linux-kernel - Re: [PATCH] mtd: cfi_util: mark expected switch fall-throughs

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Date:   Wed, 10 Apr 2019 14:46:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Linux mtd <linux-mtd@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: cfi_util: mark expected switch fall-throughs

On Fri, Feb 8, 2019 at 10:02 AM Gustavo A. R. Silva
<gustavo@...eddedor.com> wrote:
>
> In preparation to enabling -Wimplicit-fallthrough, mark switch
> cases where we are expecting to fall through.
>
> This patch fixes the following warnings:
>
> drivers/mtd/chips/cfi_util.c: In function ‘cfi_build_cmd’:
> drivers/mtd/chips/cfi_util.c:110:10: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    onecmd |= (onecmd << (chip_mode * 32));
>    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/mtd/chips/cfi_util.c:112:2: note: here
>   case 4:
>   ^~~~
> drivers/mtd/chips/cfi_util.c:113:10: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    onecmd |= (onecmd << (chip_mode * 16));
>    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/mtd/chips/cfi_util.c:114:2: note: here
>   case 2:
>   ^~~~
> drivers/mtd/chips/cfi_util.c: In function ‘cfi_merge_status’:
> drivers/mtd/chips/cfi_util.c:163:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    res |= (onestat >> (chip_mode * 32));
>    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/mtd/chips/cfi_util.c:165:2: note: here
>   case 4:
>   ^~~~
> drivers/mtd/chips/cfi_util.c:166:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    res |= (onestat >> (chip_mode * 16));
>    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/mtd/chips/cfi_util.c:167:2: note: here
>   case 2:
>   ^~~~
>
> Warning level 3 was used: -Wimplicit-fallthrough=3
>
> This patch is part of the ongoing efforts to enabling
> -Wimplicit-fallthrough.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/mtd/chips/cfi_util.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/mtd/chips/cfi_util.c b/drivers/mtd/chips/cfi_util.c
> index 6f16552cd59f..e3b266ee06af 100644
> --- a/drivers/mtd/chips/cfi_util.c
> +++ b/drivers/mtd/chips/cfi_util.c
> @@ -109,10 +109,13 @@ map_word cfi_build_cmd(u_long cmd, struct map_info *map, struct cfi_private *cfi
>         case 8:
>                 onecmd |= (onecmd << (chip_mode * 32));
>  #endif
> +               /* fall through */
>         case 4:
>                 onecmd |= (onecmd << (chip_mode * 16));
> +               /* fall through */
>         case 2:
>                 onecmd |= (onecmd << (chip_mode * 8));
> +               /* fall through */
>         case 1:
>                 ;
>         }
> @@ -162,10 +165,13 @@ unsigned long cfi_merge_status(map_word val, struct map_info *map,
>         case 8:
>                 res |= (onestat >> (chip_mode * 32));
>  #endif
> +               /* fall through */
>         case 4:
>                 res |= (onestat >> (chip_mode * 16));
> +               /* fall through */
>         case 2:
>                 res |= (onestat >> (chip_mode * 8));
> +               /* fall through */
>         case 1:
>                 ;
>         }
> --
> 2.20.1
>


-- 
Kees Cook