Date: Fri, 1 Nov 1996 22:37:39 +0100 (MET) From: J Wunsch <j@uriah.heep.sax.de> To: freebsd-hackers@freebsd.org (FreeBSD hackers) Subject: Re: VM answer requested Message-ID: <199611012137.WAA23428@uriah.heep.sax.de> In-Reply-To: <199611011842.LAA28151@phaeton.artisoft.com> from Terry Lambert at "Nov 1, 96 11:42:21 am"
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As Terry Lambert wrote: > What about the aligned access bit in recent Intel processors? > > I'd like to be able to turn on the bit so that I get a fault (and it > kills the offending process) when an unaligned access occurs. Adding support for this should be fairly simple. I wonder why you didn't simply implement it yourself and faced us with a comparision of the results. :-) If i got it right, it requires a little magic inside machdep.c (depending on the detected CPU type), and another case label in trap.c. However, i don't think you can _force_ the AC flag, even not for a user program. Modifying the flag is IMHO not a privileged instruction, hence any user program can revert it. > I'd also like to get kernel faults if this happens in the kernel According to my 486 docs, this is impossible. The AC flag is only honored in `ring 3' mode. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)
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