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llvm-6502/lib/MC/WinCOFFObjectWriter.cpp
Peter Collingbourne 4974b972e7 COFF: Fix weak external aliases. 
Differential Revision: http://llvm-reviews.chandlerc.com/D700

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180034 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-22 18:48:56 +00:00

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//===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains an implementation of a Win32 COFF object file writer.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "WinCOFFObjectWriter"
#include "llvm/MC/MCWinCOFFObjectWriter.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/COFF.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TimeValue.h"
#include <cstdio>
using namespace llvm;
namespace {
typedef SmallString<COFF::NameSize> name;
enum AuxiliaryType {
ATFunctionDefinition,
ATbfAndefSymbol,
ATWeakExternal,
ATFile,
ATSectionDefinition
};
struct AuxSymbol {
AuxiliaryType AuxType;
COFF::Auxiliary Aux;
};
class COFFSymbol;
class COFFSection;
class COFFSymbol {
public:
COFF::symbol Data;
typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
name Name;
int Index;
AuxiliarySymbols Aux;
COFFSymbol *Other;
COFFSection *Section;
int Relocations;
MCSymbolData const *MCData;
COFFSymbol(StringRef name);
size_t size() const;
void set_name_offset(uint32_t Offset);
bool should_keep() const;
};
// This class contains staging data for a COFF relocation entry.
struct COFFRelocation {
COFF::relocation Data;
COFFSymbol *Symb;
COFFRelocation() : Symb(NULL) {}
static size_t size() { return COFF::RelocationSize; }
};
typedef std::vector<COFFRelocation> relocations;
class COFFSection {
public:
COFF::section Header;
std::string Name;
int Number;
MCSectionData const *MCData;
COFFSymbol *Symbol;
relocations Relocations;
COFFSection(StringRef name);
static size_t size();
};
// This class holds the COFF string table.
class StringTable {
typedef StringMap<size_t> map;
map Map;
void update_length();
public:
std::vector<char> Data;
StringTable();
size_t size() const;
size_t insert(StringRef String);
};
class WinCOFFObjectWriter : public MCObjectWriter {
public:
typedef std::vector<COFFSymbol*> symbols;
typedef std::vector<COFFSection*> sections;
typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
typedef DenseMap<MCSection const *, COFFSection *> section_map;
llvm::OwningPtr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
// Root level file contents.
COFF::header Header;
sections Sections;
symbols Symbols;
StringTable Strings;
// Maps used during object file creation.
section_map SectionMap;
symbol_map SymbolMap;
WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
~WinCOFFObjectWriter();
COFFSymbol *createSymbol(StringRef Name);
COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
COFFSection *createSection(StringRef Name);
template <typename object_t, typename list_t>
object_t *createCOFFEntity(StringRef Name, list_t &List);
void DefineSection(MCSectionData const &SectionData);
void DefineSymbol(MCSymbolData const &SymbolData,
MCAssembler &Assembler);
void MakeSymbolReal(COFFSymbol &S, size_t Index);
void MakeSectionReal(COFFSection &S, size_t Number);
bool ExportSection(COFFSection const *S);
bool ExportSymbol(MCSymbolData const &SymbolData, MCAssembler &Asm);
bool IsPhysicalSection(COFFSection *S);
// Entity writing methods.
void WriteFileHeader(const COFF::header &Header);
void WriteSymbol(const COFFSymbol *S);
void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
void WriteSectionHeader(const COFF::section &S);
void WriteRelocation(const COFF::relocation &R);
// MCObjectWriter interface implementation.
void ExecutePostLayoutBinding(MCAssembler &Asm, const MCAsmLayout &Layout);
void RecordRelocation(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
const MCFixup &Fixup,
MCValue Target,
uint64_t &FixedValue);
void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
};
}
static inline void write_uint32_le(void *Data, uint32_t const &Value) {
uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
Ptr[0] = (Value & 0x000000FF) >> 0;
Ptr[1] = (Value & 0x0000FF00) >> 8;
Ptr[2] = (Value & 0x00FF0000) >> 16;
Ptr[3] = (Value & 0xFF000000) >> 24;
}
static inline void write_uint16_le(void *Data, uint16_t const &Value) {
uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
Ptr[0] = (Value & 0x00FF) >> 0;
Ptr[1] = (Value & 0xFF00) >> 8;
}
static inline void write_uint8_le(void *Data, uint8_t const &Value) {
uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
Ptr[0] = (Value & 0xFF) >> 0;
}
//------------------------------------------------------------------------------
// Symbol class implementation
COFFSymbol::COFFSymbol(StringRef name)
: Name(name.begin(), name.end())
, Other(NULL)
, Section(NULL)
, Relocations(0)
, MCData(NULL) {
memset(&Data, 0, sizeof(Data));
}
size_t COFFSymbol::size() const {
return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
}
// In the case that the name does not fit within 8 bytes, the offset
// into the string table is stored in the last 4 bytes instead, leaving
// the first 4 bytes as 0.
void COFFSymbol::set_name_offset(uint32_t Offset) {
write_uint32_le(Data.Name + 0, 0);
write_uint32_le(Data.Name + 4, Offset);
}
/// logic to decide if the symbol should be reported in the symbol table
bool COFFSymbol::should_keep() const {
// no section means its external, keep it
if (Section == NULL)
return true;
// if it has relocations pointing at it, keep it
if (Relocations > 0) {
assert(Section->Number != -1 && "Sections with relocations must be real!");
return true;
}
// if the section its in is being droped, drop it
if (Section->Number == -1)
return false;
// if it is the section symbol, keep it
if (Section->Symbol == this)
return true;
// if its temporary, drop it
if (MCData && MCData->getSymbol().isTemporary())
return false;
// otherwise, keep it
return true;
}
//------------------------------------------------------------------------------
// Section class implementation
COFFSection::COFFSection(StringRef name)
: Name(name)
, MCData(NULL)
, Symbol(NULL) {
memset(&Header, 0, sizeof(Header));
}
size_t COFFSection::size() {
return COFF::SectionSize;
}
//------------------------------------------------------------------------------
// StringTable class implementation
/// Write the length of the string table into Data.
/// The length of the string table includes uint32 length header.
void StringTable::update_length() {
write_uint32_le(&Data.front(), Data.size());
}
StringTable::StringTable() {
// The string table data begins with the length of the entire string table
// including the length header. Allocate space for this header.
Data.resize(4);
update_length();
}
size_t StringTable::size() const {
return Data.size();
}
/// Add String to the table iff it is not already there.
/// @returns the index into the string table where the string is now located.
size_t StringTable::insert(StringRef String) {
map::iterator i = Map.find(String);
if (i != Map.end())
return i->second;
size_t Offset = Data.size();
// Insert string data into string table.
Data.insert(Data.end(), String.begin(), String.end());
Data.push_back('\0');
// Put a reference to it in the map.
Map[String] = Offset;
// Update the internal length field.
update_length();
return Offset;
}
//------------------------------------------------------------------------------
// WinCOFFObjectWriter class implementation
WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
raw_ostream &OS)
: MCObjectWriter(OS, true)
, TargetObjectWriter(MOTW) {
memset(&Header, 0, sizeof(Header));
Header.Machine = TargetObjectWriter->getMachine();
}
WinCOFFObjectWriter::~WinCOFFObjectWriter() {
for (symbols::iterator I = Symbols.begin(), E = Symbols.end(); I != E; ++I)
delete *I;
for (sections::iterator I = Sections.begin(), E = Sections.end(); I != E; ++I)
delete *I;
}
COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
return createCOFFEntity<COFFSymbol>(Name, Symbols);
}
COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
symbol_map::iterator i = SymbolMap.find(Symbol);
if (i != SymbolMap.end())
return i->second;
COFFSymbol *RetSymbol
= createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
SymbolMap[Symbol] = RetSymbol;
return RetSymbol;
}
COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
return createCOFFEntity<COFFSection>(Name, Sections);
}
/// A template used to lookup or create a symbol/section, and initialize it if
/// needed.
template <typename object_t, typename list_t>
object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
list_t &List) {
object_t *Object = new object_t(Name);
List.push_back(Object);
return Object;
}
/// This function takes a section data object from the assembler
/// and creates the associated COFF section staging object.
void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
&& "Got non COFF section in the COFF backend!");
// FIXME: Not sure how to verify this (at least in a debug build).
MCSectionCOFF const &Sec =
static_cast<MCSectionCOFF const &>(SectionData.getSection());
COFFSection *coff_section = createSection(Sec.getSectionName());
COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
coff_section->Symbol = coff_symbol;
coff_symbol->Section = coff_section;
coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
// In this case the auxiliary symbol is a Section Definition.
coff_symbol->Aux.resize(1);
memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
coff_symbol->Aux[0].AuxType = ATSectionDefinition;
coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
coff_section->Header.Characteristics = Sec.getCharacteristics();
uint32_t &Characteristics = coff_section->Header.Characteristics;
switch (SectionData.getAlignment()) {
case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
default:
llvm_unreachable("unsupported section alignment");
}
// Bind internal COFF section to MC section.
coff_section->MCData = &SectionData;
SectionMap[&SectionData.getSection()] = coff_section;
}
/// This function takes a section data object from the assembler
/// and creates the associated COFF symbol staging object.
void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
MCAssembler &Assembler) {
MCSymbol const &Symbol = SymbolData.getSymbol();
COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
SymbolMap[&Symbol] = coff_symbol;
if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
if (Symbol.isVariable()) {
const MCSymbolRefExpr *SymRef =
dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
if (!SymRef)
report_fatal_error("Weak externals may only alias symbols");
coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
} else {
std::string WeakName = std::string(".weak.")
+ Symbol.getName().str()
+ ".default";
COFFSymbol *WeakDefault = createSymbol(WeakName);
WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
WeakDefault->Data.Type = 0;
WeakDefault->Data.Value = 0;
coff_symbol->Other = WeakDefault;
}
// Setup the Weak External auxiliary symbol.
coff_symbol->Aux.resize(1);
memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
coff_symbol->Aux[0].AuxType = ATWeakExternal;
coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
coff_symbol->MCData = &SymbolData;
} else {
const MCSymbolData &ResSymData =
Assembler.getSymbolData(Symbol.AliasedSymbol());
coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
// If no storage class was specified in the streamer, define it here.
if (coff_symbol->Data.StorageClass == 0) {
bool external = ResSymData.isExternal() || (ResSymData.Fragment == NULL);
coff_symbol->Data.StorageClass =
external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
}
if (ResSymData.Fragment != NULL)
coff_symbol->Section =
SectionMap[&ResSymData.Fragment->getParent()->getSection()];
coff_symbol->MCData = &ResSymData;
}
}
/// making a section real involves assigned it a number and putting
/// name into the string table if needed
void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
if (S.Name.size() > COFF::NameSize) {
size_t StringTableEntry = Strings.insert(S.Name.c_str());
// FIXME: Why is this number 999999? This number is never mentioned in the
// spec. I'm assuming this is due to the printed value needing to fit into
// the S.Header.Name field. In which case why not 9999999 (7 9's instead of
// 6)? The spec does not state if this entry should be null terminated in
// this case, and thus this seems to be the best way to do it. I think I
// just solved my own FIXME...
if (StringTableEntry > 999999)
report_fatal_error("COFF string table is greater than 999999 bytes.");
std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
} else
std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
S.Number = Number;
S.Symbol->Data.SectionNumber = S.Number;
S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
}
void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
if (S.Name.size() > COFF::NameSize) {
size_t StringTableEntry = Strings.insert(S.Name.c_str());
S.set_name_offset(StringTableEntry);
} else
std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
S.Index = Index;
}
bool WinCOFFObjectWriter::ExportSection(COFFSection const *S) {
return !S->MCData->getFragmentList().empty();
}
bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
MCAssembler &Asm) {
// This doesn't seem to be right. Strings referred to from the .data section
// need symbols so they can be linked to code in the .text section right?
// return Asm.isSymbolLinkerVisible (&SymbolData);
// For now, all non-variable symbols are exported,
// the linker will sort the rest out for us.
return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
}
bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
return (S->Header.Characteristics
& COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
}
//------------------------------------------------------------------------------
// entity writing methods
void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
WriteLE16(Header.Machine);
WriteLE16(Header.NumberOfSections);
WriteLE32(Header.TimeDateStamp);
WriteLE32(Header.PointerToSymbolTable);
WriteLE32(Header.NumberOfSymbols);
WriteLE16(Header.SizeOfOptionalHeader);
WriteLE16(Header.Characteristics);
}
void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol *S) {
WriteBytes(StringRef(S->Data.Name, COFF::NameSize));
WriteLE32(S->Data.Value);
WriteLE16(S->Data.SectionNumber);
WriteLE16(S->Data.Type);
Write8(S->Data.StorageClass);
Write8(S->Data.NumberOfAuxSymbols);
WriteAuxiliarySymbols(S->Aux);
}
void WinCOFFObjectWriter::WriteAuxiliarySymbols(
const COFFSymbol::AuxiliarySymbols &S) {
for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
i != e; ++i) {
switch(i->AuxType) {
case ATFunctionDefinition:
WriteLE32(i->Aux.FunctionDefinition.TagIndex);
WriteLE32(i->Aux.FunctionDefinition.TotalSize);
WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
break;
case ATbfAndefSymbol:
WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
break;
case ATWeakExternal:
WriteLE32(i->Aux.WeakExternal.TagIndex);
WriteLE32(i->Aux.WeakExternal.Characteristics);
WriteZeros(sizeof(i->Aux.WeakExternal.unused));
break;
case ATFile:
WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
sizeof(i->Aux.File.FileName)));
break;
case ATSectionDefinition:
WriteLE32(i->Aux.SectionDefinition.Length);
WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
WriteLE32(i->Aux.SectionDefinition.CheckSum);
WriteLE16(i->Aux.SectionDefinition.Number);
Write8(i->Aux.SectionDefinition.Selection);
WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
break;
}
}
}
void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
WriteBytes(StringRef(S.Name, COFF::NameSize));
WriteLE32(S.VirtualSize);
WriteLE32(S.VirtualAddress);
WriteLE32(S.SizeOfRawData);
WriteLE32(S.PointerToRawData);
WriteLE32(S.PointerToRelocations);
WriteLE32(S.PointerToLineNumbers);
WriteLE16(S.NumberOfRelocations);
WriteLE16(S.NumberOfLineNumbers);
WriteLE32(S.Characteristics);
}
void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
WriteLE32(R.VirtualAddress);
WriteLE32(R.SymbolTableIndex);
WriteLE16(R.Type);
}
////////////////////////////////////////////////////////////////////////////////
// MCObjectWriter interface implementations
void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
const MCAsmLayout &Layout) {
// "Define" each section & symbol. This creates section & symbol
// entries in the staging area.
for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; i++)
DefineSection(*i);
for (MCAssembler::const_symbol_iterator i = Asm.symbol_begin(),
e = Asm.symbol_end(); i != e; i++) {
if (ExportSymbol(*i, Asm)) {
DefineSymbol(*i, Asm);
}
}
}
void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
const MCFixup &Fixup,
MCValue Target,
uint64_t &FixedValue) {
assert(Target.getSymA() != NULL && "Relocation must reference a symbol!");
const MCSymbol *A = &Target.getSymA()->getSymbol();
MCSymbolData &A_SD = Asm.getSymbolData(*A);
MCSectionData const *SectionData = Fragment->getParent();
// Mark this symbol as requiring an entry in the symbol table.
assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
"Section must already have been defined in ExecutePostLayoutBinding!");
assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
"Symbol must already have been defined in ExecutePostLayoutBinding!");
COFFSection *coff_section = SectionMap[&SectionData->getSection()];
COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
const MCSymbolRefExpr *SymA = Target.getSymA();
const MCSymbolRefExpr *SymB = Target.getSymB();
const bool CrossSection = SymB &&
&SymA->getSymbol().getSection() != &SymB->getSymbol().getSection();
if (Target.getSymB()) {
const MCSymbol *B = &Target.getSymB()->getSymbol();
MCSymbolData &B_SD = Asm.getSymbolData(*B);
// Offset of the symbol in the section
int64_t a = Layout.getSymbolOffset(&B_SD);
// Ofeset of the relocation in the section
int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
FixedValue = b - a;
// In the case where we have SymbA and SymB, we just need to store the delta
// between the two symbols. Update FixedValue to account for the delta, and
// skip recording the relocation.
if (!CrossSection)
return;
} else {
FixedValue = Target.getConstant();
}
COFFRelocation Reloc;
Reloc.Data.SymbolTableIndex = 0;
Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
// Turn relocations for temporary symbols into section relocations.
if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
Reloc.Symb = coff_symbol->Section->Symbol;
FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
+ coff_symbol->MCData->getOffset();
} else
Reloc.Symb = coff_symbol;
++Reloc.Symb->Relocations;
Reloc.Data.VirtualAddress += Fixup.getOffset();
Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
CrossSection);
// FIXME: Can anyone explain what this does other than adjust for the size
// of the offset?
if (Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32 ||
Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)
FixedValue += 4;
coff_section->Relocations.push_back(Reloc);
}
void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
const MCAsmLayout &Layout) {
// Assign symbol and section indexes and offsets.
Header.NumberOfSections = 0;
for (sections::iterator i = Sections.begin(),
e = Sections.end(); i != e; i++) {
if (Layout.getSectionAddressSize((*i)->MCData) > 0) {
MakeSectionReal(**i, ++Header.NumberOfSections);
} else {
(*i)->Number = -1;
}
}
Header.NumberOfSymbols = 0;
for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
COFFSymbol *coff_symbol = *i;
MCSymbolData const *SymbolData = coff_symbol->MCData;
// Update section number & offset for symbols that have them.
if ((SymbolData != NULL) && (SymbolData->Fragment != NULL)) {
assert(coff_symbol->Section != NULL);
coff_symbol->Data.SectionNumber = coff_symbol->Section->Number;
coff_symbol->Data.Value = Layout.getFragmentOffset(SymbolData->Fragment)
+ SymbolData->Offset;
}
if (coff_symbol->should_keep()) {
MakeSymbolReal(*coff_symbol, Header.NumberOfSymbols++);
// Update auxiliary symbol info.
coff_symbol->Data.NumberOfAuxSymbols = coff_symbol->Aux.size();
Header.NumberOfSymbols += coff_symbol->Data.NumberOfAuxSymbols;
} else
coff_symbol->Index = -1;
}
// Fixup weak external references.
for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
COFFSymbol *coff_symbol = *i;
if (coff_symbol->Other != NULL) {
assert(coff_symbol->Index != -1);
assert(coff_symbol->Aux.size() == 1 &&
"Symbol must contain one aux symbol!");
assert(coff_symbol->Aux[0].AuxType == ATWeakExternal &&
"Symbol's aux symbol must be a Weak External!");
coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = coff_symbol->Other->Index;
}
}
// Assign file offsets to COFF object file structures.
unsigned offset = 0;
offset += COFF::HeaderSize;
offset += COFF::SectionSize * Header.NumberOfSections;
for (MCAssembler::const_iterator i = Asm.begin(),
e = Asm.end();
i != e; i++) {
COFFSection *Sec = SectionMap[&i->getSection()];
if (Sec->Number == -1)
continue;
Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(i);
if (IsPhysicalSection(Sec)) {
Sec->Header.PointerToRawData = offset;
offset += Sec->Header.SizeOfRawData;
}
if (Sec->Relocations.size() > 0) {
bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
if (RelocationsOverflow) {
// Signal overflow by setting NumberOfSections to max value. Actual
// size is found in reloc #0. Microsoft tools understand this.
Sec->Header.NumberOfRelocations = 0xffff;
} else {
Sec->Header.NumberOfRelocations = Sec->Relocations.size();
}
Sec->Header.PointerToRelocations = offset;
if (RelocationsOverflow) {
// Reloc #0 will contain actual count, so make room for it.
offset += COFF::RelocationSize;
}
offset += COFF::RelocationSize * Sec->Relocations.size();
for (relocations::iterator cr = Sec->Relocations.begin(),
er = Sec->Relocations.end();
cr != er; ++cr) {
assert((*cr).Symb->Index != -1);
(*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
}
}
assert(Sec->Symbol->Aux.size() == 1
&& "Section's symbol must have one aux!");
AuxSymbol &Aux = Sec->Symbol->Aux[0];
assert(Aux.AuxType == ATSectionDefinition &&
"Section's symbol's aux symbol must be a Section Definition!");
Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
Aux.Aux.SectionDefinition.NumberOfRelocations =
Sec->Header.NumberOfRelocations;
Aux.Aux.SectionDefinition.NumberOfLinenumbers =
Sec->Header.NumberOfLineNumbers;
}
Header.PointerToSymbolTable = offset;
Header.TimeDateStamp = sys::TimeValue::now().toEpochTime();
// Write it all to disk...
WriteFileHeader(Header);
{
sections::iterator i, ie;
MCAssembler::const_iterator j, je;
for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
if ((*i)->Number != -1) {
if ((*i)->Relocations.size() >= 0xffff) {
(*i)->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
}
WriteSectionHeader((*i)->Header);
}
for (i = Sections.begin(), ie = Sections.end(),
j = Asm.begin(), je = Asm.end();
(i != ie) && (j != je); ++i, ++j) {
if ((*i)->Number == -1)
continue;
if ((*i)->Header.PointerToRawData != 0) {
assert(OS.tell() == (*i)->Header.PointerToRawData &&
"Section::PointerToRawData is insane!");
Asm.writeSectionData(j, Layout);
}
if ((*i)->Relocations.size() > 0) {
assert(OS.tell() == (*i)->Header.PointerToRelocations &&
"Section::PointerToRelocations is insane!");
if ((*i)->Relocations.size() >= 0xffff) {
// In case of overflow, write actual relocation count as first
// relocation. Including the synthetic reloc itself (+ 1).
COFF::relocation r;
r.VirtualAddress = (*i)->Relocations.size() + 1;
r.SymbolTableIndex = 0;
r.Type = 0;
WriteRelocation(r);
}
for (relocations::const_iterator k = (*i)->Relocations.begin(),
ke = (*i)->Relocations.end();
k != ke; k++) {
WriteRelocation(k->Data);
}
} else
assert((*i)->Header.PointerToRelocations == 0 &&
"Section::PointerToRelocations is insane!");
}
}
assert(OS.tell() == Header.PointerToSymbolTable &&
"Header::PointerToSymbolTable is insane!");
for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
if ((*i)->Index != -1)
WriteSymbol(*i);
OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
}
MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
Machine(Machine_) {
}
//------------------------------------------------------------------------------
// WinCOFFObjectWriter factory function
namespace llvm {
MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
raw_ostream &OS) {
return new WinCOFFObjectWriter(MOTW, OS);
}
}
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