CS439-project0/design_doc.txt at master · rackerbenoit/CS439-project0 · GitHub

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################
Paul Benoit
################
Name1: Paul Benoit
EID1: pjb742
CS login: paulbeno
Email: paul.benoit36@gmail.com
Unique Number: 53015

Slip days used: 0

****EACH student submits a (unique) design document.****

################
Zoe Lamb
################
Name1: Zoe Lamb
EID1: zl2866
CS login: zoe
Email: zlamb@utexas.edu
Unique Number: 53005

Your partner's ranking (scale below): Excellent

################
PARTNER EVALUATION SCALE
################
Excellent: Consistently went above and beyond - tutored others, carried
more than his/her fair share of the load.

Very Good: Consistently did what he/she was supposed to do, very well
prepared and cooperative.

Satisfactory: Usually did what he/she was supposed to do, minimally
prepared and cooperative.

Marginal: Sometimes failed to show up and/or rarely prepared.

Deficient: Often failed to show up and/or rarely prepared.

Unsatisfactory: Consistently failed to show up and/or unprepared.

Superficial: Practically no participation.

No Show: No participation at all.

################
Preliminaries
################
(1) If you have any preliminary comments on your submission, notes for
  the TAs, or extra credit, please give them here.

(2) Please cite any offline or online sources you consulted while
  preparing your submission, other than the Linux documentation,
  course text, and lecture notes.

Computer Systems A Programmer's Perspective by Bryant and O'Hallaron

################
Questions regarding Part 0
################
(1) How many child processes are created when doFib() begins with
  an input of 5?  Show the return value for each child process, numbering
  the processes beginning with 0 (the original process) and incrementing for
  each child process.

14 child processes.
Process 0 returns 5
Process 1a returns 3
Process 1b returns 2
Process 2a returns 1
Process 2b returns 1
Process 2c returns 1
Process 2d returns 2
PRocess 3a returns 0;
Process 3b returns 1;
Process 3c returns 0;
Process 3d returns 1;
Process 3e returns 1;
Process 3f returns 1;
Process 4a returns 0;
Process 4b returns 1;

Other process 2 retuns 1 from process
(2) In part 0.3, which flavor of exec did you choose to use?  Why?

We used execv since we did not need to utilize the environment variable.

################
Questions regarding Part 1
################
(1) In the provided utility function Signal(), what does the call to
  sigaction() do?  Why was sigaction() used instead of signal()?

	sigaction allows users to clearly specify the signal handling
	semantics they want, and the user has to set the entries of a
	structure.

(2) What is the last assembly language instruction executed by the
  signal handler function that you write?  (You may choose either signal
  handler.)

	The last instruction was retq.

(3) After the instruction identified in the previous question executes,
  what is the next assembly language instruction executed?

	The next instruction was in main(): mov %eax, -0x4(%rbp)

(4) When the signal handler finishes running, it must restore all of
  the registers from the interrupted thread to exactly their values
  before the signal occurred. How is this done?

	The register values that are going to be restored are stored in the PCB,
	so before the handler returns to main it has to restore the values
	from the PCB, only after that does it return to user mode.


################
Questions regarding Part 2
################
(1) In msh.c, we use three separate signal handlers to catch our signals.
  You can also use a single signal handler to catch all three signals.  Is
  there a design advantage of one over the other?  Explain your answer.

	If there is only one handler then any other signals that are sent to
        that handler are blocked. On the other hand, if you have separate
        handlers for each signal type, then pending signals of different types
        are not blocked.