lib/random32.c - kernel/msm-5.4 - Gitiles

 // SPDX-License-Identifier: GPL-2.0
 /*
  * This is a maximally equidistributed combined Tausworthe generator
  * based on code from GNU Scientific Library 1.5 (30 Jun 2004)
  *
  * lfsr113 version:
  *
  * x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)
  *
  * s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n <<  6) ^ s1_n) >> 13))
  * s2_{n+1} = (((s2_n & 4294967288) <<  2) ^ (((s2_n <<  2) ^ s2_n) >> 27))
  * s3_{n+1} = (((s3_n & 4294967280) <<  7) ^ (((s3_n << 13) ^ s3_n) >> 21))
  * s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n <<  3) ^ s4_n) >> 12))
  *
  * The period of this generator is about 2^113 (see erratum paper).
  *
  * From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
  * Generators", Mathematics of Computation, 65, 213 (1996), 203--213:
  * http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
  * ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
  *
  * There is an erratum in the paper "Tables of Maximally Equidistributed
  * Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999),
  * 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
  *
  *      ... the k_j most significant bits of z_j must be non-zero,
  *      for each j. (Note: this restriction also applies to the
  *      computer code given in [4], but was mistakenly not mentioned
  *      in that paper.)
  *
  * This affects the seeding procedure by imposing the requirement
  * s1 > 1, s2 > 7, s3 > 15, s4 > 127.
  */

 #include <linux/types.h>
 #include <linux/percpu.h>
 #include <linux/export.h>
 #include <linux/jiffies.h>
 #include <linux/random.h>
 #include <linux/sched.h>
 #include <asm/unaligned.h>

 /**
  *	prandom_u32_state - seeded pseudo-random number generator.
  *	@state: pointer to state structure holding seeded state.
  *
  *	This is used for pseudo-randomness with no outside seeding.
  *	For more random results, use prandom_u32().
  */
 u32 prandom_u32_state(struct rnd_state *state)
 {
 #define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)
 	state->s1 = TAUSWORTHE(state->s1,  6U, 13U, 4294967294U, 18U);
 	state->s2 = TAUSWORTHE(state->s2,  2U, 27U, 4294967288U,  2U);
 	state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U,  7U);
 	state->s4 = TAUSWORTHE(state->s4,  3U, 12U, 4294967168U, 13U);

 	return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
 }
 EXPORT_SYMBOL(prandom_u32_state);

 /**
  *	prandom_bytes_state - get the requested number of pseudo-random bytes
  *
  *	@state: pointer to state structure holding seeded state.
  *	@buf: where to copy the pseudo-random bytes to
  *	@bytes: the requested number of bytes
  *
  *	This is used for pseudo-randomness with no outside seeding.
  *	For more random results, use prandom_bytes().
  */
 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes)
 {
 	u8 *ptr = buf;

 	while (bytes >= sizeof(u32)) {
 		put_unaligned(prandom_u32_state(state), (u32 *) ptr);
 		ptr += sizeof(u32);
 		bytes -= sizeof(u32);
 	}

 	if (bytes > 0) {
 		u32 rem = prandom_u32_state(state);
 		do {
 			*ptr++ = (u8) rem;
 			bytes--;
 			rem >>= BITS_PER_BYTE;
 		} while (bytes > 0);
 	}
 }
 EXPORT_SYMBOL(prandom_bytes_state);

 static void prandom_warmup(struct rnd_state *state)
 {
 	/* Calling RNG ten times to satisfy recurrence condition */
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 }

 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
 {
 	int i;

 	for_each_possible_cpu(i) {
 		struct rnd_state *state = per_cpu_ptr(pcpu_state, i);
 		u32 seeds[4];

 		get_random_bytes(&seeds, sizeof(seeds));
 		state->s1 = __seed(seeds[0],   2U);
 		state->s2 = __seed(seeds[1],   8U);
 		state->s3 = __seed(seeds[2],  16U);
 		state->s4 = __seed(seeds[3], 128U);

 		prandom_warmup(state);
 	}
 }
 EXPORT_SYMBOL(prandom_seed_full_state);

 #ifdef CONFIG_RANDOM32_SELFTEST
 static struct prandom_test1 {
 	u32 seed;
 	u32 result;
 } test1[] = {
 	{ 1U, 3484351685U },
 	{ 2U, 2623130059U },
 	{ 3U, 3125133893U },
 	{ 4U,  984847254U },
 };

 static struct prandom_test2 {
 	u32 seed;
 	u32 iteration;
 	u32 result;
 } test2[] = {
 	/* Test cases against taus113 from GSL library. */
 	{  931557656U, 959U, 2975593782U },
 	{ 1339693295U, 876U, 3887776532U },
 	{ 1545556285U, 961U, 1615538833U },
 	{  601730776U, 723U, 1776162651U },
 	{ 1027516047U, 687U,  511983079U },
 	{  416526298U, 700U,  916156552U },
 	{ 1395522032U, 652U, 2222063676U },
 	{  366221443U, 617U, 2992857763U },
 	{ 1539836965U, 714U, 3783265725U },
 	{  556206671U, 994U,  799626459U },
 	{  684907218U, 799U,  367789491U },
 	{ 2121230701U, 931U, 2115467001U },
 	{ 1668516451U, 644U, 3620590685U },
 	{  768046066U, 883U, 2034077390U },
 	{ 1989159136U, 833U, 1195767305U },
 	{  536585145U, 996U, 3577259204U },
 	{ 1008129373U, 642U, 1478080776U },
 	{ 1740775604U, 939U, 1264980372U },
 	{ 1967883163U, 508U,   10734624U },
 	{ 1923019697U, 730U, 3821419629U },
 	{  442079932U, 560U, 3440032343U },
 	{ 1961302714U, 845U,  841962572U },
 	{ 2030205964U, 962U, 1325144227U },
 	{ 1160407529U, 507U,  240940858U },
 	{  635482502U, 779U, 4200489746U },
 	{ 1252788931U, 699U,  867195434U },
 	{ 1961817131U, 719U,  668237657U },
 	{ 1071468216U, 983U,  917876630U },
 	{ 1281848367U, 932U, 1003100039U },
 	{  582537119U, 780U, 1127273778U },
 	{ 1973672777U, 853U, 1071368872U },
 	{ 1896756996U, 762U, 1127851055U },
 	{  847917054U, 500U, 1717499075U },
 	{ 1240520510U, 951U, 2849576657U },
 	{ 1685071682U, 567U, 1961810396U },
 	{ 1516232129U, 557U,    3173877U },
 	{ 1208118903U, 612U, 1613145022U },
 	{ 1817269927U, 693U, 4279122573U },
 	{ 1510091701U, 717U,  638191229U },
 	{  365916850U, 807U,  600424314U },
 	{  399324359U, 702U, 1803598116U },
 	{ 1318480274U, 779U, 2074237022U },
 	{  697758115U, 840U, 1483639402U },
 	{ 1696507773U, 840U,  577415447U },
 	{ 2081979121U, 981U, 3041486449U },
 	{  955646687U, 742U, 3846494357U },
 	{ 1250683506U, 749U,  836419859U },
 	{  595003102U, 534U,  366794109U },
 	{   47485338U, 558U, 3521120834U },
 	{  619433479U, 610U, 3991783875U },
 	{  704096520U, 518U, 4139493852U },
 	{ 1712224984U, 606U, 2393312003U },
 	{ 1318233152U, 922U, 3880361134U },
 	{  855572992U, 761U, 1472974787U },
 	{   64721421U, 703U,  683860550U },
 	{  678931758U, 840U,  380616043U },
 	{  692711973U, 778U, 1382361947U },
 	{  677703619U, 530U, 2826914161U },
 	{   92393223U, 586U, 1522128471U },
 	{ 1222592920U, 743U, 3466726667U },
 	{  358288986U, 695U, 1091956998U },
 	{ 1935056945U, 958U,  514864477U },
 	{  735675993U, 990U, 1294239989U },
 	{ 1560089402U, 897U, 2238551287U },
 	{   70616361U, 829U,   22483098U },
 	{  368234700U, 731U, 2913875084U },
 	{   20221190U, 879U, 1564152970U },
 	{  539444654U, 682U, 1835141259U },
 	{ 1314987297U, 840U, 1801114136U },
 	{ 2019295544U, 645U, 3286438930U },
 	{  469023838U, 716U, 1637918202U },
 	{ 1843754496U, 653U, 2562092152U },
 	{  400672036U, 809U, 4264212785U },
 	{  404722249U, 965U, 2704116999U },
 	{  600702209U, 758U,  584979986U },
 	{  519953954U, 667U, 2574436237U },
 	{ 1658071126U, 694U, 2214569490U },
 	{  420480037U, 749U, 3430010866U },
 	{  690103647U, 969U, 3700758083U },
 	{ 1029424799U, 937U, 3787746841U },
 	{ 2012608669U, 506U, 3362628973U },
 	{ 1535432887U, 998U,   42610943U },
 	{ 1330635533U, 857U, 3040806504U },
 	{ 1223800550U, 539U, 3954229517U },
 	{ 1322411537U, 680U, 3223250324U },
 	{ 1877847898U, 945U, 2915147143U },
 	{ 1646356099U, 874U,  965988280U },
 	{  805687536U, 744U, 4032277920U },
 	{ 1948093210U, 633U, 1346597684U },
 	{  392609744U, 783U, 1636083295U },
 	{  690241304U, 770U, 1201031298U },
 	{ 1360302965U, 696U, 1665394461U },
 	{ 1220090946U, 780U, 1316922812U },
 	{  447092251U, 500U, 3438743375U },
 	{ 1613868791U, 592U,  828546883U },
 	{  523430951U, 548U, 2552392304U },
 	{  726692899U, 810U, 1656872867U },
 	{ 1364340021U, 836U, 3710513486U },
 	{ 1986257729U, 931U,  935013962U },
 	{  407983964U, 921U,  728767059U },
 };

 static u32 __extract_hwseed(void)
 {
 	unsigned int val = 0;

 	(void)(arch_get_random_seed_int(&val) ||
 	       arch_get_random_int(&val));

 	return val;
 }

 static void prandom_seed_early(struct rnd_state *state, u32 seed,
 			       bool mix_with_hwseed)
 {
 #define LCG(x)	 ((x) * 69069U)	/* super-duper LCG */
 #define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0)
 	state->s1 = __seed(HWSEED() ^ LCG(seed),        2U);
 	state->s2 = __seed(HWSEED() ^ LCG(state->s1),   8U);
 	state->s3 = __seed(HWSEED() ^ LCG(state->s2),  16U);
 	state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U);
 }

 static int __init prandom_state_selftest(void)
 {
 	int i, j, errors = 0, runs = 0;
 	bool error = false;

 	for (i = 0; i < ARRAY_SIZE(test1); i++) {
 		struct rnd_state state;

 		prandom_seed_early(&state, test1[i].seed, false);
 		prandom_warmup(&state);

 		if (test1[i].result != prandom_u32_state(&state))
 			error = true;
 	}

 	if (error)
 		pr_warn("prandom: seed boundary self test failed\n");
 	else
 		pr_info("prandom: seed boundary self test passed\n");

 	for (i = 0; i < ARRAY_SIZE(test2); i++) {
 		struct rnd_state state;

 		prandom_seed_early(&state, test2[i].seed, false);
 		prandom_warmup(&state);

 		for (j = 0; j < test2[i].iteration - 1; j++)
 			prandom_u32_state(&state);

 		if (test2[i].result != prandom_u32_state(&state))
 			errors++;

 		runs++;
 		cond_resched();
 	}

 	if (errors)
 		pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
 	else
 		pr_info("prandom: %d self tests passed\n", runs);
 	return 0;
 }
 core_initcall(prandom_state_selftest);
 #endif

 /*
  * The prandom_u32() implementation is now completely separate from the
  * prandom_state() functions, which are retained (for now) for compatibility.
  *
  * Because of (ab)use in the networking code for choosing random TCP/UDP port
  * numbers, which open DoS possibilities if guessable, we want something
  * stronger than a standard PRNG.  But the performance requirements of
  * the network code do not allow robust crypto for this application.
  *
  * So this is a homebrew Junior Spaceman implementation, based on the
  * lowest-latency trustworthy crypto primitive available, SipHash.
  * (The authors of SipHash have not been consulted about this abuse of
  * their work.)
  *
  * Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to
  * one word of output.  This abbreviated version uses 2 rounds per word
  * of output.
  */

 struct siprand_state {
 	unsigned long v0;
 	unsigned long v1;
 	unsigned long v2;
 	unsigned long v3;
 };

 static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy;

 /*
  * This is the core CPRNG function.  As "pseudorandom", this is not used
  * for truly valuable things, just intended to be a PITA to guess.
  * For maximum speed, we do just two SipHash rounds per word.  This is
  * the same rate as 4 rounds per 64 bits that SipHash normally uses,
  * so hopefully it's reasonably secure.
  *
  * There are two changes from the official SipHash finalization:
  * - We omit some constants XORed with v2 in the SipHash spec as irrelevant;
  *   they are there only to make the output rounds distinct from the input
  *   rounds, and this application has no input rounds.
  * - Rather than returning v0^v1^v2^v3, return v1+v3.
  *   If you look at the SipHash round, the last operation on v3 is
  *   "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time.
  *   Likewise "v1 ^= v2".  (The rotate of v2 makes a difference, but
  *   it still cancels out half of the bits in v2 for no benefit.)
  *   Second, since the last combining operation was xor, continue the
  *   pattern of alternating xor/add for a tiny bit of extra non-linearity.
  */
 static inline u32 siprand_u32(struct siprand_state *s)
 {
 	unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3;

 	PRND_SIPROUND(v0, v1, v2, v3);
 	PRND_SIPROUND(v0, v1, v2, v3);
 	s->v0 = v0;  s->v1 = v1;  s->v2 = v2;  s->v3 = v3;
 	return v1 + v3;
 }


 /**
  *	prandom_u32 - pseudo random number generator
  *
  *	A 32 bit pseudo-random number is generated using a fast
  *	algorithm suitable for simulation. This algorithm is NOT
  *	considered safe for cryptographic use.
  */
 u32 prandom_u32(void)
 {
 	struct siprand_state *state = get_cpu_ptr(&net_rand_state);
 	u32 res = siprand_u32(state);

 	put_cpu_ptr(&net_rand_state);
 	return res;
 }
 EXPORT_SYMBOL(prandom_u32);

 /**
  *	prandom_bytes - get the requested number of pseudo-random bytes
  *	@buf: where to copy the pseudo-random bytes to
  *	@bytes: the requested number of bytes
  */
 void prandom_bytes(void *buf, size_t bytes)
 {
 	struct siprand_state *state = get_cpu_ptr(&net_rand_state);
 	u8 *ptr = buf;

 	while (bytes >= sizeof(u32)) {
 		put_unaligned(siprand_u32(state), (u32 *)ptr);
 		ptr += sizeof(u32);
 		bytes -= sizeof(u32);
 	}

 	if (bytes > 0) {
 		u32 rem = siprand_u32(state);

 		do {
 			*ptr++ = (u8)rem;
 			rem >>= BITS_PER_BYTE;
 		} while (--bytes > 0);
 	}
 	put_cpu_ptr(&net_rand_state);
 }
 EXPORT_SYMBOL(prandom_bytes);

 /**
  *	prandom_seed - add entropy to pseudo random number generator
  *	@entropy: entropy value
  *
  *	Add some additional seed material to the prandom pool.
  *	The "entropy" is actually our IP address (the only caller is
  *	the network code), not for unpredictability, but to ensure that
  *	different machines are initialized differently.
  */
 void prandom_seed(u32 entropy)
 {
 	int i;

 	add_device_randomness(&entropy, sizeof(entropy));

 	for_each_possible_cpu(i) {
 		struct siprand_state *state = per_cpu_ptr(&net_rand_state, i);
 		unsigned long v0 = state->v0, v1 = state->v1;
 		unsigned long v2 = state->v2, v3 = state->v3;

 		do {
 			v3 ^= entropy;
 			PRND_SIPROUND(v0, v1, v2, v3);
 			PRND_SIPROUND(v0, v1, v2, v3);
 			v0 ^= entropy;
 		} while (unlikely(!v0 || !v1 || !v2 || !v3));

 		WRITE_ONCE(state->v0, v0);
 		WRITE_ONCE(state->v1, v1);
 		WRITE_ONCE(state->v2, v2);
 		WRITE_ONCE(state->v3, v3);
 	}
 }
 EXPORT_SYMBOL(prandom_seed);

 /*
  *	Generate some initially weak seeding values to allow
  *	the prandom_u32() engine to be started.
  */
 static int __init prandom_init_early(void)
 {
 	int i;
 	unsigned long v0, v1, v2, v3;

 	if (!arch_get_random_long(&v0))
 		v0 = jiffies;
 	if (!arch_get_random_long(&v1))
 		v1 = random_get_entropy();
 	v2 = v0 ^ PRND_K0;
 	v3 = v1 ^ PRND_K1;

 	for_each_possible_cpu(i) {
 		struct siprand_state *state;

 		v3 ^= i;
 		PRND_SIPROUND(v0, v1, v2, v3);
 		PRND_SIPROUND(v0, v1, v2, v3);
 		v0 ^= i;

 		state = per_cpu_ptr(&net_rand_state, i);
 		state->v0 = v0;  state->v1 = v1;
 		state->v2 = v2;  state->v3 = v3;
 	}

 	return 0;
 }
 core_initcall(prandom_init_early);


 /* Stronger reseeding when available, and periodically thereafter. */
 static void prandom_reseed(struct timer_list *unused);

 static DEFINE_TIMER(seed_timer, prandom_reseed);

 static void prandom_reseed(struct timer_list *unused)
 {
 	unsigned long expires;
 	int i;

 	/*
 	 * Reinitialize each CPU's PRNG with 128 bits of key.
 	 * No locking on the CPUs, but then somewhat random results are,
 	 * well, expected.
 	 */
 	for_each_possible_cpu(i) {
 		struct siprand_state *state;
 		unsigned long v0 = get_random_long(), v2 = v0 ^ PRND_K0;
 		unsigned long v1 = get_random_long(), v3 = v1 ^ PRND_K1;
 #if BITS_PER_LONG == 32
 		int j;

 		/*
 		 * On 32-bit machines, hash in two extra words to
 		 * approximate 128-bit key length.  Not that the hash
 		 * has that much security, but this prevents a trivial
 		 * 64-bit brute force.
 		 */
 		for (j = 0; j < 2; j++) {
 			unsigned long m = get_random_long();

 			v3 ^= m;
 			PRND_SIPROUND(v0, v1, v2, v3);
 			PRND_SIPROUND(v0, v1, v2, v3);
 			v0 ^= m;
 		}
 #endif
 		/*
 		 * Probably impossible in practice, but there is a
 		 * theoretical risk that a race between this reseeding
 		 * and the target CPU writing its state back could
 		 * create the all-zero SipHash fixed point.
 		 *
 		 * To ensure that never happens, ensure the state
 		 * we write contains no zero words.
 		 */
 		state = per_cpu_ptr(&net_rand_state, i);
 		WRITE_ONCE(state->v0, v0 ? v0 : -1ul);
 		WRITE_ONCE(state->v1, v1 ? v1 : -1ul);
 		WRITE_ONCE(state->v2, v2 ? v2 : -1ul);
 		WRITE_ONCE(state->v3, v3 ? v3 : -1ul);
 	}

 	/* reseed every ~60 seconds, in [40 .. 80) interval with slack */
 	expires = round_jiffies(jiffies + 40 * HZ + prandom_u32_max(40 * HZ));
 	mod_timer(&seed_timer, expires);
 }

 /*
  * The random ready callback can be called from almost any interrupt.
  * To avoid worrying about whether it's safe to delay that interrupt
  * long enough to seed all CPUs, just schedule an immediate timer event.
  */
 static void prandom_timer_start(struct random_ready_callback *unused)
 {
 	mod_timer(&seed_timer, jiffies);
 }

 /*
  * Start periodic full reseeding as soon as strong
  * random numbers are available.
  */
 static int __init prandom_init_late(void)
 {
 	static struct random_ready_callback random_ready = {
 		.func = prandom_timer_start
 	};
 	int ret = add_random_ready_callback(&random_ready);

 	if (ret == -EALREADY) {
 		prandom_timer_start(&random_ready);
 		ret = 0;
 	}
 	return ret;
 }
 late_initcall(prandom_init_late);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* This is a maximally equidistributed combined Tausworthe generator
	* based on code from GNU Scientific Library 1.5 (30 Jun 2004)
	*
	* lfsr113 version:
	*
	* x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)
	*
	* s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13))
	* s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27))
	* s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21))
	* s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12))
	*
	* The period of this generator is about 2^113 (see erratum paper).
	*
	* From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
	* Generators", Mathematics of Computation, 65, 213 (1996), 203--213:
	* http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
	* ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
	*
	* There is an erratum in the paper "Tables of Maximally Equidistributed
	* Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999),
	* 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
	*
	* ... the k_j most significant bits of z_j must be non-zero,
	* for each j. (Note: this restriction also applies to the
	* computer code given in [4], but was mistakenly not mentioned
	* in that paper.)
	*
	* This affects the seeding procedure by imposing the requirement
	* s1 > 1, s2 > 7, s3 > 15, s4 > 127.
	*/

	#include <linux/types.h>
	#include <linux/percpu.h>
	#include <linux/export.h>
	#include <linux/jiffies.h>
	#include <linux/random.h>
	#include <linux/sched.h>
	#include <asm/unaligned.h>

	/**
	* prandom_u32_state - seeded pseudo-random number generator.
	* @state: pointer to state structure holding seeded state.
	*
	* This is used for pseudo-randomness with no outside seeding.
	* For more random results, use prandom_u32().
	*/
	u32 prandom_u32_state(struct rnd_state *state)
	{
	#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)
	state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U);
	state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U);
	state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U);
	state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U);

	return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
	}
	EXPORT_SYMBOL(prandom_u32_state);

	/**
	* prandom_bytes_state - get the requested number of pseudo-random bytes
	*
	* @state: pointer to state structure holding seeded state.
	* @buf: where to copy the pseudo-random bytes to
	* @bytes: the requested number of bytes
	*
	* This is used for pseudo-randomness with no outside seeding.
	* For more random results, use prandom_bytes().
	*/
	void prandom_bytes_state(struct rnd_state state, void buf, size_t bytes)
	{
	u8 *ptr = buf;

	while (bytes >= sizeof(u32)) {
	put_unaligned(prandom_u32_state(state), (u32 *) ptr);
	ptr += sizeof(u32);
	bytes -= sizeof(u32);
	}

	if (bytes > 0) {
	u32 rem = prandom_u32_state(state);
	do {
	*ptr++ = (u8) rem;
	bytes--;
	rem >>= BITS_PER_BYTE;
	} while (bytes > 0);
	}
	}
	EXPORT_SYMBOL(prandom_bytes_state);

	static void prandom_warmup(struct rnd_state *state)
	{
	/* Calling RNG ten times to satisfy recurrence condition */
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	prandom_u32_state(state);
	}

	void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
	{
	int i;

	for_each_possible_cpu(i) {
	struct rnd_state *state = per_cpu_ptr(pcpu_state, i);
	u32 seeds[4];

	get_random_bytes(&seeds, sizeof(seeds));
	state->s1 = __seed(seeds[0], 2U);
	state->s2 = __seed(seeds[1], 8U);
	state->s3 = __seed(seeds[2], 16U);
	state->s4 = __seed(seeds[3], 128U);

	prandom_warmup(state);
	}
	}
	EXPORT_SYMBOL(prandom_seed_full_state);

	#ifdef CONFIG_RANDOM32_SELFTEST
	static struct prandom_test1 {
	u32 seed;
	u32 result;
	} test1[] = {
	{ 1U, 3484351685U },
	{ 2U, 2623130059U },
	{ 3U, 3125133893U },
	{ 4U, 984847254U },
	};

	static struct prandom_test2 {
	u32 seed;
	u32 iteration;
	u32 result;
	} test2[] = {
	/* Test cases against taus113 from GSL library. */
	{ 931557656U, 959U, 2975593782U },
	{ 1339693295U, 876U, 3887776532U },
	{ 1545556285U, 961U, 1615538833U },
	{ 601730776U, 723U, 1776162651U },
	{ 1027516047U, 687U, 511983079U },
	{ 416526298U, 700U, 916156552U },
	{ 1395522032U, 652U, 2222063676U },
	{ 366221443U, 617U, 2992857763U },
	{ 1539836965U, 714U, 3783265725U },
	{ 556206671U, 994U, 799626459U },
	{ 684907218U, 799U, 367789491U },
	{ 2121230701U, 931U, 2115467001U },
	{ 1668516451U, 644U, 3620590685U },
	{ 768046066U, 883U, 2034077390U },
	{ 1989159136U, 833U, 1195767305U },
	{ 536585145U, 996U, 3577259204U },
	{ 1008129373U, 642U, 1478080776U },
	{ 1740775604U, 939U, 1264980372U },
	{ 1967883163U, 508U, 10734624U },
	{ 1923019697U, 730U, 3821419629U },
	{ 442079932U, 560U, 3440032343U },
	{ 1961302714U, 845U, 841962572U },
	{ 2030205964U, 962U, 1325144227U },
	{ 1160407529U, 507U, 240940858U },
	{ 635482502U, 779U, 4200489746U },
	{ 1252788931U, 699U, 867195434U },
	{ 1961817131U, 719U, 668237657U },
	{ 1071468216U, 983U, 917876630U },
	{ 1281848367U, 932U, 1003100039U },
	{ 582537119U, 780U, 1127273778U },
	{ 1973672777U, 853U, 1071368872U },
	{ 1896756996U, 762U, 1127851055U },
	{ 847917054U, 500U, 1717499075U },
	{ 1240520510U, 951U, 2849576657U },
	{ 1685071682U, 567U, 1961810396U },
	{ 1516232129U, 557U, 3173877U },
	{ 1208118903U, 612U, 1613145022U },
	{ 1817269927U, 693U, 4279122573U },
	{ 1510091701U, 717U, 638191229U },
	{ 365916850U, 807U, 600424314U },
	{ 399324359U, 702U, 1803598116U },
	{ 1318480274U, 779U, 2074237022U },
	{ 697758115U, 840U, 1483639402U },
	{ 1696507773U, 840U, 577415447U },
	{ 2081979121U, 981U, 3041486449U },
	{ 955646687U, 742U, 3846494357U },
	{ 1250683506U, 749U, 836419859U },
	{ 595003102U, 534U, 366794109U },
	{ 47485338U, 558U, 3521120834U },
	{ 619433479U, 610U, 3991783875U },
	{ 704096520U, 518U, 4139493852U },
	{ 1712224984U, 606U, 2393312003U },
	{ 1318233152U, 922U, 3880361134U },
	{ 855572992U, 761U, 1472974787U },
	{ 64721421U, 703U, 683860550U },
	{ 678931758U, 840U, 380616043U },
	{ 692711973U, 778U, 1382361947U },
	{ 677703619U, 530U, 2826914161U },
	{ 92393223U, 586U, 1522128471U },
	{ 1222592920U, 743U, 3466726667U },
	{ 358288986U, 695U, 1091956998U },
	{ 1935056945U, 958U, 514864477U },
	{ 735675993U, 990U, 1294239989U },
	{ 1560089402U, 897U, 2238551287U },
	{ 70616361U, 829U, 22483098U },
	{ 368234700U, 731U, 2913875084U },
	{ 20221190U, 879U, 1564152970U },
	{ 539444654U, 682U, 1835141259U },
	{ 1314987297U, 840U, 1801114136U },
	{ 2019295544U, 645U, 3286438930U },
	{ 469023838U, 716U, 1637918202U },
	{ 1843754496U, 653U, 2562092152U },
	{ 400672036U, 809U, 4264212785U },
	{ 404722249U, 965U, 2704116999U },
	{ 600702209U, 758U, 584979986U },
	{ 519953954U, 667U, 2574436237U },
	{ 1658071126U, 694U, 2214569490U },
	{ 420480037U, 749U, 3430010866U },
	{ 690103647U, 969U, 3700758083U },
	{ 1029424799U, 937U, 3787746841U },
	{ 2012608669U, 506U, 3362628973U },
	{ 1535432887U, 998U, 42610943U },
	{ 1330635533U, 857U, 3040806504U },
	{ 1223800550U, 539U, 3954229517U },
	{ 1322411537U, 680U, 3223250324U },
	{ 1877847898U, 945U, 2915147143U },
	{ 1646356099U, 874U, 965988280U },
	{ 805687536U, 744U, 4032277920U },
	{ 1948093210U, 633U, 1346597684U },
	{ 392609744U, 783U, 1636083295U },
	{ 690241304U, 770U, 1201031298U },
	{ 1360302965U, 696U, 1665394461U },
	{ 1220090946U, 780U, 1316922812U },
	{ 447092251U, 500U, 3438743375U },
	{ 1613868791U, 592U, 828546883U },
	{ 523430951U, 548U, 2552392304U },
	{ 726692899U, 810U, 1656872867U },
	{ 1364340021U, 836U, 3710513486U },
	{ 1986257729U, 931U, 935013962U },
	{ 407983964U, 921U, 728767059U },
	};

	static u32 __extract_hwseed(void)
	{
	unsigned int val = 0;

	(void)(arch_get_random_seed_int(&val) \|\|
	arch_get_random_int(&val));

	return val;
	}

	static void prandom_seed_early(struct rnd_state *state, u32 seed,
	bool mix_with_hwseed)
	{
	#define LCG(x) ((x) * 69069U) /* super-duper LCG */
	#define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0)
	state->s1 = __seed(HWSEED() ^ LCG(seed), 2U);
	state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U);
	state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U);
	state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U);
	}

	static int __init prandom_state_selftest(void)
	{
	int i, j, errors = 0, runs = 0;
	bool error = false;

	for (i = 0; i < ARRAY_SIZE(test1); i++) {
	struct rnd_state state;

	prandom_seed_early(&state, test1[i].seed, false);
	prandom_warmup(&state);

	if (test1[i].result != prandom_u32_state(&state))
	error = true;
	}

	if (error)
	pr_warn("prandom: seed boundary self test failed\n");
	else
	pr_info("prandom: seed boundary self test passed\n");

	for (i = 0; i < ARRAY_SIZE(test2); i++) {
	struct rnd_state state;

	prandom_seed_early(&state, test2[i].seed, false);
	prandom_warmup(&state);

	for (j = 0; j < test2[i].iteration - 1; j++)
	prandom_u32_state(&state);

	if (test2[i].result != prandom_u32_state(&state))
	errors++;

	runs++;
	cond_resched();
	}

	if (errors)
	pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
	else
	pr_info("prandom: %d self tests passed\n", runs);
	return 0;
	}
	core_initcall(prandom_state_selftest);
	#endif

	/*
	* The prandom_u32() implementation is now completely separate from the
	* prandom_state() functions, which are retained (for now) for compatibility.
	*
	* Because of (ab)use in the networking code for choosing random TCP/UDP port
	* numbers, which open DoS possibilities if guessable, we want something
	* stronger than a standard PRNG. But the performance requirements of
	* the network code do not allow robust crypto for this application.
	*
	* So this is a homebrew Junior Spaceman implementation, based on the
	* lowest-latency trustworthy crypto primitive available, SipHash.
	* (The authors of SipHash have not been consulted about this abuse of
	* their work.)
	*
	* Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to
	* one word of output. This abbreviated version uses 2 rounds per word
	* of output.
	*/

	struct siprand_state {
	unsigned long v0;
	unsigned long v1;
	unsigned long v2;
	unsigned long v3;
	};

	static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy;

	/*
	* This is the core CPRNG function. As "pseudorandom", this is not used
	* for truly valuable things, just intended to be a PITA to guess.
	* For maximum speed, we do just two SipHash rounds per word. This is
	* the same rate as 4 rounds per 64 bits that SipHash normally uses,
	* so hopefully it's reasonably secure.
	*
	* There are two changes from the official SipHash finalization:
	* - We omit some constants XORed with v2 in the SipHash spec as irrelevant;
	* they are there only to make the output rounds distinct from the input
	* rounds, and this application has no input rounds.
	* - Rather than returning v0^v1^v2^v3, return v1+v3.
	* If you look at the SipHash round, the last operation on v3 is
	* "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time.
	* Likewise "v1 ^= v2". (The rotate of v2 makes a difference, but
	* it still cancels out half of the bits in v2 for no benefit.)
	* Second, since the last combining operation was xor, continue the
	* pattern of alternating xor/add for a tiny bit of extra non-linearity.
	*/
	static inline u32 siprand_u32(struct siprand_state *s)
	{
	unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3;

	PRND_SIPROUND(v0, v1, v2, v3);
	PRND_SIPROUND(v0, v1, v2, v3);
	s->v0 = v0; s->v1 = v1; s->v2 = v2; s->v3 = v3;
	return v1 + v3;
	}


	/**
	* prandom_u32 - pseudo random number generator
	*
	* A 32 bit pseudo-random number is generated using a fast
	* algorithm suitable for simulation. This algorithm is NOT
	* considered safe for cryptographic use.
	*/
	u32 prandom_u32(void)
	{
	struct siprand_state *state = get_cpu_ptr(&net_rand_state);
	u32 res = siprand_u32(state);

	put_cpu_ptr(&net_rand_state);
	return res;
	}
	EXPORT_SYMBOL(prandom_u32);

	/**
	* prandom_bytes - get the requested number of pseudo-random bytes
	* @buf: where to copy the pseudo-random bytes to
	* @bytes: the requested number of bytes
	*/
	void prandom_bytes(void *buf, size_t bytes)
	{
	struct siprand_state *state = get_cpu_ptr(&net_rand_state);
	u8 *ptr = buf;

	while (bytes >= sizeof(u32)) {
	put_unaligned(siprand_u32(state), (u32 *)ptr);
	ptr += sizeof(u32);
	bytes -= sizeof(u32);
	}

	if (bytes > 0) {
	u32 rem = siprand_u32(state);

	do {
	*ptr++ = (u8)rem;
	rem >>= BITS_PER_BYTE;
	} while (--bytes > 0);
	}
	put_cpu_ptr(&net_rand_state);
	}
	EXPORT_SYMBOL(prandom_bytes);

	/**
	* prandom_seed - add entropy to pseudo random number generator
	* @entropy: entropy value
	*
	* Add some additional seed material to the prandom pool.
	* The "entropy" is actually our IP address (the only caller is
	* the network code), not for unpredictability, but to ensure that
	* different machines are initialized differently.
	*/
	void prandom_seed(u32 entropy)
	{
	int i;

	add_device_randomness(&entropy, sizeof(entropy));

	for_each_possible_cpu(i) {
	struct siprand_state *state = per_cpu_ptr(&net_rand_state, i);
	unsigned long v0 = state->v0, v1 = state->v1;
	unsigned long v2 = state->v2, v3 = state->v3;

	do {
	v3 ^= entropy;
	PRND_SIPROUND(v0, v1, v2, v3);
	PRND_SIPROUND(v0, v1, v2, v3);
	v0 ^= entropy;
	} while (unlikely(!v0 \|\| !v1 \|\| !v2 \|\| !v3));

	WRITE_ONCE(state->v0, v0);
	WRITE_ONCE(state->v1, v1);
	WRITE_ONCE(state->v2, v2);
	WRITE_ONCE(state->v3, v3);
	}
	}
	EXPORT_SYMBOL(prandom_seed);

	/*
	* Generate some initially weak seeding values to allow
	* the prandom_u32() engine to be started.
	*/
	static int __init prandom_init_early(void)
	{
	int i;
	unsigned long v0, v1, v2, v3;

	if (!arch_get_random_long(&v0))
	v0 = jiffies;
	if (!arch_get_random_long(&v1))
	v1 = random_get_entropy();
	v2 = v0 ^ PRND_K0;
	v3 = v1 ^ PRND_K1;

	for_each_possible_cpu(i) {
	struct siprand_state *state;

	v3 ^= i;
	PRND_SIPROUND(v0, v1, v2, v3);
	PRND_SIPROUND(v0, v1, v2, v3);
	v0 ^= i;

	state = per_cpu_ptr(&net_rand_state, i);
	state->v0 = v0; state->v1 = v1;
	state->v2 = v2; state->v3 = v3;
	}

	return 0;
	}
	core_initcall(prandom_init_early);


	/* Stronger reseeding when available, and periodically thereafter. */
	static void prandom_reseed(struct timer_list *unused);

	static DEFINE_TIMER(seed_timer, prandom_reseed);

	static void prandom_reseed(struct timer_list *unused)
	{
	unsigned long expires;
	int i;

	/*
	* Reinitialize each CPU's PRNG with 128 bits of key.
	* No locking on the CPUs, but then somewhat random results are,
	* well, expected.
	*/
	for_each_possible_cpu(i) {
	struct siprand_state *state;
	unsigned long v0 = get_random_long(), v2 = v0 ^ PRND_K0;
	unsigned long v1 = get_random_long(), v3 = v1 ^ PRND_K1;
	#if BITS_PER_LONG == 32
	int j;

	/*
	* On 32-bit machines, hash in two extra words to
	* approximate 128-bit key length. Not that the hash
	* has that much security, but this prevents a trivial
	* 64-bit brute force.
	*/
	for (j = 0; j < 2; j++) {
	unsigned long m = get_random_long();

	v3 ^= m;
	PRND_SIPROUND(v0, v1, v2, v3);
	PRND_SIPROUND(v0, v1, v2, v3);
	v0 ^= m;
	}
	#endif
	/*
	* Probably impossible in practice, but there is a
	* theoretical risk that a race between this reseeding
	* and the target CPU writing its state back could
	* create the all-zero SipHash fixed point.
	*
	* To ensure that never happens, ensure the state
	* we write contains no zero words.
	*/
	state = per_cpu_ptr(&net_rand_state, i);
	WRITE_ONCE(state->v0, v0 ? v0 : -1ul);
	WRITE_ONCE(state->v1, v1 ? v1 : -1ul);
	WRITE_ONCE(state->v2, v2 ? v2 : -1ul);
	WRITE_ONCE(state->v3, v3 ? v3 : -1ul);
	}

	/* reseed every ~60 seconds, in [40 .. 80) interval with slack */
	expires = round_jiffies(jiffies + 40 * HZ + prandom_u32_max(40 * HZ));
	mod_timer(&seed_timer, expires);
	}

	/*
	* The random ready callback can be called from almost any interrupt.
	* To avoid worrying about whether it's safe to delay that interrupt
	* long enough to seed all CPUs, just schedule an immediate timer event.
	*/
	static void prandom_timer_start(struct random_ready_callback *unused)
	{
	mod_timer(&seed_timer, jiffies);
	}

	/*
	* Start periodic full reseeding as soon as strong
	* random numbers are available.
	*/
	static int __init prandom_init_late(void)
	{
	static struct random_ready_callback random_ready = {
	.func = prandom_timer_start
	};
	int ret = add_random_ready_callback(&random_ready);

	if (ret == -EALREADY) {
	prandom_timer_start(&random_ready);
	ret = 0;
	}
	return ret;
	}
	late_initcall(prandom_init_late);