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 //===----------------------------------------------------------------------===//
29 #include "Filesystem.h"
31 #include "InputFiles.h"
32 #include "InputSection.h"
33 #include "LinkerScript.h"
35 #include "OutputSections.h"
36 #include "ScriptParser.h"
38 #include "SymbolTable.h"
39 #include "SyntheticSections.h"
43 #include "lld/Config/Version.h"
44 #include "lld/Driver/Driver.h"
45 #include "llvm/ADT/StringExtras.h"
46 #include "llvm/ADT/StringSwitch.h"
47 #include "llvm/Support/CommandLine.h"
48 #include "llvm/Support/Compression.h"
49 #include "llvm/Support/Path.h"
50 #include "llvm/Support/TarWriter.h"
51 #include "llvm/Support/TargetSelect.h"
52 #include "llvm/Support/raw_ostream.h"
57 using namespace llvm::ELF;
58 using namespace llvm::object;
59 using namespace llvm::sys;
62 using namespace lld::elf;
64 Configuration *elf::Config;
65 LinkerDriver *elf::Driver;
67 BumpPtrAllocator elf::BAlloc;
68 StringSaver elf::Saver{BAlloc};
69 std::vector<SpecificAllocBase *> elf::SpecificAllocBase::Instances;
71 static void setConfigs();
73 bool elf::link(ArrayRef<const char *> Args, bool CanExitEarly,
78 InputSections.clear();
81 Config = make<Configuration>();
82 Driver = make<LinkerDriver>();
83 Script = make<LinkerScript>();
85 Driver->main(Args, CanExitEarly);
90 // Parses a linker -m option.
91 static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef Emul) {
94 if (S.endswith("_fbsd")) {
96 OSABI = ELFOSABI_FREEBSD;
99 std::pair<ELFKind, uint16_t> Ret =
100 StringSwitch<std::pair<ELFKind, uint16_t>>(S)
101 .Cases("aarch64elf", "aarch64linux", {ELF64LEKind, EM_AARCH64})
102 .Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM})
103 .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
104 .Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS})
105 .Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS})
106 .Case("elf32ppc", {ELF32BEKind, EM_PPC})
107 .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
108 .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
109 .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
110 .Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64})
111 .Case("elf_i386", {ELF32LEKind, EM_386})
112 .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
113 .Default({ELFNoneKind, EM_NONE});
115 if (Ret.first == ELFNoneKind) {
116 if (S == "i386pe" || S == "i386pep" || S == "thumb2pe")
117 error("Windows targets are not supported on the ELF frontend: " + Emul);
119 error("unknown emulation: " + Emul);
121 return std::make_tuple(Ret.first, Ret.second, OSABI);
124 // Returns slices of MB by parsing MB as an archive file.
125 // Each slice consists of a member file in the archive.
126 std::vector<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers(
127 MemoryBufferRef MB) {
128 std::unique_ptr<Archive> File =
129 check(Archive::create(MB),
130 MB.getBufferIdentifier() + ": failed to parse archive");
132 std::vector<std::pair<MemoryBufferRef, uint64_t>> V;
133 Error Err = Error::success();
134 for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
136 check(COrErr, MB.getBufferIdentifier() +
137 ": could not get the child of the archive");
138 MemoryBufferRef MBRef =
139 check(C.getMemoryBufferRef(),
140 MB.getBufferIdentifier() +
141 ": could not get the buffer for a child of the archive");
142 V.push_back(std::make_pair(MBRef, C.getChildOffset()));
145 fatal(MB.getBufferIdentifier() + ": Archive::children failed: " +
146 toString(std::move(Err)));
148 // Take ownership of memory buffers created for members of thin archives.
149 for (std::unique_ptr<MemoryBuffer> &MB : File->takeThinBuffers())
150 make<std::unique_ptr<MemoryBuffer>>(std::move(MB));
155 // Opens a file and create a file object. Path has to be resolved already.
156 void LinkerDriver::addFile(StringRef Path, bool WithLOption) {
157 using namespace sys::fs;
159 Optional<MemoryBufferRef> Buffer = readFile(Path);
160 if (!Buffer.hasValue())
162 MemoryBufferRef MBRef = *Buffer;
165 Files.push_back(make<BinaryFile>(MBRef));
169 switch (identify_magic(MBRef.getBuffer())) {
170 case file_magic::unknown:
171 readLinkerScript(MBRef);
173 case file_magic::archive: {
174 // Handle -whole-archive.
175 if (InWholeArchive) {
176 for (const auto &P : getArchiveMembers(MBRef))
177 Files.push_back(createObjectFile(P.first, Path, P.second));
181 std::unique_ptr<Archive> File =
182 check(Archive::create(MBRef), Path + ": failed to parse archive");
184 // If an archive file has no symbol table, it is likely that a user
185 // is attempting LTO and using a default ar command that doesn't
186 // understand the LLVM bitcode file. It is a pretty common error, so
187 // we'll handle it as if it had a symbol table.
188 if (!File->isEmpty() && !File->hasSymbolTable()) {
189 for (const auto &P : getArchiveMembers(MBRef))
190 Files.push_back(make<LazyObjectFile>(P.first, Path, P.second));
194 // Handle the regular case.
195 Files.push_back(make<ArchiveFile>(std::move(File)));
198 case file_magic::elf_shared_object:
199 if (Config->Relocatable) {
200 error("attempted static link of dynamic object " + Path);
204 // DSOs usually have DT_SONAME tags in their ELF headers, and the
205 // sonames are used to identify DSOs. But if they are missing,
206 // they are identified by filenames. We don't know whether the new
207 // file has a DT_SONAME or not because we haven't parsed it yet.
208 // Here, we set the default soname for the file because we might
211 // If a file was specified by -lfoo, the directory part is not
212 // significant, as a user did not specify it. This behavior is
213 // compatible with GNU.
215 createSharedFile(MBRef, WithLOption ? path::filename(Path) : Path));
219 Files.push_back(make<LazyObjectFile>(MBRef, "", 0));
221 Files.push_back(createObjectFile(MBRef));
225 // Add a given library by searching it from input search paths.
226 void LinkerDriver::addLibrary(StringRef Name) {
227 if (Optional<std::string> Path = searchLibrary(Name))
228 addFile(*Path, /*WithLOption=*/true);
230 error("unable to find library -l" + Name);
233 // This function is called on startup. We need this for LTO since
234 // LTO calls LLVM functions to compile bitcode files to native code.
235 // Technically this can be delayed until we read bitcode files, but
236 // we don't bother to do lazily because the initialization is fast.
237 static void initLLVM(opt::InputArgList &Args) {
238 InitializeAllTargets();
239 InitializeAllTargetMCs();
240 InitializeAllAsmPrinters();
241 InitializeAllAsmParsers();
243 // Parse and evaluate -mllvm options.
244 std::vector<const char *> V;
245 V.push_back("lld (LLVM option parsing)");
246 for (auto *Arg : Args.filtered(OPT_mllvm))
247 V.push_back(Arg->getValue());
248 cl::ParseCommandLineOptions(V.size(), V.data());
251 // Some command line options or some combinations of them are not allowed.
252 // This function checks for such errors.
253 static void checkOptions(opt::InputArgList &Args) {
254 // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
255 // table which is a relatively new feature.
256 if (Config->EMachine == EM_MIPS && Config->GnuHash)
257 error("the .gnu.hash section is not compatible with the MIPS target.");
259 if (Config->Pie && Config->Shared)
260 error("-shared and -pie may not be used together");
262 if (!Config->Shared && !Config->AuxiliaryList.empty())
263 error("-f may not be used without -shared");
265 if (Config->Relocatable) {
267 error("-r and -shared may not be used together");
268 if (Config->GcSections)
269 error("-r and --gc-sections may not be used together");
271 error("-r and --icf may not be used together");
273 error("-r and -pie may not be used together");
277 static int getInteger(opt::InputArgList &Args, unsigned Key, int Default) {
279 if (auto *Arg = Args.getLastArg(Key)) {
280 StringRef S = Arg->getValue();
281 if (!to_integer(S, V, 10))
282 error(Arg->getSpelling() + ": number expected, but got " + S);
287 static const char *getReproduceOption(opt::InputArgList &Args) {
288 if (auto *Arg = Args.getLastArg(OPT_reproduce))
289 return Arg->getValue();
290 return getenv("LLD_REPRODUCE");
293 static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
294 for (auto *Arg : Args.filtered(OPT_z))
295 if (Key == Arg->getValue())
300 static uint64_t getZOptionValue(opt::InputArgList &Args, StringRef Key,
302 for (auto *Arg : Args.filtered(OPT_z)) {
303 std::pair<StringRef, StringRef> KV = StringRef(Arg->getValue()).split('=');
304 if (KV.first == Key) {
305 uint64_t Result = Default;
306 if (!to_integer(KV.second, Result))
307 error("invalid " + Key + ": " + KV.second);
314 void LinkerDriver::main(ArrayRef<const char *> ArgsArr, bool CanExitEarly) {
316 opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
318 // Interpret this flag early because error() depends on them.
319 Config->ErrorLimit = getInteger(Args, OPT_error_limit, 20);
322 if (Args.hasArg(OPT_help)) {
323 printHelp(ArgsArr[0]);
327 // Handle -v or -version.
329 // A note about "compatible with GNU linkers" message: this is a hack for
330 // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
331 // still the newest version in March 2017) or earlier to recognize LLD as
332 // a GNU compatible linker. As long as an output for the -v option
333 // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
335 // This is somewhat ugly hack, but in reality, we had no choice other
336 // than doing this. Considering the very long release cycle of Libtool,
337 // it is not easy to improve it to recognize LLD as a GNU compatible
338 // linker in a timely manner. Even if we can make it, there are still a
339 // lot of "configure" scripts out there that are generated by old version
340 // of Libtool. We cannot convince every software developer to migrate to
341 // the latest version and re-generate scripts. So we have this hack.
342 if (Args.hasArg(OPT_v) || Args.hasArg(OPT_version))
343 message(getLLDVersion() + " (compatible with GNU linkers)");
345 // ld.bfd always exits after printing out the version string.
346 // ld.gold proceeds if a given option is -v. Because gold's behavior
347 // is more permissive than ld.bfd, we chose what gold does here.
348 if (Args.hasArg(OPT_version))
351 Config->ExitEarly = CanExitEarly && !Args.hasArg(OPT_full_shutdown);
353 if (const char *Path = getReproduceOption(Args)) {
354 // Note that --reproduce is a debug option so you can ignore it
355 // if you are trying to understand the whole picture of the code.
356 Expected<std::unique_ptr<TarWriter>> ErrOrWriter =
357 TarWriter::create(Path, path::stem(Path));
359 Tar = ErrOrWriter->get();
360 Tar->append("response.txt", createResponseFile(Args));
361 Tar->append("version.txt", getLLDVersion() + "\n");
362 make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter));
364 error(Twine("--reproduce: failed to open ") + Path + ": " +
365 toString(ErrOrWriter.takeError()));
378 switch (Config->EKind) {
392 llvm_unreachable("unknown Config->EKind");
396 static bool getArg(opt::InputArgList &Args, unsigned K1, unsigned K2,
398 if (auto *Arg = Args.getLastArg(K1, K2))
399 return Arg->getOption().getID() == K1;
403 static std::vector<StringRef> getArgs(opt::InputArgList &Args, int Id) {
404 std::vector<StringRef> V;
405 for (auto *Arg : Args.filtered(Id))
406 V.push_back(Arg->getValue());
410 static std::string getRpath(opt::InputArgList &Args) {
411 std::vector<StringRef> V = getArgs(Args, OPT_rpath);
412 return llvm::join(V.begin(), V.end(), ":");
415 // Determines what we should do if there are remaining unresolved
416 // symbols after the name resolution.
417 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
418 // -noinhibit-exec or -r imply some default values.
419 if (Args.hasArg(OPT_noinhibit_exec))
420 return UnresolvedPolicy::WarnAll;
421 if (Args.hasArg(OPT_relocatable))
422 return UnresolvedPolicy::IgnoreAll;
424 UnresolvedPolicy ErrorOrWarn = getArg(Args, OPT_error_unresolved_symbols,
425 OPT_warn_unresolved_symbols, true)
426 ? UnresolvedPolicy::ReportError
427 : UnresolvedPolicy::Warn;
429 // Process the last of -unresolved-symbols, -no-undefined or -z defs.
430 for (auto *Arg : llvm::reverse(Args)) {
431 switch (Arg->getOption().getID()) {
432 case OPT_unresolved_symbols: {
433 StringRef S = Arg->getValue();
434 if (S == "ignore-all" || S == "ignore-in-object-files")
435 return UnresolvedPolicy::Ignore;
436 if (S == "ignore-in-shared-libs" || S == "report-all")
438 error("unknown --unresolved-symbols value: " + S);
441 case OPT_no_undefined:
444 if (StringRef(Arg->getValue()) == "defs")
450 // -shared implies -unresolved-symbols=ignore-all because missing
451 // symbols are likely to be resolved at runtime using other DSOs.
453 return UnresolvedPolicy::Ignore;
457 static Target2Policy getTarget2(opt::InputArgList &Args) {
458 StringRef S = Args.getLastArgValue(OPT_target2, "got-rel");
460 return Target2Policy::Rel;
462 return Target2Policy::Abs;
464 return Target2Policy::GotRel;
465 error("unknown --target2 option: " + S);
466 return Target2Policy::GotRel;
469 static bool isOutputFormatBinary(opt::InputArgList &Args) {
470 if (auto *Arg = Args.getLastArg(OPT_oformat)) {
471 StringRef S = Arg->getValue();
474 error("unknown --oformat value: " + S);
479 static DiscardPolicy getDiscard(opt::InputArgList &Args) {
480 if (Args.hasArg(OPT_relocatable))
481 return DiscardPolicy::None;
484 Args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
486 return DiscardPolicy::Default;
487 if (Arg->getOption().getID() == OPT_discard_all)
488 return DiscardPolicy::All;
489 if (Arg->getOption().getID() == OPT_discard_locals)
490 return DiscardPolicy::Locals;
491 return DiscardPolicy::None;
494 static StringRef getDynamicLinker(opt::InputArgList &Args) {
495 auto *Arg = Args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
496 if (!Arg || Arg->getOption().getID() == OPT_no_dynamic_linker)
498 return Arg->getValue();
501 static StripPolicy getStrip(opt::InputArgList &Args) {
502 if (Args.hasArg(OPT_relocatable))
503 return StripPolicy::None;
505 auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug);
507 return StripPolicy::None;
508 if (Arg->getOption().getID() == OPT_strip_all)
509 return StripPolicy::All;
510 return StripPolicy::Debug;
513 static uint64_t parseSectionAddress(StringRef S, opt::Arg *Arg) {
515 if (S.startswith("0x"))
517 if (!to_integer(S, VA, 16))
518 error("invalid argument: " + toString(Arg));
522 static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) {
523 StringMap<uint64_t> Ret;
524 for (auto *Arg : Args.filtered(OPT_section_start)) {
527 std::tie(Name, Addr) = StringRef(Arg->getValue()).split('=');
528 Ret[Name] = parseSectionAddress(Addr, Arg);
531 if (auto *Arg = Args.getLastArg(OPT_Ttext))
532 Ret[".text"] = parseSectionAddress(Arg->getValue(), Arg);
533 if (auto *Arg = Args.getLastArg(OPT_Tdata))
534 Ret[".data"] = parseSectionAddress(Arg->getValue(), Arg);
535 if (auto *Arg = Args.getLastArg(OPT_Tbss))
536 Ret[".bss"] = parseSectionAddress(Arg->getValue(), Arg);
540 static SortSectionPolicy getSortSection(opt::InputArgList &Args) {
541 StringRef S = Args.getLastArgValue(OPT_sort_section);
542 if (S == "alignment")
543 return SortSectionPolicy::Alignment;
545 return SortSectionPolicy::Name;
547 error("unknown --sort-section rule: " + S);
548 return SortSectionPolicy::Default;
551 static std::pair<bool, bool> getHashStyle(opt::InputArgList &Args) {
552 StringRef S = Args.getLastArgValue(OPT_hash_style, "sysv");
554 return {true, false};
556 return {false, true};
558 error("unknown -hash-style: " + S);
562 // Parse --build-id or --build-id=<style>. We handle "tree" as a
563 // synonym for "sha1" because all our hash functions including
564 // -build-id=sha1 are actually tree hashes for performance reasons.
565 static std::pair<BuildIdKind, std::vector<uint8_t>>
566 getBuildId(opt::InputArgList &Args) {
567 auto *Arg = Args.getLastArg(OPT_build_id, OPT_build_id_eq);
569 return {BuildIdKind::None, {}};
571 if (Arg->getOption().getID() == OPT_build_id)
572 return {BuildIdKind::Fast, {}};
574 StringRef S = Arg->getValue();
576 return {BuildIdKind::Md5, {}};
577 if (S == "sha1" || S == "tree")
578 return {BuildIdKind::Sha1, {}};
580 return {BuildIdKind::Uuid, {}};
581 if (S.startswith("0x"))
582 return {BuildIdKind::Hexstring, parseHex(S.substr(2))};
585 error("unknown --build-id style: " + S);
586 return {BuildIdKind::None, {}};
589 static std::vector<StringRef> getLines(MemoryBufferRef MB) {
590 SmallVector<StringRef, 0> Arr;
591 MB.getBuffer().split(Arr, '\n');
593 std::vector<StringRef> Ret;
594 for (StringRef S : Arr) {
602 static bool getCompressDebugSections(opt::InputArgList &Args) {
603 StringRef S = Args.getLastArgValue(OPT_compress_debug_sections, "none");
607 error("unknown --compress-debug-sections value: " + S);
608 if (!zlib::isAvailable())
609 error("--compress-debug-sections: zlib is not available");
613 // Initializes Config members by the command line options.
614 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
615 Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
616 Config->AuxiliaryList = getArgs(Args, OPT_auxiliary);
617 Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
618 Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
619 Config->CompressDebugSections = getCompressDebugSections(Args);
620 Config->DefineCommon = getArg(Args, OPT_define_common, OPT_no_define_common,
621 !Args.hasArg(OPT_relocatable));
622 Config->Demangle = getArg(Args, OPT_demangle, OPT_no_demangle, true);
623 Config->DisableVerify = Args.hasArg(OPT_disable_verify);
624 Config->Discard = getDiscard(Args);
625 Config->DynamicLinker = getDynamicLinker(Args);
626 Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
627 Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
628 Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
629 Config->Entry = Args.getLastArgValue(OPT_entry);
630 Config->ExportDynamic =
631 getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false);
632 Config->FatalWarnings =
633 getArg(Args, OPT_fatal_warnings, OPT_no_fatal_warnings, false);
634 Config->Fini = Args.getLastArgValue(OPT_fini, "_fini");
635 Config->GcSections = getArg(Args, OPT_gc_sections, OPT_no_gc_sections, false);
636 Config->GdbIndex = Args.hasArg(OPT_gdb_index);
637 Config->ICF = Args.hasArg(OPT_icf);
638 Config->Init = Args.getLastArgValue(OPT_init, "_init");
639 Config->LTOAAPipeline = Args.getLastArgValue(OPT_lto_aa_pipeline);
640 Config->LTONewPmPasses = Args.getLastArgValue(OPT_lto_newpm_passes);
641 Config->LTOO = getInteger(Args, OPT_lto_O, 2);
642 Config->LTOPartitions = getInteger(Args, OPT_lto_partitions, 1);
643 Config->MapFile = Args.getLastArgValue(OPT_Map);
644 Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
645 Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
646 Config->Nostdlib = Args.hasArg(OPT_nostdlib);
647 Config->OFormatBinary = isOutputFormatBinary(Args);
648 Config->Omagic = Args.hasArg(OPT_omagic);
649 Config->OptRemarksFilename = Args.getLastArgValue(OPT_opt_remarks_filename);
650 Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness);
651 Config->Optimize = getInteger(Args, OPT_O, 1);
652 Config->OutputFile = Args.getLastArgValue(OPT_o);
653 Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false);
654 Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
655 Config->Rpath = getRpath(Args);
656 Config->Relocatable = Args.hasArg(OPT_relocatable);
657 Config->SaveTemps = Args.hasArg(OPT_save_temps);
658 Config->SearchPaths = getArgs(Args, OPT_L);
659 Config->SectionStartMap = getSectionStartMap(Args);
660 Config->Shared = Args.hasArg(OPT_shared);
661 Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
662 Config->SoName = Args.getLastArgValue(OPT_soname);
663 Config->SortSection = getSortSection(Args);
664 Config->Strip = getStrip(Args);
665 Config->Sysroot = Args.getLastArgValue(OPT_sysroot);
666 Config->Target1Rel = getArg(Args, OPT_target1_rel, OPT_target1_abs, false);
667 Config->Target2 = getTarget2(Args);
668 Config->ThinLTOCacheDir = Args.getLastArgValue(OPT_thinlto_cache_dir);
669 Config->ThinLTOCachePolicy = check(
670 parseCachePruningPolicy(Args.getLastArgValue(OPT_thinlto_cache_policy)),
671 "--thinlto-cache-policy: invalid cache policy");
672 Config->ThinLTOJobs = getInteger(Args, OPT_thinlto_jobs, -1u);
673 Config->Threads = getArg(Args, OPT_threads, OPT_no_threads, true);
674 Config->Trace = Args.hasArg(OPT_trace);
675 Config->Undefined = getArgs(Args, OPT_undefined);
676 Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args);
677 Config->Verbose = Args.hasArg(OPT_verbose);
678 Config->WarnCommon = Args.hasArg(OPT_warn_common);
679 Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
680 Config->ZExecstack = hasZOption(Args, "execstack");
681 Config->ZNocopyreloc = hasZOption(Args, "nocopyreloc");
682 Config->ZNodelete = hasZOption(Args, "nodelete");
683 Config->ZNodlopen = hasZOption(Args, "nodlopen");
684 Config->ZNow = hasZOption(Args, "now");
685 Config->ZOrigin = hasZOption(Args, "origin");
686 Config->ZRelro = !hasZOption(Args, "norelro");
687 Config->ZRodynamic = hasZOption(Args, "rodynamic");
688 Config->ZStackSize = getZOptionValue(Args, "stack-size", 0);
689 Config->ZText = !hasZOption(Args, "notext");
690 Config->ZWxneeded = hasZOption(Args, "wxneeded");
692 if (Config->LTOO > 3)
693 error("invalid optimization level for LTO: " +
694 Args.getLastArgValue(OPT_lto_O));
695 if (Config->LTOPartitions == 0)
696 error("--lto-partitions: number of threads must be > 0");
697 if (Config->ThinLTOJobs == 0)
698 error("--thinlto-jobs: number of threads must be > 0");
700 if (auto *Arg = Args.getLastArg(OPT_m)) {
701 // Parse ELF{32,64}{LE,BE} and CPU type.
702 StringRef S = Arg->getValue();
703 std::tie(Config->EKind, Config->EMachine, Config->OSABI) =
705 Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32");
706 Config->Emulation = S;
709 if (Args.hasArg(OPT_print_map))
710 Config->MapFile = "-";
712 // --omagic is an option to create old-fashioned executables in which
713 // .text segments are writable. Today, the option is still in use to
714 // create special-purpose programs such as boot loaders. It doesn't
715 // make sense to create PT_GNU_RELRO for such executables.
717 Config->ZRelro = false;
719 std::tie(Config->SysvHash, Config->GnuHash) = getHashStyle(Args);
720 std::tie(Config->BuildId, Config->BuildIdVector) = getBuildId(Args);
722 if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
723 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
724 Config->SymbolOrderingFile = getLines(*Buffer);
726 // If --retain-symbol-file is used, we'll keep only the symbols listed in
727 // the file and discard all others.
728 if (auto *Arg = Args.getLastArg(OPT_retain_symbols_file)) {
729 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
730 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
731 for (StringRef S : getLines(*Buffer))
732 Config->VersionScriptGlobals.push_back(
733 {S, /*IsExternCpp*/ false, /*HasWildcard*/ false});
736 bool HasExportDynamic =
737 getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false);
739 // Parses -dynamic-list and -export-dynamic-symbol. They make some
740 // symbols private. Note that -export-dynamic takes precedence over them
741 // as it says all symbols should be exported.
742 if (!HasExportDynamic) {
743 for (auto *Arg : Args.filtered(OPT_dynamic_list))
744 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
745 readDynamicList(*Buffer);
747 for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
748 Config->VersionScriptGlobals.push_back(
749 {Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
751 // Dynamic lists are a simplified linker script that doesn't need the
752 // "global:" and implicitly ends with a "local:*". Set the variables
753 // needed to simulate that.
754 if (Args.hasArg(OPT_dynamic_list) ||
755 Args.hasArg(OPT_export_dynamic_symbol)) {
756 Config->ExportDynamic = true;
758 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
762 if (auto *Arg = Args.getLastArg(OPT_version_script))
763 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
764 readVersionScript(*Buffer);
767 // Some Config members do not directly correspond to any particular
768 // command line options, but computed based on other Config values.
769 // This function initialize such members. See Config.h for the details
771 static void setConfigs() {
772 ELFKind Kind = Config->EKind;
773 uint16_t Machine = Config->EMachine;
775 // There is an ILP32 ABI for x86-64, although it's not very popular.
776 // It is called the x32 ABI.
777 bool IsX32 = (Kind == ELF32LEKind && Machine == EM_X86_64);
779 Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs);
780 Config->Is64 = (Kind == ELF64LEKind || Kind == ELF64BEKind);
781 Config->IsLE = (Kind == ELF32LEKind || Kind == ELF64LEKind);
783 Config->IsLE ? support::endianness::little : support::endianness::big;
784 Config->IsMips64EL = (Kind == ELF64LEKind && Machine == EM_MIPS);
785 Config->IsRela = Config->Is64 || IsX32 || Config->MipsN32Abi;
786 Config->Pic = Config->Pie || Config->Shared;
787 Config->Wordsize = Config->Is64 ? 8 : 4;
790 // Returns a value of "-format" option.
791 static bool getBinaryOption(StringRef S) {
794 if (S == "elf" || S == "default")
796 error("unknown -format value: " + S +
797 " (supported formats: elf, default, binary)");
801 void LinkerDriver::createFiles(opt::InputArgList &Args) {
802 for (auto *Arg : Args) {
803 switch (Arg->getOption().getID()) {
805 addLibrary(Arg->getValue());
808 addFile(Arg->getValue(), /*WithLOption=*/false);
810 case OPT_alias_script_T:
812 if (Optional<MemoryBufferRef> MB = readFile(Arg->getValue()))
813 readLinkerScript(*MB);
816 Config->AsNeeded = true;
819 InBinary = getBinaryOption(Arg->getValue());
821 case OPT_no_as_needed:
822 Config->AsNeeded = false;
825 Config->Static = true;
828 Config->Static = false;
830 case OPT_whole_archive:
831 InWholeArchive = true;
833 case OPT_no_whole_archive:
834 InWholeArchive = false;
845 if (Files.empty() && ErrorCount == 0)
846 error("no input files");
849 // If -m <machine_type> was not given, infer it from object files.
850 void LinkerDriver::inferMachineType() {
851 if (Config->EKind != ELFNoneKind)
854 for (InputFile *F : Files) {
855 if (F->EKind == ELFNoneKind)
857 Config->EKind = F->EKind;
858 Config->EMachine = F->EMachine;
859 Config->OSABI = F->OSABI;
860 Config->MipsN32Abi = Config->EMachine == EM_MIPS && isMipsN32Abi(F);
863 error("target emulation unknown: -m or at least one .o file required");
866 // Parse -z max-page-size=<value>. The default value is defined by
868 static uint64_t getMaxPageSize(opt::InputArgList &Args) {
870 getZOptionValue(Args, "max-page-size", Target->DefaultMaxPageSize);
871 if (!isPowerOf2_64(Val))
872 error("max-page-size: value isn't a power of 2");
876 // Parses -image-base option.
877 static uint64_t getImageBase(opt::InputArgList &Args) {
878 // Use default if no -image-base option is given.
879 // Because we are using "Target" here, this function
880 // has to be called after the variable is initialized.
881 auto *Arg = Args.getLastArg(OPT_image_base);
883 return Config->Pic ? 0 : Target->DefaultImageBase;
885 StringRef S = Arg->getValue();
887 if (!to_integer(S, V)) {
888 error("-image-base: number expected, but got " + S);
891 if ((V % Config->MaxPageSize) != 0)
892 warn("-image-base: address isn't multiple of page size: " + S);
896 // Parses --defsym=alias option.
897 static std::vector<std::pair<StringRef, StringRef>>
898 getDefsym(opt::InputArgList &Args) {
899 std::vector<std::pair<StringRef, StringRef>> Ret;
900 for (auto *Arg : Args.filtered(OPT_defsym)) {
903 std::tie(From, To) = StringRef(Arg->getValue()).split('=');
904 if (!isValidCIdentifier(To))
905 error("--defsym: symbol name expected, but got " + To);
906 Ret.push_back({From, To});
911 // Parses `--exclude-libs=lib,lib,...`.
912 // The library names may be delimited by commas or colons.
913 static DenseSet<StringRef> getExcludeLibs(opt::InputArgList &Args) {
914 DenseSet<StringRef> Ret;
915 for (auto *Arg : Args.filtered(OPT_exclude_libs)) {
916 StringRef S = Arg->getValue();
918 size_t Pos = S.find_first_of(",:");
919 if (Pos == StringRef::npos)
921 Ret.insert(S.substr(0, Pos));
922 S = S.substr(Pos + 1);
929 // Handles the -exclude-libs option. If a static library file is specified
930 // by the -exclude-libs option, all public symbols from the archive become
931 // private unless otherwise specified by version scripts or something.
932 // A special library name "ALL" means all archive files.
934 // This is not a popular option, but some programs such as bionic libc use it.
935 static void excludeLibs(opt::InputArgList &Args, ArrayRef<InputFile *> Files) {
936 DenseSet<StringRef> Libs = getExcludeLibs(Args);
937 bool All = Libs.count("ALL");
939 for (InputFile *File : Files)
940 if (auto *F = dyn_cast<ArchiveFile>(File))
941 if (All || Libs.count(path::filename(F->getName())))
942 for (Symbol *Sym : F->getSymbols())
943 Sym->VersionId = VER_NDX_LOCAL;
946 // Do actual linking. Note that when this function is called,
947 // all linker scripts have already been parsed.
948 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
949 SymbolTable<ELFT> Symtab;
950 elf::Symtab<ELFT>::X = &Symtab;
951 Target = getTarget();
953 Config->MaxPageSize = getMaxPageSize(Args);
954 Config->ImageBase = getImageBase(Args);
956 // Default output filename is "a.out" by the Unix tradition.
957 if (Config->OutputFile.empty())
958 Config->OutputFile = "a.out";
960 // Fail early if the output file or map file is not writable. If a user has a
961 // long link, e.g. due to a large LTO link, they do not wish to run it and
962 // find that it failed because there was a mistake in their command-line.
963 if (auto E = tryCreateFile(Config->OutputFile))
964 error("cannot open output file " + Config->OutputFile + ": " + E.message());
965 if (auto E = tryCreateFile(Config->MapFile))
966 error("cannot open map file " + Config->MapFile + ": " + E.message());
970 // Use default entry point name if no name was given via the command
971 // line nor linker scripts. For some reason, MIPS entry point name is
972 // different from others.
973 Config->WarnMissingEntry =
974 (!Config->Entry.empty() || (!Config->Shared && !Config->Relocatable));
975 if (Config->Entry.empty() && !Config->Relocatable)
976 Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
978 // Handle --trace-symbol.
979 for (auto *Arg : Args.filtered(OPT_trace_symbol))
980 Symtab.trace(Arg->getValue());
982 // Add all files to the symbol table. This will add almost all
983 // symbols that we need to the symbol table.
984 for (InputFile *F : Files)
987 // If an entry symbol is in a static archive, pull out that file now
988 // to complete the symbol table. After this, no new names except a
989 // few linker-synthesized ones will be added to the symbol table.
990 if (Symtab.find(Config->Entry))
991 Symtab.addUndefined(Config->Entry);
993 // Return if there were name resolution errors.
997 // Handle the `--undefined <sym>` options.
998 Symtab.scanUndefinedFlags();
1000 // Handle undefined symbols in DSOs.
1001 Symtab.scanShlibUndefined();
1003 // Handle the -exclude-libs option.
1004 if (Args.hasArg(OPT_exclude_libs))
1005 excludeLibs(Args, Files);
1007 // Apply version scripts.
1008 Symtab.scanVersionScript();
1010 // Create wrapped symbols for -wrap option.
1011 for (auto *Arg : Args.filtered(OPT_wrap))
1012 Symtab.addSymbolWrap(Arg->getValue());
1014 // Create alias symbols for -defsym option.
1015 for (std::pair<StringRef, StringRef> &Def : getDefsym(Args))
1016 Symtab.addSymbolAlias(Def.first, Def.second);
1018 Symtab.addCombinedLTOObject();
1022 // Some symbols (such as __ehdr_start) are defined lazily only when there
1023 // are undefined symbols for them, so we add these to trigger that logic.
1024 for (StringRef Sym : Script->Opt.ReferencedSymbols)
1025 Symtab.addUndefined(Sym);
1027 // Apply symbol renames for -wrap and -defsym
1028 Symtab.applySymbolRenames();
1030 // Now that we have a complete list of input files.
1031 // Beyond this point, no new files are added.
1032 // Aggregate all input sections into one place.
1033 for (elf::ObjectFile<ELFT> *F : Symtab.getObjectFiles())
1034 for (InputSectionBase *S : F->getSections())
1035 if (S && S != &InputSection::Discarded)
1036 InputSections.push_back(S);
1037 for (BinaryFile *F : Symtab.getBinaryFiles())
1038 for (InputSectionBase *S : F->getSections())
1039 InputSections.push_back(cast<InputSection>(S));
1041 // This adds a .comment section containing a version string. We have to add it
1042 // before decompressAndMergeSections because the .comment section is a
1043 // mergeable section.
1044 if (!Config->Relocatable)
1045 InputSections.push_back(createCommentSection<ELFT>());
1047 // Do size optimizations: garbage collection, merging of SHF_MERGE sections
1048 // and identical code folding.
1049 if (Config->GcSections)
1051 decompressAndMergeSections();
1055 // Write the result to the file.
1056 writeResult<ELFT>();