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1.\" Copyright (c) 1993 Michael Haardt (michael@moria.de),
2.\" Fri Apr 2 11:32:09 MET DST 1993
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3.\"
4.\" This is free documentation; you can redistribute it and/or
5.\" modify it under the terms of the GNU General Public License as
6.\" published by the Free Software Foundation; either version 2 of
7.\" the License, or (at your option) any later version.
8.\"
9.\" The GNU General Public License's references to "object code"
10.\" and "executables" are to be interpreted as the output of any
11.\" document formatting or typesetting system, including
12.\" intermediate and printed output.
13.\"
14.\" This manual is distributed in the hope that it will be useful,
15.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
16.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17.\" GNU General Public License for more details.
18.\"
19.\" You should have received a copy of the GNU General Public
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20.\" License along with this manual; if not, see
21.\" <http://www.gnu.org/licenses/>.
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22.\"
23.\" Modified Sat Jul 24 16:59:10 1993 by Rik Faith (faith@cs.unc.edu)
24.TH MEM 4 1992-11-21 "Linux" "Linux Programmer's Manual"
25.SH NAME
26mem, kmem, port \- system memory, kernel memory and system ports
27.SH DESCRIPTION
e8046fd0 28\fBmem\fP is a character device file
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29that is an image of the main memory of the computer.
30It may be used, for example, to examine (and even patch) the system.
fea681da 31.LP
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32Byte addresses in
33.B mem
e8046fd0 34are interpreted as physical memory addresses.
c382a365 35References to nonexistent locations cause errors to be returned.
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36.LP
37Examining and patching is likely to lead to unexpected results
38when read-only or write-only bits are present.
39.LP
40It is typically created by:
41.RS
42.sp
4d9b6984 43mknod \-m 660 /dev/mem c 1 1
fea681da 44.br
9df0bd1d 45chown root:kmem /dev/mem
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46.RE
47.LP
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48The file
49.B kmem
50is the same as
51.BR mem ,
e8046fd0 52except that the kernel virtual memory
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53rather than physical memory is accessed.
54.LP
55It is typically created by:
56.RS
57.sp
4d9b6984 58mknod \-m 640 /dev/kmem c 1 2
fea681da 59.br
9df0bd1d 60chown root:kmem /dev/kmem
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61.RE
62.LP
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63\fBport\fP is similar to
64.BR mem ,
a28e26a1 65but the I/O ports are accessed.
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66.LP
67It is typically created by:
68.RS
69.sp
4d9b6984 70mknod \-m 660 /dev/port c 1 4
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71.br
72chown root:mem /dev/port
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73.RE
74.SH FILES
75.I /dev/mem
76.br
77.I /dev/kmem
78.br
79.I /dev/port
47297adb 80.SH SEE ALSO
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81.BR chown (1),
82.BR mknod (1),
83.BR ioperm (2)