[PATCH] ARM: alignment: Mark expected switch fall-throughs

[PATCH] ARM: alignment: Mark expected switch fall-throughs

[Gustavo A. R. Silva]

Mark switch cases where we are expecting to fall through.

This patch fixes the following warnings:

arch/arm/mm/alignment.c: In function 'thumb2arm':
arch/arm/mm/alignment.c:688:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if ((tinstr & (3 << 9)) == 0x0400) {
      ^
arch/arm/mm/alignment.c:700:2: note: here
  default:
  ^~~~~~~
arch/arm/mm/alignment.c: In function 'do_alignment_t32_to_handler':
arch/arm/mm/alignment.c:753:15: warning: this statement may fall through [-Wimplicit-fallthrough=]
   poffset->un = (tinst2 & 0xff) << 2;
   ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
arch/arm/mm/alignment.c:754:2: note: here
  case 0xe940:
  ^~~~

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 arch/arm/mm/alignment.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index 8cdb78642e93..04b36436cbc0 100644
--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -695,7 +695,7 @@ thumb2arm(u16 tinstr)
 			return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
 			    (tinstr & 255);		/* register_list */
 		}
-		/* Else fall through for illegal instruction case */
+		/* Else, fall through - for illegal instruction case */
 
 	default:
 		return BAD_INSTR;
@@ -751,6 +751,8 @@ do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
 	case 0xe8e0:
 	case 0xe9e0:
 		poffset->un = (tinst2 & 0xff) << 2;
+		/* Fall through */
+
 	case 0xe940:
 	case 0xe9c0:
 		return do_alignment_ldrdstrd;
-- 
2.22.0

Re: [PATCH] ARM: alignment: Mark expected switch fall-throughs

[Kees Cook]

On Sun, Jul 28, 2019 at 06:19:20PM -0500, Gustavo A. R. Silva wrote:
> Mark switch cases where we are expecting to fall through.
> 
> This patch fixes the following warnings:
> 
> arch/arm/mm/alignment.c: In function 'thumb2arm':
> arch/arm/mm/alignment.c:688:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if ((tinstr & (3 << 9)) == 0x0400) {
>       ^
> arch/arm/mm/alignment.c:700:2: note: here
>   default:
>   ^~~~~~~
> arch/arm/mm/alignment.c: In function 'do_alignment_t32_to_handler':
> arch/arm/mm/alignment.c:753:15: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    poffset->un = (tinst2 & 0xff) << 2;
>    ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
> arch/arm/mm/alignment.c:754:2: note: here
>   case 0xe940:
>   ^~~~
> 
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

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

-Kees

> ---
>  arch/arm/mm/alignment.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
> index 8cdb78642e93..04b36436cbc0 100644
> --- a/arch/arm/mm/alignment.c
> +++ b/arch/arm/mm/alignment.c
> @@ -695,7 +695,7 @@ thumb2arm(u16 tinstr)
>  			return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
>  			    (tinstr & 255);		/* register_list */
>  		}
> -		/* Else fall through for illegal instruction case */
> +		/* Else, fall through - for illegal instruction case */
>  
>  	default:
>  		return BAD_INSTR;
> @@ -751,6 +751,8 @@ do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
>  	case 0xe8e0:
>  	case 0xe9e0:
>  		poffset->un = (tinst2 & 0xff) << 2;
> +		/* Fall through */
> +
>  	case 0xe940:
>  	case 0xe9c0:
>  		return do_alignment_ldrdstrd;
> -- 
> 2.22.0
> 

-- 
Kees Cook