Re: [PATCH bpf-next] libbpf: Ignore the modules that failed to load BTF object

[Bixuan Cui]

在 2025/10/29 2:21, Alan Maguire 写道:
> > It's not an expected condition to have kernel module with corrupted
> > BTF, so I don't think we should be doing this.
> >
> > pw-bot: cr
> Would be good to understand this failure better. If the module is being
> built out-of-tree with relatively new pahole, it will have a .BTF.base
> section and a .BTF section; the .BTF.base section allows the module to
> carry stable references to vmlinux BTF types which then get fixed up to
> the real vmlinux BTF id references when the module is loaded. It is
> possible there are bugs in that code however, so it woul be good to
> figure that out. bpftool should dump BTF for your module using the
> .BTF.base section as base, so
>
> bpftool btf dump file mymod.ko
>
> should work (provided "objdump -h mymod.ko" shows a .BTF.base and .BTF
> section).  If it does, the BTF id relocation may be breaking and we
> might need to do further digging to understand where. It should relocate
> BTF kfunc ids also, but again there may be a bug lurking here.
>
> If the BTF is loading into the kernel, comparing
>
> bpftool btf dump -B /sys/kernel/btf file /sys/kernel/btf/mymod
>
> ...to the .ko BTF would be valuable.
>
> If your module only has a .BTF section and no .BTF.base section, it is
> possible it did not get (re)built against an updated vmlinux and has
> outdated type id references as a result.
Thank you, I will first look at the error reported by this module.

Bixuan Cui