The following assembly code includes a call to the function “secretFunc” and the

Question

The following assembly code includes a call to the function

“secretFunc” and the content of that same function.

a. (2 pt) What is the return address of “secretFunc” _________

b. (6 pts) Comment each line as to what it is doing. The comment

should be in plain English as shown.

004014FF push 0FFFFFF80h push -128, the 2nd parameter of “SecretFunc”

NOTE: “push 0xFFFFFF80 to the stack” is not acceptable

00401501 push 0FFFFFFFFh ___________

00401503 call secretFunc ___________

00401508 add esp, 8 ___________

0040150B mov [ebp-1], al ; declare a char in C for this

0040150E nop ---

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

00401000 secretFunc

00401000 push ebp

00401001 mov ebp, esp Copy stack pointer to ebp to use as a frame pointer for this function. It references both parameters and local variables.

00401003 push ecx

00401004 movsx eax, [ebp+8]

00401008 movsx ecx, [ebp+12]

0040100C add eax, ecx

0040100E mov [ebp-1], al

00401011 mov al, [ebp-1]

00401014 mov esp, ebp

00401016 pop ebp

00401017 ret

2.) Description of Function – what does it do?

Explanation / Answer

1)

a) return address of "secretFunc: = 0x00401508
b)
00401501 push 0FFFFFFFFh ___________ push the value 0FFFFFFFFh into stack
00401503 call secretFunc ___________ jumping to label secretFunc and storing the next address as return address
00401508 add esp, 8 ___________ retaining the stack pointer position
0040150B mov [ebp-1], al ; declare a char in C for this
0040150E nop ---
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
00401000 secretFunc
00401000 push ebp ________ base pointer address is stored which is retained later
00401001 mov ebp, esp Copy stack pointer to ebp to use as a frame pointer for this function. It references both parameters and local variables.
00401003 push ecx ________ ecx value is stored in stack  
00401004 movsx eax, [ebp+8] ___________ 0FFFFFFFFh value is popped and stored in eax
00401008 movsx ecx, [ebp+12] ____________ 0FFFFFF80h value is popped and stored in ecx
0040100C add eax, ecx _____________ values are added and stored in eax
0040100E mov [ebp-1], al _____________ first byte of result is stored in stack
00401011 mov al, [ebp-1]
00401014 mov esp, ebp _______ starting stack pointer is retained
00401016 pop ebp ________ base pointer value is popped and stored
00401017 ret ___________ return to caller function

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