netdev - Re: [PATCH bpf-next 4/5] bpftool: Add SEC name for xdp programs attached to device map

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Date:   Wed, 27 May 2020 17:43:18 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     David Ahern <dsahern@...il.com>, David Ahern <dsahern@...nel.org>,
        netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
        brouer@...hat.com
Subject: Re: [PATCH bpf-next 4/5] bpftool: Add SEC name for xdp programs
 attached to device map

On Wed, 27 May 2020 17:01:10 +0200
Toke Høiland-Jørgensen <toke@...hat.com> wrote:

> David Ahern <dsahern@...il.com> writes:
> 
> > On 5/27/20 4:02 AM, Toke Høiland-Jørgensen wrote:  
> >> David Ahern <dsahern@...nel.org> writes:
> >>   
> >>> Support SEC("xdp_dm*") as a short cut for loading the program with
> >>> type BPF_PROG_TYPE_XDP and expected attach type BPF_XDP_DEVMAP.  
> >> 
> >> You're not using this in the selftest; shouldn't you be? Also, the
> >> prefix should be libbpf: not bpftool:, no?
> >>   
> >
> > The selftest is exercising kernel APIs - what is allowed and what is
> > not.  
> 
> Sure, but they also de facto serve as example code for features that are
> not documented anywhere else, so just seemed a bit odd to me that you
> were not using this to mark the programs.
> 
> Anyway, not going to insist if you prefer explicitly setting
> expected_attach_type...

I actually think that it is better to demonstrate that it is possible to set:	

 attr.expected_attach_type = BPF_XDP_DEVMAP;

Because people will be grepping the source code to find examples ;-)

We could add a comment, that say SEC("xdp_dm") can be used as short cut.
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer