linux-kernel - Re: [PATCH] arm64: hw_breakpoint: mark expected switch fall-through

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Date:   Sun, 28 Jul 2019 18:45:31 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Matteo Croce <mcroce@...hat.com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: hw_breakpoint: mark expected switch fall-through



On 7/28/19 6:36 PM, Matteo Croce wrote:
> Feel free di discard the patch then.
> What compiler are you using? I' using gcc version 8.3.0 (Ubuntu/Linaro
> 8.3.0-6ubuntu1)
> 

My bad. My patch address the ones in arch/arm/kernel/hw_breakpoint.c

Your patch should be fine.

--
Gustavo

> On Mon, Jul 29, 2019 at 1:34 AM Gustavo A. R. Silva
> <gustavo@...eddedor.com> wrote:
>>
>> Hi Matteo,
>>
>> I sent a patch for this some minutes ago:
>>
>> https://lore.kernel.org/patchwork/patch/1106585/
>>
>> It seems there are more warnings in that file than the ones you are
>> addressing.
>>
>> Thanks
>> --
>> Gustavo
>>
>> On 7/28/19 6:27 PM, Matteo Croce wrote:
>>> Mark switch cases where we are expecting to fall through,
>>> fixes the following warning:
>>>
>>>   CC      arch/arm64/kernel/hw_breakpoint.o
>>> arch/arm64/kernel/hw_breakpoint.c: In function ‘hw_breakpoint_arch_parse’:
>>> arch/arm64/kernel/hw_breakpoint.c:540:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
>>>     if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
>>>        ^
>>> arch/arm64/kernel/hw_breakpoint.c:542:3: note: here
>>>    case 2:
>>>    ^~~~
>>> arch/arm64/kernel/hw_breakpoint.c:544:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
>>>     if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
>>>        ^
>>> arch/arm64/kernel/hw_breakpoint.c:546:3: note: here
>>>    default:
>>>    ^~~~~~~
>>>
>>> Signed-off-by: Matteo Croce <mcroce@...hat.com>
>>> ---
>>>  arch/arm64/kernel/hw_breakpoint.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
>>> index dceb84520948..7d846985b133 100644
>>> --- a/arch/arm64/kernel/hw_breakpoint.c
>>> +++ b/arch/arm64/kernel/hw_breakpoint.c
>>> @@ -539,10 +539,12 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
>>>                       /* Allow single byte watchpoint. */
>>>                       if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
>>>                               break;
>>> +                     /* fallthrough */
>>>               case 2:
>>>                       /* Allow halfword watchpoints and breakpoints. */
>>>                       if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
>>>                               break;
>>> +                     /* fallthrough */
>>>               default:
>>>                       return -EINVAL;
>>>               }
>>>
> 
> 
>