Re: FOR REVIEW: New x86-64 vsyscall vgetcpu()

Jakub Jelinek
2006-06-16T15:58:28Z

On Fri, Jun 16, 2006 at 05:37:06PM +0200, Andi Kleen wrote:
> On Friday 16 June 2006 17:31, Zoltan Menyhart wrote:
> > Andi Kleen wrote:
> >
> > > That is not how user space TLS works. It usually has a base a register.
> >
> > Can you please give me a real life (simplified) example?
>
> On x86-64 it's just %fs:offset. gcc is a bit dumb on this and usually
> loads the base address from %fs:0 first.

GCC is not dumb, unless you force it with -mno-tls-direct-seg-refs.
Guess you are bitten by SUSE GCC hack which makes -mno-tls-direct-seg-refs
the default (especially on x86-64 it is a really bad idea).

Jakub