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Diffstat (limited to 'contrib/llvm/tools/lld/ELF/Driver.cpp')
| -rw-r--r-- | contrib/llvm/tools/lld/ELF/Driver.cpp | 1651 |
1 files changed, 1651 insertions, 0 deletions
diff --git a/contrib/llvm/tools/lld/ELF/Driver.cpp b/contrib/llvm/tools/lld/ELF/Driver.cpp new file mode 100644 index 000000000000..407f1734f143 --- /dev/null +++ b/contrib/llvm/tools/lld/ELF/Driver.cpp @@ -0,0 +1,1651 @@ +//===- 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 "MarkLive.h" +#include "OutputSections.h" +#include "ScriptParser.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/Strings.h" +#include "lld/Common/TargetOptionsCommandFlags.h" +#include "lld/Common/Threads.h" +#include "lld/Common/Version.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/StringExtras.h" +#include "llvm/ADT/StringSwitch.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Compression.h" +#include "llvm/Support/LEB128.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 llvm::support; + +using namespace lld; +using namespace lld::elf; + +Configuration *elf::Config; +LinkerDriver *elf::Driver; + +static void setConfigs(opt::InputArgList &Args); + +bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly, + raw_ostream &Error) { + errorHandler().LogName = args::getFilenameWithoutExe(Args[0]); + errorHandler().ErrorLimitExceededMsg = + "too many errors emitted, stopping now (use " + "-error-limit=0 to see all errors)"; + errorHandler().ErrorOS = &Error; + errorHandler().ExitEarly = CanExitEarly; + errorHandler().ColorDiagnostics = Error.has_colors(); + + InputSections.clear(); + OutputSections.clear(); + BinaryFiles.clear(); + BitcodeFiles.clear(); + ObjectFiles.clear(); + SharedFiles.clear(); + + Config = make<Configuration>(); + Driver = make<LinkerDriver>(); + Script = make<LinkerScript>(); + Symtab = make<SymbolTable>(); + + Tar = nullptr; + memset(&In, 0, sizeof(In)); + + Config->ProgName = Args[0]; + + Driver->main(Args); + + // 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 (CanExitEarly) + 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", "aarch64_elf64_le_vec", + {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("elf32lriscv", {ELF32LEKind, EM_RISCV}) + .Cases("elf32ppc", "elf32ppclinux", {ELF32BEKind, EM_PPC}) + .Case("elf64btsmip", {ELF64BEKind, EM_MIPS}) + .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS}) + .Case("elf64lriscv", {ELF64LEKind, EM_RISCV}) + .Case("elf64ppc", {ELF64BEKind, EM_PPC64}) + .Case("elf64lppc", {ELF64LEKind, 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 (Config->FormatBinary) { + 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->Static || 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; + case file_magic::bitcode: + case file_magic::elf_relocatable: + if (InLib) + Files.push_back(make<LazyObjFile>(MBRef, "", 0)); + else + Files.push_back(createObjectFile(MBRef)); + break; + default: + error(Path + ": unknown file type"); + } +} + +// 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() { + InitializeAllTargets(); + InitializeAllTargetMCs(); + InitializeAllAsmPrinters(); + InitializeAllAsmParsers(); +} + +// Some command line options or some combinations of them are not allowed. +// This function checks for such errors. +static void checkOptions() { + // 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->TocOptimize && Config->EMachine != EM_PPC64) + error("--toc-optimize is only supported on the PowerPC64 target"); + + 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->GdbIndex) + error("-r and --gdb-index may not be used together"); + if (Config->ICF != ICFLevel::None) + error("-r and --icf may not be used together"); + if (Config->Pie) + error("-r and -pie may not be used together"); + } + + if (Config->ExecuteOnly) { + if (Config->EMachine != EM_AARCH64) + error("-execute-only is only supported on AArch64 targets"); + + if (Config->SingleRoRx && !Script->HasSectionsCommand) + error("-execute-only and -no-rosegment cannot 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; +} + +static bool getZFlag(opt::InputArgList &Args, StringRef K1, StringRef K2, + bool Default) { + for (auto *Arg : Args.filtered_reverse(OPT_z)) { + if (K1 == Arg->getValue()) + return true; + if (K2 == Arg->getValue()) + return false; + } + return Default; +} + +static bool isKnownZFlag(StringRef S) { + return S == "combreloc" || S == "copyreloc" || S == "defs" || + S == "execstack" || S == "global" || S == "hazardplt" || + S == "ifunc-noplt" || + S == "initfirst" || S == "interpose" || + S == "keep-text-section-prefix" || S == "lazy" || S == "muldefs" || + S == "nocombreloc" || S == "nocopyreloc" || S == "nodefaultlib" || + S == "nodelete" || S == "nodlopen" || S == "noexecstack" || + S == "nokeep-text-section-prefix" || S == "norelro" || S == "notext" || + S == "now" || S == "origin" || S == "relro" || S == "retpolineplt" || + S == "rodynamic" || S == "text" || S == "wxneeded" || + S.startswith("max-page-size=") || S.startswith("stack-size="); +} + +// Report an error for an unknown -z option. +static void checkZOptions(opt::InputArgList &Args) { + for (auto *Arg : Args.filtered(OPT_z)) + if (!isKnownZFlag(Arg->getValue())) + error("unknown -z value: " + StringRef(Arg->getValue())); +} + +void LinkerDriver::main(ArrayRef<const char *> ArgsArr) { + 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(); + 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)"); + + 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 = std::move(*ErrOrWriter); + Tar->append("response.txt", createResponseFile(Args)); + Tar->append("version.txt", getLLDVersion() + "\n"); + } else { + error("--reproduce: " + toString(ErrOrWriter.takeError())); + } + } + + readConfigs(Args); + checkZOptions(Args); + + // 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; + + initLLVM(); + createFiles(Args); + if (errorCount()) + return; + + inferMachineType(); + setConfigs(Args); + checkOptions(); + 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) { + 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) { + StringRef S = Args.getLastArgValue(OPT_oformat, "elf"); + if (S == "binary") + return true; + if (!S.startswith("elf")) + 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 ICFLevel getICF(opt::InputArgList &Args) { + auto *Arg = Args.getLastArg(OPT_icf_none, OPT_icf_safe, OPT_icf_all); + if (!Arg || Arg->getOption().getID() == OPT_icf_none) + return ICFLevel::None; + if (Arg->getOption().getID() == OPT_icf_safe) + return ICFLevel::Safe; + return ICFLevel::All; +} + +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 == "fast") + return {BuildIdKind::Fast, {}}; + 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 std::pair<bool, bool> getPackDynRelocs(opt::InputArgList &Args) { + StringRef S = Args.getLastArgValue(OPT_pack_dyn_relocs, "none"); + if (S == "android") + return {true, false}; + if (S == "relr") + return {false, true}; + if (S == "android+relr") + return {true, true}; + + if (S != "none") + error("unknown -pack-dyn-relocs format: " + S); + return {false, false}; +} + +static void readCallGraph(MemoryBufferRef MB) { + // Build a map from symbol name to section + DenseMap<StringRef, Symbol *> Map; + for (InputFile *File : ObjectFiles) + for (Symbol *Sym : File->getSymbols()) + Map[Sym->getName()] = Sym; + + auto FindSection = [&](StringRef Name) -> InputSectionBase * { + Symbol *Sym = Map.lookup(Name); + if (!Sym) { + if (Config->WarnSymbolOrdering) + warn(MB.getBufferIdentifier() + ": no such symbol: " + Name); + return nullptr; + } + maybeWarnUnorderableSymbol(Sym); + + if (Defined *DR = dyn_cast_or_null<Defined>(Sym)) + return dyn_cast_or_null<InputSectionBase>(DR->Section); + return nullptr; + }; + + for (StringRef Line : args::getLines(MB)) { + SmallVector<StringRef, 3> Fields; + Line.split(Fields, ' '); + uint64_t Count; + + if (Fields.size() != 3 || !to_integer(Fields[2], Count)) { + error(MB.getBufferIdentifier() + ": parse error"); + return; + } + + if (InputSectionBase *From = FindSection(Fields[0])) + if (InputSectionBase *To = FindSection(Fields[1])) + Config->CallGraphProfile[std::make_pair(From, To)] += Count; + } +} + +template <class ELFT> static void readCallGraphsFromObjectFiles() { + for (auto File : ObjectFiles) { + auto *Obj = cast<ObjFile<ELFT>>(File); + + for (const Elf_CGProfile_Impl<ELFT> &CGPE : Obj->CGProfile) { + auto *FromSym = dyn_cast<Defined>(&Obj->getSymbol(CGPE.cgp_from)); + auto *ToSym = dyn_cast<Defined>(&Obj->getSymbol(CGPE.cgp_to)); + if (!FromSym || !ToSym) + continue; + + auto *From = dyn_cast_or_null<InputSectionBase>(FromSym->Section); + auto *To = dyn_cast_or_null<InputSectionBase>(ToSym->Section); + if (From && To) + Config->CallGraphProfile[{From, To}] += CGPE.cgp_weight; + } + } +} + +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 std::pair<StringRef, StringRef> getOldNewOptions(opt::InputArgList &Args, + unsigned Id) { + auto *Arg = Args.getLastArg(Id); + if (!Arg) + return {"", ""}; + + StringRef S = Arg->getValue(); + std::pair<StringRef, StringRef> Ret = S.split(';'); + if (Ret.second.empty()) + error(Arg->getSpelling() + " expects 'old;new' format, but got " + S); + return Ret; +} + +// Parse the symbol ordering file and warn for any duplicate entries. +static std::vector<StringRef> getSymbolOrderingFile(MemoryBufferRef MB) { + SetVector<StringRef> Names; + for (StringRef S : args::getLines(MB)) + if (!Names.insert(S) && Config->WarnSymbolOrdering) + warn(MB.getBufferIdentifier() + ": duplicate ordered symbol: " + S); + + return Names.takeVector(); +} + +static void parseClangOption(StringRef Opt, const Twine &Msg) { + std::string Err; + raw_string_ostream OS(Err); + + const char *Argv[] = {Config->ProgName.data(), Opt.data()}; + if (cl::ParseCommandLineOptions(2, Argv, "", &OS)) + return; + OS.flush(); + error(Msg + ": " + StringRef(Err).trim()); +} + +// Initializes Config members by the command line options. +void LinkerDriver::readConfigs(opt::InputArgList &Args) { + errorHandler().Verbose = Args.hasArg(OPT_verbose); + errorHandler().FatalWarnings = + Args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false); + ThreadsEnabled = Args.hasFlag(OPT_threads, OPT_no_threads, true); + + Config->AllowMultipleDefinition = + Args.hasFlag(OPT_allow_multiple_definition, + OPT_no_allow_multiple_definition, false) || + hasZOption(Args, "muldefs"); + Config->AuxiliaryList = args::getStrings(Args, OPT_auxiliary); + Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic); + Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions); + Config->CheckSections = + Args.hasFlag(OPT_check_sections, OPT_no_check_sections, true); + Config->Chroot = Args.getLastArgValue(OPT_chroot); + Config->CompressDebugSections = getCompressDebugSections(Args); + Config->Cref = Args.hasFlag(OPT_cref, OPT_no_cref, false); + 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->DwoDir = Args.getLastArgValue(OPT_plugin_opt_dwo_dir_eq); + Config->DynamicLinker = getDynamicLinker(Args); + Config->EhFrameHdr = + Args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false); + Config->EmitLLVM = Args.hasArg(OPT_plugin_opt_emit_llvm, false); + Config->EmitRelocs = Args.hasArg(OPT_emit_relocs); + Config->CallGraphProfileSort = Args.hasFlag( + OPT_call_graph_profile_sort, OPT_no_call_graph_profile_sort, true); + Config->EnableNewDtags = + Args.hasFlag(OPT_enable_new_dtags, OPT_disable_new_dtags, true); + Config->Entry = Args.getLastArgValue(OPT_entry); + Config->ExecuteOnly = + Args.hasFlag(OPT_execute_only, OPT_no_execute_only, false); + Config->ExportDynamic = + Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, 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->GnuUnique = Args.hasFlag(OPT_gnu_unique, OPT_no_gnu_unique, true); + Config->GdbIndex = Args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false); + Config->ICF = getICF(Args); + Config->IgnoreDataAddressEquality = + Args.hasArg(OPT_ignore_data_address_equality); + Config->IgnoreFunctionAddressEquality = + Args.hasArg(OPT_ignore_function_address_equality); + Config->Init = Args.getLastArgValue(OPT_init, "_init"); + Config->LTOAAPipeline = Args.getLastArgValue(OPT_lto_aa_pipeline); + Config->LTODebugPassManager = Args.hasArg(OPT_lto_debug_pass_manager); + Config->LTONewPassManager = Args.hasArg(OPT_lto_new_pass_manager); + Config->LTONewPmPasses = Args.getLastArgValue(OPT_lto_newpm_passes); + Config->LTOO = args::getInteger(Args, OPT_lto_O, 2); + Config->LTOObjPath = Args.getLastArgValue(OPT_plugin_opt_obj_path_eq); + Config->LTOPartitions = args::getInteger(Args, OPT_lto_partitions, 1); + Config->LTOSampleProfile = Args.getLastArgValue(OPT_lto_sample_profile); + Config->MapFile = Args.getLastArgValue(OPT_Map); + Config->MipsGotSize = args::getInteger(Args, OPT_mips_got_size, 0xfff0); + Config->MergeArmExidx = + Args.hasFlag(OPT_merge_exidx_entries, OPT_no_merge_exidx_entries, true); + 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_no_pie, false); + Config->PrintIcfSections = + Args.hasFlag(OPT_print_icf_sections, OPT_no_print_icf_sections, 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->SplitStackAdjustSize = args::getInteger(Args, OPT_split_stack_adjust_size, 16384); + 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->ThinLTOEmitImportsFiles = + Args.hasArg(OPT_plugin_opt_thinlto_emit_imports_files); + Config->ThinLTOIndexOnly = Args.hasArg(OPT_plugin_opt_thinlto_index_only) || + Args.hasArg(OPT_plugin_opt_thinlto_index_only_eq); + Config->ThinLTOIndexOnlyArg = + Args.getLastArgValue(OPT_plugin_opt_thinlto_index_only_eq); + Config->ThinLTOJobs = args::getInteger(Args, OPT_thinlto_jobs, -1u); + Config->ThinLTOObjectSuffixReplace = + getOldNewOptions(Args, OPT_plugin_opt_thinlto_object_suffix_replace_eq); + Config->ThinLTOPrefixReplace = + getOldNewOptions(Args, OPT_plugin_opt_thinlto_prefix_replace_eq); + Config->Trace = Args.hasArg(OPT_trace); + Config->Undefined = args::getStrings(Args, OPT_undefined); + Config->UndefinedVersion = + Args.hasFlag(OPT_undefined_version, OPT_no_undefined_version, true); + Config->UseAndroidRelrTags = Args.hasFlag( + OPT_use_android_relr_tags, OPT_no_use_android_relr_tags, false); + Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args); + Config->WarnBackrefs = + Args.hasFlag(OPT_warn_backrefs, OPT_no_warn_backrefs, false); + Config->WarnCommon = Args.hasFlag(OPT_warn_common, OPT_no_warn_common, false); + Config->WarnIfuncTextrel = + Args.hasFlag(OPT_warn_ifunc_textrel, OPT_no_warn_ifunc_textrel, false); + Config->WarnSymbolOrdering = + Args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true); + Config->ZCombreloc = getZFlag(Args, "combreloc", "nocombreloc", true); + Config->ZCopyreloc = getZFlag(Args, "copyreloc", "nocopyreloc", true); + Config->ZExecstack = getZFlag(Args, "execstack", "noexecstack", false); + Config->ZGlobal = hasZOption(Args, "global"); + Config->ZHazardplt = hasZOption(Args, "hazardplt"); + Config->ZIfuncnoplt = hasZOption(Args, "ifunc-noplt"); + Config->ZInitfirst = hasZOption(Args, "initfirst"); + Config->ZInterpose = hasZOption(Args, "interpose"); + Config->ZKeepTextSectionPrefix = getZFlag( + Args, "keep-text-section-prefix", "nokeep-text-section-prefix", false); + Config->ZNodefaultlib = hasZOption(Args, "nodefaultlib"); + Config->ZNodelete = hasZOption(Args, "nodelete"); + Config->ZNodlopen = hasZOption(Args, "nodlopen"); + Config->ZNow = getZFlag(Args, "now", "lazy", false); + Config->ZOrigin = hasZOption(Args, "origin"); + Config->ZRelro = getZFlag(Args, "relro", "norelro", true); + Config->ZRetpolineplt = hasZOption(Args, "retpolineplt"); + Config->ZRodynamic = hasZOption(Args, "rodynamic"); + Config->ZStackSize = args::getZOptionValue(Args, OPT_z, "stack-size", 0); + Config->ZText = getZFlag(Args, "text", "notext", true); + Config->ZWxneeded = hasZOption(Args, "wxneeded"); + + // Parse LTO options. + if (auto *Arg = Args.getLastArg(OPT_plugin_opt_mcpu_eq)) + parseClangOption(Saver.save("-mcpu=" + StringRef(Arg->getValue())), + Arg->getSpelling()); + + for (auto *Arg : Args.filtered(OPT_plugin_opt)) + parseClangOption(Arg->getValue(), Arg->getSpelling()); + + // Parse -mllvm options. + for (auto *Arg : Args.filtered(OPT_mllvm)) + parseClangOption(Arg->getValue(), Arg->getSpelling()); + + 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"); + + if (Config->SplitStackAdjustSize < 0) + error("--split-stack-adjust-size: size 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); + + std::tie(Config->AndroidPackDynRelocs, Config->RelrPackDynRelocs) = + getPackDynRelocs(Args); + + if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file)) + if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue())) + Config->SymbolOrderingFile = getSymbolOrderingFile(*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}); + } + + // If --export-dynamic-symbol=foo is given and symbol foo is defined in + // an object file in an archive file, that object file should be pulled + // out and linked. (It doesn't have to behave like that from technical + // point of view, but this is needed for compatibility with GNU.) + for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol)) + Config->Undefined.push_back(Arg->getValue()); + + for (auto *Arg : Args.filtered(OPT_version_script)) + if (Optional<std::string> Path = searchScript(Arg->getValue())) { + if (Optional<MemoryBufferRef> Buffer = readFile(*Path)) + readVersionScript(*Buffer); + } else { + error(Twine("cannot find version script ") + Arg->getValue()); + } +} + +// 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(opt::InputArgList &Args) { + ELFKind K = Config->EKind; + uint16_t M = Config->EMachine; + + Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs); + Config->Is64 = (K == ELF64LEKind || K == ELF64BEKind); + Config->IsLE = (K == ELF32LEKind || K == ELF64LEKind); + Config->Endianness = Config->IsLE ? endianness::little : endianness::big; + Config->IsMips64EL = (K == ELF64LEKind && M == EM_MIPS); + Config->Pic = Config->Pie || Config->Shared; + Config->PicThunk = Args.hasArg(OPT_pic_veneer, Config->Pic); + Config->Wordsize = Config->Is64 ? 8 : 4; + + // ELF defines two different ways to store relocation addends as shown below: + // + // Rel: Addends are stored to the location where relocations are applied. + // Rela: Addends are stored as part of relocation entry. + // + // In other words, Rela makes it easy to read addends at the price of extra + // 4 or 8 byte for each relocation entry. We don't know why ELF defined two + // different mechanisms in the first place, but this is how the spec is + // defined. + // + // You cannot choose which one, Rel or Rela, you want to use. Instead each + // ABI defines which one you need to use. The following expression expresses + // that. + Config->IsRela = M == EM_AARCH64 || M == EM_AMDGPU || M == EM_HEXAGON || + M == EM_PPC || M == EM_PPC64 || M == EM_RISCV || + M == EM_X86_64; + + // If the output uses REL relocations we must store the dynamic relocation + // addends to the output sections. We also store addends for RELA relocations + // if --apply-dynamic-relocs is used. + // We default to not writing the addends when using RELA relocations since + // any standard conforming tool can find it in r_addend. + Config->WriteAddends = Args.hasFlag(OPT_apply_dynamic_relocs, + OPT_no_apply_dynamic_relocs, false) || + !Config->IsRela; + + Config->TocOptimize = + Args.hasFlag(OPT_toc_optimize, OPT_no_toc_optimize, M == EM_PPC64); +} + +// Returns a value of "-format" option. +static bool isFormatBinary(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 --{push,pop}-state. + std::vector<std::tuple<bool, bool, bool>> Stack; + + // Iterate over argv to process input files and positional arguments. + 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_defsym: { + StringRef From; + StringRef To; + std::tie(From, To) = StringRef(Arg->getValue()).split('='); + if (From.empty() || To.empty()) + error("-defsym: syntax error: " + StringRef(Arg->getValue())); + else + readDefsym(From, MemoryBufferRef(To, "-defsym")); + break; + } + case OPT_script: + if (Optional<std::string> Path = searchScript(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: + Config->FormatBinary = isFormatBinary(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_just_symbols: + if (Optional<MemoryBufferRef> MB = readFile(Arg->getValue())) { + Files.push_back(createObjectFile(*MB)); + Files.back()->JustSymbols = true; + } + break; + case OPT_start_group: + if (InputFile::IsInGroup) + error("nested --start-group"); + InputFile::IsInGroup = true; + break; + case OPT_end_group: + if (!InputFile::IsInGroup) + error("stray --end-group"); + InputFile::IsInGroup = false; + ++InputFile::NextGroupId; + break; + case OPT_start_lib: + if (InLib) + error("nested --start-lib"); + if (InputFile::IsInGroup) + error("may not nest --start-lib in --start-group"); + InLib = true; + InputFile::IsInGroup = true; + break; + case OPT_end_lib: + if (!InLib) + error("stray --end-lib"); + InLib = false; + InputFile::IsInGroup = false; + ++InputFile::NextGroupId; + break; + case OPT_push_state: + Stack.emplace_back(Config->AsNeeded, Config->Static, InWholeArchive); + break; + case OPT_pop_state: + if (Stack.empty()) { + error("unbalanced --push-state/--pop-state"); + break; + } + std::tie(Config->AsNeeded, Config->Static, InWholeArchive) = Stack.back(); + Stack.pop_back(); + 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; +} + +// 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) { + DenseSet<StringRef> Libs = getExcludeLibs(Args); + bool All = Libs.count("ALL"); + + auto Visit = [&](InputFile *File) { + if (!File->ArchiveName.empty()) + if (All || Libs.count(path::filename(File->ArchiveName))) + for (Symbol *Sym : File->getSymbols()) + if (!Sym->isLocal() && Sym->File == File) + Sym->VersionId = VER_NDX_LOCAL; + }; + + for (InputFile *File : ObjectFiles) + Visit(File); + + for (BitcodeFile *File : BitcodeFiles) + Visit(File); +} + +// Force Sym to be entered in the output. Used for -u or equivalent. +template <class ELFT> static void handleUndefined(StringRef Name) { + Symbol *Sym = Symtab->find(Name); + if (!Sym) + return; + + // Since symbol S may not be used inside the program, LTO may + // eliminate it. Mark the symbol as "used" to prevent it. + Sym->IsUsedInRegularObj = true; + + if (Sym->isLazy()) + Symtab->fetchLazy<ELFT>(Sym); +} + +template <class ELFT> static void handleLibcall(StringRef Name) { + Symbol *Sym = Symtab->find(Name); + if (!Sym || !Sym->isLazy()) + return; + + MemoryBufferRef MB; + if (auto *LO = dyn_cast<LazyObject>(Sym)) + MB = LO->File->MB; + else + MB = cast<LazyArchive>(Sym)->getMemberBuffer(); + + if (isBitcode(MB)) + Symtab->fetchLazy<ELFT>(Sym); +} + +// If all references to a DSO happen to be weak, the DSO is not added +// to DT_NEEDED. If that happens, we need to eliminate shared symbols +// created from the DSO. Otherwise, they become dangling references +// that point to a non-existent DSO. +template <class ELFT> static void demoteSharedSymbols() { + for (Symbol *Sym : Symtab->getSymbols()) { + if (auto *S = dyn_cast<SharedSymbol>(Sym)) { + if (!S->getFile<ELFT>().IsNeeded) { + bool Used = S->Used; + replaceSymbol<Undefined>(S, nullptr, S->getName(), STB_WEAK, S->StOther, + S->Type); + S->Used = Used; + } + } + } +} + +// The section referred to by S is considered address-significant. Set the +// KeepUnique flag on the section if appropriate. +static void markAddrsig(Symbol *S) { + if (auto *D = dyn_cast_or_null<Defined>(S)) + if (D->Section) + // We don't need to keep text sections unique under --icf=all even if they + // are address-significant. + if (Config->ICF == ICFLevel::Safe || !(D->Section->Flags & SHF_EXECINSTR)) + D->Section->KeepUnique = true; +} + +// Record sections that define symbols mentioned in --keep-unique <symbol> +// and symbols referred to by address-significance tables. These sections are +// ineligible for ICF. +template <class ELFT> +static void findKeepUniqueSections(opt::InputArgList &Args) { + for (auto *Arg : Args.filtered(OPT_keep_unique)) { + StringRef Name = Arg->getValue(); + auto *D = dyn_cast_or_null<Defined>(Symtab->find(Name)); + if (!D || !D->Section) { + warn("could not find symbol " + Name + " to keep unique"); + continue; + } + D->Section->KeepUnique = true; + } + + // --icf=all --ignore-data-address-equality means that we can ignore + // the dynsym and address-significance tables entirely. + if (Config->ICF == ICFLevel::All && Config->IgnoreDataAddressEquality) + return; + + // Symbols in the dynsym could be address-significant in other executables + // or DSOs, so we conservatively mark them as address-significant. + for (Symbol *S : Symtab->getSymbols()) + if (S->includeInDynsym()) + markAddrsig(S); + + // Visit the address-significance table in each object file and mark each + // referenced symbol as address-significant. + for (InputFile *F : ObjectFiles) { + auto *Obj = cast<ObjFile<ELFT>>(F); + ArrayRef<Symbol *> Syms = Obj->getSymbols(); + if (Obj->AddrsigSec) { + ArrayRef<uint8_t> Contents = + check(Obj->getObj().getSectionContents(Obj->AddrsigSec)); + const uint8_t *Cur = Contents.begin(); + while (Cur != Contents.end()) { + unsigned Size; + const char *Err; + uint64_t SymIndex = decodeULEB128(Cur, &Size, Contents.end(), &Err); + if (Err) + fatal(toString(F) + ": could not decode addrsig section: " + Err); + markAddrsig(Syms[SymIndex]); + Cur += Size; + } + } else { + // If an object file does not have an address-significance table, + // conservatively mark all of its symbols as address-significant. + for (Symbol *S : Syms) + markAddrsig(S); + } + } +} + +template <class ELFT> static Symbol *addUndefined(StringRef Name) { + return Symtab->addUndefined<ELFT>(Name, STB_GLOBAL, STV_DEFAULT, 0, false, + nullptr); +} + +// The --wrap option is a feature to rename symbols so that you can write +// wrappers for existing functions. If you pass `-wrap=foo`, all +// occurrences of symbol `foo` are resolved to `wrap_foo` (so, you are +// expected to write `wrap_foo` function as a wrapper). The original +// symbol becomes accessible as `real_foo`, so you can call that from your +// wrapper. +// +// This data structure is instantiated for each -wrap option. +struct WrappedSymbol { + Symbol *Sym; + Symbol *Real; + Symbol *Wrap; +}; + +// Handles -wrap option. +// +// This function instantiates wrapper symbols. At this point, they seem +// like they are not being used at all, so we explicitly set some flags so +// that LTO won't eliminate them. +template <class ELFT> +static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &Args) { + std::vector<WrappedSymbol> V; + DenseSet<StringRef> Seen; + + for (auto *Arg : Args.filtered(OPT_wrap)) { + StringRef Name = Arg->getValue(); + if (!Seen.insert(Name).second) + continue; + + Symbol *Sym = Symtab->find(Name); + if (!Sym) + continue; + + Symbol *Real = addUndefined<ELFT>(Saver.save("__real_" + Name)); + Symbol *Wrap = addUndefined<ELFT>(Saver.save("__wrap_" + Name)); + V.push_back({Sym, Real, Wrap}); + + // We want to tell LTO not to inline symbols to be overwritten + // because LTO doesn't know the final symbol contents after renaming. + Real->CanInline = false; + Sym->CanInline = false; + + // Tell LTO not to eliminate these symbols. + Sym->IsUsedInRegularObj = true; + Wrap->IsUsedInRegularObj = true; + } + return V; +} + +// Do renaming for -wrap by updating pointers to symbols. +// +// When this function is executed, only InputFiles and symbol table +// contain pointers to symbol objects. We visit them to replace pointers, +// so that wrapped symbols are swapped as instructed by the command line. +template <class ELFT> static void wrapSymbols(ArrayRef<WrappedSymbol> Wrapped) { + DenseMap<Symbol *, Symbol *> Map; + for (const WrappedSymbol &W : Wrapped) { + Map[W.Sym] = W.Wrap; + Map[W.Real] = W.Sym; + } + + // Update pointers in input files. + parallelForEach(ObjectFiles, [&](InputFile *File) { + std::vector<Symbol *> &Syms = File->getMutableSymbols(); + for (size_t I = 0, E = Syms.size(); I != E; ++I) + if (Symbol *S = Map.lookup(Syms[I])) + Syms[I] = S; + }); + + // Update pointers in the symbol table. + for (const WrappedSymbol &W : Wrapped) + Symtab->wrap(W.Sym, W.Real, W.Wrap); +} + +static const char *LibcallRoutineNames[] = { +#define HANDLE_LIBCALL(code, name) name, +#include "llvm/IR/RuntimeLibcalls.def" +#undef HANDLE_LIBCALL +}; + +// 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(); + InX<ELFT>::VerSym = nullptr; + InX<ELFT>::VerNeed = nullptr; + + 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); + + // 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 Name : Script->ReferencedSymbols) + addUndefined<ELFT>(Name); + + // Handle the `--undefined <sym>` options. + for (StringRef S : Config->Undefined) + handleUndefined<ELFT>(S); + + // If an entry symbol is in a static archive, pull out that file now. + handleUndefined<ELFT>(Config->Entry); + + // If any of our inputs are bitcode files, the LTO code generator may create + // references to certain library functions that might not be explicit in the + // bitcode file's symbol table. If any of those library functions are defined + // in a bitcode file in an archive member, we need to arrange to use LTO to + // compile those archive members by adding them to the link beforehand. + // + // However, adding all libcall symbols to the link can have undesired + // consequences. For example, the libgcc implementation of + // __sync_val_compare_and_swap_8 on 32-bit ARM pulls in an .init_array entry + // that aborts the program if the Linux kernel does not support 64-bit + // atomics, which would prevent the program from running even if it does not + // use 64-bit atomics. + // + // Therefore, we only add libcall symbols to the link before LTO if we have + // to, i.e. if the symbol's definition is in bitcode. Any other required + // libcall symbols will be added to the link after LTO when we add the LTO + // object file to the link. + if (!BitcodeFiles.empty()) + for (const char *S : LibcallRoutineNames) + handleLibcall<ELFT>(S); + + // Return if there were name resolution errors. + if (errorCount()) + return; + + // Now when we read all script files, we want to finalize order of linker + // script commands, which can be not yet final because of INSERT commands. + Script->processInsertCommands(); + + // We want to declare linker script's symbols early, + // so that we can version them. + // They also might be exported if referenced by DSOs. + Script->declareSymbols(); + + // Handle the -exclude-libs option. + if (Args.hasArg(OPT_exclude_libs)) + excludeLibs<ELFT>(Args); + + // 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); + + // Create wrapped symbols for -wrap option. + std::vector<WrappedSymbol> Wrapped = addWrappedSymbols<ELFT>(Args); + + // 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(); + + // Do link-time optimization if given files are LLVM bitcode files. + // This compiles bitcode files into real object files. + // + // With this the symbol table should be complete. After this, no new names + // except a few linker-synthesized ones will be added to the symbol table. + Symtab->addCombinedLTOObject<ELFT>(); + if (errorCount()) + return; + + // If -thinlto-index-only is given, we should create only "index + // files" and not object files. Index file creation is already done + // in addCombinedLTOObject, so we are done if that's the case. + if (Config->ThinLTOIndexOnly) + return; + + // Likewise, --plugin-opt=emit-llvm is an option to make LTO create + // an output file in bitcode and exit, so that you can just get a + // combined bitcode file. + if (Config->EmitLLVM) + return; + + // Apply symbol renames for -wrap. + if (!Wrapped.empty()) + wrapSymbols<ELFT>(Wrapped); + + // 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"); + } + + // This adds a .comment section containing a version string. We have to add it + // before mergeSections 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. + splitSections<ELFT>(); + markLive<ELFT>(); + demoteSharedSymbols<ELFT>(); + mergeSections(); + if (Config->ICF != ICFLevel::None) { + findKeepUniqueSections<ELFT>(Args); + doIcf<ELFT>(); + } + + // Read the callgraph now that we know what was gced or icfed + if (Config->CallGraphProfileSort) { + if (auto *Arg = Args.getLastArg(OPT_call_graph_ordering_file)) + if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue())) + readCallGraph(*Buffer); + readCallGraphsFromObjectFiles<ELFT>(); + } + + // Write the result to the file. + writeResult<ELFT>(); +} |