lib/MC/MCWin64EH.cpp

   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/MCSymbol.h"
  14 #include "llvm/MC/MCSectionCOFF.h"
  15 #include "llvm/MC/MCExpr.h"
  16 #include "llvm/Target/TargetAsmInfo.h"
  17
  18 namespace llvm {
  19
  20 // NOTE: All relocations generated here are 4-byte image-relative.
  21
  22 static uint8_t CountOfUnwindCodes(std::vector<MCWin64EHInstruction> &instArray){
  23   uint8_t count = 0;
  24   for (std::vector<MCWin64EHInstruction>::const_iterator I = instArray.begin(),
  25        E = instArray.end(); I != E; ++I) {
  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       if (I->getSize() > 512*1024-8)
  43         count += 3;
  44       else
  45         count += 2;
  46       break;
  47     }
  48   }
  49   return count;
  50 }
  51
  52 static void EmitAbsDifference(MCStreamer &streamer, MCSymbol *lhs,
  53                               MCSymbol *rhs) {
  54   MCContext &context = streamer.getContext();
  55   const MCExpr *diff = MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create(
  56                                                                   lhs, context),
  57                                                MCSymbolRefExpr::Create(
  58                                                                   rhs, context),
  59                                                context);
  60   streamer.EmitAbsValue(diff, 1);
  61
  62 }
  63
  64 static void EmitUnwindCode(MCStreamer &streamer, MCSymbol *begin,
  65                            MCWin64EHInstruction &inst) {
  66   uint8_t b1, b2;
  67   uint16_t w;
  68   b2 = (inst.getOperation() & 0x0F);
  69   switch (inst.getOperation()) {
  70   case Win64EH::UOP_PushNonVol:
  71     EmitAbsDifference(streamer, inst.getLabel(), begin);
  72     b2 |= (inst.getRegister() & 0x0F) << 4;
  73     streamer.EmitIntValue(b2, 1);
  74     break;
  75   case Win64EH::UOP_AllocLarge:
  76     EmitAbsDifference(streamer, inst.getLabel(), begin);
  77     if (inst.getSize() > 512*1024-8) {
  78       b2 |= 0x10;
  79       streamer.EmitIntValue(b2, 1);
  80       w = inst.getSize() & 0xFFF8;
  81       streamer.EmitIntValue(w, 2);
  82       w = inst.getSize() >> 16;
  83     } else {
  84       streamer.EmitIntValue(b2, 1);
  85       w = inst.getSize() >> 3;
  86     }
  87     streamer.EmitIntValue(w, 2);
  88     break;
  89   case Win64EH::UOP_AllocSmall:
  90     b2 |= (((inst.getSize()-8) >> 3) & 0x0F) << 4;
  91     EmitAbsDifference(streamer, inst.getLabel(), begin);
  92     streamer.EmitIntValue(b2, 1);
  93     break;
  94   case Win64EH::UOP_SetFPReg:
  95     b1 = inst.getOffset() & 0xF0;
  96     streamer.EmitIntValue(b1, 1);
  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
 131 static void EmitRuntimeFunction(MCStreamer &streamer,
 132                                 const MCWin64EHUnwindInfo *info) {
 133   MCContext &context = streamer.getContext();
 134
 135   streamer.EmitValueToAlignment(4);
 136   streamer.EmitValue(MCSymbolRefExpr::Create(info->Begin, context), 4);
 137   streamer.EmitValue(MCSymbolRefExpr::Create(info->End, context), 4);
 138   streamer.EmitValue(MCSymbolRefExpr::Create(info->Symbol, context), 4);
 139 }
 140
 141 static void EmitUnwindInfo(MCStreamer &streamer, MCWin64EHUnwindInfo *info) {
 142   // If this UNWIND_INFO already has a symbol, it's already been emitted.
 143   if (info->Symbol) return;
 144
 145   MCContext &context = streamer.getContext();
 146   streamer.EmitValueToAlignment(4);
 147   // Upper 3 bits are the version number (currently 1).
 148   uint8_t flags = 0x01;
 149   info->Symbol = context.CreateTempSymbol();
 150   streamer.EmitLabel(info->Symbol);
 151
 152   if (info->ChainedParent)
 153     flags |= Win64EH::UNW_ChainInfo << 3;
 154   else {
 155     if (info->HandlesUnwind)
 156       flags |= Win64EH::UNW_TerminateHandler << 3;
 157     if (info->HandlesExceptions)
 158       flags |= Win64EH::UNW_ExceptionHandler << 3;
 159   }
 160   streamer.EmitIntValue(flags, 1);
 161
 162   if (info->PrologEnd)
 163     EmitAbsDifference(streamer, info->PrologEnd, info->Begin);
 164   else
 165     streamer.EmitIntValue(0, 1);
 166
 167   uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
 168   streamer.EmitIntValue(numCodes, 1);
 169
 170   uint8_t frame = 0;
 171   if (info->LastFrameInst >= 0) {
 172     MCWin64EHInstruction &frameInst = info->Instructions[info->LastFrameInst];
 173     assert(frameInst.getOperation() == Win64EH::UOP_SetFPReg);
 174     frame = (frameInst.getRegister() & 0x0F) |
 175             (frameInst.getOffset() & 0xF0);
 176   }
 177   streamer.EmitIntValue(frame, 1);
 178
 179   // Emit unwind instructions (in reverse order).
 180   uint8_t numInst = info->Instructions.size();
 181   for (uint8_t c = 0; c < numInst; ++c) {
 182     MCWin64EHInstruction inst = info->Instructions.back();
 183     info->Instructions.pop_back();
 184     EmitUnwindCode(streamer, info->Begin, inst);
 185   }
 186
 187   if (flags & (Win64EH::UNW_ChainInfo << 3))
 188     EmitRuntimeFunction(streamer, info->ChainedParent);
 189   else if (flags &
 190            ((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3))
 191     streamer.EmitValue(MCSymbolRefExpr::Create(info->ExceptionHandler, context),
 192                        4);
 193   else if (numCodes < 2) {
 194     // The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not
 195     // a chained unwind info, if there is no handler, and if there are fewer
 196     // than 2 slots used in the unwind code array, we have to pad to 8 bytes.
 197     if (numCodes == 1)
 198       streamer.EmitIntValue(0, 2);
 199     else
 200       streamer.EmitIntValue(0, 4);
 201   }
 202 }
 203
 204 StringRef MCWin64EHUnwindEmitter::GetSectionSuffix(const MCSymbol *func) {
 205   if (!func || !func->isInSection()) return "";
 206   const MCSection *section = &func->getSection();
 207   const MCSectionCOFF *COFFSection;
 208   if ((COFFSection = dyn_cast<MCSectionCOFF>(section))) {
 209     StringRef name = COFFSection->getSectionName();
 210     size_t dollar = name.find('$');
 211     size_t dot = name.find('.', 1);
 212     if (dollar == StringRef::npos && dot == StringRef::npos)
 213       return "";
 214     if (dot == StringRef::npos)
 215       return name.substr(dollar);
 216     if (dollar == StringRef::npos || dot < dollar)
 217       return name.substr(dot);
 218     return name.substr(dollar);
 219   }
 220   return "";
 221 }
 222
 223 void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer,
 224                                             MCWin64EHUnwindInfo *info) {
 225   // Switch sections (the static function above is meant to be called from
 226   // here and from Emit().
 227   MCContext &context = streamer.getContext();
 228   const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
 229   const MCSection *xdataSect =
 230     asmInfo.getWin64EHTableSection(GetSectionSuffix(info->Function));
 231   streamer.SwitchSection(xdataSect);
 232
 233   llvm::EmitUnwindInfo(streamer, info);
 234 }
 235
 236 void MCWin64EHUnwindEmitter::Emit(MCStreamer &streamer) {
 237   MCContext &context = streamer.getContext();
 238   // Emit the unwind info structs first.
 239   const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
 240   for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) {
 241     MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i);
 242     const MCSection *xdataSect =
 243       asmInfo.getWin64EHTableSection(GetSectionSuffix(info.Function));
 244     streamer.SwitchSection(xdataSect);
 245     llvm::EmitUnwindInfo(streamer, &info);
 246   }
 247   // Now emit RUNTIME_FUNCTION entries.
 248   for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) {
 249     MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i);
 250     const MCSection *pdataSect =
 251       asmInfo.getWin64EHFuncTableSection(GetSectionSuffix(info.Function));
 252     streamer.SwitchSection(pdataSect);
 253     EmitRuntimeFunction(streamer, &info);
 254   }
 255 }
 256
 257 } // End of namespace llvm
 258