Assembly Language

Assembly Language - Programmer Sheet

Copying Data
Instruction Effect Examples
mov src,dest Copy src to dest mov $10,%eax movw %eax,(2000)
Arithmetic
Instruction Effect Examples
add src,dest dest = dest + src add $10, %esi
sub src,dest dest = dest – src sub %eax,%ebx
mul reg edx:eax = eax * reg mul %esi
div reg edx = edx:eax mod reg
eax = edx:eax ÷ reg		 div %edi
inc dest Increment destination inc %eax
dec dest Decrement destination dec (0x1000)
Function Calls
Instruction Effect Examples
call label Push eip, transfer control call format_disk
ret Pop eip and return ret
push item Push item (constant or register) to stack pushl $32
push %eax
pop [reg] Pop item from stack; optionally store to register pop %eax
popl
Bitwise Operations
Instruction Effect Examples
and src,dest dest = src & dest and %ebx, %eax
or src,dest dest = src | dest orl (0x2000),%eax
xor src,dest dest = src ^ dest xor $0xffffffff,%ebx
shl count,dest dest = dest << count shl $2,%eax
shr count,dest dest = dest >> count shr $4,(%eax)
Conditionals and Jumps
Instruction Effect Examples
cmp arg1,arg2 Compare arg1 to arg2; must immediately precede any of the conditional jump instructions cmp $0,%eax
je label Jump to label if arg1 == arg2 je endloop
jne label Jump to label if arg1 != arg2 jne loopstart
jg label Jump to label if arg2 > arg1 jg exit
jge label Jump to label if arg2 > arg1 jge format_disk
jl label Jump to label if arg2 < arg1 jl error
jle label Jump to label if arg2 < arg1 jle finish
test reg,imm Bitwise compare of register and constant; must immediately precede the jz or jnz instructions test $0xffff,%eax
jz label Jump to label if bits were not set (“zero”) jz looparound
jnz label Jump to label if bits were set (“not zero”) jnz error
jmp label Unconditional relative jump jmp exit
jmp *reg Unconditional absolute jump; arg is a register jmp *%eax
ljmp segment,offs Unconditional absolute far jump ljmp $0x10,$0
Miscellaneous
Instruction Effect Examples
nop No-op (opcode 0x90) nop
hlt Halt the CPU hlt

Suffixes: b=byte (8 bits); w=word (16 bits); l=long (32 bits). Optional if instruction is unambiguous.
Arguments to instructions: Note that it is not possible for both src and dest to be memory addresses.
Constant (decimal or hex):$10 or $0xff Fixed address:(2000) or (0x1000+53)
Register:%eax %bl Dynamic address:(%eax) or 16(%esp)
32-bit registers: %eax, %ebx, %ecx, %edx, %esi, %edi, %esp, %ebp
16-bit registers: %ax, %bx, %cx, %dx, %si, %di, %sp, %bp
8-bit registers: %al, %ah, %bl, %bh, %cl, %ch, %dl, %dh