Re: [PATCH v2] mm/vmalloc: widen guard region to defeat ENTER-based stack pivot

[Peter Zijlstra]

On Mon, Jun 29, 2026 at 03:29:50PM -0700, Dave Hansen wrote:

> But, really, if ENTER is so evil and nobody uses it, shouldn't we just
> have an MSR bit somewhere to tell the CPU to #UD for it rather than
> playing these stack games?

For supervisor mode only, I suppose. We can't ever get rid of userspace
ENTER because legacy I suppose. But we can make sure the kernel is
clean.

So yeah, having a knob to make supervisor-ENTER trap would be useful I
suppose.