[coyotos-dev] Last IDL issue

[Jonathan S. Shapiro]

On Tue, 2007-07-10 at 09:47 -0700, Charles Landau wrote:
> At 12:25 PM -0400 7/10/07, Jonathan S. Shapiro wrote:
> >There is another IDL issue. It's not really a discussion topic; this is
> >more of a status update.
> >
> >We initially thought that the Coyotos syscall interface should use
> >capitem_t. A capitem_t is a discriminated union that can either be a
> >memory address or a register number.
> >
> >That implementation looked pretty ugly, so we switched to a scheme where
> >the kernel-level interface wants registers but the system call has four
> >phases:
> >
> >    load multiple caps
> >    send phase
> >    receive phase
> >    store multiple caps
> 
> I'm guessing the capability registers into which the caps are loaded 
> and from which they are stored are dedicated registers.

Actually, that was not the original plan -- which is part of why this
doesn't work. For the load phase, there is actually no need to dedicate
registers -- you can have a marshalling structure within the kernel. The
tricky part is the store phase, because you are trying to avoid
receive-side aults.

I'll say more shortly on this. I need to get something else out first.

shap
-- 
Jonathan S. Shapiro, Ph.D.
Managing Director
The EROS Group, LLC