Hello Zwane,
Zwane Mwaikambo wrote:
>
> > On Mon, 11 Jul 2005, Oleg Nesterov wrote:
> >
> > Could you explain this change? I think it breaks do_signal/handle_signal,
> > they check orig_eax >= 0 to handle -ERESTARTSYS:
> >
> > /* Are we from a system call? */
> > if (regs->orig_eax >= 0) {
> > /* If so, check system call restarting.. */
> > switch (regs->eax) {
> > case -ERESTART_RESTARTBLOCK:
> > case -ERESTARTNOHAND:
>
> The change is so that we can send IRQs higher than 256 to do_IRQ. That
> looks like it tries to check if we came in via system_call since we'd save
> the system call number as orig_eax. Now that i think about it, doesn't
> that path always get taken when we interrupt userspace and have pending
> signals on return from interrupt?
As far as I can see, we always have orig_eax < 0 on interrupt, because
irq_entries_start:
pushl $vector-256 <----- orig_eax
jmp common_interrupt
and NR_IRQS < 256. So if we have pending signals on return from interrupt,
do_signal() will not corrupt userspace registers when regs->eax == -ERESTART...
accidentally.
Probably it makes sense to change it to
pushl $vector - 0xFFFF - 1
and in do_IRQ()
int irq = regs->orig_eax & 0xFFFF
if you need to send IRQs higher than 256 to do_IRQ.
Oleg.
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