Re: [PATCH v3] drivers/char: kmem: disable on arm64

From: gregkh@xxxxxxxxxxxxxxxxxxx
Date: Mon Jul 17 2017 - 10:18:52 EST


On Tue, Jun 20, 2017 at 01:20:49PM +0200, Ard Biesheuvel wrote:
> On 20 June 2017 at 08:59, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> > As it turns out, arm64 deviates from other architectures in the way it
> > maps the VMALLOC region: on most (all?) other architectures, it resides
> > strictly above the kernel's direct mapping of DRAM, but on arm64, this
> > is the other way around. For instance, for a 48-bit VA configuration,
> > we have
> >
> > modules : 0xffff000000000000 - 0xffff000008000000 ( 128 MB)
> > vmalloc : 0xffff000008000000 - 0xffff7dffbfff0000 (129022 GB)
> > ...
> > vmemmap : 0xffff7e0000000000 - 0xffff800000000000 ( 2048 GB maximum)
> > 0xffff7e0000000000 - 0xffff7e0003ff0000 ( 63 MB actual)
> > memory : 0xffff800000000000 - 0xffff8000ffc00000 ( 4092 MB)
> >
> > This has mostly gone unnoticed until now, but it does appear that it
> > breaks an assumption in the kcore
>
> s/kcore/kmem/

v4? :)