> -----Original Message-----
> From:	Peter Teichmann [SMTP:teich-p@Rcs1.urz.tu-dresden.de]
> Sent:	Thursday, October 22, 1998 4:44 PM
> To:	Gilbert, Christopher
> Cc:	port-arm32@netbsd.org
> Subject:	RE: Some not working packages use Lesstif or XAw3d
> 
> > ( I'm not too sure on this part, but this is the bit that doesn't
> work...)
> > When an LDM is the last instruction on the end of a page it causes the
> fault
> > to return to the wrong place, IE back to the LDM instruction on the end
> of
> > the page
> > 
> > This is how I interpretted what I've seen.
> 
Oops only posted the message to peter (doh)  Actually having read the doc on
digital's page it does return to the correct place but gets a corrupt
instruction.

> Hm. But if it is that would'nt it be possible to do a workaround in the
> VM system? It should be possible. You could have a look where the fault
> wants to return to. If it is a LDM instruction just before a page boundary
> you increase the return address by 4 so that it points just behind the LDM
> as it should. Could there be problems with such a workaround?
> 
The problem is the overhead on decoding the last instruction on every page
fault, with a page being 4k (I think) which makes for a lot of checks.  It's
also because the problem can be fixed by new silicon,  so the problem
doesn't exist with the CATS and shark which all have rev 3 chips (I think)

Chris









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