Re: [PATCH v3 03/10] arm64, kfence: enable KFENCE for ARM64

[Alexander Potapenko]

> > On x86 we just do `char __kfence_pool[KFENCE_POOL_SIZE] ...;` to
> > statically allocate the pool. On arm64 this doesn't seem to work
> > because static memory doesn't have struct pages?
>
> Are you using virt_to_page() directly on that statically-allocated
> __kfence_pool? If so you'll need to use lm_alias() if so, as is done in
> mm/kasan/init.c.
>
> Anything statically allocated is part of the kernel image address range
> rather than the linear/direct map, and doesn't have a valid virt addr,
> but its linear map alias does.
>
> If you enable CONFIG_DEBUG_VIRTUAL you should get warnings if missing
> lm_alias() calls.

I just checked that on x86 CONFIG_DEBUG_VIRTUAL prints no warnings on our tests.
virt_addr_valid() also returns true for addresses belonging to
__kfence_pool declared in BSS.
Could this be related to x86 mapping the kernel twice?