contrib/llvm/tools/lld/lib/ReaderWriter/MachO/MachONormalizedFileBinaryReader.cpp

   1 //===- lib/ReaderWriter/MachO/MachONormalizedFileBinaryReader.cpp ---------===//
   2 //
   3 //                             The LLVM Linker
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 ///
  11 /// \file For mach-o object files, this implementation converts from
  12 /// mach-o on-disk binary format to in-memory normalized mach-o.
  13 ///
  14 ///                 +---------------+
  15 ///                 | binary mach-o |
  16 ///                 +---------------+
  17 ///                        |
  18 ///                        |
  19 ///                        v
  20 ///                  +------------+
  21 ///                  | normalized |
  22 ///                  +------------+
  23
  24 #include "ArchHandler.h"
  25 #include "MachONormalizedFile.h"
  26 #include "MachONormalizedFileBinaryUtils.h"
  27 #include "lld/Core/Error.h"
  28 #include "lld/Core/LLVM.h"
  29 #include "lld/Core/SharedLibraryFile.h"
  30 #include "llvm/ADT/STLExtras.h"
  31 #include "llvm/ADT/SmallString.h"
  32 #include "llvm/ADT/StringRef.h"
  33 #include "llvm/ADT/StringSwitch.h"
  34 #include "llvm/ADT/Twine.h"
  35 #include "llvm/BinaryFormat/MachO.h"
  36 #include "llvm/BinaryFormat/Magic.h"
  37 #include "llvm/Object/MachO.h"
  38 #include "llvm/Support/Casting.h"
  39 #include "llvm/Support/Errc.h"
  40 #include "llvm/Support/ErrorHandling.h"
  41 #include "llvm/Support/FileOutputBuffer.h"
  42 #include "llvm/Support/Host.h"
  43 #include "llvm/Support/MemoryBuffer.h"
  44 #include "llvm/Support/raw_ostream.h"
  45 #include <functional>
  46 #include <system_error>
  47
  48 using namespace llvm::MachO;
  49 using llvm::object::ExportEntry;
  50 using llvm::file_magic;
  51 using llvm::object::MachOObjectFile;
  52
  53 namespace lld {
  54 namespace mach_o {
  55 namespace normalized {
  56
  57 // Utility to call a lambda expression on each load command.
  58 static llvm::Error forEachLoadCommand(
  59     StringRef lcRange, unsigned lcCount, bool isBig, bool is64,
  60     std::function<bool(uint32_t cmd, uint32_t size, const char *lc)> func) {
  61   const char* p = lcRange.begin();
  62   for (unsigned i=0; i < lcCount; ++i) {
  63     const load_command *lc = reinterpret_cast<const load_command*>(p);
  64     load_command lcCopy;
  65     const load_command *slc = lc;
  66     if (isBig != llvm::sys::IsBigEndianHost) {
  67       memcpy(&lcCopy, lc, sizeof(load_command));
  68       swapStruct(lcCopy);
  69       slc = &lcCopy;
  70     }
  71     if ( (p + slc->cmdsize) > lcRange.end() )
  72       return llvm::make_error<GenericError>("Load command exceeds range");
  73
  74     if (func(slc->cmd, slc->cmdsize, p))
  75       return llvm::Error::success();
  76
  77     p += slc->cmdsize;
  78   }
  79
  80   return llvm::Error::success();
  81 }
  82
  83 static std::error_code appendRelocations(Relocations &relocs, StringRef buffer,
  84                                          bool bigEndian,
  85                                          uint32_t reloff, uint32_t nreloc) {
  86   if ((reloff + nreloc*8) > buffer.size())
  87     return make_error_code(llvm::errc::executable_format_error);
  88   const any_relocation_info* relocsArray =
  89             reinterpret_cast<const any_relocation_info*>(buffer.begin()+reloff);
  90
  91   for(uint32_t i=0; i < nreloc; ++i) {
  92     relocs.push_back(unpackRelocation(relocsArray[i], bigEndian));
  93   }
  94   return std::error_code();
  95 }
  96
  97 static std::error_code
  98 appendIndirectSymbols(IndirectSymbols &isyms, StringRef buffer, bool isBig,
  99                       uint32_t istOffset, uint32_t istCount,
 100                       uint32_t startIndex, uint32_t count) {
 101   if ((istOffset + istCount*4) > buffer.size())
 102     return make_error_code(llvm::errc::executable_format_error);
 103   if (startIndex+count  > istCount)
 104     return make_error_code(llvm::errc::executable_format_error);
 105   const uint8_t *indirectSymbolArray = (const uint8_t *)buffer.data();
 106
 107   for(uint32_t i=0; i < count; ++i) {
 108     isyms.push_back(read32(
 109         indirectSymbolArray + (startIndex + i) * sizeof(uint32_t), isBig));
 110   }
 111   return std::error_code();
 112 }
 113
 114
 115 template <typename T> static T readBigEndian(T t) {
 116   if (llvm::sys::IsLittleEndianHost)
 117     llvm::sys::swapByteOrder(t);
 118   return t;
 119 }
 120
 121
 122 static bool isMachOHeader(const mach_header *mh, bool &is64, bool &isBig) {
 123   switch (read32(&mh->magic, false)) {
 124   case llvm::MachO::MH_MAGIC:
 125     is64 = false;
 126     isBig = false;
 127     return true;
 128   case llvm::MachO::MH_MAGIC_64:
 129     is64 = true;
 130     isBig = false;
 131     return true;
 132   case llvm::MachO::MH_CIGAM:
 133     is64 = false;
 134     isBig = true;
 135     return true;
 136   case llvm::MachO::MH_CIGAM_64:
 137     is64 = true;
 138     isBig = true;
 139     return true;
 140   default:
 141     return false;
 142   }
 143 }
 144
 145
 146 bool isThinObjectFile(StringRef path, MachOLinkingContext::Arch &arch) {
 147   // Try opening and mapping file at path.
 148   ErrorOr<std::unique_ptr<MemoryBuffer>> b = MemoryBuffer::getFileOrSTDIN(path);
 149   if (b.getError())
 150     return false;
 151
 152   // If file length < 32 it is too small to be mach-o object file.
 153   StringRef fileBuffer = b->get()->getBuffer();
 154   if (fileBuffer.size() < 32)
 155     return false;
 156
 157   // If file buffer does not start with MH_MAGIC (and variants), not obj file.
 158   const mach_header *mh = reinterpret_cast<const mach_header *>(
 159                                                             fileBuffer.begin());
 160   bool is64, isBig;
 161   if (!isMachOHeader(mh, is64, isBig))
 162     return false;
 163
 164   // If not MH_OBJECT, not object file.
 165   if (read32(&mh->filetype, isBig) != MH_OBJECT)
 166     return false;
 167
 168   // Lookup up arch from cpu/subtype pair.
 169   arch = MachOLinkingContext::archFromCpuType(
 170       read32(&mh->cputype, isBig),
 171       read32(&mh->cpusubtype, isBig));
 172   return true;
 173 }
 174
 175 bool sliceFromFatFile(MemoryBufferRef mb, MachOLinkingContext::Arch arch,
 176                       uint32_t &offset, uint32_t &size) {
 177   const char *start = mb.getBufferStart();
 178   const llvm::MachO::fat_header *fh =
 179       reinterpret_cast<const llvm::MachO::fat_header *>(start);
 180   if (readBigEndian(fh->magic) != llvm::MachO::FAT_MAGIC)
 181     return false;
 182   uint32_t nfat_arch = readBigEndian(fh->nfat_arch);
 183   const fat_arch *fstart =
 184       reinterpret_cast<const fat_arch *>(start + sizeof(fat_header));
 185   const fat_arch *fend =
 186       reinterpret_cast<const fat_arch *>(start + sizeof(fat_header) +
 187                                          sizeof(fat_arch) * nfat_arch);
 188   const uint32_t reqCpuType = MachOLinkingContext::cpuTypeFromArch(arch);
 189   const uint32_t reqCpuSubtype = MachOLinkingContext::cpuSubtypeFromArch(arch);
 190   for (const fat_arch *fa = fstart; fa < fend; ++fa) {
 191     if ((readBigEndian(fa->cputype) == reqCpuType) &&
 192         (readBigEndian(fa->cpusubtype) == reqCpuSubtype)) {
 193       offset = readBigEndian(fa->offset);
 194       size = readBigEndian(fa->size);
 195       if ((offset + size) > mb.getBufferSize())
 196         return false;
 197       return true;
 198     }
 199   }
 200   return false;
 201 }
 202
 203 /// Reads a mach-o file and produces an in-memory normalized view.
 204 llvm::Expected<std::unique_ptr<NormalizedFile>>
 205 readBinary(std::unique_ptr<MemoryBuffer> &mb,
 206            const MachOLinkingContext::Arch arch) {
 207   // Make empty NormalizedFile.
 208   std::unique_ptr<NormalizedFile> f(new NormalizedFile());
 209
 210   const char *start = mb->getBufferStart();
 211   size_t objSize = mb->getBufferSize();
 212   const mach_header *mh = reinterpret_cast<const mach_header *>(start);
 213
 214   uint32_t sliceOffset;
 215   uint32_t sliceSize;
 216   if (sliceFromFatFile(mb->getMemBufferRef(), arch, sliceOffset, sliceSize)) {
 217     start = &start[sliceOffset];
 218     objSize = sliceSize;
 219     mh = reinterpret_cast<const mach_header *>(start);
 220   }
 221
 222   // Determine endianness and pointer size for mach-o file.
 223   bool is64, isBig;
 224   if (!isMachOHeader(mh, is64, isBig))
 225     return llvm::make_error<GenericError>("File is not a mach-o");
 226
 227   // Endian swap header, if needed.
 228   mach_header headerCopy;
 229   const mach_header *smh = mh;
 230   if (isBig != llvm::sys::IsBigEndianHost) {
 231     memcpy(&headerCopy, mh, sizeof(mach_header));
 232     swapStruct(headerCopy);
 233     smh = &headerCopy;
 234   }
 235
 236   // Validate head and load commands fit in buffer.
 237   const uint32_t lcCount = smh->ncmds;
 238   const char *lcStart =
 239       start + (is64 ? sizeof(mach_header_64) : sizeof(mach_header));
 240   StringRef lcRange(lcStart, smh->sizeofcmds);
 241   if (lcRange.end() > (start + objSize))
 242     return llvm::make_error<GenericError>("Load commands exceed file size");
 243
 244   // Get architecture from mach_header.
 245   f->arch = MachOLinkingContext::archFromCpuType(smh->cputype, smh->cpusubtype);
 246   if (f->arch != arch) {
 247     return llvm::make_error<GenericError>(
 248                                   Twine("file is wrong architecture. Expected "
 249                                   "(" + MachOLinkingContext::nameFromArch(arch)
 250                                   + ") found ("
 251                                   + MachOLinkingContext::nameFromArch(f->arch)
 252                                   + ")" ));
 253   }
 254   // Copy file type and flags
 255   f->fileType = HeaderFileType(smh->filetype);
 256   f->flags = smh->flags;
 257
 258
 259   // Pre-scan load commands looking for indirect symbol table.
 260   uint32_t indirectSymbolTableOffset = 0;
 261   uint32_t indirectSymbolTableCount = 0;
 262   auto ec = forEachLoadCommand(lcRange, lcCount, isBig, is64,
 263                                [&](uint32_t cmd, uint32_t size,
 264                                    const char *lc) -> bool {
 265     if (cmd == LC_DYSYMTAB) {
 266       const dysymtab_command *d = reinterpret_cast<const dysymtab_command*>(lc);
 267       indirectSymbolTableOffset = read32(&d->indirectsymoff, isBig);
 268       indirectSymbolTableCount = read32(&d->nindirectsyms, isBig);
 269       return true;
 270     }
 271     return false;
 272   });
 273   if (ec)
 274     return std::move(ec);
 275
 276   // Walk load commands looking for segments/sections and the symbol table.
 277   const data_in_code_entry *dataInCode = nullptr;
 278   const dyld_info_command *dyldInfo = nullptr;
 279   uint32_t dataInCodeSize = 0;
 280   ec = forEachLoadCommand(lcRange, lcCount, isBig, is64,
 281                     [&] (uint32_t cmd, uint32_t size, const char* lc) -> bool {
 282     switch(cmd) {
 283     case LC_SEGMENT_64:
 284       if (is64) {
 285         const segment_command_64 *seg =
 286                               reinterpret_cast<const segment_command_64*>(lc);
 287         const unsigned sectionCount = read32(&seg->nsects, isBig);
 288         const section_64 *sects = reinterpret_cast<const section_64*>
 289                                   (lc + sizeof(segment_command_64));
 290         const unsigned lcSize = sizeof(segment_command_64)
 291                                               + sectionCount*sizeof(section_64);
 292         // Verify sections don't extend beyond end of segment load command.
 293         if (lcSize > size)
 294           return true;
 295         for (unsigned i=0; i < sectionCount; ++i) {
 296           const section_64 *sect = &sects[i];
 297           Section section;
 298           section.segmentName = getString16(sect->segname);
 299           section.sectionName = getString16(sect->sectname);
 300           section.type = (SectionType)(read32(&sect->flags, isBig) &
 301                                        SECTION_TYPE);
 302           section.attributes  = read32(&sect->flags, isBig) & SECTION_ATTRIBUTES;
 303           section.alignment   = 1 << read32(&sect->align, isBig);
 304           section.address     = read64(&sect->addr, isBig);
 305           const uint8_t *content =
 306             (const uint8_t *)start + read32(&sect->offset, isBig);
 307           size_t contentSize = read64(&sect->size, isBig);
 308           // Note: this assign() is copying the content bytes.  Ideally,
 309           // we can use a custom allocator for vector to avoid the copy.
 310           section.content = llvm::makeArrayRef(content, contentSize);
 311           appendRelocations(section.relocations, mb->getBuffer(), isBig,
 312                             read32(&sect->reloff, isBig),
 313                             read32(&sect->nreloc, isBig));
 314           if (section.type == S_NON_LAZY_SYMBOL_POINTERS) {
 315             appendIndirectSymbols(section.indirectSymbols, mb->getBuffer(),
 316                                   isBig,
 317                                   indirectSymbolTableOffset,
 318                                   indirectSymbolTableCount,
 319                                   read32(&sect->reserved1, isBig),
 320                                   contentSize/4);
 321           }
 322           f->sections.push_back(section);
 323         }
 324       }
 325       break;
 326     case LC_SEGMENT:
 327       if (!is64) {
 328         const segment_command *seg =
 329                               reinterpret_cast<const segment_command*>(lc);
 330         const unsigned sectionCount = read32(&seg->nsects, isBig);
 331         const section *sects = reinterpret_cast<const section*>
 332                                   (lc + sizeof(segment_command));
 333         const unsigned lcSize = sizeof(segment_command)
 334                                               + sectionCount*sizeof(section);
 335         // Verify sections don't extend beyond end of segment load command.
 336         if (lcSize > size)
 337           return true;
 338         for (unsigned i=0; i < sectionCount; ++i) {
 339           const section *sect = &sects[i];
 340           Section section;
 341           section.segmentName = getString16(sect->segname);
 342           section.sectionName = getString16(sect->sectname);
 343           section.type = (SectionType)(read32(&sect->flags, isBig) &
 344                                        SECTION_TYPE);
 345           section.attributes =
 346               read32((const uint8_t *)&sect->flags, isBig) & SECTION_ATTRIBUTES;
 347           section.alignment   = 1 << read32(&sect->align, isBig);
 348           section.address     = read32(&sect->addr, isBig);
 349           const uint8_t *content =
 350             (const uint8_t *)start + read32(&sect->offset, isBig);
 351           size_t contentSize = read32(&sect->size, isBig);
 352           // Note: this assign() is copying the content bytes.  Ideally,
 353           // we can use a custom allocator for vector to avoid the copy.
 354           section.content = llvm::makeArrayRef(content, contentSize);
 355           appendRelocations(section.relocations, mb->getBuffer(), isBig,
 356                             read32(&sect->reloff, isBig),
 357                             read32(&sect->nreloc, isBig));
 358           if (section.type == S_NON_LAZY_SYMBOL_POINTERS) {
 359             appendIndirectSymbols(
 360                 section.indirectSymbols, mb->getBuffer(), isBig,
 361                 indirectSymbolTableOffset, indirectSymbolTableCount,
 362                 read32(&sect->reserved1, isBig), contentSize / 4);
 363           }
 364           f->sections.push_back(section);
 365         }
 366       }
 367       break;
 368     case LC_SYMTAB: {
 369       const symtab_command *st = reinterpret_cast<const symtab_command*>(lc);
 370       const char *strings = start + read32(&st->stroff, isBig);
 371       const uint32_t strSize = read32(&st->strsize, isBig);
 372       // Validate string pool and symbol table all in buffer.
 373       if (read32((const uint8_t *)&st->stroff, isBig) +
 374               read32((const uint8_t *)&st->strsize, isBig) >
 375           objSize)
 376         return true;
 377       if (is64) {
 378         const uint32_t symOffset = read32(&st->symoff, isBig);
 379         const uint32_t symCount = read32(&st->nsyms, isBig);
 380         if ( symOffset+(symCount*sizeof(nlist_64)) > objSize)
 381           return true;
 382         const nlist_64 *symbols =
 383             reinterpret_cast<const nlist_64 *>(start + symOffset);
 384         // Convert each nlist_64 to a lld::mach_o::normalized::Symbol.
 385         for(uint32_t i=0; i < symCount; ++i) {
 386           nlist_64 tempSym;
 387           memcpy(&tempSym, &symbols[i], sizeof(nlist_64));
 388           const nlist_64 *sin = &tempSym;
 389           if (isBig != llvm::sys::IsBigEndianHost)
 390             swapStruct(tempSym);
 391           Symbol sout;
 392           if (sin->n_strx > strSize)
 393             return true;
 394           sout.name  = &strings[sin->n_strx];
 395           sout.type = static_cast<NListType>(sin->n_type & (N_STAB|N_TYPE));
 396           sout.scope = (sin->n_type & (N_PEXT|N_EXT));
 397           sout.sect  = sin->n_sect;
 398           sout.desc  = sin->n_desc;
 399           sout.value = sin->n_value;
 400           if (sin->n_type & N_STAB)
 401             f->stabsSymbols.push_back(sout);
 402           else if (sout.type == N_UNDF)
 403             f->undefinedSymbols.push_back(sout);
 404           else if (sin->n_type & N_EXT)
 405             f->globalSymbols.push_back(sout);
 406           else
 407             f->localSymbols.push_back(sout);
 408         }
 409       } else {
 410         const uint32_t symOffset = read32(&st->symoff, isBig);
 411         const uint32_t symCount = read32(&st->nsyms, isBig);
 412         if ( symOffset+(symCount*sizeof(nlist)) > objSize)
 413           return true;
 414         const nlist *symbols =
 415             reinterpret_cast<const nlist *>(start + symOffset);
 416         // Convert each nlist to a lld::mach_o::normalized::Symbol.
 417         for(uint32_t i=0; i < symCount; ++i) {
 418           const nlist *sin = &symbols[i];
 419           nlist tempSym;
 420           if (isBig != llvm::sys::IsBigEndianHost) {
 421             tempSym = *sin; swapStruct(tempSym); sin = &tempSym;
 422           }
 423           Symbol sout;
 424           if (sin->n_strx > strSize)
 425             return true;
 426           sout.name  = &strings[sin->n_strx];
 427           sout.type  = (NListType)(sin->n_type & N_TYPE);
 428           sout.scope = (sin->n_type & (N_PEXT|N_EXT));
 429           sout.sect  = sin->n_sect;
 430           sout.desc  = sin->n_desc;
 431           sout.value = sin->n_value;
 432           if (sout.type == N_UNDF)
 433             f->undefinedSymbols.push_back(sout);
 434           else if (sout.scope == (SymbolScope)N_EXT)
 435             f->globalSymbols.push_back(sout);
 436           else if (sin->n_type & N_STAB)
 437             f->stabsSymbols.push_back(sout);
 438           else
 439             f->localSymbols.push_back(sout);
 440         }
 441       }
 442       }
 443       break;
 444     case LC_ID_DYLIB: {
 445       const dylib_command *dl = reinterpret_cast<const dylib_command*>(lc);
 446       f->installName = lc + read32(&dl->dylib.name, isBig);
 447       f->currentVersion = read32(&dl->dylib.current_version, isBig);
 448       f->compatVersion = read32(&dl->dylib.compatibility_version, isBig);
 449       }
 450       break;
 451     case LC_DATA_IN_CODE: {
 452       const linkedit_data_command *ldc =
 453                             reinterpret_cast<const linkedit_data_command*>(lc);
 454       dataInCode = reinterpret_cast<const data_in_code_entry *>(
 455           start + read32(&ldc->dataoff, isBig));
 456       dataInCodeSize = read32(&ldc->datasize, isBig);
 457       }
 458       break;
 459     case LC_LOAD_DYLIB:
 460     case LC_LOAD_WEAK_DYLIB:
 461     case LC_REEXPORT_DYLIB:
 462     case LC_LOAD_UPWARD_DYLIB: {
 463       const dylib_command *dl = reinterpret_cast<const dylib_command*>(lc);
 464       DependentDylib entry;
 465       entry.path = lc + read32(&dl->dylib.name, isBig);
 466       entry.kind = LoadCommandType(cmd);
 467       entry.compatVersion = read32(&dl->dylib.compatibility_version, isBig);
 468       entry.currentVersion = read32(&dl->dylib.current_version, isBig);
 469       f->dependentDylibs.push_back(entry);
 470      }
 471       break;
 472     case LC_RPATH: {
 473       const rpath_command *rpc = reinterpret_cast<const rpath_command *>(lc);
 474       f->rpaths.push_back(lc + read32(&rpc->path, isBig));
 475      }
 476       break;
 477     case LC_DYLD_INFO:
 478     case LC_DYLD_INFO_ONLY:
 479       dyldInfo = reinterpret_cast<const dyld_info_command*>(lc);
 480       break;
 481     case LC_VERSION_MIN_MACOSX:
 482     case LC_VERSION_MIN_IPHONEOS:
 483     case LC_VERSION_MIN_WATCHOS:
 484     case LC_VERSION_MIN_TVOS:
 485       // If we are emitting an object file, then we may take the load command
 486       // kind from these commands and pass it on to the output
 487       // file.
 488       f->minOSVersionKind = (LoadCommandType)cmd;
 489       break;
 490     }
 491     return false;
 492   });
 493   if (ec)
 494     return std::move(ec);
 495
 496   if (dataInCode) {
 497     // Convert on-disk data_in_code_entry array to DataInCode vector.
 498     for (unsigned i=0; i < dataInCodeSize/sizeof(data_in_code_entry); ++i) {
 499       DataInCode entry;
 500       entry.offset = read32(&dataInCode[i].offset, isBig);
 501       entry.length = read16(&dataInCode[i].length, isBig);
 502       entry.kind =
 503           (DataRegionType)read16((const uint8_t *)&dataInCode[i].kind, isBig);
 504       f->dataInCode.push_back(entry);
 505     }
 506   }
 507
 508   if (dyldInfo) {
 509     // If any exports, extract and add to normalized exportInfo vector.
 510     if (dyldInfo->export_size) {
 511       const uint8_t *trieStart = reinterpret_cast<const uint8_t *>(
 512           start + read32(&dyldInfo->export_off, isBig));
 513       ArrayRef<uint8_t> trie(trieStart, read32(&dyldInfo->export_size, isBig));
 514       for (const ExportEntry &trieExport : MachOObjectFile::exports(trie)) {
 515         Export normExport;
 516         normExport.name = trieExport.name().copy(f->ownedAllocations);
 517         normExport.offset = trieExport.address();
 518         normExport.kind = ExportSymbolKind(trieExport.flags() & EXPORT_SYMBOL_FLAGS_KIND_MASK);
 519         normExport.flags = trieExport.flags() & ~EXPORT_SYMBOL_FLAGS_KIND_MASK;
 520         normExport.otherOffset = trieExport.other();
 521         if (!trieExport.otherName().empty())
 522           normExport.otherName = trieExport.otherName().copy(f->ownedAllocations);
 523         f->exportInfo.push_back(normExport);
 524       }
 525     }
 526   }
 527
 528   return std::move(f);
 529 }
 530
 531 class MachOObjectReader : public Reader {
 532 public:
 533   MachOObjectReader(MachOLinkingContext &ctx) : _ctx(ctx) {}
 534
 535   bool canParse(file_magic magic, MemoryBufferRef mb) const override {
 536     return (magic == file_magic::macho_object && mb.getBufferSize() > 32);
 537   }
 538
 539   ErrorOr<std::unique_ptr<File>>
 540   loadFile(std::unique_ptr<MemoryBuffer> mb,
 541            const Registry &registry) const override {
 542     std::unique_ptr<File> ret =
 543       llvm::make_unique<MachOFile>(std::move(mb), &_ctx);
 544     return std::move(ret);
 545   }
 546
 547 private:
 548   MachOLinkingContext &_ctx;
 549 };
 550
 551 class MachODylibReader : public Reader {
 552 public:
 553   MachODylibReader(MachOLinkingContext &ctx) : _ctx(ctx) {}
 554
 555   bool canParse(file_magic magic, MemoryBufferRef mb) const override {
 556     switch (magic) {
 557     case file_magic::macho_dynamically_linked_shared_lib:
 558     case file_magic::macho_dynamically_linked_shared_lib_stub:
 559       return mb.getBufferSize() > 32;
 560     default:
 561       return false;
 562     }
 563   }
 564
 565   ErrorOr<std::unique_ptr<File>>
 566   loadFile(std::unique_ptr<MemoryBuffer> mb,
 567            const Registry &registry) const override {
 568     std::unique_ptr<File> ret =
 569         llvm::make_unique<MachODylibFile>(std::move(mb), &_ctx);
 570     return std::move(ret);
 571   }
 572
 573 private:
 574   MachOLinkingContext &_ctx;
 575 };
 576
 577 } // namespace normalized
 578 } // namespace mach_o
 579
 580 void Registry::addSupportMachOObjects(MachOLinkingContext &ctx) {
 581   MachOLinkingContext::Arch arch = ctx.arch();
 582   add(std::unique_ptr<Reader>(new mach_o::normalized::MachOObjectReader(ctx)));
 583   add(std::unique_ptr<Reader>(new mach_o::normalized::MachODylibReader(ctx)));
 584   addKindTable(Reference::KindNamespace::mach_o, ctx.archHandler().kindArch(),
 585                ctx.archHandler().kindStrings());
 586   add(std::unique_ptr<YamlIOTaggedDocumentHandler>(
 587                            new mach_o::MachOYamlIOTaggedDocumentHandler(arch)));
 588 }
 589
 590
 591 } // namespace lld