[v3,bpf-next,10/17] bpftool: add BTF dump "format meta" to dump header/metadata

Commit Message

Alan Maguire Nov. 10, 2023, 11:02 a.m. UTC

Provide a way to dump BTF metadata info via bpftool; this
consists of BTF size, header fields and kind layout info
(if available); for example

$ bpftool btf dump file vmlinux format meta
size 5161076
magic 0xeb9f
version 1
flags 0x1
hdr_len 40
type_len 3036368
type_off 0
str_len 2124588
str_off 3036368
kind_layout_len 80
kind_layout_off 5160956
crc 0x64af901b
base_crc 0x0
kind 0    UNKNOWN    flags 0x0    info_sz 0    elem_sz 0
kind 1    INT        flags 0x0    info_sz 0    elem_sz 0
kind 2    PTR        flags 0x0    info_sz 0    elem_sz 0
kind 3    ARRAY      flags 0x0    info_sz 0    elem_sz 0
kind 4    STRUCT     flags 0x35   info_sz 0    elem_sz 0
...

JSON output is also supported:

$ bpftool -j btf dump file vmlinux format meta
{"size":5161076,"header":{"magic":60319,"version":1,"flags":1,"hdr_len":40,"type_len":3036368,"type_off":0,"str_len":2124588,"str_off":3036368,"kind_layout_len":80,"kind_layout_offset":5160956,"crc":1689227291,"base_crc":0},"kind_layouts":[{"kind":0,"name":"UNKNOWN","flags":0,"info_sz":0,"elem_sz":0},{"kind":1,"name":"INT","flags":0,"info_sz":0,"elem_sz":0},{"kind":2,"name":"PTR","flags":0,"info_sz":0,"elem_sz":0},{"kind":3,"name":"ARRAY","flags":0,"info_sz":0,"elem_sz":0},{"kind":4,"name":"STRUCT","flags":53,"info_sz":0,"elem_sz":0},{"kind":5,"name":"UNION","flags":0,"info_sz":0,"elem_sz":0},{"kind":6,"name":"ENUM","flags":60319,"info_sz":1,"elem_sz":1},{"kind":7,"name":"FWD","flags":40,"info_sz":0,"elem_sz":0},{"kind":8,"name":"TYPEDEF","flags":0,"info_sz":0,"elem_sz":0},{"kind":9,"name":"VOLATILE","flags":0,"info_sz":0,"elem_sz":0},{"kind":10,"name":"CONST","flags":0,"info_sz":0,"elem_sz":0},{"kind":11,"name":"RESTRICT","flags":1,"info_sz":0,"elem_sz":0},{"kind":12,"name":"FUNC","flags":0,"info_sz":0,"elem_sz":0},{"kind":13,"name":"FUNC_PROTO","flags":80,"info_sz":0,"elem_sz":0},{"kind":14,"name":"VAR","flags":0,"info_sz":0,"elem_sz":0},{"kind":15,"name":"DATASEC","flags":0,"info_sz":0,"elem_sz":0},{"kind":16,"name":"FLOAT","flags":53,"info_sz":0,"elem_sz":0},{"kind":17,"name":"DECL_TAG","flags":0,"info_sz":0,"elem_sz":0},{"kind":18,"name":"TYPE_TAG","flags":11441,"info_sz":3,"elem_sz":0},{"kind":19,"name":"ENUM64","flags":0,"info_sz":0,"elem_sz":0}]}

Signed-off-by: Alan Maguire <[e-mail]>
---
 tools/bpf/bpftool/bash-completion/bpftool |  2 +-
 tools/bpf/bpftool/btf.c                   | 91 ++++++++++++++++++++++-
 2 files changed, 90 insertions(+), 3 deletions(-)

Patch

diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 6e4f7ce6bc01..157c3afd8247 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -937,7 +937,7 @@  _bpftool()
                             return 0
                             ;;
                         format)
-                            COMPREPLY=( $( compgen -W "c raw" -- "$cur" ) )
+                            COMPREPLY=( $( compgen -W "c raw meta" -- "$cur" ) )
                             ;;
                         *)
                             # emit extra options
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 91fcb75babe3..208f3a587534 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -504,6 +504,88 @@  static int dump_btf_c(const struct btf *btf,
 	return err;
 }
 
+static int dump_btf_meta(const struct btf *btf)
+{
+	const struct btf_header *hdr;
+	const struct btf_kind_layout *k;
+	__u8 i, nr_kinds = 0;
+	const void *data;
+	__u32 data_sz;
+
+	data = btf__raw_data(btf, &data_sz);
+	if (!data)
+		return -ENOMEM;
+	hdr = data;
+	if (json_output) {
+		jsonw_start_object(json_wtr);   /* btf metadata object */
+		jsonw_uint_field(json_wtr, "size", data_sz);
+		jsonw_name(json_wtr, "header");
+		jsonw_start_object(json_wtr);	/* btf header object */
+		jsonw_uint_field(json_wtr, "magic", hdr->magic);
+		jsonw_uint_field(json_wtr, "version", hdr->version);
+		jsonw_uint_field(json_wtr, "flags", hdr->flags);
+		jsonw_uint_field(json_wtr, "hdr_len", hdr->hdr_len);
+		jsonw_uint_field(json_wtr, "type_len", hdr->type_len);
+		jsonw_uint_field(json_wtr, "type_off", hdr->type_off);
+		jsonw_uint_field(json_wtr, "str_len", hdr->str_len);
+		jsonw_uint_field(json_wtr, "str_off", hdr->str_off);
+	} else {
+		printf("size %-10d\n", data_sz);
+		printf("magic 0x%-10x\nversion %-10d\nflags 0x%-10x\nhdr_len %-10d\n",
+		       hdr->magic, hdr->version, hdr->flags, hdr->hdr_len);
+		printf("type_len %-10d\ntype_off %-10d\n", hdr->type_len, hdr->type_off);
+		printf("str_len %-10d\nstr_off %-10d\n", hdr->str_len, hdr->str_off);
+	}
+
+	if (hdr->hdr_len < sizeof(struct btf_header)) {
+		if (json_output) {
+			jsonw_end_object(json_wtr); /* header object */
+			jsonw_end_object(json_wtr); /* metadata object */
+		}
+		return 0;
+	}
+	if (hdr->kind_layout_len > 0 && hdr->kind_layout_off > 0) {
+		k = (void *)hdr + hdr->hdr_len + hdr->kind_layout_off;
+		nr_kinds = hdr->kind_layout_len / sizeof(*k);
+	}
+	if (json_output) {
+		jsonw_uint_field(json_wtr, "kind_layout_len", hdr->kind_layout_len);
+		jsonw_uint_field(json_wtr, "kind_layout_offset", hdr->kind_layout_off);
+		jsonw_uint_field(json_wtr, "crc", hdr->crc);
+		jsonw_uint_field(json_wtr, "base_crc", hdr->base_crc);
+		jsonw_end_object(json_wtr); /* end header object */
+
+		if (nr_kinds > 0) {
+			jsonw_name(json_wtr, "kind_layouts");
+			jsonw_start_array(json_wtr);
+			for (i = 0; i < nr_kinds; i++) {
+				jsonw_start_object(json_wtr);
+				jsonw_uint_field(json_wtr, "kind", i);
+				if (i < NR_BTF_KINDS)
+					jsonw_string_field(json_wtr, "name", btf_kind_str[i]);
+				jsonw_uint_field(json_wtr, "flags", k[i].flags);
+				jsonw_uint_field(json_wtr, "info_sz", k[i].info_sz);
+				jsonw_uint_field(json_wtr, "elem_sz", k[i].elem_sz);
+				jsonw_end_object(json_wtr);
+			}
+			jsonw_end_array(json_wtr);
+		}
+		jsonw_end_object(json_wtr);	/* end metadata */
+	} else {
+		printf("kind_layout_len %-10d\nkind_layout_off %-10d\n",
+		       hdr->kind_layout_len, hdr->kind_layout_off);
+		printf("crc 0x%-10x\nbase_crc 0x%-10x\n",
+		       hdr->crc, hdr->base_crc);
+		for (i = 0; i < nr_kinds; i++) {
+			printf("kind %-4d %-10s flags 0x%-4x info_sz %-4d elem_sz %-4d\n",
+			       i, i < NR_BTF_KINDS ? btf_kind_str[i] : "?",
+			       k[i].flags, k[i].info_sz, k[i].elem_sz);
+		}
+	}
+
+	return 0;
+}
+
 static const char sysfs_vmlinux[] = "/sys/kernel/btf/vmlinux";
 
 static struct btf *get_vmlinux_btf_from_sysfs(void)
@@ -553,6 +635,7 @@  static int do_dump(int argc, char **argv)
 	__u32 root_type_ids[2];
 	int root_type_cnt = 0;
 	bool dump_c = false;
+	bool dump_meta = false;
 	__u32 btf_id = -1;
 	const char *src;
 	int fd = -1;
@@ -654,10 +737,12 @@  static int do_dump(int argc, char **argv)
 			}
 			if (strcmp(*argv, "c") == 0) {
 				dump_c = true;
+			} else if (is_prefix(*argv, "meta")) {
+				dump_meta = true;
 			} else if (strcmp(*argv, "raw") == 0) {
 				dump_c = false;
 			} else {
-				p_err("unrecognized format specifier: '%s', possible values: raw, c",
+				p_err("unrecognized format specifier: '%s', possible values: raw, c, meta",
 				      *argv);
 				err = -EINVAL;
 				goto done;
@@ -692,6 +777,8 @@  static int do_dump(int argc, char **argv)
 			goto done;
 		}
 		err = dump_btf_c(btf, root_type_ids, root_type_cnt);
+	} else if (dump_meta) {
+		err = dump_btf_meta(btf);
 	} else {
 		err = dump_btf_raw(btf, root_type_ids, root_type_cnt);
 	}
@@ -1063,7 +1150,7 @@  static int do_help(int argc, char **argv)
 		"       %1$s %2$s help\n"
 		"\n"
 		"       BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }\n"
-		"       FORMAT  := { raw | c }\n"
+		"       FORMAT  := { raw | c | meta }\n"
 		"       " HELP_SPEC_MAP "\n"
 		"       " HELP_SPEC_PROGRAM "\n"
 		"       " HELP_SPEC_OPTIONS " |\n"