MEM
Section: Linux Programmer's Manual (4)
Updated: 2015-01-02
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NAME
mem, kmem, port - system memory, kernel memory and system ports
DESCRIPTION
/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
SEE ALSO
chown(1),
mknod(1),
ioperm(2)
COLOPHON
This page is part of release 4.13 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/.
Index
- NAME
-
- DESCRIPTION
-
- FILES
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- SEE ALSO
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- COLOPHON
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