linux-kernel - Re: [PATCH] fixup! kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL

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Date:   Mon, 23 May 2022 14:04:04 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nicolas Schier <nicolas@...sle.eu>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-modules@...r.kernel.org, llvm@...ts.linux.dev,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>
Subject: Re: [PATCH] fixup! kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS

On Sun, May 22, 2022 at 9:04 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> I will squash this into
>
>   https://patchwork.kernel.org/project/linux-kbuild/patch/20220513113930.10488-3-masahiroy@kernel.org/
>
> Sedat Reported an error:
>
>   https://lore.kernel.org/linux-kbuild/CA+icZUWttwjhDNPO1VuVyiMoReH5e83nsYDd0rEoY8-Uwv6pHw@mail.gmail.com/T/#md82f561e348b7959b7270c33ac86fa3edb0d773a
>
> __used is needed to make the combination of
> CONFIG_MODVERSIONS and CONFIG_LTO_CLANG working.

Yep, vaguely reminiscent of
commit f3751ad0116f ("tracepoint: Mark __tracepoint_string's __used")

Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  include/linux/export-internal.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/export-internal.h b/include/linux/export-internal.h
> index 77175d561058..c2b1d4fd5987 100644
> --- a/include/linux/export-internal.h
> +++ b/include/linux/export-internal.h
> @@ -10,7 +10,8 @@
>  #include <linux/compiler.h>
>  #include <linux/types.h>
>
> +/* __used is needed to keep __crc_* for LTO */
>  #define SYMBOL_CRC(sym, crc, sec)   \
> -       u32 __section("___kcrctab" sec "+" #sym) __crc_##sym = crc
> +       u32 __section("___kcrctab" sec "+" #sym) __used __crc_##sym = crc
>
>  #endif /* __LINUX_EXPORT_INTERNAL_H__ */
> --
> 2.32.0
>


-- 
Thanks,
~Nick Desaulniers