A fellow employee is writing a device driver that had a bug in it.
In its attach() routine it was calling:
	first pci_mem_find()
	then  bus_space_map().

In another part of the driver it is calling bus_space_read_4()
and passing a bad offset argument that is beyong the length returned
by pci_mem_find(), which was passed to bus_space_map().

This bad access, I would thing should cause a mem fault or seg fault
but instead hangs the system!

I could use the extent region info ra_start & ra_end in subroutine
pci_swiz_mem_read_4() but I don't know if limit checking their is the
correct thing todo!

What is the correct thing todo to crash (ie panic() netbsd is a pci
access is not on a board?

PS Isn't this the same idea as a pci configuration read getting a master
   abort?