1.\" $OpenBSD: mem.4,v 1.2 2007/05/31 19:19:55 jmc Exp $ 2.\" 3.\" Copyright (c) 1991 The Regents of the University of California. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" from: @(#)mem.4 5.3 (Berkeley) 5/2/91 31.\" 32.Dd $Mdocdate: May 31 2007 $ 33.Dt MEM 4 landisk 34.Os 35.Sh NAME 36.Nm mem , 37.Nm kmem 38.Nd memory files 39.Sh DESCRIPTION 40The special file 41.Pa /dev/mem 42is an interface to the physical memory of the computer. 43Byte offsets in this file are interpreted as physical memory addresses. 44Reading and writing this file is equivalent to reading and writing 45memory itself. 46Only offsets within the bounds of 47.Pa /dev/mem 48are allowed. 49.Pp 50Kernel virtual memory is accessed through the interface 51.Pa /dev/kmem 52in the same manner as 53.Pa /dev/mem . 54Only kernel virtual addresses that are currently mapped to memory are allowed. 55.Pp 56On landisk, physical memory is contiguous. 57The kernel virtual memory begins at address 58.Li 0xc0000000 . 59.Pp 60Writeability of these devices is controlled by the system 61.Xr securelevel 7 . 62.Sh FILES 63.Bl -tag -width Pa -compact 64.It Pa /dev/mem 65.It Pa /dev/kmem 66.El 67.Sh SEE ALSO 68.Xr securelevel 7 69.Sh HISTORY 70The 71.Pa /dev/mem 72and 73.Pa /dev/kmem 74files appeared in 75.At v6 . 76