System Extensions and DriverKit – WWDC 2019 [video]

[pjmlp]

https://developer.apple.com/videos/play/wwdc2019/702/

[monocasa]

Didn't NeXTSTEP already have DriverKit? That for some reason they didn't want ObjC in the kernel, so it was replaced with IOKit?

Edit: lol, yep. http://www.nextcomputers.org/NeXTfiles/Docs/Developer/Driver...

You'd think they wouldn't name it something that literally conflicts their previous deprecated framework.

[mrpippy → monocasa]

Yep, it's amusing that both these APIs recycle the names of what Mac OS X's parents used (DriverKit for NeXTSTEP, and the infamous System Extensions of classic Mac OS).

Obviously no technical recycling going on though; the new DriverKit allows user-mode drivers, not ObjC in the kernel or willy-nilly patching of the OS.

[jjtheblunt → mrpippy]

NeXT's driverkit allowed user-mode drivers, as I recall, having written one in 1993.

[pjmlp → monocasa]

You can do some archeology here, https://www.geeklair.net/~dluke/PCIdevice_tutorial.txt

[urda → monocasa]

Considering NeXTSTEP is long gone, why does it matter if the name conflicts? The name has no bearing on this discussion.

[monocasa → urda]

I mean, it's the previous driver framework for the XNU kernel before the current one IOKit. Which they are deprecating in favor of another DriverKit.

Like, the XNU kernel has now had three driver frameworks. Two of them are named DriverKit but are completely separate, and not even back to back.

[aequitas]

I love how wholesome this presentation is. It's clearly noticeable the speaker nervous and is not used to doing this, especially compared to a natural like what Jobs used to be. But he clearly bring over all information and cracks a nice joke on top of that.

[drudru11]

Hmmm. We’re headed back to a microkernel.

[pjmlp → drudru11]

Slowly leaving BSD/Linux and other UNIX clones as the surviving monoliths.

[monocasa → pjmlp]

Eh, NT is pretty much still a monolith.

[pjmlp → monocasa]

NT 4.0 might be, Windows 10 not really, specially since Vista, MinWin and WinRT related changes.

[monocasa → pjmlp]

Yes really. Vista even with UMDF kept pretty much everything of note in kernel space; only the network looking stuff like USB drivers could be pulled out into user space. MinWin and WinRT have literally nothing to do with the kernel/user boundary.

Edit: you might have an argument on the WSL-WSL2 transition. But, IMO, that feels more like a exokernel than a microkernel since it's running on the side over Hyper-V.

[pjmlp → monocasa]

USB and GPU drivers are also user space.

[monocasa → pjmlp]

As much as they are in Linux. Honestly Linux puts more in user space, and allows USB target drivers in user space too (ie. an implementation of the backing USB device).

Edit: and the GPU drivers still very much have a kernel component, and more or less have to. The creation of a GPU instance is super duper privileged, since it's setting up page tables. If you allowed user space to do that, you'd be able to circumvent the MMU.

[pjmlp → monocasa]

My GPU drivers never bork the machine like they do on Linux, just a couple of seconds black screen and business as usual.

Same applies to USB drivers not doing a kernel panic when plugged on.

Naturally there is always a part that only the kernel is allowed to own control over.

[monocasa → pjmlp]

> My GPU drivers never bork the machine like they do on Linux, just a couple of seconds black screen and business as usual.

None of that has to do with the kernel/user boundary. It's that dwm does a better job recovering than x11. Wayland also does a better job recovering.

> Same applies to USB drivers not doing a kernel panic when plugged on.

Like I said, Linux has had USB drivers in user space for longer than NT, and I've def recently had NT USB drivers bluescreen my system.

> Naturally there is always a part that only the kernel is allowed to own control over.

I mean, not necessarily. I've seen true ukernels run GPU drivers entirely in user space. It's just that NT isn't at all a ukernel. They just like to call it a hybrid because the executive is a different folder in their source code, lol.