xref: /freebsd/share/man/man4/mem.4 (revision ef5d438ed4bc17ad7ece3e40fe4d1f9baf3aadf7)
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32.\"	@(#)mem.4	5.3 (Berkeley) 5/2/91
33.\"
34.Dd May 2, 1991
35.Dt MEM 4 i386
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.Pp
58On
59.Tn ISA
60the
61.Tn I/O
62memory space begins at physical address 0x000a0000
63and runs to 0x00100000.
64The
65per-process data
66size
67for the current process
68is
69.Dv UPAGES
70long, and ends at virtual
71address 0xf0000000.
72.Sh FILES
73.Bl -tag -width Pa -compact
74.It Pa /dev/mem
75.It Pa /dev/kmem
76.El
77.Sh HISTORY
78The
79.Nm mem ,
80.Nm kmem
81files appeared in
82.At v6 .
83