Nachos Projects Overview and Project 1 TA : 王映智 2007/10/24

Outline What’s Nachos? Why do we use Nachos? Nachos Project Overview Nachos installation Nachos Assignment 1 Reference

What ’ s Nachos? Nachos  Not Another Completely Heuristic Operating System Developed by Tom Anderson and his students at UC, Berkeley. 

What ’ s Nachos? 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.) Conceptually, Nachos has two modes of execution, namely, MIPS simulator and Nachos “kernel” Reference : nachos.ps

Why do we use Nachos? For understanding operating system concepts, nothing is better than building an operating system. Nachos is simpler than UNIX. Simulator makes debugging easier.  Deterministic

Nachos Project Overview 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.  Multiprogramming  Thread management  File Systems and Virtual Memory  Networking

Nachos Installation Platforms you may use  Unix, Linux, Linux over VMware, or Cygwin. Environment  Checking g++ version g++ -v  Both g or g are ok. Get Nachos-4.0  os-4.0.tar.gz os-4.0.tar.gz wget

Nachos Installation Get Cross Compiler  hos/mips-decstation.linux-xgcc.tgz Move Cross Compiler to / mv./mips-decstation.linux-xgcc.tgz / Untar Cross Compiler cd / tar zxvf mips-decstation.linux-xgcc.tgz

Nachos Installation Untar Nachos tar zxvf nachos-4.0.tar.gz Make Nachos-4.0 cd./nachos-4.0/code make Test cd./userprog./nachos –e../test/test1./nachos –e../test/test2

Nachos Installation You should see the result of test1

Nachos Installation You should see the result of test2

Some Important Things Nachos arguments  Help./nachos –h  Debugging Mode./nachos –s  Execute files./nachos –e [file_name] Recompilation of modified nachos code cd nachos-4.0/code make clean (optional) make

Nachos Assignment 1 Abstract  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 cd./userprog./nachos –e../test/test1 –e../test/test2 you should see the following result.

Result of simultaneously execution 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:17

Result of simultaneously execution 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: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  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. A Road Map Through Nachos  Trace for NachoOS-4.0 with GLOBAL 

Hints To know why the result is wrong, you may trace the following files.  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/userprog/translate.h  nachos-4.0/code/userprog/translate.cc

Hints 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 constructor destructor initRegister Load

Assignment Requirements Progress Report (11/7 on the class)  Prepare a presentation about the following topics: Your understanding about Nachos Your progress  Installation of Nachos  Knowing why the result is not congruent with expected  Your Plan for modifying Nachos Everything you consider important

Assignment Requirements Assignment Report (11/21 on the class)  Prepare a presentation about the following topics: 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. Please compress your code with tar.  source code only  tar zcvf r tar.gz nachos-4.0 your code and presentation files(report) to TA Deadline: 2007/11/21 23:59

Grading Policy Progress Report20% Correct Result30% Report50%

Reference Author’s Web Page  Thomas Narten's Nachos Roadmap  Other Reference   