| //===- ELFObjcopy.cpp -----------------------------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "ELFObjcopy.h" |
| #include "Buffer.h" |
| #include "CopyConfig.h" |
| #include "Object.h" |
| #include "llvm-objcopy.h" |
| |
| #include "llvm/ADT/BitmaskEnum.h" |
| #include "llvm/ADT/Optional.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/ADT/Twine.h" |
| #include "llvm/BinaryFormat/ELF.h" |
| #include "llvm/MC/MCTargetOptions.h" |
| #include "llvm/Object/Binary.h" |
| #include "llvm/Object/ELFObjectFile.h" |
| #include "llvm/Object/ELFTypes.h" |
| #include "llvm/Object/Error.h" |
| #include "llvm/Option/Option.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Compression.h" |
| #include "llvm/Support/Errc.h" |
| #include "llvm/Support/Error.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/ErrorOr.h" |
| #include "llvm/Support/Memory.h" |
| #include "llvm/Support/Path.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <cstdlib> |
| #include <functional> |
| #include <iterator> |
| #include <memory> |
| #include <string> |
| #include <system_error> |
| #include <utility> |
| |
| namespace llvm { |
| namespace objcopy { |
| namespace elf { |
| |
| using namespace object; |
| using namespace ELF; |
| using SectionPred = std::function<bool(const SectionBase &Sec)>; |
| |
| static bool isDebugSection(const SectionBase &Sec) { |
| return StringRef(Sec.Name).startswith(".debug") || |
| StringRef(Sec.Name).startswith(".zdebug") || Sec.Name == ".gdb_index"; |
| } |
| |
| static bool isDWOSection(const SectionBase &Sec) { |
| return StringRef(Sec.Name).endswith(".dwo"); |
| } |
| |
| static bool onlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) { |
| // We can't remove the section header string table. |
| if (&Sec == Obj.SectionNames) |
| return false; |
| // Short of keeping the string table we want to keep everything that is a DWO |
| // section and remove everything else. |
| return !isDWOSection(Sec); |
| } |
| |
| static ElfType getOutputElfType(const Binary &Bin) { |
| // Infer output ELF type from the input ELF object |
| if (isa<ELFObjectFile<ELF32LE>>(Bin)) |
| return ELFT_ELF32LE; |
| if (isa<ELFObjectFile<ELF64LE>>(Bin)) |
| return ELFT_ELF64LE; |
| if (isa<ELFObjectFile<ELF32BE>>(Bin)) |
| return ELFT_ELF32BE; |
| if (isa<ELFObjectFile<ELF64BE>>(Bin)) |
| return ELFT_ELF64BE; |
| llvm_unreachable("Invalid ELFType"); |
| } |
| |
| static ElfType getOutputElfType(const MachineInfo &MI) { |
| // Infer output ELF type from the binary arch specified |
| if (MI.Is64Bit) |
| return MI.IsLittleEndian ? ELFT_ELF64LE : ELFT_ELF64BE; |
| else |
| return MI.IsLittleEndian ? ELFT_ELF32LE : ELFT_ELF32BE; |
| } |
| |
| static std::unique_ptr<Writer> createWriter(const CopyConfig &Config, |
| Object &Obj, Buffer &Buf, |
| ElfType OutputElfType) { |
| if (Config.OutputFormat == "binary") { |
| return llvm::make_unique<BinaryWriter>(Obj, Buf); |
| } |
| // Depending on the initial ELFT and OutputFormat we need a different Writer. |
| switch (OutputElfType) { |
| case ELFT_ELF32LE: |
| return llvm::make_unique<ELFWriter<ELF32LE>>(Obj, Buf, |
| !Config.StripSections); |
| case ELFT_ELF64LE: |
| return llvm::make_unique<ELFWriter<ELF64LE>>(Obj, Buf, |
| !Config.StripSections); |
| case ELFT_ELF32BE: |
| return llvm::make_unique<ELFWriter<ELF32BE>>(Obj, Buf, |
| !Config.StripSections); |
| case ELFT_ELF64BE: |
| return llvm::make_unique<ELFWriter<ELF64BE>>(Obj, Buf, |
| !Config.StripSections); |
| } |
| llvm_unreachable("Invalid output format"); |
| } |
| |
| template <class ELFT> |
| static Expected<ArrayRef<uint8_t>> |
| findBuildID(const object::ELFFile<ELFT> &In) { |
| for (const auto &Phdr : unwrapOrError(In.program_headers())) { |
| if (Phdr.p_type != PT_NOTE) |
| continue; |
| Error Err = Error::success(); |
| for (const auto &Note : In.notes(Phdr, Err)) |
| if (Note.getType() == NT_GNU_BUILD_ID && Note.getName() == ELF_NOTE_GNU) |
| return Note.getDesc(); |
| if (Err) |
| return std::move(Err); |
| } |
| return createStringError(llvm::errc::invalid_argument, |
| "Could not find build ID."); |
| } |
| |
| static Expected<ArrayRef<uint8_t>> |
| findBuildID(const object::ELFObjectFileBase &In) { |
| if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(&In)) |
| return findBuildID(*O->getELFFile()); |
| else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(&In)) |
| return findBuildID(*O->getELFFile()); |
| else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(&In)) |
| return findBuildID(*O->getELFFile()); |
| else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(&In)) |
| return findBuildID(*O->getELFFile()); |
| |
| llvm_unreachable("Bad file format"); |
| } |
| |
| static void linkToBuildIdDir(const CopyConfig &Config, StringRef ToLink, |
| StringRef Suffix, ArrayRef<uint8_t> BuildIdBytes) { |
| SmallString<128> Path = Config.BuildIdLinkDir; |
| sys::path::append(Path, llvm::toHex(BuildIdBytes[0], /*LowerCase*/ true)); |
| if (auto EC = sys::fs::create_directories(Path)) |
| error("cannot create build ID link directory " + Path + ": " + |
| EC.message()); |
| |
| sys::path::append(Path, |
| llvm::toHex(BuildIdBytes.slice(1), /*LowerCase*/ true)); |
| Path += Suffix; |
| if (auto EC = sys::fs::create_hard_link(ToLink, Path)) { |
| // Hard linking failed, try to remove the file first if it exists. |
| if (sys::fs::exists(Path)) |
| sys::fs::remove(Path); |
| EC = sys::fs::create_hard_link(ToLink, Path); |
| if (EC) |
| error("cannot link " + ToLink + " to " + Path + ": " + EC.message()); |
| } |
| } |
| |
| static void splitDWOToFile(const CopyConfig &Config, const Reader &Reader, |
| StringRef File, ElfType OutputElfType) { |
| auto DWOFile = Reader.create(); |
| DWOFile->removeSections( |
| [&](const SectionBase &Sec) { return onlyKeepDWOPred(*DWOFile, Sec); }); |
| if (Config.OutputArch) |
| DWOFile->Machine = Config.OutputArch.getValue().EMachine; |
| FileBuffer FB(File); |
| auto Writer = createWriter(Config, *DWOFile, FB, OutputElfType); |
| Writer->finalize(); |
| Writer->write(); |
| } |
| |
| static Error dumpSectionToFile(StringRef SecName, StringRef Filename, |
| Object &Obj) { |
| for (auto &Sec : Obj.sections()) { |
| if (Sec.Name == SecName) { |
| if (Sec.OriginalData.empty()) |
| return make_error<StringError>("Can't dump section \"" + SecName + |
| "\": it has no contents", |
| object_error::parse_failed); |
| Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr = |
| FileOutputBuffer::create(Filename, Sec.OriginalData.size()); |
| if (!BufferOrErr) |
| return BufferOrErr.takeError(); |
| std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufferOrErr); |
| std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), |
| Buf->getBufferStart()); |
| if (Error E = Buf->commit()) |
| return E; |
| return Error::success(); |
| } |
| } |
| return make_error<StringError>("Section not found", |
| object_error::parse_failed); |
| } |
| |
| static bool isCompressed(const SectionBase &Section) { |
| const char *Magic = "ZLIB"; |
| return StringRef(Section.Name).startswith(".zdebug") || |
| (Section.OriginalData.size() > strlen(Magic) && |
| !strncmp(reinterpret_cast<const char *>(Section.OriginalData.data()), |
| Magic, strlen(Magic))) || |
| (Section.Flags & ELF::SHF_COMPRESSED); |
| } |
| |
| static bool isCompressable(const SectionBase &Section) { |
| return !isCompressed(Section) && isDebugSection(Section) && |
| Section.Name != ".gdb_index"; |
| } |
| |
| static void replaceDebugSections( |
| const CopyConfig &Config, Object &Obj, SectionPred &RemovePred, |
| function_ref<bool(const SectionBase &)> shouldReplace, |
| function_ref<SectionBase *(const SectionBase *)> addSection) { |
| SmallVector<SectionBase *, 13> ToReplace; |
| SmallVector<RelocationSection *, 13> RelocationSections; |
| for (auto &Sec : Obj.sections()) { |
| if (RelocationSection *R = dyn_cast<RelocationSection>(&Sec)) { |
| if (shouldReplace(*R->getSection())) |
| RelocationSections.push_back(R); |
| continue; |
| } |
| |
| if (shouldReplace(Sec)) |
| ToReplace.push_back(&Sec); |
| } |
| |
| for (SectionBase *S : ToReplace) { |
| SectionBase *NewSection = addSection(S); |
| |
| for (RelocationSection *RS : RelocationSections) { |
| if (RS->getSection() == S) |
| RS->setSection(NewSection); |
| } |
| } |
| |
| RemovePred = [shouldReplace, RemovePred](const SectionBase &Sec) { |
| return shouldReplace(Sec) || RemovePred(Sec); |
| }; |
| } |
| |
| // This function handles the high level operations of GNU objcopy including |
| // handling command line options. It's important to outline certain properties |
| // we expect to hold of the command line operations. Any operation that "keeps" |
| // should keep regardless of a remove. Additionally any removal should respect |
| // any previous removals. Lastly whether or not something is removed shouldn't |
| // depend a) on the order the options occur in or b) on some opaque priority |
| // system. The only priority is that keeps/copies overrule removes. |
| static void handleArgs(const CopyConfig &Config, Object &Obj, |
| const Reader &Reader, ElfType OutputElfType) { |
| |
| if (!Config.SplitDWO.empty()) { |
| splitDWOToFile(Config, Reader, Config.SplitDWO, OutputElfType); |
| } |
| if (Config.OutputArch) |
| Obj.Machine = Config.OutputArch.getValue().EMachine; |
| |
| // TODO: update or remove symbols only if there is an option that affects |
| // them. |
| if (Obj.SymbolTable) { |
| Obj.SymbolTable->updateSymbols([&](Symbol &Sym) { |
| if (!Sym.isCommon() && |
| ((Config.LocalizeHidden && |
| (Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL)) || |
| is_contained(Config.SymbolsToLocalize, Sym.Name))) |
| Sym.Binding = STB_LOCAL; |
| |
| // Note: these two globalize flags have very similar names but different |
| // meanings: |
| // |
| // --globalize-symbol: promote a symbol to global |
| // --keep-global-symbol: all symbols except for these should be made local |
| // |
| // If --globalize-symbol is specified for a given symbol, it will be |
| // global in the output file even if it is not included via |
| // --keep-global-symbol. Because of that, make sure to check |
| // --globalize-symbol second. |
| if (!Config.SymbolsToKeepGlobal.empty() && |
| !is_contained(Config.SymbolsToKeepGlobal, Sym.Name) && |
| Sym.getShndx() != SHN_UNDEF) |
| Sym.Binding = STB_LOCAL; |
| |
| if (is_contained(Config.SymbolsToGlobalize, Sym.Name) && |
| Sym.getShndx() != SHN_UNDEF) |
| Sym.Binding = STB_GLOBAL; |
| |
| if (is_contained(Config.SymbolsToWeaken, Sym.Name) && |
| Sym.Binding == STB_GLOBAL) |
| Sym.Binding = STB_WEAK; |
| |
| if (Config.Weaken && Sym.Binding == STB_GLOBAL && |
| Sym.getShndx() != SHN_UNDEF) |
| Sym.Binding = STB_WEAK; |
| |
| const auto I = Config.SymbolsToRename.find(Sym.Name); |
| if (I != Config.SymbolsToRename.end()) |
| Sym.Name = I->getValue(); |
| |
| if (!Config.SymbolsPrefix.empty() && Sym.Type != STT_SECTION) |
| Sym.Name = (Config.SymbolsPrefix + Sym.Name).str(); |
| }); |
| |
| // The purpose of this loop is to mark symbols referenced by sections |
| // (like GroupSection or RelocationSection). This way, we know which |
| // symbols are still 'needed' and which are not. |
| if (Config.StripUnneeded) { |
| for (auto &Section : Obj.sections()) |
| Section.markSymbols(); |
| } |
| |
| Obj.removeSymbols([&](const Symbol &Sym) { |
| if (is_contained(Config.SymbolsToKeep, Sym.Name) || |
| (Config.KeepFileSymbols && Sym.Type == STT_FILE)) |
| return false; |
| |
| if (Config.DiscardAll && Sym.Binding == STB_LOCAL && |
| Sym.getShndx() != SHN_UNDEF && Sym.Type != STT_FILE && |
| Sym.Type != STT_SECTION) |
| return true; |
| |
| if (Config.StripAll || Config.StripAllGNU) |
| return true; |
| |
| if (is_contained(Config.SymbolsToRemove, Sym.Name)) |
| return true; |
| |
| if (Config.StripUnneeded && !Sym.Referenced && |
| (Sym.Binding == STB_LOCAL || Sym.getShndx() == SHN_UNDEF) && |
| Sym.Type != STT_FILE && Sym.Type != STT_SECTION) |
| return true; |
| |
| return false; |
| }); |
| } |
| |
| SectionPred RemovePred = [](const SectionBase &) { return false; }; |
| |
| // Removes: |
| if (!Config.ToRemove.empty()) { |
| RemovePred = [&Config](const SectionBase &Sec) { |
| return is_contained(Config.ToRemove, Sec.Name); |
| }; |
| } |
| |
| if (Config.StripDWO || !Config.SplitDWO.empty()) |
| RemovePred = [RemovePred](const SectionBase &Sec) { |
| return isDWOSection(Sec) || RemovePred(Sec); |
| }; |
| |
| if (Config.ExtractDWO) |
| RemovePred = [RemovePred, &Obj](const SectionBase &Sec) { |
| return onlyKeepDWOPred(Obj, Sec) || RemovePred(Sec); |
| }; |
| |
| if (Config.StripAllGNU) |
| RemovePred = [RemovePred, &Obj](const SectionBase &Sec) { |
| if (RemovePred(Sec)) |
| return true; |
| if ((Sec.Flags & SHF_ALLOC) != 0) |
| return false; |
| if (&Sec == Obj.SectionNames) |
| return false; |
| switch (Sec.Type) { |
| case SHT_SYMTAB: |
| case SHT_REL: |
| case SHT_RELA: |
| case SHT_STRTAB: |
| return true; |
| } |
| return isDebugSection(Sec); |
| }; |
| |
| if (Config.StripSections) { |
| RemovePred = [RemovePred](const SectionBase &Sec) { |
| return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0; |
| }; |
| } |
| |
| if (Config.StripDebug) { |
| RemovePred = [RemovePred](const SectionBase &Sec) { |
| return RemovePred(Sec) || isDebugSection(Sec); |
| }; |
| } |
| |
| if (Config.StripNonAlloc) |
| RemovePred = [RemovePred, &Obj](const SectionBase &Sec) { |
| if (RemovePred(Sec)) |
| return true; |
| if (&Sec == Obj.SectionNames) |
| return false; |
| return (Sec.Flags & SHF_ALLOC) == 0; |
| }; |
| |
| if (Config.StripAll) |
| RemovePred = [RemovePred, &Obj](const SectionBase &Sec) { |
| if (RemovePred(Sec)) |
| return true; |
| if (&Sec == Obj.SectionNames) |
| return false; |
| if (StringRef(Sec.Name).startswith(".gnu.warning")) |
| return false; |
| return (Sec.Flags & SHF_ALLOC) == 0; |
| }; |
| |
| // Explicit copies: |
| if (!Config.OnlySection.empty()) { |
| RemovePred = [&Config, RemovePred, &Obj](const SectionBase &Sec) { |
| // Explicitly keep these sections regardless of previous removes. |
| if (is_contained(Config.OnlySection, Sec.Name)) |
| return false; |
| |
| // Allow all implicit removes. |
| if (RemovePred(Sec)) |
| return true; |
| |
| // Keep special sections. |
| if (Obj.SectionNames == &Sec) |
| return false; |
| if (Obj.SymbolTable == &Sec || |
| (Obj.SymbolTable && Obj.SymbolTable->getStrTab() == &Sec)) |
| return false; |
| |
| // Remove everything else. |
| return true; |
| }; |
| } |
| |
| if (!Config.KeepSection.empty()) { |
| RemovePred = [&Config, RemovePred](const SectionBase &Sec) { |
| // Explicitly keep these sections regardless of previous removes. |
| if (is_contained(Config.KeepSection, Sec.Name)) |
| return false; |
| // Otherwise defer to RemovePred. |
| return RemovePred(Sec); |
| }; |
| } |
| |
| // This has to be the last predicate assignment. |
| // If the option --keep-symbol has been specified |
| // and at least one of those symbols is present |
| // (equivalently, the updated symbol table is not empty) |
| // the symbol table and the string table should not be removed. |
| if ((!Config.SymbolsToKeep.empty() || Config.KeepFileSymbols) && |
| Obj.SymbolTable && !Obj.SymbolTable->empty()) { |
| RemovePred = [&Obj, RemovePred](const SectionBase &Sec) { |
| if (&Sec == Obj.SymbolTable || &Sec == Obj.SymbolTable->getStrTab()) |
| return false; |
| return RemovePred(Sec); |
| }; |
| } |
| |
| if (Config.CompressionType != DebugCompressionType::None) |
| replaceDebugSections(Config, Obj, RemovePred, isCompressable, |
| [&Config, &Obj](const SectionBase *S) { |
| return &Obj.addSection<CompressedSection>( |
| *S, Config.CompressionType); |
| }); |
| else if (Config.DecompressDebugSections) |
| replaceDebugSections( |
| Config, Obj, RemovePred, |
| [](const SectionBase &S) { return isa<CompressedSection>(&S); }, |
| [&Obj](const SectionBase *S) { |
| auto CS = cast<CompressedSection>(S); |
| return &Obj.addSection<DecompressedSection>(*CS); |
| }); |
| |
| Obj.removeSections(RemovePred); |
| |
| if (!Config.SectionsToRename.empty()) { |
| for (auto &Sec : Obj.sections()) { |
| const auto Iter = Config.SectionsToRename.find(Sec.Name); |
| if (Iter != Config.SectionsToRename.end()) { |
| const SectionRename &SR = Iter->second; |
| Sec.Name = SR.NewName; |
| if (SR.NewFlags.hasValue()) { |
| // Preserve some flags which should not be dropped when setting flags. |
| // Also, preserve anything OS/processor dependant. |
| const uint64_t PreserveMask = ELF::SHF_COMPRESSED | ELF::SHF_EXCLUDE | |
| ELF::SHF_GROUP | ELF::SHF_LINK_ORDER | |
| ELF::SHF_MASKOS | ELF::SHF_MASKPROC | |
| ELF::SHF_TLS | ELF::SHF_INFO_LINK; |
| Sec.Flags = (Sec.Flags & PreserveMask) | |
| (SR.NewFlags.getValue() & ~PreserveMask); |
| } |
| } |
| } |
| } |
| |
| if (!Config.AddSection.empty()) { |
| for (const auto &Flag : Config.AddSection) { |
| auto SecPair = Flag.split("="); |
| auto SecName = SecPair.first; |
| auto File = SecPair.second; |
| auto BufOrErr = MemoryBuffer::getFile(File); |
| if (!BufOrErr) |
| reportError(File, BufOrErr.getError()); |
| auto Buf = std::move(*BufOrErr); |
| auto BufPtr = reinterpret_cast<const uint8_t *>(Buf->getBufferStart()); |
| auto BufSize = Buf->getBufferSize(); |
| Obj.addSection<OwnedDataSection>(SecName, |
| ArrayRef<uint8_t>(BufPtr, BufSize)); |
| } |
| } |
| |
| if (!Config.DumpSection.empty()) { |
| for (const auto &Flag : Config.DumpSection) { |
| std::pair<StringRef, StringRef> SecPair = Flag.split("="); |
| StringRef SecName = SecPair.first; |
| StringRef File = SecPair.second; |
| if (Error E = dumpSectionToFile(SecName, File, Obj)) |
| reportError(Config.InputFilename, std::move(E)); |
| } |
| } |
| |
| if (!Config.AddGnuDebugLink.empty()) |
| Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink); |
| } |
| |
| void executeObjcopyOnRawBinary(const CopyConfig &Config, MemoryBuffer &In, |
| Buffer &Out) { |
| BinaryReader Reader(Config.BinaryArch, &In); |
| std::unique_ptr<Object> Obj = Reader.create(); |
| |
| // Prefer OutputArch (-O<format>) if set, otherwise fallback to BinaryArch |
| // (-B<arch>). |
| const ElfType OutputElfType = getOutputElfType( |
| Config.OutputArch ? Config.OutputArch.getValue() : Config.BinaryArch); |
| handleArgs(Config, *Obj, Reader, OutputElfType); |
| std::unique_ptr<Writer> Writer = |
| createWriter(Config, *Obj, Out, OutputElfType); |
| Writer->finalize(); |
| Writer->write(); |
| } |
| |
| void executeObjcopyOnBinary(const CopyConfig &Config, |
| object::ELFObjectFileBase &In, Buffer &Out) { |
| ELFReader Reader(&In); |
| std::unique_ptr<Object> Obj = Reader.create(); |
| // Prefer OutputArch (-O<format>) if set, otherwise infer it from the input. |
| const ElfType OutputElfType = |
| Config.OutputArch ? getOutputElfType(Config.OutputArch.getValue()) |
| : getOutputElfType(In); |
| ArrayRef<uint8_t> BuildIdBytes; |
| |
| if (!Config.BuildIdLinkDir.empty()) { |
| BuildIdBytes = unwrapOrError(findBuildID(In)); |
| if (BuildIdBytes.size() < 2) |
| error("build ID in file '" + Config.InputFilename + |
| "' is smaller than two bytes"); |
| } |
| |
| if (!Config.BuildIdLinkDir.empty() && Config.BuildIdLinkInput) { |
| linkToBuildIdDir(Config, Config.InputFilename, |
| Config.BuildIdLinkInput.getValue(), BuildIdBytes); |
| } |
| handleArgs(Config, *Obj, Reader, OutputElfType); |
| std::unique_ptr<Writer> Writer = |
| createWriter(Config, *Obj, Out, OutputElfType); |
| Writer->finalize(); |
| Writer->write(); |
| if (!Config.BuildIdLinkDir.empty() && Config.BuildIdLinkOutput) { |
| linkToBuildIdDir(Config, Config.OutputFilename, |
| Config.BuildIdLinkOutput.getValue(), BuildIdBytes); |
| } |
| } |
| |
| } // end namespace elf |
| } // end namespace objcopy |
| } // end namespace llvm |
