OSTEP Chapter 15: Address Translation

This is part of our series going through OSTEP book chapters. The OSTEP textbook is freely available at Remzi's website if you like to follow along.This chapter extends the CPU virtualization playbook to memory. It's the same recipe: let the program run directly on the hardware, but interpose at carefully chosen points so the OS retains control. For memory, this happens at every memory access. Every load, store, and instruction fetch gets translated by hardware from a virtual to a physical address.The mechanism here is called dynamic relocation, dating to the late 1950s. The base register holds the physical address where the process's address space starts, the bounds register holds its size. On every memory reference the hardware adds base and checks against bounds. If the address is out of range, the CPU raises an exception, and the OS kills the offender.This takes collaboration between hardware and the OS. Hardware provides privileged mode, the base/bounds registers, translation…