From:   Tom Saeger <tom.saeger@oracle.com>
To:     Naresh Kamboju <naresh.kamboju@linaro.org>
Cc:     John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        Rich Felker <dalias@libc.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Dennis Gilmore <dennis@ausil.us>,
        Palmer Dabbelt <palmer@rivosinc.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tom Saeger <tom.saeger@oracle.com>, stable@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org
Subject: [PATCH 5.4 fix build id for arm64 5/6] s390: define RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36
Date:   Tue, 24 Jan 2023 14:14:22 -0700
Message-Id: <02aed8d0fad05a87a02c226d8e9f55792e41c47b.1674588616.git.tom.saeger@oracle.com>
In-Reply-To: <cover.1674588616.git.tom.saeger@oracle.com>
References: <cover.1674588616.git.tom.saeger@oracle.com>
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From: Masahiro Yamada <masahiroy@kernel.org>

commit a494398bde273143c2352dd373cad8211f7d94b2 upstream.

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>
Link: https://lore.kernel.org/r/20230105031306.1455409-1-masahiroy@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
 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 4df41695caec..a471bd480397 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -15,6 +15,8 @@
 /* Handle ro_after_init data on our own. */
 #define RO_AFTER_INIT_DATA
 
+#define RUNTIME_DISCARD_EXIT
+
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/vmlinux.lds.h>
 
-- 
2.39.1