rax = returned variable
rcx = counter variable
rbx = variable
rdi = 1st argument function
rsi = 2nd argument function
rdx = 3th argument function
al, bl, cl, dl = char (8bits var)
mov rcx, 0 ; i = 0
xor rcx, rcx ; i = 0 // fast
inc rcx ; i++
dec rcx ; i--
cmp byte [rdi + rcx], 0 ; *(str + i) == '\0' // str = rdi = 1st function arg
call function ; function() // function extern of the file
jmp label ; function() // label = function in same file
je label ; if (True) function()
jne label ; if (False) function()
jl label ; if (value1 < value2) function()
ret ; return (var) // var = rax
movzx rbx, al ; str = (char *)c // (approximately) cast 8bits var to 64bits
syscall ; syscall ¯\_(ツ)_/¯ (after move rax, syscall_id)section .text
extern __errno_location
main:
mov rax, syscall_id
syscall
cmp rax, 0
jl error
ret
error:
neg rax
mov rbx, rax
call __errno_location
mov [rax], rbx
mov rax, -1
rethttps://syscalls.w3challs.com/?arch=x86_64
https://www.fil.univ-lille1.fr/portail/archive19-20/~meftali/PdM/Theme1.pdf
https://www.youtube.com/watch?v=yxzUi8MdOAA&list=PLcT0DaY68xGzzmj47WSbb8XaIwWFjVlKz&index=1
https://www.youtube.com/watch?v=fvtd2Ut3MHw&list=PLrSOXFDHBtfEs7PCC6r44iXiX5gMlbjcR&index=1