Re: [PATCHv4 0/6] perf/bpftool: Allow to link libbpf dynamically

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Michael Petlan <mpetlan@redhat.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	Quentin Monnet <quentin.monnet@netronome.com>
Subject: Re: [PATCHv4 0/6] perf/bpftool: Allow to link libbpf dynamically
Date: Wed, 4 Dec 2019 09:39:59 -0800	[thread overview]
Message-ID: <CAADnVQJeC9FQDXhv34KTiFSRq-=x4cBaspj-bTXdQ1=7prphcA@mail.gmail.com> (raw)
In-Reply-To: <877e3cpdc9.fsf@toke.dk>

On Wed, Dec 4, 2019 at 2:58 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
>
> > On Mon, Dec 2, 2019 at 1:15 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> >>
> >> Ah, that is my mistake: I was getting dynamic libbpf symbols with this
> >> approach, but that was because I had the version of libbpf.so in my
> >> $LIBDIR that had the patch to expose the netlink APIs as versioned
> >> symbols; so it was just pulling in everything from the shared library.
> >>
> >> So what I was going for was exactly what you described above; but it
> >> seems that doesn't actually work. Too bad, and sorry for wasting your
> >> time on this :/
> >
> > bpftool is currently tightly coupled with libbpf and very likely
> > in the future the dependency will be even tighter.
> > In that sense bpftool is an extension of libbpf and libbpf is an extension
> > of bpftool.
> > Andrii is working on set of patches to generate user space .c code
> > from bpf program.
> > bpftool will be generating the code that is specific for the version
> > bpftool and for
> > the version of libbpf. There will be compatibility layers as usual.
> > But in general the situation where a bug in libbpf is so criticial
> > that bpftool needs to repackaged is imo less likely than a bug in
> > bpftool that will require re-packaging of libbpf.
> > bpftool is quite special. It's not a typical user of libbpf.
> > The other way around is more correct. libbpf is a user of the code
> > that bpftool generates and both depend on each other.
> > perf on the other side is what typical user space app that uses
> > libbpf will look like.
> > I think keeping bpftool in the kernel while packaging libbpf
> > out of github was an oversight.
> > I think we need to mirror bpftool into github/libbpf as well
> > and make sure they stay together. The version of libbpf == version of bpftool.
> > Both should come from the same package and so on.
> > May be they can be two different packages but
> > upgrading one should trigger upgrade of another and vice versa.
> > I think one package would be easier though.
> > Thoughts?
>
> Yup, making bpftool explicitly the "libbpf command line interface" makes
> sense and would help clarify the relationship between the two. As Jiri
> said, we are already moving in that direction packaging-wise...

Awesome. Let's figure out the logistics.
Should we do:
git mv tools/bpf/bpftool/ tools/lib/bpf/
and appropriate adjustment to Makefiles ?
or keep it where it is and only add to
https://github.com/libbpf/libbpf/blob/master/scripts/sync-kernel.sh ?