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 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 <li...@roeck-us.net>
---
 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 a3ec87d198ac..d87bf8bab238 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -23,18 +23,28 @@
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 
+#if IS_ENABLED(CONFIG_KUNIT)
+# 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 /* IS_ENABLED(CONFIG_KUNIT) */
+
 #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)
@@ -80,7 +90,8 @@ do {                                                          
\
 do {                                                           \
        __auto_type __flags = BUGFLAG_WARNING|(flags);          \
        instrumentation_begin();                                \
-       _BUG_FLAGS(ASM_UD2, __flags, ASM_REACHABLE);            \
+       if (!IS_SUPPRESSED_WARNING(__func__))                   \
+               _BUG_FLAGS(ASM_UD2, __flags, ASM_REACHABLE);    \
        instrumentation_end();                                  \
 } while (0)
 
-- 
2.39.2

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