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 "ELFObjectWriter.h" 15 #include "llvm/ADT/STLExtras.h" 16 #include "llvm/ADT/StringMap.h" 17 #include "llvm/ADT/Twine.h" 18 #include "llvm/MC/MCAsmLayout.h" 19 #include "llvm/MC/MCContext.h" 20 #include "llvm/MC/MCExpr.h" 21 #include "llvm/MC/MCSectionELF.h" 22 #include "llvm/MC/MCValue.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/ErrorHandling.h" 25 #include "llvm/Support/ELF.h" 26 #include "llvm/Target/TargetAsmBackend.h" 27 #include "llvm/ADT/StringSwitch.h" 28 29 #include "../Target/X86/X86FixupKinds.h" 30 #include "../Target/ARM/ARMFixupKinds.h" 31 32 #include <vector> 33 using namespace llvm; 34 35 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { 36 const MCFixupKindInfo &FKI = 37 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind); 38 39 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; 40 } 41 42 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) { 43 switch (Variant) { 44 default: 45 return false; 46 case MCSymbolRefExpr::VK_GOT: 47 case MCSymbolRefExpr::VK_PLT: 48 case MCSymbolRefExpr::VK_GOTPCREL: 49 case MCSymbolRefExpr::VK_TPOFF: 50 case MCSymbolRefExpr::VK_TLSGD: 51 case MCSymbolRefExpr::VK_GOTTPOFF: 52 case MCSymbolRefExpr::VK_INDNTPOFF: 53 case MCSymbolRefExpr::VK_NTPOFF: 54 case MCSymbolRefExpr::VK_GOTNTPOFF: 55 case MCSymbolRefExpr::VK_TLSLDM: 56 case MCSymbolRefExpr::VK_DTPOFF: 57 case MCSymbolRefExpr::VK_TLSLD: 58 return true; 59 } 60 } 61 62 ELFObjectWriter::~ELFObjectWriter() 63 {} 64 65 // Emit the ELF header. 66 void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize, 67 unsigned NumberOfSections) { 68 // ELF Header 69 // ---------- 70 // 71 // Note 72 // ---- 73 // emitWord method behaves differently for ELF32 and ELF64, writing 74 // 4 bytes in the former and 8 in the latter. 75 76 Write8(0x7f); // e_ident[EI_MAG0] 77 Write8('E'); // e_ident[EI_MAG1] 78 Write8('L'); // e_ident[EI_MAG2] 79 Write8('F'); // e_ident[EI_MAG3] 80 81 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS] 82 83 // e_ident[EI_DATA] 84 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); 85 86 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] 87 // e_ident[EI_OSABI] 88 switch (TargetObjectWriter->getOSType()) { 89 case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break; 90 case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break; 91 default: Write8(ELF::ELFOSABI_NONE); break; 92 } 93 Write8(0); // e_ident[EI_ABIVERSION] 94 95 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); 96 97 Write16(ELF::ET_REL); // e_type 98 99 Write16(TargetObjectWriter->getEMachine()); // e_machine = target 100 101 Write32(ELF::EV_CURRENT); // e_version 102 WriteWord(0); // e_entry, no entry point in .o file 103 WriteWord(0); // e_phoff, no program header for .o 104 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 105 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes 106 107 // e_flags = whatever the target wants 108 WriteEFlags(); 109 110 // e_ehsize = ELF header size 111 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr)); 112 113 Write16(0); // e_phentsize = prog header entry size 114 Write16(0); // e_phnum = # prog header entries = 0 115 116 // e_shentsize = Section header entry size 117 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr)); 118 119 // e_shnum = # of section header ents 120 if (NumberOfSections >= ELF::SHN_LORESERVE) 121 Write16(0); 122 else 123 Write16(NumberOfSections); 124 125 // e_shstrndx = Section # of '.shstrtab' 126 if (NumberOfSections >= ELF::SHN_LORESERVE) 127 Write16(ELF::SHN_XINDEX); 128 else 129 Write16(ShstrtabIndex); 130 } 131 132 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF, 133 MCDataFragment *ShndxF, 134 uint64_t name, 135 uint8_t info, uint64_t value, 136 uint64_t size, uint8_t other, 137 uint32_t shndx, 138 bool Reserved) { 139 if (ShndxF) { 140 if (shndx >= ELF::SHN_LORESERVE && !Reserved) 141 String32(*ShndxF, shndx); 142 else 143 String32(*ShndxF, 0); 144 } 145 146 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ? 147 uint16_t(ELF::SHN_XINDEX) : shndx; 148 149 if (is64Bit()) { 150 String32(*SymtabF, name); // st_name 151 String8(*SymtabF, info); // st_info 152 String8(*SymtabF, other); // st_other 153 String16(*SymtabF, Index); // st_shndx 154 String64(*SymtabF, value); // st_value 155 String64(*SymtabF, size); // st_size 156 } else { 157 String32(*SymtabF, name); // st_name 158 String32(*SymtabF, value); // st_value 159 String32(*SymtabF, size); // st_size 160 String8(*SymtabF, info); // st_info 161 String8(*SymtabF, other); // st_other 162 String16(*SymtabF, Index); // st_shndx 163 } 164 } 165 166 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data, 167 const MCAsmLayout &Layout) { 168 if (Data.isCommon() && Data.isExternal()) 169 return Data.getCommonAlignment(); 170 171 const MCSymbol &Symbol = Data.getSymbol(); 172 173 if (Symbol.isAbsolute() && Symbol.isVariable()) { 174 if (const MCExpr *Value = Symbol.getVariableValue()) { 175 int64_t IntValue; 176 if (Value->EvaluateAsAbsolute(IntValue, Layout)) 177 return (uint64_t)IntValue; 178 } 179 } 180 181 if (!Symbol.isInSection()) 182 return 0; 183 184 if (Data.getFragment()) 185 return Layout.getSymbolOffset(&Data); 186 187 return 0; 188 } 189 190 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 191 const MCAsmLayout &Layout) { 192 // The presence of symbol versions causes undefined symbols and 193 // versions declared with @@@ to be renamed. 194 195 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 196 ie = Asm.symbol_end(); it != ie; ++it) { 197 const MCSymbol &Alias = it->getSymbol(); 198 const MCSymbol &Symbol = Alias.AliasedSymbol(); 199 MCSymbolData &SD = Asm.getSymbolData(Symbol); 200 201 // Not an alias. 202 if (&Symbol == &Alias) 203 continue; 204 205 StringRef AliasName = Alias.getName(); 206 size_t Pos = AliasName.find('@'); 207 if (Pos == StringRef::npos) 208 continue; 209 210 // Aliases defined with .symvar copy the binding from the symbol they alias. 211 // This is the first place we are able to copy this information. 212 it->setExternal(SD.isExternal()); 213 MCELF::SetBinding(*it, MCELF::GetBinding(SD)); 214 215 StringRef Rest = AliasName.substr(Pos); 216 if (!Symbol.isUndefined() && !Rest.startswith("@@@")) 217 continue; 218 219 // FIXME: produce a better error message. 220 if (Symbol.isUndefined() && Rest.startswith("@@") && 221 !Rest.startswith("@@@")) 222 report_fatal_error("A @@ version cannot be undefined"); 223 224 Renames.insert(std::make_pair(&Symbol, &Alias)); 225 } 226 } 227 228 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF, 229 MCDataFragment *ShndxF, 230 ELFSymbolData &MSD, 231 const MCAsmLayout &Layout) { 232 MCSymbolData &OrigData = *MSD.SymbolData; 233 MCSymbolData &Data = 234 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol()); 235 236 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() || 237 Data.getSymbol().isVariable(); 238 239 uint8_t Binding = MCELF::GetBinding(OrigData); 240 uint8_t Visibility = MCELF::GetVisibility(OrigData); 241 uint8_t Type = MCELF::GetType(Data); 242 243 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); 244 uint8_t Other = Visibility; 245 246 uint64_t Value = SymbolValue(Data, Layout); 247 uint64_t Size = 0; 248 249 assert(!(Data.isCommon() && !Data.isExternal())); 250 251 const MCExpr *ESize = Data.getSize(); 252 if (ESize) { 253 int64_t Res; 254 if (!ESize->EvaluateAsAbsolute(Res, Layout)) 255 report_fatal_error("Size expression must be absolute."); 256 Size = Res; 257 } 258 259 // Write out the symbol table entry 260 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value, 261 Size, Other, MSD.SectionIndex, IsReserved); 262 } 263 264 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF, 265 MCDataFragment *ShndxF, 266 const MCAssembler &Asm, 267 const MCAsmLayout &Layout, 268 const SectionIndexMapTy &SectionIndexMap) { 269 // The string table must be emitted first because we need the index 270 // into the string table for all the symbol names. 271 assert(StringTable.size() && "Missing string table"); 272 273 // FIXME: Make sure the start of the symbol table is aligned. 274 275 // The first entry is the undefined symbol entry. 276 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false); 277 278 // Write the symbol table entries. 279 LastLocalSymbolIndex = LocalSymbolData.size() + 1; 280 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) { 281 ELFSymbolData &MSD = LocalSymbolData[i]; 282 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 283 } 284 285 // Write out a symbol table entry for each regular section. 286 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; 287 ++i) { 288 const MCSectionELF &Section = 289 static_cast<const MCSectionELF&>(i->getSection()); 290 if (Section.getType() == ELF::SHT_RELA || 291 Section.getType() == ELF::SHT_REL || 292 Section.getType() == ELF::SHT_STRTAB || 293 Section.getType() == ELF::SHT_SYMTAB) 294 continue; 295 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0, 296 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false); 297 LastLocalSymbolIndex++; 298 } 299 300 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { 301 ELFSymbolData &MSD = ExternalSymbolData[i]; 302 MCSymbolData &Data = *MSD.SymbolData; 303 assert(((Data.getFlags() & ELF_STB_Global) || 304 (Data.getFlags() & ELF_STB_Weak)) && 305 "External symbol requires STB_GLOBAL or STB_WEAK flag"); 306 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 307 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 308 LastLocalSymbolIndex++; 309 } 310 311 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { 312 ELFSymbolData &MSD = UndefinedSymbolData[i]; 313 MCSymbolData &Data = *MSD.SymbolData; 314 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 315 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 316 LastLocalSymbolIndex++; 317 } 318 } 319 320 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm, 321 const MCValue &Target, 322 const MCFragment &F) const { 323 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 324 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 325 const MCSymbol *Renamed = Renames.lookup(&Symbol); 326 const MCSymbolData &SD = Asm.getSymbolData(Symbol); 327 328 if (ASymbol.isUndefined()) { 329 if (Renamed) 330 return Renamed; 331 return &ASymbol; 332 } 333 334 if (SD.isExternal()) { 335 if (Renamed) 336 return Renamed; 337 return &Symbol; 338 } 339 340 const MCSectionELF &Section = 341 static_cast<const MCSectionELF&>(ASymbol.getSection()); 342 const SectionKind secKind = Section.getKind(); 343 344 if (secKind.isBSS()) 345 return ExplicitRelSym(Asm, Target, F, true); 346 347 if (secKind.isThreadLocal()) { 348 if (Renamed) 349 return Renamed; 350 return &Symbol; 351 } 352 353 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 354 const MCSectionELF &Sec2 = 355 static_cast<const MCSectionELF&>(F.getParent()->getSection()); 356 357 if (&Sec2 != &Section && 358 (Kind == MCSymbolRefExpr::VK_PLT || 359 Kind == MCSymbolRefExpr::VK_GOTPCREL || 360 Kind == MCSymbolRefExpr::VK_GOTOFF)) { 361 if (Renamed) 362 return Renamed; 363 return &Symbol; 364 } 365 366 if (Section.getFlags() & ELF::SHF_MERGE) { 367 if (Target.getConstant() == 0) 368 return NULL; 369 if (Renamed) 370 return Renamed; 371 return &Symbol; 372 } 373 374 return ExplicitRelSym(Asm, Target, F, false); 375 } 376 377 378 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, 379 const MCAsmLayout &Layout, 380 const MCFragment *Fragment, 381 const MCFixup &Fixup, 382 MCValue Target, 383 uint64_t &FixedValue) { 384 int64_t Addend = 0; 385 int Index = 0; 386 int64_t Value = Target.getConstant(); 387 const MCSymbol *RelocSymbol = NULL; 388 389 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind()); 390 if (!Target.isAbsolute()) { 391 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 392 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 393 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment); 394 395 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 396 const MCSymbol &SymbolB = RefB->getSymbol(); 397 MCSymbolData &SDB = Asm.getSymbolData(SymbolB); 398 IsPCRel = true; 399 400 // Offset of the symbol in the section 401 int64_t a = Layout.getSymbolOffset(&SDB); 402 403 // Ofeset of the relocation in the section 404 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 405 Value += b - a; 406 } 407 408 if (!RelocSymbol) { 409 MCSymbolData &SD = Asm.getSymbolData(ASymbol); 410 MCFragment *F = SD.getFragment(); 411 412 Index = F->getParent()->getOrdinal() + 1; 413 414 // Offset of the symbol in the section 415 Value += Layout.getSymbolOffset(&SD); 416 } else { 417 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref) 418 WeakrefUsedInReloc.insert(RelocSymbol); 419 else 420 UsedInReloc.insert(RelocSymbol); 421 Index = -1; 422 } 423 Addend = Value; 424 // Compensate for the addend on i386. 425 if (is64Bit()) 426 Value = 0; 427 } 428 429 FixedValue = Value; 430 unsigned Type = GetRelocType(Target, Fixup, IsPCRel, 431 (RelocSymbol != 0), Addend); 432 433 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) + 434 Fixup.getOffset(); 435 436 if (!hasRelocationAddend()) 437 Addend = 0; 438 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend); 439 Relocations[Fragment->getParent()].push_back(ERE); 440 } 441 442 443 uint64_t 444 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm, 445 const MCSymbol *S) { 446 MCSymbolData &SD = Asm.getSymbolData(*S); 447 return SD.getIndex(); 448 } 449 450 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm, 451 const MCSymbolData &Data, 452 bool Used, bool Renamed) { 453 if (Data.getFlags() & ELF_Other_Weakref) 454 return false; 455 456 if (Used) 457 return true; 458 459 if (Renamed) 460 return false; 461 462 const MCSymbol &Symbol = Data.getSymbol(); 463 464 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_") 465 return true; 466 467 const MCSymbol &A = Symbol.AliasedSymbol(); 468 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined()) 469 return false; 470 471 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL; 472 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal) 473 return false; 474 475 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) 476 return false; 477 478 if (Symbol.isTemporary()) 479 return false; 480 481 return true; 482 } 483 484 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature, 485 bool isUsedInReloc) { 486 if (Data.isExternal()) 487 return false; 488 489 const MCSymbol &Symbol = Data.getSymbol(); 490 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 491 492 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) { 493 if (isSignature && !isUsedInReloc) 494 return true; 495 496 return false; 497 } 498 499 return true; 500 } 501 502 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm, 503 SectionIndexMapTy &SectionIndexMap, 504 const RelMapTy &RelMap) { 505 unsigned Index = 1; 506 for (MCAssembler::iterator it = Asm.begin(), 507 ie = Asm.end(); it != ie; ++it) { 508 const MCSectionELF &Section = 509 static_cast<const MCSectionELF &>(it->getSection()); 510 if (Section.getType() != ELF::SHT_GROUP) 511 continue; 512 SectionIndexMap[&Section] = Index++; 513 } 514 515 for (MCAssembler::iterator it = Asm.begin(), 516 ie = Asm.end(); it != ie; ++it) { 517 const MCSectionELF &Section = 518 static_cast<const MCSectionELF &>(it->getSection()); 519 if (Section.getType() == ELF::SHT_GROUP || 520 Section.getType() == ELF::SHT_REL || 521 Section.getType() == ELF::SHT_RELA) 522 continue; 523 SectionIndexMap[&Section] = Index++; 524 const MCSectionELF *RelSection = RelMap.lookup(&Section); 525 if (RelSection) 526 SectionIndexMap[RelSection] = Index++; 527 } 528 } 529 530 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, 531 const SectionIndexMapTy &SectionIndexMap, 532 RevGroupMapTy RevGroupMap, 533 unsigned NumRegularSections) { 534 // FIXME: Is this the correct place to do this? 535 if (NeedsGOT) { 536 llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_"; 537 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); 538 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); 539 Data.setExternal(true); 540 MCELF::SetBinding(Data, ELF::STB_GLOBAL); 541 } 542 543 // Index 0 is always the empty string. 544 StringMap<uint64_t> StringIndexMap; 545 StringTable += '\x00'; 546 547 // FIXME: We could optimize suffixes in strtab in the same way we 548 // optimize them in shstrtab. 549 550 // Add the data for the symbols. 551 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 552 ie = Asm.symbol_end(); it != ie; ++it) { 553 const MCSymbol &Symbol = it->getSymbol(); 554 555 bool Used = UsedInReloc.count(&Symbol); 556 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol); 557 bool isSignature = RevGroupMap.count(&Symbol); 558 559 if (!isInSymtab(Asm, *it, 560 Used || WeakrefUsed || isSignature, 561 Renames.count(&Symbol))) 562 continue; 563 564 ELFSymbolData MSD; 565 MSD.SymbolData = it; 566 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 567 568 // Undefined symbols are global, but this is the first place we 569 // are able to set it. 570 bool Local = isLocal(*it, isSignature, Used); 571 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) { 572 MCSymbolData &SD = Asm.getSymbolData(RefSymbol); 573 MCELF::SetBinding(*it, ELF::STB_GLOBAL); 574 MCELF::SetBinding(SD, ELF::STB_GLOBAL); 575 } 576 577 if (RefSymbol.isUndefined() && !Used && WeakrefUsed) 578 MCELF::SetBinding(*it, ELF::STB_WEAK); 579 580 if (it->isCommon()) { 581 assert(!Local); 582 MSD.SectionIndex = ELF::SHN_COMMON; 583 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) { 584 MSD.SectionIndex = ELF::SHN_ABS; 585 } else if (RefSymbol.isUndefined()) { 586 if (isSignature && !Used) 587 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]); 588 else 589 MSD.SectionIndex = ELF::SHN_UNDEF; 590 } else { 591 const MCSectionELF &Section = 592 static_cast<const MCSectionELF&>(RefSymbol.getSection()); 593 MSD.SectionIndex = SectionIndexMap.lookup(&Section); 594 if (MSD.SectionIndex >= ELF::SHN_LORESERVE) 595 NeedsSymtabShndx = true; 596 assert(MSD.SectionIndex && "Invalid section index!"); 597 } 598 599 // The @@@ in symbol version is replaced with @ in undefined symbols and 600 // @@ in defined ones. 601 StringRef Name = Symbol.getName(); 602 SmallString<32> Buf; 603 604 size_t Pos = Name.find("@@@"); 605 if (Pos != StringRef::npos) { 606 Buf += Name.substr(0, Pos); 607 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1; 608 Buf += Name.substr(Pos + Skip); 609 Name = Buf; 610 } 611 612 uint64_t &Entry = StringIndexMap[Name]; 613 if (!Entry) { 614 Entry = StringTable.size(); 615 StringTable += Name; 616 StringTable += '\x00'; 617 } 618 MSD.StringIndex = Entry; 619 if (MSD.SectionIndex == ELF::SHN_UNDEF) 620 UndefinedSymbolData.push_back(MSD); 621 else if (Local) 622 LocalSymbolData.push_back(MSD); 623 else 624 ExternalSymbolData.push_back(MSD); 625 } 626 627 // Symbols are required to be in lexicographic order. 628 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end()); 629 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); 630 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); 631 632 // Set the symbol indices. Local symbols must come before all other 633 // symbols with non-local bindings. 634 unsigned Index = 1; 635 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) 636 LocalSymbolData[i].SymbolData->setIndex(Index++); 637 638 Index += NumRegularSections; 639 640 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) 641 ExternalSymbolData[i].SymbolData->setIndex(Index++); 642 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) 643 UndefinedSymbolData[i].SymbolData->setIndex(Index++); 644 } 645 646 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm, 647 MCAsmLayout &Layout, 648 RelMapTy &RelMap) { 649 for (MCAssembler::const_iterator it = Asm.begin(), 650 ie = Asm.end(); it != ie; ++it) { 651 const MCSectionData &SD = *it; 652 if (Relocations[&SD].empty()) 653 continue; 654 655 MCContext &Ctx = Asm.getContext(); 656 const MCSectionELF &Section = 657 static_cast<const MCSectionELF&>(SD.getSection()); 658 659 const StringRef SectionName = Section.getSectionName(); 660 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel"; 661 RelaSectionName += SectionName; 662 663 unsigned EntrySize; 664 if (hasRelocationAddend()) 665 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela); 666 else 667 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel); 668 669 const MCSectionELF *RelaSection = 670 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ? 671 ELF::SHT_RELA : ELF::SHT_REL, 0, 672 SectionKind::getReadOnly(), 673 EntrySize, ""); 674 RelMap[&Section] = RelaSection; 675 Asm.getOrCreateSectionData(*RelaSection); 676 } 677 } 678 679 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, 680 const RelMapTy &RelMap) { 681 for (MCAssembler::const_iterator it = Asm.begin(), 682 ie = Asm.end(); it != ie; ++it) { 683 const MCSectionData &SD = *it; 684 const MCSectionELF &Section = 685 static_cast<const MCSectionELF&>(SD.getSection()); 686 687 const MCSectionELF *RelaSection = RelMap.lookup(&Section); 688 if (!RelaSection) 689 continue; 690 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); 691 RelaSD.setAlignment(is64Bit() ? 8 : 4); 692 693 MCDataFragment *F = new MCDataFragment(&RelaSD); 694 WriteRelocationsFragment(Asm, F, &*it); 695 } 696 } 697 698 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, 699 uint64_t Flags, uint64_t Address, 700 uint64_t Offset, uint64_t Size, 701 uint32_t Link, uint32_t Info, 702 uint64_t Alignment, 703 uint64_t EntrySize) { 704 Write32(Name); // sh_name: index into string table 705 Write32(Type); // sh_type 706 WriteWord(Flags); // sh_flags 707 WriteWord(Address); // sh_addr 708 WriteWord(Offset); // sh_offset 709 WriteWord(Size); // sh_size 710 Write32(Link); // sh_link 711 Write32(Info); // sh_info 712 WriteWord(Alignment); // sh_addralign 713 WriteWord(EntrySize); // sh_entsize 714 } 715 716 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm, 717 MCDataFragment *F, 718 const MCSectionData *SD) { 719 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD]; 720 // sort by the r_offset just like gnu as does 721 array_pod_sort(Relocs.begin(), Relocs.end()); 722 723 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { 724 ELFRelocationEntry entry = Relocs[e - i - 1]; 725 726 if (!entry.Index) 727 ; 728 else if (entry.Index < 0) 729 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); 730 else 731 entry.Index += LocalSymbolData.size(); 732 if (is64Bit()) { 733 String64(*F, entry.r_offset); 734 735 struct ELF::Elf64_Rela ERE64; 736 ERE64.setSymbolAndType(entry.Index, entry.Type); 737 String64(*F, ERE64.r_info); 738 739 if (hasRelocationAddend()) 740 String64(*F, entry.r_addend); 741 } else { 742 String32(*F, entry.r_offset); 743 744 struct ELF::Elf32_Rela ERE32; 745 ERE32.setSymbolAndType(entry.Index, entry.Type); 746 String32(*F, ERE32.r_info); 747 748 if (hasRelocationAddend()) 749 String32(*F, entry.r_addend); 750 } 751 } 752 } 753 754 static int compareBySuffix(const void *a, const void *b) { 755 const MCSectionELF *secA = *static_cast<const MCSectionELF* const *>(a); 756 const MCSectionELF *secB = *static_cast<const MCSectionELF* const *>(b); 757 const StringRef &NameA = secA->getSectionName(); 758 const StringRef &NameB = secB->getSectionName(); 759 const unsigned sizeA = NameA.size(); 760 const unsigned sizeB = NameB.size(); 761 const unsigned len = std::min(sizeA, sizeB); 762 for (unsigned int i = 0; i < len; ++i) { 763 char ca = NameA[sizeA - i - 1]; 764 char cb = NameB[sizeB - i - 1]; 765 if (ca != cb) 766 return cb - ca; 767 } 768 769 return sizeB - sizeA; 770 } 771 772 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm, 773 MCAsmLayout &Layout, 774 SectionIndexMapTy &SectionIndexMap, 775 const RelMapTy &RelMap) { 776 MCContext &Ctx = Asm.getContext(); 777 MCDataFragment *F; 778 779 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; 780 781 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. 782 const MCSectionELF *ShstrtabSection = 783 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, 784 SectionKind::getReadOnly()); 785 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); 786 ShstrtabSD.setAlignment(1); 787 788 const MCSectionELF *SymtabSection = 789 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, 790 SectionKind::getReadOnly(), 791 EntrySize, ""); 792 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); 793 SymtabSD.setAlignment(is64Bit() ? 8 : 4); 794 795 MCSectionData *SymtabShndxSD = NULL; 796 797 if (NeedsSymtabShndx) { 798 const MCSectionELF *SymtabShndxSection = 799 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 800 SectionKind::getReadOnly(), 4, ""); 801 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection); 802 SymtabShndxSD->setAlignment(4); 803 } 804 805 const MCSectionELF *StrtabSection; 806 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, 807 SectionKind::getReadOnly()); 808 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); 809 StrtabSD.setAlignment(1); 810 811 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 812 813 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection); 814 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection); 815 StringTableIndex = SectionIndexMap.lookup(StrtabSection); 816 817 // Symbol table 818 F = new MCDataFragment(&SymtabSD); 819 MCDataFragment *ShndxF = NULL; 820 if (NeedsSymtabShndx) { 821 ShndxF = new MCDataFragment(SymtabShndxSD); 822 } 823 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap); 824 825 F = new MCDataFragment(&StrtabSD); 826 F->getContents().append(StringTable.begin(), StringTable.end()); 827 828 F = new MCDataFragment(&ShstrtabSD); 829 830 std::vector<const MCSectionELF*> Sections; 831 for (MCAssembler::const_iterator it = Asm.begin(), 832 ie = Asm.end(); it != ie; ++it) { 833 const MCSectionELF &Section = 834 static_cast<const MCSectionELF&>(it->getSection()); 835 Sections.push_back(&Section); 836 } 837 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix); 838 839 // Section header string table. 840 // 841 // The first entry of a string table holds a null character so skip 842 // section 0. 843 uint64_t Index = 1; 844 F->getContents() += '\x00'; 845 846 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) { 847 const MCSectionELF &Section = *Sections[I]; 848 849 StringRef Name = Section.getSectionName(); 850 if (I != 0) { 851 StringRef PreviousName = Sections[I - 1]->getSectionName(); 852 if (PreviousName.endswith(Name)) { 853 SectionStringTableIndex[&Section] = Index - Name.size() - 1; 854 continue; 855 } 856 } 857 // Remember the index into the string table so we can write it 858 // into the sh_name field of the section header table. 859 SectionStringTableIndex[&Section] = Index; 860 861 Index += Name.size() + 1; 862 F->getContents() += Name; 863 F->getContents() += '\x00'; 864 } 865 } 866 867 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm, 868 MCAsmLayout &Layout, 869 GroupMapTy &GroupMap, 870 RevGroupMapTy &RevGroupMap, 871 SectionIndexMapTy &SectionIndexMap, 872 const RelMapTy &RelMap) { 873 // Create the .note.GNU-stack section if needed. 874 MCContext &Ctx = Asm.getContext(); 875 if (Asm.getNoExecStack()) { 876 const MCSectionELF *GnuStackSection = 877 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0, 878 SectionKind::getReadOnly()); 879 Asm.getOrCreateSectionData(*GnuStackSection); 880 } 881 882 // Build the groups 883 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 884 it != ie; ++it) { 885 const MCSectionELF &Section = 886 static_cast<const MCSectionELF&>(it->getSection()); 887 if (!(Section.getFlags() & ELF::SHF_GROUP)) 888 continue; 889 890 const MCSymbol *SignatureSymbol = Section.getGroup(); 891 Asm.getOrCreateSymbolData(*SignatureSymbol); 892 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol]; 893 if (!Group) { 894 Group = Ctx.CreateELFGroupSection(); 895 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 896 Data.setAlignment(4); 897 MCDataFragment *F = new MCDataFragment(&Data); 898 String32(*F, ELF::GRP_COMDAT); 899 } 900 GroupMap[Group] = SignatureSymbol; 901 } 902 903 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 904 905 // Add sections to the groups 906 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 907 it != ie; ++it) { 908 const MCSectionELF &Section = 909 static_cast<const MCSectionELF&>(it->getSection()); 910 if (!(Section.getFlags() & ELF::SHF_GROUP)) 911 continue; 912 const MCSectionELF *Group = RevGroupMap[Section.getGroup()]; 913 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 914 // FIXME: we could use the previous fragment 915 MCDataFragment *F = new MCDataFragment(&Data); 916 unsigned Index = SectionIndexMap.lookup(&Section); 917 String32(*F, Index); 918 } 919 } 920 921 void ELFObjectWriter::WriteSection(MCAssembler &Asm, 922 const SectionIndexMapTy &SectionIndexMap, 923 uint32_t GroupSymbolIndex, 924 uint64_t Offset, uint64_t Size, 925 uint64_t Alignment, 926 const MCSectionELF &Section) { 927 uint64_t sh_link = 0; 928 uint64_t sh_info = 0; 929 930 switch(Section.getType()) { 931 case ELF::SHT_DYNAMIC: 932 sh_link = SectionStringTableIndex[&Section]; 933 sh_info = 0; 934 break; 935 936 case ELF::SHT_REL: 937 case ELF::SHT_RELA: { 938 const MCSectionELF *SymtabSection; 939 const MCSectionELF *InfoSection; 940 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 941 0, 942 SectionKind::getReadOnly()); 943 sh_link = SectionIndexMap.lookup(SymtabSection); 944 assert(sh_link && ".symtab not found"); 945 946 // Remove ".rel" and ".rela" prefixes. 947 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5; 948 StringRef SectionName = Section.getSectionName().substr(SecNameLen); 949 950 InfoSection = Asm.getContext().getELFSection(SectionName, 951 ELF::SHT_PROGBITS, 0, 952 SectionKind::getReadOnly()); 953 sh_info = SectionIndexMap.lookup(InfoSection); 954 break; 955 } 956 957 case ELF::SHT_SYMTAB: 958 case ELF::SHT_DYNSYM: 959 sh_link = StringTableIndex; 960 sh_info = LastLocalSymbolIndex; 961 break; 962 963 case ELF::SHT_SYMTAB_SHNDX: 964 sh_link = SymbolTableIndex; 965 break; 966 967 case ELF::SHT_PROGBITS: 968 case ELF::SHT_STRTAB: 969 case ELF::SHT_NOBITS: 970 case ELF::SHT_NOTE: 971 case ELF::SHT_NULL: 972 case ELF::SHT_ARM_ATTRIBUTES: 973 case ELF::SHT_INIT_ARRAY: 974 case ELF::SHT_FINI_ARRAY: 975 case ELF::SHT_PREINIT_ARRAY: 976 case ELF::SHT_X86_64_UNWIND: 977 // Nothing to do. 978 break; 979 980 case ELF::SHT_GROUP: { 981 sh_link = SymbolTableIndex; 982 sh_info = GroupSymbolIndex; 983 break; 984 } 985 986 default: 987 assert(0 && "FIXME: sh_type value not supported!"); 988 break; 989 } 990 991 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(), 992 Section.getFlags(), 0, Offset, Size, sh_link, sh_info, 993 Alignment, Section.getEntrySize()); 994 } 995 996 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) { 997 return SD.getOrdinal() == ~UINT32_C(0) && 998 !SD.getSection().isVirtualSection(); 999 } 1000 1001 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) { 1002 uint64_t Ret = 0; 1003 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1004 ++i) { 1005 const MCFragment &F = *i; 1006 assert(F.getKind() == MCFragment::FT_Data); 1007 Ret += cast<MCDataFragment>(F).getContents().size(); 1008 } 1009 return Ret; 1010 } 1011 1012 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout, 1013 const MCSectionData &SD) { 1014 if (IsELFMetaDataSection(SD)) 1015 return DataSectionSize(SD); 1016 return Layout.getSectionFileSize(&SD); 1017 } 1018 1019 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout, 1020 const MCSectionData &SD) { 1021 if (IsELFMetaDataSection(SD)) 1022 return DataSectionSize(SD); 1023 return Layout.getSectionAddressSize(&SD); 1024 } 1025 1026 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm, 1027 const MCAsmLayout &Layout, 1028 const MCSectionELF &Section) { 1029 uint64_t FileOff = OS.tell(); 1030 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1031 1032 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment()); 1033 WriteZeros(Padding); 1034 FileOff += Padding; 1035 1036 FileOff += GetSectionFileSize(Layout, SD); 1037 1038 if (IsELFMetaDataSection(SD)) { 1039 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1040 ++i) { 1041 const MCFragment &F = *i; 1042 assert(F.getKind() == MCFragment::FT_Data); 1043 WriteBytes(cast<MCDataFragment>(F).getContents().str()); 1044 } 1045 } else { 1046 Asm.WriteSectionData(&SD, Layout); 1047 } 1048 } 1049 1050 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm, 1051 const GroupMapTy &GroupMap, 1052 const MCAsmLayout &Layout, 1053 const SectionIndexMapTy &SectionIndexMap, 1054 const SectionOffsetMapTy &SectionOffsetMap) { 1055 const unsigned NumSections = Asm.size() + 1; 1056 1057 std::vector<const MCSectionELF*> Sections; 1058 Sections.resize(NumSections - 1); 1059 1060 for (SectionIndexMapTy::const_iterator i= 1061 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) { 1062 const std::pair<const MCSectionELF*, uint32_t> &p = *i; 1063 Sections[p.second - 1] = p.first; 1064 } 1065 1066 // Null section first. 1067 uint64_t FirstSectionSize = 1068 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0; 1069 uint32_t FirstSectionLink = 1070 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0; 1071 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0); 1072 1073 for (unsigned i = 0; i < NumSections - 1; ++i) { 1074 const MCSectionELF &Section = *Sections[i]; 1075 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1076 uint32_t GroupSymbolIndex; 1077 if (Section.getType() != ELF::SHT_GROUP) 1078 GroupSymbolIndex = 0; 1079 else 1080 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, 1081 GroupMap.lookup(&Section)); 1082 1083 uint64_t Size = GetSectionAddressSize(Layout, SD); 1084 1085 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex, 1086 SectionOffsetMap.lookup(&Section), Size, 1087 SD.getAlignment(), Section); 1088 } 1089 } 1090 1091 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm, 1092 std::vector<const MCSectionELF*> &Sections) { 1093 for (MCAssembler::iterator it = Asm.begin(), 1094 ie = Asm.end(); it != ie; ++it) { 1095 const MCSectionELF &Section = 1096 static_cast<const MCSectionELF &>(it->getSection()); 1097 if (Section.getType() == ELF::SHT_GROUP) 1098 Sections.push_back(&Section); 1099 } 1100 1101 for (MCAssembler::iterator it = Asm.begin(), 1102 ie = Asm.end(); it != ie; ++it) { 1103 const MCSectionELF &Section = 1104 static_cast<const MCSectionELF &>(it->getSection()); 1105 if (Section.getType() != ELF::SHT_GROUP && 1106 Section.getType() != ELF::SHT_REL && 1107 Section.getType() != ELF::SHT_RELA) 1108 Sections.push_back(&Section); 1109 } 1110 1111 for (MCAssembler::iterator it = Asm.begin(), 1112 ie = Asm.end(); it != ie; ++it) { 1113 const MCSectionELF &Section = 1114 static_cast<const MCSectionELF &>(it->getSection()); 1115 if (Section.getType() == ELF::SHT_REL || 1116 Section.getType() == ELF::SHT_RELA) 1117 Sections.push_back(&Section); 1118 } 1119 } 1120 1121 void ELFObjectWriter::WriteObject(MCAssembler &Asm, 1122 const MCAsmLayout &Layout) { 1123 GroupMapTy GroupMap; 1124 RevGroupMapTy RevGroupMap; 1125 SectionIndexMapTy SectionIndexMap; 1126 1127 unsigned NumUserSections = Asm.size(); 1128 1129 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap; 1130 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1131 1132 const unsigned NumUserAndRelocSections = Asm.size(); 1133 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap, 1134 RevGroupMap, SectionIndexMap, RelMap); 1135 const unsigned AllSections = Asm.size(); 1136 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections; 1137 1138 unsigned NumRegularSections = NumUserSections + NumIndexedSections; 1139 1140 // Compute symbol table information. 1141 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections); 1142 1143 1144 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1145 1146 CreateMetadataSections(const_cast<MCAssembler&>(Asm), 1147 const_cast<MCAsmLayout&>(Layout), 1148 SectionIndexMap, 1149 RelMap); 1150 1151 uint64_t NaturalAlignment = is64Bit() ? 8 : 4; 1152 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 1153 sizeof(ELF::Elf32_Ehdr); 1154 uint64_t FileOff = HeaderSize; 1155 1156 std::vector<const MCSectionELF*> Sections; 1157 ComputeSectionOrder(Asm, Sections); 1158 unsigned NumSections = Sections.size(); 1159 SectionOffsetMapTy SectionOffsetMap; 1160 for (unsigned i = 0; i < NumRegularSections + 1; ++i) { 1161 const MCSectionELF &Section = *Sections[i]; 1162 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1163 1164 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1165 1166 // Remember the offset into the file for this section. 1167 SectionOffsetMap[&Section] = FileOff; 1168 1169 // Get the size of the section in the output file (including padding). 1170 FileOff += GetSectionFileSize(Layout, SD); 1171 } 1172 1173 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); 1174 1175 const unsigned SectionHeaderOffset = FileOff - HeaderSize; 1176 1177 uint64_t SectionHeaderEntrySize = is64Bit() ? 1178 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr); 1179 FileOff += (NumSections + 1) * SectionHeaderEntrySize; 1180 1181 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) { 1182 const MCSectionELF &Section = *Sections[i]; 1183 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1184 1185 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1186 1187 // Remember the offset into the file for this section. 1188 SectionOffsetMap[&Section] = FileOff; 1189 1190 // Get the size of the section in the output file (including padding). 1191 FileOff += GetSectionFileSize(Layout, SD); 1192 } 1193 1194 // Write out the ELF header ... 1195 WriteHeader(SectionHeaderOffset, NumSections + 1); 1196 1197 // ... then the regular sections ... 1198 // + because of .shstrtab 1199 for (unsigned i = 0; i < NumRegularSections + 1; ++i) 1200 WriteDataSectionData(Asm, Layout, *Sections[i]); 1201 1202 FileOff = OS.tell(); 1203 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment); 1204 WriteZeros(Padding); 1205 1206 // ... then the section header table ... 1207 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap, 1208 SectionOffsetMap); 1209 1210 FileOff = OS.tell(); 1211 1212 // ... and then the remainting sections ... 1213 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) 1214 WriteDataSectionData(Asm, Layout, *Sections[i]); 1215 } 1216 1217 bool 1218 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 1219 const MCSymbolData &DataA, 1220 const MCFragment &FB, 1221 bool InSet, 1222 bool IsPCRel) const { 1223 if (DataA.getFlags() & ELF_STB_Weak) 1224 return false; 1225 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 1226 Asm, DataA, FB,InSet, IsPCRel); 1227 } 1228 1229 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1230 raw_ostream &OS, 1231 bool IsLittleEndian) { 1232 switch (MOTW->getEMachine()) { 1233 case ELF::EM_386: 1234 case ELF::EM_X86_64: 1235 return new X86ELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1236 case ELF::EM_ARM: 1237 return new ARMELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1238 case ELF::EM_MBLAZE: 1239 return new MBlazeELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1240 default: llvm_unreachable("Unsupported architecture"); break; 1241 } 1242 } 1243 1244 1245 /// START OF SUBCLASSES for ELFObjectWriter 1246 //===- ARMELFObjectWriter -------------------------------------------===// 1247 1248 ARMELFObjectWriter::ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1249 raw_ostream &_OS, 1250 bool IsLittleEndian) 1251 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1252 {} 1253 1254 ARMELFObjectWriter::~ARMELFObjectWriter() 1255 {} 1256 1257 // FIXME: get the real EABI Version from the Triple. 1258 void ARMELFObjectWriter::WriteEFlags() { 1259 Write32(ELF::EF_ARM_EABIMASK & DefaultEABIVersion); 1260 } 1261 1262 // In ARM, _MergedGlobals and other most symbols get emitted directly. 1263 // I.e. not as an offset to a section symbol. 1264 // This code is a first-cut approximation of what ARM/gcc does. 1265 1266 const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 1267 const MCValue &Target, 1268 const MCFragment &F, 1269 bool IsBSS) const { 1270 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 1271 bool EmitThisSym = false; 1272 1273 if (IsBSS) { 1274 EmitThisSym = StringSwitch<bool>(Symbol.getName()) 1275 .Case("_MergedGlobals", true) 1276 .Default(false); 1277 } else { 1278 EmitThisSym = StringSwitch<bool>(Symbol.getName()) 1279 .Case("_MergedGlobals", true) 1280 .StartsWith(".L.str", true) 1281 .Default(false); 1282 } 1283 if (EmitThisSym) 1284 return &Symbol; 1285 if (! Symbol.isTemporary()) 1286 return &Symbol; 1287 return NULL; 1288 } 1289 1290 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 1291 const MCFixup &Fixup, 1292 bool IsPCRel, 1293 bool IsRelocWithSymbol, 1294 int64_t Addend) { 1295 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1296 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1297 1298 unsigned Type = 0; 1299 if (IsPCRel) { 1300 switch ((unsigned)Fixup.getKind()) { 1301 default: assert(0 && "Unimplemented"); 1302 case FK_Data_4: 1303 switch (Modifier) { 1304 default: llvm_unreachable("Unsupported Modifier"); 1305 case MCSymbolRefExpr::VK_None: 1306 Type = ELF::R_ARM_BASE_PREL; 1307 break; 1308 case MCSymbolRefExpr::VK_ARM_TLSGD: 1309 assert(0 && "unimplemented"); 1310 break; 1311 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1312 Type = ELF::R_ARM_TLS_IE32; 1313 break; 1314 } 1315 break; 1316 case ARM::fixup_arm_uncondbranch: 1317 switch (Modifier) { 1318 case MCSymbolRefExpr::VK_ARM_PLT: 1319 Type = ELF::R_ARM_PLT32; 1320 break; 1321 default: 1322 Type = ELF::R_ARM_CALL; 1323 break; 1324 } 1325 break; 1326 case ARM::fixup_arm_condbranch: 1327 Type = ELF::R_ARM_JUMP24; 1328 break; 1329 case ARM::fixup_arm_movt_hi16: 1330 case ARM::fixup_arm_movt_hi16_pcrel: 1331 Type = ELF::R_ARM_MOVT_PREL; 1332 break; 1333 case ARM::fixup_arm_movw_lo16: 1334 case ARM::fixup_arm_movw_lo16_pcrel: 1335 Type = ELF::R_ARM_MOVW_PREL_NC; 1336 break; 1337 case ARM::fixup_t2_movt_hi16: 1338 case ARM::fixup_t2_movt_hi16_pcrel: 1339 Type = ELF::R_ARM_THM_MOVT_PREL; 1340 break; 1341 case ARM::fixup_t2_movw_lo16: 1342 case ARM::fixup_t2_movw_lo16_pcrel: 1343 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 1344 break; 1345 } 1346 } else { 1347 switch ((unsigned)Fixup.getKind()) { 1348 default: llvm_unreachable("invalid fixup kind!"); 1349 case FK_Data_4: 1350 switch (Modifier) { 1351 default: llvm_unreachable("Unsupported Modifier"); break; 1352 case MCSymbolRefExpr::VK_ARM_GOT: 1353 Type = ELF::R_ARM_GOT_BREL; 1354 break; 1355 case MCSymbolRefExpr::VK_ARM_TLSGD: 1356 Type = ELF::R_ARM_TLS_GD32; 1357 break; 1358 case MCSymbolRefExpr::VK_ARM_TPOFF: 1359 Type = ELF::R_ARM_TLS_LE32; 1360 break; 1361 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1362 Type = ELF::R_ARM_TLS_IE32; 1363 break; 1364 case MCSymbolRefExpr::VK_None: 1365 Type = ELF::R_ARM_ABS32; 1366 break; 1367 case MCSymbolRefExpr::VK_ARM_GOTOFF: 1368 Type = ELF::R_ARM_GOTOFF32; 1369 break; 1370 } 1371 break; 1372 case ARM::fixup_arm_ldst_pcrel_12: 1373 case ARM::fixup_arm_pcrel_10: 1374 case ARM::fixup_arm_adr_pcrel_12: 1375 case ARM::fixup_arm_thumb_bl: 1376 case ARM::fixup_arm_thumb_cb: 1377 case ARM::fixup_arm_thumb_cp: 1378 case ARM::fixup_arm_thumb_br: 1379 assert(0 && "Unimplemented"); 1380 break; 1381 case ARM::fixup_arm_uncondbranch: 1382 Type = ELF::R_ARM_CALL; 1383 break; 1384 case ARM::fixup_arm_condbranch: 1385 Type = ELF::R_ARM_JUMP24; 1386 break; 1387 case ARM::fixup_arm_movt_hi16: 1388 Type = ELF::R_ARM_MOVT_ABS; 1389 break; 1390 case ARM::fixup_arm_movw_lo16: 1391 Type = ELF::R_ARM_MOVW_ABS_NC; 1392 break; 1393 case ARM::fixup_t2_movt_hi16: 1394 Type = ELF::R_ARM_THM_MOVT_ABS; 1395 break; 1396 case ARM::fixup_t2_movw_lo16: 1397 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 1398 break; 1399 } 1400 } 1401 1402 if (RelocNeedsGOT(Modifier)) 1403 NeedsGOT = true; 1404 1405 return Type; 1406 } 1407 1408 //===- MBlazeELFObjectWriter -------------------------------------------===// 1409 1410 MBlazeELFObjectWriter::MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1411 raw_ostream &_OS, 1412 bool IsLittleEndian) 1413 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) { 1414 } 1415 1416 MBlazeELFObjectWriter::~MBlazeELFObjectWriter() { 1417 } 1418 1419 unsigned MBlazeELFObjectWriter::GetRelocType(const MCValue &Target, 1420 const MCFixup &Fixup, 1421 bool IsPCRel, 1422 bool IsRelocWithSymbol, 1423 int64_t Addend) { 1424 // determine the type of the relocation 1425 unsigned Type; 1426 if (IsPCRel) { 1427 switch ((unsigned)Fixup.getKind()) { 1428 default: 1429 llvm_unreachable("Unimplemented"); 1430 case FK_PCRel_4: 1431 Type = ELF::R_MICROBLAZE_64_PCREL; 1432 break; 1433 case FK_PCRel_2: 1434 Type = ELF::R_MICROBLAZE_32_PCREL; 1435 break; 1436 } 1437 } else { 1438 switch ((unsigned)Fixup.getKind()) { 1439 default: llvm_unreachable("invalid fixup kind!"); 1440 case FK_Data_4: 1441 Type = ((IsRelocWithSymbol || Addend !=0) 1442 ? ELF::R_MICROBLAZE_32 1443 : ELF::R_MICROBLAZE_64); 1444 break; 1445 case FK_Data_2: 1446 Type = ELF::R_MICROBLAZE_32; 1447 break; 1448 } 1449 } 1450 return Type; 1451 } 1452 1453 //===- X86ELFObjectWriter -------------------------------------------===// 1454 1455 1456 X86ELFObjectWriter::X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1457 raw_ostream &_OS, 1458 bool IsLittleEndian) 1459 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1460 {} 1461 1462 X86ELFObjectWriter::~X86ELFObjectWriter() 1463 {} 1464 1465 unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target, 1466 const MCFixup &Fixup, 1467 bool IsPCRel, 1468 bool IsRelocWithSymbol, 1469 int64_t Addend) { 1470 // determine the type of the relocation 1471 1472 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1473 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1474 unsigned Type; 1475 if (is64Bit()) { 1476 if (IsPCRel) { 1477 switch ((unsigned)Fixup.getKind()) { 1478 default: llvm_unreachable("invalid fixup kind!"); 1479 case FK_PCRel_8: 1480 assert(Modifier == MCSymbolRefExpr::VK_None); 1481 Type = ELF::R_X86_64_PC64; 1482 break; 1483 case X86::reloc_signed_4byte: 1484 case X86::reloc_riprel_4byte_movq_load: 1485 case FK_Data_4: // FIXME? 1486 case X86::reloc_riprel_4byte: 1487 case FK_PCRel_4: 1488 switch (Modifier) { 1489 default: 1490 llvm_unreachable("Unimplemented"); 1491 case MCSymbolRefExpr::VK_None: 1492 Type = ELF::R_X86_64_PC32; 1493 break; 1494 case MCSymbolRefExpr::VK_PLT: 1495 Type = ELF::R_X86_64_PLT32; 1496 break; 1497 case MCSymbolRefExpr::VK_GOTPCREL: 1498 Type = ELF::R_X86_64_GOTPCREL; 1499 break; 1500 case MCSymbolRefExpr::VK_GOTTPOFF: 1501 Type = ELF::R_X86_64_GOTTPOFF; 1502 break; 1503 case MCSymbolRefExpr::VK_TLSGD: 1504 Type = ELF::R_X86_64_TLSGD; 1505 break; 1506 case MCSymbolRefExpr::VK_TLSLD: 1507 Type = ELF::R_X86_64_TLSLD; 1508 break; 1509 } 1510 break; 1511 case FK_PCRel_2: 1512 assert(Modifier == MCSymbolRefExpr::VK_None); 1513 Type = ELF::R_X86_64_PC16; 1514 break; 1515 case FK_PCRel_1: 1516 assert(Modifier == MCSymbolRefExpr::VK_None); 1517 Type = ELF::R_X86_64_PC8; 1518 break; 1519 } 1520 } else { 1521 switch ((unsigned)Fixup.getKind()) { 1522 default: llvm_unreachable("invalid fixup kind!"); 1523 case FK_Data_8: Type = ELF::R_X86_64_64; break; 1524 case X86::reloc_signed_4byte: 1525 assert(isInt<32>(Target.getConstant())); 1526 switch (Modifier) { 1527 default: 1528 llvm_unreachable("Unimplemented"); 1529 case MCSymbolRefExpr::VK_None: 1530 Type = ELF::R_X86_64_32S; 1531 break; 1532 case MCSymbolRefExpr::VK_GOT: 1533 Type = ELF::R_X86_64_GOT32; 1534 break; 1535 case MCSymbolRefExpr::VK_GOTPCREL: 1536 Type = ELF::R_X86_64_GOTPCREL; 1537 break; 1538 case MCSymbolRefExpr::VK_TPOFF: 1539 Type = ELF::R_X86_64_TPOFF32; 1540 break; 1541 case MCSymbolRefExpr::VK_DTPOFF: 1542 Type = ELF::R_X86_64_DTPOFF32; 1543 break; 1544 } 1545 break; 1546 case FK_Data_4: 1547 Type = ELF::R_X86_64_32; 1548 break; 1549 case FK_Data_2: Type = ELF::R_X86_64_16; break; 1550 case FK_PCRel_1: 1551 case FK_Data_1: Type = ELF::R_X86_64_8; break; 1552 } 1553 } 1554 } else { 1555 if (IsPCRel) { 1556 switch (Modifier) { 1557 default: 1558 llvm_unreachable("Unimplemented"); 1559 case MCSymbolRefExpr::VK_None: 1560 Type = ELF::R_386_PC32; 1561 break; 1562 case MCSymbolRefExpr::VK_PLT: 1563 Type = ELF::R_386_PLT32; 1564 break; 1565 } 1566 } else { 1567 switch ((unsigned)Fixup.getKind()) { 1568 default: llvm_unreachable("invalid fixup kind!"); 1569 1570 case X86::reloc_global_offset_table: 1571 Type = ELF::R_386_GOTPC; 1572 break; 1573 1574 // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode 1575 // instead? 1576 case X86::reloc_signed_4byte: 1577 case FK_PCRel_4: 1578 case FK_Data_4: 1579 switch (Modifier) { 1580 default: 1581 llvm_unreachable("Unimplemented"); 1582 case MCSymbolRefExpr::VK_None: 1583 Type = ELF::R_386_32; 1584 break; 1585 case MCSymbolRefExpr::VK_GOT: 1586 Type = ELF::R_386_GOT32; 1587 break; 1588 case MCSymbolRefExpr::VK_GOTOFF: 1589 Type = ELF::R_386_GOTOFF; 1590 break; 1591 case MCSymbolRefExpr::VK_TLSGD: 1592 Type = ELF::R_386_TLS_GD; 1593 break; 1594 case MCSymbolRefExpr::VK_TPOFF: 1595 Type = ELF::R_386_TLS_LE_32; 1596 break; 1597 case MCSymbolRefExpr::VK_INDNTPOFF: 1598 Type = ELF::R_386_TLS_IE; 1599 break; 1600 case MCSymbolRefExpr::VK_NTPOFF: 1601 Type = ELF::R_386_TLS_LE; 1602 break; 1603 case MCSymbolRefExpr::VK_GOTNTPOFF: 1604 Type = ELF::R_386_TLS_GOTIE; 1605 break; 1606 case MCSymbolRefExpr::VK_TLSLDM: 1607 Type = ELF::R_386_TLS_LDM; 1608 break; 1609 case MCSymbolRefExpr::VK_DTPOFF: 1610 Type = ELF::R_386_TLS_LDO_32; 1611 break; 1612 } 1613 break; 1614 case FK_Data_2: Type = ELF::R_386_16; break; 1615 case FK_PCRel_1: 1616 case FK_Data_1: Type = ELF::R_386_8; break; 1617 } 1618 } 1619 } 1620 1621 if (RelocNeedsGOT(Modifier)) 1622 NeedsGOT = true; 1623 1624 return Type; 1625 } 1626