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 { 40 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB, 41 MCCodeEmitter &CE, raw_pwrite_stream &OS) 42 : MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(nullptr) {} 43 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 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 78 void MCWinCOFFStreamer::EmitLabel(MCSymbol *S) { 79 auto *Symbol = cast<MCSymbolCOFF>(S); 80 assert(Symbol->isUndefined() && "Cannot define a symbol twice!"); 81 MCObjectStreamer::EmitLabel(Symbol); 82 } 83 84 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) { 85 llvm_unreachable("not implemented"); 86 } 87 88 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) { 89 llvm_unreachable("not implemented"); 90 } 91 92 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *S, 93 MCSymbolAttr Attribute) { 94 auto *Symbol = cast<MCSymbolCOFF>(S); 95 getAssembler().registerSymbol(*Symbol); 96 97 switch (Attribute) { 98 default: return false; 99 case MCSA_WeakReference: 100 case MCSA_Weak: 101 Symbol->setIsWeakExternal(); 102 Symbol->setExternal(true); 103 break; 104 case MCSA_Global: 105 Symbol->setExternal(true); 106 break; 107 case MCSA_AltEntry: 108 llvm_unreachable("COFF doesn't support the .alt_entry attribute"); 109 } 110 111 return true; 112 } 113 114 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) { 115 llvm_unreachable("not implemented"); 116 } 117 118 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) { 119 auto *Symbol = cast<MCSymbolCOFF>(S); 120 if (CurSymbol) 121 Error("starting a new symbol definition without completing the " 122 "previous one"); 123 CurSymbol = Symbol; 124 } 125 126 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) { 127 if (!CurSymbol) { 128 Error("storage class specified outside of symbol definition"); 129 return; 130 } 131 132 if (StorageClass & ~COFF::SSC_Invalid) { 133 Error("storage class value '" + Twine(StorageClass) + 134 "' out of range"); 135 return; 136 } 137 138 getAssembler().registerSymbol(*CurSymbol); 139 cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass); 140 } 141 142 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) { 143 if (!CurSymbol) { 144 Error("symbol type specified outside of a symbol definition"); 145 return; 146 } 147 148 if (Type & ~0xffff) { 149 Error("type value '" + Twine(Type) + "' out of range"); 150 return; 151 } 152 153 getAssembler().registerSymbol(*CurSymbol); 154 cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type); 155 } 156 157 void MCWinCOFFStreamer::EndCOFFSymbolDef() { 158 if (!CurSymbol) 159 Error("ending symbol definition without starting one"); 160 CurSymbol = nullptr; 161 } 162 163 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) { 164 // SafeSEH is a feature specific to 32-bit x86. It does not exist (and is 165 // unnecessary) on all platforms which use table-based exception dispatch. 166 if (getContext().getObjectFileInfo()->getTargetTriple().getArch() != 167 Triple::x86) 168 return; 169 170 const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol); 171 if (CSymbol->isSafeSEH()) 172 return; 173 174 MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection(); 175 getAssembler().registerSection(*SXData); 176 if (SXData->getAlignment() < 4) 177 SXData->setAlignment(4); 178 179 new MCSafeSEHFragment(Symbol, SXData); 180 181 getAssembler().registerSymbol(*Symbol); 182 CSymbol->setIsSafeSEH(); 183 184 // The Microsoft linker requires that the symbol type of a handler be 185 // function. Go ahead and oblige it here. 186 CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION 187 << COFF::SCT_COMPLEX_TYPE_SHIFT); 188 } 189 190 void MCWinCOFFStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) { 191 MCDataFragment *DF = getOrCreateDataFragment(); 192 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext()); 193 MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2); 194 DF->getFixups().push_back(Fixup); 195 DF->getContents().resize(DF->getContents().size() + 2, 0); 196 } 197 198 void MCWinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) { 199 MCDataFragment *DF = getOrCreateDataFragment(); 200 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext()); 201 MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_4); 202 DF->getFixups().push_back(Fixup); 203 DF->getContents().resize(DF->getContents().size() + 4, 0); 204 } 205 206 void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size, 207 unsigned ByteAlignment) { 208 auto *Symbol = cast<MCSymbolCOFF>(S); 209 210 const Triple &T = getContext().getObjectFileInfo()->getTargetTriple(); 211 if (T.isKnownWindowsMSVCEnvironment()) { 212 if (ByteAlignment > 32) 213 report_fatal_error("alignment is limited to 32-bytes"); 214 215 // Round size up to alignment so that we will honor the alignment request. 216 Size = std::max(Size, static_cast<uint64_t>(ByteAlignment)); 217 } 218 219 getAssembler().registerSymbol(*Symbol); 220 Symbol->setExternal(true); 221 Symbol->setCommon(Size, ByteAlignment); 222 223 if (!T.isKnownWindowsMSVCEnvironment() && ByteAlignment > 1) { 224 SmallString<128> Directive; 225 raw_svector_ostream OS(Directive); 226 const MCObjectFileInfo *MFI = getContext().getObjectFileInfo(); 227 228 OS << " -aligncomm:\"" << Symbol->getName() << "\"," 229 << Log2_32_Ceil(ByteAlignment); 230 231 PushSection(); 232 SwitchSection(MFI->getDrectveSection()); 233 EmitBytes(Directive); 234 PopSection(); 235 } 236 } 237 238 void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size, 239 unsigned ByteAlignment) { 240 auto *Symbol = cast<MCSymbolCOFF>(S); 241 242 MCSection *Section = getContext().getObjectFileInfo()->getBSSSection(); 243 getAssembler().registerSection(*Section); 244 if (Section->getAlignment() < ByteAlignment) 245 Section->setAlignment(ByteAlignment); 246 247 getAssembler().registerSymbol(*Symbol); 248 Symbol->setExternal(false); 249 250 if (ByteAlignment != 1) 251 new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0, 252 ByteAlignment, Section); 253 254 MCFillFragment *Fragment = new MCFillFragment( 255 /*Value=*/0, Size, Section); 256 Symbol->setFragment(Fragment); 257 } 258 259 void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol, 260 uint64_t Size, unsigned ByteAlignment) { 261 llvm_unreachable("not implemented"); 262 } 263 264 void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, 265 uint64_t Size, unsigned ByteAlignment) { 266 llvm_unreachable("not implemented"); 267 } 268 269 void MCWinCOFFStreamer::EmitFileDirective(StringRef Filename) { 270 getAssembler().addFileName(Filename); 271 } 272 273 // TODO: Implement this if you want to emit .comment section in COFF obj files. 274 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) { 275 llvm_unreachable("not implemented"); 276 } 277 278 void MCWinCOFFStreamer::EmitWinEHHandlerData() { 279 llvm_unreachable("not implemented"); 280 } 281 282 void MCWinCOFFStreamer::FinishImpl() { 283 MCObjectStreamer::FinishImpl(); 284 } 285 286 void MCWinCOFFStreamer::Error(const Twine &Msg) const { 287 getContext().reportError(SMLoc(), Msg); 288 } 289 } 290 291
