Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation

Peter Zijlstra
2020-04-07T19:39:35Z

On Tue, Apr 07, 2020 at 11:55:21AM -0700, Nadav Amit wrote:
> > On Apr 7, 2020, at 4:02 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > Since we now have infrastructure to analyze module text, disallow
> > modules that write to CRn and DRn registers.
>
> Assuming the kernel is built without CONFIG_PARAVIRT, what is the right way
> for out-of-tree modules to write to CRs? Let’s say CR2?

Most of them there is no real justification for ever writing to. CR2 I
suppose we can have an exception for given a sane rationale for why
you'd need to rewrite the fault address.