Re: [Fwd: Re: [RFA 3/5] Prec: x86 segment register support: target]

[Mark Kettenis <mark dot kettenis at xs4all dot nl>]

> From: Hui Zhu <teawater@gmail.com>
> Date: Fri, 30 Apr 2010 14:29:09 +0800
> 
> On Thu, Mar 25, 2010 at 10:14, Hui Zhu <teawater@gmail.com> wrote:
> > On Thu, Mar 25, 2010 at 02:44, Doug Evans <dje@google.com> wrote:
> >>
> >> On Mon, Mar 22, 2010 at 7:59 PM, Hui Zhu <teawater@gmail.com> wrote:
> >> > On Tue, Mar 23, 2010 at 02:47, Doug Evans <dje@google.com> wrote:
> >> >> On Mon, Mar 22, 2010 at 11:26 AM, Michael Snyder <msnyder@vmware.com> wrote:
> >> >>> I'd just like to point out that while all this sounds great,
> >> >>> it shouldn't be a prerequisite to the original task of just
> >> >>> getting prec to record the segments and offsets correctly.
> >> >>>
> >> >>> Maybe we should split these two tasks, so that Teawater can
> >> >>> go ahead and accomplish his.
> >> >>
> >> >> To the extent that they can be split, IWBN alright.
> >> >>
> >> >> I wonder if the interface is sufficient though (setting aside where to
> >> >> put it and how it will look).
> >> >> Any particular o/s might not provide sufficient hooks of course.
> >> >> linux's modify_ldt, AIUI, let's one change more than just foo_base.
> >> >> NativeClient http://code.google.com/p/nativeclient/ uses it, for example.
> >> >>
> >> >
> >> > Thanks Doug.
> >> >
> >> > I suggest we support segment base step by step.
> >> > When the OS that support it will show the xxx_base to user, the
> >> > unsupport OS will show nothing.
> >> >
> >> > What do you think about it?
> >>
> >> Is supporting segment base sufficient?
> >> Or do you also need to support, e.g., segment limit and flags too?
> >> There may be more, but they're the two that come to mind.
> >> [That's what I was referring to regarding whether the interface was sufficient.]
> >
> > Prec just need the base to get the insn memory operate address. ?Do
> > you think we need other message of segment?
> >
> > If need, do we need divide all message like eflags?
> >
> > Thanks,
> > Hui
> >
> 
> Hi all,
> 
> X86 looks stab now.  Shall we wake up this patch?

Thanks for the reminder.

Let me first ask a question.  What do people expect out of this?  Do
they really want support for fully segmented code, or is it just for
small deviations like accessing per-thread storage through %fs/%gs?