offlineasm/offsets.rb

   1 # Copyright (C) 2011 Apple Inc. All rights reserved.
   2 #
   3 # Redistribution and use in source and binary forms, with or without
   4 # modification, are permitted provided that the following conditions
   5 # are met:
   6 # 1. Redistributions of source code must retain the above copyright
   7 #    notice, this list of conditions and the following disclaimer.
   8 # 2. Redistributions in binary form must reproduce the above copyright
   9 #    notice, this list of conditions and the following disclaimer in the
  10 #    documentation and/or other materials provided with the distribution.
  11 #
  12 # THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  13 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  14 # THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  15 # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  16 # BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  17 # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  18 # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  19 # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  20 # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  21 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  22 # THE POSSIBILITY OF SUCH DAMAGE.
  23
  24 require "ast"
  25
  26 OFFSET_HEADER_MAGIC_NUMBERS = [ 0x9e43fd66, 0x4379bfba ]
  27 OFFSET_MAGIC_NUMBERS = [ 0xec577ac7, 0x0ff5e755 ]
  28
  29 #
  30 # MissingMagicValuesException
  31 #
  32 # Thrown when magic values are missing from the binary.
  33 # This is usually an indication that the classic interpreter is enabled.
  34 #
  35
  36 class MissingMagicValuesException < Exception
  37 end
  38
  39 #
  40 # offsetsList(ast)
  41 # sizesList(ast)
  42 #
  43 # Returns a list of offsets and sizes used by the AST.
  44 #
  45
  46 def offsetsList(ast)
  47     ast.filter(StructOffset).uniq.sort
  48 end
  49
  50 def sizesList(ast)
  51     ast.filter(Sizeof).uniq.sort
  52 end
  53
  54 #
  55 # offsetsAndConfigurationIndex(ast, file) ->
  56 #     [[offsets, index], ...]
  57 #
  58 # Parses the offsets from a file and returns a list of offsets and the
  59 # index of the configuration that is valid in this build target.
  60 #
  61
  62 def offsetsAndConfigurationIndex(file)
  63     endiannessMarkerBytes = nil
  64     result = []
  65
  66     def readInt(endianness, bytes)
  67         if endianness == :little
  68             # Little endian
  69             (bytes[0] << 0 |
  70              bytes[1] << 8 |
  71              bytes[2] << 16 |
  72              bytes[3] << 24)
  73         else
  74             # Big endian
  75             (bytes[0] << 24 |
  76              bytes[1] << 16 |
  77              bytes[2] << 8 |
  78              bytes[3] << 0)
  79         end
  80     end
  81
  82     def prepareMagic(endianness, numbers)
  83         magicBytes = []
  84         numbers.each {
  85             | number |
  86             currentBytes = []
  87             4.times {
  88                 currentBytes << (number & 0xff)
  89                 number >>= 8
  90             }
  91             if endianness == :big
  92                 currentBytes.reverse!
  93             end
  94             magicBytes += currentBytes
  95         }
  96         magicBytes
  97     end
  98
  99     fileBytes = []
 100
 101     File.open(file, "r") {
 102         | inp |
 103         loop {
 104             byte = inp.getbyte
 105             break unless byte
 106             fileBytes << byte
 107         }
 108     }
 109
 110     def sliceByteArrays(byteArray, pattern)
 111         result = []
 112         lastSlicePoint = 0
 113         (byteArray.length - pattern.length + 1).times {
 114             | index |
 115             foundOne = true
 116             pattern.length.times {
 117                 | subIndex |
 118                 if byteArray[index + subIndex] != pattern[subIndex]
 119                     foundOne = false
 120                     break
 121                 end
 122             }
 123             if foundOne
 124                 result << byteArray[lastSlicePoint...index]
 125                 lastSlicePoint = index + pattern.length
 126             end
 127         }
 128
 129         result << byteArray[lastSlicePoint...(byteArray.length)]
 130
 131         result
 132     end
 133
 134     [:little, :big].each {
 135         | endianness |
 136         headerMagicBytes = prepareMagic(endianness, OFFSET_HEADER_MAGIC_NUMBERS)
 137         magicBytes = prepareMagic(endianness, OFFSET_MAGIC_NUMBERS)
 138
 139         bigArray = sliceByteArrays(fileBytes, headerMagicBytes)
 140         unless bigArray.size <= 1
 141             bigArray[1..-1].each {
 142                 | configArray |
 143                 array = sliceByteArrays(configArray, magicBytes)
 144                 index = readInt(endianness, array[1])
 145                 offsets = []
 146                 array[2..-1].each {
 147                     | data |
 148                     offsets << readInt(endianness, data)
 149                 }
 150                 result << [offsets, index]
 151             }
 152         end
 153     }
 154
 155     raise MissingMagicValuesException unless result.length >= 1
 156     raise if result.map{|v| v[1]}.uniq.size < result.map{|v| v[1]}.size
 157
 158     result
 159 end
 160
 161 #
 162 # buildOffsetsMap(ast, offsetsList) -> [offsets, sizes]
 163 #
 164 # Builds a mapping between StructOffset nodes and their values.
 165 #
 166
 167 def buildOffsetsMap(ast, offsetsList)
 168     offsetsMap = {}
 169     sizesMap = {}
 170     astOffsetsList = offsetsList(ast)
 171     astSizesList = sizesList(ast)
 172     raise unless astOffsetsList.size + astSizesList.size == offsetsList.size
 173     offsetsList(ast).each_with_index {
 174         | structOffset, index |
 175         offsetsMap[structOffset] = offsetsList.shift
 176     }
 177     sizesList(ast).each_with_index {
 178         | sizeof, index |
 179         sizesMap[sizeof] = offsetsList.shift
 180     }
 181     [offsetsMap, sizesMap]
 182 end
 183