man4/mem.4

   1 .\" Copyright (c) 1993 Michael Haardt (michael@moria.de), Fri Apr  2 11:32:09 MET DST 1993
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  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
  26 mem, kmem, port \- system memory, kernel memory and system ports
  27 .SH DESCRIPTION
  28 \fBmem\fP is a character device file
  29 that is an image of the main memory of the computer.
  30 It may be used, for example, to examine (and even patch) the system.
  31 .LP
  32 Byte addresses in
  33 .B mem
  34 are interpreted as physical memory addresses.
  35 References to non-existent locations cause errors to be returned.
  36 .LP
  37 Examining and patching is likely to lead to unexpected results
  38 when read-only or write-only bits are present.
  39 .LP
  40 It is typically created by:
  41 .RS
  42 .sp
  43 mknod \-m 660 /dev/mem c 1 1
  44 .br
  45 chown root:kmem /dev/mem
  46 .RE
  47 .LP
  48 The file
  49 .B kmem
  50 is the same as
  51 .BR mem ,
  52 except that the kernel virtual memory
  53 rather than physical memory is accessed.
  54 .LP
  55 It is typically created by:
  56 .RS
  57 .sp
  58 mknod \-m 640 /dev/kmem c 1 2
  59 .br
  60 chown root:kmem /dev/kmem
  61 .RE
  62 .LP
  63 \fBport\fP is similar to
  64 .BR mem ,
  65 but the I/O ports are accessed.
  66 .LP
  67 It is typically created by:
  68 .RS
  69 .sp
  70 mknod \-m 660 /dev/port c 1 4
  71 .br
  72 chown root:mem /dev/port
  73 .RE
  74 .SH FILES
  75 .I /dev/mem
  76 .br
  77 .I /dev/kmem
  78 .br
  79 .I /dev/port
  80 .SH "SEE ALSO"
  81 .BR chown (1),
  82 .BR mknod (1),
  83 .BR ioperm (2)