MEM(7)									MEM(7)

NAME    [Toc]    [Back]

     mem, kmem,	mmem - core memory

DESCRIPTION    [Toc]    [Back]

     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    [Toc]    [Back]

     /dev/mem
     /dev/kmem
     /dev/mmem

WARNING    [Toc]    [Back]

     Some of /dev/kmem cannot be read because of write-only addresses or
     unequipped	memory addresses.


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