Date: Mon, 10 Feb 1997 09:46:22 +0100 From: j@uriah.heep.sax.de (J Wunsch) To: cmott@srv.net (Charles Mott) Cc: freebsd-hackers@freebsd.org Subject: Re: Bus Errors Message-ID: <Mutt.19970210094622.j@uriah.heep.sax.de> In-Reply-To: <Pine.BSF.3.91.970209174624.3664A-100000@darkstar>; from Charles Mott on Feb 9, 1997 17:48:27 -0700 References: <Pine.BSF.3.91.970209174624.3664A-100000@darkstar>
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As Charles Mott wrote: > What does "Bus error" mean? UTSL :-) Various possible reasons. What quickly comes to mind are various access violations, like trying to do direct port IO from an unprivileged program, or messing up the (uh!) segment registers so you get a GPF. Also, there's something with access violations on a mapped region vs. touching unmapped memory, that is currently differentiated between SIGBUS vs. SIGSEGV. We've been recently discussing this (in -core) since it confuses our Linuxulator, and is also inconsisten with other systems. It's likely that somebody will be changed there in the future. I think an unaligned access on a 486+ with the AC flag set causes a SIGBUS, too. On the PDP-11, unaligned access and access to bus addresses that were not existent (and thus timed out in the bus controller) were the original reasons for a SIGBUS. -- 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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