bpftool: Adding support for BTF program names

`bpftool prog list` and other bpftool subcommands that show
BPF program names currently get them from bpf_prog_info.name.
That field is limited to 16 (BPF_OBJ_NAME_LEN) chars which leads
to truncated names since many progs have much longer names.

The idea of this change is to improve all bpftool commands that
output prog name so that bpftool uses info from BTF to print
program names if available.

It tries bpf_prog_info.name first and fall back to btf only if
the name is suspected to be truncated (has 15 chars length).

Right now `bpftool p show id <id>` returns capped prog name

<id>: kprobe  name example_cap_cap  tag 712e...
...

With this change it would return

<id>: kprobe  name example_cap_capable  tag 712e...
...

Note, other commands that print prog names (e.g. "bpftool
cgroup tree") are also addressed in this change.

Signed-off-by: Raman Shukhau <ramasha@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220119100255.1068997-1-ramasha@fb.com

1 files changed, 18 insertions, 10 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 33ca834d5f51..cf935c63e6f5 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -424,8 +424,10 @@ out_free:
 	free(value);
 }
 
-static void print_prog_header_json(struct bpf_prog_info *info)
+static void print_prog_header_json(struct bpf_prog_info *info, int fd)
 {
+	char prog_name[MAX_PROG_FULL_NAME];
+
 	jsonw_uint_field(json_wtr, "id", info->id);
 	if (info->type < ARRAY_SIZE(prog_type_name))
 		jsonw_string_field(json_wtr, "type",
@@ -433,8 +435,10 @@ static void print_prog_header_json(struct bpf_prog_info *info)
 	else
 		jsonw_uint_field(json_wtr, "type", info->type);
 
-	if (*info->name)
-		jsonw_string_field(json_wtr, "name", info->name);
+	if (*info->name) {
+		get_prog_full_name(info, fd, prog_name, sizeof(prog_name));
+		jsonw_string_field(json_wtr, "name", prog_name);
+	}
 
 	jsonw_name(json_wtr, "tag");
 	jsonw_printf(json_wtr, "\"" BPF_TAG_FMT "\"",
@@ -455,7 +459,7 @@ static void print_prog_json(struct bpf_prog_info *info, int fd)
 	char *memlock;
 
 	jsonw_start_object(json_wtr);
-	print_prog_header_json(info);
+	print_prog_header_json(info, fd);
 	print_dev_json(info->ifindex, info->netns_dev, info->netns_ino);
 
 	if (info->load_time) {
@@ -507,16 +511,20 @@ static void print_prog_json(struct bpf_prog_info *info, int fd)
 	jsonw_end_object(json_wtr);
 }
 
-static void print_prog_header_plain(struct bpf_prog_info *info)
+static void print_prog_header_plain(struct bpf_prog_info *info, int fd)
 {
+	char prog_name[MAX_PROG_FULL_NAME];
+
 	printf("%u: ", info->id);
 	if (info->type < ARRAY_SIZE(prog_type_name))
 		printf("%s  ", prog_type_name[info->type]);
 	else
 		printf("type %u  ", info->type);
 
-	if (*info->name)
-		printf("name %s  ", info->name);
+	if (*info->name) {
+		get_prog_full_name(info, fd, prog_name, sizeof(prog_name));
+		printf("name %s  ", prog_name);
+	}
 
 	printf("tag ");
 	fprint_hex(stdout, info->tag, BPF_TAG_SIZE, "");
@@ -534,7 +542,7 @@ static void print_prog_plain(struct bpf_prog_info *info, int fd)
 {
 	char *memlock;
 
-	print_prog_header_plain(info);
+	print_prog_header_plain(info, fd);
 
 	if (info->load_time) {
 		char buf[32];
@@ -972,10 +980,10 @@ static int do_dump(int argc, char **argv)
 
 		if (json_output && nb_fds > 1) {
 			jsonw_start_object(json_wtr);	/* prog object */
-			print_prog_header_json(&info);
+			print_prog_header_json(&info, fds[i]);
 			jsonw_name(json_wtr, "insns");
 		} else if (nb_fds > 1) {
-			print_prog_header_plain(&info);
+			print_prog_header_plain(&info, fds[i]);
 		}
 
 		err = prog_dump(&info, mode, filepath, opcodes, visual, linum);