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From: alexande@drivax.UUCP (Mark Alexander)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 386 rumors, questions, and comments
Message-ID: <2372@drivax.UUCP>
Date: Fri, 11-Sep-87 13:29:44 EDT
Article-I.D.: drivax.2372
Posted: Fri Sep 11 13:29:44 1987
Date-Received: Sat, 12-Sep-87 21:37:24 EDT
References: <1014@vi.ri.cmu.edu> <1197@cartan.Berkeley.EDU>
Reply-To: alexande@drivax.UUCP (Mark Alexander)
Organization: Bob-ist Temple of Monterey
Lines: 19
Keywords: protection sun machine
Summary: I/O permission bit map in TSS

In article <1197@cartan.Berkeley.EDU> ballou@wheatena.UUCP (Kenneth R. Ballou) writes:
>	I was surprised while reading the 80386 Programmer's Reference
>Manual to see that in Virtual 8086 mode, the instructions IN, INS, OUT,
>and OUTS are *not* IOPL (I/O Privilege Level) sensitive.  So, for example,
>a user task could reset the CPU in the same way as one resets the 80286 in
>the AT by sending an appropriate command to the 8042.

However, there is an I/O permission bitmap in the TSS that protects
against unwanted I/O instructions.  So if the OS sets up the TSS
correctly, the system will be protected.

[stuff
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-- 
Mark Alexander	...{hplabs,seismo,sun,ihnp4}!amdahl!drivax!alexande
"Bob-ism: the Faith that changes to meet YOUR needs." -- Bob