NAME
mem,
kmem,
kUmem —
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 currently mapped to memory are allowed.
The file
/dev/kUmem also refers to kernel virtual memory, but
may be used to access areas mapped to UNIBUS address space and other I/O
areas. It forces all accesses to use word (short integer) accesses.
On the VAX-11/780, 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 process is
UPAGES
long and
ends at the virtual address 80000000(16).
FILES
- /dev/mem
-
- /dev/kmem
-
- /dev/kUmem
-
HISTORY
The
mem,
kmem files appeared in
Version 6 AT&T UNIX. The file
kUmem appeared in
3.0BSD.