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Date:      Sun, 14 Jan 1996 18:05:58 +0000
From:      Gary Jennejohn <garyj@munich.netsurf.de>
To:        Bruce Evans <bde@zeta.org.au>
Cc:        freebsd-hackers@freefall.freebsd.org, isdn@muc.ditec.de
Subject:   Re: Status of ISDN drivers 
Message-ID:  <199601141805.SAA12195@peedub.gj.org>
In-Reply-To: Your message of "Mon, 15 Jan 1996 00:13:06 %2B1100." <199601141313.AAA05940@godzilla.zeta.org.au> 

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Bruce Evans writes:
>>I've become aware of a horrible bug somewhere in the ISDN code in the
>>last few days which apparently trashes the kernel stack somehow.
>
>Someone actually uses the isdn drivers in FreeBSD? :-)  Perhaps they
>have been broken by recent cleanups.  OTOH, perhaps they have been
>fixed by recent cleanups.  What version are you using?
>
I'm using a version is is not based on the 2.1R sources. May be that the
changes/fixes in 2.1R could eliminate the problem. I'm planning to merge the
modifications in the sources I'm using into -stable and see what happens.

>>This bug is extrememly hard to track down beacuse the fault address is
>>totally bogus, e.g. 8:0. That's why I suspect that the stack is getting
>>trashed. It also crops up under circumstances which I can't identify.
>
>This fault address (but not a trashed stack) is normal for a call or
>jump through a null pointer.  Calls through null pointers are very
>easy to debug since the return address is on the stack, while jumps
>through null pointers are hard to debug.
>
actually, it's the instruction pointer that's 0x8:0x0, as I noted in
a followup I posted.

---
Gary Jennejohn
Home - Gary.Jennejohn@munich.netsurf.de
Work - gjennejohn@frt.dec.com




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