On Fri, Feb 4, 2022 at 2:58 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> The commit e5043894b21f ("bpftool: Use libbpf_get_error() to check
> error") forced map dump with pretty print enabled to has BTF loaded,
> which is not necessarily needed.
>
> Keeping the libbpf_get_error call, but setting errno to 0 because
> get_map_kv_btf does nothing for this case.
>
> This fixes test_offload.py for me, which failed because of the
> pretty print fails with:
>
> Test map dump...
> Traceback (most recent call last):
> File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 1251, in <module>
> _, entries = bpftool("map dump id %d" % (m["id"]))
> File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 169, in bpftool
> return tool("bpftool", args, {"json":"-p"}, JSON=JSON, ns=ns,
> File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 155, in tool
> ret, stdout = cmd(ns + name + " " + params + args,
> File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 109, in cmd
> return cmd_result(proc, include_stderr=include_stderr, fail=fail)
> File "/root/bpf-next/tools/testing/selftests/bpf/./test_offload.py", line 131, in cmd_result
> raise Exception("Command failed: %s\n%s" % (proc.args, stderr))
> Exception: Command failed: bpftool -p map dump id 4325
>
> Fixes: e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> tools/bpf/bpftool/map.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index c66a3c979b7a..2ccf85042e75 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -862,6 +862,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
> prev_key = NULL;
>
> if (wtr) {
> + errno = 0;
I don't think that's right. errno can be modified by something inside
get_map_kv_btf() so this is unreliable approach. It's better to change
get_map_kv_btf() to return an error explicitly and a btf pointer
separate from error. Because btf == NULL isn't necessarily due to an
error anymore.
> btf = get_map_kv_btf(info);
> err = libbpf_get_error(btf);
> if (err) {
> --
> 2.34.1
>
