My understanding from WWDC is that it does AOT compilation at install time when possible. If an app marks a page executable at runtime (such as a JIT) it will interpret that.
Newer instructions are still encumbered by patents.
What these instructions do so that someone working on their own couldn't figure out? I am sick of patents lodged just because particular engineers got there first. When you finally save money to do your own research often you learn that your idea has already been patented. It just made work more expensive as I had to spend time finding way around the patent. Such monopoly on ideas should not be legal.
> patents lodged just because particular engineers got there first
That is what patents are. They encourage you to actually get there by giving you a time-limited monopoly on the implementation. It is easy to say "a freshman CS student could have figured this out", but if they did, they could have had the patent instead and licensed it to Intel and Apple. Instead, Intel and Apple had to figure it out on their own.
That is what patents attempt to be. There are many reasons that make them less effective at this than their ideal.
In particular, costs are high, litigation to protect is expensive, and so your average student wouldn't be able to afford this. The fact that software is typically shipped virtually means that borders are practically non-existent, and wide patents are often needed, or a company needs to give up on defending their patent outside their primary market.
To patent an idea will probably be around $10-100k per market. To cover US, EU, and large Asian markets, you're looking at $500k-1m, and thats just to get the patent. Then you'll need to defend it, which can be hard to do against entities based in non-compliant countries such as China.
This all means that unless you're defending the very core of your entire business proposition, you probably need to be a >$100m before it's worth pursuing patents, and even for the core of your business you probably need to have several million in funding.
I don't think a freshman CS student could afford to apply for a patent. This is only reserved for big companies or engineers backed up by wealth. You also often get things patented that nobody thought about patenting as they are that obvious. It's just a mechanism to gate keep and secure profits for big guys. I have a friend who has multiple patents and their investor only agreed to put money in their project if they patented it and shared all revenue. They were not actually interested in the product itself apart from likelihood the patents will bring money. The project is now dead, but patents stay blocking anyone from trying the same idea.
Actually, speaking from experience, you can do this yourself (or mostly yourself with some guidance from professionals). Nolo press has a book ("Patent it Yourself") on the topic.
"If an app marks a page executable at runtime (such as a JIT) it will interpret that."
Was that from a presentation on Rosetta2 that I have missed? It certainly makes sense, but also you'd need to watch for writes to executable pages that have been already AOT translated.
JITs usually mark +x pages -w again after they've written them for sanity, so watching in platform libc mprotect could do it, but you could also force them to be -w anyway and then maybe use the page fault handler. How much integration with the kernel does it have?
Javascript being the extreme example here (no one is going to run Chrome or Firefox in Rosetta2 probably) but it is re-JITing very often (I think Firefox starts with interpreting JS code, and then replaces hot code paths with JIT compiled equivalents when they become available).
I also see issues with self-modifying code, but this is also very rare (I knew some .NET code that was injecting/manipulating its own JIT code to go around C# private/protected encapsulation).
> no one is going to run Chrome or Firefox in Rosetta2 probably
Browsers themselves no, but there's many apps out there based on browser tech (e.g. electron apps). Also many apps shipping with their own JVM or other JIT engine.
Anecdote incoming, my pet project is based on electron, I am currently building a mac x86 version but don't plan to ship an ARM version (since testing it without an actual physical mac is going to be even more difficult / impossible).
Ah, the question is whether Darwin enforces W^X, because if so, the problem becomes very easy. Then you re-translate whenever a page becomes executable [again].