[PATCH v3 15/15] powerpc: Add support for suppressing warning backtraces

Guenter Roeck
2024-04-03T13:20:08Z

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: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2:
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
- Introduced KUNIT_SUPPRESS_BACKTRACE configuration option
v3:
- Rebased to v6.9-rc2

arch/powerpc/include/asm/bug.h | 37 +++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 1db485aacbd9..5b06745d20aa 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/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)); \
} \
--
2.39.2