libbpf: report vmlinux vs module name when dealing with ksyms

Currently libbpf always reports "kernel" as a source of ksym BTF type,
which is ambiguous given ksym's BTF can come from either vmlinux or
kernel module BTFs. Make this explicit and log module name, if used BTF
is from kernel module.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230418002148.3255690-3-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/libbpf.c

@@ -7538,8 +7538,9 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
 	ret = bpf_core_types_are_compat(obj->btf, local_func_proto_id,
 					kern_btf, kfunc_proto_id);
 	if (ret <= 0) {
-		pr_warn("extern (func ksym) '%s': func_proto [%d] incompatible with kernel [%d]\n",
-			ext->name, local_func_proto_id, kfunc_proto_id);
+		pr_warn("extern (func ksym) '%s': func_proto [%d] incompatible with %s [%d]\n",
+			ext->name, local_func_proto_id,
+			mod_btf ? mod_btf->name : "vmlinux", kfunc_proto_id);
 		return -EINVAL;
 	}
 
@@ -7573,8 +7574,8 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
 	 * {kernel_btf_id, kernel_btf_obj_fd} -> fixup ld_imm64.
 	 */
 	ext->ksym.kernel_btf_obj_fd = mod_btf ? mod_btf->fd : 0;
-	pr_debug("extern (func ksym) '%s': resolved to kernel [%d]\n",
-		 ext->name, kfunc_id);
+	pr_debug("extern (func ksym) '%s': resolved to %s [%d]\n",
+		 ext->name, mod_btf ? mod_btf->name : "vmlinux", kfunc_id);
 
 	return 0;
 }