xv6-2023-mit-labs

This repository stores my solutions to labs in MIT 6.S081 Operating System Engineering 2023.

By now I have successfully scored full marks for all the labs and you may refer to different branches for specific implementations.

In summary, I have augmented the Xv6, a simple Unix-like teaching operating system by adding numerous features as below. You may refer to 6.S081 Home Page for detailed instructions of each lab.

• Lab Utilities at branch util
  • user-level sleep program to sleep for specified ticks
  • user-level pingpong program to achieve inter-process communication
  • user-level prime sieve program with pipes and fork
  • simple version of UNIX find program
  • simple version of UNIX xargs program
• Lab System Call at branch syscall
  • add a system-call tracing feature via new trace system call
  • add a system-info collection feature via new sysinfo system call
• Lab Page Tables at branch pgtbl
  • add read-only page to eliminate need for context switch during getpid system call
  • add function to print a page table
  • add system call pgaccess to report which pages have been accessed (read or write)
• Lab Traps at branch trap
  • add backtrace to trace stack-frame pointers to return to in the caller stack
  • add a system call alarm to periodically run specified function after specified ticks
• Lab Copy-on-Write Fork at branch cow
  • implement copy-on-write fork
• Lab Multithreading at branch thread
  • implement context switch for threads
  • fix ph.c program with mutex
  • achieve correct barrier behaviour
• Lab Networking at branch net
  • implement transmit and receive function on provided E1000 network driver
• Lab Locks at branch lock
  • implement per-CPU freelist (each with locks) and stealing mechanism to reduce kmem lock contention
  • modify buffer cache with hash-table search and lock for each bucket to reduce bcache lock contention
• Lab File System at branch fs
  • add double-indirect block in inode to support big files
  • add symlink system call to create a soft link
• Lab Memory Mapping at branch mmap
  • implement mmap and munmap to allow detailed control over address spaces via memory mapping