1 //===- lib/MC/MCWin64EH.cpp - MCWin64EH implementation --------------------===// 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 #include "llvm/MC/MCWin64EH.h" 11 #include "llvm/ADT/Twine.h" 12 #include "llvm/MC/MCContext.h" 13 #include "llvm/MC/MCExpr.h" 14 #include "llvm/MC/MCObjectFileInfo.h" 15 #include "llvm/MC/MCSectionCOFF.h" 16 #include "llvm/MC/MCStreamer.h" 17 #include "llvm/MC/MCSymbol.h" 18 19 namespace llvm { 20 21 // NOTE: All relocations generated here are 4-byte image-relative. 22 23 static uint8_t CountOfUnwindCodes(std::vector<MCWin64EHInstruction> &Insns) { 24 uint8_t Count = 0; 25 for (const auto &I : Insns) { 26 switch (I.getOperation()) { 27 case Win64EH::UOP_PushNonVol: 28 case Win64EH::UOP_AllocSmall: 29 case Win64EH::UOP_SetFPReg: 30 case Win64EH::UOP_PushMachFrame: 31 Count += 1; 32 break; 33 case Win64EH::UOP_SaveNonVol: 34 case Win64EH::UOP_SaveXMM128: 35 Count += 2; 36 break; 37 case Win64EH::UOP_SaveNonVolBig: 38 case Win64EH::UOP_SaveXMM128Big: 39 Count += 3; 40 break; 41 case Win64EH::UOP_AllocLarge: 42 Count += (I.getSize() > 512 * 1024 - 8) ? 3 : 2; 43 break; 44 } 45 } 46 return Count; 47 } 48 49 static void EmitAbsDifference(MCStreamer &streamer, MCSymbol *lhs, 50 MCSymbol *rhs) { 51 MCContext &context = streamer.getContext(); 52 const MCExpr *diff = MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create( 53 lhs, context), 54 MCSymbolRefExpr::Create( 55 rhs, context), 56 context); 57 streamer.EmitAbsValue(diff, 1); 58 59 } 60 61 static void EmitUnwindCode(MCStreamer &streamer, MCSymbol *begin, 62 MCWin64EHInstruction &inst) { 63 uint8_t b2; 64 uint16_t w; 65 b2 = (inst.getOperation() & 0x0F); 66 switch (inst.getOperation()) { 67 case Win64EH::UOP_PushNonVol: 68 EmitAbsDifference(streamer, inst.getLabel(), begin); 69 b2 |= (inst.getRegister() & 0x0F) << 4; 70 streamer.EmitIntValue(b2, 1); 71 break; 72 case Win64EH::UOP_AllocLarge: 73 EmitAbsDifference(streamer, inst.getLabel(), begin); 74 if (inst.getSize() > 512*1024-8) { 75 b2 |= 0x10; 76 streamer.EmitIntValue(b2, 1); 77 w = inst.getSize() & 0xFFF8; 78 streamer.EmitIntValue(w, 2); 79 w = inst.getSize() >> 16; 80 } else { 81 streamer.EmitIntValue(b2, 1); 82 w = inst.getSize() >> 3; 83 } 84 streamer.EmitIntValue(w, 2); 85 break; 86 case Win64EH::UOP_AllocSmall: 87 b2 |= (((inst.getSize()-8) >> 3) & 0x0F) << 4; 88 EmitAbsDifference(streamer, inst.getLabel(), begin); 89 streamer.EmitIntValue(b2, 1); 90 break; 91 case Win64EH::UOP_SetFPReg: 92 EmitAbsDifference(streamer, inst.getLabel(), begin); 93 streamer.EmitIntValue(b2, 1); 94 break; 95 case Win64EH::UOP_SaveNonVol: 96 case Win64EH::UOP_SaveXMM128: 97 b2 |= (inst.getRegister() & 0x0F) << 4; 98 EmitAbsDifference(streamer, inst.getLabel(), begin); 99 streamer.EmitIntValue(b2, 1); 100 w = inst.getOffset() >> 3; 101 if (inst.getOperation() == Win64EH::UOP_SaveXMM128) 102 w >>= 1; 103 streamer.EmitIntValue(w, 2); 104 break; 105 case Win64EH::UOP_SaveNonVolBig: 106 case Win64EH::UOP_SaveXMM128Big: 107 b2 |= (inst.getRegister() & 0x0F) << 4; 108 EmitAbsDifference(streamer, inst.getLabel(), begin); 109 streamer.EmitIntValue(b2, 1); 110 if (inst.getOperation() == Win64EH::UOP_SaveXMM128Big) 111 w = inst.getOffset() & 0xFFF0; 112 else 113 w = inst.getOffset() & 0xFFF8; 114 streamer.EmitIntValue(w, 2); 115 w = inst.getOffset() >> 16; 116 streamer.EmitIntValue(w, 2); 117 break; 118 case Win64EH::UOP_PushMachFrame: 119 if (inst.isPushCodeFrame()) 120 b2 |= 0x10; 121 EmitAbsDifference(streamer, inst.getLabel(), begin); 122 streamer.EmitIntValue(b2, 1); 123 break; 124 } 125 } 126 127 static void EmitSymbolRefWithOfs(MCStreamer &streamer, 128 const MCSymbol *Base, 129 const MCSymbol *Other) { 130 MCContext &Context = streamer.getContext(); 131 const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::Create(Base, Context); 132 const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::Create(Other, Context); 133 const MCExpr *Ofs = MCBinaryExpr::CreateSub(OtherRef, BaseRef, Context); 134 const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::Create(Base, 135 MCSymbolRefExpr::VK_COFF_IMGREL32, 136 Context); 137 streamer.EmitValue(MCBinaryExpr::CreateAdd(BaseRefRel, Ofs, Context), 4); 138 } 139 140 static void EmitRuntimeFunction(MCStreamer &streamer, 141 const MCWin64EHUnwindInfo *info) { 142 MCContext &context = streamer.getContext(); 143 144 streamer.EmitValueToAlignment(4); 145 EmitSymbolRefWithOfs(streamer, info->Function, info->Begin); 146 EmitSymbolRefWithOfs(streamer, info->Function, info->End); 147 streamer.EmitValue(MCSymbolRefExpr::Create(info->Symbol, 148 MCSymbolRefExpr::VK_COFF_IMGREL32, 149 context), 4); 150 } 151 152 static void EmitUnwindInfo(MCStreamer &streamer, MCWin64EHUnwindInfo *info) { 153 // If this UNWIND_INFO already has a symbol, it's already been emitted. 154 if (info->Symbol) return; 155 156 MCContext &context = streamer.getContext(); 157 streamer.EmitValueToAlignment(4); 158 info->Symbol = context.CreateTempSymbol(); 159 streamer.EmitLabel(info->Symbol); 160 161 // Upper 3 bits are the version number (currently 1). 162 uint8_t flags = 0x01; 163 if (info->ChainedParent) 164 flags |= Win64EH::UNW_ChainInfo << 3; 165 else { 166 if (info->HandlesUnwind) 167 flags |= Win64EH::UNW_TerminateHandler << 3; 168 if (info->HandlesExceptions) 169 flags |= Win64EH::UNW_ExceptionHandler << 3; 170 } 171 streamer.EmitIntValue(flags, 1); 172 173 if (info->PrologEnd) 174 EmitAbsDifference(streamer, info->PrologEnd, info->Begin); 175 else 176 streamer.EmitIntValue(0, 1); 177 178 uint8_t numCodes = CountOfUnwindCodes(info->Instructions); 179 streamer.EmitIntValue(numCodes, 1); 180 181 uint8_t frame = 0; 182 if (info->LastFrameInst >= 0) { 183 MCWin64EHInstruction &frameInst = info->Instructions[info->LastFrameInst]; 184 assert(frameInst.getOperation() == Win64EH::UOP_SetFPReg); 185 frame = (frameInst.getRegister() & 0x0F) | 186 (frameInst.getOffset() & 0xF0); 187 } 188 streamer.EmitIntValue(frame, 1); 189 190 // Emit unwind instructions (in reverse order). 191 uint8_t numInst = info->Instructions.size(); 192 for (uint8_t c = 0; c < numInst; ++c) { 193 MCWin64EHInstruction inst = info->Instructions.back(); 194 info->Instructions.pop_back(); 195 EmitUnwindCode(streamer, info->Begin, inst); 196 } 197 198 // For alignment purposes, the instruction array will always have an even 199 // number of entries, with the final entry potentially unused (in which case 200 // the array will be one longer than indicated by the count of unwind codes 201 // field). 202 if (numCodes & 1) { 203 streamer.EmitIntValue(0, 2); 204 } 205 206 if (flags & (Win64EH::UNW_ChainInfo << 3)) 207 EmitRuntimeFunction(streamer, info->ChainedParent); 208 else if (flags & 209 ((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3)) 210 streamer.EmitValue(MCSymbolRefExpr::Create(info->ExceptionHandler, 211 MCSymbolRefExpr::VK_COFF_IMGREL32, 212 context), 4); 213 else if (numCodes == 0) { 214 // The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not 215 // a chained unwind info, if there is no handler, and if there are fewer 216 // than 2 slots used in the unwind code array, we have to pad to 8 bytes. 217 streamer.EmitIntValue(0, 4); 218 } 219 } 220 221 StringRef MCWin64EHUnwindEmitter::GetSectionSuffix(const MCSymbol *func) { 222 if (!func || !func->isInSection()) return ""; 223 const MCSection *section = &func->getSection(); 224 const MCSectionCOFF *COFFSection; 225 if ((COFFSection = dyn_cast<MCSectionCOFF>(section))) { 226 StringRef name = COFFSection->getSectionName(); 227 size_t dollar = name.find('$'); 228 size_t dot = name.find('.', 1); 229 if (dollar == StringRef::npos && dot == StringRef::npos) 230 return ""; 231 if (dot == StringRef::npos) 232 return name.substr(dollar); 233 if (dollar == StringRef::npos || dot < dollar) 234 return name.substr(dot); 235 return name.substr(dollar); 236 } 237 return ""; 238 } 239 240 static const MCSection *getWin64EHTableSection(StringRef suffix, 241 MCContext &context) { 242 if (suffix == "") 243 return context.getObjectFileInfo()->getXDataSection(); 244 245 return context.getCOFFSection((".xdata"+suffix).str(), 246 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 247 COFF::IMAGE_SCN_MEM_READ, 248 SectionKind::getDataRel()); 249 } 250 251 static const MCSection *getWin64EHFuncTableSection(StringRef suffix, 252 MCContext &context) { 253 if (suffix == "") 254 return context.getObjectFileInfo()->getPDataSection(); 255 return context.getCOFFSection((".pdata"+suffix).str(), 256 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 257 COFF::IMAGE_SCN_MEM_READ, 258 SectionKind::getDataRel()); 259 } 260 261 void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer, 262 MCWin64EHUnwindInfo *info) { 263 // Switch sections (the static function above is meant to be called from 264 // here and from Emit(). 265 MCContext &context = streamer.getContext(); 266 const MCSection *xdataSect = 267 getWin64EHTableSection(GetSectionSuffix(info->Function), context); 268 streamer.SwitchSection(xdataSect); 269 270 llvm::EmitUnwindInfo(streamer, info); 271 } 272 273 void MCWin64EHUnwindEmitter::Emit(MCStreamer &Streamer) { 274 MCContext &Context = Streamer.getContext(); 275 276 // Emit the unwind info structs first. 277 for (const auto &CFI : Streamer.getW64UnwindInfos()) { 278 const MCSection *XData = 279 getWin64EHTableSection(GetSectionSuffix(CFI->Function), Context); 280 Streamer.SwitchSection(XData); 281 EmitUnwindInfo(Streamer, CFI); 282 } 283 284 // Now emit RUNTIME_FUNCTION entries. 285 for (const auto &CFI : Streamer.getW64UnwindInfos()) { 286 const MCSection *PData = 287 getWin64EHFuncTableSection(GetSectionSuffix(CFI->Function), Context); 288 Streamer.SwitchSection(PData); 289 EmitRuntimeFunction(Streamer, CFI); 290 } 291 } 292 293 } // End of namespace llvm 294 295
