Due date:
    Test: 04/20/2022 @ 11:59pm
    Code: 04/22/2022 @ 11:59pm

Assignment:
~~~~~~~~~~~

- More system calls
- Donate a test case (<csid>.ok and <csid>.dir)

Virtual Address Space:
~~~~~~~~~~~~~~~~~~~~~~

0x00000000 - 0x80000000       (shared kernel RWX)
0x80000000 - 0xFFFFFFFF+1     (private user RWX)
                              (except ioPIC and laPIC, shared kernel)

User code should not be able to access anything outside the user range

System calls:
~~~~~~~~~~~~~

Look in t0.dir/sbin/sys.h for information about the system calls you need
to implement

Our system calls will be modeled after their Unix counterparts with a few
exceptions:

- our semaphores will be much simpler than Sys-V semaphores
- process ID's are not global, they are parent-scoped
- our ext2 implementation will not support writing
- we don't implement file permissions, cwd, uid, gid, etc.
- each process can have a maximum of 10 active descriptors for
  each descriptor type: file, semaphore, and child process
- processes are single-threaded
- no page-out, no swap space.
- no signals

Those limitations are easy to overcome and we'll be relaxing them
over the next few weeks


Rules:
~~~~~~

- The kernel directory is yours. Make any changes you want but leave the
  build-related files alone (Makefile, kernel/Makefile, kernel/script.ld)

- You need to preserve the system call interfaces defined in
  t0.dir/sbin/{sys.h,sysS}. This includes:

   * The implemented system calls and their numbers
   * The system call arguments and return values
   * The system call semantics

- You need to honor the virtual address space rules:
   * the lower half is for kernel use
   * the upper half is for process private use except for the two APICs

- You can use any language or build environment to produce your tests but:
   * please provide sources and makefiles for use by your peers during testing
   * make sure you commit your binaries as well as sources. The build
     environment will not build your test
   * stay within the 100KB limit

Files:
~~~~~~

- kernel/          contains the kernel files. Do what you want with it.
                   But leave the build related files alone
                     - Makefile
                     - kernel/Makefile
                     - kernel/sciprt.ld