Question

;Assembly x86-64

;Q9:

What is the value of eax (in decimal) after the function call in _start returns?

global _start
_start:
  mov edi, 4
  call function1

global function1
function1:
  push rdi
  inc edi
  mov esi, 2
  call function2
  pop rdi
  mul edi
ret

global function2
function2:
  mov eax, edi
  mov edx, 0
  div esi
  add eax, edi
  add eax, edx
ret

;Q10:

A function uses 10 integer arguments. What is the appropriate value for the blank operand to clear the arguments off the stack after the call?

add rsp, __________________

Answer 1

In global start instrctions

first command value of edi become 4.

after that function 1 is call

In function 1 in

step1 :- rdi is push onto the stack

step2:-increamenet edi by 1 which now 5 .

step3:-function 2 is calling

in function 2

step1:-edi values moves into eax value.

step2:- edx value become 0

step3:- eax and edi is added

step4:- eax and edx is added

after function return goes to function 1

execute the remaining command

pop the rdi from the stack and multiply with edi

the final value of eax is 10