Re: [PATCH v8 13/14] x86/kasan: Logical bit shift for kasan_mem_to_shadow

[Andrey Konovalov]

On Wed, Jan 14, 2026 at 5:52 PM Maciej Wieczor-Retman
<maciej.wieczor-retman@xxxxxxxxx> wrote:
>
> I'm a fan of trying to keep as much arch code in the arch directories.
>
> How about before putting a call here instead like:
>
>         if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
>                 if (addr < (unsigned long)kasan_mem_to_shadow((void *)(0ULL)) ||
>                     addr > (unsigned long)kasan_mem_to_shadow((void *)(~0ULL)))
>                         return;
>         }
>
>         arch_kasan_non_canonical_hook()
> There would be the generic non-arch part above (and anything shared that might
> make sense here in the future) and all the arch related code would be hidden in
> the per-arch helper.
>
> So then we could move the part below:
>         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) && IS_ENABLED(CONFIG_ARM64)) {
>                 if (addr < (unsigned long)kasan_mem_to_shadow((void *)(0xFFULL << 56)) ||
>                     addr > (unsigned long)kasan_mem_to_shadow((void *)(~0ULL)))
>                         return;
>         }
> to /arch/arm64.
>
> For x86 we'd need to duplicate the generic part into
> arch_kasan_non_canonical_hook() call in /arch/x86. That seems quiet tidy to me,
> granted the duplication isn't great but it would keep the non-arch part as
> shared as possible. What do you think?

Sounds good to me too, thanks!