Re: livepatch: reuse module loader code to write relocations

From: Josh Poimboeuf
Date: Thu Nov 12 2015 - 15:32:28 EST

On Thu, Nov 12, 2015 at 03:22:44PM -0500, Jessica Yu wrote:
> Looking into this more, I think we do need one __klp_rela section per
> function being patched. Each rela section is linked to the section to
> which the relocations apply via the rela section's sh_info field. In
> SHT_RELA sections, the sh_info field contains the section index to
> which the relocs apply. We cannot have one single combined rela
> section per object as the call to apply_relocate_add() simply won't
> work, because we would have relocs that apply to different functions
> (and hence different sections).
> So I guess instead of a single field in klp_object specifying the
> __klp_rela section index, we could probably just have an array of
> section indices.

Ok, makes sense, sounds like we need multiple klp relas per object.

I still don't quite understand the benefit of caching the klp_rela
section indices. What problem does it solve? It seems simpler to just
iterate over all the sections in klp_write_object_relocations().

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