[jerf]

Arguably, the issue with these features isn't their existence, since it's not even that hard to add them to a kernel, relative to the generalized difficulty of adding things to a kernel in general. The problem has been the need for mass awareness and desire for the feature, and that's what's taken multiple decades to emerge. It does no good for a kernel to have a security feature that only a vanishing fraction of developers care about and use.

(And I say "vanishing fraction" relative to the pool of developers as a whole; even if a particular subcommunity uses it extensively that doesn't make it a pervasive request. I can name subcommunities with all sorts of exotic interests that have not penetrated the mainstream yet, like the capabilities-based security community. Someday, when that emerges, we'll all point back to E as a pioneer, but in the meantime, effectively nobody wants it right now.)