svn commit: r364219 - in head: share/man/man9 sys/conf sys/contrib/pcg-c/include sys/kern sys/libkern sys/sys
Conrad Meyer
cem at FreeBSD.org
Thu Aug 13 20:48:16 UTC 2020
Author: cem
Date: Thu Aug 13 20:48:14 2020
New Revision: 364219
URL: https://svnweb.freebsd.org/changeset/base/364219
Log:
Add prng(9) API
Add prng(9) as a replacement for random(9) in the kernel.
There are two major differences from random(9) and random(3):
- General prng(9) APIs (prng32(9), etc) do not guarantee an
implementation or particular sequence; they should not be used for
repeatable simulations.
- However, specific named API families are also exposed (for now: PCG),
and those are expected to be repeatable (when so-guaranteed by the named
algorithm).
Some minor differences from random(3) and earlier random(9):
- PRNG state for the general prng(9) APIs is per-CPU; this eliminates
contention on PRNG state in SMP workloads. Each PCPU generator in an
SMP system produces a unique sequence.
- Better statistical properties than the Park-Miller ("minstd") PRNG
(longer period, uniform distribution in all bits, passes
BigCrush/PractRand analysis).
- Faster than Park-Miller ("minstd") PRNG -- no division is required to
step PCG-family PRNGs.
For now, random(9) becomes a thin shim around prng32(). Eventually I
would like to mechanically switch consumers over to the explicit API.
Reviewed by: kib, markj (previous version both)
Discussed with: markm
Differential Revision: https://reviews.freebsd.org/D25916
Added:
head/share/man/man9/prng.9 (contents, props changed)
head/sys/kern/subr_prng.c (contents, props changed)
head/sys/sys/prng.h (contents, props changed)
Modified:
head/share/man/man9/Makefile
head/sys/conf/files
head/sys/contrib/pcg-c/include/pcg_variants.h
head/sys/libkern/random.c
Modified: head/share/man/man9/Makefile
==============================================================================
--- head/share/man/man9/Makefile Thu Aug 13 20:28:35 2020 (r364218)
+++ head/share/man/man9/Makefile Thu Aug 13 20:48:14 2020 (r364219)
@@ -272,6 +272,7 @@ MAN= accept_filter.9 \
printf.9 \
prison_check.9 \
priv.9 \
+ prng.9 \
proc_rwmem.9 \
pseudofs.9 \
psignal.9 \
@@ -1745,6 +1746,10 @@ MLINKS+=printf.9 log.9 \
printf.9 uprintf.9
MLINKS+=priv.9 priv_check.9 \
priv.9 priv_check_cred.9
+MLINKS+=prng.9 prng32.9 \
+ prng.9 prng32_bounded.9 \
+ prng.9 prng64.9 \
+ prng.9 prng64_bounded.9
MLINKS+=proc_rwmem.9 proc_readmem.9 \
proc_rwmem.9 proc_writemem.9
MLINKS+=psignal.9 gsignal.9 \
Added: head/share/man/man9/prng.9
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/share/man/man9/prng.9 Thu Aug 13 20:48:14 2020 (r364219)
@@ -0,0 +1,99 @@
+.\"-
+.\" Copyright 2020 Conrad Meyer <cem at 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.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd August 5, 2020
+.Dt PRNG 9
+.Os
+.Sh NAME
+.Nm prng
+.Nd "Kernel pseudo-random number generators"
+.Sh SYNOPSIS
+.In sys/prng.h
+.Ft uint32_t
+.Fn prng32 void
+.Ft uint32_t
+.Fn prng32_bounded "uint32_t bound"
+.Ft uint64_t
+.Fn prng64 void
+.Ft uint64_t
+.Fn prng64_bounded "uint64_t bound"
+.Sh DESCRIPTION
+.Ss GENERIC PRNG ROUTINES
+.Nm
+is a family of fast,
+.Em non-cryptographic
+pseudo-random number generators.
+Unlike
+.Xr random 9 ,
+.Fn prng32 ,
+.Fn prng32_bounded ,
+.Fn prng64 ,
+and
+.Fn prng64_bounded
+avoid shared global state, removing unnecessary contention on SMP
+systems.
+The routines are not explicitly tied to any specific implementation, and
+may produce different specific sequences on different hosts, reboots, or
+versions of
+.Fx .
+Different CPUs in SMP systems are guaranteed to produce different sequences of
+integers.
+.Pp
+For
+.Em cryptographically secure
+random numbers generated by the
+.Xr random 4
+kernel cryptographically secure random number generator subsystem, see
+.Xr arc4random 9 .
+.Pp
+.Bl -tag -width indent
+.It Fn prng32
+Generate a 32-bit integer uniformly distributed in [0, 2^32-1].
+.It Fn prng32_bounded bound
+Generate an integer uniformly in the range [0, bound-1].
+.It Fn prng64
+Generate a 64-bit integer uniformly distributed in [0, 2^64-1].
+.It Fn prng64_bounded bound
+Generate an integer uniformly in the range [0, bound-1].
+.El
+.Pp
+These routines are not reentrant; they are not safe to use in interrupt
+handlers ("interrupt filters" in
+.Xr bus_setup_intr 9
+terminology).
+They are safe to use in all other kernel contexts, including interrupt threads
+("ithreads").
+.Ss REPRODUCIBLE PRNG APIS
+In addition to these per-CPU helpers, the
+.In sys/prng.h
+header also exposes the entire API of the PCG family of PRNGs as inline
+functions.
+The PCG-C API is described in full at
+.Lk https://www.pcg-random.org/using-pcg-c.html .
+.Sh HISTORY
+.Nm
+was introduced in
+.Fx 13 .
Modified: head/sys/conf/files
==============================================================================
--- head/sys/conf/files Thu Aug 13 20:28:35 2020 (r364218)
+++ head/sys/conf/files Thu Aug 13 20:48:14 2020 (r364219)
@@ -3834,6 +3834,7 @@ kern/subr_pctrie.c standard
kern/subr_pidctrl.c standard
kern/subr_power.c standard
kern/subr_prf.c standard
+kern/subr_prng.c standard
kern/subr_prof.c standard
kern/subr_rangeset.c standard
kern/subr_rman.c standard
Modified: head/sys/contrib/pcg-c/include/pcg_variants.h
==============================================================================
--- head/sys/contrib/pcg-c/include/pcg_variants.h Thu Aug 13 20:28:35 2020 (r364218)
+++ head/sys/contrib/pcg-c/include/pcg_variants.h Thu Aug 13 20:48:14 2020 (r364219)
@@ -36,22 +36,16 @@
#ifndef PCG_VARIANTS_H_INCLUDED
#define PCG_VARIANTS_H_INCLUDED 1
-#include <inttypes.h>
-
-#if __SIZEOF_INT128__
+#if defined(__SIZEOF_INT128__) && __SIZEOF_INT128__
typedef __uint128_t pcg128_t;
#define PCG_128BIT_CONSTANT(high,low) \
((((pcg128_t)high) << 64) + low)
#define PCG_HAS_128BIT_OPS 1
+#else
+ #define PCG_HAS_128BIT_OPS 0
#endif
-#if __GNUC_GNU_INLINE__ && !defined(__cplusplus)
- #error Nonstandard GNU inlining semantics. Compile with -std=c99 or better.
- /* We could instead use macros PCG_INLINE and PCG_EXTERN_INLINE
- but better to just reject ancient C code. */
-#endif
-
-#if __cplusplus
+#ifdef __cplusplus
extern "C" {
#endif
@@ -65,8 +59,8 @@ inline uint8_t pcg_rotr_8(uint8_t value, unsigned int
* recognizing idiomatic rotate code, so for clang we actually provide
* assembler directives (enabled with PCG_USE_INLINE_ASM). Boo, hiss.
*/
-#if PCG_USE_INLINE_ASM && __clang__ && (__x86_64__ || __i386__)
- asm ("rorb %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
+#if PCG_USE_INLINE_ASM && defined(__clang__) && (defined(__x86_64__) || defined(__i386__))
+ __asm__ ("rorb %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
return value;
#else
return (value >> rot) | (value << ((- rot) & 7));
@@ -75,8 +69,8 @@ inline uint8_t pcg_rotr_8(uint8_t value, unsigned int
inline uint16_t pcg_rotr_16(uint16_t value, unsigned int rot)
{
-#if PCG_USE_INLINE_ASM && __clang__ && (__x86_64__ || __i386__)
- asm ("rorw %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
+#if PCG_USE_INLINE_ASM && defined(__clang__) && (defined(__x86_64__) || defined(__i386__))
+ __asm__ ("rorw %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
return value;
#else
return (value >> rot) | (value << ((- rot) & 15));
@@ -85,8 +79,8 @@ inline uint16_t pcg_rotr_16(uint16_t value, unsigned i
inline uint32_t pcg_rotr_32(uint32_t value, unsigned int rot)
{
-#if PCG_USE_INLINE_ASM && __clang__ && (__x86_64__ || __i386__)
- asm ("rorl %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
+#if PCG_USE_INLINE_ASM && defined(__clang__) && (defined(__x86_64__) || defined(__i386__))
+ __asm__ ("rorl %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
return value;
#else
return (value >> rot) | (value << ((- rot) & 31));
@@ -95,10 +89,10 @@ inline uint32_t pcg_rotr_32(uint32_t value, unsigned i
inline uint64_t pcg_rotr_64(uint64_t value, unsigned int rot)
{
-#if 0 && PCG_USE_INLINE_ASM && __clang__ && __x86_64__
+#if 0 && PCG_USE_INLINE_ASM && defined(__clang__) && (defined(__x86_64__) || defined(__i386__))
/* For whatever reason, clang actually *does* generate rotq by
itself, so we don't need this code. */
- asm ("rorq %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
+ __asm__ ("rorq %%cl, %0" : "=r" (value) : "0" (value), "c" (rot));
return value;
#else
return (value >> rot) | (value << ((- rot) & 63));
@@ -2491,18 +2485,6 @@ typedef struct pcg_state_setseq_128 pcg128i_random_t
#define pcg128i_advance_r pcg_setseq_128_advance_r
#endif
-extern uint32_t pcg32_random(void);
-extern uint32_t pcg32_boundedrand(uint32_t bound);
-extern void pcg32_srandom(uint64_t seed, uint64_t seq);
-extern void pcg32_advance(uint64_t delta);
-
-#if PCG_HAS_128BIT_OPS
-extern uint64_t pcg64_random(void);
-extern uint64_t pcg64_boundedrand(uint64_t bound);
-extern void pcg64_srandom(pcg128_t seed, pcg128_t seq);
-extern void pcg64_advance(pcg128_t delta);
-#endif
-
/*
* Static initialization constants (if you can't call srandom for some
* bizarre reason).
@@ -2536,7 +2518,7 @@ extern void pcg64_advance(pcg128_t delta);
#define PCG128I_INITIALIZER PCG_STATE_SETSEQ_128_INITIALIZER
#endif
-#if __cplusplus
+#ifdef __cplusplus
}
#endif
Added: head/sys/kern/subr_prng.c
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/sys/kern/subr_prng.c Thu Aug 13 20:48:14 2020 (r364219)
@@ -0,0 +1,131 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright 2020 Conrad Meyer <cem at 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);
+}
Modified: head/sys/libkern/random.c
==============================================================================
--- head/sys/libkern/random.c Thu Aug 13 20:28:35 2020 (r364218)
+++ head/sys/libkern/random.c Thu Aug 13 20:48:14 2020 (r364219)
@@ -36,43 +36,14 @@ __FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/libkern.h>
+#include <sys/prng.h>
#include <sys/systm.h>
-static u_long randseed = 937186357; /* after srandom(1), NSHUFF counted */
-
/*
- * Pseudo-random number generator for perturbing the profiling clock,
- * and whatever else we might use it for. The result is uniform on
- * [0, 2^31 - 1].
+ * Pseudo-random number generator. The result is uniform in [0, 2^31 - 1].
*/
u_long
random(void)
{
- static bool warned = false;
-
- long x, hi, lo, t;
-
- /* Warn only once, or it gets very spammy. */
- if (!warned) {
- gone_in(13,
- "random(9) is the obsolete Park-Miller LCG from 1988");
- warned = true;
- }
-
- /*
- * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
- * From "Random number generators: good ones are hard to find",
- * Park and Miller, Communications of the ACM, vol. 31, no. 10,
- * October 1988, p. 1195.
- */
- /* Can't be initialized with 0, so use another value. */
- if ((x = randseed) == 0)
- x = 123459876;
- hi = x / 127773;
- lo = x % 127773;
- t = 16807 * lo - 2836 * hi;
- if (t < 0)
- t += 0x7fffffff;
- randseed = t;
- return (t);
+ return (prng32());
}
Added: head/sys/sys/prng.h
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/sys/sys/prng.h Thu Aug 13 20:48:14 2020 (r364219)
@@ -0,0 +1,20 @@
+/*-
+ * This file is in the public domain.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS_PRNG_H_
+#define _SYS_PRNG_H_
+
+#define PCG_USE_INLINE_ASM 1
+#include <contrib/pcg-c/include/pcg_variants.h>
+
+#ifdef _KERNEL
+__uint32_t prng32(void);
+__uint32_t prng32_bounded(__uint32_t bound);
+__uint64_t prng64(void);
+__uint64_t prng64_bounded(__uint64_t bound);
+#endif
+
+#endif
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