xdp fails to attach dispatcher

Question

xdp fails to attach dispatcher

gizahNL opened this issue 3 years ago · comments

And unfortunately doesn't fall back to single program mode.

libbpf: elf: skipping unrecognized data section(7) .xdp_run_config
libbpf: elf: skipping unrecognized data section(7) xdp_metadata
libbpf: prog 'xdp_dispatcher': BPF program load failed: Invalid argument
libbpf: prog 'xdp_dispatcher': -- BEGIN PROG LOAD LOG --
Validating prog0() func#1...
btf_vmlinux is malformed
Arg#0 type PTR in prog0() is not supported yet.
processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
-- END PROG LOAD LOG --
libbpf: failed to load program 'xdp_dispatcher'
libbpf: failed to load object './xdp-dispatcher.o'
libxdp: Failed to load dispatcher: Invalid argument

Kernel version is: 5.10.109

Toke Høiland-Jørgensen · Answer 1 · Mon Apr 04 2022 23:14:28 GMT+0800 (China Standard Time)

Gijs Peskens ***@***.***> writes:

And unfortunately doesn't fall back to single program mode. ``` libbpf: elf: skipping unrecognized data section(7) .xdp_run_config libbpf: elf: skipping unrecognized data section(7) xdp_metadata libbpf: prog 'xdp_dispatcher': BPF program load failed: Invalid argument libbpf: prog 'xdp_dispatcher': -- BEGIN PROG LOAD LOG -- Validating prog0() func#1... btf_vmlinux is malformed Arg#0 type PTR in prog0() is not supported yet. processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0 -- END PROG LOAD LOG -- libbpf: failed to load program 'xdp_dispatcher' libbpf: failed to load object './xdp-dispatcher.o' libxdp: Failed to load dispatcher: Invalid argument ```

What kernel version are you running this on?

Gijs Peskens · Answer 2 · Mon Apr 04 2022 23:15:38 GMT+0800 (China Standard Time)

Gijs Peskens @.***> writes:
And unfortunately doesn't fall back to single program mode. libbpf: elf: skipping unrecognized data section(7) .xdp_run_config libbpf: elf: skipping unrecognized data section(7) xdp_metadata libbpf: prog 'xdp_dispatcher': BPF program load failed: Invalid argument libbpf: prog 'xdp_dispatcher': -- BEGIN PROG LOAD LOG -- Validating prog0() func#1... btf_vmlinux is malformed Arg#0 type PTR in prog0() is not supported yet. processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0 -- END PROG LOAD LOG -- libbpf: failed to load program 'xdp_dispatcher' libbpf: failed to load object './xdp-dispatcher.o' libxdp: Failed to load dispatcher: Invalid argument
What kernel version are you running this on?

Sorry, ninja edited before you replied.. Kernel is 5.10.109

Toke Høiland-Jørgensen · Answer 3 · Mon Apr 04 2022 23:29:36 GMT+0800 (China Standard Time)

btf_vmlinux is malformed

Hmm, so this indicates something odd is going on with that kernel; did you compile it yourself?

Gijs Peskens · Answer 4 · Mon Apr 04 2022 23:32:40 GMT+0800 (China Standard Time)

Yes it's compiled part of a custom video broadcast based distribution.

Arg#0 type PTR in prog0() is not supported yet.

I believe that's the cause btw. With the patch I submitted via the PR it is successful in attaching both the default XDP sock program and our custom program.

Toke Høiland-Jørgensen · Answer 5 · Mon Apr 04 2022 23:43:59 GMT+0800 (China Standard Time)

Ah, the fallback fails because libbpf is once again changing things in a non-backwards-compatible manner; see 2eda2145ebfc ("libbpf: Preserve kernel error code and remove kprobe prog type guessing"). So the check we have to detect the verifier error fails...

Gijs Peskens · Answer 6 · Mon Apr 04 2022 23:47:12 GMT+0800 (China Standard Time)

Ah, the fallback fails because libbpf is once again changing things in a non-backwards-compatible manner; see 2eda2145ebfc ("libbpf: Preserve kernel error code and remove kprobe prog type guessing"). So the check we have to detect the verifier error fails...

Oh joy... If the kernel verifier can throw more errors than the one I checked against than my patch might not be sufficient :/