1 files changed, 45 insertions, 3 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 28923b776cdc..0dad862b3b9d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3613,6 +3613,42 @@ static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map)
 	return 0;
 }
 
+static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
+{
+	char file[PATH_MAX], buff[4096];
+	FILE *fp;
+	__u32 val;
+	int err;
+
+	snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
+	memset(info, 0, sizeof(*info));
+
+	fp = fopen(file, "r");
+	if (!fp) {
+		err = -errno;
+		pr_warn("failed to open %s: %d. No procfs support?\n", file,
+			err);
+		return err;
+	}
+
+	while (fgets(buff, sizeof(buff), fp)) {
+		if (sscanf(buff, "map_type:\t%u", &val) == 1)
+			info->type = val;
+		else if (sscanf(buff, "key_size:\t%u", &val) == 1)
+			info->key_size = val;
+		else if (sscanf(buff, "value_size:\t%u", &val) == 1)
+			info->value_size = val;
+		else if (sscanf(buff, "max_entries:\t%u", &val) == 1)
+			info->max_entries = val;
+		else if (sscanf(buff, "map_flags:\t%i", &val) == 1)
+			info->map_flags = val;
+	}
+
+	fclose(fp);
+
+	return 0;
+}
+
 int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 {
 	struct bpf_map_info info = {};
@@ -3621,6 +3657,8 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 	char *new_name;
 
 	err = bpf_obj_get_info_by_fd(fd, &info, &len);
+	if (err && errno == EINVAL)
+		err = bpf_get_map_info_from_fdinfo(fd, &info);
 	if (err)
 		return err;
 
@@ -4032,12 +4070,16 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
 	struct bpf_map_info map_info = {};
 	char msg[STRERR_BUFSIZE];
 	__u32 map_info_len;
+	int err;
 
 	map_info_len = sizeof(map_info);
 
-	if (bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len)) {
-		pr_warn("failed to get map info for map FD %d: %s\n",
-			map_fd, libbpf_strerror_r(errno, msg, sizeof(msg)));
+	err = bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len);
+	if (err && errno == EINVAL)
+		err = bpf_get_map_info_from_fdinfo(map_fd, &map_info);
+	if (err) {
+		pr_warn("failed to get map info for map FD %d: %s\n", map_fd,
+			libbpf_strerror_r(errno, msg, sizeof(msg)));
 		return false;
 	}