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Date:      Tue, 17 Feb 1998 15:00:34 -0800
From:      Mike Smith <mike@smith.net.au>
To:        Eivind Eklund <eivind@yes.no>
Cc:        Mike Smith <mike@smith.net.au>, hackers@FreeBSD.ORG
Subject:   Re: ed overwrite clue? 
Message-ID:  <199802172300.PAA03354@dingo.cdrom.com>
In-Reply-To: Your message of "Tue, 17 Feb 1998 23:48:52 %2B0100." <19980217234852.01126@follo.net> 

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> On Tue, Feb 17, 1998 at 02:27:32PM -0800, Mike Smith wrote:
> > > > One question; the destination of the insw - is that actually a
> > > > legitimate address?  ie. is it on the kernel stack, or somewhere
> > > > else?
> > > 
> > > It looks like the destination is on the kernel stack.  The source
> > > looks more suspicious - it is at 0x6200...
> > 
> > That's not unreasonable; the onboard memory on an NE card isn't based 
> > at zero.  See the comments and code in the Novell-specific probe 
> > section for details on this.
> 
> I've been looking more closesly now - I'm having the destination
> addresses switch between 0xefbX XXXX and 0xf01X XXXX.  The
> 0xf01*-addresses never crash.  And there are much more of the
> 0xf01*-addresses - I've seen hundreds of 0xf01* pass without getting
> any crashes, while between 10% and 20% of the 0xefb* crash.  (But not
> 100%, which makes this more complicated).

I think what you're seeing there is you're taking interrupts on two 
different stacks.  The 0xefb* addresses are around _kstack, which is at 
0xefbfe000.  The other one could be the user stack.

Beware that the kernel stack is small (only a few K).  You might want 
to see whether the values that are causing the problem are all below 
some threshold (IIRC the kernel stack allocation is about 7K).

> I'm about to start trigging some crashdumps on purpose now, so I can
> get a good look at how a dump for an OK case is.

Do you have any custom code in the kernel?
-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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