linux-kernel - [PATCH] kernel/compat.c: mark expected switch fall-throughs

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Message-ID: <20190515152352.26dac479@canb.auug.org.au>
Date:   Wed, 15 May 2019 15:23:52 +1000
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Linus <torvalds@...ux-foundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>,
        Linux-kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] kernel/compat.c: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

This patch aims to suppress 3 missing-break-in-switch false positives
on some architectures.

Acked-by: Arnd Bergmann <arnd@...db.de>
Cc: Deepa Dinamani <deepa.kernel@...il.com>
Cc: Gustavo A. R. Silva <gustavo@...eddedor.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Jann Horn <jannh@...gle.com>
Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
---
 kernel/compat.c | 3 +++
 1 file changed, 3 insertions(+)

Hi Linus,

This has been sitting in my fixes tree in linux-next for quite some
time.  It silences some warnings that irritated me in my builds since I
am building with -Wimplicit-fallthrough to help Gustavo catch new
additions.

diff --git a/kernel/compat.c b/kernel/compat.c
index d8a36c6ad7c9..b5f7063c0db6 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -346,8 +346,11 @@ get_compat_sigset(sigset_t *set, const compat_sigset_t __user *compat)
 		return -EFAULT;
 	switch (_NSIG_WORDS) {
 	case 4: set->sig[3] = v.sig[6] | (((long)v.sig[7]) << 32 );
+		/* fall through */
 	case 3: set->sig[2] = v.sig[4] | (((long)v.sig[5]) << 32 );
+		/* fall through */
 	case 2: set->sig[1] = v.sig[2] | (((long)v.sig[3]) << 32 );
+		/* fall through */
 	case 1: set->sig[0] = v.sig[0] | (((long)v.sig[1]) << 32 );
 	}
 #else
-- 
2.20.1

-- 
Cheers,
Stephen Rothwell

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