random.c 53.2 KB
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/*
 * random.c -- A strong random number generator
 *
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 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
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 *
 * 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 three exported interfaces; the first is one designed to
 * be used from within the kernel:
 *
 * 	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.
 *
 * The two other 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 ---- input
 * ==============================
 *
 * The current exported interfaces for gathering environmental noise
 * from the devices are:
 *
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 *	void add_device_randomness(const void *buf, unsigned int size);
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 * 	void add_input_randomness(unsigned int type, unsigned int code,
 *                                unsigned int value);
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 *	void add_interrupt_randomness(int irq, int irq_flags);
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 * 	void add_disk_randomness(struct gendisk *disk);
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 *
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 * 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).
 *
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 * add_input_randomness() uses the input layer interrupt timing, as well as
 * the event type information from the hardware.
 *
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 * 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.
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 *
 * 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.
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 *
 * 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>
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#include <linux/mm.h>
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#include <linux/spinlock.h>
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#include <linux/kthread.h>
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#include <linux/percpu.h>
#include <linux/cryptohash.h>
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#include <linux/fips.h>
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#include <linux/ptrace.h>
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#include <linux/kmemcheck.h>
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#include <linux/workqueue.h>
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#include <linux/irq.h>
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#include <linux/syscalls.h>
#include <linux/completion.h>
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#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
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#include <asm/irq_regs.h>
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#include <asm/io.h>

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#define CREATE_TRACE_POINTS
#include <trace/events/random.h>

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/* #define ADD_INTERRUPT_BENCH */

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/*
 * Configuration information
 */
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#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
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#define DEBUG_RANDOM_BOOT 0
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#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))

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/*
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 * To allow fractional bits to be tracked, the entropy_count field is
 * denominated in units of 1/8th bits.
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 *
 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
 * credit_entropy_bits() needs to be 64 bits wide.
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 */
#define ENTROPY_SHIFT 3
#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)

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/*
 * The minimum number of bits of entropy before we wake up a read on
 * /dev/random.  Should be enough to do a significant reseed.
 */
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static int random_read_wakeup_bits = 64;
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/*
 * 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.
 */
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static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
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/*
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 * The minimum number of seconds between urandom pool reseeding.  We
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 * do this to limit the amount of entropy that can be drained from the
 * input pool even if there are heavy demands on /dev/urandom.
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 */
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static int random_min_urandom_seed = 60;
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/*
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 * 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
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 * GFSR generators II.  ACM Transactions on Modeling and Computer
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 * 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.
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 */
static struct poolinfo {
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	int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
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	int tap1, tap2, tap3, tap4, tap5;
} poolinfo_table[] = {
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	/* 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 },
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#if 0
	/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
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	{ S(2048),	1638,	1231,	819,	411,	1 },
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	/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
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	{ S(1024),	817,	615,	412,	204,	1 },
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	/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
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	{ S(1024),	819,	616,	410,	207,	2 },
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	/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
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	{ S(512),	411,	308,	208,	104,	1 },
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	/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
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	{ S(512),	409,	307,	206,	102,	2 },
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	/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
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	{ S(512),	409,	309,	205,	103,	2 },
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	/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
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	{ S(256),	205,	155,	101,	52,	1 },
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	/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
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	{ S(128),	103,	78,	51,	27,	2 },
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	/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
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	{ S(64),	52,	39,	26,	14,	1 },
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#endif
};

/*
 * Static global variables
 */
static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
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static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
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static struct fasync_struct *fasync;
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/**********************************************************************
 *
 * OS independent entropy store.   Here are the functions which handle
 * storing entropy in an entropy pool.
 *
 **********************************************************************/

struct entropy_store;
struct entropy_store {
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	/* read-only data: */
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	const struct poolinfo *poolinfo;
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	__u32 *pool;
	const char *name;
	struct entropy_store *pull;
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	struct work_struct push_work;
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	/* read-write data: */
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	unsigned long last_pulled;
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	spinlock_t lock;
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	unsigned short add_ptr;
	unsigned short input_rotate;
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	int entropy_count;
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	int entropy_total;
	unsigned int initialized:1;
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	unsigned int limit:1;
	unsigned int last_data_init:1;
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	__u8 last_data[EXTRACT_SIZE];
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};

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static void push_to_pool(struct work_struct *work);
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static __u32 input_pool_data[INPUT_POOL_WORDS];
static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];

static struct entropy_store input_pool = {
	.poolinfo = &poolinfo_table[0],
	.name = "input",
	.limit = 1,
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	.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
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	.pool = input_pool_data
};

static struct entropy_store blocking_pool = {
	.poolinfo = &poolinfo_table[1],
	.name = "blocking",
	.limit = 1,
	.pull = &input_pool,
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	.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
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	.pool = blocking_pool_data,
	.push_work = __WORK_INITIALIZER(blocking_pool.push_work,
					push_to_pool),
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};

static struct entropy_store nonblocking_pool = {
	.poolinfo = &poolinfo_table[1],
	.name = "nonblocking",
	.pull = &input_pool,
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	.lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
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	.pool = nonblocking_pool_data,
	.push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
					push_to_pool),
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};

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static __u32 const twist_table[8] = {
	0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
	0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };

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/*
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 * This function adds bytes into the entropy "pool".  It does not
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 * update the entropy estimate.  The caller should call
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 * credit_entropy_bits if this is appropriate.
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 *
 * 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.
 */
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static void _mix_pool_bytes(struct entropy_store *r, const void *in,
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			    int nbytes)
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{
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	unsigned long i, tap1, tap2, tap3, tap4, tap5;
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	int input_rotate;
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	int wordmask = r->poolinfo->poolwords - 1;
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	const char *bytes = in;
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	__u32 w;
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	tap1 = r->poolinfo->tap1;
	tap2 = r->poolinfo->tap2;
	tap3 = r->poolinfo->tap3;
	tap4 = r->poolinfo->tap4;
	tap5 = r->poolinfo->tap5;

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	input_rotate = r->input_rotate;
	i = r->add_ptr;
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	/* mix one byte at a time to simplify size handling and churn faster */
	while (nbytes--) {
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		w = rol32(*bytes++, input_rotate);
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		i = (i - 1) & wordmask;
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		/* XOR in the various taps */
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		w ^= r->pool[i];
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		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];
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		/* Mix the result back in with a twist */
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		r->pool[i] = (w >> 3) ^ twist_table[w & 7];
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		/*
		 * 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.
		 */
529
		input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
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	}

532 533
	r->input_rotate = input_rotate;
	r->add_ptr = i;
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}

536
static void __mix_pool_bytes(struct entropy_store *r, const void *in,
537
			     int nbytes)
538 539
{
	trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
540
	_mix_pool_bytes(r, in, nbytes);
541 542 543
}

static void mix_pool_bytes(struct entropy_store *r, const void *in,
544
			   int nbytes)
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545
{
546 547
	unsigned long flags;

548
	trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
549
	spin_lock_irqsave(&r->lock, flags);
550
	_mix_pool_bytes(r, in, nbytes);
551
	spin_unlock_irqrestore(&r->lock, flags);
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}

554 555 556
struct fast_pool {
	__u32		pool[4];
	unsigned long	last;
557
	unsigned short	reg_idx;
558
	unsigned char	count;
559 560 561 562 563 564 565
};

/*
 * 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.
 */
566
static void fast_mix(struct fast_pool *f)
567
{
568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588
	__u32 a = f->pool[0],	b = f->pool[1];
	__u32 c = f->pool[2],	d = f->pool[3];

	a += b;			c += d;
	b = rol32(a, 6);	d = rol32(c, 27);
	d ^= a;			b ^= c;

	a += b;			c += d;
	b = rol32(a, 16);	d = rol32(c, 14);
	d ^= a;			b ^= c;

	a += b;			c += d;
	b = rol32(a, 6);	d = rol32(c, 27);
	d ^= a;			b ^= c;

	a += b;			c += d;
	b = rol32(a, 16);	d = rol32(c, 14);
	d ^= a;			b ^= c;

	f->pool[0] = a;  f->pool[1] = b;
	f->pool[2] = c;  f->pool[3] = d;
589
	f->count++;
590 591
}

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/*
593 594 595
 * 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.
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 */
597
static void credit_entropy_bits(struct entropy_store *r, int nbits)
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{
599
	int entropy_count, orig;
600 601
	const int pool_size = r->poolinfo->poolfracbits;
	int nfrac = nbits << ENTROPY_SHIFT;
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603 604 605
	if (!nbits)
		return;

606 607
retry:
	entropy_count = orig = ACCESS_ONCE(r->entropy_count);
608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645
	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));
	}
646

647
	if (unlikely(entropy_count < 0)) {
648 649 650
		pr_warn("random: negative entropy/overflow: pool %s count %d\n",
			r->name, entropy_count);
		WARN_ON(1);
651
		entropy_count = 0;
652 653
	} else if (entropy_count > pool_size)
		entropy_count = pool_size;
654 655
	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
		goto retry;
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657
	r->entropy_total += nbits;
658 659 660 661 662
	if (!r->initialized && r->entropy_total > 128) {
		r->initialized = 1;
		r->entropy_total = 0;
		if (r == &nonblocking_pool) {
			prandom_reseed_late();
663
			wake_up_interruptible(&urandom_init_wait);
664
			pr_notice("random: %s pool is initialized\n", r->name);
665
		}
666 667
	}

668 669
	trace_credit_entropy_bits(r->name, nbits,
				  entropy_count >> ENTROPY_SHIFT,
670 671
				  r->entropy_total, _RET_IP_);

672
	if (r == &input_pool) {
673
		int entropy_bits = entropy_count >> ENTROPY_SHIFT;
674 675

		/* should we wake readers? */
676
		if (entropy_bits >= random_read_wakeup_bits) {
677 678 679 680 681 682 683 684
			wake_up_interruptible(&random_read_wait);
			kill_fasync(&fasync, SIGIO, POLL_IN);
		}
		/* If the input pool is getting full, send some
		 * entropy to the two output pools, flipping back and
		 * forth between them, until the output pools are 75%
		 * full.
		 */
685
		if (entropy_bits > random_write_wakeup_bits &&
686
		    r->initialized &&
687
		    r->entropy_total >= 2*random_read_wakeup_bits) {
688 689 690 691 692 693 694 695 696 697 698 699 700 701
			static struct entropy_store *last = &blocking_pool;
			struct entropy_store *other = &blocking_pool;

			if (last == &blocking_pool)
				other = &nonblocking_pool;
			if (other->entropy_count <=
			    3 * other->poolinfo->poolfracbits / 4)
				last = other;
			if (last->entropy_count <=
			    3 * last->poolinfo->poolfracbits / 4) {
				schedule_work(&last->push_work);
				r->entropy_total = 0;
			}
		}
702
	}
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}

705 706 707 708 709 710 711 712 713 714 715
static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
{
	const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));

	/* Cap the value to avoid overflows */
	nbits = min(nbits,  nbits_max);
	nbits = max(nbits, -nbits_max);

	credit_entropy_bits(r, nbits);
}

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/*********************************************************************
 *
 * Entropy input management
 *
 *********************************************************************/

/* There is one of these per entropy source */
struct timer_rand_state {
	cycles_t last_time;
725
	long last_delta, last_delta2;
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	unsigned dont_count_entropy:1;
};

729 730
#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };

731 732 733 734 735 736 737 738 739 740
/*
 * Add device- or boot-specific data to the input and nonblocking
 * pools to help initialize them to unique values.
 *
 * None of this adds any entropy, it is meant to avoid the
 * problem of the nonblocking pool having similar initial state
 * across largely identical devices.
 */
void add_device_randomness(const void *buf, unsigned int size)
{
741
	unsigned long time = random_get_entropy() ^ jiffies;
742
	unsigned long flags;
743

744
	trace_add_device_randomness(size, _RET_IP_);
745
	spin_lock_irqsave(&input_pool.lock, flags);
746 747
	_mix_pool_bytes(&input_pool, buf, size);
	_mix_pool_bytes(&input_pool, &time, sizeof(time));
748 749 750
	spin_unlock_irqrestore(&input_pool.lock, flags);

	spin_lock_irqsave(&nonblocking_pool.lock, flags);
751 752
	_mix_pool_bytes(&nonblocking_pool, buf, size);
	_mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
753
	spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
754 755 756
}
EXPORT_SYMBOL(add_device_randomness);

757
static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
758

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/*
 * 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)
{
771
	struct entropy_store	*r;
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772 773
	struct {
		long jiffies;
774
		unsigned cycles;
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		unsigned num;
	} sample;
	long delta, delta2, delta3;

	preempt_disable();

	sample.jiffies = jiffies;
782
	sample.cycles = random_get_entropy();
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	sample.num = num;
784
	r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
785
	mix_pool_bytes(r, &sample, sizeof(sample));
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	/*
	 * 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.
	 */

	if (!state->dont_count_entropy) {
		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.
		 */
819
		credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
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	}
	preempt_enable();
}

824
void add_input_randomness(unsigned int type, unsigned int code,
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				 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);
836
	trace_add_input_randomness(ENTROPY_BITS(&input_pool));
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837
}
838
EXPORT_SYMBOL_GPL(add_input_randomness);
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839

840 841
static DEFINE_PER_CPU(struct fast_pool, irq_randomness);

842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862
#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

863 864 865 866 867 868 869 870 871 872 873
static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
{
	__u32 *ptr = (__u32 *) regs;

	if (regs == NULL)
		return 0;
	if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
		f->reg_idx = 0;
	return *(ptr + f->reg_idx++);
}

874
void add_interrupt_randomness(int irq, int irq_flags)
L
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875
{
876 877 878 879
	struct entropy_store	*r;
	struct fast_pool	*fast_pool = &__get_cpu_var(irq_randomness);
	struct pt_regs		*regs = get_irq_regs();
	unsigned long		now = jiffies;
880
	cycles_t		cycles = random_get_entropy();
881
	__u32			c_high, j_high;
882
	__u64			ip;
883
	unsigned long		seed;
884
	int			credit = 0;
885

886 887
	if (cycles == 0)
		cycles = get_reg(fast_pool, regs);
888 889
	c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
	j_high = (sizeof(now) > 4) ? now >> 32 : 0;
890 891
	fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
	fast_pool->pool[1] ^= now ^ c_high;
892
	ip = regs ? instruction_pointer(regs) : _RET_IP_;
893
	fast_pool->pool[2] ^= ip;
894 895
	fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
		get_reg(fast_pool, regs);
896

897 898
	fast_mix(fast_pool);
	add_interrupt_bench(cycles);
899

900 901
	if ((fast_pool->count < 64) &&
	    !time_after(now, fast_pool->last + HZ))
L
Linus Torvalds 已提交
902 903
		return;

904
	r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
905
	if (!spin_trylock(&r->lock))
906
		return;
907

908
	fast_pool->last = now;
909
	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
910 911 912

	/*
	 * If we have architectural seed generator, produce a seed and
913 914 915
	 * add it to the pool.  For the sake of paranoia don't let the
	 * architectural seed generator dominate the input from the
	 * interrupt noise.
916 917
	 */
	if (arch_get_random_seed_long(&seed)) {
918
		__mix_pool_bytes(r, &seed, sizeof(seed));
919
		credit = 1;
920
	}
921
	spin_unlock(&r->lock);
922

923
	fast_pool->count = 0;
924

925 926
	/* award one bit for the contents of the fast pool */
	credit_entropy_bits(r, credit + 1);
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927 928
}

929
#ifdef CONFIG_BLOCK
L
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930 931 932 933 934
void add_disk_randomness(struct gendisk *disk)
{
	if (!disk || !disk->random)
		return;
	/* first major is 1, so we get >= 0x200 here */
935
	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
936
	trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
L
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937
}
938
EXPORT_SYMBOL_GPL(add_disk_randomness);
939
#endif
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940 941 942 943 944 945 946

/*********************************************************************
 *
 * Entropy extraction routines
 *
 *********************************************************************/

947
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
L
Linus Torvalds 已提交
948 949 950
			       size_t nbytes, int min, int rsvd);

/*
L
Lucas De Marchi 已提交
951
 * This utility inline function is responsible for transferring entropy
L
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952 953 954
 * from the primary pool to the secondary extraction pool. We make
 * sure we pull enough for a 'catastrophic reseed'.
 */
955
static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
L
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956 957
static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
958 959 960 961 962
	if (!r->pull ||
	    r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
	    r->entropy_count > r->poolinfo->poolfracbits)
		return;

963 964
	if (r->limit == 0 && random_min_urandom_seed) {
		unsigned long now = jiffies;
L
Linus Torvalds 已提交
965

966 967 968 969
		if (time_before(now,
				r->last_pulled + random_min_urandom_seed * HZ))
			return;
		r->last_pulled = now;
L
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970
	}
971 972

	_xfer_secondary_pool(r, nbytes);
973 974 975 976 977 978
}

static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
{
	__u32	tmp[OUTPUT_POOL_WORDS];

979 980
	/* For /dev/random's pool, always leave two wakeups' worth */
	int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
981 982
	int bytes = nbytes;

983 984
	/* pull at least as much as a wakeup */
	bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
985 986 987
	/* but never more than the buffer size */
	bytes = min_t(int, bytes, sizeof(tmp));

988 989
	trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
				  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
990
	bytes = extract_entropy(r->pull, tmp, bytes,
991
				random_read_wakeup_bits / 8, rsvd_bytes);
992
	mix_pool_bytes(r, tmp, bytes);
993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006
	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);
1007
	_xfer_secondary_pool(r, random_read_wakeup_bits/8);
1008 1009
	trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
			   r->pull->entropy_count >> ENTROPY_SHIFT);
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1010 1011 1012
}

/*
G
Greg Price 已提交
1013 1014
 * This function decides how many bytes to actually take from the
 * given pool, and also debits the entropy count accordingly.
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1015 1016 1017 1018
 */
static size_t account(struct entropy_store *r, size_t nbytes, int min,
		      int reserved)
{
1019
	int entropy_count, orig;
1020
	size_t ibytes, nfrac;
L
Linus Torvalds 已提交
1021

1022
	BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
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1023 1024

	/* Can we pull enough? */
1025
retry:
1026 1027
	entropy_count = orig = ACCESS_ONCE(r->entropy_count);
	ibytes = nbytes;
G
Greg Price 已提交
1028
	/* If limited, never pull more than available */
1029 1030 1031 1032 1033 1034 1035
	if (r->limit) {
		int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);

		if ((have_bytes -= reserved) < 0)
			have_bytes = 0;
		ibytes = min_t(size_t, ibytes, have_bytes);
	}
G
Greg Price 已提交
1036
	if (ibytes < min)
1037
		ibytes = 0;
1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048

	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
1049
		entropy_count = 0;
1050

G
Greg Price 已提交
1051 1052
	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
		goto retry;
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Linus Torvalds 已提交
1053

1054
	trace_debit_entropy(r->name, 8 * ibytes);
G
Greg Price 已提交
1055
	if (ibytes &&
1056
	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1057 1058 1059 1060
		wake_up_interruptible(&random_write_wait);
		kill_fasync(&fasync, SIGIO, POLL_OUT);
	}

1061
	return ibytes;
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Linus Torvalds 已提交
1062 1063
}

G
Greg Price 已提交
1064 1065 1066 1067 1068 1069
/*
 * This function does the actual extraction for extract_entropy and
 * extract_entropy_user.
 *
 * Note: we assume that .poolwords is a multiple of 16 words.
 */
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1070 1071
static void extract_buf(struct entropy_store *r, __u8 *out)
{
1072
	int i;
1073 1074
	union {
		__u32 w[5];
1075
		unsigned long l[LONGS(20)];
1076 1077
	} hash;
	__u32 workspace[SHA_WORKSPACE_WORDS];
1078
	unsigned long flags;
L
Linus Torvalds 已提交
1079

1080
	/*
1081
	 * If we have an architectural hardware random number
1082
	 * generator, use it for SHA's initial vector
1083
	 */
1084
	sha_init(hash.w);
1085 1086 1087 1088
	for (i = 0; i < LONGS(20); i++) {
		unsigned long v;
		if (!arch_get_random_long(&v))
			break;
1089
		hash.l[i] = v;
1090 1091
	}

1092 1093 1094 1095 1096
	/* 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);

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	/*
1098 1099 1100 1101 1102 1103 1104
	 * 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.
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1105
	 */
1106
	__mix_pool_bytes(r, hash.w, sizeof(hash.w));
1107
	spin_unlock_irqrestore(&r->lock, flags);
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1108

1109
	memset(workspace, 0, sizeof(workspace));
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	/*
1112 1113 1114
	 * 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.
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	 */
1116 1117 1118 1119 1120 1121
	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);
	memset(&hash, 0, sizeof(hash));
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}

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1124 1125 1126 1127 1128 1129 1130 1131 1132
/*
 * 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.
 */
1133
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1134
				 size_t nbytes, int min, int reserved)
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{
	ssize_t ret = 0, i;
	__u8 tmp[EXTRACT_SIZE];
1138
	unsigned long flags;
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1140
	/* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1141 1142 1143
	if (fips_enabled) {
		spin_lock_irqsave(&r->lock, flags);
		if (!r->last_data_init) {
1144
			r->last_data_init = 1;
1145 1146
			spin_unlock_irqrestore(&r->lock, flags);
			trace_extract_entropy(r->name, EXTRACT_SIZE,
1147
					      ENTROPY_BITS(r), _RET_IP_);
1148 1149 1150 1151 1152 1153 1154
			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);
	}
1155

1156
	trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
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	xfer_secondary_pool(r, nbytes);
	nbytes = account(r, nbytes, min, reserved);

	while (nbytes) {
		extract_buf(r, tmp);
1162

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		if (fips_enabled) {
1164 1165 1166 1167 1168 1169
			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);
		}
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		i = min_t(int, nbytes, EXTRACT_SIZE);
		memcpy(buf, tmp, i);
		nbytes -= i;
		buf += i;
		ret += i;
	}

	/* Wipe data just returned from memory */
	memset(tmp, 0, sizeof(tmp));

	return ret;
}

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/*
 * This function extracts randomness from the "entropy pool", and
 * returns it in a userspace buffer.
 */
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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];
1192
	int large_request = (nbytes > 256);
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1194
	trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
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	xfer_secondary_pool(r, nbytes);
	nbytes = account(r, nbytes, 0, 0);

	while (nbytes) {
1199
		if (large_request && need_resched()) {
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			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 */
	memset(tmp, 0, sizeof(tmp));

	return ret;
}

/*
 * This function is the exported kernel interface.  It returns some
1228
 * number of good random numbers, suitable for key generation, seeding
1229 1230 1231
 * 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().
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 */
void get_random_bytes(void *buf, int nbytes)
1234
{
1235 1236 1237 1238 1239 1240 1241
#if DEBUG_RANDOM_BOOT > 0
	if (unlikely(nonblocking_pool.initialized == 0))
		printk(KERN_NOTICE "random: %pF get_random_bytes called "
		       "with %d bits of entropy available\n",
		       (void *) _RET_IP_,
		       nonblocking_pool.entropy_total);
#endif
1242
	trace_get_random_bytes(nbytes, _RET_IP_);
1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257
	extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
}
EXPORT_SYMBOL(get_random_bytes);

/*
 * 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.
 */
void get_random_bytes_arch(void *buf, int nbytes)
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{
1259 1260
	char *p = buf;

1261
	trace_get_random_bytes_arch(nbytes, _RET_IP_);
1262 1263 1264
	while (nbytes) {
		unsigned long v;
		int chunk = min(nbytes, (int)sizeof(unsigned long));
1265

1266 1267 1268
		if (!arch_get_random_long(&v))
			break;
		
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		memcpy(p, &v, chunk);
1270 1271 1272 1273
		p += chunk;
		nbytes -= chunk;
	}

1274 1275
	if (nbytes)
		extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
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}
1277 1278
EXPORT_SYMBOL(get_random_bytes_arch);

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/*
 * 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_std_data(struct entropy_store *r)
{
1291
	int i;
1292 1293
	ktime_t now = ktime_get_real();
	unsigned long rv;
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1295
	r->last_pulled = jiffies;
1296
	mix_pool_bytes(r, &now, sizeof(now));
1297
	for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1298 1299
		if (!arch_get_random_seed_long(&rv) &&
		    !arch_get_random_long(&rv))
1300
			rv = random_get_entropy();
1301
		mix_pool_bytes(r, &rv, sizeof(rv));
1302
	}
1303
	mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
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}

1306 1307 1308 1309 1310 1311 1312 1313 1314 1315
/*
 * 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.
 */
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static int rand_initialize(void)
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{
	init_std_data(&input_pool);
	init_std_data(&blocking_pool);
	init_std_data(&nonblocking_pool);
	return 0;
}
1323
early_initcall(rand_initialize);
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1325
#ifdef CONFIG_BLOCK
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void rand_initialize_disk(struct gendisk *disk)
{
	struct timer_rand_state *state;

	/*
1331
	 * If kzalloc returns null, we just won't use that entropy
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	 * source.
	 */
1334
	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1335 1336
	if (state) {
		state->last_time = INITIAL_JIFFIES;
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		disk->random = state;
1338
	}
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}
1340
#endif
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static ssize_t
1343
_random_read(int nonblock, char __user *buf, size_t nbytes)
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{
1345
	ssize_t n;
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	if (nbytes == 0)
		return 0;

1350 1351 1352 1353 1354
	nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
	while (1) {
		n = extract_entropy_user(&blocking_pool, buf, nbytes);
		if (n < 0)
			return n;
1355 1356 1357
		trace_random_read(n*8, (nbytes-n)*8,
				  ENTROPY_BITS(&blocking_pool),
				  ENTROPY_BITS(&input_pool));
1358 1359
		if (n > 0)
			return n;
1360

1361
		/* Pool is (near) empty.  Maybe wait and retry. */
1362
		if (nonblock)
1363 1364 1365 1366
			return -EAGAIN;

		wait_event_interruptible(random_read_wait,
			ENTROPY_BITS(&input_pool) >=
1367
			random_read_wakeup_bits);
1368 1369
		if (signal_pending(current))
			return -ERESTARTSYS;
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	}
}

1373 1374 1375 1376 1377 1378
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);
}

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static ssize_t
1380
urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
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{
1382 1383 1384 1385 1386 1387 1388
	int ret;

	if (unlikely(nonblocking_pool.initialized == 0))
		printk_once(KERN_NOTICE "random: %s urandom read "
			    "with %d bits of entropy available\n",
			    current->comm, nonblocking_pool.entropy_total);

1389
	nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1390
	ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1391 1392 1393 1394

	trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
			   ENTROPY_BITS(&input_pool));
	return ret;
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}

static unsigned int
random_poll(struct file *file, poll_table * wait)
{
	unsigned int mask;

	poll_wait(file, &random_read_wait, wait);
	poll_wait(file, &random_write_wait, wait);
	mask = 0;
1405
	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
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		mask |= POLLIN | POLLRDNORM;
1407
	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
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		mask |= POLLOUT | POLLWRNORM;
	return mask;
}

1412 1413
static int
write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
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{
	size_t bytes;
	__u32 buf[16];
	const char __user *p = buffer;

1419 1420 1421 1422
	while (count > 0) {
		bytes = min(count, sizeof(buf));
		if (copy_from_user(&buf, p, bytes))
			return -EFAULT;
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1424
		count -= bytes;
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		p += bytes;

1427
		mix_pool_bytes(r, buf, bytes);
1428
		cond_resched();
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	}
1430 1431 1432 1433

	return 0;
}

1434 1435
static ssize_t random_write(struct file *file, const char __user *buffer,
			    size_t count, loff_t *ppos)
1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446
{
	size_t ret;

	ret = write_pool(&blocking_pool, buffer, count);
	if (ret)
		return ret;
	ret = write_pool(&nonblocking_pool, buffer, count);
	if (ret)
		return ret;

	return (ssize_t)count;
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}

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static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
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{
	int size, ent_count;
	int __user *p = (int __user *)arg;
	int retval;

	switch (cmd) {
	case RNDGETENTCNT:
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		/* inherently racy, no point locking */
1458 1459
		ent_count = ENTROPY_BITS(&input_pool);
		if (put_user(ent_count, p))
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			return -EFAULT;
		return 0;
	case RNDADDTOENTCNT:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		if (get_user(ent_count, p))
			return -EFAULT;
1467
		credit_entropy_bits_safe(&input_pool, ent_count);
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		return 0;
	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;
1478 1479
		retval = write_pool(&input_pool, (const char __user *)p,
				    size);
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		if (retval < 0)
			return retval;
1482
		credit_entropy_bits_safe(&input_pool, ent_count);
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		return 0;
	case RNDZAPENTCNT:
	case RNDCLEARPOOL:
1486 1487 1488 1489
		/*
		 * Clear the entropy pool counters. We no longer clear
		 * the entropy pool, as that's silly.
		 */
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		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
1492 1493 1494
		input_pool.entropy_count = 0;
		nonblocking_pool.entropy_count = 0;
		blocking_pool.entropy_count = 0;
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		return 0;
	default:
		return -EINVAL;
	}
}

1501 1502 1503 1504 1505
static int random_fasync(int fd, struct file *filp, int on)
{
	return fasync_helper(fd, filp, on, &fasync);
}

1506
const struct file_operations random_fops = {
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	.read  = random_read,
	.write = random_write,
	.poll  = random_poll,
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	.unlocked_ioctl = random_ioctl,
1511
	.fasync = random_fasync,
1512
	.llseek = noop_llseek,
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};

1515
const struct file_operations urandom_fops = {
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	.read  = urandom_read,
	.write = random_write,
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	.unlocked_ioctl = random_ioctl,
1519
	.fasync = random_fasync,
1520
	.llseek = noop_llseek,
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};

1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545
SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
		unsigned int, flags)
{
	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 (unlikely(nonblocking_pool.initialized == 0)) {
		if (flags & GRND_NONBLOCK)
			return -EAGAIN;
		wait_event_interruptible(urandom_init_wait,
					 nonblocking_pool.initialized);
		if (signal_pending(current))
			return -ERESTARTSYS;
	}
	return urandom_read(NULL, buf, count, NULL);
}

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/***************************************************************
 * Random UUID interface
 *
 * Used here for a Boot ID, but can be useful for other kernel
 * drivers.
 ***************************************************************/

/*
 * Generate random UUID
 */
void generate_random_uuid(unsigned char uuid_out[16])
{
	get_random_bytes(uuid_out, 16);
1559
	/* Set UUID version to 4 --- truly random generation */
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	uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
	/* Set the UUID variant to DCE */
	uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
}
EXPORT_SYMBOL(generate_random_uuid);

/********************************************************************
 *
 * Sysctl interface
 *
 ********************************************************************/

#ifdef CONFIG_SYSCTL

#include <linux/sysctl.h>

static int min_read_thresh = 8, min_write_thresh;
1577
static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
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static int max_write_thresh = INPUT_POOL_WORDS * 32;
static char sysctl_bootid[16];

/*
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 * This function is used to return both the bootid UUID, and random
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 * UUID.  The difference is in whether table->data is NULL; if it is,
 * then a new UUID is generated and returned to the user.
 *
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 * 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.
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 */
1590
static int proc_do_uuid(struct ctl_table *table, int write,
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			void __user *buffer, size_t *lenp, loff_t *ppos)
{
1593
	struct ctl_table fake_table;
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	unsigned char buf[64], tmp_uuid[16], *uuid;

	uuid = table->data;
	if (!uuid) {
		uuid = tmp_uuid;
		generate_random_uuid(uuid);
1600 1601 1602 1603 1604 1605 1606 1607
	} else {
		static DEFINE_SPINLOCK(bootid_spinlock);

		spin_lock(&bootid_spinlock);
		if (!uuid[8])
			generate_random_uuid(uuid);
		spin_unlock(&bootid_spinlock);
	}
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	sprintf(buf, "%pU", uuid);

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	fake_table.data = buf;
	fake_table.maxlen = sizeof(buf);

1614
	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
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}

1617 1618 1619
/*
 * Return entropy available scaled to integral bits
 */
1620
static int proc_do_entropy(struct ctl_table *table, int write,
1621 1622
			   void __user *buffer, size_t *lenp, loff_t *ppos)
{
1623
	struct ctl_table fake_table;
1624 1625 1626 1627 1628 1629 1630 1631 1632 1633
	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);
}

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static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1635 1636
extern struct ctl_table random_table[];
struct ctl_table random_table[] = {
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	{
		.procname	= "poolsize",
		.data		= &sysctl_poolsize,
		.maxlen		= sizeof(int),
		.mode		= 0444,
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		.proc_handler	= proc_dointvec,
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	},
	{
		.procname	= "entropy_avail",
		.maxlen		= sizeof(int),
		.mode		= 0444,
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		.proc_handler	= proc_do_entropy,
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		.data		= &input_pool.entropy_count,
	},
	{
		.procname	= "read_wakeup_threshold",
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		.data		= &random_read_wakeup_bits,
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		.maxlen		= sizeof(int),
		.mode		= 0644,
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		.proc_handler	= proc_dointvec_minmax,
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		.extra1		= &min_read_thresh,
		.extra2		= &max_read_thresh,
	},
	{
		.procname	= "write_wakeup_threshold",
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		.data		= &random_write_wakeup_bits,
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		.maxlen		= sizeof(int),
		.mode		= 0644,
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		.proc_handler	= proc_dointvec_minmax,
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		.extra1		= &min_write_thresh,
		.extra2		= &max_write_thresh,
	},
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	{
		.procname	= "urandom_min_reseed_secs",
		.data		= &random_min_urandom_seed,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
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	{
		.procname	= "boot_id",
		.data		= &sysctl_bootid,
		.maxlen		= 16,
		.mode		= 0444,
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		.proc_handler	= proc_do_uuid,
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	},
	{
		.procname	= "uuid",
		.maxlen		= 16,
		.mode		= 0444,
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		.proc_handler	= proc_do_uuid,
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	},
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#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
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	{ }
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};
#endif 	/* CONFIG_SYSCTL */

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static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
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int random_int_secret_init(void)
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{
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	get_random_bytes(random_int_secret, sizeof(random_int_secret));
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	return 0;
}

/*
 * Get a random word for internal kernel use only. Similar to urandom but
 * with the goal of minimal entropy pool depletion. As a result, the random
 * value is not cryptographically secure but for several uses the cost of
 * depleting entropy is too high
 */
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static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
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unsigned int get_random_int(void)
{
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	__u32 *hash;
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	unsigned int ret;
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	if (arch_get_random_int(&ret))
		return ret;

	hash = get_cpu_var(get_random_int_hash);
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	hash[0] += current->pid + jiffies + random_get_entropy();
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	md5_transform(hash, random_int_secret);
	ret = hash[0];
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	put_cpu_var(get_random_int_hash);

	return ret;
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}
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EXPORT_SYMBOL(get_random_int);
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/*
 * randomize_range() returns a start address such that
 *
 *    [...... <range> .....]
 *  start                  end
 *
 * a <range> with size "len" starting at the return value is inside in the
 * area defined by [start, end], but is otherwise randomized.
 */
unsigned long
randomize_range(unsigned long start, unsigned long end, unsigned long len)
{
	unsigned long range = end - len - start;

	if (end <= start + len)
		return 0;
	return PAGE_ALIGN(get_random_int() % range + start);
}
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/* 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;

	/* 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);