1.\" Copyright (c) 1992, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This software was developed by the Computer Systems Engineering group 5.\" at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 6.\" contributed to Berkeley. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)mem.4 8.1 (Berkeley) 6/5/93 33.\" $OpenBSD: mem.4,v 1.7 2018/01/12 04:36:44 deraadt Exp $ 34.\" $NetBSD: mem.4,v 1.1 1997/06/08 17:40:57 ender Exp $ 35.\" 36.Dd $Mdocdate: January 12 2018 $ 37.Dt MEM 4 macppc 38.Os 39.Sh NAME 40.Nm mem , 41.Nm kmem 42.Nd memory files 43.Sh DESCRIPTION 44The file 45.Pa /dev/mem 46is an interface to the physical memory of the computer. 47Byte offsets in this file are interpreted as physical memory addresses. 48Reading and writing this file is equivalent to reading and writing 49memory itself. 50An error will be returned if an attempt is made to reference 51an offset outside of 52.Pa /dev/mem . 53.Pp 54Kernel virtual memory is accessed via the file 55.Pa /dev/kmem 56in the same manner as 57.Pa /dev/mem . 58Only kernel virtual addresses that are currently mapped to memory are allowed. 59.Pp 60On the Macintosh, physical memory may be discontiguous; 61kernel virtual memory begins at 62.Ad 0x00000000 . 63.Pp 64Even with sufficient file system permissions, 65these devices can only be opened when the 66.Xr securelevel 7 67is insecure or when the 68.Va kern.allowkmem 69.Xr sysctl 2 70variable is set. 71.Sh FILES 72.Bl -tag -width /dev/kmem -compact 73.It /dev/mem 74.It /dev/kmem 75.El 76.Sh SEE ALSO 77.Xr securelevel 7 78.Sh HISTORY 79The 80.Pa /dev/mem 81and 82.Pa /dev/kmem 83files appeared in 84.At v6 . 85