text: //===- ELF.cpp - ELF object file implementation ---------------------------===//
  //
  // 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 "llvm/Object/ELF.h"
  #include "llvm/BinaryFormat/ELF.h"
  #include "llvm/Support/LEB128.h"
  
  using namespace llvm;
  using namespace object;
  
  #define STRINGIFY_ENUM_CASE(ns, name)                                          \
    case ns::name:                                                               \
      return #name;
  
  #define ELF_RELOC(name, value) STRINGIFY_ENUM_CASE(ELF, name)
  
  StringRef llvm::object::getELFRelocationTypeName(uint32_t Machine,
                                                   uint32_t Type) {
    switch (Machine) {
    case ELF::EM_X86_64:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/x86_64.def"
      default:
        break;
      }
      break;
    case ELF::EM_386:
    case ELF::EM_IAMCU:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/i386.def"
      default:
        break;
      }
      break;
    case ELF::EM_MIPS:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/Mips.def"
      default:
        break;
      }
      break;
    case ELF::EM_AARCH64:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/AArch64.def"
      default:
        break;
      }
      break;
    case ELF::EM_ARM:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/ARM.def"
      default:
        break;
      }
      break;
    case ELF::EM_ARC_COMPACT:
    case ELF::EM_ARC_COMPACT2:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/ARC.def"
      default:
        break;
      }
      break;
    case ELF::EM_AVR:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/AVR.def"
      default:
        break;
      }
      break;
    case ELF::EM_HEXAGON:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/Hexagon.def"
      default:
        break;
      }
      break;
    case ELF::EM_LANAI:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/Lanai.def"
      default:
        break;
      }
      break;
    case ELF::EM_PPC:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/PowerPC.def"
      default:
        break;
      }
      break;
    case ELF::EM_PPC64:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def"
      default:
        break;
      }
      break;
    case ELF::EM_RISCV:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/RISCV.def"
      default:
        break;
      }
      break;
    case ELF::EM_S390:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/SystemZ.def"
      default:
        break;
      }
      break;
    case ELF::EM_SPARC:
    case ELF::EM_SPARC32PLUS:
    case ELF::EM_SPARCV9:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/Sparc.def"
      default:
        break;
      }
      break;
    case ELF::EM_AMDGPU:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/AMDGPU.def"
      default:
        break;
      }
      break;
    case ELF::EM_BPF:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/BPF.def"
      default:
        break;
      }
      break;
    case ELF::EM_MSP430:
      switch (Type) {
  #include "llvm/BinaryFormat/ELFRelocs/MSP430.def"
      default:
        break;
      }
      break;
    default:
      break;
    }
    return "Unknown";
  }
  
  #undef ELF_RELOC
  
  uint32_t llvm::object::getELFRelativeRelocationType(uint32_t Machine) {
    switch (Machine) {
    case ELF::EM_X86_64:
      return ELF::R_X86_64_RELATIVE;
    case ELF::EM_386:
    case ELF::EM_IAMCU:
      return ELF::R_386_RELATIVE;
    case ELF::EM_MIPS:
      break;
    case ELF::EM_AARCH64:
      return ELF::R_AARCH64_RELATIVE;
    case ELF::EM_ARM:
      return ELF::R_ARM_RELATIVE;
    case ELF::EM_ARC_COMPACT:
    case ELF::EM_ARC_COMPACT2:
      return ELF::R_ARC_RELATIVE;
    case ELF::EM_AVR:
      break;
    case ELF::EM_HEXAGON:
      return ELF::R_HEX_RELATIVE;
    case ELF::EM_LANAI:
      break;
    case ELF::EM_PPC:
      break;
    case ELF::EM_PPC64:
      return ELF::R_PPC64_RELATIVE;
    case ELF::EM_RISCV:
      return ELF::R_RISCV_RELATIVE;
    case ELF::EM_S390:
      return ELF::R_390_RELATIVE;
    case ELF::EM_SPARC:
    case ELF::EM_SPARC32PLUS:
    case ELF::EM_SPARCV9:
      return ELF::R_SPARC_RELATIVE;
    case ELF::EM_AMDGPU:
      break;
    case ELF::EM_BPF:
      break;
    default:
      break;
    }
    return 0;
  }
  
  StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
    switch (Machine) {
    case ELF::EM_ARM:
      switch (Type) {
        STRINGIFY_ENUM_CASE(ELF, SHT_ARM_EXIDX);
        STRINGIFY_ENUM_CASE(ELF, SHT_ARM_PREEMPTMAP);
        STRINGIFY_ENUM_CASE(ELF, SHT_ARM_ATTRIBUTES);
        STRINGIFY_ENUM_CASE(ELF, SHT_ARM_DEBUGOVERLAY);
        STRINGIFY_ENUM_CASE(ELF, SHT_ARM_OVERLAYSECTION);
      }
      break;
    case ELF::EM_HEXAGON:
      switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_HEX_ORDERED); }
      break;
    case ELF::EM_X86_64:
      switch (Type) { STRINGIFY_ENUM_CASE(ELF, SHT_X86_64_UNWIND); }
      break;
    case ELF::EM_MIPS:
    case ELF::EM_MIPS_RS3_LE:
      switch (Type) {
        STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_REGINFO);
        STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_OPTIONS);
        STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_DWARF);
        STRINGIFY_ENUM_CASE(ELF, SHT_MIPS_ABIFLAGS);
      }
      break;
    default:
      break;
    }
  
    switch (Type) {
      STRINGIFY_ENUM_CASE(ELF, SHT_NULL);
      STRINGIFY_ENUM_CASE(ELF, SHT_PROGBITS);
      STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB);
      STRINGIFY_ENUM_CASE(ELF, SHT_STRTAB);
      STRINGIFY_ENUM_CASE(ELF, SHT_RELA);
      STRINGIFY_ENUM_CASE(ELF, SHT_HASH);
      STRINGIFY_ENUM_CASE(ELF, SHT_DYNAMIC);
      STRINGIFY_ENUM_CASE(ELF, SHT_NOTE);
      STRINGIFY_ENUM_CASE(ELF, SHT_NOBITS);
      STRINGIFY_ENUM_CASE(ELF, SHT_REL);
      STRINGIFY_ENUM_CASE(ELF, SHT_SHLIB);
      STRINGIFY_ENUM_CASE(ELF, SHT_DYNSYM);
      STRINGIFY_ENUM_CASE(ELF, SHT_INIT_ARRAY);
      STRINGIFY_ENUM_CASE(ELF, SHT_FINI_ARRAY);
      STRINGIFY_ENUM_CASE(ELF, SHT_PREINIT_ARRAY);
      STRINGIFY_ENUM_CASE(ELF, SHT_GROUP);
      STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB_SHNDX);
      STRINGIFY_ENUM_CASE(ELF, SHT_RELR);
      STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_REL);
      STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELA);
      STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELR);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ODRTAB);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LINKER_OPTIONS);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CALL_GRAPH_PROFILE);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ADDRSIG);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_DEPENDENT_LIBRARIES);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_SYMPART);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_EHDR);
      STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_PHDR);
      STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
      STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);
      STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);
      STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verneed);
      STRINGIFY_ENUM_CASE(ELF, SHT_GNU_versym);
    default:
      return "Unknown";
    }
  }
  
  template <class ELFT>
  Expected<std::vector<typename ELFT::Rela>>
  ELFFile<ELFT>::decode_relrs(Elf_Relr_Range relrs) const {
    // This function decodes the contents of an SHT_RELR packed relocation
    // section.
    //
    // Proposal for adding SHT_RELR sections to generic-abi is here:
    //   https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg
    //
    // The encoded sequence of Elf64_Relr entries in a SHT_RELR section looks
    // like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ]
    //
    // i.e. start with an address, followed by any number of bitmaps. The address
    // entry encodes 1 relocation. The subsequent bitmap entries encode up to 63
    // relocations each, at subsequent offsets following the last address entry.
    //
    // The bitmap entries must have 1 in the least significant bit. The assumption
    // here is that an address cannot have 1 in lsb. Odd addresses are not
    // supported.
    //
    // Excluding the least significant bit in the bitmap, each non-zero bit in
    // the bitmap represents a relocation to be applied to a corresponding machine
    // word that follows the base address word. The second least significant bit
    // represents the machine word immediately following the initial address, and
    // each bit that follows represents the next word, in linear order. As such,
    // a single bitmap can encode up to 31 relocations in a 32-bit object, and
    // 63 relocations in a 64-bit object.
    //
    // This encoding has a couple of interesting properties:
    // 1. Looking at any entry, it is clear whether it's an address or a bitmap:
    //    even means address, odd means bitmap.
    // 2. Just a simple list of addresses is a valid encoding.
  
    Elf_Rela Rela;
    Rela.r_info = 0;
    Rela.r_addend = 0;
    Rela.setType(getRelativeRelocationType(), false);
    std::vector<Elf_Rela> Relocs;
  
    // Word type: uint32_t for Elf32, and uint64_t for Elf64.
    typedef typename ELFT::uint Word;
  
    // Word size in number of bytes.
    const size_t WordSize = sizeof(Word);
  
    // Number of bits used for the relocation offsets bitmap.
    // These many relative relocations can be encoded in a single entry.
    const size_t NBits = 8*WordSize - 1;
  
    Word Base = 0;
    for (const Elf_Relr &R : relrs) {
      Word Entry = R;
      if ((Entry&1) == 0) {
        // Even entry: encodes the offset for next relocation.
        Rela.r_offset = Entry;
        Relocs.push_back(Rela);
        // Set base offset for subsequent bitmap entries.
        Base = Entry + WordSize;
        continue;
      }
  
      // Odd entry: encodes bitmap for relocations starting at base.
      Word Offset = Base;
      while (Entry != 0) {
        Entry >>= 1;
        if ((Entry&1) != 0) {
          Rela.r_offset = Offset;
          Relocs.push_back(Rela);
        }
        Offset += WordSize;
      }
  
      // Advance base offset by NBits words.
      Base += NBits * WordSize;
    }
  
    return Relocs;
  }
  
  template <class ELFT>
  Expected<std::vector<typename ELFT::Rela>>
  ELFFile<ELFT>::android_relas(const Elf_Shdr *Sec) const {
    // This function reads relocations in Android's packed relocation format,
    // which is based on SLEB128 and delta encoding.
    Expected<ArrayRef<uint8_t>> ContentsOrErr = getSectionContents(Sec);
    if (!ContentsOrErr)
      return ContentsOrErr.takeError();
    const uint8_t *Cur = ContentsOrErr->begin();
    const uint8_t *End = ContentsOrErr->end();
    if (ContentsOrErr->size() < 4 || Cur[0] != 'A' || Cur[1] != 'P' ||
        Cur[2] != 'S' || Cur[3] != '2')
      return createError("invalid packed relocation header");
    Cur += 4;
  
    const char *ErrStr = nullptr;
    auto ReadSLEB = [&]() -> int64_t {
      if (ErrStr)
        return 0;
      unsigned Len;
      int64_t Result = decodeSLEB128(Cur, &Len, End, &ErrStr);
      Cur += Len;
      return Result;
    };
  
    uint64_t NumRelocs = ReadSLEB();
    uint64_t Offset = ReadSLEB();
    uint64_t Addend = 0;
  
    if (ErrStr)
      return createError(ErrStr);
  
    std::vector<Elf_Rela> Relocs;
    Relocs.reserve(NumRelocs);
    while (NumRelocs) {
      uint64_t NumRelocsInGroup = ReadSLEB();
      if (NumRelocsInGroup > NumRelocs)
        return createError("relocation group unexpectedly large");
      NumRelocs -= NumRelocsInGroup;
  
      uint64_t GroupFlags = ReadSLEB();
      bool GroupedByInfo = GroupFlags & ELF::RELOCATION_GROUPED_BY_INFO_FLAG;
      bool GroupedByOffsetDelta = GroupFlags & ELF::RELOCATION_GROUPED_BY_OFFSET_DELTA_FLAG;
      bool GroupedByAddend = GroupFlags & ELF::RELOCATION_GROUPED_BY_ADDEND_FLAG;
      bool GroupHasAddend = GroupFlags & ELF::RELOCATION_GROUP_HAS_ADDEND_FLAG;
  
      uint64_t GroupOffsetDelta;
      if (GroupedByOffsetDelta)
        GroupOffsetDelta = ReadSLEB();
  
      uint64_t GroupRInfo;
      if (GroupedByInfo)
        GroupRInfo = ReadSLEB();
  
      if (GroupedByAddend && GroupHasAddend)
        Addend += ReadSLEB();
  
      if (!GroupHasAddend)
        Addend = 0;
  
      for (uint64_t I = 0; I != NumRelocsInGroup; ++I) {
        Elf_Rela R;
        Offset += GroupedByOffsetDelta ? GroupOffsetDelta : ReadSLEB();
        R.r_offset = Offset;
        R.r_info = GroupedByInfo ? GroupRInfo : ReadSLEB();
        if (GroupHasAddend && !GroupedByAddend)
          Addend += ReadSLEB();
        R.r_addend = Addend;
        Relocs.push_back(R);
  
        if (ErrStr)
          return createError(ErrStr);
      }
  
      if (ErrStr)
        return createError(ErrStr);
    }
  
    return Relocs;
  }
  
  template <class ELFT>
  std::string ELFFile<ELFT>::getDynamicTagAsString(unsigned Arch,
                                                   uint64_t Type) const {
  #define DYNAMIC_STRINGIFY_ENUM(tag, value)                                     \
    case value:                                                                  \
      return #tag;
  
  #define DYNAMIC_TAG(n, v)
    switch (Arch) {
    case ELF::EM_AARCH64:
      switch (Type) {
  #define AARCH64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
  #include "llvm/BinaryFormat/DynamicTags.def"
  #undef AARCH64_DYNAMIC_TAG
      }
      break;
  
    case ELF::EM_HEXAGON:
      switch (Type) {
  #define HEXAGON_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
  #include "llvm/BinaryFormat/DynamicTags.def"
  #undef HEXAGON_DYNAMIC_TAG
      }
      break;
  
    case ELF::EM_MIPS:
      switch (Type) {
  #define MIPS_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
  #include "llvm/BinaryFormat/DynamicTags.def"
  #undef MIPS_DYNAMIC_TAG
      }
      break;
  
    case ELF::EM_PPC64:
      switch (Type) {
  #define PPC64_DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
  #include "llvm/BinaryFormat/DynamicTags.def"
  #undef PPC64_DYNAMIC_TAG
      }
      break;
    }
  #undef DYNAMIC_TAG
    switch (Type) {
  // Now handle all dynamic tags except the architecture specific ones
  #define AARCH64_DYNAMIC_TAG(name, value)
  #define MIPS_DYNAMIC_TAG(name, value)
  #define HEXAGON_DYNAMIC_TAG(name, value)
  #define PPC64_DYNAMIC_TAG(name, value)
  // Also ignore marker tags such as DT_HIOS (maps to DT_VERNEEDNUM), etc.
  #define DYNAMIC_TAG_MARKER(name, value)
  #define DYNAMIC_TAG(name, value) DYNAMIC_STRINGIFY_ENUM(name, value)
  #include "llvm/BinaryFormat/DynamicTags.def"
  #undef DYNAMIC_TAG
  #undef AARCH64_DYNAMIC_TAG
  #undef MIPS_DYNAMIC_TAG
  #undef HEXAGON_DYNAMIC_TAG
  #undef PPC64_DYNAMIC_TAG
  #undef DYNAMIC_TAG_MARKER
  #undef DYNAMIC_STRINGIFY_ENUM
    default:
      return "<unknown:>0x" + utohexstr(Type, true);
    }
  }
  
  template <class ELFT>
  std::string ELFFile<ELFT>::getDynamicTagAsString(uint64_t Type) const {
    return getDynamicTagAsString(getHeader()->e_machine, Type);
  }
  
  template <class ELFT>
  Expected<typename ELFT::DynRange> ELFFile<ELFT>::dynamicEntries() const {
    ArrayRef<Elf_Dyn> Dyn;
    size_t DynSecSize = 0;
  
    auto ProgramHeadersOrError = program_headers();
    if (!ProgramHeadersOrError)
      return ProgramHeadersOrError.takeError();
  
    for (const Elf_Phdr &Phdr : *ProgramHeadersOrError) {
      if (Phdr.p_type == ELF::PT_DYNAMIC) {
        Dyn = makeArrayRef(
            reinterpret_cast<const Elf_Dyn *>(base() + Phdr.p_offset),
            Phdr.p_filesz / sizeof(Elf_Dyn));
        DynSecSize = Phdr.p_filesz;
        break;
      }
    }
  
    // If we can't find the dynamic section in the program headers, we just fall
    // back on the sections.
    if (Dyn.empty()) {
      auto SectionsOrError = sections();
      if (!SectionsOrError)
        return SectionsOrError.takeError();
  
      for (const Elf_Shdr &Sec : *SectionsOrError) {
        if (Sec.sh_type == ELF::SHT_DYNAMIC) {
          Expected<ArrayRef<Elf_Dyn>> DynOrError =
              getSectionContentsAsArray<Elf_Dyn>(&Sec);
          if (!DynOrError)
            return DynOrError.takeError();
          Dyn = *DynOrError;
          DynSecSize = Sec.sh_size;
          break;
        }
      }
  
      if (!Dyn.data())
        return ArrayRef<Elf_Dyn>();
    }
  
    if (Dyn.empty())
      // TODO: this error is untested.
      return createError("invalid empty dynamic section");
  
    if (DynSecSize % sizeof(Elf_Dyn) != 0)
      // TODO: this error is untested.
      return createError("malformed dynamic section");
  
    if (Dyn.back().d_tag != ELF::DT_NULL)
      // TODO: this error is untested.
      return createError("dynamic sections must be DT_NULL terminated");
  
    return Dyn;
  }
  
  template <class ELFT>
  Expected<const uint8_t *> ELFFile<ELFT>::toMappedAddr(uint64_t VAddr) const {
    auto ProgramHeadersOrError = program_headers();
    if (!ProgramHeadersOrError)
      return ProgramHeadersOrError.takeError();
  
    llvm::SmallVector<Elf_Phdr *, 4> LoadSegments;
  
    for (const Elf_Phdr &Phdr : *ProgramHeadersOrError)
      if (Phdr.p_type == ELF::PT_LOAD)
        LoadSegments.push_back(const_cast<Elf_Phdr *>(&Phdr));
  
    const Elf_Phdr *const *I =
        std::upper_bound(LoadSegments.begin(), LoadSegments.end(), VAddr,
                         [](uint64_t VAddr, const Elf_Phdr_Impl<ELFT> *Phdr) {
                           return VAddr < Phdr->p_vaddr;
                         });
  
    if (I == LoadSegments.begin())
      return createError("virtual address is not in any segment: 0x" +
                         Twine::utohexstr(VAddr));
    --I;
    const Elf_Phdr &Phdr = **I;
    uint64_t Delta = VAddr - Phdr.p_vaddr;
    if (Delta >= Phdr.p_filesz)
      return createError("virtual address is not in any segment: 0x" +
                         Twine::utohexstr(VAddr));
    return base() + Phdr.p_offset + Delta;
  }
  
  template class llvm::object::ELFFile<ELF32LE>;
  template class llvm::object::ELFFile<ELF32BE>;
  template class llvm::object::ELFFile<ELF64LE>;
  template class llvm::object::ELFFile<ELF64BE>;
  