linux-kernel - Re: [PATCH] kbuild: avoid static

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Date:   Sun, 6 Dec 2020 11:48:21 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Arnd Bergmann <arnd@...db.de>, stable <stable@...r.kernel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Rikard Falkeborn <rikard.falkeborn@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kbuild: avoid static_assert for genksyms

On Fri, Dec 4, 2020 at 8:10 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> genksyms does not know or care about the _Static_assert() built-in,
> and sometimes falls back to ignoring the later symbols, which causes
> undefined behavior such as
>
> WARNING: modpost: EXPORT symbol "ethtool_set_ethtool_phy_ops" [vmlinux] version generation failed, symbol will not be versioned.
> ld: net/ethtool/common.o: relocation R_AARCH64_ABS32 against `__crc_ethtool_set_ethtool_phy_ops' can not be used when making a shared object
> net/ethtool/common.o:(_ftrace_annotated_branch+0x0): dangerous relocation: unsupported relocation
>
> Redefine static_assert for genksyms to avoid that.


Please tell the CONFIG options needed to reproduce this.
I do not see it.


>
> Cc: stable@...r.kernel.org
> Suggested-by: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  include/linux/build_bug.h | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
> index e3a0be2c90ad..7bb66e15b481 100644
> --- a/include/linux/build_bug.h
> +++ b/include/linux/build_bug.h
> @@ -77,4 +77,9 @@
>  #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
>  #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
>
> +#ifdef __GENKSYMS__
> +/* genksyms gets confused by _Static_assert */
> +#define _Static_assert(expr, ...)
> +#endif
> +
>  #endif /* _LINUX_BUILD_BUG_H */
> --
> 2.27.0
>


-- 
Best Regards
Masahiro Yamada