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SubjectRe: livepatch: reuse module loader code to write relocations
+++ Josh Poimboeuf [12/11/15 14:32 -0600]:
>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().

I was trying to accomodate Miroslav's dislike of klp_reloc_sec :-)
But now that we are sure that we need multiple __klp_rela sections
per object, I think an array of indices might still be somewhat
complicated (we need to figure out its size and everything, a list
here would be easier). I think it might be fine to leave things the
way they are here.

Jessica


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