netdev - Re: [PATCH bpf-next 3/6] bpftool: Use $(OUTPUT) and not $(O) for VMLINUX_BTF

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Date:   Thu, 11 Nov 2021 17:52:39 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Quentin Monnet <quentin@...valent.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next 3/6] bpftool: Use $(OUTPUT) and not $(O) for
 VMLINUX_BTF_PATHS in Makefile

On Thu, Nov 11, 2021 at 3:39 PM Quentin Monnet <quentin@...valent.com> wrote:
>
> On Thu, 11 Nov 2021 at 18:59, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
> >
> > On Wed, Nov 10, 2021 at 3:46 AM Quentin Monnet <quentin@...valent.com> wrote:
> > >
> > > The Makefile for bpftool relies on $(OUTPUT), and not on $(O), for
> > > passing the output directory. So $(VMLINUX_BTF_PATHS), used for
> > > searching for kernel BTF info, should use the same variable.
> > >
> > > Fixes: 05aca6da3b5a ("tools/bpftool: Generalize BPF skeleton support and generate vmlinux.h")
> > > Signed-off-by: Quentin Monnet <quentin@...valent.com>
> > > ---
> > >  tools/bpf/bpftool/Makefile | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > > index 2a846cb92120..40abf50b59d4 100644
> > > --- a/tools/bpf/bpftool/Makefile
> > > +++ b/tools/bpf/bpftool/Makefile
> > > @@ -150,7 +150,7 @@ $(BOOTSTRAP_OBJS): $(LIBBPF_BOOTSTRAP)
> > >  OBJS = $(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o
> > >  $(OBJS): $(LIBBPF) $(LIBBPF_INTERNAL_HDRS)
> > >
> > > -VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)                           \
> > > +VMLINUX_BTF_PATHS ?= $(if $(OUTPUT),$(OUTPUT)/vmlinux)                 \
> > >                      $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)    \
> >
> > But you still check KBUILD_OUTPUT? O overrides KBUILD_OUTPUT as far as
> > kernel build goes. So if you still support KBUILD_OUTPUT, you should
> > support O. And the $(OUTPUT) seems to be completely unrelated, as that
> > defines the output of bpftool build files, not the vmlinux image. Or
> > am I missing something?
>
> OK, I think I'm the one who missed the point. I simply figured we
> meant to search the output directory, and that it should be $(OUTPUT)
> like everywhere else in the Makefile. But from what I understand now,
> it's not the case. Let's drop this patch.
>
> If the rest of the set looks good to you, can you just skip this
> patch, or do you prefer me to send a v2?
>

I can just drop it when applying.

> Quentin