1 //===- ELF.h - ELF object file implementation -------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file declares the ELFFile template class.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #ifndef LLVM_OBJECT_ELF_H
14 #define LLVM_OBJECT_ELF_H
15
16 #include "llvm/ADT/ArrayRef.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/BinaryFormat/ELF.h"
20 #include "llvm/Object/ELFTypes.h"
21 #include "llvm/Object/Error.h"
22 #include "llvm/Support/Endian.h"
23 #include "llvm/Support/Error.h"
24 #include <cassert>
25 #include <cstddef>
26 #include <cstdint>
27 #include <limits>
28 #include <utility>
29
30 namespace llvm {
31 namespace object {
32
33 StringRef getELFRelocationTypeName(uint32_t Machine, uint32_t Type);
34 uint32_t getELFRelativeRelocationType(uint32_t Machine);
35 StringRef getELFSectionTypeName(uint32_t Machine, uint32_t Type);
36
37 // Subclasses of ELFFile may need this for template instantiation
38 inline std::pair<unsigned char, unsigned char>
getElfArchType(StringRef Object)39 getElfArchType(StringRef Object) {
40 if (Object.size() < ELF::EI_NIDENT)
41 return std::make_pair((uint8_t)ELF::ELFCLASSNONE,
42 (uint8_t)ELF::ELFDATANONE);
43 return std::make_pair((uint8_t)Object[ELF::EI_CLASS],
44 (uint8_t)Object[ELF::EI_DATA]);
45 }
46
createError(const Twine & Err)47 static inline Error createError(const Twine &Err) {
48 return make_error<StringError>(Err, object_error::parse_failed);
49 }
50
51 template <class ELFT> class ELFFile;
52
53 template <class ELFT>
getSecIndexForError(const ELFFile<ELFT> * Obj,const typename ELFT::Shdr * Sec)54 std::string getSecIndexForError(const ELFFile<ELFT> *Obj,
55 const typename ELFT::Shdr *Sec) {
56 auto TableOrErr = Obj->sections();
57 if (TableOrErr)
58 return "[index " + std::to_string(Sec - &TableOrErr->front()) + "]";
59 // To make this helper be more convenient for error reporting purposes we
60 // drop the error. But really it should never be triggered. Before this point,
61 // our code should have called 'sections()' and reported a proper error on
62 // failure.
63 llvm::consumeError(TableOrErr.takeError());
64 return "[unknown index]";
65 }
66
67 template <class ELFT>
getPhdrIndexForError(const ELFFile<ELFT> * Obj,const typename ELFT::Phdr * Phdr)68 std::string getPhdrIndexForError(const ELFFile<ELFT> *Obj,
69 const typename ELFT::Phdr *Phdr) {
70 auto Headers = Obj->program_headers();
71 if (Headers)
72 return ("[index " + Twine(Phdr - &Headers->front()) + "]").str();
73 // See comment in the getSecIndexForError() above.
74 llvm::consumeError(Headers.takeError());
75 return "[unknown index]";
76 }
77
defaultWarningHandler(const Twine & Msg)78 static inline Error defaultWarningHandler(const Twine &Msg) {
79 return createError(Msg);
80 }
81
82 template <class ELFT>
83 class ELFFile {
84 public:
85 LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
86 using uintX_t = typename ELFT::uint;
87 using Elf_Ehdr = typename ELFT::Ehdr;
88 using Elf_Shdr = typename ELFT::Shdr;
89 using Elf_Sym = typename ELFT::Sym;
90 using Elf_Dyn = typename ELFT::Dyn;
91 using Elf_Phdr = typename ELFT::Phdr;
92 using Elf_Rel = typename ELFT::Rel;
93 using Elf_Rela = typename ELFT::Rela;
94 using Elf_Relr = typename ELFT::Relr;
95 using Elf_Verdef = typename ELFT::Verdef;
96 using Elf_Verdaux = typename ELFT::Verdaux;
97 using Elf_Verneed = typename ELFT::Verneed;
98 using Elf_Vernaux = typename ELFT::Vernaux;
99 using Elf_Versym = typename ELFT::Versym;
100 using Elf_Hash = typename ELFT::Hash;
101 using Elf_GnuHash = typename ELFT::GnuHash;
102 using Elf_Nhdr = typename ELFT::Nhdr;
103 using Elf_Note = typename ELFT::Note;
104 using Elf_Note_Iterator = typename ELFT::NoteIterator;
105 using Elf_Dyn_Range = typename ELFT::DynRange;
106 using Elf_Shdr_Range = typename ELFT::ShdrRange;
107 using Elf_Sym_Range = typename ELFT::SymRange;
108 using Elf_Rel_Range = typename ELFT::RelRange;
109 using Elf_Rela_Range = typename ELFT::RelaRange;
110 using Elf_Relr_Range = typename ELFT::RelrRange;
111 using Elf_Phdr_Range = typename ELFT::PhdrRange;
112
113 // This is a callback that can be passed to a number of functions.
114 // It can be used to ignore non-critical errors (warnings), which is
115 // useful for dumpers, like llvm-readobj.
116 // It accepts a warning message string and returns a success
117 // when the warning should be ignored or an error otherwise.
118 using WarningHandler = llvm::function_ref<Error(const Twine &Msg)>;
119
base()120 const uint8_t *base() const { return Buf.bytes_begin(); }
121
getBufSize()122 size_t getBufSize() const { return Buf.size(); }
123
124 private:
125 StringRef Buf;
126
127 ELFFile(StringRef Object);
128
129 public:
getHeader()130 const Elf_Ehdr *getHeader() const {
131 return reinterpret_cast<const Elf_Ehdr *>(base());
132 }
133
134 template <typename T>
135 Expected<const T *> getEntry(uint32_t Section, uint32_t Entry) const;
136 template <typename T>
137 Expected<const T *> getEntry(const Elf_Shdr *Section, uint32_t Entry) const;
138
139 Expected<StringRef>
140 getStringTable(const Elf_Shdr *Section,
141 WarningHandler WarnHandler = &defaultWarningHandler) const;
142 Expected<StringRef> getStringTableForSymtab(const Elf_Shdr &Section) const;
143 Expected<StringRef> getStringTableForSymtab(const Elf_Shdr &Section,
144 Elf_Shdr_Range Sections) const;
145
146 Expected<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section) const;
147 Expected<ArrayRef<Elf_Word>> getSHNDXTable(const Elf_Shdr &Section,
148 Elf_Shdr_Range Sections) const;
149
150 StringRef getRelocationTypeName(uint32_t Type) const;
151 void getRelocationTypeName(uint32_t Type,
152 SmallVectorImpl<char> &Result) const;
153 uint32_t getRelativeRelocationType() const;
154
155 std::string getDynamicTagAsString(unsigned Arch, uint64_t Type) const;
156 std::string getDynamicTagAsString(uint64_t Type) const;
157
158 /// Get the symbol for a given relocation.
159 Expected<const Elf_Sym *> getRelocationSymbol(const Elf_Rel *Rel,
160 const Elf_Shdr *SymTab) const;
161
162 static Expected<ELFFile> create(StringRef Object);
163
isLE()164 bool isLE() const {
165 return getHeader()->getDataEncoding() == ELF::ELFDATA2LSB;
166 }
167
isMipsELF64()168 bool isMipsELF64() const {
169 return getHeader()->e_machine == ELF::EM_MIPS &&
170 getHeader()->getFileClass() == ELF::ELFCLASS64;
171 }
172
isMips64EL()173 bool isMips64EL() const { return isMipsELF64() && isLE(); }
174
175 Expected<Elf_Shdr_Range> sections() const;
176
177 Expected<Elf_Dyn_Range> dynamicEntries() const;
178
179 Expected<const uint8_t *> toMappedAddr(uint64_t VAddr) const;
180
symbols(const Elf_Shdr * Sec)181 Expected<Elf_Sym_Range> symbols(const Elf_Shdr *Sec) const {
182 if (!Sec)
183 return makeArrayRef<Elf_Sym>(nullptr, nullptr);
184 return getSectionContentsAsArray<Elf_Sym>(Sec);
185 }
186
relas(const Elf_Shdr * Sec)187 Expected<Elf_Rela_Range> relas(const Elf_Shdr *Sec) const {
188 return getSectionContentsAsArray<Elf_Rela>(Sec);
189 }
190
rels(const Elf_Shdr * Sec)191 Expected<Elf_Rel_Range> rels(const Elf_Shdr *Sec) const {
192 return getSectionContentsAsArray<Elf_Rel>(Sec);
193 }
194
relrs(const Elf_Shdr * Sec)195 Expected<Elf_Relr_Range> relrs(const Elf_Shdr *Sec) const {
196 return getSectionContentsAsArray<Elf_Relr>(Sec);
197 }
198
199 Expected<std::vector<Elf_Rela>> decode_relrs(Elf_Relr_Range relrs) const;
200
201 Expected<std::vector<Elf_Rela>> android_relas(const Elf_Shdr *Sec) const;
202
203 /// Iterate over program header table.
program_headers()204 Expected<Elf_Phdr_Range> program_headers() const {
205 if (getHeader()->e_phnum && getHeader()->e_phentsize != sizeof(Elf_Phdr))
206 return createError("invalid e_phentsize: " +
207 Twine(getHeader()->e_phentsize));
208
209 uint64_t HeadersSize =
210 (uint64_t)getHeader()->e_phnum * getHeader()->e_phentsize;
211 uint64_t PhOff = getHeader()->e_phoff;
212 if (PhOff + HeadersSize < PhOff || PhOff + HeadersSize > getBufSize())
213 return createError("program headers are longer than binary of size " +
214 Twine(getBufSize()) + ": e_phoff = 0x" +
215 Twine::utohexstr(getHeader()->e_phoff) +
216 ", e_phnum = " + Twine(getHeader()->e_phnum) +
217 ", e_phentsize = " + Twine(getHeader()->e_phentsize));
218
219 auto *Begin = reinterpret_cast<const Elf_Phdr *>(base() + PhOff);
220 return makeArrayRef(Begin, Begin + getHeader()->e_phnum);
221 }
222
223 /// Get an iterator over notes in a program header.
224 ///
225 /// The program header must be of type \c PT_NOTE.
226 ///
227 /// \param Phdr the program header to iterate over.
228 /// \param Err [out] an error to support fallible iteration, which should
229 /// be checked after iteration ends.
notes_begin(const Elf_Phdr & Phdr,Error & Err)230 Elf_Note_Iterator notes_begin(const Elf_Phdr &Phdr, Error &Err) const {
231 assert(Phdr.p_type == ELF::PT_NOTE && "Phdr is not of type PT_NOTE");
232 ErrorAsOutParameter ErrAsOutParam(&Err);
233 if (Phdr.p_offset + Phdr.p_filesz > getBufSize()) {
234 Err = createError("PT_NOTE header has invalid offset (0x" +
235 Twine::utohexstr(Phdr.p_offset) + ") or size (0x" +
236 Twine::utohexstr(Phdr.p_filesz) + ")");
237 return Elf_Note_Iterator(Err);
238 }
239 return Elf_Note_Iterator(base() + Phdr.p_offset, Phdr.p_filesz, Err);
240 }
241
242 /// Get an iterator over notes in a section.
243 ///
244 /// The section must be of type \c SHT_NOTE.
245 ///
246 /// \param Shdr the section to iterate over.
247 /// \param Err [out] an error to support fallible iteration, which should
248 /// be checked after iteration ends.
notes_begin(const Elf_Shdr & Shdr,Error & Err)249 Elf_Note_Iterator notes_begin(const Elf_Shdr &Shdr, Error &Err) const {
250 assert(Shdr.sh_type == ELF::SHT_NOTE && "Shdr is not of type SHT_NOTE");
251 ErrorAsOutParameter ErrAsOutParam(&Err);
252 if (Shdr.sh_offset + Shdr.sh_size > getBufSize()) {
253 Err = createError("SHT_NOTE section " + getSecIndexForError(this, &Shdr) +
254 " has invalid offset (0x" +
255 Twine::utohexstr(Shdr.sh_offset) + ") or size (0x" +
256 Twine::utohexstr(Shdr.sh_size) + ")");
257 return Elf_Note_Iterator(Err);
258 }
259 return Elf_Note_Iterator(base() + Shdr.sh_offset, Shdr.sh_size, Err);
260 }
261
262 /// Get the end iterator for notes.
notes_end()263 Elf_Note_Iterator notes_end() const {
264 return Elf_Note_Iterator();
265 }
266
267 /// Get an iterator range over notes of a program header.
268 ///
269 /// The program header must be of type \c PT_NOTE.
270 ///
271 /// \param Phdr the program header to iterate over.
272 /// \param Err [out] an error to support fallible iteration, which should
273 /// be checked after iteration ends.
notes(const Elf_Phdr & Phdr,Error & Err)274 iterator_range<Elf_Note_Iterator> notes(const Elf_Phdr &Phdr,
275 Error &Err) const {
276 return make_range(notes_begin(Phdr, Err), notes_end());
277 }
278
279 /// Get an iterator range over notes of a section.
280 ///
281 /// The section must be of type \c SHT_NOTE.
282 ///
283 /// \param Shdr the section to iterate over.
284 /// \param Err [out] an error to support fallible iteration, which should
285 /// be checked after iteration ends.
notes(const Elf_Shdr & Shdr,Error & Err)286 iterator_range<Elf_Note_Iterator> notes(const Elf_Shdr &Shdr,
287 Error &Err) const {
288 return make_range(notes_begin(Shdr, Err), notes_end());
289 }
290
291 Expected<StringRef> getSectionStringTable(
292 Elf_Shdr_Range Sections,
293 WarningHandler WarnHandler = &defaultWarningHandler) const;
294 Expected<uint32_t> getSectionIndex(const Elf_Sym *Sym, Elf_Sym_Range Syms,
295 ArrayRef<Elf_Word> ShndxTable) const;
296 Expected<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
297 const Elf_Shdr *SymTab,
298 ArrayRef<Elf_Word> ShndxTable) const;
299 Expected<const Elf_Shdr *> getSection(const Elf_Sym *Sym,
300 Elf_Sym_Range Symtab,
301 ArrayRef<Elf_Word> ShndxTable) const;
302 Expected<const Elf_Shdr *> getSection(uint32_t Index) const;
303
304 Expected<const Elf_Sym *> getSymbol(const Elf_Shdr *Sec,
305 uint32_t Index) const;
306
307 Expected<StringRef>
308 getSectionName(const Elf_Shdr *Section,
309 WarningHandler WarnHandler = &defaultWarningHandler) const;
310 Expected<StringRef> getSectionName(const Elf_Shdr *Section,
311 StringRef DotShstrtab) const;
312 template <typename T>
313 Expected<ArrayRef<T>> getSectionContentsAsArray(const Elf_Shdr *Sec) const;
314 Expected<ArrayRef<uint8_t>> getSectionContents(const Elf_Shdr *Sec) const;
315 Expected<ArrayRef<uint8_t>> getSegmentContents(const Elf_Phdr *Phdr) const;
316 };
317
318 using ELF32LEFile = ELFFile<ELF32LE>;
319 using ELF64LEFile = ELFFile<ELF64LE>;
320 using ELF32BEFile = ELFFile<ELF32BE>;
321 using ELF64BEFile = ELFFile<ELF64BE>;
322
323 template <class ELFT>
324 inline Expected<const typename ELFT::Shdr *>
getSection(typename ELFT::ShdrRange Sections,uint32_t Index)325 getSection(typename ELFT::ShdrRange Sections, uint32_t Index) {
326 if (Index >= Sections.size())
327 return createError("invalid section index: " + Twine(Index));
328 return &Sections[Index];
329 }
330
331 template <class ELFT>
332 inline Expected<uint32_t>
getExtendedSymbolTableIndex(const typename ELFT::Sym * Sym,const typename ELFT::Sym * FirstSym,ArrayRef<typename ELFT::Word> ShndxTable)333 getExtendedSymbolTableIndex(const typename ELFT::Sym *Sym,
334 const typename ELFT::Sym *FirstSym,
335 ArrayRef<typename ELFT::Word> ShndxTable) {
336 assert(Sym->st_shndx == ELF::SHN_XINDEX);
337 unsigned Index = Sym - FirstSym;
338 if (Index >= ShndxTable.size())
339 return createError(
340 "extended symbol index (" + Twine(Index) +
341 ") is past the end of the SHT_SYMTAB_SHNDX section of size " +
342 Twine(ShndxTable.size()));
343
344 // The size of the table was checked in getSHNDXTable.
345 return ShndxTable[Index];
346 }
347
348 template <class ELFT>
349 Expected<uint32_t>
getSectionIndex(const Elf_Sym * Sym,Elf_Sym_Range Syms,ArrayRef<Elf_Word> ShndxTable)350 ELFFile<ELFT>::getSectionIndex(const Elf_Sym *Sym, Elf_Sym_Range Syms,
351 ArrayRef<Elf_Word> ShndxTable) const {
352 uint32_t Index = Sym->st_shndx;
353 if (Index == ELF::SHN_XINDEX) {
354 auto ErrorOrIndex = getExtendedSymbolTableIndex<ELFT>(
355 Sym, Syms.begin(), ShndxTable);
356 if (!ErrorOrIndex)
357 return ErrorOrIndex.takeError();
358 return *ErrorOrIndex;
359 }
360 if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
361 return 0;
362 return Index;
363 }
364
365 template <class ELFT>
366 Expected<const typename ELFT::Shdr *>
getSection(const Elf_Sym * Sym,const Elf_Shdr * SymTab,ArrayRef<Elf_Word> ShndxTable)367 ELFFile<ELFT>::getSection(const Elf_Sym *Sym, const Elf_Shdr *SymTab,
368 ArrayRef<Elf_Word> ShndxTable) const {
369 auto SymsOrErr = symbols(SymTab);
370 if (!SymsOrErr)
371 return SymsOrErr.takeError();
372 return getSection(Sym, *SymsOrErr, ShndxTable);
373 }
374
375 template <class ELFT>
376 Expected<const typename ELFT::Shdr *>
getSection(const Elf_Sym * Sym,Elf_Sym_Range Symbols,ArrayRef<Elf_Word> ShndxTable)377 ELFFile<ELFT>::getSection(const Elf_Sym *Sym, Elf_Sym_Range Symbols,
378 ArrayRef<Elf_Word> ShndxTable) const {
379 auto IndexOrErr = getSectionIndex(Sym, Symbols, ShndxTable);
380 if (!IndexOrErr)
381 return IndexOrErr.takeError();
382 uint32_t Index = *IndexOrErr;
383 if (Index == 0)
384 return nullptr;
385 return getSection(Index);
386 }
387
388 template <class ELFT>
389 Expected<const typename ELFT::Sym *>
getSymbol(const Elf_Shdr * Sec,uint32_t Index)390 ELFFile<ELFT>::getSymbol(const Elf_Shdr *Sec, uint32_t Index) const {
391 auto SymsOrErr = symbols(Sec);
392 if (!SymsOrErr)
393 return SymsOrErr.takeError();
394
395 Elf_Sym_Range Symbols = *SymsOrErr;
396 if (Index >= Symbols.size())
397 return createError("unable to get symbol from section " +
398 getSecIndexForError(this, Sec) +
399 ": invalid symbol index (" + Twine(Index) + ")");
400 return &Symbols[Index];
401 }
402
403 template <class ELFT>
404 template <typename T>
405 Expected<ArrayRef<T>>
getSectionContentsAsArray(const Elf_Shdr * Sec)406 ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr *Sec) const {
407 if (Sec->sh_entsize != sizeof(T) && sizeof(T) != 1)
408 return createError("section " + getSecIndexForError(this, Sec) +
409 " has an invalid sh_entsize: " + Twine(Sec->sh_entsize));
410
411 uintX_t Offset = Sec->sh_offset;
412 uintX_t Size = Sec->sh_size;
413
414 if (Size % sizeof(T))
415 return createError("section " + getSecIndexForError(this, Sec) +
416 " has an invalid sh_size (" + Twine(Size) +
417 ") which is not a multiple of its sh_entsize (" +
418 Twine(Sec->sh_entsize) + ")");
419 if (std::numeric_limits<uintX_t>::max() - Offset < Size)
420 return createError("section " + getSecIndexForError(this, Sec) +
421 " has a sh_offset (0x" + Twine::utohexstr(Offset) +
422 ") + sh_size (0x" + Twine::utohexstr(Size) +
423 ") that cannot be represented");
424 if (Offset + Size > Buf.size())
425 return createError("section " + getSecIndexForError(this, Sec) +
426 " has a sh_offset (0x" + Twine::utohexstr(Offset) +
427 ") + sh_size (0x" + Twine::utohexstr(Size) +
428 ") that is greater than the file size (0x" +
429 Twine::utohexstr(Buf.size()) + ")");
430
431 if (Offset % alignof(T))
432 // TODO: this error is untested.
433 return createError("unaligned data");
434
435 const T *Start = reinterpret_cast<const T *>(base() + Offset);
436 return makeArrayRef(Start, Size / sizeof(T));
437 }
438
439 template <class ELFT>
440 Expected<ArrayRef<uint8_t>>
getSegmentContents(const Elf_Phdr * Phdr)441 ELFFile<ELFT>::getSegmentContents(const Elf_Phdr *Phdr) const {
442 uintX_t Offset = Phdr->p_offset;
443 uintX_t Size = Phdr->p_filesz;
444
445 if (std::numeric_limits<uintX_t>::max() - Offset < Size)
446 return createError("program header " + getPhdrIndexForError(this, Phdr) +
447 " has a p_offset (0x" + Twine::utohexstr(Offset) +
448 ") + p_filesz (0x" + Twine::utohexstr(Size) +
449 ") that cannot be represented");
450 if (Offset + Size > Buf.size())
451 return createError("program header " + getPhdrIndexForError(this, Phdr) +
452 " has a p_offset (0x" + Twine::utohexstr(Offset) +
453 ") + p_filesz (0x" + Twine::utohexstr(Size) +
454 ") that is greater than the file size (0x" +
455 Twine::utohexstr(Buf.size()) + ")");
456 return makeArrayRef(base() + Offset, Size);
457 }
458
459 template <class ELFT>
460 Expected<ArrayRef<uint8_t>>
getSectionContents(const Elf_Shdr * Sec)461 ELFFile<ELFT>::getSectionContents(const Elf_Shdr *Sec) const {
462 return getSectionContentsAsArray<uint8_t>(Sec);
463 }
464
465 template <class ELFT>
getRelocationTypeName(uint32_t Type)466 StringRef ELFFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
467 return getELFRelocationTypeName(getHeader()->e_machine, Type);
468 }
469
470 template <class ELFT>
getRelocationTypeName(uint32_t Type,SmallVectorImpl<char> & Result)471 void ELFFile<ELFT>::getRelocationTypeName(uint32_t Type,
472 SmallVectorImpl<char> &Result) const {
473 if (!isMipsELF64()) {
474 StringRef Name = getRelocationTypeName(Type);
475 Result.append(Name.begin(), Name.end());
476 } else {
477 // The Mips N64 ABI allows up to three operations to be specified per
478 // relocation record. Unfortunately there's no easy way to test for the
479 // presence of N64 ELFs as they have no special flag that identifies them
480 // as being N64. We can safely assume at the moment that all Mips
481 // ELFCLASS64 ELFs are N64. New Mips64 ABIs should provide enough
482 // information to disambiguate between old vs new ABIs.
483 uint8_t Type1 = (Type >> 0) & 0xFF;
484 uint8_t Type2 = (Type >> 8) & 0xFF;
485 uint8_t Type3 = (Type >> 16) & 0xFF;
486
487 // Concat all three relocation type names.
488 StringRef Name = getRelocationTypeName(Type1);
489 Result.append(Name.begin(), Name.end());
490
491 Name = getRelocationTypeName(Type2);
492 Result.append(1, '/');
493 Result.append(Name.begin(), Name.end());
494
495 Name = getRelocationTypeName(Type3);
496 Result.append(1, '/');
497 Result.append(Name.begin(), Name.end());
498 }
499 }
500
501 template <class ELFT>
getRelativeRelocationType()502 uint32_t ELFFile<ELFT>::getRelativeRelocationType() const {
503 return getELFRelativeRelocationType(getHeader()->e_machine);
504 }
505
506 template <class ELFT>
507 Expected<const typename ELFT::Sym *>
getRelocationSymbol(const Elf_Rel * Rel,const Elf_Shdr * SymTab)508 ELFFile<ELFT>::getRelocationSymbol(const Elf_Rel *Rel,
509 const Elf_Shdr *SymTab) const {
510 uint32_t Index = Rel->getSymbol(isMips64EL());
511 if (Index == 0)
512 return nullptr;
513 return getEntry<Elf_Sym>(SymTab, Index);
514 }
515
516 template <class ELFT>
517 Expected<StringRef>
getSectionStringTable(Elf_Shdr_Range Sections,WarningHandler WarnHandler)518 ELFFile<ELFT>::getSectionStringTable(Elf_Shdr_Range Sections,
519 WarningHandler WarnHandler) const {
520 uint32_t Index = getHeader()->e_shstrndx;
521 if (Index == ELF::SHN_XINDEX) {
522 // If the section name string table section index is greater than
523 // or equal to SHN_LORESERVE, then the actual index of the section name
524 // string table section is contained in the sh_link field of the section
525 // header at index 0.
526 if (Sections.empty())
527 return createError(
528 "e_shstrndx == SHN_XINDEX, but the section header table is empty");
529
530 Index = Sections[0].sh_link;
531 }
532
533 if (!Index) // no section string table.
534 return "";
535 if (Index >= Sections.size())
536 return createError("section header string table index " + Twine(Index) +
537 " does not exist");
538 return getStringTable(&Sections[Index], WarnHandler);
539 }
540
ELFFile(StringRef Object)541 template <class ELFT> ELFFile<ELFT>::ELFFile(StringRef Object) : Buf(Object) {}
542
543 template <class ELFT>
create(StringRef Object)544 Expected<ELFFile<ELFT>> ELFFile<ELFT>::create(StringRef Object) {
545 if (sizeof(Elf_Ehdr) > Object.size())
546 return createError("invalid buffer: the size (" + Twine(Object.size()) +
547 ") is smaller than an ELF header (" +
548 Twine(sizeof(Elf_Ehdr)) + ")");
549 return ELFFile(Object);
550 }
551
552 template <class ELFT>
sections()553 Expected<typename ELFT::ShdrRange> ELFFile<ELFT>::sections() const {
554 const uintX_t SectionTableOffset = getHeader()->e_shoff;
555 if (SectionTableOffset == 0)
556 return ArrayRef<Elf_Shdr>();
557
558 if (getHeader()->e_shentsize != sizeof(Elf_Shdr))
559 return createError("invalid e_shentsize in ELF header: " +
560 Twine(getHeader()->e_shentsize));
561
562 const uint64_t FileSize = Buf.size();
563 if (SectionTableOffset + sizeof(Elf_Shdr) > FileSize ||
564 SectionTableOffset + (uintX_t)sizeof(Elf_Shdr) < SectionTableOffset)
565 return createError(
566 "section header table goes past the end of the file: e_shoff = 0x" +
567 Twine::utohexstr(SectionTableOffset));
568
569 // Invalid address alignment of section headers
570 if (SectionTableOffset & (alignof(Elf_Shdr) - 1))
571 // TODO: this error is untested.
572 return createError("invalid alignment of section headers");
573
574 const Elf_Shdr *First =
575 reinterpret_cast<const Elf_Shdr *>(base() + SectionTableOffset);
576
577 uintX_t NumSections = getHeader()->e_shnum;
578 if (NumSections == 0)
579 NumSections = First->sh_size;
580
581 if (NumSections > UINT64_MAX / sizeof(Elf_Shdr))
582 return createError("invalid number of sections specified in the NULL "
583 "section's sh_size field (" +
584 Twine(NumSections) + ")");
585
586 const uint64_t SectionTableSize = NumSections * sizeof(Elf_Shdr);
587 if (SectionTableOffset + SectionTableSize < SectionTableOffset)
588 return createError(
589 "invalid section header table offset (e_shoff = 0x" +
590 Twine::utohexstr(SectionTableOffset) +
591 ") or invalid number of sections specified in the first section "
592 "header's sh_size field (0x" +
593 Twine::utohexstr(NumSections) + ")");
594
595 // Section table goes past end of file!
596 if (SectionTableOffset + SectionTableSize > FileSize)
597 return createError("section table goes past the end of file");
598 return makeArrayRef(First, NumSections);
599 }
600
601 template <class ELFT>
602 template <typename T>
getEntry(uint32_t Section,uint32_t Entry)603 Expected<const T *> ELFFile<ELFT>::getEntry(uint32_t Section,
604 uint32_t Entry) const {
605 auto SecOrErr = getSection(Section);
606 if (!SecOrErr)
607 return SecOrErr.takeError();
608 return getEntry<T>(*SecOrErr, Entry);
609 }
610
611 template <class ELFT>
612 template <typename T>
getEntry(const Elf_Shdr * Section,uint32_t Entry)613 Expected<const T *> ELFFile<ELFT>::getEntry(const Elf_Shdr *Section,
614 uint32_t Entry) const {
615 if (sizeof(T) != Section->sh_entsize)
616 return createError("section " + getSecIndexForError(this, Section) +
617 " has invalid sh_entsize: expected " + Twine(sizeof(T)) +
618 ", but got " + Twine(Section->sh_entsize));
619 uint64_t Pos = Section->sh_offset + (uint64_t)Entry * sizeof(T);
620 if (Pos + sizeof(T) > Buf.size())
621 return createError("unable to access section " +
622 getSecIndexForError(this, Section) + " data at 0x" +
623 Twine::utohexstr(Pos) +
624 ": offset goes past the end of file");
625 return reinterpret_cast<const T *>(base() + Pos);
626 }
627
628 template <class ELFT>
629 Expected<const typename ELFT::Shdr *>
getSection(uint32_t Index)630 ELFFile<ELFT>::getSection(uint32_t Index) const {
631 auto TableOrErr = sections();
632 if (!TableOrErr)
633 return TableOrErr.takeError();
634 return object::getSection<ELFT>(*TableOrErr, Index);
635 }
636
637 template <class ELFT>
638 Expected<StringRef>
getStringTable(const Elf_Shdr * Section,WarningHandler WarnHandler)639 ELFFile<ELFT>::getStringTable(const Elf_Shdr *Section,
640 WarningHandler WarnHandler) const {
641 if (Section->sh_type != ELF::SHT_STRTAB)
642 if (Error E = WarnHandler("invalid sh_type for string table section " +
643 getSecIndexForError(this, Section) +
644 ": expected SHT_STRTAB, but got " +
645 object::getELFSectionTypeName(
646 getHeader()->e_machine, Section->sh_type)))
647 return std::move(E);
648
649 auto V = getSectionContentsAsArray<char>(Section);
650 if (!V)
651 return V.takeError();
652 ArrayRef<char> Data = *V;
653 if (Data.empty())
654 return createError("SHT_STRTAB string table section " +
655 getSecIndexForError(this, Section) + " is empty");
656 if (Data.back() != '\0')
657 return createError("SHT_STRTAB string table section " +
658 getSecIndexForError(this, Section) +
659 " is non-null terminated");
660 return StringRef(Data.begin(), Data.size());
661 }
662
663 template <class ELFT>
664 Expected<ArrayRef<typename ELFT::Word>>
getSHNDXTable(const Elf_Shdr & Section)665 ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section) const {
666 auto SectionsOrErr = sections();
667 if (!SectionsOrErr)
668 return SectionsOrErr.takeError();
669 return getSHNDXTable(Section, *SectionsOrErr);
670 }
671
672 template <class ELFT>
673 Expected<ArrayRef<typename ELFT::Word>>
getSHNDXTable(const Elf_Shdr & Section,Elf_Shdr_Range Sections)674 ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section,
675 Elf_Shdr_Range Sections) const {
676 assert(Section.sh_type == ELF::SHT_SYMTAB_SHNDX);
677 auto VOrErr = getSectionContentsAsArray<Elf_Word>(&Section);
678 if (!VOrErr)
679 return VOrErr.takeError();
680 ArrayRef<Elf_Word> V = *VOrErr;
681 auto SymTableOrErr = object::getSection<ELFT>(Sections, Section.sh_link);
682 if (!SymTableOrErr)
683 return SymTableOrErr.takeError();
684 const Elf_Shdr &SymTable = **SymTableOrErr;
685 if (SymTable.sh_type != ELF::SHT_SYMTAB &&
686 SymTable.sh_type != ELF::SHT_DYNSYM)
687 return createError("SHT_SYMTAB_SHNDX section is linked with " +
688 object::getELFSectionTypeName(getHeader()->e_machine,
689 SymTable.sh_type) +
690 " section (expected SHT_SYMTAB/SHT_DYNSYM)");
691
692 uint64_t Syms = SymTable.sh_size / sizeof(Elf_Sym);
693 if (V.size() != Syms)
694 return createError("SHT_SYMTAB_SHNDX has " + Twine(V.size()) +
695 " entries, but the symbol table associated has " +
696 Twine(Syms));
697
698 return V;
699 }
700
701 template <class ELFT>
702 Expected<StringRef>
getStringTableForSymtab(const Elf_Shdr & Sec)703 ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec) const {
704 auto SectionsOrErr = sections();
705 if (!SectionsOrErr)
706 return SectionsOrErr.takeError();
707 return getStringTableForSymtab(Sec, *SectionsOrErr);
708 }
709
710 template <class ELFT>
711 Expected<StringRef>
getStringTableForSymtab(const Elf_Shdr & Sec,Elf_Shdr_Range Sections)712 ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec,
713 Elf_Shdr_Range Sections) const {
714
715 if (Sec.sh_type != ELF::SHT_SYMTAB && Sec.sh_type != ELF::SHT_DYNSYM)
716 return createError(
717 "invalid sh_type for symbol table, expected SHT_SYMTAB or SHT_DYNSYM");
718 auto SectionOrErr = object::getSection<ELFT>(Sections, Sec.sh_link);
719 if (!SectionOrErr)
720 return SectionOrErr.takeError();
721 return getStringTable(*SectionOrErr);
722 }
723
724 template <class ELFT>
725 Expected<StringRef>
getSectionName(const Elf_Shdr * Section,WarningHandler WarnHandler)726 ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section,
727 WarningHandler WarnHandler) const {
728 auto SectionsOrErr = sections();
729 if (!SectionsOrErr)
730 return SectionsOrErr.takeError();
731 auto Table = getSectionStringTable(*SectionsOrErr, WarnHandler);
732 if (!Table)
733 return Table.takeError();
734 return getSectionName(Section, *Table);
735 }
736
737 template <class ELFT>
getSectionName(const Elf_Shdr * Section,StringRef DotShstrtab)738 Expected<StringRef> ELFFile<ELFT>::getSectionName(const Elf_Shdr *Section,
739 StringRef DotShstrtab) const {
740 uint32_t Offset = Section->sh_name;
741 if (Offset == 0)
742 return StringRef();
743 if (Offset >= DotShstrtab.size())
744 return createError("a section " + getSecIndexForError(this, Section) +
745 " has an invalid sh_name (0x" +
746 Twine::utohexstr(Offset) +
747 ") offset which goes past the end of the "
748 "section name string table");
749 return StringRef(DotShstrtab.data() + Offset);
750 }
751
752 /// This function returns the hash value for a symbol in the .dynsym section
753 /// Name of the API remains consistent as specified in the libelf
754 /// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
hashSysV(StringRef SymbolName)755 inline unsigned hashSysV(StringRef SymbolName) {
756 unsigned h = 0, g;
757 for (char C : SymbolName) {
758 h = (h << 4) + C;
759 g = h & 0xf0000000L;
760 if (g != 0)
761 h ^= g >> 24;
762 h &= ~g;
763 }
764 return h;
765 }
766
767 } // end namespace object
768 } // end namespace llvm
769
770 #endif // LLVM_OBJECT_ELF_H
771