Comment by bun_at_work
5 years ago
I can only speculate, but Apple seems to have very tightly coupled software and hardware. Since this coupling probably holds trade secrets (which we don't know about by definition), it seems likely to me that they are controlling access to as much of the stack as they can while still protecting those secrets.
Yes, but that doesn’t really make sense for things they have already shipped: researchers have to reverse engineer those for what seems like no reason. For example, the newest iPhones have entirely custom privilege levels that are lateral to the typical ARM exception levels and entered using proprietary instructions that their own silicon understands. This is something you can find if you load the kernel into a disassembler and poke at it a bit. But Apple doesn’t mention it at all or document it…what’s the point? Why put up such petty barriers in the face of people trying to audit this?
Likely the documentation that does exist internal would take a relatively large amount of cost to extract without pulling other stuff with it.
But they go through the effort of stripping all mentions of these things from the source code they release?
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wouldn’t the public interest in that be obvious at design time? why would apple write internal docs in such a way that they could never be released?