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