arm: perf: Mark expected switch fall-through

Message ID 20190726112732.19257-1-anders.roxell@linaro.org
State New
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Series
  • arm: perf: Mark expected switch fall-through
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Commit Message

Anders Roxell July 26, 2019, 11:27 a.m.
When fall-through warnings was enabled by default, d93512ef0f0e
("Makefile: Globally enable fall-through warning"), we could see the
following warnings was starting to show up. However, this was originally
introduced in commit 6ee33c2712fc ("ARM: hw_breakpoint: correct and
simplify alignment fixup code"). Commit d968d2b801d8 ("ARM: 7497/1:
hw_breakpoint: allow single-byte watchpoints on all addresses") was
written with the intent to allow single-byte watchpoints on all
addresses but forgot to move 'case 1:' down below 'case 2:'.

../arch/arm/kernel/hw_breakpoint.c: In function ‘hw_breakpoint_arch_parse’:
../arch/arm/kernel/hw_breakpoint.c:609:7: warning: this statement may fall
 through [-Wimplicit-fallthrough=]
    if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
       ^
../arch/arm/kernel/hw_breakpoint.c:611:3: note: here
   case 3:
   ^~~~
../arch/arm/kernel/hw_breakpoint.c:613:7: warning: this statement may fall
 through [-Wimplicit-fallthrough=]
    if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
       ^
../arch/arm/kernel/hw_breakpoint.c:615:3: note: here
   default:
   ^~~~~~~

Rework so 'case 1:' are next to 'case 3:' and also add '/* Fall through
*/' so that the compiler doesn't warn about fall-through.

Cc: stable@vger.kernel.org # v3.16
Fixes: 6ee33c2712fc ("ARM: hw_breakpoint: correct and simplify alignment fixup code")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

---
 arch/arm/kernel/hw_breakpoint.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

-- 
2.20.1

Comments

Will Deacon July 26, 2019, 1:08 p.m. | #1
On Fri, Jul 26, 2019 at 01:27:32PM +0200, Anders Roxell wrote:
> When fall-through warnings was enabled by default, d93512ef0f0e

> ("Makefile: Globally enable fall-through warning"), we could see the

> following warnings was starting to show up. However, this was originally

> introduced in commit 6ee33c2712fc ("ARM: hw_breakpoint: correct and

> simplify alignment fixup code"). Commit d968d2b801d8 ("ARM: 7497/1:

> hw_breakpoint: allow single-byte watchpoints on all addresses") was

> written with the intent to allow single-byte watchpoints on all

> addresses but forgot to move 'case 1:' down below 'case 2:'.

> 

> ../arch/arm/kernel/hw_breakpoint.c: In function ‘hw_breakpoint_arch_parse’:

> ../arch/arm/kernel/hw_breakpoint.c:609:7: warning: this statement may fall

>  through [-Wimplicit-fallthrough=]

>     if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)

>        ^

> ../arch/arm/kernel/hw_breakpoint.c:611:3: note: here

>    case 3:

>    ^~~~

> ../arch/arm/kernel/hw_breakpoint.c:613:7: warning: this statement may fall

>  through [-Wimplicit-fallthrough=]

>     if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)

>        ^

> ../arch/arm/kernel/hw_breakpoint.c:615:3: note: here

>    default:

>    ^~~~~~~

> 

> Rework so 'case 1:' are next to 'case 3:' and also add '/* Fall through

> */' so that the compiler doesn't warn about fall-through.

> 

> Cc: stable@vger.kernel.org # v3.16

> Fixes: 6ee33c2712fc ("ARM: hw_breakpoint: correct and simplify alignment fixup code")

> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

> ---

>  arch/arm/kernel/hw_breakpoint.c | 4 +++-

>  1 file changed, 3 insertions(+), 1 deletion(-)

> 

> diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c

> index af8b8e15f589..c14d506969ba 100644

> --- a/arch/arm/kernel/hw_breakpoint.c

> +++ b/arch/arm/kernel/hw_breakpoint.c

> @@ -603,15 +603,17 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,

>  	case 0:

>  		/* Aligned */

>  		break;

> -	case 1:

>  	case 2:

>  		/* Allow halfword watchpoints and breakpoints. */

>  		if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)

>  			break;

> +		/* Fall through */

> +	case 1:


Why are you moving the 'case 1:' here? AFAICT, your patch now rejects
byte-aligned watchpoints of length 2.

Will

Patch

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index af8b8e15f589..c14d506969ba 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -603,15 +603,17 @@  int hw_breakpoint_arch_parse(struct perf_event *bp,
 	case 0:
 		/* Aligned */
 		break;
-	case 1:
 	case 2:
 		/* Allow halfword watchpoints and breakpoints. */
 		if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
 			break;
+		/* Fall through */
+	case 1:
 	case 3:
 		/* Allow single byte watchpoint. */
 		if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
 			break;
+		/* Fall through */
 	default:
 		ret = -EINVAL;
 		goto out;