NASM: parser: instruction expected rep movs

Question

I\'ve been turning an executable into some NASM shellcode (for windows if it\'s relevant) but i\'m encountering \"error: parser: instruction expected\" errors all over the place

Answer 1

I would make sure to initialize ECX to string length for rep instruction, initialize EDI and ESI to destination and source string respectively, make sure direction flag is set accordingly then:

label_0000641:
lea    edi,[esp+0x164] ;initializing destination?                   
label_0000648:
rep movsd
label_000064a:
and    DWORD [esp+0x168],0x0