[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 15:27:00 GMT 2017


Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
                 CC|                            |mark at klomp dot org

--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
I haven't investigated fully yet.
But I did take a quick look at the paes_s390.ko.debug file.
A few quick comments as early feedback.

Note that it doesn't contain .debug_frame but only a .eh_frame section.
Other architectures force .debug_frame for kernel modules to store the CFI.

The .eh_frame is a loaded section, which means it won't go into the .debug
file. So you would need to load the CFI from the main ELF .ko.

One tricky issue here is the fact that kernel modules are ET_REL files
that still need relocations applied (you can see there is also a .rela.eh_frame
section). libdwfl can do simple relocations, but might not know about all
relocation types used in an .eh_frame section (I haven't checked yet).

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