bits 64
global _start

_start:
	push rbp
	push rsp
	push rbx
	push r13
	push rax
	push rcx
	push rdx
	push rsi
	push rdi
	push r8
	push r9

	mov rdi, 1
	lea rsi, [rel msg]
	mov rbx, rsi
	;mov rbx, qword [rel text_section]
	sub rbx, qword [rel text_section] ;text_section address because of this and that
	mov r8, qword [rel section_size] ;text_section size
	mov r9, 0 ;increment register
	xor r13, r13
	mov r13, qword [rel private_key]

	decrypt_whole_blocks:
		; check left to decrypt < block_size
		mov rcx, r8
		sub rcx, r9
		cmp rcx, 8
		jle decrypt_last_block
		; xor section with private_key
		mov rdx, rbx
		add rdx, r9
		xor [rdx], r13
		; increase section address
		; increase counter
		add r9, 8
		jmp decrypt_whole_blocks

	decrypt_last_block:
		mov rdx, 8
		sub rdx, rcx
		mov rcx, rdx
		mov rax, 8
		mul cl
		mov rcx, rax
		shl r13, cl
		shr r13, cl
		mov rdx, rbx
		add rdx, r9
		xor [rdx], r13

	end_decrypt:
		mov rdx, 14
		mov rax, 1
		syscall

		pop r9
		pop r8
		pop rdi
		pop rsi
		pop rdx
		pop rcx
		pop rax
		pop r13
		pop rbx
		pop rsp
		pop rbp

        jmp 0xdadadada ; this needs to be just before that
		msg db "....WOODY....",10 ; that needs to be just after this
		text_section dq 0xbabababababababa
		section_size dq 0xcacacacacacacaca
		private_key dq 0xabcdefabcdefabcd