Handling division-by-zero

[Norman Feske]

Hi Sven,

> One might call that a proper handling, in fact, it's correct, but it
> would have been very nice to have a real handler inside of core giving a
> simple hint on the error. The current implementation makes it very hard
> to debug such errors (In fact, I had to debug into core to see where the
> 'copy_utcb_to_msgbuf' failed, then into the kernel itself to see what
> was actually signalled to core and then finally into my application's
> threads upon the very faint idea what to look for).
> 
> Furthermore, if the message buffer inside of core would have been big
> enough to take the kernel's ipc, even the initial 'hint' where to start
> debugging would have been missing ;)
> 
> Could you please make core at least a little more verbose at this point?

thanks a lot for this useful suggestion. In fact, currently we set
L4_roottask as exception handler for each thread, which results in the
behaviour you observed. We will investigate how to best remove this
inconvenience. One short-term idea would be registering the pager
thread as both exception handler and page-fault handler and let this
thread print a message on each occurrence of an exception.

Cheers
Norman