iovisor-dev@lists.iovisor.org | Error loading xdp program that worked with bpf_load

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Error loading xdp program that worked with bpf_load

Jesper Dangaard Brouer #1859 (Cross-posting to iovisor-dev) Seeking input from BPF-llvm developers. How come Clang/LLVM 10+ is generating incompatible BTF-info in ELF file, and downgrading to LLVM-9 fixes the issue ? toggle quoted message Show quoted text On Wed, 10 Jun 2020 14:50:27 -0700 Elerion <elerion1000@...> wrote: Never mind, I fixed it by downgrading to Clang 9. It appears to be an issue with Clang/LLVM 10+ https://github.com/cilium/ebpf/issues/43 On Wed, Jun 10, 2020 at 2:38 PM Toke Høiland-Jørgensen <toke@...> wrote: Elerion <elerion1000@...> writes: [69] FUNC xdp_program type_id=68 vlen != 0 'vlen != 0' is the error. Not sure why you hit that; what's the output of 'bpftool btf dump file yourprog.o' ? -Toke -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
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Andrii Nakryiko #1860 On Thu, Jun 11, 2020 at 4:00 AM Jesper Dangaard Brouer <brouer@...> wrote: (Cross-posting to iovisor-dev) Seeking input from BPF-llvm developers. How come Clang/LLVM 10+ is generating incompatible BTF-info in ELF file, and downgrading to LLVM-9 fixes the issue ? On Wed, 10 Jun 2020 14:50:27 -0700 Elerion <elerion1000@...> wrote: Never mind, I fixed it by downgrading to Clang 9. It appears to be an issue with Clang/LLVM 10+ https://github.com/cilium/ebpf/issues/43 This is newer Clang recording that function is global, not static. libbpf is sanitizing BTF to remove this flag, if kernel doesn't support this. But given this is re-implementation of libbpf, that's probably not happening, right? On Wed, Jun 10, 2020 at 2:38 PM Toke Høiland-Jørgensen <toke@...> wrote: Elerion <elerion1000@...> writes: [69] FUNC xdp_program type_id=68 vlen != 0 'vlen != 0' is the error. Not sure why you hit that; what's the output of 'bpftool btf dump file yourprog.o' ? -Toke -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
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Alexei Starovoitov #1861 On Thu, Jun 11, 2020 at 9:35 AM Andrii Nakryiko <andrii.nakryiko@...> wrote: On Thu, Jun 11, 2020 at 4:00 AM Jesper Dangaard Brouer <brouer@...> wrote: (Cross-posting to iovisor-dev) Seeking input from BPF-llvm developers. How come Clang/LLVM 10+ is generating incompatible BTF-info in ELF file, and downgrading to LLVM-9 fixes the issue ? On Wed, 10 Jun 2020 14:50:27 -0700 Elerion <elerion1000@...> wrote: Never mind, I fixed it by downgrading to Clang 9. It appears to be an issue with Clang/LLVM 10+ https://github.com/cilium/ebpf/issues/43 This is newer Clang recording that function is global, not static. libbpf is sanitizing BTF to remove this flag, if kernel doesn't support this. But given this is re-implementation of libbpf, that's probably not happening, right? just running ./test_xdp_veth.sh on the latest bpf-next with the latest clang I see: BTF debug data section '.BTF' rejected: Invalid argument (22)! - Length: 514 Verifier analysis: ... [11] VAR _license type_id=9 linkage=1 [12] DATASEC license size=0 vlen=1 size == 0 BTF debug data section '.BTF' rejected: Invalid argument (22)! - Length: 494 Verifier analysis: ... [11] VAR _license type_id=9 linkage=1 [12] DATASEC license size=0 vlen=1 size == 0 BTF debug data section '.BTF' rejected: Invalid argument (22)! 11] VAR _license type_id=9 linkage=1 [12] DATASEC license size=0 vlen=1 size == 0 PING 10.1.1.33 (10.1.1.33) 56(84) bytes of data. 64 bytes from 10.1.1.33: icmp_seq=1 ttl=64 time=0.042 ms --- 10.1.1.33 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.042/0.042/0.042/0.000 ms selftests: xdp_veth [PASS] Is that just the noise from libbpf probing or what?
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Andrii Nakryiko #1862 On Thu, Jun 11, 2020 at 1:41 PM Elerion <elerion1000@...> wrote: I am using libbpf from here https://github.com/libbpf/libbpf I'm not using ebpf. I just linked to the ebpf issue because it seems like the only thing related to this problem when I googled it. Ok, that I can help with, then. What's the kernel version? Where I can find repro? Steps, etc. Basically, a bit more context would help, as I wasn't part of initial discussion. On Thu, Jun 11, 2020 at 9:34 AM Andrii Nakryiko <andrii.nakryiko@...> wrote: On Thu, Jun 11, 2020 at 4:00 AM Jesper Dangaard Brouer <brouer@...> wrote: (Cross-posting to iovisor-dev) Seeking input from BPF-llvm developers. How come Clang/LLVM 10+ is generating incompatible BTF-info in ELF file, and downgrading to LLVM-9 fixes the issue ? On Wed, 10 Jun 2020 14:50:27 -0700 Elerion <elerion1000@...> wrote: Never mind, I fixed it by downgrading to Clang 9. It appears to be an issue with Clang/LLVM 10+ https://github.com/cilium/ebpf/issues/43 This is newer Clang recording that function is global, not static. libbpf is sanitizing BTF to remove this flag, if kernel doesn't support this. But given this is re-implementation of libbpf, that's probably not happening, right? On Wed, Jun 10, 2020 at 2:38 PM Toke Høiland-Jørgensen <toke@...> wrote: Elerion <elerion1000@...> writes: [69] FUNC xdp_program type_id=68 vlen != 0 'vlen != 0' is the error. Not sure why you hit that; what's the output of 'bpftool btf dump file yourprog.o' ? -Toke -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
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