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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 3 Jul 2018 22:04:57 +0200
Message-ID: <CAK8P3a3jqib-GiWcRVo6ds8Q50nZTaRmC3ACW5xJJVJzV6=7NA@mail.gmail.com>
Subject: Re: [PATCH V2 13/19] csky: Library functions
To:     Guo Ren <ren_guo@c-sky.com>
Cc:     linux-arch <linux-arch@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Jason Cooper <jason@lakedaemon.net>,
        c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com,
        thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org,
        Greentime Hu <green.hu@gmail.com>
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On Sun, Jul 1, 2018 at 7:30 PM, Guo Ren <ren_guo@c-sky.com> wrote:
>
> diff --git a/arch/csky/kernel/cskyksyms.c b/arch/csky/kernel/cskyksyms.c
> new file mode 100644
> index 0000000..3f13594
> --- /dev/null
> +++ b/arch/csky/kernel/cskyksyms.c
> @@ -0,0 +1,31 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <asm/cacheflush.h>
> +
> +/*
> + * Defined in libgcc
> + *
> + * See arch/csky/Makefile:
> + *     -print-libgcc-file-name
> + */
> +extern void __ashldi3 (void);
> +extern void __ashrdi3 (void);
> +extern void __lshrdi3 (void);
> +extern void __muldi3 (void);
> +extern void __ucmpdi2 (void);
> +EXPORT_SYMBOL(__ashldi3);
> +EXPORT_SYMBOL(__ashrdi3);
> +EXPORT_SYMBOL(__lshrdi3);
> +EXPORT_SYMBOL(__muldi3);
> +EXPORT_SYMBOL(__ucmpdi2);

It's better to avoid relying on libgcc here. Please use the
CONFIG_GENERIC_LIB_ASHLDI3/ASHRDI3/LSHRDI3/etc
helpers that we already have in the kernel.

       Arnd