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d8ee23f34c
The only difference from r219829 is using getOrCreateSectionSymbol(*ELFSec) instead of GetOrCreateSymbol(ELFSec->getSectionName()) in ELFObjectWriter which causes us to use the correct section symbol even if we have multiple sections with the same name. Original messages: r219829: Correctly handle references to section symbols. When processing assembly like .long .text we were creating a new undefined symbol .text. GAS on the other hand would handle that as a reference to the .text section. This patch implements that by creating the section symbols earlier so that they are visible during asm parsing. The patch also updates llvm-readobj to print the symbol number in the relocation dump so that the test can differentiate between two sections with the same name. r219835: Allow forward references to section symbols. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220021 91177308-0d34-0410-b5e6-96231b3b80d8
1811 lines
64 KiB
C++
1811 lines
64 KiB
C++
//===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
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//
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// The LLVM Compiler Infrastructure
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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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//
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// This file implements ELF object file writer information.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCELF.h"
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#include "llvm/MC/MCELFSymbolFlags.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixupKindInfo.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSectionELF.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/MC/StringTableBuilder.h"
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#include "llvm/Support/Compression.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/Endian.h"
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#include "llvm/Support/ELF.h"
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#include "llvm/Support/ErrorHandling.h"
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#include <vector>
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using namespace llvm;
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#undef DEBUG_TYPE
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#define DEBUG_TYPE "reloc-info"
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namespace {
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class FragmentWriter {
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bool IsLittleEndian;
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public:
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FragmentWriter(bool IsLittleEndian);
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template <typename T> void write(MCDataFragment &F, T Val);
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};
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typedef DenseMap<const MCSectionELF *, uint32_t> SectionIndexMapTy;
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class SymbolTableWriter {
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MCAssembler &Asm;
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FragmentWriter &FWriter;
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bool Is64Bit;
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SectionIndexMapTy &SectionIndexMap;
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// The symbol .symtab fragment we are writting to.
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MCDataFragment *SymtabF;
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// .symtab_shndx fragment we are writting to.
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MCDataFragment *ShndxF;
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// The numbel of symbols written so far.
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unsigned NumWritten;
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void createSymtabShndx();
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template <typename T> void write(MCDataFragment &F, T Value);
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public:
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SymbolTableWriter(MCAssembler &Asm, FragmentWriter &FWriter, bool Is64Bit,
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SectionIndexMapTy &SectionIndexMap,
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MCDataFragment *SymtabF);
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void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
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uint8_t other, uint32_t shndx, bool Reserved);
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};
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struct ELFRelocationEntry {
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uint64_t Offset; // Where is the relocation.
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const MCSymbol *Symbol; // The symbol to relocate with.
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unsigned Type; // The type of the relocation.
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uint64_t Addend; // The addend to use.
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ELFRelocationEntry(uint64_t Offset, const MCSymbol *Symbol, unsigned Type,
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uint64_t Addend)
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: Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend) {}
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};
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class ELFObjectWriter : public MCObjectWriter {
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FragmentWriter FWriter;
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protected:
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static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
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static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
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static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
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static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolData &Data,
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bool Used, bool Renamed);
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static bool isLocal(const MCSymbolData &Data, bool isUsedInReloc);
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static bool IsELFMetaDataSection(const MCSectionData &SD);
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static uint64_t DataSectionSize(const MCSectionData &SD);
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static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
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const MCSectionData &SD);
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static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
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const MCSectionData &SD);
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void WriteDataSectionData(MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCSectionELF &Section);
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/*static bool isFixupKindX86RIPRel(unsigned Kind) {
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return Kind == X86::reloc_riprel_4byte ||
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Kind == X86::reloc_riprel_4byte_movq_load;
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}*/
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/// ELFSymbolData - Helper struct for containing some precomputed
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/// information on symbols.
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struct ELFSymbolData {
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MCSymbolData *SymbolData;
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uint64_t StringIndex;
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uint32_t SectionIndex;
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StringRef Name;
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// Support lexicographic sorting.
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bool operator<(const ELFSymbolData &RHS) const {
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unsigned LHSType = MCELF::GetType(*SymbolData);
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unsigned RHSType = MCELF::GetType(*RHS.SymbolData);
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if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
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return false;
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if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
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return true;
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if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
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return SectionIndex < RHS.SectionIndex;
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return Name < RHS.Name;
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}
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};
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/// The target specific ELF writer instance.
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std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
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SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
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SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
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DenseMap<const MCSymbol *, const MCSymbol *> Renames;
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llvm::DenseMap<const MCSectionData *, std::vector<ELFRelocationEntry>>
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Relocations;
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StringTableBuilder ShStrTabBuilder;
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/// @}
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/// @name Symbol Table Data
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/// @{
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StringTableBuilder StrTabBuilder;
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std::vector<uint64_t> FileSymbolData;
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std::vector<ELFSymbolData> LocalSymbolData;
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std::vector<ELFSymbolData> ExternalSymbolData;
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std::vector<ELFSymbolData> UndefinedSymbolData;
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/// @}
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bool NeedsGOT;
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// This holds the symbol table index of the last local symbol.
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unsigned LastLocalSymbolIndex;
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// This holds the .strtab section index.
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unsigned StringTableIndex;
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// This holds the .symtab section index.
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unsigned SymbolTableIndex;
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unsigned ShstrtabIndex;
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// TargetObjectWriter wrappers.
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bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
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bool hasRelocationAddend() const {
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return TargetObjectWriter->hasRelocationAddend();
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}
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unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
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bool IsPCRel) const {
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return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel);
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}
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public:
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ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_ostream &_OS,
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bool IsLittleEndian)
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: MCObjectWriter(_OS, IsLittleEndian), FWriter(IsLittleEndian),
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TargetObjectWriter(MOTW), NeedsGOT(false) {}
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virtual ~ELFObjectWriter();
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void WriteWord(uint64_t W) {
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if (is64Bit())
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Write64(W);
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else
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Write32(W);
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}
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template <typename T> void write(MCDataFragment &F, T Value) {
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FWriter.write(F, Value);
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}
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void WriteHeader(const MCAssembler &Asm,
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uint64_t SectionDataSize,
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unsigned NumberOfSections);
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void WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
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const MCAsmLayout &Layout);
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void WriteSymbolTable(MCDataFragment *SymtabF, MCAssembler &Asm,
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const MCAsmLayout &Layout,
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SectionIndexMapTy &SectionIndexMap);
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bool shouldRelocateWithSymbol(const MCAssembler &Asm,
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const MCSymbolRefExpr *RefA,
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const MCSymbolData *SD, uint64_t C,
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unsigned Type) const;
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void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
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const MCFragment *Fragment, const MCFixup &Fixup,
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MCValue Target, bool &IsPCRel,
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uint64_t &FixedValue) override;
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uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
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const MCSymbol *S);
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// Map from a group section to the signature symbol
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typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
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// Map from a signature symbol to the group section
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typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
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// Map from a section to the section with the relocations
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typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
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// Map from a section to its offset
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typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
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/// Compute the symbol table data
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///
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/// \param Asm - The assembler.
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/// \param SectionIndexMap - Maps a section to its index.
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/// \param RevGroupMap - Maps a signature symbol to the group section.
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/// \param NumRegularSections - Number of non-relocation sections.
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void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
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const SectionIndexMapTy &SectionIndexMap,
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const RevGroupMapTy &RevGroupMap,
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unsigned NumRegularSections);
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void ComputeIndexMap(MCAssembler &Asm,
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SectionIndexMapTy &SectionIndexMap,
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const RelMapTy &RelMap);
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void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
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RelMapTy &RelMap);
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void CompressDebugSections(MCAssembler &Asm, MCAsmLayout &Layout);
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void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
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const RelMapTy &RelMap);
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void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
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SectionIndexMapTy &SectionIndexMap,
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const RelMapTy &RelMap);
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// Create the sections that show up in the symbol table. Currently
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// those are the .note.GNU-stack section and the group sections.
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void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
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GroupMapTy &GroupMap,
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RevGroupMapTy &RevGroupMap,
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SectionIndexMapTy &SectionIndexMap,
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const RelMapTy &RelMap);
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void ExecutePostLayoutBinding(MCAssembler &Asm,
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const MCAsmLayout &Layout) override;
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void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
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const MCAsmLayout &Layout,
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const SectionIndexMapTy &SectionIndexMap,
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const SectionOffsetMapTy &SectionOffsetMap);
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void ComputeSectionOrder(MCAssembler &Asm,
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std::vector<const MCSectionELF*> &Sections);
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void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
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uint64_t Address, uint64_t Offset,
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uint64_t Size, uint32_t Link, uint32_t Info,
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uint64_t Alignment, uint64_t EntrySize);
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void WriteRelocationsFragment(const MCAssembler &Asm,
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MCDataFragment *F,
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const MCSectionData *SD);
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bool
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IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
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const MCSymbolData &DataA,
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const MCFragment &FB,
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bool InSet,
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bool IsPCRel) const override;
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void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
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void WriteSection(MCAssembler &Asm,
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const SectionIndexMapTy &SectionIndexMap,
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uint32_t GroupSymbolIndex,
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uint64_t Offset, uint64_t Size, uint64_t Alignment,
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const MCSectionELF &Section);
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};
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}
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FragmentWriter::FragmentWriter(bool IsLittleEndian)
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: IsLittleEndian(IsLittleEndian) {}
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template <typename T> void FragmentWriter::write(MCDataFragment &F, T Val) {
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if (IsLittleEndian)
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Val = support::endian::byte_swap<T, support::little>(Val);
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else
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Val = support::endian::byte_swap<T, support::big>(Val);
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const char *Start = (const char *)&Val;
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F.getContents().append(Start, Start + sizeof(T));
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}
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void SymbolTableWriter::createSymtabShndx() {
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if (ShndxF)
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return;
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MCContext &Ctx = Asm.getContext();
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const MCSectionELF *SymtabShndxSection =
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Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0,
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SectionKind::getReadOnly(), 4, "");
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MCSectionData *SymtabShndxSD =
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&Asm.getOrCreateSectionData(*SymtabShndxSection);
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SymtabShndxSD->setAlignment(4);
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ShndxF = new MCDataFragment(SymtabShndxSD);
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unsigned Index = SectionIndexMap.size() + 1;
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SectionIndexMap[SymtabShndxSection] = Index;
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for (unsigned I = 0; I < NumWritten; ++I)
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write(*ShndxF, uint32_t(0));
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}
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template <typename T>
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void SymbolTableWriter::write(MCDataFragment &F, T Value) {
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FWriter.write(F, Value);
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}
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SymbolTableWriter::SymbolTableWriter(MCAssembler &Asm, FragmentWriter &FWriter,
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bool Is64Bit,
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SectionIndexMapTy &SectionIndexMap,
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MCDataFragment *SymtabF)
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: Asm(Asm), FWriter(FWriter), Is64Bit(Is64Bit),
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SectionIndexMap(SectionIndexMap), SymtabF(SymtabF), ShndxF(nullptr),
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NumWritten(0) {}
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void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
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uint64_t size, uint8_t other,
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uint32_t shndx, bool Reserved) {
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bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
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if (LargeIndex)
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createSymtabShndx();
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if (ShndxF) {
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if (LargeIndex)
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write(*ShndxF, shndx);
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else
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write(*ShndxF, uint32_t(0));
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}
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uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
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raw_svector_ostream OS(SymtabF->getContents());
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if (Is64Bit) {
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write(*SymtabF, name); // st_name
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write(*SymtabF, info); // st_info
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write(*SymtabF, other); // st_other
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write(*SymtabF, Index); // st_shndx
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write(*SymtabF, value); // st_value
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write(*SymtabF, size); // st_size
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} else {
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write(*SymtabF, name); // st_name
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write(*SymtabF, uint32_t(value)); // st_value
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write(*SymtabF, uint32_t(size)); // st_size
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write(*SymtabF, info); // st_info
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write(*SymtabF, other); // st_other
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write(*SymtabF, Index); // st_shndx
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}
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++NumWritten;
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}
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bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
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const MCFixupKindInfo &FKI =
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Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
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return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
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}
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bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
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switch (Variant) {
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default:
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return false;
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case MCSymbolRefExpr::VK_GOT:
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case MCSymbolRefExpr::VK_PLT:
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case MCSymbolRefExpr::VK_GOTPCREL:
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case MCSymbolRefExpr::VK_GOTOFF:
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case MCSymbolRefExpr::VK_TPOFF:
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case MCSymbolRefExpr::VK_TLSGD:
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case MCSymbolRefExpr::VK_GOTTPOFF:
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case MCSymbolRefExpr::VK_INDNTPOFF:
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case MCSymbolRefExpr::VK_NTPOFF:
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case MCSymbolRefExpr::VK_GOTNTPOFF:
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case MCSymbolRefExpr::VK_TLSLDM:
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case MCSymbolRefExpr::VK_DTPOFF:
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case MCSymbolRefExpr::VK_TLSLD:
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return true;
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}
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}
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ELFObjectWriter::~ELFObjectWriter()
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{}
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// Emit the ELF header.
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void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
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uint64_t SectionDataSize,
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unsigned NumberOfSections) {
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// ELF Header
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// ----------
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//
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// Note
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// ----
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// emitWord method behaves differently for ELF32 and ELF64, writing
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// 4 bytes in the former and 8 in the latter.
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Write8(0x7f); // e_ident[EI_MAG0]
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Write8('E'); // e_ident[EI_MAG1]
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Write8('L'); // e_ident[EI_MAG2]
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Write8('F'); // e_ident[EI_MAG3]
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Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
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// e_ident[EI_DATA]
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Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
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Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
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// e_ident[EI_OSABI]
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Write8(TargetObjectWriter->getOSABI());
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Write8(0); // e_ident[EI_ABIVERSION]
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WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
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Write16(ELF::ET_REL); // e_type
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Write16(TargetObjectWriter->getEMachine()); // e_machine = target
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Write32(ELF::EV_CURRENT); // e_version
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WriteWord(0); // e_entry, no entry point in .o file
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WriteWord(0); // e_phoff, no program header for .o
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WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
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sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
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// e_flags = whatever the target wants
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Write32(Asm.getELFHeaderEFlags());
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|
|
|
// e_ehsize = ELF header size
|
|
Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
|
|
|
|
Write16(0); // e_phentsize = prog header entry size
|
|
Write16(0); // e_phnum = # prog header entries = 0
|
|
|
|
// e_shentsize = Section header entry size
|
|
Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
|
|
|
|
// e_shnum = # of section header ents
|
|
if (NumberOfSections >= ELF::SHN_LORESERVE)
|
|
Write16(ELF::SHN_UNDEF);
|
|
else
|
|
Write16(NumberOfSections);
|
|
|
|
// e_shstrndx = Section # of '.shstrtab'
|
|
if (ShstrtabIndex >= ELF::SHN_LORESERVE)
|
|
Write16(ELF::SHN_XINDEX);
|
|
else
|
|
Write16(ShstrtabIndex);
|
|
}
|
|
|
|
uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
|
|
const MCAsmLayout &Layout) {
|
|
if (Data.isCommon() && Data.isExternal())
|
|
return Data.getCommonAlignment();
|
|
|
|
uint64_t Res;
|
|
if (!Layout.getSymbolOffset(&Data, Res))
|
|
return 0;
|
|
|
|
if (Layout.getAssembler().isThumbFunc(&Data.getSymbol()))
|
|
Res |= 1;
|
|
|
|
return Res;
|
|
}
|
|
|
|
void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
|
|
const MCAsmLayout &Layout) {
|
|
// The presence of symbol versions causes undefined symbols and
|
|
// versions declared with @@@ to be renamed.
|
|
|
|
for (MCSymbolData &OriginalData : Asm.symbols()) {
|
|
const MCSymbol &Alias = OriginalData.getSymbol();
|
|
|
|
// Not an alias.
|
|
if (!Alias.isVariable())
|
|
continue;
|
|
auto *Ref = dyn_cast<MCSymbolRefExpr>(Alias.getVariableValue());
|
|
if (!Ref)
|
|
continue;
|
|
const MCSymbol &Symbol = Ref->getSymbol();
|
|
MCSymbolData &SD = Asm.getSymbolData(Symbol);
|
|
|
|
StringRef AliasName = Alias.getName();
|
|
size_t Pos = AliasName.find('@');
|
|
if (Pos == StringRef::npos)
|
|
continue;
|
|
|
|
// Aliases defined with .symvar copy the binding from the symbol they alias.
|
|
// This is the first place we are able to copy this information.
|
|
OriginalData.setExternal(SD.isExternal());
|
|
MCELF::SetBinding(OriginalData, MCELF::GetBinding(SD));
|
|
|
|
StringRef Rest = AliasName.substr(Pos);
|
|
if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
|
|
continue;
|
|
|
|
// FIXME: produce a better error message.
|
|
if (Symbol.isUndefined() && Rest.startswith("@@") &&
|
|
!Rest.startswith("@@@"))
|
|
report_fatal_error("A @@ version cannot be undefined");
|
|
|
|
Renames.insert(std::make_pair(&Symbol, &Alias));
|
|
}
|
|
}
|
|
|
|
static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
|
|
uint8_t Type = newType;
|
|
|
|
// Propagation rules:
|
|
// IFUNC > FUNC > OBJECT > NOTYPE
|
|
// TLS_OBJECT > OBJECT > NOTYPE
|
|
//
|
|
// dont let the new type degrade the old type
|
|
switch (origType) {
|
|
default:
|
|
break;
|
|
case ELF::STT_GNU_IFUNC:
|
|
if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
|
|
Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
|
|
Type = ELF::STT_GNU_IFUNC;
|
|
break;
|
|
case ELF::STT_FUNC:
|
|
if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
|
|
Type == ELF::STT_TLS)
|
|
Type = ELF::STT_FUNC;
|
|
break;
|
|
case ELF::STT_OBJECT:
|
|
if (Type == ELF::STT_NOTYPE)
|
|
Type = ELF::STT_OBJECT;
|
|
break;
|
|
case ELF::STT_TLS:
|
|
if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
|
|
Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
|
|
Type = ELF::STT_TLS;
|
|
break;
|
|
}
|
|
|
|
return Type;
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
|
|
const MCAsmLayout &Layout) {
|
|
MCSymbolData &OrigData = *MSD.SymbolData;
|
|
assert((!OrigData.getFragment() ||
|
|
(&OrigData.getFragment()->getParent()->getSection() ==
|
|
&OrigData.getSymbol().getSection())) &&
|
|
"The symbol's section doesn't match the fragment's symbol");
|
|
const MCSymbol *Base = Layout.getBaseSymbol(OrigData.getSymbol());
|
|
|
|
// This has to be in sync with when computeSymbolTable uses SHN_ABS or
|
|
// SHN_COMMON.
|
|
bool IsReserved = !Base || OrigData.isCommon();
|
|
|
|
// Binding and Type share the same byte as upper and lower nibbles
|
|
uint8_t Binding = MCELF::GetBinding(OrigData);
|
|
uint8_t Type = MCELF::GetType(OrigData);
|
|
MCSymbolData *BaseSD = nullptr;
|
|
if (Base) {
|
|
BaseSD = &Layout.getAssembler().getSymbolData(*Base);
|
|
Type = mergeTypeForSet(Type, MCELF::GetType(*BaseSD));
|
|
}
|
|
uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
|
|
|
|
// Other and Visibility share the same byte with Visibility using the lower
|
|
// 2 bits
|
|
uint8_t Visibility = MCELF::GetVisibility(OrigData);
|
|
uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
|
|
Other |= Visibility;
|
|
|
|
uint64_t Value = SymbolValue(OrigData, Layout);
|
|
uint64_t Size = 0;
|
|
|
|
const MCExpr *ESize = OrigData.getSize();
|
|
if (!ESize && Base)
|
|
ESize = BaseSD->getSize();
|
|
|
|
if (ESize) {
|
|
int64_t Res;
|
|
if (!ESize->EvaluateAsAbsolute(Res, Layout))
|
|
report_fatal_error("Size expression must be absolute.");
|
|
Size = Res;
|
|
}
|
|
|
|
// Write out the symbol table entry
|
|
Writer.writeSymbol(MSD.StringIndex, Info, Value, Size, Other,
|
|
MSD.SectionIndex, IsReserved);
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
|
|
MCAssembler &Asm,
|
|
const MCAsmLayout &Layout,
|
|
SectionIndexMapTy &SectionIndexMap) {
|
|
// The string table must be emitted first because we need the index
|
|
// into the string table for all the symbol names.
|
|
|
|
// FIXME: Make sure the start of the symbol table is aligned.
|
|
|
|
SymbolTableWriter Writer(Asm, FWriter, is64Bit(), SectionIndexMap, SymtabF);
|
|
|
|
// The first entry is the undefined symbol entry.
|
|
Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
|
|
|
|
for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
|
|
Writer.writeSymbol(FileSymbolData[i], ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
|
|
ELF::STV_DEFAULT, ELF::SHN_ABS, true);
|
|
}
|
|
|
|
// Write the symbol table entries.
|
|
LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
|
|
|
|
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
|
|
ELFSymbolData &MSD = LocalSymbolData[i];
|
|
WriteSymbol(Writer, MSD, Layout);
|
|
}
|
|
|
|
for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
|
|
ELFSymbolData &MSD = ExternalSymbolData[i];
|
|
MCSymbolData &Data = *MSD.SymbolData;
|
|
assert(((Data.getFlags() & ELF_STB_Global) ||
|
|
(Data.getFlags() & ELF_STB_Weak)) &&
|
|
"External symbol requires STB_GLOBAL or STB_WEAK flag");
|
|
WriteSymbol(Writer, MSD, Layout);
|
|
if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
|
|
LastLocalSymbolIndex++;
|
|
}
|
|
|
|
for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
|
|
ELFSymbolData &MSD = UndefinedSymbolData[i];
|
|
MCSymbolData &Data = *MSD.SymbolData;
|
|
WriteSymbol(Writer, MSD, Layout);
|
|
if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
|
|
LastLocalSymbolIndex++;
|
|
}
|
|
}
|
|
|
|
// It is always valid to create a relocation with a symbol. It is preferable
|
|
// to use a relocation with a section if that is possible. Using the section
|
|
// allows us to omit some local symbols from the symbol table.
|
|
bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
|
|
const MCSymbolRefExpr *RefA,
|
|
const MCSymbolData *SD,
|
|
uint64_t C,
|
|
unsigned Type) const {
|
|
// A PCRel relocation to an absolute value has no symbol (or section). We
|
|
// represent that with a relocation to a null section.
|
|
if (!RefA)
|
|
return false;
|
|
|
|
MCSymbolRefExpr::VariantKind Kind = RefA->getKind();
|
|
switch (Kind) {
|
|
default:
|
|
break;
|
|
// The .odp creation emits a relocation against the symbol ".TOC." which
|
|
// create a R_PPC64_TOC relocation. However the relocation symbol name
|
|
// in final object creation should be NULL, since the symbol does not
|
|
// really exist, it is just the reference to TOC base for the current
|
|
// object file. Since the symbol is undefined, returning false results
|
|
// in a relocation with a null section which is the desired result.
|
|
case MCSymbolRefExpr::VK_PPC_TOCBASE:
|
|
return false;
|
|
|
|
// These VariantKind cause the relocation to refer to something other than
|
|
// the symbol itself, like a linker generated table. Since the address of
|
|
// symbol is not relevant, we cannot replace the symbol with the
|
|
// section and patch the difference in the addend.
|
|
case MCSymbolRefExpr::VK_GOT:
|
|
case MCSymbolRefExpr::VK_PLT:
|
|
case MCSymbolRefExpr::VK_GOTPCREL:
|
|
case MCSymbolRefExpr::VK_Mips_GOT:
|
|
case MCSymbolRefExpr::VK_PPC_GOT_LO:
|
|
case MCSymbolRefExpr::VK_PPC_GOT_HI:
|
|
case MCSymbolRefExpr::VK_PPC_GOT_HA:
|
|
return true;
|
|
}
|
|
|
|
// An undefined symbol is not in any section, so the relocation has to point
|
|
// to the symbol itself.
|
|
const MCSymbol &Sym = SD->getSymbol();
|
|
if (Sym.isUndefined())
|
|
return true;
|
|
|
|
unsigned Binding = MCELF::GetBinding(*SD);
|
|
switch(Binding) {
|
|
default:
|
|
llvm_unreachable("Invalid Binding");
|
|
case ELF::STB_LOCAL:
|
|
break;
|
|
case ELF::STB_WEAK:
|
|
// If the symbol is weak, it might be overridden by a symbol in another
|
|
// file. The relocation has to point to the symbol so that the linker
|
|
// can update it.
|
|
return true;
|
|
case ELF::STB_GLOBAL:
|
|
// Global ELF symbols can be preempted by the dynamic linker. The relocation
|
|
// has to point to the symbol for a reason analogous to the STB_WEAK case.
|
|
return true;
|
|
}
|
|
|
|
// If a relocation points to a mergeable section, we have to be careful.
|
|
// If the offset is zero, a relocation with the section will encode the
|
|
// same information. With a non-zero offset, the situation is different.
|
|
// For example, a relocation can point 42 bytes past the end of a string.
|
|
// If we change such a relocation to use the section, the linker would think
|
|
// that it pointed to another string and subtracting 42 at runtime will
|
|
// produce the wrong value.
|
|
auto &Sec = cast<MCSectionELF>(Sym.getSection());
|
|
unsigned Flags = Sec.getFlags();
|
|
if (Flags & ELF::SHF_MERGE) {
|
|
if (C != 0)
|
|
return true;
|
|
|
|
// It looks like gold has a bug (http://sourceware.org/PR16794) and can
|
|
// only handle section relocations to mergeable sections if using RELA.
|
|
if (!hasRelocationAddend())
|
|
return true;
|
|
}
|
|
|
|
// Most TLS relocations use a got, so they need the symbol. Even those that
|
|
// are just an offset (@tpoff), require a symbol in gold versions before
|
|
// 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
|
|
// http://sourceware.org/PR16773.
|
|
if (Flags & ELF::SHF_TLS)
|
|
return true;
|
|
|
|
// If the symbol is a thumb function the final relocation must set the lowest
|
|
// bit. With a symbol that is done by just having the symbol have that bit
|
|
// set, so we would lose the bit if we relocated with the section.
|
|
// FIXME: We could use the section but add the bit to the relocation value.
|
|
if (Asm.isThumbFunc(&Sym))
|
|
return true;
|
|
|
|
if (TargetObjectWriter->needsRelocateWithSymbol(*SD, Type))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
static const MCSymbol *getWeakRef(const MCSymbolRefExpr &Ref) {
|
|
const MCSymbol &Sym = Ref.getSymbol();
|
|
|
|
if (Ref.getKind() == MCSymbolRefExpr::VK_WEAKREF)
|
|
return &Sym;
|
|
|
|
if (!Sym.isVariable())
|
|
return nullptr;
|
|
|
|
const MCExpr *Expr = Sym.getVariableValue();
|
|
const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
|
|
if (!Inner)
|
|
return nullptr;
|
|
|
|
if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
|
|
return &Inner->getSymbol();
|
|
return nullptr;
|
|
}
|
|
|
|
void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
|
|
const MCAsmLayout &Layout,
|
|
const MCFragment *Fragment,
|
|
const MCFixup &Fixup,
|
|
MCValue Target,
|
|
bool &IsPCRel,
|
|
uint64_t &FixedValue) {
|
|
const MCSectionData *FixupSection = Fragment->getParent();
|
|
uint64_t C = Target.getConstant();
|
|
uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
|
|
|
|
if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
|
|
assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
|
|
"Should not have constructed this");
|
|
|
|
// Let A, B and C being the components of Target and R be the location of
|
|
// the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
|
|
// If it is pcrel, we want to compute (A - B + C - R).
|
|
|
|
// In general, ELF has no relocations for -B. It can only represent (A + C)
|
|
// or (A + C - R). If B = R + K and the relocation is not pcrel, we can
|
|
// replace B to implement it: (A - R - K + C)
|
|
if (IsPCRel)
|
|
Asm.getContext().FatalError(
|
|
Fixup.getLoc(),
|
|
"No relocation available to represent this relative expression");
|
|
|
|
const MCSymbol &SymB = RefB->getSymbol();
|
|
|
|
if (SymB.isUndefined())
|
|
Asm.getContext().FatalError(
|
|
Fixup.getLoc(),
|
|
Twine("symbol '") + SymB.getName() +
|
|
"' can not be undefined in a subtraction expression");
|
|
|
|
assert(!SymB.isAbsolute() && "Should have been folded");
|
|
const MCSection &SecB = SymB.getSection();
|
|
if (&SecB != &FixupSection->getSection())
|
|
Asm.getContext().FatalError(
|
|
Fixup.getLoc(), "Cannot represent a difference across sections");
|
|
|
|
const MCSymbolData &SymBD = Asm.getSymbolData(SymB);
|
|
uint64_t SymBOffset = Layout.getSymbolOffset(&SymBD);
|
|
uint64_t K = SymBOffset - FixupOffset;
|
|
IsPCRel = true;
|
|
C -= K;
|
|
}
|
|
|
|
// We either rejected the fixup or folded B into C at this point.
|
|
const MCSymbolRefExpr *RefA = Target.getSymA();
|
|
const MCSymbol *SymA = RefA ? &RefA->getSymbol() : nullptr;
|
|
const MCSymbolData *SymAD = SymA ? &Asm.getSymbolData(*SymA) : nullptr;
|
|
|
|
unsigned Type = GetRelocType(Target, Fixup, IsPCRel);
|
|
bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymAD, C, Type);
|
|
if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
|
|
C += Layout.getSymbolOffset(SymAD);
|
|
|
|
uint64_t Addend = 0;
|
|
if (hasRelocationAddend()) {
|
|
Addend = C;
|
|
C = 0;
|
|
}
|
|
|
|
FixedValue = C;
|
|
|
|
// FIXME: What is this!?!?
|
|
MCSymbolRefExpr::VariantKind Modifier =
|
|
RefA ? RefA->getKind() : MCSymbolRefExpr::VK_None;
|
|
if (RelocNeedsGOT(Modifier))
|
|
NeedsGOT = true;
|
|
|
|
if (!RelocateWithSymbol) {
|
|
const MCSection *SecA =
|
|
(SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
|
|
auto *ELFSec = cast_or_null<MCSectionELF>(SecA);
|
|
MCSymbol *SectionSymbol =
|
|
ELFSec ? Asm.getContext().getOrCreateSectionSymbol(*ELFSec)
|
|
: nullptr;
|
|
ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend);
|
|
Relocations[FixupSection].push_back(Rec);
|
|
return;
|
|
}
|
|
|
|
if (SymA) {
|
|
if (const MCSymbol *R = Renames.lookup(SymA))
|
|
SymA = R;
|
|
|
|
if (const MCSymbol *WeakRef = getWeakRef(*RefA))
|
|
WeakrefUsedInReloc.insert(WeakRef);
|
|
else
|
|
UsedInReloc.insert(SymA);
|
|
}
|
|
ELFRelocationEntry Rec(FixupOffset, SymA, Type, Addend);
|
|
Relocations[FixupSection].push_back(Rec);
|
|
return;
|
|
}
|
|
|
|
|
|
uint64_t
|
|
ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
|
|
const MCSymbol *S) {
|
|
const MCSymbolData &SD = Asm.getSymbolData(*S);
|
|
return SD.getIndex();
|
|
}
|
|
|
|
bool ELFObjectWriter::isInSymtab(const MCAsmLayout &Layout,
|
|
const MCSymbolData &Data, bool Used,
|
|
bool Renamed) {
|
|
const MCSymbol &Symbol = Data.getSymbol();
|
|
if (Symbol.isVariable()) {
|
|
const MCExpr *Expr = Symbol.getVariableValue();
|
|
if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
|
|
if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
|
|
return false;
|
|
}
|
|
}
|
|
|
|
if (Used)
|
|
return true;
|
|
|
|
if (Renamed)
|
|
return false;
|
|
|
|
if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
|
|
return true;
|
|
|
|
if (Symbol.isVariable()) {
|
|
const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
|
|
if (Base && Base->isUndefined())
|
|
return false;
|
|
}
|
|
|
|
bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
|
|
if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
|
|
return false;
|
|
|
|
if (Symbol.isTemporary())
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isUsedInReloc) {
|
|
if (Data.isExternal())
|
|
return false;
|
|
|
|
const MCSymbol &Symbol = Data.getSymbol();
|
|
if (Symbol.isDefined())
|
|
return true;
|
|
|
|
if (isUsedInReloc)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
|
|
SectionIndexMapTy &SectionIndexMap,
|
|
const RelMapTy &RelMap) {
|
|
unsigned Index = 1;
|
|
for (MCAssembler::iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF &>(it->getSection());
|
|
if (Section.getType() != ELF::SHT_GROUP)
|
|
continue;
|
|
SectionIndexMap[&Section] = Index++;
|
|
}
|
|
|
|
for (MCAssembler::iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF &>(it->getSection());
|
|
if (Section.getType() == ELF::SHT_GROUP ||
|
|
Section.getType() == ELF::SHT_REL ||
|
|
Section.getType() == ELF::SHT_RELA)
|
|
continue;
|
|
SectionIndexMap[&Section] = Index++;
|
|
const MCSectionELF *RelSection = RelMap.lookup(&Section);
|
|
if (RelSection)
|
|
SectionIndexMap[RelSection] = Index++;
|
|
}
|
|
}
|
|
|
|
void
|
|
ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
|
|
const SectionIndexMapTy &SectionIndexMap,
|
|
const RevGroupMapTy &RevGroupMap,
|
|
unsigned NumRegularSections) {
|
|
// FIXME: Is this the correct place to do this?
|
|
// FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
|
|
if (NeedsGOT) {
|
|
StringRef Name = "_GLOBAL_OFFSET_TABLE_";
|
|
MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
|
|
MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
|
|
Data.setExternal(true);
|
|
MCELF::SetBinding(Data, ELF::STB_GLOBAL);
|
|
}
|
|
|
|
// Add the data for the symbols.
|
|
for (MCSymbolData &SD : Asm.symbols()) {
|
|
const MCSymbol &Symbol = SD.getSymbol();
|
|
|
|
bool Used = UsedInReloc.count(&Symbol);
|
|
bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
|
|
bool isSignature = RevGroupMap.count(&Symbol);
|
|
|
|
if (!isInSymtab(Layout, SD,
|
|
Used || WeakrefUsed || isSignature,
|
|
Renames.count(&Symbol)))
|
|
continue;
|
|
|
|
ELFSymbolData MSD;
|
|
MSD.SymbolData = &SD;
|
|
const MCSymbol *BaseSymbol = Layout.getBaseSymbol(Symbol);
|
|
|
|
// Undefined symbols are global, but this is the first place we
|
|
// are able to set it.
|
|
bool Local = isLocal(SD, Used);
|
|
if (!Local && MCELF::GetBinding(SD) == ELF::STB_LOCAL) {
|
|
assert(BaseSymbol);
|
|
MCSymbolData &BaseData = Asm.getSymbolData(*BaseSymbol);
|
|
MCELF::SetBinding(SD, ELF::STB_GLOBAL);
|
|
MCELF::SetBinding(BaseData, ELF::STB_GLOBAL);
|
|
}
|
|
|
|
if (!BaseSymbol) {
|
|
MSD.SectionIndex = ELF::SHN_ABS;
|
|
} else if (SD.isCommon()) {
|
|
assert(!Local);
|
|
MSD.SectionIndex = ELF::SHN_COMMON;
|
|
} else if (BaseSymbol->isUndefined()) {
|
|
if (isSignature && !Used)
|
|
MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap.lookup(&Symbol));
|
|
else
|
|
MSD.SectionIndex = ELF::SHN_UNDEF;
|
|
if (!Used && WeakrefUsed)
|
|
MCELF::SetBinding(SD, ELF::STB_WEAK);
|
|
} else {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(BaseSymbol->getSection());
|
|
MSD.SectionIndex = SectionIndexMap.lookup(&Section);
|
|
assert(MSD.SectionIndex && "Invalid section index!");
|
|
}
|
|
|
|
// The @@@ in symbol version is replaced with @ in undefined symbols and
|
|
// @@ in defined ones.
|
|
StringRef Name = Symbol.getName();
|
|
SmallString<32> Buf;
|
|
size_t Pos = Name.find("@@@");
|
|
if (Pos != StringRef::npos) {
|
|
Buf += Name.substr(0, Pos);
|
|
unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
|
|
Buf += Name.substr(Pos + Skip);
|
|
Name = Buf;
|
|
}
|
|
|
|
// Sections have their own string table
|
|
if (MCELF::GetType(SD) != ELF::STT_SECTION)
|
|
MSD.Name = StrTabBuilder.add(Name);
|
|
|
|
if (MSD.SectionIndex == ELF::SHN_UNDEF)
|
|
UndefinedSymbolData.push_back(MSD);
|
|
else if (Local)
|
|
LocalSymbolData.push_back(MSD);
|
|
else
|
|
ExternalSymbolData.push_back(MSD);
|
|
}
|
|
|
|
for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i)
|
|
StrTabBuilder.add(*i);
|
|
|
|
StrTabBuilder.finalize(StringTableBuilder::ELF);
|
|
|
|
for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i)
|
|
FileSymbolData.push_back(StrTabBuilder.getOffset(*i));
|
|
|
|
for (ELFSymbolData &MSD : LocalSymbolData)
|
|
MSD.StringIndex = MCELF::GetType(*MSD.SymbolData) == ELF::STT_SECTION
|
|
? 0
|
|
: StrTabBuilder.getOffset(MSD.Name);
|
|
for (ELFSymbolData &MSD : ExternalSymbolData)
|
|
MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
|
|
for (ELFSymbolData& MSD : UndefinedSymbolData)
|
|
MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
|
|
|
|
// Symbols are required to be in lexicographic order.
|
|
array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
|
|
array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
|
|
array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
|
|
|
|
// Set the symbol indices. Local symbols must come before all other
|
|
// symbols with non-local bindings.
|
|
unsigned Index = FileSymbolData.size() + 1;
|
|
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
|
|
LocalSymbolData[i].SymbolData->setIndex(Index++);
|
|
|
|
for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
|
|
ExternalSymbolData[i].SymbolData->setIndex(Index++);
|
|
for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
|
|
UndefinedSymbolData[i].SymbolData->setIndex(Index++);
|
|
}
|
|
|
|
void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
|
|
MCAsmLayout &Layout,
|
|
RelMapTy &RelMap) {
|
|
for (MCAssembler::const_iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionData &SD = *it;
|
|
if (Relocations[&SD].empty())
|
|
continue;
|
|
|
|
MCContext &Ctx = Asm.getContext();
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(SD.getSection());
|
|
|
|
const StringRef SectionName = Section.getSectionName();
|
|
std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
|
|
RelaSectionName += SectionName;
|
|
|
|
unsigned EntrySize;
|
|
if (hasRelocationAddend())
|
|
EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
|
|
else
|
|
EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
|
|
|
|
unsigned Flags = 0;
|
|
StringRef Group = "";
|
|
if (Section.getFlags() & ELF::SHF_GROUP) {
|
|
Flags = ELF::SHF_GROUP;
|
|
Group = Section.getGroup()->getName();
|
|
}
|
|
|
|
const MCSectionELF *RelaSection =
|
|
Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
|
|
ELF::SHT_RELA : ELF::SHT_REL, Flags,
|
|
SectionKind::getReadOnly(),
|
|
EntrySize, Group);
|
|
RelMap[&Section] = RelaSection;
|
|
Asm.getOrCreateSectionData(*RelaSection);
|
|
}
|
|
}
|
|
|
|
static SmallVector<char, 128>
|
|
getUncompressedData(MCAsmLayout &Layout,
|
|
MCSectionData::FragmentListType &Fragments) {
|
|
SmallVector<char, 128> UncompressedData;
|
|
for (const MCFragment &F : Fragments) {
|
|
const SmallVectorImpl<char> *Contents;
|
|
switch (F.getKind()) {
|
|
case MCFragment::FT_Data:
|
|
Contents = &cast<MCDataFragment>(F).getContents();
|
|
break;
|
|
case MCFragment::FT_Dwarf:
|
|
Contents = &cast<MCDwarfLineAddrFragment>(F).getContents();
|
|
break;
|
|
case MCFragment::FT_DwarfFrame:
|
|
Contents = &cast<MCDwarfCallFrameFragment>(F).getContents();
|
|
break;
|
|
default:
|
|
llvm_unreachable(
|
|
"Not expecting any other fragment types in a debug_* section");
|
|
}
|
|
UncompressedData.append(Contents->begin(), Contents->end());
|
|
}
|
|
return UncompressedData;
|
|
}
|
|
|
|
// Include the debug info compression header:
|
|
// "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
|
|
// useful for consumers to preallocate a buffer to decompress into.
|
|
static bool
|
|
prependCompressionHeader(uint64_t Size,
|
|
SmallVectorImpl<char> &CompressedContents) {
|
|
static const StringRef Magic = "ZLIB";
|
|
if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
|
|
return false;
|
|
if (sys::IsLittleEndianHost)
|
|
sys::swapByteOrder(Size);
|
|
CompressedContents.insert(CompressedContents.begin(),
|
|
Magic.size() + sizeof(Size), 0);
|
|
std::copy(Magic.begin(), Magic.end(), CompressedContents.begin());
|
|
std::copy(reinterpret_cast<char *>(&Size),
|
|
reinterpret_cast<char *>(&Size + 1),
|
|
CompressedContents.begin() + Magic.size());
|
|
return true;
|
|
}
|
|
|
|
// Return a single fragment containing the compressed contents of the whole
|
|
// section. Null if the section was not compressed for any reason.
|
|
static std::unique_ptr<MCDataFragment>
|
|
getCompressedFragment(MCAsmLayout &Layout,
|
|
MCSectionData::FragmentListType &Fragments) {
|
|
std::unique_ptr<MCDataFragment> CompressedFragment(new MCDataFragment());
|
|
|
|
// Gather the uncompressed data from all the fragments, recording the
|
|
// alignment fragment, if seen, and any fixups.
|
|
SmallVector<char, 128> UncompressedData =
|
|
getUncompressedData(Layout, Fragments);
|
|
|
|
SmallVectorImpl<char> &CompressedContents = CompressedFragment->getContents();
|
|
|
|
zlib::Status Success = zlib::compress(
|
|
StringRef(UncompressedData.data(), UncompressedData.size()),
|
|
CompressedContents);
|
|
if (Success != zlib::StatusOK)
|
|
return nullptr;
|
|
|
|
if (!prependCompressionHeader(UncompressedData.size(), CompressedContents))
|
|
return nullptr;
|
|
|
|
return CompressedFragment;
|
|
}
|
|
|
|
typedef DenseMap<const MCSectionData *, std::vector<MCSymbolData *>>
|
|
DefiningSymbolMap;
|
|
|
|
static void UpdateSymbols(const MCAsmLayout &Layout,
|
|
const std::vector<MCSymbolData *> &Symbols,
|
|
MCFragment &NewFragment) {
|
|
for (MCSymbolData *Sym : Symbols) {
|
|
Sym->setOffset(Sym->getOffset() +
|
|
Layout.getFragmentOffset(Sym->getFragment()));
|
|
Sym->setFragment(&NewFragment);
|
|
}
|
|
}
|
|
|
|
static void CompressDebugSection(MCAssembler &Asm, MCAsmLayout &Layout,
|
|
const DefiningSymbolMap &DefiningSymbols,
|
|
const MCSectionELF &Section,
|
|
MCSectionData &SD) {
|
|
StringRef SectionName = Section.getSectionName();
|
|
MCSectionData::FragmentListType &Fragments = SD.getFragmentList();
|
|
|
|
std::unique_ptr<MCDataFragment> CompressedFragment =
|
|
getCompressedFragment(Layout, Fragments);
|
|
|
|
// Leave the section as-is if the fragments could not be compressed.
|
|
if (!CompressedFragment)
|
|
return;
|
|
|
|
// Update the fragment+offsets of any symbols referring to fragments in this
|
|
// section to refer to the new fragment.
|
|
auto I = DefiningSymbols.find(&SD);
|
|
if (I != DefiningSymbols.end())
|
|
UpdateSymbols(Layout, I->second, *CompressedFragment);
|
|
|
|
// Invalidate the layout for the whole section since it will have new and
|
|
// different fragments now.
|
|
Layout.invalidateFragmentsFrom(&Fragments.front());
|
|
Fragments.clear();
|
|
|
|
// Complete the initialization of the new fragment
|
|
CompressedFragment->setParent(&SD);
|
|
CompressedFragment->setLayoutOrder(0);
|
|
Fragments.push_back(CompressedFragment.release());
|
|
|
|
// Rename from .debug_* to .zdebug_*
|
|
Asm.getContext().renameELFSection(&Section,
|
|
(".z" + SectionName.drop_front(1)).str());
|
|
}
|
|
|
|
void ELFObjectWriter::CompressDebugSections(MCAssembler &Asm,
|
|
MCAsmLayout &Layout) {
|
|
if (!Asm.getContext().getAsmInfo()->compressDebugSections())
|
|
return;
|
|
|
|
DefiningSymbolMap DefiningSymbols;
|
|
|
|
for (MCSymbolData &SD : Asm.symbols())
|
|
if (MCFragment *F = SD.getFragment())
|
|
DefiningSymbols[F->getParent()].push_back(&SD);
|
|
|
|
for (MCSectionData &SD : Asm) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF &>(SD.getSection());
|
|
StringRef SectionName = Section.getSectionName();
|
|
|
|
// Compressing debug_frame requires handling alignment fragments which is
|
|
// more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
|
|
// for writing to arbitrary buffers) for little benefit.
|
|
if (!SectionName.startswith(".debug_") || SectionName == ".debug_frame")
|
|
continue;
|
|
|
|
CompressDebugSection(Asm, Layout, DefiningSymbols, Section, SD);
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
|
|
const RelMapTy &RelMap) {
|
|
for (MCAssembler::const_iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionData &SD = *it;
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(SD.getSection());
|
|
|
|
const MCSectionELF *RelaSection = RelMap.lookup(&Section);
|
|
if (!RelaSection)
|
|
continue;
|
|
MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
|
|
RelaSD.setAlignment(is64Bit() ? 8 : 4);
|
|
|
|
MCDataFragment *F = new MCDataFragment(&RelaSD);
|
|
WriteRelocationsFragment(Asm, F, &*it);
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
|
|
uint64_t Flags, uint64_t Address,
|
|
uint64_t Offset, uint64_t Size,
|
|
uint32_t Link, uint32_t Info,
|
|
uint64_t Alignment,
|
|
uint64_t EntrySize) {
|
|
Write32(Name); // sh_name: index into string table
|
|
Write32(Type); // sh_type
|
|
WriteWord(Flags); // sh_flags
|
|
WriteWord(Address); // sh_addr
|
|
WriteWord(Offset); // sh_offset
|
|
WriteWord(Size); // sh_size
|
|
Write32(Link); // sh_link
|
|
Write32(Info); // sh_info
|
|
WriteWord(Alignment); // sh_addralign
|
|
WriteWord(EntrySize); // sh_entsize
|
|
}
|
|
|
|
// ELF doesn't require relocations to be in any order. We sort by the r_offset,
|
|
// just to match gnu as for easier comparison. The use type is an arbitrary way
|
|
// of making the sort deterministic.
|
|
static int cmpRel(const ELFRelocationEntry *AP, const ELFRelocationEntry *BP) {
|
|
const ELFRelocationEntry &A = *AP;
|
|
const ELFRelocationEntry &B = *BP;
|
|
if (A.Offset != B.Offset)
|
|
return B.Offset - A.Offset;
|
|
if (B.Type != A.Type)
|
|
return A.Type - B.Type;
|
|
llvm_unreachable("ELFRelocs might be unstable!");
|
|
}
|
|
|
|
static void sortRelocs(const MCAssembler &Asm,
|
|
std::vector<ELFRelocationEntry> &Relocs) {
|
|
array_pod_sort(Relocs.begin(), Relocs.end(), cmpRel);
|
|
}
|
|
|
|
void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
|
|
MCDataFragment *F,
|
|
const MCSectionData *SD) {
|
|
std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
|
|
|
|
sortRelocs(Asm, Relocs);
|
|
|
|
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
|
|
const ELFRelocationEntry &Entry = Relocs[e - i - 1];
|
|
unsigned Index =
|
|
Entry.Symbol ? getSymbolIndexInSymbolTable(Asm, Entry.Symbol) : 0;
|
|
|
|
if (is64Bit()) {
|
|
write(*F, Entry.Offset);
|
|
if (TargetObjectWriter->isN64()) {
|
|
write(*F, uint32_t(Index));
|
|
|
|
write(*F, TargetObjectWriter->getRSsym(Entry.Type));
|
|
write(*F, TargetObjectWriter->getRType3(Entry.Type));
|
|
write(*F, TargetObjectWriter->getRType2(Entry.Type));
|
|
write(*F, TargetObjectWriter->getRType(Entry.Type));
|
|
} else {
|
|
struct ELF::Elf64_Rela ERE64;
|
|
ERE64.setSymbolAndType(Index, Entry.Type);
|
|
write(*F, ERE64.r_info);
|
|
}
|
|
if (hasRelocationAddend())
|
|
write(*F, Entry.Addend);
|
|
} else {
|
|
write(*F, uint32_t(Entry.Offset));
|
|
|
|
struct ELF::Elf32_Rela ERE32;
|
|
ERE32.setSymbolAndType(Index, Entry.Type);
|
|
write(*F, ERE32.r_info);
|
|
|
|
if (hasRelocationAddend())
|
|
write(*F, uint32_t(Entry.Addend));
|
|
}
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
|
|
MCAsmLayout &Layout,
|
|
SectionIndexMapTy &SectionIndexMap,
|
|
const RelMapTy &RelMap) {
|
|
MCContext &Ctx = Asm.getContext();
|
|
MCDataFragment *F;
|
|
|
|
unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
|
|
|
|
// We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
|
|
const MCSectionELF *ShstrtabSection =
|
|
Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
|
|
SectionKind::getReadOnly());
|
|
MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
|
|
ShstrtabSD.setAlignment(1);
|
|
|
|
const MCSectionELF *SymtabSection =
|
|
Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
|
|
SectionKind::getReadOnly(),
|
|
EntrySize, "");
|
|
MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
|
|
SymtabSD.setAlignment(is64Bit() ? 8 : 4);
|
|
|
|
const MCSectionELF *StrtabSection;
|
|
StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
|
|
SectionKind::getReadOnly());
|
|
MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
|
|
StrtabSD.setAlignment(1);
|
|
|
|
ComputeIndexMap(Asm, SectionIndexMap, RelMap);
|
|
|
|
ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
|
|
SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
|
|
StringTableIndex = SectionIndexMap.lookup(StrtabSection);
|
|
|
|
// Symbol table
|
|
F = new MCDataFragment(&SymtabSD);
|
|
WriteSymbolTable(F, Asm, Layout, SectionIndexMap);
|
|
|
|
F = new MCDataFragment(&StrtabSD);
|
|
F->getContents().append(StrTabBuilder.data().begin(),
|
|
StrTabBuilder.data().end());
|
|
|
|
F = new MCDataFragment(&ShstrtabSD);
|
|
|
|
// Section header string table.
|
|
for (auto it = Asm.begin(), ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(it->getSection());
|
|
ShStrTabBuilder.add(Section.getSectionName());
|
|
}
|
|
ShStrTabBuilder.finalize(StringTableBuilder::ELF);
|
|
F->getContents().append(ShStrTabBuilder.data().begin(),
|
|
ShStrTabBuilder.data().end());
|
|
}
|
|
|
|
void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
|
|
MCAsmLayout &Layout,
|
|
GroupMapTy &GroupMap,
|
|
RevGroupMapTy &RevGroupMap,
|
|
SectionIndexMapTy &SectionIndexMap,
|
|
const RelMapTy &RelMap) {
|
|
MCContext &Ctx = Asm.getContext();
|
|
|
|
// Build the groups
|
|
for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
|
|
it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(it->getSection());
|
|
if (!(Section.getFlags() & ELF::SHF_GROUP))
|
|
continue;
|
|
|
|
const MCSymbol *SignatureSymbol = Section.getGroup();
|
|
Asm.getOrCreateSymbolData(*SignatureSymbol);
|
|
const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
|
|
if (!Group) {
|
|
Group = Ctx.CreateELFGroupSection();
|
|
MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
|
|
Data.setAlignment(4);
|
|
MCDataFragment *F = new MCDataFragment(&Data);
|
|
write(*F, uint32_t(ELF::GRP_COMDAT));
|
|
}
|
|
GroupMap[Group] = SignatureSymbol;
|
|
}
|
|
|
|
ComputeIndexMap(Asm, SectionIndexMap, RelMap);
|
|
|
|
// Add sections to the groups
|
|
for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
|
|
it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(it->getSection());
|
|
if (!(Section.getFlags() & ELF::SHF_GROUP))
|
|
continue;
|
|
const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
|
|
MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
|
|
// FIXME: we could use the previous fragment
|
|
MCDataFragment *F = new MCDataFragment(&Data);
|
|
uint32_t Index = SectionIndexMap.lookup(&Section);
|
|
write(*F, Index);
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSection(MCAssembler &Asm,
|
|
const SectionIndexMapTy &SectionIndexMap,
|
|
uint32_t GroupSymbolIndex,
|
|
uint64_t Offset, uint64_t Size,
|
|
uint64_t Alignment,
|
|
const MCSectionELF &Section) {
|
|
uint64_t sh_link = 0;
|
|
uint64_t sh_info = 0;
|
|
|
|
switch(Section.getType()) {
|
|
case ELF::SHT_DYNAMIC:
|
|
sh_link = ShStrTabBuilder.getOffset(Section.getSectionName());
|
|
sh_info = 0;
|
|
break;
|
|
|
|
case ELF::SHT_REL:
|
|
case ELF::SHT_RELA: {
|
|
const MCSectionELF *SymtabSection;
|
|
const MCSectionELF *InfoSection;
|
|
SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
|
|
0,
|
|
SectionKind::getReadOnly());
|
|
sh_link = SectionIndexMap.lookup(SymtabSection);
|
|
assert(sh_link && ".symtab not found");
|
|
|
|
// Remove ".rel" and ".rela" prefixes.
|
|
unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
|
|
StringRef SectionName = Section.getSectionName().substr(SecNameLen);
|
|
StringRef GroupName =
|
|
Section.getGroup() ? Section.getGroup()->getName() : "";
|
|
|
|
InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
|
|
0, SectionKind::getReadOnly(),
|
|
0, GroupName);
|
|
sh_info = SectionIndexMap.lookup(InfoSection);
|
|
break;
|
|
}
|
|
|
|
case ELF::SHT_SYMTAB:
|
|
case ELF::SHT_DYNSYM:
|
|
sh_link = StringTableIndex;
|
|
sh_info = LastLocalSymbolIndex;
|
|
break;
|
|
|
|
case ELF::SHT_SYMTAB_SHNDX:
|
|
sh_link = SymbolTableIndex;
|
|
break;
|
|
|
|
case ELF::SHT_PROGBITS:
|
|
case ELF::SHT_STRTAB:
|
|
case ELF::SHT_NOBITS:
|
|
case ELF::SHT_NOTE:
|
|
case ELF::SHT_NULL:
|
|
case ELF::SHT_ARM_ATTRIBUTES:
|
|
case ELF::SHT_INIT_ARRAY:
|
|
case ELF::SHT_FINI_ARRAY:
|
|
case ELF::SHT_PREINIT_ARRAY:
|
|
case ELF::SHT_X86_64_UNWIND:
|
|
case ELF::SHT_MIPS_REGINFO:
|
|
case ELF::SHT_MIPS_OPTIONS:
|
|
case ELF::SHT_MIPS_ABIFLAGS:
|
|
// Nothing to do.
|
|
break;
|
|
|
|
case ELF::SHT_GROUP:
|
|
sh_link = SymbolTableIndex;
|
|
sh_info = GroupSymbolIndex;
|
|
break;
|
|
|
|
default:
|
|
llvm_unreachable("FIXME: sh_type value not supported!");
|
|
}
|
|
|
|
if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
|
|
Section.getType() == ELF::SHT_ARM_EXIDX) {
|
|
StringRef SecName(Section.getSectionName());
|
|
if (SecName == ".ARM.exidx") {
|
|
sh_link = SectionIndexMap.lookup(
|
|
Asm.getContext().getELFSection(".text",
|
|
ELF::SHT_PROGBITS,
|
|
ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
|
|
SectionKind::getText()));
|
|
} else if (SecName.startswith(".ARM.exidx")) {
|
|
StringRef GroupName =
|
|
Section.getGroup() ? Section.getGroup()->getName() : "";
|
|
sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
|
|
SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
|
|
ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
|
|
GroupName));
|
|
}
|
|
}
|
|
|
|
WriteSecHdrEntry(ShStrTabBuilder.getOffset(Section.getSectionName()),
|
|
Section.getType(),
|
|
Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
|
|
Alignment, Section.getEntrySize());
|
|
}
|
|
|
|
bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
|
|
return SD.getOrdinal() == ~UINT32_C(0) &&
|
|
!SD.getSection().isVirtualSection();
|
|
}
|
|
|
|
uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
|
|
uint64_t Ret = 0;
|
|
for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
|
|
++i) {
|
|
const MCFragment &F = *i;
|
|
assert(F.getKind() == MCFragment::FT_Data);
|
|
Ret += cast<MCDataFragment>(F).getContents().size();
|
|
}
|
|
return Ret;
|
|
}
|
|
|
|
uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
|
|
const MCSectionData &SD) {
|
|
if (IsELFMetaDataSection(SD))
|
|
return DataSectionSize(SD);
|
|
return Layout.getSectionFileSize(&SD);
|
|
}
|
|
|
|
uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
|
|
const MCSectionData &SD) {
|
|
if (IsELFMetaDataSection(SD))
|
|
return DataSectionSize(SD);
|
|
return Layout.getSectionAddressSize(&SD);
|
|
}
|
|
|
|
void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
|
|
const MCAsmLayout &Layout,
|
|
const MCSectionELF &Section) {
|
|
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
|
|
|
|
uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
|
|
WriteZeros(Padding);
|
|
|
|
if (IsELFMetaDataSection(SD)) {
|
|
for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
|
|
++i) {
|
|
const MCFragment &F = *i;
|
|
assert(F.getKind() == MCFragment::FT_Data);
|
|
WriteBytes(cast<MCDataFragment>(F).getContents());
|
|
}
|
|
} else {
|
|
Asm.writeSectionData(&SD, Layout);
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
|
|
const GroupMapTy &GroupMap,
|
|
const MCAsmLayout &Layout,
|
|
const SectionIndexMapTy &SectionIndexMap,
|
|
const SectionOffsetMapTy &SectionOffsetMap) {
|
|
const unsigned NumSections = Asm.size() + 1;
|
|
|
|
std::vector<const MCSectionELF*> Sections;
|
|
Sections.resize(NumSections - 1);
|
|
|
|
for (SectionIndexMapTy::const_iterator i=
|
|
SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
|
|
const std::pair<const MCSectionELF*, uint32_t> &p = *i;
|
|
Sections[p.second - 1] = p.first;
|
|
}
|
|
|
|
// Null section first.
|
|
uint64_t FirstSectionSize =
|
|
NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
|
|
uint32_t FirstSectionLink =
|
|
ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
|
|
WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
|
|
|
|
for (unsigned i = 0; i < NumSections - 1; ++i) {
|
|
const MCSectionELF &Section = *Sections[i];
|
|
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
|
|
uint32_t GroupSymbolIndex;
|
|
if (Section.getType() != ELF::SHT_GROUP)
|
|
GroupSymbolIndex = 0;
|
|
else
|
|
GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
|
|
GroupMap.lookup(&Section));
|
|
|
|
uint64_t Size = GetSectionAddressSize(Layout, SD);
|
|
|
|
WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
|
|
SectionOffsetMap.lookup(&Section), Size,
|
|
SD.getAlignment(), Section);
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
|
|
std::vector<const MCSectionELF*> &Sections) {
|
|
for (MCAssembler::iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF &>(it->getSection());
|
|
if (Section.getType() == ELF::SHT_GROUP)
|
|
Sections.push_back(&Section);
|
|
}
|
|
|
|
for (MCAssembler::iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF &>(it->getSection());
|
|
if (Section.getType() != ELF::SHT_GROUP &&
|
|
Section.getType() != ELF::SHT_REL &&
|
|
Section.getType() != ELF::SHT_RELA)
|
|
Sections.push_back(&Section);
|
|
}
|
|
|
|
for (MCAssembler::iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF &>(it->getSection());
|
|
if (Section.getType() == ELF::SHT_REL ||
|
|
Section.getType() == ELF::SHT_RELA)
|
|
Sections.push_back(&Section);
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::WriteObject(MCAssembler &Asm,
|
|
const MCAsmLayout &Layout) {
|
|
GroupMapTy GroupMap;
|
|
RevGroupMapTy RevGroupMap;
|
|
SectionIndexMapTy SectionIndexMap;
|
|
|
|
unsigned NumUserSections = Asm.size();
|
|
|
|
CompressDebugSections(Asm, const_cast<MCAsmLayout &>(Layout));
|
|
|
|
DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
|
|
CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
|
|
|
|
const unsigned NumUserAndRelocSections = Asm.size();
|
|
CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
|
|
RevGroupMap, SectionIndexMap, RelMap);
|
|
const unsigned AllSections = Asm.size();
|
|
const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
|
|
|
|
unsigned NumRegularSections = NumUserSections + NumIndexedSections;
|
|
|
|
// Compute symbol table information.
|
|
computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
|
|
NumRegularSections);
|
|
|
|
WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
|
|
|
|
CreateMetadataSections(const_cast<MCAssembler&>(Asm),
|
|
const_cast<MCAsmLayout&>(Layout),
|
|
SectionIndexMap,
|
|
RelMap);
|
|
|
|
uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
|
|
uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
|
|
sizeof(ELF::Elf32_Ehdr);
|
|
uint64_t FileOff = HeaderSize;
|
|
|
|
std::vector<const MCSectionELF*> Sections;
|
|
ComputeSectionOrder(Asm, Sections);
|
|
unsigned NumSections = Sections.size();
|
|
SectionOffsetMapTy SectionOffsetMap;
|
|
for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
|
|
const MCSectionELF &Section = *Sections[i];
|
|
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
|
|
|
|
FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
|
|
|
|
// Remember the offset into the file for this section.
|
|
SectionOffsetMap[&Section] = FileOff;
|
|
|
|
// Get the size of the section in the output file (including padding).
|
|
FileOff += GetSectionFileSize(Layout, SD);
|
|
}
|
|
|
|
FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
|
|
|
|
const unsigned SectionHeaderOffset = FileOff - HeaderSize;
|
|
|
|
uint64_t SectionHeaderEntrySize = is64Bit() ?
|
|
sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
|
|
FileOff += (NumSections + 1) * SectionHeaderEntrySize;
|
|
|
|
for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) {
|
|
const MCSectionELF &Section = *Sections[i];
|
|
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
|
|
|
|
FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
|
|
|
|
// Remember the offset into the file for this section.
|
|
SectionOffsetMap[&Section] = FileOff;
|
|
|
|
// Get the size of the section in the output file (including padding).
|
|
FileOff += GetSectionFileSize(Layout, SD);
|
|
}
|
|
|
|
// Write out the ELF header ...
|
|
WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
|
|
|
|
// ... then the regular sections ...
|
|
// + because of .shstrtab
|
|
for (unsigned i = 0; i < NumRegularSections + 1; ++i)
|
|
WriteDataSectionData(Asm, Layout, *Sections[i]);
|
|
|
|
uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
|
|
WriteZeros(Padding);
|
|
|
|
// ... then the section header table ...
|
|
WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
|
|
SectionOffsetMap);
|
|
|
|
// ... and then the remaining sections ...
|
|
for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
|
|
WriteDataSectionData(Asm, Layout, *Sections[i]);
|
|
}
|
|
|
|
bool
|
|
ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
|
|
const MCSymbolData &DataA,
|
|
const MCFragment &FB,
|
|
bool InSet,
|
|
bool IsPCRel) const {
|
|
if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC)
|
|
return false;
|
|
return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
|
|
Asm, DataA, FB,InSet, IsPCRel);
|
|
}
|
|
|
|
MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
|
|
raw_ostream &OS,
|
|
bool IsLittleEndian) {
|
|
return new ELFObjectWriter(MOTW, OS, IsLittleEndian);
|
|
}
|