Add PE64 support to courgette

Add tests for PE64

BUG=38784

Review URL: https://chromiumcodereview.appspot.com/23600063

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224789 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 732 insertions, 0 deletions

diff --git a/courgette/disassembler_win32_x64.cc b/courgette/disassembler_win32_x64.cc
new file mode 100644
index 0000000..1da5951
--- /dev/null
+++ b/courgette/disassembler_win32_x64.cc
@@ -0,0 +1,732 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "courgette/disassembler_win32_x64.h"
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+
+#include "courgette/assembly_program.h"
+#include "courgette/courgette.h"
+#include "courgette/encoded_program.h"
+
+namespace courgette {
+
+DisassemblerWin32X64::DisassemblerWin32X64(const void* start, size_t length)
+  : Disassembler(start, length),
+    incomplete_disassembly_(false),
+    is_PE32_plus_(false),
+    optional_header_(NULL),
+    size_of_optional_header_(0),
+    offset_of_data_directories_(0),
+    machine_type_(0),
+    number_of_sections_(0),
+    sections_(NULL),
+    has_text_section_(false),
+    size_of_code_(0),
+    size_of_initialized_data_(0),
+    size_of_uninitialized_data_(0),
+    base_of_code_(0),
+    base_of_data_(0),
+    image_base_(0),
+    size_of_image_(0),
+    number_of_data_directories_(0) {
+}
+
+// ParseHeader attempts to match up the buffer with the Windows data
+// structures that exist within a Windows 'Portable Executable' format file.
+// Returns 'true' if the buffer matches, and 'false' if the data looks
+// suspicious.  Rather than try to 'map' the buffer to the numerous windows
+// structures, we extract the information we need into the courgette::PEInfo
+// structure.
+//
+bool DisassemblerWin32X64::ParseHeader() {
+  if (length() < kOffsetOfFileAddressOfNewExeHeader + 4 /*size*/)
+    return Bad("Too small");
+
+  // Have 'MZ' magic for a DOS header?
+  if (start()[0] != 'M' || start()[1] != 'Z')
+    return Bad("Not MZ");
+
+  // offset from DOS header to PE header is stored in DOS header.
+  uint32 offset = ReadU32(start(),
+                          kOffsetOfFileAddressOfNewExeHeader);
+
+  if (offset >= length())
+    return Bad("Bad offset to PE header");
+
+  const uint8* const pe_header = OffsetToPointer(offset);
+  const size_t kMinPEHeaderSize = 4 /*signature*/ + kSizeOfCoffHeader;
+  if (pe_header <= start() ||
+      pe_header >= end() - kMinPEHeaderSize)
+    return Bad("Bad offset to PE header");
+
+  if (offset % 8 != 0)
+    return Bad("Misaligned PE header");
+
+  // The 'PE' header is an IMAGE_NT_HEADERS structure as defined in WINNT.H.
+  // See http://msdn.microsoft.com/en-us/library/ms680336(VS.85).aspx
+  //
+  // The first field of the IMAGE_NT_HEADERS is the signature.
+  if (!(pe_header[0] == 'P' &&
+        pe_header[1] == 'E' &&
+        pe_header[2] == 0 &&
+        pe_header[3] == 0))
+    return Bad("no PE signature");
+
+  // The second field of the IMAGE_NT_HEADERS is the COFF header.
+  // The COFF header is also called an IMAGE_FILE_HEADER
+  //   http://msdn.microsoft.com/en-us/library/ms680313(VS.85).aspx
+  const uint8* const coff_header = pe_header + 4;
+  machine_type_       = ReadU16(coff_header, 0);
+  number_of_sections_ = ReadU16(coff_header, 2);
+  size_of_optional_header_ = ReadU16(coff_header, 16);
+
+  // The rest of the IMAGE_NT_HEADERS is the IMAGE_OPTIONAL_HEADER(32|64)
+  const uint8* const optional_header = coff_header + kSizeOfCoffHeader;
+  optional_header_ = optional_header;
+
+  if (optional_header + size_of_optional_header_ >= end())
+    return Bad("optional header past end of file");
+
+  // Check we can read the magic.
+  if (size_of_optional_header_ < 2)
+    return Bad("optional header no magic");
+
+  uint16 magic = ReadU16(optional_header, 0);
+
+  if (magic == kImageNtOptionalHdr32Magic) {
+    is_PE32_plus_ = false;
+    offset_of_data_directories_ =
+      kOffsetOfDataDirectoryFromImageOptionalHeader32;
+  } else if (magic == kImageNtOptionalHdr64Magic) {
+    is_PE32_plus_ = true;
+    offset_of_data_directories_ =
+      kOffsetOfDataDirectoryFromImageOptionalHeader64;
+  } else {
+    return Bad("unrecognized magic");
+  }
+
+  // Check that we can read the rest of the the fixed fields.  Data directories
+  // directly follow the fixed fields of the IMAGE_OPTIONAL_HEADER.
+  if (size_of_optional_header_ < offset_of_data_directories_)
+    return Bad("optional header too short");
+
+  // The optional header is either an IMAGE_OPTIONAL_HEADER32 or
+  // IMAGE_OPTIONAL_HEADER64
+  // http://msdn.microsoft.com/en-us/library/ms680339(VS.85).aspx
+  //
+  // Copy the fields we care about.
+  size_of_code_               = ReadU32(optional_header, 4);
+  size_of_initialized_data_   = ReadU32(optional_header, 8);
+  size_of_uninitialized_data_ = ReadU32(optional_header, 12);
+  base_of_code_               = ReadU32(optional_header, 20);
+  if (is_PE32_plus_) {
+    base_of_data_ = 0;
+    image_base_  = ReadU64(optional_header, 24);
+  } else {
+    base_of_data_ = ReadU32(optional_header, 24);
+    image_base_   = ReadU32(optional_header, 28);
+  }
+  size_of_image_ = ReadU32(optional_header, 56);
+  number_of_data_directories_ =
+    ReadU32(optional_header, (is_PE32_plus_ ? 108 : 92));
+
+  if (size_of_code_ >= length() ||
+      size_of_initialized_data_ >= length() ||
+      size_of_code_ + size_of_initialized_data_ >= length()) {
+    // This validation fires on some perfectly fine executables.
+    //  return Bad("code or initialized data too big");
+  }
+
+  // TODO(sra): we can probably get rid of most of the data directories.
+  bool b = true;
+  // 'b &= ...' could be short circuit 'b = b && ...' but it is not necessary
+  // for correctness and it compiles smaller this way.
+  b &= ReadDataDirectory(0, &export_table_);
+  b &= ReadDataDirectory(1, &import_table_);
+  b &= ReadDataDirectory(2, &resource_table_);
+  b &= ReadDataDirectory(3, &exception_table_);
+  b &= ReadDataDirectory(5, &base_relocation_table_);
+  b &= ReadDataDirectory(11, &bound_import_table_);
+  b &= ReadDataDirectory(12, &import_address_table_);
+  b &= ReadDataDirectory(13, &delay_import_descriptor_);
+  b &= ReadDataDirectory(14, &clr_runtime_header_);
+  if (!b) {
+    return Bad("malformed data directory");
+  }
+
+  // Sections follow the optional header.
+  sections_ =
+      reinterpret_cast<const Section*>(optional_header +
+                                       size_of_optional_header_);
+  size_t detected_length = 0;
+
+  for (int i = 0;  i < number_of_sections_;  ++i) {
+    const Section* section = &sections_[i];
+
+    // TODO(sra): consider using the 'characteristics' field of the section
+    // header to see if the section contains instructions.
+    if (memcmp(section->name, ".text", 6) == 0)
+      has_text_section_ = true;
+
+    uint32 section_end =
+        section->file_offset_of_raw_data + section->size_of_raw_data;
+    if (section_end > detected_length)
+      detected_length = section_end;
+  }
+
+  // Pretend our in-memory copy is only as long as our detected length.
+  ReduceLength(detected_length);
+
+  if (is_32bit()) {
+    return Bad("32 bit executables are not supported by this disassembler");
+  }
+
+  if (!has_text_section()) {
+    return Bad("Resource-only executables are not yet supported");
+  }
+
+  return Good();
+}
+
+bool DisassemblerWin32X64::Disassemble(AssemblyProgram* target) {
+  if (!ok())
+    return false;
+
+  target->set_image_base(image_base());
+
+  if (!ParseAbs32Relocs())
+    return false;
+
+  ParseRel32RelocsFromSections();
+
+  if (!ParseFile(target))
+    return false;
+
+  target->DefaultAssignIndexes();
+
+  return true;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+bool DisassemblerWin32X64::ParseRelocs(std::vector<RVA> *relocs) {
+  relocs->clear();
+
+  size_t relocs_size = base_relocation_table_.size_;
+  if (relocs_size == 0)
+    return true;
+
+  // The format of the base relocation table is a sequence of variable sized
+  // IMAGE_BASE_RELOCATION blocks.  Search for
+  //   "The format of the base relocation data is somewhat quirky"
+  // at http://msdn.microsoft.com/en-us/library/ms809762.aspx
+
+  const uint8* relocs_start = RVAToPointer(base_relocation_table_.address_);
+  const uint8* relocs_end = relocs_start + relocs_size;
+
+  // Make sure entire base relocation table is within the buffer.
+  if (relocs_start < start() ||
+      relocs_start >= end() ||
+      relocs_end <= start() ||
+      relocs_end > end()) {
+    return Bad(".relocs outside image");
+  }
+
+  const uint8* block = relocs_start;
+
+  // Walk the variable sized blocks.
+  while (block + 8 < relocs_end) {
+    RVA page_rva = ReadU32(block, 0);
+    uint32 size = ReadU32(block, 4);
+    if (size < 8 ||        // Size includes header ...
+        size % 4  !=  0)   // ... and is word aligned.
+      return Bad("unreasonable relocs block");
+
+    const uint8* end_entries = block + size;
+
+    if (end_entries <= block ||
+        end_entries <= start() ||
+        end_entries > end())
+      return Bad(".relocs block outside image");
+
+    // Walk through the two-byte entries.
+    for (const uint8* p = block + 8;  p < end_entries;  p += 2) {
+      uint16 entry = ReadU16(p, 0);
+      int type = entry >> 12;
+      int offset = entry & 0xFFF;
+
+      RVA rva = page_rva + offset;
+      if (type == 10) {         // IMAGE_REL_BASED_DIR64
+        relocs->push_back(rva);
+      } else if (type == 0) {  // IMAGE_REL_BASED_ABSOLUTE
+        // Ignore, used as padding.
+      } else {
+        // Does not occur in Windows x64 executables.
+        return Bad("unknown type of reloc");
+      }
+    }
+
+    block += size;
+  }
+
+  std::sort(relocs->begin(), relocs->end());
+
+  return true;
+}
+
+const Section* DisassemblerWin32X64::RVAToSection(RVA rva) const {
+  for (int i = 0; i < number_of_sections_; i++) {
+    const Section* section = &sections_[i];
+    uint32 offset = rva - section->virtual_address;
+    if (offset < section->virtual_size) {
+      return section;
+    }
+  }
+  return NULL;
+}
+
+int DisassemblerWin32X64::RVAToFileOffset(RVA rva) const {
+  const Section* section = RVAToSection(rva);
+  if (section) {
+    uint32 offset = rva - section->virtual_address;
+    if (offset < section->size_of_raw_data) {
+      return section->file_offset_of_raw_data + offset;
+    } else {
+      return kNoOffset;  // In section but not in file (e.g. uninit data).
+    }
+  }
+
+  // Small RVA values point into the file header in the loaded image.
+  // RVA 0 is the module load address which Windows uses as the module handle.
+  // RVA 2 sometimes occurs, I'm not sure what it is, but it would map into the
+  // DOS header.
+  if (rva == 0 || rva == 2)
+    return rva;
+
+  NOTREACHED();
+  return kNoOffset;
+}
+
+const uint8* DisassemblerWin32X64::RVAToPointer(RVA rva) const {
+  int file_offset = RVAToFileOffset(rva);
+  if (file_offset == kNoOffset)
+    return NULL;
+  else
+    return OffsetToPointer(file_offset);
+}
+
+std::string DisassemblerWin32X64::SectionName(const Section* section) {
+  if (section == NULL)
+    return "<none>";
+  char name[9];
+  memcpy(name, section->name, 8);
+  name[8] = '\0';  // Ensure termination.
+  return name;
+}
+
+CheckBool DisassemblerWin32X64::ParseFile(AssemblyProgram* program) {
+  // Walk all the bytes in the file, whether or not in a section.
+  uint32 file_offset = 0;
+  while (file_offset < length()) {
+    const Section* section = FindNextSection(file_offset);
+    if (section == NULL) {
+      // No more sections.  There should not be extra stuff following last
+      // section.
+      //   ParseNonSectionFileRegion(file_offset, pe_info().length(), program);
+      break;
+    }
+    if (file_offset < section->file_offset_of_raw_data) {
+      uint32 section_start_offset = section->file_offset_of_raw_data;
+      if(!ParseNonSectionFileRegion(file_offset, section_start_offset,
+                                    program))
+        return false;
+
+      file_offset = section_start_offset;
+    }
+    uint32 end = file_offset + section->size_of_raw_data;
+    if (!ParseFileRegion(section, file_offset, end, program))
+      return false;
+    file_offset = end;
+  }
+
+#if COURGETTE_HISTOGRAM_TARGETS
+  HistogramTargets("abs32 relocs", abs32_target_rvas_);
+  HistogramTargets("rel32 relocs", rel32_target_rvas_);
+#endif
+
+  return true;
+}
+
+bool DisassemblerWin32X64::ParseAbs32Relocs() {
+  abs32_locations_.clear();
+  if (!ParseRelocs(&abs32_locations_))
+    return false;
+
+  std::sort(abs32_locations_.begin(), abs32_locations_.end());
+
+#if COURGETTE_HISTOGRAM_TARGETS
+  for (size_t i = 0;  i < abs32_locations_.size(); ++i) {
+    RVA rva = abs32_locations_[i];
+    // The 4 bytes at the relocation are a reference to some address.
+    uint32 target_address = Read32LittleEndian(RVAToPointer(rva));
+    ++abs32_target_rvas_[target_address - image_base()];
+  }
+#endif
+  return true;
+}
+
+void DisassemblerWin32X64::ParseRel32RelocsFromSections() {
+  uint32 file_offset = 0;
+  while (file_offset < length()) {
+    const Section* section = FindNextSection(file_offset);
+    if (section == NULL)
+      break;
+    if (file_offset < section->file_offset_of_raw_data)
+      file_offset = section->file_offset_of_raw_data;
+    ParseRel32RelocsFromSection(section);
+    file_offset += section->size_of_raw_data;
+  }
+  std::sort(rel32_locations_.begin(), rel32_locations_.end());
+
+#if COURGETTE_HISTOGRAM_TARGETS
+  VLOG(1) << "abs32_locations_ " << abs32_locations_.size()
+          << "\nrel32_locations_ " << rel32_locations_.size()
+          << "\nabs32_target_rvas_ " << abs32_target_rvas_.size()
+          << "\nrel32_target_rvas_ " << rel32_target_rvas_.size();
+
+  int common = 0;
+  std::map<RVA, int>::iterator abs32_iter = abs32_target_rvas_.begin();
+  std::map<RVA, int>::iterator rel32_iter = rel32_target_rvas_.begin();
+  while (abs32_iter != abs32_target_rvas_.end() &&
+         rel32_iter != rel32_target_rvas_.end()) {
+    if (abs32_iter->first < rel32_iter->first)
+      ++abs32_iter;
+    else if (rel32_iter->first < abs32_iter->first)
+      ++rel32_iter;
+    else {
+      ++common;
+      ++abs32_iter;
+      ++rel32_iter;
+    }
+  }
+  VLOG(1) << "common " << common;
+#endif
+}
+
+void DisassemblerWin32X64::ParseRel32RelocsFromSection(const Section* section) {
+  // TODO(sra): use characteristic.
+  bool isCode = strcmp(section->name, ".text") == 0;
+  if (!isCode)
+    return;
+
+  uint32 start_file_offset = section->file_offset_of_raw_data;
+  uint32 end_file_offset = start_file_offset + section->size_of_raw_data;
+  RVA relocs_start_rva = base_relocation_table().address_;
+
+  const uint8* start_pointer = OffsetToPointer(start_file_offset);
+  const uint8* end_pointer = OffsetToPointer(end_file_offset);
+
+  RVA start_rva = FileOffsetToRVA(start_file_offset);
+  RVA end_rva = start_rva + section->virtual_size;
+
+  // Quick way to convert from Pointer to RVA within a single Section is to
+  // subtract 'pointer_to_rva'.
+  const uint8* const adjust_pointer_to_rva = start_pointer - start_rva;
+
+  std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin();
+
+  // Find the rel32 relocations.
+  const uint8* p = start_pointer;
+  while (p < end_pointer) {
+    RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva);
+    if (current_rva == relocs_start_rva) {
+      uint32 relocs_size = base_relocation_table().size_;
+      if (relocs_size) {
+        p += relocs_size;
+        continue;
+      }
+    }
+
+    //while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva)
+    //  ++abs32_pos;
+
+    // Heuristic discovery of rel32 locations in instruction stream: are the
+    // next few bytes the start of an instruction containing a rel32
+    // addressing mode?
+    const uint8* rel32 = NULL;
+
+    if (p + 5 <= end_pointer) {
+      if (*p == 0xE8 || *p == 0xE9) {  // jmp rel32 and call rel32
+        rel32 = p + 1;
+      }
+    }
+    if (p + 6 <= end_pointer) {
+      if (*p == 0x0F  &&  (*(p+1) & 0xF0) == 0x80) {  // Jcc long form
+        if (p[1] != 0x8A && p[1] != 0x8B)  // JPE/JPO unlikely
+          rel32 = p + 2;
+      }
+    }
+    if (rel32) {
+      RVA rel32_rva = static_cast<RVA>(rel32 - adjust_pointer_to_rva);
+
+      // Is there an abs32 reloc overlapping the candidate?
+      while (abs32_pos != abs32_locations_.end() && *abs32_pos < rel32_rva - 3)
+        ++abs32_pos;
+      // Now: (*abs32_pos > rel32_rva - 4) i.e. the lowest addressed 4-byte
+      // region that could overlap rel32_rva.
+      if (abs32_pos != abs32_locations_.end()) {
+        if (*abs32_pos < rel32_rva + 4) {
+          // Beginning of abs32 reloc is before end of rel32 reloc so they
+          // overlap.  Skip four bytes past the abs32 reloc.
+          p += (*abs32_pos + 4) - current_rva;
+          continue;
+        }
+      }
+
+      RVA target_rva = rel32_rva + 4 + Read32LittleEndian(rel32);
+      // To be valid, rel32 target must be within image, and within this
+      // section.
+      if (IsValidRVA(target_rva) &&
+          start_rva <= target_rva && target_rva < end_rva) {
+        rel32_locations_.push_back(rel32_rva);
+#if COURGETTE_HISTOGRAM_TARGETS
+        ++rel32_target_rvas_[target_rva];
+#endif
+        p = rel32 + 4;
+        continue;
+      }
+    }
+    p += 1;
+  }
+}
+
+CheckBool DisassemblerWin32X64::ParseNonSectionFileRegion(
+    uint32 start_file_offset,
+    uint32 end_file_offset,
+    AssemblyProgram* program) {
+  if (incomplete_disassembly_)
+    return true;
+
+  const uint8* start = OffsetToPointer(start_file_offset);
+  const uint8* end = OffsetToPointer(end_file_offset);
+
+  const uint8* p = start;
+
+  while (p < end) {
+    if (!program->EmitByteInstruction(*p))
+      return false;
+    ++p;
+  }
+
+  return true;
+}
+
+CheckBool DisassemblerWin32X64::ParseFileRegion(
+    const Section* section,
+    uint32 start_file_offset, uint32 end_file_offset,
+    AssemblyProgram* program) {
+  RVA relocs_start_rva = base_relocation_table().address_;
+
+  const uint8* start_pointer = OffsetToPointer(start_file_offset);
+  const uint8* end_pointer = OffsetToPointer(end_file_offset);
+
+  RVA start_rva = FileOffsetToRVA(start_file_offset);
+  RVA end_rva = start_rva + section->virtual_size;
+
+  // Quick way to convert from Pointer to RVA within a single Section is to
+  // subtract 'pointer_to_rva'.
+  const uint8* const adjust_pointer_to_rva = start_pointer - start_rva;
+
+  std::vector<RVA>::iterator rel32_pos = rel32_locations_.begin();
+  std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin();
+
+  if (!program->EmitOriginInstruction(start_rva))
+    return false;
+
+  const uint8* p = start_pointer;
+
+  while (p < end_pointer) {
+    RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva);
+
+    // The base relocation table is usually in the .relocs section, but it could
+    // actually be anywhere.  Make sure we skip it because we will regenerate it
+    // during assembly.
+    if (current_rva == relocs_start_rva) {
+      if (!program->EmitPeRelocsInstruction())
+        return false;
+      uint32 relocs_size = base_relocation_table().size_;
+      if (relocs_size) {
+        p += relocs_size;
+        continue;
+      }
+    }
+
+    while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva)
+      ++abs32_pos;
+
+    if (abs32_pos != abs32_locations_.end() && *abs32_pos == current_rva) {
+      uint32 target_address = Read32LittleEndian(p);
+      RVA target_rva = target_address - image_base();
+      // TODO(sra): target could be Label+offset.  It is not clear how to guess
+      // which it might be.  We assume offset==0.
+      if (!program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva)))
+        return false;
+      p += 4;
+      continue;
+    }
+
+    while (rel32_pos != rel32_locations_.end() && *rel32_pos < current_rva)
+      ++rel32_pos;
+
+    if (rel32_pos != rel32_locations_.end() && *rel32_pos == current_rva) {
+      RVA target_rva = current_rva + 4 + Read32LittleEndian(p);
+      if (!program->EmitRel32(program->FindOrMakeRel32Label(target_rva)))
+        return false;
+      p += 4;
+      continue;
+    }
+
+    if (incomplete_disassembly_) {
+      if ((abs32_pos == abs32_locations_.end() || end_rva <= *abs32_pos) &&
+          (rel32_pos == rel32_locations_.end() || end_rva <= *rel32_pos) &&
+          (end_rva <= relocs_start_rva || current_rva >= relocs_start_rva)) {
+        // No more relocs in this section, don't bother encoding bytes.
+        break;
+      }
+    }
+
+    if (!program->EmitByteInstruction(*p))
+      return false;
+    p += 1;
+  }
+
+  return true;
+}
+
+#if COURGETTE_HISTOGRAM_TARGETS
+// Histogram is printed to std::cout.  It is purely for debugging the algorithm
+// and is only enabled manually in 'exploration' builds.  I don't want to add
+// command-line configuration for this feature because this code has to be
+// small, which means compiled-out.
+void DisassemblerWin32X64::HistogramTargets(const char* kind,
+                                            const std::map<RVA, int>& map) {
+  int total = 0;
+  std::map<int, std::vector<RVA> > h;
+  for (std::map<RVA, int>::const_iterator p = map.begin();
+       p != map.end();
+       ++p) {
+    h[p->second].push_back(p->first);
+    total += p->second;
+  }
+
+  std::cout << total << " " << kind << " to "
+            << map.size() << " unique targets" << std::endl;
+
+  std::cout << "indegree: #targets-with-indegree (example)" << std::endl;
+  const int kFirstN = 15;
+  bool someSkipped = false;
+  int index = 0;
+  for (std::map<int, std::vector<RVA> >::reverse_iterator p = h.rbegin();
+       p != h.rend();
+       ++p) {
+    ++index;
+    if (index <= kFirstN || p->first <= 3) {
+      if (someSkipped) {
+        std::cout << "..." << std::endl;
+      }
+      size_t count = p->second.size();
+      std::cout << std::dec << p->first << ": " << count;
+      if (count <= 2) {
+        for (size_t i = 0;  i < count;  ++i)
+          std::cout << "  " << DescribeRVA(p->second[i]);
+      }
+      std::cout << std::endl;
+      someSkipped = false;
+    } else {
+      someSkipped = true;
+    }
+  }
+}
+#endif  // COURGETTE_HISTOGRAM_TARGETS
+
+
+// DescribeRVA is for debugging only.  I would put it under #ifdef DEBUG except
+// that during development I'm finding I need to call it when compiled in
+// Release mode.  Hence:
+// TODO(sra): make this compile only for debug mode.
+std::string DisassemblerWin32X64::DescribeRVA(RVA rva) const {
+  const Section* section = RVAToSection(rva);
+  std::ostringstream s;
+  s << std::hex << rva;
+  if (section) {
+    s << " (";
+    s << SectionName(section) << "+"
+      << std::hex << (rva - section->virtual_address)
+      << ")";
+  }
+  return s.str();
+}
+
+const Section* DisassemblerWin32X64::FindNextSection(uint32 fileOffset) const {
+  const Section* best = 0;
+  for (int i = 0; i < number_of_sections_; i++) {
+    const Section* section = &sections_[i];
+    if (section->size_of_raw_data > 0) {  // i.e. has data in file.
+      if (fileOffset <= section->file_offset_of_raw_data) {
+        if (best == 0 ||
+            section->file_offset_of_raw_data < best->file_offset_of_raw_data) {
+          best = section;
+        }
+      }
+    }
+  }
+  return best;
+}
+
+RVA DisassemblerWin32X64::FileOffsetToRVA(uint32 file_offset) const {
+  for (int i = 0; i < number_of_sections_; i++) {
+    const Section* section = &sections_[i];
+    uint32 offset = file_offset - section->file_offset_of_raw_data;
+    if (offset < section->size_of_raw_data) {
+      return section->virtual_address + offset;
+    }
+  }
+  return 0;
+}
+
+bool DisassemblerWin32X64::ReadDataDirectory(
+    int index,
+    ImageDataDirectory* directory) {
+
+  if (index < number_of_data_directories_) {
+    size_t offset = index * 8 + offset_of_data_directories_;
+    if (offset >= size_of_optional_header_)
+      return Bad("number of data directories inconsistent");
+    const uint8* data_directory = optional_header_ + offset;
+    if (data_directory < start() ||
+        data_directory + 8 >= end())
+      return Bad("data directory outside image");
+    RVA rva = ReadU32(data_directory, 0);
+    size_t size  = ReadU32(data_directory, 4);
+    if (size > size_of_image_)
+      return Bad("data directory size too big");
+
+    // TODO(sra): validate RVA.
+    directory->address_ = rva;
+    directory->size_ = static_cast<uint32>(size);
+    return true;
+  } else {
+    directory->address_ = 0;
+    directory->size_ = 0;
+    return true;
+  }
+}
+
+}  // namespace courgette