linux-kernel - Re: [PATCH] spi: rockchip: avoid objtool warning

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Date:   Thu, 25 Feb 2021 13:16:38 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Arnd Bergmann <arnd@...db.de>,
        Jon Lin <jon.lin@...k-chips.com>,
        Chris Ruehl <chris.ruehl@...ys.com.hk>,
        Alexander Kochetkov <al.kochet@...il.com>,
        Johan Jonker <jbx6244@...il.com>,
        Vincent Pelletier <plr.vincent@...il.com>,
        linux-spi@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-rockchip@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] spi: rockchip: avoid objtool warning

On Thu, Feb 25, 2021 at 4:55 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> Building this file with clang leads to a an unreachable code path
> causing a warning from objtool:
>
> drivers/spi/spi-rockchip.o: warning: objtool: rockchip_spi_transfer_one()+0x2e0: sibling call from callable instruction with modified stack frame
>
> Use BUG() instead of unreachable() to avoid the undefined behavior
> if it does happen.

Thanks for the patch!

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

>
> Fixes: 65498c6ae241 ("spi: rockchip: support 4bit words")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/spi/spi-rockchip.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
> index 936ef54e0903..972beac1169a 100644
> --- a/drivers/spi/spi-rockchip.c
> +++ b/drivers/spi/spi-rockchip.c
> @@ -521,7 +521,7 @@ static void rockchip_spi_config(struct rockchip_spi *rs,
>                  * ctlr->bits_per_word_mask, so this shouldn't
>                  * happen
>                  */
> -               unreachable();
> +               BUG();
>         }
>
>         if (use_dma) {
> --
> 2.29.2
>


-- 
Thanks,
~Nick Desaulniers