Re: [PATCH] s390: define RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36

[Heiko Carstens <hca@linux.ibm.com>]

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@kernel.org>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
>  arch/s390/kernel/vmlinux.lds.S | 2 ++
>  1 file changed, 2 insertions(+)

Applied, thanks!