Re: [patch] i386: annotate the rest of entry.s::nmi

["Jan Beulich" <jbeulich@novell.com>]

>> 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.

Jan