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llvm-6502/lib/MC/ELFObjectWriter.cpp
Rafael Espindola 1f4f9e3d35 Handle a peculiar comdat case: Creating a section with an undefined 
signature symbol causes a local symbol to be created unless there is
some other use of the symbol.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119026 91177308-0d34-0410-b5e6-96231b3b80d8
2010-11-14 04:17:37 +00:00

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//===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements ELF object file writer information.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCELFSymbolFlags.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ELF.h"
#include "llvm/Target/TargetAsmBackend.h"
#include "../Target/X86/X86FixupKinds.h"
#include <vector>
using namespace llvm;
static unsigned GetType(const MCSymbolData &SD) {
uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift;
assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
Type == ELF::STT_TLS);
return Type;
}
static unsigned GetBinding(const MCSymbolData &SD) {
uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
Binding == ELF::STB_WEAK);
return Binding;
}
static void SetBinding(MCSymbolData &SD, unsigned Binding) {
assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
Binding == ELF::STB_WEAK);
uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
}
static unsigned GetVisibility(MCSymbolData &SD) {
unsigned Visibility =
(SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift;
assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
return Visibility;
}
static bool isFixupKindX86PCRel(unsigned Kind) {
switch (Kind) {
default:
return false;
case X86::reloc_pcrel_1byte:
case X86::reloc_pcrel_4byte:
case X86::reloc_riprel_4byte:
case X86::reloc_riprel_4byte_movq_load:
return true;
}
}
static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
switch (Variant) {
default:
return false;
case MCSymbolRefExpr::VK_GOT:
case MCSymbolRefExpr::VK_PLT:
case MCSymbolRefExpr::VK_GOTPCREL:
case MCSymbolRefExpr::VK_TPOFF:
case MCSymbolRefExpr::VK_TLSGD:
case MCSymbolRefExpr::VK_GOTTPOFF:
case MCSymbolRefExpr::VK_INDNTPOFF:
case MCSymbolRefExpr::VK_NTPOFF:
case MCSymbolRefExpr::VK_GOTNTPOFF:
case MCSymbolRefExpr::VK_TLSLDM:
case MCSymbolRefExpr::VK_DTPOFF:
case MCSymbolRefExpr::VK_TLSLD:
return true;
}
}
namespace {
class ELFObjectWriter : public MCObjectWriter {
/*static bool isFixupKindX86RIPRel(unsigned Kind) {
return Kind == X86::reloc_riprel_4byte ||
Kind == X86::reloc_riprel_4byte_movq_load;
}*/
/// ELFSymbolData - Helper struct for containing some precomputed information
/// on symbols.
struct ELFSymbolData {
MCSymbolData *SymbolData;
uint64_t StringIndex;
uint32_t SectionIndex;
// Support lexicographic sorting.
bool operator<(const ELFSymbolData &RHS) const {
if (GetType(*SymbolData) == ELF::STT_FILE)
return true;
if (GetType(*RHS.SymbolData) == ELF::STT_FILE)
return false;
return SymbolData->getSymbol().getName() <
RHS.SymbolData->getSymbol().getName();
}
};
/// @name Relocation Data
/// @{
struct ELFRelocationEntry {
// Make these big enough for both 32-bit and 64-bit
uint64_t r_offset;
int Index;
unsigned Type;
const MCSymbol *Symbol;
uint64_t r_addend;
// Support lexicographic sorting.
bool operator<(const ELFRelocationEntry &RE) const {
return RE.r_offset < r_offset;
}
};
SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
DenseMap<const MCSymbol *, const MCSymbol *> Renames;
llvm::DenseMap<const MCSectionData*,
std::vector<ELFRelocationEntry> > Relocations;
DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
/// @}
/// @name Symbol Table Data
/// @{
SmallString<256> StringTable;
std::vector<ELFSymbolData> LocalSymbolData;
std::vector<ELFSymbolData> ExternalSymbolData;
std::vector<ELFSymbolData> UndefinedSymbolData;
/// @}
bool NeedsGOT;
bool NeedsSymtabShndx;
unsigned Is64Bit : 1;
bool HasRelocationAddend;
Triple::OSType OSType;
uint16_t EMachine;
// This holds the symbol table index of the last local symbol.
unsigned LastLocalSymbolIndex;
// This holds the .strtab section index.
unsigned StringTableIndex;
// This holds the .symtab section index.
unsigned SymbolTableIndex;
unsigned ShstrtabIndex;
public:
ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
uint16_t _EMachine, bool _HasRelAddend,
Triple::OSType _OSType)
: MCObjectWriter(_OS, IsLittleEndian),
NeedsGOT(false), NeedsSymtabShndx(false),
Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend),
OSType(_OSType), EMachine(_EMachine) {
}
void WriteWord(uint64_t W) {
if (Is64Bit)
Write64(W);
else
Write32(W);
}
void StringLE16(char *buf, uint16_t Value) {
buf[0] = char(Value >> 0);
buf[1] = char(Value >> 8);
}
void StringLE32(char *buf, uint32_t Value) {
StringLE16(buf, uint16_t(Value >> 0));
StringLE16(buf + 2, uint16_t(Value >> 16));
}
void StringLE64(char *buf, uint64_t Value) {
StringLE32(buf, uint32_t(Value >> 0));
StringLE32(buf + 4, uint32_t(Value >> 32));
}
void StringBE16(char *buf ,uint16_t Value) {
buf[0] = char(Value >> 8);
buf[1] = char(Value >> 0);
}
void StringBE32(char *buf, uint32_t Value) {
StringBE16(buf, uint16_t(Value >> 16));
StringBE16(buf + 2, uint16_t(Value >> 0));
}
void StringBE64(char *buf, uint64_t Value) {
StringBE32(buf, uint32_t(Value >> 32));
StringBE32(buf + 4, uint32_t(Value >> 0));
}
void String8(MCDataFragment &F, uint8_t Value) {
char buf[1];
buf[0] = Value;
F.getContents() += StringRef(buf, 1);
}
void String16(MCDataFragment &F, uint16_t Value) {
char buf[2];
if (isLittleEndian())
StringLE16(buf, Value);
else
StringBE16(buf, Value);
F.getContents() += StringRef(buf, 2);
}
void String32(MCDataFragment &F, uint32_t Value) {
char buf[4];
if (isLittleEndian())
StringLE32(buf, Value);
else
StringBE32(buf, Value);
F.getContents() += StringRef(buf, 4);
}
void String64(MCDataFragment &F, uint64_t Value) {
char buf[8];
if (isLittleEndian())
StringLE64(buf, Value);
else
StringBE64(buf, Value);
F.getContents() += StringRef(buf, 8);
}
void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
void WriteSymbolEntry(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
uint64_t name, uint8_t info,
uint64_t value, uint64_t size,
uint8_t other, uint32_t shndx,
bool Reserved);
void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
ELFSymbolData &MSD,
const MCAsmLayout &Layout);
typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
void WriteSymbolTable(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
const MCAssembler &Asm,
const MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap);
void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup,
MCValue Target, uint64_t &FixedValue);
uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
const MCSymbol *S);
// Map from a group section to the signature symbol
typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
// Map from a signature symbol to the group section
typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
/// ComputeSymbolTable - Compute the symbol table data
///
/// \param StringTable [out] - The string table data.
/// \param StringIndexMap [out] - Map from symbol names to offsets in the
/// string table.
void ComputeSymbolTable(MCAssembler &Asm,
const SectionIndexMapTy &SectionIndexMap,
RevGroupMapTy RevGroupMap);
void ComputeIndexMap(MCAssembler &Asm,
SectionIndexMapTy &SectionIndexMap);
void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
const MCSectionData &SD);
void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
for (MCAssembler::const_iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it) {
WriteRelocation(Asm, Layout, *it);
}
}
void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap);
void CreateGroupSections(MCAssembler &Asm, MCAsmLayout &Layout,
GroupMapTy &GroupMap, RevGroupMapTy &RevGroupMap);
void ExecutePostLayoutBinding(MCAssembler &Asm);
void 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);
void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
const MCSectionData *SD);
bool IsFixupFullyResolved(const MCAssembler &Asm,
const MCValue Target,
bool IsPCRel,
const MCFragment *DF) const;
void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
void WriteSection(MCAssembler &Asm,
const SectionIndexMapTy &SectionIndexMap,
uint32_t GroupSymbolIndex,
uint64_t Offset, uint64_t Size, uint64_t Alignment,
const MCSectionELF &Section);
};
}
// Emit the ELF header.
void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize,
unsigned NumberOfSections) {
// ELF Header
// ----------
//
// Note
// ----
// emitWord method behaves differently for ELF32 and ELF64, writing
// 4 bytes in the former and 8 in the latter.
Write8(0x7f); // e_ident[EI_MAG0]
Write8('E'); // e_ident[EI_MAG1]
Write8('L'); // e_ident[EI_MAG2]
Write8('F'); // e_ident[EI_MAG3]
Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
// e_ident[EI_DATA]
Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
// e_ident[EI_OSABI]
switch (OSType) {
case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break;
case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break;
default: Write8(ELF::ELFOSABI_NONE); break;
}
Write8(0); // e_ident[EI_ABIVERSION]
WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
Write16(ELF::ET_REL); // e_type
Write16(EMachine); // e_machine = target
Write32(ELF::EV_CURRENT); // e_version
WriteWord(0); // e_entry, no entry point in .o file
WriteWord(0); // e_phoff, no program header for .o
WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
// FIXME: Make this configurable.
Write32(0); // e_flags = whatever the target wants
// 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(0);
else
Write16(NumberOfSections);
// e_shstrndx = Section # of '.shstrtab'
if (NumberOfSections >= ELF::SHN_LORESERVE)
Write16(ELF::SHN_XINDEX);
else
Write16(ShstrtabIndex);
}
void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
MCDataFragment *ShndxF,
uint64_t name,
uint8_t info, uint64_t value,
uint64_t size, uint8_t other,
uint32_t shndx,
bool Reserved) {
if (ShndxF) {
if (shndx >= ELF::SHN_LORESERVE && !Reserved)
String32(*ShndxF, shndx);
else
String32(*ShndxF, 0);
}
uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
uint16_t(ELF::SHN_XINDEX) : shndx;
if (Is64Bit) {
String32(*SymtabF, name); // st_name
String8(*SymtabF, info); // st_info
String8(*SymtabF, other); // st_other
String16(*SymtabF, Index); // st_shndx
String64(*SymtabF, value); // st_value
String64(*SymtabF, size); // st_size
} else {
String32(*SymtabF, name); // st_name
String32(*SymtabF, value); // st_value
String32(*SymtabF, size); // st_size
String8(*SymtabF, info); // st_info
String8(*SymtabF, other); // st_other
String16(*SymtabF, Index); // st_shndx
}
}
static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) {
if (Data.isCommon() && Data.isExternal())
return Data.getCommonAlignment();
const MCSymbol &Symbol = Data.getSymbol();
if (!Symbol.isInSection())
return 0;
if (MCFragment *FF = Data.getFragment())
return Layout.getSymbolAddress(&Data) -
Layout.getSectionAddress(FF->getParent());
return 0;
}
static const MCSymbol &AliasedSymbol(const MCSymbol &Symbol) {
const MCSymbol *S = &Symbol;
while (S->isVariable()) {
const MCExpr *Value = S->getVariableValue();
MCExpr::ExprKind Kind = Value->getKind();
switch (Kind) {
case MCExpr::SymbolRef: {
const MCSymbolRefExpr *Ref = static_cast<const MCSymbolRefExpr*>(Value);
S = &Ref->getSymbol();
break;
}
case MCExpr::Target: {
const MCTargetExpr *TExp = static_cast<const MCTargetExpr*>(Value);
MCValue Res;
TExp->EvaluateAsRelocatableImpl(Res, NULL);
S = &Res.getSymA()->getSymbol();
break;
}
default:
return *S;
}
}
return *S;
}
void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
// 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 = AliasedSymbol(Alias);
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());
SetBinding(*it, 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(AliasedSymbol(OrigData.getSymbol()));
bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
Data.getSymbol().isVariable();
uint8_t Binding = GetBinding(OrigData);
uint8_t Visibility = GetVisibility(OrigData);
uint8_t Type = 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;
const MCExpr *ESize;
assert(!(Data.isCommon() && !Data.isExternal()));
ESize = Data.getSize();
if (Data.getSize()) {
MCValue Res;
if (ESize->getKind() == MCExpr::Binary) {
const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
if (BE->EvaluateAsRelocatable(Res, &Layout)) {
assert(!Res.getSymA() || !Res.getSymA()->getSymbol().isDefined());
assert(!Res.getSymB() || !Res.getSymB()->getSymbol().isDefined());
Size = Res.getConstant();
}
} else if (ESize->getKind() == MCExpr::Constant) {
Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
} else {
assert(0 && "Unsupported size expression");
}
}
// 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)
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 (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 (GetBinding(Data) == ELF::STB_LOCAL)
LastLocalSymbolIndex++;
}
}
static bool ShouldRelocOnSymbol(const MCSymbolData &SD,
const MCValue &Target,
const MCFragment &F) {
const MCSymbol &Symbol = SD.getSymbol();
if (Symbol.isUndefined())
return true;
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(Symbol.getSection());
if (SD.isExternal())
return true;
MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
const MCSectionELF &Sec2 =
static_cast<const MCSectionELF&>(F.getParent()->getSection());
if (Section.getKind().isBSS())
return false;
if (&Sec2 != &Section &&
(Kind == MCSymbolRefExpr::VK_PLT ||
Kind == MCSymbolRefExpr::VK_GOTPCREL ||
Kind == MCSymbolRefExpr::VK_GOTOFF))
return true;
if (Section.getFlags() & MCSectionELF::SHF_MERGE)
return Target.getConstant() != 0;
return false;
}
// FIXME: this is currently X86/X86_64 only
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 &Symbol = Target.getSymA()->getSymbol();
const MCSymbol &ASymbol = AliasedSymbol(Symbol);
const MCSymbol *RenamedP = Renames.lookup(&Symbol);
if (!RenamedP)
RenamedP = &ASymbol;
const MCSymbol &Renamed = *RenamedP;
bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
if (!Target.isAbsolute()) {
MCSymbolData &SD = Asm.getSymbolData(Symbol);
MCFragment *F = SD.getFragment();
if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
const MCSymbol &SymbolB = RefB->getSymbol();
MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
IsPCRel = true;
MCSectionData *Sec = Fragment->getParent();
// Offset of the symbol in the section
int64_t a = Layout.getSymbolAddress(&SDB) - Layout.getSectionAddress(Sec);
// Ofeset of the relocation in the section
int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
Value += b - a;
}
bool RelocOnSymbol = ShouldRelocOnSymbol(SD, Target, *Fragment);
if (!RelocOnSymbol) {
Index = F->getParent()->getOrdinal();
MCSectionData *FSD = F->getParent();
// Offset of the symbol in the section
Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
} else {
if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
WeakrefUsedInReloc.insert(&Renamed);
else
UsedInReloc.insert(&Renamed);
Index = -1;
}
Addend = Value;
// Compensate for the addend on i386.
if (Is64Bit)
Value = 0;
}
FixedValue = Value;
// determine the type of the relocation
MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
unsigned Type;
if (Is64Bit) {
if (IsPCRel) {
switch (Modifier) {
default:
llvm_unreachable("Unimplemented");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_X86_64_PC32;
break;
case MCSymbolRefExpr::VK_PLT:
Type = ELF::R_X86_64_PLT32;
break;
case MCSymbolRefExpr::VK_GOTPCREL:
Type = ELF::R_X86_64_GOTPCREL;
break;
case MCSymbolRefExpr::VK_GOTTPOFF:
Type = ELF::R_X86_64_GOTTPOFF;
break;
case MCSymbolRefExpr::VK_TLSGD:
Type = ELF::R_X86_64_TLSGD;
break;
case MCSymbolRefExpr::VK_TLSLD:
Type = ELF::R_X86_64_TLSLD;
break;
}
} else {
switch ((unsigned)Fixup.getKind()) {
default: llvm_unreachable("invalid fixup kind!");
case FK_Data_8: Type = ELF::R_X86_64_64; break;
case X86::reloc_signed_4byte:
case X86::reloc_pcrel_4byte:
assert(isInt<32>(Target.getConstant()));
switch (Modifier) {
default:
llvm_unreachable("Unimplemented");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_X86_64_32S;
break;
case MCSymbolRefExpr::VK_GOT:
Type = ELF::R_X86_64_GOT32;
break;
case MCSymbolRefExpr::VK_GOTPCREL:
Type = ELF::R_X86_64_GOTPCREL;
break;
case MCSymbolRefExpr::VK_TPOFF:
Type = ELF::R_X86_64_TPOFF32;
break;
case MCSymbolRefExpr::VK_DTPOFF:
Type = ELF::R_X86_64_DTPOFF32;
break;
}
break;
case FK_Data_4:
Type = ELF::R_X86_64_32;
break;
case FK_Data_2: Type = ELF::R_X86_64_16; break;
case X86::reloc_pcrel_1byte:
case FK_Data_1: Type = ELF::R_X86_64_8; break;
}
}
} else {
if (IsPCRel) {
switch (Modifier) {
default:
llvm_unreachable("Unimplemented");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_386_PC32;
break;
case MCSymbolRefExpr::VK_PLT:
Type = ELF::R_386_PLT32;
break;
}
} else {
switch ((unsigned)Fixup.getKind()) {
default: llvm_unreachable("invalid fixup kind!");
case X86::reloc_global_offset_table:
Type = ELF::R_386_GOTPC;
break;
// FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode
// instead?
case X86::reloc_signed_4byte:
case X86::reloc_pcrel_4byte:
case FK_Data_4:
switch (Modifier) {
default:
llvm_unreachable("Unimplemented");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_386_32;
break;
case MCSymbolRefExpr::VK_GOT:
Type = ELF::R_386_GOT32;
break;
case MCSymbolRefExpr::VK_GOTOFF:
Type = ELF::R_386_GOTOFF;
break;
case MCSymbolRefExpr::VK_TLSGD:
Type = ELF::R_386_TLS_GD;
break;
case MCSymbolRefExpr::VK_TPOFF:
Type = ELF::R_386_TLS_LE_32;
break;
case MCSymbolRefExpr::VK_INDNTPOFF:
Type = ELF::R_386_TLS_IE;
break;
case MCSymbolRefExpr::VK_NTPOFF:
Type = ELF::R_386_TLS_LE;
break;
case MCSymbolRefExpr::VK_GOTNTPOFF:
Type = ELF::R_386_TLS_GOTIE;
break;
case MCSymbolRefExpr::VK_TLSLDM:
Type = ELF::R_386_TLS_LDM;
break;
case MCSymbolRefExpr::VK_DTPOFF:
Type = ELF::R_386_TLS_LDO_32;
break;
}
break;
case FK_Data_2: Type = ELF::R_386_16; break;
case X86::reloc_pcrel_1byte:
case FK_Data_1: Type = ELF::R_386_8; break;
}
}
}
if (RelocNeedsGOT(Modifier))
NeedsGOT = true;
ELFRelocationEntry ERE;
ERE.Index = Index;
ERE.Type = Type;
ERE.Symbol = &Renamed;
ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
if (HasRelocationAddend)
ERE.r_addend = Addend;
else
ERE.r_addend = 0; // Silence compiler warning.
Relocations[Fragment->getParent()].push_back(ERE);
}
uint64_t
ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
const MCSymbol *S) {
MCSymbolData &SD = Asm.getSymbolData(*S);
return SD.getIndex();
}
static bool 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 = AliasedSymbol(Symbol);
if (!A.isVariable() && A.isUndefined() && !Data.isCommon())
return false;
if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
return false;
if (Symbol.isTemporary())
return false;
return true;
}
static bool isLocal(const MCSymbolData &Data, bool isSignature,
bool isUsedInReloc) {
if (Data.isExternal())
return false;
const MCSymbol &Symbol = Data.getSymbol();
const MCSymbol &RefSymbol = AliasedSymbol(Symbol);
if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
if (isSignature && !isUsedInReloc)
return true;
return false;
}
return true;
}
void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
SectionIndexMapTy &SectionIndexMap) {
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)
continue;
SectionIndexMap[&Section] = Index++;
}
}
void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
const SectionIndexMapTy &SectionIndexMap,
RevGroupMapTy RevGroupMap) {
// FIXME: Is this the correct place to do this?
if (NeedsGOT) {
llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_";
MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
Data.setExternal(true);
SetBinding(Data, ELF::STB_GLOBAL);
}
// Build section lookup table.
int NumRegularSections = Asm.size();
// Index 0 is always the empty string.
StringMap<uint64_t> StringIndexMap;
StringTable += '\x00';
// 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 = AliasedSymbol(Symbol);
// Undefined symbols are global, but this is the first place we
// are able to set it.
bool Local = isLocal(*it, isSignature, Used);
if (!Local && GetBinding(*it) == ELF::STB_LOCAL) {
MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
SetBinding(*it, ELF::STB_GLOBAL);
SetBinding(SD, ELF::STB_GLOBAL);
}
if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
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++);
}
void ELFObjectWriter::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
const MCSectionData &SD) {
if (!Relocations[&SD].empty()) {
MCContext &Ctx = Asm.getContext();
const MCSectionELF *RelaSection;
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);
RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
ELF::SHT_RELA : ELF::SHT_REL, 0,
SectionKind::getReadOnly(),
EntrySize, "");
MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
RelaSD.setAlignment(Is64Bit ? 8 : 4);
MCDataFragment *F = new MCDataFragment(&RelaSD);
WriteRelocationsFragment(Asm, F, &SD);
Asm.AddSectionToTheEnd(*this, RelaSD, Layout);
}
}
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 by the r_offset just like gnu as does
array_pod_sort(Relocs.begin(), Relocs.end());
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
ELFRelocationEntry entry = Relocs[e - i - 1];
if (entry.Index < 0)
entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
else
entry.Index += LocalSymbolData.size() + 1;
if (Is64Bit) {
String64(*F, entry.r_offset);
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);
}
}
}
void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap) {
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);
ShstrtabIndex = Asm.size();
const MCSectionELF *SymtabSection =
Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
SectionKind::getReadOnly(),
EntrySize, "");
MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
SymtabSD.setAlignment(Is64Bit ? 8 : 4);
SymbolTableIndex = Asm.size();
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 MCSection *StrtabSection;
StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
SectionKind::getReadOnly());
MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
StrtabSD.setAlignment(1);
StringTableIndex = Asm.size();
WriteRelocations(Asm, Layout);
// Symbol table
F = new MCDataFragment(&SymtabSD);
MCDataFragment *ShndxF = NULL;
if (NeedsSymtabShndx) {
ShndxF = new MCDataFragment(SymtabShndxSD);
Asm.AddSectionToTheEnd(*this, *SymtabShndxSD, Layout);
}
WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
Asm.AddSectionToTheEnd(*this, SymtabSD, Layout);
F = new MCDataFragment(&StrtabSD);
F->getContents().append(StringTable.begin(), StringTable.end());
Asm.AddSectionToTheEnd(*this, StrtabSD, Layout);
F = new MCDataFragment(&ShstrtabSD);
// 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() += '\x00';
StringMap<uint64_t> SecStringMap;
for (MCAssembler::const_iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it) {
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(it->getSection());
// FIXME: We could merge suffixes like in .text and .rela.text.
StringRef Name = Section.getSectionName();
if (SecStringMap.count(Name)) {
SectionStringTableIndex[&Section] = SecStringMap[Name];
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;
SecStringMap[Name] = Index;
Index += Name.size() + 1;
F->getContents() += Name;
F->getContents() += '\x00';
}
Asm.AddSectionToTheEnd(*this, ShstrtabSD, Layout);
}
bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm,
const MCValue Target,
bool IsPCRel,
const MCFragment *DF) const {
// If this is a PCrel relocation, find the section this fixup value is
// relative to.
const MCSection *BaseSection = 0;
if (IsPCRel) {
BaseSection = &DF->getParent()->getSection();
assert(BaseSection);
}
const MCSection *SectionA = 0;
const MCSymbol *SymbolA = 0;
if (const MCSymbolRefExpr *A = Target.getSymA()) {
SymbolA = &A->getSymbol();
SectionA = &SymbolA->getSection();
}
const MCSection *SectionB = 0;
if (const MCSymbolRefExpr *B = Target.getSymB()) {
SectionB = &B->getSymbol().getSection();
}
if (!BaseSection)
return SectionA == SectionB;
const MCSymbolData &DataA = Asm.getSymbolData(*SymbolA);
if (DataA.isExternal())
return false;
return !SectionB && BaseSection == SectionA;
}
void ELFObjectWriter::CreateGroupSections(MCAssembler &Asm,
MCAsmLayout &Layout,
GroupMapTy &GroupMap,
RevGroupMapTy &RevGroupMap) {
// 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() & MCSectionELF::SHF_GROUP))
continue;
const MCSymbol *SignatureSymbol = Section.getGroup();
Asm.getOrCreateSymbolData(*SignatureSymbol);
const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
if (!Group) {
Group = Asm.getContext().CreateELFGroupSection();
MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
Data.setAlignment(4);
MCDataFragment *F = new MCDataFragment(&Data);
String32(*F, ELF::GRP_COMDAT);
}
GroupMap[Group] = SignatureSymbol;
}
// Add sections to the groups
unsigned Index = 1;
unsigned NumGroups = RevGroupMap.size();
for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
it != ie; ++it, ++Index) {
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(it->getSection());
if (!(Section.getFlags() & MCSectionELF::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);
String32(*F, NumGroups + Index);
}
for (RevGroupMapTy::const_iterator i = RevGroupMap.begin(),
e = RevGroupMap.end(); i != e; ++i) {
const MCSectionELF *Group = i->second;
MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
Asm.AddSectionToTheEnd(*this, Data, Layout);
}
}
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_NULL:
case ELF::SHT_ARM_ATTRIBUTES:
// 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());
}
void ELFObjectWriter::WriteObject(MCAssembler &Asm,
const MCAsmLayout &Layout) {
GroupMapTy GroupMap;
RevGroupMapTy RevGroupMap;
CreateGroupSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
RevGroupMap);
SectionIndexMapTy SectionIndexMap;
ComputeIndexMap(Asm, SectionIndexMap);
// Compute symbol table information.
ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap);
CreateMetadataSections(const_cast<MCAssembler&>(Asm),
const_cast<MCAsmLayout&>(Layout),
SectionIndexMap);
// Update to include the metadata sections.
ComputeIndexMap(Asm, SectionIndexMap);
// Add 1 for the null section.
unsigned NumSections = Asm.size() + 1;
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;
Sections.resize(NumSections);
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] = p.first;
}
for (unsigned i = 1; i < NumSections; ++i) {
const MCSectionELF &Section = *Sections[i];
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
// Get the size of the section in the output file (including padding).
uint64_t Size = Layout.getSectionFileSize(&SD);
FileOff += Size;
}
FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
// Write out the ELF header ...
WriteHeader(FileOff - HeaderSize, NumSections);
FileOff = HeaderSize;
// ... then all of the sections ...
DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
for (unsigned i = 1; i < NumSections; ++i) {
const MCSectionELF &Section = *Sections[i];
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
WriteZeros(Padding);
FileOff += Padding;
// Remember the offset into the file for this section.
SectionOffsetMap[&Section] = FileOff;
FileOff += Layout.getSectionFileSize(&SD);
Asm.WriteSectionData(&SD, Layout, this);
}
uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
WriteZeros(Padding);
FileOff += Padding;
// ... and then the section header table.
// Should we align the section header table?
//
// 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 = 1; i < NumSections; ++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[&Section]);
WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
SectionOffsetMap[&Section], Layout.getSectionSize(&SD),
SD.getAlignment(), Section);
}
}
MCObjectWriter *llvm::createELFObjectWriter(raw_ostream &OS,
bool Is64Bit,
Triple::OSType OSType,
uint16_t EMachine,
bool IsLittleEndian,
bool HasRelocationAddend) {
return new ELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
HasRelocationAddend, OSType);
}
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