netdev - Re: [PATCH v2] samples/bpf: xdpsock: fix swap.cocci warning

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Date:   Sun, 12 Dec 2021 11:46:57 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Yihao Han <hanyihao@...o.com>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, kernel@...o.com
Subject: Re: [PATCH v2] samples/bpf: xdpsock: fix swap.cocci warning

On Sat, Dec 11, 2021 at 10:07 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> Andrii Nakryiko <andrii.nakryiko@...il.com> writes:
>
> > On Fri, Dec 10, 2021 at 6:26 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
> >>
> >> Yihao Han <hanyihao@...o.com> writes:
> >>
> >> > Fix following swap.cocci warning:
> >> > ./samples/bpf/xdpsock_user.c:528:22-23:
> >> > WARNING opportunity for swap()
> >> >
> >> > Signed-off-by: Yihao Han <hanyihao@...o.com>
> >>
> >> Erm, did this get applied without anyone actually trying to compile
> >> samples? I'm getting build errors as:
> >
> > Good news: I actually do build samples/bpf nowadays after fixing a
> > bunch of compilation issues recently.
>
> Awesome!
>
> > Bad news: seems like I didn't pay too much attention after building
> > samples/bpf for this particular patch, sorry about that. I've dropped
> > this patch, samples/bpf builds for me. We should be good now.
>
> Yup, looks good, thanks!
>
> >>   CC  /home/build/linux/samples/bpf/xsk_fwd.o
> >> /home/build/linux/samples/bpf/xsk_fwd.c: In function ‘swap_mac_addresses’:
> >> /home/build/linux/samples/bpf/xsk_fwd.c:658:9: warning: implicit declaration of function ‘swap’; did you mean ‘swab’? [-Wimplicit-function-declaration]
> >>   658 |         swap(*src_addr, *dst_addr);
> >>       |         ^~~~
> >>       |         swab
> >>
> >> /usr/bin/ld: /home/build/linux/samples/bpf/xsk_fwd.o: in function `thread_func':
> >> xsk_fwd.c:(.text+0x440): undefined reference to `swap'
> >> collect2: error: ld returned 1 exit status
> >>
> >>
> >> Could we maybe get samples/bpf added to the BPF CI builds? :)
> >
> > Maybe we could, if someone dedicated their effort towards making this
> > happen.
>
> Is it documented anywhere what that would entail? Is it just a matter of
> submitting a change to https://github.com/kernel-patches/vmtest ?

I think the right way would be to build samples/bpf from
selftests/bpf's Makefile. At the very least we should not require make
headers_install (I never understood that with samples/bpf, all those
up-to-date UAPI headers are right there in the same repo). Once that
is done, at the very least we'll build tests samples/bpf during CI
runs.

>
> -Toke
>