lkml.org 
[lkml]   [2020]   [Apr]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation
From
Date
> On Apr 7, 2020, at 12:38 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> 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.

For the same reason that KVM writes to CR2 - to restore CR2 before entering
a guest, since CR2 not architecturally loaded from the VMCS. I suspect there
are additional use-cases which are not covered by the kernel interfaces.

\
 
 \ /
  Last update: 2020-04-07 22:28    [W:0.066 / U:7.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site