linux-kernel - Re: [PATCH] objtool: move libelf detection to Kconfig from Makefile

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Date:   Mon, 9 Jul 2018 14:21:34 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>
Subject: Re: [PATCH] objtool: move libelf detection to Kconfig from Makefile

On Sun, Jul 08, 2018 at 06:59:42PM +0900, Masahiro Yamada wrote:
> Currently, users are allowed to enable STACK_VALIDATION regardless
> of the compiler capability.  The top-level Makefile warns or breaks
> the build if it turns out that the host compiler cannot link libelf.
> 
> Move the libelf test to Kconfig so that users can enable the feature
> only when the host compiler can build the objtool.  The ugly check
> in the Makefile will go away.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

Thanks for cleaning this up!

> I am sure about this patch only from the build system point of view.
> 
> Please review this from x86 and objtool point of view.
> 
> In my understanding:
> 
>  - UNWINDER_ORC _requires_ objtool,
>    so I added 'depends on STACK_VALIDATION'.
>    ('select' would end up with unmet depenency)

Correct.

>  - RETPOLINE _wants_ objtool, so I added 'imply'

Yeah, I think this is fine.

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh