Finally, email the compressed zip file to sjengle@ucdavis.edu with the subject line "ECS150 Lab 3"

Interactive Grading

Interactive grading will take place in the Kemper Hall TA room. Interactive grading sign up sheets for lab 3 are located outside the Kemper Hall TA room. Please sign up ASAP. Grading will occur on:

• Tuesday March 16th, 4:00pm - 5:30pm
• Wednesday March 17th, 1:00pm - 5:00pm
• Thursday March 18th, 1:00pm - 4:30pm

Since interactive grading for this lab occurs at the end of the quarter, I am going to be strict about several issues:

• ALL group members must be present for interactive grading to begin.
• All group members must be ON TIME. If any group member is more than 10 minutes late, the entire group may have to reschedule.
• If the handin instructions are not followed correctly, 5% will be deducted from the final grade.

Hints and Tips

I am posting some hints and tips that may help some people get started. I have to thank all the students that stopped by today to help hash a lot of these problems out (and those students posting on the discussion board).

Also, all the line numbers I provide are the actual line numbers in the Minix source code. This means the line numbers do not correspond to the line numbers the book.

Part 1

First, if you are modifying /usr/src/kernel/tty.c, you will have to test your changes at the login prompt. This means you will have to test your changes when noname login: shows up (before you login to Minix). After you actually login, the shell sh is running (and sh defines its own actions for CTRL-P).

Next, you want to test if the user pressed CTRP-P. I recommend doing this in the function in_process (in tty.c). There are basically two different methods of testing if the user pressed CTRL-P. The easiest way is to make use of the C(c) macro defined in /usr/include/minix/keymap.h. Therefore you should be able to do something like:

Both if statements worked for me. The second method involves a little bit more work. You should notice that tty.c uses a field c_cc to test for control characters. For example, in the function in_process, you will see the line:

This actually checks to see if CTRL-H was pressed. We can use a similar method to check for CTRL-P. First, look at /usr/include/termios.h. Notice that c_cc is actually a field in the structure termios (lines 14-21). We will use this knowledge in a little bit.

Now we must define our own entry in c_cc. The indices into the c_cc array are defined on lines 65-75 and on lines 161-163. Lets add our own index VREPLACE on line 164. Since the last index was 13, we should do something like:

The next step is to define what control sequence VREPLACE actually corresponds to. This is done for all the other control sequences on lines 177 - 193. So we should add another define similar to:

The '\20' refers to the octal value for CTRL-P. (Note that some people had to actually use '\16' instead.)

The last step is to initialize c_cc[VREPLACE] to TREPLACE_DEF. We can do this by taking advantage of termios_defaults on line 120 of /usr/src/kernel/tty.c. We just need to add TREPLACE_DEF to the end of the definition, giving us:

PRIVATE struct termios termios_defaults = {
  TINPUT_DEF, TOUTPUT_DEF, TCTRL_DEF, TLOCAL_DEF, TSPEED_DEF, TSPEED_DEF,
  {
		TEOF_DEF, TEOL_DEF, TERASE_DEF, TINTR_DEF, TKILL_DEF, TMIN_DEF,
		TQUIT_DEF, TTIME_DEF, TSUSP_DEF, TSTART_DEF, TSTOP_DEF,
		TREPRINT_DEF, TLNEXT_DEF, TDISCARD_DEF, TREPLACE_DEF,
  },
};

Finally, you should be able to do the following test in in_process:

You will have to figure out where in in_process to place this check. Also, you still have to worry about catching the interger and character parameters required. I suggest using flags. So when you know CTRL-P has been pressed, set a flag to indicate that now you are looking for CTRL-# (where # is some number 1-9). Then set another flag indicating you are looking for a character, etc. You might find other macros defined in keymap.h to be useful.

Part 2

For this part of lab 3, you only have to write a test program. This is because:

• Minix already releases a zombie’s memory as soon as it exits and enters the zombie state. (See the book on pages 367-368, or look at the source code.)
• The hotkey F2 already prints out a memory map.

Part 3

It may be easier to add a new system call for this part, versus modifying lseek. You can find a short guide on adding a system call to Minix on last quarter's TA website. The URL is http://wwwcsif.cs.ucdavis.edu/~cs150/syscall.html. (rest pending)