On Wed, Feb 16, 2022 at 1:21 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> 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.
>
> Cc: Yinjun Zhang <yinjun.zhang@xxxxxxxxxxxx>
> Fixes: e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
> Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> tools/bpf/bpftool/map.c | 29 +++++++++++++----------------
> 1 file changed, 13 insertions(+), 16 deletions(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index 7a341a472ea4..8562add7417d 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -805,29 +805,28 @@ 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);
> - }
> }
get_map_kv_btf is supposed to set btf to NULL, otherwise you can get a
crash in the caller
I've added
else {
*btf = NULL;
}
and force-pushed
>
> - return btf;
> + return err;
> }
>
> static void free_map_kv_btf(struct btf *btf)
> @@ -862,8 +861,7 @@ 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 +1052,7 @@ 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) {
> --
> 2.35.1
>
