assembler.py

import os
import argparse
import sys

"""
**************** SOME FORMATS *************
_dpi_format = _InstructionFormat("Cond 0 0 I Opcode S Rn Rd Operand2")
_branch_format = _InstructionFormat("Cond 1 0 1 L Offset")
_bx_format = _InstructionFormat("Cond 0 0 0 1 0 0 1 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 L 1 Rm")
_load_store_format = _InstructionFormat("Cond 0 1 I P U B W L Rn Rd Operand2")
_load_store_multi_format = _InstructionFormat("Cond 1 0 0 P U S W L Rn RegisterList")
_mul_format = _InstructionFormat("Cond 0 0 0 0 0 0 0 S Rd 0 0 0 0 Rs 1 0 0 1 Rm")
_mla_format = _InstructionFormat("Cond 0 0 0 0 0 0 1 S Rd Rn Rs 1 0 0 1 Rm")
_clz_format = _InstructionFormat("Cond 0 0 0 1 0 1 1 0 1 1 1 1 Rd 1 1 1 1 0 0 0 1 Rm")
_mrs_format = _InstructionFormat("Cond 0 0 0 1 0 R 0 0 1 1 1 1 Rd 0 0 0 0 0 0 0 0 0 0 0 0")
_msr_format_reg = _InstructionFormat("Cond 0 0 0 1 0 R 1 0 f s x c 1 1 1 1 0 0 0 0 0 0 0 0 Rm")
_msr_format_imm = _InstructionFormat("Cond 0 0 1 1 0 R 1 0 f s x c 1 1 1 1 Operand2")
_swi_format = _InstructionFormat("Cond 1 1 1 1 Imm24")

"""

labels = []
operands = []
registers = []

conditions = [
 "EQ", "NE", "CS", "CC",
 "MI", "PL", "VS", "VC",
 "HI", "LS", "GE", "LT",
 "GT", "LE"]
 
data_proc = {
"AND":"0000",
"EOR":"0001",
"SUB":"0010",
"RSB":"0011", 
"ADD":"0100",
"ADC":"0101",
"SBC":"0110",
"RSC":"0111",
"TST":"1000",
"TEQ":"1001",
"CMP":"1010",
"CMN":"1011", 
"ORR":"1100",
"MOV":"1101", 
"BIC":"1110", 
"MVN":"1111"
}

single_data_transfer = {
"LDR": 1, "STR":0
}
software_interrupt = {
 "SWI": 0, "SVC": 1,
}
def parse_branch(line, ins, lineNumber): 
  cond = ins[1:]
  idx = 0
  for x in conditions: 
    idx += 1
    if x == cond: 
      cond = str(bin(int(idx - 1)))
  binary = cond + "1010"
  createBinaryFile(binary)
# TODO need support for offset
def parse_branch_with_link(line, ins, lineNumber):
  cond = ins[1:]
  idx = 0
  for x in conditions: 
    idx += 1
    if x == cond: 
      cond = str(bin(int(idx - 1)))
  binary = cond + "1011"
  createBinaryFile(binary)

def parse_branch_and_exchange(line, ins, lineNumber):   
  cond = ins[2:]
  line = line.strip()
  line = line.split(" ")
  reg = line[1]
  idx = 0
  Rn = 0
  for x in conditions: 
    idx += 1
    if x == cond: 
      cond = str(bin(int(idx - 1)))
  for r in registers: 
    for k,v in r.items():
      if reg == k:  
        Rn = v
  binary = cond + "000100101111111111110001" + Rn  
  createBinaryFile(binary)

def parse_swp(line, ins, lineNumber):
  line = line.strip()
  line = line.split(" ")
  # TODO add condition bits - default as 0000/ empty
  dest_reg = line[1].strip(",")
  source_reg = line[2].strip(",")
  base_reg = line[3]
  dest_reg_bin = 0
  source_reg_bin = 0
  base_reg_bin = 0
  for reg in registers: 
    for k,v in reg.items(): 
      if k == dest_reg:
        dest_reg_bin = v
      if k == source_reg: 
        source_reg_bin = v
      if k == base_reg: 
        base_reg_bin = v
  binary = "000000010000"+str(base_reg_bin)+str(dest_reg_bin)+"00001001"+str(source_reg_bin)
  createBinaryFile(binary)  

def parse_swi(line,lineNumber): 
  # TODO add condition bits - default as 0000
  line = line.strip()
  line = line.split(" ")
  inte = line[0] 
  val = line[1]
  val = bin(int(val.replace("&","").lower(),16))
  binary = "0000"+"1111"+str(val)
  createBinaryFile(binary)

def checkIfLabel(reg):
  for keys in labels: 
    k = keys.get(reg)
    if k != None:
      return k 

def createBinaryFile(binary):
  f = open("binary.obj","a")
  f.write(binary)
  f.close()

def parse_sdt(line, lineNumber): 
  line = line.strip();
  line = line.split(" ")
  sdt = line[0]
  if sdt == "LDR":  
    source_reg = line[1].strip(',')
    # check if source_reg can be converted to binary else use 00000000 
    base_reg = line[2] 
    bit = single_data_transfer[line[0]]
    # check if base_reg is label, if label then get value
    new_base_reg = checkIfLabel(base_reg)
    if new_base_reg != None:
      for x in range(len(line)): 
        if line[x] == base_reg:
          line[x] = new_base_reg
    # write this instruction to file 
    # TODO: Add support for checking condition & offset, default 0000
    try: 
      new_base_reg_bin = str(bin(int(new_base_reg.replace("&","").lower(),16)))
      binary = "0000"+"01"+"0"+"0"+"0"+"1"+new_base_reg_bin+"00000000"
      createBinaryFile(binary)
      registers.append({source_reg : new_base_reg_bin}) 
    except: 
      print "Syntax Error. Unable to parse label" 
    # save reference of new_base_reg and source_reg which will be used later 
  else: 
    source_reg = line[1].strip(',')
    source_reg_binary = 0
    base_reg = line[2]
    bit = single_data_transfer[line[0]]
    for reg in registers: 
      for k,v in reg.items(): 
        if k == source_reg: 
          source_reg_binary = v
    registers.append({base_reg: source_reg_binary})
    binary = "0000010001" + source_reg_binary + "00000000"
    createBinaryFile(binary)

def parse_dpi(line, lineNumber): 
  # TODO Add support for checking condition & offset, default 0000
  line =  line.strip()
  line = line.split(" ")
  opcode = line[0]
  # convert opcode to its binary 
  for proc in data_proc: 
    if opcode == proc: 
      opcode = data_proc[proc]
  # get value of registers from array
  if len(line) > 3:
    source_reg = line[1]
    source_reg = source_reg.split(",")[0]
    dest_reg = line[2]
    dest_reg = dest_reg.split(",")[0] 
    operand_reg = line[3]
  else: 
    source_reg = line[1].split(",")[0]
    operand_reg = line[2].split(",")[0]
    dest_reg = '' 
  for reg in registers:
    for k,v in reg.items(): 
      if k == dest_reg: 
        dest_reg = v
      if k == operand_reg: 
        operand_reg = v

  binary = "0000"+"00"+"0"+opcode+"1"+operand_reg+dest_reg
  createBinaryFile(binary)

def parse_condition(line,lineNumber):
  """
  different types of conditions have different
  number of bits in them which is denoted by their idx
  """
def parse_label(line, lineNumber):
  try: 
    line = line.strip()
    line = line.split(" ")
    label_name = line[0] 
    command = line[1]
    value = line[2]
    labels.append({label_name : value})
  except: 
    print "Syntax Error! Cannot parse label due to spaces in line "+ lineNumber
    print "Tip: Replace spaces with tabs in source" 

def parseFile(f): 
  # read each file and get each line
  if os.access(f, os.R_OK):
    with open(f) as fp: 
      file = fp.read()
  lineNumber = 0
  lineOfLabels = 0
  file = file.split('\n') 
  for line in file: 
    lineOfLabels += 1
    line = line.split(';')
    line = line[0] 
    # parse label and push instruction to label array
    label = ["DCW","DCD"]
    for lbl in label:
      if lbl in line: 
        parse_label(line,lineNumber)
  # second loop for !label
  lineNumber += lineOfLabels 
  for line in file: 
    lineNumber += 1
    line = line.split(';')
    line = line[0]
    # look for condition
    for cond in conditions:
      if cond in line:
        parse_condition(line,lineNumber)
    # look for data processing instructions
    for dpi in data_proc: 
      if dpi in line:
        parse_dpi(line, lineNumber)
    # look for single data transfer instructions
    for sdt in single_data_transfer: 
      if sdt in line:
        parse_sdt(line, lineNumber) 
    # look for interrupts
    for swi in software_interrupt: 
      if swi in line: 
        parse_swi(line, lineNumber)   
    # look for branches B, BL, BLX(branch-line-exchnge) 
    for _i in range(len(conditions)): 
      ins = "B" + conditions[_i]
      if ins in line: 
        parse_branch(line, ins, lineNumber)
      ins = "BL" + conditions[_i]
      if ins in line:   
        parse_branch_with_link(line, ins, lineNumber)
      ins = "BX" + conditions[_i]
      if ins in line:
        parse_branch_and_exchange(line, ins, lineNumber)     
    # look for single data swap
    ins = "SWP" 
    if ins in line: 
       parse_swp(line, ins, lineNumber)  

debug = 0;
def showDebug(): 
  print "*** LABEL ***"
  for label in labels: 
    print label
  print "*** REGISTERS ***"
  for reg in registers:
    print reg
  print "*** OPERANDS ***"
  for op in operands: 
    print op

def getfile(f):
  print "getting file",f 
  path = os.path
  if path.exists(f): 
    try: 
      parseFile(f) 
      if debug == 1: 
        showDebug() 
      print "Binary File 'binary.obj' has been created"
      # checkLoops()
    except:
      if debug == 1: 
        showDebug()
      print "Stopped Parsing! Unknown ARM syntax."
  else:
    print "File Not Found!"


if __name__ == "__main__":
  print "Assembler running..." 
  try: 
    flag = sys.argv[1] 
    fileName = sys.argv[2]
    if flag == "-f": 
      getfile(fileName)
  except: 
    print "Type python assembler.py -f <fileName>.s"