linux-kernel - Re: [PATCH bpf-next 4/5] libbpf: Introduce a BPF

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Message-ID: <CAEf4BzZvWnmUm0T4Q5WM9i1TUs=8FumeNwbbO8fhSOM59PU_rA@mail.gmail.com>
Date:   Mon, 15 Mar 2021 21:39:39 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Florent Revest <revest@...omium.org>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Yonghong Song <yhs@...com>, KP Singh <kpsingh@...nel.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 4/5] libbpf: Introduce a BPF_SNPRINTF helper macro

On Wed, Mar 10, 2021 at 2:02 PM Florent Revest <revest@...omium.org> wrote:
>
> Similarly to BPF_SEQ_PRINTF, this macro turns variadic arguments into an
> array of u64, making it more natural to call the bpf_snprintf helper.
>
> Signed-off-by: Florent Revest <revest@...omium.org>
> ---
>  tools/lib/bpf/bpf_tracing.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
> index f6a2deb3cd5b..89e82da9b8a0 100644
> --- a/tools/lib/bpf/bpf_tracing.h
> +++ b/tools/lib/bpf/bpf_tracing.h
> @@ -457,4 +457,19 @@ static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
>                 ___ret;                                                     \
>         })
>
> +/*
> + * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of
> + * an array of u64.
> + */
> +#define BPF_SNPRINTF(out, out_size, fmt, args...)                          \
> +       ({                                                                  \
> +               _Pragma("GCC diagnostic push")                              \
> +               _Pragma("GCC diagnostic ignored \"-Wint-conversion\"")      \
> +               ___bpf_build_param(args);                                   \
> +               _Pragma("GCC diagnostic pop")                               \
> +               int ___ret = bpf_snprintf(out, out_size, fmt,               \
> +                                           ___param, sizeof(___param));    \

same problem, mixing variable declarations and code

> +               ___ret;                                                     \
> +       })
> +
>  #endif
> --
> 2.30.1.766.gb4fecdf3b7-goog
>