MCWin64EH.cpp revision ea434e4bca15383418ac65788fdb8bc3b5725fe2 
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 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    EmitAbsDifference(streamer, inst.getLabel(), begin);
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
131static 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
141static 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
204StringRef 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
223static const MCSection *getWin64EHTableSection(StringRef suffix,
224                                               MCContext &context) {
225  if (suffix == "")
226    return context.getObjectFileInfo()->getXDataSection();
227
228  return context.getCOFFSection((".xdata"+suffix).str(),
229                                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
230                                COFF::IMAGE_SCN_MEM_READ,
231                                SectionKind::getDataRel());
232}
233
234static const MCSection *getWin64EHFuncTableSection(StringRef suffix,
235                                                   MCContext &context) {
236  if (suffix == "")
237    return context.getObjectFileInfo()->getPDataSection();
238  return context.getCOFFSection((".pdata"+suffix).str(),
239                                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
240                                COFF::IMAGE_SCN_MEM_READ,
241                                SectionKind::getDataRel());
242}
243
244void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer,
245                                            MCWin64EHUnwindInfo *info) {
246  // Switch sections (the static function above is meant to be called from
247  // here and from Emit().
248  MCContext &context = streamer.getContext();
249  const MCSection *xdataSect =
250    getWin64EHTableSection(GetSectionSuffix(info->Function), context);
251  streamer.SwitchSection(xdataSect);
252
253  llvm::EmitUnwindInfo(streamer, info);
254}
255
256void MCWin64EHUnwindEmitter::Emit(MCStreamer &streamer) {
257  MCContext &context = streamer.getContext();
258  // Emit the unwind info structs first.
259  for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) {
260    MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i);
261    const MCSection *xdataSect =
262      getWin64EHTableSection(GetSectionSuffix(info.Function), context);
263    streamer.SwitchSection(xdataSect);
264    llvm::EmitUnwindInfo(streamer, &info);
265  }
266  // Now emit RUNTIME_FUNCTION entries.
267  for (unsigned i = 0; i < streamer.getNumW64UnwindInfos(); ++i) {
268    MCWin64EHUnwindInfo &info = streamer.getW64UnwindInfo(i);
269    const MCSection *pdataSect =
270      getWin64EHFuncTableSection(GetSectionSuffix(info.Function), context);
271    streamer.SwitchSection(pdataSect);
272    EmitRuntimeFunction(streamer, &info);
273  }
274}
275
276} // End of namespace llvm
277
278