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From: John Baldwin <jhb@freebsd.org>
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Cc: freebsd-net@freebsd.org, Ivan Voras <ivoras@freebsd.org>
Subject: Re: 8-stable crashes in vmware (possible em driver issue?)
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On Wednesday 24 February 2010 7:23:44 pm Ivan Voras wrote:
> Ivan Voras wrote:
> > I have a fairly recent 8-stable machine running under VMWare ESXi 3.5 
> > (amd64 guest), which apparently crashes every few days from the same 
> > causes:
> > 
> > em0: discard frame w/o packet header
> > em0: discard frame w/o packet header
> > em0: discard frame w/o packet header
> > Panic string: sbsndptr: sockbuf 0xffffff007cca8c20 and mbuf 
> > 0xffffff00490a6400 clashing
> 
> In case someone is interested or has an idea - on this machine I have 
> multiple crashed cores with similarily strange problems all connected 
> with networking and/or the em driver:
> 
> 1)
> em0: watchdog timeout -- resetting
> Fatal trap 12: page fault while in kernel mode
> current process         = 0 (em0 taskq)
> 
> 2)
> em0: watchdog timeout -- resetting
> Fatal trap 9: general protection fault while in kernel mode
> current process         = 1219 (slapd)
> 
> 3)
> em0: discard frame w/o packet header
> panic: sbdrop
> 
> I'm scratching my head about the #2 above - I don't think trap#9 is usual.

Certain bad pointer values on amd64 trigger a GP# rather than a PF#, so for 
those you would get trap 9 instead of trap 12.  Specifically, the top N bits 
of a pointer in amd64 have to either be all 0 or all 1.  If there is a mix, 
then you get a GP# instead of a PF#.

-- 
John Baldwin