nasm -f elf64 -o hello.o hello.asmld hello.o -o hello
| 8-bit | 16-bit | 32-bit | 64-bit |
|---|---|---|---|
| al | ax | eax | rax |
| bl | bx | ebx | rbx |
| cl | cx | ecx | rcx |
| dl | dx | edx | rdx |
| sil | si | esi | rsi |
| dil | di | edi | rdi |
| bpl | bp | ebp | rbp |
| spl | sp | esp | rsp |
| r8b | r8w | r8d | r8 |
| r9b | r9w | r9d | r9 |
| r10b | r10w | r10d | r10 |
| r11b | r11w | r11d | r11 |
| r12b | r12w | r12d | r12 |
| r13b | r13w | r13d | r13 |
| r14b | r14w | r14d | r14 |
| r15b | r15w | r15d | r15 |
Usually where registers are used, pointers can also be used.
Like instead of pop reg pop [label] to pop a value off the stack directily into memory.
Can be found here
| rax | System Call | rdi | rsi | rdx | r10 | r8 | r9 |
|---|---|---|---|---|---|---|---|
| 0 | sys_read | unsigned int fd (filedescriptor) | char* buf | size_t count | |||
| 1 | sys_write | unsigned int fd | char* buf | size_t count | |||
| 60 | sys_exit | int error_code |
| Flag Symbol | Description |
|---|---|
| CF | carry |
| PF | parity |
| ZF | zero |
| SF | sign |
| OF | overflow |
| AF | adjust |
| IF | interrup enabled |
Individual flags are part of a register.
32- and 16-bit versions in parentheses
| Name | Meaning | Desciption |
|---|---|---|
| rip (eip, ip) | index pointer | address to be executed in control flow |
| rsp (esp, sp) | stack pointer | top of stack |
| rbp (ebp, bp) | stack base pointer | bottom of stack |
unsigned version in parentheses
| Jump Symbol | Result of cmp a,b / Condition |
|---|---|
| je | a=b |
| jne | a!=b |
| jg (ja) | a>b |
| jge (jae) | a>=b |
| jl (jb) | a<b |
| jle (jbe) | a<=b |
| jz | a=0 |
| jnz | a!=0 |
| jo | overflow occurred |
| jno | overflow didn't occur |
| js | is signed |
| jns | not signed |
unsigned version in parentheses
| Name | Description |
|---|---|
| add a, b | a = a+b |
| sub a, b | a = a-b |
| mul a (imul a) | rax = rax*a |
| div a (idiv a) | rax = rax/a, rdx = rax%a |
| neg a | a = -a |
| inc a | a = a+1 |
| dec a | a = a-1 |
| adc a, b | a = a+b+CF |
| sbb a, b | a = a-b-CF |
div operates on rax and rdx. To prevent the concatenation, use:
mov rdx, 0
div rbxrdx contains the remainder in the end.
; prevent symbol collision
%macro freeze 0
%%loop:
jmp %%loop
%endmacro