Re: [PATCH RFC bpf-next v1 5/8] bpf: Introduce a new program type bpf_view.

[Yonghong Song <yhs@fb.com>]

On 1/6/22 1:50 PM, Hao Luo wrote:
> Introduce a new program type called "bpf_view", which can be used to
> print out a kernel object's state to a seq file. So the signature of
> this program consists of two parameters: a seq file and a kernel object.
> Currently only 'struct cgroup' is supported.
> 
> The following patches will introduce a call site for this program type
> and allow users to customize the format of printing out the state of
> kernel objects to userspace.
> 
> Signed-off-by: Hao Luo <haoluo@google.com>
> ---
>   include/linux/bpf.h            |   4 +
>   include/uapi/linux/bpf.h       |   2 +
>   kernel/bpf/Makefile            |   2 +-
>   kernel/bpf/bpf_view.c          | 179 +++++++++++++++++++++++++++++++++
>   kernel/bpf/bpf_view.h          |  24 +++++
>   kernel/bpf/syscall.c           |   3 +
>   kernel/bpf/verifier.c          |   6 ++
>   kernel/trace/bpf_trace.c       |  12 ++-
>   tools/include/uapi/linux/bpf.h |   2 +
>   9 files changed, 230 insertions(+), 4 deletions(-)
>   create mode 100644 kernel/bpf/bpf_view.c
>   create mode 100644 kernel/bpf/bpf_view.h
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 2ec693c3d6f6..16f582dfff7e 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1622,6 +1622,10 @@ void bpf_iter_map_show_fdinfo(const struct bpf_iter_aux_info *aux,
>   int bpf_iter_map_fill_link_info(const struct bpf_iter_aux_info *aux,
>   				struct bpf_link_info *info);
>   
> +bool bpf_view_prog_supported(struct bpf_prog *prog);
> +int bpf_view_link_attach(const union bpf_attr *attr, bpfptr_t uattr,
> +			 struct bpf_prog *prog);
> +
>   int map_set_for_each_callback_args(struct bpf_verifier_env *env,
>   				   struct bpf_func_state *caller,
>   				   struct bpf_func_state *callee);
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index b0383d371b9a..efa0f21d13ba 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -982,6 +982,7 @@ enum bpf_attach_type {
>   	BPF_MODIFY_RETURN,
>   	BPF_LSM_MAC,
>   	BPF_TRACE_ITER,
> +	BPF_TRACE_VIEW,

Please add the new entry to the end of enum list. Otherwise,
this will break backward compatibility.

>   	BPF_CGROUP_INET4_GETPEERNAME,
>   	BPF_CGROUP_INET6_GETPEERNAME,
>   	BPF_CGROUP_INET4_GETSOCKNAME,
> @@ -1009,6 +1010,7 @@ enum bpf_link_type {
>   	BPF_LINK_TYPE_NETNS = 5,
>   	BPF_LINK_TYPE_XDP = 6,
>   	BPF_LINK_TYPE_PERF_EVENT = 7,
> +	BPF_LINK_TYPE_VIEW = 8,
>   
>   	MAX_BPF_LINK_TYPE,
>   };
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