On Mon, Jun 20, 2022 at 12:45 AM Arnout Vandecappelle <arn...@mind.be> wrote: > > > > On 20/06/2022 01:19, James Hilliard wrote: > > On Sun, Jun 19, 2022 at 9:20 AM Arnout Vandecappelle <arn...@mind.be> wrote: > >> > >> > >> > >> On 16/06/2022 10:11, Shahab Vahedi wrote: > >>> On 6/16/22 01:27, James Hilliard wrote: > >>>> On Wed, Jun 15, 2022 at 5:10 AM Shahab Vahedi via buildroot > >>>> <buildr...@buildroot.org> wrote: > >>>>> > >>>>> On 6/14/22 19:14, Arnout Vandecappelle wrote: > >>>>>> > >>>>>> On 14/06/2022 11:31, Shahab Vahedi wrote: > >>>>>>> Building bpftool on Debian 11 (bullseye) with kernel v5.10 and > >>>>>>> clang-11 > >>>>>> > >>>>>> How do you build host-bpftool with clang in Buildroot context? > >>>>>> HOSTCC is set to gcc in the Makefile... Do you supply an explicit > >>>>>> HOSTCC= on the Buildroot command line? I'm not sure if we are really > >>>>>> interested in carrying fixes for such exotic and not-really-supported > >>>>>> situations... > >>>>> > >>>>> No, I don't do any sort of trickery to build bpftool on my end. The > >>>>> bootstrapping, if becomes available for your configuration, uses clang > >>>>> and only clang. I tried to explain this in v4 of the patch [1], the > >>>>> second paragraph of the commit message. > >>>> > >>>> I think clang/llvm support isn't going to work correctly yet since we > >>>> only have > >>>> version 9.0.1, there's a series bumping to version 11.1.0 that should > >>>> fix that: > >>>> https://patchwork.ozlabs.org/project/buildroot/list/?series=291585 > >>>> > >>>> Minimum clang/llvm version for libbpf co-re is version 10: > >>>> https://github.com/libbpf/libbpf*bpf-co-re-compile-once--run-everywhere > >>> > >>> You're right about the clang version, but it doesn't have anything to do > >>> with Buildroot's clang. The build process uses the clang that is installed > >>> on the host. For Debian bullseye, that is clang 11. > >> > > >>> To emphasise, I am cross-building bpftool for my "arc-linux" target, and > >>> yet > >>> the bootstrap part of bpftool, uses the x86 clang of the Debian machine. > >> > >> > >> Hm, that smells like we actually want to build host-clang (after > >> updating it > >> to 11.1.0 of course) so that we are sure a known version of clang is used. > >> Possibly with a check-host-clang check to avoid building it if the > >> installed > >> clang is good enough. > > > > Dealing with multiple external clang versions may be a bit tricky and > > difficult > > We do it for GCC, so we can do something similar for clang. > > > to test properly, we don't really want to use the system clang/llvm although > > clang/llvm external toolchain support may be desirable here as those could > > be tested by the autobuilders. > > For GCC, the host toolchain is completely unrelated to the target toolchain. > With clang, it's true that it's possible to use the target compiler for host > builds as well, but don't we still need binutils? So in my mind, there would > be > a separate host clang toolchain and target clang toolchain.
BPF is kinda weird...for both clang and GCC. It's sorta a separate architecture in the compiler...but is also sorta not architecture specific in what it builds for. > > > > It would be good to get clang/llvm updated soon as systemd is now using bpf > > for > > some service security/isolation features that we currently aren't able > > to support > > due to clang/llvm being too old. > > Unfortunately your series is rather large and has no Reviewed or Acked by > tags... So it tends to languish on patchwork. The tested-by for the v12 series ended up in the wrong thread I think: https://lore.kernel.org/buildroot/bn2p110mb16408dc4537e54ef7ecc7906f2...@bn2p110mb1640.namp110.prod.outlook.com/ > > > >> And we probably want a user-visible option to enable co-re then, > >> because it's > >> going to be expensive to build. > > > > We may want to make llvm/clang part of the pre-built toolchains > > eventually, but for > > now I'd say we should just conditionally enable co-re here if we are > > already building > > a clang/llvm toolchain. > > Although I'm usually in favour of automatic dependencies, in this case I'd > say > it's worth adding an explicit config option. > > > > There's some early GCC support for co-re in 12.1 which I was experimenting > > with > > But then it would depend on both host and target GCC >= 12... I thought we don't support GCC on the target. We would essentially have a 2 architecture cross-toolchain(one real target arch, and the BPF virtual architecture compiler/assemblers and such). > > > as well which may reduce the need for a llvm/clang toolchain for co-re. The > > GCC > > toolchain BPF support build process is a bit complex however as one needs to > > sorta do a hybrid multitarget build with GCC and binutils since GCC > > treats BPF as > > a separate target(and since GCC along with the binutils GAS assembler > > don't natively > > handle multi-target toolchain builds themselves). > > Ouch, so we still can't reuse the existing host toolchain for the host > parts? > then it doesn't help that much, does it? We can create a GCC toolchain that can target both BPF and the normal target architecture...but it's sorta a strange multiarch style toolchain. > > Regards, > Arnout > > > > > I have an experimental branch for that here: > > https://github.com/buildroot/buildroot/compare/master...jameshilliard:ebpf > > > > I'll try and clean that up a bit once the GCC 12.1 series it is based > > on is merged: > > https://patchwork.ozlabs.org/project/buildroot/list/?series=302389 > > > >> > >> Regards, > >> Arnout > >> _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
