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

Alessandro Carminati
2025-03-13T12:03:08Z

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