Comment by mrweasel
11 hours ago
Maybe someone more familiar with operating systems kernels can answer this: Is Darwin really all the exiting? It is different from both the BSD kernels and Linux, but less so than Windows. Other than the ability to run macOS applications (assuming you can clone the libraries and APIs from macOS) is there some benefit of Darwin that I'm not seeing?
XNU has some interesting features.
It’s Mach based, so it has Mach ports, which are an IPC system that is fairly heavily used by macOS.
It has DriverKit, which is a C++ framework for drivers that’s got morecsuppirt than the usual Unix driver model.
Mach-O does more than ELF, and enables the two-layer namespacing that makes macOS able to manage dynamic linking dependencies better than ELF.
Nothing really earth-shattering but interesting enough. And far easier to build a macOS environment on than FreeBSD.
> Mach-O does more than ELF, and enables the two-layer namespacing that makes macOS able to manage dynamic linking dependencies better than ELF.
I've always admired that mach-o supports fat binaries.
I honestly think the kernel interface is by far the easiest part of building a MacOS compat layer. The userland is gigantic, super complex, and totally closed source. That's the hard part.
AFAIK all macos software only talks to the kernel via userland APIs - so there's no particular benefit to basing ravynOS on XNU anyway. (Just the opinion of a layman.)
The Mach APIs are available to userland applications, if you used a different kernel you’d have to implement them somehow
But do real apps actually use them directly? Or only through the userland libraries?
Just FYI, the https://www.darlinghq.org project is doing MacOS app compat on Linux - i.e. building the userland libraries.
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Most kernels are kind of the same really. Some have slightly fancier inter-process communication. Leading to my all-time favorite YouTube video, an explainer on Android IPC cut like a spy thriller. I'm not even joking: https://www.youtube.com/watch?v=Fb4UoqXPEtI
I have got to say this is one of the single most interesting things I've seen in a while. And she ... she's a goddess - so quirky! :)
I don't think it's all that exciting. The hybrid BSD/mach personalities is somewhat interesting, as are some of the available mach machineries.
It's been a stable foundation for several of the most successful operating systems in history though