unpackisf.py

import sys

from construct import *
from subprocess import PIPE, Popen

# http://www.qnx.com/developers/docs/660/index.jsp?topic=%2Fcom.qnx.doc.neutrino.building%2Ftopic%2Fload_process_Boot_header.html

boot_header = Struct("boot_header",
  Enum(ULInt32("signature"),
        CORRECT = 0x00FF7EEB,
        _default_ = Pass,
    ),
  ULInt16("version"),
  BitStruct("flags1",
        Flag("STARTUP_HDR_FLAGS1_VIRTUAL"),
        Flag("STARTUP_HDR_FLAGS1_BIGENDIAN"),
        Enum(BitField("Compression", 4),
            STARTUP_HDR_FLAGS1_COMPRESS_NONE = 0,
            STARTUP_HDR_FLAGS1_COMPRESS_ZLIB = 0x01,
            STARTUP_HDR_FLAGS1_COMPRESS_LZO  = 0x02,
            STARTUP_HDR_FLAGS1_COMPRESS_UCL  = 0x03,
          _default_ = Pass
        ),
        Padding(2),
  ),
  ULInt8("flags2_unused"),
  ULInt16("header_size"),
  Enum(ULInt16("machine"),
        EM_NONE = 0,
        EM_M32 = 1,                 # /* AT&T WE 32100 */
        EM_SPARC = 2,               # /* Sun SPARC */
        EM_386 = 3,                 # /* Intel 80386 */
        EM_68k = 4,                 # /* Motorola 68000 */
        EM_88k = 5,                 # /* Motorola 88000 */
        EM_486 = 6,                 # /* Intel 80486 */
        EM_860 = 7,                 # /* Intel i860 */
        EM_MIPS = 8,                # /* MIPS RS3000 Big-Endian */
        EM_S370 = 9,                # /* IBM system 370 */
        EM_MIPS_RS3_LE = 10, # /* MIPS RS3000 Little-Endian */
        EM_RS6000 = 11,              # /* RS6000 */
        EM_UNKNOWN12 = 12,
        EM_UNKNOWN13 = 13,
        EM_UNKNOWN14 = 14,
        EM_PA_RISC = 15,             # /* PA_RISC */
        EM_nCUBE = 16,               # /* nCUBE */
        EM_VPP500 = 17,              # /* Fujitsu VPP500 */
        EM_SPARC32PLUS = 18, # /* Sun Sparc 32+ */
        EM_UNKNOWN19 = 19,
        EM_PPC = 20,                 # /* Power PC */
        EM_ARM = 40,    # /* ARM */
        EM_SH = 42,             # /* Hitachi SH */
        _default_ = Pass
    ),
  ULInt32("startup_vaddr"),
  ULInt32("paddr_bias"),
  ULInt32("image_paddr"),
  ULInt32("ram_paddr"),
  ULInt32("ram_size"),
  ULInt32("startup_size"),
  ULInt32("stored_size"),
  ULInt32("imagefs_paddr"),
  ULInt32("imagefs_size"),
  ULInt16("preboot_size"),
  ULInt16("zero0"),
  Array(3, ULInt32("zero3"))
)

input = open(sys.argv[1], "rb")
data = input.read()
input.close()

header = boot_header.parse(data)
print header
if header.stored_size == len(data):
    print "stored_size OK"
else:
    print "stored_size NOK"

stored_imagefs = header.stored_size - header.startup_size
if stored_imagefs == header.imagefs_size:
    print "imagefs_size OK, uncompressed"
elif stored_imagefs < header.imagefs_size:
    print "imagefs_size OK, compressed %d -> %d" % (header.imagefs_size, stored_imagefs)
else:
    print "imagefs_size NOK: imagefs %d, stored %d" % (header.imagefs_size, stored_imagefs)

startup = open(sys.argv[1] + ".startup", "wb")
startup.write(data[:header.startup_size])
print "Wrote " + str(startup)
startup.close()

imagefs = open(sys.argv[1] + ".imagefs", "wb")
imagefs_data = data[header.startup_size:]
imagefs.write(imagefs_data)
print "Wrote " + str(imagefs)
imagefs.close()

imagefs_struct = GreedyRange(PascalString("imagefs", length_field = UBInt16("length")))
imagefs_parsed = imagefs_struct.parse(imagefs_data)
print "Found %d LZO blocks" % len(imagefs_parsed)

imagefs = open(sys.argv[1] + ".imagefs.decompressed", "wb")
for i in range(len(imagefs_parsed)):
    sys.stdout.write("\rDecompress: %d/%d " % (i, len(imagefs_parsed)))
    if len(imagefs_parsed[i]) == 0:
        continue
    lzod = Popen("./lzod", stdin=PIPE, stdout=imagefs, stderr=PIPE)
    lzod_result = lzod.communicate(imagefs_parsed[i])
    if (lzod.returncode != 0):
        print "Failed: %d" % lzod.returncode
        print lzod_result
        raise Exception

print "\nWrote " + str(imagefs)
imagefs.close()