diff options
Diffstat (limited to 'sys/kern/subr_prng.c')
| -rw-r--r-- | sys/kern/subr_prng.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/sys/kern/subr_prng.c b/sys/kern/subr_prng.c new file mode 100644 index 000000000000..124a56e0e4ea --- /dev/null +++ b/sys/kern/subr_prng.c @@ -0,0 +1,131 @@ +/*- + * 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); +} |