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assembler.py
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assembler.py
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#!/usr/bin/env python
"""
assembler.py: rather primitive two-pass assembler. Get the labels, then
assemble the instructions.
"""
import re
import sys
import optparse
symbols = {}
instructions = []
relocations = []
class AssemblerError(Exception):
pass
class AssemblerSyntaxError(AssemblerError):
def __init__(self,line,reason):
self.line = line
self.reason = reason
def __str__(self):
return "Syntax error on line %d: %s" % (self.line,self.reason)
class AssemblerRangeError(AssemblerError):
def __init__(self,line,reason):
self.line = line
self.reason = reason
def __str__(self):
return "Range error on line %d: %s" % (self.line,self.reason)
labelre = re.compile(r"""^(?P<labels>.*:)?(?P<gunk>[^:]*)$""")
commentre = re.compile(r"""^(?P<important>[^#]*)(?P<comment>#.*)?$""")
alnumunderre = re.compile(r"""^\w+$""")
rtype_re = re.compile(r'''^(?P<instr>(or|and|add|sub|slt|sltu|addu|subu))\s+(?P<rd>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<rs>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))$''')
new_re = re.compile(r'''^(?P<instr>(bitpal|lfsr))\s+(?P<rd>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<rs>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))$''')
shift_re = re.compile(r'''^(?P<instr>(sll|srl|sra))\s+(?P<rd>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<immed>-?(0x)?[0-9a-fA-F]+)$''')
immed_re = re.compile(r'''^(?P<instr>(ori|addiu|andi))\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<rs>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|sp|fp|ra))\s+(?P<immed>-?(0x)?[0-9a-fA-F]+)$''')
lui_re = re.compile(r'''^(?P<instr>lui)\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<immed>-?(0x)?[0-9a-fA-F]+)$''')
mem_re = re.compile(r'''^(?P<instr>(lw|sw|lb|lbu|sb))\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<immed>-?(0x)?[0-9a-fA-F]+)\s*\(\s*(?P<rs>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s*\)$''')
j_re = re.compile(r'''^(?P<instr>(j|jal))\s+(?P<label>\w+)$''')
branch_re = re.compile(r'''^(?P<instr>(beq|bne))\s+(?P<rs>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|sp|fp|ra))\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|sp|fp|ra))\s+(?P<label>\w+)$''') #note switch
jr_re = re.compile(r'''^(?P<instr>(jr))\s+(?P<rs>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))$''')
signed_re = re.compile(r'addiu|beq|bne|lw|sw|sb|lb|lbu')
la_re = re.compile(r'''^(?P<instr>(la))\s+(?P<rt>\$(0|zero|at|v[0,1]|a[0-3]|t[0-9]|s[0-7]|k[0-1]|gp|fp|sp|ra))\s+(?P<label>\w+)$''')
both_allowed_re = re.compile(r'ori|andi')
opcodes = {
'jal':0x3,
'j':0x2,
'beq':0x4,
'bne':0x5,
'addiu':0x9,
'andi':0xc,
'ori':0xd,
'sw':0x2b,
'lui':0xf,
'lw':0x23,
'sb':0x28,
'lb':0x20,
'lbu':0x24
}
functs = {
'mfhi':0x10,
'mflo':0x12,
'add':0x20,
'addu':0x21,
'sub':0x22,
'subu':0x23,
'sll':0,
'srl':2,
'sra':3,
'jr':8,
'slt':0x2a,
'sltu':0x2b,
'or':0x25,
'and':0x24,
'mulad':0x3e,
'divsubu':0x3f
}
registers = {
'0':0,
'zero':0,
'at':1,
'v0':2,
'v1':3,
'a0':4,
'a1':5,
'a2':6,
'a3':7,
't0':8,
't1':9,
't2':10,
't3':11,
't4':12,
't5':13,
't6':14,
't7':15,
's0':16,
's1':17,
's2':18,
's3':19,
's4':20,
's5':21,
's6':22,
's7':23,
't8':24,
't9':25,
'k0':26,
'k1':27,
'gp':28,
'sp':29,
'fp':30,
'ra':31
}
def isPseudoInstruction(s):
return la_re.match(s) or li_re.match(s)
def validLabel(s):
return alnumunderre.match(s) != None
def fill_symbol_table(inputFile):
lineNo = 1
instructionsSeen = 0
for line in inputFile:
#strip any comments
match = commentre.match(line)
if not match:
raise AssemblerSyntaxError(lineNo,"Unable to parse line: %s" % line)
line = match.group('important')
line = line.strip()
match = labelre.match(line)
if not match:
raise AssemblerSyntaxError(lineNo,"Unable to parse line: %s" % line)
labels_string = match.group('labels')
if labels_string:
labels = labels_string[:-1].split(':')
else:
labels = []
for label in labels:
if not validLabel(label):
raise AssemblerSyntaxError(lineNo,"Invalid label: '%s'"%label)
if label in symbols:
raise AssemblerSyntaxError(lineNo,"Label %s already defined" % label)
symbols[label] = instructionsSeen
instruction = match.group('gunk').replace(',',' ').strip()
if len(instruction) != 0:
#there's an instruction here, so increment the number of instructions
#if we had any pseudoinstructions, we'd do analysis and increment by
#more than one here
instructionsSeen += 1
lineNo+=1
def imm_check(signed,both_allowed,immediate,lineNo):
if both_allowed:
if (immediate > 2 ** 16 - 1 or immediate < -(2 ** 16)):
raise AssemblerSyntaxError(lineNo,"immediate out of range")
else:
if signed and (immediate > 2 ** 16 - 1 or immediate < -(2 ** 16)):
raise AssemblerSyntaxError(lineNo,"signed immediate out of range")
if (not signed) and (immediate > 2 ** 16 - 1 or immediate < 0):
raise AssemblerSyntaxError(lineNo,"unsigned immediate out of range")
def shamt_check(shamt,lineNo):
if(shamt > 31 or shamt < 0):
raise AssemblerSyntaxError(lineNo,"shamt out of range")
def assemble_instructions(inputFile):
lineNo = 1
instructionsSeen = 0
instructions = []
for line in inputFile:
#strip any comments
match = commentre.match(line)
assert(match)
line = match.group('important')
line = line.strip()
match = labelre.match(line)
instruction = match.group('gunk').replace(',',' ').strip()
rtype = rtype_re.match(instruction)
new = new_re.match(instruction)
shift = shift_re.match(instruction)
immed = immed_re.match(instruction)
lui = lui_re.match(instruction)
mem = mem_re.match(instruction)
j = j_re.match(instruction)
branch = branch_re.match(instruction)
jr = jr_re.match(instruction)
signed = signed_re.match(instruction)
both_allowed = both_allowed_re.match(instruction)
if len(instruction) != 0:
num = 0
if rtype:
rs = registers[rtype.group('rs')[1:]]
rt = registers[rtype.group('rt')[1:]]
rd = registers[rtype.group('rd')[1:]]
funct = functs[rtype.group('instr')]
num = 0 << 26 | rs << 21 | rt << 16 | rd << 11 | 0 << 6 | funct
debug("instruction: %s rtype: rs: %d rt: %d rd: %d funct:%d num: %04x" % (instruction,rs,rt,rd,funct,num))
elif new:
rs = registers[new.group('rs')[1:]]
rd = registers[new.group('rd')[1:]]
funct = functs[new.group('instr')]
num = 0 << 26 | rs << 21 | 0 << 16 | rd << 11 | 0 << 6 | funct
debug("instruction: %s rtype: rs: %d rd: %d funct:%d num: %04x" % (instruction,rs,rd,funct,num))
elif shift:
rt = registers[shift.group('rt')[1:]]
rd = registers[shift.group('rd')[1:]]
immediate = int(shift.group('immed'),0)
funct = functs[shift.group('instr')]
shamt_check(immediate,lineNo)
num = 0 << 26 | 0 << 21 | rt << 16 | rd << 11 | (immediate & 31) << 6 | funct
debug("instruction: %s rtype: rs: %d rd: %d shamt: %d funct:%d num: %04x" % (instruction,rt,rd,immediate,funct,num))
elif immed:
rs = registers[immed.group('rs')[1:]]
rt = registers[immed.group('rt')[1:]]
opcode = opcodes[immed.group('instr')]
immediate = int(immed.group('immed'),0)
imm_check(signed,both_allowed,immediate,lineNo)
num = opcode << 26 | rs << 21 | rt << 16 | (immediate & 0xFFFF)
debug("instruction: %s rs: %d rt: %d opcode: %d immediate: %d num: %04x" % (instruction,rs,rt,opcode,immediate,num))
elif lui:
rt = registers[lui.group('rt')[1:]]
opcode = opcodes[lui.group('instr')]
immediate = int(lui.group('immed'),0)
imm_check(signed,both_allowed,immediate,lineNo)
num = opcode << 26 | 0 << 21 | rt << 16 | (immediate & 0xFFFF)
debug("instruction: %s rt: %d opcode: %d immediate: %d num: %04x" % (instruction,rt,opcode,immediate,num))
elif mem:
opcode = opcodes[mem.group('instr')]
rs = registers[mem.group('rs')[1:]]
rt = registers[mem.group('rt')[1:]]
immediate = int(mem.group('immed'),0)
imm_check(signed,both_allowed,immediate,lineNo)
num = opcode << 26 | rs << 21 | rt << 16 | (immediate & 0xFFFF)
debug("instruction: %s rs: %d rt: %d opcode: %d immediate: %d num: %04x" % (instruction,rs,rt,opcode,immediate,num))
elif j:
opcode = opcodes[j.group('instr')]
#find label
label = j.group('label')
if label not in symbols:
raise AssemblerSyntaxError(lineNo,"unknown label %s" % j.group('label'))
instructionNo = symbols[label]
thisInstruction = instructionsSeen
if thisInstruction & 0x3000000 != instructionNo & 0x3000000:
raise AssemblerRangeError(lineNo,"label %s is in another jump zone (instr: %04x, target:%04x)" % (label,thisInstruction,instructionNo))
instructionNo += 0x100000
num = opcode << 26 | (instructionNo & 0x3FFFFFF)
debug("instruction: %s addr: %d num: %04x" % (instruction,instructionNo & 0x3FFFFFF,num))
elif branch:
rs = registers[branch.group('rs')[1:]]
rt = registers[branch.group('rt')[1:]]
opcode = opcodes[branch.group('instr')]
#find label
label = branch.group('label')
if label not in symbols:
raise AssemblerSyntaxError(lineNo,"unknown label %s" % branch.group('label'))
instructionNo = symbols[label]
offset = instructionNo - (instructionsSeen + 1)
if offset > 2 ** 16 - 1 or offset < -(2 ** 16):
raise AssemblerRangeError(lineNo,"label %s is too far away: %d instructions from pc+1" % (label,offset))
num = opcode << 26 | rs << 21 | rt << 16 | (offset & 0xFFFF)
debug("instruction: %s rs: %d rt: %d opcode: %d offset: %d num: %04x" % (instruction,rs,rt,opcode,offset,num))
elif jr:
rs = registers[jr.group('rs')[1:]]
funct = functs[jr.group('instr')]
num = 0 << 26 | rs << 21 | 0 << 16 | 0 << 11 | 0 << 6 | funct
debug("instruction: %s rs: %d num: %04x" % (instruction,rs,num))
else:
raise AssemblerSyntaxError(lineNo,"Can't parse instruction '%s'" % instruction)
#there's an instruction here, so increment the number of instructions
#if we had any pseudoinstructions, we'd do analysis and increment by
#more than one here
instructionsSeen += 1
instructions.append(num)
lineNo+=1
return instructions
def print_instructions(instructions,outfile):
print >> outfile, "v2.0 raw"
for instruction in instructions:
print >> outfile, "%04x" % instruction
verbose = False
def debug(*args):
if verbose:
sys.stdout.write(' '.join([str(arg) for arg in args]) + '\n')
if __name__ == "__main__":
usage = "%prog infile [options]"
parser = optparse.OptionParser(usage=usage)
parser.add_option('-o','--out',dest='output_file',type='string',
default='a.hex',help="Specify output filename")
parser.add_option('-v','--verbose',dest='verbose',
action='store_true',default=False, help='verbose debug mode')
options,args = parser.parse_args()
if len(args) != 1:
parser.error("Incorrect command line arguments")
sys.exit(1)
verbose = options.verbose
output_file = options.output_file
input_file = args[0]
if re.match(r""".*(?P<extension>\.s)$""",input_file,re.I) and output_file == 'a.hex':
output_file = input_file[:-1] + "hex"
try:
infile = open(input_file)
except IOError,e:
print >> sys.stderr, "Unable to open input file %s" % input_file
sys.exit(1)
try:
fill_symbol_table(infile)
infile.seek(0)
instructions = assemble_instructions(infile)
infile.close()
except AssemblerError, e:
print >> sys.stderr, str(e)
sys.exit(1)
try:
outfile = open(output_file,'w')
print_instructions(instructions,outfile)
outfile.close()
except IOError,e:
print >> sys.stderr, "Unable to write to output file %s" % output_file
sys.exit(1)
sys.exit(0)