[RFC PATCH 1/5] bug: Core support for suppressing warning backtraces

[Kees Cook]

On Tue, Mar 05, 2024 at 10:40:29AM -0800, Guenter Roeck wrote:
> [...]
>  	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;
> +

I had to re-read __report_bug() more carefully, but yes, this works --
it's basically leaving early, like "once" does.

This looks like a reasonable approach!

Something very similar to this is checking that a warning happens. i.e.
you talk about drm selftests checking function return values, but I've
got a bunch of tests (LKDTM) that live outside of KUnit because I haven't
had a clean way to check for specific warnings/bugs. I feel like future
changes built on top of this series could add counters or something that
KUnit could examine. E.g. I did this manually for some fortify tests:

https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/hardening&id=4ce615e798a752d4431fcc52960478906dec2f0e

-Kees

-- 
Kees Cook