Re: [PATCH] Pentium Pro - sysenter - doublefault

[Jamie Lokier]

Jakob Oestergaard wrote:
> > Jim you can answer this as you have such a Ppro.  Could you please run
> > this very simple userspace program for me, and report the result?
> > 
> > 	int main() { __asm__ ("sysenter"); return 0; }
> 
> I tested on two boxes:
> 
> Stepping 1 ppro:  SIGSEGV
> Stepping 7 ppro:  SIGSEGV

Thank you!

So that means the sysenter instruction _does_ exist on the PPro and
early Pentium II, but it isn't usable.

It's safe so long as it is disabled, but as you found, when you enable
and use it, it doesn't work as expected.  (I wonder what the actual
behaviour of sysenter/sysexit are on these CPUs.)

-- Jamie
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