The details you're talking about are pretty much just details; for instance, a foreign function interface for C functions (and thus system calls) is a pretty straightforward exercise that involves just a bit about the C ABI for your platform.
It's much easier to teach someone who knows how to build a basic register machine how to set up the stack for a call to a C function than it is to teach someone who doesn't know how a register machine works how to build one.
Also: there are reasons you might want to build a simple VM that has no access to system services and no notion of an exception. BPF is a good example of such a virtual machine.
If there's something frustrating about this article to me, it's that it lacks a motivating example. Why would you want to build this VM? What are you compiling down to it from?
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The details you're talking about are pretty much just details; for instance, a foreign function interface for C functions (and thus system calls) is a pretty straightforward exercise that involves just a bit about the C ABI for your platform.
It's much easier to teach someone who knows how to build a basic register machine how to set up the stack for a call to a C function than it is to teach someone who doesn't know how a register machine works how to build one.
Also: there are reasons you might want to build a simple VM that has no access to system services and no notion of an exception. BPF is a good example of such a virtual machine.
If there's something frustrating about this article to me, it's that it lacks a motivating example. Why would you want to build this VM? What are you compiling down to it from?