grokdump: Simple windows minidump analysis on linux.

tools/grokdump.py

Index: tools/grokdump.py
diff --git a/tools/grokdump.py b/tools/grokdump.py
new file mode 100755
index 0000000000000000000000000000000000000000..de681b2b4de3d999c0a225119a020bb4d3b30b12
--- /dev/null
+++ b/tools/grokdump.py
@@ -0,0 +1,840 @@
+#!/usr/bin/env python
+#
+# Copyright 2011 the V8 project authors. All rights reserved.
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+#     * Neither the name of Google Inc. nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+import ctypes
+import mmap
+import optparse
+import os
+import disasm
+import sys
+import types
+import codecs
+import re
+
+
+USAGE="""usage: %prog [OPTION]...
+
+Minidump analyzer.
+
+Shows the processor state at the point of exception including the
+stack of the active thread and the referenced objects in the V8
+heap. Code objects are disassembled and the addresses linked from the
+stack (pushed return addresses) are marked with "=>".
+
+
+Examples:
+  $ %prog 12345678-1234-1234-1234-123456789abcd-full.dmp
+"""
+
+DEBUG=False
+
+
+def DebugPrint(s):
+  if not DEBUG: return
+  print s
+
+
+class Descriptor(object):
+  """Descriptor of a structure in a memory."""
+
+  def __init__(self, fields):
+    self.fields = fields
+    self.is_flexible = False
+    for _, type_or_func in fields:
+      if isinstance(type_or_func, types.FunctionType):
+        self.is_flexible = True
+        break
+    if not self.is_flexible:
+      self.ctype = Descriptor._GetCtype(fields)
+      self.size = ctypes.sizeof(self.ctype)
+
+  def Read(self, memory, offset):
+    if self.is_flexible:
+      fields_copy = self.fields[:]
+      last = 0
+      for name, type_or_func in fields_copy:
+        if isinstance(type_or_func, types.FunctionType):
+          partial_ctype = Descriptor._GetCtype(fields_copy[:last])
+          partial_object = partial_ctype.from_buffer(memory, offset)
+          type = type_or_func(partial_object)
+          if type is not None:
+            fields_copy[last] = (name, type)
+            last += 1
+        else:
+          last += 1
+      complete_ctype = Descriptor._GetCtype(fields_copy[:last])
+    else:
+      complete_ctype = self.ctype
+    return complete_ctype.from_buffer(memory, offset)
+
+  @staticmethod
+  def _GetCtype(fields):
+    class Raw(ctypes.Structure):
+      _fields_ = fields
+      _pack_ = 1
+
+      def __str__(self):
+        return "{" + ", ".join("%s: %s" % (field, self.__getattribute__(field))
+                               for field, _ in Raw._fields_) + "}"
+    return Raw
+
+
+# Set of structures and constants that describe the layout of minidump
+# files. Based on MSDN and Google Breakpad.
+
+MINIDUMP_HEADER = Descriptor([
+  ("signature", ctypes.c_uint32),
+  ("version", ctypes.c_uint32),
+  ("stream_count", ctypes.c_uint32),
+  ("stream_directories_rva", ctypes.c_uint32),
+  ("checksum", ctypes.c_uint32),
+  ("time_date_stampt", ctypes.c_uint32),
+  ("flags", ctypes.c_uint64)
+])
+
+MINIDUMP_LOCATION_DESCRIPTOR = Descriptor([
+  ("data_size", ctypes.c_uint32),
+  ("rva", ctypes.c_uint32)
+])
+
+MINIDUMP_DIRECTORY = Descriptor([
+  ("stream_type", ctypes.c_uint32),
+  ("location", MINIDUMP_LOCATION_DESCRIPTOR.ctype)
+])
+
+MD_EXCEPTION_MAXIMUM_PARAMETERS = 15
+
+MINIDUMP_EXCEPTION = Descriptor([
+  ("code", ctypes.c_uint32),
+  ("flags", ctypes.c_uint32),
+  ("record", ctypes.c_uint64),
+  ("address", ctypes.c_uint64),
+  ("parameter_count", ctypes.c_uint32),
+  ("unused_alignment", ctypes.c_uint32),
+  ("information", ctypes.c_uint64 * MD_EXCEPTION_MAXIMUM_PARAMETERS)
+])
+
+MINIDUMP_EXCEPTION_STREAM = Descriptor([
+  ("thread_id", ctypes.c_uint32),
+  ("unused_alignment", ctypes.c_uint32),
+  ("exception", MINIDUMP_EXCEPTION.ctype),
+  ("thread_context", MINIDUMP_LOCATION_DESCRIPTOR.ctype)
+])
+
+# Stream types.
+MD_UNUSED_STREAM = 0
+MD_RESERVED_STREAM_0 = 1
+MD_RESERVED_STREAM_1 = 2
+MD_THREAD_LIST_STREAM = 3
+MD_MODULE_LIST_STREAM = 4
+MD_MEMORY_LIST_STREAM = 5
+MD_EXCEPTION_STREAM = 6
+MD_SYSTEM_INFO_STREAM = 7
+MD_THREAD_EX_LIST_STREAM = 8
+MD_MEMORY_64_LIST_STREAM = 9
+MD_COMMENT_STREAM_A = 10
+MD_COMMENT_STREAM_W = 11
+MD_HANDLE_DATA_STREAM = 12
+MD_FUNCTION_TABLE_STREAM = 13
+MD_UNLOADED_MODULE_LIST_STREAM = 14
+MD_MISC_INFO_STREAM = 15
+MD_MEMORY_INFO_LIST_STREAM = 16
+MD_THREAD_INFO_LIST_STREAM = 17
+MD_HANDLE_OPERATION_LIST_STREAM = 18
+
+MD_FLOATINGSAVEAREA_X86_REGISTERAREA_SIZE = 80
+
+MINIDUMP_FLOATING_SAVE_AREA_X86 = Descriptor([
+  ("control_word", ctypes.c_uint32),
+  ("status_word", ctypes.c_uint32),
+  ("tag_word", ctypes.c_uint32),
+  ("error_offset", ctypes.c_uint32),
+  ("error_selector", ctypes.c_uint32),
+  ("data_offset", ctypes.c_uint32),
+  ("data_selector", ctypes.c_uint32),
+  ("register_area", ctypes.c_uint8 * MD_FLOATINGSAVEAREA_X86_REGISTERAREA_SIZE),
+  ("cr0_npx_state", ctypes.c_uint32)
+])
+
+MD_CONTEXT_X86_EXTENDED_REGISTERS_SIZE = 512
+
+# Context flags.
+MD_CONTEXT_X86 = 0x00010000
+MD_CONTEXT_X86_CONTROL = (MD_CONTEXT_X86 | 0x00000001)
+MD_CONTEXT_X86_INTEGER = (MD_CONTEXT_X86 | 0x00000002)
+MD_CONTEXT_X86_SEGMENTS = (MD_CONTEXT_X86 | 0x00000004)
+MD_CONTEXT_X86_FLOATING_POINT = (MD_CONTEXT_X86 | 0x00000008)
+MD_CONTEXT_X86_DEBUG_REGISTERS = (MD_CONTEXT_X86 | 0x00000010)
+MD_CONTEXT_X86_EXTENDED_REGISTERS = (MD_CONTEXT_X86 | 0x00000020)
+
+def EnableOnFlag(type, flag):
+  return lambda o: [None, type][int((o.context_flags & flag) != 0)]
+
+MINIDUMP_CONTEXT_X86 = Descriptor([
+  ("context_flags", ctypes.c_uint32),
+  # MD_CONTEXT_X86_DEBUG_REGISTERS.
+  ("dr0", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_DEBUG_REGISTERS)),
+  ("dr1", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_DEBUG_REGISTERS)),
+  ("dr2", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_DEBUG_REGISTERS)),
+  ("dr3", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_DEBUG_REGISTERS)),
+  ("dr6", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_DEBUG_REGISTERS)),
+  ("dr7", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_DEBUG_REGISTERS)),
+  # MD_CONTEXT_X86_FLOATING_POINT.
+  ("float_save", EnableOnFlag(MINIDUMP_FLOATING_SAVE_AREA_X86.ctype,
+                              MD_CONTEXT_X86_FLOATING_POINT)),
+  # MD_CONTEXT_X86_SEGMENTS.
+  ("gs", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_SEGMENTS)),
+  ("fs", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_SEGMENTS)),
+  ("es", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_SEGMENTS)),
+  ("ds", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_SEGMENTS)),
+  # MD_CONTEXT_X86_INTEGER.
+  ("edi", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_INTEGER)),
+  ("esi", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_INTEGER)),
+  ("ebx", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_INTEGER)),
+  ("edx", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_INTEGER)),
+  ("ecx", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_INTEGER)),
+  ("eax", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_INTEGER)),
+  # MD_CONTEXT_X86_CONTROL.
+  ("ebp", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_CONTROL)),
+  ("eip", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_CONTROL)),
+  ("cs", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_CONTROL)),
+  ("eflags", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_CONTROL)),
+  ("esp", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_CONTROL)),
+  ("ss", EnableOnFlag(ctypes.c_uint32, MD_CONTEXT_X86_CONTROL)),
+  # MD_CONTEXT_X86_EXTENDED_REGISTERS.
+  ("extended_registers",
+   EnableOnFlag(ctypes.c_uint8 * MD_CONTEXT_X86_EXTENDED_REGISTERS_SIZE,
+                MD_CONTEXT_X86_EXTENDED_REGISTERS))
+])
+
+MINIDUMP_MEMORY_DESCRIPTOR = Descriptor([
+  ("start", ctypes.c_uint64),
+  ("memory", MINIDUMP_LOCATION_DESCRIPTOR.ctype)
+])
+
+MINIDUMP_MEMORY_DESCRIPTOR64 = Descriptor([
+  ("start", ctypes.c_uint64),
+  ("size", ctypes.c_uint64)
+])
+
+MINIDUMP_MEMORY_LIST = Descriptor([
+  ("range_count", ctypes.c_uint32),
+  ("ranges", lambda m: MINIDUMP_MEMORY_DESCRIPTOR.ctype * m.range_count)
+])
+
+MINIDUMP_MEMORY_LIST64 = Descriptor([
+  ("range_count", ctypes.c_uint64),
+  ("base_rva", ctypes.c_uint64),
+  ("ranges", lambda m: MINIDUMP_MEMORY_DESCRIPTOR64.ctype * m.range_count)
+])
+
+MINIDUMP_THREAD = Descriptor([
+  ("id", ctypes.c_uint32),
+  ("suspend_count", ctypes.c_uint32),
+  ("priority_class", ctypes.c_uint32),
+  ("priority", ctypes.c_uint32),
+  ("ted", ctypes.c_uint64),
+  ("stack", MINIDUMP_MEMORY_DESCRIPTOR.ctype),
+  ("context", MINIDUMP_LOCATION_DESCRIPTOR.ctype)
+])
+
+MINIDUMP_THREAD_LIST = Descriptor([
+  ("thread_count", ctypes.c_uint32),
+  ("threads", lambda t: MINIDUMP_THREAD.ctype * t.thread_count)
+])
+
+
+class MinidumpReader(object):
+  """Minidump (.dmp) reader."""
+
+  _HEADER_MAGIC = 0x504d444d
+
+  def __init__(self, options, minidump_name):
+    self.minidump_name = minidump_name
+    self.minidump_file = open(minidump_name, "r")
+    self.minidump = mmap.mmap(self.minidump_file.fileno(), 0, mmap.MAP_PRIVATE)
+    self.header = MINIDUMP_HEADER.Read(self.minidump, 0)
+    if self.header.signature != MinidumpReader._HEADER_MAGIC:
+      print >>sys.stderr, "Warning: unsupported minidump header magic"
+    DebugPrint(self.header)
+    directories = []
+    offset = self.header.stream_directories_rva
+    for _ in xrange(self.header.stream_count):
+      directories.append(MINIDUMP_DIRECTORY.Read(self.minidump, offset))
+      offset += MINIDUMP_DIRECTORY.size
+    self.exception = None
+    self.exception_context = None
+    self.memory_list = None
+    self.thread_map = {}
+    for d in directories:
+      DebugPrint(d)
+      # TODO(vitalyr): extract system info including CPU features.
+      if d.stream_type == MD_EXCEPTION_STREAM:
+        self.exception = MINIDUMP_EXCEPTION_STREAM.Read(
+          self.minidump, d.location.rva)
+        DebugPrint(self.exception)
+        self.exception_context = MINIDUMP_CONTEXT_X86.Read(
+          self.minidump, self.exception.thread_context.rva)
+        DebugPrint(self.exception_context)
+      elif d.stream_type == MD_THREAD_LIST_STREAM:
+        thread_list = MINIDUMP_THREAD_LIST.Read(self.minidump, d.location.rva)
+        assert ctypes.sizeof(thread_list) == d.location.data_size
+        DebugPrint(thread_list)
+        for thread in thread_list.threads:
+          DebugPrint(thread)
+          self.thread_map[thread.id] = thread
+      elif d.stream_type == MD_MEMORY_LIST_STREAM:
+        print >>sys.stderr, "Warning: not a full minidump"
+        ml = MINIDUMP_MEMORY_LIST.Read(self.minidump, d.location.rva)
+        DebugPrint(ml)
+        for m in ml.ranges:
+          DebugPrint(m)
+      elif d.stream_type == MD_MEMORY_64_LIST_STREAM:
+        assert self.memory_list is None
+        self.memory_list = MINIDUMP_MEMORY_LIST64.Read(
+          self.minidump, d.location.rva)
+        assert ctypes.sizeof(self.memory_list) == d.location.data_size
+        DebugPrint(self.memory_list)
+
+  def IsValidAddress(self, address):
+    return self.FindLocation(address) is not None
+
+  def ReadU8(self, address):
+    location = self.FindLocation(address)
+    return ctypes.c_uint8.from_buffer(self.minidump, location).value
+
+  def ReadU32(self, address):
+    location = self.FindLocation(address)
+    return ctypes.c_uint32.from_buffer(self.minidump, location).value
+
+  def ReadBytes(self, address, size):
+    location = self.FindLocation(address)
+    return self.minidump[location:location + size]
+
+  def FindLocation(self, address):
+    # TODO(vitalyr): only works for full minidumps (...64 structure variants).
+    offset = 0
+    for r in self.memory_list.ranges:
+      if r.start <= address < r.start + r.size:
+        return self.memory_list.base_rva + offset + address - r.start
+      offset += r.size
+    return None
+
+  def GetDisasmLines(self, address, size):
+    location = self.FindLocation(address)
+    if location is None: return []
+    return disasm.GetDisasmLines(self.minidump_name,
+                                 location,
+                                 size,
+                                 "ia32",
+                                 False)
+
+
+  def Dispose(self):
+    self.minidump.close()
+    self.minidump_file.close()
+
+
+# List of V8 instance types. Obtained by adding the code below to any .cc file.
+#
+# #define DUMP_TYPE(T) printf("%d: \"%s\",\n", T, #T);
+# struct P {
+#   P() {
+#     printf("{\n");
+#     INSTANCE_TYPE_LIST(DUMP_TYPE)
+#     printf("}\n");
+#   }
+# };
+# static P p;
+INSTANCE_TYPES = {
+  64: "SYMBOL_TYPE",
+  68: "ASCII_SYMBOL_TYPE",
+  65: "CONS_SYMBOL_TYPE",
+  69: "CONS_ASCII_SYMBOL_TYPE",
+  66: "EXTERNAL_SYMBOL_TYPE",
+  74: "EXTERNAL_SYMBOL_WITH_ASCII_DATA_TYPE",
+  70: "EXTERNAL_ASCII_SYMBOL_TYPE",
+  0: "STRING_TYPE",
+  4: "ASCII_STRING_TYPE",
+  1: "CONS_STRING_TYPE",
+  5: "CONS_ASCII_STRING_TYPE",
+  2: "EXTERNAL_STRING_TYPE",
+  10: "EXTERNAL_STRING_WITH_ASCII_DATA_TYPE",
+  6: "EXTERNAL_ASCII_STRING_TYPE",
+  6: "PRIVATE_EXTERNAL_ASCII_STRING_TYPE",
+  128: "MAP_TYPE",
+  129: "CODE_TYPE",
+  130: "ODDBALL_TYPE",
+  131: "JS_GLOBAL_PROPERTY_CELL_TYPE",
+  132: "HEAP_NUMBER_TYPE",
+  133: "PROXY_TYPE",
+  134: "BYTE_ARRAY_TYPE",
+  135: "PIXEL_ARRAY_TYPE",
+  136: "EXTERNAL_BYTE_ARRAY_TYPE",
+  137: "EXTERNAL_UNSIGNED_BYTE_ARRAY_TYPE",
+  138: "EXTERNAL_SHORT_ARRAY_TYPE",
+  139: "EXTERNAL_UNSIGNED_SHORT_ARRAY_TYPE",
+  140: "EXTERNAL_INT_ARRAY_TYPE",
+  141: "EXTERNAL_UNSIGNED_INT_ARRAY_TYPE",
+  142: "EXTERNAL_FLOAT_ARRAY_TYPE",
+  143: "FILLER_TYPE",
+  144: "ACCESSOR_INFO_TYPE",
+  145: "ACCESS_CHECK_INFO_TYPE",
+  146: "INTERCEPTOR_INFO_TYPE",
+  147: "CALL_HANDLER_INFO_TYPE",
+  148: "FUNCTION_TEMPLATE_INFO_TYPE",
+  149: "OBJECT_TEMPLATE_INFO_TYPE",
+  150: "SIGNATURE_INFO_TYPE",
+  151: "TYPE_SWITCH_INFO_TYPE",
+  152: "SCRIPT_TYPE",
+  153: "CODE_CACHE_TYPE",
+  156: "FIXED_ARRAY_TYPE",
+  157: "SHARED_FUNCTION_INFO_TYPE",
+  158: "JS_MESSAGE_OBJECT_TYPE",
+  159: "JS_VALUE_TYPE",
+  160: "JS_OBJECT_TYPE",
+  161: "JS_CONTEXT_EXTENSION_OBJECT_TYPE",
+  162: "JS_GLOBAL_OBJECT_TYPE",
+  163: "JS_BUILTINS_OBJECT_TYPE",
+  164: "JS_GLOBAL_PROXY_TYPE",
+  165: "JS_ARRAY_TYPE",
+  166: "JS_REGEXP_TYPE",
+  167: "JS_FUNCTION_TYPE",
+  154: "DEBUG_INFO_TYPE",
+  155: "BREAK_POINT_INFO_TYPE",
+}
+
+
+class Printer(object):
+  """Printer with indentation support."""
+
+  def __init__(self):
+    self.indent = 0
+
+  def Indent(self):
+    self.indent += 2
+
+  def Dedent(self):
+    self.indent -= 2
+
+  def Print(self, string):
+    print "%s%s" % (self._IndentString(), string)
+
+  def PrintLines(self, lines):
+    indent = self._IndentString()
+    print "\n".join("%s%s" % (indent, line) for line in lines)
+
+  def _IndentString(self):
+    return self.indent * " "
+
+
+ADDRESS_RE = re.compile(r"0x[0-9a-fA-F]+")
+
+
+def FormatDisasmLine(start, heap, line):
+  line_address = start + line[0]
+  stack_slot = heap.stack_map.get(line_address)
+  marker = "  "
+  if stack_slot:
+    marker = "=>"
+  code = AnnotateAddresses(heap, line[1])
+  return "%s%08x %08x: %s" % (marker, line_address, line[0], code)
+
+
+def AnnotateAddresses(heap, line):
+  extra = []
+  for m in ADDRESS_RE.finditer(line):
+    maybe_address = int(m.group(0), 16)
+    object = heap.FindObject(maybe_address)
+    if not object: continue
+    extra.append(str(object))
+  if len(extra) == 0: return line
+  return "%s  ;; %s" % (line, ", ".join(extra))
+
+
+class HeapObject(object):
+  def __init__(self, heap, map, address):
+    self.heap = heap
+    self.map = map
+    self.address = address
+
+  def Is(self, cls):
+    return isinstance(self, cls)
+
+  def Print(self, p):
+    p.Print(str(self))
+
+  def __str__(self):
+    return "HeapObject(%08x, %s)" % (self.address,
+                                     INSTANCE_TYPES[self.map.instance_type])
+
+  def ObjectField(self, offset):
+    field_value = self.heap.reader.ReadU32(self.address + offset)
+    return self.heap.FindObjectOrSmi(field_value)
+
+  def SmiField(self, offset):
+    field_value = self.heap.reader.ReadU32(self.address + offset)
+    assert (field_value & 1) == 0
+    return field_value / 2
+
+
+class Map(HeapObject):
+  INSTANCE_TYPE_OFFSET = 8
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.instance_type = \
+        heap.reader.ReadU8(self.address + Map.INSTANCE_TYPE_OFFSET)
+
+
+class String(HeapObject):
+  LENGTH_OFFSET = 4
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.length = self.SmiField(String.LENGTH_OFFSET)
+
+  def GetChars(self):
+    return "?string?"
+
+  def Print(self, p):
+    p.Print(str(self))
+
+  def __str__(self):
+    return "\"%s\"" % self.GetChars()
+
+
+class SeqString(String):
+  CHARS_OFFSET = 12
+
+  def __init__(self, heap, map, address):
+    String.__init__(self, heap, map, address)
+    self.chars = heap.reader.ReadBytes(self.address + SeqString.CHARS_OFFSET,
+                                       self.length)
+
+  def GetChars(self):
+    return self.chars
+
+
+class ExternalString(String):
+  RESOURCE_OFFSET = 12
+
+  WEBKIT_RESOUCE_STRING_IMPL_OFFSET = 4
+  WEBKIT_STRING_IMPL_CHARS_OFFSET = 8
+
+  def __init__(self, heap, map, address):
+    String.__init__(self, heap, map, address)
+    reader = heap.reader
+    self.resource = \
+        reader.ReadU32(self.address + ExternalString.RESOURCE_OFFSET)
+    self.chars = "?external string?"
+    if not reader.IsValidAddress(self.resource): return
+    string_impl_address = self.resource + \
+        ExternalString.WEBKIT_RESOUCE_STRING_IMPL_OFFSET
+    if not reader.IsValidAddress(string_impl_address): return
+    string_impl = reader.ReadU32(string_impl_address)
+    chars_ptr_address = string_impl + \
+        ExternalString.WEBKIT_STRING_IMPL_CHARS_OFFSET
+    if not reader.IsValidAddress(chars_ptr_address): return
+    chars_ptr = reader.ReadU32(chars_ptr_address)
+    if not reader.IsValidAddress(chars_ptr): return
+    raw_chars = reader.ReadBytes(chars_ptr, 2 * self.length)
+    self.chars = codecs.getdecoder("utf16")(raw_chars)[0]
+
+  def GetChars(self):
+    return self.chars
+
+
+class ConsString(String):
+  LEFT_OFFSET = 12
+  RIGHT_OFFSET = 16
+
+  def __init__(self, heap, map, address):
+    String.__init__(self, heap, map, address)
+    self.left = self.ObjectField(ConsString.LEFT_OFFSET)
+    self.right = self.ObjectField(ConsString.RIGHT_OFFSET)
+
+  def GetChars(self):
+    return self.left.GetChars() + self.right.GetChars()
+
+
+class Oddball(HeapObject):
+  TO_STRING_OFFSET = 4
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.to_string = self.ObjectField(Oddball.TO_STRING_OFFSET)
+
+  def Print(self, p):
+    p.Print(str(self))
+
+  def __str__(self):
+    return "<%s>" % self.to_string.GetChars()
+
+
+class FixedArray(HeapObject):
+  LENGTH_OFFSET = 4
+  ELEMENTS_OFFSET = 8
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.length = self.SmiField(FixedArray.LENGTH_OFFSET)
+
+  def Print(self, p):
+    p.Print("FixedArray(%08x) {" % self.address)
+    p.Indent()
+    p.Print("length: %d" % self.length)
+    for i in xrange(self.length):
+      offset = FixedArray.ELEMENTS_OFFSET + 4 * i
+      p.Print("[%08d] = %s" % (i, self.ObjectField(offset)))
+    p.Dedent()
+    p.Print("}")
+
+  def __str__(self):
+    return "FixedArray(%08x, length=%d)" % (self.address, self.length)
+
+
+class JSFunction(HeapObject):
+  CODE_ENTRY_OFFSET = 12
+  SHARED_OFFSET = 20
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    code_entry = \
+        heap.reader.ReadU32(self.address + JSFunction.CODE_ENTRY_OFFSET)
+    self.code = heap.FindObject(code_entry - Code.ENTRY_OFFSET + 1)
+    self.shared = self.ObjectField(JSFunction.SHARED_OFFSET)
+
+  def Print(self, p):
+    source = "\n".join("  %s" % line for line in self._GetSource().split("\n"))
+    p.Print("JSFunction(%08x) {" % self.address)
+    p.Indent()
+    p.Print("inferred name: %s" % self.shared.inferred_name)
+    if self.shared.script.Is(Script) and self.shared.script.name.Is(String):
+      p.Print("script name: %s" % self.shared.script.name)
+    p.Print("source:")
+    p.PrintLines(self._GetSource().split("\n"))
+    p.Print("code:")
+    self.code.Print(p)
+    if self.code != self.shared.code:
+      p.Print("unoptimized code:")
+      self.shared.code.Print(p)
+    p.Dedent()
+    p.Print("}")
+
+  def __str__(self):
+    inferred_name = ""
+    if self.shared.Is(SharedFunctionInfo):
+      inferred_name = self.shared.inferred_name
+    return "JSFunction(%08x, %s)" % (self.address, inferred_name)
+
+  def _GetSource(self):
+    source = "?source?"
+    start = self.shared.start_position
+    end = self.shared.end_position
+    if not self.shared.script.Is(Script): return source
+    script_source = self.shared.script.source
+    if not script_source.Is(String): return source
+    return script_source.GetChars()[start:end]
+
+
+class SharedFunctionInfo(HeapObject):
+  CODE_OFFSET = 2 * 4
+  SCRIPT_OFFSET = 7 * 4
+  INFERRED_NAME_OFFSET = 9 * 4
+  START_POSITION_AND_TYPE_OFFSET = 17 * 4
+  END_POSITION_OFFSET = 18 * 4
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.code = self.ObjectField(SharedFunctionInfo.CODE_OFFSET)
+    self.script = self.ObjectField(SharedFunctionInfo.SCRIPT_OFFSET)
+    self.inferred_name = \
+        self.ObjectField(SharedFunctionInfo.INFERRED_NAME_OFFSET)
+    start_position_and_type = \
+        self.SmiField(SharedFunctionInfo.START_POSITION_AND_TYPE_OFFSET)
+    self.start_position = start_position_and_type >> 2
+    self.end_position = self.SmiField(SharedFunctionInfo.END_POSITION_OFFSET)
+
+
+class Script(HeapObject):
+  SOURCE_OFFSET = 4
+  NAME_OFFSET = 8
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.source = self.ObjectField(Script.SOURCE_OFFSET)
+    self.name = self.ObjectField(Script.NAME_OFFSET)
+
+
+class Code(HeapObject):
+  INSTRUCTION_SIZE_OFFSET = 4
+  ENTRY_OFFSET = 32
+
+  def __init__(self, heap, map, address):
+    HeapObject.__init__(self, heap, map, address)
+    self.entry = self.address + Code.ENTRY_OFFSET
+    self.instruction_size = \
+        heap.reader.ReadU32(self.address + Code.INSTRUCTION_SIZE_OFFSET)
+
+  def Print(self, p):
+    lines = self.heap.reader.GetDisasmLines(self.entry, self.instruction_size)
+    p.Print("Code(%08x) {" % self.address)
+    p.Indent()
+    p.Print("instruction_size: %d" % self.instruction_size)
+    p.PrintLines(self._FormatLine(line) for line in lines)
+    p.Dedent()
+    p.Print("}")
+
+  def _FormatLine(self, line):
+    return FormatDisasmLine(self.entry, self.heap, line)
+
+
+class V8Heap(object):
+  CLASS_MAP = {
+    "SYMBOL_TYPE": SeqString,
+    "ASCII_SYMBOL_TYPE": SeqString,
+    "CONS_SYMBOL_TYPE": ConsString,
+    "CONS_ASCII_SYMBOL_TYPE": ConsString,
+    "EXTERNAL_SYMBOL_TYPE": ExternalString,
+    "EXTERNAL_SYMBOL_WITH_ASCII_DATA_TYPE": ExternalString,
+    "EXTERNAL_ASCII_SYMBOL_TYPE": ExternalString,
+    "STRING_TYPE": SeqString,
+    "ASCII_STRING_TYPE": SeqString,
+    "CONS_STRING_TYPE": ConsString,
+    "CONS_ASCII_STRING_TYPE": ConsString,
+    "EXTERNAL_STRING_TYPE": ExternalString,
+    "EXTERNAL_STRING_WITH_ASCII_DATA_TYPE": ExternalString,
+    "EXTERNAL_ASCII_STRING_TYPE": ExternalString,
+
+    "MAP_TYPE": Map,
+    "ODDBALL_TYPE": Oddball,
+    "FIXED_ARRAY_TYPE": FixedArray,
+    "JS_FUNCTION_TYPE": JSFunction,
+    "SHARED_FUNCTION_INFO_TYPE": SharedFunctionInfo,
+    "SCRIPT_TYPE": Script,
+    "CODE_TYPE": Code
+  }
+
+  def __init__(self, reader, stack_map):
+    self.reader = reader
+    self.stack_map = stack_map
+    self.objects = {}
+
+  def FindObjectOrSmi(self, tagged_address):
+    if (tagged_address & 1) == 0: return tagged_address / 2
+    return self.FindObject(tagged_address)
+
+  def FindObject(self, tagged_address):
+    if tagged_address in self.objects:
+      return self.objects[tagged_address]
+    if (tagged_address & 1) != 1: return None
+    address = tagged_address - 1
+    if not self.reader.IsValidAddress(address): return None
+    map_tagged_address = self.reader.ReadU32(address)
+    if tagged_address == map_tagged_address:
+      # Meta map?
+      meta_map = Map(self, None, address)
+      instance_type_name = INSTANCE_TYPES.get(meta_map.instance_type)
+      if instance_type_name != "MAP_TYPE": return None
+      meta_map.map = meta_map
+      object = meta_map
+    else:
+      map = self.FindObject(map_tagged_address)
+      if map is None: return None
+      instance_type_name = INSTANCE_TYPES.get(map.instance_type)
+      if instance_type_name is None: return None
+      cls = V8Heap.CLASS_MAP.get(instance_type_name, HeapObject)
+      object = cls(self, map, address)
+    self.objects[tagged_address] = object
+    return object
+
+
+EIP_PROXIMITY = 64
+
+
+def AnalyzeMinidump(options, minidump_name):
+  reader = MinidumpReader(options, minidump_name)
+  DebugPrint("========================================")
+  if reader.exception is None:
+    print "Minidump has no exception info"
+    return
+  print "Exception info:"
+  exception_thread = reader.thread_map[reader.exception.thread_id]
+  print "  thread id: %d" % exception_thread.id
+  print "  code: %08X" % reader.exception.exception.code
+  print "  context:"
+  print "    eax: %08x" % reader.exception_context.eax
+  print "    ebx: %08x" % reader.exception_context.ebx
+  print "    ecx: %08x" % reader.exception_context.ecx
+  print "    edx: %08x" % reader.exception_context.edx
+  print "    edi: %08x" % reader.exception_context.edi
+  print "    esi: %08x" % reader.exception_context.esi
+  print "    ebp: %08x" % reader.exception_context.ebp
+  print "    esp: %08x" % reader.exception_context.esp
+  print "    eip: %08x" % reader.exception_context.eip
+  # TODO(vitalyr): decode eflags.
+  print "    eflags: %s" % bin(reader.exception_context.eflags)[2:]
+  print
+
+  stack_bottom = exception_thread.stack.start + \
+      exception_thread.stack.memory.data_size
+  stack_map = {reader.exception_context.eip: -1}
+  for slot in xrange(reader.exception_context.esp, stack_bottom, 4):
+    maybe_address = reader.ReadU32(slot)
+    if not maybe_address in stack_map:
+      stack_map[maybe_address] = slot
+  heap = V8Heap(reader, stack_map)
+
+  print "Disassembly around exception.eip:"
+  start = reader.exception_context.eip - EIP_PROXIMITY
+  lines = reader.GetDisasmLines(start, 2 * EIP_PROXIMITY)
+  for line in lines:
+    print FormatDisasmLine(start, heap, line)
+  print
+
+  print "Annotated stack (from exception.esp to bottom):"
+  for slot in xrange(reader.exception_context.esp, stack_bottom, 4):
+    maybe_address = reader.ReadU32(slot)
+    heap_object = heap.FindObject(maybe_address)
+    print "%08x: %08x" % (slot, maybe_address)
+    if heap_object:
+      heap_object.Print(Printer())
+      print
+
+  reader.Dispose()
+
+
+if __name__ == "__main__":
+  parser = optparse.OptionParser(USAGE)
+  options, args = parser.parse_args()
+  if len(args) != 1:
+    parser.print_help()
+    sys.exit(1)
+  AnalyzeMinidump(options, args[0])