Test #2 will be given in class on Friday, Apr 1st
The test is closed book, no notes or computers are allowed.

An IA32 Instruction reference will be distributed with the test.

          pop %ebp
          ret
          

Practice Problems

• Practice Problem 3.3 (know leal!)

• Practice Problem 3.24 (Buffer Overflow)

• Problem 3.31 (Assembly to C)

• Problem 3.36 (Assembly to C)

• Look over the labs and HWs!

• Write the following function in IA32 assembly language:

  int factorial(int x) {
     if (x==1) return 1;
     else return(x * factorial(x-1));
  }
  

• Consider the following C function and corresponding IA32 assembly:

  int namelength(char *name) { char buff[4]; strcpy(buff,name); return(strlen(buff)); }

  namelength: pushl %ebp movl %esp, %ebp subl $16, %esp pushl 8(%ebp) leal -4(%ebp), %eax pushl %eax call strcpy addl $16, %esp leal -4(%ebp), %eax subl $12, %esp pushl %eax call strlen addl $16, %esp leave ret

  • If the pointer name points to the string "abcdefghijklmnop", what is the address of the instruction the function tries to return to?.
  • What value will be in %ebp after the leave instruction has executed?
  • if the pointer name points to the string "abcdef", what will the return value be?

• Below is the C code and corresponding assembly code for a function that deals with 2-dimensional arrays (we did this one in class):

  int arr[R][C]; int arr1[C][R]; int foo(int x, int y) { int i; i = arr[x][y]; i += arr1[x][y]; return(i); }

  foo: pushl %ebp movl %esp, %ebp subl $4, %esp movl 8(%ebp), %edx movl %edx, %eax sall $3, %eax subl %edx, %eax addl 12(%ebp), %eax movl arr(,%eax,4), %eax movl %eax, -4(%ebp) movl 8(%ebp), %eax sall $2, %eax addl 12(%ebp), %eax movl arr1(,%eax,4), %edx leal -4(%ebp), %eax addl %edx, (%eax) movl -4(%ebp), %eax leave ret

  What is the value of R?

  What is the value of C?

  answers: R is 4 and C is 7

• Build an circuit that computes a AND b using only OR gates and NOT gates.
• Build an circuit that computes a OR b using only AND gates and NOT gates.
• Build a circuit that multiplies two IEEE single precision floating point numbers using only 6 AND gates and 1 NOT gate (this one is a joke! Get it! Ha!?!).