netdev - Re: [PATCH bpf] bpf: fix "unresolved symbol" build error with resolve

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Date:   Wed, 30 Sep 2020 11:40:37 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH bpf] bpf: fix "unresolved symbol" build error with resolve_btfids

On Wed, Sep 30, 2020 at 9:41 AM Yonghong Song <yhs@...com> wrote:
>
> Michal reported a build failure likes below:
>    BTFIDS  vmlinux
>    FAILED unresolved symbol tcp_timewait_sock
>    make[1]: *** [/.../linux-5.9-rc7/Makefile:1176: vmlinux] Error 255
>
> This error can be triggered when config has CONFIG_NET enabled
> but CONFIG_INET disabled. In this case, there is no user of
> structs inet_timewait_sock and tcp_timewait_sock and hence vmlinux BTF
> types are not generated for these two structures.
>
> To fix the problem, omit the above two types for BTF_SOCK_TYPE_xxx
> macro if CONFIG_INET is not defined.
>
> Fixes: fce557bcef11 ("bpf: Make btf_sock_ids global")
> Reported-by: Michal Kubecek <mkubecek@...e.cz>
> Signed-off-by: Yonghong Song <yhs@...com>
> ---
>  include/linux/btf_ids.h | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> index 4867d549e3c1..d9a1e18d0921 100644
> --- a/include/linux/btf_ids.h
> +++ b/include/linux/btf_ids.h
> @@ -102,24 +102,36 @@ asm(                                                      \
>   * skc_to_*_sock() helpers. All these sockets should have
>   * sock_common as the first argument in its memory layout.
>   */
> -#define BTF_SOCK_TYPE_xxx \
> +
> +#define __BTF_SOCK_TYPE_xxx \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET, inet_sock)                    \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_CONN, inet_connection_sock)    \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_REQ, inet_request_sock)        \
> -       BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_TW, inet_timewait_sock)        \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_REQ, request_sock)                  \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK, sock)                         \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK_COMMON, sock_common)           \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP, tcp_sock)                      \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_REQ, tcp_request_sock)          \
> -       BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_TW, tcp_timewait_sock)          \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP6, tcp6_sock)                    \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP, udp_sock)                      \
>         BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP6, udp6_sock)
>
> +#define __BTF_SOCK_TW_TYPE_xxx \
> +       BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_TW, inet_timewait_sock)        \
> +       BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_TW, tcp_timewait_sock)
> +
> +#ifdef CONFIG_INET
> +#define BTF_SOCK_TYPE_xxx                                              \
> +       __BTF_SOCK_TYPE_xxx                                             \
> +       __BTF_SOCK_TW_TYPE_xxx
> +#else
> +#define BTF_SOCK_TYPE_xxx      __BTF_SOCK_TYPE_xxx
> +#endif
> +
>  enum {
>  #define BTF_SOCK_TYPE(name, str) name,
> -BTF_SOCK_TYPE_xxx
> +__BTF_SOCK_TYPE_xxx
> +__BTF_SOCK_TW_TYPE_xxx

Why BTF_SOCK_TYPE_xxx doesn't still work here after the above changes?

>  #undef BTF_SOCK_TYPE
>  MAX_BTF_SOCK_TYPE,
>  };
> --
> 2.24.1
>