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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 Windows COFF object file streamer.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/MC/MCAsmBackend.h"
15 #include "llvm/MC/MCAsmLayout.h"
16 #include "llvm/MC/MCAssembler.h"
17 #include "llvm/MC/MCCodeEmitter.h"
18 #include "llvm/MC/MCContext.h"
19 #include "llvm/MC/MCExpr.h"
20 #include "llvm/MC/MCObjectFileInfo.h"
21 #include "llvm/MC/MCObjectStreamer.h"
22 #include "llvm/MC/MCSection.h"
23 #include "llvm/MC/MCSectionCOFF.h"
24 #include "llvm/MC/MCStreamer.h"
25 #include "llvm/MC/MCSymbolCOFF.h"
26 #include "llvm/MC/MCValue.h"
27 #include "llvm/MC/MCWinCOFFStreamer.h"
28 #include "llvm/Support/COFF.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/Support/TargetRegistry.h"
33 #include "llvm/Support/raw_ostream.h"
34 
35 using namespace llvm;
36 
37 #define DEBUG_TYPE "WinCOFFStreamer"
38 
39 namespace llvm {
MCWinCOFFStreamer(MCContext & Context,MCAsmBackend & MAB,MCCodeEmitter & CE,raw_pwrite_stream & OS)40 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
41                                      MCCodeEmitter &CE, raw_pwrite_stream &OS)
42     : MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(nullptr) {}
43 
EmitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)44 void MCWinCOFFStreamer::EmitInstToData(const MCInst &Inst,
45                                        const MCSubtargetInfo &STI) {
46   MCDataFragment *DF = getOrCreateDataFragment();
47 
48   SmallVector<MCFixup, 4> Fixups;
49   SmallString<256> Code;
50   raw_svector_ostream VecOS(Code);
51   getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
52 
53   // Add the fixups and data.
54   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
55     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
56     DF->getFixups().push_back(Fixups[i]);
57   }
58 
59   DF->getContents().append(Code.begin(), Code.end());
60 }
61 
InitSections(bool NoExecStack)62 void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
63   // FIXME: this is identical to the ELF one.
64   // This emulates the same behavior of GNU as. This makes it easier
65   // to compare the output as the major sections are in the same order.
66   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
67   EmitCodeAlignment(4);
68 
69   SwitchSection(getContext().getObjectFileInfo()->getDataSection());
70   EmitCodeAlignment(4);
71 
72   SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
73   EmitCodeAlignment(4);
74 
75   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
76 }
77 
EmitLabel(MCSymbol * Symbol)78 void MCWinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
79   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
80   MCObjectStreamer::EmitLabel(Symbol);
81 }
82 
EmitAssemblerFlag(MCAssemblerFlag Flag)83 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
84   llvm_unreachable("not implemented");
85 }
86 
EmitThumbFunc(MCSymbol * Func)87 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
88   llvm_unreachable("not implemented");
89 }
90 
EmitSymbolAttribute(MCSymbol * Symbol,MCSymbolAttr Attribute)91 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
92                                             MCSymbolAttr Attribute) {
93   assert(Symbol && "Symbol must be non-null!");
94   assert((!Symbol->isInSection() ||
95           Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
96          "Got non-COFF section in the COFF backend!");
97 
98   getAssembler().registerSymbol(*Symbol);
99 
100   switch (Attribute) {
101   default: return false;
102   case MCSA_WeakReference:
103   case MCSA_Weak:
104     cast<MCSymbolCOFF>(Symbol)->setIsWeakExternal();
105     Symbol->setExternal(true);
106     break;
107   case MCSA_Global:
108     Symbol->setExternal(true);
109     break;
110   }
111 
112   return true;
113 }
114 
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)115 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
116   llvm_unreachable("not implemented");
117 }
118 
BeginCOFFSymbolDef(MCSymbol const * Symbol)119 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
120   assert((!Symbol->isInSection() ||
121           Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
122          "Got non-COFF section in the COFF backend!");
123 
124   if (CurSymbol)
125     Error("starting a new symbol definition without completing the "
126           "previous one");
127   CurSymbol = Symbol;
128 }
129 
EmitCOFFSymbolStorageClass(int StorageClass)130 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
131   if (!CurSymbol) {
132     Error("storage class specified outside of symbol definition");
133     return;
134   }
135 
136   if (StorageClass & ~COFF::SSC_Invalid) {
137     Error("storage class value '" + Twine(StorageClass) +
138                "' out of range");
139     return;
140   }
141 
142   getAssembler().registerSymbol(*CurSymbol);
143   cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
144 }
145 
EmitCOFFSymbolType(int Type)146 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
147   if (!CurSymbol) {
148     Error("symbol type specified outside of a symbol definition");
149     return;
150   }
151 
152   if (Type & ~0xffff) {
153     Error("type value '" + Twine(Type) + "' out of range");
154     return;
155   }
156 
157   getAssembler().registerSymbol(*CurSymbol);
158   cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
159 }
160 
EndCOFFSymbolDef()161 void MCWinCOFFStreamer::EndCOFFSymbolDef() {
162   if (!CurSymbol)
163     Error("ending symbol definition without starting one");
164   CurSymbol = nullptr;
165 }
166 
EmitCOFFSafeSEH(MCSymbol const * Symbol)167 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
168   // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
169   // unnecessary) on all platforms which use table-based exception dispatch.
170   if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
171       Triple::x86)
172     return;
173 
174   const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
175   if (CSymbol->isSafeSEH())
176     return;
177 
178   MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
179   getAssembler().registerSection(*SXData);
180   if (SXData->getAlignment() < 4)
181     SXData->setAlignment(4);
182 
183   new MCSafeSEHFragment(Symbol, SXData);
184 
185   getAssembler().registerSymbol(*Symbol);
186   CSymbol->setIsSafeSEH();
187 
188   // The Microsoft linker requires that the symbol type of a handler be
189   // function. Go ahead and oblige it here.
190   CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
191                    << COFF::SCT_COMPLEX_TYPE_SHIFT);
192 }
193 
EmitCOFFSectionIndex(MCSymbol const * Symbol)194 void MCWinCOFFStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {
195   MCDataFragment *DF = getOrCreateDataFragment();
196   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
197   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
198   DF->getFixups().push_back(Fixup);
199   DF->getContents().resize(DF->getContents().size() + 2, 0);
200 }
201 
EmitCOFFSecRel32(MCSymbol const * Symbol)202 void MCWinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) {
203   MCDataFragment *DF = getOrCreateDataFragment();
204   const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
205   MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_4);
206   DF->getFixups().push_back(Fixup);
207   DF->getContents().resize(DF->getContents().size() + 4, 0);
208 }
209 
EmitCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)210 void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
211                                          unsigned ByteAlignment) {
212   assert((!Symbol->isInSection() ||
213           Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
214          "Got non-COFF section in the COFF backend!");
215 
216   const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
217   if (T.isKnownWindowsMSVCEnvironment()) {
218     if (ByteAlignment > 32)
219       report_fatal_error("alignment is limited to 32-bytes");
220 
221     // Round size up to alignment so that we will honor the alignment request.
222     Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
223   }
224 
225   getAssembler().registerSymbol(*Symbol);
226   Symbol->setExternal(true);
227   Symbol->setCommon(Size, ByteAlignment);
228 
229   if (!T.isKnownWindowsMSVCEnvironment() && ByteAlignment > 1) {
230     SmallString<128> Directive;
231     raw_svector_ostream OS(Directive);
232     const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
233 
234     OS << " -aligncomm:\"" << Symbol->getName() << "\","
235        << Log2_32_Ceil(ByteAlignment);
236 
237     PushSection();
238     SwitchSection(MFI->getDrectveSection());
239     EmitBytes(Directive);
240     PopSection();
241   }
242 }
243 
EmitLocalCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)244 void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
245                                               unsigned ByteAlignment) {
246   assert(!Symbol->isInSection() && "Symbol must not already have a section!");
247 
248   MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
249   getAssembler().registerSection(*Section);
250   if (Section->getAlignment() < ByteAlignment)
251     Section->setAlignment(ByteAlignment);
252 
253   getAssembler().registerSymbol(*Symbol);
254   Symbol->setExternal(false);
255 
256   if (ByteAlignment != 1)
257     new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0,
258                         ByteAlignment, Section);
259 
260   MCFillFragment *Fragment = new MCFillFragment(
261       /*Value=*/0, /*ValueSize=*/0, Size, Section);
262   Symbol->setFragment(Fragment);
263 }
264 
EmitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)265 void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
266                                      uint64_t Size, unsigned ByteAlignment) {
267   llvm_unreachable("not implemented");
268 }
269 
EmitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)270 void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
271                                        uint64_t Size, unsigned ByteAlignment) {
272   llvm_unreachable("not implemented");
273 }
274 
EmitFileDirective(StringRef Filename)275 void MCWinCOFFStreamer::EmitFileDirective(StringRef Filename) {
276   getAssembler().addFileName(Filename);
277 }
278 
279 // TODO: Implement this if you want to emit .comment section in COFF obj files.
EmitIdent(StringRef IdentString)280 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
281   llvm_unreachable("not implemented");
282 }
283 
EmitWinEHHandlerData()284 void MCWinCOFFStreamer::EmitWinEHHandlerData() {
285   llvm_unreachable("not implemented");
286 }
287 
FinishImpl()288 void MCWinCOFFStreamer::FinishImpl() {
289   MCObjectStreamer::FinishImpl();
290 }
291 
Error(const Twine & Msg) const292 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
293   getContext().reportError(SMLoc(), Msg);
294 }
295 }
296 
297