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by mrweasel12 hours ago |
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upvoteby __d12 hours ago|
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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.

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upvoteby yjftsjthsd-h10 hours ago|
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> 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.

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upvoteby ripdog12 hours ago|
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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.)

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upvoteby mrpippy11 hours ago|
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The Mach APIs are available to userland applications, if you used a different kernel you’d have to implement them somehow
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upvoteby ripdog11 hours ago|
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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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upvoteby mrpippy9 hours ago|
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Yes, real apps use Mach messaging directly. i.e.: https://source.chromium.org/chromium/chromium/src/+/main:ipc...
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upvoteby ChocolateGod8 hours ago|
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Chrome is an outlier to how most apps will do things.
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upvoteby nrr7 hours ago|
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The illustration that Chrome uses Mach ports is a counterexample to an (implied) insinuation that nothing in running in macOS user space uses Mach ports. Outlier or not, the fact there is at least one (albeit also very useful and very popular) application that uses them ties back to the conversation about how they're a kernel feature worth having for Mac compatibility.
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upvoteby phendrenad210 hours ago|
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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
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upvoteby Cockbrand20 minutes ago|
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This is great stuff, thank you for sharing!
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upvoteby Bluestein9 hours ago|
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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! :)
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upvoteby jabedude12 hours ago|
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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

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