1 //===- Driver.cpp ---------------------------------------------------------===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The driver drives the entire linking process. It is responsible for
11 // parsing command line options and doing whatever it is instructed to do.
13 // One notable thing in the LLD's driver when compared to other linkers is
14 // that the LLD's driver is agnostic on the host operating system.
15 // Other linkers usually have implicit default values (such as a dynamic
16 // linker path or library paths) for each host OS.
18 // I don't think implicit default values are useful because they are
19 // usually explicitly specified by the compiler driver. They can even
20 // be harmful when you are doing cross-linking. Therefore, in LLD, we
21 // simply trust the compiler driver to pass all required options and
22 // don't try to make effort on our side.
24 //===----------------------------------------------------------------------===//
28 #include "Filesystem.h"
30 #include "InputFiles.h"
31 #include "InputSection.h"
32 #include "LinkerScript.h"
34 #include "OutputSections.h"
35 #include "ScriptParser.h"
36 #include "SymbolTable.h"
38 #include "SyntheticSections.h"
41 #include "lld/Common/Args.h"
42 #include "lld/Common/Driver.h"
43 #include "lld/Common/ErrorHandler.h"
44 #include "lld/Common/Memory.h"
45 #include "lld/Common/Strings.h"
46 #include "lld/Common/TargetOptionsCommandFlags.h"
47 #include "lld/Common/Threads.h"
48 #include "lld/Common/Version.h"
49 #include "llvm/ADT/SetVector.h"
50 #include "llvm/ADT/StringExtras.h"
51 #include "llvm/ADT/StringSwitch.h"
52 #include "llvm/Support/CommandLine.h"
53 #include "llvm/Support/Compression.h"
54 #include "llvm/Support/LEB128.h"
55 #include "llvm/Support/Path.h"
56 #include "llvm/Support/TarWriter.h"
57 #include "llvm/Support/TargetSelect.h"
58 #include "llvm/Support/raw_ostream.h"
63 using namespace llvm::ELF;
64 using namespace llvm::object;
65 using namespace llvm::sys;
68 using namespace lld::elf;
70 Configuration *elf::Config;
71 LinkerDriver *elf::Driver;
73 static void setConfigs(opt::InputArgList &Args);
75 bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly,
77 errorHandler().LogName = sys::path::filename(Args[0]);
78 errorHandler().ErrorLimitExceededMsg =
79 "too many errors emitted, stopping now (use "
80 "-error-limit=0 to see all errors)";
81 errorHandler().ErrorOS = &Error;
82 errorHandler().ExitEarly = CanExitEarly;
83 errorHandler().ColorDiagnostics = Error.has_colors();
85 InputSections.clear();
86 OutputSections.clear();
93 Config = make<Configuration>();
94 Driver = make<LinkerDriver>();
95 Script = make<LinkerScript>();
96 Symtab = make<SymbolTable>();
97 Config->ProgName = Args[0];
101 // Exit immediately if we don't need to return to the caller.
102 // This saves time because the overhead of calling destructors
103 // for all globally-allocated objects is not negligible.
105 exitLld(errorCount() ? 1 : 0);
108 return !errorCount();
111 // Parses a linker -m option.
112 static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef Emul) {
115 if (S.endswith("_fbsd")) {
117 OSABI = ELFOSABI_FREEBSD;
120 std::pair<ELFKind, uint16_t> Ret =
121 StringSwitch<std::pair<ELFKind, uint16_t>>(S)
122 .Cases("aarch64elf", "aarch64linux", "aarch64_elf64_le_vec",
123 {ELF64LEKind, EM_AARCH64})
124 .Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM})
125 .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
126 .Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS})
127 .Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS})
128 .Case("elf32ppc", {ELF32BEKind, EM_PPC})
129 .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
130 .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
131 .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
132 .Case("elf64lppc", {ELF64LEKind, EM_PPC64})
133 .Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64})
134 .Case("elf_i386", {ELF32LEKind, EM_386})
135 .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
136 .Default({ELFNoneKind, EM_NONE});
138 if (Ret.first == ELFNoneKind)
139 error("unknown emulation: " + Emul);
140 return std::make_tuple(Ret.first, Ret.second, OSABI);
143 // Returns slices of MB by parsing MB as an archive file.
144 // Each slice consists of a member file in the archive.
145 std::vector<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers(
146 MemoryBufferRef MB) {
147 std::unique_ptr<Archive> File =
148 CHECK(Archive::create(MB),
149 MB.getBufferIdentifier() + ": failed to parse archive");
151 std::vector<std::pair<MemoryBufferRef, uint64_t>> V;
152 Error Err = Error::success();
153 bool AddToTar = File->isThin() && Tar;
154 for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
156 CHECK(COrErr, MB.getBufferIdentifier() +
157 ": could not get the child of the archive");
158 MemoryBufferRef MBRef =
159 CHECK(C.getMemoryBufferRef(),
160 MB.getBufferIdentifier() +
161 ": could not get the buffer for a child of the archive");
163 Tar->append(relativeToRoot(check(C.getFullName())), MBRef.getBuffer());
164 V.push_back(std::make_pair(MBRef, C.getChildOffset()));
167 fatal(MB.getBufferIdentifier() + ": Archive::children failed: " +
168 toString(std::move(Err)));
170 // Take ownership of memory buffers created for members of thin archives.
171 for (std::unique_ptr<MemoryBuffer> &MB : File->takeThinBuffers())
172 make<std::unique_ptr<MemoryBuffer>>(std::move(MB));
177 // Opens a file and create a file object. Path has to be resolved already.
178 void LinkerDriver::addFile(StringRef Path, bool WithLOption) {
179 using namespace sys::fs;
181 Optional<MemoryBufferRef> Buffer = readFile(Path);
182 if (!Buffer.hasValue())
184 MemoryBufferRef MBRef = *Buffer;
187 Files.push_back(make<BinaryFile>(MBRef));
191 switch (identify_magic(MBRef.getBuffer())) {
192 case file_magic::unknown:
193 readLinkerScript(MBRef);
195 case file_magic::archive: {
196 // Handle -whole-archive.
197 if (InWholeArchive) {
198 for (const auto &P : getArchiveMembers(MBRef))
199 Files.push_back(createObjectFile(P.first, Path, P.second));
203 std::unique_ptr<Archive> File =
204 CHECK(Archive::create(MBRef), Path + ": failed to parse archive");
206 // If an archive file has no symbol table, it is likely that a user
207 // is attempting LTO and using a default ar command that doesn't
208 // understand the LLVM bitcode file. It is a pretty common error, so
209 // we'll handle it as if it had a symbol table.
210 if (!File->isEmpty() && !File->hasSymbolTable()) {
211 for (const auto &P : getArchiveMembers(MBRef))
212 Files.push_back(make<LazyObjFile>(P.first, Path, P.second));
216 // Handle the regular case.
217 Files.push_back(make<ArchiveFile>(std::move(File)));
220 case file_magic::elf_shared_object:
221 if (Config->Relocatable) {
222 error("attempted static link of dynamic object " + Path);
226 // DSOs usually have DT_SONAME tags in their ELF headers, and the
227 // sonames are used to identify DSOs. But if they are missing,
228 // they are identified by filenames. We don't know whether the new
229 // file has a DT_SONAME or not because we haven't parsed it yet.
230 // Here, we set the default soname for the file because we might
233 // If a file was specified by -lfoo, the directory part is not
234 // significant, as a user did not specify it. This behavior is
235 // compatible with GNU.
237 createSharedFile(MBRef, WithLOption ? path::filename(Path) : Path));
239 case file_magic::bitcode:
240 case file_magic::elf_relocatable:
242 Files.push_back(make<LazyObjFile>(MBRef, "", 0));
244 Files.push_back(createObjectFile(MBRef));
247 error(Path + ": unknown file type");
251 // Add a given library by searching it from input search paths.
252 void LinkerDriver::addLibrary(StringRef Name) {
253 if (Optional<std::string> Path = searchLibrary(Name))
254 addFile(*Path, /*WithLOption=*/true);
256 error("unable to find library -l" + Name);
259 // This function is called on startup. We need this for LTO since
260 // LTO calls LLVM functions to compile bitcode files to native code.
261 // Technically this can be delayed until we read bitcode files, but
262 // we don't bother to do lazily because the initialization is fast.
263 static void initLLVM() {
264 InitializeAllTargets();
265 InitializeAllTargetMCs();
266 InitializeAllAsmPrinters();
267 InitializeAllAsmParsers();
270 // Some command line options or some combinations of them are not allowed.
271 // This function checks for such errors.
272 static void checkOptions(opt::InputArgList &Args) {
273 // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
274 // table which is a relatively new feature.
275 if (Config->EMachine == EM_MIPS && Config->GnuHash)
276 error("the .gnu.hash section is not compatible with the MIPS target.");
278 if (Config->FixCortexA53Errata843419 && Config->EMachine != EM_AARCH64)
279 error("--fix-cortex-a53-843419 is only supported on AArch64 targets.");
281 if (Config->Pie && Config->Shared)
282 error("-shared and -pie may not be used together");
284 if (!Config->Shared && !Config->FilterList.empty())
285 error("-F may not be used without -shared");
287 if (!Config->Shared && !Config->AuxiliaryList.empty())
288 error("-f may not be used without -shared");
290 if (!Config->Relocatable && !Config->DefineCommon)
291 error("-no-define-common not supported in non relocatable output");
293 if (Config->Relocatable) {
295 error("-r and -shared may not be used together");
296 if (Config->GcSections)
297 error("-r and --gc-sections may not be used together");
298 if (Config->GdbIndex)
299 error("-r and --gdb-index may not be used together");
300 if (Config->ICF != ICFLevel::None)
301 error("-r and --icf may not be used together");
303 error("-r and -pie may not be used together");
306 if (Config->ExecuteOnly) {
307 if (Config->EMachine != EM_AARCH64)
308 error("-execute-only is only supported on AArch64 targets");
310 if (Config->SingleRoRx && !Script->HasSectionsCommand)
311 error("-execute-only and -no-rosegment cannot be used together");
315 static const char *getReproduceOption(opt::InputArgList &Args) {
316 if (auto *Arg = Args.getLastArg(OPT_reproduce))
317 return Arg->getValue();
318 return getenv("LLD_REPRODUCE");
321 static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
322 for (auto *Arg : Args.filtered(OPT_z))
323 if (Key == Arg->getValue())
328 static bool getZFlag(opt::InputArgList &Args, StringRef K1, StringRef K2,
330 for (auto *Arg : Args.filtered_reverse(OPT_z)) {
331 if (K1 == Arg->getValue())
333 if (K2 == Arg->getValue())
339 static bool isKnown(StringRef S) {
340 return S == "combreloc" || S == "copyreloc" || S == "defs" ||
341 S == "execstack" || S == "hazardplt" || S == "initfirst" ||
342 S == "keep-text-section-prefix" || S == "lazy" || S == "muldefs" ||
343 S == "nocombreloc" || S == "nocopyreloc" || S == "nodelete" ||
344 S == "nodlopen" || S == "noexecstack" ||
345 S == "nokeep-text-section-prefix" || S == "norelro" || S == "notext" ||
346 S == "now" || S == "origin" || S == "relro" || S == "retpolineplt" ||
347 S == "rodynamic" || S == "text" || S == "wxneeded" ||
348 S.startswith("max-page-size=") || S.startswith("stack-size=");
351 // Report an error for an unknown -z option.
352 static void checkZOptions(opt::InputArgList &Args) {
353 for (auto *Arg : Args.filtered(OPT_z))
354 if (!isKnown(Arg->getValue()))
355 error("unknown -z value: " + StringRef(Arg->getValue()));
358 void LinkerDriver::main(ArrayRef<const char *> ArgsArr) {
360 opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
362 // Interpret this flag early because error() depends on them.
363 errorHandler().ErrorLimit = args::getInteger(Args, OPT_error_limit, 20);
366 if (Args.hasArg(OPT_help)) {
371 // Handle -v or -version.
373 // A note about "compatible with GNU linkers" message: this is a hack for
374 // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
375 // still the newest version in March 2017) or earlier to recognize LLD as
376 // a GNU compatible linker. As long as an output for the -v option
377 // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
379 // This is somewhat ugly hack, but in reality, we had no choice other
380 // than doing this. Considering the very long release cycle of Libtool,
381 // it is not easy to improve it to recognize LLD as a GNU compatible
382 // linker in a timely manner. Even if we can make it, there are still a
383 // lot of "configure" scripts out there that are generated by old version
384 // of Libtool. We cannot convince every software developer to migrate to
385 // the latest version and re-generate scripts. So we have this hack.
386 if (Args.hasArg(OPT_v) || Args.hasArg(OPT_version))
387 message(getLLDVersion() + " (compatible with GNU linkers)");
389 // The behavior of -v or --version is a bit strange, but this is
390 // needed for compatibility with GNU linkers.
391 if (Args.hasArg(OPT_v) && !Args.hasArg(OPT_INPUT))
393 if (Args.hasArg(OPT_version))
396 if (const char *Path = getReproduceOption(Args)) {
397 // Note that --reproduce is a debug option so you can ignore it
398 // if you are trying to understand the whole picture of the code.
399 Expected<std::unique_ptr<TarWriter>> ErrOrWriter =
400 TarWriter::create(Path, path::stem(Path));
402 Tar = ErrOrWriter->get();
403 Tar->append("response.txt", createResponseFile(Args));
404 Tar->append("version.txt", getLLDVersion() + "\n");
405 make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter));
407 error(Twine("--reproduce: failed to open ") + Path + ": " +
408 toString(ErrOrWriter.takeError()));
425 switch (Config->EKind) {
439 llvm_unreachable("unknown Config->EKind");
443 static std::string getRpath(opt::InputArgList &Args) {
444 std::vector<StringRef> V = args::getStrings(Args, OPT_rpath);
445 return llvm::join(V.begin(), V.end(), ":");
448 // Determines what we should do if there are remaining unresolved
449 // symbols after the name resolution.
450 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
451 if (Args.hasArg(OPT_relocatable))
452 return UnresolvedPolicy::IgnoreAll;
454 UnresolvedPolicy ErrorOrWarn = Args.hasFlag(OPT_error_unresolved_symbols,
455 OPT_warn_unresolved_symbols, true)
456 ? UnresolvedPolicy::ReportError
457 : UnresolvedPolicy::Warn;
459 // Process the last of -unresolved-symbols, -no-undefined or -z defs.
460 for (auto *Arg : llvm::reverse(Args)) {
461 switch (Arg->getOption().getID()) {
462 case OPT_unresolved_symbols: {
463 StringRef S = Arg->getValue();
464 if (S == "ignore-all" || S == "ignore-in-object-files")
465 return UnresolvedPolicy::Ignore;
466 if (S == "ignore-in-shared-libs" || S == "report-all")
468 error("unknown --unresolved-symbols value: " + S);
471 case OPT_no_undefined:
474 if (StringRef(Arg->getValue()) == "defs")
480 // -shared implies -unresolved-symbols=ignore-all because missing
481 // symbols are likely to be resolved at runtime using other DSOs.
483 return UnresolvedPolicy::Ignore;
487 static Target2Policy getTarget2(opt::InputArgList &Args) {
488 StringRef S = Args.getLastArgValue(OPT_target2, "got-rel");
490 return Target2Policy::Rel;
492 return Target2Policy::Abs;
494 return Target2Policy::GotRel;
495 error("unknown --target2 option: " + S);
496 return Target2Policy::GotRel;
499 static bool isOutputFormatBinary(opt::InputArgList &Args) {
500 if (auto *Arg = Args.getLastArg(OPT_oformat)) {
501 StringRef S = Arg->getValue();
504 if (S.startswith("elf"))
506 error("unknown --oformat value: " + S);
511 static DiscardPolicy getDiscard(opt::InputArgList &Args) {
512 if (Args.hasArg(OPT_relocatable))
513 return DiscardPolicy::None;
516 Args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
518 return DiscardPolicy::Default;
519 if (Arg->getOption().getID() == OPT_discard_all)
520 return DiscardPolicy::All;
521 if (Arg->getOption().getID() == OPT_discard_locals)
522 return DiscardPolicy::Locals;
523 return DiscardPolicy::None;
526 static StringRef getDynamicLinker(opt::InputArgList &Args) {
527 auto *Arg = Args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
528 if (!Arg || Arg->getOption().getID() == OPT_no_dynamic_linker)
530 return Arg->getValue();
533 static ICFLevel getICF(opt::InputArgList &Args) {
534 auto *Arg = Args.getLastArg(OPT_icf_none, OPT_icf_safe, OPT_icf_all);
535 if (!Arg || Arg->getOption().getID() == OPT_icf_none)
536 return ICFLevel::None;
537 if (Arg->getOption().getID() == OPT_icf_safe)
538 return ICFLevel::Safe;
539 return ICFLevel::All;
542 static StripPolicy getStrip(opt::InputArgList &Args) {
543 if (Args.hasArg(OPT_relocatable))
544 return StripPolicy::None;
546 auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug);
548 return StripPolicy::None;
549 if (Arg->getOption().getID() == OPT_strip_all)
550 return StripPolicy::All;
551 return StripPolicy::Debug;
554 static uint64_t parseSectionAddress(StringRef S, const opt::Arg &Arg) {
556 if (S.startswith("0x"))
558 if (!to_integer(S, VA, 16))
559 error("invalid argument: " + toString(Arg));
563 static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) {
564 StringMap<uint64_t> Ret;
565 for (auto *Arg : Args.filtered(OPT_section_start)) {
568 std::tie(Name, Addr) = StringRef(Arg->getValue()).split('=');
569 Ret[Name] = parseSectionAddress(Addr, *Arg);
572 if (auto *Arg = Args.getLastArg(OPT_Ttext))
573 Ret[".text"] = parseSectionAddress(Arg->getValue(), *Arg);
574 if (auto *Arg = Args.getLastArg(OPT_Tdata))
575 Ret[".data"] = parseSectionAddress(Arg->getValue(), *Arg);
576 if (auto *Arg = Args.getLastArg(OPT_Tbss))
577 Ret[".bss"] = parseSectionAddress(Arg->getValue(), *Arg);
581 static SortSectionPolicy getSortSection(opt::InputArgList &Args) {
582 StringRef S = Args.getLastArgValue(OPT_sort_section);
583 if (S == "alignment")
584 return SortSectionPolicy::Alignment;
586 return SortSectionPolicy::Name;
588 error("unknown --sort-section rule: " + S);
589 return SortSectionPolicy::Default;
592 static OrphanHandlingPolicy getOrphanHandling(opt::InputArgList &Args) {
593 StringRef S = Args.getLastArgValue(OPT_orphan_handling, "place");
595 return OrphanHandlingPolicy::Warn;
597 return OrphanHandlingPolicy::Error;
599 error("unknown --orphan-handling mode: " + S);
600 return OrphanHandlingPolicy::Place;
603 // Parse --build-id or --build-id=<style>. We handle "tree" as a
604 // synonym for "sha1" because all our hash functions including
605 // -build-id=sha1 are actually tree hashes for performance reasons.
606 static std::pair<BuildIdKind, std::vector<uint8_t>>
607 getBuildId(opt::InputArgList &Args) {
608 auto *Arg = Args.getLastArg(OPT_build_id, OPT_build_id_eq);
610 return {BuildIdKind::None, {}};
612 if (Arg->getOption().getID() == OPT_build_id)
613 return {BuildIdKind::Fast, {}};
615 StringRef S = Arg->getValue();
617 return {BuildIdKind::Fast, {}};
619 return {BuildIdKind::Md5, {}};
620 if (S == "sha1" || S == "tree")
621 return {BuildIdKind::Sha1, {}};
623 return {BuildIdKind::Uuid, {}};
624 if (S.startswith("0x"))
625 return {BuildIdKind::Hexstring, parseHex(S.substr(2))};
628 error("unknown --build-id style: " + S);
629 return {BuildIdKind::None, {}};
632 static std::pair<bool, bool> getPackDynRelocs(opt::InputArgList &Args) {
633 StringRef S = Args.getLastArgValue(OPT_pack_dyn_relocs, "none");
635 return {true, false};
637 return {false, true};
638 if (S == "android+relr")
642 error("unknown -pack-dyn-relocs format: " + S);
643 return {false, false};
646 static void readCallGraph(MemoryBufferRef MB) {
647 // Build a map from symbol name to section
648 DenseMap<StringRef, const Symbol *> SymbolNameToSymbol;
649 for (InputFile *File : ObjectFiles)
650 for (Symbol *Sym : File->getSymbols())
651 SymbolNameToSymbol[Sym->getName()] = Sym;
653 for (StringRef L : args::getLines(MB)) {
654 SmallVector<StringRef, 3> Fields;
655 L.split(Fields, ' ');
657 if (Fields.size() != 3 || !to_integer(Fields[2], Count))
658 fatal(MB.getBufferIdentifier() + ": parse error");
659 const Symbol *FromSym = SymbolNameToSymbol.lookup(Fields[0]);
660 const Symbol *ToSym = SymbolNameToSymbol.lookup(Fields[1]);
661 if (Config->WarnSymbolOrdering) {
663 warn(MB.getBufferIdentifier() + ": no such symbol: " + Fields[0]);
665 warn(MB.getBufferIdentifier() + ": no such symbol: " + Fields[1]);
667 if (!FromSym || !ToSym || Count == 0)
669 warnUnorderableSymbol(FromSym);
670 warnUnorderableSymbol(ToSym);
671 const Defined *FromSymD = dyn_cast<Defined>(FromSym);
672 const Defined *ToSymD = dyn_cast<Defined>(ToSym);
673 if (!FromSymD || !ToSymD)
675 const auto *FromSB = dyn_cast_or_null<InputSectionBase>(FromSymD->Section);
676 const auto *ToSB = dyn_cast_or_null<InputSectionBase>(ToSymD->Section);
677 if (!FromSB || !ToSB)
679 Config->CallGraphProfile[std::make_pair(FromSB, ToSB)] += Count;
683 static bool getCompressDebugSections(opt::InputArgList &Args) {
684 StringRef S = Args.getLastArgValue(OPT_compress_debug_sections, "none");
688 error("unknown --compress-debug-sections value: " + S);
689 if (!zlib::isAvailable())
690 error("--compress-debug-sections: zlib is not available");
694 static std::pair<StringRef, StringRef> getOldNewOptions(opt::InputArgList &Args,
696 auto *Arg = Args.getLastArg(Id);
700 StringRef S = Arg->getValue();
701 std::pair<StringRef, StringRef> Ret = S.split(';');
702 if (Ret.second.empty())
703 error(Arg->getSpelling() + " expects 'old;new' format, but got " + S);
707 // Parse the symbol ordering file and warn for any duplicate entries.
708 static std::vector<StringRef> getSymbolOrderingFile(MemoryBufferRef MB) {
709 SetVector<StringRef> Names;
710 for (StringRef S : args::getLines(MB))
711 if (!Names.insert(S) && Config->WarnSymbolOrdering)
712 warn(MB.getBufferIdentifier() + ": duplicate ordered symbol: " + S);
714 return Names.takeVector();
717 static void parseClangOption(StringRef Opt, const Twine &Msg) {
719 raw_string_ostream OS(Err);
721 const char *Argv[] = {Config->ProgName.data(), Opt.data()};
722 if (cl::ParseCommandLineOptions(2, Argv, "", &OS))
725 error(Msg + ": " + StringRef(Err).trim());
728 // Initializes Config members by the command line options.
729 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
730 errorHandler().Verbose = Args.hasArg(OPT_verbose);
731 errorHandler().FatalWarnings =
732 Args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
733 ThreadsEnabled = Args.hasFlag(OPT_threads, OPT_no_threads, true);
735 Config->AllowMultipleDefinition =
736 Args.hasFlag(OPT_allow_multiple_definition,
737 OPT_no_allow_multiple_definition, false) ||
738 hasZOption(Args, "muldefs");
739 Config->AuxiliaryList = args::getStrings(Args, OPT_auxiliary);
740 Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
741 Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
742 Config->CheckSections =
743 Args.hasFlag(OPT_check_sections, OPT_no_check_sections, true);
744 Config->Chroot = Args.getLastArgValue(OPT_chroot);
745 Config->CompressDebugSections = getCompressDebugSections(Args);
746 Config->Cref = Args.hasFlag(OPT_cref, OPT_no_cref, false);
747 Config->DefineCommon = Args.hasFlag(OPT_define_common, OPT_no_define_common,
748 !Args.hasArg(OPT_relocatable));
749 Config->Demangle = Args.hasFlag(OPT_demangle, OPT_no_demangle, true);
750 Config->DisableVerify = Args.hasArg(OPT_disable_verify);
751 Config->Discard = getDiscard(Args);
752 Config->DwoDir = Args.getLastArgValue(OPT_plugin_opt_dwo_dir_eq);
753 Config->DynamicLinker = getDynamicLinker(Args);
755 Args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false);
756 Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
757 Config->EnableNewDtags =
758 Args.hasFlag(OPT_enable_new_dtags, OPT_disable_new_dtags, true);
759 Config->Entry = Args.getLastArgValue(OPT_entry);
760 Config->ExecuteOnly =
761 Args.hasFlag(OPT_execute_only, OPT_no_execute_only, false);
762 Config->ExportDynamic =
763 Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
764 Config->FilterList = args::getStrings(Args, OPT_filter);
765 Config->Fini = Args.getLastArgValue(OPT_fini, "_fini");
766 Config->FixCortexA53Errata843419 = Args.hasArg(OPT_fix_cortex_a53_843419);
767 Config->GcSections = Args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, false);
768 Config->GnuUnique = Args.hasFlag(OPT_gnu_unique, OPT_no_gnu_unique, true);
769 Config->GdbIndex = Args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false);
770 Config->ICF = getICF(Args);
771 Config->IgnoreDataAddressEquality =
772 Args.hasArg(OPT_ignore_data_address_equality);
773 Config->IgnoreFunctionAddressEquality =
774 Args.hasArg(OPT_ignore_function_address_equality);
775 Config->Init = Args.getLastArgValue(OPT_init, "_init");
776 Config->LTOAAPipeline = Args.getLastArgValue(OPT_lto_aa_pipeline);
777 Config->LTODebugPassManager = Args.hasArg(OPT_lto_debug_pass_manager);
778 Config->LTONewPassManager = Args.hasArg(OPT_lto_new_pass_manager);
779 Config->LTONewPmPasses = Args.getLastArgValue(OPT_lto_newpm_passes);
780 Config->LTOO = args::getInteger(Args, OPT_lto_O, 2);
781 Config->LTOObjPath = Args.getLastArgValue(OPT_plugin_opt_obj_path_eq);
782 Config->LTOPartitions = args::getInteger(Args, OPT_lto_partitions, 1);
783 Config->LTOSampleProfile = Args.getLastArgValue(OPT_lto_sample_profile);
784 Config->MapFile = Args.getLastArgValue(OPT_Map);
785 Config->MipsGotSize = args::getInteger(Args, OPT_mips_got_size, 0xfff0);
786 Config->MergeArmExidx =
787 Args.hasFlag(OPT_merge_exidx_entries, OPT_no_merge_exidx_entries, true);
788 Config->NoinhibitExec = Args.hasArg(OPT_noinhibit_exec);
789 Config->Nostdlib = Args.hasArg(OPT_nostdlib);
790 Config->OFormatBinary = isOutputFormatBinary(Args);
791 Config->Omagic = Args.hasFlag(OPT_omagic, OPT_no_omagic, false);
792 Config->OptRemarksFilename = Args.getLastArgValue(OPT_opt_remarks_filename);
793 Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness);
794 Config->Optimize = args::getInteger(Args, OPT_O, 1);
795 Config->OrphanHandling = getOrphanHandling(Args);
796 Config->OutputFile = Args.getLastArgValue(OPT_o);
797 Config->Pie = Args.hasFlag(OPT_pie, OPT_no_pie, false);
798 Config->PrintIcfSections =
799 Args.hasFlag(OPT_print_icf_sections, OPT_no_print_icf_sections, false);
800 Config->PrintGcSections =
801 Args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
802 Config->Rpath = getRpath(Args);
803 Config->Relocatable = Args.hasArg(OPT_relocatable);
804 Config->SaveTemps = Args.hasArg(OPT_save_temps);
805 Config->SearchPaths = args::getStrings(Args, OPT_library_path);
806 Config->SectionStartMap = getSectionStartMap(Args);
807 Config->Shared = Args.hasArg(OPT_shared);
808 Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
809 Config->SoName = Args.getLastArgValue(OPT_soname);
810 Config->SortSection = getSortSection(Args);
811 Config->Strip = getStrip(Args);
812 Config->Sysroot = Args.getLastArgValue(OPT_sysroot);
813 Config->Target1Rel = Args.hasFlag(OPT_target1_rel, OPT_target1_abs, false);
814 Config->Target2 = getTarget2(Args);
815 Config->ThinLTOCacheDir = Args.getLastArgValue(OPT_thinlto_cache_dir);
816 Config->ThinLTOCachePolicy = CHECK(
817 parseCachePruningPolicy(Args.getLastArgValue(OPT_thinlto_cache_policy)),
818 "--thinlto-cache-policy: invalid cache policy");
819 Config->ThinLTOEmitImportsFiles =
820 Args.hasArg(OPT_plugin_opt_thinlto_emit_imports_files);
821 Config->ThinLTOIndexOnly = Args.hasArg(OPT_plugin_opt_thinlto_index_only) ||
822 Args.hasArg(OPT_plugin_opt_thinlto_index_only_eq);
823 Config->ThinLTOIndexOnlyArg =
824 Args.getLastArgValue(OPT_plugin_opt_thinlto_index_only_eq);
825 Config->ThinLTOJobs = args::getInteger(Args, OPT_thinlto_jobs, -1u);
826 Config->ThinLTOObjectSuffixReplace =
827 getOldNewOptions(Args, OPT_plugin_opt_thinlto_object_suffix_replace_eq);
828 Config->ThinLTOPrefixReplace =
829 getOldNewOptions(Args, OPT_plugin_opt_thinlto_prefix_replace_eq);
830 Config->Trace = Args.hasArg(OPT_trace);
831 Config->Undefined = args::getStrings(Args, OPT_undefined);
832 Config->UndefinedVersion =
833 Args.hasFlag(OPT_undefined_version, OPT_no_undefined_version, true);
834 Config->UseAndroidRelrTags = Args.hasFlag(
835 OPT_use_android_relr_tags, OPT_no_use_android_relr_tags, false);
836 Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args);
837 Config->WarnBackrefs =
838 Args.hasFlag(OPT_warn_backrefs, OPT_no_warn_backrefs, false);
839 Config->WarnCommon = Args.hasFlag(OPT_warn_common, OPT_no_warn_common, false);
840 Config->WarnSymbolOrdering =
841 Args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true);
842 Config->ZCombreloc = getZFlag(Args, "combreloc", "nocombreloc", true);
843 Config->ZCopyreloc = getZFlag(Args, "copyreloc", "nocopyreloc", true);
844 Config->ZExecstack = getZFlag(Args, "execstack", "noexecstack", false);
845 Config->ZHazardplt = hasZOption(Args, "hazardplt");
846 Config->ZInitfirst = hasZOption(Args, "initfirst");
847 Config->ZKeepTextSectionPrefix = getZFlag(
848 Args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
849 Config->ZNodelete = hasZOption(Args, "nodelete");
850 Config->ZNodlopen = hasZOption(Args, "nodlopen");
851 Config->ZNow = getZFlag(Args, "now", "lazy", false);
852 Config->ZOrigin = hasZOption(Args, "origin");
853 Config->ZRelro = getZFlag(Args, "relro", "norelro", true);
854 Config->ZRetpolineplt = hasZOption(Args, "retpolineplt");
855 Config->ZRodynamic = hasZOption(Args, "rodynamic");
856 Config->ZStackSize = args::getZOptionValue(Args, OPT_z, "stack-size", 0);
857 Config->ZText = getZFlag(Args, "text", "notext", true);
858 Config->ZWxneeded = hasZOption(Args, "wxneeded");
860 // Parse LTO options.
861 if (auto *Arg = Args.getLastArg(OPT_plugin_opt_mcpu_eq))
862 parseClangOption(Saver.save("-mcpu=" + StringRef(Arg->getValue())),
865 for (auto *Arg : Args.filtered(OPT_plugin_opt))
866 parseClangOption(Arg->getValue(), Arg->getSpelling());
868 // Parse -mllvm options.
869 for (auto *Arg : Args.filtered(OPT_mllvm))
870 parseClangOption(Arg->getValue(), Arg->getSpelling());
872 if (Config->LTOO > 3)
873 error("invalid optimization level for LTO: " + Twine(Config->LTOO));
874 if (Config->LTOPartitions == 0)
875 error("--lto-partitions: number of threads must be > 0");
876 if (Config->ThinLTOJobs == 0)
877 error("--thinlto-jobs: number of threads must be > 0");
879 // Parse ELF{32,64}{LE,BE} and CPU type.
880 if (auto *Arg = Args.getLastArg(OPT_m)) {
881 StringRef S = Arg->getValue();
882 std::tie(Config->EKind, Config->EMachine, Config->OSABI) =
884 Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32");
885 Config->Emulation = S;
888 // Parse -hash-style={sysv,gnu,both}.
889 if (auto *Arg = Args.getLastArg(OPT_hash_style)) {
890 StringRef S = Arg->getValue();
892 Config->SysvHash = true;
894 Config->GnuHash = true;
895 else if (S == "both")
896 Config->SysvHash = Config->GnuHash = true;
898 error("unknown -hash-style: " + S);
901 if (Args.hasArg(OPT_print_map))
902 Config->MapFile = "-";
904 // --omagic is an option to create old-fashioned executables in which
905 // .text segments are writable. Today, the option is still in use to
906 // create special-purpose programs such as boot loaders. It doesn't
907 // make sense to create PT_GNU_RELRO for such executables.
909 Config->ZRelro = false;
911 std::tie(Config->BuildId, Config->BuildIdVector) = getBuildId(Args);
913 std::tie(Config->AndroidPackDynRelocs, Config->RelrPackDynRelocs) =
914 getPackDynRelocs(Args);
916 if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
917 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
918 Config->SymbolOrderingFile = getSymbolOrderingFile(*Buffer);
920 // If --retain-symbol-file is used, we'll keep only the symbols listed in
921 // the file and discard all others.
922 if (auto *Arg = Args.getLastArg(OPT_retain_symbols_file)) {
923 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
924 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
925 for (StringRef S : args::getLines(*Buffer))
926 Config->VersionScriptGlobals.push_back(
927 {S, /*IsExternCpp*/ false, /*HasWildcard*/ false});
930 bool HasExportDynamic =
931 Args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
933 // Parses -dynamic-list and -export-dynamic-symbol. They make some
934 // symbols private. Note that -export-dynamic takes precedence over them
935 // as it says all symbols should be exported.
936 if (!HasExportDynamic) {
937 for (auto *Arg : Args.filtered(OPT_dynamic_list))
938 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
939 readDynamicList(*Buffer);
941 for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
942 Config->DynamicList.push_back(
943 {Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
946 // If --export-dynamic-symbol=foo is given and symbol foo is defined in
947 // an object file in an archive file, that object file should be pulled
948 // out and linked. (It doesn't have to behave like that from technical
949 // point of view, but this is needed for compatibility with GNU.)
950 for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
951 Config->Undefined.push_back(Arg->getValue());
953 for (auto *Arg : Args.filtered(OPT_version_script))
954 if (Optional<std::string> Path = searchScript(Arg->getValue())) {
955 if (Optional<MemoryBufferRef> Buffer = readFile(*Path))
956 readVersionScript(*Buffer);
958 error(Twine("cannot find version script ") + Arg->getValue());
962 // Some Config members do not directly correspond to any particular
963 // command line options, but computed based on other Config values.
964 // This function initialize such members. See Config.h for the details
966 static void setConfigs(opt::InputArgList &Args) {
967 ELFKind Kind = Config->EKind;
968 uint16_t Machine = Config->EMachine;
970 Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs);
971 Config->Is64 = (Kind == ELF64LEKind || Kind == ELF64BEKind);
972 Config->IsLE = (Kind == ELF32LEKind || Kind == ELF64LEKind);
974 Config->IsLE ? support::endianness::little : support::endianness::big;
975 Config->IsMips64EL = (Kind == ELF64LEKind && Machine == EM_MIPS);
976 Config->Pic = Config->Pie || Config->Shared;
977 Config->Wordsize = Config->Is64 ? 8 : 4;
979 // There is an ILP32 ABI for x86-64, although it's not very popular.
980 // It is called the x32 ABI.
981 bool IsX32 = (Kind == ELF32LEKind && Machine == EM_X86_64);
983 // ELF defines two different ways to store relocation addends as shown below:
985 // Rel: Addends are stored to the location where relocations are applied.
986 // Rela: Addends are stored as part of relocation entry.
988 // In other words, Rela makes it easy to read addends at the price of extra
989 // 4 or 8 byte for each relocation entry. We don't know why ELF defined two
990 // different mechanisms in the first place, but this is how the spec is
993 // You cannot choose which one, Rel or Rela, you want to use. Instead each
994 // ABI defines which one you need to use. The following expression expresses
997 (Config->Is64 || IsX32 || Machine == EM_PPC) && Machine != EM_MIPS;
999 // If the output uses REL relocations we must store the dynamic relocation
1000 // addends to the output sections. We also store addends for RELA relocations
1001 // if --apply-dynamic-relocs is used.
1002 // We default to not writing the addends when using RELA relocations since
1003 // any standard conforming tool can find it in r_addend.
1004 Config->WriteAddends = Args.hasFlag(OPT_apply_dynamic_relocs,
1005 OPT_no_apply_dynamic_relocs, false) ||
1009 // Returns a value of "-format" option.
1010 static bool getBinaryOption(StringRef S) {
1013 if (S == "elf" || S == "default")
1015 error("unknown -format value: " + S +
1016 " (supported formats: elf, default, binary)");
1020 void LinkerDriver::createFiles(opt::InputArgList &Args) {
1021 // For --{push,pop}-state.
1022 std::vector<std::tuple<bool, bool, bool>> Stack;
1024 // Iterate over argv to process input files and positional arguments.
1025 for (auto *Arg : Args) {
1026 switch (Arg->getOption().getUnaliasedOption().getID()) {
1028 addLibrary(Arg->getValue());
1031 addFile(Arg->getValue(), /*WithLOption=*/false);
1036 std::tie(From, To) = StringRef(Arg->getValue()).split('=');
1037 readDefsym(From, MemoryBufferRef(To, "-defsym"));
1041 if (Optional<std::string> Path = searchScript(Arg->getValue())) {
1042 if (Optional<MemoryBufferRef> MB = readFile(*Path))
1043 readLinkerScript(*MB);
1046 error(Twine("cannot find linker script ") + Arg->getValue());
1049 Config->AsNeeded = true;
1052 InBinary = getBinaryOption(Arg->getValue());
1054 case OPT_no_as_needed:
1055 Config->AsNeeded = false;
1058 Config->Static = true;
1061 Config->Static = false;
1063 case OPT_whole_archive:
1064 InWholeArchive = true;
1066 case OPT_no_whole_archive:
1067 InWholeArchive = false;
1069 case OPT_just_symbols:
1070 if (Optional<MemoryBufferRef> MB = readFile(Arg->getValue())) {
1071 Files.push_back(createObjectFile(*MB));
1072 Files.back()->JustSymbols = true;
1075 case OPT_start_group:
1076 if (InputFile::IsInGroup)
1077 error("nested --start-group");
1078 InputFile::IsInGroup = true;
1081 if (!InputFile::IsInGroup)
1082 error("stray --end-group");
1083 InputFile::IsInGroup = false;
1084 ++InputFile::NextGroupId;
1088 error("nested --start-lib");
1089 if (InputFile::IsInGroup)
1090 error("may not nest --start-lib in --start-group");
1092 InputFile::IsInGroup = true;
1096 error("stray --end-lib");
1098 InputFile::IsInGroup = false;
1099 ++InputFile::NextGroupId;
1101 case OPT_push_state:
1102 Stack.emplace_back(Config->AsNeeded, Config->Static, InWholeArchive);
1105 if (Stack.empty()) {
1106 error("unbalanced --push-state/--pop-state");
1109 std::tie(Config->AsNeeded, Config->Static, InWholeArchive) = Stack.back();
1115 if (Files.empty() && errorCount() == 0)
1116 error("no input files");
1119 // If -m <machine_type> was not given, infer it from object files.
1120 void LinkerDriver::inferMachineType() {
1121 if (Config->EKind != ELFNoneKind)
1124 for (InputFile *F : Files) {
1125 if (F->EKind == ELFNoneKind)
1127 Config->EKind = F->EKind;
1128 Config->EMachine = F->EMachine;
1129 Config->OSABI = F->OSABI;
1130 Config->MipsN32Abi = Config->EMachine == EM_MIPS && isMipsN32Abi(F);
1133 error("target emulation unknown: -m or at least one .o file required");
1136 // Parse -z max-page-size=<value>. The default value is defined by
1138 static uint64_t getMaxPageSize(opt::InputArgList &Args) {
1139 uint64_t Val = args::getZOptionValue(Args, OPT_z, "max-page-size",
1140 Target->DefaultMaxPageSize);
1141 if (!isPowerOf2_64(Val))
1142 error("max-page-size: value isn't a power of 2");
1146 // Parses -image-base option.
1147 static Optional<uint64_t> getImageBase(opt::InputArgList &Args) {
1148 // Because we are using "Config->MaxPageSize" here, this function has to be
1149 // called after the variable is initialized.
1150 auto *Arg = Args.getLastArg(OPT_image_base);
1154 StringRef S = Arg->getValue();
1156 if (!to_integer(S, V)) {
1157 error("-image-base: number expected, but got " + S);
1160 if ((V % Config->MaxPageSize) != 0)
1161 warn("-image-base: address isn't multiple of page size: " + S);
1165 // Parses `--exclude-libs=lib,lib,...`.
1166 // The library names may be delimited by commas or colons.
1167 static DenseSet<StringRef> getExcludeLibs(opt::InputArgList &Args) {
1168 DenseSet<StringRef> Ret;
1169 for (auto *Arg : Args.filtered(OPT_exclude_libs)) {
1170 StringRef S = Arg->getValue();
1172 size_t Pos = S.find_first_of(",:");
1173 if (Pos == StringRef::npos)
1175 Ret.insert(S.substr(0, Pos));
1176 S = S.substr(Pos + 1);
1183 // Handles the -exclude-libs option. If a static library file is specified
1184 // by the -exclude-libs option, all public symbols from the archive become
1185 // private unless otherwise specified by version scripts or something.
1186 // A special library name "ALL" means all archive files.
1188 // This is not a popular option, but some programs such as bionic libc use it.
1189 template <class ELFT>
1190 static void excludeLibs(opt::InputArgList &Args) {
1191 DenseSet<StringRef> Libs = getExcludeLibs(Args);
1192 bool All = Libs.count("ALL");
1194 auto Visit = [&](InputFile *File) {
1195 if (!File->ArchiveName.empty())
1196 if (All || Libs.count(path::filename(File->ArchiveName)))
1197 for (Symbol *Sym : File->getSymbols())
1198 if (!Sym->isLocal() && Sym->File == File)
1199 Sym->VersionId = VER_NDX_LOCAL;
1202 for (InputFile *File : ObjectFiles)
1205 for (BitcodeFile *File : BitcodeFiles)
1209 // Force Sym to be entered in the output. Used for -u or equivalent.
1210 template <class ELFT> static void handleUndefined(StringRef Name) {
1211 Symbol *Sym = Symtab->find(Name);
1215 // Since symbol S may not be used inside the program, LTO may
1216 // eliminate it. Mark the symbol as "used" to prevent it.
1217 Sym->IsUsedInRegularObj = true;
1220 Symtab->fetchLazy<ELFT>(Sym);
1223 template <class ELFT> static bool shouldDemote(Symbol &Sym) {
1224 // If all references to a DSO happen to be weak, the DSO is not added to
1225 // DT_NEEDED. If that happens, we need to eliminate shared symbols created
1226 // from the DSO. Otherwise, they become dangling references that point to a
1227 // non-existent DSO.
1228 if (auto *S = dyn_cast<SharedSymbol>(&Sym))
1229 return !S->getFile<ELFT>().IsNeeded;
1231 // We are done processing archives, so lazy symbols that were used but not
1232 // found can be converted to undefined. We could also just delete the other
1233 // lazy symbols, but that seems to be more work than it is worth.
1234 return Sym.isLazy() && Sym.IsUsedInRegularObj;
1237 // Some files, such as .so or files between -{start,end}-lib may be removed
1238 // after their symbols are added to the symbol table. If that happens, we
1239 // need to remove symbols that refer files that no longer exist, so that
1240 // they won't appear in the symbol table of the output file.
1242 // We remove symbols by demoting them to undefined symbol.
1243 template <class ELFT> static void demoteSymbols() {
1244 for (Symbol *Sym : Symtab->getSymbols()) {
1245 if (shouldDemote<ELFT>(*Sym)) {
1246 bool Used = Sym->Used;
1247 replaceSymbol<Undefined>(Sym, nullptr, Sym->getName(), Sym->Binding,
1248 Sym->StOther, Sym->Type);
1254 // The section referred to by S is considered address-significant. Set the
1255 // KeepUnique flag on the section if appropriate.
1256 static void markAddrsig(Symbol *S) {
1257 if (auto *D = dyn_cast_or_null<Defined>(S))
1259 // We don't need to keep text sections unique under --icf=all even if they
1260 // are address-significant.
1261 if (Config->ICF == ICFLevel::Safe || !(D->Section->Flags & SHF_EXECINSTR))
1262 D->Section->KeepUnique = true;
1265 // Record sections that define symbols mentioned in --keep-unique <symbol>
1266 // and symbols referred to by address-significance tables. These sections are
1267 // ineligible for ICF.
1268 template <class ELFT>
1269 static void findKeepUniqueSections(opt::InputArgList &Args) {
1270 for (auto *Arg : Args.filtered(OPT_keep_unique)) {
1271 StringRef Name = Arg->getValue();
1272 auto *D = dyn_cast_or_null<Defined>(Symtab->find(Name));
1273 if (!D || !D->Section) {
1274 warn("could not find symbol " + Name + " to keep unique");
1277 D->Section->KeepUnique = true;
1280 // --icf=all --ignore-data-address-equality means that we can ignore
1281 // the dynsym and address-significance tables entirely.
1282 if (Config->ICF == ICFLevel::All && Config->IgnoreDataAddressEquality)
1285 // Symbols in the dynsym could be address-significant in other executables
1286 // or DSOs, so we conservatively mark them as address-significant.
1287 for (Symbol *S : Symtab->getSymbols())
1288 if (S->includeInDynsym())
1291 // Visit the address-significance table in each object file and mark each
1292 // referenced symbol as address-significant.
1293 for (InputFile *F : ObjectFiles) {
1294 auto *Obj = cast<ObjFile<ELFT>>(F);
1295 ArrayRef<Symbol *> Syms = Obj->getSymbols();
1296 if (Obj->AddrsigSec) {
1297 ArrayRef<uint8_t> Contents =
1298 check(Obj->getObj().getSectionContents(Obj->AddrsigSec));
1299 const uint8_t *Cur = Contents.begin();
1300 while (Cur != Contents.end()) {
1303 uint64_t SymIndex = decodeULEB128(Cur, &Size, Contents.end(), &Err);
1305 fatal(toString(F) + ": could not decode addrsig section: " + Err);
1306 markAddrsig(Syms[SymIndex]);
1310 // If an object file does not have an address-significance table,
1311 // conservatively mark all of its symbols as address-significant.
1312 for (Symbol *S : Syms)
1318 static const char *LibcallRoutineNames[] = {
1319 #define HANDLE_LIBCALL(code, name) name,
1320 #include "llvm/IR/RuntimeLibcalls.def"
1321 #undef HANDLE_LIBCALL
1324 // Do actual linking. Note that when this function is called,
1325 // all linker scripts have already been parsed.
1326 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
1327 Target = getTarget();
1329 Config->MaxPageSize = getMaxPageSize(Args);
1330 Config->ImageBase = getImageBase(Args);
1332 // If a -hash-style option was not given, set to a default value,
1333 // which varies depending on the target.
1334 if (!Args.hasArg(OPT_hash_style)) {
1335 if (Config->EMachine == EM_MIPS)
1336 Config->SysvHash = true;
1338 Config->SysvHash = Config->GnuHash = true;
1341 // Default output filename is "a.out" by the Unix tradition.
1342 if (Config->OutputFile.empty())
1343 Config->OutputFile = "a.out";
1345 // Fail early if the output file or map file is not writable. If a user has a
1346 // long link, e.g. due to a large LTO link, they do not wish to run it and
1347 // find that it failed because there was a mistake in their command-line.
1348 if (auto E = tryCreateFile(Config->OutputFile))
1349 error("cannot open output file " + Config->OutputFile + ": " + E.message());
1350 if (auto E = tryCreateFile(Config->MapFile))
1351 error("cannot open map file " + Config->MapFile + ": " + E.message());
1355 // Use default entry point name if no name was given via the command
1356 // line nor linker scripts. For some reason, MIPS entry point name is
1357 // different from others.
1358 Config->WarnMissingEntry =
1359 (!Config->Entry.empty() || (!Config->Shared && !Config->Relocatable));
1360 if (Config->Entry.empty() && !Config->Relocatable)
1361 Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
1363 // Handle --trace-symbol.
1364 for (auto *Arg : Args.filtered(OPT_trace_symbol))
1365 Symtab->trace(Arg->getValue());
1367 // Add all files to the symbol table. This will add almost all
1368 // symbols that we need to the symbol table.
1369 for (InputFile *F : Files)
1370 Symtab->addFile<ELFT>(F);
1372 // Now that we have every file, we can decide if we will need a
1373 // dynamic symbol table.
1374 // We need one if we were asked to export dynamic symbols or if we are
1375 // producing a shared library.
1376 // We also need one if any shared libraries are used and for pie executables
1377 // (probably because the dynamic linker needs it).
1378 Config->HasDynSymTab =
1379 !SharedFiles.empty() || Config->Pic || Config->ExportDynamic;
1381 // Some symbols (such as __ehdr_start) are defined lazily only when there
1382 // are undefined symbols for them, so we add these to trigger that logic.
1383 for (StringRef Sym : Script->ReferencedSymbols)
1384 Symtab->addUndefined<ELFT>(Sym);
1386 // Handle the `--undefined <sym>` options.
1387 for (StringRef S : Config->Undefined)
1388 handleUndefined<ELFT>(S);
1390 // If an entry symbol is in a static archive, pull out that file now.
1391 handleUndefined<ELFT>(Config->Entry);
1393 // If any of our inputs are bitcode files, the LTO code generator may create
1394 // references to certain library functions that might not be explicit in the
1395 // bitcode file's symbol table. If any of those library functions are defined
1396 // in a bitcode file in an archive member, we need to arrange to use LTO to
1397 // compile those archive members by adding them to the link beforehand.
1399 // With this the symbol table should be complete. After this, no new names
1400 // except a few linker-synthesized ones will be added to the symbol table.
1401 if (!BitcodeFiles.empty())
1402 for (const char *S : LibcallRoutineNames)
1403 handleUndefined<ELFT>(S);
1405 // Return if there were name resolution errors.
1409 // Now when we read all script files, we want to finalize order of linker
1410 // script commands, which can be not yet final because of INSERT commands.
1411 Script->processInsertCommands();
1413 // We want to declare linker script's symbols early,
1414 // so that we can version them.
1415 // They also might be exported if referenced by DSOs.
1416 Script->declareSymbols();
1418 // Handle the -exclude-libs option.
1419 if (Args.hasArg(OPT_exclude_libs))
1420 excludeLibs<ELFT>(Args);
1422 // Create ElfHeader early. We need a dummy section in
1423 // addReservedSymbols to mark the created symbols as not absolute.
1424 Out::ElfHeader = make<OutputSection>("", 0, SHF_ALLOC);
1425 Out::ElfHeader->Size = sizeof(typename ELFT::Ehdr);
1427 // We need to create some reserved symbols such as _end. Create them.
1428 if (!Config->Relocatable)
1429 addReservedSymbols();
1431 // Apply version scripts.
1433 // For a relocatable output, version scripts don't make sense, and
1434 // parsing a symbol version string (e.g. dropping "@ver1" from a symbol
1435 // name "foo@ver1") rather do harm, so we don't call this if -r is given.
1436 if (!Config->Relocatable)
1437 Symtab->scanVersionScript();
1439 // Create wrapped symbols for -wrap option.
1440 for (auto *Arg : Args.filtered(OPT_wrap))
1441 Symtab->addSymbolWrap<ELFT>(Arg->getValue());
1443 // Do link-time optimization if given files are LLVM bitcode files.
1444 // This compiles bitcode files into real object files.
1445 Symtab->addCombinedLTOObject<ELFT>();
1449 // If -thinlto-index-only is given, we should create only "index
1450 // files" and not object files. Index file creation is already done
1451 // in addCombinedLTOObject, so we are done if that's the case.
1452 if (Config->ThinLTOIndexOnly)
1455 // Apply symbol renames for -wrap.
1456 Symtab->applySymbolWrap();
1458 // Now that we have a complete list of input files.
1459 // Beyond this point, no new files are added.
1460 // Aggregate all input sections into one place.
1461 for (InputFile *F : ObjectFiles)
1462 for (InputSectionBase *S : F->getSections())
1463 if (S && S != &InputSection::Discarded)
1464 InputSections.push_back(S);
1465 for (BinaryFile *F : BinaryFiles)
1466 for (InputSectionBase *S : F->getSections())
1467 InputSections.push_back(cast<InputSection>(S));
1469 // We do not want to emit debug sections if --strip-all
1470 // or -strip-debug are given.
1471 if (Config->Strip != StripPolicy::None)
1472 llvm::erase_if(InputSections, [](InputSectionBase *S) {
1473 return S->Name.startswith(".debug") || S->Name.startswith(".zdebug");
1476 Config->EFlags = Target->calcEFlags();
1478 if (Config->EMachine == EM_ARM) {
1479 // FIXME: These warnings can be removed when lld only uses these features
1480 // when the input objects have been compiled with an architecture that
1482 if (Config->ARMHasBlx == false)
1483 warn("lld uses blx instruction, no object with architecture supporting "
1484 "feature detected.");
1485 if (Config->ARMJ1J2BranchEncoding == false)
1486 warn("lld uses extended branch encoding, no object with architecture "
1487 "supporting feature detected.");
1488 if (Config->ARMHasMovtMovw == false)
1489 warn("lld may use movt/movw, no object with architecture supporting "
1490 "feature detected.");
1493 // This adds a .comment section containing a version string. We have to add it
1494 // before decompressAndMergeSections because the .comment section is a
1495 // mergeable section.
1496 if (!Config->Relocatable)
1497 InputSections.push_back(createCommentSection());
1499 // Do size optimizations: garbage collection, merging of SHF_MERGE sections
1500 // and identical code folding.
1501 decompressSections();
1502 splitSections<ELFT>();
1504 demoteSymbols<ELFT>();
1506 if (Config->ICF != ICFLevel::None) {
1507 findKeepUniqueSections<ELFT>(Args);
1511 // Read the callgraph now that we know what was gced or icfed
1512 if (auto *Arg = Args.getLastArg(OPT_call_graph_ordering_file))
1513 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
1514 readCallGraph(*Buffer);
1516 // Write the result to the file.
1517 writeResult<ELFT>();