This chapter deals with addressing techniques. Luckily, an operating system is not forced to keep track of physical memory all by itself; today's microprocessors include several hardware circuits to make memory management both more efficient and more robust so that programming errors cannot cause improper accesses to memory outside the program.
As in the rest of this book, we offer details in this chapter on how 80 × 86 microprocessors address memory chips and how Linux uses the available addressing circuits. You will find, we hope, that when you learn the implementation details on Linux's most popular platform you will better understand both the general theory of paging and how to research the implementation on other platforms.
This is the first of three chapters related to memory management; Chapter 8 discusses how the kernel allocates main memory to itself, while Chapter 9 considers how linear addresses are assigned to processes.