linux-kernel - Re: [bpf-next v6 2/3] bpftool: Update doc (add autoattach to prog load)

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Message-ID: <2b001fcb-4340-e1ba-4b84-a69c670cf09a@iogearbox.net>
Date:   Mon, 26 Sep 2022 18:20:35 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Wang Yufen <wangyufen@...wei.com>, quentin@...valent.com,
        ast@...nel.org, andrii@...nel.org, martin.lau@...ux.dev,
        song@...nel.org, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, davem@...emloft.net, kuba@...nel.org,
        hawk@...nel.org, nathan@...nel.org, ndesaulniers@...gle.com,
        trix@...hat.com
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [bpf-next v6 2/3] bpftool: Update doc (add autoattach to prog
 load)

On 9/24/22 12:13 PM, Wang Yufen wrote:
> Add autoattach optional to prog load|loadall for supporting
> one-step load-attach-pin_link.
> 
> Signed-off-by: Wang Yufen <wangyufen@...wei.com>
> ---
>   tools/bpf/bpftool/Documentation/bpftool-prog.rst | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> index eb1b2a254eb1..2d9f27a0120f 100644
> --- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> +++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
> @@ -31,7 +31,7 @@ PROG COMMANDS
>   |	**bpftool** **prog dump xlated** *PROG* [{**file** *FILE* | **opcodes** | **visual** | **linum**}]
>   |	**bpftool** **prog dump jited**  *PROG* [{**file** *FILE* | **opcodes** | **linum**}]
>   |	**bpftool** **prog pin** *PROG* *FILE*
> -|	**bpftool** **prog** { **load** | **loadall** } *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*]
> +|	**bpftool** **prog** { **load** | **loadall** } *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*] [**autoattach**]
>   |	**bpftool** **prog attach** *PROG* *ATTACH_TYPE* [*MAP*]
>   |	**bpftool** **prog detach** *PROG* *ATTACH_TYPE* [*MAP*]
>   |	**bpftool** **prog tracelog**
> @@ -131,7 +131,7 @@ DESCRIPTION
>   		  contain a dot character ('.'), which is reserved for future
>   		  extensions of *bpffs*.
>   
> -	**bpftool prog { load | loadall }** *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*]
> +	**bpftool prog { load | loadall }** *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*] [**autoattach**]
>   		  Load bpf program(s) from binary *OBJ* and pin as *PATH*.
>   		  **bpftool prog load** pins only the first program from the
>   		  *OBJ* as *PATH*. **bpftool prog loadall** pins all programs
> @@ -150,6 +150,15 @@ DESCRIPTION
>   		  Optional **pinmaps** argument can be provided to pin all
>   		  maps under *MAP_DIR* directory.
>   
> +		  If **autoattach** is specified program will be attached
> +		  before pin. In that case, only the link (representing the
> +		  program attached to its hook) is pinned, not the program as
> +		  such, so the path won't show in "**bpftool prog show -f**",
> +		  only show in "**bpftool link show -f**". Also, this only works
> +		  when bpftool (libbpf) is able to infer all necessary information
> +		  from the objectfile, in particular, it's not supported for all
> +		  program types.

Related to Quentin's comment, the documentation should also describe clear semantics
on what happens in failure case. I presume the use case you have in mind is to use
this facility for scripts e.g. to run/load some tests objs? Thus would be good to describe
to users what they need to do/clean up when things only partially succeed etc..

>   		  Note: *PATH* must be located in *bpffs* mount. It must not
>   		  contain a dot character ('.'), which is reserved for future
>   		  extensions of *bpffs*.
>