DF5531: (A) ifp set,   if_bpf==NULL : 1256 cycles/call
DF5531: (B) ifp NULL (early-return) : 34 cycles/call
DF5531: overhead ratio A/B          : 36.2 x
TAP_RESULT=done
DF5530: calling bpfdetach() on not-bpf-attached usbus0 (simulating usbpf_clone_destroy() winning the usb_pf.c:157->177 window)
Fatal user address access from kernel mode from kldload at ffffffff802aac53


Fatal trap 12: page fault while in kernel mode
cpuid = 2; lapic id = 2
fault virtual address	= 0x20
fault code		= supervisor read data, page not present
instruction pointer	= 0x8:0xffffffff802aac53
stack pointer	        = 0x10:0xfffff801181f47a8
frame pointer	        = 0x10:0xfffff801181f47c8
code segment		= base 0x0, limit 0xfffff, type 0x1b
			= DPL 0, pres 1, long 0, def32 0, gran 1
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 1278
current thread          = pri 6 
kernel: type 12 trap, code=0

CPU2 stopping CPUs: 0x0000003b
 stopped
Stopped at      bpfdetach.cold.7:       movq    0x20,%rax
db>