On Thu, Oct 19, 2017 at 03:24:51PM +0200, Miroslav Benes wrote: > On Thu, 19 Oct 2017, Josh Poimboeuf wrote: > > > On Wed, Oct 11, 2017 at 09:42:09AM -0300, Joao Moreira wrote: > > > > Sounds good! For klp-convert to be successful, we really need a > > > > strategy for dealing with such optimizations. I'm thinking that a > > > > '-fpreserve-function-abi' flag would be the cleanest way to handle it. > > > > > > > > If we don't have a strategy for dealing with optimizations, then we may > > > > instead need to go with a binary diff-based tool like kpatch-build. > > > > > > I'm currently looking into binary diff-based solutions to deal with this > > > problem. My plan is to submit a second patch set once I have it functional > > > and land both things (klp-convert and bin-diff) in two different steps. > > > > Instead of having multiple approaches, I'd strongly prefer that we > > converge on a single in-tree approach that works for everybody. > > > > (Whether that will be source-based like klp-convert or binary-based like > > kpatch-build, I don't know.) > > I think that klp-convert can work with both. Even with non-source-based > solution you need something to generate those relocation records. I > consider klp-convert as a part of the building pipeline.
Hm. If I understand correctly, the binary diff tool (or some tool in the pipeline) would create the .klp.module_relocs.* section, and then klp-convert would convert that to the .klp.sym.* and .klp.rela.* sections which livepatch needs. But if the original tool is creating a relocation section, can't it instead just create the livepatch .klp.* sections directly? What's the benefit of the extra conversion step? > > BTW, what is bin-diff? Have you seen kpatch-build? > > I'm speaking for Joao here, but we discussed this personally and I think > he meant approach based on asmtool > (https://github.com/joergroedel/asmtool). We'd like to explore as much as > possible. Ok, I'd be interested in seeing that, and also what its benefits are compared to kpatch-build. > We also considered complete source-based solution. Nicolai Stange works on > that (or at least on something which would make it possible). What is a complete source-based solution? Is it just "klp-convert + some GCC optimization strategy" or is it something more? > We can decide what to have in upstream afterwards. But I still think that > klp-convert will be part of it in some form. Am I missing something? I guess it really depends on what the solution looks like. If we decided on kpatch-build (or some variation of its tooling) then we might not need klp-convert. > > > Is there any issue with following this schedule? Meaning, do you guys > > > still > > > plan on reviewing this patch set or do you prefer me to do something > > > differently in terms of approach? > > > > IMO, klp-convert will only be useful if we have a realistic strategy for > > dealing with GCC optimizations. So I'd say we should follow through on > > that with the compiler folks before spending too much more time on it. > > Yes, I'm all for a solution on GCC side, but that may take a while and > even then it is still a huge step to get it into a distribution (we have > GCC 4.8.5 in SLE12 :)). > > However, there is an easy temporary solution. You can add all > referenced optimized functions to a livepatch and let klp-convert process > the rest. How do you find all referenced optimized functions? -- Josh
