How do I get the machine code of an assembly instruction known at compile time?

Question

I want to be able to convert a single line of ASM into shellcode. I.E:

CALL EBX

How do I go about doing this, and also being able to properly convert this shellcode so that I can store it in a variable in a delphi application. I.E:

var ShellCodeArray:  array[0..3] of Byte = ($55,$8B,$EC,$81);

Answer 1

If I get you right, you want to obtain a machine code of a single assembler instruction CALL EBX using Delphi built-in assembler.

function CodeSize: Integer;
asm
    lea EAX, @@end
    lea EDX, @@start
    sub EAX, EDX
    JMP @@end
@@start:
    call EBX
@@end:
end;

procedure Code;
asm
    call EBX
end;

function CodeToBytes: TBytes;
var
  I, N: Integer;
  P: PByte;

begin
  N:= CodeSize;
  SetLength(Result, N);
  P:= @Code;
  for I:= 0 to N - 1 do begin
    Result[I]:= P^;
    Inc(P);
  end;
end;