NAME
mem,
kmem —
memory
files and memory controller
SYNOPSIS
mem* at mainbus0
DESCRIPTION
The
mem driver controls and restricts access to the systems
memory by the hardware buses and the processor.
It also provides an interface to userland through the special files
/dev/mem and
/dev/kmem. Physical memory is
accessed through
/dev/mem, while kernel virtual memory is
accessed through
/dev/kmem. Access to kernel virtual
addresses not currently mapped to memory will fail. On hppa, the physical
memory range is always contiguous and starts at address 0; kernel virtual
memory begins at address 0 as well.
The writeability of the
/dev/mem and
/dev/kmem special files are controlled by the system
securelevel in addition to the filesystem permissions.
FILES
- /dev/mem
-
- /dev/kmem
-
HISTORY
The
mem driver originates from
OpenBSD. It was ported to
NetBSD
1.6 by Matthew Fredette.
BUGS
On some systems featuring a “Viper” memory controller,
NetBSD may not configure bus arbitration correctly,
causing the boot process to freeze during either
mem or
hppa/cpu(4) device
probe.