#!/usr/bin/env python2
# Copyright 2017 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.

"""Statically analyze stack usage of EC firmware.

  Example:
    extra/stack_analyzer/stack_analyzer.py \
        --export_taskinfo ./build/elm/util/export_taskinfo.so \
        --section RW \
        ./build/elm/RW/ec.RW.elf

"""

from __future__ import print_function

import argparse
import collections
import ctypes
import os
import re
import subprocess
import yaml


SECTION_RO = 'RO'
SECTION_RW = 'RW'
# Default size of extra stack frame needed by exception context switch.
# This value is for cortex-m with FPU enabled.
DEFAULT_EXCEPTION_FRAME_SIZE = 224


class StackAnalyzerError(Exception):
  """Exception class for stack analyzer utility."""


class TaskInfo(ctypes.Structure):
  """Taskinfo ctypes structure.

  The structure definition is corresponding to the "struct taskinfo"
  in "util/export_taskinfo.so.c".
  """
  _fields_ = [('name', ctypes.c_char_p),
              ('routine', ctypes.c_char_p),
              ('stack_size', ctypes.c_uint32)]


class Task(object):
  """Task information.

  Attributes:
    name: Task name.
    routine_name: Routine function name.
    stack_max_size: Max stack size.
    routine_address: Resolved routine address. None if it hasn't been resolved.
  """

  def __init__(self, name, routine_name, stack_max_size, routine_address=None):
    """Constructor.

    Args:
      name: Task name.
      routine_name: Routine function name.
      stack_max_size: Max stack size.
      routine_address: Resolved routine address.
    """
    self.name = name
    self.routine_name = routine_name
    self.stack_max_size = stack_max_size
    self.routine_address = routine_address

  def __eq__(self, other):
    """Task equality.

    Args:
      other: The compared object.

    Returns:
      True if equal, False if not.
    """
    if not isinstance(other, Task):
      return False

    return (self.name == other.name and
            self.routine_name == other.routine_name and
            self.stack_max_size == other.stack_max_size and
            self.routine_address == other.routine_address)


class Symbol(object):
  """Symbol information.

  Attributes:
    address: Symbol address.
    symtype: Symbol type, 'O' (data, object) or 'F' (function).
    size: Symbol size.
    name: Symbol name.
  """

  def __init__(self, address, symtype, size, name):
    """Constructor.

    Args:
      address: Symbol address.
      symtype: Symbol type.
      size: Symbol size.
      name: Symbol name.
    """
    assert symtype in ['O', 'F']
    self.address = address
    self.symtype = symtype
    self.size = size
    self.name = name

  def __eq__(self, other):
    """Symbol equality.

    Args:
      other: The compared object.

    Returns:
      True if equal, False if not.
    """
    if not isinstance(other, Symbol):
      return False

    return (self.address == other.address and
            self.symtype == other.symtype and
            self.size == other.size and
            self.name == other.name)


class Callsite(object):
  """Function callsite.

  Attributes:
    address: Address of callsite location. None if it is unknown.
    target: Callee address. None if it is unknown.
    is_tail: A bool indicates that it is a tailing call.
    callee: Resolved callee function. None if it hasn't been resolved.
  """

  def __init__(self, address, target, is_tail, callee=None):
    """Constructor.

    Args:
      address: Address of callsite location. None if it is unknown.
      target: Callee address. None if it is unknown.
      is_tail: A bool indicates that it is a tailing call. (function jump to
               another function without restoring the stack frame)
      callee: Resolved callee function.
    """
    # It makes no sense that both address and target are unknown.
    assert not (address is None and target is None)
    self.address = address
    self.target = target
    self.is_tail = is_tail
    self.callee = callee

  def __eq__(self, other):
    """Callsite equality.

    Args:
      other: The compared object.

    Returns:
      True if equal, False if not.
    """
    if not isinstance(other, Callsite):
      return False

    if not (self.address == other.address and
            self.target == other.target and
            self.is_tail == other.is_tail):
      return False

    if self.callee is None:
      return other.callee is None
    elif other.callee is None:
      return False

    # Assume the addresses of functions are unique.
    return self.callee.address == other.callee.address


class Function(object):
  """Function.

  Attributes:
    address: Address of function.
    name: Name of function from its symbol.
    stack_frame: Size of stack frame.
    callsites: Callsite list.
    stack_max_usage: Max stack usage. None if it hasn't been analyzed.
    stack_max_path: Max stack usage path. None if it hasn't been analyzed.
  """

  def __init__(self, address, name, stack_frame, callsites):
    """Constructor.

    Args:
      address: Address of function.
      name: Name of function from its symbol.
      stack_frame: Size of stack frame.
      callsites: Callsite list.
    """
    self.address = address
    self.name = name
    self.stack_frame = stack_frame
    self.callsites = callsites
    self.stack_max_usage = None
    self.stack_max_path = None

  def __eq__(self, other):
    """Function equality.

    Args:
      other: The compared object.

    Returns:
      True if equal, False if not.
    """
    if not isinstance(other, Function):
      return False

    if not (self.address == other.address and
            self.name == other.name and
            self.stack_frame == other.stack_frame and
            self.callsites == other.callsites and
            self.stack_max_usage == other.stack_max_usage):
      return False

    if self.stack_max_path is None:
      return other.stack_max_path is None
    elif other.stack_max_path is None:
      return False

    if len(self.stack_max_path) != len(other.stack_max_path):
      return False

    for self_func, other_func in zip(self.stack_max_path, other.stack_max_path):
      # Assume the addresses of functions are unique.
      if self_func.address != other_func.address:
        return False

    return True

class AndesAnalyzer(object):
  """Disassembly analyzer for Andes architecture.

  Public Methods:
    AnalyzeFunction: Analyze stack frame and callsites of the function.
  """

  GENERAL_PURPOSE_REGISTER_SIZE = 4

  # Possible condition code suffixes.
  CONDITION_CODES = [ 'eq', 'eqz', 'gez', 'gtz', 'lez', 'ltz', 'ne', 'nez',
                      'eqc', 'nec', 'nezs', 'nes', 'eqs']
  CONDITION_CODES_RE = '({})'.format('|'.join(CONDITION_CODES))

  IMM_ADDRESS_RE = r'([0-9A-Fa-f]+)\s+<([^>]+)>'
  # Branch instructions.
  JUMP_OPCODE_RE = re.compile(r'^(b{0}|j|jr|jr.|jrnez)(\d?|\d\d)$' \
                  .format(CONDITION_CODES_RE))
  # Call instructions.
  CALL_OPCODE_RE = re.compile \
                  (r'^(jal|jral|jral.|jralnez|beqzal|bltzal|bgezal)(\d)?$')
  CALL_OPERAND_RE = re.compile(r'^{}$'.format(IMM_ADDRESS_RE))
  # Ignore lp register because it's for return.
  INDIRECT_CALL_OPERAND_RE = re.compile \
                  (r'^\$r\d{1,}$|\$fp$|\$gp$|\$ta$|\$sp$|\$pc$')
  # TODO: Handle other kinds of store instructions.
  PUSH_OPCODE_RE = re.compile(r'^push(\d{1,})$')
  PUSH_OPERAND_RE = re.compile(r'^\$r\d{1,}, \#\d{1,}    \! \{([^\]]+)\}')
  SMW_OPCODE_RE = re.compile(r'^smw(\.\w\w|\.\w\w\w)$')
  SMW_OPERAND_RE = re.compile(r'^(\$r\d{1,}|\$\w\p), \[\$\w\p\], '
                   r'(\$r\d{1,}|\$\w\p), \#\d\w\d    \! \{([^\]]+)\}')
  OPERANDGROUP_RE = re.compile(r'^\$r\d{1,}\~\$r\d{1,}')

  LWI_OPCODE_RE = re.compile(r'^lwi(\.\w\w)$')
  LWI_PC_OPERAND_RE = re.compile(r'^\$pc, \[([^\]]+)\]')
  # Example: "34280:  3f c8 0f ec   addi.gp $fp, #0xfec"
  # Assume there is always a "\t" after the hex data.
  DISASM_REGEX_RE = re.compile(r'^(?P<address>[0-9A-Fa-f]+):\s+'
                    r'(?P<words>[0-9A-Fa-f ]+)'
                    r'\t\s*(?P<opcode>\S+)(\s+(?P<operand>[^;]*))?')

  def ParseInstruction(self, line, function_end):
    """Parse the line of instruction.

    Args:
      line: Text of disassembly.
      function_end: End address of the current function. None if unknown.

    Returns:
      (address, words, opcode, operand_text): The instruction address, words,
                                        opcode, and the text of operands.
                                        None if it isn't an instruction line.
    """
    result = self.DISASM_REGEX_RE.match(line)
    if result is None:
      return None

    address = int(result.group('address'), 16)
    # Check if it's out of bound.
    if function_end is not None and address >= function_end:
      return None

    opcode = result.group('opcode').strip()
    operand_text = result.group('operand')
    words = result.group('words')
    if operand_text is None:
      operand_text = ''
    else:
      operand_text = operand_text.strip()

    return (address, words, opcode, operand_text)

  def AnalyzeFunction(self, function_symbol, instructions):

    stack_frame = 0
    callsites = []
    for address, words, opcode, operand_text in instructions:
      is_jump_opcode = self.JUMP_OPCODE_RE.match(opcode) is not None
      is_call_opcode = self.CALL_OPCODE_RE.match(opcode) is not None

      if is_jump_opcode or is_call_opcode:
        is_tail = is_jump_opcode

        result = self.CALL_OPERAND_RE.match(operand_text)

        if result is None:
          if (self.INDIRECT_CALL_OPERAND_RE.match(operand_text) is not None):
            # Found an indirect call.
            callsites.append(Callsite(address, None, is_tail))

        else:
          target_address = int(result.group(1), 16)
          # Filter out the in-function target (branches and in-function calls,
          # which are actually branches).
          if not (function_symbol.size > 0 and
                  function_symbol.address < target_address <
                  (function_symbol.address + function_symbol.size)):
            # Maybe it is a callsite.
            callsites.append(Callsite(address, target_address, is_tail))

      elif self.LWI_OPCODE_RE.match(opcode) is not None:
        result = self.LWI_PC_OPERAND_RE.match(operand_text)
        if result is not None:
          # Ignore "lwi $pc, [$sp], xx" because it's usually a return.
          if result.group(1) != '$sp':
            # Found an indirect call.
            callsites.append(Callsite(address, None, True))

      elif self.PUSH_OPCODE_RE.match(opcode) is not None:
        # Example: fc 20    push25 $r8, #0    ! {$r6~$r8, $fp, $gp, $lp}
        if self.PUSH_OPERAND_RE.match(operand_text) is not None:
          # capture fc 20
          imm5u = int(words.split(' ')[1], 16)
          # sp = sp - (imm5u << 3)
          imm8u = (imm5u<<3) & 0xff
          stack_frame += imm8u

          result = self.PUSH_OPERAND_RE.match(operand_text)
          operandgroup_text = result.group(1)
          # capture $rx~$ry
          if self.OPERANDGROUP_RE.match(operandgroup_text) is not None:
            # capture number & transfer string to integer
            oprandgrouphead = operandgroup_text.split(',')[0]
            rx=int(filter(str.isdigit, oprandgrouphead.split('~')[0]))
            ry=int(filter(str.isdigit, oprandgrouphead.split('~')[1]))

            stack_frame += ((len(operandgroup_text.split(','))+ry-rx) *
                          self.GENERAL_PURPOSE_REGISTER_SIZE)
          else:
            stack_frame += (len(operandgroup_text.split(',')) *
                          self.GENERAL_PURPOSE_REGISTER_SIZE)

      elif self.SMW_OPCODE_RE.match(opcode) is not None:
        # Example: smw.adm $r6, [$sp], $r10, #0x2    ! {$r6~$r10, $lp}
        if self.SMW_OPERAND_RE.match(operand_text) is not None:
          result = self.SMW_OPERAND_RE.match(operand_text)
          operandgroup_text = result.group(3)
          # capture $rx~$ry
          if self.OPERANDGROUP_RE.match(operandgroup_text) is not None:
            # capture number & transfer string to integer
            oprandgrouphead = operandgroup_text.split(',')[0]
            rx=int(filter(str.isdigit, oprandgrouphead.split('~')[0]))
            ry=int(filter(str.isdigit, oprandgrouphead.split('~')[1]))

            stack_frame += ((len(operandgroup_text.split(','))+ry-rx) *
                          self.GENERAL_PURPOSE_REGISTER_SIZE)
          else:
            stack_frame += (len(operandgroup_text.split(',')) *
                          self.GENERAL_PURPOSE_REGISTER_SIZE)

    return (stack_frame, callsites)

class ArmAnalyzer(object):
  """Disassembly analyzer for ARM architecture.

  Public Methods:
    AnalyzeFunction: Analyze stack frame and callsites of the function.
  """

  GENERAL_PURPOSE_REGISTER_SIZE = 4

  # Possible condition code suffixes.
  CONDITION_CODES = ['', 'eq', 'ne', 'cs', 'hs', 'cc', 'lo', 'mi', 'pl', 'vs',
                     'vc', 'hi', 'ls', 'ge', 'lt', 'gt', 'le']
  CONDITION_CODES_RE = '({})'.format('|'.join(CONDITION_CODES))
  # Assume there is no function name containing ">".
  IMM_ADDRESS_RE = r'([0-9A-Fa-f]+)\s+<([^>]+)>'

  # Fuzzy regular expressions for instruction and operand parsing.
  # Branch instructions.
  JUMP_OPCODE_RE = re.compile(
      r'^(b{0}|bx{0})(\.\w)?$'.format(CONDITION_CODES_RE))
  # Call instructions.
  CALL_OPCODE_RE = re.compile(
      r'^(bl{0}|blx{0})(\.\w)?$'.format(CONDITION_CODES_RE))
  CALL_OPERAND_RE = re.compile(r'^{}$'.format(IMM_ADDRESS_RE))
  CBZ_CBNZ_OPCODE_RE = re.compile(r'^(cbz|cbnz)(\.\w)?$')
  # Example: "r0, 1009bcbe <host_cmd_motion_sense+0x1d2>"
  CBZ_CBNZ_OPERAND_RE = re.compile(r'^[^,]+,\s+{}$'.format(IMM_ADDRESS_RE))
  # Ignore lr register because it's for return.
  INDIRECT_CALL_OPERAND_RE = re.compile(r'^r\d+|sb|sl|fp|ip|sp|pc$')
  # TODO(cheyuw): Handle conditional versions of following
  #               instructions.
  # TODO(cheyuw): Handle other kinds of pc modifying instructions (e.g. mov pc).
  LDR_OPCODE_RE = re.compile(r'^ldr(\.\w)?$')
  # Example: "pc, [sp], #4"
  LDR_PC_OPERAND_RE = re.compile(r'^pc, \[([^\]]+)\]')
  # TODO(cheyuw): Handle other kinds of stm instructions.
  PUSH_OPCODE_RE = re.compile(r'^push$')
  STM_OPCODE_RE = re.compile(r'^stmdb$')
  # Stack subtraction instructions.
  SUB_OPCODE_RE = re.compile(r'^sub(s|w)?(\.\w)?$')
  SUB_OPERAND_RE = re.compile(r'^sp[^#]+#(\d+)')
  # Example: "44d94:  f893 0068   ldrb.w  r0, [r3, #104]  ; 0x68"
  # Assume there is always a "\t" after the hex data.
  DISASM_REGEX_RE = re.compile(r'^(?P<address>[0-9A-Fa-f]+):\s+[0-9A-Fa-f ]+'
                               r'\t\s*(?P<opcode>\S+)(\s+(?P<operand>[^;]*))?')

  def ParseInstruction(self, line, function_end):
    """Parse the line of instruction.

    Args:
      line: Text of disassembly.
      function_end: End address of the current function. None if unknown.

    Returns:
      (address, opcode, operand_text): The instruction address, opcode,
                                       and the text of operands. None if it
                                       isn't an instruction line.
    """
    result = self.DISASM_REGEX_RE.match(line)
    if result is None:
      return None

    address = int(result.group('address'), 16)
    # Check if it's out of bound.
    if function_end is not None and address >= function_end:
      return None

    opcode = result.group('opcode').strip()
    operand_text = result.group('operand')
    if operand_text is None:
      operand_text = ''
    else:
      operand_text = operand_text.strip()

    return (address, opcode, operand_text)

  def AnalyzeFunction(self, function_symbol, instructions):
    """Analyze function, resolve the size of stack frame and callsites.

    Args:
      function_symbol: Function symbol.
      instructions: Instruction list.

    Returns:
      (stack_frame, callsites): Size of stack frame, callsite list.
    """
    stack_frame = 0
    callsites = []
    for address, opcode, operand_text in instructions:
      is_jump_opcode = self.JUMP_OPCODE_RE.match(opcode) is not None
      is_call_opcode = self.CALL_OPCODE_RE.match(opcode) is not None
      is_cbz_cbnz_opcode = self.CBZ_CBNZ_OPCODE_RE.match(opcode) is not None
      if is_jump_opcode or is_call_opcode or is_cbz_cbnz_opcode:
        is_tail = is_jump_opcode or is_cbz_cbnz_opcode

        if is_cbz_cbnz_opcode:
          result = self.CBZ_CBNZ_OPERAND_RE.match(operand_text)
        else:
          result = self.CALL_OPERAND_RE.match(operand_text)

        if result is None:
          # Failed to match immediate address, maybe it is an indirect call.
          # CBZ and CBNZ can't be indirect calls.
          if (not is_cbz_cbnz_opcode and
              self.INDIRECT_CALL_OPERAND_RE.match(operand_text) is not None):
            # Found an indirect call.
            callsites.append(Callsite(address, None, is_tail))

        else:
          target_address = int(result.group(1), 16)
          # Filter out the in-function target (branches and in-function calls,
          # which are actually branches).
          if not (function_symbol.size > 0 and
                  function_symbol.address < target_address <
                  (function_symbol.address + function_symbol.size)):
            # Maybe it is a callsite.
            callsites.append(Callsite(address, target_address, is_tail))

      elif self.LDR_OPCODE_RE.match(opcode) is not None:
        result = self.LDR_PC_OPERAND_RE.match(operand_text)
        if result is not None:
          # Ignore "ldr pc, [sp], xx" because it's usually a return.
          if result.group(1) != 'sp':
            # Found an indirect call.
            callsites.append(Callsite(address, None, True))

      elif self.PUSH_OPCODE_RE.match(opcode) is not None:
        # Example: "{r4, r5, r6, r7, lr}"
        stack_frame += (len(operand_text.split(',')) *
                        self.GENERAL_PURPOSE_REGISTER_SIZE)
      elif self.SUB_OPCODE_RE.match(opcode) is not None:
        result = self.SUB_OPERAND_RE.match(operand_text)
        if result is not None:
          stack_frame += int(result.group(1))
        else:
          # Unhandled stack register subtraction.
          assert not operand_text.startswith('sp')

      elif self.STM_OPCODE_RE.match(opcode) is not None:
        if operand_text.startswith('sp!'):
          # Subtract and writeback to stack register.
          # Example: "sp!, {r4, r5, r6, r7, r8, r9, lr}"
          # Get the text of pushed register list.
          unused_sp, unused_sep, parameter_text = operand_text.partition(',')
          stack_frame += (len(parameter_text.split(',')) *
                          self.GENERAL_PURPOSE_REGISTER_SIZE)

    return (stack_frame, callsites)


class StackAnalyzer(object):
  """Class to analyze stack usage.

  Public Methods:
    Analyze: Run the stack analysis.
  """

  C_FUNCTION_NAME = r'_A-Za-z0-9'

  # Assume there is no ":" in the path.
  # Example: "driver/accel_kionix.c:321 (discriminator 3)"
  ADDRTOLINE_RE = re.compile(
      r'^(?P<path>[^:]+):(?P<linenum>\d+)(\s+\(discriminator\s+\d+\))?$')
  # To eliminate the suffix appended by compilers, try to extract the
  # C function name from the prefix of symbol name.
  # Example: "SHA256_transform.constprop.28"
  FUNCTION_PREFIX_NAME_RE = re.compile(
      r'^(?P<name>[{0}]+)([^{0}].*)?$'.format(C_FUNCTION_NAME))

  # Errors of annotation resolving.
  ANNOTATION_ERROR_INVALID = 'invalid signature'
  ANNOTATION_ERROR_NOTFOUND = 'function is not found'
  ANNOTATION_ERROR_AMBIGUOUS = 'signature is ambiguous'

  def __init__(self, options, symbols, rodata, tasklist, annotation):
    """Constructor.

    Args:
      options: Namespace from argparse.parse_args().
      symbols: Symbol list.
      rodata: Content of .rodata section (offset, data)
      tasklist: Task list.
      annotation: Annotation config.
    """
    self.options = options
    self.symbols = symbols
    self.rodata_offset = rodata[0]
    self.rodata = rodata[1]
    self.tasklist = tasklist
    self.annotation = annotation
    self.address_to_line_cache = {}

  def AddressToLine(self, address, resolve_inline=False):
    """Convert address to line.

    Args:
      address: Target address.
      resolve_inline: Output the stack of inlining.

    Returns:
      lines: List of the corresponding lines.

    Raises:
      StackAnalyzerError: If addr2line is failed.
    """
    cache_key = (address, resolve_inline)
    if cache_key in self.address_to_line_cache:
      return self.address_to_line_cache[cache_key]

    try:
      args = [self.options.addr2line,
              '-f',
              '-e',
              self.options.elf_path,
              '{:x}'.format(address)]
      if resolve_inline:
        args.append('-i')

      line_text = subprocess.check_output(args)
    except subprocess.CalledProcessError:
      raise StackAnalyzerError('addr2line failed to resolve lines.')
    except OSError:
      raise StackAnalyzerError('Failed to run addr2line.')

    lines = [line.strip() for line in line_text.splitlines()]
    # Assume the output has at least one pair like "function\nlocation\n", and
    # they always show up in pairs.
    # Example: "handle_request\n
    #           common/usb_pd_protocol.c:1191\n"
    assert len(lines) >= 2 and len(lines) % 2 == 0

    line_infos = []
    for index in range(0, len(lines), 2):
      (function_name, line_text) = lines[index:index + 2]
      if line_text in ['??:0', ':?']:
        line_infos.append(None)
      else:
        result = self.ADDRTOLINE_RE.match(line_text)
        # Assume the output is always well-formed.
        assert result is not None
        line_infos.append((function_name.strip(),
                           os.path.realpath(result.group('path').strip()),
                           int(result.group('linenum'))))

    self.address_to_line_cache[cache_key] = line_infos
    return line_infos

  def AnalyzeDisassembly(self, disasm_text):
    """Parse the disassembly text, analyze, and build a map of all functions.

    Args:
      disasm_text: Disassembly text.

    Returns:
      function_map: Dict of functions.
    """
    disasm_lines = [line.strip() for line in disasm_text.splitlines()]

    if (disasm_lines[1].find("nds") != -1):
      analyzer = AndesAnalyzer()
    elif (disasm_lines[1].find("arm") != -1):
      analyzer = ArmAnalyzer()
    else:
      raise StackAnalyzerError('Unsupported architecture.')

    # Example: "08028c8c <motion_lid_calc>:"
    function_signature_regex = re.compile(
        r'^(?P<address>[0-9A-Fa-f]+)\s+<(?P<name>[^>]+)>:$')

    def DetectFunctionHead(line):
      """Check if the line is a function head.

      Args:
        line: Text of disassembly.

      Returns:
        symbol: Function symbol. None if it isn't a function head.
      """
      result = function_signature_regex.match(line)
      if result is None:
        return None

      address = int(result.group('address'), 16)
      symbol = symbol_map.get(address)

      # Check if the function exists and matches.
      if symbol is None or symbol.symtype != 'F':
        return None

      return symbol

    # Build symbol map, indexed by symbol address.
    symbol_map = {}
    for symbol in self.symbols:
      # If there are multiple symbols with same address, keeping any of them is
      # good enough.
      symbol_map[symbol.address] = symbol

    # Parse the disassembly text. We update the variable "line" to next line
    # when needed. There are two steps of parser:
    #
    # Step 1: Searching for the function head. Once reach the function head,
    # move to the next line, which is the first line of function body.
    #
    # Step 2: Parsing each instruction line of function body. Once reach a
    # non-instruction line, stop parsing and analyze the parsed instructions.
    #
    # Finally turn back to the step 1 without updating the line, because the
    # current non-instruction line can be another function head.
    function_map = {}
    # The following three variables are the states of the parsing processing.
    # They will be initialized properly during the state changes.
    function_symbol = None
    function_end = None
    instructions = []

    # Remove heading and tailing spaces for each line.
    line_index = 0
    while line_index < len(disasm_lines):
      # Get the current line.
      line = disasm_lines[line_index]

      if function_symbol is None:
        # Step 1: Search for the function head.

        function_symbol = DetectFunctionHead(line)
        if function_symbol is not None:
          # Assume there is no empty function. If the function head is followed
          # by EOF, it is an empty function.
          assert line_index + 1 < len(disasm_lines)

          # Found the function head, initialize and turn to the step 2.
          instructions = []
          # If symbol size exists, use it as a hint of function size.
          if function_symbol.size > 0:
            function_end = function_symbol.address + function_symbol.size
          else:
            function_end = None

      else:
        # Step 2: Parse the function body.

        instruction = analyzer.ParseInstruction(line, function_end)
        if instruction is not None:
          instructions.append(instruction)

        if instruction is None or line_index + 1 == len(disasm_lines):
          # Either the invalid instruction or EOF indicates the end of the
          # function, finalize the function analysis.

          # Assume there is no empty function.
          assert len(instructions) > 0

          (stack_frame, callsites) = analyzer.AnalyzeFunction(function_symbol,
                                                              instructions)
          # Assume the function addresses are unique in the disassembly.
          assert function_symbol.address not in function_map
          function_map[function_symbol.address] = Function(
              function_symbol.address,
              function_symbol.name,
              stack_frame,
              callsites)

          # Initialize and turn back to the step 1.
          function_symbol = None

          # If the current line isn't an instruction, it can be another function
          # head, skip moving to the next line.
          if instruction is None:
            continue

      # Move to the next line.
      line_index += 1

    # Resolve callees of functions.
    for function in function_map.values():
      for callsite in function.callsites:
        if callsite.target is not None:
          # Remain the callee as None if we can't resolve it.
          callsite.callee = function_map.get(callsite.target)

    return function_map

  def MapAnnotation(self, function_map, signature_set):
    """Map annotation signatures to functions.

    Args:
      function_map: Function map.
      signature_set: Set of annotation signatures.

    Returns:
      Map of signatures to functions, map of signatures which can't be resolved.
    """
    # Build the symbol map indexed by symbol name. If there are multiple symbols
    # with the same name, add them into a set. (e.g. symbols of static function
    # with the same name)
    symbol_map = collections.defaultdict(set)
    for symbol in self.symbols:
      if symbol.symtype == 'F':
        # Function symbol.
        result = self.FUNCTION_PREFIX_NAME_RE.match(symbol.name)
        if result is not None:
          function = function_map.get(symbol.address)
          # Ignore the symbol not in disassembly.
          if function is not None:
            # If there are multiple symbol with the same name and point to the
            # same function, the set will deduplicate them.
            symbol_map[result.group('name').strip()].add(function)

    # Build the signature map indexed by annotation signature.
    signature_map = {}
    sig_error_map = {}
    symbol_path_map = {}
    for sig in signature_set:
      (name, path, _) = sig

      functions = symbol_map.get(name)
      if functions is None:
        sig_error_map[sig] = self.ANNOTATION_ERROR_NOTFOUND
        continue

      if name not in symbol_path_map:
        # Lazy symbol path resolving. Since the addr2line isn't fast, only
        # resolve needed symbol paths.
        group_map = collections.defaultdict(list)
        for function in functions:
          line_info = self.AddressToLine(function.address)[0]
          if line_info is None:
            continue

          (_, symbol_path, _) = line_info

          # Group the functions with the same symbol signature (symbol name +
          # symbol path). Assume they are the same copies and do the same
          # annotation operations of them because we don't know which copy is
          # indicated by the users.
          group_map[symbol_path].append(function)

        symbol_path_map[name] = group_map

      # Symbol matching.
      function_group = None
      group_map = symbol_path_map[name]
      if len(group_map) > 0:
        if path is None:
          if len(group_map) > 1:
            # There is ambiguity but the path isn't specified.
            sig_error_map[sig] = self.ANNOTATION_ERROR_AMBIGUOUS
            continue

          # No path signature but all symbol signatures of functions are same.
          # Assume they are the same functions, so there is no ambiguity.
          (function_group,) = group_map.values()
        else:
          function_group = group_map.get(path)

      if function_group is None:
        sig_error_map[sig] = self.ANNOTATION_ERROR_NOTFOUND
        continue

      # The function_group is a list of all the same functions (according to
      # our assumption) which should be annotated together.
      signature_map[sig] = function_group

    return (signature_map, sig_error_map)

  def LoadAnnotation(self):
    """Load annotation rules.

    Returns:
      Map of add rules, set of remove rules, set of text signatures which can't
      be parsed.
    """
    # Assume there is no ":" in the path.
    # Example: "get_range.lto.2501[driver/accel_kionix.c:327]"
    annotation_signature_regex = re.compile(
        r'^(?P<name>[^\[]+)(\[(?P<path>[^:]+)(:(?P<linenum>\d+))?\])?$')

    def NormalizeSignature(signature_text):
      """Parse and normalize the annotation signature.

      Args:
        signature_text: Text of the annotation signature.

      Returns:
        (function name, path, line number) of the signature. The path and line
        number can be None if not exist. None if failed to parse.
      """
      result = annotation_signature_regex.match(signature_text.strip())
      if result is None:
        return None

      name_result = self.FUNCTION_PREFIX_NAME_RE.match(
          result.group('name').strip())
      if name_result is None:
        return None

      path = result.group('path')
      if path is not None:
        path = os.path.realpath(path.strip())

      linenum = result.group('linenum')
      if linenum is not None:
        linenum = int(linenum.strip())

      return (name_result.group('name').strip(), path, linenum)

    def ExpandArray(dic):
      """Parse and expand a symbol array

      Args:
        dic: Dictionary for the array annotation

      Returns:
        array of (symbol name, None, None).
      """
      # TODO(drinkcat): This function is quite inefficient, as it goes through
      # the symbol table multiple times.

      begin_name = dic['name']
      end_name = dic['name'] + "_end"
      offset = dic['offset'] if 'offset' in dic else 0
      stride = dic['stride']

      begin_address = None
      end_address = None

      for symbol in self.symbols:
        if (symbol.name == begin_name):
          begin_address = symbol.address
        if (symbol.name == end_name):
          end_address = symbol.address

      if (not begin_address or not end_address):
        return None

      output = []
      # TODO(drinkcat): This is inefficient as we go from address to symbol
      # object then to symbol name, and later on we'll go back from symbol name
      # to symbol object.
      for addr in range(begin_address+offset, end_address, stride):
        # TODO(drinkcat): Not all architectures need to drop the first bit.
        val = self.rodata[(addr-self.rodata_offset)/4] & 0xfffffffe
        name = None
        for symbol in self.symbols:
          if (symbol.address == val):
            result = self.FUNCTION_PREFIX_NAME_RE.match(symbol.name)
            name = result.group('name')
            break

        if not name:
          raise StackAnalyzerError('Cannot find function for address %s.',
                                   hex(val))

        output.append((name, None, None))

      return output

    add_rules = collections.defaultdict(set)
    remove_rules = list()
    invalid_sigtxts = set()

    if 'add' in self.annotation and self.annotation['add'] is not None:
      for src_sigtxt, dst_sigtxts in self.annotation['add'].items():
        src_sig = NormalizeSignature(src_sigtxt)
        if src_sig is None:
          invalid_sigtxts.add(src_sigtxt)
          continue

        for dst_sigtxt in dst_sigtxts:
          if isinstance(dst_sigtxt, dict):
            dst_sig = ExpandArray(dst_sigtxt)
            if dst_sig is None:
              invalid_sigtxts.add(str(dst_sigtxt))
            else:
              add_rules[src_sig].update(dst_sig)
          else:
            dst_sig = NormalizeSignature(dst_sigtxt)
            if dst_sig is None:
              invalid_sigtxts.add(dst_sigtxt)
            else:
              add_rules[src_sig].add(dst_sig)

    if 'remove' in self.annotation and self.annotation['remove'] is not None:
      for sigtxt_path in self.annotation['remove']:
        if isinstance(sigtxt_path, str):
          # The path has only one vertex.
          sigtxt_path = [sigtxt_path]

        if len(sigtxt_path) == 0:
          continue

        # Generate multiple remove paths from all the combinations of the
        # signatures of each vertex.
        sig_paths = [[]]
        broken_flag = False
        for sigtxt_node in sigtxt_path:
          if isinstance(sigtxt_node, str):
            # The vertex has only one signature.
            sigtxt_set = {sigtxt_node}
          elif isinstance(sigtxt_node, list):
            # The vertex has multiple signatures.
            sigtxt_set = set(sigtxt_node)
          else:
            # Assume the format of annotation is verified. There should be no
            # invalid case.
            assert False

          sig_set = set()
          for sigtxt in sigtxt_set:
            sig = NormalizeSignature(sigtxt)
            if sig is None:
              invalid_sigtxts.add(sigtxt)
              broken_flag = True
            elif not broken_flag:
              sig_set.add(sig)

          if broken_flag:
            continue

          # Append each signature of the current node to the all previous
          # remove paths.
          sig_paths = [path + [sig] for path in sig_paths for sig in sig_set]

        if not broken_flag:
          # All signatures are normalized. The remove path has no error.
          remove_rules.extend(sig_paths)

    return (add_rules, remove_rules, invalid_sigtxts)

  def ResolveAnnotation(self, function_map):
    """Resolve annotation.

    Args:
      function_map: Function map.

    Returns:
      Set of added call edges, list of remove paths, set of eliminated
      callsite addresses, set of annotation signatures which can't be resolved.
    """
    def StringifySignature(signature):
      """Stringify the tupled signature.

      Args:
        signature: Tupled signature.

      Returns:
        Signature string.
      """
      (name, path, linenum) = signature
      bracket_text = ''
      if path is not None:
        path = os.path.relpath(path)
        if linenum is None:
          bracket_text = '[{}]'.format(path)
        else:
          bracket_text = '[{}:{}]'.format(path, linenum)

      return name + bracket_text

    (add_rules, remove_rules, invalid_sigtxts) = self.LoadAnnotation()

    signature_set = set()
    for src_sig, dst_sigs in add_rules.items():
      signature_set.add(src_sig)
      signature_set.update(dst_sigs)

    for remove_sigs in remove_rules:
      signature_set.update(remove_sigs)

    # Map signatures to functions.
    (signature_map, sig_error_map) = self.MapAnnotation(function_map,
                                                        signature_set)

    # Build the indirect callsite map indexed by callsite signature.
    indirect_map = collections.defaultdict(set)
    for function in function_map.values():
      for callsite in function.callsites:
        if callsite.target is not None:
          continue

        # Found an indirect callsite.
        line_info = self.AddressToLine(callsite.address)[0]
        if line_info is None:
          continue

        (name, path, linenum) = line_info
        result = self.FUNCTION_PREFIX_NAME_RE.match(name)
        if result is None:
          continue

        indirect_map[(result.group('name').strip(), path, linenum)].add(
            (function, callsite.address))

    # Generate the annotation sets.
    add_set = set()
    remove_list = list()
    eliminated_addrs = set()

    for src_sig, dst_sigs in add_rules.items():
      src_funcs = set(signature_map.get(src_sig, []))
      # Try to match the source signature to the indirect callsites. Even if it
      # can't be found in disassembly.
      indirect_calls = indirect_map.get(src_sig)
      if indirect_calls is not None:
        for function, callsite_address in indirect_calls:
          # Add the caller of the indirect callsite to the source functions.
          src_funcs.add(function)
          # Assume each callsite can be represented by a unique address.
          eliminated_addrs.add(callsite_address)

        if src_sig in sig_error_map:
          # Assume the error is always the not found error. Since the signature
          # found in indirect callsite map must be a full signature, it can't
          # happen the ambiguous error.
          assert sig_error_map[src_sig] == self.ANNOTATION_ERROR_NOTFOUND
          # Found in inline stack, remove the not found error.
          del sig_error_map[src_sig]

      for dst_sig in dst_sigs:
        dst_funcs = signature_map.get(dst_sig)
        if dst_funcs is None:
          continue

        # Duplicate the call edge for all the same source and destination
        # functions.
        for src_func in src_funcs:
          for dst_func in dst_funcs:
            add_set.add((src_func, dst_func))

    for remove_sigs in remove_rules:
      # Since each signature can be mapped to multiple functions, generate
      # multiple remove paths from all the combinations of these functions.
      remove_paths = [[]]
      skip_flag = False
      for remove_sig in remove_sigs:
        # Transform each signature to the corresponding functions.
        remove_funcs = signature_map.get(remove_sig)
        if remove_funcs is None:
          # There is an unresolved signature in the remove path. Ignore the
          # whole broken remove path.
          skip_flag = True
          break
        else:
          # Append each function of the current signature to the all previous
          # remove paths.
          remove_paths = [p + [f] for p in remove_paths for f in remove_funcs]

      if skip_flag:
        # Ignore the broken remove path.
        continue

      for remove_path in remove_paths:
        # Deduplicate the remove paths.
        if remove_path not in remove_list:
          remove_list.append(remove_path)

    # Format the error messages.
    failed_sigtxts = set()
    for sigtxt in invalid_sigtxts:
      failed_sigtxts.add((sigtxt, self.ANNOTATION_ERROR_INVALID))

    for sig, error in sig_error_map.items():
      failed_sigtxts.add((StringifySignature(sig), error))

    return (add_set, remove_list, eliminated_addrs, failed_sigtxts)

  def PreprocessAnnotation(self, function_map, add_set, remove_list,
                           eliminated_addrs):
    """Preprocess the annotation and callgraph.

    Add the missing call edges, and delete simple remove paths (the paths have
    one or two vertices) from the function_map.

    Eliminate the annotated indirect callsites.

    Return the remaining remove list.

    Args:
      function_map: Function map.
      add_set: Set of missing call edges.
      remove_list: List of remove paths.
      eliminated_addrs: Set of eliminated callsite addresses.

    Returns:
      List of remaining remove paths.
    """
    def CheckEdge(path):
      """Check if all edges of the path are on the callgraph.

      Args:
        path: Path.

      Returns:
        True or False.
      """
      for index in range(len(path) - 1):
        if (path[index], path[index + 1]) not in edge_set:
          return False

      return True

    for src_func, dst_func in add_set:
      # TODO(cheyuw): Support tailing call annotation.
      src_func.callsites.append(
          Callsite(None, dst_func.address, False, dst_func))

    # Delete simple remove paths.
    remove_simple = set(tuple(p) for p in remove_list if len(p) <= 2)
    edge_set = set()
    for function in function_map.values():
      cleaned_callsites = []
      for callsite in function.callsites:
        if ((callsite.callee,) in remove_simple or
            (function, callsite.callee) in remove_simple):
          continue

        if callsite.target is None and callsite.address in eliminated_addrs:
          continue

        cleaned_callsites.append(callsite)
        if callsite.callee is not None:
          edge_set.add((function, callsite.callee))

      function.callsites = cleaned_callsites

    return [p for p in remove_list if len(p) >= 3 and CheckEdge(p)]

  def AnalyzeCallGraph(self, function_map, remove_list):
    """Analyze callgraph.

    It will update the max stack size and path for each function.

    Args:
      function_map: Function map.
      remove_list: List of remove paths.

    Returns:
      List of function cycles.
    """
    def Traverse(curr_state):
      """Traverse the callgraph and calculate the max stack usages of functions.

      Args:
        curr_state: Current state.

      Returns:
        SCC lowest link.
      """
      scc_index = scc_index_counter[0]
      scc_index_counter[0] += 1
      scc_index_map[curr_state] = scc_index
      scc_lowlink = scc_index
      scc_stack.append(curr_state)
      # Push the current state in the stack. We can use a set to maintain this
      # because the stacked states are unique; otherwise we will find a cycle
      # first.
      stacked_states.add(curr_state)

      (curr_address, curr_positions) = curr_state
      curr_func = function_map[curr_address]

      invalid_flag = False
      new_positions = list(curr_positions)
      for index, position in enumerate(curr_positions):
        remove_path = remove_list[index]

        # The position of each remove path in the state is the length of the
        # longest matching path between the prefix of the remove path and the
        # suffix of the current traversing path. We maintain this length when
        # appending the next callee to the traversing path. And it can be used
        # to check if the remove path appears in the traversing path.

        # TODO(cheyuw): Implement KMP algorithm to match remove paths
        #               efficiently.
        if remove_path[position] is curr_func:
          # Matches the current function, extend the length.
          new_positions[index] = position + 1
          if new_positions[index] == len(remove_path):
            # The length of the longest matching path is equal to the length of
            # the remove path, which means the suffix of the current traversing
            # path matches the remove path.
            invalid_flag = True
            break

        else:
          # We can't get the new longest matching path by extending the previous
          # one directly. Fallback to search the new longest matching path.

          # If we can't find any matching path in the following search, reset
          # the matching length to 0.
          new_positions[index] = 0

          # We want to find the new longest matching prefix of remove path with
          # the suffix of the current traversing path. Because the new longest
          # matching path won't be longer than the prevous one now, and part of
          # the suffix matches the prefix of remove path, we can get the needed
          # suffix from the previous matching prefix of the invalid path.
          suffix = remove_path[:position] + [curr_func]
          for offset in range(1, len(suffix)):
            length = position - offset
            if remove_path[:length] == suffix[offset:]:
              new_positions[index] = length
              break

      new_positions = tuple(new_positions)

      # If the current suffix is invalid, set the max stack usage to 0.
      max_stack_usage = 0
      max_callee_state = None
      self_loop = False

      if not invalid_flag:
        # Max stack usage is at least equal to the stack frame.
        max_stack_usage = curr_func.stack_frame
        for callsite in curr_func.callsites:
          callee = callsite.callee
          if callee is None:
            continue

          callee_state = (callee.address, new_positions)
          if callee_state not in scc_index_map:
            # Unvisited state.
            scc_lowlink = min(scc_lowlink, Traverse(callee_state))
          elif callee_state in stacked_states:
            # The state is shown in the stack. There is a cycle.
            sub_stack_usage = 0
            scc_lowlink = min(scc_lowlink, scc_index_map[callee_state])
            if callee_state == curr_state:
              self_loop = True

          done_result = done_states.get(callee_state)
          if done_result is not None:
            # Already done this state and use its result. If the state reaches a
            # cycle, reusing the result will cause inaccuracy (the stack usage
            # of cycle depends on where the entrance is). But it's fine since we
            # can't get accurate stack usage under this situation, and we rely
            # on user-provided annotations to break the cycle, after which the
            # result will be accurate again.
            (sub_stack_usage, _) = done_result

            if callsite.is_tail:
              # For tailing call, since the callee reuses the stack frame of the
              # caller, choose the larger one directly.
              stack_usage = max(curr_func.stack_frame, sub_stack_usage)
            else:
              stack_usage = curr_func.stack_frame + sub_stack_usage

            if stack_usage > max_stack_usage:
              max_stack_usage = stack_usage
              max_callee_state = callee_state

      if scc_lowlink == scc_index:
        group = []
        while scc_stack[-1] != curr_state:
          scc_state = scc_stack.pop()
          stacked_states.remove(scc_state)
          group.append(scc_state)

        scc_stack.pop()
        stacked_states.remove(curr_state)

        # If the cycle is not empty, record it.
        if len(group) > 0 or self_loop:
          group.append(curr_state)
          cycle_groups.append(group)

      # Store the done result.
      done_states[curr_state] = (max_stack_usage, max_callee_state)

      if curr_positions == initial_positions:
        # If the current state is initial state, we traversed the callgraph by
        # using the current function as start point. Update the stack usage of
        # the function.
        # If the function matches a single vertex remove path, this will set its
        # max stack usage to 0, which is not expected (we still calculate its
        # max stack usage, but prevent any function from calling it). However,
        # all the single vertex remove paths have been preprocessed and removed.
        curr_func.stack_max_usage = max_stack_usage

        # Reconstruct the max stack path by traversing the state transitions.
        max_stack_path = [curr_func]
        callee_state = max_callee_state
        while callee_state is not None:
          # The first element of state tuple is function address.
          max_stack_path.append(function_map[callee_state[0]])
          done_result = done_states.get(callee_state)
          # All of the descendants should be done.
          assert done_result is not None
          (_, callee_state) = done_result

        curr_func.stack_max_path = max_stack_path

      return scc_lowlink

    # The state is the concatenation of the current function address and the
    # state of matching position.
    initial_positions = (0,) * len(remove_list)
    done_states = {}
    stacked_states = set()
    scc_index_counter = [0]
    scc_index_map = {}
    scc_stack = []
    cycle_groups = []
    for function in function_map.values():
      if function.stack_max_usage is None:
        Traverse((function.address, initial_positions))

    cycle_functions = []
    for group in cycle_groups:
      cycle = set(function_map[state[0]] for state in group)
      if cycle not in cycle_functions:
        cycle_functions.append(cycle)

    return cycle_functions

  def Analyze(self):
    """Run the stack analysis.

    Raises:
      StackAnalyzerError: If disassembly fails.
    """
    def OutputInlineStack(address, prefix=''):
      """Output beautiful inline stack.

      Args:
        address: Address.
        prefix: Prefix of each line.

      Returns:
        Key for sorting, output text
      """
      line_infos = self.AddressToLine(address, True)

      if line_infos[0] is None:
        order_key = (None, None)
      else:
        (_, path, linenum) = line_infos[0]
        order_key = (linenum, path)

      line_texts = []
      for line_info in reversed(line_infos):
        if line_info is None:
          (function_name, path, linenum) = ('??', '??', 0)
        else:
          (function_name, path, linenum) = line_info

        line_texts.append('{}[{}:{}]'.format(function_name,
                                             os.path.relpath(path),
                                             linenum))

      output = '{}-> {} {:x}\n'.format(prefix, line_texts[0], address)
      for depth, line_text in enumerate(line_texts[1:]):
        output += '{}   {}- {}\n'.format(prefix, '  ' * depth, line_text)

      # Remove the last newline character.
      return (order_key, output.rstrip('\n'))

    # Analyze disassembly.
    try:
      disasm_text = subprocess.check_output([self.options.objdump,
                                             '-d',
                                             self.options.elf_path])
    except subprocess.CalledProcessError:
      raise StackAnalyzerError('objdump failed to disassemble.')
    except OSError:
      raise StackAnalyzerError('Failed to run objdump.')

    function_map = self.AnalyzeDisassembly(disasm_text)
    result = self.ResolveAnnotation(function_map)
    (add_set, remove_list, eliminated_addrs, failed_sigtxts) = result
    remove_list = self.PreprocessAnnotation(function_map,
                                            add_set,
                                            remove_list,
                                            eliminated_addrs)
    cycle_functions = self.AnalyzeCallGraph(function_map, remove_list)

    # Print the results of task-aware stack analysis.
    extra_stack_frame = self.annotation.get('exception_frame_size',
                                            DEFAULT_EXCEPTION_FRAME_SIZE)
    for task in self.tasklist:
      routine_func = function_map[task.routine_address]
      print('Task: {}, Max size: {} ({} + {}), Allocated size: {}'.format(
          task.name,
          routine_func.stack_max_usage + extra_stack_frame,
          routine_func.stack_max_usage,
          extra_stack_frame,
          task.stack_max_size))

      print('Call Trace:')
      max_stack_path = routine_func.stack_max_path
      # Assume the routine function is resolved.
      assert max_stack_path is not None
      for depth, curr_func in enumerate(max_stack_path):
        line_info = self.AddressToLine(curr_func.address)[0]
        if line_info is None:
          (path, linenum) = ('??', 0)
        else:
          (_, path, linenum) = line_info

        print('    {} ({}) [{}:{}] {:x}'.format(curr_func.name,
                                                curr_func.stack_frame,
                                                os.path.relpath(path),
                                                linenum,
                                                curr_func.address))

        if depth + 1 < len(max_stack_path):
          succ_func = max_stack_path[depth + 1]
          text_list = []
          for callsite in curr_func.callsites:
            if callsite.callee is succ_func:
              indent_prefix = '        '
              if callsite.address is None:
                order_text = (None, '{}-> [annotation]'.format(indent_prefix))
              else:
                order_text = OutputInlineStack(callsite.address, indent_prefix)

              text_list.append(order_text)

          for _, text in sorted(text_list, key=lambda (k, _): k):
            print(text)

    print('Unresolved indirect callsites:')
    for function in function_map.values():
      indirect_callsites = []
      for callsite in function.callsites:
        if callsite.target is None:
          indirect_callsites.append(callsite.address)

      if len(indirect_callsites) > 0:
        print('    In function {}:'.format(function.name))
        text_list = []
        for address in indirect_callsites:
          text_list.append(OutputInlineStack(address, '        '))

        for _, text in sorted(text_list, key=lambda (k, _): k):
          print(text)

    print('Unresolved annotation signatures:')
    for sigtxt, error in failed_sigtxts:
      print('    {}: {}'.format(sigtxt, error))

    if len(cycle_functions) > 0:
      print('There are cycles in the following function sets:')
      for functions in cycle_functions:
        print('[{}]'.format(', '.join(function.name for function in functions)))


def ParseArgs():
  """Parse commandline arguments.

  Returns:
    options: Namespace from argparse.parse_args().
  """
  parser = argparse.ArgumentParser(description="EC firmware stack analyzer.")
  parser.add_argument('elf_path', help="the path of EC firmware ELF")
  parser.add_argument('--export_taskinfo', required=True,
                      help="the path of export_taskinfo.so utility")
  parser.add_argument('--section', required=True, help='the section.',
                      choices=[SECTION_RO, SECTION_RW])
  parser.add_argument('--objdump', default='objdump',
                      help='the path of objdump')
  parser.add_argument('--addr2line', default='addr2line',
                      help='the path of addr2line')
  parser.add_argument('--annotation', default=None,
                      help='the path of annotation file')

  # TODO(cheyuw): Add an option for dumping stack usage of all functions.

  return parser.parse_args()


def ParseSymbolText(symbol_text):
  """Parse the content of the symbol text.

  Args:
    symbol_text: Text of the symbols.

  Returns:
    symbols: Symbol list.
  """
  # Example: "10093064 g     F .text  0000015c .hidden hook_task"
  symbol_regex = re.compile(r'^(?P<address>[0-9A-Fa-f]+)\s+[lwg]\s+'
                            r'((?P<type>[OF])\s+)?\S+\s+'
                            r'(?P<size>[0-9A-Fa-f]+)\s+'
                            r'(\S+\s+)?(?P<name>\S+)$')

  symbols = []
  for line in symbol_text.splitlines():
    line = line.strip()
    result = symbol_regex.match(line)
    if result is not None:
      address = int(result.group('address'), 16)
      symtype = result.group('type')
      if symtype is None:
        symtype = 'O'

      size = int(result.group('size'), 16)
      name = result.group('name')
      symbols.append(Symbol(address, symtype, size, name))

  return symbols


def ParseRoDataText(rodata_text):
  """Parse the content of rodata

  Args:
    symbol_text: Text of the rodata dump.

  Returns:
    symbols: Symbol list.
  """
  # Examples: 8018ab0 00040048 00010000 10020000 4b8e0108  ...H........K...
  #           100a7294 00000000 00000000 01000000           ............

  base_offset = None
  offset = None
  rodata = []
  for line in rodata_text.splitlines():
    line = line.strip()
    space = line.find(' ')
    if space < 0:
        continue
    try:
      address = int(line[0:space], 16)
    except ValueError:
      continue

    if not base_offset:
      base_offset = address
      offset = address
    elif address != offset:
      raise StackAnalyzerError('objdump of rodata not contiguous.')

    for i in range(0, 4):
      num = line[(space + 1 + i*9):(space + 9 + i*9)]
      if len(num.strip()) > 0:
        val = int(num, 16)
      else:
        val = 0
      # TODO(drinkcat): Not all platforms are necessarily big-endian
      rodata.append((val & 0x000000ff) << 24 |
                    (val & 0x0000ff00) << 8 |
                    (val & 0x00ff0000) >> 8 |
                    (val & 0xff000000) >> 24)

    offset = offset + 4*4

  return (base_offset, rodata)


def LoadTasklist(section, export_taskinfo, symbols):
  """Load the task information.

  Args:
    section: Section (RO | RW).
    export_taskinfo: Handle of export_taskinfo.so.
    symbols: Symbol list.

  Returns:
    tasklist: Task list.
  """

  TaskInfoPointer = ctypes.POINTER(TaskInfo)
  taskinfos = TaskInfoPointer()
  if section == SECTION_RO:
    get_taskinfos_func = export_taskinfo.get_ro_taskinfos
  else:
    get_taskinfos_func = export_taskinfo.get_rw_taskinfos

  taskinfo_num = get_taskinfos_func(ctypes.pointer(taskinfos))

  tasklist = []
  for index in range(taskinfo_num):
    taskinfo = taskinfos[index]
    tasklist.append(Task(taskinfo.name, taskinfo.routine, taskinfo.stack_size))

  # Resolve routine address for each task. It's more efficient to resolve all
  # routine addresses of tasks together.
  routine_map = dict((task.routine_name, None) for task in tasklist)

  for symbol in symbols:
    # Resolve task routine address.
    if symbol.name in routine_map:
      # Assume the symbol of routine is unique.
      assert routine_map[symbol.name] is None
      routine_map[symbol.name] = symbol.address

  for task in tasklist:
    address = routine_map[task.routine_name]
    # Assume we have resolved all routine addresses.
    assert address is not None
    task.routine_address = address

  return tasklist


def main():
  """Main function."""
  try:
    options = ParseArgs()

    # Load annotation config.
    if options.annotation is None:
      annotation = {}
    elif not os.path.exists(options.annotation):
      print('Warning: Annotation file {} does not exist.'
            .format(options.annotation))
      annotation = {}
    else:
      try:
        with open(options.annotation, 'r') as annotation_file:
          annotation = yaml.safe_load(annotation_file)

      except yaml.YAMLError:
        raise StackAnalyzerError('Failed to parse annotation file {}.'
                                 .format(options.annotation))
      except IOError:
        raise StackAnalyzerError('Failed to open annotation file {}.'
                                 .format(options.annotation))

      # TODO(cheyuw): Do complete annotation format verification.
      if not isinstance(annotation, dict):
        raise StackAnalyzerError('Invalid annotation file {}.'
                                 .format(options.annotation))

    # Generate and parse the symbols.
    try:
      symbol_text = subprocess.check_output([options.objdump,
                                             '-t',
                                             options.elf_path])
      rodata_text = subprocess.check_output([options.objdump,
                                             '-s',
                                             '-j', '.rodata',
                                             options.elf_path])
    except subprocess.CalledProcessError:
      raise StackAnalyzerError('objdump failed to dump symbol table or rodata.')
    except OSError:
      raise StackAnalyzerError('Failed to run objdump.')

    symbols = ParseSymbolText(symbol_text)
    rodata = ParseRoDataText(rodata_text)

    # Load the tasklist.
    try:
      export_taskinfo = ctypes.CDLL(options.export_taskinfo)
    except OSError:
      raise StackAnalyzerError('Failed to load export_taskinfo.')

    tasklist = LoadTasklist(options.section, export_taskinfo, symbols)

    analyzer = StackAnalyzer(options, symbols, rodata, tasklist, annotation)
    analyzer.Analyze()
  except StackAnalyzerError as e:
    print('Error: {}'.format(e))


if __name__ == '__main__':
  main()
