Date: Sat, 08 Nov 1997 19:25:04 +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: <199711080855.TAA00364@word.smith.net.au> In-Reply-To: Your message of "Fri, 07 Nov 1997 19:27:15 -0800." <19971107192715.29070@micron.mini.net>
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> > > 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. > > Well. Te only thing I can think of is to set up a task gate that will > 'jump' you into a 32bit protected mode TSS, preferably the one where you > started. (I'm assuming the kernel's) This was suggested by another respondent. I'd be very interested in knowing how I could arrange such a thing, either overloading the existing syscall callgate or making another for temporary use (I have another free descriptor that I can hijack for the purpose). > When is this code being run? Are we talkign about a during-boot-cycle type > setup, or is the scheduler online and tickign away at this point in time? Both. The initial PnP calls have to be made very early, in order to ascertain system resource availability. Then later a pass can be made to pick up peripheral details. > > 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. > > Hmm. I'. not using kernel code for this. (it's all userland) You've been able to run vm86 stuff in userland for ages; what is it that you are missing? Unless someone can identify any serious security holes in the implementation, vm86 support will stop being optional (at least for the APM case, I hope). mike
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