bits 64
global _start

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

	lea rsi, [rel msg]
	mov rbx, rsi
	sub rbx, qword [rel text_section] ;text_section address because of this and that
	mov r8, qword [rel section_size] ;text_section size
	mov rdx, qword [rel private_key]

	decrypt_last_block:
		; rcx = 8 * (8 - section_size % 8)
		; Then crop the private key by rcx bits
		; That's to decrypt the end of the section in case the section size
		; isn't a multiple of 64 bits
		mov rcx, r8
		not rcx
		and rcx, 7
		inc rcx
		shl rcx, 3
		mov rax, rdx
		shl rax, cl
		shr rax, cl
		; make section size a multiple of 64bits with this and
		and r8, 0xfffffffffffffff8
		xor [rbx + r8], rax

	decrypt_whole_blocks:
		sub r8, 8
		cmp r8, -8
		je end_decrypt
		xor [rbx + r8], rdx
		jmp decrypt_whole_blocks

	end_decrypt:
		mov rdi, 1
		mov rdx, 14
		mov rax, 1
		syscall

		pop r8
		pop rdi
		pop rsi
		pop rdx
		pop rcx
		pop rax
		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