1 //===- bolt/Core/Exceptions.cpp - Helpers for C++ exceptions --------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements functions for handling C++ exception meta data. 10 // 11 // Some of the code is taken from examples/ExceptionDemo 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "bolt/Core/Exceptions.h" 16 #include "bolt/Core/BinaryFunction.h" 17 #include "llvm/ADT/ArrayRef.h" 18 #include "llvm/ADT/Twine.h" 19 #include "llvm/BinaryFormat/Dwarf.h" 20 #include "llvm/DebugInfo/DWARF/DWARFDebugFrame.h" 21 #include "llvm/Support/Casting.h" 22 #include "llvm/Support/CommandLine.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/Errc.h" 25 #include "llvm/Support/LEB128.h" 26 #include "llvm/Support/MathExtras.h" 27 #include "llvm/Support/raw_ostream.h" 28 #include <map> 29 30 #undef DEBUG_TYPE 31 #define DEBUG_TYPE "bolt-exceptions" 32 33 using namespace llvm::dwarf; 34 35 namespace opts { 36 37 extern llvm::cl::OptionCategory BoltCategory; 38 39 extern llvm::cl::opt<unsigned> Verbosity; 40 41 static llvm::cl::opt<bool> 42 PrintExceptions("print-exceptions", 43 llvm::cl::desc("print exception handling data"), 44 llvm::cl::Hidden, llvm::cl::cat(BoltCategory)); 45 46 } // namespace opts 47 48 namespace llvm { 49 namespace bolt { 50 51 // Read and dump the .gcc_exception_table section entry. 52 // 53 // .gcc_except_table section contains a set of Language-Specific Data Areas - 54 // a fancy name for exception handling tables. There's one LSDA entry per 55 // function. However, we can't actually tell which function LSDA refers to 56 // unless we parse .eh_frame entry that refers to the LSDA. 57 // Then inside LSDA most addresses are encoded relative to the function start, 58 // so we need the function context in order to get to real addresses. 59 // 60 // The best visual representation of the tables comprising LSDA and 61 // relationships between them is illustrated at: 62 // https://github.com/itanium-cxx-abi/cxx-abi/blob/master/exceptions.pdf 63 // Keep in mind that GCC implementation deviates slightly from that document. 64 // 65 // To summarize, there are 4 tables in LSDA: call site table, actions table, 66 // types table, and types index table (for indirection). The main table contains 67 // call site entries. Each call site includes a PC range that can throw an 68 // exception, a handler (landing pad), and a reference to an entry in the action 69 // table. The handler and/or action could be 0. The action entry is a head 70 // of a list of actions associated with a call site. The action table contains 71 // all such lists (it could be optimized to share list tails). Each action could 72 // be either to catch an exception of a given type, to perform a cleanup, or to 73 // propagate the exception after filtering it out (e.g. to make sure function 74 // exception specification is not violated). Catch action contains a reference 75 // to an entry in the type table, and filter action refers to an entry in the 76 // type index table to encode a set of types to filter. 77 // 78 // Call site table follows LSDA header. Action table immediately follows the 79 // call site table. 80 // 81 // Both types table and type index table start at the same location, but they 82 // grow in opposite directions (types go up, indices go down). The beginning of 83 // these tables is encoded in LSDA header. Sizes for both of the tables are not 84 // included anywhere. 85 // 86 // We have to parse all of the tables to determine their sizes. Then we have 87 // to parse the call site table and associate discovered information with 88 // actual call instructions and landing pad blocks. 89 // 90 // For the purpose of rewriting exception handling tables, we can reuse action, 91 // and type index tables in their original binary format. 92 // 93 // Type table could be encoded using position-independent references, and thus 94 // may require relocation. 95 // 96 // Ideally we should be able to re-write LSDA in-place, without the need to 97 // allocate a new space for it. Sadly there's no guarantee that the new call 98 // site table will be the same size as GCC uses uleb encodings for PC offsets. 99 // 100 // Note: some functions have LSDA entries with 0 call site entries. 101 void BinaryFunction::parseLSDA(ArrayRef<uint8_t> LSDASectionData, 102 uint64_t LSDASectionAddress) { 103 assert(CurrentState == State::Disassembled && "unexpected function state"); 104 105 if (!getLSDAAddress()) 106 return; 107 108 DWARFDataExtractor Data( 109 StringRef(reinterpret_cast<const char *>(LSDASectionData.data()), 110 LSDASectionData.size()), 111 BC.DwCtx->getDWARFObj().isLittleEndian(), 8); 112 uint64_t Offset = getLSDAAddress() - LSDASectionAddress; 113 assert(Data.isValidOffset(Offset) && "wrong LSDA address"); 114 115 uint8_t LPStartEncoding = Data.getU8(&Offset); 116 uint64_t LPStart = 0; 117 if (Optional<uint64_t> MaybeLPStart = Data.getEncodedPointer( 118 &Offset, LPStartEncoding, Offset + LSDASectionAddress)) 119 LPStart = *MaybeLPStart; 120 121 assert(LPStart == 0 && "support for split functions not implemented"); 122 123 const uint8_t TTypeEncoding = Data.getU8(&Offset); 124 size_t TTypeEncodingSize = 0; 125 uintptr_t TTypeEnd = 0; 126 if (TTypeEncoding != DW_EH_PE_omit) { 127 TTypeEnd = Data.getULEB128(&Offset); 128 TTypeEncodingSize = BC.getDWARFEncodingSize(TTypeEncoding); 129 } 130 131 if (opts::PrintExceptions) { 132 outs() << "[LSDA at 0x" << Twine::utohexstr(getLSDAAddress()) 133 << " for function " << *this << "]:\n"; 134 outs() << "LPStart Encoding = 0x" << Twine::utohexstr(LPStartEncoding) 135 << '\n'; 136 outs() << "LPStart = 0x" << Twine::utohexstr(LPStart) << '\n'; 137 outs() << "TType Encoding = 0x" << Twine::utohexstr(TTypeEncoding) << '\n'; 138 outs() << "TType End = " << TTypeEnd << '\n'; 139 } 140 141 // Table to store list of indices in type table. Entries are uleb128 values. 142 const uint64_t TypeIndexTableStart = Offset + TTypeEnd; 143 144 // Offset past the last decoded index. 145 uint64_t MaxTypeIndexTableOffset = 0; 146 147 // Max positive index used in type table. 148 unsigned MaxTypeIndex = 0; 149 150 // The actual type info table starts at the same location, but grows in 151 // opposite direction. TTypeEncoding is used to encode stored values. 152 const uint64_t TypeTableStart = Offset + TTypeEnd; 153 154 uint8_t CallSiteEncoding = Data.getU8(&Offset); 155 uint32_t CallSiteTableLength = Data.getULEB128(&Offset); 156 uint64_t CallSiteTableStart = Offset; 157 uint64_t CallSiteTableEnd = CallSiteTableStart + CallSiteTableLength; 158 uint64_t CallSitePtr = CallSiteTableStart; 159 uint64_t ActionTableStart = CallSiteTableEnd; 160 161 if (opts::PrintExceptions) { 162 outs() << "CallSite Encoding = " << (unsigned)CallSiteEncoding << '\n'; 163 outs() << "CallSite table length = " << CallSiteTableLength << '\n'; 164 outs() << '\n'; 165 } 166 167 this->HasEHRanges = CallSitePtr < CallSiteTableEnd; 168 const uint64_t RangeBase = getAddress(); 169 while (CallSitePtr < CallSiteTableEnd) { 170 uint64_t Start = *Data.getEncodedPointer(&CallSitePtr, CallSiteEncoding, 171 CallSitePtr + LSDASectionAddress); 172 uint64_t Length = *Data.getEncodedPointer(&CallSitePtr, CallSiteEncoding, 173 CallSitePtr + LSDASectionAddress); 174 uint64_t LandingPad = *Data.getEncodedPointer( 175 &CallSitePtr, CallSiteEncoding, CallSitePtr + LSDASectionAddress); 176 uint64_t ActionEntry = Data.getULEB128(&CallSitePtr); 177 178 if (opts::PrintExceptions) { 179 outs() << "Call Site: [0x" << Twine::utohexstr(RangeBase + Start) 180 << ", 0x" << Twine::utohexstr(RangeBase + Start + Length) 181 << "); landing pad: 0x" << Twine::utohexstr(LPStart + LandingPad) 182 << "; action entry: 0x" << Twine::utohexstr(ActionEntry) << "\n"; 183 outs() << " current offset is " << (CallSitePtr - CallSiteTableStart) 184 << '\n'; 185 } 186 187 // Create a handler entry if necessary. 188 MCSymbol *LPSymbol = nullptr; 189 if (LandingPad) { 190 if (!getInstructionAtOffset(LandingPad)) { 191 if (opts::Verbosity >= 1) 192 errs() << "BOLT-WARNING: landing pad " << Twine::utohexstr(LandingPad) 193 << " not pointing to an instruction in function " << *this 194 << " - ignoring.\n"; 195 } else { 196 auto Label = Labels.find(LandingPad); 197 if (Label != Labels.end()) { 198 LPSymbol = Label->second; 199 } else { 200 LPSymbol = BC.Ctx->createNamedTempSymbol("LP"); 201 Labels[LandingPad] = LPSymbol; 202 } 203 } 204 } 205 206 // Mark all call instructions in the range. 207 auto II = Instructions.find(Start); 208 auto IE = Instructions.end(); 209 assert(II != IE && "exception range not pointing to an instruction"); 210 do { 211 MCInst &Instruction = II->second; 212 if (BC.MIB->isCall(Instruction) && 213 !BC.MIB->getConditionalTailCall(Instruction)) { 214 assert(!BC.MIB->isInvoke(Instruction) && 215 "overlapping exception ranges detected"); 216 // Add extra operands to a call instruction making it an invoke from 217 // now on. 218 BC.MIB->addEHInfo(Instruction, 219 MCPlus::MCLandingPad(LPSymbol, ActionEntry)); 220 } 221 ++II; 222 } while (II != IE && II->first < Start + Length); 223 224 if (ActionEntry != 0) { 225 auto printType = [&](int Index, raw_ostream &OS) { 226 assert(Index > 0 && "only positive indices are valid"); 227 uint64_t TTEntry = TypeTableStart - Index * TTypeEncodingSize; 228 const uint64_t TTEntryAddress = TTEntry + LSDASectionAddress; 229 uint64_t TypeAddress = 230 *Data.getEncodedPointer(&TTEntry, TTypeEncoding, TTEntryAddress); 231 if ((TTypeEncoding & DW_EH_PE_pcrel) && TypeAddress == TTEntryAddress) 232 TypeAddress = 0; 233 if (TypeAddress == 0) { 234 OS << "<all>"; 235 return; 236 } 237 if (TTypeEncoding & DW_EH_PE_indirect) { 238 ErrorOr<uint64_t> PointerOrErr = BC.getPointerAtAddress(TypeAddress); 239 assert(PointerOrErr && "failed to decode indirect address"); 240 TypeAddress = *PointerOrErr; 241 } 242 if (BinaryData *TypeSymBD = BC.getBinaryDataAtAddress(TypeAddress)) 243 OS << TypeSymBD->getName(); 244 else 245 OS << "0x" << Twine::utohexstr(TypeAddress); 246 }; 247 if (opts::PrintExceptions) 248 outs() << " actions: "; 249 uint64_t ActionPtr = ActionTableStart + ActionEntry - 1; 250 int64_t ActionType; 251 int64_t ActionNext; 252 const char *Sep = ""; 253 do { 254 ActionType = Data.getSLEB128(&ActionPtr); 255 const uint32_t Self = ActionPtr; 256 ActionNext = Data.getSLEB128(&ActionPtr); 257 if (opts::PrintExceptions) 258 outs() << Sep << "(" << ActionType << ", " << ActionNext << ") "; 259 if (ActionType == 0) { 260 if (opts::PrintExceptions) 261 outs() << "cleanup"; 262 } else if (ActionType > 0) { 263 // It's an index into a type table. 264 MaxTypeIndex = 265 std::max(MaxTypeIndex, static_cast<unsigned>(ActionType)); 266 if (opts::PrintExceptions) { 267 outs() << "catch type "; 268 printType(ActionType, outs()); 269 } 270 } else { // ActionType < 0 271 if (opts::PrintExceptions) 272 outs() << "filter exception types "; 273 const char *TSep = ""; 274 // ActionType is a negative *byte* offset into *uleb128-encoded* table 275 // of indices with base 1. 276 // E.g. -1 means offset 0, -2 is offset 1, etc. The indices are 277 // encoded using uleb128 thus we cannot directly dereference them. 278 uint64_t TypeIndexTablePtr = TypeIndexTableStart - ActionType - 1; 279 while (uint64_t Index = Data.getULEB128(&TypeIndexTablePtr)) { 280 MaxTypeIndex = std::max(MaxTypeIndex, static_cast<unsigned>(Index)); 281 if (opts::PrintExceptions) { 282 outs() << TSep; 283 printType(Index, outs()); 284 TSep = ", "; 285 } 286 } 287 MaxTypeIndexTableOffset = std::max( 288 MaxTypeIndexTableOffset, TypeIndexTablePtr - TypeIndexTableStart); 289 } 290 291 Sep = "; "; 292 293 ActionPtr = Self + ActionNext; 294 } while (ActionNext); 295 if (opts::PrintExceptions) 296 outs() << '\n'; 297 } 298 } 299 if (opts::PrintExceptions) 300 outs() << '\n'; 301 302 assert(TypeIndexTableStart + MaxTypeIndexTableOffset <= 303 Data.getData().size() && 304 "LSDA entry has crossed section boundary"); 305 306 if (TTypeEnd) { 307 LSDAActionTable = LSDASectionData.slice( 308 ActionTableStart, TypeIndexTableStart - 309 MaxTypeIndex * TTypeEncodingSize - 310 ActionTableStart); 311 for (unsigned Index = 1; Index <= MaxTypeIndex; ++Index) { 312 uint64_t TTEntry = TypeTableStart - Index * TTypeEncodingSize; 313 const uint64_t TTEntryAddress = TTEntry + LSDASectionAddress; 314 uint64_t TypeAddress = 315 *Data.getEncodedPointer(&TTEntry, TTypeEncoding, TTEntryAddress); 316 if ((TTypeEncoding & DW_EH_PE_pcrel) && (TypeAddress == TTEntryAddress)) 317 TypeAddress = 0; 318 if (TTypeEncoding & DW_EH_PE_indirect) { 319 LSDATypeAddressTable.emplace_back(TypeAddress); 320 if (TypeAddress) { 321 ErrorOr<uint64_t> PointerOrErr = BC.getPointerAtAddress(TypeAddress); 322 assert(PointerOrErr && "failed to decode indirect address"); 323 TypeAddress = *PointerOrErr; 324 } 325 } 326 LSDATypeTable.emplace_back(TypeAddress); 327 } 328 LSDATypeIndexTable = 329 LSDASectionData.slice(TypeIndexTableStart, MaxTypeIndexTableOffset); 330 } 331 } 332 333 void BinaryFunction::updateEHRanges() { 334 if (getSize() == 0) 335 return; 336 337 assert(CurrentState == State::CFG_Finalized && "unexpected state"); 338 339 // Build call sites table. 340 struct EHInfo { 341 const MCSymbol *LP; // landing pad 342 uint64_t Action; 343 }; 344 345 // If previous call can throw, this is its exception handler. 346 EHInfo PreviousEH = {nullptr, 0}; 347 348 // Marker for the beginning of exceptions range. 349 const MCSymbol *StartRange = nullptr; 350 351 // Indicates whether the start range is located in a cold part. 352 bool IsStartInCold = false; 353 354 // Have we crossed hot/cold border for split functions? 355 bool SeenCold = false; 356 357 // Sites to update - either regular or cold. 358 CallSitesType *Sites = &CallSites; 359 360 for (BinaryBasicBlock *&BB : BasicBlocksLayout) { 361 362 if (BB->isCold() && !SeenCold) { 363 SeenCold = true; 364 365 // Close the range (if any) and change the target call sites. 366 if (StartRange) { 367 Sites->emplace_back(CallSite{StartRange, getFunctionEndLabel(), 368 PreviousEH.LP, PreviousEH.Action}); 369 } 370 Sites = &ColdCallSites; 371 372 // Reset the range. 373 StartRange = nullptr; 374 PreviousEH = {nullptr, 0}; 375 } 376 377 for (auto II = BB->begin(); II != BB->end(); ++II) { 378 if (!BC.MIB->isCall(*II)) 379 continue; 380 381 // Instruction can throw an exception that should be handled. 382 const bool Throws = BC.MIB->isInvoke(*II); 383 384 // Ignore the call if it's a continuation of a no-throw gap. 385 if (!Throws && !StartRange) 386 continue; 387 388 // Extract exception handling information from the instruction. 389 const MCSymbol *LP = nullptr; 390 uint64_t Action = 0; 391 if (const Optional<MCPlus::MCLandingPad> EHInfo = BC.MIB->getEHInfo(*II)) 392 std::tie(LP, Action) = *EHInfo; 393 394 // No action if the exception handler has not changed. 395 if (Throws && StartRange && PreviousEH.LP == LP && 396 PreviousEH.Action == Action) 397 continue; 398 399 // Same symbol is used for the beginning and the end of the range. 400 const MCSymbol *EHSymbol; 401 MCInst EHLabel; 402 { 403 std::unique_lock<std::shared_timed_mutex> Lock(BC.CtxMutex); 404 EHSymbol = BC.Ctx->createNamedTempSymbol("EH"); 405 BC.MIB->createEHLabel(EHLabel, EHSymbol, BC.Ctx.get()); 406 } 407 408 II = std::next(BB->insertPseudoInstr(II, EHLabel)); 409 410 // At this point we could be in one of the following states: 411 // 412 // I. Exception handler has changed and we need to close previous range 413 // and start a new one. 414 // 415 // II. Start a new exception range after the gap. 416 // 417 // III. Close current exception range and start a new gap. 418 const MCSymbol *EndRange; 419 if (StartRange) { 420 // I, III: 421 EndRange = EHSymbol; 422 } else { 423 // II: 424 StartRange = EHSymbol; 425 IsStartInCold = SeenCold; 426 EndRange = nullptr; 427 } 428 429 // Close the previous range. 430 if (EndRange) { 431 Sites->emplace_back( 432 CallSite{StartRange, EndRange, PreviousEH.LP, PreviousEH.Action}); 433 } 434 435 if (Throws) { 436 // I, II: 437 StartRange = EHSymbol; 438 IsStartInCold = SeenCold; 439 PreviousEH = EHInfo{LP, Action}; 440 } else { 441 StartRange = nullptr; 442 } 443 } 444 } 445 446 // Check if we need to close the range. 447 if (StartRange) { 448 assert((!isSplit() || Sites == &ColdCallSites) && "sites mismatch"); 449 const MCSymbol *EndRange = 450 IsStartInCold ? getFunctionColdEndLabel() : getFunctionEndLabel(); 451 Sites->emplace_back( 452 CallSite{StartRange, EndRange, PreviousEH.LP, PreviousEH.Action}); 453 } 454 } 455 456 const uint8_t DWARF_CFI_PRIMARY_OPCODE_MASK = 0xc0; 457 458 CFIReaderWriter::CFIReaderWriter(const DWARFDebugFrame &EHFrame) { 459 // Prepare FDEs for fast lookup 460 for (const dwarf::FrameEntry &Entry : EHFrame.entries()) { 461 const auto *CurFDE = dyn_cast<dwarf::FDE>(&Entry); 462 // Skip CIEs. 463 if (!CurFDE) 464 continue; 465 // There could me multiple FDEs with the same initial address, and perhaps 466 // different sizes (address ranges). Use the first entry with non-zero size. 467 auto FDEI = FDEs.lower_bound(CurFDE->getInitialLocation()); 468 if (FDEI != FDEs.end() && FDEI->first == CurFDE->getInitialLocation()) { 469 if (CurFDE->getAddressRange()) { 470 if (FDEI->second->getAddressRange() == 0) { 471 FDEI->second = CurFDE; 472 } else if (opts::Verbosity > 0) { 473 errs() << "BOLT-WARNING: different FDEs for function at 0x" 474 << Twine::utohexstr(FDEI->first) 475 << " detected; sizes: " << FDEI->second->getAddressRange() 476 << " and " << CurFDE->getAddressRange() << '\n'; 477 } 478 } 479 } else { 480 FDEs.emplace_hint(FDEI, CurFDE->getInitialLocation(), CurFDE); 481 } 482 } 483 } 484 485 bool CFIReaderWriter::fillCFIInfoFor(BinaryFunction &Function) const { 486 uint64_t Address = Function.getAddress(); 487 auto I = FDEs.find(Address); 488 // Ignore zero-length FDE ranges. 489 if (I == FDEs.end() || !I->second->getAddressRange()) 490 return true; 491 492 const FDE &CurFDE = *I->second; 493 Optional<uint64_t> LSDA = CurFDE.getLSDAAddress(); 494 Function.setLSDAAddress(LSDA ? *LSDA : 0); 495 496 uint64_t Offset = Function.getFirstInstructionOffset(); 497 uint64_t CodeAlignment = CurFDE.getLinkedCIE()->getCodeAlignmentFactor(); 498 uint64_t DataAlignment = CurFDE.getLinkedCIE()->getDataAlignmentFactor(); 499 if (CurFDE.getLinkedCIE()->getPersonalityAddress()) { 500 Function.setPersonalityFunction( 501 *CurFDE.getLinkedCIE()->getPersonalityAddress()); 502 Function.setPersonalityEncoding( 503 *CurFDE.getLinkedCIE()->getPersonalityEncoding()); 504 } 505 506 auto decodeFrameInstruction = [&Function, &Offset, Address, CodeAlignment, 507 DataAlignment]( 508 const CFIProgram::Instruction &Instr) { 509 uint8_t Opcode = Instr.Opcode; 510 if (Opcode & DWARF_CFI_PRIMARY_OPCODE_MASK) 511 Opcode &= DWARF_CFI_PRIMARY_OPCODE_MASK; 512 switch (Instr.Opcode) { 513 case DW_CFA_nop: 514 break; 515 case DW_CFA_advance_loc4: 516 case DW_CFA_advance_loc2: 517 case DW_CFA_advance_loc1: 518 case DW_CFA_advance_loc: 519 // Advance our current address 520 Offset += CodeAlignment * int64_t(Instr.Ops[0]); 521 break; 522 case DW_CFA_offset_extended_sf: 523 Function.addCFIInstruction( 524 Offset, 525 MCCFIInstruction::createOffset( 526 nullptr, Instr.Ops[0], DataAlignment * int64_t(Instr.Ops[1]))); 527 break; 528 case DW_CFA_offset_extended: 529 case DW_CFA_offset: 530 Function.addCFIInstruction( 531 Offset, MCCFIInstruction::createOffset(nullptr, Instr.Ops[0], 532 DataAlignment * Instr.Ops[1])); 533 break; 534 case DW_CFA_restore_extended: 535 case DW_CFA_restore: 536 Function.addCFIInstruction( 537 Offset, MCCFIInstruction::createRestore(nullptr, Instr.Ops[0])); 538 break; 539 case DW_CFA_set_loc: 540 assert(Instr.Ops[0] >= Address && "set_loc out of function bounds"); 541 assert(Instr.Ops[0] <= Address + Function.getSize() && 542 "set_loc out of function bounds"); 543 Offset = Instr.Ops[0] - Address; 544 break; 545 546 case DW_CFA_undefined: 547 Function.addCFIInstruction( 548 Offset, MCCFIInstruction::createUndefined(nullptr, Instr.Ops[0])); 549 break; 550 case DW_CFA_same_value: 551 Function.addCFIInstruction( 552 Offset, MCCFIInstruction::createSameValue(nullptr, Instr.Ops[0])); 553 break; 554 case DW_CFA_register: 555 Function.addCFIInstruction( 556 Offset, MCCFIInstruction::createRegister(nullptr, Instr.Ops[0], 557 Instr.Ops[1])); 558 break; 559 case DW_CFA_remember_state: 560 Function.addCFIInstruction( 561 Offset, MCCFIInstruction::createRememberState(nullptr)); 562 break; 563 case DW_CFA_restore_state: 564 Function.addCFIInstruction(Offset, 565 MCCFIInstruction::createRestoreState(nullptr)); 566 break; 567 case DW_CFA_def_cfa: 568 Function.addCFIInstruction( 569 Offset, 570 MCCFIInstruction::cfiDefCfa(nullptr, Instr.Ops[0], Instr.Ops[1])); 571 break; 572 case DW_CFA_def_cfa_sf: 573 Function.addCFIInstruction( 574 Offset, 575 MCCFIInstruction::cfiDefCfa(nullptr, Instr.Ops[0], 576 DataAlignment * int64_t(Instr.Ops[1]))); 577 break; 578 case DW_CFA_def_cfa_register: 579 Function.addCFIInstruction(Offset, MCCFIInstruction::createDefCfaRegister( 580 nullptr, Instr.Ops[0])); 581 break; 582 case DW_CFA_def_cfa_offset: 583 Function.addCFIInstruction( 584 Offset, MCCFIInstruction::cfiDefCfaOffset(nullptr, Instr.Ops[0])); 585 break; 586 case DW_CFA_def_cfa_offset_sf: 587 Function.addCFIInstruction( 588 Offset, MCCFIInstruction::cfiDefCfaOffset( 589 nullptr, DataAlignment * int64_t(Instr.Ops[0]))); 590 break; 591 case DW_CFA_GNU_args_size: 592 Function.addCFIInstruction( 593 Offset, MCCFIInstruction::createGnuArgsSize(nullptr, Instr.Ops[0])); 594 Function.setUsesGnuArgsSize(); 595 break; 596 case DW_CFA_val_offset_sf: 597 case DW_CFA_val_offset: 598 if (opts::Verbosity >= 1) { 599 errs() << "BOLT-WARNING: DWARF val_offset() unimplemented\n"; 600 } 601 return false; 602 case DW_CFA_def_cfa_expression: 603 case DW_CFA_val_expression: 604 case DW_CFA_expression: { 605 StringRef ExprBytes = Instr.Expression->getData(); 606 std::string Str; 607 raw_string_ostream OS(Str); 608 // Manually encode this instruction using CFI escape 609 OS << Opcode; 610 if (Opcode != DW_CFA_def_cfa_expression) 611 encodeULEB128(Instr.Ops[0], OS); 612 encodeULEB128(ExprBytes.size(), OS); 613 OS << ExprBytes; 614 Function.addCFIInstruction( 615 Offset, MCCFIInstruction::createEscape(nullptr, OS.str())); 616 break; 617 } 618 case DW_CFA_MIPS_advance_loc8: 619 if (opts::Verbosity >= 1) 620 errs() << "BOLT-WARNING: DW_CFA_MIPS_advance_loc unimplemented\n"; 621 return false; 622 case DW_CFA_GNU_window_save: 623 case DW_CFA_lo_user: 624 case DW_CFA_hi_user: 625 if (opts::Verbosity >= 1) { 626 errs() << "BOLT-WARNING: DW_CFA_GNU_* and DW_CFA_*_user " 627 "unimplemented\n"; 628 } 629 return false; 630 default: 631 if (opts::Verbosity >= 1) { 632 errs() << "BOLT-WARNING: Unrecognized CFI instruction: " << Instr.Opcode 633 << '\n'; 634 } 635 return false; 636 } 637 638 return true; 639 }; 640 641 for (const CFIProgram::Instruction &Instr : CurFDE.getLinkedCIE()->cfis()) 642 if (!decodeFrameInstruction(Instr)) 643 return false; 644 645 for (const CFIProgram::Instruction &Instr : CurFDE.cfis()) 646 if (!decodeFrameInstruction(Instr)) 647 return false; 648 649 return true; 650 } 651 652 std::vector<char> CFIReaderWriter::generateEHFrameHeader( 653 const DWARFDebugFrame &OldEHFrame, const DWARFDebugFrame &NewEHFrame, 654 uint64_t EHFrameHeaderAddress, 655 std::vector<uint64_t> &FailedAddresses) const { 656 // Common PC -> FDE map to be written into .eh_frame_hdr. 657 std::map<uint64_t, uint64_t> PCToFDE; 658 659 // Presort array for binary search. 660 std::sort(FailedAddresses.begin(), FailedAddresses.end()); 661 662 // Initialize PCToFDE using NewEHFrame. 663 for (dwarf::FrameEntry &Entry : NewEHFrame.entries()) { 664 const dwarf::FDE *FDE = dyn_cast<dwarf::FDE>(&Entry); 665 if (FDE == nullptr) 666 continue; 667 const uint64_t FuncAddress = FDE->getInitialLocation(); 668 const uint64_t FDEAddress = 669 NewEHFrame.getEHFrameAddress() + FDE->getOffset(); 670 671 // Ignore unused FDEs. 672 if (FuncAddress == 0) 673 continue; 674 675 // Add the address to the map unless we failed to write it. 676 if (!std::binary_search(FailedAddresses.begin(), FailedAddresses.end(), 677 FuncAddress)) { 678 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: FDE for function at 0x" 679 << Twine::utohexstr(FuncAddress) << " is at 0x" 680 << Twine::utohexstr(FDEAddress) << '\n'); 681 PCToFDE[FuncAddress] = FDEAddress; 682 } 683 }; 684 685 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: new .eh_frame contains " 686 << std::distance(NewEHFrame.entries().begin(), 687 NewEHFrame.entries().end()) 688 << " entries\n"); 689 690 // Add entries from the original .eh_frame corresponding to the functions 691 // that we did not update. 692 for (const dwarf::FrameEntry &Entry : OldEHFrame) { 693 const dwarf::FDE *FDE = dyn_cast<dwarf::FDE>(&Entry); 694 if (FDE == nullptr) 695 continue; 696 const uint64_t FuncAddress = FDE->getInitialLocation(); 697 const uint64_t FDEAddress = 698 OldEHFrame.getEHFrameAddress() + FDE->getOffset(); 699 700 // Add the address if we failed to write it. 701 if (PCToFDE.count(FuncAddress) == 0) { 702 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: old FDE for function at 0x" 703 << Twine::utohexstr(FuncAddress) << " is at 0x" 704 << Twine::utohexstr(FDEAddress) << '\n'); 705 PCToFDE[FuncAddress] = FDEAddress; 706 } 707 }; 708 709 LLVM_DEBUG(dbgs() << "BOLT-DEBUG: old .eh_frame contains " 710 << std::distance(OldEHFrame.entries().begin(), 711 OldEHFrame.entries().end()) 712 << " entries\n"); 713 714 // Generate a new .eh_frame_hdr based on the new map. 715 716 // Header plus table of entries of size 8 bytes. 717 std::vector<char> EHFrameHeader(12 + PCToFDE.size() * 8); 718 719 // Version is 1. 720 EHFrameHeader[0] = 1; 721 // Encoding of the eh_frame pointer. 722 EHFrameHeader[1] = DW_EH_PE_pcrel | DW_EH_PE_sdata4; 723 // Encoding of the count field to follow. 724 EHFrameHeader[2] = DW_EH_PE_udata4; 725 // Encoding of the table entries - 4-byte offset from the start of the header. 726 EHFrameHeader[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4; 727 728 // Address of eh_frame. Use the new one. 729 support::ulittle32_t::ref(EHFrameHeader.data() + 4) = 730 NewEHFrame.getEHFrameAddress() - (EHFrameHeaderAddress + 4); 731 732 // Number of entries in the table (FDE count). 733 support::ulittle32_t::ref(EHFrameHeader.data() + 8) = PCToFDE.size(); 734 735 // Write the table at offset 12. 736 char *Ptr = EHFrameHeader.data(); 737 uint32_t Offset = 12; 738 for (const auto &PCI : PCToFDE) { 739 int64_t InitialPCOffset = PCI.first - EHFrameHeaderAddress; 740 assert(isInt<32>(InitialPCOffset) && "PC offset out of bounds"); 741 support::ulittle32_t::ref(Ptr + Offset) = InitialPCOffset; 742 Offset += 4; 743 int64_t FDEOffset = PCI.second - EHFrameHeaderAddress; 744 assert(isInt<32>(FDEOffset) && "FDE offset out of bounds"); 745 support::ulittle32_t::ref(Ptr + Offset) = FDEOffset; 746 Offset += 4; 747 } 748 749 return EHFrameHeader; 750 } 751 752 Error EHFrameParser::parseCIE(uint64_t StartOffset) { 753 uint8_t Version = Data.getU8(&Offset); 754 const char *Augmentation = Data.getCStr(&Offset); 755 StringRef AugmentationString(Augmentation ? Augmentation : ""); 756 uint8_t AddressSize = 757 Version < 4 ? Data.getAddressSize() : Data.getU8(&Offset); 758 Data.setAddressSize(AddressSize); 759 // Skip segment descriptor size 760 if (Version >= 4) 761 Offset += 1; 762 // Skip code alignment factor 763 Data.getULEB128(&Offset); 764 // Skip data alignment 765 Data.getSLEB128(&Offset); 766 // Skip return address register 767 if (Version == 1) 768 Offset += 1; 769 else 770 Data.getULEB128(&Offset); 771 772 uint32_t FDEPointerEncoding = DW_EH_PE_absptr; 773 uint32_t LSDAPointerEncoding = DW_EH_PE_omit; 774 // Walk the augmentation string to get all the augmentation data. 775 for (unsigned i = 0, e = AugmentationString.size(); i != e; ++i) { 776 switch (AugmentationString[i]) { 777 default: 778 return createStringError( 779 errc::invalid_argument, 780 "unknown augmentation character in entry at 0x%" PRIx64, StartOffset); 781 case 'L': 782 LSDAPointerEncoding = Data.getU8(&Offset); 783 break; 784 case 'P': { 785 uint32_t PersonalityEncoding = Data.getU8(&Offset); 786 Optional<uint64_t> Personality = 787 Data.getEncodedPointer(&Offset, PersonalityEncoding, 788 EHFrameAddress ? EHFrameAddress + Offset : 0); 789 // Patch personality address 790 if (Personality) 791 PatcherCallback(*Personality, Offset, PersonalityEncoding); 792 break; 793 } 794 case 'R': 795 FDEPointerEncoding = Data.getU8(&Offset); 796 break; 797 case 'z': 798 if (i) 799 return createStringError( 800 errc::invalid_argument, 801 "'z' must be the first character at 0x%" PRIx64, StartOffset); 802 // Skip augmentation length 803 Data.getULEB128(&Offset); 804 break; 805 case 'S': 806 case 'B': 807 break; 808 } 809 } 810 Entries.emplace_back(std::make_unique<CIEInfo>( 811 FDEPointerEncoding, LSDAPointerEncoding, AugmentationString)); 812 CIEs[StartOffset] = &*Entries.back(); 813 return Error::success(); 814 } 815 816 Error EHFrameParser::parseFDE(uint64_t CIEPointer, 817 uint64_t StartStructureOffset) { 818 Optional<uint64_t> LSDAAddress; 819 CIEInfo *Cie = CIEs[StartStructureOffset - CIEPointer]; 820 821 // The address size is encoded in the CIE we reference. 822 if (!Cie) 823 return createStringError(errc::invalid_argument, 824 "parsing FDE data at 0x%" PRIx64 825 " failed due to missing CIE", 826 StartStructureOffset); 827 // Patch initial location 828 if (auto Val = Data.getEncodedPointer(&Offset, Cie->FDEPtrEncoding, 829 EHFrameAddress + Offset)) { 830 PatcherCallback(*Val, Offset, Cie->FDEPtrEncoding); 831 } 832 // Skip address range 833 Data.getEncodedPointer(&Offset, Cie->FDEPtrEncoding, 0); 834 835 // Process augmentation data for this FDE. 836 StringRef AugmentationString = Cie->AugmentationString; 837 if (!AugmentationString.empty() && Cie->LSDAPtrEncoding != DW_EH_PE_omit) { 838 // Skip augmentation length 839 Data.getULEB128(&Offset); 840 LSDAAddress = 841 Data.getEncodedPointer(&Offset, Cie->LSDAPtrEncoding, 842 EHFrameAddress ? Offset + EHFrameAddress : 0); 843 // Patch LSDA address 844 PatcherCallback(*LSDAAddress, Offset, Cie->LSDAPtrEncoding); 845 } 846 return Error::success(); 847 } 848 849 Error EHFrameParser::parse() { 850 while (Data.isValidOffset(Offset)) { 851 const uint64_t StartOffset = Offset; 852 853 uint64_t Length; 854 DwarfFormat Format; 855 std::tie(Length, Format) = Data.getInitialLength(&Offset); 856 857 // If the Length is 0, then this CIE is a terminator 858 if (Length == 0) 859 break; 860 861 const uint64_t StartStructureOffset = Offset; 862 const uint64_t EndStructureOffset = Offset + Length; 863 864 Error Err = Error::success(); 865 const uint64_t Id = Data.getRelocatedValue(4, &Offset, 866 /*SectionIndex=*/nullptr, &Err); 867 if (Err) 868 return Err; 869 870 if (!Id) { 871 if (Error Err = parseCIE(StartOffset)) 872 return Err; 873 } else { 874 if (Error Err = parseFDE(Id, StartStructureOffset)) 875 return Err; 876 } 877 Offset = EndStructureOffset; 878 } 879 880 return Error::success(); 881 } 882 883 Error EHFrameParser::parse(DWARFDataExtractor Data, uint64_t EHFrameAddress, 884 PatcherCallbackTy PatcherCallback) { 885 EHFrameParser Parser(Data, EHFrameAddress, PatcherCallback); 886 return Parser.parse(); 887 } 888 889 } // namespace bolt 890 } // namespace llvm 891