netdev - Re: [PATCH bpf-next 1/5] bpf: merge printk and seq

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Date:   Mon, 23 Aug 2021 21:38:41 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Dave Marchevsky <davemarchevsky@...com>
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>,
        Florent Revest <revest@...omium.org>,
        Networking <netdev@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/5] bpf: merge printk and seq_printf VARARG max macros

On Fri, Aug 20, 2021 at 7:59 PM Dave Marchevsky <davemarchevsky@...com> wrote:
>
> MAX_SNPRINTF_VARARGS and MAX_SEQ_PRINTF_VARARGS are used by bpf helpers
> bpf_snprintf and bpf_seq_printf to limit their varargs. Both call into
> bpf_bprintf_prepare for print formatting logic and have convenience
> macros in libbpf (BPF_SNPRINTF, BPF_SEQ_PRINTF) which use the same
> helper macros to convert varargs to a byte array.
>
> Changing shared functionality to support more varargs for either bpf
> helper would affect the other as well, so let's combine the _VARARGS
> macros to make this more obvious.
>
> Signed-off-by: Dave Marchevsky <davemarchevsky@...com>
> ---

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

>  include/linux/bpf.h      | 2 ++
>  kernel/bpf/helpers.c     | 4 +---
>  kernel/trace/bpf_trace.c | 4 +---
>  3 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index f4c16f19f83e..be8d57e6e78a 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -2216,6 +2216,8 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
>  struct btf_id_set;
>  bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
>
> +#define MAX_BPRINTF_VARARGS            12
> +
>  int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
>                         u32 **bin_buf, u32 num_args);
>  void bpf_bprintf_cleanup(void);
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 4e8540716187..5ce19b376ef7 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -969,15 +969,13 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
>         return err;
>  }
>
> -#define MAX_SNPRINTF_VARARGS           12
> -
>  BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt,
>            const void *, data, u32, data_len)
>  {
>         int err, num_args;
>         u32 *bin_args;
>
> -       if (data_len % 8 || data_len > MAX_SNPRINTF_VARARGS * 8 ||
> +       if (data_len % 8 || data_len > MAX_BPRINTF_VARARGS * 8 ||
>             (data_len && !data))
>                 return -EINVAL;
>         num_args = data_len / 8;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index cbc73c08c4a4..2cf4bfa1ab7b 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -414,15 +414,13 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
>         return &bpf_trace_printk_proto;
>  }
>
> -#define MAX_SEQ_PRINTF_VARARGS         12
> -
>  BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
>            const void *, data, u32, data_len)
>  {
>         int err, num_args;
>         u32 *bin_args;
>
> -       if (data_len & 7 || data_len > MAX_SEQ_PRINTF_VARARGS * 8 ||
> +       if (data_len & 7 || data_len > MAX_BPRINTF_VARARGS * 8 ||
>             (data_len && !data))
>                 return -EINVAL;
>         num_args = data_len / 8;
> --
> 2.30.2
>