linux-kernel - Re: [RFC PATCH net-next] tools/bpftool: use version from the kernel source tree

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Message-ID: <20171220205332.GA28352@castle>
Date:   Wed, 20 Dec 2017 20:53:41 +0000
From:   Roman Gushchin <guro@...com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kernel-team@...com>, <scientist@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [RFC PATCH net-next] tools/bpftool: use version from the kernel
 source tree

On Wed, Dec 20, 2017 at 12:29:21PM -0800, Jakub Kicinski wrote:
> On Wed, 20 Dec 2017 20:19:43 +0000, 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
> 
> Thanks for the patch, this would indeed use some improvement.
> 
> How about we just run make to get the version like liblockdep does?
> 
> LIBLOCKDEP_VERSION=$(shell make --no-print-directory -sC ../../.. kernelversion)
> 
> probably s@...../..@$(srctree)@
> 
> $(srctree)/usr/include is not going to be there for out-of-source builds.

Hm, why it's better? It's not only about the kernel version,
IMO it's generally better to use includes from the source tree,
rather then system-wide installed kernel headers.

I've got about out-of-source builds, but do we support it in general?
How can I build bpftool outside of the kernel tree?
I've tried a bit, but failed.

Thank you!