Date: Thu, 14 May 1998 17:47:36 -0700 From: Mike Smith <mike@smith.net.au> To: Jonathan Lemon <jlemon@americantv.com> Cc: Mike Smith <mike@smith.net.au>, Chuck Robey <chuckr@Glue.umd.edu>, Luigi Rizzo <luigi@labinfo.iet.unipi.it>, Nicolas.Souchu@prism.uvsq.fr, freebsd-hackers@FreeBSD.ORG Subject: Re: ISA PnP / snd PnP developments? Message-ID: <199805150047.RAA00975@antipodes.cdrom.com> In-Reply-To: Your message of "Wed, 06 May 1998 11:32:22 CDT." <19980506113222.38033@right.PCS>
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> No, the showstopper I ran into at this point has to do with stack > handling for the 16-bit BIOS. Consider: > > - the stack must be located in the first 64K following %ss, > (the stack base address) since the BIOS often throws away > the upper 16-bits. eg: push %esp, pop %sp > > - %ss is also used to handle kernel interrupts. > > - trap.c takes a stack-relative address and tries to use this > as an absolute address, which normally works, since the stack > base is normally at 0. This breaks if we change the stack base > location in order to make the BIOS happy. Eek. Trap.c should be able to adjust to be stack-relative though, right? I'm not sure what else depends on the stack location though - you might want to run any proposal past Peter Wemm, who seems to be familiar with the BSD/OS and NetBSD compatibility issues. > So, I either play some tricks to move the stack into page 0, so that > absolute addressing works as well as base:offset addressing, or I need > to come up with some form of switching stacks when the kernel is entered. > > The latter would probably impact fastintr handlers as well, and (IMHO) > generate an unacceptable performance impact. The former is probably > feasable, but finals here have prevented me from looking at it in more > detail. I'm inclined to think that moving the stack is easier, if possible. Failing that, perhaps it'd be simpler to stick to the real-mode interfaces where possible. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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