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Date:   Thu, 4 Nov 2021 17:45:28 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Quentin Monnet <quentin@isovalent.com>
Cc:     Andrii Nakryiko <andrii.nakryiko@gmail.com>,
        Song Liu <songliubraving@fb.com>, Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>, bpf <bpf@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: perf build broken looking for bpf/{libbpf,bpf}.h after merge
 with upstream
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Em Thu, Nov 04, 2021 at 05:15:20PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Nov 04, 2021 at 06:15:57PM +0000, Quentin Monnet escreveu:
> > 2021-11-04 15:09 UTC-0300 ~ Arnaldo Carvalho de Melo <acme@kernel.org>
> > > Em Thu, Nov 04, 2021 at 10:47:12AM -0700, Andrii Nakryiko escreveu:
> > >> On Thu, Nov 4, 2021 at 10:38 AM Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote:
> > >> cc Quentin as well, might be related to recent Makefiles revamp for
> > >> users of libbpf. But in bpf-next perf builds perfectly fine, so not
> > >> sure.

> > > This did the trick:

> > > ⬢[acme@toolbox perf]$ git show
> > > commit 504afe6757ec646539ca3b4aa0431820e8c92b45 (HEAD -> perf/core)
> > > Author: Arnaldo Carvalho de Melo <acme@redhat.com>
> > > Date:   Thu Nov 4 14:58:56 2021 -0300

> > >     Revert "bpftool: Remove Makefile dep. on $(LIBBPF) for $(LIBBPF_INTERNAL_HDRS)"

> > >     This reverts commit 8b6c46241c774c83998092a4eafe40f054568881.

> > >     Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

> > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > > index c0c30e56988f2cbe..c5ad996ee95d4e87 100644
> > > --- a/tools/bpf/bpftool/Makefile
> > > +++ b/tools/bpf/bpftool/Makefile
> > > @@ -39,14 +39,14 @@ ifeq ($(BPFTOOL_VERSION),)
> > >  BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
> > >  endif

> > > -$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR):
> > > +$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT):
> > >         $(QUIET_MKDIR)mkdir -p $@

> > >  $(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
> > >         $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
> > >                 DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers

> > > -$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_DIR)
> > > +$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h $(LIBBPF)
> > >         $(call QUIET_INSTALL, $@)
> > >         $(Q)install -m 644 -t $(LIBBPF_HDRS_DIR) $<

> > Interesting. I needed that patch because otherwise I'd get errors when
> > compiling bpftool after the switch to libbpf's hashmap implementation.
> > For the current breakage, it could be a matter of how we pass variables
> > when descending into bpftool/ from perf's Makefile.perf. I'll try to
> > look at this in details, and to experiment tonight, if I can. (Thanks
> > Andrii for the CC!)
 
> yeah, if we pass the location for those headers from the perf side, it
> should work.

But it isn't obvious how perf should communicate to bpftool where to
find bpf/bpf.h for the bootstrap make target, which seems something
bpftool should know.

Anyway, I'm calling it a day, will get back to this tomorrow, if you
don't beat me to it.

- Arnaldo