linux-kernel - Re: [PATCHv2 bpf-next] bpf: fix building without CONFIG

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Date:   Mon, 8 Oct 2018 13:52:42 -0700
From:   Song Liu <liu.song.a23@...il.com>
To:     joe@...d.net.nz
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Arnd Bergmann <arnd@...db.de>,
        Alexei Starovoitov <ast@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        makita.toshiaki@....ntt.co.jp, Lawrence Brakmo <brakmo@...com>,
        Andrey Ignatov <rdna@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Mathieu Xhonneux <m.xhonneux@...il.com>,
        David Ahern <dsahern@...il.com>,
        Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 bpf-next] bpf: fix building without CONFIG_INET

On Mon, Oct 8, 2018 at 11:30 AM Joe Stringer <joe@...d.net.nz> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> The newly added TCP and UDP handling fails to link when CONFIG_INET
> is disabled:
>
> net/core/filter.o: In function `sk_lookup':
> filter.c:(.text+0x7ff8): undefined reference to `tcp_hashinfo'
> filter.c:(.text+0x7ffc): undefined reference to `tcp_hashinfo'
> filter.c:(.text+0x8020): undefined reference to `__inet_lookup_established'
> filter.c:(.text+0x8058): undefined reference to `__inet_lookup_listener'
> filter.c:(.text+0x8068): undefined reference to `udp_table'
> filter.c:(.text+0x8070): undefined reference to `udp_table'
> filter.c:(.text+0x808c): undefined reference to `__udp4_lib_lookup'
> net/core/filter.o: In function `bpf_sk_release':
> filter.c:(.text+0x82e8): undefined reference to `sock_gen_put'
>
> Wrap the related sections of code in #ifdefs for the config option.
>
> Furthermore, sk_lookup() should always have been marked 'static', this
> also avoids a warning about a missing prototype when building with
> 'make W=1'.
>
> Fixes: 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Joe Stringer <joe@...d.net.nz>

Acked-by: Song Liu <songliubraving@...com>


> ---
> v2: Modify the patch to remove the related code in preprocessor rather
>     than relying on compiler optimizations to remove the code.
> ---
>  net/core/filter.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 30c6b2d3ef16..4bbc6567fcb8 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4817,8 +4817,9 @@ static const struct bpf_func_proto bpf_lwt_seg6_adjust_srh_proto = {
>  };
>  #endif /* CONFIG_IPV6_SEG6_BPF */
>
> -struct sock *sk_lookup(struct net *net, struct bpf_sock_tuple *tuple,
> -                      struct sk_buff *skb, u8 family, u8 proto)
> +#ifdef CONFIG_INET
> +static struct sock *sk_lookup(struct net *net, struct bpf_sock_tuple *tuple,
> +                             struct sk_buff *skb, u8 family, u8 proto)
>  {
>         int dif = skb->dev->ifindex;
>         bool refcounted = false;
> @@ -4951,6 +4952,7 @@ static const struct bpf_func_proto bpf_sk_release_proto = {
>         .ret_type       = RET_INTEGER,
>         .arg1_type      = ARG_PTR_TO_SOCKET,
>  };
> +#endif /* CONFIG_INET */
>
>  bool bpf_helper_changes_pkt_data(void *func)
>  {
> @@ -5158,12 +5160,14 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>         case BPF_FUNC_skb_ancestor_cgroup_id:
>                 return &bpf_skb_ancestor_cgroup_id_proto;
>  #endif
> +#ifdef CONFIG_INET
>         case BPF_FUNC_sk_lookup_tcp:
>                 return &bpf_sk_lookup_tcp_proto;
>         case BPF_FUNC_sk_lookup_udp:
>                 return &bpf_sk_lookup_udp_proto;
>         case BPF_FUNC_sk_release:
>                 return &bpf_sk_release_proto;
> +#endif
>         default:
>                 return bpf_base_func_proto(func_id);
>         }
> @@ -5264,12 +5268,14 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>                 return &bpf_sk_redirect_hash_proto;
>         case BPF_FUNC_get_local_storage:
>                 return &bpf_get_local_storage_proto;
> +#ifdef CONFIG_INET
>         case BPF_FUNC_sk_lookup_tcp:
>                 return &bpf_sk_lookup_tcp_proto;
>         case BPF_FUNC_sk_lookup_udp:
>                 return &bpf_sk_lookup_udp_proto;
>         case BPF_FUNC_sk_release:
>                 return &bpf_sk_release_proto;
> +#endif
>         default:
>                 return bpf_base_func_proto(func_id);
>         }
> --
> 2.17.1
>