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llvm-6502/lib/MC/WinCOFFObjectWriter.cpp
Saleem Abdulrasool 3f6dea4864 ARM: fail less catastrophically on invalid Windows input 
Windows supports a restricted set of relocations (compared to ARM ELF).  In some
cases, we may end up generating an unsupported relocation.  This can occur with
bad input to the assembler in particular (the frontend should never generate
code that cannot be compiled).  Generate an error rather than just aborting.

The change in the API is driven by the desire to provide a slightly more helpful
message for debugging purposes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226779 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-22 04:03:32 +00:00

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36 KiB
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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/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/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/TimeValue.h"
#include <cstdio>
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;
MCSymbolData const *MCData;
COFFSymbol(StringRef name);
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(nullptr) {}
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();
};
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;
// Maps used during object file creation.
section_map SectionMap;
symbol_map SymbolMap;
bool UseBigObj;
WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &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(MCSectionData const &SectionData);
void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler,
const MCAsmLayout &Layout);
void SetSymbolName(COFFSymbol &S);
void SetSectionName(COFFSection &S);
bool ExportSymbol(const MCSymbol &Symbol, 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) override;
bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
const MCSymbolData &DataA,
const MCFragment &FB, bool InSet,
bool IsPCRel) 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)
, MCData(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);
}
/// 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)
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(nullptr)
, Symbol(nullptr) {
memset(&Header, 0, sizeof(Header));
}
size_t COFFSection::size() {
return COFF::SectionSize;
}
//------------------------------------------------------------------------------
// WinCOFFObjectWriter class implementation
WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
raw_ostream &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(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());
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 (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;
}
static uint64_t getSymbolValue(const MCSymbolData &Data,
const MCAsmLayout &Layout) {
if (Data.isCommon() && Data.isExternal())
return Data.getCommonSize();
uint64_t Res;
if (!Layout.getSymbolOffset(&Data, Res))
return 0;
return Res;
}
/// This function takes a symbol data object from the assembler
/// and creates the associated COFF symbol staging object.
void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
MCAssembler &Assembler,
const MCAsmLayout &Layout) {
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);
const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
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 IsExternal =
ResSymData.isExternal() ||
(!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable());
coff_symbol->Data.StorageClass = IsExternal
? COFF::IMAGE_SYM_CLASS_EXTERNAL
: COFF::IMAGE_SYM_CLASS_STATIC;
}
if (!Base) {
coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
} else {
const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
if (BaseData.getFragment()) {
COFFSection *Sec =
SectionMap[&BaseData.getFragment()->getParent()->getSection()];
if (coff_symbol->Section && coff_symbol->Section != Sec)
report_fatal_error("conflicting sections for symbol");
coff_symbol->Section = Sec;
}
}
coff_symbol->MCData = &ResSymData;
}
}
// Maximum offsets for different string table entry encodings.
static const unsigned Max6DecimalOffset = 999999;
static const unsigned Max7DecimalOffset = 9999999;
static const 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 <= Max6DecimalOffset) {
std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
} else if (StringTableEntry <= Max7DecimalOffset) {
// With seven digits, we have to skip the terminating null. Because
// sprintf always appends it, we use a larger temporary buffer.
char buffer[9] = { };
std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
std::memcpy(S.Header.Name, buffer, 8);
} 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::ExportSymbol(const MCSymbol &Symbol,
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(Symbol);
// Non-temporary labels should always be visible to the linker.
if (!Symbol.isTemporary())
return true;
// Absolute temporary labels are never visible.
if (!Symbol.isInSection())
return false;
// For now, all non-variable symbols are exported,
// the linker will sort the rest out for us.
return !Symbol.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) {
if (UseBigObj) {
WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
WriteLE16(0xFFFF);
WriteLE16(COFF::BigObjHeader::MinBigObjectVersion);
WriteLE16(Header.Machine);
WriteLE32(Header.TimeDateStamp);
for (uint8_t MagicChar : COFF::BigObjMagic)
Write8(MagicChar);
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(Section);
for (MCSymbolData &SD : Asm.symbols())
if (ExportSymbol(SD.getSymbol(), Asm))
DefineSymbol(SD, Asm, Layout);
}
bool WinCOFFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
const MCAssembler &Asm, const MCSymbolData &DataA, 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.
if ((((DataA.getFlags() & COFF::SF_TypeMask) >> COFF::SF_TypeShift) >>
COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
return false;
return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA, FB,
InSet, IsPCRel);
}
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 &Symbol = Target.getSymA()->getSymbol();
const MCSymbol &A = Symbol.AliasedSymbol();
if (!Asm.hasSymbolData(A))
Asm.getContext().FatalError(
Fixup.getLoc(),
Twine("symbol '") + A.getName() + "' can not be undefined");
const 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 *SymB = Target.getSymB();
bool CrossSection = false;
if (SymB) {
const MCSymbol *B = &SymB->getSymbol();
const MCSymbolData &B_SD = Asm.getSymbolData(*B);
if (!B_SD.getFragment())
Asm.getContext().FatalError(
Fixup.getLoc(),
Twine("symbol '") + B->getName() +
"' can not be undefined in a subtraction expression");
if (!A_SD.getFragment())
Asm.getContext().FatalError(
Fixup.getLoc(),
Twine("symbol '") + Symbol.getName() +
"' can not be undefined in a subtraction expression");
CrossSection = &Symbol.getSection() != &B->getSection();
// Offset of the symbol in the section
int64_t a = Layout.getSymbolOffset(&B_SD);
// Offset 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->getFragment()) +
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,
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;
}
}
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;
DenseMap<COFFSection *, int32_t> SectionIndices(
NextPowerOf2(NumberOfSections));
// Assign section numbers.
size_t Number = 1;
for (const auto &Section : Sections) {
SectionIndices[Section.get()] = Number;
Section->Number = Number;
Section->Symbol->Data.SectionNumber = Number;
Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
++Number;
}
Header.NumberOfSections = NumberOfSections;
Header.NumberOfSymbols = 0;
for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
FI != FE; ++FI) {
// round up to calculate the number of auxiliary symbols required
unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
unsigned Count = (FI->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 = FI->size();
for (auto &Aux : file->Aux) {
Aux.AuxType = ATFile;
if (Length > SymbolSize) {
memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize);
Length = Length - SymbolSize;
} else {
memcpy(&Aux.Aux, FI->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;
if (Symbol->should_keep()) {
Symbol->Index = Header.NumberOfSymbols++;
// Update auxiliary symbol info.
Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
} else
Symbol->Index = -1;
}
// 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->should_keep() && S->Name.size() > COFF::NameSize)
Strings.add(S->Name);
Strings.finalize(StringTableBuilder::WinCOFF);
// Set names.
for (const auto &S : Sections)
SetSectionName(*S);
for (auto &S : Symbols)
if (S->should_keep())
SetSymbolName(*S);
// Fixup weak external references.
for (auto &Symbol : Symbols) {
if (Symbol->Other) {
assert(Symbol->Index != -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->Index;
}
}
// 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 =
static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
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 = SectionIndices[Assoc];
}
// Assign file offsets to COFF object file structures.
unsigned offset = 0;
if (UseBigObj)
offset += COFF::Header32Size;
else
offset += COFF::Header16Size;
offset += COFF::SectionSize * Header.NumberOfSections;
for (const auto &Section : Asm) {
COFFSection *Sec = SectionMap[&Section.getSection()];
if (Sec->Number == -1)
continue;
Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
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 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->Index != -1);
Relocation.Data.SymbolTableIndex = Relocation.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;
// We want a deterministic output. It looks like GNU as also writes 0 in here.
Header.TimeDateStamp = 0;
// Write it all to disk...
WriteFileHeader(Header);
{
sections::iterator i, ie;
MCAssembler::const_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);
}
}
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 (const auto &Relocation : (*i)->Relocations)
WriteRelocation(Relocation.Data);
} else
assert((*i)->Header.PointerToRelocations == 0 &&
"Section::PointerToRelocations is insane!");
}
}
assert(OS.tell() == Header.PointerToSymbolTable &&
"Header::PointerToSymbolTable is insane!");
for (auto &Symbol : Symbols)
if (Symbol->Index != -1)
WriteSymbol(*Symbol);
OS.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
namespace llvm {
MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
raw_ostream &OS) {
return new WinCOFFObjectWriter(MOTW, OS);
}
}
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