On 2018-10-31 14:35, Dave Hansen wrote:
> On 10/31/18 2:30 PM, Sean Christopherson wrote:
>> AFAIK there isn't a way to prevent userspace from manually invoking
>> EENTER, short of doing some really nasty text poking or PTE swizzling.
>> We could declare using EENTER as unsupported,
> 
> Yep, userspace can call it all it wants, and we can also say that
> calling it outside the vdso is "undefined".

Is there a precedent for this? Are there any other ring 3 x86 
instructions that Linux is claiming to be "undefined" when executed by a 
user process?

--
Jethro Beekman | Fortanix