DF-1017: secsize=0 divide-by-zero demonstration
  block_len (from READ_CAPACITY): 0
  secsize (set at dasetgeom:2289): 0
  bio_offset: 0
  b_bcount:   512

  BUG CONFIRMED: secsize=0 would trigger #DE at:
    dadump()       :797  ap->a_offset / secsize  => DIVIDE BY ZERO (#DE trap -> panic)
    dadump()       :798  ap->a_length / secsize  => DIVIDE BY ZERO
    dastart()      :1341 bp->b_bcount / secsize  => DIVIDE BY ZERO
    dastart()      :1342 bio_offset / secsize    => DIVIDE BY ZERO
    dastart()      :1490 bio_offset % secsize    => DIVIDE BY ZERO
    dastart()      :1500 bio_offset / secsize    => DIVIDE BY ZERO
    dastart()      :1501 b_bcount / secsize      => DIVIDE BY ZERO

  Kernel would panic with fatal trap 0 (#DE) in dastart/dadump.
  No user interaction needed: automatic partition probe triggers it.