> > figuring out what's causing an apparently- spontaneous reboot can
> > be ... difficult.  8-)
> 
> No way at all to gracefully deal with the fault when we hit the
> unmapped page?

That depends largely on the architecture and/or the designer of the
machine. Receiving a trap (as a result of running off the stack)
when there is no more stack available (i.e. hitting the an unmapped page)
is pretty desastrous for most ports. Maybe on some architectures you could
rapidly switch to an "emergency" stack.. I don't know..

The sparc processor, upon hitting a "double" trap, will simply collapse
into an error state. A few special wires between CPU and MMU will cause
a processor reset in this case and set some bits in a control register.
These bits get noticed by the firmware, which then barfs "Watchdog reset"
(and "ok" :-).

I believe sun3's have a similar mechanism, as do alpha's if I understand
from Chris' comment.

-pk