// Copyright 2016 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <assert.h>
#include <stdio.h>

#include <algorithm>
#include <initializer_list>
#include <iostream>
#include <limits>
#include <memory>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "absl/base/attributes.h"
#include "absl/base/macros.h"
#include "absl/strings/string_view.h"
#include "absl/strings/substitute.h"
#include "absl/types/optional.h"
#include "bloaty.h"
#include "bloaty.pb.h"
#include "dwarf_constants.h"
#include "util.h"

using namespace dwarf2reader;
using absl::string_view;

namespace bloaty {

extern int verbose_level;

namespace dwarf {

int DivRoundUp(int n, int d) {
  return (n + (d - 1)) / d;
}

namespace {

// uint64/32 max is a tombstone value added by https://reviews.llvm.org/D81784.
bool IsValidDwarfAddress(uint64_t addr, uint8_t address_size) {
  if (addr == 0)
    return false;
  if (address_size == 4 && addr == std::numeric_limits<uint32_t>::max())
    return false;
  if (address_size == 8 && addr == std::numeric_limits<uint64_t>::max())
    return false;
  return true;
}

}  // namespace

// Low-level Parsing Routines //////////////////////////////////////////////////

// For parsing the low-level values found in DWARF files.  These are the only
// routines that touch the bytes of the input buffer directly.  Everything else
// is layered on top of these.

// Parses the LEB128 format defined by DWARF (both signed and unsigned
// versions).

uint64_t ReadLEB128Internal(bool is_signed, string_view* data) {
  uint64_t ret = 0;
  int shift = 0;
  int maxshift = 70;
  const char* ptr = data->data();
  const char* limit = ptr + data->size();

  while (ptr < limit && shift < maxshift) {
    char byte = *(ptr++);
    ret |= static_cast<uint64_t>(byte & 0x7f) << shift;
    shift += 7;
    if ((byte & 0x80) == 0) {
      data->remove_prefix(ptr - data->data());
      if (is_signed && shift < 64 && (byte & 0x40)) {
        ret |= -(1ULL << shift);
      }
      return ret;
    }
  }

  THROW("corrupt DWARF data, unterminated LEB128");
}

template <typename T>
T ReadLEB128(string_view* data) {
  typedef typename std::conditional<std::is_signed<T>::value, int64_t,
                                    uint64_t>::type Int64Type;
  Int64Type val = ReadLEB128Internal(std::is_signed<T>::value, data);
  if (val > std::numeric_limits<T>::max() ||
      val < std::numeric_limits<T>::min()) {
    THROW("DWARF data contained larger LEB128 than we were expecting");
  }
  return static_cast<T>(val);
}

void SkipLEB128(string_view* data) {
  size_t limit =
      std::min(static_cast<size_t>(data->size()), static_cast<size_t>(10));
  for (size_t i = 0; i < limit; i++) {
    if (((*data)[i] & 0x80) == 0) {
      data->remove_prefix(i + 1);
      return;
    }
  }

  THROW("corrupt DWARF data, unterminated LEB128");
}

// Some size information attached to each compilation unit.  The size of an
// address or offset in the DWARF data depends on this state which is parsed
// from the header.
class CompilationUnitSizes {
 public:
  // When true, DWARF offsets are 64 bits, otherwise they are 32 bit.
  bool dwarf64() const { return dwarf64_; }

  // The size of addresses.  Guaranteed to be either 4 or 8.
  uint8_t address_size() const { return address_size_; }

  // DWARF version of this unit.
  uint8_t dwarf_version() const { return dwarf_version_; }

  void SetAddressSize(uint8_t address_size) {
    if (address_size != 4 && address_size != 8) {
      THROWF("Unexpected address size: $0", address_size);
    }
    address_size_ = address_size;
  }

  // To allow this as the key in a map.
  bool operator<(const CompilationUnitSizes& rhs) const {
    return std::tie(dwarf64_, address_size_) <
           std::tie(rhs.dwarf64_, rhs.address_size_);
  }

  // Reads a DWARF offset based on whether we are reading dwarf32 or dwarf64
  // format.
  uint64_t ReadDWARFOffset(string_view* data) const {
    if (dwarf64_) {
      return ReadFixed<uint64_t>(data);
    } else {
      return ReadFixed<uint32_t>(data);
    }
  }

  // Reads an address according to the expected address_size.
  uint64_t ReadAddress(string_view* data) const {
    if (address_size_ == 8) {
      return ReadFixed<uint64_t>(data);
    } else if (address_size_ == 4) {
      return ReadFixed<uint32_t>(data);
    } else {
      BLOATY_UNREACHABLE();
    }
  }

  // Reads an "initial length" as specified in many DWARF headers.  This
  // contains either a 32-bit or a 64-bit length, and signals whether we are
  // using the 32-bit or 64-bit DWARF format (so it sets dwarf64 appropriately).
  //
  // Returns the range for this section and stores the remaining data
  // in |remaining|.
  string_view ReadInitialLength(string_view* remaining) {
    uint64_t len = ReadFixed<uint32_t>(remaining);

    if (len == 0xffffffff) {
      dwarf64_ = true;
      len = ReadFixed<uint64_t>(remaining);
    } else {
      dwarf64_ = false;
    }

    if (remaining->size() < len) {
      THROW("short DWARF compilation unit");
    }

    string_view unit = *remaining;
    unit.remove_suffix(remaining->size() - len);
    *remaining = remaining->substr(len);
    return unit;
  }

  void ReadDWARFVersion(string_view* data) {
    dwarf_version_ = ReadFixed<uint16_t>(data);
  }

 private:
  uint16_t dwarf_version_;
  bool dwarf64_;
  uint8_t address_size_;
};


// AbbrevTable /////////////////////////////////////////////////////////////////

// Parses and stores a representation of (a portion of) the .debug_abbrev
// section of a DWARF file.  An abbreviation is defined by a unique "code"
// (unique within one table), and defines the DIE tag and set of attributes.
// The encoding of the DIE then contains just the abbreviation code and the
// attribute values -- thanks to the abbreviation table, the tag and attribute
// keys/names are not required.
//
// The abbreviations are an internal detail of the DWARF format and users should
// not need to care about them.

class AbbrevTable {
 public:
  // Reads abbreviations until a terminating abbreviation is seen.
  string_view ReadAbbrevs(string_view data);

  // In a DWARF abbreviation, each attribute has a name and a form.
  struct Attribute {
    uint16_t name;
    uint8_t form;
  };

  // The representation of a single abbreviation.
  struct Abbrev {
    uint32_t code;
    uint16_t tag;
    bool has_child;
    std::vector<Attribute> attr;
  };

  bool IsEmpty() const { return abbrev_.empty(); }

  // Looks for an abbreviation with the given code.  Returns true if the lookup
  // succeeded.
  bool GetAbbrev(uint32_t code, const Abbrev** abbrev) const {
    auto it = abbrev_.find(code);
    if (it != abbrev_.end()) {
      *abbrev = &it->second;
      return true;
    } else {
      return false;
    }
  }

 private:
  // Keyed by abbreviation code.
  // Generally we expect these to be small, so we could almost use a vector<>.
  // But you never know what crazy input data is going to do...
  std::unordered_map<uint32_t, Abbrev> abbrev_;
};

string_view AbbrevTable::ReadAbbrevs(string_view data) {
  while (true) {
    uint32_t code = ReadLEB128<uint32_t>(&data);

    if (code == 0) {
      return data;  // Terminator entry.
    }

    Abbrev& abbrev = abbrev_[code];

    if (abbrev.code) {
      THROW("DWARF data contained duplicate abbrev code");
    }

    uint8_t has_child;

    abbrev.code = code;
    abbrev.tag = ReadLEB128<uint16_t>(&data);
    has_child = ReadFixed<uint8_t>(&data);

    switch (has_child) {
      case DW_children_yes:
        abbrev.has_child = true;
        break;
      case DW_children_no:
        abbrev.has_child = false;
        break;
      default:
        THROW("DWARF has_child is neither true nor false.");
    }

    while (true) {
      Attribute attr;
      attr.name = ReadLEB128<uint16_t>(&data);
      attr.form = ReadLEB128<uint8_t>(&data);

      if (attr.name == 0 && attr.form == 0) {
        break;  // End of this abbrev
      }

      abbrev.attr.push_back(attr);
    }
  }
}


// StringTable /////////////////////////////////////////////////////////////////

// Represents the .debug_str portion of a DWARF file and contains code for
// reading strings out of it.  This is an internal detail of the DWARF format
// and users should not need to care about it.

class StringTable {
 public:
  // Construct with the debug_str data from a DWARF file.
  StringTable(string_view debug_str) : debug_str_(debug_str) {}

  // Read a string from the table.
  string_view ReadEntry(size_t ofs) const;

 private:
  string_view debug_str_;
};

string_view StringTable::ReadEntry(size_t ofs) const {
  string_view str = debug_str_;
  SkipBytes(ofs, &str);
  return ReadNullTerminated(&str);
}


// AddressRanges ///////////////////////////////////////////////////////////////

// Code for reading address ranges out of .debug_aranges.

class AddressRanges {
 public:
  AddressRanges(string_view data) : section_(data), next_unit_(data) {}

  // Offset into .debug_info for the current compilation unit.
  uint64_t debug_info_offset() { return debug_info_offset_; }

  // Address and length for this range.
  uint64_t address() { return address_; }
  uint64_t length() { return length_; }

  // Advance to the next range.  The values will be available in address() and
  // length().  Returns false when the end of this compilation unit is hit.
  // Must call this once before reading the first range.
  bool NextRange();

  // Advance to the next compilation unit.  The unit offset will be available in
  // debug_info_offset().  Must call this once before reading the first unit.
  bool NextUnit();

  uint8_t address_size() const { return sizes_.address_size(); }

 private:
  CompilationUnitSizes sizes_;
  string_view section_;
  string_view unit_remaining_;
  string_view next_unit_;
  uint64_t debug_info_offset_;
  uint64_t address_;
  uint64_t length_;
};

bool AddressRanges::NextRange() {
  if (unit_remaining_.empty()) {
    return false;
  }

  address_ = sizes_.ReadAddress(&unit_remaining_);
  length_ = sizes_.ReadAddress(&unit_remaining_);
  return true;
}

bool AddressRanges::NextUnit() {
  if (next_unit_.empty()) {
    return false;
  }

  unit_remaining_ = sizes_.ReadInitialLength(&next_unit_);
  sizes_.ReadDWARFVersion(&unit_remaining_);

  if (sizes_.dwarf_version() > 4) {
    THROW("DWARF data is too new for us");
  }

  debug_info_offset_ = sizes_.ReadDWARFOffset(&unit_remaining_);

  uint8_t segment_size;

  sizes_.SetAddressSize(ReadFixed<uint8_t>(&unit_remaining_));
  segment_size = ReadFixed<uint8_t>(&unit_remaining_);

  if (segment_size) {
    THROW("we don't know how to handle segmented addresses.");
  }

  size_t ofs = unit_remaining_.data() - section_.data();
  size_t aligned_ofs = AlignUp(ofs, sizes_.address_size() * 2);
  SkipBytes(aligned_ofs - ofs, &unit_remaining_);
  return true;
}


// LocationList ////////////////////////////////////////////////////////////////

// Code for reading entries out of a location list.
// For the moment we only care about finding the bounds of a list given its
// offset, so we don't actually vend any of the data.

class LocationList {
 public:
  LocationList(CompilationUnitSizes sizes, string_view data)
      : sizes_(sizes), remaining_(data) {}

  const char* read_offset() const { return remaining_.data(); }
  bool NextEntry();

 private:
  CompilationUnitSizes sizes_;
  string_view remaining_;
};

bool LocationList::NextEntry() {
  uint64_t start, end;
  start = sizes_.ReadAddress(&remaining_);
  end = sizes_.ReadAddress(&remaining_);
  if (start == 0 && end == 0) {
    return false;
  } else if (start == UINT64_MAX ||
             (start == UINT32_MAX && sizes_.address_size() == 4)) {
    // Base address selection, nothing more to do.
  } else {
    // Need to skip the location description.
    uint16_t length = ReadFixed<uint16_t>(&remaining_);
    SkipBytes(length, &remaining_);
  }
  return true;
}

string_view GetLocationListRange(CompilationUnitSizes sizes,
                                 string_view available) {
  LocationList list(sizes, available);
  while (list.NextEntry()) {}
  return available.substr(0, list.read_offset() - available.data());
}


// RangeList ///////////////////////////////////////////////////////////////////

// Code for reading entries out of a range list.
// For the moment we only care about finding the bounds of a list given its
// offset, so we don't actually vend any of the data.

class RangeList {
 public:
  RangeList(CompilationUnitSizes sizes, string_view data)
      : sizes_(sizes), remaining_(data) {}

  const char* read_offset() const { return remaining_.data(); }
  bool NextEntry();

 private:
  CompilationUnitSizes sizes_;
  string_view remaining_;
};

bool RangeList::NextEntry() {
  uint64_t start, end;
  start = sizes_.ReadAddress(&remaining_);
  end = sizes_.ReadAddress(&remaining_);
  if (start == 0 && end == 0) {
    return false;
  }
  return true;
}

string_view GetRangeListRange(CompilationUnitSizes sizes,
                              string_view available) {
  RangeList list(sizes, available);
  while (list.NextEntry()) {
  }
  return available.substr(0, list.read_offset() - available.data());
}

// DIEReader ///////////////////////////////////////////////////////////////////

// Reads a sequence of DWARF DIE's (Debugging Information Entries) from the
// .debug_info or .debug_types section of a binary.
//
// Each DIE contains a tag and a set of attribute/value pairs.  We rely on the
// abbreviations in an AbbrevTable to decode the DIEs.

class DIEReader {
 public:
  // Constructs a new DIEReader.  Cannot be used until you call one of the
  // Seek() methods below.
  DIEReader(const File& file) : dwarf_(file) {}
  DIEReader(const DIEReader&) = delete;
  DIEReader& operator=(const DIEReader&) = delete;

  // Returns true if we are at the end of DIEs for this compilation unit.
  bool IsEof() const { return state_ == State::kEof; }

  // DIEs exist in both .debug_info and .debug_types.
  enum class Section {
    kDebugInfo,
    kDebugTypes
  };

  // Seeks to the overall start or the start of a specific compilation unit.
  // Note that |header_offset| is the offset of the compilation unit *header*,
  // not the offset of the first DIE.
  bool SeekToCompilationUnit(Section section, uint64_t header_offset);
  bool SeekToStart(Section section) {
    return SeekToCompilationUnit(section, 0);
  }

  bool NextCompilationUnit();

  // Advances to the next overall DIE, ignoring whether it happens to be a
  // child, a sibling, or an uncle/aunt.  Returns false at error or EOF.
  bool NextDIE();

  // Skips children of the current DIE, so that the next call to NextDIE()
  // will read the next sibling (or parent, if no sibling exists).
  bool SkipChildren();

  const AbbrevTable::Abbrev& GetAbbrev() const {
    assert(!IsEof());
    return *current_abbrev_;
  }

  // Returns the current read offset within the current compilation unit.
  int64_t GetReadOffset() const { return remaining_.data() - start_; }

  int GetDepth() const { return depth_; }

  // Returns the tag of the current DIE.
  // Requires that ReadCode() has been called at least once.
  uint16_t GetTag() const { return GetAbbrev().tag; }

  // Returns whether the current DIE has a child.
  // Requires that ReadCode() has been called at least once.
  bool HasChild() const { return GetAbbrev().has_child; }

  const File& dwarf() const { return dwarf_; }

  string_view unit_range() const { return unit_range_; }
  CompilationUnitSizes unit_sizes() const { return unit_sizes_; }
  uint32_t abbrev_version() const { return abbrev_version_; }
  uint64_t debug_abbrev_offset() const { return debug_abbrev_offset_; }

  // If both compileunit_name and strp_sink are set, this will automatically
  // call strp_sink->AddFileRange(compileunit_name, <string range>) for every
  // DW_FORM_strp attribute encountered.  These strings occur in the .debug_str
  // section.
  void set_compileunit_name(absl::string_view name) {
    unit_name_ = std::string(name);
  }
  void set_strp_sink(RangeSink* sink) { strp_sink_ = sink; }

  void AddIndirectString(string_view range) const {
    if (strp_sink_) {
      strp_sink_->AddFileRange("dwarf_strp", unit_name_, range);
    }
  }

 private:
  template<typename> friend class AttrReader;

  // APIs for our friends to use to update our state.

  // Call to get the current read head where attributes should be parsed.
  string_view ReadAttributesBegin() {
    assert(state_ == State::kReadyToReadAttributes);
    return remaining_;
  }

  // When some data has been parsed, this updates our read head.
  bool ReadAttributesEnd(string_view remaining, uint64_t sibling) {
    assert(state_ == State::kReadyToReadAttributes);
    if (remaining.data() == nullptr) {
      THROW("premature EOF reading DWARF attributes");
    } else {
      remaining_ = remaining;
      sibling_offset_ = sibling;
      state_ = State::kReadyToNext;
      return true;
    }
  }

  // Internal APIs.

  bool ReadCompilationUnitHeader();
  bool ReadCode();
  void SkipNullEntries();

  enum class State {
    kReadyToReadAttributes,
    kReadyToNext,
    kEof,
  } state_;

  std::string error_;

  const File& dwarf_;
  RangeSink* strp_sink_ = nullptr;
  const char *start_ = nullptr;

  // Abbreviation for the current entry.
  const AbbrevTable::Abbrev* current_abbrev_;

  // Our current read position.
  string_view remaining_;
  uint64_t sibling_offset_;
  int depth_ = 0;

  // Data for the next compilation unit.
  string_view next_unit_;

  // All of the AbbrevTables we've read from .debug_abbrev, indexed by their
  // offset within .debug_abbrev.
  std::unordered_map<uint64_t, AbbrevTable> abbrev_tables_;

  // Whether we are in .debug_types or .debug_info.
  Section section_;

  // Information about the current compilation unit.
  uint64_t debug_abbrev_offset_;
  std::string unit_name_;
  string_view unit_range_;
  CompilationUnitSizes unit_sizes_;
  AbbrevTable* unit_abbrev_;

  // A small integer that uniquely identifies the combination of unit_abbrev_
  // and unit_sizes_.  Attribute readers use this to know when they can reuse an
  // existing (abbrev code) -> (Actions) mapping, since this table depends on
  // both the current abbrev. table and the sizes.
  uint32_t abbrev_version_;

  std::map<std::pair<AbbrevTable*, CompilationUnitSizes>, uint32_t>
      abbrev_versions_;

  // Only for .debug_types
  uint64_t unit_type_signature_;
  uint64_t unit_type_offset_;
};

void DIEReader::SkipNullEntries() {
  while (!remaining_.empty() && remaining_[0] == 0) {
    // null entry terminates a chain of sibling entries.
    remaining_.remove_prefix(1);
    depth_--;
  }
}

bool DIEReader::ReadCode() {
  SkipNullEntries();
  if (remaining_.empty()) {
    state_ = State::kEof;
    return false;
  }
  uint32_t code = ReadLEB128<uint32_t>(&remaining_);
  if (!unit_abbrev_->GetAbbrev(code, &current_abbrev_)) {
    THROW("couldn't find abbreviation for code");
  }
  state_ = State::kReadyToReadAttributes;
  sibling_offset_ = 0;

  if (HasChild()) {
    depth_++;
  }

  return true;
}

bool DIEReader::NextCompilationUnit() {
  return ReadCompilationUnitHeader();
}

bool DIEReader::NextDIE() {
  if (state_ == State::kEof) {
    return false;
  }

  assert(state_ == State::kReadyToNext);
  return ReadCode();
}

bool DIEReader::SeekToCompilationUnit(Section section, uint64_t offset) {
  section_ = section;

  if (section == Section::kDebugInfo) {
    next_unit_ = dwarf_.debug_info;
  } else {
    next_unit_ = dwarf_.debug_types;
  }

  start_ = next_unit_.data();
  SkipBytes(offset, &next_unit_);
  return ReadCompilationUnitHeader();
}

bool DIEReader::ReadCompilationUnitHeader() {
  if (next_unit_.empty()) {
    state_ = State::kEof;
    return false;
  }

  unit_range_ = next_unit_;
  remaining_ = unit_sizes_.ReadInitialLength(&next_unit_);
  unit_range_ = unit_range_.substr(
      0, remaining_.size() + (remaining_.data() - unit_range_.data()));

  unit_sizes_.ReadDWARFVersion(&remaining_);

  if (unit_sizes_.dwarf_version() > 4) {
    THROWF("Data for $0 is in DWARF $1 format which we don't understand",
        unit_name_, unit_sizes_.dwarf_version());
  }

  debug_abbrev_offset_ = unit_sizes_.ReadDWARFOffset(&remaining_);
  unit_abbrev_ = &abbrev_tables_[debug_abbrev_offset_];

  // If we haven't already read abbreviations for this debug_abbrev_offset_, we
  // need to do so now.
  if (unit_abbrev_->IsEmpty()) {
    string_view abbrev_data = dwarf_.debug_abbrev;
    SkipBytes(debug_abbrev_offset_, &abbrev_data);
    unit_abbrev_->ReadAbbrevs(abbrev_data);
  }

  unit_sizes_.SetAddressSize(ReadFixed<uint8_t>(&remaining_));

  if (section_ == Section::kDebugTypes) {
    unit_type_signature_ = ReadFixed<uint64_t>(&remaining_);
    unit_type_offset_ = unit_sizes_.ReadDWARFOffset(&remaining_);
  }

  auto abbrev_id = std::make_pair(unit_abbrev_, unit_sizes_);
  auto insert_pair = abbrev_versions_.insert(
      std::make_pair(abbrev_id, abbrev_versions_.size()));

  // This will be either the newly inserted value or the existing one, if there
  // was one.
  abbrev_version_ = insert_pair.first->second;

  return ReadCode();
}


// DWARF form parsing //////////////////////////////////////////////////////////

class AttrValue {
 public:
  AttrValue(uint64_t val) : uint_(val), type_(Type::kUint) {}
  AttrValue(string_view val) : string_(val), type_(Type::kString) {}

  enum class Type {
    kUint,
    kString
  };

  Type type() const { return type_; }
  bool IsUint() const { return type_ == Type::kUint; }
  bool IsString() const { return type_ == Type::kString; }

  absl::optional<uint64_t> ToUint() const {
    if (IsUint()) return uint_;
    string_view str = string_;
    switch (str.size()) {
      case 1:
        return ReadFixed<uint8_t>(&str);
      case 2:
        return ReadFixed<uint8_t>(&str);
      case 4:
        return ReadFixed<uint32_t>(&str);
      case 8:
        return ReadFixed<uint64_t>(&str);
    }
    return absl::nullopt;
  }

  uint64_t GetUint() const {
    assert(type_ == Type::kUint);
    return uint_;
  }

  string_view GetString() const {
    assert(type_ == Type::kString);
    return string_;
  }

 private:
  union {
    uint64_t uint_;
    string_view string_;
  };

  Type type_;
};

template <class D>
string_view ReadBlock(string_view* data) {
  D len = ReadFixed<D>(data);
  return ReadBytes(len, data);
}

string_view ReadVariableBlock(string_view* data) {
  uint64_t len = ReadLEB128<uint64_t>(data);
  return ReadBytes(len, data);
}

template <class D>
string_view ReadIndirectString(const DIEReader& reader, string_view* data) {
  D ofs = ReadFixed<D>(data);
  StringTable table(reader.dwarf().debug_str);
  string_view ret = table.ReadEntry(ofs);
  reader.AddIndirectString(ret);
  return ret;
}

AttrValue ParseAttr(const DIEReader& reader, uint8_t form, string_view* data) {
  switch (form) {
    case DW_FORM_indirect: {
      uint16_t indirect_form = ReadLEB128<uint16_t>(data);
      if (indirect_form == DW_FORM_indirect) {
        THROW("indirect attribute has indirect form type");
      }
      return ParseAttr(reader, indirect_form, data);
    }
    case DW_FORM_ref1:
      return AttrValue(ReadFixed<uint8_t>(data));
    case DW_FORM_ref2:
      return AttrValue(ReadFixed<uint16_t>(data));
    case DW_FORM_ref4:
      return AttrValue(ReadFixed<uint32_t>(data));
    case DW_FORM_ref_sig8:
    case DW_FORM_ref8:
      return AttrValue(ReadFixed<uint64_t>(data));
    case DW_FORM_ref_udata:
      return AttrValue(ReadLEB128<uint64_t>(data));
    case DW_FORM_addr:
    address_size:
      switch (reader.unit_sizes().address_size()) {
        case 4:
          return AttrValue(ReadFixed<uint32_t>(data));
        case 8:
          return AttrValue(ReadFixed<uint64_t>(data));
        default:
          BLOATY_UNREACHABLE();
      }
    case DW_FORM_ref_addr:
      if (reader.unit_sizes().dwarf_version() <= 2) {
        goto address_size;
      }
      ABSL_FALLTHROUGH_INTENDED;
    case DW_FORM_sec_offset:
      if (reader.unit_sizes().dwarf64()) {
        return AttrValue(ReadFixed<uint64_t>(data));
      } else {
        return AttrValue(ReadFixed<uint32_t>(data));
      }
    case DW_FORM_udata:
      return AttrValue(ReadLEB128<uint64_t>(data));
    case DW_FORM_block1:
      return AttrValue(ReadBlock<uint8_t>(data));
    case DW_FORM_block2:
      return AttrValue(ReadBlock<uint16_t>(data));
    case DW_FORM_block4:
      return AttrValue(ReadBlock<uint32_t>(data));
    case DW_FORM_block:
    case DW_FORM_exprloc:
      return AttrValue(ReadVariableBlock(data));
    case DW_FORM_string:
      return AttrValue(ReadNullTerminated(data));
    case DW_FORM_strp:
      if (reader.unit_sizes().dwarf64()) {
        return AttrValue(ReadIndirectString<uint64_t>(reader, data));
      } else {
        return AttrValue(ReadIndirectString<uint32_t>(reader, data));
      }
    case DW_FORM_data1:
      return AttrValue(ReadBytes(1, data));
    case DW_FORM_data2:
      return AttrValue(ReadBytes(2, data));
    case DW_FORM_data4:
      return AttrValue(ReadBytes(4, data));
    case DW_FORM_data8:
      return AttrValue(ReadBytes(8, data));

    // Bloaty doesn't currently care about any bool or signed data.
    // So we fudge it a bit and just stuff these in a uint64.
    case DW_FORM_flag_present:
      return AttrValue(1);
    case DW_FORM_flag:
      return AttrValue(ReadFixed<uint8_t>(data));
    case DW_FORM_sdata:
      return AttrValue(ReadLEB128<uint64_t>(data));
    default:
      THROWF("Don't know how to parse DWARF form: $0", form);
  }
}


// AttrReader //////////////////////////////////////////////////////////////////

// Parses a DIE's attributes, calling user callbacks with the parsed values.

template <class T>
class AttrReader {
 public:
  typedef void CallbackFunc(T* container, AttrValue val);

  void OnAttribute(DwarfAttribute attr, CallbackFunc* func) {
    attributes_[attr] = func;
  }

  // Reads all attributes for this DIE, storing the ones we were expecting.
  void ReadAttributes(DIEReader* reader, T* container) {
    string_view data = reader->ReadAttributesBegin();
    const AbbrevTable::Abbrev& abbrev = reader->GetAbbrev();

    for (auto attr : abbrev.attr) {
      AttrValue value = ParseAttr(*reader, attr.form, &data);
      auto it = attributes_.find(attr.name);
      if (it != attributes_.end()) {
        it->second(container, value);
      }
    }

    reader->ReadAttributesEnd(data, 0);
  }

 private:
  std::unordered_map<int, CallbackFunc*> attributes_;
};

// From DIEReader, defined here because it depends on FixedAttrReader.
bool DIEReader::SkipChildren() {
  assert(state_ == State::kReadyToNext);
  if (!HasChild()) {
    return true;
  }

  int target_depth = depth_ - 1;
  dwarf::AttrReader<void> attr_reader;
  SkipNullEntries();
  while (depth_ > target_depth) {
    // TODO(haberman): use DW_AT_sibling to optimize skipping when it is
    // available.
    if (!NextDIE()) {
      return false;
    }
    attr_reader.ReadAttributes(this, nullptr);
    SkipNullEntries();
  }
  return true;
}

// LineInfoReader //////////////////////////////////////////////////////////////

// Code to read the .line_info programs in a DWARF file.

class LineInfoReader {
 public:
  LineInfoReader(const File& file) : file_(file), info_(0) {}

  struct LineInfo {
    LineInfo(bool default_is_stmt) : is_stmt(default_is_stmt) {}
    uint64_t address = 0;
    uint32_t file = 1;
    uint32_t line = 1;
    uint32_t column = 0;
    uint32_t discriminator = 0;
    bool end_sequence = false;
    bool basic_block = false;
    bool prologue_end = false;
    bool epilogue_begin = false;
    bool is_stmt;
    uint8_t op_index = 0;
    uint8_t isa = 0;
  };

  struct FileName {
    string_view name;
    uint32_t directory_index;
    uint64_t modified_time;
    uint64_t file_size;
  };

  void SeekToOffset(uint64_t offset, uint8_t address_size);
  bool ReadLineInfo();
  const LineInfo& lineinfo() const { return info_; }
  const FileName& filename(size_t i) const { return filenames_[i]; }
  string_view include_directory(size_t i) const {
    return include_directories_[i];
  }

  const std::string& GetExpandedFilename(size_t index) {
    if (index >= filenames_.size()) {
      THROW("filename index out of range");
    }

    // Generate these lazily.
    if (expanded_filenames_.size() <= index) {
      expanded_filenames_.resize(filenames_.size());
    }

    std::string& ret = expanded_filenames_[index];
    if (ret.empty()) {
      const FileName& filename = filenames_[index];
      string_view directory = include_directories_[filename.directory_index];
      ret = std::string(directory);
      if (!ret.empty()) {
        ret += "/";
      }
      ret += std::string(filename.name);
    }
    return ret;
  }

 private:
  struct Params {
    uint8_t minimum_instruction_length;
    uint8_t maximum_operations_per_instruction;
    uint8_t default_is_stmt;
    int8_t line_base;
    uint8_t line_range;
    uint8_t opcode_base;
  } params_;

  const File& file_;

  CompilationUnitSizes sizes_;
  std::vector<string_view> include_directories_;
  std::vector<FileName> filenames_;
  std::vector<uint8_t> standard_opcode_lengths_;
  std::vector<std::string> expanded_filenames_;

  string_view remaining_;

  // Whether we are in a "shadow" part of the bytecode program.  Sometimes
  // parts of the line info program make it into the final binary even though
  // the corresponding code was stripped.  We can tell when this happened by
  // looking for DW_LNE_set_address ops where the operand is 0.  This
  // indicates that a relocation for that argument never got applied, which
  // probably means that the code got stripped.
  //
  // While this is true, we don't yield any LineInfo entries, because the
  // "address" value is garbage.
  bool shadow_;

  LineInfo info_;

  void DoAdvance(uint64_t advance, uint8_t max_per_instr) {
    info_.address += params_.minimum_instruction_length *
                     ((info_.op_index + advance) / max_per_instr);
    info_.op_index = (info_.op_index + advance) % max_per_instr;
  }

  void Advance(uint64_t amount) {
    if (params_.maximum_operations_per_instruction == 1) {
      // This is by far the common case (only false on VLIW architectuers),
      // and this inlining/specialization avoids a costly division.
      DoAdvance(amount, 1);
    } else {
      DoAdvance(amount, params_.maximum_operations_per_instruction);
    }
  }

  uint8_t AdjustedOpcode(uint8_t op) { return op - params_.opcode_base; }

  void SpecialOpcodeAdvance(uint8_t op) {
    Advance(AdjustedOpcode(op) / params_.line_range);
  }
};

void LineInfoReader::SeekToOffset(uint64_t offset, uint8_t address_size) {
  string_view data = file_.debug_line;
  SkipBytes(offset, &data);

  sizes_.SetAddressSize(address_size);
  data = sizes_.ReadInitialLength(&data);
  sizes_.ReadDWARFVersion(&data);
  uint64_t header_length = sizes_.ReadDWARFOffset(&data);
  string_view program = data;
  SkipBytes(header_length, &program);

  params_.minimum_instruction_length = ReadFixed<uint8_t>(&data);
  if (sizes_.dwarf_version() == 4) {
    params_.maximum_operations_per_instruction = ReadFixed<uint8_t>(&data);

    if (params_.maximum_operations_per_instruction == 0) {
      THROW("DWARF line info had maximum_operations_per_instruction=0");
    }
  } else {
    params_.maximum_operations_per_instruction = 1;
  }
  params_.default_is_stmt = ReadFixed<uint8_t>(&data);
  params_.line_base = ReadFixed<int8_t>(&data);
  params_.line_range = ReadFixed<uint8_t>(&data);
  params_.opcode_base = ReadFixed<uint8_t>(&data);
  if (params_.line_range == 0) {
    THROW("line_range of zero will cause divide by zero");
  }

  standard_opcode_lengths_.resize(params_.opcode_base);
  for (size_t i = 1; i < params_.opcode_base; i++) {
    standard_opcode_lengths_[i] = ReadFixed<uint8_t>(&data);
  }

  // Read include_directories.
  include_directories_.clear();

  // Implicit current directory entry.
  include_directories_.push_back(string_view());

  while (true) {
    string_view dir = ReadNullTerminated(&data);
    if (dir.empty()) {
      break;
    }
    include_directories_.push_back(dir);
  }

  // Read file_names.
  filenames_.clear();
  expanded_filenames_.clear();

  // Filename 0 is unused.
  filenames_.push_back(FileName());
  while (true) {
    FileName file_name;
    file_name.name = ReadNullTerminated(&data);
    if (file_name.name.empty()) {
      break;
    }
    file_name.directory_index = ReadLEB128<uint32_t>(&data);
    file_name.modified_time = ReadLEB128<uint64_t>(&data);
    file_name.file_size = ReadLEB128<uint64_t>(&data);
    if (file_name.directory_index >= include_directories_.size()) {
      THROW("directory index out of range");
    }
    filenames_.push_back(file_name);
  }

  info_ = LineInfo(params_.default_is_stmt);
  remaining_ = program;
  shadow_ = false;
}

bool LineInfoReader::ReadLineInfo() {
  // Final step of last DW_LNS_copy / special opcode.
  info_.discriminator = 0;
  info_.basic_block = false;
  info_.prologue_end = false;
  info_.epilogue_begin = false;

  // Final step of DW_LNE_end_sequence.
  info_.end_sequence = false;

  string_view data = remaining_;

  while (true) {
    if (data.empty()) {
      remaining_ = data;
      return false;
    }

    uint8_t op = ReadFixed<uint8_t>(&data);

    if (op >= params_.opcode_base) {
      SpecialOpcodeAdvance(op);
      info_.line +=
          params_.line_base + (AdjustedOpcode(op) % params_.line_range);
      if (!shadow_) {
        remaining_ = data;
        return true;
      }
    } else {
      switch (op) {
        case DW_LNS_extended_op: {
          uint16_t len = ReadLEB128<uint16_t>(&data);
          uint8_t extended_op = ReadFixed<uint8_t>(&data);
          switch (extended_op) {
            case DW_LNE_end_sequence: {
              // Preserve address and set end_sequence, but reset everything
              // else.
              uint64_t addr = info_.address;
              info_ = LineInfo(params_.default_is_stmt);
              info_.address = addr;
              info_.end_sequence = true;
              if (!shadow_) {
                remaining_ = data;
                return true;
              }
              break;
            }
            case DW_LNE_set_address:
              info_.address = sizes_.ReadAddress(&data);
              info_.op_index = 0;
              shadow_ = (info_.address == 0);
              break;
            case DW_LNE_define_file: {
              FileName file_name;
              file_name.name = ReadNullTerminated(&data);
              file_name.directory_index = ReadLEB128<uint32_t>(&data);
              file_name.modified_time = ReadLEB128<uint64_t>(&data);
              file_name.file_size = ReadLEB128<uint64_t>(&data);
              if (file_name.directory_index >= include_directories_.size()) {
                THROW("directory index out of range");
              }
              filenames_.push_back(file_name);
              break;
            }
            case DW_LNE_set_discriminator:
              info_.discriminator = ReadLEB128<uint32_t>(&data);
              break;
            default:
              // We don't understand this opcode, skip it.
              SkipBytes(len, &data);
              if (verbose_level > 0) {
                fprintf(stderr,
                        "bloaty: warning: unknown DWARF line table extended "
                        "opcode: %d\n",
                        extended_op);
              }
              break;
          }
          break;
        }
        case DW_LNS_copy:
          if (!shadow_) {
            remaining_ = data;
            return true;
          }
          break;
        case DW_LNS_advance_pc:
          Advance(ReadLEB128<uint64_t>(&data));
          break;
        case DW_LNS_advance_line:
          info_.line += ReadLEB128<int32_t>(&data);
          break;
        case DW_LNS_set_file:
          info_.file = ReadLEB128<uint32_t>(&data);
          if (info_.file >= filenames_.size()) {
            THROW("filename index too big");
          }
          break;
        case DW_LNS_set_column:
          info_.column = ReadLEB128<uint32_t>(&data);
          break;
        case DW_LNS_negate_stmt:
          info_.is_stmt = !info_.is_stmt;
          break;
        case DW_LNS_set_basic_block:
          info_.basic_block = true;
          break;
        case DW_LNS_const_add_pc:
          SpecialOpcodeAdvance(255);
          break;
        case DW_LNS_fixed_advance_pc:
          info_.address += ReadFixed<uint16_t>(&data);
          info_.op_index = 0;
          break;
        case DW_LNS_set_prologue_end:
          info_.prologue_end = true;
          break;
        case DW_LNS_set_epilogue_begin:
          info_.epilogue_begin = true;
          break;
        case DW_LNS_set_isa:
          info_.isa = ReadLEB128<uint8_t>(&data);
          break;
        default:
          // Unknown opcode, but we know its length so can skip it.
          SkipBytes(standard_opcode_lengths_[op], &data);
          if (verbose_level > 0) {
            fprintf(stderr,
                    "bloaty: warning: unknown DWARF line table opcode: %d\n",
                    op);
          }
          break;
      }
    }
  }
}

string_view* File::GetFieldByName(string_view name) {
  if (name == "aranges") {
    return &debug_aranges;
  } else if (name == "str") {
    return &debug_str;
  } else if (name == "info") {
    return &debug_info;
  } else if (name == "types") {
    return &debug_types;
  } else if (name == "abbrev") {
    return &debug_abbrev;
  } else if (name == "line") {
    return &debug_line;
  } else if (name == "loc") {
    return &debug_loc;
  } else if (name == "pubnames") {
    return &debug_pubnames;
  } else if (name == "pubtypes") {
    return &debug_pubtypes;
  } else if (name == "ranges") {
    return &debug_ranges;
  } else {
    return nullptr;
  }
}

}  // namespace dwarf

// Bloaty DWARF Data Sources ///////////////////////////////////////////////////

// The DWARF .debug_aranges section should, in theory, give us exactly the
// information we need to map file ranges in linked binaries to compilation
// units from where that code came.  However, .debug_aranges is often incomplete
// or missing completely, so we use it as just one of several data sources for
// the "compileunits" data source.
static bool ReadDWARFAddressRanges(const dwarf::File& file, RangeSink* sink) {
  // Maps compilation unit offset -> source filename
  // Lazily initialized.
  class FilenameMap {
   public:
    FilenameMap(const dwarf::File& file)
        : die_reader_(file),
          missing_("[DWARF is missing filename]") {
      attr_reader_.OnAttribute(
          DW_AT_name, [](string_view* s, dwarf::AttrValue data) {
            if (!data.IsString()) return;
            *s = data.GetString();
          });
    }

    std::string GetFilename(uint64_t compilation_unit_offset) {
      auto& name = map_[compilation_unit_offset];
      if (name.empty()) {
        name = LookupFilename(compilation_unit_offset);
      }
      return name;
    }

   private:
    std::string LookupFilename(uint64_t compilation_unit_offset) {
      auto section = dwarf::DIEReader::Section::kDebugInfo;
      string_view name;
      if (die_reader_.SeekToCompilationUnit(section, compilation_unit_offset) &&
          die_reader_.GetTag() == DW_TAG_compile_unit &&
          (attr_reader_.ReadAttributes(&die_reader_, &name),
           !name.empty())) {
        return std::string(name);
      } else {
        return missing_;
      }
    }

    dwarf::DIEReader die_reader_;
    dwarf::AttrReader<string_view> attr_reader_;
    std::unordered_map<uint64_t, std::string> map_;
    std::string missing_;
  } map(file);

  dwarf::AddressRanges ranges(file.debug_aranges);

  while (ranges.NextUnit()) {
    std::string filename = map.GetFilename(ranges.debug_info_offset());

    while (ranges.NextRange()) {
      if (dwarf::IsValidDwarfAddress(ranges.address(), ranges.address_size())) {
        sink->AddVMRangeIgnoreDuplicate("dwarf_aranges", ranges.address(),
                                        ranges.length(), filename);
      }
    }
  }

  return true;
}

// TODO(haberman): make these into real protobufs once proto supports
// string_view.
class GeneralDIE {
 public:
  bool has_name() const { return has_name_; }
  bool has_linkage_name() const { return has_linkage_name_; }
  bool has_location_string() const { return has_location_string_; }
  bool has_low_pc() const { return has_low_pc_; }
  bool has_high_pc() const { return has_high_pc_; }
  bool has_location_uint64() const { return has_location_uint64_; }
  bool has_stmt_list() const { return has_stmt_list_; }
  bool has_ranges() const { return has_ranges_; }
  bool has_start_scope() const { return has_start_scope_; }

  std::string DebugString() {
    std::string ret;
    if (has_name()) {
      ret += absl::Substitute("name: $0\n", name());
    }
    if (has_linkage_name()) {
      ret += absl::Substitute("linkage_name: $0\n", linkage_name());
    }
    if (has_location_string()) {
      ret += absl::Substitute("location_string: $0\n", location_string());
    }
    if (has_low_pc()) {
      ret += absl::Substitute("low_pc: $0\n", low_pc());
    }
    if (has_high_pc()) {
      ret += absl::Substitute("high_pc: $0\n", high_pc());
    }
    if (has_location_uint64()) {
      ret += absl::Substitute("location_uint64: $0\n", location_uint64());
    }
    if (has_stmt_list()) {
      ret += absl::Substitute("stmt_list: $0\n", stmt_list());
    }
    if (has_ranges()) {
      ret += absl::Substitute("ranges: $0\n", ranges());
    }
    if (has_start_scope()) {
      ret += absl::Substitute("start_scope: $0\n", start_scope());
    }
    return ret;
  }

  string_view name() const { return name_; }
  string_view linkage_name() const { return linkage_name_; }
  string_view location_string() const { return location_string_; }
  uint64_t low_pc() const { return low_pc_; }
  uint64_t high_pc() const { return high_pc_; }
  uint64_t location_uint64() const { return location_uint64_; }
  uint64_t stmt_list() const { return stmt_list_; }
  uint64_t ranges() const { return ranges_; }
  uint64_t start_scope() const { return start_scope_; }

  void set_name(string_view val) {
    has_name_ = true;
    name_ = val;
  }
  void set_linkage_name(string_view val) {
    has_linkage_name_ = true;
    location_string_ = val;
  }
  void set_location_string(string_view val) {
    has_location_string_ = true;
    location_string_ = val;
  }
  void set_low_pc(uint64_t val) {
    has_low_pc_ = true;
    low_pc_ = val;
  }
  void set_high_pc(uint64_t val) {
    has_high_pc_ = true;
    high_pc_ = val;
  }
  void set_location_uint64(uint64_t val) {
    has_location_uint64_ = true;
    location_uint64_ = val;
  }
  void set_stmt_list(uint64_t val) {
    has_stmt_list_ = true;
    stmt_list_ = val;
  }
  void set_ranges(uint64_t val) {
    has_ranges_ = true;
    ranges_ = val;
  }
  void set_start_scope(uint64_t val) {
    has_start_scope_ = true;
    start_scope_ = val;
  }

 private:
  bool has_name_ = false;
  bool has_linkage_name_ = false;
  bool has_location_string_ = false;
  bool has_low_pc_ = false;
  bool has_high_pc_ = false;
  bool has_location_uint64_ = false;
  bool has_stmt_list_ = false;
  bool has_ranges_ = false;
  bool has_start_scope_ = false;

  string_view name_;
  string_view linkage_name_;
  string_view location_string_;
  uint64_t low_pc_ = 0;
  uint64_t high_pc_ = 0;
  uint64_t location_uint64_ = 0;
  uint64_t stmt_list_ = 0;
  uint64_t ranges_ = 0;
  uint64_t start_scope_ = 0;
};

class InlinesDIE {
 public:
  bool has_stmt_list() const { return has_stmt_list_; }

  uint64_t stmt_list() const { return stmt_list_; }

  void set_stmt_list(uint64_t val) {
    has_stmt_list_ = true;
    stmt_list_ = val;
  }

 private:
  bool has_stmt_list_ = false;
  uint64_t stmt_list_ = 0;
};

// To view DIEs for a given file, try:
//   readelf --debug-dump=info foo.bin
void AddDIE(const dwarf::File& file, const std::string& name,
            const GeneralDIE& die, const SymbolTable& symtab,
            const DualMap& symbol_map, const dwarf::CompilationUnitSizes& sizes,
            RangeSink* sink) {
  // Some DIEs mark address ranges with high_pc/low_pc pairs (especially
  // functions).
  if (die.has_low_pc() && die.has_high_pc() &&
      dwarf::IsValidDwarfAddress(die.low_pc(), sizes.address_size())) {
    uint64_t high_pc = die.high_pc();

    // It appears that some compilers make high_pc a size, and others make it an
    // address.
    if (high_pc >= die.low_pc()) {
      high_pc -= die.low_pc();
    }
    sink->AddVMRangeIgnoreDuplicate("dwarf_pcpair", die.low_pc(), high_pc,
                                    name);
  }

  // Sometimes a DIE has a linkage_name, which we can look up in the symbol
  // table.
  if (die.has_linkage_name()) {
    auto it = symtab.find(die.linkage_name());
    if (it != symtab.end()) {
      sink->AddVMRangeIgnoreDuplicate("dwarf_linkagename", it->second.first,
                                      it->second.second, name);
    }
  }

  // Sometimes the DIE has a "location", which gives the location as an address.
  // This parses a very small subset of the overall DWARF expression grammar.
  if (die.has_location_string()) {
    string_view location = die.location_string();
    if (location.size() == sizes.address_size() + 1 &&
        location[0] == DW_OP_addr) {
      location.remove_prefix(1);
      uint64_t addr;
      // TODO(haberman): endian?
      if (sizes.address_size() == 4) {
        addr = ReadFixed<uint32_t>(&location);
      } else if (sizes.address_size() == 8) {
        addr = ReadFixed<uint64_t>(&location);
      } else {
        BLOATY_UNREACHABLE();
      }

      // Unfortunately the location doesn't include a size, so we look that part
      // up in the symbol map.
      uint64_t size;
      if (symbol_map.vm_map.TryGetSize(addr, &size)) {
        sink->AddVMRangeIgnoreDuplicate("dwarf_location", addr, size, name);
      } else {
        if (verbose_level > 0) {
          fprintf(stderr,
                  "bloaty: warning: couldn't find DWARF location in symbol "
                  "table, address: %" PRIx64 ", name: %s\n",
                  addr, name.c_str());
        }
      }
    }
  }

  // Sometimes a location is given as an offset into debug_loc.
  if (die.has_location_uint64()) {
    if (die.location_uint64() < file.debug_loc.size()) {
      absl::string_view loc_range = file.debug_loc.substr(die.location_uint64());
      loc_range = GetLocationListRange(sizes, loc_range);
      sink->AddFileRange("dwarf_locrange", name, loc_range);
    } else if (verbose_level > 0) {
      fprintf(stderr,
              "bloaty: warning: DWARF location out of range, location=%" PRIx64
              "\n",
              die.location_uint64());
    }
  }

  uint64_t ranges_offset = UINT64_MAX;

  // There are two different attributes that sometimes contain an offset into
  // debug_ranges.
  if (die.has_ranges()) {
    ranges_offset = die.ranges();
  } else if (die.has_start_scope()) {
    ranges_offset = die.start_scope();
  }

  if (ranges_offset != UINT64_MAX) {
    if (ranges_offset < file.debug_ranges.size()) {
      absl::string_view ranges_range = file.debug_ranges.substr(ranges_offset);
      ranges_range = GetRangeListRange(sizes, ranges_range);
      sink->AddFileRange("dwarf_debugrange", name, ranges_range);
    } else if (verbose_level > 0) {
      fprintf(stderr,
              "bloaty: warning: DWARF debug range out of range, "
              "ranges_offset=%" PRIx64 "\n",
              ranges_offset);
    }
  }
}

static void ReadDWARFPubNames(const dwarf::File& file, string_view section,
                              RangeSink* sink) {
  dwarf::DIEReader die_reader(file);
  dwarf::AttrReader<string_view> attr_reader;
  string_view remaining = section;

  attr_reader.OnAttribute(
      DW_AT_name, [](string_view* s, dwarf::AttrValue data) {
        if (data.type() == dwarf::AttrValue::Type::kString) {
          *s = data.GetString();
        }
      });

  while (remaining.size() > 0) {
    dwarf::CompilationUnitSizes sizes;
    string_view full_unit = remaining;
    string_view unit = sizes.ReadInitialLength(&remaining);
    full_unit =
        full_unit.substr(0, unit.size() + (unit.data() - full_unit.data()));
    sizes.ReadDWARFVersion(&unit);
    uint64_t debug_info_offset = sizes.ReadDWARFOffset(&unit);
    bool ok = die_reader.SeekToCompilationUnit(
        dwarf::DIEReader::Section::kDebugInfo, debug_info_offset);
    if (!ok) {
      THROW("Couldn't seek to debug_info section");
    }
    string_view compileunit_name;
    attr_reader.ReadAttributes(&die_reader, &compileunit_name);
    if (!compileunit_name.empty()) {
      sink->AddFileRange("dwarf_pubnames", compileunit_name, full_unit);
    }
  }
}

uint64_t ReadEncodedPointer(uint8_t encoding, bool is_64bit, string_view* data,
                            const char* data_base, RangeSink* sink) {
  uint64_t value;
  const char* ptr = data->data();
  uint8_t format = encoding & DW_EH_PE_FORMAT_MASK;

  switch (format) {
    case DW_EH_PE_omit:
      return 0;
    case DW_EH_PE_absptr:
      if (is_64bit) {
        value = ReadFixed<uint64_t>(data);
      } else {
        value = ReadFixed<uint32_t>(data);
      }
      break;
    case DW_EH_PE_uleb128:
      value = dwarf::ReadLEB128<uint64_t>(data);
      break;
    case DW_EH_PE_udata2:
      value = ReadFixed<uint16_t>(data);
      break;
    case DW_EH_PE_udata4:
      value = ReadFixed<uint32_t>(data);
      break;
    case DW_EH_PE_udata8:
      value = ReadFixed<uint64_t>(data);
      break;
    case DW_EH_PE_sleb128:
      value = dwarf::ReadLEB128<int64_t>(data);
      break;
    case DW_EH_PE_sdata2:
      value = ReadFixed<int16_t>(data);
      break;
    case DW_EH_PE_sdata4:
      value = ReadFixed<int32_t>(data);
      break;
    case DW_EH_PE_sdata8:
      value = ReadFixed<int64_t>(data);
      break;
    default:
      THROWF("Unexpected eh_frame format value: $0", format);
  }

  uint8_t application = encoding & DW_EH_PE_APPLICATION_MASK;

  switch (application) {
    case 0:
      break;
    case DW_EH_PE_pcrel:
      value += sink->TranslateFileToVM(ptr);
      break;
    case DW_EH_PE_datarel:
      if (data_base == nullptr) {
        THROW("datarel requested but no data_base provided");
      }
      value += sink->TranslateFileToVM(data_base);
      break;
    case DW_EH_PE_textrel:
    case DW_EH_PE_funcrel:
    case DW_EH_PE_aligned:
      THROWF("Unimplemented eh_frame application value: $0", application);
  }

  if (encoding & DW_EH_PE_indirect) {
    string_view location = sink->TranslateVMToFile(value);
    if (is_64bit) {
      value = ReadFixed<uint64_t>(&location);
    } else {
      value = ReadFixed<uint32_t>(&location);
    }
  }

  return value;
}

// Code to read the .eh_frame section.  This is not technically DWARF, but it
// is similar to .debug_frame (which is DWARF) so it's convenient to put it
// here.
//
// The best documentation I can find for this format comes from:
//
// *
// http://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
// * https://www.airs.com/blog/archives/460
//
// However these are both under-specified.  Some details are not mentioned in
// either of these (for example, the fact that the function length uses the FDE
// encoding, but always absolute).  libdwarf's implementation contains a comment
// saying "It is not clear if this is entirely correct".  Basically the only
// thing you can trust for some of these details is the code that actually
// implements unwinding in production:
//
// * libunwind http://www.nongnu.org/libunwind/
//   https://github.com/pathscale/libunwind/blob/master/src/dwarf/Gfde.c
// * LLVM libunwind (a different project!!)
//   https://github.com/llvm-mirror/libunwind/blob/master/src/DwarfParser.hpp
// * libgcc
//   https://github.com/gcc-mirror/gcc/blob/master/libgcc/unwind-dw2-fde.c
void ReadEhFrame(string_view data, RangeSink* sink) {
  string_view remaining = data;

  struct CIEInfo {
    int version = 0;
    uint32_t code_align = 0;
    int32_t data_align = 0;
    uint8_t fde_encoding = 0;
    uint8_t lsda_encoding = 0;
    bool is_signal_handler = false;
    bool has_augmentation_length = false;
    uint64_t personality_function = 0;
    uint32_t return_address_reg = 0;
  };

  std::unordered_map<const void*, CIEInfo> cie_map;

  while (remaining.size() > 0) {
    dwarf::CompilationUnitSizes sizes;
    string_view full_entry = remaining;
    string_view entry = sizes.ReadInitialLength(&remaining);
    if (entry.size() == 0 && remaining.size() == 0) {
      return;
    }
    full_entry =
        full_entry.substr(0, entry.size() + (entry.data() - full_entry.data()));
    uint32_t id = ReadFixed<uint32_t>(&entry);
    if (id == 0) {
      // CIE, we don't attribute this yet.
      CIEInfo& cie_info = cie_map[full_entry.data()];
      cie_info.version = ReadFixed<uint8_t>(&entry);
      string_view aug_string = ReadNullTerminated(&entry);
      cie_info.code_align = dwarf::ReadLEB128<uint32_t>(&entry);
      cie_info.data_align = dwarf::ReadLEB128<int32_t>(&entry);
      switch (cie_info.version) {
        case 1:
          cie_info.return_address_reg = ReadFixed<uint8_t>(&entry);
          break;
        case 3:
          cie_info.return_address_reg = dwarf::ReadLEB128<uint32_t>(&entry);
          break;
        default:
          THROW("Unexpected eh_frame CIE version");
      }
      while (aug_string.size() > 0) {
        switch (aug_string[0]) {
          case 'z':
            // Length until the end of augmentation data.
            cie_info.has_augmentation_length = true;
            dwarf::ReadLEB128<uint32_t>(&entry);
            break;
          case 'L':
            cie_info.lsda_encoding = ReadFixed<uint8_t>(&entry);
            break;
          case 'R':
            cie_info.fde_encoding = ReadFixed<uint8_t>(&entry);
            break;
          case 'S':
            cie_info.is_signal_handler = true;
            break;
          case 'P': {
            uint8_t encoding = ReadFixed<uint8_t>(&entry);
            cie_info.personality_function =
                ReadEncodedPointer(encoding, true, &entry, nullptr, sink);
            break;
          }
          default:
            THROW("Unexepcted augmentation character");
        }
        aug_string.remove_prefix(1);
      }
    } else {
      auto iter = cie_map.find(entry.data() - id - 4);
      if (iter == cie_map.end()) {
        THROW("Couldn't find CIE for FDE");
      }
      const CIEInfo& cie_info = iter->second;
      // TODO(haberman): don't hard-code 64-bit.
      uint64_t address = ReadEncodedPointer(cie_info.fde_encoding, true, &entry,
                                            nullptr, sink);
      // TODO(haberman); Technically the FDE addresses could span a
      // function/compilation unit?  They can certainly span inlines.
      /*
      uint64_t length =
        ReadEncodedPointer(cie_info.fde_encoding & 0xf, true, &entry, sink);
      (void)length;

      if (cie_info.has_augmentation_length) {
        uint32_t augmentation_length = dwarf::ReadLEB128<uint32_t>(&entry);
        (void)augmentation_length;
      }

      uint64_t lsda =
          ReadEncodedPointer(cie_info.lsda_encoding, true, &entry, sink);
      if (lsda) {
      }
      */

      sink->AddFileRangeForVMAddr("dwarf_fde", address, full_entry);
    }
  }
}

// See documentation here:
//   http://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html#EHFRAME
void ReadEhFrameHdr(string_view data, RangeSink* sink) {
  const char* base = data.data();
  uint8_t version = ReadFixed<uint8_t>(&data);
  uint8_t eh_frame_ptr_enc = ReadFixed<uint8_t>(&data);
  uint8_t fde_count_enc = ReadFixed<uint8_t>(&data);
  uint8_t table_enc = ReadFixed<uint8_t>(&data);

  if (version != 1) {
    THROWF("Unknown eh_frame_hdr version: $0", version);
  }

  // TODO(haberman): don't hard-code 64-bit.
  uint64_t eh_frame_ptr =
      ReadEncodedPointer(eh_frame_ptr_enc, true, &data, base, sink);
  (void)eh_frame_ptr;
  uint64_t fde_count =
      ReadEncodedPointer(fde_count_enc, true, &data, base, sink);

  for (uint64_t i = 0; i < fde_count; i++) {
    string_view entry_data = data;
    uint64_t initial_location =
        ReadEncodedPointer(table_enc, true, &data, base, sink);
    uint64_t fde_addr = ReadEncodedPointer(table_enc, true, &data, base, sink);
    entry_data.remove_suffix(data.size());
    sink->AddFileRangeForVMAddr("dwarf_fde_table", initial_location,
                                entry_data);

    // We could add fde_addr with an unknown length if we wanted to skip reading
    // eh_frame.  We can't count on this table being available though, so we
    // don't want to remove the eh_frame reading code altogether.
    (void)fde_addr;
  }
}

static void ReadDWARFStmtListRange(const dwarf::File& file, uint64_t offset,
                                   string_view unit_name, RangeSink* sink) {
  string_view data = file.debug_line;
  SkipBytes(offset, &data);
  string_view data_with_length = data;
  dwarf::CompilationUnitSizes sizes;
  data = sizes.ReadInitialLength(&data);
  data = data_with_length.substr(
      0, data.size() + (data.data() - data_with_length.data()));
  sink->AddFileRange("dwarf_stmtlistrange", unit_name, data);
}

// The DWARF debug info can help us get compileunits info.  DIEs for compilation
// units, functions, and global variables often have attributes that will
// resolve to addresses.
static void ReadDWARFDebugInfo(
    const dwarf::File& file, dwarf::DIEReader::Section section,
    const SymbolTable& symtab, const DualMap& symbol_map, RangeSink* sink,
    std::unordered_map<uint64_t, std::string>* stmt_list_map) {
  dwarf::DIEReader die_reader(file);
  die_reader.set_strp_sink(sink);
  dwarf::AttrReader<GeneralDIE> attr_reader;

  attr_reader.OnAttribute(DW_AT_name,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            if (!val.IsString()) return;
                            die->set_name(val.GetString());
                          });
  attr_reader.OnAttribute(DW_AT_linkage_name,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            if (!val.IsString()) return;
                            die->set_linkage_name(val.GetString());
                          });
  attr_reader.OnAttribute(DW_AT_location,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            if (val.IsString()) {
                              die->set_location_string(val.GetString());
                            } else {
                              die->set_location_uint64(val.GetUint());
                            }
                          });
  attr_reader.OnAttribute(DW_AT_low_pc,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            absl::optional<uint64_t> uint = val.ToUint();
                            if (!uint.has_value()) return;
                            die->set_low_pc(uint.value());
                          });
  attr_reader.OnAttribute(DW_AT_high_pc,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            absl::optional<uint64_t> uint = val.ToUint();
                            if (!uint.has_value()) return;
                            die->set_high_pc(uint.value());
                          });
  attr_reader.OnAttribute(DW_AT_stmt_list,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            absl::optional<uint64_t> uint = val.ToUint();
                            if (!uint.has_value()) return;
                            die->set_stmt_list(uint.value());
                          });
  attr_reader.OnAttribute(DW_AT_ranges,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            absl::optional<uint64_t> uint = val.ToUint();
                            if (!uint.has_value()) return;
                            die->set_ranges(uint.value());
                          });
  attr_reader.OnAttribute(DW_AT_start_scope,
                          [](GeneralDIE* die, dwarf::AttrValue val) {
                            absl::optional<uint64_t> uint = val.ToUint();
                            if (!uint.has_value()) return;
                            die->set_start_scope(uint.value());
                          });

  if (!die_reader.SeekToStart(section)) {
    return;
  }

  do {
    GeneralDIE compileunit_die;
    attr_reader.ReadAttributes(&die_reader, &compileunit_die);
    std::string compileunit_name = std::string(compileunit_die.name());

    if (compileunit_die.has_stmt_list()) {
      uint64_t stmt_list = compileunit_die.stmt_list();
      if (compileunit_name.empty()) {
        auto iter = stmt_list_map->find(stmt_list);
        if (iter != stmt_list_map->end()) {
          compileunit_name = iter->second;
        }
      } else {
        (*stmt_list_map)[stmt_list] = compileunit_name;
      }
    }

    if (compileunit_name.empty()) {
      continue;
    }

    die_reader.set_compileunit_name(compileunit_name);
    sink->AddFileRange("dwarf_debuginfo", compileunit_name,
                       die_reader.unit_range());
    AddDIE(file, compileunit_name, compileunit_die, symtab, symbol_map,
           die_reader.unit_sizes(), sink);

    if (compileunit_die.has_stmt_list()) {
      uint64_t offset = compileunit_die.stmt_list();
      ReadDWARFStmtListRange(file, offset, compileunit_name, sink);
    }

    string_view abbrev_data = file.debug_abbrev;
    SkipBytes(die_reader.debug_abbrev_offset(), &abbrev_data);
    dwarf::AbbrevTable unit_abbrev;
    abbrev_data = unit_abbrev.ReadAbbrevs(abbrev_data);
    sink->AddFileRange("dwarf_abbrev", compileunit_name, abbrev_data);

    while (die_reader.NextDIE()) {
      GeneralDIE die;
      attr_reader.ReadAttributes(&die_reader, &die);

      // low_pc == 0 is a signal that this routine was stripped out of the
      // final binary.  Skip this DIE and all of its children.
      if (die.has_low_pc() && die.low_pc() == 0) {
        die_reader.SkipChildren();
      } else {
        AddDIE(file, compileunit_name, die, symtab, symbol_map,
               die_reader.unit_sizes(), sink);
      }
    }
  } while (die_reader.NextCompilationUnit());
}

void ReadDWARFCompileUnits(const dwarf::File& file, const SymbolTable& symtab,
                           const DualMap& symbol_map, RangeSink* sink) {
  if (!file.debug_info.size()) {
    THROW("missing debug info");
  }

  if (file.debug_aranges.size()) {
    ReadDWARFAddressRanges(file, sink);
  }

  std::unordered_map<uint64_t, std::string> stmt_list_map;
  ReadDWARFDebugInfo(file, dwarf::DIEReader::Section::kDebugInfo, symtab,
                     symbol_map, sink, &stmt_list_map);
  ReadDWARFDebugInfo(file, dwarf::DIEReader::Section::kDebugTypes, symtab,
                     symbol_map, sink, &stmt_list_map);
  ReadDWARFPubNames(file, file.debug_pubnames, sink);
  ReadDWARFPubNames(file, file.debug_pubtypes, sink);
}

static std::string LineInfoKey(const std::string& file, uint32_t line,
                               bool include_line) {
  if (include_line) {
    return file + ":" + std::to_string(line);
  } else {
    return file;
  }
}

static void ReadDWARFStmtList(bool include_line,
                              dwarf::LineInfoReader* line_info_reader,
                              RangeSink* sink) {
  uint64_t span_startaddr = 0;
  std::string last_source;

  while (line_info_reader->ReadLineInfo()) {
    const auto& line_info = line_info_reader->lineinfo();
    auto addr = line_info.address;
    auto number = line_info.line;
    auto name =
        line_info.end_sequence
            ? last_source
            : LineInfoKey(line_info_reader->GetExpandedFilename(line_info.file),
                          number, include_line);
    if (!span_startaddr) {
      span_startaddr = addr;
    } else if (line_info.end_sequence ||
               (!last_source.empty() && name != last_source)) {
      sink->AddVMRange("dwarf_stmtlist", span_startaddr, addr - span_startaddr,
                       last_source);
      if (line_info.end_sequence) {
        span_startaddr = 0;
      } else {
        span_startaddr = addr;
      }
    }
    last_source = name;
  }
}

void ReadDWARFInlines(const dwarf::File& file, RangeSink* sink,
                      bool include_line) {
  if (!file.debug_info.size() || !file.debug_line.size()) {
    THROW("no debug info");
  }

  dwarf::DIEReader die_reader(file);
  dwarf::LineInfoReader line_info_reader(file);
  dwarf::AttrReader<InlinesDIE> attr_reader;

  attr_reader.OnAttribute(
      DW_AT_stmt_list, [](InlinesDIE* die, dwarf::AttrValue data) {
        absl::optional<uint64_t> uint = data.ToUint();
        if (!uint.has_value()) return;
        die->set_stmt_list(uint.value());
      });

  if (!die_reader.SeekToStart(dwarf::DIEReader::Section::kDebugInfo)) {
    THROW("debug info is present, but empty");
  }

  while (true) {
    InlinesDIE die;
    attr_reader.ReadAttributes(&die_reader, &die);

    if (die.has_stmt_list()) {
      uint64_t offset = die.stmt_list();
      line_info_reader.SeekToOffset(offset,
                                    die_reader.unit_sizes().address_size());
      ReadDWARFStmtList(include_line, &line_info_reader, sink);
    }

    if (!die_reader.NextCompilationUnit()) {
      return;
    }
  }
}

}  // namespace bloaty