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llvm/lib/MC/ELFObjectWriter.cpp
Jason W Kim e964d1192a Address the last bit of relocation flag related divergence betweeen 
LLVM and binutils.

With this patch, there are no functional differences between the .o
produced directly from LLVM versus the .s to .o via GNU as, for relocation tags
at least, for both PIC and non-PIC modes.

Because some non-PIC reloc tags are used (legally) on PIC, so IsPCRel flag is
necessary but not sufficient to determine whether the overall codegen mode is
PIC or not. Why is this necessary? There is an incompatibility of how relocs
are emitted in the .rodata section.  Binutils PIC likes to emit certain relocs
as section relative offsets.  Non-PIC does not do this.

So I added a hidden switch on the ELFObjectwriter "-arm-elf-force-pic" which
forces the objectwriter to pretend that all relocs are for PIC mode.


Todo: Activate ForceARMElfPIC to true if -relocation-model=pic is selected
on llc.

Todo: There are probably more issues for PIC mode on ARM/MC/ELF...

Todo: Existing tests in MC/ARM/elf-reloc*.ll need to be converted over to .s 
tests as well as expanded to cover the gamut.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131205 91177308-0d34-0410-b5e6-96231b3b80d8
2011-05-11 22:53:06 +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 "ELFObjectWriter.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSectionELF.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 "llvm/ADT/StringSwitch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/ADT/Statistic.h"
#include "../Target/X86/X86FixupKinds.h"
#include "../Target/ARM/ARMFixupKinds.h"
#include <vector>
using namespace llvm;
#undef DEBUG_TYPE
#define DEBUG_TYPE "reloc-info"
// Emulate the wierd behavior of GNU-as for relocation types
namespace llvm {
cl::opt<bool>
ForceARMElfPIC("arm-elf-force-pic", cl::Hidden, cl::init(false),
cl::desc("Force ELF emitter to emit PIC style relocations"));
}
bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
const MCFixupKindInfo &FKI =
Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
}
bool ELFObjectWriter::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;
}
}
ELFObjectWriter::~ELFObjectWriter()
{}
// 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 (TargetObjectWriter->getOSType()) {
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(TargetObjectWriter->getEMachine()); // 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
// e_flags = whatever the target wants
WriteEFlags();
// 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
}
}
uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
const MCAsmLayout &Layout) {
if (Data.isCommon() && Data.isExternal())
return Data.getCommonAlignment();
const MCSymbol &Symbol = Data.getSymbol();
if (Symbol.isAbsolute() && Symbol.isVariable()) {
if (const MCExpr *Value = Symbol.getVariableValue()) {
int64_t IntValue;
if (Value->EvaluateAsAbsolute(IntValue, Layout))
return (uint64_t)IntValue;
}
}
if (!Symbol.isInSection())
return 0;
if (Data.getFragment())
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)
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 &ASymbol;
}
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);
// Ofeset 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();
Index = F->getParent()->getOrdinal() + 1;
// Offset of the symbol in the section
Value += Layout.getSymbolOffset(&SD);
} else {
if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
WeakrefUsedInReloc.insert(RelocSymbol);
else
UsedInReloc.insert(RelocSymbol);
Index = -1;
}
Addend = Value;
// Compensate for the addend on i386.
if (is64Bit())
Value = 0;
}
FixedValue = Value;
unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
(RelocSymbol != 0), Addend);
uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
Fixup.getOffset();
if (!hasRelocationAddend())
Addend = 0;
ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend);
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?
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++);
}
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 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)
;
else if (entry.Index < 0)
entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
else
entry.Index += LocalSymbolData.size();
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);
}
}
}
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() += '\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() += Name;
F->getContents() += '\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) {
uint64_t FileOff = OS.tell();
const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
WriteZeros(Padding);
FileOff += Padding;
FileOff += GetSectionFileSize(Layout, SD);
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().str());
}
} 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]);
FileOff = OS.tell();
uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
WriteZeros(Padding);
// ... then the section header table ...
WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
SectionOffsetMap);
FileOff = OS.tell();
// ... and then the remainting 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) {
switch (MOTW->getEMachine()) {
case ELF::EM_386:
case ELF::EM_X86_64:
return new X86ELFObjectWriter(MOTW, OS, IsLittleEndian); break;
case ELF::EM_ARM:
return new ARMELFObjectWriter(MOTW, OS, IsLittleEndian); break;
case ELF::EM_MBLAZE:
return new MBlazeELFObjectWriter(MOTW, OS, IsLittleEndian); break;
default: llvm_unreachable("Unsupported architecture"); break;
}
}
/// START OF SUBCLASSES for ELFObjectWriter
//===- ARMELFObjectWriter -------------------------------------------===//
ARMELFObjectWriter::ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW,
raw_ostream &_OS,
bool IsLittleEndian)
: ELFObjectWriter(MOTW, _OS, IsLittleEndian)
{}
ARMELFObjectWriter::~ARMELFObjectWriter()
{}
// FIXME: get the real EABI Version from the Triple.
void ARMELFObjectWriter::WriteEFlags() {
Write32(ELF::EF_ARM_EABIMASK & DefaultEABIVersion);
}
// In ARM, _MergedGlobals and other most symbols get emitted directly.
// I.e. not as an offset to a section symbol.
// This code is an approximation of what ARM/gcc does.
STATISTIC(PCRelCount, "Total number of PIC Relocations");
STATISTIC(NonPCRelCount, "Total number of non-PIC relocations");
const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
const MCValue &Target,
const MCFragment &F,
const MCFixup &Fixup,
bool IsPCRel) const {
const MCSymbol &Symbol = Target.getSymA()->getSymbol();
bool EmitThisSym = false;
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(Symbol.getSection());
const SectionKind secKind = Section.getKind();
const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
MCSymbolRefExpr::VariantKind Kind2;
Kind2 = Target.getSymB() ? Target.getSymB()->getKind() :
MCSymbolRefExpr::VK_None;
bool InNormalSection = true;
unsigned RelocType = 0;
RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel);
DEBUG(dbgs() << "considering symbol "
<< Section.getSectionName() << "/"
<< Symbol.getName() << "/"
<< " Rel:" << (unsigned)RelocType
<< " Kind: " << (int)Kind << "/" << (int)Kind2
<< " Tmp:"
<< Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/"
<< Symbol.isVariable() << "/" << Symbol.isTemporary()
<< " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n");
if (IsPCRel || ForceARMElfPIC) { ++PCRelCount;
switch (RelocType) {
default:
// Most relocation types are emitted as explicit symbols
InNormalSection =
StringSwitch<bool>(Section.getSectionName())
.Case(".data.rel.ro.local", false)
.Case(".data.rel", false)
.Case(".bss", false)
.Default(true);
EmitThisSym = true;
break;
case ELF::R_ARM_ABS32:
// But things get strange with R_ARM_ABS32
// In this case, most things that go in .rodata show up
// as section relative relocations
InNormalSection =
StringSwitch<bool>(Section.getSectionName())
.Case(".data.rel.ro.local", false)
.Case(".data.rel", false)
.Case(".rodata", false)
.Case(".bss", false)
.Default(true);
EmitThisSym = false;
break;
}
} else {
NonPCRelCount++;
InNormalSection =
StringSwitch<bool>(Section.getSectionName())
.Case(".data.rel.ro.local", false)
.Case(".rodata", false)
.Case(".data.rel", false)
.Case(".bss", false)
.Default(true);
switch (RelocType) {
default: EmitThisSym = true; break;
case ELF::R_ARM_ABS32: EmitThisSym = false; break;
}
}
if (EmitThisSym)
return &Symbol;
if (! Symbol.isTemporary() && InNormalSection) {
return &Symbol;
}
return NULL;
}
// Need to examine the Fixup when determining whether to
// emit the relocation as an explicit symbol or as a section relative
// offset
unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel,
bool IsRelocWithSymbol,
int64_t Addend) {
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
unsigned Type = GetRelocTypeInner(Target, Fixup, IsPCRel);
if (RelocNeedsGOT(Modifier))
NeedsGOT = true;
return Type;
}
unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
unsigned Type = 0;
if (IsPCRel) {
switch ((unsigned)Fixup.getKind()) {
default: assert(0 && "Unimplemented");
case FK_Data_4:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
Type = ELF::R_ARM_REL32;
break;
case MCSymbolRefExpr::VK_ARM_TLSGD:
assert(0 && "unimplemented");
break;
case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
Type = ELF::R_ARM_TLS_IE32;
break;
}
break;
case ARM::fixup_arm_uncondbranch:
switch (Modifier) {
case MCSymbolRefExpr::VK_ARM_PLT:
Type = ELF::R_ARM_PLT32;
break;
default:
Type = ELF::R_ARM_CALL;
break;
}
break;
case ARM::fixup_arm_condbranch:
Type = ELF::R_ARM_JUMP24;
break;
case ARM::fixup_arm_movt_hi16:
case ARM::fixup_arm_movt_hi16_pcrel:
Type = ELF::R_ARM_MOVT_PREL;
break;
case ARM::fixup_arm_movw_lo16:
case ARM::fixup_arm_movw_lo16_pcrel:
Type = ELF::R_ARM_MOVW_PREL_NC;
break;
case ARM::fixup_t2_movt_hi16:
case ARM::fixup_t2_movt_hi16_pcrel:
Type = ELF::R_ARM_THM_MOVT_PREL;
break;
case ARM::fixup_t2_movw_lo16:
case ARM::fixup_t2_movw_lo16_pcrel:
Type = ELF::R_ARM_THM_MOVW_PREL_NC;
break;
}
} else {
switch ((unsigned)Fixup.getKind()) {
default: llvm_unreachable("invalid fixup kind!");
case FK_Data_4:
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier"); break;
case MCSymbolRefExpr::VK_ARM_GOT:
Type = ELF::R_ARM_GOT_BREL;
break;
case MCSymbolRefExpr::VK_ARM_TLSGD:
Type = ELF::R_ARM_TLS_GD32;
break;
case MCSymbolRefExpr::VK_ARM_TPOFF:
Type = ELF::R_ARM_TLS_LE32;
break;
case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
Type = ELF::R_ARM_TLS_IE32;
break;
case MCSymbolRefExpr::VK_None:
Type = ELF::R_ARM_ABS32;
break;
case MCSymbolRefExpr::VK_ARM_GOTOFF:
Type = ELF::R_ARM_GOTOFF32;
break;
}
break;
case ARM::fixup_arm_ldst_pcrel_12:
case ARM::fixup_arm_pcrel_10:
case ARM::fixup_arm_adr_pcrel_12:
case ARM::fixup_arm_thumb_bl:
case ARM::fixup_arm_thumb_cb:
case ARM::fixup_arm_thumb_cp:
case ARM::fixup_arm_thumb_br:
assert(0 && "Unimplemented");
break;
case ARM::fixup_arm_uncondbranch:
Type = ELF::R_ARM_CALL;
break;
case ARM::fixup_arm_condbranch:
Type = ELF::R_ARM_JUMP24;
break;
case ARM::fixup_arm_movt_hi16:
Type = ELF::R_ARM_MOVT_ABS;
break;
case ARM::fixup_arm_movw_lo16:
Type = ELF::R_ARM_MOVW_ABS_NC;
break;
case ARM::fixup_t2_movt_hi16:
Type = ELF::R_ARM_THM_MOVT_ABS;
break;
case ARM::fixup_t2_movw_lo16:
Type = ELF::R_ARM_THM_MOVW_ABS_NC;
break;
}
}
return Type;
}
//===- MBlazeELFObjectWriter -------------------------------------------===//
MBlazeELFObjectWriter::MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW,
raw_ostream &_OS,
bool IsLittleEndian)
: ELFObjectWriter(MOTW, _OS, IsLittleEndian) {
}
MBlazeELFObjectWriter::~MBlazeELFObjectWriter() {
}
unsigned MBlazeELFObjectWriter::GetRelocType(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel,
bool IsRelocWithSymbol,
int64_t Addend) {
// determine the type of the relocation
unsigned Type;
if (IsPCRel) {
switch ((unsigned)Fixup.getKind()) {
default:
llvm_unreachable("Unimplemented");
case FK_PCRel_4:
Type = ELF::R_MICROBLAZE_64_PCREL;
break;
case FK_PCRel_2:
Type = ELF::R_MICROBLAZE_32_PCREL;
break;
}
} else {
switch ((unsigned)Fixup.getKind()) {
default: llvm_unreachable("invalid fixup kind!");
case FK_Data_4:
Type = ((IsRelocWithSymbol || Addend !=0)
? ELF::R_MICROBLAZE_32
: ELF::R_MICROBLAZE_64);
break;
case FK_Data_2:
Type = ELF::R_MICROBLAZE_32;
break;
}
}
return Type;
}
//===- X86ELFObjectWriter -------------------------------------------===//
X86ELFObjectWriter::X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
raw_ostream &_OS,
bool IsLittleEndian)
: ELFObjectWriter(MOTW, _OS, IsLittleEndian)
{}
X86ELFObjectWriter::~X86ELFObjectWriter()
{}
unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel,
bool IsRelocWithSymbol,
int64_t Addend) {
// determine the type of the relocation
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
unsigned Type;
if (is64Bit()) {
if (IsPCRel) {
switch ((unsigned)Fixup.getKind()) {
default: llvm_unreachable("invalid fixup kind!");
case FK_Data_8: Type = ELF::R_X86_64_PC64; break;
case FK_Data_4: Type = ELF::R_X86_64_PC32; break;
case FK_Data_2: Type = ELF::R_X86_64_PC16; break;
case FK_PCRel_8:
assert(Modifier == MCSymbolRefExpr::VK_None);
Type = ELF::R_X86_64_PC64;
break;
case X86::reloc_signed_4byte:
case X86::reloc_riprel_4byte_movq_load:
case X86::reloc_riprel_4byte:
case FK_PCRel_4:
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;
}
break;
case FK_PCRel_2:
assert(Modifier == MCSymbolRefExpr::VK_None);
Type = ELF::R_X86_64_PC16;
break;
case FK_PCRel_1:
assert(Modifier == MCSymbolRefExpr::VK_None);
Type = ELF::R_X86_64_PC8;
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:
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 FK_PCRel_1:
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 FK_PCRel_4:
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 FK_PCRel_1:
case FK_Data_1: Type = ELF::R_386_8; break;
}
}
}
if (RelocNeedsGOT(Modifier))
NeedsGOT = true;
return Type;
}
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