LLVM  9.0.0svn
ELFObjectWriter.cpp
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1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements ELF object file writer information.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/ADT/ArrayRef.h"
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallString.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Twine.h"
20 #include "llvm/BinaryFormat/ELF.h"
21 #include "llvm/MC/MCAsmBackend.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCAsmLayout.h"
24 #include "llvm/MC/MCAssembler.h"
25 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCFixup.h"
30 #include "llvm/MC/MCFragment.h"
32 #include "llvm/MC/MCObjectWriter.h"
33 #include "llvm/MC/MCSection.h"
34 #include "llvm/MC/MCSectionELF.h"
35 #include "llvm/MC/MCSymbol.h"
36 #include "llvm/MC/MCSymbolELF.h"
37 #include "llvm/MC/MCValue.h"
39 #include "llvm/Support/Allocator.h"
40 #include "llvm/Support/Casting.h"
42 #include "llvm/Support/Endian.h"
43 #include "llvm/Support/Error.h"
45 #include "llvm/Support/Host.h"
46 #include "llvm/Support/LEB128.h"
48 #include "llvm/Support/SMLoc.h"
52 #include <algorithm>
53 #include <cassert>
54 #include <cstddef>
55 #include <cstdint>
56 #include <map>
57 #include <memory>
58 #include <string>
59 #include <utility>
60 #include <vector>
61 
62 using namespace llvm;
63 
64 #undef DEBUG_TYPE
65 #define DEBUG_TYPE "reloc-info"
66 
67 namespace {
68 
69 using SectionIndexMapTy = DenseMap<const MCSectionELF *, uint32_t>;
70 
71 class ELFObjectWriter;
72 struct ELFWriter;
73 
74 bool isDwoSection(const MCSectionELF &Sec) {
75  return Sec.getSectionName().endswith(".dwo");
76 }
77 
78 class SymbolTableWriter {
79  ELFWriter &EWriter;
80  bool Is64Bit;
81 
82  // indexes we are going to write to .symtab_shndx.
83  std::vector<uint32_t> ShndxIndexes;
84 
85  // The numbel of symbols written so far.
86  unsigned NumWritten;
87 
88  void createSymtabShndx();
89 
90  template <typename T> void write(T Value);
91 
92 public:
93  SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit);
94 
95  void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
96  uint8_t other, uint32_t shndx, bool Reserved);
97 
98  ArrayRef<uint32_t> getShndxIndexes() const { return ShndxIndexes; }
99 };
100 
101 struct ELFWriter {
102  ELFObjectWriter &OWriter;
104 
105  enum DwoMode {
106  AllSections,
107  NonDwoOnly,
108  DwoOnly,
109  } Mode;
110 
111  static uint64_t SymbolValue(const MCSymbol &Sym, const MCAsmLayout &Layout);
112  static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
113  bool Used, bool Renamed);
114 
115  /// Helper struct for containing some precomputed information on symbols.
116  struct ELFSymbolData {
117  const MCSymbolELF *Symbol;
118  uint32_t SectionIndex;
119  StringRef Name;
120 
121  // Support lexicographic sorting.
122  bool operator<(const ELFSymbolData &RHS) const {
123  unsigned LHSType = Symbol->getType();
124  unsigned RHSType = RHS.Symbol->getType();
125  if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
126  return false;
127  if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
128  return true;
129  if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
130  return SectionIndex < RHS.SectionIndex;
131  return Name < RHS.Name;
132  }
133  };
134 
135  /// @}
136  /// @name Symbol Table Data
137  /// @{
138 
140 
141  /// @}
142 
143  // This holds the symbol table index of the last local symbol.
144  unsigned LastLocalSymbolIndex;
145  // This holds the .strtab section index.
146  unsigned StringTableIndex;
147  // This holds the .symtab section index.
148  unsigned SymbolTableIndex;
149 
150  // Sections in the order they are to be output in the section table.
151  std::vector<const MCSectionELF *> SectionTable;
152  unsigned addToSectionTable(const MCSectionELF *Sec);
153 
154  // TargetObjectWriter wrappers.
155  bool is64Bit() const;
156  bool hasRelocationAddend() const;
157 
158  void align(unsigned Alignment);
159 
160  bool maybeWriteCompression(uint64_t Size,
161  SmallVectorImpl<char> &CompressedContents,
162  bool ZLibStyle, unsigned Alignment);
163 
164 public:
165  ELFWriter(ELFObjectWriter &OWriter, raw_pwrite_stream &OS,
166  bool IsLittleEndian, DwoMode Mode)
167  : OWriter(OWriter),
168  W(OS, IsLittleEndian ? support::little : support::big), Mode(Mode) {}
169 
170  void WriteWord(uint64_t Word) {
171  if (is64Bit())
172  W.write<uint64_t>(Word);
173  else
174  W.write<uint32_t>(Word);
175  }
176 
177  template <typename T> void write(T Val) {
178  W.write(Val);
179  }
180 
181  void writeHeader(const MCAssembler &Asm);
182 
183  void writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
184  ELFSymbolData &MSD, const MCAsmLayout &Layout);
185 
186  // Start and end offset of each section
187  using SectionOffsetsTy =
188  std::map<const MCSectionELF *, std::pair<uint64_t, uint64_t>>;
189 
190  // Map from a signature symbol to the group section index
191  using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
192 
193  /// Compute the symbol table data
194  ///
195  /// \param Asm - The assembler.
196  /// \param SectionIndexMap - Maps a section to its index.
197  /// \param RevGroupMap - Maps a signature symbol to the group section.
198  void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
199  const SectionIndexMapTy &SectionIndexMap,
200  const RevGroupMapTy &RevGroupMap,
201  SectionOffsetsTy &SectionOffsets);
202 
203  void writeAddrsigSection();
204 
205  MCSectionELF *createRelocationSection(MCContext &Ctx,
206  const MCSectionELF &Sec);
207 
208  const MCSectionELF *createStringTable(MCContext &Ctx);
209 
210  void writeSectionHeader(const MCAsmLayout &Layout,
211  const SectionIndexMapTy &SectionIndexMap,
212  const SectionOffsetsTy &SectionOffsets);
213 
214  void writeSectionData(const MCAssembler &Asm, MCSection &Sec,
215  const MCAsmLayout &Layout);
216 
217  void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
218  uint64_t Address, uint64_t Offset, uint64_t Size,
219  uint32_t Link, uint32_t Info, uint64_t Alignment,
220  uint64_t EntrySize);
221 
222  void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
223 
224  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout);
225  void writeSection(const SectionIndexMapTy &SectionIndexMap,
226  uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
227  const MCSectionELF &Section);
228 };
229 
230 class ELFObjectWriter : public MCObjectWriter {
231  /// The target specific ELF writer instance.
232  std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
233 
235 
237 
238  bool EmitAddrsigSection = false;
239  std::vector<const MCSymbol *> AddrsigSyms;
240 
241  bool hasRelocationAddend() const;
242 
243  bool shouldRelocateWithSymbol(const MCAssembler &Asm,
244  const MCSymbolRefExpr *RefA,
245  const MCSymbolELF *Sym, uint64_t C,
246  unsigned Type) const;
247 
248 public:
249  ELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW)
250  : TargetObjectWriter(std::move(MOTW)) {}
251 
252  void reset() override {
253  Relocations.clear();
254  Renames.clear();
256  }
257 
258  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
259  const MCSymbol &SymA,
260  const MCFragment &FB, bool InSet,
261  bool IsPCRel) const override;
262 
263  virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
264  const MCSectionELF *From,
265  const MCSectionELF *To) {
266  return true;
267  }
268 
269  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
270  const MCFragment *Fragment, const MCFixup &Fixup,
271  MCValue Target, uint64_t &FixedValue) override;
272 
273  void executePostLayoutBinding(MCAssembler &Asm,
274  const MCAsmLayout &Layout) override;
275 
276  void emitAddrsigSection() override { EmitAddrsigSection = true; }
277  void addAddrsigSymbol(const MCSymbol *Sym) override {
278  AddrsigSyms.push_back(Sym);
279  }
280 
281  friend struct ELFWriter;
282 };
283 
284 class ELFSingleObjectWriter : public ELFObjectWriter {
285  raw_pwrite_stream &OS;
286  bool IsLittleEndian;
287 
288 public:
289  ELFSingleObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
290  raw_pwrite_stream &OS, bool IsLittleEndian)
291  : ELFObjectWriter(std::move(MOTW)), OS(OS),
292  IsLittleEndian(IsLittleEndian) {}
293 
294  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
295  return ELFWriter(*this, OS, IsLittleEndian, ELFWriter::AllSections)
296  .writeObject(Asm, Layout);
297  }
298 
299  friend struct ELFWriter;
300 };
301 
302 class ELFDwoObjectWriter : public ELFObjectWriter {
303  raw_pwrite_stream &OS, &DwoOS;
304  bool IsLittleEndian;
305 
306 public:
307  ELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
309  bool IsLittleEndian)
310  : ELFObjectWriter(std::move(MOTW)), OS(OS), DwoOS(DwoOS),
311  IsLittleEndian(IsLittleEndian) {}
312 
313  virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
314  const MCSectionELF *From,
315  const MCSectionELF *To) override {
316  if (isDwoSection(*From)) {
317  Ctx.reportError(Loc, "A dwo section may not contain relocations");
318  return false;
319  }
320  if (To && isDwoSection(*To)) {
321  Ctx.reportError(Loc, "A relocation may not refer to a dwo section");
322  return false;
323  }
324  return true;
325  }
326 
327  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
328  uint64_t Size = ELFWriter(*this, OS, IsLittleEndian, ELFWriter::NonDwoOnly)
329  .writeObject(Asm, Layout);
330  Size += ELFWriter(*this, DwoOS, IsLittleEndian, ELFWriter::DwoOnly)
331  .writeObject(Asm, Layout);
332  return Size;
333  }
334 };
335 
336 } // end anonymous namespace
337 
338 void ELFWriter::align(unsigned Alignment) {
339  uint64_t Padding = OffsetToAlignment(W.OS.tell(), Alignment);
340  W.OS.write_zeros(Padding);
341 }
342 
343 unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) {
344  SectionTable.push_back(Sec);
345  StrTabBuilder.add(Sec->getSectionName());
346  return SectionTable.size();
347 }
348 
349 void SymbolTableWriter::createSymtabShndx() {
350  if (!ShndxIndexes.empty())
351  return;
352 
353  ShndxIndexes.resize(NumWritten);
354 }
355 
356 template <typename T> void SymbolTableWriter::write(T Value) {
357  EWriter.write(Value);
358 }
359 
360 SymbolTableWriter::SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit)
361  : EWriter(EWriter), Is64Bit(Is64Bit), NumWritten(0) {}
362 
363 void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
364  uint64_t size, uint8_t other,
365  uint32_t shndx, bool Reserved) {
366  bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
367 
368  if (LargeIndex)
369  createSymtabShndx();
370 
371  if (!ShndxIndexes.empty()) {
372  if (LargeIndex)
373  ShndxIndexes.push_back(shndx);
374  else
375  ShndxIndexes.push_back(0);
376  }
377 
378  uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
379 
380  if (Is64Bit) {
381  write(name); // st_name
382  write(info); // st_info
383  write(other); // st_other
384  write(Index); // st_shndx
385  write(value); // st_value
386  write(size); // st_size
387  } else {
388  write(name); // st_name
389  write(uint32_t(value)); // st_value
390  write(uint32_t(size)); // st_size
391  write(info); // st_info
392  write(other); // st_other
393  write(Index); // st_shndx
394  }
395 
396  ++NumWritten;
397 }
398 
399 bool ELFWriter::is64Bit() const {
400  return OWriter.TargetObjectWriter->is64Bit();
401 }
402 
403 bool ELFWriter::hasRelocationAddend() const {
404  return OWriter.hasRelocationAddend();
405 }
406 
407 // Emit the ELF header.
408 void ELFWriter::writeHeader(const MCAssembler &Asm) {
409  // ELF Header
410  // ----------
411  //
412  // Note
413  // ----
414  // emitWord method behaves differently for ELF32 and ELF64, writing
415  // 4 bytes in the former and 8 in the latter.
416 
417  W.OS << ELF::ElfMagic; // e_ident[EI_MAG0] to e_ident[EI_MAG3]
418 
419  W.OS << char(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
420 
421  // e_ident[EI_DATA]
422  W.OS << char(W.Endian == support::little ? ELF::ELFDATA2LSB
423  : ELF::ELFDATA2MSB);
424 
425  W.OS << char(ELF::EV_CURRENT); // e_ident[EI_VERSION]
426  // e_ident[EI_OSABI]
427  W.OS << char(OWriter.TargetObjectWriter->getOSABI());
428  // e_ident[EI_ABIVERSION]
429  W.OS << char(OWriter.TargetObjectWriter->getABIVersion());
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: Get source locations for these errors or diagnose them earlier.
1279  if (Symbol.isUndefined() && Rest.startswith("@@") &&
1280  !Rest.startswith("@@@")) {
1281  Asm.getContext().reportError(SMLoc(), "versioned symbol " + AliasName +
1282  " must be defined");
1283  continue;
1284  }
1285 
1286  if (Renames.count(&Symbol) && Renames[&Symbol] != Alias) {
1287  Asm.getContext().reportError(
1288  SMLoc(), llvm::Twine("multiple symbol versions defined for ") +
1289  Symbol.getName());
1290  continue;
1291  }
1292 
1293  Renames.insert(std::make_pair(&Symbol, Alias));
1294  }
1295 
1296  for (const MCSymbol *&Sym : AddrsigSyms) {
1297  if (const MCSymbol *R = Renames.lookup(cast<MCSymbolELF>(Sym)))
1298  Sym = R;
1299  if (Sym->isInSection() && Sym->getName().startswith(".L"))
1300  Sym = Sym->getSection().getBeginSymbol();
1301  Sym->setUsedInReloc();
1302  }
1303 }
1304 
1305 // It is always valid to create a relocation with a symbol. It is preferable
1306 // to use a relocation with a section if that is possible. Using the section
1307 // allows us to omit some local symbols from the symbol table.
1308 bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
1309  const MCSymbolRefExpr *RefA,
1310  const MCSymbolELF *Sym,
1311  uint64_t C,
1312  unsigned Type) const {
1313  // A PCRel relocation to an absolute value has no symbol (or section). We
1314  // represent that with a relocation to a null section.
1315  if (!RefA)
1316  return false;
1317 
1319  switch (Kind) {
1320  default:
1321  break;
1322  // The .odp creation emits a relocation against the symbol ".TOC." which
1323  // create a R_PPC64_TOC relocation. However the relocation symbol name
1324  // in final object creation should be NULL, since the symbol does not
1325  // really exist, it is just the reference to TOC base for the current
1326  // object file. Since the symbol is undefined, returning false results
1327  // in a relocation with a null section which is the desired result.
1329  return false;
1330 
1331  // These VariantKind cause the relocation to refer to something other than
1332  // the symbol itself, like a linker generated table. Since the address of
1333  // symbol is not relevant, we cannot replace the symbol with the
1334  // section and patch the difference in the addend.
1341  return true;
1342  }
1343 
1344  // An undefined symbol is not in any section, so the relocation has to point
1345  // to the symbol itself.
1346  assert(Sym && "Expected a symbol");
1347  if (Sym->isUndefined())
1348  return true;
1349 
1350  unsigned Binding = Sym->getBinding();
1351  switch(Binding) {
1352  default:
1353  llvm_unreachable("Invalid Binding");
1354  case ELF::STB_LOCAL:
1355  break;
1356  case ELF::STB_WEAK:
1357  // If the symbol is weak, it might be overridden by a symbol in another
1358  // file. The relocation has to point to the symbol so that the linker
1359  // can update it.
1360  return true;
1361  case ELF::STB_GLOBAL:
1362  // Global ELF symbols can be preempted by the dynamic linker. The relocation
1363  // has to point to the symbol for a reason analogous to the STB_WEAK case.
1364  return true;
1365  }
1366 
1367  // If a relocation points to a mergeable section, we have to be careful.
1368  // If the offset is zero, a relocation with the section will encode the
1369  // same information. With a non-zero offset, the situation is different.
1370  // For example, a relocation can point 42 bytes past the end of a string.
1371  // If we change such a relocation to use the section, the linker would think
1372  // that it pointed to another string and subtracting 42 at runtime will
1373  // produce the wrong value.
1374  if (Sym->isInSection()) {
1375  auto &Sec = cast<MCSectionELF>(Sym->getSection());
1376  unsigned Flags = Sec.getFlags();
1377  if (Flags & ELF::SHF_MERGE) {
1378  if (C != 0)
1379  return true;
1380 
1381  // It looks like gold has a bug (http://sourceware.org/PR16794) and can
1382  // only handle section relocations to mergeable sections if using RELA.
1383  if (!hasRelocationAddend())
1384  return true;
1385  }
1386 
1387  // Most TLS relocations use a got, so they need the symbol. Even those that
1388  // are just an offset (@tpoff), require a symbol in gold versions before
1389  // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
1390  // http://sourceware.org/PR16773.
1391  if (Flags & ELF::SHF_TLS)
1392  return true;
1393  }
1394 
1395  // If the symbol is a thumb function the final relocation must set the lowest
1396  // bit. With a symbol that is done by just having the symbol have that bit
1397  // set, so we would lose the bit if we relocated with the section.
1398  // FIXME: We could use the section but add the bit to the relocation value.
1399  if (Asm.isThumbFunc(Sym))
1400  return true;
1401 
1402  if (TargetObjectWriter->needsRelocateWithSymbol(*Sym, Type))
1403  return true;
1404  return false;
1405 }
1406 
1407 void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
1408  const MCAsmLayout &Layout,
1409  const MCFragment *Fragment,
1410  const MCFixup &Fixup, MCValue Target,
1411  uint64_t &FixedValue) {
1412  MCAsmBackend &Backend = Asm.getBackend();
1413  bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
1415  const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent());
1416  uint64_t C = Target.getConstant();
1417  uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
1418  MCContext &Ctx = Asm.getContext();
1419 
1420  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
1421  // Let A, B and C being the components of Target and R be the location of
1422  // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
1423  // If it is pcrel, we want to compute (A - B + C - R).
1424 
1425  // In general, ELF has no relocations for -B. It can only represent (A + C)
1426  // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
1427  // replace B to implement it: (A - R - K + C)
1428  if (IsPCRel) {
1429  Ctx.reportError(
1430  Fixup.getLoc(),
1431  "No relocation available to represent this relative expression");
1432  return;
1433  }
1434 
1435  const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
1436 
1437  if (SymB.isUndefined()) {
1438  Ctx.reportError(Fixup.getLoc(),
1439  Twine("symbol '") + SymB.getName() +
1440  "' can not be undefined in a subtraction expression");
1441  return;
1442  }
1443 
1444  assert(!SymB.isAbsolute() && "Should have been folded");
1445  const MCSection &SecB = SymB.getSection();
1446  if (&SecB != &FixupSection) {
1447  Ctx.reportError(Fixup.getLoc(),
1448  "Cannot represent a difference across sections");
1449  return;
1450  }
1451 
1452  uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
1453  uint64_t K = SymBOffset - FixupOffset;
1454  IsPCRel = true;
1455  C -= K;
1456  }
1457 
1458  // We either rejected the fixup or folded B into C at this point.
1459  const MCSymbolRefExpr *RefA = Target.getSymA();
1460  const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
1461 
1462  bool ViaWeakRef = false;
1463  if (SymA && SymA->isVariable()) {
1464  const MCExpr *Expr = SymA->getVariableValue();
1465  if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
1466  if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
1467  SymA = cast<MCSymbolELF>(&Inner->getSymbol());
1468  ViaWeakRef = true;
1469  }
1470  }
1471  }
1472 
1473  unsigned Type = TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
1474  uint64_t OriginalC = C;
1475  bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
1476  if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
1477  C += Layout.getSymbolOffset(*SymA);
1478 
1479  uint64_t Addend = 0;
1480  if (hasRelocationAddend()) {
1481  Addend = C;
1482  C = 0;
1483  }
1484 
1485  FixedValue = C;
1486 
1487  const MCSectionELF *SecA = (SymA && SymA->isInSection())
1488  ? cast<MCSectionELF>(&SymA->getSection())
1489  : nullptr;
1490  if (!checkRelocation(Ctx, Fixup.getLoc(), &FixupSection, SecA))
1491  return;
1492 
1493  if (!RelocateWithSymbol) {
1494  const auto *SectionSymbol =
1495  SecA ? cast<MCSymbolELF>(SecA->getBeginSymbol()) : nullptr;
1496  if (SectionSymbol)
1497  SectionSymbol->setUsedInReloc();
1498  ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA,
1499  OriginalC);
1500  Relocations[&FixupSection].push_back(Rec);
1501  return;
1502  }
1503 
1504  const auto *RenamedSymA = SymA;
1505  if (SymA) {
1506  if (const MCSymbolELF *R = Renames.lookup(SymA))
1507  RenamedSymA = R;
1508 
1509  if (ViaWeakRef)
1510  RenamedSymA->setIsWeakrefUsedInReloc();
1511  else
1512  RenamedSymA->setUsedInReloc();
1513  }
1514  ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA,
1515  OriginalC);
1516  Relocations[&FixupSection].push_back(Rec);
1517 }
1518 
1519 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
1520  const MCAssembler &Asm, const MCSymbol &SA, const MCFragment &FB,
1521  bool InSet, bool IsPCRel) const {
1522  const auto &SymA = cast<MCSymbolELF>(SA);
1523  if (IsPCRel) {
1524  assert(!InSet);
1525  if (isWeak(SymA))
1526  return false;
1527  }
1529  InSet, IsPCRel);
1530 }
1531 
1532 std::unique_ptr<MCObjectWriter>
1533 llvm::createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
1534  raw_pwrite_stream &OS, bool IsLittleEndian) {
1535  return llvm::make_unique<ELFSingleObjectWriter>(std::move(MOTW), OS,
1536  IsLittleEndian);
1537 }
1538 
1539 std::unique_ptr<MCObjectWriter>
1540 llvm::createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
1542  bool IsLittleEndian) {
1543  return llvm::make_unique<ELFDwoObjectWriter>(std::move(MOTW), OS, DwoOS,
1544  IsLittleEndian);
1545 }
const MCAsmInfo * getAsmInfo() const
Definition: MCContext.h:292
uint64_t CallInst * C
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:38
uint32_t getIndex() const
Get the (implementation defined) index.
Definition: MCSymbol.h:309
void setUsedInReloc() const
Definition: MCSymbol.h:212
void setSymbolAndType(Elf32_Word s, unsigned char t)
Definition: ELF.h:1104
SI Whole Quad Mode
LLVM_NODISCARD bool endswith(StringRef Suffix) const
Check if this string ends with the given Suffix.
Definition: StringRef.h:267
static const MCSymbolRefExpr * create(const MCSymbol *Symbol, MCContext &Ctx)
Definition: MCExpr.h:322
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:23
bool isVariable() const
isVariable - Check if this is a variable symbol.
Definition: MCSymbol.h:293
This represents an "assembler immediate".
Definition: MCValue.h:39
Elf32_Word r_info
Definition: ELF.h:1095
uint64_t getSectionAddressSize(const MCSection *Sec) const
Get the address space size of the given section, as it effects layout.
Definition: MCFragment.cpp:175
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:41
VariantKind getKind() const
Definition: MCExpr.h:337
amdgpu Simplify well known AMD library false FunctionCallee Value const Twine & Name
LLVM_NODISCARD bool startswith(StringRef Prefix) const
Check if this string starts with the given Prefix.
Definition: StringRef.h:256
unsigned getBinding() const
Definition: MCSymbolELF.cpp:66
virtual const MCFixupKindInfo & getFixupKindInfo(MCFixupKind Kind) const
Get information on a fixup kind.
void setAlignment(unsigned Value)
Definition: MCSection.h:121
Offsets
Offsets in bytes from the start of the input buffer.
Definition: SIInstrInfo.h:1026
A raw_ostream that writes to an SmallVector or SmallString.
Definition: raw_ostream.h:509
void registerSymbol(const MCSymbol &Symbol, bool *Created=nullptr)
unsigned getCommonAlignment() const
Return the alignment of a &#39;common&#39; symbol.
Definition: MCSymbol.h:358
ELFYAML::ELF_STV Visibility
Definition: ELFYAML.cpp:809
void setSymbolAndType(Elf64_Word s, Elf64_Word t)
Definition: ELF.h:1140
bool isCommon() const
Is this a &#39;common&#39; symbol.
Definition: MCSymbol.h:379
Defines the object file and target independent interfaces used by the assembler backend to write nati...
Elf64_Xword r_info
Definition: ELF.h:1131
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:73
unsigned getAlignment() const
Definition: MCSection.h:120
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:284
int64_t getConstant() const
Definition: MCValue.h:46
const MCSymbolRefExpr * getSymB() const
Definition: MCValue.h:48
Error compress(StringRef InputBuffer, SmallVectorImpl< char > &CompressedBuffer, int Level=DefaultCompression)
Definition: Compression.cpp:49
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:80
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:28
LLVM_NODISCARD 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:620
const MCSection * getAssociatedSection() const
Definition: MCSectionELF.h:86
const MCSymbolRefExpr * From
Definition: MCAssembler.h:429
support::ulittle32_t Word
Definition: IRSymtab.h:50
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
bool isInSection() const
isInSection - Check if this symbol is defined in some section (i.e., it is defined but not absolute)...
Definition: MCSymbol.h:251
The access may reference the value stored in memory.
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:165
LLVM_NODISCARD StringRef substr(size_t Start, size_t N=npos) const
Return a reference to the substring from [Start, Start + N).
Definition: StringRef.h:578
zlib-gnu style compression
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:810
DebugCompressionType compressDebugSections() const
Definition: MCAsmInfo.h:624
ArrayRef< std::string > getFileNames()
Definition: MCAssembler.h:442
Context object for machine code objects.
Definition: MCContext.h:62
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:266
Utility for building string tables with deduplicated suffixes.
bool isBindingSet() const
LLVM_NODISCARD size_t size() const
size - Get the string size.
Definition: StringRef.h:130
const MCSymbolRefExpr * To
Definition: MCAssembler.h:430
MCAssembler & getAssembler() const
Get the assembler object this is a layout for.
Definition: MCAsmLayout.h:50
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)
Analysis containing CSE Info
Definition: CSEInfo.cpp:20
void write(void *memory, value_type value, endianness endian)
Write a value to memory with a particular endianness.
Definition: Endian.h:99
#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:1082
bool evaluateKnownAbsolute(int64_t &Res, const MCAsmLayout &Layout) const
Definition: MCExpr.cpp:469
const MCSymbolELF * getGroup() const
Definition: MCSectionELF.h:75
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
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:146
#define offsetof(TYPE, MEMBER)
LLVM_NODISCARD size_t find(char C, size_t From=0) const
Search for the first character C in the string.
Definition: StringRef.h:285
void setFlags(unsigned F)
Definition: MCSectionELF.h:74
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:129
bool isTemporary() const
isTemporary - Check if this is an assembler temporary symbol.
Definition: MCSymbol.h:219
void pwrite(const char *Ptr, size_t Size, uint64_t Offset)
Definition: raw_ostream.h:347
const MCSymbolRefExpr * getSymA() const
Definition: MCValue.h:47
void reportError(SMLoc L, const Twine &Msg)
Definition: MCContext.cpp:611
uint32_t getOffset() const
Definition: MCFixup.h:124
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:254
static void write(bool isBE, void *P, T V)
void consumeError(Error Err)
Consume a Error without doing anything.
Definition: Error.h:981
bool isExternal() const
Definition: MCSymbol.h:392
size_t size() const
Definition: SmallVector.h:52
static wasm::ValType getType(const TargetRegisterClass *RC)
unsigned getEntrySize() const
Definition: MCSectionELF.h:73
#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:77
PowerPC TLS Dynamic Call Fixup
static const char *const Magic
Definition: Archive.cpp:41
MCSectionELF * createELFRelSection(const Twine &Name, unsigned Type, unsigned Flags, unsigned EntrySize, const MCSymbolELF *Group, const MCSectionELF *RelInfoSection)
Definition: MCContext.cpp:351
static const X86InstrFMA3Group Groups[]
SMLoc getLoc() const
Definition: MCFixup.h:165
static const char ElfMagic[]
Definition: ELF.h:43
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:1166
BlockVerifier::State From
void write(ArrayRef< value_type > Val)
Definition: EndianStream.h:55
bool isWeakrefUsedInReloc() const
MCAsmBackend & getBackend() const
Definition: MCAssembler.h:292
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:80
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:335
bool isUndefined(bool SetUsed=true) const
isUndefined - Check if this symbol undefined (i.e., implicitly defined).
Definition: MCSymbol.h:256
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:839
unsigned getType() const
Definition: MCSectionELF.h:71
MCSymbol * getBeginSymbol()
Definition: MCSection.h:109
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:98
static bool isWeak(const MCSymbolELF &Sym)
MCSection & getSection() const
Get the section associated with a defined, non-absolute symbol.
Definition: MCSymbol.h:266
bool isAbsolute() const
isAbsolute - Check if this is an absolute symbol.
Definition: MCSymbol.h:261
bool isUsedInReloc() const
Definition: MCSymbol.h:213
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:51
pointer data()
Return a pointer to the vector&#39;s buffer, even if empty().
Definition: SmallVector.h:144
static const size_t npos
Definition: StringRef.h:50
MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition: MCContext.cpp:122
This represents a section on linux, lots of unix variants and some bare metal systems.
Definition: MCSectionELF.h:27
uint32_t Size
Definition: Profile.cpp:46
bool isSignature() const
symbol_range symbols()
Definition: MCAssembler.h:353
MCSectionELF * createELFGroupSection(const MCSymbolELF *Group)
Definition: MCContext.cpp:415
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:202
An abstract base class for streams implementations that also support a pwrite operation.
Definition: raw_ostream.h:340
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:298
bool operator<(int64_t V1, const APSInt &V2)
Definition: APSInt.h:325
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:388
LLVM Value Representation.
Definition: Value.h:72
Generic interface to target specific assembler backends.
Definition: MCAsmBackend.h:41
static const char * name
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157
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:726
const char SectionName[]
Definition: AMDGPUPTNote.h:23
const MCSymbol * getAssociatedSymbol() const
Definition: MCSectionELF.h:87
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
const MCSymbolELF * Symbol
unsigned getFlags() const
Definition: MCSectionELF.h:72
Represents a location in source code.
Definition: SMLoc.h:23
static bool isInSymtab(const MCSymbolWasm &Sym)
std::vector< std::pair< StringRef, const MCSymbol * > > Symvers
Definition: MCAssembler.h:213
const MCSymbol * getBaseSymbol(const MCSymbol &Symbol) const
If this symbol is equivalent to A + Constant, return A.
Definition: MCFragment.cpp:139
MCFixupKind getKind() const
Definition: MCFixup.h:122
StringRef getSectionName() const
Definition: MCSectionELF.h:70
bool empty() const
empty - Check if the array is empty.
Definition: ArrayRef.h:143