Re: Need help in understanding x86 syscall

Coywolf Qi Hunt
2005-08-11T15:13:18Z

On 8/11/05, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Thu, 2005-08-11 at 10:04 -0400, linux-os (Dick Johnson) wrote:
> > Every interrupt software, or hardware, results in the branched
> > procedure being executed with the interrupts OFF. That's why
> > one of the first instructions in the kernel entry for a syscall
> > is 'sti' to turn them back on. Look at entry.S, line 182. This
> > occurs any time a trap occurs as well (Page 26-168, i486
> > Programmer's reference manual). FYI, this is helpful when
> > designing/debugging complex interrupt-service routines since
> > you can execute the interrupt with a software 'INT' instruction
> > (with the correct offset from the IRQ you are using). The software
> > doesn't 'know' where the interrupt came from, HW or SW.
>
> I'm looking at 2.6.13-rc6-git1 line 182 of entry.S and I don't see it.
> Must be a different kernel.
>
> According to the documentation that I was looking at, a trap in x86 does
> _not_ turn off interrupts.
>
...
>
> I don't see a sti here.
>
> -- Steve

He is RBJ, Richard B. Johnson, the LKML defacto official troll.

--
Coywolf Qi Hunt