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.Dd August 5, 2020 26.Dt PRNG 9 27.Os 28.Sh NAME 29.Nm prng 30.Nd "Kernel pseudo-random number generators" 31.Sh SYNOPSIS 32.In sys/prng.h 33.Ft uint32_t 34.Fn prng32 void 35.Ft uint32_t 36.Fn prng32_bounded "uint32_t bound" 37.Ft uint64_t 38.Fn prng64 void 39.Ft uint64_t 40.Fn prng64_bounded "uint64_t bound" 41.Sh DESCRIPTION 42.Ss GENERIC PRNG ROUTINES 43.Nm 44is a family of fast, 45.Em non-cryptographic 46pseudo-random number generators. 47Unlike 48.Xr random 9 , 49.Fn prng32 , 50.Fn prng32_bounded , 51.Fn prng64 , 52and 53.Fn prng64_bounded 54avoid shared global state, removing unnecessary contention on SMP 55systems. 56The routines are not explicitly tied to any specific implementation, and 57may produce different specific sequences on different hosts, reboots, or 58versions of 59.Fx . 60Different CPUs in SMP systems are guaranteed to produce different sequences of 61integers. 62.Pp 63For 64.Em cryptographically secure 65random numbers generated by the 66.Xr random 4 67kernel cryptographically secure random number generator subsystem, see 68.Xr arc4random 9 . 69.Bl -tag -width indent 70.It Fn prng32 71Generate a 32-bit integer uniformly distributed in [0, 2^32-1]. 72.It Fn prng32_bounded bound 73Generate an integer uniformly in the range [0, bound-1]. 74.It Fn prng64 75Generate a 64-bit integer uniformly distributed in [0, 2^64-1]. 76.It Fn prng64_bounded bound 77Generate an integer uniformly in the range [0, bound-1]. 78.El 79.Pp 80These routines are not reentrant; they are not safe to use in interrupt 81handlers ("interrupt filters" in 82.Xr bus_setup_intr 9 83terminology). 84They are safe to use in all other kernel contexts, including interrupt threads 85("ithreads"). 86.Ss REPRODUCIBLE PRNG APIS 87In addition to these per-CPU helpers, the 88.In sys/prng.h 89header also exposes the entire API of the PCG family of PRNGs as inline 90functions. 91The PCG-C API is described in full at 92.Lk https://www.pcg-random.org/using-pcg-c.html . 93.Sh HISTORY 94.Nm 95was introduced in 96.Fx 13 . 97