On Wed, 27 Sep 2006 23:49:49 -0700
Jeremy Fitzhardinge <[email protected]> wrote:
> Andrew Morton wrote:
> > hm. Bigger vmlinux, smaller .text.
> >
>
> Yep.
>
> > It means that we'll hit handle_BUG with that extra EIP pushed on the stack.
> > What does that do to the stack trace, and to the unwinder?
> >
> Dunno. I was hoping Andi would pop up with the appropriate CFI gunk, if
> necessary. But the reason for making it a call was to make it as
> unwindable as possible.
>
> > It'll also muck up the displayed EIP, not that that matters a lot (well, it
> > might matter a bit if the BUG is in an inlined function).
> >
> > We could get the correct EIP by fishing it off the stack (and subtracting
> > five from it?)
> >
>
> Yes, that's possible.
>
> > Or we could assume that BUG doesn't return (it doesn't) and make that call
> > a jmp. But then we'd really lose the EIP.
>
> Right. Or it could save the EIP along with the line and filename.
>
Plan #17 is to just put the BUG inline and then put the EIP+file*+line into
a separate section, then search that section at BUG time to find the record
whose EIP points back at this ud2a.
It's a bit messy for modules, but it minimises the .text impact and keeps
disassembly happy, no?
And if done right it can probably be used by other architectures.
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