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Checkpoint start syscall lab

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Frans Kaashoek 2019-07-25 08:19:14 -04:00
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@ -215,41 +215,6 @@ initial file system. You just ran one of them: <tt>ls</tt>.
to declare an argv.
</ul>
<h2>System call tracing</h2>
<p>In this exercise you will modify the xv6 kernel to print out a line
for each system call invocation. It is enough to print the name of the
system call and the return value; you don't need to print the system
call arguments.
<p>
When you're done, you should see output like this when booting
xv6:
<pre>
...
fork -> 2
exec -> 0
open -> 3
close -> 0
$write -> 1
write -> 1
</pre>
<p>
That's init forking and execing sh, sh making sure only two file descriptors are
open, and sh writing the $ prompt. (Note: the output of the shell and the
system call trace are intermixed, because the shell uses the write syscall to
print its output.)
<p> Hint: modify the syscall() function in kernel/syscall.c.
<p>Run the programs you wrote in the previous exercises and inspect
the system call trace. Are there many system calls? Which systems
calls correspond to code in the applications you wrote above?
<p>Optional: print the system call arguments.
<h2>Optional: modify the shell</h2>
There are endless ways in which the shell could be extended. Here are