[RFC bpf-next 07/13] resolve_btfids: use .BTF.base_ref BTF as base BTF if -r option is used

[Alan Maguire <alan.maguire@oracle.com>]

When resolving BTF ids, use the base reference BTF in the module
when passed the -r option.  Both references to base BTF from split
BTF and BTF ids will be reconciled with base vmlinux on module
load.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
 tools/bpf/resolve_btfids/main.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index d9520cb826b3..cdab366bd4d6 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -115,6 +115,7 @@ struct object {
 	const char *path;
 	const char *btf;
 	const char *base_btf_path;
+	int base_ref;
 
 	struct {
 		int		 fd;
@@ -532,11 +533,21 @@ static int symbols_resolve(struct object *obj)
 	__u32 nr_types;
 
 	if (obj->base_btf_path) {
-		base_btf = btf__parse(obj->base_btf_path, NULL);
+		LIBBPF_OPTS(btf_parse_opts, optp);
+		const char *path;
+
+		if (obj->base_ref) {
+			optp.btf_sec = BTF_BASE_REF_ELF_SEC;
+			path = obj->path;
+		} else {
+			optp.btf_sec = BTF_ELF_SEC;
+			path = obj->base_btf_path;
+		}
+		base_btf = btf__parse_opts(path, &optp);
 		err = libbpf_get_error(base_btf);
 		if (err) {
 			pr_err("FAILED: load base BTF from %s: %s\n",
-			       obj->base_btf_path, strerror(-err));
+			       path, strerror(-err));
 			return -1;
 		}
 	}
@@ -781,6 +792,8 @@ int main(int argc, const char **argv)
 			   "BTF data"),
 		OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
 			   "path of file providing base BTF"),
+		OPT_INCR('r', "base_ref", &obj.base_ref,
+			 "use base reference BTF as base"),
 		OPT_END()
 	};
 	int err = -1;
-- 
2.39.3