mem(4) - NetBSD Manual Pages

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MEM(4)               NetBSD/hppa Kernel Interfaces Manual               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 con- trolled by the system securelevel in addition to the filesystem permis- sions.
/dev/mem /dev/kmem
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. NetBSD 9.0 February 17, 2017 NetBSD 9.0
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