1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===// 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 // This file implements ELF object file writer information. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/MC/MCELFObjectWriter.h" 15 #include "llvm/ADT/OwningPtr.h" 16 #include "llvm/ADT/STLExtras.h" 17 #include "llvm/ADT/SmallPtrSet.h" 18 #include "llvm/ADT/SmallString.h" 19 #include "llvm/ADT/StringMap.h" 20 #include "llvm/MC/MCAsmBackend.h" 21 #include "llvm/MC/MCAsmLayout.h" 22 #include "llvm/MC/MCAssembler.h" 23 #include "llvm/MC/MCContext.h" 24 #include "llvm/MC/MCELF.h" 25 #include "llvm/MC/MCELFSymbolFlags.h" 26 #include "llvm/MC/MCExpr.h" 27 #include "llvm/MC/MCFixupKindInfo.h" 28 #include "llvm/MC/MCObjectWriter.h" 29 #include "llvm/MC/MCSectionELF.h" 30 #include "llvm/MC/MCValue.h" 31 #include "llvm/Support/Debug.h" 32 #include "llvm/Support/ELF.h" 33 #include "llvm/Support/ErrorHandling.h" 34 #include <vector> 35 using namespace llvm; 36 37 #undef DEBUG_TYPE 38 #define DEBUG_TYPE "reloc-info" 39 40 namespace { 41 class ELFObjectWriter : public MCObjectWriter { 42 protected: 43 44 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); 45 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant); 46 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout); 47 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data, 48 bool Used, bool Renamed); 49 static bool isLocal(const MCSymbolData &Data, bool isSignature, 50 bool isUsedInReloc); 51 static bool IsELFMetaDataSection(const MCSectionData &SD); 52 static uint64_t DataSectionSize(const MCSectionData &SD); 53 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout, 54 const MCSectionData &SD); 55 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout, 56 const MCSectionData &SD); 57 58 void WriteDataSectionData(MCAssembler &Asm, 59 const MCAsmLayout &Layout, 60 const MCSectionELF &Section); 61 62 /*static bool isFixupKindX86RIPRel(unsigned Kind) { 63 return Kind == X86::reloc_riprel_4byte || 64 Kind == X86::reloc_riprel_4byte_movq_load; 65 }*/ 66 67 /// ELFSymbolData - Helper struct for containing some precomputed 68 /// information on symbols. 69 struct ELFSymbolData { 70 MCSymbolData *SymbolData; 71 uint64_t StringIndex; 72 uint32_t SectionIndex; 73 74 // Support lexicographic sorting. 75 bool operator<(const ELFSymbolData &RHS) const { 76 return SymbolData->getSymbol().getName() < 77 RHS.SymbolData->getSymbol().getName(); 78 } 79 }; 80 81 /// The target specific ELF writer instance. 82 llvm::OwningPtr<MCELFObjectTargetWriter> TargetObjectWriter; 83 84 SmallPtrSet<const MCSymbol *, 16> UsedInReloc; 85 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc; 86 DenseMap<const MCSymbol *, const MCSymbol *> Renames; 87 88 llvm::DenseMap<const MCSectionData*, 89 std::vector<ELFRelocationEntry> > Relocations; 90 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex; 91 92 /// @} 93 /// @name Symbol Table Data 94 /// @{ 95 96 SmallString<256> StringTable; 97 std::vector<uint64_t> FileSymbolData; 98 std::vector<ELFSymbolData> LocalSymbolData; 99 std::vector<ELFSymbolData> ExternalSymbolData; 100 std::vector<ELFSymbolData> UndefinedSymbolData; 101 102 /// @} 103 104 bool NeedsGOT; 105 106 bool NeedsSymtabShndx; 107 108 // This holds the symbol table index of the last local symbol. 109 unsigned LastLocalSymbolIndex; 110 // This holds the .strtab section index. 111 unsigned StringTableIndex; 112 // This holds the .symtab section index. 113 unsigned SymbolTableIndex; 114 115 unsigned ShstrtabIndex; 116 117 118 const MCSymbol *SymbolToReloc(const MCAssembler &Asm, 119 const MCValue &Target, 120 const MCFragment &F, 121 const MCFixup &Fixup, 122 bool IsPCRel) const; 123 124 // TargetObjectWriter wrappers. 125 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, 126 const MCValue &Target, 127 const MCFragment &F, 128 const MCFixup &Fixup, 129 bool IsPCRel) const { 130 return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 131 } 132 const MCSymbol *undefinedExplicitRelSym(const MCValue &Target, 133 const MCFixup &Fixup, 134 bool IsPCRel) const { 135 return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup, 136 IsPCRel); 137 } 138 139 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } 140 bool hasRelocationAddend() const { 141 return TargetObjectWriter->hasRelocationAddend(); 142 } 143 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 144 bool IsPCRel, bool IsRelocWithSymbol, 145 int64_t Addend) const { 146 return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel, 147 IsRelocWithSymbol, Addend); 148 } 149 150 public: 151 ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 152 raw_ostream &_OS, bool IsLittleEndian) 153 : MCObjectWriter(_OS, IsLittleEndian), 154 TargetObjectWriter(MOTW), 155 NeedsGOT(false), NeedsSymtabShndx(false) { 156 } 157 158 virtual ~ELFObjectWriter(); 159 160 void WriteWord(uint64_t W) { 161 if (is64Bit()) 162 Write64(W); 163 else 164 Write32(W); 165 } 166 167 void StringLE16(char *buf, uint16_t Value) { 168 buf[0] = char(Value >> 0); 169 buf[1] = char(Value >> 8); 170 } 171 172 void StringLE32(char *buf, uint32_t Value) { 173 StringLE16(buf, uint16_t(Value >> 0)); 174 StringLE16(buf + 2, uint16_t(Value >> 16)); 175 } 176 177 void StringLE64(char *buf, uint64_t Value) { 178 StringLE32(buf, uint32_t(Value >> 0)); 179 StringLE32(buf + 4, uint32_t(Value >> 32)); 180 } 181 182 void StringBE16(char *buf ,uint16_t Value) { 183 buf[0] = char(Value >> 8); 184 buf[1] = char(Value >> 0); 185 } 186 187 void StringBE32(char *buf, uint32_t Value) { 188 StringBE16(buf, uint16_t(Value >> 16)); 189 StringBE16(buf + 2, uint16_t(Value >> 0)); 190 } 191 192 void StringBE64(char *buf, uint64_t Value) { 193 StringBE32(buf, uint32_t(Value >> 32)); 194 StringBE32(buf + 4, uint32_t(Value >> 0)); 195 } 196 197 void String8(MCDataFragment &F, uint8_t Value) { 198 char buf[1]; 199 buf[0] = Value; 200 F.getContents().append(&buf[0], &buf[1]); 201 } 202 203 void String16(MCDataFragment &F, uint16_t Value) { 204 char buf[2]; 205 if (isLittleEndian()) 206 StringLE16(buf, Value); 207 else 208 StringBE16(buf, Value); 209 F.getContents().append(&buf[0], &buf[2]); 210 } 211 212 void String32(MCDataFragment &F, uint32_t Value) { 213 char buf[4]; 214 if (isLittleEndian()) 215 StringLE32(buf, Value); 216 else 217 StringBE32(buf, Value); 218 F.getContents().append(&buf[0], &buf[4]); 219 } 220 221 void String64(MCDataFragment &F, uint64_t Value) { 222 char buf[8]; 223 if (isLittleEndian()) 224 StringLE64(buf, Value); 225 else 226 StringBE64(buf, Value); 227 F.getContents().append(&buf[0], &buf[8]); 228 } 229 230 void WriteHeader(const MCAssembler &Asm, 231 uint64_t SectionDataSize, 232 unsigned NumberOfSections); 233 234 void WriteSymbolEntry(MCDataFragment *SymtabF, 235 MCDataFragment *ShndxF, 236 uint64_t name, uint8_t info, 237 uint64_t value, uint64_t size, 238 uint8_t other, uint32_t shndx, 239 bool Reserved); 240 241 void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF, 242 ELFSymbolData &MSD, 243 const MCAsmLayout &Layout); 244 245 typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy; 246 void WriteSymbolTable(MCDataFragment *SymtabF, 247 MCDataFragment *ShndxF, 248 const MCAssembler &Asm, 249 const MCAsmLayout &Layout, 250 const SectionIndexMapTy &SectionIndexMap); 251 252 virtual void RecordRelocation(const MCAssembler &Asm, 253 const MCAsmLayout &Layout, 254 const MCFragment *Fragment, 255 const MCFixup &Fixup, 256 MCValue Target, uint64_t &FixedValue); 257 258 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm, 259 const MCSymbol *S); 260 261 // Map from a group section to the signature symbol 262 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy; 263 // Map from a signature symbol to the group section 264 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy; 265 // Map from a section to the section with the relocations 266 typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy; 267 // Map from a section to its offset 268 typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy; 269 270 /// ComputeSymbolTable - Compute the symbol table data 271 /// 272 /// \param Asm - The assembler. 273 /// \param SectionIndexMap - Maps a section to its index. 274 /// \param RevGroupMap - Maps a signature symbol to the group section. 275 /// \param NumRegularSections - Number of non-relocation sections. 276 void ComputeSymbolTable(MCAssembler &Asm, 277 const SectionIndexMapTy &SectionIndexMap, 278 RevGroupMapTy RevGroupMap, 279 unsigned NumRegularSections); 280 281 void ComputeIndexMap(MCAssembler &Asm, 282 SectionIndexMapTy &SectionIndexMap, 283 const RelMapTy &RelMap); 284 285 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout, 286 RelMapTy &RelMap); 287 288 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, 289 const RelMapTy &RelMap); 290 291 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout, 292 SectionIndexMapTy &SectionIndexMap, 293 const RelMapTy &RelMap); 294 295 // Create the sections that show up in the symbol table. Currently 296 // those are the .note.GNU-stack section and the group sections. 297 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout, 298 GroupMapTy &GroupMap, 299 RevGroupMapTy &RevGroupMap, 300 SectionIndexMapTy &SectionIndexMap, 301 const RelMapTy &RelMap); 302 303 virtual void ExecutePostLayoutBinding(MCAssembler &Asm, 304 const MCAsmLayout &Layout); 305 306 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap, 307 const MCAsmLayout &Layout, 308 const SectionIndexMapTy &SectionIndexMap, 309 const SectionOffsetMapTy &SectionOffsetMap); 310 311 void ComputeSectionOrder(MCAssembler &Asm, 312 std::vector<const MCSectionELF*> &Sections); 313 314 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags, 315 uint64_t Address, uint64_t Offset, 316 uint64_t Size, uint32_t Link, uint32_t Info, 317 uint64_t Alignment, uint64_t EntrySize); 318 319 void WriteRelocationsFragment(const MCAssembler &Asm, 320 MCDataFragment *F, 321 const MCSectionData *SD); 322 323 virtual bool 324 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 325 const MCSymbolData &DataA, 326 const MCFragment &FB, 327 bool InSet, 328 bool IsPCRel) const; 329 330 virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout); 331 void WriteSection(MCAssembler &Asm, 332 const SectionIndexMapTy &SectionIndexMap, 333 uint32_t GroupSymbolIndex, 334 uint64_t Offset, uint64_t Size, uint64_t Alignment, 335 const MCSectionELF &Section); 336 }; 337 } 338 339 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { 340 const MCFixupKindInfo &FKI = 341 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind); 342 343 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; 344 } 345 346 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) { 347 switch (Variant) { 348 default: 349 return false; 350 case MCSymbolRefExpr::VK_GOT: 351 case MCSymbolRefExpr::VK_PLT: 352 case MCSymbolRefExpr::VK_GOTPCREL: 353 case MCSymbolRefExpr::VK_GOTOFF: 354 case MCSymbolRefExpr::VK_TPOFF: 355 case MCSymbolRefExpr::VK_TLSGD: 356 case MCSymbolRefExpr::VK_GOTTPOFF: 357 case MCSymbolRefExpr::VK_INDNTPOFF: 358 case MCSymbolRefExpr::VK_NTPOFF: 359 case MCSymbolRefExpr::VK_GOTNTPOFF: 360 case MCSymbolRefExpr::VK_TLSLDM: 361 case MCSymbolRefExpr::VK_DTPOFF: 362 case MCSymbolRefExpr::VK_TLSLD: 363 return true; 364 } 365 } 366 367 ELFObjectWriter::~ELFObjectWriter() 368 {} 369 370 // Emit the ELF header. 371 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm, 372 uint64_t SectionDataSize, 373 unsigned NumberOfSections) { 374 // ELF Header 375 // ---------- 376 // 377 // Note 378 // ---- 379 // emitWord method behaves differently for ELF32 and ELF64, writing 380 // 4 bytes in the former and 8 in the latter. 381 382 Write8(0x7f); // e_ident[EI_MAG0] 383 Write8('E'); // e_ident[EI_MAG1] 384 Write8('L'); // e_ident[EI_MAG2] 385 Write8('F'); // e_ident[EI_MAG3] 386 387 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS] 388 389 // e_ident[EI_DATA] 390 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); 391 392 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] 393 // e_ident[EI_OSABI] 394 Write8(TargetObjectWriter->getOSABI()); 395 Write8(0); // e_ident[EI_ABIVERSION] 396 397 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); 398 399 Write16(ELF::ET_REL); // e_type 400 401 Write16(TargetObjectWriter->getEMachine()); // e_machine = target 402 403 Write32(ELF::EV_CURRENT); // e_version 404 WriteWord(0); // e_entry, no entry point in .o file 405 WriteWord(0); // e_phoff, no program header for .o 406 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 407 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes 408 409 // e_flags = whatever the target wants 410 Write32(Asm.getELFHeaderEFlags()); 411 412 // e_ehsize = ELF header size 413 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr)); 414 415 Write16(0); // e_phentsize = prog header entry size 416 Write16(0); // e_phnum = # prog header entries = 0 417 418 // e_shentsize = Section header entry size 419 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr)); 420 421 // e_shnum = # of section header ents 422 if (NumberOfSections >= ELF::SHN_LORESERVE) 423 Write16(ELF::SHN_UNDEF); 424 else 425 Write16(NumberOfSections); 426 427 // e_shstrndx = Section # of '.shstrtab' 428 if (ShstrtabIndex >= ELF::SHN_LORESERVE) 429 Write16(ELF::SHN_XINDEX); 430 else 431 Write16(ShstrtabIndex); 432 } 433 434 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF, 435 MCDataFragment *ShndxF, 436 uint64_t name, 437 uint8_t info, uint64_t value, 438 uint64_t size, uint8_t other, 439 uint32_t shndx, 440 bool Reserved) { 441 if (ShndxF) { 442 if (shndx >= ELF::SHN_LORESERVE && !Reserved) 443 String32(*ShndxF, shndx); 444 else 445 String32(*ShndxF, 0); 446 } 447 448 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ? 449 uint16_t(ELF::SHN_XINDEX) : shndx; 450 451 if (is64Bit()) { 452 String32(*SymtabF, name); // st_name 453 String8(*SymtabF, info); // st_info 454 String8(*SymtabF, other); // st_other 455 String16(*SymtabF, Index); // st_shndx 456 String64(*SymtabF, value); // st_value 457 String64(*SymtabF, size); // st_size 458 } else { 459 String32(*SymtabF, name); // st_name 460 String32(*SymtabF, value); // st_value 461 String32(*SymtabF, size); // st_size 462 String8(*SymtabF, info); // st_info 463 String8(*SymtabF, other); // st_other 464 String16(*SymtabF, Index); // st_shndx 465 } 466 } 467 468 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data, 469 const MCAsmLayout &Layout) { 470 if (Data.isCommon() && Data.isExternal()) 471 return Data.getCommonAlignment(); 472 473 const MCSymbol &Symbol = Data.getSymbol(); 474 475 if (Symbol.isAbsolute() && Symbol.isVariable()) { 476 if (const MCExpr *Value = Symbol.getVariableValue()) { 477 int64_t IntValue; 478 if (Value->EvaluateAsAbsolute(IntValue, Layout)) 479 return (uint64_t)IntValue; 480 } 481 } 482 483 if (!Symbol.isInSection()) 484 return 0; 485 486 487 if (Data.getFragment()) { 488 if (Data.getFlags() & ELF_Other_ThumbFunc) 489 return Layout.getSymbolOffset(&Data)+1; 490 else 491 return Layout.getSymbolOffset(&Data); 492 } 493 494 return 0; 495 } 496 497 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 498 const MCAsmLayout &Layout) { 499 // The presence of symbol versions causes undefined symbols and 500 // versions declared with @@@ to be renamed. 501 502 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 503 ie = Asm.symbol_end(); it != ie; ++it) { 504 const MCSymbol &Alias = it->getSymbol(); 505 const MCSymbol &Symbol = Alias.AliasedSymbol(); 506 MCSymbolData &SD = Asm.getSymbolData(Symbol); 507 508 // Not an alias. 509 if (&Symbol == &Alias) 510 continue; 511 512 StringRef AliasName = Alias.getName(); 513 size_t Pos = AliasName.find('@'); 514 if (Pos == StringRef::npos) 515 continue; 516 517 // Aliases defined with .symvar copy the binding from the symbol they alias. 518 // This is the first place we are able to copy this information. 519 it->setExternal(SD.isExternal()); 520 MCELF::SetBinding(*it, MCELF::GetBinding(SD)); 521 522 StringRef Rest = AliasName.substr(Pos); 523 if (!Symbol.isUndefined() && !Rest.startswith("@@@")) 524 continue; 525 526 // FIXME: produce a better error message. 527 if (Symbol.isUndefined() && Rest.startswith("@@") && 528 !Rest.startswith("@@@")) 529 report_fatal_error("A @@ version cannot be undefined"); 530 531 Renames.insert(std::make_pair(&Symbol, &Alias)); 532 } 533 } 534 535 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF, 536 MCDataFragment *ShndxF, 537 ELFSymbolData &MSD, 538 const MCAsmLayout &Layout) { 539 MCSymbolData &OrigData = *MSD.SymbolData; 540 MCSymbolData &Data = 541 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol()); 542 543 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() || 544 Data.getSymbol().isVariable(); 545 546 // Binding and Type share the same byte as upper and lower nibbles 547 uint8_t Binding = MCELF::GetBinding(OrigData); 548 uint8_t Type = MCELF::GetType(Data); 549 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); 550 551 // Other and Visibility share the same byte with Visibility using the lower 552 // 2 bits 553 uint8_t Visibility = MCELF::GetVisibility(OrigData); 554 uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift); 555 Other |= Visibility; 556 557 uint64_t Value = SymbolValue(Data, Layout); 558 uint64_t Size = 0; 559 560 assert(!(Data.isCommon() && !Data.isExternal())); 561 562 const MCExpr *ESize = Data.getSize(); 563 if (ESize) { 564 int64_t Res; 565 if (!ESize->EvaluateAsAbsolute(Res, Layout)) 566 report_fatal_error("Size expression must be absolute."); 567 Size = Res; 568 } 569 570 // Write out the symbol table entry 571 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value, 572 Size, Other, MSD.SectionIndex, IsReserved); 573 } 574 575 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF, 576 MCDataFragment *ShndxF, 577 const MCAssembler &Asm, 578 const MCAsmLayout &Layout, 579 const SectionIndexMapTy &SectionIndexMap) { 580 // The string table must be emitted first because we need the index 581 // into the string table for all the symbol names. 582 assert(StringTable.size() && "Missing string table"); 583 584 // FIXME: Make sure the start of the symbol table is aligned. 585 586 // The first entry is the undefined symbol entry. 587 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false); 588 589 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) { 590 WriteSymbolEntry(SymtabF, ShndxF, FileSymbolData[i], 591 ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, 592 ELF::STV_DEFAULT, ELF::SHN_ABS, true); 593 } 594 595 // Write the symbol table entries. 596 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1; 597 598 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) { 599 ELFSymbolData &MSD = LocalSymbolData[i]; 600 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 601 } 602 603 // Write out a symbol table entry for each regular section. 604 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; 605 ++i) { 606 const MCSectionELF &Section = 607 static_cast<const MCSectionELF&>(i->getSection()); 608 if (Section.getType() == ELF::SHT_RELA || 609 Section.getType() == ELF::SHT_REL || 610 Section.getType() == ELF::SHT_STRTAB || 611 Section.getType() == ELF::SHT_SYMTAB || 612 Section.getType() == ELF::SHT_SYMTAB_SHNDX) 613 continue; 614 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0, 615 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), 616 false); 617 LastLocalSymbolIndex++; 618 } 619 620 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { 621 ELFSymbolData &MSD = ExternalSymbolData[i]; 622 MCSymbolData &Data = *MSD.SymbolData; 623 assert(((Data.getFlags() & ELF_STB_Global) || 624 (Data.getFlags() & ELF_STB_Weak)) && 625 "External symbol requires STB_GLOBAL or STB_WEAK flag"); 626 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 627 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 628 LastLocalSymbolIndex++; 629 } 630 631 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { 632 ELFSymbolData &MSD = UndefinedSymbolData[i]; 633 MCSymbolData &Data = *MSD.SymbolData; 634 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 635 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 636 LastLocalSymbolIndex++; 637 } 638 } 639 640 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm, 641 const MCValue &Target, 642 const MCFragment &F, 643 const MCFixup &Fixup, 644 bool IsPCRel) const { 645 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 646 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 647 const MCSymbol *Renamed = Renames.lookup(&Symbol); 648 const MCSymbolData &SD = Asm.getSymbolData(Symbol); 649 650 if (ASymbol.isUndefined()) { 651 if (Renamed) 652 return Renamed; 653 return undefinedExplicitRelSym(Target, Fixup, IsPCRel); 654 } 655 656 if (SD.isExternal()) { 657 if (Renamed) 658 return Renamed; 659 return &Symbol; 660 } 661 662 const MCSectionELF &Section = 663 static_cast<const MCSectionELF&>(ASymbol.getSection()); 664 const SectionKind secKind = Section.getKind(); 665 666 if (secKind.isBSS()) 667 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 668 669 if (secKind.isThreadLocal()) { 670 if (Renamed) 671 return Renamed; 672 return &Symbol; 673 } 674 675 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 676 const MCSectionELF &Sec2 = 677 static_cast<const MCSectionELF&>(F.getParent()->getSection()); 678 679 if (&Sec2 != &Section && 680 (Kind == MCSymbolRefExpr::VK_PLT || 681 Kind == MCSymbolRefExpr::VK_GOTPCREL || 682 Kind == MCSymbolRefExpr::VK_GOTOFF)) { 683 if (Renamed) 684 return Renamed; 685 return &Symbol; 686 } 687 688 if (Section.getFlags() & ELF::SHF_MERGE) { 689 if (Target.getConstant() == 0) 690 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 691 if (Renamed) 692 return Renamed; 693 return &Symbol; 694 } 695 696 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 697 698 } 699 700 701 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, 702 const MCAsmLayout &Layout, 703 const MCFragment *Fragment, 704 const MCFixup &Fixup, 705 MCValue Target, 706 uint64_t &FixedValue) { 707 int64_t Addend = 0; 708 int Index = 0; 709 int64_t Value = Target.getConstant(); 710 const MCSymbol *RelocSymbol = NULL; 711 712 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind()); 713 if (!Target.isAbsolute()) { 714 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 715 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 716 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel); 717 718 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 719 const MCSymbol &SymbolB = RefB->getSymbol(); 720 MCSymbolData &SDB = Asm.getSymbolData(SymbolB); 721 IsPCRel = true; 722 723 // Offset of the symbol in the section 724 int64_t a = Layout.getSymbolOffset(&SDB); 725 726 // Offset of the relocation in the section 727 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 728 Value += b - a; 729 } 730 731 if (!RelocSymbol) { 732 MCSymbolData &SD = Asm.getSymbolData(ASymbol); 733 MCFragment *F = SD.getFragment(); 734 735 if (F) { 736 Index = F->getParent()->getOrdinal() + 1; 737 // Offset of the symbol in the section 738 Value += Layout.getSymbolOffset(&SD); 739 } else { 740 Index = 0; 741 } 742 } else { 743 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref) 744 WeakrefUsedInReloc.insert(RelocSymbol); 745 else 746 UsedInReloc.insert(RelocSymbol); 747 Index = -1; 748 } 749 Addend = Value; 750 if (hasRelocationAddend()) 751 Value = 0; 752 } 753 754 FixedValue = Value; 755 unsigned Type = GetRelocType(Target, Fixup, IsPCRel, 756 (RelocSymbol != 0), Addend); 757 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 758 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 759 if (RelocNeedsGOT(Modifier)) 760 NeedsGOT = true; 761 762 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) + 763 Fixup.getOffset(); 764 765 if (!hasRelocationAddend()) 766 Addend = 0; 767 768 if (is64Bit()) 769 assert(isInt<64>(Addend)); 770 else 771 assert(isInt<32>(Addend)); 772 773 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup); 774 Relocations[Fragment->getParent()].push_back(ERE); 775 } 776 777 778 uint64_t 779 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm, 780 const MCSymbol *S) { 781 MCSymbolData &SD = Asm.getSymbolData(*S); 782 return SD.getIndex(); 783 } 784 785 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm, 786 const MCSymbolData &Data, 787 bool Used, bool Renamed) { 788 if (Data.getFlags() & ELF_Other_Weakref) 789 return false; 790 791 if (Used) 792 return true; 793 794 if (Renamed) 795 return false; 796 797 const MCSymbol &Symbol = Data.getSymbol(); 798 799 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_") 800 return true; 801 802 const MCSymbol &A = Symbol.AliasedSymbol(); 803 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined()) 804 return false; 805 806 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL; 807 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal) 808 return false; 809 810 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) 811 return false; 812 813 if (Symbol.isTemporary()) 814 return false; 815 816 return true; 817 } 818 819 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature, 820 bool isUsedInReloc) { 821 if (Data.isExternal()) 822 return false; 823 824 const MCSymbol &Symbol = Data.getSymbol(); 825 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 826 827 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) { 828 if (isSignature && !isUsedInReloc) 829 return true; 830 831 return false; 832 } 833 834 return true; 835 } 836 837 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm, 838 SectionIndexMapTy &SectionIndexMap, 839 const RelMapTy &RelMap) { 840 unsigned Index = 1; 841 for (MCAssembler::iterator it = Asm.begin(), 842 ie = Asm.end(); it != ie; ++it) { 843 const MCSectionELF &Section = 844 static_cast<const MCSectionELF &>(it->getSection()); 845 if (Section.getType() != ELF::SHT_GROUP) 846 continue; 847 SectionIndexMap[&Section] = Index++; 848 } 849 850 for (MCAssembler::iterator it = Asm.begin(), 851 ie = Asm.end(); it != ie; ++it) { 852 const MCSectionELF &Section = 853 static_cast<const MCSectionELF &>(it->getSection()); 854 if (Section.getType() == ELF::SHT_GROUP || 855 Section.getType() == ELF::SHT_REL || 856 Section.getType() == ELF::SHT_RELA) 857 continue; 858 SectionIndexMap[&Section] = Index++; 859 const MCSectionELF *RelSection = RelMap.lookup(&Section); 860 if (RelSection) 861 SectionIndexMap[RelSection] = Index++; 862 } 863 } 864 865 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, 866 const SectionIndexMapTy &SectionIndexMap, 867 RevGroupMapTy RevGroupMap, 868 unsigned NumRegularSections) { 869 // FIXME: Is this the correct place to do this? 870 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed? 871 if (NeedsGOT) { 872 StringRef Name = "_GLOBAL_OFFSET_TABLE_"; 873 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); 874 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); 875 Data.setExternal(true); 876 MCELF::SetBinding(Data, ELF::STB_GLOBAL); 877 } 878 879 // Index 0 is always the empty string. 880 StringMap<uint64_t> StringIndexMap; 881 StringTable += '\x00'; 882 883 // FIXME: We could optimize suffixes in strtab in the same way we 884 // optimize them in shstrtab. 885 886 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(), 887 ie = Asm.file_names_end(); 888 it != ie; 889 ++it) { 890 StringRef Name = *it; 891 uint64_t &Entry = StringIndexMap[Name]; 892 if (!Entry) { 893 Entry = StringTable.size(); 894 StringTable += Name; 895 StringTable += '\x00'; 896 } 897 FileSymbolData.push_back(Entry); 898 } 899 900 // Add the data for the symbols. 901 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 902 ie = Asm.symbol_end(); it != ie; ++it) { 903 const MCSymbol &Symbol = it->getSymbol(); 904 905 bool Used = UsedInReloc.count(&Symbol); 906 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol); 907 bool isSignature = RevGroupMap.count(&Symbol); 908 909 if (!isInSymtab(Asm, *it, 910 Used || WeakrefUsed || isSignature, 911 Renames.count(&Symbol))) 912 continue; 913 914 ELFSymbolData MSD; 915 MSD.SymbolData = it; 916 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 917 918 // Undefined symbols are global, but this is the first place we 919 // are able to set it. 920 bool Local = isLocal(*it, isSignature, Used); 921 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) { 922 MCSymbolData &SD = Asm.getSymbolData(RefSymbol); 923 MCELF::SetBinding(*it, ELF::STB_GLOBAL); 924 MCELF::SetBinding(SD, ELF::STB_GLOBAL); 925 } 926 927 if (RefSymbol.isUndefined() && !Used && WeakrefUsed) 928 MCELF::SetBinding(*it, ELF::STB_WEAK); 929 930 if (it->isCommon()) { 931 assert(!Local); 932 MSD.SectionIndex = ELF::SHN_COMMON; 933 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) { 934 MSD.SectionIndex = ELF::SHN_ABS; 935 } else if (RefSymbol.isUndefined()) { 936 if (isSignature && !Used) 937 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]); 938 else 939 MSD.SectionIndex = ELF::SHN_UNDEF; 940 } else { 941 const MCSectionELF &Section = 942 static_cast<const MCSectionELF&>(RefSymbol.getSection()); 943 MSD.SectionIndex = SectionIndexMap.lookup(&Section); 944 if (MSD.SectionIndex >= ELF::SHN_LORESERVE) 945 NeedsSymtabShndx = true; 946 assert(MSD.SectionIndex && "Invalid section index!"); 947 } 948 949 // The @@@ in symbol version is replaced with @ in undefined symbols and 950 // @@ in defined ones. 951 StringRef Name = Symbol.getName(); 952 SmallString<32> Buf; 953 954 size_t Pos = Name.find("@@@"); 955 if (Pos != StringRef::npos) { 956 Buf += Name.substr(0, Pos); 957 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1; 958 Buf += Name.substr(Pos + Skip); 959 Name = Buf; 960 } 961 962 uint64_t &Entry = StringIndexMap[Name]; 963 if (!Entry) { 964 Entry = StringTable.size(); 965 StringTable += Name; 966 StringTable += '\x00'; 967 } 968 MSD.StringIndex = Entry; 969 if (MSD.SectionIndex == ELF::SHN_UNDEF) 970 UndefinedSymbolData.push_back(MSD); 971 else if (Local) 972 LocalSymbolData.push_back(MSD); 973 else 974 ExternalSymbolData.push_back(MSD); 975 } 976 977 // Symbols are required to be in lexicographic order. 978 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end()); 979 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); 980 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); 981 982 // Set the symbol indices. Local symbols must come before all other 983 // symbols with non-local bindings. 984 unsigned Index = FileSymbolData.size() + 1; 985 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) 986 LocalSymbolData[i].SymbolData->setIndex(Index++); 987 988 Index += NumRegularSections; 989 990 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) 991 ExternalSymbolData[i].SymbolData->setIndex(Index++); 992 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) 993 UndefinedSymbolData[i].SymbolData->setIndex(Index++); 994 995 if (Index >= ELF::SHN_LORESERVE) 996 NeedsSymtabShndx = true; 997 } 998 999 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm, 1000 MCAsmLayout &Layout, 1001 RelMapTy &RelMap) { 1002 for (MCAssembler::const_iterator it = Asm.begin(), 1003 ie = Asm.end(); it != ie; ++it) { 1004 const MCSectionData &SD = *it; 1005 if (Relocations[&SD].empty()) 1006 continue; 1007 1008 MCContext &Ctx = Asm.getContext(); 1009 const MCSectionELF &Section = 1010 static_cast<const MCSectionELF&>(SD.getSection()); 1011 1012 const StringRef SectionName = Section.getSectionName(); 1013 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel"; 1014 RelaSectionName += SectionName; 1015 1016 unsigned EntrySize; 1017 if (hasRelocationAddend()) 1018 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela); 1019 else 1020 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel); 1021 1022 unsigned Flags = 0; 1023 StringRef Group = ""; 1024 if (Section.getFlags() & ELF::SHF_GROUP) { 1025 Flags = ELF::SHF_GROUP; 1026 Group = Section.getGroup()->getName(); 1027 } 1028 1029 const MCSectionELF *RelaSection = 1030 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ? 1031 ELF::SHT_RELA : ELF::SHT_REL, Flags, 1032 SectionKind::getReadOnly(), 1033 EntrySize, Group); 1034 RelMap[&Section] = RelaSection; 1035 Asm.getOrCreateSectionData(*RelaSection); 1036 } 1037 } 1038 1039 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, 1040 const RelMapTy &RelMap) { 1041 for (MCAssembler::const_iterator it = Asm.begin(), 1042 ie = Asm.end(); it != ie; ++it) { 1043 const MCSectionData &SD = *it; 1044 const MCSectionELF &Section = 1045 static_cast<const MCSectionELF&>(SD.getSection()); 1046 1047 const MCSectionELF *RelaSection = RelMap.lookup(&Section); 1048 if (!RelaSection) 1049 continue; 1050 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); 1051 RelaSD.setAlignment(is64Bit() ? 8 : 4); 1052 1053 MCDataFragment *F = new MCDataFragment(&RelaSD); 1054 WriteRelocationsFragment(Asm, F, &*it); 1055 } 1056 } 1057 1058 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, 1059 uint64_t Flags, uint64_t Address, 1060 uint64_t Offset, uint64_t Size, 1061 uint32_t Link, uint32_t Info, 1062 uint64_t Alignment, 1063 uint64_t EntrySize) { 1064 Write32(Name); // sh_name: index into string table 1065 Write32(Type); // sh_type 1066 WriteWord(Flags); // sh_flags 1067 WriteWord(Address); // sh_addr 1068 WriteWord(Offset); // sh_offset 1069 WriteWord(Size); // sh_size 1070 Write32(Link); // sh_link 1071 Write32(Info); // sh_info 1072 WriteWord(Alignment); // sh_addralign 1073 WriteWord(EntrySize); // sh_entsize 1074 } 1075 1076 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm, 1077 MCDataFragment *F, 1078 const MCSectionData *SD) { 1079 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD]; 1080 1081 // Sort the relocation entries. Most targets just sort by r_offset, but some 1082 // (e.g., MIPS) have additional constraints. 1083 TargetObjectWriter->sortRelocs(Asm, Relocs); 1084 1085 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { 1086 ELFRelocationEntry entry = Relocs[e - i - 1]; 1087 1088 if (!entry.Index) 1089 ; 1090 else if (entry.Index < 0) 1091 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); 1092 else 1093 entry.Index += FileSymbolData.size() + LocalSymbolData.size(); 1094 if (is64Bit()) { 1095 String64(*F, entry.r_offset); 1096 if (TargetObjectWriter->isN64()) { 1097 String32(*F, entry.Index); 1098 1099 String8(*F, TargetObjectWriter->getRSsym(entry.Type)); 1100 String8(*F, TargetObjectWriter->getRType3(entry.Type)); 1101 String8(*F, TargetObjectWriter->getRType2(entry.Type)); 1102 String8(*F, TargetObjectWriter->getRType(entry.Type)); 1103 } 1104 else { 1105 struct ELF::Elf64_Rela ERE64; 1106 ERE64.setSymbolAndType(entry.Index, entry.Type); 1107 String64(*F, ERE64.r_info); 1108 } 1109 if (hasRelocationAddend()) 1110 String64(*F, entry.r_addend); 1111 } else { 1112 String32(*F, entry.r_offset); 1113 1114 struct ELF::Elf32_Rela ERE32; 1115 ERE32.setSymbolAndType(entry.Index, entry.Type); 1116 String32(*F, ERE32.r_info); 1117 1118 if (hasRelocationAddend()) 1119 String32(*F, entry.r_addend); 1120 } 1121 } 1122 } 1123 1124 static int compareBySuffix(const MCSectionELF *const *a, 1125 const MCSectionELF *const *b) { 1126 const StringRef &NameA = (*a)->getSectionName(); 1127 const StringRef &NameB = (*b)->getSectionName(); 1128 const unsigned sizeA = NameA.size(); 1129 const unsigned sizeB = NameB.size(); 1130 const unsigned len = std::min(sizeA, sizeB); 1131 for (unsigned int i = 0; i < len; ++i) { 1132 char ca = NameA[sizeA - i - 1]; 1133 char cb = NameB[sizeB - i - 1]; 1134 if (ca != cb) 1135 return cb - ca; 1136 } 1137 1138 return sizeB - sizeA; 1139 } 1140 1141 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm, 1142 MCAsmLayout &Layout, 1143 SectionIndexMapTy &SectionIndexMap, 1144 const RelMapTy &RelMap) { 1145 MCContext &Ctx = Asm.getContext(); 1146 MCDataFragment *F; 1147 1148 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; 1149 1150 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. 1151 const MCSectionELF *ShstrtabSection = 1152 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, 1153 SectionKind::getReadOnly()); 1154 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); 1155 ShstrtabSD.setAlignment(1); 1156 1157 const MCSectionELF *SymtabSection = 1158 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, 1159 SectionKind::getReadOnly(), 1160 EntrySize, ""); 1161 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); 1162 SymtabSD.setAlignment(is64Bit() ? 8 : 4); 1163 1164 MCSectionData *SymtabShndxSD = NULL; 1165 1166 if (NeedsSymtabShndx) { 1167 const MCSectionELF *SymtabShndxSection = 1168 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 1169 SectionKind::getReadOnly(), 4, ""); 1170 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection); 1171 SymtabShndxSD->setAlignment(4); 1172 } 1173 1174 const MCSectionELF *StrtabSection; 1175 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, 1176 SectionKind::getReadOnly()); 1177 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); 1178 StrtabSD.setAlignment(1); 1179 1180 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 1181 1182 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection); 1183 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection); 1184 StringTableIndex = SectionIndexMap.lookup(StrtabSection); 1185 1186 // Symbol table 1187 F = new MCDataFragment(&SymtabSD); 1188 MCDataFragment *ShndxF = NULL; 1189 if (NeedsSymtabShndx) { 1190 ShndxF = new MCDataFragment(SymtabShndxSD); 1191 } 1192 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap); 1193 1194 F = new MCDataFragment(&StrtabSD); 1195 F->getContents().append(StringTable.begin(), StringTable.end()); 1196 1197 F = new MCDataFragment(&ShstrtabSD); 1198 1199 std::vector<const MCSectionELF*> Sections; 1200 for (MCAssembler::const_iterator it = Asm.begin(), 1201 ie = Asm.end(); it != ie; ++it) { 1202 const MCSectionELF &Section = 1203 static_cast<const MCSectionELF&>(it->getSection()); 1204 Sections.push_back(&Section); 1205 } 1206 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix); 1207 1208 // Section header string table. 1209 // 1210 // The first entry of a string table holds a null character so skip 1211 // section 0. 1212 uint64_t Index = 1; 1213 F->getContents().push_back('\x00'); 1214 1215 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) { 1216 const MCSectionELF &Section = *Sections[I]; 1217 1218 StringRef Name = Section.getSectionName(); 1219 if (I != 0) { 1220 StringRef PreviousName = Sections[I - 1]->getSectionName(); 1221 if (PreviousName.endswith(Name)) { 1222 SectionStringTableIndex[&Section] = Index - Name.size() - 1; 1223 continue; 1224 } 1225 } 1226 // Remember the index into the string table so we can write it 1227 // into the sh_name field of the section header table. 1228 SectionStringTableIndex[&Section] = Index; 1229 1230 Index += Name.size() + 1; 1231 F->getContents().append(Name.begin(), Name.end()); 1232 F->getContents().push_back('\x00'); 1233 } 1234 } 1235 1236 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm, 1237 MCAsmLayout &Layout, 1238 GroupMapTy &GroupMap, 1239 RevGroupMapTy &RevGroupMap, 1240 SectionIndexMapTy &SectionIndexMap, 1241 const RelMapTy &RelMap) { 1242 // Create the .note.GNU-stack section if needed. 1243 MCContext &Ctx = Asm.getContext(); 1244 if (Asm.getNoExecStack()) { 1245 const MCSectionELF *GnuStackSection = 1246 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0, 1247 SectionKind::getReadOnly()); 1248 Asm.getOrCreateSectionData(*GnuStackSection); 1249 } 1250 1251 // Build the groups 1252 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 1253 it != ie; ++it) { 1254 const MCSectionELF &Section = 1255 static_cast<const MCSectionELF&>(it->getSection()); 1256 if (!(Section.getFlags() & ELF::SHF_GROUP)) 1257 continue; 1258 1259 const MCSymbol *SignatureSymbol = Section.getGroup(); 1260 Asm.getOrCreateSymbolData(*SignatureSymbol); 1261 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol]; 1262 if (!Group) { 1263 Group = Ctx.CreateELFGroupSection(); 1264 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 1265 Data.setAlignment(4); 1266 MCDataFragment *F = new MCDataFragment(&Data); 1267 String32(*F, ELF::GRP_COMDAT); 1268 } 1269 GroupMap[Group] = SignatureSymbol; 1270 } 1271 1272 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 1273 1274 // Add sections to the groups 1275 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 1276 it != ie; ++it) { 1277 const MCSectionELF &Section = 1278 static_cast<const MCSectionELF&>(it->getSection()); 1279 if (!(Section.getFlags() & ELF::SHF_GROUP)) 1280 continue; 1281 const MCSectionELF *Group = RevGroupMap[Section.getGroup()]; 1282 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 1283 // FIXME: we could use the previous fragment 1284 MCDataFragment *F = new MCDataFragment(&Data); 1285 unsigned Index = SectionIndexMap.lookup(&Section); 1286 String32(*F, Index); 1287 } 1288 } 1289 1290 void ELFObjectWriter::WriteSection(MCAssembler &Asm, 1291 const SectionIndexMapTy &SectionIndexMap, 1292 uint32_t GroupSymbolIndex, 1293 uint64_t Offset, uint64_t Size, 1294 uint64_t Alignment, 1295 const MCSectionELF &Section) { 1296 uint64_t sh_link = 0; 1297 uint64_t sh_info = 0; 1298 1299 switch(Section.getType()) { 1300 case ELF::SHT_DYNAMIC: 1301 sh_link = SectionStringTableIndex[&Section]; 1302 sh_info = 0; 1303 break; 1304 1305 case ELF::SHT_REL: 1306 case ELF::SHT_RELA: { 1307 const MCSectionELF *SymtabSection; 1308 const MCSectionELF *InfoSection; 1309 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 1310 0, 1311 SectionKind::getReadOnly()); 1312 sh_link = SectionIndexMap.lookup(SymtabSection); 1313 assert(sh_link && ".symtab not found"); 1314 1315 // Remove ".rel" and ".rela" prefixes. 1316 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5; 1317 StringRef SectionName = Section.getSectionName().substr(SecNameLen); 1318 StringRef GroupName = 1319 Section.getGroup() ? Section.getGroup()->getName() : ""; 1320 1321 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS, 1322 0, SectionKind::getReadOnly(), 1323 0, GroupName); 1324 sh_info = SectionIndexMap.lookup(InfoSection); 1325 break; 1326 } 1327 1328 case ELF::SHT_SYMTAB: 1329 case ELF::SHT_DYNSYM: 1330 sh_link = StringTableIndex; 1331 sh_info = LastLocalSymbolIndex; 1332 break; 1333 1334 case ELF::SHT_SYMTAB_SHNDX: 1335 sh_link = SymbolTableIndex; 1336 break; 1337 1338 case ELF::SHT_PROGBITS: 1339 case ELF::SHT_STRTAB: 1340 case ELF::SHT_NOBITS: 1341 case ELF::SHT_NOTE: 1342 case ELF::SHT_NULL: 1343 case ELF::SHT_ARM_ATTRIBUTES: 1344 case ELF::SHT_INIT_ARRAY: 1345 case ELF::SHT_FINI_ARRAY: 1346 case ELF::SHT_PREINIT_ARRAY: 1347 case ELF::SHT_X86_64_UNWIND: 1348 case ELF::SHT_MIPS_REGINFO: 1349 case ELF::SHT_MIPS_OPTIONS: 1350 // Nothing to do. 1351 break; 1352 1353 case ELF::SHT_GROUP: 1354 sh_link = SymbolTableIndex; 1355 sh_info = GroupSymbolIndex; 1356 break; 1357 1358 default: 1359 assert(0 && "FIXME: sh_type value not supported!"); 1360 break; 1361 } 1362 1363 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM && 1364 Section.getType() == ELF::SHT_ARM_EXIDX) { 1365 StringRef SecName(Section.getSectionName()); 1366 if (SecName == ".ARM.exidx") { 1367 sh_link = SectionIndexMap.lookup( 1368 Asm.getContext().getELFSection(".text", 1369 ELF::SHT_PROGBITS, 1370 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, 1371 SectionKind::getText())); 1372 } else if (SecName.startswith(".ARM.exidx")) { 1373 StringRef GroupName = 1374 Section.getGroup() ? Section.getGroup()->getName() : ""; 1375 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection( 1376 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS, 1377 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0, 1378 GroupName)); 1379 } 1380 } 1381 1382 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(), 1383 Section.getFlags(), 0, Offset, Size, sh_link, sh_info, 1384 Alignment, Section.getEntrySize()); 1385 } 1386 1387 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) { 1388 return SD.getOrdinal() == ~UINT32_C(0) && 1389 !SD.getSection().isVirtualSection(); 1390 } 1391 1392 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) { 1393 uint64_t Ret = 0; 1394 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1395 ++i) { 1396 const MCFragment &F = *i; 1397 assert(F.getKind() == MCFragment::FT_Data); 1398 Ret += cast<MCDataFragment>(F).getContents().size(); 1399 } 1400 return Ret; 1401 } 1402 1403 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout, 1404 const MCSectionData &SD) { 1405 if (IsELFMetaDataSection(SD)) 1406 return DataSectionSize(SD); 1407 return Layout.getSectionFileSize(&SD); 1408 } 1409 1410 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout, 1411 const MCSectionData &SD) { 1412 if (IsELFMetaDataSection(SD)) 1413 return DataSectionSize(SD); 1414 return Layout.getSectionAddressSize(&SD); 1415 } 1416 1417 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm, 1418 const MCAsmLayout &Layout, 1419 const MCSectionELF &Section) { 1420 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1421 1422 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment()); 1423 WriteZeros(Padding); 1424 1425 if (IsELFMetaDataSection(SD)) { 1426 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1427 ++i) { 1428 const MCFragment &F = *i; 1429 assert(F.getKind() == MCFragment::FT_Data); 1430 WriteBytes(cast<MCDataFragment>(F).getContents()); 1431 } 1432 } else { 1433 Asm.writeSectionData(&SD, Layout); 1434 } 1435 } 1436 1437 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm, 1438 const GroupMapTy &GroupMap, 1439 const MCAsmLayout &Layout, 1440 const SectionIndexMapTy &SectionIndexMap, 1441 const SectionOffsetMapTy &SectionOffsetMap) { 1442 const unsigned NumSections = Asm.size() + 1; 1443 1444 std::vector<const MCSectionELF*> Sections; 1445 Sections.resize(NumSections - 1); 1446 1447 for (SectionIndexMapTy::const_iterator i= 1448 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) { 1449 const std::pair<const MCSectionELF*, uint32_t> &p = *i; 1450 Sections[p.second - 1] = p.first; 1451 } 1452 1453 // Null section first. 1454 uint64_t FirstSectionSize = 1455 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0; 1456 uint32_t FirstSectionLink = 1457 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0; 1458 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0); 1459 1460 for (unsigned i = 0; i < NumSections - 1; ++i) { 1461 const MCSectionELF &Section = *Sections[i]; 1462 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1463 uint32_t GroupSymbolIndex; 1464 if (Section.getType() != ELF::SHT_GROUP) 1465 GroupSymbolIndex = 0; 1466 else 1467 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, 1468 GroupMap.lookup(&Section)); 1469 1470 uint64_t Size = GetSectionAddressSize(Layout, SD); 1471 1472 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex, 1473 SectionOffsetMap.lookup(&Section), Size, 1474 SD.getAlignment(), Section); 1475 } 1476 } 1477 1478 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm, 1479 std::vector<const MCSectionELF*> &Sections) { 1480 for (MCAssembler::iterator it = Asm.begin(), 1481 ie = Asm.end(); it != ie; ++it) { 1482 const MCSectionELF &Section = 1483 static_cast<const MCSectionELF &>(it->getSection()); 1484 if (Section.getType() == ELF::SHT_GROUP) 1485 Sections.push_back(&Section); 1486 } 1487 1488 for (MCAssembler::iterator it = Asm.begin(), 1489 ie = Asm.end(); it != ie; ++it) { 1490 const MCSectionELF &Section = 1491 static_cast<const MCSectionELF &>(it->getSection()); 1492 if (Section.getType() != ELF::SHT_GROUP && 1493 Section.getType() != ELF::SHT_REL && 1494 Section.getType() != ELF::SHT_RELA) 1495 Sections.push_back(&Section); 1496 } 1497 1498 for (MCAssembler::iterator it = Asm.begin(), 1499 ie = Asm.end(); it != ie; ++it) { 1500 const MCSectionELF &Section = 1501 static_cast<const MCSectionELF &>(it->getSection()); 1502 if (Section.getType() == ELF::SHT_REL || 1503 Section.getType() == ELF::SHT_RELA) 1504 Sections.push_back(&Section); 1505 } 1506 } 1507 1508 void ELFObjectWriter::WriteObject(MCAssembler &Asm, 1509 const MCAsmLayout &Layout) { 1510 GroupMapTy GroupMap; 1511 RevGroupMapTy RevGroupMap; 1512 SectionIndexMapTy SectionIndexMap; 1513 1514 unsigned NumUserSections = Asm.size(); 1515 1516 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap; 1517 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1518 1519 const unsigned NumUserAndRelocSections = Asm.size(); 1520 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap, 1521 RevGroupMap, SectionIndexMap, RelMap); 1522 const unsigned AllSections = Asm.size(); 1523 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections; 1524 1525 unsigned NumRegularSections = NumUserSections + NumIndexedSections; 1526 1527 // Compute symbol table information. 1528 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections); 1529 1530 1531 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1532 1533 CreateMetadataSections(const_cast<MCAssembler&>(Asm), 1534 const_cast<MCAsmLayout&>(Layout), 1535 SectionIndexMap, 1536 RelMap); 1537 1538 uint64_t NaturalAlignment = is64Bit() ? 8 : 4; 1539 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 1540 sizeof(ELF::Elf32_Ehdr); 1541 uint64_t FileOff = HeaderSize; 1542 1543 std::vector<const MCSectionELF*> Sections; 1544 ComputeSectionOrder(Asm, Sections); 1545 unsigned NumSections = Sections.size(); 1546 SectionOffsetMapTy SectionOffsetMap; 1547 for (unsigned i = 0; i < NumRegularSections + 1; ++i) { 1548 const MCSectionELF &Section = *Sections[i]; 1549 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1550 1551 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1552 1553 // Remember the offset into the file for this section. 1554 SectionOffsetMap[&Section] = FileOff; 1555 1556 // Get the size of the section in the output file (including padding). 1557 FileOff += GetSectionFileSize(Layout, SD); 1558 } 1559 1560 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); 1561 1562 const unsigned SectionHeaderOffset = FileOff - HeaderSize; 1563 1564 uint64_t SectionHeaderEntrySize = is64Bit() ? 1565 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr); 1566 FileOff += (NumSections + 1) * SectionHeaderEntrySize; 1567 1568 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) { 1569 const MCSectionELF &Section = *Sections[i]; 1570 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1571 1572 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1573 1574 // Remember the offset into the file for this section. 1575 SectionOffsetMap[&Section] = FileOff; 1576 1577 // Get the size of the section in the output file (including padding). 1578 FileOff += GetSectionFileSize(Layout, SD); 1579 } 1580 1581 // Write out the ELF header ... 1582 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1); 1583 1584 // ... then the regular sections ... 1585 // + because of .shstrtab 1586 for (unsigned i = 0; i < NumRegularSections + 1; ++i) 1587 WriteDataSectionData(Asm, Layout, *Sections[i]); 1588 1589 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment); 1590 WriteZeros(Padding); 1591 1592 // ... then the section header table ... 1593 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap, 1594 SectionOffsetMap); 1595 1596 // ... and then the remaining sections ... 1597 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) 1598 WriteDataSectionData(Asm, Layout, *Sections[i]); 1599 } 1600 1601 bool 1602 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 1603 const MCSymbolData &DataA, 1604 const MCFragment &FB, 1605 bool InSet, 1606 bool IsPCRel) const { 1607 if (DataA.getFlags() & ELF_STB_Weak) 1608 return false; 1609 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 1610 Asm, DataA, FB,InSet, IsPCRel); 1611 } 1612 1613 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1614 raw_ostream &OS, 1615 bool IsLittleEndian) { 1616 return new ELFObjectWriter(MOTW, OS, IsLittleEndian); 1617 } 1618