> I'll give a simple example: Burrough's 1961 product
But the key there is "simple" - I imagine that's a tiny fraction of the size and complexity of a modern smartphone ecosystem. Scaling it up to a device that can be manufactured at a profit and will sell hundreds of millions is surely more involved than "we could adopt such methods relatively inexpensive today".
That was a mainframe, actually. They're quite complex. The mechanism is simple. I have designs that apply it to a smartphone by a tiny change to the processor and its I/O system. Far as the hardware, that's it. For the software, the C (or Objective-C) compiler just has to use the appropriate tags or instructions when generating the binary. Any hand-written assembler, a tiny portion of the program, must do the same. That's it for the pointer & code protection. On a smartphone, this is the main SOC, drivers, part of the compiler, and any assembler functions. That's it.
There's no need to speculate, though. Several academic projects involving a few amateurs with six to seven digit funding have (a) modified processors for security, (b) modified toolchain to support it, and (c) ported BSD/Linux to it. Others did it for embedded systems. Their schemes are usually much more complex (see Cambrige CHERI processor). Unrealistic to think Apple can't do with 9+ digits less than what academics do with 6-7.
But the key there is "simple" - I imagine that's a tiny fraction of the size and complexity of a modern smartphone ecosystem. Scaling it up to a device that can be manufactured at a profit and will sell hundreds of millions is surely more involved than "we could adopt such methods relatively inexpensive today".