Re: buildd macs, was Re: [buildd] Etch?
On Tue, 15 Aug 2006, Michael Schmitz wrote:
> > On Tue, Aug 15, 2006 at 11:31:01AM +1000, Finn Thain wrote:
> > > Anyway, I have the logs, what I was after was a kernel core dump,
> > > like kdump, netdump or lkcd provides on other architectures, so as
> > > to do a postmortem in gdb.
> > ... which may be pretty hard to do through a serial port. Got it.
> Well, there used to be kgdb in the old days (before Macs) but no one
> ever used it, so it was dropped. It was explicitly meant to work through
> the serial port (though performing a full dump wasn't the point; the
> kernel kdgb code would examine storage in the kernel as directed by a
> remote gdb process). There were some hooks in the serial driver for it,
> the rest was pretty much self contained IIRC. No idea how difficult it
> would be to revive that code. We'll need a serial driver first, anyway.
The advantage of crash dumps is they make it possible to analyse a problem
in another location (after crashing unexpectedly or deliberately inducing
a dump). And because the kernel is not live, inconsistent data is more
meaningful than with kgdb (or so I read somewhere).
Probably the best candidate for crash dumps is kdump, which is already in
the mainline. But it would require deep arch-specific support that is
beyond my ability.