Mon, Oct 30, 2023 at 02:19:41PM CET, olsajiri@xxxxxxxxx wrote: >On Mon, Oct 30, 2023 at 12:02:13PM +0100, Jiri Pirko wrote: >> Mon, Oct 30, 2023 at 11:14:51AM CET, olsajiri@xxxxxxxxx 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? Hmm, I managed to get some debug print from libbpf (docs more or less suck btw), and here it is: libbpf: loading bpftest2.o libbpf: elf: section(2) .text, size 48, link 0, flags 6, type=1 libbpf: sec '.text': found program 'parse_nl_attr' at insn offset 0 (0 bytes), code size 6 insns (48 bytes) libbpf: elf: section(3) .rel.text, size 16, link 25, flags 40, type=9 libbpf: elf: section(4) socket, size 248, link 0, flags 6, type=1 libbpf: sec 'socket': found program 'main_prog' at insn offset 0 (0 bytes), code size 31 insns (248 bytes) libbpf: elf: section(5) .relsocket, size 48, link 25, flags 40, type=9 libbpf: elf: section(6) .rodata, size 50, link 0, flags 2, type=1 libbpf: elf: section(7) license, size 4, link 0, flags 3, type=1 libbpf: license of bpftest2.o is GPL libbpf: elf: section(16) .BTF, size 2032, link 0, flags 0, type=1 libbpf: elf: section(18) .BTF.ext, size 280, link 0, flags 0, type=1 libbpf: elf: section(25) .symtab, size 432, link 1, flags 0, type=2 libbpf: looking for externs among 18 symbols... libbpf: collected 1 externs total libbpf: extern (ksym) #0: symbol 16, name bpf_dynptr_from_skb libbpf: map 'bpftest2.rodata' (global data): at sec_idx 6, offset 0, flags 480. libbpf: map 0 is "bpftest2.rodata" libbpf: sec '.rel.text': collecting relocation for section(2) '.text' libbpf: sec '.rel.text': relo #0: insn #0 against '.rodata' libbpf: prog 'parse_nl_attr': found data map 0 (bpftest2.rodata, sec 6, off 0) for insn 0 libbpf: sec '.relsocket': collecting relocation for section(4) 'socket' libbpf: sec '.relsocket': relo #0: insn #7 against '.rodata' libbpf: prog 'main_prog': found data map 0 (bpftest2.rodata, sec 6, off 0) for insn 7 libbpf: sec '.relsocket': relo #1: insn #15 against 'bpf_dynptr_from_skb' libbpf: prog 'main_prog': found extern #0 'bpf_dynptr_from_skb' (sym 16) for insn #15 libbpf: sec '.relsocket': relo #2: insn #24 against '.text' libbpf: Unsupported BTF_KIND:19 libbpf: loading kernel BTF '/sys/kernel/btf/vmlinux': -22 libbpf: failed to find valid kernel BTF libbpf: Error loading vmlinux BTF: -3 libbpf: failed to load object 'bpftest2.o' 19 is BTF_KIND_ENUM64 Looks like I'm using some old libbpf (libbpf-0.8.0-2.fc37.x86_64): https://lwn.net/ml/bpf/20220603015937.1190992-1-yhs@xxxxxx/ Will update, I'm sure it will help. Thanks! > >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 >> >>
