CMSC 421: Principles of Operating Systems

Final Study Guide

General

Ensure you can perform decimal to hexadecimal conversion, and vice versa.

Memory Systems

• What is the purpose of mmap()?
• What are the different ways that an operating system provides contiguous virtual addresses, even though physical RAM may be fragmented?
• Given the page table on slide 12 of lecture 14, what is the physical address given the virtual address 0xF?
• Within a page table, what do the protection and valid bits mean?
• What are some issues when restarting instructions?
• What is the benefit of a hierarchical paging system?
• What happens when a page fault occurs?
• What are the advantages and disadvantages of the various page replacement algorithms?
• What is an overlay? What is swapping? How are they implemented?
• What is the purpose of the different program segments?

Device Drivers

• What is the difference between character, block, and network devices? Give examples of each.
• How does a kernel know which device driver to use given a particular piece of hardware?
• What is involved when loading a program? When loading a kernel?
• What are the steps involved in handling a hardware interrupt? What is a top-half versus bottom-half?

Linux Kernel Modules

• What is the difference between a driver's init, probe, remove, and exit functions? When are they called?
• What is the relationship between a function's return value and the errno variable?
• What is the difference between user and interrupt context? Give an example of each.
• What do the tokens __init, __exit, and __user mean?
• How does a driver allocate memory?
• What is the difference between a mutex and a spinlock? When would a driver use one or the other?
• What are kthreads? What are completion variables?

Mass Storage

• What schedulers exist for a hard disk drives? What are the advantages and disadvantages of each?
• What is the difference between a partition and a volume? What are the different ways that files are stored?
• Why does the operating system have a system-wide open file table? What does it do with it?
• How do filesystems allocate space for files?
• Why do manufacturers recommend against defragging a solid state drive?
• What is a FAT? Where is it stored?
• What features of UBIFS make it desirable for solid state drives?

Kernel Security

• What do CPU rings do?
• Name three ways how an access matrix could be implemented.
• In Linux, what does struct cred do?
• What kinds of capabilities does Linux support?

Embedded I/O

• What are four ways interrupts can be generated?
• What are scatter/gather lists used for?
• What is the difference between half-duplex and full-duplex? Serial versus parallel?
• What values does a DMA engine use?