1.\" Copyright (c) 1980, 1991 Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. 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 6.3 (Berkeley) 3/27/91 33.\" $Id: mem.4,v 1.2 1993/08/01 07:36:09 mycroft Exp $ 34.\" 35.Dd March 27, 1991 36.Dt MEM 4 vax 37.Os BSD 4 38.Sh NAME 39.Nm mem , 40.Nm kmem , 41.Nm kUmem 42.Nd memory files 43.Sh DESCRIPTION 44The special file 45.Nm /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.Nm /dev/mem 52are allowed. 53.Pp 54Kernel virtual memory is accessed through the interface 55.Nm /dev/kmem 56in the same manner as 57.Nm /dev/mem . 58Only kernel virtual addresses that are currently mapped to memory are allowed. 59.Pp 60The file 61.Nm /dev/kUmem 62also refers to kernel virtual memory, 63but may be used to access areas mapped to 64.Tn UNIBUS 65address space 66and other 67.Tn I/O 68areas. 69It forces all accesses to use word (short integer) accesses. 70.Pp 71On the 72.Tn VAX 7311/780, 74the 75.Tn I/O 76space base address is 7720000000(16); 78on an 11/750 79the 80.Tn I/O space addresses are of the form fxxxxx(16). 81On all 82.Tn VAX Ns 'en 83the 84per-process data 85size 86for the current process 87is 88.Dv UPAGES 89long and ends at the virtual address 80000000(16). 90.Sh FILES 91.Bl -tag -width Pa -compact 92.It Pa /dev/mem 93.It Pa /dev/kmem 94.It Pa /dev/kUmem 95.El 96.Sh HISTORY 97The 98.Nm mem , 99.Nm kmem 100files appeared in 101.At v6 . 102The file 103.Nm kUmem 104appeared in 105.Bx 3.0 . 106