linux-kernel - Re: [PATCH v3 1/2] bpftool: Print map ID upon creation and support JSON output

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAADnVQLe6a8Kae892sVaND-2p1DQDXGD5gqxHWHHUC85ntLCqw@mail.gmail.com>
Date: Tue, 4 Nov 2025 09:54:48 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc: bpf <bpf@...r.kernel.org>, Alan Maguire <alan.maguire@...cle.com>, 
	Yonghong Song <yonghong.song@...ux.dev>, Quentin Monnet <qmo@...nel.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] bpftool: Print map ID upon creation and support
 JSON output

On Sat, Nov 1, 2025 at 12:34 PM Harshit Mogalapalli
<harshit.m.mogalapalli@...cle.com> wrote:
>
> It is useful to print map ID on successful creation.
>
> JSON case:
> $ ./bpftool -j map create /sys/fs/bpf/test_map4 type hash key 4 value 8 entries 128 name map4
> {"id":12}
>
> Generic case:
> $ ./bpftool  map create /sys/fs/bpf/test_map5 type hash key 4 value 8 entries 128 name map5
> Map successfully created with ID: 15
>
> Bpftool Issue: https://github.com/libbpf/bpftool/issues/121
> Acked-by: Yonghong Song <yonghong.song@...ux.dev>
> Reviewed-by: Quentin Monnet <qmo@...nel.org>
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> ---
> v2->v3: remove a line break("\n" ) in p_err statement. [Thanks Quentin]
> ---
>  tools/bpf/bpftool/map.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index c9de44a45778..f32ae5476d76 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -1251,6 +1251,8 @@ static int do_create(int argc, char **argv)
>         LIBBPF_OPTS(bpf_map_create_opts, attr);
>         enum bpf_map_type map_type = BPF_MAP_TYPE_UNSPEC;
>         __u32 key_size = 0, value_size = 0, max_entries = 0;
> +       struct bpf_map_info map_info = {};
> +       __u32 map_info_len = sizeof(map_info);
>         const char *map_name = NULL;
>         const char *pinfile;
>         int err = -1, fd;
> @@ -1353,13 +1355,24 @@ static int do_create(int argc, char **argv)
>         }
>
>         err = do_pin_fd(fd, pinfile);
> -       close(fd);
>         if (err)
> -               goto exit;
> +               goto close_fd;
>
> -       if (json_output)
> -               jsonw_null(json_wtr);
> +       err = bpf_obj_get_info_by_fd(fd, &map_info, &map_info_len);
> +       if (err) {
> +               p_err("Failed to fetch map info: %s", strerror(errno));
> +               goto close_fd;
> +       }
>
> +       if (json_output) {
> +               jsonw_start_object(json_wtr);
> +               jsonw_int_field(json_wtr, "id", map_info.id);
> +               jsonw_end_object(json_wtr);
> +       } else {
> +               printf("Map successfully created with ID: %u\n", map_info.id);
> +       }

bpftool doesn't print it today and some scripts may depend on that.
Let's drop this 'printf'. Json can do it unconditionally, since
json parsing scripts should filter things they care about.

pw-bot: cr