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 "config"
  25 require "ast"
  26
  27 def to32Bit(value)
  28     if value > 0x7fffffff
  29         value -= 1 << 32
  30     end
  31     value
  32 end
  33
  34 OFFSET_HEADER_MAGIC_NUMBERS = [ to32Bit(0x9e43fd66), to32Bit(0x4379bfba) ]
  35 OFFSET_MAGIC_NUMBERS = [ to32Bit(0xec577ac7), to32Bit(0x0ff5e755) ]
  36
  37 #
  38 # MissingMagicValuesException
  39 #
  40 # Thrown when magic values are missing from the binary.
  41 #
  42
  43 class MissingMagicValuesException < Exception
  44 end
  45
  46 #
  47 # offsetsList(ast)
  48 # sizesList(ast)
  49 #
  50 # Returns a list of offsets and sizes used by the AST.
  51 #
  52
  53 def offsetsList(ast)
  54     ast.filter(StructOffset).uniq.sort
  55 end
  56
  57 def sizesList(ast)
  58     ast.filter(Sizeof).uniq.sort
  59 end
  60
  61 #
  62 # offsetsAndConfigurationIndex(ast, file) ->
  63 #     [[offsets, index], ...]
  64 #
  65 # Parses the offsets from a file and returns a list of offsets and the
  66 # index of the configuration that is valid in this build target.
  67 #
  68
  69 def offsetsAndConfigurationIndex(file)
  70     endiannessMarkerBytes = nil
  71     result = {}
  72
  73     def readInt(endianness, bytes)
  74         if endianness == :little
  75             # Little endian
  76             (bytes[0] << 0 |
  77              bytes[1] << 8 |
  78              bytes[2] << 16 |
  79              bytes[3] << 24)
  80         else
  81             # Big endian
  82             (bytes[0] << 24 |
  83              bytes[1] << 16 |
  84              bytes[2] << 8 |
  85              bytes[3] << 0)
  86         end
  87     end
  88
  89     def prepareMagic(endianness, numbers)
  90         magicBytes = []
  91         numbers.each {
  92             | number |
  93             currentBytes = []
  94             4.times {
  95                 currentBytes << (number & 0xff)
  96                 number >>= 8
  97             }
  98             if endianness == :big
  99                 currentBytes.reverse!
 100             end
 101             magicBytes += currentBytes
 102         }
 103         magicBytes
 104     end
 105
 106     fileBytes = []
 107
 108     File.open(file, "rb") {
 109         | inp |
 110         loop {
 111             byte = inp.getbyte
 112             break unless byte
 113             fileBytes << byte
 114         }
 115     }
 116
 117     def sliceByteArrays(byteArray, pattern)
 118         result = []
 119         lastSlicePoint = 0
 120         (byteArray.length - pattern.length + 1).times {
 121             | index |
 122             foundOne = true
 123             pattern.length.times {
 124                 | subIndex |
 125                 if byteArray[index + subIndex] != pattern[subIndex]
 126                     foundOne = false
 127                     break
 128                 end
 129             }
 130             if foundOne
 131                 result << byteArray[lastSlicePoint...index]
 132                 lastSlicePoint = index + pattern.length
 133             end
 134         }
 135
 136         result << byteArray[lastSlicePoint...(byteArray.length)]
 137
 138         result
 139     end
 140
 141     [:little, :big].each {
 142         | endianness |
 143         headerMagicBytes = prepareMagic(endianness, OFFSET_HEADER_MAGIC_NUMBERS)
 144         magicBytes = prepareMagic(endianness, OFFSET_MAGIC_NUMBERS)
 145
 146         bigArray = sliceByteArrays(fileBytes, headerMagicBytes)
 147         unless bigArray.size <= 1
 148             bigArray[1..-1].each {
 149                 | configArray |
 150                 array = sliceByteArrays(configArray, magicBytes)
 151                 index = readInt(endianness, array[1])
 152                 offsets = []
 153                 array[2..-1].each {
 154                     | data |
 155                     offsets << readInt(endianness, data)
 156                 }
 157                 result[index] = offsets
 158             }
 159         end
 160     }
 161
 162     raise MissingMagicValuesException unless result.length >= 1
 163
 164     # result is {index1=>offsets1, index2=>offsets2} but we want to return
 165     # [[offsets1, index1], [offsets2, index2]].
 166     return result.map {
 167         | pair |
 168         pair.reverse
 169     }
 170 end
 171
 172 #
 173 # buildOffsetsMap(ast, offsetsList) -> [offsets, sizes]
 174 #
 175 # Builds a mapping between StructOffset nodes and their values.
 176 #
 177
 178 def buildOffsetsMap(ast, offsetsList)
 179     offsetsMap = {}
 180     sizesMap = {}
 181     astOffsetsList = offsetsList(ast)
 182     astSizesList = sizesList(ast)
 183     raise unless astOffsetsList.size + astSizesList.size == offsetsList.size
 184     offsetsList(ast).each_with_index {
 185         | structOffset, index |
 186         offsetsMap[structOffset] = offsetsList.shift
 187     }
 188     sizesList(ast).each_with_index {
 189         | sizeof, index |
 190         sizesMap[sizeof] = offsetsList.shift
 191     }
 192     [offsetsMap, sizesMap]
 193 end
 194