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 // DSOs usually have DT_SONAME tags in their ELF headers, and the
188 // sonames are used to identify DSOs. But if they are missing,
189 // they are identified by filenames. We don't know whether the new
190 // file has a DT_SONAME or not because we haven't parsed it yet.
191 // Here, we set the default soname for the file because we might
194 // If a file was specified by -lfoo, the directory part is not
195 // significant, as a user did not specify it. This behavior is
196 // compatible with GNU.
197 Files.push_back(createSharedFile(
198 MBRef, WithLOption ? sys::path::filename(Path) : Path));
202 Files.push_back(make<LazyObjectFile>(MBRef));
204 Files.push_back(createObjectFile(MBRef));
208 // Add a given library by searching it from input search paths.
209 void LinkerDriver::addLibrary(StringRef Name) {
210 if (Optional<std::string> Path = searchLibrary(Name))
211 addFile(*Path, /*WithLOption=*/true);
213 error("unable to find library -l" + Name);
216 // This function is called on startup. We need this for LTO since
217 // LTO calls LLVM functions to compile bitcode files to native code.
218 // Technically this can be delayed until we read bitcode files, but
219 // we don't bother to do lazily because the initialization is fast.
220 static void initLLVM(opt::InputArgList &Args) {
221 InitializeAllTargets();
222 InitializeAllTargetMCs();
223 InitializeAllAsmPrinters();
224 InitializeAllAsmParsers();
226 // Parse and evaluate -mllvm options.
227 std::vector<const char *> V;
228 V.push_back("lld (LLVM option parsing)");
229 for (auto *Arg : Args.filtered(OPT_mllvm))
230 V.push_back(Arg->getValue());
231 cl::ParseCommandLineOptions(V.size(), V.data());
234 // Some command line options or some combinations of them are not allowed.
235 // This function checks for such errors.
236 static void checkOptions(opt::InputArgList &Args) {
237 // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
238 // table which is a relatively new feature.
239 if (Config->EMachine == EM_MIPS && Config->GnuHash)
240 error("the .gnu.hash section is not compatible with the MIPS target.");
242 if (Config->Pie && Config->Shared)
243 error("-shared and -pie may not be used together");
245 if (Config->Relocatable) {
247 error("-r and -shared may not be used together");
248 if (Config->GcSections)
249 error("-r and --gc-sections may not be used together");
251 error("-r and --icf may not be used together");
253 error("-r and -pie may not be used together");
257 static StringRef getString(opt::InputArgList &Args, unsigned Key,
258 StringRef Default = "") {
259 if (auto *Arg = Args.getLastArg(Key))
260 return Arg->getValue();
264 static int getInteger(opt::InputArgList &Args, unsigned Key, int Default) {
266 if (auto *Arg = Args.getLastArg(Key)) {
267 StringRef S = Arg->getValue();
268 if (S.getAsInteger(10, V))
269 error(Arg->getSpelling() + ": number expected, but got " + S);
274 static const char *getReproduceOption(opt::InputArgList &Args) {
275 if (auto *Arg = Args.getLastArg(OPT_reproduce))
276 return Arg->getValue();
277 return getenv("LLD_REPRODUCE");
280 static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
281 for (auto *Arg : Args.filtered(OPT_z))
282 if (Key == Arg->getValue())
287 static uint64_t getZOptionValue(opt::InputArgList &Args, StringRef Key,
289 for (auto *Arg : Args.filtered(OPT_z)) {
290 StringRef Value = Arg->getValue();
291 size_t Pos = Value.find("=");
292 if (Pos != StringRef::npos && Key == Value.substr(0, Pos)) {
293 Value = Value.substr(Pos + 1);
295 if (Value.getAsInteger(0, Result))
296 error("invalid " + Key + ": " + Value);
303 void LinkerDriver::main(ArrayRef<const char *> ArgsArr, bool CanExitEarly) {
305 opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
307 // Interpret this flag early because error() depends on them.
308 Config->ErrorLimit = getInteger(Args, OPT_error_limit, 20);
311 if (Args.hasArg(OPT_help)) {
312 printHelp(ArgsArr[0]);
316 // Handle -v or -version.
318 // A note about "compatible with GNU linkers" message: this is a hack for
319 // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
320 // still the newest version in March 2017) or earlier to recognize LLD as
321 // a GNU compatible linker. As long as an output for the -v option
322 // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
324 // This is somewhat ugly hack, but in reality, we had no choice other
325 // than doing this. Considering the very long release cycle of Libtool,
326 // it is not easy to improve it to recognize LLD as a GNU compatible
327 // linker in a timely manner. Even if we can make it, there are still a
328 // lot of "configure" scripts out there that are generated by old version
329 // of Libtool. We cannot convince every software developer to migrate to
330 // the latest version and re-generate scripts. So we have this hack.
331 if (Args.hasArg(OPT_v) || Args.hasArg(OPT_version))
332 message(getLLDVersion() + " (compatible with GNU linkers)");
334 // ld.bfd always exits after printing out the version string.
335 // ld.gold proceeds if a given option is -v. Because gold's behavior
336 // is more permissive than ld.bfd, we chose what gold does here.
337 if (Args.hasArg(OPT_version))
340 Config->ExitEarly = CanExitEarly && !Args.hasArg(OPT_full_shutdown);
342 if (const char *Path = getReproduceOption(Args)) {
343 // Note that --reproduce is a debug option so you can ignore it
344 // if you are trying to understand the whole picture of the code.
345 Expected<std::unique_ptr<TarWriter>> ErrOrWriter =
346 TarWriter::create(Path, path::stem(Path));
348 Tar = ErrOrWriter->get();
349 Tar->append("response.txt", createResponseFile(Args));
350 Tar->append("version.txt", getLLDVersion() + "\n");
351 make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter));
353 error(Twine("--reproduce: failed to open ") + Path + ": " +
354 toString(ErrOrWriter.takeError()));
367 switch (Config->EKind) {
381 llvm_unreachable("unknown Config->EKind");
385 static bool getArg(opt::InputArgList &Args, unsigned K1, unsigned K2,
387 if (auto *Arg = Args.getLastArg(K1, K2))
388 return Arg->getOption().getID() == K1;
392 static std::vector<StringRef> getArgs(opt::InputArgList &Args, int Id) {
393 std::vector<StringRef> V;
394 for (auto *Arg : Args.filtered(Id))
395 V.push_back(Arg->getValue());
399 static std::string getRPath(opt::InputArgList &Args) {
400 std::vector<StringRef> V = getArgs(Args, OPT_rpath);
401 return llvm::join(V.begin(), V.end(), ":");
404 // Determines what we should do if there are remaining unresolved
405 // symbols after the name resolution.
406 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
407 // -noinhibit-exec or -r imply some default values.
408 if (Args.hasArg(OPT_noinhibit_exec))
409 return UnresolvedPolicy::WarnAll;
410 if (Args.hasArg(OPT_relocatable))
411 return UnresolvedPolicy::IgnoreAll;
413 UnresolvedPolicy ErrorOrWarn = getArg(Args, OPT_error_unresolved_symbols,
414 OPT_warn_unresolved_symbols, true)
415 ? UnresolvedPolicy::ReportError
416 : UnresolvedPolicy::Warn;
418 // Process the last of -unresolved-symbols, -no-undefined or -z defs.
419 for (auto *Arg : llvm::reverse(Args)) {
420 switch (Arg->getOption().getID()) {
421 case OPT_unresolved_symbols: {
422 StringRef S = Arg->getValue();
423 if (S == "ignore-all" || S == "ignore-in-object-files")
424 return UnresolvedPolicy::Ignore;
425 if (S == "ignore-in-shared-libs" || S == "report-all")
427 error("unknown --unresolved-symbols value: " + S);
430 case OPT_no_undefined:
433 if (StringRef(Arg->getValue()) == "defs")
439 // -shared implies -unresolved-symbols=ignore-all because missing
440 // symbols are likely to be resolved at runtime using other DSOs.
442 return UnresolvedPolicy::Ignore;
446 static Target2Policy getTarget2(opt::InputArgList &Args) {
447 if (auto *Arg = Args.getLastArg(OPT_target2)) {
448 StringRef S = Arg->getValue();
450 return Target2Policy::Rel;
452 return Target2Policy::Abs;
454 return Target2Policy::GotRel;
455 error("unknown --target2 option: " + S);
457 return Target2Policy::GotRel;
460 static bool isOutputFormatBinary(opt::InputArgList &Args) {
461 if (auto *Arg = Args.getLastArg(OPT_oformat)) {
462 StringRef S = Arg->getValue();
465 error("unknown --oformat value: " + S);
470 static DiscardPolicy getDiscard(opt::InputArgList &Args) {
471 if (Args.hasArg(OPT_relocatable))
472 return DiscardPolicy::None;
475 Args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
477 return DiscardPolicy::Default;
478 if (Arg->getOption().getID() == OPT_discard_all)
479 return DiscardPolicy::All;
480 if (Arg->getOption().getID() == OPT_discard_locals)
481 return DiscardPolicy::Locals;
482 return DiscardPolicy::None;
485 static StringRef getDynamicLinker(opt::InputArgList &Args) {
486 auto *Arg = Args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
487 if (!Arg || Arg->getOption().getID() == OPT_no_dynamic_linker)
489 return Arg->getValue();
492 static StripPolicy getStrip(opt::InputArgList &Args) {
493 if (Args.hasArg(OPT_relocatable))
494 return StripPolicy::None;
496 auto *Arg = Args.getLastArg(OPT_strip_all, OPT_strip_debug);
498 return StripPolicy::None;
499 if (Arg->getOption().getID() == OPT_strip_all)
500 return StripPolicy::All;
501 return StripPolicy::Debug;
504 static uint64_t parseSectionAddress(StringRef S, opt::Arg *Arg) {
506 if (S.startswith("0x"))
508 if (S.getAsInteger(16, VA))
509 error("invalid argument: " + toString(Arg));
513 static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &Args) {
514 StringMap<uint64_t> Ret;
515 for (auto *Arg : Args.filtered(OPT_section_start)) {
518 std::tie(Name, Addr) = StringRef(Arg->getValue()).split('=');
519 Ret[Name] = parseSectionAddress(Addr, Arg);
522 if (auto *Arg = Args.getLastArg(OPT_Ttext))
523 Ret[".text"] = parseSectionAddress(Arg->getValue(), Arg);
524 if (auto *Arg = Args.getLastArg(OPT_Tdata))
525 Ret[".data"] = parseSectionAddress(Arg->getValue(), Arg);
526 if (auto *Arg = Args.getLastArg(OPT_Tbss))
527 Ret[".bss"] = parseSectionAddress(Arg->getValue(), Arg);
531 static SortSectionPolicy getSortSection(opt::InputArgList &Args) {
532 StringRef S = getString(Args, OPT_sort_section);
533 if (S == "alignment")
534 return SortSectionPolicy::Alignment;
536 return SortSectionPolicy::Name;
538 error("unknown --sort-section rule: " + S);
539 return SortSectionPolicy::Default;
542 static std::pair<bool, bool> getHashStyle(opt::InputArgList &Args) {
543 StringRef S = getString(Args, OPT_hash_style, "sysv");
545 return {true, false};
547 return {false, true};
549 error("unknown -hash-style: " + S);
553 static std::vector<StringRef> getLines(MemoryBufferRef MB) {
554 SmallVector<StringRef, 0> Arr;
555 MB.getBuffer().split(Arr, '\n');
557 std::vector<StringRef> Ret;
558 for (StringRef S : Arr) {
566 static bool getCompressDebugSections(opt::InputArgList &Args) {
567 if (auto *Arg = Args.getLastArg(OPT_compress_debug_sections)) {
568 StringRef S = Arg->getValue();
570 return zlib::isAvailable();
572 error("unknown --compress-debug-sections value: " + S);
577 // Initializes Config members by the command line options.
578 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
579 Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
580 Config->AuxiliaryList = getArgs(Args, OPT_auxiliary);
581 Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
582 Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
583 Config->CompressDebugSections = getCompressDebugSections(Args);
584 Config->DefineCommon = getArg(Args, OPT_define_common, OPT_no_define_common,
585 !Args.hasArg(OPT_relocatable));
586 Config->Demangle = getArg(Args, OPT_demangle, OPT_no_demangle, true);
587 Config->DisableVerify = Args.hasArg(OPT_disable_verify);
588 Config->Discard = getDiscard(Args);
589 Config->DynamicLinker = getDynamicLinker(Args);
590 Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
591 Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
592 Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
593 Config->Entry = getString(Args, OPT_entry);
594 Config->ExportDynamic =
595 getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false);
596 Config->FatalWarnings =
597 getArg(Args, OPT_fatal_warnings, OPT_no_fatal_warnings, false);
598 Config->Fini = getString(Args, OPT_fini, "_fini");
599 Config->GcSections = getArg(Args, OPT_gc_sections, OPT_no_gc_sections, false);
600 Config->GdbIndex = Args.hasArg(OPT_gdb_index);
601 Config->ICF = Args.hasArg(OPT_icf);
602 Config->Init = getString(Args, OPT_init, "_init");
603 Config->LTOAAPipeline = getString(Args, OPT_lto_aa_pipeline);
604 Config->LTONewPmPasses = getString(Args, OPT_lto_newpm_passes);
605 Config->LTOO = getInteger(Args, OPT_lto_O, 2);
606 Config->LTOPartitions = getInteger(Args, OPT_lto_partitions, 1);
607 Config->MapFile = getString(Args, OPT_Map);
608 Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
609 Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
610 Config->Nostdlib = Args.hasArg(OPT_nostdlib);
611 Config->OFormatBinary = isOutputFormatBinary(Args);
612 Config->Omagic = Args.hasArg(OPT_omagic);
613 Config->OptRemarksFilename = getString(Args, OPT_opt_remarks_filename);
614 Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness);
615 Config->Optimize = getInteger(Args, OPT_O, 1);
616 Config->OutputFile = getString(Args, OPT_o);
617 Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false);
618 Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
619 Config->RPath = getRPath(Args);
620 Config->Relocatable = Args.hasArg(OPT_relocatable);
621 Config->SaveTemps = Args.hasArg(OPT_save_temps);
622 Config->SearchPaths = getArgs(Args, OPT_L);
623 Config->SectionStartMap = getSectionStartMap(Args);
624 Config->Shared = Args.hasArg(OPT_shared);
625 Config->SingleRoRx = Args.hasArg(OPT_no_rosegment);
626 Config->SoName = getString(Args, OPT_soname);
627 Config->SortSection = getSortSection(Args);
628 Config->Strip = getStrip(Args);
629 Config->Sysroot = getString(Args, OPT_sysroot);
630 Config->Target1Rel = getArg(Args, OPT_target1_rel, OPT_target1_abs, false);
631 Config->Target2 = getTarget2(Args);
632 Config->ThinLTOCacheDir = getString(Args, OPT_thinlto_cache_dir);
633 Config->ThinLTOCachePolicy =
634 check(parseCachePruningPolicy(getString(Args, OPT_thinlto_cache_policy)),
635 "--thinlto-cache-policy: invalid cache policy");
636 Config->ThinLTOJobs = getInteger(Args, OPT_thinlto_jobs, -1u);
637 Config->Threads = getArg(Args, OPT_threads, OPT_no_threads, true);
638 Config->Trace = Args.hasArg(OPT_trace);
639 Config->Undefined = getArgs(Args, OPT_undefined);
640 Config->UnresolvedSymbols = getUnresolvedSymbolPolicy(Args);
641 Config->Verbose = Args.hasArg(OPT_verbose);
642 Config->WarnCommon = Args.hasArg(OPT_warn_common);
643 Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
644 Config->ZExecstack = hasZOption(Args, "execstack");
645 Config->ZNocopyreloc = hasZOption(Args, "nocopyreloc");
646 Config->ZNodelete = hasZOption(Args, "nodelete");
647 Config->ZNodlopen = hasZOption(Args, "nodlopen");
648 Config->ZNow = hasZOption(Args, "now");
649 Config->ZOrigin = hasZOption(Args, "origin");
650 Config->ZRelro = !hasZOption(Args, "norelro");
651 Config->ZStackSize = getZOptionValue(Args, "stack-size", 0);
652 Config->ZText = !hasZOption(Args, "notext");
653 Config->ZWxneeded = hasZOption(Args, "wxneeded");
655 if (Config->LTOO > 3)
656 error("invalid optimization level for LTO: " + getString(Args, OPT_lto_O));
657 if (Config->LTOPartitions == 0)
658 error("--lto-partitions: number of threads must be > 0");
659 if (Config->ThinLTOJobs == 0)
660 error("--thinlto-jobs: number of threads must be > 0");
662 if (auto *Arg = Args.getLastArg(OPT_m)) {
663 // Parse ELF{32,64}{LE,BE} and CPU type.
664 StringRef S = Arg->getValue();
665 std::tie(Config->EKind, Config->EMachine, Config->OSABI) =
667 Config->MipsN32Abi = (S == "elf32btsmipn32" || S == "elf32ltsmipn32");
668 Config->Emulation = S;
671 if (Args.hasArg(OPT_print_map))
672 Config->MapFile = "-";
674 // --omagic is an option to create old-fashioned executables in which
675 // .text segments are writable. Today, the option is still in use to
676 // create special-purpose programs such as boot loaders. It doesn't
677 // make sense to create PT_GNU_RELRO for such executables.
679 Config->ZRelro = false;
681 std::tie(Config->SysvHash, Config->GnuHash) = getHashStyle(Args);
683 // Parse --build-id or --build-id=<style>. We handle "tree" as a
684 // synonym for "sha1" because all of our hash functions including
685 // -build-id=sha1 are tree hashes for performance reasons.
686 if (Args.hasArg(OPT_build_id))
687 Config->BuildId = BuildIdKind::Fast;
688 if (auto *Arg = Args.getLastArg(OPT_build_id_eq)) {
689 StringRef S = Arg->getValue();
691 Config->BuildId = BuildIdKind::Md5;
692 } else if (S == "sha1" || S == "tree") {
693 Config->BuildId = BuildIdKind::Sha1;
694 } else if (S == "uuid") {
695 Config->BuildId = BuildIdKind::Uuid;
696 } else if (S == "none") {
697 Config->BuildId = BuildIdKind::None;
698 } else if (S.startswith("0x")) {
699 Config->BuildId = BuildIdKind::Hexstring;
700 Config->BuildIdVector = parseHex(S.substr(2));
702 error("unknown --build-id style: " + S);
706 if (!Config->Shared && !Config->AuxiliaryList.empty())
707 error("-f may not be used without -shared");
709 if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
710 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
711 Config->SymbolOrderingFile = getLines(*Buffer);
713 // If --retain-symbol-file is used, we'll keep only the symbols listed in
714 // the file and discard all others.
715 if (auto *Arg = Args.getLastArg(OPT_retain_symbols_file)) {
716 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
717 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
718 for (StringRef S : getLines(*Buffer))
719 Config->VersionScriptGlobals.push_back(
720 {S, /*IsExternCpp*/ false, /*HasWildcard*/ false});
723 bool HasExportDynamic =
724 getArg(Args, OPT_export_dynamic, OPT_no_export_dynamic, false);
726 // Parses -dynamic-list and -export-dynamic-symbol. They make some
727 // symbols private. Note that -export-dynamic takes precedence over them
728 // as it says all symbols should be exported.
729 if (!HasExportDynamic) {
730 for (auto *Arg : Args.filtered(OPT_dynamic_list))
731 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
732 readDynamicList(*Buffer);
734 for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
735 Config->VersionScriptGlobals.push_back(
736 {Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
738 // Dynamic lists are a simplified linker script that doesn't need the
739 // "global:" and implicitly ends with a "local:*". Set the variables
740 // needed to simulate that.
741 if (Args.hasArg(OPT_dynamic_list) ||
742 Args.hasArg(OPT_export_dynamic_symbol)) {
743 Config->ExportDynamic = true;
745 Config->DefaultSymbolVersion = VER_NDX_LOCAL;
749 if (auto *Arg = Args.getLastArg(OPT_version_script))
750 if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
751 readVersionScript(*Buffer);
754 // Some Config members do not directly correspond to any particular
755 // command line options, but computed based on other Config values.
756 // This function initialize such members. See Config.h for the details
758 static void setConfigs() {
759 ELFKind Kind = Config->EKind;
760 uint16_t Machine = Config->EMachine;
762 // There is an ILP32 ABI for x86-64, although it's not very popular.
763 // It is called the x32 ABI.
764 bool IsX32 = (Kind == ELF32LEKind && Machine == EM_X86_64);
766 Config->CopyRelocs = (Config->Relocatable || Config->EmitRelocs);
767 Config->Is64 = (Kind == ELF64LEKind || Kind == ELF64BEKind);
768 Config->IsLE = (Kind == ELF32LEKind || Kind == ELF64LEKind);
770 Config->IsLE ? support::endianness::little : support::endianness::big;
771 Config->IsMips64EL = (Kind == ELF64LEKind && Machine == EM_MIPS);
772 Config->IsRela = Config->Is64 || IsX32 || Config->MipsN32Abi;
773 Config->Pic = Config->Pie || Config->Shared;
774 Config->Wordsize = Config->Is64 ? 8 : 4;
777 // Returns a value of "-format" option.
778 static bool getBinaryOption(StringRef S) {
781 if (S == "elf" || S == "default")
783 error("unknown -format value: " + S +
784 " (supported formats: elf, default, binary)");
788 void LinkerDriver::createFiles(opt::InputArgList &Args) {
789 for (auto *Arg : Args) {
790 switch (Arg->getOption().getID()) {
792 addLibrary(Arg->getValue());
795 addFile(Arg->getValue(), /*WithLOption=*/false);
797 case OPT_alias_script_T:
799 if (Optional<MemoryBufferRef> MB = readFile(Arg->getValue()))
800 readLinkerScript(*MB);
803 Config->AsNeeded = true;
806 InBinary = getBinaryOption(Arg->getValue());
808 case OPT_no_as_needed:
809 Config->AsNeeded = false;
812 Config->Static = true;
815 Config->Static = false;
817 case OPT_whole_archive:
818 InWholeArchive = true;
820 case OPT_no_whole_archive:
821 InWholeArchive = false;
832 if (Files.empty() && ErrorCount == 0)
833 error("no input files");
836 // If -m <machine_type> was not given, infer it from object files.
837 void LinkerDriver::inferMachineType() {
838 if (Config->EKind != ELFNoneKind)
841 for (InputFile *F : Files) {
842 if (F->EKind == ELFNoneKind)
844 Config->EKind = F->EKind;
845 Config->EMachine = F->EMachine;
846 Config->OSABI = F->OSABI;
847 Config->MipsN32Abi = Config->EMachine == EM_MIPS && isMipsN32Abi(F);
850 error("target emulation unknown: -m or at least one .o file required");
853 // Parse -z max-page-size=<value>. The default value is defined by
855 static uint64_t getMaxPageSize(opt::InputArgList &Args) {
857 getZOptionValue(Args, "max-page-size", Target->DefaultMaxPageSize);
858 if (!isPowerOf2_64(Val))
859 error("max-page-size: value isn't a power of 2");
863 // Parses -image-base option.
864 static uint64_t getImageBase(opt::InputArgList &Args) {
865 // Use default if no -image-base option is given.
866 // Because we are using "Target" here, this function
867 // has to be called after the variable is initialized.
868 auto *Arg = Args.getLastArg(OPT_image_base);
870 return Config->Pic ? 0 : Target->DefaultImageBase;
872 StringRef S = Arg->getValue();
874 if (S.getAsInteger(0, V)) {
875 error("-image-base: number expected, but got " + S);
878 if ((V % Config->MaxPageSize) != 0)
879 warn("-image-base: address isn't multiple of page size: " + S);
883 // Parses --defsym=alias option.
884 static std::vector<std::pair<StringRef, StringRef>>
885 getDefsym(opt::InputArgList &Args) {
886 std::vector<std::pair<StringRef, StringRef>> Ret;
887 for (auto *Arg : Args.filtered(OPT_defsym)) {
890 std::tie(From, To) = StringRef(Arg->getValue()).split('=');
891 if (!isValidCIdentifier(To))
892 error("--defsym: symbol name expected, but got " + To);
893 Ret.push_back({From, To});
898 // Do actual linking. Note that when this function is called,
899 // all linker scripts have already been parsed.
900 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
901 SymbolTable<ELFT> Symtab;
902 elf::Symtab<ELFT>::X = &Symtab;
903 Target = createTarget();
905 Config->MaxPageSize = getMaxPageSize(Args);
906 Config->ImageBase = getImageBase(Args);
908 // Default output filename is "a.out" by the Unix tradition.
909 if (Config->OutputFile.empty())
910 Config->OutputFile = "a.out";
912 // Fail early if the output file or map file is not writable. If a user has a
913 // long link, e.g. due to a large LTO link, they do not wish to run it and
914 // find that it failed because there was a mistake in their command-line.
915 if (auto E = tryCreateFile(Config->OutputFile))
916 error("cannot open output file " + Config->OutputFile + ": " + E.message());
917 if (auto E = tryCreateFile(Config->MapFile))
918 error("cannot open map file " + Config->MapFile + ": " + E.message());
922 // Use default entry point name if no name was given via the command
923 // line nor linker scripts. For some reason, MIPS entry point name is
924 // different from others.
925 Config->WarnMissingEntry =
926 (!Config->Entry.empty() || (!Config->Shared && !Config->Relocatable));
927 if (Config->Entry.empty() && !Config->Relocatable)
928 Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
930 // Handle --trace-symbol.
931 for (auto *Arg : Args.filtered(OPT_trace_symbol))
932 Symtab.trace(Arg->getValue());
934 // Add all files to the symbol table. This will add almost all
935 // symbols that we need to the symbol table.
936 for (InputFile *F : Files)
939 // If an entry symbol is in a static archive, pull out that file now
940 // to complete the symbol table. After this, no new names except a
941 // few linker-synthesized ones will be added to the symbol table.
942 if (Symtab.find(Config->Entry))
943 Symtab.addUndefined(Config->Entry);
945 // Return if there were name resolution errors.
949 Symtab.scanUndefinedFlags();
950 Symtab.scanShlibUndefined();
951 Symtab.scanVersionScript();
953 Symtab.addCombinedLTOObject();
957 // Some symbols (such as __ehdr_start) are defined lazily only when there
958 // are undefined symbols for them, so we add these to trigger that logic.
959 for (StringRef Sym : Script->Opt.ReferencedSymbols)
960 Symtab.addUndefined(Sym);
962 for (auto *Arg : Args.filtered(OPT_wrap))
963 Symtab.wrap(Arg->getValue());
965 // Handle --defsym=sym=alias option.
966 for (std::pair<StringRef, StringRef> &Def : getDefsym(Args))
967 Symtab.alias(Def.first, Def.second);
969 // Now that we have a complete list of input files.
970 // Beyond this point, no new files are added.
971 // Aggregate all input sections into one place.
972 for (elf::ObjectFile<ELFT> *F : Symtab.getObjectFiles())
973 for (InputSectionBase *S : F->getSections())
974 if (S && S != &InputSection::Discarded)
975 InputSections.push_back(S);
976 for (BinaryFile *F : Symtab.getBinaryFiles())
977 for (InputSectionBase *S : F->getSections())
978 InputSections.push_back(cast<InputSection>(S));
980 // Do size optimizations: garbage collection and identical code folding.
981 if (Config->GcSections)
986 // MergeInputSection::splitIntoPieces needs to be called before
987 // any call of MergeInputSection::getOffset. Do that.
988 parallelForEach(InputSections.begin(), InputSections.end(),
989 [](InputSectionBase *S) {
992 if (Decompressor::isCompressedELFSection(S->Flags, S->Name))
994 if (auto *MS = dyn_cast<MergeInputSection>(S))
995 MS->splitIntoPieces();
998 // Write the result to the file.