Assembly

Front 1

Assembly
What are the compilation stages of gcc?

Back 1

Pre-processing -> Compilation -> Assembly -> Linking

Front 2

Define Pre-processing

Back 2

Expanding Macros

Front 3

Define Compilation

Back 3

Converting source code into assembly language

Front 4

Define Assembly

Back 4

assembly -> machine code

Front 5

Define Linking

Back 5

Adding runtime library to create the final executable

Front 6

Name the registers rsi/ rdi/ rsp/ rbp/

Back 6

source index/destination index/ stack pointer/base pointer

Front 7

Function of the rip register

Back 7

Holds the address of the next instruction to be executed.

Front 8

Function of rflags register

Back 8

Bits represent various Cpu state, updated after various instructions.

Front 9

Main memory info on Intel 64

Back 9

Little endian/byte addressable/non-aligned access

Front 10

What is the nasm instruction format

Back 10

Label: Opcode operand operand

Front 11

How what is the syntax which allows you to access the higher/lower bytes of the first 16 bits of a register?

Back 11

{a...d}+h/l and rsi -> sil/rdi -> dil/rsp -> spl/rbp -> bpl

What is the size in bits of a byte, word, doubleword, quadword?, 8/16/32/64 bits

Front 12

What are data declaration directives?

Back 12

They are special commands that allow global data variables to be declared

Front 13

What is the syntax for declaring data declaration directives?

Back 13

Var_name <size(s)> <value(s)>

Front 14

What is the syntax for declaring bytes

Back 14

words, double words, quad words? , db, dw, dd, dq

Front 15

Declare a variable called users of size 1 byte with the value 4

Back 15

users db 3

Front 16

Declare a variable string variable called name with value "hello"

Back 16

name db "hello"

Front 17

Declare a sequence seq

Back 17

of size double word and values 1/2/3 , seq dw 1, 2, 3

Front 18

Declare an array with size of 100 double words each with a value of 43

Back 18

array times 100 dw 43

Front 19

How do you create uninitialized data?

Back 19

name res<b/w/d/q> <quantity>

Front 20

How do you create constants?

Back 20

Name equ <value>

Front 21

Name the three types of operands

Back 21

Register/Immediate/Memory operands*

Front 22

How do you use a memory operand?

Back 22

Only one memory location per instruction/ [mem_location]

Front 23

Name the addition and subtraction instructions and their effects

Back 23

They all change the rflags value
add/sub
inc/dec
cmp a b: compares a - b
neg

Front 24

Usage of the multiply instruction

Back 24

imul op1 op2 op3*/ operations can set both the carry and overflow flags

Front 25

Integer divide operation usage

Back 25

for 8bit integers   idiv <operand>  => ah = ax div op |
al = ax mod op else idiv <operand>  => ?ax* = rax div op |
?dx = rax mod op

Front 26

Name instructions for bit shifting and its usage

Back 26

Sal dest n: Shift arithmetic left by n

Front 27

Sar dest

Back 27

n: Shift arithmetic right by n

Front 28

Name the instruction used to convert a byte into a word

Back 28

cbw  => ax = al

Front 29

Name the instruction used to convert a word into a double word

Back 29

cwde => eax = ax

Front 30

Name the instruction used to convert a double word into a quad word

Back 30

cdq => eax:edx = eax

Front 31

Name the instruction used to sign extend a quad word

Back 31

cdo => rdx:rax = rax*

Front 32

Convert to assembly alpha dw 7/ beta dw 4/ gamma dw -3 :- alpha = (alpha * beta + 5* gamma) * (alpha - beta)

Back 32

1. mov rax, [alpha]
2. imul rax [beta]
3. mov rbx, [gamma]
4. imul gamma, 5
5. add rax, rbx
6. mov rbx [alpha]
7. sub rbx [beta]
8. imul rax, rbx
9. mov [alpha], rax

Front 33

Write some code to test for overflow after adding two integers

Back 33

1. add rax, rbx
2. jo ov_label
3. ov_label:

Front 34

Write some code to test for integer divide by 0

Back 34

1. cmp rbx, 0
2. je div_label
3. idiv rbx

Front 35

List the five bit level instructions

Back 35

and, or, xor, not, test

Front 36

What does the bit level instruction "test" do?

Back 36

test rax , rbx set rflags.* to 1 if bit patterns match 0 otherwise

Front 37

Assuming the variables are bytes with value 1

Back 37

convert this to assembly:- okay = (london && grey) || (! london),
1. mov rax [london]
2. and rax, [grey]
3. mov rbx, [london]
4. not rbx
5. or rax, rbx
6. mov [okay], rax

Front 38

What is the format of jump instructions?

Back 38

jmp_intr label

What are the instructions for jumps?,
1. jmp : unconditional jump
2. Je: jump if equal
3. Jz: jump if equal to zero
4. Jnz: jump if not equal to zero
5. Jl: jump if <
6. Jle: jump if <=
7. Jg: jump if >
8. Jge: jump if >=

Front 39

Convert if(age < 100) …

Back 39

1. if: cmp word[age], 100
2. jl endif
3. …
4. endif: …

Front 40

Write a do while loop in assembly

Back 40

1. While:
2. Statements
3. Cmp x, y
4. Jump_instruction while label

Front 41

Write a while loop in assembly

Back 41

1. While:
2. Cmp x, y
3. Jump_instruction end_while label
4. Statements
5. Jump while
6. Endwhile

Front 42

Write a for loop in assembly

Back 42

1. For mov word[age], 1
2. Next:
3. Cmp statement
4. Jump endfor
5. Statements
6. Inc word[age]
7. Jmp next
8. Endfor:

Front 43

Convert if(age < 100) && (age > 12)

Back 43

1. cmp [age], 100
2. jg label…
3. cmp [age], 12
4. jl label.. 5# statements

Front 44

Convert if(age > 100) statements else statements

Back 44

1. cmp word[age] 100
2. jl else_label
3. statements
4. elseif 5#stats


Describe what the stack is, The stack is a region in memory that is access via push and popping data of/on the top of the stack via the LIFO principle.

Front 45

What is the relationship between rsp and the stack?

Back 45

rsp always points to the address at the top of the stack.

Front 46

What is the relationship between rbp and the stack?

Back 46

rbp is used to point to the addresses of data on the stack. Like local variables

Front 47

What data sizes can be pushed to the stack on the intel 64 architecture?

Back 47

Only multiples of words.

Front 48

How does the stack change when pushing/popping data?

Back 48

The stack grows downward in memory, lower address are written to with each push, opposite for popping.

Front 49

How does the register used effect push/pop operations?

Back 49

The size of the register/operand determines how much data is pushed/popped to the stack. Only 2 or 8 bytes are transferred at a time.

Front 50

Name the instruction for pushing data and the effect on rsp.

Back 50

push <operand>, rsp = rsp - 2OR8

Front 51

Name the instruction for popping data and the effect on rsp.

Back 51

pop <operand>, rsp = rsp + 2OR8

Front 52

Name the instruction for pushing rflags and the effect on rsp.

Back 52

pushfq , rsp = rsp - 2OR8

Front 53

Name the instruction for popping rflags and the effect on rsp.

Back 53

popfq, rsp = rsp + 2OR8

Front 54

What are the CALLER conventions before calling a method?

Back 54

1. Push parameters in order first to last
2. Push object instance
3. call method

Front 55

What are the CALLEE conventions?

Back 55

1. Save registers
2. Execution
3. Copy any results to <r/e>ax
4. Restore register
5. return

Front 56

What are the CALLER conventions after calling a method?

Back 56

Remove object instance from stack
Remove parameter from stack

Front 57

Implement max(a, b) in assembly,

Back 57

1# max: