CSE 120 Nachos Project 0: Install

Summer 2010

Due: Thursday, July 1, at 11:59PM

Note: This is an individual assignment. Each student must submit a copy of their session's output.

In this "project" you will familiarize yourself with installing and compiling the Nachos distribution. You will also practice using the debugger on the nachos executable as it runs. The tutorial below should not take that much time at all; if you seem to be having serious problems, send us mail immediately.

  1. Download or copy the nachos distribution, and unpack it using gunzip and tar (see Distributions in the class project guide):
    % tar xvzf cse120su10-nachos.tar.gz

    Be sure that you have "prepped" your account for the class. If you were not prompted to prep "cs120u" when you logged in, do it from the command line:

    % prep cs120u

    Build a nachos executable using the gmake command in the code directory:

    % cd nachos-3.4/code
    % gmake

    This will create versions of the nachos executable in various subdirectories. We will be using the threads directory for the upcoming project 1, so let's use that nachos exectuable. Run it without any arguments -- it should produce output similar to the following:

    [cs120f@sdcc7]$ cd threads
    [cs120f@sdcc7]$ ./nachos
    *** thread 0 looped 0 times
    *** thread 1 looped 0 times
    *** thread 0 looped 1 times
    *** thread 1 looped 1 times
    *** thread 0 looped 2 times
    *** thread 1 looped 2 times
    *** thread 0 looped 3 times
    *** thread 1 looped 3 times
    *** thread 0 looped 4 times
    *** thread 1 looped 4 times
    No threads ready or runnable, and no pending interrupts.
    Assuming the program completed.
    Machine halting!
    Ticks: total 130, idle 0, system 130, user 0
    Disk I/O: reads 0, writes 0
    Console I/O: reads 0, writes 0
    Paging: faults 0
    Network I/O: packets received 0, sent 0
    Cleaning up...

  2. Nachos is like any other program in that it starts by running the main() procedure. In Nachos, main() is in threads/main.cc. If you examine threads/main.cc, you will see that you are executing the ThreadTest function (in threadtest.cc). It is the printf in the SimpleTest class that produced the initial output when you ran the nachos executable. ThreadTest is a simple example of a concurrent program. In this case there are two independent threads of control executing "at the same time" and accessing the same data.

    Your first goal is to understand the thread primitives used by this program, and to do some experiments to help you understand what really happens with multiple threads at runtime. To understand the execution path, trace through the code for the simple test case. See the notes in Tracing and Debugging Nachos Programs from the Duke equivalent of this course for some tips on how to do this.

    Specifically, run the nachos executable in gdb (be sure you are in the threads subdirectory):

    % gdb ./nachos

    Set a breakpoint in SimpleThread (try using tab completion!):

    (gdb) break SimpleThread(int)

    Start running the program:

    (gdb) run

    Step through the program to see what happens during the execution:

    (gdb) n

    Continue to step through until you see "*** thread 1 looped 3 times" printed. Print out the stack for the current thread, and print the value of the variables "which" and "num":

    (gdb) where
    (gdb) print num
    (gdb) print which

    We're done stepping, continue the program:

    (gdb) c

    Copy the output of your session of running gdb on nachos and paste it into a file named project0.txt. Be sure to include all of the commands that you executed and all of the output generated. Then run:

    $ turnin project0.txt

    Be sure to submit your output by the deadline (turnin will be disabled by then).