[RFC dwarves] dwarves: encode BTF metadata if --btf_gen_meta is set

[Alan Maguire <alan.maguire@xxxxxxxxxx>]

Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
 btf_encoder.c | 13 +++++++++++--
 btf_encoder.h |  2 +-
 lib/bpf       |  2 +-
 pahole.c      | 12 +++++++++++-
 4 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/btf_encoder.c b/btf_encoder.c
index 65f6e71..d3d6c67 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -1625,17 +1625,26 @@ out:
 	return err;
 }
 
-struct btf_encoder *btf_encoder__new(struct cu *cu, const char *detached_filename, struct btf *base_btf, bool skip_encoding_vars, bool force, bool gen_floats, bool verbose)
+struct btf_encoder *btf_encoder__new(struct cu *cu, const char *detached_filename, struct btf *base_btf, bool skip_encoding_vars, bool force, bool gen_floats, bool gen_meta, bool verbose)
 {
 	struct btf_encoder *encoder = zalloc(sizeof(*encoder));
 
 	if (encoder) {
+		LIBBPF_OPTS(btf_new_opts, opts);
+		char description[128];
+
+		snprintf(description, sizeof(description), "generated by dwarves v%u.%u",
+			 DWARVES_MAJOR_VERSION, DWARVES_MINOR_VERSION);
+		opts.base_btf = base_btf;
+		opts.add_meta = gen_meta;
+		opts.description = description;
+
 		encoder->raw_output = detached_filename != NULL;
 		encoder->filename = strdup(encoder->raw_output ? detached_filename : cu->filename);
 		if (encoder->filename == NULL)
 			goto out_delete;
 
-		encoder->btf = btf__new_empty_split(base_btf);
+		encoder->btf = btf__new_empty_opts(&opts);
 		if (encoder->btf == NULL)
 			goto out_delete;
 
diff --git a/btf_encoder.h b/btf_encoder.h
index 34516bb..0c8ea1a 100644
--- a/btf_encoder.h
+++ b/btf_encoder.h
@@ -16,7 +16,7 @@ struct btf;
 struct cu;
 struct list_head;
 
-struct btf_encoder *btf_encoder__new(struct cu *cu, const char *detached_filename, struct btf *base_btf, bool skip_encoding_vars, bool force, bool gen_floats, bool verbose);
+struct btf_encoder *btf_encoder__new(struct cu *cu, const char *detached_filename, struct btf *base_btf, bool skip_encoding_vars, bool force, bool gen_floats, bool gen_meta, bool verbose);
 void btf_encoder__delete(struct btf_encoder *encoder);
 
 int btf_encoder__encode(struct btf_encoder *encoder);
diff --git a/lib/bpf b/lib/bpf
index 6597330..3f591a6 160000
--- a/lib/bpf
+++ b/lib/bpf
@@ -1 +1 @@
-Subproject commit 6597330c45d185381900037f0130712cd326ae59
+Subproject commit d40a48fbfa2a357a6245c59e7bb811f72b5fc94d
diff --git a/pahole.c b/pahole.c
index 6fc4ed6..78fa778 100644
--- a/pahole.c
+++ b/pahole.c
@@ -40,6 +40,7 @@ static bool first_obj_only;
 static bool skip_encoding_btf_vars;
 static bool btf_encode_force;
 static const char *base_btf_file;
+static bool btf_gen_meta;
 
 static const char *prettify_input_filename;
 static FILE *prettify_input;
@@ -1232,6 +1233,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
 #define ARGP_skip_emitting_atomic_typedefs 338
 #define ARGP_btf_gen_optimized  339
 #define ARGP_skip_encoding_btf_inconsistent_proto 340
+#define ARGP_btf_gen_meta          341
 
 static const struct argp_option pahole__options[] = {
 	{
@@ -1654,6 +1656,11 @@ static const struct argp_option pahole__options[] = {
 		.key = ARGP_skip_encoding_btf_inconsistent_proto,
 		.doc = "Skip functions that have multiple inconsistent function prototypes sharing the same name, or that use unexpected registers for parameter values."
 	},
+	{
+		.name = "btf_gen_meta",
+		.key  = ARGP_btf_gen_meta,
+		.doc  = "Generate BTF metadata including kinds available."
+	},
 	{
 		.name = NULL,
 	}
@@ -1829,6 +1836,8 @@ static error_t pahole__options_parser(int key, char *arg,
 		conf_load.btf_gen_optimized = true;		break;
 	case ARGP_skip_encoding_btf_inconsistent_proto:
 		conf_load.skip_encoding_btf_inconsistent_proto = true; break;
+	case ARGP_btf_gen_meta:
+		btf_gen_meta = true;			break;
 	default:
 		return ARGP_ERR_UNKNOWN;
 	}
@@ -3064,7 +3073,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
 			 * create it.
 			 */
 			btf_encoder = btf_encoder__new(cu, detached_btf_filename, conf_load->base_btf, skip_encoding_btf_vars,
-						       btf_encode_force, btf_gen_floats, global_verbose);
+						       btf_encode_force, btf_gen_floats, btf_gen_meta, global_verbose);
 			if (btf_encoder && thr_data) {
 				struct thread_data *thread = thr_data;
 
@@ -3096,6 +3105,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
 							 skip_encoding_btf_vars,
 							 btf_encode_force,
 							 btf_gen_floats,
+							 btf_gen_meta,
 							 global_verbose);
 				thread->btf = btf_encoder__btf(thread->encoder);
 			}
-- 
2.31.1