Anything that can be userspace should be userspace

It continually disappoints me that the kernel has to do things that are really the job of userspace because in many domains in which Linux is used, userspace is so brittle and hard to modify that even linking to glibc is considered risky.

I don't think I buy a performance argument for a kernel-mode process builder: you're running the dynamic linker interpreter anyway (all your binaries are PIE, right? Right??). The interpreter has to load the actual program anyway, and I don't see why the interpreter couldn't be made to do a bit of process setup before transferring control to the main program. There are multiple ways to get correctness too.

But deployment? Yeah, I can see how that can be hard in some godforsaken Kubernetes hell. That's a good, if tragic, ecological argument for doing this kernel-side. That said, I can't wait for ten years of being unable to use this feature because gvisor won't implement it or some provider has seccomp-ed out every system call invented since 1995.

It shouldn't be this way. It doesn't have to be this way. And if I were building an OS from scratch, I'd strictly adhere to the rule that *everything* that could *plausibly* be outside the kernel *is* outside the kernel. But that's not the OS we have.