[Qemu-devel] Re: Something is probably wrong with "int 3"

[Alexander E. Patrakov]

Andr? Braga wrote:

> On Tue, 04 Jan 2005 18:09:32 +0500, Alexander E. Patrakov
> <address@hidden> wrote:
>> clearly state that the fault is at the "int 3" instruction, not at "ret".
>> Can anyone explain this difference? Is this a bug in qemu?
> 
> Uh... INT 3 is the debugger services interrupt. It usually triggers a
> resident debugger so it attaches to the calling process.

Yes, in this case DrWatson pops up.

> It might be that Firefox reached a situation where it knew it would
> crash, so it called the debugger first and then failed returning to an
> invalid address (maybe the stack was corrupt?)

Look at the crash dump - the DbgBreakPoint() is called from
kernel32!SetThreadExecutionState, i.e. from deep inside the Windows kernel.
Firefox just happens to be an easy way to trigger this. And yes, the error
that causes Firefox to crash is actually before this. Consider my first
mail in this thread as additional bug report, unrelated to Firefox in any
way. I know that fixing "wrong fault address after int 3" will not cure
Firefox, but it's a bug anyway, if I understand that correctly.

> Anyway, I don't think that QEMU handles INT 3 at all; the fault must
> be somewhere else. Are you absolutely sure your Firefox build isn't
> calling MMX/SSE instructions? Is it a contributed build or is it
> official?

It is the official build, and it runs perfectly on old i586 machines.

-- 
Alexander E. Patrakov