On Mon, Feb 7, 2022 at 8:00 AM Yinjun Zhang <yinjun.zhang@xxxxxxxxxxxx> wrote:
>
> When reworking btf__get_from_id() in commit a19f93cfafdf the error
> handling when calling bpf_btf_get_fd_by_id() changed. Before the rework
> if bpf_btf_get_fd_by_id() failed the error would not be propagated to
> callers of btf__get_from_id(), after the rework it is. This lead to a
> change in behavior in print_key_value() that now prints an error when
> trying to lookup keys in maps with no btf available.
>
> Fix this by following the way used in dumping maps to allow to look up
> keys in no-btf maps, by which it decides whether and where to get the
> btf info according to the btf value type.
>
> Fixes: a19f93cfafdf ("libbpf: Add internal helper to load BTF data by FD")
> Signed-off-by: Yinjun Zhang <yinjun.zhang@xxxxxxxxxxxx>
> Reviewed-by: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx>
> Signed-off-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
> ---
> tools/bpf/bpftool/map.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index cc530a229812..4fc772d66e3a 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -1054,11 +1054,9 @@ static void print_key_value(struct bpf_map_info *info, void *key,
> json_writer_t *btf_wtr;
> struct btf *btf;
>
> - btf = btf__load_from_kernel_by_id(info->btf_id);
> - if (libbpf_get_error(btf)) {
> - p_err("failed to get btf");
> + btf = get_map_kv_btf(info);
> + if (libbpf_get_error(btf))
See discussion in [0], it seems relevant.
[0] https://lore.kernel.org/bpf/20220204225823.339548-3-jolsa@xxxxxxxxxx/
> return;
> - }
>
> if (json_output) {
> print_entry_json(info, key, value, btf);
> --
> 1.8.3.1
>
