You may use your textbook, your notes and programs, and any publically accessible on-line resources while working on this exam. You may not consult with other people, nor may you consult books other than the textbook.

Please submit your test on paper, printed 2- or 4-up.

1. (15 points) The Unix signal numbers 10 (SIGBUS) and 11 (SIGSEGV) often get sent to the processes run by beginning C programmers. Perhaps you have even encountered a Bus Error or Segmentation Fault yourself (though, no doubt, only while you were helping a CS 127 student in the lab). For this problem, describe the circumstances in which Linux sends SIGBUS and SIGSEGV signals. To help your exposition, you will probably want to include simple C programs that cause the errors in question, and excerpts from (or references to) relevant Linux source code. Don't forget about grep.

2. (10 points) Do problems 2 and 12 on pages 262-263 of Tanenbaum.

3. (15 points) Write a "Hello, world" program on a Linux machine. When you run your program, how many page faults occur, and for which pages? (I want you to modify the kernel to report this information so you will have actual observations rather than guesses.) Discuss the order in which the pages get referenced for your program. Does the order make sense? What portions of the program are causing the various page faults?

4. (15 points) Write a description of what happens when you type the name of a simple executable program in response to a Unix prompt. Tell the story of the program from the moment the shell receives your command line to the moment the shell prints the prompt again (assume the program is running in the foreground). Your story should discuss (briefly) the relevant file system, virtual memory, and process control actions. This story could hundreds of pages long. Keep it under two pages.

5. Clean up your mess on the Linux machine you've been using. Have a nice summer and beyond.