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

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Message-ID: <fd312c26-db8e-cae3-1c14-869d8e3a62ae@fb.com>
Date:   Tue, 2 Jul 2019 16:04:55 +0000
From:   Yonghong Song <yhs@...com>
To:     YueHaibing <yuehaibing@...wei.com>
CC:     Stanislav Fomichev <sdf@...ichev.me>,
        "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>,
        "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 8:53 AM, Stanislav Fomichev wrote:
> 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;

Ah. Just send another email without checking inbox.
Looks like the above change is preferred.
YueHaibing, could you make change and resubmit your patch?

> 
>> 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
>>
>>