linux-kernel - Re: [PATCH] s390: define RUNTIME_DISCARD_EXIT to fix link error with GNU ld

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Date:   Thu, 5 Jan 2023 08:57:27 +0100
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ardb@...nel.org>, linux-kbuild@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] s390: define RUNTIME_DISCARD_EXIT to fix link error with
 GNU ld < 2.36

On Thu, Jan 05, 2023 at 12:13:06PM +0900, Masahiro Yamada wrote:
> Nathan Chancellor reports that the s390 vmlinux fails to link with
> GNU ld < 2.36 since commit 99cb0d917ffa ("arch: fix broken BuildID
> for arm64 and riscv").
> 
> It happens for defconfig, or more specifically for CONFIG_EXPOLINE=y.
> 
>   $ s390x-linux-gnu-ld --version | head -n1
>   GNU ld (GNU Binutils for Debian) 2.35.2
>   $ make -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- allnoconfig
>   $ ./scripts/config -e CONFIG_EXPOLINE
>   $ make -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- olddefconfig
>   $ make -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu-
>   `.exit.text' referenced in section `.s390_return_reg' of drivers/base/dd.o: defined in discarded section `.exit.text' of drivers/base/dd.o
>   make[1]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
>   make: *** [Makefile:1252: vmlinux] Error 2
> 
> arch/s390/kernel/vmlinux.lds.S wants to keep EXIT_TEXT:
> 
>         .exit.text : {
>                 EXIT_TEXT
>         }
> 
> But, at the same time, EXIT_TEXT is thrown away by DISCARD because
> s390 does not define RUNTIME_DISCARD_EXIT.
> 
> I still do not understand why the latter wins after 99cb0d917ffa,
> but defining RUNTIME_DISCARD_EXIT seems correct because the comment
> line in arch/s390/kernel/vmlinux.lds.S says:
> 
>         /*
>          * .exit.text is discarded at runtime, not link time,
>          * to deal with references from __bug_table
>          */
> 
> Nathan also found that binutils commit 21401fc7bf67 ("Duplicate output
> sections in scripts") cured this issue, so we cannot reproduce it with
> binutils 2.36+, but it is better to not rely on it.
> 
> Fixes: 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
> Link: https://lore.kernel.org/all/Y7Jal56f6UBh1abE@dev-arch.thelio-3990X/
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  arch/s390/kernel/vmlinux.lds.S | 2 ++
>  1 file changed, 2 insertions(+)

Applied, thanks!