Re: kfunc use newbie question

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Oct 30, 2023 at 12:02:13PM +0100, Jiri Pirko wrote:
> Mon, Oct 30, 2023 at 11:14:51AM CET, olsajiri@gmail.com wrote:
> >On Mon, Oct 30, 2023 at 10:35:59AM +0100, Jiri Pirko wrote:
> >> Hi BPF :)
> >> 
> >> I'm trying to use bpf_dynptr_from_skb() kfunc in my program. I compiled
> >> it with having following declaration in the bpf .c file:
> >> extern int bpf_dynptr_from_skb(struct __sk_buff *skb, __u64 flags,
> >>                                struct bpf_dynptr *ptr__uninit) __ksym;
> >> 
> >> I have all "BPF/BTF" kernel config options on. During load,
> >> I'm still getting:
> >> 
> >> libbpf: failed to find BTF for extern 'bpf_dynptr_from_skb': -3
> >
> >heya,
> >error -3 suggests there's no BTF generated, is there .BTF section
> >in the object ? did you compile with -g ?
> 
> w/o -g. If I compile with -g, I'm getting this:
> libbpf: failed to find valid kernel BTF
> libbpf: Error loading vmlinux BTF: -3

hum, this one seems straightforward missing vmlinux btf,
(check btf__load_vmlinux_btf in tools/lib/bpf/btf.c)
could you please send your .config?

jirka

> 
> 
> >
> >jirka
> >
> >> 
> >> I'm pretty much clueless about what may be wrong. Documentation didn't
> >> help me either :/
> >> 
> >> Any idea what I may be doing wrong?
> >> 
> >> Thanks
> >> 
> >> Jiri
> >>