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