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Diffstat (limited to 'lib/ReaderWriter/ELF/SectionChunks.cpp')
| -rw-r--r-- | lib/ReaderWriter/ELF/SectionChunks.cpp | 996 |
1 files changed, 996 insertions, 0 deletions
diff --git a/lib/ReaderWriter/ELF/SectionChunks.cpp b/lib/ReaderWriter/ELF/SectionChunks.cpp new file mode 100644 index 0000000000000..520fbe24af3b6 --- /dev/null +++ b/lib/ReaderWriter/ELF/SectionChunks.cpp @@ -0,0 +1,996 @@ +//===- lib/ReaderWriter/ELF/SectionChunks.h -------------------------------===// +// +// The LLVM Linker +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "SectionChunks.h" +#include "TargetLayout.h" +#include "lld/Core/Parallel.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/Support/Dwarf.h" + +namespace lld { +namespace elf { + +template <class ELFT> +Section<ELFT>::Section(const ELFLinkingContext &ctx, StringRef sectionName, + StringRef chunkName, typename Chunk<ELFT>::Kind k) + : Chunk<ELFT>(chunkName, k, ctx), _inputSectionName(sectionName), + _outputSectionName(sectionName) {} + +template <class ELFT> int Section<ELFT>::getContentType() const { + if (_flags & llvm::ELF::SHF_EXECINSTR) + return Chunk<ELFT>::ContentType::Code; + else if (_flags & llvm::ELF::SHF_WRITE) + return Chunk<ELFT>::ContentType::Data; + else if (_flags & llvm::ELF::SHF_ALLOC) + return Chunk<ELFT>::ContentType::Code; + else + return Chunk<ELFT>::ContentType::Unknown; +} + +template <class ELFT> +AtomSection<ELFT>::AtomSection(const ELFLinkingContext &ctx, + StringRef sectionName, int32_t contentType, + int32_t permissions, int32_t order) + : Section<ELFT>(ctx, sectionName, "AtomSection", + Chunk<ELFT>::Kind::AtomSection), + _contentType(contentType), _contentPermissions(permissions) { + this->setOrder(order); + + switch (contentType) { + case DefinedAtom::typeCode: + case DefinedAtom::typeDataFast: + case DefinedAtom::typeData: + case DefinedAtom::typeConstant: + case DefinedAtom::typeGOT: + case DefinedAtom::typeStub: + case DefinedAtom::typeResolver: + case DefinedAtom::typeThreadData: + this->_type = SHT_PROGBITS; + break; + + case DefinedAtom::typeThreadZeroFill: + case DefinedAtom::typeZeroFillFast: + case DefinedAtom::typeZeroFill: + this->_type = SHT_NOBITS; + break; + + case DefinedAtom::typeRONote: + case DefinedAtom::typeRWNote: + this->_type = SHT_NOTE; + break; + + case DefinedAtom::typeNoAlloc: + this->_type = SHT_PROGBITS; + this->_isLoadedInMemory = false; + break; + } + + switch (permissions) { + case DefinedAtom::permR__: + this->_flags = SHF_ALLOC; + break; + case DefinedAtom::permR_X: + this->_flags = SHF_ALLOC | SHF_EXECINSTR; + break; + case DefinedAtom::permRW_: + case DefinedAtom::permRW_L: + this->_flags = SHF_ALLOC | SHF_WRITE; + if (_contentType == DefinedAtom::typeThreadData || + _contentType == DefinedAtom::typeThreadZeroFill) + this->_flags |= SHF_TLS; + break; + case DefinedAtom::permRWX: + this->_flags = SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR; + break; + case DefinedAtom::perm___: + this->_flags = 0; + break; + } +} + +template <class ELFT> +void AtomSection<ELFT>::assignVirtualAddress(uint64_t addr) { + parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) { + ai->_virtualAddr = addr + ai->_fileOffset; + }); +} + +template <class ELFT> +void AtomSection<ELFT>::assignFileOffsets(uint64_t offset) { + parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) { + ai->_fileOffset = offset + ai->_fileOffset; + }); +} + +template <class ELFT> +const AtomLayout * +AtomSection<ELFT>::findAtomLayoutByName(StringRef name) const { + for (auto ai : _atoms) + if (ai->_atom->name() == name) + return ai; + return nullptr; +} + +template <class ELFT> +std::string AtomSection<ELFT>::formatError(const std::string &errorStr, + const AtomLayout &atom, + const Reference &ref) const { + StringRef kindValStr; + if (!this->_ctx.registry().referenceKindToString( + ref.kindNamespace(), ref.kindArch(), ref.kindValue(), kindValStr)) { + kindValStr = "unknown"; + } + + return + (Twine(errorStr) + " in file " + atom._atom->file().path() + + ": reference from " + atom._atom->name() + "+" + + Twine(ref.offsetInAtom()) + " to " + ref.target()->name() + "+" + + Twine(ref.addend()) + " of type " + Twine(ref.kindValue()) + " (" + + kindValStr + ")\n") + .str(); +} + +/// Align the offset to the required modulus defined by the atom alignment +template <class ELFT> +uint64_t AtomSection<ELFT>::alignOffset(uint64_t offset, + DefinedAtom::Alignment &atomAlign) { + uint64_t requiredModulus = atomAlign.modulus; + uint64_t alignment = atomAlign.value; + uint64_t currentModulus = (offset % alignment); + uint64_t retOffset = offset; + if (currentModulus != requiredModulus) { + if (requiredModulus > currentModulus) + retOffset += requiredModulus - currentModulus; + else + retOffset += alignment + requiredModulus - currentModulus; + } + return retOffset; +} + +// \brief Append an atom to a Section. The atom gets pushed into a vector +// contains the atom, the atom file offset, the atom virtual address +// the atom file offset is aligned appropriately as set by the Reader +template <class ELFT> +const AtomLayout *AtomSection<ELFT>::appendAtom(const Atom *atom) { + const DefinedAtom *definedAtom = cast<DefinedAtom>(atom); + + DefinedAtom::Alignment atomAlign = definedAtom->alignment(); + uint64_t alignment = atomAlign.value; + // Align the atom to the required modulus/ align the file offset and the + // memory offset separately this is required so that BSS symbols are handled + // properly as the BSS symbols only occupy memory size and not file size + uint64_t fOffset = alignOffset(this->fileSize(), atomAlign); + uint64_t mOffset = alignOffset(this->memSize(), atomAlign); + switch (definedAtom->contentType()) { + case DefinedAtom::typeCode: + case DefinedAtom::typeConstant: + case DefinedAtom::typeData: + case DefinedAtom::typeDataFast: + case DefinedAtom::typeZeroFillFast: + case DefinedAtom::typeGOT: + case DefinedAtom::typeStub: + case DefinedAtom::typeResolver: + case DefinedAtom::typeThreadData: + case DefinedAtom::typeRONote: + case DefinedAtom::typeRWNote: + _atoms.push_back(new (_alloc) AtomLayout(atom, fOffset, 0)); + this->_fsize = fOffset + definedAtom->size(); + this->_msize = mOffset + definedAtom->size(); + DEBUG_WITH_TYPE("Section", llvm::dbgs() + << "[" << this->name() << " " << this << "] " + << "Adding atom: " << atom->name() << "@" + << fOffset << "\n"); + break; + case DefinedAtom::typeNoAlloc: + _atoms.push_back(new (_alloc) AtomLayout(atom, fOffset, 0)); + this->_fsize = fOffset + definedAtom->size(); + DEBUG_WITH_TYPE("Section", llvm::dbgs() + << "[" << this->name() << " " << this << "] " + << "Adding atom: " << atom->name() << "@" + << fOffset << "\n"); + break; + case DefinedAtom::typeThreadZeroFill: + case DefinedAtom::typeZeroFill: + _atoms.push_back(new (_alloc) AtomLayout(atom, mOffset, 0)); + this->_msize = mOffset + definedAtom->size(); + break; + default: + llvm::dbgs() << definedAtom->contentType() << "\n"; + llvm_unreachable("Uexpected content type."); + } + // Set the section alignment to the largest alignment + // std::max doesn't support uint64_t + if (this->_alignment < alignment) + this->_alignment = alignment; + + if (_atoms.size()) + return _atoms.back(); + return nullptr; +} + +/// \brief convert the segment type to a String for diagnostics +/// and printing purposes +template <class ELFT> StringRef Section<ELFT>::segmentKindToStr() const { + switch (_segmentType) { + case llvm::ELF::PT_DYNAMIC: + return "DYNAMIC"; + case llvm::ELF::PT_INTERP: + return "INTERP"; + case llvm::ELF::PT_LOAD: + return "LOAD"; + case llvm::ELF::PT_GNU_EH_FRAME: + return "EH_FRAME"; + case llvm::ELF::PT_GNU_RELRO: + return "GNU_RELRO"; + case llvm::ELF::PT_NOTE: + return "NOTE"; + case llvm::ELF::PT_NULL: + return "NULL"; + case llvm::ELF::PT_TLS: + return "TLS"; + default: + return "UNKNOWN"; + } +} + +/// \brief Write the section and the atom contents to the buffer +template <class ELFT> +void AtomSection<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + bool success = true; + + // parallel_for_each() doesn't have deterministic order. To guarantee + // deterministic error output, collect errors in this vector and sort it + // by atom file offset before printing all errors. + std::vector<std::pair<size_t, std::string>> errors; + parallel_for_each(_atoms.begin(), _atoms.end(), [&](AtomLayout *ai) { + DEBUG_WITH_TYPE("Section", llvm::dbgs() + << "Writing atom: " << ai->_atom->name() + << " | " << ai->_fileOffset << "\n"); + const DefinedAtom *definedAtom = cast<DefinedAtom>(ai->_atom); + if (!definedAtom->occupiesDiskSpace()) + return; + // Copy raw content of atom to file buffer. + ArrayRef<uint8_t> content = definedAtom->rawContent(); + uint64_t contentSize = content.size(); + if (contentSize == 0) + return; + uint8_t *atomContent = chunkBuffer + ai->_fileOffset; + std::memcpy(atomContent, content.data(), contentSize); + const TargetRelocationHandler &relHandler = + this->_ctx.getTargetHandler().getRelocationHandler(); + for (const auto ref : *definedAtom) { + if (std::error_code ec = + relHandler.applyRelocation(*writer, buffer, *ai, *ref)) { + std::lock_guard<std::mutex> lock(_outputMutex); + errors.push_back(std::make_pair(ai->_fileOffset, + formatError(ec.message(), *ai, *ref))); + success = false; + } + } + }); + if (!success) { + std::sort(errors.begin(), errors.end()); + for (auto &&error : errors) + llvm::errs() << error.second; + llvm::report_fatal_error("relocating output"); + } +} + +template <class ELFT> +void OutputSection<ELFT>::appendSection(Section<ELFT> *section) { + if (section->alignment() > _alignment) + _alignment = section->alignment(); + assert(!_link && "Section already has a link!"); + _link = section->getLink(); + _shInfo = section->getInfo(); + _entSize = section->getEntSize(); + _type = section->getType(); + if (_flags < section->getFlags()) + _flags = section->getFlags(); + section->setOutputSection(this, (_sections.size() == 0)); + _kind = section->kind(); + _sections.push_back(section); +} + +template <class ELFT> +StringTable<ELFT>::StringTable(const ELFLinkingContext &ctx, const char *str, + int32_t order, bool dynamic) + : Section<ELFT>(ctx, str, "StringTable") { + // the string table has a NULL entry for which + // add an empty string + _strings.push_back(""); + this->_fsize = 1; + this->_alignment = 1; + this->setOrder(order); + this->_type = SHT_STRTAB; + if (dynamic) { + this->_flags = SHF_ALLOC; + this->_msize = this->_fsize; + } +} + +template <class ELFT> uint64_t StringTable<ELFT>::addString(StringRef symname) { + if (symname.empty()) + return 0; + StringMapTIter stringIter = _stringMap.find(symname); + if (stringIter == _stringMap.end()) { + _strings.push_back(symname); + uint64_t offset = this->_fsize; + this->_fsize += symname.size() + 1; + if (this->_flags & SHF_ALLOC) + this->_msize = this->_fsize; + _stringMap[symname] = offset; + return offset; + } + return stringIter->second; +} + +template <class ELFT> +void StringTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + for (auto si : _strings) { + memcpy(dest, si.data(), si.size()); + dest += si.size(); + memcpy(dest, "", 1); + dest += 1; + } +} + +/// ELF Symbol Table +template <class ELFT> +SymbolTable<ELFT>::SymbolTable(const ELFLinkingContext &ctx, const char *str, + int32_t order) + : Section<ELFT>(ctx, str, "SymbolTable") { + this->setOrder(order); + Elf_Sym symbol; + std::memset(&symbol, 0, sizeof(Elf_Sym)); + _symbolTable.push_back(SymbolEntry(nullptr, symbol, nullptr)); + this->_entSize = sizeof(Elf_Sym); + this->_fsize = sizeof(Elf_Sym); + this->_alignment = sizeof(Elf_Addr); + this->_type = SHT_SYMTAB; +} + +template <class ELFT> +void SymbolTable<ELFT>::addDefinedAtom(Elf_Sym &sym, const DefinedAtom *da, + int64_t addr) { + unsigned char binding = 0, type = 0; + sym.st_size = da->size(); + DefinedAtom::ContentType ct; + switch (ct = da->contentType()) { + case DefinedAtom::typeCode: + case DefinedAtom::typeStub: + sym.st_value = addr; + type = llvm::ELF::STT_FUNC; + break; + case DefinedAtom::typeResolver: + sym.st_value = addr; + type = llvm::ELF::STT_GNU_IFUNC; + break; + case DefinedAtom::typeDataFast: + case DefinedAtom::typeData: + case DefinedAtom::typeConstant: + sym.st_value = addr; + type = llvm::ELF::STT_OBJECT; + break; + case DefinedAtom::typeGOT: + sym.st_value = addr; + type = llvm::ELF::STT_NOTYPE; + break; + case DefinedAtom::typeZeroFill: + case DefinedAtom::typeZeroFillFast: + type = llvm::ELF::STT_OBJECT; + sym.st_value = addr; + break; + case DefinedAtom::typeThreadData: + case DefinedAtom::typeThreadZeroFill: + type = llvm::ELF::STT_TLS; + sym.st_value = addr; + break; + default: + type = llvm::ELF::STT_NOTYPE; + } + if (da->customSectionName() == da->name()) + type = llvm::ELF::STT_SECTION; + + if (da->scope() == DefinedAtom::scopeTranslationUnit) + binding = llvm::ELF::STB_LOCAL; + else + binding = llvm::ELF::STB_GLOBAL; + + sym.setBindingAndType(binding, type); +} + +template <class ELFT> +void SymbolTable<ELFT>::addAbsoluteAtom(Elf_Sym &sym, const AbsoluteAtom *aa, + int64_t addr) { + unsigned char binding = 0, type = 0; + type = llvm::ELF::STT_OBJECT; + sym.st_shndx = llvm::ELF::SHN_ABS; + switch (aa->scope()) { + case AbsoluteAtom::scopeLinkageUnit: + sym.setVisibility(llvm::ELF::STV_HIDDEN); + binding = llvm::ELF::STB_LOCAL; + break; + case AbsoluteAtom::scopeTranslationUnit: + binding = llvm::ELF::STB_LOCAL; + break; + case AbsoluteAtom::scopeGlobal: + binding = llvm::ELF::STB_GLOBAL; + break; + } + sym.st_value = addr; + sym.setBindingAndType(binding, type); +} + +template <class ELFT> +void SymbolTable<ELFT>::addSharedLibAtom(Elf_Sym &sym, + const SharedLibraryAtom *aa) { + unsigned char binding = 0, type = 0; + if (aa->type() == SharedLibraryAtom::Type::Data) { + type = llvm::ELF::STT_OBJECT; + sym.st_size = aa->size(); + } else + type = llvm::ELF::STT_FUNC; + sym.st_shndx = llvm::ELF::SHN_UNDEF; + binding = llvm::ELF::STB_GLOBAL; + sym.setBindingAndType(binding, type); +} + +template <class ELFT> +void SymbolTable<ELFT>::addUndefinedAtom(Elf_Sym &sym, + const UndefinedAtom *ua) { + unsigned char binding = 0, type = 0; + sym.st_value = 0; + type = llvm::ELF::STT_NOTYPE; + if (ua->canBeNull()) + binding = llvm::ELF::STB_WEAK; + else + binding = llvm::ELF::STB_GLOBAL; + sym.setBindingAndType(binding, type); +} + +/// Add a symbol to the symbol Table, definedAtoms which get added to the symbol +/// section don't have their virtual addresses set at the time of adding the +/// symbol to the symbol table(Example: dynamic symbols), the addresses needs +/// to be updated in the table before writing the dynamic symbol table +/// information +template <class ELFT> +void SymbolTable<ELFT>::addSymbol(const Atom *atom, int32_t sectionIndex, + uint64_t addr, const AtomLayout *atomLayout) { + Elf_Sym symbol; + + if (atom->name().empty()) + return; + + symbol.st_name = _stringSection->addString(atom->name()); + symbol.st_size = 0; + symbol.st_shndx = sectionIndex; + symbol.st_value = 0; + symbol.st_other = 0; + symbol.setVisibility(llvm::ELF::STV_DEFAULT); + + // Add all the atoms + if (const DefinedAtom *da = dyn_cast<const DefinedAtom>(atom)) + addDefinedAtom(symbol, da, addr); + else if (const AbsoluteAtom *aa = dyn_cast<const AbsoluteAtom>(atom)) + addAbsoluteAtom(symbol, aa, addr); + else if (isa<const SharedLibraryAtom>(atom)) + addSharedLibAtom(symbol, dyn_cast<SharedLibraryAtom>(atom)); + else + addUndefinedAtom(symbol, dyn_cast<UndefinedAtom>(atom)); + + // If --discard-all is on, don't add to the symbol table + // symbols with local binding. + if (this->_ctx.discardLocals() && symbol.getBinding() == llvm::ELF::STB_LOCAL) + return; + + // Temporary locals are all the symbols which name starts with .L. + // This is defined by the ELF standard. + if (this->_ctx.discardTempLocals() && atom->name().startswith(".L")) + return; + + _symbolTable.push_back(SymbolEntry(atom, symbol, atomLayout)); + this->_fsize += sizeof(Elf_Sym); + if (this->_flags & SHF_ALLOC) + this->_msize = this->_fsize; +} + +template <class ELFT> void SymbolTable<ELFT>::finalize(bool sort) { + // sh_info should be one greater than last symbol with STB_LOCAL binding + // we sort the symbol table to keep all local symbols at the beginning + if (sort) + sortSymbols(); + + uint16_t shInfo = 0; + for (const auto &i : _symbolTable) { + if (i._symbol.getBinding() != llvm::ELF::STB_LOCAL) + break; + shInfo++; + } + this->_info = shInfo; + this->_link = _stringSection->ordinal(); + if (this->_outputSection) { + this->_outputSection->setInfo(this->_info); + this->_outputSection->setLink(this->_link); + } +} + +template <class ELFT> +void SymbolTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + for (const auto &sti : _symbolTable) { + memcpy(dest, &sti._symbol, sizeof(Elf_Sym)); + dest += sizeof(Elf_Sym); + } +} + +template <class ELFT> +DynamicSymbolTable<ELFT>::DynamicSymbolTable(const ELFLinkingContext &ctx, + TargetLayout<ELFT> &layout, + const char *str, int32_t order) + : SymbolTable<ELFT>(ctx, str, order), _layout(layout) { + this->_type = SHT_DYNSYM; + this->_flags = SHF_ALLOC; + this->_msize = this->_fsize; +} + +template <class ELFT> void DynamicSymbolTable<ELFT>::addSymbolsToHashTable() { + int index = 0; + for (auto &ste : this->_symbolTable) { + if (!ste._atom) + _hashTable->addSymbol("", index); + else + _hashTable->addSymbol(ste._atom->name(), index); + ++index; + } +} + +template <class ELFT> void DynamicSymbolTable<ELFT>::finalize() { + // Defined symbols which have been added into the dynamic symbol table + // don't have their addresses known until addresses have been assigned + // so let's update the symbol values after they have got assigned + for (auto &ste : this->_symbolTable) { + const AtomLayout *atomLayout = ste._atomLayout; + if (!atomLayout) + continue; + ste._symbol.st_value = atomLayout->_virtualAddr; + } + + // Don't sort the symbols + SymbolTable<ELFT>::finalize(false); +} + +template <class ELFT> +RelocationTable<ELFT>::RelocationTable(const ELFLinkingContext &ctx, + StringRef str, int32_t order) + : Section<ELFT>(ctx, str, "RelocationTable") { + this->setOrder(order); + this->_flags = SHF_ALLOC; + // Set the alignment properly depending on the target architecture + this->_alignment = ELFT::Is64Bits ? 8 : 4; + if (ctx.isRelaOutputFormat()) { + this->_entSize = sizeof(Elf_Rela); + this->_type = SHT_RELA; + } else { + this->_entSize = sizeof(Elf_Rel); + this->_type = SHT_REL; + } +} + +template <class ELFT> +uint32_t RelocationTable<ELFT>::addRelocation(const DefinedAtom &da, + const Reference &r) { + _relocs.emplace_back(&da, &r); + this->_fsize = _relocs.size() * this->_entSize; + this->_msize = this->_fsize; + return _relocs.size() - 1; +} + +template <class ELFT> +bool RelocationTable<ELFT>::getRelocationIndex(const Reference &r, + uint32_t &res) { + auto rel = std::find_if( + _relocs.begin(), _relocs.end(), + [&](const std::pair<const DefinedAtom *, const Reference *> &p) { + if (p.second == &r) + return true; + return false; + }); + if (rel == _relocs.end()) + return false; + res = std::distance(_relocs.begin(), rel); + return true; +} + +template <class ELFT> +bool RelocationTable<ELFT>::canModifyReadonlySection() const { + for (const auto &rel : _relocs) { + const DefinedAtom *atom = rel.first; + if ((atom->permissions() & DefinedAtom::permRW_) != DefinedAtom::permRW_) + return true; + } + return false; +} + +template <class ELFT> void RelocationTable<ELFT>::finalize() { + this->_link = _symbolTable ? _symbolTable->ordinal() : 0; + if (this->_outputSection) + this->_outputSection->setLink(this->_link); +} + +template <class ELFT> +void RelocationTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + for (const auto &rel : _relocs) { + if (this->_ctx.isRelaOutputFormat()) { + auto &r = *reinterpret_cast<Elf_Rela *>(dest); + writeRela(writer, r, *rel.first, *rel.second); + DEBUG_WITH_TYPE("ELFRelocationTable", + llvm::dbgs() + << rel.second->kindValue() << " relocation at " + << rel.first->name() << "@" << r.r_offset << " to " + << rel.second->target()->name() << "@" << r.r_addend + << "\n";); + } else { + auto &r = *reinterpret_cast<Elf_Rel *>(dest); + writeRel(writer, r, *rel.first, *rel.second); + DEBUG_WITH_TYPE("ELFRelocationTable", + llvm::dbgs() << rel.second->kindValue() + << " relocation at " << rel.first->name() + << "@" << r.r_offset << " to " + << rel.second->target()->name() << "\n";); + } + dest += this->_entSize; + } +} + +template <class ELFT> +void RelocationTable<ELFT>::writeRela(ELFWriter *writer, Elf_Rela &r, + const DefinedAtom &atom, + const Reference &ref) { + r.setSymbolAndType(getSymbolIndex(ref.target()), ref.kindValue(), false); + r.r_offset = writer->addressOfAtom(&atom) + ref.offsetInAtom(); + // The addend is used only by relative relocations + if (this->_ctx.isRelativeReloc(ref)) + r.r_addend = writer->addressOfAtom(ref.target()) + ref.addend(); + else + r.r_addend = 0; +} + +template <class ELFT> +void RelocationTable<ELFT>::writeRel(ELFWriter *writer, Elf_Rel &r, + const DefinedAtom &atom, + const Reference &ref) { + r.setSymbolAndType(getSymbolIndex(ref.target()), ref.kindValue(), false); + r.r_offset = writer->addressOfAtom(&atom) + ref.offsetInAtom(); +} + +template <class ELFT> +uint32_t RelocationTable<ELFT>::getSymbolIndex(const Atom *a) { + return _symbolTable ? _symbolTable->getSymbolTableIndex(a) + : (uint32_t)STN_UNDEF; +} + +template <class ELFT> +DynamicTable<ELFT>::DynamicTable(const ELFLinkingContext &ctx, + TargetLayout<ELFT> &layout, StringRef str, + int32_t order) + : Section<ELFT>(ctx, str, "DynamicSection"), _layout(layout) { + this->setOrder(order); + this->_entSize = sizeof(Elf_Dyn); + this->_alignment = ELFT::Is64Bits ? 8 : 4; + // Reserve space for the DT_NULL entry. + this->_fsize = sizeof(Elf_Dyn); + this->_msize = sizeof(Elf_Dyn); + this->_type = SHT_DYNAMIC; + this->_flags = SHF_ALLOC; +} + +template <class ELFT> +std::size_t DynamicTable<ELFT>::addEntry(int64_t tag, uint64_t val) { + Elf_Dyn dyn; + dyn.d_tag = tag; + dyn.d_un.d_val = val; + _entries.push_back(dyn); + this->_fsize = (_entries.size() * sizeof(Elf_Dyn)) + sizeof(Elf_Dyn); + this->_msize = this->_fsize; + return _entries.size() - 1; +} + +template <class ELFT> +void DynamicTable<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + // Add the null entry. + Elf_Dyn d; + d.d_tag = 0; + d.d_un.d_val = 0; + _entries.push_back(d); + std::memcpy(dest, _entries.data(), this->_fsize); +} + +template <class ELFT> void DynamicTable<ELFT>::createDefaultEntries() { + bool isRela = this->_ctx.isRelaOutputFormat(); + _dt_hash = addEntry(DT_HASH, 0); + _dt_strtab = addEntry(DT_STRTAB, 0); + _dt_symtab = addEntry(DT_SYMTAB, 0); + _dt_strsz = addEntry(DT_STRSZ, 0); + _dt_syment = addEntry(DT_SYMENT, 0); + if (_layout.hasDynamicRelocationTable()) { + _dt_rela = addEntry(isRela ? DT_RELA : DT_REL, 0); + _dt_relasz = addEntry(isRela ? DT_RELASZ : DT_RELSZ, 0); + _dt_relaent = addEntry(isRela ? DT_RELAENT : DT_RELENT, 0); + if (_layout.getDynamicRelocationTable()->canModifyReadonlySection()) + _dt_textrel = addEntry(DT_TEXTREL, 0); + } + if (_layout.hasPLTRelocationTable()) { + _dt_pltrelsz = addEntry(DT_PLTRELSZ, 0); + _dt_pltgot = addEntry(getGotPltTag(), 0); + _dt_pltrel = addEntry(DT_PLTREL, isRela ? DT_RELA : DT_REL); + _dt_jmprel = addEntry(DT_JMPREL, 0); + } +} + +template <class ELFT> void DynamicTable<ELFT>::doPreFlight() { + auto initArray = _layout.findOutputSection(".init_array"); + auto finiArray = _layout.findOutputSection(".fini_array"); + if (initArray) { + _dt_init_array = addEntry(DT_INIT_ARRAY, 0); + _dt_init_arraysz = addEntry(DT_INIT_ARRAYSZ, 0); + } + if (finiArray) { + _dt_fini_array = addEntry(DT_FINI_ARRAY, 0); + _dt_fini_arraysz = addEntry(DT_FINI_ARRAYSZ, 0); + } + if (getInitAtomLayout()) + _dt_init = addEntry(DT_INIT, 0); + if (getFiniAtomLayout()) + _dt_fini = addEntry(DT_FINI, 0); +} + +template <class ELFT> void DynamicTable<ELFT>::finalize() { + StringTable<ELFT> *dynamicStringTable = _dynamicSymbolTable->getStringTable(); + this->_link = dynamicStringTable->ordinal(); + if (this->_outputSection) { + this->_outputSection->setType(this->_type); + this->_outputSection->setInfo(this->_info); + this->_outputSection->setLink(this->_link); + } +} + +template <class ELFT> void DynamicTable<ELFT>::updateDynamicTable() { + StringTable<ELFT> *dynamicStringTable = _dynamicSymbolTable->getStringTable(); + _entries[_dt_hash].d_un.d_val = _hashTable->virtualAddr(); + _entries[_dt_strtab].d_un.d_val = dynamicStringTable->virtualAddr(); + _entries[_dt_symtab].d_un.d_val = _dynamicSymbolTable->virtualAddr(); + _entries[_dt_strsz].d_un.d_val = dynamicStringTable->memSize(); + _entries[_dt_syment].d_un.d_val = _dynamicSymbolTable->getEntSize(); + auto initArray = _layout.findOutputSection(".init_array"); + if (initArray) { + _entries[_dt_init_array].d_un.d_val = initArray->virtualAddr(); + _entries[_dt_init_arraysz].d_un.d_val = initArray->memSize(); + } + auto finiArray = _layout.findOutputSection(".fini_array"); + if (finiArray) { + _entries[_dt_fini_array].d_un.d_val = finiArray->virtualAddr(); + _entries[_dt_fini_arraysz].d_un.d_val = finiArray->memSize(); + } + if (const auto *al = getInitAtomLayout()) + _entries[_dt_init].d_un.d_val = getAtomVirtualAddress(al); + if (const auto *al = getFiniAtomLayout()) + _entries[_dt_fini].d_un.d_val = getAtomVirtualAddress(al); + if (_layout.hasDynamicRelocationTable()) { + auto relaTbl = _layout.getDynamicRelocationTable(); + _entries[_dt_rela].d_un.d_val = relaTbl->virtualAddr(); + _entries[_dt_relasz].d_un.d_val = relaTbl->memSize(); + _entries[_dt_relaent].d_un.d_val = relaTbl->getEntSize(); + } + if (_layout.hasPLTRelocationTable()) { + auto relaTbl = _layout.getPLTRelocationTable(); + _entries[_dt_jmprel].d_un.d_val = relaTbl->virtualAddr(); + _entries[_dt_pltrelsz].d_un.d_val = relaTbl->memSize(); + auto gotplt = _layout.findOutputSection(".got.plt"); + _entries[_dt_pltgot].d_un.d_val = gotplt->virtualAddr(); + } +} + +template <class ELFT> +const AtomLayout *DynamicTable<ELFT>::getInitAtomLayout() { + auto al = _layout.findAtomLayoutByName(this->_ctx.initFunction()); + if (al && isa<DefinedAtom>(al->_atom)) + return al; + return nullptr; +} + +template <class ELFT> +const AtomLayout *DynamicTable<ELFT>::getFiniAtomLayout() { + auto al = _layout.findAtomLayoutByName(this->_ctx.finiFunction()); + if (al && isa<DefinedAtom>(al->_atom)) + return al; + return nullptr; +} + +template <class ELFT> +InterpSection<ELFT>::InterpSection(const ELFLinkingContext &ctx, StringRef str, + int32_t order, StringRef interp) + : Section<ELFT>(ctx, str, "Dynamic:Interp"), _interp(interp) { + this->setOrder(order); + this->_alignment = 1; + // + 1 for null term. + this->_fsize = interp.size() + 1; + this->_msize = this->_fsize; + this->_type = SHT_PROGBITS; + this->_flags = SHF_ALLOC; +} + +template <class ELFT> +void InterpSection<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + std::memcpy(dest, _interp.data(), _interp.size()); +} + +template <class ELFT> +HashSection<ELFT>::HashSection(const ELFLinkingContext &ctx, StringRef name, + int32_t order) + : Section<ELFT>(ctx, name, "Dynamic:Hash") { + this->setOrder(order); + this->_entSize = 4; + this->_type = SHT_HASH; + this->_flags = SHF_ALLOC; + this->_alignment = ELFT::Is64Bits ? 8 : 4; + this->_fsize = 0; + this->_msize = 0; +} + +template <class ELFT> +void HashSection<ELFT>::addSymbol(StringRef name, uint32_t index) { + SymbolTableEntry ste; + ste._name = name; + ste._index = index; + _entries.push_back(ste); +} + +/// \brief Set the dynamic symbol table +template <class ELFT> +void HashSection<ELFT>::setSymbolTable( + const DynamicSymbolTable<ELFT> *symbolTable) { + _symbolTable = symbolTable; +} + +template <class ELFT> void HashSection<ELFT>::doPreFlight() { + // The number of buckets to use for a certain number of symbols. + // If there are less than 3 symbols, 1 bucket will be used. If + // there are less than 17 symbols, 3 buckets will be used, and so + // forth. The bucket numbers are defined by GNU ld. We use the + // same rules here so we generate hash sections with the same + // size as those generated by GNU ld. + uint32_t hashBuckets[] = {1, 3, 17, 37, 67, 97, 131, + 197, 263, 521, 1031, 2053, 4099, 8209, + 16411, 32771, 65537, 131101, 262147}; + int hashBucketsCount = sizeof(hashBuckets) / sizeof(uint32_t); + + unsigned int bucketsCount = 0; + unsigned int dynSymCount = _entries.size(); + + // Get the number of buckes that we want to use + for (int i = 0; i < hashBucketsCount; ++i) { + if (dynSymCount < hashBuckets[i]) + break; + bucketsCount = hashBuckets[i]; + } + _buckets.resize(bucketsCount); + _chains.resize(_entries.size()); + + // Create the hash table for the dynamic linker + for (auto ai : _entries) { + unsigned int dynsymIndex = ai._index; + unsigned int bucketpos = llvm::object::elf_hash(ai._name) % bucketsCount; + _chains[dynsymIndex] = _buckets[bucketpos]; + _buckets[bucketpos] = dynsymIndex; + } + + this->_fsize = (2 + _chains.size() + _buckets.size()) * sizeof(uint32_t); + this->_msize = this->_fsize; +} + +template <class ELFT> void HashSection<ELFT>::finalize() { + this->_link = _symbolTable ? _symbolTable->ordinal() : 0; + if (this->_outputSection) + this->_outputSection->setLink(this->_link); +} + +template <class ELFT> +void HashSection<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + Elf_Word bucketChainCounts[2]; + bucketChainCounts[0] = _buckets.size(); + bucketChainCounts[1] = _chains.size(); + std::memcpy(dest, bucketChainCounts, sizeof(bucketChainCounts)); + dest += sizeof(bucketChainCounts); + // write bucket values + std::memcpy(dest, _buckets.data(), _buckets.size() * sizeof(Elf_Word)); + dest += _buckets.size() * sizeof(Elf_Word); + // write chain values + std::memcpy(dest, _chains.data(), _chains.size() * sizeof(Elf_Word)); +} + +template <class ELFT> +EHFrameHeader<ELFT>::EHFrameHeader(const ELFLinkingContext &ctx, StringRef name, + TargetLayout<ELFT> &layout, int32_t order) + : Section<ELFT>(ctx, name, "EHFrameHeader"), _layout(layout) { + this->setOrder(order); + this->_entSize = 0; + this->_type = SHT_PROGBITS; + this->_flags = SHF_ALLOC; + this->_alignment = ELFT::Is64Bits ? 8 : 4; + // Minimum size for empty .eh_frame_hdr. + this->_fsize = 1 + 1 + 1 + 1 + 4; + this->_msize = this->_fsize; +} + +template <class ELFT> void EHFrameHeader<ELFT>::doPreFlight() { + // TODO: Generate a proper binary search table. +} + +template <class ELFT> void EHFrameHeader<ELFT>::finalize() { + OutputSection<ELFT> *s = _layout.findOutputSection(".eh_frame"); + OutputSection<ELFT> *h = _layout.findOutputSection(".eh_frame_hdr"); + if (s && h) + _ehFrameOffset = s->virtualAddr() - (h->virtualAddr() + 4); +} + +template <class ELFT> +void EHFrameHeader<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout, + llvm::FileOutputBuffer &buffer) { + uint8_t *chunkBuffer = buffer.getBufferStart(); + uint8_t *dest = chunkBuffer + this->fileOffset(); + int pos = 0; + dest[pos++] = 1; // version + dest[pos++] = llvm::dwarf::DW_EH_PE_pcrel | + llvm::dwarf::DW_EH_PE_sdata4; // eh_frame_ptr_enc + dest[pos++] = llvm::dwarf::DW_EH_PE_omit; // fde_count_enc + dest[pos++] = llvm::dwarf::DW_EH_PE_omit; // table_enc + *reinterpret_cast<typename llvm::object::ELFFile<ELFT>::Elf_Sword *>( + dest + pos) = _ehFrameOffset; +} + +#define INSTANTIATE(klass) \ + template class klass<ELF32LE>; \ + template class klass<ELF32BE>; \ + template class klass<ELF64LE>; \ + template class klass<ELF64BE> + +INSTANTIATE(AtomSection); +INSTANTIATE(DynamicSymbolTable); +INSTANTIATE(DynamicTable); +INSTANTIATE(EHFrameHeader); +INSTANTIATE(HashSection); +INSTANTIATE(InterpSection); +INSTANTIATE(OutputSection); +INSTANTIATE(RelocationTable); +INSTANTIATE(Section); +INSTANTIATE(StringTable); +INSTANTIATE(SymbolTable); + +} // end namespace elf +} // end namespace lld |