On Mon, Jul 02, 2018 at 05:48:32PM +0200, Michael Matz wrote:
> Hi,
>
> On Thu, 28 Jun 2018, Jeff Law wrote:
>
> > I believe "dumb" is referring to the fact that we're already in a bit of
> > a weird state as evidenced by the NULL FDE. Blindly trying to read the
> > contents of the PC that we couldn't map to an FDE is, IMHO, dumb.
> >
> > One might even be able to argue in this day and age that we should have
> > suitable descriptors for everything. If no suitable descriptor is found
> > then backtracing should stop. Lack of suitable descriptors in any code
> > would be considered a bug in that scenario.
>
> I disagree. ASM code often lacks unwind descriptors (now less than in the
> past, but still). My rule of thumb is always: no descriptor -> has to be
> a framepointer-using routine with standard calling sequence. (I.e.
> declare the combination of no descriptor and no fp to be a bug). Some of
> the callee-saved register will temporarily be wrong but unwinding can
> continue.
Doesn't that clash with the x86-64 ABI which says what kind of FDE use by
default if none is found (essentially a standard leaf routine that doesn't
change sp, nor save any registers)?
Jakub
