MineSwepperASM/ASM_CHEATSHEET.md

Registers

General Purpose

Register	Usage
rax	Accumulator for general use and syscall number
eax	Lower 32 bits of rax
ax	Lower 16 bits of rax
al	Lower 8 bits of ax
rbx	Base register
ebx	Lower 32 bits of rbx
bx	Lower 16 bits of rbx
bl	Lower 8 bits of bx
rcx	Counter register (loops)
ecx	Lower 32 bits of rcx
cx	Lower 16 bits of rcx
cl	Lower 8 bits of cx
rdx	Data register
edx	Lower 32 bits of rdx
dx	Lower 16 bits of rdx
dl	Lower 8 bits of dx

Index and Pointer

Register	Usage
rsi	Source for data (string operations)
esi	Lower 32 bits of rsi
si	Lower 16 bits of rsi
sil	Lower 8 bits of si
rdi	Destination for data
edi	Lower 32 bits of rdi
di	Lower 16 bits of rdi
dil	Lower 8 bits of di
rsp	Stack pointer
esp	Lower 32 bits of rsp
sp	Lower 16 bits of rsp
spl	Lower 8 bits of sp
rbp	Base pointer for stack frames
ebp	Lower 32 bits of rbp
bp	Lower 16 bits of rbp
bpl	Lower 8 bits of bp

Extended

Register	Usage
r8–r15	Extra general-purpose registers
r8d–r15d	Lower 32 bits of r8–r15
r8w–r15w	Lower 16 bits of r8–r15
r8b–r15b	Lower 8 bits of r8–r15

Data Movement

Command	Description
mov dest, src	Copy data from src to dest
movzx dest, src	Zero-extend src into dest
movsx dest, src	Sign-extend src into dest
lea dest, [addr]	Load effective address into dest
rel addr	Relative address
push src	Push value of src onto the stack
pop dest	Pop value from the stack into dest
pusa	Pushes all registers to the stack
popa	Pops all registers from the stack
xchg dest, src	Exchange values of dest and src
cmovcc dest, src	Conditional move
movs dest, src	Move string
movsb	Move byte from [rsi] to [rdi]
movsw	Move word from [rsi] to [rdi]
movsd	Move doubleword from [rsi] to [rdi]
movsq	Move quadword from [rsi] to [rdi]

Arithmetic

Command	Description
add dest, src	Add src to dest
sub dest, src	Subtract src from dest
imul dest, src	Multiply dest by src (signed)
mul src	Multiply rax by src (result in rdx:rax)
idiv src	Divide rdx:rax by src (quotient in rax, remainder in rdx)
xor dest, src	XOR (useful for clearing, e.g., xor rax, rax)
inc reg	Increment reg by 1
dec reg	Decrement reg by 1
adc dest, src	Add with carry
sbb dest, src	Subtract with borrow
neg dest	Negate (two's complement)
div src	Unsigned divide rdx:rax by src
cbw	Convert byte to word
cwd	Convert word to doubleword
cdq	Convert doubleword to quadword
cqo	Convert quadword to octword

Logical

Command	Description
and dest, src	Bitwise AND
or dest, src	Bitwise OR
xor dest, src	Bitwise XOR
not dest	Bitwise NOT
shl dest, imm	Shift bits in dest left by imm
shr dest, imm	Shift bits in dest right by imm
sal dest, imm	Arithmetic shift left
sar dest, imm	Arithmetic shift right
rol dest, imm	Rotate bits left
ror dest, imm	Rotate bits right
rcl dest, imm	Rotate through carry left
rcr dest, imm	Rotate through carry right
test dest, src	Test bits (AND without storing result)

Control Flow

Command	Description
jmp label	Unconditional jump to label
cmp op1, op2	Compare op1 and op2
je label	Jump if equal
jne label	Jump if not equal
jg label	Jump if greater (signed)
jl label	Jump if less (signed)
jge label	Jump if greater or equal (signed)
jle label	Jump if less or equal (signed)
ja label	Jump if above (unsigned)
jb label	Jump if below (unsigned)
jae label	Jump if above or equal (unsigned)
jbe label	Jump if below or equal (unsigned)
call label	Call a function at label
ret	Return from a function
loop label	Loop to label
loope label	Loop while equal
loopne label	Loop while not equal
jecxz label	Jump if ecx is zero
jrcxz label	Jump if rcx is zero

Syscall Interface (Linux/macOS)

Register	Description
rax	Syscall number
rdi	First argument
rsi	Second argument
rdx	Third argument
r10	Fourth argument
r8	Fifth argument
r9	Sixth argument

Common Syscall Numbers

Syscall	rax	Description
sys_exit	0x2000001	Exit program
sys_write	0x2000004	Write to file descriptor
sys_read	0x2000003	Read from file descriptor

Stack Manipulation

Command	Description
push reg	Push register value onto the stack
pop reg	Pop top of stack into register
call addr	Call a subroutine at addr
ret	Return from subroutine
enter imm, imm	Create stack frame
leave	Destroy stack frame

String Operations

Command	Description
movsb	Move byte from [rsi] to [rdi]
movsw	Move word from [rsi] to [rdi]
movsd	Move doubleword from [rsi] to [rdi]
movsq	Move quadword from [rsi] to [rdi]
stosb	Store byte from al to [rdi]
stosw	Store word from ax to [rdi]
stosd	Store doubleword from eax to [rdi]
stosq	Store quadword from rax to [rdi]
lodsb	Load byte from [rsi] into al
lodsw	Load word from [rsi] into ax
lodsd	Load doubleword from [rsi] into eax
lodsq	Load quadword from [rsi] into rax
scasb	Scan byte in al against [rdi]
scasw	Scan word in ax against [rdi]
scasd	Scan doubleword in eax against [rdi]
scasq	Scan quadword in rax against [rdi]
cmpsb	Compare byte at [rsi] with byte at [rdi]
cmpsw	Compare word at [rsi] with word at [rdi]
cmpsd	Compare doubleword at [rsi] with doubleword at [rdi]
cmpsq	Compare quadword at [rsi] with quadword at [rdi]

Data Definition

Command	Description
db value	Define byte (1 byte)
dw value	Define word (2 bytes)
dd value	Define doubleword (4 bytes)
dq value	Define quadword (8 bytes)
dt value	Define ten bytes (80 bits)

Examples:

assembly:

    section .data
        byteVar db 0x1                  ; Define a byte variable
        wordVar dw 0x1234               ; Define a word variable
        dwordVar dd 0x12345678          ; Define a doubleword variable
        qwordVar dq 0x123456789ABCDEF0  ; Define a quadword variable

    section .text
        global main

    main:
        mov al, [byteVar]               ; Move byteVar into al
        mov ax, [wordVar]               ; Move wordVar into ax
        mov eax, [dwordVar]             ; Move dwordVar into eax
        mov rax, [qwordVar]             ; Move qwordVar into rax

Tips for Debugging

• Use xor rax, rax or mov rax, 0 to zero out rax.
• Use comments liberally to track which registers hold what values!
• Step through your code with gdb or an equivalent debugger to watch registers change.
• If things seem off, double-check your mov, cmp, and syscall logic.