InputFiles.cpp revision 314564 
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 "Chunks.h"
12#include "Config.h"
13#include "Driver.h"
14#include "Error.h"
15#include "Memory.h"
16#include "SymbolTable.h"
17#include "Symbols.h"
18#include "llvm-c/lto.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/ADT/Triple.h"
21#include "llvm/ADT/Twine.h"
22#include "llvm/IR/LLVMContext.h"
23#include "llvm/LTO/legacy/LTOModule.h"
24#include "llvm/Object/Binary.h"
25#include "llvm/Object/COFF.h"
26#include "llvm/Support/COFF.h"
27#include "llvm/Support/Casting.h"
28#include "llvm/Support/Endian.h"
29#include "llvm/Support/Error.h"
30#include "llvm/Support/ErrorOr.h"
31#include "llvm/Support/FileSystem.h"
32#include "llvm/Target/TargetOptions.h"
33#include <cstring>
34#include <system_error>
35#include <utility>
36
37using namespace llvm;
38using namespace llvm::COFF;
39using namespace llvm::object;
40using namespace llvm::support::endian;
41
42using llvm::Triple;
43using llvm::support::ulittle32_t;
44using llvm::sys::fs::file_magic;
45using llvm::sys::fs::identify_magic;
46
47namespace lld {
48namespace coff {
49
50LLVMContext BitcodeFile::Context;
51
52ArchiveFile::ArchiveFile(MemoryBufferRef M) : InputFile(ArchiveKind, M) {}
53
54void ArchiveFile::parse() {
55  // Parse a MemoryBufferRef as an archive file.
56  File = check(Archive::create(MB), toString(this));
57
58  // Read the symbol table to construct Lazy objects.
59  for (const Archive::Symbol &Sym : File->symbols())
60    Symtab->addLazy(this, Sym);
61}
62
63// Returns a buffer pointing to a member file containing a given symbol.
64void ArchiveFile::addMember(const Archive::Symbol *Sym) {
65  const Archive::Child &C =
66      check(Sym->getMember(),
67            "could not get the member for symbol " + Sym->getName());
68
69  // Return an empty buffer if we have already returned the same buffer.
70  if (!Seen.insert(C.getChildOffset()).second)
71    return;
72
73  Driver->enqueueArchiveMember(C, Sym->getName(), getName());
74}
75
76void ObjectFile::parse() {
77  // Parse a memory buffer as a COFF file.
78  std::unique_ptr<Binary> Bin = check(createBinary(MB), toString(this));
79
80  if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
81    Bin.release();
82    COFFObj.reset(Obj);
83  } else {
84    fatal(toString(this) + " is not a COFF file");
85  }
86
87  // Read section and symbol tables.
88  initializeChunks();
89  initializeSymbols();
90  initializeSEH();
91}
92
93void ObjectFile::initializeChunks() {
94  uint32_t NumSections = COFFObj->getNumberOfSections();
95  Chunks.reserve(NumSections);
96  SparseChunks.resize(NumSections + 1);
97  for (uint32_t I = 1; I < NumSections + 1; ++I) {
98    const coff_section *Sec;
99    StringRef Name;
100    if (auto EC = COFFObj->getSection(I, Sec))
101      fatal(EC, "getSection failed: #" + Twine(I));
102    if (auto EC = COFFObj->getSectionName(Sec, Name))
103      fatal(EC, "getSectionName failed: #" + Twine(I));
104    if (Name == ".sxdata") {
105      SXData = Sec;
106      continue;
107    }
108    if (Name == ".drectve") {
109      ArrayRef<uint8_t> Data;
110      COFFObj->getSectionContents(Sec, Data);
111      Directives = std::string((const char *)Data.data(), Data.size());
112      continue;
113    }
114
115    // Object files may have DWARF debug info or MS CodeView debug info
116    // (or both).
117    //
118    // DWARF sections don't need any special handling from the perspective
119    // of the linker; they are just a data section containing relocations.
120    // We can just link them to complete debug info.
121    //
122    // CodeView needs a linker support. We need to interpret and debug
123    // info, and then write it to a separate .pdb file.
124
125    // Ignore debug info unless /debug is given.
126    if (!Config->Debug && Name.startswith(".debug"))
127      continue;
128
129    // CodeView sections are stored to a different vector because they are
130    // not linked in the regular manner.
131    if (Name == ".debug" || Name.startswith(".debug$")) {
132      DebugChunks.push_back(new (Alloc) SectionChunk(this, Sec));
133      continue;
134    }
135
136    if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
137      continue;
138    auto *C = new (Alloc) SectionChunk(this, Sec);
139    Chunks.push_back(C);
140    SparseChunks[I] = C;
141  }
142}
143
144void ObjectFile::initializeSymbols() {
145  uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
146  SymbolBodies.reserve(NumSymbols);
147  SparseSymbolBodies.resize(NumSymbols);
148  SmallVector<std::pair<SymbolBody *, uint32_t>, 8> WeakAliases;
149  int32_t LastSectionNumber = 0;
150  for (uint32_t I = 0; I < NumSymbols; ++I) {
151    // Get a COFFSymbolRef object.
152    ErrorOr<COFFSymbolRef> SymOrErr = COFFObj->getSymbol(I);
153    if (!SymOrErr)
154      fatal(SymOrErr.getError(), "broken object file: " + toString(this));
155    COFFSymbolRef Sym = *SymOrErr;
156
157    const void *AuxP = nullptr;
158    if (Sym.getNumberOfAuxSymbols())
159      AuxP = COFFObj->getSymbol(I + 1)->getRawPtr();
160    bool IsFirst = (LastSectionNumber != Sym.getSectionNumber());
161
162    SymbolBody *Body = nullptr;
163    if (Sym.isUndefined()) {
164      Body = createUndefined(Sym);
165    } else if (Sym.isWeakExternal()) {
166      Body = createUndefined(Sym);
167      uint32_t TagIndex =
168          static_cast<const coff_aux_weak_external *>(AuxP)->TagIndex;
169      WeakAliases.emplace_back(Body, TagIndex);
170    } else {
171      Body = createDefined(Sym, AuxP, IsFirst);
172    }
173    if (Body) {
174      SymbolBodies.push_back(Body);
175      SparseSymbolBodies[I] = Body;
176    }
177    I += Sym.getNumberOfAuxSymbols();
178    LastSectionNumber = Sym.getSectionNumber();
179  }
180  for (auto WeakAlias : WeakAliases) {
181    auto *U = dyn_cast<Undefined>(WeakAlias.first);
182    if (!U)
183      continue;
184    // Report an error if two undefined symbols have different weak aliases.
185    if (U->WeakAlias && U->WeakAlias != SparseSymbolBodies[WeakAlias.second])
186      Symtab->reportDuplicate(U->symbol(), this);
187    U->WeakAlias = SparseSymbolBodies[WeakAlias.second];
188  }
189}
190
191SymbolBody *ObjectFile::createUndefined(COFFSymbolRef Sym) {
192  StringRef Name;
193  COFFObj->getSymbolName(Sym, Name);
194  return Symtab->addUndefined(Name, this, Sym.isWeakExternal())->body();
195}
196
197SymbolBody *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
198                                      bool IsFirst) {
199  StringRef Name;
200  if (Sym.isCommon()) {
201    auto *C = new (Alloc) CommonChunk(Sym);
202    Chunks.push_back(C);
203    return Symtab->addCommon(this, Sym, C)->body();
204  }
205  if (Sym.isAbsolute()) {
206    COFFObj->getSymbolName(Sym, Name);
207    // Skip special symbols.
208    if (Name == "@comp.id")
209      return nullptr;
210    // COFF spec 5.10.1. The .sxdata section.
211    if (Name == "@feat.00") {
212      if (Sym.getValue() & 1)
213        SEHCompat = true;
214      return nullptr;
215    }
216    if (Sym.isExternal())
217      return Symtab->addAbsolute(Name, Sym)->body();
218    else
219      return new (Alloc) DefinedAbsolute(Name, Sym);
220  }
221  int32_t SectionNumber = Sym.getSectionNumber();
222  if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
223    return nullptr;
224
225  // Reserved sections numbers don't have contents.
226  if (llvm::COFF::isReservedSectionNumber(SectionNumber))
227    fatal("broken object file: " + toString(this));
228
229  // This symbol references a section which is not present in the section
230  // header.
231  if ((uint32_t)SectionNumber >= SparseChunks.size())
232    fatal("broken object file: " + toString(this));
233
234  // Nothing else to do without a section chunk.
235  auto *SC = cast_or_null<SectionChunk>(SparseChunks[SectionNumber]);
236  if (!SC)
237    return nullptr;
238
239  // Handle section definitions
240  if (IsFirst && AuxP) {
241    auto *Aux = reinterpret_cast<const coff_aux_section_definition *>(AuxP);
242    if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
243      if (auto *ParentSC = cast_or_null<SectionChunk>(
244              SparseChunks[Aux->getNumber(Sym.isBigObj())]))
245        ParentSC->addAssociative(SC);
246    SC->Checksum = Aux->CheckSum;
247  }
248
249  DefinedRegular *B;
250  if (Sym.isExternal())
251    B = cast<DefinedRegular>(Symtab->addRegular(this, Sym, SC)->body());
252  else
253    B = new (Alloc) DefinedRegular(this, Sym, SC);
254  if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
255    SC->setSymbol(B);
256
257  return B;
258}
259
260void ObjectFile::initializeSEH() {
261  if (!SEHCompat || !SXData)
262    return;
263  ArrayRef<uint8_t> A;
264  COFFObj->getSectionContents(SXData, A);
265  if (A.size() % 4 != 0)
266    fatal(".sxdata must be an array of symbol table indices");
267  auto *I = reinterpret_cast<const ulittle32_t *>(A.data());
268  auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size());
269  for (; I != E; ++I)
270    SEHandlers.insert(SparseSymbolBodies[*I]);
271}
272
273MachineTypes ObjectFile::getMachineType() {
274  if (COFFObj)
275    return static_cast<MachineTypes>(COFFObj->getMachine());
276  return IMAGE_FILE_MACHINE_UNKNOWN;
277}
278
279StringRef ltrim1(StringRef S, const char *Chars) {
280  if (!S.empty() && strchr(Chars, S[0]))
281    return S.substr(1);
282  return S;
283}
284
285void ImportFile::parse() {
286  const char *Buf = MB.getBufferStart();
287  const char *End = MB.getBufferEnd();
288  const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);
289
290  // Check if the total size is valid.
291  if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
292    fatal("broken import library");
293
294  // Read names and create an __imp_ symbol.
295  StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr)));
296  StringRef ImpName = StringAlloc.save("__imp_" + Name);
297  const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
298  DLLName = StringRef(NameStart);
299  StringRef ExtName;
300  switch (Hdr->getNameType()) {
301  case IMPORT_ORDINAL:
302    ExtName = "";
303    break;
304  case IMPORT_NAME:
305    ExtName = Name;
306    break;
307  case IMPORT_NAME_NOPREFIX:
308    ExtName = ltrim1(Name, "?@_");
309    break;
310  case IMPORT_NAME_UNDECORATE:
311    ExtName = ltrim1(Name, "?@_");
312    ExtName = ExtName.substr(0, ExtName.find('@'));
313    break;
314  }
315
316  this->Hdr = Hdr;
317  ExternalName = ExtName;
318
319  ImpSym = cast<DefinedImportData>(
320      Symtab->addImportData(ImpName, this)->body());
321
322  // If type is function, we need to create a thunk which jump to an
323  // address pointed by the __imp_ symbol. (This allows you to call
324  // DLL functions just like regular non-DLL functions.)
325  if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
326    return;
327  ThunkSym = cast<DefinedImportThunk>(
328      Symtab->addImportThunk(Name, ImpSym, Hdr->Machine)->body());
329}
330
331void BitcodeFile::parse() {
332  Context.enableDebugTypeODRUniquing();
333  ErrorOr<std::unique_ptr<LTOModule>> ModOrErr = LTOModule::createFromBuffer(
334      Context, MB.getBufferStart(), MB.getBufferSize(), llvm::TargetOptions());
335  M = check(std::move(ModOrErr), "could not create LTO module");
336
337  StringSaver Saver(Alloc);
338  for (unsigned I = 0, E = M->getSymbolCount(); I != E; ++I) {
339    lto_symbol_attributes Attrs = M->getSymbolAttributes(I);
340    if ((Attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
341      continue;
342
343    StringRef SymName = Saver.save(M->getSymbolName(I));
344    int SymbolDef = Attrs & LTO_SYMBOL_DEFINITION_MASK;
345    if (SymbolDef == LTO_SYMBOL_DEFINITION_UNDEFINED) {
346      SymbolBodies.push_back(Symtab->addUndefined(SymName, this, false)->body());
347    } else {
348      bool Replaceable =
349          (SymbolDef == LTO_SYMBOL_DEFINITION_TENTATIVE || // common
350           (Attrs & LTO_SYMBOL_COMDAT) ||                  // comdat
351           (SymbolDef == LTO_SYMBOL_DEFINITION_WEAK &&     // weak external
352            (Attrs & LTO_SYMBOL_ALIAS)));
353      SymbolBodies.push_back(
354          Symtab->addBitcode(this, SymName, Replaceable)->body());
355    }
356  }
357
358  Directives = M->getLinkerOpts();
359}
360
361MachineTypes BitcodeFile::getMachineType() {
362  if (!M)
363    return IMAGE_FILE_MACHINE_UNKNOWN;
364  switch (Triple(M->getTargetTriple()).getArch()) {
365  case Triple::x86_64:
366    return AMD64;
367  case Triple::x86:
368    return I386;
369  case Triple::arm:
370    return ARMNT;
371  default:
372    return IMAGE_FILE_MACHINE_UNKNOWN;
373  }
374}
375} // namespace coff
376} // namespace lld
377
378// Returns the last element of a path, which is supposed to be a filename.
379static StringRef getBasename(StringRef Path) {
380  size_t Pos = Path.find_last_of("\\/");
381  if (Pos == StringRef::npos)
382    return Path;
383  return Path.substr(Pos + 1);
384}
385
386// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
387std::string lld::toString(coff::InputFile *File) {
388  if (!File)
389    return "(internal)";
390  if (File->ParentName.empty())
391    return File->getName().lower();
392
393  std::string Res =
394      (getBasename(File->ParentName) + "(" + getBasename(File->getName()) + ")")
395          .str();
396  return StringRef(Res).lower();
397}
398