Re: help with assembly (2)

[Manuel Bouyer <bouyer%antioche.lip6.fr@localhost>]

On Thu, Jan 20, 2005 at 08:52:00PM +0100, Manuel Bouyer wrote:
> Hi,
> Again I'm stuck with some assembly code (I don't know much about i386 
> assembly,
> and I've never mixed assembly and C). I have this code in xen/i386/vector.S:
> #define hypervisor_asm_unmask(num)                      \
>         movl    irq_to_evtchn + (num) * 4,%ecx          ;\
>       movl    HYPERVISOR_shared_info,%eax             ;\
>       lock                                            ;\
>       btrl    %ecx,EVENTS_MASK(%eax)
> (BTW, what does the "lock" instruction ?)
> I need to add a call to this C function at the end of this asm
> statement:
>       pirq_notify(num)
> num being a constant. The prototype for the function is:
> void pirq_notify(int irq);
> 
> I tried
>               pushl   $(num)                                  ;\
>               call    _C_LABEL(pirq_notify) 
> but I get a page fault trap at the first call, with something that doesn't
> make much sense on the stack. So I guess I missed something, but I don't
> know what ... I assume registers are callee-saved, but maybe I'm wrong
> on this.

I've not been able to figure out how to call pirq_notify, however I've
been able to inline the needed hypercall here. Now I need to figure out
how to test a bit in a int32_t array, and avoid the hypercall when not
needed ...

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--