InputFiles.cpp revision 292934 
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 "Chunks.h"
11#include "Error.h"
12#include "InputFiles.h"
13#include "Symbols.h"
14#include "llvm/ADT/STLExtras.h"
15#include "llvm/IR/LLVMContext.h"
16#include "llvm/LTO/LTOModule.h"
17#include "llvm/Object/COFF.h"
18#include "llvm/Support/COFF.h"
19#include "llvm/Support/Debug.h"
20#include "llvm/Support/Endian.h"
21#include "llvm/Support/raw_ostream.h"
22
23using namespace llvm::COFF;
24using namespace llvm::object;
25using namespace llvm::support::endian;
26using llvm::RoundUpToAlignment;
27using llvm::Triple;
28using llvm::support::ulittle32_t;
29using llvm::sys::fs::file_magic;
30using llvm::sys::fs::identify_magic;
31
32namespace lld {
33namespace coff {
34
35int InputFile::NextIndex = 0;
36
37// Returns the last element of a path, which is supposed to be a filename.
38static StringRef getBasename(StringRef Path) {
39  size_t Pos = Path.find_last_of("\\/");
40  if (Pos == StringRef::npos)
41    return Path;
42  return Path.substr(Pos + 1);
43}
44
45// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
46std::string InputFile::getShortName() {
47  if (ParentName == "")
48    return getName().lower();
49  std::string Res = (getBasename(ParentName) + "(" +
50                     getBasename(getName()) + ")").str();
51  return StringRef(Res).lower();
52}
53
54void ArchiveFile::parse() {
55  // Parse a MemoryBufferRef as an archive file.
56  auto ArchiveOrErr = Archive::create(MB);
57  error(ArchiveOrErr, "Failed to parse static library");
58  File = std::move(*ArchiveOrErr);
59
60  // Allocate a buffer for Lazy objects.
61  size_t NumSyms = File->getNumberOfSymbols();
62  LazySymbols.reserve(NumSyms);
63
64  // Read the symbol table to construct Lazy objects.
65  for (const Archive::Symbol &Sym : File->symbols())
66    LazySymbols.emplace_back(this, Sym);
67
68  // Seen is a map from member files to boolean values. Initially
69  // all members are mapped to false, which indicates all these files
70  // are not read yet.
71  for (auto &ChildOrErr : File->children()) {
72    error(ChildOrErr, "Failed to parse static library");
73    const Archive::Child &Child = *ChildOrErr;
74    Seen[Child.getChildOffset()].clear();
75  }
76}
77
78// Returns a buffer pointing to a member file containing a given symbol.
79// This function is thread-safe.
80MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
81  auto COrErr = Sym->getMember();
82  error(COrErr, Twine("Could not get the member for symbol ") + Sym->getName());
83  const Archive::Child &C = *COrErr;
84
85  // Return an empty buffer if we have already returned the same buffer.
86  if (Seen[C.getChildOffset()].test_and_set())
87    return MemoryBufferRef();
88  ErrorOr<MemoryBufferRef> Ret = C.getMemoryBufferRef();
89  error(Ret, Twine("Could not get the buffer for the member defining symbol ") +
90                 Sym->getName());
91  return *Ret;
92}
93
94void ObjectFile::parse() {
95  // Parse a memory buffer as a COFF file.
96  auto BinOrErr = createBinary(MB);
97  error(BinOrErr, "Failed to parse object file");
98  std::unique_ptr<Binary> Bin = std::move(*BinOrErr);
99
100  if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
101    Bin.release();
102    COFFObj.reset(Obj);
103  } else {
104    error(Twine(getName()) + " is not a COFF file.");
105  }
106
107  // Read section and symbol tables.
108  initializeChunks();
109  initializeSymbols();
110  initializeSEH();
111}
112
113void ObjectFile::initializeChunks() {
114  uint32_t NumSections = COFFObj->getNumberOfSections();
115  Chunks.reserve(NumSections);
116  SparseChunks.resize(NumSections + 1);
117  for (uint32_t I = 1; I < NumSections + 1; ++I) {
118    const coff_section *Sec;
119    StringRef Name;
120    std::error_code EC = COFFObj->getSection(I, Sec);
121    error(EC, Twine("getSection failed: #") + Twine(I));
122    EC = COFFObj->getSectionName(Sec, Name);
123    error(EC, Twine("getSectionName failed: #") + Twine(I));
124    if (Name == ".sxdata") {
125      SXData = Sec;
126      continue;
127    }
128    if (Name == ".drectve") {
129      ArrayRef<uint8_t> Data;
130      COFFObj->getSectionContents(Sec, Data);
131      Directives = std::string((const char *)Data.data(), Data.size());
132      continue;
133    }
134    // Skip non-DWARF debug info. MSVC linker converts the sections into
135    // a PDB file, but we don't support that.
136    if (Name == ".debug" || Name.startswith(".debug$"))
137      continue;
138    // We want to preserve DWARF debug sections only when /debug is on.
139    if (!Config->Debug && Name.startswith(".debug"))
140      continue;
141    if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
142      continue;
143    auto *C = new (Alloc) SectionChunk(this, Sec);
144    Chunks.push_back(C);
145    SparseChunks[I] = C;
146  }
147}
148
149void ObjectFile::initializeSymbols() {
150  uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
151  SymbolBodies.reserve(NumSymbols);
152  SparseSymbolBodies.resize(NumSymbols);
153  llvm::SmallVector<Undefined *, 8> WeakAliases;
154  int32_t LastSectionNumber = 0;
155  for (uint32_t I = 0; I < NumSymbols; ++I) {
156    // Get a COFFSymbolRef object.
157    auto SymOrErr = COFFObj->getSymbol(I);
158    error(SymOrErr, Twine("broken object file: ") + getName());
159
160    COFFSymbolRef Sym = *SymOrErr;
161
162    const void *AuxP = nullptr;
163    if (Sym.getNumberOfAuxSymbols())
164      AuxP = COFFObj->getSymbol(I + 1)->getRawPtr();
165    bool IsFirst = (LastSectionNumber != Sym.getSectionNumber());
166
167    SymbolBody *Body = nullptr;
168    if (Sym.isUndefined()) {
169      Body = createUndefined(Sym);
170    } else if (Sym.isWeakExternal()) {
171      Body = createWeakExternal(Sym, AuxP);
172      WeakAliases.push_back((Undefined *)Body);
173    } else {
174      Body = createDefined(Sym, AuxP, IsFirst);
175    }
176    if (Body) {
177      SymbolBodies.push_back(Body);
178      SparseSymbolBodies[I] = Body;
179    }
180    I += Sym.getNumberOfAuxSymbols();
181    LastSectionNumber = Sym.getSectionNumber();
182  }
183  for (Undefined *U : WeakAliases)
184    U->WeakAlias = SparseSymbolBodies[(uintptr_t)U->WeakAlias];
185}
186
187Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) {
188  StringRef Name;
189  COFFObj->getSymbolName(Sym, Name);
190  return new (Alloc) Undefined(Name);
191}
192
193Undefined *ObjectFile::createWeakExternal(COFFSymbolRef Sym, const void *AuxP) {
194  StringRef Name;
195  COFFObj->getSymbolName(Sym, Name);
196  auto *U = new (Alloc) Undefined(Name);
197  auto *Aux = (const coff_aux_weak_external *)AuxP;
198  U->WeakAlias = (Undefined *)(uintptr_t)Aux->TagIndex;
199  return U;
200}
201
202Defined *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
203                                   bool IsFirst) {
204  StringRef Name;
205  if (Sym.isCommon()) {
206    auto *C = new (Alloc) CommonChunk(Sym);
207    Chunks.push_back(C);
208    return new (Alloc) DefinedCommon(this, Sym, C);
209  }
210  if (Sym.isAbsolute()) {
211    COFFObj->getSymbolName(Sym, Name);
212    // Skip special symbols.
213    if (Name == "@comp.id")
214      return nullptr;
215    // COFF spec 5.10.1. The .sxdata section.
216    if (Name == "@feat.00") {
217      if (Sym.getValue() & 1)
218        SEHCompat = true;
219      return nullptr;
220    }
221    return new (Alloc) DefinedAbsolute(Name, Sym);
222  }
223  if (Sym.getSectionNumber() == llvm::COFF::IMAGE_SYM_DEBUG)
224    return nullptr;
225
226  // Nothing else to do without a section chunk.
227  auto *SC = cast_or_null<SectionChunk>(SparseChunks[Sym.getSectionNumber()]);
228  if (!SC)
229    return nullptr;
230
231  // Handle section definitions
232  if (IsFirst && AuxP) {
233    auto *Aux = reinterpret_cast<const coff_aux_section_definition *>(AuxP);
234    if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
235      if (auto *ParentSC = cast_or_null<SectionChunk>(
236              SparseChunks[Aux->getNumber(Sym.isBigObj())]))
237        ParentSC->addAssociative(SC);
238    SC->Checksum = Aux->CheckSum;
239  }
240
241  auto *B = new (Alloc) DefinedRegular(this, Sym, SC);
242  if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
243    SC->setSymbol(B);
244
245  return B;
246}
247
248void ObjectFile::initializeSEH() {
249  if (!SEHCompat || !SXData)
250    return;
251  ArrayRef<uint8_t> A;
252  COFFObj->getSectionContents(SXData, A);
253  if (A.size() % 4 != 0)
254    error(".sxdata must be an array of symbol table indices");
255  auto *I = reinterpret_cast<const ulittle32_t *>(A.data());
256  auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size());
257  for (; I != E; ++I)
258    SEHandlers.insert(SparseSymbolBodies[*I]);
259}
260
261MachineTypes ObjectFile::getMachineType() {
262  if (COFFObj)
263    return static_cast<MachineTypes>(COFFObj->getMachine());
264  return IMAGE_FILE_MACHINE_UNKNOWN;
265}
266
267StringRef ltrim1(StringRef S, const char *Chars) {
268  if (!S.empty() && strchr(Chars, S[0]))
269    return S.substr(1);
270  return S;
271}
272
273void ImportFile::parse() {
274  const char *Buf = MB.getBufferStart();
275  const char *End = MB.getBufferEnd();
276  const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);
277
278  // Check if the total size is valid.
279  if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
280    error("broken import library");
281
282  // Read names and create an __imp_ symbol.
283  StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr)));
284  StringRef ImpName = StringAlloc.save(Twine("__imp_") + Name);
285  const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
286  DLLName = StringRef(NameStart);
287  StringRef ExtName;
288  switch (Hdr->getNameType()) {
289  case IMPORT_ORDINAL:
290    ExtName = "";
291    break;
292  case IMPORT_NAME:
293    ExtName = Name;
294    break;
295  case IMPORT_NAME_NOPREFIX:
296    ExtName = ltrim1(Name, "?@_");
297    break;
298  case IMPORT_NAME_UNDECORATE:
299    ExtName = ltrim1(Name, "?@_");
300    ExtName = ExtName.substr(0, ExtName.find('@'));
301    break;
302  }
303  ImpSym = new (Alloc) DefinedImportData(DLLName, ImpName, ExtName, Hdr);
304  SymbolBodies.push_back(ImpSym);
305
306  // If type is function, we need to create a thunk which jump to an
307  // address pointed by the __imp_ symbol. (This allows you to call
308  // DLL functions just like regular non-DLL functions.)
309  if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
310    return;
311  ThunkSym = new (Alloc) DefinedImportThunk(Name, ImpSym, Hdr->Machine);
312  SymbolBodies.push_back(ThunkSym);
313}
314
315void BitcodeFile::parse() {
316  // Usually parse() is thread-safe, but bitcode file is an exception.
317  std::lock_guard<std::mutex> Lock(Mu);
318
319  ErrorOr<std::unique_ptr<LTOModule>> ModOrErr =
320      LTOModule::createFromBuffer(llvm::getGlobalContext(), MB.getBufferStart(),
321                                  MB.getBufferSize(), llvm::TargetOptions());
322  error(ModOrErr, "Could not create lto module");
323  M = std::move(*ModOrErr);
324
325  llvm::StringSaver Saver(Alloc);
326  for (unsigned I = 0, E = M->getSymbolCount(); I != E; ++I) {
327    lto_symbol_attributes Attrs = M->getSymbolAttributes(I);
328    if ((Attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
329      continue;
330
331    StringRef SymName = Saver.save(M->getSymbolName(I));
332    int SymbolDef = Attrs & LTO_SYMBOL_DEFINITION_MASK;
333    if (SymbolDef == LTO_SYMBOL_DEFINITION_UNDEFINED) {
334      SymbolBodies.push_back(new (Alloc) Undefined(SymName));
335    } else {
336      bool Replaceable =
337          (SymbolDef == LTO_SYMBOL_DEFINITION_TENTATIVE || // common
338           (Attrs & LTO_SYMBOL_COMDAT) ||                  // comdat
339           (SymbolDef == LTO_SYMBOL_DEFINITION_WEAK &&     // weak external
340            (Attrs & LTO_SYMBOL_ALIAS)));
341      SymbolBodies.push_back(new (Alloc) DefinedBitcode(this, SymName,
342                                                        Replaceable));
343    }
344  }
345
346  Directives = M->getLinkerOpts();
347}
348
349MachineTypes BitcodeFile::getMachineType() {
350  if (!M)
351    return IMAGE_FILE_MACHINE_UNKNOWN;
352  switch (Triple(M->getTargetTriple()).getArch()) {
353  case Triple::x86_64:
354    return AMD64;
355  case Triple::x86:
356    return I386;
357  case Triple::arm:
358    return ARMNT;
359  default:
360    return IMAGE_FILE_MACHINE_UNKNOWN;
361  }
362}
363
364std::mutex BitcodeFile::Mu;
365
366} // namespace coff
367} // namespace lld
368