netdev - Re: [PATCH bpf-next v2 11/15] selftests/xsk: get rid of built-in XDP program

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Date:   Wed, 4 Jan 2023 15:44:01 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Magnus Karlsson <magnus.karlsson@...il.com>,
        magnus.karlsson@...el.com, bjorn@...nel.org, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        maciej.fijalkowski@...el.com, bpf@...r.kernel.org, yhs@...com,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        john.fastabend@...il.com, kpsingh@...nel.org, haoluo@...gle.com,
        jolsa@...nel.org, tirthendu.sarkar@...el.com,
        jonathan.lemon@...il.com
Subject: Re: [PATCH bpf-next v2 11/15] selftests/xsk: get rid of built-in XDP program

On Wed, Jan 4, 2023 at 3:15 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Wed, Jan 4, 2023 at 4:19 AM Magnus Karlsson
> <magnus.karlsson@...il.com> wrote:
> >
> > From: Magnus Karlsson <magnus.karlsson@...el.com>
> >
> > Get rid of the built-in XDP program that was part of the old libbpf
> > code in xsk.c and replace it with an eBPF program build using the
> > framework by all the other bpf selftests. This will form the base for
> > adding more programs in later commits.
> >
> > Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> > ---
> >  tools/testing/selftests/bpf/Makefile          |  2 +-
> >  .../selftests/bpf/progs/xsk_xdp_progs.c       | 19 ++++
> >  tools/testing/selftests/bpf/xsk.c             | 88 ++++---------------
> >  tools/testing/selftests/bpf/xsk.h             |  6 +-
> >  tools/testing/selftests/bpf/xskxceiver.c      | 72 ++++++++-------
> >  tools/testing/selftests/bpf/xskxceiver.h      |  7 +-
> >  6 files changed, 88 insertions(+), 106 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
> >
> > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > index 205e8c3c346a..a0193a8f9da6 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -240,7 +240,7 @@ $(OUTPUT)/flow_dissector_load: $(TESTING_HELPERS)
> >  $(OUTPUT)/test_maps: $(TESTING_HELPERS)
> >  $(OUTPUT)/test_verifier: $(TESTING_HELPERS) $(CAP_HELPERS)
> >  $(OUTPUT)/xsk.o: $(BPFOBJ)
>
> shouldn't $(OUTPUT)/xsk_xdp_progs.skel.h be added as a dependency
> here, at .o file?

Not sure we can:
xsk.o is a 'generic' library and xsk_xdp_progs.skel.h is xskxceiver-specific.

I was trying to see how it works for the other cases where we depend
on the headers and saw the following:

$(OUTPUT)/test_verifier: test_verifier.c verifier/tests.h $(BPFOBJ) | $(OUTPUT)
        $(call msg,BINARY,,$@)
        $(Q)$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@

So at least for test_verifier, we explicitly filter out anything
non-.[aoc]. Presumably because of the same issue?
Should we do the same for xskxceiver? I've sent similar changes for my
xdp_hw_metadata binary about an hour ago..

> > -$(OUTPUT)/xskxceiver: $(OUTPUT)/xsk.o
> > +$(OUTPUT)/xskxceiver: $(OUTPUT)/xsk.o $(OUTPUT)/xsk_xdp_progs.skel.h
>
> and not here. Is that why we have this clang compilation failure?
>
> >
> >  BPFTOOL ?= $(DEFAULT_BPFTOOL)
> >  $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
>
> [...]