Messages in this thread | | | Date | Thu, 31 May 2012 14:09:05 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 4/5] x86: Allow nesting of the debug stack IDT setting |
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On 05/31/2012 01:56 PM, Steven Rostedt wrote: > On Thu, 2012-05-31 at 13:39 -0700, H. Peter Anvin wrote: >> On 05/31/2012 01:35 PM, Steven Rostedt wrote: >>> >>> Thus only the debug stack does the stack TSS trick. >>> >>> Is this what you were looking for? (God, it just shows how much time >>> I've been spending on this crap, as I was able to find all this by >>> memory and not grepping for it :-p ) >>> >> >> That's why I asked instead of pulled it up myself. >> >> However, what is missing is what the permitted transitions are. This >> affects the options. > > Only the debug stack changes. These happen in the two places I already > mentioned. > > One, the switch of the IDT in NMI (to convert the IST from 4 to 0, and > just keep the same stack). > > Two, is the trick in the paranoidzeroentry_ist code (adding the debug > stack). That changes the DEBUG stack pointer. >
No, I'm asking what environments (alternate stacks) are permitted where. That is the important information.
The interaction of the above two things is part of the problem, of course, and I think it can (and should) be avoided.
-hpa
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