> I think the only call to cpu_switch is from mi_switch, as such its
> current return value (the proc pointer) is never actually used.

Then why not just redefine its return value in toto?

> This means that the botton 2 bits of the return value are currently
> always zero.

But do you want to assume something like that about pointers, in MI
code?  I wouldn't.  (Cf the NetBSD/pdp10 effort - I don't know what
their pointer format looks like, but it wouldn't surprise me at all if
it broke assumptions like your "any valid struct proc *'s low two bits
are zero".  Word-addressed machines are like that.)

/~\ The ASCII				der Mouse
\ / Ribbon Campaign
 X  Against HTML	       mouse@rodents.montreal.qc.ca
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B