netdev - Re: [PATCH] libbpf: fix array

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Date:   Mon, 7 Mar 2022 09:04:12 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Guo Zhengkui <guozhengkui@...o.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libbpf: fix array_size.cocci warning

On Sun, Mar 6, 2022 at 5:20 AM Guo Zhengkui <guozhengkui@...o.com> wrote:
>
> Fix the following coccicheck warning:
> tools/lib/bpf/bpf.c:114:31-32: WARNING: Use ARRAY_SIZE
> tools/lib/bpf/xsk.c:484:34-35: WARNING: Use ARRAY_SIZE
> tools/lib/bpf/xsk.c:485:35-36: WARNING: Use ARRAY_SIZE

Thanks for the fix. Note that the AF_XDP support has been deprecated
and will be removed in the 1.0 libbpf release. So there is no point in
fixing this for the xsk.c file. These days, the AF_XDP support resides
in libxdp. I checked if your patch would apply to libxdp, but the
loading of the default program is handled differently there, so this
line does not exist anymore.

> It has been tested with gcc (Debian 8.3.0-6) 8.3.0 on x86_64.
>
> Signed-off-by: Guo Zhengkui <guozhengkui@...o.com>
> ---
>  tools/lib/bpf/bpf.c | 3 ++-
>  tools/lib/bpf/xsk.c | 4 ++--
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 418b259166f8..3c7c180294fa 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -29,6 +29,7 @@
>  #include <errno.h>
>  #include <linux/bpf.h>
>  #include <linux/filter.h>
> +#include <linux/kernel.h>
>  #include <limits.h>
>  #include <sys/resource.h>
>  #include "bpf.h"
> @@ -111,7 +112,7 @@ int probe_memcg_account(void)
>                 BPF_EMIT_CALL(BPF_FUNC_ktime_get_coarse_ns),
>                 BPF_EXIT_INSN(),
>         };
> -       size_t insn_cnt = sizeof(insns) / sizeof(insns[0]);
> +       size_t insn_cnt = ARRAY_SIZE(insns);
>         union bpf_attr attr;
>         int prog_fd;
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index edafe56664f3..19dbefb1caf1 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -481,8 +481,8 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>                 BPF_EMIT_CALL(BPF_FUNC_redirect_map),
>                 BPF_EXIT_INSN(),
>         };
> -       size_t insns_cnt[] = {sizeof(prog) / sizeof(struct bpf_insn),
> -                             sizeof(prog_redirect_flags) / sizeof(struct bpf_insn),
> +       size_t insns_cnt[] = {ARRAY_SIZE(prog),
> +                             ARRAY_SIZE(prog_redirect_flags),
>         };
>         struct bpf_insn *progs[] = {prog, prog_redirect_flags};
>         enum xsk_prog option = get_xsk_prog();
> --
> 2.20.1
>