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

[Hui Zhu <teawater@gmail.com>]

On Fri, Apr 30, 2010 at 17:33, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
>> 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?
>

Prec must know the each base of segment register.

If you don't like it.  What about the old way that I use?  It doesn't
add anything to reg list.
But for the each way, we need add interface to the target part that
prec can get the value.

Thanks,
Hui