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

NAME
     mem, kmem - memory files

DESCRIPTION
     The special 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.  Only offsets within the bounds of /dev/mem are
     allowed.

     Kernel virtual memory is accessed through the interface /dev/kmem in the
     same manner as /dev/mem.  Only kernel virtual addresses that are current-
     ly mapped to memory are allowed.

     On the VAX 11/780 (and others), the I/O space base address is
     20000000(16); on an 11/750 the I/O space addresses are of the form
     fxxxxx(16).  On all VAX'en the per-process data size for the current pro-
     cess is UPAGES long and ends at the virtual address 80000000(16).

     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                      May 31, 2007                                1
