[PATCH v4 13/14] riscv: 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).

To simplify the implementation, unify the __BUG_ENTRY_ADDR and
__BUG_ENTRY_FILE macros into a single macro named __BUG_REL() which takes
the address, file, or function reference as parameter.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
---
 arch/riscv/include/asm/bug.h | 38 ++++++++++++++++++++++++------------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
index 1aaea81fb141..79f360af4ad8 100644
--- a/arch/riscv/include/asm/bug.h
+++ b/arch/riscv/include/asm/bug.h
@@ -30,26 +30,39 @@
 typedef u32 bug_insn_t;
 
 #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
-#define __BUG_ENTRY_ADDR	RISCV_INT " 1b - ."
-#define __BUG_ENTRY_FILE	RISCV_INT " %0 - ."
+#define __BUG_REL(val)	RISCV_INT " " __stringify(val) " - ."
 #else
-#define __BUG_ENTRY_ADDR	RISCV_PTR " 1b"
-#define __BUG_ENTRY_FILE	RISCV_PTR " %0"
+#define __BUG_REL(val)	RISCV_PTR " " __stringify(val)
 #endif
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	__BUG_REL(%1)
+#else
+# define __BUG_FUNC_PTR
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
 #define __BUG_ENTRY			\
-	__BUG_ENTRY_ADDR "\n\t"		\
-	__BUG_ENTRY_FILE "\n\t"		\
-	RISCV_SHORT " %1\n\t"		\
-	RISCV_SHORT " %2"
+	__BUG_REL(1b) "\n\t"		\
+	__BUG_REL(%0) "\n\t"		\
+	__BUG_FUNC_PTR "\n\t"		\
+	RISCV_SHORT " %2\n\t"		\
+	RISCV_SHORT " %3"
 #else
 #define __BUG_ENTRY			\
-	__BUG_ENTRY_ADDR "\n\t"		\
-	RISCV_SHORT " %2"
+	__BUG_REL(1b) "\n\t"		\
+	RISCV_SHORT " %3"
 #endif
 
 #ifdef CONFIG_GENERIC_BUG
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define __BUG_FLAGS(flags)					\
 do {								\
 	__asm__ __volatile__ (					\
@@ -58,10 +71,11 @@ do {								\
 			".pushsection __bug_table,\"aw\"\n\t"	\
 		"2:\n\t"					\
 			__BUG_ENTRY "\n\t"			\
-			".org 2b + %3\n\t"                      \
+			".org 2b + %4\n\t"                      \
 			".popsection"				\
 		:						\
-		: "i" (__FILE__), "i" (__LINE__),		\
+		: "i" (__FILE__), "i" (__BUG_FUNC),		\
+		  "i" (__LINE__),				\
 		  "i" (flags),					\
 		  "i" (sizeof(struct bug_entry)));              \
 } while (0)
-- 
2.34.1