Date: Sat, 08 Nov 1997 13:08:13 +1030 From: Mike Smith <mike@smith.net.au> To: Jonathan Mini <mini@d198-232.uoregon.edu> Cc: hackers@FreeBSD.ORG Subject: Re: x86 gods; advice? Suggestions? Message-ID: <199711080238.NAA00641@word.smith.net.au> In-Reply-To: Your message of "Fri, 07 Nov 1997 18:16:14 -0800." <19971107181614.32380@micron.mini.net>
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> > > > It has to run with DPL = 0. > > > > > > Why? > > > > Because it has to in order to meet the spec. If you're interested, or > > think you have some ideas on this, you can grab the spec from > > microsoft's website. Make sure you get the clarification as well, as > > there's a very confusing error in one of the critical digrams... > > hehehe. It should be possible to just give it i/o access to all of the ports, > or if you feel parinoid, just a subset, and then ``emulate'' the exception 13 > instruction cases. (there aren't many) Ugh. You are taking a very small piece of code and making it *very* complicated. It *must* be called from inside the kernel because at the point where it's needed there is nowhere else to be calling it from. > Personally, I feel very insecure running a BIOS at DPL = 0. I certainly > woulndn't like letting third party software muck with everything. (even if it > is on a ROM (ok, a flashable ROM)) Like I said, if you have a better idea, I am seriously interested in pursuing it. > > It's actually pretty easy; with any luck I'll be happy enough with the > > vm86 stuff to commit it tomorrow. > > Hear me cheer! I have been working on vm86 BIOS/DOS interaction for a while > now for my own projects. If you have something elegant it will be a godsend. > :) It's not entirely elegant, or even mostly mine, but there's a single-line call you can make anywhere (once its safe to sleep) inside the kernel that will run a vm86-mode interrupt for you. mike
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