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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/MCStreamer.h"
15 : #include "llvm/MC/MCSymbol.h"
16 : #include "llvm/Support/Win64EH.h"
17 :
18 : using namespace llvm;
19 :
20 : // NOTE: All relocations generated here are 4-byte image-relative.
21 :
22 108 : static uint8_t CountOfUnwindCodes(std::vector<WinEH::Instruction> &Insns) {
23 : uint8_t Count = 0;
24 266 : for (const auto &I : Insns) {
25 158 : switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
26 147 : case Win64EH::UOP_PushNonVol:
27 : case Win64EH::UOP_AllocSmall:
28 : case Win64EH::UOP_SetFPReg:
29 : case Win64EH::UOP_PushMachFrame:
30 147 : Count += 1;
31 147 : break;
32 4 : case Win64EH::UOP_SaveNonVol:
33 : case Win64EH::UOP_SaveXMM128:
34 4 : Count += 2;
35 4 : break;
36 0 : case Win64EH::UOP_SaveNonVolBig:
37 : case Win64EH::UOP_SaveXMM128Big:
38 0 : Count += 3;
39 0 : break;
40 7 : case Win64EH::UOP_AllocLarge:
41 7 : Count += (I.Offset > 512 * 1024 - 8) ? 3 : 2;
42 7 : break;
43 : }
44 : }
45 108 : return Count;
46 : }
47 :
48 261 : static void EmitAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
49 : const MCSymbol *RHS) {
50 261 : MCContext &Context = Streamer.getContext();
51 : const MCExpr *Diff =
52 : MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
53 : MCSymbolRefExpr::create(RHS, Context), Context);
54 261 : Streamer.EmitValue(Diff, 1);
55 261 : }
56 :
57 158 : static void EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
58 : WinEH::Instruction &inst) {
59 : uint8_t b2;
60 : uint16_t w;
61 158 : b2 = (inst.Operation & 0x0F);
62 158 : switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
63 49 : case Win64EH::UOP_PushNonVol:
64 49 : EmitAbsDifference(streamer, inst.Label, begin);
65 49 : b2 |= (inst.Register & 0x0F) << 4;
66 49 : streamer.EmitIntValue(b2, 1);
67 49 : break;
68 7 : case Win64EH::UOP_AllocLarge:
69 7 : EmitAbsDifference(streamer, inst.Label, begin);
70 7 : if (inst.Offset > 512 * 1024 - 8) {
71 0 : b2 |= 0x10;
72 0 : streamer.EmitIntValue(b2, 1);
73 0 : w = inst.Offset & 0xFFF8;
74 0 : streamer.EmitIntValue(w, 2);
75 0 : w = inst.Offset >> 16;
76 : } else {
77 7 : streamer.EmitIntValue(b2, 1);
78 7 : w = inst.Offset >> 3;
79 : }
80 7 : streamer.EmitIntValue(w, 2);
81 7 : break;
82 93 : case Win64EH::UOP_AllocSmall:
83 93 : b2 |= (((inst.Offset - 8) >> 3) & 0x0F) << 4;
84 93 : EmitAbsDifference(streamer, inst.Label, begin);
85 93 : streamer.EmitIntValue(b2, 1);
86 93 : break;
87 4 : case Win64EH::UOP_SetFPReg:
88 4 : EmitAbsDifference(streamer, inst.Label, begin);
89 4 : streamer.EmitIntValue(b2, 1);
90 4 : break;
91 4 : case Win64EH::UOP_SaveNonVol:
92 : case Win64EH::UOP_SaveXMM128:
93 4 : b2 |= (inst.Register & 0x0F) << 4;
94 4 : EmitAbsDifference(streamer, inst.Label, begin);
95 4 : streamer.EmitIntValue(b2, 1);
96 4 : w = inst.Offset >> 3;
97 4 : if (inst.Operation == Win64EH::UOP_SaveXMM128)
98 3 : w >>= 1;
99 4 : streamer.EmitIntValue(w, 2);
100 4 : break;
101 0 : case Win64EH::UOP_SaveNonVolBig:
102 : case Win64EH::UOP_SaveXMM128Big:
103 0 : b2 |= (inst.Register & 0x0F) << 4;
104 0 : EmitAbsDifference(streamer, inst.Label, begin);
105 0 : streamer.EmitIntValue(b2, 1);
106 0 : if (inst.Operation == Win64EH::UOP_SaveXMM128Big)
107 0 : w = inst.Offset & 0xFFF0;
108 : else
109 0 : w = inst.Offset & 0xFFF8;
110 0 : streamer.EmitIntValue(w, 2);
111 0 : w = inst.Offset >> 16;
112 0 : streamer.EmitIntValue(w, 2);
113 0 : break;
114 1 : case Win64EH::UOP_PushMachFrame:
115 1 : if (inst.Offset == 1)
116 1 : b2 |= 0x10;
117 1 : EmitAbsDifference(streamer, inst.Label, begin);
118 1 : streamer.EmitIntValue(b2, 1);
119 1 : break;
120 : }
121 158 : }
122 :
123 212 : static void EmitSymbolRefWithOfs(MCStreamer &streamer,
124 : const MCSymbol *Base,
125 : const MCSymbol *Other) {
126 212 : MCContext &Context = streamer.getContext();
127 : const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::create(Base, Context);
128 : const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::create(Other, Context);
129 : const MCExpr *Ofs = MCBinaryExpr::createSub(OtherRef, BaseRef, Context);
130 424 : const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::create(Base,
131 : MCSymbolRefExpr::VK_COFF_IMGREL32,
132 212 : Context);
133 212 : streamer.EmitValue(MCBinaryExpr::createAdd(BaseRefRel, Ofs, Context), 4);
134 212 : }
135 :
136 106 : static void EmitRuntimeFunction(MCStreamer &streamer,
137 : const WinEH::FrameInfo *info) {
138 106 : MCContext &context = streamer.getContext();
139 :
140 106 : streamer.EmitValueToAlignment(4);
141 106 : EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
142 106 : EmitSymbolRefWithOfs(streamer, info->Function, info->End);
143 106 : streamer.EmitValue(MCSymbolRefExpr::create(info->Symbol,
144 : MCSymbolRefExpr::VK_COFF_IMGREL32,
145 106 : context), 4);
146 106 : }
147 :
148 204 : static void EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
149 : // If this UNWIND_INFO already has a symbol, it's already been emitted.
150 204 : if (info->Symbol)
151 : return;
152 :
153 108 : MCContext &context = streamer.getContext();
154 108 : MCSymbol *Label = context.createTempSymbol();
155 :
156 108 : streamer.EmitValueToAlignment(4);
157 108 : streamer.EmitLabel(Label);
158 108 : info->Symbol = Label;
159 :
160 : // Upper 3 bits are the version number (currently 1).
161 : uint8_t flags = 0x01;
162 108 : if (info->ChainedParent)
163 : flags |= Win64EH::UNW_ChainInfo << 3;
164 : else {
165 107 : if (info->HandlesUnwind)
166 : flags |= Win64EH::UNW_TerminateHandler << 3;
167 107 : if (info->HandlesExceptions)
168 4 : flags |= Win64EH::UNW_ExceptionHandler << 3;
169 : }
170 108 : streamer.EmitIntValue(flags, 1);
171 :
172 108 : if (info->PrologEnd)
173 103 : EmitAbsDifference(streamer, info->PrologEnd, info->Begin);
174 : else
175 5 : streamer.EmitIntValue(0, 1);
176 :
177 108 : uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
178 108 : streamer.EmitIntValue(numCodes, 1);
179 :
180 : uint8_t frame = 0;
181 108 : if (info->LastFrameInst >= 0) {
182 4 : WinEH::Instruction &frameInst = info->Instructions[info->LastFrameInst];
183 : assert(frameInst.Operation == Win64EH::UOP_SetFPReg);
184 4 : frame = (frameInst.Register & 0x0F) | (frameInst.Offset & 0xF0);
185 : }
186 108 : streamer.EmitIntValue(frame, 1);
187 :
188 : // Emit unwind instructions (in reverse order).
189 216 : uint8_t numInst = info->Instructions.size();
190 266 : for (uint8_t c = 0; c < numInst; ++c) {
191 158 : WinEH::Instruction inst = info->Instructions.back();
192 : info->Instructions.pop_back();
193 158 : EmitUnwindCode(streamer, info->Begin, inst);
194 : }
195 :
196 : // For alignment purposes, the instruction array will always have an even
197 : // number of entries, with the final entry potentially unused (in which case
198 : // the array will be one longer than indicated by the count of unwind codes
199 : // field).
200 108 : if (numCodes & 1) {
201 77 : streamer.EmitIntValue(0, 2);
202 : }
203 :
204 108 : if (flags & (Win64EH::UNW_ChainInfo << 3))
205 1 : EmitRuntimeFunction(streamer, info->ChainedParent);
206 107 : else if (flags &
207 : ((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3))
208 4 : streamer.EmitValue(MCSymbolRefExpr::create(info->ExceptionHandler,
209 : MCSymbolRefExpr::VK_COFF_IMGREL32,
210 4 : context), 4);
211 103 : else if (numCodes == 0) {
212 : // The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not
213 : // a chained unwind info, if there is no handler, and if there are fewer
214 : // than 2 slots used in the unwind code array, we have to pad to 8 bytes.
215 5 : streamer.EmitIntValue(0, 4);
216 : }
217 : }
218 :
219 52 : void llvm::Win64EH::UnwindEmitter::Emit(MCStreamer &Streamer) const {
220 : // Emit the unwind info structs first.
221 157 : for (const auto &CFI : Streamer.getWinFrameInfos()) {
222 105 : MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
223 105 : Streamer.SwitchSection(XData);
224 105 : ::EmitUnwindInfo(Streamer, CFI.get());
225 : }
226 :
227 : // Now emit RUNTIME_FUNCTION entries.
228 157 : for (const auto &CFI : Streamer.getWinFrameInfos()) {
229 105 : MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
230 105 : Streamer.SwitchSection(PData);
231 105 : EmitRuntimeFunction(Streamer, CFI.get());
232 : }
233 52 : }
234 :
235 99 : void llvm::Win64EH::UnwindEmitter::EmitUnwindInfo(
236 : MCStreamer &Streamer, WinEH::FrameInfo *info) const {
237 : // Switch sections (the static function above is meant to be called from
238 : // here and from Emit().
239 99 : MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
240 99 : Streamer.SwitchSection(XData);
241 :
242 99 : ::EmitUnwindInfo(Streamer, info);
243 99 : }
244 :
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