1.\"- 2.\" Copyright 2020 Conrad Meyer <cem@FreeBSD.org>. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd August 5, 2020 28.Dt PRNG 9 29.Os 30.Sh NAME 31.Nm prng 32.Nd "Kernel pseudo-random number generators" 33.Sh SYNOPSIS 34.In sys/prng.h 35.Ft uint32_t 36.Fn prng32 void 37.Ft uint32_t 38.Fn prng32_bounded "uint32_t bound" 39.Ft uint64_t 40.Fn prng64 void 41.Ft uint64_t 42.Fn prng64_bounded "uint64_t bound" 43.Sh DESCRIPTION 44.Ss GENERIC PRNG ROUTINES 45.Nm 46is a family of fast, 47.Em non-cryptographic 48pseudo-random number generators. 49Unlike 50.Xr random 9 , 51.Fn prng32 , 52.Fn prng32_bounded , 53.Fn prng64 , 54and 55.Fn prng64_bounded 56avoid shared global state, removing unnecessary contention on SMP 57systems. 58The routines are not explicitly tied to any specific implementation, and 59may produce different specific sequences on different hosts, reboots, or 60versions of 61.Fx . 62Different CPUs in SMP systems are guaranteed to produce different sequences of 63integers. 64.Pp 65For 66.Em cryptographically secure 67random numbers generated by the 68.Xr random 4 69kernel cryptographically secure random number generator subsystem, see 70.Xr arc4random 9 . 71.Bl -tag -width indent 72.It Fn prng32 73Generate a 32-bit integer uniformly distributed in [0, 2^32-1]. 74.It Fn prng32_bounded bound 75Generate an integer uniformly in the range [0, bound-1]. 76.It Fn prng64 77Generate a 64-bit integer uniformly distributed in [0, 2^64-1]. 78.It Fn prng64_bounded bound 79Generate an integer uniformly in the range [0, bound-1]. 80.El 81.Pp 82These routines are not reentrant; they are not safe to use in interrupt 83handlers ("interrupt filters" in 84.Xr bus_setup_intr 9 85terminology). 86They are safe to use in all other kernel contexts, including interrupt threads 87("ithreads"). 88.Ss REPRODUCIBLE PRNG APIS 89In addition to these per-CPU helpers, the 90.In sys/prng.h 91header also exposes the entire API of the PCG family of PRNGs as inline 92functions. 93The PCG-C API is described in full at 94.Lk https://www.pcg-random.org/using-pcg-c.html . 95.Sh HISTORY 96.Nm 97was introduced in 98.Fx 13 . 99