Assembly Chapters 5 and 8

Question 1

5.1 How does the PUSH instruction work?

Answer 1

first decrements ESP and then copies a source operand into the stack. A 16 bit operand causes ESP to be decremented by 2. A 32-bit operand causes ESP to be decremented by 4.

Question 2

5.1 What are the instruction formats for PUSH

Answer 2

PUSH reg/mem16
PUSH reg/mem32
PUSH imm32

Question 3

How does the POP instruction work?

Answer 3

first copies the contents of the stack element pointed to by ESP into a 16 or 32 bit destination operand and then increments ESP.

Question 4

What are the instruction formats of POP?

Answer 4

POP reg/mem16

POP reg/mem32

Question 5

What is PUSHFD?

Answer 5

instruction that pushes the 32-bit EFLAGS register on the stack

Question 6

What POPFD?

Answer 6

pops the stack into EFLAGS

Question 7

MOV instruction can be used to copy the flags to a variable. True or False?

Answer 7

False. use PUSHFD

Question 8

What is PUSHAD?

Answer 8

pushes all of the 32 bit general purpose registers on the stack in the following order: EAX, ECX, EDX, EBX, ESP EBP, ESI & EDI

Question 9

What is going on in the following lines of code?

MySub PROC
   pushad
   mov eax, ...
   mov edx,...
   mov ecx,...
   popad
   ret
MySub ENDP

Answer 9

saving the 32 bit general purpose registers by pushing them on stack and then modifying them and then restoring values before call ret

Question 10

What is RET

Answer 10

forces program to return to location where it was before procedure was called

Question 11

How does the CALL instruction work?

Answer 11

pushes its return address on the stack and copies the called procedure’s address into the instruction pointer

Question 12

How much memory does a CALL statement use?

Answer 12

5 bytes

Question 13

8.2 What is the stack frame?

Answer 13

AKA activation record, the area of the stack set aside for passed arguments, subroutine return address, local variables, and saved registers.

Question 14

What is a prologue and epilogue?

Answer 14

statements that save EBP register and point EBP to the top of the stack. The Epilogue is statements that restore the EBP register and calls the RET