On Mon, Jan 12, 2015 at 11:46:53AM -0800, Andy Lutomirski wrote:
> Dumb example:
>
> pushq_cfi $__KERNEL_DS /* ss */
>
> This doesn't save anything that the unwinder would care about.
And? The unwinder or whatever looks at that info simply ignores stuff it
is not interested in, no?
> Better example:
>
> pushq_cfi \child_rip /* rip */
> CFI_REL_OFFSET rip,0
>
> Doing this with a macro would need a fancier macro.
I'd ask first whether we really need this at all.
> Then there's crap like:
>
> pushq_cfi %rdi
> SCHEDULE_USER
> popq_cfi %rdi
I guess we can add a gas regname argument optional and if it is set, use
it and if not, use the reg itself... Or something like that in the best
effort type of approach.
> I would need to look a lot more carefully to figure out whether this
> would need CFI_REL_OFFSET.
>
> If we actually had a DWARF unwinder in the kernel, maybe we could have
> real test cases :-/
I don't think that's ever going to happen.
I'd say we do the CFI annotation on a best effort basis but not
sacrifice readability in the process. If it can't be annotated, well,
tough luck.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
