Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 27 Jan 2014 16:44:45 -0800 | Subject | Re: [RFC] de-asmify the x86-64 system call slowpath |
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On Mon, Jan 27, 2014 at 4:22 PM, H. Peter Anvin <hpa@zytor.com> wrote: > On 01/27/2014 02:46 PM, Andy Lutomirski wrote: >> >> I think that sysret for sigreturn is probably not very interesting. >> On the other hand, sysret for #PF might be a huge win, despite being >> even scarier. >> > > SYSRET for #PF or other exceptions is a nonstarter; register state is > live at that point.
I mean sysret-via-trampoline for #PF.
It's scary, it probably has issues with ptrace and interrupts that hit while the trampoline is still running, and it could break anything that writes past the red zone, but I think it could work.
No, I don't particularly want to implement (and debug) such a beast.
(I will continue cursing Intel -- why can't we have a fast way to return to 64-bit userspace with complete control of all non-segment registers? sysret is *almost* the right thing.)
--Andy
> > -hpa > >
-- Andy Lutomirski AMA Capital Management, LLC
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