1//===- ELF.h - ELF object file implementation -------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file declares the ELFFile template class.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_OBJECT_ELF_H
15#define LLVM_OBJECT_ELF_H
16
17#include "llvm/ADT/SmallVector.h"
18#include "llvm/Object/ELFTypes.h"
19#include "llvm/Support/MemoryBuffer.h"
20
21namespace llvm {
22namespace object {
23
24StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type);
25
26// Subclasses of ELFFile may need this for template instantiation
27inline std::pair<unsigned char, unsigned char>
28getElfArchType(StringRef Object) {
29  if (Object.size() < ELF::EI_NIDENT)
30    return std::make_pair((uint8_t)ELF::ELFCLASSNONE,
31                          (uint8_t)ELF::ELFDATANONE);
32  return std::make_pair((uint8_t)Object[ELF::EI_CLASS],
33                        (uint8_t)Object[ELF::EI_DATA]);
34}
35
36template <class ELFT>
37class ELFFile {
38public:
39  LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
40  typedef typename std::conditional<ELFT::Is64Bits,
41                                    uint64_t, uint32_t>::type uintX_t;
42
43  typedef Elf_Ehdr_Impl<ELFT> Elf_Ehdr;
44  typedef Elf_Shdr_Impl<ELFT> Elf_Shdr;
45  typedef Elf_Sym_Impl<ELFT> Elf_Sym;
46  typedef Elf_Dyn_Impl<ELFT> Elf_Dyn;
47  typedef Elf_Phdr_Impl<ELFT> Elf_Phdr;
48  typedef Elf_Rel_Impl<ELFT, false> Elf_Rel;
49  typedef Elf_Rel_Impl<ELFT, true> Elf_Rela;
50  typedef Elf_Verdef_Impl<ELFT> Elf_Verdef;
51  typedef Elf_Verdaux_Impl<ELFT> Elf_Verdaux;
52  typedef Elf_Verneed_Impl<ELFT> Elf_Verneed;
53  typedef Elf_Vernaux_Impl<ELFT> Elf_Vernaux;
54  typedef Elf_Versym_Impl<ELFT> Elf_Versym;
55  typedef Elf_Hash_Impl<ELFT> Elf_Hash;
56  typedef Elf_GnuHash_Impl<ELFT> Elf_GnuHash;
57  typedef iterator_range<const Elf_Dyn *> Elf_Dyn_Range;
58  typedef iterator_range<const Elf_Shdr *> Elf_Shdr_Range;
59  typedef iterator_range<const Elf_Sym *> Elf_Sym_Range;
60
61  const uint8_t *base() const {
62    return reinterpret_cast<const uint8_t *>(Buf.data());
63  }
64
65private:
66
67  StringRef Buf;
68
69  const Elf_Ehdr *Header;
70  const Elf_Shdr *SectionHeaderTable = nullptr;
71  StringRef DotShstrtab;                    // Section header string table.
72
73public:
74  template<typename T>
75  const T        *getEntry(uint32_t Section, uint32_t Entry) const;
76  template <typename T>
77  const T *getEntry(const Elf_Shdr *Section, uint32_t Entry) const;
78
79  ErrorOr<StringRef> getStringTable(const Elf_Shdr *Section) const;
80  ErrorOr<StringRef> getStringTableForSymtab(const Elf_Shdr &Section) const;
81
82  ErrorOr<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section) const;
83
84  void VerifyStrTab(const Elf_Shdr *sh) const;
85
86  StringRef getRelocationTypeName(uint32_t Type) const;
87  void getRelocationTypeName(uint32_t Type,
88                             SmallVectorImpl<char> &Result) const;
89
90  /// \brief Get the symbol for a given relocation.
91  const Elf_Sym *getRelocationSymbol(const Elf_Rel *Rel,
92                                     const Elf_Shdr *SymTab) const;
93
94  ELFFile(StringRef Object, std::error_code &EC);
95
96  bool isMipsELF64() const {
97    return Header->e_machine == ELF::EM_MIPS &&
98      Header->getFileClass() == ELF::ELFCLASS64;
99  }
100
101  bool isMips64EL() const {
102    return Header->e_machine == ELF::EM_MIPS &&
103      Header->getFileClass() == ELF::ELFCLASS64 &&
104      Header->getDataEncoding() == ELF::ELFDATA2LSB;
105  }
106
107  ErrorOr<const Elf_Dyn *> dynamic_table_begin(const Elf_Phdr *Phdr) const;
108  ErrorOr<const Elf_Dyn *> dynamic_table_end(const Elf_Phdr *Phdr) const;
109  ErrorOr<Elf_Dyn_Range> dynamic_table(const Elf_Phdr *Phdr) const {
110    ErrorOr<const Elf_Dyn *> Begin = dynamic_table_begin(Phdr);
111    if (std::error_code EC = Begin.getError())
112      return EC;
113    ErrorOr<const Elf_Dyn *> End = dynamic_table_end(Phdr);
114    if (std::error_code EC = End.getError())
115      return EC;
116    return make_range(*Begin, *End);
117  }
118
119  const Elf_Shdr *section_begin() const;
120  const Elf_Shdr *section_end() const;
121  Elf_Shdr_Range sections() const {
122    return make_range(section_begin(), section_end());
123  }
124
125  const Elf_Sym *symbol_begin(const Elf_Shdr *Sec) const {
126    if (!Sec)
127      return nullptr;
128    if (Sec->sh_entsize != sizeof(Elf_Sym))
129      report_fatal_error("Invalid symbol size");
130    return reinterpret_cast<const Elf_Sym *>(base() + Sec->sh_offset);
131  }
132  const Elf_Sym *symbol_end(const Elf_Shdr *Sec) const {
133    if (!Sec)
134      return nullptr;
135    uint64_t Size = Sec->sh_size;
136    if (Size % sizeof(Elf_Sym))
137      report_fatal_error("Invalid symbol table size");
138    return symbol_begin(Sec) + Size / sizeof(Elf_Sym);
139  }
140  Elf_Sym_Range symbols(const Elf_Shdr *Sec) const {
141    return make_range(symbol_begin(Sec), symbol_end(Sec));
142  }
143
144  typedef iterator_range<const Elf_Rela *> Elf_Rela_Range;
145
146  const Elf_Rela *rela_begin(const Elf_Shdr *sec) const {
147    if (sec->sh_entsize != sizeof(Elf_Rela))
148      report_fatal_error("Invalid relocation entry size");
149    return reinterpret_cast<const Elf_Rela *>(base() + sec->sh_offset);
150  }
151
152  const Elf_Rela *rela_end(const Elf_Shdr *sec) const {
153    uint64_t Size = sec->sh_size;
154    if (Size % sizeof(Elf_Rela))
155      report_fatal_error("Invalid relocation table size");
156    return rela_begin(sec) + Size / sizeof(Elf_Rela);
157  }
158
159  Elf_Rela_Range relas(const Elf_Shdr *Sec) const {
160    return make_range(rela_begin(Sec), rela_end(Sec));
161  }
162
163  const Elf_Rel *rel_begin(const Elf_Shdr *sec) const {
164    if (sec->sh_entsize != sizeof(Elf_Rel))
165      report_fatal_error("Invalid relocation entry size");
166    return reinterpret_cast<const Elf_Rel *>(base() + sec->sh_offset);
167  }
168
169  const Elf_Rel *rel_end(const Elf_Shdr *sec) const {
170    uint64_t Size = sec->sh_size;
171    if (Size % sizeof(Elf_Rel))
172      report_fatal_error("Invalid relocation table size");
173    return rel_begin(sec) + Size / sizeof(Elf_Rel);
174  }
175
176  typedef iterator_range<const Elf_Rel *> Elf_Rel_Range;
177  Elf_Rel_Range rels(const Elf_Shdr *Sec) const {
178    return make_range(rel_begin(Sec), rel_end(Sec));
179  }
180
181  /// \brief Iterate over program header table.
182  const Elf_Phdr *program_header_begin() const {
183    if (Header->e_phnum && Header->e_phentsize != sizeof(Elf_Phdr))
184      report_fatal_error("Invalid program header size");
185    return reinterpret_cast<const Elf_Phdr *>(base() + Header->e_phoff);
186  }
187
188  const Elf_Phdr *program_header_end() const {
189    return program_header_begin() + Header->e_phnum;
190  }
191
192  typedef iterator_range<const Elf_Phdr *> Elf_Phdr_Range;
193
194  const Elf_Phdr_Range program_headers() const {
195    return make_range(program_header_begin(), program_header_end());
196  }
197
198  uint64_t getNumSections() const;
199  uintX_t getStringTableIndex() const;
200  uint32_t getExtendedSymbolTableIndex(const Elf_Sym *Sym,
201                                       const Elf_Shdr *SymTab,
202                                       ArrayRef<Elf_Word> ShndxTable) const;
203  const Elf_Ehdr *getHeader() const { return Header; }
204  ErrorOr<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
205                                       const Elf_Shdr *SymTab,
206                                       ArrayRef<Elf_Word> ShndxTable) const;
207  ErrorOr<const Elf_Shdr *> getSection(uint32_t Index) const;
208
209  const Elf_Sym *getSymbol(const Elf_Shdr *Sec, uint32_t Index) const {
210    return &*(symbol_begin(Sec) + Index);
211  }
212
213  ErrorOr<StringRef> getSectionName(const Elf_Shdr *Section) const;
214  template <typename T>
215  ErrorOr<ArrayRef<T>> getSectionContentsAsArray(const Elf_Shdr *Sec) const;
216  ErrorOr<ArrayRef<uint8_t> > getSectionContents(const Elf_Shdr *Sec) const;
217};
218
219typedef ELFFile<ELFType<support::little, false>> ELF32LEFile;
220typedef ELFFile<ELFType<support::little, true>> ELF64LEFile;
221typedef ELFFile<ELFType<support::big, false>> ELF32BEFile;
222typedef ELFFile<ELFType<support::big, true>> ELF64BEFile;
223
224template <class ELFT>
225uint32_t ELFFile<ELFT>::getExtendedSymbolTableIndex(
226    const Elf_Sym *Sym, const Elf_Shdr *SymTab,
227    ArrayRef<Elf_Word> ShndxTable) const {
228  assert(Sym->st_shndx == ELF::SHN_XINDEX);
229  unsigned Index = Sym - symbol_begin(SymTab);
230
231  // The size of the table was checked in getSHNDXTable.
232  return ShndxTable[Index];
233}
234
235template <class ELFT>
236ErrorOr<const typename ELFFile<ELFT>::Elf_Shdr *>
237ELFFile<ELFT>::getSection(const Elf_Sym *Sym, const Elf_Shdr *SymTab,
238                          ArrayRef<Elf_Word> ShndxTable) const {
239  uint32_t Index = Sym->st_shndx;
240  if (Index == ELF::SHN_XINDEX)
241    return getSection(getExtendedSymbolTableIndex(Sym, SymTab, ShndxTable));
242
243  if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
244    return nullptr;
245  return getSection(Sym->st_shndx);
246}
247
248template <class ELFT>
249template <typename T>
250ErrorOr<ArrayRef<T>>
251ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr *Sec) const {
252  uintX_t Offset = Sec->sh_offset;
253  uintX_t Size = Sec->sh_size;
254
255  if (Size % sizeof(T))
256    return object_error::parse_failed;
257  if (Offset + Size > Buf.size())
258    return object_error::parse_failed;
259
260  const T *Start = reinterpret_cast<const T *>(base() + Offset);
261  return makeArrayRef(Start, Size / sizeof(T));
262}
263
264template <class ELFT>
265ErrorOr<ArrayRef<uint8_t>>
266ELFFile<ELFT>::getSectionContents(const Elf_Shdr *Sec) const {
267  return getSectionContentsAsArray<uint8_t>(Sec);
268}
269
270template <class ELFT>
271StringRef ELFFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
272  return getELFRelocationTypeName(Header->e_machine, Type);
273}
274
275template <class ELFT>
276void ELFFile<ELFT>::getRelocationTypeName(uint32_t Type,
277                                          SmallVectorImpl<char> &Result) const {
278  if (!isMipsELF64()) {
279    StringRef Name = getRelocationTypeName(Type);
280    Result.append(Name.begin(), Name.end());
281  } else {
282    // The Mips N64 ABI allows up to three operations to be specified per
283    // relocation record. Unfortunately there's no easy way to test for the
284    // presence of N64 ELFs as they have no special flag that identifies them
285    // as being N64. We can safely assume at the moment that all Mips
286    // ELFCLASS64 ELFs are N64. New Mips64 ABIs should provide enough
287    // information to disambiguate between old vs new ABIs.
288    uint8_t Type1 = (Type >> 0) & 0xFF;
289    uint8_t Type2 = (Type >> 8) & 0xFF;
290    uint8_t Type3 = (Type >> 16) & 0xFF;
291
292    // Concat all three relocation type names.
293    StringRef Name = getRelocationTypeName(Type1);
294    Result.append(Name.begin(), Name.end());
295
296    Name = getRelocationTypeName(Type2);
297    Result.append(1, '/');
298    Result.append(Name.begin(), Name.end());
299
300    Name = getRelocationTypeName(Type3);
301    Result.append(1, '/');
302    Result.append(Name.begin(), Name.end());
303  }
304}
305
306template <class ELFT>
307const typename ELFFile<ELFT>::Elf_Sym *
308ELFFile<ELFT>::getRelocationSymbol(const Elf_Rel *Rel,
309                                   const Elf_Shdr *SymTab) const {
310  uint32_t Index = Rel->getSymbol(isMips64EL());
311  if (Index == 0)
312    return nullptr;
313  return getEntry<Elf_Sym>(SymTab, Index);
314}
315
316template <class ELFT>
317uint64_t ELFFile<ELFT>::getNumSections() const {
318  assert(Header && "Header not initialized!");
319  if (Header->e_shnum == ELF::SHN_UNDEF && Header->e_shoff > 0) {
320    assert(SectionHeaderTable && "SectionHeaderTable not initialized!");
321    return SectionHeaderTable->sh_size;
322  }
323  return Header->e_shnum;
324}
325
326template <class ELFT>
327typename ELFFile<ELFT>::uintX_t ELFFile<ELFT>::getStringTableIndex() const {
328  if (Header->e_shnum == ELF::SHN_UNDEF) {
329    if (Header->e_shstrndx == ELF::SHN_HIRESERVE)
330      return SectionHeaderTable->sh_link;
331    if (Header->e_shstrndx >= getNumSections())
332      return 0;
333  }
334  return Header->e_shstrndx;
335}
336
337template <class ELFT>
338ELFFile<ELFT>::ELFFile(StringRef Object, std::error_code &EC)
339    : Buf(Object) {
340  const uint64_t FileSize = Buf.size();
341
342  if (sizeof(Elf_Ehdr) > FileSize) {
343    // File too short!
344    EC = object_error::parse_failed;
345    return;
346  }
347
348  Header = reinterpret_cast<const Elf_Ehdr *>(base());
349
350  if (Header->e_shoff == 0)
351    return;
352
353  const uint64_t SectionTableOffset = Header->e_shoff;
354
355  if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize) {
356    // Section header table goes past end of file!
357    EC = object_error::parse_failed;
358    return;
359  }
360
361  // The getNumSections() call below depends on SectionHeaderTable being set.
362  SectionHeaderTable =
363    reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
364  const uint64_t SectionTableSize = getNumSections() * Header->e_shentsize;
365
366  if (SectionTableOffset + SectionTableSize > FileSize) {
367    // Section table goes past end of file!
368    EC = object_error::parse_failed;
369    return;
370  }
371
372  // Get string table sections.
373  uintX_t StringTableIndex = getStringTableIndex();
374  if (StringTableIndex) {
375    ErrorOr<const Elf_Shdr *> StrTabSecOrErr = getSection(StringTableIndex);
376    if ((EC = StrTabSecOrErr.getError()))
377      return;
378
379    ErrorOr<StringRef> StringTableOrErr = getStringTable(*StrTabSecOrErr);
380    if ((EC = StringTableOrErr.getError()))
381      return;
382    DotShstrtab = *StringTableOrErr;
383  }
384
385  EC = std::error_code();
386}
387
388template <class ELFT>
389static bool compareAddr(uint64_t VAddr, const Elf_Phdr_Impl<ELFT> *Phdr) {
390  return VAddr < Phdr->p_vaddr;
391}
392
393template <class ELFT>
394const typename ELFFile<ELFT>::Elf_Shdr *ELFFile<ELFT>::section_begin() const {
395  if (Header->e_shentsize != sizeof(Elf_Shdr))
396    report_fatal_error(
397        "Invalid section header entry size (e_shentsize) in ELF header");
398  return reinterpret_cast<const Elf_Shdr *>(base() + Header->e_shoff);
399}
400
401template <class ELFT>
402const typename ELFFile<ELFT>::Elf_Shdr *ELFFile<ELFT>::section_end() const {
403  return section_begin() + getNumSections();
404}
405
406template <class ELFT>
407ErrorOr<const typename ELFFile<ELFT>::Elf_Dyn *>
408ELFFile<ELFT>::dynamic_table_begin(const Elf_Phdr *Phdr) const {
409  if (!Phdr)
410    return nullptr;
411  assert(Phdr->p_type == ELF::PT_DYNAMIC && "Got the wrong program header");
412  uintX_t Offset = Phdr->p_offset;
413  if (Offset > Buf.size())
414    return object_error::parse_failed;
415  return reinterpret_cast<const Elf_Dyn *>(base() + Offset);
416}
417
418template <class ELFT>
419ErrorOr<const typename ELFFile<ELFT>::Elf_Dyn *>
420ELFFile<ELFT>::dynamic_table_end(const Elf_Phdr *Phdr) const {
421  if (!Phdr)
422    return nullptr;
423  assert(Phdr->p_type == ELF::PT_DYNAMIC && "Got the wrong program header");
424  uintX_t Size = Phdr->p_filesz;
425  if (Size % sizeof(Elf_Dyn))
426    return object_error::elf_invalid_dynamic_table_size;
427  // FIKME: Check for overflow?
428  uintX_t End = Phdr->p_offset + Size;
429  if (End > Buf.size())
430    return object_error::parse_failed;
431  return reinterpret_cast<const Elf_Dyn *>(base() + End);
432}
433
434template <class ELFT>
435template <typename T>
436const T *ELFFile<ELFT>::getEntry(uint32_t Section, uint32_t Entry) const {
437  ErrorOr<const Elf_Shdr *> Sec = getSection(Section);
438  if (std::error_code EC = Sec.getError())
439    report_fatal_error(EC.message());
440  return getEntry<T>(*Sec, Entry);
441}
442
443template <class ELFT>
444template <typename T>
445const T *ELFFile<ELFT>::getEntry(const Elf_Shdr *Section,
446                                 uint32_t Entry) const {
447  return reinterpret_cast<const T *>(base() + Section->sh_offset +
448                                     (Entry * Section->sh_entsize));
449}
450
451template <class ELFT>
452ErrorOr<const typename ELFFile<ELFT>::Elf_Shdr *>
453ELFFile<ELFT>::getSection(uint32_t Index) const {
454  assert(SectionHeaderTable && "SectionHeaderTable not initialized!");
455  if (Index >= getNumSections())
456    return object_error::invalid_section_index;
457
458  return reinterpret_cast<const Elf_Shdr *>(
459      reinterpret_cast<const char *>(SectionHeaderTable) +
460      (Index * Header->e_shentsize));
461}
462
463template <class ELFT>
464ErrorOr<StringRef>
465ELFFile<ELFT>::getStringTable(const Elf_Shdr *Section) const {
466  if (Section->sh_type != ELF::SHT_STRTAB)
467    return object_error::parse_failed;
468  uint64_t Offset = Section->sh_offset;
469  uint64_t Size = Section->sh_size;
470  if (Offset + Size > Buf.size())
471    return object_error::parse_failed;
472  StringRef Data((const char *)base() + Section->sh_offset, Size);
473  if (Data[Size - 1] != '\0')
474    return object_error::string_table_non_null_end;
475  return Data;
476}
477
478template <class ELFT>
479ErrorOr<ArrayRef<typename ELFFile<ELFT>::Elf_Word>>
480ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section) const {
481  assert(Section.sh_type == ELF::SHT_SYMTAB_SHNDX);
482  const Elf_Word *ShndxTableBegin =
483      reinterpret_cast<const Elf_Word *>(base() + Section.sh_offset);
484  uintX_t Size = Section.sh_size;
485  if (Size % sizeof(uint32_t))
486    return object_error::parse_failed;
487  uintX_t NumSymbols = Size / sizeof(uint32_t);
488  const Elf_Word *ShndxTableEnd = ShndxTableBegin + NumSymbols;
489  if (reinterpret_cast<const char *>(ShndxTableEnd) > Buf.end())
490    return object_error::parse_failed;
491  ErrorOr<const Elf_Shdr *> SymTableOrErr = getSection(Section.sh_link);
492  if (std::error_code EC = SymTableOrErr.getError())
493    return EC;
494  const Elf_Shdr &SymTable = **SymTableOrErr;
495  if (SymTable.sh_type != ELF::SHT_SYMTAB &&
496      SymTable.sh_type != ELF::SHT_DYNSYM)
497    return object_error::parse_failed;
498  if (NumSymbols != (SymTable.sh_size / sizeof(Elf_Sym)))
499    return object_error::parse_failed;
500  return makeArrayRef(ShndxTableBegin, ShndxTableEnd);
501}
502
503template <class ELFT>
504ErrorOr<StringRef>
505ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec) const {
506  if (Sec.sh_type != ELF::SHT_SYMTAB && Sec.sh_type != ELF::SHT_DYNSYM)
507    return object_error::parse_failed;
508  ErrorOr<const Elf_Shdr *> SectionOrErr = getSection(Sec.sh_link);
509  if (std::error_code EC = SectionOrErr.getError())
510    return EC;
511  return getStringTable(*SectionOrErr);
512}
513
514template <class ELFT>
515ErrorOr<StringRef>
516ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section) const {
517  uint32_t Offset = Section->sh_name;
518  if (Offset == 0)
519    return StringRef();
520  if (Offset >= DotShstrtab.size())
521    return object_error::parse_failed;
522  return StringRef(DotShstrtab.data() + Offset);
523}
524
525/// This function returns the hash value for a symbol in the .dynsym section
526/// Name of the API remains consistent as specified in the libelf
527/// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
528static inline unsigned elf_hash(StringRef &symbolName) {
529  unsigned h = 0, g;
530  for (unsigned i = 0, j = symbolName.size(); i < j; i++) {
531    h = (h << 4) + symbolName[i];
532    g = h & 0xf0000000L;
533    if (g != 0)
534      h ^= g >> 24;
535    h &= ~g;
536  }
537  return h;
538}
539} // end namespace object
540} // end namespace llvm
541
542#endif
543