From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roman Gushchin <guro@fb.com>
Subject: Re: [RFC PATCH net-next] tools/bpftool: use version from the kernel
 source tree
Date: Wed, 20 Dec 2017 20:56:00 +0000
Message-ID: <20171220205559.GB28352@castle>
References: <20171220201943.24440-1-guro@fb.com>
 <1fa179c1-4725-7e37-b5a9-5d7d8d36a37a@fb.com>
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Cc: <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kernel-team@fb.com>, <scientist@fb.com>,
        Jakub Kicinski <jakub.kicinski@netronome.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>
To: Yonghong Song <yhs@fb.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
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On Wed, Dec 20, 2017 at 12:26:30PM -0800, Yonghong Song wrote:
> 
> 
> On 12/20/17 12:19 PM, Roman Gushchin wrote:
> > Bpftool determines it's own version based on the kernel
> > version, which is picked from the linux/version.h header.
> > 
> > It's strange to use the version of the installed kernel
> > headers, and makes much more sense to use the version
> > of the actual source tree, where bpftool sources are.
> > 
> > This patch adds $(srctree)/usr/include to the list
> > of include files, which causes bpftool to use the version
> > from the source tree.
> > 
> > Example:
> > before:
> > 
> > $ bpftool version
> > bpftool v4.14.6
> > 
> > after:
> > $ bpftool version
> > bpftool v4.15.0
> > 
> > Signed-off-by: Roman Gushchin <guro@fb.com>
> > Cc: Jakub Kicinski <jakub.kicinski@netronome.com>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > ---
> >   tools/bpf/bpftool/Makefile | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > index 9c089cfa5f3f..6864d416c49e 100644
> > --- a/tools/bpf/bpftool/Makefile
> > +++ b/tools/bpf/bpftool/Makefile
> > @@ -37,7 +37,9 @@ CC = gcc
> >   CFLAGS += -O2
> >   CFLAGS += -W -Wall -Wextra -Wno-unused-parameter -Wshadow
> > -CFLAGS += -D__EXPORTED_HEADERS__ -I$(srctree)/tools/include/uapi -I$(srctree)/tools/include -I$(srctree)/tools/lib/bpf -I$(srctree)/kernel/bpf/
> > +CFLAGS += -D__EXPORTED_HEADERS__ -I$(srctree)/tools/include/uapi
> > +CFLAGS += -I$(srctree)/tools/include -I$(srctree)/tools/lib/bpf
> > +CFLAGS += -I$(srctree)/kernel/bpf/ -I$(srctree)/usr/include
> 
> -I$(srctree)/usr/include may not work if build directory is not the same as
> the source directory. You probably should use
> -I$(objtree)/usr/include?

$(objtree) is not defined there, so it doesn't work.
Tbh, I struggle to say if it's supposed to work there or not.

Thanks!