mbrprobe: dev=vn0 blksize=0x80000000 blocks=64 media_size=137438953472
panic: assertion "obj != NULL" failed in vm_object_hold_shared at /usr/src/sys/vm/vm_object.c:330
cpuid = 3
Trace beginning at frame 0xfffff8011836afe8
vm_object_hold_shared() at vm_object_hold_shared+0x3f 0xffffffff809ab9bf 
vm_object_hold_shared() at vm_object_hold_shared+0x3f 0xffffffff809ab9bf 
vm_fault() at vm_fault+0x408 0xffffffff8099e0b8 
trap_pfault() at trap_pfault+0x9a 0xffffffff80bd52ca 
trap() at trap+0x17c 0xffffffff80bd5bcc 
calltrap() at calltrap+0x9 0xffffffff80b991fa 
--- trap 000000000000000c, rip = ffffffff80bcaa0a, rsp = fffff8011836b400, rbp = fffff8011836b468 ---
memmove() at memmove+0x10a 0xffffffff80bcaa0a 
Debugger("panic")

CPU3 stopping CPUs: 0x00000037
 stopped
Stopped at      Debugger+0x7c:  movb    $0,0xbdaf09(%rip)
db>