Win64EHDumper.cpp

//===- Win64EHDumper.cpp - Win64 EH Printer ---------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "Win64EHDumper.h"
#include "llvm-readobj.h"
#include "llvm/Object/COFF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"

using namespace llvm;
using namespace llvm::object;
using namespace llvm::Win64EH;

const EnumEntry<unsigned> UnwindFlags[] = {
  { "ExceptionHandler", UNW_ExceptionHandler },
  { "TerminateHandler", UNW_TerminateHandler },
  { "ChainInfo"       , UNW_ChainInfo        }
};

const EnumEntry<unsigned> UnwindOpInfo[] = {
  { "RAX",  0 },
  { "RCX",  1 },
  { "RDX",  2 },
  { "RBX",  3 },
  { "RSP",  4 },
  { "RBP",  5 },
  { "RSI",  6 },
  { "RDI",  7 },
  { "R8",   8 },
  { "R9",   9 },
  { "R10", 10 },
  { "R11", 11 },
  { "R12", 12 },
  { "R13", 13 },
  { "R14", 14 },
  { "R15", 15 }
};

static uint64_t getOffsetOfLSDA(const UnwindInfo& UI) {
  return static_cast<const char*>(UI.getLanguageSpecificData())
         - reinterpret_cast<const char*>(&UI);
}

static uint32_t getLargeSlotValue(ArrayRef<UnwindCode> UC) {
  if (UC.size() < 3)
    return 0;
  return UC[1].FrameOffset + (static_cast<uint32_t>(UC[2].FrameOffset) << 16);
}

// Returns the name of the unwind code.
static StringRef getUnwindCodeTypeName(uint8_t Code) {
  switch (Code) {
  default: llvm_unreachable("Invalid unwind code");
  case UOP_PushNonVol: return "PUSH_NONVOL";
  case UOP_AllocLarge: return "ALLOC_LARGE";
  case UOP_AllocSmall: return "ALLOC_SMALL";
  case UOP_SetFPReg: return "SET_FPREG";
  case UOP_SaveNonVol: return "SAVE_NONVOL";
  case UOP_SaveNonVolBig: return "SAVE_NONVOL_FAR";
  case UOP_SaveXMM128: return "SAVE_XMM128";
  case UOP_SaveXMM128Big: return "SAVE_XMM128_FAR";
  case UOP_PushMachFrame: return "PUSH_MACHFRAME";
  case UOP_Epilog:
    return "EPILOG";
  }
}

// Returns the name of a referenced register.
static StringRef getUnwindRegisterName(uint8_t Reg) {
  switch (Reg) {
  default: llvm_unreachable("Invalid register");
  case 0: return "RAX";
  case 1: return "RCX";
  case 2: return "RDX";
  case 3: return "RBX";
  case 4: return "RSP";
  case 5: return "RBP";
  case 6: return "RSI";
  case 7: return "RDI";
  case 8: return "R8";
  case 9: return "R9";
  case 10: return "R10";
  case 11: return "R11";
  case 12: return "R12";
  case 13: return "R13";
  case 14: return "R14";
  case 15: return "R15";
  }
}

// Calculates the number of array slots required for the unwind code.
static unsigned getNumUsedSlots(const UnwindCode &UnwindCode) {
  switch (UnwindCode.getUnwindOp()) {
  default: llvm_unreachable("Invalid unwind code");
  case UOP_PushNonVol:
  case UOP_AllocSmall:
  case UOP_SetFPReg:
  case UOP_PushMachFrame:
  case UOP_Epilog:
    return 1;
  case UOP_SaveNonVol:
  case UOP_SaveXMM128:
    return 2;
  case UOP_SaveNonVolBig:
  case UOP_SaveXMM128Big:
    return 3;
  case UOP_AllocLarge:
    return (UnwindCode.getOpInfo() == 0) ? 2 : 3;
  }
}

static std::error_code getSymbol(const COFFObjectFile &COFF, uint64_t VA,
                                 object::SymbolRef &Sym) {
  for (const auto &Symbol : COFF.symbols()) {
    Expected<uint64_t> Address = Symbol.getAddress();
    if (!Address)
      return errorToErrorCode(Address.takeError());
    if (*Address == VA) {
      Sym = Symbol;
      return std::error_code();
    }
  }
  return inconvertibleErrorCode();
}

static object::SymbolRef getPreferredSymbol(const COFFObjectFile &COFF,
                                            object::SymbolRef Sym,
                                            uint32_t &SymbolOffset,
                                            bool IsRangeEnd) {
  // The symbol resolved by ResolveSymbol can be any internal
  // nondescriptive symbol; try to resolve a more descriptive one.
  COFFSymbolRef CoffSym = COFF.getCOFFSymbol(Sym);
  if (CoffSym.getStorageClass() != COFF::IMAGE_SYM_CLASS_LABEL &&
      CoffSym.getSectionDefinition() == nullptr)
    return Sym;
  for (const auto &S : COFF.symbols()) {
    COFFSymbolRef CS = COFF.getCOFFSymbol(S);
    if (CS.getSectionNumber() == CoffSym.getSectionNumber() &&
        CS.getValue() <= CoffSym.getValue() + SymbolOffset &&
        CS.getStorageClass() != COFF::IMAGE_SYM_CLASS_LABEL &&
        CS.getSectionDefinition() == nullptr) {
      uint32_t Offset = CoffSym.getValue() + SymbolOffset - CS.getValue();
      // For the end of a range, don't pick a symbol with a zero offset;
      // prefer a symbol with a small positive offset.
      if (Offset <= SymbolOffset && (!IsRangeEnd || Offset > 0)) {
        SymbolOffset = Offset;
        Sym = S;
        CoffSym = CS;
        if (CS.isExternal() && SymbolOffset == 0)
          return Sym;
      }
    }
  }
  return Sym;
}

static std::string formatSymbol(const Dumper::Context &Ctx,
                                const coff_section *Section, uint64_t Offset,
                                uint32_t Displacement,
                                bool IsRangeEnd = false) {
  std::string Buffer;
  raw_string_ostream OS(Buffer);

  SymbolRef Symbol;
  if (!Ctx.ResolveSymbol(Section, Offset, Symbol, Ctx.UserData)) {
    // We found a relocation at the given offset in the section, pointing
    // at a symbol.

    // Try to resolve label/section symbols into function names.
    Symbol = getPreferredSymbol(Ctx.COFF, Symbol, Displacement, IsRangeEnd);

    Expected<StringRef> Name = Symbol.getName();
    if (Name) {
      OS << *Name;
      if (Displacement > 0)
        OS << format(" +0x%X (0x%" PRIX64 ")", Displacement, Offset);
      else
        OS << format(" (0x%" PRIX64 ")", Offset);
      return OS.str();
    } else {
      // TODO: Actually report errors helpfully.
      consumeError(Name.takeError());
    }
  } else if (!getSymbol(Ctx.COFF, Ctx.COFF.getImageBase() + Displacement,
                        Symbol)) {
    Expected<StringRef> Name = Symbol.getName();
    if (Name) {
      OS << *Name;
      OS << format(" (0x%" PRIX64 ")", Ctx.COFF.getImageBase() + Displacement);
      return OS.str();
    } else {
      consumeError(Name.takeError());
    }
  }

  if (Displacement > 0)
    OS << format("(0x%" PRIX64 ")", Ctx.COFF.getImageBase() + Displacement);
  else
    OS << format("(0x%" PRIX64 ")", Offset);
  return OS.str();
}

static std::error_code resolveRelocation(const Dumper::Context &Ctx,
                                         const coff_section *Section,
                                         uint64_t Offset,
                                         const coff_section *&ResolvedSection,
                                         uint64_t &ResolvedAddress) {
  SymbolRef Symbol;
  if (std::error_code EC =
          Ctx.ResolveSymbol(Section, Offset, Symbol, Ctx.UserData))
    return EC;

  Expected<uint64_t> ResolvedAddressOrErr = Symbol.getAddress();
  if (!ResolvedAddressOrErr)
    return errorToErrorCode(ResolvedAddressOrErr.takeError());
  ResolvedAddress = *ResolvedAddressOrErr;

  Expected<section_iterator> SI = Symbol.getSection();
  if (!SI)
    return errorToErrorCode(SI.takeError());
  ResolvedSection = Ctx.COFF.getCOFFSection(**SI);
  return std::error_code();
}

static const object::coff_section *
getSectionContaining(const COFFObjectFile &COFF, uint64_t VA) {
  for (const auto &Section : COFF.sections()) {
    uint64_t Address = Section.getAddress();
    uint64_t Size = Section.getSize();

    if (VA >= Address && (VA - Address) <= Size)
      return COFF.getCOFFSection(Section);
  }
  return nullptr;
}

namespace llvm {
namespace Win64EH {
void Dumper::printRuntimeFunctionEntry(const Context &Ctx,
                                       const coff_section *Section,
                                       uint64_t Offset,
                                       const RuntimeFunction &RF) {
  SW.printString("StartAddress",
                 formatSymbol(Ctx, Section, Offset + 0, RF.StartAddress));
  SW.printString("EndAddress",
                 formatSymbol(Ctx, Section, Offset + 4, RF.EndAddress,
                              /*IsRangeEnd=*/true));
  SW.printString("UnwindInfoAddress",
                 formatSymbol(Ctx, Section, Offset + 8, RF.UnwindInfoOffset));
}

// Prints one unwind code. Because an unwind code can occupy up to 3 slots in
// the unwind codes array, this function requires that the correct number of
// slots is provided.
void Dumper::printUnwindCode(const UnwindInfo &UI, ArrayRef<UnwindCode> UC,
                             bool &SeenFirstEpilog) {
  assert(UC.size() >= getNumUsedSlots(UC[0]));

  SW.startLine() << format("0x%02X: ", unsigned(UC[0].u.CodeOffset))
                 << getUnwindCodeTypeName(UC[0].getUnwindOp());

  switch (UC[0].getUnwindOp()) {
  case UOP_PushNonVol:
    OS << " reg=" << getUnwindRegisterName(UC[0].getOpInfo());
    break;

  case UOP_AllocLarge:
    OS << " size="
       << ((UC[0].getOpInfo() == 0) ? UC[1].FrameOffset * 8
                                    : getLargeSlotValue(UC));
    break;

  case UOP_AllocSmall:
    OS << " size=" << (UC[0].getOpInfo() + 1) * 8;
    break;

  case UOP_SetFPReg:
    if (UI.getFrameRegister() == 0)
      OS << " reg=<invalid>";
    else
      OS << " reg=" << getUnwindRegisterName(UI.getFrameRegister())
         << format(", offset=0x%X", UI.getFrameOffset() * 16);
    break;

  case UOP_SaveNonVol:
    OS << " reg=" << getUnwindRegisterName(UC[0].getOpInfo())
       << format(", offset=0x%X", UC[1].FrameOffset * 8);
    break;

  case UOP_SaveNonVolBig:
    OS << " reg=" << getUnwindRegisterName(UC[0].getOpInfo())
       << format(", offset=0x%X", getLargeSlotValue(UC));
    break;

  case UOP_SaveXMM128:
    OS << " reg=XMM" << static_cast<uint32_t>(UC[0].getOpInfo())
       << format(", offset=0x%X", UC[1].FrameOffset * 16);
    break;

  case UOP_SaveXMM128Big:
    OS << " reg=XMM" << static_cast<uint32_t>(UC[0].getOpInfo())
       << format(", offset=0x%X", getLargeSlotValue(UC));
    break;

  case UOP_PushMachFrame:
    OS << " errcode=" << (UC[0].getOpInfo() == 0 ? "no" : "yes");
    break;

  case UOP_Epilog:
    if (SeenFirstEpilog) {
      uint32_t Offset = UC[0].getEpilogOffset();
      if (Offset == 0) {
        OS << " padding";
      } else {
        OS << " offset=" << format("0x%X", Offset);
      }
    } else {
      SeenFirstEpilog = true;
      bool AtEnd = (UC[0].getOpInfo() & 0x1) != 0;
      uint32_t Length = UC[0].u.CodeOffset;
      OS << " atend=" << (AtEnd ? "yes" : "no")
         << ", length=" << format("0x%X", Length);
    }
    break;
  }

  OS << "\n";
}

void Dumper::printUnwindInfo(const Context &Ctx, const coff_section *Section,
                             off_t Offset, const UnwindInfo &UI) {
  DictScope UIS(SW, "UnwindInfo");
  SW.printNumber("Version", UI.getVersion());
  SW.printFlags("Flags", UI.getFlags(), ArrayRef(UnwindFlags));
  SW.printNumber("PrologSize", UI.PrologSize);
  if (UI.getFrameRegister()) {
    SW.printEnum("FrameRegister", UI.getFrameRegister(),
                 ArrayRef(UnwindOpInfo));
    SW.printHex("FrameOffset", UI.getFrameOffset());
  } else {
    SW.printString("FrameRegister", StringRef("-"));
    SW.printString("FrameOffset", StringRef("-"));
  }

  SW.printNumber("UnwindCodeCount", UI.NumCodes);
  {
    ListScope UCS(SW, "UnwindCodes");
    ArrayRef<UnwindCode> UC(&UI.UnwindCodes[0], UI.NumCodes);
    bool SeenFirstEpilog = false;
    for (const UnwindCode *UCI = UC.begin(), *UCE = UC.end(); UCI < UCE; ++UCI) {
      unsigned UsedSlots = getNumUsedSlots(*UCI);
      if (UsedSlots > UC.size()) {
        errs() << "corrupt unwind data";
        return;
      }

      printUnwindCode(UI, ArrayRef(UCI, UCE), SeenFirstEpilog);
      UCI = UCI + UsedSlots - 1;
    }
  }

  uint64_t LSDAOffset = Offset + getOffsetOfLSDA(UI);
  if (UI.getFlags() & (UNW_ExceptionHandler | UNW_TerminateHandler)) {
    SW.printString("Handler",
                   formatSymbol(Ctx, Section, LSDAOffset,
                                UI.getLanguageSpecificHandlerOffset()));
  } else if (UI.getFlags() & UNW_ChainInfo) {
    if (const RuntimeFunction *Chained = UI.getChainedFunctionEntry()) {
      DictScope CS(SW, "Chained");
      printRuntimeFunctionEntry(Ctx, Section, LSDAOffset, *Chained);
    }
  }
}

void Dumper::printRuntimeFunction(const Context &Ctx,
                                  const coff_section *Section,
                                  uint64_t SectionOffset,
                                  const RuntimeFunction &RF) {
  DictScope RFS(SW, "RuntimeFunction");
  printRuntimeFunctionEntry(Ctx, Section, SectionOffset, RF);

  const coff_section *XData = nullptr;
  uint64_t Offset;
  resolveRelocation(Ctx, Section, SectionOffset + 8, XData, Offset);
  Offset = Offset + RF.UnwindInfoOffset;

  if (!XData) {
    uint64_t Address = Ctx.COFF.getImageBase() + RF.UnwindInfoOffset;
    XData = getSectionContaining(Ctx.COFF, Address);
    if (!XData)
      return;
    Offset = RF.UnwindInfoOffset - XData->VirtualAddress;
  }

  ArrayRef<uint8_t> Contents;
  if (Error E = Ctx.COFF.getSectionContents(XData, Contents))
    reportError(std::move(E), Ctx.COFF.getFileName());

  if (Contents.empty())
    return;

  if (Offset > Contents.size())
    return;

  const auto UI = reinterpret_cast<const UnwindInfo*>(Contents.data() + Offset);
  printUnwindInfo(Ctx, XData, Offset, *UI);
}

void Dumper::printData(const Context &Ctx) {
  for (const auto &Section : Ctx.COFF.sections()) {
    StringRef Name;
    if (Expected<StringRef> NameOrErr = Section.getName())
      Name = *NameOrErr;
    else
      consumeError(NameOrErr.takeError());

    if (Name != ".pdata" && !Name.starts_with(".pdata$"))
      continue;

    const coff_section *PData = Ctx.COFF.getCOFFSection(Section);
    ArrayRef<uint8_t> Contents;

    if (Error E = Ctx.COFF.getSectionContents(PData, Contents))
      reportError(std::move(E), Ctx.COFF.getFileName());
    if (Contents.empty())
      continue;

    const RuntimeFunction *Entries =
      reinterpret_cast<const RuntimeFunction *>(Contents.data());
    const size_t Count = Contents.size() / sizeof(RuntimeFunction);
    ArrayRef<RuntimeFunction> RuntimeFunctions(Entries, Count);

    size_t Index = 0;
    for (const auto &RF : RuntimeFunctions) {
      printRuntimeFunction(Ctx, Ctx.COFF.getCOFFSection(Section),
                           Index * sizeof(RuntimeFunction), RF);
      ++Index;
    }
  }
}
}
}