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 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { 41 const MCFixupKindInfo &FKI = 42 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind); 43 44 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; 45 } 46 47 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) { 48 switch (Variant) { 49 default: 50 return false; 51 case MCSymbolRefExpr::VK_GOT: 52 case MCSymbolRefExpr::VK_PLT: 53 case MCSymbolRefExpr::VK_GOTPCREL: 54 case MCSymbolRefExpr::VK_GOTOFF: 55 case MCSymbolRefExpr::VK_TPOFF: 56 case MCSymbolRefExpr::VK_TLSGD: 57 case MCSymbolRefExpr::VK_GOTTPOFF: 58 case MCSymbolRefExpr::VK_INDNTPOFF: 59 case MCSymbolRefExpr::VK_NTPOFF: 60 case MCSymbolRefExpr::VK_GOTNTPOFF: 61 case MCSymbolRefExpr::VK_TLSLDM: 62 case MCSymbolRefExpr::VK_DTPOFF: 63 case MCSymbolRefExpr::VK_TLSLD: 64 return true; 65 } 66 } 67 68 ELFObjectWriter::~ELFObjectWriter() 69 {} 70 71 // Emit the ELF header. 72 void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize, 73 unsigned NumberOfSections) { 74 // ELF Header 75 // ---------- 76 // 77 // Note 78 // ---- 79 // emitWord method behaves differently for ELF32 and ELF64, writing 80 // 4 bytes in the former and 8 in the latter. 81 82 Write8(0x7f); // e_ident[EI_MAG0] 83 Write8('E'); // e_ident[EI_MAG1] 84 Write8('L'); // e_ident[EI_MAG2] 85 Write8('F'); // e_ident[EI_MAG3] 86 87 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS] 88 89 // e_ident[EI_DATA] 90 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); 91 92 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] 93 // e_ident[EI_OSABI] 94 switch (TargetObjectWriter->getOSType()) { 95 case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break; 96 case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break; 97 default: Write8(ELF::ELFOSABI_NONE); break; 98 } 99 Write8(0); // e_ident[EI_ABIVERSION] 100 101 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); 102 103 Write16(ELF::ET_REL); // e_type 104 105 Write16(TargetObjectWriter->getEMachine()); // e_machine = target 106 107 Write32(ELF::EV_CURRENT); // e_version 108 WriteWord(0); // e_entry, no entry point in .o file 109 WriteWord(0); // e_phoff, no program header for .o 110 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 111 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes 112 113 // e_flags = whatever the target wants 114 WriteEFlags(); 115 116 // e_ehsize = ELF header size 117 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr)); 118 119 Write16(0); // e_phentsize = prog header entry size 120 Write16(0); // e_phnum = # prog header entries = 0 121 122 // e_shentsize = Section header entry size 123 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr)); 124 125 // e_shnum = # of section header ents 126 if (NumberOfSections >= ELF::SHN_LORESERVE) 127 Write16(0); 128 else 129 Write16(NumberOfSections); 130 131 // e_shstrndx = Section # of '.shstrtab' 132 if (NumberOfSections >= ELF::SHN_LORESERVE) 133 Write16(ELF::SHN_XINDEX); 134 else 135 Write16(ShstrtabIndex); 136 } 137 138 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF, 139 MCDataFragment *ShndxF, 140 uint64_t name, 141 uint8_t info, uint64_t value, 142 uint64_t size, uint8_t other, 143 uint32_t shndx, 144 bool Reserved) { 145 if (ShndxF) { 146 if (shndx >= ELF::SHN_LORESERVE && !Reserved) 147 String32(*ShndxF, shndx); 148 else 149 String32(*ShndxF, 0); 150 } 151 152 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ? 153 uint16_t(ELF::SHN_XINDEX) : shndx; 154 155 if (is64Bit()) { 156 String32(*SymtabF, name); // st_name 157 String8(*SymtabF, info); // st_info 158 String8(*SymtabF, other); // st_other 159 String16(*SymtabF, Index); // st_shndx 160 String64(*SymtabF, value); // st_value 161 String64(*SymtabF, size); // st_size 162 } else { 163 String32(*SymtabF, name); // st_name 164 String32(*SymtabF, value); // st_value 165 String32(*SymtabF, size); // st_size 166 String8(*SymtabF, info); // st_info 167 String8(*SymtabF, other); // st_other 168 String16(*SymtabF, Index); // st_shndx 169 } 170 } 171 172 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data, 173 const MCAsmLayout &Layout) { 174 if (Data.isCommon() && Data.isExternal()) 175 return Data.getCommonAlignment(); 176 177 const MCSymbol &Symbol = Data.getSymbol(); 178 179 if (Symbol.isAbsolute() && Symbol.isVariable()) { 180 if (const MCExpr *Value = Symbol.getVariableValue()) { 181 int64_t IntValue; 182 if (Value->EvaluateAsAbsolute(IntValue, Layout)) 183 return (uint64_t)IntValue; 184 } 185 } 186 187 if (!Symbol.isInSection()) 188 return 0; 189 190 191 if (Data.getFragment()) { 192 if (Data.getFlags() & ELF_Other_ThumbFunc) 193 return Layout.getSymbolOffset(&Data)+1; 194 else 195 return Layout.getSymbolOffset(&Data); 196 } 197 198 return 0; 199 } 200 201 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 202 const MCAsmLayout &Layout) { 203 // The presence of symbol versions causes undefined symbols and 204 // versions declared with @@@ to be renamed. 205 206 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 207 ie = Asm.symbol_end(); it != ie; ++it) { 208 const MCSymbol &Alias = it->getSymbol(); 209 const MCSymbol &Symbol = Alias.AliasedSymbol(); 210 MCSymbolData &SD = Asm.getSymbolData(Symbol); 211 212 // Not an alias. 213 if (&Symbol == &Alias) 214 continue; 215 216 StringRef AliasName = Alias.getName(); 217 size_t Pos = AliasName.find('@'); 218 if (Pos == StringRef::npos) 219 continue; 220 221 // Aliases defined with .symvar copy the binding from the symbol they alias. 222 // This is the first place we are able to copy this information. 223 it->setExternal(SD.isExternal()); 224 MCELF::SetBinding(*it, MCELF::GetBinding(SD)); 225 226 StringRef Rest = AliasName.substr(Pos); 227 if (!Symbol.isUndefined() && !Rest.startswith("@@@")) 228 continue; 229 230 // FIXME: produce a better error message. 231 if (Symbol.isUndefined() && Rest.startswith("@@") && 232 !Rest.startswith("@@@")) 233 report_fatal_error("A @@ version cannot be undefined"); 234 235 Renames.insert(std::make_pair(&Symbol, &Alias)); 236 } 237 } 238 239 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF, 240 MCDataFragment *ShndxF, 241 ELFSymbolData &MSD, 242 const MCAsmLayout &Layout) { 243 MCSymbolData &OrigData = *MSD.SymbolData; 244 MCSymbolData &Data = 245 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol()); 246 247 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() || 248 Data.getSymbol().isVariable(); 249 250 uint8_t Binding = MCELF::GetBinding(OrigData); 251 uint8_t Visibility = MCELF::GetVisibility(OrigData); 252 uint8_t Type = MCELF::GetType(Data); 253 254 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); 255 uint8_t Other = Visibility; 256 257 uint64_t Value = SymbolValue(Data, Layout); 258 uint64_t Size = 0; 259 260 assert(!(Data.isCommon() && !Data.isExternal())); 261 262 const MCExpr *ESize = Data.getSize(); 263 if (ESize) { 264 int64_t Res; 265 if (!ESize->EvaluateAsAbsolute(Res, Layout)) 266 report_fatal_error("Size expression must be absolute."); 267 Size = Res; 268 } 269 270 // Write out the symbol table entry 271 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value, 272 Size, Other, MSD.SectionIndex, IsReserved); 273 } 274 275 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF, 276 MCDataFragment *ShndxF, 277 const MCAssembler &Asm, 278 const MCAsmLayout &Layout, 279 const SectionIndexMapTy &SectionIndexMap) { 280 // The string table must be emitted first because we need the index 281 // into the string table for all the symbol names. 282 assert(StringTable.size() && "Missing string table"); 283 284 // FIXME: Make sure the start of the symbol table is aligned. 285 286 // The first entry is the undefined symbol entry. 287 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false); 288 289 // Write the symbol table entries. 290 LastLocalSymbolIndex = LocalSymbolData.size() + 1; 291 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) { 292 ELFSymbolData &MSD = LocalSymbolData[i]; 293 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 294 } 295 296 // Write out a symbol table entry for each regular section. 297 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; 298 ++i) { 299 const MCSectionELF &Section = 300 static_cast<const MCSectionELF&>(i->getSection()); 301 if (Section.getType() == ELF::SHT_RELA || 302 Section.getType() == ELF::SHT_REL || 303 Section.getType() == ELF::SHT_STRTAB || 304 Section.getType() == ELF::SHT_SYMTAB) 305 continue; 306 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0, 307 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false); 308 LastLocalSymbolIndex++; 309 } 310 311 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { 312 ELFSymbolData &MSD = ExternalSymbolData[i]; 313 MCSymbolData &Data = *MSD.SymbolData; 314 assert(((Data.getFlags() & ELF_STB_Global) || 315 (Data.getFlags() & ELF_STB_Weak)) && 316 "External symbol requires STB_GLOBAL or STB_WEAK flag"); 317 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 318 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 319 LastLocalSymbolIndex++; 320 } 321 322 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { 323 ELFSymbolData &MSD = UndefinedSymbolData[i]; 324 MCSymbolData &Data = *MSD.SymbolData; 325 WriteSymbol(SymtabF, ShndxF, MSD, Layout); 326 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) 327 LastLocalSymbolIndex++; 328 } 329 } 330 331 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm, 332 const MCValue &Target, 333 const MCFragment &F, 334 const MCFixup &Fixup, 335 bool IsPCRel) const { 336 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 337 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 338 const MCSymbol *Renamed = Renames.lookup(&Symbol); 339 const MCSymbolData &SD = Asm.getSymbolData(Symbol); 340 341 if (ASymbol.isUndefined()) { 342 if (Renamed) 343 return Renamed; 344 return &ASymbol; 345 } 346 347 if (SD.isExternal()) { 348 if (Renamed) 349 return Renamed; 350 return &Symbol; 351 } 352 353 const MCSectionELF &Section = 354 static_cast<const MCSectionELF&>(ASymbol.getSection()); 355 const SectionKind secKind = Section.getKind(); 356 357 if (secKind.isBSS()) 358 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 359 360 if (secKind.isThreadLocal()) { 361 if (Renamed) 362 return Renamed; 363 return &Symbol; 364 } 365 366 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 367 const MCSectionELF &Sec2 = 368 static_cast<const MCSectionELF&>(F.getParent()->getSection()); 369 370 if (&Sec2 != &Section && 371 (Kind == MCSymbolRefExpr::VK_PLT || 372 Kind == MCSymbolRefExpr::VK_GOTPCREL || 373 Kind == MCSymbolRefExpr::VK_GOTOFF)) { 374 if (Renamed) 375 return Renamed; 376 return &Symbol; 377 } 378 379 if (Section.getFlags() & ELF::SHF_MERGE) { 380 if (Target.getConstant() == 0) 381 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 382 if (Renamed) 383 return Renamed; 384 return &Symbol; 385 } 386 387 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel); 388 389 } 390 391 392 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, 393 const MCAsmLayout &Layout, 394 const MCFragment *Fragment, 395 const MCFixup &Fixup, 396 MCValue Target, 397 uint64_t &FixedValue) { 398 int64_t Addend = 0; 399 int Index = 0; 400 int64_t Value = Target.getConstant(); 401 const MCSymbol *RelocSymbol = NULL; 402 403 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind()); 404 if (!Target.isAbsolute()) { 405 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 406 const MCSymbol &ASymbol = Symbol.AliasedSymbol(); 407 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel); 408 409 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 410 const MCSymbol &SymbolB = RefB->getSymbol(); 411 MCSymbolData &SDB = Asm.getSymbolData(SymbolB); 412 IsPCRel = true; 413 414 // Offset of the symbol in the section 415 int64_t a = Layout.getSymbolOffset(&SDB); 416 417 // Ofeset of the relocation in the section 418 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 419 Value += b - a; 420 } 421 422 if (!RelocSymbol) { 423 MCSymbolData &SD = Asm.getSymbolData(ASymbol); 424 MCFragment *F = SD.getFragment(); 425 426 Index = F->getParent()->getOrdinal() + 1; 427 428 // Offset of the symbol in the section 429 Value += Layout.getSymbolOffset(&SD); 430 } else { 431 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref) 432 WeakrefUsedInReloc.insert(RelocSymbol); 433 else 434 UsedInReloc.insert(RelocSymbol); 435 Index = -1; 436 } 437 Addend = Value; 438 // Compensate for the addend on i386. 439 if (is64Bit()) 440 Value = 0; 441 } 442 443 FixedValue = Value; 444 unsigned Type = GetRelocType(Target, Fixup, IsPCRel, 445 (RelocSymbol != 0), Addend); 446 447 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) + 448 Fixup.getOffset(); 449 450 if (!hasRelocationAddend()) 451 Addend = 0; 452 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend); 453 Relocations[Fragment->getParent()].push_back(ERE); 454 } 455 456 457 uint64_t 458 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm, 459 const MCSymbol *S) { 460 MCSymbolData &SD = Asm.getSymbolData(*S); 461 return SD.getIndex(); 462 } 463 464 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm, 465 const MCSymbolData &Data, 466 bool Used, bool Renamed) { 467 if (Data.getFlags() & ELF_Other_Weakref) 468 return false; 469 470 if (Used) 471 return true; 472 473 if (Renamed) 474 return false; 475 476 const MCSymbol &Symbol = Data.getSymbol(); 477 478 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_") 479 return true; 480 481 const MCSymbol &A = Symbol.AliasedSymbol(); 482 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined()) 483 return false; 484 485 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL; 486 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal) 487 return false; 488 489 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) 490 return false; 491 492 if (Symbol.isTemporary()) 493 return false; 494 495 return true; 496 } 497 498 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature, 499 bool isUsedInReloc) { 500 if (Data.isExternal()) 501 return false; 502 503 const MCSymbol &Symbol = Data.getSymbol(); 504 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 505 506 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) { 507 if (isSignature && !isUsedInReloc) 508 return true; 509 510 return false; 511 } 512 513 return true; 514 } 515 516 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm, 517 SectionIndexMapTy &SectionIndexMap, 518 const RelMapTy &RelMap) { 519 unsigned Index = 1; 520 for (MCAssembler::iterator it = Asm.begin(), 521 ie = Asm.end(); it != ie; ++it) { 522 const MCSectionELF &Section = 523 static_cast<const MCSectionELF &>(it->getSection()); 524 if (Section.getType() != ELF::SHT_GROUP) 525 continue; 526 SectionIndexMap[&Section] = Index++; 527 } 528 529 for (MCAssembler::iterator it = Asm.begin(), 530 ie = Asm.end(); it != ie; ++it) { 531 const MCSectionELF &Section = 532 static_cast<const MCSectionELF &>(it->getSection()); 533 if (Section.getType() == ELF::SHT_GROUP || 534 Section.getType() == ELF::SHT_REL || 535 Section.getType() == ELF::SHT_RELA) 536 continue; 537 SectionIndexMap[&Section] = Index++; 538 const MCSectionELF *RelSection = RelMap.lookup(&Section); 539 if (RelSection) 540 SectionIndexMap[RelSection] = Index++; 541 } 542 } 543 544 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, 545 const SectionIndexMapTy &SectionIndexMap, 546 RevGroupMapTy RevGroupMap, 547 unsigned NumRegularSections) { 548 // FIXME: Is this the correct place to do this? 549 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed? 550 if (NeedsGOT) { 551 llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_"; 552 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); 553 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); 554 Data.setExternal(true); 555 MCELF::SetBinding(Data, ELF::STB_GLOBAL); 556 } 557 558 // Index 0 is always the empty string. 559 StringMap<uint64_t> StringIndexMap; 560 StringTable += '\x00'; 561 562 // FIXME: We could optimize suffixes in strtab in the same way we 563 // optimize them in shstrtab. 564 565 // Add the data for the symbols. 566 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), 567 ie = Asm.symbol_end(); it != ie; ++it) { 568 const MCSymbol &Symbol = it->getSymbol(); 569 570 bool Used = UsedInReloc.count(&Symbol); 571 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol); 572 bool isSignature = RevGroupMap.count(&Symbol); 573 574 if (!isInSymtab(Asm, *it, 575 Used || WeakrefUsed || isSignature, 576 Renames.count(&Symbol))) 577 continue; 578 579 ELFSymbolData MSD; 580 MSD.SymbolData = it; 581 const MCSymbol &RefSymbol = Symbol.AliasedSymbol(); 582 583 // Undefined symbols are global, but this is the first place we 584 // are able to set it. 585 bool Local = isLocal(*it, isSignature, Used); 586 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) { 587 MCSymbolData &SD = Asm.getSymbolData(RefSymbol); 588 MCELF::SetBinding(*it, ELF::STB_GLOBAL); 589 MCELF::SetBinding(SD, ELF::STB_GLOBAL); 590 } 591 592 if (RefSymbol.isUndefined() && !Used && WeakrefUsed) 593 MCELF::SetBinding(*it, ELF::STB_WEAK); 594 595 if (it->isCommon()) { 596 assert(!Local); 597 MSD.SectionIndex = ELF::SHN_COMMON; 598 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) { 599 MSD.SectionIndex = ELF::SHN_ABS; 600 } else if (RefSymbol.isUndefined()) { 601 if (isSignature && !Used) 602 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]); 603 else 604 MSD.SectionIndex = ELF::SHN_UNDEF; 605 } else { 606 const MCSectionELF &Section = 607 static_cast<const MCSectionELF&>(RefSymbol.getSection()); 608 MSD.SectionIndex = SectionIndexMap.lookup(&Section); 609 if (MSD.SectionIndex >= ELF::SHN_LORESERVE) 610 NeedsSymtabShndx = true; 611 assert(MSD.SectionIndex && "Invalid section index!"); 612 } 613 614 // The @@@ in symbol version is replaced with @ in undefined symbols and 615 // @@ in defined ones. 616 StringRef Name = Symbol.getName(); 617 SmallString<32> Buf; 618 619 size_t Pos = Name.find("@@@"); 620 if (Pos != StringRef::npos) { 621 Buf += Name.substr(0, Pos); 622 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1; 623 Buf += Name.substr(Pos + Skip); 624 Name = Buf; 625 } 626 627 uint64_t &Entry = StringIndexMap[Name]; 628 if (!Entry) { 629 Entry = StringTable.size(); 630 StringTable += Name; 631 StringTable += '\x00'; 632 } 633 MSD.StringIndex = Entry; 634 if (MSD.SectionIndex == ELF::SHN_UNDEF) 635 UndefinedSymbolData.push_back(MSD); 636 else if (Local) 637 LocalSymbolData.push_back(MSD); 638 else 639 ExternalSymbolData.push_back(MSD); 640 } 641 642 // Symbols are required to be in lexicographic order. 643 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end()); 644 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); 645 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); 646 647 // Set the symbol indices. Local symbols must come before all other 648 // symbols with non-local bindings. 649 unsigned Index = 1; 650 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) 651 LocalSymbolData[i].SymbolData->setIndex(Index++); 652 653 Index += NumRegularSections; 654 655 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) 656 ExternalSymbolData[i].SymbolData->setIndex(Index++); 657 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) 658 UndefinedSymbolData[i].SymbolData->setIndex(Index++); 659 } 660 661 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm, 662 MCAsmLayout &Layout, 663 RelMapTy &RelMap) { 664 for (MCAssembler::const_iterator it = Asm.begin(), 665 ie = Asm.end(); it != ie; ++it) { 666 const MCSectionData &SD = *it; 667 if (Relocations[&SD].empty()) 668 continue; 669 670 MCContext &Ctx = Asm.getContext(); 671 const MCSectionELF &Section = 672 static_cast<const MCSectionELF&>(SD.getSection()); 673 674 const StringRef SectionName = Section.getSectionName(); 675 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel"; 676 RelaSectionName += SectionName; 677 678 unsigned EntrySize; 679 if (hasRelocationAddend()) 680 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela); 681 else 682 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel); 683 684 const MCSectionELF *RelaSection = 685 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ? 686 ELF::SHT_RELA : ELF::SHT_REL, 0, 687 SectionKind::getReadOnly(), 688 EntrySize, ""); 689 RelMap[&Section] = RelaSection; 690 Asm.getOrCreateSectionData(*RelaSection); 691 } 692 } 693 694 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, 695 const RelMapTy &RelMap) { 696 for (MCAssembler::const_iterator it = Asm.begin(), 697 ie = Asm.end(); it != ie; ++it) { 698 const MCSectionData &SD = *it; 699 const MCSectionELF &Section = 700 static_cast<const MCSectionELF&>(SD.getSection()); 701 702 const MCSectionELF *RelaSection = RelMap.lookup(&Section); 703 if (!RelaSection) 704 continue; 705 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); 706 RelaSD.setAlignment(is64Bit() ? 8 : 4); 707 708 MCDataFragment *F = new MCDataFragment(&RelaSD); 709 WriteRelocationsFragment(Asm, F, &*it); 710 } 711 } 712 713 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, 714 uint64_t Flags, uint64_t Address, 715 uint64_t Offset, uint64_t Size, 716 uint32_t Link, uint32_t Info, 717 uint64_t Alignment, 718 uint64_t EntrySize) { 719 Write32(Name); // sh_name: index into string table 720 Write32(Type); // sh_type 721 WriteWord(Flags); // sh_flags 722 WriteWord(Address); // sh_addr 723 WriteWord(Offset); // sh_offset 724 WriteWord(Size); // sh_size 725 Write32(Link); // sh_link 726 Write32(Info); // sh_info 727 WriteWord(Alignment); // sh_addralign 728 WriteWord(EntrySize); // sh_entsize 729 } 730 731 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm, 732 MCDataFragment *F, 733 const MCSectionData *SD) { 734 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD]; 735 // sort by the r_offset just like gnu as does 736 array_pod_sort(Relocs.begin(), Relocs.end()); 737 738 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { 739 ELFRelocationEntry entry = Relocs[e - i - 1]; 740 741 if (!entry.Index) 742 ; 743 else if (entry.Index < 0) 744 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); 745 else 746 entry.Index += LocalSymbolData.size(); 747 if (is64Bit()) { 748 String64(*F, entry.r_offset); 749 750 struct ELF::Elf64_Rela ERE64; 751 ERE64.setSymbolAndType(entry.Index, entry.Type); 752 String64(*F, ERE64.r_info); 753 754 if (hasRelocationAddend()) 755 String64(*F, entry.r_addend); 756 } else { 757 String32(*F, entry.r_offset); 758 759 struct ELF::Elf32_Rela ERE32; 760 ERE32.setSymbolAndType(entry.Index, entry.Type); 761 String32(*F, ERE32.r_info); 762 763 if (hasRelocationAddend()) 764 String32(*F, entry.r_addend); 765 } 766 } 767 } 768 769 static int compareBySuffix(const void *a, const void *b) { 770 const MCSectionELF *secA = *static_cast<const MCSectionELF* const *>(a); 771 const MCSectionELF *secB = *static_cast<const MCSectionELF* const *>(b); 772 const StringRef &NameA = secA->getSectionName(); 773 const StringRef &NameB = secB->getSectionName(); 774 const unsigned sizeA = NameA.size(); 775 const unsigned sizeB = NameB.size(); 776 const unsigned len = std::min(sizeA, sizeB); 777 for (unsigned int i = 0; i < len; ++i) { 778 char ca = NameA[sizeA - i - 1]; 779 char cb = NameB[sizeB - i - 1]; 780 if (ca != cb) 781 return cb - ca; 782 } 783 784 return sizeB - sizeA; 785 } 786 787 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm, 788 MCAsmLayout &Layout, 789 SectionIndexMapTy &SectionIndexMap, 790 const RelMapTy &RelMap) { 791 MCContext &Ctx = Asm.getContext(); 792 MCDataFragment *F; 793 794 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; 795 796 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. 797 const MCSectionELF *ShstrtabSection = 798 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, 799 SectionKind::getReadOnly()); 800 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); 801 ShstrtabSD.setAlignment(1); 802 803 const MCSectionELF *SymtabSection = 804 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, 805 SectionKind::getReadOnly(), 806 EntrySize, ""); 807 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); 808 SymtabSD.setAlignment(is64Bit() ? 8 : 4); 809 810 MCSectionData *SymtabShndxSD = NULL; 811 812 if (NeedsSymtabShndx) { 813 const MCSectionELF *SymtabShndxSection = 814 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 815 SectionKind::getReadOnly(), 4, ""); 816 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection); 817 SymtabShndxSD->setAlignment(4); 818 } 819 820 const MCSectionELF *StrtabSection; 821 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, 822 SectionKind::getReadOnly()); 823 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); 824 StrtabSD.setAlignment(1); 825 826 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 827 828 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection); 829 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection); 830 StringTableIndex = SectionIndexMap.lookup(StrtabSection); 831 832 // Symbol table 833 F = new MCDataFragment(&SymtabSD); 834 MCDataFragment *ShndxF = NULL; 835 if (NeedsSymtabShndx) { 836 ShndxF = new MCDataFragment(SymtabShndxSD); 837 } 838 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap); 839 840 F = new MCDataFragment(&StrtabSD); 841 F->getContents().append(StringTable.begin(), StringTable.end()); 842 843 F = new MCDataFragment(&ShstrtabSD); 844 845 std::vector<const MCSectionELF*> Sections; 846 for (MCAssembler::const_iterator it = Asm.begin(), 847 ie = Asm.end(); it != ie; ++it) { 848 const MCSectionELF &Section = 849 static_cast<const MCSectionELF&>(it->getSection()); 850 Sections.push_back(&Section); 851 } 852 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix); 853 854 // Section header string table. 855 // 856 // The first entry of a string table holds a null character so skip 857 // section 0. 858 uint64_t Index = 1; 859 F->getContents() += '\x00'; 860 861 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) { 862 const MCSectionELF &Section = *Sections[I]; 863 864 StringRef Name = Section.getSectionName(); 865 if (I != 0) { 866 StringRef PreviousName = Sections[I - 1]->getSectionName(); 867 if (PreviousName.endswith(Name)) { 868 SectionStringTableIndex[&Section] = Index - Name.size() - 1; 869 continue; 870 } 871 } 872 // Remember the index into the string table so we can write it 873 // into the sh_name field of the section header table. 874 SectionStringTableIndex[&Section] = Index; 875 876 Index += Name.size() + 1; 877 F->getContents() += Name; 878 F->getContents() += '\x00'; 879 } 880 } 881 882 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm, 883 MCAsmLayout &Layout, 884 GroupMapTy &GroupMap, 885 RevGroupMapTy &RevGroupMap, 886 SectionIndexMapTy &SectionIndexMap, 887 const RelMapTy &RelMap) { 888 // Create the .note.GNU-stack section if needed. 889 MCContext &Ctx = Asm.getContext(); 890 if (Asm.getNoExecStack()) { 891 const MCSectionELF *GnuStackSection = 892 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0, 893 SectionKind::getReadOnly()); 894 Asm.getOrCreateSectionData(*GnuStackSection); 895 } 896 897 // Build the groups 898 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 899 it != ie; ++it) { 900 const MCSectionELF &Section = 901 static_cast<const MCSectionELF&>(it->getSection()); 902 if (!(Section.getFlags() & ELF::SHF_GROUP)) 903 continue; 904 905 const MCSymbol *SignatureSymbol = Section.getGroup(); 906 Asm.getOrCreateSymbolData(*SignatureSymbol); 907 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol]; 908 if (!Group) { 909 Group = Ctx.CreateELFGroupSection(); 910 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 911 Data.setAlignment(4); 912 MCDataFragment *F = new MCDataFragment(&Data); 913 String32(*F, ELF::GRP_COMDAT); 914 } 915 GroupMap[Group] = SignatureSymbol; 916 } 917 918 ComputeIndexMap(Asm, SectionIndexMap, RelMap); 919 920 // Add sections to the groups 921 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); 922 it != ie; ++it) { 923 const MCSectionELF &Section = 924 static_cast<const MCSectionELF&>(it->getSection()); 925 if (!(Section.getFlags() & ELF::SHF_GROUP)) 926 continue; 927 const MCSectionELF *Group = RevGroupMap[Section.getGroup()]; 928 MCSectionData &Data = Asm.getOrCreateSectionData(*Group); 929 // FIXME: we could use the previous fragment 930 MCDataFragment *F = new MCDataFragment(&Data); 931 unsigned Index = SectionIndexMap.lookup(&Section); 932 String32(*F, Index); 933 } 934 } 935 936 void ELFObjectWriter::WriteSection(MCAssembler &Asm, 937 const SectionIndexMapTy &SectionIndexMap, 938 uint32_t GroupSymbolIndex, 939 uint64_t Offset, uint64_t Size, 940 uint64_t Alignment, 941 const MCSectionELF &Section) { 942 uint64_t sh_link = 0; 943 uint64_t sh_info = 0; 944 945 switch(Section.getType()) { 946 case ELF::SHT_DYNAMIC: 947 sh_link = SectionStringTableIndex[&Section]; 948 sh_info = 0; 949 break; 950 951 case ELF::SHT_REL: 952 case ELF::SHT_RELA: { 953 const MCSectionELF *SymtabSection; 954 const MCSectionELF *InfoSection; 955 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 956 0, 957 SectionKind::getReadOnly()); 958 sh_link = SectionIndexMap.lookup(SymtabSection); 959 assert(sh_link && ".symtab not found"); 960 961 // Remove ".rel" and ".rela" prefixes. 962 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5; 963 StringRef SectionName = Section.getSectionName().substr(SecNameLen); 964 965 InfoSection = Asm.getContext().getELFSection(SectionName, 966 ELF::SHT_PROGBITS, 0, 967 SectionKind::getReadOnly()); 968 sh_info = SectionIndexMap.lookup(InfoSection); 969 break; 970 } 971 972 case ELF::SHT_SYMTAB: 973 case ELF::SHT_DYNSYM: 974 sh_link = StringTableIndex; 975 sh_info = LastLocalSymbolIndex; 976 break; 977 978 case ELF::SHT_SYMTAB_SHNDX: 979 sh_link = SymbolTableIndex; 980 break; 981 982 case ELF::SHT_PROGBITS: 983 case ELF::SHT_STRTAB: 984 case ELF::SHT_NOBITS: 985 case ELF::SHT_NOTE: 986 case ELF::SHT_NULL: 987 case ELF::SHT_ARM_ATTRIBUTES: 988 case ELF::SHT_INIT_ARRAY: 989 case ELF::SHT_FINI_ARRAY: 990 case ELF::SHT_PREINIT_ARRAY: 991 case ELF::SHT_X86_64_UNWIND: 992 // Nothing to do. 993 break; 994 995 case ELF::SHT_GROUP: { 996 sh_link = SymbolTableIndex; 997 sh_info = GroupSymbolIndex; 998 break; 999 } 1000 1001 default: 1002 assert(0 && "FIXME: sh_type value not supported!"); 1003 break; 1004 } 1005 1006 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(), 1007 Section.getFlags(), 0, Offset, Size, sh_link, sh_info, 1008 Alignment, Section.getEntrySize()); 1009 } 1010 1011 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) { 1012 return SD.getOrdinal() == ~UINT32_C(0) && 1013 !SD.getSection().isVirtualSection(); 1014 } 1015 1016 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) { 1017 uint64_t Ret = 0; 1018 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1019 ++i) { 1020 const MCFragment &F = *i; 1021 assert(F.getKind() == MCFragment::FT_Data); 1022 Ret += cast<MCDataFragment>(F).getContents().size(); 1023 } 1024 return Ret; 1025 } 1026 1027 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout, 1028 const MCSectionData &SD) { 1029 if (IsELFMetaDataSection(SD)) 1030 return DataSectionSize(SD); 1031 return Layout.getSectionFileSize(&SD); 1032 } 1033 1034 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout, 1035 const MCSectionData &SD) { 1036 if (IsELFMetaDataSection(SD)) 1037 return DataSectionSize(SD); 1038 return Layout.getSectionAddressSize(&SD); 1039 } 1040 1041 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm, 1042 const MCAsmLayout &Layout, 1043 const MCSectionELF &Section) { 1044 uint64_t FileOff = OS.tell(); 1045 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1046 1047 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment()); 1048 WriteZeros(Padding); 1049 FileOff += Padding; 1050 1051 FileOff += GetSectionFileSize(Layout, SD); 1052 1053 if (IsELFMetaDataSection(SD)) { 1054 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; 1055 ++i) { 1056 const MCFragment &F = *i; 1057 assert(F.getKind() == MCFragment::FT_Data); 1058 WriteBytes(cast<MCDataFragment>(F).getContents().str()); 1059 } 1060 } else { 1061 Asm.WriteSectionData(&SD, Layout); 1062 } 1063 } 1064 1065 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm, 1066 const GroupMapTy &GroupMap, 1067 const MCAsmLayout &Layout, 1068 const SectionIndexMapTy &SectionIndexMap, 1069 const SectionOffsetMapTy &SectionOffsetMap) { 1070 const unsigned NumSections = Asm.size() + 1; 1071 1072 std::vector<const MCSectionELF*> Sections; 1073 Sections.resize(NumSections - 1); 1074 1075 for (SectionIndexMapTy::const_iterator i= 1076 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) { 1077 const std::pair<const MCSectionELF*, uint32_t> &p = *i; 1078 Sections[p.second - 1] = p.first; 1079 } 1080 1081 // Null section first. 1082 uint64_t FirstSectionSize = 1083 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0; 1084 uint32_t FirstSectionLink = 1085 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0; 1086 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0); 1087 1088 for (unsigned i = 0; i < NumSections - 1; ++i) { 1089 const MCSectionELF &Section = *Sections[i]; 1090 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1091 uint32_t GroupSymbolIndex; 1092 if (Section.getType() != ELF::SHT_GROUP) 1093 GroupSymbolIndex = 0; 1094 else 1095 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, 1096 GroupMap.lookup(&Section)); 1097 1098 uint64_t Size = GetSectionAddressSize(Layout, SD); 1099 1100 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex, 1101 SectionOffsetMap.lookup(&Section), Size, 1102 SD.getAlignment(), Section); 1103 } 1104 } 1105 1106 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm, 1107 std::vector<const MCSectionELF*> &Sections) { 1108 for (MCAssembler::iterator it = Asm.begin(), 1109 ie = Asm.end(); it != ie; ++it) { 1110 const MCSectionELF &Section = 1111 static_cast<const MCSectionELF &>(it->getSection()); 1112 if (Section.getType() == ELF::SHT_GROUP) 1113 Sections.push_back(&Section); 1114 } 1115 1116 for (MCAssembler::iterator it = Asm.begin(), 1117 ie = Asm.end(); it != ie; ++it) { 1118 const MCSectionELF &Section = 1119 static_cast<const MCSectionELF &>(it->getSection()); 1120 if (Section.getType() != ELF::SHT_GROUP && 1121 Section.getType() != ELF::SHT_REL && 1122 Section.getType() != ELF::SHT_RELA) 1123 Sections.push_back(&Section); 1124 } 1125 1126 for (MCAssembler::iterator it = Asm.begin(), 1127 ie = Asm.end(); it != ie; ++it) { 1128 const MCSectionELF &Section = 1129 static_cast<const MCSectionELF &>(it->getSection()); 1130 if (Section.getType() == ELF::SHT_REL || 1131 Section.getType() == ELF::SHT_RELA) 1132 Sections.push_back(&Section); 1133 } 1134 } 1135 1136 void ELFObjectWriter::WriteObject(MCAssembler &Asm, 1137 const MCAsmLayout &Layout) { 1138 GroupMapTy GroupMap; 1139 RevGroupMapTy RevGroupMap; 1140 SectionIndexMapTy SectionIndexMap; 1141 1142 unsigned NumUserSections = Asm.size(); 1143 1144 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap; 1145 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1146 1147 const unsigned NumUserAndRelocSections = Asm.size(); 1148 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap, 1149 RevGroupMap, SectionIndexMap, RelMap); 1150 const unsigned AllSections = Asm.size(); 1151 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections; 1152 1153 unsigned NumRegularSections = NumUserSections + NumIndexedSections; 1154 1155 // Compute symbol table information. 1156 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections); 1157 1158 1159 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); 1160 1161 CreateMetadataSections(const_cast<MCAssembler&>(Asm), 1162 const_cast<MCAsmLayout&>(Layout), 1163 SectionIndexMap, 1164 RelMap); 1165 1166 uint64_t NaturalAlignment = is64Bit() ? 8 : 4; 1167 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) : 1168 sizeof(ELF::Elf32_Ehdr); 1169 uint64_t FileOff = HeaderSize; 1170 1171 std::vector<const MCSectionELF*> Sections; 1172 ComputeSectionOrder(Asm, Sections); 1173 unsigned NumSections = Sections.size(); 1174 SectionOffsetMapTy SectionOffsetMap; 1175 for (unsigned i = 0; i < NumRegularSections + 1; ++i) { 1176 const MCSectionELF &Section = *Sections[i]; 1177 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1178 1179 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1180 1181 // Remember the offset into the file for this section. 1182 SectionOffsetMap[&Section] = FileOff; 1183 1184 // Get the size of the section in the output file (including padding). 1185 FileOff += GetSectionFileSize(Layout, SD); 1186 } 1187 1188 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); 1189 1190 const unsigned SectionHeaderOffset = FileOff - HeaderSize; 1191 1192 uint64_t SectionHeaderEntrySize = is64Bit() ? 1193 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr); 1194 FileOff += (NumSections + 1) * SectionHeaderEntrySize; 1195 1196 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) { 1197 const MCSectionELF &Section = *Sections[i]; 1198 const MCSectionData &SD = Asm.getOrCreateSectionData(Section); 1199 1200 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); 1201 1202 // Remember the offset into the file for this section. 1203 SectionOffsetMap[&Section] = FileOff; 1204 1205 // Get the size of the section in the output file (including padding). 1206 FileOff += GetSectionFileSize(Layout, SD); 1207 } 1208 1209 // Write out the ELF header ... 1210 WriteHeader(SectionHeaderOffset, NumSections + 1); 1211 1212 // ... then the regular sections ... 1213 // + because of .shstrtab 1214 for (unsigned i = 0; i < NumRegularSections + 1; ++i) 1215 WriteDataSectionData(Asm, Layout, *Sections[i]); 1216 1217 FileOff = OS.tell(); 1218 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment); 1219 WriteZeros(Padding); 1220 1221 // ... then the section header table ... 1222 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap, 1223 SectionOffsetMap); 1224 1225 FileOff = OS.tell(); 1226 1227 // ... and then the remainting sections ... 1228 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) 1229 WriteDataSectionData(Asm, Layout, *Sections[i]); 1230 } 1231 1232 bool 1233 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 1234 const MCSymbolData &DataA, 1235 const MCFragment &FB, 1236 bool InSet, 1237 bool IsPCRel) const { 1238 if (DataA.getFlags() & ELF_STB_Weak) 1239 return false; 1240 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 1241 Asm, DataA, FB,InSet, IsPCRel); 1242 } 1243 1244 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1245 raw_ostream &OS, 1246 bool IsLittleEndian) { 1247 switch (MOTW->getEMachine()) { 1248 case ELF::EM_386: 1249 case ELF::EM_X86_64: 1250 return new X86ELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1251 case ELF::EM_ARM: 1252 return new ARMELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1253 case ELF::EM_MBLAZE: 1254 return new MBlazeELFObjectWriter(MOTW, OS, IsLittleEndian); break; 1255 default: llvm_unreachable("Unsupported architecture"); break; 1256 } 1257 } 1258 1259 1260 /// START OF SUBCLASSES for ELFObjectWriter 1261 //===- ARMELFObjectWriter -------------------------------------------===// 1262 1263 ARMELFObjectWriter::ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1264 raw_ostream &_OS, 1265 bool IsLittleEndian) 1266 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1267 {} 1268 1269 ARMELFObjectWriter::~ARMELFObjectWriter() 1270 {} 1271 1272 // FIXME: get the real EABI Version from the Triple. 1273 void ARMELFObjectWriter::WriteEFlags() { 1274 Write32(ELF::EF_ARM_EABIMASK & DefaultEABIVersion); 1275 } 1276 1277 // In ARM, _MergedGlobals and other most symbols get emitted directly. 1278 // I.e. not as an offset to a section symbol. 1279 // This code is an approximation of what ARM/gcc does. 1280 1281 STATISTIC(PCRelCount, "Total number of PIC Relocations"); 1282 STATISTIC(NonPCRelCount, "Total number of non-PIC relocations"); 1283 1284 const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm, 1285 const MCValue &Target, 1286 const MCFragment &F, 1287 const MCFixup &Fixup, 1288 bool IsPCRel) const { 1289 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 1290 bool EmitThisSym = false; 1291 1292 const MCSectionELF &Section = 1293 static_cast<const MCSectionELF&>(Symbol.getSection()); 1294 bool InNormalSection = true; 1295 unsigned RelocType = 0; 1296 RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel); 1297 1298 DEBUG( 1299 const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); 1300 MCSymbolRefExpr::VariantKind Kind2; 1301 Kind2 = Target.getSymB() ? Target.getSymB()->getKind() : 1302 MCSymbolRefExpr::VK_None; 1303 dbgs() << "considering symbol " 1304 << Section.getSectionName() << "/" 1305 << Symbol.getName() << "/" 1306 << " Rel:" << (unsigned)RelocType 1307 << " Kind: " << (int)Kind << "/" << (int)Kind2 1308 << " Tmp:" 1309 << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/" 1310 << Symbol.isVariable() << "/" << Symbol.isTemporary() 1311 << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n"); 1312 1313 if (IsPCRel) { ++PCRelCount; 1314 switch (RelocType) { 1315 default: 1316 // Most relocation types are emitted as explicit symbols 1317 InNormalSection = 1318 StringSwitch<bool>(Section.getSectionName()) 1319 .Case(".data.rel.ro.local", false) 1320 .Case(".data.rel", false) 1321 .Case(".bss", false) 1322 .Default(true); 1323 EmitThisSym = true; 1324 break; 1325 case ELF::R_ARM_ABS32: 1326 // But things get strange with R_ARM_ABS32 1327 // In this case, most things that go in .rodata show up 1328 // as section relative relocations 1329 InNormalSection = 1330 StringSwitch<bool>(Section.getSectionName()) 1331 .Case(".data.rel.ro.local", false) 1332 .Case(".data.rel", false) 1333 .Case(".rodata", false) 1334 .Case(".bss", false) 1335 .Default(true); 1336 EmitThisSym = false; 1337 break; 1338 } 1339 } else { 1340 NonPCRelCount++; 1341 InNormalSection = 1342 StringSwitch<bool>(Section.getSectionName()) 1343 .Case(".data.rel.ro.local", false) 1344 .Case(".rodata", false) 1345 .Case(".data.rel", false) 1346 .Case(".bss", false) 1347 .Default(true); 1348 1349 switch (RelocType) { 1350 default: EmitThisSym = true; break; 1351 case ELF::R_ARM_ABS32: EmitThisSym = false; break; 1352 } 1353 } 1354 1355 if (EmitThisSym) 1356 return &Symbol; 1357 if (! Symbol.isTemporary() && InNormalSection) { 1358 return &Symbol; 1359 } 1360 return NULL; 1361 } 1362 1363 // Need to examine the Fixup when determining whether to 1364 // emit the relocation as an explicit symbol or as a section relative 1365 // offset 1366 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target, 1367 const MCFixup &Fixup, 1368 bool IsPCRel, 1369 bool IsRelocWithSymbol, 1370 int64_t Addend) { 1371 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1372 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1373 1374 unsigned Type = GetRelocTypeInner(Target, Fixup, IsPCRel); 1375 1376 if (RelocNeedsGOT(Modifier)) 1377 NeedsGOT = true; 1378 1379 return Type; 1380 } 1381 1382 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target, 1383 const MCFixup &Fixup, 1384 bool IsPCRel) const { 1385 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1386 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1387 1388 unsigned Type = 0; 1389 if (IsPCRel) { 1390 switch ((unsigned)Fixup.getKind()) { 1391 default: assert(0 && "Unimplemented"); 1392 case FK_Data_4: 1393 switch (Modifier) { 1394 default: llvm_unreachable("Unsupported Modifier"); 1395 case MCSymbolRefExpr::VK_None: 1396 Type = ELF::R_ARM_REL32; 1397 break; 1398 case MCSymbolRefExpr::VK_ARM_TLSGD: 1399 assert(0 && "unimplemented"); 1400 break; 1401 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1402 Type = ELF::R_ARM_TLS_IE32; 1403 break; 1404 } 1405 break; 1406 case ARM::fixup_arm_uncondbranch: 1407 switch (Modifier) { 1408 case MCSymbolRefExpr::VK_ARM_PLT: 1409 Type = ELF::R_ARM_PLT32; 1410 break; 1411 default: 1412 Type = ELF::R_ARM_CALL; 1413 break; 1414 } 1415 break; 1416 case ARM::fixup_arm_condbranch: 1417 Type = ELF::R_ARM_JUMP24; 1418 break; 1419 case ARM::fixup_arm_movt_hi16: 1420 case ARM::fixup_arm_movt_hi16_pcrel: 1421 Type = ELF::R_ARM_MOVT_PREL; 1422 break; 1423 case ARM::fixup_arm_movw_lo16: 1424 case ARM::fixup_arm_movw_lo16_pcrel: 1425 Type = ELF::R_ARM_MOVW_PREL_NC; 1426 break; 1427 case ARM::fixup_t2_movt_hi16: 1428 case ARM::fixup_t2_movt_hi16_pcrel: 1429 Type = ELF::R_ARM_THM_MOVT_PREL; 1430 break; 1431 case ARM::fixup_t2_movw_lo16: 1432 case ARM::fixup_t2_movw_lo16_pcrel: 1433 Type = ELF::R_ARM_THM_MOVW_PREL_NC; 1434 break; 1435 case ARM::fixup_arm_thumb_bl: 1436 case ARM::fixup_arm_thumb_blx: 1437 switch (Modifier) { 1438 case MCSymbolRefExpr::VK_ARM_PLT: 1439 Type = ELF::R_ARM_THM_CALL; 1440 break; 1441 default: 1442 Type = ELF::R_ARM_NONE; 1443 break; 1444 } 1445 break; 1446 } 1447 } else { 1448 switch ((unsigned)Fixup.getKind()) { 1449 default: llvm_unreachable("invalid fixup kind!"); 1450 case FK_Data_4: 1451 switch (Modifier) { 1452 default: llvm_unreachable("Unsupported Modifier"); break; 1453 case MCSymbolRefExpr::VK_ARM_GOT: 1454 Type = ELF::R_ARM_GOT_BREL; 1455 break; 1456 case MCSymbolRefExpr::VK_ARM_TLSGD: 1457 Type = ELF::R_ARM_TLS_GD32; 1458 break; 1459 case MCSymbolRefExpr::VK_ARM_TPOFF: 1460 Type = ELF::R_ARM_TLS_LE32; 1461 break; 1462 case MCSymbolRefExpr::VK_ARM_GOTTPOFF: 1463 Type = ELF::R_ARM_TLS_IE32; 1464 break; 1465 case MCSymbolRefExpr::VK_None: 1466 Type = ELF::R_ARM_ABS32; 1467 break; 1468 case MCSymbolRefExpr::VK_ARM_GOTOFF: 1469 Type = ELF::R_ARM_GOTOFF32; 1470 break; 1471 } 1472 break; 1473 case ARM::fixup_arm_ldst_pcrel_12: 1474 case ARM::fixup_arm_pcrel_10: 1475 case ARM::fixup_arm_adr_pcrel_12: 1476 case ARM::fixup_arm_thumb_bl: 1477 case ARM::fixup_arm_thumb_cb: 1478 case ARM::fixup_arm_thumb_cp: 1479 case ARM::fixup_arm_thumb_br: 1480 assert(0 && "Unimplemented"); 1481 break; 1482 case ARM::fixup_arm_uncondbranch: 1483 Type = ELF::R_ARM_CALL; 1484 break; 1485 case ARM::fixup_arm_condbranch: 1486 Type = ELF::R_ARM_JUMP24; 1487 break; 1488 case ARM::fixup_arm_movt_hi16: 1489 Type = ELF::R_ARM_MOVT_ABS; 1490 break; 1491 case ARM::fixup_arm_movw_lo16: 1492 Type = ELF::R_ARM_MOVW_ABS_NC; 1493 break; 1494 case ARM::fixup_t2_movt_hi16: 1495 Type = ELF::R_ARM_THM_MOVT_ABS; 1496 break; 1497 case ARM::fixup_t2_movw_lo16: 1498 Type = ELF::R_ARM_THM_MOVW_ABS_NC; 1499 break; 1500 } 1501 } 1502 1503 return Type; 1504 } 1505 1506 //===- MBlazeELFObjectWriter -------------------------------------------===// 1507 1508 MBlazeELFObjectWriter::MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1509 raw_ostream &_OS, 1510 bool IsLittleEndian) 1511 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) { 1512 } 1513 1514 MBlazeELFObjectWriter::~MBlazeELFObjectWriter() { 1515 } 1516 1517 unsigned MBlazeELFObjectWriter::GetRelocType(const MCValue &Target, 1518 const MCFixup &Fixup, 1519 bool IsPCRel, 1520 bool IsRelocWithSymbol, 1521 int64_t Addend) { 1522 // determine the type of the relocation 1523 unsigned Type; 1524 if (IsPCRel) { 1525 switch ((unsigned)Fixup.getKind()) { 1526 default: 1527 llvm_unreachable("Unimplemented"); 1528 case FK_PCRel_4: 1529 Type = ELF::R_MICROBLAZE_64_PCREL; 1530 break; 1531 case FK_PCRel_2: 1532 Type = ELF::R_MICROBLAZE_32_PCREL; 1533 break; 1534 } 1535 } else { 1536 switch ((unsigned)Fixup.getKind()) { 1537 default: llvm_unreachable("invalid fixup kind!"); 1538 case FK_Data_4: 1539 Type = ((IsRelocWithSymbol || Addend !=0) 1540 ? ELF::R_MICROBLAZE_32 1541 : ELF::R_MICROBLAZE_64); 1542 break; 1543 case FK_Data_2: 1544 Type = ELF::R_MICROBLAZE_32; 1545 break; 1546 } 1547 } 1548 return Type; 1549 } 1550 1551 //===- X86ELFObjectWriter -------------------------------------------===// 1552 1553 1554 X86ELFObjectWriter::X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW, 1555 raw_ostream &_OS, 1556 bool IsLittleEndian) 1557 : ELFObjectWriter(MOTW, _OS, IsLittleEndian) 1558 {} 1559 1560 X86ELFObjectWriter::~X86ELFObjectWriter() 1561 {} 1562 1563 unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target, 1564 const MCFixup &Fixup, 1565 bool IsPCRel, 1566 bool IsRelocWithSymbol, 1567 int64_t Addend) { 1568 // determine the type of the relocation 1569 1570 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ? 1571 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind(); 1572 unsigned Type; 1573 if (is64Bit()) { 1574 if (IsPCRel) { 1575 switch ((unsigned)Fixup.getKind()) { 1576 default: llvm_unreachable("invalid fixup kind!"); 1577 1578 case FK_Data_8: Type = ELF::R_X86_64_PC64; break; 1579 case FK_Data_4: Type = ELF::R_X86_64_PC32; break; 1580 case FK_Data_2: Type = ELF::R_X86_64_PC16; break; 1581 1582 case FK_PCRel_8: 1583 assert(Modifier == MCSymbolRefExpr::VK_None); 1584 Type = ELF::R_X86_64_PC64; 1585 break; 1586 case X86::reloc_signed_4byte: 1587 case X86::reloc_riprel_4byte_movq_load: 1588 case X86::reloc_riprel_4byte: 1589 case FK_PCRel_4: 1590 switch (Modifier) { 1591 default: 1592 llvm_unreachable("Unimplemented"); 1593 case MCSymbolRefExpr::VK_None: 1594 Type = ELF::R_X86_64_PC32; 1595 break; 1596 case MCSymbolRefExpr::VK_PLT: 1597 Type = ELF::R_X86_64_PLT32; 1598 break; 1599 case MCSymbolRefExpr::VK_GOTPCREL: 1600 Type = ELF::R_X86_64_GOTPCREL; 1601 break; 1602 case MCSymbolRefExpr::VK_GOTTPOFF: 1603 Type = ELF::R_X86_64_GOTTPOFF; 1604 break; 1605 case MCSymbolRefExpr::VK_TLSGD: 1606 Type = ELF::R_X86_64_TLSGD; 1607 break; 1608 case MCSymbolRefExpr::VK_TLSLD: 1609 Type = ELF::R_X86_64_TLSLD; 1610 break; 1611 } 1612 break; 1613 case FK_PCRel_2: 1614 assert(Modifier == MCSymbolRefExpr::VK_None); 1615 Type = ELF::R_X86_64_PC16; 1616 break; 1617 case FK_PCRel_1: 1618 assert(Modifier == MCSymbolRefExpr::VK_None); 1619 Type = ELF::R_X86_64_PC8; 1620 break; 1621 } 1622 } else { 1623 switch ((unsigned)Fixup.getKind()) { 1624 default: llvm_unreachable("invalid fixup kind!"); 1625 case FK_Data_8: Type = ELF::R_X86_64_64; break; 1626 case X86::reloc_signed_4byte: 1627 assert(isInt<32>(Target.getConstant())); 1628 switch (Modifier) { 1629 default: 1630 llvm_unreachable("Unimplemented"); 1631 case MCSymbolRefExpr::VK_None: 1632 Type = ELF::R_X86_64_32S; 1633 break; 1634 case MCSymbolRefExpr::VK_GOT: 1635 Type = ELF::R_X86_64_GOT32; 1636 break; 1637 case MCSymbolRefExpr::VK_GOTPCREL: 1638 Type = ELF::R_X86_64_GOTPCREL; 1639 break; 1640 case MCSymbolRefExpr::VK_TPOFF: 1641 Type = ELF::R_X86_64_TPOFF32; 1642 break; 1643 case MCSymbolRefExpr::VK_DTPOFF: 1644 Type = ELF::R_X86_64_DTPOFF32; 1645 break; 1646 } 1647 break; 1648 case FK_Data_4: 1649 Type = ELF::R_X86_64_32; 1650 break; 1651 case FK_Data_2: Type = ELF::R_X86_64_16; break; 1652 case FK_PCRel_1: 1653 case FK_Data_1: Type = ELF::R_X86_64_8; break; 1654 } 1655 } 1656 } else { 1657 if (IsPCRel) { 1658 switch (Modifier) { 1659 default: 1660 llvm_unreachable("Unimplemented"); 1661 case MCSymbolRefExpr::VK_None: 1662 Type = ELF::R_386_PC32; 1663 break; 1664 case MCSymbolRefExpr::VK_PLT: 1665 Type = ELF::R_386_PLT32; 1666 break; 1667 } 1668 } else { 1669 switch ((unsigned)Fixup.getKind()) { 1670 default: llvm_unreachable("invalid fixup kind!"); 1671 1672 case X86::reloc_global_offset_table: 1673 Type = ELF::R_386_GOTPC; 1674 break; 1675 1676 // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode 1677 // instead? 1678 case X86::reloc_signed_4byte: 1679 case FK_PCRel_4: 1680 case FK_Data_4: 1681 switch (Modifier) { 1682 default: 1683 llvm_unreachable("Unimplemented"); 1684 case MCSymbolRefExpr::VK_None: 1685 Type = ELF::R_386_32; 1686 break; 1687 case MCSymbolRefExpr::VK_GOT: 1688 Type = ELF::R_386_GOT32; 1689 break; 1690 case MCSymbolRefExpr::VK_GOTOFF: 1691 Type = ELF::R_386_GOTOFF; 1692 break; 1693 case MCSymbolRefExpr::VK_TLSGD: 1694 Type = ELF::R_386_TLS_GD; 1695 break; 1696 case MCSymbolRefExpr::VK_TPOFF: 1697 Type = ELF::R_386_TLS_LE_32; 1698 break; 1699 case MCSymbolRefExpr::VK_INDNTPOFF: 1700 Type = ELF::R_386_TLS_IE; 1701 break; 1702 case MCSymbolRefExpr::VK_NTPOFF: 1703 Type = ELF::R_386_TLS_LE; 1704 break; 1705 case MCSymbolRefExpr::VK_GOTNTPOFF: 1706 Type = ELF::R_386_TLS_GOTIE; 1707 break; 1708 case MCSymbolRefExpr::VK_TLSLDM: 1709 Type = ELF::R_386_TLS_LDM; 1710 break; 1711 case MCSymbolRefExpr::VK_DTPOFF: 1712 Type = ELF::R_386_TLS_LDO_32; 1713 break; 1714 case MCSymbolRefExpr::VK_GOTTPOFF: 1715 Type = ELF::R_386_TLS_IE_32; 1716 break; 1717 } 1718 break; 1719 case FK_Data_2: Type = ELF::R_386_16; break; 1720 case FK_PCRel_1: 1721 case FK_Data_1: Type = ELF::R_386_8; break; 1722 } 1723 } 1724 } 1725 1726 if (RelocNeedsGOT(Modifier)) 1727 NeedsGOT = true; 1728 1729 return Type; 1730 } 1731
