netdev - Re: [PATCH bpf-next 0/2] bpftool: fix feature output when helper probes fail

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Date:   Thu, 5 May 2022 11:15:48 +0100
From:   Quentin Monnet <quentin@...valent.com>
To:     Milan Landaverde <milan@...verde.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Paul Chaignon <paul@...valent.com>,
        Niklas Söderlund <niklas.soderlund@...igine.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 0/2] bpftool: fix feature output when helper
 probes fail

2022-05-04 12:13 UTC-0400 ~ Milan Landaverde <milan@...verde.com>
> Currently in bpftool's feature probe, we incorrectly tell the user that
> all of the helper functions are supported for program types where helper
> probing fails or is explicitly unsupported[1]:
> 
> $ bpftool feature probe
> ...
> eBPF helpers supported for program type tracing:
> 	- bpf_map_lookup_elem
> 	- bpf_map_update_elem
> 	- bpf_map_delete_elem
> 	...
> 	- bpf_redirect_neigh
> 	- bpf_check_mtu
> 	- bpf_sys_bpf
> 	- bpf_sys_close
> 
> This patch adjusts bpftool to relay to the user when helper support
> can't be determined:
> 
> $ bpftool feature probe
> ...
> eBPF helpers supported for program type lirc_mode2:
>     Program type not supported
> eBPF helpers supported for program type tracing:
>     Could not determine which helpers are available
> eBPF helpers supported for program type struct_opts:
>     Could not determine which helpers are available
> eBPF helpers supported for program type ext:
>     Could not determine which helpers are available
> 
> Rather than imply that no helpers are available for the program type, we
> let the user know that helper function probing failed entirely.
> 
> [1] https://lore.kernel.org/bpf/20211217171202.3352835-2-andrii@kernel.org/
> 
> Milan Landaverde (2):
>   bpftool: adjust for error codes from libbpf probes
>   bpftool: output message if no helpers found in feature probing
> 
>  tools/bpf/bpftool/feature.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> --
> 2.32.0
> 

Looks good to me, thank you

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