Josh Poimboeuf <jpoim...@redhat.com> writes: > On Sun, Mar 27, 2022 at 09:09:20AM +0000, Christophe Leroy wrote: >> Second point is the endianess and 32/64 selection, especially when >> crossbuilding. There is already some stuff regarding endianess based on >> bswap_if_needed() but that's based on constant selection at build time >> and I couldn't find an easy way to set it conditionaly based on the >> target being built. >> >> Regarding 32/64 selection, there is almost nothing, it's based on using >> type 'long' which means that at the time being the target and the build >> platform must both be 32 bits or 64 bits. >> >> For both cases (endianess and 32/64) I think the solution should >> probably be to start with the fileformat of the object file being >> reworked by objtool. > > Do we really need to detect the endianness/bitness at runtime? Objtool > is built with the kernel, why not just build-in the same target > assumptions as the kernel itself?
I don't think we need runtime detection. But it will need to support basically most combinations of objtool running as 32-bit/64-bit LE/BE while the kernel it's analysing is 32-bit/64-bit LE/BE. >> 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?). > 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. cheers
