bug/kunit: core support for suppressing warning backtraces

bug/kunit: core support for suppressing warning backtraces

Patch series "Add support for suppressing warning backtraces", v4.

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 patch (of 14):

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.

Link: https://lkml.kernel.org/r/20250313114329.284104-1-acarmina@redhat.com
Link: https://lkml.kernel.org/r/20250313114329.284104-2-acarmina@redhat.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Daniel Diaz <daniel.diaz@linaro.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Arthur Grillo <arthurgrillo@riseup.net>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>
Cc: David Gow <davidgow@google.com>
Cc: Guenetr Roeck <linux@roeck-us.net>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maíra Canal <mcanal@igalia.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimemrmann <tzimmermann@suse.de>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Charlie Jenkins <charlie@rivosinc.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Rae Moar <rmoar@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Simon Horman <horms@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>