Re: [PATCH bpf-next 4/4] kbuild: Add resolve_btfids clean to root clean target

From: Nathan Chancellor <nathan@kernel.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>,
	Song Liu <songliubraving@fb.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH bpf-next 4/4] kbuild: Add resolve_btfids clean to root clean target
Date: Wed, 10 Feb 2021 11:02:15 -0700	[thread overview]
Message-ID: <20210210180215.GA2374611@ubuntu-m3-large-x86> (raw)
In-Reply-To: <CAEf4BzZvz4-STv3OQxyNDiFKkrFM-+GOM-yXURzoDtXiRiuT_g@mail.gmail.com>

On Wed, Feb 10, 2021 at 09:52:42AM -0800, Andrii Nakryiko wrote:
> On Wed, Feb 10, 2021 at 9:47 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > On Fri, Feb 05, 2021 at 01:40:20PM +0100, Jiri Olsa wrote:
> > > The resolve_btfids tool is used during the kernel build,
> > > so we should clean it on kernel's make clean.
> > >
> > > Invoking the the resolve_btfids clean as part of root
> > > 'make clean'.
> > >
> > > Acked-by: Song Liu <songliubraving@fb.com>
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > > ---
> > >  Makefile | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Makefile b/Makefile
> > > index b0e4767735dc..159d9592b587 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -1086,6 +1086,11 @@ ifdef CONFIG_STACK_VALIDATION
> > >    endif
> > >  endif
> > >
> > > +PHONY += resolve_btfids_clean
> > > +
> > > +resolve_btfids_clean:
> > > +     $(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(abspath $(objtree))/tools/bpf/resolve_btfids clean
> > > +
> > >  ifdef CONFIG_BPF
> > >  ifdef CONFIG_DEBUG_INFO_BTF
> > >    ifeq ($(has_libelf),1)
> > > @@ -1495,7 +1500,7 @@ vmlinuxclean:
> > >       $(Q)$(CONFIG_SHELL) $(srctree)/scripts/link-vmlinux.sh clean
> > >       $(Q)$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) clean)
> > >
> > > -clean: archclean vmlinuxclean
> > > +clean: archclean vmlinuxclean resolve_btfids_clean
> > >
> > >  # mrproper - Delete all generated files, including .config
> > >  #
> > > --
> > > 2.26.2
> > >
> >
> > This breaks running distclean on a clean tree (my script just
> > unconditionally runs distclean regardless of the tree state):
> >
> > $ make -s O=build distclean
> > ../../scripts/Makefile.include:4: *** O=/home/nathan/cbl/src/linux-next/build/tools/bpf/resolve_btfids does not exist.  Stop.
> >
> 
> Can't reproduce it. It works in all kinds of variants (relative and
> absolute O=, clean and not clean trees, etc). Jiri, please check as
> well.
> 

Odd, this reproduces for me on a completely clean checkout of bpf-next:

$ git clone --depth=1 https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/

$ cd bpf-next

$ make -s O=build distclean
../../scripts/Makefile.include:4: *** O=/tmp/bpf-next/build/tools/bpf/resolve_btfids does not exist.  Stop.

I do not really see how this could be environment related. It seems like
this comes from tools/scripts/Makefile.include, where there is no
guarantee that $(O) is created before being used like in the main
Makefile?

Cheers,
Nathan