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@ -43,22 +43,15 @@ systems Engineering</a>. We hope that xv6 will be useful in other
courses too. This page collects resources to aid the use of xv6 in
other courses, including a commentary on the source code itself.
<p><font color="red">Status: The xv6 code is in pretty good shape, but
the commentary is rough.</font>
<h2>History and Background</h2>
<p>For many years, MIT had no operating systems course. In the fall
of 2002, Frans Kaashoek, Josh Cates, and Emil Sit created a new,
experimental course (6.097) to teach operating systems engineering.
In the course lectures, the class worked through <a href="#v6">Sixth
Edition Unix (aka V6)</a> using John Lions's famous commentary. In
the lab assignments, students wrote most of an exokernel operating
system, eventually named Jos, for the Intel x86. Exposing students to
multiple systems&ndash;V6 and Jos&ndash;helped develop a sense of the
spectrum of operating system designs. In the fall of 2003, the
experimental 6.097 became the official course 6.828; the course has
been offered each fall since then.
<p>For many years, MIT had no operating systems course. In the fall of 2002,
one was created to teach operating systems engineering. In the course lectures,
the class worked through <a href="#v6">Sixth Edition Unix (aka V6)</a> using
John Lions's famous commentary. In the lab assignments, students wrote most of
an exokernel operating system, eventually named Jos, for the Intel x86.
Exposing students to multiple systems&ndash;V6 and Jos&ndash;helped develop a
sense of the spectrum of operating system designs.
<p>
V6 presented pedagogic challenges from the start.
@ -80,27 +73,18 @@ uniprocessors such as
enabling/disabling interrupts) and helps relevance.
Finally, writing a new system allowed us to write cleaner versions
of the rougher parts of V6, like the scheduler and file system.
<p> 6.828 substituted xv6 for V6 in the fall of 2006. Based on
that experience, we cleaned up rough patches of xv6. Since then, xv6
has stabilized, so we are making it available in the hopes that others
will find it useful too.
<p>
6.828 uses both xv6 and Jos.
Courses taught at UCLA, NYU, Peking University, Stanford, Tsinghua,
and University Texas (Austin) have used
Jos without xv6; we believe other courses could use
xv6 without Jos, though we are not aware of any that have.
6.828 substituted xv6 for V6 in the fall of 2006.
<h2>Xv6 sources</h2>
The latest xv6 is <a href="xv6-rev5.tar.gz">xv6-rev5.tar.gz</a>.
We distribute the sources in electronic form but also as
a printed booklet with line numbers that keep everyone
together during lectures. The booklet is available as
<a href="xv6-rev5.pdf">xv6-rev5.pdf</a>.
The xv6 source code is licensed under the traditional <a href="http://www.opensource.org/licenses/mit-license.php">MIT license</a>;
see the LICENSE file in the source distribution.
The latest xv6 is <a href="xv6-rev5.tar.gz">xv6-rev5.tar.gz</a>. We distribute
the sources in electronic form but also as a printed booklet with line numbers
that keep everyone together during lectures. The booklet is available as <a
href="xv6-rev5.pdf">xv6-rev5.pdf</a>. The xv6 source code is licensed under
the traditional <a href="http://www.opensource.org/licenses/mit-license.php">MIT
license</a>; see the LICENSE file in the source distribution. To help students
read through xv6 and learn about the main ideas in operating systems we also
distribute a <a href="book-rev6.pdf">textbook/commentary</a> for the latest xv6.
<p>
xv6 compiles using the GNU C compiler,
@ -115,89 +99,10 @@ can be found on the <a href="../2010/tools.html">6.828 tools page</a>.
<h2>Xv6 lecture material</h2>
In 6.828, the lectures in the first half of the course introduce the
PC hardware, the Intel x86, and then xv6. The lectures in the second
half consider advanced topics using research papers; for some, xv6
serves as a useful base for making discussions concrete. The lecture
notes are available from the 6.828 schedule page, and the chapters of
the commentary are below.
<h2>Xv6 commentary (rough)</h2>
<p>The chapters are rough drafts.
<p>Introduction yet to be written.<br>
<ul>
<li>read with the code side by side
<li>code references look like (xxxx) or (xxxx-yyyy) in small text.
<li><a href="xv6-rev5.pdf">this pdf</a> is the one with matching line numbers.
<li>each chapter starts with an introduction to the topic,
spends most of the text on code,
and then wraps up talking about how xv6
compares to real-world operating systems.
</ul>
<a href="unix.pdf">Chapter 0: Operating system interfaces</a>
<blockquote>
The Unix system call interface. (rev 4)
</blockquote>
<a href="boot.pdf">Chapter 1: Bootstrap</a>
<blockquote>
From power on to kernel start. (rev 4)
</blockquote>
<a href="mem.pdf">Chapter 2: Processes</a>
<blockquote>
Memory and process allocation, segments, the first user process. (rev 4)
</blockquote>
<a href="trap.pdf">Chapter 3: Traps</a>
<blockquote>
Low-level trap mechanism, trap handler, system call arguments, sbrk, fork.
</blockquote>
<a href="lock.pdf">Chapter 4: Locks</a>
<blockquote>
Locks and interrupts.
</blockquote>
<a href="sched.pdf">Chapter 5: Scheduling and coordination</a>
<blockquote>
Scheduling, sleep and wakeup, pipes, wait and exit.
</blockquote>
<a href="disk.pdf">Chapter 6: Buffer cache</a>
<blockquote>
Buffer cache and IDE disk driver.
</blockquote>
<a href="fsdata.pdf">Chapter 7: File system data</a>
<blockquote>
Block in use bitmap, block allocation, inode structure, inode contents,
directories, path names.
</blockquote>
<a href="fscall.pdf">Chapter 8: File system calls</a>
<blockquote>
FIle descriptors, open, close, dup, read, write.
</blockquote>
<a href="exec.pdf">Chapter 9: Exec</a>
<blockquote>
Exec
</blockquote>
Appendix A: Low-level C and inline assembly
<blockquote>
Intro to C and inline assembly for people who only know Java (say).
Examples drawn entirely from xv6 source.
</blockquote>
Appendix B: Additional drivers.
<blockquote>
Keyboard, screen, probably MP hardware.
</blockquote>
In 6.828, the lectures in the first half of the course cover the xv6 sources and
text. The lectures in the second half consider advanced topics using research
papers; for some, xv6 serves as a useful base for making discussions concrete.
The lecture notes are available from the 6.828 schedule page.
<a name="v6"></a>
<h2>Unix Version 6</h2>