MEM(4) | Device Drivers Manual (hppa) | MEM(4) |
mem
, kmem
—
memory files and memory controller
mem* at mainbus0
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.
The mem
driver originates from
OpenBSD. It was ported to NetBSD
1.6 by Matthew Fredette.
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.
February 17, 2017 | NetBSD 10.99 |