[PATCH -next 0/3] replace open coded VA->PA calculation

[Ard Biesheuvel]

On Wed, 22 Dec 2021 at 03:31, Linus Walleij <linus.walleij at linaro.org> wrote:
>
> On Tue, Dec 21, 2021 at 10:16 AM Arnd Bergmann <arnd at arndb.de> wrote:
>
> > I think for CPUs that can use LPAE, we want to eventually move to the 4G:4G
> > memory model, which in turn depends on having the kernel in vmalloc space, as
> > implemented by Linus Walleij in
> > https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-integrator.git/log/?h=kernel-in-vmalloc-v5.14-rc1
>
> Yeah I'm still working on this series. The 4/4 split works pretty well,
> but it breaks KASan and I was in the process of fixing that when I left
> for parental leave.
>
> The reason it breaks would be related to KASan not expecting
> executable code in the vmalloc area, and since the shadowing
> algorithm is a simple pointer offset, and since we go to lengths
> to chisel shadow memory out of lowmem at a fixed offset from
> TEXT_OFFSET, we have a problem.
>

Vmap'ed stacks actually has a similar problem, which is why it is
disabled when KAsan is enabled. But this can be fixed by enabling arch
support for KASAN_VMALLOC, and I suspect it may address the vmap'ed
kernel as well.