MEM(4) | Device Drivers Manual (vax) | MEM(4) |
mem
, kmem
,
kUmem
— memory
files
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).
The mem
, kmem
files appeared in Version 6 AT&T UNIX.
The file kUmem
appeared in
3.0BSD.
June 5, 1993 | NetBSD 10.99 |