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// 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>
#ifdef CONFIG_RANDOM32_SELFTEST
static void __init prandom_state_selftest(void);
#else
static inline void prandom_state_selftest(void)
{
}
#endif
static DEFINE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;
/**
* 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_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 rnd_state *state = &get_cpu_var(net_rand_state);
u32 res;
res = prandom_u32_state(state);
put_cpu_var(net_rand_state);
return res;
}
EXPORT_SYMBOL(prandom_u32);
/**
* 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);
/**
* 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 rnd_state *state = &get_cpu_var(net_rand_state);
prandom_bytes_state(state, buf, bytes);
put_cpu_var(net_rand_state);
}
EXPORT_SYMBOL(prandom_bytes);
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);
}
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);
}
/**
* prandom_seed - add entropy to pseudo random number generator
* @seed: seed value
*
* Add some additional seeding to the prandom pool.
*/
void prandom_seed(u32 entropy)
{
int i;
/*
* No locking on the CPUs, but then somewhat random results are, well,
* expected.
*/
for_each_possible_cpu(i) {
struct rnd_state *state = &per_cpu(net_rand_state, i);
state->s1 = __seed(state->s1 ^ entropy, 2U);
prandom_warmup(state);
}
}
EXPORT_SYMBOL(prandom_seed);
/*
* Generate some initially weak seeding values to allow
* to start the prandom_u32() engine.
*/
static int __init prandom_init(void)
{
int i;
prandom_state_selftest();
for_each_possible_cpu(i) {
struct rnd_state *state = &per_cpu(net_rand_state, i);
u32 weak_seed = (i + jiffies) ^ random_get_entropy();
prandom_seed_early(state, weak_seed, true);
prandom_warmup(state);
}
return 0;
}
core_initcall(prandom_init);
static void __prandom_timer(struct timer_list *unused);
static DEFINE_TIMER(seed_timer, __prandom_timer);
static void __prandom_timer(struct timer_list *unused)
{
u32 entropy;
unsigned long expires;
get_random_bytes(&entropy, sizeof(entropy));
prandom_seed(entropy);
/* reseed every ~60 seconds, in [40 .. 80) interval with slack */
expires = 40 + prandom_u32_max(40);
seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC);
add_timer(&seed_timer);
}
static void __init __prandom_start_seed_timer(void)
{
seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC);
add_timer(&seed_timer);
}
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);
/*
* Generate better values after random number generator
* is fully initialized.
*/
static void __prandom_reseed(bool late)
{
unsigned long flags;
static bool latch = false;
static DEFINE_SPINLOCK(lock);
/* Asking for random bytes might result in bytes getting
* moved into the nonblocking pool and thus marking it
* as initialized. In this case we would double back into
* this function and attempt to do a late reseed.
* Ignore the pointless attempt to reseed again if we're
* already waiting for bytes when the nonblocking pool
* got initialized.
*/
/* only allow initial seeding (late == false) once */
if (!spin_trylock_irqsave(&lock, flags))
return;
if (latch && !late)
goto out;
latch = true;
prandom_seed_full_state(&net_rand_state);
out:
spin_unlock_irqrestore(&lock, flags);
}
void prandom_reseed_late(void)
{
__prandom_reseed(true);
}
static int __init prandom_reseed(void)
{
__prandom_reseed(false);
__prandom_start_seed_timer();
return 0;
}
late_initcall(prandom_reseed);
#ifdef CONFIG_RANDOM32_SELFTEST
static struct prandom_test1 {
u32 seed;
u32 result;
} test1[] = {
{ 1U, 3484351685U },
{ 2U, 2623130059U },
{ 3U, 3125133893U },
{ 4U, 984847254U
|