mem (4)
Leading comments
Copyright (c) 1993 Michael Haardt (michael@moria.de),
Fri Apr 2 11:32:09 MET DST 1993
%%%LICENSE_START(GPLv2+_DOC_FULL)
This is free documentation; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
The GNU General Public License's references to "object code"
and "executables" are to be interpreted as the output of any
document fo...
NAME
mem, kmem, port - system memory, kernel memory and system portsDESCRIPTION
/dev/mem is a character device file that is an image of the main memory of the computer. It may be used, for example, to examine (and even patch) the system.Byte addresses in /dev/mem are interpreted as physical memory addresses. References to nonexistent locations cause errors to be returned.
Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present.
Since Linux 2.6.26, and depending on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration option limits the areas which can be accessed through this file. For example: on x86, RAM access is not allowed but accessing memory-mapped PCI regions is.
It is typically created by:
-
mknod -m 660 /dev/mem c 1 1
chown root:kmem /dev/mem
The file /dev/kmem is the same as /dev/mem, except that the kernel virtual memory rather than physical memory is accessed. Since Linux 2.6.26, this file is available only if the CONFIG_DEVKMEM kernel configuration option is enabled.
It is typically created by:
-
mknod -m 640 /dev/kmem c 1 2
chown root:kmem /dev/kmem
/dev/port is similar to /dev/mem, but the I/O ports are accessed.
It is typically created by:
-
mknod -m 660 /dev/port c 1 4
chown root:kmem /dev/port
FILES
/dev/mem/dev/kmem
/dev/port