linux-kernel - [PATCH 5.4 023/108] powerpc: align syscall table for ppc32

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Message-Id: <20220913140354.625153846@linuxfoundation.org>
Date:   Tue, 13 Sep 2022 16:05:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.4 023/108] powerpc: align syscall table for ppc32

From: Masahiro Yamada <masahiroy@...nel.org>

commit c7acee3d2f128a38b68fb7af85dbbd91bfd0b4ad upstream.

Christophe Leroy reported that commit 7b4537199a4a ("kbuild: link
symbol CRCs at final link,  removing CONFIG_MODULE_REL_CRCS") broke
mpc85xx_defconfig + CONFIG_RELOCATABLE=y.

    LD      vmlinux
    SYSMAP  System.map
    SORTTAB vmlinux
    CHKREL  vmlinux
  WARNING: 451 bad relocations
  c0b312a9 R_PPC_UADDR32     .head.text-0x3ff9ed54
  c0b312ad R_PPC_UADDR32     .head.text-0x3ffac224
  c0b312b1 R_PPC_UADDR32     .head.text-0x3ffb09f4
  c0b312b5 R_PPC_UADDR32     .head.text-0x3fe184dc
  c0b312b9 R_PPC_UADDR32     .head.text-0x3fe183a8
      ...

The compiler emits a bunch of R_PPC_UADDR32, which is not supported by
arch/powerpc/kernel/reloc_32.S.

The reason is there exists an unaligned symbol.

  $ powerpc-linux-gnu-nm -n vmlinux
    ...
  c0b31258 d spe_aligninfo
  c0b31298 d __func__.0
  c0b312a9 D sys_call_table
  c0b319b8 d __func__.0

Commit 7b4537199a4a is not the root cause. Even before that, I can
reproduce the same issue for mpc85xx_defconfig + CONFIG_RELOCATABLE=y
+ CONFIG_MODVERSIONS=n.

It is just that nobody noticed because when CONFIG_MODVERSIONS is
enabled, a __crc_* symbol inserted before sys_call_table was hiding the
unalignment issue.

Adding alignment to the syscall table for ppc32 fixes the issue.

Cc: stable@...r.kernel.org
Reported-by: Christophe Leroy <christophe.leroy@...roup.eu>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Tested-by: Christophe Leroy <christophe.leroy@...roup.eu>
[mpe: Trim change log discussion, add Cc stable]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/lkml/38605f6a-a568-f884-f06f-ea4da5b214f0@csgroup.eu/
Link: https://lore.kernel.org/r/20220820165129.1147589-1-masahiroy@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/powerpc/kernel/systbl.S |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/powerpc/kernel/systbl.S
+++ b/arch/powerpc/kernel/systbl.S
@@ -25,6 +25,7 @@ sys_call_table:
 #include <asm/syscall_table_64.h>
 #undef __SYSCALL
 #else
+	.p2align	2
 #define __SYSCALL(nr, entry)	.long entry
 #include <asm/syscall_table_32.h>
 #undef __SYSCALL