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

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Date:   Thu, 11 Feb 2021 13:17:22 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.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 11:26:28AM -0800, Andrii Nakryiko wrote:

SNIP

> > > > 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?

yes, it's not connected to global make clean

> 
> >
> > ---
> > 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

ok

thanks,
jirka