Avoid forcible mounting a dirty filessystem. Mount such filesystems
read-only instead. This means that writing to the filesystem will fail.
As a consequence chmod'ing of files in the bootloader will fail, but that
will fix itself on the next clean boot.

ok kn@

Only fall back on using the first potential root disk as the boot disk if
the boot kernel didn't hand us a valid bootduid.

ok visa@

Improve detection of the proper boot device by picking the disk that
matches the bootduid of the boot kernel.

ok visa@

First stab at a bootloader for OpenBSD/powerpc64.
Based on the same principle (and mostly copied from) the bootloader
written by visa@ for OpenBSD/octeon.

Needed because the petitboot environment provided by the OpenPower
firmware is unsuitable for loading OpenBSD kernels properly.

Only fall back on using the first potential root disk as the boot disk if
the boot kernel didn't hand us a valid bootduid.

ok visa@

Improve detection of the proper boot device by picking the disk that
matches the bootduid of the boot kernel.

ok visa@

First stab at a bootloader for OpenBSD/powerpc64.
Based on the same principle (and mostly copied from) the bootloader
written by visa@ for OpenBSD/octeon.

Needed because the petitboot environment provided by the OpenPower
firmware is unsuitable for loading OpenBSD kernels properly.

Improve detection of the proper boot device by picking the disk that
matches the bootduid of the boot kernel.

ok visa@

First stab at a bootloader for OpenBSD/powerpc64.
Based on the same principle (and mostly copied from) the bootloader
written by visa@ for OpenBSD/octeon.

Needed because the petitboot environment provided by the OpenPower
firmware is unsuitable for loading OpenBSD kernels properly.