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.