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