Welcome to Nachos for Java. We believe that working in Java rather than C++ will greatly simplify the development process by preventing bugs arising from memory management errors, and improving debugging support.
- Additional software
Nachos requires the Java Devlopment Kit, version 1.5 or later. A recent version of the JDK is already installed on the instructional machines. If you are working at home, you will need to download the JDK. It is available from:
http://www.oracle.com/technetwork/java/javase/downloads/index.html
Please DO NOT DOWNLOAD the JDK into your class account! Use the preinstalled version instead.
The build process for Nachos relies on GNU make. If you are running on one of the instructional machines, it is the default make in your path. If you are running on Windows, you will need to download and install a port. The most popular is the Cygwin toolkit, available at:
The Cygwin package includes ports of most common GNU utilities to Windows.
For projects 2 and 3, you will need a MIPS cross compiler, which is a specially compiled GCC which will run on one architecture (e.g. x86) and produce files for the MIPS processor. These compilers are already installed on the instructional machines, and are available in the directory specified by the $ARCHDIR environment variable.
If you are working at home, you will need to get a cross-compiler for yourself. The cross-compiler for Linux is available from the project web page, along with instructions for installing it.
- Compiling Nachos
You should now have a directory called nachos, containing a Makefile, this README, and a number of subdirectories.
The "nachos" command invokes java to run Nachos. It is a script that we have configured to already be in your path, and it is also available in the "bin" directory.
To compile Nachos, go to the subdirectory for the project you wish to compile (I will assume 'proj0/' for Project 0 in these examples), and run make:
cd proj0
make
This will compile those portions of Nachos which are relevant to the project, and place the compiled .class files in the proj0/nachos directory.
You can now test Nachos from the proj0/ directory with:
nachos
You should see output resembling the following:
nachos 5.0j initializing... config interrupt timer elevators user-check grader *** 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 Machine halting!
Ticks: total 24750, kernel 24750, user 0 Disk I/O: reads 0, writes 0 Console I/O: reads 0, writes 0 Paging: page faults 0, TLB misses 0 Network I/O: received 0, sent 0
This is the correct output for the "bare bones" Nachos, without any of the features you will add during the projects.
If you are working on a project which runs user programs (projects 2-3), you will also need to compile the MIPS test programs with:
make test
- Command Line Arguments
For a summary of the command line arguments, run:
nachos -h
The commands are:
-d <debug flags>
Enable some debug flags, e.g. -d ti
-h
Print this help message.
-s <seed>
Specify the seed for the random number generator
-x <program>
Specify a program that UserKernel.run() should execute,
instead of the value of the configuration variable
Kernel.shellProgram
-z
print the copyright message
-- <grader class>
Specify an autograder class to use, instead of
nachos.ag.AutoGrader
-# <grader arguments>
Specify the argument string to pass to the autograder.
-[] <config file>
Specifiy a config file to use, instead of nachos.conf
Nachos offers the following debug flags:
c: COFF loader info
i: HW interrupt controller info
p: processor info
m: disassembly
M: more disassembly
t: thread info
a: process info (formerly "address space", hence a)
To use multiple debug flags, clump them all together. For example, to monitor coff info and process info, run:
nachos -d ac
- nachos.conf
When Nachos starts, it reads in nachos.conf from the current directory. It contains a bunch of keys and values, in the simple format "key = value" with one key/value pair per line. To change the default scheduler, default shell program, to change the amount of memory the simulator provides, or to reduce network reliability, modify this file.
Machine.stubFileSystem: Specifies whether the machine should provide a stub file system. A stub file system just provides direct access to the test directory. Since we're not doing the file system project, this should always be true.
Machine.processor: Specifies whether the machine should provide a MIPS processor. In the first project, we only run kernel code, so this is false. In the other projects it should be true.
Machine.console: Specifies whether the machine should provide a console. Again, the first project doesn't need it, but the rest of them do.
Machine.disk: Specifies whether the machine should provide a simulated disk. No file system project, so this should always be false.
ElevatorBank.allowElevatorGUI: Normally true. When we grade, this will be false, to prevent malicious students from running a GUI during grading.
NachosSecurityManager.fullySecure: Normally false. When we grade, this will be true, to enable additional security checks.
Kernel.kernel: Specifies what kernel class to dynmically load. For proj1, this is nachos.threads.ThreadedKernel. For proj2, this should be nachos.userprog.UserKernel. For proj3, nachos.vm.VMKernel. For proj4, nachos.network.NetKernel.
Processor.usingTLB: Specifies whether the MIPS processor provides a page table interface or a TLB interface. In page table mode (proj2), the processor accesses an arbitrarily large kernel data structure to do address translation. In TLB mode (proj3 and proj4), the processor maintains a small TLB (4 entries).
Processor.numPhysPages: The number of pages of physical memory. Each page is 1K. This is normally 64, but we can lower it in proj3 to see whether projects thrash or crash.
Documentation:
The JDK provides a command to create a set of HTML pages showing all classes and methods in program. We will make these pages available on the webpage, but you can create your own for your home machine by doing the following (from the nachos/ directory):
mkdir ../doc
make doc
Troubleshooting:
If you receive an error about "class not found exception", it may be because you have not set the CLASSPATH environment variable. Add the following to your .cshrc:
setenv CLASSPATH .
or to your .bashrc:
export CLASSPATH=.
- Credits
Nachos was originally written by Wayne A. Christopher, Steven J. Procter, and Thomas E. Anderson. It incorporates the SPIM simulator written by John Ousterhout. Nachos was rewritten in Java by Daniel Hettena.
This version of Nachos was borrowed from CS162 at Berkeley and modified for use at UCSD.
- Copyright
Copyright (c) 1992-2001 The Regents of the University of California. All rights reserved.
Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without written agreement is hereby granted, provided that the above copyright notice and the following two paragraphs appear in all copies of this software.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.