lld/COFF/InputFiles.cpp

   1 //===- InputFiles.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 #include "InputFiles.h"
  11 #include "Chunks.h"
  12 #include "Config.h"
  13 #include "Driver.h"
  14 #include "Error.h"
  15 #include "Memory.h"
  16 #include "SymbolTable.h"
  17 #include "Symbols.h"
  18 #include "llvm-c/lto.h"
  19 #include "llvm/ADT/SmallVector.h"
  20 #include "llvm/ADT/Triple.h"
  21 #include "llvm/ADT/Twine.h"
  22 #include "llvm/BinaryFormat/COFF.h"
  23 #include "llvm/Object/Binary.h"
  24 #include "llvm/Object/COFF.h"
  25 #include "llvm/Support/Casting.h"
  26 #include "llvm/Support/Endian.h"
  27 #include "llvm/Support/Error.h"
  28 #include "llvm/Support/ErrorOr.h"
  29 #include "llvm/Support/FileSystem.h"
  30 #include "llvm/Target/TargetOptions.h"
  31 #include <cstring>
  32 #include <system_error>
  33 #include <utility>
  34
  35 using namespace llvm;
  36 using namespace llvm::COFF;
  37 using namespace llvm::object;
  38 using namespace llvm::support::endian;
  39
  40 using llvm::Triple;
  41 using llvm::support::ulittle32_t;
  42
  43 namespace lld {
  44 namespace coff {
  45
  46 std::vector<ObjFile *> ObjFile::Instances;
  47 std::vector<ImportFile *> ImportFile::Instances;
  48 std::vector<BitcodeFile *> BitcodeFile::Instances;
  49
  50 /// Checks that Source is compatible with being a weak alias to Target.
  51 /// If Source is Undefined and has no weak alias set, makes it a weak
  52 /// alias to Target.
  53 static void checkAndSetWeakAlias(SymbolTable *Symtab, InputFile *F,
  54                                  SymbolBody *Source, SymbolBody *Target) {
  55   if (auto *U = dyn_cast<Undefined>(Source)) {
  56     if (U->WeakAlias && U->WeakAlias != Target)
  57       Symtab->reportDuplicate(Source->symbol(), F);
  58     U->WeakAlias = Target;
  59   }
  60 }
  61
  62 ArchiveFile::ArchiveFile(MemoryBufferRef M) : InputFile(ArchiveKind, M) {}
  63
  64 void ArchiveFile::parse() {
  65   // Parse a MemoryBufferRef as an archive file.
  66   File = check(Archive::create(MB), toString(this));
  67
  68   // Read the symbol table to construct Lazy objects.
  69   for (const Archive::Symbol &Sym : File->symbols())
  70     Symtab->addLazy(this, Sym);
  71 }
  72
  73 // Returns a buffer pointing to a member file containing a given symbol.
  74 void ArchiveFile::addMember(const Archive::Symbol *Sym) {
  75   const Archive::Child &C =
  76       check(Sym->getMember(),
  77             "could not get the member for symbol " + Sym->getName());
  78
  79   // Return an empty buffer if we have already returned the same buffer.
  80   if (!Seen.insert(C.getChildOffset()).second)
  81     return;
  82
  83   Driver->enqueueArchiveMember(C, Sym->getName(), getName());
  84 }
  85
  86 void ObjFile::parse() {
  87   // Parse a memory buffer as a COFF file.
  88   std::unique_ptr<Binary> Bin = check(createBinary(MB), toString(this));
  89
  90   if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
  91     Bin.release();
  92     COFFObj.reset(Obj);
  93   } else {
  94     fatal(toString(this) + " is not a COFF file");
  95   }
  96
  97   // Read section and symbol tables.
  98   initializeChunks();
  99   initializeSymbols();
 100   initializeSEH();
 101 }
 102
 103 void ObjFile::initializeChunks() {
 104   uint32_t NumSections = COFFObj->getNumberOfSections();
 105   Chunks.reserve(NumSections);
 106   SparseChunks.resize(NumSections + 1);
 107   for (uint32_t I = 1; I < NumSections + 1; ++I) {
 108     const coff_section *Sec;
 109     StringRef Name;
 110     if (auto EC = COFFObj->getSection(I, Sec))
 111       fatal(EC, "getSection failed: #" + Twine(I));
 112     if (auto EC = COFFObj->getSectionName(Sec, Name))
 113       fatal(EC, "getSectionName failed: #" + Twine(I));
 114     if (Name == ".sxdata") {
 115       SXData = Sec;
 116       continue;
 117     }
 118     if (Name == ".drectve") {
 119       ArrayRef<uint8_t> Data;
 120       COFFObj->getSectionContents(Sec, Data);
 121       Directives = std::string((const char *)Data.data(), Data.size());
 122       continue;
 123     }
 124
 125     // Object files may have DWARF debug info or MS CodeView debug info
 126     // (or both).
 127     //
 128     // DWARF sections don't need any special handling from the perspective
 129     // of the linker; they are just a data section containing relocations.
 130     // We can just link them to complete debug info.
 131     //
 132     // CodeView needs a linker support. We need to interpret and debug
 133     // info, and then write it to a separate .pdb file.
 134
 135     // Ignore debug info unless /debug is given.
 136     if (!Config->Debug && Name.startswith(".debug"))
 137       continue;
 138
 139     if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
 140       continue;
 141     auto *C = make<SectionChunk>(this, Sec);
 142
 143     // CodeView sections are stored to a different vector because they are not
 144     // linked in the regular manner.
 145     if (C->isCodeView())
 146       DebugChunks.push_back(C);
 147     else
 148       Chunks.push_back(C);
 149
 150     SparseChunks[I] = C;
 151   }
 152 }
 153
 154 void ObjFile::initializeSymbols() {
 155   uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
 156   SymbolBodies.reserve(NumSymbols);
 157   SparseSymbolBodies.resize(NumSymbols);
 158
 159   SmallVector<std::pair<SymbolBody *, uint32_t>, 8> WeakAliases;
 160   int32_t LastSectionNumber = 0;
 161
 162   for (uint32_t I = 0; I < NumSymbols; ++I) {
 163     // Get a COFFSymbolRef object.
 164     ErrorOr<COFFSymbolRef> SymOrErr = COFFObj->getSymbol(I);
 165     if (!SymOrErr)
 166       fatal(SymOrErr.getError(), "broken object file: " + toString(this));
 167     COFFSymbolRef Sym = *SymOrErr;
 168
 169     const void *AuxP = nullptr;
 170     if (Sym.getNumberOfAuxSymbols())
 171       AuxP = COFFObj->getSymbol(I + 1)->getRawPtr();
 172     bool IsFirst = (LastSectionNumber != Sym.getSectionNumber());
 173
 174     SymbolBody *Body = nullptr;
 175     if (Sym.isUndefined()) {
 176       Body = createUndefined(Sym);
 177     } else if (Sym.isWeakExternal()) {
 178       Body = createUndefined(Sym);
 179       uint32_t TagIndex =
 180           static_cast<const coff_aux_weak_external *>(AuxP)->TagIndex;
 181       WeakAliases.emplace_back(Body, TagIndex);
 182     } else {
 183       Body = createDefined(Sym, AuxP, IsFirst);
 184     }
 185     if (Body) {
 186       SymbolBodies.push_back(Body);
 187       SparseSymbolBodies[I] = Body;
 188     }
 189     I += Sym.getNumberOfAuxSymbols();
 190     LastSectionNumber = Sym.getSectionNumber();
 191   }
 192
 193   for (auto &KV : WeakAliases) {
 194     SymbolBody *Sym = KV.first;
 195     uint32_t Idx = KV.second;
 196     checkAndSetWeakAlias(Symtab, this, Sym, SparseSymbolBodies[Idx]);
 197   }
 198 }
 199
 200 SymbolBody *ObjFile::createUndefined(COFFSymbolRef Sym) {
 201   StringRef Name;
 202   COFFObj->getSymbolName(Sym, Name);
 203   return Symtab->addUndefined(Name, this, Sym.isWeakExternal())->body();
 204 }
 205
 206 SymbolBody *ObjFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
 207                                    bool IsFirst) {
 208   StringRef Name;
 209   if (Sym.isCommon()) {
 210     auto *C = make<CommonChunk>(Sym);
 211     Chunks.push_back(C);
 212     COFFObj->getSymbolName(Sym, Name);
 213     Symbol *S =
 214         Symtab->addCommon(this, Name, Sym.getValue(), Sym.getGeneric(), C);
 215     return S->body();
 216   }
 217   if (Sym.isAbsolute()) {
 218     COFFObj->getSymbolName(Sym, Name);
 219     // Skip special symbols.
 220     if (Name == "@comp.id")
 221       return nullptr;
 222     // COFF spec 5.10.1. The .sxdata section.
 223     if (Name == "@feat.00") {
 224       if (Sym.getValue() & 1)
 225         SEHCompat = true;
 226       return nullptr;
 227     }
 228     if (Sym.isExternal())
 229       return Symtab->addAbsolute(Name, Sym)->body();
 230     else
 231       return make<DefinedAbsolute>(Name, Sym);
 232   }
 233   int32_t SectionNumber = Sym.getSectionNumber();
 234   if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
 235     return nullptr;
 236
 237   // Reserved sections numbers don't have contents.
 238   if (llvm::COFF::isReservedSectionNumber(SectionNumber))
 239     fatal("broken object file: " + toString(this));
 240
 241   // This symbol references a section which is not present in the section
 242   // header.
 243   if ((uint32_t)SectionNumber >= SparseChunks.size())
 244     fatal("broken object file: " + toString(this));
 245
 246   // Nothing else to do without a section chunk.
 247   auto *SC = cast_or_null<SectionChunk>(SparseChunks[SectionNumber]);
 248   if (!SC)
 249     return nullptr;
 250
 251   // Handle section definitions
 252   if (IsFirst && AuxP) {
 253     auto *Aux = reinterpret_cast<const coff_aux_section_definition *>(AuxP);
 254     if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
 255       if (auto *ParentSC = cast_or_null<SectionChunk>(
 256               SparseChunks[Aux->getNumber(Sym.isBigObj())])) {
 257         ParentSC->addAssociative(SC);
 258         // If we already discarded the parent, discard the child.
 259         if (ParentSC->isDiscarded())
 260           SC->markDiscarded();
 261       }
 262     SC->Checksum = Aux->CheckSum;
 263   }
 264
 265   DefinedRegular *B;
 266   if (Sym.isExternal()) {
 267     COFFObj->getSymbolName(Sym, Name);
 268     Symbol *S =
 269         Symtab->addRegular(this, Name, SC->isCOMDAT(), Sym.getGeneric(), SC);
 270     B = cast<DefinedRegular>(S->body());
 271   } else
 272     B = make<DefinedRegular>(this, /*Name*/ "", SC->isCOMDAT(),
 273                              /*IsExternal*/ false, Sym.getGeneric(), SC);
 274   if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
 275     SC->setSymbol(B);
 276
 277   return B;
 278 }
 279
 280 void ObjFile::initializeSEH() {
 281   if (!SEHCompat || !SXData)
 282     return;
 283   ArrayRef<uint8_t> A;
 284   COFFObj->getSectionContents(SXData, A);
 285   if (A.size() % 4 != 0)
 286     fatal(".sxdata must be an array of symbol table indices");
 287   auto *I = reinterpret_cast<const ulittle32_t *>(A.data());
 288   auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size());
 289   for (; I != E; ++I)
 290     SEHandlers.insert(SparseSymbolBodies[*I]);
 291 }
 292
 293 MachineTypes ObjFile::getMachineType() {
 294   if (COFFObj)
 295     return static_cast<MachineTypes>(COFFObj->getMachine());
 296   return IMAGE_FILE_MACHINE_UNKNOWN;
 297 }
 298
 299 StringRef ltrim1(StringRef S, const char *Chars) {
 300   if (!S.empty() && strchr(Chars, S[0]))
 301     return S.substr(1);
 302   return S;
 303 }
 304
 305 void ImportFile::parse() {
 306   const char *Buf = MB.getBufferStart();
 307   const char *End = MB.getBufferEnd();
 308   const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);
 309
 310   // Check if the total size is valid.
 311   if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
 312     fatal("broken import library");
 313
 314   // Read names and create an __imp_ symbol.
 315   StringRef Name = Saver.save(StringRef(Buf + sizeof(*Hdr)));
 316   StringRef ImpName = Saver.save("__imp_" + Name);
 317   const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
 318   DLLName = StringRef(NameStart);
 319   StringRef ExtName;
 320   switch (Hdr->getNameType()) {
 321   case IMPORT_ORDINAL:
 322     ExtName = "";
 323     break;
 324   case IMPORT_NAME:
 325     ExtName = Name;
 326     break;
 327   case IMPORT_NAME_NOPREFIX:
 328     ExtName = ltrim1(Name, "?@_");
 329     break;
 330   case IMPORT_NAME_UNDECORATE:
 331     ExtName = ltrim1(Name, "?@_");
 332     ExtName = ExtName.substr(0, ExtName.find('@'));
 333     break;
 334   }
 335
 336   this->Hdr = Hdr;
 337   ExternalName = ExtName;
 338
 339   ImpSym = cast<DefinedImportData>(
 340       Symtab->addImportData(ImpName, this)->body());
 341   if (Hdr->getType() == llvm::COFF::IMPORT_CONST)
 342     ConstSym =
 343         cast<DefinedImportData>(Symtab->addImportData(Name, this)->body());
 344
 345   // If type is function, we need to create a thunk which jump to an
 346   // address pointed by the __imp_ symbol. (This allows you to call
 347   // DLL functions just like regular non-DLL functions.)
 348   if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
 349     return;
 350   ThunkSym = cast<DefinedImportThunk>(
 351       Symtab->addImportThunk(Name, ImpSym, Hdr->Machine)->body());
 352 }
 353
 354 void BitcodeFile::parse() {
 355   Obj = check(lto::InputFile::create(MemoryBufferRef(
 356       MB.getBuffer(), Saver.save(ParentName + MB.getBufferIdentifier()))));
 357   for (const lto::InputFile::Symbol &ObjSym : Obj->symbols()) {
 358     StringRef SymName = Saver.save(ObjSym.getName());
 359     Symbol *Sym;
 360     if (ObjSym.isUndefined()) {
 361       Sym = Symtab->addUndefined(SymName, this, false);
 362     } else if (ObjSym.isCommon()) {
 363       Sym = Symtab->addCommon(this, SymName, ObjSym.getCommonSize());
 364     } else if (ObjSym.isWeak() && ObjSym.isIndirect()) {
 365       // Weak external.
 366       Sym = Symtab->addUndefined(SymName, this, true);
 367       std::string Fallback = ObjSym.getCOFFWeakExternalFallback();
 368       SymbolBody *Alias = Symtab->addUndefined(Saver.save(Fallback));
 369       checkAndSetWeakAlias(Symtab, this, Sym->body(), Alias);
 370     } else {
 371       bool IsCOMDAT = ObjSym.getComdatIndex() != -1;
 372       Sym = Symtab->addRegular(this, SymName, IsCOMDAT);
 373     }
 374     SymbolBodies.push_back(Sym->body());
 375   }
 376   Directives = Obj->getCOFFLinkerOpts();
 377 }
 378
 379 MachineTypes BitcodeFile::getMachineType() {
 380   switch (Triple(Obj->getTargetTriple()).getArch()) {
 381   case Triple::x86_64:
 382     return AMD64;
 383   case Triple::x86:
 384     return I386;
 385   case Triple::arm:
 386     return ARMNT;
 387   case Triple::aarch64:
 388     return ARM64;
 389   default:
 390     return IMAGE_FILE_MACHINE_UNKNOWN;
 391   }
 392 }
 393 } // namespace coff
 394 } // namespace lld
 395
 396 // Returns the last element of a path, which is supposed to be a filename.
 397 static StringRef getBasename(StringRef Path) {
 398   size_t Pos = Path.find_last_of("\\/");
 399   if (Pos == StringRef::npos)
 400     return Path;
 401   return Path.substr(Pos + 1);
 402 }
 403
 404 // Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
 405 std::string lld::toString(coff::InputFile *File) {
 406   if (!File)
 407     return "(internal)";
 408   if (File->ParentName.empty())
 409     return File->getName().lower();
 410
 411   std::string Res =
 412       (getBasename(File->ParentName) + "(" + getBasename(File->getName()) + ")")
 413           .str();
 414   return StringRef(Res).lower();
 415 }