Messages in this thread | | | Date | Mon, 14 Aug 2006 08:55:28 +0200 | From | "Jan Beulich" <> | Subject | Re: [patch] i386: annotate the rest of entry.s::nmi |
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>> I understand now, but am still uncertain >> about the need to annotate FIX_STACK() - especially since you use >> .cfi_undefined, meaning the return point cannot be established anyway. >> If at all I'd annotate the initial pushes with either just the normal >> CFI_ADJUST_CFA_OFFSET, and the final one with one setting back the >> CFA base to the now adjusted frame. That way, until the pushes are >> complete the old frame will be used for determining the call origin, >> and once complete the (full) new state will be used. > >But that's the whole point of the new annotations -- we have just >overwritten %esp with a new value and the old assumptions are >completely broken: > > movl TSS_sysenter_esp0+offset(%esp),%esp; \ > >After this the old frame cannot be located by using %esp as a base >and the new frame is incomplete. So the only choice is to make eip >undefined until the new value is available -- if not then the >unwinder will try to use whatever random values are on the new frame. >Either that or I'm still unclear on how unwind works...
Hmm, yes, on a second look I agree.
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