On: Mach kernel

[blank_pattern]

They seem really big on keeping iOS things secret-ish, but the XNU kernel for both iOS and macOS seem to be built from the same code base.

Up until a couple years ago, they'd strip out ARM specific things from the releases macOS XNU code. Then they started leaving that stuff in!

[vbezhenar → blank_pattern]

What about their embedded OS? Like one they're running on T2 chip or inside Airpods? Is it still based on XNU kernel?

[my123 → vbezhenar]

T2 is a variant of A10 and runs XNU for the main CPU.

Firmware cores and AirPods run Apple RTKit.

[cnasc → vbezhenar]

They use L4 in the Secure Enclave. Perhaps they do the same for other embedded devices

[antoinealb → vbezhenar]

I would be surprised if that was the case. Low-power micro-controllers, such as ARM's Cortex-M series usually do not have support for virtual memory, which is required for running XNU.