forked from OSchip/llvm-project
1571 lines
54 KiB
C++
1571 lines
54 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/OwningPtr.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/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/Support/Debug.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 ELFObjectWriter : public MCObjectWriter {
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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 MCAssembler &Asm, const MCSymbolData &Data,
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bool Used, bool Renamed);
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static bool isLocal(const MCSymbolData &Data, bool isSignature,
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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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// Support lexicographic sorting.
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bool operator<(const ELFSymbolData &RHS) const {
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if (MCELF::GetType(*SymbolData) == ELF::STT_FILE)
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return true;
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if (MCELF::GetType(*RHS.SymbolData) == ELF::STT_FILE)
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return false;
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return SymbolData->getSymbol().getName() <
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RHS.SymbolData->getSymbol().getName();
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}
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};
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/// The target specific ELF writer instance.
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llvm::OwningPtr<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*,
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std::vector<ELFRelocationEntry> > Relocations;
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DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
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/// @}
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/// @name Symbol Table Data
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/// @{
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SmallString<256> StringTable;
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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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bool NeedsSymtabShndx;
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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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const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
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const MCValue &Target,
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const MCFragment &F,
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const MCFixup &Fixup,
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bool IsPCRel) const;
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// TargetObjectWriter wrappers.
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const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
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const MCValue &Target,
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const MCFragment &F,
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const MCFixup &Fixup,
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bool IsPCRel) const {
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return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
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}
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const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
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const MCFixup &Fixup,
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bool IsPCRel) const {
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return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup, IsPCRel);
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}
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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 getEFlags() const {
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return TargetObjectWriter->getEFlags();
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}
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unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
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bool IsPCRel, bool IsRelocWithSymbol,
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int64_t Addend) const {
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return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
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IsRelocWithSymbol, Addend);
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}
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public:
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ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
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raw_ostream &_OS, bool IsLittleEndian)
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: MCObjectWriter(_OS, IsLittleEndian),
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TargetObjectWriter(MOTW),
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NeedsGOT(false), NeedsSymtabShndx(false){
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}
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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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void StringLE16(char *buf, uint16_t Value) {
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buf[0] = char(Value >> 0);
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buf[1] = char(Value >> 8);
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}
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void StringLE32(char *buf, uint32_t Value) {
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StringLE16(buf, uint16_t(Value >> 0));
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StringLE16(buf + 2, uint16_t(Value >> 16));
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}
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void StringLE64(char *buf, uint64_t Value) {
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StringLE32(buf, uint32_t(Value >> 0));
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StringLE32(buf + 4, uint32_t(Value >> 32));
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}
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void StringBE16(char *buf ,uint16_t Value) {
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buf[0] = char(Value >> 8);
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buf[1] = char(Value >> 0);
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}
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void StringBE32(char *buf, uint32_t Value) {
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StringBE16(buf, uint16_t(Value >> 16));
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StringBE16(buf + 2, uint16_t(Value >> 0));
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}
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void StringBE64(char *buf, uint64_t Value) {
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StringBE32(buf, uint32_t(Value >> 32));
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StringBE32(buf + 4, uint32_t(Value >> 0));
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}
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void String8(MCDataFragment &F, uint8_t Value) {
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char buf[1];
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buf[0] = Value;
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F.getContents().append(&buf[0], &buf[1]);
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}
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void String16(MCDataFragment &F, uint16_t Value) {
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char buf[2];
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if (isLittleEndian())
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StringLE16(buf, Value);
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else
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StringBE16(buf, Value);
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F.getContents().append(&buf[0], &buf[2]);
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}
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void String32(MCDataFragment &F, uint32_t Value) {
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char buf[4];
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if (isLittleEndian())
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StringLE32(buf, Value);
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else
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StringBE32(buf, Value);
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F.getContents().append(&buf[0], &buf[4]);
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}
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void String64(MCDataFragment &F, uint64_t Value) {
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char buf[8];
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if (isLittleEndian())
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StringLE64(buf, Value);
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else
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StringBE64(buf, Value);
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F.getContents().append(&buf[0], &buf[8]);
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}
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void WriteHeader(uint64_t SectionDataSize,
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unsigned NumberOfSections);
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void WriteSymbolEntry(MCDataFragment *SymtabF,
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MCDataFragment *ShndxF,
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uint64_t name, uint8_t info,
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uint64_t value, uint64_t size,
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uint8_t other, uint32_t shndx,
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bool Reserved);
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void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
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ELFSymbolData &MSD,
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const MCAsmLayout &Layout);
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typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
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void WriteSymbolTable(MCDataFragment *SymtabF,
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MCDataFragment *ShndxF,
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const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const SectionIndexMapTy &SectionIndexMap);
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virtual void RecordRelocation(const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup,
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MCValue Target, uint64_t &FixedValue);
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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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/// ComputeSymbolTable - 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,
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const SectionIndexMapTy &SectionIndexMap,
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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 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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virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
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const MCAsmLayout &Layout);
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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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virtual 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;
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virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
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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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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(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(getEFlags());
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// e_ehsize = ELF header size
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Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
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Write16(0); // e_phentsize = prog header entry size
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Write16(0); // e_phnum = # prog header entries = 0
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// e_shentsize = Section header entry size
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Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
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// e_shnum = # of section header ents
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if (NumberOfSections >= ELF::SHN_LORESERVE)
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Write16(ELF::SHN_UNDEF);
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else
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Write16(NumberOfSections);
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// e_shstrndx = Section # of '.shstrtab'
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if (ShstrtabIndex >= ELF::SHN_LORESERVE)
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Write16(ELF::SHN_XINDEX);
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else
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Write16(ShstrtabIndex);
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}
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void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
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MCDataFragment *ShndxF,
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uint64_t name,
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uint8_t info, uint64_t value,
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uint64_t size, uint8_t other,
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uint32_t shndx,
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bool Reserved) {
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if (ShndxF) {
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if (shndx >= ELF::SHN_LORESERVE && !Reserved)
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String32(*ShndxF, shndx);
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else
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String32(*ShndxF, 0);
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}
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uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
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uint16_t(ELF::SHN_XINDEX) : shndx;
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if (is64Bit()) {
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String32(*SymtabF, name); // st_name
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String8(*SymtabF, info); // st_info
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String8(*SymtabF, other); // st_other
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String16(*SymtabF, Index); // st_shndx
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String64(*SymtabF, value); // st_value
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String64(*SymtabF, size); // st_size
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} else {
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String32(*SymtabF, name); // st_name
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String32(*SymtabF, value); // st_value
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String32(*SymtabF, size); // st_size
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String8(*SymtabF, info); // st_info
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String8(*SymtabF, other); // st_other
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String16(*SymtabF, Index); // st_shndx
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}
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}
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uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
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const MCAsmLayout &Layout) {
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if (Data.isCommon() && Data.isExternal())
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return Data.getCommonAlignment();
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const MCSymbol &Symbol = Data.getSymbol();
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if (Symbol.isAbsolute() && Symbol.isVariable()) {
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if (const MCExpr *Value = Symbol.getVariableValue()) {
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int64_t IntValue;
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if (Value->EvaluateAsAbsolute(IntValue, Layout))
|
|
return (uint64_t)IntValue;
|
|
}
|
|
}
|
|
|
|
if (!Symbol.isInSection())
|
|
return 0;
|
|
|
|
|
|
if (Data.getFragment()) {
|
|
if (Data.getFlags() & ELF_Other_ThumbFunc)
|
|
return Layout.getSymbolOffset(&Data)+1;
|
|
else
|
|
return Layout.getSymbolOffset(&Data);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
|
|
const MCAsmLayout &Layout) {
|
|
// The presence of symbol versions causes undefined symbols and
|
|
// versions declared with @@@ to be renamed.
|
|
|
|
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
|
|
ie = Asm.symbol_end(); it != ie; ++it) {
|
|
const MCSymbol &Alias = it->getSymbol();
|
|
const MCSymbol &Symbol = Alias.AliasedSymbol();
|
|
MCSymbolData &SD = Asm.getSymbolData(Symbol);
|
|
|
|
// Not an alias.
|
|
if (&Symbol == &Alias)
|
|
continue;
|
|
|
|
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.
|
|
it->setExternal(SD.isExternal());
|
|
MCELF::SetBinding(*it, 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));
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
|
|
MCDataFragment *ShndxF,
|
|
ELFSymbolData &MSD,
|
|
const MCAsmLayout &Layout) {
|
|
MCSymbolData &OrigData = *MSD.SymbolData;
|
|
MCSymbolData &Data =
|
|
Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
|
|
|
|
bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
|
|
Data.getSymbol().isVariable();
|
|
|
|
uint8_t Binding = MCELF::GetBinding(OrigData);
|
|
uint8_t Visibility = MCELF::GetVisibility(OrigData);
|
|
uint8_t Type = MCELF::GetType(Data);
|
|
|
|
uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
|
|
uint8_t Other = Visibility;
|
|
|
|
uint64_t Value = SymbolValue(Data, Layout);
|
|
uint64_t Size = 0;
|
|
|
|
assert(!(Data.isCommon() && !Data.isExternal()));
|
|
|
|
const MCExpr *ESize = Data.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
|
|
WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
|
|
Size, Other, MSD.SectionIndex, IsReserved);
|
|
}
|
|
|
|
void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
|
|
MCDataFragment *ShndxF,
|
|
const MCAssembler &Asm,
|
|
const MCAsmLayout &Layout,
|
|
const SectionIndexMapTy &SectionIndexMap) {
|
|
// The string table must be emitted first because we need the index
|
|
// into the string table for all the symbol names.
|
|
assert(StringTable.size() && "Missing string table");
|
|
|
|
// FIXME: Make sure the start of the symbol table is aligned.
|
|
|
|
// The first entry is the undefined symbol entry.
|
|
WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
|
|
|
|
// Write the symbol table entries.
|
|
LastLocalSymbolIndex = LocalSymbolData.size() + 1;
|
|
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
|
|
ELFSymbolData &MSD = LocalSymbolData[i];
|
|
WriteSymbol(SymtabF, ShndxF, MSD, Layout);
|
|
}
|
|
|
|
// Write out a symbol table entry for each regular section.
|
|
for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
|
|
++i) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(i->getSection());
|
|
if (Section.getType() == ELF::SHT_RELA ||
|
|
Section.getType() == ELF::SHT_REL ||
|
|
Section.getType() == ELF::SHT_STRTAB ||
|
|
Section.getType() == ELF::SHT_SYMTAB ||
|
|
Section.getType() == ELF::SHT_SYMTAB_SHNDX)
|
|
continue;
|
|
WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
|
|
ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section),
|
|
false);
|
|
LastLocalSymbolIndex++;
|
|
}
|
|
|
|
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(SymtabF, ShndxF, 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(SymtabF, ShndxF, MSD, Layout);
|
|
if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
|
|
LastLocalSymbolIndex++;
|
|
}
|
|
}
|
|
|
|
const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
|
|
const MCValue &Target,
|
|
const MCFragment &F,
|
|
const MCFixup &Fixup,
|
|
bool IsPCRel) const {
|
|
const MCSymbol &Symbol = Target.getSymA()->getSymbol();
|
|
const MCSymbol &ASymbol = Symbol.AliasedSymbol();
|
|
const MCSymbol *Renamed = Renames.lookup(&Symbol);
|
|
const MCSymbolData &SD = Asm.getSymbolData(Symbol);
|
|
|
|
if (ASymbol.isUndefined()) {
|
|
if (Renamed)
|
|
return Renamed;
|
|
return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
|
|
}
|
|
|
|
if (SD.isExternal()) {
|
|
if (Renamed)
|
|
return Renamed;
|
|
return &Symbol;
|
|
}
|
|
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(ASymbol.getSection());
|
|
const SectionKind secKind = Section.getKind();
|
|
|
|
if (secKind.isBSS())
|
|
return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
|
|
|
|
if (secKind.isThreadLocal()) {
|
|
if (Renamed)
|
|
return Renamed;
|
|
return &Symbol;
|
|
}
|
|
|
|
MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
|
|
const MCSectionELF &Sec2 =
|
|
static_cast<const MCSectionELF&>(F.getParent()->getSection());
|
|
|
|
if (&Sec2 != &Section &&
|
|
(Kind == MCSymbolRefExpr::VK_PLT ||
|
|
Kind == MCSymbolRefExpr::VK_GOTPCREL ||
|
|
Kind == MCSymbolRefExpr::VK_GOTOFF)) {
|
|
if (Renamed)
|
|
return Renamed;
|
|
return &Symbol;
|
|
}
|
|
|
|
if (Section.getFlags() & ELF::SHF_MERGE) {
|
|
if (Target.getConstant() == 0)
|
|
return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
|
|
if (Renamed)
|
|
return Renamed;
|
|
return &Symbol;
|
|
}
|
|
|
|
return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
|
|
|
|
}
|
|
|
|
|
|
void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
|
|
const MCAsmLayout &Layout,
|
|
const MCFragment *Fragment,
|
|
const MCFixup &Fixup,
|
|
MCValue Target,
|
|
uint64_t &FixedValue) {
|
|
int64_t Addend = 0;
|
|
int Index = 0;
|
|
int64_t Value = Target.getConstant();
|
|
const MCSymbol *RelocSymbol = NULL;
|
|
|
|
bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
|
|
if (!Target.isAbsolute()) {
|
|
const MCSymbol &Symbol = Target.getSymA()->getSymbol();
|
|
const MCSymbol &ASymbol = Symbol.AliasedSymbol();
|
|
RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
|
|
|
|
if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
|
|
const MCSymbol &SymbolB = RefB->getSymbol();
|
|
MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
|
|
IsPCRel = true;
|
|
|
|
// Offset of the symbol in the section
|
|
int64_t a = Layout.getSymbolOffset(&SDB);
|
|
|
|
// Offset of the relocation in the section
|
|
int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
|
|
Value += b - a;
|
|
}
|
|
|
|
if (!RelocSymbol) {
|
|
MCSymbolData &SD = Asm.getSymbolData(ASymbol);
|
|
MCFragment *F = SD.getFragment();
|
|
|
|
if (F) {
|
|
Index = F->getParent()->getOrdinal() + 1;
|
|
// Offset of the symbol in the section
|
|
Value += Layout.getSymbolOffset(&SD);
|
|
} else {
|
|
Index = 0;
|
|
}
|
|
} else {
|
|
if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
|
|
WeakrefUsedInReloc.insert(RelocSymbol);
|
|
else
|
|
UsedInReloc.insert(RelocSymbol);
|
|
Index = -1;
|
|
}
|
|
Addend = Value;
|
|
if (hasRelocationAddend())
|
|
Value = 0;
|
|
}
|
|
|
|
FixedValue = Value;
|
|
unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
|
|
(RelocSymbol != 0), Addend);
|
|
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
|
|
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
|
|
if (RelocNeedsGOT(Modifier))
|
|
NeedsGOT = true;
|
|
|
|
uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
|
|
Fixup.getOffset();
|
|
|
|
// FIXME: no tests cover this. Is adjustFixupOffset dead code?
|
|
TargetObjectWriter->adjustFixupOffset(Fixup, RelocOffset);
|
|
|
|
if (!hasRelocationAddend())
|
|
Addend = 0;
|
|
|
|
if (is64Bit())
|
|
assert(isInt<64>(Addend));
|
|
else
|
|
assert(isInt<32>(Addend));
|
|
|
|
ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
|
|
Relocations[Fragment->getParent()].push_back(ERE);
|
|
}
|
|
|
|
|
|
uint64_t
|
|
ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
|
|
const MCSymbol *S) {
|
|
MCSymbolData &SD = Asm.getSymbolData(*S);
|
|
return SD.getIndex();
|
|
}
|
|
|
|
bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
|
|
const MCSymbolData &Data,
|
|
bool Used, bool Renamed) {
|
|
if (Data.getFlags() & ELF_Other_Weakref)
|
|
return false;
|
|
|
|
if (Used)
|
|
return true;
|
|
|
|
if (Renamed)
|
|
return false;
|
|
|
|
const MCSymbol &Symbol = Data.getSymbol();
|
|
|
|
if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
|
|
return true;
|
|
|
|
const MCSymbol &A = Symbol.AliasedSymbol();
|
|
if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
|
|
return false;
|
|
|
|
bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
|
|
if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
|
|
return false;
|
|
|
|
if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
|
|
return false;
|
|
|
|
if (Symbol.isTemporary())
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
|
|
bool isUsedInReloc) {
|
|
if (Data.isExternal())
|
|
return false;
|
|
|
|
const MCSymbol &Symbol = Data.getSymbol();
|
|
const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
|
|
|
|
if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
|
|
if (isSignature && !isUsedInReloc)
|
|
return true;
|
|
|
|
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 SectionIndexMapTy &SectionIndexMap,
|
|
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) {
|
|
llvm::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);
|
|
}
|
|
|
|
// Index 0 is always the empty string.
|
|
StringMap<uint64_t> StringIndexMap;
|
|
StringTable += '\x00';
|
|
|
|
// FIXME: We could optimize suffixes in strtab in the same way we
|
|
// optimize them in shstrtab.
|
|
|
|
// Add the data for the symbols.
|
|
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
|
|
ie = Asm.symbol_end(); it != ie; ++it) {
|
|
const MCSymbol &Symbol = it->getSymbol();
|
|
|
|
bool Used = UsedInReloc.count(&Symbol);
|
|
bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
|
|
bool isSignature = RevGroupMap.count(&Symbol);
|
|
|
|
if (!isInSymtab(Asm, *it,
|
|
Used || WeakrefUsed || isSignature,
|
|
Renames.count(&Symbol)))
|
|
continue;
|
|
|
|
ELFSymbolData MSD;
|
|
MSD.SymbolData = it;
|
|
const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
|
|
|
|
// Undefined symbols are global, but this is the first place we
|
|
// are able to set it.
|
|
bool Local = isLocal(*it, isSignature, Used);
|
|
if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
|
|
MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
|
|
MCELF::SetBinding(*it, ELF::STB_GLOBAL);
|
|
MCELF::SetBinding(SD, ELF::STB_GLOBAL);
|
|
}
|
|
|
|
if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
|
|
MCELF::SetBinding(*it, ELF::STB_WEAK);
|
|
|
|
if (it->isCommon()) {
|
|
assert(!Local);
|
|
MSD.SectionIndex = ELF::SHN_COMMON;
|
|
} else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
|
|
MSD.SectionIndex = ELF::SHN_ABS;
|
|
} else if (RefSymbol.isUndefined()) {
|
|
if (isSignature && !Used)
|
|
MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
|
|
else
|
|
MSD.SectionIndex = ELF::SHN_UNDEF;
|
|
} else {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(RefSymbol.getSection());
|
|
MSD.SectionIndex = SectionIndexMap.lookup(&Section);
|
|
if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
|
|
NeedsSymtabShndx = true;
|
|
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;
|
|
}
|
|
|
|
uint64_t &Entry = StringIndexMap[Name];
|
|
if (!Entry) {
|
|
Entry = StringTable.size();
|
|
StringTable += Name;
|
|
StringTable += '\x00';
|
|
}
|
|
MSD.StringIndex = Entry;
|
|
if (MSD.SectionIndex == ELF::SHN_UNDEF)
|
|
UndefinedSymbolData.push_back(MSD);
|
|
else if (Local)
|
|
LocalSymbolData.push_back(MSD);
|
|
else
|
|
ExternalSymbolData.push_back(MSD);
|
|
}
|
|
|
|
// 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 = 1;
|
|
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
|
|
LocalSymbolData[i].SymbolData->setIndex(Index++);
|
|
|
|
Index += NumRegularSections;
|
|
|
|
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++);
|
|
|
|
if (NumRegularSections > ELF::SHN_LORESERVE)
|
|
NeedsSymtabShndx = true;
|
|
}
|
|
|
|
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);
|
|
|
|
const MCSectionELF *RelaSection =
|
|
Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
|
|
ELF::SHT_RELA : ELF::SHT_REL, 0,
|
|
SectionKind::getReadOnly(),
|
|
EntrySize, "");
|
|
RelMap[&Section] = RelaSection;
|
|
Asm.getOrCreateSectionData(*RelaSection);
|
|
}
|
|
}
|
|
|
|
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
|
|
}
|
|
|
|
void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
|
|
MCDataFragment *F,
|
|
const MCSectionData *SD) {
|
|
std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
|
|
|
|
// Sort the relocation entries. Most targets just sort by r_offset, but some
|
|
// (e.g., MIPS) have additional constraints.
|
|
TargetObjectWriter->sortRelocs(Asm, Relocs);
|
|
|
|
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
|
|
ELFRelocationEntry entry = Relocs[e - i - 1];
|
|
|
|
if (!entry.Index)
|
|
;
|
|
else if (entry.Index < 0)
|
|
entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
|
|
else
|
|
entry.Index += LocalSymbolData.size();
|
|
if (is64Bit()) {
|
|
String64(*F, entry.r_offset);
|
|
if (TargetObjectWriter->isN64()) {
|
|
String32(*F, entry.Index);
|
|
|
|
String8(*F, TargetObjectWriter->getRSsym(entry.Type));
|
|
String8(*F, TargetObjectWriter->getRType3(entry.Type));
|
|
String8(*F, TargetObjectWriter->getRType2(entry.Type));
|
|
String8(*F, TargetObjectWriter->getRType(entry.Type));
|
|
}
|
|
else {
|
|
struct ELF::Elf64_Rela ERE64;
|
|
ERE64.setSymbolAndType(entry.Index, entry.Type);
|
|
String64(*F, ERE64.r_info);
|
|
}
|
|
if (hasRelocationAddend())
|
|
String64(*F, entry.r_addend);
|
|
} else {
|
|
String32(*F, entry.r_offset);
|
|
|
|
struct ELF::Elf32_Rela ERE32;
|
|
ERE32.setSymbolAndType(entry.Index, entry.Type);
|
|
String32(*F, ERE32.r_info);
|
|
|
|
if (hasRelocationAddend())
|
|
String32(*F, entry.r_addend);
|
|
}
|
|
}
|
|
}
|
|
|
|
static int compareBySuffix(const void *a, const void *b) {
|
|
const MCSectionELF *secA = *static_cast<const MCSectionELF* const *>(a);
|
|
const MCSectionELF *secB = *static_cast<const MCSectionELF* const *>(b);
|
|
const StringRef &NameA = secA->getSectionName();
|
|
const StringRef &NameB = secB->getSectionName();
|
|
const unsigned sizeA = NameA.size();
|
|
const unsigned sizeB = NameB.size();
|
|
const unsigned len = std::min(sizeA, sizeB);
|
|
for (unsigned int i = 0; i < len; ++i) {
|
|
char ca = NameA[sizeA - i - 1];
|
|
char cb = NameB[sizeB - i - 1];
|
|
if (ca != cb)
|
|
return cb - ca;
|
|
}
|
|
|
|
return sizeB - sizeA;
|
|
}
|
|
|
|
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);
|
|
|
|
MCSectionData *SymtabShndxSD = NULL;
|
|
|
|
if (NeedsSymtabShndx) {
|
|
const MCSectionELF *SymtabShndxSection =
|
|
Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
|
|
SectionKind::getReadOnly(), 4, "");
|
|
SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
|
|
SymtabShndxSD->setAlignment(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);
|
|
MCDataFragment *ShndxF = NULL;
|
|
if (NeedsSymtabShndx) {
|
|
ShndxF = new MCDataFragment(SymtabShndxSD);
|
|
}
|
|
WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
|
|
|
|
F = new MCDataFragment(&StrtabSD);
|
|
F->getContents().append(StringTable.begin(), StringTable.end());
|
|
|
|
F = new MCDataFragment(&ShstrtabSD);
|
|
|
|
std::vector<const MCSectionELF*> Sections;
|
|
for (MCAssembler::const_iterator it = Asm.begin(),
|
|
ie = Asm.end(); it != ie; ++it) {
|
|
const MCSectionELF &Section =
|
|
static_cast<const MCSectionELF&>(it->getSection());
|
|
Sections.push_back(&Section);
|
|
}
|
|
array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
|
|
|
|
// Section header string table.
|
|
//
|
|
// The first entry of a string table holds a null character so skip
|
|
// section 0.
|
|
uint64_t Index = 1;
|
|
F->getContents().push_back('\x00');
|
|
|
|
for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
|
|
const MCSectionELF &Section = *Sections[I];
|
|
|
|
StringRef Name = Section.getSectionName();
|
|
if (I != 0) {
|
|
StringRef PreviousName = Sections[I - 1]->getSectionName();
|
|
if (PreviousName.endswith(Name)) {
|
|
SectionStringTableIndex[&Section] = Index - Name.size() - 1;
|
|
continue;
|
|
}
|
|
}
|
|
// Remember the index into the string table so we can write it
|
|
// into the sh_name field of the section header table.
|
|
SectionStringTableIndex[&Section] = Index;
|
|
|
|
Index += Name.size() + 1;
|
|
F->getContents().append(Name.begin(), Name.end());
|
|
F->getContents().push_back('\x00');
|
|
}
|
|
}
|
|
|
|
void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
|
|
MCAsmLayout &Layout,
|
|
GroupMapTy &GroupMap,
|
|
RevGroupMapTy &RevGroupMap,
|
|
SectionIndexMapTy &SectionIndexMap,
|
|
const RelMapTy &RelMap) {
|
|
// Create the .note.GNU-stack section if needed.
|
|
MCContext &Ctx = Asm.getContext();
|
|
if (Asm.getNoExecStack()) {
|
|
const MCSectionELF *GnuStackSection =
|
|
Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
|
|
SectionKind::getReadOnly());
|
|
Asm.getOrCreateSectionData(*GnuStackSection);
|
|
}
|
|
|
|
// 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);
|
|
String32(*F, 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);
|
|
unsigned Index = SectionIndexMap.lookup(&Section);
|
|
String32(*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 = SectionStringTableIndex[&Section];
|
|
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);
|
|
|
|
InfoSection = Asm.getContext().getELFSection(SectionName,
|
|
ELF::SHT_PROGBITS, 0,
|
|
SectionKind::getReadOnly());
|
|
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:
|
|
// Nothing to do.
|
|
break;
|
|
|
|
case ELF::SHT_GROUP:
|
|
sh_link = SymbolTableIndex;
|
|
sh_info = GroupSymbolIndex;
|
|
break;
|
|
|
|
default:
|
|
assert(0 && "FIXME: sh_type value not supported!");
|
|
break;
|
|
}
|
|
|
|
WriteSecHdrEntry(SectionStringTableIndex[&Section], 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();
|
|
|
|
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, 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(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)
|
|
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);
|
|
}
|