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This function is global ([0]) and libbpf >> expects it to be marked as such in BTF. >> >> https://github.com/systemd/systemd/blob/main/src/core/bpf/restrict_ifaces/restrict-ifaces.bpf.c#L42-L50 >> >> > > How about updating the BTF format documentation in btf.rst to reflect > the specification for BTF_KIND_FUNC ? The below patch sounds good. Could you send a patch for this? Thanks! > > Thanks > > diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst > index f49aeef62d0c..b3a9d5ac882c 100644 > --- a/Documentation/bpf/btf.rst > +++ b/Documentation/bpf/btf.rst > @@ -369,7 +369,7 @@ No additional type data follow ``btf_type``. >    * ``name_off``: offset to a valid C identifier >    * ``info.kind_flag``: 0 >    * ``info.kind``: BTF_KIND_FUNC > -  * ``info.vlen``: 0 > +  * ``info.vlen``: linkage information (static=0, global=1) >    * ``type``: a BTF_KIND_FUNC_PROTO type > >  No additional type data follow ``btf_type``. > >> >>> GCC: >>> >>> [1] INT 'signed char' size=1 bits_offset=0 nr_bits=8 encoding=UNKN >>> [2] INT 'unsigned char' size=1 bits_offset=0 nr_bits=8 encoding=CHAR >>> [3] TYPEDEF '__u8' type_id=2 >>> [4] CONST '(anon)' type_id=3 >> >> [...] >> >