1.\" $OpenBSD: mem.4,v 1.6 2001/06/23 07:04:14 pjanzen 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)mem.4 5.3 (Berkeley) 5/2/91 35.\" 36.Dd May 2, 1991 37.Dt MEM 4 i386 38.Os 39.Sh NAME 40.Nm mem , 41.Nm kmem 42.Nd memory files 43.Sh DESCRIPTION 44The special 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. 50Only offsets within the bounds of 51.Pa /dev/mem 52are allowed. 53.Pp 54Kernel virtual memory is accessed through the interface 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 ISA the I/O memory space begins at physical address 61.Li 0x000a0000 62and runs to 63.Li 0x00100000. 64The per-process data size for the current process is 65.Dv UPAGES 66long, and ends at virtual address 67.Li 0xfe000000 . 68.Pp 69Writeability of these devices is controlled by the system 70.Xr securelevel 7 . 71.Sh FILES 72.Bl -tag -width Pa -compact 73.It Pa /dev/mem 74.It Pa /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