read = 0
write = 1
exit  = 60
buffer_size = 201

        .global _start
        .type _start, @function
        .section .text

_start:
read_input:
        sub     $buffer_size, %rsp              # allocate buffer
        mov     $read, %rax
        mov     $0, %rdi
        mov     %rsp, %rsi                      # *buff
        mov     $buffer_size, %rdx              # size_t
        dec     %rdx                            # 1 byte for \0
        syscall

        #       setup data
        mov     $1, %rdx                        # write 1 byte each iteration

        mov     %rax, %r9                       # how many bytes read
        mov     %rax, %rcx

        mov     %rsp, %r8                       #
        add     %r9, %r8                        #
        sub     $1, %r8                         # char addr

check_exit_status:
        cmp     $0, %rcx
        je      end


        mov     $write, %rax
write_reversed:
        cmp     $0, %r9
        je      read_input

        dec     %r9
        mov     %r8, %rsi
        dec     %r8

        syscall
        jmp     write_reversed


end:
        add     $buffer_size, %rsp              # dealloc buffer
        mov     $exit, %rax
        mov     $0, %rdi
        syscall

        .size   _start, . - _start