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ELFObjectWriter.cpp
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1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements ELF object file writer information.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/ArrayRef.h"
15 #include "llvm/ADT/DenseMap.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/Twine.h"
21 #include "llvm/BinaryFormat/ELF.h"
22 #include "llvm/MC/MCAsmBackend.h"
23 #include "llvm/MC/MCAsmInfo.h"
24 #include "llvm/MC/MCAsmLayout.h"
25 #include "llvm/MC/MCAssembler.h"
26 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCFixup.h"
31 #include "llvm/MC/MCFragment.h"
33 #include "llvm/MC/MCObjectWriter.h"
34 #include "llvm/MC/MCSection.h"
35 #include "llvm/MC/MCSectionELF.h"
36 #include "llvm/MC/MCSymbol.h"
37 #include "llvm/MC/MCSymbolELF.h"
38 #include "llvm/MC/MCValue.h"
40 #include "llvm/Support/Allocator.h"
41 #include "llvm/Support/Casting.h"
43 #include "llvm/Support/Endian.h"
44 #include "llvm/Support/Error.h"
46 #include "llvm/Support/Host.h"
47 #include "llvm/Support/LEB128.h"
49 #include "llvm/Support/SMLoc.h"
53 #include <algorithm>
54 #include <cassert>
55 #include <cstddef>
56 #include <cstdint>
57 #include <map>
58 #include <memory>
59 #include <string>
60 #include <utility>
61 #include <vector>
62 
63 using namespace llvm;
64 
65 #undef DEBUG_TYPE
66 #define DEBUG_TYPE "reloc-info"
67 
68 namespace {
69 
70 using SectionIndexMapTy = DenseMap<const MCSectionELF *, uint32_t>;
71 
72 class ELFObjectWriter;
73 struct ELFWriter;
74 
75 bool isDwoSection(const MCSectionELF &Sec) {
76  return Sec.getSectionName().endswith(".dwo");
77 }
78 
79 class SymbolTableWriter {
80  ELFWriter &EWriter;
81  bool Is64Bit;
82 
83  // indexes we are going to write to .symtab_shndx.
84  std::vector<uint32_t> ShndxIndexes;
85 
86  // The numbel of symbols written so far.
87  unsigned NumWritten;
88 
89  void createSymtabShndx();
90 
91  template <typename T> void write(T Value);
92 
93 public:
94  SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit);
95 
96  void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
97  uint8_t other, uint32_t shndx, bool Reserved);
98 
99  ArrayRef<uint32_t> getShndxIndexes() const { return ShndxIndexes; }
100 };
101 
102 struct ELFWriter {
103  ELFObjectWriter &OWriter;
105 
106  enum DwoMode {
107  AllSections,
108  NonDwoOnly,
109  DwoOnly,
110  } Mode;
111 
112  static uint64_t SymbolValue(const MCSymbol &Sym, const MCAsmLayout &Layout);
113  static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
114  bool Used, bool Renamed);
115 
116  /// Helper struct for containing some precomputed information on symbols.
117  struct ELFSymbolData {
118  const MCSymbolELF *Symbol;
119  uint32_t SectionIndex;
120  StringRef Name;
121 
122  // Support lexicographic sorting.
123  bool operator<(const ELFSymbolData &RHS) const {
124  unsigned LHSType = Symbol->getType();
125  unsigned RHSType = RHS.Symbol->getType();
126  if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
127  return false;
128  if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
129  return true;
130  if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
131  return SectionIndex < RHS.SectionIndex;
132  return Name < RHS.Name;
133  }
134  };
135 
136  /// @}
137  /// @name Symbol Table Data
138  /// @{
139 
141 
142  /// @}
143 
144  // This holds the symbol table index of the last local symbol.
145  unsigned LastLocalSymbolIndex;
146  // This holds the .strtab section index.
147  unsigned StringTableIndex;
148  // This holds the .symtab section index.
149  unsigned SymbolTableIndex;
150 
151  // Sections in the order they are to be output in the section table.
152  std::vector<const MCSectionELF *> SectionTable;
153  unsigned addToSectionTable(const MCSectionELF *Sec);
154 
155  // TargetObjectWriter wrappers.
156  bool is64Bit() const;
157  bool hasRelocationAddend() const;
158 
159  void align(unsigned Alignment);
160 
161  bool maybeWriteCompression(uint64_t Size,
162  SmallVectorImpl<char> &CompressedContents,
163  bool ZLibStyle, unsigned Alignment);
164 
165 public:
166  ELFWriter(ELFObjectWriter &OWriter, raw_pwrite_stream &OS,
167  bool IsLittleEndian, DwoMode Mode)
168  : OWriter(OWriter),
169  W(OS, IsLittleEndian ? support::little : support::big), Mode(Mode) {}
170 
171  void WriteWord(uint64_t Word) {
172  if (is64Bit())
173  W.write<uint64_t>(Word);
174  else
175  W.write<uint32_t>(Word);
176  }
177 
178  template <typename T> void write(T Val) {
179  W.write(Val);
180  }
181 
182  void writeHeader(const MCAssembler &Asm);
183 
184  void writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
185  ELFSymbolData &MSD, const MCAsmLayout &Layout);
186 
187  // Start and end offset of each section
188  using SectionOffsetsTy =
189  std::map<const MCSectionELF *, std::pair<uint64_t, uint64_t>>;
190 
191  // Map from a signature symbol to the group section index
192  using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
193 
194  /// Compute the symbol table data
195  ///
196  /// \param Asm - The assembler.
197  /// \param SectionIndexMap - Maps a section to its index.
198  /// \param RevGroupMap - Maps a signature symbol to the group section.
199  void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
200  const SectionIndexMapTy &SectionIndexMap,
201  const RevGroupMapTy &RevGroupMap,
202  SectionOffsetsTy &SectionOffsets);
203 
204  void writeAddrsigSection();
205 
206  MCSectionELF *createRelocationSection(MCContext &Ctx,
207  const MCSectionELF &Sec);
208 
209  const MCSectionELF *createStringTable(MCContext &Ctx);
210 
211  void writeSectionHeader(const MCAsmLayout &Layout,
212  const SectionIndexMapTy &SectionIndexMap,
213  const SectionOffsetsTy &SectionOffsets);
214 
215  void writeSectionData(const MCAssembler &Asm, MCSection &Sec,
216  const MCAsmLayout &Layout);
217 
218  void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
219  uint64_t Address, uint64_t Offset, uint64_t Size,
220  uint32_t Link, uint32_t Info, uint64_t Alignment,
221  uint64_t EntrySize);
222 
223  void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
224 
225  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout);
226  void writeSection(const SectionIndexMapTy &SectionIndexMap,
227  uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
228  const MCSectionELF &Section);
229 };
230 
231 class ELFObjectWriter : public MCObjectWriter {
232  /// The target specific ELF writer instance.
233  std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
234 
236 
238 
239  bool EmitAddrsigSection = false;
240  std::vector<const MCSymbol *> AddrsigSyms;
241 
242  bool hasRelocationAddend() const;
243 
244  bool shouldRelocateWithSymbol(const MCAssembler &Asm,
245  const MCSymbolRefExpr *RefA,
246  const MCSymbolELF *Sym, uint64_t C,
247  unsigned Type) const;
248 
249 public:
250  ELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW)
251  : TargetObjectWriter(std::move(MOTW)) {}
252 
253  void reset() override {
254  Relocations.clear();
255  Renames.clear();
257  }
258 
259  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
260  const MCSymbol &SymA,
261  const MCFragment &FB, bool InSet,
262  bool IsPCRel) const override;
263 
264  virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
265  const MCSectionELF *From,
266  const MCSectionELF *To) {
267  return true;
268  }
269 
270  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
271  const MCFragment *Fragment, const MCFixup &Fixup,
272  MCValue Target, uint64_t &FixedValue) override;
273 
274  void executePostLayoutBinding(MCAssembler &Asm,
275  const MCAsmLayout &Layout) override;
276 
277  void emitAddrsigSection() override { EmitAddrsigSection = true; }
278  void addAddrsigSymbol(const MCSymbol *Sym) override {
279  AddrsigSyms.push_back(Sym);
280  }
281 
282  friend struct ELFWriter;
283 };
284 
285 class ELFSingleObjectWriter : public ELFObjectWriter {
286  raw_pwrite_stream &OS;
287  bool IsLittleEndian;
288 
289 public:
290  ELFSingleObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
291  raw_pwrite_stream &OS, bool IsLittleEndian)
292  : ELFObjectWriter(std::move(MOTW)), OS(OS),
293  IsLittleEndian(IsLittleEndian) {}
294 
295  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
296  return ELFWriter(*this, OS, IsLittleEndian, ELFWriter::AllSections)
297  .writeObject(Asm, Layout);
298  }
299 
300  friend struct ELFWriter;
301 };
302 
303 class ELFDwoObjectWriter : public ELFObjectWriter {
304  raw_pwrite_stream &OS, &DwoOS;
305  bool IsLittleEndian;
306 
307 public:
308  ELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
310  bool IsLittleEndian)
311  : ELFObjectWriter(std::move(MOTW)), OS(OS), DwoOS(DwoOS),
312  IsLittleEndian(IsLittleEndian) {}
313 
314  virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
315  const MCSectionELF *From,
316  const MCSectionELF *To) override {
317  if (isDwoSection(*From)) {
318  Ctx.reportError(Loc, "A dwo section may not contain relocations");
319  return false;
320  }
321  if (To && isDwoSection(*To)) {
322  Ctx.reportError(Loc, "A relocation may not refer to a dwo section");
323  return false;
324  }
325  return true;
326  }
327 
328  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
329  uint64_t Size = ELFWriter(*this, OS, IsLittleEndian, ELFWriter::NonDwoOnly)
330  .writeObject(Asm, Layout);
331  Size += ELFWriter(*this, DwoOS, IsLittleEndian, ELFWriter::DwoOnly)
332  .writeObject(Asm, Layout);
333  return Size;
334  }
335 };
336 
337 } // end anonymous namespace
338 
339 void ELFWriter::align(unsigned Alignment) {
340  uint64_t Padding = OffsetToAlignment(W.OS.tell(), Alignment);
341  W.OS.write_zeros(Padding);
342 }
343 
344 unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) {
345  SectionTable.push_back(Sec);
346  StrTabBuilder.add(Sec->getSectionName());
347  return SectionTable.size();
348 }
349 
350 void SymbolTableWriter::createSymtabShndx() {
351  if (!ShndxIndexes.empty())
352  return;
353 
354  ShndxIndexes.resize(NumWritten);
355 }
356 
357 template <typename T> void SymbolTableWriter::write(T Value) {
358  EWriter.write(Value);
359 }
360 
361 SymbolTableWriter::SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit)
362  : EWriter(EWriter), Is64Bit(Is64Bit), NumWritten(0) {}
363 
364 void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
365  uint64_t size, uint8_t other,
366  uint32_t shndx, bool Reserved) {
367  bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
368 
369  if (LargeIndex)
370  createSymtabShndx();
371 
372  if (!ShndxIndexes.empty()) {
373  if (LargeIndex)
374  ShndxIndexes.push_back(shndx);
375  else
376  ShndxIndexes.push_back(0);
377  }
378 
379  uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
380 
381  if (Is64Bit) {
382  write(name); // st_name
383  write(info); // st_info
384  write(other); // st_other
385  write(Index); // st_shndx
386  write(value); // st_value
387  write(size); // st_size
388  } else {
389  write(name); // st_name
390  write(uint32_t(value)); // st_value
391  write(uint32_t(size)); // st_size
392  write(info); // st_info
393  write(other); // st_other
394  write(Index); // st_shndx
395  }
396 
397  ++NumWritten;
398 }
399 
400 bool ELFWriter::is64Bit() const {
401  return OWriter.TargetObjectWriter->is64Bit();
402 }
403 
404 bool ELFWriter::hasRelocationAddend() const {
405  return OWriter.hasRelocationAddend();
406 }
407 
408 // Emit the ELF header.
409 void ELFWriter::writeHeader(const MCAssembler &Asm) {
410  // ELF Header
411  // ----------
412  //
413  // Note
414  // ----
415  // emitWord method behaves differently for ELF32 and ELF64, writing
416  // 4 bytes in the former and 8 in the latter.
417 
418  W.OS << ELF::ElfMagic; // e_ident[EI_MAG0] to e_ident[EI_MAG3]
419 
420  W.OS << char(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
421 
422  // e_ident[EI_DATA]
423  W.OS << char(W.Endian == support::little ? ELF::ELFDATA2LSB
424  : ELF::ELFDATA2MSB);
425 
426  W.OS << char(ELF::EV_CURRENT); // e_ident[EI_VERSION]
427  // e_ident[EI_OSABI]
428  W.OS << char(OWriter.TargetObjectWriter->getOSABI());
429  W.OS << char(0); // e_ident[EI_ABIVERSION]
430 
431  W.OS.write_zeros(ELF::EI_NIDENT - ELF::EI_PAD);
432 
433  W.write<uint16_t>(ELF::ET_REL); // e_type
434 
435  W.write<uint16_t>(OWriter.TargetObjectWriter->getEMachine()); // e_machine = target
436 
437  W.write<uint32_t>(ELF::EV_CURRENT); // e_version
438  WriteWord(0); // e_entry, no entry point in .o file
439  WriteWord(0); // e_phoff, no program header for .o
440  WriteWord(0); // e_shoff = sec hdr table off in bytes
441 
442  // e_flags = whatever the target wants
443  W.write<uint32_t>(Asm.getELFHeaderEFlags());
444 
445  // e_ehsize = ELF header size
446  W.write<uint16_t>(is64Bit() ? sizeof(ELF::Elf64_Ehdr)
447  : sizeof(ELF::Elf32_Ehdr));
448 
449  W.write<uint16_t>(0); // e_phentsize = prog header entry size
450  W.write<uint16_t>(0); // e_phnum = # prog header entries = 0
451 
452  // e_shentsize = Section header entry size
453  W.write<uint16_t>(is64Bit() ? sizeof(ELF::Elf64_Shdr)
454  : sizeof(ELF::Elf32_Shdr));
455 
456  // e_shnum = # of section header ents
457  W.write<uint16_t>(0);
458 
459  // e_shstrndx = Section # of '.shstrtab'
460  assert(StringTableIndex < ELF::SHN_LORESERVE);
461  W.write<uint16_t>(StringTableIndex);
462 }
463 
464 uint64_t ELFWriter::SymbolValue(const MCSymbol &Sym,
465  const MCAsmLayout &Layout) {
466  if (Sym.isCommon() && Sym.isExternal())
467  return Sym.getCommonAlignment();
468 
469  uint64_t Res;
470  if (!Layout.getSymbolOffset(Sym, Res))
471  return 0;
472 
473  if (Layout.getAssembler().isThumbFunc(&Sym))
474  Res |= 1;
475 
476  return Res;
477 }
478 
479 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
480  uint8_t Type = newType;
481 
482  // Propagation rules:
483  // IFUNC > FUNC > OBJECT > NOTYPE
484  // TLS_OBJECT > OBJECT > NOTYPE
485  //
486  // dont let the new type degrade the old type
487  switch (origType) {
488  default:
489  break;
490  case ELF::STT_GNU_IFUNC:
491  if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
492  Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
493  Type = ELF::STT_GNU_IFUNC;
494  break;
495  case ELF::STT_FUNC:
496  if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
497  Type == ELF::STT_TLS)
498  Type = ELF::STT_FUNC;
499  break;
500  case ELF::STT_OBJECT:
501  if (Type == ELF::STT_NOTYPE)
502  Type = ELF::STT_OBJECT;
503  break;
504  case ELF::STT_TLS:
505  if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
506  Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
507  Type = ELF::STT_TLS;
508  break;
509  }
510 
511  return Type;
512 }
513 
514 void ELFWriter::writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
515  ELFSymbolData &MSD, const MCAsmLayout &Layout) {
516  const auto &Symbol = cast<MCSymbolELF>(*MSD.Symbol);
517  const MCSymbolELF *Base =
518  cast_or_null<MCSymbolELF>(Layout.getBaseSymbol(Symbol));
519 
520  // This has to be in sync with when computeSymbolTable uses SHN_ABS or
521  // SHN_COMMON.
522  bool IsReserved = !Base || Symbol.isCommon();
523 
524  // Binding and Type share the same byte as upper and lower nibbles
525  uint8_t Binding = Symbol.getBinding();
526  uint8_t Type = Symbol.getType();
527  if (Base) {
528  Type = mergeTypeForSet(Type, Base->getType());
529  }
530  uint8_t Info = (Binding << 4) | Type;
531 
532  // Other and Visibility share the same byte with Visibility using the lower
533  // 2 bits
534  uint8_t Visibility = Symbol.getVisibility();
535  uint8_t Other = Symbol.getOther() | Visibility;
536 
537  uint64_t Value = SymbolValue(*MSD.Symbol, Layout);
538  uint64_t Size = 0;
539 
540  const MCExpr *ESize = MSD.Symbol->getSize();
541  if (!ESize && Base)
542  ESize = Base->getSize();
543 
544  if (ESize) {
545  int64_t Res;
546  if (!ESize->evaluateKnownAbsolute(Res, Layout))
547  report_fatal_error("Size expression must be absolute.");
548  Size = Res;
549  }
550 
551  // Write out the symbol table entry
552  Writer.writeSymbol(StringIndex, Info, Value, Size, Other, MSD.SectionIndex,
553  IsReserved);
554 }
555 
556 // True if the assembler knows nothing about the final value of the symbol.
557 // This doesn't cover the comdat issues, since in those cases the assembler
558 // can at least know that all symbols in the section will move together.
559 static bool isWeak(const MCSymbolELF &Sym) {
560  if (Sym.getType() == ELF::STT_GNU_IFUNC)
561  return true;
562 
563  switch (Sym.getBinding()) {
564  default:
565  llvm_unreachable("Unknown binding");
566  case ELF::STB_LOCAL:
567  return false;
568  case ELF::STB_GLOBAL:
569  return false;
570  case ELF::STB_WEAK:
571  case ELF::STB_GNU_UNIQUE:
572  return true;
573  }
574 }
575 
576 bool ELFWriter::isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
577  bool Used, bool Renamed) {
578  if (Symbol.isVariable()) {
579  const MCExpr *Expr = Symbol.getVariableValue();
580  if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
581  if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
582  return false;
583  }
584  }
585 
586  if (Used)
587  return true;
588 
589  if (Renamed)
590  return false;
591 
592  if (Symbol.isVariable() && Symbol.isUndefined()) {
593  // FIXME: this is here just to diagnose the case of a var = commmon_sym.
594  Layout.getBaseSymbol(Symbol);
595  return false;
596  }
597 
598  if (Symbol.isUndefined() && !Symbol.isBindingSet())
599  return false;
600 
601  if (Symbol.isTemporary())
602  return false;
603 
604  if (Symbol.getType() == ELF::STT_SECTION)
605  return false;
606 
607  return true;
608 }
609 
610 void ELFWriter::computeSymbolTable(
611  MCAssembler &Asm, const MCAsmLayout &Layout,
612  const SectionIndexMapTy &SectionIndexMap, const RevGroupMapTy &RevGroupMap,
613  SectionOffsetsTy &SectionOffsets) {
614  MCContext &Ctx = Asm.getContext();
615  SymbolTableWriter Writer(*this, is64Bit());
616 
617  // Symbol table
618  unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
619  MCSectionELF *SymtabSection =
620  Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
621  SymtabSection->setAlignment(is64Bit() ? 8 : 4);
622  SymbolTableIndex = addToSectionTable(SymtabSection);
623 
624  align(SymtabSection->getAlignment());
625  uint64_t SecStart = W.OS.tell();
626 
627  // The first entry is the undefined symbol entry.
628  Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
629 
630  std::vector<ELFSymbolData> LocalSymbolData;
631  std::vector<ELFSymbolData> ExternalSymbolData;
632 
633  // Add the data for the symbols.
634  bool HasLargeSectionIndex = false;
635  for (const MCSymbol &S : Asm.symbols()) {
636  const auto &Symbol = cast<MCSymbolELF>(S);
637  bool Used = Symbol.isUsedInReloc();
638  bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
639  bool isSignature = Symbol.isSignature();
640 
641  if (!isInSymtab(Layout, Symbol, Used || WeakrefUsed || isSignature,
642  OWriter.Renames.count(&Symbol)))
643  continue;
644 
645  if (Symbol.isTemporary() && Symbol.isUndefined()) {
646  Ctx.reportError(SMLoc(), "Undefined temporary symbol");
647  continue;
648  }
649 
650  ELFSymbolData MSD;
651  MSD.Symbol = cast<MCSymbolELF>(&Symbol);
652 
653  bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
654  assert(Local || !Symbol.isTemporary());
655 
656  if (Symbol.isAbsolute()) {
657  MSD.SectionIndex = ELF::SHN_ABS;
658  } else if (Symbol.isCommon()) {
659  assert(!Local);
660  MSD.SectionIndex = ELF::SHN_COMMON;
661  } else if (Symbol.isUndefined()) {
662  if (isSignature && !Used) {
663  MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
664  if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
665  HasLargeSectionIndex = true;
666  } else {
667  MSD.SectionIndex = ELF::SHN_UNDEF;
668  }
669  } else {
670  const MCSectionELF &Section =
671  static_cast<const MCSectionELF &>(Symbol.getSection());
672 
673  // We may end up with a situation when section symbol is technically
674  // defined, but should not be. That happens because we explicitly
675  // pre-create few .debug_* sections to have accessors.
676  // And if these sections were not really defined in the code, but were
677  // referenced, we simply error out.
678  if (!Section.isRegistered()) {
679  assert(static_cast<const MCSymbolELF &>(Symbol).getType() ==
681  Ctx.reportError(SMLoc(),
682  "Undefined section reference: " + Symbol.getName());
683  continue;
684  }
685 
686  if (Mode == NonDwoOnly && isDwoSection(Section))
687  continue;
688  MSD.SectionIndex = SectionIndexMap.lookup(&Section);
689  assert(MSD.SectionIndex && "Invalid section index!");
690  if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
691  HasLargeSectionIndex = true;
692  }
693 
694  StringRef Name = Symbol.getName();
695 
696  // Sections have their own string table
697  if (Symbol.getType() != ELF::STT_SECTION) {
698  MSD.Name = Name;
699  StrTabBuilder.add(Name);
700  }
701 
702  if (Local)
703  LocalSymbolData.push_back(MSD);
704  else
705  ExternalSymbolData.push_back(MSD);
706  }
707 
708  // This holds the .symtab_shndx section index.
709  unsigned SymtabShndxSectionIndex = 0;
710 
711  if (HasLargeSectionIndex) {
712  MCSectionELF *SymtabShndxSection =
713  Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
714  SymtabShndxSectionIndex = addToSectionTable(SymtabShndxSection);
715  SymtabShndxSection->setAlignment(4);
716  }
717 
718  ArrayRef<std::string> FileNames = Asm.getFileNames();
719  for (const std::string &Name : FileNames)
720  StrTabBuilder.add(Name);
721 
722  StrTabBuilder.finalize();
723 
724  // File symbols are emitted first and handled separately from normal symbols,
725  // i.e. a non-STT_FILE symbol with the same name may appear.
726  for (const std::string &Name : FileNames)
727  Writer.writeSymbol(StrTabBuilder.getOffset(Name),
729  ELF::SHN_ABS, true);
730 
731  // Symbols are required to be in lexicographic order.
732  array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
733  array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
734 
735  // Set the symbol indices. Local symbols must come before all other
736  // symbols with non-local bindings.
737  unsigned Index = FileNames.size() + 1;
738 
739  for (ELFSymbolData &MSD : LocalSymbolData) {
740  unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
741  ? 0
742  : StrTabBuilder.getOffset(MSD.Name);
743  MSD.Symbol->setIndex(Index++);
744  writeSymbol(Writer, StringIndex, MSD, Layout);
745  }
746 
747  // Write the symbol table entries.
748  LastLocalSymbolIndex = Index;
749 
750  for (ELFSymbolData &MSD : ExternalSymbolData) {
751  unsigned StringIndex = StrTabBuilder.getOffset(MSD.Name);
752  MSD.Symbol->setIndex(Index++);
753  writeSymbol(Writer, StringIndex, MSD, Layout);
754  assert(MSD.Symbol->getBinding() != ELF::STB_LOCAL);
755  }
756 
757  uint64_t SecEnd = W.OS.tell();
758  SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
759 
760  ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
761  if (ShndxIndexes.empty()) {
762  assert(SymtabShndxSectionIndex == 0);
763  return;
764  }
765  assert(SymtabShndxSectionIndex != 0);
766 
767  SecStart = W.OS.tell();
768  const MCSectionELF *SymtabShndxSection =
769  SectionTable[SymtabShndxSectionIndex - 1];
770  for (uint32_t Index : ShndxIndexes)
771  write(Index);
772  SecEnd = W.OS.tell();
773  SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
774 }
775 
776 void ELFWriter::writeAddrsigSection() {
777  for (const MCSymbol *Sym : OWriter.AddrsigSyms)
778  encodeULEB128(Sym->getIndex(), W.OS);
779 }
780 
781 MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
782  const MCSectionELF &Sec) {
783  if (OWriter.Relocations[&Sec].empty())
784  return nullptr;
785 
786  const StringRef SectionName = Sec.getSectionName();
787  std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
788  RelaSectionName += SectionName;
789 
790  unsigned EntrySize;
791  if (hasRelocationAddend())
792  EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
793  else
794  EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
795 
796  unsigned Flags = 0;
797  if (Sec.getFlags() & ELF::SHF_GROUP)
798  Flags = ELF::SHF_GROUP;
799 
800  MCSectionELF *RelaSection = Ctx.createELFRelSection(
801  RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
802  Flags, EntrySize, Sec.getGroup(), &Sec);
803  RelaSection->setAlignment(is64Bit() ? 8 : 4);
804  return RelaSection;
805 }
806 
807 // Include the debug info compression header.
808 bool ELFWriter::maybeWriteCompression(
809  uint64_t Size, SmallVectorImpl<char> &CompressedContents, bool ZLibStyle,
810  unsigned Alignment) {
811  if (ZLibStyle) {
812  uint64_t HdrSize =
813  is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
814  if (Size <= HdrSize + CompressedContents.size())
815  return false;
816  // Platform specific header is followed by compressed data.
817  if (is64Bit()) {
818  // Write Elf64_Chdr header.
819  write(static_cast<ELF::Elf64_Word>(ELF::ELFCOMPRESS_ZLIB));
820  write(static_cast<ELF::Elf64_Word>(0)); // ch_reserved field.
821  write(static_cast<ELF::Elf64_Xword>(Size));
822  write(static_cast<ELF::Elf64_Xword>(Alignment));
823  } else {
824  // Write Elf32_Chdr header otherwise.
825  write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
826  write(static_cast<ELF::Elf32_Word>(Size));
827  write(static_cast<ELF::Elf32_Word>(Alignment));
828  }
829  return true;
830  }
831 
832  // "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
833  // useful for consumers to preallocate a buffer to decompress into.
834  const StringRef Magic = "ZLIB";
835  if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
836  return false;
837  W.OS << Magic;
839  return true;
840 }
841 
842 void ELFWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
843  const MCAsmLayout &Layout) {
844  MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
846 
847  auto &MC = Asm.getContext();
848  const auto &MAI = MC.getAsmInfo();
849 
850  // Compressing debug_frame requires handling alignment fragments which is
851  // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
852  // for writing to arbitrary buffers) for little benefit.
853  bool CompressionEnabled =
855  if (!CompressionEnabled || !SectionName.startswith(".debug_") ||
856  SectionName == ".debug_frame") {
857  Asm.writeSectionData(W.OS, &Section, Layout);
858  return;
859  }
860 
861  assert((MAI->compressDebugSections() == DebugCompressionType::Z ||
862  MAI->compressDebugSections() == DebugCompressionType::GNU) &&
863  "expected zlib or zlib-gnu style compression");
864 
865  SmallVector<char, 128> UncompressedData;
866  raw_svector_ostream VecOS(UncompressedData);
867  Asm.writeSectionData(VecOS, &Section, Layout);
868 
869  SmallVector<char, 128> CompressedContents;
870  if (Error E = zlib::compress(
871  StringRef(UncompressedData.data(), UncompressedData.size()),
872  CompressedContents)) {
873  consumeError(std::move(E));
874  W.OS << UncompressedData;
875  return;
876  }
877 
878  bool ZlibStyle = MAI->compressDebugSections() == DebugCompressionType::Z;
879  if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
880  ZlibStyle, Sec.getAlignment())) {
881  W.OS << UncompressedData;
882  return;
883  }
884 
885  if (ZlibStyle)
886  // Set the compressed flag. That is zlib style.
887  Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
888  else
889  // Add "z" prefix to section name. This is zlib-gnu style.
890  MC.renameELFSection(&Section, (".z" + SectionName.drop_front(1)).str());
891  W.OS << CompressedContents;
892 }
893 
894 void ELFWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
895  uint64_t Address, uint64_t Offset,
896  uint64_t Size, uint32_t Link, uint32_t Info,
897  uint64_t Alignment, uint64_t EntrySize) {
898  W.write<uint32_t>(Name); // sh_name: index into string table
899  W.write<uint32_t>(Type); // sh_type
900  WriteWord(Flags); // sh_flags
901  WriteWord(Address); // sh_addr
902  WriteWord(Offset); // sh_offset
903  WriteWord(Size); // sh_size
904  W.write<uint32_t>(Link); // sh_link
905  W.write<uint32_t>(Info); // sh_info
906  WriteWord(Alignment); // sh_addralign
907  WriteWord(EntrySize); // sh_entsize
908 }
909 
910 void ELFWriter::writeRelocations(const MCAssembler &Asm,
911  const MCSectionELF &Sec) {
912  std::vector<ELFRelocationEntry> &Relocs = OWriter.Relocations[&Sec];
913 
914  // We record relocations by pushing to the end of a vector. Reverse the vector
915  // to get the relocations in the order they were created.
916  // In most cases that is not important, but it can be for special sections
917  // (.eh_frame) or specific relocations (TLS optimizations on SystemZ).
918  std::reverse(Relocs.begin(), Relocs.end());
919 
920  // Sort the relocation entries. MIPS needs this.
921  OWriter.TargetObjectWriter->sortRelocs(Asm, Relocs);
922 
923  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
924  const ELFRelocationEntry &Entry = Relocs[e - i - 1];
925  unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
926 
927  if (is64Bit()) {
928  write(Entry.Offset);
929  if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
930  write(uint32_t(Index));
931 
932  write(OWriter.TargetObjectWriter->getRSsym(Entry.Type));
933  write(OWriter.TargetObjectWriter->getRType3(Entry.Type));
934  write(OWriter.TargetObjectWriter->getRType2(Entry.Type));
935  write(OWriter.TargetObjectWriter->getRType(Entry.Type));
936  } else {
937  struct ELF::Elf64_Rela ERE64;
938  ERE64.setSymbolAndType(Index, Entry.Type);
939  write(ERE64.r_info);
940  }
941  if (hasRelocationAddend())
942  write(Entry.Addend);
943  } else {
944  write(uint32_t(Entry.Offset));
945 
946  struct ELF::Elf32_Rela ERE32;
947  ERE32.setSymbolAndType(Index, Entry.Type);
948  write(ERE32.r_info);
949 
950  if (hasRelocationAddend())
951  write(uint32_t(Entry.Addend));
952 
953  if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
954  if (uint32_t RType =
955  OWriter.TargetObjectWriter->getRType2(Entry.Type)) {
956  write(uint32_t(Entry.Offset));
957 
958  ERE32.setSymbolAndType(0, RType);
959  write(ERE32.r_info);
960  write(uint32_t(0));
961  }
962  if (uint32_t RType =
963  OWriter.TargetObjectWriter->getRType3(Entry.Type)) {
964  write(uint32_t(Entry.Offset));
965 
966  ERE32.setSymbolAndType(0, RType);
967  write(ERE32.r_info);
968  write(uint32_t(0));
969  }
970  }
971  }
972  }
973 }
974 
975 const MCSectionELF *ELFWriter::createStringTable(MCContext &Ctx) {
976  const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
977  StrTabBuilder.write(W.OS);
978  return StrtabSection;
979 }
980 
981 void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
982  uint32_t GroupSymbolIndex, uint64_t Offset,
983  uint64_t Size, const MCSectionELF &Section) {
984  uint64_t sh_link = 0;
985  uint64_t sh_info = 0;
986 
987  switch(Section.getType()) {
988  default:
989  // Nothing to do.
990  break;
991 
992  case ELF::SHT_DYNAMIC:
993  llvm_unreachable("SHT_DYNAMIC in a relocatable object");
994 
995  case ELF::SHT_REL:
996  case ELF::SHT_RELA: {
997  sh_link = SymbolTableIndex;
998  assert(sh_link && ".symtab not found");
999  const MCSection *InfoSection = Section.getAssociatedSection();
1000  sh_info = SectionIndexMap.lookup(cast<MCSectionELF>(InfoSection));
1001  break;
1002  }
1003 
1004  case ELF::SHT_SYMTAB:
1005  sh_link = StringTableIndex;
1006  sh_info = LastLocalSymbolIndex;
1007  break;
1008 
1009  case ELF::SHT_SYMTAB_SHNDX:
1011  case ELF::SHT_LLVM_ADDRSIG:
1012  sh_link = SymbolTableIndex;
1013  break;
1014 
1015  case ELF::SHT_GROUP:
1016  sh_link = SymbolTableIndex;
1017  sh_info = GroupSymbolIndex;
1018  break;
1019  }
1020 
1021  if (Section.getFlags() & ELF::SHF_LINK_ORDER) {
1022  const MCSymbol *Sym = Section.getAssociatedSymbol();
1023  const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
1024  sh_link = SectionIndexMap.lookup(Sec);
1025  }
1026 
1027  WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
1028  Section.getType(), Section.getFlags(), 0, Offset, Size,
1029  sh_link, sh_info, Section.getAlignment(),
1030  Section.getEntrySize());
1031 }
1032 
1033 void ELFWriter::writeSectionHeader(
1034  const MCAsmLayout &Layout, const SectionIndexMapTy &SectionIndexMap,
1035  const SectionOffsetsTy &SectionOffsets) {
1036  const unsigned NumSections = SectionTable.size();
1037 
1038  // Null section first.
1039  uint64_t FirstSectionSize =
1040  (NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
1041  WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
1042 
1043  for (const MCSectionELF *Section : SectionTable) {
1044  uint32_t GroupSymbolIndex;
1045  unsigned Type = Section->getType();
1046  if (Type != ELF::SHT_GROUP)
1047  GroupSymbolIndex = 0;
1048  else
1049  GroupSymbolIndex = Section->getGroup()->getIndex();
1050 
1051  const std::pair<uint64_t, uint64_t> &Offsets =
1052  SectionOffsets.find(Section)->second;
1053  uint64_t Size;
1054  if (Type == ELF::SHT_NOBITS)
1055  Size = Layout.getSectionAddressSize(Section);
1056  else
1057  Size = Offsets.second - Offsets.first;
1058 
1059  writeSection(SectionIndexMap, GroupSymbolIndex, Offsets.first, Size,
1060  *Section);
1061  }
1062 }
1063 
1064 uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
1065  uint64_t StartOffset = W.OS.tell();
1066 
1067  MCContext &Ctx = Asm.getContext();
1068  MCSectionELF *StrtabSection =
1069  Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
1070  StringTableIndex = addToSectionTable(StrtabSection);
1071 
1072  RevGroupMapTy RevGroupMap;
1073  SectionIndexMapTy SectionIndexMap;
1074 
1075  std::map<const MCSymbol *, std::vector<const MCSectionELF *>> GroupMembers;
1076 
1077  // Write out the ELF header ...
1078  writeHeader(Asm);
1079 
1080  // ... then the sections ...
1081  SectionOffsetsTy SectionOffsets;
1082  std::vector<MCSectionELF *> Groups;
1083  std::vector<MCSectionELF *> Relocations;
1084  for (MCSection &Sec : Asm) {
1085  MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
1086  if (Mode == NonDwoOnly && isDwoSection(Section))
1087  continue;
1088  if (Mode == DwoOnly && !isDwoSection(Section))
1089  continue;
1090 
1091  align(Section.getAlignment());
1092 
1093  // Remember the offset into the file for this section.
1094  uint64_t SecStart = W.OS.tell();
1095 
1096  const MCSymbolELF *SignatureSymbol = Section.getGroup();
1097  writeSectionData(Asm, Section, Layout);
1098 
1099  uint64_t SecEnd = W.OS.tell();
1100  SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
1101 
1102  MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
1103 
1104  if (SignatureSymbol) {
1105  Asm.registerSymbol(*SignatureSymbol);
1106  unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
1107  if (!GroupIdx) {
1108  MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
1109  GroupIdx = addToSectionTable(Group);
1110  Group->setAlignment(4);
1111  Groups.push_back(Group);
1112  }
1113  std::vector<const MCSectionELF *> &Members =
1114  GroupMembers[SignatureSymbol];
1115  Members.push_back(&Section);
1116  if (RelSection)
1117  Members.push_back(RelSection);
1118  }
1119 
1120  SectionIndexMap[&Section] = addToSectionTable(&Section);
1121  if (RelSection) {
1122  SectionIndexMap[RelSection] = addToSectionTable(RelSection);
1123  Relocations.push_back(RelSection);
1124  }
1125 
1126  OWriter.TargetObjectWriter->addTargetSectionFlags(Ctx, Section);
1127  }
1128 
1129  MCSectionELF *CGProfileSection = nullptr;
1130  if (!Asm.CGProfile.empty()) {
1131  CGProfileSection = Ctx.getELFSection(".llvm.call-graph-profile",
1133  ELF::SHF_EXCLUDE, 16, "");
1134  SectionIndexMap[CGProfileSection] = addToSectionTable(CGProfileSection);
1135  }
1136 
1137  for (MCSectionELF *Group : Groups) {
1138  align(Group->getAlignment());
1139 
1140  // Remember the offset into the file for this section.
1141  uint64_t SecStart = W.OS.tell();
1142 
1143  const MCSymbol *SignatureSymbol = Group->getGroup();
1144  assert(SignatureSymbol);
1146  for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
1147  uint32_t SecIndex = SectionIndexMap.lookup(Member);
1148  write(SecIndex);
1149  }
1150 
1151  uint64_t SecEnd = W.OS.tell();
1152  SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
1153  }
1154 
1155  if (Mode == DwoOnly) {
1156  // dwo files don't have symbol tables or relocations, but they do have
1157  // string tables.
1158  StrTabBuilder.finalize();
1159  } else {
1160  MCSectionELF *AddrsigSection;
1161  if (OWriter.EmitAddrsigSection) {
1162  AddrsigSection = Ctx.getELFSection(".llvm_addrsig", ELF::SHT_LLVM_ADDRSIG,
1164  addToSectionTable(AddrsigSection);
1165  }
1166 
1167  // Compute symbol table information.
1168  computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
1169  SectionOffsets);
1170 
1171  for (MCSectionELF *RelSection : Relocations) {
1172  align(RelSection->getAlignment());
1173 
1174  // Remember the offset into the file for this section.
1175  uint64_t SecStart = W.OS.tell();
1176 
1177  writeRelocations(Asm,
1178  cast<MCSectionELF>(*RelSection->getAssociatedSection()));
1179 
1180  uint64_t SecEnd = W.OS.tell();
1181  SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
1182  }
1183 
1184  if (OWriter.EmitAddrsigSection) {
1185  uint64_t SecStart = W.OS.tell();
1186  writeAddrsigSection();
1187  uint64_t SecEnd = W.OS.tell();
1188  SectionOffsets[AddrsigSection] = std::make_pair(SecStart, SecEnd);
1189  }
1190  }
1191 
1192  if (CGProfileSection) {
1193  uint64_t SecStart = W.OS.tell();
1194  for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
1195  W.write<uint32_t>(CGPE.From->getSymbol().getIndex());
1196  W.write<uint32_t>(CGPE.To->getSymbol().getIndex());
1197  W.write<uint64_t>(CGPE.Count);
1198  }
1199  uint64_t SecEnd = W.OS.tell();
1200  SectionOffsets[CGProfileSection] = std::make_pair(SecStart, SecEnd);
1201  }
1202 
1203  {
1204  uint64_t SecStart = W.OS.tell();
1205  const MCSectionELF *Sec = createStringTable(Ctx);
1206  uint64_t SecEnd = W.OS.tell();
1207  SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
1208  }
1209 
1210  uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1211  align(NaturalAlignment);
1212 
1213  const uint64_t SectionHeaderOffset = W.OS.tell();
1214 
1215  // ... then the section header table ...
1216  writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
1217 
1218  uint16_t NumSections = support::endian::byte_swap<uint16_t>(
1219  (SectionTable.size() + 1 >= ELF::SHN_LORESERVE) ? (uint16_t)ELF::SHN_UNDEF
1220  : SectionTable.size() + 1,
1221  W.Endian);
1222  unsigned NumSectionsOffset;
1223 
1224  auto &Stream = static_cast<raw_pwrite_stream &>(W.OS);
1225  if (is64Bit()) {
1226  uint64_t Val =
1227  support::endian::byte_swap<uint64_t>(SectionHeaderOffset, W.Endian);
1228  Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
1229  offsetof(ELF::Elf64_Ehdr, e_shoff));
1230  NumSectionsOffset = offsetof(ELF::Elf64_Ehdr, e_shnum);
1231  } else {
1232  uint32_t Val =
1233  support::endian::byte_swap<uint32_t>(SectionHeaderOffset, W.Endian);
1234  Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
1235  offsetof(ELF::Elf32_Ehdr, e_shoff));
1236  NumSectionsOffset = offsetof(ELF::Elf32_Ehdr, e_shnum);
1237  }
1238  Stream.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
1239  NumSectionsOffset);
1240 
1241  return W.OS.tell() - StartOffset;
1242 }
1243 
1244 bool ELFObjectWriter::hasRelocationAddend() const {
1245  return TargetObjectWriter->hasRelocationAddend();
1246 }
1247 
1248 void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
1249  const MCAsmLayout &Layout) {
1250  // The presence of symbol versions causes undefined symbols and
1251  // versions declared with @@@ to be renamed.
1252  for (const std::pair<StringRef, const MCSymbol *> &P : Asm.Symvers) {
1253  StringRef AliasName = P.first;
1254  const auto &Symbol = cast<MCSymbolELF>(*P.second);
1255  size_t Pos = AliasName.find('@');
1256  assert(Pos != StringRef::npos);
1257 
1258  StringRef Prefix = AliasName.substr(0, Pos);
1259  StringRef Rest = AliasName.substr(Pos);
1260  StringRef Tail = Rest;
1261  if (Rest.startswith("@@@"))
1262  Tail = Rest.substr(Symbol.isUndefined() ? 2 : 1);
1263 
1264  auto *Alias =
1265  cast<MCSymbolELF>(Asm.getContext().getOrCreateSymbol(Prefix + Tail));
1266  Asm.registerSymbol(*Alias);
1267  const MCExpr *Value = MCSymbolRefExpr::create(&Symbol, Asm.getContext());
1268  Alias->setVariableValue(Value);
1269 
1270  // Aliases defined with .symvar copy the binding from the symbol they alias.
1271  // This is the first place we are able to copy this information.
1272  Alias->setExternal(Symbol.isExternal());
1273  Alias->setBinding(Symbol.getBinding());
1274 
1275  if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
1276  continue;
1277 
1278  // FIXME: produce a better error message.
1279  if (Symbol.isUndefined() && Rest.startswith("@@") &&
1280  !Rest.startswith("@@@"))
1281  report_fatal_error("A @@ version cannot be undefined");
1282 
1283  if (Renames.count(&Symbol) && Renames[&Symbol] != Alias)
1284  report_fatal_error(llvm::Twine("Multiple symbol versions defined for ") +
1285  Symbol.getName());
1286 
1287  Renames.insert(std::make_pair(&Symbol, Alias));
1288  }
1289 
1290  for (const MCSymbol *&Sym : AddrsigSyms) {
1291  if (const MCSymbol *R = Renames.lookup(cast<MCSymbolELF>(Sym)))
1292  Sym = R;
1293  if (Sym->isInSection() && Sym->getName().startswith(".L"))
1294  Sym = Sym->getSection().getBeginSymbol();
1295  Sym->setUsedInReloc();
1296  }
1297 }
1298 
1299 // It is always valid to create a relocation with a symbol. It is preferable
1300 // to use a relocation with a section if that is possible. Using the section
1301 // allows us to omit some local symbols from the symbol table.
1302 bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
1303  const MCSymbolRefExpr *RefA,
1304  const MCSymbolELF *Sym,
1305  uint64_t C,
1306  unsigned Type) const {
1307  // A PCRel relocation to an absolute value has no symbol (or section). We
1308  // represent that with a relocation to a null section.
1309  if (!RefA)
1310  return false;
1311 
1313  switch (Kind) {
1314  default:
1315  break;
1316  // The .odp creation emits a relocation against the symbol ".TOC." which
1317  // create a R_PPC64_TOC relocation. However the relocation symbol name
1318  // in final object creation should be NULL, since the symbol does not
1319  // really exist, it is just the reference to TOC base for the current
1320  // object file. Since the symbol is undefined, returning false results
1321  // in a relocation with a null section which is the desired result.
1323  return false;
1324 
1325  // These VariantKind cause the relocation to refer to something other than
1326  // the symbol itself, like a linker generated table. Since the address of
1327  // symbol is not relevant, we cannot replace the symbol with the
1328  // section and patch the difference in the addend.
1335  return true;
1336  }
1337 
1338  // An undefined symbol is not in any section, so the relocation has to point
1339  // to the symbol itself.
1340  assert(Sym && "Expected a symbol");
1341  if (Sym->isUndefined())
1342  return true;
1343 
1344  unsigned Binding = Sym->getBinding();
1345  switch(Binding) {
1346  default:
1347  llvm_unreachable("Invalid Binding");
1348  case ELF::STB_LOCAL:
1349  break;
1350  case ELF::STB_WEAK:
1351  // If the symbol is weak, it might be overridden by a symbol in another
1352  // file. The relocation has to point to the symbol so that the linker
1353  // can update it.
1354  return true;
1355  case ELF::STB_GLOBAL:
1356  // Global ELF symbols can be preempted by the dynamic linker. The relocation
1357  // has to point to the symbol for a reason analogous to the STB_WEAK case.
1358  return true;
1359  }
1360 
1361  // If a relocation points to a mergeable section, we have to be careful.
1362  // If the offset is zero, a relocation with the section will encode the
1363  // same information. With a non-zero offset, the situation is different.
1364  // For example, a relocation can point 42 bytes past the end of a string.
1365  // If we change such a relocation to use the section, the linker would think
1366  // that it pointed to another string and subtracting 42 at runtime will
1367  // produce the wrong value.
1368  if (Sym->isInSection()) {
1369  auto &Sec = cast<MCSectionELF>(Sym->getSection());
1370  unsigned Flags = Sec.getFlags();
1371  if (Flags & ELF::SHF_MERGE) {
1372  if (C != 0)
1373  return true;
1374 
1375  // It looks like gold has a bug (http://sourceware.org/PR16794) and can
1376  // only handle section relocations to mergeable sections if using RELA.
1377  if (!hasRelocationAddend())
1378  return true;
1379  }
1380 
1381  // Most TLS relocations use a got, so they need the symbol. Even those that
1382  // are just an offset (@tpoff), require a symbol in gold versions before
1383  // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
1384  // http://sourceware.org/PR16773.
1385  if (Flags & ELF::SHF_TLS)
1386  return true;
1387  }
1388 
1389  // If the symbol is a thumb function the final relocation must set the lowest
1390  // bit. With a symbol that is done by just having the symbol have that bit
1391  // set, so we would lose the bit if we relocated with the section.
1392  // FIXME: We could use the section but add the bit to the relocation value.
1393  if (Asm.isThumbFunc(Sym))
1394  return true;
1395 
1396  if (TargetObjectWriter->needsRelocateWithSymbol(*Sym, Type))
1397  return true;
1398  return false;
1399 }
1400 
1401 void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
1402  const MCAsmLayout &Layout,
1403  const MCFragment *Fragment,
1404  const MCFixup &Fixup, MCValue Target,
1405  uint64_t &FixedValue) {
1406  MCAsmBackend &Backend = Asm.getBackend();
1407  bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
1409  const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent());
1410  uint64_t C = Target.getConstant();
1411  uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
1412  MCContext &Ctx = Asm.getContext();
1413 
1414  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
1415  // Let A, B and C being the components of Target and R be the location of
1416  // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
1417  // If it is pcrel, we want to compute (A - B + C - R).
1418 
1419  // In general, ELF has no relocations for -B. It can only represent (A + C)
1420  // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
1421  // replace B to implement it: (A - R - K + C)
1422  if (IsPCRel) {
1423  Ctx.reportError(
1424  Fixup.getLoc(),
1425  "No relocation available to represent this relative expression");
1426  return;
1427  }
1428 
1429  const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
1430 
1431  if (SymB.isUndefined()) {
1432  Ctx.reportError(Fixup.getLoc(),
1433  Twine("symbol '") + SymB.getName() +
1434  "' can not be undefined in a subtraction expression");
1435  return;
1436  }
1437 
1438  assert(!SymB.isAbsolute() && "Should have been folded");
1439  const MCSection &SecB = SymB.getSection();
1440  if (&SecB != &FixupSection) {
1441  Ctx.reportError(Fixup.getLoc(),
1442  "Cannot represent a difference across sections");
1443  return;
1444  }
1445 
1446  uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
1447  uint64_t K = SymBOffset - FixupOffset;
1448  IsPCRel = true;
1449  C -= K;
1450  }
1451 
1452  // We either rejected the fixup or folded B into C at this point.
1453  const MCSymbolRefExpr *RefA = Target.getSymA();
1454  const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
1455 
1456  bool ViaWeakRef = false;
1457  if (SymA && SymA->isVariable()) {
1458  const MCExpr *Expr = SymA->getVariableValue();
1459  if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
1460  if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
1461  SymA = cast<MCSymbolELF>(&Inner->getSymbol());
1462  ViaWeakRef = true;
1463  }
1464  }
1465  }
1466 
1467  unsigned Type = TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
1468  uint64_t OriginalC = C;
1469  bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
1470  if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
1471  C += Layout.getSymbolOffset(*SymA);
1472 
1473  uint64_t Addend = 0;
1474  if (hasRelocationAddend()) {
1475  Addend = C;
1476  C = 0;
1477  }
1478 
1479  FixedValue = C;
1480 
1481  const MCSectionELF *SecA = (SymA && SymA->isInSection())
1482  ? cast<MCSectionELF>(&SymA->getSection())
1483  : nullptr;
1484  if (!checkRelocation(Ctx, Fixup.getLoc(), &FixupSection, SecA))
1485  return;
1486 
1487  if (!RelocateWithSymbol) {
1488  const auto *SectionSymbol =
1489  SecA ? cast<MCSymbolELF>(SecA->getBeginSymbol()) : nullptr;
1490  if (SectionSymbol)
1491  SectionSymbol->setUsedInReloc();
1492  ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA,
1493  OriginalC);
1494  Relocations[&FixupSection].push_back(Rec);
1495  return;
1496  }
1497 
1498  const auto *RenamedSymA = SymA;
1499  if (SymA) {
1500  if (const MCSymbolELF *R = Renames.lookup(SymA))
1501  RenamedSymA = R;
1502 
1503  if (ViaWeakRef)
1504  RenamedSymA->setIsWeakrefUsedInReloc();
1505  else
1506  RenamedSymA->setUsedInReloc();
1507  }
1508  ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA,
1509  OriginalC);
1510  Relocations[&FixupSection].push_back(Rec);
1511 }
1512 
1513 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
1514  const MCAssembler &Asm, const MCSymbol &SA, const MCFragment &FB,
1515  bool InSet, bool IsPCRel) const {
1516  const auto &SymA = cast<MCSymbolELF>(SA);
1517  if (IsPCRel) {
1518  assert(!InSet);
1519  if (isWeak(SymA))
1520  return false;
1521  }
1523  InSet, IsPCRel);
1524 }
1525 
1526 std::unique_ptr<MCObjectWriter>
1527 llvm::createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
1528  raw_pwrite_stream &OS, bool IsLittleEndian) {
1529  return llvm::make_unique<ELFSingleObjectWriter>(std::move(MOTW), OS,
1530  IsLittleEndian);
1531 }
1532 
1533 std::unique_ptr<MCObjectWriter>
1534 llvm::createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
1536  bool IsLittleEndian) {
1537  return llvm::make_unique<ELFDwoObjectWriter>(std::move(MOTW), OS, DwoOS,
1538  IsLittleEndian);
1539 }
const MCAsmInfo * getAsmInfo() const
Definition: MCContext.h:293
uint64_t CallInst * C
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
uint32_t getIndex() const
Get the (implementation defined) index.
Definition: MCSymbol.h:310
void setUsedInReloc() const
Definition: MCSymbol.h:213
void setSymbolAndType(Elf32_Word s, unsigned char t)
Definition: ELF.h:1105
SI Whole Quad Mode
static const MCSymbolRefExpr * create(const MCSymbol *Symbol, MCContext &Ctx)
Definition: MCExpr.h:323
LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:139
This class represents lattice values for constants.
Definition: AllocatorList.h:24
bool isVariable() const
isVariable - Check if this is a variable symbol.
Definition: MCSymbol.h:294
This represents an "assembler immediate".
Definition: MCValue.h:40
Elf32_Word r_info
Definition: ELF.h:1096
uint64_t getSectionAddressSize(const MCSection *Sec) const
Get the address space size of the given section, as it effects layout.
Definition: MCFragment.cpp:176
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
VariantKind getKind() const
Definition: MCExpr.h:338
unsigned getBinding() const
Definition: MCSymbolELF.cpp:67
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE size_t size() const
size - Get the string size.
Definition: StringRef.h:138
virtual const MCFixupKindInfo & getFixupKindInfo(MCFixupKind Kind) const
Get information on a fixup kind.
void setAlignment(unsigned Value)
Definition: MCSection.h:122
Offsets
Offsets in bytes from the start of the input buffer.
Definition: SIInstrInfo.h:1023
A raw_ostream that writes to an SmallVector or SmallString.
Definition: raw_ostream.h:510
void registerSymbol(const MCSymbol &Symbol, bool *Created=nullptr)
unsigned getCommonAlignment() const
Return the alignment of a &#39;common&#39; symbol.
Definition: MCSymbol.h:359
ELFYAML::ELF_STV Visibility
Definition: ELFYAML.cpp:782
void setSymbolAndType(Elf64_Word s, Elf64_Word t)
Definition: ELF.h:1141
bool isCommon() const
Is this a &#39;common&#39; symbol.
Definition: MCSymbol.h:380
Defines the object file and target independent interfaces used by the assembler backend to write nati...
Elf64_Xword r_info
Definition: ELF.h:1132
This file defines the MallocAllocator and BumpPtrAllocator interfaces.
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:74
unsigned getAlignment() const
Definition: MCSection.h:121
Is this fixup kind PCrelative? This is used by the assembler backend to evaluate fixup values in a ta...
MCContext & getContext() const
Definition: MCAssembler.h:285
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool endswith(StringRef Suffix) const
Check if this string ends with the given Suffix.
Definition: StringRef.h:279
int64_t getConstant() const
Definition: MCValue.h:47
const MCSymbolRefExpr * getSymB() const
Definition: MCValue.h:49
amdgpu Simplify well known AMD library false Value Value const Twine & Name
Error compress(StringRef InputBuffer, SmallVectorImpl< char > &CompressedBuffer, int Level=DefaultCompression)
Definition: Compression.cpp:50
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:29
const MCSection * getAssociatedSection() const
Definition: MCSectionELF.h:89
const MCSymbolRefExpr * From
Definition: MCAssembler.h:430
support::ulittle32_t Word
Definition: IRSymtab.h:51
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:36
bool isInSection() const
isInSection - Check if this symbol is defined in some section (i.e., it is defined but not absolute)...
Definition: MCSymbol.h:252
The access may reference the value stored in memory.
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:166
zlib-gnu style compression
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:783
DebugCompressionType compressDebugSections() const
Definition: MCAsmInfo.h:625
ArrayRef< std::string > getFileNames()
Definition: MCAssembler.h:443
Context object for machine code objects.
Definition: MCContext.h:63
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:261
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool startswith(StringRef Prefix) const
Check if this string starts with the given Prefix.
Definition: StringRef.h:267
Utility for building string tables with deduplicated suffixes.
bool isBindingSet() const
const MCSymbolRefExpr * To
Definition: MCAssembler.h:431
MCAssembler & getAssembler() const
Get the assembler object this is a layout for.
Definition: MCAsmLayout.h:51
std::unique_ptr< MCObjectWriter > createELFObjectWriter(std::unique_ptr< MCELFObjectTargetWriter > MOTW, raw_pwrite_stream &OS, bool IsLittleEndian)
Construct a new ELF writer instance.
static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType)
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE StringRef substr(size_t Start, size_t N=npos) const
Return a reference to the substring from [Start, Start + N).
Definition: StringRef.h:598
void write(void *memory, value_type value, endianness endian)
Write a value to memory with a particular endianness.
Definition: Endian.h:100
#define P(N)
void array_pod_sort(IteratorTy Start, IteratorTy End)
array_pod_sort - This sorts an array with the specified start and end extent.
Definition: STLExtras.h:1077
bool evaluateKnownAbsolute(int64_t &Res, const MCAsmLayout &Layout) const
Definition: MCExpr.cpp:470
const MCSymbolELF * getGroup() const
Definition: MCSectionELF.h:78
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
static bool is64Bit(const char *name)
virtual void reset()
lifetime management
bool isRegistered() const
Definition: MCSection.h:147
#define offsetof(TYPE, MEMBER)
void setFlags(unsigned F)
Definition: MCSectionELF.h:77
bool getSymbolOffset(const MCSymbol &S, uint64_t &Val) const
Get the offset of the given symbol, as computed in the current layout.
Definition: MCFragment.cpp:130
bool isTemporary() const
isTemporary - Check if this is an assembler temporary symbol.
Definition: MCSymbol.h:220
void pwrite(const char *Ptr, size_t Size, uint64_t Offset)
Definition: raw_ostream.h:348
const MCSymbolRefExpr * getSymA() const
Definition: MCValue.h:48
void reportError(SMLoc L, const Twine &Msg)
Definition: MCContext.cpp:612
uint32_t getOffset() const
Definition: MCFixup.h:125
void writeSectionData(raw_ostream &OS, const MCSection *Section, const MCAsmLayout &Layout) const
Emit the section contents to OS.
lazy value info
unsigned getELFHeaderEFlags() const
ELF e_header flags.
Definition: MCAssembler.h:255
static void write(bool isBE, void *P, T V)
void consumeError(Error Err)
Consume a Error without doing anything.
Definition: Error.h:982
bool isExternal() const
Definition: MCSymbol.h:393
size_t size() const
Definition: SmallVector.h:53
static wasm::ValType getType(const TargetRegisterClass *RC)
unsigned getEntrySize() const
Definition: MCSectionELF.h:76
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
uint64_t getFragmentOffset(const MCFragment *F) const
Get the offset of the given fragment inside its containing section.
Definition: MCFragment.cpp:78
PowerPC TLS Dynamic Call Fixup
static const char *const Magic
Definition: Archive.cpp:42
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE StringRef drop_front(size_t N=1) const
Return a StringRef equal to &#39;this&#39; but with the first N elements dropped.
Definition: StringRef.h:645
MCSectionELF * createELFRelSection(const Twine &Name, unsigned Type, unsigned Flags, unsigned EntrySize, const MCSymbolELF *Group, const MCSectionELF *RelInfoSection)
Definition: MCContext.cpp:352
static const X86InstrFMA3Group Groups[]
SMLoc getLoc() const
Definition: MCFixup.h:166
static const char ElfMagic[]
Definition: ELF.h:44
auto size(R &&Range, typename std::enable_if< std::is_same< typename std::iterator_traits< decltype(Range.begin())>::iterator_category, std::random_access_iterator_tag >::value, void >::type *=nullptr) -> decltype(std::distance(Range.begin(), Range.end()))
Get the size of a range.
Definition: STLExtras.h:1161
BlockVerifier::State From
void write(ArrayRef< value_type > Val)
Definition: EndianStream.h:56
bool isWeakrefUsedInReloc() const
MCAsmBackend & getBackend() const
Definition: MCAssembler.h:293
unsigned encodeULEB128(uint64_t Value, raw_ostream &OS, unsigned PadTo=0)
Utility function to encode a ULEB128 value to an output stream.
Definition: LEB128.h:81
std::unique_ptr< MCObjectWriter > createELFDwoObjectWriter(std::unique_ptr< MCELFObjectTargetWriter > MOTW, raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS, bool IsLittleEndian)
const MCSymbol & getSymbol() const
Definition: MCExpr.h:336
bool isUndefined(bool SetUsed=true) const
isUndefined - Check if this symbol undefined (i.e., implicitly defined).
Definition: MCSymbol.h:257
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
unsigned getType() const
Definition: MCSectionELF.h:74
MCSymbol * getBeginSymbol()
Definition: MCSection.h:110
Target - Wrapper for Target specific information.
bool isThumbFunc(const MCSymbol *Func) const
Check whether a given symbol has been flagged with .thumb_func.
MCSection * getParent() const
Definition: MCFragment.h:99
static bool isWeak(const MCSymbolELF &Sym)
MCSection & getSection() const
Get the section associated with a defined, non-absolute symbol.
Definition: MCSymbol.h:267
bool isAbsolute() const
isAbsolute - Check if this is an absolute symbol.
Definition: MCSymbol.h:262
bool isUsedInReloc() const
Definition: MCSymbol.h:214
unsigned getType() const
virtual bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, const MCSymbol &A, const MCSymbol &B, bool InSet) const
Adapter to write values to a stream in a particular byte order.
Definition: EndianStream.h:52
pointer data()
Return a pointer to the vector&#39;s buffer, even if empty().
Definition: SmallVector.h:149
static const size_t npos
Definition: StringRef.h:51
MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition: MCContext.cpp:123
This represents a section on linux, lots of unix variants and some bare metal systems.
Definition: MCSectionELF.h:28
uint32_t Size
Definition: Profile.cpp:47
bool isSignature() const
symbol_range symbols()
Definition: MCAssembler.h:354
MCSectionELF * createELFGroupSection(const MCSymbolELF *Group)
Definition: MCContext.cpp:416
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:203
An abstract base class for streams implementations that also support a pwrite operation.
Definition: raw_ostream.h:341
const unsigned Kind
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const MCExpr * getVariableValue(bool SetUsed=true) const
getVariableValue - Get the value for variable symbols.
Definition: MCSymbol.h:299
bool operator<(int64_t V1, const APSInt &V2)
Definition: APSInt.h:326
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:389
LLVM Value Representation.
Definition: Value.h:73
Generic interface to target specific assembler backends.
Definition: MCAsmBackend.h:42
static const char * name
Lightweight error class with error context and mandatory checking.
Definition: Error.h:158
uint64_t OffsetToAlignment(uint64_t Value, uint64_t Align)
Returns the offset to the next integer (mod 2**64) that is greater than or equal to Value and is a mu...
Definition: MathExtras.h:727
const char SectionName[]
Definition: AMDGPUPTNote.h:24
const MCSymbol * getAssociatedSymbol() const
Definition: MCSectionELF.h:90
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
const MCSymbolELF * Symbol
unsigned getFlags() const
Definition: MCSectionELF.h:75
Represents a location in source code.
Definition: SMLoc.h:24
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE size_t find(char C, size_t From=0) const
Search for the first character C in the string.
Definition: StringRef.h:298
static bool isInSymtab(const MCSymbolWasm &Sym)
std::vector< std::pair< StringRef, const MCSymbol * > > Symvers
Definition: MCAssembler.h:214
const MCSymbol * getBaseSymbol(const MCSymbol &Symbol) const
If this symbol is equivalent to A + Constant, return A.
Definition: MCFragment.cpp:140
MCFixupKind getKind() const
Definition: MCFixup.h:123
StringRef getSectionName() const
Definition: MCSectionELF.h:73
bool empty() const
empty - Check if the array is empty.
Definition: ArrayRef.h:144