On Wed, May 28, 2025 at 03:47:42PM -0700, Kees Cook wrote: > On Mon, May 26, 2025 at 01:27:51PM +0000, Alessandro Carminati 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. > > > > 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. > > > > Implementation details: > > Check suppression directly in the `WARN()` Macros. > > This avoids the need for function symbol resolution or ELF section > > modification. > > Suppression is implemented directly in the `WARN*()` macros. > > > > A helper function, `__kunit_is_suppressed_warning()`, is used to determine > > whether suppression applies. It is marked as `noinstr`, since some `WARN*()` > > sites reside in non-instrumentable sections. As it uses `strcmp`, a > > `noinstr` version of `strcmp` was introduced. > > The implementation is deliberately simple and avoids architecture-specific > > optimizations to preserve portability. Since this mechanism compares > > function names and is intended for test usage only, performance is not a > > primary concern. > > > > Signed-off-by: Guenter Roeck <li...@roeck-us.net> > > I like this -- it's very simple, it doesn't need to be fast-path, so > a linear list walker with strcmp is fine. Nice!
But it is on the fast path! This is still bloating every UD2 site instead of doing it on the other end.
