Acquiring Source Code for PAs

Getting Source Code

Go back to the home directory by

cd ~

Usually, all works unrelated to system should be performed under the home directory. Other directories under the root of file system (/) are related to system. Therefore, do NOT finish your PAs and Labs under these directories by sudo.

Now acquire source code for PA by the following command:

git clone https://github.com/NJU-ProjectN/ics2015

A directory called ics2015 will be created. This is the project directory for PAs. Details will be explained in PA1.

Compiling and Running NEMU

Before compiling the project, you should install the readline library:

apt-get install libreadline-dev

Another important thing to do is git configuration. Issue the following commands:

git config --global user.name "141220000-Zhang San"    # your student ID and name
git config --global user.email "zhangsan@foo.com"    # your email
git config --global core.editor vim            # your favorite editor
git config --global color.ui true

You should configure git with your student ID, name, and email. This finishes git configuration.

Finally, you should modify the STU_ID variable in config/Makefile.git:

STU_ID=141220000            # your student ID

Now enter the project directory, and compile the project by make:

make

If nothing goes wrong, NEMU will be compiled successfully.

To perform a fresh compilation, type

make clean

to remove the old compilation result, then make again.

To run NEMU, type

make run

However, you will see an error message:

nemu: nemu/src/cpu/reg.c:21: reg_test: Assertion `(cpu.gpr[check_reg_index(i)]._16) == (sample[i] & 0xffff)' failed.

This message tells you that the program has triggered an assertion fail at line 21 of the file nemu/src/cpu/reg.c. If you do not know what is assertion, blame the 程序设计基础 course. If you go to see the line 21 of nemu/src/cpu/reg.c, you will discover the failure is in a test function. This failure is expected, because you have not implemented the register structure correctly. Just ignore it now, and you will fix it in PA1.

To debug NEMU with gdb, type

make gdb

Development Tracing

Once the compilation succeeds, the change of source code will be traced by git. Type

git log

If you see something like

commit 4072d39e5b6c6b6837077f2d673cb0b5014e6ef9
Author: tracer-ics2015 <tracer@njuics.org>
Date:   Sun Jul 26 14:30:31 2015 +0800

    > compile NEMU
    141220000
    user
    Linux debian 3.16.0-4-686-pae #1 SMP Debian 3.16.7-3 i686 GNU/Linux
     14:30:31 up  3:44,  2 users,  load average: 0.28, 0.09, 0.07
    3860572d5cc66412bf85332837c381c5c8c1009f

this means the change is traced successfully.

If you see the following message while executing make, this means the tracing fails.

fatal: Unable to create '/home/user/ics2015/.git/index.lock': File exists.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.

Try to clean the compilation result and compile again:

make clean
make

If the error message above always appears, please contact us as soon as possible.

Local Commit

Although the development tracing system will trace the change of your code after every successful compilation, the trace record is not suitable for your development. This is because the code is still buggy at most of the time. Also, it is not easy for you to identify those bug-free traces. Therefore, you should trace your bug-free code manually. But before continuing, please read this git tutorial to learn some basics of git.

When you want to commit the change, type

git add .
git commit --allow-empty

The --allow-empty option is necessary, because usually the change is already committed by development tracing system. Without this option, git will reject no-change commits. If the commit succeeds, you can see a log labeled with your student ID and name by

git log

To filter out the commit logs corresponding to your manual commit, use --author option with git log. For details of how to use this option, RTFM.

Submission

Finally, you should submit your project to the submission website. To submit PA0, put your report file (ONLY .pdf file is accepted) under the project directory. Then issue

make submit

This command does 2 things:

1. Clean all unnecessary files for submission
2. Create an archive containing the source code and your report. The archive is located in the father directory of the project directory, and it is named by your student ID set in Makefile.

If nothing goes wrong, transfer the archive to your host. Open the archive to double check whether everything is fine. And you can manually submit this archive to the submission website.

RTFSC and Enjoy

If you are new to GNU/Linux and finish this tutorial by yourself, congratulations! You have learn a lot! The most important, you have learn searching the Internet and RTFM for using new tools and trouble-shooting. With these skills, you can solve lots of troubles by yourself during PAs, as well as in the future.

In PA1, the first thing you will do is to RTFSC. If you have troubles during reading the source code, go to RTFM:

• If you can not find the definition of a function, it is probably a library function. Read man for more information about that function.
• If you can not understand the code related to hardware details, refer to the i386 manual.

By the way, you will use C language for programming in all PAs. Here is an excellent tutorial about C language. It contains not only C language (such as how to use printf() and scanf()), but also other elements in a computer system (data structure, computer architecture, assembly language, linking, operating system, network...). It covers most parts of this course. You are strongly recommended to read this tutorial.

Finally, enjoy the journey of PAs, and you will find hardware is not mysterious, so does the computer system! But remember:

• The machine is always right.
• Every line of untested code is always wrong.
• RTFM.