Suggestions

Suggested Order of Implementation

We suggest first implementing the following, which can happen in parallel:

• Argument passing. Every user program will page fault immediately until argument passing is implemented.

• halt system call. This is the easiest system call to implement, but it is a big step to have a working system call infrastructure. You should implement enough code to read the system call number from the user stack and dispatch it to a handler based on it.

• The exit system call. Every user program that finishes in the normal way calls exit. Even a program that returns from main() calls exit indirectly (see _start() in lib/user/entry.c).

• The write system call for writing to fd 1, the system console. All of our test programs write to the console (the user process version of printf() is implemented this way), so they will all malfunction until write is available.

• For now, change** process_wait() to an infinite loop (one that waits forever). ** The provided implementation returns immediately, so Pintos will power off before any processes actually get to run. You will eventually need to provide a correct implementation.

• After the above are implemented, user processes should work minimally. At the very least, they can write to the console and exit correctly. You can then refine your implementation so that some of the tests start to pass.