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

From: Jiri Olsa <[email-masked]>
Date: Wed, 10 Feb 2021 19:29:31 +0100

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 <[email-masked]> 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 <[email-masked]>
> > > > Signed-off-by: Jiri Olsa <[email-masked]>
> > > > ---
> > > >  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

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