1 //===- llvm/MC/MCWinCOFFStreamer.cpp --------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file contains an implementation of a Windows COFF object file streamer. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/ADT/SmallString.h" 14 #include "llvm/ADT/SmallVector.h" 15 #include "llvm/ADT/Triple.h" 16 #include "llvm/ADT/Twine.h" 17 #include "llvm/BinaryFormat/COFF.h" 18 #include "llvm/MC/MCAsmBackend.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/MCFixup.h" 24 #include "llvm/MC/MCFragment.h" 25 #include "llvm/MC/MCObjectFileInfo.h" 26 #include "llvm/MC/MCObjectStreamer.h" 27 #include "llvm/MC/MCObjectWriter.h" 28 #include "llvm/MC/MCSection.h" 29 #include "llvm/MC/MCSymbolCOFF.h" 30 #include "llvm/MC/MCWinCOFFStreamer.h" 31 #include "llvm/Support/Casting.h" 32 #include "llvm/Support/ErrorHandling.h" 33 #include "llvm/Support/MathExtras.h" 34 #include "llvm/Support/SMLoc.h" 35 #include "llvm/Support/raw_ostream.h" 36 #include <algorithm> 37 #include <cassert> 38 #include <cstdint> 39 40 using namespace llvm; 41 42 #define DEBUG_TYPE "WinCOFFStreamer" 43 44 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, 45 std::unique_ptr<MCAsmBackend> MAB, 46 std::unique_ptr<MCCodeEmitter> CE, 47 std::unique_ptr<MCObjectWriter> OW) 48 : MCObjectStreamer(Context, std::move(MAB), std::move(OW), std::move(CE)), 49 CurSymbol(nullptr) {} 50 51 void MCWinCOFFStreamer::EmitInstToData(const MCInst &Inst, 52 const MCSubtargetInfo &STI) { 53 MCDataFragment *DF = getOrCreateDataFragment(); 54 55 SmallVector<MCFixup, 4> Fixups; 56 SmallString<256> Code; 57 raw_svector_ostream VecOS(Code); 58 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI); 59 60 // Add the fixups and data. 61 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) { 62 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size()); 63 DF->getFixups().push_back(Fixups[i]); 64 } 65 DF->setHasInstructions(STI); 66 DF->getContents().append(Code.begin(), Code.end()); 67 } 68 69 void MCWinCOFFStreamer::InitSections(bool NoExecStack) { 70 // FIXME: this is identical to the ELF one. 71 // This emulates the same behavior of GNU as. This makes it easier 72 // to compare the output as the major sections are in the same order. 73 SwitchSection(getContext().getObjectFileInfo()->getTextSection()); 74 EmitCodeAlignment(4); 75 76 SwitchSection(getContext().getObjectFileInfo()->getDataSection()); 77 EmitCodeAlignment(4); 78 79 SwitchSection(getContext().getObjectFileInfo()->getBSSSection()); 80 EmitCodeAlignment(4); 81 82 SwitchSection(getContext().getObjectFileInfo()->getTextSection()); 83 } 84 85 void MCWinCOFFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) { 86 auto *Symbol = cast<MCSymbolCOFF>(S); 87 MCObjectStreamer::EmitLabel(Symbol, Loc); 88 } 89 90 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) { 91 // Let the target do whatever target specific stuff it needs to do. 92 getAssembler().getBackend().handleAssemblerFlag(Flag); 93 94 switch (Flag) { 95 // None of these require COFF specific handling. 96 case MCAF_SyntaxUnified: 97 case MCAF_Code16: 98 case MCAF_Code32: 99 case MCAF_Code64: 100 break; 101 case MCAF_SubsectionsViaSymbols: 102 llvm_unreachable("COFF doesn't support .subsections_via_symbols"); 103 } 104 } 105 106 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) { 107 llvm_unreachable("not implemented"); 108 } 109 110 bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *S, 111 MCSymbolAttr Attribute) { 112 auto *Symbol = cast<MCSymbolCOFF>(S); 113 getAssembler().registerSymbol(*Symbol); 114 115 switch (Attribute) { 116 default: return false; 117 case MCSA_WeakReference: 118 case MCSA_Weak: 119 Symbol->setIsWeakExternal(); 120 Symbol->setExternal(true); 121 break; 122 case MCSA_Global: 123 Symbol->setExternal(true); 124 break; 125 case MCSA_AltEntry: 126 llvm_unreachable("COFF doesn't support the .alt_entry attribute"); 127 } 128 129 return true; 130 } 131 132 void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) { 133 llvm_unreachable("not implemented"); 134 } 135 136 void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) { 137 auto *Symbol = cast<MCSymbolCOFF>(S); 138 if (CurSymbol) 139 Error("starting a new symbol definition without completing the " 140 "previous one"); 141 CurSymbol = Symbol; 142 } 143 144 void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) { 145 if (!CurSymbol) { 146 Error("storage class specified outside of symbol definition"); 147 return; 148 } 149 150 if (StorageClass & ~COFF::SSC_Invalid) { 151 Error("storage class value '" + Twine(StorageClass) + 152 "' out of range"); 153 return; 154 } 155 156 getAssembler().registerSymbol(*CurSymbol); 157 cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass); 158 } 159 160 void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) { 161 if (!CurSymbol) { 162 Error("symbol type specified outside of a symbol definition"); 163 return; 164 } 165 166 if (Type & ~0xffff) { 167 Error("type value '" + Twine(Type) + "' out of range"); 168 return; 169 } 170 171 getAssembler().registerSymbol(*CurSymbol); 172 cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type); 173 } 174 175 void MCWinCOFFStreamer::EndCOFFSymbolDef() { 176 if (!CurSymbol) 177 Error("ending symbol definition without starting one"); 178 CurSymbol = nullptr; 179 } 180 181 void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) { 182 // SafeSEH is a feature specific to 32-bit x86. It does not exist (and is 183 // unnecessary) on all platforms which use table-based exception dispatch. 184 if (getContext().getObjectFileInfo()->getTargetTriple().getArch() != 185 Triple::x86) 186 return; 187 188 const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol); 189 if (CSymbol->isSafeSEH()) 190 return; 191 192 MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection(); 193 getAssembler().registerSection(*SXData); 194 if (SXData->getAlignment() < 4) 195 SXData->setAlignment(Align(4)); 196 197 new MCSymbolIdFragment(Symbol, SXData); 198 199 getAssembler().registerSymbol(*Symbol); 200 CSymbol->setIsSafeSEH(); 201 202 // The Microsoft linker requires that the symbol type of a handler be 203 // function. Go ahead and oblige it here. 204 CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION 205 << COFF::SCT_COMPLEX_TYPE_SHIFT); 206 } 207 208 void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) { 209 MCSection *Sec = getCurrentSectionOnly(); 210 getAssembler().registerSection(*Sec); 211 if (Sec->getAlignment() < 4) 212 Sec->setAlignment(Align(4)); 213 214 new MCSymbolIdFragment(Symbol, getCurrentSectionOnly()); 215 216 getAssembler().registerSymbol(*Symbol); 217 } 218 219 void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) { 220 visitUsedSymbol(*Symbol); 221 MCDataFragment *DF = getOrCreateDataFragment(); 222 const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext()); 223 MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2); 224 DF->getFixups().push_back(Fixup); 225 DF->getContents().resize(DF->getContents().size() + 2, 0); 226 } 227 228 void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol, 229 uint64_t Offset) { 230 visitUsedSymbol(*Symbol); 231 MCDataFragment *DF = getOrCreateDataFragment(); 232 // Create Symbol A for the relocation relative reference. 233 const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext()); 234 // Add the constant offset, if given. 235 if (Offset) 236 MCE = MCBinaryExpr::createAdd( 237 MCE, MCConstantExpr::create(Offset, getContext()), getContext()); 238 // Build the secrel32 relocation. 239 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4); 240 // Record the relocation. 241 DF->getFixups().push_back(Fixup); 242 // Emit 4 bytes (zeros) to the object file. 243 DF->getContents().resize(DF->getContents().size() + 4, 0); 244 } 245 246 void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol, 247 int64_t Offset) { 248 visitUsedSymbol(*Symbol); 249 MCDataFragment *DF = getOrCreateDataFragment(); 250 // Create Symbol A for the relocation relative reference. 251 const MCExpr *MCE = MCSymbolRefExpr::create( 252 Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext()); 253 // Add the constant offset, if given. 254 if (Offset) 255 MCE = MCBinaryExpr::createAdd( 256 MCE, MCConstantExpr::create(Offset, getContext()), getContext()); 257 // Build the imgrel relocation. 258 MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4); 259 // Record the relocation. 260 DF->getFixups().push_back(Fixup); 261 // Emit 4 bytes (zeros) to the object file. 262 DF->getContents().resize(DF->getContents().size() + 4, 0); 263 } 264 265 void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size, 266 unsigned ByteAlignment) { 267 auto *Symbol = cast<MCSymbolCOFF>(S); 268 269 const Triple &T = getContext().getObjectFileInfo()->getTargetTriple(); 270 if (T.isWindowsMSVCEnvironment()) { 271 if (ByteAlignment > 32) 272 report_fatal_error("alignment is limited to 32-bytes"); 273 274 // Round size up to alignment so that we will honor the alignment request. 275 Size = std::max(Size, static_cast<uint64_t>(ByteAlignment)); 276 } 277 278 getAssembler().registerSymbol(*Symbol); 279 Symbol->setExternal(true); 280 Symbol->setCommon(Size, ByteAlignment); 281 282 if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) { 283 SmallString<128> Directive; 284 raw_svector_ostream OS(Directive); 285 const MCObjectFileInfo *MFI = getContext().getObjectFileInfo(); 286 287 OS << " -aligncomm:\"" << Symbol->getName() << "\"," 288 << Log2_32_Ceil(ByteAlignment); 289 290 PushSection(); 291 SwitchSection(MFI->getDrectveSection()); 292 EmitBytes(Directive); 293 PopSection(); 294 } 295 } 296 297 void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size, 298 unsigned ByteAlignment) { 299 auto *Symbol = cast<MCSymbolCOFF>(S); 300 301 MCSection *Section = getContext().getObjectFileInfo()->getBSSSection(); 302 PushSection(); 303 SwitchSection(Section); 304 EmitValueToAlignment(ByteAlignment, 0, 1, 0); 305 EmitLabel(Symbol); 306 Symbol->setExternal(false); 307 EmitZeros(Size); 308 PopSection(); 309 } 310 311 void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol, 312 uint64_t Size, unsigned ByteAlignment, 313 SMLoc Loc) { 314 llvm_unreachable("not implemented"); 315 } 316 317 void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, 318 uint64_t Size, unsigned ByteAlignment) { 319 llvm_unreachable("not implemented"); 320 } 321 322 // TODO: Implement this if you want to emit .comment section in COFF obj files. 323 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) { 324 llvm_unreachable("not implemented"); 325 } 326 327 void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) { 328 llvm_unreachable("not implemented"); 329 } 330 331 void MCWinCOFFStreamer::FinishImpl() { 332 MCObjectStreamer::FinishImpl(); 333 } 334 335 void MCWinCOFFStreamer::Error(const Twine &Msg) const { 336 getContext().reportError(SMLoc(), Msg); 337 } 338