/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright 2020 Conrad Meyer <cem@FreeBSD.org>. 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, this list of conditions and the following disclaimer.
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS 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 ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/pcpu.h>
#include <sys/prng.h>
#include <sys/smp.h>
#include <sys/systm.h>
#if !PCG_HAS_128BIT_OPS
/* On 32-bit platforms, gang together two 32-bit generators. */
typedef struct {
pcg32u_random_t states[2];
} pcg64u_random_t;
static inline void
pcg64u_srandom_r(pcg64u_random_t *state64, uint64_t seed)
{
pcg32u_srandom_r(&state64->states[0], seed);
pcg32u_srandom_r(&state64->states[1], seed);
}
static inline uint64_t
pcg64u_random_r(pcg64u_random_t *state64)
{
return ((((uint64_t)pcg32u_random_r(&state64->states[0])) << 32) |
pcg32u_random_r(&state64->states[1]));
}
static inline uint64_t
pcg64u_boundedrand_r(pcg64u_random_t *state64, uint64_t bound)
{
uint64_t threshold = -bound % bound;
for (;;) {
uint64_t r = pcg64u_random_r(state64);
if (r >= threshold)
return (r % bound);
}
}
#endif
DPCPU_DEFINE_STATIC(pcg32u_random_t, pcpu_prng32_state);
DPCPU_DEFINE_STATIC(pcg64u_random_t, pcpu_prng64_state);
static void
prng_init(void *dummy __unused)
{
pcg32u_random_t *state;
pcg64u_random_t *state64;
int i;
CPU_FOREACH(i) {
state = DPCPU_ID_PTR(i, pcpu_prng32_state);
pcg32u_srandom_r(state, 1);
state64 = DPCPU_ID_PTR(i, pcpu_prng64_state);
pcg64u_srandom_r(state64, 1);
}
}
SYSINIT(prng_init, SI_SUB_CPU, SI_ORDER_ANY, prng_init, NULL);
uint32_t
prng32(void)
{
uint32_t r;
critical_enter();
r = pcg32u_random_r(DPCPU_PTR(pcpu_prng32_state));
critical_exit();
return (r);
}
uint32_t
prng32_bounded(uint32_t bound)
{
uint32_t r;
critical_enter();
r = pcg32u_boundedrand_r(DPCPU_PTR(pcpu_prng32_state), bound);
critical_exit();
return (r);
}
uint64_t
prng64(void)
{
uint64_t r;
critical_enter();
r = pcg64u_random_r(DPCPU_PTR(pcpu_prng64_state));
critical_exit();
return (r);
}
uint64_t
prng64_bounded(uint64_t bound)
{
uint64_t r;
critical_enter();
r = pcg64u_boundedrand_r(DPCPU_PTR(pcpu_prng64_state), bound);
critical_exit();
return (r);
}
