xref: /NextBSD/contrib/llvm/include/llvm/Object/ELF.h (revision 84d351007654069f9643c8e4b4802a7f5f08ee42) 
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/ArrayRef.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/IntervalMap.h"
20 #include "llvm/ADT/PointerIntPair.h"
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/ADT/StringSwitch.h"
23 #include "llvm/ADT/Triple.h"
24 #include "llvm/Object/ELFTypes.h"
25 #include "llvm/Object/Error.h"
26 #include "llvm/Support/Casting.h"
27 #include "llvm/Support/ELF.h"
28 #include "llvm/Support/Endian.h"
29 #include "llvm/Support/ErrorHandling.h"
30 #include "llvm/Support/ErrorOr.h"
31 #include "llvm/Support/MemoryBuffer.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include <algorithm>
34 #include <limits>
35 #include <utility>
36 
37 namespace llvm {
38 namespace object {
39 
40 StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type);
41 
42 // Subclasses of ELFFile may need this for template instantiation
43 inline std::pair<unsigned char, unsigned char>
getElfArchType(StringRef Object)44 getElfArchType(StringRef Object) {
45   if (Object.size() < ELF::EI_NIDENT)
46     return std::make_pair((uint8_t)ELF::ELFCLASSNONE,
47                           (uint8_t)ELF::ELFDATANONE);
48   return std::make_pair((uint8_t)Object[ELF::EI_CLASS],
49                         (uint8_t)Object[ELF::EI_DATA]);
50 }
51 
52 template <class ELFT>
53 class ELFFile {
54 public:
55   LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
56   typedef typename std::conditional<ELFT::Is64Bits,
57                                     uint64_t, uint32_t>::type uintX_t;
58 
59   /// \brief Iterate over constant sized entities.
60   template <class EntT>
61   class ELFEntityIterator {
62   public:
63     typedef ptrdiff_t difference_type;
64     typedef EntT value_type;
65     typedef std::forward_iterator_tag iterator_category;
66     typedef value_type &reference;
67     typedef value_type *pointer;
68 
69     /// \brief Default construct iterator.
ELFEntityIterator()70     ELFEntityIterator() : EntitySize(0), Current(nullptr) {}
ELFEntityIterator(uintX_t EntSize,const char * Start)71     ELFEntityIterator(uintX_t EntSize, const char *Start)
72         : EntitySize(EntSize), Current(Start) {}
73 
74     reference operator *() {
75       assert(Current && "Attempted to dereference an invalid iterator!");
76       return *reinterpret_cast<pointer>(Current);
77     }
78 
79     pointer operator ->() {
80       assert(Current && "Attempted to dereference an invalid iterator!");
81       return reinterpret_cast<pointer>(Current);
82     }
83 
84     bool operator ==(const ELFEntityIterator &Other) {
85       return Current == Other.Current;
86     }
87 
88     bool operator !=(const ELFEntityIterator &Other) {
89       return !(*this == Other);
90     }
91 
92     ELFEntityIterator &operator ++() {
93       assert(Current && "Attempted to increment an invalid iterator!");
94       Current += EntitySize;
95       return *this;
96     }
97 
98     ELFEntityIterator &operator+(difference_type n) {
99       assert(Current && "Attempted to increment an invalid iterator!");
100       Current += (n * EntitySize);
101       return *this;
102     }
103 
104     ELFEntityIterator &operator-(difference_type n) {
105       assert(Current && "Attempted to subtract an invalid iterator!");
106       Current -= (n * EntitySize);
107       return *this;
108     }
109 
110     ELFEntityIterator operator ++(int) {
111       ELFEntityIterator Tmp = *this;
112       ++*this;
113       return Tmp;
114     }
115 
116     difference_type operator -(const ELFEntityIterator &Other) const {
117       assert(EntitySize == Other.EntitySize &&
118              "Subtracting iterators of different EntitySize!");
119       return (Current - Other.Current) / EntitySize;
120     }
121 
get()122     const char *get() const { return Current; }
123 
getEntSize()124     uintX_t getEntSize() const { return EntitySize; }
125 
126   private:
127     uintX_t EntitySize;
128     const char *Current;
129   };
130 
131   typedef Elf_Ehdr_Impl<ELFT> Elf_Ehdr;
132   typedef Elf_Shdr_Impl<ELFT> Elf_Shdr;
133   typedef Elf_Sym_Impl<ELFT> Elf_Sym;
134   typedef Elf_Dyn_Impl<ELFT> Elf_Dyn;
135   typedef Elf_Phdr_Impl<ELFT> Elf_Phdr;
136   typedef Elf_Rel_Impl<ELFT, false> Elf_Rel;
137   typedef Elf_Rel_Impl<ELFT, true> Elf_Rela;
138   typedef Elf_Verdef_Impl<ELFT> Elf_Verdef;
139   typedef Elf_Verdaux_Impl<ELFT> Elf_Verdaux;
140   typedef Elf_Verneed_Impl<ELFT> Elf_Verneed;
141   typedef Elf_Vernaux_Impl<ELFT> Elf_Vernaux;
142   typedef Elf_Versym_Impl<ELFT> Elf_Versym;
143   typedef Elf_Hash_Impl<ELFT> Elf_Hash;
144   typedef ELFEntityIterator<const Elf_Dyn> Elf_Dyn_Iter;
145   typedef iterator_range<Elf_Dyn_Iter> Elf_Dyn_Range;
146   typedef ELFEntityIterator<const Elf_Rela> Elf_Rela_Iter;
147   typedef ELFEntityIterator<const Elf_Rel> Elf_Rel_Iter;
148   typedef iterator_range<const Elf_Shdr *> Elf_Shdr_Range;
149 
150   /// \brief Archive files are 2 byte aligned, so we need this for
151   ///     PointerIntPair to work.
152   template <typename T>
153   class ArchivePointerTypeTraits {
154   public:
getAsVoidPointer(T * P)155     static inline const void *getAsVoidPointer(T *P) { return P; }
getFromVoidPointer(const void * P)156     static inline T *getFromVoidPointer(const void *P) {
157       return static_cast<T *>(P);
158     }
159     enum { NumLowBitsAvailable = 1 };
160   };
161 
162   typedef iterator_range<const Elf_Sym *> Elf_Sym_Range;
163 
164 private:
165   typedef SmallVector<const Elf_Shdr *, 2> Sections_t;
166   typedef DenseMap<unsigned, unsigned> IndexMap_t;
167 
168   StringRef Buf;
169 
base()170   const uint8_t *base() const {
171     return reinterpret_cast<const uint8_t *>(Buf.data());
172   }
173 
174   const Elf_Ehdr *Header;
175   const Elf_Shdr *SectionHeaderTable = nullptr;
176   StringRef DotShstrtab;                    // Section header string table.
177   StringRef DotStrtab;                      // Symbol header string table.
178   const Elf_Shdr *dot_symtab_sec = nullptr; // Symbol table section.
179   const Elf_Shdr *DotDynSymSec = nullptr;   // Dynamic symbol table section.
180   const Elf_Hash *HashTable = nullptr;
181 
182   const Elf_Shdr *SymbolTableSectionHeaderIndex = nullptr;
183   DenseMap<const Elf_Sym *, ELF::Elf64_Word> ExtendedSymbolTable;
184 
185   const Elf_Shdr *dot_gnu_version_sec = nullptr;   // .gnu.version
186   const Elf_Shdr *dot_gnu_version_r_sec = nullptr; // .gnu.version_r
187   const Elf_Shdr *dot_gnu_version_d_sec = nullptr; // .gnu.version_d
188 
189   /// \brief Represents a region described by entries in the .dynamic table.
190   struct DynRegionInfo {
DynRegionInfoDynRegionInfo191     DynRegionInfo() : Addr(nullptr), Size(0), EntSize(0) {}
192     /// \brief Address in current address space.
193     const void *Addr;
194     /// \brief Size in bytes of the region.
195     uintX_t Size;
196     /// \brief Size of each entity in the region.
197     uintX_t EntSize;
198   };
199 
200   DynRegionInfo DynamicRegion;
201   DynRegionInfo DynHashRegion;
202   DynRegionInfo DynStrRegion;
203   DynRegionInfo DynRelaRegion;
204 
205   // Pointer to SONAME entry in dynamic string table
206   // This is set the first time getLoadName is called.
207   mutable const char *dt_soname = nullptr;
208 
209   // Records for each version index the corresponding Verdef or Vernaux entry.
210   // This is filled the first time LoadVersionMap() is called.
211   class VersionMapEntry : public PointerIntPair<const void*, 1> {
212     public:
213     // If the integer is 0, this is an Elf_Verdef*.
214     // If the integer is 1, this is an Elf_Vernaux*.
VersionMapEntry()215     VersionMapEntry() : PointerIntPair<const void*, 1>(nullptr, 0) { }
VersionMapEntry(const Elf_Verdef * verdef)216     VersionMapEntry(const Elf_Verdef *verdef)
217         : PointerIntPair<const void*, 1>(verdef, 0) { }
VersionMapEntry(const Elf_Vernaux * vernaux)218     VersionMapEntry(const Elf_Vernaux *vernaux)
219         : PointerIntPair<const void*, 1>(vernaux, 1) { }
isNull()220     bool isNull() const { return getPointer() == nullptr; }
isVerdef()221     bool isVerdef() const { return !isNull() && getInt() == 0; }
isVernaux()222     bool isVernaux() const { return !isNull() && getInt() == 1; }
getVerdef()223     const Elf_Verdef *getVerdef() const {
224       return isVerdef() ? (const Elf_Verdef*)getPointer() : nullptr;
225     }
getVernaux()226     const Elf_Vernaux *getVernaux() const {
227       return isVernaux() ? (const Elf_Vernaux*)getPointer() : nullptr;
228     }
229   };
230   mutable SmallVector<VersionMapEntry, 16> VersionMap;
231   void LoadVersionDefs(const Elf_Shdr *sec) const;
232   void LoadVersionNeeds(const Elf_Shdr *ec) const;
233   void LoadVersionMap() const;
234 
235   void scanDynamicTable();
236 
237 public:
238   template<typename T>
239   const T        *getEntry(uint32_t Section, uint32_t Entry) const;
240   template <typename T>
241   const T *getEntry(const Elf_Shdr *Section, uint32_t Entry) const;
242 
getDotSymtabSec()243   const Elf_Shdr *getDotSymtabSec() const { return dot_symtab_sec; }
getDotDynSymSec()244   const Elf_Shdr *getDotDynSymSec() const { return DotDynSymSec; }
getHashTable()245   const Elf_Hash *getHashTable() const { return HashTable; }
246 
247   ErrorOr<StringRef> getStringTable(const Elf_Shdr *Section) const;
248   const char *getDynamicString(uintX_t Offset) const;
249   ErrorOr<StringRef> getSymbolVersion(const Elf_Shdr *section,
250                                       const Elf_Sym *Symb,
251                                       bool &IsDefault) const;
252   void VerifyStrTab(const Elf_Shdr *sh) const;
253 
254   StringRef getRelocationTypeName(uint32_t Type) const;
255   void getRelocationTypeName(uint32_t Type,
256                              SmallVectorImpl<char> &Result) const;
257 
258   /// \brief Get the symbol table section and symbol for a given relocation.
259   template <class RelT>
260   std::pair<const Elf_Shdr *, const Elf_Sym *>
261   getRelocationSymbol(const Elf_Shdr *RelSec, const RelT *Rel) const;
262 
263   ELFFile(StringRef Object, std::error_code &EC);
264 
isMipsELF64()265   bool isMipsELF64() const {
266     return Header->e_machine == ELF::EM_MIPS &&
267       Header->getFileClass() == ELF::ELFCLASS64;
268   }
269 
isMips64EL()270   bool isMips64EL() const {
271     return Header->e_machine == ELF::EM_MIPS &&
272       Header->getFileClass() == ELF::ELFCLASS64 &&
273       Header->getDataEncoding() == ELF::ELFDATA2LSB;
274   }
275 
276   const Elf_Shdr *section_begin() const;
277   const Elf_Shdr *section_end() const;
sections()278   Elf_Shdr_Range sections() const {
279     return make_range(section_begin(), section_end());
280   }
281 
282   const Elf_Sym *symbol_begin() const;
283   const Elf_Sym *symbol_end() const;
symbols()284   Elf_Sym_Range symbols() const {
285     return make_range(symbol_begin(), symbol_end());
286   }
287 
288   Elf_Dyn_Iter dynamic_table_begin() const;
289   /// \param NULLEnd use one past the first DT_NULL entry as the end instead of
290   /// the section size.
291   Elf_Dyn_Iter dynamic_table_end(bool NULLEnd = false) const;
292   Elf_Dyn_Range dynamic_table(bool NULLEnd = false) const {
293     return make_range(dynamic_table_begin(), dynamic_table_end(NULLEnd));
294   }
295 
dynamic_symbol_begin()296   const Elf_Sym *dynamic_symbol_begin() const {
297     if (!DotDynSymSec)
298       return nullptr;
299     if (DotDynSymSec->sh_entsize != sizeof(Elf_Sym))
300       report_fatal_error("Invalid symbol size");
301     return reinterpret_cast<const Elf_Sym *>(base() + DotDynSymSec->sh_offset);
302   }
303 
dynamic_symbol_end()304   const Elf_Sym *dynamic_symbol_end() const {
305     if (!DotDynSymSec)
306       return nullptr;
307     return reinterpret_cast<const Elf_Sym *>(base() + DotDynSymSec->sh_offset +
308                                              DotDynSymSec->sh_size);
309   }
310 
dynamic_symbols()311   Elf_Sym_Range dynamic_symbols() const {
312     return make_range(dynamic_symbol_begin(), dynamic_symbol_end());
313   }
314 
dyn_rela_begin()315   Elf_Rela_Iter dyn_rela_begin() const {
316     if (DynRelaRegion.Addr)
317       return Elf_Rela_Iter(DynRelaRegion.EntSize,
318         (const char *)DynRelaRegion.Addr);
319     return Elf_Rela_Iter(0, nullptr);
320   }
321 
dyn_rela_end()322   Elf_Rela_Iter dyn_rela_end() const {
323     if (DynRelaRegion.Addr)
324       return Elf_Rela_Iter(
325         DynRelaRegion.EntSize,
326         (const char *)DynRelaRegion.Addr + DynRelaRegion.Size);
327     return Elf_Rela_Iter(0, nullptr);
328   }
329 
rela_begin(const Elf_Shdr * sec)330   Elf_Rela_Iter rela_begin(const Elf_Shdr *sec) const {
331     return Elf_Rela_Iter(sec->sh_entsize,
332                          (const char *)(base() + sec->sh_offset));
333   }
334 
rela_end(const Elf_Shdr * sec)335   Elf_Rela_Iter rela_end(const Elf_Shdr *sec) const {
336     return Elf_Rela_Iter(
337         sec->sh_entsize,
338         (const char *)(base() + sec->sh_offset + sec->sh_size));
339   }
340 
rel_begin(const Elf_Shdr * sec)341   Elf_Rel_Iter rel_begin(const Elf_Shdr *sec) const {
342     return Elf_Rel_Iter(sec->sh_entsize,
343                         (const char *)(base() + sec->sh_offset));
344   }
345 
rel_end(const Elf_Shdr * sec)346   Elf_Rel_Iter rel_end(const Elf_Shdr *sec) const {
347     return Elf_Rel_Iter(sec->sh_entsize,
348                         (const char *)(base() + sec->sh_offset + sec->sh_size));
349   }
350 
351   /// \brief Iterate over program header table.
352   typedef ELFEntityIterator<const Elf_Phdr> Elf_Phdr_Iter;
353 
program_header_begin()354   Elf_Phdr_Iter program_header_begin() const {
355     return Elf_Phdr_Iter(Header->e_phentsize,
356                          (const char*)base() + Header->e_phoff);
357   }
358 
program_header_end()359   Elf_Phdr_Iter program_header_end() const {
360     return Elf_Phdr_Iter(Header->e_phentsize,
361                          (const char*)base() +
362                            Header->e_phoff +
363                            (Header->e_phnum * Header->e_phentsize));
364   }
365 
366   uint64_t getNumSections() const;
367   uintX_t getStringTableIndex() const;
368   ELF::Elf64_Word getExtendedSymbolTableIndex(const Elf_Sym *symb) const;
getHeader()369   const Elf_Ehdr *getHeader() const { return Header; }
370   ErrorOr<const Elf_Shdr *> getSection(const Elf_Sym *symb) const;
371   ErrorOr<const Elf_Shdr *> getSection(uint32_t Index) const;
372   const Elf_Sym *getSymbol(uint32_t index) const;
373 
374   ErrorOr<StringRef> getStaticSymbolName(const Elf_Sym *Symb) const;
375   ErrorOr<StringRef> getDynamicSymbolName(const Elf_Sym *Symb) const;
376   ErrorOr<StringRef> getSymbolName(const Elf_Sym *Symb, bool IsDynamic) const;
377 
378   ErrorOr<StringRef> getSectionName(const Elf_Shdr *Section) const;
379   ErrorOr<ArrayRef<uint8_t> > getSectionContents(const Elf_Shdr *Sec) const;
380   StringRef getLoadName() const;
381 };
382 
383 typedef ELFFile<ELFType<support::little, false>> ELF32LEFile;
384 typedef ELFFile<ELFType<support::little, true>> ELF64LEFile;
385 typedef ELFFile<ELFType<support::big, false>> ELF32BEFile;
386 typedef ELFFile<ELFType<support::big, true>> ELF64BEFile;
387 
388 // Iterate through the version definitions, and place each Elf_Verdef
389 // in the VersionMap according to its index.
390 template <class ELFT>
LoadVersionDefs(const Elf_Shdr * sec)391 void ELFFile<ELFT>::LoadVersionDefs(const Elf_Shdr *sec) const {
392   unsigned vd_size = sec->sh_size;  // Size of section in bytes
393   unsigned vd_count = sec->sh_info; // Number of Verdef entries
394   const char *sec_start = (const char*)base() + sec->sh_offset;
395   const char *sec_end = sec_start + vd_size;
396   // The first Verdef entry is at the start of the section.
397   const char *p = sec_start;
398   for (unsigned i = 0; i < vd_count; i++) {
399     if (p + sizeof(Elf_Verdef) > sec_end)
400       report_fatal_error("Section ended unexpectedly while scanning "
401                          "version definitions.");
402     const Elf_Verdef *vd = reinterpret_cast<const Elf_Verdef *>(p);
403     if (vd->vd_version != ELF::VER_DEF_CURRENT)
404       report_fatal_error("Unexpected verdef version");
405     size_t index = vd->vd_ndx & ELF::VERSYM_VERSION;
406     if (index >= VersionMap.size())
407       VersionMap.resize(index + 1);
408     VersionMap[index] = VersionMapEntry(vd);
409     p += vd->vd_next;
410   }
411 }
412 
413 // Iterate through the versions needed section, and place each Elf_Vernaux
414 // in the VersionMap according to its index.
415 template <class ELFT>
LoadVersionNeeds(const Elf_Shdr * sec)416 void ELFFile<ELFT>::LoadVersionNeeds(const Elf_Shdr *sec) const {
417   unsigned vn_size = sec->sh_size;  // Size of section in bytes
418   unsigned vn_count = sec->sh_info; // Number of Verneed entries
419   const char *sec_start = (const char *)base() + sec->sh_offset;
420   const char *sec_end = sec_start + vn_size;
421   // The first Verneed entry is at the start of the section.
422   const char *p = sec_start;
423   for (unsigned i = 0; i < vn_count; i++) {
424     if (p + sizeof(Elf_Verneed) > sec_end)
425       report_fatal_error("Section ended unexpectedly while scanning "
426                          "version needed records.");
427     const Elf_Verneed *vn = reinterpret_cast<const Elf_Verneed *>(p);
428     if (vn->vn_version != ELF::VER_NEED_CURRENT)
429       report_fatal_error("Unexpected verneed version");
430     // Iterate through the Vernaux entries
431     const char *paux = p + vn->vn_aux;
432     for (unsigned j = 0; j < vn->vn_cnt; j++) {
433       if (paux + sizeof(Elf_Vernaux) > sec_end)
434         report_fatal_error("Section ended unexpected while scanning auxiliary "
435                            "version needed records.");
436       const Elf_Vernaux *vna = reinterpret_cast<const Elf_Vernaux *>(paux);
437       size_t index = vna->vna_other & ELF::VERSYM_VERSION;
438       if (index >= VersionMap.size())
439         VersionMap.resize(index + 1);
440       VersionMap[index] = VersionMapEntry(vna);
441       paux += vna->vna_next;
442     }
443     p += vn->vn_next;
444   }
445 }
446 
447 template <class ELFT>
LoadVersionMap()448 void ELFFile<ELFT>::LoadVersionMap() const {
449   // If there is no dynamic symtab or version table, there is nothing to do.
450   if (!DotDynSymSec || !dot_gnu_version_sec)
451     return;
452 
453   // Has the VersionMap already been loaded?
454   if (VersionMap.size() > 0)
455     return;
456 
457   // The first two version indexes are reserved.
458   // Index 0 is LOCAL, index 1 is GLOBAL.
459   VersionMap.push_back(VersionMapEntry());
460   VersionMap.push_back(VersionMapEntry());
461 
462   if (dot_gnu_version_d_sec)
463     LoadVersionDefs(dot_gnu_version_d_sec);
464 
465   if (dot_gnu_version_r_sec)
466     LoadVersionNeeds(dot_gnu_version_r_sec);
467 }
468 
469 template <class ELFT>
470 ELF::Elf64_Word
getExtendedSymbolTableIndex(const Elf_Sym * symb)471 ELFFile<ELFT>::getExtendedSymbolTableIndex(const Elf_Sym *symb) const {
472   assert(symb->st_shndx == ELF::SHN_XINDEX);
473   return ExtendedSymbolTable.lookup(symb);
474 }
475 
476 template <class ELFT>
477 ErrorOr<const typename ELFFile<ELFT>::Elf_Shdr *>
getSection(const Elf_Sym * symb)478 ELFFile<ELFT>::getSection(const Elf_Sym *symb) const {
479   uint32_t Index = symb->st_shndx;
480   if (Index == ELF::SHN_XINDEX)
481     return getSection(ExtendedSymbolTable.lookup(symb));
482   if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
483     return nullptr;
484   return getSection(symb->st_shndx);
485 }
486 
487 template <class ELFT>
488 const typename ELFFile<ELFT>::Elf_Sym *
getSymbol(uint32_t Index)489 ELFFile<ELFT>::getSymbol(uint32_t Index) const {
490   return &*(symbol_begin() + Index);
491 }
492 
493 template <class ELFT>
494 ErrorOr<ArrayRef<uint8_t> >
getSectionContents(const Elf_Shdr * Sec)495 ELFFile<ELFT>::getSectionContents(const Elf_Shdr *Sec) const {
496   if (Sec->sh_offset + Sec->sh_size > Buf.size())
497     return object_error::parse_failed;
498   const uint8_t *Start = base() + Sec->sh_offset;
499   return makeArrayRef(Start, Sec->sh_size);
500 }
501 
502 template <class ELFT>
getRelocationTypeName(uint32_t Type)503 StringRef ELFFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
504   return getELFRelocationTypeName(Header->e_machine, Type);
505 }
506 
507 template <class ELFT>
getRelocationTypeName(uint32_t Type,SmallVectorImpl<char> & Result)508 void ELFFile<ELFT>::getRelocationTypeName(uint32_t Type,
509                                           SmallVectorImpl<char> &Result) const {
510   if (!isMipsELF64()) {
511     StringRef Name = getRelocationTypeName(Type);
512     Result.append(Name.begin(), Name.end());
513   } else {
514     // The Mips N64 ABI allows up to three operations to be specified per
515     // relocation record. Unfortunately there's no easy way to test for the
516     // presence of N64 ELFs as they have no special flag that identifies them
517     // as being N64. We can safely assume at the moment that all Mips
518     // ELFCLASS64 ELFs are N64. New Mips64 ABIs should provide enough
519     // information to disambiguate between old vs new ABIs.
520     uint8_t Type1 = (Type >> 0) & 0xFF;
521     uint8_t Type2 = (Type >> 8) & 0xFF;
522     uint8_t Type3 = (Type >> 16) & 0xFF;
523 
524     // Concat all three relocation type names.
525     StringRef Name = getRelocationTypeName(Type1);
526     Result.append(Name.begin(), Name.end());
527 
528     Name = getRelocationTypeName(Type2);
529     Result.append(1, '/');
530     Result.append(Name.begin(), Name.end());
531 
532     Name = getRelocationTypeName(Type3);
533     Result.append(1, '/');
534     Result.append(Name.begin(), Name.end());
535   }
536 }
537 
538 template <class ELFT>
539 template <class RelT>
540 std::pair<const typename ELFFile<ELFT>::Elf_Shdr *,
541           const typename ELFFile<ELFT>::Elf_Sym *>
getRelocationSymbol(const Elf_Shdr * Sec,const RelT * Rel)542 ELFFile<ELFT>::getRelocationSymbol(const Elf_Shdr *Sec, const RelT *Rel) const {
543   if (!Sec->sh_link)
544     return std::make_pair(nullptr, nullptr);
545   ErrorOr<const Elf_Shdr *> SymTableOrErr = getSection(Sec->sh_link);
546   if (std::error_code EC = SymTableOrErr.getError())
547     report_fatal_error(EC.message());
548   const Elf_Shdr *SymTable = *SymTableOrErr;
549   return std::make_pair(
550       SymTable, getEntry<Elf_Sym>(SymTable, Rel->getSymbol(isMips64EL())));
551 }
552 
553 template <class ELFT>
getNumSections()554 uint64_t ELFFile<ELFT>::getNumSections() const {
555   assert(Header && "Header not initialized!");
556   if (Header->e_shnum == ELF::SHN_UNDEF && Header->e_shoff > 0) {
557     assert(SectionHeaderTable && "SectionHeaderTable not initialized!");
558     return SectionHeaderTable->sh_size;
559   }
560   return Header->e_shnum;
561 }
562 
563 template <class ELFT>
getStringTableIndex()564 typename ELFFile<ELFT>::uintX_t ELFFile<ELFT>::getStringTableIndex() const {
565   if (Header->e_shnum == ELF::SHN_UNDEF) {
566     if (Header->e_shstrndx == ELF::SHN_HIRESERVE)
567       return SectionHeaderTable->sh_link;
568     if (Header->e_shstrndx >= getNumSections())
569       return 0;
570   }
571   return Header->e_shstrndx;
572 }
573 
574 template <class ELFT>
ELFFile(StringRef Object,std::error_code & EC)575 ELFFile<ELFT>::ELFFile(StringRef Object, std::error_code &EC)
576     : Buf(Object) {
577   const uint64_t FileSize = Buf.size();
578 
579   if (sizeof(Elf_Ehdr) > FileSize) {
580     // File too short!
581     EC = object_error::parse_failed;
582     return;
583   }
584 
585   Header = reinterpret_cast<const Elf_Ehdr *>(base());
586 
587   if (Header->e_shoff == 0) {
588     scanDynamicTable();
589     return;
590   }
591 
592   const uint64_t SectionTableOffset = Header->e_shoff;
593 
594   if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize) {
595     // Section header table goes past end of file!
596     EC = object_error::parse_failed;
597     return;
598   }
599 
600   // The getNumSections() call below depends on SectionHeaderTable being set.
601   SectionHeaderTable =
602     reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
603   const uint64_t SectionTableSize = getNumSections() * Header->e_shentsize;
604 
605   if (SectionTableOffset + SectionTableSize > FileSize) {
606     // Section table goes past end of file!
607     EC = object_error::parse_failed;
608     return;
609   }
610 
611   // Scan sections for special sections.
612 
613   for (const Elf_Shdr &Sec : sections()) {
614     switch (Sec.sh_type) {
615     case ELF::SHT_HASH:
616       if (HashTable) {
617         EC = object_error::parse_failed;
618         return;
619       }
620       HashTable = reinterpret_cast<const Elf_Hash *>(base() + Sec.sh_offset);
621       break;
622     case ELF::SHT_SYMTAB_SHNDX:
623       if (SymbolTableSectionHeaderIndex) {
624         // More than one .symtab_shndx!
625         EC = object_error::parse_failed;
626         return;
627       }
628       SymbolTableSectionHeaderIndex = &Sec;
629       break;
630     case ELF::SHT_SYMTAB: {
631       if (dot_symtab_sec) {
632         // More than one .symtab!
633         EC = object_error::parse_failed;
634         return;
635       }
636       dot_symtab_sec = &Sec;
637       ErrorOr<const Elf_Shdr *> SectionOrErr = getSection(Sec.sh_link);
638       if ((EC = SectionOrErr.getError()))
639         return;
640       ErrorOr<StringRef> SymtabOrErr = getStringTable(*SectionOrErr);
641       if ((EC = SymtabOrErr.getError()))
642         return;
643       DotStrtab = *SymtabOrErr;
644     } break;
645     case ELF::SHT_DYNSYM: {
646       if (DotDynSymSec) {
647         // More than one .dynsym!
648         EC = object_error::parse_failed;
649         return;
650       }
651       DotDynSymSec = &Sec;
652       ErrorOr<const Elf_Shdr *> SectionOrErr = getSection(Sec.sh_link);
653       if ((EC = SectionOrErr.getError()))
654         return;
655       ErrorOr<StringRef> SymtabOrErr = getStringTable(*SectionOrErr);
656       if ((EC = SymtabOrErr.getError()))
657         return;
658       DynStrRegion.Addr = SymtabOrErr->data();
659       DynStrRegion.Size = SymtabOrErr->size();
660       DynStrRegion.EntSize = 1;
661       break;
662     }
663     case ELF::SHT_DYNAMIC:
664       if (DynamicRegion.Addr) {
665         // More than one .dynamic!
666         EC = object_error::parse_failed;
667         return;
668       }
669       DynamicRegion.Addr = base() + Sec.sh_offset;
670       DynamicRegion.Size = Sec.sh_size;
671       DynamicRegion.EntSize = Sec.sh_entsize;
672       break;
673     case ELF::SHT_GNU_versym:
674       if (dot_gnu_version_sec != nullptr) {
675         // More than one .gnu.version section!
676         EC = object_error::parse_failed;
677         return;
678       }
679       dot_gnu_version_sec = &Sec;
680       break;
681     case ELF::SHT_GNU_verdef:
682       if (dot_gnu_version_d_sec != nullptr) {
683         // More than one .gnu.version_d section!
684         EC = object_error::parse_failed;
685         return;
686       }
687       dot_gnu_version_d_sec = &Sec;
688       break;
689     case ELF::SHT_GNU_verneed:
690       if (dot_gnu_version_r_sec != nullptr) {
691         // More than one .gnu.version_r section!
692         EC = object_error::parse_failed;
693         return;
694       }
695       dot_gnu_version_r_sec = &Sec;
696       break;
697     }
698   }
699 
700   // Get string table sections.
701   ErrorOr<const Elf_Shdr *> StrTabSecOrErr = getSection(getStringTableIndex());
702   if ((EC = StrTabSecOrErr.getError()))
703     return;
704 
705   ErrorOr<StringRef> SymtabOrErr = getStringTable(*StrTabSecOrErr);
706   if ((EC = SymtabOrErr.getError()))
707     return;
708   DotShstrtab = *SymtabOrErr;
709 
710   // Build symbol name side-mapping if there is one.
711   if (SymbolTableSectionHeaderIndex) {
712     const Elf_Word *ShndxTable = reinterpret_cast<const Elf_Word*>(base() +
713                                       SymbolTableSectionHeaderIndex->sh_offset);
714     for (const Elf_Sym &S : symbols()) {
715       if (*ShndxTable != ELF::SHN_UNDEF)
716         ExtendedSymbolTable[&S] = *ShndxTable;
717       ++ShndxTable;
718     }
719   }
720 
721   scanDynamicTable();
722 
723   EC = std::error_code();
724 }
725 
726 template <class ELFT>
scanDynamicTable()727 void ELFFile<ELFT>::scanDynamicTable() {
728   // Build load-address to file-offset map.
729   typedef IntervalMap<
730       uintX_t, uintptr_t,
731       IntervalMapImpl::NodeSizer<uintX_t, uintptr_t>::LeafSize,
732       IntervalMapHalfOpenInfo<uintX_t>> LoadMapT;
733   typename LoadMapT::Allocator Alloc;
734   // Allocate the IntervalMap on the heap to work around MSVC bug where the
735   // stack doesn't get realigned despite LoadMap having alignment 8 (PR24113).
736   std::unique_ptr<LoadMapT> LoadMap(new LoadMapT(Alloc));
737 
738   for (Elf_Phdr_Iter PhdrI = program_header_begin(),
739                      PhdrE = program_header_end();
740        PhdrI != PhdrE; ++PhdrI) {
741     if (PhdrI->p_type == ELF::PT_DYNAMIC) {
742       DynamicRegion.Addr = base() + PhdrI->p_offset;
743       DynamicRegion.Size = PhdrI->p_filesz;
744       DynamicRegion.EntSize = sizeof(Elf_Dyn);
745       continue;
746     }
747     if (PhdrI->p_type != ELF::PT_LOAD)
748       continue;
749     if (PhdrI->p_filesz == 0)
750       continue;
751     LoadMap->insert(PhdrI->p_vaddr, PhdrI->p_vaddr + PhdrI->p_filesz,
752                     PhdrI->p_offset);
753   }
754 
755   auto toMappedAddr = [&](uint64_t VAddr) -> const uint8_t * {
756     auto I = LoadMap->find(VAddr);
757     if (I == LoadMap->end())
758       return nullptr;
759     return this->base() + I.value() + (VAddr - I.start());
760   };
761 
762   for (Elf_Dyn_Iter DynI = dynamic_table_begin(), DynE = dynamic_table_end();
763        DynI != DynE; ++DynI) {
764     switch (DynI->d_tag) {
765     case ELF::DT_HASH:
766       if (HashTable)
767         continue;
768       HashTable =
769           reinterpret_cast<const Elf_Hash *>(toMappedAddr(DynI->getPtr()));
770       break;
771     case ELF::DT_STRTAB:
772       if (!DynStrRegion.Addr)
773         DynStrRegion.Addr = toMappedAddr(DynI->getPtr());
774       break;
775     case ELF::DT_STRSZ:
776       if (!DynStrRegion.Size)
777         DynStrRegion.Size = DynI->getVal();
778       break;
779     case ELF::DT_RELA:
780       if (!DynRelaRegion.Addr)
781         DynRelaRegion.Addr = toMappedAddr(DynI->getPtr());
782       break;
783     case ELF::DT_RELASZ:
784       DynRelaRegion.Size = DynI->getVal();
785       break;
786     case ELF::DT_RELAENT:
787       DynRelaRegion.EntSize = DynI->getVal();
788     }
789   }
790 }
791 
792 template <class ELFT>
section_begin()793 const typename ELFFile<ELFT>::Elf_Shdr *ELFFile<ELFT>::section_begin() const {
794   if (Header->e_shentsize != sizeof(Elf_Shdr))
795     report_fatal_error(
796         "Invalid section header entry size (e_shentsize) in ELF header");
797   return reinterpret_cast<const Elf_Shdr *>(base() + Header->e_shoff);
798 }
799 
800 template <class ELFT>
section_end()801 const typename ELFFile<ELFT>::Elf_Shdr *ELFFile<ELFT>::section_end() const {
802   return section_begin() + getNumSections();
803 }
804 
805 template <class ELFT>
symbol_begin()806 const typename ELFFile<ELFT>::Elf_Sym *ELFFile<ELFT>::symbol_begin() const {
807   if (!dot_symtab_sec)
808     return nullptr;
809   if (dot_symtab_sec->sh_entsize != sizeof(Elf_Sym))
810     report_fatal_error("Invalid symbol size");
811   return reinterpret_cast<const Elf_Sym *>(base() + dot_symtab_sec->sh_offset);
812 }
813 
814 template <class ELFT>
symbol_end()815 const typename ELFFile<ELFT>::Elf_Sym *ELFFile<ELFT>::symbol_end() const {
816   if (!dot_symtab_sec)
817     return nullptr;
818   return reinterpret_cast<const Elf_Sym *>(base() + dot_symtab_sec->sh_offset +
819                                            dot_symtab_sec->sh_size);
820 }
821 
822 template <class ELFT>
823 typename ELFFile<ELFT>::Elf_Dyn_Iter
dynamic_table_begin()824 ELFFile<ELFT>::dynamic_table_begin() const {
825   if (DynamicRegion.Addr)
826     return Elf_Dyn_Iter(DynamicRegion.EntSize,
827                         (const char *)DynamicRegion.Addr);
828   return Elf_Dyn_Iter(0, nullptr);
829 }
830 
831 template <class ELFT>
832 typename ELFFile<ELFT>::Elf_Dyn_Iter
dynamic_table_end(bool NULLEnd)833 ELFFile<ELFT>::dynamic_table_end(bool NULLEnd) const {
834   if (!DynamicRegion.Addr)
835     return Elf_Dyn_Iter(0, nullptr);
836   Elf_Dyn_Iter Ret(DynamicRegion.EntSize,
837                     (const char *)DynamicRegion.Addr + DynamicRegion.Size);
838 
839   if (NULLEnd) {
840     Elf_Dyn_Iter Start = dynamic_table_begin();
841     while (Start != Ret && Start->getTag() != ELF::DT_NULL)
842       ++Start;
843 
844     // Include the DT_NULL.
845     if (Start != Ret)
846       ++Start;
847     Ret = Start;
848   }
849   return Ret;
850 }
851 
852 template <class ELFT>
getLoadName()853 StringRef ELFFile<ELFT>::getLoadName() const {
854   if (!dt_soname) {
855     dt_soname = "";
856     // Find the DT_SONAME entry
857     for (const auto &Entry : dynamic_table())
858       if (Entry.getTag() == ELF::DT_SONAME) {
859         dt_soname = getDynamicString(Entry.getVal());
860         break;
861       }
862   }
863   return dt_soname;
864 }
865 
866 template <class ELFT>
867 template <typename T>
getEntry(uint32_t Section,uint32_t Entry)868 const T *ELFFile<ELFT>::getEntry(uint32_t Section, uint32_t Entry) const {
869   ErrorOr<const Elf_Shdr *> Sec = getSection(Section);
870   if (std::error_code EC = Sec.getError())
871     report_fatal_error(EC.message());
872   return getEntry<T>(*Sec, Entry);
873 }
874 
875 template <class ELFT>
876 template <typename T>
getEntry(const Elf_Shdr * Section,uint32_t Entry)877 const T *ELFFile<ELFT>::getEntry(const Elf_Shdr *Section,
878                                  uint32_t Entry) const {
879   return reinterpret_cast<const T *>(base() + Section->sh_offset +
880                                      (Entry * Section->sh_entsize));
881 }
882 
883 template <class ELFT>
884 ErrorOr<const typename ELFFile<ELFT>::Elf_Shdr *>
getSection(uint32_t Index)885 ELFFile<ELFT>::getSection(uint32_t Index) const {
886   assert(SectionHeaderTable && "SectionHeaderTable not initialized!");
887   if (Index >= getNumSections())
888     return object_error::invalid_section_index;
889 
890   return reinterpret_cast<const Elf_Shdr *>(
891       reinterpret_cast<const char *>(SectionHeaderTable) +
892       (Index * Header->e_shentsize));
893 }
894 
895 template <class ELFT>
896 ErrorOr<StringRef>
getStringTable(const Elf_Shdr * Section)897 ELFFile<ELFT>::getStringTable(const Elf_Shdr *Section) const {
898   if (Section->sh_type != ELF::SHT_STRTAB)
899     return object_error::parse_failed;
900   uint64_t Offset = Section->sh_offset;
901   uint64_t Size = Section->sh_size;
902   if (Offset + Size > Buf.size())
903     return object_error::parse_failed;
904   StringRef Data((const char *)base() + Section->sh_offset, Size);
905   if (Data[Size - 1] != '\0')
906     return object_error::string_table_non_null_end;
907   return Data;
908 }
909 
910 template <class ELFT>
getDynamicString(uintX_t Offset)911 const char *ELFFile<ELFT>::getDynamicString(uintX_t Offset) const {
912   if (Offset >= DynStrRegion.Size)
913     return nullptr;
914   return (const char *)DynStrRegion.Addr + Offset;
915 }
916 
917 template <class ELFT>
918 ErrorOr<StringRef>
getStaticSymbolName(const Elf_Sym * Symb)919 ELFFile<ELFT>::getStaticSymbolName(const Elf_Sym *Symb) const {
920   return Symb->getName(DotStrtab);
921 }
922 
923 template <class ELFT>
924 ErrorOr<StringRef>
getDynamicSymbolName(const Elf_Sym * Symb)925 ELFFile<ELFT>::getDynamicSymbolName(const Elf_Sym *Symb) const {
926   return StringRef(getDynamicString(Symb->st_name));
927 }
928 
929 template <class ELFT>
getSymbolName(const Elf_Sym * Symb,bool IsDynamic)930 ErrorOr<StringRef> ELFFile<ELFT>::getSymbolName(const Elf_Sym *Symb,
931                                                 bool IsDynamic) const {
932   if (IsDynamic)
933     return getDynamicSymbolName(Symb);
934   return getStaticSymbolName(Symb);
935 }
936 
937 template <class ELFT>
938 ErrorOr<StringRef>
getSectionName(const Elf_Shdr * Section)939 ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section) const {
940   uint32_t Offset = Section->sh_name;
941   if (Offset >= DotShstrtab.size())
942     return object_error::parse_failed;
943   return StringRef(DotShstrtab.data() + Offset);
944 }
945 
946 template <class ELFT>
getSymbolVersion(const Elf_Shdr * section,const Elf_Sym * symb,bool & IsDefault)947 ErrorOr<StringRef> ELFFile<ELFT>::getSymbolVersion(const Elf_Shdr *section,
948                                                    const Elf_Sym *symb,
949                                                    bool &IsDefault) const {
950   StringRef StrTab;
951   if (section) {
952     ErrorOr<StringRef> StrTabOrErr = getStringTable(section);
953     if (std::error_code EC = StrTabOrErr.getError())
954       return EC;
955     StrTab = *StrTabOrErr;
956   }
957   // Handle non-dynamic symbols.
958   if (section != DotDynSymSec && section != nullptr) {
959     // Non-dynamic symbols can have versions in their names
960     // A name of the form 'foo@V1' indicates version 'V1', non-default.
961     // A name of the form 'foo@@V2' indicates version 'V2', default version.
962     ErrorOr<StringRef> SymName = symb->getName(StrTab);
963     if (!SymName)
964       return SymName;
965     StringRef Name = *SymName;
966     size_t atpos = Name.find('@');
967     if (atpos == StringRef::npos) {
968       IsDefault = false;
969       return StringRef("");
970     }
971     ++atpos;
972     if (atpos < Name.size() && Name[atpos] == '@') {
973       IsDefault = true;
974       ++atpos;
975     } else {
976       IsDefault = false;
977     }
978     return Name.substr(atpos);
979   }
980 
981   // This is a dynamic symbol. Look in the GNU symbol version table.
982   if (!dot_gnu_version_sec) {
983     // No version table.
984     IsDefault = false;
985     return StringRef("");
986   }
987 
988   // Determine the position in the symbol table of this entry.
989   size_t entry_index =
990       (reinterpret_cast<uintptr_t>(symb) - DotDynSymSec->sh_offset -
991        reinterpret_cast<uintptr_t>(base())) /
992       sizeof(Elf_Sym);
993 
994   // Get the corresponding version index entry
995   const Elf_Versym *vs = getEntry<Elf_Versym>(dot_gnu_version_sec, entry_index);
996   size_t version_index = vs->vs_index & ELF::VERSYM_VERSION;
997 
998   // Special markers for unversioned symbols.
999   if (version_index == ELF::VER_NDX_LOCAL ||
1000       version_index == ELF::VER_NDX_GLOBAL) {
1001     IsDefault = false;
1002     return StringRef("");
1003   }
1004 
1005   // Lookup this symbol in the version table
1006   LoadVersionMap();
1007   if (version_index >= VersionMap.size() || VersionMap[version_index].isNull())
1008     return object_error::parse_failed;
1009   const VersionMapEntry &entry = VersionMap[version_index];
1010 
1011   // Get the version name string
1012   size_t name_offset;
1013   if (entry.isVerdef()) {
1014     // The first Verdaux entry holds the name.
1015     name_offset = entry.getVerdef()->getAux()->vda_name;
1016   } else {
1017     name_offset = entry.getVernaux()->vna_name;
1018   }
1019 
1020   // Set IsDefault
1021   if (entry.isVerdef()) {
1022     IsDefault = !(vs->vs_index & ELF::VERSYM_HIDDEN);
1023   } else {
1024     IsDefault = false;
1025   }
1026 
1027   if (name_offset >= DynStrRegion.Size)
1028     return object_error::parse_failed;
1029   return StringRef(getDynamicString(name_offset));
1030 }
1031 
1032 /// This function returns the hash value for a symbol in the .dynsym section
1033 /// Name of the API remains consistent as specified in the libelf
1034 /// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
elf_hash(StringRef & symbolName)1035 static inline unsigned elf_hash(StringRef &symbolName) {
1036   unsigned h = 0, g;
1037   for (unsigned i = 0, j = symbolName.size(); i < j; i++) {
1038     h = (h << 4) + symbolName[i];
1039     g = h & 0xf0000000L;
1040     if (g != 0)
1041       h ^= g >> 24;
1042     h &= ~g;
1043   }
1044   return h;
1045 }
1046 } // end namespace object
1047 } // end namespace llvm
1048 
1049 #endif
1050