text: /*
   * random.c -- A strong random number generator
   *
   * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All
   * Rights Reserved.
   *
   * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
   *
   * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
   * rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, and the entire permission notice in its entirety,
   *    including the disclaimer of warranties.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. The name of the author may not be used to endorse or promote
   *    products derived from this software without specific prior
   *    written permission.
   *
   * ALTERNATIVELY, this product may be distributed under the terms of
   * the GNU General Public License, in which case the provisions of the GPL are
   * required INSTEAD OF the above restrictions.  (This clause is
   * necessary due to a potential bad interaction between the GPL and
   * the restrictions contained in a BSD-style copyright.)
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
   * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
   * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
   * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
   * DAMAGE.
   */
  
  /*
   * (now, with legal B.S. out of the way.....)
   *
   * This routine gathers environmental noise from device drivers, etc.,
   * and returns good random numbers, suitable for cryptographic use.
   * Besides the obvious cryptographic uses, these numbers are also good
   * for seeding TCP sequence numbers, and other places where it is
   * desirable to have numbers which are not only random, but hard to
   * predict by an attacker.
   *
   * Theory of operation
   * ===================
   *
   * Computers are very predictable devices.  Hence it is extremely hard
   * to produce truly random numbers on a computer --- as opposed to
   * pseudo-random numbers, which can easily generated by using a
   * algorithm.  Unfortunately, it is very easy for attackers to guess
   * the sequence of pseudo-random number generators, and for some
   * applications this is not acceptable.  So instead, we must try to
   * gather "environmental noise" from the computer's environment, which
   * must be hard for outside attackers to observe, and use that to
   * generate random numbers.  In a Unix environment, this is best done
   * from inside the kernel.
   *
   * Sources of randomness from the environment include inter-keyboard
   * timings, inter-interrupt timings from some interrupts, and other
   * events which are both (a) non-deterministic and (b) hard for an
   * outside observer to measure.  Randomness from these sources are
   * added to an "entropy pool", which is mixed using a CRC-like function.
   * This is not cryptographically strong, but it is adequate assuming
   * the randomness is not chosen maliciously, and it is fast enough that
   * the overhead of doing it on every interrupt is very reasonable.
   * As random bytes are mixed into the entropy pool, the routines keep
   * an *estimate* of how many bits of randomness have been stored into
   * the random number generator's internal state.
   *
   * When random bytes are desired, they are obtained by taking the SHA
   * hash of the contents of the "entropy pool".  The SHA hash avoids
   * exposing the internal state of the entropy pool.  It is believed to
   * be computationally infeasible to derive any useful information
   * about the input of SHA from its output.  Even if it is possible to
   * analyze SHA in some clever way, as long as the amount of data
   * returned from the generator is less than the inherent entropy in
   * the pool, the output data is totally unpredictable.  For this
   * reason, the routine decreases its internal estimate of how many
   * bits of "true randomness" are contained in the entropy pool as it
   * outputs random numbers.
   *
   * If this estimate goes to zero, the routine can still generate
   * random numbers; however, an attacker may (at least in theory) be
   * able to infer the future output of the generator from prior
   * outputs.  This requires successful cryptanalysis of SHA, which is
   * not believed to be feasible, but there is a remote possibility.
   * Nonetheless, these numbers should be useful for the vast majority
   * of purposes.
   *
   * Exported interfaces ---- output
   * ===============================
   *
   * There are four exported interfaces; two for use within the kernel,
   * and two or use from userspace.
   *
   * Exported interfaces ---- userspace output
   * -----------------------------------------
   *
   * The userspace interfaces are two character devices /dev/random and
   * /dev/urandom.  /dev/random is suitable for use when very high
   * quality randomness is desired (for example, for key generation or
   * one-time pads), as it will only return a maximum of the number of
   * bits of randomness (as estimated by the random number generator)
   * contained in the entropy pool.
   *
   * The /dev/urandom device does not have this limit, and will return
   * as many bytes as are requested.  As more and more random bytes are
   * requested without giving time for the entropy pool to recharge,
   * this will result in random numbers that are merely cryptographically
   * strong.  For many applications, however, this is acceptable.
   *
   * Exported interfaces ---- kernel output
   * --------------------------------------
   *
   * The primary kernel interface is
   *
   * 	void get_random_bytes(void *buf, int nbytes);
   *
   * This interface will return the requested number of random bytes,
   * and place it in the requested buffer.  This is equivalent to a
   * read from /dev/urandom.
   *
   * For less critical applications, there are the functions:
   *
   * 	u32 get_random_u32()
   * 	u64 get_random_u64()
   * 	unsigned int get_random_int()
   * 	unsigned long get_random_long()
   *
   * These are produced by a cryptographic RNG seeded from get_random_bytes,
   * and so do not deplete the entropy pool as much.  These are recommended
   * for most in-kernel operations *if the result is going to be stored in
   * the kernel*.
   *
   * Specifically, the get_random_int() family do not attempt to do
   * "anti-backtracking".  If you capture the state of the kernel (e.g.
   * by snapshotting the VM), you can figure out previous get_random_int()
   * return values.  But if the value is stored in the kernel anyway,
   * this is not a problem.
   *
   * It *is* safe to expose get_random_int() output to attackers (e.g. as
   * network cookies); given outputs 1..n, it's not feasible to predict
   * outputs 0 or n+1.  The only concern is an attacker who breaks into
   * the kernel later; the get_random_int() engine is not reseeded as
   * often as the get_random_bytes() one.
   *
   * get_random_bytes() is needed for keys that need to stay secret after
   * they are erased from the kernel.  For example, any key that will
   * be wrapped and stored encrypted.  And session encryption keys: we'd
   * like to know that after the session is closed and the keys erased,
   * the plaintext is unrecoverable to someone who recorded the ciphertext.
   *
   * But for network ports/cookies, stack canaries, PRNG seeds, address
   * space layout randomization, session *authentication* keys, or other
   * applications where the sensitive data is stored in the kernel in
   * plaintext for as long as it's sensitive, the get_random_int() family
   * is just fine.
   *
   * Consider ASLR.  We want to keep the address space secret from an
   * outside attacker while the process is running, but once the address
   * space is torn down, it's of no use to an attacker any more.  And it's
   * stored in kernel data structures as long as it's alive, so worrying
   * about an attacker's ability to extrapolate it from the get_random_int()
   * CRNG is silly.
   *
   * Even some cryptographic keys are safe to generate with get_random_int().
   * In particular, keys for SipHash are generally fine.  Here, knowledge
   * of the key authorizes you to do something to a kernel object (inject
   * packets to a network connection, or flood a hash table), and the
   * key is stored with the object being protected.  Once it goes away,
   * we no longer care if anyone knows the key.
   *
   * prandom_u32()
   * -------------
   *
   * For even weaker applications, see the pseudorandom generator
   * prandom_u32(), prandom_max(), and prandom_bytes().  If the random
   * numbers aren't security-critical at all, these are *far* cheaper.
   * Useful for self-tests, random error simulation, randomized backoffs,
   * and any other application where you trust that nobody is trying to
   * maliciously mess with you by guessing the "random" numbers.
   *
   * Exported interfaces ---- input
   * ==============================
   *
   * The current exported interfaces for gathering environmental noise
   * from the devices are:
   *
   *	void add_device_randomness(const void *buf, unsigned int size);
   * 	void add_input_randomness(unsigned int type, unsigned int code,
   *                                unsigned int value);
   *	void add_interrupt_randomness(int irq, int irq_flags);
   * 	void add_disk_randomness(struct gendisk *disk);
   *
   * add_device_randomness() is for adding data to the random pool that
   * is likely to differ between two devices (or possibly even per boot).
   * This would be things like MAC addresses or serial numbers, or the
   * read-out of the RTC. This does *not* add any actual entropy to the
   * pool, but it initializes the pool to different values for devices
   * that might otherwise be identical and have very little entropy
   * available to them (particularly common in the embedded world).
   *
   * add_input_randomness() uses the input layer interrupt timing, as well as
   * the event type information from the hardware.
   *
   * add_interrupt_randomness() uses the interrupt timing as random
   * inputs to the entropy pool. Using the cycle counters and the irq source
   * as inputs, it feeds the randomness roughly once a second.
   *
   * add_disk_randomness() uses what amounts to the seek time of block
   * layer request events, on a per-disk_devt basis, as input to the
   * entropy pool. Note that high-speed solid state drives with very low
   * seek times do not make for good sources of entropy, as their seek
   * times are usually fairly consistent.
   *
   * All of these routines try to estimate how many bits of randomness a
   * particular randomness source.  They do this by keeping track of the
   * first and second order deltas of the event timings.
   *
   * Ensuring unpredictability at system startup
   * ============================================
   *
   * When any operating system starts up, it will go through a sequence
   * of actions that are fairly predictable by an adversary, especially
   * if the start-up does not involve interaction with a human operator.
   * This reduces the actual number of bits of unpredictability in the
   * entropy pool below the value in entropy_count.  In order to
   * counteract this effect, it helps to carry information in the
   * entropy pool across shut-downs and start-ups.  To do this, put the
   * following lines an appropriate script which is run during the boot
   * sequence:
   *
   *	echo "Initializing random number generator..."
   *	random_seed=/var/run/random-seed
   *	# Carry a random seed from start-up to start-up
   *	# Load and then save the whole entropy pool
   *	if [ -f $random_seed ]; then
   *		cat $random_seed >/dev/urandom
   *	else
   *		touch $random_seed
   *	fi
   *	chmod 600 $random_seed
   *	dd if=/dev/urandom of=$random_seed count=1 bs=512
   *
   * and the following lines in an appropriate script which is run as
   * the system is shutdown:
   *
   *	# Carry a random seed from shut-down to start-up
   *	# Save the whole entropy pool
   *	echo "Saving random seed..."
   *	random_seed=/var/run/random-seed
   *	touch $random_seed
   *	chmod 600 $random_seed
   *	dd if=/dev/urandom of=$random_seed count=1 bs=512
   *
   * For example, on most modern systems using the System V init
   * scripts, such code fragments would be found in
   * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
   * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
   *
   * Effectively, these commands cause the contents of the entropy pool
   * to be saved at shut-down time and reloaded into the entropy pool at
   * start-up.  (The 'dd' in the addition to the bootup script is to
   * make sure that /etc/random-seed is different for every start-up,
   * even if the system crashes without executing rc.0.)  Even with
   * complete knowledge of the start-up activities, predicting the state
   * of the entropy pool requires knowledge of the previous history of
   * the system.
   *
   * Configuring the /dev/random driver under Linux
   * ==============================================
   *
   * The /dev/random driver under Linux uses minor numbers 8 and 9 of
   * the /dev/mem major number (#1).  So if your system does not have
   * /dev/random and /dev/urandom created already, they can be created
   * by using the commands:
   *
   * 	mknod /dev/random c 1 8
   * 	mknod /dev/urandom c 1 9
   *
   * Acknowledgements:
   * =================
   *
   * Ideas for constructing this random number generator were derived
   * from Pretty Good Privacy's random number generator, and from private
   * discussions with Phil Karn.  Colin Plumb provided a faster random
   * number generator, which speed up the mixing function of the entropy
   * pool, taken from PGPfone.  Dale Worley has also contributed many
   * useful ideas and suggestions to improve this driver.
   *
   * Any flaws in the design are solely my responsibility, and should
   * not be attributed to the Phil, Colin, or any of authors of PGP.
   *
   * Further background information on this topic may be obtained from
   * RFC 1750, "Randomness Recommendations for Security", by Donald
   * Eastlake, Steve Crocker, and Jeff Schiller.
   */
  
  #include <linux/utsname.h>
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/major.h>
  #include <linux/string.h>
  #include <linux/fcntl.h>
  #include <linux/slab.h>
  #include <linux/random.h>
  #include <linux/poll.h>
  #include <linux/init.h>
  #include <linux/fs.h>
  #include <linux/genhd.h>
  #include <linux/interrupt.h>
  #include <linux/mm.h>
  #include <linux/nodemask.h>
  #include <linux/spinlock.h>
  #include <linux/kthread.h>
  #include <linux/percpu.h>
  #include <linux/cryptohash.h>
  #include <linux/fips.h>
  #include <linux/ptrace.h>
  #include <linux/workqueue.h>
  #include <linux/irq.h>
  #include <linux/ratelimit.h>
  #include <linux/syscalls.h>
  #include <linux/completion.h>
  #include <linux/uuid.h>
  #include <crypto/chacha.h>
  
  #include <asm/processor.h>
  #include <linux/uaccess.h>
  #include <asm/irq.h>
  #include <asm/irq_regs.h>
  #include <asm/io.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/random.h>
  
  /* #define ADD_INTERRUPT_BENCH */
  
  /*
   * Configuration information
   */
  #define INPUT_POOL_SHIFT	12
  #define INPUT_POOL_WORDS	(1 << (INPUT_POOL_SHIFT-5))
  #define OUTPUT_POOL_SHIFT	10
  #define OUTPUT_POOL_WORDS	(1 << (OUTPUT_POOL_SHIFT-5))
  #define SEC_XFER_SIZE		512
  #define EXTRACT_SIZE		10
  
  
  #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
  
  /*
   * To allow fractional bits to be tracked, the entropy_count field is
   * denominated in units of 1/8th bits.
   *
   * 2*(ENTROPY_SHIFT + poolbitshift) must <= 31, or the multiply in
   * credit_entropy_bits() needs to be 64 bits wide.
   */
  #define ENTROPY_SHIFT 3
  #define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
  
  /*
   * The minimum number of bits of entropy before we wake up a read on
   * /dev/random.  Should be enough to do a significant reseed.
   */
  static int random_read_wakeup_bits = 64;
  
  /*
   * If the entropy count falls under this number of bits, then we
   * should wake up processes which are selecting or polling on write
   * access to /dev/random.
   */
  static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
  
  /*
   * Originally, we used a primitive polynomial of degree .poolwords
   * over GF(2).  The taps for various sizes are defined below.  They
   * were chosen to be evenly spaced except for the last tap, which is 1
   * to get the twisting happening as fast as possible.
   *
   * For the purposes of better mixing, we use the CRC-32 polynomial as
   * well to make a (modified) twisted Generalized Feedback Shift
   * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
   * generators.  ACM Transactions on Modeling and Computer Simulation
   * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
   * GFSR generators II.  ACM Transactions on Modeling and Computer
   * Simulation 4:254-266)
   *
   * Thanks to Colin Plumb for suggesting this.
   *
   * The mixing operation is much less sensitive than the output hash,
   * where we use SHA-1.  All that we want of mixing operation is that
   * it be a good non-cryptographic hash; i.e. it not produce collisions
   * when fed "random" data of the sort we expect to see.  As long as
   * the pool state differs for different inputs, we have preserved the
   * input entropy and done a good job.  The fact that an intelligent
   * attacker can construct inputs that will produce controlled
   * alterations to the pool's state is not important because we don't
   * consider such inputs to contribute any randomness.  The only
   * property we need with respect to them is that the attacker can't
   * increase his/her knowledge of the pool's state.  Since all
   * additions are reversible (knowing the final state and the input,
   * you can reconstruct the initial state), if an attacker has any
   * uncertainty about the initial state, he/she can only shuffle that
   * uncertainty about, but never cause any collisions (which would
   * decrease the uncertainty).
   *
   * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
   * Videau in their paper, "The Linux Pseudorandom Number Generator
   * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
   * paper, they point out that we are not using a true Twisted GFSR,
   * since Matsumoto & Kurita used a trinomial feedback polynomial (that
   * is, with only three taps, instead of the six that we are using).
   * As a result, the resulting polynomial is neither primitive nor
   * irreducible, and hence does not have a maximal period over
   * GF(2**32).  They suggest a slight change to the generator
   * polynomial which improves the resulting TGFSR polynomial to be
   * irreducible, which we have made here.
   */
  static const struct poolinfo {
  	int poolbitshift, poolwords, poolbytes, poolfracbits;
  #define S(x) ilog2(x)+5, (x), (x)*4, (x) << (ENTROPY_SHIFT+5)
  	int tap1, tap2, tap3, tap4, tap5;
  } poolinfo_table[] = {
  	/* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
  	/* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
  	{ S(128),	104,	76,	51,	25,	1 },
  	/* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
  	/* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
  	{ S(32),	26,	19,	14,	7,	1 },
  #if 0
  	/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
  	{ S(2048),	1638,	1231,	819,	411,	1 },
  
  	/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
  	{ S(1024),	817,	615,	412,	204,	1 },
  
  	/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
  	{ S(1024),	819,	616,	410,	207,	2 },
  
  	/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
  	{ S(512),	411,	308,	208,	104,	1 },
  
  	/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
  	{ S(512),	409,	307,	206,	102,	2 },
  	/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
  	{ S(512),	409,	309,	205,	103,	2 },
  
  	/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
  	{ S(256),	205,	155,	101,	52,	1 },
  
  	/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
  	{ S(128),	103,	78,	51,	27,	2 },
  
  	/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
  	{ S(64),	52,	39,	26,	14,	1 },
  #endif
  };
  
  /*
   * Static global variables
   */
  static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
  static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
  static struct fasync_struct *fasync;
  
  static DEFINE_SPINLOCK(random_ready_list_lock);
  static LIST_HEAD(random_ready_list);
  
  struct crng_state {
  	__u32		state[16];
  	unsigned long	init_time;
  	spinlock_t	lock;
  };
  
  static struct crng_state primary_crng = {
  	.lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
  };
  
  /*
   * crng_init =  0 --> Uninitialized
   *		1 --> Initialized
   *		2 --> Initialized from input_pool
   *
   * crng_init is protected by primary_crng->lock, and only increases
   * its value (from 0->1->2).
   */
  static int crng_init = 0;
  #define crng_ready() (likely(crng_init > 1))
  static int crng_init_cnt = 0;
  static unsigned long crng_global_init_time = 0;
  #define CRNG_INIT_CNT_THRESH (2*CHACHA_KEY_SIZE)
  static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA_BLOCK_SIZE]);
  static void _crng_backtrack_protect(struct crng_state *crng,
  				    __u8 tmp[CHACHA_BLOCK_SIZE], int used);
  static void process_random_ready_list(void);
  static void _get_random_bytes(void *buf, int nbytes);
  
  static struct ratelimit_state unseeded_warning =
  	RATELIMIT_STATE_INIT("warn_unseeded_randomness", HZ, 3);
  static struct ratelimit_state urandom_warning =
  	RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
  
  static int ratelimit_disable __read_mostly;
  
  module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
  MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
  
  /**********************************************************************
   *
   * OS independent entropy store.   Here are the functions which handle
   * storing entropy in an entropy pool.
   *
   **********************************************************************/
  
  struct entropy_store;
  struct entropy_store {
  	/* read-only data: */
  	const struct poolinfo *poolinfo;
  	__u32 *pool;
  	const char *name;
  	struct entropy_store *pull;
  	struct work_struct push_work;
  
  	/* read-write data: */
  	unsigned long last_pulled;
  	spinlock_t lock;
  	unsigned short add_ptr;
  	unsigned short input_rotate;
  	int entropy_count;
  	unsigned int initialized:1;
  	unsigned int last_data_init:1;
  	__u8 last_data[EXTRACT_SIZE];
  };
  
  static ssize_t extract_entropy(struct entropy_store *r, void *buf,
  			       size_t nbytes, int min, int rsvd);
  static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
  				size_t nbytes, int fips);
  
  static void crng_reseed(struct crng_state *crng, struct entropy_store *r);
  static void push_to_pool(struct work_struct *work);
  static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy;
  static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy;
  
  static struct entropy_store input_pool = {
  	.poolinfo = &poolinfo_table[0],
  	.name = "input",
  	.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
  	.pool = input_pool_data
  };
  
  static struct entropy_store blocking_pool = {
  	.poolinfo = &poolinfo_table[1],
  	.name = "blocking",
  	.pull = &input_pool,
  	.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
  	.pool = blocking_pool_data,
  	.push_work = __WORK_INITIALIZER(blocking_pool.push_work,
  					push_to_pool),
  };
  
  static __u32 const twist_table[8] = {
  	0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
  	0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
  
  /*
   * This function adds bytes into the entropy "pool".  It does not
   * update the entropy estimate.  The caller should call
   * credit_entropy_bits if this is appropriate.
   *
   * The pool is stirred with a primitive polynomial of the appropriate
   * degree, and then twisted.  We twist by three bits at a time because
   * it's cheap to do so and helps slightly in the expected case where
   * the entropy is concentrated in the low-order bits.
   */
  static void _mix_pool_bytes(struct entropy_store *r, const void *in,
  			    int nbytes)
  {
  	unsigned long i, tap1, tap2, tap3, tap4, tap5;
  	int input_rotate;
  	int wordmask = r->poolinfo->poolwords - 1;
  	const char *bytes = in;
  	__u32 w;
  
  	tap1 = r->poolinfo->tap1;
  	tap2 = r->poolinfo->tap2;
  	tap3 = r->poolinfo->tap3;
  	tap4 = r->poolinfo->tap4;
  	tap5 = r->poolinfo->tap5;
  
  	input_rotate = r->input_rotate;
  	i = r->add_ptr;
  
  	/* mix one byte at a time to simplify size handling and churn faster */
  	while (nbytes--) {
  		w = rol32(*bytes++, input_rotate);
  		i = (i - 1) & wordmask;
  
  		/* XOR in the various taps */
  		w ^= r->pool[i];
  		w ^= r->pool[(i + tap1) & wordmask];
  		w ^= r->pool[(i + tap2) & wordmask];
  		w ^= r->pool[(i + tap3) & wordmask];
  		w ^= r->pool[(i + tap4) & wordmask];
  		w ^= r->pool[(i + tap5) & wordmask];
  
  		/* Mix the result back in with a twist */
  		r->pool[i] = (w >> 3) ^ twist_table[w & 7];
  
  		/*
  		 * Normally, we add 7 bits of rotation to the pool.
  		 * At the beginning of the pool, add an extra 7 bits
  		 * rotation, so that successive passes spread the
  		 * input bits across the pool evenly.
  		 */
  		input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
  	}
  
  	r->input_rotate = input_rotate;
  	r->add_ptr = i;
  }
  
  static void __mix_pool_bytes(struct entropy_store *r, const void *in,
  			     int nbytes)
  {
  	trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
  	_mix_pool_bytes(r, in, nbytes);
  }
  
  static void mix_pool_bytes(struct entropy_store *r, const void *in,
  			   int nbytes)
  {
  	unsigned long flags;
  
  	trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
  	spin_lock_irqsave(&r->lock, flags);
  	_mix_pool_bytes(r, in, nbytes);
  	spin_unlock_irqrestore(&r->lock, flags);
  }
  
  struct fast_pool {
  	__u32		pool[4];
  	unsigned long	last;
  	unsigned short	reg_idx;
  	unsigned char	count;
  };
  
  /*
   * This is a fast mixing routine used by the interrupt randomness
   * collector.  It's hardcoded for an 128 bit pool and assumes that any
   * locks that might be needed are taken by the caller.
   */
  static void fast_mix(struct fast_pool *f)
  {
  	__u32 a = f->pool[0],	b = f->pool[1];
  	__u32 c = f->pool[2],	d = f->pool[3];
  
  	a += b;			c += d;
  	b = rol32(b, 6);	d = rol32(d, 27);
  	d ^= a;			b ^= c;
  
  	a += b;			c += d;
  	b = rol32(b, 16);	d = rol32(d, 14);
  	d ^= a;			b ^= c;
  
  	a += b;			c += d;
  	b = rol32(b, 6);	d = rol32(d, 27);
  	d ^= a;			b ^= c;
  
  	a += b;			c += d;
  	b = rol32(b, 16);	d = rol32(d, 14);
  	d ^= a;			b ^= c;
  
  	f->pool[0] = a;  f->pool[1] = b;
  	f->pool[2] = c;  f->pool[3] = d;
  	f->count++;
  }
  
  static void process_random_ready_list(void)
  {
  	unsigned long flags;
  	struct random_ready_callback *rdy, *tmp;
  
  	spin_lock_irqsave(&random_ready_list_lock, flags);
  	list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
  		struct module *owner = rdy->owner;
  
  		list_del_init(&rdy->list);
  		rdy->func(rdy);
  		module_put(owner);
  	}
  	spin_unlock_irqrestore(&random_ready_list_lock, flags);
  }
  
  /*
   * Credit (or debit) the entropy store with n bits of entropy.
   * Use credit_entropy_bits_safe() if the value comes from userspace
   * or otherwise should be checked for extreme values.
   */
  static void credit_entropy_bits(struct entropy_store *r, int nbits)
  {
  	int entropy_count, orig, has_initialized = 0;
  	const int pool_size = r->poolinfo->poolfracbits;
  	int nfrac = nbits << ENTROPY_SHIFT;
  
  	if (!nbits)
  		return;
  
  retry:
  	entropy_count = orig = READ_ONCE(r->entropy_count);
  	if (nfrac < 0) {
  		/* Debit */
  		entropy_count += nfrac;
  	} else {
  		/*
  		 * Credit: we have to account for the possibility of
  		 * overwriting already present entropy.	 Even in the
  		 * ideal case of pure Shannon entropy, new contributions
  		 * approach the full value asymptotically:
  		 *
  		 * entropy <- entropy + (pool_size - entropy) *
  		 *	(1 - exp(-add_entropy/pool_size))
  		 *
  		 * For add_entropy <= pool_size/2 then
  		 * (1 - exp(-add_entropy/pool_size)) >=
  		 *    (add_entropy/pool_size)*0.7869...
  		 * so we can approximate the exponential with
  		 * 3/4*add_entropy/pool_size and still be on the
  		 * safe side by adding at most pool_size/2 at a time.
  		 *
  		 * The use of pool_size-2 in the while statement is to
  		 * prevent rounding artifacts from making the loop
  		 * arbitrarily long; this limits the loop to log2(pool_size)*2
  		 * turns no matter how large nbits is.
  		 */
  		int pnfrac = nfrac;
  		const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
  		/* The +2 corresponds to the /4 in the denominator */
  
  		do {
  			unsigned int anfrac = min(pnfrac, pool_size/2);
  			unsigned int add =
  				((pool_size - entropy_count)*anfrac*3) >> s;
  
  			entropy_count += add;
  			pnfrac -= anfrac;
  		} while (unlikely(entropy_count < pool_size-2 && pnfrac));
  	}
  
  	if (unlikely(entropy_count < 0)) {
  		pr_warn("random: negative entropy/overflow: pool %s count %d\n",
  			r->name, entropy_count);
  		WARN_ON(1);
  		entropy_count = 0;
  	} else if (entropy_count > pool_size)
  		entropy_count = pool_size;
  	if ((r == &blocking_pool) && !r->initialized &&
  	    (entropy_count >> ENTROPY_SHIFT) > 128)
  		has_initialized = 1;
  	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
  		goto retry;
  
  	if (has_initialized) {
  		r->initialized = 1;
  		wake_up_interruptible(&random_read_wait);
  		kill_fasync(&fasync, SIGIO, POLL_IN);
  	}
  
  	trace_credit_entropy_bits(r->name, nbits,
  				  entropy_count >> ENTROPY_SHIFT, _RET_IP_);
  
  	if (r == &input_pool) {
  		int entropy_bits = entropy_count >> ENTROPY_SHIFT;
  		struct entropy_store *other = &blocking_pool;
  
  		if (crng_init < 2) {
  			if (entropy_bits < 128)
  				return;
  			crng_reseed(&primary_crng, r);
  			entropy_bits = r->entropy_count >> ENTROPY_SHIFT;
  		}
  
  		/* initialize the blocking pool if necessary */
  		if (entropy_bits >= random_read_wakeup_bits &&
  		    !other->initialized) {
  			schedule_work(&other->push_work);
  			return;
  		}
  
  		/* should we wake readers? */
  		if (entropy_bits >= random_read_wakeup_bits &&
  		    wq_has_sleeper(&random_read_wait)) {
  			wake_up_interruptible(&random_read_wait);
  			kill_fasync(&fasync, SIGIO, POLL_IN);
  		}
  		/* If the input pool is getting full, and the blocking
  		 * pool has room, send some entropy to the blocking
  		 * pool.
  		 */
  		if (!work_pending(&other->push_work) &&
  		    (ENTROPY_BITS(r) > 6 * r->poolinfo->poolbytes) &&
  		    (ENTROPY_BITS(other) <= 6 * other->poolinfo->poolbytes))
  			schedule_work(&other->push_work);
  	}
  }
  
  static int credit_entropy_bits_safe(struct entropy_store *r, int nbits)
  {
  	const int nbits_max = r->poolinfo->poolwords * 32;
  
  	if (nbits < 0)
  		return -EINVAL;
  
  	/* Cap the value to avoid overflows */
  	nbits = min(nbits,  nbits_max);
  
  	credit_entropy_bits(r, nbits);
  	return 0;
  }
  
  /*********************************************************************
   *
   * CRNG using CHACHA20
   *
   *********************************************************************/
  
  #define CRNG_RESEED_INTERVAL (300*HZ)
  
  static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
  
  #ifdef CONFIG_NUMA
  /*
   * Hack to deal with crazy userspace progams when they are all trying
   * to access /dev/urandom in parallel.  The programs are almost
   * certainly doing something terribly wrong, but we'll work around
   * their brain damage.
   */
  static struct crng_state **crng_node_pool __read_mostly;
  #endif
  
  static void invalidate_batched_entropy(void);
  static void numa_crng_init(void);
  
  static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
  static int __init parse_trust_cpu(char *arg)
  {
  	return kstrtobool(arg, &trust_cpu);
  }
  early_param("random.trust_cpu", parse_trust_cpu);
  
  static void crng_initialize(struct crng_state *crng)
  {
  	int		i;
  	int		arch_init = 1;
  	unsigned long	rv;
  
  	memcpy(&crng->state[0], "expand 32-byte k", 16);
  	if (crng == &primary_crng)
  		_extract_entropy(&input_pool, &crng->state[4],
  				 sizeof(__u32) * 12, 0);
  	else
  		_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
  	for (i = 4; i < 16; i++) {
  		if (!arch_get_random_seed_long(&rv) &&
  		    !arch_get_random_long(&rv)) {
  			rv = random_get_entropy();
  			arch_init = 0;
  		}
  		crng->state[i] ^= rv;
  	}
  	if (trust_cpu && arch_init && crng == &primary_crng) {
  		invalidate_batched_entropy();
  		numa_crng_init();
  		crng_init = 2;
  		pr_notice("random: crng done (trusting CPU's manufacturer)\n");
  	}
  	crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
  }
  
  #ifdef CONFIG_NUMA
  static void do_numa_crng_init(struct work_struct *work)
  {
  	int i;
  	struct crng_state *crng;
  	struct crng_state **pool;
  
  	pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
  	for_each_online_node(i) {
  		crng = kmalloc_node(sizeof(struct crng_state),
  				    GFP_KERNEL | __GFP_NOFAIL, i);
  		spin_lock_init(&crng->lock);
  		crng_initialize(crng);
  		pool[i] = crng;
  	}
  	mb();
  	if (cmpxchg(&crng_node_pool, NULL, pool)) {
  		for_each_node(i)
  			kfree(pool[i]);
  		kfree(pool);
  	}
  }
  
  static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init);
  
  static void numa_crng_init(void)
  {
  	schedule_work(&numa_crng_init_work);
  }
  #else
  static void numa_crng_init(void) {}
  #endif
  
  /*
   * crng_fast_load() can be called by code in the interrupt service
   * path.  So we can't afford to dilly-dally.
   */
  static int crng_fast_load(const char *cp, size_t len)
  {
  	unsigned long flags;
  	char *p;
  
  	if (!spin_trylock_irqsave(&primary_crng.lock, flags))
  		return 0;
  	if (crng_init != 0) {
  		spin_unlock_irqrestore(&primary_crng.lock, flags);
  		return 0;
  	}
  	p = (unsigned char *) &primary_crng.state[4];
  	while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) {
  		p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp;
  		cp++; crng_init_cnt++; len--;
  	}
  	spin_unlock_irqrestore(&primary_crng.lock, flags);
  	if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) {
  		invalidate_batched_entropy();
  		crng_init = 1;
  		wake_up_interruptible(&crng_init_wait);
  		pr_notice("random: fast init done\n");
  	}
  	return 1;
  }
  
  /*
   * crng_slow_load() is called by add_device_randomness, which has two
   * attributes.  (1) We can't trust the buffer passed to it is
   * guaranteed to be unpredictable (so it might not have any entropy at
   * all), and (2) it doesn't have the performance constraints of
   * crng_fast_load().
   *
   * So we do something more comprehensive which is guaranteed to touch
   * all of the primary_crng's state, and which uses a LFSR with a
   * period of 255 as part of the mixing algorithm.  Finally, we do
   * *not* advance crng_init_cnt since buffer we may get may be something
   * like a fixed DMI table (for example), which might very well be
   * unique to the machine, but is otherwise unvarying.
   */
  static int crng_slow_load(const char *cp, size_t len)
  {
  	unsigned long		flags;
  	static unsigned char	lfsr = 1;
  	unsigned char		tmp;
  	unsigned		i, max = CHACHA_KEY_SIZE;
  	const char *		src_buf = cp;
  	char *			dest_buf = (char *) &primary_crng.state[4];
  
  	if (!spin_trylock_irqsave(&primary_crng.lock, flags))
  		return 0;
  	if (crng_init != 0) {
  		spin_unlock_irqrestore(&primary_crng.lock, flags);
  		return 0;
  	}
  	if (len > max)
  		max = len;
  
  	for (i = 0; i < max ; i++) {
  		tmp = lfsr;
  		lfsr >>= 1;
  		if (tmp & 1)
  			lfsr ^= 0xE1;
  		tmp = dest_buf[i % CHACHA_KEY_SIZE];
  		dest_buf[i % CHACHA_KEY_SIZE] ^= src_buf[i % len] ^ lfsr;
  		lfsr += (tmp << 3) | (tmp >> 5);
  	}
  	spin_unlock_irqrestore(&primary_crng.lock, flags);
  	return 1;
  }
  
  static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
  {
  	unsigned long	flags;
  	int		i, num;
  	union {
  		__u8	block[CHACHA_BLOCK_SIZE];
  		__u32	key[8];
  	} buf;
  
  	if (r) {
  		num = extract_entropy(r, &buf, 32, 16, 0);
  		if (num == 0)
  			return;
  	} else {
  		_extract_crng(&primary_crng, buf.block);
  		_crng_backtrack_protect(&primary_crng, buf.block,
  					CHACHA_KEY_SIZE);
  	}
  	spin_lock_irqsave(&crng->lock, flags);
  	for (i = 0; i < 8; i++) {
  		unsigned long	rv;
  		if (!arch_get_random_seed_long(&rv) &&
  		    !arch_get_random_long(&rv))
  			rv = random_get_entropy();
  		crng->state[i+4] ^= buf.key[i] ^ rv;
  	}
  	memzero_explicit(&buf, sizeof(buf));
  	crng->init_time = jiffies;
  	spin_unlock_irqrestore(&crng->lock, flags);
  	if (crng == &primary_crng && crng_init < 2) {
  		invalidate_batched_entropy();
  		numa_crng_init();
  		crng_init = 2;
  		process_random_ready_list();
  		wake_up_interruptible(&crng_init_wait);
  		pr_notice("random: crng init done\n");
  		if (unseeded_warning.missed) {
  			pr_notice("random: %d get_random_xx warning(s) missed "
  				  "due to ratelimiting\n",
  				  unseeded_warning.missed);
  			unseeded_warning.missed = 0;
  		}
  		if (urandom_warning.missed) {
  			pr_notice("random: %d urandom warning(s) missed "
  				  "due to ratelimiting\n",
  				  urandom_warning.missed);
  			urandom_warning.missed = 0;
  		}
  	}
  }
  
  static void _extract_crng(struct crng_state *crng,
  			  __u8 out[CHACHA_BLOCK_SIZE])
  {
  	unsigned long v, flags;
  
  	if (crng_ready() &&
  	    (time_after(crng_global_init_time, crng->init_time) ||
  	     time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
  		crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
  	spin_lock_irqsave(&crng->lock, flags);
  	if (arch_get_random_long(&v))
  		crng->state[14] ^= v;
  	chacha20_block(&crng->state[0], out);
  	if (crng->state[12] == 0)
  		crng->state[13]++;
  	spin_unlock_irqrestore(&crng->lock, flags);
  }
  
  static void extract_crng(__u8 out[CHACHA_BLOCK_SIZE])
  {
  	struct crng_state *crng = NULL;
  
  #ifdef CONFIG_NUMA
  	if (crng_node_pool)
  		crng = crng_node_pool[numa_node_id()];
  	if (crng == NULL)
  #endif
  		crng = &primary_crng;
  	_extract_crng(crng, out);
  }
  
  /*
   * Use the leftover bytes from the CRNG block output (if there is
   * enough) to mutate the CRNG key to provide backtracking protection.
   */
  static void _crng_backtrack_protect(struct crng_state *crng,
  				    __u8 tmp[CHACHA_BLOCK_SIZE], int used)
  {
  	unsigned long	flags;
  	__u32		*s, *d;
  	int		i;
  
  	used = round_up(used, sizeof(__u32));
  	if (used + CHACHA_KEY_SIZE > CHACHA_BLOCK_SIZE) {
  		extract_crng(tmp);
  		used = 0;
  	}
  	spin_lock_irqsave(&crng->lock, flags);
  	s = (__u32 *) &tmp[used];
  	d = &crng->state[4];
  	for (i=0; i < 8; i++)
  		*d++ ^= *s++;
  	spin_unlock_irqrestore(&crng->lock, flags);
  }
  
  static void crng_backtrack_protect(__u8 tmp[CHACHA_BLOCK_SIZE], int used)
  {
  	struct crng_state *crng = NULL;
  
  #ifdef CONFIG_NUMA
  	if (crng_node_pool)
  		crng = crng_node_pool[numa_node_id()];
  	if (crng == NULL)
  #endif
  		crng = &primary_crng;
  	_crng_backtrack_protect(crng, tmp, used);
  }
  
  static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
  {
  	ssize_t ret = 0, i = CHACHA_BLOCK_SIZE;
  	__u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
  	int large_request = (nbytes > 256);
  
  	while (nbytes) {
  		if (large_request && need_resched()) {
  			if (signal_pending(current)) {
  				if (ret == 0)
  					ret = -ERESTARTSYS;
  				break;
  			}
  			schedule();
  		}
  
  		extract_crng(tmp);
  		i = min_t(int, nbytes, CHACHA_BLOCK_SIZE);
  		if (copy_to_user(buf, tmp, i)) {
  			ret = -EFAULT;
  			break;
  		}
  
  		nbytes -= i;
  		buf += i;
  		ret += i;
  	}
  	crng_backtrack_protect(tmp, i);
  
  	/* Wipe data just written to memory */
  	memzero_explicit(tmp, sizeof(tmp));
  
  	return ret;
  }
  
  
  /*********************************************************************
   *
   * Entropy input management
   *
   *********************************************************************/
  
  /* There is one of these per entropy source */
  struct timer_rand_state {
  	cycles_t last_time;
  	long last_delta, last_delta2;
  };
  
  #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
  
  /*
   * Add device- or boot-specific data to the input pool to help
   * initialize it.
   *
   * None of this adds any entropy; it is meant to avoid the problem of
   * the entropy pool having similar initial state across largely
   * identical devices.
   */
  void add_device_randomness(const void *buf, unsigned int size)
  {
  	unsigned long time = random_get_entropy() ^ jiffies;
  	unsigned long flags;
  
  	if (!crng_ready() && size)
  		crng_slow_load(buf, size);
  
  	trace_add_device_randomness(size, _RET_IP_);
  	spin_lock_irqsave(&input_pool.lock, flags);
  	_mix_pool_bytes(&input_pool, buf, size);
  	_mix_pool_bytes(&input_pool, &time, sizeof(time));
  	spin_unlock_irqrestore(&input_pool.lock, flags);
  }
  EXPORT_SYMBOL(add_device_randomness);
  
  static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
  
  /*
   * This function adds entropy to the entropy "pool" by using timing
   * delays.  It uses the timer_rand_state structure to make an estimate
   * of how many bits of entropy this call has added to the pool.
   *
   * The number "num" is also added to the pool - it should somehow describe
   * the type of event which just happened.  This is currently 0-255 for
   * keyboard scan codes, and 256 upwards for interrupts.
   *
   */
  static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
  {
  	struct entropy_store	*r;
  	struct {
  		long jiffies;
  		unsigned cycles;
  		unsigned num;
  	} sample;
  	long delta, delta2, delta3;
  
  	sample.jiffies = jiffies;
  	sample.cycles = random_get_entropy();
  	sample.num = num;
  	r = &input_pool;
  	mix_pool_bytes(r, &sample, sizeof(sample));
  
  	/*
  	 * Calculate number of bits of randomness we probably added.
  	 * We take into account the first, second and third-order deltas
  	 * in order to make our estimate.
  	 */
  	delta = sample.jiffies - state->last_time;
  	state->last_time = sample.jiffies;
  
  	delta2 = delta - state->last_delta;
  	state->last_delta = delta;
  
  	delta3 = delta2 - state->last_delta2;
  	state->last_delta2 = delta2;
  
  	if (delta < 0)
  		delta = -delta;
  	if (delta2 < 0)
  		delta2 = -delta2;
  	if (delta3 < 0)
  		delta3 = -delta3;
  	if (delta > delta2)
  		delta = delta2;
  	if (delta > delta3)
  		delta = delta3;
  
  	/*
  	 * delta is now minimum absolute delta.
  	 * Round down by 1 bit on general principles,
  	 * and limit entropy entimate to 12 bits.
  	 */
  	credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
  }
  
  void add_input_randomness(unsigned int type, unsigned int code,
  				 unsigned int value)
  {
  	static unsigned char last_value;
  
  	/* ignore autorepeat and the like */
  	if (value == last_value)
  		return;
  
  	last_value = value;
  	add_timer_randomness(&input_timer_state,
  			     (type << 4) ^ code ^ (code >> 4) ^ value);
  	trace_add_input_randomness(ENTROPY_BITS(&input_pool));
  }
  EXPORT_SYMBOL_GPL(add_input_randomness);
  
  static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
  
  #ifdef ADD_INTERRUPT_BENCH
  static unsigned long avg_cycles, avg_deviation;
  
  #define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
  #define FIXED_1_2 (1 << (AVG_SHIFT-1))
  
  static void add_interrupt_bench(cycles_t start)
  {
          long delta = random_get_entropy() - start;
  
          /* Use a weighted moving average */
          delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
          avg_cycles += delta;
          /* And average deviation */
          delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
          avg_deviation += delta;
  }
  #else
  #define add_interrupt_bench(x)
  #endif
  
  static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
  {
  	__u32 *ptr = (__u32 *) regs;
  	unsigned int idx;
  
  	if (regs == NULL)
  		return 0;
  	idx = READ_ONCE(f->reg_idx);
  	if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
  		idx = 0;
  	ptr += idx++;
  	WRITE_ONCE(f->reg_idx, idx);
  	return *ptr;
  }
  
  void add_interrupt_randomness(int irq, int irq_flags)
  {
  	struct entropy_store	*r;
  	struct fast_pool	*fast_pool = this_cpu_ptr(&irq_randomness);
  	struct pt_regs		*regs = get_irq_regs();
  	unsigned long		now = jiffies;
  	cycles_t		cycles = random_get_entropy();
  	__u32			c_high, j_high;
  	__u64			ip;
  	unsigned long		seed;
  	int			credit = 0;
  
  	if (cycles == 0)
  		cycles = get_reg(fast_pool, regs);
  	c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
  	j_high = (sizeof(now) > 4) ? now >> 32 : 0;
  	fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
  	fast_pool->pool[1] ^= now ^ c_high;
  	ip = regs ? instruction_pointer(regs) : _RET_IP_;
  	fast_pool->pool[2] ^= ip;
  	fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
  		get_reg(fast_pool, regs);
  
  	fast_mix(fast_pool);
  	add_interrupt_bench(cycles);
  
  	if (unlikely(crng_init == 0)) {
  		if ((fast_pool->count >= 64) &&
  		    crng_fast_load((char *) fast_pool->pool,
  				   sizeof(fast_pool->pool))) {
  			fast_pool->count = 0;
  			fast_pool->last = now;
  		}
  		return;
  	}
  
  	if ((fast_pool->count < 64) &&
  	    !time_after(now, fast_pool->last + HZ))
  		return;
  
  	r = &input_pool;
  	if (!spin_trylock(&r->lock))
  		return;
  
  	fast_pool->last = now;
  	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
  
  	/*
  	 * If we have architectural seed generator, produce a seed and
  	 * add it to the pool.  For the sake of paranoia don't let the
  	 * architectural seed generator dominate the input from the
  	 * interrupt noise.
  	 */
  	if (arch_get_random_seed_long(&seed)) {
  		__mix_pool_bytes(r, &seed, sizeof(seed));
  		credit = 1;
  	}
  	spin_unlock(&r->lock);
  
  	fast_pool->count = 0;
  
  	/* award one bit for the contents of the fast pool */
  	credit_entropy_bits(r, credit + 1);
  }
  EXPORT_SYMBOL_GPL(add_interrupt_randomness);
  
  #ifdef CONFIG_BLOCK
  void add_disk_randomness(struct gendisk *disk)
  {
  	if (!disk || !disk->random)
  		return;
  	/* first major is 1, so we get >= 0x200 here */
  	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
  	trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
  }
  EXPORT_SYMBOL_GPL(add_disk_randomness);
  #endif
  
  /*********************************************************************
   *
   * Entropy extraction routines
   *
   *********************************************************************/
  
  /*
   * This utility inline function is responsible for transferring entropy
   * from the primary pool to the secondary extraction pool. We make
   * sure we pull enough for a 'catastrophic reseed'.
   */
  static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
  static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
  {
  	if (!r->pull ||
  	    r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
  	    r->entropy_count > r->poolinfo->poolfracbits)
  		return;
  
  	_xfer_secondary_pool(r, nbytes);
  }
  
  static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
  {
  	__u32	tmp[OUTPUT_POOL_WORDS];
  
  	int bytes = nbytes;
  
  	/* pull at least as much as a wakeup */
  	bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
  	/* but never more than the buffer size */
  	bytes = min_t(int, bytes, sizeof(tmp));
  
  	trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
  				  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
  	bytes = extract_entropy(r->pull, tmp, bytes,
  				random_read_wakeup_bits / 8, 0);
  	mix_pool_bytes(r, tmp, bytes);
  	credit_entropy_bits(r, bytes*8);
  }
  
  /*
   * Used as a workqueue function so that when the input pool is getting
   * full, we can "spill over" some entropy to the output pools.  That
   * way the output pools can store some of the excess entropy instead
   * of letting it go to waste.
   */
  static void push_to_pool(struct work_struct *work)
  {
  	struct entropy_store *r = container_of(work, struct entropy_store,
  					      push_work);
  	BUG_ON(!r);
  	_xfer_secondary_pool(r, random_read_wakeup_bits/8);
  	trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
  			   r->pull->entropy_count >> ENTROPY_SHIFT);
  }
  
  /*
   * This function decides how many bytes to actually take from the
   * given pool, and also debits the entropy count accordingly.
   */
  static size_t account(struct entropy_store *r, size_t nbytes, int min,
  		      int reserved)
  {
  	int entropy_count, orig, have_bytes;
  	size_t ibytes, nfrac;
  
  	BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
  
  	/* Can we pull enough? */
  retry:
  	entropy_count = orig = READ_ONCE(r->entropy_count);
  	ibytes = nbytes;
  	/* never pull more than available */
  	have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
  
  	if ((have_bytes -= reserved) < 0)
  		have_bytes = 0;
  	ibytes = min_t(size_t, ibytes, have_bytes);
  	if (ibytes < min)
  		ibytes = 0;
  
  	if (unlikely(entropy_count < 0)) {
  		pr_warn("random: negative entropy count: pool %s count %d\n",
  			r->name, entropy_count);
  		WARN_ON(1);
  		entropy_count = 0;
  	}
  	nfrac = ibytes << (ENTROPY_SHIFT + 3);
  	if ((size_t) entropy_count > nfrac)
  		entropy_count -= nfrac;
  	else
  		entropy_count = 0;
  
  	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
  		goto retry;
  
  	trace_debit_entropy(r->name, 8 * ibytes);
  	if (ibytes &&
  	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
  		wake_up_interruptible(&random_write_wait);
  		kill_fasync(&fasync, SIGIO, POLL_OUT);
  	}
  
  	return ibytes;
  }
  
  /*
   * This function does the actual extraction for extract_entropy and
   * extract_entropy_user.
   *
   * Note: we assume that .poolwords is a multiple of 16 words.
   */
  static void extract_buf(struct entropy_store *r, __u8 *out)
  {
  	int i;
  	union {
  		__u32 w[5];
  		unsigned long l[LONGS(20)];
  	} hash;
  	__u32 workspace[SHA_WORKSPACE_WORDS];
  	unsigned long flags;
  
  	/*
  	 * If we have an architectural hardware random number
  	 * generator, use it for SHA's initial vector
  	 */
  	sha_init(hash.w);
  	for (i = 0; i < LONGS(20); i++) {
  		unsigned long v;
  		if (!arch_get_random_long(&v))
  			break;
  		hash.l[i] = v;
  	}
  
  	/* Generate a hash across the pool, 16 words (512 bits) at a time */
  	spin_lock_irqsave(&r->lock, flags);
  	for (i = 0; i < r->poolinfo->poolwords; i += 16)
  		sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
  
  	/*
  	 * We mix the hash back into the pool to prevent backtracking
  	 * attacks (where the attacker knows the state of the pool
  	 * plus the current outputs, and attempts to find previous
  	 * ouputs), unless the hash function can be inverted. By
  	 * mixing at least a SHA1 worth of hash data back, we make
  	 * brute-forcing the feedback as hard as brute-forcing the
  	 * hash.
  	 */
  	__mix_pool_bytes(r, hash.w, sizeof(hash.w));
  	spin_unlock_irqrestore(&r->lock, flags);
  
  	memzero_explicit(workspace, sizeof(workspace));
  
  	/*
  	 * In case the hash function has some recognizable output
  	 * pattern, we fold it in half. Thus, we always feed back
  	 * twice as much data as we output.
  	 */
  	hash.w[0] ^= hash.w[3];
  	hash.w[1] ^= hash.w[4];
  	hash.w[2] ^= rol32(hash.w[2], 16);
  
  	memcpy(out, &hash, EXTRACT_SIZE);
  	memzero_explicit(&hash, sizeof(hash));
  }
  
  static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
  				size_t nbytes, int fips)
  {
  	ssize_t ret = 0, i;
  	__u8 tmp[EXTRACT_SIZE];
  	unsigned long flags;
  
  	while (nbytes) {
  		extract_buf(r, tmp);
  
  		if (fips) {
  			spin_lock_irqsave(&r->lock, flags);
  			if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
  				panic("Hardware RNG duplicated output!\n");
  			memcpy(r->last_data, tmp, EXTRACT_SIZE);
  			spin_unlock_irqrestore(&r->lock, flags);
  		}
  		i = min_t(int, nbytes, EXTRACT_SIZE);
  		memcpy(buf, tmp, i);
  		nbytes -= i;
  		buf += i;
  		ret += i;
  	}
  
  	/* Wipe data just returned from memory */
  	memzero_explicit(tmp, sizeof(tmp));
  
  	return ret;
  }
  
  /*
   * This function extracts randomness from the "entropy pool", and
   * returns it in a buffer.
   *
   * The min parameter specifies the minimum amount we can pull before
   * failing to avoid races that defeat catastrophic reseeding while the
   * reserved parameter indicates how much entropy we must leave in the
   * pool after each pull to avoid starving other readers.
   */
  static ssize_t extract_entropy(struct entropy_store *r, void *buf,
  				 size_t nbytes, int min, int reserved)
  {
  	__u8 tmp[EXTRACT_SIZE];
  	unsigned long flags;
  
  	/* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
  	if (fips_enabled) {
  		spin_lock_irqsave(&r->lock, flags);
  		if (!r->last_data_init) {
  			r->last_data_init = 1;
  			spin_unlock_irqrestore(&r->lock, flags);
  			trace_extract_entropy(r->name, EXTRACT_SIZE,
  					      ENTROPY_BITS(r), _RET_IP_);
  			xfer_secondary_pool(r, EXTRACT_SIZE);
  			extract_buf(r, tmp);
  			spin_lock_irqsave(&r->lock, flags);
  			memcpy(r->last_data, tmp, EXTRACT_SIZE);
  		}
  		spin_unlock_irqrestore(&r->lock, flags);
  	}
  
  	trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
  	xfer_secondary_pool(r, nbytes);
  	nbytes = account(r, nbytes, min, reserved);
  
  	return _extract_entropy(r, buf, nbytes, fips_enabled);
  }
  
  /*
   * This function extracts randomness from the "entropy pool", and
   * returns it in a userspace buffer.
   */
  static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
  				    size_t nbytes)
  {
  	ssize_t ret = 0, i;
  	__u8 tmp[EXTRACT_SIZE];
  	int large_request = (nbytes > 256);
  
  	trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
  	if (!r->initialized && r->pull) {
  		xfer_secondary_pool(r, ENTROPY_BITS(r->pull)/8);
  		if (!r->initialized)
  			return 0;
  	}
  	xfer_secondary_pool(r, nbytes);
  	nbytes = account(r, nbytes, 0, 0);
  
  	while (nbytes) {
  		if (large_request && need_resched()) {
  			if (signal_pending(current)) {
  				if (ret == 0)
  					ret = -ERESTARTSYS;
  				break;
  			}
  			schedule();
  		}
  
  		extract_buf(r, tmp);
  		i = min_t(int, nbytes, EXTRACT_SIZE);
  		if (copy_to_user(buf, tmp, i)) {
  			ret = -EFAULT;
  			break;
  		}
  
  		nbytes -= i;
  		buf += i;
  		ret += i;
  	}
  
  	/* Wipe data just returned from memory */
  	memzero_explicit(tmp, sizeof(tmp));
  
  	return ret;
  }
  
  #define warn_unseeded_randomness(previous) \
  	_warn_unseeded_randomness(__func__, (void *) _RET_IP_, (previous))
  
  static void _warn_unseeded_randomness(const char *func_name, void *caller,
  				      void **previous)
  {
  #ifdef CONFIG_WARN_ALL_UNSEEDED_RANDOM
  	const bool print_once = false;
  #else
  	static bool print_once __read_mostly;
  #endif
  
  	if (print_once ||
  	    crng_ready() ||
  	    (previous && (caller == READ_ONCE(*previous))))
  		return;
  	WRITE_ONCE(*previous, caller);
  #ifndef CONFIG_WARN_ALL_UNSEEDED_RANDOM
  	print_once = true;
  #endif
  	if (__ratelimit(&unseeded_warning))
  		pr_notice("random: %s called from %pS with crng_init=%d\n",
  			  func_name, caller, crng_init);
  }
  
  /*
   * This function is the exported kernel interface.  It returns some
   * number of good random numbers, suitable for key generation, seeding
   * TCP sequence numbers, etc.  It does not rely on the hardware random
   * number generator.  For random bytes direct from the hardware RNG
   * (when available), use get_random_bytes_arch(). In order to ensure
   * that the randomness provided by this function is okay, the function
   * wait_for_random_bytes() should be called and return 0 at least once
   * at any point prior.
   */
  static void _get_random_bytes(void *buf, int nbytes)
  {
  	__u8 tmp[CHACHA_BLOCK_SIZE] __aligned(4);
  
  	trace_get_random_bytes(nbytes, _RET_IP_);
  
  	while (nbytes >= CHACHA_BLOCK_SIZE) {
  		extract_crng(buf);
  		buf += CHACHA_BLOCK_SIZE;
  		nbytes -= CHACHA_BLOCK_SIZE;
  	}
  
  	if (nbytes > 0) {
  		extract_crng(tmp);
  		memcpy(buf, tmp, nbytes);
  		crng_backtrack_protect(tmp, nbytes);
  	} else
  		crng_backtrack_protect(tmp, CHACHA_BLOCK_SIZE);
  	memzero_explicit(tmp, sizeof(tmp));
  }
  
  void get_random_bytes(void *buf, int nbytes)
  {
  	static void *previous;
  
  	warn_unseeded_randomness(&previous);
  	_get_random_bytes(buf, nbytes);
  }
  EXPORT_SYMBOL(get_random_bytes);
  
  
  /*
   * Each time the timer fires, we expect that we got an unpredictable
   * jump in the cycle counter. Even if the timer is running on another
   * CPU, the timer activity will be touching the stack of the CPU that is
   * generating entropy..
   *
   * Note that we don't re-arm the timer in the timer itself - we are
   * happy to be scheduled away, since that just makes the load more
   * complex, but we do not want the timer to keep ticking unless the
   * entropy loop is running.
   *
   * So the re-arming always happens in the entropy loop itself.
   */
  static void entropy_timer(struct timer_list *t)
  {
  	credit_entropy_bits(&input_pool, 1);
  }
  
  /*
   * If we have an actual cycle counter, see if we can
   * generate enough entropy with timing noise
   */
  static void try_to_generate_entropy(void)
  {
  	struct {
  		unsigned long now;
  		struct timer_list timer;
  	} stack;
  
  	stack.now = random_get_entropy();
  
  	/* Slow counter - or none. Don't even bother */
  	if (stack.now == random_get_entropy())
  		return;
  
  	timer_setup_on_stack(&stack.timer, entropy_timer, 0);
  	while (!crng_ready()) {
  		if (!timer_pending(&stack.timer))
  			mod_timer(&stack.timer, jiffies+1);
  		mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
  		schedule();
  		stack.now = random_get_entropy();
  	}
  
  	del_timer_sync(&stack.timer);
  	destroy_timer_on_stack(&stack.timer);
  	mix_pool_bytes(&input_pool, &stack.now, sizeof(stack.now));
  }
  
  /*
   * Wait for the urandom pool to be seeded and thus guaranteed to supply
   * cryptographically secure random numbers. This applies to: the /dev/urandom
   * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
   * family of functions. Using any of these functions without first calling
   * this function forfeits the guarantee of security.
   *
   * Returns: 0 if the urandom pool has been seeded.
   *          -ERESTARTSYS if the function was interrupted by a signal.
   */
  int wait_for_random_bytes(void)
  {
  	if (likely(crng_ready()))
  		return 0;
  
  	do {
  		int ret;
  		ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
  		if (ret)
  			return ret > 0 ? 0 : ret;
  
  		try_to_generate_entropy();
  	} while (!crng_ready());
  
  	return 0;
  }
  EXPORT_SYMBOL(wait_for_random_bytes);
  
  /*
   * Returns whether or not the urandom pool has been seeded and thus guaranteed
   * to supply cryptographically secure random numbers. This applies to: the
   * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
   * ,u64,int,long} family of functions.
   *
   * Returns: true if the urandom pool has been seeded.
   *          false if the urandom pool has not been seeded.
   */
  bool rng_is_initialized(void)
  {
  	return crng_ready();
  }
  EXPORT_SYMBOL(rng_is_initialized);
  
  /*
   * Add a callback function that will be invoked when the nonblocking
   * pool is initialised.
   *
   * returns: 0 if callback is successfully added
   *	    -EALREADY if pool is already initialised (callback not called)
   *	    -ENOENT if module for callback is not alive
   */
  int add_random_ready_callback(struct random_ready_callback *rdy)
  {
  	struct module *owner;
  	unsigned long flags;
  	int err = -EALREADY;
  
  	if (crng_ready())
  		return err;
  
  	owner = rdy->owner;
  	if (!try_module_get(owner))
  		return -ENOENT;
  
  	spin_lock_irqsave(&random_ready_list_lock, flags);
  	if (crng_ready())
  		goto out;
  
  	owner = NULL;
  
  	list_add(&rdy->list, &random_ready_list);
  	err = 0;
  
  out:
  	spin_unlock_irqrestore(&random_ready_list_lock, flags);
  
  	module_put(owner);
  
  	return err;
  }
  EXPORT_SYMBOL(add_random_ready_callback);
  
  /*
   * Delete a previously registered readiness callback function.
   */
  void del_random_ready_callback(struct random_ready_callback *rdy)
  {
  	unsigned long flags;
  	struct module *owner = NULL;
  
  	spin_lock_irqsave(&random_ready_list_lock, flags);
  	if (!list_empty(&rdy->list)) {
  		list_del_init(&rdy->list);
  		owner = rdy->owner;
  	}
  	spin_unlock_irqrestore(&random_ready_list_lock, flags);
  
  	module_put(owner);
  }
  EXPORT_SYMBOL(del_random_ready_callback);
  
  /*
   * This function will use the architecture-specific hardware random
   * number generator if it is available.  The arch-specific hw RNG will
   * almost certainly be faster than what we can do in software, but it
   * is impossible to verify that it is implemented securely (as
   * opposed, to, say, the AES encryption of a sequence number using a
   * key known by the NSA).  So it's useful if we need the speed, but
   * only if we're willing to trust the hardware manufacturer not to
   * have put in a back door.
   *
   * Return number of bytes filled in.
   */
  int __must_check get_random_bytes_arch(void *buf, int nbytes)
  {
  	int left = nbytes;
  	char *p = buf;
  
  	trace_get_random_bytes_arch(left, _RET_IP_);
  	while (left) {
  		unsigned long v;
  		int chunk = min_t(int, left, sizeof(unsigned long));
  
  		if (!arch_get_random_long(&v))
  			break;
  
  		memcpy(p, &v, chunk);
  		p += chunk;
  		left -= chunk;
  	}
  
  	return nbytes - left;
  }
  EXPORT_SYMBOL(get_random_bytes_arch);
  
  /*
   * init_std_data - initialize pool with system data
   *
   * @r: pool to initialize
   *
   * This function clears the pool's entropy count and mixes some system
   * data into the pool to prepare it for use. The pool is not cleared
   * as that can only decrease the entropy in the pool.
   */
  static void __init init_std_data(struct entropy_store *r)
  {
  	int i;
  	ktime_t now = ktime_get_real();
  	unsigned long rv;
  
  	r->last_pulled = jiffies;
  	mix_pool_bytes(r, &now, sizeof(now));
  	for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
  		if (!arch_get_random_seed_long(&rv) &&
  		    !arch_get_random_long(&rv))
  			rv = random_get_entropy();
  		mix_pool_bytes(r, &rv, sizeof(rv));
  	}
  	mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
  }
  
  /*
   * Note that setup_arch() may call add_device_randomness()
   * long before we get here. This allows seeding of the pools
   * with some platform dependent data very early in the boot
   * process. But it limits our options here. We must use
   * statically allocated structures that already have all
   * initializations complete at compile time. We should also
   * take care not to overwrite the precious per platform data
   * we were given.
   */
  int __init rand_initialize(void)
  {
  	init_std_data(&input_pool);
  	init_std_data(&blocking_pool);
  	crng_initialize(&primary_crng);
  	crng_global_init_time = jiffies;
  	if (ratelimit_disable) {
  		urandom_warning.interval = 0;
  		unseeded_warning.interval = 0;
  	}
  	return 0;
  }
  
  #ifdef CONFIG_BLOCK
  void rand_initialize_disk(struct gendisk *disk)
  {
  	struct timer_rand_state *state;
  
  	/*
  	 * If kzalloc returns null, we just won't use that entropy
  	 * source.
  	 */
  	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
  	if (state) {
  		state->last_time = INITIAL_JIFFIES;
  		disk->random = state;
  	}
  }
  #endif
  
  static ssize_t
  _random_read(int nonblock, char __user *buf, size_t nbytes)
  {
  	ssize_t n;
  
  	if (nbytes == 0)
  		return 0;
  
  	nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
  	while (1) {
  		n = extract_entropy_user(&blocking_pool, buf, nbytes);
  		if (n < 0)
  			return n;
  		trace_random_read(n*8, (nbytes-n)*8,
  				  ENTROPY_BITS(&blocking_pool),
  				  ENTROPY_BITS(&input_pool));
  		if (n > 0)
  			return n;
  
  		/* Pool is (near) empty.  Maybe wait and retry. */
  		if (nonblock)
  			return -EAGAIN;
  
  		wait_event_interruptible(random_read_wait,
  		    blocking_pool.initialized &&
  		    (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits));
  		if (signal_pending(current))
  			return -ERESTARTSYS;
  	}
  }
  
  static ssize_t
  random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
  {
  	return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
  }
  
  static ssize_t
  urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
  {
  	unsigned long flags;
  	static int maxwarn = 10;
  	int ret;
  
  	if (!crng_ready() && maxwarn > 0) {
  		maxwarn--;
  		if (__ratelimit(&urandom_warning))
  			printk(KERN_NOTICE "random: %s: uninitialized "
  			       "urandom read (%zd bytes read)\n",
  			       current->comm, nbytes);
  		spin_lock_irqsave(&primary_crng.lock, flags);
  		crng_init_cnt = 0;
  		spin_unlock_irqrestore(&primary_crng.lock, flags);
  	}
  	nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
  	ret = extract_crng_user(buf, nbytes);
  	trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
  	return ret;
  }
  
  static __poll_t
  random_poll(struct file *file, poll_table * wait)
  {
  	__poll_t mask;
  
  	poll_wait(file, &random_read_wait, wait);
  	poll_wait(file, &random_write_wait, wait);
  	mask = 0;
  	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
  		mask |= EPOLLIN | EPOLLRDNORM;
  	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
  		mask |= EPOLLOUT | EPOLLWRNORM;
  	return mask;
  }
  
  static int
  write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
  {
  	size_t bytes;
  	__u32 t, buf[16];
  	const char __user *p = buffer;
  
  	while (count > 0) {
  		int b, i = 0;
  
  		bytes = min(count, sizeof(buf));
  		if (copy_from_user(&buf, p, bytes))
  			return -EFAULT;
  
  		for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
  			if (!arch_get_random_int(&t))
  				break;
  			buf[i] ^= t;
  		}
  
  		count -= bytes;
  		p += bytes;
  
  		mix_pool_bytes(r, buf, bytes);
  		cond_resched();
  	}
  
  	return 0;
  }
  
  static ssize_t random_write(struct file *file, const char __user *buffer,
  			    size_t count, loff_t *ppos)
  {
  	size_t ret;
  
  	ret = write_pool(&input_pool, buffer, count);
  	if (ret)
  		return ret;
  
  	return (ssize_t)count;
  }
  
  static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
  {
  	int size, ent_count;
  	int __user *p = (int __user *)arg;
  	int retval;
  
  	switch (cmd) {
  	case RNDGETENTCNT:
  		/* inherently racy, no point locking */
  		ent_count = ENTROPY_BITS(&input_pool);
  		if (put_user(ent_count, p))
  			return -EFAULT;
  		return 0;
  	case RNDADDTOENTCNT:
  		if (!capable(CAP_SYS_ADMIN))
  			return -EPERM;
  		if (get_user(ent_count, p))
  			return -EFAULT;
  		return credit_entropy_bits_safe(&input_pool, ent_count);
  	case RNDADDENTROPY:
  		if (!capable(CAP_SYS_ADMIN))
  			return -EPERM;
  		if (get_user(ent_count, p++))
  			return -EFAULT;
  		if (ent_count < 0)
  			return -EINVAL;
  		if (get_user(size, p++))
  			return -EFAULT;
  		retval = write_pool(&input_pool, (const char __user *)p,
  				    size);
  		if (retval < 0)
  			return retval;
  		return credit_entropy_bits_safe(&input_pool, ent_count);
  	case RNDZAPENTCNT:
  	case RNDCLEARPOOL:
  		/*
  		 * Clear the entropy pool counters. We no longer clear
  		 * the entropy pool, as that's silly.
  		 */
  		if (!capable(CAP_SYS_ADMIN))
  			return -EPERM;
  		input_pool.entropy_count = 0;
  		blocking_pool.entropy_count = 0;
  		return 0;
  	case RNDRESEEDCRNG:
  		if (!capable(CAP_SYS_ADMIN))
  			return -EPERM;
  		if (crng_init < 2)
  			return -ENODATA;
  		crng_reseed(&primary_crng, NULL);
  		crng_global_init_time = jiffies - 1;
  		return 0;
  	default:
  		return -EINVAL;
  	}
  }
  
  static int random_fasync(int fd, struct file *filp, int on)
  {
  	return fasync_helper(fd, filp, on, &fasync);
  }
  
  const struct file_operations random_fops = {
  	.read  = random_read,
  	.write = random_write,
  	.poll  = random_poll,
  	.unlocked_ioctl = random_ioctl,
  	.compat_ioctl = compat_ptr_ioctl,
  	.fasync = random_fasync,
  	.llseek = noop_llseek,
  };
  
  const struct file_operations urandom_fops = {
  	.read  = urandom_read,
  	.write = random_write,
  	.unlocked_ioctl = random_ioctl,
  	.compat_ioctl = compat_ptr_ioctl,
  	.fasync = random_fasync,
  	.llseek = noop_llseek,
  };
  
  SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
  		unsigned int, flags)
  {
  	int ret;
  
  	if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
  		return -EINVAL;
  
  	if (count > INT_MAX)
  		count = INT_MAX;
  
  	if (flags & GRND_RANDOM)
  		return _random_read(flags & GRND_NONBLOCK, buf, count);
  
  	if (!crng_ready()) {
  		if (flags & GRND_NONBLOCK)
  			return -EAGAIN;
  		ret = wait_for_random_bytes();
  		if (unlikely(ret))
  			return ret;
  	}
  	return urandom_read(NULL, buf, count, NULL);
  }
  
  /********************************************************************
   *
   * Sysctl interface
   *
   ********************************************************************/
  
  #ifdef CONFIG_SYSCTL
  
  #include <linux/sysctl.h>
  
  static int min_read_thresh = 8, min_write_thresh;
  static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
  static int max_write_thresh = INPUT_POOL_WORDS * 32;
  static int random_min_urandom_seed = 60;
  static char sysctl_bootid[16];
  
  /*
   * This function is used to return both the bootid UUID, and random
   * UUID.  The difference is in whether table->data is NULL; if it is,
   * then a new UUID is generated and returned to the user.
   *
   * If the user accesses this via the proc interface, the UUID will be
   * returned as an ASCII string in the standard UUID format; if via the
   * sysctl system call, as 16 bytes of binary data.
   */
  static int proc_do_uuid(struct ctl_table *table, int write,
  			void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	struct ctl_table fake_table;
  	unsigned char buf[64], tmp_uuid[16], *uuid;
  
  	uuid = table->data;
  	if (!uuid) {
  		uuid = tmp_uuid;
  		generate_random_uuid(uuid);
  	} else {
  		static DEFINE_SPINLOCK(bootid_spinlock);
  
  		spin_lock(&bootid_spinlock);
  		if (!uuid[8])
  			generate_random_uuid(uuid);
  		spin_unlock(&bootid_spinlock);
  	}
  
  	sprintf(buf, "%pU", uuid);
  
  	fake_table.data = buf;
  	fake_table.maxlen = sizeof(buf);
  
  	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
  }
  
  /*
   * Return entropy available scaled to integral bits
   */
  static int proc_do_entropy(struct ctl_table *table, int write,
  			   void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	struct ctl_table fake_table;
  	int entropy_count;
  
  	entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
  
  	fake_table.data = &entropy_count;
  	fake_table.maxlen = sizeof(entropy_count);
  
  	return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
  }
  
  static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
  extern struct ctl_table random_table[];
  struct ctl_table random_table[] = {
  	{
  		.procname	= "poolsize",
  		.data		= &sysctl_poolsize,
  		.maxlen		= sizeof(int),
  		.mode		= 0444,
  		.proc_handler	= proc_dointvec,
  	},
  	{
  		.procname	= "entropy_avail",
  		.maxlen		= sizeof(int),
  		.mode		= 0444,
  		.proc_handler	= proc_do_entropy,
  		.data		= &input_pool.entropy_count,
  	},
  	{
  		.procname	= "read_wakeup_threshold",
  		.data		= &random_read_wakeup_bits,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &min_read_thresh,
  		.extra2		= &max_read_thresh,
  	},
  	{
  		.procname	= "write_wakeup_threshold",
  		.data		= &random_write_wakeup_bits,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &min_write_thresh,
  		.extra2		= &max_write_thresh,
  	},
  	{
  		.procname	= "urandom_min_reseed_secs",
  		.data		= &random_min_urandom_seed,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec,
  	},
  	{
  		.procname	= "boot_id",
  		.data		= &sysctl_bootid,
  		.maxlen		= 16,
  		.mode		= 0444,
  		.proc_handler	= proc_do_uuid,
  	},
  	{
  		.procname	= "uuid",
  		.maxlen		= 16,
  		.mode		= 0444,
  		.proc_handler	= proc_do_uuid,
  	},
  #ifdef ADD_INTERRUPT_BENCH
  	{
  		.procname	= "add_interrupt_avg_cycles",
  		.data		= &avg_cycles,
  		.maxlen		= sizeof(avg_cycles),
  		.mode		= 0444,
  		.proc_handler	= proc_doulongvec_minmax,
  	},
  	{
  		.procname	= "add_interrupt_avg_deviation",
  		.data		= &avg_deviation,
  		.maxlen		= sizeof(avg_deviation),
  		.mode		= 0444,
  		.proc_handler	= proc_doulongvec_minmax,
  	},
  #endif
  	{ }
  };
  #endif 	/* CONFIG_SYSCTL */
  
  struct batched_entropy {
  	union {
  		u64 entropy_u64[CHACHA_BLOCK_SIZE / sizeof(u64)];
  		u32 entropy_u32[CHACHA_BLOCK_SIZE / sizeof(u32)];
  	};
  	unsigned int position;
  	spinlock_t batch_lock;
  };
  
  /*
   * Get a random word for internal kernel use only. The quality of the random
   * number is either as good as RDRAND or as good as /dev/urandom, with the
   * goal of being quite fast and not depleting entropy. In order to ensure
   * that the randomness provided by this function is okay, the function
   * wait_for_random_bytes() should be called and return 0 at least once
   * at any point prior.
   */
  static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
  	.batch_lock	= __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock),
  };
  
  u64 get_random_u64(void)
  {
  	u64 ret;
  	unsigned long flags;
  	struct batched_entropy *batch;
  	static void *previous;
  
  #if BITS_PER_LONG == 64
  	if (arch_get_random_long((unsigned long *)&ret))
  		return ret;
  #else
  	if (arch_get_random_long((unsigned long *)&ret) &&
  	    arch_get_random_long((unsigned long *)&ret + 1))
  	    return ret;
  #endif
  
  	warn_unseeded_randomness(&previous);
  
  	batch = raw_cpu_ptr(&batched_entropy_u64);
  	spin_lock_irqsave(&batch->batch_lock, flags);
  	if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
  		extract_crng((u8 *)batch->entropy_u64);
  		batch->position = 0;
  	}
  	ret = batch->entropy_u64[batch->position++];
  	spin_unlock_irqrestore(&batch->batch_lock, flags);
  	return ret;
  }
  EXPORT_SYMBOL(get_random_u64);
  
  static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = {
  	.batch_lock	= __SPIN_LOCK_UNLOCKED(batched_entropy_u32.lock),
  };
  u32 get_random_u32(void)
  {
  	u32 ret;
  	unsigned long flags;
  	struct batched_entropy *batch;
  	static void *previous;
  
  	if (arch_get_random_int(&ret))
  		return ret;
  
  	warn_unseeded_randomness(&previous);
  
  	batch = raw_cpu_ptr(&batched_entropy_u32);
  	spin_lock_irqsave(&batch->batch_lock, flags);
  	if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
  		extract_crng((u8 *)batch->entropy_u32);
  		batch->position = 0;
  	}
  	ret = batch->entropy_u32[batch->position++];
  	spin_unlock_irqrestore(&batch->batch_lock, flags);
  	return ret;
  }
  EXPORT_SYMBOL(get_random_u32);
  
  /* It's important to invalidate all potential batched entropy that might
   * be stored before the crng is initialized, which we can do lazily by
   * simply resetting the counter to zero so that it's re-extracted on the
   * next usage. */
  static void invalidate_batched_entropy(void)
  {
  	int cpu;
  	unsigned long flags;
  
  	for_each_possible_cpu (cpu) {
  		struct batched_entropy *batched_entropy;
  
  		batched_entropy = per_cpu_ptr(&batched_entropy_u32, cpu);
  		spin_lock_irqsave(&batched_entropy->batch_lock, flags);
  		batched_entropy->position = 0;
  		spin_unlock(&batched_entropy->batch_lock);
  
  		batched_entropy = per_cpu_ptr(&batched_entropy_u64, cpu);
  		spin_lock(&batched_entropy->batch_lock);
  		batched_entropy->position = 0;
  		spin_unlock_irqrestore(&batched_entropy->batch_lock, flags);
  	}
  }
  
  /**
   * randomize_page - Generate a random, page aligned address
   * @start:	The smallest acceptable address the caller will take.
   * @range:	The size of the area, starting at @start, within which the
   *		random address must fall.
   *
   * If @start + @range would overflow, @range is capped.
   *
   * NOTE: Historical use of randomize_range, which this replaces, presumed that
   * @start was already page aligned.  We now align it regardless.
   *
   * Return: A page aligned address within [start, start + range).  On error,
   * @start is returned.
   */
  unsigned long
  randomize_page(unsigned long start, unsigned long range)
  {
  	if (!PAGE_ALIGNED(start)) {
  		range -= PAGE_ALIGN(start) - start;
  		start = PAGE_ALIGN(start);
  	}
  
  	if (start > ULONG_MAX - range)
  		range = ULONG_MAX - start;
  
  	range >>= PAGE_SHIFT;
  
  	if (range == 0)
  		return start;
  
  	return start + (get_random_long() % range << PAGE_SHIFT);
  }
  
  /* Interface for in-kernel drivers of true hardware RNGs.
   * Those devices may produce endless random bits and will be throttled
   * when our pool is full.
   */
  void add_hwgenerator_randomness(const char *buffer, size_t count,
  				size_t entropy)
  {
  	struct entropy_store *poolp = &input_pool;
  
  	if (unlikely(crng_init == 0)) {
  		crng_fast_load(buffer, count);
  		return;
  	}
  
  	/* Suspend writing if we're above the trickle threshold.
  	 * We'll be woken up again once below random_write_wakeup_thresh,
  	 * or when the calling thread is about to terminate.
  	 */
  	wait_event_interruptible(random_write_wait, kthread_should_stop() ||
  			ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
  	mix_pool_bytes(poolp, buffer, count);
  	credit_entropy_bits(poolp, entropy);
  }
  EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
  
  /* Handle random seed passed by bootloader.
   * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
   * it would be regarded as device data.
   * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
   */
  void add_bootloader_randomness(const void *buf, unsigned int size)
  {
  	if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
  		add_hwgenerator_randomness(buf, size, size * 8);
  	else
  		add_device_randomness(buf, size);
  }
  EXPORT_SYMBOL_GPL(add_bootloader_randomness);
  