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           } else if (0 == strncmp(&Sec.sectname[0], "__debug_info", 16)) {
 282             yaml2debug_info(OS, Obj.DWARF);
 283           }
 284         } else {
 285           // Fills section data with 0xDEADBEEF
 286           Fill(OS, Sec.size, 0xDEADBEEFu);
 287         }
 288       }
 289       uint64_t segSize = is64Bit ? LC.Data.segment_command_64_data.filesize
 290                                  : LC.Data.segment_command_data.filesize;
 291       ZeroToOffset(OS, segOff + segSize);
 292       break;
 293     }
 294   }
 295   // Old PPC Object Files didn't have __LINKEDIT segments, the data was just
 296   // stuck at the end of the file.
 297   if (!FoundLinkEditSeg) {
 298     if (auto Err = writeLinkEditData(OS))
 299       return Err;
 300   }
 301   return Error::success();
 302 }
 303
 304 void MachOWriter::writeBindOpcodes(
 305     raw_ostream &OS, std::vector<MachOYAML::BindOpcode> &BindOpcodes) {
 306
 307   for (auto Opcode : BindOpcodes) {
 308     uint8_t OpByte = Opcode.Opcode | Opcode.Imm;
 309     OS.write(reinterpret_cast<char *>(&OpByte), 1);
 310     for (auto Data : Opcode.ULEBExtraData) {
 311       encodeULEB128(Data, OS);
 312     }
 313     for (auto Data : Opcode.SLEBExtraData) {
 314       encodeSLEB128(Data, OS);
 315     }
 316     if (!Opcode.Symbol.empty()) {
 317       OS.write(Opcode.Symbol.data(), Opcode.Symbol.size());
 318       OS.write('\0');
 319     }
 320   }
 321 }
 322
 323 void MachOWriter::dumpExportEntry(raw_ostream &OS,
 324                                   MachOYAML::ExportEntry &Entry) {
 325   encodeSLEB128(Entry.TerminalSize, OS);
 326   if (Entry.TerminalSize > 0) {
 327     encodeSLEB128(Entry.Flags, OS);
 328     if (Entry.Flags & MachO::EXPORT_SYMBOL_FLAGS_REEXPORT) {
 329       encodeSLEB128(Entry.Other, OS);
 330       OS << Entry.ImportName;
 331       OS.write('\0');
 332     } else {
 333       encodeSLEB128(Entry.Address, OS);
 334       if (Entry.Flags & MachO::EXPORT_SYMBOL_FLAGS_STUB_AND_RESOLVER)
 335         encodeSLEB128(Entry.Other, OS);
 336     }
 337   }
 338   OS.write(static_cast<uint8_t>(Entry.Children.size()));
 339   for (auto EE : Entry.Children) {
 340     OS << EE.Name;
 341     OS.write('\0');
 342     encodeSLEB128(EE.NodeOffset, OS);
 343   }
 344   for (auto EE : Entry.Children)
 345     dumpExportEntry(OS, EE);
 346 }
 347
 348 Error MachOWriter::writeExportTrie(raw_ostream &OS) {
 349   dumpExportEntry(OS, Obj.LinkEdit.ExportTrie);
 350   return Error::success();
 351 }
 352
 353 template <typename NListType>
 354 void writeNListEntry(MachOYAML::NListEntry &NLE, raw_ostream &OS,
 355                      bool IsLittleEndian) {
 356   NListType ListEntry;
 357   ListEntry.n_strx = NLE.n_strx;
 358   ListEntry.n_type = NLE.n_type;
 359   ListEntry.n_sect = NLE.n_sect;
 360   ListEntry.n_desc = NLE.n_desc;
 361   ListEntry.n_value = NLE.n_value;
 362
 363   if (IsLittleEndian != sys::IsLittleEndianHost)
 364     MachO::swapStruct(ListEntry);
 365   OS.write(reinterpret_cast<const char *>(&ListEntry), sizeof(NListType));
 366 }
 367
 368 Error MachOWriter::writeLinkEditData(raw_ostream &OS) {
 369   typedef Error (MachOWriter::*writeHandler)(raw_ostream &);
 370   typedef std::pair<uint64_t, writeHandler> writeOperation;
 371   std::vector<writeOperation> WriteQueue;
 372
 373   MachO::dyld_info_command *DyldInfoOnlyCmd = 0;
 374   MachO::symtab_command *SymtabCmd = 0;
 375   for (auto &LC : Obj.LoadCommands) {
 376     switch (LC.Data.load_command_data.cmd) {
 377     case MachO::LC_SYMTAB:
 378       SymtabCmd = &LC.Data.symtab_command_data;
 379       WriteQueue.push_back(
 380           std::make_pair(SymtabCmd->symoff, &MachOWriter::writeNameList));
 381       WriteQueue.push_back(
 382           std::make_pair(SymtabCmd->stroff, &MachOWriter::writeStringTable));
 383       break;
 384     case MachO::LC_DYLD_INFO_ONLY:
 385       DyldInfoOnlyCmd = &LC.Data.dyld_info_command_data;
 386       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->rebase_off,
 387                                           &MachOWriter::writeRebaseOpcodes));
 388       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->bind_off,
 389                                           &MachOWriter::writeBasicBindOpcodes));
 390       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->weak_bind_off,
 391                                           &MachOWriter::writeWeakBindOpcodes));
 392       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->lazy_bind_off,
 393                                           &MachOWriter::writeLazyBindOpcodes));
 394       WriteQueue.push_back(std::make_pair(DyldInfoOnlyCmd->export_off,
 395                                           &MachOWriter::writeExportTrie));
 396       break;
 397     }
 398   }
 399
 400   std::sort(WriteQueue.begin(), WriteQueue.end(),
 401             [](const writeOperation &a, const writeOperation &b) {
 402               return a.first < b.first;
 403             });
 404
 405   for (auto writeOp : WriteQueue) {
 406     ZeroToOffset(OS, writeOp.first);
 407     if (auto Err = (this->*writeOp.second)(OS))
 408       return Err;
 409   }
 410
 411   return Error::success();
 412 }
 413
 414 Error MachOWriter::writeRebaseOpcodes(raw_ostream &OS) {
 415   MachOYAML::LinkEditData &LinkEdit = Obj.LinkEdit;
 416
 417   for (auto Opcode : LinkEdit.RebaseOpcodes) {
 418     uint8_t OpByte = Opcode.Opcode | Opcode.Imm;
 419     OS.write(reinterpret_cast<char *>(&OpByte), 1);
 420     for (auto Data : Opcode.ExtraData) {
 421       encodeULEB128(Data, OS);
 422     }
 423   }
 424   return Error::success();
 425 }
 426
 427 Error MachOWriter::writeBasicBindOpcodes(raw_ostream &OS) {
 428   writeBindOpcodes(OS, Obj.LinkEdit.BindOpcodes);
 429   return Error::success();
 430 }
 431
 432 Error MachOWriter::writeWeakBindOpcodes(raw_ostream &OS) {
 433   writeBindOpcodes(OS, Obj.LinkEdit.WeakBindOpcodes);
 434   return Error::success();
 435 }
 436
 437 Error MachOWriter::writeLazyBindOpcodes(raw_ostream &OS) {
 438   writeBindOpcodes(OS, Obj.LinkEdit.LazyBindOpcodes);
 439   return Error::success();
 440 }
 441
 442 Error MachOWriter::writeNameList(raw_ostream &OS) {
 443   for (auto NLE : Obj.LinkEdit.NameList) {
 444     if (is64Bit)
 445       writeNListEntry<MachO::nlist_64>(NLE, OS, Obj.IsLittleEndian);
 446     else
 447       writeNListEntry<MachO::nlist>(NLE, OS, Obj.IsLittleEndian);
 448   }
 449   return Error::success();
 450 }
 451
 452 Error MachOWriter::writeStringTable(raw_ostream &OS) {
 453   for (auto Str : Obj.LinkEdit.StringTable) {
 454     OS.write(Str.data(), Str.size());
 455     OS.write('\0');
 456   }
 457   return Error::success();
 458 }
 459
 460 class UniversalWriter {
 461 public:
 462   UniversalWriter(yaml::YamlObjectFile &ObjectFile)
 463       : ObjectFile(ObjectFile), fileStart(0) {}
 464
 465   Error writeMachO(raw_ostream &OS);
 466
 467 private:
 468   Error writeFatHeader(raw_ostream &OS);
 469   Error writeFatArchs(raw_ostream &OS);
 470
 471   void ZeroToOffset(raw_ostream &OS, size_t offset);
 472
 473   yaml::YamlObjectFile &ObjectFile;
 474   uint64_t fileStart;
 475 };
 476
 477 Error UniversalWriter::writeMachO(raw_ostream &OS) {
 478   fileStart = OS.tell();
 479   if (ObjectFile.MachO) {
 480     MachOWriter Writer(*ObjectFile.MachO);
 481     return Writer.writeMachO(OS);
 482   }
 483   if (auto Err = writeFatHeader(OS))
 484     return Err;
 485   if (auto Err = writeFatArchs(OS))
 486     return Err;
 487   auto &FatFile = *ObjectFile.FatMachO;
 488   assert(FatFile.FatArchs.size() == FatFile.Slices.size());
 489   for (size_t i = 0; i < FatFile.Slices.size(); i++) {
 490     ZeroToOffset(OS, FatFile.FatArchs[i].offset);
 491     MachOWriter Writer(FatFile.Slices[i]);
 492     if (auto Err = Writer.writeMachO(OS))
 493       return Err;
 494     auto SliceEnd = FatFile.FatArchs[i].offset + FatFile.FatArchs[i].size;
 495     ZeroToOffset(OS, SliceEnd);
 496   }
 497   return Error::success();
 498 }
 499
 500 Error UniversalWriter::writeFatHeader(raw_ostream &OS) {
 501   auto &FatFile = *ObjectFile.FatMachO;
 502   MachO::fat_header header;
 503   header.magic = FatFile.Header.magic;
 504   header.nfat_arch = FatFile.Header.nfat_arch;
 505   if (sys::IsLittleEndianHost)
 506     swapStruct(header);
 507   OS.write(reinterpret_cast<const char *>(&header), sizeof(MachO::fat_header));
 508   return Error::success();
 509 }
 510
 511 template <typename FatArchType>
 512 FatArchType constructFatArch(MachOYAML::FatArch &Arch) {
 513   FatArchType FatArch;
 514   FatArch.cputype = Arch.cputype;
 515   FatArch.cpusubtype = Arch.cpusubtype;
 516   FatArch.offset = Arch.offset;
 517   FatArch.size = Arch.size;
 518   FatArch.align = Arch.align;
 519   return FatArch;
 520 }
 521
 522 template <typename StructType>
 523 void writeFatArch(MachOYAML::FatArch &LC, raw_ostream &OS) {}
 524
 525 template <>
 526 void writeFatArch<MachO::fat_arch>(MachOYAML::FatArch &Arch, raw_ostream &OS) {
 527   auto FatArch = constructFatArch<MachO::fat_arch>(Arch);
 528   if (sys::IsLittleEndianHost)
 529     swapStruct(FatArch);
 530   OS.write(reinterpret_cast<const char *>(&FatArch), sizeof(MachO::fat_arch));
 531 }
 532
 533 template <>
 534 void writeFatArch<MachO::fat_arch_64>(MachOYAML::FatArch &Arch,
 535                                       raw_ostream &OS) {
 536   auto FatArch = constructFatArch<MachO::fat_arch_64>(Arch);
 537   FatArch.reserved = Arch.reserved;
 538   if (sys::IsLittleEndianHost)
 539     swapStruct(FatArch);
 540   OS.write(reinterpret_cast<const char *>(&FatArch),
 541            sizeof(MachO::fat_arch_64));
 542 }
 543
 544 Error UniversalWriter::writeFatArchs(raw_ostream &OS) {
 545   auto &FatFile = *ObjectFile.FatMachO;
 546   bool is64Bit = FatFile.Header.magic == MachO::FAT_MAGIC_64;
 547   for (auto Arch : FatFile.FatArchs) {
 548     if (is64Bit)
 549       writeFatArch<MachO::fat_arch_64>(Arch, OS);
 550     else
 551       writeFatArch<MachO::fat_arch>(Arch, OS);
 552   }
 553
 554   return Error::success();
 555 }
 556
 557 void UniversalWriter::ZeroToOffset(raw_ostream &OS, size_t Offset) {
 558   auto currOffset = OS.tell() - fileStart;
 559   if (currOffset < Offset)
 560     ZeroFillBytes(OS, Offset - currOffset);
 561 }
 562
 563 } // end anonymous namespace
 564
 565 int yaml2macho(yaml::YamlObjectFile &Doc, raw_ostream &Out) {
 566   UniversalWriter Writer(Doc);
 567   if (auto Err = Writer.writeMachO(Out)) {
 568     errs() << toString(std::move(Err));
 569     return 1;
 570   }
 571   return 0;
 572 }