usr/src/share/man/man4/man4.i386/mem.4

.\" Copyright (c) 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.roff%
.\"
.\"     @(#)mem.4       5.3 (Berkeley) %G%
.\"
.Dd
.Dt MEM 4 i386
.Os
.Sh NAME
.Nm mem ,
.Nm kmem
.Nd memory files
.Sh DESCRIPTION
The special file
.Nm /dev/mem
is an interface to the physical memory of the computer.
Byte offsets in this file are interpreted as physical memory addresses.
Reading and writing this file is equivalent to reading and writing
memory itself.
Only offsets within the bounds of
.Nm /dev/mem
are allowed.
.Pp
Kernel virtual memory is accessed through the interface
.Nm /dev/kmem
in the same manner as
.Nm /dev/mem .
Only kernel virtual addresses that are currently mapped to memory are allowed.
.Pp
On
.Tn ISA
the
.Tn I/O
memory space begins at physical address 0x000a0000
and runs to 0x00100000.
The
per-process data
size
for the current process
is
.Dv UPAGES
long, and ends at virtual
address 0xfe000000.
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/mem
.It Pa /dev/kmem
.El
.Sh HISTORY
The
.Nm mem ,
.Nm kmem
files appeared in
.At v6 .