Re: [PATCH v2] compiler_types: Provide __no_kstack_erase to disable coverage only on Clang

[Kees Cook <kees@kernel.org>]

On Tue, Jul 29, 2025 at 04:41:00PM -0700, Kees Cook wrote:
> In order to support Clang's stack depth tracking (for Linux's kstack_erase
> feature), the coverage sanitizer needed to be disabled for __init (and
> __head) section code. Doing this universally (i.e. for GCC too) created
> a number of unexpected problems, ranging from changes to inlining logic
> to failures to DCE code on earlier GCC versions.
> 
> Since this change is only needed for Clang, specialize it so that GCC
> doesn't see the change as it isn't needed there (the GCC implementation
> of kstack_erase uses a GCC plugin that removes stack depth tracking
> instrumentation from __init sections during a late pass in the IR).
> 
> Successfully build and boot tested with GCC 12 and Clang 22.
> 
> Fixes: 381a38ea53d2 ("init.h: Disable sanitizer coverage for __init and __head")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202507270258.neWuiXLd-lkp@intel.com/
> Reported-by: syzbot+5245cb609175fb6e8122@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/6888d004.a00a0220.26d0e1.0004.GAE@google.com/
> Signed-off-by: Kees Cook <kees@kernel.org>

I've now sent the PR that includes this fix:
https://lore.kernel.org/lkml/202507291728.51BAA26@keescook/

Thank you everyone for suffering through the mess I made! :P

-Kees

-- 
Kees Cook