build/unix/elfhack/elf.cpp
author Sylvestre Ledru <sledru@mozilla.com>
Fri, 30 Nov 2018 11:46:48 +0100
changeset 448947 6f3709b3878117466168c40affa7bca0b60cf75b
parent 442868 0988f87f6bd2504463cea12fe0f2ba9ef5317b38
child 469667 04eccd9f23a1ac4f5805765aa69ed183713157a3
permissions -rw-r--r--
Bug 1511181 - Reformat everything to the Google coding style r=ehsan a=clang-format # ignore-this-changeset

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#undef NDEBUG
#include <cstring>
#include <assert.h>
#include "elfxx.h"

template <class endian, typename R, typename T>
void Elf_Ehdr_Traits::swap(T &t, R &r) {
  memcpy(r.e_ident, t.e_ident, sizeof(r.e_ident));
  r.e_type = endian::swap(t.e_type);
  r.e_machine = endian::swap(t.e_machine);
  r.e_version = endian::swap(t.e_version);
  r.e_entry = endian::swap(t.e_entry);
  r.e_phoff = endian::swap(t.e_phoff);
  r.e_shoff = endian::swap(t.e_shoff);
  r.e_flags = endian::swap(t.e_flags);
  r.e_ehsize = endian::swap(t.e_ehsize);
  r.e_phentsize = endian::swap(t.e_phentsize);
  r.e_phnum = endian::swap(t.e_phnum);
  r.e_shentsize = endian::swap(t.e_shentsize);
  r.e_shnum = endian::swap(t.e_shnum);
  r.e_shstrndx = endian::swap(t.e_shstrndx);
}

template <class endian, typename R, typename T>
void Elf_Phdr_Traits::swap(T &t, R &r) {
  r.p_type = endian::swap(t.p_type);
  r.p_offset = endian::swap(t.p_offset);
  r.p_vaddr = endian::swap(t.p_vaddr);
  r.p_paddr = endian::swap(t.p_paddr);
  r.p_filesz = endian::swap(t.p_filesz);
  r.p_memsz = endian::swap(t.p_memsz);
  r.p_flags = endian::swap(t.p_flags);
  r.p_align = endian::swap(t.p_align);
}

template <class endian, typename R, typename T>
void Elf_Shdr_Traits::swap(T &t, R &r) {
  r.sh_name = endian::swap(t.sh_name);
  r.sh_type = endian::swap(t.sh_type);
  r.sh_flags = endian::swap(t.sh_flags);
  r.sh_addr = endian::swap(t.sh_addr);
  r.sh_offset = endian::swap(t.sh_offset);
  r.sh_size = endian::swap(t.sh_size);
  r.sh_link = endian::swap(t.sh_link);
  r.sh_info = endian::swap(t.sh_info);
  r.sh_addralign = endian::swap(t.sh_addralign);
  r.sh_entsize = endian::swap(t.sh_entsize);
}

template <class endian, typename R, typename T>
void Elf_Dyn_Traits::swap(T &t, R &r) {
  r.d_tag = endian::swap(t.d_tag);
  r.d_un.d_val = endian::swap(t.d_un.d_val);
}

template <class endian, typename R, typename T>
void Elf_Sym_Traits::swap(T &t, R &r) {
  r.st_name = endian::swap(t.st_name);
  r.st_value = endian::swap(t.st_value);
  r.st_size = endian::swap(t.st_size);
  r.st_info = t.st_info;
  r.st_other = t.st_other;
  r.st_shndx = endian::swap(t.st_shndx);
}

template <class endian>
struct _Rel_info {
  static inline void swap(Elf32_Word &t, Elf32_Word &r) { r = endian::swap(t); }
  static inline void swap(Elf64_Xword &t, Elf64_Xword &r) {
    r = endian::swap(t);
  }
  static inline void swap(Elf64_Xword &t, Elf32_Word &r) {
    r = endian::swap(ELF32_R_INFO(ELF64_R_SYM(t), ELF64_R_TYPE(t)));
  }
  static inline void swap(Elf32_Word &t, Elf64_Xword &r) {
    r = endian::swap(ELF64_R_INFO(ELF32_R_SYM(t), ELF32_R_TYPE(t)));
  }
};

template <class endian, typename R, typename T>
void Elf_Rel_Traits::swap(T &t, R &r) {
  r.r_offset = endian::swap(t.r_offset);
  _Rel_info<endian>::swap(t.r_info, r.r_info);
}

template <class endian, typename R, typename T>
void Elf_Rela_Traits::swap(T &t, R &r) {
  r.r_offset = endian::swap(t.r_offset);
  _Rel_info<endian>::swap(t.r_info, r.r_info);
  r.r_addend = endian::swap(t.r_addend);
}

static const Elf32_Shdr null32_section = {0, SHT_NULL,  0, 0, 0,
                                          0, SHN_UNDEF, 0, 0, 0};

Elf_Shdr null_section(null32_section);

Elf_Ehdr::Elf_Ehdr(std::ifstream &file, char ei_class, char ei_data)
    : serializable<Elf_Ehdr_Traits>(file, ei_class, ei_data),
      ElfSection(null_section, nullptr, nullptr) {
  shdr.sh_size = Elf_Ehdr::size(ei_class);
}

Elf::Elf(std::ifstream &file) {
  if (!file.is_open()) throw std::runtime_error("Error opening file");

  file.exceptions(std::ifstream::eofbit | std::ifstream::failbit |
                  std::ifstream::badbit);
  // Read ELF magic number and identification information
  char e_ident[EI_VERSION];
  file.seekg(0);
  file.read(e_ident, sizeof(e_ident));
  file.seekg(0);
  ehdr = new Elf_Ehdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);

  // ELFOSABI_LINUX is kept unsupported because I haven't looked whether
  // STB_GNU_UNIQUE or STT_GNU_IFUNC would need special casing.
  if ((ehdr->e_ident[EI_OSABI] != ELFOSABI_NONE) &&
      (ehdr->e_ident[EI_ABIVERSION] != 0))
    throw std::runtime_error("unsupported ELF ABI");

  if (ehdr->e_version != 1) throw std::runtime_error("unsupported ELF version");

  // Sanity checks
  if (ehdr->e_shnum == 0)
    throw std::runtime_error("sstripped ELF files aren't supported");

  if (ehdr->e_ehsize != Elf_Ehdr::size(e_ident[EI_CLASS]))
    throw std::runtime_error(
        "unsupported ELF inconsistency: ehdr.e_ehsize != sizeof(ehdr)");

  if (ehdr->e_shentsize != Elf_Shdr::size(e_ident[EI_CLASS]))
    throw std::runtime_error(
        "unsupported ELF inconsistency: ehdr.e_shentsize != sizeof(shdr)");

  if (ehdr->e_phnum == 0) {
    if (ehdr->e_phoff != 0)
      throw std::runtime_error(
          "unsupported ELF inconsistency: e_phnum == 0 && e_phoff != 0");
    if (ehdr->e_phentsize != 0)
      throw std::runtime_error(
          "unsupported ELF inconsistency: e_phnum == 0 && e_phentsize != 0");
  } else if (ehdr->e_phoff != ehdr->e_ehsize)
    throw std::runtime_error(
        "unsupported ELF inconsistency: ehdr->e_phoff != ehdr->e_ehsize");
  else if (ehdr->e_phentsize != Elf_Phdr::size(e_ident[EI_CLASS]))
    throw std::runtime_error(
        "unsupported ELF inconsistency: ehdr->e_phentsize != sizeof(phdr)");

  // Read section headers
  Elf_Shdr **shdr = new Elf_Shdr *[ehdr->e_shnum];
  file.seekg(ehdr->e_shoff);
  for (int i = 0; i < ehdr->e_shnum; i++)
    shdr[i] = new Elf_Shdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);

  // Sanity check in section header for index 0
  if ((shdr[0]->sh_name != 0) || (shdr[0]->sh_type != SHT_NULL) ||
      (shdr[0]->sh_flags != 0) || (shdr[0]->sh_addr != 0) ||
      (shdr[0]->sh_offset != 0) || (shdr[0]->sh_size != 0) ||
      (shdr[0]->sh_link != SHN_UNDEF) || (shdr[0]->sh_info != 0) ||
      (shdr[0]->sh_addralign != 0) || (shdr[0]->sh_entsize != 0))
    throw std::runtime_error(
        "Section header for index 0 contains unsupported values");

  if ((shdr[ehdr->e_shstrndx]->sh_link != 0) ||
      (shdr[ehdr->e_shstrndx]->sh_info != 0))
    throw std::runtime_error(
        "unsupported ELF content: string table with sh_link != 0 || sh_info != "
        "0");

  // Store these temporarily
  tmp_shdr = shdr;
  tmp_file = &file;

  // Fill sections list
  sections = new ElfSection *[ehdr->e_shnum];
  for (int i = 0; i < ehdr->e_shnum; i++) sections[i] = nullptr;
  for (int i = 1; i < ehdr->e_shnum; i++) {
    if (sections[i] != nullptr) continue;
    getSection(i);
  }
  Elf_Shdr s;
  s.sh_name = 0;
  s.sh_type = SHT_NULL;
  s.sh_flags = 0;
  s.sh_addr = 0;
  s.sh_offset = ehdr->e_shoff;
  s.sh_entsize = Elf_Shdr::size(e_ident[EI_CLASS]);
  s.sh_size = s.sh_entsize * ehdr->e_shnum;
  s.sh_link = 0;
  s.sh_info = 0;
  s.sh_addralign = (e_ident[EI_CLASS] == ELFCLASS32) ? 4 : 8;
  shdr_section = new ElfSection(s, nullptr, nullptr);

  // Fake section for program headers
  s.sh_offset = ehdr->e_phoff;
  s.sh_addr = ehdr->e_phoff;
  s.sh_entsize = Elf_Phdr::size(e_ident[EI_CLASS]);
  s.sh_size = s.sh_entsize * ehdr->e_phnum;
  phdr_section = new ElfSection(s, nullptr, nullptr);

  phdr_section->insertAfter(ehdr, false);

  sections[1]->insertAfter(phdr_section, false);
  for (int i = 2; i < ehdr->e_shnum; i++) {
    // TODO: this should be done in a better way
    if ((shdr_section->getPrevious() == nullptr) &&
        (shdr[i]->sh_offset > ehdr->e_shoff)) {
      shdr_section->insertAfter(sections[i - 1], false);
      sections[i]->insertAfter(shdr_section, false);
    } else
      sections[i]->insertAfter(sections[i - 1], false);
  }
  if (shdr_section->getPrevious() == nullptr)
    shdr_section->insertAfter(sections[ehdr->e_shnum - 1], false);

  tmp_file = nullptr;
  tmp_shdr = nullptr;
  for (int i = 0; i < ehdr->e_shnum; i++) delete shdr[i];
  delete[] shdr;

  eh_shstrndx = (ElfStrtab_Section *)sections[ehdr->e_shstrndx];

  // Skip reading program headers if there aren't any
  if (ehdr->e_phnum == 0) return;

  bool adjusted_phdr_section = false;
  // Read program headers
  file.seekg(ehdr->e_phoff);
  for (int i = 0; i < ehdr->e_phnum; i++) {
    Elf_Phdr phdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);
    if (phdr.p_type == PT_LOAD) {
      // Default alignment for PT_LOAD on x86-64 prevents elfhack from
      // doing anything useful. However, the system doesn't actually
      // require such a big alignment, so in order for elfhack to work
      // efficiently, reduce alignment when it's originally the default
      // one.
      if ((ehdr->e_machine == EM_X86_64) && (phdr.p_align == 0x200000))
        phdr.p_align = 0x1000;
    }
    ElfSegment *segment = new ElfSegment(&phdr);
    // Some segments aren't entirely filled (if at all) by sections
    // For those, we use fake sections
    if ((phdr.p_type == PT_LOAD) && (phdr.p_offset == 0)) {
      // Use a fake section for ehdr and phdr
      ehdr->getShdr().sh_addr = phdr.p_vaddr;
      if (!adjusted_phdr_section) {
        phdr_section->getShdr().sh_addr += phdr.p_vaddr;
        adjusted_phdr_section = true;
      }
      segment->addSection(ehdr);
      segment->addSection(phdr_section);
    }
    if (phdr.p_type == PT_PHDR) {
      if (!adjusted_phdr_section) {
        phdr_section->getShdr().sh_addr = phdr.p_vaddr;
        adjusted_phdr_section = true;
      }
      segment->addSection(phdr_section);
    }
    for (int j = 1; j < ehdr->e_shnum; j++)
      if (phdr.contains(sections[j])) segment->addSection(sections[j]);
    // Make sure that our view of segments corresponds to the original
    // ELF file.
    // GNU gold likes to start some segments before the first section
    // they contain. https://sourceware.org/bugzilla/show_bug.cgi?id=19392
    unsigned int gold_adjustment = segment->getAddr() - phdr.p_vaddr;
    assert(segment->getFileSize() == phdr.p_filesz - gold_adjustment);
    // gold makes TLS segments end on an aligned virtual address, even
    // when the underlying section ends before that, while bfd ld
    // doesn't. It's fine if we don't keep that alignment.
    unsigned int memsize = segment->getMemSize();
    if (phdr.p_type == PT_TLS && memsize != phdr.p_memsz) {
      unsigned int align = segment->getAlign();
      memsize = (memsize + align - 1) & ~(align - 1);
    }
    assert(memsize == phdr.p_memsz - gold_adjustment);
    segments.push_back(segment);
  }

  new (&eh_entry) ElfLocation(ehdr->e_entry, this);
}

Elf::~Elf() {
  for (std::vector<ElfSegment *>::iterator seg = segments.begin();
       seg != segments.end(); seg++)
    delete *seg;
  delete[] sections;
  ElfSection *section = ehdr;
  while (section != nullptr) {
    ElfSection *next = section->getNext();
    delete section;
    section = next;
  }
}

// TODO: This shouldn't fail after inserting sections
ElfSection *Elf::getSection(int index) {
  if ((index < -1) || (index >= ehdr->e_shnum))
    throw std::runtime_error("Section index out of bounds");
  if (index == -1)
    index = ehdr->e_shstrndx;  // TODO: should be fixed to use the actual
                               // current number
  // Special case: the section at index 0 is void
  if (index == 0) return nullptr;
  // Infinite recursion guard
  if (sections[index] == (ElfSection *)this) return nullptr;
  if (sections[index] == nullptr) {
    sections[index] = (ElfSection *)this;
    switch (tmp_shdr[index]->sh_type) {
      case SHT_DYNAMIC:
        sections[index] =
            new ElfDynamic_Section(*tmp_shdr[index], tmp_file, this);
        break;
      case SHT_REL:
        sections[index] =
            new ElfRel_Section<Elf_Rel>(*tmp_shdr[index], tmp_file, this);
        break;
      case SHT_RELA:
        sections[index] =
            new ElfRel_Section<Elf_Rela>(*tmp_shdr[index], tmp_file, this);
        break;
      case SHT_DYNSYM:
      case SHT_SYMTAB:
        sections[index] =
            new ElfSymtab_Section(*tmp_shdr[index], tmp_file, this);
        break;
      case SHT_STRTAB:
        sections[index] =
            new ElfStrtab_Section(*tmp_shdr[index], tmp_file, this);
        break;
      default:
        sections[index] = new ElfSection(*tmp_shdr[index], tmp_file, this);
    }
  }
  return sections[index];
}

ElfSection *Elf::getSectionAt(unsigned int offset) {
  for (int i = 1; i < ehdr->e_shnum; i++) {
    ElfSection *section = getSection(i);
    if ((section != nullptr) && (section->getFlags() & SHF_ALLOC) &&
        !(section->getFlags() & SHF_TLS) && (offset >= section->getAddr()) &&
        (offset < section->getAddr() + section->getSize()))
      return section;
  }
  return nullptr;
}

ElfSegment *Elf::getSegmentByType(unsigned int type, ElfSegment *last) {
  std::vector<ElfSegment *>::iterator seg;
  if (last) {
    seg = std::find(segments.begin(), segments.end(), last);
    ++seg;
  } else
    seg = segments.begin();
  for (; seg != segments.end(); seg++)
    if ((*seg)->getType() == type) return *seg;
  return nullptr;
}

void Elf::removeSegment(ElfSegment *segment) {
  if (!segment) return;
  std::vector<ElfSegment *>::iterator seg;
  seg = std::find(segments.begin(), segments.end(), segment);
  if (seg == segments.end()) return;
  segment->clear();
  segments.erase(seg);
}

ElfDynamic_Section *Elf::getDynSection() {
  for (std::vector<ElfSegment *>::iterator seg = segments.begin();
       seg != segments.end(); seg++)
    if (((*seg)->getType() == PT_DYNAMIC) &&
        ((*seg)->getFirstSection() != nullptr) &&
        (*seg)->getFirstSection()->getType() == SHT_DYNAMIC)
      return (ElfDynamic_Section *)(*seg)->getFirstSection();

  return nullptr;
}

void Elf::normalize() {
  // fixup section headers sh_name; TODO: that should be done by sections
  // themselves
  for (ElfSection *section = ehdr; section != nullptr;
       section = section->getNext()) {
    if (section->getIndex() == 0)
      continue;
    else
      ehdr->e_shnum = section->getIndex() + 1;
    section->getShdr().sh_name = eh_shstrndx->getStrIndex(section->getName());
  }
  ehdr->markDirty();
  // Check segments consistency
  int i = 0;
  for (std::vector<ElfSegment *>::iterator seg = segments.begin();
       seg != segments.end(); seg++, i++) {
    std::list<ElfSection *>::iterator it = (*seg)->begin();
    for (ElfSection *last = *(it++); it != (*seg)->end(); last = *(it++)) {
      if (((*it)->getType() != SHT_NOBITS) &&
          ((*it)->getAddr() - last->getAddr()) !=
              ((*it)->getOffset() - last->getOffset())) {
        throw std::runtime_error("Segments inconsistency");
      }
    }
  }

  ElfSegment *prevLoad = nullptr;
  for (auto &it : segments) {
    if (it->getType() == PT_LOAD) {
      if (prevLoad) {
        size_t alignedPrevEnd = (prevLoad->getAddr() + prevLoad->getMemSize() +
                                 prevLoad->getAlign() - 1) &
                                ~(prevLoad->getAlign() - 1);
        size_t alignedStart = it->getAddr() & ~(it->getAlign() - 1);
        if (alignedPrevEnd > alignedStart) {
          throw std::runtime_error("Segments overlap");
        }
      }
      prevLoad = it;
    }
  }

  // fixup ehdr before writing
  if (ehdr->e_phnum != segments.size()) {
    ehdr->e_phnum = segments.size();
    phdr_section->getShdr().sh_size =
        segments.size() * Elf_Phdr::size(ehdr->e_ident[EI_CLASS]);
    phdr_section->getNext()->markDirty();
  }
  // fixup shdr before writing
  if (ehdr->e_shnum != shdr_section->getSize() / shdr_section->getEntSize())
    shdr_section->getShdr().sh_size =
        ehdr->e_shnum * Elf_Shdr::size(ehdr->e_ident[EI_CLASS]);
  ehdr->e_shoff = shdr_section->getOffset();
  ehdr->e_entry = eh_entry.getValue();
  ehdr->e_shstrndx = eh_shstrndx->getIndex();

  // Check sections consistency
  unsigned int minOffset = 0;
  for (ElfSection *section = ehdr; section != nullptr;
       section = section->getNext()) {
    unsigned int offset = section->getOffset();
    if (offset < minOffset) {
      throw std::runtime_error("Sections overlap");
    }
    if (section->getType() != SHT_NOBITS) {
      minOffset = offset + section->getSize();
    }
  }
}

void Elf::write(std::ofstream &file) {
  normalize();
  for (ElfSection *section = ehdr; section != nullptr;
       section = section->getNext()) {
    file.seekp(section->getOffset());
    if (section == phdr_section) {
      for (std::vector<ElfSegment *>::iterator seg = segments.begin();
           seg != segments.end(); seg++) {
        Elf_Phdr phdr;
        phdr.p_type = (*seg)->getType();
        phdr.p_flags = (*seg)->getFlags();
        phdr.p_offset = (*seg)->getOffset();
        phdr.p_vaddr = (*seg)->getAddr();
        phdr.p_paddr = phdr.p_vaddr + (*seg)->getVPDiff();
        phdr.p_filesz = (*seg)->getFileSize();
        phdr.p_memsz = (*seg)->getMemSize();
        phdr.p_align = (*seg)->getAlign();
        phdr.serialize(file, ehdr->e_ident[EI_CLASS], ehdr->e_ident[EI_DATA]);
      }
    } else if (section == shdr_section) {
      null_section.serialize(file, ehdr->e_ident[EI_CLASS],
                             ehdr->e_ident[EI_DATA]);
      for (ElfSection *sec = ehdr; sec != nullptr; sec = sec->getNext()) {
        if (sec->getType() != SHT_NULL)
          sec->getShdr().serialize(file, ehdr->e_ident[EI_CLASS],
                                   ehdr->e_ident[EI_DATA]);
      }
    } else
      section->serialize(file, ehdr->e_ident[EI_CLASS], ehdr->e_ident[EI_DATA]);
  }
}

ElfSection::ElfSection(Elf_Shdr &s, std::ifstream *file, Elf *parent)
    : shdr(s),
      link(shdr.sh_link == SHN_UNDEF ? nullptr
                                     : parent->getSection(shdr.sh_link)),
      next(nullptr),
      previous(nullptr),
      index(-1) {
  if ((file == nullptr) || (shdr.sh_type == SHT_NULL) ||
      (shdr.sh_type == SHT_NOBITS))
    data = nullptr;
  else {
    data = new char[shdr.sh_size];
    int pos = file->tellg();
    file->seekg(shdr.sh_offset);
    file->read(data, shdr.sh_size);
    file->seekg(pos);
  }
  if (shdr.sh_name == 0)
    name = nullptr;
  else {
    ElfStrtab_Section *strtab = (ElfStrtab_Section *)parent->getSection(-1);
    // Special case (see elfgeneric.cpp): if strtab is nullptr, the
    // section being created is the strtab.
    if (strtab == nullptr)
      name = &data[shdr.sh_name];
    else
      name = strtab->getStr(shdr.sh_name);
  }
  // Only SHT_REL/SHT_RELA sections use sh_info to store a section
  // number.
  if ((shdr.sh_type == SHT_REL) || (shdr.sh_type == SHT_RELA))
    info.section = shdr.sh_info ? parent->getSection(shdr.sh_info) : nullptr;
  else
    info.index = shdr.sh_info;
}

unsigned int ElfSection::getAddr() {
  if (shdr.sh_addr != (Elf32_Word)-1) return shdr.sh_addr;

  // It should be safe to adjust sh_addr for all allocated sections that
  // are neither SHT_NOBITS nor SHT_PROGBITS
  if ((previous != nullptr) && isRelocatable()) {
    unsigned int addr = previous->getAddr();
    if (previous->getType() != SHT_NOBITS) addr += previous->getSize();

    if (addr & (getAddrAlign() - 1)) addr = (addr | (getAddrAlign() - 1)) + 1;

    return (shdr.sh_addr = addr);
  }
  return shdr.sh_addr;
}

unsigned int ElfSection::getOffset() {
  if (shdr.sh_offset != (Elf32_Word)-1) return shdr.sh_offset;

  if (previous == nullptr) return (shdr.sh_offset = 0);

  unsigned int offset = previous->getOffset();

  ElfSegment *ptload = getSegmentByType(PT_LOAD);
  ElfSegment *prev_ptload = previous->getSegmentByType(PT_LOAD);

  if (ptload && (ptload == prev_ptload)) {
    offset += getAddr() - previous->getAddr();
    return (shdr.sh_offset = offset);
  }

  if (previous->getType() != SHT_NOBITS) offset += previous->getSize();

  Elf32_Word align = 0x1000;
  for (std::vector<ElfSegment *>::iterator seg = segments.begin();
       seg != segments.end(); seg++)
    align = std::max(align, (*seg)->getAlign());

  Elf32_Word mask = align - 1;
  // SHF_TLS is used for .tbss which is some kind of special case.
  if (((getType() != SHT_NOBITS) || (getFlags() & SHF_TLS)) &&
      (getFlags() & SHF_ALLOC)) {
    if ((getAddr() & mask) < (offset & mask))
      offset = (offset | mask) + (getAddr() & mask) + 1;
    else
      offset = (offset & ~mask) + (getAddr() & mask);
  }
  if ((getType() != SHT_NOBITS) && (offset & (getAddrAlign() - 1)))
    offset = (offset | (getAddrAlign() - 1)) + 1;

  return (shdr.sh_offset = offset);
}

int ElfSection::getIndex() {
  if (index != -1) return index;
  if (getType() == SHT_NULL) return (index = 0);
  ElfSection *reference;
  for (reference = previous;
       (reference != nullptr) && (reference->getType() == SHT_NULL);
       reference = reference->getPrevious())
    ;
  if (reference == nullptr) return (index = 1);
  return (index = reference->getIndex() + 1);
}

Elf_Shdr &ElfSection::getShdr() {
  getOffset();
  if (shdr.sh_link == (Elf32_Word)-1)
    shdr.sh_link = getLink() ? getLink()->getIndex() : 0;
  if (shdr.sh_info == (Elf32_Word)-1)
    shdr.sh_info = ((getType() == SHT_REL) || (getType() == SHT_RELA))
                       ? (getInfo().section ? getInfo().section->getIndex() : 0)
                       : getInfo().index;

  return shdr;
}

ElfSegment::ElfSegment(Elf_Phdr *phdr)
    : type(phdr->p_type),
      v_p_diff(phdr->p_paddr - phdr->p_vaddr),
      flags(phdr->p_flags),
      align(phdr->p_align),
      vaddr(phdr->p_vaddr),
      filesz(phdr->p_filesz),
      memsz(phdr->p_memsz) {}

void ElfSegment::addSection(ElfSection *section) {
  // Make sure all sections in PT_GNU_RELRO won't be moved by elfhack
  assert(!((type == PT_GNU_RELRO) && (section->isRelocatable())));

  // TODO: Check overlapping sections
  std::list<ElfSection *>::iterator i;
  for (i = sections.begin(); i != sections.end(); ++i)
    if ((*i)->getAddr() > section->getAddr()) break;
  sections.insert(i, section);
  section->addToSegment(this);
}

void ElfSegment::removeSection(ElfSection *section) {
  sections.remove(section);
  section->removeFromSegment(this);
}

unsigned int ElfSegment::getFileSize() {
  if (type == PT_GNU_RELRO) return filesz;

  if (sections.empty()) return 0;
  // Search the last section that is not SHT_NOBITS
  std::list<ElfSection *>::reverse_iterator i;
  for (i = sections.rbegin();
       (i != sections.rend()) && ((*i)->getType() == SHT_NOBITS); ++i)
    ;
  // All sections are SHT_NOBITS
  if (i == sections.rend()) return 0;

  unsigned int end = (*i)->getAddr() + (*i)->getSize();

  return end - sections.front()->getAddr();
}

unsigned int ElfSegment::getMemSize() {
  if (type == PT_GNU_RELRO) return memsz;

  if (sections.empty()) return 0;

  unsigned int end = sections.back()->getAddr() + sections.back()->getSize();

  return end - sections.front()->getAddr();
}

unsigned int ElfSegment::getOffset() {
  if ((type == PT_GNU_RELRO) && !sections.empty() &&
      (sections.front()->getAddr() != vaddr))
    throw std::runtime_error(
        "PT_GNU_RELRO segment doesn't start on a section start");

  return sections.empty() ? 0 : sections.front()->getOffset();
}

unsigned int ElfSegment::getAddr() {
  if ((type == PT_GNU_RELRO) && !sections.empty() &&
      (sections.front()->getAddr() != vaddr))
    throw std::runtime_error(
        "PT_GNU_RELRO segment doesn't start on a section start");

  return sections.empty() ? 0 : sections.front()->getAddr();
}

void ElfSegment::clear() {
  for (std::list<ElfSection *>::iterator i = sections.begin();
       i != sections.end(); ++i)
    (*i)->removeFromSegment(this);
  sections.clear();
}

ElfValue *ElfDynamic_Section::getValueForType(unsigned int tag) {
  for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++)
    if (dyns[i].tag == tag) return dyns[i].value;

  return nullptr;
}

ElfSection *ElfDynamic_Section::getSectionForType(unsigned int tag) {
  ElfValue *value = getValueForType(tag);
  return value ? value->getSection() : nullptr;
}

bool ElfDynamic_Section::setValueForType(unsigned int tag, ElfValue *val) {
  unsigned int i;
  unsigned int shnum = shdr.sh_size / shdr.sh_entsize;
  for (i = 0; (i < shnum) && (dyns[i].tag != DT_NULL); i++)
    if (dyns[i].tag == tag) {
      delete dyns[i].value;
      dyns[i].value = val;
      return true;
    }
  // If we get here, this means we didn't match for the given tag
  // Most of the time, there are a few DT_NULL entries, that we can
  // use to add our value, but if we are on the last entry, we can't.
  if (i >= shnum - 1) return false;

  dyns[i].tag = tag;
  dyns[i].value = val;
  return true;
}

ElfDynamic_Section::ElfDynamic_Section(Elf_Shdr &s, std::ifstream *file,
                                       Elf *parent)
    : ElfSection(s, file, parent) {
  int pos = file->tellg();
  dyns.resize(s.sh_size / s.sh_entsize);
  file->seekg(shdr.sh_offset);
  // Here we assume tags refer to only one section (e.g. DT_RELSZ accounts
  // for .rel.dyn size)
  for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++) {
    Elf_Dyn dyn(*file, parent->getClass(), parent->getData());
    dyns[i].tag = dyn.d_tag;
    switch (dyn.d_tag) {
      case DT_NULL:
      case DT_SYMBOLIC:
      case DT_TEXTREL:
      case DT_BIND_NOW:
        dyns[i].value = new ElfValue();
        break;
      case DT_NEEDED:
      case DT_SONAME:
      case DT_RPATH:
      case DT_PLTREL:
      case DT_RUNPATH:
      case DT_FLAGS:
      case DT_RELACOUNT:
      case DT_RELCOUNT:
      case DT_VERDEFNUM:
      case DT_VERNEEDNUM:
        dyns[i].value = new ElfPlainValue(dyn.d_un.d_val);
        break;
      case DT_PLTGOT:
      case DT_HASH:
      case DT_STRTAB:
      case DT_SYMTAB:
      case DT_RELA:
      case DT_INIT:
      case DT_FINI:
      case DT_REL:
      case DT_JMPREL:
      case DT_INIT_ARRAY:
      case DT_FINI_ARRAY:
      case DT_GNU_HASH:
      case DT_VERSYM:
      case DT_VERNEED:
      case DT_VERDEF:
        dyns[i].value = new ElfLocation(dyn.d_un.d_ptr, parent);
        break;
      default:
        dyns[i].value = nullptr;
    }
  }
  // Another loop to get the section sizes
  for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++)
    switch (dyns[i].tag) {
      case DT_PLTRELSZ:
        dyns[i].value = new ElfSize(getSectionForType(DT_JMPREL));
        break;
      case DT_RELASZ:
        dyns[i].value = new ElfSize(getSectionForType(DT_RELA));
        break;
      case DT_STRSZ:
        dyns[i].value = new ElfSize(getSectionForType(DT_STRTAB));
        break;
      case DT_RELSZ:
        dyns[i].value = new ElfSize(getSectionForType(DT_REL));
        break;
      case DT_INIT_ARRAYSZ:
        dyns[i].value = new ElfSize(getSectionForType(DT_INIT_ARRAY));
        break;
      case DT_FINI_ARRAYSZ:
        dyns[i].value = new ElfSize(getSectionForType(DT_FINI_ARRAY));
        break;
      case DT_RELAENT:
        dyns[i].value = new ElfEntSize(getSectionForType(DT_RELA));
        break;
      case DT_SYMENT:
        dyns[i].value = new ElfEntSize(getSectionForType(DT_SYMTAB));
        break;
      case DT_RELENT:
        dyns[i].value = new ElfEntSize(getSectionForType(DT_REL));
        break;
    }

  file->seekg(pos);
}

ElfDynamic_Section::~ElfDynamic_Section() {
  for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++)
    delete dyns[i].value;
}

void ElfDynamic_Section::serialize(std::ofstream &file, char ei_class,
                                   char ei_data) {
  for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) {
    Elf_Dyn dyn;
    dyn.d_tag = dyns[i].tag;
    dyn.d_un.d_val = (dyns[i].value != nullptr) ? dyns[i].value->getValue() : 0;
    dyn.serialize(file, ei_class, ei_data);
  }
}

ElfSymtab_Section::ElfSymtab_Section(Elf_Shdr &s, std::ifstream *file,
                                     Elf *parent)
    : ElfSection(s, file, parent) {
  int pos = file->tellg();
  syms.resize(s.sh_size / s.sh_entsize);
  ElfStrtab_Section *strtab = (ElfStrtab_Section *)getLink();
  file->seekg(shdr.sh_offset);
  for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) {
    Elf_Sym sym(*file, parent->getClass(), parent->getData());
    syms[i].name = strtab->getStr(sym.st_name);
    syms[i].info = sym.st_info;
    syms[i].other = sym.st_other;
    ElfSection *section =
        (sym.st_shndx == SHN_ABS) ? nullptr : parent->getSection(sym.st_shndx);
    new (&syms[i].value)
        ElfLocation(section, sym.st_value, ElfLocation::ABSOLUTE);
    syms[i].size = sym.st_size;
    syms[i].defined = (sym.st_shndx != SHN_UNDEF);
  }
  file->seekg(pos);
}

void ElfSymtab_Section::serialize(std::ofstream &file, char ei_class,
                                  char ei_data) {
  ElfStrtab_Section *strtab = (ElfStrtab_Section *)getLink();
  for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) {
    Elf_Sym sym;
    sym.st_name = strtab->getStrIndex(syms[i].name);
    sym.st_info = syms[i].info;
    sym.st_other = syms[i].other;
    sym.st_value = syms[i].value.getValue();
    ElfSection *section = syms[i].value.getSection();
    if (syms[i].defined)
      sym.st_shndx = section ? section->getIndex() : SHN_ABS;
    else
      sym.st_shndx = SHN_UNDEF;
    sym.st_size = syms[i].size;
    sym.serialize(file, ei_class, ei_data);
  }
}

Elf_SymValue *ElfSymtab_Section::lookup(const char *name,
                                        unsigned int type_filter) {
  for (std::vector<Elf_SymValue>::iterator sym = syms.begin();
       sym != syms.end(); sym++) {
    if ((type_filter & (1 << ELF32_ST_TYPE(sym->info))) &&
        (strcmp(sym->name, name) == 0)) {
      return &*sym;
    }
  }
  return nullptr;
}

const char *ElfStrtab_Section::getStr(unsigned int index) {
  for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
       t++) {
    if (index < t->used) return t->buf + index;
    index -= t->used;
  }
  assert(1 == 0);
  return nullptr;
}

const char *ElfStrtab_Section::getStr(const char *string) {
  if (string == nullptr) return nullptr;

  // If the given string is within the section, return it
  for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
       t++)
    if ((string >= t->buf) && (string < t->buf + t->used)) return string;

  // TODO: should scan in the section to find an existing string

  // If not, we need to allocate the string in the section
  size_t len = strlen(string) + 1;

  if (table.back().size - table.back().used < len)
    table.resize(table.size() + 1);

  char *alloc_str = table.back().buf + table.back().used;
  memcpy(alloc_str, string, len);
  table.back().used += len;

  shdr.sh_size += len;
  markDirty();

  return alloc_str;
}

unsigned int ElfStrtab_Section::getStrIndex(const char *string) {
  if (string == nullptr) return 0;

  unsigned int index = 0;
  string = getStr(string);
  for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
       t++) {
    if ((string >= t->buf) && (string < t->buf + t->used))
      return index + (string - t->buf);
    index += t->used;
  }

  assert(1 == 0);
  return 0;
}

void ElfStrtab_Section::serialize(std::ofstream &file, char ei_class,
                                  char ei_data) {
  file.seekp(getOffset());
  for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
       t++)
    file.write(t->buf, t->used);
}