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/PointerIntPair.h"
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/StringSwitch.h"
22 #include "llvm/ADT/Triple.h"
23 #include "llvm/Object/ELFTypes.h"
24 #include "llvm/Object/Error.h"
25 #include "llvm/Support/Casting.h"
26 #include "llvm/Support/ELF.h"
27 #include "llvm/Support/Endian.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/ErrorOr.h"
30 #include "llvm/Support/MemoryBuffer.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include <algorithm>
33 #include <limits>
34 #include <utility>
35
36 namespace llvm {
37 namespace object {
38
39 StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type);
40
41 // Subclasses of ELFFile may need this for template instantiation
42 inline std::pair<unsigned char, unsigned char>
getElfArchType(StringRef Object)43 getElfArchType(StringRef Object) {
44 if (Object.size() < ELF::EI_NIDENT)
45 return std::make_pair((uint8_t)ELF::ELFCLASSNONE,
46 (uint8_t)ELF::ELFDATANONE);
47 return std::make_pair((uint8_t)Object[ELF::EI_CLASS],
48 (uint8_t)Object[ELF::EI_DATA]);
49 }
50
51 template <class ELFT>
52 class ELFFile {
53 public:
54 LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
55 typedef typename std::conditional<ELFT::Is64Bits,
56 uint64_t, uint32_t>::type uintX_t;
57
58 /// \brief Iterate over constant sized entities.
59 template <class EntT>
60 class ELFEntityIterator {
61 public:
62 typedef ptrdiff_t difference_type;
63 typedef EntT value_type;
64 typedef std::forward_iterator_tag iterator_category;
65 typedef value_type &reference;
66 typedef value_type *pointer;
67
68 /// \brief Default construct iterator.
ELFEntityIterator()69 ELFEntityIterator() : EntitySize(0), Current(nullptr) {}
ELFEntityIterator(uintX_t EntSize,const char * Start)70 ELFEntityIterator(uintX_t EntSize, const char *Start)
71 : EntitySize(EntSize), Current(Start) {}
72
73 reference operator *() {
74 assert(Current && "Attempted to dereference an invalid iterator!");
75 return *reinterpret_cast<pointer>(Current);
76 }
77
78 pointer operator ->() {
79 assert(Current && "Attempted to dereference an invalid iterator!");
80 return reinterpret_cast<pointer>(Current);
81 }
82
83 bool operator ==(const ELFEntityIterator &Other) {
84 return Current == Other.Current;
85 }
86
87 bool operator !=(const ELFEntityIterator &Other) {
88 return !(*this == Other);
89 }
90
91 ELFEntityIterator &operator ++() {
92 assert(Current && "Attempted to increment an invalid iterator!");
93 Current += EntitySize;
94 return *this;
95 }
96
97 ELFEntityIterator &operator+(difference_type n) {
98 assert(Current && "Attempted to increment an invalid iterator!");
99 Current += (n * EntitySize);
100 return *this;
101 }
102
103 ELFEntityIterator &operator-(difference_type n) {
104 assert(Current && "Attempted to subtract an invalid iterator!");
105 Current -= (n * EntitySize);
106 return *this;
107 }
108
109 ELFEntityIterator operator ++(int) {
110 ELFEntityIterator Tmp = *this;
111 ++*this;
112 return Tmp;
113 }
114
115 difference_type operator -(const ELFEntityIterator &Other) const {
116 assert(EntitySize == Other.EntitySize &&
117 "Subtracting iterators of different EntitySize!");
118 return (Current - Other.Current) / EntitySize;
119 }
120
get()121 const char *get() const { return Current; }
122
getEntSize()123 uintX_t getEntSize() const { return EntitySize; }
124
125 private:
126 uintX_t EntitySize;
127 const char *Current;
128 };
129
130 typedef Elf_Ehdr_Impl<ELFT> Elf_Ehdr;
131 typedef Elf_Shdr_Impl<ELFT> Elf_Shdr;
132 typedef Elf_Sym_Impl<ELFT> Elf_Sym;
133 typedef Elf_Dyn_Impl<ELFT> Elf_Dyn;
134 typedef Elf_Phdr_Impl<ELFT> Elf_Phdr;
135 typedef Elf_Rel_Impl<ELFT, false> Elf_Rel;
136 typedef Elf_Rel_Impl<ELFT, true> Elf_Rela;
137 typedef Elf_Verdef_Impl<ELFT> Elf_Verdef;
138 typedef Elf_Verdaux_Impl<ELFT> Elf_Verdaux;
139 typedef Elf_Verneed_Impl<ELFT> Elf_Verneed;
140 typedef Elf_Vernaux_Impl<ELFT> Elf_Vernaux;
141 typedef Elf_Versym_Impl<ELFT> Elf_Versym;
142 typedef ELFEntityIterator<const Elf_Dyn> Elf_Dyn_Iter;
143 typedef iterator_range<Elf_Dyn_Iter> Elf_Dyn_Range;
144 typedef ELFEntityIterator<const Elf_Rela> Elf_Rela_Iter;
145 typedef ELFEntityIterator<const Elf_Rel> Elf_Rel_Iter;
146 typedef ELFEntityIterator<const Elf_Shdr> Elf_Shdr_Iter;
147 typedef iterator_range<Elf_Shdr_Iter> Elf_Shdr_Range;
148
149 /// \brief Archive files are 2 byte aligned, so we need this for
150 /// PointerIntPair to work.
151 template <typename T>
152 class ArchivePointerTypeTraits {
153 public:
getAsVoidPointer(T * P)154 static inline const void *getAsVoidPointer(T *P) { return P; }
getFromVoidPointer(const void * P)155 static inline T *getFromVoidPointer(const void *P) {
156 return static_cast<T *>(P);
157 }
158 enum { NumLowBitsAvailable = 1 };
159 };
160
161 class Elf_Sym_Iter {
162 public:
163 typedef ptrdiff_t difference_type;
164 typedef const Elf_Sym value_type;
165 typedef std::random_access_iterator_tag iterator_category;
166 typedef value_type &reference;
167 typedef value_type *pointer;
168
169 /// \brief Default construct iterator.
Elf_Sym_Iter()170 Elf_Sym_Iter() : EntitySize(0), Current(0, false) {}
Elf_Sym_Iter(uintX_t EntSize,const char * Start,bool IsDynamic)171 Elf_Sym_Iter(uintX_t EntSize, const char *Start, bool IsDynamic)
172 : EntitySize(EntSize), Current(Start, IsDynamic) {}
173
174 reference operator*() {
175 assert(Current.getPointer() &&
176 "Attempted to dereference an invalid iterator!");
177 return *reinterpret_cast<pointer>(Current.getPointer());
178 }
179
180 pointer operator->() {
181 assert(Current.getPointer() &&
182 "Attempted to dereference an invalid iterator!");
183 return reinterpret_cast<pointer>(Current.getPointer());
184 }
185
186 bool operator==(const Elf_Sym_Iter &Other) {
187 return Current == Other.Current;
188 }
189
190 bool operator!=(const Elf_Sym_Iter &Other) { return !(*this == Other); }
191
192 Elf_Sym_Iter &operator++() {
193 assert(Current.getPointer() &&
194 "Attempted to increment an invalid iterator!");
195 Current.setPointer(Current.getPointer() + EntitySize);
196 return *this;
197 }
198
199 Elf_Sym_Iter operator++(int) {
200 Elf_Sym_Iter Tmp = *this;
201 ++*this;
202 return Tmp;
203 }
204
205 Elf_Sym_Iter operator+(difference_type Dist) {
206 assert(Current.getPointer() &&
207 "Attempted to increment an invalid iterator!");
208 Current.setPointer(Current.getPointer() + EntitySize * Dist);
209 return *this;
210 }
211
212 difference_type operator-(const Elf_Sym_Iter &Other) const {
213 assert(EntitySize == Other.EntitySize &&
214 "Subtracting iterators of different EntitySize!");
215 return (Current.getPointer() - Other.Current.getPointer()) / EntitySize;
216 }
217
get()218 const char *get() const { return Current.getPointer(); }
219
isDynamic()220 bool isDynamic() const { return Current.getInt(); }
221
getEntSize()222 uintX_t getEntSize() const { return EntitySize; }
223
224 private:
225 uintX_t EntitySize;
226 PointerIntPair<const char *, 1, bool,
227 ArchivePointerTypeTraits<const char> > Current;
228 };
229
230 private:
231 typedef SmallVector<const Elf_Shdr *, 2> Sections_t;
232 typedef DenseMap<unsigned, unsigned> IndexMap_t;
233
234 StringRef Buf;
235
base()236 const uint8_t *base() const {
237 return reinterpret_cast<const uint8_t *>(Buf.data());
238 }
239
240 const Elf_Ehdr *Header;
241 const Elf_Shdr *SectionHeaderTable;
242 const Elf_Shdr *dot_shstrtab_sec; // Section header string table.
243 const Elf_Shdr *dot_strtab_sec; // Symbol header string table.
244 const Elf_Shdr *dot_symtab_sec; // Symbol table section.
245
246 const Elf_Shdr *SymbolTableSectionHeaderIndex;
247 DenseMap<const Elf_Sym *, ELF::Elf64_Word> ExtendedSymbolTable;
248
249 const Elf_Shdr *dot_gnu_version_sec; // .gnu.version
250 const Elf_Shdr *dot_gnu_version_r_sec; // .gnu.version_r
251 const Elf_Shdr *dot_gnu_version_d_sec; // .gnu.version_d
252
253 /// \brief Represents a region described by entries in the .dynamic table.
254 struct DynRegionInfo {
DynRegionInfoDynRegionInfo255 DynRegionInfo() : Addr(nullptr), Size(0), EntSize(0) {}
256 /// \brief Address in current address space.
257 const void *Addr;
258 /// \brief Size in bytes of the region.
259 uintX_t Size;
260 /// \brief Size of each entity in the region.
261 uintX_t EntSize;
262 };
263
264 DynRegionInfo DynamicRegion;
265 DynRegionInfo DynHashRegion;
266 DynRegionInfo DynStrRegion;
267 DynRegionInfo DynSymRegion;
268
269 // Pointer to SONAME entry in dynamic string table
270 // This is set the first time getLoadName is called.
271 mutable const char *dt_soname;
272
273 // Records for each version index the corresponding Verdef or Vernaux entry.
274 // This is filled the first time LoadVersionMap() is called.
275 class VersionMapEntry : public PointerIntPair<const void*, 1> {
276 public:
277 // If the integer is 0, this is an Elf_Verdef*.
278 // If the integer is 1, this is an Elf_Vernaux*.
VersionMapEntry()279 VersionMapEntry() : PointerIntPair<const void*, 1>(nullptr, 0) { }
VersionMapEntry(const Elf_Verdef * verdef)280 VersionMapEntry(const Elf_Verdef *verdef)
281 : PointerIntPair<const void*, 1>(verdef, 0) { }
VersionMapEntry(const Elf_Vernaux * vernaux)282 VersionMapEntry(const Elf_Vernaux *vernaux)
283 : PointerIntPair<const void*, 1>(vernaux, 1) { }
isNull()284 bool isNull() const { return getPointer() == nullptr; }
isVerdef()285 bool isVerdef() const { return !isNull() && getInt() == 0; }
isVernaux()286 bool isVernaux() const { return !isNull() && getInt() == 1; }
getVerdef()287 const Elf_Verdef *getVerdef() const {
288 return isVerdef() ? (const Elf_Verdef*)getPointer() : nullptr;
289 }
getVernaux()290 const Elf_Vernaux *getVernaux() const {
291 return isVernaux() ? (const Elf_Vernaux*)getPointer() : nullptr;
292 }
293 };
294 mutable SmallVector<VersionMapEntry, 16> VersionMap;
295 void LoadVersionDefs(const Elf_Shdr *sec) const;
296 void LoadVersionNeeds(const Elf_Shdr *ec) const;
297 void LoadVersionMap() const;
298
299 public:
300 template<typename T>
301 const T *getEntry(uint32_t Section, uint32_t Entry) const;
302 template <typename T>
303 const T *getEntry(const Elf_Shdr *Section, uint32_t Entry) const;
304 const char *getString(uint32_t section, uint32_t offset) const;
305 const char *getString(const Elf_Shdr *section, uint32_t offset) const;
306 const char *getDynamicString(uintX_t Offset) const;
307 ErrorOr<StringRef> getSymbolVersion(const Elf_Shdr *section,
308 const Elf_Sym *Symb,
309 bool &IsDefault) const;
310 void VerifyStrTab(const Elf_Shdr *sh) const;
311
312 StringRef getRelocationTypeName(uint32_t Type) const;
313 void getRelocationTypeName(uint32_t Type,
314 SmallVectorImpl<char> &Result) const;
315
316 /// \brief Get the symbol table section and symbol for a given relocation.
317 template <class RelT>
318 std::pair<const Elf_Shdr *, const Elf_Sym *>
319 getRelocationSymbol(const Elf_Shdr *RelSec, const RelT *Rel) const;
320
321 ELFFile(StringRef Object, std::error_code &ec);
322
isMipsELF64()323 bool isMipsELF64() const {
324 return Header->e_machine == ELF::EM_MIPS &&
325 Header->getFileClass() == ELF::ELFCLASS64;
326 }
327
isMips64EL()328 bool isMips64EL() const {
329 return Header->e_machine == ELF::EM_MIPS &&
330 Header->getFileClass() == ELF::ELFCLASS64 &&
331 Header->getDataEncoding() == ELF::ELFDATA2LSB;
332 }
333
334 Elf_Shdr_Iter begin_sections() const;
335 Elf_Shdr_Iter end_sections() const;
sections()336 Elf_Shdr_Range sections() const {
337 return make_range(begin_sections(), end_sections());
338 }
339
340 Elf_Sym_Iter begin_symbols() const;
341 Elf_Sym_Iter end_symbols() const;
342
343 Elf_Dyn_Iter begin_dynamic_table() const;
344 /// \param NULLEnd use one past the first DT_NULL entry as the end instead of
345 /// the section size.
346 Elf_Dyn_Iter end_dynamic_table(bool NULLEnd = false) const;
347 Elf_Dyn_Range dynamic_table(bool NULLEnd = false) const {
348 return make_range(begin_dynamic_table(), end_dynamic_table(NULLEnd));
349 }
350
begin_dynamic_symbols()351 Elf_Sym_Iter begin_dynamic_symbols() const {
352 if (DynSymRegion.Addr)
353 return Elf_Sym_Iter(DynSymRegion.EntSize, (const char *)DynSymRegion.Addr,
354 true);
355 return Elf_Sym_Iter(0, nullptr, true);
356 }
357
end_dynamic_symbols()358 Elf_Sym_Iter end_dynamic_symbols() const {
359 if (DynSymRegion.Addr)
360 return Elf_Sym_Iter(DynSymRegion.EntSize,
361 (const char *)DynSymRegion.Addr + DynSymRegion.Size,
362 true);
363 return Elf_Sym_Iter(0, nullptr, true);
364 }
365
begin_rela(const Elf_Shdr * sec)366 Elf_Rela_Iter begin_rela(const Elf_Shdr *sec) const {
367 return Elf_Rela_Iter(sec->sh_entsize,
368 (const char *)(base() + sec->sh_offset));
369 }
370
end_rela(const Elf_Shdr * sec)371 Elf_Rela_Iter end_rela(const Elf_Shdr *sec) const {
372 return Elf_Rela_Iter(
373 sec->sh_entsize,
374 (const char *)(base() + sec->sh_offset + sec->sh_size));
375 }
376
begin_rel(const Elf_Shdr * sec)377 Elf_Rel_Iter begin_rel(const Elf_Shdr *sec) const {
378 return Elf_Rel_Iter(sec->sh_entsize,
379 (const char *)(base() + sec->sh_offset));
380 }
381
end_rel(const Elf_Shdr * sec)382 Elf_Rel_Iter end_rel(const Elf_Shdr *sec) const {
383 return Elf_Rel_Iter(sec->sh_entsize,
384 (const char *)(base() + sec->sh_offset + sec->sh_size));
385 }
386
387 /// \brief Iterate over program header table.
388 typedef ELFEntityIterator<const Elf_Phdr> Elf_Phdr_Iter;
389
begin_program_headers()390 Elf_Phdr_Iter begin_program_headers() const {
391 return Elf_Phdr_Iter(Header->e_phentsize,
392 (const char*)base() + Header->e_phoff);
393 }
394
end_program_headers()395 Elf_Phdr_Iter end_program_headers() const {
396 return Elf_Phdr_Iter(Header->e_phentsize,
397 (const char*)base() +
398 Header->e_phoff +
399 (Header->e_phnum * Header->e_phentsize));
400 }
401
402 uint64_t getNumSections() const;
403 uintX_t getStringTableIndex() const;
404 ELF::Elf64_Word getSymbolTableIndex(const Elf_Sym *symb) const;
getHeader()405 const Elf_Ehdr *getHeader() const { return Header; }
406 const Elf_Shdr *getSection(const Elf_Sym *symb) const;
407 const Elf_Shdr *getSection(uint32_t Index) const;
408 const Elf_Sym *getSymbol(uint32_t index) const;
409
410 ErrorOr<StringRef> getSymbolName(Elf_Sym_Iter Sym) const;
411
412 /// \brief Get the name of \p Symb.
413 /// \param SymTab The symbol table section \p Symb is contained in.
414 /// \param Symb The symbol to get the name of.
415 ///
416 /// \p SymTab is used to lookup the string table to use to get the symbol's
417 /// name.
418 ErrorOr<StringRef> getSymbolName(const Elf_Shdr *SymTab,
419 const Elf_Sym *Symb) const;
420 ErrorOr<StringRef> getSectionName(const Elf_Shdr *Section) const;
421 uint64_t getSymbolIndex(const Elf_Sym *sym) const;
422 ErrorOr<ArrayRef<uint8_t> > getSectionContents(const Elf_Shdr *Sec) const;
423 StringRef getLoadName() const;
424 };
425
426 // Use an alignment of 2 for the typedefs since that is the worst case for
427 // ELF files in archives.
428 typedef ELFFile<ELFType<support::little, 2, false> > ELF32LEFile;
429 typedef ELFFile<ELFType<support::little, 2, true> > ELF64LEFile;
430 typedef ELFFile<ELFType<support::big, 2, false> > ELF32BEFile;
431 typedef ELFFile<ELFType<support::big, 2, true> > ELF64BEFile;
432
433 // Iterate through the version definitions, and place each Elf_Verdef
434 // in the VersionMap according to its index.
435 template <class ELFT>
LoadVersionDefs(const Elf_Shdr * sec)436 void ELFFile<ELFT>::LoadVersionDefs(const Elf_Shdr *sec) const {
437 unsigned vd_size = sec->sh_size; // Size of section in bytes
438 unsigned vd_count = sec->sh_info; // Number of Verdef entries
439 const char *sec_start = (const char*)base() + sec->sh_offset;
440 const char *sec_end = sec_start + vd_size;
441 // The first Verdef entry is at the start of the section.
442 const char *p = sec_start;
443 for (unsigned i = 0; i < vd_count; i++) {
444 if (p + sizeof(Elf_Verdef) > sec_end)
445 report_fatal_error("Section ended unexpectedly while scanning "
446 "version definitions.");
447 const Elf_Verdef *vd = reinterpret_cast<const Elf_Verdef *>(p);
448 if (vd->vd_version != ELF::VER_DEF_CURRENT)
449 report_fatal_error("Unexpected verdef version");
450 size_t index = vd->vd_ndx & ELF::VERSYM_VERSION;
451 if (index >= VersionMap.size())
452 VersionMap.resize(index + 1);
453 VersionMap[index] = VersionMapEntry(vd);
454 p += vd->vd_next;
455 }
456 }
457
458 // Iterate through the versions needed section, and place each Elf_Vernaux
459 // in the VersionMap according to its index.
460 template <class ELFT>
LoadVersionNeeds(const Elf_Shdr * sec)461 void ELFFile<ELFT>::LoadVersionNeeds(const Elf_Shdr *sec) const {
462 unsigned vn_size = sec->sh_size; // Size of section in bytes
463 unsigned vn_count = sec->sh_info; // Number of Verneed entries
464 const char *sec_start = (const char *)base() + sec->sh_offset;
465 const char *sec_end = sec_start + vn_size;
466 // The first Verneed entry is at the start of the section.
467 const char *p = sec_start;
468 for (unsigned i = 0; i < vn_count; i++) {
469 if (p + sizeof(Elf_Verneed) > sec_end)
470 report_fatal_error("Section ended unexpectedly while scanning "
471 "version needed records.");
472 const Elf_Verneed *vn = reinterpret_cast<const Elf_Verneed *>(p);
473 if (vn->vn_version != ELF::VER_NEED_CURRENT)
474 report_fatal_error("Unexpected verneed version");
475 // Iterate through the Vernaux entries
476 const char *paux = p + vn->vn_aux;
477 for (unsigned j = 0; j < vn->vn_cnt; j++) {
478 if (paux + sizeof(Elf_Vernaux) > sec_end)
479 report_fatal_error("Section ended unexpected while scanning auxiliary "
480 "version needed records.");
481 const Elf_Vernaux *vna = reinterpret_cast<const Elf_Vernaux *>(paux);
482 size_t index = vna->vna_other & ELF::VERSYM_VERSION;
483 if (index >= VersionMap.size())
484 VersionMap.resize(index + 1);
485 VersionMap[index] = VersionMapEntry(vna);
486 paux += vna->vna_next;
487 }
488 p += vn->vn_next;
489 }
490 }
491
492 template <class ELFT>
LoadVersionMap()493 void ELFFile<ELFT>::LoadVersionMap() const {
494 // If there is no dynamic symtab or version table, there is nothing to do.
495 if (!DynSymRegion.Addr || !dot_gnu_version_sec)
496 return;
497
498 // Has the VersionMap already been loaded?
499 if (VersionMap.size() > 0)
500 return;
501
502 // The first two version indexes are reserved.
503 // Index 0 is LOCAL, index 1 is GLOBAL.
504 VersionMap.push_back(VersionMapEntry());
505 VersionMap.push_back(VersionMapEntry());
506
507 if (dot_gnu_version_d_sec)
508 LoadVersionDefs(dot_gnu_version_d_sec);
509
510 if (dot_gnu_version_r_sec)
511 LoadVersionNeeds(dot_gnu_version_r_sec);
512 }
513
514 template <class ELFT>
getSymbolTableIndex(const Elf_Sym * symb)515 ELF::Elf64_Word ELFFile<ELFT>::getSymbolTableIndex(const Elf_Sym *symb) const {
516 if (symb->st_shndx == ELF::SHN_XINDEX)
517 return ExtendedSymbolTable.lookup(symb);
518 return symb->st_shndx;
519 }
520
521 template <class ELFT>
522 const typename ELFFile<ELFT>::Elf_Shdr *
getSection(const Elf_Sym * symb)523 ELFFile<ELFT>::getSection(const Elf_Sym *symb) const {
524 if (symb->st_shndx == ELF::SHN_XINDEX)
525 return getSection(ExtendedSymbolTable.lookup(symb));
526 if (symb->st_shndx >= ELF::SHN_LORESERVE)
527 return nullptr;
528 return getSection(symb->st_shndx);
529 }
530
531 template <class ELFT>
532 const typename ELFFile<ELFT>::Elf_Sym *
getSymbol(uint32_t Index)533 ELFFile<ELFT>::getSymbol(uint32_t Index) const {
534 return &*(begin_symbols() + Index);
535 }
536
537 template <class ELFT>
538 ErrorOr<ArrayRef<uint8_t> >
getSectionContents(const Elf_Shdr * Sec)539 ELFFile<ELFT>::getSectionContents(const Elf_Shdr *Sec) const {
540 if (Sec->sh_offset + Sec->sh_size > Buf.size())
541 return object_error::parse_failed;
542 const uint8_t *Start = base() + Sec->sh_offset;
543 return makeArrayRef(Start, Sec->sh_size);
544 }
545
546 template <class ELFT>
getRelocationTypeName(uint32_t Type)547 StringRef ELFFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
548 return getELFRelocationTypeName(Header->e_machine, Type);
549 }
550
551 template <class ELFT>
getRelocationTypeName(uint32_t Type,SmallVectorImpl<char> & Result)552 void ELFFile<ELFT>::getRelocationTypeName(uint32_t Type,
553 SmallVectorImpl<char> &Result) const {
554 if (!isMipsELF64()) {
555 StringRef Name = getRelocationTypeName(Type);
556 Result.append(Name.begin(), Name.end());
557 } else {
558 // The Mips N64 ABI allows up to three operations to be specified per
559 // relocation record. Unfortunately there's no easy way to test for the
560 // presence of N64 ELFs as they have no special flag that identifies them
561 // as being N64. We can safely assume at the moment that all Mips
562 // ELFCLASS64 ELFs are N64. New Mips64 ABIs should provide enough
563 // information to disambiguate between old vs new ABIs.
564 uint8_t Type1 = (Type >> 0) & 0xFF;
565 uint8_t Type2 = (Type >> 8) & 0xFF;
566 uint8_t Type3 = (Type >> 16) & 0xFF;
567
568 // Concat all three relocation type names.
569 StringRef Name = getRelocationTypeName(Type1);
570 Result.append(Name.begin(), Name.end());
571
572 Name = getRelocationTypeName(Type2);
573 Result.append(1, '/');
574 Result.append(Name.begin(), Name.end());
575
576 Name = getRelocationTypeName(Type3);
577 Result.append(1, '/');
578 Result.append(Name.begin(), Name.end());
579 }
580 }
581
582 template <class ELFT>
583 template <class RelT>
584 std::pair<const typename ELFFile<ELFT>::Elf_Shdr *,
585 const typename ELFFile<ELFT>::Elf_Sym *>
getRelocationSymbol(const Elf_Shdr * Sec,const RelT * Rel)586 ELFFile<ELFT>::getRelocationSymbol(const Elf_Shdr *Sec, const RelT *Rel) const {
587 if (!Sec->sh_link)
588 return std::make_pair(nullptr, nullptr);
589 const Elf_Shdr *SymTable = getSection(Sec->sh_link);
590 return std::make_pair(
591 SymTable, getEntry<Elf_Sym>(SymTable, Rel->getSymbol(isMips64EL())));
592 }
593
594 // Verify that the last byte in the string table in a null.
595 template <class ELFT>
VerifyStrTab(const Elf_Shdr * sh)596 void ELFFile<ELFT>::VerifyStrTab(const Elf_Shdr *sh) const {
597 const char *strtab = (const char *)base() + sh->sh_offset;
598 if (strtab[sh->sh_size - 1] != 0)
599 // FIXME: Proper error handling.
600 report_fatal_error("String table must end with a null terminator!");
601 }
602
603 template <class ELFT>
getNumSections()604 uint64_t ELFFile<ELFT>::getNumSections() const {
605 assert(Header && "Header not initialized!");
606 if (Header->e_shnum == ELF::SHN_UNDEF && Header->e_shoff > 0) {
607 assert(SectionHeaderTable && "SectionHeaderTable not initialized!");
608 return SectionHeaderTable->sh_size;
609 }
610 return Header->e_shnum;
611 }
612
613 template <class ELFT>
getStringTableIndex()614 typename ELFFile<ELFT>::uintX_t ELFFile<ELFT>::getStringTableIndex() const {
615 if (Header->e_shnum == ELF::SHN_UNDEF) {
616 if (Header->e_shstrndx == ELF::SHN_HIRESERVE)
617 return SectionHeaderTable->sh_link;
618 if (Header->e_shstrndx >= getNumSections())
619 return 0;
620 }
621 return Header->e_shstrndx;
622 }
623
624 template <class ELFT>
ELFFile(StringRef Object,std::error_code & ec)625 ELFFile<ELFT>::ELFFile(StringRef Object, std::error_code &ec)
626 : Buf(Object), SectionHeaderTable(nullptr), dot_shstrtab_sec(nullptr),
627 dot_strtab_sec(nullptr), dot_symtab_sec(nullptr),
628 SymbolTableSectionHeaderIndex(nullptr), dot_gnu_version_sec(nullptr),
629 dot_gnu_version_r_sec(nullptr), dot_gnu_version_d_sec(nullptr),
630 dt_soname(nullptr) {
631 const uint64_t FileSize = Buf.size();
632
633 if (sizeof(Elf_Ehdr) > FileSize)
634 // FIXME: Proper error handling.
635 report_fatal_error("File too short!");
636
637 Header = reinterpret_cast<const Elf_Ehdr *>(base());
638
639 if (Header->e_shoff == 0)
640 return;
641
642 const uint64_t SectionTableOffset = Header->e_shoff;
643
644 if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize)
645 // FIXME: Proper error handling.
646 report_fatal_error("Section header table goes past end of file!");
647
648 // The getNumSections() call below depends on SectionHeaderTable being set.
649 SectionHeaderTable =
650 reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
651 const uint64_t SectionTableSize = getNumSections() * Header->e_shentsize;
652
653 if (SectionTableOffset + SectionTableSize > FileSize)
654 // FIXME: Proper error handling.
655 report_fatal_error("Section table goes past end of file!");
656
657 // Scan sections for special sections.
658
659 for (const Elf_Shdr &Sec : sections()) {
660 switch (Sec.sh_type) {
661 case ELF::SHT_SYMTAB_SHNDX:
662 if (SymbolTableSectionHeaderIndex)
663 // FIXME: Proper error handling.
664 report_fatal_error("More than one .symtab_shndx!");
665 SymbolTableSectionHeaderIndex = &Sec;
666 break;
667 case ELF::SHT_SYMTAB:
668 if (dot_symtab_sec)
669 // FIXME: Proper error handling.
670 report_fatal_error("More than one .symtab!");
671 dot_symtab_sec = &Sec;
672 dot_strtab_sec = getSection(Sec.sh_link);
673 break;
674 case ELF::SHT_DYNSYM: {
675 if (DynSymRegion.Addr)
676 // FIXME: Proper error handling.
677 report_fatal_error("More than one .dynsym!");
678 DynSymRegion.Addr = base() + Sec.sh_offset;
679 DynSymRegion.Size = Sec.sh_size;
680 DynSymRegion.EntSize = Sec.sh_entsize;
681 const Elf_Shdr *DynStr = getSection(Sec.sh_link);
682 DynStrRegion.Addr = base() + DynStr->sh_offset;
683 DynStrRegion.Size = DynStr->sh_size;
684 DynStrRegion.EntSize = DynStr->sh_entsize;
685 break;
686 }
687 case ELF::SHT_DYNAMIC:
688 if (DynamicRegion.Addr)
689 // FIXME: Proper error handling.
690 report_fatal_error("More than one .dynamic!");
691 DynamicRegion.Addr = base() + Sec.sh_offset;
692 DynamicRegion.Size = Sec.sh_size;
693 DynamicRegion.EntSize = Sec.sh_entsize;
694 break;
695 case ELF::SHT_GNU_versym:
696 if (dot_gnu_version_sec != nullptr)
697 // FIXME: Proper error handling.
698 report_fatal_error("More than one .gnu.version section!");
699 dot_gnu_version_sec = &Sec;
700 break;
701 case ELF::SHT_GNU_verdef:
702 if (dot_gnu_version_d_sec != nullptr)
703 // FIXME: Proper error handling.
704 report_fatal_error("More than one .gnu.version_d section!");
705 dot_gnu_version_d_sec = &Sec;
706 break;
707 case ELF::SHT_GNU_verneed:
708 if (dot_gnu_version_r_sec != nullptr)
709 // FIXME: Proper error handling.
710 report_fatal_error("More than one .gnu.version_r section!");
711 dot_gnu_version_r_sec = &Sec;
712 break;
713 }
714 }
715
716 // Get string table sections.
717 dot_shstrtab_sec = getSection(getStringTableIndex());
718 if (dot_shstrtab_sec) {
719 // Verify that the last byte in the string table in a null.
720 VerifyStrTab(dot_shstrtab_sec);
721 }
722
723 // Build symbol name side-mapping if there is one.
724 if (SymbolTableSectionHeaderIndex) {
725 const Elf_Word *ShndxTable = reinterpret_cast<const Elf_Word*>(base() +
726 SymbolTableSectionHeaderIndex->sh_offset);
727 for (Elf_Sym_Iter SI = begin_symbols(), SE = end_symbols(); SI != SE;
728 ++SI) {
729 if (*ShndxTable != ELF::SHN_UNDEF)
730 ExtendedSymbolTable[&*SI] = *ShndxTable;
731 ++ShndxTable;
732 }
733 }
734
735 // Scan program headers.
736 for (Elf_Phdr_Iter PhdrI = begin_program_headers(),
737 PhdrE = end_program_headers();
738 PhdrI != PhdrE; ++PhdrI) {
739 if (PhdrI->p_type == ELF::PT_DYNAMIC) {
740 DynamicRegion.Addr = base() + PhdrI->p_offset;
741 DynamicRegion.Size = PhdrI->p_filesz;
742 DynamicRegion.EntSize = sizeof(Elf_Dyn);
743 break;
744 }
745 }
746
747 ec = std::error_code();
748 }
749
750 // Get the symbol table index in the symtab section given a symbol
751 template <class ELFT>
getSymbolIndex(const Elf_Sym * Sym)752 uint64_t ELFFile<ELFT>::getSymbolIndex(const Elf_Sym *Sym) const {
753 uintptr_t SymLoc = uintptr_t(Sym);
754 uintptr_t SymTabLoc = uintptr_t(base() + dot_symtab_sec->sh_offset);
755 assert(SymLoc > SymTabLoc && "Symbol not in symbol table!");
756 uint64_t SymOffset = SymLoc - SymTabLoc;
757 assert(SymOffset % dot_symtab_sec->sh_entsize == 0 &&
758 "Symbol not multiple of symbol size!");
759 return SymOffset / dot_symtab_sec->sh_entsize;
760 }
761
762 template <class ELFT>
begin_sections()763 typename ELFFile<ELFT>::Elf_Shdr_Iter ELFFile<ELFT>::begin_sections() const {
764 return Elf_Shdr_Iter(Header->e_shentsize,
765 (const char *)base() + Header->e_shoff);
766 }
767
768 template <class ELFT>
end_sections()769 typename ELFFile<ELFT>::Elf_Shdr_Iter ELFFile<ELFT>::end_sections() const {
770 return Elf_Shdr_Iter(Header->e_shentsize,
771 (const char *)base() + Header->e_shoff +
772 (getNumSections() * Header->e_shentsize));
773 }
774
775 template <class ELFT>
begin_symbols()776 typename ELFFile<ELFT>::Elf_Sym_Iter ELFFile<ELFT>::begin_symbols() const {
777 if (!dot_symtab_sec)
778 return Elf_Sym_Iter(0, nullptr, false);
779 return Elf_Sym_Iter(dot_symtab_sec->sh_entsize,
780 (const char *)base() + dot_symtab_sec->sh_offset, false);
781 }
782
783 template <class ELFT>
end_symbols()784 typename ELFFile<ELFT>::Elf_Sym_Iter ELFFile<ELFT>::end_symbols() const {
785 if (!dot_symtab_sec)
786 return Elf_Sym_Iter(0, nullptr, false);
787 return Elf_Sym_Iter(dot_symtab_sec->sh_entsize,
788 (const char *)base() + dot_symtab_sec->sh_offset +
789 dot_symtab_sec->sh_size,
790 false);
791 }
792
793 template <class ELFT>
794 typename ELFFile<ELFT>::Elf_Dyn_Iter
begin_dynamic_table()795 ELFFile<ELFT>::begin_dynamic_table() const {
796 if (DynamicRegion.Addr)
797 return Elf_Dyn_Iter(DynamicRegion.EntSize,
798 (const char *)DynamicRegion.Addr);
799 return Elf_Dyn_Iter(0, nullptr);
800 }
801
802 template <class ELFT>
803 typename ELFFile<ELFT>::Elf_Dyn_Iter
end_dynamic_table(bool NULLEnd)804 ELFFile<ELFT>::end_dynamic_table(bool NULLEnd) const {
805 if (!DynamicRegion.Addr)
806 return Elf_Dyn_Iter(0, nullptr);
807 Elf_Dyn_Iter Ret(DynamicRegion.EntSize,
808 (const char *)DynamicRegion.Addr + DynamicRegion.Size);
809
810 if (NULLEnd) {
811 Elf_Dyn_Iter Start = begin_dynamic_table();
812 while (Start != Ret && Start->getTag() != ELF::DT_NULL)
813 ++Start;
814
815 // Include the DT_NULL.
816 if (Start != Ret)
817 ++Start;
818 Ret = Start;
819 }
820 return Ret;
821 }
822
823 template <class ELFT>
getLoadName()824 StringRef ELFFile<ELFT>::getLoadName() const {
825 if (!dt_soname) {
826 dt_soname = "";
827 // Find the DT_SONAME entry
828 for (const auto &Entry : dynamic_table())
829 if (Entry.getTag() == ELF::DT_SONAME) {
830 dt_soname = getDynamicString(Entry.getVal());
831 break;
832 }
833 }
834 return dt_soname;
835 }
836
837 template <class ELFT>
838 template <typename T>
getEntry(uint32_t Section,uint32_t Entry)839 const T *ELFFile<ELFT>::getEntry(uint32_t Section, uint32_t Entry) const {
840 return getEntry<T>(getSection(Section), Entry);
841 }
842
843 template <class ELFT>
844 template <typename T>
getEntry(const Elf_Shdr * Section,uint32_t Entry)845 const T *ELFFile<ELFT>::getEntry(const Elf_Shdr *Section,
846 uint32_t Entry) const {
847 return reinterpret_cast<const T *>(base() + Section->sh_offset +
848 (Entry * Section->sh_entsize));
849 }
850
851 template <class ELFT>
852 const typename ELFFile<ELFT>::Elf_Shdr *
getSection(uint32_t index)853 ELFFile<ELFT>::getSection(uint32_t index) const {
854 if (index == 0)
855 return nullptr;
856 if (!SectionHeaderTable || index >= getNumSections())
857 // FIXME: Proper error handling.
858 report_fatal_error("Invalid section index!");
859
860 return reinterpret_cast<const Elf_Shdr *>(
861 reinterpret_cast<const char *>(SectionHeaderTable)
862 + (index * Header->e_shentsize));
863 }
864
865 template <class ELFT>
getString(uint32_t section,ELF::Elf32_Word offset)866 const char *ELFFile<ELFT>::getString(uint32_t section,
867 ELF::Elf32_Word offset) const {
868 return getString(getSection(section), offset);
869 }
870
871 template <class ELFT>
getString(const Elf_Shdr * section,ELF::Elf32_Word offset)872 const char *ELFFile<ELFT>::getString(const Elf_Shdr *section,
873 ELF::Elf32_Word offset) const {
874 assert(section && section->sh_type == ELF::SHT_STRTAB && "Invalid section!");
875 if (offset >= section->sh_size)
876 // FIXME: Proper error handling.
877 report_fatal_error("Symbol name offset outside of string table!");
878 return (const char *)base() + section->sh_offset + offset;
879 }
880
881 template <class ELFT>
getDynamicString(uintX_t Offset)882 const char *ELFFile<ELFT>::getDynamicString(uintX_t Offset) const {
883 if (!DynStrRegion.Addr || Offset >= DynStrRegion.Size)
884 return nullptr;
885 return (const char *)DynStrRegion.Addr + Offset;
886 }
887
888 template <class ELFT>
getSymbolName(Elf_Sym_Iter Sym)889 ErrorOr<StringRef> ELFFile<ELFT>::getSymbolName(Elf_Sym_Iter Sym) const {
890 if (!Sym.isDynamic())
891 return getSymbolName(dot_symtab_sec, &*Sym);
892
893 if (!DynStrRegion.Addr || Sym->st_name >= DynStrRegion.Size)
894 return object_error::parse_failed;
895 return StringRef(getDynamicString(Sym->st_name));
896 }
897
898 template <class ELFT>
getSymbolName(const Elf_Shdr * Section,const Elf_Sym * Symb)899 ErrorOr<StringRef> ELFFile<ELFT>::getSymbolName(const Elf_Shdr *Section,
900 const Elf_Sym *Symb) const {
901 if (Symb->st_name == 0) {
902 const Elf_Shdr *ContainingSec = getSection(Symb);
903 if (ContainingSec)
904 return getSectionName(ContainingSec);
905 }
906
907 const Elf_Shdr *StrTab = getSection(Section->sh_link);
908 if (Symb->st_name >= StrTab->sh_size)
909 return object_error::parse_failed;
910 return StringRef(getString(StrTab, Symb->st_name));
911 }
912
913 template <class ELFT>
914 ErrorOr<StringRef>
getSectionName(const Elf_Shdr * Section)915 ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section) const {
916 if (Section->sh_name >= dot_shstrtab_sec->sh_size)
917 return object_error::parse_failed;
918 return StringRef(getString(dot_shstrtab_sec, Section->sh_name));
919 }
920
921 template <class ELFT>
getSymbolVersion(const Elf_Shdr * section,const Elf_Sym * symb,bool & IsDefault)922 ErrorOr<StringRef> ELFFile<ELFT>::getSymbolVersion(const Elf_Shdr *section,
923 const Elf_Sym *symb,
924 bool &IsDefault) const {
925 // Handle non-dynamic symbols.
926 if (section != DynSymRegion.Addr && section != nullptr) {
927 // Non-dynamic symbols can have versions in their names
928 // A name of the form 'foo@V1' indicates version 'V1', non-default.
929 // A name of the form 'foo@@V2' indicates version 'V2', default version.
930 ErrorOr<StringRef> SymName = getSymbolName(section, symb);
931 if (!SymName)
932 return SymName;
933 StringRef Name = *SymName;
934 size_t atpos = Name.find('@');
935 if (atpos == StringRef::npos) {
936 IsDefault = false;
937 return StringRef("");
938 }
939 ++atpos;
940 if (atpos < Name.size() && Name[atpos] == '@') {
941 IsDefault = true;
942 ++atpos;
943 } else {
944 IsDefault = false;
945 }
946 return Name.substr(atpos);
947 }
948
949 // This is a dynamic symbol. Look in the GNU symbol version table.
950 if (!dot_gnu_version_sec) {
951 // No version table.
952 IsDefault = false;
953 return StringRef("");
954 }
955
956 // Determine the position in the symbol table of this entry.
957 size_t entry_index = ((const char *)symb - (const char *)DynSymRegion.Addr) /
958 DynSymRegion.EntSize;
959
960 // Get the corresponding version index entry
961 const Elf_Versym *vs = getEntry<Elf_Versym>(dot_gnu_version_sec, entry_index);
962 size_t version_index = vs->vs_index & ELF::VERSYM_VERSION;
963
964 // Special markers for unversioned symbols.
965 if (version_index == ELF::VER_NDX_LOCAL ||
966 version_index == ELF::VER_NDX_GLOBAL) {
967 IsDefault = false;
968 return StringRef("");
969 }
970
971 // Lookup this symbol in the version table
972 LoadVersionMap();
973 if (version_index >= VersionMap.size() || VersionMap[version_index].isNull())
974 return object_error::parse_failed;
975 const VersionMapEntry &entry = VersionMap[version_index];
976
977 // Get the version name string
978 size_t name_offset;
979 if (entry.isVerdef()) {
980 // The first Verdaux entry holds the name.
981 name_offset = entry.getVerdef()->getAux()->vda_name;
982 } else {
983 name_offset = entry.getVernaux()->vna_name;
984 }
985
986 // Set IsDefault
987 if (entry.isVerdef()) {
988 IsDefault = !(vs->vs_index & ELF::VERSYM_HIDDEN);
989 } else {
990 IsDefault = false;
991 }
992
993 if (name_offset >= DynStrRegion.Size)
994 return object_error::parse_failed;
995 return StringRef(getDynamicString(name_offset));
996 }
997
998 /// This function returns the hash value for a symbol in the .dynsym section
999 /// Name of the API remains consistent as specified in the libelf
1000 /// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
elf_hash(StringRef & symbolName)1001 static inline unsigned elf_hash(StringRef &symbolName) {
1002 unsigned h = 0, g;
1003 for (unsigned i = 0, j = symbolName.size(); i < j; i++) {
1004 h = (h << 4) + symbolName[i];
1005 g = h & 0xf0000000L;
1006 if (g != 0)
1007 h ^= g >> 24;
1008 h &= ~g;
1009 }
1010 return h;
1011 }
1012 } // end namespace object
1013 } // end namespace llvm
1014
1015 #endif
1016