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/ADT/OwningPtr.h" 15 #include "llvm/ADT/SmallPtrSet.h" 16 #include "llvm/ADT/STLExtras.h" 17 #include "llvm/ADT/StringMap.h" 18 #include "llvm/ADT/Twine.h" 19 #include "llvm/MC/MCAssembler.h" 20 #include "llvm/MC/MCAsmLayout.h" 21 #include "llvm/MC/MCContext.h" 22 #include "llvm/MC/MCELFSymbolFlags.h" 23 #include "llvm/MC/MCExpr.h" 24 #include "llvm/MC/MCELFObjectWriter.h" 25 #include "llvm/MC/MCObjectWriter.h" 26 #include "llvm/MC/MCSectionELF.h" 27 #include "llvm/MC/MCSymbol.h" 28 #include "llvm/MC/MCValue.h" 29 #include "llvm/Support/Debug.h" 30 #include "llvm/Support/ErrorHandling.h" 31 #include "llvm/Support/ELF.h" 32 #include "llvm/Target/TargetAsmBackend.h" 33 34 #include "../Target/X86/X86FixupKinds.h" 35 #include "../Target/ARM/ARMFixupKinds.h" 36 37 #include <vector> 38 using namespace llvm; 39 40 static unsigned GetType(const MCSymbolData &SD) { 41 uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift; 42 assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT || 43 Type == ELF::STT_FUNC || Type == ELF::STT_SECTION || 44 Type == ELF::STT_FILE || Type == ELF::STT_COMMON || 45 Type == ELF::STT_TLS); 46 return Type; 47 } 48 49 static unsigned GetBinding(const MCSymbolData &SD) { 50 uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift; 51 assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL || 52 Binding == ELF::STB_WEAK); 53 return Binding; 54 } 55 56 static void SetBinding(MCSymbolData &SD, unsigned Binding) { 57 assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL || 58 Binding == ELF::STB_WEAK); 59 uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift); 60 SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift)); 61 } 62 63 static unsigned GetVisibility(MCSymbolData &SD) { 64 unsigned Visibility = 65 (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift; 66 assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL || 67 Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED); 68 return Visibility; 69 } 70 71 72 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) { 73 switch (Variant) { 74 default: 75 return false; 76 case MCSymbolRefExpr::VK_GOT: 77 case MCSymbolRefExpr::VK_PLT: 78 case MCSymbolRefExpr::VK_GOTPCREL: 79 case MCSymbolRefExpr::VK_TPOFF: 80 case MCSymbolRefExpr::VK_TLSGD: 81 case MCSymbolRefExpr::VK_GOTTPOFF: 82 case MCSymbolRefExpr::VK_INDNTPOFF: 83 case MCSymbolRefExpr::VK_NTPOFF: 84 case MCSymbolRefExpr::VK_GOTNTPOFF: 85 case MCSymbolRefExpr::VK_TLSLDM: 86 case MCSymbolRefExpr::VK_DTPOFF: 87 case MCSymbolRefExpr::VK_TLSLD: 88 return true; 89 } 90 } 91 92 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { 93 const MCFixupKindInfo &FKI = 94 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind); 95 96 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; 97 } 98 99 namespace { 100 class ELFObjectWriter : public MCObjectWriter { 101 protected: 102 /*static bool isFixupKindX86RIPRel(unsigned Kind) { 103 return Kind == X86::reloc_riprel_4byte || 104 Kind == X86::reloc_riprel_4byte_movq_load; 105 }*/ 106 107 108 /// ELFSymbolData - Helper struct for containing some precomputed information 109 /// on symbols. 110 struct ELFSymbolData { 111 MCSymbolData *SymbolData; 112 uint64_t StringIndex; 113 uint32_t SectionIndex; 114 115 // Support lexicographic sorting. 116 bool operator<(const ELFSymbolData &RHS) const { 117 if (GetType(*SymbolData) == ELF::STT_FILE) 118 return true; 119 if (GetType(*RHS.SymbolData) == ELF::STT_FILE) 120 return false; 121 return SymbolData->getSymbol().getName() < 122 RHS.SymbolData->getSymbol().getName(); 123 } 124 }; 125 126 /// @name Relocation Data 127 /// @{ 128 129 struct ELFRelocationEntry { 130 // Make these big enough for both 32-bit and 64-bit 131 uint64_t r_offset; 132 int Index; 133 unsigned Type; 134 const MCSymbol *Symbol; 135 uint64_t r_addend; 136 137 ELFRelocationEntry() 138 : r_offset(0), Index(0), Type(0), Symbol(0), r_addend(0) {} 139 140 ELFRelocationEntry(uint64_t RelocOffset, int Idx, 141 unsigned RelType, const MCSymbol *Sym, 142 uint64_t Addend) 143 : r_offset(RelocOffset), Index(Idx), Type(RelType), 144 Symbol(Sym), r_addend(Addend) {} 145 146 // Support lexicographic sorting. 147 bool operator<(const ELFRelocationEntry &RE) const { 148 return RE.r_offset < r_offset; 149 } 150 }; 151 152 /// The target specific ELF writer instance. 153 llvm::OwningPtr<MCELFObjectTargetWriter> TargetObjectWriter; 154 155 SmallPtrSet<const MCSymbol *, 16> UsedInReloc; 156 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc; 157 DenseMap<const MCSymbol *, const MCSymbol *> Renames; 158 159 llvm::DenseMap<const MCSectionData*, 160 std::vector<ELFRelocationEntry> > Relocations; 161 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex; 162 163 /// @} 164 /// @name Symbol Table Data 165 /// @{ 166 167 SmallString<256> StringTable; 168 std::vector<ELFSymbolData> LocalSymbolData; 169 std::vector<ELFSymbolData> ExternalSymbolData; 170 std::vector<ELFSymbolData> UndefinedSymbolData; 171 172 /// @} 173 174 bool NeedsGOT; 175 176 bool NeedsSymtabShndx; 177 178 // This holds the symbol table index of the last local symbol. 179 unsigned LastLocalSymbolIndex; 180 // This holds the .strtab section index. 181 unsigned StringTableIndex; 182 // This holds the .symtab section index. 183 unsigned SymbolTableIndex; 184 185 unsigned ShstrtabIndex; 186 187 188 const MCSymbol *SymbolToReloc(const MCAssembler &Asm, 189 const MCValue &Target, 190 const MCFragment &F) const; 191 192 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } 193 bool hasRelocationAddend() const { 194 return TargetObjectWriter->hasRelocationAddend(); 195 } 196 197 public: 198 ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 199 raw_ostream &_OS, bool IsLittleEndian) 200 : MCObjectWriter(_OS, IsLittleEndian), 201 TargetObjectWriter(MOTW), 202 NeedsGOT(false), NeedsSymtabShndx(false){ 203 } 204 205 virtual ~ELFObjectWriter(); 206 207 void WriteWord(uint64_t W) { 208 if (is64Bit()) 209 Write64(W); 210 else 211 Write32(W); 212 } 213 214 void StringLE16(char *buf, uint16_t Value) { 215 buf[0] = char(Value >> 0); 216 buf[1] = char(Value >> 8); 217 } 218 219 void StringLE32(char *buf, uint32_t Value) { 220 StringLE16(buf, uint16_t(Value >> 0)); 221 StringLE16(buf + 2, uint16_t(Value >> 16)); 222 } 223 224 void StringLE64(char *buf, uint64_t Value) { 225 StringLE32(buf, uint32_t(Value >> 0)); 226 StringLE32(buf + 4, uint32_t(Value >> 32)); 227 } 228 229 void StringBE16(char *buf ,uint16_t Value) { 230 buf[0] = char(Value >> 8); 231 buf[1] = char(Value >> 0); 232 } 233 234 void StringBE32(char *buf, uint32_t Value) { 235 StringBE16(buf, uint16_t(Value >> 16)); 236 StringBE16(buf + 2, uint16_t(Value >> 0)); 237 } 238 239 void StringBE64(char *buf, uint64_t Value) { 240 StringBE32(buf, uint32_t(Value >> 32)); 241 StringBE32(buf + 4, uint32_t(Value >> 0)); 242 } 243 244 void String8(MCDataFragment &F, uint8_t Value) { 245 char buf[1]; 246 buf[0] = Value; 247 F.getContents() += StringRef(buf, 1); 248 } 249 250 void String16(MCDataFragment &F, uint16_t Value) { 251 char buf[2]; 252 if (isLittleEndian()) 253 StringLE16(buf, Value); 254 else 255 StringBE16(buf, Value); 256 F.getContents() += StringRef(buf, 2); 257 } 258 259 void String32(MCDataFragment &F, uint32_t Value) { 260 char buf[4]; 261 if (isLittleEndian()) 262 StringLE32(buf, Value); 263 else 264 StringBE32(buf, Value); 265 F.getContents() += StringRef(buf, 4); 266 } 267 268 void String64(MCDataFragment &F, uint64_t Value) { 269 char buf[8]; 270 if (isLittleEndian()) 271 StringLE64(buf, Value); 272 else 273 StringBE64(buf, Value); 274 F.getContents() += StringRef(buf, 8); 275 } 276 277 virtual void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections); 278 279 virtual void WriteSymbolEntry(MCDataFragment *SymtabF, MCDataFragment *ShndxF, 280 uint64_t name, uint8_t info, 281 uint64_t value, uint64_t size, 282 uint8_t other, uint32_t shndx, 283 bool Reserved); 284 285 virtual void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF, 286 ELFSymbolData &MSD, 287 const MCAsmLayout &Layout); 288 289 typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy; 290 virtual void WriteSymbolTable(MCDataFragment *SymtabF, MCDataFragment *ShndxF, 291 const MCAssembler &Asm, 292 const MCAsmLayout &Layout, 293 const SectionIndexMapTy &SectionIndexMap); 294 295 virtual void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, 296 const MCFragment *Fragment, const MCFixup &Fixup, 297 MCValue Target, uint64_t &FixedValue); 298 299 virtual uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm, 300 const MCSymbol *S); 301 302 // Map from a group section to the signature symbol 303 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy; 304 // Map from a signature symbol to the group section 305 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy; 306 307 /// ComputeSymbolTable - Compute the symbol table data 308 /// 309 /// \param StringTable [out] - The string table data. 310 /// \param StringIndexMap [out] - Map from symbol names to offsets in the 311 /// string table. 312 virtual void ComputeSymbolTable(MCAssembler &Asm, 313 const SectionIndexMapTy &SectionIndexMap, 314 RevGroupMapTy RevGroupMap); 315 316 virtual void ComputeIndexMap(MCAssembler &Asm, 317 SectionIndexMapTy &SectionIndexMap); 318 319 virtual void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout, 320 const MCSectionData &SD); 321 322 virtual void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) { 323 for (MCAssembler::const_iterator it = Asm.begin(), 324 ie = Asm.end(); it != ie; ++it) { 325 WriteRelocation(Asm, Layout, *it); 326 } 327 } 328 329 virtual void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout, 330 const SectionIndexMapTy &SectionIndexMap); 331 332 virtual void CreateGroupSections(MCAssembler &Asm, MCAsmLayout &Layout, 333 GroupMapTy &GroupMap, RevGroupMapTy &RevGroupMap); 334 335 virtual void ExecutePostLayoutBinding(MCAssembler &Asm, 336 const MCAsmLayout &Layout); 337 338 virtual void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags, 339 uint64_t Address, uint64_t Offset, 340 uint64_t Size, uint32_t Link, uint32_t Info, 341 uint64_t Alignment, uint64_t EntrySize); 342 343 virtual void WriteRelocationsFragment(const MCAssembler &Asm, 344 MCDataFragment *F, 345 const MCSectionData *SD); 346 347 virtual bool 348 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 349 const MCSymbolData &DataA, 350 const MCFragment &FB, 351 bool InSet, 352 bool IsPCRel) const; 353 354 virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout); 355 virtual void WriteSection(MCAssembler &Asm, 356 const SectionIndexMapTy &SectionIndexMap, 357 uint32_t GroupSymbolIndex, 358 uint64_t Offset, uint64_t Size, uint64_t Alignment, 359 const MCSectionELF &Section); 360 361 protected: 362 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 363 bool IsPCRel, bool IsRelocWithSymbol, 364 int64_t Addend) = 0; 365 }; 366 367 //===- X86ELFObjectWriter -------------------------------------------===// 368 369 class X86ELFObjectWriter : public ELFObjectWriter { 370 public: 371 X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 372 raw_ostream &_OS, 373 bool IsLittleEndian); 374 375 virtual ~X86ELFObjectWriter(); 376 protected: 377 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 378 bool IsPCRel, bool IsRelocWithSymbol, 379 int64_t Addend); 380 }; 381 382 383 //===- ARMELFObjectWriter -------------------------------------------===// 384 385 class ARMELFObjectWriter : public ELFObjectWriter { 386 public: 387 ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW, 388 raw_ostream &_OS, 389 bool IsLittleEndian); 390 391 virtual ~ARMELFObjectWriter(); 392 protected: 393 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 394 bool IsPCRel, bool IsRelocWithSymbol, 395 int64_t Addend); 396 }; 397 398 //===- MBlazeELFObjectWriter -------------------------------------------===// 399 400 class MBlazeELFObjectWriter : public ELFObjectWriter { 401 public: 402 MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW, 403 raw_ostream &_OS, 404 bool IsLittleEndian); 405 406 virtual ~MBlazeELFObjectWriter(); 407 protected: 408 virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 409 bool IsPCRel, bool IsRelocWithSymbol, 410 int64_t Addend); 411 }; 412 } 413 414 ELFObjectWriter::~ELFObjectWriter() 415 {} 416 417 // Emit the ELF header. 418 void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize, 419 unsigned NumberOfSections) { 420 // ELF Header 421 // ---------- 422 // 423 // Note 424 // ---- 425 // emitWord method behaves differently for ELF32 and ELF64, writing 426 // 4 bytes in the former and 8 in the latter. 427 428 Write8(0x7f); // e_ident[EI_MAG0] 429 Write8('E'); // e_ident[EI_MAG1] 430 Write8('L'); // e_ident[EI_MAG2] 431 Write8('F'); // e_ident[EI_MAG3] 432 433 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS] 434 435 // e_ident[EI_DATA] 436 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); 437 438 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] 439 // e_ident[EI_OSABI] 440 switch (TargetObjectWriter->getOSType()) { 441 case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break; 442 case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break; 443 default: Write8(ELF::ELFOSABI_NONE); break; 444 } 445 Write8(0); // e_ident[EI_ABIVERSION] 446 447 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); 448 449 Write16(ELF::ET_REL); // e_type 450 451 Write16(TargetObjectWriter->getEMachine()); // e_machine = target 452 453 Write32(ELF::EV_CURRENT); // e_version 454 WriteWord(0); // e_entry, no entry point in .o file 455 WriteWord(0); // e_phoff, no program header for .o 456 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 457 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes 458 459 // FIXME: Make this configurable. 460 Write32(0); // e_flags = whatever the target wants 461 462 // e_ehsize = ELF header size 463 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr)); 464 465 Write16(0); // e_phentsize = prog header entry size 466 Write16(0); // e_phnum = # prog header entries = 0 467 468 // e_shentsize = Section header entry size 469 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr)); 470 471 // e_shnum = # of section header ents 472 if (NumberOfSections >= ELF::SHN_LORESERVE) 473 Write16(0); 474 else 475 Write16(NumberOfSections); 476 477 // e_shstrndx = Section # of '.shstrtab' 478 if (NumberOfSections >= ELF::SHN_LORESERVE) 479 Write16(ELF::SHN_XINDEX); 480 else 481 Write16(ShstrtabIndex); 482 } 483 484 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF, 485 MCDataFragment *ShndxF, 486 uint64_t name, 487 uint8_t info, uint64_t value, 488 uint64_t size, uint8_t other, 489 uint32_t shndx, 490 bool Reserved) { 491 if (ShndxF) { 492 if (shndx >= ELF::SHN_LORESERVE && !Reserved) 493 String32(*ShndxF, shndx); 494 else 495 String32(*ShndxF, 0); 496 } 497 498 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ? 499 uint16_t(ELF::SHN_XINDEX) : shndx; 500 501 if (is64Bit()) { 502 String32(*SymtabF, name); // st_name 503 String8(*SymtabF, info); // st_info 504 String8(*SymtabF, other); // st_other 505 String16(*SymtabF, Index); // st_shndx 506 String64(*SymtabF, value); // st_value 507 String64(*SymtabF, size); // st_size 508 } else { 509 String32(*SymtabF, name); // st_name 510 String32(*SymtabF, value); // st_value 511 String32(*SymtabF, size); // st_size 512 String8(*SymtabF, info); // st_info 513 String8(*SymtabF, other); // st_other 514 String16(*SymtabF, Index); // st_shndx 515 } 516 } 517 518 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) { 519 if (Data.isCommon() && Data.isExternal()) 520 return Data.getCommonAlignment(); 521 522 const MCSymbol &Symbol = Data.getSymbol(); 523 524 if (Symbol.isAbsolute() && Symbol.isVariable()) { 525 if (const MCExpr *Value = Symbol.getVariableValue()) { 526 int64_t IntValue; 527 if (Value->EvaluateAsAbsolute(IntValue, Layout)) 528 return (uint64_t)IntValue; 529 } 530 } 531 532 if (!Symbol.isInSection()) 533 return 0; 534 535 if (Data.getFragment()) 536 return Layout.getSymbolOffset(&Data); 537 538 return 0; 539 } 540 541 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 542 const MCAsmLayout &Layout) { 543 // The presence of symbol versions causes undefined symbols and 544 // versions declared with @@@ to be renamed. 545 546 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 547 ie = Asm.symbol_end(); it != ie; ++it) { 548 const MCSymbol &Alias = it->getSymbol(); 549 const MCSymbol &Symbol = Alias.AliasedSymbol(); 550 MCSymbolData &SD = Asm.getSymbolData(Symbol); 551 552 // Not an alias. 553 if (&Symbol == &Alias) 554 continue; 555 556 StringRef AliasName = Alias.getName(); 557 size_t Pos = AliasName.find('@'); 558 if (Pos == StringRef::npos) 559 continue; 560 561 // Aliases defined with .symvar copy the binding from the symbol they alias. 562 // This is the first place we are able to copy this information. 563 it->setExternal(SD.isExternal()); 564 SetBinding(*it, GetBinding(SD)); 565 566 StringRef Rest = AliasName.substr(Pos); 567 if (!Symbol.isUndefined() && !Rest.startswith("@@@")) 568 continue; 569 570 // FIXME: produce a better error message. 571 if (Symbol.isUndefined() && Rest.startswith("@@") && 572 !Rest.startswith("@@@")) 573 report_fatal_error("A @@ version cannot be undefined"); 574 575 Renames.insert(std::make_pair(&Symbol, &Alias)); 576 } 577 } 578 579 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF, 580 MCDataFragment *ShndxF, 581 ELFSymbolData &MSD, 582 const MCAsmLayout &Layout) { 583 MCSymbolData &OrigData = *MSD.SymbolData; 584 MCSymbolData &Data = 585 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol()); 586 587 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() || 588 Data.getSymbol().isVariable(); 589 590 uint8_t Binding = GetBinding(OrigData); 591 uint8_t Visibility = GetVisibility(OrigData); 592 uint8_t Type = GetType(Data); 593 594 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); 595 uint8_t Other = Visibility; 596 597 uint64_t Value = SymbolValue(Data, Layout); 598 uint64_t Size = 0; 599 600 assert(!(Data.isCommon() && !Data.isExternal())); 601 602 const MCExpr *ESize = Data.getSize(); 603 if (ESize) { 604 int64_t Res; 605 if (!ESize->EvaluateAsAbsolute(Res, Layout)) 606 report_fatal_error("Size expression must be absolute."); 607 Size = Res; 608 } 609 610 // Write out the symbol table entry 611 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value, 612 Size, Other, MSD.SectionIndex, IsReserved); 613 } 614 615 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF, 616 MCDataFragment *ShndxF, 617 const MCAssembler &Asm, 618 const MCAsmLayout &Layout, 619 const SectionIndexMapTy &SectionIndexMap) { 620 // The string table must be emitted first because we need the index 621 // into the string table for all the symbol names. 622 assert(StringTable.size() && "Missing string table"); 623 624 // FIXME: Make sure the start of the symbol table is aligned. 625 626 // The first entry is the undefined symbol entry. 627 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false); 628 629 // Write the symbol table entries. 630 LastLocalSymbolIndex = LocalSymbolData.size() + 1; 631 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) { 632 ELFSymbolData &MSD = LocalSymbolData[i]; 633 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 634 } 635 636 // Write out a symbol table entry for each regular section. 637 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; 638 ++i) { 639 const MCSectionELF &Section = 640 static_cast<const MCSectionELF&>(i->getSection()); 641 if (Section.getType() == ELF::SHT_RELA || 642 Section.getType() == ELF::SHT_REL || 643 Section.getType() == ELF::SHT_STRTAB || 644 Section.getType() == ELF::SHT_SYMTAB) 645 continue; 646 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0, 647 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false); 648 LastLocalSymbolIndex++; 649 } 650 651 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { 652 ELFSymbolData &MSD = ExternalSymbolData[i]; 653 MCSymbolData &Data = *MSD.SymbolData; 654 assert(((Data.getFlags() & ELF_STB_Global) || 655 (Data.getFlags() & ELF_STB_Weak)) && 656 "External symbol requires STB_GLOBAL or STB_WEAK flag"); 657 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 658 if (GetBinding(Data) == ELF::STB_LOCAL) 659 LastLocalSymbolIndex++; 660 } 661 662 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { 663 ELFSymbolData &MSD = UndefinedSymbolData[i]; 664 MCSymbolData &Data = *MSD.SymbolData; 665 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 666 if (GetBinding(Data) == ELF::STB_LOCAL) 667 LastLocalSymbolIndex++; 668 } 669 } 670 671 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm, 672 const MCValue &Target, 673 const MCFragment &F) const { 674 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 675 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 676 const MCSymbol *Renamed = Renames.lookup(&Symbol); 677 const MCSymbolData &SD = Asm.getSymbolData(Symbol); 678 679 if (ASymbol.isUndefined()) { 680 if (Renamed) 681 return Renamed; 682 return &ASymbol; 683 } 684 685 if (SD.isExternal()) { 686 if (Renamed) 687 return Renamed; 688 return &Symbol; 689 } 690 691 const MCSectionELF &Section = 692 static_cast<const MCSectionELF&>(ASymbol.getSection()); 693 const SectionKind secKind = Section.getKind(); 694 695 if (secKind.isBSS()) 696 return NULL; 697 698 if (secKind.isThreadLocal()) { 699 if (Renamed) 700 return Renamed; 701 return &Symbol; 702 } 703 704 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 705 const MCSectionELF &Sec2 = 706 static_cast<const MCSectionELF&>(F.getParent()->getSection()); 707 708 if (&Sec2 != &Section && 709 (Kind == MCSymbolRefExpr::VK_PLT || 710 Kind == MCSymbolRefExpr::VK_GOTPCREL || 711 Kind == MCSymbolRefExpr::VK_GOTOFF)) { 712 if (Renamed) 713 return Renamed; 714 return &Symbol; 715 } 716 717 if (Section.getFlags() & MCSectionELF::SHF_MERGE) { 718 if (Target.getConstant() == 0) 719 return NULL; 720 if (Renamed) 721 return Renamed; 722 return &Symbol; 723 } 724 725 return NULL; 726 } 727 728 729 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, 730 const MCAsmLayout &Layout, 731 const MCFragment *Fragment, 732 const MCFixup &Fixup, 733 MCValue Target, 734 uint64_t &FixedValue) { 735 int64_t Addend = 0; 736 int Index = 0; 737 int64_t Value = Target.getConstant(); 738 const MCSymbol *RelocSymbol = NULL; 739 740 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind()); 741 if (!Target.isAbsolute()) { 742 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 743 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 744 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment); 745 746 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 747 const MCSymbol &SymbolB = RefB->getSymbol(); 748 MCSymbolData &SDB = Asm.getSymbolData(SymbolB); 749 IsPCRel = true; 750 751 // Offset of the symbol in the section 752 int64_t a = Layout.getSymbolOffset(&SDB); 753 754 // Ofeset of the relocation in the section 755 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 756 Value += b - a; 757 } 758 759 if (!RelocSymbol) { 760 MCSymbolData &SD = Asm.getSymbolData(ASymbol); 761 MCFragment *F = SD.getFragment(); 762 763 Index = F->getParent()->getOrdinal() + 1; 764 765 // Offset of the symbol in the section 766 Value += Layout.getSymbolOffset(&SD); 767 } else { 768 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref) 769 WeakrefUsedInReloc.insert(RelocSymbol); 770 else 771 UsedInReloc.insert(RelocSymbol); 772 Index = -1; 773 } 774 Addend = Value; 775 // Compensate for the addend on i386. 776 if (is64Bit()) 777 Value = 0; 778 } 779 780 FixedValue = Value; 781 unsigned Type = GetRelocType(Target, Fixup, IsPCRel, 782 (RelocSymbol != 0), Addend); 783 784 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) + 785 Fixup.getOffset(); 786 787 if (!hasRelocationAddend()) 788 Addend = 0; 789 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend); 790 Relocations[Fragment->getParent()].push_back(ERE); 791 } 792 793 794 uint64_t 795 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm, 796 const MCSymbol *S) { 797 MCSymbolData &SD = Asm.getSymbolData(*S); 798 return SD.getIndex(); 799 } 800 801 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data, 802 bool Used, bool Renamed) { 803 if (Data.getFlags() & ELF_Other_Weakref) 804 return false; 805 806 if (Used) 807 return true; 808 809 if (Renamed) 810 return false; 811 812 const MCSymbol &Symbol = Data.getSymbol(); 813 814 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_") 815 return true; 816 817 const MCSymbol &A = Symbol.AliasedSymbol(); 818 if (!A.isVariable() && A.isUndefined() && !Data.isCommon()) 819 return false; 820 821 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) 822 return false; 823 824 if (Symbol.isTemporary()) 825 return false; 826 827 return true; 828 } 829 830 static bool isLocal(const MCSymbolData &Data, bool isSignature, 831 bool isUsedInReloc) { 832 if (Data.isExternal()) 833 return false; 834 835 const MCSymbol &Symbol = Data.getSymbol(); 836 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 837 838 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) { 839 if (isSignature && !isUsedInReloc) 840 return true; 841 842 return false; 843 } 844 845 return true; 846 } 847 848 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm, 849 SectionIndexMapTy &SectionIndexMap) { 850 unsigned Index = 1; 851 for (MCAssembler::iterator it = Asm.begin(), 852 ie = Asm.end(); it != ie; ++it) { 853 const MCSectionELF &Section = 854 static_cast<const MCSectionELF &>(it->getSection()); 855 if (Section.getType() != ELF::SHT_GROUP) 856 continue; 857 SectionIndexMap[&Section] = Index++; 858 } 859 860 for (MCAssembler::iterator it = Asm.begin(), 861 ie = Asm.end(); it != ie; ++it) { 862 const MCSectionELF &Section = 863 static_cast<const MCSectionELF &>(it->getSection()); 864 if (Section.getType() == ELF::SHT_GROUP) 865 continue; 866 SectionIndexMap[&Section] = Index++; 867 } 868 } 869 870 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, 871 const SectionIndexMapTy &SectionIndexMap, 872 RevGroupMapTy RevGroupMap) { 873 // FIXME: Is this the correct place to do this? 874 if (NeedsGOT) { 875 llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_"; 876 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); 877 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); 878 Data.setExternal(true); 879 SetBinding(Data, ELF::STB_GLOBAL); 880 } 881 882 // Build section lookup table. 883 int NumRegularSections = Asm.size(); 884 885 // Index 0 is always the empty string. 886 StringMap<uint64_t> StringIndexMap; 887 StringTable += '\x00'; 888 889 // Add the data for the symbols. 890 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 891 ie = Asm.symbol_end(); it != ie; ++it) { 892 const MCSymbol &Symbol = it->getSymbol(); 893 894 bool Used = UsedInReloc.count(&Symbol); 895 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol); 896 bool isSignature = RevGroupMap.count(&Symbol); 897 898 if (!isInSymtab(Asm, *it, 899 Used || WeakrefUsed || isSignature, 900 Renames.count(&Symbol))) 901 continue; 902 903 ELFSymbolData MSD; 904 MSD.SymbolData = it; 905 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 906 907 // Undefined symbols are global, but this is the first place we 908 // are able to set it. 909 bool Local = isLocal(*it, isSignature, Used); 910 if (!Local && GetBinding(*it) == ELF::STB_LOCAL) { 911 MCSymbolData &SD = Asm.getSymbolData(RefSymbol); 912 SetBinding(*it, ELF::STB_GLOBAL); 913 SetBinding(SD, ELF::STB_GLOBAL); 914 } 915 916 if (RefSymbol.isUndefined() && !Used && WeakrefUsed) 917 SetBinding(*it, ELF::STB_WEAK); 918 919 if (it->isCommon()) { 920 assert(!Local); 921 MSD.SectionIndex = ELF::SHN_COMMON; 922 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) { 923 MSD.SectionIndex = ELF::SHN_ABS; 924 } else if (RefSymbol.isUndefined()) { 925 if (isSignature && !Used) 926 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]); 927 else 928 MSD.SectionIndex = ELF::SHN_UNDEF; 929 } else { 930 const MCSectionELF &Section = 931 static_cast<const MCSectionELF&>(RefSymbol.getSection()); 932 MSD.SectionIndex = SectionIndexMap.lookup(&Section); 933 if (MSD.SectionIndex >= ELF::SHN_LORESERVE) 934 NeedsSymtabShndx = true; 935 assert(MSD.SectionIndex && "Invalid section index!"); 936 } 937 938 // The @@@ in symbol version is replaced with @ in undefined symbols and 939 // @@ in defined ones. 940 StringRef Name = Symbol.getName(); 941 SmallString<32> Buf; 942 943 size_t Pos = Name.find("@@@"); 944 if (Pos != StringRef::npos) { 945 Buf += Name.substr(0, Pos); 946 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1; 947 Buf += Name.substr(Pos + Skip); 948 Name = Buf; 949 } 950 951 uint64_t &Entry = StringIndexMap[Name]; 952 if (!Entry) { 953 Entry = StringTable.size(); 954 StringTable += Name; 955 StringTable += '\x00'; 956 } 957 MSD.StringIndex = Entry; 958 if (MSD.SectionIndex == ELF::SHN_UNDEF) 959 UndefinedSymbolData.push_back(MSD); 960 else if (Local) 961 LocalSymbolData.push_back(MSD); 962 else 963 ExternalSymbolData.push_back(MSD); 964 } 965 966 // Symbols are required to be in lexicographic order. 967 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end()); 968 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); 969 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); 970 971 // Set the symbol indices. Local symbols must come before all other 972 // symbols with non-local bindings. 973 unsigned Index = 1; 974 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) 975 LocalSymbolData[i].SymbolData->setIndex(Index++); 976 977 Index += NumRegularSections; 978 979 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) 980 ExternalSymbolData[i].SymbolData->setIndex(Index++); 981 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) 982 UndefinedSymbolData[i].SymbolData->setIndex(Index++); 983 } 984 985 void ELFObjectWriter::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout, 986 const MCSectionData &SD) { 987 if (!Relocations[&SD].empty()) { 988 MCContext &Ctx = Asm.getContext(); 989 const MCSectionELF *RelaSection; 990 const MCSectionELF &Section = 991 static_cast<const MCSectionELF&>(SD.getSection()); 992 993 const StringRef SectionName = Section.getSectionName(); 994 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel"; 995 RelaSectionName += SectionName; 996 997 unsigned EntrySize; 998 if (hasRelocationAddend()) 999 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela); 1000 else 1001 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel); 1002 1003 RelaSection = Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ? 1004 ELF::SHT_RELA : ELF::SHT_REL, 0, 1005 SectionKind::getReadOnly(), 1006 EntrySize, ""); 1007 1008 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); 1009 RelaSD.setAlignment(is64Bit() ? 8 : 4); 1010 1011 MCDataFragment *F = new MCDataFragment(&RelaSD); 1012 1013 WriteRelocationsFragment(Asm, F, &SD); 1014 } 1015 } 1016 1017 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, 1018 uint64_t Flags, uint64_t Address, 1019 uint64_t Offset, uint64_t Size, 1020 uint32_t Link, uint32_t Info, 1021 uint64_t Alignment, 1022 uint64_t EntrySize) { 1023 Write32(Name); // sh_name: index into string table 1024 Write32(Type); // sh_type 1025 WriteWord(Flags); // sh_flags 1026 WriteWord(Address); // sh_addr 1027 WriteWord(Offset); // sh_offset 1028 WriteWord(Size); // sh_size 1029 Write32(Link); // sh_link 1030 Write32(Info); // sh_info 1031 WriteWord(Alignment); // sh_addralign 1032 WriteWord(EntrySize); // sh_entsize 1033 } 1034 1035 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm, 1036 MCDataFragment *F, 1037 const MCSectionData *SD) { 1038 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD]; 1039 // sort by the r_offset just like gnu as does 1040 array_pod_sort(Relocs.begin(), Relocs.end()); 1041 1042 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { 1043 ELFRelocationEntry entry = Relocs[e - i - 1]; 1044 1045 if (!entry.Index) 1046 ; 1047 else if (entry.Index < 0) 1048 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); 1049 else 1050 entry.Index += LocalSymbolData.size(); 1051 if (is64Bit()) { 1052 String64(*F, entry.r_offset); 1053 1054 struct ELF::Elf64_Rela ERE64; 1055 ERE64.setSymbolAndType(entry.Index, entry.Type); 1056 String64(*F, ERE64.r_info); 1057 1058 if (hasRelocationAddend()) 1059 String64(*F, entry.r_addend); 1060 } else { 1061 String32(*F, entry.r_offset); 1062 1063 struct ELF::Elf32_Rela ERE32; 1064 ERE32.setSymbolAndType(entry.Index, entry.Type); 1065 String32(*F, ERE32.r_info); 1066 1067 if (hasRelocationAddend()) 1068 String32(*F, entry.r_addend); 1069 } 1070 } 1071 } 1072 1073 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm, 1074 MCAsmLayout &Layout, 1075 const SectionIndexMapTy &SectionIndexMap) { 1076 MCContext &Ctx = Asm.getContext(); 1077 MCDataFragment *F; 1078 1079 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; 1080 1081 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. 1082 const MCSectionELF *ShstrtabSection = 1083 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, 1084 SectionKind::getReadOnly()); 1085 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); 1086 ShstrtabSD.setAlignment(1); 1087 ShstrtabIndex = Asm.size(); 1088 1089 const MCSectionELF *SymtabSection = 1090 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, 1091 SectionKind::getReadOnly(), 1092 EntrySize, ""); 1093 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); 1094 SymtabSD.setAlignment(is64Bit() ? 8 : 4); 1095 SymbolTableIndex = Asm.size(); 1096 1097 MCSectionData *SymtabShndxSD = NULL; 1098 1099 if (NeedsSymtabShndx) { 1100 const MCSectionELF *SymtabShndxSection = 1101 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 1102 SectionKind::getReadOnly(), 4, ""); 1103 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection); 1104 SymtabShndxSD->setAlignment(4); 1105 } 1106 1107 const MCSection *StrtabSection; 1108 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, 1109 SectionKind::getReadOnly()); 1110 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); 1111 StrtabSD.setAlignment(1); 1112 StringTableIndex = Asm.size(); 1113 1114 WriteRelocations(Asm, Layout); 1115 1116 // Symbol table 1117 F = new MCDataFragment(&SymtabSD); 1118 MCDataFragment *ShndxF = NULL; 1119 if (NeedsSymtabShndx) { 1120 ShndxF = new MCDataFragment(SymtabShndxSD); 1121 } 1122 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap); 1123 1124 F = new MCDataFragment(&StrtabSD); 1125 F->getContents().append(StringTable.begin(), StringTable.end()); 1126 1127 F = new MCDataFragment(&ShstrtabSD); 1128 1129 // Section header string table. 1130 // 1131 // The first entry of a string table holds a null character so skip 1132 // section 0. 1133 uint64_t Index = 1; 1134 F->getContents() += '\x00'; 1135 1136 StringMap<uint64_t> SecStringMap; 1137 for (MCAssembler::const_iterator it = Asm.begin(), 1138 ie = Asm.end(); it != ie; ++it) { 1139 const MCSectionELF &Section = 1140 static_cast<const MCSectionELF&>(it->getSection()); 1141 // FIXME: We could merge suffixes like in .text and .rela.text. 1142 1143 StringRef Name = Section.getSectionName(); 1144 if (SecStringMap.count(Name)) { 1145 SectionStringTableIndex[&Section] = SecStringMap[Name]; 1146 continue; 1147 } 1148 // Remember the index into the string table so we can write it 1149 // into the sh_name field of the section header table. 1150 SectionStringTableIndex[&Section] = Index; 1151 SecStringMap[Name] = Index; 1152 1153 Index += Name.size() + 1; 1154 F->getContents() += Name; 1155 F->getContents() += '\x00'; 1156 } 1157 } 1158 1159 bool 1160 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 1161 const MCSymbolData &DataA, 1162 const MCFragment &FB, 1163 bool InSet, 1164 bool IsPCRel) const { 1165 // FIXME: This is in here just to match gnu as output. If the two ends 1166 // are in the same section, there is nothing that the linker can do to 1167 // break it. 1168 if (DataA.isExternal()) 1169 return false; 1170 1171 const MCSection &SecA = DataA.getSymbol().AliasedSymbol().getSection(); 1172 const MCSection &SecB = FB.getParent()->getSection(); 1173 // On ELF A - B is absolute if A and B are in the same section. 1174 return &SecA == &SecB; 1175 } 1176 1177 void ELFObjectWriter::CreateGroupSections(MCAssembler &Asm, 1178 MCAsmLayout &Layout, 1179 GroupMapTy &GroupMap, 1180 RevGroupMapTy &RevGroupMap) { 1181 // Build the groups 1182 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 1183 it != ie; ++it) { 1184 const MCSectionELF &Section = 1185 static_cast<const MCSectionELF&>(it->getSection()); 1186 if (!(Section.getFlags() & MCSectionELF::SHF_GROUP)) 1187 continue; 1188 1189 const MCSymbol *SignatureSymbol = Section.getGroup(); 1190 Asm.getOrCreateSymbolData(*SignatureSymbol); 1191 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol]; 1192 if (!Group) { 1193 Group = Asm.getContext().CreateELFGroupSection(); 1194 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 1195 Data.setAlignment(4); 1196 MCDataFragment *F = new MCDataFragment(&Data); 1197 String32(*F, ELF::GRP_COMDAT); 1198 } 1199 GroupMap[Group] = SignatureSymbol; 1200 } 1201 1202 // Add sections to the groups 1203 unsigned Index = 1; 1204 unsigned NumGroups = RevGroupMap.size(); 1205 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 1206 it != ie; ++it, ++Index) { 1207 const MCSectionELF &Section = 1208 static_cast<const MCSectionELF&>(it->getSection()); 1209 if (!(Section.getFlags() & MCSectionELF::SHF_GROUP)) 1210 continue; 1211 const MCSectionELF *Group = RevGroupMap[Section.getGroup()]; 1212 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 1213 // FIXME: we could use the previous fragment 1214 MCDataFragment *F = new MCDataFragment(&Data); 1215 String32(*F, NumGroups + Index); 1216 } 1217 } 1218 1219 void ELFObjectWriter::WriteSection(MCAssembler &Asm, 1220 const SectionIndexMapTy &SectionIndexMap, 1221 uint32_t GroupSymbolIndex, 1222 uint64_t Offset, uint64_t Size, 1223 uint64_t Alignment, 1224 const MCSectionELF &Section) { 1225 uint64_t sh_link = 0; 1226 uint64_t sh_info = 0; 1227 1228 switch(Section.getType()) { 1229 case ELF::SHT_DYNAMIC: 1230 sh_link = SectionStringTableIndex[&Section]; 1231 sh_info = 0; 1232 break; 1233 1234 case ELF::SHT_REL: 1235 case ELF::SHT_RELA: { 1236 const MCSectionELF *SymtabSection; 1237 const MCSectionELF *InfoSection; 1238 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 1239 0, 1240 SectionKind::getReadOnly()); 1241 sh_link = SectionIndexMap.lookup(SymtabSection); 1242 assert(sh_link && ".symtab not found"); 1243 1244 // Remove ".rel" and ".rela" prefixes. 1245 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5; 1246 StringRef SectionName = Section.getSectionName().substr(SecNameLen); 1247 1248 InfoSection = Asm.getContext().getELFSection(SectionName, 1249 ELF::SHT_PROGBITS, 0, 1250 SectionKind::getReadOnly()); 1251 sh_info = SectionIndexMap.lookup(InfoSection); 1252 break; 1253 } 1254 1255 case ELF::SHT_SYMTAB: 1256 case ELF::SHT_DYNSYM: 1257 sh_link = StringTableIndex; 1258 sh_info = LastLocalSymbolIndex; 1259 break; 1260 1261 case ELF::SHT_SYMTAB_SHNDX: 1262 sh_link = SymbolTableIndex; 1263 break; 1264 1265 case ELF::SHT_PROGBITS: 1266 case ELF::SHT_STRTAB: 1267 case ELF::SHT_NOBITS: 1268 case ELF::SHT_NOTE: 1269 case ELF::SHT_NULL: 1270 case ELF::SHT_ARM_ATTRIBUTES: 1271 // Nothing to do. 1272 break; 1273 1274 case ELF::SHT_GROUP: { 1275 sh_link = SymbolTableIndex; 1276 sh_info = GroupSymbolIndex; 1277 break; 1278 } 1279 1280 default: 1281 assert(0 && "FIXME: sh_type value not supported!"); 1282 break; 1283 } 1284 1285 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(), 1286 Section.getFlags(), 0, Offset, Size, sh_link, sh_info, 1287 Alignment, Section.getEntrySize()); 1288 } 1289 1290 static bool IsELFMetaDataSection(const MCSectionData &SD) { 1291 return SD.getOrdinal() == ~UINT32_C(0) && 1292 !SD.getSection().isVirtualSection(); 1293 } 1294 1295 static uint64_t DataSectionSize(const MCSectionData &SD) { 1296 uint64_t Ret = 0; 1297 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1298 ++i) { 1299 const MCFragment &F = *i; 1300 assert(F.getKind() == MCFragment::FT_Data); 1301 Ret += cast<MCDataFragment>(F).getContents().size(); 1302 } 1303 return Ret; 1304 } 1305 1306 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout, 1307 const MCSectionData &SD) { 1308 if (IsELFMetaDataSection(SD)) 1309 return DataSectionSize(SD); 1310 return Layout.getSectionFileSize(&SD); 1311 } 1312 1313 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout, 1314 const MCSectionData &SD) { 1315 if (IsELFMetaDataSection(SD)) 1316 return DataSectionSize(SD); 1317 return Layout.getSectionAddressSize(&SD); 1318 } 1319 1320 static void WriteDataSectionData(ELFObjectWriter *W, const MCSectionData &SD) { 1321 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1322 ++i) { 1323 const MCFragment &F = *i; 1324 assert(F.getKind() == MCFragment::FT_Data); 1325 W->WriteBytes(cast<MCDataFragment>(F).getContents().str()); 1326 } 1327 } 1328 1329 void ELFObjectWriter::WriteObject(MCAssembler &Asm, 1330 const MCAsmLayout &Layout) { 1331 GroupMapTy GroupMap; 1332 RevGroupMapTy RevGroupMap; 1333 CreateGroupSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap, 1334 RevGroupMap); 1335 1336 SectionIndexMapTy SectionIndexMap; 1337 1338 ComputeIndexMap(Asm, SectionIndexMap); 1339 1340 // Compute symbol table information. 1341 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap); 1342 1343 CreateMetadataSections(const_cast<MCAssembler&>(Asm), 1344 const_cast<MCAsmLayout&>(Layout), 1345 SectionIndexMap); 1346 1347 // Update to include the metadata sections. 1348 ComputeIndexMap(Asm, SectionIndexMap); 1349 1350 // Add 1 for the null section. 1351 unsigned NumSections = Asm.size() + 1; 1352 uint64_t NaturalAlignment = is64Bit() ? 8 : 4; 1353 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 1354 sizeof(ELF::Elf32_Ehdr); 1355 uint64_t FileOff = HeaderSize; 1356 1357 std::vector<const MCSectionELF*> Sections; 1358 Sections.resize(NumSections); 1359 1360 for (SectionIndexMapTy::const_iterator i= 1361 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) { 1362 const std::pair<const MCSectionELF*, uint32_t> &p = *i; 1363 Sections[p.second] = p.first; 1364 } 1365 1366 for (unsigned i = 1; i < NumSections; ++i) { 1367 const MCSectionELF &Section = *Sections[i]; 1368 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1369 1370 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1371 1372 // Get the size of the section in the output file (including padding). 1373 FileOff += GetSectionFileSize(Layout, SD); 1374 } 1375 1376 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); 1377 1378 // Write out the ELF header ... 1379 WriteHeader(FileOff - HeaderSize, NumSections); 1380 1381 FileOff = HeaderSize; 1382 1383 // ... then all of the sections ... 1384 DenseMap<const MCSection*, uint64_t> SectionOffsetMap; 1385 1386 for (unsigned i = 1; i < NumSections; ++i) { 1387 const MCSectionELF &Section = *Sections[i]; 1388 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1389 1390 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment()); 1391 WriteZeros(Padding); 1392 FileOff += Padding; 1393 1394 // Remember the offset into the file for this section. 1395 SectionOffsetMap[&Section] = FileOff; 1396 1397 FileOff += GetSectionFileSize(Layout, SD); 1398 1399 if (IsELFMetaDataSection(SD)) 1400 WriteDataSectionData(this, SD); 1401 else 1402 Asm.WriteSectionData(&SD, Layout); 1403 } 1404 1405 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment); 1406 WriteZeros(Padding); 1407 FileOff += Padding; 1408 1409 // ... and then the section header table. 1410 // Should we align the section header table? 1411 // 1412 // Null section first. 1413 uint64_t FirstSectionSize = 1414 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0; 1415 uint32_t FirstSectionLink = 1416 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0; 1417 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0); 1418 1419 for (unsigned i = 1; i < NumSections; ++i) { 1420 const MCSectionELF &Section = *Sections[i]; 1421 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1422 uint32_t GroupSymbolIndex; 1423 if (Section.getType() != ELF::SHT_GROUP) 1424 GroupSymbolIndex = 0; 1425 else 1426 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, GroupMap[&Section]); 1427 1428 uint64_t Size = GetSectionAddressSize(Layout, SD); 1429 1430 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex, 1431 SectionOffsetMap[&Section], Size, 1432 SD.getAlignment(), Section); 1433 } 1434 } 1435 1436 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1437 raw_ostream &OS, 1438 bool IsLittleEndian) { 1439 switch (MOTW->getEMachine()) { 1440 case ELF::EM_386: 1441 case ELF::EM_X86_64: 1442 return new X86ELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1443 case ELF::EM_ARM: 1444 return new ARMELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1445 case ELF::EM_MBLAZE: 1446 return new MBlazeELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1447 default: llvm_unreachable("Unsupported architecture"); break; 1448 } 1449 } 1450 1451 1452 /// START OF SUBCLASSES for ELFObjectWriter 1453 //===- ARMELFObjectWriter -------------------------------------------===// 1454 1455 ARMELFObjectWriter::ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1456 raw_ostream &_OS, 1457 bool IsLittleEndian) 1458 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1459 {} 1460 1461 ARMELFObjectWriter::~ARMELFObjectWriter() 1462 {} 1463 1464 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 1465 const MCFixup &Fixup, 1466 bool IsPCRel, 1467 bool IsRelocWithSymbol, 1468 int64_t Addend) { 1469 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1470 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1471 1472 unsigned Type = 0; 1473 if (IsPCRel) { 1474 switch ((unsigned)Fixup.getKind()) { 1475 default: assert(0 && "Unimplemented"); 1476 case FK_Data_4: 1477 switch (Modifier) { 1478 default: llvm_unreachable("Unsupported Modifier"); 1479 case MCSymbolRefExpr::VK_None: 1480 Type = ELF::R_ARM_BASE_PREL; break; 1481 case MCSymbolRefExpr::VK_ARM_TLSGD: 1482 assert(0 && "unimplemented"); break; 1483 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1484 Type = ELF::R_ARM_TLS_IE32; 1485 } break; 1486 case ARM::fixup_arm_branch: 1487 switch (Modifier) { 1488 case MCSymbolRefExpr::VK_ARM_PLT: 1489 Type = ELF::R_ARM_PLT32; break; 1490 default: 1491 Type = ELF::R_ARM_CALL; break; 1492 } break; 1493 } 1494 } else { 1495 switch ((unsigned)Fixup.getKind()) { 1496 default: llvm_unreachable("invalid fixup kind!"); 1497 case FK_Data_4: 1498 switch (Modifier) { 1499 default: llvm_unreachable("Unsupported Modifier"); break; 1500 case MCSymbolRefExpr::VK_ARM_GOT: 1501 Type = ELF::R_ARM_GOT_BREL; break; 1502 case MCSymbolRefExpr::VK_ARM_TLSGD: 1503 Type = ELF::R_ARM_TLS_GD32; break; 1504 case MCSymbolRefExpr::VK_ARM_TPOFF: 1505 Type = ELF::R_ARM_TLS_LE32; break; 1506 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1507 Type = ELF::R_ARM_TLS_IE32; break; 1508 case MCSymbolRefExpr::VK_None: 1509 Type = ELF::R_ARM_ABS32; break; 1510 case MCSymbolRefExpr::VK_ARM_GOTOFF: 1511 Type = ELF::R_ARM_GOTOFF32; break; 1512 } break; 1513 case ARM::fixup_arm_ldst_pcrel_12: 1514 case ARM::fixup_arm_pcrel_10: 1515 case ARM::fixup_arm_adr_pcrel_12: 1516 case ARM::fixup_arm_thumb_bl: 1517 case ARM::fixup_arm_thumb_cb: 1518 case ARM::fixup_arm_thumb_cp: 1519 case ARM::fixup_arm_thumb_br: 1520 assert(0 && "Unimplemented"); break; 1521 case ARM::fixup_arm_branch: 1522 // FIXME: Differentiate between R_ARM_CALL and 1523 // R_ARM_JUMP24 (latter used for conditional jumps) 1524 Type = ELF::R_ARM_CALL; break; 1525 case ARM::fixup_arm_movt_hi16: 1526 Type = ELF::R_ARM_MOVT_ABS; break; 1527 case ARM::fixup_arm_movw_lo16: 1528 Type = ELF::R_ARM_MOVW_ABS_NC; break; 1529 } 1530 } 1531 1532 if (RelocNeedsGOT(Modifier)) 1533 NeedsGOT = true; 1534 1535 return Type; 1536 } 1537 1538 //===- MBlazeELFObjectWriter -------------------------------------------===// 1539 1540 MBlazeELFObjectWriter::MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1541 raw_ostream &_OS, 1542 bool IsLittleEndian) 1543 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) { 1544 } 1545 1546 MBlazeELFObjectWriter::~MBlazeELFObjectWriter() { 1547 } 1548 1549 unsigned MBlazeELFObjectWriter::GetRelocType(const MCValue &Target, 1550 const MCFixup &Fixup, 1551 bool IsPCRel, 1552 bool IsRelocWithSymbol, 1553 int64_t Addend) { 1554 // determine the type of the relocation 1555 unsigned Type; 1556 if (IsPCRel) { 1557 switch ((unsigned)Fixup.getKind()) { 1558 default: 1559 llvm_unreachable("Unimplemented"); 1560 case FK_PCRel_4: 1561 Type = ELF::R_MICROBLAZE_64_PCREL; 1562 break; 1563 case FK_PCRel_2: 1564 Type = ELF::R_MICROBLAZE_32_PCREL; 1565 break; 1566 } 1567 } else { 1568 switch ((unsigned)Fixup.getKind()) { 1569 default: llvm_unreachable("invalid fixup kind!"); 1570 case FK_Data_4: 1571 Type = ((IsRelocWithSymbol || Addend !=0) 1572 ? ELF::R_MICROBLAZE_32 1573 : ELF::R_MICROBLAZE_64); 1574 break; 1575 case FK_Data_2: 1576 Type = ELF::R_MICROBLAZE_32; 1577 break; 1578 } 1579 } 1580 return Type; 1581 } 1582 1583 //===- X86ELFObjectWriter -------------------------------------------===// 1584 1585 1586 X86ELFObjectWriter::X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1587 raw_ostream &_OS, 1588 bool IsLittleEndian) 1589 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1590 {} 1591 1592 X86ELFObjectWriter::~X86ELFObjectWriter() 1593 {} 1594 1595 unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target, 1596 const MCFixup &Fixup, 1597 bool IsPCRel, 1598 bool IsRelocWithSymbol, 1599 int64_t Addend) { 1600 // determine the type of the relocation 1601 1602 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1603 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1604 unsigned Type; 1605 if (is64Bit()) { 1606 if (IsPCRel) { 1607 switch ((unsigned)Fixup.getKind()) { 1608 default: llvm_unreachable("invalid fixup kind!"); 1609 case FK_PCRel_8: 1610 assert(Modifier == MCSymbolRefExpr::VK_None); 1611 Type = ELF::R_X86_64_PC64; 1612 break; 1613 case X86::reloc_signed_4byte: 1614 case X86::reloc_riprel_4byte_movq_load: 1615 case FK_Data_4: // FIXME? 1616 case X86::reloc_riprel_4byte: 1617 case FK_PCRel_4: 1618 switch (Modifier) { 1619 default: 1620 llvm_unreachable("Unimplemented"); 1621 case MCSymbolRefExpr::VK_None: 1622 Type = ELF::R_X86_64_PC32; 1623 break; 1624 case MCSymbolRefExpr::VK_PLT: 1625 Type = ELF::R_X86_64_PLT32; 1626 break; 1627 case MCSymbolRefExpr::VK_GOTPCREL: 1628 Type = ELF::R_X86_64_GOTPCREL; 1629 break; 1630 case MCSymbolRefExpr::VK_GOTTPOFF: 1631 Type = ELF::R_X86_64_GOTTPOFF; 1632 break; 1633 case MCSymbolRefExpr::VK_TLSGD: 1634 Type = ELF::R_X86_64_TLSGD; 1635 break; 1636 case MCSymbolRefExpr::VK_TLSLD: 1637 Type = ELF::R_X86_64_TLSLD; 1638 break; 1639 } 1640 break; 1641 case FK_PCRel_2: 1642 assert(Modifier == MCSymbolRefExpr::VK_None); 1643 Type = ELF::R_X86_64_PC16; 1644 break; 1645 } 1646 } else { 1647 switch ((unsigned)Fixup.getKind()) { 1648 default: llvm_unreachable("invalid fixup kind!"); 1649 case FK_Data_8: Type = ELF::R_X86_64_64; break; 1650 case X86::reloc_signed_4byte: 1651 assert(isInt<32>(Target.getConstant())); 1652 switch (Modifier) { 1653 default: 1654 llvm_unreachable("Unimplemented"); 1655 case MCSymbolRefExpr::VK_None: 1656 Type = ELF::R_X86_64_32S; 1657 break; 1658 case MCSymbolRefExpr::VK_GOT: 1659 Type = ELF::R_X86_64_GOT32; 1660 break; 1661 case MCSymbolRefExpr::VK_GOTPCREL: 1662 Type = ELF::R_X86_64_GOTPCREL; 1663 break; 1664 case MCSymbolRefExpr::VK_TPOFF: 1665 Type = ELF::R_X86_64_TPOFF32; 1666 break; 1667 case MCSymbolRefExpr::VK_DTPOFF: 1668 Type = ELF::R_X86_64_DTPOFF32; 1669 break; 1670 } 1671 break; 1672 case FK_Data_4: 1673 Type = ELF::R_X86_64_32; 1674 break; 1675 case FK_Data_2: Type = ELF::R_X86_64_16; break; 1676 case FK_PCRel_1: 1677 case FK_Data_1: Type = ELF::R_X86_64_8; break; 1678 } 1679 } 1680 } else { 1681 if (IsPCRel) { 1682 switch (Modifier) { 1683 default: 1684 llvm_unreachable("Unimplemented"); 1685 case MCSymbolRefExpr::VK_None: 1686 Type = ELF::R_386_PC32; 1687 break; 1688 case MCSymbolRefExpr::VK_PLT: 1689 Type = ELF::R_386_PLT32; 1690 break; 1691 } 1692 } else { 1693 switch ((unsigned)Fixup.getKind()) { 1694 default: llvm_unreachable("invalid fixup kind!"); 1695 1696 case X86::reloc_global_offset_table: 1697 Type = ELF::R_386_GOTPC; 1698 break; 1699 1700 // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode 1701 // instead? 1702 case X86::reloc_signed_4byte: 1703 case FK_PCRel_4: 1704 case FK_Data_4: 1705 switch (Modifier) { 1706 default: 1707 llvm_unreachable("Unimplemented"); 1708 case MCSymbolRefExpr::VK_None: 1709 Type = ELF::R_386_32; 1710 break; 1711 case MCSymbolRefExpr::VK_GOT: 1712 Type = ELF::R_386_GOT32; 1713 break; 1714 case MCSymbolRefExpr::VK_GOTOFF: 1715 Type = ELF::R_386_GOTOFF; 1716 break; 1717 case MCSymbolRefExpr::VK_TLSGD: 1718 Type = ELF::R_386_TLS_GD; 1719 break; 1720 case MCSymbolRefExpr::VK_TPOFF: 1721 Type = ELF::R_386_TLS_LE_32; 1722 break; 1723 case MCSymbolRefExpr::VK_INDNTPOFF: 1724 Type = ELF::R_386_TLS_IE; 1725 break; 1726 case MCSymbolRefExpr::VK_NTPOFF: 1727 Type = ELF::R_386_TLS_LE; 1728 break; 1729 case MCSymbolRefExpr::VK_GOTNTPOFF: 1730 Type = ELF::R_386_TLS_GOTIE; 1731 break; 1732 case MCSymbolRefExpr::VK_TLSLDM: 1733 Type = ELF::R_386_TLS_LDM; 1734 break; 1735 case MCSymbolRefExpr::VK_DTPOFF: 1736 Type = ELF::R_386_TLS_LDO_32; 1737 break; 1738 } 1739 break; 1740 case FK_Data_2: Type = ELF::R_386_16; break; 1741 case FK_PCRel_1: 1742 case FK_Data_1: Type = ELF::R_386_8; break; 1743 } 1744 } 1745 } 1746 1747 if (RelocNeedsGOT(Modifier)) 1748 NeedsGOT = true; 1749 1750 return Type; 1751 } 1752