How to read crash log of NetBSD 7.0.2?

[Jia-Ju Bai <baijiaju1990%163.com@localhost>]

Hello,

I am trying to rewrite an Ethernet driver (if_vr) in NetBSD 7.0.2 for a 
real device. And my driver is implemented as a kernel module.
Currently, my driver can be successfully loaded, but it can cause system 
crash. Thus, I write some "printf" sentences in the code, and I want to 
read crash log to debug my driver code.

Unluckily, after my driver is loaded, I do not see any my "printf" 
messages on the screen before the crash occurs :(
After the rebooting of the crash, I do not see useful messages in 
/var/log/messages or using "dmesg" command. I find two files in 
/var/crash: netbsd.0.gz and netbsd.0.core.gz. And I uncompress them and 
open them using "vim", but they are not readable :(

So how to read crash log of the system?
And how to let my "printf" messages show on the screen (or show on 
another computer via serial port) ?


Thanks in advance,
Jia-Ju Bai