1 //===- Driver.cpp ---------------------------------------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // The driver drives the entire linking process. It is responsible for
10 // parsing command line options and doing whatever it is instructed to do.
12 // One notable thing in the LLD's driver when compared to other linkers is
13 // that the LLD's driver is agnostic on the host operating system.
14 // Other linkers usually have implicit default values (such as a dynamic
15 // linker path or library paths) for each host OS.
17 // I don't think implicit default values are useful because they are
18 // usually explicitly specified by the compiler driver. They can even
19 // be harmful when you are doing cross-linking. Therefore, in LLD, we
20 // simply trust the compiler driver to pass all required options and
21 // don't try to make effort on our side.
23 //===----------------------------------------------------------------------===//
28 #include "InputFiles.h"
29 #include "InputSection.h"
30 #include "LinkerScript.h"
32 #include "OutputSections.h"
33 #include "ScriptParser.h"
34 #include "SymbolTable.h"
36 #include "SyntheticSections.h"
39 #include "lld/Common/Args.h"
40 #include "lld/Common/Driver.h"
41 #include "lld/Common/ErrorHandler.h"
42 #include "lld/Common/Filesystem.h"
43 #include "lld/Common/Memory.h"
44 #include "lld/Common/Strings.h"
45 #include "lld/Common/TargetOptionsCommandFlags.h"
46 #include "lld/Common/Threads.h"
47 #include "lld/Common/Version.h"
48 #include "llvm/ADT/SetVector.h"
49 #include "llvm/ADT/StringExtras.h"
50 #include "llvm/ADT/StringSwitch.h"
51 #include "llvm/LTO/LTO.h"
52 #include "llvm/Support/CommandLine.h"
53 #include "llvm/Support/Compression.h"
54 #include "llvm/Support/GlobPattern.h"
55 #include "llvm/Support/LEB128.h"
56 #include "llvm/Support/Path.h"
57 #include "llvm/Support/TarWriter.h"
58 #include "llvm/Support/TargetSelect.h"
59 #include "llvm/Support/raw_ostream.h"
64 using namespace llvm::ELF;
65 using namespace llvm::object;
66 using namespace llvm::sys;
67 using namespace llvm::support;
72 Configuration *config;
75 static void setConfigs(opt::InputArgList &args);
76 static void readConfigs(opt::InputArgList &args);
78 bool link(ArrayRef<const char *> args, bool canExitEarly, raw_ostream &stdoutOS,
79 raw_ostream &stderrOS) {
80 lld::stdoutOS = &stdoutOS;
81 lld::stderrOS = &stderrOS;
83 errorHandler().logName = args::getFilenameWithoutExe(args[0]);
84 errorHandler().errorLimitExceededMsg =
85 "too many errors emitted, stopping now (use "
86 "-error-limit=0 to see all errors)";
87 errorHandler().exitEarly = canExitEarly;
88 stderrOS.enable_colors(stderrOS.has_colors());
90 inputSections.clear();
91 outputSections.clear();
97 config = make<Configuration>();
98 driver = make<LinkerDriver>();
99 script = make<LinkerScript>();
100 symtab = make<SymbolTable>();
103 memset(&in, 0, sizeof(in));
105 partitions = {Partition()};
107 SharedFile::vernauxNum = 0;
109 config->progName = args[0];
113 // Exit immediately if we don't need to return to the caller.
114 // This saves time because the overhead of calling destructors
115 // for all globally-allocated objects is not negligible.
117 exitLld(errorCount() ? 1 : 0);
120 return !errorCount();
123 // Parses a linker -m option.
124 static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef emul) {
127 if (s.endswith("_fbsd")) {
129 osabi = ELFOSABI_FREEBSD;
132 std::pair<ELFKind, uint16_t> ret =
133 StringSwitch<std::pair<ELFKind, uint16_t>>(s)
134 .Cases("aarch64elf", "aarch64linux", "aarch64_elf64_le_vec",
135 {ELF64LEKind, EM_AARCH64})
136 .Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM})
137 .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
138 .Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS})
139 .Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS})
140 .Case("elf32lriscv", {ELF32LEKind, EM_RISCV})
141 .Cases("elf32ppc", "elf32ppclinux", {ELF32BEKind, EM_PPC})
142 .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
143 .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
144 .Case("elf64lriscv", {ELF64LEKind, EM_RISCV})
145 .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
146 .Case("elf64lppc", {ELF64LEKind, EM_PPC64})
147 .Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64})
148 .Case("elf_i386", {ELF32LEKind, EM_386})
149 .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
150 .Default({ELFNoneKind, EM_NONE});
152 if (ret.first == ELFNoneKind)
153 error("unknown emulation: " + emul);
154 return std::make_tuple(ret.first, ret.second, osabi);
157 // Returns slices of MB by parsing MB as an archive file.
158 // Each slice consists of a member file in the archive.
159 std::vector<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers(
160 MemoryBufferRef mb) {
161 std::unique_ptr<Archive> file =
162 CHECK(Archive::create(mb),
163 mb.getBufferIdentifier() + ": failed to parse archive");
165 std::vector<std::pair<MemoryBufferRef, uint64_t>> v;
166 Error err = Error::success();
167 bool addToTar = file->isThin() && tar;
168 for (const Archive::Child &c : file->children(err)) {
169 MemoryBufferRef mbref =
170 CHECK(c.getMemoryBufferRef(),
171 mb.getBufferIdentifier() +
172 ": could not get the buffer for a child of the archive");
174 tar->append(relativeToRoot(check(c.getFullName())), mbref.getBuffer());
175 v.push_back(std::make_pair(mbref, c.getChildOffset()));
178 fatal(mb.getBufferIdentifier() + ": Archive::children failed: " +
179 toString(std::move(err)));
181 // Take ownership of memory buffers created for members of thin archives.
182 for (std::unique_ptr<MemoryBuffer> &mb : file->takeThinBuffers())
183 make<std::unique_ptr<MemoryBuffer>>(std::move(mb));
188 // Opens a file and create a file object. Path has to be resolved already.
189 void LinkerDriver::addFile(StringRef path, bool withLOption) {
190 using namespace sys::fs;
192 Optional<MemoryBufferRef> buffer = readFile(path);
193 if (!buffer.hasValue())
195 MemoryBufferRef mbref = *buffer;
197 if (config->formatBinary) {
198 files.push_back(make<BinaryFile>(mbref));
202 switch (identify_magic(mbref.getBuffer())) {
203 case file_magic::unknown:
204 readLinkerScript(mbref);
206 case file_magic::archive: {
207 // Handle -whole-archive.
208 if (inWholeArchive) {
209 for (const auto &p : getArchiveMembers(mbref))
210 files.push_back(createObjectFile(p.first, path, p.second));
214 std::unique_ptr<Archive> file =
215 CHECK(Archive::create(mbref), path + ": failed to parse archive");
217 // If an archive file has no symbol table, it is likely that a user
218 // is attempting LTO and using a default ar command that doesn't
219 // understand the LLVM bitcode file. It is a pretty common error, so
220 // we'll handle it as if it had a symbol table.
221 if (!file->isEmpty() && !file->hasSymbolTable()) {
222 // Check if all members are bitcode files. If not, ignore, which is the
223 // default action without the LTO hack described above.
224 for (const std::pair<MemoryBufferRef, uint64_t> &p :
225 getArchiveMembers(mbref))
226 if (identify_magic(p.first.getBuffer()) != file_magic::bitcode) {
227 error(path + ": archive has no index; run ranlib to add one");
231 for (const std::pair<MemoryBufferRef, uint64_t> &p :
232 getArchiveMembers(mbref))
233 files.push_back(make<LazyObjFile>(p.first, path, p.second));
237 // Handle the regular case.
238 files.push_back(make<ArchiveFile>(std::move(file)));
241 case file_magic::elf_shared_object:
242 if (config->isStatic || config->relocatable) {
243 error("attempted static link of dynamic object " + path);
247 // DSOs usually have DT_SONAME tags in their ELF headers, and the
248 // sonames are used to identify DSOs. But if they are missing,
249 // they are identified by filenames. We don't know whether the new
250 // file has a DT_SONAME or not because we haven't parsed it yet.
251 // Here, we set the default soname for the file because we might
254 // If a file was specified by -lfoo, the directory part is not
255 // significant, as a user did not specify it. This behavior is
256 // compatible with GNU.
258 make<SharedFile>(mbref, withLOption ? path::filename(path) : path));
260 case file_magic::bitcode:
261 case file_magic::elf_relocatable:
263 files.push_back(make<LazyObjFile>(mbref, "", 0));
265 files.push_back(createObjectFile(mbref));
268 error(path + ": unknown file type");
272 // Add a given library by searching it from input search paths.
273 void LinkerDriver::addLibrary(StringRef name) {
274 if (Optional<std::string> path = searchLibrary(name))
275 addFile(*path, /*withLOption=*/true);
277 error("unable to find library -l" + name);
280 // This function is called on startup. We need this for LTO since
281 // LTO calls LLVM functions to compile bitcode files to native code.
282 // Technically this can be delayed until we read bitcode files, but
283 // we don't bother to do lazily because the initialization is fast.
284 static void initLLVM() {
285 InitializeAllTargets();
286 InitializeAllTargetMCs();
287 InitializeAllAsmPrinters();
288 InitializeAllAsmParsers();
291 // Some command line options or some combinations of them are not allowed.
292 // This function checks for such errors.
293 static void checkOptions() {
294 // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
295 // table which is a relatively new feature.
296 if (config->emachine == EM_MIPS && config->gnuHash)
297 error("the .gnu.hash section is not compatible with the MIPS target");
299 if (config->fixCortexA53Errata843419 && config->emachine != EM_AARCH64)
300 error("--fix-cortex-a53-843419 is only supported on AArch64 targets");
302 if (config->fixCortexA8 && config->emachine != EM_ARM)
303 error("--fix-cortex-a8 is only supported on ARM targets");
305 if (config->tocOptimize && config->emachine != EM_PPC64)
306 error("--toc-optimize is only supported on the PowerPC64 target");
308 if (config->pie && config->shared)
309 error("-shared and -pie may not be used together");
311 if (!config->shared && !config->filterList.empty())
312 error("-F may not be used without -shared");
314 if (!config->shared && !config->auxiliaryList.empty())
315 error("-f may not be used without -shared");
317 if (!config->relocatable && !config->defineCommon)
318 error("-no-define-common not supported in non relocatable output");
320 if (config->strip == StripPolicy::All && config->emitRelocs)
321 error("--strip-all and --emit-relocs may not be used together");
323 if (config->zText && config->zIfuncNoplt)
324 error("-z text and -z ifunc-noplt may not be used together");
326 if (config->relocatable) {
328 error("-r and -shared may not be used together");
329 if (config->gcSections)
330 error("-r and --gc-sections may not be used together");
331 if (config->gdbIndex)
332 error("-r and --gdb-index may not be used together");
333 if (config->icf != ICFLevel::None)
334 error("-r and --icf may not be used together");
336 error("-r and -pie may not be used together");
337 if (config->exportDynamic)
338 error("-r and --export-dynamic may not be used together");
341 if (config->executeOnly) {
342 if (config->emachine != EM_AARCH64)
343 error("-execute-only is only supported on AArch64 targets");
345 if (config->singleRoRx && !script->hasSectionsCommand)
346 error("-execute-only and -no-rosegment cannot be used together");
349 if (config->zRetpolineplt && config->zForceIbt)
350 error("-z force-ibt may not be used with -z retpolineplt");
352 if (config->emachine != EM_AARCH64) {
354 error("-z pac-plt only supported on AArch64");
355 if (config->forceBTI)
356 error("-z force-bti only supported on AArch64");
360 static const char *getReproduceOption(opt::InputArgList &args) {
361 if (auto *arg = args.getLastArg(OPT_reproduce))
362 return arg->getValue();
363 return getenv("LLD_REPRODUCE");
366 static bool hasZOption(opt::InputArgList &args, StringRef key) {
367 for (auto *arg : args.filtered(OPT_z))
368 if (key == arg->getValue())
373 static bool getZFlag(opt::InputArgList &args, StringRef k1, StringRef k2,
375 for (auto *arg : args.filtered_reverse(OPT_z)) {
376 if (k1 == arg->getValue())
378 if (k2 == arg->getValue())
384 static SeparateSegmentKind getZSeparate(opt::InputArgList &args) {
385 for (auto *arg : args.filtered_reverse(OPT_z)) {
386 StringRef v = arg->getValue();
387 if (v == "noseparate-code")
388 return SeparateSegmentKind::None;
389 if (v == "separate-code")
390 return SeparateSegmentKind::Code;
391 if (v == "separate-loadable-segments")
392 return SeparateSegmentKind::Loadable;
394 return SeparateSegmentKind::None;
397 static GnuStackKind getZGnuStack(opt::InputArgList &args) {
398 for (auto *arg : args.filtered_reverse(OPT_z)) {
399 if (StringRef("execstack") == arg->getValue())
400 return GnuStackKind::Exec;
401 if (StringRef("noexecstack") == arg->getValue())
402 return GnuStackKind::NoExec;
403 if (StringRef("nognustack") == arg->getValue())
404 return GnuStackKind::None;
407 return GnuStackKind::NoExec;
410 static bool isKnownZFlag(StringRef s) {
411 return s == "combreloc" || s == "copyreloc" || s == "defs" ||
412 s == "execstack" || s == "force-bti" || s == "force-ibt" ||
413 s == "global" || s == "hazardplt" || s == "ifunc-noplt" ||
414 s == "initfirst" || s == "interpose" ||
415 s == "keep-text-section-prefix" || s == "lazy" || s == "muldefs" ||
416 s == "separate-code" || s == "separate-loadable-segments" ||
417 s == "nocombreloc" || s == "nocopyreloc" || s == "nodefaultlib" ||
418 s == "nodelete" || s == "nodlopen" || s == "noexecstack" ||
419 s == "nognustack" || s == "nokeep-text-section-prefix" ||
420 s == "norelro" || s == "noseparate-code" || s == "notext" ||
421 s == "now" || s == "origin" || s == "pac-plt" || s == "relro" ||
422 s == "retpolineplt" || s == "rodynamic" || s == "shstk" ||
423 s == "text" || s == "undefs" || s == "wxneeded" ||
424 s.startswith("common-page-size=") || s.startswith("max-page-size=") ||
425 s.startswith("stack-size=");
428 // Report an error for an unknown -z option.
429 static void checkZOptions(opt::InputArgList &args) {
430 for (auto *arg : args.filtered(OPT_z))
431 if (!isKnownZFlag(arg->getValue()))
432 error("unknown -z value: " + StringRef(arg->getValue()));
435 void LinkerDriver::main(ArrayRef<const char *> argsArr) {
437 opt::InputArgList args = parser.parse(argsArr.slice(1));
439 // Interpret this flag early because error() depends on them.
440 errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
444 if (args.hasArg(OPT_help)) {
449 // Handle -v or -version.
451 // A note about "compatible with GNU linkers" message: this is a hack for
452 // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
453 // still the newest version in March 2017) or earlier to recognize LLD as
454 // a GNU compatible linker. As long as an output for the -v option
455 // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
457 // This is somewhat ugly hack, but in reality, we had no choice other
458 // than doing this. Considering the very long release cycle of Libtool,
459 // it is not easy to improve it to recognize LLD as a GNU compatible
460 // linker in a timely manner. Even if we can make it, there are still a
461 // lot of "configure" scripts out there that are generated by old version
462 // of Libtool. We cannot convince every software developer to migrate to
463 // the latest version and re-generate scripts. So we have this hack.
464 if (args.hasArg(OPT_v) || args.hasArg(OPT_version))
465 message(getLLDVersion() + " (compatible with GNU linkers)");
467 if (const char *path = getReproduceOption(args)) {
468 // Note that --reproduce is a debug option so you can ignore it
469 // if you are trying to understand the whole picture of the code.
470 Expected<std::unique_ptr<TarWriter>> errOrWriter =
471 TarWriter::create(path, path::stem(path));
473 tar = std::move(*errOrWriter);
474 tar->append("response.txt", createResponseFile(args));
475 tar->append("version.txt", getLLDVersion() + "\n");
477 error("--reproduce: " + toString(errOrWriter.takeError()));
483 // The behavior of -v or --version is a bit strange, but this is
484 // needed for compatibility with GNU linkers.
485 if (args.hasArg(OPT_v) && !args.hasArg(OPT_INPUT))
487 if (args.hasArg(OPT_version))
501 // The Target instance handles target-specific stuff, such as applying
502 // relocations or writing a PLT section. It also contains target-dependent
503 // values such as a default image base address.
504 target = getTarget();
506 switch (config->ekind) {
520 llvm_unreachable("unknown Config->EKind");
524 static std::string getRpath(opt::InputArgList &args) {
525 std::vector<StringRef> v = args::getStrings(args, OPT_rpath);
526 return llvm::join(v.begin(), v.end(), ":");
529 // Determines what we should do if there are remaining unresolved
530 // symbols after the name resolution.
531 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &args) {
532 UnresolvedPolicy errorOrWarn = args.hasFlag(OPT_error_unresolved_symbols,
533 OPT_warn_unresolved_symbols, true)
534 ? UnresolvedPolicy::ReportError
535 : UnresolvedPolicy::Warn;
537 // Process the last of -unresolved-symbols, -no-undefined or -z defs.
538 for (auto *arg : llvm::reverse(args)) {
539 switch (arg->getOption().getID()) {
540 case OPT_unresolved_symbols: {
541 StringRef s = arg->getValue();
542 if (s == "ignore-all" || s == "ignore-in-object-files")
543 return UnresolvedPolicy::Ignore;
544 if (s == "ignore-in-shared-libs" || s == "report-all")
546 error("unknown --unresolved-symbols value: " + s);
549 case OPT_no_undefined:
552 if (StringRef(arg->getValue()) == "defs")
554 if (StringRef(arg->getValue()) == "undefs")
555 return UnresolvedPolicy::Ignore;
560 // -shared implies -unresolved-symbols=ignore-all because missing
561 // symbols are likely to be resolved at runtime using other DSOs.
563 return UnresolvedPolicy::Ignore;
567 static Target2Policy getTarget2(opt::InputArgList &args) {
568 StringRef s = args.getLastArgValue(OPT_target2, "got-rel");
570 return Target2Policy::Rel;
572 return Target2Policy::Abs;
574 return Target2Policy::GotRel;
575 error("unknown --target2 option: " + s);
576 return Target2Policy::GotRel;
579 static bool isOutputFormatBinary(opt::InputArgList &args) {
580 StringRef s = args.getLastArgValue(OPT_oformat, "elf");
583 if (!s.startswith("elf"))
584 error("unknown --oformat value: " + s);
588 static DiscardPolicy getDiscard(opt::InputArgList &args) {
589 if (args.hasArg(OPT_relocatable))
590 return DiscardPolicy::None;
593 args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
595 return DiscardPolicy::Default;
596 if (arg->getOption().getID() == OPT_discard_all)
597 return DiscardPolicy::All;
598 if (arg->getOption().getID() == OPT_discard_locals)
599 return DiscardPolicy::Locals;
600 return DiscardPolicy::None;
603 static StringRef getDynamicLinker(opt::InputArgList &args) {
604 auto *arg = args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
607 if (arg->getOption().getID() == OPT_no_dynamic_linker) {
608 // --no-dynamic-linker suppresses undefined weak symbols in .dynsym
609 config->noDynamicLinker = true;
612 return arg->getValue();
615 static ICFLevel getICF(opt::InputArgList &args) {
616 auto *arg = args.getLastArg(OPT_icf_none, OPT_icf_safe, OPT_icf_all);
617 if (!arg || arg->getOption().getID() == OPT_icf_none)
618 return ICFLevel::None;
619 if (arg->getOption().getID() == OPT_icf_safe)
620 return ICFLevel::Safe;
621 return ICFLevel::All;
624 static StripPolicy getStrip(opt::InputArgList &args) {
625 if (args.hasArg(OPT_relocatable))
626 return StripPolicy::None;
628 auto *arg = args.getLastArg(OPT_strip_all, OPT_strip_debug);
630 return StripPolicy::None;
631 if (arg->getOption().getID() == OPT_strip_all)
632 return StripPolicy::All;
633 return StripPolicy::Debug;
636 static uint64_t parseSectionAddress(StringRef s, opt::InputArgList &args,
637 const opt::Arg &arg) {
639 if (s.startswith("0x"))
641 if (!to_integer(s, va, 16))
642 error("invalid argument: " + arg.getAsString(args));
646 static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &args) {
647 StringMap<uint64_t> ret;
648 for (auto *arg : args.filtered(OPT_section_start)) {
651 std::tie(name, addr) = StringRef(arg->getValue()).split('=');
652 ret[name] = parseSectionAddress(addr, args, *arg);
655 if (auto *arg = args.getLastArg(OPT_Ttext))
656 ret[".text"] = parseSectionAddress(arg->getValue(), args, *arg);
657 if (auto *arg = args.getLastArg(OPT_Tdata))
658 ret[".data"] = parseSectionAddress(arg->getValue(), args, *arg);
659 if (auto *arg = args.getLastArg(OPT_Tbss))
660 ret[".bss"] = parseSectionAddress(arg->getValue(), args, *arg);
664 static SortSectionPolicy getSortSection(opt::InputArgList &args) {
665 StringRef s = args.getLastArgValue(OPT_sort_section);
666 if (s == "alignment")
667 return SortSectionPolicy::Alignment;
669 return SortSectionPolicy::Name;
671 error("unknown --sort-section rule: " + s);
672 return SortSectionPolicy::Default;
675 static OrphanHandlingPolicy getOrphanHandling(opt::InputArgList &args) {
676 StringRef s = args.getLastArgValue(OPT_orphan_handling, "place");
678 return OrphanHandlingPolicy::Warn;
680 return OrphanHandlingPolicy::Error;
682 error("unknown --orphan-handling mode: " + s);
683 return OrphanHandlingPolicy::Place;
686 // Parse --build-id or --build-id=<style>. We handle "tree" as a
687 // synonym for "sha1" because all our hash functions including
688 // -build-id=sha1 are actually tree hashes for performance reasons.
689 static std::pair<BuildIdKind, std::vector<uint8_t>>
690 getBuildId(opt::InputArgList &args) {
691 auto *arg = args.getLastArg(OPT_build_id, OPT_build_id_eq);
693 return {BuildIdKind::None, {}};
695 if (arg->getOption().getID() == OPT_build_id)
696 return {BuildIdKind::Fast, {}};
698 StringRef s = arg->getValue();
700 return {BuildIdKind::Fast, {}};
702 return {BuildIdKind::Md5, {}};
703 if (s == "sha1" || s == "tree")
704 return {BuildIdKind::Sha1, {}};
706 return {BuildIdKind::Uuid, {}};
707 if (s.startswith("0x"))
708 return {BuildIdKind::Hexstring, parseHex(s.substr(2))};
711 error("unknown --build-id style: " + s);
712 return {BuildIdKind::None, {}};
715 static std::pair<bool, bool> getPackDynRelocs(opt::InputArgList &args) {
716 StringRef s = args.getLastArgValue(OPT_pack_dyn_relocs, "none");
718 return {true, false};
720 return {false, true};
721 if (s == "android+relr")
725 error("unknown -pack-dyn-relocs format: " + s);
726 return {false, false};
729 static void readCallGraph(MemoryBufferRef mb) {
730 // Build a map from symbol name to section
731 DenseMap<StringRef, Symbol *> map;
732 for (InputFile *file : objectFiles)
733 for (Symbol *sym : file->getSymbols())
734 map[sym->getName()] = sym;
736 auto findSection = [&](StringRef name) -> InputSectionBase * {
737 Symbol *sym = map.lookup(name);
739 if (config->warnSymbolOrdering)
740 warn(mb.getBufferIdentifier() + ": no such symbol: " + name);
743 maybeWarnUnorderableSymbol(sym);
745 if (Defined *dr = dyn_cast_or_null<Defined>(sym))
746 return dyn_cast_or_null<InputSectionBase>(dr->section);
750 for (StringRef line : args::getLines(mb)) {
751 SmallVector<StringRef, 3> fields;
752 line.split(fields, ' ');
755 if (fields.size() != 3 || !to_integer(fields[2], count)) {
756 error(mb.getBufferIdentifier() + ": parse error");
760 if (InputSectionBase *from = findSection(fields[0]))
761 if (InputSectionBase *to = findSection(fields[1]))
762 config->callGraphProfile[std::make_pair(from, to)] += count;
766 template <class ELFT> static void readCallGraphsFromObjectFiles() {
767 for (auto file : objectFiles) {
768 auto *obj = cast<ObjFile<ELFT>>(file);
770 for (const Elf_CGProfile_Impl<ELFT> &cgpe : obj->cgProfile) {
771 auto *fromSym = dyn_cast<Defined>(&obj->getSymbol(cgpe.cgp_from));
772 auto *toSym = dyn_cast<Defined>(&obj->getSymbol(cgpe.cgp_to));
773 if (!fromSym || !toSym)
776 auto *from = dyn_cast_or_null<InputSectionBase>(fromSym->section);
777 auto *to = dyn_cast_or_null<InputSectionBase>(toSym->section);
779 config->callGraphProfile[{from, to}] += cgpe.cgp_weight;
784 static bool getCompressDebugSections(opt::InputArgList &args) {
785 StringRef s = args.getLastArgValue(OPT_compress_debug_sections, "none");
789 error("unknown --compress-debug-sections value: " + s);
790 if (!zlib::isAvailable())
791 error("--compress-debug-sections: zlib is not available");
795 static StringRef getAliasSpelling(opt::Arg *arg) {
796 if (const opt::Arg *alias = arg->getAlias())
797 return alias->getSpelling();
798 return arg->getSpelling();
801 static std::pair<StringRef, StringRef> getOldNewOptions(opt::InputArgList &args,
803 auto *arg = args.getLastArg(id);
807 StringRef s = arg->getValue();
808 std::pair<StringRef, StringRef> ret = s.split(';');
809 if (ret.second.empty())
810 error(getAliasSpelling(arg) + " expects 'old;new' format, but got " + s);
814 // Parse the symbol ordering file and warn for any duplicate entries.
815 static std::vector<StringRef> getSymbolOrderingFile(MemoryBufferRef mb) {
816 SetVector<StringRef> names;
817 for (StringRef s : args::getLines(mb))
818 if (!names.insert(s) && config->warnSymbolOrdering)
819 warn(mb.getBufferIdentifier() + ": duplicate ordered symbol: " + s);
821 return names.takeVector();
824 static void parseClangOption(StringRef opt, const Twine &msg) {
826 raw_string_ostream os(err);
828 const char *argv[] = {config->progName.data(), opt.data()};
829 if (cl::ParseCommandLineOptions(2, argv, "", &os))
832 error(msg + ": " + StringRef(err).trim());
835 // Initializes Config members by the command line options.
836 static void readConfigs(opt::InputArgList &args) {
837 errorHandler().verbose = args.hasArg(OPT_verbose);
838 errorHandler().fatalWarnings =
839 args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
840 errorHandler().vsDiagnostics =
841 args.hasArg(OPT_visual_studio_diagnostics_format, false);
842 threadsEnabled = args.hasFlag(OPT_threads, OPT_no_threads, true);
844 config->allowMultipleDefinition =
845 args.hasFlag(OPT_allow_multiple_definition,
846 OPT_no_allow_multiple_definition, false) ||
847 hasZOption(args, "muldefs");
848 config->allowShlibUndefined =
849 args.hasFlag(OPT_allow_shlib_undefined, OPT_no_allow_shlib_undefined,
850 args.hasArg(OPT_shared));
851 config->auxiliaryList = args::getStrings(args, OPT_auxiliary);
852 config->bsymbolic = args.hasArg(OPT_Bsymbolic);
853 config->bsymbolicFunctions = args.hasArg(OPT_Bsymbolic_functions);
854 config->checkSections =
855 args.hasFlag(OPT_check_sections, OPT_no_check_sections, true);
856 config->chroot = args.getLastArgValue(OPT_chroot);
857 config->compressDebugSections = getCompressDebugSections(args);
858 config->cref = args.hasFlag(OPT_cref, OPT_no_cref, false);
859 config->defineCommon = args.hasFlag(OPT_define_common, OPT_no_define_common,
860 !args.hasArg(OPT_relocatable));
861 config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
862 config->dependentLibraries = args.hasFlag(OPT_dependent_libraries, OPT_no_dependent_libraries, true);
863 config->disableVerify = args.hasArg(OPT_disable_verify);
864 config->discard = getDiscard(args);
865 config->dwoDir = args.getLastArgValue(OPT_plugin_opt_dwo_dir_eq);
866 config->dynamicLinker = getDynamicLinker(args);
868 args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false);
869 config->emitLLVM = args.hasArg(OPT_plugin_opt_emit_llvm, false);
870 config->emitRelocs = args.hasArg(OPT_emit_relocs);
871 config->callGraphProfileSort = args.hasFlag(
872 OPT_call_graph_profile_sort, OPT_no_call_graph_profile_sort, true);
873 config->enableNewDtags =
874 args.hasFlag(OPT_enable_new_dtags, OPT_disable_new_dtags, true);
875 config->entry = args.getLastArgValue(OPT_entry);
876 config->executeOnly =
877 args.hasFlag(OPT_execute_only, OPT_no_execute_only, false);
878 config->exportDynamic =
879 args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
880 config->filterList = args::getStrings(args, OPT_filter);
881 config->fini = args.getLastArgValue(OPT_fini, "_fini");
882 config->fixCortexA53Errata843419 = args.hasArg(OPT_fix_cortex_a53_843419);
883 config->fixCortexA8 = args.hasArg(OPT_fix_cortex_a8);
884 config->forceBTI = hasZOption(args, "force-bti");
885 config->gcSections = args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, false);
886 config->gnuUnique = args.hasFlag(OPT_gnu_unique, OPT_no_gnu_unique, true);
887 config->gdbIndex = args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false);
888 config->icf = getICF(args);
889 config->ignoreDataAddressEquality =
890 args.hasArg(OPT_ignore_data_address_equality);
891 config->ignoreFunctionAddressEquality =
892 args.hasArg(OPT_ignore_function_address_equality);
893 config->init = args.getLastArgValue(OPT_init, "_init");
894 config->ltoAAPipeline = args.getLastArgValue(OPT_lto_aa_pipeline);
895 config->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate);
896 config->ltoCSProfileFile = args.getLastArgValue(OPT_lto_cs_profile_file);
897 config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
898 config->ltoNewPassManager = args.hasArg(OPT_lto_new_pass_manager);
899 config->ltoNewPmPasses = args.getLastArgValue(OPT_lto_newpm_passes);
900 config->ltoo = args::getInteger(args, OPT_lto_O, 2);
901 config->ltoObjPath = args.getLastArgValue(OPT_lto_obj_path_eq);
902 config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
903 config->ltoSampleProfile = args.getLastArgValue(OPT_lto_sample_profile);
904 config->mapFile = args.getLastArgValue(OPT_Map);
905 config->mipsGotSize = args::getInteger(args, OPT_mips_got_size, 0xfff0);
906 config->mergeArmExidx =
907 args.hasFlag(OPT_merge_exidx_entries, OPT_no_merge_exidx_entries, true);
908 config->mmapOutputFile =
909 args.hasFlag(OPT_mmap_output_file, OPT_no_mmap_output_file, true);
910 config->nmagic = args.hasFlag(OPT_nmagic, OPT_no_nmagic, false);
911 config->noinhibitExec = args.hasArg(OPT_noinhibit_exec);
912 config->nostdlib = args.hasArg(OPT_nostdlib);
913 config->oFormatBinary = isOutputFormatBinary(args);
914 config->omagic = args.hasFlag(OPT_omagic, OPT_no_omagic, false);
915 config->optRemarksFilename = args.getLastArgValue(OPT_opt_remarks_filename);
916 config->optRemarksPasses = args.getLastArgValue(OPT_opt_remarks_passes);
917 config->optRemarksWithHotness = args.hasArg(OPT_opt_remarks_with_hotness);
918 config->optRemarksFormat = args.getLastArgValue(OPT_opt_remarks_format);
919 config->optimize = args::getInteger(args, OPT_O, 1);
920 config->orphanHandling = getOrphanHandling(args);
921 config->outputFile = args.getLastArgValue(OPT_o);
922 config->pacPlt = hasZOption(args, "pac-plt");
923 config->pie = args.hasFlag(OPT_pie, OPT_no_pie, false);
924 config->printIcfSections =
925 args.hasFlag(OPT_print_icf_sections, OPT_no_print_icf_sections, false);
926 config->printGcSections =
927 args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
928 config->printSymbolOrder =
929 args.getLastArgValue(OPT_print_symbol_order);
930 config->rpath = getRpath(args);
931 config->relocatable = args.hasArg(OPT_relocatable);
932 config->saveTemps = args.hasArg(OPT_save_temps);
933 config->searchPaths = args::getStrings(args, OPT_library_path);
934 config->sectionStartMap = getSectionStartMap(args);
935 config->shared = args.hasArg(OPT_shared);
936 config->singleRoRx = args.hasArg(OPT_no_rosegment);
937 config->soName = args.getLastArgValue(OPT_soname);
938 config->sortSection = getSortSection(args);
939 config->splitStackAdjustSize = args::getInteger(args, OPT_split_stack_adjust_size, 16384);
940 config->strip = getStrip(args);
941 config->sysroot = args.getLastArgValue(OPT_sysroot);
942 config->target1Rel = args.hasFlag(OPT_target1_rel, OPT_target1_abs, false);
943 config->target2 = getTarget2(args);
944 config->thinLTOCacheDir = args.getLastArgValue(OPT_thinlto_cache_dir);
945 config->thinLTOCachePolicy = CHECK(
946 parseCachePruningPolicy(args.getLastArgValue(OPT_thinlto_cache_policy)),
947 "--thinlto-cache-policy: invalid cache policy");
948 config->thinLTOEmitImportsFiles = args.hasArg(OPT_thinlto_emit_imports_files);
949 config->thinLTOIndexOnly = args.hasArg(OPT_thinlto_index_only) ||
950 args.hasArg(OPT_thinlto_index_only_eq);
951 config->thinLTOIndexOnlyArg = args.getLastArgValue(OPT_thinlto_index_only_eq);
952 config->thinLTOJobs = args::getInteger(args, OPT_thinlto_jobs, -1u);
953 config->thinLTOObjectSuffixReplace =
954 getOldNewOptions(args, OPT_thinlto_object_suffix_replace_eq);
955 config->thinLTOPrefixReplace =
956 getOldNewOptions(args, OPT_thinlto_prefix_replace_eq);
957 config->trace = args.hasArg(OPT_trace);
958 config->undefined = args::getStrings(args, OPT_undefined);
959 config->undefinedVersion =
960 args.hasFlag(OPT_undefined_version, OPT_no_undefined_version, true);
961 config->useAndroidRelrTags = args.hasFlag(
962 OPT_use_android_relr_tags, OPT_no_use_android_relr_tags, false);
963 config->unresolvedSymbols = getUnresolvedSymbolPolicy(args);
964 config->warnBackrefs =
965 args.hasFlag(OPT_warn_backrefs, OPT_no_warn_backrefs, false);
966 config->warnCommon = args.hasFlag(OPT_warn_common, OPT_no_warn_common, false);
967 config->warnIfuncTextrel =
968 args.hasFlag(OPT_warn_ifunc_textrel, OPT_no_warn_ifunc_textrel, false);
969 config->warnSymbolOrdering =
970 args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true);
971 config->zCombreloc = getZFlag(args, "combreloc", "nocombreloc", true);
972 config->zCopyreloc = getZFlag(args, "copyreloc", "nocopyreloc", true);
973 config->zForceIbt = hasZOption(args, "force-ibt");
974 config->zGlobal = hasZOption(args, "global");
975 config->zGnustack = getZGnuStack(args);
976 config->zHazardplt = hasZOption(args, "hazardplt");
977 config->zIfuncNoplt = hasZOption(args, "ifunc-noplt");
978 config->zInitfirst = hasZOption(args, "initfirst");
979 config->zInterpose = hasZOption(args, "interpose");
980 config->zKeepTextSectionPrefix = getZFlag(
981 args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
982 config->zNodefaultlib = hasZOption(args, "nodefaultlib");
983 config->zNodelete = hasZOption(args, "nodelete");
984 config->zNodlopen = hasZOption(args, "nodlopen");
985 config->zNow = getZFlag(args, "now", "lazy", false);
986 config->zOrigin = hasZOption(args, "origin");
987 config->zRelro = getZFlag(args, "relro", "norelro", true);
988 config->zRetpolineplt = hasZOption(args, "retpolineplt");
989 config->zRodynamic = hasZOption(args, "rodynamic");
990 config->zSeparate = getZSeparate(args);
991 config->zShstk = hasZOption(args, "shstk");
992 config->zStackSize = args::getZOptionValue(args, OPT_z, "stack-size", 0);
993 config->zText = getZFlag(args, "text", "notext", true);
994 config->zWxneeded = hasZOption(args, "wxneeded");
996 // Parse LTO options.
997 if (auto *arg = args.getLastArg(OPT_plugin_opt_mcpu_eq))
998 parseClangOption(saver.save("-mcpu=" + StringRef(arg->getValue())),
1001 for (auto *arg : args.filtered(OPT_plugin_opt))
1002 parseClangOption(arg->getValue(), arg->getSpelling());
1004 // Parse -mllvm options.
1005 for (auto *arg : args.filtered(OPT_mllvm))
1006 parseClangOption(arg->getValue(), arg->getSpelling());
1008 if (config->ltoo > 3)
1009 error("invalid optimization level for LTO: " + Twine(config->ltoo));
1010 if (config->ltoPartitions == 0)
1011 error("--lto-partitions: number of threads must be > 0");
1012 if (config->thinLTOJobs == 0)
1013 error("--thinlto-jobs: number of threads must be > 0");
1015 if (config->splitStackAdjustSize < 0)
1016 error("--split-stack-adjust-size: size must be >= 0");
1018 // The text segment is traditionally the first segment, whose address equals
1019 // the base address. However, lld places the R PT_LOAD first. -Ttext-segment
1020 // is an old-fashioned option that does not play well with lld's layout.
1021 // Suggest --image-base as a likely alternative.
1022 if (args.hasArg(OPT_Ttext_segment))
1023 error("-Ttext-segment is not supported. Use --image-base if you "
1024 "intend to set the base address");
1026 // Parse ELF{32,64}{LE,BE} and CPU type.
1027 if (auto *arg = args.getLastArg(OPT_m)) {
1028 StringRef s = arg->getValue();
1029 std::tie(config->ekind, config->emachine, config->osabi) =
1031 config->mipsN32Abi =
1032 (s.startswith("elf32btsmipn32") || s.startswith("elf32ltsmipn32"));
1033 config->emulation = s;
1036 // Parse -hash-style={sysv,gnu,both}.
1037 if (auto *arg = args.getLastArg(OPT_hash_style)) {
1038 StringRef s = arg->getValue();
1040 config->sysvHash = true;
1041 else if (s == "gnu")
1042 config->gnuHash = true;
1043 else if (s == "both")
1044 config->sysvHash = config->gnuHash = true;
1046 error("unknown -hash-style: " + s);
1049 if (args.hasArg(OPT_print_map))
1050 config->mapFile = "-";
1052 // Page alignment can be disabled by the -n (--nmagic) and -N (--omagic).
1053 // As PT_GNU_RELRO relies on Paging, do not create it when we have disabled
1055 if (config->nmagic || config->omagic)
1056 config->zRelro = false;
1058 std::tie(config->buildId, config->buildIdVector) = getBuildId(args);
1060 std::tie(config->androidPackDynRelocs, config->relrPackDynRelocs) =
1061 getPackDynRelocs(args);
1063 if (auto *arg = args.getLastArg(OPT_symbol_ordering_file)){
1064 if (args.hasArg(OPT_call_graph_ordering_file))
1065 error("--symbol-ordering-file and --call-graph-order-file "
1066 "may not be used together");
1067 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue())){
1068 config->symbolOrderingFile = getSymbolOrderingFile(*buffer);
1069 // Also need to disable CallGraphProfileSort to prevent
1070 // LLD order symbols with CGProfile
1071 config->callGraphProfileSort = false;
1075 assert(config->versionDefinitions.empty());
1076 config->versionDefinitions.push_back({"local", (uint16_t)VER_NDX_LOCAL, {}});
1077 config->versionDefinitions.push_back(
1078 {"global", (uint16_t)VER_NDX_GLOBAL, {}});
1080 // If --retain-symbol-file is used, we'll keep only the symbols listed in
1081 // the file and discard all others.
1082 if (auto *arg = args.getLastArg(OPT_retain_symbols_file)) {
1083 config->versionDefinitions[VER_NDX_LOCAL].patterns.push_back(
1084 {"*", /*isExternCpp=*/false, /*hasWildcard=*/true});
1085 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
1086 for (StringRef s : args::getLines(*buffer))
1087 config->versionDefinitions[VER_NDX_GLOBAL].patterns.push_back(
1088 {s, /*isExternCpp=*/false, /*hasWildcard=*/false});
1091 // Parses -dynamic-list and -export-dynamic-symbol. They make some
1092 // symbols private. Note that -export-dynamic takes precedence over them
1093 // as it says all symbols should be exported.
1094 if (!config->exportDynamic) {
1095 for (auto *arg : args.filtered(OPT_dynamic_list))
1096 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
1097 readDynamicList(*buffer);
1099 for (auto *arg : args.filtered(OPT_export_dynamic_symbol))
1100 config->dynamicList.push_back(
1101 {arg->getValue(), /*isExternCpp=*/false, /*hasWildcard=*/false});
1104 // If --export-dynamic-symbol=foo is given and symbol foo is defined in
1105 // an object file in an archive file, that object file should be pulled
1106 // out and linked. (It doesn't have to behave like that from technical
1107 // point of view, but this is needed for compatibility with GNU.)
1108 for (auto *arg : args.filtered(OPT_export_dynamic_symbol))
1109 config->undefined.push_back(arg->getValue());
1111 for (auto *arg : args.filtered(OPT_version_script))
1112 if (Optional<std::string> path = searchScript(arg->getValue())) {
1113 if (Optional<MemoryBufferRef> buffer = readFile(*path))
1114 readVersionScript(*buffer);
1116 error(Twine("cannot find version script ") + arg->getValue());
1120 // Some Config members do not directly correspond to any particular
1121 // command line options, but computed based on other Config values.
1122 // This function initialize such members. See Config.h for the details
1124 static void setConfigs(opt::InputArgList &args) {
1125 ELFKind k = config->ekind;
1126 uint16_t m = config->emachine;
1128 config->copyRelocs = (config->relocatable || config->emitRelocs);
1129 config->is64 = (k == ELF64LEKind || k == ELF64BEKind);
1130 config->isLE = (k == ELF32LEKind || k == ELF64LEKind);
1131 config->endianness = config->isLE ? endianness::little : endianness::big;
1132 config->isMips64EL = (k == ELF64LEKind && m == EM_MIPS);
1133 config->isPic = config->pie || config->shared;
1134 config->picThunk = args.hasArg(OPT_pic_veneer, config->isPic);
1135 config->wordsize = config->is64 ? 8 : 4;
1137 // ELF defines two different ways to store relocation addends as shown below:
1139 // Rel: Addends are stored to the location where relocations are applied.
1140 // Rela: Addends are stored as part of relocation entry.
1142 // In other words, Rela makes it easy to read addends at the price of extra
1143 // 4 or 8 byte for each relocation entry. We don't know why ELF defined two
1144 // different mechanisms in the first place, but this is how the spec is
1147 // You cannot choose which one, Rel or Rela, you want to use. Instead each
1148 // ABI defines which one you need to use. The following expression expresses
1150 config->isRela = m == EM_AARCH64 || m == EM_AMDGPU || m == EM_HEXAGON ||
1151 m == EM_PPC || m == EM_PPC64 || m == EM_RISCV ||
1154 // If the output uses REL relocations we must store the dynamic relocation
1155 // addends to the output sections. We also store addends for RELA relocations
1156 // if --apply-dynamic-relocs is used.
1157 // We default to not writing the addends when using RELA relocations since
1158 // any standard conforming tool can find it in r_addend.
1159 config->writeAddends = args.hasFlag(OPT_apply_dynamic_relocs,
1160 OPT_no_apply_dynamic_relocs, false) ||
1163 config->tocOptimize =
1164 args.hasFlag(OPT_toc_optimize, OPT_no_toc_optimize, m == EM_PPC64);
1167 // Returns a value of "-format" option.
1168 static bool isFormatBinary(StringRef s) {
1171 if (s == "elf" || s == "default")
1173 error("unknown -format value: " + s +
1174 " (supported formats: elf, default, binary)");
1178 void LinkerDriver::createFiles(opt::InputArgList &args) {
1179 // For --{push,pop}-state.
1180 std::vector<std::tuple<bool, bool, bool>> stack;
1182 // Iterate over argv to process input files and positional arguments.
1183 for (auto *arg : args) {
1184 switch (arg->getOption().getID()) {
1186 addLibrary(arg->getValue());
1189 addFile(arg->getValue(), /*withLOption=*/false);
1194 std::tie(from, to) = StringRef(arg->getValue()).split('=');
1195 if (from.empty() || to.empty())
1196 error("-defsym: syntax error: " + StringRef(arg->getValue()));
1198 readDefsym(from, MemoryBufferRef(to, "-defsym"));
1202 if (Optional<std::string> path = searchScript(arg->getValue())) {
1203 if (Optional<MemoryBufferRef> mb = readFile(*path))
1204 readLinkerScript(*mb);
1207 error(Twine("cannot find linker script ") + arg->getValue());
1210 config->asNeeded = true;
1213 config->formatBinary = isFormatBinary(arg->getValue());
1215 case OPT_no_as_needed:
1216 config->asNeeded = false;
1221 config->isStatic = true;
1224 config->isStatic = false;
1226 case OPT_whole_archive:
1227 inWholeArchive = true;
1229 case OPT_no_whole_archive:
1230 inWholeArchive = false;
1232 case OPT_just_symbols:
1233 if (Optional<MemoryBufferRef> mb = readFile(arg->getValue())) {
1234 files.push_back(createObjectFile(*mb));
1235 files.back()->justSymbols = true;
1238 case OPT_start_group:
1239 if (InputFile::isInGroup)
1240 error("nested --start-group");
1241 InputFile::isInGroup = true;
1244 if (!InputFile::isInGroup)
1245 error("stray --end-group");
1246 InputFile::isInGroup = false;
1247 ++InputFile::nextGroupId;
1251 error("nested --start-lib");
1252 if (InputFile::isInGroup)
1253 error("may not nest --start-lib in --start-group");
1255 InputFile::isInGroup = true;
1259 error("stray --end-lib");
1261 InputFile::isInGroup = false;
1262 ++InputFile::nextGroupId;
1264 case OPT_push_state:
1265 stack.emplace_back(config->asNeeded, config->isStatic, inWholeArchive);
1268 if (stack.empty()) {
1269 error("unbalanced --push-state/--pop-state");
1272 std::tie(config->asNeeded, config->isStatic, inWholeArchive) = stack.back();
1278 if (files.empty() && errorCount() == 0)
1279 error("no input files");
1282 // If -m <machine_type> was not given, infer it from object files.
1283 void LinkerDriver::inferMachineType() {
1284 if (config->ekind != ELFNoneKind)
1287 for (InputFile *f : files) {
1288 if (f->ekind == ELFNoneKind)
1290 config->ekind = f->ekind;
1291 config->emachine = f->emachine;
1292 config->osabi = f->osabi;
1293 config->mipsN32Abi = config->emachine == EM_MIPS && isMipsN32Abi(f);
1296 error("target emulation unknown: -m or at least one .o file required");
1299 // Parse -z max-page-size=<value>. The default value is defined by
1301 static uint64_t getMaxPageSize(opt::InputArgList &args) {
1302 uint64_t val = args::getZOptionValue(args, OPT_z, "max-page-size",
1303 target->defaultMaxPageSize);
1304 if (!isPowerOf2_64(val))
1305 error("max-page-size: value isn't a power of 2");
1306 if (config->nmagic || config->omagic) {
1307 if (val != target->defaultMaxPageSize)
1308 warn("-z max-page-size set, but paging disabled by omagic or nmagic");
1314 // Parse -z common-page-size=<value>. The default value is defined by
1316 static uint64_t getCommonPageSize(opt::InputArgList &args) {
1317 uint64_t val = args::getZOptionValue(args, OPT_z, "common-page-size",
1318 target->defaultCommonPageSize);
1319 if (!isPowerOf2_64(val))
1320 error("common-page-size: value isn't a power of 2");
1321 if (config->nmagic || config->omagic) {
1322 if (val != target->defaultCommonPageSize)
1323 warn("-z common-page-size set, but paging disabled by omagic or nmagic");
1326 // commonPageSize can't be larger than maxPageSize.
1327 if (val > config->maxPageSize)
1328 val = config->maxPageSize;
1332 // Parses -image-base option.
1333 static Optional<uint64_t> getImageBase(opt::InputArgList &args) {
1334 // Because we are using "Config->maxPageSize" here, this function has to be
1335 // called after the variable is initialized.
1336 auto *arg = args.getLastArg(OPT_image_base);
1340 StringRef s = arg->getValue();
1342 if (!to_integer(s, v)) {
1343 error("-image-base: number expected, but got " + s);
1346 if ((v % config->maxPageSize) != 0)
1347 warn("-image-base: address isn't multiple of page size: " + s);
1351 // Parses `--exclude-libs=lib,lib,...`.
1352 // The library names may be delimited by commas or colons.
1353 static DenseSet<StringRef> getExcludeLibs(opt::InputArgList &args) {
1354 DenseSet<StringRef> ret;
1355 for (auto *arg : args.filtered(OPT_exclude_libs)) {
1356 StringRef s = arg->getValue();
1358 size_t pos = s.find_first_of(",:");
1359 if (pos == StringRef::npos)
1361 ret.insert(s.substr(0, pos));
1362 s = s.substr(pos + 1);
1369 // Handles the -exclude-libs option. If a static library file is specified
1370 // by the -exclude-libs option, all public symbols from the archive become
1371 // private unless otherwise specified by version scripts or something.
1372 // A special library name "ALL" means all archive files.
1374 // This is not a popular option, but some programs such as bionic libc use it.
1375 static void excludeLibs(opt::InputArgList &args) {
1376 DenseSet<StringRef> libs = getExcludeLibs(args);
1377 bool all = libs.count("ALL");
1379 auto visit = [&](InputFile *file) {
1380 if (!file->archiveName.empty())
1381 if (all || libs.count(path::filename(file->archiveName)))
1382 for (Symbol *sym : file->getSymbols())
1383 if (!sym->isUndefined() && !sym->isLocal() && sym->file == file)
1384 sym->versionId = VER_NDX_LOCAL;
1387 for (InputFile *file : objectFiles)
1390 for (BitcodeFile *file : bitcodeFiles)
1394 // Force Sym to be entered in the output. Used for -u or equivalent.
1395 static void handleUndefined(Symbol *sym) {
1396 // Since a symbol may not be used inside the program, LTO may
1397 // eliminate it. Mark the symbol as "used" to prevent it.
1398 sym->isUsedInRegularObj = true;
1404 // As an extension to GNU linkers, lld supports a variant of `-u`
1405 // which accepts wildcard patterns. All symbols that match a given
1406 // pattern are handled as if they were given by `-u`.
1407 static void handleUndefinedGlob(StringRef arg) {
1408 Expected<GlobPattern> pat = GlobPattern::create(arg);
1410 error("--undefined-glob: " + toString(pat.takeError()));
1414 std::vector<Symbol *> syms;
1415 for (Symbol *sym : symtab->symbols()) {
1416 // Calling Sym->fetch() from here is not safe because it may
1417 // add new symbols to the symbol table, invalidating the
1418 // current iterator. So we just keep a note.
1419 if (pat->match(sym->getName()))
1420 syms.push_back(sym);
1423 for (Symbol *sym : syms)
1424 handleUndefined(sym);
1427 static void handleLibcall(StringRef name) {
1428 Symbol *sym = symtab->find(name);
1429 if (!sym || !sym->isLazy())
1433 if (auto *lo = dyn_cast<LazyObject>(sym))
1436 mb = cast<LazyArchive>(sym)->getMemberBuffer();
1442 // Replaces common symbols with defined symbols reside in .bss sections.
1443 // This function is called after all symbol names are resolved. As a
1444 // result, the passes after the symbol resolution won't see any
1445 // symbols of type CommonSymbol.
1446 static void replaceCommonSymbols() {
1447 for (Symbol *sym : symtab->symbols()) {
1448 auto *s = dyn_cast<CommonSymbol>(sym);
1452 auto *bss = make<BssSection>("COMMON", s->size, s->alignment);
1453 bss->file = s->file;
1455 inputSections.push_back(bss);
1456 s->replace(Defined{s->file, s->getName(), s->binding, s->stOther, s->type,
1457 /*value=*/0, s->size, bss});
1461 // If all references to a DSO happen to be weak, the DSO is not added
1462 // to DT_NEEDED. If that happens, we need to eliminate shared symbols
1463 // created from the DSO. Otherwise, they become dangling references
1464 // that point to a non-existent DSO.
1465 static void demoteSharedSymbols() {
1466 for (Symbol *sym : symtab->symbols()) {
1467 auto *s = dyn_cast<SharedSymbol>(sym);
1468 if (!s || s->getFile().isNeeded)
1471 bool used = s->used;
1472 s->replace(Undefined{nullptr, s->getName(), STB_WEAK, s->stOther, s->type});
1477 // The section referred to by `s` is considered address-significant. Set the
1478 // keepUnique flag on the section if appropriate.
1479 static void markAddrsig(Symbol *s) {
1480 if (auto *d = dyn_cast_or_null<Defined>(s))
1482 // We don't need to keep text sections unique under --icf=all even if they
1483 // are address-significant.
1484 if (config->icf == ICFLevel::Safe || !(d->section->flags & SHF_EXECINSTR))
1485 d->section->keepUnique = true;
1488 // Record sections that define symbols mentioned in --keep-unique <symbol>
1489 // and symbols referred to by address-significance tables. These sections are
1490 // ineligible for ICF.
1491 template <class ELFT>
1492 static void findKeepUniqueSections(opt::InputArgList &args) {
1493 for (auto *arg : args.filtered(OPT_keep_unique)) {
1494 StringRef name = arg->getValue();
1495 auto *d = dyn_cast_or_null<Defined>(symtab->find(name));
1496 if (!d || !d->section) {
1497 warn("could not find symbol " + name + " to keep unique");
1500 d->section->keepUnique = true;
1503 // --icf=all --ignore-data-address-equality means that we can ignore
1504 // the dynsym and address-significance tables entirely.
1505 if (config->icf == ICFLevel::All && config->ignoreDataAddressEquality)
1508 // Symbols in the dynsym could be address-significant in other executables
1509 // or DSOs, so we conservatively mark them as address-significant.
1510 for (Symbol *sym : symtab->symbols())
1511 if (sym->includeInDynsym())
1514 // Visit the address-significance table in each object file and mark each
1515 // referenced symbol as address-significant.
1516 for (InputFile *f : objectFiles) {
1517 auto *obj = cast<ObjFile<ELFT>>(f);
1518 ArrayRef<Symbol *> syms = obj->getSymbols();
1519 if (obj->addrsigSec) {
1520 ArrayRef<uint8_t> contents =
1521 check(obj->getObj().getSectionContents(obj->addrsigSec));
1522 const uint8_t *cur = contents.begin();
1523 while (cur != contents.end()) {
1526 uint64_t symIndex = decodeULEB128(cur, &size, contents.end(), &err);
1528 fatal(toString(f) + ": could not decode addrsig section: " + err);
1529 markAddrsig(syms[symIndex]);
1533 // If an object file does not have an address-significance table,
1534 // conservatively mark all of its symbols as address-significant.
1535 for (Symbol *s : syms)
1541 // This function reads a symbol partition specification section. These sections
1542 // are used to control which partition a symbol is allocated to. See
1543 // https://lld.llvm.org/Partitions.html for more details on partitions.
1544 template <typename ELFT>
1545 static void readSymbolPartitionSection(InputSectionBase *s) {
1546 // Read the relocation that refers to the partition's entry point symbol.
1548 if (s->areRelocsRela)
1549 sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template relas<ELFT>()[0]);
1551 sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template rels<ELFT>()[0]);
1552 if (!isa<Defined>(sym) || !sym->includeInDynsym())
1555 StringRef partName = reinterpret_cast<const char *>(s->data().data());
1556 for (Partition &part : partitions) {
1557 if (part.name == partName) {
1558 sym->partition = part.getNumber();
1563 // Forbid partitions from being used on incompatible targets, and forbid them
1564 // from being used together with various linker features that assume a single
1565 // set of output sections.
1566 if (script->hasSectionsCommand)
1567 error(toString(s->file) +
1568 ": partitions cannot be used with the SECTIONS command");
1569 if (script->hasPhdrsCommands())
1570 error(toString(s->file) +
1571 ": partitions cannot be used with the PHDRS command");
1572 if (!config->sectionStartMap.empty())
1573 error(toString(s->file) + ": partitions cannot be used with "
1574 "--section-start, -Ttext, -Tdata or -Tbss");
1575 if (config->emachine == EM_MIPS)
1576 error(toString(s->file) + ": partitions cannot be used on this target");
1578 // Impose a limit of no more than 254 partitions. This limit comes from the
1579 // sizes of the Partition fields in InputSectionBase and Symbol, as well as
1580 // the amount of space devoted to the partition number in RankFlags.
1581 if (partitions.size() == 254)
1582 fatal("may not have more than 254 partitions");
1584 partitions.emplace_back();
1585 Partition &newPart = partitions.back();
1586 newPart.name = partName;
1587 sym->partition = newPart.getNumber();
1590 static Symbol *addUndefined(StringRef name) {
1591 return symtab->addSymbol(
1592 Undefined{nullptr, name, STB_GLOBAL, STV_DEFAULT, 0});
1595 // This function is where all the optimizations of link-time
1596 // optimization takes place. When LTO is in use, some input files are
1597 // not in native object file format but in the LLVM bitcode format.
1598 // This function compiles bitcode files into a few big native files
1599 // using LLVM functions and replaces bitcode symbols with the results.
1600 // Because all bitcode files that the program consists of are passed to
1601 // the compiler at once, it can do a whole-program optimization.
1602 template <class ELFT> void LinkerDriver::compileBitcodeFiles() {
1603 // Compile bitcode files and replace bitcode symbols.
1604 lto.reset(new BitcodeCompiler);
1605 for (BitcodeFile *file : bitcodeFiles)
1608 for (InputFile *file : lto->compile()) {
1609 auto *obj = cast<ObjFile<ELFT>>(file);
1610 obj->parse(/*ignoreComdats=*/true);
1611 for (Symbol *sym : obj->getGlobalSymbols())
1612 sym->parseSymbolVersion();
1613 objectFiles.push_back(file);
1617 // The --wrap option is a feature to rename symbols so that you can write
1618 // wrappers for existing functions. If you pass `-wrap=foo`, all
1619 // occurrences of symbol `foo` are resolved to `wrap_foo` (so, you are
1620 // expected to write `wrap_foo` function as a wrapper). The original
1621 // symbol becomes accessible as `real_foo`, so you can call that from your
1624 // This data structure is instantiated for each -wrap option.
1625 struct WrappedSymbol {
1631 // Handles -wrap option.
1633 // This function instantiates wrapper symbols. At this point, they seem
1634 // like they are not being used at all, so we explicitly set some flags so
1635 // that LTO won't eliminate them.
1636 static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &args) {
1637 std::vector<WrappedSymbol> v;
1638 DenseSet<StringRef> seen;
1640 for (auto *arg : args.filtered(OPT_wrap)) {
1641 StringRef name = arg->getValue();
1642 if (!seen.insert(name).second)
1645 Symbol *sym = symtab->find(name);
1649 Symbol *real = addUndefined(saver.save("__real_" + name));
1650 Symbol *wrap = addUndefined(saver.save("__wrap_" + name));
1651 v.push_back({sym, real, wrap});
1653 // We want to tell LTO not to inline symbols to be overwritten
1654 // because LTO doesn't know the final symbol contents after renaming.
1655 real->canInline = false;
1656 sym->canInline = false;
1658 // Tell LTO not to eliminate these symbols.
1659 sym->isUsedInRegularObj = true;
1660 wrap->isUsedInRegularObj = true;
1665 // Do renaming for -wrap by updating pointers to symbols.
1667 // When this function is executed, only InputFiles and symbol table
1668 // contain pointers to symbol objects. We visit them to replace pointers,
1669 // so that wrapped symbols are swapped as instructed by the command line.
1670 static void wrapSymbols(ArrayRef<WrappedSymbol> wrapped) {
1671 DenseMap<Symbol *, Symbol *> map;
1672 for (const WrappedSymbol &w : wrapped) {
1673 map[w.sym] = w.wrap;
1674 map[w.real] = w.sym;
1677 // Update pointers in input files.
1678 parallelForEach(objectFiles, [&](InputFile *file) {
1679 MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
1680 for (size_t i = 0, e = syms.size(); i != e; ++i)
1681 if (Symbol *s = map.lookup(syms[i]))
1685 // Update pointers in the symbol table.
1686 for (const WrappedSymbol &w : wrapped)
1687 symtab->wrap(w.sym, w.real, w.wrap);
1690 // To enable CET (x86's hardware-assited control flow enforcement), each
1691 // source file must be compiled with -fcf-protection. Object files compiled
1692 // with the flag contain feature flags indicating that they are compatible
1693 // with CET. We enable the feature only when all object files are compatible
1696 // This is also the case with AARCH64's BTI and PAC which use the similar
1697 // GNU_PROPERTY_AARCH64_FEATURE_1_AND mechanism.
1698 template <class ELFT> static uint32_t getAndFeatures() {
1699 if (config->emachine != EM_386 && config->emachine != EM_X86_64 &&
1700 config->emachine != EM_AARCH64)
1704 for (InputFile *f : objectFiles) {
1705 uint32_t features = cast<ObjFile<ELFT>>(f)->andFeatures;
1706 if (config->forceBTI && !(features & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) {
1707 warn(toString(f) + ": -z force-bti: file does not have BTI property");
1708 features |= GNU_PROPERTY_AARCH64_FEATURE_1_BTI;
1709 } else if (config->zForceIbt &&
1710 !(features & GNU_PROPERTY_X86_FEATURE_1_IBT)) {
1711 warn(toString(f) + ": -z force-ibt: file does not have "
1712 "GNU_PROPERTY_X86_FEATURE_1_IBT property");
1713 features |= GNU_PROPERTY_X86_FEATURE_1_IBT;
1718 // Force enable pointer authentication Plt, we don't warn in this case as
1719 // this does not require support in the object for correctness.
1721 ret |= GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
1722 // Force enable Shadow Stack.
1724 ret |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
1729 // Do actual linking. Note that when this function is called,
1730 // all linker scripts have already been parsed.
1731 template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
1732 // If a -hash-style option was not given, set to a default value,
1733 // which varies depending on the target.
1734 if (!args.hasArg(OPT_hash_style)) {
1735 if (config->emachine == EM_MIPS)
1736 config->sysvHash = true;
1738 config->sysvHash = config->gnuHash = true;
1741 // Default output filename is "a.out" by the Unix tradition.
1742 if (config->outputFile.empty())
1743 config->outputFile = "a.out";
1745 // Fail early if the output file or map file is not writable. If a user has a
1746 // long link, e.g. due to a large LTO link, they do not wish to run it and
1747 // find that it failed because there was a mistake in their command-line.
1748 if (auto e = tryCreateFile(config->outputFile))
1749 error("cannot open output file " + config->outputFile + ": " + e.message());
1750 if (auto e = tryCreateFile(config->mapFile))
1751 error("cannot open map file " + config->mapFile + ": " + e.message());
1755 // Use default entry point name if no name was given via the command
1756 // line nor linker scripts. For some reason, MIPS entry point name is
1757 // different from others.
1758 config->warnMissingEntry =
1759 (!config->entry.empty() || (!config->shared && !config->relocatable));
1760 if (config->entry.empty() && !config->relocatable)
1761 config->entry = (config->emachine == EM_MIPS) ? "__start" : "_start";
1763 // Handle --trace-symbol.
1764 for (auto *arg : args.filtered(OPT_trace_symbol))
1765 symtab->insert(arg->getValue())->traced = true;
1767 // Add all files to the symbol table. This will add almost all
1768 // symbols that we need to the symbol table. This process might
1769 // add files to the link, via autolinking, these files are always
1770 // appended to the Files vector.
1771 for (size_t i = 0; i < files.size(); ++i)
1772 parseFile(files[i]);
1774 // Now that we have every file, we can decide if we will need a
1775 // dynamic symbol table.
1776 // We need one if we were asked to export dynamic symbols or if we are
1777 // producing a shared library.
1778 // We also need one if any shared libraries are used and for pie executables
1779 // (probably because the dynamic linker needs it).
1780 config->hasDynSymTab =
1781 !sharedFiles.empty() || config->isPic || config->exportDynamic;
1783 // Some symbols (such as __ehdr_start) are defined lazily only when there
1784 // are undefined symbols for them, so we add these to trigger that logic.
1785 for (StringRef name : script->referencedSymbols)
1788 // Handle the `--undefined <sym>` options.
1789 for (StringRef arg : config->undefined)
1790 if (Symbol *sym = symtab->find(arg))
1791 handleUndefined(sym);
1793 // If an entry symbol is in a static archive, pull out that file now.
1794 if (Symbol *sym = symtab->find(config->entry))
1795 handleUndefined(sym);
1797 // Handle the `--undefined-glob <pattern>` options.
1798 for (StringRef pat : args::getStrings(args, OPT_undefined_glob))
1799 handleUndefinedGlob(pat);
1801 // Mark -init and -fini symbols so that the LTO doesn't eliminate them.
1802 if (Symbol *sym = symtab->find(config->init))
1803 sym->isUsedInRegularObj = true;
1804 if (Symbol *sym = symtab->find(config->fini))
1805 sym->isUsedInRegularObj = true;
1807 // If any of our inputs are bitcode files, the LTO code generator may create
1808 // references to certain library functions that might not be explicit in the
1809 // bitcode file's symbol table. If any of those library functions are defined
1810 // in a bitcode file in an archive member, we need to arrange to use LTO to
1811 // compile those archive members by adding them to the link beforehand.
1813 // However, adding all libcall symbols to the link can have undesired
1814 // consequences. For example, the libgcc implementation of
1815 // __sync_val_compare_and_swap_8 on 32-bit ARM pulls in an .init_array entry
1816 // that aborts the program if the Linux kernel does not support 64-bit
1817 // atomics, which would prevent the program from running even if it does not
1818 // use 64-bit atomics.
1820 // Therefore, we only add libcall symbols to the link before LTO if we have
1821 // to, i.e. if the symbol's definition is in bitcode. Any other required
1822 // libcall symbols will be added to the link after LTO when we add the LTO
1823 // object file to the link.
1824 if (!bitcodeFiles.empty())
1825 for (auto *s : lto::LTO::getRuntimeLibcallSymbols())
1828 // Return if there were name resolution errors.
1832 // Now when we read all script files, we want to finalize order of linker
1833 // script commands, which can be not yet final because of INSERT commands.
1834 script->processInsertCommands();
1836 // We want to declare linker script's symbols early,
1837 // so that we can version them.
1838 // They also might be exported if referenced by DSOs.
1839 script->declareSymbols();
1841 // Handle the -exclude-libs option.
1842 if (args.hasArg(OPT_exclude_libs))
1845 // Create elfHeader early. We need a dummy section in
1846 // addReservedSymbols to mark the created symbols as not absolute.
1847 Out::elfHeader = make<OutputSection>("", 0, SHF_ALLOC);
1848 Out::elfHeader->size = sizeof(typename ELFT::Ehdr);
1850 // Create wrapped symbols for -wrap option.
1851 std::vector<WrappedSymbol> wrapped = addWrappedSymbols(args);
1853 // We need to create some reserved symbols such as _end. Create them.
1854 if (!config->relocatable)
1855 addReservedSymbols();
1857 // Apply version scripts.
1859 // For a relocatable output, version scripts don't make sense, and
1860 // parsing a symbol version string (e.g. dropping "@ver1" from a symbol
1861 // name "foo@ver1") rather do harm, so we don't call this if -r is given.
1862 if (!config->relocatable)
1863 symtab->scanVersionScript();
1865 // Do link-time optimization if given files are LLVM bitcode files.
1866 // This compiles bitcode files into real object files.
1868 // With this the symbol table should be complete. After this, no new names
1869 // except a few linker-synthesized ones will be added to the symbol table.
1870 compileBitcodeFiles<ELFT>();
1874 // If -thinlto-index-only is given, we should create only "index
1875 // files" and not object files. Index file creation is already done
1876 // in addCombinedLTOObject, so we are done if that's the case.
1877 if (config->thinLTOIndexOnly)
1880 // Likewise, --plugin-opt=emit-llvm is an option to make LTO create
1881 // an output file in bitcode and exit, so that you can just get a
1882 // combined bitcode file.
1883 if (config->emitLLVM)
1886 // Apply symbol renames for -wrap.
1887 if (!wrapped.empty())
1888 wrapSymbols(wrapped);
1890 // Now that we have a complete list of input files.
1891 // Beyond this point, no new files are added.
1892 // Aggregate all input sections into one place.
1893 for (InputFile *f : objectFiles)
1894 for (InputSectionBase *s : f->getSections())
1895 if (s && s != &InputSection::discarded)
1896 inputSections.push_back(s);
1897 for (BinaryFile *f : binaryFiles)
1898 for (InputSectionBase *s : f->getSections())
1899 inputSections.push_back(cast<InputSection>(s));
1901 llvm::erase_if(inputSections, [](InputSectionBase *s) {
1902 if (s->type == SHT_LLVM_SYMPART) {
1903 readSymbolPartitionSection<ELFT>(s);
1907 // We do not want to emit debug sections if --strip-all
1908 // or -strip-debug are given.
1909 if (config->strip == StripPolicy::None)
1912 if (isDebugSection(*s))
1914 if (auto *isec = dyn_cast<InputSection>(s))
1915 if (InputSectionBase *rel = isec->getRelocatedSection())
1916 if (isDebugSection(*rel))
1922 // Now that the number of partitions is fixed, save a pointer to the main
1924 mainPart = &partitions[0];
1926 // Read .note.gnu.property sections from input object files which
1927 // contain a hint to tweak linker's and loader's behaviors.
1928 config->andFeatures = getAndFeatures<ELFT>();
1930 // The Target instance handles target-specific stuff, such as applying
1931 // relocations or writing a PLT section. It also contains target-dependent
1932 // values such as a default image base address.
1933 target = getTarget();
1935 config->eflags = target->calcEFlags();
1936 // maxPageSize (sometimes called abi page size) is the maximum page size that
1937 // the output can be run on. For example if the OS can use 4k or 64k page
1938 // sizes then maxPageSize must be 64k for the output to be useable on both.
1939 // All important alignment decisions must use this value.
1940 config->maxPageSize = getMaxPageSize(args);
1941 // commonPageSize is the most common page size that the output will be run on.
1942 // For example if an OS can use 4k or 64k page sizes and 4k is more common
1943 // than 64k then commonPageSize is set to 4k. commonPageSize can be used for
1944 // optimizations such as DATA_SEGMENT_ALIGN in linker scripts. LLD's use of it
1945 // is limited to writing trap instructions on the last executable segment.
1946 config->commonPageSize = getCommonPageSize(args);
1948 config->imageBase = getImageBase(args);
1950 if (config->emachine == EM_ARM) {
1951 // FIXME: These warnings can be removed when lld only uses these features
1952 // when the input objects have been compiled with an architecture that
1954 if (config->armHasBlx == false)
1955 warn("lld uses blx instruction, no object with architecture supporting "
1956 "feature detected");
1959 // This adds a .comment section containing a version string.
1960 if (!config->relocatable)
1961 inputSections.push_back(createCommentSection());
1963 // Replace common symbols with regular symbols.
1964 replaceCommonSymbols();
1966 // Split SHF_MERGE and .eh_frame sections into pieces in preparation for garbage collection.
1967 splitSections<ELFT>();
1969 // Garbage collection and removal of shared symbols from unused shared objects.
1971 demoteSharedSymbols();
1973 // Make copies of any input sections that need to be copied into each
1975 copySectionsIntoPartitions();
1977 // Create synthesized sections such as .got and .plt. This is called before
1978 // processSectionCommands() so that they can be placed by SECTIONS commands.
1979 createSyntheticSections<ELFT>();
1981 // Some input sections that are used for exception handling need to be moved
1982 // into synthetic sections. Do that now so that they aren't assigned to
1983 // output sections in the usual way.
1984 if (!config->relocatable)
1985 combineEhSections();
1987 // Create output sections described by SECTIONS commands.
1988 script->processSectionCommands();
1990 // Linker scripts control how input sections are assigned to output sections.
1991 // Input sections that were not handled by scripts are called "orphans", and
1992 // they are assigned to output sections by the default rule. Process that.
1993 script->addOrphanSections();
1995 // Migrate InputSectionDescription::sectionBases to sections. This includes
1996 // merging MergeInputSections into a single MergeSyntheticSection. From this
1997 // point onwards InputSectionDescription::sections should be used instead of
1999 for (BaseCommand *base : script->sectionCommands)
2000 if (auto *sec = dyn_cast<OutputSection>(base))
2001 sec->finalizeInputSections();
2002 llvm::erase_if(inputSections,
2003 [](InputSectionBase *s) { return isa<MergeInputSection>(s); });
2005 // Two input sections with different output sections should not be folded.
2006 // ICF runs after processSectionCommands() so that we know the output sections.
2007 if (config->icf != ICFLevel::None) {
2008 findKeepUniqueSections<ELFT>(args);
2012 // Read the callgraph now that we know what was gced or icfed
2013 if (config->callGraphProfileSort) {
2014 if (auto *arg = args.getLastArg(OPT_call_graph_ordering_file))
2015 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
2016 readCallGraph(*buffer);
2017 readCallGraphsFromObjectFiles<ELFT>();
2020 // Write the result to the file.
2021 writeResult<ELFT>();