeup_bits &&
 707                    r->initialized &&
 708                    r->entropy_total >= 2*random_read_wakeup_bits) {
 709                        static struct entropy_store *last = &blocking_pool;
 710                        struct entropy_store *other = &blocking_pool;
 711
 712                        if (last == &blocking_pool)
 713                                other = &nonblocking_pool;
 714                        if (other->entropy_count <=
 715                            3 * other->poolinfo->poolfracbits / 4)
 716                                last = other;
 717                        if (last->entropy_count <=
 718                            3 * last->poolinfo->poolfracbits / 4) {
 719                                schedule_work(&last->push_work);
 720                                r->entropy_total = 0;
 721                        }
 722                }
 723        }
 724}
 725
 726static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
 727{
 728        const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
 729
 730        /* Cap the value to avoid overflows */
 731        nbits = min(nbits,  nbits_max);
 732        nbits = max(nbits, -nbits_max);
 733
 734        credit_entropy_bits(r, nbits);
 735}
 736
 737/*********************************************************************
 738 *
 739 * Entropy input management
 740 *
 741 *********************************************************************/
 742
 743/* There is one of these per entropy source */
 744struct timer_rand_state {
 745        cycles_t last_time;
 746        long last_delta, last_delta2;
 747        unsigned dont_count_entropy:1;
 748};
 749
 750#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
 751
 752/*
 753 * Add device- or boot-specific data to the input and nonblocking
 754 * pools to help initialize them to unique values.
 755 *
 756 * None of this adds any entropy, it is meant to avoid the
 757 * problem of the nonblocking pool having similar initial state
 758 * across largely identical devices.
 759 */
 760void add_device_randomness(const void *buf, unsigned int size)
 761{
 762        unsigned long time = random_get_entropy() ^ jiffies;
 763        unsigned long flags;
 764
 765        trace_add_device_randomness(size, _RET_IP_);
 766        spin_lock_irqsave(&input_pool.lock, flags);
 767        _mix_pool_bytes(&input_pool, buf, size);
 768        _mix_pool_bytes(&input_pool, &time, sizeof(time));
 769        spin_unlock_irqrestore(&input_pool.lock, flags);
 770
 771        spin_lock_irqsave(&nonblocking_pool.lock, flags);
 772        _mix_pool_bytes(&nonblocking_pool, buf, size);
 773        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
 774        spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
 775}
 776EXPORT_SYMBOL(add_device_randomness);
 777
 778static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
 779
 780/*
 781 * This function adds entropy to the entropy "pool" by using timing
 782 * delays.  It uses the timer_rand_state structure to make an estimate
 783 * of how many bits of entropy this call has added to the pool.
 784 *
 785 * The number "num" is also added to the pool - it should somehow describe
 786 * the type of event which just happened.  This is currently 0-255 for
 787 * keyboard scan codes, and 256 upwards for interrupts.
 788 *
 789 */
 790static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 791{
 792        struct entropy_store    *r;
 793        struct {
 794                long jiffies;
 795                unsigned cycles;
 796                unsigned num;
 797        } sample;
 798        long delta, delta2, delta3;
 799
 800        preempt_disable();
 801
 802        sample.jiffies = jiffies;
 803        sample.cycles = random_get_entropy();
 804        sample.num = num;
 805        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 806        mix_pool_bytes(r, &sample, sizeof(sample));
 807
 808        /*
 809         * Calculate number of bits of randomness we probably added.
 810         * We take into account the first, second and third-order deltas
 811         * in order to make our estimate.
 812         */
 813
 814        if (!state->dont_count_entropy) {
 815                delta = sample.jiffies - state->last_time;
 816                state->last_time = sample.jiffies;
 817
 818                delta2 = delta - state->last_delta;
 819                state->last_delta = delta;
 820
 821                delta3 = delta2 - state->last_delta2;
 822                state->last_delta2 = delta2;
 823
 824                if (delta < 0)
 825                        delta = -delta;
 826                if (delta2 < 0)
 827                        delta2 = -delta2;
 828                if (delta3 < 0)
 829                        delta3 = -delta3;
 830                if (delta > delta2)
 831                        delta = delta2;
 832                if (delta > delta3)
 833                        delta = delta3;
 834
 835                /*
 836                 * delta is now minimum absolute delta.
 837                 * Round down by 1 bit on general principles,
 838                 * and limit entropy entimate to 12 bits.
 839                 */
 840                credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
 841        }
 842        preempt_enable();
 843}
 844
 845void add_input_randomness(unsigned int type, unsigned int code,
 846                                 unsigned int value)
 847{
 848        static unsigned char last_value;
 849
 850        /* ignore autorepeat and the like */
 851        if (value == last_value)
 852                return;
 853
 854        last_value = value;
 855        add_timer_randomness(&input_timer_state,
 856                             (type << 4) ^ code ^ (code >> 4) ^ value);
 857        trace_add_input_randomness(ENTROPY_BITS(&input_pool));
 858}
 859EXPORT_SYMBOL_GPL(add_input_randomness);
 860
 861static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 862
 863#ifdef ADD_INTERRUPT_BENCH
 864static unsigned long avg_cycles, avg_deviation;
 865
 866#define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
 867#define FIXED_1_2 (1 << (AVG_SHIFT-1))
 868
 869static void add_interrupt_bench(cycles_t start)
 870{
 871        long delta = random_get_entropy() - start;
 872
 873        /* Use a weighted moving average */
 874        delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
 875        avg_cycles += delta;
 876        /* And average deviation */
 877        delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
 878        avg_deviation += delta;
 879}
 880#else
 881#define add_interrupt_bench(x)
 882#endif
 883
 884static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
 885{
 886        __u32 *ptr = (__u32 *) regs;
 887
 888        if (regs == NULL)
 889                return 0;
 890        if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
 891                f->reg_idx = 0;
 892        return *(ptr + f->reg_idx++);
 893}
 894
 895void add_interrupt_randomness(int irq, int irq_flags)
 896{
 897        struct entropy_store    *r;
 898        struct fast_pool        *fast_pool = this_cpu_ptr(&irq_randomness);
 899        struct pt_regs          *regs = get_irq_regs();
 900        unsigned long           now = jiffies;
 901        cycles_t                cycles = random_get_entropy();
 902        __u32                   c_high, j_high;
 903        __u64                   ip;
 904        unsigned long           seed;
 905        int                     credit = 0;
 906
 907        if (cycles == 0)
 908                cycles = get_reg(fast_pool, regs);
 909        c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
 910        j_high = (sizeof(now) > 4) ? now >> 32 : 0;
 911        fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
 912        fast_pool->pool[1] ^= now ^ c_high;
 913        ip = regs ? instruction_pointer(regs) : _RET_IP_;
 914        fast_pool->pool[2] ^= ip;
 915        fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
 916                get_reg(fast_pool, regs);
 917
 918        fast_mix(fast_pool);
 919        add_interrupt_bench(cycles);
 920
 921        if ((fast_pool->count < 64) &&
 922            !time_after(now, fast_pool->last + HZ))
 923                return;
 924
 925        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 926        if (!spin_trylock(&r->lock))
 927                return;
 928
 929        fast_pool->last = now;
 930        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
 931
 932        /*
 933         * If we have architectural seed generator, produce a seed and
 934         * add it to the pool.  For the sake of paranoia don't let the
 935         * architectural seed generator dominate the input from the
 936         * interrupt noise.
 937         */
 938        if (arch_get_random_seed_long(&seed)) {
 939                __mix_pool_bytes(r, &seed, sizeof(seed));
 940                credit = 1;
 941        }
 942        spin_unlock(&r->lock);
 943
 944        fast_pool->count = 0;
 945
 946        /* award one bit for the contents of the fast pool */
 947        credit_entropy_bits(r, credit + 1);
 948}
 949
 950#ifdef CONFIG_BLOCK
 951void add_disk_randomness(struct gendisk *disk)
 952{
 953        if (!disk || !disk->random)
 954                return;
 955        /* first major is 1, so we get >= 0x200 here */
 956        add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 957        trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
 958}
 959EXPORT_SYMBOL_GPL(add_disk_randomness);
 960#endif
 961
 962/*********************************************************************
 963 *
 964 * Entropy extraction routines
 965 *
 966 *********************************************************************/
 967
 968static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 969                               size_t nbytes, int min, int rsvd);
 970
 971/*
 972 * This utility inline function is responsible for transferring entropy
 973 * from the primary pool to the secondary extraction pool. We make
 974 * sure we pull enough for a 'catastrophic reseed'.
 975 */
 976static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
 977static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 978{
 979        if (!r->pull ||
 980            r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
 981            r->entropy_count > r->poolinfo->poolfracbits)
 982                return;
 983
 984        if (r->limit == 0 && random_min_urandom_seed) {
 985                unsigned long now = jiffies;
 986
 987                if (time_before(now,
 988                                r->last_pulled + random_min_urandom_seed * HZ))
 989                        return;
 990                r->last_pulled = now;
 991        }
 992
 993        _xfer_secondary_pool(r, nbytes);
 994}
 995
 996static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 997{
 998        __u32   tmp[OUTPUT_POOL_WORDS];
 999
1000        /* For /dev/random's pool, always leave two wakeups' worth */
1001        int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
1002        int bytes = nbytes;
1003
1004        /* pull at least as much as a wakeup */
1005        bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1006        /* but never more than the buffer size */
1007        bytes = min_t(int, bytes, sizeof(tmp));
1008
1009        trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1010                                  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1011        bytes = extract_entropy(r->pull, tmp, bytes,
1012                                random_read_wakeup_bits / 8, rsvd_bytes);
1013        mix_pool_bytes(r, tmp, bytes);
1014        credit_entropy_bits(r, bytes*8);
1015}
1016
1017/*
1018 * Used as a workqueue function so that when the input pool is getting
1019 * full, we can "spill over" some entropy to the output pools.  That
1020 * way the output pools can store some of the excess entropy instead
1021 * of letting it go to waste.
1022 */
1023static void push_to_pool(struct work_struct *work)
1024{
1025        struct entropy_store *r = container_of(work, struct entropy_store,
1026                                              push_work);
1027        BUG_ON(!r);
1028        _xfer_secondary_pool(r, random_read_wakeup_bits/8);
1029        trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1030                           r->pull->entropy_count >> ENTROPY_SHIFT);
1031}
1032
1033/*
1034 * This function decides how many bytes to actually take from the
1035 * given pool, and also debits the entropy count accordingly.
1036 */
1037static size_t account(struct entropy_store *r, size_t nbytes, int min,
1038                      int reserved)
1039{
1040        int entropy_count, orig;
1041        size_t ibytes, nfrac;
1042
1043        BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1044
1045        /* Can we pull enough? */
1046retry:
1047        entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1048        ibytes = nbytes;
1049        /* If limited, never pull more than available */
1050        if (r->limit) {
1051                int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1052
1053                if ((have_bytes -= reserved) < 0)
1054                        have_bytes = 0;
1055                ibytes = min_t(size_t, ibytes, have_bytes);
1056        }
1057        if (ibytes < min)
1058                ibytes = 0;
1059
1060        if (unlikely(entropy_count < 0)) {
1061                pr_warn("random: negative entropy count: pool %s count %d\n",
1062                        r->name, entropy_count);
1063                WARN_ON(1);
1064                entropy_count = 0;
1065        }
1066        nfrac = ibytes << (ENTROPY_SHIFT + 3);
1067        if ((size_t) entropy_count > nfrac)
1068                entropy_count -= nfrac;
1069        else
1070                entropy_count = 0;
1071
1072        if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1073                goto retry;
1074
1075        trace_debit_entropy(r->name, 8 * ibytes);
1076        if (ibytes &&
1077            (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1078                wake_up_interruptible(&random_write_wait);
1079                kill_fasync(&fasync, SIGIO, POLL_OUT);
1080        }
1081
1082        return ibytes;
1083}
1084
1085/*
1086 * This function does the actual extraction for extract_entropy and
1087 * extract_entropy_user.
1088 *
1089 * Note: we assume that .poolwords is a multiple of 16 words.
1090 */
1091static void extract_buf(struct entropy_store *r, __u8 *out)
1092{
1093        int i;
1094        union {
1095                __u32 w[5];
1096                unsigned long l[LONGS(20)];
1097        } hash;
1098        __u32 workspace[SHA_WORKSPACE_WORDS];
1099        unsigned long flags;
1100
1101        /*
1102         * If we have an architectural hardware random number
1103         * generator, use it for SHA's initial vector
1104         */
1105        sha_init(hash.w);
1106        for (i = 0; i < LONGS(20); i++) {
1107                unsigned long v;
1108                if (!arch_get_random_long(&v))
1109                        break;
1110                hash.l[i] = v;
1111        }
1112
1113        /* Generate a hash across the pool, 16 words (512 bits) at a time */
1114        spin_lock_irqsave(&r->lock, flags);
1115        for (i = 0; i < r->poolinfo->poolwords; i += 16)
1116                sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1117
1118        /*
1119         * We mix the hash back into the pool to prevent backtracking
1120         * attacks (where the attacker knows the state of the pool
1121         * plus the current outputs, and attempts to find previous
1122         * ouputs), unless the hash function can be inverted. By
1123         * mixing at least a SHA1 worth of hash data back, we make
1124         * brute-forcing the feedback as hard as brute-forcing the
1125         * hash.
1126         */
1127        __mix_pool_bytes(r, hash.w, sizeof(hash.w));
1128        spin_unlock_irqrestore(&r->lock, flags);
1129
1130        memzero_explicit(workspace, sizeof(workspace));
1131
1132        /*
1133         * In case the hash function has some recognizable output
1134         * pattern, we fold it in half. Thus, we always feed back
1135         * twice as much data as we output.
1136         */
1137        hash.w[0] ^= hash.w[3];
1138        hash.w[1] ^= hash.w[4];
1139        hash.w[2] ^= rol32(hash.w[2], 16);
1140
1141        memcpy(out, &hash, EXTRACT_SIZE);
1142        memzero_explicit(&hash, sizeof(hash));
1143}
1144
1145/*
1146 * This function extracts randomness from the "entropy pool", and
1147 * returns it in a buffer.
1148 *
1149 * The min parameter specifies the minimum amount we can pull before
1150 * failing to avoid races that defeat catastrophic reseeding while the
1151 * reserved parameter indicates how much entropy we must leave in the
1152 * pool after each pull to avoid starving other readers.
1153 */
1154static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1155                                 size_t nbytes, int min, int reserved)
1156{
1157        ssize_t ret = 0, i;
1158        __u8 tmp[EXTRACT_SIZE];
1159        unsigned long flags;
1160
1161        /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1162        if (fips_enabled) {
1163                spin_lock_irqsave(&r->lock, flags);
1164                if (!r->last_data_init) {
1165                        r->last_data_init = 1;
1166                        spin_unlock_irqrestore(&r->lock, flags);
1167                        trace_extract_entropy(r->name, EXTRACT_SIZE,
1168                                              ENTROPY_BITS(r), _RET_IP_);
1169                        xfer_secondary_pool(r, EXTRACT_SIZE);
1170                        extract_buf(r, tmp);
1171                        spin_lock_irqsave(&r->lock, flags);
1172                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1173                }
1174                spin_unlock_irqrestore(&r->lock, flags);
1175        }
1176
1177        trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1178        xfer_secondary_pool(r, nbytes);
1179        nbytes = account(r, nbytes, min, reserved);
1180
1181        while (nbytes) {
1182                extract_buf(r, tmp);
1183
1184                if (fips_enabled) {
1185                        spin_lock_irqsave(&r->lock, flags);
1186                        if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1187                                panic("Hardware RNG duplicated output!\n");
1188                        memcpy(r->last_data, tmp, EXTRACT_SIZE);
1189                        spin_unlock_irqrestore(&r->lock, flags);
1190                }
1191                i = min_t(int, nbytes, EXTRACT_SIZE);
1192                memcpy(buf, tmp, i);
1193                nbytes -= i;
1194                buf += i;
1195                ret += i;
1196        }
1197
1198        /* Wipe data just returned from memory */
1199        memzero_explicit(tmp, sizeof(tmp));
1200
1201        return ret;
1202}
1203
1204/*
1205 * This function extracts randomness from the "entropy pool", and
1206 * returns it in a userspace buffer.
1207 */
1208static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1209                                    size_t nbytes)
1210{
1211        ssize_t ret = 0, i;
1212        __u8 tmp[EXTRACT_SIZE];
1213        int large_request = (nbytes > 256);
1214
1215        trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1216        xfer_secondary_pool(r, nbytes);
1217        nbytes = account(r, nbytes, 0, 0);
1218
1219        while (nbytes) {
1220                if (large_request && need_resched()) {
1221                        if (signal_pending(current)) {
1222                                if (ret == 0)
1223                                        ret = -ERESTARTSYS;
1224                                break;
1225                        }
1226                        schedule();
1227                }
1228
1229                extract_buf(r, tmp);
1230                i = min_t(int, nbytes, EXTRACT_SIZE);
1231                if (copy_to_user(buf, tmp, i)) {
1232                        ret = -EFAULT;
1233                        break;
1234                }
1235
1236                nbytes -= i;
1237                buf += i;
1238                ret += i;
1239        }
1240
1241        /* Wipe data just returned from memory */
1242        memzero_explicit(tmp, sizeof(tmp));
1243
1244        return ret;
1245}
1246
1247/*
1248 * This function is the exported kernel interface.  It returns some
1249 * number of good random numbers, suitable for key generation, seeding
1250 * TCP sequence numbers, etc.  It does not rely on the hardware random
1251 * number generator.  For random bytes direct from the hardware RNG
1252 * (when available), use get_random_bytes_arch().
1253 */
1254void get_random_bytes(void *buf, int nbytes)
1255{
1256#if DEBUG_RANDOM_BOOT > 0
1257        if (unlikely(nonblocking_pool.initialized == 0))
1258                printk(KERN_NOTICE "random: %pF get_random_bytes called "
1259                       "with %d bits of entropy available\n",
1260                       (void *) _RET_IP_,
1261                       nonblocking_pool.entropy_total);
1262#endif
1263        trace_get_random_bytes(nbytes, _RET_IP_);
1264        extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
1265}
1266EXPORT_SYMBOL(get_random_bytes);
1267
1268/*
1269 * Add a callback function that will be invoked when the nonblocking
1270 * pool is initialised.
1271 *
1272 * returns: 0 if callback is successfully added
1273 *          -EALREADY if pool is already initialised (callback not called)
1274 *          -ENOENT if module for callback is not alive
1275 */
1276int add_random_ready_callback(struct random_ready_callback *rdy)
1277{
1278        struct module *owner;
1279        unsigned long flags;
1280        int err = -EALREADY;
1281
1282        if (likely(nonblocking_pool.initialized))
1283                return err;
1284
1285        owner = rdy->owner;
1286        if (!try_module_get(owner))
1287                return -ENOENT;
1288
1289        spin_lock_irqsave(&random_ready_list_lock, flags);
1290        if (nonblocking_pool.initialized)
1291                goto out;
1292
1293        owner = NULL;
1294
1295        list_add(&rdy->list, &random_ready_list);
1296        err = 0;
1297
1298out:
1299        spin_unlock_irqrestore(&random_ready_list_lock, flags);
1300
1301        module_put(owner);
1302
1303        return err;
1304}
1305EXPORT_SYMBOL(add_random_ready_callback);
1306
1307/*
1308 * Delete a previously registered readiness callback function.
1309 */
1310void del_random_ready_callback(struct random_ready_callback *rdy)
1311{
1312        unsigned long flags;
1313        struct module *owner = NULL;
1314
1315        spin_lock_irqsave(&random_ready_list_lock, flags);
1316        if (!list_empty(&rdy->list)) {
1317                list_del_init(&rdy->list);
1318                owner = rdy->owner;
1319        }
1320        spin_unlock_irqrestore(&random_ready_list_lock, flags);
1321
1322        module_put(owner);
1323}
1324EXPORT_SYMBOL(del_random_ready_callback);
1325
1326/*
1327 * This function will use the architecture-specific hardware random
1328 * number generator if it is available.  The arch-specific hw RNG will
1329 * almost certainly be faster than what we can do in software, but it
1330 * is impossible to verify that it is implemented securely (as
1331 * opposed, to, say, the AES encryption of a sequence number using a
1332 * key known by the NSA).  So it's useful if we need the speed, but
1333 * only if we're willing to trust the hardware manufacturer not to
1334 * have put in a back door.
1335 */
1336void get_random_bytes_arch(void *buf, int nbytes)
1337{
1338        char *p = buf;
1339
1340        trace_get_random_bytes_arch(nbytes, _RET_IP_);
1341        while (nbytes) {
1342                unsigned long v;
1343                int chunk = min(nbytes, (int)sizeof(unsigned long));
1344
1345                if (!arch_get_random_long(&v))
1346                        break;
1347                
1348                memcpy(p, &v, chunk);
1349                p += chunk;
1350                nbytes -= chunk;
1351        }
1352
1353        if (nbytes)
1354                extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1355}
1356EXPORT_SYMBOL(get_random_bytes_arch);
1357
1358
1359/*
1360 * init_std_data - initialize pool with system data
1361 *
1362 * @r: pool to initialize
1363 *
1364 * This function clears the pool's entropy count and mixes some system
1365 * data into the pool to prepare it for use. The pool is not cleared
1366 * as that can only decrease the entropy in the pool.
1367 */
1368static void init_std_data(struct entropy_store *r)
1369{
1370        int i;
1371        ktime_t now = ktime_get_real();
1372        unsigned long rv;
1373
1374        r->last_pulled = jiffies;
1375        mix_pool_bytes(r, &now, sizeof(now));
1376        for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1377                if (!arch_get_random_seed_long(&rv) &&
1378                    !arch_get_random_long(&rv))
1379                        rv = random_get_entropy();
1380                mix_pool_bytes(r, &rv, sizeof(rv));
1381        }
1382        mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1383}
1384
1385/*
1386 * Note that setup_arch() may call add_device_randomness()
1387 * long before we get here. This allows seeding of the pools
1388 * with some platform dependent data very early in the boot
1389 * process. But it limits our options here. We must use
1390 * statically allocated structures that already have all
1391 * initializations complete at compile time. We should also
1392 * take care not to overwrite the precious per platform data
1393 * we were given.
1394 */
1395static int rand_initialize(void)
1396{
1397        init_std_data(&input_pool);
1398        init_std_data(&blocking_pool);
1399        init_std_data(&nonblocking_pool);
1400        return 0;
1401}
1402early_initcall(rand_initialize);
1403
1404#ifdef CONFIG_BLOCK
1405void rand_initialize_disk(struct gendisk *disk)
1406{
1407        struct timer_rand_state *state;
1408
1409        /*
1410         * If kzalloc returns null, we just won't use that entropy
1411         * source.
1412         */
1413        state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1414        if (state) {
1415                state->last_time = INITIAL_JIFFIES;
1416                disk->random = state;
1417        }
1418}
1419#endif
1420
1421static ssize_t
1422_random_read(int nonblock, char __user *buf, size_t nbytes)
1423{
1424        ssize_t n;
1425
1426        if (nbytes == 0)
1427                return 0;
1428
1429        nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1430        while (1) {
1431                n = extract_entropy_user(&blocking_pool, buf, nbytes);
1432                if (n < 0)
1433                        return n;
1434                trace_random_read(n*8, (nbytes-n)*8,
1435                                  ENTROPY_BITS(&blocking_pool),
1436                                  ENTROPY_BITS(&input_pool));
1437                if (n > 0)
1438                        return n;
1439
1440                /* Pool is (near) empty.  Maybe wait and retry. */
1441                if (nonblock)
1442                        return -EAGAIN;
1443
1444                wait_event_interruptible(random_read_wait,
1445                        ENTROPY_BITS(&input_pool) >=
1446                        random_read_wakeup_bits);
1447                if (signal_pending(current))
1448                        return -ERESTARTSYS;
1449        }
1450}
1451
1452static ssize_t
1453random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1454{
1455        return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1456}
1457
1458static ssize_t
1459urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1460{
1461        int ret;
1462
1463        if (unlikely(nonblocking_pool.initialized == 0))
1464                printk_once(KERN_NOTICE "random: %s urandom read "
1465                            "with %d bits of entropy available\n",
1466                            current->comm, nonblocking_pool.entropy_total);
1467
1468        nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1469        ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1470
1471        trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1472                           ENTROPY_BITS(&input_pool));
1473        return ret;
1474}
1475
1476static unsigned int
1477random_poll(struct file *file, poll_table * wait)
1478{
1479        unsigned int mask;
1480
1481        poll_wait(file, &random_read_wait, wait);
1482        poll_wait(file, &random_write_wait, wait);
1483        mask = 0;
1484        if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1485                mask |= POLLIN | POLLRDNORM;
1486        if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1487                mask |= POLLOUT | POLLWRNORM;
1488        return mask;
1489}
1490
1491static int
1492write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1493{
1494        size_t bytes;
1495        __u32 buf[16];
1496        const char __user *p = buffer;
1497
1498        while (count > 0) {
1499                bytes = min(count, sizeof(buf));
1500                if (copy_from_user(&buf, p, bytes))
1501                        return -EFAULT;
1502
1503                count -= bytes;
1504                p += bytes;
1505
1506                mix_pool_bytes(r, buf, bytes);
1507                cond_resched();
1508        }
1509
1510        return 0;
1511}
1512
1513static ssize_t random_write(struct file *file, const char __user *buffer,
1514                            size_t count, loff_t *ppos)
1515{
1516        size_t ret;
1517
1518        ret = write_pool(&blocking_pool, buffer, count);
1519        if (ret)
1520                return ret;
1521        ret = write_pool(&nonblocking_pool, buffer, count);
1522        if (ret)
1523                return ret;
1524
1525        return (ssize_t)count;
1526}
1527
1528static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1529{
1530        int size, ent_count;
1531        int __user *p = (int __user *)arg;
1532        int retval;
1533
1534        switch (cmd) {
1535        case RNDGETENTCNT:
1536                /* inherently racy, no point locking */
1537                ent_count = ENTROPY_BITS(&input_pool);
1538                if (put_user(ent_count, p))
1539                        return -EFAULT;
1540                return 0;
1541        case RNDADDTOENTCNT:
1542                if (!capable(CAP_SYS_ADMIN))
1543                        return -EPERM;
1544                if (get_user(ent_count, p))
1545                        return -EFAULT;
1546                credit_entropy_bits_safe(&input_pool, ent_count);
1547                return 0;
1548        case RNDADDENTROPY:
1549                if (!capable(CAP_SYS_ADMIN))
1550                        return -EPERM;
1551                if (get_user(ent_count, p++))
1552                        return -EFAULT;
1553                if (ent_count < 0)
1554                        return -EINVAL;
1555                if (get_user(size, p++))
1556                        return -EFAULT;
1557                retval = write_pool(&input_pool, (const char __user *)p,
1558                                    size);
1559                if (retval < 0)
1560                        return retval;
1561                credit_entropy_bits_safe(&input_pool, ent_count);
1562                return 0;
1563        case RNDZAPENTCNT:
1564        case RNDCLEARPOOL:
1565                /*
1566                 * Clear the entropy pool counters. We no longer clear
1567                 * the entropy pool, as that's silly.
1568                 */
1569                if (!capable(CAP_SYS_ADMIN))
1570                        return -EPERM;
1571                input_pool.entropy_count = 0;
1572                nonblocking_pool.entropy_count = 0;
1573                blocking_pool.entropy_count = 0;
1574                return 0;
1575        default:
1576                return -EINVAL;
1577        }
1578}
1579
1580static int random_fasync(int fd, struct file *filp, int on)
1581{
1582        return fasync_helper(fd, filp, on, &fasync);
1583}
1584
1585const struct file_operations random_fops = {
1586        .read  = random_read,
1587        .write = random_write,
1588        .poll  = random_poll,
1589        .unlocked_ioctl = random_ioctl,
1590        .fasync = random_fasync,
1591        .llseek = noop_llseek,
1592};
1593
1594const struct file_operations urandom_fops = {
1595        .read  = urandom_read,
1596        .write = random_write,
1597        .unlocked_ioctl = random_ioctl,
1598        .fasync = random_fasync,
1599        .llseek = noop_llseek,
1600};
1601
1602SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1603                unsigned int, flags)
1604{
1605        if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1606                return -EINVAL;
1607
1608        if (count > INT_MAX)
1609                count = INT_MAX;
1610
1611        if (flags & GRND_RANDOM)
1612                return _random_read(flags & GRND_NONBLOCK, buf, count);
1613
1614        if (unlikely(nonblocking_pool.initialized == 0)) {
1615                if (flags & GRND_NONBLOCK)
1616                        return -EAGAIN;
1617                wait_event_interruptible(urandom_init_wait,
1618                                         nonblocking_pool.initialized);
1619                if (signal_pending(current))
1620                        return -ERESTARTSYS;
1621        }
1622        return urandom_read(NULL, buf, count, NULL);
1623}
1624
1625/********************************************************************
1626 *
1627 * Sysctl interface
1628 *
1629 ********************************************************************/
1630
1631#ifdef CONFIG_SYSCTL
1632
1633#include <linux/sysctl.h>
1634
1635static int min_read_thresh = 8, min_write_thresh;
1636static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1637static int max_write_thresh = INPUT_POOL_WORDS * 32;
1638static char sysctl_bootid[16];
1639
1640/*
1641 * This function is used to return both the bootid UUID, and random
1642 * UUID.  The difference is in whether table->data is NULL; if it is,
1643 * then a new UUID is generated and returned to the user.
1644 *
1645 * If the user accesses this via the proc interface, the UUID will be
1646 * returned as an ASCII string in the standard UUID format; if via the
1647 * sysctl system call, as 16 bytes of binary data.
1648 */
1649static int proc_do_uuid(struct ctl_table *table, int write,
1650                        void __user *buffer, size_t *lenp, loff_t *ppos)
1651{
1652        struct ctl_table fake_table;
1653        unsigned char buf[64], tmp_uuid[16], *uuid;
1654
1655        uuid = table->data;
1656        if (!uuid) {
1657                uuid = tmp_uuid;
1658                generate_random_uuid(uuid);
1659        } else {
1660                static DEFINE_SPINLOCK(bootid_spinlock);
1661
1662                spin_lock(&bootid_spinlock);
1663                if (!uuid[8])
1664                        generate_random_uuid(uuid);
1665                spin_unlock(&bootid_spinlock);
1666        }
1667
1668        sprintf(buf, "%pU", uuid);
1669
1670        fake_table.data = buf;
1671        fake_table.maxlen = sizeof(buf);
1672
1673        return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1674}
1675
1676/*
1677 * Return entropy available scaled to integral bits
1678 */
1679static int proc_do_entropy(struct ctl_table *table, int write,
1680                           void __user *buffer, size_t *lenp, loff_t *ppos)
1681{
1682        struct ctl_table fake_table;
1683        int entropy_count;
1684
1685        entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1686
1687        fake_table.data = &entropy_count;
1688        fake_table.maxlen = sizeof(entropy_count);
1689
1690        return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1691}
1692
1693static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1694extern struct ctl_table random_table[];
1695struct ctl_table random_table[] = {
1696        {
1697                .procname       = "poolsize",
1698                .data           = &sysctl_poolsize,
1699                .maxlen         = sizeof(int),
1700                .mode           = 0444,
1701                .proc_handler   = proc_dointvec,
1702        },
1703        {
1704                .procname       = "entropy_avail",
1705                .maxlen         = sizeof(int),
1706                .mode           = 0444,
1707                .proc_handler   = proc_do_entropy,
1708                .data           = &input_pool.entropy_count,
1709        },
1710        {
1711                .procname       = "read_wakeup_threshold",
1712                .data           = &random_read_wakeup_bits,
1713                .maxlen         = sizeof(int),
1714                .mode           = 0644,
1715                .proc_handler   = proc_dointvec_minmax,
1716                .extra1         = &min_read_thresh,
1717                .extra2         = &max_read_thresh,
1718        },
1719        {
1720                .procname       = "write_wakeup_threshold",
1721                .data           = &random_write_wakeup_bits,
1722                .maxlen         = sizeof(int),
1723                .mode           = 0644,
1724                .proc_handler   = proc_dointvec_minmax,
1725                .extra1         = &min_write_thresh,
1726                .extra2         = &max_write_thresh,
1727        },
1728        {
1729                .procname       = "urandom_min_reseed_secs",
1730                .data           = &random_min_urandom_seed,
1731                .maxlen         = sizeof(int),
1732                .mode           = 0644,
1733                .proc_handler   = proc_dointvec,
1734        },
1735        {
1736                .procname       = "boot_id",
1737                .data           = &sysctl_bootid,
1738                .maxlen         = 16,
1739                .mode           = 0444,
1740                .proc_handler   = proc_do_uuid,
1741        },
1742        {
1743                .procname       = "uuid",
1744                .maxlen         = 16,
1745                .mode           = 0444,
1746                .proc_handler   = proc_do_uuid,
1747        },
1748#ifdef ADD_INTERRUPT_BENCH
1749        {
1750                .procname       = "add_interrupt_avg_cycles",
1751                .data           = &avg_cycles,
1752                .maxlen         = sizeof(avg_cycles),
1753                .mode           = 0444,
1754                .proc_handler   = proc_doulongvec_minmax,
1755        },
1756        {
1757                .procname       = "add_interrupt_avg_deviation",
1758                .data           = &avg_deviation,
1759                .maxlen         = sizeof(avg_deviation),
1760                .mode           = 0444,
1761                .proc_handler   = proc_doulongvec_minmax,
1762        },
1763#endif
1764        { }
1765};
1766#endif  /* CONFIG_SYSCTL */
1767
1768static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1769
1770int random_int_secret_init(void)
1771{
1772        get_random_bytes(random_int_secret, sizeof(random_int_secret));
1773        return 0;
1774}
1775
1776/*
1777 * Get a random word for internal kernel use only. Similar to urandom but
1778 * with the goal of minimal entropy pool depletion. As a result, the random
1779 * value is not cryptographically secure but for several uses the cost of
1780 * depleting entropy is too high
1781 */
1782static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1783unsigned int get_random_int(void)
1784{
1785        __u32 *hash;
1786        unsigned int ret;
1787
1788        if (arch_get_random_int(&ret))
1789                return ret;
1790
1791        hash = get_cpu_var(get_random_int_hash);
1792
1793        hash[0] += current->pid + jiffies + random_get_entropy();
1794        md5_transform(hash, random_int_secret);
1795        ret = hash[0];
1796        put_cpu_var(get_random_int_hash);
1797
1798        return ret;
1799}
1800EXPORT_SYMBOL(get_random_int);
1801
1802/*
1803 * Same as get_random_int(), but returns unsigned long.
1804 */
1805unsigned long get_random_long(void)
1806{
1807        __u32 *hash;
1808        unsigned long ret;
1809
1810        if (arch_get_random_long(&ret))
1811                return ret;
1812
1813        hash = get_cpu_var(get_random_int_hash);
1814
1815        hash[0] += current->pid + jiffies + random_get_entropy();
1816        md5_transform(hash, random_int_secret);
1817        ret = *(unsigned long *)hash;
1818        put_cpu_var(get_random_int_hash);
1819
1820        return ret;
1821}
1822EXPORT_SYMBOL(get_random_long);
1823
1824/*
1825 * randomize_range() returns a start address such that
1826 *
1827 *    [...... <range> .....]
1828 *  start                  end
1829 *
1830 * a <range> with size "len" starting at the return value is inside in the
1831 * area defined by [start, end], but is otherwise randomized.
1832 */
1833unsigned long
1834randomize_range(unsigned long start, unsigned long end, unsigned long len)
1835{
1836        unsigned long range = end - len - start;
1837
1838        if (end <= start + len)
1839                return 0;
1840        return PAGE_ALIGN(get_random_int() % range + start);
1841}
1842
1843/* Interface for in-kernel drivers of true hardware RNGs.
1844 * Those devices may produce endless random bits and will be throttled
1845 * when our pool is full.
1846 */
1847void add_hwgenerator_randomness(const char *buffer, size_t count,
1848                                size_t entropy)
1849{
1850        struct entropy_store *poolp = &input_pool;
1851
1852        /* Suspend writing if we're above the trickle threshold.
1853         * We'll be woken up again once below random_write_wakeup_thresh,
1854         * or when the calling thread is about to terminate.
1855         */
1856        wait_event_interruptible(random_write_wait, kthread_should_stop() ||
1857                        ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
1858        mix_pool_bytes(poolp, buffer, count);
1859        credit_entropy_bits(poolp, entropy);
1860}
1861EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
1862
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