On Wed, 9 Sep 2020 at 07:27, Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> wrote: > > Em Wed, Sep 09, 2020 at 11:02:24AM +0200, Ilya Leoshkevich escreveu: > > On Tue, 2020-09-08 at 13:18 -0700, Andrii Nakryiko wrote: > > > On Mon, Sep 7, 2020 at 9:02 AM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote: > > > > On Sat, 2020-09-05 at 21:16 -0700, Tony Ambardar wrote: > [...] > > > > > Is this expected? Is DEBUG_INFO_BTF supported in general when > > > > > cross-compiling? How does one generate BTF encoded for the > > > > > target endianness with pahole? > > The BTF loader has support for endianness, its just the encoder that > doesn't :-\ > > I.e. pahole can grok a big endian BTF payload on a little endian machine > and vice-versa, just can't cross-build BTF payloads ATM. > > > > Yes, it's expected, unfortunately. Right now cross-compiling to a > > > different endianness isn't supported. You can cross-compile only if > > > target endianness matches host endianness. > > I agree that having this in libbpf is better, it should be done as part > of producing the result of the deduplication phase. > Thanks for confirming this wasn't a case of operator error. My platforms for learning/experimenting with BPF have been small embedded ones, including cross-compiling to different archs, word-size and endianness, which have "helped" me run into multiple problems till now. This one is the first I couldn't work around however... [...] > > > I'm working on extending BTF APIs in libbpf at the moment. Switching > > > endianness would be rather easy once all that is done. With these new > > > APIs it will be possible to switch pahole to use libbpf APIs to > > > produce BTF output and support arbitrary endianness as well. Right > > > now, I'd rather avoid implementing this in pahole, libbpf is a much > > > better place for this (and will require ongoing updates if/when we > > > introduce new types and fields to BTF). > > Right, we could do it right after btf_dedup() and before > btf_elf__write(), doing the same process as in btf_loader.c, i.e. > checking if the ELF target arch is different in endianness and doing the > reverse of the loader. > > > > Hope this plan works for you guys. > > > > That sounds really good to me, thanks! > Andrii and Arnaldo, I really appreciate your working on a proper endianness fix. If you have a WIP or staging branch and could use some help please let me know. Best regards, Tony
