1.\" Copyright (c) 1991 The 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.\" $Id$ 33.\" 34.Dd June 2, 1994 35.Dt MEM 4 36.Os 37.Sh NAME 38.Nm mem , 39.Nm kmem 40.Nd memory files 41.Sh DESCRIPTION 42The special file 43.Nm /dev/mem 44is an interface to the physical memory of the computer. 45Byte offsets in this file are interpreted as physical memory addresses. 46Reading and writing this file is equivalent to reading and writing 47memory itself. 48Only offsets within the bounds of 49.Nm /dev/mem 50are allowed. 51.Pp 52Kernel virtual memory is accessed through the interface 53.Nm /dev/kmem 54in the same manner as 55.Nm /dev/mem . 56Only kernel virtual addresses that are currently mapped to memory are allowed. 57.Sh "I386 ARCHETECTURE DETAILS" 58.Pp 59On 60.Tn ISA 61the 62.Tn I/O 63memory space begins at physical address 0x000a0000 64and runs to 0x00100000. 65The kernel virtual address space (usually) starts at address 0xfe000000, 66and each process/thread kernel stack is uniquely located in the kernel 67heap above the kernel program. 68.Sh FILES 69.Bl -tag -width Pa -compact 70.It Pa /dev/mem 71.It Pa /dev/kmem 72.El 73.Sh HISTORY 74The 75.Nm mem , 76.Nm kmem 77files appeared in 78.At v6 . 79