Re: [PATCH v2 1/4] perf build: Add ability to build with a generated vmlinux.h

[Ian Rogers]

On Tue, Jun 6, 2023 at 11:06 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> Em Mon, Jun 05, 2023 at 09:25:54PM -0700, Ian Rogers escreveu:
> > On Mon, Jun 5, 2023 at 7:57 PM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
> > >
> > > On Mon, Jun 05, 2023 at 01:27:09PM -0700, Ian Rogers wrote:
> > > > Commit a887466562b4 ("perf bpf skels: Stop using vmlinux.h generated
> > > > from BTF, use subset of used structs + CO-RE") made it so that
> > > > vmlinux.h was uncondtionally included from
> > > > tools/perf/util/vmlinux.h. This change reverts part of that change (so
> > > > that vmlinux.h is once again generated) and makes it so that the
> > > > vmlinux.h used at build time is selected from the VMLINUX_H
> > > > variable. By default the VMLINUX_H variable is set to the vmlinux.h
> > > > added in change a887466562b4, but if GEN_VMLINUX_H=1 is passed on the
> > > > build command line then the previous generation behavior kicks in.
> > > >
> > > > The build with GEN_VMLINUX_H=1 currently fails with:
> > > > ```
> > > > util/bpf_skel/lock_contention.bpf.c:419:8: error: redefinition of 'rq'
> > > > struct rq {};
> > > >        ^
> > > > /tmp/perf/util/bpf_skel/.tmp/../vmlinux.h:45630:8: note: previous definition is here
> > > > struct rq {
> > > >        ^
> > > > 1 error generated.
> > > > ```
> > > >
> > > > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > > > Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > > > ---
> > > >  tools/perf/Makefile.config                       |  4 ++++
> > > >  tools/perf/Makefile.perf                         | 16 +++++++++++++++-
> > > >  tools/perf/util/bpf_skel/.gitignore              |  1 +
> > > >  tools/perf/util/bpf_skel/{ => vmlinux}/vmlinux.h |  0
> > > >  4 files changed, 20 insertions(+), 1 deletion(-)
> > > >  rename tools/perf/util/bpf_skel/{ => vmlinux}/vmlinux.h (100%)
> > >
> > > looks good, but I don't understand why you moved the vmlinux.h
> > >
> > > jirka
> >
> > Dumb reason, as headers in the same directory take priority, I had to
> > move the vmlinux.h out of the directory with the C code for skeletons
> > so that it could be selected via a -I.
>
> Can this be in a separate patch, i.e. moving vmlinux to a separate
> directory? I was going to cherry pick the 'struct rq' fix but then it
> touches the vmlinux/vmlinux.h file that is in this first patch that has
> review comments.

I think the comments were more of a question of why the move?
Hopefully I answered that, the move is necessary to defeat the include
path order preferring files in the same directory. We need the move,
we could vary the directory name.

Thanks,
Ian

> - Arnaldo
>
> > Thanks,
> > Ian
> >
> > > >
> > > > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > > > index a794d9eca93d..08d4e7eaa721 100644
> > > > --- a/tools/perf/Makefile.config
> > > > +++ b/tools/perf/Makefile.config
> > > > @@ -680,6 +680,10 @@ ifdef BUILD_BPF_SKEL
> > > >    CFLAGS += -DHAVE_BPF_SKEL
> > > >  endif
> > > >
> > > > +ifndef GEN_VMLINUX_H
> > > > +  VMLINUX_H=$(src-perf)/util/bpf_skel/vmlinux/vmlinux.h
> > > > +endif
> > > > +
> > > >  dwarf-post-unwind := 1
> > > >  dwarf-post-unwind-text := BUG
> > > >
> > > > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > > > index f48794816d82..f1840af195c0 100644
> > > > --- a/tools/perf/Makefile.perf
> > > > +++ b/tools/perf/Makefile.perf
> > > > @@ -1080,7 +1080,21 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
> > > >       $(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
> > > >               OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
> > > >
> > > > -$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) | $(SKEL_TMP_OUT)
> > > > +VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)                         \
> > > > +                  $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)    \
> > > > +                  ../../vmlinux                                      \
> > > > +                  /sys/kernel/btf/vmlinux                            \
> > > > +                  /boot/vmlinux-$(shell uname -r)
> > > > +VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
> > > > +
> > > > +$(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
> > > > +ifeq ($(VMLINUX_H),)
> > > > +     $(QUIET_GEN)$(BPFTOOL) btf dump file $< format c > $@
> > > > +else
> > > > +     $(Q)cp "$(VMLINUX_H)" $@
> > > > +endif
> > > > +
> > > > +$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) $(SKEL_OUT)/vmlinux.h | $(SKEL_TMP_OUT)
> > > >       $(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -Wall -Werror $(BPF_INCLUDE) $(TOOLS_UAPI_INCLUDE) \
> > > >         -c $(filter util/bpf_skel/%.bpf.c,$^) -o $@
> > > >
> > > > diff --git a/tools/perf/util/bpf_skel/.gitignore b/tools/perf/util/bpf_skel/.gitignore
> > > > index 7a1c832825de..cd01455e1b53 100644
> > > > --- a/tools/perf/util/bpf_skel/.gitignore
> > > > +++ b/tools/perf/util/bpf_skel/.gitignore
> > > > @@ -1,3 +1,4 @@
> > > >  # SPDX-License-Identifier: GPL-2.0-only
> > > >  .tmp
> > > >  *.skel.h
> > > > +vmlinux.h
> > > > diff --git a/tools/perf/util/bpf_skel/vmlinux.h b/tools/perf/util/bpf_skel/vmlinux/vmlinux.h
> > > > similarity index 100%
> > > > rename from tools/perf/util/bpf_skel/vmlinux.h
> > > > rename to tools/perf/util/bpf_skel/vmlinux/vmlinux.h
> > > > --
> > > > 2.41.0.rc0.172.g3f132b7071-goog
> > > >
>
> --
>
> - Arnaldo