On Sat, Jun 28, 2025 at 3:25 PM Sabyrzhan Tasbolatov
[off-list ref] wrote:

On Sat, Jun 28, 2025 at 3:57 PM Andrey Konovalov [off-list ref] wrote:

quoted

On Thu, Jun 26, 2025 at 5:32 PM Sabyrzhan Tasbolatov
[off-list ref] wrote:

quoted

This patch series unifies the kasan_arch_is_ready() and kasan_enabled()
interfaces by extending the existing kasan_enabled() infrastructure to
work consistently across all KASAN modes (Generic, SW_TAGS, HW_TAGS).

Currently, kasan_enabled() only works for HW_TAGS mode using a static key,
while other modes either return IS_ENABLED(CONFIG_KASAN) (compile-time
constant) or rely on architecture-specific kasan_arch_is_ready()
implementations with custom static keys and global variables.

This leads to:
- Code duplication across architectures
- Inconsistent runtime behavior between KASAN modes
- Architecture-specific readiness tracking

After this series:
- All KASAN modes use the same kasan_flag_enabled static key
- Consistent runtime enable/disable behavior across modes
- Simplified architecture code with unified kasan_init_generic() calls
- Elimination of arch specific kasan_arch_is_ready() implementations
- Unified vmalloc integration using kasan_enabled() checks

This addresses the bugzilla issue [1] about making
kasan_flag_enabled and kasan_enabled() work for Generic mode,
and extends it to provide true unification across all modes.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=217049

Hi Sabyrzhan,

Thank you for working on this!

One aspect that is missing from the patches is moving the
kasan_arch_is_ready() calls into the include/linux/kasan.h (this is
not explicitly mentioned in the issue, but this is what the "adding
__wrappers" part is about).

Another thing that needs careful consideration is whether it's
possible to combine kasan_arch_is_ready() and kasan_enabled() into the
same check logically at all. There's one issue mentioned in [1]:

Hello,
I've removed kasan_arch_is_ready() at all in this series:
[PATCH v2 11/11] kasan: replace kasan_arch_is_ready with kasan_enabled

Is it not what's expected by unification?

I guess the issue description diverged a bit from what needs to be
done, sorry about that.

The core 2 things I wanted to address with the unification are:

1. Avoid spraying kasan_arch_is_ready() throughout the KASAN
implementation and move these checks into include/linux/kasan.h (and
add __wrappers when required).

2. Avoid architectures redefining the same kasan_enabled global
variable/static key.

Initially, I thought that s/kasan_arch_is_ready/kasan_enabled + simply
moving the calls into affected include/linux/kasan.h functions would
be enough. But then, based on [1], turns out it's not that simple.

So now, I think we likely still need two separate checks/flags:
kasan_enabled() that controls whether KASAN is enabled at all and
kasan_arch_is_ready() that gets turned on by kasan_init() when shadow
is initialized (should we rename it to kasan_shadow_initialized()?).
But then we can still move kasan_arch_is_ready() into
include/linux/kasan.h and use the proper combination of checks for
each affected function before calling __wrappers. And we can still
remove the duplicated flags/keys code from the arch code.

[1] https://lore.kernel.org/linux-mm/CA+fCnZf7JqTH46C7oG2Wk9NnLU7hgiVDEK0EA8RAtyr-KgkHdg@mail.gmail.com/ (local)