1 //===- InputFiles.cpp -----------------------------------------------------===//
2 //
3 //                             The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "InputFiles.h"
11 #include "InputSection.h"
12 #include "Error.h"
13 #include "Symbols.h"
14 #include "llvm/ADT/STLExtras.h"
15 
16 using namespace llvm;
17 using namespace llvm::ELF;
18 using namespace llvm::object;
19 using namespace llvm::sys::fs;
20 
21 using namespace lld;
22 using namespace lld::elf2;
23 
24 namespace {
25 class ECRAII {
26   std::error_code EC;
27 
28 public:
29   std::error_code &getEC() { return EC; }
30   ~ECRAII() { error(EC); }
31 };
32 }
33 
34 template <class ELFT>
35 ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef M)
36     : InputFile(K, M), ELFObj(MB.getBuffer(), ECRAII().getEC()) {}
37 
38 template <class ELFT>
39 ELFKind ELFFileBase<ELFT>::getELFKind() {
40   using llvm::support::little;
41   if (ELFT::Is64Bits)
42     return ELFT::TargetEndianness == little ? ELF64LEKind : ELF64BEKind;
43   return ELFT::TargetEndianness == little ? ELF32LEKind : ELF32BEKind;
44 }
45 
46 template <class ELFT>
47 typename ELFFileBase<ELFT>::Elf_Sym_Range
48 ELFFileBase<ELFT>::getSymbolsHelper(bool Local) {
49   if (!Symtab)
50     return Elf_Sym_Range(nullptr, nullptr);
51   Elf_Sym_Range Syms = ELFObj.symbols(Symtab);
52   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
53   uint32_t FirstNonLocal = Symtab->sh_info;
54   if (FirstNonLocal > NumSymbols)
55     error("Invalid sh_info in symbol table");
56   if (!Local)
57     return make_range(Syms.begin() + FirstNonLocal, Syms.end());
58   // +1 to skip over dummy symbol.
59   return make_range(Syms.begin() + 1, Syms.begin() + FirstNonLocal);
60 }
61 
62 template <class ELFT>
63 uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
64   uint32_t Index = Sym.st_shndx;
65   if (Index == ELF::SHN_XINDEX)
66     Index = this->ELFObj.getExtendedSymbolTableIndex(&Sym, this->Symtab,
67                                                      SymtabSHNDX);
68   else if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
69     return 0;
70 
71   if (!Index)
72     error("Invalid section index");
73   return Index;
74 }
75 
76 template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
77   if (!Symtab)
78     return;
79   ErrorOr<StringRef> StringTableOrErr = ELFObj.getStringTableForSymtab(*Symtab);
80   error(StringTableOrErr.getError());
81   StringTable = *StringTableOrErr;
82 }
83 
84 template <class ELFT>
85 typename ELFFileBase<ELFT>::Elf_Sym_Range
86 ELFFileBase<ELFT>::getNonLocalSymbols() {
87   return getSymbolsHelper(false);
88 }
89 
90 template <class ELFT>
91 ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
92     : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
93 
94 template <class ELFT>
95 typename ObjectFile<ELFT>::Elf_Sym_Range ObjectFile<ELFT>::getLocalSymbols() {
96   return this->getSymbolsHelper(true);
97 }
98 
99 template <class ELFT>
100 const typename ObjectFile<ELFT>::Elf_Sym *
101 ObjectFile<ELFT>::getLocalSymbol(uintX_t SymIndex) {
102   uint32_t FirstNonLocal = this->Symtab->sh_info;
103   if (SymIndex >= FirstNonLocal)
104     return nullptr;
105   Elf_Sym_Range Syms = this->ELFObj.symbols(this->Symtab);
106   return Syms.begin() + SymIndex;
107 }
108 
109 template <class ELFT>
110 void elf2::ObjectFile<ELFT>::parse(DenseSet<StringRef> &Comdats) {
111   // Read section and symbol tables.
112   initializeSections(Comdats);
113   initializeSymbols();
114 }
115 
116 template <class ELFT>
117 StringRef ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
118   const ELFFile<ELFT> &Obj = this->ELFObj;
119   uint32_t SymtabdSectionIndex = Sec.sh_link;
120   ErrorOr<const Elf_Shdr *> SecOrErr = Obj.getSection(SymtabdSectionIndex);
121   error(SecOrErr);
122   const Elf_Shdr *SymtabSec = *SecOrErr;
123   uint32_t SymIndex = Sec.sh_info;
124   const Elf_Sym *Sym = Obj.getSymbol(SymtabSec, SymIndex);
125   ErrorOr<StringRef> StringTableOrErr = Obj.getStringTableForSymtab(*SymtabSec);
126   error(StringTableOrErr);
127   ErrorOr<StringRef> SignatureOrErr = Sym->getName(*StringTableOrErr);
128   error(SignatureOrErr);
129   return *SignatureOrErr;
130 }
131 
132 template <class ELFT>
133 ArrayRef<typename ObjectFile<ELFT>::GroupEntryType>
134 ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
135   const ELFFile<ELFT> &Obj = this->ELFObj;
136   ErrorOr<ArrayRef<GroupEntryType>> EntriesOrErr =
137       Obj.template getSectionContentsAsArray<GroupEntryType>(&Sec);
138   error(EntriesOrErr.getError());
139   ArrayRef<GroupEntryType> Entries = *EntriesOrErr;
140   if (Entries.empty() || Entries[0] != GRP_COMDAT)
141     error("Unsupported SHT_GROUP format");
142   return Entries.slice(1);
143 }
144 
145 template <class ELFT>
146 static bool shouldMerge(const typename ELFFile<ELFT>::Elf_Shdr &Sec) {
147   typedef typename ELFFile<ELFT>::uintX_t uintX_t;
148   uintX_t Flags = Sec.sh_flags;
149   if (!(Flags & SHF_MERGE))
150     return false;
151   if (Flags & SHF_WRITE)
152     error("Writable SHF_MERGE sections are not supported");
153   uintX_t EntSize = Sec.sh_entsize;
154   if (!EntSize || Sec.sh_size % EntSize)
155     error("SHF_MERGE section size must be a multiple of sh_entsize");
156 
157   // Don't try to merge if the aligment is larger than the sh_entsize.
158   //
159   // If this is not a SHF_STRINGS, we would need to pad after every entity. It
160   // would be equivalent for the producer of the .o to just set a larger
161   // sh_entsize.
162   //
163   // If this is a SHF_STRINGS, the larger alignment makes sense. Unfortunately
164   // it would complicate tail merging. This doesn't seem that common to
165   // justify the effort.
166   if (Sec.sh_addralign > EntSize)
167     return false;
168 
169   return true;
170 }
171 
172 template <class ELFT>
173 void elf2::ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &Comdats) {
174   uint64_t Size = this->ELFObj.getNumSections();
175   Sections.resize(Size);
176   unsigned I = -1;
177   const ELFFile<ELFT> &Obj = this->ELFObj;
178   for (const Elf_Shdr &Sec : Obj.sections()) {
179     ++I;
180     if (Sections[I] == &InputSection<ELFT>::Discarded)
181       continue;
182 
183     switch (Sec.sh_type) {
184     case SHT_GROUP:
185       Sections[I] = &InputSection<ELFT>::Discarded;
186       if (Comdats.insert(getShtGroupSignature(Sec)).second)
187         continue;
188       for (GroupEntryType E : getShtGroupEntries(Sec)) {
189         uint32_t SecIndex = E;
190         if (SecIndex >= Size)
191           error("Invalid section index in group");
192         Sections[SecIndex] = &InputSection<ELFT>::Discarded;
193       }
194       break;
195     case SHT_SYMTAB:
196       this->Symtab = &Sec;
197       break;
198     case SHT_SYMTAB_SHNDX: {
199       ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
200       error(ErrorOrTable);
201       this->SymtabSHNDX = *ErrorOrTable;
202       break;
203     }
204     case SHT_STRTAB:
205     case SHT_NULL:
206       break;
207     case SHT_RELA:
208     case SHT_REL: {
209       uint32_t RelocatedSectionIndex = Sec.sh_info;
210       if (RelocatedSectionIndex >= Size)
211         error("Invalid relocated section index");
212       InputSectionBase<ELFT> *RelocatedSection =
213           Sections[RelocatedSectionIndex];
214       if (!RelocatedSection)
215         error("Unsupported relocation reference");
216       if (auto *S = dyn_cast<InputSection<ELFT>>(RelocatedSection)) {
217         S->RelocSections.push_back(&Sec);
218       } else if (auto *S = dyn_cast<EHInputSection<ELFT>>(RelocatedSection)) {
219         if (S->RelocSection)
220           error("Multiple relocation sections to .eh_frame are not supported");
221         S->RelocSection = &Sec;
222       } else {
223         error("Relocations pointing to SHF_MERGE are not supported");
224       }
225       break;
226     }
227     default:
228       ErrorOr<StringRef> NameOrErr = this->ELFObj.getSectionName(&Sec);
229       error(NameOrErr);
230       StringRef Name = *NameOrErr;
231       if (Name == ".note.GNU-stack")
232         Sections[I] = &InputSection<ELFT>::Discarded;
233       else if (Name == ".eh_frame")
234         Sections[I] = new (this->Alloc) EHInputSection<ELFT>(this, &Sec);
235       else if (shouldMerge<ELFT>(Sec))
236         Sections[I] = new (this->Alloc) MergeInputSection<ELFT>(this, &Sec);
237       else
238         Sections[I] = new (this->Alloc) InputSection<ELFT>(this, &Sec);
239       break;
240     }
241   }
242 }
243 
244 template <class ELFT> void elf2::ObjectFile<ELFT>::initializeSymbols() {
245   this->initStringTable();
246   Elf_Sym_Range Syms = this->getNonLocalSymbols();
247   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
248   this->SymbolBodies.reserve(NumSymbols);
249   for (const Elf_Sym &Sym : Syms)
250     this->SymbolBodies.push_back(createSymbolBody(this->StringTable, &Sym));
251 }
252 
253 template <class ELFT>
254 InputSectionBase<ELFT> *
255 elf2::ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
256   uint32_t Index = this->getSectionIndex(Sym);
257   if (Index == 0)
258     return nullptr;
259   if (Index >= Sections.size() || !Sections[Index])
260     error("Invalid section index");
261   return Sections[Index];
262 }
263 
264 template <class ELFT>
265 SymbolBody *elf2::ObjectFile<ELFT>::createSymbolBody(StringRef StringTable,
266                                                      const Elf_Sym *Sym) {
267   ErrorOr<StringRef> NameOrErr = Sym->getName(StringTable);
268   error(NameOrErr.getError());
269   StringRef Name = *NameOrErr;
270 
271   switch (Sym->st_shndx) {
272   case SHN_ABS:
273     return new (this->Alloc) DefinedAbsolute<ELFT>(Name, *Sym);
274   case SHN_UNDEF:
275     return new (this->Alloc) Undefined<ELFT>(Name, *Sym);
276   case SHN_COMMON:
277     return new (this->Alloc) DefinedCommon<ELFT>(Name, *Sym);
278   }
279 
280   switch (Sym->getBinding()) {
281   default:
282     error("unexpected binding");
283   case STB_GLOBAL:
284   case STB_WEAK:
285   case STB_GNU_UNIQUE: {
286     InputSectionBase<ELFT> *Sec = getSection(*Sym);
287     if (Sec == &InputSection<ELFT>::Discarded)
288       return new (this->Alloc) Undefined<ELFT>(Name, *Sym);
289     return new (this->Alloc) DefinedRegular<ELFT>(Name, *Sym, *Sec);
290   }
291   }
292 }
293 
294 static std::unique_ptr<Archive> openArchive(MemoryBufferRef MB) {
295   ErrorOr<std::unique_ptr<Archive>> ArchiveOrErr = Archive::create(MB);
296   error(ArchiveOrErr, "Failed to parse archive");
297   return std::move(*ArchiveOrErr);
298 }
299 
300 void ArchiveFile::parse() {
301   File = openArchive(MB);
302 
303   // Allocate a buffer for Lazy objects.
304   size_t NumSyms = File->getNumberOfSymbols();
305   LazySymbols.reserve(NumSyms);
306 
307   // Read the symbol table to construct Lazy objects.
308   for (const Archive::Symbol &Sym : File->symbols())
309     LazySymbols.emplace_back(this, Sym);
310 }
311 
312 // Returns a buffer pointing to a member file containing a given symbol.
313 MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
314   ErrorOr<Archive::Child> COrErr = Sym->getMember();
315   error(COrErr, "Could not get the member for symbol " + Sym->getName());
316   const Archive::Child &C = *COrErr;
317 
318   if (!Seen.insert(C.getChildOffset()).second)
319     return MemoryBufferRef();
320 
321   ErrorOr<MemoryBufferRef> Ret = C.getMemoryBufferRef();
322   error(Ret, "Could not get the buffer for the member defining symbol " +
323                  Sym->getName());
324   return *Ret;
325 }
326 
327 std::vector<MemoryBufferRef> ArchiveFile::getMembers() {
328   File = openArchive(MB);
329 
330   std::vector<MemoryBufferRef> Result;
331   for (auto &ChildOrErr : File->children()) {
332     error(ChildOrErr,
333           "Could not get the child of the archive " + File->getFileName());
334     const Archive::Child Child(*ChildOrErr);
335     ErrorOr<MemoryBufferRef> MbOrErr = Child.getMemoryBufferRef();
336     error(MbOrErr, "Could not get the buffer for a child of the archive " +
337                        File->getFileName());
338     Result.push_back(MbOrErr.get());
339   }
340   return Result;
341 }
342 
343 template <class ELFT>
344 SharedFile<ELFT>::SharedFile(MemoryBufferRef M)
345     : ELFFileBase<ELFT>(Base::SharedKind, M) {
346   AsNeeded = Config->AsNeeded;
347 }
348 
349 template <class ELFT>
350 const typename ELFFile<ELFT>::Elf_Shdr *
351 SharedFile<ELFT>::getSection(const Elf_Sym &Sym) const {
352   uint32_t Index = this->getSectionIndex(Sym);
353   if (Index == 0)
354     return nullptr;
355   ErrorOr<const Elf_Shdr *> Ret = this->ELFObj.getSection(Index);
356   error(Ret);
357   return *Ret;
358 }
359 
360 template <class ELFT> void SharedFile<ELFT>::parseSoName() {
361   typedef typename ELFFile<ELFT>::Elf_Dyn Elf_Dyn;
362   typedef typename ELFFile<ELFT>::uintX_t uintX_t;
363   const Elf_Shdr *DynamicSec = nullptr;
364 
365   const ELFFile<ELFT> Obj = this->ELFObj;
366   for (const Elf_Shdr &Sec : Obj.sections()) {
367     switch (Sec.sh_type) {
368     default:
369       continue;
370     case SHT_DYNSYM:
371       this->Symtab = &Sec;
372       break;
373     case SHT_DYNAMIC:
374       DynamicSec = &Sec;
375       break;
376     case SHT_SYMTAB_SHNDX: {
377       ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
378       error(ErrorOrTable);
379       this->SymtabSHNDX = *ErrorOrTable;
380       break;
381     }
382     }
383   }
384 
385   this->initStringTable();
386   this->SoName = this->getName();
387 
388   if (!DynamicSec)
389     return;
390   auto *Begin =
391       reinterpret_cast<const Elf_Dyn *>(Obj.base() + DynamicSec->sh_offset);
392   const Elf_Dyn *End = Begin + DynamicSec->sh_size / sizeof(Elf_Dyn);
393 
394   for (const Elf_Dyn &Dyn : make_range(Begin, End)) {
395     if (Dyn.d_tag == DT_SONAME) {
396       uintX_t Val = Dyn.getVal();
397       if (Val >= this->StringTable.size())
398         error("Invalid DT_SONAME entry");
399       this->SoName = StringRef(this->StringTable.data() + Val);
400       return;
401     }
402   }
403 }
404 
405 template <class ELFT> void SharedFile<ELFT>::parse() {
406   Elf_Sym_Range Syms = this->getNonLocalSymbols();
407   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
408   SymbolBodies.reserve(NumSymbols);
409   for (const Elf_Sym &Sym : Syms) {
410     ErrorOr<StringRef> NameOrErr = Sym.getName(this->StringTable);
411     error(NameOrErr.getError());
412     StringRef Name = *NameOrErr;
413 
414     if (Sym.isUndefined())
415       Undefs.push_back(Name);
416     else
417       SymbolBodies.emplace_back(this, Name, Sym);
418   }
419 }
420 
421 template <typename T>
422 static std::unique_ptr<InputFile> createELFFileAux(MemoryBufferRef MB) {
423   std::unique_ptr<T> Ret = llvm::make_unique<T>(MB);
424 
425   if (!Config->FirstElf)
426     Config->FirstElf = Ret.get();
427 
428   if (Config->EKind == ELFNoneKind) {
429     Config->EKind = Ret->getELFKind();
430     Config->EMachine = Ret->getEMachine();
431   }
432 
433   return std::move(Ret);
434 }
435 
436 template <template <class> class T>
437 std::unique_ptr<InputFile> lld::elf2::createELFFile(MemoryBufferRef MB) {
438   std::pair<unsigned char, unsigned char> Type = getElfArchType(MB.getBuffer());
439   if (Type.second != ELF::ELFDATA2LSB && Type.second != ELF::ELFDATA2MSB)
440     error("Invalid data encoding: " + MB.getBufferIdentifier());
441 
442   if (Type.first == ELF::ELFCLASS32) {
443     if (Type.second == ELF::ELFDATA2LSB)
444       return createELFFileAux<T<ELF32LE>>(MB);
445     return createELFFileAux<T<ELF32BE>>(MB);
446   }
447   if (Type.first == ELF::ELFCLASS64) {
448     if (Type.second == ELF::ELFDATA2LSB)
449       return createELFFileAux<T<ELF64LE>>(MB);
450     return createELFFileAux<T<ELF64BE>>(MB);
451   }
452   error("Invalid file class: " + MB.getBufferIdentifier());
453 }
454 
455 template class elf2::ELFFileBase<ELF32LE>;
456 template class elf2::ELFFileBase<ELF32BE>;
457 template class elf2::ELFFileBase<ELF64LE>;
458 template class elf2::ELFFileBase<ELF64BE>;
459 
460 template class elf2::ObjectFile<ELF32LE>;
461 template class elf2::ObjectFile<ELF32BE>;
462 template class elf2::ObjectFile<ELF64LE>;
463 template class elf2::ObjectFile<ELF64BE>;
464 
465 template class elf2::SharedFile<ELF32LE>;
466 template class elf2::SharedFile<ELF32BE>;
467 template class elf2::SharedFile<ELF64LE>;
468 template class elf2::SharedFile<ELF64BE>;
469 
470 template std::unique_ptr<InputFile>
471 elf2::createELFFile<ObjectFile>(MemoryBufferRef);
472 
473 template std::unique_ptr<InputFile>
474 elf2::createELFFile<SharedFile>(MemoryBufferRef);
475