Date: Tue, 21 Nov 2000 20:13:07 -0500 (EST) From: Daniel Eischen <eischen@vigrid.com> To: John Baldwin <jhb@FreeBSD.org> Cc: arch@FreeBSD.org, Jonathan Lemon <jlemon@flugsvamp.com> Subject: Re: Thread-specific data and KSEs Message-ID: <Pine.SUN.3.91.1001121201152.11654A-100000@pcnet1.pcnet.com> In-Reply-To: <XFMail.001121171036.jhb@FreeBSD.org>
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On Tue, 21 Nov 2000, John Baldwin wrote:
>
> On 22-Nov-00 Daniel Eischen wrote:
> > On Tue, 21 Nov 2000, Jonathan Lemon wrote:
> >> On Tue, Nov 21, 2000 at 06:51:59PM -0500, Daniel Eischen wrote:
> >> > I'm going to start working on the user-side of the new threads
> >> > library. I need to be able to quickly get at the current KSE
> >> > (or perhaps KSEG). Can we define a register on each architecture
> >> > that should not be used by FreeBSD ABI compliant applications?
> >> > The register doesn't have to be 32 bits or larger, just large
> >> > enough to hold the maximum number of KSEs (or KSEGs).
> >>
> >> Um. On a i386 I'm not sure this will be practical, there aren't
> >> a whole lot of architecturally visible registers for use by the
> >> application.
> >
> > Why can't we use a segment register?
>
> %cs = code segment and is taken
> %ds = data segment and is taken
> %es = not sure, but bet it isn't safe
> %ss = stack, taken
> %fs = per-CPU data
Isn't this kernel-only?
> %gs ? as I mentioned in my other message, this one might be useful for
> addressing a structure of thread-local variables much like %fs is used for
> per-CPU data. It also has value in that supposedly x86-64 (aka k64) has both
> %fs and %gs, but no other seg regs.
All I need is one.
--
"Some may prefer open source, but me, I prefer open bar."
-- Spencer F. Katt
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