On Tue, May 21, 2024 at 12:08 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote: > > On Tue, 2024-05-21 at 11:54 -0700, Andrii Nakryiko wrote: > > [...] > > > I'm probably leaning towards not doing automatic relocations in > > btf__parse(), tbh. Distilled BTF is a rather special kernel-specific > > feature, if we need to teach resolve_btfids and bpftool to do > > something extra for that case (i.e., call another API for relocation, > > if necessary), then it's fine, doesn't seems like a problem. > > My point is that with current implementation it does not even make > sense to call btf__parse() for an ELF with distilled base, > because it would fail. True (unless application loaded .BTF.base as stand-alone BTF first, but it's pretty advanced scenario) > > And selecting BTF encoding based on a few retries seems like a kludge > if there is a simple way to check if distilled base has to be used > (presence of the .BTF.base section). agreed > > > Much worse is having to do some workarounds to prevent an API from > > doing some undesired extra steps (like in resolve_btfids not wanting a > > relocation). Orthogonality FTW, IMO. > > For resolve_btfids it is a bit different, imo. > It does want some base: for in-tree modules it wants vmlinux, > for out-of-tree it wants distilled base. > So it has to be adjusted either way. Ok, so I read some more code and re-read your discussion w/ Alan. I agree with your proposal, I think it's logical (even if relocation does feel a bit "extra" for "parse"-like API, but ok, whatever). I see what you are saying about resolve_btfids needing the changes either way, and that's true. But instead of adding (unnecessary, IMO) -R argument, resolve_btfids should be able to detect .BTF.base section presence and infer that this is distilled BTF case, and thus proceed with ignoring `-B <vmlinux>` argument (we can even complain that `-B vmlinux` is specified if distilled BTF is used, not sure.
