[PATCH v4 10/14] s390: Add support for suppressing warning backtraces

Alessandro Carminati
2025-03-13T12:06:32Z

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: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
---
arch/s390/include/asm/bug.h | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
index c500d45fb465..44d4e9f24ae0 100644
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -8,6 +8,15 @@

#ifdef CONFIG_DEBUG_BUGVERBOSE

+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR " .long %0-.\n"
+# define __BUG_FUNC __func__
+#else
+# define __BUG_FUNC_PTR
+# define __BUG_FUNC NULL
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
#define __EMIT_BUG(x) do { \
asm_inline volatile( \
"0: mc 0,0\n" \
@@ -17,10 +26,12 @@
".section __bug_table,\"aw\"\n" \
"2: .long 0b-.\n" \
" .long 1b-.\n" \
- " .short %0,%1\n" \
- " .org 2b+%2\n" \
+ __BUG_FUNC_PTR \
+ " .short %1,%2\n" \
+ " .org 2b+%3\n" \
".previous\n" \
- : : "i" (__LINE__), \
+ : : "i" (__BUG_FUNC), \
+ "i" (__LINE__), \
"i" (x), \
"i" (sizeof(struct bug_entry))); \
} while (0)
--
2.34.1