[PATCH v2] x86/syscalls: Mark expected switch fall-throughs

[Gustavo A. R. Silva]

In preparation to enable -Wimplicit-fallthrough by default, mark
switch-case statements where fall-through is intentional, explicitly
in order to fix a bunch of -Wimplicit-fallthrough warnings.

In order to get the warnings mentioned above, the following
line was added to the top Makefile:

KBUILD_CFLAGS  += $(call cc-option,-Wimplicit-fallthrough=3,)

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
---
Changes in v2:
 - Expand commit text as requested by Thomas Gleixner.
 - Add Kees' Reviewed-by.

 arch/x86/include/asm/syscall.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d653139857af..04fc5c120558 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -125,23 +125,30 @@ static inline void syscall_get_arguments(struct task_struct *task,
 		case 0:
 			if (!n--) break;
 			*args++ = regs->bx;
+			/* fall through */
 		case 1:
 			if (!n--) break;
 			*args++ = regs->cx;
+			/* fall through */
 		case 2:
 			if (!n--) break;
 			*args++ = regs->dx;
+			/* fall through */
 		case 3:
 			if (!n--) break;
 			*args++ = regs->si;
+			/* fall through */
 		case 4:
 			if (!n--) break;
 			*args++ = regs->di;
+			/* fall through */
 		case 5:
 			if (!n--) break;
 			*args++ = regs->bp;
+			/* fall through */
 		case 6:
 			if (!n--) break;
+			/* fall through */
 		default:
 			BUG();
 			break;
@@ -152,23 +159,30 @@ static inline void syscall_get_arguments(struct task_struct *task,
 		case 0:
 			if (!n--) break;
 			*args++ = regs->di;
+			/* fall through */
 		case 1:
 			if (!n--) break;
 			*args++ = regs->si;
+			/* fall through */
 		case 2:
 			if (!n--) break;
 			*args++ = regs->dx;
+			/* fall through */
 		case 3:
 			if (!n--) break;
 			*args++ = regs->r10;
+			/* fall through */
 		case 4:
 			if (!n--) break;
 			*args++ = regs->r8;
+			/* fall through */
 		case 5:
 			if (!n--) break;
 			*args++ = regs->r9;
+			/* fall through */
 		case 6:
 			if (!n--) break;
+			/* fall through */
 		default:
 			BUG();
 			break;
@@ -186,23 +200,30 @@ static inline void syscall_set_arguments(struct task_struct *task,
 		case 0:
 			if (!n--) break;
 			regs->bx = *args++;
+			/* fall through */
 		case 1:
 			if (!n--) break;
 			regs->cx = *args++;
+			/* fall through */
 		case 2:
 			if (!n--) break;
 			regs->dx = *args++;
+			/* fall through */
 		case 3:
 			if (!n--) break;
 			regs->si = *args++;
+			/* fall through */
 		case 4:
 			if (!n--) break;
 			regs->di = *args++;
+			/* fall through */
 		case 5:
 			if (!n--) break;
 			regs->bp = *args++;
+			/* fall through */
 		case 6:
 			if (!n--) break;
+			/* fall through */
 		default:
 			BUG();
 			break;
@@ -213,23 +234,30 @@ static inline void syscall_set_arguments(struct task_struct *task,
 		case 0:
 			if (!n--) break;
 			regs->di = *args++;
+			/* fall through */
 		case 1:
 			if (!n--) break;
 			regs->si = *args++;
+			/* fall through */
 		case 2:
 			if (!n--) break;
 			regs->dx = *args++;
+			/* fall through */
 		case 3:
 			if (!n--) break;
 			regs->r10 = *args++;
+			/* fall through */
 		case 4:
 			if (!n--) break;
 			regs->r8 = *args++;
+			/* fall through */
 		case 5:
 			if (!n--) break;
 			regs->r9 = *args++;
+			/* fall through */
 		case 6:
 			if (!n--) break;
+			/* fall through */
 		default:
 			BUG();
 			break;
-- 
2.21.0