Subject: Re: [PATCH v2 bpf-next 04/10] bpf: add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Tue, 28 Apr 2020 11:46:34 +0200

Andrii Nakryiko <[email-masked]> writes:

> Add ability to fetch bpf_link details through BPF_OBJ_GET_INFO_BY_FD command.
> Also enhance show_fdinfo to potentially include bpf_link type-specific
> information (similarly to obj_info).
>
> Also introduce enum bpf_link_type stored in bpf_link itself and expose it in
> UAPI. bpf_link_tracing also now will store and return bpf_attach_type.
>
> Signed-off-by: Andrii Nakryiko <[email-masked]>
> ---
>  include/linux/bpf-cgroup.h     |   2 -
>  include/linux/bpf.h            |  10 +-
>  include/linux/bpf_types.h      |   6 ++
>  include/uapi/linux/bpf.h       |  28 ++++++
>  kernel/bpf/btf.c               |   2 +
>  kernel/bpf/cgroup.c            |  45 ++++++++-
>  kernel/bpf/syscall.c           | 164 +++++++++++++++++++++++++++++----
>  kernel/bpf/verifier.c          |   2 +
>  tools/include/uapi/linux/bpf.h |  31 +++++++
>  9 files changed, 266 insertions(+), 24 deletions(-)
>
> diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> index d2d969669564..ab95824a1d99 100644
> --- a/include/linux/bpf-cgroup.h
> +++ b/include/linux/bpf-cgroup.h
> @@ -57,8 +57,6 @@ struct bpf_cgroup_link {
>  	enum bpf_attach_type type;
>  };
>  
> -extern const struct bpf_link_ops bpf_cgroup_link_lops;
> -
>  struct bpf_prog_list {
>  	struct list_head node;
>  	struct bpf_prog *prog;
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 875d1f0af803..701c4387c711 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1026,9 +1026,11 @@ extern const struct file_operations bpf_prog_fops;
>  	extern const struct bpf_verifier_ops _name ## _verifier_ops;
>  #define BPF_MAP_TYPE(_id, _ops) \
>  	extern const struct bpf_map_ops _ops;
> +#define BPF_LINK_TYPE(_id, _name)
>  #include <linux/bpf_types.h>
>  #undef BPF_PROG_TYPE
>  #undef BPF_MAP_TYPE
> +#undef BPF_LINK_TYPE
>  
>  extern const struct bpf_prog_ops bpf_offload_prog_ops;
>  extern const struct bpf_verifier_ops tc_cls_act_analyzer_ops;
> @@ -1086,6 +1088,7 @@ int bpf_prog_new_fd(struct bpf_prog *prog);
>  struct bpf_link {
>  	atomic64_t refcnt;
>  	u32 id;
> +	enum bpf_link_type type;
>  	const struct bpf_link_ops *ops;
>  	struct bpf_prog *prog;
>  	struct work_struct work;
> @@ -1103,9 +1106,14 @@ struct bpf_link_ops {
>  	void (*dealloc)(struct bpf_link *link);
>  	int (*update_prog)(struct bpf_link *link, struct bpf_prog *new_prog,
>  			   struct bpf_prog *old_prog);
> +	void (*show_fdinfo)(const struct bpf_link *link, struct seq_file *seq);
> +	int (*fill_link_info)(const struct bpf_link *link,
> +			      struct bpf_link_info *info,
> +			      const struct bpf_link_info *uinfo,
> +			      u32 info_len);
>  };
>  
> -void bpf_link_init(struct bpf_link *link,
> +void bpf_link_init(struct bpf_link *link, enum bpf_link_type type,
>  		   const struct bpf_link_ops *ops, struct bpf_prog *prog);
>  int bpf_link_prime(struct bpf_link *link, struct bpf_link_primer *primer);
>  int bpf_link_settle(struct bpf_link_primer *primer);
> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> index ba0c2d56f8a3..8345cdf553b8 100644
> --- a/include/linux/bpf_types.h
> +++ b/include/linux/bpf_types.h
> @@ -118,3 +118,9 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_STACK, stack_map_ops)
>  #if defined(CONFIG_BPF_JIT)
>  BPF_MAP_TYPE(BPF_MAP_TYPE_STRUCT_OPS, bpf_struct_ops_map_ops)
>  #endif
> +
> +BPF_LINK_TYPE(BPF_LINK_TYPE_RAW_TRACEPOINT, raw_tracepoint)
> +BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing)
> +#ifdef CONFIG_CGROUP_BPF
> +BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup)
> +#endif
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7e6541fceade..0eccafae55bb 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -222,6 +222,15 @@ enum bpf_attach_type {
>  
>  #define MAX_BPF_ATTACH_TYPE __MAX_BPF_ATTACH_TYPE
>  
> +enum bpf_link_type {
> +	BPF_LINK_TYPE_UNSPEC = 0,
> +	BPF_LINK_TYPE_RAW_TRACEPOINT = 1,
> +	BPF_LINK_TYPE_TRACING = 2,
> +	BPF_LINK_TYPE_CGROUP = 3,
> +
> +	MAX_BPF_LINK_TYPE,
> +};
> +
>  /* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
>   *
>   * NONE(default): No further bpf programs allowed in the subtree.
> @@ -3612,6 +3621,25 @@ struct bpf_btf_info {
>  	__u32 id;
>  } __attribute__((aligned(8)));
>  
> +struct bpf_link_info {
> +	__u32 type;
> +	__u32 id;
> +	__u32 prog_id;
> +	union {
> +		struct {
> +			__aligned_u64 tp_name; /* in/out: tp_name buffer ptr */
> +			__u32 tp_name_len;     /* in/out: tp_name buffer len */
> +		} raw_tracepoint;
> +		struct {
> +			__u32 attach_type;
> +		} tracing;

On the RFC I asked whether we could get the attach target here as well.
You said you'd look into it; what happened to that? :)

-Toke