netdev - Re: [PATCH bpf-next] bpf: cgroup: Fix build error without CONFIG

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Date:   Tue, 2 Jul 2019 16:01:16 +0000
From:   Yonghong Song <yhs@...com>
To:     YueHaibing <yuehaibing@...wei.com>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Martin Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        "sdf@...gle.com" <sdf@...gle.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpf: cgroup: Fix build error without CONFIG_NET



On 7/2/19 6:29 AM, YueHaibing wrote:
> If CONFIG_NET is not set, gcc building fails:
> 
> kernel/bpf/cgroup.o: In function `cg_sockopt_func_proto':
> cgroup.c:(.text+0x237e): undefined reference to `bpf_sk_storage_get_proto'
> cgroup.c:(.text+0x2394): undefined reference to `bpf_sk_storage_delete_proto'
> kernel/bpf/cgroup.o: In function `__cgroup_bpf_run_filter_getsockopt':
> (.text+0x2a1f): undefined reference to `lock_sock_nested'
> (.text+0x2ca2): undefined reference to `release_sock'
> kernel/bpf/cgroup.o: In function `__cgroup_bpf_run_filter_setsockopt':
> (.text+0x3006): undefined reference to `lock_sock_nested'
> (.text+0x32bb): undefined reference to `release_sock'
> 
> Add CONFIG_NET dependency to fix this.
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>   init/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index e2e51b5..341cf2a 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -998,6 +998,7 @@ config CGROUP_PERF
>   config CGROUP_BPF
>   	bool "Support for eBPF programs attached to cgroups"
>   	depends on BPF_SYSCALL
> +	depends on NET
>   	select SOCK_CGROUP_DATA
>   	help
>   	  Allow attaching eBPF programs to a cgroup using the bpf(2)


Adding CGROUP_BPF depending on CONFIG_NET is not a good idea.
There should be really independent.

How about the following change?

-bash-4.4$ git diff
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 76fa0076f20d..0a00eaca6fae 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -939,6 +939,7 @@ int __cgroup_bpf_run_filter_sysctl(struct 
ctl_table_header *head,
  }
  EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl);

+#ifdef CONFIG_NET
  static bool __cgroup_bpf_prog_array_is_empty(struct cgroup *cgrp,
                                              enum bpf_attach_type 
attach_type)
  {
@@ -1120,6 +1121,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock 
*sk, int level,
         return ret;
  }
  EXPORT_SYMBOL(__cgroup_bpf_run_filter_getsockopt);
+#endif

  static ssize_t sysctl_cpy_dir(const struct ctl_dir *dir, char **bufp,
                               size_t *lenp)
@@ -1386,10 +1388,12 @@ static const struct bpf_func_proto *
  cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog 
*prog)
  {
         switch (func_id) {
+#ifdef CONFIG_NET
         case BPF_FUNC_sk_storage_get:
                 return &bpf_sk_storage_get_proto;
         case BPF_FUNC_sk_storage_delete:
                 return &bpf_sk_storage_delete_proto;
+#endif
  #ifdef CONFIG_INET
         case BPF_FUNC_tcp_sock:
                 return &bpf_tcp_sock_proto;

Stanislav, you introduced getsockopt and setsockopt hooks which
have this compilation issues if CONFIG_NET=n.
What do you think for the above change?