DwarfCFIEHPrinter.h

//===--- DwarfCFIEHPrinter.h - DWARF-based Unwind Information Printer -----===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TOOLS_LLVM_READOBJ_DWARFCFIEHPRINTER_H
#define LLVM_TOOLS_LLVM_READOBJ_DWARFCFIEHPRINTER_H

#include "llvm-readobj.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
#include "llvm/DebugInfo/DWARF/DWARFDebugFrame.h"
#include "llvm/Object/ELF.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/ELFTypes.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/ScopedPrinter.h"
#include "llvm/Support/type_traits.h"

namespace llvm {
namespace DwarfCFIEH {

template <typename ELFT> class PrinterContext {
  using Elf_Shdr = typename ELFT::Shdr;
  using Elf_Phdr = typename ELFT::Phdr;

  ScopedPrinter &W;
  const object::ELFObjectFile<ELFT> &ObjF;

  void printEHFrameHdr(const Elf_Phdr *EHFramePHdr) const;
  void printEHFrame(const Elf_Shdr *EHFrameShdr) const;

public:
  PrinterContext(ScopedPrinter &W, const object::ELFObjectFile<ELFT> &ObjF)
      : W(W), ObjF(ObjF) {}

  void printUnwindInformation() const;
};

template <class ELFT>
static const typename ELFT::Shdr *
findSectionByAddress(const object::ELFObjectFile<ELFT> &ObjF, uint64_t Addr) {
  Expected<typename ELFT::ShdrRange> SectionsOrErr =
      ObjF.getELFFile().sections();
  if (!SectionsOrErr)
    reportError(SectionsOrErr.takeError(), ObjF.getFileName());

  for (const typename ELFT::Shdr &Shdr : *SectionsOrErr)
    if (Shdr.sh_addr == Addr)
      return &Shdr;
  return nullptr;
}

template <typename ELFT>
void PrinterContext<ELFT>::printUnwindInformation() const {
  const object::ELFFile<ELFT> &Obj = ObjF.getELFFile();

  Expected<typename ELFT::PhdrRange> PhdrsOrErr = Obj.program_headers();
  if (!PhdrsOrErr)
    reportError(PhdrsOrErr.takeError(), ObjF.getFileName());

  for (const Elf_Phdr &Phdr : *PhdrsOrErr) {
    if (Phdr.p_type != ELF::PT_GNU_EH_FRAME)
      continue;

    if (Phdr.p_memsz != Phdr.p_filesz)
      reportError(object::createError(
                      "p_memsz does not match p_filesz for GNU_EH_FRAME"),
                  ObjF.getFileName());
    printEHFrameHdr(&Phdr);
    break;
  }

  Expected<typename ELFT::ShdrRange> SectionsOrErr = Obj.sections();
  if (!SectionsOrErr)
    reportError(SectionsOrErr.takeError(), ObjF.getFileName());

  for (const Elf_Shdr &Shdr : *SectionsOrErr) {
    Expected<StringRef> NameOrErr = Obj.getSectionName(Shdr);
    if (!NameOrErr)
      reportError(NameOrErr.takeError(), ObjF.getFileName());
    if (*NameOrErr == ".eh_frame")
      printEHFrame(&Shdr);
  }
}

template <typename ELFT>
void PrinterContext<ELFT>::printEHFrameHdr(const Elf_Phdr *EHFramePHdr) const {
  DictScope L(W, "EHFrameHeader");
  uint64_t EHFrameHdrAddress = EHFramePHdr->p_vaddr;
  W.startLine() << format("Address: 0x%" PRIx64 "\n", EHFrameHdrAddress);
  W.startLine() << format("Offset: 0x%" PRIx64 "\n", (uint64_t)EHFramePHdr->p_offset);
  W.startLine() << format("Size: 0x%" PRIx64 "\n", (uint64_t)EHFramePHdr->p_memsz);

  const object::ELFFile<ELFT> &Obj = ObjF.getELFFile();
  if (const Elf_Shdr *EHFrameHdr =
          findSectionByAddress(ObjF, EHFramePHdr->p_vaddr)) {
    Expected<StringRef> NameOrErr = Obj.getSectionName(*EHFrameHdr);
    if (!NameOrErr)
      reportError(NameOrErr.takeError(), ObjF.getFileName());
    W.printString("Corresponding Section", *NameOrErr);
  }

  Expected<ArrayRef<uint8_t>> Content = Obj.getSegmentContents(*EHFramePHdr);
  if (!Content)
    reportError(Content.takeError(), ObjF.getFileName());

  DataExtractor DE(*Content, ELFT::Endianness == llvm::endianness::little,
                   ELFT::Is64Bits ? 8 : 4);

  DictScope D(W, "Header");
  uint64_t Offset = 0;

  auto Version = DE.getU8(&Offset);
  W.printNumber("version", Version);
  if (Version != 1)
    reportError(
        object::createError("only version 1 of .eh_frame_hdr is supported"),
        ObjF.getFileName());

  uint64_t EHFramePtrEnc = DE.getU8(&Offset);
  W.startLine() << format("eh_frame_ptr_enc: 0x%" PRIx64 "\n", EHFramePtrEnc);
  if (EHFramePtrEnc != (dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4))
    reportError(object::createError("unexpected encoding eh_frame_ptr_enc"),
                ObjF.getFileName());

  uint64_t FDECountEnc = DE.getU8(&Offset);
  W.startLine() << format("fde_count_enc: 0x%" PRIx64 "\n", FDECountEnc);
  if (FDECountEnc != dwarf::DW_EH_PE_udata4)
    reportError(object::createError("unexpected encoding fde_count_enc"),
                ObjF.getFileName());

  uint64_t TableEnc = DE.getU8(&Offset);
  W.startLine() << format("table_enc: 0x%" PRIx64 "\n", TableEnc);
  if (TableEnc != (dwarf::DW_EH_PE_datarel | dwarf::DW_EH_PE_sdata4))
    reportError(object::createError("unexpected encoding table_enc"),
                ObjF.getFileName());

  auto EHFramePtr = DE.getSigned(&Offset, 4) + EHFrameHdrAddress + 4;
  W.startLine() << format("eh_frame_ptr: 0x%" PRIx64 "\n", EHFramePtr);

  auto FDECount = DE.getUnsigned(&Offset, 4);
  W.printNumber("fde_count", FDECount);

  unsigned NumEntries = 0;
  uint64_t PrevPC = 0;
  while (Offset + 8 <= EHFramePHdr->p_memsz && NumEntries < FDECount) {
    DictScope D(W, std::string("entry ") + std::to_string(NumEntries));

    auto InitialPC = DE.getSigned(&Offset, 4) + EHFrameHdrAddress;
    W.startLine() << format("initial_location: 0x%" PRIx64 "\n", InitialPC);
    auto Address = DE.getSigned(&Offset, 4) + EHFrameHdrAddress;
    W.startLine() << format("address: 0x%" PRIx64 "\n", Address);

    if (InitialPC < PrevPC)
      reportError(object::createError("initial_location is out of order"),
                  ObjF.getFileName());

    PrevPC = InitialPC;
    ++NumEntries;
  }
}

template <typename ELFT>
void PrinterContext<ELFT>::printEHFrame(const Elf_Shdr *EHFrameShdr) const {
  uint64_t Address = EHFrameShdr->sh_addr;
  uint64_t ShOffset = EHFrameShdr->sh_offset;
  W.startLine() << format(".eh_frame section at offset 0x%" PRIx64
                          " address 0x%" PRIx64 ":\n",
                          ShOffset, Address);
  W.indent();

  Expected<ArrayRef<uint8_t>> DataOrErr =
      ObjF.getELFFile().getSectionContents(*EHFrameShdr);
  if (!DataOrErr)
    reportError(DataOrErr.takeError(), ObjF.getFileName());

  // Construct DWARFDataExtractor to handle relocations ("PC Begin" fields).
  std::unique_ptr<DWARFContext> DICtx = DWARFContext::create(
      ObjF, DWARFContext::ProcessDebugRelocations::Process, nullptr);
  DWARFDataExtractor DE(
      DICtx->getDWARFObj(), DICtx->getDWARFObj().getEHFrameSection(),
      ELFT::Endianness == llvm::endianness::little, ELFT::Is64Bits ? 8 : 4);
  DWARFDebugFrame EHFrame(Triple::ArchType(ObjF.getArch()), /*IsEH=*/true,
                          /*EHFrameAddress=*/Address);
  if (Error E = EHFrame.parse(DE))
    reportError(std::move(E), ObjF.getFileName());

  for (const dwarf::FrameEntry &Entry : EHFrame) {
    std::optional<uint64_t> InitialLocation;
    if (const dwarf::CIE *CIE = dyn_cast<dwarf::CIE>(&Entry)) {
      W.startLine() << format("[0x%" PRIx64 "] CIE length=%" PRIu64 "\n",
                              Address + CIE->getOffset(), CIE->getLength());
      W.indent();

      W.printNumber("version", CIE->getVersion());
      W.printString("augmentation", CIE->getAugmentationString());
      W.printNumber("code_alignment_factor", CIE->getCodeAlignmentFactor());
      W.printNumber("data_alignment_factor", CIE->getDataAlignmentFactor());
      W.printNumber("return_address_register", CIE->getReturnAddressRegister());
    } else {
      const dwarf::FDE *FDE = cast<dwarf::FDE>(&Entry);
      W.startLine() << format("[0x%" PRIx64 "] FDE length=%" PRIu64
                              " cie=[0x%" PRIx64 "]\n",
                              Address + FDE->getOffset(), FDE->getLength(),
                              Address + FDE->getLinkedCIE()->getOffset());
      W.indent();

      InitialLocation = FDE->getInitialLocation();
      W.startLine() << format("initial_location: 0x%" PRIx64 "\n",
                              *InitialLocation);
      W.startLine() << format(
          "address_range: 0x%" PRIx64 " (end : 0x%" PRIx64 ")\n",
          FDE->getAddressRange(),
          FDE->getInitialLocation() + FDE->getAddressRange());
    }

    W.getOStream() << "\n";
    W.startLine() << "Program:\n";
    W.indent();
    auto DumpOpts = DIDumpOptions();
    DumpOpts.IsEH = true;
    Entry.cfis().dump(W.getOStream(), DumpOpts, W.getIndentLevel(),
                      InitialLocation);
    W.unindent();
    W.unindent();
    W.getOStream() << "\n";
  }

  W.unindent();
}
} // namespace DwarfCFIEH
} // namespace llvm

#endif