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/MC/MCStreamer.h" 12 #include "llvm/MC/MCContext.h" 13 #include "llvm/MC/MCObjectFileInfo.h" 14 #include "llvm/MC/MCSymbol.h" 15 #include "llvm/MC/MCSectionCOFF.h" 16 #include "llvm/MC/MCExpr.h" 17 #include "llvm/ADT/Twine.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> &instArray){ 24 uint8_t count = 0; 25 for (std::vector<MCWin64EHInstruction>::const_iterator I = instArray.begin(), 26 E = instArray.end(); I != E; ++I) { 27 switch (I->getOperation()) { 28 case Win64EH::UOP_PushNonVol: 29 case Win64EH::UOP_AllocSmall: 30 case Win64EH::UOP_SetFPReg: 31 case Win64EH::UOP_PushMachFrame: 32 count += 1; 33 break; 34 case Win64EH::UOP_SaveNonVol: 35 case Win64EH::UOP_SaveXMM128: 36 count += 2; 37 break; 38 case Win64EH::UOP_SaveNonVolBig: 39 case Win64EH::UOP_SaveXMM128Big: 40 count += 3; 41 break; 42 case Win64EH::UOP_AllocLarge: 43 if (I->getSize() > 512*1024-8) 44 count += 3; 45 else 46 count += 2; 47 break; 48 } 49 } 50 return count; 51 } 52 53 static void EmitAbsDifference(MCStreamer &streamer, MCSymbol *lhs, 54 MCSymbol *rhs) { 55 MCContext &context = streamer.getContext(); 56 const MCExpr *diff = MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create( 57 lhs, context), 58 MCSymbolRefExpr::Create( 59 rhs, context), 60 context); 61 streamer.EmitAbsValue(diff, 1); 62 63 } 64 65 static void EmitUnwindCode(MCStreamer &streamer, MCSymbol *begin, 66 MCWin64EHInstruction &inst) { 67 uint8_t b1, b2; 68 uint16_t w; 69 b2 = (inst.getOperation() & 0x0F); 70 switch (inst.getOperation()) { 71 case Win64EH::UOP_PushNonVol: 72 EmitAbsDifference(streamer, inst.getLabel(), begin); 73 b2 |= (inst.getRegister() & 0x0F) << 4; 74 streamer.EmitIntValue(b2, 1); 75 break; 76 case Win64EH::UOP_AllocLarge: 77 EmitAbsDifference(streamer, inst.getLabel(), begin); 78 if (inst.getSize() > 512*1024-8) { 79 b2 |= 0x10; 80 streamer.EmitIntValue(b2, 1); 81 w = inst.getSize() & 0xFFF8; 82 streamer.EmitIntValue(w, 2); 83 w = inst.getSize() >> 16; 84 } else { 85 streamer.EmitIntValue(b2, 1); 86 w = inst.getSize() >> 3; 87 } 88 streamer.EmitIntValue(w, 2); 89 break; 90 case Win64EH::UOP_AllocSmall: 91 b2 |= (((inst.getSize()-8) >> 3) & 0x0F) << 4; 92 EmitAbsDifference(streamer, inst.getLabel(), begin); 93 streamer.EmitIntValue(b2, 1); 94 break; 95 case Win64EH::UOP_SetFPReg: 96 b1 = inst.getOffset() & 0xF0; 97 streamer.EmitIntValue(b1, 1); 98 streamer.EmitIntValue(b2, 1); 99 break; 100 case Win64EH::UOP_SaveNonVol: 101 case Win64EH::UOP_SaveXMM128: 102 b2 |= (inst.getRegister() & 0x0F) << 4; 103 EmitAbsDifference(streamer, inst.getLabel(), begin); 104 streamer.EmitIntValue(b2, 1); 105 w = inst.getOffset() >> 3; 106 if (inst.getOperation() == Win64EH::UOP_SaveXMM128) 107 w >>= 1; 108 streamer.EmitIntValue(w, 2); 109 break; 110 case Win64EH::UOP_SaveNonVolBig: 111 case Win64EH::UOP_SaveXMM128Big: 112 b2 |= (inst.getRegister() & 0x0F) << 4; 113 EmitAbsDifference(streamer, inst.getLabel(), begin); 114 streamer.EmitIntValue(b2, 1); 115 if (inst.getOperation() == Win64EH::UOP_SaveXMM128Big) 116 w = inst.getOffset() & 0xFFF0; 117 else 118 w = inst.getOffset() & 0xFFF8; 119 streamer.EmitIntValue(w, 2); 120 w = inst.getOffset() >> 16; 121 streamer.EmitIntValue(w, 2); 122 break; 123 case Win64EH::UOP_PushMachFrame: 124 if (inst.isPushCodeFrame()) 125 b2 |= 0x10; 126 EmitAbsDifference(streamer, inst.getLabel(), begin); 127 streamer.EmitIntValue(b2, 1); 128 break; 129 } 130 } 131 132 static void EmitRuntimeFunction(MCStreamer &streamer, 133 const MCWin64EHUnwindInfo *info) { 134 MCContext &context = streamer.getContext(); 135 136 streamer.EmitValueToAlignment(4); 137 streamer.EmitValue(MCSymbolRefExpr::Create(info->Begin, context), 4); 138 streamer.EmitValue(MCSymbolRefExpr::Create(info->End, context), 4); 139 streamer.EmitValue(MCSymbolRefExpr::Create(info->Symbol, context), 4); 140 } 141 142 static void EmitUnwindInfo(MCStreamer &streamer, MCWin64EHUnwindInfo *info) { 143 // If this UNWIND_INFO already has a symbol, it's already been emitted. 144 if (info->Symbol) return; 145 146 MCContext &context = streamer.getContext(); 147 streamer.EmitValueToAlignment(4); 148 // Upper 3 bits are the version number (currently 1). 149 uint8_t flags = 0x01; 150 info->Symbol = context.CreateTempSymbol(); 151 streamer.EmitLabel(info->Symbol); 152 153 if (info->ChainedParent) 154 flags |= Win64EH::UNW_ChainInfo << 3; 155 else { 156 if (info->HandlesUnwind) 157 flags |= Win64EH::UNW_TerminateHandler << 3; 158 if (info->HandlesExceptions) 159 flags |= Win64EH::UNW_ExceptionHandler << 3; 160 } 161 streamer.EmitIntValue(flags, 1); 162 163 if (info->PrologEnd) 164 EmitAbsDifference(streamer, info->PrologEnd, info->Begin); 165 else 166 streamer.EmitIntValue(0, 1); 167 168 uint8_t numCodes = CountOfUnwindCodes(info->Instructions); 169 streamer.EmitIntValue(numCodes, 1); 170 171 uint8_t frame = 0; 172 if (info->LastFrameInst >= 0) { 173 MCWin64EHInstruction &frameInst = info->Instructions[info->LastFrameInst]; 174 assert(frameInst.getOperation() == Win64EH::UOP_SetFPReg); 175 frame = (frameInst.getRegister() & 0x0F) | 176 (frameInst.getOffset() & 0xF0); 177 } 178 streamer.EmitIntValue(frame, 1); 179 180 // Emit unwind instructions (in reverse order). 181 uint8_t numInst = info->Instructions.size(); 182 for (uint8_t c = 0; c < numInst; ++c) { 183 MCWin64EHInstruction inst = info->Instructions.back(); 184 info->Instructions.pop_back(); 185 EmitUnwindCode(streamer, info->Begin, inst); 186 } 187 188 if (flags & (Win64EH::UNW_ChainInfo << 3)) 189 EmitRuntimeFunction(streamer, info->ChainedParent); 190 else if (flags & 191 ((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3)) 192 streamer.EmitValue(MCSymbolRefExpr::Create(info->ExceptionHandler, context), 193 4); 194 else if (numCodes < 2) { 195 // The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not 196 // a chained unwind info, if there is no handler, and if there are fewer 197 // than 2 slots used in the unwind code array, we have to pad to 8 bytes. 198 if (numCodes == 1) 199 streamer.EmitIntValue(0, 2); 200 else 201 streamer.EmitIntValue(0, 4); 202 } 203 } 204 205 StringRef MCWin64EHUnwindEmitter::GetSectionSuffix(const MCSymbol *func) { 206 if (!func || !func->isInSection()) return ""; 207 const MCSection *section = &func->getSection(); 208 const MCSectionCOFF *COFFSection; 209 if ((COFFSection = dyn_cast<MCSectionCOFF>(section))) { 210 StringRef name = COFFSection->getSectionName(); 211 size_t dollar = name.find('$'); 212 size_t dot = name.find('.', 1); 213 if (dollar == StringRef::npos && dot == StringRef::npos) 214 return ""; 215 if (dot == StringRef::npos) 216 return name.substr(dollar); 217 if (dollar == StringRef::npos || dot < dollar) 218 return name.substr(dot); 219 return name.substr(dollar); 220 } 221 return ""; 222 } 223 224 static const MCSection *getWin64EHTableSection(StringRef suffix, 225 MCContext &context) { 226 if (suffix == "") 227 return context.getObjectFileInfo()->getXDataSection(); 228 229 return context.getCOFFSection((".xdata"+suffix).str(), 230 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 231 COFF::IMAGE_SCN_MEM_READ | 232 COFF::IMAGE_SCN_MEM_WRITE, 233 SectionKind::getDataRel()); 234 } 235 236 static const MCSection *getWin64EHFuncTableSection(StringRef suffix, 237 MCContext &context) { 238 if (suffix == "") 239 return context.getObjectFileInfo()->getPDataSection(); 240 return context.getCOFFSection((".pdata"+suffix).str(), 241 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 242 COFF::IMAGE_SCN_MEM_READ | 243 COFF::IMAGE_SCN_MEM_WRITE, 244 SectionKind::getDataRel()); 245 } 246 247 void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer, 248 MCWin64EHUnwindInfo *info) { 249 // Switch sections (the static function above is meant to be called from 250 // here and from Emit(). 251 MCContext &context = streamer.getContext(); 252 const MCSection *xdataSect = 253 getWin64EHTableSection(GetSectionSuffix(info->Function), context); 254 streamer.SwitchSection(xdataSect); 255 256 llvm::EmitUnwindInfo(streamer, info); 257 } 258 259 void MCWin64EHUnwindEmitter::Emit(MCStreamer &streamer) { 260 MCContext &context = streamer.getContext(); 261 // Emit the unwind info structs first. 262 for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) { 263 MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i); 264 const MCSection *xdataSect = 265 getWin64EHTableSection(GetSectionSuffix(info.Function), context); 266 streamer.SwitchSection(xdataSect); 267 llvm::EmitUnwindInfo(streamer, &info); 268 } 269 // Now emit RUNTIME_FUNCTION entries. 270 for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) { 271 MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i); 272 const MCSection *pdataSect = 273 getWin64EHFuncTableSection(GetSectionSuffix(info.Function), context); 274 streamer.SwitchSection(pdataSect); 275 EmitRuntimeFunction(streamer, &info); 276 } 277 } 278 279 } // End of namespace llvm 280 281
