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: <CAK7LNATKh4DrgSeN+E1r7xmh1YL6mwWL_g2zL-rz=NYuzXT1bA@mail.gmail.com>
Date:   Sat, 20 Aug 2022 21:51:46 +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 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


-- 
Best Regards
Masahiro Yamada