Messages in this thread | | | Date | Thu, 31 Mar 2022 00:10:20 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [RFC PATCH 3/3] objtool/mcount: Add powerpc specific functions |
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Christophe Leroy wrote: > > > Le 29/03/2022 à 14:01, Michael Ellerman a écrit : >> Josh Poimboeuf <jpoimboe@redhat.com> writes: >>> On Sun, Mar 27, 2022 at 09:09:20AM +0000, Christophe Leroy wrote: >>>> What are current works in progress on objtool ? Should I wait Josh's >>>> changes before starting looking at all this ? Should I wait for anything >>>> else ? >>> >>> I'm not making any major changes to the code, just shuffling things >>> around to make the interface more modular. I hope to have something >>> soon (this week). Peter recently added a big feature (Intel IBT) which >>> is already in -next. >>> >>> Contributions are welcome, with the understanding that you'll help >>> maintain it ;-) >>> >>> Some years ago Kamalesh Babulal had a prototype of objtool for ppc64le >>> which did the full stack validation. I'm not sure what ever became of >>> that. >> >> From memory he was starting to clean the patches up in late 2019, but I >> guess that probably got derailed by COVID. AFAIK he never posted >> anything. Maybe someone at IBM has a copy internally (Naveen?).
Kamalesh had a WIP series to enable stack validation on powerpc. From what I recall, he was waiting on and/or working with the arm64 folks around some of the common changes needed in objtool.
>> >>> FWIW, there have been some objtool patches for arm64 stack validation, >>> but the arm64 maintainers have been hesitant to get on board with >>> objtool, as it brings a certain maintenance burden. Especially for the >>> full stack validation and ORC unwinder. But if you only want inline >>> static calls and/or mcount then it'd probably be much easier to >>> maintain. >> >> I would like to have the stack validation, but I am also worried about >> the maintenance burden. >> >> I guess we start with mcount, which looks pretty minimal judging by this >> series, and see how we go from there. >> > > I'm not sure mcount is really needed as we have recordmcount, but at > least it is an easy one to start with and as we have recordmount we can > easily compare the results and check it works as expected.
On the contrary, I think support for mcount in objtool is something we want to get going soon (hopefully, in time for v5.19) given the issues we are seeing with recordmcount: - https://github.com/linuxppc/issues/issues/388 - https://lore.kernel.org/all/20220211014313.1790140-1-aik@ozlabs.ru/
- Naveen
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