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Comment by jamesfmilne | Hacker News Reader

Port qemu-arm to iOS and run it in syscall emulation mode. You’d then need to implement translations for all the Linux system calls. This would make it quite similar to Windows Subsystem for Linux.

No way Apple will let you put that on the App Store though!

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qemu relies on being able to JIT compile, which isn't allowed in the sandbox.

You can JIT compile in the sandbox with certain entitlements that Apple is happy to grant you, as long as you don’t try to put your binary on the App Store.

Care to show how to do this or even an example of this being done?

Extraordinary claims require proof.

Sure. If you have an Xcode and an iOS device on hand, make a new project and cast “\x00\x00\x80\x52\xc0\x03\x5f\xd6” (or your own assembly) to an int (*)(), and check to see if the return value is 42 in the debugger.

That’s not getting the JIT entitlement as your prior comment claimed. ;)

It is, the entitlement is called “get-task-allow” and is usually used for saying that it’s ok to be attached to in the debugger, but serves a useful double life in making it possible to JIT. Xcode injects this entitlement for you when you create a debug build.

But it only works when debugger is attached I thought (which isn’t a practical work around).

Nope, all you need to do is call ptrace: https://news.ycombinator.com/item?id=18431524

How?

https://news.ycombinator.com/item?id=18431524

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