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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/MCObjectStreamer.h"
17 #include "llvm/MC/MCContext.h"
18 #include "llvm/MC/MCSection.h"
19 #include "llvm/MC/MCSymbol.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCValue.h"
22 #include "llvm/MC/MCAssembler.h"
23 #include "llvm/MC/MCAsmLayout.h"
24 #include "llvm/MC/MCCodeEmitter.h"
25 #include "llvm/MC/MCSectionCOFF.h"
26 #include "llvm/MC/MCWin64EH.h"
27 #include "llvm/MC/MCAsmBackend.h"
28 
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 EmitLabel(MCSymbol *Symbol);
54   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
55   virtual void EmitThumbFunc(MCSymbol *Func);
56   virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
57   virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
58   virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
59   virtual void BeginCOFFSymbolDef(MCSymbol const *Symbol);
60   virtual void EmitCOFFSymbolStorageClass(int StorageClass);
61   virtual void EmitCOFFSymbolType(int Type);
62   virtual void EndCOFFSymbolDef();
63   virtual void EmitCOFFSecRel32(MCSymbol const *Symbol);
64   virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value);
65   virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
66                                 unsigned ByteAlignment);
67   virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
68                                      unsigned ByteAlignment);
69   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
70                             unsigned Size,unsigned ByteAlignment);
71   virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
72                               uint64_t Size, unsigned ByteAlignment);
73   virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
74   virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
75                                    unsigned ValueSize, unsigned MaxBytesToEmit);
76   virtual void EmitCodeAlignment(unsigned ByteAlignment,
77                                  unsigned MaxBytesToEmit);
78   virtual void EmitFileDirective(StringRef Filename);
79   virtual void EmitInstruction(const MCInst &Instruction);
80   virtual void EmitWin64EHHandlerData();
81   virtual void FinishImpl();
82 
83 private:
EmitInstToFragment(const MCInst & Inst)84   virtual void EmitInstToFragment(const MCInst &Inst) {
85     llvm_unreachable("Not used by WinCOFF.");
86   }
EmitInstToData(const MCInst & Inst)87   virtual void EmitInstToData(const MCInst &Inst) {
88     llvm_unreachable("Not used by WinCOFF.");
89   }
90 
SetSection(StringRef Section,unsigned Characteristics,SectionKind Kind)91   void SetSection(StringRef Section,
92                   unsigned Characteristics,
93                   SectionKind Kind) {
94     SwitchSection(getContext().getCOFFSection(Section, Characteristics, Kind));
95   }
96 
SetSectionText()97   void SetSectionText() {
98     SetSection(".text",
99                COFF::IMAGE_SCN_CNT_CODE
100              | COFF::IMAGE_SCN_MEM_EXECUTE
101              | COFF::IMAGE_SCN_MEM_READ,
102                SectionKind::getText());
103     EmitCodeAlignment(4, 0);
104   }
105 
SetSectionData()106   void SetSectionData() {
107     SetSection(".data",
108                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
109              | COFF::IMAGE_SCN_MEM_READ
110              | COFF::IMAGE_SCN_MEM_WRITE,
111                SectionKind::getDataRel());
112     EmitCodeAlignment(4, 0);
113   }
114 
SetSectionBSS()115   void SetSectionBSS() {
116     SetSection(".bss",
117                COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA
118              | COFF::IMAGE_SCN_MEM_READ
119              | COFF::IMAGE_SCN_MEM_WRITE,
120                SectionKind::getBSS());
121     EmitCodeAlignment(4, 0);
122   }
123 
124 };
125 } // end anonymous namespace.
126 
WinCOFFStreamer(MCContext & Context,MCAsmBackend & MAB,MCCodeEmitter & CE,raw_ostream & OS)127 WinCOFFStreamer::WinCOFFStreamer(MCContext &Context,
128                                  MCAsmBackend &MAB,
129                                  MCCodeEmitter &CE,
130                                  raw_ostream &OS)
131     : MCObjectStreamer(Context, MAB, OS, &CE)
132     , CurSymbol(NULL) {
133 }
134 
AddCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,bool External)135 void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
136                                       unsigned ByteAlignment, bool External) {
137   assert(!Symbol->isInSection() && "Symbol must not already have a section!");
138 
139   std::string SectionName(".bss$linkonce");
140   SectionName.append(Symbol->getName().begin(), Symbol->getName().end());
141 
142   MCSymbolData &SymbolData = getAssembler().getOrCreateSymbolData(*Symbol);
143 
144   unsigned Characteristics =
145     COFF::IMAGE_SCN_LNK_COMDAT |
146     COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
147     COFF::IMAGE_SCN_MEM_READ |
148     COFF::IMAGE_SCN_MEM_WRITE;
149 
150   int Selection = COFF::IMAGE_COMDAT_SELECT_LARGEST;
151 
152   const MCSection *Section = MCStreamer::getContext().getCOFFSection(
153     SectionName, Characteristics, Selection, SectionKind::getBSS());
154 
155   MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
156 
157   if (SectionData.getAlignment() < ByteAlignment)
158     SectionData.setAlignment(ByteAlignment);
159 
160   SymbolData.setExternal(External);
161 
162   Symbol->setSection(*Section);
163 
164   if (ByteAlignment != 1)
165       new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectionData);
166 
167   SymbolData.setFragment(new MCFillFragment(0, 0, Size, &SectionData));
168 }
169 
170 // MCStreamer interface
171 
InitSections()172 void WinCOFFStreamer::InitSections() {
173   SetSectionText();
174   SetSectionData();
175   SetSectionBSS();
176   SetSectionText();
177 }
178 
EmitLabel(MCSymbol * Symbol)179 void WinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
180   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
181   MCObjectStreamer::EmitLabel(Symbol);
182 }
183 
EmitAssemblerFlag(MCAssemblerFlag Flag)184 void WinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
185   llvm_unreachable("not implemented");
186 }
187 
EmitThumbFunc(MCSymbol * Func)188 void WinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
189   llvm_unreachable("not implemented");
190 }
191 
EmitAssignment(MCSymbol * Symbol,const MCExpr * Value)192 void WinCOFFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
193   assert((Symbol->isInSection()
194          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
195          : true) && "Got non COFF section in the COFF backend!");
196   // FIXME: This is all very ugly and depressing. What needs to happen here
197   // depends on quite a few things that are all part of relaxation, which we
198   // don't really even do.
199 
200   if (Value->getKind() != MCExpr::SymbolRef) {
201     // TODO: This is exactly the same as MachOStreamer. Consider merging into
202     // MCObjectStreamer.
203     getAssembler().getOrCreateSymbolData(*Symbol);
204     AddValueSymbols(Value);
205     Symbol->setVariableValue(Value);
206   } else {
207     // FIXME: This is a horrible way to do this :(. This should really be
208     // handled after we are done with the MC* objects and immediately before
209     // writing out the object file when we know exactly what the symbol should
210     // look like in the coff symbol table. I'm not doing that now because the
211     // COFF object writer doesn't have a clearly defined separation between MC
212     // data structures, the object writers data structures, and the raw, POD,
213     // data structures that get written to disk.
214 
215     // Copy over the aliased data.
216     MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
217     const MCSymbolData &RealSD = getAssembler().getOrCreateSymbolData(
218       dyn_cast<const MCSymbolRefExpr>(Value)->getSymbol());
219 
220     // FIXME: This is particularly nasty because it breaks as soon as any data
221     // members of MCSymbolData change.
222     SD.CommonAlign     = RealSD.CommonAlign;
223     SD.CommonSize      = RealSD.CommonSize;
224     SD.Flags           = RealSD.Flags;
225     SD.Fragment        = RealSD.Fragment;
226     SD.Index           = RealSD.Index;
227     SD.IsExternal      = RealSD.IsExternal;
228     SD.IsPrivateExtern = RealSD.IsPrivateExtern;
229     SD.Offset          = RealSD.Offset;
230     SD.SymbolSize      = RealSD.SymbolSize;
231   }
232 }
233 
EmitSymbolAttribute(MCSymbol * Symbol,MCSymbolAttr Attribute)234 void WinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
235                                           MCSymbolAttr Attribute) {
236   assert(Symbol && "Symbol must be non-null!");
237   assert((Symbol->isInSection()
238          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
239          : true) && "Got non COFF section in the COFF backend!");
240   switch (Attribute) {
241   case MCSA_WeakReference:
242   case MCSA_Weak: {
243       MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
244       SD.modifyFlags(COFF::SF_WeakExternal, COFF::SF_WeakExternal);
245       SD.setExternal(true);
246     }
247     break;
248 
249   case MCSA_Global:
250     getAssembler().getOrCreateSymbolData(*Symbol).setExternal(true);
251     break;
252 
253   default:
254     llvm_unreachable("unsupported attribute");
255   }
256 }
257 
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)258 void WinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
259   llvm_unreachable("not implemented");
260 }
261 
BeginCOFFSymbolDef(MCSymbol const * Symbol)262 void WinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
263   assert((Symbol->isInSection()
264          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
265          : true) && "Got non COFF section in the COFF backend!");
266   assert(CurSymbol == NULL && "EndCOFFSymbolDef must be called between calls "
267                               "to BeginCOFFSymbolDef!");
268   CurSymbol = Symbol;
269 }
270 
EmitCOFFSymbolStorageClass(int StorageClass)271 void WinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
272   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
273   assert((StorageClass & ~0xFF) == 0 && "StorageClass must only have data in "
274                                         "the first byte!");
275 
276   getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
277     StorageClass << COFF::SF_ClassShift,
278     COFF::SF_ClassMask);
279 }
280 
EmitCOFFSymbolType(int Type)281 void WinCOFFStreamer::EmitCOFFSymbolType(int Type) {
282   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
283   assert((Type & ~0xFFFF) == 0 && "Type must only have data in the first 2 "
284                                   "bytes");
285 
286   getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
287     Type << COFF::SF_TypeShift,
288     COFF::SF_TypeMask);
289 }
290 
EndCOFFSymbolDef()291 void WinCOFFStreamer::EndCOFFSymbolDef() {
292   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
293   CurSymbol = NULL;
294 }
295 
EmitCOFFSecRel32(MCSymbol const * Symbol)296 void WinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol)
297 {
298   MCDataFragment *DF = getOrCreateDataFragment();
299 
300   DF->addFixup(MCFixup::Create(DF->getContents().size(),
301                                MCSymbolRefExpr::Create (Symbol, getContext ()),
302                                FK_SecRel_4));
303   DF->getContents().resize(DF->getContents().size() + 4, 0);
304 }
305 
EmitELFSize(MCSymbol * Symbol,const MCExpr * Value)306 void WinCOFFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
307   llvm_unreachable("not implemented");
308 }
309 
EmitCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)310 void WinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
311                                        unsigned ByteAlignment) {
312   assert((Symbol->isInSection()
313          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
314          : true) && "Got non COFF section in the COFF backend!");
315   AddCommonSymbol(Symbol, Size, ByteAlignment, true);
316 }
317 
EmitLocalCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)318 void WinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
319                                             unsigned ByteAlignment) {
320   assert((Symbol->isInSection()
321          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
322          : true) && "Got non COFF section in the COFF backend!");
323   AddCommonSymbol(Symbol, Size, ByteAlignment, false);
324 }
325 
EmitZerofill(const MCSection * Section,MCSymbol * Symbol,unsigned Size,unsigned ByteAlignment)326 void WinCOFFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
327                                    unsigned Size,unsigned ByteAlignment) {
328   llvm_unreachable("not implemented");
329 }
330 
EmitTBSSSymbol(const MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)331 void WinCOFFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
332                                      uint64_t Size, unsigned ByteAlignment) {
333   llvm_unreachable("not implemented");
334 }
335 
EmitBytes(StringRef Data,unsigned AddrSpace)336 void WinCOFFStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
337   // TODO: This is copied exactly from the MachOStreamer. Consider merging into
338   // MCObjectStreamer?
339   getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
340 }
341 
EmitValueToAlignment(unsigned ByteAlignment,int64_t Value,unsigned ValueSize,unsigned MaxBytesToEmit)342 void WinCOFFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
343                                            int64_t Value,
344                                            unsigned ValueSize,
345                                            unsigned MaxBytesToEmit) {
346   // TODO: This is copied exactly from the MachOStreamer. Consider merging into
347   // MCObjectStreamer?
348   if (MaxBytesToEmit == 0)
349     MaxBytesToEmit = ByteAlignment;
350   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
351                       getCurrentSectionData());
352 
353   // Update the maximum alignment on the current section if necessary.
354   if (ByteAlignment > getCurrentSectionData()->getAlignment())
355     getCurrentSectionData()->setAlignment(ByteAlignment);
356 }
357 
EmitCodeAlignment(unsigned ByteAlignment,unsigned MaxBytesToEmit)358 void WinCOFFStreamer::EmitCodeAlignment(unsigned ByteAlignment,
359                                         unsigned MaxBytesToEmit) {
360   // TODO: This is copied exactly from the MachOStreamer. Consider merging into
361   // MCObjectStreamer?
362   if (MaxBytesToEmit == 0)
363     MaxBytesToEmit = ByteAlignment;
364   MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
365                                            getCurrentSectionData());
366   F->setEmitNops(true);
367 
368   // Update the maximum alignment on the current section if necessary.
369   if (ByteAlignment > getCurrentSectionData()->getAlignment())
370     getCurrentSectionData()->setAlignment(ByteAlignment);
371 }
372 
EmitFileDirective(StringRef Filename)373 void WinCOFFStreamer::EmitFileDirective(StringRef Filename) {
374   // Ignore for now, linkers don't care, and proper debug
375   // info will be a much large effort.
376 }
377 
EmitInstruction(const MCInst & Instruction)378 void WinCOFFStreamer::EmitInstruction(const MCInst &Instruction) {
379   for (unsigned i = 0, e = Instruction.getNumOperands(); i != e; ++i)
380     if (Instruction.getOperand(i).isExpr())
381       AddValueSymbols(Instruction.getOperand(i).getExpr());
382 
383   getCurrentSectionData()->setHasInstructions(true);
384 
385   MCInstFragment *Fragment =
386     new MCInstFragment(Instruction, getCurrentSectionData());
387 
388   raw_svector_ostream VecOS(Fragment->getCode());
389 
390   getAssembler().getEmitter().EncodeInstruction(Instruction, VecOS,
391                                                 Fragment->getFixups());
392 }
393 
EmitWin64EHHandlerData()394 void WinCOFFStreamer::EmitWin64EHHandlerData() {
395   MCStreamer::EmitWin64EHHandlerData();
396 
397   // We have to emit the unwind info now, because this directive
398   // actually switches to the .xdata section!
399   MCWin64EHUnwindEmitter::EmitUnwindInfo(*this, getCurrentW64UnwindInfo());
400 }
401 
FinishImpl()402 void WinCOFFStreamer::FinishImpl() {
403   EmitW64Tables();
404   MCObjectStreamer::FinishImpl();
405 }
406 
407 namespace llvm
408 {
createWinCOFFStreamer(MCContext & Context,MCAsmBackend & MAB,MCCodeEmitter & CE,raw_ostream & OS,bool RelaxAll)409   MCStreamer *createWinCOFFStreamer(MCContext &Context,
410                                     MCAsmBackend &MAB,
411                                     MCCodeEmitter &CE,
412                                     raw_ostream &OS,
413                                     bool RelaxAll) {
414     WinCOFFStreamer *S = new WinCOFFStreamer(Context, MAB, CE, OS);
415     S->getAssembler().setRelaxAll(RelaxAll);
416     return S;
417   }
418 }
419