- Ensure that both systems have firewire(4) support, and that the kernel of the remote system includes the dcons(4) and dcons_crom(4) drivers. If they are not compiled into the kernel, load the KLDs:
"kldload firewire"
On the remote system only:
kldload dcons
kldload dcons_crom
You should see something like this in the dmesg(8) output of the remote system:
fwohci0: BUS reset
fwohci0: node_id=0x8800ffc0, gen=2, non CYCLEMASTER mode
firewire0: 2 nodes, maxhop <= 1, cable IRM = 1
firewire0: bus manager 1
firewire0: New S400 device ID:00c04f3226e88061
dcons_crom0: <dcons configuration ROM> on firewire0
dcons_crom0: bus_addr 0x22a000
It is a good idea to load these modules at boot time with the following entry in /boot/loader.conf:
dcons_crom_enable= "YES"
This ensures that all three modules are loaded. There is no harm in loading dcons(4) and dcons_crom(4) on the local system, but if you only want to load the firewire(4) module, include the following in /boot/loader.conf:
firewire_enable= "YES"
- Next, use fwcontrol(8) to find the firewire node corresponding to the remote machine. On the local machine you might see:
# fwcontrol
2 devices (info_len=2)
node EUI64 status
1 0x00c04f3226e88061 0
0 0x000199000003622b 1
The first node is always the local system, so in this case, node 0 is the remote system. If there are more than two systems, check from the other end to find which node corresponds to the remote system. On the remote machine, it looks like this:
# fwcontrol
2 devices (info_len=2)
node EUI64 status
0 0x000199000003622b 0
1 0x00c04f3226e88061 1
- Next, establish a firewire connection with dconschat(8):
"dconschat -br -G 5556 -t 0x000199000003622b"
0x000199000003622b is the EUI64 address of the remote node, as determined from the output of fwcontrol(8) above. When started in this manner, dconschat(8) establishes a local tunnel connection from port localhost:5556 to the remote debugger. You can also establish a console port connection with the -C option to the same invocation dconschat(8). See the dconschat(8) manpage for further details.
The dconschat(8) utility does not return control to the user. It displays error messages and console output for the remote system, so it is a good idea to start it in its own window.
- Finally, establish connection:
# gdb kernel.debug
GNU gdb 5.2.1 (FreeBSD)
"(political statements omitted)"
Ready to go. Enter ’tr’ to connect to the remote target
with /dev/cuad0, ’tr /dev/cuad1’ to connect to a different port
or ’trf portno’ to connect to the remote target with the firewire
interface. portno defaults to 5556.
Type ’getsyms’ after connection to load kld symbols.
If you are debugging a local system, you can use ’kldsyms’ instead
to load the kld symbols. That is a less obnoxious interface.
(gdb) trf
0xc21bd378 in ?? ()
The trf macro assumes a connection on port 5556. If you want to use a different port (by changing the invocation of dconschat(8) above), use the tr macro instead. For example, if you want to use port 4711, run dconschat(8) like this:
"dconschat -br -G 4711 -t 0x000199000003622b"
Then establish connection with:
(gdb) tr localhost:4711
0xc21bd378 in ?? ()
