All OS lab projects offered at University of Tehran - Spring 2023

Contributors:

1. Seyedeh Zeinab Pishbeen
2. Mohammad Javad Besharati

---

Description:

During 5 labs, new features added to xv6 operating system.

---

Lab 1:

• A text message added to boot messages.
• Cursor comes to beginning of line by pressing shift + '[' keys.
• Cursor goes to end of line by pressing shift + ']' keys.
• Pressing Ctrl + 'W' will remove the word before cursor.
• A user level program has been written called mmm.c. This program receives at most 7 numbers and shows their mean, median and mode. Result is saved to mmm_result.txt file.
• A new kernel module has been created. This module shows the names of group members in the output of the dmsg command. You can find its code in new_module file.

---

Lab 2:

Some new system calls added to xv6:

• System call to find most called system call.
• System call to find current process childern count.
• System call to kill the first child of current process.

---

Lab 3:

Some new schedulers and required system calls added to xv6:

• Aging mechanism has been implemented.
• Round Robin scheduler has been implemented.
• Lottery scheduler has been implemented.
• FCFS scheduler has been implemented.
• Modifying processes queue system call added.
• Initializing lottery ticket system call added.
• Printing processes info system call added.
• A user level program called foo.c has been written to test mentioned modifications.

---

Lab 4:

This lab was about synchronization and readers-priority readers-writers problem was implemented. Some new system calls to simulate this problem added to xv6:

• sem_init(i, v)
• sem_aquire(i)
• sem_release(i)

---

Lab 5:

This lab was about memory management in xv6. In this lab we modified xv6 address space such that it becomes like linux address space.