tools/llvm-objcopy/ELF/ELFObjcopy.cpp

   1 //===- ELFObjcopy.cpp -----------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "ELFObjcopy.h"
  10 #include "Buffer.h"
  11 #include "CopyConfig.h"
  12 #include "Object.h"
  13 #include "llvm-objcopy.h"
  14
  15 #include "llvm/ADT/BitmaskEnum.h"
  16 #include "llvm/ADT/DenseSet.h"
  17 #include "llvm/ADT/Optional.h"
  18 #include "llvm/ADT/STLExtras.h"
  19 #include "llvm/ADT/SmallVector.h"
  20 #include "llvm/ADT/StringRef.h"
  21 #include "llvm/ADT/Twine.h"
  22 #include "llvm/BinaryFormat/ELF.h"
  23 #include "llvm/MC/MCTargetOptions.h"
  24 #include "llvm/Object/Binary.h"
  25 #include "llvm/Object/ELFObjectFile.h"
  26 #include "llvm/Object/ELFTypes.h"
  27 #include "llvm/Object/Error.h"
  28 #include "llvm/Option/Option.h"
  29 #include "llvm/Support/Casting.h"
  30 #include "llvm/Support/Compression.h"
  31 #include "llvm/Support/Errc.h"
  32 #include "llvm/Support/Error.h"
  33 #include "llvm/Support/ErrorHandling.h"
  34 #include "llvm/Support/ErrorOr.h"
  35 #include "llvm/Support/Memory.h"
  36 #include "llvm/Support/Path.h"
  37 #include "llvm/Support/raw_ostream.h"
  38 #include <algorithm>
  39 #include <cassert>
  40 #include <cstdlib>
  41 #include <functional>
  42 #include <iterator>
  43 #include <memory>
  44 #include <string>
  45 #include <system_error>
  46 #include <utility>
  47
  48 namespace llvm {
  49 namespace objcopy {
  50 namespace elf {
  51
  52 using namespace object;
  53 using namespace ELF;
  54 using SectionPred = std::function<bool(const SectionBase &Sec)>;
  55
  56 static bool isDebugSection(const SectionBase &Sec) {
  57   return StringRef(Sec.Name).startswith(".debug") ||
  58          StringRef(Sec.Name).startswith(".zdebug") || Sec.Name == ".gdb_index";
  59 }
  60
  61 static bool isDWOSection(const SectionBase &Sec) {
  62   return StringRef(Sec.Name).endswith(".dwo");
  63 }
  64
  65 static bool onlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) {
  66   // We can't remove the section header string table.
  67   if (&Sec == Obj.SectionNames)
  68     return false;
  69   // Short of keeping the string table we want to keep everything that is a DWO
  70   // section and remove everything else.
  71   return !isDWOSection(Sec);
  72 }
  73
  74 uint64_t getNewShfFlags(SectionFlag AllFlags) {
  75   uint64_t NewFlags = 0;
  76   if (AllFlags & SectionFlag::SecAlloc)
  77     NewFlags |= ELF::SHF_ALLOC;
  78   if (!(AllFlags & SectionFlag::SecReadonly))
  79     NewFlags |= ELF::SHF_WRITE;
  80   if (AllFlags & SectionFlag::SecCode)
  81     NewFlags |= ELF::SHF_EXECINSTR;
  82   if (AllFlags & SectionFlag::SecMerge)
  83     NewFlags |= ELF::SHF_MERGE;
  84   if (AllFlags & SectionFlag::SecStrings)
  85     NewFlags |= ELF::SHF_STRINGS;
  86   return NewFlags;
  87 }
  88
  89 static uint64_t getSectionFlagsPreserveMask(uint64_t OldFlags,
  90                                             uint64_t NewFlags) {
  91   // Preserve some flags which should not be dropped when setting flags.
  92   // Also, preserve anything OS/processor dependant.
  93   const uint64_t PreserveMask = ELF::SHF_COMPRESSED | ELF::SHF_EXCLUDE |
  94                                 ELF::SHF_GROUP | ELF::SHF_LINK_ORDER |
  95                                 ELF::SHF_MASKOS | ELF::SHF_MASKPROC |
  96                                 ELF::SHF_TLS | ELF::SHF_INFO_LINK;
  97   return (OldFlags & PreserveMask) | (NewFlags & ~PreserveMask);
  98 }
  99
 100 static void setSectionFlagsAndType(SectionBase &Sec, SectionFlag Flags) {
 101   Sec.Flags = getSectionFlagsPreserveMask(Sec.Flags, getNewShfFlags(Flags));
 102
 103   // In GNU objcopy, certain flags promote SHT_NOBITS to SHT_PROGBITS. This rule
 104   // may promote more non-ALLOC sections than GNU objcopy, but it is fine as
 105   // non-ALLOC SHT_NOBITS sections do not make much sense.
 106   if (Sec.Type == SHT_NOBITS &&
 107       (!(Sec.Flags & ELF::SHF_ALLOC) ||
 108        Flags & (SectionFlag::SecContents | SectionFlag::SecLoad)))
 109     Sec.Type = SHT_PROGBITS;
 110 }
 111
 112 static ElfType getOutputElfType(const Binary &Bin) {
 113   // Infer output ELF type from the input ELF object
 114   if (isa<ELFObjectFile<ELF32LE>>(Bin))
 115     return ELFT_ELF32LE;
 116   if (isa<ELFObjectFile<ELF64LE>>(Bin))
 117     return ELFT_ELF64LE;
 118   if (isa<ELFObjectFile<ELF32BE>>(Bin))
 119     return ELFT_ELF32BE;
 120   if (isa<ELFObjectFile<ELF64BE>>(Bin))
 121     return ELFT_ELF64BE;
 122   llvm_unreachable("Invalid ELFType");
 123 }
 124
 125 static ElfType getOutputElfType(const MachineInfo &MI) {
 126   // Infer output ELF type from the binary arch specified
 127   if (MI.Is64Bit)
 128     return MI.IsLittleEndian ? ELFT_ELF64LE : ELFT_ELF64BE;
 129   else
 130     return MI.IsLittleEndian ? ELFT_ELF32LE : ELFT_ELF32BE;
 131 }
 132
 133 static std::unique_ptr<Writer> createELFWriter(const CopyConfig &Config,
 134                                                Object &Obj, Buffer &Buf,
 135                                                ElfType OutputElfType) {
 136   // Depending on the initial ELFT and OutputFormat we need a different Writer.
 137   switch (OutputElfType) {
 138   case ELFT_ELF32LE:
 139     return llvm::make_unique<ELFWriter<ELF32LE>>(Obj, Buf,
 140                                                  !Config.StripSections);
 141   case ELFT_ELF64LE:
 142     return llvm::make_unique<ELFWriter<ELF64LE>>(Obj, Buf,
 143                                                  !Config.StripSections);
 144   case ELFT_ELF32BE:
 145     return llvm::make_unique<ELFWriter<ELF32BE>>(Obj, Buf,
 146                                                  !Config.StripSections);
 147   case ELFT_ELF64BE:
 148     return llvm::make_unique<ELFWriter<ELF64BE>>(Obj, Buf,
 149                                                  !Config.StripSections);
 150   }
 151   llvm_unreachable("Invalid output format");
 152 }
 153
 154 static std::unique_ptr<Writer> createWriter(const CopyConfig &Config,
 155                                             Object &Obj, Buffer &Buf,
 156                                             ElfType OutputElfType) {
 157   switch (Config.OutputFormat) {
 158   case FileFormat::Binary:
 159     return llvm::make_unique<BinaryWriter>(Obj, Buf);
 160   case FileFormat::IHex:
 161     return llvm::make_unique<IHexWriter>(Obj, Buf);
 162   default:
 163     return createELFWriter(Config, Obj, Buf, OutputElfType);
 164   }
 165 }
 166
 167 template <class ELFT>
 168 static Expected<ArrayRef<uint8_t>>
 169 findBuildID(const CopyConfig &Config, const object::ELFFile<ELFT> &In) {
 170   auto PhdrsOrErr = In.program_headers();
 171   if (auto Err = PhdrsOrErr.takeError())
 172     return createFileError(Config.InputFilename, std::move(Err));
 173
 174   for (const auto &Phdr : *PhdrsOrErr) {
 175     if (Phdr.p_type != PT_NOTE)
 176       continue;
 177     Error Err = Error::success();
 178     for (const auto &Note : In.notes(Phdr, Err))
 179       if (Note.getType() == NT_GNU_BUILD_ID && Note.getName() == ELF_NOTE_GNU)
 180         return Note.getDesc();
 181     if (Err)
 182       return createFileError(Config.InputFilename, std::move(Err));
 183   }
 184
 185   return createFileError(
 186       Config.InputFilename,
 187       createStringError(llvm::errc::invalid_argument,
 188                         "could not find build ID"));
 189 }
 190
 191 static Expected<ArrayRef<uint8_t>>
 192 findBuildID(const CopyConfig &Config, const object::ELFObjectFileBase &In) {
 193   if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(&In))
 194     return findBuildID(Config, *O->getELFFile());
 195   else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(&In))
 196     return findBuildID(Config, *O->getELFFile());
 197   else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(&In))
 198     return findBuildID(Config, *O->getELFFile());
 199   else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(&In))
 200     return findBuildID(Config, *O->getELFFile());
 201
 202   llvm_unreachable("Bad file format");
 203 }
 204
 205 template <class... Ts>
 206 static Error makeStringError(std::error_code EC, const Twine &Msg, Ts &&... Args) {
 207   std::string FullMsg = (EC.message() + ": " + Msg).str();
 208   return createStringError(EC, FullMsg.c_str(), std::forward<Ts>(Args)...);
 209 }
 210
 211 #define MODEL_8 "%%%%%%%%"
 212 #define MODEL_16 MODEL_8 MODEL_8
 213 #define MODEL_32 (MODEL_16 MODEL_16)
 214
 215 static Error linkToBuildIdDir(const CopyConfig &Config, StringRef ToLink,
 216                               StringRef Suffix,
 217                               ArrayRef<uint8_t> BuildIdBytes) {
 218   SmallString<128> Path = Config.BuildIdLinkDir;
 219   sys::path::append(Path, llvm::toHex(BuildIdBytes[0], /*LowerCase*/ true));
 220   if (auto EC = sys::fs::create_directories(Path))
 221     return createFileError(
 222         Path.str(),
 223         makeStringError(EC, "cannot create build ID link directory"));
 224
 225   sys::path::append(Path,
 226                     llvm::toHex(BuildIdBytes.slice(1), /*LowerCase*/ true));
 227   Path += Suffix;
 228   SmallString<128> TmpPath;
 229   // create_hard_link races so we need to link to a temporary path but
 230   // we want to make sure that we choose a filename that does not exist.
 231   // By using 32 model characters we get 128-bits of entropy. It is
 232   // unlikely that this string has ever existed before much less exists
 233   // on this disk or in the current working directory.
 234   // Additionally we prepend the original Path for debugging but also
 235   // because it ensures that we're linking within a directory on the same
 236   // partition on the same device which is critical. It has the added
 237   // win of yet further decreasing the odds of a conflict.
 238   sys::fs::createUniquePath(Twine(Path) + "-" + MODEL_32 + ".tmp", TmpPath,
 239                             /*MakeAbsolute*/ false);
 240   if (auto EC = sys::fs::create_hard_link(ToLink, TmpPath)) {
 241     Path.push_back('\0');
 242     return makeStringError(EC, "cannot link '%s' to '%s'", ToLink.data(),
 243                            Path.data());
 244   }
 245   // We then atomically rename the link into place which will just move the
 246   // link. If rename fails something is more seriously wrong so just return
 247   // an error.
 248   if (auto EC = sys::fs::rename(TmpPath, Path)) {
 249     Path.push_back('\0');
 250     return makeStringError(EC, "cannot link '%s' to '%s'", ToLink.data(),
 251                            Path.data());
 252   }
 253   // If `Path` was already a hard-link to the same underlying file then the
 254   // temp file will be left so we need to remove it. Remove will not cause
 255   // an error by default if the file is already gone so just blindly remove
 256   // it rather than checking.
 257   if (auto EC = sys::fs::remove(TmpPath)) {
 258     TmpPath.push_back('\0');
 259     return makeStringError(EC, "could not remove '%s'", TmpPath.data());
 260   }
 261   return Error::success();
 262 }
 263
 264 static Error splitDWOToFile(const CopyConfig &Config, const Reader &Reader,
 265                             StringRef File, ElfType OutputElfType) {
 266   auto DWOFile = Reader.create();
 267   auto OnlyKeepDWOPred = [&DWOFile](const SectionBase &Sec) {
 268     return onlyKeepDWOPred(*DWOFile, Sec);
 269   };
 270   if (Error E = DWOFile->removeSections(Config.AllowBrokenLinks,
 271                                         OnlyKeepDWOPred))
 272     return E;
 273   if (Config.OutputArch) {
 274     DWOFile->Machine = Config.OutputArch.getValue().EMachine;
 275     DWOFile->OSABI = Config.OutputArch.getValue().OSABI;
 276   }
 277   FileBuffer FB(File);
 278   auto Writer = createWriter(Config, *DWOFile, FB, OutputElfType);
 279   if (Error E = Writer->finalize())
 280     return E;
 281   return Writer->write();
 282 }
 283
 284 static Error dumpSectionToFile(StringRef SecName, StringRef Filename,
 285                                Object &Obj) {
 286   for (auto &Sec : Obj.sections()) {
 287     if (Sec.Name == SecName) {
 288       if (Sec.OriginalData.empty())
 289         return createStringError(object_error::parse_failed,
 290                                  "cannot dump section '%s': it has no contents",
 291                                  SecName.str().c_str());
 292       Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
 293           FileOutputBuffer::create(Filename, Sec.OriginalData.size());
 294       if (!BufferOrErr)
 295         return BufferOrErr.takeError();
 296       std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufferOrErr);
 297       std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(),
 298                 Buf->getBufferStart());
 299       if (Error E = Buf->commit())
 300         return E;
 301       return Error::success();
 302     }
 303   }
 304   return createStringError(object_error::parse_failed, "section '%s' not found",
 305                            SecName.str().c_str());
 306 }
 307
 308 static bool isCompressable(const SectionBase &Section) {
 309   return !(Section.Flags & ELF::SHF_COMPRESSED) &&
 310          StringRef(Section.Name).startswith(".debug");
 311 }
 312
 313 static void replaceDebugSections(
 314     Object &Obj, SectionPred &RemovePred,
 315     function_ref<bool(const SectionBase &)> shouldReplace,
 316     function_ref<SectionBase *(const SectionBase *)> addSection) {
 317   // Build a list of the debug sections we are going to replace.
 318   // We can't call `addSection` while iterating over sections,
 319   // because it would mutate the sections array.
 320   SmallVector<SectionBase *, 13> ToReplace;
 321   for (auto &Sec : Obj.sections())
 322     if (shouldReplace(Sec))
 323       ToReplace.push_back(&Sec);
 324
 325   // Build a mapping from original section to a new one.
 326   DenseMap<SectionBase *, SectionBase *> FromTo;
 327   for (SectionBase *S : ToReplace)
 328     FromTo[S] = addSection(S);
 329
 330   // Now we want to update the target sections of relocation
 331   // sections. Also we will update the relocations themselves
 332   // to update the symbol references.
 333   for (auto &Sec : Obj.sections())
 334     Sec.replaceSectionReferences(FromTo);
 335
 336   RemovePred = [shouldReplace, RemovePred](const SectionBase &Sec) {
 337     return shouldReplace(Sec) || RemovePred(Sec);
 338   };
 339 }
 340
 341 static bool isUnneededSymbol(const Symbol &Sym) {
 342   return !Sym.Referenced &&
 343          (Sym.Binding == STB_LOCAL || Sym.getShndx() == SHN_UNDEF) &&
 344          Sym.Type != STT_SECTION;
 345 }
 346
 347 static Error updateAndRemoveSymbols(const CopyConfig &Config, Object &Obj) {
 348   // TODO: update or remove symbols only if there is an option that affects
 349   // them.
 350   if (!Obj.SymbolTable)
 351     return Error::success();
 352
 353   Obj.SymbolTable->updateSymbols([&](Symbol &Sym) {
 354     // Common and undefined symbols don't make sense as local symbols, and can
 355     // even cause crashes if we localize those, so skip them.
 356     if (!Sym.isCommon() && Sym.getShndx() != SHN_UNDEF &&
 357         ((Config.LocalizeHidden &&
 358           (Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL)) ||
 359          is_contained(Config.SymbolsToLocalize, Sym.Name)))
 360       Sym.Binding = STB_LOCAL;
 361
 362     // Note: these two globalize flags have very similar names but different
 363     // meanings:
 364     //
 365     // --globalize-symbol: promote a symbol to global
 366     // --keep-global-symbol: all symbols except for these should be made local
 367     //
 368     // If --globalize-symbol is specified for a given symbol, it will be
 369     // global in the output file even if it is not included via
 370     // --keep-global-symbol. Because of that, make sure to check
 371     // --globalize-symbol second.
 372     if (!Config.SymbolsToKeepGlobal.empty() &&
 373         !is_contained(Config.SymbolsToKeepGlobal, Sym.Name) &&
 374         Sym.getShndx() != SHN_UNDEF)
 375       Sym.Binding = STB_LOCAL;
 376
 377     if (is_contained(Config.SymbolsToGlobalize, Sym.Name) &&
 378         Sym.getShndx() != SHN_UNDEF)
 379       Sym.Binding = STB_GLOBAL;
 380
 381     if (is_contained(Config.SymbolsToWeaken, Sym.Name) &&
 382         Sym.Binding == STB_GLOBAL)
 383       Sym.Binding = STB_WEAK;
 384
 385     if (Config.Weaken && Sym.Binding == STB_GLOBAL &&
 386         Sym.getShndx() != SHN_UNDEF)
 387       Sym.Binding = STB_WEAK;
 388
 389     const auto I = Config.SymbolsToRename.find(Sym.Name);
 390     if (I != Config.SymbolsToRename.end())
 391       Sym.Name = I->getValue();
 392
 393     if (!Config.SymbolsPrefix.empty() && Sym.Type != STT_SECTION)
 394       Sym.Name = (Config.SymbolsPrefix + Sym.Name).str();
 395   });
 396
 397   // The purpose of this loop is to mark symbols referenced by sections
 398   // (like GroupSection or RelocationSection). This way, we know which
 399   // symbols are still 'needed' and which are not.
 400   if (Config.StripUnneeded || !Config.UnneededSymbolsToRemove.empty() ||
 401       !Config.OnlySection.empty()) {
 402     for (auto &Section : Obj.sections())
 403       Section.markSymbols();
 404   }
 405
 406   auto RemoveSymbolsPred = [&](const Symbol &Sym) {
 407     if (is_contained(Config.SymbolsToKeep, Sym.Name) ||
 408         (Config.KeepFileSymbols && Sym.Type == STT_FILE))
 409       return false;
 410
 411     if ((Config.DiscardMode == DiscardType::All ||
 412          (Config.DiscardMode == DiscardType::Locals &&
 413           StringRef(Sym.Name).startswith(".L"))) &&
 414         Sym.Binding == STB_LOCAL && Sym.getShndx() != SHN_UNDEF &&
 415         Sym.Type != STT_FILE && Sym.Type != STT_SECTION)
 416       return true;
 417
 418     if (Config.StripAll || Config.StripAllGNU)
 419       return true;
 420
 421     if (is_contained(Config.SymbolsToRemove, Sym.Name))
 422       return true;
 423
 424     if ((Config.StripUnneeded ||
 425          is_contained(Config.UnneededSymbolsToRemove, Sym.Name)) &&
 426         (!Obj.isRelocatable() || isUnneededSymbol(Sym)))
 427       return true;
 428
 429     // We want to remove undefined symbols if all references have been stripped.
 430     if (!Config.OnlySection.empty() && !Sym.Referenced &&
 431         Sym.getShndx() == SHN_UNDEF)
 432       return true;
 433
 434     return false;
 435   };
 436
 437   return Obj.removeSymbols(RemoveSymbolsPred);
 438 }
 439
 440 static Error replaceAndRemoveSections(const CopyConfig &Config, Object &Obj) {
 441   SectionPred RemovePred = [](const SectionBase &) { return false; };
 442
 443   // Removes:
 444   if (!Config.ToRemove.empty()) {
 445     RemovePred = [&Config](const SectionBase &Sec) {
 446       return is_contained(Config.ToRemove, Sec.Name);
 447     };
 448   }
 449
 450   if (Config.StripDWO || !Config.SplitDWO.empty())
 451     RemovePred = [RemovePred](const SectionBase &Sec) {
 452       return isDWOSection(Sec) || RemovePred(Sec);
 453     };
 454
 455   if (Config.ExtractDWO)
 456     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
 457       return onlyKeepDWOPred(Obj, Sec) || RemovePred(Sec);
 458     };
 459
 460   if (Config.StripAllGNU)
 461     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
 462       if (RemovePred(Sec))
 463         return true;
 464       if ((Sec.Flags & SHF_ALLOC) != 0)
 465         return false;
 466       if (&Sec == Obj.SectionNames)
 467         return false;
 468       switch (Sec.Type) {
 469       case SHT_SYMTAB:
 470       case SHT_REL:
 471       case SHT_RELA:
 472       case SHT_STRTAB:
 473         return true;
 474       }
 475       return isDebugSection(Sec);
 476     };
 477
 478   if (Config.StripSections) {
 479     RemovePred = [RemovePred](const SectionBase &Sec) {
 480       return RemovePred(Sec) || Sec.ParentSegment == nullptr;
 481     };
 482   }
 483
 484   if (Config.StripDebug) {
 485     RemovePred = [RemovePred](const SectionBase &Sec) {
 486       return RemovePred(Sec) || isDebugSection(Sec);
 487     };
 488   }
 489
 490   if (Config.StripNonAlloc)
 491     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
 492       if (RemovePred(Sec))
 493         return true;
 494       if (&Sec == Obj.SectionNames)
 495         return false;
 496       return (Sec.Flags & SHF_ALLOC) == 0 && Sec.ParentSegment == nullptr;
 497     };
 498
 499   if (Config.StripAll)
 500     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
 501       if (RemovePred(Sec))
 502         return true;
 503       if (&Sec == Obj.SectionNames)
 504         return false;
 505       if (StringRef(Sec.Name).startswith(".gnu.warning"))
 506         return false;
 507       if (Sec.ParentSegment != nullptr)
 508         return false;
 509       return (Sec.Flags & SHF_ALLOC) == 0;
 510     };
 511
 512   if (Config.ExtractPartition || Config.ExtractMainPartition) {
 513     RemovePred = [RemovePred](const SectionBase &Sec) {
 514       if (RemovePred(Sec))
 515         return true;
 516       if (Sec.Type == SHT_LLVM_PART_EHDR || Sec.Type == SHT_LLVM_PART_PHDR)
 517         return true;
 518       return (Sec.Flags & SHF_ALLOC) != 0 && !Sec.ParentSegment;
 519     };
 520   }
 521
 522   // Explicit copies:
 523   if (!Config.OnlySection.empty()) {
 524     RemovePred = [&Config, RemovePred, &Obj](const SectionBase &Sec) {
 525       // Explicitly keep these sections regardless of previous removes.
 526       if (is_contained(Config.OnlySection, Sec.Name))
 527         return false;
 528
 529       // Allow all implicit removes.
 530       if (RemovePred(Sec))
 531         return true;
 532
 533       // Keep special sections.
 534       if (Obj.SectionNames == &Sec)
 535         return false;
 536       if (Obj.SymbolTable == &Sec ||
 537           (Obj.SymbolTable && Obj.SymbolTable->getStrTab() == &Sec))
 538         return false;
 539
 540       // Remove everything else.
 541       return true;
 542     };
 543   }
 544
 545   if (!Config.KeepSection.empty()) {
 546     RemovePred = [&Config, RemovePred](const SectionBase &Sec) {
 547       // Explicitly keep these sections regardless of previous removes.
 548       if (is_contained(Config.KeepSection, Sec.Name))
 549         return false;
 550       // Otherwise defer to RemovePred.
 551       return RemovePred(Sec);
 552     };
 553   }
 554
 555   // This has to be the last predicate assignment.
 556   // If the option --keep-symbol has been specified
 557   // and at least one of those symbols is present
 558   // (equivalently, the updated symbol table is not empty)
 559   // the symbol table and the string table should not be removed.
 560   if ((!Config.SymbolsToKeep.empty() || Config.KeepFileSymbols) &&
 561       Obj.SymbolTable && !Obj.SymbolTable->empty()) {
 562     RemovePred = [&Obj, RemovePred](const SectionBase &Sec) {
 563       if (&Sec == Obj.SymbolTable || &Sec == Obj.SymbolTable->getStrTab())
 564         return false;
 565       return RemovePred(Sec);
 566     };
 567   }
 568
 569   if (Config.CompressionType != DebugCompressionType::None)
 570     replaceDebugSections(Obj, RemovePred, isCompressable,
 571                          [&Config, &Obj](const SectionBase *S) {
 572                            return &Obj.addSection<CompressedSection>(
 573                                 *S, Config.CompressionType);
 574                         });
 575   else if (Config.DecompressDebugSections)
 576     replaceDebugSections(
 577         Obj, RemovePred,
 578         [](const SectionBase &S) { return isa<CompressedSection>(&S); },
 579         [&Obj](const SectionBase *S) {
 580           auto CS = cast<CompressedSection>(S);
 581           return &Obj.addSection<DecompressedSection>(*CS);
 582         });
 583
 584   return Obj.removeSections(Config.AllowBrokenLinks, RemovePred);
 585 }
 586
 587 // This function handles the high level operations of GNU objcopy including
 588 // handling command line options. It's important to outline certain properties
 589 // we expect to hold of the command line operations. Any operation that "keeps"
 590 // should keep regardless of a remove. Additionally any removal should respect
 591 // any previous removals. Lastly whether or not something is removed shouldn't
 592 // depend a) on the order the options occur in or b) on some opaque priority
 593 // system. The only priority is that keeps/copies overrule removes.
 594 static Error handleArgs(const CopyConfig &Config, Object &Obj,
 595                         const Reader &Reader, ElfType OutputElfType) {
 596
 597   if (!Config.SplitDWO.empty())
 598     if (Error E =
 599             splitDWOToFile(Config, Reader, Config.SplitDWO, OutputElfType))
 600       return E;
 601
 602   if (Config.OutputArch) {
 603     Obj.Machine = Config.OutputArch.getValue().EMachine;
 604     Obj.OSABI = Config.OutputArch.getValue().OSABI;
 605   }
 606
 607   // It is important to remove the sections first. For example, we want to
 608   // remove the relocation sections before removing the symbols. That allows
 609   // us to avoid reporting the inappropriate errors about removing symbols
 610   // named in relocations.
 611   if (Error E = replaceAndRemoveSections(Config, Obj))
 612     return E;
 613
 614   if (Error E = updateAndRemoveSymbols(Config, Obj))
 615     return E;
 616
 617   if (!Config.SectionsToRename.empty() || !Config.AllocSectionsPrefix.empty()) {
 618     DenseSet<SectionBase *> PrefixedSections;
 619     for (auto &Sec : Obj.sections()) {
 620       const auto Iter = Config.SectionsToRename.find(Sec.Name);
 621       if (Iter != Config.SectionsToRename.end()) {
 622         const SectionRename &SR = Iter->second;
 623         Sec.Name = SR.NewName;
 624         if (SR.NewFlags.hasValue())
 625           setSectionFlagsAndType(Sec, SR.NewFlags.getValue());
 626       }
 627
 628       // Add a prefix to allocated sections and their relocation sections. This
 629       // should be done after renaming the section by Config.SectionToRename to
 630       // imitate the GNU objcopy behavior.
 631       if (!Config.AllocSectionsPrefix.empty()) {
 632         if (Sec.Flags & SHF_ALLOC) {
 633           Sec.Name = (Config.AllocSectionsPrefix + Sec.Name).str();
 634           PrefixedSections.insert(&Sec);
 635
 636           // Rename relocation sections associated to the allocated sections.
 637           // For example, if we rename .text to .prefix.text, we also rename
 638           // .rel.text to .rel.prefix.text.
 639           //
 640           // Dynamic relocation sections (SHT_REL[A] with SHF_ALLOC) are handled
 641           // above, e.g., .rela.plt is renamed to .prefix.rela.plt, not
 642           // .rela.prefix.plt since GNU objcopy does so.
 643         } else if (auto *RelocSec = dyn_cast<RelocationSectionBase>(&Sec)) {
 644           auto *TargetSec = RelocSec->getSection();
 645           if (TargetSec && (TargetSec->Flags & SHF_ALLOC)) {
 646             StringRef prefix;
 647             switch (Sec.Type) {
 648             case SHT_REL:
 649               prefix = ".rel";
 650               break;
 651             case SHT_RELA:
 652               prefix = ".rela";
 653               break;
 654             default:
 655               continue;
 656             }
 657
 658             // If the relocation section comes *after* the target section, we
 659             // don't add Config.AllocSectionsPrefix because we've already added
 660             // the prefix to TargetSec->Name. Otherwise, if the relocation
 661             // section comes *before* the target section, we add the prefix.
 662             if (PrefixedSections.count(TargetSec)) {
 663               Sec.Name = (prefix + TargetSec->Name).str();
 664             } else {
 665               const auto Iter = Config.SectionsToRename.find(TargetSec->Name);
 666               if (Iter != Config.SectionsToRename.end()) {
 667                 // Both `--rename-section` and `--prefix-alloc-sections` are
 668                 // given but the target section is not yet renamed.
 669                 Sec.Name =
 670                     (prefix + Config.AllocSectionsPrefix + Iter->second.NewName)
 671                         .str();
 672               } else {
 673                 Sec.Name =
 674                     (prefix + Config.AllocSectionsPrefix + TargetSec->Name)
 675                         .str();
 676               }
 677             }
 678           }
 679         }
 680       }
 681     }
 682   }
 683
 684   if (!Config.SetSectionFlags.empty()) {
 685     for (auto &Sec : Obj.sections()) {
 686       const auto Iter = Config.SetSectionFlags.find(Sec.Name);
 687       if (Iter != Config.SetSectionFlags.end()) {
 688         const SectionFlagsUpdate &SFU = Iter->second;
 689         setSectionFlagsAndType(Sec, SFU.NewFlags);
 690       }
 691     }
 692   }
 693
 694   for (const auto &Flag : Config.AddSection) {
 695     std::pair<StringRef, StringRef> SecPair = Flag.split("=");
 696     StringRef SecName = SecPair.first;
 697     StringRef File = SecPair.second;
 698     ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
 699         MemoryBuffer::getFile(File);
 700     if (!BufOrErr)
 701       return createFileError(File, errorCodeToError(BufOrErr.getError()));
 702     std::unique_ptr<MemoryBuffer> Buf = std::move(*BufOrErr);
 703     ArrayRef<uint8_t> Data(
 704         reinterpret_cast<const uint8_t *>(Buf->getBufferStart()),
 705         Buf->getBufferSize());
 706     OwnedDataSection &NewSection =
 707         Obj.addSection<OwnedDataSection>(SecName, Data);
 708     if (SecName.startswith(".note") && SecName != ".note.GNU-stack")
 709       NewSection.Type = SHT_NOTE;
 710   }
 711
 712   for (const auto &Flag : Config.DumpSection) {
 713     std::pair<StringRef, StringRef> SecPair = Flag.split("=");
 714     StringRef SecName = SecPair.first;
 715     StringRef File = SecPair.second;
 716     if (Error E = dumpSectionToFile(SecName, File, Obj))
 717       return E;
 718   }
 719
 720   if (!Config.AddGnuDebugLink.empty())
 721     Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink,
 722                                         Config.GnuDebugLinkCRC32);
 723
 724   for (const NewSymbolInfo &SI : Config.SymbolsToAdd) {
 725     SectionBase *Sec = Obj.findSection(SI.SectionName);
 726     uint64_t Value = Sec ? Sec->Addr + SI.Value : SI.Value;
 727     Obj.SymbolTable->addSymbol(
 728         SI.SymbolName, SI.Bind, SI.Type, Sec, Value, SI.Visibility,
 729         Sec ? (uint16_t)SYMBOL_SIMPLE_INDEX : (uint16_t)SHN_ABS, 0);
 730   }
 731
 732   if (Config.EntryExpr)
 733     Obj.Entry = Config.EntryExpr(Obj.Entry);
 734   return Error::success();
 735 }
 736
 737 static Error writeOutput(const CopyConfig &Config, Object &Obj, Buffer &Out,
 738                          ElfType OutputElfType) {
 739   std::unique_ptr<Writer> Writer =
 740       createWriter(Config, Obj, Out, OutputElfType);
 741   if (Error E = Writer->finalize())
 742     return E;
 743   return Writer->write();
 744 }
 745
 746 Error executeObjcopyOnIHex(const CopyConfig &Config, MemoryBuffer &In,
 747                            Buffer &Out) {
 748   IHexReader Reader(&In);
 749   std::unique_ptr<Object> Obj = Reader.create();
 750   const ElfType OutputElfType =
 751       getOutputElfType(Config.OutputArch.getValueOr(Config.BinaryArch));
 752   if (Error E = handleArgs(Config, *Obj, Reader, OutputElfType))
 753     return E;
 754   return writeOutput(Config, *Obj, Out, OutputElfType);
 755 }
 756
 757 Error executeObjcopyOnRawBinary(const CopyConfig &Config, MemoryBuffer &In,
 758                                 Buffer &Out) {
 759   BinaryReader Reader(Config.BinaryArch, &In);
 760   std::unique_ptr<Object> Obj = Reader.create();
 761
 762   // Prefer OutputArch (-O<format>) if set, otherwise fallback to BinaryArch
 763   // (-B<arch>).
 764   const ElfType OutputElfType =
 765       getOutputElfType(Config.OutputArch.getValueOr(Config.BinaryArch));
 766   if (Error E = handleArgs(Config, *Obj, Reader, OutputElfType))
 767     return E;
 768   return writeOutput(Config, *Obj, Out, OutputElfType);
 769 }
 770
 771 Error executeObjcopyOnBinary(const CopyConfig &Config,
 772                              object::ELFObjectFileBase &In, Buffer &Out) {
 773   ELFReader Reader(&In, Config.ExtractPartition);
 774   std::unique_ptr<Object> Obj = Reader.create();
 775   // Prefer OutputArch (-O<format>) if set, otherwise infer it from the input.
 776   const ElfType OutputElfType =
 777       Config.OutputArch ? getOutputElfType(Config.OutputArch.getValue())
 778                         : getOutputElfType(In);
 779   ArrayRef<uint8_t> BuildIdBytes;
 780
 781   if (!Config.BuildIdLinkDir.empty()) {
 782     auto BuildIdBytesOrErr = findBuildID(Config, In);
 783     if (auto E = BuildIdBytesOrErr.takeError())
 784       return E;
 785     BuildIdBytes = *BuildIdBytesOrErr;
 786
 787     if (BuildIdBytes.size() < 2)
 788       return createFileError(
 789           Config.InputFilename,
 790           createStringError(object_error::parse_failed,
 791                             "build ID is smaller than two bytes"));
 792   }
 793
 794   if (!Config.BuildIdLinkDir.empty() && Config.BuildIdLinkInput)
 795     if (Error E =
 796             linkToBuildIdDir(Config, Config.InputFilename,
 797                              Config.BuildIdLinkInput.getValue(), BuildIdBytes))
 798       return E;
 799
 800   if (Error E = handleArgs(Config, *Obj, Reader, OutputElfType))
 801     return createFileError(Config.InputFilename, std::move(E));
 802
 803   if (Error E = writeOutput(Config, *Obj, Out, OutputElfType))
 804     return createFileError(Config.InputFilename, std::move(E));
 805   if (!Config.BuildIdLinkDir.empty() && Config.BuildIdLinkOutput)
 806     if (Error E =
 807             linkToBuildIdDir(Config, Config.OutputFilename,
 808                              Config.BuildIdLinkOutput.getValue(), BuildIdBytes))
 809       return createFileError(Config.OutputFilename, std::move(E));
 810
 811   return Error::success();
 812 }
 813
 814 } // end namespace elf
 815 } // end namespace objcopy
 816 } // end namespace llvm