Date:	Sun, 4 Apr 1999 09:35:35 +0200 (IST)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender:	eliz AT is
To:	Martin Str|mberg <ams AT ludd DOT luth DOT se>
cc:	djgpp AT delorie DOT com
Subject:	Re: LONG: My INT31 handler isn't feeling too swell
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Reply-To:	djgpp AT delorie DOT com
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On 3 Apr 1999, Martin Str|mberg wrote:

> I wonder what you people out there knowledgable in crash dumps have to
> say about this one.

Too many things went wrong there, so it's difficult to tell without
spending a nice long debugging session with your program (which I
cannot afford currently).

> After hooking INT31, the program simply spawnl()s
> bash.

Why did you need to spawn Bash?  I suggest to try COMMAND.COM first,
since Bash does some very complex tricks with DPMI functions.  It's
better to begin at the first grade...

> General Protection Fault at eip=000003c0, error=fffc

Mystery no.1: the EIP is *way* too low.
Mystery no.2: the error code in GPF, if not zero, is the descriptor
that a program was trying to load and which caused the GPF.  But what
kind of a descriptor is FFFCh?

> eax=00000300 ebx=00020021 ecx=00003c00 edx=000001df esi=00000000
> edi=00001000
> ebp=00160912 esp=0000075a program=F:\hackery\ds\apams

Mystery no.3: the EBP value is not inside stack limits of any of the
two stacks.  And neither is ESP, but note that ESP is very low and too
far from EBP.

> cs: sel=01c7  base=0001f3c0  limit=0000ffff
> ds: sel=01bf  base=0001f3c0  limit=0000ffff
> es: sel=01bf  base=0001f3c0  limit=0000ffff
> ss: sel=01bf  base=0001f3c0  limit=0000ffff

These all have a limit of 64K.  How can this be?  Mystery no.4.

> fs: sel=0000
> gs: sel=0000

And these are invalid: mystery no.5.

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