Messages in this thread |  | | Date | Fri, 8 Dec 2000 21:31:59 +0100 (CET) | From | Mikulas Patocka <> | Subject | Re: Why is double_fault serviced by a trap gate? |
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> No no. That's that the whole point of a gate. You make a controlled > transition to ring 0 including stack switching. There are complex > protection checking rules, however as long as the DPL of the gate > descriptor is 3 then ring 3 is allowed to make the transition to ring 0. A > stack fault in user mode cannot kill the system. If it ever did it would be > a blatant bug of the most crass kind.
Setting DPL == 3 of any interrupt/trap/fault gate is bad idea because it allows the user to kill the machine with INT 8 or something like that. DPL is checked only if interrupt is generated with INT, INT3 or INTO (IA manual, vol 3, section 5.10.1.1).
Mikulas
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