[PATCH v3 00/15] Add support for suppressing warning backtraces

[PATCH v3 00/15] Add support for suppressing warning backtraces

[Guenter Roeck]

Some unit tests intentionally trigger warning backtraces by passing bad
parameters to kernel API functions. Such unit tests typically check the
return value from such calls, not the existence of the warning backtrace.

Such intentionally generated warning backtraces are neither desirable
nor useful for a number of reasons.
- They can result in overlooked real problems.
- A warning that suddenly starts to show up in unit tests needs to be
  investigated and has to be marked to be ignored, for example by
  adjusting filter scripts. Such filters are ad-hoc because there is
  no real standard format for warnings. On top of that, such filter
  scripts would require constant maintenance.

One option to address problem would be to add messages such as "expected
warning backtraces start / end here" to the kernel log.  However, that
would again require filter scripts, it might result in missing real
problematic warning backtraces triggered while the test is running, and
the irrelevant backtrace(s) would still clog the kernel log.

Solve the problem by providing a means to identify and suppress specific
warning backtraces while executing test code. Support suppressing multiple
backtraces while at the same time limiting changes to generic code to the
absolute minimum. Architecture specific changes are kept at minimum by
retaining function names only if both CONFIG_DEBUG_BUGVERBOSE and
CONFIG_KUNIT are enabled.

The first patch of the series introduces the necessary infrastructure.
The second patch introduces support for counting suppressed backtraces.
This capability is used in patch three to implement unit tests.
Patch four documents the new API.
The next two patches add support for suppressing backtraces in drm_rect
and dev_addr_lists unit tests. These patches are intended to serve as
examples for the use of the functionality introduced with this series.
The remaining patches implement the necessary changes for all
architectures with GENERIC_BUG support.

With CONFIG_KUNIT enabled, image size increase with this series applied is
approximately 1%. The image size increase (and with it the functionality
introduced by this series) can be avoided by disabling
CONFIG_KUNIT_SUPPRESS_BACKTRACE.

This series is based on the RFC patch and subsequent discussion at
https://patchwork.kernel.org/project/linux-kselftest/patch/02546e59-1afe-4b08-ba81-d94f3b691c9a@moroto.mountain/
and offers a more comprehensive solution of the problem discussed there.

Design note:
  Function pointers are only added to the __bug_table section if both
  CONFIG_KUNIT_SUPPRESS_BACKTRACE and CONFIG_DEBUG_BUGVERBOSE are enabled
  to avoid image size increases if CONFIG_KUNIT is disabled. There would be
  some benefits to adding those pointers all the time (reduced complexity,
  ability to display function names in BUG/WARNING messages). That change,
  if desired, can be made later.

Checkpatch note:
  Remaining checkpatch errors and warnings were deliberately ignored.
  Some are triggered by matching coding style or by comments interpreted
  as code, others by assembler macros which are disliked by checkpatch.
  Suggestions for improvements are welcome.

Changes since RFC:
- Introduced CONFIG_KUNIT_SUPPRESS_BACKTRACE
- Minor cleanups and bug fixes
- Added support for all affected architectures
- Added support for counting suppressed warnings
- Added unit tests using those counters
- Added patch to suppress warning backtraces in dev_addr_lists tests

Changes since v1:
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
  [I retained those tags since there have been no functional changes]
- Introduced KUNIT_SUPPRESS_BACKTRACE configuration option, enabled by
  default.

Changes since v2:
- Rebased to v6.9-rc2
- Added comments to drm warning suppression explaining why it is needed.
- Added patch to move conditional code in arch/sh/include/asm/bug.h
  to avoid kerneldoc warning
- Added architecture maintainers to Cc: for architecture specific patches
- No functional changes

----------------------------------------------------------------
Guenter Roeck (15):
      bug/kunit: Core support for suppressing warning backtraces
      kunit: bug: Count suppressed warning backtraces
      kunit: Add test cases for backtrace warning suppression
      kunit: Add documentation for warning backtrace suppression API
      drm: Suppress intentional warning backtraces in scaling unit tests
      net: kunit: Suppress lock warning noise at end of dev_addr_lists tests
      x86: Add support for suppressing warning backtraces
      arm64: Add support for suppressing warning backtraces
      loongarch: Add support for suppressing warning backtraces
      parisc: Add support for suppressing warning backtraces
      s390: Add support for suppressing warning backtraces
      sh: Add support for suppressing warning backtraces
      sh: Move defines needed for suppressing warning backtraces
      riscv: Add support for suppressing warning backtraces
      powerpc: Add support for suppressing warning backtraces

 Documentation/dev-tools/kunit/usage.rst |  30 ++++++++-
 arch/arm64/include/asm/asm-bug.h        |  29 ++++++---
 arch/arm64/include/asm/bug.h            |   8 ++-
 arch/loongarch/include/asm/bug.h        |  38 ++++++++----
 arch/parisc/include/asm/bug.h           |  29 ++++++---
 arch/powerpc/include/asm/bug.h          |  37 +++++++++---
 arch/riscv/include/asm/bug.h            |  38 ++++++++----
 arch/s390/include/asm/bug.h             |  17 +++++-
 arch/sh/include/asm/bug.h               |  28 +++++++--
 arch/x86/include/asm/bug.h              |  21 +++++--
 drivers/gpu/drm/tests/drm_rect_test.c   |  16 +++++
 include/asm-generic/bug.h               |  16 ++++-
 include/kunit/bug.h                     |  56 +++++++++++++++++
 include/kunit/test.h                    |   1 +
 include/linux/bug.h                     |  13 ++++
 lib/bug.c                               |  51 ++++++++++++++--
 lib/kunit/Kconfig                       |   9 +++
 lib/kunit/Makefile                      |   7 ++-
 lib/kunit/backtrace-suppression-test.c  | 104 ++++++++++++++++++++++++++++++++
 lib/kunit/bug.c                         |  42 +++++++++++++
 net/core/dev_addr_lists_test.c          |   6 ++
 21 files changed, 524 insertions(+), 72 deletions(-)
 create mode 100644 include/kunit/bug.h
 create mode 100644 lib/kunit/backtrace-suppression-test.c
 create mode 100644 lib/kunit/bug.c

[PATCH v3 01/15] bug/kunit: Core support for suppressing warning backtraces

[Guenter Roeck]

Some unit tests intentionally trigger warning backtraces by passing
bad parameters to API functions. Such unit tests typically check the
return value from those calls, not the existence of the warning backtrace.

Such intentionally generated warning backtraces are neither desirable
nor useful for a number of reasons.
- They can result in overlooked real problems.
- A warning that suddenly starts to show up in unit tests needs to be
  investigated and has to be marked to be ignored, for example by
  adjusting filter scripts. Such filters are ad-hoc because there is
  no real standard format for warnings. On top of that, such filter
  scripts would require constant maintenance.

One option to address problem would be to add messages such as "expected
warning backtraces start / end here" to the kernel log.  However, that
would again require filter scripts, it might result in missing real
problematic warning backtraces triggered while the test is running, and
the irrelevant backtrace(s) would still clog the kernel log.

Solve the problem by providing a means to identify and suppress specific
warning backtraces while executing test code. Since the new functionality
results in an image size increase of about 1% if CONFIG_KUNIT is enabled,
provide configuration option KUNIT_SUPPRESS_BACKTRACE to be able to disable
the new functionality. This option is by default enabled since almost all
systems with CONFIG_KUNIT enabled will want to benefit from it.

Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Daniel Diaz <daniel.diaz@linaro.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Kees Cook <keescook@chromium.org>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2:
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
- Added CONFIG_KUNIT_SUPPRESS_BACKTRACE configuration option,
  enabled by default
v3:
- Rebased to v6.9-rc2

 include/asm-generic/bug.h | 16 +++++++++---
 include/kunit/bug.h       | 51 +++++++++++++++++++++++++++++++++++++++
 include/kunit/test.h      |  1 +
 include/linux/bug.h       | 13 ++++++++++
 lib/bug.c                 | 51 ++++++++++++++++++++++++++++++++++++---
 lib/kunit/Kconfig         |  9 +++++++
 lib/kunit/Makefile        |  6 +++--
 lib/kunit/bug.c           | 40 ++++++++++++++++++++++++++++++
 8 files changed, 178 insertions(+), 9 deletions(-)
 create mode 100644 include/kunit/bug.h
 create mode 100644 lib/kunit/bug.c

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 6e794420bd39..c170b6477689 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -18,6 +18,7 @@
 #endif
 
 #ifndef __ASSEMBLY__
+#include <kunit/bug.h>
 #include <linux/panic.h>
 #include <linux/printk.h>
 
@@ -39,8 +40,14 @@ struct bug_entry {
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 	const char	*file;
+#ifdef HAVE_BUG_FUNCTION
+	const char      *function;
+#endif
 #else
 	signed int	file_disp;
+#ifdef HAVE_BUG_FUNCTION
+	signed int	function_disp;
+#endif
 #endif
 	unsigned short	line;
 #endif
@@ -96,15 +103,18 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
 #define __WARN()		__WARN_printf(TAINT_WARN, NULL)
 #define __WARN_printf(taint, arg...) do {				\
 		instrumentation_begin();				\
-		warn_slowpath_fmt(__FILE__, __LINE__, taint, arg);	\
+		if (!IS_SUPPRESSED_WARNING(__func__))			\
+			warn_slowpath_fmt(__FILE__, __LINE__, taint, arg);\
 		instrumentation_end();					\
 	} while (0)
 #else
 #define __WARN()		__WARN_FLAGS(BUGFLAG_TAINT(TAINT_WARN))
 #define __WARN_printf(taint, arg...) do {				\
 		instrumentation_begin();				\
-		__warn_printk(arg);					\
-		__WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
+		if (!IS_SUPPRESSED_WARNING(__func__)) {			\
+			__warn_printk(arg);				\
+			__WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
+		}							\
 		instrumentation_end();					\
 	} while (0)
 #define WARN_ON_ONCE(condition) ({				\
diff --git a/include/kunit/bug.h b/include/kunit/bug.h
new file mode 100644
index 000000000000..bd0fe047572b
--- /dev/null
+++ b/include/kunit/bug.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KUnit helpers for backtrace suppression
+ *
+ * Copyright (c) 2024 Guenter Roeck <linux@roeck-us.net>
+ */
+
+#ifndef _KUNIT_BUG_H
+#define _KUNIT_BUG_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/kconfig.h>
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+
+#include <linux/stringify.h>
+#include <linux/types.h>
+
+struct __suppressed_warning {
+	struct list_head node;
+	const char *function;
+};
+
+void __start_suppress_warning(struct __suppressed_warning *warning);
+void __end_suppress_warning(struct __suppressed_warning *warning);
+bool __is_suppressed_warning(const char *function);
+
+#define DEFINE_SUPPRESSED_WARNING(func)	\
+	struct __suppressed_warning __kunit_suppress_##func = \
+		{ .function = __stringify(func) }
+
+#define START_SUPPRESSED_WARNING(func) \
+	__start_suppress_warning(&__kunit_suppress_##func)
+
+#define END_SUPPRESSED_WARNING(func) \
+	__end_suppress_warning(&__kunit_suppress_##func)
+
+#define IS_SUPPRESSED_WARNING(func) \
+	__is_suppressed_warning(func)
+
+#else /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
+#define DEFINE_SUPPRESSED_WARNING(func)
+#define START_SUPPRESSED_WARNING(func)
+#define END_SUPPRESSED_WARNING(func)
+#define IS_SUPPRESSED_WARNING(func) (false)
+
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+#endif /* __ASSEMBLY__ */
+#endif /* _KUNIT_BUG_H */
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 61637ef32302..d0c44594d34c 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -10,6 +10,7 @@
 #define _KUNIT_TEST_H
 
 #include <kunit/assert.h>
+#include <kunit/bug.h>
 #include <kunit/try-catch.h>
 
 #include <linux/args.h>
diff --git a/include/linux/bug.h b/include/linux/bug.h
index 348acf2558f3..c668762dc76a 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -36,6 +36,9 @@ static inline int is_warning_bug(const struct bug_entry *bug)
 	return bug->flags & BUGFLAG_WARNING;
 }
 
+void bug_get_file_function_line(struct bug_entry *bug, const char **file,
+				const char **function, unsigned int *line);
+
 void bug_get_file_line(struct bug_entry *bug, const char **file,
 		       unsigned int *line);
 
@@ -62,6 +65,16 @@ static inline enum bug_trap_type report_bug(unsigned long bug_addr,
 }
 
 struct bug_entry;
+static inline void bug_get_file_function_line(struct bug_entry *bug,
+					      const char **file,
+					      const char **function,
+					      unsigned int *line)
+{
+	*file = NULL;
+	*function = NULL;
+	*line = 0;
+}
+
 static inline void bug_get_file_line(struct bug_entry *bug, const char **file,
 				     unsigned int *line)
 {
diff --git a/lib/bug.c b/lib/bug.c
index e0ff21989990..aa8bb12b9809 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -26,6 +26,14 @@
        when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
        the values accordingly.
 
+  2a.Optionally implement support for the "function" entry in struct
+     bug_entry. This entry must point to the name of the function triggering
+     the warning or bug trap (normally __func__). This is only needed if
+     both CONFIG_DEBUG_BUGVERBOSE and CONFIG_KUNIT_SUPPRESS_BACKTRACE are
+     enabled and if the architecture wants to implement support for suppressing
+     warning backtraces. The architecture must define HAVE_BUG_FUNCTION if it
+     adds pointers to function names to struct bug_entry.
+
   3. Implement the trap
      - In the illegal instruction trap handler (typically), verify
        that the fault was in kernel mode, and call report_bug()
@@ -127,14 +135,21 @@ static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
 }
 #endif
 
-void bug_get_file_line(struct bug_entry *bug, const char **file,
-		       unsigned int *line)
+void bug_get_file_function_line(struct bug_entry *bug, const char **file,
+				const char **function, unsigned int *line)
 {
+	*function = NULL;
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 	*file = (const char *)&bug->file_disp + bug->file_disp;
+#ifdef HAVE_BUG_FUNCTION
+	*function = (const char *)&bug->function_disp + bug->function_disp;
+#endif
 #else
 	*file = bug->file;
+#ifdef HAVE_BUG_FUNCTION
+	*function = bug->function;
+#endif
 #endif
 	*line = bug->line;
 #else
@@ -143,6 +158,13 @@ void bug_get_file_line(struct bug_entry *bug, const char **file,
 #endif
 }
 
+void bug_get_file_line(struct bug_entry *bug, const char **file, unsigned int *line)
+{
+	const char *function;
+
+	bug_get_file_function_line(bug, file, &function, line);
+}
+
 struct bug_entry *find_bug(unsigned long bugaddr)
 {
 	struct bug_entry *bug;
@@ -157,8 +179,9 @@ struct bug_entry *find_bug(unsigned long bugaddr)
 static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs *regs)
 {
 	struct bug_entry *bug;
-	const char *file;
+	const char *file, *function;
 	unsigned line, warning, once, done;
+	char __maybe_unused sym[KSYM_SYMBOL_LEN];
 
 	if (!is_valid_bugaddr(bugaddr))
 		return BUG_TRAP_TYPE_NONE;
@@ -169,12 +192,32 @@ static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs *re
 
 	disable_trace_on_warning();
 
-	bug_get_file_line(bug, &file, &line);
+	bug_get_file_function_line(bug, &file, &function, &line);
+#if defined(CONFIG_KUNIT_SUPPRESS_BACKTRACE) && defined(CONFIG_KALLSYMS)
+	if (!function) {
+		/*
+		 * This will be seen if report_bug is called on an architecture
+		 * with no architecture-specific support for suppressing warning
+		 * backtraces, if CONFIG_DEBUG_BUGVERBOSE is not enabled, or if
+		 * the calling code is from assembler which does not record a
+		 * function name. Extracting the function name from the bug
+		 * address is less than perfect since compiler optimization may
+		 * result in 'bugaddr' pointing to a function which does not
+		 * actually trigger the warning, but it is better than no
+		 * suppression at all.
+		 */
+		sprint_symbol_no_offset(sym, bugaddr);
+		function = sym;
+	}
+#endif /* defined(CONFIG_KUNIT_SUPPRESS_BACKTRACE) && defined(CONFIG_KALLSYMS) */
 
 	warning = (bug->flags & BUGFLAG_WARNING) != 0;
 	once = (bug->flags & BUGFLAG_ONCE) != 0;
 	done = (bug->flags & BUGFLAG_DONE) != 0;
 
+	if (warning && IS_SUPPRESSED_WARNING(function))
+		return BUG_TRAP_TYPE_WARN;
+
 	if (warning && once) {
 		if (done)
 			return BUG_TRAP_TYPE_WARN;
diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig
index 68a6daec0aef..b1b899265acc 100644
--- a/lib/kunit/Kconfig
+++ b/lib/kunit/Kconfig
@@ -15,6 +15,15 @@ menuconfig KUNIT
 
 if KUNIT
 
+config KUNIT_SUPPRESS_BACKTRACE
+	bool "KUnit - Enable backtrace suppression"
+	default y
+	help
+	  Enable backtrace suppression for KUnit. If enabled, backtraces
+	  generated intentionally by KUnit tests are suppressed. Disable
+	  to reduce kernel image size if image size is more important than
+	  suppression of backtraces generated by KUnit tests.
+
 config KUNIT_DEBUGFS
 	bool "KUnit - Enable /sys/kernel/debug/kunit debugfs representation" if !KUNIT_ALL_TESTS
 	default KUNIT_ALL_TESTS
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 309659a32a78..545b57c3be48 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -14,8 +14,10 @@ ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
 kunit-objs +=				debugfs.o
 endif
 
-# KUnit 'hooks' are built-in even when KUnit is built as a module.
-obj-y +=				hooks.o
+# KUnit 'hooks' and bug handling are built-in even when KUnit is built
+# as a module.
+obj-y +=				hooks.o \
+					bug.o
 
 obj-$(CONFIG_KUNIT_TEST) +=		kunit-test.o
 
diff --git a/lib/kunit/bug.c b/lib/kunit/bug.c
new file mode 100644
index 000000000000..f93544d7a9d1
--- /dev/null
+++ b/lib/kunit/bug.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit helpers for backtrace suppression
+ *
+ * Copyright (c) 2024 Guenter Roeck <linux@roeck-us.net>
+ */
+
+#include <kunit/bug.h>
+#include <linux/export.h>
+#include <linux/list.h>
+#include <linux/string.h>
+
+static LIST_HEAD(suppressed_warnings);
+
+void __start_suppress_warning(struct __suppressed_warning *warning)
+{
+	list_add(&warning->node, &suppressed_warnings);
+}
+EXPORT_SYMBOL_GPL(__start_suppress_warning);
+
+void __end_suppress_warning(struct __suppressed_warning *warning)
+{
+	list_del(&warning->node);
+}
+EXPORT_SYMBOL_GPL(__end_suppress_warning);
+
+bool __is_suppressed_warning(const char *function)
+{
+	struct __suppressed_warning *warning;
+
+	if (!function)
+		return false;
+
+	list_for_each_entry(warning, &suppressed_warnings, node) {
+		if (!strcmp(function, warning->function))
+			return true;
+	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(__is_suppressed_warning);
-- 
2.39.2

[PATCH v3 02/15] kunit: bug: Count suppressed warning backtraces

[Guenter Roeck]

Count suppressed warning backtraces to enable code which suppresses
warning backtraces to check if the expected backtrace(s) have been
observed.

Using atomics for the backtrace count resulted in build errors on some
architectures due to include file recursion, so use a plain integer
for now.

Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
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

 include/kunit/bug.h | 7 ++++++-
 lib/kunit/bug.c     | 4 +++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/kunit/bug.h b/include/kunit/bug.h
index bd0fe047572b..72e9fb23bbd5 100644
--- a/include/kunit/bug.h
+++ b/include/kunit/bug.h
@@ -20,6 +20,7 @@
 struct __suppressed_warning {
 	struct list_head node;
 	const char *function;
+	int counter;
 };
 
 void __start_suppress_warning(struct __suppressed_warning *warning);
@@ -28,7 +29,7 @@ bool __is_suppressed_warning(const char *function);
 
 #define DEFINE_SUPPRESSED_WARNING(func)	\
 	struct __suppressed_warning __kunit_suppress_##func = \
-		{ .function = __stringify(func) }
+		{ .function = __stringify(func), .counter = 0 }
 
 #define START_SUPPRESSED_WARNING(func) \
 	__start_suppress_warning(&__kunit_suppress_##func)
@@ -39,12 +40,16 @@ bool __is_suppressed_warning(const char *function);
 #define IS_SUPPRESSED_WARNING(func) \
 	__is_suppressed_warning(func)
 
+#define SUPPRESSED_WARNING_COUNT(func) \
+	(__kunit_suppress_##func.counter)
+
 #else /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
 
 #define DEFINE_SUPPRESSED_WARNING(func)
 #define START_SUPPRESSED_WARNING(func)
 #define END_SUPPRESSED_WARNING(func)
 #define IS_SUPPRESSED_WARNING(func) (false)
+#define SUPPRESSED_WARNING_COUNT(func) (0)
 
 #endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
 #endif /* __ASSEMBLY__ */
diff --git a/lib/kunit/bug.c b/lib/kunit/bug.c
index f93544d7a9d1..13b3d896c114 100644
--- a/lib/kunit/bug.c
+++ b/lib/kunit/bug.c
@@ -32,8 +32,10 @@ bool __is_suppressed_warning(const char *function)
 		return false;
 
 	list_for_each_entry(warning, &suppressed_warnings, node) {
-		if (!strcmp(function, warning->function))
+		if (!strcmp(function, warning->function)) {
+			warning->counter++;
 			return true;
+		}
 	}
 	return false;
 }
-- 
2.39.2

[PATCH v3 03/15] kunit: Add test cases for backtrace warning suppression

[Guenter Roeck]

Add unit tests to verify that warning backtrace suppression works.

If backtrace suppression does _not_ work, the unit tests will likely
trigger unsuppressed backtraces, which should actually help to get
the affected architectures / platforms fixed.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
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

 lib/kunit/Makefile                     |   7 +-
 lib/kunit/backtrace-suppression-test.c | 104 +++++++++++++++++++++++++
 2 files changed, 109 insertions(+), 2 deletions(-)
 create mode 100644 lib/kunit/backtrace-suppression-test.c

diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 545b57c3be48..3eee1bd0ce5e 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -16,10 +16,13 @@ endif
 
 # KUnit 'hooks' and bug handling are built-in even when KUnit is built
 # as a module.
-obj-y +=				hooks.o \
-					bug.o
+obj-y +=				hooks.o
+obj-$(CONFIG_KUNIT_SUPPRESS_BACKTRACE) += bug.o
 
 obj-$(CONFIG_KUNIT_TEST) +=		kunit-test.o
+ifeq ($(CCONFIG_KUNIT_SUPPRESS_BACKTRACE),y)
+obj-$(CONFIG_KUNIT_TEST) +=		backtrace-suppression-test.o
+endif
 
 # string-stream-test compiles built-in only.
 ifeq ($(CONFIG_KUNIT_TEST),y)
diff --git a/lib/kunit/backtrace-suppression-test.c b/lib/kunit/backtrace-suppression-test.c
new file mode 100644
index 000000000000..47c619283802
--- /dev/null
+++ b/lib/kunit/backtrace-suppression-test.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for suppressing warning tracebacks
+ *
+ * Copyright (C) 2024, Guenter Roeck
+ * Author: Guenter Roeck <linux@roeck-us.net>
+ */
+
+#include <kunit/test.h>
+#include <linux/bug.h>
+
+static void backtrace_suppression_test_warn_direct(struct kunit *test)
+{
+	DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+
+	START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+	WARN(1, "This backtrace should be suppressed");
+	END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+
+	KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_direct), 1);
+}
+
+static void trigger_backtrace_warn(void)
+{
+	WARN(1, "This backtrace should be suppressed");
+}
+
+static void backtrace_suppression_test_warn_indirect(struct kunit *test)
+{
+	DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
+
+	START_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	trigger_backtrace_warn();
+	END_SUPPRESSED_WARNING(trigger_backtrace_warn);
+
+	KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 1);
+}
+
+static void backtrace_suppression_test_warn_multi(struct kunit *test)
+{
+	DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+
+	START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+	START_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	WARN(1, "This backtrace should be suppressed");
+	trigger_backtrace_warn();
+	END_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+
+	KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_multi), 1);
+	KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 1);
+}
+
+static void backtrace_suppression_test_warn_on_direct(struct kunit *test)
+{
+	DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+
+	if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE) && !IS_ENABLED(CONFIG_KALLSYMS))
+		kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE or CONFIG_KALLSYMS");
+
+	START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+	WARN_ON(1);
+	END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+
+	KUNIT_EXPECT_EQ(test,
+			SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_on_direct), 1);
+}
+
+static void trigger_backtrace_warn_on(void)
+{
+	WARN_ON(1);
+}
+
+static void backtrace_suppression_test_warn_on_indirect(struct kunit *test)
+{
+	DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+
+	if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE))
+		kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE");
+
+	START_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+	trigger_backtrace_warn_on();
+	END_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+
+	KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn_on), 1);
+}
+
+static struct kunit_case backtrace_suppression_test_cases[] = {
+	KUNIT_CASE(backtrace_suppression_test_warn_direct),
+	KUNIT_CASE(backtrace_suppression_test_warn_indirect),
+	KUNIT_CASE(backtrace_suppression_test_warn_multi),
+	KUNIT_CASE(backtrace_suppression_test_warn_on_direct),
+	KUNIT_CASE(backtrace_suppression_test_warn_on_indirect),
+	{}
+};
+
+static struct kunit_suite backtrace_suppression_test_suite = {
+	.name = "backtrace-suppression-test",
+	.test_cases = backtrace_suppression_test_cases,
+};
+kunit_test_suites(&backtrace_suppression_test_suite);
+
+MODULE_LICENSE("GPL");
-- 
2.39.2

[PATCH v3 04/15] kunit: Add documentation for warning backtrace suppression API

[Guenter Roeck]

Document API functions for suppressing warning backtraces.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2:
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
v3:
- Rebased to v6.9-rc2

 Documentation/dev-tools/kunit/usage.rst | 30 ++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 22955d56b379..8d3d36d4103d 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -157,6 +157,34 @@ Alternatively, one can take full control over the error message by using
 	if (some_setup_function())
 		KUNIT_FAIL(test, "Failed to setup thing for testing");
 
+Suppressing warning backtraces
+------------------------------
+
+Some unit tests trigger warning backtraces either intentionally or as side
+effect. Such backtraces are normally undesirable since they distract from
+the actual test and may result in the impression that there is a problem.
+
+Such backtraces can be suppressed. To suppress a backtrace in some_function(),
+use the following code.
+
+.. code-block:: c
+
+	static void some_test(struct kunit *test)
+	{
+		DEFINE_SUPPRESSED_WARNING(some_function);
+
+		START_SUPPRESSED_WARNING(some_function);
+		trigger_backtrace();
+		END_SUPPRESSED_WARNING(some_function);
+	}
+
+SUPPRESSED_WARNING_COUNT() returns the number of suppressed backtraces. If the
+suppressed backtrace was triggered on purpose, this can be used to check if
+the backtrace was actually triggered.
+
+.. code-block:: c
+
+	KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(some_function), 1);
 
 Test Suites
 ~~~~~~~~~~~
@@ -857,4 +885,4 @@ For example:
 		dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");
 
 		// Everything is cleaned up automatically when the test ends.
-	}
\ No newline at end of file
+	}
-- 
2.39.2

[PATCH v3 05/15] drm: Suppress intentional warning backtraces in scaling unit tests

[Guenter Roeck]

The drm_test_rect_calc_hscale and drm_test_rect_calc_vscale unit tests
intentionally trigger warning backtraces by providing bad parameters to
the tested functions. What is tested is the return value, not the existence
of a warning backtrace. Suppress the backtraces to avoid clogging the
kernel log and distraction from real problems.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Acked-by: Maíra Canal <mcanal@igalia.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2:
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
v3:
- Rebased to v6.9-rc2

 drivers/gpu/drm/tests/drm_rect_test.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/tests/drm_rect_test.c b/drivers/gpu/drm/tests/drm_rect_test.c
index 76332cd2ead8..66851769ee32 100644
--- a/drivers/gpu/drm/tests/drm_rect_test.c
+++ b/drivers/gpu/drm/tests/drm_rect_test.c
@@ -406,22 +406,38 @@ KUNIT_ARRAY_PARAM(drm_rect_scale, drm_rect_scale_cases, drm_rect_scale_case_desc
 
 static void drm_test_rect_calc_hscale(struct kunit *test)
 {
+	DEFINE_SUPPRESSED_WARNING(drm_calc_scale);
 	const struct drm_rect_scale_case *params = test->param_value;
 	int scaling_factor;
 
+	/*
+	 * drm_rect_calc_hscale() generates a warning backtrace whenever bad
+	 * parameters are passed to it. This affects all unit tests with an
+	 * error code in expected_scaling_factor.
+	 */
+	START_SUPPRESSED_WARNING(drm_calc_scale);
 	scaling_factor = drm_rect_calc_hscale(&params->src, &params->dst,
 					      params->min_range, params->max_range);
+	END_SUPPRESSED_WARNING(drm_calc_scale);
 
 	KUNIT_EXPECT_EQ(test, scaling_factor, params->expected_scaling_factor);
 }
 
 static void drm_test_rect_calc_vscale(struct kunit *test)
 {
+	DEFINE_SUPPRESSED_WARNING(drm_calc_scale);
 	const struct drm_rect_scale_case *params = test->param_value;
 	int scaling_factor;
 
+	/*
+	 * drm_rect_calc_vscale() generates a warning backtrace whenever bad
+	 * parameters are passed to it. This affects all unit tests with an
+	 * error code in expected_scaling_factor.
+	 */
+	START_SUPPRESSED_WARNING(drm_calc_scale);
 	scaling_factor = drm_rect_calc_vscale(&params->src, &params->dst,
 					      params->min_range, params->max_range);
+	END_SUPPRESSED_WARNING(drm_calc_scale);
 
 	KUNIT_EXPECT_EQ(test, scaling_factor, params->expected_scaling_factor);
 }
-- 
2.39.2

[PATCH v3 06/15] net: kunit: Suppress lock warning noise at end of dev_addr_lists tests

[Guenter Roeck]

dev_addr_lists_test generates lock warning noise at the end of tests
if lock debugging is enabled. There are two sets of warnings.

WARNING: CPU: 0 PID: 689 at kernel/locking/mutex.c:923 __mutex_unlock_slowpath.constprop.0+0x13c/0x368
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != __get_current())

WARNING: kunit_try_catch/1336 still has locks held!

KUnit test cleanup is not guaranteed to run in the same thread as the test
itself. For this test, this means that rtnl_lock() and rtnl_unlock() may
be called from different threads. This triggers the warnings.
Suppress the warnings because they are irrelevant for the test and just
confusing and distracting.

The first warning can be suppressed by using START_SUPPRESSED_WARNING()
and END_SUPPRESSED_WARNING() around the call to rtnl_unlock(). To suppress
the second warning, it is necessary to set debug_locks_silent while the
rtnl lock is held.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Cc: David Gow <davidgow@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2:
- Rebased to v6.9-rc1
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
v3:
- Rebased to v6.9-rc2

 net/core/dev_addr_lists_test.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/core/dev_addr_lists_test.c b/net/core/dev_addr_lists_test.c
index 4dbd0dc6aea2..b427dd1a3c93 100644
--- a/net/core/dev_addr_lists_test.c
+++ b/net/core/dev_addr_lists_test.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <kunit/test.h>
+#include <linux/debug_locks.h>
 #include <linux/etherdevice.h>
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
@@ -49,6 +50,7 @@ static int dev_addr_test_init(struct kunit *test)
 		KUNIT_FAIL(test, "Can't register netdev %d", err);
 	}
 
+	debug_locks_silent = 1;
 	rtnl_lock();
 	return 0;
 }
@@ -56,8 +58,12 @@ static int dev_addr_test_init(struct kunit *test)
 static void dev_addr_test_exit(struct kunit *test)
 {
 	struct net_device *netdev = test->priv;
+	DEFINE_SUPPRESSED_WARNING(__mutex_unlock_slowpath);
 
+	START_SUPPRESSED_WARNING(__mutex_unlock_slowpath);
 	rtnl_unlock();
+	END_SUPPRESSED_WARNING(__mutex_unlock_slowpath);
+	debug_locks_silent = 0;
 	unregister_netdev(netdev);
 	free_netdev(netdev);
 }
-- 
2.39.2

[PATCH v3 07/15] x86: Add support for suppressing warning backtraces

[Guenter Roeck]

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>
---
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/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..7698dfa74c98 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -23,18 +23,28 @@
 
 #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)
@@ -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

[PATCH v3 08/15] arm64: Add support for suppressing warning backtraces

[Guenter Roeck]

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: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
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/arm64/include/asm/asm-bug.h | 29 +++++++++++++++++++----------
 arch/arm64/include/asm/bug.h     |  8 +++++++-
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/asm-bug.h b/arch/arm64/include/asm/asm-bug.h
index c762038ba400..c6d22e3cd840 100644
--- a/arch/arm64/include/asm/asm-bug.h
+++ b/arch/arm64/include/asm/asm-bug.h
@@ -8,36 +8,45 @@
 #include <asm/brk-imm.h>
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
-#define __BUGVERBOSE_LOCATION(file, line)			\
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR(func)	.long func - .;
+#else
+# define __BUG_FUNC_PTR(func)
+#endif
+
+#define _BUGVERBOSE_LOCATION(file, func, line) __BUGVERBOSE_LOCATION(file, func, line)
+#define __BUGVERBOSE_LOCATION(file, func, line)		\
 		.pushsection .rodata.str,"aMS",@progbits,1;	\
 	14472:	.string file;					\
 		.popsection;					\
 								\
 		.long 14472b - .;				\
+		__BUG_FUNC_PTR(func)				\
 		.short line;
 #else
-#define _BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line)
 #endif
 
 #ifdef CONFIG_GENERIC_BUG
 
-#define __BUG_ENTRY(flags) 				\
+#define __BUG_ENTRY(flags, func)			\
 		.pushsection __bug_table,"aw";		\
 		.align 2;				\
 	14470:	.long 14471f - .;			\
-_BUGVERBOSE_LOCATION(__FILE__, __LINE__)		\
-		.short flags; 				\
+_BUGVERBOSE_LOCATION(__FILE__, func, __LINE__)		\
+		.short flags;				\
 		.popsection;				\
 	14471:
 #else
-#define __BUG_ENTRY(flags)
+#define __BUG_ENTRY(flags, func)
 #endif
 
-#define ASM_BUG_FLAGS(flags)				\
-	__BUG_ENTRY(flags)				\
+#define ASM_BUG_FLAGS(flags, func)			\
+	__BUG_ENTRY(flags, func)			\
 	brk	BUG_BRK_IMM
 
-#define ASM_BUG()	ASM_BUG_FLAGS(0)
+#define ASM_BUG()	ASM_BUG_FLAGS(0, .)
 
 #endif /* __ASM_ASM_BUG_H */
diff --git a/arch/arm64/include/asm/bug.h b/arch/arm64/include/asm/bug.h
index 28be048db3f6..044c5e24a17d 100644
--- a/arch/arm64/include/asm/bug.h
+++ b/arch/arm64/include/asm/bug.h
@@ -11,8 +11,14 @@
 
 #include <asm/asm-bug.h>
 
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define __BUG_FLAGS(flags)				\
-	asm volatile (__stringify(ASM_BUG_FLAGS(flags)));
+	asm volatile (__stringify(ASM_BUG_FLAGS(flags, %c0)) : : "i" (__BUG_FUNC));
 
 #define BUG() do {					\
 	__BUG_FLAGS(0);					\
-- 
2.39.2

[PATCH v3 09/15] loongarch: Add support for suppressing warning backtraces

[Guenter Roeck]

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: Huacai Chen <chenhuacai@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2:
- Rebased to v6.9-rc1; resolved context conflict
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
- Introduced KUNIT_SUPPRESS_BACKTRACE configuration option
v3:
- Rebased to v6.9-rc2; resolved context conflict

 arch/loongarch/include/asm/bug.h | 38 +++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/arch/loongarch/include/asm/bug.h b/arch/loongarch/include/asm/bug.h
index 08388876ade4..193f396d81a0 100644
--- a/arch/loongarch/include/asm/bug.h
+++ b/arch/loongarch/include/asm/bug.h
@@ -3,47 +3,63 @@
 #define __ASM_BUG_H
 
 #include <asm/break.h>
+#include <kunit/bug.h>
 #include <linux/stringify.h>
 
 #ifndef CONFIG_DEBUG_BUGVERBOSE
-#define _BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line)
 #else
-#define __BUGVERBOSE_LOCATION(file, line)			\
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR(func)  .long func - .;
+#else
+# define __BUG_FUNC_PTR(func)
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
+#define __BUGVERBOSE_LOCATION(file, func, line)			\
 		.pushsection .rodata.str, "aMS", @progbits, 1;	\
 	10002:	.string file;					\
 		.popsection;					\
 								\
 		.long 10002b - .;				\
+		__BUG_FUNC_PTR(func)				\
 		.short line;
-#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
+#define _BUGVERBOSE_LOCATION(file, func, line) __BUGVERBOSE_LOCATION(file, func, line)
 #endif
 
 #ifndef CONFIG_GENERIC_BUG
-#define __BUG_ENTRY(flags)
+#define __BUG_ENTRY(flags, func)
 #else
-#define __BUG_ENTRY(flags) 					\
+#define __BUG_ENTRY(flags, func)				\
 		.pushsection __bug_table, "aw";			\
 		.align 2;					\
 	10000:	.long 10001f - .;				\
-		_BUGVERBOSE_LOCATION(__FILE__, __LINE__)	\
+		_BUGVERBOSE_LOCATION(__FILE__, func, __LINE__)	\
 		.short flags; 					\
 		.popsection;					\
 	10001:
 #endif
 
-#define ASM_BUG_FLAGS(flags)					\
-	__BUG_ENTRY(flags)					\
+#define ASM_BUG_FLAGS(flags, func)				\
+	__BUG_ENTRY(flags, func)				\
 	break		BRK_BUG
 
-#define ASM_BUG()	ASM_BUG_FLAGS(0)
+#define ASM_BUG()	ASM_BUG_FLAGS(0, .)
+
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC    __func__
+#else
+# define __BUG_FUNC    NULL
+#endif
 
 #define __BUG_FLAGS(flags)					\
-	asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags)));
+	asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags, %0)) : : "i" (__BUG_FUNC));
 
 #define __WARN_FLAGS(flags)					\
 do {								\
 	instrumentation_begin();				\
-	__BUG_FLAGS(BUGFLAG_WARNING|(flags));			\
+	if (!IS_SUPPRESSED_WARNING(__func__))			\
+		__BUG_FLAGS(BUGFLAG_WARNING|(flags));		\
 	annotate_reachable();					\
 	instrumentation_end();					\
 } while (0)
-- 
2.39.2

[PATCH v3 10/15] parisc: Add support for suppressing warning backtraces

[Guenter Roeck]

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).

While at it, declare assembler parameters as constants where possible.
Refine .blockz instructions to calculate the necessary padding instead
of using fixed values.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Acked-by: Helge Deller <deller@gmx.de>
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/parisc/include/asm/bug.h | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/arch/parisc/include/asm/bug.h b/arch/parisc/include/asm/bug.h
index 833555f74ffa..b59c3f7380bf 100644
--- a/arch/parisc/include/asm/bug.h
+++ b/arch/parisc/include/asm/bug.h
@@ -23,8 +23,17 @@
 # define __BUG_REL(val) ".word " __stringify(val)
 #endif
 
-
 #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()								\
 	do {								\
 		asm volatile("\n"					\
@@ -33,10 +42,12 @@
 			     "\t.align 4\n"				\
 			     "2:\t" __BUG_REL(1b) "\n"			\
 			     "\t" __BUG_REL(%c0)  "\n"			\
-			     "\t.short %1, %2\n"			\
-			     "\t.blockz %3-2*4-2*2\n"			\
+			     "\t" __BUG_FUNC_PTR  "\n"			\
+			     "\t.short %c2, %c3\n"			\
+			     "\t.blockz %c4-(.-2b)\n"			\
 			     "\t.popsection"				\
-			     : : "i" (__FILE__), "i" (__LINE__),	\
+			     : : "i" (__FILE__), "i" (__BUG_FUNC),	\
+			     "i" (__LINE__),				\
 			     "i" (0), "i" (sizeof(struct bug_entry)) );	\
 		unreachable();						\
 	} while(0)
@@ -58,10 +69,12 @@
 			     "\t.align 4\n"				\
 			     "2:\t" __BUG_REL(1b) "\n"			\
 			     "\t" __BUG_REL(%c0)  "\n"			\
-			     "\t.short %1, %2\n"			\
-			     "\t.blockz %3-2*4-2*2\n"			\
+			     "\t" __BUG_FUNC_PTR  "\n"			\
+			     "\t.short %c2, %3\n"			\
+			     "\t.blockz %c4-(.-2b)\n"			\
 			     "\t.popsection"				\
-			     : : "i" (__FILE__), "i" (__LINE__),	\
+			     : : "i" (__FILE__), "i" (__BUG_FUNC),	\
+			     "i" (__LINE__),				\
 			     "i" (BUGFLAG_WARNING|(flags)),		\
 			     "i" (sizeof(struct bug_entry)) );		\
 	} while(0)
@@ -74,7 +87,7 @@
 			     "\t.align 4\n"				\
 			     "2:\t" __BUG_REL(1b) "\n"			\
 			     "\t.short %0\n"				\
-			     "\t.blockz %1-4-2\n"			\
+			     "\t.blockz %c1-(.-2b)\n"			\
 			     "\t.popsection"				\
 			     : : "i" (BUGFLAG_WARNING|(flags)),		\
 			     "i" (sizeof(struct bug_entry)) );		\
-- 
2.39.2

[PATCH v3 11/15] s390: Add support for suppressing warning backtraces

[Guenter Roeck]

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>
---
v2:
- Rebased to v6.9-rc1 (simplified assembler changes after upstream commit
  3938490e78f4 ("s390/bug: remove entry size from __bug_table section")
- Added Tested-by:, Acked-by:, and Reviewed-by: tags
- Introduced KUNIT_SUPPRESS_BACKTRACE configuration option
v3:
- Rebased to v6.9-rc2

 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)
-- 
2.39.2

[PATCH v3 12/15] sh: Add support for suppressing warning backtraces

[Guenter Roeck]

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: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
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/sh/include/asm/bug.h | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
index 05a485c4fabc..470ce6567d20 100644
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -24,21 +24,36 @@
  * The offending file and line are encoded in the __bug_table section.
  */
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	"\t.long %O2\n"
+#else
+# define __BUG_FUNC_PTR
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
 #define _EMIT_BUG_ENTRY				\
 	"\t.pushsection __bug_table,\"aw\"\n"	\
 	"2:\t.long 1b, %O1\n"			\
-	"\t.short %O2, %O3\n"			\
-	"\t.org 2b+%O4\n"			\
+	__BUG_FUNC_PTR				\
+	"\t.short %O3, %O4\n"			\
+	"\t.org 2b+%O5\n"			\
 	"\t.popsection\n"
 #else
 #define _EMIT_BUG_ENTRY				\
 	"\t.pushsection __bug_table,\"aw\"\n"	\
 	"2:\t.long 1b\n"			\
-	"\t.short %O3\n"			\
-	"\t.org 2b+%O4\n"			\
+	"\t.short %O4\n"			\
+	"\t.org 2b+%O5\n"			\
 	"\t.popsection\n"
 #endif
 
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define BUG()						\
 do {							\
 	__asm__ __volatile__ (				\
@@ -47,6 +62,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__), "i" (0),		\
 		   "i" (sizeof(struct bug_entry)));	\
 	unreachable();					\
@@ -60,6 +76,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__),			\
 		   "i" (BUGFLAG_WARNING|(flags)),	\
 		   "i" (sizeof(struct bug_entry)));	\
@@ -85,6 +102,7 @@ do {							\
 		 :					\
 		 : "n" (TRAPA_BUG_OPCODE),		\
 		   "i" (__FILE__),			\
+		   "i" (__BUG_FUNC),			\
 		   "i" (__LINE__),			\
 		   "i" (BUGFLAG_UNWINDER),		\
 		   "i" (sizeof(struct bug_entry)));	\
-- 
2.39.2

[PATCH v3 13/15] sh: Move defines needed for suppressing warning backtraces

[Guenter Roeck]

Declaring the defines needed for suppressing warning inside
'#ifdef CONFIG_DEBUG_BUGVERBOSE' results in a kerneldoc warning.

.../bug.h:29: warning: expecting prototype for _EMIT_BUG_ENTRY().
	Prototype was for HAVE_BUG_FUNCTION() instead

Move the defines above the kerneldoc entry for _EMIT_BUG_ENTRY
to make kerneldoc happy.

Reported-by: Simon Horman <horms@kernel.org>
Cc: Simon Horman <horms@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v3: Added patch. Possibly squash into previous patch.

 arch/sh/include/asm/bug.h | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
index 470ce6567d20..bf4947d51d69 100644
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -11,6 +11,15 @@
 #define HAVE_ARCH_BUG
 #define HAVE_ARCH_WARN_ON
 
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	"\t.long %O2\n"
+#else
+# define __BUG_FUNC_PTR
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+#endif /* CONFIG_DEBUG_BUGVERBOSE */
+
 /**
  * _EMIT_BUG_ENTRY
  * %1 - __FILE__
@@ -25,13 +34,6 @@
  */
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 
-#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
-# define HAVE_BUG_FUNCTION
-# define __BUG_FUNC_PTR	"\t.long %O2\n"
-#else
-# define __BUG_FUNC_PTR
-#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
-
 #define _EMIT_BUG_ENTRY				\
 	"\t.pushsection __bug_table,\"aw\"\n"	\
 	"2:\t.long 1b, %O1\n"			\
-- 
2.39.2

[PATCH v3 14/15] riscv: Add support for suppressing warning backtraces

[Guenter Roeck]

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).

To simplify the implementation, unify the __BUG_ENTRY_ADDR and
__BUG_ENTRY_FILE macros into a single macro named __BUG_REL() which takes
the address, file, or function reference as parameter.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
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/riscv/include/asm/bug.h | 38 ++++++++++++++++++++++++------------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
index 1aaea81fb141..79f360af4ad8 100644
--- a/arch/riscv/include/asm/bug.h
+++ b/arch/riscv/include/asm/bug.h
@@ -30,26 +30,39 @@
 typedef u32 bug_insn_t;
 
 #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
-#define __BUG_ENTRY_ADDR	RISCV_INT " 1b - ."
-#define __BUG_ENTRY_FILE	RISCV_INT " %0 - ."
+#define __BUG_REL(val)	RISCV_INT " " __stringify(val) " - ."
 #else
-#define __BUG_ENTRY_ADDR	RISCV_PTR " 1b"
-#define __BUG_ENTRY_FILE	RISCV_PTR " %0"
+#define __BUG_REL(val)	RISCV_PTR " " __stringify(val)
 #endif
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+
+#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
+# define HAVE_BUG_FUNCTION
+# define __BUG_FUNC_PTR	__BUG_REL(%1)
+#else
+# define __BUG_FUNC_PTR
+#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
+
 #define __BUG_ENTRY			\
-	__BUG_ENTRY_ADDR "\n\t"		\
-	__BUG_ENTRY_FILE "\n\t"		\
-	RISCV_SHORT " %1\n\t"		\
-	RISCV_SHORT " %2"
+	__BUG_REL(1b) "\n\t"		\
+	__BUG_REL(%0) "\n\t"		\
+	__BUG_FUNC_PTR "\n\t"		\
+	RISCV_SHORT " %2\n\t"		\
+	RISCV_SHORT " %3"
 #else
 #define __BUG_ENTRY			\
-	__BUG_ENTRY_ADDR "\n\t"		\
-	RISCV_SHORT " %2"
+	__BUG_REL(1b) "\n\t"		\
+	RISCV_SHORT " %3"
 #endif
 
 #ifdef CONFIG_GENERIC_BUG
+#ifdef HAVE_BUG_FUNCTION
+# define __BUG_FUNC	__func__
+#else
+# define __BUG_FUNC	NULL
+#endif
+
 #define __BUG_FLAGS(flags)					\
 do {								\
 	__asm__ __volatile__ (					\
@@ -58,10 +71,11 @@ do {								\
 			".pushsection __bug_table,\"aw\"\n\t"	\
 		"2:\n\t"					\
 			__BUG_ENTRY "\n\t"			\
-			".org 2b + %3\n\t"                      \
+			".org 2b + %4\n\t"                      \
 			".popsection"				\
 		:						\
-		: "i" (__FILE__), "i" (__LINE__),		\
+		: "i" (__FILE__), "i" (__BUG_FUNC),		\
+		  "i" (__LINE__),				\
 		  "i" (flags),					\
 		  "i" (sizeof(struct bug_entry)));              \
 } while (0)
-- 
2.39.2

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

[Guenter Roeck]

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

Re: [PATCH v3 00/15] Add support for suppressing warning backtraces

[Kees Cook]

On Wed, Apr 03, 2024 at 06:19:21AM -0700, Guenter Roeck wrote:
> Some unit tests intentionally trigger warning backtraces by passing bad
> parameters to kernel API functions. Such unit tests typically check the
> return value from such calls, not the existence of the warning backtrace.
> 
> Such intentionally generated warning backtraces are neither desirable
> nor useful for a number of reasons.
> - They can result in overlooked real problems.
> - A warning that suddenly starts to show up in unit tests needs to be
>   investigated and has to be marked to be ignored, for example by
>   adjusting filter scripts. Such filters are ad-hoc because there is
>   no real standard format for warnings. On top of that, such filter
>   scripts would require constant maintenance.
> 
> One option to address problem would be to add messages such as "expected
> warning backtraces start / end here" to the kernel log.  However, that
> would again require filter scripts, it might result in missing real
> problematic warning backtraces triggered while the test is running, and
> the irrelevant backtrace(s) would still clog the kernel log.
> 
> Solve the problem by providing a means to identify and suppress specific
> warning backtraces while executing test code. Support suppressing multiple
> backtraces while at the same time limiting changes to generic code to the
> absolute minimum. Architecture specific changes are kept at minimum by
> retaining function names only if both CONFIG_DEBUG_BUGVERBOSE and
> CONFIG_KUNIT are enabled.
> 
> The first patch of the series introduces the necessary infrastructure.
> The second patch introduces support for counting suppressed backtraces.
> This capability is used in patch three to implement unit tests.
> Patch four documents the new API.
> The next two patches add support for suppressing backtraces in drm_rect
> and dev_addr_lists unit tests. These patches are intended to serve as
> examples for the use of the functionality introduced with this series.
> The remaining patches implement the necessary changes for all
> architectures with GENERIC_BUG support.
> 
> With CONFIG_KUNIT enabled, image size increase with this series applied is
> approximately 1%. The image size increase (and with it the functionality
> introduced by this series) can be avoided by disabling
> CONFIG_KUNIT_SUPPRESS_BACKTRACE.
> 
> This series is based on the RFC patch and subsequent discussion at
> https://patchwork.kernel.org/project/linux-kselftest/patch/02546e59-1afe-4b08-ba81-d94f3b691c9a@moroto.mountain/
> and offers a more comprehensive solution of the problem discussed there.
> 
> Design note:
>   Function pointers are only added to the __bug_table section if both
>   CONFIG_KUNIT_SUPPRESS_BACKTRACE and CONFIG_DEBUG_BUGVERBOSE are enabled
>   to avoid image size increases if CONFIG_KUNIT is disabled. There would be
>   some benefits to adding those pointers all the time (reduced complexity,
>   ability to display function names in BUG/WARNING messages). That change,
>   if desired, can be made later.
> 
> Checkpatch note:
>   Remaining checkpatch errors and warnings were deliberately ignored.
>   Some are triggered by matching coding style or by comments interpreted
>   as code, others by assembler macros which are disliked by checkpatch.
>   Suggestions for improvements are welcome.
> 
> Changes since RFC:
> - Introduced CONFIG_KUNIT_SUPPRESS_BACKTRACE
> - Minor cleanups and bug fixes
> - Added support for all affected architectures
> - Added support for counting suppressed warnings
> - Added unit tests using those counters
> - Added patch to suppress warning backtraces in dev_addr_lists tests
> 
> Changes since v1:
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
>   [I retained those tags since there have been no functional changes]
> - Introduced KUNIT_SUPPRESS_BACKTRACE configuration option, enabled by
>   default.
> 
> Changes since v2:
> - Rebased to v6.9-rc2
> - Added comments to drm warning suppression explaining why it is needed.
> - Added patch to move conditional code in arch/sh/include/asm/bug.h
>   to avoid kerneldoc warning
> - Added architecture maintainers to Cc: for architecture specific patches
> - No functional changes
> 
> ----------------------------------------------------------------
> Guenter Roeck (15):
>       bug/kunit: Core support for suppressing warning backtraces
>       kunit: bug: Count suppressed warning backtraces
>       kunit: Add test cases for backtrace warning suppression
>       kunit: Add documentation for warning backtrace suppression API
>       drm: Suppress intentional warning backtraces in scaling unit tests
>       net: kunit: Suppress lock warning noise at end of dev_addr_lists tests
>       x86: Add support for suppressing warning backtraces
>       arm64: Add support for suppressing warning backtraces
>       loongarch: Add support for suppressing warning backtraces
>       parisc: Add support for suppressing warning backtraces
>       s390: Add support for suppressing warning backtraces
>       sh: Add support for suppressing warning backtraces
>       sh: Move defines needed for suppressing warning backtraces
>       riscv: Add support for suppressing warning backtraces
>       powerpc: Add support for suppressing warning backtraces

Tested-by: Kees Cook <keescook@chromium.org>

(for x86 and um)

I was planning to add warning suppression for the "overflow" KUnit
tests, but it seems the vmalloc routines aren't calling warn_alloc() any
more for impossible sizes. So, I think, no patches needed for
lib/overflow_kunit.c, but at the end of the day, I've tested this series
is working for me. :P

-- 
Kees Cook

Re: [PATCH v3 06/15] net: kunit: Suppress lock warning noise at end of dev_addr_lists tests

[Jakub Kicinski]

On Wed,  3 Apr 2024 06:19:27 -0700 Guenter Roeck wrote:
> dev_addr_lists_test generates lock warning noise at the end of tests
> if lock debugging is enabled. There are two sets of warnings.
> 
> WARNING: CPU: 0 PID: 689 at kernel/locking/mutex.c:923 __mutex_unlock_slowpath.constprop.0+0x13c/0x368
> DEBUG_LOCKS_WARN_ON(__owner_task(owner) != __get_current())
> 
> WARNING: kunit_try_catch/1336 still has locks held!
> 
> KUnit test cleanup is not guaranteed to run in the same thread as the test
> itself. For this test, this means that rtnl_lock() and rtnl_unlock() may
> be called from different threads. This triggers the warnings.
> Suppress the warnings because they are irrelevant for the test and just
> confusing and distracting.
> 
> The first warning can be suppressed by using START_SUPPRESSED_WARNING()
> and END_SUPPRESSED_WARNING() around the call to rtnl_unlock(). To suppress
> the second warning, it is necessary to set debug_locks_silent while the
> rtnl lock is held.

Is it okay if I move the locking into the tests, instead?
It's only 4 lines more and no magic required, seems to work fine.

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

[Michael Ellerman]

Guenter Roeck <linux@roeck-us.net> writes:
> 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(-)

I ran it through some build and boot tests, LGTM.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

Re: [PATCH v3 13/15] sh: Move defines needed for suppressing warning backtraces

[Simon Horman]

On Wed, Apr 03, 2024 at 06:19:34AM -0700, Guenter Roeck wrote:
> Declaring the defines needed for suppressing warning inside
> '#ifdef CONFIG_DEBUG_BUGVERBOSE' results in a kerneldoc warning.
> 
> .../bug.h:29: warning: expecting prototype for _EMIT_BUG_ENTRY().
> 	Prototype was for HAVE_BUG_FUNCTION() instead
> 
> Move the defines above the kerneldoc entry for _EMIT_BUG_ENTRY
> to make kerneldoc happy.
> 
> Reported-by: Simon Horman <horms@kernel.org>
> Cc: Simon Horman <horms@kernel.org>
> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v3: Added patch. Possibly squash into previous patch.

FWIIW, this looks good to me.

>  arch/sh/include/asm/bug.h | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
> index 470ce6567d20..bf4947d51d69 100644
> --- a/arch/sh/include/asm/bug.h
> +++ b/arch/sh/include/asm/bug.h
> @@ -11,6 +11,15 @@
>  #define HAVE_ARCH_BUG
>  #define HAVE_ARCH_WARN_ON
>  
> +#ifdef CONFIG_DEBUG_BUGVERBOSE
> +#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> +# define HAVE_BUG_FUNCTION
> +# define __BUG_FUNC_PTR	"\t.long %O2\n"
> +#else
> +# define __BUG_FUNC_PTR
> +#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +#endif /* CONFIG_DEBUG_BUGVERBOSE */
> +
>  /**
>   * _EMIT_BUG_ENTRY
>   * %1 - __FILE__
> @@ -25,13 +34,6 @@
>   */
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
>  
> -#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> -# define HAVE_BUG_FUNCTION
> -# define __BUG_FUNC_PTR	"\t.long %O2\n"
> -#else
> -# define __BUG_FUNC_PTR
> -#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> -
>  #define _EMIT_BUG_ENTRY				\
>  	"\t.pushsection __bug_table,\"aw\"\n"	\
>  	"2:\t.long 1b, %O1\n"			\
> -- 
> 2.39.2
> 

Re: [PATCH v3 06/15] net: kunit: Suppress lock warning noise at end of dev_addr_lists tests

[Guenter Roeck]

On Wed, Apr 03, 2024 at 06:34:12PM -0700, Jakub Kicinski wrote:
> On Wed,  3 Apr 2024 06:19:27 -0700 Guenter Roeck wrote:
> > dev_addr_lists_test generates lock warning noise at the end of tests
> > if lock debugging is enabled. There are two sets of warnings.
> > 
> > WARNING: CPU: 0 PID: 689 at kernel/locking/mutex.c:923 __mutex_unlock_slowpath.constprop.0+0x13c/0x368
> > DEBUG_LOCKS_WARN_ON(__owner_task(owner) != __get_current())
> > 
> > WARNING: kunit_try_catch/1336 still has locks held!
> > 
> > KUnit test cleanup is not guaranteed to run in the same thread as the test
> > itself. For this test, this means that rtnl_lock() and rtnl_unlock() may
> > be called from different threads. This triggers the warnings.
> > Suppress the warnings because they are irrelevant for the test and just
> > confusing and distracting.
> > 
> > The first warning can be suppressed by using START_SUPPRESSED_WARNING()
> > and END_SUPPRESSED_WARNING() around the call to rtnl_unlock(). To suppress
> > the second warning, it is necessary to set debug_locks_silent while the
> > rtnl lock is held.
> 
> Is it okay if I move the locking into the tests, instead?
> It's only 4 lines more and no magic required, seems to work fine.

I don't think it is that simple. Unit tests run in a kernel thread
and exit immediately if a test fails. While the unit test code _looks_
sequential, that isn't really the case. Every instance of KUNIT_ASSERT_x
or KUNIT_FAIL() results in immediate kernel thread termination. If
that happens, any rtnl_unlock() in the failed function would not be
executed. I am not aware of an equivalent of atexit() for kernel threads
which would fix the problem. My understanding is that the kunit system
doesn't support an equivalent either, but at least sometimes executes
the exit function in a different thread context.

Guenter

Re: [PATCH v3 01/15] bug/kunit: Core support for suppressing warning backtraces

[David Gow]

[-- Attachment #1: Type: text/plain, Size: 18263 bytes --]

On Wed, 3 Apr 2024 at 21:19, Guenter Roeck <linux@roeck-us.net> wrote:
>
> Some unit tests intentionally trigger warning backtraces by passing
> bad parameters to API functions. Such unit tests typically check the
> return value from those calls, not the existence of the warning backtrace.
>
> Such intentionally generated warning backtraces are neither desirable
> nor useful for a number of reasons.
> - They can result in overlooked real problems.
> - A warning that suddenly starts to show up in unit tests needs to be
>   investigated and has to be marked to be ignored, for example by
>   adjusting filter scripts. Such filters are ad-hoc because there is
>   no real standard format for warnings. On top of that, such filter
>   scripts would require constant maintenance.
>
> One option to address problem would be to add messages such as "expected
> warning backtraces start / end here" to the kernel log.  However, that
> would again require filter scripts, it might result in missing real
> problematic warning backtraces triggered while the test is running, and
> the irrelevant backtrace(s) would still clog the kernel log.
>
> Solve the problem by providing a means to identify and suppress specific
> warning backtraces while executing test code. Since the new functionality
> results in an image size increase of about 1% if CONFIG_KUNIT is enabled,
> provide configuration option KUNIT_SUPPRESS_BACKTRACE to be able to disable
> the new functionality. This option is by default enabled since almost all
> systems with CONFIG_KUNIT enabled will want to benefit from it.
>
> Cc: Dan Carpenter <dan.carpenter@linaro.org>
> Cc: Daniel Diaz <daniel.diaz@linaro.org>
> Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
> Cc: Kees Cook <keescook@chromium.org>
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---

Sorry it took so long to get to this.

I love the idea, we've needed this for a while.

There are some downsides to this being entirely based on the name of
the function which contains WARN(). Partly because there could be
several WARN()s within a function, and there'd be overlap, and partly
because the function name is never actually printed during a warning
(it may come from the stack trace, but that can be misleading with
inlined functions).  I don't think either of these are showstoppers,
though, but it'd be nice to extend this in the future with (a) other
ways of identifying warnings, such as the format string, and (b) print
the function name in the report, if it's present. The function name is
probably a good middle ground, complexity-wise, though, so I'm happy
to have it thus far.

 I also think we're missing some opportunities to integrate this
better with existing KUnit infrastructure, like the
action/resource/cleanup system. In particular, it'd be nice to have a
way of ensuring that suppressions won't get leaked if the test aborts
between START_SUPPRESSED_WARNING() and END_SUPPRESSED_WARNING(). It's
not difficult to use this as-is, but it'd be nice to have some
helpers, rather than having to, for instance:
KUNIT_DEFINE_ACTION_WRAPPER(kunit_stop_suppressing_warning,
__end_suppress_warning, struct __suppressed_warning *);
DEFINE_SUPPRESSED_WARNING(vfree);
START_SUPPRESSED_WARNING(vfree);
kunit_add_action(test, kunit_stop_suppressing_warning, (void
*)&__kunit_suppress_vfree);

(With the note that the DEFINE_SUPPRESSED_WARNING() will have to be
global, or put on the heap, lest it become a dangling pointer by the
time the suppression has stopped.)

Equally, do we want to make the
__{start,end,is}_suppress[ed]_warning()  functions KUnit 'hooks'? This
would allow them to be used in modules which don't depend directly on
KUnit. I suspect it's not important in this case: but worth keeping in
mind in case we find a situation where we'd need to suppress a warning
elsewhere.

These are all things which could be added/changed in follow-up
patches, though, so I don't think they're blockers. Otherwise, this
looks good: perhaps the naming could be a bit more consistent with
other KUnit things, but that depends on how much we want this to be 'a
part of KUnit' versus an independent bit of functionality.

> v2:
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
> - Added CONFIG_KUNIT_SUPPRESS_BACKTRACE configuration option,
>   enabled by default
> v3:
> - Rebased to v6.9-rc2
>
>  include/asm-generic/bug.h | 16 +++++++++---
>  include/kunit/bug.h       | 51 +++++++++++++++++++++++++++++++++++++++
>  include/kunit/test.h      |  1 +
>  include/linux/bug.h       | 13 ++++++++++
>  lib/bug.c                 | 51 ++++++++++++++++++++++++++++++++++++---
>  lib/kunit/Kconfig         |  9 +++++++
>  lib/kunit/Makefile        |  6 +++--
>  lib/kunit/bug.c           | 40 ++++++++++++++++++++++++++++++
>  8 files changed, 178 insertions(+), 9 deletions(-)
>  create mode 100644 include/kunit/bug.h
>  create mode 100644 lib/kunit/bug.c
>
> diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> index 6e794420bd39..c170b6477689 100644
> --- a/include/asm-generic/bug.h
> +++ b/include/asm-generic/bug.h
> @@ -18,6 +18,7 @@
>  #endif
>
>  #ifndef __ASSEMBLY__
> +#include <kunit/bug.h>
>  #include <linux/panic.h>
>  #include <linux/printk.h>
>
> @@ -39,8 +40,14 @@ struct bug_entry {
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
>  #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>         const char      *file;
> +#ifdef HAVE_BUG_FUNCTION
> +       const char      *function;
> +#endif
>  #else
>         signed int      file_disp;
> +#ifdef HAVE_BUG_FUNCTION
> +       signed int      function_disp;
> +#endif
>  #endif
>         unsigned short  line;
>  #endif
> @@ -96,15 +103,18 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
>  #define __WARN()               __WARN_printf(TAINT_WARN, NULL)
>  #define __WARN_printf(taint, arg...) do {                              \
>                 instrumentation_begin();                                \
> -               warn_slowpath_fmt(__FILE__, __LINE__, taint, arg);      \
> +               if (!IS_SUPPRESSED_WARNING(__func__))                   \
> +                       warn_slowpath_fmt(__FILE__, __LINE__, taint, arg);\
>                 instrumentation_end();                                  \
>         } while (0)
>  #else
>  #define __WARN()               __WARN_FLAGS(BUGFLAG_TAINT(TAINT_WARN))
>  #define __WARN_printf(taint, arg...) do {                              \
>                 instrumentation_begin();                                \
> -               __warn_printk(arg);                                     \
> -               __WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
> +               if (!IS_SUPPRESSED_WARNING(__func__)) {                 \
> +                       __warn_printk(arg);                             \
> +                       __WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
> +               }                                                       \
>                 instrumentation_end();                                  \
>         } while (0)
>  #define WARN_ON_ONCE(condition) ({                             \
> diff --git a/include/kunit/bug.h b/include/kunit/bug.h
> new file mode 100644
> index 000000000000..bd0fe047572b
> --- /dev/null
> +++ b/include/kunit/bug.h
> @@ -0,0 +1,51 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * KUnit helpers for backtrace suppression
> + *
> + * Copyright (c) 2024 Guenter Roeck <linux@roeck-us.net>
> + */
> +
> +#ifndef _KUNIT_BUG_H
> +#define _KUNIT_BUG_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <linux/kconfig.h>
> +
> +#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> +
> +#include <linux/stringify.h>
> +#include <linux/types.h>
> +
> +struct __suppressed_warning {
> +       struct list_head node;
> +       const char *function;
> +};
> +
> +void __start_suppress_warning(struct __suppressed_warning *warning);
> +void __end_suppress_warning(struct __suppressed_warning *warning);
> +bool __is_suppressed_warning(const char *function);

Do we want to call these '__kunit_start_suppress_warning', etc., to
match other similar functions exported by KUnit to be used in macros,
et al.

> +
> +#define DEFINE_SUPPRESSED_WARNING(func)        \
> +       struct __suppressed_warning __kunit_suppress_##func = \

We use the __kunit_ prefix here...

> +               { .function = __stringify(func) }
> +
> +#define START_SUPPRESSED_WARNING(func) \
> +       __start_suppress_warning(&__kunit_suppress_##func)
> +
> +#define END_SUPPRESSED_WARNING(func) \
> +       __end_suppress_warning(&__kunit_suppress_##func)
> +
> +#define IS_SUPPRESSED_WARNING(func) \
> +       __is_suppressed_warning(func)
> +

Similarly, do we want to give these KUNIT_ prefixes to match other KUnit macros.

One possibility would be to have both KUNIT_- and non-KUNIT_-
variants, the latter of which accepts a struct kunit*, and registers
the suppression with the test for automated cleanup.


> +#else /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +
> +#define DEFINE_SUPPRESSED_WARNING(func)
> +#define START_SUPPRESSED_WARNING(func)
> +#define END_SUPPRESSED_WARNING(func)
> +#define IS_SUPPRESSED_WARNING(func) (false)
> +
> +#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +#endif /* __ASSEMBLY__ */
> +#endif /* _KUNIT_BUG_H */
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index 61637ef32302..d0c44594d34c 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -10,6 +10,7 @@
>  #define _KUNIT_TEST_H
>
>  #include <kunit/assert.h>
> +#include <kunit/bug.h>
>  #include <kunit/try-catch.h>
>
>  #include <linux/args.h>
> diff --git a/include/linux/bug.h b/include/linux/bug.h
> index 348acf2558f3..c668762dc76a 100644
> --- a/include/linux/bug.h
> +++ b/include/linux/bug.h
> @@ -36,6 +36,9 @@ static inline int is_warning_bug(const struct bug_entry *bug)
>         return bug->flags & BUGFLAG_WARNING;
>  }
>
> +void bug_get_file_function_line(struct bug_entry *bug, const char **file,
> +                               const char **function, unsigned int *line);
> +
>  void bug_get_file_line(struct bug_entry *bug, const char **file,
>                        unsigned int *line);
>
> @@ -62,6 +65,16 @@ static inline enum bug_trap_type report_bug(unsigned long bug_addr,
>  }
>
>  struct bug_entry;
> +static inline void bug_get_file_function_line(struct bug_entry *bug,
> +                                             const char **file,
> +                                             const char **function,
> +                                             unsigned int *line)
> +{
> +       *file = NULL;
> +       *function = NULL;
> +       *line = 0;
> +}
> +
>  static inline void bug_get_file_line(struct bug_entry *bug, const char **file,
>                                      unsigned int *line)
>  {
> diff --git a/lib/bug.c b/lib/bug.c
> index e0ff21989990..aa8bb12b9809 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -26,6 +26,14 @@
>         when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
>         the values accordingly.
>
> +  2a.Optionally implement support for the "function" entry in struct
> +     bug_entry. This entry must point to the name of the function triggering
> +     the warning or bug trap (normally __func__). This is only needed if
> +     both CONFIG_DEBUG_BUGVERBOSE and CONFIG_KUNIT_SUPPRESS_BACKTRACE are
> +     enabled and if the architecture wants to implement support for suppressing
> +     warning backtraces. The architecture must define HAVE_BUG_FUNCTION if it
> +     adds pointers to function names to struct bug_entry.
> +
>    3. Implement the trap
>       - In the illegal instruction trap handler (typically), verify
>         that the fault was in kernel mode, and call report_bug()
> @@ -127,14 +135,21 @@ static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
>  }
>  #endif
>
> -void bug_get_file_line(struct bug_entry *bug, const char **file,
> -                      unsigned int *line)
> +void bug_get_file_function_line(struct bug_entry *bug, const char **file,
> +                               const char **function, unsigned int *line)
>  {
> +       *function = NULL;
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
>  #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>         *file = (const char *)&bug->file_disp + bug->file_disp;
> +#ifdef HAVE_BUG_FUNCTION
> +       *function = (const char *)&bug->function_disp + bug->function_disp;
> +#endif
>  #else
>         *file = bug->file;
> +#ifdef HAVE_BUG_FUNCTION
> +       *function = bug->function;
> +#endif
>  #endif
>         *line = bug->line;
>  #else
> @@ -143,6 +158,13 @@ void bug_get_file_line(struct bug_entry *bug, const char **file,
>  #endif
>  }
>
> +void bug_get_file_line(struct bug_entry *bug, const char **file, unsigned int *line)
> +{
> +       const char *function;
> +
> +       bug_get_file_function_line(bug, file, &function, line);
> +}
> +
>  struct bug_entry *find_bug(unsigned long bugaddr)
>  {
>         struct bug_entry *bug;
> @@ -157,8 +179,9 @@ struct bug_entry *find_bug(unsigned long bugaddr)
>  static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs *regs)
>  {
>         struct bug_entry *bug;
> -       const char *file;
> +       const char *file, *function;

As mentioned, I'd love to see the function plumbed through and
reported some day, both to make it easier to know what to suppress,
and also because it's possibly more reliable even outside the
suppression use-case. Could be a follow-up patch later, though.


>         unsigned line, warning, once, done;
> +       char __maybe_unused sym[KSYM_SYMBOL_LEN];
>
>         if (!is_valid_bugaddr(bugaddr))
>                 return BUG_TRAP_TYPE_NONE;
> @@ -169,12 +192,32 @@ static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_regs *re
>
>         disable_trace_on_warning();
>
> -       bug_get_file_line(bug, &file, &line);
> +       bug_get_file_function_line(bug, &file, &function, &line);
> +#if defined(CONFIG_KUNIT_SUPPRESS_BACKTRACE) && defined(CONFIG_KALLSYMS)
> +       if (!function) {
> +               /*
> +                * This will be seen if report_bug is called on an architecture
> +                * with no architecture-specific support for suppressing warning
> +                * backtraces, if CONFIG_DEBUG_BUGVERBOSE is not enabled, or if
> +                * the calling code is from assembler which does not record a
> +                * function name. Extracting the function name from the bug
> +                * address is less than perfect since compiler optimization may
> +                * result in 'bugaddr' pointing to a function which does not
> +                * actually trigger the warning, but it is better than no
> +                * suppression at all.
> +                */
> +               sprint_symbol_no_offset(sym, bugaddr);
> +               function = sym;
> +       }
> +#endif /* defined(CONFIG_KUNIT_SUPPRESS_BACKTRACE) && defined(CONFIG_KALLSYMS) */
>
>         warning = (bug->flags & BUGFLAG_WARNING) != 0;
>         once = (bug->flags & BUGFLAG_ONCE) != 0;
>         done = (bug->flags & BUGFLAG_DONE) != 0;
>
> +       if (warning && IS_SUPPRESSED_WARNING(function))
> +               return BUG_TRAP_TYPE_WARN;
> +
>         if (warning && once) {
>                 if (done)
>                         return BUG_TRAP_TYPE_WARN;
> diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig
> index 68a6daec0aef..b1b899265acc 100644
> --- a/lib/kunit/Kconfig
> +++ b/lib/kunit/Kconfig
> @@ -15,6 +15,15 @@ menuconfig KUNIT
>
>  if KUNIT
>
> +config KUNIT_SUPPRESS_BACKTRACE
> +       bool "KUnit - Enable backtrace suppression"
> +       default y
> +       help
> +         Enable backtrace suppression for KUnit. If enabled, backtraces
> +         generated intentionally by KUnit tests are suppressed. Disable
> +         to reduce kernel image size if image size is more important than
> +         suppression of backtraces generated by KUnit tests.
> +
>  config KUNIT_DEBUGFS
>         bool "KUnit - Enable /sys/kernel/debug/kunit debugfs representation" if !KUNIT_ALL_TESTS
>         default KUNIT_ALL_TESTS
> diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
> index 309659a32a78..545b57c3be48 100644
> --- a/lib/kunit/Makefile
> +++ b/lib/kunit/Makefile
> @@ -14,8 +14,10 @@ ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
>  kunit-objs +=                          debugfs.o
>  endif
>
> -# KUnit 'hooks' are built-in even when KUnit is built as a module.
> -obj-y +=                               hooks.o
> +# KUnit 'hooks' and bug handling are built-in even when KUnit is built
> +# as a module.
> +obj-y +=                               hooks.o \
> +                                       bug.o
>
>  obj-$(CONFIG_KUNIT_TEST) +=            kunit-test.o
>
> diff --git a/lib/kunit/bug.c b/lib/kunit/bug.c
> new file mode 100644
> index 000000000000..f93544d7a9d1
> --- /dev/null
> +++ b/lib/kunit/bug.c
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * KUnit helpers for backtrace suppression
> + *
> + * Copyright (c) 2024 Guenter Roeck <linux@roeck-us.net>
> + */
> +
> +#include <kunit/bug.h>
> +#include <linux/export.h>
> +#include <linux/list.h>
> +#include <linux/string.h>
> +
> +static LIST_HEAD(suppressed_warnings);
> +
> +void __start_suppress_warning(struct __suppressed_warning *warning)
> +{
> +       list_add(&warning->node, &suppressed_warnings);
> +}
> +EXPORT_SYMBOL_GPL(__start_suppress_warning);
> +
> +void __end_suppress_warning(struct __suppressed_warning *warning)
> +{
> +       list_del(&warning->node);
> +}
> +EXPORT_SYMBOL_GPL(__end_suppress_warning);
> +
> +bool __is_suppressed_warning(const char *function)
> +{
> +       struct __suppressed_warning *warning;
> +
> +       if (!function)
> +               return false;
> +
> +       list_for_each_entry(warning, &suppressed_warnings, node) {
> +               if (!strcmp(function, warning->function))
> +                       return true;
> +       }
> +       return false;
> +}
> +EXPORT_SYMBOL_GPL(__is_suppressed_warning);
> --
> 2.39.2
>

Thanks,
-- David

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Re: [PATCH v3 02/15] kunit: bug: Count suppressed warning backtraces

[David Gow]

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On Wed, 3 Apr 2024 at 21:19, Guenter Roeck <linux@roeck-us.net> wrote:
>
> Count suppressed warning backtraces to enable code which suppresses
> warning backtraces to check if the expected backtrace(s) have been
> observed.
>
> Using atomics for the backtrace count resulted in build errors on some
> architectures due to include file recursion, so use a plain integer
> for now.
>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---

Looks good to me, thanks.

Reviewed-by: David Gow <davidgow@google.com>

Cheers,
-- David


> 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
>
>  include/kunit/bug.h | 7 ++++++-
>  lib/kunit/bug.c     | 4 +++-
>  2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/include/kunit/bug.h b/include/kunit/bug.h
> index bd0fe047572b..72e9fb23bbd5 100644
> --- a/include/kunit/bug.h
> +++ b/include/kunit/bug.h
> @@ -20,6 +20,7 @@
>  struct __suppressed_warning {
>         struct list_head node;
>         const char *function;
> +       int counter;
>  };
>
>  void __start_suppress_warning(struct __suppressed_warning *warning);
> @@ -28,7 +29,7 @@ bool __is_suppressed_warning(const char *function);
>
>  #define DEFINE_SUPPRESSED_WARNING(func)        \
>         struct __suppressed_warning __kunit_suppress_##func = \
> -               { .function = __stringify(func) }
> +               { .function = __stringify(func), .counter = 0 }
>
>  #define START_SUPPRESSED_WARNING(func) \
>         __start_suppress_warning(&__kunit_suppress_##func)
> @@ -39,12 +40,16 @@ bool __is_suppressed_warning(const char *function);
>  #define IS_SUPPRESSED_WARNING(func) \
>         __is_suppressed_warning(func)
>
> +#define SUPPRESSED_WARNING_COUNT(func) \
> +       (__kunit_suppress_##func.counter)
> +
>  #else /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
>
>  #define DEFINE_SUPPRESSED_WARNING(func)
>  #define START_SUPPRESSED_WARNING(func)
>  #define END_SUPPRESSED_WARNING(func)
>  #define IS_SUPPRESSED_WARNING(func) (false)
> +#define SUPPRESSED_WARNING_COUNT(func) (0)
>
>  #endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
>  #endif /* __ASSEMBLY__ */
> diff --git a/lib/kunit/bug.c b/lib/kunit/bug.c
> index f93544d7a9d1..13b3d896c114 100644
> --- a/lib/kunit/bug.c
> +++ b/lib/kunit/bug.c
> @@ -32,8 +32,10 @@ bool __is_suppressed_warning(const char *function)
>                 return false;
>
>         list_for_each_entry(warning, &suppressed_warnings, node) {
> -               if (!strcmp(function, warning->function))
> +               if (!strcmp(function, warning->function)) {
> +                       warning->counter++;
>                         return true;
> +               }
>         }
>         return false;
>  }
> --
> 2.39.2
>
> --
> You received this message because you are subscribed to the Google Groups "KUnit Development" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kunit-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kunit-dev/20240403131936.787234-3-linux%40roeck-us.net.

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Re: [PATCH v3 03/15] kunit: Add test cases for backtrace warning suppression

[David Gow]

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On Wed, 3 Apr 2024 at 21:19, Guenter Roeck <linux@roeck-us.net> wrote:
>
> Add unit tests to verify that warning backtrace suppression works.
>
> If backtrace suppression does _not_ work, the unit tests will likely
> trigger unsuppressed backtraces, which should actually help to get
> the affected architectures / platforms fixed.
>
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---

There's a typo in the Makefile, which stops this from being built at
all. Otherwise, it seems good to me.

-- David

> 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
>
>  lib/kunit/Makefile                     |   7 +-
>  lib/kunit/backtrace-suppression-test.c | 104 +++++++++++++++++++++++++
>  2 files changed, 109 insertions(+), 2 deletions(-)
>  create mode 100644 lib/kunit/backtrace-suppression-test.c
>
> diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
> index 545b57c3be48..3eee1bd0ce5e 100644
> --- a/lib/kunit/Makefile
> +++ b/lib/kunit/Makefile
> @@ -16,10 +16,13 @@ endif
>
>  # KUnit 'hooks' and bug handling are built-in even when KUnit is built
>  # as a module.
> -obj-y +=                               hooks.o \
> -                                       bug.o
> +obj-y +=                               hooks.o
> +obj-$(CONFIG_KUNIT_SUPPRESS_BACKTRACE) += bug.o
>
>  obj-$(CONFIG_KUNIT_TEST) +=            kunit-test.o
> +ifeq ($(CCONFIG_KUNIT_SUPPRESS_BACKTRACE),y)

s/CCONFIG_/CONFIG_/ ?




> +obj-$(CONFIG_KUNIT_TEST) +=            backtrace-suppression-test.o
> +endif
>
>  # string-stream-test compiles built-in only.
>  ifeq ($(CONFIG_KUNIT_TEST),y)
> diff --git a/lib/kunit/backtrace-suppression-test.c b/lib/kunit/backtrace-suppression-test.c
> new file mode 100644
> index 000000000000..47c619283802
> --- /dev/null
> +++ b/lib/kunit/backtrace-suppression-test.c
> @@ -0,0 +1,104 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * KUnit test for suppressing warning tracebacks
> + *
> + * Copyright (C) 2024, Guenter Roeck
> + * Author: Guenter Roeck <linux@roeck-us.net>
> + */
> +
> +#include <kunit/test.h>
> +#include <linux/bug.h>
> +
> +static void backtrace_suppression_test_warn_direct(struct kunit *test)
> +{
> +       DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
> +
> +       START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
> +       WARN(1, "This backtrace should be suppressed");
> +       END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
> +
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_direct), 1);
> +}
> +
> +static void trigger_backtrace_warn(void)
> +{
> +       WARN(1, "This backtrace should be suppressed");
> +}
> +
> +static void backtrace_suppression_test_warn_indirect(struct kunit *test)
> +{
> +       DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
> +
> +       START_SUPPRESSED_WARNING(trigger_backtrace_warn);
> +       trigger_backtrace_warn();
> +       END_SUPPRESSED_WARNING(trigger_backtrace_warn);
> +
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 1);
> +}
> +
> +static void backtrace_suppression_test_warn_multi(struct kunit *test)
> +{
> +       DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
> +       DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
> +
> +       START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
> +       START_SUPPRESSED_WARNING(trigger_backtrace_warn);
> +       WARN(1, "This backtrace should be suppressed");
> +       trigger_backtrace_warn();
> +       END_SUPPRESSED_WARNING(trigger_backtrace_warn);
> +       END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
> +
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_multi), 1);
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 1);
> +}
> +
> +static void backtrace_suppression_test_warn_on_direct(struct kunit *test)
> +{
> +       DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
> +
> +       if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE) && !IS_ENABLED(CONFIG_KALLSYMS))
> +               kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE or CONFIG_KALLSYMS");
> +
> +       START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
> +       WARN_ON(1);
> +       END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
> +
> +       KUNIT_EXPECT_EQ(test,
> +                       SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_on_direct), 1);
> +}
> +
> +static void trigger_backtrace_warn_on(void)
> +{
> +       WARN_ON(1);
> +}
> +
> +static void backtrace_suppression_test_warn_on_indirect(struct kunit *test)
> +{
> +       DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
> +
> +       if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE))
> +               kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE");
> +
> +       START_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
> +       trigger_backtrace_warn_on();
> +       END_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
> +
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn_on), 1);
> +}
> +
> +static struct kunit_case backtrace_suppression_test_cases[] = {
> +       KUNIT_CASE(backtrace_suppression_test_warn_direct),
> +       KUNIT_CASE(backtrace_suppression_test_warn_indirect),
> +       KUNIT_CASE(backtrace_suppression_test_warn_multi),
> +       KUNIT_CASE(backtrace_suppression_test_warn_on_direct),
> +       KUNIT_CASE(backtrace_suppression_test_warn_on_indirect),
> +       {}
> +};
> +
> +static struct kunit_suite backtrace_suppression_test_suite = {
> +       .name = "backtrace-suppression-test",
> +       .test_cases = backtrace_suppression_test_cases,
> +};
> +kunit_test_suites(&backtrace_suppression_test_suite);
> +
> +MODULE_LICENSE("GPL");
> --
> 2.39.2
>

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Re: [PATCH v3 04/15] kunit: Add documentation for warning backtrace suppression API

[David Gow]

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On Wed, 3 Apr 2024 at 21:19, Guenter Roeck <linux@roeck-us.net> wrote:
>
> Document API functions for suppressing warning backtraces.
>
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---

This looks good to me: thanks for adding the documentation!

If we add integration between this and the KUnit resource system,
we'll need to add that to this documentation.

I wonder if it would make sense to have an example where the
DEFINE_SUPPRESSED_WARNING() is global, e.g., in the test init/exit
functions. That might overcomplicate it a bit.

It also might be nice to document the individual macros with kerneldoc
comments. (Though, that could equally fit in patch #1).

Still, this is the most important bit, so I'm happy to have it as-is.

Reviewed-by: David Gow <davidgow@google.com>

Cheers,
-- David


> v2:
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
> v3:
> - Rebased to v6.9-rc2
>
>  Documentation/dev-tools/kunit/usage.rst | 30 ++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
> index 22955d56b379..8d3d36d4103d 100644
> --- a/Documentation/dev-tools/kunit/usage.rst
> +++ b/Documentation/dev-tools/kunit/usage.rst
> @@ -157,6 +157,34 @@ Alternatively, one can take full control over the error message by using
>         if (some_setup_function())
>                 KUNIT_FAIL(test, "Failed to setup thing for testing");
>
> +Suppressing warning backtraces
> +------------------------------
> +
> +Some unit tests trigger warning backtraces either intentionally or as side
> +effect. Such backtraces are normally undesirable since they distract from
> +the actual test and may result in the impression that there is a problem.
> +
> +Such backtraces can be suppressed. To suppress a backtrace in some_function(),
> +use the following code.
> +
> +.. code-block:: c
> +
> +       static void some_test(struct kunit *test)
> +       {
> +               DEFINE_SUPPRESSED_WARNING(some_function);
> +
> +               START_SUPPRESSED_WARNING(some_function);
> +               trigger_backtrace();
> +               END_SUPPRESSED_WARNING(some_function);
> +       }
> +
> +SUPPRESSED_WARNING_COUNT() returns the number of suppressed backtraces. If the
> +suppressed backtrace was triggered on purpose, this can be used to check if
> +the backtrace was actually triggered.
> +
> +.. code-block:: c
> +
> +       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(some_function), 1);
>
>  Test Suites
>  ~~~~~~~~~~~
> @@ -857,4 +885,4 @@ For example:
>                 dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");
>
>                 // Everything is cleaned up automatically when the test ends.
> -       }
> \ No newline at end of file
> +       }
> --
> 2.39.2
>

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Re: [PATCH v3 03/15] kunit: Add test cases for backtrace warning suppression

[Guenter Roeck]

On Tue, Apr 09, 2024 at 04:29:42PM +0800, David Gow wrote:
> > +ifeq ($(CCONFIG_KUNIT_SUPPRESS_BACKTRACE),y)
> 
> s/CCONFIG_/CONFIG_/ ?
> 
> 
Odd, I know I tested this (and it still works ;-).
The additional "C" must have slipped in at some point.
Thanks for noticing!

Guenter

Re: [PATCH v3 14/15] riscv: Add support for suppressing warning backtraces

[Charlie Jenkins]

On Wed, Apr 03, 2024 at 06:19:35AM -0700, Guenter Roeck wrote:
> 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).
> 
> To simplify the implementation, unify the __BUG_ENTRY_ADDR and
> __BUG_ENTRY_FILE macros into a single macro named __BUG_REL() which takes
> the address, file, or function reference as parameter.
> 
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> 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/riscv/include/asm/bug.h | 38 ++++++++++++++++++++++++------------
>  1 file changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
> index 1aaea81fb141..79f360af4ad8 100644
> --- a/arch/riscv/include/asm/bug.h
> +++ b/arch/riscv/include/asm/bug.h
> @@ -30,26 +30,39 @@
>  typedef u32 bug_insn_t;
>  
>  #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
> -#define __BUG_ENTRY_ADDR	RISCV_INT " 1b - ."
> -#define __BUG_ENTRY_FILE	RISCV_INT " %0 - ."
> +#define __BUG_REL(val)	RISCV_INT " " __stringify(val) " - ."
>  #else
> -#define __BUG_ENTRY_ADDR	RISCV_PTR " 1b"
> -#define __BUG_ENTRY_FILE	RISCV_PTR " %0"
> +#define __BUG_REL(val)	RISCV_PTR " " __stringify(val)
>  #endif
>  
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
> +
> +#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> +# define HAVE_BUG_FUNCTION
> +# define __BUG_FUNC_PTR	__BUG_REL(%1)
> +#else
> +# define __BUG_FUNC_PTR
> +#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +
>  #define __BUG_ENTRY			\
> -	__BUG_ENTRY_ADDR "\n\t"		\
> -	__BUG_ENTRY_FILE "\n\t"		\
> -	RISCV_SHORT " %1\n\t"		\
> -	RISCV_SHORT " %2"
> +	__BUG_REL(1b) "\n\t"		\
> +	__BUG_REL(%0) "\n\t"		\
> +	__BUG_FUNC_PTR "\n\t"		\
> +	RISCV_SHORT " %2\n\t"		\
> +	RISCV_SHORT " %3"
>  #else
>  #define __BUG_ENTRY			\
> -	__BUG_ENTRY_ADDR "\n\t"		\
> -	RISCV_SHORT " %2"
> +	__BUG_REL(1b) "\n\t"		\
> +	RISCV_SHORT " %3"
>  #endif
>  
>  #ifdef CONFIG_GENERIC_BUG
> +#ifdef HAVE_BUG_FUNCTION
> +# define __BUG_FUNC	__func__
> +#else
> +# define __BUG_FUNC	NULL
> +#endif
> +
>  #define __BUG_FLAGS(flags)					\
>  do {								\
>  	__asm__ __volatile__ (					\
> @@ -58,10 +71,11 @@ do {								\
>  			".pushsection __bug_table,\"aw\"\n\t"	\
>  		"2:\n\t"					\
>  			__BUG_ENTRY "\n\t"			\
> -			".org 2b + %3\n\t"                      \
> +			".org 2b + %4\n\t"                      \
>  			".popsection"				\
>  		:						\
> -		: "i" (__FILE__), "i" (__LINE__),		\
> +		: "i" (__FILE__), "i" (__BUG_FUNC),		\
> +		  "i" (__LINE__),				\
>  		  "i" (flags),					\
>  		  "i" (sizeof(struct bug_entry)));              \
>  } while (0)
> -- 
> 2.39.2
> 
> 
> _______________________________________________
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> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>

- Charlie