courgette/disassembler_win32_x86.cc

   1 // Copyright (c) 2011 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 "courgette/disassembler_win32_x86.h"
   6
   7 #include <algorithm>
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/logging.h"
  13
  14 #include "courgette/assembly_program.h"
  15 #include "courgette/courgette.h"
  16 #include "courgette/encoded_program.h"
  17
  18 namespace courgette {
  19
  20 DisassemblerWin32X86::DisassemblerWin32X86(const void* start, size_t length)
  21   : Disassembler(start, length),
  22     incomplete_disassembly_(false),
  23     is_PE32_plus_(false),
  24     optional_header_(NULL),
  25     size_of_optional_header_(0),
  26     offset_of_data_directories_(0),
  27     machine_type_(0),
  28     number_of_sections_(0),
  29     sections_(NULL),
  30     has_text_section_(false),
  31     size_of_code_(0),
  32     size_of_initialized_data_(0),
  33     size_of_uninitialized_data_(0),
  34     base_of_code_(0),
  35     base_of_data_(0),
  36     image_base_(0),
  37     size_of_image_(0),
  38     number_of_data_directories_(0) {
  39 }
  40
  41 // ParseHeader attempts to match up the buffer with the Windows data
  42 // structures that exist within a Windows 'Portable Executable' format file.
  43 // Returns 'true' if the buffer matches, and 'false' if the data looks
  44 // suspicious.  Rather than try to 'map' the buffer to the numerous windows
  45 // structures, we extract the information we need into the courgette::PEInfo
  46 // structure.
  47 //
  48 bool DisassemblerWin32X86::ParseHeader() {
  49   if (length() < kOffsetOfFileAddressOfNewExeHeader + 4 /*size*/)
  50     return Bad("Too small");
  51
  52   // Have 'MZ' magic for a DOS header?
  53   if (start()[0] != 'M' || start()[1] != 'Z')
  54     return Bad("Not MZ");
  55
  56   // offset from DOS header to PE header is stored in DOS header.
  57   uint32 offset = ReadU32(start(),
  58                           kOffsetOfFileAddressOfNewExeHeader);
  59
  60   if (offset >= length())
  61     return Bad("Bad offset to PE header");
  62
  63   const uint8* const pe_header = OffsetToPointer(offset);
  64   const size_t kMinPEHeaderSize = 4 /*signature*/ + kSizeOfCoffHeader;
  65   if (pe_header <= start() ||
  66       pe_header >= end() - kMinPEHeaderSize)
  67     return Bad("Bad offset to PE header");
  68
  69   if (offset % 8 != 0)
  70     return Bad("Misaligned PE header");
  71
  72   // The 'PE' header is an IMAGE_NT_HEADERS structure as defined in WINNT.H.
  73   // See http://msdn.microsoft.com/en-us/library/ms680336(VS.85).aspx
  74   //
  75   // The first field of the IMAGE_NT_HEADERS is the signature.
  76   if (!(pe_header[0] == 'P' &&
  77         pe_header[1] == 'E' &&
  78         pe_header[2] == 0 &&
  79         pe_header[3] == 0))
  80     return Bad("no PE signature");
  81
  82   // The second field of the IMAGE_NT_HEADERS is the COFF header.
  83   // The COFF header is also called an IMAGE_FILE_HEADER
  84   //   http://msdn.microsoft.com/en-us/library/ms680313(VS.85).aspx
  85   const uint8* const coff_header = pe_header + 4;
  86   machine_type_       = ReadU16(coff_header, 0);
  87   number_of_sections_ = ReadU16(coff_header, 2);
  88   size_of_optional_header_ = ReadU16(coff_header, 16);
  89
  90   // The rest of the IMAGE_NT_HEADERS is the IMAGE_OPTIONAL_HEADER(32|64)
  91   const uint8* const optional_header = coff_header + kSizeOfCoffHeader;
  92   optional_header_ = optional_header;
  93
  94   if (optional_header + size_of_optional_header_ >= end())
  95     return Bad("optional header past end of file");
  96
  97   // Check we can read the magic.
  98   if (size_of_optional_header_ < 2)
  99     return Bad("optional header no magic");
 100
 101   uint16 magic = ReadU16(optional_header, 0);
 102
 103   if (magic == kImageNtOptionalHdr32Magic) {
 104     is_PE32_plus_ = false;
 105     offset_of_data_directories_ =
 106       kOffsetOfDataDirectoryFromImageOptionalHeader32;
 107   } else if (magic == kImageNtOptionalHdr64Magic) {
 108     is_PE32_plus_ = true;
 109     offset_of_data_directories_ =
 110       kOffsetOfDataDirectoryFromImageOptionalHeader64;
 111   } else {
 112     return Bad("unrecognized magic");
 113   }
 114
 115   // Check that we can read the rest of the the fixed fields.  Data directories
 116   // directly follow the fixed fields of the IMAGE_OPTIONAL_HEADER.
 117   if (size_of_optional_header_ < offset_of_data_directories_)
 118     return Bad("optional header too short");
 119
 120   // The optional header is either an IMAGE_OPTIONAL_HEADER32 or
 121   // IMAGE_OPTIONAL_HEADER64
 122   // http://msdn.microsoft.com/en-us/library/ms680339(VS.85).aspx
 123   //
 124   // Copy the fields we care about.
 125   size_of_code_               = ReadU32(optional_header, 4);
 126   size_of_initialized_data_   = ReadU32(optional_header, 8);
 127   size_of_uninitialized_data_ = ReadU32(optional_header, 12);
 128   base_of_code_               = ReadU32(optional_header, 20);
 129   if (is_PE32_plus_) {
 130     base_of_data_ = 0;
 131     image_base_  = ReadU64(optional_header, 24);
 132   } else {
 133     base_of_data_ = ReadU32(optional_header, 24);
 134     image_base_   = ReadU32(optional_header, 28);
 135   }
 136   size_of_image_ = ReadU32(optional_header, 56);
 137   number_of_data_directories_ =
 138     ReadU32(optional_header, (is_PE32_plus_ ? 108 : 92));
 139
 140   if (size_of_code_ >= length() ||
 141       size_of_initialized_data_ >= length() ||
 142       size_of_code_ + size_of_initialized_data_ >= length()) {
 143     // This validation fires on some perfectly fine executables.
 144     //  return Bad("code or initialized data too big");
 145   }
 146
 147   // TODO(sra): we can probably get rid of most of the data directories.
 148   bool b = true;
 149   // 'b &= ...' could be short circuit 'b = b && ...' but it is not necessary
 150   // for correctness and it compiles smaller this way.
 151   b &= ReadDataDirectory(0, &export_table_);
 152   b &= ReadDataDirectory(1, &import_table_);
 153   b &= ReadDataDirectory(2, &resource_table_);
 154   b &= ReadDataDirectory(3, &exception_table_);
 155   b &= ReadDataDirectory(5, &base_relocation_table_);
 156   b &= ReadDataDirectory(11, &bound_import_table_);
 157   b &= ReadDataDirectory(12, &import_address_table_);
 158   b &= ReadDataDirectory(13, &delay_import_descriptor_);
 159   b &= ReadDataDirectory(14, &clr_runtime_header_);
 160   if (!b) {
 161     return Bad("malformed data directory");
 162   }
 163
 164   // Sections follow the optional header.
 165   sections_ =
 166       reinterpret_cast<const Section*>(optional_header +
 167                                        size_of_optional_header_);
 168   size_t detected_length = 0;
 169
 170   for (int i = 0;  i < number_of_sections_;  ++i) {
 171     const Section* section = &sections_[i];
 172
 173     // TODO(sra): consider using the 'characteristics' field of the section
 174     // header to see if the section contains instructions.
 175     if (memcmp(section->name, ".text", 6) == 0)
 176       has_text_section_ = true;
 177
 178     uint32 section_end =
 179         section->file_offset_of_raw_data + section->size_of_raw_data;
 180     if (section_end > detected_length)
 181       detected_length = section_end;
 182   }
 183
 184   // Pretend our in-memory copy is only as long as our detected length.
 185   ReduceLength(detected_length);
 186
 187   if (!is_32bit()) {
 188     return Bad("64 bit executables are not supported by this disassembler");
 189   }
 190
 191   if (!has_text_section()) {
 192     return Bad("Resource-only executables are not yet supported");
 193   }
 194
 195   return Good();
 196 }
 197
 198 bool DisassemblerWin32X86::Disassemble(AssemblyProgram* target) {
 199   if (!ok())
 200     return false;
 201
 202   target->set_image_base(image_base());
 203
 204   if (!ParseAbs32Relocs())
 205     return false;
 206
 207   ParseRel32RelocsFromSections();
 208
 209   if (!ParseFile(target))
 210     return false;
 211
 212   target->DefaultAssignIndexes();
 213
 214   return true;
 215 }
 216
 217 ////////////////////////////////////////////////////////////////////////////////
 218
 219 bool DisassemblerWin32X86::ParseRelocs(std::vector<RVA> *relocs) {
 220   relocs->clear();
 221
 222   size_t relocs_size = base_relocation_table_.size_;
 223   if (relocs_size == 0)
 224     return true;
 225
 226   // The format of the base relocation table is a sequence of variable sized
 227   // IMAGE_BASE_RELOCATION blocks.  Search for
 228   //   "The format of the base relocation data is somewhat quirky"
 229   // at http://msdn.microsoft.com/en-us/library/ms809762.aspx
 230
 231   const uint8* relocs_start = RVAToPointer(base_relocation_table_.address_);
 232   const uint8* relocs_end = relocs_start + relocs_size;
 233
 234   // Make sure entire base relocation table is within the buffer.
 235   if (relocs_start < start() ||
 236       relocs_start >= end() ||
 237       relocs_end <= start() ||
 238       relocs_end > end()) {
 239     return Bad(".relocs outside image");
 240   }
 241
 242   const uint8* block = relocs_start;
 243
 244   // Walk the variable sized blocks.
 245   while (block + 8 < relocs_end) {
 246     RVA page_rva = ReadU32(block, 0);
 247     uint32 size = ReadU32(block, 4);
 248     if (size < 8 ||        // Size includes header ...
 249         size % 4  !=  0)   // ... and is word aligned.
 250       return Bad("unreasonable relocs block");
 251
 252     const uint8* end_entries = block + size;
 253
 254     if (end_entries <= block ||
 255         end_entries <= start() ||
 256         end_entries > end())
 257       return Bad(".relocs block outside image");
 258
 259     // Walk through the two-byte entries.
 260     for (const uint8* p = block + 8;  p < end_entries;  p += 2) {
 261       uint16 entry = ReadU16(p, 0);
 262       int type = entry >> 12;
 263       int offset = entry & 0xFFF;
 264
 265       RVA rva = page_rva + offset;
 266       // Skip the relocs that live outside of the image. It might be the case
 267       // if a reloc is relative to a register, e.g.:
 268       //     mov    ecx,dword ptr [eax+044D5888h]
 269       uint32 target_address = Read32LittleEndian(RVAToPointer(rva));
 270       if (target_address < image_base_ ||
 271           target_address > (image_base_ + size_of_image_)) {
 272         continue;
 273       }
 274       if (type == 3) {         // IMAGE_REL_BASED_HIGHLOW
 275         relocs->push_back(rva);
 276       } else if (type == 0) {  // IMAGE_REL_BASED_ABSOLUTE
 277         // Ignore, used as padding.
 278       } else {
 279         // Does not occur in Windows x86 executables.
 280         return Bad("unknown type of reloc");
 281       }
 282     }
 283
 284     block += size;
 285   }
 286
 287   std::sort(relocs->begin(), relocs->end());
 288
 289   return true;
 290 }
 291
 292 const Section* DisassemblerWin32X86::RVAToSection(RVA rva) const {
 293   for (int i = 0; i < number_of_sections_; i++) {
 294     const Section* section = &sections_[i];
 295     uint32 offset = rva - section->virtual_address;
 296     if (offset < section->virtual_size) {
 297       return section;
 298     }
 299   }
 300   return NULL;
 301 }
 302
 303 int DisassemblerWin32X86::RVAToFileOffset(RVA rva) const {
 304   const Section* section = RVAToSection(rva);
 305   if (section) {
 306     uint32 offset = rva - section->virtual_address;
 307     if (offset < section->size_of_raw_data) {
 308       return section->file_offset_of_raw_data + offset;
 309     } else {
 310       return kNoOffset;  // In section but not in file (e.g. uninit data).
 311     }
 312   }
 313
 314   // Small RVA values point into the file header in the loaded image.
 315   // RVA 0 is the module load address which Windows uses as the module handle.
 316   // RVA 2 sometimes occurs, I'm not sure what it is, but it would map into the
 317   // DOS header.
 318   if (rva == 0 || rva == 2)
 319     return rva;
 320
 321   NOTREACHED();
 322   return kNoOffset;
 323 }
 324
 325 const uint8* DisassemblerWin32X86::RVAToPointer(RVA rva) const {
 326   int file_offset = RVAToFileOffset(rva);
 327   if (file_offset == kNoOffset)
 328     return NULL;
 329   else
 330     return OffsetToPointer(file_offset);
 331 }
 332
 333 std::string DisassemblerWin32X86::SectionName(const Section* section) {
 334   if (section == NULL)
 335     return "<none>";
 336   char name[9];
 337   memcpy(name, section->name, 8);
 338   name[8] = '\0';  // Ensure termination.
 339   return name;
 340 }
 341
 342 CheckBool DisassemblerWin32X86::ParseFile(AssemblyProgram* program) {
 343   // Walk all the bytes in the file, whether or not in a section.
 344   uint32 file_offset = 0;
 345   while (file_offset < length()) {
 346     const Section* section = FindNextSection(file_offset);
 347     if (section == NULL) {
 348       // No more sections.  There should not be extra stuff following last
 349       // section.
 350       //   ParseNonSectionFileRegion(file_offset, pe_info().length(), program);
 351       break;
 352     }
 353     if (file_offset < section->file_offset_of_raw_data) {
 354       uint32 section_start_offset = section->file_offset_of_raw_data;
 355       if(!ParseNonSectionFileRegion(file_offset, section_start_offset,
 356                                     program))
 357         return false;
 358
 359       file_offset = section_start_offset;
 360     }
 361     uint32 end = file_offset + section->size_of_raw_data;
 362     if (!ParseFileRegion(section, file_offset, end, program))
 363       return false;
 364     file_offset = end;
 365   }
 366
 367 #if COURGETTE_HISTOGRAM_TARGETS
 368   HistogramTargets("abs32 relocs", abs32_target_rvas_);
 369   HistogramTargets("rel32 relocs", rel32_target_rvas_);
 370 #endif
 371
 372   return true;
 373 }
 374
 375 bool DisassemblerWin32X86::ParseAbs32Relocs() {
 376   abs32_locations_.clear();
 377   if (!ParseRelocs(&abs32_locations_))
 378     return false;
 379
 380   std::sort(abs32_locations_.begin(), abs32_locations_.end());
 381
 382 #if COURGETTE_HISTOGRAM_TARGETS
 383   for (size_t i = 0;  i < abs32_locations_.size(); ++i) {
 384     RVA rva = abs32_locations_[i];
 385     // The 4 bytes at the relocation are a reference to some address.
 386     uint32 target_address = Read32LittleEndian(RVAToPointer(rva));
 387     ++abs32_target_rvas_[target_address - image_base()];
 388   }
 389 #endif
 390   return true;
 391 }
 392
 393 void DisassemblerWin32X86::ParseRel32RelocsFromSections() {
 394   uint32 file_offset = 0;
 395   while (file_offset < length()) {
 396     const Section* section = FindNextSection(file_offset);
 397     if (section == NULL)
 398       break;
 399     if (file_offset < section->file_offset_of_raw_data)
 400       file_offset = section->file_offset_of_raw_data;
 401     ParseRel32RelocsFromSection(section);
 402     file_offset += section->size_of_raw_data;
 403   }
 404   std::sort(rel32_locations_.begin(), rel32_locations_.end());
 405
 406 #if COURGETTE_HISTOGRAM_TARGETS
 407   VLOG(1) << "abs32_locations_ " << abs32_locations_.size()
 408           << "\nrel32_locations_ " << rel32_locations_.size()
 409           << "\nabs32_target_rvas_ " << abs32_target_rvas_.size()
 410           << "\nrel32_target_rvas_ " << rel32_target_rvas_.size();
 411
 412   int common = 0;
 413   std::map<RVA, int>::iterator abs32_iter = abs32_target_rvas_.begin();
 414   std::map<RVA, int>::iterator rel32_iter = rel32_target_rvas_.begin();
 415   while (abs32_iter != abs32_target_rvas_.end() &&
 416          rel32_iter != rel32_target_rvas_.end()) {
 417     if (abs32_iter->first < rel32_iter->first)
 418       ++abs32_iter;
 419     else if (rel32_iter->first < abs32_iter->first)
 420       ++rel32_iter;
 421     else {
 422       ++common;
 423       ++abs32_iter;
 424       ++rel32_iter;
 425     }
 426   }
 427   VLOG(1) << "common " << common;
 428 #endif
 429 }
 430
 431 void DisassemblerWin32X86::ParseRel32RelocsFromSection(const Section* section) {
 432   // TODO(sra): use characteristic.
 433   bool isCode = strcmp(section->name, ".text") == 0;
 434   if (!isCode)
 435     return;
 436
 437   uint32 start_file_offset = section->file_offset_of_raw_data;
 438   uint32 end_file_offset = start_file_offset + section->size_of_raw_data;
 439   RVA relocs_start_rva = base_relocation_table().address_;
 440
 441   const uint8* start_pointer = OffsetToPointer(start_file_offset);
 442   const uint8* end_pointer = OffsetToPointer(end_file_offset);
 443
 444   RVA start_rva = FileOffsetToRVA(start_file_offset);
 445   RVA end_rva = start_rva + section->virtual_size;
 446
 447   // Quick way to convert from Pointer to RVA within a single Section is to
 448   // subtract 'pointer_to_rva'.
 449   const uint8* const adjust_pointer_to_rva = start_pointer - start_rva;
 450
 451   std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin();
 452
 453   // Find the rel32 relocations.
 454   const uint8* p = start_pointer;
 455   while (p < end_pointer) {
 456     RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva);
 457     if (current_rva == relocs_start_rva) {
 458       uint32 relocs_size = base_relocation_table().size_;
 459       if (relocs_size) {
 460         p += relocs_size;
 461         continue;
 462       }
 463     }
 464
 465     //while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva)
 466     //  ++abs32_pos;
 467
 468     // Heuristic discovery of rel32 locations in instruction stream: are the
 469     // next few bytes the start of an instruction containing a rel32
 470     // addressing mode?
 471     const uint8* rel32 = NULL;
 472
 473     if (p + 5 <= end_pointer) {
 474       if (*p == 0xE8 || *p == 0xE9) {  // jmp rel32 and call rel32
 475         rel32 = p + 1;
 476       }
 477     }
 478     if (p + 6 <= end_pointer) {
 479       if (*p == 0x0F  &&  (*(p+1) & 0xF0) == 0x80) {  // Jcc long form
 480         if (p[1] != 0x8A && p[1] != 0x8B)  // JPE/JPO unlikely
 481           rel32 = p + 2;
 482       }
 483     }
 484     if (rel32) {
 485       RVA rel32_rva = static_cast<RVA>(rel32 - adjust_pointer_to_rva);
 486
 487       // Is there an abs32 reloc overlapping the candidate?
 488       while (abs32_pos != abs32_locations_.end() && *abs32_pos < rel32_rva - 3)
 489         ++abs32_pos;
 490       // Now: (*abs32_pos > rel32_rva - 4) i.e. the lowest addressed 4-byte
 491       // region that could overlap rel32_rva.
 492       if (abs32_pos != abs32_locations_.end()) {
 493         if (*abs32_pos < rel32_rva + 4) {
 494           // Beginning of abs32 reloc is before end of rel32 reloc so they
 495           // overlap.  Skip four bytes past the abs32 reloc.
 496           p += (*abs32_pos + 4) - current_rva;
 497           continue;
 498         }
 499       }
 500
 501       RVA target_rva = rel32_rva + 4 + Read32LittleEndian(rel32);
 502       // To be valid, rel32 target must be within image, and within this
 503       // section.
 504       if (IsValidRVA(target_rva) &&
 505           start_rva <= target_rva && target_rva < end_rva) {
 506         rel32_locations_.push_back(rel32_rva);
 507 #if COURGETTE_HISTOGRAM_TARGETS
 508         ++rel32_target_rvas_[target_rva];
 509 #endif
 510         p = rel32 + 4;
 511         continue;
 512       }
 513     }
 514     p += 1;
 515   }
 516 }
 517
 518 CheckBool DisassemblerWin32X86::ParseNonSectionFileRegion(
 519     uint32 start_file_offset,
 520     uint32 end_file_offset,
 521     AssemblyProgram* program) {
 522   if (incomplete_disassembly_)
 523     return true;
 524
 525   if (end_file_offset > start_file_offset) {
 526     if (!program->EmitBytesInstruction(OffsetToPointer(start_file_offset),
 527                                        end_file_offset - start_file_offset)) {
 528       return false;
 529     }
 530   }
 531
 532   return true;
 533 }
 534
 535 CheckBool DisassemblerWin32X86::ParseFileRegion(
 536     const Section* section,
 537     uint32 start_file_offset, uint32 end_file_offset,
 538     AssemblyProgram* program) {
 539   RVA relocs_start_rva = base_relocation_table().address_;
 540
 541   const uint8* start_pointer = OffsetToPointer(start_file_offset);
 542   const uint8* end_pointer = OffsetToPointer(end_file_offset);
 543
 544   RVA start_rva = FileOffsetToRVA(start_file_offset);
 545   RVA end_rva = start_rva + section->virtual_size;
 546
 547   // Quick way to convert from Pointer to RVA within a single Section is to
 548   // subtract 'pointer_to_rva'.
 549   const uint8* const adjust_pointer_to_rva = start_pointer - start_rva;
 550
 551   std::vector<RVA>::iterator rel32_pos = rel32_locations_.begin();
 552   std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin();
 553
 554   if (!program->EmitOriginInstruction(start_rva))
 555     return false;
 556
 557   const uint8* p = start_pointer;
 558
 559   while (p < end_pointer) {
 560     RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva);
 561
 562     // The base relocation table is usually in the .relocs section, but it could
 563     // actually be anywhere.  Make sure we skip it because we will regenerate it
 564     // during assembly.
 565     if (current_rva == relocs_start_rva) {
 566       if (!program->EmitPeRelocsInstruction())
 567         return false;
 568       uint32 relocs_size = base_relocation_table().size_;
 569       if (relocs_size) {
 570         p += relocs_size;
 571         continue;
 572       }
 573     }
 574
 575     while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva)
 576       ++abs32_pos;
 577
 578     if (abs32_pos != abs32_locations_.end() && *abs32_pos == current_rva) {
 579       uint32 target_address = Read32LittleEndian(p);
 580       RVA target_rva = target_address - image_base();
 581       // TODO(sra): target could be Label+offset.  It is not clear how to guess
 582       // which it might be.  We assume offset==0.
 583       if (!program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva)))
 584         return false;
 585       p += 4;
 586       continue;
 587     }
 588
 589     while (rel32_pos != rel32_locations_.end() && *rel32_pos < current_rva)
 590       ++rel32_pos;
 591
 592     if (rel32_pos != rel32_locations_.end() && *rel32_pos == current_rva) {
 593       RVA target_rva = current_rva + 4 + Read32LittleEndian(p);
 594       if (!program->EmitRel32(program->FindOrMakeRel32Label(target_rva)))
 595         return false;
 596       p += 4;
 597       continue;
 598     }
 599
 600     if (incomplete_disassembly_) {
 601       if ((abs32_pos == abs32_locations_.end() || end_rva <= *abs32_pos) &&
 602           (rel32_pos == rel32_locations_.end() || end_rva <= *rel32_pos) &&
 603           (end_rva <= relocs_start_rva || current_rva >= relocs_start_rva)) {
 604         // No more relocs in this section, don't bother encoding bytes.
 605         break;
 606       }
 607     }
 608
 609     if (!program->EmitByteInstruction(*p))
 610       return false;
 611     p += 1;
 612   }
 613
 614   return true;
 615 }
 616
 617 #if COURGETTE_HISTOGRAM_TARGETS
 618 // Histogram is printed to std::cout.  It is purely for debugging the algorithm
 619 // and is only enabled manually in 'exploration' builds.  I don't want to add
 620 // command-line configuration for this feature because this code has to be
 621 // small, which means compiled-out.
 622 void DisassemblerWin32X86::HistogramTargets(const char* kind,
 623                                             const std::map<RVA, int>& map) {
 624   int total = 0;
 625   std::map<int, std::vector<RVA> > h;
 626   for (std::map<RVA, int>::const_iterator p = map.begin();
 627        p != map.end();
 628        ++p) {
 629     h[p->second].push_back(p->first);
 630     total += p->second;
 631   }
 632
 633   std::cout << total << " " << kind << " to "
 634             << map.size() << " unique targets" << std::endl;
 635
 636   std::cout << "indegree: #targets-with-indegree (example)" << std::endl;
 637   const int kFirstN = 15;
 638   bool someSkipped = false;
 639   int index = 0;
 640   for (std::map<int, std::vector<RVA> >::reverse_iterator p = h.rbegin();
 641        p != h.rend();
 642        ++p) {
 643     ++index;
 644     if (index <= kFirstN || p->first <= 3) {
 645       if (someSkipped) {
 646         std::cout << "..." << std::endl;
 647       }
 648       size_t count = p->second.size();
 649       std::cout << std::dec << p->first << ": " << count;
 650       if (count <= 2) {
 651         for (size_t i = 0;  i < count;  ++i)
 652           std::cout << "  " << DescribeRVA(p->second[i]);
 653       }
 654       std::cout << std::endl;
 655       someSkipped = false;
 656     } else {
 657       someSkipped = true;
 658     }
 659   }
 660 }
 661 #endif  // COURGETTE_HISTOGRAM_TARGETS
 662
 663
 664 // DescribeRVA is for debugging only.  I would put it under #ifdef DEBUG except
 665 // that during development I'm finding I need to call it when compiled in
 666 // Release mode.  Hence:
 667 // TODO(sra): make this compile only for debug mode.
 668 std::string DisassemblerWin32X86::DescribeRVA(RVA rva) const {
 669   const Section* section = RVAToSection(rva);
 670   std::ostringstream s;
 671   s << std::hex << rva;
 672   if (section) {
 673     s << " (";
 674     s << SectionName(section) << "+"
 675       << std::hex << (rva - section->virtual_address)
 676       << ")";
 677   }
 678   return s.str();
 679 }
 680
 681 const Section* DisassemblerWin32X86::FindNextSection(uint32 fileOffset) const {
 682   const Section* best = 0;
 683   for (int i = 0; i < number_of_sections_; i++) {
 684     const Section* section = &sections_[i];
 685     if (section->size_of_raw_data > 0) {  // i.e. has data in file.
 686       if (fileOffset <= section->file_offset_of_raw_data) {
 687         if (best == 0 ||
 688             section->file_offset_of_raw_data < best->file_offset_of_raw_data) {
 689           best = section;
 690         }
 691       }
 692     }
 693   }
 694   return best;
 695 }
 696
 697 RVA DisassemblerWin32X86::FileOffsetToRVA(uint32 file_offset) const {
 698   for (int i = 0; i < number_of_sections_; i++) {
 699     const Section* section = &sections_[i];
 700     uint32 offset = file_offset - section->file_offset_of_raw_data;
 701     if (offset < section->size_of_raw_data) {
 702       return section->virtual_address + offset;
 703     }
 704   }
 705   return 0;
 706 }
 707
 708 bool DisassemblerWin32X86::ReadDataDirectory(
 709     int index,
 710     ImageDataDirectory* directory) {
 711
 712   if (index < number_of_data_directories_) {
 713     size_t offset = index * 8 + offset_of_data_directories_;
 714     if (offset >= size_of_optional_header_)
 715       return Bad("number of data directories inconsistent");
 716     const uint8* data_directory = optional_header_ + offset;
 717     if (data_directory < start() ||
 718         data_directory + 8 >= end())
 719       return Bad("data directory outside image");
 720     RVA rva = ReadU32(data_directory, 0);
 721     size_t size  = ReadU32(data_directory, 4);
 722     if (size > size_of_image_)
 723       return Bad("data directory size too big");
 724
 725     // TODO(sra): validate RVA.
 726     directory->address_ = rva;
 727     directory->size_ = static_cast<uint32>(size);
 728     return true;
 729   } else {
 730     directory->address_ = 0;
 731     directory->size_ = 0;
 732     return true;
 733   }
 734 }
 735
 736 }  // namespace courgette