lib/Object/ArchiveWriter.cpp

   1 //===- ArchiveWriter.cpp - ar File Format implementation --------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file defines the writeArchive function.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Object/ArchiveWriter.h"
  15 #include "llvm/ADT/ArrayRef.h"
  16 #include "llvm/ADT/StringRef.h"
  17 #include "llvm/BinaryFormat/Magic.h"
  18 #include "llvm/IR/LLVMContext.h"
  19 #include "llvm/Object/Archive.h"
  20 #include "llvm/Object/ObjectFile.h"
  21 #include "llvm/Object/SymbolicFile.h"
  22 #include "llvm/Support/EndianStream.h"
  23 #include "llvm/Support/Errc.h"
  24 #include "llvm/Support/ErrorHandling.h"
  25 #include "llvm/Support/Format.h"
  26 #include "llvm/Support/Path.h"
  27 #include "llvm/Support/ToolOutputFile.h"
  28 #include "llvm/Support/raw_ostream.h"
  29
  30 #if !defined(_MSC_VER) && !defined(__MINGW32__)
  31 #include <unistd.h>
  32 #else
  33 #include <io.h>
  34 #endif
  35
  36 using namespace llvm;
  37
  38 NewArchiveMember::NewArchiveMember(MemoryBufferRef BufRef)
  39     : Buf(MemoryBuffer::getMemBuffer(BufRef, false)),
  40       MemberName(BufRef.getBufferIdentifier()) {}
  41
  42 Expected<NewArchiveMember>
  43 NewArchiveMember::getOldMember(const object::Archive::Child &OldMember,
  44                                bool Deterministic) {
  45   Expected<llvm::MemoryBufferRef> BufOrErr = OldMember.getMemoryBufferRef();
  46   if (!BufOrErr)
  47     return BufOrErr.takeError();
  48
  49   NewArchiveMember M;
  50   assert(M.IsNew == false);
  51   M.Buf = MemoryBuffer::getMemBuffer(*BufOrErr, false);
  52   M.MemberName = M.Buf->getBufferIdentifier();
  53   if (!Deterministic) {
  54     auto ModTimeOrErr = OldMember.getLastModified();
  55     if (!ModTimeOrErr)
  56       return ModTimeOrErr.takeError();
  57     M.ModTime = ModTimeOrErr.get();
  58     Expected<unsigned> UIDOrErr = OldMember.getUID();
  59     if (!UIDOrErr)
  60       return UIDOrErr.takeError();
  61     M.UID = UIDOrErr.get();
  62     Expected<unsigned> GIDOrErr = OldMember.getGID();
  63     if (!GIDOrErr)
  64       return GIDOrErr.takeError();
  65     M.GID = GIDOrErr.get();
  66     Expected<sys::fs::perms> AccessModeOrErr = OldMember.getAccessMode();
  67     if (!AccessModeOrErr)
  68       return AccessModeOrErr.takeError();
  69     M.Perms = AccessModeOrErr.get();
  70   }
  71   return std::move(M);
  72 }
  73
  74 Expected<NewArchiveMember> NewArchiveMember::getFile(StringRef FileName,
  75                                                      bool Deterministic) {
  76   sys::fs::file_status Status;
  77   int FD;
  78   if (auto EC = sys::fs::openFileForRead(FileName, FD))
  79     return errorCodeToError(EC);
  80   assert(FD != -1);
  81
  82   if (auto EC = sys::fs::status(FD, Status))
  83     return errorCodeToError(EC);
  84
  85   // Opening a directory doesn't make sense. Let it fail.
  86   // Linux cannot open directories with open(2), although
  87   // cygwin and *bsd can.
  88   if (Status.type() == sys::fs::file_type::directory_file)
  89     return errorCodeToError(make_error_code(errc::is_a_directory));
  90
  91   ErrorOr<std::unique_ptr<MemoryBuffer>> MemberBufferOrErr =
  92       MemoryBuffer::getOpenFile(FD, FileName, Status.getSize(), false);
  93   if (!MemberBufferOrErr)
  94     return errorCodeToError(MemberBufferOrErr.getError());
  95
  96   if (close(FD) != 0)
  97     return errorCodeToError(std::error_code(errno, std::generic_category()));
  98
  99   NewArchiveMember M;
 100   M.IsNew = true;
 101   M.Buf = std::move(*MemberBufferOrErr);
 102   M.MemberName = M.Buf->getBufferIdentifier();
 103   if (!Deterministic) {
 104     M.ModTime = std::chrono::time_point_cast<std::chrono::seconds>(
 105         Status.getLastModificationTime());
 106     M.UID = Status.getUser();
 107     M.GID = Status.getGroup();
 108     M.Perms = Status.permissions();
 109   }
 110   return std::move(M);
 111 }
 112
 113 template <typename T>
 114 static void printWithSpacePadding(raw_ostream &OS, T Data, unsigned Size) {
 115   uint64_t OldPos = OS.tell();
 116   OS << Data;
 117   unsigned SizeSoFar = OS.tell() - OldPos;
 118   assert(SizeSoFar <= Size && "Data doesn't fit in Size");
 119   OS.indent(Size - SizeSoFar);
 120 }
 121
 122 static bool isBSDLike(object::Archive::Kind Kind) {
 123   switch (Kind) {
 124   case object::Archive::K_GNU:
 125   case object::Archive::K_GNU64:
 126     return false;
 127   case object::Archive::K_BSD:
 128   case object::Archive::K_DARWIN:
 129     return true;
 130   case object::Archive::K_DARWIN64:
 131   case object::Archive::K_COFF:
 132     break;
 133   }
 134   llvm_unreachable("not supported for writting");
 135 }
 136
 137 template <class T>
 138 static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val) {
 139   support::endian::write(Out, Val,
 140                          isBSDLike(Kind) ? support::little : support::big);
 141 }
 142
 143 static void printRestOfMemberHeader(
 144     raw_ostream &Out, const sys::TimePoint<std::chrono::seconds> &ModTime,
 145     unsigned UID, unsigned GID, unsigned Perms, unsigned Size) {
 146   printWithSpacePadding(Out, sys::toTimeT(ModTime), 12);
 147
 148   // The format has only 6 chars for uid and gid. Truncate if the provided
 149   // values don't fit.
 150   printWithSpacePadding(Out, UID % 1000000, 6);
 151   printWithSpacePadding(Out, GID % 1000000, 6);
 152
 153   printWithSpacePadding(Out, format("%o", Perms), 8);
 154   printWithSpacePadding(Out, Size, 10);
 155   Out << "`\n";
 156 }
 157
 158 static void
 159 printGNUSmallMemberHeader(raw_ostream &Out, StringRef Name,
 160                           const sys::TimePoint<std::chrono::seconds> &ModTime,
 161                           unsigned UID, unsigned GID, unsigned Perms,
 162                           unsigned Size) {
 163   printWithSpacePadding(Out, Twine(Name) + "/", 16);
 164   printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
 165 }
 166
 167 static void
 168 printBSDMemberHeader(raw_ostream &Out, uint64_t Pos, StringRef Name,
 169                      const sys::TimePoint<std::chrono::seconds> &ModTime,
 170                      unsigned UID, unsigned GID, unsigned Perms,
 171                      unsigned Size) {
 172   uint64_t PosAfterHeader = Pos + 60 + Name.size();
 173   // Pad so that even 64 bit object files are aligned.
 174   unsigned Pad = OffsetToAlignment(PosAfterHeader, 8);
 175   unsigned NameWithPadding = Name.size() + Pad;
 176   printWithSpacePadding(Out, Twine("#1/") + Twine(NameWithPadding), 16);
 177   printRestOfMemberHeader(Out, ModTime, UID, GID, Perms,
 178                           NameWithPadding + Size);
 179   Out << Name;
 180   while (Pad--)
 181     Out.write(uint8_t(0));
 182 }
 183
 184 static bool useStringTable(bool Thin, StringRef Name) {
 185   return Thin || Name.size() >= 16 || Name.contains('/');
 186 }
 187
 188 // Compute the relative path from From to To.
 189 static std::string computeRelativePath(StringRef From, StringRef To) {
 190   if (sys::path::is_absolute(From) || sys::path::is_absolute(To))
 191     return To;
 192
 193   StringRef DirFrom = sys::path::parent_path(From);
 194   auto FromI = sys::path::begin(DirFrom);
 195   auto ToI = sys::path::begin(To);
 196   while (*FromI == *ToI) {
 197     ++FromI;
 198     ++ToI;
 199   }
 200
 201   SmallString<128> Relative;
 202   for (auto FromE = sys::path::end(DirFrom); FromI != FromE; ++FromI)
 203     sys::path::append(Relative, "..");
 204
 205   for (auto ToE = sys::path::end(To); ToI != ToE; ++ToI)
 206     sys::path::append(Relative, *ToI);
 207
 208 #ifdef _WIN32
 209   // Replace backslashes with slashes so that the path is portable between *nix
 210   // and Windows.
 211   std::replace(Relative.begin(), Relative.end(), '\\', '/');
 212 #endif
 213
 214   return Relative.str();
 215 }
 216
 217 static bool is64BitKind(object::Archive::Kind Kind) {
 218   switch (Kind) {
 219   case object::Archive::K_GNU:
 220   case object::Archive::K_BSD:
 221   case object::Archive::K_DARWIN:
 222   case object::Archive::K_COFF:
 223     return false;
 224   case object::Archive::K_DARWIN64:
 225   case object::Archive::K_GNU64:
 226     return true;
 227   }
 228   llvm_unreachable("not supported for writting");
 229 }
 230
 231 static void addToStringTable(raw_ostream &Out, StringRef ArcName,
 232                              const NewArchiveMember &M, bool Thin) {
 233   StringRef ID = M.Buf->getBufferIdentifier();
 234   if (Thin) {
 235     if (M.IsNew)
 236       Out << computeRelativePath(ArcName, ID);
 237     else
 238       Out << ID;
 239   } else
 240     Out << M.MemberName;
 241   Out << "/\n";
 242 }
 243
 244 static void printMemberHeader(raw_ostream &Out, uint64_t Pos,
 245                               raw_ostream &StringTable,
 246                               object::Archive::Kind Kind, bool Thin,
 247                               StringRef ArcName, const NewArchiveMember &M,
 248                               unsigned Size) {
 249   if (isBSDLike(Kind))
 250     return printBSDMemberHeader(Out, Pos, M.MemberName, M.ModTime, M.UID, M.GID,
 251                                 M.Perms, Size);
 252   if (!useStringTable(Thin, M.MemberName))
 253     return printGNUSmallMemberHeader(Out, M.MemberName, M.ModTime, M.UID, M.GID,
 254                                      M.Perms, Size);
 255   Out << '/';
 256   uint64_t NamePos = StringTable.tell();
 257   addToStringTable(StringTable, ArcName, M, Thin);
 258   printWithSpacePadding(Out, NamePos, 15);
 259   printRestOfMemberHeader(Out, M.ModTime, M.UID, M.GID, M.Perms, Size);
 260 }
 261
 262 namespace {
 263 struct MemberData {
 264   std::vector<unsigned> Symbols;
 265   std::string Header;
 266   StringRef Data;
 267   StringRef Padding;
 268 };
 269 } // namespace
 270
 271 static MemberData computeStringTable(StringRef Names) {
 272   unsigned Size = Names.size();
 273   unsigned Pad = OffsetToAlignment(Size, 2);
 274   std::string Header;
 275   raw_string_ostream Out(Header);
 276   printWithSpacePadding(Out, "//", 48);
 277   printWithSpacePadding(Out, Size + Pad, 10);
 278   Out << "`\n";
 279   Out.flush();
 280   return {{}, std::move(Header), Names, Pad ? "\n" : ""};
 281 }
 282
 283 static sys::TimePoint<std::chrono::seconds> now(bool Deterministic) {
 284   using namespace std::chrono;
 285
 286   if (!Deterministic)
 287     return time_point_cast<seconds>(system_clock::now());
 288   return sys::TimePoint<seconds>();
 289 }
 290
 291 static bool isArchiveSymbol(const object::BasicSymbolRef &S) {
 292   uint32_t Symflags = S.getFlags();
 293   if (Symflags & object::SymbolRef::SF_FormatSpecific)
 294     return false;
 295   if (!(Symflags & object::SymbolRef::SF_Global))
 296     return false;
 297   if (Symflags & object::SymbolRef::SF_Undefined)
 298     return false;
 299   return true;
 300 }
 301
 302 static void printNBits(raw_ostream &Out, object::Archive::Kind Kind,
 303                        uint64_t Val) {
 304   if (is64BitKind(Kind))
 305     print<uint64_t>(Out, Kind, Val);
 306   else
 307     print<uint32_t>(Out, Kind, Val);
 308 }
 309
 310 static void writeSymbolTable(raw_ostream &Out, object::Archive::Kind Kind,
 311                              bool Deterministic, ArrayRef<MemberData> Members,
 312                              StringRef StringTable) {
 313   if (StringTable.empty())
 314     return;
 315
 316   unsigned NumSyms = 0;
 317   for (const MemberData &M : Members)
 318     NumSyms += M.Symbols.size();
 319
 320   unsigned Size = 0;
 321   Size += is64BitKind(Kind) ? 8 : 4; // Number of entries
 322   if (isBSDLike(Kind))
 323     Size += NumSyms * 8; // Table
 324   else if (is64BitKind(Kind))
 325     Size += NumSyms * 8; // Table
 326   else
 327     Size += NumSyms * 4; // Table
 328   if (isBSDLike(Kind))
 329     Size += 4; // byte count
 330   Size += StringTable.size();
 331   // ld64 expects the members to be 8-byte aligned for 64-bit content and at
 332   // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
 333   // uniformly.
 334   // We do this for all bsd formats because it simplifies aligning members.
 335   unsigned Alignment = isBSDLike(Kind) ? 8 : 2;
 336   unsigned Pad = OffsetToAlignment(Size, Alignment);
 337   Size += Pad;
 338
 339   if (isBSDLike(Kind))
 340     printBSDMemberHeader(Out, Out.tell(), "__.SYMDEF", now(Deterministic), 0, 0,
 341                          0, Size);
 342   else if (is64BitKind(Kind))
 343     printGNUSmallMemberHeader(Out, "/SYM64", now(Deterministic), 0, 0, 0, Size);
 344   else
 345     printGNUSmallMemberHeader(Out, "", now(Deterministic), 0, 0, 0, Size);
 346
 347   uint64_t Pos = Out.tell() + Size;
 348
 349   if (isBSDLike(Kind))
 350     print<uint32_t>(Out, Kind, NumSyms * 8);
 351   else
 352     printNBits(Out, Kind, NumSyms);
 353
 354   for (const MemberData &M : Members) {
 355     for (unsigned StringOffset : M.Symbols) {
 356       if (isBSDLike(Kind))
 357         print<uint32_t>(Out, Kind, StringOffset);
 358       printNBits(Out, Kind, Pos); // member offset
 359     }
 360     Pos += M.Header.size() + M.Data.size() + M.Padding.size();
 361   }
 362
 363   if (isBSDLike(Kind))
 364     // byte count of the string table
 365     print<uint32_t>(Out, Kind, StringTable.size());
 366   Out << StringTable;
 367
 368   while (Pad--)
 369     Out.write(uint8_t(0));
 370 }
 371
 372 static Expected<std::vector<unsigned>>
 373 getSymbols(MemoryBufferRef Buf, raw_ostream &SymNames, bool &HasObject) {
 374   std::vector<unsigned> Ret;
 375
 376   // In the scenario when LLVMContext is populated SymbolicFile will contain a
 377   // reference to it, thus SymbolicFile should be destroyed first.
 378   LLVMContext Context;
 379   std::unique_ptr<object::SymbolicFile> Obj;
 380   if (identify_magic(Buf.getBuffer()) == file_magic::bitcode) {
 381     auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
 382         Buf, file_magic::bitcode, &Context);
 383     if (!ObjOrErr) {
 384       // FIXME: check only for "not an object file" errors.
 385       consumeError(ObjOrErr.takeError());
 386       return Ret;
 387     }
 388     Obj = std::move(*ObjOrErr);
 389   } else {
 390     auto ObjOrErr = object::SymbolicFile::createSymbolicFile(Buf);
 391     if (!ObjOrErr) {
 392       // FIXME: check only for "not an object file" errors.
 393       consumeError(ObjOrErr.takeError());
 394       return Ret;
 395     }
 396     Obj = std::move(*ObjOrErr);
 397   }
 398
 399   HasObject = true;
 400   for (const object::BasicSymbolRef &S : Obj->symbols()) {
 401     if (!isArchiveSymbol(S))
 402       continue;
 403     Ret.push_back(SymNames.tell());
 404     if (auto EC = S.printName(SymNames))
 405       return errorCodeToError(EC);
 406     SymNames << '\0';
 407   }
 408   return Ret;
 409 }
 410
 411 static Expected<std::vector<MemberData>>
 412 computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
 413                   object::Archive::Kind Kind, bool Thin, StringRef ArcName,
 414                   ArrayRef<NewArchiveMember> NewMembers) {
 415   static char PaddingData[8] = {'\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n'};
 416
 417   // This ignores the symbol table, but we only need the value mod 8 and the
 418   // symbol table is aligned to be a multiple of 8 bytes
 419   uint64_t Pos = 0;
 420
 421   std::vector<MemberData> Ret;
 422   bool HasObject = false;
 423   for (const NewArchiveMember &M : NewMembers) {
 424     std::string Header;
 425     raw_string_ostream Out(Header);
 426
 427     MemoryBufferRef Buf = M.Buf->getMemBufferRef();
 428     StringRef Data = Thin ? "" : Buf.getBuffer();
 429
 430     // ld64 expects the members to be 8-byte aligned for 64-bit content and at
 431     // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
 432     // uniformly.  This matches the behaviour with cctools and ensures that ld64
 433     // is happy with archives that we generate.
 434     unsigned MemberPadding = Kind == object::Archive::K_DARWIN
 435                                  ? OffsetToAlignment(Data.size(), 8)
 436                                  : 0;
 437     unsigned TailPadding = OffsetToAlignment(Data.size() + MemberPadding, 2);
 438     StringRef Padding = StringRef(PaddingData, MemberPadding + TailPadding);
 439
 440     printMemberHeader(Out, Pos, StringTable, Kind, Thin, ArcName, M,
 441                       Buf.getBufferSize() + MemberPadding);
 442     Out.flush();
 443
 444     Expected<std::vector<unsigned>> Symbols =
 445         getSymbols(Buf, SymNames, HasObject);
 446     if (auto E = Symbols.takeError())
 447       return std::move(E);
 448
 449     Pos += Header.size() + Data.size() + Padding.size();
 450     Ret.push_back({std::move(*Symbols), std::move(Header), Data, Padding});
 451   }
 452   // If there are no symbols, emit an empty symbol table, to satisfy Solaris
 453   // tools, older versions of which expect a symbol table in a non-empty
 454   // archive, regardless of whether there are any symbols in it.
 455   if (HasObject && SymNames.tell() == 0)
 456     SymNames << '\0' << '\0' << '\0';
 457   return Ret;
 458 }
 459
 460 Error llvm::writeArchive(StringRef ArcName,
 461                          ArrayRef<NewArchiveMember> NewMembers,
 462                          bool WriteSymtab, object::Archive::Kind Kind,
 463                          bool Deterministic, bool Thin,
 464                          std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
 465   assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
 466
 467   SmallString<0> SymNamesBuf;
 468   raw_svector_ostream SymNames(SymNamesBuf);
 469   SmallString<0> StringTableBuf;
 470   raw_svector_ostream StringTable(StringTableBuf);
 471
 472   Expected<std::vector<MemberData>> DataOrErr =
 473       computeMemberData(StringTable, SymNames, Kind, Thin, ArcName, NewMembers);
 474   if (Error E = DataOrErr.takeError())
 475     return E;
 476   std::vector<MemberData> &Data = *DataOrErr;
 477
 478   if (!StringTableBuf.empty())
 479     Data.insert(Data.begin(), computeStringTable(StringTableBuf));
 480
 481   // We would like to detect if we need to switch to a 64-bit symbol table.
 482   if (WriteSymtab) {
 483     uint64_t MaxOffset = 0;
 484     uint64_t LastOffset = MaxOffset;
 485     for (const auto &M : Data) {
 486       // Record the start of the member's offset
 487       LastOffset = MaxOffset;
 488       // Account for the size of each part associated with the member.
 489       MaxOffset += M.Header.size() + M.Data.size() + M.Padding.size();
 490       // We assume 32-bit symbols to see if 32-bit symbols are possible or not.
 491       MaxOffset += M.Symbols.size() * 4;
 492     }
 493
 494     // The SYM64 format is used when an archive's member offsets are larger than
 495     // 32-bits can hold. The need for this shift in format is detected by
 496     // writeArchive. To test this we need to generate a file with a member that
 497     // has an offset larger than 32-bits but this demands a very slow test. To
 498     // speed the test up we use this environment variable to pretend like the
 499     // cutoff happens before 32-bits and instead happens at some much smaller
 500     // value.
 501     const char *Sym64Env = std::getenv("SYM64_THRESHOLD");
 502     int Sym64Threshold = 32;
 503     if (Sym64Env)
 504       StringRef(Sym64Env).getAsInteger(10, Sym64Threshold);
 505
 506     // If LastOffset isn't going to fit in a 32-bit varible we need to switch
 507     // to 64-bit. Note that the file can be larger than 4GB as long as the last
 508     // member starts before the 4GB offset.
 509     if (LastOffset >= (1ULL << Sym64Threshold))
 510       Kind = object::Archive::K_GNU64;
 511   }
 512
 513   Expected<sys::fs::TempFile> Temp =
 514       sys::fs::TempFile::create(ArcName + ".temp-archive-%%%%%%%.a");
 515   if (!Temp)
 516     return Temp.takeError();
 517
 518   raw_fd_ostream Out(Temp->FD, false);
 519   if (Thin)
 520     Out << "!<thin>\n";
 521   else
 522     Out << "!<arch>\n";
 523
 524   if (WriteSymtab)
 525     writeSymbolTable(Out, Kind, Deterministic, Data, SymNamesBuf);
 526
 527   for (const MemberData &M : Data)
 528     Out << M.Header << M.Data << M.Padding;
 529
 530   Out.flush();
 531
 532   // At this point, we no longer need whatever backing memory
 533   // was used to generate the NewMembers. On Windows, this buffer
 534   // could be a mapped view of the file we want to replace (if
 535   // we're updating an existing archive, say). In that case, the
 536   // rename would still succeed, but it would leave behind a
 537   // temporary file (actually the original file renamed) because
 538   // a file cannot be deleted while there's a handle open on it,
 539   // only renamed. So by freeing this buffer, this ensures that
 540   // the last open handle on the destination file, if any, is
 541   // closed before we attempt to rename.
 542   OldArchiveBuf.reset();
 543
 544   return Temp->keep(ArcName);
 545 }