mem(4) - NetBSD Manual Pages

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MEM(4)                NetBSD/vax Kernel Interfaces Manual               MEM(4)


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 cur-
     rently 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.

NetBSD 10.1                      June 5, 1993                      NetBSD 10.1