linux-kernel - Re: [PATCH bpf-next v3 5/6] libbpf: Introduce a BPF

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Message-ID: <CAEf4Bzb-wSXzyaRfcHQT6Q2bMn-WZsz6aX8V=PtTpia6i6eQNg@mail.gmail.com>
Date:   Tue, 13 Apr 2021 16:18:45 -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 v3 5/6] libbpf: Introduce a BPF_SNPRINTF helper macro

On Mon, Apr 12, 2021 at 8:38 AM 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>
> ---

Nice!

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  tools/lib/bpf/bpf_tracing.h | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
> index 1c2e91ee041d..8c954ebc0c7c 100644
> --- a/tools/lib/bpf/bpf_tracing.h
> +++ b/tools/lib/bpf/bpf_tracing.h
> @@ -447,4 +447,22 @@ static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
>                        ___param, sizeof(___param));             \
>  })
>
> +/*
> + * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of
> + * an array of u64.
> + */
> +#define BPF_SNPRINTF(out, out_size, fmt, args...)              \
> +({                                                             \
> +       static const char ___fmt[] = fmt;                       \
> +       unsigned long long ___param[___bpf_narg(args)];         \
> +                                                               \
> +       _Pragma("GCC diagnostic push")                          \
> +       _Pragma("GCC diagnostic ignored \"-Wint-conversion\"")  \
> +       ___bpf_fill(___param, args);                            \
> +       _Pragma("GCC diagnostic pop")                           \
> +                                                               \
> +       bpf_snprintf(out, out_size, ___fmt,                     \
> +                    ___param, sizeof(___param));               \
> +})
> +
>  #endif
> --
> 2.31.1.295.g9ea45b61b8-goog
>