linux-kernel - Re: [PATCH v2] Makefile: add comment to discourage tools/* addition for kernel builds

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Message-ID: <CAK7LNARkW74PP73oGLUaPhYvOcku39qNRr-0U6kwEUr6b9b5UQ@mail.gmail.com>
Date: Sat, 20 Jul 2024 23:22:13 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jiri Olsa <jolsa@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Peter Zijlstra <peterz@...radead.org>, Nicolas Schier <nicolas@...sle.eu>, 
	Brian Norris <briannorris@...omium.org>, Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH v2] Makefile: add comment to discourage tools/* addition
 for kernel builds

On Sat, Jul 20, 2024 at 7:55 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> On Thu, Jul 18, 2024 at 03:28:19AM +0900, Masahiro Yamada wrote:
> > Kbuild provides scripts/Makefile.host to build host programs used for
> > building the kernel. Unfortunately, there are two exceptions that opt
> > out of Kbuild. The build system under tools/ is a cheesy replica, and
> > cause issues. I was recently poked about a problem in the tools build
> > system, which I do not maintain (and nobody maintains). [1]
> >
> > Without a comment, people might believe this is the right location
> > because that is where objtool lives, even if a more robust Kbuild
> > syntax satisfies their needs. [2]
>
> I think the original idea (from Ingo?) was to make objtool portable so
> it could be easily copied and built separately without getting too
> intertwined with the kernel source.
>
> I think that's still a useful goal.  To my knowledge it's been used in
> at least one other code base and could be used elsewhere going forward
> as much of its functionality might be transferable to other code bases.
>
> Also being in tools helps it shares library code (libsubcmd) and
> synced headers with perf (and others).
>
> If there's some other way to make it portable and allow it to share code
> with other tools that then I wouldn't object to moving it to scripts.
>
> Or, if the main problem is that there are two custom build systems (one
> of them being a cheap knockoff), could kbuild be made portable enough to
> be used in tools?


I checked Debian and Fedora, but I did not find such a package that provides
objtool as a standalone tool.

In reality, objtool is tightly bound to the kernel source.
If people had thought it useful outside the kernel tree,
such a disto package would have been widely available.

I do not think there is a good reason to complicate Kbuild
based on the hypothetical statement.


-- 
Best Regards
Masahiro Yamada