MEM(7)MEM(7)NAME
mem, kmem, mmem - core memory
DESCRIPTION
The file /dev/mem is a special file that is an image of the core memory
of the computer. It may be used, for example, to examine, and even to
patch the system.
Byte addresses in /dev/mem are interpreted as memory addresses.
References to non-existent locations cause errors to be returned.
Examining and patching device registers is likely to lead to unexpected
results when read-only or write-only bits are present.
The file /dev/kmem is similar to /dev/mem except that kernel virtual
memory, rather than physical memory, is accessed. read(2) and write(2)
access is supported, to kernel virtual space that represents physical
memory. mmap(2) access to /dev/kmem is not supported. This is due to
mmap creating data consistency problems which could lead to corrupted
data and kernel panics.
The file /dev/mmem is similar to /dev/kmem except that only mmap(2)
access is permitted (both read and write), and only for those addresses
configured into the system via the file /var/sysgen/master.d/mem and the
/etc/autoconfig script.
FILES
/dev/mem
/dev/kmem
/dev/mmem
WARNING
Some of /dev/kmem cannot be read because of write-only addresses or
unequipped memory addresses.
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