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Nachos Projects Overview
and Project 1
TA : 吳哲榮
2010/10/21
Outline
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What’s Nachos?
Why do we use Nachos?
Nachos Project Overview
Nachos installation
Nachos Assignment 1
Reference
What’s Nachos?
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Nachos
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Not Another Completely Heuristic Operating System
Developed by Tom Anderson and his
students at UC, Berkeley.

http://www.cs.washington.edu/homes/tom/nachos/
What’s Nachos?
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Nachos is an instrumental software that
allows students to study and modify a “real”
operating system.
The only difference between Nachos and a
real operating system is that Nachos runs a
Unix process, whereas a real operating
system runs on a real machine.
What’s Nachos?

Nachos simulates a
MIPS machine (MIPS
R2/3000) on the host
system (Unix, Linux,
etc.)
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Conceptually, Nachos
has two modes of
execution, namely,
MIPS simulator and
Nachos “kernel”
Reference :
http://course.cs.ust.hk/comp252/web07fall/Lab1/Nachos%20architecture/
nachos.ps
Why do we use Nachos?
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For understanding operating system
concepts, nothing is better than building an
operating system.
Nachos is simpler than UNIX.
Simulator makes debugging easier.
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Deterministic
Nachos Project Overview
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The project for this course is to build an
operating system for scratch. The project
contains four phases, corresponding to each
of the major pieces of a modern OS.
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Multiprogramming
Thread management
File Systems and Virtual Memory
Networking
Nachos Installation
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Platforms you may use
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Unix, Linux, Linux over VMware, or Cygwin.
Environment
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Checking g++ version
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g++ -v
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Both g++ 3.3.3 or g++ 3.2.2 are ok.
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If your current gcc version is 4.x.x version, you
should install the gcc 3.4.6 version. The gcc 3.4.6
version is the watershed.
Nachos Installation
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Download the gcc source code.
http://ftp.twaren.net/Unix/GNU/gnu/gcc/
The following command is the installing flow.
# wget http://ftp.twaren.net/Unix/GNU/gnu/gcc/gcc-3.3.3/ gcc-3.3.3.tar.gz
# tar zxvf gcc-3.3.3.tar.gz
# mkdir gcc-build
# cd gcc-build/
# ../gcc-3.3.3/configure --prefix=/usr/local/gcc-3.3.3 --enable-threads=posix --disablechecking --enable--long-long --host=i386-redhat-linux --with-system-zlib --enablelanguages=c,c++,java
# make
# make install
# export PATH=/usr/local/gcc-3.3.3/bin/:$PATH
Add the new gcc path to the current command searching path.
# export LD_LIBRARY_PATH=/usr/local/gcc-3.3.3/lib/:$LD_LIBRARY_PATH
Add the related library to the current library searching path.
Nachos Installation
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Get Nachos-4.0
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Get Cross Compiler
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http://cc.ee.ntu.edu.tw/~farn/courses/OS2010/nachos/nachos4.0.tar.gz
http://cc.ee.ntu.edu.tw/~farn/courses/OS2010/nachos/mipsdecstation.linux-xgcc.tgz
Move Cross Compiler to /
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mv ./mips-decstation.linux-xgcc.tgz /
Untar Cross Compiler
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cd /
tar zxvf mips-decstation.linux-xgcc.tgz
Nachos Installation
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Untar Nachos
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Make Nachos-4.0
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tar zxvf nachos-4.0.tar.gz
cd ./nachos-4.0/code
make
Test
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cd ./userprog
./nachos –e ../test/test1
./nachos –e ../test/test2
Nachos Installation

You should see the result of test1
Nachos Installation
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You should see the result of test2
Some Important Things
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Nachos arguments
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Help
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Debugging Mode
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./nachos –s
Execute files
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./nachos –h
./nachos –e [file_name]
Recompilation of modified nachos code
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cd nachos-4.0/code
make clean (optional)
make
Nachos Assignment 1
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Abstract
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The assignment is to support multiprogramming. We give
some of the code you need, and you have to complete the
system.
Try execute two programs at the same time
on Nachos
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cd ./userprog
./nachos –e ../test/test1 –e ../test/test2
you should see the following result.
Result of simultaneously execution
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Total threads number is 2
Thread ../test/test1 is executing.
Thread ../test/test2 is executing.
Print integer:9
Print integer:8
Print integer:7
Print integer:20
Print integer:21
Print integer:22
Print integer:23
Print integer:24
Print integer:6
Print integer:7
Print integer:8
Print integer:9
Print integer:10
Print integer:12
Print integer:13
Print integer:14
Print integer:15
Print integer:16
Print integer:16
Print integer:17
Result of simultaneously execution
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Print integer:18
Print integer:19
Print integer:20
Print integer:17
Print integer:18
Print integer:19
Print integer:20
Print integer:21
Print integer:21
Print integer:23
Print integer:24
Print integer:25
return value:0
Print integer:26
return value:0
No threads ready or runnable, and no pending interrupts.
Assuming the program completed.
Machine halting!
Ticks: total 800, idle 67, system 120, user 613
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
Why the output result of executing
two program simultaneously differs
from the result of executing two
programs separately?
Why should you do?

Trace Nachos
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Read *.h and *.cc to understand the whole system
and see how it is implemented.
You might use some documentations to help
yourself understand the system.
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A Road Map Through Nachos
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http://cc.ee.ntu.edu.tw/~farn/courses/OS2010/ref/Nachos%20Road%20Map.pdf
Trace for NachoOS-4.0 with GLOBAL

http://cc.ee.ntu.edu.tw/~farn/courses/OS2010/nachos/HTML/index.html
Hints
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To know why the result is wrong, you may
trace the following files.
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nachos-4.0/code/userprog/addrspace.h
nachos-4.0/code/userprog/addrspace.cc
nachos-4.0/code/userprog/userkernel.cc
nachos-4.0/code/machine/translate.h
nachos-4.0/code/machine/translate.cc
Hints
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You have to modify the Nachos code to
achieve the correct result.
You may try to modify the following functions

nachos-4.0/code/userprog/addrspace.cc
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constructor
destructor
initRegister
Load
Assignment Requirements
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2 person per team
Assignment Report (11/18 on the class)
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Prepare a presentation about the following topics:
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Why the result is not congruent with expected
How you modified Nachos to make it support
multiprogramming – important code segments
Everything you consider important
Hand in your reports.
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Please compress the following in a .zip.
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modified source code(s) with path
presentation power-point
final report
E-mail your .zip
(project1_b99901000_b99901001.zip) to TA.
Deadline: 2010/11/18 23:59
Grading Policy
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Progress Report
Correct Result
Report
20%
30%
50%
Reference
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Author’s Web Page
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http://www.cs.washington.edu/homes/tom/nachos/
Thomas Narten's Nachos Roadmap

http://www.cs.duke.edu/~narten/110/nachos/main/main.html

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