On 10/31/18 2:53 PM, Jethro Beekman wrote: > 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? We did it for MPX. "Don't use MPX unless you first tell the kernel, or we'll eat your puppy."
