linux-kernel - Re: [PATCH] x86/build: Use cc-option to validate stack alignment parameter

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Message-ID: <20170821075309.pqppfsxmyy2oqoow@gmail.com>
Date:   Mon, 21 Aug 2017 09:53:09 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        dianders@...omium.org, Michael Davidson <md@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Stephen Hines <srhines@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>, Bernhard.Rosenkranzer@...aro.org
Subject: Re: [PATCH] x86/build: Use cc-option to validate stack alignment
 parameter


* Matthias Kaehlcke <mka@...omium.org> wrote:

> With 8f91869766c0 ("x86/build: Fix stack alignment for CLang") cc-option
> is only used to determine the name of the stack alignment option supported
> by the compiler, but not to verify that the actual parameter <option>=N is
> valid in combination with the other CFLAGS. This causes problems with older
> gcc versions which only support stack alignment on a boundary of 16 bytes
> or higher.
> 
> Also use (__)cc_option to add the stack alignment option to CFLAGS to
> make sure only valid options are added.
> 
> Fixes: 8f91869766c0 ("x86/build: Fix stack alignment for CLang")
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>

I've added the kbuild-bot Reported-by tag to document (and credit) how this bug 
was found.

Thanks,

	Ingo