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NAME | DESCRIPTION | FILES | SEE ALSO | COLOPHON |
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MEM(4) Linux Programmer's Manual MEM(4)
mem, kmem, port - system memory, kernel memory and system ports
/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 con‐
figuration 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
/dev/mem
/dev/kmem
/dev/port
chown(1), mknod(1), ioperm(2)
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2015-01-02 MEM(4)
Copyright and license for this manual page
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