[PATCH v4 08/14] loongarch: Add support for suppressing warning backtraces

[Alessandro Carminati <acarmina@redhat.com>]

From: Guenter Roeck <linux@roeck-us.net>

Add name of functions triggering warning backtraces to the __bug_table
object section to enable support for suppressing WARNING backtraces.

To limit image size impact, the pointer to the function name is only added
to the __bug_table section if both CONFIG_KUNIT_SUPPRESS_BACKTRACE 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).

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
---
 arch/loongarch/include/asm/bug.h | 42 ++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/arch/loongarch/include/asm/bug.h b/arch/loongarch/include/asm/bug.h
index f6f254f2c5db..b79ff6696ce6 100644
--- a/arch/loongarch/include/asm/bug.h
+++ b/arch/loongarch/include/asm/bug.h
@@ -3,49 +3,65 @@
 #define __ASM_BUG_H
 
 #include <asm/break.h>
+#include <kunit/bug.h>
 #include <linux/stringify.h>
 #include <linux/objtool.h>
 
 #ifndef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line)
 #else
-#define __BUGVERBOSE_LOCATION(file, line)			\
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR(func)  .long func - .;
+#else
+# define __BUG_FUNC_PTR(func)
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
+#define __BUGVERBOSE_LOCATION(file, func, line)			\
 		.pushsection .rodata.str, "aMS", @progbits, 1;	\
 	10002:	.string file;					\
 		.popsection;					\
 								\
 		.long 10002b - .;				\
+		__BUG_FUNC_PTR(func)				\
 		.short line;
-#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line) __BUGVERBOSE_LOCATION(file, func, line)
 #endif
 
 #ifndef CONFIG_GENERIC_BUG
-#define __BUG_ENTRY(flags)
+#define __BUG_ENTRY(flags, func)
 #else
-#define __BUG_ENTRY(flags) 					\
+#define __BUG_ENTRY(flags, func)				\
 		.pushsection __bug_table, "aw";			\
 		.align 2;					\
 	10000:	.long 10001f - .;				\
-		_BUGVERBOSE_LOCATION(__FILE__, __LINE__)	\
+		_BUGVERBOSE_LOCATION(__FILE__, func, __LINE__)	\
 		.short flags; 					\
 		.popsection;					\
 	10001:
 #endif
 
-#define ASM_BUG_FLAGS(flags)					\
-	__BUG_ENTRY(flags)					\
+#define ASM_BUG_FLAGS(flags, func)				\
+	__BUG_ENTRY(flags, func)				\
 	break		BRK_BUG;
 
-#define ASM_BUG()	ASM_BUG_FLAGS(0)
+#define ASM_BUG()	ASM_BUG_FLAGS(0, .)
+
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC    __func__
+#else
+# define __BUG_FUNC    NULL
+#endif
 
-#define __BUG_FLAGS(flags, extra)					\
-	asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags))		\
-			     extra);
+#define __BUG_FLAGS(flags, extra)				\
+	asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags, %0)) \
+			     extra : : "i" (__BUG_FUNC) );
 
 #define __WARN_FLAGS(flags)					\
 do {								\
 	instrumentation_begin();				\
-	__BUG_FLAGS(BUGFLAG_WARNING|(flags), ANNOTATE_REACHABLE(10001b));\
+	if (!KUNIT_IS_SUPPRESSED_WARNING(__func__))			\
+		__BUG_FLAGS(BUGFLAG_WARNING|(flags), ANNOTATE_REACHABLE(10001b));\
 	instrumentation_end();					\
 } while (0)
 
-- 
2.34.1