[RFC PATCH 4/5] arm64: Add support for suppressing warning tracebacks

[Guenter Roeck <linux@roeck-us.net>]

Add support for selectively suppressing WARNING tracebacks to arm64.
This requires adding the function triggering tracebacks to the __bug_table
object section.

To limit image size impact, the pointer to the function name is only added
to the __bug_table section if both CONFIG_KUNIT and CONFIG_DEBUG_BUGVERBOSE
are enabled. Otherwise, the __func__ assembly parameter is replaced with a
(dummy) NULL parameter to avoid an image size increase due to unused
__func__ entries (this is necessary because __func__ is not a define but a
virtual variable).

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 arch/arm64/include/asm/asm-bug.h | 29 +++++++++++++++++++----------
 arch/arm64/include/asm/bug.h     |  8 +++++++-
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/asm-bug.h b/arch/arm64/include/asm/asm-bug.h
index c762038ba400..6884089a7191 100644
--- a/arch/arm64/include/asm/asm-bug.h
+++ b/arch/arm64/include/asm/asm-bug.h
@@ -8,36 +8,45 @@
 #include <asm/brk-imm.h>
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
-#define __BUGVERBOSE_LOCATION(file, line)			\
+
+#if IS_ENABLED(CONFIG_KUNIT)
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR(func)	.long func - .;
+#else
+# define __BUG_FUNC_PTR(func)
+#endif
+
+#define _BUGVERBOSE_LOCATION(file, func, line) __BUGVERBOSE_LOCATION(file, func, line)
+#define __BUGVERBOSE_LOCATION(file, func, line)		\
 		.pushsection .rodata.str,"aMS",@progbits,1;	\
 	14472:	.string file;					\
 		.popsection;					\
 								\
 		.long 14472b - .;				\
+		__BUG_FUNC_PTR(func)				\
 		.short line;
 #else
-#define _BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line)
 #endif
 
 #ifdef CONFIG_GENERIC_BUG
 
-#define __BUG_ENTRY(flags) 				\
+#define __BUG_ENTRY(flags, func)			\
 		.pushsection __bug_table,"aw";		\
 		.align 2;				\
 	14470:	.long 14471f - .;			\
-_BUGVERBOSE_LOCATION(__FILE__, __LINE__)		\
-		.short flags; 				\
+_BUGVERBOSE_LOCATION(__FILE__, func, __LINE__)		\
+		.short flags;				\
 		.popsection;				\
 	14471:
 #else
-#define __BUG_ENTRY(flags)
+#define __BUG_ENTRY(flags, func)
 #endif
 
-#define ASM_BUG_FLAGS(flags)				\
-	__BUG_ENTRY(flags)				\
+#define ASM_BUG_FLAGS(flags, func)			\
+	__BUG_ENTRY(flags, func)			\
 	brk	BUG_BRK_IMM
 
-#define ASM_BUG()	ASM_BUG_FLAGS(0)
+#define ASM_BUG()	ASM_BUG_FLAGS(0, .)
 
 #endif /* __ASM_ASM_BUG_H */
diff --git a/arch/arm64/include/asm/bug.h b/arch/arm64/include/asm/bug.h
index 28be048db3f6..044c5e24a17d 100644
--- a/arch/arm64/include/asm/bug.h
+++ b/arch/arm64/include/asm/bug.h
@@ -11,8 +11,14 @@
 
 #include <asm/asm-bug.h>
 
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define __BUG_FLAGS(flags)				\
-	asm volatile (__stringify(ASM_BUG_FLAGS(flags)));
+	asm volatile (__stringify(ASM_BUG_FLAGS(flags, %c0)) : : "i" (__BUG_FUNC));
 
 #define BUG() do {					\
 	__BUG_FLAGS(0);					\
-- 
2.39.2