//===- Driver.cpp ---------------------------------------------------------===// // // The LLVM Linker // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // The driver drives the entire linking process. It is responsible for // parsing command line options and doing whatever it is instructed to do. // // One notable thing in the LLD's driver when compared to other linkers is // that the LLD's driver is agnostic on the host operating system. // Other linkers usually have implicit default values (such as a dynamic // linker path or library paths) for each host OS. // // I don't think implicit default values are useful because they are // usually explicitly specified by the compiler driver. They can even // be harmful when you are doing cross-linking. Therefore, in LLD, we // simply trust the compiler driver to pass all required options and // don't try to make effort on our side. // //===----------------------------------------------------------------------===// #include "Driver.h" #include "Config.h" #include "Filesystem.h" #include "ICF.h" #include "InputFiles.h" #include "InputSection.h" #include "LinkerScript.h" #include "OutputSections.h" #include "ScriptParser.h" #include "Strings.h" #include "SymbolTable.h" #include "Symbols.h" #include "SyntheticSections.h" #include "Target.h" #include "Writer.h" #include "lld/Common/Args.h" #include "lld/Common/Driver.h" #include "lld/Common/ErrorHandler.h" #include "lld/Common/Memory.h" #include "lld/Common/Threads.h" #include "lld/Common/Version.h" #include "llvm/ADT/StringExtras.h" #include "llvm/ADT/StringSwitch.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Compression.h" #include "llvm/Support/Path.h" #include "llvm/Support/TarWriter.h" #include "llvm/Support/TargetSelect.h" #include "llvm/Support/raw_ostream.h" #include <cstdlib> #include <utility> using namespace llvm; using namespace llvm::ELF; using namespace llvm::object; using namespace llvm::sys; using namespace lld; using namespace lld::elf; Configuration *elf::Config; LinkerDriver *elf::Driver; static void setConfigs(); bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly, raw_ostream &Error) { errorHandler().LogName = Args[0]; errorHandler().ErrorLimitExceededMsg = "too many errors emitted, stopping now (use " "-error-limit=0 to see all errors)"; errorHandler().ErrorOS = &Error; errorHandler().ColorDiagnostics = Error.has_colors(); InputSections.clear(); OutputSections.clear(); Tar = nullptr; BinaryFiles.clear(); BitcodeFiles.clear(); ObjectFiles.clear(); SharedFiles.clear(); Config = make<Configuration>(); Driver = make<LinkerDriver>(); Script = make<LinkerScript>(); Symtab = make<SymbolTable>(); Config->Argv = {Args.begin(), Args.end()}; Driver->main(Args, CanExitEarly); // Exit immediately if we don't need to return to the caller. // This saves time because the overhead of calling destructors // for all globally-allocated objects is not negligible. if (Config->ExitEarly) exitLld(errorCount() ? 1 : 0); freeArena(); return !errorCount(); } // Parses a linker -m option. static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef Emul) { uint8_t OSABI = 0; StringRef S = Emul; if (S.endswith("_fbsd")) { S = S.drop_back(5); OSABI = ELFOSABI_FREEBSD; } std::pair<ELFKind, uint16_t> Ret = StringSwitch<std::pair<ELFKind, uint16_t>>(S) .Cases("aarch64elf", "aarch64linux", {ELF64LEKind, EM_AARCH64}) .Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM}) .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64}) .Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS}) .Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS}) .Case("elf32ppc", {ELF32BEKind, EM_PPC}) .Case("elf64btsmip", {ELF64BEKind, EM_MIPS}) .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS}) .Case("elf64ppc", {ELF64BEKind, EM_PPC64}) .Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64}) .Case("elf_i386", {ELF32LEKind, EM_386}) .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU}) .Default({ELFNoneKind, EM_NONE}); if (Ret.first == ELFNoneKind) error("unknown emulation: " + Emul); return std::make_tuple(Ret.first, Ret.second, OSABI); } // Returns slices of MB by parsing MB as an archive file. // Each slice consists of a member file in the archive. std::vector<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers( MemoryBufferRef MB) { std::unique_ptr<Archive> File = CHECK(Archive::create(MB), MB.getBufferIdentifier() + ": failed to parse archive"); std::vector<std::pair<MemoryBufferRef, uint64_t>> V; Error Err = Error::success(); bool AddToTar = File->isThin() && Tar; for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) { Archive::Child C = CHECK(COrErr, MB.getBufferIdentifier() + ": could not get the child of the archive"); MemoryBufferRef MBRef = CHECK(C.getMemoryBufferRef(), MB.getBufferIdentifier() + ": could not get the buffer for a child of the archive"); if (AddToTar) Tar->append(relativeToRoot(check(C.getFullName())), MBRef.getBuffer()); V.push_back(std::make_pair(MBRef, C.getChildOffset())); } if (Err) fatal(MB.getBufferIdentifier() + ": Archive::children failed: " + toString(std::move(Err))); // Take ownership of memory buffers created for members of thin archives. for (std::unique_ptr<MemoryBuffer> &MB : File->takeThinBuffers()) make<std::unique_ptr<MemoryBuffer>>(std::move(MB)); return V; } // Opens a file and create a file object. Path has to be resolved already. void LinkerDriver::addFile(StringRef Path, bool WithLOption) { using namespace sys::fs; Optional<MemoryBufferRef> Buffer = readFile(Path); if (!Buffer.hasValue()) return; MemoryBufferRef MBRef = *Buffer; if (InBinary) { Files.push_back(make<BinaryFile>(MBRef)); return; } switch (identify_magic(MBRef.getBuffer())) { case file_magic::unknown: readLinkerScript(MBRef); return; case file_magic::archive: { // Handle -whole-archive. if (InWholeArchive) { for (const auto &P : getArchiveMembers(MBRef)) Files.push_back(createObjectFile(P.first, Path, P.second)); return; } std::unique_ptr<Archive> File = CHECK(Archive::create(MBRef), Path + ": failed to parse archive"); // If an archive file has no symbol table, it is likely that a user // is attempting LTO and using a default ar command that doesn't // understand the LLVM bitcode file. It is a pretty common error, so // we'll handle it as if it had a symbol table. if (!File->isEmpty() && !File->hasSymbolTable()) { for (const auto &P : getArchiveMembers(MBRef)) Files.push_back(make<LazyObjFile>(P.first, Path, P.second)); return; } // Handle the regular case. Files.push_back(make<ArchiveFile>(std::move(File))); return; } case file_magic::elf_shared_object: if (Config->Relocatable) { error("attempted static link of dynamic object " + Path); return; } // DSOs usually have DT_SONAME tags in their ELF headers, and the // sonames are used to identify DSOs. But if they are missing, // they are identified by filenames. We don't know whether the new // file has a DT_SONAME or not because we haven't parsed it yet. // Here, we set the default soname for the file because we might // need it later. // // If a file was specified by -lfoo, the directory part is not // significant, as a user did not specify it. This behavior is // compatible with GNU. Files.push_back( createSharedFile(MBRef, WithLOption ? path::filename(Path) : Path)); return; default: if (InLib) Files.push_back(make<LazyObjFile>(MBRef, "", 0)); else Files.push_back(createObjectFile(MBRef)); } } // Add a given library by searching it from input search paths. void LinkerDriver::addLibrary(StringRef Name) { if (Optional<std::string> Path = searchLibrary(Name)) addFile(*Path, /*WithLOption=*/true); else error("unable to find library -l" + Name); } // This function is called on startup. We need this for LTO since // LTO calls LLVM functions to compile bitcode files to native code. // Technically this can be delayed until we read bitcode files, but // we don't bother to do lazily because the initialization is fast. static void initLLVM(opt::InputArgList &Args) { InitializeAllTargets(); InitializeAllTargetMCs(); InitializeAllAsmPrinters(); InitializeAllAsmParsers(); // Parse and evaluate -mllvm options. std::vector<const char *> V; V.push_back("lld (LLVM option parsing)"); for (auto *Arg : Args.filtered(OPT_mllvm)) V.push_back(Arg->getValue()); cl::ParseCommandLineOptions(V.size(), V.data()); } // Some command line options or some combinations of them are not allowed. // This function checks for such errors. static void checkOptions(opt::InputArgList &Args) { // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup // table which is a relatively new feature. if (Config->EMachine == EM_MIPS && Config->GnuHash) error("the .gnu.hash section is not compatible with the MIPS target."); if (Config->FixCortexA53Errata843419 && Config->EMachine != EM_AARCH64) error("--fix-cortex-a53-843419 is only supported on AArch64 targets."); if (Config->Pie && Config->Shared) error("-shared and -pie may not be used together"); if (!Config->Shared && !Config->FilterList.empty()) error("-F may not be used without -shared"); if (!Config->Shared && !Config->AuxiliaryList.empty()) error("-f may not be used without -shared"); if (!Config->Relocatable && !Config->DefineCommon) error("-no-define-common not supported in non relocatable output"); if (Config->Relocatable) { if (Config->Shared) error("-r and -shared may not be used together"); if (Config->GcSections) error("-r and --gc-sections may not be used together"); if (Config->ICF) error("-r and --icf may not be used together"); if (Config->Pie) error("-r and -pie may not be used together"); } } static const char *getReproduceOption(opt::InputArgList &Args) { if (auto *Arg = Args.getLastArg(OPT_reproduce)) return Arg->getValue(); return getenv("LLD_REPRODUCE"); } static bool hasZOption(opt::InputArgList &Args, StringRef Key) { for (auto *Arg : Args.filtered(OPT_z)) if (Key == Arg->getValue()) return true; return false; } void LinkerDriver::main(ArrayRef<const char *> ArgsArr, bool CanExitEarly) { ELFOptTable Parser; opt::InputArgList Args = Parser.parse(ArgsArr.slice(1)); // Interpret this flag early because error() depends on them. errorHandler().ErrorLimit = args::getInteger(Args, OPT_error_limit, 20); // Handle -help if (Args.hasArg(OPT_help)) { printHelp(ArgsArr[0]); return; } // Handle -v or -version. // // A note about "compatible with GNU linkers" message: this is a hack for // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and // still the newest version in March 2017) or earlier to recognize LLD as // a GNU compatible linker. As long as an output for the -v option // contains "GNU" or "with BFD", they recognize us as GNU-compatible. // // This is somewhat ugly hack, but in reality, we had no choice other // than doing this. Considering the very long release cycle of Libtool, // it is not easy to improve it to recognize LLD as a GNU compatible // linker in a timely manner. Even if we can make it, there are still a // lot of "configure" scripts out there that are generated by old version // of Libtool. We cannot convince every software developer to migrate to // the latest version and re-generate scripts. So we have this hack. if (Args.hasArg(OPT_v) || Args.hasArg(OPT_version)) message(getLLDVersion() + " (compatible with GNU linkers)"); // The behavior of -v or --version is a bit strange, but this is // needed for compatibility with GNU linkers. if (Args.hasArg(OPT_v) && !Args.hasArg(OPT_INPUT)) return; if (Args.hasArg(OPT_version)) return; Config->ExitEarly = CanExitEarly && !Args.hasArg(OPT_full_shutdown); errorHandler().ExitEarly = Config->ExitEarly; if (const char *Path = getReproduceOption(Args)) { // Note that --reproduce is a debug option so you can ignore it // if you are trying to understand the whole picture of the code. Expected<std::unique_ptr<TarWriter>> ErrOrWriter = TarWriter::create(Path, path::stem(Path)); if (ErrOrWriter) { Tar = ErrOrWriter->get(); Tar->append("response.txt", createResponseFile(Args)); Tar->append("version.txt", getLLDVersion() + "\n"); make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter)); } else { error(Twine("--reproduce: failed to open ") + Path + ": " + toString(ErrOrWriter.takeError())); } } readConfigs(Args); initLLVM(Args); createFiles(Args); inferMachineType(); setConfigs(); checkOptions(Args); if (errorCount()) return; switch (Config->EKind) { case ELF32LEKind: link<ELF32LE>(Args); return; case ELF32BEKind: link<ELF32BE>(Args); return; case ELF64LEKind: link<ELF64LE>(Args); return; case ELF64BEKind: link<ELF64BE>(Args); return; default: llvm_unreachable("unknown Config->EKind"); } } static std::string getRpath(opt::InputArgList &Args) { std::vector<StringRef> V = args::getStrings(Args, OPT_rpath); return llvm::join(V.begin(), V.end(), ":"); } // Determines what we should do if there are remaining unresolved // symbols after the name resolution. static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) { if (Args.hasArg(OPT_relocatable)) return UnresolvedPolicy::IgnoreAll; UnresolvedPolicy ErrorOrWarn = Args.hasFlag(OPT_error_unresolved_symbols, OPT_warn_unresolved_symbols, true) ? UnresolvedPolicy::ReportError : UnresolvedPolicy::Warn; // Process the last of -unresolved-symbols, -no-undefined or -z defs. for (auto *Arg : llvm::reverse(Args)) { switch (Arg->getOption().getID()) { case OPT_unresolved_symbols: { StringRef S = Arg->getValue(); if (S == "ignore-all" || S == "ignore-in-object-files") return UnresolvedPolicy::Ignore; if (S == "ignore-in-shared-libs" || S == "report-all") return ErrorOrWarn; error("unknown --unresolved-symbols value: " + S); continue; } case OPT_no_undefined: return ErrorOrWarn; case OPT_z: if (StringRef(Arg->getValue()) == "defs") return ErrorOrWarn; continue; } } // -shared implies -unresolved-symbols=ignore-all because missing // symbols are likely to be resolved at runtime using other DSOs. if (Config->Shared) return UnresolvedPolicy::Ignore; return ErrorOrWarn; } static Target2Policy getTarget2(opt::InputArgList &Args) { StringRef S = Args.getLastArgValue(OPT_target2, "got-rel"); if (S == "rel") return Target2Policy::Rel; if (S == "abs") return Target2Policy::Abs; if (S == "got-rel") return Target2Policy::GotRel; error("unknown --target2 option: " + S); return Target2Policy::GotRel; } static bool isOutputFormatBinary(opt::InputArgList &Args) { if (auto *Arg = Args.getLastArg(OPT_oformat)) { StringRef S = Arg->getValue(); if (S == "binary") return true; error("unknown --oformat value: " + S); } return false; } static DiscardPolicy getDiscard(opt::InputArgList &Args) { if (Args.hasArg(OPT_relocatable)) return DiscardPolicy::None; auto *Arg = Args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none); if (!Arg) return DiscardPolicy::Default; if (Arg->getOption().getID() == OPT_discard_all) return DiscardPolicy::All; if (Arg->getOption().getID() == OPT_discard_locals) return DiscardPolicy::Locals; return DiscardPolicy::None; } static StringRef getDynamicLinker(opt::InputArgList &Args) { auto *Arg = Args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker); if (!Arg || Arg->getOption().getID() == OPT_no_dynamic_linker) return ""; return Arg->getValue(); } static StripPolicy getStrip(opt::InputArgList &Args) { if (Args.hasArg(OPT_relocatable)) return StripPolicy::None; auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug); if (!Arg) return StripPolicy::None; if (Arg->getOption().getID() == OPT_strip_all) return StripPolicy::All; return StripPolicy::Debug; } static uint64_t parseSectionAddress(StringRef S, const opt::Arg &Arg) { uint64_t VA = 0; if (S.startswith("0x")) S = S.drop_front(2); if (!to_integer(S, VA, 16)) error("invalid argument: " + toString(Arg)); return VA; } static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) { StringMap<uint64_t> Ret; for (auto *Arg : Args.filtered(OPT_section_start)) { StringRef Name; StringRef Addr; std::tie(Name, Addr) = StringRef(Arg->getValue()).split('='); Ret[Name] = parseSectionAddress(Addr, *Arg); } if (auto *Arg = Args.getLastArg(OPT_Ttext)) Ret[".text"] = parseSectionAddress(Arg->getValue(), *Arg); if (auto *Arg = Args.getLastArg(OPT_Tdata)) Ret[".data"] = parseSectionAddress(Arg->getValue(), *Arg); if (auto *Arg = Args.getLastArg(OPT_Tbss)) Ret[".bss"] = parseSectionAddress(Arg->getValue(), *Arg); return Ret; } static SortSectionPolicy getSortSection(opt::InputArgList &Args) { StringRef S = Args.getLastArgValue(OPT_sort_section); if (S == "alignment") return SortSectionPolicy::Alignment; if (S == "name") return SortSectionPolicy::Name; if (!S.empty()) error("unknown --sort-section rule: " + S); return SortSectionPolicy::Default; } static OrphanHandlingPolicy getOrphanHandling(opt::InputArgList &Args) { StringRef S = Args.getLastArgValue(OPT_orphan_handling, "place"); if (S == "warn") return OrphanHandlingPolicy::Warn; if (S == "error") return OrphanHandlingPolicy::Error; if (S != "place") error("unknown --orphan-handling mode: " + S); return OrphanHandlingPolicy::Place; } // Parse --build-id or --build-id=<style>. We handle "tree" as a // synonym for "sha1" because all our hash functions including // -build-id=sha1 are actually tree hashes for performance reasons. static std::pair<BuildIdKind, std::vector<uint8_t>> getBuildId(opt::InputArgList &Args) { auto *Arg = Args.getLastArg(OPT_build_id, OPT_build_id_eq); if (!Arg) return {BuildIdKind::None, {}}; if (Arg->getOption().getID() == OPT_build_id) return {BuildIdKind::Fast, {}}; StringRef S = Arg->getValue(); if (S == "md5") return {BuildIdKind::Md5, {}}; if (S == "sha1" || S == "tree") return {BuildIdKind::Sha1, {}}; if (S == "uuid") return {BuildIdKind::Uuid, {}}; if (S.startswith("0x")) return {BuildIdKind::Hexstring, parseHex(S.substr(2))}; if (S != "none") error("unknown --build-id style: " + S); return {BuildIdKind::None, {}}; } static bool getCompressDebugSections(opt::InputArgList &Args) { StringRef S = Args.getLastArgValue(OPT_compress_debug_sections, "none"); if (S == "none") return false; if (S != "zlib") error("unknown --compress-debug-sections value: " + S); if (!zlib::isAvailable()) error("--compress-debug-sections: zlib is not available"); return true; } static int parseInt(StringRef S, opt::Arg *Arg) { int V = 0; if (!to_integer(S, V, 10)) error(Arg->getSpelling() + ": number expected, but got '" + S + "'"); return V; } // Initializes Config members by the command line options. void LinkerDriver::readConfigs(opt::InputArgList &Args) { Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition) || hasZOption(Args, "muldefs"); Config->AuxiliaryList = args::getStrings(Args, OPT_auxiliary); Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic); Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions); Config->Chroot = Args.getLastArgValue(OPT_chroot); Config->CompressDebugSections = getCompressDebugSections(Args); Config->DefineCommon = Args.hasFlag(OPT_define_common, OPT_no_define_common, !Args.hasArg(OPT_relocatable)); Config->Demangle = Args.hasFlag(OPT_demangle, OPT_no_demangle, true); Config->DisableVerify = Args.hasArg(OPT_disable_verify); Config->Discard = getDiscard(Args); Config->DynamicLinker = getDynamicLinker(Args); Config->EhFrameHdr = Args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false); Config->EmitRelocs = Args.hasArg(OPT_emit_relocs); Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags); Config->Entry = Args.getLastArgValue(OPT_entry); Config->ExportDynamic = Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false); errorHandler().FatalWarnings = Args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false); Config->FilterList = args::getStrings(Args, OPT_filter); Config->Fini = Args.getLastArgValue(OPT_fini, "_fini"); Config->FixCortexA53Errata843419 = Args.hasArg(OPT_fix_cortex_a53_843419); Config->GcSections = Args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, false); Config->GdbIndex = Args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false); Config->ICF = Args.hasFlag(OPT_icf_all, OPT_icf_none, false); Config->ICFData = Args.hasArg(OPT_icf_data); Config->Init = Args.getLastArgValue(OPT_init, "_init"); Config->LTOAAPipeline = Args.getLastArgValue(OPT_lto_aa_pipeline); Config->LTONewPmPasses = Args.getLastArgValue(OPT_lto_newpm_passes); Config->LTOO = args::getInteger(Args, OPT_lto_O, 2); Config->LTOPartitions = args::getInteger(Args, OPT_lto_partitions, 1); Config->MapFile = Args.getLastArgValue(OPT_Map); Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique); Config->MergeArmExidx = Args.hasFlag(OPT_merge_exidx_entries, OPT_no_merge_exidx_entries, true); Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version); Config->NoinhibitExec = Args.hasArg(OPT_noinhibit_exec); Config->Nostdlib = Args.hasArg(OPT_nostdlib); Config->OFormatBinary = isOutputFormatBinary(Args); Config->Omagic = Args.hasFlag(OPT_omagic, OPT_no_omagic, false); Config->OptRemarksFilename = Args.getLastArgValue(OPT_opt_remarks_filename); Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness); Config->Optimize = args::getInteger(Args, OPT_O, 1); Config->OrphanHandling = getOrphanHandling(Args); Config->OutputFile = Args.getLastArgValue(OPT_o); Config->Pie = Args.hasFlag(OPT_pie, OPT_nopie, false); Config->PrintGcSections = Args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false); Config->Rpath = getRpath(Args); Config->Relocatable = Args.hasArg(OPT_relocatable); Config->SaveTemps = Args.hasArg(OPT_save_temps); Config->SearchPaths = args::getStrings(Args, OPT_library_path); Config->SectionStartMap = getSectionStartMap(Args); Config->Shared = Args.hasArg(OPT_shared); Config->SingleRoRx = Args.hasArg(OPT_no_rosegment); Config->SoName = Args.getLastArgValue(OPT_soname); Config->SortSection = getSortSection(Args); Config->Strip = getStrip(Args); Config->Sysroot = Args.getLastArgValue(OPT_sysroot); Config->Target1Rel = Args.hasFlag(OPT_target1_rel, OPT_target1_abs, false); Config->Target2 = getTarget2(Args); Config->ThinLTOCacheDir = Args.getLastArgValue(OPT_thinlto_cache_dir); Config->ThinLTOCachePolicy = CHECK( parseCachePruningPolicy(Args.getLastArgValue(OPT_thinlto_cache_policy)), "--thinlto-cache-policy: invalid cache policy"); Config->ThinLTOJobs = args::getInteger(Args, OPT_thinlto_jobs, -1u); ThreadsEnabled = Args.hasFlag(OPT_threads, OPT_no_threads, true); Config->Trace = Args.hasArg(OPT_trace); Config->Undefined = args::getStrings(Args, OPT_undefined); Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args); Config->Verbose = Args.hasArg(OPT_verbose); errorHandler().Verbose = Config->Verbose; Config->WarnCommon = Args.hasArg(OPT_warn_common); Config->ZCombreloc = !hasZOption(Args, "nocombreloc"); Config->ZExecstack = hasZOption(Args, "execstack"); Config->ZHazardplt = hasZOption(Args, "hazardplt"); Config->ZNocopyreloc = hasZOption(Args, "nocopyreloc"); Config->ZNodelete = hasZOption(Args, "nodelete"); Config->ZNodlopen = hasZOption(Args, "nodlopen"); Config->ZNow = hasZOption(Args, "now"); Config->ZOrigin = hasZOption(Args, "origin"); Config->ZRelro = !hasZOption(Args, "norelro"); Config->ZRetpolineplt = hasZOption(Args, "retpolineplt"); Config->ZRodynamic = hasZOption(Args, "rodynamic"); Config->ZStackSize = args::getZOptionValue(Args, OPT_z, "stack-size", 0); Config->ZText = !hasZOption(Args, "notext"); Config->ZWxneeded = hasZOption(Args, "wxneeded"); // Parse LTO plugin-related options for compatibility with gold. for (auto *Arg : Args.filtered(OPT_plugin_opt, OPT_plugin_opt_eq)) { StringRef S = Arg->getValue(); if (S == "disable-verify") Config->DisableVerify = true; else if (S == "save-temps") Config->SaveTemps = true; else if (S.startswith("O")) Config->LTOO = parseInt(S.substr(1), Arg); else if (S.startswith("lto-partitions=")) Config->LTOPartitions = parseInt(S.substr(15), Arg); else if (S.startswith("jobs=")) Config->ThinLTOJobs = parseInt(S.substr(5), Arg); else if (!S.startswith("/") && !S.startswith("-fresolution=") && !S.startswith("-pass-through=") && !S.startswith("mcpu=") && !S.startswith("thinlto") && S != "-function-sections" && S != "-data-sections") error(Arg->getSpelling() + ": unknown option: " + S); } if (Config->LTOO > 3) error("invalid optimization level for LTO: " + Twine(Config->LTOO)); if (Config->LTOPartitions == 0) error("--lto-partitions: number of threads must be > 0"); if (Config->ThinLTOJobs == 0) error("--thinlto-jobs: number of threads must be > 0"); // Parse ELF{32,64}{LE,BE} and CPU type. if (auto *Arg = Args.getLastArg(OPT_m)) { StringRef S = Arg->getValue(); std::tie(Config->EKind, Config->EMachine, Config->OSABI) = parseEmulation(S); Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32"); Config->Emulation = S; } // Parse -hash-style={sysv,gnu,both}. if (auto *Arg = Args.getLastArg(OPT_hash_style)) { StringRef S = Arg->getValue(); if (S == "sysv") Config->SysvHash = true; else if (S == "gnu") Config->GnuHash = true; else if (S == "both") Config->SysvHash = Config->GnuHash = true; else error("unknown -hash-style: " + S); } if (Args.hasArg(OPT_print_map)) Config->MapFile = "-"; // --omagic is an option to create old-fashioned executables in which // .text segments are writable. Today, the option is still in use to // create special-purpose programs such as boot loaders. It doesn't // make sense to create PT_GNU_RELRO for such executables. if (Config->Omagic) Config->ZRelro = false; std::tie(Config->BuildId, Config->BuildIdVector) = getBuildId(Args); if (auto *Arg = Args.getLastArg(OPT_pack_dyn_relocs_eq)) { StringRef S = Arg->getValue(); if (S == "android") Config->AndroidPackDynRelocs = true; else if (S != "none") error("unknown -pack-dyn-relocs format: " + S); } if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file)) if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue())) Config->SymbolOrderingFile = args::getLines(*Buffer); // If --retain-symbol-file is used, we'll keep only the symbols listed in // the file and discard all others. if (auto *Arg = Args.getLastArg(OPT_retain_symbols_file)) { Config->DefaultSymbolVersion = VER_NDX_LOCAL; if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue())) for (StringRef S : args::getLines(*Buffer)) Config->VersionScriptGlobals.push_back( {S, /*IsExternCpp*/ false, /*HasWildcard*/ false}); } bool HasExportDynamic = Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false); // Parses -dynamic-list and -export-dynamic-symbol. They make some // symbols private. Note that -export-dynamic takes precedence over them // as it says all symbols should be exported. if (!HasExportDynamic) { for (auto *Arg : Args.filtered(OPT_dynamic_list)) if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue())) readDynamicList(*Buffer); for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol)) Config->DynamicList.push_back( {Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false}); } for (auto *Arg : Args.filtered(OPT_version_script)) if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue())) readVersionScript(*Buffer); } // Some Config members do not directly correspond to any particular // command line options, but computed based on other Config values. // This function initialize such members. See Config.h for the details // of these values. static void setConfigs() { ELFKind Kind = Config->EKind; uint16_t Machine = Config->EMachine; // There is an ILP32 ABI for x86-64, although it's not very popular. // It is called the x32 ABI. bool IsX32 = (Kind == ELF32LEKind && Machine == EM_X86_64); Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs); Config->Is64 = (Kind == ELF64LEKind || Kind == ELF64BEKind); Config->IsLE = (Kind == ELF32LEKind || Kind == ELF64LEKind); Config->Endianness = Config->IsLE ? support::endianness::little : support::endianness::big; Config->IsMips64EL = (Kind == ELF64LEKind && Machine == EM_MIPS); Config->IsRela = Config->Is64 || IsX32 || Config->MipsN32Abi; Config->Pic = Config->Pie || Config->Shared; Config->Wordsize = Config->Is64 ? 8 : 4; } // Returns a value of "-format" option. static bool getBinaryOption(StringRef S) { if (S == "binary") return true; if (S == "elf" || S == "default") return false; error("unknown -format value: " + S + " (supported formats: elf, default, binary)"); return false; } void LinkerDriver::createFiles(opt::InputArgList &Args) { for (auto *Arg : Args) { switch (Arg->getOption().getUnaliasedOption().getID()) { case OPT_library: addLibrary(Arg->getValue()); break; case OPT_INPUT: addFile(Arg->getValue(), /*WithLOption=*/false); break; case OPT_script: if (Optional<std::string> Path = searchLinkerScript(Arg->getValue())) { if (Optional<MemoryBufferRef> MB = readFile(*Path)) readLinkerScript(*MB); break; } error(Twine("cannot find linker script ") + Arg->getValue()); break; case OPT_as_needed: Config->AsNeeded = true; break; case OPT_format: InBinary = getBinaryOption(Arg->getValue()); break; case OPT_no_as_needed: Config->AsNeeded = false; break; case OPT_Bstatic: Config->Static = true; break; case OPT_Bdynamic: Config->Static = false; break; case OPT_whole_archive: InWholeArchive = true; break; case OPT_no_whole_archive: InWholeArchive = false; break; case OPT_start_lib: InLib = true; break; case OPT_end_lib: InLib = false; break; } } if (Files.empty() && errorCount() == 0) error("no input files"); } // If -m <machine_type> was not given, infer it from object files. void LinkerDriver::inferMachineType() { if (Config->EKind != ELFNoneKind) return; for (InputFile *F : Files) { if (F->EKind == ELFNoneKind) continue; Config->EKind = F->EKind; Config->EMachine = F->EMachine; Config->OSABI = F->OSABI; Config->MipsN32Abi = Config->EMachine == EM_MIPS && isMipsN32Abi(F); return; } error("target emulation unknown: -m or at least one .o file required"); } // Parse -z max-page-size=<value>. The default value is defined by // each target. static uint64_t getMaxPageSize(opt::InputArgList &Args) { uint64_t Val = args::getZOptionValue(Args, OPT_z, "max-page-size", Target->DefaultMaxPageSize); if (!isPowerOf2_64(Val)) error("max-page-size: value isn't a power of 2"); return Val; } // Parses -image-base option. static Optional<uint64_t> getImageBase(opt::InputArgList &Args) { // Because we are using "Config->MaxPageSize" here, this function has to be // called after the variable is initialized. auto *Arg = Args.getLastArg(OPT_image_base); if (!Arg) return None; StringRef S = Arg->getValue(); uint64_t V; if (!to_integer(S, V)) { error("-image-base: number expected, but got " + S); return 0; } if ((V % Config->MaxPageSize) != 0) warn("-image-base: address isn't multiple of page size: " + S); return V; } // Parses `--exclude-libs=lib,lib,...`. // The library names may be delimited by commas or colons. static DenseSet<StringRef> getExcludeLibs(opt::InputArgList &Args) { DenseSet<StringRef> Ret; for (auto *Arg : Args.filtered(OPT_exclude_libs)) { StringRef S = Arg->getValue(); for (;;) { size_t Pos = S.find_first_of(",:"); if (Pos == StringRef::npos) break; Ret.insert(S.substr(0, Pos)); S = S.substr(Pos + 1); } Ret.insert(S); } return Ret; } static Optional<StringRef> getArchiveName(InputFile *File) { if (isa<ArchiveFile>(File)) return File->getName(); if (!File->ArchiveName.empty()) return File->ArchiveName; return None; } // Handles the -exclude-libs option. If a static library file is specified // by the -exclude-libs option, all public symbols from the archive become // private unless otherwise specified by version scripts or something. // A special library name "ALL" means all archive files. // // This is not a popular option, but some programs such as bionic libc use it. template <class ELFT> static void excludeLibs(opt::InputArgList &Args, ArrayRef<InputFile *> Files) { DenseSet<StringRef> Libs = getExcludeLibs(Args); bool All = Libs.count("ALL"); for (InputFile *File : Files) if (Optional<StringRef> Archive = getArchiveName(File)) if (All || Libs.count(path::filename(*Archive))) for (Symbol *Sym : File->getSymbols()) if (!Sym->isLocal()) Sym->VersionId = VER_NDX_LOCAL; } // Do actual linking. Note that when this function is called, // all linker scripts have already been parsed. template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) { Target = getTarget(); Config->MaxPageSize = getMaxPageSize(Args); Config->ImageBase = getImageBase(Args); // If a -hash-style option was not given, set to a default value, // which varies depending on the target. if (!Args.hasArg(OPT_hash_style)) { if (Config->EMachine == EM_MIPS) Config->SysvHash = true; else Config->SysvHash = Config->GnuHash = true; } // Default output filename is "a.out" by the Unix tradition. if (Config->OutputFile.empty()) Config->OutputFile = "a.out"; // Fail early if the output file or map file is not writable. If a user has a // long link, e.g. due to a large LTO link, they do not wish to run it and // find that it failed because there was a mistake in their command-line. if (auto E = tryCreateFile(Config->OutputFile)) error("cannot open output file " + Config->OutputFile + ": " + E.message()); if (auto E = tryCreateFile(Config->MapFile)) error("cannot open map file " + Config->MapFile + ": " + E.message()); if (errorCount()) return; // Use default entry point name if no name was given via the command // line nor linker scripts. For some reason, MIPS entry point name is // different from others. Config->WarnMissingEntry = (!Config->Entry.empty() || (!Config->Shared && !Config->Relocatable)); if (Config->Entry.empty() && !Config->Relocatable) Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start"; // Handle --trace-symbol. for (auto *Arg : Args.filtered(OPT_trace_symbol)) Symtab->trace(Arg->getValue()); // Add all files to the symbol table. This will add almost all // symbols that we need to the symbol table. for (InputFile *F : Files) Symtab->addFile<ELFT>(F); // Process -defsym option. for (auto *Arg : Args.filtered(OPT_defsym)) { StringRef From; StringRef To; std::tie(From, To) = StringRef(Arg->getValue()).split('='); readDefsym(From, MemoryBufferRef(To, "-defsym")); } // Now that we have every file, we can decide if we will need a // dynamic symbol table. // We need one if we were asked to export dynamic symbols or if we are // producing a shared library. // We also need one if any shared libraries are used and for pie executables // (probably because the dynamic linker needs it). Config->HasDynSymTab = !SharedFiles.empty() || Config->Pic || Config->ExportDynamic; // Some symbols (such as __ehdr_start) are defined lazily only when there // are undefined symbols for them, so we add these to trigger that logic. for (StringRef Sym : Script->ReferencedSymbols) Symtab->addUndefined<ELFT>(Sym); // Handle the `--undefined <sym>` options. for (StringRef S : Config->Undefined) Symtab->fetchIfLazy<ELFT>(S); // If an entry symbol is in a static archive, pull out that file now // to complete the symbol table. After this, no new names except a // few linker-synthesized ones will be added to the symbol table. Symtab->fetchIfLazy<ELFT>(Config->Entry); // Return if there were name resolution errors. if (errorCount()) return; // Handle undefined symbols in DSOs. if (!Config->Shared) Symtab->scanShlibUndefined<ELFT>(); // Handle the -exclude-libs option. if (Args.hasArg(OPT_exclude_libs)) excludeLibs<ELFT>(Args, Files); // Create ElfHeader early. We need a dummy section in // addReservedSymbols to mark the created symbols as not absolute. Out::ElfHeader = make<OutputSection>("", 0, SHF_ALLOC); Out::ElfHeader->Size = sizeof(typename ELFT::Ehdr); // We need to create some reserved symbols such as _end. Create them. if (!Config->Relocatable) addReservedSymbols(); // Apply version scripts. // // For a relocatable output, version scripts don't make sense, and // parsing a symbol version string (e.g. dropping "@ver1" from a symbol // name "foo@ver1") rather do harm, so we don't call this if -r is given. if (!Config->Relocatable) Symtab->scanVersionScript(); // Create wrapped symbols for -wrap option. for (auto *Arg : Args.filtered(OPT_wrap)) Symtab->addSymbolWrap<ELFT>(Arg->getValue()); Symtab->addCombinedLTOObject<ELFT>(); if (errorCount()) return; // Apply symbol renames for -wrap. Symtab->applySymbolWrap(); // Now that we have a complete list of input files. // Beyond this point, no new files are added. // Aggregate all input sections into one place. for (InputFile *F : ObjectFiles) for (InputSectionBase *S : F->getSections()) if (S && S != &InputSection::Discarded) InputSections.push_back(S); for (BinaryFile *F : BinaryFiles) for (InputSectionBase *S : F->getSections()) InputSections.push_back(cast<InputSection>(S)); // We do not want to emit debug sections if --strip-all // or -strip-debug are given. if (Config->Strip != StripPolicy::None) llvm::erase_if(InputSections, [](InputSectionBase *S) { return S->Name.startswith(".debug") || S->Name.startswith(".zdebug"); }); Config->EFlags = Target->calcEFlags(); if (Config->EMachine == EM_ARM) { // FIXME: These warnings can be removed when lld only uses these features // when the input objects have been compiled with an architecture that // supports them. if (Config->ARMHasBlx == false) warn("lld uses blx instruction, no object with architecture supporting " "feature detected."); if (Config->ARMJ1J2BranchEncoding == false) warn("lld uses extended branch encoding, no object with architecture " "supporting feature detected."); if (Config->ARMHasMovtMovw == false) warn("lld may use movt/movw, no object with architecture supporting " "feature detected."); } // This adds a .comment section containing a version string. We have to add it // before decompressAndMergeSections because the .comment section is a // mergeable section. if (!Config->Relocatable) InputSections.push_back(createCommentSection()); // Do size optimizations: garbage collection, merging of SHF_MERGE sections // and identical code folding. markLive<ELFT>(); decompressSections(); mergeSections(); if (Config->ICF) doIcf<ELFT>(); // Write the result to the file. writeResult<ELFT>(); }