On Fri, 2022-10-14 at 16:56 +0200, Roberto Sassu wrote:
> Hi everyone
>
> I want to introduce a kfunc() whose implementation is done in an eBPF
> program, which injects the result.
>
> This is what I did:
>
> int noinline
> _bpf_verify_pgp_signature(struct bpf_dynptr_kern *data_ptr,
> struct bpf_dynptr_kern *sig_ptr,
> struct bpf_key *trusted_keyring)
> {
> return -EBADMSG;
> }
> ALLOW_ERROR_INJECTION(_bpf_verify_pgp_signature, ERRNO);
>
> int bpf_verify_pgp_signature(struct bpf_dynptr_kern *data_ptr,
> struct bpf_dynptr_kern *sig_ptr,
> struct bpf_key *trusted_keyring)
> {
> [...]
>
> return _bpf_verify_pgp_signature(data_ptr, sig_ptr,
> trusted_keyring);
> }
>
> This is the sample of eBPF program doing the work:
>
> SEC("fmod_ret/_bpf_verify_pgp_signature")
> int BPF_PROG(pgp_sig_parse, struct bpf_dynptr *data_ptr,
> struct bpf_dynptr *sig_ptr,
> struct bpf_key *trusted_keyring, int ret)
> {
> return 0;
> }
>
> However, the program fails to auto attach:
>
> libbpf: prog 'pgp_sig_parse': failed to attach: Device or resource
> busy
> libbpf: prog 'pgp_sig_parse': failed to auto-attach: -16
As Florent mentioned in Slax, CC_FLAGS_FTRACE was the cause.
+CFLAGS_bpf_trace.o := -I$(src) $(CC_FLAGS_FTRACE)
solved it.
Roberto
