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

[Peter Zijlstra]

On Tue, Apr 07, 2020 at 11:55:21AM -0700, Nadav Amit wrote:
> > On Apr 7, 2020, at 4:02 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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? Letâs 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.