1 //===- InputFiles.cpp -----------------------------------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 #include "InputFiles.h"
11 #include "InputSection.h"
12 #include "LinkerScript.h"
13 #include "SymbolTable.h"
15 #include "SyntheticSections.h"
16 #include "lld/Common/DWARF.h"
17 #include "lld/Common/ErrorHandler.h"
18 #include "lld/Common/Memory.h"
19 #include "llvm/ADT/STLExtras.h"
20 #include "llvm/CodeGen/Analysis.h"
21 #include "llvm/IR/LLVMContext.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/LTO/LTO.h"
24 #include "llvm/MC/StringTableBuilder.h"
25 #include "llvm/Object/ELFObjectFile.h"
26 #include "llvm/Support/ARMAttributeParser.h"
27 #include "llvm/Support/ARMBuildAttributes.h"
28 #include "llvm/Support/Endian.h"
29 #include "llvm/Support/Path.h"
30 #include "llvm/Support/TarWriter.h"
31 #include "llvm/Support/raw_ostream.h"
34 using namespace llvm::ELF;
35 using namespace llvm::object;
36 using namespace llvm::sys;
37 using namespace llvm::sys::fs;
38 using namespace llvm::support::endian;
40 using namespace lld::elf;
42 bool InputFile::isInGroup;
43 uint32_t InputFile::nextGroupId;
45 std::vector<ArchiveFile *> elf::archiveFiles;
46 std::vector<BinaryFile *> elf::binaryFiles;
47 std::vector<BitcodeFile *> elf::bitcodeFiles;
48 std::vector<LazyObjFile *> elf::lazyObjFiles;
49 std::vector<InputFile *> elf::objectFiles;
50 std::vector<SharedFile *> elf::sharedFiles;
52 std::unique_ptr<TarWriter> elf::tar;
54 // Returns "<internal>", "foo.a(bar.o)" or "baz.o".
55 std::string lld::toString(const InputFile *f) {
59 if (f->toStringCache.empty()) {
60 if (f->archiveName.empty())
61 f->toStringCache = std::string(f->getName());
63 f->toStringCache = (f->archiveName + "(" + f->getName() + ")").str();
65 return f->toStringCache;
68 static ELFKind getELFKind(MemoryBufferRef mb, StringRef archiveName) {
71 std::tie(size, endian) = getElfArchType(mb.getBuffer());
73 auto report = [&](StringRef msg) {
74 StringRef filename = mb.getBufferIdentifier();
75 if (archiveName.empty())
76 fatal(filename + ": " + msg);
78 fatal(archiveName + "(" + filename + "): " + msg);
81 if (!mb.getBuffer().startswith(ElfMagic))
82 report("not an ELF file");
83 if (endian != ELFDATA2LSB && endian != ELFDATA2MSB)
84 report("corrupted ELF file: invalid data encoding");
85 if (size != ELFCLASS32 && size != ELFCLASS64)
86 report("corrupted ELF file: invalid file class");
88 size_t bufSize = mb.getBuffer().size();
89 if ((size == ELFCLASS32 && bufSize < sizeof(Elf32_Ehdr)) ||
90 (size == ELFCLASS64 && bufSize < sizeof(Elf64_Ehdr)))
91 report("corrupted ELF file: file is too short");
93 if (size == ELFCLASS32)
94 return (endian == ELFDATA2LSB) ? ELF32LEKind : ELF32BEKind;
95 return (endian == ELFDATA2LSB) ? ELF64LEKind : ELF64BEKind;
98 InputFile::InputFile(Kind k, MemoryBufferRef m)
99 : mb(m), groupId(nextGroupId), fileKind(k) {
100 // All files within the same --{start,end}-group get the same group ID.
101 // Otherwise, a new file will get a new group ID.
106 Optional<MemoryBufferRef> elf::readFile(StringRef path) {
107 // The --chroot option changes our virtual root directory.
108 // This is useful when you are dealing with files created by --reproduce.
109 if (!config->chroot.empty() && path.startswith("/"))
110 path = saver.save(config->chroot + path);
114 auto mbOrErr = MemoryBuffer::getFile(path, -1, false);
115 if (auto ec = mbOrErr.getError()) {
116 error("cannot open " + path + ": " + ec.message());
120 std::unique_ptr<MemoryBuffer> &mb = *mbOrErr;
121 MemoryBufferRef mbref = mb->getMemBufferRef();
122 make<std::unique_ptr<MemoryBuffer>>(std::move(mb)); // take MB ownership
125 tar->append(relativeToRoot(path), mbref.getBuffer());
129 // All input object files must be for the same architecture
130 // (e.g. it does not make sense to link x86 object files with
131 // MIPS object files.) This function checks for that error.
132 static bool isCompatible(InputFile *file) {
133 if (!file->isElf() && !isa<BitcodeFile>(file))
136 if (file->ekind == config->ekind && file->emachine == config->emachine) {
137 if (config->emachine != EM_MIPS)
139 if (isMipsN32Abi(file) == config->mipsN32Abi)
144 !config->bfdname.empty() ? config->bfdname : config->emulation;
145 if (!target.empty()) {
146 error(toString(file) + " is incompatible with " + target);
151 if (!objectFiles.empty())
152 existing = objectFiles[0];
153 else if (!sharedFiles.empty())
154 existing = sharedFiles[0];
155 else if (!bitcodeFiles.empty())
156 existing = bitcodeFiles[0];
158 llvm_unreachable("Must have -m, OUTPUT_FORMAT or existing input file to "
159 "determine target emulation");
161 error(toString(file) + " is incompatible with " + toString(existing));
165 template <class ELFT> static void doParseFile(InputFile *file) {
166 if (!isCompatible(file))
170 if (auto *f = dyn_cast<BinaryFile>(file)) {
171 binaryFiles.push_back(f);
177 if (auto *f = dyn_cast<ArchiveFile>(file)) {
178 archiveFiles.push_back(f);
184 if (auto *f = dyn_cast<LazyObjFile>(file)) {
185 lazyObjFiles.push_back(f);
191 message(toString(file));
194 if (auto *f = dyn_cast<SharedFile>(file)) {
200 if (auto *f = dyn_cast<BitcodeFile>(file)) {
201 bitcodeFiles.push_back(f);
206 // Regular object file
207 objectFiles.push_back(file);
208 cast<ObjFile<ELFT>>(file)->parse();
211 // Add symbols in File to the symbol table.
212 void elf::parseFile(InputFile *file) {
213 switch (config->ekind) {
215 doParseFile<ELF32LE>(file);
218 doParseFile<ELF32BE>(file);
221 doParseFile<ELF64LE>(file);
224 doParseFile<ELF64BE>(file);
227 llvm_unreachable("unknown ELFT");
231 // Concatenates arguments to construct a string representing an error location.
232 static std::string createFileLineMsg(StringRef path, unsigned line) {
233 std::string filename = std::string(path::filename(path));
234 std::string lineno = ":" + std::to_string(line);
235 if (filename == path)
236 return filename + lineno;
237 return filename + lineno + " (" + path.str() + lineno + ")";
240 template <class ELFT>
241 static std::string getSrcMsgAux(ObjFile<ELFT> &file, const Symbol &sym,
242 InputSectionBase &sec, uint64_t offset) {
243 // In DWARF, functions and variables are stored to different places.
244 // First, lookup a function for a given offset.
245 if (Optional<DILineInfo> info = file.getDILineInfo(&sec, offset))
246 return createFileLineMsg(info->FileName, info->Line);
248 // If it failed, lookup again as a variable.
249 if (Optional<std::pair<std::string, unsigned>> fileLine =
250 file.getVariableLoc(sym.getName()))
251 return createFileLineMsg(fileLine->first, fileLine->second);
253 // File.sourceFile contains STT_FILE symbol, and that is a last resort.
254 return std::string(file.sourceFile);
257 std::string InputFile::getSrcMsg(const Symbol &sym, InputSectionBase &sec,
259 if (kind() != ObjKind)
261 switch (config->ekind) {
263 llvm_unreachable("Invalid kind");
265 return getSrcMsgAux(cast<ObjFile<ELF32LE>>(*this), sym, sec, offset);
267 return getSrcMsgAux(cast<ObjFile<ELF32BE>>(*this), sym, sec, offset);
269 return getSrcMsgAux(cast<ObjFile<ELF64LE>>(*this), sym, sec, offset);
271 return getSrcMsgAux(cast<ObjFile<ELF64BE>>(*this), sym, sec, offset);
275 template <class ELFT> DWARFCache *ObjFile<ELFT>::getDwarf() {
276 llvm::call_once(initDwarf, [this]() {
277 dwarf = std::make_unique<DWARFCache>(std::make_unique<DWARFContext>(
278 std::make_unique<LLDDwarfObj<ELFT>>(this), "",
279 [&](Error err) { warn(getName() + ": " + toString(std::move(err))); },
281 warn(getName() + ": " + toString(std::move(warning)));
288 // Returns the pair of file name and line number describing location of data
289 // object (variable, array, etc) definition.
290 template <class ELFT>
291 Optional<std::pair<std::string, unsigned>>
292 ObjFile<ELFT>::getVariableLoc(StringRef name) {
293 return getDwarf()->getVariableLoc(name);
296 // Returns source line information for a given offset
297 // using DWARF debug info.
298 template <class ELFT>
299 Optional<DILineInfo> ObjFile<ELFT>::getDILineInfo(InputSectionBase *s,
301 // Detect SectionIndex for specified section.
302 uint64_t sectionIndex = object::SectionedAddress::UndefSection;
303 ArrayRef<InputSectionBase *> sections = s->file->getSections();
304 for (uint64_t curIndex = 0; curIndex < sections.size(); ++curIndex) {
305 if (s == sections[curIndex]) {
306 sectionIndex = curIndex;
311 return getDwarf()->getDILineInfo(offset, sectionIndex);
314 ELFFileBase::ELFFileBase(Kind k, MemoryBufferRef mb) : InputFile(k, mb) {
315 ekind = getELFKind(mb, "");
331 llvm_unreachable("getELFKind");
335 template <typename Elf_Shdr>
336 static const Elf_Shdr *findSection(ArrayRef<Elf_Shdr> sections, uint32_t type) {
337 for (const Elf_Shdr &sec : sections)
338 if (sec.sh_type == type)
343 template <class ELFT> void ELFFileBase::init() {
344 using Elf_Shdr = typename ELFT::Shdr;
345 using Elf_Sym = typename ELFT::Sym;
347 // Initialize trivial attributes.
348 const ELFFile<ELFT> &obj = getObj<ELFT>();
349 emachine = obj.getHeader()->e_machine;
350 osabi = obj.getHeader()->e_ident[llvm::ELF::EI_OSABI];
351 abiVersion = obj.getHeader()->e_ident[llvm::ELF::EI_ABIVERSION];
353 ArrayRef<Elf_Shdr> sections = CHECK(obj.sections(), this);
355 // Find a symbol table.
357 (identify_magic(mb.getBuffer()) == file_magic::elf_shared_object);
358 const Elf_Shdr *symtabSec =
359 findSection(sections, isDSO ? SHT_DYNSYM : SHT_SYMTAB);
364 // Initialize members corresponding to a symbol table.
365 firstGlobal = symtabSec->sh_info;
367 ArrayRef<Elf_Sym> eSyms = CHECK(obj.symbols(symtabSec), this);
368 if (firstGlobal == 0 || firstGlobal > eSyms.size())
369 fatal(toString(this) + ": invalid sh_info in symbol table");
371 elfSyms = reinterpret_cast<const void *>(eSyms.data());
372 numELFSyms = eSyms.size();
373 stringTable = CHECK(obj.getStringTableForSymtab(*symtabSec, sections), this);
376 template <class ELFT>
377 uint32_t ObjFile<ELFT>::getSectionIndex(const Elf_Sym &sym) const {
379 this->getObj().getSectionIndex(&sym, getELFSyms<ELFT>(), shndxTable),
383 template <class ELFT> ArrayRef<Symbol *> ObjFile<ELFT>::getLocalSymbols() {
384 if (this->symbols.empty())
386 return makeArrayRef(this->symbols).slice(1, this->firstGlobal - 1);
389 template <class ELFT> ArrayRef<Symbol *> ObjFile<ELFT>::getGlobalSymbols() {
390 return makeArrayRef(this->symbols).slice(this->firstGlobal);
393 template <class ELFT> void ObjFile<ELFT>::parse(bool ignoreComdats) {
394 // Read a section table. justSymbols is usually false.
395 if (this->justSymbols)
396 initializeJustSymbols();
398 initializeSections(ignoreComdats);
400 // Read a symbol table.
404 // Sections with SHT_GROUP and comdat bits define comdat section groups.
405 // They are identified and deduplicated by group name. This function
406 // returns a group name.
407 template <class ELFT>
408 StringRef ObjFile<ELFT>::getShtGroupSignature(ArrayRef<Elf_Shdr> sections,
409 const Elf_Shdr &sec) {
410 typename ELFT::SymRange symbols = this->getELFSyms<ELFT>();
411 if (sec.sh_info >= symbols.size())
412 fatal(toString(this) + ": invalid symbol index");
413 const typename ELFT::Sym &sym = symbols[sec.sh_info];
414 StringRef signature = CHECK(sym.getName(this->stringTable), this);
416 // As a special case, if a symbol is a section symbol and has no name,
417 // we use a section name as a signature.
419 // Such SHT_GROUP sections are invalid from the perspective of the ELF
420 // standard, but GNU gold 1.14 (the newest version as of July 2017) or
421 // older produce such sections as outputs for the -r option, so we need
422 // a bug-compatibility.
423 if (signature.empty() && sym.getType() == STT_SECTION)
424 return getSectionName(sec);
428 template <class ELFT>
429 bool ObjFile<ELFT>::shouldMerge(const Elf_Shdr &sec, StringRef name) {
430 if (!(sec.sh_flags & SHF_MERGE))
433 // On a regular link we don't merge sections if -O0 (default is -O1). This
434 // sometimes makes the linker significantly faster, although the output will
437 // Doing the same for -r would create a problem as it would combine sections
438 // with different sh_entsize. One option would be to just copy every SHF_MERGE
439 // section as is to the output. While this would produce a valid ELF file with
440 // usable SHF_MERGE sections, tools like (llvm-)?dwarfdump get confused when
441 // they see two .debug_str. We could have separate logic for combining
442 // SHF_MERGE sections based both on their name and sh_entsize, but that seems
443 // to be more trouble than it is worth. Instead, we just use the regular (-O1)
445 if (config->optimize == 0 && !config->relocatable)
448 // A mergeable section with size 0 is useless because they don't have
449 // any data to merge. A mergeable string section with size 0 can be
450 // argued as invalid because it doesn't end with a null character.
451 // We'll avoid a mess by handling them as if they were non-mergeable.
452 if (sec.sh_size == 0)
455 // Check for sh_entsize. The ELF spec is not clear about the zero
456 // sh_entsize. It says that "the member [sh_entsize] contains 0 if
457 // the section does not hold a table of fixed-size entries". We know
458 // that Rust 1.13 produces a string mergeable section with a zero
459 // sh_entsize. Here we just accept it rather than being picky about it.
460 uint64_t entSize = sec.sh_entsize;
463 if (sec.sh_size % entSize)
464 fatal(toString(this) + ":(" + name + "): SHF_MERGE section size (" +
465 Twine(sec.sh_size) + ") must be a multiple of sh_entsize (" +
466 Twine(entSize) + ")");
468 if (sec.sh_flags & SHF_WRITE)
469 fatal(toString(this) + ":(" + name +
470 "): writable SHF_MERGE section is not supported");
475 // This is for --just-symbols.
477 // --just-symbols is a very minor feature that allows you to link your
478 // output against other existing program, so that if you load both your
479 // program and the other program into memory, your output can refer the
480 // other program's symbols.
482 // When the option is given, we link "just symbols". The section table is
483 // initialized with null pointers.
484 template <class ELFT> void ObjFile<ELFT>::initializeJustSymbols() {
485 ArrayRef<Elf_Shdr> sections = CHECK(this->getObj().sections(), this);
486 this->sections.resize(sections.size());
489 // An ELF object file may contain a `.deplibs` section. If it exists, the
490 // section contains a list of library specifiers such as `m` for libm. This
491 // function resolves a given name by finding the first matching library checking
492 // the various ways that a library can be specified to LLD. This ELF extension
493 // is a form of autolinking and is called `dependent libraries`. It is currently
494 // unique to LLVM and lld.
495 static void addDependentLibrary(StringRef specifier, const InputFile *f) {
496 if (!config->dependentLibraries)
498 if (fs::exists(specifier))
499 driver->addFile(specifier, /*withLOption=*/false);
500 else if (Optional<std::string> s = findFromSearchPaths(specifier))
501 driver->addFile(*s, /*withLOption=*/true);
502 else if (Optional<std::string> s = searchLibraryBaseName(specifier))
503 driver->addFile(*s, /*withLOption=*/true);
506 ": unable to find library from dependent library specifier: " +
510 // Record the membership of a section group so that in the garbage collection
511 // pass, section group members are kept or discarded as a unit.
512 template <class ELFT>
513 static void handleSectionGroup(ArrayRef<InputSectionBase *> sections,
514 ArrayRef<typename ELFT::Word> entries) {
515 bool hasAlloc = false;
516 for (uint32_t index : entries.slice(1)) {
517 if (index >= sections.size())
519 if (InputSectionBase *s = sections[index])
520 if (s != &InputSection::discarded && s->flags & SHF_ALLOC)
524 // If any member has the SHF_ALLOC flag, the whole group is subject to garbage
525 // collection. See the comment in markLive(). This rule retains .debug_types
526 // and .rela.debug_types.
530 // Connect the members in a circular doubly-linked list via
531 // nextInSectionGroup.
532 InputSectionBase *head;
533 InputSectionBase *prev = nullptr;
534 for (uint32_t index : entries.slice(1)) {
535 InputSectionBase *s = sections[index];
536 if (!s || s == &InputSection::discarded)
539 prev->nextInSectionGroup = s;
545 prev->nextInSectionGroup = head;
548 template <class ELFT>
549 void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
550 const ELFFile<ELFT> &obj = this->getObj();
552 ArrayRef<Elf_Shdr> objSections = CHECK(obj.sections(), this);
553 uint64_t size = objSections.size();
554 this->sections.resize(size);
555 this->sectionStringTable =
556 CHECK(obj.getSectionStringTable(objSections), this);
558 std::vector<ArrayRef<Elf_Word>> selectedGroups;
560 for (size_t i = 0, e = objSections.size(); i < e; ++i) {
561 if (this->sections[i] == &InputSection::discarded)
563 const Elf_Shdr &sec = objSections[i];
565 if (sec.sh_type == ELF::SHT_LLVM_CALL_GRAPH_PROFILE)
567 check(obj.template getSectionContentsAsArray<Elf_CGProfile>(&sec));
569 // SHF_EXCLUDE'ed sections are discarded by the linker. However,
570 // if -r is given, we'll let the final link discard such sections.
571 // This is compatible with GNU.
572 if ((sec.sh_flags & SHF_EXCLUDE) && !config->relocatable) {
573 if (sec.sh_type == SHT_LLVM_ADDRSIG) {
574 // We ignore the address-significance table if we know that the object
575 // file was created by objcopy or ld -r. This is because these tools
576 // will reorder the symbols in the symbol table, invalidating the data
577 // in the address-significance table, which refers to symbols by index.
578 if (sec.sh_link != 0)
579 this->addrsigSec = &sec;
580 else if (config->icf == ICFLevel::Safe)
581 warn(toString(this) + ": --icf=safe is incompatible with object "
582 "files created using objcopy or ld -r");
584 this->sections[i] = &InputSection::discarded;
588 switch (sec.sh_type) {
590 // De-duplicate section groups by their signatures.
591 StringRef signature = getShtGroupSignature(objSections, sec);
592 this->sections[i] = &InputSection::discarded;
595 ArrayRef<Elf_Word> entries =
596 CHECK(obj.template getSectionContentsAsArray<Elf_Word>(&sec), this);
598 fatal(toString(this) + ": empty SHT_GROUP");
600 // The first word of a SHT_GROUP section contains flags. Currently,
601 // the standard defines only "GRP_COMDAT" flag for the COMDAT group.
602 // An group with the empty flag doesn't define anything; such sections
607 if (entries[0] != GRP_COMDAT)
608 fatal(toString(this) + ": unsupported SHT_GROUP format");
612 symtab->comdatGroups.try_emplace(CachedHashStringRef(signature), this)
615 if (config->relocatable)
616 this->sections[i] = createInputSection(sec);
617 selectedGroups.push_back(entries);
621 // Otherwise, discard group members.
622 for (uint32_t secIndex : entries.slice(1)) {
623 if (secIndex >= size)
624 fatal(toString(this) +
625 ": invalid section index in group: " + Twine(secIndex));
626 this->sections[secIndex] = &InputSection::discarded;
630 case SHT_SYMTAB_SHNDX:
631 shndxTable = CHECK(obj.getSHNDXTable(sec, objSections), this);
640 this->sections[i] = createInputSection(sec);
644 // We have a second loop. It is used to:
645 // 1) handle SHF_LINK_ORDER sections.
646 // 2) create SHT_REL[A] sections. In some cases the section header index of a
647 // relocation section may be smaller than that of the relocated section. In
648 // such cases, the relocation section would attempt to reference a target
649 // section that has not yet been created. For simplicity, delay creation of
650 // relocation sections until now.
651 for (size_t i = 0, e = objSections.size(); i < e; ++i) {
652 if (this->sections[i] == &InputSection::discarded)
654 const Elf_Shdr &sec = objSections[i];
656 if (sec.sh_type == SHT_REL || sec.sh_type == SHT_RELA)
657 this->sections[i] = createInputSection(sec);
659 if (!(sec.sh_flags & SHF_LINK_ORDER))
662 // .ARM.exidx sections have a reverse dependency on the InputSection they
663 // have a SHF_LINK_ORDER dependency, this is identified by the sh_link.
664 InputSectionBase *linkSec = nullptr;
665 if (sec.sh_link < this->sections.size())
666 linkSec = this->sections[sec.sh_link];
668 fatal(toString(this) + ": invalid sh_link index: " + Twine(sec.sh_link));
670 InputSection *isec = cast<InputSection>(this->sections[i]);
671 linkSec->dependentSections.push_back(isec);
672 if (!isa<InputSection>(linkSec))
673 error("a section " + isec->name +
674 " with SHF_LINK_ORDER should not refer a non-regular section: " +
678 for (ArrayRef<Elf_Word> entries : selectedGroups)
679 handleSectionGroup<ELFT>(this->sections, entries);
682 // For ARM only, to set the EF_ARM_ABI_FLOAT_SOFT or EF_ARM_ABI_FLOAT_HARD
683 // flag in the ELF Header we need to look at Tag_ABI_VFP_args to find out how
684 // the input objects have been compiled.
685 static void updateARMVFPArgs(const ARMAttributeParser &attributes,
686 const InputFile *f) {
687 Optional<unsigned> attr =
688 attributes.getAttributeValue(ARMBuildAttrs::ABI_VFP_args);
689 if (!attr.hasValue())
690 // If an ABI tag isn't present then it is implicitly given the value of 0
691 // which maps to ARMBuildAttrs::BaseAAPCS. However many assembler files,
692 // including some in glibc that don't use FP args (and should have value 3)
693 // don't have the attribute so we do not consider an implicit value of 0
697 unsigned vfpArgs = attr.getValue();
700 case ARMBuildAttrs::BaseAAPCS:
701 arg = ARMVFPArgKind::Base;
703 case ARMBuildAttrs::HardFPAAPCS:
704 arg = ARMVFPArgKind::VFP;
706 case ARMBuildAttrs::ToolChainFPPCS:
707 // Tool chain specific convention that conforms to neither AAPCS variant.
708 arg = ARMVFPArgKind::ToolChain;
710 case ARMBuildAttrs::CompatibleFPAAPCS:
711 // Object compatible with all conventions.
714 error(toString(f) + ": unknown Tag_ABI_VFP_args value: " + Twine(vfpArgs));
717 // Follow ld.bfd and error if there is a mix of calling conventions.
718 if (config->armVFPArgs != arg && config->armVFPArgs != ARMVFPArgKind::Default)
719 error(toString(f) + ": incompatible Tag_ABI_VFP_args");
721 config->armVFPArgs = arg;
724 // The ARM support in lld makes some use of instructions that are not available
725 // on all ARM architectures. Namely:
726 // - Use of BLX instruction for interworking between ARM and Thumb state.
727 // - Use of the extended Thumb branch encoding in relocation.
728 // - Use of the MOVT/MOVW instructions in Thumb Thunks.
729 // The ARM Attributes section contains information about the architecture chosen
730 // at compile time. We follow the convention that if at least one input object
731 // is compiled with an architecture that supports these features then lld is
732 // permitted to use them.
733 static void updateSupportedARMFeatures(const ARMAttributeParser &attributes) {
734 Optional<unsigned> attr =
735 attributes.getAttributeValue(ARMBuildAttrs::CPU_arch);
736 if (!attr.hasValue())
738 auto arch = attr.getValue();
740 case ARMBuildAttrs::Pre_v4:
741 case ARMBuildAttrs::v4:
742 case ARMBuildAttrs::v4T:
743 // Architectures prior to v5 do not support BLX instruction
745 case ARMBuildAttrs::v5T:
746 case ARMBuildAttrs::v5TE:
747 case ARMBuildAttrs::v5TEJ:
748 case ARMBuildAttrs::v6:
749 case ARMBuildAttrs::v6KZ:
750 case ARMBuildAttrs::v6K:
751 config->armHasBlx = true;
752 // Architectures used in pre-Cortex processors do not support
753 // The J1 = 1 J2 = 1 Thumb branch range extension, with the exception
754 // of Architecture v6T2 (arm1156t2-s and arm1156t2f-s) that do.
757 // All other Architectures have BLX and extended branch encoding
758 config->armHasBlx = true;
759 config->armJ1J2BranchEncoding = true;
760 if (arch != ARMBuildAttrs::v6_M && arch != ARMBuildAttrs::v6S_M)
761 // All Architectures used in Cortex processors with the exception
762 // of v6-M and v6S-M have the MOVT and MOVW instructions.
763 config->armHasMovtMovw = true;
768 // If a source file is compiled with x86 hardware-assisted call flow control
769 // enabled, the generated object file contains feature flags indicating that
770 // fact. This function reads the feature flags and returns it.
772 // Essentially we want to read a single 32-bit value in this function, but this
773 // function is rather complicated because the value is buried deep inside a
774 // .note.gnu.property section.
776 // The section consists of one or more NOTE records. Each NOTE record consists
777 // of zero or more type-length-value fields. We want to find a field of a
778 // certain type. It seems a bit too much to just store a 32-bit value, perhaps
779 // the ABI is unnecessarily complicated.
780 template <class ELFT>
781 static uint32_t readAndFeatures(ObjFile<ELFT> *obj, ArrayRef<uint8_t> data) {
782 using Elf_Nhdr = typename ELFT::Nhdr;
783 using Elf_Note = typename ELFT::Note;
785 uint32_t featuresSet = 0;
786 while (!data.empty()) {
787 // Read one NOTE record.
788 if (data.size() < sizeof(Elf_Nhdr))
789 fatal(toString(obj) + ": .note.gnu.property: section too short");
791 auto *nhdr = reinterpret_cast<const Elf_Nhdr *>(data.data());
792 if (data.size() < nhdr->getSize())
793 fatal(toString(obj) + ": .note.gnu.property: section too short");
795 Elf_Note note(*nhdr);
796 if (nhdr->n_type != NT_GNU_PROPERTY_TYPE_0 || note.getName() != "GNU") {
797 data = data.slice(nhdr->getSize());
801 uint32_t featureAndType = config->emachine == EM_AARCH64
802 ? GNU_PROPERTY_AARCH64_FEATURE_1_AND
803 : GNU_PROPERTY_X86_FEATURE_1_AND;
805 // Read a body of a NOTE record, which consists of type-length-value fields.
806 ArrayRef<uint8_t> desc = note.getDesc();
807 while (!desc.empty()) {
809 fatal(toString(obj) + ": .note.gnu.property: section too short");
811 uint32_t type = read32le(desc.data());
812 uint32_t size = read32le(desc.data() + 4);
814 if (type == featureAndType) {
815 // We found a FEATURE_1_AND field. There may be more than one of these
816 // in a .note.gnu.property section, for a relocatable object we
817 // accumulate the bits set.
818 featuresSet |= read32le(desc.data() + 8);
821 // On 64-bit, a payload may be followed by a 4-byte padding to make its
822 // size a multiple of 8.
824 size = alignTo(size, 8);
826 desc = desc.slice(size + 8); // +8 for Type and Size
829 // Go to next NOTE record to look for more FEATURE_1_AND descriptions.
830 data = data.slice(nhdr->getSize());
836 template <class ELFT>
837 InputSectionBase *ObjFile<ELFT>::getRelocTarget(const Elf_Shdr &sec) {
838 uint32_t idx = sec.sh_info;
839 if (idx >= this->sections.size())
840 fatal(toString(this) + ": invalid relocated section index: " + Twine(idx));
841 InputSectionBase *target = this->sections[idx];
843 // Strictly speaking, a relocation section must be included in the
844 // group of the section it relocates. However, LLVM 3.3 and earlier
845 // would fail to do so, so we gracefully handle that case.
846 if (target == &InputSection::discarded)
850 fatal(toString(this) + ": unsupported relocation reference");
854 // Create a regular InputSection class that has the same contents
855 // as a given section.
856 static InputSection *toRegularSection(MergeInputSection *sec) {
857 return make<InputSection>(sec->file, sec->flags, sec->type, sec->alignment,
858 sec->data(), sec->name);
861 template <class ELFT>
862 InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec) {
863 StringRef name = getSectionName(sec);
865 switch (sec.sh_type) {
866 case SHT_ARM_ATTRIBUTES: {
867 if (config->emachine != EM_ARM)
869 ARMAttributeParser attributes;
870 ArrayRef<uint8_t> contents = check(this->getObj().getSectionContents(&sec));
871 if (Error e = attributes.parse(contents, config->ekind == ELF32LEKind
874 auto *isec = make<InputSection>(*this, sec, name);
875 warn(toString(isec) + ": " + llvm::toString(std::move(e)));
878 updateSupportedARMFeatures(attributes);
879 updateARMVFPArgs(attributes, this);
881 // FIXME: Retain the first attribute section we see. The eglibc ARM
882 // dynamic loaders require the presence of an attribute section for dlopen
883 // to work. In a full implementation we would merge all attribute sections.
884 if (in.armAttributes == nullptr) {
885 in.armAttributes = make<InputSection>(*this, sec, name);
886 return in.armAttributes;
888 return &InputSection::discarded;
890 case SHT_LLVM_DEPENDENT_LIBRARIES: {
891 if (config->relocatable)
893 ArrayRef<char> data =
894 CHECK(this->getObj().template getSectionContentsAsArray<char>(&sec), this);
895 if (!data.empty() && data.back() != '\0') {
896 error(toString(this) +
897 ": corrupted dependent libraries section (unterminated string): " +
899 return &InputSection::discarded;
901 for (const char *d = data.begin(), *e = data.end(); d < e;) {
903 addDependentLibrary(s, this);
906 return &InputSection::discarded;
910 // Find a relocation target section and associate this section with that.
911 // Target may have been discarded if it is in a different section group
912 // and the group is discarded, even though it's a violation of the
913 // spec. We handle that situation gracefully by discarding dangling
914 // relocation sections.
915 InputSectionBase *target = getRelocTarget(sec);
919 // ELF spec allows mergeable sections with relocations, but they are
920 // rare, and it is in practice hard to merge such sections by contents,
921 // because applying relocations at end of linking changes section
922 // contents. So, we simply handle such sections as non-mergeable ones.
923 // Degrading like this is acceptable because section merging is optional.
924 if (auto *ms = dyn_cast<MergeInputSection>(target)) {
925 target = toRegularSection(ms);
926 this->sections[sec.sh_info] = target;
929 // This section contains relocation information.
930 // If -r is given, we do not interpret or apply relocation
931 // but just copy relocation sections to output.
932 if (config->relocatable) {
933 InputSection *relocSec = make<InputSection>(*this, sec, name);
934 // We want to add a dependency to target, similar like we do for
935 // -emit-relocs below. This is useful for the case when linker script
936 // contains the "/DISCARD/". It is perhaps uncommon to use a script with
937 // -r, but we faced it in the Linux kernel and have to handle such case
939 target->dependentSections.push_back(relocSec);
943 if (target->firstRelocation)
944 fatal(toString(this) +
945 ": multiple relocation sections to one section are not supported");
947 if (sec.sh_type == SHT_RELA) {
948 ArrayRef<Elf_Rela> rels = CHECK(getObj().relas(&sec), this);
949 target->firstRelocation = rels.begin();
950 target->numRelocations = rels.size();
951 target->areRelocsRela = true;
953 ArrayRef<Elf_Rel> rels = CHECK(getObj().rels(&sec), this);
954 target->firstRelocation = rels.begin();
955 target->numRelocations = rels.size();
956 target->areRelocsRela = false;
958 assert(isUInt<31>(target->numRelocations));
960 // Relocation sections processed by the linker are usually removed
961 // from the output, so returning `nullptr` for the normal case.
962 // However, if -emit-relocs is given, we need to leave them in the output.
963 // (Some post link analysis tools need this information.)
964 if (config->emitRelocs) {
965 InputSection *relocSec = make<InputSection>(*this, sec, name);
966 // We will not emit relocation section if target was discarded.
967 target->dependentSections.push_back(relocSec);
974 // The GNU linker uses .note.GNU-stack section as a marker indicating
975 // that the code in the object file does not expect that the stack is
976 // executable (in terms of NX bit). If all input files have the marker,
977 // the GNU linker adds a PT_GNU_STACK segment to tells the loader to
978 // make the stack non-executable. Most object files have this section as
981 // But making the stack non-executable is a norm today for security
982 // reasons. Failure to do so may result in a serious security issue.
983 // Therefore, we make LLD always add PT_GNU_STACK unless it is
984 // explicitly told to do otherwise (by -z execstack). Because the stack
985 // executable-ness is controlled solely by command line options,
986 // .note.GNU-stack sections are simply ignored.
987 if (name == ".note.GNU-stack")
988 return &InputSection::discarded;
990 // Object files that use processor features such as Intel Control-Flow
991 // Enforcement (CET) or AArch64 Branch Target Identification BTI, use a
992 // .note.gnu.property section containing a bitfield of feature bits like the
993 // GNU_PROPERTY_X86_FEATURE_1_IBT flag. Read a bitmap containing the flag.
995 // Since we merge bitmaps from multiple object files to create a new
996 // .note.gnu.property containing a single AND'ed bitmap, we discard an input
997 // file's .note.gnu.property section.
998 if (name == ".note.gnu.property") {
999 ArrayRef<uint8_t> contents = check(this->getObj().getSectionContents(&sec));
1000 this->andFeatures = readAndFeatures(this, contents);
1001 return &InputSection::discarded;
1004 // Split stacks is a feature to support a discontiguous stack,
1005 // commonly used in the programming language Go. For the details,
1006 // see https://gcc.gnu.org/wiki/SplitStacks. An object file compiled
1007 // for split stack will include a .note.GNU-split-stack section.
1008 if (name == ".note.GNU-split-stack") {
1009 if (config->relocatable) {
1010 error("cannot mix split-stack and non-split-stack in a relocatable link");
1011 return &InputSection::discarded;
1013 this->splitStack = true;
1014 return &InputSection::discarded;
1017 // An object file cmpiled for split stack, but where some of the
1018 // functions were compiled with the no_split_stack_attribute will
1019 // include a .note.GNU-no-split-stack section.
1020 if (name == ".note.GNU-no-split-stack") {
1021 this->someNoSplitStack = true;
1022 return &InputSection::discarded;
1025 // The linkonce feature is a sort of proto-comdat. Some glibc i386 object
1026 // files contain definitions of symbol "__x86.get_pc_thunk.bx" in linkonce
1027 // sections. Drop those sections to avoid duplicate symbol errors.
1028 // FIXME: This is glibc PR20543, we should remove this hack once that has been
1029 // fixed for a while.
1030 if (name == ".gnu.linkonce.t.__x86.get_pc_thunk.bx" ||
1031 name == ".gnu.linkonce.t.__i686.get_pc_thunk.bx")
1032 return &InputSection::discarded;
1034 // If we are creating a new .build-id section, strip existing .build-id
1035 // sections so that the output won't have more than one .build-id.
1036 // This is not usually a problem because input object files normally don't
1037 // have .build-id sections, but you can create such files by
1038 // "ld.{bfd,gold,lld} -r --build-id", and we want to guard against it.
1039 if (name == ".note.gnu.build-id" && config->buildId != BuildIdKind::None)
1040 return &InputSection::discarded;
1042 // The linker merges EH (exception handling) frames and creates a
1043 // .eh_frame_hdr section for runtime. So we handle them with a special
1044 // class. For relocatable outputs, they are just passed through.
1045 if (name == ".eh_frame" && !config->relocatable)
1046 return make<EhInputSection>(*this, sec, name);
1048 if (shouldMerge(sec, name))
1049 return make<MergeInputSection>(*this, sec, name);
1050 return make<InputSection>(*this, sec, name);
1053 template <class ELFT>
1054 StringRef ObjFile<ELFT>::getSectionName(const Elf_Shdr &sec) {
1055 return CHECK(getObj().getSectionName(&sec, sectionStringTable), this);
1058 // Initialize this->Symbols. this->Symbols is a parallel array as
1059 // its corresponding ELF symbol table.
1060 template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
1061 ArrayRef<Elf_Sym> eSyms = this->getELFSyms<ELFT>();
1062 this->symbols.resize(eSyms.size());
1064 // Fill in InputFile::symbols. Some entries have been initialized
1065 // because of LazyObjFile.
1066 for (size_t i = 0, end = eSyms.size(); i != end; ++i) {
1067 if (this->symbols[i])
1069 const Elf_Sym &eSym = eSyms[i];
1070 uint32_t secIdx = getSectionIndex(eSym);
1071 if (secIdx >= this->sections.size())
1072 fatal(toString(this) + ": invalid section index: " + Twine(secIdx));
1073 if (eSym.getBinding() != STB_LOCAL) {
1074 if (i < firstGlobal)
1075 error(toString(this) + ": non-local symbol (" + Twine(i) +
1076 ") found at index < .symtab's sh_info (" + Twine(firstGlobal) +
1079 symtab->insert(CHECK(eSyms[i].getName(this->stringTable), this));
1083 // Handle local symbols. Local symbols are not added to the symbol
1084 // table because they are not visible from other object files. We
1085 // allocate symbol instances and add their pointers to symbols.
1086 if (i >= firstGlobal)
1087 errorOrWarn(toString(this) + ": STB_LOCAL symbol (" + Twine(i) +
1088 ") found at index >= .symtab's sh_info (" +
1089 Twine(firstGlobal) + ")");
1091 InputSectionBase *sec = this->sections[secIdx];
1092 uint8_t type = eSym.getType();
1093 if (type == STT_FILE)
1094 sourceFile = CHECK(eSym.getName(this->stringTable), this);
1095 if (this->stringTable.size() <= eSym.st_name)
1096 fatal(toString(this) + ": invalid symbol name offset");
1097 StringRefZ name = this->stringTable.data() + eSym.st_name;
1099 if (eSym.st_shndx == SHN_UNDEF)
1101 make<Undefined>(this, name, STB_LOCAL, eSym.st_other, type);
1102 else if (sec == &InputSection::discarded)
1104 make<Undefined>(this, name, STB_LOCAL, eSym.st_other, type,
1105 /*discardedSecIdx=*/secIdx);
1107 this->symbols[i] = make<Defined>(this, name, STB_LOCAL, eSym.st_other,
1108 type, eSym.st_value, eSym.st_size, sec);
1111 // Symbol resolution of non-local symbols.
1112 for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i) {
1113 const Elf_Sym &eSym = eSyms[i];
1114 uint8_t binding = eSym.getBinding();
1115 if (binding == STB_LOCAL)
1116 continue; // Errored above.
1118 uint32_t secIdx = getSectionIndex(eSym);
1119 InputSectionBase *sec = this->sections[secIdx];
1120 uint8_t stOther = eSym.st_other;
1121 uint8_t type = eSym.getType();
1122 uint64_t value = eSym.st_value;
1123 uint64_t size = eSym.st_size;
1124 StringRefZ name = this->stringTable.data() + eSym.st_name;
1126 // Handle global undefined symbols.
1127 if (eSym.st_shndx == SHN_UNDEF) {
1128 this->symbols[i]->resolve(Undefined{this, name, binding, stOther, type});
1129 this->symbols[i]->referenced = true;
1133 // Handle global common symbols.
1134 if (eSym.st_shndx == SHN_COMMON) {
1135 if (value == 0 || value >= UINT32_MAX)
1136 fatal(toString(this) + ": common symbol '" + StringRef(name.data) +
1137 "' has invalid alignment: " + Twine(value));
1138 this->symbols[i]->resolve(
1139 CommonSymbol{this, name, binding, stOther, type, value, size});
1143 // If a defined symbol is in a discarded section, handle it as if it
1144 // were an undefined symbol. Such symbol doesn't comply with the
1145 // standard, but in practice, a .eh_frame often directly refer
1146 // COMDAT member sections, and if a comdat group is discarded, some
1147 // defined symbol in a .eh_frame becomes dangling symbols.
1148 if (sec == &InputSection::discarded) {
1149 Undefined und{this, name, binding, stOther, type, secIdx};
1150 Symbol *sym = this->symbols[i];
1151 // !ArchiveFile::parsed or LazyObjFile::fetched means that the file
1152 // containing this object has not finished processing, i.e. this symbol is
1153 // a result of a lazy symbol fetch. We should demote the lazy symbol to an
1154 // Undefined so that any relocations outside of the group to it will
1155 // trigger a discarded section error.
1156 if ((sym->symbolKind == Symbol::LazyArchiveKind &&
1157 !cast<ArchiveFile>(sym->file)->parsed) ||
1158 (sym->symbolKind == Symbol::LazyObjectKind &&
1159 cast<LazyObjFile>(sym->file)->fetched))
1166 // Handle global defined symbols.
1167 if (binding == STB_GLOBAL || binding == STB_WEAK ||
1168 binding == STB_GNU_UNIQUE) {
1169 this->symbols[i]->resolve(
1170 Defined{this, name, binding, stOther, type, value, size, sec});
1174 fatal(toString(this) + ": unexpected binding: " + Twine((int)binding));
1178 ArchiveFile::ArchiveFile(std::unique_ptr<Archive> &&file)
1179 : InputFile(ArchiveKind, file->getMemoryBufferRef()),
1180 file(std::move(file)) {}
1182 void ArchiveFile::parse() {
1183 for (const Archive::Symbol &sym : file->symbols())
1184 symtab->addSymbol(LazyArchive{*this, sym});
1186 // Inform a future invocation of ObjFile<ELFT>::initializeSymbols() that this
1187 // archive has been processed.
1191 // Returns a buffer pointing to a member file containing a given symbol.
1192 void ArchiveFile::fetch(const Archive::Symbol &sym) {
1194 CHECK(sym.getMember(), toString(this) +
1195 ": could not get the member for symbol " +
1198 if (!seen.insert(c.getChildOffset()).second)
1201 MemoryBufferRef mb =
1202 CHECK(c.getMemoryBufferRef(),
1204 ": could not get the buffer for the member defining symbol " +
1207 if (tar && c.getParent()->isThin())
1208 tar->append(relativeToRoot(CHECK(c.getFullName(), this)), mb.getBuffer());
1210 InputFile *file = createObjectFile(mb, getName(), c.getChildOffset());
1211 file->groupId = groupId;
1215 size_t ArchiveFile::getMemberCount() const {
1217 Error err = Error::success();
1218 for (const Archive::Child &c : file->children(err)) {
1222 // This function is used by --print-archive-stats=, where an error does not
1224 consumeError(std::move(err));
1228 unsigned SharedFile::vernauxNum;
1230 // Parse the version definitions in the object file if present, and return a
1231 // vector whose nth element contains a pointer to the Elf_Verdef for version
1232 // identifier n. Version identifiers that are not definitions map to nullptr.
1233 template <typename ELFT>
1234 static std::vector<const void *> parseVerdefs(const uint8_t *base,
1235 const typename ELFT::Shdr *sec) {
1239 // We cannot determine the largest verdef identifier without inspecting
1240 // every Elf_Verdef, but both bfd and gold assign verdef identifiers
1241 // sequentially starting from 1, so we predict that the largest identifier
1242 // will be verdefCount.
1243 unsigned verdefCount = sec->sh_info;
1244 std::vector<const void *> verdefs(verdefCount + 1);
1246 // Build the Verdefs array by following the chain of Elf_Verdef objects
1247 // from the start of the .gnu.version_d section.
1248 const uint8_t *verdef = base + sec->sh_offset;
1249 for (unsigned i = 0; i != verdefCount; ++i) {
1250 auto *curVerdef = reinterpret_cast<const typename ELFT::Verdef *>(verdef);
1251 verdef += curVerdef->vd_next;
1252 unsigned verdefIndex = curVerdef->vd_ndx;
1253 verdefs.resize(verdefIndex + 1);
1254 verdefs[verdefIndex] = curVerdef;
1259 // Parse SHT_GNU_verneed to properly set the name of a versioned undefined
1260 // symbol. We detect fatal issues which would cause vulnerabilities, but do not
1261 // implement sophisticated error checking like in llvm-readobj because the value
1262 // of such diagnostics is low.
1263 template <typename ELFT>
1264 std::vector<uint32_t> SharedFile::parseVerneed(const ELFFile<ELFT> &obj,
1265 const typename ELFT::Shdr *sec) {
1268 std::vector<uint32_t> verneeds;
1269 ArrayRef<uint8_t> data = CHECK(obj.getSectionContents(sec), this);
1270 const uint8_t *verneedBuf = data.begin();
1271 for (unsigned i = 0; i != sec->sh_info; ++i) {
1272 if (verneedBuf + sizeof(typename ELFT::Verneed) > data.end())
1273 fatal(toString(this) + " has an invalid Verneed");
1274 auto *vn = reinterpret_cast<const typename ELFT::Verneed *>(verneedBuf);
1275 const uint8_t *vernauxBuf = verneedBuf + vn->vn_aux;
1276 for (unsigned j = 0; j != vn->vn_cnt; ++j) {
1277 if (vernauxBuf + sizeof(typename ELFT::Vernaux) > data.end())
1278 fatal(toString(this) + " has an invalid Vernaux");
1279 auto *aux = reinterpret_cast<const typename ELFT::Vernaux *>(vernauxBuf);
1280 if (aux->vna_name >= this->stringTable.size())
1281 fatal(toString(this) + " has a Vernaux with an invalid vna_name");
1282 uint16_t version = aux->vna_other & VERSYM_VERSION;
1283 if (version >= verneeds.size())
1284 verneeds.resize(version + 1);
1285 verneeds[version] = aux->vna_name;
1286 vernauxBuf += aux->vna_next;
1288 verneedBuf += vn->vn_next;
1293 // We do not usually care about alignments of data in shared object
1294 // files because the loader takes care of it. However, if we promote a
1295 // DSO symbol to point to .bss due to copy relocation, we need to keep
1296 // the original alignment requirements. We infer it in this function.
1297 template <typename ELFT>
1298 static uint64_t getAlignment(ArrayRef<typename ELFT::Shdr> sections,
1299 const typename ELFT::Sym &sym) {
1300 uint64_t ret = UINT64_MAX;
1302 ret = 1ULL << countTrailingZeros((uint64_t)sym.st_value);
1303 if (0 < sym.st_shndx && sym.st_shndx < sections.size())
1304 ret = std::min<uint64_t>(ret, sections[sym.st_shndx].sh_addralign);
1305 return (ret > UINT32_MAX) ? 0 : ret;
1308 // Fully parse the shared object file.
1310 // This function parses symbol versions. If a DSO has version information,
1311 // the file has a ".gnu.version_d" section which contains symbol version
1312 // definitions. Each symbol is associated to one version through a table in
1313 // ".gnu.version" section. That table is a parallel array for the symbol
1314 // table, and each table entry contains an index in ".gnu.version_d".
1316 // The special index 0 is reserved for VERF_NDX_LOCAL and 1 is for
1317 // VER_NDX_GLOBAL. There's no table entry for these special versions in
1318 // ".gnu.version_d".
1320 // The file format for symbol versioning is perhaps a bit more complicated
1321 // than necessary, but you can easily understand the code if you wrap your
1322 // head around the data structure described above.
1323 template <class ELFT> void SharedFile::parse() {
1324 using Elf_Dyn = typename ELFT::Dyn;
1325 using Elf_Shdr = typename ELFT::Shdr;
1326 using Elf_Sym = typename ELFT::Sym;
1327 using Elf_Verdef = typename ELFT::Verdef;
1328 using Elf_Versym = typename ELFT::Versym;
1330 ArrayRef<Elf_Dyn> dynamicTags;
1331 const ELFFile<ELFT> obj = this->getObj<ELFT>();
1332 ArrayRef<Elf_Shdr> sections = CHECK(obj.sections(), this);
1334 const Elf_Shdr *versymSec = nullptr;
1335 const Elf_Shdr *verdefSec = nullptr;
1336 const Elf_Shdr *verneedSec = nullptr;
1338 // Search for .dynsym, .dynamic, .symtab, .gnu.version and .gnu.version_d.
1339 for (const Elf_Shdr &sec : sections) {
1340 switch (sec.sh_type) {
1345 CHECK(obj.template getSectionContentsAsArray<Elf_Dyn>(&sec), this);
1347 case SHT_GNU_versym:
1350 case SHT_GNU_verdef:
1353 case SHT_GNU_verneed:
1359 if (versymSec && numELFSyms == 0) {
1360 error("SHT_GNU_versym should be associated with symbol table");
1364 // Search for a DT_SONAME tag to initialize this->soName.
1365 for (const Elf_Dyn &dyn : dynamicTags) {
1366 if (dyn.d_tag == DT_NEEDED) {
1367 uint64_t val = dyn.getVal();
1368 if (val >= this->stringTable.size())
1369 fatal(toString(this) + ": invalid DT_NEEDED entry");
1370 dtNeeded.push_back(this->stringTable.data() + val);
1371 } else if (dyn.d_tag == DT_SONAME) {
1372 uint64_t val = dyn.getVal();
1373 if (val >= this->stringTable.size())
1374 fatal(toString(this) + ": invalid DT_SONAME entry");
1375 soName = this->stringTable.data() + val;
1379 // DSOs are uniquified not by filename but by soname.
1380 DenseMap<StringRef, SharedFile *>::iterator it;
1382 std::tie(it, wasInserted) = symtab->soNames.try_emplace(soName, this);
1384 // If a DSO appears more than once on the command line with and without
1385 // --as-needed, --no-as-needed takes precedence over --as-needed because a
1386 // user can add an extra DSO with --no-as-needed to force it to be added to
1387 // the dependency list.
1388 it->second->isNeeded |= isNeeded;
1392 sharedFiles.push_back(this);
1394 verdefs = parseVerdefs<ELFT>(obj.base(), verdefSec);
1395 std::vector<uint32_t> verneeds = parseVerneed<ELFT>(obj, verneedSec);
1397 // Parse ".gnu.version" section which is a parallel array for the symbol
1398 // table. If a given file doesn't have a ".gnu.version" section, we use
1400 size_t size = numELFSyms - firstGlobal;
1401 std::vector<uint16_t> versyms(size, VER_NDX_GLOBAL);
1403 ArrayRef<Elf_Versym> versym =
1404 CHECK(obj.template getSectionContentsAsArray<Elf_Versym>(versymSec),
1406 .slice(firstGlobal);
1407 for (size_t i = 0; i < size; ++i)
1408 versyms[i] = versym[i].vs_index;
1411 // System libraries can have a lot of symbols with versions. Using a
1412 // fixed buffer for computing the versions name (foo@ver) can save a
1413 // lot of allocations.
1414 SmallString<0> versionedNameBuffer;
1416 // Add symbols to the symbol table.
1417 ArrayRef<Elf_Sym> syms = this->getGlobalELFSyms<ELFT>();
1418 for (size_t i = 0; i < syms.size(); ++i) {
1419 const Elf_Sym &sym = syms[i];
1421 // ELF spec requires that all local symbols precede weak or global
1422 // symbols in each symbol table, and the index of first non-local symbol
1423 // is stored to sh_info. If a local symbol appears after some non-local
1424 // symbol, that's a violation of the spec.
1425 StringRef name = CHECK(sym.getName(this->stringTable), this);
1426 if (sym.getBinding() == STB_LOCAL) {
1427 warn("found local symbol '" + name +
1428 "' in global part of symbol table in file " + toString(this));
1432 uint16_t idx = versyms[i] & ~VERSYM_HIDDEN;
1433 if (sym.isUndefined()) {
1434 // For unversioned undefined symbols, VER_NDX_GLOBAL makes more sense but
1435 // as of binutils 2.34, GNU ld produces VER_NDX_LOCAL.
1436 if (idx != VER_NDX_LOCAL && idx != VER_NDX_GLOBAL) {
1437 if (idx >= verneeds.size()) {
1438 error("corrupt input file: version need index " + Twine(idx) +
1439 " for symbol " + name + " is out of bounds\n>>> defined in " +
1443 StringRef verName = this->stringTable.data() + verneeds[idx];
1444 versionedNameBuffer.clear();
1446 saver.save((name + "@" + verName).toStringRef(versionedNameBuffer));
1448 Symbol *s = symtab->addSymbol(
1449 Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
1450 s->exportDynamic = true;
1454 // MIPS BFD linker puts _gp_disp symbol into DSO files and incorrectly
1455 // assigns VER_NDX_LOCAL to this section global symbol. Here is a
1456 // workaround for this bug.
1457 if (config->emachine == EM_MIPS && idx == VER_NDX_LOCAL &&
1461 uint32_t alignment = getAlignment<ELFT>(sections, sym);
1462 if (!(versyms[i] & VERSYM_HIDDEN)) {
1463 symtab->addSymbol(SharedSymbol{*this, name, sym.getBinding(),
1464 sym.st_other, sym.getType(), sym.st_value,
1465 sym.st_size, alignment, idx});
1468 // Also add the symbol with the versioned name to handle undefined symbols
1469 // with explicit versions.
1470 if (idx == VER_NDX_GLOBAL)
1473 if (idx >= verdefs.size() || idx == VER_NDX_LOCAL) {
1474 error("corrupt input file: version definition index " + Twine(idx) +
1475 " for symbol " + name + " is out of bounds\n>>> defined in " +
1481 this->stringTable.data() +
1482 reinterpret_cast<const Elf_Verdef *>(verdefs[idx])->getAux()->vda_name;
1483 versionedNameBuffer.clear();
1484 name = (name + "@" + verName).toStringRef(versionedNameBuffer);
1485 symtab->addSymbol(SharedSymbol{*this, saver.save(name), sym.getBinding(),
1486 sym.st_other, sym.getType(), sym.st_value,
1487 sym.st_size, alignment, idx});
1491 static ELFKind getBitcodeELFKind(const Triple &t) {
1492 if (t.isLittleEndian())
1493 return t.isArch64Bit() ? ELF64LEKind : ELF32LEKind;
1494 return t.isArch64Bit() ? ELF64BEKind : ELF32BEKind;
1497 static uint8_t getBitcodeMachineKind(StringRef path, const Triple &t) {
1498 switch (t.getArch()) {
1499 case Triple::aarch64:
1501 case Triple::amdgcn:
1510 case Triple::mipsel:
1511 case Triple::mips64:
1512 case Triple::mips64el:
1514 case Triple::msp430:
1519 case Triple::ppc64le:
1521 case Triple::riscv32:
1522 case Triple::riscv64:
1525 return t.isOSIAMCU() ? EM_IAMCU : EM_386;
1526 case Triple::x86_64:
1529 error(path + ": could not infer e_machine from bitcode target triple " +
1535 BitcodeFile::BitcodeFile(MemoryBufferRef mb, StringRef archiveName,
1536 uint64_t offsetInArchive)
1537 : InputFile(BitcodeKind, mb) {
1538 this->archiveName = std::string(archiveName);
1540 std::string path = mb.getBufferIdentifier().str();
1541 if (config->thinLTOIndexOnly)
1542 path = replaceThinLTOSuffix(mb.getBufferIdentifier());
1544 // ThinLTO assumes that all MemoryBufferRefs given to it have a unique
1545 // name. If two archives define two members with the same name, this
1546 // causes a collision which result in only one of the objects being taken
1547 // into consideration at LTO time (which very likely causes undefined
1548 // symbols later in the link stage). So we append file offset to make
1553 : saver.save(archiveName + "(" + path::filename(path) + " at " +
1554 utostr(offsetInArchive) + ")");
1555 MemoryBufferRef mbref(mb.getBuffer(), name);
1557 obj = CHECK(lto::InputFile::create(mbref), this);
1559 Triple t(obj->getTargetTriple());
1560 ekind = getBitcodeELFKind(t);
1561 emachine = getBitcodeMachineKind(mb.getBufferIdentifier(), t);
1564 static uint8_t mapVisibility(GlobalValue::VisibilityTypes gvVisibility) {
1565 switch (gvVisibility) {
1566 case GlobalValue::DefaultVisibility:
1568 case GlobalValue::HiddenVisibility:
1570 case GlobalValue::ProtectedVisibility:
1571 return STV_PROTECTED;
1573 llvm_unreachable("unknown visibility");
1576 template <class ELFT>
1577 static Symbol *createBitcodeSymbol(const std::vector<bool> &keptComdats,
1578 const lto::InputFile::Symbol &objSym,
1580 StringRef name = saver.save(objSym.getName());
1581 uint8_t binding = objSym.isWeak() ? STB_WEAK : STB_GLOBAL;
1582 uint8_t type = objSym.isTLS() ? STT_TLS : STT_NOTYPE;
1583 uint8_t visibility = mapVisibility(objSym.getVisibility());
1584 bool canOmitFromDynSym = objSym.canBeOmittedFromSymbolTable();
1586 int c = objSym.getComdatIndex();
1587 if (objSym.isUndefined() || (c != -1 && !keptComdats[c])) {
1588 Undefined newSym(&f, name, binding, visibility, type);
1589 if (canOmitFromDynSym)
1590 newSym.exportDynamic = false;
1591 Symbol *ret = symtab->addSymbol(newSym);
1592 ret->referenced = true;
1596 if (objSym.isCommon())
1597 return symtab->addSymbol(
1598 CommonSymbol{&f, name, binding, visibility, STT_OBJECT,
1599 objSym.getCommonAlignment(), objSym.getCommonSize()});
1601 Defined newSym(&f, name, binding, visibility, type, 0, 0, nullptr);
1602 if (canOmitFromDynSym)
1603 newSym.exportDynamic = false;
1604 return symtab->addSymbol(newSym);
1607 template <class ELFT> void BitcodeFile::parse() {
1608 std::vector<bool> keptComdats;
1609 for (StringRef s : obj->getComdatTable())
1610 keptComdats.push_back(
1611 symtab->comdatGroups.try_emplace(CachedHashStringRef(s), this).second);
1613 for (const lto::InputFile::Symbol &objSym : obj->symbols())
1614 symbols.push_back(createBitcodeSymbol<ELFT>(keptComdats, objSym, *this));
1616 for (auto l : obj->getDependentLibraries())
1617 addDependentLibrary(l, this);
1620 void BinaryFile::parse() {
1621 ArrayRef<uint8_t> data = arrayRefFromStringRef(mb.getBuffer());
1622 auto *section = make<InputSection>(this, SHF_ALLOC | SHF_WRITE, SHT_PROGBITS,
1624 sections.push_back(section);
1626 // For each input file foo that is embedded to a result as a binary
1627 // blob, we define _binary_foo_{start,end,size} symbols, so that
1628 // user programs can access blobs by name. Non-alphanumeric
1629 // characters in a filename are replaced with underscore.
1630 std::string s = "_binary_" + mb.getBufferIdentifier().str();
1631 for (size_t i = 0; i < s.size(); ++i)
1635 symtab->addSymbol(Defined{nullptr, saver.save(s + "_start"), STB_GLOBAL,
1636 STV_DEFAULT, STT_OBJECT, 0, 0, section});
1637 symtab->addSymbol(Defined{nullptr, saver.save(s + "_end"), STB_GLOBAL,
1638 STV_DEFAULT, STT_OBJECT, data.size(), 0, section});
1639 symtab->addSymbol(Defined{nullptr, saver.save(s + "_size"), STB_GLOBAL,
1640 STV_DEFAULT, STT_OBJECT, data.size(), 0, nullptr});
1643 InputFile *elf::createObjectFile(MemoryBufferRef mb, StringRef archiveName,
1644 uint64_t offsetInArchive) {
1646 return make<BitcodeFile>(mb, archiveName, offsetInArchive);
1648 switch (getELFKind(mb, archiveName)) {
1650 return make<ObjFile<ELF32LE>>(mb, archiveName);
1652 return make<ObjFile<ELF32BE>>(mb, archiveName);
1654 return make<ObjFile<ELF64LE>>(mb, archiveName);
1656 return make<ObjFile<ELF64BE>>(mb, archiveName);
1658 llvm_unreachable("getELFKind");
1662 void LazyObjFile::fetch() {
1667 InputFile *file = createObjectFile(mb, archiveName, offsetInArchive);
1668 file->groupId = groupId;
1670 // Copy symbol vector so that the new InputFile doesn't have to
1671 // insert the same defined symbols to the symbol table again.
1672 file->symbols = std::move(symbols);
1677 template <class ELFT> void LazyObjFile::parse() {
1678 using Elf_Sym = typename ELFT::Sym;
1680 // A lazy object file wraps either a bitcode file or an ELF file.
1681 if (isBitcode(this->mb)) {
1682 std::unique_ptr<lto::InputFile> obj =
1683 CHECK(lto::InputFile::create(this->mb), this);
1684 for (const lto::InputFile::Symbol &sym : obj->symbols()) {
1685 if (sym.isUndefined())
1687 symtab->addSymbol(LazyObject{*this, saver.save(sym.getName())});
1692 if (getELFKind(this->mb, archiveName) != config->ekind) {
1693 error("incompatible file: " + this->mb.getBufferIdentifier());
1697 // Find a symbol table.
1698 ELFFile<ELFT> obj = check(ELFFile<ELFT>::create(mb.getBuffer()));
1699 ArrayRef<typename ELFT::Shdr> sections = CHECK(obj.sections(), this);
1701 for (const typename ELFT::Shdr &sec : sections) {
1702 if (sec.sh_type != SHT_SYMTAB)
1705 // A symbol table is found.
1706 ArrayRef<Elf_Sym> eSyms = CHECK(obj.symbols(&sec), this);
1707 uint32_t firstGlobal = sec.sh_info;
1708 StringRef strtab = CHECK(obj.getStringTableForSymtab(sec, sections), this);
1709 this->symbols.resize(eSyms.size());
1711 // Get existing symbols or insert placeholder symbols.
1712 for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i)
1713 if (eSyms[i].st_shndx != SHN_UNDEF)
1714 this->symbols[i] = symtab->insert(CHECK(eSyms[i].getName(strtab), this));
1716 // Replace existing symbols with LazyObject symbols.
1718 // resolve() may trigger this->fetch() if an existing symbol is an
1719 // undefined symbol. If that happens, this LazyObjFile has served
1720 // its purpose, and we can exit from the loop early.
1721 for (Symbol *sym : this->symbols) {
1724 sym->resolve(LazyObject{*this, sym->getName()});
1726 // If fetched, stop iterating because this->symbols has been transferred
1727 // to the instantiated ObjFile.
1735 std::string elf::replaceThinLTOSuffix(StringRef path) {
1736 StringRef suffix = config->thinLTOObjectSuffixReplace.first;
1737 StringRef repl = config->thinLTOObjectSuffixReplace.second;
1739 if (path.consume_back(suffix))
1740 return (path + repl).str();
1741 return std::string(path);
1744 template void BitcodeFile::parse<ELF32LE>();
1745 template void BitcodeFile::parse<ELF32BE>();
1746 template void BitcodeFile::parse<ELF64LE>();
1747 template void BitcodeFile::parse<ELF64BE>();
1749 template void LazyObjFile::parse<ELF32LE>();
1750 template void LazyObjFile::parse<ELF32BE>();
1751 template void LazyObjFile::parse<ELF64LE>();
1752 template void LazyObjFile::parse<ELF64BE>();
1754 template class elf::ObjFile<ELF32LE>;
1755 template class elf::ObjFile<ELF32BE>;
1756 template class elf::ObjFile<ELF64LE>;
1757 template class elf::ObjFile<ELF64BE>;
1759 template void SharedFile::parse<ELF32LE>();
1760 template void SharedFile::parse<ELF32BE>();
1761 template void SharedFile::parse<ELF64LE>();
1762 template void SharedFile::parse<ELF64BE>();