kernfs on the sparc64 port has started not working for rootdev & rrootdev:

# mount -t kernfs /kern /kern
# ls -l /kern/rootdev
ls: /kern/rootdev: Bad file descriptor
# ls -l /kern/rrootdev
ls: /kern/rrootdev: No such file or directory


this only happens with the `miniroot' (which is just a normal GENERIC kernel,
not an md_root using one), when loaded on sd0b/wd0b.  if i boot from sd0a it
works just fine.  why this matters i don't understand...


perhaps a UBC thing?  i don't recall when it started happening but it doesn't
happen in 1.5 or anything a couple of months after the branch (when i last
did real work on the installer).