libbpf: Support attachment of BPF tracing programs to kernel modules

Teach libbpf to search for BTF types in kernel modules for tracing BPF
programs. This allows attachment of raw_tp/fentry/fexit/fmod_ret/etc BPF
program types to tracepoints and functions in kernel modules.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-13-andrii@kernel.org

src/libbpf_internal.h

@@ -160,6 +160,7 @@ struct bpf_prog_load_params {
 	const char *license;
 	__u32 kern_version;
 	__u32 attach_prog_fd;
+	__u32 attach_btf_obj_fd;
 	__u32 attach_btf_id;
 	__u32 prog_ifindex;
 	__u32 prog_btf_fd;