bpftool: Fix pretty print dump for maps without BTF loaded

The commit e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
fails to dump map without BTF loaded in pretty mode (-p option).

Fixing this by making sure get_map_kv_btf won't fail in case there's
no BTF available for the map.

Fixes: e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220216092102.125448-1-jolsa@kernel.org

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 7a341a4..e746642 100644 (file)
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -805,29 +805,30 @@ static int maps_have_btf(int *fds, int nb_fds)
 
 static struct btf *btf_vmlinux;
 
-static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
+static int get_map_kv_btf(const struct bpf_map_info *info, struct btf **btf)
 {
-       struct btf *btf = NULL;
+       int err = 0;
 
        if (info->btf_vmlinux_value_type_id) {
                if (!btf_vmlinux) {
                        btf_vmlinux = libbpf_find_kernel_btf();
-                       if (libbpf_get_error(btf_vmlinux))
+                       err = libbpf_get_error(btf_vmlinux);
+                       if (err) {
                                p_err("failed to get kernel btf");
+                               return err;
+                       }
                }
-               return btf_vmlinux;
+               *btf = btf_vmlinux;
        } else if (info->btf_value_type_id) {
-               int err;
-
-               btf = btf__load_from_kernel_by_id(info->btf_id);
-               err = libbpf_get_error(btf);
-               if (err) {
+               *btf = btf__load_from_kernel_by_id(info->btf_id);
+               err = libbpf_get_error(*btf);
+               if (err)
                        p_err("failed to get btf");
-                       btf = ERR_PTR(err);
-               }
+       } else {
+               *btf = NULL;
        }
 
-       return btf;
+       return err;
 }
 
 static void free_map_kv_btf(struct btf *btf)
@@ -862,8 +863,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
        prev_key = NULL;
 
        if (wtr) {
-               btf = get_map_kv_btf(info);
-               err = libbpf_get_error(btf);
+               err = get_map_kv_btf(info, &btf);
                if (err) {
                        goto exit_free;
                }
@@ -1054,8 +1054,7 @@ static void print_key_value(struct bpf_map_info *info, void *key,
        json_writer_t *btf_wtr;
        struct btf *btf;
 
-       btf = get_map_kv_btf(info);
-       if (libbpf_get_error(btf))
+       if (get_map_kv_btf(info, &btf))
                return;
 
        if (json_output) {