[Bug libdw/22452] Failed to obtain CFI data for a OP_call_frame_CFA when looking for func entrypoc in an s390 kernel module

mark at klomp dot org sourceware-bugzilla@sourceware.org
Fri Nov 17 16:46:00 GMT 2017


--- Comment #9 from Mark Wielaard <mark at klomp dot org> ---
(In reply to H. Brueckner from comment #8)
> (In reply to Mark Wielaard from comment #5)
> > (In reply to Mark Wielaard from comment #4)
> > > So, if you could provide the output of eu-readelf --relocs paes_s390.ko (on
> > > your combined paes_s390.ko containing both code and debug) that would be
> > > helpful.
> > 
> > eu-readelf --debug-dump=frames --relocs paes_s390.ko
> > 
> > would be even better.
> Just attached the output; also the output of the binutils readelf command
> for comparision. I guess that there are some more issues because lots of
> invalid relocations are listed.

Is that eu-readelf from a distro install? Then there is something wrong with
that install. If it is a build from source then make sure LD_LIBRARY_PATH
contains the backends directory that has libebl_s390.so. Otherwise eu-readelf
won't know about machine specific ELF/DWARF mappings (like the relocation

But the output does confirm what I feared. The R_390_PC32 .rela.eh_frame
relocations are not "simple". They are load based.

It might not be too hard to add support for those. But if there is any
possibility to generate .debug_frame based CFI for the s390x kernel modules
that would IMHO a much better/simpler solution because it makes things more in
line with other arches. It should also make the kernel modules smaller. Does
anything actually use the loaded .eh_frame CFI on s390x?

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