Re: %gs:0 thread pseudoregister in oskit-mach

[Farid Hajji]

Roland McGrath wrote:

> > I know this is irrelevant for oskit-mach proper, but it may be
> > interesting to know if you're introducing any dependency in,
> > say, glibc/pthreads:
> > 
> >   In the L4 V4 spec, Appendix A (x86 Interface), register %gs
> >   is used to point to the UTCB of the current thread (read-only).
> 
> You may need to change that.  The %gs:0 word will become part of the
> ELF/x86 ABI for TLS support.

Huston, we're gonna have a BIG problem!

The UTCB is a central information page for L4 userspace threads
and it's pretty difficult to find another x86 register that can
be used to point to it.

Espen, I know the spec can't be changed at this point. Do you see
any workaround for this problem?

Regards,

-Farid.

-- 
Farid Hajji -- Unix Systems and Network Admin | Phone: +49-2131-67-555
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