1 //===- Driver.cpp ---------------------------------------------------------===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 //
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.
11 //
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.
16 //
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.
22 //
23 //===----------------------------------------------------------------------===//
24
25 #include "Driver.h"
26 #include "Config.h"
27 #include "ICF.h"
28 #include "InputFiles.h"
29 #include "InputSection.h"
30 #include "LinkerScript.h"
31 #include "MarkLive.h"
32 #include "OutputSections.h"
33 #include "ScriptParser.h"
34 #include "SymbolTable.h"
35 #include "Symbols.h"
36 #include "SyntheticSections.h"
37 #include "Target.h"
38 #include "Writer.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/Version.h"
47 #include "llvm/ADT/SetVector.h"
48 #include "llvm/ADT/StringExtras.h"
49 #include "llvm/ADT/StringSwitch.h"
50 #include "llvm/Config/llvm-config.h"
51 #include "llvm/LTO/LTO.h"
52 #include "llvm/Remarks/HotnessThresholdParser.h"
53 #include "llvm/Support/CommandLine.h"
54 #include "llvm/Support/Compression.h"
55 #include "llvm/Support/GlobPattern.h"
56 #include "llvm/Support/LEB128.h"
57 #include "llvm/Support/Parallel.h"
58 #include "llvm/Support/Path.h"
59 #include "llvm/Support/TarWriter.h"
60 #include "llvm/Support/TargetSelect.h"
61 #include "llvm/Support/TimeProfiler.h"
62 #include "llvm/Support/raw_ostream.h"
63 #include <cstdlib>
64 #include <utility>
65
66 using namespace llvm;
67 using namespace llvm::ELF;
68 using namespace llvm::object;
69 using namespace llvm::sys;
70 using namespace llvm::support;
71 using namespace lld;
72 using namespace lld::elf;
73
74 Configuration *elf::config;
75 LinkerDriver *elf::driver;
76
77 static void setConfigs(opt::InputArgList &args);
78 static void readConfigs(opt::InputArgList &args);
79
link(ArrayRef<const char * > args,bool canExitEarly,raw_ostream & stdoutOS,raw_ostream & stderrOS)80 bool elf::link(ArrayRef<const char *> args, bool canExitEarly,
81 raw_ostream &stdoutOS, raw_ostream &stderrOS) {
82 lld::stdoutOS = &stdoutOS;
83 lld::stderrOS = &stderrOS;
84
85 errorHandler().cleanupCallback = []() {
86 freeArena();
87
88 inputSections.clear();
89 outputSections.clear();
90 archiveFiles.clear();
91 binaryFiles.clear();
92 bitcodeFiles.clear();
93 lazyObjFiles.clear();
94 objectFiles.clear();
95 sharedFiles.clear();
96 backwardReferences.clear();
97
98 tar = nullptr;
99 memset(&in, 0, sizeof(in));
100
101 partitions = {Partition()};
102
103 SharedFile::vernauxNum = 0;
104 };
105
106 errorHandler().logName = args::getFilenameWithoutExe(args[0]);
107 errorHandler().errorLimitExceededMsg =
108 "too many errors emitted, stopping now (use "
109 "-error-limit=0 to see all errors)";
110 errorHandler().exitEarly = canExitEarly;
111 stderrOS.enable_colors(stderrOS.has_colors());
112
113 config = make<Configuration>();
114 driver = make<LinkerDriver>();
115 script = make<LinkerScript>();
116 symtab = make<SymbolTable>();
117
118 partitions = {Partition()};
119
120 config->progName = args[0];
121
122 driver->linkerMain(args);
123
124 // Exit immediately if we don't need to return to the caller.
125 // This saves time because the overhead of calling destructors
126 // for all globally-allocated objects is not negligible.
127 if (canExitEarly)
128 exitLld(errorCount() ? 1 : 0);
129
130 bool ret = errorCount() == 0;
131 if (!canExitEarly)
132 errorHandler().reset();
133 return ret;
134 }
135
136 // Parses a linker -m option.
parseEmulation(StringRef emul)137 static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef emul) {
138 uint8_t osabi = 0;
139 StringRef s = emul;
140 if (s.endswith("_fbsd")) {
141 s = s.drop_back(5);
142 osabi = ELFOSABI_FREEBSD;
143 }
144
145 std::pair<ELFKind, uint16_t> ret =
146 StringSwitch<std::pair<ELFKind, uint16_t>>(s)
147 .Cases("aarch64elf", "aarch64linux", "aarch64_elf64_le_vec",
148 {ELF64LEKind, EM_AARCH64})
149 .Cases("armelf", "armelf_linux_eabi", {ELF32LEKind, EM_ARM})
150 .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
151 .Cases("elf32btsmip", "elf32btsmipn32", {ELF32BEKind, EM_MIPS})
152 .Cases("elf32ltsmip", "elf32ltsmipn32", {ELF32LEKind, EM_MIPS})
153 .Case("elf32lriscv", {ELF32LEKind, EM_RISCV})
154 .Cases("elf32ppc", "elf32ppclinux", {ELF32BEKind, EM_PPC})
155 .Cases("elf32lppc", "elf32lppclinux", {ELF32LEKind, EM_PPC})
156 .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
157 .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
158 .Case("elf64lriscv", {ELF64LEKind, EM_RISCV})
159 .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
160 .Case("elf64lppc", {ELF64LEKind, EM_PPC64})
161 .Cases("elf_amd64", "elf_x86_64", {ELF64LEKind, EM_X86_64})
162 .Case("elf_i386", {ELF32LEKind, EM_386})
163 .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
164 .Case("elf64_sparc", {ELF64BEKind, EM_SPARCV9})
165 .Case("msp430elf", {ELF32LEKind, EM_MSP430})
166 .Default({ELFNoneKind, EM_NONE});
167
168 if (ret.first == ELFNoneKind)
169 error("unknown emulation: " + emul);
170 if (ret.second == EM_MSP430)
171 osabi = ELFOSABI_STANDALONE;
172 return std::make_tuple(ret.first, ret.second, osabi);
173 }
174
175 // Returns slices of MB by parsing MB as an archive file.
176 // Each slice consists of a member file in the archive.
getArchiveMembers(MemoryBufferRef mb)177 std::vector<std::pair<MemoryBufferRef, uint64_t>> static getArchiveMembers(
178 MemoryBufferRef mb) {
179 std::unique_ptr<Archive> file =
180 CHECK(Archive::create(mb),
181 mb.getBufferIdentifier() + ": failed to parse archive");
182
183 std::vector<std::pair<MemoryBufferRef, uint64_t>> v;
184 Error err = Error::success();
185 bool addToTar = file->isThin() && tar;
186 for (const Archive::Child &c : file->children(err)) {
187 MemoryBufferRef mbref =
188 CHECK(c.getMemoryBufferRef(),
189 mb.getBufferIdentifier() +
190 ": could not get the buffer for a child of the archive");
191 if (addToTar)
192 tar->append(relativeToRoot(check(c.getFullName())), mbref.getBuffer());
193 v.push_back(std::make_pair(mbref, c.getChildOffset()));
194 }
195 if (err)
196 fatal(mb.getBufferIdentifier() + ": Archive::children failed: " +
197 toString(std::move(err)));
198
199 // Take ownership of memory buffers created for members of thin archives.
200 for (std::unique_ptr<MemoryBuffer> &mb : file->takeThinBuffers())
201 make<std::unique_ptr<MemoryBuffer>>(std::move(mb));
202
203 return v;
204 }
205
206 // Opens a file and create a file object. Path has to be resolved already.
addFile(StringRef path,bool withLOption)207 void LinkerDriver::addFile(StringRef path, bool withLOption) {
208 using namespace sys::fs;
209
210 Optional<MemoryBufferRef> buffer = readFile(path);
211 if (!buffer.hasValue())
212 return;
213 MemoryBufferRef mbref = *buffer;
214
215 if (config->formatBinary) {
216 files.push_back(make<BinaryFile>(mbref));
217 return;
218 }
219
220 switch (identify_magic(mbref.getBuffer())) {
221 case file_magic::unknown:
222 readLinkerScript(mbref);
223 return;
224 case file_magic::archive: {
225 // Handle -whole-archive.
226 if (inWholeArchive) {
227 for (const auto &p : getArchiveMembers(mbref))
228 files.push_back(createObjectFile(p.first, path, p.second));
229 return;
230 }
231
232 std::unique_ptr<Archive> file =
233 CHECK(Archive::create(mbref), path + ": failed to parse archive");
234
235 // If an archive file has no symbol table, it is likely that a user
236 // is attempting LTO and using a default ar command that doesn't
237 // understand the LLVM bitcode file. It is a pretty common error, so
238 // we'll handle it as if it had a symbol table.
239 if (!file->isEmpty() && !file->hasSymbolTable()) {
240 // Check if all members are bitcode files. If not, ignore, which is the
241 // default action without the LTO hack described above.
242 for (const std::pair<MemoryBufferRef, uint64_t> &p :
243 getArchiveMembers(mbref))
244 if (identify_magic(p.first.getBuffer()) != file_magic::bitcode) {
245 error(path + ": archive has no index; run ranlib to add one");
246 return;
247 }
248
249 for (const std::pair<MemoryBufferRef, uint64_t> &p :
250 getArchiveMembers(mbref))
251 files.push_back(make<LazyObjFile>(p.first, path, p.second));
252 return;
253 }
254
255 // Handle the regular case.
256 files.push_back(make<ArchiveFile>(std::move(file)));
257 return;
258 }
259 case file_magic::elf_shared_object:
260 if (config->isStatic || config->relocatable) {
261 error("attempted static link of dynamic object " + path);
262 return;
263 }
264
265 // DSOs usually have DT_SONAME tags in their ELF headers, and the
266 // sonames are used to identify DSOs. But if they are missing,
267 // they are identified by filenames. We don't know whether the new
268 // file has a DT_SONAME or not because we haven't parsed it yet.
269 // Here, we set the default soname for the file because we might
270 // need it later.
271 //
272 // If a file was specified by -lfoo, the directory part is not
273 // significant, as a user did not specify it. This behavior is
274 // compatible with GNU.
275 files.push_back(
276 make<SharedFile>(mbref, withLOption ? path::filename(path) : path));
277 return;
278 case file_magic::bitcode:
279 case file_magic::elf_relocatable:
280 if (inLib)
281 files.push_back(make<LazyObjFile>(mbref, "", 0));
282 else
283 files.push_back(createObjectFile(mbref));
284 break;
285 default:
286 error(path + ": unknown file type");
287 }
288 }
289
290 // Add a given library by searching it from input search paths.
addLibrary(StringRef name)291 void LinkerDriver::addLibrary(StringRef name) {
292 if (Optional<std::string> path = searchLibrary(name))
293 addFile(*path, /*withLOption=*/true);
294 else
295 error("unable to find library -l" + name, ErrorTag::LibNotFound, {name});
296 }
297
298 // This function is called on startup. We need this for LTO since
299 // LTO calls LLVM functions to compile bitcode files to native code.
300 // Technically this can be delayed until we read bitcode files, but
301 // we don't bother to do lazily because the initialization is fast.
initLLVM()302 static void initLLVM() {
303 InitializeAllTargets();
304 InitializeAllTargetMCs();
305 InitializeAllAsmPrinters();
306 InitializeAllAsmParsers();
307 }
308
309 // Some command line options or some combinations of them are not allowed.
310 // This function checks for such errors.
checkOptions()311 static void checkOptions() {
312 // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
313 // table which is a relatively new feature.
314 if (config->emachine == EM_MIPS && config->gnuHash)
315 error("the .gnu.hash section is not compatible with the MIPS target");
316
317 if (config->fixCortexA53Errata843419 && config->emachine != EM_AARCH64)
318 error("--fix-cortex-a53-843419 is only supported on AArch64 targets");
319
320 if (config->fixCortexA8 && config->emachine != EM_ARM)
321 error("--fix-cortex-a8 is only supported on ARM targets");
322
323 if (config->tocOptimize && config->emachine != EM_PPC64)
324 error("--toc-optimize is only supported on PowerPC64 targets");
325
326 if (config->pcRelOptimize && config->emachine != EM_PPC64)
327 error("--pcrel-optimize is only supported on PowerPC64 targets");
328
329 if (config->pie && config->shared)
330 error("-shared and -pie may not be used together");
331
332 if (!config->shared && !config->filterList.empty())
333 error("-F may not be used without -shared");
334
335 if (!config->shared && !config->auxiliaryList.empty())
336 error("-f may not be used without -shared");
337
338 if (!config->relocatable && !config->defineCommon)
339 error("-no-define-common not supported in non relocatable output");
340
341 if (config->strip == StripPolicy::All && config->emitRelocs)
342 error("--strip-all and --emit-relocs may not be used together");
343
344 if (config->zText && config->zIfuncNoplt)
345 error("-z text and -z ifunc-noplt may not be used together");
346
347 if (config->relocatable) {
348 if (config->shared)
349 error("-r and -shared may not be used together");
350 if (config->gdbIndex)
351 error("-r and --gdb-index may not be used together");
352 if (config->icf != ICFLevel::None)
353 error("-r and --icf may not be used together");
354 if (config->pie)
355 error("-r and -pie may not be used together");
356 if (config->exportDynamic)
357 error("-r and --export-dynamic may not be used together");
358 }
359
360 if (config->executeOnly) {
361 if (config->emachine != EM_AARCH64)
362 error("-execute-only is only supported on AArch64 targets");
363
364 if (config->singleRoRx && !script->hasSectionsCommand)
365 error("-execute-only and -no-rosegment cannot be used together");
366 }
367
368 if (config->zRetpolineplt && config->zForceIbt)
369 error("-z force-ibt may not be used with -z retpolineplt");
370
371 if (config->emachine != EM_AARCH64) {
372 if (config->zPacPlt)
373 error("-z pac-plt only supported on AArch64");
374 if (config->zForceBti)
375 error("-z force-bti only supported on AArch64");
376 }
377 }
378
getReproduceOption(opt::InputArgList & args)379 static const char *getReproduceOption(opt::InputArgList &args) {
380 if (auto *arg = args.getLastArg(OPT_reproduce))
381 return arg->getValue();
382 return getenv("LLD_REPRODUCE");
383 }
384
hasZOption(opt::InputArgList & args,StringRef key)385 static bool hasZOption(opt::InputArgList &args, StringRef key) {
386 for (auto *arg : args.filtered(OPT_z))
387 if (key == arg->getValue())
388 return true;
389 return false;
390 }
391
getZFlag(opt::InputArgList & args,StringRef k1,StringRef k2,bool Default)392 static bool getZFlag(opt::InputArgList &args, StringRef k1, StringRef k2,
393 bool Default) {
394 for (auto *arg : args.filtered_reverse(OPT_z)) {
395 if (k1 == arg->getValue())
396 return true;
397 if (k2 == arg->getValue())
398 return false;
399 }
400 return Default;
401 }
402
getZSeparate(opt::InputArgList & args)403 static SeparateSegmentKind getZSeparate(opt::InputArgList &args) {
404 for (auto *arg : args.filtered_reverse(OPT_z)) {
405 StringRef v = arg->getValue();
406 if (v == "noseparate-code")
407 return SeparateSegmentKind::None;
408 if (v == "separate-code")
409 return SeparateSegmentKind::Code;
410 if (v == "separate-loadable-segments")
411 return SeparateSegmentKind::Loadable;
412 }
413 return SeparateSegmentKind::None;
414 }
415
getZGnuStack(opt::InputArgList & args)416 static GnuStackKind getZGnuStack(opt::InputArgList &args) {
417 for (auto *arg : args.filtered_reverse(OPT_z)) {
418 if (StringRef("execstack") == arg->getValue())
419 return GnuStackKind::Exec;
420 if (StringRef("noexecstack") == arg->getValue())
421 return GnuStackKind::NoExec;
422 if (StringRef("nognustack") == arg->getValue())
423 return GnuStackKind::None;
424 }
425
426 return GnuStackKind::NoExec;
427 }
428
getZStartStopVisibility(opt::InputArgList & args)429 static uint8_t getZStartStopVisibility(opt::InputArgList &args) {
430 for (auto *arg : args.filtered_reverse(OPT_z)) {
431 std::pair<StringRef, StringRef> kv = StringRef(arg->getValue()).split('=');
432 if (kv.first == "start-stop-visibility") {
433 if (kv.second == "default")
434 return STV_DEFAULT;
435 else if (kv.second == "internal")
436 return STV_INTERNAL;
437 else if (kv.second == "hidden")
438 return STV_HIDDEN;
439 else if (kv.second == "protected")
440 return STV_PROTECTED;
441 error("unknown -z start-stop-visibility= value: " + StringRef(kv.second));
442 }
443 }
444 return STV_PROTECTED;
445 }
446
isKnownZFlag(StringRef s)447 static bool isKnownZFlag(StringRef s) {
448 return s == "combreloc" || s == "copyreloc" || s == "defs" ||
449 s == "execstack" || s == "force-bti" || s == "force-ibt" ||
450 s == "global" || s == "hazardplt" || s == "ifunc-noplt" ||
451 s == "initfirst" || s == "interpose" ||
452 s == "keep-text-section-prefix" || s == "lazy" || s == "muldefs" ||
453 s == "separate-code" || s == "separate-loadable-segments" ||
454 s == "nocombreloc" || s == "nocopyreloc" || s == "nodefaultlib" ||
455 s == "nodelete" || s == "nodlopen" || s == "noexecstack" ||
456 s == "nognustack" || s == "nokeep-text-section-prefix" ||
457 s == "norelro" || s == "noseparate-code" || s == "notext" ||
458 s == "now" || s == "origin" || s == "pac-plt" || s == "rel" ||
459 s == "rela" || s == "relro" || s == "retpolineplt" ||
460 s == "rodynamic" || s == "shstk" || s == "text" || s == "undefs" ||
461 s == "wxneeded" || s.startswith("common-page-size=") ||
462 s.startswith("dead-reloc-in-nonalloc=") ||
463 s.startswith("max-page-size=") || s.startswith("stack-size=") ||
464 s.startswith("start-stop-visibility=");
465 }
466
467 // Report an error for an unknown -z option.
checkZOptions(opt::InputArgList & args)468 static void checkZOptions(opt::InputArgList &args) {
469 for (auto *arg : args.filtered(OPT_z))
470 if (!isKnownZFlag(arg->getValue()))
471 error("unknown -z value: " + StringRef(arg->getValue()));
472 }
473
linkerMain(ArrayRef<const char * > argsArr)474 void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
475 ELFOptTable parser;
476 opt::InputArgList args = parser.parse(argsArr.slice(1));
477
478 // Interpret this flag early because error() depends on them.
479 errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
480 checkZOptions(args);
481
482 // Handle -help
483 if (args.hasArg(OPT_help)) {
484 printHelp();
485 return;
486 }
487
488 // Handle -v or -version.
489 //
490 // A note about "compatible with GNU linkers" message: this is a hack for
491 // scripts generated by GNU Libtool 2.4.6 (released in February 2014 and
492 // still the newest version in March 2017) or earlier to recognize LLD as
493 // a GNU compatible linker. As long as an output for the -v option
494 // contains "GNU" or "with BFD", they recognize us as GNU-compatible.
495 //
496 // This is somewhat ugly hack, but in reality, we had no choice other
497 // than doing this. Considering the very long release cycle of Libtool,
498 // it is not easy to improve it to recognize LLD as a GNU compatible
499 // linker in a timely manner. Even if we can make it, there are still a
500 // lot of "configure" scripts out there that are generated by old version
501 // of Libtool. We cannot convince every software developer to migrate to
502 // the latest version and re-generate scripts. So we have this hack.
503 if (args.hasArg(OPT_v) || args.hasArg(OPT_version))
504 message(getLLDVersion() + " (compatible with GNU linkers)");
505
506 if (const char *path = getReproduceOption(args)) {
507 // Note that --reproduce is a debug option so you can ignore it
508 // if you are trying to understand the whole picture of the code.
509 Expected<std::unique_ptr<TarWriter>> errOrWriter =
510 TarWriter::create(path, path::stem(path));
511 if (errOrWriter) {
512 tar = std::move(*errOrWriter);
513 tar->append("response.txt", createResponseFile(args));
514 tar->append("version.txt", getLLDVersion() + "\n");
515 StringRef ltoSampleProfile = args.getLastArgValue(OPT_lto_sample_profile);
516 if (!ltoSampleProfile.empty())
517 readFile(ltoSampleProfile);
518 } else {
519 error("--reproduce: " + toString(errOrWriter.takeError()));
520 }
521 }
522
523 readConfigs(args);
524
525 // The behavior of -v or --version is a bit strange, but this is
526 // needed for compatibility with GNU linkers.
527 if (args.hasArg(OPT_v) && !args.hasArg(OPT_INPUT))
528 return;
529 if (args.hasArg(OPT_version))
530 return;
531
532 // Initialize time trace profiler.
533 if (config->timeTraceEnabled)
534 timeTraceProfilerInitialize(config->timeTraceGranularity, config->progName);
535
536 {
537 llvm::TimeTraceScope timeScope("ExecuteLinker");
538
539 initLLVM();
540 createFiles(args);
541 if (errorCount())
542 return;
543
544 inferMachineType();
545 setConfigs(args);
546 checkOptions();
547 if (errorCount())
548 return;
549
550 // The Target instance handles target-specific stuff, such as applying
551 // relocations or writing a PLT section. It also contains target-dependent
552 // values such as a default image base address.
553 target = getTarget();
554
555 switch (config->ekind) {
556 case ELF32LEKind:
557 link<ELF32LE>(args);
558 break;
559 case ELF32BEKind:
560 link<ELF32BE>(args);
561 break;
562 case ELF64LEKind:
563 link<ELF64LE>(args);
564 break;
565 case ELF64BEKind:
566 link<ELF64BE>(args);
567 break;
568 default:
569 llvm_unreachable("unknown Config->EKind");
570 }
571 }
572
573 if (config->timeTraceEnabled) {
574 if (auto E = timeTraceProfilerWrite(args.getLastArgValue(OPT_time_trace_file_eq).str(),
575 config->outputFile)) {
576 handleAllErrors(std::move(E), [&](const StringError &SE) {
577 error(SE.getMessage());
578 });
579 return;
580 }
581
582 timeTraceProfilerCleanup();
583 }
584 }
585
getRpath(opt::InputArgList & args)586 static std::string getRpath(opt::InputArgList &args) {
587 std::vector<StringRef> v = args::getStrings(args, OPT_rpath);
588 return llvm::join(v.begin(), v.end(), ":");
589 }
590
591 // Determines what we should do if there are remaining unresolved
592 // symbols after the name resolution.
setUnresolvedSymbolPolicy(opt::InputArgList & args)593 static void setUnresolvedSymbolPolicy(opt::InputArgList &args) {
594 UnresolvedPolicy errorOrWarn = args.hasFlag(OPT_error_unresolved_symbols,
595 OPT_warn_unresolved_symbols, true)
596 ? UnresolvedPolicy::ReportError
597 : UnresolvedPolicy::Warn;
598 // -shared implies -unresolved-symbols=ignore-all because missing
599 // symbols are likely to be resolved at runtime.
600 bool diagRegular = !config->shared, diagShlib = !config->shared;
601
602 for (const opt::Arg *arg : args) {
603 switch (arg->getOption().getID()) {
604 case OPT_unresolved_symbols: {
605 StringRef s = arg->getValue();
606 if (s == "ignore-all") {
607 diagRegular = false;
608 diagShlib = false;
609 } else if (s == "ignore-in-object-files") {
610 diagRegular = false;
611 diagShlib = true;
612 } else if (s == "ignore-in-shared-libs") {
613 diagRegular = true;
614 diagShlib = false;
615 } else if (s == "report-all") {
616 diagRegular = true;
617 diagShlib = true;
618 } else {
619 error("unknown --unresolved-symbols value: " + s);
620 }
621 break;
622 }
623 case OPT_no_undefined:
624 diagRegular = true;
625 break;
626 case OPT_z:
627 if (StringRef(arg->getValue()) == "defs")
628 diagRegular = true;
629 else if (StringRef(arg->getValue()) == "undefs")
630 diagRegular = false;
631 break;
632 case OPT_allow_shlib_undefined:
633 diagShlib = false;
634 break;
635 case OPT_no_allow_shlib_undefined:
636 diagShlib = true;
637 break;
638 }
639 }
640
641 config->unresolvedSymbols =
642 diagRegular ? errorOrWarn : UnresolvedPolicy::Ignore;
643 config->unresolvedSymbolsInShlib =
644 diagShlib ? errorOrWarn : UnresolvedPolicy::Ignore;
645 }
646
getTarget2(opt::InputArgList & args)647 static Target2Policy getTarget2(opt::InputArgList &args) {
648 StringRef s = args.getLastArgValue(OPT_target2, "got-rel");
649 if (s == "rel")
650 return Target2Policy::Rel;
651 if (s == "abs")
652 return Target2Policy::Abs;
653 if (s == "got-rel")
654 return Target2Policy::GotRel;
655 error("unknown --target2 option: " + s);
656 return Target2Policy::GotRel;
657 }
658
isOutputFormatBinary(opt::InputArgList & args)659 static bool isOutputFormatBinary(opt::InputArgList &args) {
660 StringRef s = args.getLastArgValue(OPT_oformat, "elf");
661 if (s == "binary")
662 return true;
663 if (!s.startswith("elf"))
664 error("unknown --oformat value: " + s);
665 return false;
666 }
667
getDiscard(opt::InputArgList & args)668 static DiscardPolicy getDiscard(opt::InputArgList &args) {
669 auto *arg =
670 args.getLastArg(OPT_discard_all, OPT_discard_locals, OPT_discard_none);
671 if (!arg)
672 return DiscardPolicy::Default;
673 if (arg->getOption().getID() == OPT_discard_all)
674 return DiscardPolicy::All;
675 if (arg->getOption().getID() == OPT_discard_locals)
676 return DiscardPolicy::Locals;
677 return DiscardPolicy::None;
678 }
679
getDynamicLinker(opt::InputArgList & args)680 static StringRef getDynamicLinker(opt::InputArgList &args) {
681 auto *arg = args.getLastArg(OPT_dynamic_linker, OPT_no_dynamic_linker);
682 if (!arg)
683 return "";
684 if (arg->getOption().getID() == OPT_no_dynamic_linker) {
685 // --no-dynamic-linker suppresses undefined weak symbols in .dynsym
686 config->noDynamicLinker = true;
687 return "";
688 }
689 return arg->getValue();
690 }
691
getICF(opt::InputArgList & args)692 static ICFLevel getICF(opt::InputArgList &args) {
693 auto *arg = args.getLastArg(OPT_icf_none, OPT_icf_safe, OPT_icf_all);
694 if (!arg || arg->getOption().getID() == OPT_icf_none)
695 return ICFLevel::None;
696 if (arg->getOption().getID() == OPT_icf_safe)
697 return ICFLevel::Safe;
698 return ICFLevel::All;
699 }
700
getStrip(opt::InputArgList & args)701 static StripPolicy getStrip(opt::InputArgList &args) {
702 if (args.hasArg(OPT_relocatable))
703 return StripPolicy::None;
704
705 auto *arg = args.getLastArg(OPT_strip_all, OPT_strip_debug);
706 if (!arg)
707 return StripPolicy::None;
708 if (arg->getOption().getID() == OPT_strip_all)
709 return StripPolicy::All;
710 return StripPolicy::Debug;
711 }
712
parseSectionAddress(StringRef s,opt::InputArgList & args,const opt::Arg & arg)713 static uint64_t parseSectionAddress(StringRef s, opt::InputArgList &args,
714 const opt::Arg &arg) {
715 uint64_t va = 0;
716 if (s.startswith("0x"))
717 s = s.drop_front(2);
718 if (!to_integer(s, va, 16))
719 error("invalid argument: " + arg.getAsString(args));
720 return va;
721 }
722
getSectionStartMap(opt::InputArgList & args)723 static StringMap<uint64_t> getSectionStartMap(opt::InputArgList &args) {
724 StringMap<uint64_t> ret;
725 for (auto *arg : args.filtered(OPT_section_start)) {
726 StringRef name;
727 StringRef addr;
728 std::tie(name, addr) = StringRef(arg->getValue()).split('=');
729 ret[name] = parseSectionAddress(addr, args, *arg);
730 }
731
732 if (auto *arg = args.getLastArg(OPT_Ttext))
733 ret[".text"] = parseSectionAddress(arg->getValue(), args, *arg);
734 if (auto *arg = args.getLastArg(OPT_Tdata))
735 ret[".data"] = parseSectionAddress(arg->getValue(), args, *arg);
736 if (auto *arg = args.getLastArg(OPT_Tbss))
737 ret[".bss"] = parseSectionAddress(arg->getValue(), args, *arg);
738 return ret;
739 }
740
getSortSection(opt::InputArgList & args)741 static SortSectionPolicy getSortSection(opt::InputArgList &args) {
742 StringRef s = args.getLastArgValue(OPT_sort_section);
743 if (s == "alignment")
744 return SortSectionPolicy::Alignment;
745 if (s == "name")
746 return SortSectionPolicy::Name;
747 if (!s.empty())
748 error("unknown --sort-section rule: " + s);
749 return SortSectionPolicy::Default;
750 }
751
getOrphanHandling(opt::InputArgList & args)752 static OrphanHandlingPolicy getOrphanHandling(opt::InputArgList &args) {
753 StringRef s = args.getLastArgValue(OPT_orphan_handling, "place");
754 if (s == "warn")
755 return OrphanHandlingPolicy::Warn;
756 if (s == "error")
757 return OrphanHandlingPolicy::Error;
758 if (s != "place")
759 error("unknown --orphan-handling mode: " + s);
760 return OrphanHandlingPolicy::Place;
761 }
762
763 // Parse --build-id or --build-id=<style>. We handle "tree" as a
764 // synonym for "sha1" because all our hash functions including
765 // -build-id=sha1 are actually tree hashes for performance reasons.
766 static std::pair<BuildIdKind, std::vector<uint8_t>>
getBuildId(opt::InputArgList & args)767 getBuildId(opt::InputArgList &args) {
768 auto *arg = args.getLastArg(OPT_build_id, OPT_build_id_eq);
769 if (!arg)
770 return {BuildIdKind::None, {}};
771
772 if (arg->getOption().getID() == OPT_build_id)
773 return {BuildIdKind::Fast, {}};
774
775 StringRef s = arg->getValue();
776 if (s == "fast")
777 return {BuildIdKind::Fast, {}};
778 if (s == "md5")
779 return {BuildIdKind::Md5, {}};
780 if (s == "sha1" || s == "tree")
781 return {BuildIdKind::Sha1, {}};
782 if (s == "uuid")
783 return {BuildIdKind::Uuid, {}};
784 if (s.startswith("0x"))
785 return {BuildIdKind::Hexstring, parseHex(s.substr(2))};
786
787 if (s != "none")
788 error("unknown --build-id style: " + s);
789 return {BuildIdKind::None, {}};
790 }
791
getPackDynRelocs(opt::InputArgList & args)792 static std::pair<bool, bool> getPackDynRelocs(opt::InputArgList &args) {
793 StringRef s = args.getLastArgValue(OPT_pack_dyn_relocs, "none");
794 if (s == "android")
795 return {true, false};
796 if (s == "relr")
797 return {false, true};
798 if (s == "android+relr")
799 return {true, true};
800
801 if (s != "none")
802 error("unknown -pack-dyn-relocs format: " + s);
803 return {false, false};
804 }
805
readCallGraph(MemoryBufferRef mb)806 static void readCallGraph(MemoryBufferRef mb) {
807 // Build a map from symbol name to section
808 DenseMap<StringRef, Symbol *> map;
809 for (InputFile *file : objectFiles)
810 for (Symbol *sym : file->getSymbols())
811 map[sym->getName()] = sym;
812
813 auto findSection = [&](StringRef name) -> InputSectionBase * {
814 Symbol *sym = map.lookup(name);
815 if (!sym) {
816 if (config->warnSymbolOrdering)
817 warn(mb.getBufferIdentifier() + ": no such symbol: " + name);
818 return nullptr;
819 }
820 maybeWarnUnorderableSymbol(sym);
821
822 if (Defined *dr = dyn_cast_or_null<Defined>(sym))
823 return dyn_cast_or_null<InputSectionBase>(dr->section);
824 return nullptr;
825 };
826
827 for (StringRef line : args::getLines(mb)) {
828 SmallVector<StringRef, 3> fields;
829 line.split(fields, ' ');
830 uint64_t count;
831
832 if (fields.size() != 3 || !to_integer(fields[2], count)) {
833 error(mb.getBufferIdentifier() + ": parse error");
834 return;
835 }
836
837 if (InputSectionBase *from = findSection(fields[0]))
838 if (InputSectionBase *to = findSection(fields[1]))
839 config->callGraphProfile[std::make_pair(from, to)] += count;
840 }
841 }
842
readCallGraphsFromObjectFiles()843 template <class ELFT> static void readCallGraphsFromObjectFiles() {
844 for (auto file : objectFiles) {
845 auto *obj = cast<ObjFile<ELFT>>(file);
846
847 for (const Elf_CGProfile_Impl<ELFT> &cgpe : obj->cgProfile) {
848 auto *fromSym = dyn_cast<Defined>(&obj->getSymbol(cgpe.cgp_from));
849 auto *toSym = dyn_cast<Defined>(&obj->getSymbol(cgpe.cgp_to));
850 if (!fromSym || !toSym)
851 continue;
852
853 auto *from = dyn_cast_or_null<InputSectionBase>(fromSym->section);
854 auto *to = dyn_cast_or_null<InputSectionBase>(toSym->section);
855 if (from && to)
856 config->callGraphProfile[{from, to}] += cgpe.cgp_weight;
857 }
858 }
859 }
860
getCompressDebugSections(opt::InputArgList & args)861 static bool getCompressDebugSections(opt::InputArgList &args) {
862 StringRef s = args.getLastArgValue(OPT_compress_debug_sections, "none");
863 if (s == "none")
864 return false;
865 if (s != "zlib")
866 error("unknown --compress-debug-sections value: " + s);
867 if (!zlib::isAvailable())
868 error("--compress-debug-sections: zlib is not available");
869 return true;
870 }
871
getAliasSpelling(opt::Arg * arg)872 static StringRef getAliasSpelling(opt::Arg *arg) {
873 if (const opt::Arg *alias = arg->getAlias())
874 return alias->getSpelling();
875 return arg->getSpelling();
876 }
877
getOldNewOptions(opt::InputArgList & args,unsigned id)878 static std::pair<StringRef, StringRef> getOldNewOptions(opt::InputArgList &args,
879 unsigned id) {
880 auto *arg = args.getLastArg(id);
881 if (!arg)
882 return {"", ""};
883
884 StringRef s = arg->getValue();
885 std::pair<StringRef, StringRef> ret = s.split(';');
886 if (ret.second.empty())
887 error(getAliasSpelling(arg) + " expects 'old;new' format, but got " + s);
888 return ret;
889 }
890
891 // Parse the symbol ordering file and warn for any duplicate entries.
getSymbolOrderingFile(MemoryBufferRef mb)892 static std::vector<StringRef> getSymbolOrderingFile(MemoryBufferRef mb) {
893 SetVector<StringRef> names;
894 for (StringRef s : args::getLines(mb))
895 if (!names.insert(s) && config->warnSymbolOrdering)
896 warn(mb.getBufferIdentifier() + ": duplicate ordered symbol: " + s);
897
898 return names.takeVector();
899 }
900
getIsRela(opt::InputArgList & args)901 static bool getIsRela(opt::InputArgList &args) {
902 // If -z rel or -z rela is specified, use the last option.
903 for (auto *arg : args.filtered_reverse(OPT_z)) {
904 StringRef s(arg->getValue());
905 if (s == "rel")
906 return false;
907 if (s == "rela")
908 return true;
909 }
910
911 // Otherwise use the psABI defined relocation entry format.
912 uint16_t m = config->emachine;
913 return m == EM_AARCH64 || m == EM_AMDGPU || m == EM_HEXAGON || m == EM_PPC ||
914 m == EM_PPC64 || m == EM_RISCV || m == EM_X86_64;
915 }
916
parseClangOption(StringRef opt,const Twine & msg)917 static void parseClangOption(StringRef opt, const Twine &msg) {
918 std::string err;
919 raw_string_ostream os(err);
920
921 const char *argv[] = {config->progName.data(), opt.data()};
922 if (cl::ParseCommandLineOptions(2, argv, "", &os))
923 return;
924 os.flush();
925 error(msg + ": " + StringRef(err).trim());
926 }
927
928 // Initializes Config members by the command line options.
readConfigs(opt::InputArgList & args)929 static void readConfigs(opt::InputArgList &args) {
930 errorHandler().verbose = args.hasArg(OPT_verbose);
931 errorHandler().fatalWarnings =
932 args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
933 errorHandler().vsDiagnostics =
934 args.hasArg(OPT_visual_studio_diagnostics_format, false);
935
936 config->allowMultipleDefinition =
937 args.hasFlag(OPT_allow_multiple_definition,
938 OPT_no_allow_multiple_definition, false) ||
939 hasZOption(args, "muldefs");
940 config->auxiliaryList = args::getStrings(args, OPT_auxiliary);
941 config->bsymbolic = args.hasArg(OPT_Bsymbolic);
942 config->bsymbolicFunctions = args.hasArg(OPT_Bsymbolic_functions);
943 config->checkSections =
944 args.hasFlag(OPT_check_sections, OPT_no_check_sections, true);
945 config->chroot = args.getLastArgValue(OPT_chroot);
946 config->compressDebugSections = getCompressDebugSections(args);
947 config->cref = args.hasFlag(OPT_cref, OPT_no_cref, false);
948 config->defineCommon = args.hasFlag(OPT_define_common, OPT_no_define_common,
949 !args.hasArg(OPT_relocatable));
950 config->optimizeBBJumps =
951 args.hasFlag(OPT_optimize_bb_jumps, OPT_no_optimize_bb_jumps, false);
952 config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
953 config->dependencyFile = args.getLastArgValue(OPT_dependency_file);
954 config->dependentLibraries = args.hasFlag(OPT_dependent_libraries, OPT_no_dependent_libraries, true);
955 config->disableVerify = args.hasArg(OPT_disable_verify);
956 config->discard = getDiscard(args);
957 config->dwoDir = args.getLastArgValue(OPT_plugin_opt_dwo_dir_eq);
958 config->dynamicLinker = getDynamicLinker(args);
959 config->ehFrameHdr =
960 args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false);
961 config->emitLLVM = args.hasArg(OPT_plugin_opt_emit_llvm, false);
962 config->emitRelocs = args.hasArg(OPT_emit_relocs);
963 config->callGraphProfileSort = args.hasFlag(
964 OPT_call_graph_profile_sort, OPT_no_call_graph_profile_sort, true);
965 config->enableNewDtags =
966 args.hasFlag(OPT_enable_new_dtags, OPT_disable_new_dtags, true);
967 config->entry = args.getLastArgValue(OPT_entry);
968
969 errorHandler().errorHandlingScript =
970 args.getLastArgValue(OPT_error_handling_script);
971
972 config->executeOnly =
973 args.hasFlag(OPT_execute_only, OPT_no_execute_only, false);
974 config->exportDynamic =
975 args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
976 config->filterList = args::getStrings(args, OPT_filter);
977 config->fini = args.getLastArgValue(OPT_fini, "_fini");
978 config->fixCortexA53Errata843419 = args.hasArg(OPT_fix_cortex_a53_843419) &&
979 !args.hasArg(OPT_relocatable);
980 config->fixCortexA8 =
981 args.hasArg(OPT_fix_cortex_a8) && !args.hasArg(OPT_relocatable);
982 config->fortranCommon =
983 args.hasFlag(OPT_fortran_common, OPT_no_fortran_common, true);
984 config->gcSections = args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, false);
985 config->gnuUnique = args.hasFlag(OPT_gnu_unique, OPT_no_gnu_unique, true);
986 config->gdbIndex = args.hasFlag(OPT_gdb_index, OPT_no_gdb_index, false);
987 config->icf = getICF(args);
988 config->ignoreDataAddressEquality =
989 args.hasArg(OPT_ignore_data_address_equality);
990 config->ignoreFunctionAddressEquality =
991 args.hasArg(OPT_ignore_function_address_equality);
992 config->init = args.getLastArgValue(OPT_init, "_init");
993 config->ltoAAPipeline = args.getLastArgValue(OPT_lto_aa_pipeline);
994 config->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate);
995 config->ltoCSProfileFile = args.getLastArgValue(OPT_lto_cs_profile_file);
996 config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
997 config->ltoEmitAsm = args.hasArg(OPT_lto_emit_asm);
998 config->ltoNewPassManager =
999 args.hasFlag(OPT_no_lto_legacy_pass_manager, OPT_lto_legacy_pass_manager,
1000 LLVM_ENABLE_NEW_PASS_MANAGER);
1001 config->ltoNewPmPasses = args.getLastArgValue(OPT_lto_newpm_passes);
1002 config->ltoWholeProgramVisibility =
1003 args.hasFlag(OPT_lto_whole_program_visibility,
1004 OPT_no_lto_whole_program_visibility, false);
1005 config->ltoo = args::getInteger(args, OPT_lto_O, 2);
1006 config->ltoObjPath = args.getLastArgValue(OPT_lto_obj_path_eq);
1007 config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
1008 config->ltoPseudoProbeForProfiling =
1009 args.hasArg(OPT_lto_pseudo_probe_for_profiling);
1010 config->ltoSampleProfile = args.getLastArgValue(OPT_lto_sample_profile);
1011 config->ltoBasicBlockSections =
1012 args.getLastArgValue(OPT_lto_basic_block_sections);
1013 config->ltoUniqueBasicBlockSectionNames =
1014 args.hasFlag(OPT_lto_unique_basic_block_section_names,
1015 OPT_no_lto_unique_basic_block_section_names, false);
1016 config->mapFile = args.getLastArgValue(OPT_Map);
1017 config->mipsGotSize = args::getInteger(args, OPT_mips_got_size, 0xfff0);
1018 config->mergeArmExidx =
1019 args.hasFlag(OPT_merge_exidx_entries, OPT_no_merge_exidx_entries, true);
1020 config->mmapOutputFile =
1021 args.hasFlag(OPT_mmap_output_file, OPT_no_mmap_output_file, true);
1022 config->nmagic = args.hasFlag(OPT_nmagic, OPT_no_nmagic, false);
1023 config->noinhibitExec = args.hasArg(OPT_noinhibit_exec);
1024 config->nostdlib = args.hasArg(OPT_nostdlib);
1025 config->oFormatBinary = isOutputFormatBinary(args);
1026 config->omagic = args.hasFlag(OPT_omagic, OPT_no_omagic, false);
1027 config->optRemarksFilename = args.getLastArgValue(OPT_opt_remarks_filename);
1028
1029 // Parse remarks hotness threshold. Valid value is either integer or 'auto'.
1030 if (auto *arg = args.getLastArg(OPT_opt_remarks_hotness_threshold)) {
1031 auto resultOrErr = remarks::parseHotnessThresholdOption(arg->getValue());
1032 if (!resultOrErr)
1033 error(arg->getSpelling() + ": invalid argument '" + arg->getValue() +
1034 "', only integer or 'auto' is supported");
1035 else
1036 config->optRemarksHotnessThreshold = *resultOrErr;
1037 }
1038
1039 config->optRemarksPasses = args.getLastArgValue(OPT_opt_remarks_passes);
1040 config->optRemarksWithHotness = args.hasArg(OPT_opt_remarks_with_hotness);
1041 config->optRemarksFormat = args.getLastArgValue(OPT_opt_remarks_format);
1042 config->optimize = args::getInteger(args, OPT_O, 1);
1043 config->orphanHandling = getOrphanHandling(args);
1044 config->outputFile = args.getLastArgValue(OPT_o);
1045 config->pie = args.hasFlag(OPT_pie, OPT_no_pie, false);
1046 config->printIcfSections =
1047 args.hasFlag(OPT_print_icf_sections, OPT_no_print_icf_sections, false);
1048 config->printGcSections =
1049 args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
1050 config->printArchiveStats = args.getLastArgValue(OPT_print_archive_stats);
1051 config->printSymbolOrder =
1052 args.getLastArgValue(OPT_print_symbol_order);
1053 config->rpath = getRpath(args);
1054 config->relocatable = args.hasArg(OPT_relocatable);
1055 config->saveTemps = args.hasArg(OPT_save_temps);
1056 if (args.hasArg(OPT_shuffle_sections))
1057 config->shuffleSectionSeed = args::getInteger(args, OPT_shuffle_sections, 0);
1058 config->searchPaths = args::getStrings(args, OPT_library_path);
1059 config->sectionStartMap = getSectionStartMap(args);
1060 config->shared = args.hasArg(OPT_shared);
1061 config->singleRoRx = !args.hasFlag(OPT_rosegment, OPT_no_rosegment, true);
1062 config->soName = args.getLastArgValue(OPT_soname);
1063 config->sortSection = getSortSection(args);
1064 config->splitStackAdjustSize = args::getInteger(args, OPT_split_stack_adjust_size, 16384);
1065 config->strip = getStrip(args);
1066 config->sysroot = args.getLastArgValue(OPT_sysroot);
1067 config->target1Rel = args.hasFlag(OPT_target1_rel, OPT_target1_abs, false);
1068 config->target2 = getTarget2(args);
1069 config->thinLTOCacheDir = args.getLastArgValue(OPT_thinlto_cache_dir);
1070 config->thinLTOCachePolicy = CHECK(
1071 parseCachePruningPolicy(args.getLastArgValue(OPT_thinlto_cache_policy)),
1072 "--thinlto-cache-policy: invalid cache policy");
1073 config->thinLTOEmitImportsFiles = args.hasArg(OPT_thinlto_emit_imports_files);
1074 config->thinLTOIndexOnly = args.hasArg(OPT_thinlto_index_only) ||
1075 args.hasArg(OPT_thinlto_index_only_eq);
1076 config->thinLTOIndexOnlyArg = args.getLastArgValue(OPT_thinlto_index_only_eq);
1077 config->thinLTOObjectSuffixReplace =
1078 getOldNewOptions(args, OPT_thinlto_object_suffix_replace_eq);
1079 config->thinLTOPrefixReplace =
1080 getOldNewOptions(args, OPT_thinlto_prefix_replace_eq);
1081 config->thinLTOModulesToCompile =
1082 args::getStrings(args, OPT_thinlto_single_module_eq);
1083 config->timeTraceEnabled = args.hasArg(OPT_time_trace);
1084 config->timeTraceGranularity =
1085 args::getInteger(args, OPT_time_trace_granularity, 500);
1086 config->trace = args.hasArg(OPT_trace);
1087 config->undefined = args::getStrings(args, OPT_undefined);
1088 config->undefinedVersion =
1089 args.hasFlag(OPT_undefined_version, OPT_no_undefined_version, true);
1090 config->unique = args.hasArg(OPT_unique);
1091 config->useAndroidRelrTags = args.hasFlag(
1092 OPT_use_android_relr_tags, OPT_no_use_android_relr_tags, false);
1093 config->warnBackrefs =
1094 args.hasFlag(OPT_warn_backrefs, OPT_no_warn_backrefs, false);
1095 config->warnCommon = args.hasFlag(OPT_warn_common, OPT_no_warn_common, false);
1096 config->warnIfuncTextrel =
1097 args.hasFlag(OPT_warn_ifunc_textrel, OPT_no_warn_ifunc_textrel, false);
1098 config->warnSymbolOrdering =
1099 args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true);
1100 config->zCombreloc = getZFlag(args, "combreloc", "nocombreloc", true);
1101 config->zCopyreloc = getZFlag(args, "copyreloc", "nocopyreloc", true);
1102 config->zForceBti = hasZOption(args, "force-bti");
1103 config->zForceIbt = hasZOption(args, "force-ibt");
1104 config->zGlobal = hasZOption(args, "global");
1105 config->zGnustack = getZGnuStack(args);
1106 config->zHazardplt = hasZOption(args, "hazardplt");
1107 config->zIfuncNoplt = hasZOption(args, "ifunc-noplt");
1108 config->zInitfirst = hasZOption(args, "initfirst");
1109 config->zInterpose = hasZOption(args, "interpose");
1110 config->zKeepTextSectionPrefix = getZFlag(
1111 args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
1112 config->zNodefaultlib = hasZOption(args, "nodefaultlib");
1113 config->zNodelete = hasZOption(args, "nodelete");
1114 config->zNodlopen = hasZOption(args, "nodlopen");
1115 config->zNow = getZFlag(args, "now", "lazy", false);
1116 config->zOrigin = hasZOption(args, "origin");
1117 config->zPacPlt = hasZOption(args, "pac-plt");
1118 config->zRelro = getZFlag(args, "relro", "norelro", true);
1119 config->zRetpolineplt = hasZOption(args, "retpolineplt");
1120 config->zRodynamic = hasZOption(args, "rodynamic");
1121 config->zSeparate = getZSeparate(args);
1122 config->zShstk = hasZOption(args, "shstk");
1123 config->zStackSize = args::getZOptionValue(args, OPT_z, "stack-size", 0);
1124 config->zStartStopVisibility = getZStartStopVisibility(args);
1125 config->zText = getZFlag(args, "text", "notext", true);
1126 config->zWxneeded = hasZOption(args, "wxneeded");
1127 setUnresolvedSymbolPolicy(args);
1128
1129 for (opt::Arg *arg : args.filtered(OPT_z)) {
1130 std::pair<StringRef, StringRef> option =
1131 StringRef(arg->getValue()).split('=');
1132 if (option.first != "dead-reloc-in-nonalloc")
1133 continue;
1134 constexpr StringRef errPrefix = "-z dead-reloc-in-nonalloc=: ";
1135 std::pair<StringRef, StringRef> kv = option.second.split('=');
1136 if (kv.first.empty() || kv.second.empty()) {
1137 error(errPrefix + "expected <section_glob>=<value>");
1138 continue;
1139 }
1140 uint64_t v;
1141 if (!to_integer(kv.second, v))
1142 error(errPrefix + "expected a non-negative integer, but got '" +
1143 kv.second + "'");
1144 else if (Expected<GlobPattern> pat = GlobPattern::create(kv.first))
1145 config->deadRelocInNonAlloc.emplace_back(std::move(*pat), v);
1146 else
1147 error(errPrefix + toString(pat.takeError()));
1148 }
1149
1150 cl::ResetAllOptionOccurrences();
1151
1152 // Parse LTO options.
1153 if (auto *arg = args.getLastArg(OPT_plugin_opt_mcpu_eq))
1154 parseClangOption(saver.save("-mcpu=" + StringRef(arg->getValue())),
1155 arg->getSpelling());
1156
1157 for (opt::Arg *arg : args.filtered(OPT_plugin_opt_eq_minus))
1158 parseClangOption(std::string("-") + arg->getValue(), arg->getSpelling());
1159
1160 // GCC collect2 passes -plugin-opt=path/to/lto-wrapper with an absolute or
1161 // relative path. Just ignore. If not ended with "lto-wrapper", consider it an
1162 // unsupported LLVMgold.so option and error.
1163 for (opt::Arg *arg : args.filtered(OPT_plugin_opt_eq))
1164 if (!StringRef(arg->getValue()).endswith("lto-wrapper"))
1165 error(arg->getSpelling() + ": unknown plugin option '" + arg->getValue() +
1166 "'");
1167
1168 // Parse -mllvm options.
1169 for (auto *arg : args.filtered(OPT_mllvm))
1170 parseClangOption(arg->getValue(), arg->getSpelling());
1171
1172 // --threads= takes a positive integer and provides the default value for
1173 // --thinlto-jobs=.
1174 if (auto *arg = args.getLastArg(OPT_threads)) {
1175 StringRef v(arg->getValue());
1176 unsigned threads = 0;
1177 if (!llvm::to_integer(v, threads, 0) || threads == 0)
1178 error(arg->getSpelling() + ": expected a positive integer, but got '" +
1179 arg->getValue() + "'");
1180 parallel::strategy = hardware_concurrency(threads);
1181 config->thinLTOJobs = v;
1182 }
1183 if (auto *arg = args.getLastArg(OPT_thinlto_jobs))
1184 config->thinLTOJobs = arg->getValue();
1185
1186 if (config->ltoo > 3)
1187 error("invalid optimization level for LTO: " + Twine(config->ltoo));
1188 if (config->ltoPartitions == 0)
1189 error("--lto-partitions: number of threads must be > 0");
1190 if (!get_threadpool_strategy(config->thinLTOJobs))
1191 error("--thinlto-jobs: invalid job count: " + config->thinLTOJobs);
1192
1193 if (config->splitStackAdjustSize < 0)
1194 error("--split-stack-adjust-size: size must be >= 0");
1195
1196 // The text segment is traditionally the first segment, whose address equals
1197 // the base address. However, lld places the R PT_LOAD first. -Ttext-segment
1198 // is an old-fashioned option that does not play well with lld's layout.
1199 // Suggest --image-base as a likely alternative.
1200 if (args.hasArg(OPT_Ttext_segment))
1201 error("-Ttext-segment is not supported. Use --image-base if you "
1202 "intend to set the base address");
1203
1204 // Parse ELF{32,64}{LE,BE} and CPU type.
1205 if (auto *arg = args.getLastArg(OPT_m)) {
1206 StringRef s = arg->getValue();
1207 std::tie(config->ekind, config->emachine, config->osabi) =
1208 parseEmulation(s);
1209 config->mipsN32Abi =
1210 (s.startswith("elf32btsmipn32") || s.startswith("elf32ltsmipn32"));
1211 config->emulation = s;
1212 }
1213
1214 // Parse -hash-style={sysv,gnu,both}.
1215 if (auto *arg = args.getLastArg(OPT_hash_style)) {
1216 StringRef s = arg->getValue();
1217 if (s == "sysv")
1218 config->sysvHash = true;
1219 else if (s == "gnu")
1220 config->gnuHash = true;
1221 else if (s == "both")
1222 config->sysvHash = config->gnuHash = true;
1223 else
1224 error("unknown -hash-style: " + s);
1225 }
1226
1227 if (args.hasArg(OPT_print_map))
1228 config->mapFile = "-";
1229
1230 // Page alignment can be disabled by the -n (--nmagic) and -N (--omagic).
1231 // As PT_GNU_RELRO relies on Paging, do not create it when we have disabled
1232 // it.
1233 if (config->nmagic || config->omagic)
1234 config->zRelro = false;
1235
1236 std::tie(config->buildId, config->buildIdVector) = getBuildId(args);
1237
1238 std::tie(config->androidPackDynRelocs, config->relrPackDynRelocs) =
1239 getPackDynRelocs(args);
1240
1241 if (auto *arg = args.getLastArg(OPT_symbol_ordering_file)){
1242 if (args.hasArg(OPT_call_graph_ordering_file))
1243 error("--symbol-ordering-file and --call-graph-order-file "
1244 "may not be used together");
1245 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue())){
1246 config->symbolOrderingFile = getSymbolOrderingFile(*buffer);
1247 // Also need to disable CallGraphProfileSort to prevent
1248 // LLD order symbols with CGProfile
1249 config->callGraphProfileSort = false;
1250 }
1251 }
1252
1253 assert(config->versionDefinitions.empty());
1254 config->versionDefinitions.push_back({"local", (uint16_t)VER_NDX_LOCAL, {}});
1255 config->versionDefinitions.push_back(
1256 {"global", (uint16_t)VER_NDX_GLOBAL, {}});
1257
1258 // If --retain-symbol-file is used, we'll keep only the symbols listed in
1259 // the file and discard all others.
1260 if (auto *arg = args.getLastArg(OPT_retain_symbols_file)) {
1261 config->versionDefinitions[VER_NDX_LOCAL].patterns.push_back(
1262 {"*", /*isExternCpp=*/false, /*hasWildcard=*/true});
1263 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
1264 for (StringRef s : args::getLines(*buffer))
1265 config->versionDefinitions[VER_NDX_GLOBAL].patterns.push_back(
1266 {s, /*isExternCpp=*/false, /*hasWildcard=*/false});
1267 }
1268
1269 for (opt::Arg *arg : args.filtered(OPT_warn_backrefs_exclude)) {
1270 StringRef pattern(arg->getValue());
1271 if (Expected<GlobPattern> pat = GlobPattern::create(pattern))
1272 config->warnBackrefsExclude.push_back(std::move(*pat));
1273 else
1274 error(arg->getSpelling() + ": " + toString(pat.takeError()));
1275 }
1276
1277 // When producing an executable, --dynamic-list specifies non-local defined
1278 // symbols whith are required to be exported. When producing a shared object,
1279 // symbols not specified by --dynamic-list are non-preemptible.
1280 config->symbolic =
1281 args.hasArg(OPT_Bsymbolic) || args.hasArg(OPT_dynamic_list);
1282 for (auto *arg : args.filtered(OPT_dynamic_list))
1283 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
1284 readDynamicList(*buffer);
1285
1286 // --export-dynamic-symbol specifies additional --dynamic-list symbols if any
1287 // other option expresses a symbolic intention: -no-pie, -pie, -Bsymbolic,
1288 // -Bsymbolic-functions (if STT_FUNC), --dynamic-list.
1289 for (auto *arg : args.filtered(OPT_export_dynamic_symbol))
1290 config->dynamicList.push_back(
1291 {arg->getValue(), /*isExternCpp=*/false,
1292 /*hasWildcard=*/hasWildcard(arg->getValue())});
1293
1294 for (auto *arg : args.filtered(OPT_version_script))
1295 if (Optional<std::string> path = searchScript(arg->getValue())) {
1296 if (Optional<MemoryBufferRef> buffer = readFile(*path))
1297 readVersionScript(*buffer);
1298 } else {
1299 error(Twine("cannot find version script ") + arg->getValue());
1300 }
1301 }
1302
1303 // Some Config members do not directly correspond to any particular
1304 // command line options, but computed based on other Config values.
1305 // This function initialize such members. See Config.h for the details
1306 // of these values.
setConfigs(opt::InputArgList & args)1307 static void setConfigs(opt::InputArgList &args) {
1308 ELFKind k = config->ekind;
1309 uint16_t m = config->emachine;
1310
1311 config->copyRelocs = (config->relocatable || config->emitRelocs);
1312 config->is64 = (k == ELF64LEKind || k == ELF64BEKind);
1313 config->isLE = (k == ELF32LEKind || k == ELF64LEKind);
1314 config->endianness = config->isLE ? endianness::little : endianness::big;
1315 config->isMips64EL = (k == ELF64LEKind && m == EM_MIPS);
1316 config->isPic = config->pie || config->shared;
1317 config->picThunk = args.hasArg(OPT_pic_veneer, config->isPic);
1318 config->wordsize = config->is64 ? 8 : 4;
1319
1320 // ELF defines two different ways to store relocation addends as shown below:
1321 //
1322 // Rel: Addends are stored to the location where relocations are applied. It
1323 // cannot pack the full range of addend values for all relocation types, but
1324 // this only affects relocation types that we don't support emitting as
1325 // dynamic relocations (see getDynRel).
1326 // Rela: Addends are stored as part of relocation entry.
1327 //
1328 // In other words, Rela makes it easy to read addends at the price of extra
1329 // 4 or 8 byte for each relocation entry.
1330 //
1331 // We pick the format for dynamic relocations according to the psABI for each
1332 // processor, but a contrary choice can be made if the dynamic loader
1333 // supports.
1334 config->isRela = getIsRela(args);
1335
1336 // If the output uses REL relocations we must store the dynamic relocation
1337 // addends to the output sections. We also store addends for RELA relocations
1338 // if --apply-dynamic-relocs is used.
1339 // We default to not writing the addends when using RELA relocations since
1340 // any standard conforming tool can find it in r_addend.
1341 config->writeAddends = args.hasFlag(OPT_apply_dynamic_relocs,
1342 OPT_no_apply_dynamic_relocs, false) ||
1343 !config->isRela;
1344
1345 config->tocOptimize =
1346 args.hasFlag(OPT_toc_optimize, OPT_no_toc_optimize, m == EM_PPC64);
1347 config->pcRelOptimize =
1348 args.hasFlag(OPT_pcrel_optimize, OPT_no_pcrel_optimize, m == EM_PPC64);
1349 }
1350
1351 // Returns a value of "-format" option.
isFormatBinary(StringRef s)1352 static bool isFormatBinary(StringRef s) {
1353 if (s == "binary")
1354 return true;
1355 if (s == "elf" || s == "default")
1356 return false;
1357 error("unknown -format value: " + s +
1358 " (supported formats: elf, default, binary)");
1359 return false;
1360 }
1361
createFiles(opt::InputArgList & args)1362 void LinkerDriver::createFiles(opt::InputArgList &args) {
1363 llvm::TimeTraceScope timeScope("Load input files");
1364 // For --{push,pop}-state.
1365 std::vector<std::tuple<bool, bool, bool>> stack;
1366
1367 // Iterate over argv to process input files and positional arguments.
1368 InputFile::isInGroup = false;
1369 for (auto *arg : args) {
1370 switch (arg->getOption().getID()) {
1371 case OPT_library:
1372 addLibrary(arg->getValue());
1373 break;
1374 case OPT_INPUT:
1375 addFile(arg->getValue(), /*withLOption=*/false);
1376 break;
1377 case OPT_defsym: {
1378 StringRef from;
1379 StringRef to;
1380 std::tie(from, to) = StringRef(arg->getValue()).split('=');
1381 if (from.empty() || to.empty())
1382 error("-defsym: syntax error: " + StringRef(arg->getValue()));
1383 else
1384 readDefsym(from, MemoryBufferRef(to, "-defsym"));
1385 break;
1386 }
1387 case OPT_script:
1388 if (Optional<std::string> path = searchScript(arg->getValue())) {
1389 if (Optional<MemoryBufferRef> mb = readFile(*path))
1390 readLinkerScript(*mb);
1391 break;
1392 }
1393 error(Twine("cannot find linker script ") + arg->getValue());
1394 break;
1395 case OPT_as_needed:
1396 config->asNeeded = true;
1397 break;
1398 case OPT_format:
1399 config->formatBinary = isFormatBinary(arg->getValue());
1400 break;
1401 case OPT_no_as_needed:
1402 config->asNeeded = false;
1403 break;
1404 case OPT_Bstatic:
1405 case OPT_omagic:
1406 case OPT_nmagic:
1407 config->isStatic = true;
1408 break;
1409 case OPT_Bdynamic:
1410 config->isStatic = false;
1411 break;
1412 case OPT_whole_archive:
1413 inWholeArchive = true;
1414 break;
1415 case OPT_no_whole_archive:
1416 inWholeArchive = false;
1417 break;
1418 case OPT_just_symbols:
1419 if (Optional<MemoryBufferRef> mb = readFile(arg->getValue())) {
1420 files.push_back(createObjectFile(*mb));
1421 files.back()->justSymbols = true;
1422 }
1423 break;
1424 case OPT_start_group:
1425 if (InputFile::isInGroup)
1426 error("nested --start-group");
1427 InputFile::isInGroup = true;
1428 break;
1429 case OPT_end_group:
1430 if (!InputFile::isInGroup)
1431 error("stray --end-group");
1432 InputFile::isInGroup = false;
1433 ++InputFile::nextGroupId;
1434 break;
1435 case OPT_start_lib:
1436 if (inLib)
1437 error("nested --start-lib");
1438 if (InputFile::isInGroup)
1439 error("may not nest --start-lib in --start-group");
1440 inLib = true;
1441 InputFile::isInGroup = true;
1442 break;
1443 case OPT_end_lib:
1444 if (!inLib)
1445 error("stray --end-lib");
1446 inLib = false;
1447 InputFile::isInGroup = false;
1448 ++InputFile::nextGroupId;
1449 break;
1450 case OPT_push_state:
1451 stack.emplace_back(config->asNeeded, config->isStatic, inWholeArchive);
1452 break;
1453 case OPT_pop_state:
1454 if (stack.empty()) {
1455 error("unbalanced --push-state/--pop-state");
1456 break;
1457 }
1458 std::tie(config->asNeeded, config->isStatic, inWholeArchive) = stack.back();
1459 stack.pop_back();
1460 break;
1461 }
1462 }
1463
1464 if (files.empty() && errorCount() == 0)
1465 error("no input files");
1466 }
1467
1468 // If -m <machine_type> was not given, infer it from object files.
inferMachineType()1469 void LinkerDriver::inferMachineType() {
1470 if (config->ekind != ELFNoneKind)
1471 return;
1472
1473 for (InputFile *f : files) {
1474 if (f->ekind == ELFNoneKind)
1475 continue;
1476 config->ekind = f->ekind;
1477 config->emachine = f->emachine;
1478 config->osabi = f->osabi;
1479 config->mipsN32Abi = config->emachine == EM_MIPS && isMipsN32Abi(f);
1480 return;
1481 }
1482 error("target emulation unknown: -m or at least one .o file required");
1483 }
1484
1485 // Parse -z max-page-size=<value>. The default value is defined by
1486 // each target.
getMaxPageSize(opt::InputArgList & args)1487 static uint64_t getMaxPageSize(opt::InputArgList &args) {
1488 uint64_t val = args::getZOptionValue(args, OPT_z, "max-page-size",
1489 target->defaultMaxPageSize);
1490 if (!isPowerOf2_64(val))
1491 error("max-page-size: value isn't a power of 2");
1492 if (config->nmagic || config->omagic) {
1493 if (val != target->defaultMaxPageSize)
1494 warn("-z max-page-size set, but paging disabled by omagic or nmagic");
1495 return 1;
1496 }
1497 return val;
1498 }
1499
1500 // Parse -z common-page-size=<value>. The default value is defined by
1501 // each target.
getCommonPageSize(opt::InputArgList & args)1502 static uint64_t getCommonPageSize(opt::InputArgList &args) {
1503 uint64_t val = args::getZOptionValue(args, OPT_z, "common-page-size",
1504 target->defaultCommonPageSize);
1505 if (!isPowerOf2_64(val))
1506 error("common-page-size: value isn't a power of 2");
1507 if (config->nmagic || config->omagic) {
1508 if (val != target->defaultCommonPageSize)
1509 warn("-z common-page-size set, but paging disabled by omagic or nmagic");
1510 return 1;
1511 }
1512 // commonPageSize can't be larger than maxPageSize.
1513 if (val > config->maxPageSize)
1514 val = config->maxPageSize;
1515 return val;
1516 }
1517
1518 // Parses -image-base option.
getImageBase(opt::InputArgList & args)1519 static Optional<uint64_t> getImageBase(opt::InputArgList &args) {
1520 // Because we are using "Config->maxPageSize" here, this function has to be
1521 // called after the variable is initialized.
1522 auto *arg = args.getLastArg(OPT_image_base);
1523 if (!arg)
1524 return None;
1525
1526 StringRef s = arg->getValue();
1527 uint64_t v;
1528 if (!to_integer(s, v)) {
1529 error("-image-base: number expected, but got " + s);
1530 return 0;
1531 }
1532 if ((v % config->maxPageSize) != 0)
1533 warn("-image-base: address isn't multiple of page size: " + s);
1534 return v;
1535 }
1536
1537 // Parses `--exclude-libs=lib,lib,...`.
1538 // The library names may be delimited by commas or colons.
getExcludeLibs(opt::InputArgList & args)1539 static DenseSet<StringRef> getExcludeLibs(opt::InputArgList &args) {
1540 DenseSet<StringRef> ret;
1541 for (auto *arg : args.filtered(OPT_exclude_libs)) {
1542 StringRef s = arg->getValue();
1543 for (;;) {
1544 size_t pos = s.find_first_of(",:");
1545 if (pos == StringRef::npos)
1546 break;
1547 ret.insert(s.substr(0, pos));
1548 s = s.substr(pos + 1);
1549 }
1550 ret.insert(s);
1551 }
1552 return ret;
1553 }
1554
1555 // Handles the -exclude-libs option. If a static library file is specified
1556 // by the -exclude-libs option, all public symbols from the archive become
1557 // private unless otherwise specified by version scripts or something.
1558 // A special library name "ALL" means all archive files.
1559 //
1560 // This is not a popular option, but some programs such as bionic libc use it.
excludeLibs(opt::InputArgList & args)1561 static void excludeLibs(opt::InputArgList &args) {
1562 DenseSet<StringRef> libs = getExcludeLibs(args);
1563 bool all = libs.count("ALL");
1564
1565 auto visit = [&](InputFile *file) {
1566 if (!file->archiveName.empty())
1567 if (all || libs.count(path::filename(file->archiveName)))
1568 for (Symbol *sym : file->getSymbols())
1569 if (!sym->isUndefined() && !sym->isLocal() && sym->file == file)
1570 sym->versionId = VER_NDX_LOCAL;
1571 };
1572
1573 for (InputFile *file : objectFiles)
1574 visit(file);
1575
1576 for (BitcodeFile *file : bitcodeFiles)
1577 visit(file);
1578 }
1579
1580 // Force Sym to be entered in the output.
handleUndefined(Symbol * sym)1581 static void handleUndefined(Symbol *sym) {
1582 // Since a symbol may not be used inside the program, LTO may
1583 // eliminate it. Mark the symbol as "used" to prevent it.
1584 sym->isUsedInRegularObj = true;
1585
1586 if (sym->isLazy())
1587 sym->fetch();
1588 }
1589
1590 // As an extension to GNU linkers, lld supports a variant of `-u`
1591 // which accepts wildcard patterns. All symbols that match a given
1592 // pattern are handled as if they were given by `-u`.
handleUndefinedGlob(StringRef arg)1593 static void handleUndefinedGlob(StringRef arg) {
1594 Expected<GlobPattern> pat = GlobPattern::create(arg);
1595 if (!pat) {
1596 error("--undefined-glob: " + toString(pat.takeError()));
1597 return;
1598 }
1599
1600 std::vector<Symbol *> syms;
1601 for (Symbol *sym : symtab->symbols()) {
1602 // Calling Sym->fetch() from here is not safe because it may
1603 // add new symbols to the symbol table, invalidating the
1604 // current iterator. So we just keep a note.
1605 if (pat->match(sym->getName()))
1606 syms.push_back(sym);
1607 }
1608
1609 for (Symbol *sym : syms)
1610 handleUndefined(sym);
1611 }
1612
handleLibcall(StringRef name)1613 static void handleLibcall(StringRef name) {
1614 Symbol *sym = symtab->find(name);
1615 if (!sym || !sym->isLazy())
1616 return;
1617
1618 MemoryBufferRef mb;
1619 if (auto *lo = dyn_cast<LazyObject>(sym))
1620 mb = lo->file->mb;
1621 else
1622 mb = cast<LazyArchive>(sym)->getMemberBuffer();
1623
1624 if (isBitcode(mb))
1625 sym->fetch();
1626 }
1627
1628 // Handle --dependency-file=<path>. If that option is given, lld creates a
1629 // file at a given path with the following contents:
1630 //
1631 // <output-file>: <input-file> ...
1632 //
1633 // <input-file>:
1634 //
1635 // where <output-file> is a pathname of an output file and <input-file>
1636 // ... is a list of pathnames of all input files. `make` command can read a
1637 // file in the above format and interpret it as a dependency info. We write
1638 // phony targets for every <input-file> to avoid an error when that file is
1639 // removed.
1640 //
1641 // This option is useful if you want to make your final executable to depend
1642 // on all input files including system libraries. Here is why.
1643 //
1644 // When you write a Makefile, you usually write it so that the final
1645 // executable depends on all user-generated object files. Normally, you
1646 // don't make your executable to depend on system libraries (such as libc)
1647 // because you don't know the exact paths of libraries, even though system
1648 // libraries that are linked to your executable statically are technically a
1649 // part of your program. By using --dependency-file option, you can make
1650 // lld to dump dependency info so that you can maintain exact dependencies
1651 // easily.
writeDependencyFile()1652 static void writeDependencyFile() {
1653 std::error_code ec;
1654 raw_fd_ostream os(config->dependencyFile, ec, sys::fs::F_None);
1655 if (ec) {
1656 error("cannot open " + config->dependencyFile + ": " + ec.message());
1657 return;
1658 }
1659
1660 // We use the same escape rules as Clang/GCC which are accepted by Make/Ninja:
1661 // * A space is escaped by a backslash which itself must be escaped.
1662 // * A hash sign is escaped by a single backslash.
1663 // * $ is escapes as $$.
1664 auto printFilename = [](raw_fd_ostream &os, StringRef filename) {
1665 llvm::SmallString<256> nativePath;
1666 llvm::sys::path::native(filename.str(), nativePath);
1667 llvm::sys::path::remove_dots(nativePath, /*remove_dot_dot=*/true);
1668 for (unsigned i = 0, e = nativePath.size(); i != e; ++i) {
1669 if (nativePath[i] == '#') {
1670 os << '\\';
1671 } else if (nativePath[i] == ' ') {
1672 os << '\\';
1673 unsigned j = i;
1674 while (j > 0 && nativePath[--j] == '\\')
1675 os << '\\';
1676 } else if (nativePath[i] == '$') {
1677 os << '$';
1678 }
1679 os << nativePath[i];
1680 }
1681 };
1682
1683 os << config->outputFile << ":";
1684 for (StringRef path : config->dependencyFiles) {
1685 os << " \\\n ";
1686 printFilename(os, path);
1687 }
1688 os << "\n";
1689
1690 for (StringRef path : config->dependencyFiles) {
1691 os << "\n";
1692 printFilename(os, path);
1693 os << ":\n";
1694 }
1695 }
1696
1697 // Replaces common symbols with defined symbols reside in .bss sections.
1698 // This function is called after all symbol names are resolved. As a
1699 // result, the passes after the symbol resolution won't see any
1700 // symbols of type CommonSymbol.
replaceCommonSymbols()1701 static void replaceCommonSymbols() {
1702 llvm::TimeTraceScope timeScope("Replace common symbols");
1703 for (Symbol *sym : symtab->symbols()) {
1704 auto *s = dyn_cast<CommonSymbol>(sym);
1705 if (!s)
1706 continue;
1707
1708 auto *bss = make<BssSection>("COMMON", s->size, s->alignment);
1709 bss->file = s->file;
1710 bss->markDead();
1711 inputSections.push_back(bss);
1712 s->replace(Defined{s->file, s->getName(), s->binding, s->stOther, s->type,
1713 /*value=*/0, s->size, bss});
1714 }
1715 }
1716
1717 // If all references to a DSO happen to be weak, the DSO is not added
1718 // to DT_NEEDED. If that happens, we need to eliminate shared symbols
1719 // created from the DSO. Otherwise, they become dangling references
1720 // that point to a non-existent DSO.
demoteSharedSymbols()1721 static void demoteSharedSymbols() {
1722 llvm::TimeTraceScope timeScope("Demote shared symbols");
1723 for (Symbol *sym : symtab->symbols()) {
1724 auto *s = dyn_cast<SharedSymbol>(sym);
1725 if (!s || s->getFile().isNeeded)
1726 continue;
1727
1728 bool used = s->used;
1729 s->replace(Undefined{nullptr, s->getName(), STB_WEAK, s->stOther, s->type});
1730 s->used = used;
1731 }
1732 }
1733
1734 // The section referred to by `s` is considered address-significant. Set the
1735 // keepUnique flag on the section if appropriate.
markAddrsig(Symbol * s)1736 static void markAddrsig(Symbol *s) {
1737 if (auto *d = dyn_cast_or_null<Defined>(s))
1738 if (d->section)
1739 // We don't need to keep text sections unique under --icf=all even if they
1740 // are address-significant.
1741 if (config->icf == ICFLevel::Safe || !(d->section->flags & SHF_EXECINSTR))
1742 d->section->keepUnique = true;
1743 }
1744
1745 // Record sections that define symbols mentioned in --keep-unique <symbol>
1746 // and symbols referred to by address-significance tables. These sections are
1747 // ineligible for ICF.
1748 template <class ELFT>
findKeepUniqueSections(opt::InputArgList & args)1749 static void findKeepUniqueSections(opt::InputArgList &args) {
1750 for (auto *arg : args.filtered(OPT_keep_unique)) {
1751 StringRef name = arg->getValue();
1752 auto *d = dyn_cast_or_null<Defined>(symtab->find(name));
1753 if (!d || !d->section) {
1754 warn("could not find symbol " + name + " to keep unique");
1755 continue;
1756 }
1757 d->section->keepUnique = true;
1758 }
1759
1760 // --icf=all --ignore-data-address-equality means that we can ignore
1761 // the dynsym and address-significance tables entirely.
1762 if (config->icf == ICFLevel::All && config->ignoreDataAddressEquality)
1763 return;
1764
1765 // Symbols in the dynsym could be address-significant in other executables
1766 // or DSOs, so we conservatively mark them as address-significant.
1767 for (Symbol *sym : symtab->symbols())
1768 if (sym->includeInDynsym())
1769 markAddrsig(sym);
1770
1771 // Visit the address-significance table in each object file and mark each
1772 // referenced symbol as address-significant.
1773 for (InputFile *f : objectFiles) {
1774 auto *obj = cast<ObjFile<ELFT>>(f);
1775 ArrayRef<Symbol *> syms = obj->getSymbols();
1776 if (obj->addrsigSec) {
1777 ArrayRef<uint8_t> contents =
1778 check(obj->getObj().getSectionContents(*obj->addrsigSec));
1779 const uint8_t *cur = contents.begin();
1780 while (cur != contents.end()) {
1781 unsigned size;
1782 const char *err;
1783 uint64_t symIndex = decodeULEB128(cur, &size, contents.end(), &err);
1784 if (err)
1785 fatal(toString(f) + ": could not decode addrsig section: " + err);
1786 markAddrsig(syms[symIndex]);
1787 cur += size;
1788 }
1789 } else {
1790 // If an object file does not have an address-significance table,
1791 // conservatively mark all of its symbols as address-significant.
1792 for (Symbol *s : syms)
1793 markAddrsig(s);
1794 }
1795 }
1796 }
1797
1798 // This function reads a symbol partition specification section. These sections
1799 // are used to control which partition a symbol is allocated to. See
1800 // https://lld.llvm.org/Partitions.html for more details on partitions.
1801 template <typename ELFT>
readSymbolPartitionSection(InputSectionBase * s)1802 static void readSymbolPartitionSection(InputSectionBase *s) {
1803 // Read the relocation that refers to the partition's entry point symbol.
1804 Symbol *sym;
1805 if (s->areRelocsRela)
1806 sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template relas<ELFT>()[0]);
1807 else
1808 sym = &s->getFile<ELFT>()->getRelocTargetSym(s->template rels<ELFT>()[0]);
1809 if (!isa<Defined>(sym) || !sym->includeInDynsym())
1810 return;
1811
1812 StringRef partName = reinterpret_cast<const char *>(s->data().data());
1813 for (Partition &part : partitions) {
1814 if (part.name == partName) {
1815 sym->partition = part.getNumber();
1816 return;
1817 }
1818 }
1819
1820 // Forbid partitions from being used on incompatible targets, and forbid them
1821 // from being used together with various linker features that assume a single
1822 // set of output sections.
1823 if (script->hasSectionsCommand)
1824 error(toString(s->file) +
1825 ": partitions cannot be used with the SECTIONS command");
1826 if (script->hasPhdrsCommands())
1827 error(toString(s->file) +
1828 ": partitions cannot be used with the PHDRS command");
1829 if (!config->sectionStartMap.empty())
1830 error(toString(s->file) + ": partitions cannot be used with "
1831 "--section-start, -Ttext, -Tdata or -Tbss");
1832 if (config->emachine == EM_MIPS)
1833 error(toString(s->file) + ": partitions cannot be used on this target");
1834
1835 // Impose a limit of no more than 254 partitions. This limit comes from the
1836 // sizes of the Partition fields in InputSectionBase and Symbol, as well as
1837 // the amount of space devoted to the partition number in RankFlags.
1838 if (partitions.size() == 254)
1839 fatal("may not have more than 254 partitions");
1840
1841 partitions.emplace_back();
1842 Partition &newPart = partitions.back();
1843 newPart.name = partName;
1844 sym->partition = newPart.getNumber();
1845 }
1846
addUndefined(StringRef name)1847 static Symbol *addUndefined(StringRef name) {
1848 return symtab->addSymbol(
1849 Undefined{nullptr, name, STB_GLOBAL, STV_DEFAULT, 0});
1850 }
1851
addUnusedUndefined(StringRef name)1852 static Symbol *addUnusedUndefined(StringRef name) {
1853 Undefined sym{nullptr, name, STB_GLOBAL, STV_DEFAULT, 0};
1854 sym.isUsedInRegularObj = false;
1855 return symtab->addSymbol(sym);
1856 }
1857
1858 // This function is where all the optimizations of link-time
1859 // optimization takes place. When LTO is in use, some input files are
1860 // not in native object file format but in the LLVM bitcode format.
1861 // This function compiles bitcode files into a few big native files
1862 // using LLVM functions and replaces bitcode symbols with the results.
1863 // Because all bitcode files that the program consists of are passed to
1864 // the compiler at once, it can do a whole-program optimization.
compileBitcodeFiles()1865 template <class ELFT> void LinkerDriver::compileBitcodeFiles() {
1866 llvm::TimeTraceScope timeScope("LTO");
1867 // Compile bitcode files and replace bitcode symbols.
1868 lto.reset(new BitcodeCompiler);
1869 for (BitcodeFile *file : bitcodeFiles)
1870 lto->add(*file);
1871
1872 for (InputFile *file : lto->compile()) {
1873 auto *obj = cast<ObjFile<ELFT>>(file);
1874 obj->parse(/*ignoreComdats=*/true);
1875
1876 // Parse '@' in symbol names for non-relocatable output.
1877 if (!config->relocatable)
1878 for (Symbol *sym : obj->getGlobalSymbols())
1879 sym->parseSymbolVersion();
1880 objectFiles.push_back(file);
1881 }
1882 }
1883
1884 // The --wrap option is a feature to rename symbols so that you can write
1885 // wrappers for existing functions. If you pass `-wrap=foo`, all
1886 // occurrences of symbol `foo` are resolved to `__wrap_foo` (so, you are
1887 // expected to write `__wrap_foo` function as a wrapper). The original
1888 // symbol becomes accessible as `__real_foo`, so you can call that from your
1889 // wrapper.
1890 //
1891 // This data structure is instantiated for each -wrap option.
1892 struct WrappedSymbol {
1893 Symbol *sym;
1894 Symbol *real;
1895 Symbol *wrap;
1896 };
1897
1898 // Handles -wrap option.
1899 //
1900 // This function instantiates wrapper symbols. At this point, they seem
1901 // like they are not being used at all, so we explicitly set some flags so
1902 // that LTO won't eliminate them.
addWrappedSymbols(opt::InputArgList & args)1903 static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &args) {
1904 std::vector<WrappedSymbol> v;
1905 DenseSet<StringRef> seen;
1906
1907 for (auto *arg : args.filtered(OPT_wrap)) {
1908 StringRef name = arg->getValue();
1909 if (!seen.insert(name).second)
1910 continue;
1911
1912 Symbol *sym = symtab->find(name);
1913 if (!sym)
1914 continue;
1915
1916 Symbol *real = addUnusedUndefined(saver.save("__real_" + name));
1917 Symbol *wrap = addUnusedUndefined(saver.save("__wrap_" + name));
1918 v.push_back({sym, real, wrap});
1919
1920 // We want to tell LTO not to inline symbols to be overwritten
1921 // because LTO doesn't know the final symbol contents after renaming.
1922 real->canInline = false;
1923 sym->canInline = false;
1924
1925 // Tell LTO not to eliminate these symbols.
1926 sym->isUsedInRegularObj = true;
1927 // If sym is referenced in any object file, bitcode file or shared object,
1928 // retain wrap which is the redirection target of sym. If the object file
1929 // defining sym has sym references, we cannot easily distinguish the case
1930 // from cases where sym is not referenced. Retain wrap because we choose to
1931 // wrap sym references regardless of whether sym is defined
1932 // (https://sourceware.org/bugzilla/show_bug.cgi?id=26358).
1933 if (sym->referenced || sym->isDefined())
1934 wrap->isUsedInRegularObj = true;
1935 }
1936 return v;
1937 }
1938
1939 // Do renaming for -wrap and foo@v1 by updating pointers to symbols.
1940 //
1941 // When this function is executed, only InputFiles and symbol table
1942 // contain pointers to symbol objects. We visit them to replace pointers,
1943 // so that wrapped symbols are swapped as instructed by the command line.
redirectSymbols(ArrayRef<WrappedSymbol> wrapped)1944 static void redirectSymbols(ArrayRef<WrappedSymbol> wrapped) {
1945 llvm::TimeTraceScope timeScope("Redirect symbols");
1946 DenseMap<Symbol *, Symbol *> map;
1947 for (const WrappedSymbol &w : wrapped) {
1948 map[w.sym] = w.wrap;
1949 map[w.real] = w.sym;
1950 }
1951 for (Symbol *sym : symtab->symbols()) {
1952 // Enumerate symbols with a non-default version (foo@v1).
1953 StringRef name = sym->getName();
1954 const char *suffix1 = sym->getVersionSuffix();
1955 if (suffix1[0] != '@' || suffix1[1] == '@')
1956 continue;
1957
1958 // Check whether the default version foo@@v1 exists. If it exists, the
1959 // symbol can be found by the name "foo" in the symbol table.
1960 Symbol *maybeDefault = symtab->find(name);
1961 if (!maybeDefault)
1962 continue;
1963 const char *suffix2 = maybeDefault->getVersionSuffix();
1964 if (suffix2[0] != '@' || suffix2[1] != '@' ||
1965 strcmp(suffix1 + 1, suffix2 + 2) != 0)
1966 continue;
1967
1968 // foo@v1 and foo@@v1 should be merged, so redirect foo@v1 to foo@@v1.
1969 map.try_emplace(sym, maybeDefault);
1970 // If both foo@v1 and foo@@v1 are defined and non-weak, report a duplicate
1971 // definition error.
1972 maybeDefault->resolve(*sym);
1973 // Eliminate foo@v1 from the symbol table.
1974 sym->symbolKind = Symbol::PlaceholderKind;
1975 }
1976
1977 if (map.empty())
1978 return;
1979
1980 // Update pointers in input files.
1981 parallelForEach(objectFiles, [&](InputFile *file) {
1982 MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
1983 for (size_t i = 0, e = syms.size(); i != e; ++i)
1984 if (Symbol *s = map.lookup(syms[i]))
1985 syms[i] = s;
1986 });
1987
1988 // Update pointers in the symbol table.
1989 for (const WrappedSymbol &w : wrapped)
1990 symtab->wrap(w.sym, w.real, w.wrap);
1991 }
1992
1993 // To enable CET (x86's hardware-assited control flow enforcement), each
1994 // source file must be compiled with -fcf-protection. Object files compiled
1995 // with the flag contain feature flags indicating that they are compatible
1996 // with CET. We enable the feature only when all object files are compatible
1997 // with CET.
1998 //
1999 // This is also the case with AARCH64's BTI and PAC which use the similar
2000 // GNU_PROPERTY_AARCH64_FEATURE_1_AND mechanism.
getAndFeatures()2001 template <class ELFT> static uint32_t getAndFeatures() {
2002 if (config->emachine != EM_386 && config->emachine != EM_X86_64 &&
2003 config->emachine != EM_AARCH64)
2004 return 0;
2005
2006 uint32_t ret = -1;
2007 for (InputFile *f : objectFiles) {
2008 uint32_t features = cast<ObjFile<ELFT>>(f)->andFeatures;
2009 if (config->zForceBti && !(features & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) {
2010 warn(toString(f) + ": -z force-bti: file does not have "
2011 "GNU_PROPERTY_AARCH64_FEATURE_1_BTI property");
2012 features |= GNU_PROPERTY_AARCH64_FEATURE_1_BTI;
2013 } else if (config->zForceIbt &&
2014 !(features & GNU_PROPERTY_X86_FEATURE_1_IBT)) {
2015 warn(toString(f) + ": -z force-ibt: file does not have "
2016 "GNU_PROPERTY_X86_FEATURE_1_IBT property");
2017 features |= GNU_PROPERTY_X86_FEATURE_1_IBT;
2018 }
2019 if (config->zPacPlt && !(features & GNU_PROPERTY_AARCH64_FEATURE_1_PAC)) {
2020 warn(toString(f) + ": -z pac-plt: file does not have "
2021 "GNU_PROPERTY_AARCH64_FEATURE_1_PAC property");
2022 features |= GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
2023 }
2024 ret &= features;
2025 }
2026
2027 // Force enable Shadow Stack.
2028 if (config->zShstk)
2029 ret |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
2030
2031 return ret;
2032 }
2033
2034 // Do actual linking. Note that when this function is called,
2035 // all linker scripts have already been parsed.
link(opt::InputArgList & args)2036 template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
2037 llvm::TimeTraceScope timeScope("Link", StringRef("LinkerDriver::Link"));
2038 // If a -hash-style option was not given, set to a default value,
2039 // which varies depending on the target.
2040 if (!args.hasArg(OPT_hash_style)) {
2041 if (config->emachine == EM_MIPS)
2042 config->sysvHash = true;
2043 else
2044 config->sysvHash = config->gnuHash = true;
2045 }
2046
2047 // Default output filename is "a.out" by the Unix tradition.
2048 if (config->outputFile.empty())
2049 config->outputFile = "a.out";
2050
2051 // Fail early if the output file or map file is not writable. If a user has a
2052 // long link, e.g. due to a large LTO link, they do not wish to run it and
2053 // find that it failed because there was a mistake in their command-line.
2054 {
2055 llvm::TimeTraceScope timeScope("Create output files");
2056 if (auto e = tryCreateFile(config->outputFile))
2057 error("cannot open output file " + config->outputFile + ": " +
2058 e.message());
2059 if (auto e = tryCreateFile(config->mapFile))
2060 error("cannot open map file " + config->mapFile + ": " + e.message());
2061 }
2062 if (errorCount())
2063 return;
2064
2065 // Use default entry point name if no name was given via the command
2066 // line nor linker scripts. For some reason, MIPS entry point name is
2067 // different from others.
2068 config->warnMissingEntry =
2069 (!config->entry.empty() || (!config->shared && !config->relocatable));
2070 if (config->entry.empty() && !config->relocatable)
2071 config->entry = (config->emachine == EM_MIPS) ? "__start" : "_start";
2072
2073 // Handle --trace-symbol.
2074 for (auto *arg : args.filtered(OPT_trace_symbol))
2075 symtab->insert(arg->getValue())->traced = true;
2076
2077 // Handle -u/--undefined before input files. If both a.a and b.so define foo,
2078 // -u foo a.a b.so will fetch a.a.
2079 for (StringRef name : config->undefined)
2080 addUnusedUndefined(name)->referenced = true;
2081
2082 // Add all files to the symbol table. This will add almost all
2083 // symbols that we need to the symbol table. This process might
2084 // add files to the link, via autolinking, these files are always
2085 // appended to the Files vector.
2086 {
2087 llvm::TimeTraceScope timeScope("Parse input files");
2088 for (size_t i = 0; i < files.size(); ++i) {
2089 llvm::TimeTraceScope timeScope("Parse input files", files[i]->getName());
2090 parseFile(files[i]);
2091 }
2092 }
2093
2094 // Now that we have every file, we can decide if we will need a
2095 // dynamic symbol table.
2096 // We need one if we were asked to export dynamic symbols or if we are
2097 // producing a shared library.
2098 // We also need one if any shared libraries are used and for pie executables
2099 // (probably because the dynamic linker needs it).
2100 config->hasDynSymTab =
2101 !sharedFiles.empty() || config->isPic || config->exportDynamic;
2102
2103 // Some symbols (such as __ehdr_start) are defined lazily only when there
2104 // are undefined symbols for them, so we add these to trigger that logic.
2105 for (StringRef name : script->referencedSymbols)
2106 addUndefined(name);
2107
2108 // Prevent LTO from removing any definition referenced by -u.
2109 for (StringRef name : config->undefined)
2110 if (Defined *sym = dyn_cast_or_null<Defined>(symtab->find(name)))
2111 sym->isUsedInRegularObj = true;
2112
2113 // If an entry symbol is in a static archive, pull out that file now.
2114 if (Symbol *sym = symtab->find(config->entry))
2115 handleUndefined(sym);
2116
2117 // Handle the `--undefined-glob <pattern>` options.
2118 for (StringRef pat : args::getStrings(args, OPT_undefined_glob))
2119 handleUndefinedGlob(pat);
2120
2121 // Mark -init and -fini symbols so that the LTO doesn't eliminate them.
2122 if (Symbol *sym = dyn_cast_or_null<Defined>(symtab->find(config->init)))
2123 sym->isUsedInRegularObj = true;
2124 if (Symbol *sym = dyn_cast_or_null<Defined>(symtab->find(config->fini)))
2125 sym->isUsedInRegularObj = true;
2126
2127 // If any of our inputs are bitcode files, the LTO code generator may create
2128 // references to certain library functions that might not be explicit in the
2129 // bitcode file's symbol table. If any of those library functions are defined
2130 // in a bitcode file in an archive member, we need to arrange to use LTO to
2131 // compile those archive members by adding them to the link beforehand.
2132 //
2133 // However, adding all libcall symbols to the link can have undesired
2134 // consequences. For example, the libgcc implementation of
2135 // __sync_val_compare_and_swap_8 on 32-bit ARM pulls in an .init_array entry
2136 // that aborts the program if the Linux kernel does not support 64-bit
2137 // atomics, which would prevent the program from running even if it does not
2138 // use 64-bit atomics.
2139 //
2140 // Therefore, we only add libcall symbols to the link before LTO if we have
2141 // to, i.e. if the symbol's definition is in bitcode. Any other required
2142 // libcall symbols will be added to the link after LTO when we add the LTO
2143 // object file to the link.
2144 if (!bitcodeFiles.empty())
2145 for (auto *s : lto::LTO::getRuntimeLibcallSymbols())
2146 handleLibcall(s);
2147
2148 // Return if there were name resolution errors.
2149 if (errorCount())
2150 return;
2151
2152 // We want to declare linker script's symbols early,
2153 // so that we can version them.
2154 // They also might be exported if referenced by DSOs.
2155 script->declareSymbols();
2156
2157 // Handle --exclude-libs. This is before scanVersionScript() due to a
2158 // workaround for Android ndk: for a defined versioned symbol in an archive
2159 // without a version node in the version script, Android does not expect a
2160 // 'has undefined version' error in -shared --exclude-libs=ALL mode (PR36295).
2161 // GNU ld errors in this case.
2162 if (args.hasArg(OPT_exclude_libs))
2163 excludeLibs(args);
2164
2165 // Create elfHeader early. We need a dummy section in
2166 // addReservedSymbols to mark the created symbols as not absolute.
2167 Out::elfHeader = make<OutputSection>("", 0, SHF_ALLOC);
2168 Out::elfHeader->size = sizeof(typename ELFT::Ehdr);
2169
2170 // Create wrapped symbols for -wrap option.
2171 std::vector<WrappedSymbol> wrapped = addWrappedSymbols(args);
2172
2173 // We need to create some reserved symbols such as _end. Create them.
2174 if (!config->relocatable)
2175 addReservedSymbols();
2176
2177 // Apply version scripts.
2178 //
2179 // For a relocatable output, version scripts don't make sense, and
2180 // parsing a symbol version string (e.g. dropping "@ver1" from a symbol
2181 // name "foo@ver1") rather do harm, so we don't call this if -r is given.
2182 if (!config->relocatable) {
2183 llvm::TimeTraceScope timeScope("Process symbol versions");
2184 symtab->scanVersionScript();
2185 }
2186
2187 // Do link-time optimization if given files are LLVM bitcode files.
2188 // This compiles bitcode files into real object files.
2189 //
2190 // With this the symbol table should be complete. After this, no new names
2191 // except a few linker-synthesized ones will be added to the symbol table.
2192 compileBitcodeFiles<ELFT>();
2193
2194 // Handle --exclude-libs again because lto.tmp may reference additional
2195 // libcalls symbols defined in an excluded archive. This may override
2196 // versionId set by scanVersionScript().
2197 if (args.hasArg(OPT_exclude_libs))
2198 excludeLibs(args);
2199
2200 // Symbol resolution finished. Report backward reference problems.
2201 reportBackrefs();
2202 if (errorCount())
2203 return;
2204
2205 // If -thinlto-index-only is given, we should create only "index
2206 // files" and not object files. Index file creation is already done
2207 // in addCombinedLTOObject, so we are done if that's the case.
2208 // Likewise, --plugin-opt=emit-llvm and --plugin-opt=emit-asm are the
2209 // options to create output files in bitcode or assembly code
2210 // repsectively. No object files are generated.
2211 // Also bail out here when only certain thinLTO modules are specified for
2212 // compilation. The intermediate object file are the expected output.
2213 if (config->thinLTOIndexOnly || config->emitLLVM || config->ltoEmitAsm ||
2214 !config->thinLTOModulesToCompile.empty())
2215 return;
2216
2217 // Apply symbol renames for -wrap and combine foo@v1 and foo@@v1.
2218 redirectSymbols(wrapped);
2219
2220 {
2221 llvm::TimeTraceScope timeScope("Aggregate sections");
2222 // Now that we have a complete list of input files.
2223 // Beyond this point, no new files are added.
2224 // Aggregate all input sections into one place.
2225 for (InputFile *f : objectFiles)
2226 for (InputSectionBase *s : f->getSections())
2227 if (s && s != &InputSection::discarded)
2228 inputSections.push_back(s);
2229 for (BinaryFile *f : binaryFiles)
2230 for (InputSectionBase *s : f->getSections())
2231 inputSections.push_back(cast<InputSection>(s));
2232 }
2233
2234 {
2235 llvm::TimeTraceScope timeScope("Strip sections");
2236 llvm::erase_if(inputSections, [](InputSectionBase *s) {
2237 if (s->type == SHT_LLVM_SYMPART) {
2238 readSymbolPartitionSection<ELFT>(s);
2239 return true;
2240 }
2241
2242 // We do not want to emit debug sections if --strip-all
2243 // or -strip-debug are given.
2244 if (config->strip == StripPolicy::None)
2245 return false;
2246
2247 if (isDebugSection(*s))
2248 return true;
2249 if (auto *isec = dyn_cast<InputSection>(s))
2250 if (InputSectionBase *rel = isec->getRelocatedSection())
2251 if (isDebugSection(*rel))
2252 return true;
2253
2254 return false;
2255 });
2256 }
2257
2258 // Since we now have a complete set of input files, we can create
2259 // a .d file to record build dependencies.
2260 if (!config->dependencyFile.empty())
2261 writeDependencyFile();
2262
2263 // Now that the number of partitions is fixed, save a pointer to the main
2264 // partition.
2265 mainPart = &partitions[0];
2266
2267 // Read .note.gnu.property sections from input object files which
2268 // contain a hint to tweak linker's and loader's behaviors.
2269 config->andFeatures = getAndFeatures<ELFT>();
2270
2271 // The Target instance handles target-specific stuff, such as applying
2272 // relocations or writing a PLT section. It also contains target-dependent
2273 // values such as a default image base address.
2274 target = getTarget();
2275
2276 config->eflags = target->calcEFlags();
2277 // maxPageSize (sometimes called abi page size) is the maximum page size that
2278 // the output can be run on. For example if the OS can use 4k or 64k page
2279 // sizes then maxPageSize must be 64k for the output to be useable on both.
2280 // All important alignment decisions must use this value.
2281 config->maxPageSize = getMaxPageSize(args);
2282 // commonPageSize is the most common page size that the output will be run on.
2283 // For example if an OS can use 4k or 64k page sizes and 4k is more common
2284 // than 64k then commonPageSize is set to 4k. commonPageSize can be used for
2285 // optimizations such as DATA_SEGMENT_ALIGN in linker scripts. LLD's use of it
2286 // is limited to writing trap instructions on the last executable segment.
2287 config->commonPageSize = getCommonPageSize(args);
2288
2289 config->imageBase = getImageBase(args);
2290
2291 if (config->emachine == EM_ARM) {
2292 // FIXME: These warnings can be removed when lld only uses these features
2293 // when the input objects have been compiled with an architecture that
2294 // supports them.
2295 if (config->armHasBlx == false)
2296 warn("lld uses blx instruction, no object with architecture supporting "
2297 "feature detected");
2298 }
2299
2300 // This adds a .comment section containing a version string.
2301 if (!config->relocatable)
2302 inputSections.push_back(createCommentSection());
2303
2304 // Replace common symbols with regular symbols.
2305 replaceCommonSymbols();
2306
2307 // Split SHF_MERGE and .eh_frame sections into pieces in preparation for garbage collection.
2308 splitSections<ELFT>();
2309
2310 // Garbage collection and removal of shared symbols from unused shared objects.
2311 markLive<ELFT>();
2312 demoteSharedSymbols();
2313
2314 // Make copies of any input sections that need to be copied into each
2315 // partition.
2316 copySectionsIntoPartitions();
2317
2318 // Create synthesized sections such as .got and .plt. This is called before
2319 // processSectionCommands() so that they can be placed by SECTIONS commands.
2320 createSyntheticSections<ELFT>();
2321
2322 // Some input sections that are used for exception handling need to be moved
2323 // into synthetic sections. Do that now so that they aren't assigned to
2324 // output sections in the usual way.
2325 if (!config->relocatable)
2326 combineEhSections();
2327
2328 {
2329 llvm::TimeTraceScope timeScope("Assign sections");
2330
2331 // Create output sections described by SECTIONS commands.
2332 script->processSectionCommands();
2333
2334 // Linker scripts control how input sections are assigned to output
2335 // sections. Input sections that were not handled by scripts are called
2336 // "orphans", and they are assigned to output sections by the default rule.
2337 // Process that.
2338 script->addOrphanSections();
2339 }
2340
2341 {
2342 llvm::TimeTraceScope timeScope("Merge/finalize input sections");
2343
2344 // Migrate InputSectionDescription::sectionBases to sections. This includes
2345 // merging MergeInputSections into a single MergeSyntheticSection. From this
2346 // point onwards InputSectionDescription::sections should be used instead of
2347 // sectionBases.
2348 for (BaseCommand *base : script->sectionCommands)
2349 if (auto *sec = dyn_cast<OutputSection>(base))
2350 sec->finalizeInputSections();
2351 llvm::erase_if(inputSections, [](InputSectionBase *s) {
2352 return isa<MergeInputSection>(s);
2353 });
2354 }
2355
2356 // Two input sections with different output sections should not be folded.
2357 // ICF runs after processSectionCommands() so that we know the output sections.
2358 if (config->icf != ICFLevel::None) {
2359 findKeepUniqueSections<ELFT>(args);
2360 doIcf<ELFT>();
2361 }
2362
2363 // Read the callgraph now that we know what was gced or icfed
2364 if (config->callGraphProfileSort) {
2365 if (auto *arg = args.getLastArg(OPT_call_graph_ordering_file))
2366 if (Optional<MemoryBufferRef> buffer = readFile(arg->getValue()))
2367 readCallGraph(*buffer);
2368 readCallGraphsFromObjectFiles<ELFT>();
2369 }
2370
2371 // Write the result to the file.
2372 writeResult<ELFT>();
2373 }
2374