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Date:      Sat, 23 Nov 2002 15:59:12 -0800
From:      Marcel Moolenaar <marcel@xcllnt.net>
To:        Doug Rabson <dfr@nlsystems.com>
Cc:        Perforce Change Reviews <perforce@freebsd.org>
Subject:   Re: PERFORCE change 21417 for review
Message-ID:  <20021123235912.GA1296@athlon.pn.xcllnt.net>
In-Reply-To: <200211232346.41171.dfr@nlsystems.com>
References:  <200211232017.gANKHAAk090869@repoman.freebsd.org> <200211232250.38412.dfr@nlsystems.com> <20021123230017.GB8744@dhcp01.pn.xcllnt.net> <200211232346.41171.dfr@nlsystems.com>

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On Sat, Nov 23, 2002 at 11:46:41PM +0000, Doug Rabson wrote:
> On Saturday 23 November 2002 11:00 pm, Marcel Moolenaar wrote:
> > On Sat, Nov 23, 2002 at 10:50:38PM +0000, Doug Rabson wrote:
> > > On Saturday 23 November 2002 8:17 pm, Marcel Moolenaar wrote:
> > > > http://perforce.freebsd.org/chv.cgi?CH=21417
> > > >
> > > > Change 21417 by marcel@marcel_nfs on 2002/11/23 12:17:09
> > > >
> > > > 	Raw, untested implementation of EPC syscalls.
> > >
> > > This seems to be missing the bit after calling syscall() which
> > > checks for a full exception_restore, e.g. after an execve and also
> > > the check for calling ast(), e.g. after a signal.
> >
> > Yes.
> >
> > [snip]
> >
> > > One other thing after re-familiarising myself with exception.s. You
> > > have added unwind records to all the kernel IVT entry points. This
> > > is quite unhelpful when trying to debug kernel faults. The previous
> > > version which manually unwound past the exception to the code which
> > > faulted was extremely useful and saved me a lot of time in
> > > debugging. Can we have it back please :-).
> >
> > If we want to use unwinding to get to the register state of the
> > process, we can never unwind over the exception code. It's probably
> > much easier to restart unwinding after it stopped at the exception
> > entry point. This would also hold for signal handlers. Would a DDB
> > command to resume unwinding work?
> 
> I think it would be ok to just put back the code in db_stack_trace_cmd() 
> which spots kernel entry points and resets the unwind state based on 
> the contents of the appropriate stack frame. That would give complete 
> stack traces in DDB without disturbing the real unwind records.

Ok. I may not get to it soon, so feel free to revert the change yourself
if you want it badly enough :-)

-- 
 Marcel Moolenaar	  USPA: A-39004		 marcel@xcllnt.net

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