Re: [PATCH] tools/bpftool: Fix error return code in do_skeleton()

From: Daniel Borkmann <daniel@iogearbox.net>
To: YueHaibing <yuehaibing@huawei.com>,
	ast@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
	andriin@fb.com, john.fastabend@gmail.com, kpsingh@chromium.org
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tools/bpftool: Fix error return code in do_skeleton()
Date: Wed, 15 Jul 2020 21:23:33 +0200	[thread overview]
Message-ID: <6cb1dfd7-6456-ef1c-d708-042ab53b3d2c@iogearbox.net> (raw)
In-Reply-To: <20200715031353.14692-1-yuehaibing@huawei.com>

On 7/15/20 5:13 AM, YueHaibing wrote:
> The error return code should be PTR_ERR(obj) other than
> PTR_ERR(NULL).
> 
> Fixes: 5dc7a8b21144 ("bpftool, selftests/bpf: Embed object file inside skeleton")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> ---
>   tools/bpf/bpftool/gen.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> index 10de76b296ba..35f62273cdbd 100644
> --- a/tools/bpf/bpftool/gen.c
> +++ b/tools/bpf/bpftool/gen.c
> @@ -305,8 +305,9 @@ static int do_skeleton(int argc, char **argv)
>   	opts.object_name = obj_name;
>   	obj = bpf_object__open_mem(obj_data, file_sz, &opts);
>   	if (IS_ERR(obj)) {
> +		err = PTR_ERR(obj);
> +		p_err("failed to open BPF object file: %ld", err);
>   		obj = NULL;
> -		p_err("failed to open BPF object file: %ld", PTR_ERR(obj));
>   		goto out;

Instead of just the error number, could we dump something useful to the user here
via libbpf_strerror() given you touch this line? Also, I think the convention in
do_skeleton() is to just return {0,-1} given this is propagated as return code
for bpftool.

>   	}
>   
> 