Messages in this thread | | | Subject | Re: [PATCH v3 0/9] klp-convert livepatch build tooling | From | Joe Lawrence <> | Date | Wed, 24 Apr 2019 15:31:21 -0400 |
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On 4/24/19 3:13 PM, Joao Moreira wrote: >>> Future Work >>> ----------- >>> >>> I don't see an easy way to support multiple homonym <object, name> >>> symbols with unique <position> values in the current livepatch module >>> Elf format. The only solutions that come to mind right now include >>> renaming homonym symbols somehow to retain the relocation->symbol >>> relationship when separate object files are combined. Perhaps an >>> intermediate linker step could make annotated symbols unique in some way >>> to achieve this. /thinking out loud >> I'd set this aside for now and we can return to it later. I think it could >> be quite rare in practice.
I agree, especially since we can detect this corner case and abort the translation.
>> I was thinking about renaming the symbol too. We can extend the symbol >> naming convention we have now and deal with it in klp_resolve_symbols(), >> but maybe Josh will come up with something clever and cleaner. > I think this could work well, but (sorry if I understood Joe's idea > wrongly) not as a linker step. Instead of modifying the linker, I think > we could create another tool and plug it into the kbuild pipeline prior > to the livepatch module linking. This way, we would parse the .o elf > files, check for homonyms and rename them based on a convention that is > later understood by klp-convert, as suggested.
My knowledge of the build tools is limited, so there was a bunch of hand-waving you couldn't see when I wrote that paragraph :) But yes, that is basically the idea: plugging into the kbuild pipeline to give these some kinda of .o-unique prefix that klp-convert would interpret and strip accordingly.
> If I am not missing something, this would fix the case where we have > homonyms pointing to the same or different positions, without additional > user intervention other then adding the SYMPOS annotations. > > If you consider this to be useful I can start experiencing. >
It's not the highest priority, but even a prototype of how to insert a script into the pipeline to achieve this would be massively time saving for myself. If renaming looks easy, we could try to work into the initial klp-convert patchset... if not, save it for a follow up enhancement.
Thanks,
-- Joe
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