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 typename ELFFileBase<ELFT>::Elf_Sym_Range
40 ELFFileBase<ELFT>::getSymbolsHelper(bool Local) {
41   if (!Symtab)
42     return Elf_Sym_Range(nullptr, nullptr);
43   Elf_Sym_Range Syms = ELFObj.symbols(Symtab);
44   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
45   uint32_t FirstNonLocal = Symtab->sh_info;
46   if (FirstNonLocal > NumSymbols)
47     error("Invalid sh_info in symbol table");
48   if (!Local)
49     return make_range(Syms.begin() + FirstNonLocal, Syms.end());
50   // +1 to skip over dummy symbol.
51   return make_range(Syms.begin() + 1, Syms.begin() + FirstNonLocal);
52 }
53 
54 template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
55   if (!Symtab)
56     return;
57   ErrorOr<StringRef> StringTableOrErr = ELFObj.getStringTableForSymtab(*Symtab);
58   error(StringTableOrErr.getError());
59   StringTable = *StringTableOrErr;
60 }
61 
62 template <class ELFT>
63 typename ELFFileBase<ELFT>::Elf_Sym_Range
64 ELFFileBase<ELFT>::getNonLocalSymbols() {
65   return getSymbolsHelper(false);
66 }
67 
68 template <class ELFT>
69 ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
70     : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
71 
72 template <class ELFT>
73 typename ObjectFile<ELFT>::Elf_Sym_Range ObjectFile<ELFT>::getLocalSymbols() {
74   return this->getSymbolsHelper(true);
75 }
76 
77 template <class ELFT>
78 const typename ObjectFile<ELFT>::Elf_Sym *
79 ObjectFile<ELFT>::getLocalSymbol(uintX_t SymIndex) {
80   uint32_t FirstNonLocal = this->Symtab->sh_info;
81   if (SymIndex >= FirstNonLocal)
82     return nullptr;
83   Elf_Sym_Range Syms = this->ELFObj.symbols(this->Symtab);
84   return Syms.begin() + SymIndex;
85 }
86 
87 template <class ELFT>
88 void elf2::ObjectFile<ELFT>::parse(DenseSet<StringRef> &Comdats) {
89   // Read section and symbol tables.
90   initializeSections(Comdats);
91   initializeSymbols();
92 }
93 
94 template <class ELFT>
95 StringRef ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
96   const ELFFile<ELFT> &Obj = this->ELFObj;
97   uint32_t SymtabdSectionIndex = Sec.sh_link;
98   ErrorOr<const Elf_Shdr *> SecOrErr = Obj.getSection(SymtabdSectionIndex);
99   error(SecOrErr);
100   const Elf_Shdr *SymtabSec = *SecOrErr;
101   uint32_t SymIndex = Sec.sh_info;
102   const Elf_Sym *Sym = Obj.getSymbol(SymtabSec, SymIndex);
103   ErrorOr<StringRef> StringTableOrErr = Obj.getStringTableForSymtab(*SymtabSec);
104   error(StringTableOrErr);
105   ErrorOr<StringRef> SignatureOrErr = Sym->getName(*StringTableOrErr);
106   error(SignatureOrErr);
107   return *SignatureOrErr;
108 }
109 
110 template <class ELFT>
111 ArrayRef<typename ObjectFile<ELFT>::GroupEntryType>
112 ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
113   const ELFFile<ELFT> &Obj = this->ELFObj;
114   ErrorOr<ArrayRef<GroupEntryType>> EntriesOrErr =
115       Obj.template getSectionContentsAsArray<GroupEntryType>(&Sec);
116   error(EntriesOrErr.getError());
117   ArrayRef<GroupEntryType> Entries = *EntriesOrErr;
118   if (Entries.empty() || Entries[0] != GRP_COMDAT)
119     error("Unsupported SHT_GROUP format");
120   return Entries.slice(1);
121 }
122 
123 template <class ELFT>
124 void elf2::ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &Comdats) {
125   uint64_t Size = this->ELFObj.getNumSections();
126   Sections.resize(Size);
127   unsigned I = -1;
128   const ELFFile<ELFT> &Obj = this->ELFObj;
129   for (const Elf_Shdr &Sec : Obj.sections()) {
130     ++I;
131     if (Sections[I] == &InputSection<ELFT>::Discarded)
132       continue;
133 
134     switch (Sec.sh_type) {
135     case SHT_GROUP:
136       Sections[I] = &InputSection<ELFT>::Discarded;
137       if (Comdats.insert(getShtGroupSignature(Sec)).second)
138         continue;
139       for (GroupEntryType E : getShtGroupEntries(Sec)) {
140         uint32_t SecIndex = E;
141         if (SecIndex >= Size)
142           error("Invalid section index in group");
143         Sections[SecIndex] = &InputSection<ELFT>::Discarded;
144       }
145       break;
146     case SHT_SYMTAB:
147       this->Symtab = &Sec;
148       break;
149     case SHT_SYMTAB_SHNDX: {
150       ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
151       error(ErrorOrTable);
152       SymtabSHNDX = *ErrorOrTable;
153       break;
154     }
155     case SHT_STRTAB:
156     case SHT_NULL:
157       break;
158     case SHT_RELA:
159     case SHT_REL: {
160       uint32_t RelocatedSectionIndex = Sec.sh_info;
161       if (RelocatedSectionIndex >= Size)
162         error("Invalid relocated section index");
163       InputSectionBase<ELFT> *RelocatedSection =
164           Sections[RelocatedSectionIndex];
165       if (!RelocatedSection)
166         error("Unsupported relocation reference");
167       if (auto *S = dyn_cast<InputSection<ELFT>>(RelocatedSection))
168         S->RelocSections.push_back(&Sec);
169       else
170         error("Relocations pointing to SHF_MERGE are not supported");
171       break;
172     }
173     default: {
174       uintX_t Flags = Sec.sh_flags;
175       if (Flags & SHF_MERGE && !(Flags & SHF_STRINGS)) {
176         if (Flags & SHF_WRITE)
177           error("Writable SHF_MERGE sections are not supported");
178         Sections[I] = new (this->Alloc) MergeInputSection<ELFT>(this, &Sec);
179       } else {
180         Sections[I] = new (this->Alloc) InputSection<ELFT>(this, &Sec);
181       }
182       break;
183     }
184     }
185   }
186 }
187 
188 template <class ELFT> void elf2::ObjectFile<ELFT>::initializeSymbols() {
189   this->initStringTable();
190   Elf_Sym_Range Syms = this->getNonLocalSymbols();
191   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
192   this->SymbolBodies.reserve(NumSymbols);
193   for (const Elf_Sym &Sym : Syms)
194     this->SymbolBodies.push_back(createSymbolBody(this->StringTable, &Sym));
195 }
196 
197 template <class ELFT>
198 InputSectionBase<ELFT> *
199 elf2::ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
200   uint32_t Index = Sym.st_shndx;
201   if (Index == ELF::SHN_XINDEX)
202     Index = this->ELFObj.getExtendedSymbolTableIndex(&Sym, this->Symtab,
203                                                      SymtabSHNDX);
204   else if (Index == ELF::SHN_UNDEF || Index >= ELF::SHN_LORESERVE)
205     return nullptr;
206 
207   if (Index >= Sections.size() || !Index || !Sections[Index])
208     error("Invalid section index");
209   return Sections[Index];
210 }
211 
212 template <class ELFT>
213 SymbolBody *elf2::ObjectFile<ELFT>::createSymbolBody(StringRef StringTable,
214                                                      const Elf_Sym *Sym) {
215   ErrorOr<StringRef> NameOrErr = Sym->getName(StringTable);
216   error(NameOrErr.getError());
217   StringRef Name = *NameOrErr;
218 
219   switch (Sym->st_shndx) {
220   case SHN_ABS:
221     return new (this->Alloc) DefinedAbsolute<ELFT>(Name, *Sym);
222   case SHN_UNDEF:
223     return new (this->Alloc) Undefined<ELFT>(Name, *Sym);
224   case SHN_COMMON:
225     return new (this->Alloc) DefinedCommon<ELFT>(Name, *Sym);
226   }
227 
228   switch (Sym->getBinding()) {
229   default:
230     error("unexpected binding");
231   case STB_GLOBAL:
232   case STB_WEAK:
233   case STB_GNU_UNIQUE: {
234     InputSectionBase<ELFT> *Sec = getSection(*Sym);
235     if (Sec == &InputSection<ELFT>::Discarded)
236       return new (this->Alloc) Undefined<ELFT>(Name, *Sym);
237     return new (this->Alloc) DefinedRegular<ELFT>(Name, *Sym, *Sec);
238   }
239   }
240 }
241 
242 static std::unique_ptr<Archive> openArchive(MemoryBufferRef MB) {
243   ErrorOr<std::unique_ptr<Archive>> ArchiveOrErr = Archive::create(MB);
244   error(ArchiveOrErr, "Failed to parse archive");
245   return std::move(*ArchiveOrErr);
246 }
247 
248 void ArchiveFile::parse() {
249   File = openArchive(MB);
250 
251   // Allocate a buffer for Lazy objects.
252   size_t NumSyms = File->getNumberOfSymbols();
253   LazySymbols.reserve(NumSyms);
254 
255   // Read the symbol table to construct Lazy objects.
256   for (const Archive::Symbol &Sym : File->symbols())
257     LazySymbols.emplace_back(this, Sym);
258 }
259 
260 // Returns a buffer pointing to a member file containing a given symbol.
261 MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
262   ErrorOr<Archive::child_iterator> ItOrErr = Sym->getMember();
263   error(ItOrErr, "Could not get the member for symbol " + Sym->getName());
264   Archive::child_iterator It = *ItOrErr;
265 
266   if (!Seen.insert(It->getChildOffset()).second)
267     return MemoryBufferRef();
268 
269   ErrorOr<MemoryBufferRef> Ret = It->getMemoryBufferRef();
270   error(Ret, "Could not get the buffer for the member defining symbol " +
271                  Sym->getName());
272   return *Ret;
273 }
274 
275 std::vector<MemoryBufferRef> ArchiveFile::getMembers() {
276   File = openArchive(MB);
277 
278   std::vector<MemoryBufferRef> Result;
279   for (const Archive::Child &Child : File->children()) {
280     ErrorOr<MemoryBufferRef> MbOrErr = Child.getMemoryBufferRef();
281     error(MbOrErr, "Could not get the buffer for a child of the archive " +
282                        File->getFileName());
283     Result.push_back(MbOrErr.get());
284   }
285   return Result;
286 }
287 
288 template <class ELFT>
289 SharedFile<ELFT>::SharedFile(MemoryBufferRef M)
290     : ELFFileBase<ELFT>(Base::SharedKind, M) {
291   AsNeeded = Config->AsNeeded;
292 }
293 
294 template <class ELFT> void SharedFile<ELFT>::parseSoName() {
295   typedef typename ELFFile<ELFT>::Elf_Dyn Elf_Dyn;
296   typedef typename ELFFile<ELFT>::uintX_t uintX_t;
297   const Elf_Shdr *DynamicSec = nullptr;
298 
299   const ELFFile<ELFT> Obj = this->ELFObj;
300   for (const Elf_Shdr &Sec : Obj.sections()) {
301     uint32_t Type = Sec.sh_type;
302     if (Type == SHT_DYNSYM)
303       this->Symtab = &Sec;
304     else if (Type == SHT_DYNAMIC)
305       DynamicSec = &Sec;
306   }
307 
308   this->initStringTable();
309   this->SoName = this->getName();
310 
311   if (!DynamicSec)
312     return;
313   auto *Begin =
314       reinterpret_cast<const Elf_Dyn *>(Obj.base() + DynamicSec->sh_offset);
315   const Elf_Dyn *End = Begin + DynamicSec->sh_size / sizeof(Elf_Dyn);
316 
317   for (const Elf_Dyn &Dyn : make_range(Begin, End)) {
318     if (Dyn.d_tag == DT_SONAME) {
319       uintX_t Val = Dyn.getVal();
320       if (Val >= this->StringTable.size())
321         error("Invalid DT_SONAME entry");
322       this->SoName = StringRef(this->StringTable.data() + Val);
323       return;
324     }
325   }
326 }
327 
328 template <class ELFT> void SharedFile<ELFT>::parse() {
329   Elf_Sym_Range Syms = this->getNonLocalSymbols();
330   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
331   SymbolBodies.reserve(NumSymbols);
332   for (const Elf_Sym &Sym : Syms) {
333     ErrorOr<StringRef> NameOrErr = Sym.getName(this->StringTable);
334     error(NameOrErr.getError());
335     StringRef Name = *NameOrErr;
336 
337     if (Sym.isUndefined())
338       Undefs.push_back(Name);
339     else
340       SymbolBodies.emplace_back(this, Name, Sym);
341   }
342 }
343 
344 template <typename T>
345 static std::unique_ptr<InputFile> createELFFileAux(MemoryBufferRef MB) {
346   std::unique_ptr<T> Ret = llvm::make_unique<T>(MB);
347 
348   if (!Config->FirstElf)
349     Config->FirstElf = Ret.get();
350 
351   if (Config->EKind == ELFNoneKind) {
352     Config->EKind = Ret->getELFKind();
353     Config->EMachine = Ret->getEMachine();
354   }
355 
356   return std::move(Ret);
357 }
358 
359 template <template <class> class T>
360 std::unique_ptr<InputFile> lld::elf2::createELFFile(MemoryBufferRef MB) {
361   using namespace llvm;
362 
363   std::pair<unsigned char, unsigned char> Type =
364     object::getElfArchType(MB.getBuffer());
365   if (Type.second != ELF::ELFDATA2LSB && Type.second != ELF::ELFDATA2MSB)
366     error("Invalid data encoding: " + MB.getBufferIdentifier());
367 
368   if (Type.first == ELF::ELFCLASS32) {
369     if (Type.second == ELF::ELFDATA2LSB)
370       return createELFFileAux<T<object::ELF32LE>>(MB);
371     return createELFFileAux<T<object::ELF32BE>>(MB);
372   }
373   if (Type.first == ELF::ELFCLASS64) {
374     if (Type.second == ELF::ELFDATA2LSB)
375       return createELFFileAux<T<object::ELF64LE>>(MB);
376     return createELFFileAux<T<object::ELF64BE>>(MB);
377   }
378   error("Invalid file class: " + MB.getBufferIdentifier());
379 }
380 
381 namespace lld {
382 namespace elf2 {
383 template class ELFFileBase<llvm::object::ELF32LE>;
384 template class ELFFileBase<llvm::object::ELF32BE>;
385 template class ELFFileBase<llvm::object::ELF64LE>;
386 template class ELFFileBase<llvm::object::ELF64BE>;
387 
388 template class ObjectFile<llvm::object::ELF32LE>;
389 template class ObjectFile<llvm::object::ELF32BE>;
390 template class ObjectFile<llvm::object::ELF64LE>;
391 template class ObjectFile<llvm::object::ELF64BE>;
392 
393 template class SharedFile<llvm::object::ELF32LE>;
394 template class SharedFile<llvm::object::ELF32BE>;
395 template class SharedFile<llvm::object::ELF64LE>;
396 template class SharedFile<llvm::object::ELF64BE>;
397 
398 template std::unique_ptr<InputFile> createELFFile<ObjectFile>(MemoryBufferRef);
399 template std::unique_ptr<InputFile> createELFFile<SharedFile>(MemoryBufferRef);
400 }
401 }
402