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  // Target Expressions that are always inlined do not appear in the symtab
581  if (const auto *T = dyn_cast<MCTargetExpr>(Expr))
582  if (T->inlineAssignedExpr())
583  return false;
584  if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
585  if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
586  return false;
587  }
588  }
589 
590  if (Used)
591  return true;
592 
593  if (Renamed)
594  return false;
595 
596  if (Symbol.isVariable() && Symbol.isUndefined()) {
597  // FIXME: this is here just to diagnose the case of a var = commmon_sym.
598  Layout.getBaseSymbol(Symbol);
599  return false;
600  }
601 
602  if (Symbol.isUndefined() && !Symbol.isBindingSet())
603  return false;
604 
605  if (Symbol.isTemporary())
606  return false;
607 
608  if (Symbol.getType() == ELF::STT_SECTION)
609  return false;
610 
611  return true;
612 }
613 
614 void ELFWriter::computeSymbolTable(
615  MCAssembler &Asm, const MCAsmLayout &Layout,
616  const SectionIndexMapTy &SectionIndexMap, const RevGroupMapTy &RevGroupMap,
617  SectionOffsetsTy &SectionOffsets) {
618  MCContext &Ctx = Asm.getContext();
619  SymbolTableWriter Writer(*this, is64Bit());
620 
621  // Symbol table
622  unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
623  MCSectionELF *SymtabSection =
624  Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
625  SymtabSection->setAlignment(is64Bit() ? 8 : 4);
626  SymbolTableIndex = addToSectionTable(SymtabSection);
627 
628  align(SymtabSection->getAlignment());
629  uint64_t SecStart = W.OS.tell();
630 
631  // The first entry is the undefined symbol entry.
632  Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
633 
634  std::vector<ELFSymbolData> LocalSymbolData;
635  std::vector<ELFSymbolData> ExternalSymbolData;
636 
637  // Add the data for the symbols.
638  bool HasLargeSectionIndex = false;
639  for (const MCSymbol &S : Asm.symbols()) {
640  const auto &Symbol = cast<MCSymbolELF>(S);
641  bool Used = Symbol.isUsedInReloc();
642  bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
643  bool isSignature = Symbol.isSignature();
644 
645  if (!isInSymtab(Layout, Symbol, Used || WeakrefUsed || isSignature,
646  OWriter.Renames.count(&Symbol)))
647  continue;
648 
649  if (Symbol.isTemporary() && Symbol.isUndefined()) {
650  Ctx.reportError(SMLoc(), "Undefined temporary symbol");
651  continue;
652  }
653 
654  ELFSymbolData MSD;
655  MSD.Symbol = cast<MCSymbolELF>(&Symbol);
656 
657  bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
658  assert(Local || !Symbol.isTemporary());
659 
660  if (Symbol.isAbsolute()) {
661  MSD.SectionIndex = ELF::SHN_ABS;
662  } else if (Symbol.isCommon()) {
663  assert(!Local);
664  MSD.SectionIndex = ELF::SHN_COMMON;
665  } else if (Symbol.isUndefined()) {
666  if (isSignature && !Used) {
667  MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
668  if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
669  HasLargeSectionIndex = true;
670  } else {
671  MSD.SectionIndex = ELF::SHN_UNDEF;
672  }
673  } else {
674  const MCSectionELF &Section =
675  static_cast<const MCSectionELF &>(Symbol.getSection());
676 
677  // We may end up with a situation when section symbol is technically
678  // defined, but should not be. That happens because we explicitly
679  // pre-create few .debug_* sections to have accessors.
680  // And if these sections were not really defined in the code, but were
681  // referenced, we simply error out.
682  if (!Section.isRegistered()) {
683  assert(static_cast<const MCSymbolELF &>(Symbol).getType() ==
685  Ctx.reportError(SMLoc(),
686  "Undefined section reference: " + Symbol.getName());
687  continue;
688  }
689 
690  if (Mode == NonDwoOnly && isDwoSection(Section))
691  continue;
692  MSD.SectionIndex = SectionIndexMap.lookup(&Section);
693  assert(MSD.SectionIndex && "Invalid section index!");
694  if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
695  HasLargeSectionIndex = true;
696  }
697 
698  StringRef Name = Symbol.getName();
699 
700  // Sections have their own string table
701  if (Symbol.getType() != ELF::STT_SECTION) {
702  MSD.Name = Name;
703  StrTabBuilder.add(Name);
704  }
705 
706  if (Local)
707  LocalSymbolData.push_back(MSD);
708  else
709  ExternalSymbolData.push_back(MSD);
710  }
711 
712  // This holds the .symtab_shndx section index.
713  unsigned SymtabShndxSectionIndex = 0;
714 
715  if (HasLargeSectionIndex) {
716  MCSectionELF *SymtabShndxSection =
717  Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
718  SymtabShndxSectionIndex = addToSectionTable(SymtabShndxSection);
719  SymtabShndxSection->setAlignment(4);
720  }
721 
722  ArrayRef<std::string> FileNames = Asm.getFileNames();
723  for (const std::string &Name : FileNames)
724  StrTabBuilder.add(Name);
725 
726  StrTabBuilder.finalize();
727 
728  // File symbols are emitted first and handled separately from normal symbols,
729  // i.e. a non-STT_FILE symbol with the same name may appear.
730  for (const std::string &Name : FileNames)
731  Writer.writeSymbol(StrTabBuilder.getOffset(Name),
733  ELF::SHN_ABS, true);
734 
735  // Symbols are required to be in lexicographic order.
736  array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
737  array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
738 
739  // Set the symbol indices. Local symbols must come before all other
740  // symbols with non-local bindings.
741  unsigned Index = FileNames.size() + 1;
742 
743  for (ELFSymbolData &MSD : LocalSymbolData) {
744  unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
745  ? 0
746  : StrTabBuilder.getOffset(MSD.Name);
747  MSD.Symbol->setIndex(Index++);
748  writeSymbol(Writer, StringIndex, MSD, Layout);
749  }
750 
751  // Write the symbol table entries.
752  LastLocalSymbolIndex = Index;
753 
754  for (ELFSymbolData &MSD : ExternalSymbolData) {
755  unsigned StringIndex = StrTabBuilder.getOffset(MSD.Name);
756  MSD.Symbol->setIndex(Index++);
757  writeSymbol(Writer, StringIndex, MSD, Layout);
758  assert(MSD.Symbol->getBinding() != ELF::STB_LOCAL);
759  }
760 
761  uint64_t SecEnd = W.OS.tell();
762  SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
763 
764  ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
765  if (ShndxIndexes.empty()) {
766  assert(SymtabShndxSectionIndex == 0);
767  return;
768  }
769  assert(SymtabShndxSectionIndex != 0);
770 
771  SecStart = W.OS.tell();
772  const MCSectionELF *SymtabShndxSection =
773  SectionTable[SymtabShndxSectionIndex - 1];
774  for (uint32_t Index : ShndxIndexes)
775  write(Index);
776  SecEnd = W.OS.tell();
777  SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
778 }
779 
780 void ELFWriter::writeAddrsigSection() {
781  for (const MCSymbol *Sym : OWriter.AddrsigSyms)
782  encodeULEB128(Sym->getIndex(), W.OS);
783 }
784 
785 MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
786  const MCSectionELF &Sec) {
787  if (OWriter.Relocations[&Sec].empty())
788  return nullptr;
789 
790  const StringRef SectionName = Sec.getSectionName();
791  std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
792  RelaSectionName += SectionName;
793 
794  unsigned EntrySize;
795  if (hasRelocationAddend())
796  EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
797  else
798  EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
799 
800  unsigned Flags = 0;
801  if (Sec.getFlags() & ELF::SHF_GROUP)
802  Flags = ELF::SHF_GROUP;
803 
804  MCSectionELF *RelaSection = Ctx.createELFRelSection(
805  RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
806  Flags, EntrySize, Sec.getGroup(), &Sec);
807  RelaSection->setAlignment(is64Bit() ? 8 : 4);
808  return RelaSection;
809 }
810 
811 // Include the debug info compression header.
812 bool ELFWriter::maybeWriteCompression(
813  uint64_t Size, SmallVectorImpl<char> &CompressedContents, bool ZLibStyle,
814  unsigned Alignment) {
815  if (ZLibStyle) {
816  uint64_t HdrSize =
817  is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
818  if (Size <= HdrSize + CompressedContents.size())
819  return false;
820  // Platform specific header is followed by compressed data.
821  if (is64Bit()) {
822  // Write Elf64_Chdr header.
823  write(static_cast<ELF::Elf64_Word>(ELF::ELFCOMPRESS_ZLIB));
824  write(static_cast<ELF::Elf64_Word>(0)); // ch_reserved field.
825  write(static_cast<ELF::Elf64_Xword>(Size));
826  write(static_cast<ELF::Elf64_Xword>(Alignment));
827  } else {
828  // Write Elf32_Chdr header otherwise.
829  write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
830  write(static_cast<ELF::Elf32_Word>(Size));
831  write(static_cast<ELF::Elf32_Word>(Alignment));
832  }
833  return true;
834  }
835 
836  // "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
837  // useful for consumers to preallocate a buffer to decompress into.
838  const StringRef Magic = "ZLIB";
839  if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
840  return false;
841  W.OS << Magic;
843  return true;
844 }
845 
846 void ELFWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
847  const MCAsmLayout &Layout) {
848  MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
850 
851  auto &MC = Asm.getContext();
852  const auto &MAI = MC.getAsmInfo();
853 
854  // Compressing debug_frame requires handling alignment fragments which is
855  // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
856  // for writing to arbitrary buffers) for little benefit.
857  bool CompressionEnabled =
859  if (!CompressionEnabled || !SectionName.startswith(".debug_") ||
860  SectionName == ".debug_frame") {
861  Asm.writeSectionData(W.OS, &Section, Layout);
862  return;
863  }
864 
865  assert((MAI->compressDebugSections() == DebugCompressionType::Z ||
866  MAI->compressDebugSections() == DebugCompressionType::GNU) &&
867  "expected zlib or zlib-gnu style compression");
868 
869  SmallVector<char, 128> UncompressedData;
870  raw_svector_ostream VecOS(UncompressedData);
871  Asm.writeSectionData(VecOS, &Section, Layout);
872 
873  SmallVector<char, 128> CompressedContents;
874  if (Error E = zlib::compress(
875  StringRef(UncompressedData.data(), UncompressedData.size()),
876  CompressedContents)) {
877  consumeError(std::move(E));
878  W.OS << UncompressedData;
879  return;
880  }
881 
882  bool ZlibStyle = MAI->compressDebugSections() == DebugCompressionType::Z;
883  if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
884  ZlibStyle, Sec.getAlignment())) {
885  W.OS << UncompressedData;
886  return;
887  }
888 
889  if (ZlibStyle)
890  // Set the compressed flag. That is zlib style.
891  Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
892  else
893  // Add "z" prefix to section name. This is zlib-gnu style.
894  MC.renameELFSection(&Section, (".z" + SectionName.drop_front(1)).str());
895  W.OS << CompressedContents;
896 }
897 
898 void ELFWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
899  uint64_t Address, uint64_t Offset,
900  uint64_t Size, uint32_t Link, uint32_t Info,
901  uint64_t Alignment, uint64_t EntrySize) {
902  W.write<uint32_t>(Name); // sh_name: index into string table
903  W.write<uint32_t>(Type); // sh_type
904  WriteWord(Flags); // sh_flags
905  WriteWord(Address); // sh_addr
906  WriteWord(Offset); // sh_offset
907  WriteWord(Size); // sh_size
908  W.write<uint32_t>(Link); // sh_link
909  W.write<uint32_t>(Info); // sh_info
910  WriteWord(Alignment); // sh_addralign
911  WriteWord(EntrySize); // sh_entsize
912 }
913 
914 void ELFWriter::writeRelocations(const MCAssembler &Asm,
915  const MCSectionELF &Sec) {
916  std::vector<ELFRelocationEntry> &Relocs = OWriter.Relocations[&Sec];
917 
918  // We record relocations by pushing to the end of a vector. Reverse the vector
919  // to get the relocations in the order they were created.
920  // In most cases that is not important, but it can be for special sections
921  // (.eh_frame) or specific relocations (TLS optimizations on SystemZ).
922  std::reverse(Relocs.begin(), Relocs.end());
923 
924  // Sort the relocation entries. MIPS needs this.
925  OWriter.TargetObjectWriter->sortRelocs(Asm, Relocs);
926 
927  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
928  const ELFRelocationEntry &Entry = Relocs[e - i - 1];
929  unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
930 
931  if (is64Bit()) {
932  write(Entry.Offset);
933  if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
934  write(uint32_t(Index));
935 
936  write(OWriter.TargetObjectWriter->getRSsym(Entry.Type));
937  write(OWriter.TargetObjectWriter->getRType3(Entry.Type));
938  write(OWriter.TargetObjectWriter->getRType2(Entry.Type));
939  write(OWriter.TargetObjectWriter->getRType(Entry.Type));
940  } else {
941  struct ELF::Elf64_Rela ERE64;
942  ERE64.setSymbolAndType(Index, Entry.Type);
943  write(ERE64.r_info);
944  }
945  if (hasRelocationAddend())
946  write(Entry.Addend);
947  } else {
948  write(uint32_t(Entry.Offset));
949 
950  struct ELF::Elf32_Rela ERE32;
951  ERE32.setSymbolAndType(Index, Entry.Type);
952  write(ERE32.r_info);
953 
954  if (hasRelocationAddend())
955  write(uint32_t(Entry.Addend));
956 
957  if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
958  if (uint32_t RType =
959  OWriter.TargetObjectWriter->getRType2(Entry.Type)) {
960  write(uint32_t(Entry.Offset));
961 
962  ERE32.setSymbolAndType(0, RType);
963  write(ERE32.r_info);
964  write(uint32_t(0));
965  }
966  if (uint32_t RType =
967  OWriter.TargetObjectWriter->getRType3(Entry.Type)) {
968  write(uint32_t(Entry.Offset));
969 
970  ERE32.setSymbolAndType(0, RType);
971  write(ERE32.r_info);
972  write(uint32_t(0));
973  }
974  }
975  }
976  }
977 }
978 
979 const MCSectionELF *ELFWriter::createStringTable(MCContext &Ctx) {
980  const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
981  StrTabBuilder.write(W.OS);
982  return StrtabSection;
983 }
984 
985 void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
986  uint32_t GroupSymbolIndex, uint64_t Offset,
987  uint64_t Size, const MCSectionELF &Section) {
988  uint64_t sh_link = 0;
989  uint64_t sh_info = 0;
990 
991  switch(Section.getType()) {
992  default:
993  // Nothing to do.
994  break;
995 
996  case ELF::SHT_DYNAMIC:
997  llvm_unreachable("SHT_DYNAMIC in a relocatable object");
998 
999  case ELF::SHT_REL:
1000  case ELF::SHT_RELA: {
1001  sh_link = SymbolTableIndex;
1002  assert(sh_link && ".symtab not found");
1003  const MCSection *InfoSection = Section.getAssociatedSection();
1004  sh_info = SectionIndexMap.lookup(cast<MCSectionELF>(InfoSection));
1005  break;
1006  }
1007 
1008  case ELF::SHT_SYMTAB:
1009  sh_link = StringTableIndex;
1010  sh_info = LastLocalSymbolIndex;
1011  break;
1012 
1013  case ELF::SHT_SYMTAB_SHNDX:
1015  case ELF::SHT_LLVM_ADDRSIG:
1016  sh_link = SymbolTableIndex;
1017  break;
1018 
1019  case ELF::SHT_GROUP:
1020  sh_link = SymbolTableIndex;
1021  sh_info = GroupSymbolIndex;
1022  break;
1023  }
1024 
1025  if (Section.getFlags() & ELF::SHF_LINK_ORDER) {
1026  const MCSymbol *Sym = Section.getAssociatedSymbol();
1027  const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
1028  sh_link = SectionIndexMap.lookup(Sec);
1029  }
1030 
1031  WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
1032  Section.getType(), Section.getFlags(), 0, Offset, Size,
1033  sh_link, sh_info, Section.getAlignment(),
1034  Section.getEntrySize());
1035 }
1036 
1037 void ELFWriter::writeSectionHeader(
1038  const MCAsmLayout &Layout, const SectionIndexMapTy &SectionIndexMap,
1039  const SectionOffsetsTy &SectionOffsets) {
1040  const unsigned NumSections = SectionTable.size();
1041 
1042  // Null section first.
1043  uint64_t FirstSectionSize =
1044  (NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
1045  WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
1046 
1047  for (const MCSectionELF *Section : SectionTable) {
1048  uint32_t GroupSymbolIndex;
1049  unsigned Type = Section->getType();
1050  if (Type != ELF::SHT_GROUP)
1051  GroupSymbolIndex = 0;
1052  else
1053  GroupSymbolIndex = Section->getGroup()->getIndex();
1054 
1055  const std::pair<uint64_t, uint64_t> &Offsets =
1056  SectionOffsets.find(Section)->second;
1057  uint64_t Size;
1058  if (Type == ELF::SHT_NOBITS)
1059  Size = Layout.getSectionAddressSize(Section);
1060  else
1061  Size = Offsets.second - Offsets.first;
1062 
1063  writeSection(SectionIndexMap, GroupSymbolIndex, Offsets.first, Size,
1064  *Section);
1065  }
1066 }
1067 
1068 uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
1069  uint64_t StartOffset = W.OS.tell();
1070 
1071  MCContext &Ctx = Asm.getContext();
1072  MCSectionELF *StrtabSection =
1073  Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
1074  StringTableIndex = addToSectionTable(StrtabSection);
1075 
1076  RevGroupMapTy RevGroupMap;
1077  SectionIndexMapTy SectionIndexMap;
1078 
1079  std::map<const MCSymbol *, std::vector<const MCSectionELF *>> GroupMembers;
1080 
1081  // Write out the ELF header ...
1082  writeHeader(Asm);
1083 
1084  // ... then the sections ...
1085  SectionOffsetsTy SectionOffsets;
1086  std::vector<MCSectionELF *> Groups;
1087  std::vector<MCSectionELF *> Relocations;
1088  for (MCSection &Sec : Asm) {
1089  MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
1090  if (Mode == NonDwoOnly && isDwoSection(Section))
1091  continue;
1092  if (Mode == DwoOnly && !isDwoSection(Section))
1093  continue;
1094 
1095  align(Section.getAlignment());
1096 
1097  // Remember the offset into the file for this section.
1098  uint64_t SecStart = W.OS.tell();
1099 
1100  const MCSymbolELF *SignatureSymbol = Section.getGroup();
1101  writeSectionData(Asm, Section, Layout);
1102 
1103  uint64_t SecEnd = W.OS.tell();
1104  SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
1105 
1106  MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
1107 
1108  if (SignatureSymbol) {
1109  Asm.registerSymbol(*SignatureSymbol);
1110  unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
1111  if (!GroupIdx) {
1112  MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
1113  GroupIdx = addToSectionTable(Group);
1114  Group->setAlignment(4);
1115  Groups.push_back(Group);
1116  }
1117  std::vector<const MCSectionELF *> &Members =
1118  GroupMembers[SignatureSymbol];
1119  Members.push_back(&Section);
1120  if (RelSection)
1121  Members.push_back(RelSection);
1122  }
1123 
1124  SectionIndexMap[&Section] = addToSectionTable(&Section);
1125  if (RelSection) {
1126  SectionIndexMap[RelSection] = addToSectionTable(RelSection);
1127  Relocations.push_back(RelSection);
1128  }
1129 
1130  OWriter.TargetObjectWriter->addTargetSectionFlags(Ctx, Section);
1131  }
1132 
1133  MCSectionELF *CGProfileSection = nullptr;
1134  if (!Asm.CGProfile.empty()) {
1135  CGProfileSection = Ctx.getELFSection(".llvm.call-graph-profile",
1137  ELF::SHF_EXCLUDE, 16, "");
1138  SectionIndexMap[CGProfileSection] = addToSectionTable(CGProfileSection);
1139  }
1140 
1141  for (MCSectionELF *Group : Groups) {
1142  align(Group->getAlignment());
1143 
1144  // Remember the offset into the file for this section.
1145  uint64_t SecStart = W.OS.tell();
1146 
1147  const MCSymbol *SignatureSymbol = Group->getGroup();
1148  assert(SignatureSymbol);
1150  for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
1151  uint32_t SecIndex = SectionIndexMap.lookup(Member);
1152  write(SecIndex);
1153  }
1154 
1155  uint64_t SecEnd = W.OS.tell();
1156  SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
1157  }
1158 
1159  if (Mode == DwoOnly) {
1160  // dwo files don't have symbol tables or relocations, but they do have
1161  // string tables.
1162  StrTabBuilder.finalize();
1163  } else {
1164  MCSectionELF *AddrsigSection;
1165  if (OWriter.EmitAddrsigSection) {
1166  AddrsigSection = Ctx.getELFSection(".llvm_addrsig", ELF::SHT_LLVM_ADDRSIG,
1168  addToSectionTable(AddrsigSection);
1169  }
1170 
1171  // Compute symbol table information.
1172  computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
1173  SectionOffsets);
1174 
1175  for (MCSectionELF *RelSection : Relocations) {
1176  align(RelSection->getAlignment());
1177 
1178  // Remember the offset into the file for this section.
1179  uint64_t SecStart = W.OS.tell();
1180 
1181  writeRelocations(Asm,
1182  cast<MCSectionELF>(*RelSection->getAssociatedSection()));
1183 
1184  uint64_t SecEnd = W.OS.tell();
1185  SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
1186  }
1187 
1188  if (OWriter.EmitAddrsigSection) {
1189  uint64_t SecStart = W.OS.tell();
1190  writeAddrsigSection();
1191  uint64_t SecEnd = W.OS.tell();
1192  SectionOffsets[AddrsigSection] = std::make_pair(SecStart, SecEnd);
1193  }
1194  }
1195 
1196  if (CGProfileSection) {
1197  uint64_t SecStart = W.OS.tell();
1198  for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
1199  W.write<uint32_t>(CGPE.From->getSymbol().getIndex());
1200  W.write<uint32_t>(CGPE.To->getSymbol().getIndex());
1201  W.write<uint64_t>(CGPE.Count);
1202  }
1203  uint64_t SecEnd = W.OS.tell();
1204  SectionOffsets[CGProfileSection] = std::make_pair(SecStart, SecEnd);
1205  }
1206 
1207  {
1208  uint64_t SecStart = W.OS.tell();
1209  const MCSectionELF *Sec = createStringTable(Ctx);
1210  uint64_t SecEnd = W.OS.tell();
1211  SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
1212  }
1213 
1214  uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1215  align(NaturalAlignment);
1216 
1217  const uint64_t SectionHeaderOffset = W.OS.tell();
1218 
1219  // ... then the section header table ...
1220  writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
1221 
1222  uint16_t NumSections = support::endian::byte_swap<uint16_t>(
1223  (SectionTable.size() + 1 >= ELF::SHN_LORESERVE) ? (uint16_t)ELF::SHN_UNDEF
1224  : SectionTable.size() + 1,
1225  W.Endian);
1226  unsigned NumSectionsOffset;
1227 
1228  auto &Stream = static_cast<raw_pwrite_stream &>(W.OS);
1229  if (is64Bit()) {
1230  uint64_t Val =
1231  support::endian::byte_swap<uint64_t>(SectionHeaderOffset, W.Endian);
1232  Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
1233  offsetof(ELF::Elf64_Ehdr, e_shoff));
1234  NumSectionsOffset = offsetof(ELF::Elf64_Ehdr, e_shnum);
1235  } else {
1236  uint32_t Val =
1237  support::endian::byte_swap<uint32_t>(SectionHeaderOffset, W.Endian);
1238  Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
1239  offsetof(ELF::Elf32_Ehdr, e_shoff));
1240  NumSectionsOffset = offsetof(ELF::Elf32_Ehdr, e_shnum);
1241  }
1242  Stream.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
1243  NumSectionsOffset);
1244 
1245  return W.OS.tell() - StartOffset;
1246 }
1247 
1248 bool ELFObjectWriter::hasRelocationAddend() const {
1249  return TargetObjectWriter->hasRelocationAddend();
1250 }
1251 
1252 void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
1253  const MCAsmLayout &Layout) {
1254  // The presence of symbol versions causes undefined symbols and
1255  // versions declared with @@@ to be renamed.
1256  for (const std::pair<StringRef, const MCSymbol *> &P : Asm.Symvers) {
1257  StringRef AliasName = P.first;
1258  const auto &Symbol = cast<MCSymbolELF>(*P.second);
1259  size_t Pos = AliasName.find('@');
1260  assert(Pos != StringRef::npos);
1261 
1262  StringRef Prefix = AliasName.substr(0, Pos);
1263  StringRef Rest = AliasName.substr(Pos);
1264  StringRef Tail = Rest;
1265  if (Rest.startswith("@@@"))
1266  Tail = Rest.substr(Symbol.isUndefined() ? 2 : 1);
1267 
1268  auto *Alias =
1269  cast<MCSymbolELF>(Asm.getContext().getOrCreateSymbol(Prefix + Tail));
1270  Asm.registerSymbol(*Alias);
1271  const MCExpr *Value = MCSymbolRefExpr::create(&Symbol, Asm.getContext());
1272  Alias->setVariableValue(Value);
1273 
1274  // Aliases defined with .symvar copy the binding from the symbol they alias.
1275  // This is the first place we are able to copy this information.
1276  Alias->setExternal(Symbol.isExternal());
1277  Alias->setBinding(Symbol.getBinding());
1278 
1279  if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
1280  continue;
1281 
1282  // FIXME: Get source locations for these errors or diagnose them earlier.
1283  if (Symbol.isUndefined() && Rest.startswith("@@") &&
1284  !Rest.startswith("@@@")) {
1285  Asm.getContext().reportError(SMLoc(), "versioned symbol " + AliasName +
1286  " must be defined");
1287  continue;
1288  }
1289 
1290  if (Renames.count(&Symbol) && Renames[&Symbol] != Alias) {
1291  Asm.getContext().reportError(
1292  SMLoc(), llvm::Twine("multiple symbol versions defined for ") +
1293  Symbol.getName());
1294  continue;
1295  }
1296 
1297  Renames.insert(std::make_pair(&Symbol, Alias));
1298  }
1299 
1300  for (const MCSymbol *&Sym : AddrsigSyms) {
1301  if (const MCSymbol *R = Renames.lookup(cast<MCSymbolELF>(Sym)))
1302  Sym = R;
1303  if (Sym->isInSection() && Sym->getName().startswith(".L"))
1304  Sym = Sym->getSection().getBeginSymbol();
1305  Sym->setUsedInReloc();
1306  }
1307 }
1308 
1309 // It is always valid to create a relocation with a symbol. It is preferable
1310 // to use a relocation with a section if that is possible. Using the section
1311 // allows us to omit some local symbols from the symbol table.
1312 bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
1313  const MCSymbolRefExpr *RefA,
1314  const MCSymbolELF *Sym,
1315  uint64_t C,
1316  unsigned Type) const {
1317  // A PCRel relocation to an absolute value has no symbol (or section). We
1318  // represent that with a relocation to a null section.
1319  if (!RefA)
1320  return false;
1321 
1323  switch (Kind) {
1324  default:
1325  break;
1326  // The .odp creation emits a relocation against the symbol ".TOC." which
1327  // create a R_PPC64_TOC relocation. However the relocation symbol name
1328  // in final object creation should be NULL, since the symbol does not
1329  // really exist, it is just the reference to TOC base for the current
1330  // object file. Since the symbol is undefined, returning false results
1331  // in a relocation with a null section which is the desired result.
1333  return false;
1334 
1335  // These VariantKind cause the relocation to refer to something other than
1336  // the symbol itself, like a linker generated table. Since the address of
1337  // symbol is not relevant, we cannot replace the symbol with the
1338  // section and patch the difference in the addend.
1345  return true;
1346  }
1347 
1348  // An undefined symbol is not in any section, so the relocation has to point
1349  // to the symbol itself.
1350  assert(Sym && "Expected a symbol");
1351  if (Sym->isUndefined())
1352  return true;
1353 
1354  unsigned Binding = Sym->getBinding();
1355  switch(Binding) {
1356  default:
1357  llvm_unreachable("Invalid Binding");
1358  case ELF::STB_LOCAL:
1359  break;
1360  case ELF::STB_WEAK:
1361  // If the symbol is weak, it might be overridden by a symbol in another
1362  // file. The relocation has to point to the symbol so that the linker
1363  // can update it.
1364  return true;
1365  case ELF::STB_GLOBAL:
1366  // Global ELF symbols can be preempted by the dynamic linker. The relocation
1367  // has to point to the symbol for a reason analogous to the STB_WEAK case.
1368  return true;
1369  }
1370 
1371  // If a relocation points to a mergeable section, we have to be careful.
1372  // If the offset is zero, a relocation with the section will encode the
1373  // same information. With a non-zero offset, the situation is different.
1374  // For example, a relocation can point 42 bytes past the end of a string.
1375  // If we change such a relocation to use the section, the linker would think
1376  // that it pointed to another string and subtracting 42 at runtime will
1377  // produce the wrong value.
1378  if (Sym->isInSection()) {
1379  auto &Sec = cast<MCSectionELF>(Sym->getSection());
1380  unsigned Flags = Sec.getFlags();
1381  if (Flags & ELF::SHF_MERGE) {
1382  if (C != 0)
1383  return true;
1384 
1385  // It looks like gold has a bug (http://sourceware.org/PR16794) and can
1386  // only handle section relocations to mergeable sections if using RELA.
1387  if (!hasRelocationAddend())
1388  return true;
1389  }
1390 
1391  // Most TLS relocations use a got, so they need the symbol. Even those that
1392  // are just an offset (@tpoff), require a symbol in gold versions before
1393  // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
1394  // http://sourceware.org/PR16773.
1395  if (Flags & ELF::SHF_TLS)
1396  return true;
1397  }
1398 
1399  // If the symbol is a thumb function the final relocation must set the lowest
1400  // bit. With a symbol that is done by just having the symbol have that bit
1401  // set, so we would lose the bit if we relocated with the section.
1402  // FIXME: We could use the section but add the bit to the relocation value.
1403  if (Asm.isThumbFunc(Sym))
1404  return true;
1405 
1406  if (TargetObjectWriter->needsRelocateWithSymbol(*Sym, Type))
1407  return true;
1408  return false;
1409 }
1410 
1411 void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
1412  const MCAsmLayout &Layout,
1413  const MCFragment *Fragment,
1414  const MCFixup &Fixup, MCValue Target,
1415  uint64_t &FixedValue) {
1416  MCAsmBackend &Backend = Asm.getBackend();
1417  bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
1419  const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent());
1420  uint64_t C = Target.getConstant();
1421  uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
1422  MCContext &Ctx = Asm.getContext();
1423 
1424  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
1425  // Let A, B and C being the components of Target and R be the location of
1426  // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
1427  // If it is pcrel, we want to compute (A - B + C - R).
1428 
1429  // In general, ELF has no relocations for -B. It can only represent (A + C)
1430  // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
1431  // replace B to implement it: (A - R - K + C)
1432  if (IsPCRel) {
1433  Ctx.reportError(
1434  Fixup.getLoc(),
1435  "No relocation available to represent this relative expression");
1436  return;
1437  }
1438 
1439  const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
1440 
1441  if (SymB.isUndefined()) {
1442  Ctx.reportError(Fixup.getLoc(),
1443  Twine("symbol '") + SymB.getName() +
1444  "' can not be undefined in a subtraction expression");
1445  return;
1446  }
1447 
1448  assert(!SymB.isAbsolute() && "Should have been folded");
1449  const MCSection &SecB = SymB.getSection();
1450  if (&SecB != &FixupSection) {
1451  Ctx.reportError(Fixup.getLoc(),
1452  "Cannot represent a difference across sections");
1453  return;
1454  }
1455 
1456  uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
1457  uint64_t K = SymBOffset - FixupOffset;
1458  IsPCRel = true;
1459  C -= K;
1460  }
1461 
1462  // We either rejected the fixup or folded B into C at this point.
1463  const MCSymbolRefExpr *RefA = Target.getSymA();
1464  const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
1465 
1466  bool ViaWeakRef = false;
1467  if (SymA && SymA->isVariable()) {
1468  const MCExpr *Expr = SymA->getVariableValue();
1469  if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
1470  if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
1471  SymA = cast<MCSymbolELF>(&Inner->getSymbol());
1472  ViaWeakRef = true;
1473  }
1474  }
1475  }
1476 
1477  unsigned Type = TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
1478  uint64_t OriginalC = C;
1479  bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
1480  if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
1481  C += Layout.getSymbolOffset(*SymA);
1482 
1483  uint64_t Addend = 0;
1484  if (hasRelocationAddend()) {
1485  Addend = C;
1486  C = 0;
1487  }
1488 
1489  FixedValue = C;
1490 
1491  const MCSectionELF *SecA = (SymA && SymA->isInSection())
1492  ? cast<MCSectionELF>(&SymA->getSection())
1493  : nullptr;
1494  if (!checkRelocation(Ctx, Fixup.getLoc(), &FixupSection, SecA))
1495  return;
1496 
1497  if (!RelocateWithSymbol) {
1498  const auto *SectionSymbol =
1499  SecA ? cast<MCSymbolELF>(SecA->getBeginSymbol()) : nullptr;
1500  if (SectionSymbol)
1501  SectionSymbol->setUsedInReloc();
1502  ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA,
1503  OriginalC);
1504  Relocations[&FixupSection].push_back(Rec);
1505  return;
1506  }
1507 
1508  const auto *RenamedSymA = SymA;
1509  if (SymA) {
1510  if (const MCSymbolELF *R = Renames.lookup(SymA))
1511  RenamedSymA = R;
1512 
1513  if (ViaWeakRef)
1514  RenamedSymA->setIsWeakrefUsedInReloc();
1515  else
1516  RenamedSymA->setUsedInReloc();
1517  }
1518  ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA,
1519  OriginalC);
1520  Relocations[&FixupSection].push_back(Rec);
1521 }
1522 
1523 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
1524  const MCAssembler &Asm, const MCSymbol &SA, const MCFragment &FB,
1525  bool InSet, bool IsPCRel) const {
1526  const auto &SymA = cast<MCSymbolELF>(SA);
1527  if (IsPCRel) {
1528  assert(!InSet);
1529  if (isWeak(SymA))
1530  return false;
1531  }
1533  InSet, IsPCRel);
1534 }
1535 
1536 std::unique_ptr<MCObjectWriter>
1537 llvm::createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
1538  raw_pwrite_stream &OS, bool IsLittleEndian) {
1539  return llvm::make_unique<ELFSingleObjectWriter>(std::move(MOTW), OS,
1540  IsLittleEndian);
1541 }
1542 
1543 std::unique_ptr<MCObjectWriter>
1544 llvm::createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
1546  bool IsLittleEndian) {
1547  return llvm::make_unique<ELFDwoObjectWriter>(std::move(MOTW), OS, DwoOS,
1548  IsLittleEndian);
1549 }
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:321
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:336
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:1034
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:848
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 style complession
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:849
DebugCompressionType compressDebugSections() const
Definition: MCAsmInfo.h:622
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:467
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:641
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:355
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
zlib-gnu style compression
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:334
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:841
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:123
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:419
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
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