original, as distributed

1 files changed, 1515 insertions, 0 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
new file mode 100644
index 0000000..0d91fe5
--- /dev/null
+++ b/drivers/char/random.c
@@ -0,0 +1,1515 @@
+/*
+ * random.c -- A strong random number generator
+ *
+ * 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 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:
+ *
+ *	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/spinlock.h>
+#include <linux/percpu.h>
+#include <linux/cryptohash.h>
+#include <linux/fips.h>
+#include <linux/ptrace.h>
+#include <linux/kmemcheck.h>
+
+#ifdef CONFIG_GENERIC_HARDIRQS
+# include <linux/irq.h>
+#endif
+
+#include <asm/processor.h>
+#include <asm/uaccess.h>
+#include <asm/irq.h>
+#include <asm/irq_regs.h>
+#include <asm/io.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/random.h>
+
+/*
+ * Configuration information
+ */
+#define INPUT_POOL_WORDS 128
+#define OUTPUT_POOL_WORDS 32
+#define SEC_XFER_SIZE 512
+#define EXTRACT_SIZE 10
+
+#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
+
+/*
+ * 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_thresh = 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_thresh = 128;
+
+/*
+ * When the input pool goes over trickle_thresh, start dropping most
+ * samples to avoid wasting CPU time and reduce lock contention.
+ */
+
+static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
+
+static DEFINE_PER_CPU(int, trickle_count);
+
+/*
+ * A pool of size .poolwords is stirred with a primitive polynomial
+ * of degree .poolwords over GF(2).  The taps for various sizes are
+ * defined below.  They are chosen to be evenly spaced (minimum RMS
+ * distance from evenly spaced; the numbers in the comments are a
+ * scaled squared error sum) except for the last tap, which is 1 to
+ * get the twisting happening as fast as possible.
+ */
+static struct poolinfo {
+	int poolwords;
+	int tap1, tap2, tap3, tap4, tap5;
+} poolinfo_table[] = {
+	/* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
+	{ 128,	103,	76,	51,	25,	1 },
+	/* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
+	{ 32,	26,	20,	14,	7,	1 },
+#if 0
+	/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
+	{ 2048,	1638,	1231,	819,	411,	1 },
+
+	/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
+	{ 1024,	817,	615,	412,	204,	1 },
+
+	/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
+	{ 1024,	819,	616,	410,	207,	2 },
+
+	/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
+	{ 512,	411,	308,	208,	104,	1 },
+
+	/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
+	{ 512,	409,	307,	206,	102,	2 },
+	/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
+	{ 512,	409,	309,	205,	103,	2 },
+
+	/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
+	{ 256,	205,	155,	101,	52,	1 },
+
+	/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
+	{ 128,	103,	78,	51,	27,	2 },
+
+	/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
+	{ 64,	52,	39,	26,	14,	1 },
+#endif
+};
+
+#define POOLBITS	poolwords*32
+#define POOLBYTES	poolwords*4
+
+/*
+ * For the purposes of better mixing, we use the CRC-32 polynomial as
+ * well to make a twisted Generalized Feedback Shift Reigster
+ *
+ * (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 Mdeling and Computer Simulation 4:254-266)
+ *
+ * Thanks to Colin Plumb for suggesting this.
+ *
+ * We have not analyzed the resultant polynomial to prove it primitive;
+ * in fact it almost certainly isn't.  Nonetheless, the irreducible factors
+ * of a random large-degree polynomial over GF(2) are more than large enough
+ * that periodicity is not a concern.
+ *
+ * The input hash is much less sensitive than the output hash.  All
+ * that we want of it 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).
+ *
+ * The chosen system lets the state of the pool be (essentially) the input
+ * modulo the generator polymnomial.  Now, for random primitive polynomials,
+ * this is a universal class of hash functions, meaning that the chance
+ * of a collision is limited by the attacker's knowledge of the generator
+ * polynomail, so if it is chosen at random, an attacker can never force
+ * a collision.  Here, we use a fixed polynomial, but we *can* assume that
+ * ###--> it is unknown to the processes generating the input entropy. <-###
+ * Because of this important property, this is a good, collision-resistant
+ * hash; hash collisions will occur no more often than chance.
+ */
+
+/*
+ * 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 bool debug;
+module_param(debug, bool, 0644);
+#define DEBUG_ENT(fmt, arg...) do { \
+	if (debug) \
+		printk(KERN_DEBUG "random %04d %04d %04d: " \
+		fmt,\
+		input_pool.entropy_count,\
+		blocking_pool.entropy_count,\
+		nonblocking_pool.entropy_count,\
+		## arg); } while (0)
+
+/**********************************************************************
+ *
+ * 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: */
+	struct poolinfo *poolinfo;
+	__u32 *pool;
+	const char *name;
+	struct entropy_store *pull;
+	int limit;
+
+	/* read-write data: */
+	spinlock_t lock;
+	unsigned add_ptr;
+	unsigned input_rotate;
+	int entropy_count;
+	int entropy_total;
+	unsigned int initialized:1;
+	bool last_data_init;
+	__u8 last_data[EXTRACT_SIZE];
+};
+
+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,
+	.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
+	.pool = input_pool_data
+};
+
+static struct entropy_store blocking_pool = {
+	.poolinfo = &poolinfo_table[1],
+	.name = "blocking",
+	.limit = 1,
+	.pull = &input_pool,
+	.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
+	.pool = blocking_pool_data
+};
+
+static struct entropy_store nonblocking_pool = {
+	.poolinfo = &poolinfo_table[1],
+	.name = "nonblocking",
+	.pull = &input_pool,
+	.lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
+	.pool = nonblocking_pool_data
+};
+
+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, __u8 out[64])
+{
+	unsigned long i, j, 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;
+
+	smp_rmb();
+	input_rotate = ACCESS_ONCE(r->input_rotate);
+	i = ACCESS_ONCE(r->add_ptr);
+
+	/* mix one byte at a time to simplify size handling and churn faster */
+	while (nbytes--) {
+		w = rol32(*bytes++, input_rotate & 31);
+		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 += i ? 7 : 14;
+	}
+
+	ACCESS_ONCE(r->input_rotate) = input_rotate;
+	ACCESS_ONCE(r->add_ptr) = i;
+	smp_wmb();
+
+	if (out)
+		for (j = 0; j < 16; j++)
+			((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
+}
+
+static void __mix_pool_bytes(struct entropy_store *r, const void *in,
+			     int nbytes, __u8 out[64])
+{
+	trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
+	_mix_pool_bytes(r, in, nbytes, out);
+}
+
+static void mix_pool_bytes(struct entropy_store *r, const void *in,
+			   int nbytes, __u8 out[64])
+{
+	unsigned long flags;
+
+	trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
+	spin_lock_irqsave(&r->lock, flags);
+	_mix_pool_bytes(r, in, nbytes, out);
+	spin_unlock_irqrestore(&r->lock, flags);
+}
+
+struct fast_pool {
+	__u32		pool[4];
+	unsigned long	last;
+	unsigned short	count;
+	unsigned char	rotate;
+	unsigned char	last_timer_intr;
+};
+
+/*
+ * 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, const void *in, int nbytes)
+{
+	const char	*bytes = in;
+	__u32		w;
+	unsigned	i = f->count;
+	unsigned	input_rotate = f->rotate;
+
+	while (nbytes--) {
+		w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
+			f->pool[(i + 1) & 3];
+		f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
+		input_rotate += (i++ & 3) ? 7 : 14;
+	}
+	f->count = i;
+	f->rotate = input_rotate;
+}
+
+/*
+ * Credit (or debit) the entropy store with n bits of entropy
+ */
+static void credit_entropy_bits(struct entropy_store *r, int nbits)
+{
+	int entropy_count, orig;
+
+	if (!nbits)
+		return;
+
+	DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
+retry:
+	entropy_count = orig = ACCESS_ONCE(r->entropy_count);
+	entropy_count += nbits;
+
+	if (entropy_count < 0) {
+		DEBUG_ENT("negative entropy/overflow\n");
+		entropy_count = 0;
+	} else if (entropy_count > r->poolinfo->POOLBITS)
+		entropy_count = r->poolinfo->POOLBITS;
+	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+		goto retry;
+
+	if (!r->initialized && nbits > 0) {
+		r->entropy_total += nbits;
+		if (r->entropy_total > 128)
+			r->initialized = 1;
+	}
+
+	trace_credit_entropy_bits(r->name, nbits, entropy_count,
+				  r->entropy_total, _RET_IP_);
+
+	/* should we wake readers? */
+	if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
+		wake_up_interruptible(&random_read_wait);
+		kill_fasync(&fasync, SIGIO, POLL_IN);
+	}
+}
+
+/*********************************************************************
+ *
+ * Entropy input management
+ *
+ *********************************************************************/
+
+/* There is one of these per entropy source */
+struct timer_rand_state {
+	cycles_t last_time;
+	long last_delta, last_delta2;
+	unsigned dont_count_entropy:1;
+};
+
+/*
+ * 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)
+{
+	unsigned long time = get_cycles() ^ jiffies;
+
+	mix_pool_bytes(&input_pool, buf, size, NULL);
+	mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
+	mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
+	mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
+}
+EXPORT_SYMBOL(add_device_randomness);
+
+static struct timer_rand_state input_timer_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 {
+		long jiffies;
+		unsigned cycles;
+		unsigned num;
+	} sample;
+	long delta, delta2, delta3;
+
+	preempt_disable();
+	/* if over the trickle threshold, use only 1 in 4096 samples */
+	if (input_pool.entropy_count > trickle_thresh &&
+	    ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
+		goto out;
+
+	sample.jiffies = jiffies;
+	sample.cycles = get_cycles();
+	sample.num = num;
+	mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
+
+	/*
+	 * 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.
+		 */
+		credit_entropy_bits(&input_pool,
+				    min_t(int, fls(delta>>1), 11));
+	}
+out:
+	preempt_enable();
+}
+
+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;
+
+	DEBUG_ENT("input event\n");
+	last_value = value;
+	add_timer_randomness(&input_timer_state,
+			     (type << 4) ^ code ^ (code >> 4) ^ value);
+}
+EXPORT_SYMBOL_GPL(add_input_randomness);
+
+static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
+
+void add_interrupt_randomness(int irq, int irq_flags)
+{
+	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;
+	__u32			input[4], cycles = get_cycles();
+
+	input[0] = cycles ^ jiffies;
+	input[1] = irq;
+	if (regs) {
+		__u64 ip = instruction_pointer(regs);
+		input[2] = ip;
+		input[3] = ip >> 32;
+	}
+
+	fast_mix(fast_pool, input, sizeof(input));
+
+	if ((fast_pool->count & 1023) &&
+	    !time_after(now, fast_pool->last + HZ))
+		return;
+
+	fast_pool->last = now;
+
+	r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
+	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
+	/*
+	 * If we don't have a valid cycle counter, and we see
+	 * back-to-back timer interrupts, then skip giving credit for
+	 * any entropy.
+	 */
+	if (cycles == 0) {
+		if (irq_flags & __IRQF_TIMER) {
+			if (fast_pool->last_timer_intr)
+				return;
+			fast_pool->last_timer_intr = 1;
+		} else
+			fast_pool->last_timer_intr = 0;
+	}
+	credit_entropy_bits(r, 1);
+}
+
+#ifdef CONFIG_BLOCK
+void add_disk_randomness(struct gendisk *disk)
+{
+	if (!disk || !disk->random)
+		return;
+	/* first major is 1, so we get >= 0x200 here */
+	DEBUG_ENT("disk event %d:%d\n",
+		  MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
+
+	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
+}
+#endif
+
+/*********************************************************************
+ *
+ * Entropy extraction routines
+ *
+ *********************************************************************/
+
+static ssize_t extract_entropy(struct entropy_store *r, void *buf,
+			       size_t nbytes, int min, int rsvd);
+
+/*
+ * 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)
+{
+	__u32	tmp[OUTPUT_POOL_WORDS];
+
+	if (r->pull && r->entropy_count < nbytes * 8 &&
+	    r->entropy_count < r->poolinfo->POOLBITS) {
+		/* If we're limited, always leave two wakeup worth's BITS */
+		int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
+		int bytes = nbytes;
+
+		/* pull at least as many as BYTES as wakeup BITS */
+		bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
+		/* but never more than the buffer size */
+		bytes = min_t(int, bytes, sizeof(tmp));
+
+		DEBUG_ENT("going to reseed %s with %d bits "
+			  "(%zu of %d requested)\n",
+			  r->name, bytes * 8, nbytes * 8, r->entropy_count);
+
+		bytes = extract_entropy(r->pull, tmp, bytes,
+					random_read_wakeup_thresh / 8, rsvd);
+		mix_pool_bytes(r, tmp, bytes, NULL);
+		credit_entropy_bits(r, bytes*8);
+	}
+}
+
+/*
+ * These functions 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.
+ *
+ * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
+ */
+
+static size_t account(struct entropy_store *r, size_t nbytes, int min,
+		      int reserved)
+{
+	unsigned long flags;
+	int wakeup_write = 0;
+
+	/* Hold lock while accounting */
+	spin_lock_irqsave(&r->lock, flags);
+
+	BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
+	DEBUG_ENT("trying to extract %zu bits from %s\n",
+		  nbytes * 8, r->name);
+
+	/* Can we pull enough? */
+	if (r->entropy_count / 8 < min + reserved) {
+		nbytes = 0;
+	} else {
+		int entropy_count, orig;
+retry:
+		entropy_count = orig = ACCESS_ONCE(r->entropy_count);
+		/* If limited, never pull more than available */
+		if (r->limit && nbytes + reserved >= entropy_count / 8)
+			nbytes = entropy_count/8 - reserved;
+
+		if (entropy_count / 8 >= nbytes + reserved) {
+			entropy_count -= nbytes*8;
+			if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+				goto retry;
+		} else {
+			entropy_count = reserved;
+			if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+				goto retry;
+		}
+
+		if (entropy_count < random_write_wakeup_thresh)
+			wakeup_write = 1;
+	}
+
+	DEBUG_ENT("debiting %zu entropy credits from %s%s\n",
+		  nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
+
+	spin_unlock_irqrestore(&r->lock, flags);
+
+	if (wakeup_write) {
+		wake_up_interruptible(&random_write_wait);
+		kill_fasync(&fasync, SIGIO, POLL_OUT);
+	}
+
+	return nbytes;
+}
+
+static void extract_buf(struct entropy_store *r, __u8 *out)
+{
+	int i;
+	union {
+		__u32 w[5];
+		unsigned long l[LONGS(EXTRACT_SIZE)];
+	} hash;
+	__u32 workspace[SHA_WORKSPACE_WORDS];
+	__u8 extract[64];
+	unsigned long flags;
+
+	/* Generate a hash across the pool, 16 words (512 bits) at a time */
+	sha_init(hash.w);
+	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), extract);
+	spin_unlock_irqrestore(&r->lock, flags);
+
+	/*
+	 * To avoid duplicates, we atomically extract a portion of the
+	 * pool while mixing, and hash one final time.
+	 */
+	sha_transform(hash.w, extract, workspace);
+	memset(extract, 0, sizeof(extract));
+	memset(workspace, 0, 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);
+
+	/*
+	 * If we have a architectural hardware random number
+	 * generator, mix that in, too.
+	 */
+	for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
+		unsigned long v;
+		if (!arch_get_random_long(&v))
+			break;
+		hash.l[i] ^= v;
+	}
+
+	memcpy(out, &hash, EXTRACT_SIZE);
+	memset(&hash, 0, sizeof(hash));
+}
+
+static ssize_t extract_entropy(struct entropy_store *r, void *buf,
+				 size_t nbytes, int min, int reserved)
+{
+	ssize_t ret = 0, i;
+	__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 = true;
+			spin_unlock_irqrestore(&r->lock, flags);
+			trace_extract_entropy(r->name, EXTRACT_SIZE,
+					      r->entropy_count, _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, r->entropy_count, _RET_IP_);
+	xfer_secondary_pool(r, nbytes);
+	nbytes = account(r, nbytes, min, reserved);
+
+	while (nbytes) {
+		extract_buf(r, tmp);
+
+		if (fips_enabled) {
+			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 */
+	memset(tmp, 0, sizeof(tmp));
+
+	return ret;
+}
+
+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];
+
+	trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
+	xfer_secondary_pool(r, nbytes);
+	nbytes = account(r, nbytes, 0, 0);
+
+	while (nbytes) {
+		if (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 */
+	memset(tmp, 0, sizeof(tmp));
+
+	return ret;
+}
+
+/*
+ * 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 use the hw random number
+ * generator, if available; use get_random_bytes_arch() for that.
+ */
+void get_random_bytes(void *buf, int nbytes)
+{
+	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)
+{
+	char *p = buf;
+
+	trace_get_random_bytes(nbytes, _RET_IP_);
+	while (nbytes) {
+		unsigned long v;
+		int chunk = min(nbytes, (int)sizeof(unsigned long));
+
+		if (!arch_get_random_long(&v))
+			break;
+		
+		memcpy(p, &v, chunk);
+		p += chunk;
+		nbytes -= chunk;
+	}
+
+	if (nbytes)
+		extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
+}
+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_std_data(struct entropy_store *r)
+{
+	int i;
+	ktime_t now = ktime_get_real();
+	unsigned long rv;
+
+	r->entropy_count = 0;
+	r->entropy_total = 0;
+	r->last_data_init = false;
+	mix_pool_bytes(r, &now, sizeof(now), NULL);
+	for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
+		if (!arch_get_random_long(&rv))
+			break;
+		mix_pool_bytes(r, &rv, sizeof(rv), NULL);
+	}
+	mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
+}
+
+/*
+ * 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.
+ */
+static int rand_initialize(void)
+{
+	init_std_data(&input_pool);
+	init_std_data(&blocking_pool);
+	init_std_data(&nonblocking_pool);
+	return 0;
+}
+module_init(rand_initialize);
+
+#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)
+		disk->random = state;
+}
+#endif
+
+static ssize_t
+random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+	ssize_t n, retval = 0, count = 0;
+
+	if (nbytes == 0)
+		return 0;
+
+	while (nbytes > 0) {
+		n = nbytes;
+		if (n > SEC_XFER_SIZE)
+			n = SEC_XFER_SIZE;
+
+		DEBUG_ENT("reading %zu bits\n", n*8);
+
+		n = extract_entropy_user(&blocking_pool, buf, n);
+
+		if (n < 0) {
+			retval = n;
+			break;
+		}
+
+		DEBUG_ENT("read got %zd bits (%zd still needed)\n",
+			  n*8, (nbytes-n)*8);
+
+		if (n == 0) {
+			if (file->f_flags & O_NONBLOCK) {
+				retval = -EAGAIN;
+				break;
+			}
+
+			DEBUG_ENT("sleeping?\n");
+
+			wait_event_interruptible(random_read_wait,
+				input_pool.entropy_count >=
+						 random_read_wakeup_thresh);
+
+			DEBUG_ENT("awake\n");
+
+			if (signal_pending(current)) {
+				retval = -ERESTARTSYS;
+				break;
+			}
+
+			continue;
+		}
+
+		count += n;
+		buf += n;
+		nbytes -= n;
+		break;		/* This break makes the device work */
+				/* like a named pipe */
+	}
+
+	return (count ? count : retval);
+}
+
+static ssize_t
+urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+	return extract_entropy_user(&nonblocking_pool, buf, nbytes);
+}
+
+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;
+	if (input_pool.entropy_count >= random_read_wakeup_thresh)
+		mask |= POLLIN | POLLRDNORM;
+	if (input_pool.entropy_count < random_write_wakeup_thresh)
+		mask |= POLLOUT | POLLWRNORM;
+	return mask;
+}
+
+static int
+write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
+{
+	size_t bytes;
+	__u32 buf[16];
+	const char __user *p = buffer;
+
+	while (count > 0) {
+		bytes = min(count, sizeof(buf));
+		if (copy_from_user(&buf, p, bytes))
+			return -EFAULT;
+
+		count -= bytes;
+		p += bytes;
+
+		mix_pool_bytes(r, buf, bytes, NULL);
+		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(&blocking_pool, buffer, count);
+	if (ret)
+		return ret;
+	ret = write_pool(&nonblocking_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 */
+		if (put_user(input_pool.entropy_count, p))
+			return -EFAULT;
+		return 0;
+	case RNDADDTOENTCNT:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		if (get_user(ent_count, p))
+			return -EFAULT;
+		credit_entropy_bits(&input_pool, ent_count);
+		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;
+		retval = write_pool(&input_pool, (const char __user *)p,
+				    size);
+		if (retval < 0)
+			return retval;
+		credit_entropy_bits(&input_pool, ent_count);
+		return 0;
+	case RNDZAPENTCNT:
+	case RNDCLEARPOOL:
+		/* Clear the entropy pool counters. */
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		rand_initialize();
+		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,
+	.fasync = random_fasync,
+	.llseek = noop_llseek,
+};
+
+const struct file_operations urandom_fops = {
+	.read  = urandom_read,
+	.write = random_write,
+	.unlocked_ioctl = random_ioctl,
+	.fasync = random_fasync,
+	.llseek = noop_llseek,
+};
+
+/***************************************************************
+ * 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);
+	/* Set UUID version to 4 --- truly random generation */
+	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;
+static int max_read_thresh = INPUT_POOL_WORDS * 32;
+static int max_write_thresh = INPUT_POOL_WORDS * 32;
+static char sysctl_bootid[16];
+
+/*
+ * These functions 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, it will be returned
+ * as an ASCII string in the standard UUID format.  If accesses via the
+ * sysctl system call, it is returned 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);
+}
+
+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_dointvec,
+		.data		= &input_pool.entropy_count,
+	},
+	{
+		.procname	= "read_wakeup_threshold",
+		.data		= &random_read_wakeup_thresh,
+		.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_thresh,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &min_write_thresh,
+		.extra2		= &max_write_thresh,
+	},
+	{
+		.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,
+	},
+	{ }
+};
+#endif 	/* CONFIG_SYSCTL */
+
+static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
+
+static int __init random_int_secret_init(void)
+{
+	get_random_bytes(random_int_secret, sizeof(random_int_secret));
+	return 0;
+}
+late_initcall(random_int_secret_init);
+
+/*
+ * 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
+ */
+static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
+unsigned int get_random_int(void)
+{
+	__u32 *hash;
+	unsigned int ret;
+
+	if (arch_get_random_int(&ret))
+		return ret;
+
+	hash = get_cpu_var(get_random_int_hash);
+
+	hash[0] += current->pid + jiffies + get_cycles();
+	md5_transform(hash, random_int_secret);
+	ret = hash[0];
+	put_cpu_var(get_random_int_hash);
+
+	return ret;
+}
+EXPORT_SYMBOL(get_random_int);
+
+/*
+ * 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);
+}