third_party/android_platform/bionic/tools/relocation_packer/src/packer.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "packer.h"
   6
   7 #include <vector>
   8
   9 #include "debug.h"
  10 #include "delta_encoder.h"
  11 #include "elf_traits.h"
  12 #include "sleb128.h"
  13
  14 namespace relocation_packer {
  15
  16 // Pack relocations into a group encoded packed representation.
  17 template <typename ELF>
  18 void RelocationPacker<ELF>::PackRelocations(const std::vector<typename ELF::Rela>& relocations,
  19                                             std::vector<uint8_t>* packed) {
  20   // Run-length encode.
  21   std::vector<typename ELF::Addr> packed_words;
  22   RelocationDeltaCodec<ELF> codec;
  23   codec.Encode(relocations, &packed_words);
  24
  25   // If insufficient data do nothing.
  26   if (packed_words.empty())
  27     return;
  28
  29   Sleb128Encoder<typename ELF::Addr> sleb128_encoder;
  30
  31   std::vector<uint8_t> sleb128_packed;
  32
  33   sleb128_encoder.EnqueueAll(packed_words);
  34   sleb128_encoder.GetEncoding(&sleb128_packed);
  35
  36   packed->push_back('A');
  37   packed->push_back('P');
  38   packed->push_back('S');
  39   packed->push_back('2');
  40   packed->insert(packed->end(), sleb128_packed.begin(), sleb128_packed.end());
  41 }
  42
  43 // Unpack relative relocations from a run-length encoded packed
  44 // representation.
  45 template <typename ELF>
  46 void RelocationPacker<ELF>::UnpackRelocations(
  47     const std::vector<uint8_t>& packed,
  48     std::vector<typename ELF::Rela>* relocations) {
  49
  50   std::vector<typename ELF::Addr> packed_words;
  51   CHECK(packed.size() > 4 &&
  52         packed[0] == 'A' &&
  53         packed[1] == 'P' &&
  54         packed[2] == 'S' &&
  55         packed[3] == '2');
  56
  57   Sleb128Decoder<typename ELF::Addr> decoder(packed, 4);
  58   decoder.DequeueAll(&packed_words);
  59
  60   RelocationDeltaCodec<ELF> codec;
  61   codec.Decode(packed_words, relocations);
  62 }
  63
  64 template class RelocationPacker<ELF32_traits>;
  65 template class RelocationPacker<ELF64_traits>;
  66
  67 }  // namespace relocation_packer