1//===- InputFiles.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#include "InputFiles.h"
10#include "Config.h"
11#include "DWARF.h"
12#include "Driver.h"
13#include "InputSection.h"
14#include "LinkerScript.h"
15#include "SymbolTable.h"
16#include "Symbols.h"
17#include "SyntheticSections.h"
18#include "Target.h"
19#include "lld/Common/DWARF.h"
20#include "llvm/ADT/CachedHashString.h"
21#include "llvm/ADT/STLExtras.h"
22#include "llvm/LTO/LTO.h"
23#include "llvm/Object/Archive.h"
24#include "llvm/Object/IRObjectFile.h"
25#include "llvm/Support/ARMAttributeParser.h"
26#include "llvm/Support/ARMBuildAttributes.h"
27#include "llvm/Support/Endian.h"
28#include "llvm/Support/FileSystem.h"
29#include "llvm/Support/Path.h"
30#include "llvm/Support/TimeProfiler.h"
31#include "llvm/Support/raw_ostream.h"
32#include <optional>
33
34using namespace llvm;
35using namespace llvm::ELF;
36using namespace llvm::object;
37using namespace llvm::sys;
38using namespace llvm::sys::fs;
39using namespace llvm::support::endian;
40using namespace lld;
41using namespace lld::elf;
42
43// This function is explicitly instantiated in ARM.cpp, don't do it here to
44// avoid warnings with MSVC.
45extern template void ObjFile<ELF32LE>::importCmseSymbols();
46extern template void ObjFile<ELF32BE>::importCmseSymbols();
47extern template void ObjFile<ELF64LE>::importCmseSymbols();
48extern template void ObjFile<ELF64BE>::importCmseSymbols();
49
50// Returns "<internal>", "foo.a(bar.o)" or "baz.o".
51std::string elf::toStr(Ctx &ctx, const InputFile *f) {
52 static std::mutex mu;
53 if (!f)
54 return "<internal>";
55
56 {
57 std::lock_guard<std::mutex> lock(mu);
58 if (f->toStringCache.empty()) {
59 if (f->archiveName.empty())
60 f->toStringCache = f->getName();
61 else
62 (f->archiveName + "(" + f->getName() + ")").toVector(Out&: f->toStringCache);
63 }
64 }
65 return std::string(f->toStringCache);
66}
67
68const ELFSyncStream &elf::operator<<(const ELFSyncStream &s,
69 const InputFile *f) {
70 return s << toStr(ctx&: s.ctx, f);
71}
72
73static ELFKind getELFKind(Ctx &ctx, MemoryBufferRef mb, StringRef archiveName) {
74 unsigned char size;
75 unsigned char endian;
76 std::tie(args&: size, args&: endian) = getElfArchType(Object: mb.getBuffer());
77
78 auto report = [&](StringRef msg) {
79 StringRef filename = mb.getBufferIdentifier();
80 if (archiveName.empty())
81 Fatal(ctx) << filename << ": " << msg;
82 else
83 Fatal(ctx) << archiveName << "(" << filename << "): " << msg;
84 };
85
86 if (!mb.getBuffer().starts_with(Prefix: ElfMagic))
87 report("not an ELF file");
88 if (endian != ELFDATA2LSB && endian != ELFDATA2MSB)
89 report("corrupted ELF file: invalid data encoding");
90 if (size != ELFCLASS32 && size != ELFCLASS64)
91 report("corrupted ELF file: invalid file class");
92
93 size_t bufSize = mb.getBuffer().size();
94 if ((size == ELFCLASS32 && bufSize < sizeof(Elf32_Ehdr)) ||
95 (size == ELFCLASS64 && bufSize < sizeof(Elf64_Ehdr)))
96 report("corrupted ELF file: file is too short");
97
98 if (size == ELFCLASS32)
99 return (endian == ELFDATA2LSB) ? ELF32LEKind : ELF32BEKind;
100 return (endian == ELFDATA2LSB) ? ELF64LEKind : ELF64BEKind;
101}
102
103// For ARM only, to set the EF_ARM_ABI_FLOAT_SOFT or EF_ARM_ABI_FLOAT_HARD
104// flag in the ELF Header we need to look at Tag_ABI_VFP_args to find out how
105// the input objects have been compiled.
106static void updateARMVFPArgs(Ctx &ctx, const ARMAttributeParser &attributes,
107 const InputFile *f) {
108 std::optional<unsigned> attr =
109 attributes.getAttributeValue(tag: ARMBuildAttrs::ABI_VFP_args);
110 if (!attr)
111 // If an ABI tag isn't present then it is implicitly given the value of 0
112 // which maps to ARMBuildAttrs::BaseAAPCS. However many assembler files,
113 // including some in glibc that don't use FP args (and should have value 3)
114 // don't have the attribute so we do not consider an implicit value of 0
115 // as a clash.
116 return;
117
118 unsigned vfpArgs = *attr;
119 ARMVFPArgKind arg;
120 switch (vfpArgs) {
121 case ARMBuildAttrs::BaseAAPCS:
122 arg = ARMVFPArgKind::Base;
123 break;
124 case ARMBuildAttrs::HardFPAAPCS:
125 arg = ARMVFPArgKind::VFP;
126 break;
127 case ARMBuildAttrs::ToolChainFPPCS:
128 // Tool chain specific convention that conforms to neither AAPCS variant.
129 arg = ARMVFPArgKind::ToolChain;
130 break;
131 case ARMBuildAttrs::CompatibleFPAAPCS:
132 // Object compatible with all conventions.
133 return;
134 default:
135 ErrAlways(ctx) << f << ": unknown Tag_ABI_VFP_args value: " << vfpArgs;
136 return;
137 }
138 // Follow ld.bfd and error if there is a mix of calling conventions.
139 if (ctx.arg.armVFPArgs != arg && ctx.arg.armVFPArgs != ARMVFPArgKind::Default)
140 ErrAlways(ctx) << f << ": incompatible Tag_ABI_VFP_args";
141 else
142 ctx.arg.armVFPArgs = arg;
143}
144
145// The ARM support in lld makes some use of instructions that are not available
146// on all ARM architectures. Namely:
147// - Use of BLX instruction for interworking between ARM and Thumb state.
148// - Use of the extended Thumb branch encoding in relocation.
149// - Use of the MOVT/MOVW instructions in Thumb Thunks.
150// The ARM Attributes section contains information about the architecture chosen
151// at compile time. We follow the convention that if at least one input object
152// is compiled with an architecture that supports these features then lld is
153// permitted to use them.
154static void updateSupportedARMFeatures(Ctx &ctx,
155 const ARMAttributeParser &attributes) {
156 std::optional<unsigned> attr =
157 attributes.getAttributeValue(tag: ARMBuildAttrs::CPU_arch);
158 if (!attr)
159 return;
160 auto arch = *attr;
161 switch (arch) {
162 case ARMBuildAttrs::Pre_v4:
163 case ARMBuildAttrs::v4:
164 case ARMBuildAttrs::v4T:
165 // Architectures prior to v5 do not support BLX instruction
166 break;
167 case ARMBuildAttrs::v5T:
168 case ARMBuildAttrs::v5TE:
169 case ARMBuildAttrs::v5TEJ:
170 case ARMBuildAttrs::v6:
171 case ARMBuildAttrs::v6KZ:
172 case ARMBuildAttrs::v6K:
173 ctx.arg.armHasBlx = true;
174 // Architectures used in pre-Cortex processors do not support
175 // The J1 = 1 J2 = 1 Thumb branch range extension, with the exception
176 // of Architecture v6T2 (arm1156t2-s and arm1156t2f-s) that do.
177 break;
178 default:
179 // All other Architectures have BLX and extended branch encoding
180 ctx.arg.armHasBlx = true;
181 ctx.arg.armJ1J2BranchEncoding = true;
182 if (arch != ARMBuildAttrs::v6_M && arch != ARMBuildAttrs::v6S_M)
183 // All Architectures used in Cortex processors with the exception
184 // of v6-M and v6S-M have the MOVT and MOVW instructions.
185 ctx.arg.armHasMovtMovw = true;
186 break;
187 }
188
189 // Only ARMv8-M or later architectures have CMSE support.
190 std::optional<unsigned> profile =
191 attributes.getAttributeValue(tag: ARMBuildAttrs::CPU_arch_profile);
192 if (!profile)
193 return;
194 if (arch >= ARMBuildAttrs::CPUArch::v8_M_Base &&
195 profile == ARMBuildAttrs::MicroControllerProfile)
196 ctx.arg.armCMSESupport = true;
197
198 // The thumb PLT entries require Thumb2 which can be used on multiple archs.
199 // For now, let's limit it to ones where ARM isn't available and we know have
200 // Thumb2.
201 std::optional<unsigned> armISA =
202 attributes.getAttributeValue(tag: ARMBuildAttrs::ARM_ISA_use);
203 std::optional<unsigned> thumb =
204 attributes.getAttributeValue(tag: ARMBuildAttrs::THUMB_ISA_use);
205 ctx.arg.armHasArmISA |= armISA && *armISA >= ARMBuildAttrs::Allowed;
206 ctx.arg.armHasThumb2ISA |= thumb && *thumb >= ARMBuildAttrs::AllowThumb32;
207}
208
209InputFile::InputFile(Ctx &ctx, Kind k, MemoryBufferRef m)
210 : ctx(ctx), mb(m), groupId(ctx.driver.nextGroupId), fileKind(k) {
211 // All files within the same --{start,end}-group get the same group ID.
212 // Otherwise, a new file will get a new group ID.
213 if (!ctx.driver.isInGroup)
214 ++ctx.driver.nextGroupId;
215}
216
217InputFile::~InputFile() {}
218
219std::optional<MemoryBufferRef> elf::readFile(Ctx &ctx, StringRef path) {
220 llvm::TimeTraceScope timeScope("Load input files", path);
221
222 // The --chroot option changes our virtual root directory.
223 // This is useful when you are dealing with files created by --reproduce.
224 if (!ctx.arg.chroot.empty() && path.starts_with(Prefix: "/"))
225 path = ctx.saver.save(S: ctx.arg.chroot + path);
226
227 bool remapped = false;
228 auto it = ctx.arg.remapInputs.find(Val: path);
229 if (it != ctx.arg.remapInputs.end()) {
230 path = it->second;
231 remapped = true;
232 } else {
233 for (const auto &[pat, toFile] : ctx.arg.remapInputsWildcards) {
234 if (pat.match(S: path)) {
235 path = toFile;
236 remapped = true;
237 break;
238 }
239 }
240 }
241 if (remapped) {
242 // Use /dev/null to indicate an input file that should be ignored. Change
243 // the path to NUL on Windows.
244#ifdef _WIN32
245 if (path == "/dev/null")
246 path = "NUL";
247#endif
248 }
249
250 Log(ctx) << path;
251 ctx.arg.dependencyFiles.insert(X: llvm::CachedHashString(path));
252
253 auto mbOrErr = MemoryBuffer::getFile(Filename: path, /*IsText=*/false,
254 /*RequiresNullTerminator=*/false);
255 if (auto ec = mbOrErr.getError()) {
256 ErrAlways(ctx) << "cannot open " << path << ": " << ec.message();
257 return std::nullopt;
258 }
259
260 MemoryBufferRef mbref = (*mbOrErr)->getMemBufferRef();
261 ctx.memoryBuffers.push_back(Elt: std::move(*mbOrErr)); // take MB ownership
262
263 if (ctx.tar)
264 ctx.tar->append(Path: relativeToRoot(path), Data: mbref.getBuffer());
265 return mbref;
266}
267
268// All input object files must be for the same architecture
269// (e.g. it does not make sense to link x86 object files with
270// MIPS object files.) This function checks for that error.
271static bool isCompatible(Ctx &ctx, InputFile *file) {
272 if (!file->isElf() && !isa<BitcodeFile>(Val: file))
273 return true;
274
275 if (file->ekind == ctx.arg.ekind && file->emachine == ctx.arg.emachine) {
276 if (ctx.arg.emachine != EM_MIPS)
277 return true;
278 if (isMipsN32Abi(ctx, f: *file) == ctx.arg.mipsN32Abi)
279 return true;
280 }
281
282 StringRef target =
283 !ctx.arg.bfdname.empty() ? ctx.arg.bfdname : ctx.arg.emulation;
284 if (!target.empty()) {
285 Err(ctx) << file << " is incompatible with " << target;
286 return false;
287 }
288
289 InputFile *existing = nullptr;
290 if (!ctx.objectFiles.empty())
291 existing = ctx.objectFiles[0];
292 else if (!ctx.sharedFiles.empty())
293 existing = ctx.sharedFiles[0];
294 else if (!ctx.bitcodeFiles.empty())
295 existing = ctx.bitcodeFiles[0];
296 auto diag = Err(ctx);
297 diag << file << " is incompatible";
298 if (existing)
299 diag << " with " << existing;
300 return false;
301}
302
303template <class ELFT> static void doParseFile(Ctx &ctx, InputFile *file) {
304 if (!isCompatible(ctx, file))
305 return;
306
307 // Lazy object file
308 if (file->lazy) {
309 if (auto *f = dyn_cast<BitcodeFile>(Val: file)) {
310 ctx.lazyBitcodeFiles.push_back(Elt: f);
311 f->parseLazy();
312 } else {
313 cast<ObjFile<ELFT>>(file)->parseLazy();
314 }
315 return;
316 }
317
318 if (ctx.arg.trace)
319 Msg(ctx) << file;
320
321 if (file->kind() == InputFile::ObjKind) {
322 ctx.objectFiles.push_back(Elt: cast<ELFFileBase>(Val: file));
323 cast<ObjFile<ELFT>>(file)->parse();
324 } else if (auto *f = dyn_cast<SharedFile>(Val: file)) {
325 f->parse<ELFT>();
326 } else if (auto *f = dyn_cast<BitcodeFile>(Val: file)) {
327 ctx.bitcodeFiles.push_back(Elt: f);
328 f->parse();
329 } else {
330 ctx.binaryFiles.push_back(Elt: cast<BinaryFile>(Val: file));
331 cast<BinaryFile>(Val: file)->parse();
332 }
333}
334
335// Add symbols in File to the symbol table.
336void elf::parseFile(Ctx &ctx, InputFile *file) {
337 invokeELFT(doParseFile, ctx, file);
338}
339
340// This function is explicitly instantiated in ARM.cpp. Mark it extern here,
341// to avoid warnings when building with MSVC.
342extern template void ObjFile<ELF32LE>::importCmseSymbols();
343extern template void ObjFile<ELF32BE>::importCmseSymbols();
344extern template void ObjFile<ELF64LE>::importCmseSymbols();
345extern template void ObjFile<ELF64BE>::importCmseSymbols();
346
347template <class ELFT>
348static void
349doParseFiles(Ctx &ctx,
350 const SmallVector<std::unique_ptr<InputFile>, 0> &files) {
351 // Add all files to the symbol table. This will add almost all symbols that we
352 // need to the symbol table. This process might add files to the link due to
353 // addDependentLibrary.
354 for (size_t i = 0; i < files.size(); ++i) {
355 llvm::TimeTraceScope timeScope("Parse input files", files[i]->getName());
356 doParseFile<ELFT>(ctx, files[i].get());
357 }
358 if (ctx.driver.armCmseImpLib)
359 cast<ObjFile<ELFT>>(*ctx.driver.armCmseImpLib).importCmseSymbols();
360}
361
362void elf::parseFiles(Ctx &ctx,
363 const SmallVector<std::unique_ptr<InputFile>, 0> &files) {
364 llvm::TimeTraceScope timeScope("Parse input files");
365 invokeELFT(doParseFiles, ctx, files);
366}
367
368// Concatenates arguments to construct a string representing an error location.
369StringRef InputFile::getNameForScript() const {
370 if (archiveName.empty())
371 return getName();
372
373 if (nameForScriptCache.empty())
374 nameForScriptCache = (archiveName + Twine(':') + getName()).str();
375
376 return nameForScriptCache;
377}
378
379// An ELF object file may contain a `.deplibs` section. If it exists, the
380// section contains a list of library specifiers such as `m` for libm. This
381// function resolves a given name by finding the first matching library checking
382// the various ways that a library can be specified to LLD. This ELF extension
383// is a form of autolinking and is called `dependent libraries`. It is currently
384// unique to LLVM and lld.
385static void addDependentLibrary(Ctx &ctx, StringRef specifier,
386 const InputFile *f) {
387 if (!ctx.arg.dependentLibraries)
388 return;
389 if (std::optional<std::string> s = searchLibraryBaseName(ctx, path: specifier))
390 ctx.driver.addFile(path: ctx.saver.save(S: *s), /*withLOption=*/true);
391 else if (std::optional<std::string> s = findFromSearchPaths(ctx, path: specifier))
392 ctx.driver.addFile(path: ctx.saver.save(S: *s), /*withLOption=*/true);
393 else if (fs::exists(Path: specifier))
394 ctx.driver.addFile(path: specifier, /*withLOption=*/false);
395 else
396 ErrAlways(ctx)
397 << f << ": unable to find library from dependent library specifier: "
398 << specifier;
399}
400
401// Record the membership of a section group so that in the garbage collection
402// pass, section group members are kept or discarded as a unit.
403template <class ELFT>
404static void handleSectionGroup(ArrayRef<InputSectionBase *> sections,
405 ArrayRef<typename ELFT::Word> entries) {
406 bool hasAlloc = false;
407 for (uint32_t index : entries.slice(1)) {
408 if (index >= sections.size())
409 return;
410 if (InputSectionBase *s = sections[index])
411 if (s != &InputSection::discarded && s->flags & SHF_ALLOC)
412 hasAlloc = true;
413 }
414
415 // If any member has the SHF_ALLOC flag, the whole group is subject to garbage
416 // collection. See the comment in markLive(). This rule retains .debug_types
417 // and .rela.debug_types.
418 if (!hasAlloc)
419 return;
420
421 // Connect the members in a circular doubly-linked list via
422 // nextInSectionGroup.
423 InputSectionBase *head;
424 InputSectionBase *prev = nullptr;
425 for (uint32_t index : entries.slice(1)) {
426 InputSectionBase *s = sections[index];
427 if (!s || s == &InputSection::discarded)
428 continue;
429 if (prev)
430 prev->nextInSectionGroup = s;
431 else
432 head = s;
433 prev = s;
434 }
435 if (prev)
436 prev->nextInSectionGroup = head;
437}
438
439template <class ELFT> void ObjFile<ELFT>::initDwarf() {
440 dwarf = std::make_unique<DWARFCache>(std::make_unique<DWARFContext>(
441 std::make_unique<LLDDwarfObj<ELFT>>(this), "",
442 [&](Error err) { Warn(ctx) << getName() + ": " << std::move(err); },
443 [&](Error warning) {
444 Warn(ctx) << getName() << ": " << std::move(warning);
445 }));
446}
447
448DWARFCache *ELFFileBase::getDwarf() {
449 assert(fileKind == ObjKind);
450 llvm::call_once(flag&: initDwarf, F: [this]() {
451 switch (ekind) {
452 default:
453 llvm_unreachable("");
454 case ELF32LEKind:
455 return cast<ObjFile<ELF32LE>>(Val: this)->initDwarf();
456 case ELF32BEKind:
457 return cast<ObjFile<ELF32BE>>(Val: this)->initDwarf();
458 case ELF64LEKind:
459 return cast<ObjFile<ELF64LE>>(Val: this)->initDwarf();
460 case ELF64BEKind:
461 return cast<ObjFile<ELF64BE>>(Val: this)->initDwarf();
462 }
463 });
464 return dwarf.get();
465}
466
467ELFFileBase::ELFFileBase(Ctx &ctx, Kind k, ELFKind ekind, MemoryBufferRef mb)
468 : InputFile(ctx, k, mb) {
469 this->ekind = ekind;
470}
471
472ELFFileBase::~ELFFileBase() {}
473
474template <typename Elf_Shdr>
475static const Elf_Shdr *findSection(ArrayRef<Elf_Shdr> sections, uint32_t type) {
476 for (const Elf_Shdr &sec : sections)
477 if (sec.sh_type == type)
478 return &sec;
479 return nullptr;
480}
481
482void ELFFileBase::init() {
483 switch (ekind) {
484 case ELF32LEKind:
485 init<ELF32LE>(k: fileKind);
486 break;
487 case ELF32BEKind:
488 init<ELF32BE>(k: fileKind);
489 break;
490 case ELF64LEKind:
491 init<ELF64LE>(k: fileKind);
492 break;
493 case ELF64BEKind:
494 init<ELF64BE>(k: fileKind);
495 break;
496 default:
497 llvm_unreachable("getELFKind");
498 }
499}
500
501template <class ELFT> void ELFFileBase::init(InputFile::Kind k) {
502 using Elf_Shdr = typename ELFT::Shdr;
503 using Elf_Sym = typename ELFT::Sym;
504
505 // Initialize trivial attributes.
506 const ELFFile<ELFT> &obj = getObj<ELFT>();
507 emachine = obj.getHeader().e_machine;
508 osabi = obj.getHeader().e_ident[llvm::ELF::EI_OSABI];
509 abiVersion = obj.getHeader().e_ident[llvm::ELF::EI_ABIVERSION];
510
511 ArrayRef<Elf_Shdr> sections = CHECK2(obj.sections(), this);
512 elfShdrs = sections.data();
513 numELFShdrs = sections.size();
514
515 // Find a symbol table.
516 const Elf_Shdr *symtabSec =
517 findSection(sections, k == SharedKind ? SHT_DYNSYM : SHT_SYMTAB);
518
519 if (!symtabSec)
520 return;
521
522 // Initialize members corresponding to a symbol table.
523 firstGlobal = symtabSec->sh_info;
524
525 ArrayRef<Elf_Sym> eSyms = CHECK2(obj.symbols(symtabSec), this);
526 if (firstGlobal == 0 || firstGlobal > eSyms.size())
527 Fatal(ctx) << this << ": invalid sh_info in symbol table";
528
529 elfSyms = reinterpret_cast<const void *>(eSyms.data());
530 numSymbols = eSyms.size();
531 stringTable = CHECK2(obj.getStringTableForSymtab(*symtabSec, sections), this);
532}
533
534template <class ELFT>
535uint32_t ObjFile<ELFT>::getSectionIndex(const Elf_Sym &sym) const {
536 return CHECK2(
537 this->getObj().getSectionIndex(sym, getELFSyms<ELFT>(), shndxTable),
538 this);
539}
540
541template <class ELFT> void ObjFile<ELFT>::parse(bool ignoreComdats) {
542 object::ELFFile<ELFT> obj = this->getObj();
543 // Read a section table. justSymbols is usually false.
544 if (this->justSymbols) {
545 initializeJustSymbols();
546 initializeSymbols(obj);
547 return;
548 }
549
550 // Handle dependent libraries and selection of section groups as these are not
551 // done in parallel.
552 ArrayRef<Elf_Shdr> objSections = getELFShdrs<ELFT>();
553 StringRef shstrtab = CHECK2(obj.getSectionStringTable(objSections), this);
554 uint64_t size = objSections.size();
555 sections.resize(size);
556 for (size_t i = 0; i != size; ++i) {
557 const Elf_Shdr &sec = objSections[i];
558 if (LLVM_LIKELY(sec.sh_type == SHT_PROGBITS))
559 continue;
560 if (LLVM_LIKELY(sec.sh_type == SHT_GROUP)) {
561 StringRef signature = getShtGroupSignature(sections: objSections, sec);
562 ArrayRef<Elf_Word> entries =
563 CHECK2(obj.template getSectionContentsAsArray<Elf_Word>(sec), this);
564 if (entries.empty())
565 Fatal(ctx) << this << ": empty SHT_GROUP";
566
567 Elf_Word flag = entries[0];
568 if (flag && flag != GRP_COMDAT)
569 Fatal(ctx) << this << ": unsupported SHT_GROUP format";
570
571 bool keepGroup = !flag || ignoreComdats ||
572 ctx.symtab->comdatGroups
573 .try_emplace(CachedHashStringRef(signature), this)
574 .second;
575 if (keepGroup) {
576 if (!ctx.arg.resolveGroups)
577 sections[i] = createInputSection(
578 idx: i, sec, name: check(obj.getSectionName(sec, shstrtab)));
579 } else {
580 // Otherwise, discard group members.
581 for (uint32_t secIndex : entries.slice(1)) {
582 if (secIndex >= size)
583 Fatal(ctx) << this
584 << ": invalid section index in group: " << secIndex;
585 sections[secIndex] = &InputSection::discarded;
586 }
587 }
588 continue;
589 }
590
591 if (sec.sh_type == SHT_LLVM_DEPENDENT_LIBRARIES && !ctx.arg.relocatable) {
592 StringRef name = check(obj.getSectionName(sec, shstrtab));
593 ArrayRef<char> data = CHECK2(
594 this->getObj().template getSectionContentsAsArray<char>(sec), this);
595 if (!data.empty() && data.back() != '\0') {
596 Err(ctx)
597 << this
598 << ": corrupted dependent libraries section (unterminated string): "
599 << name;
600 } else {
601 for (const char *d = data.begin(), *e = data.end(); d < e;) {
602 StringRef s(d);
603 addDependentLibrary(ctx, s, this);
604 d += s.size() + 1;
605 }
606 }
607 sections[i] = &InputSection::discarded;
608 continue;
609 }
610
611 switch (ctx.arg.emachine) {
612 case EM_ARM:
613 if (sec.sh_type == SHT_ARM_ATTRIBUTES) {
614 ARMAttributeParser attributes;
615 ArrayRef<uint8_t> contents =
616 check(this->getObj().getSectionContents(sec));
617 StringRef name = check(obj.getSectionName(sec, shstrtab));
618 sections[i] = &InputSection::discarded;
619 if (Error e = attributes.parse(section: contents, endian: ekind == ELF32LEKind
620 ? llvm::endianness::little
621 : llvm::endianness::big)) {
622 InputSection isec(*this, sec, name);
623 Warn(ctx) << &isec << ": " << std::move(e);
624 } else {
625 updateSupportedARMFeatures(ctx, attributes);
626 updateARMVFPArgs(ctx, attributes, this);
627
628 // FIXME: Retain the first attribute section we see. The eglibc ARM
629 // dynamic loaders require the presence of an attribute section for
630 // dlopen to work. In a full implementation we would merge all
631 // attribute sections.
632 if (ctx.in.attributes == nullptr) {
633 ctx.in.attributes =
634 std::make_unique<InputSection>(*this, sec, name);
635 sections[i] = ctx.in.attributes.get();
636 }
637 }
638 }
639 break;
640 case EM_AARCH64:
641 // FIXME: BuildAttributes have been implemented in llvm, but not yet in
642 // lld. Remove the section so that it does not accumulate in the output
643 // file. When support is implemented we expect not to output a build
644 // attributes section in files of type ET_EXEC or ET_SHARED, but ld -r
645 // ouptut will need a single merged attributes section.
646 if (sec.sh_type == SHT_AARCH64_ATTRIBUTES)
647 sections[i] = &InputSection::discarded;
648 // Producing a static binary with MTE globals is not currently supported,
649 // remove all SHT_AARCH64_MEMTAG_GLOBALS_STATIC sections as they're unused
650 // medatada, and we don't want them to end up in the output file for
651 // static executables.
652 if (sec.sh_type == SHT_AARCH64_MEMTAG_GLOBALS_STATIC &&
653 !canHaveMemtagGlobals(ctx))
654 sections[i] = &InputSection::discarded;
655 break;
656 }
657 }
658
659 // Read a symbol table.
660 initializeSymbols(obj);
661}
662
663// Sections with SHT_GROUP and comdat bits define comdat section groups.
664// They are identified and deduplicated by group name. This function
665// returns a group name.
666template <class ELFT>
667StringRef ObjFile<ELFT>::getShtGroupSignature(ArrayRef<Elf_Shdr> sections,
668 const Elf_Shdr &sec) {
669 typename ELFT::SymRange symbols = this->getELFSyms<ELFT>();
670 if (sec.sh_info >= symbols.size())
671 Fatal(ctx) << this << ": invalid symbol index";
672 const typename ELFT::Sym &sym = symbols[sec.sh_info];
673 return CHECK2(sym.getName(this->stringTable), this);
674}
675
676template <class ELFT>
677bool ObjFile<ELFT>::shouldMerge(const Elf_Shdr &sec, StringRef name) {
678 // On a regular link we don't merge sections if -O0 (default is -O1). This
679 // sometimes makes the linker significantly faster, although the output will
680 // be bigger.
681 //
682 // Doing the same for -r would create a problem as it would combine sections
683 // with different sh_entsize. One option would be to just copy every SHF_MERGE
684 // section as is to the output. While this would produce a valid ELF file with
685 // usable SHF_MERGE sections, tools like (llvm-)?dwarfdump get confused when
686 // they see two .debug_str. We could have separate logic for combining
687 // SHF_MERGE sections based both on their name and sh_entsize, but that seems
688 // to be more trouble than it is worth. Instead, we just use the regular (-O1)
689 // logic for -r.
690 if (ctx.arg.optimize == 0 && !ctx.arg.relocatable)
691 return false;
692
693 // A mergeable section with size 0 is useless because they don't have
694 // any data to merge. A mergeable string section with size 0 can be
695 // argued as invalid because it doesn't end with a null character.
696 // We'll avoid a mess by handling them as if they were non-mergeable.
697 if (sec.sh_size == 0)
698 return false;
699
700 // Check for sh_entsize. The ELF spec is not clear about the zero
701 // sh_entsize. It says that "the member [sh_entsize] contains 0 if
702 // the section does not hold a table of fixed-size entries". We know
703 // that Rust 1.13 produces a string mergeable section with a zero
704 // sh_entsize. Here we just accept it rather than being picky about it.
705 uint64_t entSize = sec.sh_entsize;
706 if (entSize == 0)
707 return false;
708 if (sec.sh_size % entSize)
709 ErrAlways(ctx) << this << ":(" << name << "): SHF_MERGE section size ("
710 << uint64_t(sec.sh_size)
711 << ") must be a multiple of sh_entsize (" << entSize << ")";
712 if (sec.sh_flags & SHF_WRITE)
713 Err(ctx) << this << ":(" << name
714 << "): writable SHF_MERGE section is not supported";
715
716 return true;
717}
718
719// This is for --just-symbols.
720//
721// --just-symbols is a very minor feature that allows you to link your
722// output against other existing program, so that if you load both your
723// program and the other program into memory, your output can refer the
724// other program's symbols.
725//
726// When the option is given, we link "just symbols". The section table is
727// initialized with null pointers.
728template <class ELFT> void ObjFile<ELFT>::initializeJustSymbols() {
729 sections.resize(numELFShdrs);
730}
731
732static bool isKnownSpecificSectionType(uint32_t t, uint32_t flags) {
733 if (SHT_LOUSER <= t && t <= SHT_HIUSER && !(flags & SHF_ALLOC))
734 return true;
735 if (SHT_LOOS <= t && t <= SHT_HIOS && !(flags & SHF_OS_NONCONFORMING))
736 return true;
737 // Allow all processor-specific types. This is different from GNU ld.
738 return SHT_LOPROC <= t && t <= SHT_HIPROC;
739}
740
741template <class ELFT>
742void ObjFile<ELFT>::initializeSections(bool ignoreComdats,
743 const llvm::object::ELFFile<ELFT> &obj) {
744 ArrayRef<Elf_Shdr> objSections = getELFShdrs<ELFT>();
745 StringRef shstrtab = CHECK2(obj.getSectionStringTable(objSections), this);
746 uint64_t size = objSections.size();
747 SmallVector<ArrayRef<Elf_Word>, 0> selectedGroups;
748 for (size_t i = 0; i != size; ++i) {
749 if (this->sections[i] == &InputSection::discarded)
750 continue;
751 const Elf_Shdr &sec = objSections[i];
752 const uint32_t type = sec.sh_type;
753
754 // SHF_EXCLUDE'ed sections are discarded by the linker. However,
755 // if -r is given, we'll let the final link discard such sections.
756 // This is compatible with GNU.
757 if ((sec.sh_flags & SHF_EXCLUDE) && !ctx.arg.relocatable) {
758 if (type == SHT_LLVM_CALL_GRAPH_PROFILE)
759 cgProfileSectionIndex = i;
760 if (type == SHT_LLVM_ADDRSIG) {
761 // We ignore the address-significance table if we know that the object
762 // file was created by objcopy or ld -r. This is because these tools
763 // will reorder the symbols in the symbol table, invalidating the data
764 // in the address-significance table, which refers to symbols by index.
765 if (sec.sh_link != 0)
766 this->addrsigSec = &sec;
767 else if (ctx.arg.icf == ICFLevel::Safe)
768 Warn(ctx) << this
769 << ": --icf=safe conservatively ignores "
770 "SHT_LLVM_ADDRSIG [index "
771 << i
772 << "] with sh_link=0 "
773 "(likely created using objcopy or ld -r)";
774 }
775 this->sections[i] = &InputSection::discarded;
776 continue;
777 }
778
779 switch (type) {
780 case SHT_GROUP: {
781 if (!ctx.arg.relocatable)
782 sections[i] = &InputSection::discarded;
783 StringRef signature =
784 cantFail(this->getELFSyms<ELFT>()[sec.sh_info].getName(stringTable));
785 ArrayRef<Elf_Word> entries =
786 cantFail(obj.template getSectionContentsAsArray<Elf_Word>(sec));
787 if ((entries[0] & GRP_COMDAT) == 0 || ignoreComdats ||
788 ctx.symtab->comdatGroups.find(Val: CachedHashStringRef(signature))
789 ->second == this)
790 selectedGroups.push_back(entries);
791 break;
792 }
793 case SHT_SYMTAB_SHNDX:
794 shndxTable = CHECK2(obj.getSHNDXTable(sec, objSections), this);
795 break;
796 case SHT_SYMTAB:
797 case SHT_STRTAB:
798 case SHT_REL:
799 case SHT_RELA:
800 case SHT_CREL:
801 case SHT_NULL:
802 break;
803 case SHT_PROGBITS:
804 case SHT_NOTE:
805 case SHT_NOBITS:
806 case SHT_INIT_ARRAY:
807 case SHT_FINI_ARRAY:
808 case SHT_PREINIT_ARRAY:
809 this->sections[i] =
810 createInputSection(idx: i, sec, name: check(obj.getSectionName(sec, shstrtab)));
811 break;
812 case SHT_LLVM_LTO:
813 // Discard .llvm.lto in a relocatable link that does not use the bitcode.
814 // The concatenated output does not properly reflect the linking
815 // semantics. In addition, since we do not use the bitcode wrapper format,
816 // the concatenated raw bitcode would be invalid.
817 if (ctx.arg.relocatable && !ctx.arg.fatLTOObjects) {
818 sections[i] = &InputSection::discarded;
819 break;
820 }
821 [[fallthrough]];
822 default:
823 this->sections[i] =
824 createInputSection(idx: i, sec, name: check(obj.getSectionName(sec, shstrtab)));
825 if (type == SHT_LLVM_SYMPART)
826 ctx.hasSympart.store(true, std::memory_order_relaxed);
827 else if (ctx.arg.rejectMismatch &&
828 !isKnownSpecificSectionType(type, sec.sh_flags))
829 Err(ctx) << this->sections[i] << ": unknown section type 0x"
830 << Twine::utohexstr(Val: type);
831 break;
832 }
833 }
834
835 // We have a second loop. It is used to:
836 // 1) handle SHF_LINK_ORDER sections.
837 // 2) create relocation sections. In some cases the section header index of a
838 // relocation section may be smaller than that of the relocated section. In
839 // such cases, the relocation section would attempt to reference a target
840 // section that has not yet been created. For simplicity, delay creation of
841 // relocation sections until now.
842 for (size_t i = 0; i != size; ++i) {
843 if (this->sections[i] == &InputSection::discarded)
844 continue;
845 const Elf_Shdr &sec = objSections[i];
846
847 if (isStaticRelSecType(sec.sh_type)) {
848 // Find a relocation target section and associate this section with that.
849 // Target may have been discarded if it is in a different section group
850 // and the group is discarded, even though it's a violation of the spec.
851 // We handle that situation gracefully by discarding dangling relocation
852 // sections.
853 const uint32_t info = sec.sh_info;
854 InputSectionBase *s = getRelocTarget(idx: i, info);
855 if (!s)
856 continue;
857
858 // ELF spec allows mergeable sections with relocations, but they are rare,
859 // and it is in practice hard to merge such sections by contents, because
860 // applying relocations at end of linking changes section contents. So, we
861 // simply handle such sections as non-mergeable ones. Degrading like this
862 // is acceptable because section merging is optional.
863 if (auto *ms = dyn_cast<MergeInputSection>(Val: s)) {
864 s = makeThreadLocal<InputSection>(args&: ms->file, args&: ms->name, args&: ms->type,
865 args&: ms->flags, args&: ms->addralign, args&: ms->entsize,
866 args: ms->contentMaybeDecompress());
867 sections[info] = s;
868 }
869
870 if (s->relSecIdx != 0)
871 ErrAlways(ctx) << s
872 << ": multiple relocation sections to one section are "
873 "not supported";
874 s->relSecIdx = i;
875
876 // Relocation sections are usually removed from the output, so return
877 // `nullptr` for the normal case. However, if -r or --emit-relocs is
878 // specified, we need to copy them to the output. (Some post link analysis
879 // tools specify --emit-relocs to obtain the information.)
880 if (ctx.arg.copyRelocs) {
881 auto *isec = makeThreadLocal<InputSection>(
882 *this, sec, check(obj.getSectionName(sec, shstrtab)));
883 // If the relocated section is discarded (due to /DISCARD/ or
884 // --gc-sections), the relocation section should be discarded as well.
885 s->dependentSections.push_back(NewVal: isec);
886 sections[i] = isec;
887 }
888 continue;
889 }
890
891 // A SHF_LINK_ORDER section with sh_link=0 is handled as if it did not have
892 // the flag.
893 if (!sec.sh_link || !(sec.sh_flags & SHF_LINK_ORDER))
894 continue;
895
896 InputSectionBase *linkSec = nullptr;
897 if (sec.sh_link < size)
898 linkSec = this->sections[sec.sh_link];
899 if (!linkSec) {
900 ErrAlways(ctx) << this
901 << ": invalid sh_link index: " << uint32_t(sec.sh_link);
902 continue;
903 }
904
905 // A SHF_LINK_ORDER section is discarded if its linked-to section is
906 // discarded.
907 InputSection *isec = cast<InputSection>(this->sections[i]);
908 linkSec->dependentSections.push_back(NewVal: isec);
909 if (!isa<InputSection>(Val: linkSec))
910 ErrAlways(ctx)
911 << "a section " << isec->name
912 << " with SHF_LINK_ORDER should not refer a non-regular section: "
913 << linkSec;
914 }
915
916 for (ArrayRef<Elf_Word> entries : selectedGroups)
917 handleSectionGroup<ELFT>(this->sections, entries);
918}
919
920template <typename ELFT>
921static void parseGnuPropertyNote(Ctx &ctx, ELFFileBase &f,
922 uint32_t featureAndType,
923 ArrayRef<uint8_t> &desc, const uint8_t *base,
924 ArrayRef<uint8_t> *data = nullptr) {
925 auto err = [&](const uint8_t *place) -> ELFSyncStream {
926 auto diag = Err(ctx);
927 diag << &f << ":(" << ".note.gnu.property+0x"
928 << Twine::utohexstr(Val: place - base) << "): ";
929 return diag;
930 };
931
932 while (!desc.empty()) {
933 const uint8_t *place = desc.data();
934 if (desc.size() < 8)
935 return void(err(place) << "program property is too short");
936 uint32_t type = read32<ELFT::Endianness>(desc.data());
937 uint32_t size = read32<ELFT::Endianness>(desc.data() + 4);
938 desc = desc.slice(N: 8);
939 if (desc.size() < size)
940 return void(err(place) << "program property is too short");
941
942 if (type == featureAndType) {
943 // We found a FEATURE_1_AND field. There may be more than one of these
944 // in a .note.gnu.property section, for a relocatable object we
945 // accumulate the bits set.
946 if (size < 4)
947 return void(err(place) << "FEATURE_1_AND entry is too short");
948 f.andFeatures |= read32<ELFT::Endianness>(desc.data());
949 } else if (ctx.arg.emachine == EM_AARCH64 &&
950 type == GNU_PROPERTY_AARCH64_FEATURE_PAUTH) {
951 ArrayRef<uint8_t> contents = data ? *data : desc;
952 if (f.aarch64PauthAbiCoreInfo) {
953 return void(
954 err(contents.data())
955 << "multiple GNU_PROPERTY_AARCH64_FEATURE_PAUTH entries are "
956 "not supported");
957 } else if (size != 16) {
958 return void(err(contents.data())
959 << "GNU_PROPERTY_AARCH64_FEATURE_PAUTH entry "
960 "is invalid: expected 16 bytes, but got "
961 << size);
962 }
963 f.aarch64PauthAbiCoreInfo = {
964 support::endian::read64<ELFT::Endianness>(&desc[0]),
965 support::endian::read64<ELFT::Endianness>(&desc[8])};
966 }
967
968 // Padding is present in the note descriptor, if necessary.
969 desc = desc.slice(alignTo<(ELFT::Is64Bits ? 8 : 4)>(size));
970 }
971}
972// Read the following info from the .note.gnu.property section and write it to
973// the corresponding fields in `ObjFile`:
974// - Feature flags (32 bits) representing x86, AArch64 or RISC-V features for
975// hardware-assisted call flow control;
976// - AArch64 PAuth ABI core info (16 bytes).
977template <class ELFT>
978static void readGnuProperty(Ctx &ctx, const InputSection &sec,
979 ObjFile<ELFT> &f) {
980 using Elf_Nhdr = typename ELFT::Nhdr;
981 using Elf_Note = typename ELFT::Note;
982
983 uint32_t featureAndType;
984 switch (ctx.arg.emachine) {
985 case EM_386:
986 case EM_X86_64:
987 featureAndType = GNU_PROPERTY_X86_FEATURE_1_AND;
988 break;
989 case EM_AARCH64:
990 featureAndType = GNU_PROPERTY_AARCH64_FEATURE_1_AND;
991 break;
992 case EM_RISCV:
993 featureAndType = GNU_PROPERTY_RISCV_FEATURE_1_AND;
994 break;
995 default:
996 return;
997 }
998
999 ArrayRef<uint8_t> data = sec.content();
1000 auto err = [&](const uint8_t *place) -> ELFSyncStream {
1001 auto diag = Err(ctx);
1002 diag << sec.file << ":(" << sec.name << "+0x"
1003 << Twine::utohexstr(Val: place - sec.content().data()) << "): ";
1004 return diag;
1005 };
1006 while (!data.empty()) {
1007 // Read one NOTE record.
1008 auto *nhdr = reinterpret_cast<const Elf_Nhdr *>(data.data());
1009 if (data.size() < sizeof(Elf_Nhdr) ||
1010 data.size() < nhdr->getSize(sec.addralign))
1011 return void(err(data.data()) << "data is too short");
1012
1013 Elf_Note note(*nhdr);
1014 if (nhdr->n_type != NT_GNU_PROPERTY_TYPE_0 || note.getName() != "GNU") {
1015 data = data.slice(nhdr->getSize(sec.addralign));
1016 continue;
1017 }
1018
1019 // Read a body of a NOTE record, which consists of type-length-value fields.
1020 ArrayRef<uint8_t> desc = note.getDesc(sec.addralign);
1021 const uint8_t *base = sec.content().data();
1022 parseGnuPropertyNote<ELFT>(ctx, f, featureAndType, desc, base, &data);
1023
1024 // Go to next NOTE record to look for more FEATURE_1_AND descriptions.
1025 data = data.slice(nhdr->getSize(sec.addralign));
1026 }
1027}
1028
1029template <class ELFT>
1030InputSectionBase *ObjFile<ELFT>::getRelocTarget(uint32_t idx, uint32_t info) {
1031 if (info < this->sections.size()) {
1032 InputSectionBase *target = this->sections[info];
1033
1034 // Strictly speaking, a relocation section must be included in the
1035 // group of the section it relocates. However, LLVM 3.3 and earlier
1036 // would fail to do so, so we gracefully handle that case.
1037 if (target == &InputSection::discarded)
1038 return nullptr;
1039
1040 if (target != nullptr)
1041 return target;
1042 }
1043
1044 Err(ctx) << this << ": relocation section (index " << idx
1045 << ") has invalid sh_info (" << info << ')';
1046 return nullptr;
1047}
1048
1049// The function may be called concurrently for different input files. For
1050// allocation, prefer makeThreadLocal which does not require holding a lock.
1051template <class ELFT>
1052InputSectionBase *ObjFile<ELFT>::createInputSection(uint32_t idx,
1053 const Elf_Shdr &sec,
1054 StringRef name) {
1055 if (name.starts_with(Prefix: ".n")) {
1056 // The GNU linker uses .note.GNU-stack section as a marker indicating
1057 // that the code in the object file does not expect that the stack is
1058 // executable (in terms of NX bit). If all input files have the marker,
1059 // the GNU linker adds a PT_GNU_STACK segment to tells the loader to
1060 // make the stack non-executable. Most object files have this section as
1061 // of 2017.
1062 //
1063 // But making the stack non-executable is a norm today for security
1064 // reasons. Failure to do so may result in a serious security issue.
1065 // Therefore, we make LLD always add PT_GNU_STACK unless it is
1066 // explicitly told to do otherwise (by -z execstack). Because the stack
1067 // executable-ness is controlled solely by command line options,
1068 // .note.GNU-stack sections are, with one exception, ignored. Report
1069 // an error if we encounter an executable .note.GNU-stack to force the
1070 // user to explicitly request an executable stack.
1071 if (name == ".note.GNU-stack") {
1072 if ((sec.sh_flags & SHF_EXECINSTR) && !ctx.arg.relocatable &&
1073 ctx.arg.zGnustack != GnuStackKind::Exec) {
1074 Err(ctx) << this
1075 << ": requires an executable stack, but -z execstack is not "
1076 "specified";
1077 }
1078 return &InputSection::discarded;
1079 }
1080
1081 // Object files that use processor features such as Intel Control-Flow
1082 // Enforcement (CET), AArch64 Branch Target Identification BTI or RISC-V
1083 // Zicfilp/Zicfiss extensions, use a .note.gnu.property section containing
1084 // a bitfield of feature bits like the GNU_PROPERTY_X86_FEATURE_1_IBT flag.
1085 //
1086 // Since we merge bitmaps from multiple object files to create a new
1087 // .note.gnu.property containing a single AND'ed bitmap, we discard an input
1088 // file's .note.gnu.property section.
1089 if (name == ".note.gnu.property") {
1090 readGnuProperty<ELFT>(ctx, InputSection(*this, sec, name), *this);
1091 return &InputSection::discarded;
1092 }
1093
1094 // Split stacks is a feature to support a discontiguous stack,
1095 // commonly used in the programming language Go. For the details,
1096 // see https://gcc.gnu.org/wiki/SplitStacks. An object file compiled
1097 // for split stack will include a .note.GNU-split-stack section.
1098 if (name == ".note.GNU-split-stack") {
1099 if (ctx.arg.relocatable) {
1100 ErrAlways(ctx) << "cannot mix split-stack and non-split-stack in a "
1101 "relocatable link";
1102 return &InputSection::discarded;
1103 }
1104 this->splitStack = true;
1105 return &InputSection::discarded;
1106 }
1107
1108 // An object file compiled for split stack, but where some of the
1109 // functions were compiled with the no_split_stack_attribute will
1110 // include a .note.GNU-no-split-stack section.
1111 if (name == ".note.GNU-no-split-stack") {
1112 this->someNoSplitStack = true;
1113 return &InputSection::discarded;
1114 }
1115
1116 // Strip existing .note.gnu.build-id sections so that the output won't have
1117 // more than one build-id. This is not usually a problem because input
1118 // object files normally don't have .build-id sections, but you can create
1119 // such files by "ld.{bfd,gold,lld} -r --build-id", and we want to guard
1120 // against it.
1121 if (name == ".note.gnu.build-id")
1122 return &InputSection::discarded;
1123 }
1124
1125 // The linker merges EH (exception handling) frames and creates a
1126 // .eh_frame_hdr section for runtime. So we handle them with a special
1127 // class. For relocatable outputs, they are just passed through.
1128 if (name == ".eh_frame" && !ctx.arg.relocatable)
1129 return makeThreadLocal<EhInputSection>(*this, sec, name);
1130
1131 if ((sec.sh_flags & SHF_MERGE) && shouldMerge(sec, name))
1132 return makeThreadLocal<MergeInputSection>(*this, sec, name);
1133 return makeThreadLocal<InputSection>(*this, sec, name);
1134}
1135
1136// Initialize symbols. symbols is a parallel array to the corresponding ELF
1137// symbol table.
1138template <class ELFT>
1139void ObjFile<ELFT>::initializeSymbols(const object::ELFFile<ELFT> &obj) {
1140 ArrayRef<Elf_Sym> eSyms = this->getELFSyms<ELFT>();
1141 if (!symbols)
1142 symbols = std::make_unique<Symbol *[]>(numSymbols);
1143
1144 // Some entries have been filled by LazyObjFile.
1145 auto *symtab = ctx.symtab.get();
1146 for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i)
1147 if (!symbols[i])
1148 symbols[i] = symtab->insert(CHECK2(eSyms[i].getName(stringTable), this));
1149
1150 // Perform symbol resolution on non-local symbols.
1151 SmallVector<unsigned, 32> undefineds;
1152 for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i) {
1153 const Elf_Sym &eSym = eSyms[i];
1154 uint32_t secIdx = eSym.st_shndx;
1155 if (secIdx == SHN_UNDEF) {
1156 undefineds.push_back(Elt: i);
1157 continue;
1158 }
1159
1160 uint8_t binding = eSym.getBinding();
1161 uint8_t stOther = eSym.st_other;
1162 uint8_t type = eSym.getType();
1163 uint64_t value = eSym.st_value;
1164 uint64_t size = eSym.st_size;
1165
1166 Symbol *sym = symbols[i];
1167 sym->isUsedInRegularObj = true;
1168 if (LLVM_UNLIKELY(eSym.st_shndx == SHN_COMMON)) {
1169 if (value == 0 || value >= UINT32_MAX)
1170 Err(ctx) << this << ": common symbol '" << sym->getName()
1171 << "' has invalid alignment: " << value;
1172 hasCommonSyms = true;
1173 sym->resolve(ctx, CommonSymbol{ctx, this, StringRef(), binding, stOther,
1174 type, value, size});
1175 continue;
1176 }
1177
1178 // Handle global defined symbols. Defined::section will be set in postParse.
1179 sym->resolve(ctx, Defined{ctx, this, StringRef(), binding, stOther, type,
1180 value, size, nullptr});
1181 }
1182
1183 // Undefined symbols (excluding those defined relative to non-prevailing
1184 // sections) can trigger recursive extract. Process defined symbols first so
1185 // that the relative order between a defined symbol and an undefined symbol
1186 // does not change the symbol resolution behavior. In addition, a set of
1187 // interconnected symbols will all be resolved to the same file, instead of
1188 // being resolved to different files.
1189 for (unsigned i : undefineds) {
1190 const Elf_Sym &eSym = eSyms[i];
1191 Symbol *sym = symbols[i];
1192 sym->resolve(ctx, Undefined{this, StringRef(), eSym.getBinding(),
1193 eSym.st_other, eSym.getType()});
1194 sym->isUsedInRegularObj = true;
1195 sym->referenced = true;
1196 }
1197}
1198
1199template <class ELFT>
1200void ObjFile<ELFT>::initSectionsAndLocalSyms(bool ignoreComdats) {
1201 if (!justSymbols)
1202 initializeSections(ignoreComdats, obj: getObj());
1203
1204 if (!firstGlobal)
1205 return;
1206 SymbolUnion *locals = makeThreadLocalN<SymbolUnion>(firstGlobal);
1207 memset(locals, 0, sizeof(SymbolUnion) * firstGlobal);
1208
1209 ArrayRef<Elf_Sym> eSyms = this->getELFSyms<ELFT>();
1210 for (size_t i = 0, end = firstGlobal; i != end; ++i) {
1211 const Elf_Sym &eSym = eSyms[i];
1212 uint32_t secIdx = eSym.st_shndx;
1213 if (LLVM_UNLIKELY(secIdx == SHN_XINDEX))
1214 secIdx = check(getExtendedSymbolTableIndex<ELFT>(eSym, i, shndxTable));
1215 else if (secIdx >= SHN_LORESERVE)
1216 secIdx = 0;
1217 if (LLVM_UNLIKELY(secIdx >= sections.size())) {
1218 Err(ctx) << this << ": invalid section index: " << secIdx;
1219 secIdx = 0;
1220 }
1221 if (LLVM_UNLIKELY(eSym.getBinding() != STB_LOCAL))
1222 ErrAlways(ctx) << this << ": non-local symbol (" << i
1223 << ") found at index < .symtab's sh_info (" << end << ")";
1224
1225 InputSectionBase *sec = sections[secIdx];
1226 uint8_t type = eSym.getType();
1227 if (type == STT_FILE)
1228 sourceFile = CHECK2(eSym.getName(stringTable), this);
1229 unsigned stName = eSym.st_name;
1230 if (LLVM_UNLIKELY(stringTable.size() <= stName)) {
1231 Err(ctx) << this << ": invalid symbol name offset";
1232 stName = 0;
1233 }
1234 StringRef name(stringTable.data() + stName);
1235
1236 symbols[i] = reinterpret_cast<Symbol *>(locals + i);
1237 if (eSym.st_shndx == SHN_UNDEF || sec == &InputSection::discarded)
1238 new (symbols[i]) Undefined(this, name, STB_LOCAL, eSym.st_other, type,
1239 /*discardedSecIdx=*/secIdx);
1240 else
1241 new (symbols[i]) Defined(ctx, this, name, STB_LOCAL, eSym.st_other, type,
1242 eSym.st_value, eSym.st_size, sec);
1243 symbols[i]->partition = 1;
1244 symbols[i]->isUsedInRegularObj = true;
1245 }
1246}
1247
1248// Called after all ObjFile::parse is called for all ObjFiles. This checks
1249// duplicate symbols and may do symbol property merge in the future.
1250template <class ELFT> void ObjFile<ELFT>::postParse() {
1251 static std::mutex mu;
1252 ArrayRef<Elf_Sym> eSyms = this->getELFSyms<ELFT>();
1253 for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i) {
1254 const Elf_Sym &eSym = eSyms[i];
1255 Symbol &sym = *symbols[i];
1256 uint32_t secIdx = eSym.st_shndx;
1257 uint8_t binding = eSym.getBinding();
1258 if (LLVM_UNLIKELY(binding != STB_GLOBAL && binding != STB_WEAK &&
1259 binding != STB_GNU_UNIQUE))
1260 Err(ctx) << this << ": symbol (" << i
1261 << ") has invalid binding: " << (int)binding;
1262
1263 // st_value of STT_TLS represents the assigned offset, not the actual
1264 // address which is used by STT_FUNC and STT_OBJECT. STT_TLS symbols can
1265 // only be referenced by special TLS relocations. It is usually an error if
1266 // a STT_TLS symbol is replaced by a non-STT_TLS symbol, vice versa.
1267 if (LLVM_UNLIKELY(sym.isTls()) && eSym.getType() != STT_TLS &&
1268 eSym.getType() != STT_NOTYPE)
1269 Err(ctx) << "TLS attribute mismatch: " << &sym << "\n>>> in " << sym.file
1270 << "\n>>> in " << this;
1271
1272 // Handle non-COMMON defined symbol below. !sym.file allows a symbol
1273 // assignment to redefine a symbol without an error.
1274 if (!sym.isDefined() || secIdx == SHN_UNDEF)
1275 continue;
1276 if (LLVM_UNLIKELY(secIdx >= SHN_LORESERVE)) {
1277 if (secIdx == SHN_COMMON)
1278 continue;
1279 if (secIdx == SHN_XINDEX)
1280 secIdx = check(getExtendedSymbolTableIndex<ELFT>(eSym, i, shndxTable));
1281 else
1282 secIdx = 0;
1283 }
1284
1285 if (LLVM_UNLIKELY(secIdx >= sections.size())) {
1286 Err(ctx) << this << ": invalid section index: " << secIdx;
1287 continue;
1288 }
1289 InputSectionBase *sec = sections[secIdx];
1290 if (sec == &InputSection::discarded) {
1291 if (sym.traced) {
1292 printTraceSymbol(sym: Undefined{this, sym.getName(), sym.binding,
1293 sym.stOther, sym.type, secIdx},
1294 name: sym.getName());
1295 }
1296 if (sym.file == this) {
1297 std::lock_guard<std::mutex> lock(mu);
1298 ctx.nonPrevailingSyms.emplace_back(&sym, secIdx);
1299 }
1300 continue;
1301 }
1302
1303 if (sym.file == this) {
1304 cast<Defined>(Val&: sym).section = sec;
1305 continue;
1306 }
1307
1308 if (sym.binding == STB_WEAK || binding == STB_WEAK)
1309 continue;
1310 std::lock_guard<std::mutex> lock(mu);
1311 ctx.duplicates.push_back(Elt: {&sym, this, sec, eSym.st_value});
1312 }
1313}
1314
1315// The handling of tentative definitions (COMMON symbols) in archives is murky.
1316// A tentative definition will be promoted to a global definition if there are
1317// no non-tentative definitions to dominate it. When we hold a tentative
1318// definition to a symbol and are inspecting archive members for inclusion
1319// there are 2 ways we can proceed:
1320//
1321// 1) Consider the tentative definition a 'real' definition (ie promotion from
1322// tentative to real definition has already happened) and not inspect
1323// archive members for Global/Weak definitions to replace the tentative
1324// definition. An archive member would only be included if it satisfies some
1325// other undefined symbol. This is the behavior Gold uses.
1326//
1327// 2) Consider the tentative definition as still undefined (ie the promotion to
1328// a real definition happens only after all symbol resolution is done).
1329// The linker searches archive members for STB_GLOBAL definitions to
1330// replace the tentative definition with. This is the behavior used by
1331// GNU ld.
1332//
1333// The second behavior is inherited from SysVR4, which based it on the FORTRAN
1334// COMMON BLOCK model. This behavior is needed for proper initialization in old
1335// (pre F90) FORTRAN code that is packaged into an archive.
1336//
1337// The following functions search archive members for definitions to replace
1338// tentative definitions (implementing behavior 2).
1339static bool isBitcodeNonCommonDef(MemoryBufferRef mb, StringRef symName,
1340 StringRef archiveName) {
1341 IRSymtabFile symtabFile = check(e: readIRSymtab(MBRef: mb));
1342 for (const irsymtab::Reader::SymbolRef &sym :
1343 symtabFile.TheReader.symbols()) {
1344 if (sym.isGlobal() && sym.getName() == symName)
1345 return !sym.isUndefined() && !sym.isWeak() && !sym.isCommon();
1346 }
1347 return false;
1348}
1349
1350template <class ELFT>
1351static bool isNonCommonDef(Ctx &ctx, ELFKind ekind, MemoryBufferRef mb,
1352 StringRef symName, StringRef archiveName) {
1353 ObjFile<ELFT> *obj = make<ObjFile<ELFT>>(ctx, ekind, mb, archiveName);
1354 obj->init();
1355 StringRef stringtable = obj->getStringTable();
1356
1357 for (auto sym : obj->template getGlobalELFSyms<ELFT>()) {
1358 Expected<StringRef> name = sym.getName(stringtable);
1359 if (name && name.get() == symName)
1360 return sym.isDefined() && sym.getBinding() == STB_GLOBAL &&
1361 !sym.isCommon();
1362 }
1363 return false;
1364}
1365
1366static bool isNonCommonDef(Ctx &ctx, MemoryBufferRef mb, StringRef symName,
1367 StringRef archiveName) {
1368 switch (getELFKind(ctx, mb, archiveName)) {
1369 case ELF32LEKind:
1370 return isNonCommonDef<ELF32LE>(ctx, ekind: ELF32LEKind, mb, symName, archiveName);
1371 case ELF32BEKind:
1372 return isNonCommonDef<ELF32BE>(ctx, ekind: ELF32BEKind, mb, symName, archiveName);
1373 case ELF64LEKind:
1374 return isNonCommonDef<ELF64LE>(ctx, ekind: ELF64LEKind, mb, symName, archiveName);
1375 case ELF64BEKind:
1376 return isNonCommonDef<ELF64BE>(ctx, ekind: ELF64BEKind, mb, symName, archiveName);
1377 default:
1378 llvm_unreachable("getELFKind");
1379 }
1380}
1381
1382SharedFile::SharedFile(Ctx &ctx, MemoryBufferRef m, StringRef defaultSoName)
1383 : ELFFileBase(ctx, SharedKind, getELFKind(ctx, mb: m, archiveName: ""), m),
1384 soName(defaultSoName), isNeeded(!ctx.arg.asNeeded) {}
1385
1386// Parse the version definitions in the object file if present, and return a
1387// vector whose nth element contains a pointer to the Elf_Verdef for version
1388// identifier n. Version identifiers that are not definitions map to nullptr.
1389template <typename ELFT>
1390static SmallVector<const void *, 0>
1391parseVerdefs(const uint8_t *base, const typename ELFT::Shdr *sec) {
1392 if (!sec)
1393 return {};
1394
1395 // Build the Verdefs array by following the chain of Elf_Verdef objects
1396 // from the start of the .gnu.version_d section.
1397 SmallVector<const void *, 0> verdefs;
1398 const uint8_t *verdef = base + sec->sh_offset;
1399 for (unsigned i = 0, e = sec->sh_info; i != e; ++i) {
1400 auto *curVerdef = reinterpret_cast<const typename ELFT::Verdef *>(verdef);
1401 verdef += curVerdef->vd_next;
1402 unsigned verdefIndex = curVerdef->vd_ndx;
1403 if (verdefIndex >= verdefs.size())
1404 verdefs.resize(N: verdefIndex + 1);
1405 verdefs[verdefIndex] = curVerdef;
1406 }
1407 return verdefs;
1408}
1409
1410// Parse SHT_GNU_verneed to properly set the name of a versioned undefined
1411// symbol. We detect fatal issues which would cause vulnerabilities, but do not
1412// implement sophisticated error checking like in llvm-readobj because the value
1413// of such diagnostics is low.
1414template <typename ELFT>
1415std::vector<uint32_t> SharedFile::parseVerneed(const ELFFile<ELFT> &obj,
1416 const typename ELFT::Shdr *sec) {
1417 if (!sec)
1418 return {};
1419 std::vector<uint32_t> verneeds;
1420 ArrayRef<uint8_t> data = CHECK2(obj.getSectionContents(*sec), this);
1421 const uint8_t *verneedBuf = data.begin();
1422 for (unsigned i = 0; i != sec->sh_info; ++i) {
1423 if (verneedBuf + sizeof(typename ELFT::Verneed) > data.end()) {
1424 Err(ctx) << this << " has an invalid Verneed";
1425 break;
1426 }
1427 auto *vn = reinterpret_cast<const typename ELFT::Verneed *>(verneedBuf);
1428 const uint8_t *vernauxBuf = verneedBuf + vn->vn_aux;
1429 for (unsigned j = 0; j != vn->vn_cnt; ++j) {
1430 if (vernauxBuf + sizeof(typename ELFT::Vernaux) > data.end()) {
1431 Err(ctx) << this << " has an invalid Vernaux";
1432 break;
1433 }
1434 auto *aux = reinterpret_cast<const typename ELFT::Vernaux *>(vernauxBuf);
1435 if (aux->vna_name >= this->stringTable.size()) {
1436 Err(ctx) << this << " has a Vernaux with an invalid vna_name";
1437 break;
1438 }
1439 uint16_t version = aux->vna_other & VERSYM_VERSION;
1440 if (version >= verneeds.size())
1441 verneeds.resize(new_size: version + 1);
1442 verneeds[version] = aux->vna_name;
1443 vernauxBuf += aux->vna_next;
1444 }
1445 verneedBuf += vn->vn_next;
1446 }
1447 return verneeds;
1448}
1449
1450// Parse PT_GNU_PROPERTY segments in DSO. The process is similar to
1451// readGnuProperty, but we don't have the InputSection information.
1452template <typename ELFT>
1453void SharedFile::parseGnuAndFeatures(const ELFFile<ELFT> &obj) {
1454 if (ctx.arg.emachine != EM_AARCH64)
1455 return;
1456 const uint8_t *base = obj.base();
1457 auto phdrs = CHECK2(obj.program_headers(), this);
1458 for (auto phdr : phdrs) {
1459 if (phdr.p_type != PT_GNU_PROPERTY)
1460 continue;
1461 typename ELFT::Note note(
1462 *reinterpret_cast<const typename ELFT::Nhdr *>(base + phdr.p_offset));
1463 if (note.getType() != NT_GNU_PROPERTY_TYPE_0 || note.getName() != "GNU")
1464 continue;
1465
1466 ArrayRef<uint8_t> desc = note.getDesc(phdr.p_align);
1467 parseGnuPropertyNote<ELFT>(ctx, *this, GNU_PROPERTY_AARCH64_FEATURE_1_AND,
1468 desc, base);
1469 }
1470}
1471
1472// We do not usually care about alignments of data in shared object
1473// files because the loader takes care of it. However, if we promote a
1474// DSO symbol to point to .bss due to copy relocation, we need to keep
1475// the original alignment requirements. We infer it in this function.
1476template <typename ELFT>
1477static uint64_t getAlignment(ArrayRef<typename ELFT::Shdr> sections,
1478 const typename ELFT::Sym &sym) {
1479 uint64_t ret = UINT64_MAX;
1480 if (sym.st_value)
1481 ret = 1ULL << llvm::countr_zero(Val: (uint64_t)sym.st_value);
1482 if (0 < sym.st_shndx && sym.st_shndx < sections.size())
1483 ret = std::min<uint64_t>(ret, sections[sym.st_shndx].sh_addralign);
1484 return (ret > UINT32_MAX) ? 0 : ret;
1485}
1486
1487// Fully parse the shared object file.
1488//
1489// This function parses symbol versions. If a DSO has version information,
1490// the file has a ".gnu.version_d" section which contains symbol version
1491// definitions. Each symbol is associated to one version through a table in
1492// ".gnu.version" section. That table is a parallel array for the symbol
1493// table, and each table entry contains an index in ".gnu.version_d".
1494//
1495// The special index 0 is reserved for VERF_NDX_LOCAL and 1 is for
1496// VER_NDX_GLOBAL. There's no table entry for these special versions in
1497// ".gnu.version_d".
1498//
1499// The file format for symbol versioning is perhaps a bit more complicated
1500// than necessary, but you can easily understand the code if you wrap your
1501// head around the data structure described above.
1502template <class ELFT> void SharedFile::parse() {
1503 using Elf_Dyn = typename ELFT::Dyn;
1504 using Elf_Shdr = typename ELFT::Shdr;
1505 using Elf_Sym = typename ELFT::Sym;
1506 using Elf_Verdef = typename ELFT::Verdef;
1507 using Elf_Versym = typename ELFT::Versym;
1508
1509 ArrayRef<Elf_Dyn> dynamicTags;
1510 const ELFFile<ELFT> obj = this->getObj<ELFT>();
1511 ArrayRef<Elf_Shdr> sections = getELFShdrs<ELFT>();
1512
1513 const Elf_Shdr *versymSec = nullptr;
1514 const Elf_Shdr *verdefSec = nullptr;
1515 const Elf_Shdr *verneedSec = nullptr;
1516 symbols = std::make_unique<Symbol *[]>(num: numSymbols);
1517
1518 // Search for .dynsym, .dynamic, .symtab, .gnu.version and .gnu.version_d.
1519 for (const Elf_Shdr &sec : sections) {
1520 switch (sec.sh_type) {
1521 default:
1522 continue;
1523 case SHT_DYNAMIC:
1524 dynamicTags =
1525 CHECK2(obj.template getSectionContentsAsArray<Elf_Dyn>(sec), this);
1526 break;
1527 case SHT_GNU_versym:
1528 versymSec = &sec;
1529 break;
1530 case SHT_GNU_verdef:
1531 verdefSec = &sec;
1532 break;
1533 case SHT_GNU_verneed:
1534 verneedSec = &sec;
1535 break;
1536 }
1537 }
1538
1539 if (versymSec && numSymbols == 0) {
1540 ErrAlways(ctx) << "SHT_GNU_versym should be associated with symbol table";
1541 return;
1542 }
1543
1544 // Search for a DT_SONAME tag to initialize this->soName.
1545 for (const Elf_Dyn &dyn : dynamicTags) {
1546 if (dyn.d_tag == DT_NEEDED) {
1547 uint64_t val = dyn.getVal();
1548 if (val >= this->stringTable.size()) {
1549 Err(ctx) << this << ": invalid DT_NEEDED entry";
1550 return;
1551 }
1552 dtNeeded.push_back(Elt: this->stringTable.data() + val);
1553 } else if (dyn.d_tag == DT_SONAME) {
1554 uint64_t val = dyn.getVal();
1555 if (val >= this->stringTable.size()) {
1556 Err(ctx) << this << ": invalid DT_SONAME entry";
1557 return;
1558 }
1559 soName = this->stringTable.data() + val;
1560 }
1561 }
1562
1563 // DSOs are uniquified not by filename but by soname.
1564 StringSaver &ss = ctx.saver;
1565 DenseMap<CachedHashStringRef, SharedFile *>::iterator it;
1566 bool wasInserted;
1567 std::tie(args&: it, args&: wasInserted) =
1568 ctx.symtab->soNames.try_emplace(Key: CachedHashStringRef(soName), Args: this);
1569
1570 // If a DSO appears more than once on the command line with and without
1571 // --as-needed, --no-as-needed takes precedence over --as-needed because a
1572 // user can add an extra DSO with --no-as-needed to force it to be added to
1573 // the dependency list.
1574 it->second->isNeeded |= isNeeded;
1575 if (!wasInserted)
1576 return;
1577
1578 ctx.sharedFiles.push_back(Elt: this);
1579
1580 verdefs = parseVerdefs<ELFT>(obj.base(), verdefSec);
1581 std::vector<uint32_t> verneeds = parseVerneed<ELFT>(obj, verneedSec);
1582 parseGnuAndFeatures<ELFT>(obj);
1583
1584 // Parse ".gnu.version" section which is a parallel array for the symbol
1585 // table. If a given file doesn't have a ".gnu.version" section, we use
1586 // VER_NDX_GLOBAL.
1587 size_t size = numSymbols - firstGlobal;
1588 std::vector<uint16_t> versyms(size, VER_NDX_GLOBAL);
1589 if (versymSec) {
1590 ArrayRef<Elf_Versym> versym =
1591 CHECK2(obj.template getSectionContentsAsArray<Elf_Versym>(*versymSec),
1592 this)
1593 .slice(firstGlobal);
1594 for (size_t i = 0; i < size; ++i)
1595 versyms[i] = versym[i].vs_index;
1596 }
1597
1598 // System libraries can have a lot of symbols with versions. Using a
1599 // fixed buffer for computing the versions name (foo@ver) can save a
1600 // lot of allocations.
1601 SmallString<0> versionedNameBuffer;
1602
1603 // Add symbols to the symbol table.
1604 ArrayRef<Elf_Sym> syms = this->getGlobalELFSyms<ELFT>();
1605 for (size_t i = 0, e = syms.size(); i != e; ++i) {
1606 const Elf_Sym &sym = syms[i];
1607
1608 // ELF spec requires that all local symbols precede weak or global
1609 // symbols in each symbol table, and the index of first non-local symbol
1610 // is stored to sh_info. If a local symbol appears after some non-local
1611 // symbol, that's a violation of the spec.
1612 StringRef name = CHECK2(sym.getName(stringTable), this);
1613 if (sym.getBinding() == STB_LOCAL) {
1614 Err(ctx) << this << ": invalid local symbol '" << name
1615 << "' in global part of symbol table";
1616 continue;
1617 }
1618
1619 const uint16_t ver = versyms[i], idx = ver & ~VERSYM_HIDDEN;
1620 if (sym.isUndefined()) {
1621 // For unversioned undefined symbols, VER_NDX_GLOBAL makes more sense but
1622 // as of binutils 2.34, GNU ld produces VER_NDX_LOCAL.
1623 if (ver != VER_NDX_LOCAL && ver != VER_NDX_GLOBAL) {
1624 if (idx >= verneeds.size()) {
1625 ErrAlways(ctx) << "corrupt input file: version need index " << idx
1626 << " for symbol " << name
1627 << " is out of bounds\n>>> defined in " << this;
1628 continue;
1629 }
1630 StringRef verName = stringTable.data() + verneeds[idx];
1631 versionedNameBuffer.clear();
1632 name = ss.save(S: (name + "@" + verName).toStringRef(Out&: versionedNameBuffer));
1633 }
1634 Symbol *s = ctx.symtab->addSymbol(
1635 newSym: Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
1636 s->isExported = true;
1637 if (sym.getBinding() != STB_WEAK &&
1638 ctx.arg.unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore)
1639 requiredSymbols.push_back(Elt: s);
1640 continue;
1641 }
1642
1643 if (ver == VER_NDX_LOCAL ||
1644 (ver != VER_NDX_GLOBAL && idx >= verdefs.size())) {
1645 // In GNU ld < 2.31 (before 3be08ea4728b56d35e136af4e6fd3086ade17764), the
1646 // MIPS port puts _gp_disp symbol into DSO files and incorrectly assigns
1647 // VER_NDX_LOCAL. Workaround this bug.
1648 if (ctx.arg.emachine == EM_MIPS && name == "_gp_disp")
1649 continue;
1650 ErrAlways(ctx) << "corrupt input file: version definition index " << idx
1651 << " for symbol " << name
1652 << " is out of bounds\n>>> defined in " << this;
1653 continue;
1654 }
1655
1656 uint32_t alignment = getAlignment<ELFT>(sections, sym);
1657 if (ver == idx) {
1658 auto *s = ctx.symtab->addSymbol(
1659 newSym: SharedSymbol{*this, name, sym.getBinding(), sym.st_other,
1660 sym.getType(), sym.st_value, sym.st_size, alignment});
1661 s->dsoDefined = true;
1662 if (s->file == this)
1663 s->versionId = ver;
1664 }
1665
1666 // Also add the symbol with the versioned name to handle undefined symbols
1667 // with explicit versions.
1668 if (ver == VER_NDX_GLOBAL)
1669 continue;
1670
1671 StringRef verName =
1672 stringTable.data() +
1673 reinterpret_cast<const Elf_Verdef *>(verdefs[idx])->getAux()->vda_name;
1674 versionedNameBuffer.clear();
1675 name = (name + "@" + verName).toStringRef(Out&: versionedNameBuffer);
1676 auto *s = ctx.symtab->addSymbol(
1677 newSym: SharedSymbol{*this, ss.save(S: name), sym.getBinding(), sym.st_other,
1678 sym.getType(), sym.st_value, sym.st_size, alignment});
1679 s->dsoDefined = true;
1680 if (s->file == this)
1681 s->versionId = idx;
1682 }
1683}
1684
1685static ELFKind getBitcodeELFKind(const Triple &t) {
1686 if (t.isLittleEndian())
1687 return t.isArch64Bit() ? ELF64LEKind : ELF32LEKind;
1688 return t.isArch64Bit() ? ELF64BEKind : ELF32BEKind;
1689}
1690
1691static uint16_t getBitcodeMachineKind(Ctx &ctx, StringRef path,
1692 const Triple &t) {
1693 switch (t.getArch()) {
1694 case Triple::aarch64:
1695 case Triple::aarch64_be:
1696 return EM_AARCH64;
1697 case Triple::amdgcn:
1698 case Triple::r600:
1699 return EM_AMDGPU;
1700 case Triple::arm:
1701 case Triple::armeb:
1702 case Triple::thumb:
1703 case Triple::thumbeb:
1704 return EM_ARM;
1705 case Triple::avr:
1706 return EM_AVR;
1707 case Triple::hexagon:
1708 return EM_HEXAGON;
1709 case Triple::loongarch32:
1710 case Triple::loongarch64:
1711 return EM_LOONGARCH;
1712 case Triple::mips:
1713 case Triple::mipsel:
1714 case Triple::mips64:
1715 case Triple::mips64el:
1716 return EM_MIPS;
1717 case Triple::msp430:
1718 return EM_MSP430;
1719 case Triple::ppc:
1720 case Triple::ppcle:
1721 return EM_PPC;
1722 case Triple::ppc64:
1723 case Triple::ppc64le:
1724 return EM_PPC64;
1725 case Triple::riscv32:
1726 case Triple::riscv64:
1727 return EM_RISCV;
1728 case Triple::sparcv9:
1729 return EM_SPARCV9;
1730 case Triple::systemz:
1731 return EM_S390;
1732 case Triple::x86:
1733 return t.isOSIAMCU() ? EM_IAMCU : EM_386;
1734 case Triple::x86_64:
1735 return EM_X86_64;
1736 default:
1737 ErrAlways(ctx) << path
1738 << ": could not infer e_machine from bitcode target triple "
1739 << t.str();
1740 return EM_NONE;
1741 }
1742}
1743
1744static uint8_t getOsAbi(const Triple &t) {
1745 switch (t.getOS()) {
1746 case Triple::AMDHSA:
1747 return ELF::ELFOSABI_AMDGPU_HSA;
1748 case Triple::AMDPAL:
1749 return ELF::ELFOSABI_AMDGPU_PAL;
1750 case Triple::Mesa3D:
1751 return ELF::ELFOSABI_AMDGPU_MESA3D;
1752 default:
1753 return ELF::ELFOSABI_NONE;
1754 }
1755}
1756
1757// For DTLTO, bitcode member names must be valid paths to files on disk.
1758// For thin archives, resolve `memberPath` relative to the archive's location.
1759// Returns true if adjusted; false otherwise. Non-thin archives are unsupported.
1760static bool dtltoAdjustMemberPathIfThinArchive(Ctx &ctx, StringRef archivePath,
1761 std::string &memberPath) {
1762 assert(!archivePath.empty());
1763
1764 if (ctx.arg.dtltoDistributor.empty())
1765 return false;
1766
1767 // Read the archive header to determine if it's a thin archive.
1768 auto bufferOrErr =
1769 MemoryBuffer::getFileSlice(Filename: archivePath, MapSize: sizeof(ThinArchiveMagic) - 1, Offset: 0);
1770 if (std::error_code ec = bufferOrErr.getError()) {
1771 ErrAlways(ctx) << "cannot open " << archivePath << ": " << ec.message();
1772 return false;
1773 }
1774
1775 if (!bufferOrErr->get()->getBuffer().starts_with(Prefix: ThinArchiveMagic))
1776 return false;
1777
1778 SmallString<128> resolvedPath;
1779 if (path::is_relative(path: memberPath)) {
1780 resolvedPath = path::parent_path(path: archivePath);
1781 path::append(path&: resolvedPath, a: memberPath);
1782 } else
1783 resolvedPath = memberPath;
1784
1785 path::remove_dots(path&: resolvedPath, /*remove_dot_dot=*/true);
1786 memberPath = resolvedPath.str();
1787 return true;
1788}
1789
1790BitcodeFile::BitcodeFile(Ctx &ctx, MemoryBufferRef mb, StringRef archiveName,
1791 uint64_t offsetInArchive, bool lazy)
1792 : InputFile(ctx, BitcodeKind, mb) {
1793 this->archiveName = archiveName;
1794 this->lazy = lazy;
1795
1796 std::string path = mb.getBufferIdentifier().str();
1797 if (ctx.arg.thinLTOIndexOnly)
1798 path = replaceThinLTOSuffix(ctx, path: mb.getBufferIdentifier());
1799
1800 StringSaver &ss = ctx.saver;
1801 StringRef name;
1802 if (archiveName.empty() ||
1803 dtltoAdjustMemberPathIfThinArchive(ctx, archivePath: archiveName, memberPath&: path)) {
1804 name = ss.save(S: path);
1805 } else {
1806 // ThinLTO assumes that all MemoryBufferRefs given to it have a unique
1807 // name. If two archives define two members with the same name, this
1808 // causes a collision which result in only one of the objects being taken
1809 // into consideration at LTO time (which very likely causes undefined
1810 // symbols later in the link stage). So we append file offset to make
1811 // filename unique.
1812 name = ss.save(S: archiveName + "(" + path::filename(path) + " at " +
1813 utostr(X: offsetInArchive) + ")");
1814 }
1815
1816 MemoryBufferRef mbref(mb.getBuffer(), name);
1817
1818 obj = CHECK2(lto::InputFile::create(mbref), this);
1819
1820 Triple t(obj->getTargetTriple());
1821 ekind = getBitcodeELFKind(t);
1822 emachine = getBitcodeMachineKind(ctx, path: mb.getBufferIdentifier(), t);
1823 osabi = getOsAbi(t);
1824}
1825
1826static uint8_t mapVisibility(GlobalValue::VisibilityTypes gvVisibility) {
1827 switch (gvVisibility) {
1828 case GlobalValue::DefaultVisibility:
1829 return STV_DEFAULT;
1830 case GlobalValue::HiddenVisibility:
1831 return STV_HIDDEN;
1832 case GlobalValue::ProtectedVisibility:
1833 return STV_PROTECTED;
1834 }
1835 llvm_unreachable("unknown visibility");
1836}
1837
1838static void createBitcodeSymbol(Ctx &ctx, Symbol *&sym,
1839 const lto::InputFile::Symbol &objSym,
1840 BitcodeFile &f) {
1841 uint8_t binding = objSym.isWeak() ? STB_WEAK : STB_GLOBAL;
1842 uint8_t type = objSym.isTLS() ? STT_TLS : STT_NOTYPE;
1843 uint8_t visibility = mapVisibility(gvVisibility: objSym.getVisibility());
1844
1845 if (!sym) {
1846 // Symbols can be duplicated in bitcode files because of '#include' and
1847 // linkonce_odr. Use uniqueSaver to save symbol names for de-duplication.
1848 // Update objSym.Name to reference (via StringRef) the string saver's copy;
1849 // this way LTO can reference the same string saver's copy rather than
1850 // keeping copies of its own.
1851 objSym.Name = ctx.uniqueSaver.save(S: objSym.getName());
1852 sym = ctx.symtab->insert(name: objSym.getName());
1853 }
1854
1855 if (objSym.isUndefined()) {
1856 Undefined newSym(&f, StringRef(), binding, visibility, type);
1857 sym->resolve(ctx, other: newSym);
1858 sym->referenced = true;
1859 return;
1860 }
1861
1862 if (objSym.isCommon()) {
1863 sym->resolve(ctx, other: CommonSymbol{ctx, &f, StringRef(), binding, visibility,
1864 STT_OBJECT, objSym.getCommonAlignment(),
1865 objSym.getCommonSize()});
1866 } else {
1867 Defined newSym(ctx, &f, StringRef(), binding, visibility, type, 0, 0,
1868 nullptr);
1869 // The definition can be omitted if all bitcode definitions satisfy
1870 // `canBeOmittedFromSymbolTable()` and isUsedInRegularObj is false.
1871 // The latter condition is tested in parseVersionAndComputeIsPreemptible.
1872 sym->ltoCanOmit = objSym.canBeOmittedFromSymbolTable() &&
1873 (!sym->isDefined() || sym->ltoCanOmit);
1874 sym->resolve(ctx, other: newSym);
1875 }
1876}
1877
1878void BitcodeFile::parse() {
1879 for (std::pair<StringRef, Comdat::SelectionKind> s : obj->getComdatTable()) {
1880 keptComdats.push_back(
1881 x: s.second == Comdat::NoDeduplicate ||
1882 ctx.symtab->comdatGroups.try_emplace(Key: CachedHashStringRef(s.first), Args: this)
1883 .second);
1884 }
1885
1886 if (numSymbols == 0) {
1887 numSymbols = obj->symbols().size();
1888 symbols = std::make_unique<Symbol *[]>(num: numSymbols);
1889 }
1890 // Process defined symbols first. See the comment in
1891 // ObjFile<ELFT>::initializeSymbols.
1892 for (auto [i, irSym] : llvm::enumerate(First: obj->symbols()))
1893 if (!irSym.isUndefined())
1894 createBitcodeSymbol(ctx, sym&: symbols[i], objSym: irSym, f&: *this);
1895 for (auto [i, irSym] : llvm::enumerate(First: obj->symbols()))
1896 if (irSym.isUndefined())
1897 createBitcodeSymbol(ctx, sym&: symbols[i], objSym: irSym, f&: *this);
1898
1899 for (auto l : obj->getDependentLibraries())
1900 addDependentLibrary(ctx, specifier: l, f: this);
1901}
1902
1903void BitcodeFile::parseLazy() {
1904 numSymbols = obj->symbols().size();
1905 symbols = std::make_unique<Symbol *[]>(num: numSymbols);
1906 for (auto [i, irSym] : llvm::enumerate(First: obj->symbols())) {
1907 // Symbols can be duplicated in bitcode files because of '#include' and
1908 // linkonce_odr. Use uniqueSaver to save symbol names for de-duplication.
1909 // Update objSym.Name to reference (via StringRef) the string saver's copy;
1910 // this way LTO can reference the same string saver's copy rather than
1911 // keeping copies of its own.
1912 irSym.Name = ctx.uniqueSaver.save(S: irSym.getName());
1913 if (!irSym.isUndefined()) {
1914 auto *sym = ctx.symtab->insert(name: irSym.getName());
1915 sym->resolve(ctx, other: LazySymbol{*this});
1916 symbols[i] = sym;
1917 }
1918 }
1919}
1920
1921void BitcodeFile::postParse() {
1922 for (auto [i, irSym] : llvm::enumerate(First: obj->symbols())) {
1923 const Symbol &sym = *symbols[i];
1924 if (sym.file == this || !sym.isDefined() || irSym.isUndefined() ||
1925 irSym.isCommon() || irSym.isWeak())
1926 continue;
1927 int c = irSym.getComdatIndex();
1928 if (c != -1 && !keptComdats[c])
1929 continue;
1930 reportDuplicate(ctx, sym, newFile: this, errSec: nullptr, errOffset: 0);
1931 }
1932}
1933
1934void BinaryFile::parse() {
1935 ArrayRef<uint8_t> data = arrayRefFromStringRef(Input: mb.getBuffer());
1936 auto *section =
1937 make<InputSection>(args: this, args: ".data", args: SHT_PROGBITS, args: SHF_ALLOC | SHF_WRITE,
1938 /*addralign=*/args: 8, /*entsize=*/args: 0, args&: data);
1939 sections.push_back(Elt: section);
1940
1941 // For each input file foo that is embedded to a result as a binary
1942 // blob, we define _binary_foo_{start,end,size} symbols, so that
1943 // user programs can access blobs by name. Non-alphanumeric
1944 // characters in a filename are replaced with underscore.
1945 std::string s = "_binary_" + mb.getBufferIdentifier().str();
1946 for (char &c : s)
1947 if (!isAlnum(C: c))
1948 c = '_';
1949
1950 llvm::StringSaver &ss = ctx.saver;
1951 ctx.symtab->addAndCheckDuplicate(
1952 ctx, newSym: Defined{ctx, this, ss.save(S: s + "_start"), STB_GLOBAL, STV_DEFAULT,
1953 STT_OBJECT, 0, 0, section});
1954 ctx.symtab->addAndCheckDuplicate(
1955 ctx, newSym: Defined{ctx, this, ss.save(S: s + "_end"), STB_GLOBAL, STV_DEFAULT,
1956 STT_OBJECT, data.size(), 0, section});
1957 ctx.symtab->addAndCheckDuplicate(
1958 ctx, newSym: Defined{ctx, this, ss.save(S: s + "_size"), STB_GLOBAL, STV_DEFAULT,
1959 STT_OBJECT, data.size(), 0, nullptr});
1960}
1961
1962InputFile *elf::createInternalFile(Ctx &ctx, StringRef name) {
1963 auto *file =
1964 make<InputFile>(args&: ctx, args: InputFile::InternalKind, args: MemoryBufferRef("", name));
1965 // References from an internal file do not lead to --warn-backrefs
1966 // diagnostics.
1967 file->groupId = 0;
1968 return file;
1969}
1970
1971std::unique_ptr<ELFFileBase> elf::createObjFile(Ctx &ctx, MemoryBufferRef mb,
1972 StringRef archiveName,
1973 bool lazy) {
1974 std::unique_ptr<ELFFileBase> f;
1975 switch (getELFKind(ctx, mb, archiveName)) {
1976 case ELF32LEKind:
1977 f = std::make_unique<ObjFile<ELF32LE>>(args&: ctx, args: ELF32LEKind, args&: mb, args&: archiveName);
1978 break;
1979 case ELF32BEKind:
1980 f = std::make_unique<ObjFile<ELF32BE>>(args&: ctx, args: ELF32BEKind, args&: mb, args&: archiveName);
1981 break;
1982 case ELF64LEKind:
1983 f = std::make_unique<ObjFile<ELF64LE>>(args&: ctx, args: ELF64LEKind, args&: mb, args&: archiveName);
1984 break;
1985 case ELF64BEKind:
1986 f = std::make_unique<ObjFile<ELF64BE>>(args&: ctx, args: ELF64BEKind, args&: mb, args&: archiveName);
1987 break;
1988 default:
1989 llvm_unreachable("getELFKind");
1990 }
1991 f->init();
1992 f->lazy = lazy;
1993 return f;
1994}
1995
1996template <class ELFT> void ObjFile<ELFT>::parseLazy() {
1997 const ArrayRef<typename ELFT::Sym> eSyms = this->getELFSyms<ELFT>();
1998 numSymbols = eSyms.size();
1999 symbols = std::make_unique<Symbol *[]>(numSymbols);
2000
2001 // resolve() may trigger this->extract() if an existing symbol is an undefined
2002 // symbol. If that happens, this function has served its purpose, and we can
2003 // exit from the loop early.
2004 auto *symtab = ctx.symtab.get();
2005 for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i) {
2006 if (eSyms[i].st_shndx == SHN_UNDEF)
2007 continue;
2008 symbols[i] = symtab->insert(CHECK2(eSyms[i].getName(stringTable), this));
2009 symbols[i]->resolve(ctx, LazySymbol{*this});
2010 if (!lazy)
2011 break;
2012 }
2013}
2014
2015bool InputFile::shouldExtractForCommon(StringRef name) const {
2016 if (isa<BitcodeFile>(Val: this))
2017 return isBitcodeNonCommonDef(mb, symName: name, archiveName);
2018
2019 return isNonCommonDef(ctx, mb, symName: name, archiveName);
2020}
2021
2022std::string elf::replaceThinLTOSuffix(Ctx &ctx, StringRef path) {
2023 auto [suffix, repl] = ctx.arg.thinLTOObjectSuffixReplace;
2024 if (path.consume_back(Suffix: suffix))
2025 return (path + repl).str();
2026 return std::string(path);
2027}
2028
2029template class elf::ObjFile<ELF32LE>;
2030template class elf::ObjFile<ELF32BE>;
2031template class elf::ObjFile<ELF64LE>;
2032template class elf::ObjFile<ELF64BE>;
2033
2034template void SharedFile::parse<ELF32LE>();
2035template void SharedFile::parse<ELF32BE>();
2036template void SharedFile::parse<ELF64LE>();
2037template void SharedFile::parse<ELF64BE>();
2038

source code of lld/ELF/InputFiles.cpp