linux-kernel - Re: [PATCH bpf-next v2] bpf: Only call sock_from_file with CONFIG

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Message-ID: <20201207213300.fy6xevnoidh2vk37@kafai-mbp.dhcp.thefacebook.com>
Date:   Mon, 7 Dec 2020 13:33:00 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     Florent Revest <revest@...omium.org>
CC:     <bpf@...r.kernel.org>, <ast@...nel.org>, <daniel@...earbox.net>,
        <andrii@...nel.org>, <kpsingh@...omium.org>,
        <rdunlap@...radead.org>, <linux-next@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2] bpf: Only call sock_from_file with CONFIG_NET

On Mon, Dec 07, 2020 at 09:06:05PM +0100, Florent Revest wrote:
> This avoids
>   ld: kernel/trace/bpf_trace.o: in function `bpf_sock_from_file':
>   bpf_trace.c:(.text+0xe23): undefined reference to `sock_from_file'
> When compiling a kernel with BPF and without NET.
> 
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Florent Revest <revest@...omium.org>
> ---
>  kernel/trace/bpf_trace.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 0cf0a6331482..29ec2b3b1cc4 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1272,7 +1272,11 @@ const struct bpf_func_proto bpf_snprintf_btf_proto = {
>  
>  BPF_CALL_1(bpf_sock_from_file, struct file *, file)
>  {
> +#ifdef CONFIG_NET
>  	return (unsigned long) sock_from_file(file);
> +#else
> +	return 0;
> +#endif
>  }
Should bpf_sock_from_file_proto belong to
tracing_prog_func_proto() instead of bpf_tracing_func_proto()?
bpf_skc_to_*_proto is also in tracing_prog_func_proto()
where there is an existing "#ifdef CONFIG_NET".

>  
>  BTF_ID_LIST(bpf_sock_from_file_btf_ids)
> -- 
> 2.29.2.576.ga3fc446d84-goog
>