gdb over Firewire

[Greg 'groggy' Lehey]

On Friday, 11 February 2005 at 10:11:31 +0100, Gerald Heinig wrote:
> Hello Current'ers,
>
> I'm trying to get two-machine kernel debugging over Firewire working,
> unfortunately without much luck so far. dconschat over Firewire works
> fine, but gdb won't attach, complaining about get_tty_state failed,
> among other things.
> Is kernel gdb over Firewire a -current-only feature?

Sorry for the slow reply; I've been busy.

No, it's not a current-only feature.  It used to work, but I've had a
lot of difficulty since the introduction of the new gdb framework.

Try this:

  $ sysctl debug.kdb
  debug.kdb.available: ddb 
  debug.kdb.current: ddb
  debug.kdb.enter: 0
  debug.kdb.stop_cpus: 1

That's what I get, and it indicates that I don't have gdb capability.
If that's what you get, try building a kernel with firewire support
built-in (as opposed to the (recommended) method of loading the
firewire klds later).  The background here is the hypothesis that the
kernel checks for debug back-ends at boot time, and not later, so if
you load the firewire klds later, it won't be registered.

Note that this is a hypothesis.  If you try this, please let us know
what happens.

Greg
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