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"
42 #include "lld/Config/Version.h"
43 #include "lld/Driver/Driver.h"
44 #include "llvm/ADT/StringExtras.h"
45 #include "llvm/ADT/StringSwitch.h"
46 #include "llvm/Object/Decompressor.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 .Case("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<MemoryBufferRef>
127 LinkerDriver::getArchiveMembers(MemoryBufferRef MB) {
128 std::unique_ptr<Archive> File =
129 check(Archive::create(MB),
130 MB.getBufferIdentifier() + ": failed to parse archive");
132 std::vector<MemoryBufferRef> 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");
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 and parses a file. Path has to be resolved already.
156 // Newly created memory buffers are owned by this driver.
157 void LinkerDriver::addFile(StringRef Path, bool WithLOption) {
158 using namespace sys::fs;
160 Optional<MemoryBufferRef> Buffer = readFile(Path);
161 if (!Buffer.hasValue())
163 MemoryBufferRef MBRef = *Buffer;
166 Files.push_back(make<BinaryFile>(MBRef));
170 switch (identify_magic(MBRef.getBuffer())) {
171 case file_magic::unknown:
172 readLinkerScript(MBRef);
174 case file_magic::archive:
175 if (InWholeArchive) {
176 for (MemoryBufferRef MB : getArchiveMembers(MBRef))
177 Files.push_back(createObjectFile(MB, Path));
180 Files.push_back(make<ArchiveFile>(MBRef));
182 case file_magic::elf_shared_object:
183 if (Config->Relocatable) {
184 error("attempted static link of dynamic object " + Path);
187 Files.push_back(createSharedFile(MBRef));
189 // DSOs usually have DT_SONAME tags in their ELF headers, and the
190 // sonames are used to identify DSOs. But if they are missing,
191 // they are identified by filenames. We don't know whether the new
192 // file has a DT_SONAME or not because we haven't parsed it yet.
193 // Here, we set the default soname for the file because we might
196 // If a file was specified by -lfoo, the directory part is not
197 // significant, as a user did not specify it. This behavior is
198 // compatible with GNU.
199 Files.back()->DefaultSoName =
200 WithLOption ? sys::path::filename(Path) : Path;
204 Files.push_back(make<LazyObjectFile>(MBRef));
206 Files.push_back(createObjectFile(MBRef));
210 // Add a given library by searching it from input search paths.
211 void LinkerDriver::addLibrary(StringRef Name) {
212 if (Optional<std::string> Path = searchLibrary(Name))
213 addFile(*Path, /*WithLOption=*/true);
215 error("unable to find library -l" + Name);
218 // This function is called on startup. We need this for LTO since
219 // LTO calls LLVM functions to compile bitcode files to native code.
220 // Technically this can be delayed until we read bitcode files, but
221 // we don't bother to do lazily because the initialization is fast.
222 static void initLLVM(opt::InputArgList &Args) {
223 InitializeAllTargets();
224 InitializeAllTargetMCs();
225 InitializeAllAsmPrinters();
226 InitializeAllAsmParsers();
228 // Parse and evaluate -mllvm options.
229 std::vector<const char *> V;
230 V.push_back("lld (LLVM option parsing)");
231 for (auto *Arg : Args.filtered(OPT_mllvm))
232 V.push_back(Arg->getValue());
233 cl::ParseCommandLineOptions(V.size(), V.data());
236 // Some command line options or some combinations of them are not allowed.
237 // This function checks for such errors.
238 static void checkOptions(opt::InputArgList &Args) {
239 // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
240 // table which is a relatively new feature.
241 if (Config->EMachine == EM_MIPS && Config->GnuHash)
242 error("the .gnu.hash section is not compatible with the MIPS target.");
244 if (Config->Pie && Config->Shared)
245 error("-shared and -pie may not be used together");
247 if (Config->Relocatable) {
249 error("-r and -shared may not be used together");
250 if (Config->GcSections)
251 error("-r and --gc-sections may not be used together");
253 error("-r and --icf may not be used together");
255 error("-r and -pie may not be used together");
259 static StringRef getString(opt::InputArgList &Args, unsigned Key,
260 StringRef Default = "") {
261 if (auto *Arg = Args.getLastArg(Key))
262 return Arg->getValue();
266 static int getInteger(opt::InputArgList &Args, unsigned Key, int Default) {
268 if (auto *Arg = Args.getLastArg(Key)) {
269 StringRef S = Arg->getValue();
270 if (S.getAsInteger(10, V))
271 error(Arg->getSpelling() + ": number expected, but got " + S);
276 static const char *getReproduceOption(opt::InputArgList &Args) {
277 if (auto *Arg = Args.getLastArg(OPT_reproduce))
278 return Arg->getValue();
279 return getenv("LLD_REPRODUCE");
282 static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
283 for (auto *Arg : Args.filtered(OPT_z))
284 if (Key == Arg->getValue())
289 static uint64_t getZOptionValue(opt::InputArgList &Args, StringRef Key,
291 for (auto *Arg : Args.filtered(OPT_z)) {
292 StringRef Value = Arg->getValue();
293 size_t Pos = Value.find("=");
294 if (Pos != StringRef::npos && Key == Value.substr(0, Pos)) {
295 Value = Value.substr(Pos + 1);
297 if (Value.getAsInteger(0, Result))
298 error("invalid " + Key + ": " + Value);
305 void LinkerDriver::main(ArrayRef<const char *> ArgsArr, bool CanExitEarly) {
307 opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
309 // Interpret this flag early because error() depends on them.
310 Config->ErrorLimit = getInteger(Args, OPT_error_limit, 20);
313 if (Args.hasArg(OPT_help)) {
314 printHelp(ArgsArr[0]);
318 // Handle -v or -version.
320 // A note about "compatible with GNU linkers" message: this is a hack for
321 // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
322 // still the newest version in March 2017) or earlier to recognize LLD as
323 // a GNU compatible linker. As long as an output for the -v option
324 // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
326 // This is somewhat ugly hack, but in reality, we had no choice other
327 // than doing this. Considering the very long release cycle of Libtool,
328 // it is not easy to improve it to recognize LLD as a GNU compatible
329 // linker in a timely manner. Even if we can make it, there are still a
330 // lot of "configure" scripts out there that are generated by old version
331 // of Libtool. We cannot convince every software developer to migrate to
332 // the latest version and re-generate scripts. So we have this hack.
333 if (Args.hasArg(OPT_v) || Args.hasArg(OPT_version))
334 message(getLLDVersion() + " (compatible with GNU linkers)");
336 // ld.bfd always exits after printing out the version string.
337 // ld.gold proceeds if a given option is -v. Because gold's behavior
338 // is more permissive than ld.bfd, we chose what gold does here.
339 if (Args.hasArg(OPT_version))
342 Config->ExitEarly = CanExitEarly && !Args.hasArg(OPT_full_shutdown);
344 if (const char *Path = getReproduceOption(Args)) {
345 // Note that --reproduce is a debug option so you can ignore it
346 // if you are trying to understand the whole picture of the code.
347 Expected<std::unique_ptr<TarWriter>> ErrOrWriter =
348 TarWriter::create(Path, path::stem(Path));
350 Tar = ErrOrWriter->get();
351 Tar->append("response.txt", createResponseFile(Args));
352 Tar->append("version.txt", getLLDVersion() + "\n");
353 make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter));
355 error(Twine("--reproduce: failed to open ") + Path + ": " +
356 toString(ErrOrWriter.takeError()));
369 switch (Config->EKind) {
383 llvm_unreachable("unknown Config->EKind");
387 static bool getArg(opt::InputArgList &Args, unsigned K1, unsigned K2,
389 if (auto *Arg = Args.getLastArg(K1, K2))
390 return Arg->getOption().getID() == K1;
394 static std::vector<StringRef> getArgs(opt::InputArgList &Args, int Id) {
395 std::vector<StringRef> V;
396 for (auto *Arg : Args.filtered(Id))
397 V.push_back(Arg->getValue());
401 static std::string getRPath(opt::InputArgList &Args) {
402 std::vector<StringRef> V = getArgs(Args, OPT_rpath);
403 return llvm::join(V.begin(), V.end(), ":");
406 // Determines what we should do if there are remaining unresolved
407 // symbols after the name resolution.
408 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
409 // -noinhibit-exec or -r imply some default values.
410 if (Args.hasArg(OPT_noinhibit_exec))
411 return UnresolvedPolicy::WarnAll;
412 if (Args.hasArg(OPT_relocatable))
413 return UnresolvedPolicy::IgnoreAll;
415 UnresolvedPolicy ErrorOrWarn = getArg(Args, OPT_error_unresolved_symbols,
416 OPT_warn_unresolved_symbols, true)
417 ? UnresolvedPolicy::ReportError
418 : UnresolvedPolicy::Warn;
420 // Process the last of -unresolved-symbols, -no-undefined or -z defs.
421 for (auto *Arg : llvm::reverse(Args)) {
422 switch (Arg->getOption().getID()) {
423 case OPT_unresolved_symbols: {
424 StringRef S = Arg->getValue();
425 if (S == "ignore-all" || S == "ignore-in-object-files")
426 return UnresolvedPolicy::Ignore;
427 if (S == "ignore-in-shared-libs" || S == "report-all")
429 error("unknown --unresolved-symbols value: " + S);
432 case OPT_no_undefined:
435 if (StringRef(Arg->getValue()) == "defs")
441 // -shared implies -unresolved-symbols=ignore-all because missing
442 // symbols are likely to be resolved at runtime using other DSOs.
444 return UnresolvedPolicy::Ignore;
448 static Target2Policy getTarget2(opt::InputArgList &Args) {
449 if (auto *Arg = Args.getLastArg(OPT_target2)) {
450 StringRef S = Arg->getValue();
452 return Target2Policy::Rel;
454 return Target2Policy::Abs;
456 return Target2Policy::GotRel;
457 error("unknown --target2 option: " + S);
459 return Target2Policy::GotRel;
462 static bool isOutputFormatBinary(opt::InputArgList &Args) {
463 if (auto *Arg = Args.getLastArg(OPT_oformat)) {
464 StringRef S = Arg->getValue();
467 error("unknown --oformat value: " + S);
472 static DiscardPolicy getDiscard(opt::InputArgList &Args) {
473 if (Args.hasArg(OPT_relocatable))
474 return DiscardPolicy::None;
477 Args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
479 return DiscardPolicy::Default;
480 if (Arg->getOption().getID() == OPT_discard_all)
481 return DiscardPolicy::All;
482 if (Arg->getOption().getID() == OPT_discard_locals)
483 return DiscardPolicy::Locals;
484 return DiscardPolicy::None;
487 static StringRef getDynamicLinker(opt::InputArgList &Args) {
488 auto *Arg = Args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
489 if (!Arg || Arg->getOption().getID() == OPT_no_dynamic_linker)
491 return Arg->getValue();
494 static StripPolicy getStrip(opt::InputArgList &Args) {
495 if (Args.hasArg(OPT_relocatable))
496 return StripPolicy::None;
498 auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug);
500 return StripPolicy::None;
501 if (Arg->getOption().getID() == OPT_strip_all)
502 return StripPolicy::All;
503 return StripPolicy::Debug;
506 static uint64_t parseSectionAddress(StringRef S, opt::Arg *Arg) {
508 if (S.startswith("0x"))
510 if (S.getAsInteger(16, VA))
511 error("invalid argument: " + toString(Arg));
515 static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) {
516 StringMap<uint64_t> Ret;
517 for (auto *Arg : Args.filtered(OPT_section_start)) {
520 std::tie(Name, Addr) = StringRef(Arg->getValue()).split('=');
521 Ret[Name] = parseSectionAddress(Addr, Arg);
524 if (auto *Arg = Args.getLastArg(OPT_Ttext))
525 Ret[".text"] = parseSectionAddress(Arg->getValue(), Arg);
526 if (auto *Arg = Args.getLastArg(OPT_Tdata))
527 Ret[".data"] = parseSectionAddress(Arg->getValue(), Arg);
528 if (auto *Arg = Args.getLastArg(OPT_Tbss))
529 Ret[".bss"] = parseSectionAddress(Arg->getValue(), Arg);
533 static SortSectionPolicy getSortSection(opt::InputArgList &Args) {
534 StringRef S = getString(Args, OPT_sort_section);
535 if (S == "alignment")
536 return SortSectionPolicy::Alignment;
538 return SortSectionPolicy::Name;
540 error("unknown --sort-section rule: " + S);
541 return SortSectionPolicy::Default;
544 static std::pair<bool, bool> getHashStyle(opt::InputArgList &Args) {
545 StringRef S = getString(Args, OPT_hash_style, "sysv");
547 return {true, false};
549 return {false, true};
551 error("unknown -hash-style: " + S);
555 static std::vector<StringRef> getLines(MemoryBufferRef MB) {
556 SmallVector<StringRef, 0> Arr;
557 MB.getBuffer().split(Arr, '\n');
559 std::vector<StringRef> Ret;
560 for (StringRef S : Arr) {
568 static bool getCompressDebugSections(opt::InputArgList &Args) {
569 if (auto *Arg = Args.getLastArg(OPT_compress_debug_sections)) {
570 StringRef S = Arg->getValue();
572 return zlib::isAvailable();
574 error("unknown --compress-debug-sections value: " + S);
579 // Initializes Config members by the command line options.
580 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
581 Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
582 Config->AuxiliaryList = getArgs(Args, OPT_auxiliary);
583 Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
584 Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
585 Config->CompressDebugSections = getCompressDebugSections(Args);
586 Config->DefineCommon = getArg(Args, OPT_define_common, OPT_no_define_common,
587 !Args.hasArg(OPT_relocatable));
588 Config->Demangle = getArg(Args, OPT_demangle, OPT_no_demangle, true);
589 Config->DisableVerify = Args.hasArg(OPT_disable_verify);
590 Config->Discard = getDiscard(Args);
591 Config->DynamicLinker = getDynamicLinker(Args);
592 Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
593 Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
594 Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
595 Config->Entry = getString(Args, OPT_entry);
596 Config->ExportDynamic =
597 getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false);
598 Config->FatalWarnings =
599 getArg(Args, OPT_fatal_warnings, OPT_no_fatal_warnings, false);
600 Config->Fini = getString(Args, OPT_fini, "_fini");
601 Config->GcSections = getArg(Args, OPT_gc_sections, OPT_no_gc_sections, false);
602 Config->GdbIndex = Args.hasArg(OPT_gdb_index);
603 Config->ICF = Args.hasArg(OPT_icf);
604 Config->Init = getString(Args, OPT_init, "_init");
605 Config->LTOAAPipeline = getString(Args, OPT_lto_aa_pipeline);
606 Config->LTONewPmPasses = getString(Args, OPT_lto_newpm_passes);
607 Config->LTOO = getInteger(Args, OPT_lto_O, 2);
608 Config->LTOPartitions = getInteger(Args, OPT_lto_partitions, 1);
609 Config->MapFile = getString(Args, OPT_Map);
610 Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
611 Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
612 Config->Nostdlib = Args.hasArg(OPT_nostdlib);
613 Config->OFormatBinary = isOutputFormatBinary(Args);
614 Config->Omagic = Args.hasArg(OPT_omagic);
615 Config->OptRemarksFilename = getString(Args, OPT_opt_remarks_filename);
616 Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness);
617 Config->Optimize = getInteger(Args, OPT_O, 1);
618 Config->OutputFile = getString(Args, OPT_o);
619 Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false);
620 Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
621 Config->RPath = getRPath(Args);
622 Config->Relocatable = Args.hasArg(OPT_relocatable);
623 Config->SaveTemps = Args.hasArg(OPT_save_temps);
624 Config->SearchPaths = getArgs(Args, OPT_L);
625 Config->SectionStartMap = getSectionStartMap(Args);
626 Config->Shared = Args.hasArg(OPT_shared);
627 Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
628 Config->SoName = getString(Args, OPT_soname);
629 Config->SortSection = getSortSection(Args);
630 Config->Strip = getStrip(Args);
631 Config->Sysroot = getString(Args, OPT_sysroot);
632 Config->Target1Rel = getArg(Args, OPT_target1_rel, OPT_target1_abs, false);
633 Config->Target2 = getTarget2(Args);
634 Config->ThinLTOCacheDir = getString(Args, OPT_thinlto_cache_dir);
635 Config->ThinLTOCachePolicy =
636 check(parseCachePruningPolicy(getString(Args, OPT_thinlto_cache_policy)),
637 "--thinlto-cache-policy: invalid cache policy");
638 Config->ThinLTOJobs = getInteger(Args, OPT_thinlto_jobs, -1u);
639 Config->Threads = getArg(Args, OPT_threads, OPT_no_threads, true);
640 Config->Trace = Args.hasArg(OPT_trace);
641 Config->Undefined = getArgs(Args, OPT_undefined);
642 Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args);
643 Config->Verbose = Args.hasArg(OPT_verbose);
644 Config->WarnCommon = Args.hasArg(OPT_warn_common);
645 Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
646 Config->ZExecstack = hasZOption(Args, "execstack");
647 Config->ZNocopyreloc = hasZOption(Args, "nocopyreloc");
648 Config->ZNodelete = hasZOption(Args, "nodelete");
649 Config->ZNodlopen = hasZOption(Args, "nodlopen");
650 Config->ZNow = hasZOption(Args, "now");
651 Config->ZOrigin = hasZOption(Args, "origin");
652 Config->ZRelro = !hasZOption(Args, "norelro");
653 Config->ZStackSize = getZOptionValue(Args, "stack-size", 0);
654 Config->ZText = !hasZOption(Args, "notext");
655 Config->ZWxneeded = hasZOption(Args, "wxneeded");
657 if (Config->LTOO > 3)
658 error("invalid optimization level for LTO: " + getString(Args, OPT_lto_O));
659 if (Config->LTOPartitions == 0)
660 error("--lto-partitions: number of threads must be > 0");
661 if (Config->ThinLTOJobs == 0)
662 error("--thinlto-jobs: number of threads must be > 0");
664 if (auto *Arg = Args.getLastArg(OPT_m)) {
665 // Parse ELF{32,64}{LE,BE} and CPU type.
666 StringRef S = Arg->getValue();
667 std::tie(Config->EKind, Config->EMachine, Config->OSABI) =
669 Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32");
670 Config->Emulation = S;
673 if (Args.hasArg(OPT_print_map))
674 Config->MapFile = "-";
676 // --omagic is an option to create old-fashioned executables in which
677 // .text segments are writable. Today, the option is still in use to
678 // create special-purpose programs such as boot loaders. It doesn't
679 // make sense to create PT_GNU_RELRO for such executables.
681 Config->ZRelro = false;
683 std::tie(Config->SysvHash, Config->GnuHash) = getHashStyle(Args);
685 // Parse --build-id or --build-id=<style>. We handle "tree" as a
686 // synonym for "sha1" because all of our hash functions including
687 // -build-id=sha1 are tree hashes for performance reasons.
688 if (Args.hasArg(OPT_build_id))
689 Config->BuildId = BuildIdKind::Fast;
690 if (auto *Arg = Args.getLastArg(OPT_build_id_eq)) {
691 StringRef S = Arg->getValue();
693 Config->BuildId = BuildIdKind::Md5;
694 } else if (S == "sha1" || S == "tree") {
695 Config->BuildId = BuildIdKind::Sha1;
696 } else if (S == "uuid") {
697 Config->BuildId = BuildIdKind::Uuid;
698 } else if (S == "none") {
699 Config->BuildId = BuildIdKind::None;
700 } else if (S.startswith("0x")) {
701 Config->BuildId = BuildIdKind::Hexstring;
702 Config->BuildIdVector = parseHex(S.substr(2));
704 error("unknown --build-id style: " + S);
708 if (!Config->Shared && !Config->AuxiliaryList.empty())
709 error("-f may not be used without -shared");
711 for (auto *Arg : Args.filtered(OPT_dynamic_list))
712 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
713 readDynamicList(*Buffer);
715 if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
716 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
717 Config->SymbolOrderingFile = getLines(*Buffer);
719 // If --retain-symbol-file is used, we'll keep only the symbols listed in
720 // the file and discard all others.
721 if (auto *Arg = Args.getLastArg(OPT_retain_symbols_file)) {
722 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
723 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
724 for (StringRef S : getLines(*Buffer))
725 Config->VersionScriptGlobals.push_back(
726 {S, /*IsExternCpp*/ false, /*HasWildcard*/ false});
729 for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
730 Config->VersionScriptGlobals.push_back(
731 {Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
733 // Dynamic lists are a simplified linker script that doesn't need the
734 // "global:" and implicitly ends with a "local:*". Set the variables needed to
736 if (Args.hasArg(OPT_dynamic_list) || Args.hasArg(OPT_export_dynamic_symbol)) {
737 Config->ExportDynamic = true;
739 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
742 if (getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false))
743 Config->DefaultSymbolVersion = VER_NDX_GLOBAL;
745 if (auto *Arg = Args.getLastArg(OPT_version_script))
746 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
747 readVersionScript(*Buffer);
750 // Some Config members do not directly correspond to any particular
751 // command line options, but computed based on other Config values.
752 // This function initialize such members. See Config.h for the details
754 static void setConfigs() {
755 ELFKind Kind = Config->EKind;
756 uint16_t Machine = Config->EMachine;
758 // There is an ILP32 ABI for x86-64, although it's not very popular.
759 // It is called the x32 ABI.
760 bool IsX32 = (Kind == ELF32LEKind && Machine == EM_X86_64);
762 Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs);
763 Config->Is64 = (Kind == ELF64LEKind || Kind == ELF64BEKind);
764 Config->IsLE = (Kind == ELF32LEKind || Kind == ELF64LEKind);
766 Config->IsLE ? support::endianness::little : support::endianness::big;
767 Config->IsMips64EL = (Kind == ELF64LEKind && Machine == EM_MIPS);
768 Config->IsRela = Config->Is64 || IsX32 || Config->MipsN32Abi;
769 Config->Pic = Config->Pie || Config->Shared;
770 Config->Wordsize = Config->Is64 ? 8 : 4;
773 // Returns a value of "-format" option.
774 static bool getBinaryOption(StringRef S) {
777 if (S == "elf" || S == "default")
779 error("unknown -format value: " + S +
780 " (supported formats: elf, default, binary)");
784 void LinkerDriver::createFiles(opt::InputArgList &Args) {
785 for (auto *Arg : Args) {
786 switch (Arg->getOption().getID()) {
788 addLibrary(Arg->getValue());
791 addFile(Arg->getValue(), /*WithLOption=*/false);
793 case OPT_alias_script_T:
795 if (Optional<MemoryBufferRef> MB = readFile(Arg->getValue()))
796 readLinkerScript(*MB);
799 Config->AsNeeded = true;
802 InBinary = getBinaryOption(Arg->getValue());
804 case OPT_no_as_needed:
805 Config->AsNeeded = false;
808 Config->Static = true;
811 Config->Static = false;
813 case OPT_whole_archive:
814 InWholeArchive = true;
816 case OPT_no_whole_archive:
817 InWholeArchive = false;
828 if (Files.empty() && ErrorCount == 0)
829 error("no input files");
832 // If -m <machine_type> was not given, infer it from object files.
833 void LinkerDriver::inferMachineType() {
834 if (Config->EKind != ELFNoneKind)
837 for (InputFile *F : Files) {
838 if (F->EKind == ELFNoneKind)
840 Config->EKind = F->EKind;
841 Config->EMachine = F->EMachine;
842 Config->OSABI = F->OSABI;
843 Config->MipsN32Abi = Config->EMachine == EM_MIPS && isMipsN32Abi(F);
846 error("target emulation unknown: -m or at least one .o file required");
849 // Parse -z max-page-size=<value>. The default value is defined by
851 static uint64_t getMaxPageSize(opt::InputArgList &Args) {
853 getZOptionValue(Args, "max-page-size", Target->DefaultMaxPageSize);
854 if (!isPowerOf2_64(Val))
855 error("max-page-size: value isn't a power of 2");
859 // Parses -image-base option.
860 static uint64_t getImageBase(opt::InputArgList &Args) {
861 // Use default if no -image-base option is given.
862 // Because we are using "Target" here, this function
863 // has to be called after the variable is initialized.
864 auto *Arg = Args.getLastArg(OPT_image_base);
866 return Config->Pic ? 0 : Target->DefaultImageBase;
868 StringRef S = Arg->getValue();
870 if (S.getAsInteger(0, V)) {
871 error("-image-base: number expected, but got " + S);
874 if ((V % Config->MaxPageSize) != 0)
875 warn("-image-base: address isn't multiple of page size: " + S);
879 // Do actual linking. Note that when this function is called,
880 // all linker scripts have already been parsed.
881 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
882 SymbolTable<ELFT> Symtab;
883 elf::Symtab<ELFT>::X = &Symtab;
884 Target = createTarget();
886 Config->MaxPageSize = getMaxPageSize(Args);
887 Config->ImageBase = getImageBase(Args);
889 // Default output filename is "a.out" by the Unix tradition.
890 if (Config->OutputFile.empty())
891 Config->OutputFile = "a.out";
893 // Fail early if the output file or map file is not writable. If a user has a
894 // long link, e.g. due to a large LTO link, they do not wish to run it and
895 // find that it failed because there was a mistake in their command-line.
896 if (!isFileWritable(Config->OutputFile, "output file"))
898 if (!isFileWritable(Config->MapFile, "map file"))
901 // Use default entry point name if no name was given via the command
902 // line nor linker scripts. For some reason, MIPS entry point name is
903 // different from others.
904 Config->WarnMissingEntry =
905 (!Config->Entry.empty() || (!Config->Shared && !Config->Relocatable));
906 if (Config->Entry.empty() && !Config->Relocatable)
907 Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
909 // Handle --trace-symbol.
910 for (auto *Arg : Args.filtered(OPT_trace_symbol))
911 Symtab.trace(Arg->getValue());
913 // Add all files to the symbol table. This will add almost all
914 // symbols that we need to the symbol table.
915 for (InputFile *F : Files)
918 // If an entry symbol is in a static archive, pull out that file now
919 // to complete the symbol table. After this, no new names except a
920 // few linker-synthesized ones will be added to the symbol table.
921 if (Symtab.find(Config->Entry))
922 Symtab.addUndefined(Config->Entry);
924 // Return if there were name resolution errors.
928 Symtab.scanUndefinedFlags();
929 Symtab.scanShlibUndefined();
930 Symtab.scanVersionScript();
932 Symtab.addCombinedLTOObject();
936 // Some symbols (such as __ehdr_start) are defined lazily only when there
937 // are undefined symbols for them, so we add these to trigger that logic.
938 for (StringRef Sym : Script->Opt.ReferencedSymbols)
939 Symtab.addUndefined(Sym);
941 for (auto *Arg : Args.filtered(OPT_wrap))
942 Symtab.wrap(Arg->getValue());
944 // Now that we have a complete list of input files.
945 // Beyond this point, no new files are added.
946 // Aggregate all input sections into one place.
947 for (elf::ObjectFile<ELFT> *F : Symtab.getObjectFiles())
948 for (InputSectionBase *S : F->getSections())
949 if (S && S != &InputSection::Discarded)
950 InputSections.push_back(S);
951 for (BinaryFile *F : Symtab.getBinaryFiles())
952 for (InputSectionBase *S : F->getSections())
953 InputSections.push_back(cast<InputSection>(S));
955 // Do size optimizations: garbage collection and identical code folding.
956 if (Config->GcSections)
961 // MergeInputSection::splitIntoPieces needs to be called before
962 // any call of MergeInputSection::getOffset. Do that.
963 parallelForEach(InputSections.begin(), InputSections.end(),
964 [](InputSectionBase *S) {
967 if (Decompressor::isCompressedELFSection(S->Flags, S->Name))
969 if (auto *MS = dyn_cast<MergeInputSection>(S))
970 MS->splitIntoPieces();
973 // Write the result to the file.