netdev - Re: [PATCH bpf-next 4/4] kbuild: Add resolve

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Date:   Wed, 10 Feb 2021 11:26:28 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Song Liu <songliubraving@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH bpf-next 4/4] kbuild: Add resolve_btfids clean to root
 clean target

On Wed, Feb 10, 2021 at 10:29 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Wed, Feb 10, 2021 at 11:02:15AM -0700, Nathan Chancellor wrote:
> > 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@...nel.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@...com>
> > > > > Signed-off-by: Jiri Olsa <jolsa@...nel.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?
>
> right, we need to handle the case where tools/bpf/resolve_btfids
> does not exist, patch below fixes it for me
>
> jirka
>

Looks good to me, please send it as a proper patch to bpf-next.

But I'm curious, why is objtool not doing something like that? Is it
not doing clean at all? Or does it do it in some different way?

>
> ---
> diff --git a/Makefile b/Makefile
> index 159d9592b587..ce9685961abe 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1088,8 +1088,14 @@ endif
>
>  PHONY += resolve_btfids_clean
>
> +resolve_btfids_O = $(abspath $(objtree))/tools/bpf/resolve_btfids
> +
> +# tools/bpf/resolve_btfids directory might not exist
> +# in output directory, skip its clean in that case
>  resolve_btfids_clean:
> -       $(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(abspath $(objtree))/tools/bpf/resolve_btfids clean
> +ifneq (,$(wildcard $(resolve_btfids_O)))

nit: kind of backwards, usually it's in a `ifneq($var,)` form

> +       $(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(resolve_btfids_O) clean
> +endif
>
>  ifdef CONFIG_BPF
>  ifdef CONFIG_DEBUG_INFO_BTF
>