#!/usr/bin/env python3

# Copyright 2021 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#
# Ignore indention messages, since legacy scripts use 2 spaces instead of 4.
# pylint: disable=bad-indentation,docstring-section-indent
# pylint: disable=docstring-trailing-quotes

# A script to pack EC binary into SPI flash image for MEC152x
# Based on MEC1521/MEC1523_ROM_Description.pdf
import argparse
import hashlib
import os
import struct
import subprocess
import tempfile
import zlib # CRC32

# MEC152xH has 256KB SRAM from 0xE0000 - 0x120000
# SRAM is divided into contiguous CODE & DATA
# CODE at [0xE0000, 0x117FFF] DATA at [0x118000, 0x11FFFF]
# SPI flash size for board is 512KB
# Boot-ROM TAG is located at SPI offset 0 (two 4-byte tags)

LFW_SIZE = 0x1000
LOAD_ADDR = 0x0E0000
LOAD_ADDR_RW = 0xE1000
MEC152X_HEADER_SIZE = 0x140
MEC152X_HEADER_VERSION = 0x02
PAYLOAD_PAD_BYTE = b'\xff'
SPI_ERASE_BLOCK_SIZE = 0x1000
SPI_CLOCK_LIST = [48, 24, 16, 12]
SPI_READ_CMD_LIST = [0x3, 0xb, 0x3b, 0x6b]
SPI_DRIVE_STR_DICT = {2:0, 4:1, 8:2, 12:3}
CHIP_MAX_CODE_SRAM_KB = 224

MEC152X_DICT = {
                "HEADER_SIZE":0x140,
                "HEADER_VER":0x02,
                "PAYLOAD_OFFSET":0x140,
                "PAYLOAD_GRANULARITY":128,
                "EC_INFO_BLK_SZ":128,
                "ENCR_KEY_HDR_SZ":128,
                "COSIG_SZ":96,
                "TRAILER_SZ":160,
                "TAILER_PAD_BYTE":b'\xff',
                "PAD_SIZE":128
                }

CRC_TABLE = [0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15,
             0x38, 0x3f, 0x36, 0x31, 0x24, 0x23, 0x2a, 0x2d]

def mock_print(*args, **kwargs):
  pass

debug_print = mock_print

# Debug helper routine
def dumpsects(spi_list):
  debug_print("spi_list has {0} entries".format(len(spi_list)))
  for s in spi_list:
    debug_print("0x{0:x} 0x{1:x} {2:s}".format(s[0],len(s[1]),s[2]))

def printByteArrayAsHex(ba, title):
  debug_print(title,"= ")
  if ba == None:
      debug_print("None")
      return

  count = 0
  for b in ba:
    count = count + 1
    debug_print("0x{0:02x}, ".format(b),end="")
    if (count % 8) == 0:
      debug_print("")
  debug_print("")

def Crc8(crc, data):
  """Update CRC8 value."""
  for v in data:
    crc = ((crc << 4) & 0xff) ^ (CRC_TABLE[(crc >> 4) ^ (v >> 4)]);
    crc = ((crc << 4) & 0xff) ^ (CRC_TABLE[(crc >> 4) ^ (v & 0xf)]);
  return crc ^ 0x55

def GetEntryPoint(payload_file):
  """Read entry point from payload EC image."""
  with open(payload_file, 'rb') as f:
    f.seek(4)
    s = f.read(4)
  return int.from_bytes(s, byteorder='little')

def GetPayloadFromOffset(payload_file, offset, padsize):
  """Read payload and pad it to padsize."""
  with open(payload_file, 'rb') as f:
    f.seek(offset)
    payload = bytearray(f.read())
  rem_len = len(payload) % padsize
  debug_print("GetPayload: padsize={0:0x} len(payload)={1:0x} rem={2:0x}".format(padsize,len(payload),rem_len))

  if rem_len:
    payload += PAYLOAD_PAD_BYTE * (padsize - rem_len)
    debug_print("GetPayload: Added {0} padding bytes".format(padsize - rem_len))

  return payload

def GetPayload(payload_file, padsize):
  """Read payload and pad it to padsize"""
  return GetPayloadFromOffset(payload_file, 0, padsize)

def GetPublicKey(pem_file):
  """Extract public exponent and modulus from PEM file."""
  result = subprocess.run(['openssl', 'rsa', '-in', pem_file, '-text',
                           '-noout'], stdout=subprocess.PIPE, encoding='utf-8')
  modulus_raw = []
  in_modulus = False
  for line in result.stdout.splitlines():
    if line.startswith('modulus'):
      in_modulus = True
    elif not line.startswith(' '):
      in_modulus = False
    elif in_modulus:
      modulus_raw.extend(line.strip().strip(':').split(':'))
    if line.startswith('publicExponent'):
      exp = int(line.split(' ')[1], 10)
  modulus_raw.reverse()
  modulus = bytearray((int(x, 16) for x in modulus_raw[:256]))
  return struct.pack('<Q', exp), modulus

def GetSpiClockParameter(args):
  assert args.spi_clock in SPI_CLOCK_LIST, \
         "Unsupported SPI clock speed %d MHz" % args.spi_clock
  return SPI_CLOCK_LIST.index(args.spi_clock)

def GetSpiReadCmdParameter(args):
  assert args.spi_read_cmd in SPI_READ_CMD_LIST, \
         "Unsupported SPI read command 0x%x" % args.spi_read_cmd
  return SPI_READ_CMD_LIST.index(args.spi_read_cmd)

def GetEncodedSpiDriveStrength(args):
  assert args.spi_drive_str in SPI_DRIVE_STR_DICT, \
         "Unsupported SPI drive strength %d mA" % args.spi_drive_str
  return SPI_DRIVE_STR_DICT.get(args.spi_drive_str)

# Return 0=Slow slew rate or 1=Fast slew rate
def GetSpiSlewRate(args):
    if args.spi_slew_fast == True:
        return 1
    return 0

# Return SPI CPOL = 0 or 1
def GetSpiCpol(args):
    if args.spi_cpol == 0:
        return 0
    return 1

# Return SPI CPHA_MOSI
# 0 = SPI Master drives data is stable on inactive to clock edge
# 1 = SPI Master drives data is stable on active to inactive clock edge
def GetSpiCphaMosi(args):
    if args.spi_cpha_mosi == 0:
        return 0
    return 1

# Return SPI CPHA_MISO 0 or 1
# 0 = SPI Master samples data on inactive to active clock edge
# 1 = SPI Master samples data on active to inactive clock edge
def GetSpiCphaMiso(args):
    if args.spi_cpha_miso == 0:
        return 0
    return 1

def PadZeroTo(data, size):
  data.extend(b'\0' * (size - len(data)))

#
# Boot-ROM SPI image encryption not used with Chromebooks
#
def EncryptPayload(args, chip_dict, payload):
    return None

#
# Build SPI image header for MEC152x
# MEC152x image header size = 320(0x140) bytes
#
# Description using Python slice notation [start:start+len]
#
# header[0:4] = 'PHCM'
# header[4] = header version = 0x02(MEC152x)
# header[5] = SPI clock speed, drive strength, sampling mode
#   bits[1:0] = SPI clock speed: 0=48, 1=24, 2=16, 3=12
#   bits[3:2] = SPI controller pins drive strength
#               00b=2mA, 01b=4mA, 10b=8mA, 11b=12mA
#   bit[4] = SPI controller pins slew rate: 0=slow, 1=fast
#   bit[5] = SPI CPOL: 0=SPI clock idle is low, 1=idle is high
#   bit[6] = CHPHA_MOSI
#       1:data change on first inactive to active clock edge
#       0:data change on first active to inactive clock edge
#   bit[7] = CHPHA_MISO:
#       1: Data captured on first inactive to active clock edge
#       0: Data captured on first active to inactive clock edge
# header[6] Boot-ROM loader flags
#   bits[2:0] = VTR0,1,2 rails. 0=3.3V, 1=1.8V. NOTE VTR1=0 always
#   bits[5:3] = 111b
#   bit[6]: For MEC152x controls authentication
#           0=Authentication disabled. Signature is SHA-384 of FW payload
#           1=Authentication enabled. Signature is ECDSA P-384
#   bit[7]: 0=FW pyload not encrypted, 1=FW payload is encrypted
# header[7]: SPI Flash read command
#            0x03 1-1-1 read freq < 33MHz
#            0x0B 1-1-1 + 8 clocks(data tri-stated)
#            0x3B 1-1-2 + 8 clocks(data tri-stated). Data phase is dual I/O
#            0x6B 1-1-4 + 8 clocks(data tri-stated). Data phase is Quad I/O
#            NOTE: Quad requires SPI flash device QE(quad enable) bit
#            to be factory set. Enabling QE disables HOLD# and WP#
#            functionality of the SPI flash device.
# header[0x8:0xC] SRAM Load address little-endian format
# header[0xC:0x10] SRAM FW entry point. Boot-ROM jumps to
#                  this address on successful load. (little-endian)
# header[0x10:0x12] little-endian format: FW binary size in units of
#                   128 bytes(MEC152x)
# header[0x12:0x14] = 0 reserved
# header[0x14:0x18] = Little-ending format: Unsigned offset from start of
#                     header to FW payload.
#                     MEC152x: Offset must be a multiple of 128
#                     Offset must be > header size.
#                     NOTE: If Authentication is enabled size includes
#                     the appended signature.
# MEC152x:
# header[0x18] = Authentication key select. Set to 0 for no Authentication.
# header[0x19:0x50] = 0 reserved.
# header[0x50:0x80] = ECDSA-384 public key x-coord. = 0 Auth. disabled
# header[0x80:0xB0] = ECDSA-384 public key y-coord. = 0 Auth. disabled
# header[0xB0:0xE0] = SHA-384 digest of header[0:0xB0]
# header[0xE0:0x110] = Header ECDSA-384 signature x-coord. = 0 Auth. disabled
# header[0x110:0x140] = Header ECDSA-384 signature y-coor. = 0 Auth. disabled
#
def BuildHeader2(args, chip_dict, payload_len, load_addr, payload_entry):
  header_size = MEC152X_HEADER_SIZE

  # allocate zero filled header
  header = bytearray(b'\x00' * header_size)
  debug_print("len(header) = ", len(header))

  # Identifier and header version
  header[0:4] = b'PHCM'
  header[4] = MEC152X_HEADER_VERSION

  # SPI frequency, drive strength, CPOL/CPHA encoding same for both chips
  spiFreqMHz = GetSpiClockParameter(args)
  header[5] = (int(spiFreqMHz // 48) - 1) & 0x03
  header[5] |= ((GetEncodedSpiDriveStrength(args) & 0x03) << 2)
  header[5] |= ((GetSpiSlewRate(args) & 0x01) << 4)
  header[5] |= ((GetSpiCpol(args) & 0x01) << 5)
  header[5] |= ((GetSpiCphaMosi(args) & 0x01) << 6)
  header[5] |= ((GetSpiCphaMiso(args) & 0x01) << 7)

  # b[0]=0 VTR1 must be 3.3V
  # b[1]=0(VTR2 3.3V), 1(VTR2 1.8V)
  # b[2]=0(VTR3 3.3V), 1(VTR3 1.8V)
  # b[5:3]=111b
  # b[6]=0 No ECDSA
  # b[7]=0 No encrypted FW image
  header[6] = 0x7 << 3
  if args.vtr2_V18 == True:
      header[6] |= 0x02
  if args.vtr3_V18 == True:
      header[6] |= 0x04

  # SPI read command set same for both chips
  header[7] = GetSpiReadCmdParameter(args) & 0xFF

  # bytes 0x08 - 0x0b
  header[0x08:0x0C] = load_addr.to_bytes(4, byteorder='little')
  # bytes 0x0c - 0x0f
  header[0x0C:0x10] = payload_entry.to_bytes(4, byteorder='little')
  # bytes 0x10 - 0x11 payload length in units of 128 bytes

  payload_units = int(payload_len // chip_dict["PAYLOAD_GRANULARITY"])
  assert payload_units < 0x10000, \
      print("Payload too large: len={0} units={1}".format(payload_len, payload_units))

  header[0x10:0x12] = payload_units.to_bytes(2, 'little')

  # bytes 0x14 - 0x17
  header[0x14:0x18] = chip_dict["PAYLOAD_OFFSET"].to_bytes(4, 'little')

  # MEC152x: Disable ECDSA and encryption
  header[0x18] = 0

  # header[0xB0:0xE0] = SHA384(header[0:0xB0])
  header[0xB0:0xE0] = hashlib.sha384(header[0:0xB0]).digest()
  # When ECDSA authentication is disabled MCHP SPI image generator
  # is filling the last 48 bytes of the Header with 0xff
  header[-48:] = b'\xff' * 48

  debug_print("After hash: len(header) = ", len(header))

  return header

#
# MEC152x 128-byte EC Info Block appended to
# end of padded FW binary
# bytes 0 through 103 are undefined, we set to 0xFF
# bytes 104 through 119 are rollback permissions
# bytes 120 through 123 are key revocation permissions
# byte 124 = customer platform ID[7:0]
# byte 125 = customer platform ID[15:8]
# byte 126 = customer auto rollback flags
# byte 127 = customer current image revision
#
def GenEcInfoBlock(args, chip_dict):
  ecinfo = bytearray(chip_dict["EC_INFO_BLK_SZ"])
  return ecinfo

#
# Generate SPI FW image co-signature.
# MEC152X cosignature is 96 bytes used by OEM FW
# developer to sign their binary with ECDSA-P384-SHA384 or
# some other signature algorithm that fits in 96 bytes.
# At this time Cros-EC is not using this field, fill with 0xFF.
# If this feature is implemented we need to read the OEM's
# generated signature from a file and extract the binary
# signature.
#
def GenCoSignature(args, chip_dict, payload):
    return bytearray(b'\xff' * chip_dict["COSIG_SZ"])

#
# Generate SPI FW Image trailer.
# MEC152X: Size = 160 bytes
#   binary = payload || encryption_key_header || ec_info_block || cosignature
#   trailer[0:48] = SHA384(binary)
#   trailer[48:144] = 0xFF
#   trailer[144:160] = 0xFF. Boot-ROM spec. says these bytes should be random.
#       Authentication & encryption are not used therefore random data
#       is not necessary.
def GenTrailer(args, chip_dict, payload, encryption_key_header,
               ec_info_block, cosignature):
    trailer = bytearray(chip_dict["TAILER_PAD_BYTE"] * chip_dict["TRAILER_SZ"])
    hasher = hashlib.sha384()
    hasher.update(payload)
    if ec_info_block != None:
      hasher.update(ec_info_block)
    if encryption_key_header != None:
      hasher.update(encryption_key_header)
    if cosignature != None:
      hasher.update(cosignature)
    trailer[0:48] = hasher.digest()
    trailer[-16:] = 16 * b'\xff'

    return trailer

# MEC152xH supports two 32-bit Tags located at offsets 0x0 and 0x4
# in the SPI flash.
# Tag format:
#   bits[23:0] correspond to bits[31:8] of the Header SPI address
#       Header is always on a 256-byte boundary.
#   bits[31:24] = CRC8-ITU of bits[23:0].
# Notice there is no chip-select field in the Tag both Tag's point
# to the same flash part.
#
def BuildTag(args):
  tag = bytearray([(args.header_loc >> 8) & 0xff,
                   (args.header_loc >> 16) & 0xff,
                   (args.header_loc >> 24) & 0xff])
  tag.append(Crc8(0, tag))
  return tag

def BuildTagFromHdrAddr(header_loc):
    tag = bytearray([(header_loc >> 8) & 0xff,
                     (header_loc >> 16) & 0xff,
                     (header_loc >> 24) & 0xff])
    tag.append(Crc8(0, tag))
    return tag


# FlashMap is an option for MEC152x
# It is a 32 bit structure
# bits[18:0] = bits[30:12] of second SPI flash base address
# bits[23:19] = 0 reserved
# bits[31:24] = CRC8 of bits[23:0]
# Input:
#   integer containing base address of second SPI flash
#   This value is usually equal to the size of the first
#   SPI flash and should be a multiple of 4KB
# Output:
#   bytearray of length 4
def BuildFlashMap(secondSpiFlashBaseAddr):
  flashmap = bytearray(4)
  flashmap[0] = (secondSpiFlashBaseAddr >> 12) & 0xff
  flashmap[1] = (secondSpiFlashBaseAddr >> 20) & 0xff
  flashmap[2] = (secondSpiFlashBaseAddr >> 28) & 0xff
  flashmap[3] = Crc8(0, flashmap)
  return flashmap

#
# Creates temporary file for read/write
# Reads binary file containing LFW image_size (loader_file)
# Writes LFW image to temporary file
# Reads RO image at beginning of rorw_file up to image_size
#  (assumes RO/RW images have been padded with 0xFF
# Returns temporary file name
#
def PacklfwRoImage(rorw_file, loader_file, image_size):
  """Create a temp file with the
  first image_size bytes from the loader file and append bytes
  from the rorw file.
  return the filename"""
  fo=tempfile.NamedTemporaryFile(delete=False) # Need to keep file around
  with open(loader_file,'rb') as fin1: # read 4KB loader file
    pro = fin1.read()
  fo.write(pro)            # write 4KB loader data to temp file
  with open(rorw_file, 'rb') as fin:
    ro = fin.read(image_size)

  fo.write(ro)
  fo.close()

  return fo.name

#
# Generate a test EC_RW image of same size
# as original.
# Preserve image_data structure and fill all
# other bytes with 0xA5.
# useful for testing SPI read and EC build
# process hash generation.
#
def gen_test_ecrw(pldrw):
  debug_print("gen_test_ecrw: pldrw type =", type(pldrw))
  debug_print("len pldrw =", len(pldrw), " = ", hex(len(pldrw)))
  cookie1_pos = pldrw.find(b'\x99\x88\x77\xce')
  cookie2_pos = pldrw.find(b'\xdd\xbb\xaa\xce', cookie1_pos+4)
  t = struct.unpack("<L", pldrw[cookie1_pos+0x24:cookie1_pos+0x28])
  size = t[0]
  debug_print("EC_RW size =", size, " = ", hex(size))

  debug_print("Found cookie1 at ", hex(cookie1_pos))
  debug_print("Found cookie2 at ", hex(cookie2_pos))

  if cookie1_pos > 0 and cookie2_pos > cookie1_pos:
    for i in range(0, cookie1_pos):
      pldrw[i] = 0xA5
    for i in range(cookie2_pos+4, len(pldrw)):
      pldrw[i] = 0xA5

  with open("ec_RW_test.bin", "wb") as fecrw:
      fecrw.write(pldrw[:size])

def parseargs():
  #TODO I commented this out. Why?
  rpath = os.path.dirname(os.path.relpath(__file__))

  parser = argparse.ArgumentParser()
  parser.add_argument("-i", "--input",
              help="EC binary to pack, usually ec.bin or ec.RO.flat.",
              metavar="EC_BIN", default="ec.bin")
  parser.add_argument("-o", "--output",
                      help="Output flash binary file",
                      metavar="EC_SPI_FLASH", default="ec.packed.bin")
  parser.add_argument("--loader_file",
                      help="EC loader binary",
                      default="ecloader.bin")
  parser.add_argument("-s", "--spi_size", type=int,
                      help="Size of the SPI flash in KB",
                      default=512)
  parser.add_argument("-l", "--header_loc", type=int,
                      help="Location of header in SPI flash",
                      default=0x1000)
  parser.add_argument("-r", "--rw_loc", type=int,
                      help="Start offset of EC_RW. Default is -1 meaning 1/2 flash size",
                      default=-1)
  parser.add_argument("--spi_clock", type=int,
                      help="SPI clock speed. 8, 12, 24, or 48 MHz.",
                      default=24)
  parser.add_argument("--spi_read_cmd", type=int,
                      help="SPI read command. 0x3, 0xB, or 0x3B.",
                      default=0xb)
  parser.add_argument("--image_size", type=int,
                      help="Size of a single image. Default 220KB",
                      default=(220 * 1024))
  parser.add_argument("--test_spi", action='store_true',
                      help="Test SPI data integrity by adding CRC32 in last 4-bytes of RO/RW binaries",
                      default=False)
  parser.add_argument("--test_ecrw", action='store_true',
                      help="Use fixed pattern for EC_RW but preserve image_data",
                      default=False)
  parser.add_argument("--verbose", action='store_true',
                      help="Enable verbose output",
                      default=False)
  parser.add_argument("--tag0_loc", type=int,
                      help="MEC152X TAG0 SPI offset",
                      default=0)
  parser.add_argument("--tag1_loc", type=int,
                      help="MEC152X TAG1 SPI offset",
                      default=4)
  parser.add_argument("--spi_drive_str", type=int,
                      help="Chip SPI drive strength in mA: 2, 4, 8, or 12",
                      default=4)
  parser.add_argument("--spi_slew_fast", action='store_true',
                      help="SPI use fast slew rate. Default is False",
                      default=False)
  parser.add_argument("--spi_cpol", type=int,
                      help="SPI clock polarity when idle. Defealt is 0(low)",
                      default=0)
  parser.add_argument("--spi_cpha_mosi", type=int,
                      help="""SPI clock phase master drives data.
                              0=Data driven on active to inactive clock edge,
                              1=Data driven on inactive to active clock edge""",
                      default=0)
  parser.add_argument("--spi_cpha_miso", type=int,
                      help="""SPI clock phase master samples data.
                              0=Data sampled on inactive to active clock edge,
                              1=Data sampled on active to inactive clock edge""",
                      default=0)

  parser.add_argument("--vtr2_V18", action='store_true',
                      help="Chip VTR2 rail is 1.8V. Default is False(3.3V)",
                      default=False)

  parser.add_argument("--vtr3_V18", action='store_true',
                      help="Chip VTR3 rail is 1.8V. Default is False(3.3V)",
                      default=False)

  return parser.parse_args()

def print_args(args):
  debug_print("parsed arguments:")
  debug_print(".input  = ", args.input)
  debug_print(".output = ", args.output)
  debug_print(".loader_file = ", args.loader_file)
  debug_print(".spi_size (KB) = ", hex(args.spi_size))
  debug_print(".image_size = ", hex(args.image_size))
  debug_print(".tag0_loc = ", hex(args.tag0_loc))
  debug_print(".tag1_loc = ", hex(args.tag1_loc))
  debug_print(".header_loc = ", hex(args.header_loc))
  if args.rw_loc < 0:
    debug_print(".rw_loc = ", args.rw_loc)
  else:
    debug_print(".rw_loc = ", hex(args.rw_loc))
  debug_print(".spi_clock (MHz) = ", args.spi_clock)
  debug_print(".spi_read_cmd = ", hex(args.spi_read_cmd))
  debug_print(".test_spi = ", args.test_spi)
  debug_print(".test_ecrw = ", args.test_ecrw)
  debug_print(".verbose = ", args.verbose)
  debug_print(".spi_drive_str = ", args.spi_drive_str)
  debug_print(".spi_slew_fast = ", args.spi_slew_fast)
  debug_print(".spi_cpol = ", args.spi_cpol)
  debug_print(".spi_cpha_mosi = ", args.spi_cpha_mosi)
  debug_print(".spi_cpha_miso = ", args.spi_cpha_miso)
  debug_print(".vtr2_V18 = ", args.vtr2_V18)
  debug_print(".vtr3_V18 = ", args.vtr3_V18)

#
# Handle quiet mode build from Makefile
# Quiet mode when V is unset or V=0
# Verbose mode when V=1
#
# MEC152x SPI Image Generator
# No authentication
# No payload encryption
#
# SPI Offset 0x0 = TAG0 points to Header for EC-RO FW
# SPI Offset 0x4 = TAG1 points to Header for EC-RO FW
# TAG Size = 4 bytes
#  bits[23:0] = bits[31:8] of Header SPI offset
#  bits[31:24] = CRC8-ITU checksum of bits[23:0].
#
# MEC152X SPI header and payload layout for minimum size
# header offset aligned on 256 byte boundary
# header_spi_address:
#   header[0:0x4F] = Header data
#   header[0x50:0x80] = ECDSA-P384 public key x for Header authentication
#   header[0x80:0xB0] = ECDSA-P384 public key y for Header authentication
#   header[0xB0:0xE0] = SHA384 digest of header[0:0xB0]
#   header[0xE0:0x110] = ECDSA-P384-SHA384 Signature.R of header[0:0xB0]
#   header[0x110:0x140] = ECDSA-P384-SHA384 Signature.S of header[0:0xB0]
# payload_spi_address = header_spi_address + len(Header)
#       Payload had been padded such that len(padded_payload) % 128 == 0
#   padded_payload[padded_payload_len]
# payload_signature_address = payload_spi_address + len(padded_payload)
#  payload_encryption_key_header[128] Not present if encryption disabled
#  payload_cosignature[96] = 0 if Authentication is disabled
#  payload_trailer[160] = SHA384(padded_payload ||
#                                optional payload_encryption_key_header)
#                       || 48 * [0]
#                       || 48 * [0]
#
def main():
  global debug_print

  args = parseargs()

  if args.verbose:
    debug_print = print

  debug_print("Begin pack_ec_mec152x.py script")

  print_args(args)

  chip_dict = MEC152X_DICT

  # Boot-ROM requires header location aligned >= 256 bytes.
  # CrOS EC flash image update code requires EC_RO/RW location to be aligned
  # on a flash erase size boundary and EC_RO/RW size to be a multiple of
  # the smallest flash erase block size.
  #
  assert (args.header_loc % SPI_ERASE_BLOCK_SIZE) == 0, \
      "Header location %d is not on a flash erase block boundary boundary" % args.header_loc

  max_image_size = CHIP_MAX_CODE_SRAM_KB - LFW_SIZE
  if args.test_spi:
      max_image_size -= 32 # SHA256 digest

  assert args.image_size > max_image_size, \
      "Image size exceeds maximum" % args.image_size

  spi_size = args.spi_size * 1024
  debug_print("SPI Flash image size in bytes =", hex(spi_size))

  # !!! IMPORTANT !!!
  # These values MUST match chip/mchp/config_flash_layout.h
  # defines.
  # MEC152x Boot-ROM TAGs are at offset 0 and 4.
  # lfw + EC_RO starts at beginning of second 4KB sector
  # EC_RW starts at (flash size / 2) i.e. 0x40000 for a 512KB flash.

  spi_list = []

  debug_print("args.input = ",args.input)
  debug_print("args.loader_file = ",args.loader_file)
  debug_print("args.image_size = ",hex(args.image_size))

  rorofile=PacklfwRoImage(args.input, args.loader_file, args.image_size)
  debug_print("Temporary file containing LFW + EC_RO is ", rorofile)

  lfw_ecro = GetPayload(rorofile, chip_dict["PAD_SIZE"])
  lfw_ecro_len = len(lfw_ecro)
  debug_print("Padded LFW + EC_RO length = ", hex(lfw_ecro_len))

  # SPI test mode compute CRC32 of EC_RO and store in last 4 bytes
  if args.test_spi:
      crc32_ecro = zlib.crc32(bytes(lfw_ecro[LFW_SIZE:-4]))
      crc32_ecro_bytes = crc32_ecro.to_bytes(4, byteorder='little')
      lfw_ecro[-4:] = crc32_ecro_bytes
      debug_print("ecro len = ", hex(len(lfw_ecro) - LFW_SIZE))
      debug_print("CRC32(ecro-4) = ", hex(crc32_ecro))

  # Reads entry point from offset 4 of file.
  # This assumes binary has Cortex-M4 vector table at offset 0.
  # 32-bit word at offset 0x0 initial stack pointer value
  # 32-bit word at offset 0x4 address of reset handler
  # NOTE: reset address will have bit[0]=1 to ensure thumb mode.
  lfw_ecro_entry = GetEntryPoint(rorofile)

  # Chromebooks are not using MEC BootROM SPI header/payload authentication
  # or payload encryption. In this case the header authentication signature
  # is filled with the hash digest of the respective entity.
  # BuildHeader2 computes the hash digest and stores it in the correct
  # header location.
  header = BuildHeader2(args, chip_dict, lfw_ecro_len,
                        LOAD_ADDR, lfw_ecro_entry)
  printByteArrayAsHex(header, "Header(lfw_ecro)")

  # If payload encryption used then encrypt payload and
  # generate Payload Key Header. If encryption not used
  # payload is not modified and the method returns None
  encryption_key_header = EncryptPayload(args, chip_dict, lfw_ecro)
  printByteArrayAsHex(encryption_key_header,
                      "LFW + EC_RO encryption_key_header")

  ec_info_block = GenEcInfoBlock(args, chip_dict)
  printByteArrayAsHex(ec_info_block, "EC Info Block")

  cosignature = GenCoSignature(args, chip_dict, lfw_ecro)
  printByteArrayAsHex(cosignature, "LFW + EC_RO cosignature")

  trailer = GenTrailer(args, chip_dict, lfw_ecro, encryption_key_header,
                       ec_info_block, cosignature)

  printByteArrayAsHex(trailer, "LFW + EC_RO trailer")

  # Build TAG0. Set TAG1=TAG0 Boot-ROM is allowed to load EC-RO only.
  tag0 = BuildTag(args)
  tag1 = tag0

  debug_print("Call to GetPayloadFromOffset")
  debug_print("args.input = ", args.input)
  debug_print("args.image_size = ", hex(args.image_size))

  ecrw = GetPayloadFromOffset(args.input, args.image_size,
                              chip_dict["PAD_SIZE"])
  debug_print("type(ecrw) is ", type(ecrw))
  debug_print("len(ecrw) is ", hex(len(ecrw)))

  # truncate to args.image_size
  ecrw_len = len(ecrw)
  if ecrw_len > args.image_size:
      debug_print("Truncate EC_RW len={0:0x} to image_size={1:0x}".format(ecrw_len,args.image_size))
      ecrw = ecrw[:args.image_size]
      ecrw_len = len(ecrw)

  debug_print("len(EC_RW) = ", hex(ecrw_len))

  # SPI test mode compute CRC32 of EC_RW and store in last 4 bytes
  if args.test_spi:
      crc32_ecrw = zlib.crc32(bytes(ecrw[0:-4]))
      crc32_ecrw_bytes = crc32_ecrw.to_bytes(4, byteorder='little')
      ecrw[-4:] = crc32_ecrw_bytes
      debug_print("ecrw len = ", hex(len(ecrw)))
      debug_print("CRC32(ecrw) = ", hex(crc32_ecrw))

  # Assume FW layout is standard Cortex-M style with vector
  # table at start of binary.
  # 32-bit word at offset 0x0 = Initial stack pointer
  # 32-bit word at offset 0x4 = Address of reset handler
  ecrw_entry_tuple = struct.unpack_from('<I', ecrw, 4)
  debug_print("ecrw_entry_tuple[0] = ", hex(ecrw_entry_tuple[0]))

  ecrw_entry = ecrw_entry_tuple[0]
  debug_print("ecrw_entry = ", hex(ecrw_entry))

  # Note: payload_rw is a bytearray therefore is mutable
  if args.test_ecrw:
    gen_test_ecrw(ecrw)

  os.remove(rorofile)           # clean up the temp file

  # MEC152X Add TAG's
  spi_list.append((args.tag0_loc, tag0, "tag0"))
  spi_list.append((args.tag1_loc, tag1, "tag1"))

  # flashmap is non-zero only for systems with two external
  # SPI flash chips.
  flashmap = BuildFlashMap(0)
  spi_list.append((8, flashmap, "flashmap"))

  # Boot-ROM SPI image header for LFW+EC-RO
  spi_list.append((args.header_loc, header, "header(lfw + ro)"))
  spi_list.append((args.header_loc + chip_dict["PAYLOAD_OFFSET"], lfw_ecro,
                   "lfw_ecro"))

  offset = args.header_loc + chip_dict["PAYLOAD_OFFSET"] + lfw_ecro_len

  if ec_info_block != None:
    spi_list.append((offset, ec_info_block, "EC Info Block"))
    offset += len(ec_info_block)

  if cosignature != None:
    spi_list.append((offset, cosignature, "ECRO Cosignature"))
    offset += len(cosignature)

  if trailer != None:
    spi_list.append((offset, trailer, "ECRO Trailer"))
    offset += len(trailer)

  # EC_RW location
  rw_offset = int(spi_size // 2)
  if args.rw_loc >= 0:
    rw_offset = args.rw_loc

  debug_print("rw_offset = 0x{0:08x}".format(rw_offset))

  assert rw_offset >= offset, \
      print("""Offset of EC_RW at {0:08x} overlaps end
               of EC_RO at {0:08x}""".format(rw_offset, offset))

  spi_list.append((rw_offset, ecrw, "ecrw"))
  offset = rw_offset + len(ecrw)

  spi_list = sorted(spi_list)

  dumpsects(spi_list)

  #
  # MEC152X Boot-ROM locates TAG0/1 at SPI offset 0
  # instead of end of SPI.
  #
  with open(args.output, 'wb') as f:
    debug_print("Write spi list to file", args.output)
    addr = 0
    for s in spi_list:
      if addr < s[0]:
        debug_print("Offset ",hex(addr)," Length", hex(s[0]-addr),
                "fill with 0xff")
        f.write(b'\xff' * (s[0] - addr))
        addr = s[0]
        debug_print("Offset ",hex(addr), " Length", hex(len(s[1])), "write data")

      f.write(s[1])
      addr += len(s[1])

    if addr < spi_size:
      debug_print("Offset ",hex(addr), " Length", hex(spi_size - addr),
              "fill with 0xff")
      f.write(b'\xff' * (spi_size - addr))

    f.flush()

if __name__ == '__main__':
  main()