CS153 xv6 Repo

Lab 1 Overview

Part 1: Adding a system call

1. Change exit() to exit(int)

• the argument passed updates the process's exit status

2. Change wait() to wait(int\*)

• the pointer gets updated with the exit status of the child

3. Add waitpid(int,int\*,int)

• acts like wait(int*), but with additional functionality.
  1. First argument is the pid of the process that the caller wants to wait for
  2. Second argument is a pointer that gets updated with the exit status of the process the caller is waiting for
  3. Third argument represents the options for waitpid

Part 2: Implementing priority scheduling

1. Add setpriority(int)

• changes the caller's priority value to the passed in argument. If argument is not a valid priority level, function will return -1. It yields once priority is set to make sure highest priority process is running.

2. Change scheduler to priority scheduler

• changed from round-robin to priority scheduling. Priority values range from 0 - 63. 0 is the highest.

Lab 2 Overview

Part 1: Growing Stack

• Pages are now mapped below KERNBASE. Pointer points to bottom of the page. Allows stack to grow downwards. Added cases for page faults in trap.c.

Part 2: Implement Shared Memory

• Implemented memory that can be shared among other processes.