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llvm-project/llvm/lib/MC/WinCOFFObjectWriter.cpp

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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.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCWinCOFFObjectWriter.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Config/config.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSymbolCOFF.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Support/COFF.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/JamCRC.h"
#include "llvm/Support/TimeValue.h"
#include <cstdio>
#include <ctime>
using namespace llvm;
#define DEBUG_TYPE "WinCOFFObjectWriter"
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;
const MCSymbol *MC;
COFFSymbol(StringRef name);
void set_name_offset(uint32_t Offset);
int64_t getIndex() const { return Index; }
void setIndex(int Value) {
Index = Value;
if (MC)
MC->setIndex(static_cast<uint32_t>(Value));
}
};
// This class contains staging data for a COFF relocation entry.
struct COFFRelocation {
COFF::relocation Data;
COFFSymbol *Symb;
COFFRelocation() : Symb(nullptr) {}
static size_t size() { return COFF::RelocationSize; }
};
typedef std::vector<COFFRelocation> relocations;
class COFFSection {
public:
COFF::section Header;
std::string Name;
int Number;
MCSectionCOFF const *MCSection;
COFFSymbol *Symbol;
relocations Relocations;
COFFSection(StringRef name);
static size_t size();
};
class WinCOFFObjectWriter : public MCObjectWriter {
public:
typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
typedef std::vector<std::unique_ptr<COFFSection>> sections;
typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
typedef DenseMap<MCSection const *, COFFSection *> section_map;
std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
// Root level file contents.
COFF::header Header;
sections Sections;
symbols Symbols;
StringTableBuilder Strings{StringTableBuilder::WinCOFF};
// Maps used during object file creation.
section_map SectionMap;
symbol_map SymbolMap;
bool UseBigObj;
WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS);
void reset() override {
memset(&Header, 0, sizeof(Header));
Header.Machine = TargetObjectWriter->getMachine();
Sections.clear();
Symbols.clear();
Strings.clear();
SectionMap.clear();
SymbolMap.clear();
MCObjectWriter::reset();
}
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(MCSectionCOFF const &Sec);
COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
const MCAsmLayout &Layout);
void SetSymbolName(COFFSymbol &S);
void SetSectionName(COFFSection &S);
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) override;
bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
const MCSymbol &SymA,
const MCFragment &FB, bool InSet,
bool IsPCRel) const override;
bool isWeak(const MCSymbol &Sym) const override;
void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup,
MCValue Target, bool &IsPCRel,
uint64_t &FixedValue) override;
void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
};
}
static inline void write_uint32_le(void *Data, uint32_t Value) {
support::endian::write<uint32_t, support::little, support::unaligned>(Data,
Value);
}
//------------------------------------------------------------------------------
// Symbol class implementation
COFFSymbol::COFFSymbol(StringRef name)
: Name(name.begin(), name.end()), Other(nullptr), Section(nullptr),
Relocations(0), MC(nullptr) {
memset(&Data, 0, sizeof(Data));
}
// 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);
}
//------------------------------------------------------------------------------
// Section class implementation
COFFSection::COFFSection(StringRef name)
: Name(name), MCSection(nullptr), Symbol(nullptr) {
memset(&Header, 0, sizeof(Header));
}
size_t COFFSection::size() { return COFF::SectionSize; }
//------------------------------------------------------------------------------
// WinCOFFObjectWriter class implementation
WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
raw_pwrite_stream &OS)
: MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
memset(&Header, 0, sizeof(Header));
Header.Machine = TargetObjectWriter->getMachine();
}
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) {
List.push_back(make_unique<object_t>(Name));
return List.back().get();
}
/// This function takes a section data object from the assembler
/// and creates the associated COFF section staging object.
void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) {
COFFSection *coff_section = createSection(Sec.getSectionName());
COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
if (COMDATSymbol->Section)
report_fatal_error("two sections have the same comdat");
COMDATSymbol->Section = coff_section;
}
}
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 (Sec.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->MCSection = &Sec;
SectionMap[&Sec] = coff_section;
}
static uint64_t getSymbolValue(const MCSymbol &Symbol,
const MCAsmLayout &Layout) {
if (Symbol.isCommon() && Symbol.isExternal())
return Symbol.getCommonSize();
uint64_t Res;
if (!Layout.getSymbolOffset(Symbol, Res))
return 0;
return Res;
}
COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) {
if (!Symbol.isVariable())
return nullptr;
const MCSymbolRefExpr *SymRef =
dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
if (!SymRef)
return nullptr;
const MCSymbol &Aliasee = SymRef->getSymbol();
if (!Aliasee.isUndefined())
return nullptr;
return GetOrCreateCOFFSymbol(&Aliasee);
}
/// This function takes a symbol data object from the assembler
/// and creates the associated COFF symbol staging object.
void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
MCAssembler &Assembler,
const MCAsmLayout &Layout) {
COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
COFFSection *Sec = nullptr;
if (Base && Base->getFragment()) {
Sec = SectionMap[Base->getFragment()->getParent()];
if (coff_symbol->Section && coff_symbol->Section != Sec)
report_fatal_error("conflicting sections for symbol");
}
COFFSymbol *Local = nullptr;
if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) {
coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
COFFSymbol *WeakDefault = getLinkedSymbol(Symbol);
if (!WeakDefault) {
std::string WeakName = (".weak." + Symbol.getName() + ".default").str();
WeakDefault = createSymbol(WeakName);
if (!Sec)
WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
else
WeakDefault->Section = Sec;
Local = WeakDefault;
}
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;
} else {
if (!Base)
coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
else
coff_symbol->Section = Sec;
Local = coff_symbol;
}
if (Local) {
Local->Data.Value = getSymbolValue(Symbol, Layout);
const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol);
Local->Data.Type = SymbolCOFF.getType();
Local->Data.StorageClass = SymbolCOFF.getClass();
// If no storage class was specified in the streamer, define it here.
if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
bool IsExternal = Symbol.isExternal() ||
(!Symbol.getFragment() && !Symbol.isVariable());
Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
: COFF::IMAGE_SYM_CLASS_STATIC;
}
}
coff_symbol->MC = &Symbol;
}
// Maximum offsets for different string table entry encodings.
enum : unsigned { Max7DecimalOffset = 9999999U };
enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0
// Encode a string table entry offset in base 64, padded to 6 chars, and
// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
// Buffer must be at least 8 bytes large. No terminating null appended.
static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
"Illegal section name encoding for value");
static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
Buffer[0] = '/';
Buffer[1] = '/';
char *Ptr = Buffer + 7;
for (unsigned i = 0; i < 6; ++i) {
unsigned Rem = Value % 64;
Value /= 64;
*(Ptr--) = Alphabet[Rem];
}
}
void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
if (S.Name.size() > COFF::NameSize) {
uint64_t StringTableEntry = Strings.getOffset(S.Name);
if (StringTableEntry <= Max7DecimalOffset) {
SmallVector<char, COFF::NameSize> Buffer;
Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer);
assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
std::memcpy(S.Header.Name, Buffer.data(), Buffer.size());
} else if (StringTableEntry <= MaxBase64Offset) {
// Starting with 10,000,000, offsets are encoded as base64.
encodeBase64StringEntry(S.Header.Name, StringTableEntry);
} else {
report_fatal_error("COFF string table is greater than 64 GB.");
}
} else {
std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
}
}
void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
if (S.Name.size() > COFF::NameSize)
S.set_name_offset(Strings.getOffset(S.Name));
else
std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
}
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) {
if (UseBigObj) {
writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
writeLE16(0xFFFF);
writeLE16(COFF::BigObjHeader::MinBigObjectVersion);
writeLE16(Header.Machine);
writeLE32(Header.TimeDateStamp);
writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic)));
writeLE32(0);
writeLE32(0);
writeLE32(0);
writeLE32(0);
writeLE32(Header.NumberOfSections);
writeLE32(Header.PointerToSymbolTable);
writeLE32(Header.NumberOfSymbols);
} else {
writeLE16(Header.Machine);
writeLE16(static_cast<int16_t>(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);
if (UseBigObj)
writeLE32(S.Data.SectionNumber);
else
writeLE16(static_cast<int16_t>(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));
if (UseBigObj)
WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
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));
if (UseBigObj)
WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
break;
case ATWeakExternal:
writeLE32(i->Aux.WeakExternal.TagIndex);
writeLE32(i->Aux.WeakExternal.Characteristics);
WriteZeros(sizeof(i->Aux.WeakExternal.unused));
if (UseBigObj)
WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
break;
case ATFile:
writeBytes(
StringRef(reinterpret_cast<const char *>(&i->Aux),
UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
break;
case ATSectionDefinition:
writeLE32(i->Aux.SectionDefinition.Length);
writeLE16(i->Aux.SectionDefinition.NumberOfRelocations);
writeLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
writeLE32(i->Aux.SectionDefinition.CheckSum);
writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
write8(i->Aux.SectionDefinition.Selection);
WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
if (UseBigObj)
WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
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 (const auto &Section : Asm)
defineSection(static_cast<const MCSectionCOFF &>(Section));
for (const MCSymbol &Symbol : Asm.symbols())
if (!Symbol.isTemporary())
DefineSymbol(Symbol, Asm, Layout);
}
bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
bool InSet, bool IsPCRel) const {
// MS LINK expects to be able to replace all references to a function with a
// thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
// away any relocations to functions.
uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
if (Asm.isIncrementalLinkerCompatible() &&
(Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
return false;
return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
InSet, IsPCRel);
}
bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const {
if (!Sym.isExternal())
return false;
if (!Sym.isInSection())
return false;
const auto &Sec = cast<MCSectionCOFF>(Sym.getSection());
if (!Sec.getCOMDATSymbol())
return false;
// It looks like for COFF it is invalid to replace a reference to a global
// in a comdat with a reference to a local.
// FIXME: Add a specification reference if available.
return true;
}
void WinCOFFObjectWriter::recordRelocation(
MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
assert(Target.getSymA() && "Relocation must reference a symbol!");
const MCSymbol &A = Target.getSymA()->getSymbol();
if (!A.isRegistered()) {
Asm.getContext().reportError(Fixup.getLoc(),
Twine("symbol '") + A.getName() +
"' can not be undefined");
return;
}
if (A.isTemporary() && A.isUndefined()) {
Asm.getContext().reportError(Fixup.getLoc(),
Twine("assembler label '") + A.getName() +
"' can not be undefined");
return;
}
MCSection *Section = Fragment->getParent();
// Mark this symbol as requiring an entry in the symbol table.
assert(SectionMap.find(Section) != SectionMap.end() &&
"Section must already have been defined in executePostLayoutBinding!");
COFFSection *coff_section = SectionMap[Section];
const MCSymbolRefExpr *SymB = Target.getSymB();
bool CrossSection = false;
if (SymB) {
const MCSymbol *B = &SymB->getSymbol();
if (!B->getFragment()) {
Asm.getContext().reportError(
Fixup.getLoc(),
Twine("symbol '") + B->getName() +
"' can not be undefined in a subtraction expression");
return;
}
if (!A.getFragment()) {
Asm.getContext().reportError(
Fixup.getLoc(),
Twine("symbol '") + A.getName() +
"' can not be undefined in a subtraction expression");
return;
}
CrossSection = &A.getSection() != &B->getSection();
// Offset of the symbol in the section
int64_t OffsetOfB = Layout.getSymbolOffset(*B);
// 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) {
int64_t OffsetOfA = Layout.getSymbolOffset(A);
FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant();
return;
}
// Offset of the relocation in the section
int64_t OffsetOfRelocation =
Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
} 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 (A.isTemporary() || CrossSection) {
MCSection *TargetSection = &A.getSection();
assert(
SectionMap.find(TargetSection) != SectionMap.end() &&
"Section must already have been defined in executePostLayoutBinding!");
Reloc.Symb = SectionMap[TargetSection]->Symbol;
FixedValue += Layout.getSymbolOffset(A);
} else {
assert(
SymbolMap.find(&A) != SymbolMap.end() &&
"Symbol must already have been defined in executePostLayoutBinding!");
Reloc.Symb = SymbolMap[&A];
}
++Reloc.Symb->Relocations;
Reloc.Data.VirtualAddress += Fixup.getOffset();
Reloc.Data.Type = TargetObjectWriter->getRelocType(
Target, Fixup, CrossSection, Asm.getBackend());
// FIXME: Can anyone explain what this does other than adjust for the size
// of the offset?
if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
(Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
FixedValue += 4;
if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
switch (Reloc.Data.Type) {
case COFF::IMAGE_REL_ARM_ABSOLUTE:
case COFF::IMAGE_REL_ARM_ADDR32:
case COFF::IMAGE_REL_ARM_ADDR32NB:
case COFF::IMAGE_REL_ARM_TOKEN:
case COFF::IMAGE_REL_ARM_SECTION:
case COFF::IMAGE_REL_ARM_SECREL:
break;
case COFF::IMAGE_REL_ARM_BRANCH11:
case COFF::IMAGE_REL_ARM_BLX11:
// IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
// pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
// for Windows CE).
case COFF::IMAGE_REL_ARM_BRANCH24:
case COFF::IMAGE_REL_ARM_BLX24:
case COFF::IMAGE_REL_ARM_MOV32A:
// IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
// only used for ARM mode code, which is documented as being unsupported
// by Windows on ARM. Empirical proof indicates that masm is able to
// generate the relocations however the rest of the MSVC toolchain is
// unable to handle it.
llvm_unreachable("unsupported relocation");
break;
case COFF::IMAGE_REL_ARM_MOV32T:
break;
case COFF::IMAGE_REL_ARM_BRANCH20T:
case COFF::IMAGE_REL_ARM_BRANCH24T:
case COFF::IMAGE_REL_ARM_BLX23T:
// IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
// perform a 4 byte adjustment to the relocation. Relative branches are
// offset by 4 on ARM, however, because there is no RELA relocations, all
// branches are offset by 4.
FixedValue = FixedValue + 4;
break;
}
}
// The fixed value never makes sense for section indicies, ignore it.
if (Fixup.getKind() == FK_SecRel_2)
FixedValue = 0;
if (TargetObjectWriter->recordRelocation(Fixup))
coff_section->Relocations.push_back(Reloc);
}
void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
const MCAsmLayout &Layout) {
size_t SectionsSize = Sections.size();
if (SectionsSize > static_cast<size_t>(INT32_MAX))
report_fatal_error(
"PE COFF object files can't have more than 2147483647 sections");
// Assign symbol and section indexes and offsets.
int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
// Assign section numbers.
size_t Number = 1;
for (const auto &Section : Sections) {
Section->Number = Number;
Section->Symbol->Data.SectionNumber = Number;
Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
++Number;
}
Header.NumberOfSections = NumberOfSections;
Header.NumberOfSymbols = 0;
for (const std::string &Name : Asm.getFileNames()) {
// round up to calculate the number of auxiliary symbols required
unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
COFFSymbol *file = createSymbol(".file");
file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
file->Aux.resize(Count);
unsigned Offset = 0;
unsigned Length = Name.size();
for (auto &Aux : file->Aux) {
Aux.AuxType = ATFile;
if (Length > SymbolSize) {
memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
Length = Length - SymbolSize;
} else {
memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
break;
}
Offset += SymbolSize;
}
}
for (auto &Symbol : Symbols) {
// Update section number & offset for symbols that have them.
if (Symbol->Section)
Symbol->Data.SectionNumber = Symbol->Section->Number;
Symbol->setIndex(Header.NumberOfSymbols++);
// Update auxiliary symbol info.
Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
}
// Build string table.
for (const auto &S : Sections)
if (S->Name.size() > COFF::NameSize)
Strings.add(S->Name);
for (const auto &S : Symbols)
if (S->Name.size() > COFF::NameSize)
Strings.add(S->Name);
Strings.finalize();
// Set names.
for (const auto &S : Sections)
SetSectionName(*S);
for (auto &S : Symbols)
SetSymbolName(*S);
// Fixup weak external references.
for (auto &Symbol : Symbols) {
if (Symbol->Other) {
assert(Symbol->getIndex() != -1);
assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
"Symbol's aux symbol must be a Weak External!");
Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
}
}
// Fixup associative COMDAT sections.
for (auto &Section : Sections) {
if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
continue;
const MCSectionCOFF &MCSec = *Section->MCSection;
const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
assert(COMDAT);
COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
assert(COMDATSymbol);
COFFSection *Assoc = COMDATSymbol->Section;
if (!Assoc)
report_fatal_error(
Twine("Missing associated COMDAT section for section ") +
MCSec.getSectionName());
// Skip this section if the associated section is unused.
if (Assoc->Number == -1)
continue;
Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
}
// Assign file offsets to COFF object file structures.
unsigned offset = getInitialOffset();
if (UseBigObj)
offset += COFF::Header32Size;
else
offset += COFF::Header16Size;
offset += COFF::SectionSize * Header.NumberOfSections;
for (const auto &Section : Asm) {
COFFSection *Sec = SectionMap[&Section];
if (Sec->Number == -1)
continue;
Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
if (IsPhysicalSection(Sec)) {
// Align the section data to a four byte boundary.
offset = alignTo(offset, 4);
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 NumberOfRelocations 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 (auto &Relocation : Sec->Relocations) {
assert(Relocation.Symb->getIndex() != -1);
Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
}
}
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;
// MS LINK expects to be able to use this timestamp to implement their
// /INCREMENTAL feature.
if (Asm.isIncrementalLinkerCompatible()) {
std::time_t Now = time(nullptr);
if (Now < 0 || !isUInt<32>(Now))
Now = UINT32_MAX;
Header.TimeDateStamp = Now;
} else {
// Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
Header.TimeDateStamp = 0;
}
// Write it all to disk...
WriteFileHeader(Header);
{
sections::iterator i, ie;
MCAssembler::iterator j, je;
for (auto &Section : Sections) {
if (Section->Number != -1) {
if (Section->Relocations.size() >= 0xffff)
Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
writeSectionHeader(Section->Header);
}
}
SmallVector<char, 128> SectionContents;
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(getStream().tell() <= (*i)->Header.PointerToRawData &&
"Section::PointerToRawData is insane!");
unsigned SectionDataPadding =
(*i)->Header.PointerToRawData - getStream().tell();
assert(SectionDataPadding < 4 &&
"Should only need at most three bytes of padding!");
WriteZeros(SectionDataPadding);
// Save the contents of the section to a temporary buffer, we need this
// to CRC the data before we dump it into the object file.
SectionContents.clear();
raw_svector_ostream VecOS(SectionContents);
raw_pwrite_stream &OldStream = getStream();
// Redirect the output stream to our buffer.
setStream(VecOS);
// Fill our buffer with the section data.
Asm.writeSectionData(&*j, Layout);
// Reset the stream back to what it was before.
setStream(OldStream);
// Calculate our CRC with an initial value of '0', this is not how
// JamCRC is specified but it aligns with the expected output.
JamCRC JC(/*Init=*/0x00000000U);
JC.update(SectionContents);
// Write the section contents to the object file.
getStream() << SectionContents;
// Update the section definition auxiliary symbol to record the CRC.
COFFSection *Sec = SectionMap[&*j];
COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
assert(AuxSyms.size() == 1 &&
AuxSyms[0].AuxType == ATSectionDefinition);
AuxSymbol &SecDef = AuxSyms[0];
SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC();
}
if ((*i)->Relocations.size() > 0) {
assert(getStream().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 (const auto &Relocation : (*i)->Relocations)
WriteRelocation(Relocation.Data);
} else
assert((*i)->Header.PointerToRelocations == 0 &&
"Section::PointerToRelocations is insane!");
}
}
assert(getStream().tell() == Header.PointerToSymbolTable &&
"Header::PointerToSymbolTable is insane!");
for (auto &Symbol : Symbols)
if (Symbol->getIndex() != -1)
WriteSymbol(*Symbol);
getStream().write(Strings.data().data(), Strings.data().size());
}
MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
: Machine(Machine_) {}
// Pin the vtable to this file.
void MCWinCOFFObjectTargetWriter::anchor() {}
//------------------------------------------------------------------------------
// WinCOFFObjectWriter factory function
MCObjectWriter *
llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
raw_pwrite_stream &OS) {
return new WinCOFFObjectWriter(MOTW, OS);
}
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