Stack and Functions

Question 1

type of data structure where items are added and then removed in reverse order

Answer 1

stack

Question 2

stack is often referred to as ___

Answer 2

LIFO (Last In, First Out)

Question 3

stack is heavily used for _____

Answer 3

the storage of information during procedure or function calls

Question 4

adding an item to a stack is referred to as a ______

Answer 4

push operation

Question 5

removing an item from a stack is referred to as a _______

Answer 5

pop operation

Question 6

pop and push syntax

Answer 6

pop <operand64>
push <operand64>

Question 7

how is stack implemented in memory?

Answer 7

it is implemented growing downward

Question 8

register used to point to the current top of stack in memory

Answer 8

RSP (stack pointer register)

Question 9

what is being adjusted when performing push and pop operations?

Answer 9

the stack pointer register (RSP)

Question 10

what happens in a push operation?

Answer 10

1. rsp is decreased by 8
2. operand is copied to the stack at [rsp]

Question 11

what happens in a pop operation?

Answer 11

1. current top-of-stack [rsp], is copied into the operand
2. rsp is increased by 8

Question 12

general format for declaring/defining a function

Answer 12

global <funcName>
 - is typically placed before any of the sections

<funcName>:
      ; function body
      ret (return statement)

Question 13

a function may be defined how many times?

Answer 13

only once

Question 14

true/false

there is a specific order required for how functions are defined

Answer 14

false, there is no specific order

Question 15

two (2) main actions that function(s) calls

Answer 15

1. linkage
2. argument transmission

Question 16

function must be able to return to the correct place in which it was originally called

Answer 16

linkage

Question 17

function must be able to access parameters to operate on or return results

Answer 17

argument transmission

Question 18

two (2) instructions that handle the linkage

Answer 18

1. call <funcName>

2. ret

Question 19

how does

call <funcName>

handle linkage?

Answer 19

it transfers control to the stated function

ex. from the _start label to the function specified in the function call

Question 20

how does ‘ret’ handle linkage?

Answer 20

from the current function, it returns control back to the calling routine (from where it was called)

Question 21

how does

call <funcName>

work?

Answer 21

saves the address of where to return by placing the contents of the RIP on the stack

Question 22

where does rip point to?

Answer 22

the next instruction

note: rip = instruction pointer register

Question 23

how does ‘ret’ work?

Answer 23

ret pops the current top of stack (rsp) into the rip which points the control back to the return address initially saved into the stack when the function was first called

Question 24

refers to sending information to a function and obtaining a result as appropriate for the specific function

Answer 24

argument transmission

Question 25

transmitting values to a function is referred to as _____

Answer 25

call-by-value

Question 26

transmitting addresses to a function is referred to as _____

Answer 26

call-by-reference

Question 27

what is/are used to pass parameters to and/or from a function

Answer 27

a combination of registers and the stack

Question 28

which arguments are passed in the registers?

Answer 28

the first six (6) integer arguments are passed in registers

Question 29

which arguments are passed on the stack

Answer 29

the seventh and any additional arguments are passed on the stack

Question 30

which registers are used to pass arguments?

Answer 30

1st arg: rdi 2nd arg: rsi 3rd arg: rdx 4th arg: rcx 5th arg: r8 6th arg: r9

Question 31

what register is used to store the return value of a function?

Answer 31

rax

Question 32

which registers can be used as a temporary storage (usually for swapping two values)?

Answer 32

r10 and r11

Question 33

convert high-level code to assembly stats1(&arr, len, &sum, &ave); *assume all are of quadword size

Answer 33

``` mov rdi, arr mov rsi, qword[len] mov rdx, sum mov rcx, ave call stats1 ```

Question 34

what is responsible for clearing the arguments from the stack when the function is completed?

Answer 34

calling routine

Question 35

items on the stack as part of a function call

Answer 35

call frame

Question 36

call frame is also referred to as _____

Answer 36

activation record or stack frame

Question 37

possible items in the call frame (4)

Answer 37

1. return address (required): RIP 2. preserved registers (if any): RBP 3. passed arguments (if any) 4. stack dynamic local variables (if any)

Question 38

local variables that are allocated on the stack

Answer 38

stack-based local variables

Question 39

additional memory on the stack for local variables is allocated by adjusting the _____

Answer 39

rsp

Question 40

what happens to the allocated memory for stack-based local variables when the function is completed

Answer 40

the allocated memory is released