bpftool: Match maps by name

This patch implements lookup by name for maps and changes the behavior of
lookups by tag to be consistent with prog subcommands.  Similarly to
program subcommands, the show and dump commands will return all maps with
the given name (or tag), whereas other commands will error out if several
maps have the same name (resp. tag).

When a map has BTF info, it is dumped in JSON with available BTF info.
This patch requires that all matched maps have BTF info before switching
the output format to JSON.

Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/8de1c9f273860b3ea1680502928f4da2336b853e.1576263640.git.paul.chaignon@gmail.com

1 files changed, 310 insertions, 74 deletions

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index de61d73b9030..c01f76fa6876 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -91,10 +91,66 @@ static void *alloc_value(struct bpf_map_info *info)
 		return malloc(info->value_size);
 }
 
-int map_parse_fd(int *argc, char ***argv)
+static int map_fd_by_name(char *name, int **fds)
 {
-	int fd;
+	unsigned int id = 0;
+	int fd, nb_fds = 0;
+	void *tmp;
+	int err;
+
+	while (true) {
+		struct bpf_map_info info = {};
+		__u32 len = sizeof(info);
+
+		err = bpf_map_get_next_id(id, &id);
+		if (err) {
+			if (errno != ENOENT) {
+				p_err("%s", strerror(errno));
+				goto err_close_fds;
+			}
+			return nb_fds;
+		}
+
+		fd = bpf_map_get_fd_by_id(id);
+		if (fd < 0) {
+			p_err("can't get map by id (%u): %s",
+			      id, strerror(errno));
+			goto err_close_fds;
+		}
+
+		err = bpf_obj_get_info_by_fd(fd, &info, &len);
+		if (err) {
+			p_err("can't get map info (%u): %s",
+			      id, strerror(errno));
+			goto err_close_fd;
+		}
+
+		if (strncmp(name, info.name, BPF_OBJ_NAME_LEN)) {
+			close(fd);
+			continue;
+		}
+
+		if (nb_fds > 0) {
+			tmp = realloc(*fds, (nb_fds + 1) * sizeof(int));
+			if (!tmp) {
+				p_err("failed to realloc");
+				goto err_close_fd;
+			}
+			*fds = tmp;
+		}
+		(*fds)[nb_fds++] = fd;
+	}
+
+err_close_fd:
+	close(fd);
+err_close_fds:
+	while (--nb_fds >= 0)
+		close((*fds)[nb_fds]);
+	return -1;
+}
 
+static int map_parse_fds(int *argc, char ***argv, int **fds)
+{
 	if (is_prefix(**argv, "id")) {
 		unsigned int id;
 		char *endptr;
@@ -108,10 +164,25 @@ int map_parse_fd(int *argc, char ***argv)
 		}
 		NEXT_ARGP();
 
-		fd = bpf_map_get_fd_by_id(id);
-		if (fd < 0)
+		(*fds)[0] = bpf_map_get_fd_by_id(id);
+		if ((*fds)[0] < 0) {
 			p_err("get map by id (%u): %s", id, strerror(errno));
-		return fd;
+			return -1;
+		}
+		return 1;
+	} else if (is_prefix(**argv, "name")) {
+		char *name;
+
+		NEXT_ARGP();
+
+		name = **argv;
+		if (strlen(name) > BPF_OBJ_NAME_LEN - 1) {
+			p_err("can't parse name");
+			return -1;
+		}
+		NEXT_ARGP();
+
+		return map_fd_by_name(name, fds);
 	} else if (is_prefix(**argv, "pinned")) {
 		char *path;
 
@@ -120,13 +191,43 @@ int map_parse_fd(int *argc, char ***argv)
 		path = **argv;
 		NEXT_ARGP();
 
-		return open_obj_pinned_any(path, BPF_OBJ_MAP);
+		(*fds)[0] = open_obj_pinned_any(path, BPF_OBJ_MAP);
+		if ((*fds)[0] < 0)
+			return -1;
+		return 1;
 	}
 
-	p_err("expected 'id' or 'pinned', got: '%s'?", **argv);
+	p_err("expected 'id', 'name' or 'pinned', got: '%s'?", **argv);
 	return -1;
 }
 
+int map_parse_fd(int *argc, char ***argv)
+{
+	int *fds = NULL;
+	int nb_fds, fd;
+
+	fds = malloc(sizeof(int));
+	if (!fds) {
+		p_err("mem alloc failed");
+		return -1;
+	}
+	nb_fds = map_parse_fds(argc, argv, &fds);
+	if (nb_fds != 1) {
+		if (nb_fds > 1) {
+			p_err("several maps match this handle");
+			while (nb_fds--)
+				close(fds[nb_fds]);
+		}
+		fd = -1;
+		goto exit_free;
+	}
+
+	fd = fds[0];
+exit_free:
+	free(fds);
+	return fd;
+}
+
 int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len)
 {
 	int err;
@@ -479,6 +580,21 @@ static int parse_elem(char **argv, struct bpf_map_info *info,
 	return -1;
 }
 
+static void show_map_header_json(struct bpf_map_info *info, json_writer_t *wtr)
+{
+	jsonw_uint_field(wtr, "id", info->id);
+	if (info->type < ARRAY_SIZE(map_type_name))
+		jsonw_string_field(wtr, "type", map_type_name[info->type]);
+	else
+		jsonw_uint_field(wtr, "type", info->type);
+
+	if (*info->name)
+		jsonw_string_field(wtr, "name", info->name);
+
+	jsonw_name(wtr, "flags");
+	jsonw_printf(wtr, "%d", info->map_flags);
+}
+
 static int show_map_close_json(int fd, struct bpf_map_info *info)
 {
 	char *memlock, *frozen_str;
@@ -489,18 +605,7 @@ static int show_map_close_json(int fd, struct bpf_map_info *info)
 
 	jsonw_start_object(json_wtr);
 
-	jsonw_uint_field(json_wtr, "id", info->id);
-	if (info->type < ARRAY_SIZE(map_type_name))
-		jsonw_string_field(json_wtr, "type",
-				   map_type_name[info->type]);
-	else
-		jsonw_uint_field(json_wtr, "type", info->type);
-
-	if (*info->name)
-		jsonw_string_field(json_wtr, "name", info->name);
-
-	jsonw_name(json_wtr, "flags");
-	jsonw_printf(json_wtr, "%d", info->map_flags);
+	show_map_header_json(info, json_wtr);
 
 	print_dev_json(info->ifindex, info->netns_dev, info->netns_ino);
 
@@ -561,14 +666,8 @@ static int show_map_close_json(int fd, struct bpf_map_info *info)
 	return 0;
 }
 
-static int show_map_close_plain(int fd, struct bpf_map_info *info)
+static void show_map_header_plain(struct bpf_map_info *info)
 {
-	char *memlock, *frozen_str;
-	int frozen = 0;
-
-	memlock = get_fdinfo(fd, "memlock");
-	frozen_str = get_fdinfo(fd, "frozen");
-
 	printf("%u: ", info->id);
 	if (info->type < ARRAY_SIZE(map_type_name))
 		printf("%s  ", map_type_name[info->type]);
@@ -581,6 +680,17 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info)
 	printf("flags 0x%x", info->map_flags);
 	print_dev_plain(info->ifindex, info->netns_dev, info->netns_ino);
 	printf("\n");
+}
+
+static int show_map_close_plain(int fd, struct bpf_map_info *info)
+{
+	char *memlock, *frozen_str;
+	int frozen = 0;
+
+	memlock = get_fdinfo(fd, "memlock");
+	frozen_str = get_fdinfo(fd, "frozen");
+
+	show_map_header_plain(info);
 	printf("\tkey %uB  value %uB  max_entries %u",
 	       info->key_size, info->value_size, info->max_entries);
 
@@ -642,6 +752,50 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info)
 	return 0;
 }
 
+static int do_show_subset(int argc, char **argv)
+{
+	struct bpf_map_info info = {};
+	__u32 len = sizeof(info);
+	int *fds = NULL;
+	int nb_fds, i;
+	int err = -1;
+
+	fds = malloc(sizeof(int));
+	if (!fds) {
+		p_err("mem alloc failed");
+		return -1;
+	}
+	nb_fds = map_parse_fds(&argc, &argv, &fds);
+	if (nb_fds < 1)
+		goto exit_free;
+
+	if (json_output && nb_fds > 1)
+		jsonw_start_array(json_wtr);	/* root array */
+	for (i = 0; i < nb_fds; i++) {
+		err = bpf_obj_get_info_by_fd(fds[i], &info, &len);
+		if (err) {
+			p_err("can't get map info: %s",
+			      strerror(errno));
+			for (; i < nb_fds; i++)
+				close(fds[i]);
+			break;
+		}
+
+		if (json_output)
+			show_map_close_json(fds[i], &info);
+		else
+			show_map_close_plain(fds[i], &info);
+
+		close(fds[i]);
+	}
+	if (json_output && nb_fds > 1)
+		jsonw_end_array(json_wtr);	/* root array */
+
+exit_free:
+	free(fds);
+	return err;
+}
+
 static int do_show(int argc, char **argv)
 {
 	struct bpf_map_info info = {};
@@ -653,16 +807,8 @@ static int do_show(int argc, char **argv)
 	if (show_pinned)
 		build_pinned_obj_table(&map_table, BPF_OBJ_MAP);
 
-	if (argc == 2) {
-		fd = map_parse_fd_and_info(&argc, &argv, &info, &len);
-		if (fd < 0)
-			return -1;
-
-		if (json_output)
-			return show_map_close_json(fd, &info);
-		else
-			return show_map_close_plain(fd, &info);
-	}
+	if (argc == 2)
+		return do_show_subset(argc, argv);
 
 	if (argc)
 		return BAD_ARG();
@@ -765,26 +911,49 @@ static int dump_map_elem(int fd, void *key, void *value,
 	return 0;
 }
 
-static int do_dump(int argc, char **argv)
+static int maps_have_btf(int *fds, int nb_fds)
 {
 	struct bpf_map_info info = {};
-	void *key, *value, *prev_key;
-	unsigned int num_elems = 0;
 	__u32 len = sizeof(info);
-	json_writer_t *btf_wtr;
 	struct btf *btf = NULL;
-	int err;
-	int fd;
+	int err, i;
 
-	if (argc != 2)
-		usage();
+	for (i = 0; i < nb_fds; i++) {
+		err = bpf_obj_get_info_by_fd(fds[i], &info, &len);
+		if (err) {
+			p_err("can't get map info: %s", strerror(errno));
+			goto err_close;
+		}
 
-	fd = map_parse_fd_and_info(&argc, &argv, &info, &len);
-	if (fd < 0)
-		return -1;
+		err = btf__get_from_id(info.btf_id, &btf);
+		if (err) {
+			p_err("failed to get btf");
+			goto err_close;
+		}
 
-	key = malloc(info.key_size);
-	value = alloc_value(&info);
+		if (!btf)
+			return 0;
+	}
+
+	return 1;
+
+err_close:
+	for (; i < nb_fds; i++)
+		close(fds[i]);
+	return -1;
+}
+
+static int
+map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
+	 bool enable_btf, bool show_header)
+{
+	void *key, *value, *prev_key;
+	unsigned int num_elems = 0;
+	struct btf *btf = NULL;
+	int err;
+
+	key = malloc(info->key_size);
+	value = alloc_value(info);
 	if (!key || !value) {
 		p_err("mem alloc failed");
 		err = -1;
@@ -793,30 +962,32 @@ static int do_dump(int argc, char **argv)
 
 	prev_key = NULL;
 
-	err = btf__get_from_id(info.btf_id, &btf);
-	if (err) {
-		p_err("failed to get btf");
-		goto exit_free;
+	if (enable_btf) {
+		err = btf__get_from_id(info->btf_id, &btf);
+		if (err || !btf) {
+			/* enable_btf is true only if we've already checked
+			 * that all maps have BTF information.
+			 */
+			p_err("failed to get btf");
+			goto exit_free;
+		}
 	}
 
-	if (json_output)
-		jsonw_start_array(json_wtr);
-	else
-		if (btf) {
-			btf_wtr = get_btf_writer();
-			if (!btf_wtr) {
-				p_info("failed to create json writer for btf. falling back to plain output");
-				btf__free(btf);
-				btf = NULL;
-			} else {
-				jsonw_start_array(btf_wtr);
-			}
+	if (wtr) {
+		if (show_header) {
+			jsonw_start_object(wtr);	/* map object */
+			show_map_header_json(info, wtr);
+			jsonw_name(wtr, "elements");
 		}
+		jsonw_start_array(wtr);		/* elements */
+	} else if (show_header) {
+		show_map_header_plain(info);
+	}
 
-	if (info.type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY &&
-	    info.value_size != 8)
+	if (info->type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY &&
+	    info->value_size != 8)
 		p_info("Warning: cannot read values from %s map with value_size != 8",
-		       map_type_name[info.type]);
+		       map_type_name[info->type]);
 	while (true) {
 		err = bpf_map_get_next_key(fd, prev_key, key);
 		if (err) {
@@ -824,15 +995,14 @@ static int do_dump(int argc, char **argv)
 				err = 0;
 			break;
 		}
-		num_elems += dump_map_elem(fd, key, value, &info, btf, btf_wtr);
+		num_elems += dump_map_elem(fd, key, value, info, btf, wtr);
 		prev_key = key;
 	}
 
-	if (json_output)
-		jsonw_end_array(json_wtr);
-	else if (btf) {
-		jsonw_end_array(btf_wtr);
-		jsonw_destroy(&btf_wtr);
+	if (wtr) {
+		jsonw_end_array(wtr);	/* elements */
+		if (show_header)
+			jsonw_end_object(wtr);	/* map object */
 	} else {
 		printf("Found %u element%s\n", num_elems,
 		       num_elems != 1 ? "s" : "");
@@ -847,6 +1017,72 @@ exit_free:
 	return err;
 }
 
+static int do_dump(int argc, char **argv)
+{
+	json_writer_t *wtr = NULL, *btf_wtr = NULL;
+	struct bpf_map_info info = {};
+	int nb_fds, i = 0, btf = 0;
+	__u32 len = sizeof(info);
+	int *fds = NULL;
+	int err = -1;
+
+	if (argc != 2)
+		usage();
+
+	fds = malloc(sizeof(int));
+	if (!fds) {
+		p_err("mem alloc failed");
+		return -1;
+	}
+	nb_fds = map_parse_fds(&argc, &argv, &fds);
+	if (nb_fds < 1)
+		goto exit_free;
+
+	if (json_output) {
+		wtr = json_wtr;
+	} else {
+		btf = maps_have_btf(fds, nb_fds);
+		if (btf < 0)
+			goto exit_close;
+		if (btf) {
+			btf_wtr = get_btf_writer();
+			if (btf_wtr) {
+				wtr = btf_wtr;
+			} else {
+				p_info("failed to create json writer for btf. falling back to plain output");
+				btf = 0;
+			}
+		}
+	}
+
+	if (wtr && nb_fds > 1)
+		jsonw_start_array(wtr);	/* root array */
+	for (i = 0; i < nb_fds; i++) {
+		if (bpf_obj_get_info_by_fd(fds[i], &info, &len)) {
+			p_err("can't get map info: %s", strerror(errno));
+			break;
+		}
+		err = map_dump(fds[i], &info, wtr, btf, nb_fds > 1);
+		if (!wtr && i != nb_fds - 1)
+			printf("\n");
+
+		if (err)
+			break;
+		close(fds[i]);
+	}
+	if (wtr && nb_fds > 1)
+		jsonw_end_array(wtr);	/* root array */
+
+	if (btf)
+		jsonw_destroy(&btf_wtr);
+exit_close:
+	for (; i < nb_fds; i++)
+		close(fds[i]);
+exit_free:
+	free(fds);
+	return err;
+}
+
 static int alloc_key_value(struct bpf_map_info *info, void **key, void **value)
 {
 	*key = NULL;