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/dead_code_finder.h"
  16    :  
  17    :  namespace reorder {
  18    :  
  19    :  DeadCodeFinder::DeadCodeFinder()
  20  E :      : Reorderer::OrderGenerator("Dead Code Finder") {
  21  E :  }
  22    :  
  23  E :  DeadCodeFinder::~DeadCodeFinder() {
  24  E :  }
  25    :  
  26    :  bool DeadCodeFinder::OnCodeBlockEntry(const Block* block,
  27    :                                        RelativeAddress /*address*/,
  28    :                                        uint32 /*process_id*/,
  29    :                                        uint32 /*thread_id*/,
  30  E :                                        const UniqueTime& /*time*/) {
  31  E :    visited_blocks_.insert(block);
  32  E :    return true;
  33  E :  }
  34    :  
  35  E :  bool DeadCodeFinder::IsDead(const Block* block) const {
  36    :    // We don't consider gap blocks as interesting for the purposes of dead code
  37    :    // identification. We don't have good names for these blocks, so they end up
  38    :    // just being noise (not easily actionable) for the consumer of the dead code
  39    :    // finder's output.
  40    :    return ((block->attributes() & BlockGraph::GAP_BLOCK) == 0)
  41  E :        && (visited_blocks_.find(block) == visited_blocks_.end());
  42  E :  }
  43    :  
  44    :  bool DeadCodeFinder::CalculateReordering(const PEFile& pe_file,
  45    :                                           const ImageLayout& image,
  46    :                                           bool reorder_code,
  47    :                                           bool reorder_data,
  48  E :                                           Order* order) {
  49  E :    DCHECK(order != NULL);
  50    :  
  51  E :    order->comment = "Unvisited blocks per section";
  52  E :    order->sections.clear();
  53  E :    order->sections.resize(image.sections.size());
  54  E :    for (size_t i = 0; i < image.sections.size(); ++i) {
  55  E :      const ImageLayout::SectionInfo& section = image.sections[i];
  56  E :      order->sections[i].id = i;
  57  E :      order->sections[i].name = section.name;
  58  E :      order->sections[i].characteristics = section.characteristics;
  59  E :      if ((section.characteristics & IMAGE_SCN_CNT_CODE) == 0)
  60  E :        continue;
  61    :  
  62    :      // Prepare to iterate over all block in the section.
  63  E :      BlockGraph::AddressSpace::Range section_range(section.addr, section.size);
  64    :      AddressSpace::RangeMapConstIterPair section_blocks(
  65    :          image.blocks.GetIntersectingBlocks(
  66  E :              section_range.start(), section_range.size()));
  67    :  
  68    :      // Gather up all unvisited blocks within the section in the "order".
  69  E :      AddressSpace::RangeMapConstIter& section_it = section_blocks.first;
  70  E :      const AddressSpace::RangeMapConstIter& section_end = section_blocks.second;
  71  E :      Order::BlockSpecVector& block_vector = order->sections[i].blocks;
  72  E :      for (; section_it != section_end; ++section_it) {
  73  E :        const BlockGraph::Block* block = section_it->second;
  74  E :        if (IsDead(block)) {
  75  E :          block_vector.push_back(Order::BlockSpec(block));
  76    :        }
  77  E :      }
  78  E :    }
  79    :  
  80  E :    return true;
  81  E :  }
  82    :  
  83    :  }  // namespace reorder