MCWin64EH.cpp revision 263508
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 19namespace llvm { 20 21// NOTE: All relocations generated here are 4-byte image-relative. 22 23static 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 53static 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 65static void EmitUnwindCode(MCStreamer &streamer, MCSymbol *begin, 66 MCWin64EHInstruction &inst) { 67 uint8_t 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 EmitAbsDifference(streamer, inst.getLabel(), begin); 97 streamer.EmitIntValue(b2, 1); 98 break; 99 case Win64EH::UOP_SaveNonVol: 100 case Win64EH::UOP_SaveXMM128: 101 b2 |= (inst.getRegister() & 0x0F) << 4; 102 EmitAbsDifference(streamer, inst.getLabel(), begin); 103 streamer.EmitIntValue(b2, 1); 104 w = inst.getOffset() >> 3; 105 if (inst.getOperation() == Win64EH::UOP_SaveXMM128) 106 w >>= 1; 107 streamer.EmitIntValue(w, 2); 108 break; 109 case Win64EH::UOP_SaveNonVolBig: 110 case Win64EH::UOP_SaveXMM128Big: 111 b2 |= (inst.getRegister() & 0x0F) << 4; 112 EmitAbsDifference(streamer, inst.getLabel(), begin); 113 streamer.EmitIntValue(b2, 1); 114 if (inst.getOperation() == Win64EH::UOP_SaveXMM128Big) 115 w = inst.getOffset() & 0xFFF0; 116 else 117 w = inst.getOffset() & 0xFFF8; 118 streamer.EmitIntValue(w, 2); 119 w = inst.getOffset() >> 16; 120 streamer.EmitIntValue(w, 2); 121 break; 122 case Win64EH::UOP_PushMachFrame: 123 if (inst.isPushCodeFrame()) 124 b2 |= 0x10; 125 EmitAbsDifference(streamer, inst.getLabel(), begin); 126 streamer.EmitIntValue(b2, 1); 127 break; 128 } 129} 130 131static void EmitSymbolRefWithOfs(MCStreamer &streamer, 132 const MCSymbol *Base, 133 const MCSymbol *Other) { 134 MCContext &Context = streamer.getContext(); 135 const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::Create(Base, Context); 136 const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::Create(Other, Context); 137 const MCExpr *Ofs = MCBinaryExpr::CreateSub(OtherRef, BaseRef, Context); 138 const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::Create(Base, 139 MCSymbolRefExpr::VK_COFF_IMGREL32, 140 Context); 141 streamer.EmitValue(MCBinaryExpr::CreateAdd(BaseRefRel, Ofs, Context), 4); 142} 143 144static void EmitRuntimeFunction(MCStreamer &streamer, 145 const MCWin64EHUnwindInfo *info) { 146 MCContext &context = streamer.getContext(); 147 148 streamer.EmitValueToAlignment(4); 149 EmitSymbolRefWithOfs(streamer, info->Function, info->Begin); 150 EmitSymbolRefWithOfs(streamer, info->Function, info->End); 151 streamer.EmitValue(MCSymbolRefExpr::Create(info->Symbol, 152 MCSymbolRefExpr::VK_COFF_IMGREL32, 153 context), 4); 154} 155 156static void EmitUnwindInfo(MCStreamer &streamer, MCWin64EHUnwindInfo *info) { 157 // If this UNWIND_INFO already has a symbol, it's already been emitted. 158 if (info->Symbol) return; 159 160 MCContext &context = streamer.getContext(); 161 streamer.EmitValueToAlignment(4); 162 info->Symbol = context.CreateTempSymbol(); 163 streamer.EmitLabel(info->Symbol); 164 165 // Upper 3 bits are the version number (currently 1). 166 uint8_t flags = 0x01; 167 if (info->ChainedParent) 168 flags |= Win64EH::UNW_ChainInfo << 3; 169 else { 170 if (info->HandlesUnwind) 171 flags |= Win64EH::UNW_TerminateHandler << 3; 172 if (info->HandlesExceptions) 173 flags |= Win64EH::UNW_ExceptionHandler << 3; 174 } 175 streamer.EmitIntValue(flags, 1); 176 177 if (info->PrologEnd) 178 EmitAbsDifference(streamer, info->PrologEnd, info->Begin); 179 else 180 streamer.EmitIntValue(0, 1); 181 182 uint8_t numCodes = CountOfUnwindCodes(info->Instructions); 183 streamer.EmitIntValue(numCodes, 1); 184 185 uint8_t frame = 0; 186 if (info->LastFrameInst >= 0) { 187 MCWin64EHInstruction &frameInst = info->Instructions[info->LastFrameInst]; 188 assert(frameInst.getOperation() == Win64EH::UOP_SetFPReg); 189 frame = (frameInst.getRegister() & 0x0F) | 190 (frameInst.getOffset() & 0xF0); 191 } 192 streamer.EmitIntValue(frame, 1); 193 194 // Emit unwind instructions (in reverse order). 195 uint8_t numInst = info->Instructions.size(); 196 for (uint8_t c = 0; c < numInst; ++c) { 197 MCWin64EHInstruction inst = info->Instructions.back(); 198 info->Instructions.pop_back(); 199 EmitUnwindCode(streamer, info->Begin, inst); 200 } 201 202 // For alignment purposes, the instruction array will always have an even 203 // number of entries, with the final entry potentially unused (in which case 204 // the array will be one longer than indicated by the count of unwind codes 205 // field). 206 if (numCodes & 1) { 207 streamer.EmitIntValue(0, 2); 208 } 209 210 if (flags & (Win64EH::UNW_ChainInfo << 3)) 211 EmitRuntimeFunction(streamer, info->ChainedParent); 212 else if (flags & 213 ((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3)) 214 streamer.EmitValue(MCSymbolRefExpr::Create(info->ExceptionHandler, 215 MCSymbolRefExpr::VK_COFF_IMGREL32, 216 context), 4); 217 else if (numCodes == 0) { 218 // The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not 219 // a chained unwind info, if there is no handler, and if there are fewer 220 // than 2 slots used in the unwind code array, we have to pad to 8 bytes. 221 streamer.EmitIntValue(0, 4); 222 } 223} 224 225StringRef MCWin64EHUnwindEmitter::GetSectionSuffix(const MCSymbol *func) { 226 if (!func || !func->isInSection()) return ""; 227 const MCSection *section = &func->getSection(); 228 const MCSectionCOFF *COFFSection; 229 if ((COFFSection = dyn_cast<MCSectionCOFF>(section))) { 230 StringRef name = COFFSection->getSectionName(); 231 size_t dollar = name.find('$'); 232 size_t dot = name.find('.', 1); 233 if (dollar == StringRef::npos && dot == StringRef::npos) 234 return ""; 235 if (dot == StringRef::npos) 236 return name.substr(dollar); 237 if (dollar == StringRef::npos || dot < dollar) 238 return name.substr(dot); 239 return name.substr(dollar); 240 } 241 return ""; 242} 243 244static const MCSection *getWin64EHTableSection(StringRef suffix, 245 MCContext &context) { 246 if (suffix == "") 247 return context.getObjectFileInfo()->getXDataSection(); 248 249 return context.getCOFFSection((".xdata"+suffix).str(), 250 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 251 COFF::IMAGE_SCN_MEM_READ, 252 SectionKind::getDataRel()); 253} 254 255static const MCSection *getWin64EHFuncTableSection(StringRef suffix, 256 MCContext &context) { 257 if (suffix == "") 258 return context.getObjectFileInfo()->getPDataSection(); 259 return context.getCOFFSection((".pdata"+suffix).str(), 260 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 261 COFF::IMAGE_SCN_MEM_READ, 262 SectionKind::getDataRel()); 263} 264 265void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer, 266 MCWin64EHUnwindInfo *info) { 267 // Switch sections (the static function above is meant to be called from 268 // here and from Emit(). 269 MCContext &context = streamer.getContext(); 270 const MCSection *xdataSect = 271 getWin64EHTableSection(GetSectionSuffix(info->Function), context); 272 streamer.SwitchSection(xdataSect); 273 274 llvm::EmitUnwindInfo(streamer, info); 275} 276 277void MCWin64EHUnwindEmitter::Emit(MCStreamer &streamer) { 278 MCContext &context = streamer.getContext(); 279 // Emit the unwind info structs first. 280 for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) { 281 MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i); 282 const MCSection *xdataSect = 283 getWin64EHTableSection(GetSectionSuffix(info.Function), context); 284 streamer.SwitchSection(xdataSect); 285 llvm::EmitUnwindInfo(streamer, &info); 286 } 287 // Now emit RUNTIME_FUNCTION entries. 288 for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) { 289 MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i); 290 const MCSection *pdataSect = 291 getWin64EHFuncTableSection(GetSectionSuffix(info.Function), context); 292 streamer.SwitchSection(pdataSect); 293 EmitRuntimeFunction(streamer, &info); 294 } 295} 296 297} // End of namespace llvm 298 299