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From:   Lecopzer Chen <lecopzer.chen@mediatek.com>
To:     <nathan@kernel.org>
CC:     <clang-built-linux@googlegroups.com>, <keescook@chromium.org>,
        <lecopzer.chen@mediatek.com>, <linux-kbuild@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <masahiroy@kernel.org>,
        <michal.lkml@markovi.net>, <samitolvanen@google.com>,
        <yj.chiang@mediatek.com>
Subject: Re: [PATCH 2/2] Kbuild: lto: add make version checking
Date:   Thu, 1 Jul 2021 16:55:09 +0800
Message-ID: <20210701085509.395-1-lecopzer.chen@mediatek.com>
In-Reply-To: <6d687b9a-c295-ce8b-9472-d2859977be2d@kernel.org>
References: <6d687b9a-c295-ce8b-9472-d2859977be2d@kernel.org>
MIME-Version: 1.0
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> On 6/30/2021 5:14 AM, Lecopzer Chen wrote:
> > LTO with MODVERSION will fail in generating correct CRC because
> > the makefile rule doesn't work for make with version 3.8X.[1]
> > 
> > Thus we need to check make version during selecting on LTO Kconfig.
> > and the suitable version should be 4.2(40200) which release in 2016[2].
> > 
> > [1] https://lore.kernel.org/lkml/20210616080252.32046-1-lecopzer.chen@mediatek.com/
> > [2] https://ftp.gnu.org/gnu/make/
> > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
> > ---
> >   arch/Kconfig | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index c45b770d3579..1571957bade5 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -632,6 +632,7 @@ config HAS_LTO_CLANG
> >   	def_bool y
> >   	# Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
> >   	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
> > +	depends on MAKE_VERSION_INT >= 40200
> 
> If the bug depends on CONFIG_MODVERSIONS, should this be
> 
> depends on !MODVERSIONS || MAKE_VERSION >= 40200
> 
> ? Especially since the problematic block in your original report is 
> gated on CONFIG_LTO_CLANG + CONFIG_MODVERSIONS.
> 

You're right, I'll fix it in v2, thanks for reviewing.


> >   	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
> >   	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
> >   	depends on ARCH_SUPPORTS_LTO_CLANG
> >