[PATCH v2 12/14] sh: Add support for suppressing warning backtraces

[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>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
- Introduced KUNIT_SUPPRESS_BACKTRACE configuration option

 arch/sh/include/asm/bug.h | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
index 05a485c4fabc..470ce6567d20 100644
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -24,21 +24,36 @@
  * The offending file and line are encoded in the __bug_table section.
  */
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	"\t.long %O2\n"
+#else
+# define __BUG_FUNC_PTR
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
 #define _EMIT_BUG_ENTRY				\
 	"\t.pushsection __bug_table,\"aw\"\n"	\
 	"2:\t.long 1b, %O1\n"			\
-	"\t.short %O2, %O3\n"			\
-	"\t.org 2b+%O4\n"			\
+	__BUG_FUNC_PTR				\
+	"\t.short %O3, %O4\n"			\
+	"\t.org 2b+%O5\n"			\
 	"\t.popsection\n"
 #else
 #define _EMIT_BUG_ENTRY				\
 	"\t.pushsection __bug_table,\"aw\"\n"	\
 	"2:\t.long 1b\n"			\
-	"\t.short %O3\n"			\
-	"\t.org 2b+%O4\n"			\
+	"\t.short %O4\n"			\
+	"\t.org 2b+%O5\n"			\
 	"\t.popsection\n"
 #endif
 
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define BUG()						\
 do {							\
 	__asm__ __volatile__ (				\
@@ -47,6 +62,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__), "i" (0),		\
 		   "i" (sizeof(struct bug_entry)));	\
 	unreachable();					\
@@ -60,6 +76,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__),			\
 		   "i" (BUGFLAG_WARNING|(flags)),	\
 		   "i" (sizeof(struct bug_entry)));	\
@@ -85,6 +102,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__),			\
 		   "i" (BUGFLAG_UNWINDER),		\
 		   "i" (sizeof(struct bug_entry)));	\
-- 
2.39.2