powerpc: add support for suppressing warning backtraces

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).

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Alessandro Carminati <[email protected]>
Tested-by: Linux Kernel Functional Testing <[email protected]>
Acked-by: Dan Carpenter <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: Brendan Higgins <[email protected]>
Cc: David Gow <[email protected]>
Cc: Rae Moar <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Arthur Grillo <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Charlie Jenkins <[email protected]>
Cc: Daniel Diaz <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: John Paul Adrian Glaubitz <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Maíra Canal <[email protected]>
Cc: Naresh Kamboju <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Simon Horman <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Thomas Zimemrmann <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Ville Syrjala <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: groeck

arch/powerpc/include/asm/bug.h

@@ -14,6 +14,9 @@
 	 .section __bug_table,"aw"
 5001:	 .4byte \addr - .
 	 .4byte 5002f - .
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+	 .4byte 0
+#endif
 	 .short \line, \flags
 	 .org 5001b+BUG_ENTRY_SIZE
 	 .previous
@@ -32,30 +35,46 @@
 #endif /* verbose */
 
 #else /* !__ASSEMBLY__ */
-/* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
-   sizeof(struct bug_entry), respectively */
+/* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3,%4 to be FILE, __func__, LINE, flags
+   and sizeof(struct bug_entry), respectively */
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	"	.4byte %1 - .\n"
+#else
+# define __BUG_FUNC_PTR
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
 #define _EMIT_BUG_ENTRY				\
 	".section __bug_table,\"aw\"\n"		\
 	"2:	.4byte 1b - .\n"		\
 	"	.4byte %0 - .\n"		\
-	"	.short %1, %2\n"		\
-	".org 2b+%3\n"				\
+	__BUG_FUNC_PTR				\
+	"	.short %2, %3\n"		\
+	".org 2b+%4\n"				\
 	".previous\n"
 #else
 #define _EMIT_BUG_ENTRY				\
 	".section __bug_table,\"aw\"\n"		\
 	"2:	.4byte 1b - .\n"		\
-	"	.short %2\n"			\
-	".org 2b+%3\n"				\
+	"	.short %3\n"			\
+	".org 2b+%4\n"				\
 	".previous\n"
 #endif
 
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define BUG_ENTRY(insn, flags, ...)			\
 	__asm__ __volatile__(				\
 		"1:	" insn "\n"			\
 		_EMIT_BUG_ENTRY				\
-		: : "i" (__FILE__), "i" (__LINE__),	\
+		: : "i" (__FILE__), "i" (__BUG_FUNC),	\
+		  "i" (__LINE__),			\
 		  "i" (flags),				\
 		  "i" (sizeof(struct bug_entry)),	\
 		  ##__VA_ARGS__)
@@ -80,7 +99,7 @@
 		if (x)						\
 			BUG();					\
 	} else {						\
-		BUG_ENTRY(PPC_TLNEI " %4, 0", 0, "r" ((__force long)(x)));	\
+		BUG_ENTRY(PPC_TLNEI " %5, 0", 0, "r" ((__force long)(x)));	\
 	}							\
 } while (0)
 
@@ -90,7 +109,7 @@
 		if (__ret_warn_on)				\
 			__WARN();				\
 	} else {						\
-		BUG_ENTRY(PPC_TLNEI " %4, 0",			\
+		BUG_ENTRY(PPC_TLNEI " %5, 0",			\
 			  BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN),	\
 			  "r" (__ret_warn_on));	\
 	}							\