MCWin64EH.cpp revision 5310cdbcc909a7c35d4c7df0fd5703850a9db2a5 
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 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
132static 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
142static 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
205StringRef 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
224static 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                                SectionKind::getDataRel());
233}
234
235static const MCSection *getWin64EHFuncTableSection(StringRef suffix,
236                                                   MCContext &context) {
237  if (suffix == "")
238    return context.getObjectFileInfo()->getPDataSection();
239  return context.getCOFFSection((".pdata"+suffix).str(),
240                                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
241                                COFF::IMAGE_SCN_MEM_READ,
242                                SectionKind::getDataRel());
243}
244
245void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer,
246                                            MCWin64EHUnwindInfo *info) {
247  // Switch sections (the static function above is meant to be called from
248  // here and from Emit().
249  MCContext &context = streamer.getContext();
250  const MCSection *xdataSect =
251    getWin64EHTableSection(GetSectionSuffix(info->Function), context);
252  streamer.SwitchSection(xdataSect);
253
254  llvm::EmitUnwindInfo(streamer, info);
255}
256
257void MCWin64EHUnwindEmitter::Emit(MCStreamer &streamer) {
258  MCContext &context = streamer.getContext();
259  // Emit the unwind info structs first.
260  for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) {
261    MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i);
262    const MCSection *xdataSect =
263      getWin64EHTableSection(GetSectionSuffix(info.Function), context);
264    streamer.SwitchSection(xdataSect);
265    llvm::EmitUnwindInfo(streamer, &info);
266  }
267  // Now emit RUNTIME_FUNCTION entries.
268  for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) {
269    MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i);
270    const MCSection *pdataSect =
271      getWin64EHFuncTableSection(GetSectionSuffix(info.Function), context);
272    streamer.SwitchSection(pdataSect);
273    EmitRuntimeFunction(streamer, &info);
274  }
275}
276
277} // End of namespace llvm
278
279