tools/yaml2obj/yaml2macho.cpp

   1 //===- yaml2macho - Convert YAML to a Mach object file --------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 ///
  10 /// \file
  11 /// \brief The Mach component of yaml2obj.
  12 ///
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "yaml2obj.h"
  16 #include "llvm/ObjectYAML/ObjectYAML.h"
  17 #include "llvm/Support/Error.h"
  18 #include "llvm/Support/LEB128.h"
  19 #include "llvm/Support/MachO.h"
  20 #include "llvm/Support/YAMLTraits.h"
  21 #include "llvm/Support/raw_ostream.h"
  22
  23 #include "llvm/Support/Format.h"
  24
  25 using namespace llvm;
  26
  27 namespace {
  28
  29 class MachOWriter {
  30 public:
  31   MachOWriter(MachOYAML::Object &Obj) : Obj(Obj), is64Bit(true), fileStart(0) {
  32     is64Bit = Obj.Header.magic == MachO::MH_MAGIC_64 ||
  33               Obj.Header.magic == MachO::MH_CIGAM_64;
  34     memset(reinterpret_cast<void *>(&Header), 0, sizeof(MachO::mach_header_64));
  35   }
  36
  37   Error writeMachO(raw_ostream &OS);
  38
  39 private:
  40   Error writeHeader(raw_ostream &OS);
  41   Error writeLoadCommands(raw_ostream &OS);
  42   Error writeSectionData(raw_ostream &OS);
  43   Error writeLinkEditData(raw_ostream &OS);
  44
  45   void writeBindOpcodes(raw_ostream &OS,
  46                         std::vector<MachOYAML::BindOpcode> &BindOpcodes);
  47   // LinkEdit writers
  48   Error writeRebaseOpcodes(raw_ostream &OS);
  49   Error writeBasicBindOpcodes(raw_ostream &OS);
  50   Error writeWeakBindOpcodes(raw_ostream &OS);
  51   Error writeLazyBindOpcodes(raw_ostream &OS);
  52   Error writeNameList(raw_ostream &OS);
  53   Error writeStringTable(raw_ostream &OS);
  54   Error writeExportTrie(raw_ostream &OS);
  55
  56   void dumpExportEntry(raw_ostream &OS, MachOYAML::ExportEntry &Entry);
  57   void ZeroToOffset(raw_ostream &OS, size_t offset);
  58
  59   MachOYAML::Object &Obj;
  60   bool is64Bit;
  61   uint64_t fileStart;
  62
  63   MachO::mach_header_64 Header;
  64 };
  65
  66 Error MachOWriter::writeMachO(raw_ostream &OS) {
  67   fileStart = OS.tell();
  68   if (auto Err = writeHeader(OS))
  69     return Err;
  70   if (auto Err = writeLoadCommands(OS))
  71     return Err;
  72   if (auto Err = writeSectionData(OS))
  73     return Err;
  74   return Error::success();
  75 }
  76
  77 Error MachOWriter::writeHeader(raw_ostream &OS) {
  78   Header.magic = Obj.Header.magic;
  79   Header.cputype = Obj.Header.cputype;
  80   Header.cpusubtype = Obj.Header.cpusubtype;
  81   Header.filetype = Obj.Header.filetype;
  82   Header.ncmds = Obj.Header.ncmds;
  83   Header.sizeofcmds = Obj.Header.sizeofcmds;
  84   Header.flags = Obj.Header.flags;
  85   Header.reserved = Obj.Header.reserved;
  86
  87   if (Obj.IsLittleEndian != sys::IsLittleEndianHost)
  88     MachO::swapStruct(Header);
  89
  90   auto header_size =
  91       is64Bit ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
  92   OS.write((const char *)&Header, header_size);
  93
  94   return Error::success();
  95 }
  96
  97 template <typename SectionType>
  98 SectionType constructSection(MachOYAML::Section Sec) {
  99   SectionType TempSec;
 100   memcpy(reinterpret_cast<void *>(&TempSec.sectname[0]), &Sec.sectname[0], 16);
 101   memcpy(reinterpret_cast<void *>(&TempSec.segname[0]), &Sec.segname[0], 16);
 102   TempSec.addr = Sec.addr;
 103   TempSec.size = Sec.size;
 104   TempSec.offset = Sec.offset;
 105   TempSec.align = Sec.align;
 106   TempSec.reloff = Sec.reloff;
 107   TempSec.nreloc = Sec.nreloc;
 108   TempSec.flags = Sec.flags;
 109   TempSec.reserved1 = Sec.reserved1;
 110   TempSec.reserved2 = Sec.reserved2;
 111   return TempSec;
 112 }
 113
 114 template <typename StructType>
 115 size_t writeLoadCommandData(MachOYAML::LoadCommand &LC, raw_ostream &OS,
 116                             bool IsLittleEndian) {
 117   return 0;
 118 }
 119
 120 template <>
 121 size_t writeLoadCommandData<MachO::segment_command>(MachOYAML::LoadCommand &LC,
 122                                                     raw_ostream &OS,
 123                                                     bool IsLittleEndian) {
 124   size_t BytesWritten = 0;
 125   for (const auto &Sec : LC.Sections) {
 126     auto TempSec = constructSection<MachO::section>(Sec);
 127     if (IsLittleEndian != sys::IsLittleEndianHost)
 128       MachO::swapStruct(TempSec);
 129     OS.write(reinterpret_cast<const char *>(&(TempSec)),
 130              sizeof(MachO::section));
 131     BytesWritten += sizeof(MachO::section);
 132   }
 133   return BytesWritten;
 134 }
 135
 136 template <>
 137 size_t writeLoadCommandData<MachO::segment_command_64>(
 138     MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
 139   size_t BytesWritten = 0;
 140   for (const auto &Sec : LC.Sections) {
 141     auto TempSec = constructSection<MachO::section_64>(Sec);
 142     TempSec.reserved3 = Sec.reserved3;
 143     if (IsLittleEndian != sys::IsLittleEndianHost)
 144       MachO::swapStruct(TempSec);
 145     OS.write(reinterpret_cast<const char *>(&(TempSec)),
 146              sizeof(MachO::section_64));
 147     BytesWritten += sizeof(MachO::section_64);
 148   }
 149   return BytesWritten;
 150 }
 151
 152 size_t writePayloadString(MachOYAML::LoadCommand &LC, raw_ostream &OS) {
 153   size_t BytesWritten = 0;
 154   if (!LC.PayloadString.empty()) {
 155     OS.write(LC.PayloadString.c_str(), LC.PayloadString.length());
 156     BytesWritten = LC.PayloadString.length();
 157   }
 158   return BytesWritten;
 159 }
 160
 161 template <>
 162 size_t writeLoadCommandData<MachO::dylib_command>(MachOYAML::LoadCommand &LC,
 163                                                   raw_ostream &OS,
 164                                                   bool IsLittleEndian) {
 165   return writePayloadString(LC, OS);
 166 }
 167
 168 template <>
 169 size_t writeLoadCommandData<MachO::dylinker_command>(MachOYAML::LoadCommand &LC,
 170                                                      raw_ostream &OS,
 171                                                      bool IsLittleEndian) {
 172   return writePayloadString(LC, OS);
 173 }
 174
 175 template <>
 176 size_t writeLoadCommandData<MachO::rpath_command>(MachOYAML::LoadCommand &LC,
 177                                                   raw_ostream &OS,
 178                                                   bool IsLittleEndian) {
 179   return writePayloadString(LC, OS);
 180 }
 181
 182 void ZeroFillBytes(raw_ostream &OS, size_t Size) {
 183   std::vector<uint8_t> FillData;
 184   FillData.insert(FillData.begin(), Size, 0);
 185   OS.write(reinterpret_cast<char *>(FillData.data()), Size);
 186 }
 187
 188 void Fill(raw_ostream &OS, size_t Size, uint32_t Data) {
 189   std::vector<uint32_t> FillData;
 190   FillData.insert(FillData.begin(), (Size / 4) + 1, Data);
 191   OS.write(reinterpret_cast<char *>(FillData.data()), Size);
 192 }
 193
 194 void MachOWriter::ZeroToOffset(raw_ostream &OS, size_t Offset) {
 195   auto currOffset = OS.tell() - fileStart;
 196   if (currOffset < Offset)
 197     ZeroFillBytes(OS, Offset - currOffset);
 198 }
 199
 200 Error MachOWriter::writeLoadCommands(raw_ostream &OS) {
 201   for (auto &LC : Obj.LoadCommands) {
 202     size_t BytesWritten = 0;
 203     llvm::MachO::macho_load_command Data = LC.Data;
 204
 205 #define HANDLE_LOAD_COMMAND(LCName, LCValue, LCStruct)                         \
 206   case MachO::LCName:                                                          \
 207     if (Obj.IsLittleEndian != sys::IsLittleEndianHost)                         \
 208       MachO::swapStruct(Data.LCStruct##_data);                                 \
 209     OS.write(reinterpret_cast<const char *>(&(Data.LCStruct##_data)),          \
 210              sizeof(MachO::LCStruct));                                         \
 211     BytesWritten = sizeof(MachO::LCStruct);                                    \
 212     BytesWritten +=                                                            \
 213         writeLoadCommandData<MachO::LCStruct>(LC, OS, Obj.IsLittleEndian);     \
 214     break;
 215
 216     switch (LC.Data.load_command_data.cmd) {
 217     default:
 218       if (Obj.IsLittleEndian != sys::IsLittleEndianHost)
 219         MachO::swapStruct(Data.load_command_data);
 220       OS.write(reinterpret_cast<const char *>(&(Data.load_command_data)),
 221                sizeof(MachO::load_command));
 222       BytesWritten = sizeof(MachO::load_command);
 223       BytesWritten +=
 224           writeLoadCommandData<MachO::load_command>(LC, OS, Obj.IsLittleEndian);
 225       break;
 226 #include "llvm/Support/MachO.def"
 227     }
 228
 229     if (LC.PayloadBytes.size() > 0) {
 230       OS.write(reinterpret_cast<const char *>(LC.PayloadBytes.data()),
 231                LC.PayloadBytes.size());
 232       BytesWritten += LC.PayloadBytes.size();
 233     }
 234
 235     if (LC.ZeroPadBytes > 0) {
 236       ZeroFillBytes(OS, LC.ZeroPadBytes);
 237       BytesWritten += LC.ZeroPadBytes;
 238     }
 239
 240     // Fill remaining bytes with 0. This will only get hit in partially
 241     // specified test cases.
 242     auto BytesRemaining = LC.Data.load_command_data.cmdsize - BytesWritten;
 243     if (BytesRemaining > 0) {
 244       ZeroFillBytes(OS, BytesRemaining);
 245     }
 246   }
 247   return Error::success();
 248 }
 249
 250 Error MachOWriter::writeSectionData(raw_ostream &OS) {
 251   bool FoundLinkEditSeg = false;
 252   for (auto &LC : Obj.LoadCommands) {
 253     switch (LC.Data.load_command_data.cmd) {
 254     case MachO::LC_SEGMENT:
 255     case MachO::LC_SEGMENT_64:
 256       uint64_t segOff = is64Bit ? LC.Data.segment_command_64_data.fileoff
 257                                 : LC.Data.segment_command_data.fileoff;
 258       if (0 == strncmp(&LC.Data.segment_command_data.segname[0], "__LINKEDIT", 16)) {
 259         FoundLinkEditSeg = true;
 260         if (auto Err = writeLinkEditData(OS))
 261           return Err;
 262       }
 263       for (auto &Sec : LC.Sections) {
 264         ZeroToOffset(OS, Sec.offset);
 265         // Zero Fill any data between the end of the last thing we wrote and the
 266         // start of this section.
 267         assert((OS.tell() - fileStart <= Sec.offset ||
 268                 Sec.offset == (uint32_t)0) &&
 269                "Wrote too much data somewhere, section offsets don't line up.");
 270         if (0 == strncmp(&Sec.segname[0], "__DWARF", 16)) {
 271           if (0 == strncmp(&Sec.sectname[0], "__debug_str", 16)) {
 272             yaml2debug_str(OS, Obj.DWARF);
 273           } else if (0 == strncmp(&Sec.sectname[0], "__debug_abbrev", 16)) {
 274             yaml2debug_abbrev(OS, Obj.DWARF);
 275           } else if (0 == strncmp(&Sec.sectname[0], "__debug_aranges", 16)) {
 276             yaml2debug_aranges(OS, Obj.DWARF);
 277           } else if (0 == strncmp(&Sec.sectname[0], "__debug_pubnames", 16)) {
 278             yaml2pubsection(OS, Obj.DWARF.PubNames, Obj.IsLittleEndian);
 279           } else if (0 == strncmp(&Sec.sectname[0], "__debug_pubtypes", 16)) {
 280             yaml2pubsection(OS, Obj.DWARF.PubTypes, Obj.IsLittleEndian);
 281           }
 282         } else {
 283           // Fills section data with 0xDEADBEEF
 284           Fill(OS, Sec.size, 0xDEADBEEFu);
 285         }
 286       }
 287       uint64_t segSize = is64Bit ? LC.Data.segment_command_64_data.filesize
 288                                  : LC.Data.segment_command_data.filesize;
 289       ZeroToOffset(OS, segOff + segSize);
 290       break;
 291     }
 292   }
 293   // Old PPC Object Files didn't have __LINKEDIT segments, the data was just
 294   // stuck at the end of the file.
 295   if (!FoundLinkEditSeg) {
 296     if (auto Err = writeLinkEditData(OS))
 297       return Err;
 298   }
 299   return Error::success();
 300 }
 301
 302 void MachOWriter::writeBindOpcodes(
 303     raw_ostream &OS, std::vector<MachOYAML::BindOpcode> &BindOpcodes) {
 304
 305   for (auto Opcode : BindOpcodes) {
 306     uint8_t OpByte = Opcode.Opcode | Opcode.Imm;
 307     OS.write(reinterpret_cast<char *>(&OpByte), 1);
 308     for (auto Data : Opcode.ULEBExtraData) {
 309       encodeULEB128(Data, OS);
 310     }
 311     for (auto Data : Opcode.SLEBExtraData) {
 312       encodeSLEB128(Data, OS);
 313     }
 314     if (!Opcode.Symbol.empty()) {
 315       OS.write(Opcode.Symbol.data(), Opcode.Symbol.size());
 316       OS.write('\0');
 317     }
 318   }
 319 }
 320
 321 void MachOWriter::dumpExportEntry(raw_ostream &OS,
 322                                   MachOYAML::ExportEntry &Entry) {
 323   encodeSLEB128(Entry.TerminalSize, OS);
 324   if (Entry.TerminalSize > 0) {
 325     encodeSLEB128(Entry.Flags, OS);
 326     if (Entry.Flags & MachO::EXPORT_SYMBOL_FLAGS_REEXPORT) {
 327       encodeSLEB128(Entry.Other, OS);
 328       OS << Entry.ImportName;
 329       OS.write('\0');
 330     } else {
 331       encodeSLEB128(Entry.Address, OS);
 332       if (Entry.Flags & MachO::EXPORT_SYMBOL_FLAGS_STUB_AND_RESOLVER)
 333         encodeSLEB128(Entry.Other, OS);
 334     }
 335   }
 336   OS.write(static_cast<uint8_t>(Entry.Children.size()));
 337   for (auto EE : Entry.Children) {
 338     OS << EE.Name;
 339     OS.write('\0');
 340     encodeSLEB128(EE.NodeOffset, OS);
 341   }
 342   for (auto EE : Entry.Children)
 343     dumpExportEntry(OS, EE);
 344 }
 345
 346 Error MachOWriter::writeExportTrie(raw_ostream &OS) {
 347   dumpExportEntry(OS, Obj.LinkEdit.ExportTrie);
 348   return Error::success();
 349 }
 350
 351 template <typename NListType>
 352 void writeNListEntry(MachOYAML::NListEntry &NLE, raw_ostream &OS,
 353                      bool IsLittleEndian) {
 354   NListType ListEntry;
 355   ListEntry.n_strx = NLE.n_strx;
 356   ListEntry.n_type = NLE.n_type;
 357   ListEntry.n_sect = NLE.n_sect;
 358   ListEntry.n_desc = NLE.n_desc;
 359   ListEntry.n_value = NLE.n_value;
 360
 361   if (IsLittleEndian != sys::IsLittleEndianHost)
 362     MachO::swapStruct(ListEntry);
 363   OS.write(reinterpret_cast<const char *>(&ListEntry), sizeof(NListType));
 364 }
 365
 366 Error MachOWriter::writeLinkEditData(raw_ostream &OS) {
 367   typedef Error (MachOWriter::*writeHandler)(raw_ostream &);
 368   typedef std::pair<uint64_t, writeHandler> writeOperation;
 369   std::vector<writeOperation> WriteQueue;
 370
 371   MachO::dyld_info_command *DyldInfoOnlyCmd = 0;
 372   MachO::symtab_command *SymtabCmd = 0;
 373   for (auto &LC : Obj.LoadCommands) {
 374     switch (LC.Data.load_command_data.cmd) {
 375     case MachO::LC_SYMTAB:
 376       SymtabCmd = &LC.Data.symtab_command_data;
 377       WriteQueue.push_back(
 378           std::make_pair(SymtabCmd->symoff, &MachOWriter::writeNameList));
 379       WriteQueue.push_back(
 380           std::make_pair(SymtabCmd->stroff, &MachOWriter::writeStringTable));
 381       break;
 382     case MachO::LC_DYLD_INFO_ONLY:
 383       DyldInfoOnlyCmd = &LC.Data.dyld_info_command_data;
 384       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->rebase_off,
 385                                           &MachOWriter::writeRebaseOpcodes));
 386       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->bind_off,
 387                                           &MachOWriter::writeBasicBindOpcodes));
 388       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->weak_bind_off,
 389                                           &MachOWriter::writeWeakBindOpcodes));
 390       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->lazy_bind_off,
 391                                           &MachOWriter::writeLazyBindOpcodes));
 392       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->export_off,
 393                                           &MachOWriter::writeExportTrie));
 394       break;
 395     }
 396   }
 397
 398   std::sort(WriteQueue.begin(), WriteQueue.end(),
 399             [](const writeOperation &a, const writeOperation &b) {
 400               return a.first < b.first;
 401             });
 402
 403   for (auto writeOp : WriteQueue) {
 404     ZeroToOffset(OS, writeOp.first);
 405     if (auto Err = (this->*writeOp.second)(OS))
 406       return Err;
 407   }
 408
 409   return Error::success();
 410 }
 411
 412 Error MachOWriter::writeRebaseOpcodes(raw_ostream &OS) {
 413   MachOYAML::LinkEditData &LinkEdit = Obj.LinkEdit;
 414
 415   for (auto Opcode : LinkEdit.RebaseOpcodes) {
 416     uint8_t OpByte = Opcode.Opcode | Opcode.Imm;
 417     OS.write(reinterpret_cast<char *>(&OpByte), 1);
 418     for (auto Data : Opcode.ExtraData) {
 419       encodeULEB128(Data, OS);
 420     }
 421   }
 422   return Error::success();
 423 }
 424
 425 Error MachOWriter::writeBasicBindOpcodes(raw_ostream &OS) {
 426   writeBindOpcodes(OS, Obj.LinkEdit.BindOpcodes);
 427   return Error::success();
 428 }
 429
 430 Error MachOWriter::writeWeakBindOpcodes(raw_ostream &OS) {
 431   writeBindOpcodes(OS, Obj.LinkEdit.WeakBindOpcodes);
 432   return Error::success();
 433 }
 434
 435 Error MachOWriter::writeLazyBindOpcodes(raw_ostream &OS) {
 436   writeBindOpcodes(OS, Obj.LinkEdit.LazyBindOpcodes);
 437   return Error::success();
 438 }
 439
 440 Error MachOWriter::writeNameList(raw_ostream &OS) {
 441   for (auto NLE : Obj.LinkEdit.NameList) {
 442     if (is64Bit)
 443       writeNListEntry<MachO::nlist_64>(NLE, OS, Obj.IsLittleEndian);
 444     else
 445       writeNListEntry<MachO::nlist>(NLE, OS, Obj.IsLittleEndian);
 446   }
 447   return Error::success();
 448 }
 449
 450 Error MachOWriter::writeStringTable(raw_ostream &OS) {
 451   for (auto Str : Obj.LinkEdit.StringTable) {
 452     OS.write(Str.data(), Str.size());
 453     OS.write('\0');
 454   }
 455   return Error::success();
 456 }
 457
 458 class UniversalWriter {
 459 public:
 460   UniversalWriter(yaml::YamlObjectFile &ObjectFile)
 461       : ObjectFile(ObjectFile), fileStart(0) {}
 462
 463   Error writeMachO(raw_ostream &OS);
 464
 465 private:
 466   Error writeFatHeader(raw_ostream &OS);
 467   Error writeFatArchs(raw_ostream &OS);
 468
 469   void ZeroToOffset(raw_ostream &OS, size_t offset);
 470
 471   yaml::YamlObjectFile &ObjectFile;
 472   uint64_t fileStart;
 473 };
 474
 475 Error UniversalWriter::writeMachO(raw_ostream &OS) {
 476   fileStart = OS.tell();
 477   if (ObjectFile.MachO) {
 478     MachOWriter Writer(*ObjectFile.MachO);
 479     return Writer.writeMachO(OS);
 480   }
 481   if (auto Err = writeFatHeader(OS))
 482     return Err;
 483   if (auto Err = writeFatArchs(OS))
 484     return Err;
 485   auto &FatFile = *ObjectFile.FatMachO;
 486   assert(FatFile.FatArchs.size() == FatFile.Slices.size());
 487   for (size_t i = 0; i < FatFile.Slices.size(); i++) {
 488     ZeroToOffset(OS, FatFile.FatArchs[i].offset);
 489     MachOWriter Writer(FatFile.Slices[i]);
 490     if (auto Err = Writer.writeMachO(OS))
 491       return Err;
 492     auto SliceEnd = FatFile.FatArchs[i].offset + FatFile.FatArchs[i].size;
 493     ZeroToOffset(OS, SliceEnd);
 494   }
 495   return Error::success();
 496 }
 497
 498 Error UniversalWriter::writeFatHeader(raw_ostream &OS) {
 499   auto &FatFile = *ObjectFile.FatMachO;
 500   MachO::fat_header header;
 501   header.magic = FatFile.Header.magic;
 502   header.nfat_arch = FatFile.Header.nfat_arch;
 503   if (sys::IsLittleEndianHost)
 504     swapStruct(header);
 505   OS.write(reinterpret_cast<const char *>(&header), sizeof(MachO::fat_header));
 506   return Error::success();
 507 }
 508
 509 template <typename FatArchType>
 510 FatArchType constructFatArch(MachOYAML::FatArch &Arch) {
 511   FatArchType FatArch;
 512   FatArch.cputype = Arch.cputype;
 513   FatArch.cpusubtype = Arch.cpusubtype;
 514   FatArch.offset = Arch.offset;
 515   FatArch.size = Arch.size;
 516   FatArch.align = Arch.align;
 517   return FatArch;
 518 }
 519
 520 template <typename StructType>
 521 void writeFatArch(MachOYAML::FatArch &LC, raw_ostream &OS) {}
 522
 523 template <>
 524 void writeFatArch<MachO::fat_arch>(MachOYAML::FatArch &Arch, raw_ostream &OS) {
 525   auto FatArch = constructFatArch<MachO::fat_arch>(Arch);
 526   if (sys::IsLittleEndianHost)
 527     swapStruct(FatArch);
 528   OS.write(reinterpret_cast<const char *>(&FatArch), sizeof(MachO::fat_arch));
 529 }
 530
 531 template <>
 532 void writeFatArch<MachO::fat_arch_64>(MachOYAML::FatArch &Arch,
 533                                       raw_ostream &OS) {
 534   auto FatArch = constructFatArch<MachO::fat_arch_64>(Arch);
 535   FatArch.reserved = Arch.reserved;
 536   if (sys::IsLittleEndianHost)
 537     swapStruct(FatArch);
 538   OS.write(reinterpret_cast<const char *>(&FatArch),
 539            sizeof(MachO::fat_arch_64));
 540 }
 541
 542 Error UniversalWriter::writeFatArchs(raw_ostream &OS) {
 543   auto &FatFile = *ObjectFile.FatMachO;
 544   bool is64Bit = FatFile.Header.magic == MachO::FAT_MAGIC_64;
 545   for (auto Arch : FatFile.FatArchs) {
 546     if (is64Bit)
 547       writeFatArch<MachO::fat_arch_64>(Arch, OS);
 548     else
 549       writeFatArch<MachO::fat_arch>(Arch, OS);
 550   }
 551
 552   return Error::success();
 553 }
 554
 555 void UniversalWriter::ZeroToOffset(raw_ostream &OS, size_t Offset) {
 556   auto currOffset = OS.tell() - fileStart;
 557   if (currOffset < Offset)
 558     ZeroFillBytes(OS, Offset - currOffset);
 559 }
 560
 561 } // end anonymous namespace
 562
 563 int yaml2macho(yaml::YamlObjectFile &Doc, raw_ostream &Out) {
 564   UniversalWriter Writer(Doc);
 565   if (auto Err = Writer.writeMachO(Out)) {
 566     errs() << toString(std::move(Err));
 567     return 1;
 568   }
 569   return 0;
 570 }