/contrib/llvm/tools/lld/ELF/InputFiles.cpp
C++ | 1336 lines | 873 code | 165 blank | 298 comment | 263 complexity | e246f46e883d03bacf2abf66fc391fd4 MD5 | raw file
- //===- InputFiles.cpp -----------------------------------------------------===//
- //
- // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
- // See https://llvm.org/LICENSE.txt for license information.
- // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
- //
- //===----------------------------------------------------------------------===//
- #include "InputFiles.h"
- #include "Driver.h"
- #include "InputSection.h"
- #include "LinkerScript.h"
- #include "SymbolTable.h"
- #include "Symbols.h"
- #include "SyntheticSections.h"
- #include "lld/Common/ErrorHandler.h"
- #include "lld/Common/Memory.h"
- #include "llvm/ADT/STLExtras.h"
- #include "llvm/CodeGen/Analysis.h"
- #include "llvm/DebugInfo/DWARF/DWARFContext.h"
- #include "llvm/IR/LLVMContext.h"
- #include "llvm/IR/Module.h"
- #include "llvm/LTO/LTO.h"
- #include "llvm/MC/StringTableBuilder.h"
- #include "llvm/Object/ELFObjectFile.h"
- #include "llvm/Support/ARMAttributeParser.h"
- #include "llvm/Support/ARMBuildAttributes.h"
- #include "llvm/Support/Endian.h"
- #include "llvm/Support/Path.h"
- #include "llvm/Support/TarWriter.h"
- #include "llvm/Support/raw_ostream.h"
- using namespace llvm;
- using namespace llvm::ELF;
- using namespace llvm::object;
- using namespace llvm::sys;
- using namespace llvm::sys::fs;
- using namespace llvm::support::endian;
- using namespace lld;
- using namespace lld::elf;
- bool InputFile::isInGroup;
- uint32_t InputFile::nextGroupId;
- std::vector<BinaryFile *> elf::binaryFiles;
- std::vector<BitcodeFile *> elf::bitcodeFiles;
- std::vector<LazyObjFile *> elf::lazyObjFiles;
- std::vector<InputFile *> elf::objectFiles;
- std::vector<SharedFile *> elf::sharedFiles;
- std::unique_ptr<TarWriter> elf::tar;
- static ELFKind getELFKind(MemoryBufferRef mb, StringRef archiveName) {
- unsigned char size;
- unsigned char endian;
- std::tie(size, endian) = getElfArchType(mb.getBuffer());
- auto report = [&](StringRef msg) {
- StringRef filename = mb.getBufferIdentifier();
- if (archiveName.empty())
- fatal(filename + ": " + msg);
- else
- fatal(archiveName + "(" + filename + "): " + msg);
- };
- if (!mb.getBuffer().startswith(ElfMagic))
- report("not an ELF file");
- if (endian != ELFDATA2LSB && endian != ELFDATA2MSB)
- report("corrupted ELF file: invalid data encoding");
- if (size != ELFCLASS32 && size != ELFCLASS64)
- report("corrupted ELF file: invalid file class");
- size_t bufSize = mb.getBuffer().size();
- if ((size == ELFCLASS32 && bufSize < sizeof(Elf32_Ehdr)) ||
- (size == ELFCLASS64 && bufSize < sizeof(Elf64_Ehdr)))
- report("corrupted ELF file: file is too short");
- if (size == ELFCLASS32)
- return (endian == ELFDATA2LSB) ? ELF32LEKind : ELF32BEKind;
- return (endian == ELFDATA2LSB) ? ELF64LEKind : ELF64BEKind;
- }
- InputFile::InputFile(Kind k, MemoryBufferRef m)
- : mb(m), groupId(nextGroupId), fileKind(k) {
- // All files within the same --{start,end}-group get the same group ID.
- // Otherwise, a new file will get a new group ID.
- if (!isInGroup)
- ++nextGroupId;
- }
- Optional<MemoryBufferRef> elf::readFile(StringRef path) {
- // The --chroot option changes our virtual root directory.
- // This is useful when you are dealing with files created by --reproduce.
- if (!config->chroot.empty() && path.startswith("/"))
- path = saver.save(config->chroot + path);
- log(path);
- auto mbOrErr = MemoryBuffer::getFile(path, -1, false);
- if (auto ec = mbOrErr.getError()) {
- error("cannot open " + path + ": " + ec.message());
- return None;
- }
- std::unique_ptr<MemoryBuffer> &mb = *mbOrErr;
- MemoryBufferRef mbref = mb->getMemBufferRef();
- make<std::unique_ptr<MemoryBuffer>>(std::move(mb)); // take MB ownership
- if (tar)
- tar->append(relativeToRoot(path), mbref.getBuffer());
- return mbref;
- }
- // All input object files must be for the same architecture
- // (e.g. it does not make sense to link x86 object files with
- // MIPS object files.) This function checks for that error.
- static bool isCompatible(InputFile *file) {
- if (!file->isElf() && !isa<BitcodeFile>(file))
- return true;
- if (file->ekind == config->ekind && file->emachine == config->emachine) {
- if (config->emachine != EM_MIPS)
- return true;
- if (isMipsN32Abi(file) == config->mipsN32Abi)
- return true;
- }
- if (!config->emulation.empty()) {
- error(toString(file) + " is incompatible with " + config->emulation);
- } else {
- InputFile *existing;
- if (!objectFiles.empty())
- existing = objectFiles[0];
- else if (!sharedFiles.empty())
- existing = sharedFiles[0];
- else
- existing = bitcodeFiles[0];
- error(toString(file) + " is incompatible with " + toString(existing));
- }
- return false;
- }
- template <class ELFT> static void doParseFile(InputFile *file) {
- if (!isCompatible(file))
- return;
- // Binary file
- if (auto *f = dyn_cast<BinaryFile>(file)) {
- binaryFiles.push_back(f);
- f->parse();
- return;
- }
- // .a file
- if (auto *f = dyn_cast<ArchiveFile>(file)) {
- f->parse();
- return;
- }
- // Lazy object file
- if (auto *f = dyn_cast<LazyObjFile>(file)) {
- lazyObjFiles.push_back(f);
- f->parse<ELFT>();
- return;
- }
- if (config->trace)
- message(toString(file));
- // .so file
- if (auto *f = dyn_cast<SharedFile>(file)) {
- f->parse<ELFT>();
- return;
- }
- // LLVM bitcode file
- if (auto *f = dyn_cast<BitcodeFile>(file)) {
- bitcodeFiles.push_back(f);
- f->parse<ELFT>();
- return;
- }
- // Regular object file
- objectFiles.push_back(file);
- cast<ObjFile<ELFT>>(file)->parse();
- }
- // Add symbols in File to the symbol table.
- void elf::parseFile(InputFile *file) {
- switch (config->ekind) {
- case ELF32LEKind:
- doParseFile<ELF32LE>(file);
- return;
- case ELF32BEKind:
- doParseFile<ELF32BE>(file);
- return;
- case ELF64LEKind:
- doParseFile<ELF64LE>(file);
- return;
- case ELF64BEKind:
- doParseFile<ELF64BE>(file);
- return;
- default:
- llvm_unreachable("unknown ELFT");
- }
- }
- // Concatenates arguments to construct a string representing an error location.
- static std::string createFileLineMsg(StringRef path, unsigned line) {
- std::string filename = path::filename(path);
- std::string lineno = ":" + std::to_string(line);
- if (filename == path)
- return filename + lineno;
- return filename + lineno + " (" + path.str() + lineno + ")";
- }
- template <class ELFT>
- static std::string getSrcMsgAux(ObjFile<ELFT> &file, const Symbol &sym,
- InputSectionBase &sec, uint64_t offset) {
- // In DWARF, functions and variables are stored to different places.
- // First, lookup a function for a given offset.
- if (Optional<DILineInfo> info = file.getDILineInfo(&sec, offset))
- return createFileLineMsg(info->FileName, info->Line);
- // If it failed, lookup again as a variable.
- if (Optional<std::pair<std::string, unsigned>> fileLine =
- file.getVariableLoc(sym.getName()))
- return createFileLineMsg(fileLine->first, fileLine->second);
- // File.sourceFile contains STT_FILE symbol, and that is a last resort.
- return file.sourceFile;
- }
- std::string InputFile::getSrcMsg(const Symbol &sym, InputSectionBase &sec,
- uint64_t offset) {
- if (kind() != ObjKind)
- return "";
- switch (config->ekind) {
- default:
- llvm_unreachable("Invalid kind");
- case ELF32LEKind:
- return getSrcMsgAux(cast<ObjFile<ELF32LE>>(*this), sym, sec, offset);
- case ELF32BEKind:
- return getSrcMsgAux(cast<ObjFile<ELF32BE>>(*this), sym, sec, offset);
- case ELF64LEKind:
- return getSrcMsgAux(cast<ObjFile<ELF64LE>>(*this), sym, sec, offset);
- case ELF64BEKind:
- return getSrcMsgAux(cast<ObjFile<ELF64BE>>(*this), sym, sec, offset);
- }
- }
- template <class ELFT> void ObjFile<ELFT>::initializeDwarf() {
- dwarf = llvm::make_unique<DWARFContext>(make_unique<LLDDwarfObj<ELFT>>(this));
- for (std::unique_ptr<DWARFUnit> &cu : dwarf->compile_units()) {
- auto report = [](Error err) {
- handleAllErrors(std::move(err),
- [](ErrorInfoBase &info) { warn(info.message()); });
- };
- Expected<const DWARFDebugLine::LineTable *> expectedLT =
- dwarf->getLineTableForUnit(cu.get(), report);
- const DWARFDebugLine::LineTable *lt = nullptr;
- if (expectedLT)
- lt = *expectedLT;
- else
- report(expectedLT.takeError());
- if (!lt)
- continue;
- lineTables.push_back(lt);
- // Loop over variable records and insert them to variableLoc.
- for (const auto &entry : cu->dies()) {
- DWARFDie die(cu.get(), &entry);
- // Skip all tags that are not variables.
- if (die.getTag() != dwarf::DW_TAG_variable)
- continue;
- // Skip if a local variable because we don't need them for generating
- // error messages. In general, only non-local symbols can fail to be
- // linked.
- if (!dwarf::toUnsigned(die.find(dwarf::DW_AT_external), 0))
- continue;
- // Get the source filename index for the variable.
- unsigned file = dwarf::toUnsigned(die.find(dwarf::DW_AT_decl_file), 0);
- if (!lt->hasFileAtIndex(file))
- continue;
- // Get the line number on which the variable is declared.
- unsigned line = dwarf::toUnsigned(die.find(dwarf::DW_AT_decl_line), 0);
- // Here we want to take the variable name to add it into variableLoc.
- // Variable can have regular and linkage name associated. At first, we try
- // to get linkage name as it can be different, for example when we have
- // two variables in different namespaces of the same object. Use common
- // name otherwise, but handle the case when it also absent in case if the
- // input object file lacks some debug info.
- StringRef name =
- dwarf::toString(die.find(dwarf::DW_AT_linkage_name),
- dwarf::toString(die.find(dwarf::DW_AT_name), ""));
- if (!name.empty())
- variableLoc.insert({name, {lt, file, line}});
- }
- }
- }
- // Returns the pair of file name and line number describing location of data
- // object (variable, array, etc) definition.
- template <class ELFT>
- Optional<std::pair<std::string, unsigned>>
- ObjFile<ELFT>::getVariableLoc(StringRef name) {
- llvm::call_once(initDwarfLine, [this]() { initializeDwarf(); });
- // Return if we have no debug information about data object.
- auto it = variableLoc.find(name);
- if (it == variableLoc.end())
- return None;
- // Take file name string from line table.
- std::string fileName;
- if (!it->second.lt->getFileNameByIndex(
- it->second.file, {},
- DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, fileName))
- return None;
- return std::make_pair(fileName, it->second.line);
- }
- // Returns source line information for a given offset
- // using DWARF debug info.
- template <class ELFT>
- Optional<DILineInfo> ObjFile<ELFT>::getDILineInfo(InputSectionBase *s,
- uint64_t offset) {
- llvm::call_once(initDwarfLine, [this]() { initializeDwarf(); });
- // Detect SectionIndex for specified section.
- uint64_t sectionIndex = object::SectionedAddress::UndefSection;
- ArrayRef<InputSectionBase *> sections = s->file->getSections();
- for (uint64_t curIndex = 0; curIndex < sections.size(); ++curIndex) {
- if (s == sections[curIndex]) {
- sectionIndex = curIndex;
- break;
- }
- }
- // Use fake address calcuated by adding section file offset and offset in
- // section. See comments for ObjectInfo class.
- DILineInfo info;
- for (const llvm::DWARFDebugLine::LineTable *lt : lineTables) {
- if (lt->getFileLineInfoForAddress(
- {s->getOffsetInFile() + offset, sectionIndex}, nullptr,
- DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, info))
- return info;
- }
- return None;
- }
- // Returns "<internal>", "foo.a(bar.o)" or "baz.o".
- std::string lld::toString(const InputFile *f) {
- if (!f)
- return "<internal>";
- if (f->toStringCache.empty()) {
- if (f->archiveName.empty())
- f->toStringCache = f->getName();
- else
- f->toStringCache = (f->archiveName + "(" + f->getName() + ")").str();
- }
- return f->toStringCache;
- }
- ELFFileBase::ELFFileBase(Kind k, MemoryBufferRef mb) : InputFile(k, mb) {
- ekind = getELFKind(mb, "");
- switch (ekind) {
- case ELF32LEKind:
- init<ELF32LE>();
- break;
- case ELF32BEKind:
- init<ELF32BE>();
- break;
- case ELF64LEKind:
- init<ELF64LE>();
- break;
- case ELF64BEKind:
- init<ELF64BE>();
- break;
- default:
- llvm_unreachable("getELFKind");
- }
- }
- template <typename Elf_Shdr>
- static const Elf_Shdr *findSection(ArrayRef<Elf_Shdr> sections, uint32_t type) {
- for (const Elf_Shdr &sec : sections)
- if (sec.sh_type == type)
- return &sec;
- return nullptr;
- }
- template <class ELFT> void ELFFileBase::init() {
- using Elf_Shdr = typename ELFT::Shdr;
- using Elf_Sym = typename ELFT::Sym;
- // Initialize trivial attributes.
- const ELFFile<ELFT> &obj = getObj<ELFT>();
- emachine = obj.getHeader()->e_machine;
- osabi = obj.getHeader()->e_ident[llvm::ELF::EI_OSABI];
- abiVersion = obj.getHeader()->e_ident[llvm::ELF::EI_ABIVERSION];
- ArrayRef<Elf_Shdr> sections = CHECK(obj.sections(), this);
- // Find a symbol table.
- bool isDSO =
- (identify_magic(mb.getBuffer()) == file_magic::elf_shared_object);
- const Elf_Shdr *symtabSec =
- findSection(sections, isDSO ? SHT_DYNSYM : SHT_SYMTAB);
- if (!symtabSec)
- return;
- // Initialize members corresponding to a symbol table.
- firstGlobal = symtabSec->sh_info;
- ArrayRef<Elf_Sym> eSyms = CHECK(obj.symbols(symtabSec), this);
- if (firstGlobal == 0 || firstGlobal > eSyms.size())
- fatal(toString(this) + ": invalid sh_info in symbol table");
- elfSyms = reinterpret_cast<const void *>(eSyms.data());
- numELFSyms = eSyms.size();
- stringTable = CHECK(obj.getStringTableForSymtab(*symtabSec, sections), this);
- }
- template <class ELFT>
- uint32_t ObjFile<ELFT>::getSectionIndex(const Elf_Sym &sym) const {
- return CHECK(
- this->getObj().getSectionIndex(&sym, getELFSyms<ELFT>(), shndxTable),
- this);
- }
- template <class ELFT> ArrayRef<Symbol *> ObjFile<ELFT>::getLocalSymbols() {
- if (this->symbols.empty())
- return {};
- return makeArrayRef(this->symbols).slice(1, this->firstGlobal - 1);
- }
- template <class ELFT> ArrayRef<Symbol *> ObjFile<ELFT>::getGlobalSymbols() {
- return makeArrayRef(this->symbols).slice(this->firstGlobal);
- }
- template <class ELFT> void ObjFile<ELFT>::parse(bool ignoreComdats) {
- // Read a section table. justSymbols is usually false.
- if (this->justSymbols)
- initializeJustSymbols();
- else
- initializeSections(ignoreComdats);
- // Read a symbol table.
- initializeSymbols();
- }
- // Sections with SHT_GROUP and comdat bits define comdat section groups.
- // They are identified and deduplicated by group name. This function
- // returns a group name.
- template <class ELFT>
- StringRef ObjFile<ELFT>::getShtGroupSignature(ArrayRef<Elf_Shdr> sections,
- const Elf_Shdr &sec) {
- typename ELFT::SymRange symbols = this->getELFSyms<ELFT>();
- if (sec.sh_info >= symbols.size())
- fatal(toString(this) + ": invalid symbol index");
- const typename ELFT::Sym &sym = symbols[sec.sh_info];
- StringRef signature = CHECK(sym.getName(this->stringTable), this);
- // As a special case, if a symbol is a section symbol and has no name,
- // we use a section name as a signature.
- //
- // Such SHT_GROUP sections are invalid from the perspective of the ELF
- // standard, but GNU gold 1.14 (the newest version as of July 2017) or
- // older produce such sections as outputs for the -r option, so we need
- // a bug-compatibility.
- if (signature.empty() && sym.getType() == STT_SECTION)
- return getSectionName(sec);
- return signature;
- }
- template <class ELFT> bool ObjFile<ELFT>::shouldMerge(const Elf_Shdr &sec) {
- // On a regular link we don't merge sections if -O0 (default is -O1). This
- // sometimes makes the linker significantly faster, although the output will
- // be bigger.
- //
- // Doing the same for -r would create a problem as it would combine sections
- // with different sh_entsize. One option would be to just copy every SHF_MERGE
- // section as is to the output. While this would produce a valid ELF file with
- // usable SHF_MERGE sections, tools like (llvm-)?dwarfdump get confused when
- // they see two .debug_str. We could have separate logic for combining
- // SHF_MERGE sections based both on their name and sh_entsize, but that seems
- // to be more trouble than it is worth. Instead, we just use the regular (-O1)
- // logic for -r.
- if (config->optimize == 0 && !config->relocatable)
- return false;
- // A mergeable section with size 0 is useless because they don't have
- // any data to merge. A mergeable string section with size 0 can be
- // argued as invalid because it doesn't end with a null character.
- // We'll avoid a mess by handling them as if they were non-mergeable.
- if (sec.sh_size == 0)
- return false;
- // Check for sh_entsize. The ELF spec is not clear about the zero
- // sh_entsize. It says that "the member [sh_entsize] contains 0 if
- // the section does not hold a table of fixed-size entries". We know
- // that Rust 1.13 produces a string mergeable section with a zero
- // sh_entsize. Here we just accept it rather than being picky about it.
- uint64_t entSize = sec.sh_entsize;
- if (entSize == 0)
- return false;
- if (sec.sh_size % entSize)
- fatal(toString(this) +
- ": SHF_MERGE section size must be a multiple of sh_entsize");
- uint64_t flags = sec.sh_flags;
- if (!(flags & SHF_MERGE))
- return false;
- if (flags & SHF_WRITE)
- fatal(toString(this) + ": writable SHF_MERGE section is not supported");
- return true;
- }
- // This is for --just-symbols.
- //
- // --just-symbols is a very minor feature that allows you to link your
- // output against other existing program, so that if you load both your
- // program and the other program into memory, your output can refer the
- // other program's symbols.
- //
- // When the option is given, we link "just symbols". The section table is
- // initialized with null pointers.
- template <class ELFT> void ObjFile<ELFT>::initializeJustSymbols() {
- ArrayRef<Elf_Shdr> sections = CHECK(this->getObj().sections(), this);
- this->sections.resize(sections.size());
- }
- // An ELF object file may contain a `.deplibs` section. If it exists, the
- // section contains a list of library specifiers such as `m` for libm. This
- // function resolves a given name by finding the first matching library checking
- // the various ways that a library can be specified to LLD. This ELF extension
- // is a form of autolinking and is called `dependent libraries`. It is currently
- // unique to LLVM and lld.
- static void addDependentLibrary(StringRef specifier, const InputFile *f) {
- if (!config->dependentLibraries)
- return;
- if (fs::exists(specifier))
- driver->addFile(specifier, /*withLOption=*/false);
- else if (Optional<std::string> s = findFromSearchPaths(specifier))
- driver->addFile(*s, /*withLOption=*/true);
- else if (Optional<std::string> s = searchLibraryBaseName(specifier))
- driver->addFile(*s, /*withLOption=*/true);
- else
- error(toString(f) +
- ": unable to find library from dependent library specifier: " +
- specifier);
- }
- template <class ELFT>
- void ObjFile<ELFT>::initializeSections(bool ignoreComdats) {
- const ELFFile<ELFT> &obj = this->getObj();
- ArrayRef<Elf_Shdr> objSections = CHECK(obj.sections(), this);
- uint64_t size = objSections.size();
- this->sections.resize(size);
- this->sectionStringTable =
- CHECK(obj.getSectionStringTable(objSections), this);
- for (size_t i = 0, e = objSections.size(); i < e; i++) {
- if (this->sections[i] == &InputSection::discarded)
- continue;
- const Elf_Shdr &sec = objSections[i];
- if (sec.sh_type == ELF::SHT_LLVM_CALL_GRAPH_PROFILE)
- cgProfile =
- check(obj.template getSectionContentsAsArray<Elf_CGProfile>(&sec));
- // SHF_EXCLUDE'ed sections are discarded by the linker. However,
- // if -r is given, we'll let the final link discard such sections.
- // This is compatible with GNU.
- if ((sec.sh_flags & SHF_EXCLUDE) && !config->relocatable) {
- if (sec.sh_type == SHT_LLVM_ADDRSIG) {
- // We ignore the address-significance table if we know that the object
- // file was created by objcopy or ld -r. This is because these tools
- // will reorder the symbols in the symbol table, invalidating the data
- // in the address-significance table, which refers to symbols by index.
- if (sec.sh_link != 0)
- this->addrsigSec = &sec;
- else if (config->icf == ICFLevel::Safe)
- warn(toString(this) + ": --icf=safe is incompatible with object "
- "files created using objcopy or ld -r");
- }
- this->sections[i] = &InputSection::discarded;
- continue;
- }
- switch (sec.sh_type) {
- case SHT_GROUP: {
- // De-duplicate section groups by their signatures.
- StringRef signature = getShtGroupSignature(objSections, sec);
- this->sections[i] = &InputSection::discarded;
- ArrayRef<Elf_Word> entries =
- CHECK(obj.template getSectionContentsAsArray<Elf_Word>(&sec), this);
- if (entries.empty())
- fatal(toString(this) + ": empty SHT_GROUP");
- // The first word of a SHT_GROUP section contains flags. Currently,
- // the standard defines only "GRP_COMDAT" flag for the COMDAT group.
- // An group with the empty flag doesn't define anything; such sections
- // are just skipped.
- if (entries[0] == 0)
- continue;
- if (entries[0] != GRP_COMDAT)
- fatal(toString(this) + ": unsupported SHT_GROUP format");
- bool isNew =
- ignoreComdats ||
- symtab->comdatGroups.try_emplace(CachedHashStringRef(signature), this)
- .second;
- if (isNew) {
- if (config->relocatable)
- this->sections[i] = createInputSection(sec);
- continue;
- }
- // Otherwise, discard group members.
- for (uint32_t secIndex : entries.slice(1)) {
- if (secIndex >= size)
- fatal(toString(this) +
- ": invalid section index in group: " + Twine(secIndex));
- this->sections[secIndex] = &InputSection::discarded;
- }
- break;
- }
- case SHT_SYMTAB_SHNDX:
- shndxTable = CHECK(obj.getSHNDXTable(sec, objSections), this);
- break;
- case SHT_SYMTAB:
- case SHT_STRTAB:
- case SHT_NULL:
- break;
- default:
- this->sections[i] = createInputSection(sec);
- }
- // .ARM.exidx sections have a reverse dependency on the InputSection they
- // have a SHF_LINK_ORDER dependency, this is identified by the sh_link.
- if (sec.sh_flags & SHF_LINK_ORDER) {
- InputSectionBase *linkSec = nullptr;
- if (sec.sh_link < this->sections.size())
- linkSec = this->sections[sec.sh_link];
- if (!linkSec)
- fatal(toString(this) +
- ": invalid sh_link index: " + Twine(sec.sh_link));
- InputSection *isec = cast<InputSection>(this->sections[i]);
- linkSec->dependentSections.push_back(isec);
- if (!isa<InputSection>(linkSec))
- error("a section " + isec->name +
- " with SHF_LINK_ORDER should not refer a non-regular "
- "section: " +
- toString(linkSec));
- }
- }
- }
- // For ARM only, to set the EF_ARM_ABI_FLOAT_SOFT or EF_ARM_ABI_FLOAT_HARD
- // flag in the ELF Header we need to look at Tag_ABI_VFP_args to find out how
- // the input objects have been compiled.
- static void updateARMVFPArgs(const ARMAttributeParser &attributes,
- const InputFile *f) {
- if (!attributes.hasAttribute(ARMBuildAttrs::ABI_VFP_args))
- // If an ABI tag isn't present then it is implicitly given the value of 0
- // which maps to ARMBuildAttrs::BaseAAPCS. However many assembler files,
- // including some in glibc that don't use FP args (and should have value 3)
- // don't have the attribute so we do not consider an implicit value of 0
- // as a clash.
- return;
- unsigned vfpArgs = attributes.getAttributeValue(ARMBuildAttrs::ABI_VFP_args);
- ARMVFPArgKind arg;
- switch (vfpArgs) {
- case ARMBuildAttrs::BaseAAPCS:
- arg = ARMVFPArgKind::Base;
- break;
- case ARMBuildAttrs::HardFPAAPCS:
- arg = ARMVFPArgKind::VFP;
- break;
- case ARMBuildAttrs::ToolChainFPPCS:
- // Tool chain specific convention that conforms to neither AAPCS variant.
- arg = ARMVFPArgKind::ToolChain;
- break;
- case ARMBuildAttrs::CompatibleFPAAPCS:
- // Object compatible with all conventions.
- return;
- default:
- error(toString(f) + ": unknown Tag_ABI_VFP_args value: " + Twine(vfpArgs));
- return;
- }
- // Follow ld.bfd and error if there is a mix of calling conventions.
- if (config->armVFPArgs != arg && config->armVFPArgs != ARMVFPArgKind::Default)
- error(toString(f) + ": incompatible Tag_ABI_VFP_args");
- else
- config->armVFPArgs = arg;
- }
- // The ARM support in lld makes some use of instructions that are not available
- // on all ARM architectures. Namely:
- // - Use of BLX instruction for interworking between ARM and Thumb state.
- // - Use of the extended Thumb branch encoding in relocation.
- // - Use of the MOVT/MOVW instructions in Thumb Thunks.
- // The ARM Attributes section contains information about the architecture chosen
- // at compile time. We follow the convention that if at least one input object
- // is compiled with an architecture that supports these features then lld is
- // permitted to use them.
- static void updateSupportedARMFeatures(const ARMAttributeParser &attributes) {
- if (!attributes.hasAttribute(ARMBuildAttrs::CPU_arch))
- return;
- auto arch = attributes.getAttributeValue(ARMBuildAttrs::CPU_arch);
- switch (arch) {
- case ARMBuildAttrs::Pre_v4:
- case ARMBuildAttrs::v4:
- case ARMBuildAttrs::v4T:
- // Architectures prior to v5 do not support BLX instruction
- break;
- case ARMBuildAttrs::v5T:
- case ARMBuildAttrs::v5TE:
- case ARMBuildAttrs::v5TEJ:
- case ARMBuildAttrs::v6:
- case ARMBuildAttrs::v6KZ:
- case ARMBuildAttrs::v6K:
- config->armHasBlx = true;
- // Architectures used in pre-Cortex processors do not support
- // The J1 = 1 J2 = 1 Thumb branch range extension, with the exception
- // of Architecture v6T2 (arm1156t2-s and arm1156t2f-s) that do.
- break;
- default:
- // All other Architectures have BLX and extended branch encoding
- config->armHasBlx = true;
- config->armJ1J2BranchEncoding = true;
- if (arch != ARMBuildAttrs::v6_M && arch != ARMBuildAttrs::v6S_M)
- // All Architectures used in Cortex processors with the exception
- // of v6-M and v6S-M have the MOVT and MOVW instructions.
- config->armHasMovtMovw = true;
- break;
- }
- }
- // If a source file is compiled with x86 hardware-assisted call flow control
- // enabled, the generated object file contains feature flags indicating that
- // fact. This function reads the feature flags and returns it.
- //
- // Essentially we want to read a single 32-bit value in this function, but this
- // function is rather complicated because the value is buried deep inside a
- // .note.gnu.property section.
- //
- // The section consists of one or more NOTE records. Each NOTE record consists
- // of zero or more type-length-value fields. We want to find a field of a
- // certain type. It seems a bit too much to just store a 32-bit value, perhaps
- // the ABI is unnecessarily complicated.
- template <class ELFT>
- static uint32_t readAndFeatures(ObjFile<ELFT> *obj, ArrayRef<uint8_t> data) {
- using Elf_Nhdr = typename ELFT::Nhdr;
- using Elf_Note = typename ELFT::Note;
- uint32_t featuresSet = 0;
- while (!data.empty()) {
- // Read one NOTE record.
- if (data.size() < sizeof(Elf_Nhdr))
- fatal(toString(obj) + ": .note.gnu.property: section too short");
- auto *nhdr = reinterpret_cast<const Elf_Nhdr *>(data.data());
- if (data.size() < nhdr->getSize())
- fatal(toString(obj) + ": .note.gnu.property: section too short");
- Elf_Note note(*nhdr);
- if (nhdr->n_type != NT_GNU_PROPERTY_TYPE_0 || note.getName() != "GNU") {
- data = data.slice(nhdr->getSize());
- continue;
- }
- uint32_t featureAndType = config->emachine == EM_AARCH64
- ? GNU_PROPERTY_AARCH64_FEATURE_1_AND
- : GNU_PROPERTY_X86_FEATURE_1_AND;
- // Read a body of a NOTE record, which consists of type-length-value fields.
- ArrayRef<uint8_t> desc = note.getDesc();
- while (!desc.empty()) {
- if (desc.size() < 8)
- fatal(toString(obj) + ": .note.gnu.property: section too short");
- uint32_t type = read32le(desc.data());
- uint32_t size = read32le(desc.data() + 4);
- if (type == featureAndType) {
- // We found a FEATURE_1_AND field. There may be more than one of these
- // in a .note.gnu.propery section, for a relocatable object we
- // accumulate the bits set.
- featuresSet |= read32le(desc.data() + 8);
- }
- // On 64-bit, a payload may be followed by a 4-byte padding to make its
- // size a multiple of 8.
- if (ELFT::Is64Bits)
- size = alignTo(size, 8);
- desc = desc.slice(size + 8); // +8 for Type and Size
- }
- // Go to next NOTE record to look for more FEATURE_1_AND descriptions.
- data = data.slice(nhdr->getSize());
- }
- return featuresSet;
- }
- template <class ELFT>
- InputSectionBase *ObjFile<ELFT>::getRelocTarget(const Elf_Shdr &sec) {
- uint32_t idx = sec.sh_info;
- if (idx >= this->sections.size())
- fatal(toString(this) + ": invalid relocated section index: " + Twine(idx));
- InputSectionBase *target = this->sections[idx];
- // Strictly speaking, a relocation section must be included in the
- // group of the section it relocates. However, LLVM 3.3 and earlier
- // would fail to do so, so we gracefully handle that case.
- if (target == &InputSection::discarded)
- return nullptr;
- if (!target)
- fatal(toString(this) + ": unsupported relocation reference");
- return target;
- }
- // Create a regular InputSection class that has the same contents
- // as a given section.
- static InputSection *toRegularSection(MergeInputSection *sec) {
- return make<InputSection>(sec->file, sec->flags, sec->type, sec->alignment,
- sec->data(), sec->name);
- }
- template <class ELFT>
- InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec) {
- StringRef name = getSectionName(sec);
- switch (sec.sh_type) {
- case SHT_ARM_ATTRIBUTES: {
- if (config->emachine != EM_ARM)
- break;
- ARMAttributeParser attributes;
- ArrayRef<uint8_t> contents = check(this->getObj().getSectionContents(&sec));
- attributes.Parse(contents, /*isLittle*/ config->ekind == ELF32LEKind);
- updateSupportedARMFeatures(attributes);
- updateARMVFPArgs(attributes, this);
- // FIXME: Retain the first attribute section we see. The eglibc ARM
- // dynamic loaders require the presence of an attribute section for dlopen
- // to work. In a full implementation we would merge all attribute sections.
- if (in.armAttributes == nullptr) {
- in.armAttributes = make<InputSection>(*this, sec, name);
- return in.armAttributes;
- }
- return &InputSection::discarded;
- }
- case SHT_LLVM_DEPENDENT_LIBRARIES: {
- if (config->relocatable)
- break;
- ArrayRef<char> data =
- CHECK(this->getObj().template getSectionContentsAsArray<char>(&sec), this);
- if (!data.empty() && data.back() != '\0') {
- error(toString(this) +
- ": corrupted dependent libraries section (unterminated string): " +
- name);
- return &InputSection::discarded;
- }
- for (const char *d = data.begin(), *e = data.end(); d < e;) {
- StringRef s(d);
- addDependentLibrary(s, this);
- d += s.size() + 1;
- }
- return &InputSection::discarded;
- }
- case SHT_RELA:
- case SHT_REL: {
- // Find a relocation target section and associate this section with that.
- // Target may have been discarded if it is in a different section group
- // and the group is discarded, even though it's a violation of the
- // spec. We handle that situation gracefully by discarding dangling
- // relocation sections.
- InputSectionBase *target = getRelocTarget(sec);
- if (!target)
- return nullptr;
- // This section contains relocation information.
- // If -r is given, we do not interpret or apply relocation
- // but just copy relocation sections to output.
- if (config->relocatable) {
- InputSection *relocSec = make<InputSection>(*this, sec, name);
- // We want to add a dependency to target, similar like we do for
- // -emit-relocs below. This is useful for the case when linker script
- // contains the "/DISCARD/". It is perhaps uncommon to use a script with
- // -r, but we faced it in the Linux kernel and have to handle such case
- // and not to crash.
- target->dependentSections.push_back(relocSec);
- return relocSec;
- }
- if (target->firstRelocation)
- fatal(toString(this) +
- ": multiple relocation sections to one section are not supported");
- // ELF spec allows mergeable sections with relocations, but they are
- // rare, and it is in practice hard to merge such sections by contents,
- // because applying relocations at end of linking changes section
- // contents. So, we simply handle such sections as non-mergeable ones.
- // Degrading like this is acceptable because section merging is optional.
- if (auto *ms = dyn_cast<MergeInputSection>(target)) {
- target = toRegularSection(ms);
- this->sections[sec.sh_info] = target;
- }
- if (sec.sh_type == SHT_RELA) {
- ArrayRef<Elf_Rela> rels = CHECK(getObj().relas(&sec), this);
- target->firstRelocation = rels.begin();
- target->numRelocations = rels.size();
- target->areRelocsRela = true;
- } else {
- ArrayRef<Elf_Rel> rels = CHECK(getObj().rels(&sec), this);
- target->firstRelocation = rels.begin();
- target->numRelocations = rels.size();
- target->areRelocsRela = false;
- }
- assert(isUInt<31>(target->numRelocations));
- // Relocation sections processed by the linker are usually removed
- // from the output, so returning `nullptr` for the normal case.
- // However, if -emit-relocs is given, we need to leave them in the output.
- // (Some post link analysis tools need this information.)
- if (config->emitRelocs) {
- InputSection *relocSec = make<InputSection>(*this, sec, name);
- // We will not emit relocation section if target was discarded.
- target->dependentSections.push_back(relocSec);
- return relocSec;
- }
- return nullptr;
- }
- }
- // The GNU linker uses .note.GNU-stack section as a marker indicating
- // that the code in the object file does not expect that the stack is
- // executable (in terms of NX bit). If all input files have the marker,
- // the GNU linker adds a PT_GNU_STACK segment to tells the loader to
- // make the stack non-executable. Most object files have this section as
- // of 2017.
- //
- // But making the stack non-executable is a norm today for security
- // reasons. Failure to do so may result in a serious security issue.
- // Therefore, we make LLD always add PT_GNU_STACK unless it is
- // explicitly told to do otherwise (by -z execstack). Because the stack
- // executable-ness is controlled solely by command line options,
- // .note.GNU-stack sections are simply ignored.
- if (name == ".note.GNU-stack")
- return &InputSection::discarded;
- // Object files that use processor features such as Intel Control-Flow
- // Enforcement (CET) or AArch64 Branch Target Identification BTI, use a
- // .note.gnu.property section containing a bitfield of feature bits like the
- // GNU_PROPERTY_X86_FEATURE_1_IBT flag. Read a bitmap containing the flag.
- //
- // Since we merge bitmaps from multiple object files to create a new
- // .note.gnu.property containing a single AND'ed bitmap, we discard an input
- // file's .note.gnu.property section.
- if (name == ".note.gnu.property") {
- ArrayRef<uint8_t> contents = check(this->getObj().getSectionContents(&sec));
- this->andFeatures = readAndFeatures(this, contents);
- return &InputSection::discarded;
- }
- // Split stacks is a feature to support a discontiguous stack,
- // commonly used in the programming language Go. For the details,
- // see https://gcc.gnu.org/wiki/SplitStacks. An object file compiled
- // for split stack will include a .note.GNU-split-stack section.
- if (name == ".note.GNU-split-stack") {
- if (config->relocatable) {
- error("cannot mix split-stack and non-split-stack in a relocatable link");
- return &InputSection::discarded;
- }
- this->splitStack = true;
- return &InputSection::discarded;
- }
- // An object file cmpiled for split stack, but where some of the
- // functions were compiled with the no_split_stack_attribute will
- // include a .note.GNU-no-split-stack section.
- if (name == ".note.GNU-no-split-stack") {
- this->someNoSplitStack = true;
- return &InputSection::discarded;
- }
- // The linkonce feature is a sort of proto-comdat. Some glibc i386 object
- // files contain definitions of symbol "__x86.get_pc_thunk.bx" in linkonce
- // sections. Drop those sections to avoid duplicate symbol errors.
- // FIXME: This is glibc PR20543, we should remove this hack once that has been
- // fixed for a while.
- if (name == ".gnu.linkonce.t.__x86.get_pc_thunk.bx" ||
- name == ".gnu.linkonce.t.__i686.get_pc_thunk.bx")
- return &InputSection::discarded;
- // If we are creating a new .build-id section, strip existing .build-id
- // sections so that the output won't have more than one .build-id.
- // This is not usually a problem because input object files normally don't
- // have .build-id sections, but you can create such files by
- // "ld.{bfd,gold,lld} -r --build-id", and we want to guard against it.
- if (name == ".note.gnu.build-id" && config->buildId != BuildIdKind::None)
- return &InputSection::discarded;
- // The linker merges EH (exception handling) frames and creates a
- // .eh_frame_hdr section for runtime. So we handle them with a special
- // class. For relocatable outputs, they are just passed through.
- if (name == ".eh_frame" && !config->relocatable)
- return make<EhInputSection>(*this, sec, name);
- if (shouldMerge(sec))
- return make<MergeInputSection>(*this, sec, name);
- return make<InputSection>(*this, sec, name);
- }
- template <class ELFT>
- StringRef ObjFile<ELFT>::getSectionName(const Elf_Shdr &sec) {
- return CHECK(getObj().getSectionName(&sec, sectionStringTable), this);
- }
- // Initialize this->Symbols. this->Symbols is a parallel array as
- // its corresponding ELF symbol table.
- template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
- ArrayRef<Elf_Sym> eSyms = this->getELFSyms<ELFT>();
- this->symbols.resize(eSyms.size());
- // Our symbol table may have already been partially initialized
- // because of LazyObjFile.
- for (size_t i = 0, end = eSyms.size(); i != end; ++i)
- if (!this->symbols[i] && eSyms[i].getBinding() != STB_LOCAL)
- this->symbols[i] =
- symtab->insert(CHECK(eSyms[i].getName(this->stringTable), this));
- // Fill this->Symbols. A symbol is either local or global.
- for (size_t i = 0, end = eSyms.size(); i != end; ++i) {
- const Elf_Sym &eSym = eSyms[i];
- // Read symbol attributes.
- uint32_t secIdx = getSectionIndex(eSym);
- if (secIdx >= this->sections.size())
- fatal(toString(this) + ": invalid section index: " + Twine(secIdx));
- InputSectionBase *sec = this->sections[secIdx];
- uint8_t binding = eSym.getBinding();
- uint8_t stOther = eSym.st_other;
- uint8_t type = eSym.getType();
- uint64_t value = eSym.st_value;
- uint64_t size = eSym.st_size;
- StringRefZ name = this->stringTable.data() + eSym.st_name;
- // Handle local symbols. Local symbols are not added to the symbol
- // table because they are not visible from other object files. We
- // allocate symbol instances and add their pointers to Symbols.
- if (binding == STB_LOCAL) {
- if (eSym.getType() == STT_FILE)
- sourceFile = CHECK(eSym.getName(this->stringTable), this);
- if (this->stringTable.size() <= eSym.st_name)
- fatal(toString(this) + ": invalid symbol name offset");
- if (eSym.st_shndx == SHN_UNDEF)
- this->symbols[i] = make<Undefined>(this, name, binding, stOther, type);
- else if (sec == &InputSection::discarded)
- this->symbols[i] = make<Undefined>(this, name, binding, stOther, type,
- /*DiscardedSecIdx=*/secIdx);
- else
- this->symbols[i] =
- make<Defined>(this, name, binding, stOther, type, value, size, sec);
- continue;
- }
- // Handle global undefined symbols.
- if (eSym.st_shndx == SHN_UNDEF) {
- this->symbols[i]->resolve(Undefined{this, name, binding, stOther, type});
- continue;
- }
- // Handle global common symbols.
- if (eSym.st_shndx == SHN_COMMON) {
- if (value == 0 || value >= UINT32_MAX)
- fatal(toString(this) + ": common symbol '" + StringRef(name.data) +
- "' has invalid alignment: " + Twine(value));
- this->symbols[i]->resolve(
- CommonSymbol{this, name, binding, stOther, type, value, size});
- continue;
- }
- // If a defined symbol is in a discarded section, handle it as if it
- // were an undefined symbol. Such symbol doesn't comply with the
- // standard, but in practice, a .eh_frame often directly refer
- // COMDAT member sections, and if a comdat group is discarded, some
- // defined symbol in a .eh_frame becomes dangling symbols.
- if (sec == &InputSection::discarded) {
- this->symbols[i]->resolve(
- Undefined{this, name, binding, stOther, type, secIdx});
- continue;
- }
- // Handle global defined symbols.
- if (binding == STB_GLOBAL || binding == STB_WEAK ||
- binding == STB_GNU_UNIQUE) {
- this->symbols[i]->resolve(
- Defined{this, name, binding, stOther, type, value, size, sec});
- continue;
- }
- fatal(toString(this) + ": unexpected binding: " + Twine((int)binding));
- }
- }
- ArchiveFile::ArchiveFile(std::unique_ptr<Archive> &&file)
- : InputFile(ArchiveKind, file->getMemoryBufferRef()),
- file(std::move(file)) {}
- void ArchiveFile::parse() {
- for (const Archive::Symbol &sym : file->symbols())
- symtab->addSymbol(LazyArchive{*this, sym});
- }
- // Returns a buffer pointing to a member file containing a given symbol.
- void ArchiveFile::fetch(const Archive::Symbol &sym) {
- Archive::Child c =
- CHECK(sym.getMember(), toString(this) +
- ": could not get the member for symbol " +
- toELFString(sym));
- if (!seen.insert(c.getChildOffset()).second)
- return;
- MemoryBufferRef mb =
- CHECK(c.getMemoryBufferRef(),
- toString(this) +
- ": could not get the buffer for the member defining symbol " +
- toELFString(sym));
- if (tar && c.getParent()->isThin())
- tar->append(relativeToRoot(CHECK(c.getFullName(), this)), mb.getBuffer());
- InputFile *file = createObjectFile(
- mb, getName(), c.getParent()->isThin() ? 0 : c.getChildOffset());
- file->groupId = groupId;
- parseFile(file);
- }
- unsigned SharedFile::vernauxNum;
- // Parse the version definitions in the object file if present, and return a
- // vector whose nth element contains a pointer to the Elf_Verdef for version
- // identifier n. Version identifiers that are not definitions map to nullptr.
- template <typename ELFT>
- static std::vector<const void *> parseVerdefs(const uint8_t *base,
- const typename ELFT::Shdr *sec) {
- if (!sec)
- return {};
- // We cannot determine the largest verdef identifier without inspecting
- // every Elf_Verdef, but both bfd and gold assign verdef identifiers
- // sequentially starting from 1, so we predict that the largest identifier
- // will be verdefCount.
- unsigned verdefCount = sec->sh_info;
- std::vector<const void *> verdefs(verdefCount + 1);
- // Build the Verdefs array by following the chain of Elf_Verdef objects
- // from the start of the .gnu.version_d section.
- const uint8_t *verdef = base + sec->sh_offset;
- for (unsigned i = 0; i != verdefCount; ++i) {
- auto *curVerdef = reinterpret_cast<const typename ELFT::Verdef *>(verdef);
- verdef += curVerdef->vd_next;
- unsigned verdefIndex = curVerdef->vd_ndx;
- verdefs.resize(verdefIndex + 1);
- verdefs[verdefIndex] = curVerdef;
- }
- return verdefs;
- }
- // We do not usually care about alignments of data in shared object
- // files because the loader takes care of it. However, if we promote a
- // DSO symbol to point to .bss due to copy relocation, we need to keep
- // the original alignment requirements. We infer it in this function.
- template <typename ELFT>
- static uint64_t getAlignment(ArrayRef<typename ELFT::Shdr> sections,
- const typename ELFT::Sym &sym) {
- uint64_t ret = UINT64_MAX;
- if (sym.st_value)
- ret = 1ULL << countTrailingZeros((uint64_t)sym.st_value);
- if (0 < sym.st_shndx && sym.st_shndx < sections.size())
- ret = std::min<uint64_t>(ret, sections[sym.st_shndx].sh_addralign);
- return (ret > UINT32_MAX) ? 0 : ret;
- }
- // Fully parse the shared object file.
- //
- // This function parses symbol versions. If a DSO has version information,
- // the file has a ".gnu.version_d" section which contains symbol version
- // definitions. Each symbol is associated to one version through a table in
- // ".gnu.version" section. That table is a parallel array for the symbol
- // table, and each table entry contains an index in ".gnu.version_d".
- //
- // The special index 0 is reserved for VERF_NDX_LOCAL and 1 is for
- // VER_NDX_GLOBAL. There's no table entry for these special versions in
- // ".gnu.version_d".
- //
- // The file format for symbol versioning is perhaps a bit more complicated
- // than necessary, but you can easily understand the code if you wrap your
- // head around the data structure described above.
- template <class ELFT> void SharedFile::parse() {
- using Elf_Dyn = typename ELFT::Dyn;
- using Elf_Shdr = typename ELFT::Shdr;
- using Elf_Sym = typename ELFT::Sym;
- using Elf_Verdef = typename ELFT::Verdef;
- using Elf_Versym = typename ELFT::Versym;
- ArrayRef<Elf_Dyn> dynamicTags;
- const ELFFile<ELFT> obj = this->getObj<ELFT>();
- ArrayRef<Elf_Shdr> sections = CHECK(obj.sections(), this);
- const Elf_Shdr *versymSec = nullptr;
- const Elf_Shdr *verdefSec = nullptr;
- // Search for .dynsym, .dynamic, .symtab, .gnu.version and .gnu.version_d.
- for (const Elf_Shdr &sec : sections) {
- switch (sec.sh_type) {
- default:
- continue;
- case SHT_DYNAMIC:
- dynamicTags =
- CHECK(obj.template getSectionContentsAsArray<Elf_Dyn>(&sec), this);
- break;
- case SHT_GNU_versym:
- versymSec = &sec;
- break;
- case SHT_GNU_verdef:
- verdefSec = &sec;
- break;
- }
- }
- if (versymSec && numELFSyms == 0) {
- error("SHT_GNU_versym should be associated with symbol table");
- return;
- }
- // Search for a DT_SONAME tag to initialize this->soName.
- for (const Elf_Dyn &dyn : dynamicTags) {
- if (dyn.d_tag == DT_NEEDED) {
- uint64_t val = dyn.getVal();
- if (val >= this->stringTable.size())
- fatal(toString(this) + ": invalid DT_NEEDED entry");
- dtNeeded.push_back(this->stringTable.data() + val);
- } else if (dyn.d_tag == DT_SONAME) {
- uint64_t val = dyn.getVal();
- if (val >= this->stringTable.size())
- fatal(toString(this) + ": invalid DT_SONAME entry");
- soName = this->stringTable.data() + val;
- }
- }
- // DSOs are uniquified not by filename but by soname.
- DenseMap<StringRef, SharedFile *>::iterator it;
- bool wasInserted;
- std::tie(it, wasInserted) = symtab->soNames.try_emplace(soName, this);
- // If a DSO appears more than once on the command line with and without
- // --as-needed, --no-as-needed takes precedence over --as-needed because a
- // user can add an extra DSO with --no-as-needed to force it to be added to
- // the dependency list.
- it->second->isNeeded |= isNeeded;
- if (!wasInserted)
- return;
- sharedFiles.push_back(this);
- verdefs = parseVerdefs<ELFT>(obj.base(), verdefSec);
- // Parse ".gnu.version" section which is a parallel array for the symbol
- // table. If a given file doesn't have a ".gnu.version" section, we use
- // VER_NDX_GLOBAL.
- size_t size = numELFSyms - firstGlobal;
- std::vector<uint32_t> versyms(size, VER_NDX_GLOBAL);
- if (versymSec) {
- ArrayRef<Elf_Versym> versym =
- CHECK(obj.template getSectionContentsAsArray<Elf_Versym>(versymSec),
- this)
- .slice(firstGlobal);
- for (size_t i = 0; i < size; ++i)
- versyms[i] = versym[i].vs_index;
- }
- // System libraries can have a lot of symbols with versions. Using a
- // fixed buffer for computing the versions name (foo@ver) can save a
- // lot of allocations.
- SmallString<0> versionedNameBuffer;
- // Add symbols to the symbol table.
- ArrayRef<Elf_Sym> syms = this->getGlobalELFSyms<ELFT>();
- for (size_t i = 0; i < syms.size(); ++i) {
- const Elf_Sym &sym = syms[i];
- // ELF spec requires that all local symbols precede weak or global
- // symbols in each symbol table, and the index of first non-local symbol
- // is stored to sh_info. If a local symbol appears after some non-local
- // symbol, that's a violation of the spec.
- StringRef name = CHECK(sym.getName(this->stringTable), this);
- if (sym.getBinding() == STB_LOCAL) {
- warn("found local symbol '" + name +
- "' in global part of symbol table in file " + toString(this));
- continue;
- }
- if (sym.isUndefined()) {
- Symbol *s = symtab->addSymbol(
- Undefined{this, name, sym.getBinding(), sym.st_other, sym.getType()});
- s->exportDynamic = true;
- continue;