1.\" $NetBSD: mem.4,v 1.8 2003/08/07 10:31:13 agc Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. 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 8.1 (Berkeley) 6/5/93 31.\" 32.Dd June 5, 1993 33.Dt MEM 4 vax 34.Os 35.Sh NAME 36.Nm mem , 37.Nm kmem , 38.Nm kUmem 39.Nd memory files 40.Sh DESCRIPTION 41The special file 42.Nm /dev/mem 43is an interface to the physical memory of the computer. 44Byte offsets in this file are interpreted as physical memory addresses. 45Reading and writing this file is equivalent to reading and writing 46memory itself. 47Only offsets within the bounds of 48.Nm /dev/mem 49are allowed. 50.Pp 51Kernel virtual memory is accessed through the interface 52.Nm /dev/kmem 53in the same manner as 54.Nm /dev/mem . 55Only kernel virtual addresses that are currently mapped to memory are allowed. 56.Pp 57The file 58.Nm /dev/kUmem 59also refers to kernel virtual memory, 60but may be used to access areas mapped to 61.Tn UNIBUS 62address space 63and other 64.Tn I/O 65areas. 66It forces all accesses to use word (short integer) accesses. 67.Pp 68On the 69.Tn VAX-11/780 , 70the 71.Tn I/O 72space base address is 7320000000(16); 74on an 11/750 75the 76.Tn I/O 77space addresses are of the form fxxxxx(16). 78On all 79.Tn VAX Ns 'en 80the 81per-process data 82size 83for the current process 84is 85.Dv UPAGES 86long and ends at the virtual address 80000000(16). 87.Sh FILES 88.Bl -tag -width Pa -compact 89.It Pa /dev/mem 90.It Pa /dev/kmem 91.It Pa /dev/kUmem 92.El 93.Sh HISTORY 94The 95.Nm mem , 96.Nm kmem 97files appeared in 98.At v6 . 99The file 100.Nm kUmem 101appeared in 102.Bx 3.0 . 103