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 
CountOfUnwindCodes(std::vector<MCWin64EHInstruction> & instArray)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 
EmitAbsDifference(MCStreamer & streamer,MCSymbol * lhs,MCSymbol * rhs)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 
EmitUnwindCode(MCStreamer & streamer,MCSymbol * begin,MCWin64EHInstruction & inst)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 
EmitRuntimeFunction(MCStreamer & streamer,const MCWin64EHUnwindInfo * info)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 
EmitUnwindInfo(MCStreamer & streamer,MCWin64EHUnwindInfo * info)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 
GetSectionSuffix(const MCSymbol * func)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 
getWin64EHTableSection(StringRef suffix,MCContext & context)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 
getWin64EHFuncTableSection(StringRef suffix,MCContext & context)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 
EmitUnwindInfo(MCStreamer & streamer,MCWin64EHUnwindInfo * info)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 
Emit(MCStreamer & streamer)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