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Date:   Tue, 19 Jul 2022 08:46:12 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Xu Jia <xujia39@...wei.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org
Subject: Re: [PATCH bpf-next] bpf: fix bpf compile error caused by CONFIG_CGROUP_BPF

On Tue, Jul 19, 2022 at 1:49 AM Xu Jia <xujia39@...wei.com> wrote:
>
> We failed to compile when CONFIG_BPF_LSM is enabled but CONFIG_CGROUP_BPF
> is not set. The failings are shown as below:
>
> kernel/bpf/trampoline.o: in function `bpf_trampoline_link_cgroup_shim'
> trampoline.c: undefined reference to `bpf_cgroup_atype_get'
> kernel/bpf/bpf_lsm.o: In function `bpf_lsm_find_cgroup_shim':
> bpf_lsm.c: undefined reference to `__cgroup_bpf_run_lsm_current'
> bpf_lsm.c: undefined reference to `__cgroup_bpf_run_lsm_sock'
> bpf_lsm.c: undefined reference to `__cgroup_bpf_run_lsm_socket'
>
> Fix them by protecting these functions with CONFIG_CGROUP_BPF.

Should be fixed by the following?

https://lore.kernel.org/bpf/20220714185404.3647772-1-sdf@google.com/

> Fixes: 69fd337a975c ("bpf: per-cgroup lsm flavor")
> Signed-off-by: Xu Jia <xujia39@...wei.com>
> ---
>  include/linux/bpf.h     | 12 +++++++++---
>  include/linux/bpf_lsm.h | 10 ++++++----
>  kernel/bpf/bpf_lsm.c    |  2 ++
>  kernel/bpf/trampoline.c |  2 ++
>  4 files changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 2b21f2a3452f..add8895c02cc 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1255,9 +1255,7 @@ struct bpf_dummy_ops {
>  int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
>                             union bpf_attr __user *uattr);
>  #endif
> -int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
> -                                   int cgroup_atype);
> -void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog);
> +
>  #else
>  static inline const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
>  {
> @@ -1281,6 +1279,14 @@ static inline int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map,
>  {
>         return -EINVAL;
>  }
> +#endif
> +
> +#if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL) && \
> +    defined(CONFIG_CGROUP_BPF)
> +int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
> +                                   int cgroup_atype);
> +void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog);
> +#else
>  static inline int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
>                                                   int cgroup_atype)
>  {
> diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
> index 4bcf76a9bb06..bed45a0c8a9c 100644
> --- a/include/linux/bpf_lsm.h
> +++ b/include/linux/bpf_lsm.h
> @@ -42,8 +42,6 @@ extern const struct bpf_func_proto bpf_inode_storage_get_proto;
>  extern const struct bpf_func_proto bpf_inode_storage_delete_proto;
>  void bpf_inode_storage_free(struct inode *inode);
>
> -void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func);
> -
>  #else /* !CONFIG_BPF_LSM */
>
>  static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id)
> @@ -67,11 +65,15 @@ static inline void bpf_inode_storage_free(struct inode *inode)
>  {
>  }
>
> +#endif /* CONFIG_BPF_LSM */
> +
> +#if defined(CONFIG_BPF_LSM) && defined(CONFIG_BPF_CGROUP)
> +void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func);
> +#else
>  static inline void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog,
>                                            bpf_func_t *bpf_func)
>  {
>  }
> -
> -#endif /* CONFIG_BPF_LSM */
> +#endif
>
>  #endif /* _LINUX_BPF_LSM_H */
> diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> index d469b7f3deef..29527828b38b 100644
> --- a/kernel/bpf/bpf_lsm.c
> +++ b/kernel/bpf/bpf_lsm.c
> @@ -63,6 +63,7 @@ BTF_ID(func, bpf_lsm_socket_post_create)
>  BTF_ID(func, bpf_lsm_socket_socketpair)
>  BTF_SET_END(bpf_lsm_unlocked_sockopt_hooks)
>
> +#ifdef CONFIG_BPF_CGROUP
>  void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog,
>                              bpf_func_t *bpf_func)
>  {
> @@ -86,6 +87,7 @@ void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog,
>  #endif
>                 *bpf_func = __cgroup_bpf_run_lsm_current;
>  }
> +#endif /* CONFIG_BPF_CGROUP */
>
>  int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
>                         const struct bpf_prog *prog)
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index 6cd226584c33..127924711935 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -525,6 +525,7 @@ static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
>         .dealloc = bpf_shim_tramp_link_dealloc,
>  };
>
> +#ifdef CONFIG_CGROUP_BPF
>  static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
>                                                      bpf_func_t bpf_func,
>                                                      int cgroup_atype)
> @@ -668,6 +669,7 @@ void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
>
>         bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
>  }
> +#endif /* CONFIG_CGROUP_BPF */
>  #endif
>
>  struct bpf_trampoline *bpf_trampoline_get(u64 key,
> --
> 2.25.1
>

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