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

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Message-ID: <20190702155316.GJ6757@mini-arch>
Date:   Tue, 2 Jul 2019 08:53:16 -0700
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     ast@...nel.org, daniel@...earbox.net, kafai@...com,
        songliubraving@...com, yhs@...com, sdf@...gle.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] bpf: cgroup: Fix build error without CONFIG_NET

On 07/02, 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.
Can you share the config? Do I understand correctly that you have
CONFIG_NET=n and CONFIG_BPF=y? What parts of BPF do you expect to
work in this case?

Less invasive fix would be something along the lines:

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;

> 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)
> -- 
> 2.7.4
> 
>