netdev - Re: [PATCH bpf-next v4] libbpf: Show supported ELF section names on when failed to guess a prog/attach type

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Date:   Mon, 21 Jan 2019 14:07:55 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Taeung Song <treeze.taeung@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Andrey Ignatov <rdna@...com>
Subject: Re: [PATCH bpf-next v4] libbpf: Show supported ELF section names on
 when failed to guess a prog/attach type

2019-01-21 22:06 UTC+0900 ~ Taeung Song <treeze.taeung@...il.com>
> We need to let users check their wrong ELF section name
> with proper ELF section names when failed to get a prog/attach type from it.
> Because users can't realize libbpf guess prog/attach types from
> given ELF section names.
> For example, when a 'cgroup' section name of a BPF program is used,
> show available ELF section names(types).
> 
> Before:
> 
>     $ bpftool prog load bpf-prog.o /sys/fs/bpf/prog1
>     Error: failed to guess program type based on ELF section name cgroup
> 
> After:
> 
>     libbpf: failed to guess program type based on ELF section name 'cgroup'
>     libbpf: supported section(type) names are: socket kprobe/ kretprobe/ classifier action tracepoint/ raw_tracepoint/ xdp perf_event lwt_in lwt_out lwt_xmit lwt_seg6local cgroup_skb/ingress cgroup_skb/egress cgroup/skb cgroup/sock cgroup/post_bind4 cgroup/post_bind6 cgroup/dev sockops sk_skb/stream_parser sk_skb/stream_verdict sk_skb sk_msg lirc_mode2 flow_dissector cgroup/bind4 cgroup/bind6 cgroup/connect4 cgroup/connect6 cgroup/sendmsg4 cgroup/sendmsg6
> 
> Cc: Quentin Monnet <quentin.monnet@...ronome.com>
> Cc: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Cc: Andrey Ignatov <rdna@...com>
> Signed-off-by: Taeung Song <treeze.taeung@...il.com>

Thanks for the modifications! This version looks good to me.

Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>

> ---
>  tools/bpf/bpftool/prog.c                      | 10 ++--
>  tools/lib/bpf/libbpf.c                        | 46 ++++++++++++++++++-
>  .../selftests/bpf/test_socket_cookie.c        |  4 +-
>  3 files changed, 48 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 2d1bb7d6ff51..0640e9bc0ada 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c

> @@ -2682,12 +2711,20 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
>  		*expected_attach_type = section_names[i].expected_attach_type;
>  		return 0;
>  	}
> +	pr_warning("failed to guess program type based on ELF section name '%s'\n", name);
> +	type_names = libbpf_get_type_names(false);
> +	if (type_names != NULL) {

For next time: No need for the "!= NULL" part here (just checking on
"if (type_names)" is enough). But don't respin your series just for that :).

> +		pr_info("supported section(type) names are:%s\n", type_names);
> +		free(type_names);
> +	}
> +
>  	return -EINVAL;
>  }
>  
>  int libbpf_attach_type_by_name(const char *name,
>  			       enum bpf_attach_type *attach_type)
>  {
> +	char *type_names;
>  	int i;
>  
>  	if (!name)