1    :  // Copyright 2011 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #include "syzygy/reorder/random_order_generator.h"
  16    :  
  17    :  #include <algorithm>
  18    :  
  19    :  #include "syzygy/core/random_number_generator.h"
  20    :  #include "syzygy/pe/pe_utils.h"
  21    :  
  22    :  namespace reorder {
  23    :  
  24    :  RandomOrderGenerator::RandomOrderGenerator(int seed)
  25    :      : Reorderer::OrderGenerator("Random Order Generator"),
  26  E :        seed_(seed) {
  27  E :  }
  28    :  
  29  E :  RandomOrderGenerator::~RandomOrderGenerator() {
  30  E :  }
  31    :  
  32    :  bool RandomOrderGenerator::OnCodeBlockEntry(const BlockGraph::Block* /*block*/,
  33    :                                              RelativeAddress /*address*/,
  34    :                                              uint32 /*process_id*/,
  35    :                                              uint32 /*thread_id*/,
  36  i :                                              const UniqueTime& /*time*/) {
  37    :    // This is a NOP.
  38  i :    return true;
  39  i :  }
  40    :  
  41    :  bool RandomOrderGenerator::CalculateReordering(const PEFile& pe_file,
  42    :                                                 const ImageLayout& image,
  43    :                                                 bool reorder_code,
  44    :                                                 bool reorder_data,
  45  E :                                                 Order* order) {
  46  E :    DCHECK(order != NULL);
  47  E :    order->comment = "Random block ordering";
  48  E :    order->sections.clear();
  49  E :    order->sections.resize(image.sections.size());
  50  E :    for (size_t i = 0; i < image.sections.size(); ++i) {
  51  E :      const ImageLayout::SectionInfo& section = image.sections[i];
  52  E :      order->sections[i].id = i;
  53  E :      order->sections[i].name = section.name;
  54  E :      order->sections[i].characteristics = section.characteristics;
  55    :  
  56    :      // Prepare to iterate over all block in the section.
  57  E :      BlockGraph::AddressSpace::Range section_range(section.addr, section.size);
  58    :      AddressSpace::RangeMapConstIterPair section_blocks(
  59    :          image.blocks.GetIntersectingBlocks(
  60  E :              section_range.start(), section_range.size()));
  61    :  
  62    :      // Gather up all blocks within the section.
  63  E :      AddressSpace::RangeMapConstIter& section_it = section_blocks.first;
  64  E :      const AddressSpace::RangeMapConstIter& section_end = section_blocks.second;
  65  E :      for (; section_it != section_end; ++section_it) {
  66  E :        const BlockGraph::Block* block = section_it->second;
  67  E :        order->sections[i].blocks.push_back(Order::BlockSpec(block));
  68  E :      }
  69    :  
  70  E :      bool is_code = (section.characteristics & IMAGE_SCN_CNT_CODE) != 0;
  71  E :      bool is_data = !is_code;
  72    :      // If we're not supposed to randomly reorder this section, then we're done.
  73  E :      if ((is_code && !reorder_code) || (is_data && !reorder_data))
  74  E :        continue;
  75    :  
  76    :      // Otherwise, randomly shuffle blocks in this section.
  77  E :      LOG(INFO) << "Randomizing section " << i  << " (" << section.name << ").";
  78  E :      core::RandomNumberGenerator random_number_generator(seed_ + i);
  79    :      std::random_shuffle(order->sections[i].blocks.begin(),
  80    :                          order->sections[i].blocks.end(),
  81  E :                          random_number_generator);
  82  E :    }
  83    :  
  84  E :    return true;
  85  E :  }
  86    :  
  87    :  }  // namespace reorder