Contents:

• Overview
• Practice Problems
• Problems to be Submitted

Topic: The Intel x86 ISA, x86 Assembly Programming, Procedure Calls, and the Stack Frame
Related Reading: class notes and Chapter 3 (esp. sections 3.7 and 3.8)

Practice problems from the textbook (answers are at the end of the chapter):

• Practice Problem 3.31, on p. 224.
• Practice Problem 3.33, on pp. 228-229.
• Practice Problem 3.34, on pp. 231-232.
• Practice Problem 3.35, on pp. 233.
• Practice Problem 3.36, on pp. 234.
• Practice Problem 3.38, on pp. 238.

When you turn in your assignment, you must include a signed cover sheet (PDF version) with your assignment (you're assignment will not be graded without a completed cover sheet).

You are allowed to submit your assignment via email, but if you choose to do so, you must bring a hardcopy of your assignment along with a completed cover sheet to the instructor at the next class. (Note: Do not email the instructor any .zip file attachments, as SLU's email may not accept these emails; i.e. the instructor may not receive your email.)

1. (2 points)

   What operation is performed by the following sequence of instructions?

         pushw  %ax 
         pushw  %dx 
         popw   %ax 
         popw   %dx 
   

2. (2 points)

   Given the four major sections of a process' memory organization (Text, Data, Heap, and Stack), indicate which area each of the following are stored in:

   1. local variables
   2. program code
   3. dynamically-allocated variables, instantiated via new or malloc()
   4. global variables

3. (9 points)

   Given the following code:

   
         snippet:
               pusha
               pushl $100
               pushl $25
               pushl $7
               call SomeProcedure
               pop   %eax
               pop   %eax
               pop   %eax
               popa
               ret
   
         SomeProcedure:
               pushl %ebp
               movl  %esp, %ebp
               movl  8(%ebp), %eax
               movl  12(%ebp), %ebx
               movl  16(%ebp), %edx  #Part D below refers to this line
               cmpl  %ebx, %eax
               jle   L1
               subl  %ebx, %eax
               jmp   L2
   
            L1:
               subl  %eax, %ebx
               movl  %ebx, %eax
   
            L2:
               movl  $0, %ecx
               addl  %eax, %ecx
               addl  %ecx, %edx
               leave
               ret
   

   1. (2 points)

      With respect to SomeProcedure:

      • How many input args are there?   How are they passed in?
      • How many outputs are there?   How are they passed out?

   2. (2 points)

      What does this procedure do?   Give an equation in terms of the inputs...

   3. (1 point)

      What is the purpose of the pusha and popa instructions?

   4. (4 points)

      Supposing that SomeProcedure is called from snippet, draw the program stack from 16(%ebp) to (%ebp) after executing instruction movl 16(%ebp), %edx. Also, give the contents of the registers EAX, EBX, ECX, and EDX as of the same line.

4. (12 points)

   Submit via email, if you haven't already, your six in-class programming assignments.