linux-kernel - Re: [PATCH] x86/boot/compressed: enable -Wundef

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Date:   Thu, 22 Apr 2021 12:21:33 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Joe Perches <joe@...ches.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Joerg Roedel <jroedel@...e.de>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Terrell <terrelln@...com>,
        Martin Radev <martin.b.radev@...il.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/boot/compressed: enable -Wundef

On Thu, Apr 22, 2021 at 12:04:42PM -0700, Nick Desaulniers wrote:
> A discussion around -Wundef showed that there were still a few boolean
> Kconfigs where #if was used rather than #ifdef to guard different code.
> Kconfig doesn't define boolean configs, which can result in -Wundef
> warnings.
> 
> arch/x86/boot/compressed/Makefile resets the CFLAGS used for this
> directory, and doesn't re-enable -Wundef as the top level Makefile does.
> If re-added, with RANDOMIZE_BASE and X86_NEED_RELOCS disabled, the
> following warnings are visible.
> 
> arch/x86/boot/compressed/misc.h:82:5: warning: 'CONFIG_RANDOMIZE_BASE'
> is not defined, evaluates to 0 [-Wundef]
>     ^
> arch/x86/boot/compressed/misc.c:175:5: warning: 'CONFIG_X86_NEED_RELOCS'
> is not defined, evaluates to 0 [-Wundef]
>     ^
> 
> Simply fix these and re-enable this warning for this directory.
> 
> Suggested-by: Nathan Chancellor <nathan@...nel.org>
> Suggested-by: Joe Perches <joe@...ches.com>
> Link: https://github.com/ClangBuiltLinux/linux/issues/570
> Link: https://lore.kernel.org/lkml/67f6cd269684c9aa8463ff4812c3b4605e6739c3.camel@perches.com/
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Thanks!

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook