forked from OSchip/llvm-project
1304 lines
45 KiB
C++
1304 lines
45 KiB
C++
//===- Writer.cpp ---------------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "Writer.h"
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#include "Config.h"
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#include "OutputSections.h"
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#include "SymbolTable.h"
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#include "Target.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/ADT/StringSwitch.h"
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#include "llvm/Support/FileOutputBuffer.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/StringSaver.h"
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using namespace llvm;
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using namespace llvm::ELF;
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using namespace llvm::object;
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using namespace lld;
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using namespace lld::elf2;
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namespace {
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// The writer writes a SymbolTable result to a file.
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template <class ELFT> class Writer {
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public:
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typedef typename ELFFile<ELFT>::uintX_t uintX_t;
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typedef typename ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
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typedef typename ELFFile<ELFT>::Elf_Ehdr Elf_Ehdr;
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typedef typename ELFFile<ELFT>::Elf_Phdr Elf_Phdr;
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typedef typename ELFFile<ELFT>::Elf_Sym Elf_Sym;
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typedef typename ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
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typedef typename ELFFile<ELFT>::Elf_Rela Elf_Rela;
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Writer(SymbolTable<ELFT> &S) : Symtab(S) {}
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void run();
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private:
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void copyLocalSymbols();
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void addReservedSymbols();
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void createSections();
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void addPredefinedSections();
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template <bool isRela>
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void scanRelocs(InputSectionBase<ELFT> &C,
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iterator_range<const Elf_Rel_Impl<ELFT, isRela> *> Rels);
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void scanRelocs(InputSection<ELFT> &C);
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void scanRelocs(InputSectionBase<ELFT> &S, const Elf_Shdr &RelSec);
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void updateRelro(Elf_Phdr *Cur, Elf_Phdr *GnuRelroPhdr, uintX_t VA);
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void assignAddresses();
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void buildSectionMap();
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void fixAbsoluteSymbols();
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void openFile(StringRef OutputPath);
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void writeHeader();
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void writeSections();
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bool isDiscarded(InputSectionBase<ELFT> *IS) const;
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StringRef getOutputSectionName(StringRef S) const;
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bool needsInterpSection() const {
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return !Symtab.getSharedFiles().empty() && !Config->DynamicLinker.empty();
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}
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bool isOutputDynamic() const {
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return !Symtab.getSharedFiles().empty() || Config->Shared;
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}
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int getPhdrsNum() const;
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OutputSection<ELFT> *getBss();
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void addCommonSymbols(std::vector<DefinedCommon *> &Syms);
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void addCopyRelSymbols(std::vector<SharedSymbol<ELFT> *> &Syms);
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std::unique_ptr<llvm::FileOutputBuffer> Buffer;
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BumpPtrAllocator Alloc;
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std::vector<OutputSectionBase<ELFT> *> OutputSections;
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std::vector<std::unique_ptr<OutputSectionBase<ELFT>>> OwningSections;
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unsigned getNumSections() const { return OutputSections.size() + 1; }
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void addRelIpltSymbols();
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void addStartEndSymbols();
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void addStartStopSymbols(OutputSectionBase<ELFT> *Sec);
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void setPhdr(Elf_Phdr *PH, uint32_t Type, uint32_t Flags, uintX_t FileOff,
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uintX_t VA, uintX_t Size, uintX_t Align);
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void copyPhdr(Elf_Phdr *PH, OutputSectionBase<ELFT> *From);
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bool HasRelro = false;
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SymbolTable<ELFT> &Symtab;
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std::vector<Elf_Phdr> Phdrs;
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uintX_t FileSize;
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uintX_t SectionHeaderOff;
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llvm::StringMap<llvm::StringRef> InputToOutputSection;
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};
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} // anonymous namespace
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template <class ELFT> static bool shouldUseRela() {
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ELFKind K = cast<ELFFileBase<ELFT>>(Config->FirstElf)->getELFKind();
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return K == ELF64LEKind || K == ELF64BEKind;
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}
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template <class ELFT> void elf2::writeResult(SymbolTable<ELFT> *Symtab) {
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// Initialize output sections that are handled by Writer specially.
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// Don't reorder because the order of initialization matters.
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InterpSection<ELFT> Interp;
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Out<ELFT>::Interp = &Interp;
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StringTableSection<ELFT> ShStrTab(".shstrtab", false);
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Out<ELFT>::ShStrTab = &ShStrTab;
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StringTableSection<ELFT> StrTab(".strtab", false);
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if (!Config->StripAll)
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Out<ELFT>::StrTab = &StrTab;
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StringTableSection<ELFT> DynStrTab(".dynstr", true);
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Out<ELFT>::DynStrTab = &DynStrTab;
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GotSection<ELFT> Got;
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Out<ELFT>::Got = &Got;
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GotPltSection<ELFT> GotPlt;
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if (Target->supportsLazyRelocations())
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Out<ELFT>::GotPlt = &GotPlt;
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PltSection<ELFT> Plt;
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Out<ELFT>::Plt = &Plt;
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std::unique_ptr<SymbolTableSection<ELFT>> SymTab;
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if (!Config->StripAll) {
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SymTab.reset(new SymbolTableSection<ELFT>(*Symtab, *Out<ELFT>::StrTab));
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Out<ELFT>::SymTab = SymTab.get();
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}
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SymbolTableSection<ELFT> DynSymTab(*Symtab, *Out<ELFT>::DynStrTab);
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Out<ELFT>::DynSymTab = &DynSymTab;
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HashTableSection<ELFT> HashTab;
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if (Config->SysvHash)
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Out<ELFT>::HashTab = &HashTab;
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GnuHashTableSection<ELFT> GnuHashTab;
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if (Config->GnuHash)
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Out<ELFT>::GnuHashTab = &GnuHashTab;
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bool IsRela = shouldUseRela<ELFT>();
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RelocationSection<ELFT> RelaDyn(IsRela ? ".rela.dyn" : ".rel.dyn", IsRela);
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Out<ELFT>::RelaDyn = &RelaDyn;
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RelocationSection<ELFT> RelaPlt(IsRela ? ".rela.plt" : ".rel.plt", IsRela);
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if (Target->supportsLazyRelocations())
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Out<ELFT>::RelaPlt = &RelaPlt;
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DynamicSection<ELFT> Dynamic(*Symtab);
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Out<ELFT>::Dynamic = &Dynamic;
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Writer<ELFT>(*Symtab).run();
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}
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// The main function of the writer.
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template <class ELFT> void Writer<ELFT>::run() {
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buildSectionMap();
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if (!Config->DiscardAll)
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copyLocalSymbols();
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addReservedSymbols();
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createSections();
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assignAddresses();
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fixAbsoluteSymbols();
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openFile(Config->OutputFile);
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writeHeader();
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writeSections();
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error(Buffer->commit());
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}
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namespace {
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template <bool Is64Bits> struct SectionKey {
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typedef typename std::conditional<Is64Bits, uint64_t, uint32_t>::type uintX_t;
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StringRef Name;
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uint32_t Type;
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uintX_t Flags;
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uintX_t EntSize;
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};
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}
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namespace llvm {
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template <bool Is64Bits> struct DenseMapInfo<SectionKey<Is64Bits>> {
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static SectionKey<Is64Bits> getEmptyKey() {
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return SectionKey<Is64Bits>{DenseMapInfo<StringRef>::getEmptyKey(), 0, 0,
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0};
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}
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static SectionKey<Is64Bits> getTombstoneKey() {
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return SectionKey<Is64Bits>{DenseMapInfo<StringRef>::getTombstoneKey(), 0,
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0, 0};
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}
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static unsigned getHashValue(const SectionKey<Is64Bits> &Val) {
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return hash_combine(Val.Name, Val.Type, Val.Flags, Val.EntSize);
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}
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static bool isEqual(const SectionKey<Is64Bits> &LHS,
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const SectionKey<Is64Bits> &RHS) {
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return DenseMapInfo<StringRef>::isEqual(LHS.Name, RHS.Name) &&
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LHS.Type == RHS.Type && LHS.Flags == RHS.Flags &&
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LHS.EntSize == RHS.EntSize;
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}
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};
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}
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// The reason we have to do this early scan is as follows
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// * To mmap the output file, we need to know the size
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// * For that, we need to know how many dynamic relocs we will have.
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// It might be possible to avoid this by outputting the file with write:
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// * Write the allocated output sections, computing addresses.
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// * Apply relocations, recording which ones require a dynamic reloc.
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// * Write the dynamic relocations.
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// * Write the rest of the file.
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template <class ELFT>
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template <bool isRela>
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void Writer<ELFT>::scanRelocs(
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InputSectionBase<ELFT> &C,
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iterator_range<const Elf_Rel_Impl<ELFT, isRela> *> Rels) {
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typedef Elf_Rel_Impl<ELFT, isRela> RelType;
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const ObjectFile<ELFT> &File = *C.getFile();
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for (const RelType &RI : Rels) {
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uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
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SymbolBody *Body = File.getSymbolBody(SymIndex);
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uint32_t Type = RI.getType(Config->Mips64EL);
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if (Target->isGotRelative(Type))
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HasGotOffRel = true;
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if (Target->isTlsLocalDynamicReloc(Type)) {
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if (Target->isTlsOptimized(Type, nullptr))
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continue;
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if (Out<ELFT>::Got->addCurrentModuleTlsIndex())
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Out<ELFT>::RelaDyn->addReloc({&C, &RI});
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continue;
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}
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// Set "used" bit for --as-needed.
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if (Body && Body->isUndefined() && !Body->isWeak())
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if (auto *S = dyn_cast<SharedSymbol<ELFT>>(Body->repl()))
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S->File->IsUsed = true;
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if (Body)
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Body = Body->repl();
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if (Body && Body->isTls() && Target->isTlsGlobalDynamicReloc(Type)) {
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bool Opt = Target->isTlsOptimized(Type, Body);
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if (!Opt && Out<ELFT>::Got->addDynTlsEntry(Body)) {
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Out<ELFT>::RelaDyn->addReloc({&C, &RI});
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Out<ELFT>::RelaDyn->addReloc({nullptr, nullptr});
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Body->setUsedInDynamicReloc();
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continue;
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}
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if (!canBePreempted(Body, true))
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continue;
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}
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if (Body && Body->isTls() && !Target->isTlsDynReloc(Type, *Body))
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continue;
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if (Target->relocNeedsDynRelative(Type)) {
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RelType *Rel = new (Alloc) RelType;
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Rel->setSymbolAndType(0, Target->getRelativeReloc(), Config->Mips64EL);
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Rel->r_offset = RI.r_offset;
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Out<ELFT>::RelaDyn->addReloc({&C, Rel});
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}
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bool NeedsGot = false;
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bool NeedsPlt = false;
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if (Body) {
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if (auto *E = dyn_cast<SharedSymbol<ELFT>>(Body)) {
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if (E->NeedsCopy)
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continue;
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if (Target->needsCopyRel(Type, *Body))
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E->NeedsCopy = true;
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}
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NeedsPlt = Target->relocNeedsPlt(Type, *Body);
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if (NeedsPlt) {
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if (Body->isInPlt())
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continue;
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Out<ELFT>::Plt->addEntry(Body);
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}
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NeedsGot = Target->relocNeedsGot(Type, *Body);
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if (NeedsGot) {
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if (NeedsPlt && Target->supportsLazyRelocations()) {
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Out<ELFT>::GotPlt->addEntry(Body);
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} else {
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if (Body->isInGot())
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continue;
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Out<ELFT>::Got->addEntry(Body);
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}
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}
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}
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// An STT_GNU_IFUNC symbol always uses a PLT entry, and all references
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// to the symbol go through the PLT. This is true even for a local
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// symbol, although local symbols normally do not require PLT entries.
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if (Body && isGnuIFunc<ELFT>(*Body)) {
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Body->setUsedInDynamicReloc();
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Out<ELFT>::RelaPlt->addReloc({&C, &RI});
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continue;
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}
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if (Config->EMachine == EM_MIPS && NeedsGot) {
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// MIPS ABI has special rules to process GOT entries
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// and doesn't require relocation entries for them.
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// See "Global Offset Table" in Chapter 5 in the following document
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// for detailed description:
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// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
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Body->setUsedInDynamicReloc();
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continue;
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}
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bool CBP = canBePreempted(Body, NeedsGot);
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if (!CBP && (!Config->Shared || Target->isRelRelative(Type)))
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continue;
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if (CBP)
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Body->setUsedInDynamicReloc();
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if (NeedsPlt && Target->supportsLazyRelocations())
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Out<ELFT>::RelaPlt->addReloc({&C, &RI});
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else
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Out<ELFT>::RelaDyn->addReloc({&C, &RI});
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}
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}
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template <class ELFT> void Writer<ELFT>::scanRelocs(InputSection<ELFT> &C) {
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if (!(C.getSectionHdr()->sh_flags & SHF_ALLOC))
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return;
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for (const Elf_Shdr *RelSec : C.RelocSections)
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scanRelocs(C, *RelSec);
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}
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template <class ELFT>
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void Writer<ELFT>::scanRelocs(InputSectionBase<ELFT> &S,
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const Elf_Shdr &RelSec) {
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ELFFile<ELFT> &EObj = S.getFile()->getObj();
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if (RelSec.sh_type == SHT_RELA)
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scanRelocs(S, EObj.relas(&RelSec));
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else
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scanRelocs(S, EObj.rels(&RelSec));
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}
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template <class ELFT>
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static void reportUndefined(SymbolTable<ELFT> &Symtab, SymbolBody *Sym) {
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if (Config->Shared && !Config->NoUndefined)
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return;
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std::string Msg = "undefined symbol: " + Sym->getName().str();
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if (ELFFileBase<ELFT> *File = Symtab.findFile(Sym))
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Msg += " in " + File->getName().str();
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if (Config->NoInhibitExec)
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warning(Msg);
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else
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error(Msg);
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}
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// Local symbols are not in the linker's symbol table. This function scans
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// each object file's symbol table to copy local symbols to the output.
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template <class ELFT> void Writer<ELFT>::copyLocalSymbols() {
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for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab.getObjectFiles()) {
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for (const Elf_Sym &Sym : F->getLocalSymbols()) {
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ErrorOr<StringRef> SymNameOrErr = Sym.getName(F->getStringTable());
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error(SymNameOrErr);
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StringRef SymName = *SymNameOrErr;
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if (!shouldKeepInSymtab<ELFT>(*F, SymName, Sym))
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continue;
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if (Out<ELFT>::SymTab)
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Out<ELFT>::SymTab->addLocalSymbol(SymName);
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}
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}
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}
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// PPC64 has a number of special SHT_PROGBITS+SHF_ALLOC+SHF_WRITE sections that
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// we would like to make sure appear is a specific order to maximize their
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// coverage by a single signed 16-bit offset from the TOC base pointer.
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// Conversely, the special .tocbss section should be first among all SHT_NOBITS
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// sections. This will put it next to the loaded special PPC64 sections (and,
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// thus, within reach of the TOC base pointer).
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static int getPPC64SectionRank(StringRef SectionName) {
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return StringSwitch<int>(SectionName)
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.Case(".tocbss", 0)
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.Case(".branch_lt", 2)
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.Case(".toc", 3)
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.Case(".toc1", 4)
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.Case(".opd", 5)
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.Default(1);
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}
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template <class ELFT> static bool isRelroSection(OutputSectionBase<ELFT> *Sec) {
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typename OutputSectionBase<ELFT>::uintX_t Flags = Sec->getFlags();
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if (!(Flags & SHF_ALLOC) || !(Flags & SHF_WRITE))
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return false;
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if (Flags & SHF_TLS)
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return true;
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uint32_t Type = Sec->getType();
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if (Type == SHT_INIT_ARRAY || Type == SHT_FINI_ARRAY ||
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Type == SHT_PREINIT_ARRAY)
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return true;
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if (Sec == Out<ELFT>::GotPlt)
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return Config->ZNow;
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if (Sec == Out<ELFT>::Dynamic || Sec == Out<ELFT>::Got)
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return true;
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StringRef S = Sec->getName();
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return S == ".data.rel.ro" || S == ".ctors" || S == ".dtors" || S == ".jcr" ||
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S == ".eh_frame";
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}
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// Output section ordering is determined by this function.
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template <class ELFT>
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static bool compareOutputSections(OutputSectionBase<ELFT> *A,
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OutputSectionBase<ELFT> *B) {
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typedef typename ELFFile<ELFT>::uintX_t uintX_t;
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uintX_t AFlags = A->getFlags();
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uintX_t BFlags = B->getFlags();
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// Allocatable sections go first to reduce the total PT_LOAD size and
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// so debug info doesn't change addresses in actual code.
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bool AIsAlloc = AFlags & SHF_ALLOC;
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bool BIsAlloc = BFlags & SHF_ALLOC;
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if (AIsAlloc != BIsAlloc)
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return AIsAlloc;
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// We don't have any special requirements for the relative order of
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// two non allocatable sections.
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if (!AIsAlloc)
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return false;
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// We want the read only sections first so that they go in the PT_LOAD
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// covering the program headers at the start of the file.
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bool AIsWritable = AFlags & SHF_WRITE;
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bool BIsWritable = BFlags & SHF_WRITE;
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if (AIsWritable != BIsWritable)
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return BIsWritable;
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// For a corresponding reason, put non exec sections first (the program
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// header PT_LOAD is not executable).
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bool AIsExec = AFlags & SHF_EXECINSTR;
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bool BIsExec = BFlags & SHF_EXECINSTR;
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if (AIsExec != BIsExec)
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return BIsExec;
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// If we got here we know that both A and B are in the same PT_LOAD.
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// The TLS initialization block needs to be a single contiguous block in a R/W
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// PT_LOAD, so stick TLS sections directly before R/W sections. The TLS NOBITS
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// sections are placed here as they don't take up virtual address space in the
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// PT_LOAD.
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bool AIsTls = AFlags & SHF_TLS;
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bool BIsTls = BFlags & SHF_TLS;
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if (AIsTls != BIsTls)
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return AIsTls;
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// The next requirement we have is to put nobits sections last. The
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// reason is that the only thing the dynamic linker will see about
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// them is a p_memsz that is larger than p_filesz. Seeing that it
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// zeros the end of the PT_LOAD, so that has to correspond to the
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// nobits sections.
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bool AIsNoBits = A->getType() == SHT_NOBITS;
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bool BIsNoBits = B->getType() == SHT_NOBITS;
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if (AIsNoBits != BIsNoBits)
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return BIsNoBits;
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// We place RelRo section before plain r/w ones.
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bool AIsRelRo = isRelroSection(A);
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bool BIsRelRo = isRelroSection(B);
|
|
if (AIsRelRo != BIsRelRo)
|
|
return AIsRelRo;
|
|
|
|
// Some architectures have additional ordering restrictions for sections
|
|
// within the same PT_LOAD.
|
|
if (Config->EMachine == EM_PPC64)
|
|
return getPPC64SectionRank(A->getName()) <
|
|
getPPC64SectionRank(B->getName());
|
|
|
|
return false;
|
|
}
|
|
|
|
template <class ELFT> OutputSection<ELFT> *Writer<ELFT>::getBss() {
|
|
if (!Out<ELFT>::Bss) {
|
|
Out<ELFT>::Bss =
|
|
new OutputSection<ELFT>(".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
|
|
OwningSections.emplace_back(Out<ELFT>::Bss);
|
|
OutputSections.push_back(Out<ELFT>::Bss);
|
|
}
|
|
return Out<ELFT>::Bss;
|
|
}
|
|
|
|
// Until this function is called, common symbols do not belong to any section.
|
|
// This function adds them to end of BSS section.
|
|
template <class ELFT>
|
|
void Writer<ELFT>::addCommonSymbols(std::vector<DefinedCommon *> &Syms) {
|
|
if (Syms.empty())
|
|
return;
|
|
|
|
// Sort the common symbols by alignment as an heuristic to pack them better.
|
|
std::stable_sort(Syms.begin(), Syms.end(),
|
|
[](const DefinedCommon *A, const DefinedCommon *B) {
|
|
return A->MaxAlignment > B->MaxAlignment;
|
|
});
|
|
|
|
uintX_t Off = getBss()->getSize();
|
|
for (DefinedCommon *C : Syms) {
|
|
Off = align(Off, C->MaxAlignment);
|
|
C->OffsetInBss = Off;
|
|
Off += C->Size;
|
|
}
|
|
|
|
Out<ELFT>::Bss->setSize(Off);
|
|
}
|
|
|
|
// Reserve space in .bss for copy relocations.
|
|
template <class ELFT>
|
|
void Writer<ELFT>::addCopyRelSymbols(std::vector<SharedSymbol<ELFT> *> &Syms) {
|
|
if (Syms.empty())
|
|
return;
|
|
uintX_t Off = getBss()->getSize();
|
|
for (SharedSymbol<ELFT> *C : Syms) {
|
|
const Elf_Sym &Sym = C->Sym;
|
|
const Elf_Shdr *Sec = C->File->getSection(Sym);
|
|
uintX_t SecAlign = Sec->sh_addralign;
|
|
unsigned TrailingZeros =
|
|
std::min(countTrailingZeros(SecAlign),
|
|
countTrailingZeros((uintX_t)Sym.st_value));
|
|
uintX_t Align = 1 << TrailingZeros;
|
|
Out<ELFT>::Bss->updateAlign(Align);
|
|
Off = align(Off, Align);
|
|
C->OffsetInBss = Off;
|
|
Off += Sym.st_size;
|
|
}
|
|
Out<ELFT>::Bss->setSize(Off);
|
|
}
|
|
|
|
template <class ELFT>
|
|
StringRef Writer<ELFT>::getOutputSectionName(StringRef S) const {
|
|
auto It = InputToOutputSection.find(S);
|
|
if (It != std::end(InputToOutputSection))
|
|
return It->second;
|
|
|
|
if (S.startswith(".text."))
|
|
return ".text";
|
|
if (S.startswith(".rodata."))
|
|
return ".rodata";
|
|
if (S.startswith(".data.rel.ro"))
|
|
return ".data.rel.ro";
|
|
if (S.startswith(".data."))
|
|
return ".data";
|
|
if (S.startswith(".bss."))
|
|
return ".bss";
|
|
return S;
|
|
}
|
|
|
|
template <class ELFT>
|
|
void reportDiscarded(InputSectionBase<ELFT> *IS,
|
|
const std::unique_ptr<ObjectFile<ELFT>> &File) {
|
|
if (!Config->PrintGcSections || !IS || IS->isLive())
|
|
return;
|
|
llvm::errs() << "removing unused section from '" << IS->getSectionName()
|
|
<< "' in file '" << File->getName() << "'\n";
|
|
}
|
|
|
|
template <class ELFT>
|
|
bool Writer<ELFT>::isDiscarded(InputSectionBase<ELFT> *IS) const {
|
|
if (!IS || !IS->isLive() || IS == &InputSection<ELFT>::Discarded)
|
|
return true;
|
|
return InputToOutputSection.lookup(IS->getSectionName()) == "/DISCARD/";
|
|
}
|
|
|
|
template <class ELFT>
|
|
static bool compareSections(OutputSectionBase<ELFT> *A,
|
|
OutputSectionBase<ELFT> *B) {
|
|
auto ItA = Config->OutputSections.find(A->getName());
|
|
auto ItEnd = std::end(Config->OutputSections);
|
|
if (ItA == ItEnd)
|
|
return compareOutputSections(A, B);
|
|
auto ItB = Config->OutputSections.find(B->getName());
|
|
if (ItB == ItEnd)
|
|
return compareOutputSections(A, B);
|
|
|
|
return std::distance(ItA, ItB) > 0;
|
|
}
|
|
|
|
// The beginning and the ending of .rel[a].plt section are marked
|
|
// with __rel[a]_iplt_{start,end} symbols if it is a statically linked
|
|
// executable. The runtime needs these symbols in order to resolve
|
|
// all IRELATIVE relocs on startup. For dynamic executables, we don't
|
|
// need these symbols, since IRELATIVE relocs are resolved through GOT
|
|
// and PLT. For details, see http://www.airs.com/blog/archives/403.
|
|
template <class ELFT>
|
|
void Writer<ELFT>::addRelIpltSymbols() {
|
|
if (isOutputDynamic() || !Out<ELFT>::RelaPlt)
|
|
return;
|
|
bool IsRela = shouldUseRela<ELFT>();
|
|
|
|
StringRef S = IsRela ? "__rela_iplt_start" : "__rel_iplt_start";
|
|
if (Symtab.find(S))
|
|
Symtab.addAbsolute(S, ElfSym<ELFT>::RelaIpltStart);
|
|
|
|
S = IsRela ? "__rela_iplt_end" : "__rel_iplt_end";
|
|
if (Symtab.find(S))
|
|
Symtab.addAbsolute(S, ElfSym<ELFT>::RelaIpltEnd);
|
|
}
|
|
|
|
template <class ELFT> static bool includeInSymtab(const SymbolBody &B) {
|
|
if (!B.isUsedInRegularObj())
|
|
return false;
|
|
|
|
// Don't include synthetic symbols like __init_array_start in every output.
|
|
if (auto *U = dyn_cast<DefinedRegular<ELFT>>(&B))
|
|
if (&U->Sym == &ElfSym<ELFT>::IgnoreUndef)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool includeInDynamicSymtab(const SymbolBody &B) {
|
|
uint8_t V = B.getVisibility();
|
|
if (V != STV_DEFAULT && V != STV_PROTECTED)
|
|
return false;
|
|
if (Config->ExportDynamic || Config->Shared)
|
|
return true;
|
|
return B.isUsedInDynamicReloc();
|
|
}
|
|
|
|
// This class knows how to create an output section for a given
|
|
// input section. Output section type is determined by various
|
|
// factors, including input section's sh_flags, sh_type and
|
|
// linker scripts.
|
|
namespace {
|
|
template <class ELFT> class OutputSectionFactory {
|
|
typedef typename ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
|
|
typedef typename ELFFile<ELFT>::uintX_t uintX_t;
|
|
|
|
public:
|
|
std::pair<OutputSectionBase<ELFT> *, bool> create(InputSectionBase<ELFT> *C,
|
|
StringRef OutsecName);
|
|
|
|
OutputSectionBase<ELFT> *lookup(StringRef Name, uint32_t Type, uintX_t Flags);
|
|
|
|
private:
|
|
SectionKey<ELFT::Is64Bits> createKey(InputSectionBase<ELFT> *C,
|
|
StringRef OutsecName);
|
|
OutputSectionBase<ELFT> *createAux(InputSectionBase<ELFT> *C,
|
|
const SectionKey<ELFT::Is64Bits> &Key);
|
|
|
|
SmallDenseMap<SectionKey<ELFT::Is64Bits>, OutputSectionBase<ELFT> *> Map;
|
|
};
|
|
}
|
|
|
|
template <class ELFT>
|
|
std::pair<OutputSectionBase<ELFT> *, bool>
|
|
OutputSectionFactory<ELFT>::create(InputSectionBase<ELFT> *C,
|
|
StringRef OutsecName) {
|
|
SectionKey<ELFT::Is64Bits> Key = createKey(C, OutsecName);
|
|
OutputSectionBase<ELFT> *&Sec = Map[Key];
|
|
if (Sec)
|
|
return {Sec, false};
|
|
Sec = createAux(C, Key);
|
|
return {Sec, true};
|
|
}
|
|
|
|
template <class ELFT>
|
|
OutputSectionBase<ELFT> *
|
|
OutputSectionFactory<ELFT>::createAux(InputSectionBase<ELFT> *C,
|
|
const SectionKey<ELFT::Is64Bits> &Key) {
|
|
switch (C->SectionKind) {
|
|
case InputSectionBase<ELFT>::Regular:
|
|
return new OutputSection<ELFT>(Key.Name, Key.Type, Key.Flags);
|
|
case InputSectionBase<ELFT>::EHFrame:
|
|
return new EHOutputSection<ELFT>(Key.Name, Key.Type, Key.Flags);
|
|
case InputSectionBase<ELFT>::Merge:
|
|
return new MergeOutputSection<ELFT>(Key.Name, Key.Type, Key.Flags);
|
|
case InputSectionBase<ELFT>::MipsReginfo:
|
|
return new MipsReginfoOutputSection<ELFT>();
|
|
}
|
|
llvm_unreachable("Unknown output section type");
|
|
}
|
|
|
|
template <class ELFT>
|
|
OutputSectionBase<ELFT> *OutputSectionFactory<ELFT>::lookup(StringRef Name,
|
|
uint32_t Type,
|
|
uintX_t Flags) {
|
|
return Map.lookup({Name, Type, Flags, 0});
|
|
}
|
|
|
|
template <class ELFT>
|
|
SectionKey<ELFT::Is64Bits>
|
|
OutputSectionFactory<ELFT>::createKey(InputSectionBase<ELFT> *C,
|
|
StringRef OutsecName) {
|
|
const Elf_Shdr *H = C->getSectionHdr();
|
|
uintX_t Flags = H->sh_flags & ~SHF_GROUP;
|
|
|
|
// For SHF_MERGE we create different output sections for each sh_entsize.
|
|
// This makes each output section simple and keeps a single level
|
|
// mapping from input to output.
|
|
uintX_t EntSize = isa<MergeInputSection<ELFT>>(C) ? H->sh_entsize : 0;
|
|
|
|
// GNU as can give .eh_frame secion type SHT_PROGBITS or SHT_X86_64_UNWIND
|
|
// depending on the construct. We want to canonicalize it so that
|
|
// there is only one .eh_frame in the end.
|
|
uint32_t Type = H->sh_type;
|
|
if (Type == SHT_PROGBITS && Config->EMachine == EM_X86_64 &&
|
|
isa<EHInputSection<ELFT>>(C))
|
|
Type = SHT_X86_64_UNWIND;
|
|
|
|
return SectionKey<ELFT::Is64Bits>{OutsecName, Type, Flags, EntSize};
|
|
}
|
|
|
|
// The linker is expected to define some symbols depending on
|
|
// the linking result. This function defines such symbols.
|
|
template <class ELFT> void Writer<ELFT>::addReservedSymbols() {
|
|
// __tls_get_addr is defined by the dynamic linker for dynamic ELFs. For
|
|
// static linking the linker is required to optimize away any references to
|
|
// __tls_get_addr, so it's not defined anywhere. Create a hidden definition
|
|
// to avoid the undefined symbol error.
|
|
if (!isOutputDynamic())
|
|
Symtab.addIgnored("__tls_get_addr");
|
|
|
|
// If the "_end" symbol is referenced, it is expected to point to the address
|
|
// right after the data segment. Usually, this symbol points to the end
|
|
// of .bss section or to the end of .data section if .bss section is absent.
|
|
// The order of the sections can be affected by linker script,
|
|
// so it is hard to predict which section will be the last one.
|
|
// So, if this symbol is referenced, we just add the placeholder here
|
|
// and update its value later.
|
|
if (Symtab.find("_end"))
|
|
Symtab.addAbsolute("_end", ElfSym<ELFT>::End);
|
|
|
|
// If there is an undefined symbol "end", we should initialize it
|
|
// with the same value as "_end". In any other case it should stay intact,
|
|
// because it is an allowable name for a user symbol.
|
|
if (SymbolBody *B = Symtab.find("end"))
|
|
if (B->isUndefined())
|
|
Symtab.addAbsolute("end", ElfSym<ELFT>::End);
|
|
}
|
|
|
|
// Create output section objects and add them to OutputSections.
|
|
template <class ELFT> void Writer<ELFT>::createSections() {
|
|
// Add .interp first because some loaders want to see that section
|
|
// on the first page of the executable file when loaded into memory.
|
|
if (needsInterpSection())
|
|
OutputSections.push_back(Out<ELFT>::Interp);
|
|
|
|
// Create output sections for input object file sections.
|
|
std::vector<OutputSectionBase<ELFT> *> RegularSections;
|
|
OutputSectionFactory<ELFT> Factory;
|
|
for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab.getObjectFiles()) {
|
|
for (InputSectionBase<ELFT> *C : F->getSections()) {
|
|
if (isDiscarded(C)) {
|
|
reportDiscarded(C, F);
|
|
continue;
|
|
}
|
|
OutputSectionBase<ELFT> *Sec;
|
|
bool IsNew;
|
|
std::tie(Sec, IsNew) =
|
|
Factory.create(C, getOutputSectionName(C->getSectionName()));
|
|
if (IsNew) {
|
|
OwningSections.emplace_back(Sec);
|
|
OutputSections.push_back(Sec);
|
|
RegularSections.push_back(Sec);
|
|
}
|
|
Sec->addSection(C);
|
|
}
|
|
}
|
|
|
|
Out<ELFT>::Bss = static_cast<OutputSection<ELFT> *>(
|
|
Factory.lookup(".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE));
|
|
|
|
// If we have a .opd section (used under PPC64 for function descriptors),
|
|
// store a pointer to it here so that we can use it later when processing
|
|
// relocations.
|
|
Out<ELFT>::Opd = Factory.lookup(".opd", SHT_PROGBITS, SHF_WRITE | SHF_ALLOC);
|
|
|
|
Out<ELFT>::Dynamic->PreInitArraySec = Factory.lookup(
|
|
".preinit_array", SHT_PREINIT_ARRAY, SHF_WRITE | SHF_ALLOC);
|
|
Out<ELFT>::Dynamic->InitArraySec =
|
|
Factory.lookup(".init_array", SHT_INIT_ARRAY, SHF_WRITE | SHF_ALLOC);
|
|
Out<ELFT>::Dynamic->FiniArraySec =
|
|
Factory.lookup(".fini_array", SHT_FINI_ARRAY, SHF_WRITE | SHF_ALLOC);
|
|
|
|
// The linker needs to define SECNAME_start, SECNAME_end and SECNAME_stop
|
|
// symbols for sections, so that the runtime can get the start and end
|
|
// addresses of each section by section name. Add such symbols.
|
|
addStartEndSymbols();
|
|
for (OutputSectionBase<ELFT> *Sec : RegularSections)
|
|
addStartStopSymbols(Sec);
|
|
|
|
// Scan relocations. This must be done after every symbol is declared so that
|
|
// we can correctly decide if a dynamic relocation is needed.
|
|
for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab.getObjectFiles()) {
|
|
for (InputSectionBase<ELFT> *C : F->getSections()) {
|
|
if (isDiscarded(C))
|
|
continue;
|
|
if (auto *S = dyn_cast<InputSection<ELFT>>(C))
|
|
scanRelocs(*S);
|
|
else if (auto *S = dyn_cast<EHInputSection<ELFT>>(C))
|
|
if (S->RelocSection)
|
|
scanRelocs(*S, *S->RelocSection);
|
|
}
|
|
}
|
|
|
|
// Define __rel[a]_iplt_{start,end} symbols if needed.
|
|
addRelIpltSymbols();
|
|
|
|
// Now that we have defined all possible symbols including linker-
|
|
// synthesized ones. Visit all symbols to give the finishing touches.
|
|
std::vector<DefinedCommon *> CommonSymbols;
|
|
std::vector<SharedSymbol<ELFT> *> CopyRelSymbols;
|
|
for (auto &P : Symtab.getSymbols()) {
|
|
SymbolBody *Body = P.second->Body;
|
|
if (auto *U = dyn_cast<Undefined>(Body))
|
|
if (!U->isWeak() && !U->canKeepUndefined())
|
|
reportUndefined<ELFT>(Symtab, Body);
|
|
|
|
if (auto *C = dyn_cast<DefinedCommon>(Body))
|
|
CommonSymbols.push_back(C);
|
|
if (auto *SC = dyn_cast<SharedSymbol<ELFT>>(Body))
|
|
if (SC->NeedsCopy)
|
|
CopyRelSymbols.push_back(SC);
|
|
|
|
if (!includeInSymtab<ELFT>(*Body))
|
|
continue;
|
|
if (Out<ELFT>::SymTab)
|
|
Out<ELFT>::SymTab->addSymbol(Body);
|
|
|
|
if (isOutputDynamic() && includeInDynamicSymtab(*Body))
|
|
Out<ELFT>::DynSymTab->addSymbol(Body);
|
|
}
|
|
addCommonSymbols(CommonSymbols);
|
|
addCopyRelSymbols(CopyRelSymbols);
|
|
|
|
// So far we have added sections from input object files.
|
|
// This function adds linker-created Out<ELFT>::* sections.
|
|
addPredefinedSections();
|
|
|
|
std::stable_sort(OutputSections.begin(), OutputSections.end(),
|
|
compareSections<ELFT>);
|
|
|
|
for (unsigned I = 0, N = OutputSections.size(); I < N; ++I) {
|
|
OutputSections[I]->SectionIndex = I + 1;
|
|
HasRelro |= (Config->ZRelro && isRelroSection(OutputSections[I]));
|
|
}
|
|
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections)
|
|
Out<ELFT>::ShStrTab->reserve(Sec->getName());
|
|
|
|
// Finalizers fix each section's size.
|
|
// .dynamic section's finalizer may add strings to .dynstr,
|
|
// so finalize that early.
|
|
// Likewise, .dynsym is finalized early since that may fill up .gnu.hash.
|
|
Out<ELFT>::Dynamic->finalize();
|
|
if (isOutputDynamic())
|
|
Out<ELFT>::DynSymTab->finalize();
|
|
|
|
// Fill other section headers.
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections)
|
|
Sec->finalize();
|
|
}
|
|
|
|
// This function add Out<ELFT>::* sections to OutputSections.
|
|
template <class ELFT> void Writer<ELFT>::addPredefinedSections() {
|
|
auto Add = [&](OutputSectionBase<ELFT> *C) {
|
|
if (C)
|
|
OutputSections.push_back(C);
|
|
};
|
|
|
|
// This order is not the same as the final output order
|
|
// because we sort the sections using their attributes below.
|
|
Add(Out<ELFT>::SymTab);
|
|
Add(Out<ELFT>::ShStrTab);
|
|
Add(Out<ELFT>::StrTab);
|
|
if (isOutputDynamic()) {
|
|
Add(Out<ELFT>::DynSymTab);
|
|
Add(Out<ELFT>::GnuHashTab);
|
|
Add(Out<ELFT>::HashTab);
|
|
Add(Out<ELFT>::Dynamic);
|
|
Add(Out<ELFT>::DynStrTab);
|
|
if (Out<ELFT>::RelaDyn->hasRelocs())
|
|
Add(Out<ELFT>::RelaDyn);
|
|
|
|
// This is a MIPS specific section to hold a space within the data segment
|
|
// of executable file which is pointed to by the DT_MIPS_RLD_MAP entry.
|
|
// See "Dynamic section" in Chapter 5 in the following document:
|
|
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
|
|
if (Config->EMachine == EM_MIPS && !Config->Shared) {
|
|
Out<ELFT>::MipsRldMap = new OutputSection<ELFT>(".rld_map", SHT_PROGBITS,
|
|
SHF_ALLOC | SHF_WRITE);
|
|
Out<ELFT>::MipsRldMap->setSize(ELFT::Is64Bits ? 8 : 4);
|
|
Out<ELFT>::MipsRldMap->updateAlign(ELFT::Is64Bits ? 8 : 4);
|
|
OwningSections.emplace_back(Out<ELFT>::MipsRldMap);
|
|
Add(Out<ELFT>::MipsRldMap);
|
|
}
|
|
}
|
|
|
|
// We always need to add rel[a].plt to output if it has entries.
|
|
// Even during static linking it can contain R_[*]_IRELATIVE relocations.
|
|
if (Out<ELFT>::RelaPlt && Out<ELFT>::RelaPlt->hasRelocs()) {
|
|
Add(Out<ELFT>::RelaPlt);
|
|
Out<ELFT>::RelaPlt->Static = !isOutputDynamic();
|
|
}
|
|
|
|
bool needsGot = !Out<ELFT>::Got->empty();
|
|
// We add the .got section to the result for dynamic MIPS target because
|
|
// its address and properties are mentioned in the .dynamic section.
|
|
if (Config->EMachine == EM_MIPS)
|
|
needsGot |= isOutputDynamic();
|
|
// If we have a relocation that is relative to GOT (such as GOTOFFREL),
|
|
// we need to emit a GOT even if it's empty.
|
|
if (HasGotOffRel)
|
|
needsGot = true;
|
|
|
|
if (needsGot)
|
|
Add(Out<ELFT>::Got);
|
|
if (Out<ELFT>::GotPlt && !Out<ELFT>::GotPlt->empty())
|
|
Add(Out<ELFT>::GotPlt);
|
|
if (!Out<ELFT>::Plt->empty())
|
|
Add(Out<ELFT>::Plt);
|
|
}
|
|
|
|
// The linker is expected to define SECNAME_start and SECNAME_end
|
|
// symbols for a few sections. This function defines them.
|
|
template <class ELFT> void Writer<ELFT>::addStartEndSymbols() {
|
|
auto Define = [&](StringRef Start, StringRef End,
|
|
OutputSectionBase<ELFT> *OS) {
|
|
if (OS) {
|
|
Symtab.addSynthetic(Start, *OS, 0);
|
|
Symtab.addSynthetic(End, *OS, OS->getSize());
|
|
} else {
|
|
Symtab.addIgnored(Start);
|
|
Symtab.addIgnored(End);
|
|
}
|
|
};
|
|
|
|
Define("__preinit_array_start", "__preinit_array_end",
|
|
Out<ELFT>::Dynamic->PreInitArraySec);
|
|
Define("__init_array_start", "__init_array_end",
|
|
Out<ELFT>::Dynamic->InitArraySec);
|
|
Define("__fini_array_start", "__fini_array_end",
|
|
Out<ELFT>::Dynamic->FiniArraySec);
|
|
}
|
|
|
|
static bool isAlpha(char C) {
|
|
return ('a' <= C && C <= 'z') || ('A' <= C && C <= 'Z') || C == '_';
|
|
}
|
|
|
|
static bool isAlnum(char C) { return isAlpha(C) || ('0' <= C && C <= '9'); }
|
|
|
|
// Returns true if S is valid as a C language identifier.
|
|
static bool isValidCIdentifier(StringRef S) {
|
|
if (S.empty() || !isAlpha(S[0]))
|
|
return false;
|
|
return std::all_of(S.begin() + 1, S.end(), isAlnum);
|
|
}
|
|
|
|
// If a section name is valid as a C identifier (which is rare because of
|
|
// the leading '.'), linkers are expected to define __start_<secname> and
|
|
// __stop_<secname> symbols. They are at beginning and end of the section,
|
|
// respectively. This is not requested by the ELF standard, but GNU ld and
|
|
// gold provide the feature, and used by many programs.
|
|
template <class ELFT>
|
|
void Writer<ELFT>::addStartStopSymbols(OutputSectionBase<ELFT> *Sec) {
|
|
StringRef S = Sec->getName();
|
|
if (!isValidCIdentifier(S))
|
|
return;
|
|
StringSaver Saver(Alloc);
|
|
StringRef Start = Saver.save("__start_" + S);
|
|
StringRef Stop = Saver.save("__stop_" + S);
|
|
if (SymbolBody *B = Symtab.find(Start))
|
|
if (B->isUndefined())
|
|
Symtab.addSynthetic(Start, *Sec, 0);
|
|
if (SymbolBody *B = Symtab.find(Stop))
|
|
if (B->isUndefined())
|
|
Symtab.addSynthetic(Stop, *Sec, Sec->getSize());
|
|
}
|
|
|
|
template <class ELFT> static bool needsPhdr(OutputSectionBase<ELFT> *Sec) {
|
|
return Sec->getFlags() & SHF_ALLOC;
|
|
}
|
|
|
|
static uint32_t toPhdrFlags(uint64_t Flags) {
|
|
uint32_t Ret = PF_R;
|
|
if (Flags & SHF_WRITE)
|
|
Ret |= PF_W;
|
|
if (Flags & SHF_EXECINSTR)
|
|
Ret |= PF_X;
|
|
return Ret;
|
|
}
|
|
|
|
/// For AMDGPU we need to use custom segment kinds in order to specify which
|
|
/// address space data should be loaded into.
|
|
template <class ELFT>
|
|
static uint32_t getAmdgpuPhdr(OutputSectionBase<ELFT> *Sec) {
|
|
uint32_t Flags = Sec->getFlags();
|
|
if (Flags & SHF_AMDGPU_HSA_CODE)
|
|
return PT_AMDGPU_HSA_LOAD_CODE_AGENT;
|
|
if ((Flags & SHF_AMDGPU_HSA_GLOBAL) && !(Flags & SHF_AMDGPU_HSA_AGENT))
|
|
return PT_AMDGPU_HSA_LOAD_GLOBAL_PROGRAM;
|
|
return PT_LOAD;
|
|
}
|
|
|
|
template <class ELFT>
|
|
void Writer<ELFT>::updateRelro(Elf_Phdr *Cur, Elf_Phdr *GnuRelroPhdr,
|
|
uintX_t VA) {
|
|
if (!GnuRelroPhdr->p_type)
|
|
setPhdr(GnuRelroPhdr, PT_GNU_RELRO, PF_R, Cur->p_offset, Cur->p_vaddr,
|
|
VA - Cur->p_vaddr, 1 /*p_align*/);
|
|
GnuRelroPhdr->p_filesz = VA - Cur->p_vaddr;
|
|
GnuRelroPhdr->p_memsz = VA - Cur->p_vaddr;
|
|
}
|
|
|
|
// Visits all sections to create PHDRs and to assign incremental,
|
|
// non-overlapping addresses to output sections.
|
|
template <class ELFT> void Writer<ELFT>::assignAddresses() {
|
|
uintX_t VA = Target->getVAStart() + sizeof(Elf_Ehdr);
|
|
uintX_t FileOff = sizeof(Elf_Ehdr);
|
|
|
|
// Calculate and reserve the space for the program header first so that
|
|
// the first section can start right after the program header.
|
|
Phdrs.resize(getPhdrsNum());
|
|
size_t PhdrSize = sizeof(Elf_Phdr) * Phdrs.size();
|
|
|
|
// The first phdr entry is PT_PHDR which describes the program header itself.
|
|
setPhdr(&Phdrs[0], PT_PHDR, PF_R, FileOff, VA, PhdrSize, /*Align=*/8);
|
|
FileOff += PhdrSize;
|
|
VA += PhdrSize;
|
|
|
|
// PT_INTERP must be the second entry if exists.
|
|
int PhdrIdx = 0;
|
|
Elf_Phdr *Interp = nullptr;
|
|
if (needsInterpSection())
|
|
Interp = &Phdrs[++PhdrIdx];
|
|
|
|
// Add the first PT_LOAD segment for regular output sections.
|
|
setPhdr(&Phdrs[++PhdrIdx], PT_LOAD, PF_R, 0, Target->getVAStart(), FileOff,
|
|
Target->getPageSize());
|
|
|
|
Elf_Phdr GnuRelroPhdr = {};
|
|
Elf_Phdr TlsPhdr{};
|
|
bool RelroAligned = false;
|
|
uintX_t ThreadBssOffset = 0;
|
|
// Create phdrs as we assign VAs and file offsets to all output sections.
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections) {
|
|
Elf_Phdr *PH = &Phdrs[PhdrIdx];
|
|
if (needsPhdr<ELFT>(Sec)) {
|
|
uintX_t Flags = toPhdrFlags(Sec->getFlags());
|
|
bool InRelRo = Config->ZRelro && (Flags & PF_W) && isRelroSection(Sec);
|
|
bool FirstNonRelRo = GnuRelroPhdr.p_type && !InRelRo && !RelroAligned;
|
|
if (FirstNonRelRo || PH->p_flags != Flags) {
|
|
VA = align(VA, Target->getPageSize());
|
|
FileOff = align(FileOff, Target->getPageSize());
|
|
if (FirstNonRelRo)
|
|
RelroAligned = true;
|
|
}
|
|
|
|
if (PH->p_flags != Flags) {
|
|
// Flags changed. Create a new PT_LOAD.
|
|
PH = &Phdrs[++PhdrIdx];
|
|
uint32_t PTType = (Config->EMachine != EM_AMDGPU) ? (uint32_t)PT_LOAD
|
|
: getAmdgpuPhdr(Sec);
|
|
setPhdr(PH, PTType, Flags, FileOff, VA, 0, Target->getPageSize());
|
|
}
|
|
|
|
if (Sec->getFlags() & SHF_TLS) {
|
|
if (!TlsPhdr.p_vaddr)
|
|
setPhdr(&TlsPhdr, PT_TLS, PF_R, FileOff, VA, 0, Sec->getAlign());
|
|
if (Sec->getType() != SHT_NOBITS)
|
|
VA = align(VA, Sec->getAlign());
|
|
uintX_t TVA = align(VA + ThreadBssOffset, Sec->getAlign());
|
|
Sec->setVA(TVA);
|
|
TlsPhdr.p_memsz += Sec->getSize();
|
|
if (Sec->getType() == SHT_NOBITS) {
|
|
ThreadBssOffset = TVA - VA + Sec->getSize();
|
|
} else {
|
|
TlsPhdr.p_filesz += Sec->getSize();
|
|
VA += Sec->getSize();
|
|
}
|
|
TlsPhdr.p_align = std::max<uintX_t>(TlsPhdr.p_align, Sec->getAlign());
|
|
} else {
|
|
VA = align(VA, Sec->getAlign());
|
|
Sec->setVA(VA);
|
|
VA += Sec->getSize();
|
|
if (InRelRo)
|
|
updateRelro(PH, &GnuRelroPhdr, VA);
|
|
}
|
|
}
|
|
|
|
FileOff = align(FileOff, Sec->getAlign());
|
|
Sec->setFileOffset(FileOff);
|
|
if (Sec->getType() != SHT_NOBITS)
|
|
FileOff += Sec->getSize();
|
|
if (needsPhdr<ELFT>(Sec)) {
|
|
PH->p_filesz = FileOff - PH->p_offset;
|
|
PH->p_memsz = VA - PH->p_vaddr;
|
|
}
|
|
}
|
|
|
|
if (TlsPhdr.p_vaddr) {
|
|
// The TLS pointer goes after PT_TLS. At least glibc will align it,
|
|
// so round up the size to make sure the offsets are correct.
|
|
TlsPhdr.p_memsz = align(TlsPhdr.p_memsz, TlsPhdr.p_align);
|
|
Phdrs[++PhdrIdx] = TlsPhdr;
|
|
Out<ELFT>::TlsPhdr = &Phdrs[PhdrIdx];
|
|
}
|
|
|
|
// Add an entry for .dynamic.
|
|
if (isOutputDynamic()) {
|
|
Elf_Phdr *PH = &Phdrs[++PhdrIdx];
|
|
PH->p_type = PT_DYNAMIC;
|
|
copyPhdr(PH, Out<ELFT>::Dynamic);
|
|
}
|
|
|
|
if (HasRelro) {
|
|
Elf_Phdr *PH = &Phdrs[++PhdrIdx];
|
|
*PH = GnuRelroPhdr;
|
|
}
|
|
|
|
// PT_GNU_STACK is a special section to tell the loader to make the
|
|
// pages for the stack non-executable.
|
|
if (!Config->ZExecStack) {
|
|
Elf_Phdr *PH = &Phdrs[++PhdrIdx];
|
|
PH->p_type = PT_GNU_STACK;
|
|
PH->p_flags = PF_R | PF_W;
|
|
}
|
|
|
|
// Fix up PT_INTERP as we now know the address of .interp section.
|
|
if (Interp) {
|
|
Interp->p_type = PT_INTERP;
|
|
copyPhdr(Interp, Out<ELFT>::Interp);
|
|
}
|
|
|
|
// Add space for section headers.
|
|
SectionHeaderOff = align(FileOff, ELFT::Is64Bits ? 8 : 4);
|
|
FileSize = SectionHeaderOff + getNumSections() * sizeof(Elf_Shdr);
|
|
|
|
// Update "_end" and "end" symbols so that they
|
|
// point to the end of the data segment.
|
|
ElfSym<ELFT>::End.st_value = VA;
|
|
}
|
|
|
|
// Returns the number of PHDR entries.
|
|
template <class ELFT> int Writer<ELFT>::getPhdrsNum() const {
|
|
bool Tls = false;
|
|
int I = 2; // 2 for PT_PHDR and first PT_LOAD
|
|
if (needsInterpSection())
|
|
++I;
|
|
if (isOutputDynamic())
|
|
++I;
|
|
if (!Config->ZExecStack)
|
|
++I;
|
|
uintX_t Last = PF_R;
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections) {
|
|
if (!needsPhdr<ELFT>(Sec))
|
|
continue;
|
|
if (Sec->getFlags() & SHF_TLS)
|
|
Tls = true;
|
|
uintX_t Flags = toPhdrFlags(Sec->getFlags());
|
|
if (Last != Flags) {
|
|
Last = Flags;
|
|
++I;
|
|
}
|
|
}
|
|
if (Tls)
|
|
++I;
|
|
if (HasRelro)
|
|
++I;
|
|
return I;
|
|
}
|
|
|
|
static uint32_t getELFFlags() {
|
|
if (Config->EMachine != EM_MIPS)
|
|
return 0;
|
|
// FIXME: In fact ELF flags depends on ELF flags of input object files
|
|
// and selected emulation. For now just use hadr coded values.
|
|
uint32_t V = EF_MIPS_ABI_O32 | EF_MIPS_CPIC | EF_MIPS_ARCH_32R2;
|
|
if (Config->Shared)
|
|
V |= EF_MIPS_PIC;
|
|
return V;
|
|
}
|
|
|
|
template <class ELFT>
|
|
static typename ELFFile<ELFT>::uintX_t getEntryAddr() {
|
|
if (Config->EntrySym) {
|
|
if (SymbolBody *E = Config->EntrySym->repl())
|
|
return getSymVA<ELFT>(*E);
|
|
return 0;
|
|
}
|
|
if (Config->EntryAddr != uint64_t(-1))
|
|
return Config->EntryAddr;
|
|
return 0;
|
|
}
|
|
|
|
// This function is called after we have assigned address and size
|
|
// to each section. This function fixes some predefined absolute
|
|
// symbol values that depend on section address and size.
|
|
template <class ELFT> void Writer<ELFT>::fixAbsoluteSymbols() {
|
|
// Update __rel[a]_iplt_{start,end} symbols so that they point
|
|
// to beginning or ending of .rela.plt section, respectively.
|
|
if (Out<ELFT>::RelaPlt) {
|
|
uintX_t Start = Out<ELFT>::RelaPlt->getVA();
|
|
ElfSym<ELFT>::RelaIpltStart.st_value = Start;
|
|
ElfSym<ELFT>::RelaIpltEnd.st_value = Start + Out<ELFT>::RelaPlt->getSize();
|
|
}
|
|
|
|
// Update MIPS _gp absolute symbol so that it points to the static data.
|
|
if (Config->EMachine == EM_MIPS)
|
|
ElfSym<ELFT>::MipsGp.st_value = getMipsGpAddr<ELFT>();
|
|
}
|
|
|
|
template <class ELFT> void Writer<ELFT>::writeHeader() {
|
|
uint8_t *Buf = Buffer->getBufferStart();
|
|
memcpy(Buf, "\177ELF", 4);
|
|
|
|
// Write the ELF header.
|
|
auto *EHdr = reinterpret_cast<Elf_Ehdr *>(Buf);
|
|
EHdr->e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
|
|
EHdr->e_ident[EI_DATA] = ELFT::TargetEndianness == llvm::support::little
|
|
? ELFDATA2LSB
|
|
: ELFDATA2MSB;
|
|
EHdr->e_ident[EI_VERSION] = EV_CURRENT;
|
|
|
|
auto &FirstObj = cast<ELFFileBase<ELFT>>(*Config->FirstElf);
|
|
EHdr->e_ident[EI_OSABI] = FirstObj.getOSABI();
|
|
|
|
EHdr->e_type = Config->Shared ? ET_DYN : ET_EXEC;
|
|
EHdr->e_machine = FirstObj.getEMachine();
|
|
EHdr->e_version = EV_CURRENT;
|
|
EHdr->e_entry = getEntryAddr<ELFT>();
|
|
EHdr->e_phoff = sizeof(Elf_Ehdr);
|
|
EHdr->e_shoff = SectionHeaderOff;
|
|
EHdr->e_flags = getELFFlags();
|
|
EHdr->e_ehsize = sizeof(Elf_Ehdr);
|
|
EHdr->e_phentsize = sizeof(Elf_Phdr);
|
|
EHdr->e_phnum = Phdrs.size();
|
|
EHdr->e_shentsize = sizeof(Elf_Shdr);
|
|
EHdr->e_shnum = getNumSections();
|
|
EHdr->e_shstrndx = Out<ELFT>::ShStrTab->SectionIndex;
|
|
|
|
// Write the program header table.
|
|
memcpy(Buf + EHdr->e_phoff, &Phdrs[0], Phdrs.size() * sizeof(Phdrs[0]));
|
|
|
|
// Write the section header table. Note that the first table entry is null.
|
|
auto SHdrs = reinterpret_cast<Elf_Shdr *>(Buf + EHdr->e_shoff);
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections)
|
|
Sec->writeHeaderTo(++SHdrs);
|
|
}
|
|
|
|
template <class ELFT> void Writer<ELFT>::openFile(StringRef Path) {
|
|
ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
|
|
FileOutputBuffer::create(Path, FileSize, FileOutputBuffer::F_executable);
|
|
error(BufferOrErr, "failed to open " + Path);
|
|
Buffer = std::move(*BufferOrErr);
|
|
}
|
|
|
|
// Write section contents to a mmap'ed file.
|
|
template <class ELFT> void Writer<ELFT>::writeSections() {
|
|
uint8_t *Buf = Buffer->getBufferStart();
|
|
|
|
// PPC64 needs to process relocations in the .opd section before processing
|
|
// relocations in code-containing sections.
|
|
if (OutputSectionBase<ELFT> *Sec = Out<ELFT>::Opd) {
|
|
Out<ELFT>::OpdBuf = Buf + Sec->getFileOff();
|
|
Sec->writeTo(Buf + Sec->getFileOff());
|
|
}
|
|
|
|
// Write all sections but string table sections. We know the sizes of the
|
|
// string tables already, but they may not have actual strings yet (only
|
|
// room may be reserved), because writeTo() is allowed to add actual
|
|
// strings to the string tables.
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections)
|
|
if (Sec != Out<ELFT>::Opd && Sec->getType() != SHT_STRTAB)
|
|
Sec->writeTo(Buf + Sec->getFileOff());
|
|
|
|
// Write string table sections.
|
|
for (OutputSectionBase<ELFT> *Sec : OutputSections)
|
|
if (Sec != Out<ELFT>::Opd && Sec->getType() == SHT_STRTAB)
|
|
Sec->writeTo(Buf + Sec->getFileOff());
|
|
}
|
|
|
|
template <class ELFT>
|
|
void Writer<ELFT>::setPhdr(Elf_Phdr *PH, uint32_t Type, uint32_t Flags,
|
|
uintX_t FileOff, uintX_t VA, uintX_t Size,
|
|
uintX_t Align) {
|
|
PH->p_type = Type;
|
|
PH->p_flags = Flags;
|
|
PH->p_offset = FileOff;
|
|
PH->p_vaddr = VA;
|
|
PH->p_paddr = VA;
|
|
PH->p_filesz = Size;
|
|
PH->p_memsz = Size;
|
|
PH->p_align = Align;
|
|
}
|
|
|
|
template <class ELFT>
|
|
void Writer<ELFT>::copyPhdr(Elf_Phdr *PH, OutputSectionBase<ELFT> *From) {
|
|
PH->p_flags = toPhdrFlags(From->getFlags());
|
|
PH->p_offset = From->getFileOff();
|
|
PH->p_vaddr = From->getVA();
|
|
PH->p_paddr = From->getVA();
|
|
PH->p_filesz = From->getSize();
|
|
PH->p_memsz = From->getSize();
|
|
PH->p_align = From->getAlign();
|
|
}
|
|
|
|
template <class ELFT> void Writer<ELFT>::buildSectionMap() {
|
|
for (const std::pair<StringRef, std::vector<StringRef>> &OutSec :
|
|
Config->OutputSections)
|
|
for (StringRef Name : OutSec.second)
|
|
InputToOutputSection[Name] = OutSec.first;
|
|
}
|
|
|
|
template void elf2::writeResult<ELF32LE>(SymbolTable<ELF32LE> *Symtab);
|
|
template void elf2::writeResult<ELF32BE>(SymbolTable<ELF32BE> *Symtab);
|
|
template void elf2::writeResult<ELF64LE>(SymbolTable<ELF64LE> *Symtab);
|
|
template void elf2::writeResult<ELF64BE>(SymbolTable<ELF64BE> *Symtab);
|