vermu1-emulator.py

r = open('level1','rb').read()

b = bytearray(r)

mem = bytearray([0] * 0x10000)
mem[0:len(b)] = b[0:len(b)]

pc = 0
stack = []

# def split_n(line,n=4):
    # return [line[i:i+n] for i in range(0, len(line), n)]

def tohex(val, nbits=32):
    return hex((val + (1 << nbits)) % (1 << nbits))


def parse_instruction(b):
    global pc
    if b[pc] == 0:
        print "NOP"
        pc += 1
    elif b[pc] == 0x10:
        val = int(str(b[pc+1:pc+1+4]).encode('hex'), 16)
        print "PUSH " + hex(val)
        stack.append(val)
        pc += 5
    elif b[pc] == 0x20:
        addr = stack.pop()
        value = stack.pop()
        print "STORE @ {} -> {}".format(hex(addr), hex(value))
        mem[addr] = value
        mem[addr+1] = value >> 8
        mem[addr+2] = value >> 16
        mem[addr+3] = value >> 24
        pc += 1
    elif b[pc] == 0x21:
        addr = stack.pop()
        # dst = stack.pop()
        val = 0
        val = mem[addr]
        val += mem[addr+1] << 8
        val += mem[addr+2] << 16
        val += mem[addr+3] << 24
        print "PUSH [{}] -> {}".format(hex(addr), hex(val))
        stack.append(val)
        pc += 1
    elif b[pc] == 0x30:
        n1 = stack.pop()
        n2 = stack.pop()
        stack.append(n1 + n2)
        print "ADD {} + {}".format(hex(n1), hex(n2))
        pc += 1
    elif b[pc] == 0x31:
        n1 = stack.pop()
        n2 = stack.pop()
        stack.append(n1 ^ n2)
        print "XOR {} ^ {} -> {}".format(tohex(n1), tohex(n2), tohex(n1 ^ n2))
        pc += 1
    elif b[pc] == 0x32:
        n1 = stack.pop()
        n2 = stack.pop()
        if n1 == n2:
            r = 0
        elif n1 <= n2:
            r = -1
        else:
            r = 1
        stack.append(r)
        print "CMP {} and {} -> {}".format(tohex(n1), tohex(n2), r )
        pc += 1
    elif b[pc] == 0x33:
        n1 = stack.pop()
        n2 = stack.pop()
        stack.append(n1 * n2)
        print "MULTIPLY {} * {}".format(n1, n2)
        pc += 1
    elif b[pc] == 0x38:
        n1 = stack.pop()
        stack.append(~n1)
        print "NEGATE {} -> {}".format(hex(n1), tohex(~n1))
        pc += 1
    elif b[pc] == 0x41:
        addr = stack.pop()
        print "JMP @ {}".format(hex(addr))
        pc = addr
    elif b[pc] == 0x42:
        addr = stack.pop()
        result = stack.pop()
        print "JMP CONDITIONAL {} to addr {}".format(result, hex(addr))
        if result != 0:
            pc += 1
        else:
            pc = addr
    elif b[pc] == 0x50:
        # one of the ops only 2 possible in level1
        op = stack.pop()
        if op == 0:
            n = stack.pop()
            n2 = stack.pop()
            print "READING @ {} ({} bytes) ".format(hex(n2), n)
            r = raw_input("READING {} bytes: ".format(n))
            mem[n2:n2+n] = r[:n]
        else:
            print "UNK OP"
        pc += 1

    else:
        print "UNK " + hex(b[pc])
        pc += 1

# while pc <= len(b):
while pc <= 230: #and mem[0x1000] != 1:
    parse_instruction(b)