# BASELINE run — stock /boot/kernel/drm.ko (unmodified kernel tree)
# command: kldload drm && kldload /root/zposnull/zposnull.ko
# (ssh session died at kldload; serial console shows the panic — see panic.txt)
$ kldload drm && kldstat | grep drm
 5    1 0xffffffff82601000   bbe000 drm.ko
$ kldload /root/zposnull/zposnull.ko
[connection dies — kernel panic; guest wedged at ddb prompt "db>"]

# ---- serial console (dfbsd-qemu/boot.log), decisive lines ----
zposnull: calling stock drm_atomic_normalize_zpos (expect NULL-deref panic)
Fatal user address access from kernel mode from kldload at ffffffff8260c81b

Fatal trap 12: page fault while in kernel mode
cpuid = 3; lapic id = 3
fault virtual address	= 0xa
fault code		= supervisor write data, page not present
instruction pointer	= 0x8:0xffffffff8260c81b
current process		= 1627
kernel: type 12 trap, code=2
Stopped at      drm_atomic_normalize_zpos+0x6b: orb     $0x10,0xa(%rax)
db>