On 7/20/20 2:41 PM, Alexei Starovoitov wrote: > On Mon, Jul 20, 2020 at 10:09:43AM +0200, Christoph Hellwig wrote: >> Hi BPF and selftest maintainers. I get a very strange failure >> when trying to build the bpf selftests on current net-next master: >> >> hch@brick:~/work/linux/tools/testing/selftests/bpf$ make >> GEN vmlinux.h >> Error: failed to load BTF from /home/hch/work/linux/vmlinux: No such file or directory > > That's bpftool complaining that BTF is not present in vmlinux. > You need CONFIG_DEBUG_INFO_BTF=y and pahole >= v1.16 > You also need llvm 10 to build bpf progs. > These never ending bumps to required versions to build kernels and bpf code are not friendly to users. Until a recent commit I was able to use Ubuntu 20.04 for bpf development and testing (e.g., the recent devmap changes). Ubuntu 20.04 is an LTS OS released just 3 months ago with pahole 1.15 and llvm 10. Now with v5.8-next 20.04 is out of date. These hard requirements are making BTF inaccessible to average users by *requiring* them to constantly chase new build versions. At this point I can no longer point potential BPF/XDP users to this latest OS and say try it out. Any instructions I write for getting started will be out of date in some arbitrarily short period of time. Worst, it is not even feature based within BTF; it is all or nothing. ie., try to use 5.8-next with Ubuntu 20.04 and you lose all of BTF for all use cases, not just some recently added feature. If you want people to adopt this tech, you need to make it easier to use.
