PowerRomDasm/PowerRomDasm.py
2021-03-22 15:21:27 +01:00

279 lines
11 KiB
Python

'''
Power Macintosh ROM disassembler.
Author: Max Poliakovski 2020-2021
Usage:
python3 PowerRomDasm.py --rom_path=[path to a Power Macintosh ROM dump]
'''
from argparse import ArgumentParser
from ruamel.yaml import YAML
from capstone import *
from capstone.m68k import *
import struct
def bit_not(n, numbits=32):
return (1 << numbits) - 1 - n
def align(n, m):
return (n + m - 1) & bit_not(m - 1)
''' Capstone-based disassembler for 68k code.'''
class M68KDasm:
def __init__(self, cb):
self.rom_cb = cb
self.cse = Cs(CS_ARCH_M68K, CS_MODE_M68K_040)
self.cse.detail = True
self.labels = {}
def dasm_single(self, address, code):
''' Disassble single 68k instruction with the Capstone engine. '''
# detect A-Traps and disassemble them ourselves
if (code[0] & 0xF0) == 0xA0:
from mactraps import TRAP_TABLE
trap_num = (code[0] << 8) | code[1]
if trap_num in TRAP_TABLE:
return ((TRAP_TABLE[trap_num], [], 2))
else:
return (('dc.w', [hex(trap_num)], 2))
# disassemble non-trap instructions with Capstone
instrs = self.cse.disasm(code, address)
return next(instrs)
def dasm_region(self, addr, size, data):
pp_dasm = []
last_addr = addr + size
offset = 0
while addr < last_addr:
# prefetch binary data (2 >= bytes <= 10) for the next instruction
bin_length = min(last_addr - addr, 10)
bin_prefetch = bytearray()
for i in range(bin_length):
bin_prefetch.append(data[offset+i])
instr = self.dasm_single(addr, bin_prefetch)
if not isinstance(instr, CsInsn):
pp_dasm.append({'addr': addr, 'mnem': instr[0], 'ops': instr[1]})
addr += instr[2]
offset += instr[2]
continue
op_list = instr.op_str.split(',')
#print(op_list)
ops = []
for op in instr.operands:
#print(op.type)
if op.type == M68K_OP_MEM:
#print(op.address_mode)
if op.address_mode == M68K_AM_PCI_DISP:
ea = addr + op.mem.disp + 2
flag,sym = self.rom_cb.get_symbol(ea)
if flag:
ops.append(sym)
else:
label = 'l_{:x}'.format(ea)
ops.append(label)
if ea not in self.labels:
self.labels[ea] = label
# discard current op because we've just replaced it
op_list.pop(0)
elif op.address_mode == M68K_AM_PCI_INDEX_BASE_DISP:
ops.append(instr.op_str)
else:
ops.append(op_list.pop(0))
elif op.type == M68K_OP_BR_DISP:
if op.address_mode == M68K_AM_BRANCH_DISPLACEMENT:
ea = addr + op.br_disp.disp + 2
flag,sym = self.rom_cb.get_symbol(ea)
if flag:
ops.append(sym)
else:
label = 'l_{:x}'.format(ea)
ops.append(label)
if ea not in self.labels:
self.labels[ea] = label
# discard current op because we've just replaced it
op_list.pop(0)
else:
ops.append(op_list.pop(0))
else:
ops.append(op_list.pop(0))
pp_dasm.append({'addr': addr, 'mnem': instr.mnemonic, 'ops': ops})
addr += instr.size
offset += instr.size
#print(ops)
#print(self.labels)
for instr in pp_dasm:
if instr['addr'] in self.labels:
print('\n' + self.labels[instr['addr']] + ':')
print(hex(instr['addr']).ljust(15), end='')
print(instr['mnem'], '\t', end='')
print(','.join(instr['ops']))
def dasm_regions(self, start_addr, size, data, regions):
self.labels = {}
for reg in regions:
if reg[2] == 'align':
print(hex(start_addr + reg[0]).ljust(15), end='')
print('align\t' + str(reg[3]))
elif reg[2] == 'code':
reg_size = reg[1] - reg[0] + 1
self.dasm_region(start_addr + reg[0], reg_size,
data[reg[3]:reg[3]+reg_size])
else:
print("Unknown region type " + reg[2])
class ROMDisassembler:
def __init__(self, rom_data, rom_db):
self.rom_data = rom_data
self.rom_db = rom_db
self.start_addr = rom_db['main_info']['phys_addr']
self.m68k_dasm = M68KDasm(self)
def get_symbol(self, addr):
offset = addr - self.start_addr
if offset in self.rom_db['annot_items']:
return (True, self.rom_db['annot_items'][offset]['label'])
else:
return (False, '')
def fmt_single_entry(self, format, size, offset):
print(hex(self.start_addr + offset).ljust(15), end='')
if format == 'hex':
if size == 1:
print("dc.b\t0x%X" % struct.unpack('>B', self.rom_data[offset:offset+1]))
elif size == 2:
print("dc.w\t0x%X" % struct.unpack('>H', self.rom_data[offset:offset+2]))
elif size == 4:
print("dc.l\t0x%X" % struct.unpack('>I', self.rom_data[offset:offset+4]))
else:
print("INVALID SIZE!")
elif format == 'dec':
if size == 1:
print("dc.b\t%d" % struct.unpack('>B', self.rom_data[offset:offset+1]))
elif size == 2:
print("dc.w\t%d" % struct.unpack('>H', self.rom_data[offset:offset+2]))
elif size == 4:
print("dc.l\t%d" % struct.unpack('>I', self.rom_data[offset:offset+4]))
else:
print("INVALID SIZE!")
elif format == 'offset':
dest_offset = struct.unpack('>I', self.rom_data[offset:offset+4])[0]
if dest_offset in self.rom_db['annot_items']:
symbol = self.rom_db['annot_items'][dest_offset]['label']
print("dc.l\t" + symbol + '-BaseOfRom')
else:
print("dc.l\t0x%X" % dest_offset)
def parse_subregs(self, start, size, subregs):
#print("This entry has subregions", subregs)
regs = []
reg_start = start
for reg in subregs:
if reg['type'] != 'align':
print("Unknown subregion type " + reg['type'])
return regs
offset = reg['offset']
if offset < reg_start or offset >= (start + size):
print("Invalid subregion offset: 0x%X" % offset)
return regs
regs.append((reg_start, offset - 1, 'code', reg_start - start))
boundary = reg['boundary']
reg_end = align(offset, boundary)
regs.append((offset, reg_end - 1, 'align', boundary))
reg_start = reg_end
if reg_start < (start + size):
regs.append((reg_start, (start + size) - 1, 'code', reg_start - start))
#print(regs)
return regs
def fmt_entry(self, entry, offset):
print("")
print((entry['label'] + ':').ljust(15))
if entry['type'] == 'array':
count = entry['size'] // entry['elsize']
for i in range(count):
self.fmt_single_entry(entry['format'], entry['elsize'], offset)
offset += entry['elsize']
elif entry['type'] == 'int':
self.fmt_single_entry(entry['format'], entry['size'], offset)
elif entry['type'] == 'code':
size = entry['size']
if entry['arch'] == '68k':
if 'subregs' in entry:
regs = self.parse_subregs(offset, size, entry['subregs'])
else:
regs = [(offset, offset + size - 1, 'code', 0)]
self.m68k_dasm.dasm_regions(self.start_addr, size,
self.rom_data[offset:offset+size], regs)
elif entry['arch'] == 'ppc':
print("PPC disassembler not implemented yet")
else:
print("Unknown code region architecture " + entry['arch'])
def dasm_region(self, start, end):
offset = start
while offset < end:
if offset in self.rom_db['annot_items']:
entry = self.rom_db['annot_items'][offset]
self.fmt_entry(entry, offset)
offset += entry['size']
else:
print(hex(self.start_addr + offset).ljust(15), end='')
print("dc.b\t0x%X" % struct.unpack('>B', self.rom_data[offset:offset+1]))
offset += 1
if __name__ == "__main__":
parser = ArgumentParser()
parser.add_argument('--rom_path', type=str,
dest='rom_path',
help='path to a PowerMacintosh ROM file to process',
metavar='ROM_PATH', required=True)
parser.add_argument('--start', type=lambda x: int(x,0),
dest='start_offs', default=0,
help='offset to the start of the region to disassemble',
required=False,
)
parser.add_argument('--end', type=lambda x: int(x,0),
dest='end_offs', default=0x500,
help='offset to the end of the region to disassemble',
required=False,
)
opts = parser.parse_args()
with open(opts.rom_path, 'rb') as rom_file:
rom_file.seek(0, 2)
rom_size = rom_file.tell()
if rom_size != (4 * 1024 * 1024):
print("Invalid ROM file size %d (expected 4 MB)" % rom_size)
# just load the whole ROM image into memory
rom_file.seek(0, 0)
rom_data = rom_file.read()
check_sum = struct.unpack('>I', rom_data[0:4])[0]
print("ROM Checksum: %X" % check_sum)
db_name = 'ROMDB_' + '{:x}'.format(int(check_sum)).upper() + '.yaml'
with open('database/' + db_name, 'rb') as db_file:
yaml = YAML()
annot_db = yaml.load(db_file)
print(annot_db['main_info']['name'])
rdasm = ROMDisassembler(rom_data, annot_db)
rdasm.dasm_region(opts.start_offs, opts.end_offs)