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Diffstat (limited to 'contrib/llvm-project/lld/ELF/Driver.cpp')
| -rw-r--r-- | contrib/llvm-project/lld/ELF/Driver.cpp | 1912 |
1 files changed, 1912 insertions, 0 deletions
diff --git a/contrib/llvm-project/lld/ELF/Driver.cpp b/contrib/llvm-project/lld/ELF/Driver.cpp new file mode 100644 index 000000000000..81894e98f395 --- /dev/null +++ b/contrib/llvm-project/lld/ELF/Driver.cpp @@ -0,0 +1,1912 @@ +//===- Driver.cpp ---------------------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// 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 "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/Filesystem.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/GlobPattern.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); +static void readConfigs(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)); + + partitions = {Partition()}; + + SharedFile::vernauxNum = 0; + + 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()) { + // Check if all members are bitcode files. If not, ignore, which is the + // default action without the LTO hack described above. + for (const std::pair<MemoryBufferRef, uint64_t> &p : + getArchiveMembers(mbref)) + if (identify_magic(p.first.getBuffer()) != file_magic::bitcode) { + error(path + ": archive has no index; run ranlib to add one"); + return; + } + + for (const std::pair<MemoryBufferRef, uint64_t> &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->isStatic || 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( + make<SharedFile>(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->zText && config->zIfuncNoplt) + error("-z text and -z ifunc-noplt may not be used together"); + + 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"); + } + + if (config->zRetpolineplt && config->requireCET) + error("--require-cet may not be used with -z retpolineplt"); + + if (config->emachine != EM_AARCH64) { + if (config->pacPlt) + error("--pac-plt only supported on AArch64"); + if (config->forceBTI) + error("--force-bti only supported on AArch64"); + } +} + +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("common-page-size") || 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); + checkZOptions(args); + + // 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); + + // 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; + + // The Target instance handles target-specific stuff, such as applying + // relocations or writing a PLT section. It also contains target-dependent + // values such as a default image base address. + target = getTarget(); + + 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, opt::InputArgList &args, + 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: " + arg.getAsString(args)); + 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, args, *arg); + } + + if (auto *arg = args.getLastArg(OPT_Ttext)) + ret[".text"] = parseSectionAddress(arg->getValue(), args, *arg); + if (auto *arg = args.getLastArg(OPT_Tdata)) + ret[".data"] = parseSectionAddress(arg->getValue(), args, *arg); + if (auto *arg = args.getLastArg(OPT_Tbss)) + ret[".bss"] = parseSectionAddress(arg->getValue(), args, *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. +static void readConfigs(opt::InputArgList &args) { + errorHandler().verbose = args.hasArg(OPT_verbose); + errorHandler().fatalWarnings = + args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false); + errorHandler().vsDiagnostics = + args.hasArg(OPT_visual_studio_diagnostics_format, 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->allowShlibUndefined = + args.hasFlag(OPT_allow_shlib_undefined, OPT_no_allow_shlib_undefined, + args.hasArg(OPT_shared)); + 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->dependentLibraries = args.hasFlag(OPT_dependent_libraries, OPT_no_dependent_libraries, 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->forceBTI = args.hasArg(OPT_force_bti); + config->requireCET = args.hasArg(OPT_require_cet); + 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->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate); + config->ltoCSProfileFile = args.getLastArgValue(OPT_lto_cs_profile_file); + 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->nmagic = args.hasFlag(OPT_nmagic, OPT_no_nmagic, false); + 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->optRemarksPasses = args.getLastArgValue(OPT_opt_remarks_passes); + config->optRemarksWithHotness = args.hasArg(OPT_opt_remarks_with_hotness); + config->optRemarksFormat = args.getLastArgValue(OPT_opt_remarks_format); + config->optimize = args::getInteger(args, OPT_O, 1); + config->orphanHandling = getOrphanHandling(args); + config->outputFile = args.getLastArgValue(OPT_o); + config->pacPlt = args.hasArg(OPT_pac_plt); + 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->printSymbolOrder = + args.getLastArgValue(OPT_print_symbol_order); + 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.startswith("elf32btsmipn32") || s.startswith("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 = "-"; + + // Page alignment can be disabled by the -n (--nmagic) and -N (--omagic). + // As PT_GNU_RELRO relies on Paging, do not create it when we have disabled + // it. + if (config->nmagic || 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 (args.hasArg(OPT_call_graph_ordering_file)) + error("--symbol-ordering-file and --call-graph-order-file " + "may not be used together"); + if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue())){ + config->symbolOrderingFile = getSymbolOrderingFile(*buffer); + // Also need to disable CallGraphProfileSort to prevent + // LLD order symbols with CGProfile + config->callGraphProfileSort = false; + } + } + + // 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->isPic = config->pie || config->shared; + config->picThunk = args.hasArg(OPT_pic_veneer, config->isPic); + 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().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: + case OPT_omagic: + case OPT_nmagic: + config->isStatic = true; + break; + case OPT_Bdynamic: + config->isStatic = 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->isStatic, inWholeArchive); + break; + case OPT_pop_state: + if (stack.empty()) { + error("unbalanced --push-state/--pop-state"); + break; + } + std::tie(config->asNeeded, config->isStatic, 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"); + if (config->nmagic || config->omagic) { + if (val != target->defaultMaxPageSize) + warn("-z max-page-size set, but paging disabled by omagic or nmagic"); + return 1; + } + return val; +} + +// Parse -z common-page-size=<value>. The default value is defined by +// each target. +static uint64_t getCommonPageSize(opt::InputArgList &args) { + uint64_t val = args::getZOptionValue(args, OPT_z, "common-page-size", + target->defaultCommonPageSize); + if (!isPowerOf2_64(val)) + error("common-page-size: value isn't a power of 2"); + if (config->nmagic || config->omagic) { + if (val != target->defaultCommonPageSize) + warn("-z common-page-size set, but paging disabled by omagic or nmagic"); + return 1; + } + // commonPageSize can't be larger than maxPageSize. + if (val > config->maxPageSize) + val = config->maxPageSize; + 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. +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. +static void handleUndefined(Symbol *sym) { + // Since a symbol 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()) + sym->fetch(); +} + +// As an extention to GNU linkers, lld supports a variant of `-u` +// which accepts wildcard patterns. All symbols that match a given +// pattern are handled as if they were given by `-u`. +static void handleUndefinedGlob(StringRef arg) { + Expected<GlobPattern> pat = GlobPattern::create(arg); + if (!pat) { + error("--undefined-glob: " + toString(pat.takeError())); + return; + } + + std::vector<Symbol *> syms; + symtab->forEachSymbol([&](Symbol *sym) { + // Calling Sym->fetch() from here is not safe because it may + // add new symbols to the symbol table, invalidating the + // current iterator. So we just keep a note. + if (pat->match(sym->getName())) + syms.push_back(sym); + }); + + for (Symbol *sym : syms) + handleUndefined(sym); +} + +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)) + sym->fetch(); +} + +// Replaces common symbols with defined symbols reside in .bss sections. +// This function is called after all symbol names are resolved. As a +// result, the passes after the symbol resolution won't see any +// symbols of type CommonSymbol. +static void replaceCommonSymbols() { + symtab->forEachSymbol([](Symbol *sym) { + auto *s = dyn_cast<CommonSymbol>(sym); + if (!s) + return; + + auto *bss = make<BssSection>("COMMON", s->size, s->alignment); + bss->file = s->file; + bss->markDead(); + inputSections.push_back(bss); + s->replace(Defined{s->file, s->getName(), s->binding, s->stOther, s->type, + /*value=*/0, s->size, bss}); + }); +} + +// 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. +static void demoteSharedSymbols() { + symtab->forEachSymbol([](Symbol *sym) { + auto *s = dyn_cast<SharedSymbol>(sym); + if (!s || s->getFile().isNeeded) + return; + + bool used = s->used; + s->replace(Undefined{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. + symtab->forEachSymbol([&](Symbol *sym) { + if (sym->includeInDynsym()) + markAddrsig(sym); + }); + + // 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); + } + } +} + +// This function reads a symbol partition specification section. These sections +// are used to control which partition a symbol is allocated to. See +// https://lld.llvm.org/Partitions.html for more details on partitions. +template <typename ELFT> +static void readSymbolPartitionSection(InputSectionBase *s) { + // Read the relocation that refers to the partition's entry point symbol. + Symbol *sym; + if (s->areRelocsRela) + sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template relas<ELFT>()[0]); + else + sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template rels<ELFT>()[0]); + if (!isa<Defined>(sym) || !sym->includeInDynsym()) + return; + + StringRef partName = reinterpret_cast<const char *>(s->data().data()); + for (Partition &part : partitions) { + if (part.name == partName) { + sym->partition = part.getNumber(); + return; + } + } + + // Forbid partitions from being used on incompatible targets, and forbid them + // from being used together with various linker features that assume a single + // set of output sections. + if (script->hasSectionsCommand) + error(toString(s->file) + + ": partitions cannot be used with the SECTIONS command"); + if (script->hasPhdrsCommands()) + error(toString(s->file) + + ": partitions cannot be used with the PHDRS command"); + if (!config->sectionStartMap.empty()) + error(toString(s->file) + ": partitions cannot be used with " + "--section-start, -Ttext, -Tdata or -Tbss"); + if (config->emachine == EM_MIPS) + error(toString(s->file) + ": partitions cannot be used on this target"); + + // Impose a limit of no more than 254 partitions. This limit comes from the + // sizes of the Partition fields in InputSectionBase and Symbol, as well as + // the amount of space devoted to the partition number in RankFlags. + if (partitions.size() == 254) + fatal("may not have more than 254 partitions"); + + partitions.emplace_back(); + Partition &newPart = partitions.back(); + newPart.name = partName; + sym->partition = newPart.getNumber(); +} + +static Symbol *addUndefined(StringRef name) { + return symtab->addSymbol( + Undefined{nullptr, name, STB_GLOBAL, STV_DEFAULT, 0}); +} + +// This function is where all the optimizations of link-time +// optimization takes place. When LTO is in use, some input files are +// not in native object file format but in the LLVM bitcode format. +// This function compiles bitcode files into a few big native files +// using LLVM functions and replaces bitcode symbols with the results. +// Because all bitcode files that the program consists of are passed to +// the compiler at once, it can do a whole-program optimization. +template <class ELFT> void LinkerDriver::compileBitcodeFiles() { + // Compile bitcode files and replace bitcode symbols. + lto.reset(new BitcodeCompiler); + for (BitcodeFile *file : bitcodeFiles) + lto->add(*file); + + for (InputFile *file : lto->compile()) { + auto *obj = cast<ObjFile<ELFT>>(file); + obj->parse(/*ignoreComdats=*/true); + for (Symbol *sym : obj->getGlobalSymbols()) + sym->parseSymbolVersion(); + objectFiles.push_back(file); + } +} + +// 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. +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(saver.save("__real_" + name)); + Symbol *wrap = addUndefined(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. +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) { + MutableArrayRef<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); +} + +// To enable CET (x86's hardware-assited control flow enforcement), each +// source file must be compiled with -fcf-protection. Object files compiled +// with the flag contain feature flags indicating that they are compatible +// with CET. We enable the feature only when all object files are compatible +// with CET. +// +// This function returns the merged feature flags. If 0, we cannot enable CET. +// This is also the case with AARCH64's BTI and PAC which use the similar +// GNU_PROPERTY_AARCH64_FEATURE_1_AND mechanism. +// +// Note that the CET-aware PLT is not implemented yet. We do error +// check only. +template <class ELFT> static uint32_t getAndFeatures() { + if (config->emachine != EM_386 && config->emachine != EM_X86_64 && + config->emachine != EM_AARCH64) + return 0; + + uint32_t ret = -1; + for (InputFile *f : objectFiles) { + uint32_t features = cast<ObjFile<ELFT>>(f)->andFeatures; + if (config->forceBTI && !(features & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) { + warn(toString(f) + ": --force-bti: file does not have BTI property"); + features |= GNU_PROPERTY_AARCH64_FEATURE_1_BTI; + } else if (!features && config->requireCET) + error(toString(f) + ": --require-cet: file is not compatible with CET"); + ret &= features; + } + + // Force enable pointer authentication Plt, we don't warn in this case as + // this does not require support in the object for correctness. + if (config->pacPlt) + ret |= GNU_PROPERTY_AARCH64_FEATURE_1_PAC; + + return ret; +} + +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) { + // 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->insert(arg->getValue())->traced = true; + + // Add all files to the symbol table. This will add almost all + // symbols that we need to the symbol table. This process might + // add files to the link, via autolinking, these files are always + // appended to the Files vector. + for (size_t i = 0; i < files.size(); ++i) + parseFile(files[i]); + + // 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->isPic || 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(name); + + // Handle the `--undefined <sym>` options. + for (StringRef arg : config->undefined) + if (Symbol *sym = symtab->find(arg)) + handleUndefined(sym); + + // If an entry symbol is in a static archive, pull out that file now. + if (Symbol *sym = symtab->find(config->entry)) + handleUndefined(sym); + + // Handle the `--undefined-glob <pattern>` options. + for (StringRef pat : args::getStrings(args, OPT_undefined_glob)) + handleUndefinedGlob(pat); + + // 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(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(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(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. + compileBitcodeFiles<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(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)); + + llvm::erase_if(inputSections, [](InputSectionBase *s) { + if (s->type == SHT_LLVM_SYMPART) { + readSymbolPartitionSection<ELFT>(s); + return true; + } + + // We do not want to emit debug sections if --strip-all + // or -strip-debug are given. + return config->strip != StripPolicy::None && + (s->name.startswith(".debug") || s->name.startswith(".zdebug")); + }); + + // Now that the number of partitions is fixed, save a pointer to the main + // partition. + mainPart = &partitions[0]; + + // Read .note.gnu.property sections from input object files which + // contain a hint to tweak linker's and loader's behaviors. + config->andFeatures = getAndFeatures<ELFT>(); + + // The Target instance handles target-specific stuff, such as applying + // relocations or writing a PLT section. It also contains target-dependent + // values such as a default image base address. + target = getTarget(); + + config->eflags = target->calcEFlags(); + // maxPageSize (sometimes called abi page size) is the maximum page size that + // the output can be run on. For example if the OS can use 4k or 64k page + // sizes then maxPageSize must be 64k for the output to be useable on both. + // All important alignment decisions must use this value. + config->maxPageSize = getMaxPageSize(args); + // commonPageSize is the most common page size that the output will be run on. + // For example if an OS can use 4k or 64k page sizes and 4k is more common + // than 64k then commonPageSize is set to 4k. commonPageSize can be used for + // optimizations such as DATA_SEGMENT_ALIGN in linker scripts. LLD's use of it + // is limited to writing trap instructions on the last executable segment. + config->commonPageSize = getCommonPageSize(args); + + config->imageBase = getImageBase(args); + + 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()); + + // Replace common symbols with regular symbols. + replaceCommonSymbols(); + + // Do size optimizations: garbage collection, merging of SHF_MERGE sections + // and identical code folding. + splitSections<ELFT>(); + markLive<ELFT>(); + demoteSharedSymbols(); + 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>(); +} |