From owner-freebsd-hackers  Mon Jan  8  0:37:13 2001
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Date: Mon, 8 Jan 2001 10:36:38 +0200 (IST)
From: Roman Shterenzon <roman@xpert.com>
To: Greg Lehey <grog@lemis.com>, Yonatan Bokovza <yonatan@xpert.com>
Cc: <hackers@freebsd.org>
Subject: Re: Dump analysis (was: Ideas? (fwd))
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On Mon, 8 Jan 2001, Greg Lehey wrote:

> On Monday,  8 January 2001 at 10:04:44 +0200, Roman Shterenzon wrote:
> > * Roman Shterenzon <roman@xpert.com> [010107 10:24] wrote:
> >> Hi,
> >>
> >> Could you please take a look at :
> >> http://www.freebsd.org/cgi/query-pr.cgi?pr=24019
> >> It's my friend's PR. Can you give me some hints on how can I debug this
> >> issue. I'm completely puzzled here.
> >> It panics on "goto out" with page fault. What I understand from it is that
> >> the block at the address it tries to jmp to isn't present. But it's kernel
> >> code which is never swapped out. Does it mean that the address was
> >> rewritten? If it's so, what can rewrite this address? Ideas?
>
> My first suspicion here is that the sources are out of sync with the
> kernel you're debugging.  It's very important to ensure that they are
This is not the case. The guy built it from the sam sources, he even used
"buildkernel/installkernel" for that purpose.

> absolutely in sync.  Here are a couple of incantations to throw at
> this dump (you may recognize the second one from an earlier mail
> exchange):
>
>  (kgdb) x/10i epread
>  (kgdb) x/10i 0xc012a038
>
> The first one should show  the beginning of the function; if it's in
> sync it will look like (modulo addresses):
>
> (kgdb) x/10i epread
> 0xc0165f8c <epread>:    push   %ebp
> 0xc0165f8d <epread+1>:  mov    %esp,%ebp
> 0xc0165f8f <epread+3>:  sub    $0x1c,%esp
> 0xc0165f92 <epread+6>:  push   %edi
> 0xc0165f93 <epread+7>:  push   %esi
> 0xc0165f94 <epread+8>:  push   %ebx
> 0xc0165f95 <epread+9>:  mov    0x8(%ebp),%eax
> 0xc0165f98 <epread+12>: mov    %eax,0xfffffff4(%ebp)
> 0xc0165f9b <epread+15>: mov    0x118(%eax),%edx
> 0xc0165fa1 <epread+21>: add    $0x8,%edx
>
> In particular, those first two instructions are at the beginning of
> just about every function, so if you don't find them, you should check
> whether your code is in sync.

Yonatan, please provide the requested information.

>
> >> P.S. Can it be due to faulty hardware?
>
> Or faulty Italian cuisine?  In each case, not if it's repeatable.
It's repeatable, but not predictable.

--Roman Shterenzon, UNIX System Administrator and Consultant
[ Xpert UNIX Systems Ltd., Herzlia, Israel. Tel: +972-9-9522361 ]



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