Date: Mon, 20 Nov 2000 03:10:55 -0800 From: Mike Smith <msmith@freebsd.org> To: Richard Hodges <rh@matriplex.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: page fault question Message-ID: <200011201111.eAKBAtF12436@mass.osd.bsdi.com> In-Reply-To: Your message of "Sun, 19 Nov 2000 14:56:47 PST." <Pine.BSF.4.10.10011191443280.52841-100000@mail.matriplex.com>
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> It turns out that the network stack gets really unhappy when you
> trim an mbuf chain and leave the last mbuf with a negative length :-(
Ouch. 8)
> > Typically stack overruns lead to double faults (because there's no stack
> > on which to handle the fault) and a spontaneous reboot. This just sounds
> > like there's something about your first trap that kills DDB (eg. an
> > invalid instruction pointer, etc.)
>
> I did check the SP, and it looks like the kernel stack stays in the
> "temporary" 8k stack set up in i386/i386/locore.s Does that sound right?
In some cases. AFAIK it'll also appear in the UPAGES area in userspace
if you're calling into the kernel that way.
> > Hope this helps; let us know if the first trap isn't any more
> > illuminating. You might also try using remote gdb instead of ddb.
>
> Thanks. I also had to dig out a couple bugs involving word alignment
> when doing DMA transfers, and learned NOT to mess with the data inside
> mbufs with external data ;-) I guess I've left enough offerings at
> the altar of stupidity, so maybe Loki will leave me alone now.
*grin* Good luck!
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
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