linux-kernel - Re: [PATCH] crypto: ux500/crypt: Mark expected switch fall-throughs

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Date:   Tue, 30 Jul 2019 09:58:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: ux500/crypt: Mark expected switch fall-throughs

On Mon, Jul 29, 2019 at 05:38:19PM -0500, Gustavo A. R. Silva wrote:
> Mark switch cases where we are expecting to fall through.
> 
> This patch fixes the following warning (Building: arm):
> 
> drivers/crypto/ux500/cryp/cryp.c: In function ‘cryp_save_device_context’:
> drivers/crypto/ux500/cryp/cryp.c:316:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    ctx->key_4_r = readl_relaxed(&src_reg->key_4_r);
> drivers/crypto/ux500/cryp/cryp.c:318:2: note: here
>   case CRYP_KEY_SIZE_192:
>   ^~~~
> drivers/crypto/ux500/cryp/cryp.c:320:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    ctx->key_3_r = readl_relaxed(&src_reg->key_3_r);
> drivers/crypto/ux500/cryp/cryp.c:322:2: note: here
>   case CRYP_KEY_SIZE_128:
>   ^~~~
> drivers/crypto/ux500/cryp/cryp.c:324:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    ctx->key_2_r = readl_relaxed(&src_reg->key_2_r);
> drivers/crypto/ux500/cryp/cryp.c:326:2: note: here
>   default:
>   ^~~~~~~
> In file included from ./include/linux/io.h:13:0,
>                  from drivers/crypto/ux500/cryp/cryp_p.h:14,
>                  from drivers/crypto/ux500/cryp/cryp.c:15:
> drivers/crypto/ux500/cryp/cryp.c: In function ‘cryp_restore_device_context’:
> ./arch/arm/include/asm/io.h:92:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
>  #define __raw_writel __raw_writel
>                       ^
> ./arch/arm/include/asm/io.h:299:29: note: in expansion of macro ‘__raw_writel’
>  #define writel_relaxed(v,c) __raw_writel((__force u32) cpu_to_le32(v),c)
>                              ^~~~~~~~~~~~
> drivers/crypto/ux500/cryp/cryp.c:363:3: note: in expansion of macro ‘writel_relaxed’
>    writel_relaxed(ctx->key_4_r, &reg->key_4_r);
>    ^~~~~~~~~~~~~~
> drivers/crypto/ux500/cryp/cryp.c:365:2: note: here
>   case CRYP_KEY_SIZE_192:
>   ^~~~
> In file included from ./include/linux/io.h:13:0,
>                  from drivers/crypto/ux500/cryp/cryp_p.h:14,
>                  from drivers/crypto/ux500/cryp/cryp.c:15:
> ./arch/arm/include/asm/io.h:92:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
>  #define __raw_writel __raw_writel
>                       ^
> ./arch/arm/include/asm/io.h:299:29: note: in expansion of macro ‘__raw_writel’
>  #define writel_relaxed(v,c) __raw_writel((__force u32) cpu_to_le32(v),c)
>                              ^~~~~~~~~~~~
> drivers/crypto/ux500/cryp/cryp.c:367:3: note: in expansion of macro ‘writel_relaxed’
>    writel_relaxed(ctx->key_3_r, &reg->key_3_r);
>    ^~~~~~~~~~~~~~
> drivers/crypto/ux500/cryp/cryp.c:369:2: note: here
>   case CRYP_KEY_SIZE_128:
>   ^~~~
> In file included from ./include/linux/io.h:13:0,
>                  from drivers/crypto/ux500/cryp/cryp_p.h:14,
>                  from drivers/crypto/ux500/cryp/cryp.c:15:
> ./arch/arm/include/asm/io.h:92:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
>  #define __raw_writel __raw_writel
>                       ^
> ./arch/arm/include/asm/io.h:299:29: note: in expansion of macro ‘__raw_writel’
>  #define writel_relaxed(v,c) __raw_writel((__force u32) cpu_to_le32(v),c)
>                              ^~~~~~~~~~~~
> drivers/crypto/ux500/cryp/cryp.c:371:3: note: in expansion of macro ‘writel_relaxed’
>    writel_relaxed(ctx->key_2_r, &reg->key_2_r);
>    ^~~~~~~~~~~~~~
> drivers/crypto/ux500/cryp/cryp.c:373:2: note: here
>   default:
>   ^~~~~~~
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

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

-Kees

> ---
>  drivers/crypto/ux500/cryp/cryp.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/crypto/ux500/cryp/cryp.c b/drivers/crypto/ux500/cryp/cryp.c
> index ece83a363e11..f22f6fa612b3 100644
> --- a/drivers/crypto/ux500/cryp/cryp.c
> +++ b/drivers/crypto/ux500/cryp/cryp.c
> @@ -314,14 +314,17 @@ void cryp_save_device_context(struct cryp_device_data *device_data,
>  	case CRYP_KEY_SIZE_256:
>  		ctx->key_4_l = readl_relaxed(&src_reg->key_4_l);
>  		ctx->key_4_r = readl_relaxed(&src_reg->key_4_r);
> +		/* Fall through */
>  
>  	case CRYP_KEY_SIZE_192:
>  		ctx->key_3_l = readl_relaxed(&src_reg->key_3_l);
>  		ctx->key_3_r = readl_relaxed(&src_reg->key_3_r);
> +		/* Fall through */
>  
>  	case CRYP_KEY_SIZE_128:
>  		ctx->key_2_l = readl_relaxed(&src_reg->key_2_l);
>  		ctx->key_2_r = readl_relaxed(&src_reg->key_2_r);
> +		/* Fall through */
>  
>  	default:
>  		ctx->key_1_l = readl_relaxed(&src_reg->key_1_l);
> @@ -361,14 +364,17 @@ void cryp_restore_device_context(struct cryp_device_data *device_data,
>  	case CRYP_KEY_SIZE_256:
>  		writel_relaxed(ctx->key_4_l, &reg->key_4_l);
>  		writel_relaxed(ctx->key_4_r, &reg->key_4_r);
> +		/* Fall through */
>  
>  	case CRYP_KEY_SIZE_192:
>  		writel_relaxed(ctx->key_3_l, &reg->key_3_l);
>  		writel_relaxed(ctx->key_3_r, &reg->key_3_r);
> +		/* Fall through */
>  
>  	case CRYP_KEY_SIZE_128:
>  		writel_relaxed(ctx->key_2_l, &reg->key_2_l);
>  		writel_relaxed(ctx->key_2_r, &reg->key_2_r);
> +		/* Fall through */
>  
>  	default:
>  		writel_relaxed(ctx->key_1_l, &reg->key_1_l);
> -- 
> 2.22.0
> 

-- 
Kees Cook