> > I'd like to avoid following in the footsteps of the i386 style support
> > particularly because it does require more extensive kernel support than
> > most of the other architectures. I'm still looking over the documentation
> > and the implementation details of the other architectures, but I'll put
> > something together as a proposal before I write any code.
>
> I think there are two possible approaches. As you know we need per thread
> data. This can either be in a register, which would be the fastest option,
> but our current ABI doesn't define one, so it basically means an ABI
> change to reserve a register for it so it doesn't get clobbered.
Plus we already reserve a register for the current task - we're not all
that squeezed, but can't we store the per thread data at a constant offset
from the task address which we already store in a register? Are all
threads separate tasks at kernel level?
> The other possibility is to use a memory location, this requires kernel
> support to update the memory pointer at every task switch (we don't have
> SMP, so it's a lot easier), but it has the advantage that it's otherwise
> backwards compatible.
> IMO the simpler option in the short term is via a memory pointer, an ABI
> change needs a lot more preparation (although it's desirable in the long
> term to also fix other things).
Let's focus on the simpler option first :-)
Michael
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