DWARFDebugFrame.cpp

Go to the documentation of this file.

//===- DWARFDebugFrame.h - Parsing of .debug_frame ------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/DebugInfo/DWARF/DWARFDebugFrame.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DataExtractor.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cinttypes>
#include <cstdint>
#include <string>
#include <vector>

using namespace llvm;
using namespace dwarf;


// See DWARF standard v3, section 7.23
const uint8_t DWARF_CFI_PRIMARY_OPCODE_MASK = 0xc0;
const uint8_t DWARF_CFI_PRIMARY_OPERAND_MASK = 0x3f;

Error CFIProgram::parse(DataExtractor Data, uint32_t *Offset,
                        uint32_t EndOffset) {
  while (*Offset < EndOffset) {
    uint8_t Opcode = Data.getU8(Offset);
    // Some instructions have a primary opcode encoded in the top bits.
    uint8_t Primary = Opcode & DWARF_CFI_PRIMARY_OPCODE_MASK;

    if (Primary) {
      // If it's a primary opcode, the first operand is encoded in the bottom
      // bits of the opcode itself.
      uint64_t Op1 = Opcode & DWARF_CFI_PRIMARY_OPERAND_MASK;
      switch (Primary) {
      default:
        return createStringError(errc::illegal_byte_sequence,
                                 "Invalid primary CFI opcode 0x%" PRIx8,
                                 Primary);
      case DW_CFA_advance_loc:
      case DW_CFA_restore:
        addInstruction(Primary, Op1);
        break;
      case DW_CFA_offset:
        addInstruction(Primary, Op1, Data.getULEB128(Offset));
        break;
      }
    } else {
      // Extended opcode - its value is Opcode itself.
      switch (Opcode) {
      default:
        return createStringError(errc::illegal_byte_sequence,
                                 "Invalid extended CFI opcode 0x%" PRIx8,
                                 Opcode);
      case DW_CFA_nop:
      case DW_CFA_remember_state:
      case DW_CFA_restore_state:
      case DW_CFA_GNU_window_save:
        // No operands
        addInstruction(Opcode);
        break;
      case DW_CFA_set_loc:
        // Operands: Address
        addInstruction(Opcode, Data.getAddress(Offset));
        break;
      case DW_CFA_advance_loc1:
        // Operands: 1-byte delta
        addInstruction(Opcode, Data.getU8(Offset));
        break;
      case DW_CFA_advance_loc2:
        // Operands: 2-byte delta
        addInstruction(Opcode, Data.getU16(Offset));
        break;
      case DW_CFA_advance_loc4:
        // Operands: 4-byte delta
        addInstruction(Opcode, Data.getU32(Offset));
        break;
      case DW_CFA_restore_extended:
      case DW_CFA_undefined:
      case DW_CFA_same_value:
      case DW_CFA_def_cfa_register:
      case DW_CFA_def_cfa_offset:
      case DW_CFA_GNU_args_size:
        // Operands: ULEB128
        addInstruction(Opcode, Data.getULEB128(Offset));
        break;
      case DW_CFA_def_cfa_offset_sf:
        // Operands: SLEB128
        addInstruction(Opcode, Data.getSLEB128(Offset));
        break;
      case DW_CFA_offset_extended:
      case DW_CFA_register:
      case DW_CFA_def_cfa:
      case DW_CFA_val_offset: {
        // Operands: ULEB128, ULEB128
        // Note: We can not embed getULEB128 directly into function
        // argument list. getULEB128 changes Offset and order of evaluation
        // for arguments is unspecified.
        auto op1 = Data.getULEB128(Offset);
        auto op2 = Data.getULEB128(Offset);
        addInstruction(Opcode, op1, op2);
        break;
        }
        case DW_CFA_offset_extended_sf:
        case DW_CFA_def_cfa_sf:
        case DW_CFA_val_offset_sf: {
          // Operands: ULEB128, SLEB128
          // Note: see comment for the previous case
          auto op1 = Data.getULEB128(Offset);
          auto op2 = (uint64_t)Data.getSLEB128(Offset);
          addInstruction(Opcode, op1, op2);
          break;
        }
        case DW_CFA_def_cfa_expression: {
          uint32_t ExprLength = Data.getULEB128(Offset);
          addInstruction(Opcode, 0);
          DataExtractor Extractor(
              Data.getData().slice(*Offset, *Offset + ExprLength),
              Data.isLittleEndian(), Data.getAddressSize());
          Instructions.back().Expression = DWARFExpression(
              Extractor, Data.getAddressSize(), dwarf::DWARF_VERSION);
          *Offset += ExprLength;
          break;
        }
        case DW_CFA_expression:
        case DW_CFA_val_expression: {
          auto RegNum = Data.getULEB128(Offset);
          auto BlockLength = Data.getULEB128(Offset);
          addInstruction(Opcode, RegNum, 0);
          DataExtractor Extractor(
              Data.getData().slice(*Offset, *Offset + BlockLength),
              Data.isLittleEndian(), Data.getAddressSize());
          Instructions.back().Expression = DWARFExpression(
              Extractor, Data.getAddressSize(), dwarf::DWARF_VERSION);
          *Offset += BlockLength;
          break;
        }
      }
    }
  }

  return Error::success();
}

namespace {


} // end anonymous namespace

ArrayRef<CFIProgram::OperandType[2]> CFIProgram::getOperandTypes() {
  static OperandType OpTypes[DW_CFA_restore+1][2];
  static bool Initialized = false;
  if (Initialized) {
    return ArrayRef<OperandType[2]>(&OpTypes[0], DW_CFA_restore+1);
  }
  Initialized = true;

#define DECLARE_OP2(OP, OPTYPE0, OPTYPE1)       \
  do {                                          \
    OpTypes[OP][0] = OPTYPE0;                   \
    OpTypes[OP][1] = OPTYPE1;                   \
  } while (false)
#define DECLARE_OP1(OP, OPTYPE0) DECLARE_OP2(OP, OPTYPE0, OT_None)
#define DECLARE_OP0(OP) DECLARE_OP1(OP, OT_None)

  DECLARE_OP1(DW_CFA_set_loc, OT_Address);
  DECLARE_OP1(DW_CFA_advance_loc, OT_FactoredCodeOffset);
  DECLARE_OP1(DW_CFA_advance_loc1, OT_FactoredCodeOffset);
  DECLARE_OP1(DW_CFA_advance_loc2, OT_FactoredCodeOffset);
  DECLARE_OP1(DW_CFA_advance_loc4, OT_FactoredCodeOffset);
  DECLARE_OP1(DW_CFA_MIPS_advance_loc8, OT_FactoredCodeOffset);
  DECLARE_OP2(DW_CFA_def_cfa, OT_Register, OT_Offset);
  DECLARE_OP2(DW_CFA_def_cfa_sf, OT_Register, OT_SignedFactDataOffset);
  DECLARE_OP1(DW_CFA_def_cfa_register, OT_Register);
  DECLARE_OP1(DW_CFA_def_cfa_offset, OT_Offset);
  DECLARE_OP1(DW_CFA_def_cfa_offset_sf, OT_SignedFactDataOffset);
  DECLARE_OP1(DW_CFA_def_cfa_expression, OT_Expression);
  DECLARE_OP1(DW_CFA_undefined, OT_Register);
  DECLARE_OP1(DW_CFA_same_value, OT_Register);
  DECLARE_OP2(DW_CFA_offset, OT_Register, OT_UnsignedFactDataOffset);
  DECLARE_OP2(DW_CFA_offset_extended, OT_Register, OT_UnsignedFactDataOffset);
  DECLARE_OP2(DW_CFA_offset_extended_sf, OT_Register, OT_SignedFactDataOffset);
  DECLARE_OP2(DW_CFA_val_offset, OT_Register, OT_UnsignedFactDataOffset);
  DECLARE_OP2(DW_CFA_val_offset_sf, OT_Register, OT_SignedFactDataOffset);
  DECLARE_OP2(DW_CFA_register, OT_Register, OT_Register);
  DECLARE_OP2(DW_CFA_expression, OT_Register, OT_Expression);
  DECLARE_OP2(DW_CFA_val_expression, OT_Register, OT_Expression);
  DECLARE_OP1(DW_CFA_restore, OT_Register);
  DECLARE_OP1(DW_CFA_restore_extended, OT_Register);
  DECLARE_OP0(DW_CFA_remember_state);
  DECLARE_OP0(DW_CFA_restore_state);
  DECLARE_OP0(DW_CFA_GNU_window_save);
  DECLARE_OP1(DW_CFA_GNU_args_size, OT_Offset);
  DECLARE_OP0(DW_CFA_nop);

#undef DECLARE_OP0
#undef DECLARE_OP1
#undef DECLARE_OP2

  return ArrayRef<OperandType[2]>(&OpTypes[0], DW_CFA_restore+1);
}

/// Print \p Opcode's operand number \p OperandIdx which has value \p Operand.
void CFIProgram::printOperand(raw_ostream &OS, const MCRegisterInfo *MRI,
                              bool IsEH, const Instruction &Instr,
                              unsigned OperandIdx, uint64_t Operand) const {
  assert(OperandIdx < 2);
  uint8_t Opcode = Instr.Opcode;
  OperandType Type = getOperandTypes()[Opcode][OperandIdx];

  switch (Type) {
  case OT_Unset: {
    OS << " Unsupported " << (OperandIdx ? "second" : "first") << " operand to";
    auto OpcodeName = CallFrameString(Opcode, Arch);
    if (!OpcodeName.empty())
      OS << " " << OpcodeName;
    else
      OS << format(" Opcode %x",  Opcode);
    break;
  }
  case OT_None:
    break;
  case OT_Address:
    OS << format(" %" PRIx64, Operand);
    break;
  case OT_Offset:
    // The offsets are all encoded in a unsigned form, but in practice
    // consumers use them signed. It's most certainly legacy due to
    // the lack of signed variants in the first Dwarf standards.
    OS << format(" %+" PRId64, int64_t(Operand));
    break;
  case OT_FactoredCodeOffset: // Always Unsigned
    if (CodeAlignmentFactor)
      OS << format(" %" PRId64, Operand * CodeAlignmentFactor);
    else
      OS << format(" %" PRId64 "*code_alignment_factor" , Operand);
    break;
  case OT_SignedFactDataOffset:
    if (DataAlignmentFactor)
      OS << format(" %" PRId64, int64_t(Operand) * DataAlignmentFactor);
    else
      OS << format(" %" PRId64 "*data_alignment_factor" , int64_t(Operand));
    break;
  case OT_UnsignedFactDataOffset:
    if (DataAlignmentFactor)
      OS << format(" %" PRId64, Operand * DataAlignmentFactor);
    else
      OS << format(" %" PRId64 "*data_alignment_factor" , Operand);
    break;
  case OT_Register:
    OS << format(" reg%" PRId64, Operand);
    break;
  case OT_Expression:
    assert(Instr.Expression && "missing DWARFExpression object");
    OS << " ";
    Instr.Expression->print(OS, MRI, IsEH);
    break;
  }
}

void CFIProgram::dump(raw_ostream &OS, const MCRegisterInfo *MRI, bool IsEH,
                      unsigned IndentLevel) const {
  for (const auto &Instr : Instructions) {
    uint8_t Opcode = Instr.Opcode;
    if (Opcode & DWARF_CFI_PRIMARY_OPCODE_MASK)
      Opcode &= DWARF_CFI_PRIMARY_OPCODE_MASK;
    OS.indent(2 * IndentLevel);
    OS << CallFrameString(Opcode, Arch) << ":";
    for (unsigned i = 0; i < Instr.Ops.size(); ++i)
      printOperand(OS, MRI, IsEH, Instr, i, Instr.Ops[i]);
    OS << '\n';
  }
}

void CIE::dump(raw_ostream &OS, const MCRegisterInfo *MRI, bool IsEH) const {
  OS << format("%08x %08x %08x CIE", (uint32_t)Offset, (uint32_t)Length,
               DW_CIE_ID)
     << "\n";
  OS << format("  Version:               %d\n", Version);
  OS << "  Augmentation:          \"" << Augmentation << "\"\n";
  if (Version >= 4) {
    OS << format("  Address size:          %u\n", (uint32_t)AddressSize);
    OS << format("  Segment desc size:     %u\n",
                 (uint32_t)SegmentDescriptorSize);
  }
  OS << format("  Code alignment factor: %u\n", (uint32_t)CodeAlignmentFactor);
  OS << format("  Data alignment factor: %d\n", (int32_t)DataAlignmentFactor);
  OS << format("  Return address column: %d\n", (int32_t)ReturnAddressRegister);
  if (Personality)
    OS << format("  Personality Address: %016" PRIx64 "\n", *Personality);
  if (!AugmentationData.empty()) {
    OS << "  Augmentation data:    ";
    for (uint8_t Byte : AugmentationData)
      OS << ' ' << hexdigit(Byte >> 4) << hexdigit(Byte & 0xf);
    OS << "\n";
  }
  OS << "\n";
  CFIs.dump(OS, MRI, IsEH);
  OS << "\n";
}

void FDE::dump(raw_ostream &OS, const MCRegisterInfo *MRI, bool IsEH) const {
  OS << format("%08x %08x %08x FDE ", (uint32_t)Offset, (uint32_t)Length,
               (int32_t)LinkedCIEOffset);
  OS << format("cie=%08x pc=%08x...%08x\n", (int32_t)LinkedCIEOffset,
               (uint32_t)InitialLocation,
               (uint32_t)InitialLocation + (uint32_t)AddressRange);
  if (LSDAAddress)
    OS << format("  LSDA Address: %016" PRIx64 "\n", *LSDAAddress);
  CFIs.dump(OS, MRI, IsEH);
  OS << "\n";
}

DWARFDebugFrame::DWARFDebugFrame(Triple::ArchType Arch,
    bool IsEH, uint64_t EHFrameAddress)
    : Arch(Arch), IsEH(IsEH), EHFrameAddress(EHFrameAddress) {}

DWARFDebugFrame::~DWARFDebugFrame() = default;

static void LLVM_ATTRIBUTE_UNUSED dumpDataAux(DataExtractor Data,
                                              uint32_t Offset, int Length) {
  errs() << "DUMP: ";
  for (int i = 0; i < Length; ++i) {
    uint8_t c = Data.getU8(&Offset);
    errs().write_hex(c); errs() << " ";
  }
  errs() << "\n";
}

// This is a workaround for old compilers which do not allow
// noreturn attribute usage in lambdas. Once the support for those
// compilers are phased out, we can remove this and return back to
// a ReportError lambda: [StartOffset](const char *ErrorMsg).
static void LLVM_ATTRIBUTE_NORETURN ReportError(uint32_t StartOffset,
                                                const char *ErrorMsg) {
  std::string Str;
  raw_string_ostream OS(Str);
  OS << format(ErrorMsg, StartOffset);
  OS.flush();
  report_fatal_error(Str);
}

void DWARFDebugFrame::parse(DWARFDataExtractor Data) {
  uint32_t Offset = 0;
  DenseMap<uint32_t, CIE *> CIEs;

  while (Data.isValidOffset(Offset)) {
    uint32_t StartOffset = Offset;

    bool IsDWARF64 = false;
    uint64_t Length = Data.getU32(&Offset);
    uint64_t Id;

    if (Length == UINT32_MAX) {
      // DWARF-64 is distinguished by the first 32 bits of the initial length
      // field being 0xffffffff. Then, the next 64 bits are the actual entry
      // length.
      IsDWARF64 = true;
      Length = Data.getU64(&Offset);
    }

    // At this point, Offset points to the next field after Length.
    // Length is the structure size excluding itself. Compute an offset one
    // past the end of the structure (needed to know how many instructions to
    // read).
    // TODO: For honest DWARF64 support, DataExtractor will have to treat
    //       offset_ptr as uint64_t*
    uint32_t StartStructureOffset = Offset;
    uint32_t EndStructureOffset = Offset + static_cast<uint32_t>(Length);

    // The Id field's size depends on the DWARF format
    Id = Data.getUnsigned(&Offset, (IsDWARF64 && !IsEH) ? 8 : 4);
    bool IsCIE =
        ((IsDWARF64 && Id == DW64_CIE_ID) || Id == DW_CIE_ID || (IsEH && !Id));

    if (IsCIE) {
      uint8_t Version = Data.getU8(&Offset);
      const char *Augmentation = Data.getCStr(&Offset);
      StringRef AugmentationString(Augmentation ? Augmentation : "");
      uint8_t AddressSize = Version < 4 ? Data.getAddressSize() :
                                          Data.getU8(&Offset);
      Data.setAddressSize(AddressSize);
      uint8_t SegmentDescriptorSize = Version < 4 ? 0 : Data.getU8(&Offset);
      uint64_t CodeAlignmentFactor = Data.getULEB128(&Offset);
      int64_t DataAlignmentFactor = Data.getSLEB128(&Offset);
      uint64_t ReturnAddressRegister =
          Version == 1 ? Data.getU8(&Offset) : Data.getULEB128(&Offset);

      // Parse the augmentation data for EH CIEs
      StringRef AugmentationData("");
      uint32_t FDEPointerEncoding = DW_EH_PE_absptr;
      uint32_t LSDAPointerEncoding = DW_EH_PE_omit;
      Optional<uint64_t> Personality;
      Optional<uint32_t> PersonalityEncoding;
      if (IsEH) {
        Optional<uint64_t> AugmentationLength;
        uint32_t StartAugmentationOffset;
        uint32_t EndAugmentationOffset;

        // Walk the augmentation string to get all the augmentation data.
        for (unsigned i = 0, e = AugmentationString.size(); i != e; ++i) {
          switch (AugmentationString[i]) {
            default:
              ReportError(StartOffset,
                          "Unknown augmentation character in entry at %lx");
            case 'L':
              LSDAPointerEncoding = Data.getU8(&Offset);
              break;
            case 'P': {
              if (Personality)
                ReportError(StartOffset,
                            "Duplicate personality in entry at %lx");
              PersonalityEncoding = Data.getU8(&Offset);
              Personality = Data.getEncodedPointer(
                  &Offset, *PersonalityEncoding,
                  EHFrameAddress ? EHFrameAddress + Offset : 0);
              break;
            }
            case 'R':
              FDEPointerEncoding = Data.getU8(&Offset);
              break;
            case 'S':
              // Current frame is a signal trampoline.
              break;
            case 'z':
              if (i)
                ReportError(StartOffset,
                            "'z' must be the first character at %lx");
              // Parse the augmentation length first.  We only parse it if
              // the string contains a 'z'.
              AugmentationLength = Data.getULEB128(&Offset);
              StartAugmentationOffset = Offset;
              EndAugmentationOffset = Offset +
                static_cast<uint32_t>(*AugmentationLength);
              break;
            case 'B':
              // B-Key is used for signing functions associated with this
              // augmentation string
              break;
          }
        }

        if (AugmentationLength.hasValue()) {
          if (Offset != EndAugmentationOffset)
            ReportError(StartOffset, "Parsing augmentation data at %lx failed");

          AugmentationData = Data.getData().slice(StartAugmentationOffset,
                                                  EndAugmentationOffset);
        }
      }

      auto Cie = llvm::make_unique<CIE>(
          StartOffset, Length, Version, AugmentationString, AddressSize,
          SegmentDescriptorSize, CodeAlignmentFactor, DataAlignmentFactor,
          ReturnAddressRegister, AugmentationData, FDEPointerEncoding,
          LSDAPointerEncoding, Personality, PersonalityEncoding, Arch);
      CIEs[StartOffset] = Cie.get();
      Entries.emplace_back(std::move(Cie));
    } else {
      // FDE
      uint64_t CIEPointer = Id;
      uint64_t InitialLocation = 0;
      uint64_t AddressRange = 0;
      Optional<uint64_t> LSDAAddress;
      CIE *Cie = CIEs[IsEH ? (StartStructureOffset - CIEPointer) : CIEPointer];

      if (IsEH) {
        // The address size is encoded in the CIE we reference.
        if (!Cie)
          ReportError(StartOffset,
                      "Parsing FDE data at %lx failed due to missing CIE");

        if (auto Val = Data.getEncodedPointer(
                &Offset, Cie->getFDEPointerEncoding(),
                EHFrameAddress ? EHFrameAddress + Offset : 0)) {
          InitialLocation = *Val;
        }
        if (auto Val = Data.getEncodedPointer(
                &Offset, Cie->getFDEPointerEncoding(), 0)) {
          AddressRange = *Val;
        }

        StringRef AugmentationString = Cie->getAugmentationString();
        if (!AugmentationString.empty()) {
          // Parse the augmentation length and data for this FDE.
          uint64_t AugmentationLength = Data.getULEB128(&Offset);

          uint32_t EndAugmentationOffset =
            Offset + static_cast<uint32_t>(AugmentationLength);

          // Decode the LSDA if the CIE augmentation string said we should.
          if (Cie->getLSDAPointerEncoding() != DW_EH_PE_omit) {
            LSDAAddress = Data.getEncodedPointer(
                &Offset, Cie->getLSDAPointerEncoding(),
                EHFrameAddress ? Offset + EHFrameAddress : 0);
          }

          if (Offset != EndAugmentationOffset)
            ReportError(StartOffset, "Parsing augmentation data at %lx failed");
        }
      } else {
        InitialLocation = Data.getAddress(&Offset);
        AddressRange = Data.getAddress(&Offset);
      }

      Entries.emplace_back(new FDE(StartOffset, Length, CIEPointer,
                                   InitialLocation, AddressRange,
                                   Cie, LSDAAddress, Arch));
    }

    if (Error E =
            Entries.back()->cfis().parse(Data, &Offset, EndStructureOffset)) {
      report_fatal_error(toString(std::move(E)));
    }

    if (Offset != EndStructureOffset)
      ReportError(StartOffset, "Parsing entry instructions at %lx failed");
  }
}

FrameEntry *DWARFDebugFrame::getEntryAtOffset(uint64_t Offset) const {
  auto It =
      std::lower_bound(Entries.begin(), Entries.end(), Offset,
                       [](const std::unique_ptr<FrameEntry> &E,
                          uint64_t Offset) { return E->getOffset() < Offset; });
  if (It != Entries.end() && (*It)->getOffset() == Offset)
    return It->get();
  return nullptr;
}

void DWARFDebugFrame::dump(raw_ostream &OS, const MCRegisterInfo *MRI,
                           Optional<uint64_t> Offset) const {
  if (Offset) {
    if (auto *Entry = getEntryAtOffset(*Offset))
      Entry->dump(OS, MRI, IsEH);
    return;
  }

  OS << "\n";
  for (const auto &Entry : Entries)
    Entry->dump(OS, MRI, IsEH);
}