Article View: comp.sys.ibm.pc
Article #43695Re: Brain-dead 286 - summary
From: Ralf Brown
Date: Thu, 08 Mar 1990 12:43
Date: Thu, 08 Mar 1990 12:43
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In article <4983@jarthur.Claremont.EDU> jmerrill@jarthur.Claremont.EDU (Confusion Reigns) writes:
}from getting out of line. The 286's lack of a protected -> real switch is
}not an obstacle to any 'random program'; observe the hack involving
}resetting the chip. Your 'random program' could do that just as easily as
}send the protected -> real instruction to the 386.
Not quite the same. The 386 protected->real switch can only be executed by a
process running at the greatest (kernel) privilege. And on a 386, the I/O
space can be virtualized such that unprivileged processes can't tell the
keyboard controller to reset the CPU.
--
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DISCLAIMER? | _How_to_Prove_It_ by Dana Angluin 3. by vigorous handwaving:
What's that?| Works well in a classroom or seminar setting.
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!pt.cs.cmu.edu!b.gp.cs.cmu.edu!ralf From: ralf@b.gp.cs.cmu.edu (Ralf Brown) Newsgroups: comp.sys.ibm.pc Subject: Re: Brain-dead 286 - summary Message-ID: <8332@pt.cs.cmu.edu> Date: 8 Mar 90 12:43:17 GMT References: <8681@rosevax.Rosemount.COM> <29405@amdcad.AMD.COM> <4983@jarthur.Claremont.EDU> Distribution: usa Organization: Carnegie-Mellon University, CS/RI Lines: 15