linux-kernel - Re: [PATCH] kbuild: link lib-y objects to vmlinux forcibly when CONFIG

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Message-ID: <CAKwvOdksxVa=NGtyT3hsuHg6SJG4CbNWAepf+dxwVDC1+36zyw@mail.gmail.com>
Date:   Mon, 9 Mar 2020 12:59:37 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Masahiro Yamada <masahiroy@...nel.org>
Cc:     kbuild-all@...ts.01.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        F���ng-ru��� S���ng 
        <maskray@...gle.com>, Ilie Halip <ilie.halip@...il.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH] kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=y

On Mon, Mar 9, 2020 at 3:55 AM kbuild test robot <lkp@...el.com> wrote:
>
> Hi Masahiro,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on kbuild/for-next]
> [also build test ERROR on linux/master linus/master v5.6-rc5 next-20200306]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
>
> url:    https://github.com/0day-ci/linux/commits/Masahiro-Yamada/kbuild-link-lib-y-objects-to-vmlinux-forcibly-when-CONFIG_MODULES-y/20200309-115312
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git for-next
> config: sparc-defconfig (attached as .config)
> compiler: sparc-linux-gcc (GCC) 7.5.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.5.0 make.cross ARCH=sparc
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@...el.com>
>
> All errors (new ones prefixed by >>):
>
>    arch/sparc/lib/strlen.o: In function `strlen':
> >> (.text+0x0): multiple definition of `strlen'
>    lib/string.o:string.c:(.text+0x2b0): first defined here

So this looks like a bug in 32b Sparc, that we should fix first.

arch/sparc/lib/strlen.S provides a definition of strlen, but it does
not define the preprocessor token __HAVE_ARCH_STRLEN to avoid multiple
definitions from producing a link error.

Or rather, __HAVE_ARCH_STRLEN is provided in include/asm/string_64.h,
but not for 32b sparc.  arch/sparc/strlen.o is unconditionally
required in lib-y in arch/sparc/lib/Makefile.

Either:
1. arch/sparc/lib/strlen.S supports 32b sparc, then __HAVE_ARCH_STRLEN
and a forward declaration of strlen should be provided in
arch/sparc/include/asm/string.h rather than
arch/sparc/include/asm/string_64.h, or...
2. arch/sparc/lib/strlen.S does not support 32b sparc, then the
inclusion of strlen.o in arch/sparc/lib/Makefile should be predicated
on CONFIG_SPARC64.

+ Dave who maybe can provide guidance on how to proceed?  The use of
the BRANCH32 macro in arch/sparc/lib/strlen.S seems to have different
definitions based on CONFIG_SPARC64 vs CONFIG_SPARC32, which makes me
thing it's case 1 above, but I'm not familiar with Sparc assembly to
be confident.
-- 
Thanks,
~Nick Desaulniers