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(+)

diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 5ea3830af0cc..6e101e6f499d 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -17,6 +17,8 @@
 /* Handle ro_after_init data on our own. */
 #define RO_AFTER_INIT_DATA
 
+#define RUNTIME_DISCARD_EXIT
+
 #define EMITS_PT_NOTE
 
 #include <asm-generic/vmlinux.lds.h>
-- 
2.34.1

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!