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      1 //===-- llvm/MC/WinCOFFStreamer.cpp -----------------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file contains an implementation of a Win32 COFF object file streamer.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #define DEBUG_TYPE "WinCOFFStreamer"
     15 
     16 #include "llvm/MC/MCStreamer.h"
     17 #include "llvm/MC/MCAsmBackend.h"
     18 #include "llvm/MC/MCAsmLayout.h"
     19 #include "llvm/MC/MCAssembler.h"
     20 #include "llvm/MC/MCCodeEmitter.h"
     21 #include "llvm/MC/MCContext.h"
     22 #include "llvm/MC/MCExpr.h"
     23 #include "llvm/MC/MCObjectStreamer.h"
     24 #include "llvm/MC/MCSection.h"
     25 #include "llvm/MC/MCSectionCOFF.h"
     26 #include "llvm/MC/MCSymbol.h"
     27 #include "llvm/MC/MCValue.h"
     28 #include "llvm/MC/MCWin64EH.h"
     29 #include "llvm/Support/COFF.h"
     30 #include "llvm/Support/Debug.h"
     31 #include "llvm/Support/ErrorHandling.h"
     32 #include "llvm/Support/TargetRegistry.h"
     33 #include "llvm/Support/raw_ostream.h"
     34 
     35 using namespace llvm;
     36 
     37 namespace {
     38 class WinCOFFStreamer : public MCObjectStreamer {
     39 public:
     40   MCSymbol const *CurSymbol;
     41 
     42   WinCOFFStreamer(MCContext &Context,
     43                   MCAsmBackend &MAB,
     44                   MCCodeEmitter &CE,
     45                   raw_ostream &OS);
     46 
     47   void AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
     48                        unsigned ByteAlignment, bool External);
     49 
     50   // MCStreamer interface
     51 
     52   virtual void InitSections();
     53   virtual void InitToTextSection();
     54   virtual void EmitLabel(MCSymbol *Symbol);
     55   virtual void EmitDebugLabel(MCSymbol *Symbol);
     56   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
     57   virtual void EmitThumbFunc(MCSymbol *Func);
     58   virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
     59   virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
     60   virtual void BeginCOFFSymbolDef(MCSymbol const *Symbol);
     61   virtual void EmitCOFFSymbolStorageClass(int StorageClass);
     62   virtual void EmitCOFFSymbolType(int Type);
     63   virtual void EndCOFFSymbolDef();
     64   virtual void EmitCOFFSecRel32(MCSymbol const *Symbol);
     65   virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value);
     66   virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
     67                                 unsigned ByteAlignment);
     68   virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
     69                                      unsigned ByteAlignment);
     70   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
     71                             uint64_t Size,unsigned ByteAlignment);
     72   virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
     73                               uint64_t Size, unsigned ByteAlignment);
     74   virtual void EmitFileDirective(StringRef Filename);
     75   virtual void EmitWin64EHHandlerData();
     76   virtual void FinishImpl();
     77 
     78   static bool classof(const MCStreamer *S) {
     79     return S->getKind() == SK_WinCOFFStreamer;
     80   }
     81 
     82 private:
     83   virtual void EmitInstToData(const MCInst &Inst) {
     84     MCDataFragment *DF = getOrCreateDataFragment();
     85 
     86     SmallVector<MCFixup, 4> Fixups;
     87     SmallString<256> Code;
     88     raw_svector_ostream VecOS(Code);
     89     getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
     90     VecOS.flush();
     91 
     92     // Add the fixups and data.
     93     for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
     94       Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
     95       DF->getFixups().push_back(Fixups[i]);
     96     }
     97     DF->getContents().append(Code.begin(), Code.end());
     98   }
     99 
    100   void SetSection(StringRef Section,
    101                   unsigned Characteristics,
    102                   SectionKind Kind) {
    103     SwitchSection(getContext().getCOFFSection(Section, Characteristics, Kind));
    104   }
    105 
    106   void SetSectionText() {
    107     SetSection(".text",
    108                COFF::IMAGE_SCN_CNT_CODE
    109              | COFF::IMAGE_SCN_MEM_EXECUTE
    110              | COFF::IMAGE_SCN_MEM_READ,
    111                SectionKind::getText());
    112     EmitCodeAlignment(4, 0);
    113   }
    114 
    115   void SetSectionData() {
    116     SetSection(".data",
    117                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
    118              | COFF::IMAGE_SCN_MEM_READ
    119              | COFF::IMAGE_SCN_MEM_WRITE,
    120                SectionKind::getDataRel());
    121     EmitCodeAlignment(4, 0);
    122   }
    123 
    124   void SetSectionBSS() {
    125     SetSection(".bss",
    126                COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA
    127              | COFF::IMAGE_SCN_MEM_READ
    128              | COFF::IMAGE_SCN_MEM_WRITE,
    129                SectionKind::getBSS());
    130     EmitCodeAlignment(4, 0);
    131   }
    132 };
    133 } // end anonymous namespace.
    134 
    135 WinCOFFStreamer::WinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
    136                                  MCCodeEmitter &CE, raw_ostream &OS)
    137     : MCObjectStreamer(SK_WinCOFFStreamer, Context, MAB, OS, &CE),
    138       CurSymbol(NULL) {}
    139 
    140 void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    141                                       unsigned ByteAlignment, bool External) {
    142   assert(!Symbol->isInSection() && "Symbol must not already have a section!");
    143 
    144   std::string SectionName(".bss$linkonce");
    145   SectionName.append(Symbol->getName().begin(), Symbol->getName().end());
    146 
    147   MCSymbolData &SymbolData = getAssembler().getOrCreateSymbolData(*Symbol);
    148 
    149   unsigned Characteristics =
    150     COFF::IMAGE_SCN_LNK_COMDAT |
    151     COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
    152     COFF::IMAGE_SCN_MEM_READ |
    153     COFF::IMAGE_SCN_MEM_WRITE;
    154 
    155   int Selection = COFF::IMAGE_COMDAT_SELECT_LARGEST;
    156 
    157   const MCSection *Section = MCStreamer::getContext().getCOFFSection(
    158     SectionName, Characteristics, Selection, SectionKind::getBSS());
    159 
    160   MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
    161 
    162   if (SectionData.getAlignment() < ByteAlignment)
    163     SectionData.setAlignment(ByteAlignment);
    164 
    165   SymbolData.setExternal(External);
    166 
    167   Symbol->setSection(*Section);
    168 
    169   if (ByteAlignment != 1)
    170       new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectionData);
    171 
    172   SymbolData.setFragment(new MCFillFragment(0, 0, Size, &SectionData));
    173 }
    174 
    175 // MCStreamer interface
    176 
    177 void WinCOFFStreamer::InitToTextSection() {
    178   SetSectionText();
    179 }
    180 
    181 void WinCOFFStreamer::InitSections() {
    182   SetSectionText();
    183   SetSectionData();
    184   SetSectionBSS();
    185   SetSectionText();
    186 }
    187 
    188 void WinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
    189   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
    190   MCObjectStreamer::EmitLabel(Symbol);
    191 }
    192 
    193 void WinCOFFStreamer::EmitDebugLabel(MCSymbol *Symbol) {
    194   EmitLabel(Symbol);
    195 }
    196 void WinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
    197   llvm_unreachable("not implemented");
    198 }
    199 
    200 void WinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
    201   llvm_unreachable("not implemented");
    202 }
    203 
    204 void WinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
    205                                           MCSymbolAttr Attribute) {
    206   assert(Symbol && "Symbol must be non-null!");
    207   assert((Symbol->isInSection()
    208          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    209          : true) && "Got non COFF section in the COFF backend!");
    210   switch (Attribute) {
    211   case MCSA_WeakReference:
    212   case MCSA_Weak: {
    213       MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    214       SD.modifyFlags(COFF::SF_WeakExternal, COFF::SF_WeakExternal);
    215       SD.setExternal(true);
    216     }
    217     break;
    218 
    219   case MCSA_Global:
    220     getAssembler().getOrCreateSymbolData(*Symbol).setExternal(true);
    221     break;
    222 
    223   default:
    224     llvm_unreachable("unsupported attribute");
    225   }
    226 }
    227 
    228 void WinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
    229   llvm_unreachable("not implemented");
    230 }
    231 
    232 void WinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
    233   assert((Symbol->isInSection()
    234          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    235          : true) && "Got non COFF section in the COFF backend!");
    236   assert(CurSymbol == NULL && "EndCOFFSymbolDef must be called between calls "
    237                               "to BeginCOFFSymbolDef!");
    238   CurSymbol = Symbol;
    239 }
    240 
    241 void WinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
    242   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
    243   assert((StorageClass & ~0xFF) == 0 && "StorageClass must only have data in "
    244                                         "the first byte!");
    245 
    246   getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
    247     StorageClass << COFF::SF_ClassShift,
    248     COFF::SF_ClassMask);
    249 }
    250 
    251 void WinCOFFStreamer::EmitCOFFSymbolType(int Type) {
    252   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
    253   assert((Type & ~0xFFFF) == 0 && "Type must only have data in the first 2 "
    254                                   "bytes");
    255 
    256   getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
    257     Type << COFF::SF_TypeShift,
    258     COFF::SF_TypeMask);
    259 }
    260 
    261 void WinCOFFStreamer::EndCOFFSymbolDef() {
    262   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
    263   CurSymbol = NULL;
    264 }
    265 
    266 void WinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol)
    267 {
    268   MCDataFragment *DF = getOrCreateDataFragment();
    269 
    270   DF->getFixups().push_back(
    271       MCFixup::Create(DF->getContents().size(),
    272                       MCSymbolRefExpr::Create (Symbol, getContext ()),
    273                       FK_SecRel_4));
    274   DF->getContents().resize(DF->getContents().size() + 4, 0);
    275 }
    276 
    277 void WinCOFFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
    278   llvm_unreachable("not implemented");
    279 }
    280 
    281 void WinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    282                                        unsigned ByteAlignment) {
    283   assert((Symbol->isInSection()
    284          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    285          : true) && "Got non COFF section in the COFF backend!");
    286   AddCommonSymbol(Symbol, Size, ByteAlignment, true);
    287 }
    288 
    289 void WinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    290                                             unsigned ByteAlignment) {
    291   assert((Symbol->isInSection()
    292          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    293          : true) && "Got non COFF section in the COFF backend!");
    294   AddCommonSymbol(Symbol, Size, ByteAlignment, false);
    295 }
    296 
    297 void WinCOFFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
    298                                    uint64_t Size,unsigned ByteAlignment) {
    299   llvm_unreachable("not implemented");
    300 }
    301 
    302 void WinCOFFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
    303                                      uint64_t Size, unsigned ByteAlignment) {
    304   llvm_unreachable("not implemented");
    305 }
    306 
    307 void WinCOFFStreamer::EmitFileDirective(StringRef Filename) {
    308   // Ignore for now, linkers don't care, and proper debug
    309   // info will be a much large effort.
    310 }
    311 
    312 void WinCOFFStreamer::EmitWin64EHHandlerData() {
    313   MCStreamer::EmitWin64EHHandlerData();
    314 
    315   // We have to emit the unwind info now, because this directive
    316   // actually switches to the .xdata section!
    317   MCWin64EHUnwindEmitter::EmitUnwindInfo(*this, getCurrentW64UnwindInfo());
    318 }
    319 
    320 void WinCOFFStreamer::FinishImpl() {
    321   EmitW64Tables();
    322   MCObjectStreamer::FinishImpl();
    323 }
    324 
    325 namespace llvm
    326 {
    327   MCStreamer *createWinCOFFStreamer(MCContext &Context,
    328                                     MCAsmBackend &MAB,
    329                                     MCCodeEmitter &CE,
    330                                     raw_ostream &OS,
    331                                     bool RelaxAll) {
    332     WinCOFFStreamer *S = new WinCOFFStreamer(Context, MAB, CE, OS);
    333     S->getAssembler().setRelaxAll(RelaxAll);
    334     return S;
    335   }
    336 }
    337