tools/lldbmacros/structanalyze.py

   1 import lldb
   2 from xnu import *
   3
   4 def _showStructPacking(symbol, prefix, begin_offset=0):
   5   """
   6      recursively parse the field members of structure.
   7      params : symbol (lldb.SBType) reference to symbol in binary
   8               prefix (string)      string to be prefixed for each line of output. Useful for recursive struct parsing.
   9      returns: string containing lines of output.
  10   """
  11   ctype = "unknown type"
  12   if symbol.GetTypeClass() == lldb.eTypeClassUnion :
  13     ctype = "union"
  14   if symbol.GetTypeClass() == lldb.eTypeClassStruct :
  15     ctype = "struct"
  16   outstr =  "[%4d] (%s) %s { " % (symbol.GetByteSize(), ctype, symbol.GetName()) + "\n"
  17   numFields = symbol.GetNumberOfFields()
  18   _has_memory_hole = False
  19   _compact_size = 0    # asuming the struct is perfectly packed
  20   _compact_offset = begin_offset
  21   _previous_bit_offset = 0
  22   for i in range(numFields):
  23     member = symbol.GetFieldAtIndex(i)
  24     m_offset = member.GetOffsetInBytes() + begin_offset
  25     m_offset_bits = member.GetOffsetInBits()
  26     m_type = member.GetType()
  27     m_name = member.GetName()
  28     m_size = m_type.GetByteSize()
  29     warningstr = ""
  30     debugstr = "" # + str((m_size, m_offset , m_offset_bits, _previous_bit_offset, _compact_offset, begin_offset))
  31     if _compact_offset != m_offset and (m_offset_bits -  _previous_bit_offset) > m_size*8 :
  32       _has_memory_hole = True
  33       warningstr = "   *** Possible memory hole ***"
  34       _compact_offset = m_offset
  35     _compact_offset += m_size
  36     if m_type.GetTypeClass() == lldb.eTypeClassStruct or m_type.GetTypeClass() == lldb.eTypeClassUnion :
  37       outstr += prefix + ("*%4d," % m_offset) + _showStructPacking(m_type, prefix+"    ", m_offset) + warningstr + debugstr + "\n"
  38     else:
  39       outstr += prefix + ("+%4d,[%4d] (%s) %s" % (m_offset, m_size, m_type.GetName(), m_name)) + warningstr + debugstr + "\n"
  40     if i > 0 :
  41       _previous_bit_offset = m_offset_bits
  42   outstr += prefix + "}"
  43   if _has_memory_hole == True :
  44     outstr += "   *** Warning: Struct layout leaves memory hole *** "
  45   return outstr
  46
  47 @lldb_command('showstructpacking')
  48 def showStructInfo(cmd_args=None):
  49   """Show how a structure is packed in the binary. The format is
  50      +<offset>, [<size_of_member>] (<type>) <name>
  51      For example:
  52       (lldb) script lldbmacros.showStructInfo("pollfd")
  53       [  8] (struct) pollfd {
  54       +  0,[  4] (int) fd
  55       +  4,[  2] (short) events
  56       +  6,[  2] (short) revents
  57       }
  58     syntax: showstructpacking task
  59   """
  60   if not cmd_args:
  61     raise ArgumentError("Please provide a type name.")
  62
  63   sym = gettype(cmd_args[0])
  64   if sym == None:
  65     print "No such struct found"
  66   if sym.GetTypeClass() == lldb.eTypeClassTypedef:
  67       sym = sym.GetCanonicalType()
  68   if sym.GetTypeClass() != lldb.eTypeClassStruct:
  69     print "%s is not a structure" % cmd_args[0]
  70   else:
  71     print _showStructPacking(sym,"", 0)
  72
  73 # EndMacro: showstructinto