linux-kernel - Re: [PATCH] kbuild: fix CONFIG_TRIM_UNUSED

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Date:   Fri, 12 Feb 2021 03:05:31 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kbuild: fix CONFIG_TRIM_UNUSED_KSYMS build for ppc64

On Thu, Feb 11, 2021 at 7:43 PM Jessica Yu <jeyu@...nel.org> wrote:
>
> +++ Masahiro Yamada [11/02/21 15:14 +0900]:
> >Stephen Rothwell reported a build error on ppc64 when
> >CONFIG_TRIM_UNUSED_KSYMS is enabled.
> >
> >Jessica Yu pointed out the cause of the error with the reference to the
> >ppc64 elf ABI:
> >  "Symbol names with a dot (.) prefix are reserved for holding entry
> >   point addresses. The value of a symbol named ".FN", if it exists,
> >   is the entry point of the function "FN".
> >
> >As it turned out, CONFIG_TRIM_UNUSED_KSYMS has never worked for ppc64,
> >which has been unnoticed until recently because this option depends on
> >!UNUSED_SYMBOLS hence is disabled by all{mod,yes}config. (Then, it was
> >uncovered by another patch removing UNUSED_SYMBOLS.)
> >
> >Removing the dot prefix in scripts/gen_autoksyms.sh fixes the issue.
> >Please note it must be done before 'sort -u', because modules have
> >both ._mcount and _mcount undefined when CONFIG_FUNCTION_TRACER=y.
> >
> >Link: https://lore.kernel.org/lkml/20210209210843.3af66662@canb.auug.org.au/
> >Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> >Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>
> Thanks a lot for the quick fix. This fixes the ppc64 build issue on my end:
>
>     Tested-by: Jessica Yu <jeyu@...nel.org>
>
> Do you plan to take this through the kbuild tree? If so, please let me
> know when you've applied it, then I can undo the temporary workaround
> I currently have in modules-next.
>
> Thank you!
>
> Jessica


Applied to linux-kbuild/fixes.


-- 
Best Regards
Masahiro Yamada