1    :  // Copyright 2014 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    :  
  16    :  #include "syzygy/pe/transforms/pe_remove_empty_sections_transform.h"
  17    :  
  18    :  namespace pe {
  19    :  namespace transforms {
  20    :  
  21    :  namespace {
  22    :  
  23    :  using block_graph::BlockGraph;
  24    :  
  25    :  }  // namespace
  26    :  
  27    :  const char PERemoveEmptySectionsTransform::kTransformName[] =
  28    :      "PERemoveEmptySectionsTransform";
  29    :  
  30  E :  PERemoveEmptySectionsTransform::PERemoveEmptySectionsTransform() {
  31  E :  }
  32    :  
  33    :  bool PERemoveEmptySectionsTransform::TransformBlockGraph(
  34    :      const TransformPolicyInterface* policy,
  35    :      BlockGraph* block_graph,
  36  E :      BlockGraph::Block* dos_header_block) {
  37  E :    DCHECK_NE(reinterpret_cast<TransformPolicyInterface*>(NULL), policy);
  38  E :    DCHECK_NE(reinterpret_cast<BlockGraph*>(NULL), block_graph);
  39  E :    DCHECK_NE(reinterpret_cast<BlockGraph::Block*>(NULL), dos_header_block);
  40  E :    DCHECK_EQ(BlockGraph::PE_IMAGE, block_graph->image_format());
  41    :  
  42    :    // Keep track of sections used by at least one block.
  43  E :    std::set<BlockGraph::SectionId> sections_used;
  44  E :    BlockGraph::BlockMap::const_iterator block = block_graph->blocks().begin();
  45  E :    for (; block != block_graph->blocks().end(); ++block)
  46  E :      sections_used.insert(block->second.section());
  47    :  
  48    :    // Remove unused sections.
  49  E :    std::set<BlockGraph::SectionId> sections_unused;
  50  E :    BlockGraph::SectionMap& sections = block_graph->sections_mutable();
  51  E :    BlockGraph::SectionMap::iterator it = sections.begin();
  52  E :    while (it != sections.end()) {
  53  E :      BlockGraph::Section& section = it->second;
  54  E :      ++it;
  55    :  
  56    :      // Check whether this section is used and remove it otherwise.
  57  E :      if (sections_used.find(section.id()) == sections_used.end()) {
  58  E :        LOG(INFO) << "Removing empty section: " << section.name();
  59  E :        block_graph->RemoveSectionById(section.id());
  60    :      }
  61  E :    }
  62    :  
  63  E :    return true;
  64  E :  }
  65    :  
  66    :  }  // namespace transforms
  67    :  }  // namespace pe