[PATCH] [v2] arm64: define BUG() instruction without CONFIG_BUG

From: Arnd Bergmann
Date: Tue Mar 14 2017 - 17:40:19 EST


This mirrors commit e9c38ceba8d9 ("ARM: 8455/1: define __BUG as
asm(BUG_INSTR) without CONFIG_BUG") to make the behavior of
arm64 consistent with arm and x86, and avoids lots of warnings in
randconfig builds, such as:

kernel/seccomp.c: In function '__seccomp_filter':
kernel/seccomp.c:666:1: error: no return statement in function returning non-void [-Werror=return-type]

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
Originally submitted v1 on Feb 14 as a simple addition of a few lines.
v2 is a new version doing the same thing with a cleaner rewrite of
the file, using three lines less, after a suggested from Will Deacon.

No need to get this into v4.11 though, especially as the rewrite
makes it a bit risky. Please queue this for v4.12 if you like the
new version.
---
arch/arm64/include/asm/bug.h | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/include/asm/bug.h b/arch/arm64/include/asm/bug.h
index 561190d15881..bfc6021760e5 100644
--- a/arch/arm64/include/asm/bug.h
+++ b/arch/arm64/include/asm/bug.h
@@ -20,9 +20,6 @@

#include <asm/brk-imm.h>

-#ifdef CONFIG_GENERIC_BUG
-#define HAVE_ARCH_BUG
-
#ifdef CONFIG_DEBUG_BUGVERBOSE
#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
#define __BUGVERBOSE_LOCATION(file, line) \
@@ -36,28 +33,37 @@
#define _BUGVERBOSE_LOCATION(file, line)
#endif

-#define _BUG_FLAGS(flags) __BUG_FLAGS(flags)
+#ifdef CONFIG_GENERIC_BUG

-#define __BUG_FLAGS(flags) asm volatile ( \
+#define __BUG_ENTRY(flags) \
".pushsection __bug_table,\"a\"\n\t" \
".align 2\n\t" \
"0: .long 1f - 0b\n\t" \
_BUGVERBOSE_LOCATION(__FILE__, __LINE__) \
".short " #flags "\n\t" \
".popsection\n" \
- \
- "1: brk %[imm]" \
- :: [imm] "i" (BUG_BRK_IMM) \
-)
+ "1: "
+#else
+#define __BUG_ENTRY(flags) ""
+#endif
+
+#define __BUG_FLAGS(flags) \
+ asm volatile ( \
+ __BUG_ENTRY(0) \
+ "brk %[imm]" :: [imm] "i" (BUG_BRK_IMM) \
+ );

-#define BUG() do { \
- _BUG_FLAGS(0); \
- unreachable(); \
+#define _BUG_FLAGS(flags) __BUG_FLAGS(flags)
+
+#define BUG() do { \
+ __BUG_FLAGS(0); \
+ unreachable(); \
} while (0)

-#define __WARN_TAINT(taint) _BUG_FLAGS(BUGFLAG_TAINT(taint))
+#define __WARN_TAINT(taint) \
+ __BUG_FLAGS(BUGFLAG_TAINT(taint))

-#endif /* ! CONFIG_GENERIC_BUG */
+#define HAVE_ARCH_BUG

#include <asm-generic/bug.h>

--
2.9.0