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 #include "llvm/Support/CommandLine.h" 29 #include "llvm/ADT/Statistic.h" 30 31 #include "../Target/X86/X86FixupKinds.h" 32 #include "../Target/ARM/ARMFixupKinds.h" 33 34 #include <vector> 35 using namespace llvm; 36 37 #undef DEBUG_TYPE 38 #define DEBUG_TYPE "reloc-info" 39 40 // FIXME: This switch must be removed. Since GNU as does not 41 // need a command line switch for doing its wierd thing with PIC, 42 // LLVM should not need it either. 43 // -- 44 // Emulate the wierd behavior of GNU-as for relocation types 45 namespace llvm { 46 cl::opt<bool> 47 ForceARMElfPIC("arm-elf-force-pic", cl::Hidden, cl::init(false), 48 cl::desc("Force ELF emitter to emit PIC style relocations")); 49 } 50 51 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { 52 const MCFixupKindInfo &FKI = 53 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind); 54 55 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; 56 } 57 58 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) { 59 switch (Variant) { 60 default: 61 return false; 62 case MCSymbolRefExpr::VK_GOT: 63 case MCSymbolRefExpr::VK_PLT: 64 case MCSymbolRefExpr::VK_GOTPCREL: 65 case MCSymbolRefExpr::VK_TPOFF: 66 case MCSymbolRefExpr::VK_TLSGD: 67 case MCSymbolRefExpr::VK_GOTTPOFF: 68 case MCSymbolRefExpr::VK_INDNTPOFF: 69 case MCSymbolRefExpr::VK_NTPOFF: 70 case MCSymbolRefExpr::VK_GOTNTPOFF: 71 case MCSymbolRefExpr::VK_TLSLDM: 72 case MCSymbolRefExpr::VK_DTPOFF: 73 case MCSymbolRefExpr::VK_TLSLD: 74 return true; 75 } 76 } 77 78 ELFObjectWriter::~ELFObjectWriter() 79 {} 80 81 // Emit the ELF header. 82 void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize, 83 unsigned NumberOfSections) { 84 // ELF Header 85 // ---------- 86 // 87 // Note 88 // ---- 89 // emitWord method behaves differently for ELF32 and ELF64, writing 90 // 4 bytes in the former and 8 in the latter. 91 92 Write8(0x7f); // e_ident[EI_MAG0] 93 Write8('E'); // e_ident[EI_MAG1] 94 Write8('L'); // e_ident[EI_MAG2] 95 Write8('F'); // e_ident[EI_MAG3] 96 97 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS] 98 99 // e_ident[EI_DATA] 100 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); 101 102 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] 103 // e_ident[EI_OSABI] 104 switch (TargetObjectWriter->getOSType()) { 105 case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break; 106 case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break; 107 default: Write8(ELF::ELFOSABI_NONE); break; 108 } 109 Write8(0); // e_ident[EI_ABIVERSION] 110 111 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); 112 113 Write16(ELF::ET_REL); // e_type 114 115 Write16(TargetObjectWriter->getEMachine()); // e_machine = target 116 117 Write32(ELF::EV_CURRENT); // e_version 118 WriteWord(0); // e_entry, no entry point in .o file 119 WriteWord(0); // e_phoff, no program header for .o 120 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 121 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes 122 123 // e_flags = whatever the target wants 124 WriteEFlags(); 125 126 // e_ehsize = ELF header size 127 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr)); 128 129 Write16(0); // e_phentsize = prog header entry size 130 Write16(0); // e_phnum = # prog header entries = 0 131 132 // e_shentsize = Section header entry size 133 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr)); 134 135 // e_shnum = # of section header ents 136 if (NumberOfSections >= ELF::SHN_LORESERVE) 137 Write16(0); 138 else 139 Write16(NumberOfSections); 140 141 // e_shstrndx = Section # of '.shstrtab' 142 if (NumberOfSections >= ELF::SHN_LORESERVE) 143 Write16(ELF::SHN_XINDEX); 144 else 145 Write16(ShstrtabIndex); 146 } 147 148 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF, 149 MCDataFragment *ShndxF, 150 uint64_t name, 151 uint8_t info, uint64_t value, 152 uint64_t size, uint8_t other, 153 uint32_t shndx, 154 bool Reserved) { 155 if (ShndxF) { 156 if (shndx >= ELF::SHN_LORESERVE && !Reserved) 157 String32(*ShndxF, shndx); 158 else 159 String32(*ShndxF, 0); 160 } 161 162 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ? 163 uint16_t(ELF::SHN_XINDEX) : shndx; 164 165 if (is64Bit()) { 166 String32(*SymtabF, name); // st_name 167 String8(*SymtabF, info); // st_info 168 String8(*SymtabF, other); // st_other 169 String16(*SymtabF, Index); // st_shndx 170 String64(*SymtabF, value); // st_value 171 String64(*SymtabF, size); // st_size 172 } else { 173 String32(*SymtabF, name); // st_name 174 String32(*SymtabF, value); // st_value 175 String32(*SymtabF, size); // st_size 176 String8(*SymtabF, info); // st_info 177 String8(*SymtabF, other); // st_other 178 String16(*SymtabF, Index); // st_shndx 179 } 180 } 181 182 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data, 183 const MCAsmLayout &Layout) { 184 if (Data.isCommon() && Data.isExternal()) 185 return Data.getCommonAlignment(); 186 187 const MCSymbol &Symbol = Data.getSymbol(); 188 189 if (Symbol.isAbsolute() && Symbol.isVariable()) { 190 if (const MCExpr *Value = Symbol.getVariableValue()) { 191 int64_t IntValue; 192 if (Value->EvaluateAsAbsolute(IntValue, Layout)) 193 return (uint64_t)IntValue; 194 } 195 } 196 197 if (!Symbol.isInSection()) 198 return 0; 199 200 201 if (Data.getFragment()) { 202 if (Data.getFlags() & ELF_Other_ThumbFunc) 203 return Layout.getSymbolOffset(&Data)+1; 204 else 205 return Layout.getSymbolOffset(&Data); 206 } 207 208 return 0; 209 } 210 211 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 212 const MCAsmLayout &Layout) { 213 // The presence of symbol versions causes undefined symbols and 214 // versions declared with @@@ to be renamed. 215 216 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 217 ie = Asm.symbol_end(); it != ie; ++it) { 218 const MCSymbol &Alias = it->getSymbol(); 219 const MCSymbol &Symbol = Alias.AliasedSymbol(); 220 MCSymbolData &SD = Asm.getSymbolData(Symbol); 221 222 // Not an alias. 223 if (&Symbol == &Alias) 224 continue; 225 226 StringRef AliasName = Alias.getName(); 227 size_t Pos = AliasName.find('@'); 228 if (Pos == StringRef::npos) 229 continue; 230 231 // Aliases defined with .symvar copy the binding from the symbol they alias. 232 // This is the first place we are able to copy this information. 233 it->setExternal(SD.isExternal()); 234 MCELF::SetBinding(*it, MCELF::GetBinding(SD)); 235 236 StringRef Rest = AliasName.substr(Pos); 237 if (!Symbol.isUndefined() && !Rest.startswith("@@@")) 238 continue; 239 240 // FIXME: produce a better error message. 241 if (Symbol.isUndefined() && Rest.startswith("@@") && 242 !Rest.startswith("@@@")) 243 report_fatal_error("A @@ version cannot be undefined"); 244 245 Renames.insert(std::make_pair(&Symbol, &Alias)); 246 } 247 } 248 249 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF, 250 MCDataFragment *ShndxF, 251 ELFSymbolData &MSD, 252 const MCAsmLayout &Layout) { 253 MCSymbolData &OrigData = *MSD.SymbolData; 254 MCSymbolData &Data = 255 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol()); 256 257 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() || 258 Data.getSymbol().isVariable(); 259 260 uint8_t Binding = MCELF::GetBinding(OrigData); 261 uint8_t Visibility = MCELF::GetVisibility(OrigData); 262 uint8_t Type = MCELF::GetType(Data); 263 264 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); 265 uint8_t Other = Visibility; 266 267 uint64_t Value = SymbolValue(Data, Layout); 268 uint64_t Size = 0; 269 270 assert(!(Data.isCommon() && !Data.isExternal())); 271 272 const MCExpr *ESize = Data.getSize(); 273 if (ESize) { 274 int64_t Res; 275 if (!ESize->EvaluateAsAbsolute(Res, Layout)) 276 report_fatal_error("Size expression must be absolute."); 277 Size = Res; 278 } 279 280 // Write out the symbol table entry 281 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value, 282 Size, Other, MSD.SectionIndex, IsReserved); 283 } 284 285 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF, 286 MCDataFragment *ShndxF, 287 const MCAssembler &Asm, 288 const MCAsmLayout &Layout, 289 const SectionIndexMapTy &SectionIndexMap) { 290 // The string table must be emitted first because we need the index 291 // into the string table for all the symbol names. 292 assert(StringTable.size() && "Missing string table"); 293 294 // FIXME: Make sure the start of the symbol table is aligned. 295 296 // The first entry is the undefined symbol entry. 297 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false); 298 299 // Write the symbol table entries. 300 LastLocalSymbolIndex = LocalSymbolData.size() + 1; 301 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) { 302 ELFSymbolData &MSD = LocalSymbolData[i]; 303 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 304 } 305 306 // Write out a symbol table entry for each regular section. 307 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; 308 ++i) { 309 const MCSectionELF &Section = 310 static_cast<const MCSectionELF&>(i->getSection()); 311 if (Section.getType() == ELF::SHT_RELA || 312 Section.getType() == ELF::SHT_REL || 313 Section.getType() == ELF::SHT_STRTAB || 314 Section.getType() == ELF::SHT_SYMTAB) 315 continue; 316 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0, 317 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false); 318 LastLocalSymbolIndex++; 319 } 320 321 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { 322 ELFSymbolData &MSD = ExternalSymbolData[i]; 323 MCSymbolData &Data = *MSD.SymbolData; 324 assert(((Data.getFlags() & ELF_STB_Global) || 325 (Data.getFlags() & ELF_STB_Weak)) && 326 "External symbol requires STB_GLOBAL or STB_WEAK flag"); 327 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 328 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 329 LastLocalSymbolIndex++; 330 } 331 332 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { 333 ELFSymbolData &MSD = UndefinedSymbolData[i]; 334 MCSymbolData &Data = *MSD.SymbolData; 335 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 336 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 337 LastLocalSymbolIndex++; 338 } 339 } 340 341 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm, 342 const MCValue &Target, 343 const MCFragment &F, 344 const MCFixup &Fixup, 345 bool IsPCRel) const { 346 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 347 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 348 const MCSymbol *Renamed = Renames.lookup(&Symbol); 349 const MCSymbolData &SD = Asm.getSymbolData(Symbol); 350 351 if (ASymbol.isUndefined()) { 352 if (Renamed) 353 return Renamed; 354 return &ASymbol; 355 } 356 357 if (SD.isExternal()) { 358 if (Renamed) 359 return Renamed; 360 return &Symbol; 361 } 362 363 const MCSectionELF &Section = 364 static_cast<const MCSectionELF&>(ASymbol.getSection()); 365 const SectionKind secKind = Section.getKind(); 366 367 if (secKind.isBSS()) 368 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 369 370 if (secKind.isThreadLocal()) { 371 if (Renamed) 372 return Renamed; 373 return &Symbol; 374 } 375 376 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 377 const MCSectionELF &Sec2 = 378 static_cast<const MCSectionELF&>(F.getParent()->getSection()); 379 380 if (&Sec2 != &Section && 381 (Kind == MCSymbolRefExpr::VK_PLT || 382 Kind == MCSymbolRefExpr::VK_GOTPCREL || 383 Kind == MCSymbolRefExpr::VK_GOTOFF)) { 384 if (Renamed) 385 return Renamed; 386 return &Symbol; 387 } 388 389 if (Section.getFlags() & ELF::SHF_MERGE) { 390 if (Target.getConstant() == 0) 391 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 392 if (Renamed) 393 return Renamed; 394 return &Symbol; 395 } 396 397 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 398 399 } 400 401 402 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, 403 const MCAsmLayout &Layout, 404 const MCFragment *Fragment, 405 const MCFixup &Fixup, 406 MCValue Target, 407 uint64_t &FixedValue) { 408 int64_t Addend = 0; 409 int Index = 0; 410 int64_t Value = Target.getConstant(); 411 const MCSymbol *RelocSymbol = NULL; 412 413 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind()); 414 if (!Target.isAbsolute()) { 415 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 416 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 417 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel); 418 419 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 420 const MCSymbol &SymbolB = RefB->getSymbol(); 421 MCSymbolData &SDB = Asm.getSymbolData(SymbolB); 422 IsPCRel = true; 423 424 // Offset of the symbol in the section 425 int64_t a = Layout.getSymbolOffset(&SDB); 426 427 // Ofeset of the relocation in the section 428 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 429 Value += b - a; 430 } 431 432 if (!RelocSymbol) { 433 MCSymbolData &SD = Asm.getSymbolData(ASymbol); 434 MCFragment *F = SD.getFragment(); 435 436 Index = F->getParent()->getOrdinal() + 1; 437 438 // Offset of the symbol in the section 439 Value += Layout.getSymbolOffset(&SD); 440 } else { 441 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref) 442 WeakrefUsedInReloc.insert(RelocSymbol); 443 else 444 UsedInReloc.insert(RelocSymbol); 445 Index = -1; 446 } 447 Addend = Value; 448 // Compensate for the addend on i386. 449 if (is64Bit()) 450 Value = 0; 451 } 452 453 FixedValue = Value; 454 unsigned Type = GetRelocType(Target, Fixup, IsPCRel, 455 (RelocSymbol != 0), Addend); 456 457 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) + 458 Fixup.getOffset(); 459 460 if (!hasRelocationAddend()) 461 Addend = 0; 462 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend); 463 Relocations[Fragment->getParent()].push_back(ERE); 464 } 465 466 467 uint64_t 468 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm, 469 const MCSymbol *S) { 470 MCSymbolData &SD = Asm.getSymbolData(*S); 471 return SD.getIndex(); 472 } 473 474 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm, 475 const MCSymbolData &Data, 476 bool Used, bool Renamed) { 477 if (Data.getFlags() & ELF_Other_Weakref) 478 return false; 479 480 if (Used) 481 return true; 482 483 if (Renamed) 484 return false; 485 486 const MCSymbol &Symbol = Data.getSymbol(); 487 488 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_") 489 return true; 490 491 const MCSymbol &A = Symbol.AliasedSymbol(); 492 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined()) 493 return false; 494 495 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL; 496 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal) 497 return false; 498 499 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) 500 return false; 501 502 if (Symbol.isTemporary()) 503 return false; 504 505 return true; 506 } 507 508 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature, 509 bool isUsedInReloc) { 510 if (Data.isExternal()) 511 return false; 512 513 const MCSymbol &Symbol = Data.getSymbol(); 514 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 515 516 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) { 517 if (isSignature && !isUsedInReloc) 518 return true; 519 520 return false; 521 } 522 523 return true; 524 } 525 526 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm, 527 SectionIndexMapTy &SectionIndexMap, 528 const RelMapTy &RelMap) { 529 unsigned Index = 1; 530 for (MCAssembler::iterator it = Asm.begin(), 531 ie = Asm.end(); it != ie; ++it) { 532 const MCSectionELF &Section = 533 static_cast<const MCSectionELF &>(it->getSection()); 534 if (Section.getType() != ELF::SHT_GROUP) 535 continue; 536 SectionIndexMap[&Section] = Index++; 537 } 538 539 for (MCAssembler::iterator it = Asm.begin(), 540 ie = Asm.end(); it != ie; ++it) { 541 const MCSectionELF &Section = 542 static_cast<const MCSectionELF &>(it->getSection()); 543 if (Section.getType() == ELF::SHT_GROUP || 544 Section.getType() == ELF::SHT_REL || 545 Section.getType() == ELF::SHT_RELA) 546 continue; 547 SectionIndexMap[&Section] = Index++; 548 const MCSectionELF *RelSection = RelMap.lookup(&Section); 549 if (RelSection) 550 SectionIndexMap[RelSection] = Index++; 551 } 552 } 553 554 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, 555 const SectionIndexMapTy &SectionIndexMap, 556 RevGroupMapTy RevGroupMap, 557 unsigned NumRegularSections) { 558 // FIXME: Is this the correct place to do this? 559 if (NeedsGOT) { 560 llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_"; 561 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); 562 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); 563 Data.setExternal(true); 564 MCELF::SetBinding(Data, ELF::STB_GLOBAL); 565 } 566 567 // Index 0 is always the empty string. 568 StringMap<uint64_t> StringIndexMap; 569 StringTable += '\x00'; 570 571 // FIXME: We could optimize suffixes in strtab in the same way we 572 // optimize them in shstrtab. 573 574 // Add the data for the symbols. 575 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 576 ie = Asm.symbol_end(); it != ie; ++it) { 577 const MCSymbol &Symbol = it->getSymbol(); 578 579 bool Used = UsedInReloc.count(&Symbol); 580 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol); 581 bool isSignature = RevGroupMap.count(&Symbol); 582 583 if (!isInSymtab(Asm, *it, 584 Used || WeakrefUsed || isSignature, 585 Renames.count(&Symbol))) 586 continue; 587 588 ELFSymbolData MSD; 589 MSD.SymbolData = it; 590 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 591 592 // Undefined symbols are global, but this is the first place we 593 // are able to set it. 594 bool Local = isLocal(*it, isSignature, Used); 595 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) { 596 MCSymbolData &SD = Asm.getSymbolData(RefSymbol); 597 MCELF::SetBinding(*it, ELF::STB_GLOBAL); 598 MCELF::SetBinding(SD, ELF::STB_GLOBAL); 599 } 600 601 if (RefSymbol.isUndefined() && !Used && WeakrefUsed) 602 MCELF::SetBinding(*it, ELF::STB_WEAK); 603 604 if (it->isCommon()) { 605 assert(!Local); 606 MSD.SectionIndex = ELF::SHN_COMMON; 607 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) { 608 MSD.SectionIndex = ELF::SHN_ABS; 609 } else if (RefSymbol.isUndefined()) { 610 if (isSignature && !Used) 611 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]); 612 else 613 MSD.SectionIndex = ELF::SHN_UNDEF; 614 } else { 615 const MCSectionELF &Section = 616 static_cast<const MCSectionELF&>(RefSymbol.getSection()); 617 MSD.SectionIndex = SectionIndexMap.lookup(&Section); 618 if (MSD.SectionIndex >= ELF::SHN_LORESERVE) 619 NeedsSymtabShndx = true; 620 assert(MSD.SectionIndex && "Invalid section index!"); 621 } 622 623 // The @@@ in symbol version is replaced with @ in undefined symbols and 624 // @@ in defined ones. 625 StringRef Name = Symbol.getName(); 626 SmallString<32> Buf; 627 628 size_t Pos = Name.find("@@@"); 629 if (Pos != StringRef::npos) { 630 Buf += Name.substr(0, Pos); 631 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1; 632 Buf += Name.substr(Pos + Skip); 633 Name = Buf; 634 } 635 636 uint64_t &Entry = StringIndexMap[Name]; 637 if (!Entry) { 638 Entry = StringTable.size(); 639 StringTable += Name; 640 StringTable += '\x00'; 641 } 642 MSD.StringIndex = Entry; 643 if (MSD.SectionIndex == ELF::SHN_UNDEF) 644 UndefinedSymbolData.push_back(MSD); 645 else if (Local) 646 LocalSymbolData.push_back(MSD); 647 else 648 ExternalSymbolData.push_back(MSD); 649 } 650 651 // Symbols are required to be in lexicographic order. 652 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end()); 653 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); 654 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); 655 656 // Set the symbol indices. Local symbols must come before all other 657 // symbols with non-local bindings. 658 unsigned Index = 1; 659 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) 660 LocalSymbolData[i].SymbolData->setIndex(Index++); 661 662 Index += NumRegularSections; 663 664 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) 665 ExternalSymbolData[i].SymbolData->setIndex(Index++); 666 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) 667 UndefinedSymbolData[i].SymbolData->setIndex(Index++); 668 } 669 670 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm, 671 MCAsmLayout &Layout, 672 RelMapTy &RelMap) { 673 for (MCAssembler::const_iterator it = Asm.begin(), 674 ie = Asm.end(); it != ie; ++it) { 675 const MCSectionData &SD = *it; 676 if (Relocations[&SD].empty()) 677 continue; 678 679 MCContext &Ctx = Asm.getContext(); 680 const MCSectionELF &Section = 681 static_cast<const MCSectionELF&>(SD.getSection()); 682 683 const StringRef SectionName = Section.getSectionName(); 684 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel"; 685 RelaSectionName += SectionName; 686 687 unsigned EntrySize; 688 if (hasRelocationAddend()) 689 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela); 690 else 691 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel); 692 693 const MCSectionELF *RelaSection = 694 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ? 695 ELF::SHT_RELA : ELF::SHT_REL, 0, 696 SectionKind::getReadOnly(), 697 EntrySize, ""); 698 RelMap[&Section] = RelaSection; 699 Asm.getOrCreateSectionData(*RelaSection); 700 } 701 } 702 703 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, 704 const RelMapTy &RelMap) { 705 for (MCAssembler::const_iterator it = Asm.begin(), 706 ie = Asm.end(); it != ie; ++it) { 707 const MCSectionData &SD = *it; 708 const MCSectionELF &Section = 709 static_cast<const MCSectionELF&>(SD.getSection()); 710 711 const MCSectionELF *RelaSection = RelMap.lookup(&Section); 712 if (!RelaSection) 713 continue; 714 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); 715 RelaSD.setAlignment(is64Bit() ? 8 : 4); 716 717 MCDataFragment *F = new MCDataFragment(&RelaSD); 718 WriteRelocationsFragment(Asm, F, &*it); 719 } 720 } 721 722 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, 723 uint64_t Flags, uint64_t Address, 724 uint64_t Offset, uint64_t Size, 725 uint32_t Link, uint32_t Info, 726 uint64_t Alignment, 727 uint64_t EntrySize) { 728 Write32(Name); // sh_name: index into string table 729 Write32(Type); // sh_type 730 WriteWord(Flags); // sh_flags 731 WriteWord(Address); // sh_addr 732 WriteWord(Offset); // sh_offset 733 WriteWord(Size); // sh_size 734 Write32(Link); // sh_link 735 Write32(Info); // sh_info 736 WriteWord(Alignment); // sh_addralign 737 WriteWord(EntrySize); // sh_entsize 738 } 739 740 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm, 741 MCDataFragment *F, 742 const MCSectionData *SD) { 743 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD]; 744 // sort by the r_offset just like gnu as does 745 array_pod_sort(Relocs.begin(), Relocs.end()); 746 747 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { 748 ELFRelocationEntry entry = Relocs[e - i - 1]; 749 750 if (!entry.Index) 751 ; 752 else if (entry.Index < 0) 753 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); 754 else 755 entry.Index += LocalSymbolData.size(); 756 if (is64Bit()) { 757 String64(*F, entry.r_offset); 758 759 struct ELF::Elf64_Rela ERE64; 760 ERE64.setSymbolAndType(entry.Index, entry.Type); 761 String64(*F, ERE64.r_info); 762 763 if (hasRelocationAddend()) 764 String64(*F, entry.r_addend); 765 } else { 766 String32(*F, entry.r_offset); 767 768 struct ELF::Elf32_Rela ERE32; 769 ERE32.setSymbolAndType(entry.Index, entry.Type); 770 String32(*F, ERE32.r_info); 771 772 if (hasRelocationAddend()) 773 String32(*F, entry.r_addend); 774 } 775 } 776 } 777 778 static int compareBySuffix(const void *a, const void *b) { 779 const MCSectionELF *secA = *static_cast<const MCSectionELF* const *>(a); 780 const MCSectionELF *secB = *static_cast<const MCSectionELF* const *>(b); 781 const StringRef &NameA = secA->getSectionName(); 782 const StringRef &NameB = secB->getSectionName(); 783 const unsigned sizeA = NameA.size(); 784 const unsigned sizeB = NameB.size(); 785 const unsigned len = std::min(sizeA, sizeB); 786 for (unsigned int i = 0; i < len; ++i) { 787 char ca = NameA[sizeA - i - 1]; 788 char cb = NameB[sizeB - i - 1]; 789 if (ca != cb) 790 return cb - ca; 791 } 792 793 return sizeB - sizeA; 794 } 795 796 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm, 797 MCAsmLayout &Layout, 798 SectionIndexMapTy &SectionIndexMap, 799 const RelMapTy &RelMap) { 800 MCContext &Ctx = Asm.getContext(); 801 MCDataFragment *F; 802 803 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; 804 805 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. 806 const MCSectionELF *ShstrtabSection = 807 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, 808 SectionKind::getReadOnly()); 809 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); 810 ShstrtabSD.setAlignment(1); 811 812 const MCSectionELF *SymtabSection = 813 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, 814 SectionKind::getReadOnly(), 815 EntrySize, ""); 816 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); 817 SymtabSD.setAlignment(is64Bit() ? 8 : 4); 818 819 MCSectionData *SymtabShndxSD = NULL; 820 821 if (NeedsSymtabShndx) { 822 const MCSectionELF *SymtabShndxSection = 823 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 824 SectionKind::getReadOnly(), 4, ""); 825 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection); 826 SymtabShndxSD->setAlignment(4); 827 } 828 829 const MCSectionELF *StrtabSection; 830 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, 831 SectionKind::getReadOnly()); 832 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); 833 StrtabSD.setAlignment(1); 834 835 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 836 837 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection); 838 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection); 839 StringTableIndex = SectionIndexMap.lookup(StrtabSection); 840 841 // Symbol table 842 F = new MCDataFragment(&SymtabSD); 843 MCDataFragment *ShndxF = NULL; 844 if (NeedsSymtabShndx) { 845 ShndxF = new MCDataFragment(SymtabShndxSD); 846 } 847 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap); 848 849 F = new MCDataFragment(&StrtabSD); 850 F->getContents().append(StringTable.begin(), StringTable.end()); 851 852 F = new MCDataFragment(&ShstrtabSD); 853 854 std::vector<const MCSectionELF*> Sections; 855 for (MCAssembler::const_iterator it = Asm.begin(), 856 ie = Asm.end(); it != ie; ++it) { 857 const MCSectionELF &Section = 858 static_cast<const MCSectionELF&>(it->getSection()); 859 Sections.push_back(&Section); 860 } 861 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix); 862 863 // Section header string table. 864 // 865 // The first entry of a string table holds a null character so skip 866 // section 0. 867 uint64_t Index = 1; 868 F->getContents() += '\x00'; 869 870 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) { 871 const MCSectionELF &Section = *Sections[I]; 872 873 StringRef Name = Section.getSectionName(); 874 if (I != 0) { 875 StringRef PreviousName = Sections[I - 1]->getSectionName(); 876 if (PreviousName.endswith(Name)) { 877 SectionStringTableIndex[&Section] = Index - Name.size() - 1; 878 continue; 879 } 880 } 881 // Remember the index into the string table so we can write it 882 // into the sh_name field of the section header table. 883 SectionStringTableIndex[&Section] = Index; 884 885 Index += Name.size() + 1; 886 F->getContents() += Name; 887 F->getContents() += '\x00'; 888 } 889 } 890 891 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm, 892 MCAsmLayout &Layout, 893 GroupMapTy &GroupMap, 894 RevGroupMapTy &RevGroupMap, 895 SectionIndexMapTy &SectionIndexMap, 896 const RelMapTy &RelMap) { 897 // Create the .note.GNU-stack section if needed. 898 MCContext &Ctx = Asm.getContext(); 899 if (Asm.getNoExecStack()) { 900 const MCSectionELF *GnuStackSection = 901 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0, 902 SectionKind::getReadOnly()); 903 Asm.getOrCreateSectionData(*GnuStackSection); 904 } 905 906 // Build the groups 907 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 908 it != ie; ++it) { 909 const MCSectionELF &Section = 910 static_cast<const MCSectionELF&>(it->getSection()); 911 if (!(Section.getFlags() & ELF::SHF_GROUP)) 912 continue; 913 914 const MCSymbol *SignatureSymbol = Section.getGroup(); 915 Asm.getOrCreateSymbolData(*SignatureSymbol); 916 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol]; 917 if (!Group) { 918 Group = Ctx.CreateELFGroupSection(); 919 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 920 Data.setAlignment(4); 921 MCDataFragment *F = new MCDataFragment(&Data); 922 String32(*F, ELF::GRP_COMDAT); 923 } 924 GroupMap[Group] = SignatureSymbol; 925 } 926 927 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 928 929 // Add sections to the groups 930 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 931 it != ie; ++it) { 932 const MCSectionELF &Section = 933 static_cast<const MCSectionELF&>(it->getSection()); 934 if (!(Section.getFlags() & ELF::SHF_GROUP)) 935 continue; 936 const MCSectionELF *Group = RevGroupMap[Section.getGroup()]; 937 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 938 // FIXME: we could use the previous fragment 939 MCDataFragment *F = new MCDataFragment(&Data); 940 unsigned Index = SectionIndexMap.lookup(&Section); 941 String32(*F, Index); 942 } 943 } 944 945 void ELFObjectWriter::WriteSection(MCAssembler &Asm, 946 const SectionIndexMapTy &SectionIndexMap, 947 uint32_t GroupSymbolIndex, 948 uint64_t Offset, uint64_t Size, 949 uint64_t Alignment, 950 const MCSectionELF &Section) { 951 uint64_t sh_link = 0; 952 uint64_t sh_info = 0; 953 954 switch(Section.getType()) { 955 case ELF::SHT_DYNAMIC: 956 sh_link = SectionStringTableIndex[&Section]; 957 sh_info = 0; 958 break; 959 960 case ELF::SHT_REL: 961 case ELF::SHT_RELA: { 962 const MCSectionELF *SymtabSection; 963 const MCSectionELF *InfoSection; 964 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 965 0, 966 SectionKind::getReadOnly()); 967 sh_link = SectionIndexMap.lookup(SymtabSection); 968 assert(sh_link && ".symtab not found"); 969 970 // Remove ".rel" and ".rela" prefixes. 971 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5; 972 StringRef SectionName = Section.getSectionName().substr(SecNameLen); 973 974 InfoSection = Asm.getContext().getELFSection(SectionName, 975 ELF::SHT_PROGBITS, 0, 976 SectionKind::getReadOnly()); 977 sh_info = SectionIndexMap.lookup(InfoSection); 978 break; 979 } 980 981 case ELF::SHT_SYMTAB: 982 case ELF::SHT_DYNSYM: 983 sh_link = StringTableIndex; 984 sh_info = LastLocalSymbolIndex; 985 break; 986 987 case ELF::SHT_SYMTAB_SHNDX: 988 sh_link = SymbolTableIndex; 989 break; 990 991 case ELF::SHT_PROGBITS: 992 case ELF::SHT_STRTAB: 993 case ELF::SHT_NOBITS: 994 case ELF::SHT_NOTE: 995 case ELF::SHT_NULL: 996 case ELF::SHT_ARM_ATTRIBUTES: 997 case ELF::SHT_INIT_ARRAY: 998 case ELF::SHT_FINI_ARRAY: 999 case ELF::SHT_PREINIT_ARRAY: 1000 case ELF::SHT_X86_64_UNWIND: 1001 // Nothing to do. 1002 break; 1003 1004 case ELF::SHT_GROUP: { 1005 sh_link = SymbolTableIndex; 1006 sh_info = GroupSymbolIndex; 1007 break; 1008 } 1009 1010 default: 1011 assert(0 && "FIXME: sh_type value not supported!"); 1012 break; 1013 } 1014 1015 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(), 1016 Section.getFlags(), 0, Offset, Size, sh_link, sh_info, 1017 Alignment, Section.getEntrySize()); 1018 } 1019 1020 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) { 1021 return SD.getOrdinal() == ~UINT32_C(0) && 1022 !SD.getSection().isVirtualSection(); 1023 } 1024 1025 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) { 1026 uint64_t Ret = 0; 1027 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1028 ++i) { 1029 const MCFragment &F = *i; 1030 assert(F.getKind() == MCFragment::FT_Data); 1031 Ret += cast<MCDataFragment>(F).getContents().size(); 1032 } 1033 return Ret; 1034 } 1035 1036 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout, 1037 const MCSectionData &SD) { 1038 if (IsELFMetaDataSection(SD)) 1039 return DataSectionSize(SD); 1040 return Layout.getSectionFileSize(&SD); 1041 } 1042 1043 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout, 1044 const MCSectionData &SD) { 1045 if (IsELFMetaDataSection(SD)) 1046 return DataSectionSize(SD); 1047 return Layout.getSectionAddressSize(&SD); 1048 } 1049 1050 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm, 1051 const MCAsmLayout &Layout, 1052 const MCSectionELF &Section) { 1053 uint64_t FileOff = OS.tell(); 1054 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1055 1056 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment()); 1057 WriteZeros(Padding); 1058 FileOff += Padding; 1059 1060 FileOff += GetSectionFileSize(Layout, SD); 1061 1062 if (IsELFMetaDataSection(SD)) { 1063 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1064 ++i) { 1065 const MCFragment &F = *i; 1066 assert(F.getKind() == MCFragment::FT_Data); 1067 WriteBytes(cast<MCDataFragment>(F).getContents().str()); 1068 } 1069 } else { 1070 Asm.WriteSectionData(&SD, Layout); 1071 } 1072 } 1073 1074 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm, 1075 const GroupMapTy &GroupMap, 1076 const MCAsmLayout &Layout, 1077 const SectionIndexMapTy &SectionIndexMap, 1078 const SectionOffsetMapTy &SectionOffsetMap) { 1079 const unsigned NumSections = Asm.size() + 1; 1080 1081 std::vector<const MCSectionELF*> Sections; 1082 Sections.resize(NumSections - 1); 1083 1084 for (SectionIndexMapTy::const_iterator i= 1085 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) { 1086 const std::pair<const MCSectionELF*, uint32_t> &p = *i; 1087 Sections[p.second - 1] = p.first; 1088 } 1089 1090 // Null section first. 1091 uint64_t FirstSectionSize = 1092 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0; 1093 uint32_t FirstSectionLink = 1094 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0; 1095 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0); 1096 1097 for (unsigned i = 0; i < NumSections - 1; ++i) { 1098 const MCSectionELF &Section = *Sections[i]; 1099 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1100 uint32_t GroupSymbolIndex; 1101 if (Section.getType() != ELF::SHT_GROUP) 1102 GroupSymbolIndex = 0; 1103 else 1104 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, 1105 GroupMap.lookup(&Section)); 1106 1107 uint64_t Size = GetSectionAddressSize(Layout, SD); 1108 1109 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex, 1110 SectionOffsetMap.lookup(&Section), Size, 1111 SD.getAlignment(), Section); 1112 } 1113 } 1114 1115 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm, 1116 std::vector<const MCSectionELF*> &Sections) { 1117 for (MCAssembler::iterator it = Asm.begin(), 1118 ie = Asm.end(); it != ie; ++it) { 1119 const MCSectionELF &Section = 1120 static_cast<const MCSectionELF &>(it->getSection()); 1121 if (Section.getType() == ELF::SHT_GROUP) 1122 Sections.push_back(&Section); 1123 } 1124 1125 for (MCAssembler::iterator it = Asm.begin(), 1126 ie = Asm.end(); it != ie; ++it) { 1127 const MCSectionELF &Section = 1128 static_cast<const MCSectionELF &>(it->getSection()); 1129 if (Section.getType() != ELF::SHT_GROUP && 1130 Section.getType() != ELF::SHT_REL && 1131 Section.getType() != ELF::SHT_RELA) 1132 Sections.push_back(&Section); 1133 } 1134 1135 for (MCAssembler::iterator it = Asm.begin(), 1136 ie = Asm.end(); it != ie; ++it) { 1137 const MCSectionELF &Section = 1138 static_cast<const MCSectionELF &>(it->getSection()); 1139 if (Section.getType() == ELF::SHT_REL || 1140 Section.getType() == ELF::SHT_RELA) 1141 Sections.push_back(&Section); 1142 } 1143 } 1144 1145 void ELFObjectWriter::WriteObject(MCAssembler &Asm, 1146 const MCAsmLayout &Layout) { 1147 GroupMapTy GroupMap; 1148 RevGroupMapTy RevGroupMap; 1149 SectionIndexMapTy SectionIndexMap; 1150 1151 unsigned NumUserSections = Asm.size(); 1152 1153 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap; 1154 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1155 1156 const unsigned NumUserAndRelocSections = Asm.size(); 1157 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap, 1158 RevGroupMap, SectionIndexMap, RelMap); 1159 const unsigned AllSections = Asm.size(); 1160 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections; 1161 1162 unsigned NumRegularSections = NumUserSections + NumIndexedSections; 1163 1164 // Compute symbol table information. 1165 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections); 1166 1167 1168 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1169 1170 CreateMetadataSections(const_cast<MCAssembler&>(Asm), 1171 const_cast<MCAsmLayout&>(Layout), 1172 SectionIndexMap, 1173 RelMap); 1174 1175 uint64_t NaturalAlignment = is64Bit() ? 8 : 4; 1176 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 1177 sizeof(ELF::Elf32_Ehdr); 1178 uint64_t FileOff = HeaderSize; 1179 1180 std::vector<const MCSectionELF*> Sections; 1181 ComputeSectionOrder(Asm, Sections); 1182 unsigned NumSections = Sections.size(); 1183 SectionOffsetMapTy SectionOffsetMap; 1184 for (unsigned i = 0; i < NumRegularSections + 1; ++i) { 1185 const MCSectionELF &Section = *Sections[i]; 1186 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1187 1188 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1189 1190 // Remember the offset into the file for this section. 1191 SectionOffsetMap[&Section] = FileOff; 1192 1193 // Get the size of the section in the output file (including padding). 1194 FileOff += GetSectionFileSize(Layout, SD); 1195 } 1196 1197 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); 1198 1199 const unsigned SectionHeaderOffset = FileOff - HeaderSize; 1200 1201 uint64_t SectionHeaderEntrySize = is64Bit() ? 1202 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr); 1203 FileOff += (NumSections + 1) * SectionHeaderEntrySize; 1204 1205 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) { 1206 const MCSectionELF &Section = *Sections[i]; 1207 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1208 1209 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1210 1211 // Remember the offset into the file for this section. 1212 SectionOffsetMap[&Section] = FileOff; 1213 1214 // Get the size of the section in the output file (including padding). 1215 FileOff += GetSectionFileSize(Layout, SD); 1216 } 1217 1218 // Write out the ELF header ... 1219 WriteHeader(SectionHeaderOffset, NumSections + 1); 1220 1221 // ... then the regular sections ... 1222 // + because of .shstrtab 1223 for (unsigned i = 0; i < NumRegularSections + 1; ++i) 1224 WriteDataSectionData(Asm, Layout, *Sections[i]); 1225 1226 FileOff = OS.tell(); 1227 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment); 1228 WriteZeros(Padding); 1229 1230 // ... then the section header table ... 1231 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap, 1232 SectionOffsetMap); 1233 1234 FileOff = OS.tell(); 1235 1236 // ... and then the remainting sections ... 1237 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) 1238 WriteDataSectionData(Asm, Layout, *Sections[i]); 1239 } 1240 1241 bool 1242 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 1243 const MCSymbolData &DataA, 1244 const MCFragment &FB, 1245 bool InSet, 1246 bool IsPCRel) const { 1247 if (DataA.getFlags() & ELF_STB_Weak) 1248 return false; 1249 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 1250 Asm, DataA, FB,InSet, IsPCRel); 1251 } 1252 1253 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1254 raw_ostream &OS, 1255 bool IsLittleEndian) { 1256 switch (MOTW->getEMachine()) { 1257 case ELF::EM_386: 1258 case ELF::EM_X86_64: 1259 return new X86ELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1260 case ELF::EM_ARM: 1261 return new ARMELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1262 case ELF::EM_MBLAZE: 1263 return new MBlazeELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1264 default: llvm_unreachable("Unsupported architecture"); break; 1265 } 1266 } 1267 1268 1269 /// START OF SUBCLASSES for ELFObjectWriter 1270 //===- ARMELFObjectWriter -------------------------------------------===// 1271 1272 ARMELFObjectWriter::ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1273 raw_ostream &_OS, 1274 bool IsLittleEndian) 1275 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1276 {} 1277 1278 ARMELFObjectWriter::~ARMELFObjectWriter() 1279 {} 1280 1281 // FIXME: get the real EABI Version from the Triple. 1282 void ARMELFObjectWriter::WriteEFlags() { 1283 Write32(ELF::EF_ARM_EABIMASK & DefaultEABIVersion); 1284 } 1285 1286 // In ARM, _MergedGlobals and other most symbols get emitted directly. 1287 // I.e. not as an offset to a section symbol. 1288 // This code is an approximation of what ARM/gcc does. 1289 1290 STATISTIC(PCRelCount, "Total number of PIC Relocations"); 1291 STATISTIC(NonPCRelCount, "Total number of non-PIC relocations"); 1292 1293 const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 1294 const MCValue &Target, 1295 const MCFragment &F, 1296 const MCFixup &Fixup, 1297 bool IsPCRel) const { 1298 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 1299 bool EmitThisSym = false; 1300 1301 const MCSectionELF &Section = 1302 static_cast<const MCSectionELF&>(Symbol.getSection()); 1303 bool InNormalSection = true; 1304 unsigned RelocType = 0; 1305 RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel); 1306 1307 DEBUG( 1308 const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 1309 MCSymbolRefExpr::VariantKind Kind2; 1310 Kind2 = Target.getSymB() ? Target.getSymB()->getKind() : 1311 MCSymbolRefExpr::VK_None; 1312 dbgs() << "considering symbol " 1313 << Section.getSectionName() << "/" 1314 << Symbol.getName() << "/" 1315 << " Rel:" << (unsigned)RelocType 1316 << " Kind: " << (int)Kind << "/" << (int)Kind2 1317 << " Tmp:" 1318 << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/" 1319 << Symbol.isVariable() << "/" << Symbol.isTemporary() 1320 << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n"); 1321 1322 if (IsPCRel || ForceARMElfPIC) { ++PCRelCount; 1323 switch (RelocType) { 1324 default: 1325 // Most relocation types are emitted as explicit symbols 1326 InNormalSection = 1327 StringSwitch<bool>(Section.getSectionName()) 1328 .Case(".data.rel.ro.local", false) 1329 .Case(".data.rel", false) 1330 .Case(".bss", false) 1331 .Default(true); 1332 EmitThisSym = true; 1333 break; 1334 case ELF::R_ARM_ABS32: 1335 // But things get strange with R_ARM_ABS32 1336 // In this case, most things that go in .rodata show up 1337 // as section relative relocations 1338 InNormalSection = 1339 StringSwitch<bool>(Section.getSectionName()) 1340 .Case(".data.rel.ro.local", false) 1341 .Case(".data.rel", false) 1342 .Case(".rodata", false) 1343 .Case(".bss", false) 1344 .Default(true); 1345 EmitThisSym = false; 1346 break; 1347 } 1348 } else { 1349 NonPCRelCount++; 1350 InNormalSection = 1351 StringSwitch<bool>(Section.getSectionName()) 1352 .Case(".data.rel.ro.local", false) 1353 .Case(".rodata", false) 1354 .Case(".data.rel", false) 1355 .Case(".bss", false) 1356 .Default(true); 1357 1358 switch (RelocType) { 1359 default: EmitThisSym = true; break; 1360 case ELF::R_ARM_ABS32: EmitThisSym = false; break; 1361 } 1362 } 1363 1364 if (EmitThisSym) 1365 return &Symbol; 1366 if (! Symbol.isTemporary() && InNormalSection) { 1367 return &Symbol; 1368 } 1369 return NULL; 1370 } 1371 1372 // Need to examine the Fixup when determining whether to 1373 // emit the relocation as an explicit symbol or as a section relative 1374 // offset 1375 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 1376 const MCFixup &Fixup, 1377 bool IsPCRel, 1378 bool IsRelocWithSymbol, 1379 int64_t Addend) { 1380 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1381 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1382 1383 unsigned Type = GetRelocTypeInner(Target, Fixup, IsPCRel); 1384 1385 if (RelocNeedsGOT(Modifier)) 1386 NeedsGOT = true; 1387 1388 return Type; 1389 } 1390 1391 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 1392 const MCFixup &Fixup, 1393 bool IsPCRel) const { 1394 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1395 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1396 1397 unsigned Type = 0; 1398 if (IsPCRel) { 1399 switch ((unsigned)Fixup.getKind()) { 1400 default: assert(0 && "Unimplemented"); 1401 case FK_Data_4: 1402 switch (Modifier) { 1403 default: llvm_unreachable("Unsupported Modifier"); 1404 case MCSymbolRefExpr::VK_None: 1405 Type = ELF::R_ARM_REL32; 1406 break; 1407 case MCSymbolRefExpr::VK_ARM_TLSGD: 1408 assert(0 && "unimplemented"); 1409 break; 1410 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1411 Type = ELF::R_ARM_TLS_IE32; 1412 break; 1413 } 1414 break; 1415 case ARM::fixup_arm_uncondbranch: 1416 switch (Modifier) { 1417 case MCSymbolRefExpr::VK_ARM_PLT: 1418 Type = ELF::R_ARM_PLT32; 1419 break; 1420 default: 1421 Type = ELF::R_ARM_CALL; 1422 break; 1423 } 1424 break; 1425 case ARM::fixup_arm_condbranch: 1426 Type = ELF::R_ARM_JUMP24; 1427 break; 1428 case ARM::fixup_arm_movt_hi16: 1429 case ARM::fixup_arm_movt_hi16_pcrel: 1430 Type = ELF::R_ARM_MOVT_PREL; 1431 break; 1432 case ARM::fixup_arm_movw_lo16: 1433 case ARM::fixup_arm_movw_lo16_pcrel: 1434 Type = ELF::R_ARM_MOVW_PREL_NC; 1435 break; 1436 case ARM::fixup_t2_movt_hi16: 1437 case ARM::fixup_t2_movt_hi16_pcrel: 1438 Type = ELF::R_ARM_THM_MOVT_PREL; 1439 break; 1440 case ARM::fixup_t2_movw_lo16: 1441 case ARM::fixup_t2_movw_lo16_pcrel: 1442 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 1443 break; 1444 case ARM::fixup_arm_thumb_bl: 1445 case ARM::fixup_arm_thumb_blx: 1446 switch (Modifier) { 1447 case MCSymbolRefExpr::VK_ARM_PLT: 1448 Type = ELF::R_ARM_THM_CALL; 1449 break; 1450 default: 1451 Type = ELF::R_ARM_NONE; 1452 break; 1453 } 1454 break; 1455 } 1456 } else { 1457 switch ((unsigned)Fixup.getKind()) { 1458 default: llvm_unreachable("invalid fixup kind!"); 1459 case FK_Data_4: 1460 switch (Modifier) { 1461 default: llvm_unreachable("Unsupported Modifier"); break; 1462 case MCSymbolRefExpr::VK_ARM_GOT: 1463 Type = ELF::R_ARM_GOT_BREL; 1464 break; 1465 case MCSymbolRefExpr::VK_ARM_TLSGD: 1466 Type = ELF::R_ARM_TLS_GD32; 1467 break; 1468 case MCSymbolRefExpr::VK_ARM_TPOFF: 1469 Type = ELF::R_ARM_TLS_LE32; 1470 break; 1471 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1472 Type = ELF::R_ARM_TLS_IE32; 1473 break; 1474 case MCSymbolRefExpr::VK_None: 1475 Type = ELF::R_ARM_ABS32; 1476 break; 1477 case MCSymbolRefExpr::VK_ARM_GOTOFF: 1478 Type = ELF::R_ARM_GOTOFF32; 1479 break; 1480 } 1481 break; 1482 case ARM::fixup_arm_ldst_pcrel_12: 1483 case ARM::fixup_arm_pcrel_10: 1484 case ARM::fixup_arm_adr_pcrel_12: 1485 case ARM::fixup_arm_thumb_bl: 1486 case ARM::fixup_arm_thumb_cb: 1487 case ARM::fixup_arm_thumb_cp: 1488 case ARM::fixup_arm_thumb_br: 1489 assert(0 && "Unimplemented"); 1490 break; 1491 case ARM::fixup_arm_uncondbranch: 1492 Type = ELF::R_ARM_CALL; 1493 break; 1494 case ARM::fixup_arm_condbranch: 1495 Type = ELF::R_ARM_JUMP24; 1496 break; 1497 case ARM::fixup_arm_movt_hi16: 1498 Type = ELF::R_ARM_MOVT_ABS; 1499 break; 1500 case ARM::fixup_arm_movw_lo16: 1501 Type = ELF::R_ARM_MOVW_ABS_NC; 1502 break; 1503 case ARM::fixup_t2_movt_hi16: 1504 Type = ELF::R_ARM_THM_MOVT_ABS; 1505 break; 1506 case ARM::fixup_t2_movw_lo16: 1507 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 1508 break; 1509 } 1510 } 1511 1512 return Type; 1513 } 1514 1515 //===- MBlazeELFObjectWriter -------------------------------------------===// 1516 1517 MBlazeELFObjectWriter::MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1518 raw_ostream &_OS, 1519 bool IsLittleEndian) 1520 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) { 1521 } 1522 1523 MBlazeELFObjectWriter::~MBlazeELFObjectWriter() { 1524 } 1525 1526 unsigned MBlazeELFObjectWriter::GetRelocType(const MCValue &Target, 1527 const MCFixup &Fixup, 1528 bool IsPCRel, 1529 bool IsRelocWithSymbol, 1530 int64_t Addend) { 1531 // determine the type of the relocation 1532 unsigned Type; 1533 if (IsPCRel) { 1534 switch ((unsigned)Fixup.getKind()) { 1535 default: 1536 llvm_unreachable("Unimplemented"); 1537 case FK_PCRel_4: 1538 Type = ELF::R_MICROBLAZE_64_PCREL; 1539 break; 1540 case FK_PCRel_2: 1541 Type = ELF::R_MICROBLAZE_32_PCREL; 1542 break; 1543 } 1544 } else { 1545 switch ((unsigned)Fixup.getKind()) { 1546 default: llvm_unreachable("invalid fixup kind!"); 1547 case FK_Data_4: 1548 Type = ((IsRelocWithSymbol || Addend !=0) 1549 ? ELF::R_MICROBLAZE_32 1550 : ELF::R_MICROBLAZE_64); 1551 break; 1552 case FK_Data_2: 1553 Type = ELF::R_MICROBLAZE_32; 1554 break; 1555 } 1556 } 1557 return Type; 1558 } 1559 1560 //===- X86ELFObjectWriter -------------------------------------------===// 1561 1562 1563 X86ELFObjectWriter::X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1564 raw_ostream &_OS, 1565 bool IsLittleEndian) 1566 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1567 {} 1568 1569 X86ELFObjectWriter::~X86ELFObjectWriter() 1570 {} 1571 1572 unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target, 1573 const MCFixup &Fixup, 1574 bool IsPCRel, 1575 bool IsRelocWithSymbol, 1576 int64_t Addend) { 1577 // determine the type of the relocation 1578 1579 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1580 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1581 unsigned Type; 1582 if (is64Bit()) { 1583 if (IsPCRel) { 1584 switch ((unsigned)Fixup.getKind()) { 1585 default: llvm_unreachable("invalid fixup kind!"); 1586 1587 case FK_Data_8: Type = ELF::R_X86_64_PC64; break; 1588 case FK_Data_4: Type = ELF::R_X86_64_PC32; break; 1589 case FK_Data_2: Type = ELF::R_X86_64_PC16; break; 1590 1591 case FK_PCRel_8: 1592 assert(Modifier == MCSymbolRefExpr::VK_None); 1593 Type = ELF::R_X86_64_PC64; 1594 break; 1595 case X86::reloc_signed_4byte: 1596 case X86::reloc_riprel_4byte_movq_load: 1597 case X86::reloc_riprel_4byte: 1598 case FK_PCRel_4: 1599 switch (Modifier) { 1600 default: 1601 llvm_unreachable("Unimplemented"); 1602 case MCSymbolRefExpr::VK_None: 1603 Type = ELF::R_X86_64_PC32; 1604 break; 1605 case MCSymbolRefExpr::VK_PLT: 1606 Type = ELF::R_X86_64_PLT32; 1607 break; 1608 case MCSymbolRefExpr::VK_GOTPCREL: 1609 Type = ELF::R_X86_64_GOTPCREL; 1610 break; 1611 case MCSymbolRefExpr::VK_GOTTPOFF: 1612 Type = ELF::R_X86_64_GOTTPOFF; 1613 break; 1614 case MCSymbolRefExpr::VK_TLSGD: 1615 Type = ELF::R_X86_64_TLSGD; 1616 break; 1617 case MCSymbolRefExpr::VK_TLSLD: 1618 Type = ELF::R_X86_64_TLSLD; 1619 break; 1620 } 1621 break; 1622 case FK_PCRel_2: 1623 assert(Modifier == MCSymbolRefExpr::VK_None); 1624 Type = ELF::R_X86_64_PC16; 1625 break; 1626 case FK_PCRel_1: 1627 assert(Modifier == MCSymbolRefExpr::VK_None); 1628 Type = ELF::R_X86_64_PC8; 1629 break; 1630 } 1631 } else { 1632 switch ((unsigned)Fixup.getKind()) { 1633 default: llvm_unreachable("invalid fixup kind!"); 1634 case FK_Data_8: Type = ELF::R_X86_64_64; break; 1635 case X86::reloc_signed_4byte: 1636 assert(isInt<32>(Target.getConstant())); 1637 switch (Modifier) { 1638 default: 1639 llvm_unreachable("Unimplemented"); 1640 case MCSymbolRefExpr::VK_None: 1641 Type = ELF::R_X86_64_32S; 1642 break; 1643 case MCSymbolRefExpr::VK_GOT: 1644 Type = ELF::R_X86_64_GOT32; 1645 break; 1646 case MCSymbolRefExpr::VK_GOTPCREL: 1647 Type = ELF::R_X86_64_GOTPCREL; 1648 break; 1649 case MCSymbolRefExpr::VK_TPOFF: 1650 Type = ELF::R_X86_64_TPOFF32; 1651 break; 1652 case MCSymbolRefExpr::VK_DTPOFF: 1653 Type = ELF::R_X86_64_DTPOFF32; 1654 break; 1655 } 1656 break; 1657 case FK_Data_4: 1658 Type = ELF::R_X86_64_32; 1659 break; 1660 case FK_Data_2: Type = ELF::R_X86_64_16; break; 1661 case FK_PCRel_1: 1662 case FK_Data_1: Type = ELF::R_X86_64_8; break; 1663 } 1664 } 1665 } else { 1666 if (IsPCRel) { 1667 switch (Modifier) { 1668 default: 1669 llvm_unreachable("Unimplemented"); 1670 case MCSymbolRefExpr::VK_None: 1671 Type = ELF::R_386_PC32; 1672 break; 1673 case MCSymbolRefExpr::VK_PLT: 1674 Type = ELF::R_386_PLT32; 1675 break; 1676 } 1677 } else { 1678 switch ((unsigned)Fixup.getKind()) { 1679 default: llvm_unreachable("invalid fixup kind!"); 1680 1681 case X86::reloc_global_offset_table: 1682 Type = ELF::R_386_GOTPC; 1683 break; 1684 1685 // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode 1686 // instead? 1687 case X86::reloc_signed_4byte: 1688 case FK_PCRel_4: 1689 case FK_Data_4: 1690 switch (Modifier) { 1691 default: 1692 llvm_unreachable("Unimplemented"); 1693 case MCSymbolRefExpr::VK_None: 1694 Type = ELF::R_386_32; 1695 break; 1696 case MCSymbolRefExpr::VK_GOT: 1697 Type = ELF::R_386_GOT32; 1698 break; 1699 case MCSymbolRefExpr::VK_GOTOFF: 1700 Type = ELF::R_386_GOTOFF; 1701 break; 1702 case MCSymbolRefExpr::VK_TLSGD: 1703 Type = ELF::R_386_TLS_GD; 1704 break; 1705 case MCSymbolRefExpr::VK_TPOFF: 1706 Type = ELF::R_386_TLS_LE_32; 1707 break; 1708 case MCSymbolRefExpr::VK_INDNTPOFF: 1709 Type = ELF::R_386_TLS_IE; 1710 break; 1711 case MCSymbolRefExpr::VK_NTPOFF: 1712 Type = ELF::R_386_TLS_LE; 1713 break; 1714 case MCSymbolRefExpr::VK_GOTNTPOFF: 1715 Type = ELF::R_386_TLS_GOTIE; 1716 break; 1717 case MCSymbolRefExpr::VK_TLSLDM: 1718 Type = ELF::R_386_TLS_LDM; 1719 break; 1720 case MCSymbolRefExpr::VK_DTPOFF: 1721 Type = ELF::R_386_TLS_LDO_32; 1722 break; 1723 } 1724 break; 1725 case FK_Data_2: Type = ELF::R_386_16; break; 1726 case FK_PCRel_1: 1727 case FK_Data_1: Type = ELF::R_386_8; break; 1728 } 1729 } 1730 } 1731 1732 if (RelocNeedsGOT(Modifier)) 1733 NeedsGOT = true; 1734 1735 return Type; 1736 } 1737