linux-kernel - Re: [PATCH] powerpc: align syscall table for ppc32

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Date:   Fri, 26 Aug 2022 08:51:55 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc: align syscall table for ppc32

Masahiro Yamada <masahiroy@...nel.org> writes:
> On Thu, Aug 25, 2022 at 4:53 PM Michael Ellerman <mpe@...erman.id.au> wrote:
>>
>> Masahiro Yamada <masahiroy@...nel.org> writes:
>> > 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
>
> I wrote weird English (double negation)
>
> nobody did not notice   --> nobody noticed
>
> Please fix it if you have not yet.

Yeah I did fix it up when applying :)

  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.

cheers