CompSci 143A: Principles of Operating System

Pintos Project Lab 0: Getting Real

This assignment is to prepare you for the later Pintos lab. You will mainly do a simple programming exercise to add a tiny kernel monitor to Pintos. Note that this assignment is simpler than the next lab as it is intentionally designed to help you warm up. This lab is borrowed from JHU's CS 318/418/618 course by Ryan Huang. Ryan borrwed part of this project's description and exercise from the MIT 6.828 and Caltech CS 124 course.

Lab 0 Requirements

0. Project 0 Design Document

Before you turn in your project, you must copy the lab 0 design document template into your source tree under the name pintos/src/p0/DESIGNDOC and fill it in.

1. Booting Pintos

Read the 1. Introduction section to get an overview of Pintos. Have Pintos development environment setup as described in Project Setup. Afterwards, execute

$ cd pintos/src/threads
$ make
$ cd build
$ pintos --bochs -- run alarm-zero

You can only use Bochs in Openlab (instructions above use Bochs). Bochs will be useful for the 3. Project 1: Threads. If everything works, you should see Pintos booting in the Bochs emulator, and print Execution of 'alarm-zero' complete. near the end. In addition to the shell where you execute the command, a new graphic window of Bochs will also pop up printing the same messages. If you are remotely connecting to a machine, e.g., the Openlab machines, you should make sure you use X window option in your SSH client so that the window can open.

If you have configured QEMU on your own machine, you can run Pintos with QEMU as follows.

$ cd pintos/src/threads
$ make qemu

If everything works, you should see Pintos booting in the QEMU emulator, and print Boot complete. near the end. In addition to the shell where you execute the command, a new graphic window of QEMU will also pop up printing the same messages.

Exercise 0.1

Take a screenshot of the successful booting of Pintos in Bochs or QEMU, either in the terminal or Bochs/QEMU window. Put the screenshot under pintos/src/p0.

2. Kernel Monitor

At last, you will get to make a small enhancement to Pintos and write some code! In particular, when Pintos finishes booting, it will check for the supplied command line arguments stored in the kernel image. Typically you will pass some tests for the kernel to run, e.g., pintos -- run alarm-zero. If there is no command line argument passed, the kernel will simply finish up. This is a little boring. You task is to add a tiny kernel shell to Pintos so that when no command line argument is passed, it will run this shell interactively. Note that this is a kernel-level shell. In later projects, you will be enhancing the user program and file system parts of Pintos, at which point you will get to run the regular shell.

The code place for you to add this feature is in line 136 of threads/init.c with // TODO: no command line passed to kernel. Run interactively. You only need to make this monitor very simple. It starts with a prompt ICS143A> and waits for user input. When a newline is entered, it parses the input and checks if it is whoami. If it is whoami, print your name. Afterwards, the monitor will print the command prompt ICS143A> again in the next line and repeat. If the user input is exit, the monitor will quit to allow the kernel to finish. For the other input, print invalid command.

Exercise 0.2

Enhance threads/init.c to implement a tiny kernel monitor in Pintos. Feel free to add new source files in to the Pintos code base for this task, e.g., provide a readline library function. Refer to Adding Source Files for how to do so.

Hint: You may need to use some functions provided in lib/kernel/console.c, lib/stdio.c and devices/input.c.