linux-kernel - Re: Build/boot problem with 7b4537199a4a (Re: [PATCH v6 02/10] kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL

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Message-ID: <CAK7LNAQnYQH4BhYkw2G3KMDYRY3mzU9Yd1NudCABG8qpDVRtrQ@mail.gmail.com>
Date:   Sun, 21 Aug 2022 02:01:36 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        Peter Zijlstra <peterz@...radead.org>,
        "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: Build/boot problem with 7b4537199a4a (Re: [PATCH v6 02/10]
 kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS)

On Sat, Aug 20, 2022 at 11:15 PM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
>
>
> Le 20/08/2022 à 14:51, Masahiro Yamada a écrit :
> > On Sat, Aug 20, 2022 at 7:02 PM Christophe Leroy
> > <christophe.leroy@...roup.eu> wrote:
> >>
> >> Hi,
> >>
> >> Le 13/05/2022 à 13:39, Masahiro Yamada a écrit :
> >>> include/{linux,asm-generic}/export.h defines a weak symbol, __crc_*
> >>> as a placeholder.
> >>>
> >>> Genksyms writes the version CRCs into the linker script, which will be
> >>> used for filling the __crc_* symbols. The linker script format depends
> >>> on CONFIG_MODULE_REL_CRCS. If it is enabled, __crc_* holds the offset
> >>> to the reference of CRC.
> >>>
> >>> It is time to get rid of this complexity.
> >>>
> >>> Now that modpost parses text files (.*.cmd) to collect all the CRCs,
> >>> it can generate C code that will be linked to the vmlinux or modules.
> >>>
> >>> Generate a new C file, .vmlinux.export.c, which contains the CRCs of
> >>> symbols exported by vmlinux. It is compiled and linked to vmlinux in
> >>> scripts/link-vmlinux.sh.
> >>>
> >>> Put the CRCs of symbols exported by modules into the existing *.mod.c
> >>> files. No additional build step is needed for modules. As before,
> >>> *.mod.c are compiled and linked to *.ko in scripts/Makefile.modfinal.
> >>>
> >>> No linker magic is used here. The new C implementation works in the
> >>> same way, whether CONFIG_RELOCATABLE is enabled or not.
> >>> CONFIG_MODULE_REL_CRCS is no longer needed.
> >>>
> >>> Previously, Kbuild invoked additional $(LD) to update the CRCs in
> >>> objects, but this step is unneeded too.
> >>>
> >>> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> >>> Tested-by: Nathan Chancellor <nathan@...nel.org>
> >>> Tested-by: Nicolas Schier <nicolas@...sle.eu>
> >>> Reviewed-by: Nicolas Schier <nicolas@...sle.eu>
> >>
> >> Problem with v6.0-rc1
> >> Problem with v5.19
> >> No problem with v5.18
> >>
> >> Bisected to 7b4537199a4a ("kbuild: link symbol CRCs at final link,
> >> removing CONFIG_MODULE_REL_CRCS")
> >>
> >> The above patch leads to the following problem building
> >> mpc85xx_defconfig + CONFIG_RELOCATABLE
> >
> >
> >
> > Is this because the relocation implementation on ppc is incomplete?
> > (and is it the reason why relock_check.sh exists?)
> >
> > arch/powerpc/kernel/reloc_32.S does not support R_PPC_UADDR32
> >
> >
>
> Might be the reason.
>
> Is it expected that your patch adds an unsupported relocation ?
>
> Why was that relocation type unneeded before ?
>
> Thanks
> Christophe


I posted a patch (although I believe my commit is innocent).

https://lore.kernel.org/lkml/20220820165129.1147589-1-masahiroy@kernel.org/T/#u

The relocs_check.sh warnings are gone.
Please do a boot test.
Thanks.


-- 
Best Regards
Masahiro Yamada