[ECOS] Bug in i386 interrupt handler

[ECOS] Bug in i386 interrupt handler

[Phil Hinton]

Hi,

I've been trying to get SCSII interrupt drivers working on the i386 PC
eCos using the latest tree from anoncvs, plus various patches from
Fabrice (PCI config, multi-thread, etc).

In our implementation, DSR's were being posted for the SCSII interrupt 
even though the interrupt handler returns CYG_ISR_HANDLED only.

After further investigation I found a bug in hal_pc_irq
(ecos\packages\hal\i386\arch\current\src\vectors.S).

hal_pc_irq calls the interrupt handler, invokes the hal_intc_ack macro,
then calls interrupt_end.

When the interrupt handler returns, EAX has its returned value, which is
to be passed as an argument to interrupt_end. Since the hal_intc_ack 
macro uses the EAX register, it is first stored to ESI by:

            movl %eax, %esi

The hal_intc_ack macro then uses EAX, and when interrupt_end is
called:

             pushl %edx
             pushl %eax
             call interrupt_end

Instead this should be:

             pushl %edx
             pushl %esi   <----  modification
             call interrupt_end

Did I miss a patch? Anyone having trouble with i386 PC DSR posts?

Phil Hinton
CrosStor Software, Inc.
908-226-0100 ext 138
phil@crosstor.com

Re: [ECOS] Bug in i386 interrupt handler

[Jonathan Larmour]

Phil Hinton wrote:
> 
> The hal_intc_ack macro then uses EAX, and when interrupt_end is
> called:
> 
>              pushl %edx
>              pushl %eax
>              call interrupt_end
> 
> Instead this should be:
> 
>              pushl %edx
>              pushl %esi   <----  modification
>              call interrupt_end
> 
> Did I miss a patch? Anyone having trouble with i386 PC DSR posts?

This does indeed look like it would be a problem. If you can just confirm
that this does fix your problem, I'll update our code here.

Jifl
-- 
Red Hat, 35 Cambridge Place, Cambridge, UK. CB2 1NS  Tel: +44 (1223) 728762
"Plan to be spontaneous tomorrow."  ||  These opinions are all my own fault

Re: [ECOS] Bug in i386 interrupt handler

[Phil Hinton]

Jonathan Larmour wote:

> Phil Hinton wrote:
> > 
> > The hal_intc_ack macro then uses EAX, and when interrupt_end is
> > called:
> > 
> >              pushl %edx
> >              pushl %eax
> >              call interrupt_end
> > 
> > Instead this should be:
> > 
> >              pushl %edx
> >              pushl %esi   <----  modification
> >              call interrupt_end
> > 
> > Did I miss a patch? Anyone having trouble with i386 PC DSR posts?
> 
> This does indeed look like it would be a problem. If you can just confirm
> that this does fix your problem, I'll update our code here.
> 

The SCSII interrupt handling is now working as expected. I also stepped
through the (assembly level) code to make sure the behavior is as expected.

The problem is fixed.

> Jifl
> -- 
> Red Hat, 35 Cambridge Place, Cambridge, UK. CB2 1NS  Tel: +44 (1223) 728762
> "Plan to be spontaneous tomorrow."  ||  These opinions are all my own fault
> 

Phil Hinton
CrosStor Software, Inc.
908-226-0100 ext 138
phil@crosstor.com

RE: [ECOS] Bug in i386 interrupt handler

[Fabrice Gautier]

> -----Original Message-----
> From: Phil Hinton [ mailto:phil@crosstor.com ]
> Subject: [ECOS] Bug in i386 interrupt handler
> 
> Did I miss a patch? Anyone having trouble with i386 PC DSR posts?

I didn't experienced any problem but it really looks like I should have. 

Thanks

-- 
Fabrice Gautier
fabrice_gautier@sdesigns.com