MEM(4)              OpenBSD Programmer's Manual (Loongson)              MEM(4)

NAME
     mem, kmem - memory files

DESCRIPTION
     The file /dev/mem is an interface to the physical memory of the computer.
     Byte offsets in this file are interpreted as physical memory addresses.
     Reading and writing this file is equivalent to reading and writing memory
     itself.  An error will be returned if an attempt is made to reference an
     offset outside of /dev/mem.

     Kernel virtual memory is accessed via the file /dev/kmem in the same man-
     ner as /dev/mem.  Only kernel virtual addresses that are currently mapped
     to memory are allowed.

     On the loongson, physical memory is always contiguous, but can be ac-
     cessed from two distinct physical address windows:

     o   From address 0x00000000 to 0x0fffffff, the lowest 256 megabytes of
         memory.
     o   From address 0x80000000 to 0xffffffff, the whole memory, up to 2 gi-
         gabytes.

     This layout implies that a given memory location within the first 256
     megabytes may indifferently be addressed in the 0x00000000 - 0x0fffffff
     address range or the 0x80000000 - 0x8fffffff address range.

     The kernel virtual memory begins at address 0xc000000000000000.

     Writeability of these devices is controlled by the system securelevel(7).

FILES
     /dev/mem
     /dev/kmem

SEE ALSO
     securelevel(7)

HISTORY
     The /dev/mem and /dev/kmem files appeared in Version 6 AT&T UNIX.

OpenBSD 4.7                    February 10, 2010                             1
