linux-kernel - Re: [PATCH] bpfilter: allow to build bpfilter

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Message-ID: <CAK7LNARTMt8kgRJqgRonaSHROT80yDNAG0wDiLGL=RSEz3CDig@mail.gmail.com>
Date:   Thu, 2 Jul 2020 02:50:01 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Michal Kubecek <mkubecek@...e.cz>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrii Nakryiko <andriin@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        Sam Ravnborg <sam@...nborg.org>,
        Song Liu <songliubraving@...com>,
        Valdis Kl ē tnieks <valdis.kletnieks@...edu>,
        Yonghong Song <yhs@...com>
Subject: Re: [PATCH] bpfilter: allow to build bpfilter_umh as a module without
 static library

On Thu, Jul 2, 2020 at 2:46 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Wed, Jul 01, 2020 at 06:26:44PM +0900, Masahiro Yamada wrote:
> > Originally, bpfilter_umh was linked with -static only when
> > CONFIG_BPFILTER_UMH=y.
> >
> > Commit 8a2cc0505cc4 ("bpfilter: use 'userprogs' syntax to build
> > bpfilter_umh") silently, accidentally dropped the CONFIG_BPFILTER_UMH=y
> > test in the Makefile. Revive it in order to link it dynamically when
> > CONFIG_BPFILTER_UMH=m.
> >
> > Since commit b1183b6dca3e ("bpfilter: check if $(CC) can link static
> > libc in Kconfig"), the compiler must be capable of static linking to
> > enable CONFIG_BPFILTER_UMH, but it requires more than needed.
> >
> > To loosen the compiler requirement, I changed the dependency as follows:
> >
> >     depends on CC_CAN_LINK
> >     depends on m || CC_CAN_LINK_STATIC
> >
> > If CONFIG_CC_CAN_LINK_STATIC in unset, CONFIG_BPFILTER_UMH is restricted
> > to 'm' or 'n'.
> >
> > In theory, CONFIG_CC_CAN_LINK is not required for CONFIG_BPFILTER_UMH=y,
> > but I did not come up with a good way to describe it.
> >
> > Fixes: 8a2cc0505cc4 ("bpfilter: use 'userprogs' syntax to build bpfilter_umh")
> > Reported-by: Michal Kubecek <mkubecek@...e.cz>
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>
> lgtm
> Do you mind I'll take it into bpf-next tree?
> Eric is working on a bunch of patches in this area. I'll take his set
> into bpf-next as well and then can apply this patch.
> Just to make sure there are no conflicts.

Please go ahead.

Thank you.


-- 
Best Regards
Masahiro Yamada