Hitchhiker's Guide to Openbsd

_pf_route(e28cb7e4,e28bc978,2,1fad,d0b8b120) at _pf_route+0x263
_pf_test(2,1f4ad,e28cb7e4,b4c1) at _pf_test+0x706
_pf_route(e28cbb00,e28bc978,2,d0a65440,d0b8b120) at _pf_route+0x207
_pf_test(2,d0a65440,e28cbb00,d023c282) at _pf_test+0x706
_ip_output(d0b6a200,0,0,0,0) at _ip_output+0xb67
_icmp_send(d0b6a200,0,1,a012) at _icmp_send+0x57
_icmp_reflect(d0b6a200,0,1,0,3) at _icmp_reflect+0x26b
_icmp_input(d0b6a200,14,0,0,d0b6a200) at _icmp_input+0x42c
_ipv4_input(d0b6a200,e289f140,d0a489e0,e289f140) at _ipv4_input+0x6eb
_ipintr(10,10,e289f140,e289f140,e28cbd38) at _ipintr+0x8d
Bad frame pointer: 0xe28cbcac
ddb> 
This tells us what function calls lead to the crash.
To find out the particular line of C code that caused the crash, you can do the following:
Find the source file where the crashing function is defined in. In this example, that would be pf_route() in sys/net/pf.c. 
Recompile that source file with debug information:
# cd /usr/src/sys/arch/$(uname -m)/compile/GENERIC/
# rm pf.o
# DEBUG=-g make pf.o
Then use 
objdump(1)
 to get the disassembly:
# objdump --line --disassemble --reloc pf.o >pf.dis
In the output, grep for the function name (pf_route in our example):
# grep "<_pf_route>:" pf.dis
00007d88 <_pf_route>:
Take this first hex number and add the offset from the 'Stopped at' line: 0x7d88 + 0x263 == 0x7feb.
Scroll down to that line (the assembler instruction should match the one quoted in the 'Stopped at' line), then up to the 
nearest C line number:
http://www.openbsd.org/faq/faq2.html (10 of 11)9/4/2011 10:01:52 AM

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2 - Getting to know OpenBSD
# more pf.dis
/usr/src/sys/arch/i386/compile/GENERIC/../../../../net/pf.c:3872
7fe7: 0f b7 43 02 movzwl 0x2(%ebx),%eax