I'd like to edit the first instruction and change it to jmp 100h (give or take a few bytes)
the mov edi,edi takes 2 bytes and the jmp 100h takes 5 bytes (correct me if im wrong)
I edit the machine code to jmp 100h and add a nop to round it to 6 bytes.
.text:08048DD5 mov edi, edi
.text:08048DD7 mov edi, edi
.text:08048DD9 mov edi, edi
.text:08048DDB mov edi, edi
.text:08048DDD mov edi, edi
.text:08048DDF mov edi, edi
.text:08048DE1 mov edi, edi
.text:08048DE3 mov edi, edi
.text:08048DE5 add [ebp+var_C], 1 ; Add
.text:08048DE9 mov eax, offset format ; "Message %d: %s"
.text:08048DEE lea edx, [ebp+s] ; Load Effective Address
.text:08048DF4 mov [esp+8], edx
the result looks like:
.text:08048DD5 jmp loc_8048D41
.text:08048DD5 ; ---------------------------------------------------------------------------
.text:08048DDA db 90h
.text:08048DDB db 89h, 0FFh
.text:08048DDD db 89h, 0FFh
.text:08048DDF db 89h, 0FFh
.text:08048DE1 db 89h, 0FFh
.text:08048DE3 db 89h, 0FFh
.text:08048DE5 ; ---------------------------------------------------------------------------
.text:08048DE5 add [ebp+var_C], 1
.text:08048DE9 mov eax, offset aMessageDS ; "Message %d: %s"
.text:08048DEE lea edx, [ebp+s]
.text:08048DF4 mov [esp+8], edx
.text:08048DF8 mov edx, [ebp+var_C]
what exactly goes wrong here? How do i keep the rest of the code intact?
Looks like it works, but the disassembler isn't interpreting the data as instructions. This is probably because of the preceding jmp instruction - the disassembler sees that the code right after it will never be reached, so it assumes it's not actually code (and thus interprets it as straight data).