linux-kernel - [RFC PATCH 5/5] loongarch: Add support for suppressing warning tracebacks

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Message-Id: <20240305184033.425294-6-linux@roeck-us.net>
Date: Tue,  5 Mar 2024 10:40:33 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: linux-kselftest@...r.kernel.org
Cc: David Airlie <airlied@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Maíra Canal <mcanal@...lia.com>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Kees Cook <keescook@...omium.org>,
	Daniel Diaz <daniel.diaz@...aro.org>,
	David Gow <davidgow@...gle.com>,
	Arthur Grillo <arthurgrillo@...eup.net>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maxime Ripard <mripard@...nel.org>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	kunit-dev@...glegroups.com,
	linux-arch@...r.kernel.org,
	Guenter Roeck <linux@...ck-us.net>
Subject: [RFC PATCH 5/5] loongarch: Add support for suppressing warning tracebacks

Add support for selectively suppressing WARNING tracebacks to loongarch.
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@...ck-us.net>
---
 arch/loongarch/include/asm/bug.h | 38 +++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/arch/loongarch/include/asm/bug.h b/arch/loongarch/include/asm/bug.h
index d4ca3ba25418..25f2b5ae7702 100644
--- a/arch/loongarch/include/asm/bug.h
+++ b/arch/loongarch/include/asm/bug.h
@@ -3,47 +3,63 @@
 #define __ASM_BUG_H
 
 #include <asm/break.h>
+#include <kunit/bug.h>
 #include <linux/stringify.h>
 
 #ifndef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line)
 #else
-#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)			\
 		.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)					\
-	asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags)));
+	asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags, %0)) : : "i" (__BUG_FUNC));
 
 #define __WARN_FLAGS(flags)					\
 do {								\
 	instrumentation_begin();				\
-	__BUG_FLAGS(BUGFLAG_WARNING|(flags));			\
+	if (!IS_SUPPRESSED_WARNING(__func__))			\
+		__BUG_FLAGS(BUGFLAG_WARNING|(flags));		\
 	instrumentation_end();					\
 } while (0)
 
-- 
2.39.2