Re: [PATCH] powerpc: align syscall table for ppc32
From: Christophe Leroy <hidden>
Date: 2022-08-20 17:50:29
Also in:
linux-kbuild, lkml
Le 20/08/2022 à 18:51, Masahiro Yamada a écrit :
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 did not notice it because when CONFIG_MODVERSIONS
is enabled, a __crc_* symbol inserted before sys_call_table was hiding
the unalignment issue.
I checked the commit history, but I could not understand commit
46b45b10f142 ("[POWERPC] Align the sys_call_table").
It said 'Our _GLOBAL macro does a ".align 2" so the alignment is fine
for 32 bit'. I checked the _GLOBAL in include/asm-powerpc/ppc_asm.h
at that time. _GLOBAL specifies ".align 2" for ppc64, but no .align
for ppc32.
Commit c857c43b34ec ("powerpc: Don't use a function descriptor for
system call table") removed _GLOBAL from the syscall table.
Anyway, adding alignment to the syscall table for ppc32 fixes the issue.
I am not giving Fixes tag because I do not know since when it has been
broken, but presumably it has been for a long while.
Link: https://lore.kernel.org/lkml/38605f6a-a568-f884-f06f-ea4da5b214f0@csgroup.eu/ (local)
Reported-by: Christophe Leroy <redacted>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>Tested-by: Christophe Leroy <redacted>
quoted hunk ↗ jump to hunk
--- arch/powerpc/kernel/systbl.S | 1 + 1 file changed, 1 insertion(+)diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.S index cb3358886203..6c1db3b6de2d 100644 --- a/arch/powerpc/kernel/systbl.S +++ b/arch/powerpc/kernel/systbl.S@@ -18,6 +18,7 @@ .p2align 3 #define __SYSCALL(nr, entry) .8byte entry #else + .p2align 2 #define __SYSCALL(nr, entry) .long entry #endif