[PATCH v4 06/14] x86: 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: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
---
 arch/x86/include/asm/bug.h | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index e85ac0c7c039..f6e13fc675ab 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -35,18 +35,28 @@
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	__BUG_REL(%c1)
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC_PTR
+# define __BUG_FUNC	NULL
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
 #define _BUG_FLAGS(ins, flags, extra)					\
 do {									\
 	asm_inline volatile("1:\t" ins "\n"				\
 		     ".pushsection __bug_table,\"aw\"\n"		\
 		     "2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n"	\
 		     "\t"  __BUG_REL(%c0) "\t# bug_entry::file\n"	\
-		     "\t.word %c1"        "\t# bug_entry::line\n"	\
-		     "\t.word %c2"        "\t# bug_entry::flags\n"	\
-		     "\t.org 2b+%c3\n"					\
+		     "\t"  __BUG_FUNC_PTR "\t# bug_entry::function\n"	\
+		     "\t.word %c2"        "\t# bug_entry::line\n"	\
+		     "\t.word %c3"        "\t# bug_entry::flags\n"	\
+		     "\t.org 2b+%c4\n"					\
 		     ".popsection\n"					\
 		     extra						\
-		     : : "i" (__FILE__), "i" (__LINE__),		\
+		     : : "i" (__FILE__), "i" (__BUG_FUNC), "i" (__LINE__),\
 			 "i" (flags),					\
 			 "i" (sizeof(struct bug_entry)));		\
 } while (0)
@@ -92,7 +102,8 @@ do {								\
 do {								\
 	__auto_type __flags = BUGFLAG_WARNING|(flags);		\
 	instrumentation_begin();				\
-	_BUG_FLAGS(ASM_UD2, __flags, ANNOTATE_REACHABLE(1b));	\
+	if (!KUNIT_IS_SUPPRESSED_WARNING(__func__))			\
+		_BUG_FLAGS(ASM_UD2, __flags, ANNOTATE_REACHABLE(1b));	\
 	instrumentation_end();					\
 } while (0)
 
-- 
2.34.1