InputFiles.cpp revision 303239
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 "Chunks.h" 11#include "Config.h" 12#include "Error.h" 13#include "InputFiles.h" 14#include "Symbols.h" 15#include "llvm/ADT/SmallVector.h" 16#include "llvm/ADT/Triple.h" 17#include "llvm/ADT/Twine.h" 18#include "llvm/IR/LLVMContext.h" 19#include "llvm/LTO/legacy/LTOModule.h" 20#include "llvm/Object/Binary.h" 21#include "llvm/Object/COFF.h" 22#include "llvm/Support/COFF.h" 23#include "llvm/Support/Casting.h" 24#include "llvm/Support/Endian.h" 25#include "llvm/Support/Error.h" 26#include "llvm/Support/ErrorOr.h" 27#include "llvm/Support/FileSystem.h" 28#include "llvm/Target/TargetOptions.h" 29#include "llvm-c/lto.h" 30#include <cstring> 31#include <system_error> 32#include <utility> 33 34using namespace llvm::COFF; 35using namespace llvm::object; 36using namespace llvm::support::endian; 37 38using llvm::Triple; 39using llvm::support::ulittle32_t; 40 41namespace lld { 42namespace coff { 43 44int InputFile::NextIndex = 0; 45llvm::LLVMContext BitcodeFile::Context; 46 47// Returns the last element of a path, which is supposed to be a filename. 48static StringRef getBasename(StringRef Path) { 49 size_t Pos = Path.find_last_of("\\/"); 50 if (Pos == StringRef::npos) 51 return Path; 52 return Path.substr(Pos + 1); 53} 54 55// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)". 56std::string InputFile::getShortName() { 57 if (ParentName == "") 58 return getName().lower(); 59 std::string Res = (getBasename(ParentName) + "(" + 60 getBasename(getName()) + ")").str(); 61 return StringRef(Res).lower(); 62} 63 64void ArchiveFile::parse() { 65 // Parse a MemoryBufferRef as an archive file. 66 File = check(Archive::create(MB), "failed to parse static library"); 67 68 // Allocate a buffer for Lazy objects. 69 size_t NumSyms = File->getNumberOfSymbols(); 70 LazySymbols.reserve(NumSyms); 71 72 // Read the symbol table to construct Lazy objects. 73 for (const Archive::Symbol &Sym : File->symbols()) 74 LazySymbols.emplace_back(this, Sym); 75 76 // Seen is a map from member files to boolean values. Initially 77 // all members are mapped to false, which indicates all these files 78 // are not read yet. 79 Error Err; 80 for (auto &Child : File->children(Err)) 81 Seen[Child.getChildOffset()].clear(); 82 if (Err) 83 fatal(Err, "failed to parse static library"); 84} 85 86// Returns a buffer pointing to a member file containing a given symbol. 87// This function is thread-safe. 88MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) { 89 const Archive::Child &C = 90 check(Sym->getMember(), 91 "could not get the member for symbol " + Sym->getName()); 92 93 // Return an empty buffer if we have already returned the same buffer. 94 if (Seen[C.getChildOffset()].test_and_set()) 95 return MemoryBufferRef(); 96 return check(C.getMemoryBufferRef(), 97 "could not get the buffer for the member defining symbol " + 98 Sym->getName()); 99} 100 101void ObjectFile::parse() { 102 // Parse a memory buffer as a COFF file. 103 std::unique_ptr<Binary> Bin = 104 check(createBinary(MB), "failed to parse object file"); 105 106 if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) { 107 Bin.release(); 108 COFFObj.reset(Obj); 109 } else { 110 fatal(getName() + " is not a COFF file"); 111 } 112 113 // Read section and symbol tables. 114 initializeChunks(); 115 initializeSymbols(); 116 initializeSEH(); 117} 118 119void ObjectFile::initializeChunks() { 120 uint32_t NumSections = COFFObj->getNumberOfSections(); 121 Chunks.reserve(NumSections); 122 SparseChunks.resize(NumSections + 1); 123 for (uint32_t I = 1; I < NumSections + 1; ++I) { 124 const coff_section *Sec; 125 StringRef Name; 126 if (auto EC = COFFObj->getSection(I, Sec)) 127 fatal(EC, "getSection failed: #" + Twine(I)); 128 if (auto EC = COFFObj->getSectionName(Sec, Name)) 129 fatal(EC, "getSectionName failed: #" + Twine(I)); 130 if (Name == ".sxdata") { 131 SXData = Sec; 132 continue; 133 } 134 if (Name == ".drectve") { 135 ArrayRef<uint8_t> Data; 136 COFFObj->getSectionContents(Sec, Data); 137 Directives = std::string((const char *)Data.data(), Data.size()); 138 continue; 139 } 140 // Skip non-DWARF debug info. MSVC linker converts the sections into 141 // a PDB file, but we don't support that. 142 if (Name == ".debug" || Name.startswith(".debug$")) 143 continue; 144 // We want to preserve DWARF debug sections only when /debug is on. 145 if (!Config->Debug && Name.startswith(".debug")) 146 continue; 147 if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE) 148 continue; 149 auto *C = new (Alloc) SectionChunk(this, Sec); 150 Chunks.push_back(C); 151 SparseChunks[I] = C; 152 } 153} 154 155void ObjectFile::initializeSymbols() { 156 uint32_t NumSymbols = COFFObj->getNumberOfSymbols(); 157 SymbolBodies.reserve(NumSymbols); 158 SparseSymbolBodies.resize(NumSymbols); 159 llvm::SmallVector<std::pair<Undefined *, uint32_t>, 8> WeakAliases; 160 int32_t LastSectionNumber = 0; 161 for (uint32_t I = 0; I < NumSymbols; ++I) { 162 // Get a COFFSymbolRef object. 163 COFFSymbolRef Sym = 164 check(COFFObj->getSymbol(I), "broken object file: " + getName()); 165 166 const void *AuxP = nullptr; 167 if (Sym.getNumberOfAuxSymbols()) 168 AuxP = COFFObj->getSymbol(I + 1)->getRawPtr(); 169 bool IsFirst = (LastSectionNumber != Sym.getSectionNumber()); 170 171 SymbolBody *Body = nullptr; 172 if (Sym.isUndefined()) { 173 Body = createUndefined(Sym); 174 } else if (Sym.isWeakExternal()) { 175 Body = createUndefined(Sym); 176 uint32_t TagIndex = 177 static_cast<const coff_aux_weak_external *>(AuxP)->TagIndex; 178 WeakAliases.emplace_back((Undefined *)Body, TagIndex); 179 } else { 180 Body = createDefined(Sym, AuxP, IsFirst); 181 } 182 if (Body) { 183 SymbolBodies.push_back(Body); 184 SparseSymbolBodies[I] = Body; 185 } 186 I += Sym.getNumberOfAuxSymbols(); 187 LastSectionNumber = Sym.getSectionNumber(); 188 } 189 for (auto WeakAlias : WeakAliases) 190 WeakAlias.first->WeakAlias = SparseSymbolBodies[WeakAlias.second]; 191} 192 193Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) { 194 StringRef Name; 195 COFFObj->getSymbolName(Sym, Name); 196 return new (Alloc) Undefined(Name); 197} 198 199Defined *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP, 200 bool IsFirst) { 201 StringRef Name; 202 if (Sym.isCommon()) { 203 auto *C = new (Alloc) CommonChunk(Sym); 204 Chunks.push_back(C); 205 return new (Alloc) DefinedCommon(this, Sym, C); 206 } 207 if (Sym.isAbsolute()) { 208 COFFObj->getSymbolName(Sym, Name); 209 // Skip special symbols. 210 if (Name == "@comp.id") 211 return nullptr; 212 // COFF spec 5.10.1. The .sxdata section. 213 if (Name == "@feat.00") { 214 if (Sym.getValue() & 1) 215 SEHCompat = true; 216 return nullptr; 217 } 218 return new (Alloc) DefinedAbsolute(Name, Sym); 219 } 220 int32_t SectionNumber = Sym.getSectionNumber(); 221 if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG) 222 return nullptr; 223 224 // Reserved sections numbers don't have contents. 225 if (llvm::COFF::isReservedSectionNumber(SectionNumber)) 226 fatal("broken object file: " + getName()); 227 228 // This symbol references a section which is not present in the section 229 // header. 230 if ((uint32_t)SectionNumber >= SparseChunks.size()) 231 fatal("broken object file: " + getName()); 232 233 // Nothing else to do without a section chunk. 234 auto *SC = cast_or_null<SectionChunk>(SparseChunks[SectionNumber]); 235 if (!SC) 236 return nullptr; 237 238 // Handle section definitions 239 if (IsFirst && AuxP) { 240 auto *Aux = reinterpret_cast<const coff_aux_section_definition *>(AuxP); 241 if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE) 242 if (auto *ParentSC = cast_or_null<SectionChunk>( 243 SparseChunks[Aux->getNumber(Sym.isBigObj())])) 244 ParentSC->addAssociative(SC); 245 SC->Checksum = Aux->CheckSum; 246 } 247 248 auto *B = new (Alloc) DefinedRegular(this, Sym, SC); 249 if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP) 250 SC->setSymbol(B); 251 252 return B; 253} 254 255void ObjectFile::initializeSEH() { 256 if (!SEHCompat || !SXData) 257 return; 258 ArrayRef<uint8_t> A; 259 COFFObj->getSectionContents(SXData, A); 260 if (A.size() % 4 != 0) 261 fatal(".sxdata must be an array of symbol table indices"); 262 auto *I = reinterpret_cast<const ulittle32_t *>(A.data()); 263 auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size()); 264 for (; I != E; ++I) 265 SEHandlers.insert(SparseSymbolBodies[*I]); 266} 267 268MachineTypes ObjectFile::getMachineType() { 269 if (COFFObj) 270 return static_cast<MachineTypes>(COFFObj->getMachine()); 271 return IMAGE_FILE_MACHINE_UNKNOWN; 272} 273 274StringRef ltrim1(StringRef S, const char *Chars) { 275 if (!S.empty() && strchr(Chars, S[0])) 276 return S.substr(1); 277 return S; 278} 279 280void ImportFile::parse() { 281 const char *Buf = MB.getBufferStart(); 282 const char *End = MB.getBufferEnd(); 283 const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf); 284 285 // Check if the total size is valid. 286 if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData)) 287 fatal("broken import library"); 288 289 // Read names and create an __imp_ symbol. 290 StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr))); 291 StringRef ImpName = StringAlloc.save("__imp_" + Name); 292 const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1; 293 DLLName = StringRef(NameStart); 294 StringRef ExtName; 295 switch (Hdr->getNameType()) { 296 case IMPORT_ORDINAL: 297 ExtName = ""; 298 break; 299 case IMPORT_NAME: 300 ExtName = Name; 301 break; 302 case IMPORT_NAME_NOPREFIX: 303 ExtName = ltrim1(Name, "?@_"); 304 break; 305 case IMPORT_NAME_UNDECORATE: 306 ExtName = ltrim1(Name, "?@_"); 307 ExtName = ExtName.substr(0, ExtName.find('@')); 308 break; 309 } 310 ImpSym = new (Alloc) DefinedImportData(DLLName, ImpName, ExtName, Hdr); 311 SymbolBodies.push_back(ImpSym); 312 313 // If type is function, we need to create a thunk which jump to an 314 // address pointed by the __imp_ symbol. (This allows you to call 315 // DLL functions just like regular non-DLL functions.) 316 if (Hdr->getType() != llvm::COFF::IMPORT_CODE) 317 return; 318 ThunkSym = new (Alloc) DefinedImportThunk(Name, ImpSym, Hdr->Machine); 319 SymbolBodies.push_back(ThunkSym); 320} 321 322void BitcodeFile::parse() { 323 // Usually parse() is thread-safe, but bitcode file is an exception. 324 std::lock_guard<std::mutex> Lock(Mu); 325 326 Context.enableDebugTypeODRUniquing(); 327 ErrorOr<std::unique_ptr<LTOModule>> ModOrErr = LTOModule::createFromBuffer( 328 Context, MB.getBufferStart(), MB.getBufferSize(), llvm::TargetOptions()); 329 M = check(std::move(ModOrErr), "could not create LTO module"); 330 331 llvm::StringSaver Saver(Alloc); 332 for (unsigned I = 0, E = M->getSymbolCount(); I != E; ++I) { 333 lto_symbol_attributes Attrs = M->getSymbolAttributes(I); 334 if ((Attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL) 335 continue; 336 337 StringRef SymName = Saver.save(M->getSymbolName(I)); 338 int SymbolDef = Attrs & LTO_SYMBOL_DEFINITION_MASK; 339 if (SymbolDef == LTO_SYMBOL_DEFINITION_UNDEFINED) { 340 SymbolBodies.push_back(new (Alloc) Undefined(SymName)); 341 } else { 342 bool Replaceable = 343 (SymbolDef == LTO_SYMBOL_DEFINITION_TENTATIVE || // common 344 (Attrs & LTO_SYMBOL_COMDAT) || // comdat 345 (SymbolDef == LTO_SYMBOL_DEFINITION_WEAK && // weak external 346 (Attrs & LTO_SYMBOL_ALIAS))); 347 SymbolBodies.push_back(new (Alloc) DefinedBitcode(this, SymName, 348 Replaceable)); 349 } 350 } 351 352 Directives = M->getLinkerOpts(); 353} 354 355MachineTypes BitcodeFile::getMachineType() { 356 if (!M) 357 return IMAGE_FILE_MACHINE_UNKNOWN; 358 switch (Triple(M->getTargetTriple()).getArch()) { 359 case Triple::x86_64: 360 return AMD64; 361 case Triple::x86: 362 return I386; 363 case Triple::arm: 364 return ARMNT; 365 default: 366 return IMAGE_FILE_MACHINE_UNKNOWN; 367 } 368} 369 370std::mutex BitcodeFile::Mu; 371 372} // namespace coff 373} // namespace lld 374