No. The OS's software doesn't individually read each instruction and decide what to do with it.
It passes it off to the hardware (CPU) which runs the instructions.
It passes it off to the hardware (CPU) which runs the instructions.
See also: Jazelle DBX.
Hell, on modern x86 processors, many “native” instructions are actually a series of micro-ops for a mostly undocumented and mostly poorly understood microcode architecture that differs from the natively documented instruction set.
It’s turtles all the way down.
I don’t know how I feel about micro-ops being executed in hardware - I mostly agree, but also, microcode updates exist…
https://github.com/google/security-research/blob/master/pocs...
Tavis spells it out there pretty quickly:
“ The simplest instructions (add, sub, mov, etc) are all implemented in hardware. The more complicated instructions like rdrand, fpatan and cmpxchg are microcoded. You can think of them as a bit like calling into a library of functions written in that RISC-like code.”