1.\" $NetBSD: mem.4,v 1.2 2017/02/17 22:24:46 christos Exp $ 2.\" 3.\" $OpenBSD: mem.4,v 1.1 2004/03/17 00:42:43 miod Exp $ 4.\" 5.\" Copyright (c) 2004, Miodrag Vallat. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 18.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 19.\" DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 20.\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 21.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 22.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 24.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 25.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26.\" POSSIBILITY OF SUCH DAMAGE. 27.\" 28.Dd February 17, 2017 29.Dt MEM 4 hppa 30.Os 31.Sh NAME 32.Nm mem , 33.Nm kmem 34.Nd memory files and memory controller 35.Sh SYNOPSIS 36.Cd "mem* at mainbus0" 37.Sh DESCRIPTION 38The 39.Nm 40driver controls and restricts access to the systems memory 41by the hardware buses and the processor. 42.Pp 43It also provides an interface to userland through the special files 44.Pa /dev/mem 45and 46.Pa /dev/kmem . 47Physical memory is accessed through 48.Pa /dev/mem , 49while kernel virtual memory is accessed through 50.Pa /dev/kmem . 51Access to kernel virtual addresses not currently mapped to memory will fail. 52On hppa, the physical memory range is always contiguous and starts at 53address 0; kernel virtual memory begins at address 0 as well. 54.Pp 55The writeability of the 56.Pa /dev/mem 57and 58.Pa /dev/kmem 59special files are controlled by the system securelevel in addition to the 60filesystem permissions. 61.Sh FILES 62.Bl -tag -width /dev/kmem -compact 63.It Pa /dev/mem 64.It Pa /dev/kmem 65.El 66.Sh HISTORY 67The 68.Nm 69driver originates from 70.Ox . 71It was ported to 72.Nx 1.6 73by Matthew Fredette. 74.Sh BUGS 75On some systems featuring a 76.Dq Viper 77memory controller, 78.Nx 79may not configure bus arbitration correctly, causing the boot process 80to freeze during either 81.Nm 82or 83.Xr hppa/cpu 4 84device probe. 85