netdev - Re: [PATCH bpf-next v3 6/8] bpf: add documentation for eBPF helpers (42-50)

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Date:   Wed, 18 Apr 2018 16:29:22 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Quentin Monnet <quentin.monnet@...ronome.com>
Cc:     daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org,
        oss-drivers@...ronome.com, linux-doc@...r.kernel.org,
        linux-man@...r.kernel.org, Kaixu Xia <xiakaixu@...wei.com>,
        Martin KaFai Lau <kafai@...com>,
        Sargun Dhillon <sargun@...gun.me>, Thomas Graf <tgraf@...g.ch>,
        Gianluca Borello <g.borello@...il.com>,
        Chenbo Feng <fengc@...gle.com>
Subject: Re: [PATCH bpf-next v3 6/8] bpf: add documentation for eBPF helpers
 (42-50)

On Tue, Apr 17, 2018 at 03:34:36PM +0100, Quentin Monnet wrote:
> Add documentation for eBPF helper functions to bpf.h user header file.
> This documentation can be parsed with the Python script provided in
> another commit of the patch series, in order to provide a RST document
> that can later be converted into a man page.
> 
> The objective is to make the documentation easily understandable and
> accessible to all eBPF developers, including beginners.
> 
> This patch contains descriptions for the following helper functions:
> 
> Helper from Kaixu:
> - bpf_perf_event_read()
> 
> Helpers from Martin:
> - bpf_skb_under_cgroup()
> - bpf_xdp_adjust_head()
> 
> Helpers from Sargun:
> - bpf_probe_write_user()
> - bpf_current_task_under_cgroup()
> 
> Helper from Thomas:
> - bpf_skb_change_head()
> 
> Helper from Gianluca:
> - bpf_probe_read_str()
> 
> Helpers from Chenbo:
> - bpf_get_socket_cookie()
> - bpf_get_socket_uid()
> 
> v3:
> - bpf_perf_event_read(): Fix time of selection for perf event type in
>   description. Remove occurences of "cores" to avoid confusion with
>   "CPU".
> 
> Cc: Kaixu Xia <xiakaixu@...wei.com>
> Cc: Martin KaFai Lau <kafai@...com>
> Cc: Sargun Dhillon <sargun@...gun.me>
> Cc: Thomas Graf <tgraf@...g.ch>
> Cc: Gianluca Borello <g.borello@...il.com>
> Cc: Chenbo Feng <fengc@...gle.com>
> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
...
> + *
> + * u64 bpf_get_socket_cookie(struct sk_buff *skb)
> + * 	Description
> + * 		Retrieve the socket cookie generated by the kernel from a
> + * 		**struct sk_buff** with a known socket. If none has been set

this bit could use some improvement, since it reads as cookie is
generated from sk_buff, whereas it has nothing to do with this particular
sk_buff. Cookie belongs to the socket and generated for the socket.
Would be good to explain that cookie is stable for the life of the socket.

For the rest:
Acked-by: Alexei Starovoitov <ast@...nel.org>