CS 332 s20 — Interrupts and System Calls

Table of Contents

1 Reading: Limited Direct Execution

Read Chapter 6 (p. 55–68) of the OSTEP book. It builds on the dual-mode execution reading from Wednesday and discusses how this switch from user mode to kernel mode actually occurs.

Important terms:

  • system call
  • trap
  • trap table
  • trap handler

Key questions to consider as you read:

  • Where does the CPU run after a trap?
  • What is the trap handler written in? C? Java?
  • What stack does it use?
  • Is the work the CPU had been doing before the trap lost forever?
  • If not, how does the CPU know how to resume that work?

2 Video Notes

I'm trying something different today with this narrated slideshow in place of text notes. It's a little rough, but I think it complements the reading well.1 I've uploaded the power point slides if you want those.

3 Homework

  1. Take the Week 2 quiz on Moodle. You must complete it by 9pm Wednesday, April 22.
  2. Remember that lab 1 is due 9pm April 20.

Footnotes:

1

My Simpson's reference when talking about disabling interrupts wasn't captured correctly. Go here to see what I was going for.