linux-hardening - Re: [PATCH][next] ring-buffer: Fix fall-through warning for Clang

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Date:   Fri, 28 May 2021 16:08:58 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] ring-buffer: Fix fall-through warning for Clang

On Fri, 28 May 2021 14:59:42 -0500
"Gustavo A. R. Silva" <gustavoars@...nel.org> wrote:

> In preparation to enable -Wimplicit-fallthrough for Clang, fix
> a fall-through warning by replacing a /* fall through */ comment
> with the new pseudo-keyword macro fallthrough;
> 
> Notice that Clang doesn't recognize /* fall through */ comments as
> implicit fall-through markings, so in order to globally enable
> -Wimplicit-fallthrough for Clang, these comments need to be
> replaced with fallthrough; in the whole codebase.
> 
> Link: https://github.com/KSPP/linux/issues/115
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
> JFYI: We had thousands of these sorts of warnings and now we are down
>       to just 25 in linux-next. This is one of those last remaining
>       warnings.

And I have it fixed locally already.

  https://lore.kernel.org/lkml/20210511140246.18868-1-jj251510319013@gmail.com/

I've just been on vacation and haven't pushed it to next yet. It's still in
the "to be tested" queue.

-- Steve

> 
>  kernel/trace/ring_buffer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 2c0ee6484990..d1463eac11a3 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -3391,7 +3391,7 @@ static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
>  		case RINGBUF_TYPE_PADDING:
>  			if (event->time_delta == 1)
>  				break;
> -			/* fall through */
> +			fallthrough;
>  		case RINGBUF_TYPE_DATA:
>  			ts += event->time_delta;
>  			break;