MEM(4) - Device Drivers Manual (hppa) #
MEM(4) - Device Drivers Manual (hppa)
NAME #
mem, kmem - memory files and memory controller
SYNOPSIS #
mem* at mainbus0 flags 0x0000
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.
Even with sufficient file system permissions, these devices can only be opened when the securelevel(7) is insecure or when the kern.allowkmem sysctl(2) variable is set.
FILES #
/dev/mem
/dev/kmem
SEE ALSO #
CAVEATS #
On some systems featuring a “Viper” memory controller, OpenBSD may not configure bus arbitration correctly, causing the boot process to freeze during either mem or cpu(4) device probe.
In this case, a different initialization strategy can be achieved by setting flags to 0x0001 (see boot_config(8) for details) .
OpenBSD 7.5 - January 12, 2018