1//===- ELF.h - ELF object file implementation -------------------*- C++ -*-===//
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 declares the ELFFile template class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_OBJECT_ELF_H
14#define LLVM_OBJECT_ELF_H
15
16#include "llvm/ADT/ArrayRef.h"
17#include "llvm/ADT/SmallVector.h"
18#include "llvm/ADT/StringRef.h"
19#include "llvm/BinaryFormat/ELF.h"
20#include "llvm/Object/ELFTypes.h"
21#include "llvm/Object/Error.h"
22#include "llvm/Support/Endian.h"
23#include "llvm/Support/Error.h"
24#include <cassert>
25#include <cstddef>
26#include <cstdint>
27#include <limits>
28#include <utility>
29
30namespace llvm {
31namespace object {
32
33StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type);
34uint32_t getELFRelativeRelocationType(uint32_t Machine);
35StringRef getELFSectionTypeName(uint32_t Machine, uint32_t Type);
36
37// Subclasses of ELFFile may need this for template instantiation
38inline std::pair<unsigned char, unsigned char>
39getElfArchType(StringRef Object) {
40  if (Object.size() < ELF::EI_NIDENT)
41    return std::make_pair((uint8_t)ELF::ELFCLASSNONE,
42                          (uint8_t)ELF::ELFDATANONE);
43  return std::make_pair((uint8_t)Object[ELF::EI_CLASS],
44                        (uint8_t)Object[ELF::EI_DATA]);
45}
46
47static inline Error createError(const Twine &Err) {
48  return make_error<StringError>(Err, object_error::parse_failed);
49}
50
51template <class ELFT> class ELFFile;
52
53template <class ELFT>
54std::string getSecIndexForError(const ELFFile<ELFT> *Obj,
55                                const typename ELFT::Shdr *Sec) {
56  auto TableOrErr = Obj->sections();
57  if (TableOrErr)
58    return "[index " + std::to_string(Sec - &TableOrErr->front()) + "]";
59  // To make this helper be more convenient for error reporting purposes we
60  // drop the error. But really it should never be triggered. Before this point,
61  // our code should have called 'sections()' and reported a proper error on
62  // failure.
63  llvm::consumeError(TableOrErr.takeError());
64  return "[unknown index]";
65}
66
67static inline Error defaultWarningHandler(const Twine &Msg) {
68  return createError(Msg);
69}
70
71template <class ELFT>
72class ELFFile {
73public:
74  LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
75  using uintX_t = typename ELFT::uint;
76  using Elf_Ehdr = typename ELFT::Ehdr;
77  using Elf_Shdr = typename ELFT::Shdr;
78  using Elf_Sym = typename ELFT::Sym;
79  using Elf_Dyn = typename ELFT::Dyn;
80  using Elf_Phdr = typename ELFT::Phdr;
81  using Elf_Rel = typename ELFT::Rel;
82  using Elf_Rela = typename ELFT::Rela;
83  using Elf_Relr = typename ELFT::Relr;
84  using Elf_Verdef = typename ELFT::Verdef;
85  using Elf_Verdaux = typename ELFT::Verdaux;
86  using Elf_Verneed = typename ELFT::Verneed;
87  using Elf_Vernaux = typename ELFT::Vernaux;
88  using Elf_Versym = typename ELFT::Versym;
89  using Elf_Hash = typename ELFT::Hash;
90  using Elf_GnuHash = typename ELFT::GnuHash;
91  using Elf_Nhdr = typename ELFT::Nhdr;
92  using Elf_Note = typename ELFT::Note;
93  using Elf_Note_Iterator = typename ELFT::NoteIterator;
94  using Elf_Dyn_Range = typename ELFT::DynRange;
95  using Elf_Shdr_Range = typename ELFT::ShdrRange;
96  using Elf_Sym_Range = typename ELFT::SymRange;
97  using Elf_Rel_Range = typename ELFT::RelRange;
98  using Elf_Rela_Range = typename ELFT::RelaRange;
99  using Elf_Relr_Range = typename ELFT::RelrRange;
100  using Elf_Phdr_Range = typename ELFT::PhdrRange;
101
102  // This is a callback that can be passed to a number of functions.
103  // It can be used to ignore non-critical errors (warnings), which is
104  // useful for dumpers, like llvm-readobj.
105  // It accepts a warning message string and returns a success
106  // when the warning should be ignored or an error otherwise.
107  using WarningHandler = llvm::function_ref<Error(const Twine &Msg)>;
108
109  const uint8_t *base() const { return Buf.bytes_begin(); }
110
111  size_t getBufSize() const { return Buf.size(); }
112
113private:
114  StringRef Buf;
115
116  ELFFile(StringRef Object);
117
118public:
119  const Elf_Ehdr *getHeader() const {
120    return reinterpret_cast<const Elf_Ehdr *>(base());
121  }
122
123  template <typename T>
124  Expected<const T *> getEntry(uint32_t Section, uint32_t Entry) const;
125  template <typename T>
126  Expected<const T *> getEntry(const Elf_Shdr *Section, uint32_t Entry) const;
127
128  Expected<StringRef>
129  getStringTable(const Elf_Shdr *Section,
130                 WarningHandler WarnHandler = &defaultWarningHandler) const;
131  Expected<StringRef> getStringTableForSymtab(const Elf_Shdr &Section) const;
132  Expected<StringRef> getStringTableForSymtab(const Elf_Shdr &Section,
133                                              Elf_Shdr_Range Sections) const;
134
135  Expected<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section) const;
136  Expected<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section,
137                                             Elf_Shdr_Range Sections) const;
138
139  StringRef getRelocationTypeName(uint32_t Type) const;
140  void getRelocationTypeName(uint32_t Type,
141                             SmallVectorImpl<char> &Result) const;
142  uint32_t getRelativeRelocationType() const;
143
144  std::string getDynamicTagAsString(unsigned Arch, uint64_t Type) const;
145  std::string getDynamicTagAsString(uint64_t Type) const;
146
147  /// Get the symbol for a given relocation.
148  Expected<const Elf_Sym *> getRelocationSymbol(const Elf_Rel *Rel,
149                                                const Elf_Shdr *SymTab) const;
150
151  static Expected<ELFFile> create(StringRef Object);
152
153  bool isLE() const {
154    return getHeader()->getDataEncoding() == ELF::ELFDATA2LSB;
155  }
156
157  bool isMipsELF64() const {
158    return getHeader()->e_machine == ELF::EM_MIPS &&
159           getHeader()->getFileClass() == ELF::ELFCLASS64;
160  }
161
162  bool isMips64EL() const { return isMipsELF64() && isLE(); }
163
164  Expected<Elf_Shdr_Range> sections() const;
165
166  Expected<Elf_Dyn_Range> dynamicEntries() const;
167
168  Expected<const uint8_t *> toMappedAddr(uint64_t VAddr) const;
169
170  Expected<Elf_Sym_Range> symbols(const Elf_Shdr *Sec) const {
171    if (!Sec)
172      return makeArrayRef<Elf_Sym>(nullptr, nullptr);
173    return getSectionContentsAsArray<Elf_Sym>(Sec);
174  }
175
176  Expected<Elf_Rela_Range> relas(const Elf_Shdr *Sec) const {
177    return getSectionContentsAsArray<Elf_Rela>(Sec);
178  }
179
180  Expected<Elf_Rel_Range> rels(const Elf_Shdr *Sec) const {
181    return getSectionContentsAsArray<Elf_Rel>(Sec);
182  }
183
184  Expected<Elf_Relr_Range> relrs(const Elf_Shdr *Sec) const {
185    return getSectionContentsAsArray<Elf_Relr>(Sec);
186  }
187
188  Expected<std::vector<Elf_Rela>> decode_relrs(Elf_Relr_Range relrs) const;
189
190  Expected<std::vector<Elf_Rela>> android_relas(const Elf_Shdr *Sec) const;
191
192  /// Iterate over program header table.
193  Expected<Elf_Phdr_Range> program_headers() const {
194    if (getHeader()->e_phnum && getHeader()->e_phentsize != sizeof(Elf_Phdr))
195      return createError("invalid e_phentsize: " +
196                         Twine(getHeader()->e_phentsize));
197    if (getHeader()->e_phoff +
198            (getHeader()->e_phnum * getHeader()->e_phentsize) >
199        getBufSize())
200      return createError("program headers are longer than binary of size " +
201                         Twine(getBufSize()) + ": e_phoff = 0x" +
202                         Twine::utohexstr(getHeader()->e_phoff) +
203                         ", e_phnum = " + Twine(getHeader()->e_phnum) +
204                         ", e_phentsize = " + Twine(getHeader()->e_phentsize));
205    auto *Begin =
206        reinterpret_cast<const Elf_Phdr *>(base() + getHeader()->e_phoff);
207    return makeArrayRef(Begin, Begin + getHeader()->e_phnum);
208  }
209
210  /// Get an iterator over notes in a program header.
211  ///
212  /// The program header must be of type \c PT_NOTE.
213  ///
214  /// \param Phdr the program header to iterate over.
215  /// \param Err [out] an error to support fallible iteration, which should
216  ///  be checked after iteration ends.
217  Elf_Note_Iterator notes_begin(const Elf_Phdr &Phdr, Error &Err) const {
218    assert(Phdr.p_type == ELF::PT_NOTE && "Phdr is not of type PT_NOTE");
219    ErrorAsOutParameter ErrAsOutParam(&Err);
220    if (Phdr.p_offset + Phdr.p_filesz > getBufSize()) {
221      Err = createError("PT_NOTE header has invalid offset (0x" +
222                        Twine::utohexstr(Phdr.p_offset) + ") or size (0x" +
223                        Twine::utohexstr(Phdr.p_filesz) + ")");
224      return Elf_Note_Iterator(Err);
225    }
226    return Elf_Note_Iterator(base() + Phdr.p_offset, Phdr.p_filesz, Err);
227  }
228
229  /// Get an iterator over notes in a section.
230  ///
231  /// The section must be of type \c SHT_NOTE.
232  ///
233  /// \param Shdr the section to iterate over.
234  /// \param Err [out] an error to support fallible iteration, which should
235  ///  be checked after iteration ends.
236  Elf_Note_Iterator notes_begin(const Elf_Shdr &Shdr, Error &Err) const {
237    assert(Shdr.sh_type == ELF::SHT_NOTE && "Shdr is not of type SHT_NOTE");
238    ErrorAsOutParameter ErrAsOutParam(&Err);
239    if (Shdr.sh_offset + Shdr.sh_size > getBufSize()) {
240      Err = createError("SHT_NOTE section " + getSecIndexForError(this, &Shdr) +
241                        " has invalid offset (0x" +
242                        Twine::utohexstr(Shdr.sh_offset) + ") or size (0x" +
243                        Twine::utohexstr(Shdr.sh_size) + ")");
244      return Elf_Note_Iterator(Err);
245    }
246    return Elf_Note_Iterator(base() + Shdr.sh_offset, Shdr.sh_size, Err);
247  }
248
249  /// Get the end iterator for notes.
250  Elf_Note_Iterator notes_end() const {
251    return Elf_Note_Iterator();
252  }
253
254  /// Get an iterator range over notes of a program header.
255  ///
256  /// The program header must be of type \c PT_NOTE.
257  ///
258  /// \param Phdr the program header to iterate over.
259  /// \param Err [out] an error to support fallible iteration, which should
260  ///  be checked after iteration ends.
261  iterator_range<Elf_Note_Iterator> notes(const Elf_Phdr &Phdr,
262                                          Error &Err) const {
263    return make_range(notes_begin(Phdr, Err), notes_end());
264  }
265
266  /// Get an iterator range over notes of a section.
267  ///
268  /// The section must be of type \c SHT_NOTE.
269  ///
270  /// \param Shdr the section to iterate over.
271  /// \param Err [out] an error to support fallible iteration, which should
272  ///  be checked after iteration ends.
273  iterator_range<Elf_Note_Iterator> notes(const Elf_Shdr &Shdr,
274                                          Error &Err) const {
275    return make_range(notes_begin(Shdr, Err), notes_end());
276  }
277
278  Expected<StringRef> getSectionStringTable(
279      Elf_Shdr_Range Sections,
280      WarningHandler WarnHandler = &defaultWarningHandler) const;
281  Expected<uint32_t> getSectionIndex(const Elf_Sym *Sym, Elf_Sym_Range Syms,
282                                     ArrayRef<Elf_Word> ShndxTable) const;
283  Expected<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
284                                        const Elf_Shdr *SymTab,
285                                        ArrayRef<Elf_Word> ShndxTable) const;
286  Expected<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
287                                        Elf_Sym_Range Symtab,
288                                        ArrayRef<Elf_Word> ShndxTable) const;
289  Expected<const Elf_Shdr *> getSection(uint32_t Index) const;
290
291  Expected<const Elf_Sym *> getSymbol(const Elf_Shdr *Sec,
292                                      uint32_t Index) const;
293
294  Expected<StringRef>
295  getSectionName(const Elf_Shdr *Section,
296                 WarningHandler WarnHandler = &defaultWarningHandler) const;
297  Expected<StringRef> getSectionName(const Elf_Shdr *Section,
298                                     StringRef DotShstrtab) const;
299  template <typename T>
300  Expected<ArrayRef<T>> getSectionContentsAsArray(const Elf_Shdr *Sec) const;
301  Expected<ArrayRef<uint8_t>> getSectionContents(const Elf_Shdr *Sec) const;
302};
303
304using ELF32LEFile = ELFFile<ELF32LE>;
305using ELF64LEFile = ELFFile<ELF64LE>;
306using ELF32BEFile = ELFFile<ELF32BE>;
307using ELF64BEFile = ELFFile<ELF64BE>;
308
309template <class ELFT>
310inline Expected<const typename ELFT::Shdr *>
311getSection(typename ELFT::ShdrRange Sections, uint32_t Index) {
312  if (Index >= Sections.size())
313    return createError("invalid section index: " + Twine(Index));
314  return &Sections[Index];
315}
316
317template <class ELFT>
318inline Expected<uint32_t>
319getExtendedSymbolTableIndex(const typename ELFT::Sym *Sym,
320                            const typename ELFT::Sym *FirstSym,
321                            ArrayRef<typename ELFT::Word> ShndxTable) {
322  assert(Sym->st_shndx == ELF::SHN_XINDEX);
323  unsigned Index = Sym - FirstSym;
324  if (Index >= ShndxTable.size())
325    return createError(
326        "extended symbol index (" + Twine(Index) +
327        ") is past the end of the SHT_SYMTAB_SHNDX section of size " +
328        Twine(ShndxTable.size()));
329
330  // The size of the table was checked in getSHNDXTable.
331  return ShndxTable[Index];
332}
333
334template <class ELFT>
335Expected<uint32_t>
336ELFFile<ELFT>::getSectionIndex(const Elf_Sym *Sym, Elf_Sym_Range Syms,
337                               ArrayRef<Elf_Word> ShndxTable) const {
338  uint32_t Index = Sym->st_shndx;
339  if (Index == ELF::SHN_XINDEX) {
340    auto ErrorOrIndex = getExtendedSymbolTableIndex<ELFT>(
341        Sym, Syms.begin(), ShndxTable);
342    if (!ErrorOrIndex)
343      return ErrorOrIndex.takeError();
344    return *ErrorOrIndex;
345  }
346  if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
347    return 0;
348  return Index;
349}
350
351template <class ELFT>
352Expected<const typename ELFT::Shdr *>
353ELFFile<ELFT>::getSection(const Elf_Sym *Sym, const Elf_Shdr *SymTab,
354                          ArrayRef<Elf_Word> ShndxTable) const {
355  auto SymsOrErr = symbols(SymTab);
356  if (!SymsOrErr)
357    return SymsOrErr.takeError();
358  return getSection(Sym, *SymsOrErr, ShndxTable);
359}
360
361template <class ELFT>
362Expected<const typename ELFT::Shdr *>
363ELFFile<ELFT>::getSection(const Elf_Sym *Sym, Elf_Sym_Range Symbols,
364                          ArrayRef<Elf_Word> ShndxTable) const {
365  auto IndexOrErr = getSectionIndex(Sym, Symbols, ShndxTable);
366  if (!IndexOrErr)
367    return IndexOrErr.takeError();
368  uint32_t Index = *IndexOrErr;
369  if (Index == 0)
370    return nullptr;
371  return getSection(Index);
372}
373
374template <class ELFT>
375Expected<const typename ELFT::Sym *>
376ELFFile<ELFT>::getSymbol(const Elf_Shdr *Sec, uint32_t Index) const {
377  auto SymsOrErr = symbols(Sec);
378  if (!SymsOrErr)
379    return SymsOrErr.takeError();
380
381  Elf_Sym_Range Symbols = *SymsOrErr;
382  if (Index >= Symbols.size())
383    return createError("unable to get symbol from section " +
384                       getSecIndexForError(this, Sec) +
385                       ": invalid symbol index (" + Twine(Index) + ")");
386  return &Symbols[Index];
387}
388
389template <class ELFT>
390template <typename T>
391Expected<ArrayRef<T>>
392ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr *Sec) const {
393  if (Sec->sh_entsize != sizeof(T) && sizeof(T) != 1)
394    return createError("section " + getSecIndexForError(this, Sec) +
395                       " has an invalid sh_entsize: " + Twine(Sec->sh_entsize));
396
397  uintX_t Offset = Sec->sh_offset;
398  uintX_t Size = Sec->sh_size;
399
400  if (Size % sizeof(T))
401    return createError("section " + getSecIndexForError(this, Sec) +
402                       " has an invalid sh_size (" + Twine(Size) +
403                       ") which is not a multiple of its sh_entsize (" +
404                       Twine(Sec->sh_entsize) + ")");
405  if (std::numeric_limits<uintX_t>::max() - Offset < Size)
406    return createError("section " + getSecIndexForError(this, Sec) +
407                       " has a sh_offset (0x" + Twine::utohexstr(Offset) +
408                       ") + sh_size (0x" + Twine::utohexstr(Size) +
409                       ") that cannot be represented");
410  if (Offset + Size > Buf.size())
411    return createError("section " + getSecIndexForError(this, Sec) +
412                       " has a sh_offset (0x" + Twine::utohexstr(Offset) +
413                       ") + sh_size (0x" + Twine::utohexstr(Size) +
414                       ") that is greater than the file size (0x" +
415                       Twine::utohexstr(Buf.size()) + ")");
416
417  if (Offset % alignof(T))
418    // TODO: this error is untested.
419    return createError("unaligned data");
420
421  const T *Start = reinterpret_cast<const T *>(base() + Offset);
422  return makeArrayRef(Start, Size / sizeof(T));
423}
424
425template <class ELFT>
426Expected<ArrayRef<uint8_t>>
427ELFFile<ELFT>::getSectionContents(const Elf_Shdr *Sec) const {
428  return getSectionContentsAsArray<uint8_t>(Sec);
429}
430
431template <class ELFT>
432StringRef ELFFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
433  return getELFRelocationTypeName(getHeader()->e_machine, Type);
434}
435
436template <class ELFT>
437void ELFFile<ELFT>::getRelocationTypeName(uint32_t Type,
438                                          SmallVectorImpl<char> &Result) const {
439  if (!isMipsELF64()) {
440    StringRef Name = getRelocationTypeName(Type);
441    Result.append(Name.begin(), Name.end());
442  } else {
443    // The Mips N64 ABI allows up to three operations to be specified per
444    // relocation record. Unfortunately there's no easy way to test for the
445    // presence of N64 ELFs as they have no special flag that identifies them
446    // as being N64. We can safely assume at the moment that all Mips
447    // ELFCLASS64 ELFs are N64. New Mips64 ABIs should provide enough
448    // information to disambiguate between old vs new ABIs.
449    uint8_t Type1 = (Type >> 0) & 0xFF;
450    uint8_t Type2 = (Type >> 8) & 0xFF;
451    uint8_t Type3 = (Type >> 16) & 0xFF;
452
453    // Concat all three relocation type names.
454    StringRef Name = getRelocationTypeName(Type1);
455    Result.append(Name.begin(), Name.end());
456
457    Name = getRelocationTypeName(Type2);
458    Result.append(1, '/');
459    Result.append(Name.begin(), Name.end());
460
461    Name = getRelocationTypeName(Type3);
462    Result.append(1, '/');
463    Result.append(Name.begin(), Name.end());
464  }
465}
466
467template <class ELFT>
468uint32_t ELFFile<ELFT>::getRelativeRelocationType() const {
469  return getELFRelativeRelocationType(getHeader()->e_machine);
470}
471
472template <class ELFT>
473Expected<const typename ELFT::Sym *>
474ELFFile<ELFT>::getRelocationSymbol(const Elf_Rel *Rel,
475                                   const Elf_Shdr *SymTab) const {
476  uint32_t Index = Rel->getSymbol(isMips64EL());
477  if (Index == 0)
478    return nullptr;
479  return getEntry<Elf_Sym>(SymTab, Index);
480}
481
482template <class ELFT>
483Expected<StringRef>
484ELFFile<ELFT>::getSectionStringTable(Elf_Shdr_Range Sections,
485                                     WarningHandler WarnHandler) const {
486  uint32_t Index = getHeader()->e_shstrndx;
487  if (Index == ELF::SHN_XINDEX)
488    Index = Sections[0].sh_link;
489
490  if (!Index) // no section string table.
491    return "";
492  if (Index >= Sections.size())
493    return createError("section header string table index " + Twine(Index) +
494                       " does not exist");
495  return getStringTable(&Sections[Index], WarnHandler);
496}
497
498template <class ELFT> ELFFile<ELFT>::ELFFile(StringRef Object) : Buf(Object) {}
499
500template <class ELFT>
501Expected<ELFFile<ELFT>> ELFFile<ELFT>::create(StringRef Object) {
502  if (sizeof(Elf_Ehdr) > Object.size())
503    return createError("invalid buffer: the size (" + Twine(Object.size()) +
504                       ") is smaller than an ELF header (" +
505                       Twine(sizeof(Elf_Ehdr)) + ")");
506  return ELFFile(Object);
507}
508
509template <class ELFT>
510Expected<typename ELFT::ShdrRange> ELFFile<ELFT>::sections() const {
511  const uintX_t SectionTableOffset = getHeader()->e_shoff;
512  if (SectionTableOffset == 0)
513    return ArrayRef<Elf_Shdr>();
514
515  if (getHeader()->e_shentsize != sizeof(Elf_Shdr))
516    return createError("invalid e_shentsize in ELF header: " +
517                       Twine(getHeader()->e_shentsize));
518
519  const uint64_t FileSize = Buf.size();
520  if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize ||
521      SectionTableOffset + (uintX_t)sizeof(Elf_Shdr) < SectionTableOffset)
522    return createError(
523        "section header table goes past the end of the file: e_shoff = 0x" +
524        Twine::utohexstr(SectionTableOffset));
525
526  // Invalid address alignment of section headers
527  if (SectionTableOffset & (alignof(Elf_Shdr) - 1))
528    // TODO: this error is untested.
529    return createError("invalid alignment of section headers");
530
531  const Elf_Shdr *First =
532      reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
533
534  uintX_t NumSections = getHeader()->e_shnum;
535  if (NumSections == 0)
536    NumSections = First->sh_size;
537
538  if (NumSections > UINT64_MAX / sizeof(Elf_Shdr))
539    return createError("invalid number of sections specified in the NULL "
540                       "section's sh_size field (" +
541                       Twine(NumSections) + ")");
542
543  const uint64_t SectionTableSize = NumSections * sizeof(Elf_Shdr);
544  if (SectionTableOffset + SectionTableSize < SectionTableOffset)
545    return createError(
546        "invalid section header table offset (e_shoff = 0x" +
547        Twine::utohexstr(SectionTableOffset) +
548        ") or invalid number of sections specified in the first section "
549        "header's sh_size field (0x" +
550        Twine::utohexstr(NumSections) + ")");
551
552  // Section table goes past end of file!
553  if (SectionTableOffset + SectionTableSize > FileSize)
554    return createError("section table goes past the end of file");
555  return makeArrayRef(First, NumSections);
556}
557
558template <class ELFT>
559template <typename T>
560Expected<const T *> ELFFile<ELFT>::getEntry(uint32_t Section,
561                                            uint32_t Entry) const {
562  auto SecOrErr = getSection(Section);
563  if (!SecOrErr)
564    return SecOrErr.takeError();
565  return getEntry<T>(*SecOrErr, Entry);
566}
567
568template <class ELFT>
569template <typename T>
570Expected<const T *> ELFFile<ELFT>::getEntry(const Elf_Shdr *Section,
571                                            uint32_t Entry) const {
572  if (sizeof(T) != Section->sh_entsize)
573    return createError("section " + getSecIndexForError(this, Section) +
574                       " has invalid sh_entsize: expected " + Twine(sizeof(T)) +
575                       ", but got " + Twine(Section->sh_entsize));
576  size_t Pos = Section->sh_offset + Entry * sizeof(T);
577  if (Pos + sizeof(T) > Buf.size())
578    return createError("unable to access section " +
579                       getSecIndexForError(this, Section) + " data at 0x" +
580                       Twine::utohexstr(Pos) +
581                       ": offset goes past the end of file");
582  return reinterpret_cast<const T *>(base() + Pos);
583}
584
585template <class ELFT>
586Expected<const typename ELFT::Shdr *>
587ELFFile<ELFT>::getSection(uint32_t Index) const {
588  auto TableOrErr = sections();
589  if (!TableOrErr)
590    return TableOrErr.takeError();
591  return object::getSection<ELFT>(*TableOrErr, Index);
592}
593
594template <class ELFT>
595Expected<StringRef>
596ELFFile<ELFT>::getStringTable(const Elf_Shdr *Section,
597                              WarningHandler WarnHandler) const {
598  if (Section->sh_type != ELF::SHT_STRTAB)
599    if (Error E = WarnHandler("invalid sh_type for string table section " +
600                              getSecIndexForError(this, Section) +
601                              ": expected SHT_STRTAB, but got " +
602                              object::getELFSectionTypeName(
603                                  getHeader()->e_machine, Section->sh_type)))
604      return std::move(E);
605
606  auto V = getSectionContentsAsArray<char>(Section);
607  if (!V)
608    return V.takeError();
609  ArrayRef<char> Data = *V;
610  if (Data.empty())
611    return createError("SHT_STRTAB string table section " +
612                       getSecIndexForError(this, Section) + " is empty");
613  if (Data.back() != '\0')
614    return createError("SHT_STRTAB string table section " +
615                       getSecIndexForError(this, Section) +
616                       " is non-null terminated");
617  return StringRef(Data.begin(), Data.size());
618}
619
620template <class ELFT>
621Expected<ArrayRef<typename ELFT::Word>>
622ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section) const {
623  auto SectionsOrErr = sections();
624  if (!SectionsOrErr)
625    return SectionsOrErr.takeError();
626  return getSHNDXTable(Section, *SectionsOrErr);
627}
628
629template <class ELFT>
630Expected<ArrayRef<typename ELFT::Word>>
631ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section,
632                             Elf_Shdr_Range Sections) const {
633  assert(Section.sh_type == ELF::SHT_SYMTAB_SHNDX);
634  auto VOrErr = getSectionContentsAsArray<Elf_Word>(&Section);
635  if (!VOrErr)
636    return VOrErr.takeError();
637  ArrayRef<Elf_Word> V = *VOrErr;
638  auto SymTableOrErr = object::getSection<ELFT>(Sections, Section.sh_link);
639  if (!SymTableOrErr)
640    return SymTableOrErr.takeError();
641  const Elf_Shdr &SymTable = **SymTableOrErr;
642  if (SymTable.sh_type != ELF::SHT_SYMTAB &&
643      SymTable.sh_type != ELF::SHT_DYNSYM)
644    return createError("SHT_SYMTAB_SHNDX section is linked with " +
645                       object::getELFSectionTypeName(getHeader()->e_machine,
646                                                     SymTable.sh_type) +
647                       " section (expected SHT_SYMTAB/SHT_DYNSYM)");
648
649  uint64_t Syms = SymTable.sh_size / sizeof(Elf_Sym);
650  if (V.size() != Syms)
651    return createError("SHT_SYMTAB_SHNDX has " + Twine(V.size()) +
652                       " entries, but the symbol table associated has " +
653                       Twine(Syms));
654
655  return V;
656}
657
658template <class ELFT>
659Expected<StringRef>
660ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec) const {
661  auto SectionsOrErr = sections();
662  if (!SectionsOrErr)
663    return SectionsOrErr.takeError();
664  return getStringTableForSymtab(Sec, *SectionsOrErr);
665}
666
667template <class ELFT>
668Expected<StringRef>
669ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec,
670                                       Elf_Shdr_Range Sections) const {
671
672  if (Sec.sh_type != ELF::SHT_SYMTAB && Sec.sh_type != ELF::SHT_DYNSYM)
673    // TODO: this error is untested.
674    return createError(
675        "invalid sh_type for symbol table, expected SHT_SYMTAB or SHT_DYNSYM");
676  auto SectionOrErr = object::getSection<ELFT>(Sections, Sec.sh_link);
677  if (!SectionOrErr)
678    return SectionOrErr.takeError();
679  return getStringTable(*SectionOrErr);
680}
681
682template <class ELFT>
683Expected<StringRef>
684ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section,
685                              WarningHandler WarnHandler) const {
686  auto SectionsOrErr = sections();
687  if (!SectionsOrErr)
688    return SectionsOrErr.takeError();
689  auto Table = getSectionStringTable(*SectionsOrErr, WarnHandler);
690  if (!Table)
691    return Table.takeError();
692  return getSectionName(Section, *Table);
693}
694
695template <class ELFT>
696Expected<StringRef> ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section,
697                                                  StringRef DotShstrtab) const {
698  uint32_t Offset = Section->sh_name;
699  if (Offset == 0)
700    return StringRef();
701  if (Offset >= DotShstrtab.size())
702    return createError("a section " + getSecIndexForError(this, Section) +
703                       " has an invalid sh_name (0x" +
704                       Twine::utohexstr(Offset) +
705                       ") offset which goes past the end of the "
706                       "section name string table");
707  return StringRef(DotShstrtab.data() + Offset);
708}
709
710/// This function returns the hash value for a symbol in the .dynsym section
711/// Name of the API remains consistent as specified in the libelf
712/// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
713inline unsigned hashSysV(StringRef SymbolName) {
714  unsigned h = 0, g;
715  for (char C : SymbolName) {
716    h = (h << 4) + C;
717    g = h & 0xf0000000L;
718    if (g != 0)
719      h ^= g >> 24;
720    h &= ~g;
721  }
722  return h;
723}
724
725} // end namespace object
726} // end namespace llvm
727
728#endif // LLVM_OBJECT_ELF_H
729