abg-elf-reader.cc

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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// -*- Mode: C++ -*-
//
// Copyright (C) 2022-2025 Red Hat, Inc.
//
// Author: Dodji Seketeli

/// @file
///
/// Elf reader stuff

#include "abg-internal.h"

#include <fcntl.h> /* For open(3) */
#include <unistd.h>
#include <iostream>
#include <cstring>
#include <libgen.h>
#include <fcntl.h>
#include <elfutils/libdwfl.h>


#include "abg-symtab-reader.h"
#include "abg-suppression-priv.h"
#include "abg-elf-helpers.h"

// <headers defining libabigail's API go under here>
ABG_BEGIN_EXPORT_DECLARATIONS
#include "abg-elf-reader.h"
#include "abg-tools-utils.h"
ABG_END_EXPORT_DECLARATIONS
// </headers defining libabigail's API>
namespace abigail
{

using namespace elf_helpers;

namespace elf
{

/// Find the file name of the alternate debug info file.
///
/// @param elf_module the elf module to consider.
///
/// @param out parameter.  Is set to the file name of the alternate
/// debug info file, iff this function returns true.
///
/// @return true iff the location of the alternate debug info file was
/// found.
static bool
find_alt_dwarf_debug_info_link(Dwfl_Module *elf_module,
                   string &alt_file_name)
{
  GElf_Addr bias = 0;
  Dwarf *dwarf = dwfl_module_getdwarf(elf_module, &bias);
  Elf *elf = dwarf_getelf(dwarf);
  GElf_Ehdr ehmem, *elf_header;
  elf_header = gelf_getehdr(elf, &ehmem);

  Elf_Scn* section = 0;
  while ((section = elf_nextscn(elf, section)) != 0)
    {
      GElf_Shdr header_mem, *header;
      header = gelf_getshdr(section, &header_mem);
      if (header->sh_type != SHT_PROGBITS)
    continue;

      const char *section_name = elf_strptr(elf,
                        elf_header->e_shstrndx,
                        header->sh_name);

      char *alt_name = 0;
      char *buildid = 0;
      size_t buildid_len = 0;
      if (section_name != 0
      && strcmp(section_name, ".gnu_debugaltlink") == 0)
    {
      Elf_Data *data = elf_getdata(section, 0);
      if (data != 0 && data->d_size != 0)
        {
          alt_name = (char*) data->d_buf;
          char *end_of_alt_name =
        (char *) memchr(alt_name, '\0', data->d_size);
          buildid_len = data->d_size - (end_of_alt_name - alt_name + 1);
          if (buildid_len == 0)
        return false;
          buildid = end_of_alt_name + 1;
        }
    }
      else
    continue;

      if (buildid == 0 || alt_name == 0)
    return false;

      alt_file_name = alt_name;
      return true;
    }

  return false;
}

/// Private data of the @ref elf::reader type.
struct reader::priv
{
  reader&               rdr;
  Elf*                  elf_handle      = nullptr;
  Elf_Scn*              symtab_section      = nullptr;
  string                elf_architecture;
  vector<string>            dt_needed;
  // An abstraction of the symbol table.  This is loaded lazily, on
  // demand.
  mutable symtab_reader::symtab_sptr    symt;
  // Where split debug info is to be searched for on disk.
  vector<string>            debug_info_root_paths;
  // The formatted string version of debug_info_root_paths.  The
  // format is according to what elfutils expects.  For the details of
  // what elfutils expects, please read the comments of the function
  // dwfl_build_id_find_elf in /usr/include/elfutils/libdwfl.h.
  string                formated_di_root_paths;
  // A pointer to where the string held by formated_di_root_paths is.
  // This is fed to elfutils.
  char*             raw_formated_di_root_paths = nullptr;
  // Some very useful callback functions that elfutils needs to
  // perform various tasks.
  Dwfl_Callbacks            offline_callbacks;
  // A pointer to the DWARF Front End Library handle of elfutils.
  // This is useful to perform all kind of things at a higher level.
  dwfl_sptr             dwfl_handle;
  // The address range of the offline elf file we are looking at.
  Dwfl_Module*              elf_module      = nullptr;
  // A pointer to the DWARF debug info, if found by locate_dwarf_debug_info.
  Dwarf*                dwarf_handle        = nullptr;
  // A pointer to the ALT DWARF debug info, which is the debug info
  // that is constructed by the DWZ tool.  It's made of all the type
  // information that was redundant in the DWARF.  DWZ put it there
  // and make the DWARF reference it in here.
  Dwarf*                alt_dwarf_handle    = nullptr;
  string                alt_dwarf_path;
  int                   alt_dwarf_fd        = 0;
  Elf_Scn*              ctf_section     = nullptr;
  int                   alt_ctf_fd      = 0;
  Elf*                  alt_ctf_handle      = nullptr;
  Elf_Scn*              alt_ctf_section = nullptr;
  Elf_Scn*              btf_section     = nullptr;

  priv(reader& reeder, const std::string& elf_path,
       const vector<string>& debug_info_roots)
    : rdr(reeder)
  {
    rdr.corpus_path(elf_path);
    initialize(debug_info_roots);
  }

  ~priv()
  {
    clear_alt_dwarf_debug_info_data();
    clear_alt_ctf_debug_info_data();
  }

  /// Reset the private data of @elf elf::reader.
  ///
  /// @param debug_info_roots the vector of new directories where to
  /// look for split debug info file.
  void
  initialize(const vector<string>& debug_info_roots)
  {
    clear_alt_dwarf_debug_info_data();
    clear_alt_ctf_debug_info_data();

    elf_handle = nullptr;
    symtab_section = nullptr;
    elf_architecture.clear();
    dt_needed.clear();
    symt.reset();
    debug_info_root_paths = debug_info_roots;
    formated_di_root_paths.clear();
    raw_formated_di_root_paths = nullptr;
    memset(&offline_callbacks, 0, sizeof(offline_callbacks));
    dwfl_handle.reset();
    elf_module = nullptr;
    dwarf_handle = nullptr;
    alt_dwarf_handle = nullptr;
    alt_dwarf_path.clear();
    alt_dwarf_fd = 0;
    ctf_section = nullptr;
    alt_ctf_section = nullptr;
    alt_ctf_handle = nullptr;
    alt_ctf_fd = 0;
  }

  /// Initialize the debug info root path.  The format of this path is
  /// described in /usr/include/elfutils/libdwfl.h in the comment for
  /// the function dwfl_build_id_find_elf.
  ///
  /// The string must start with '-' to disable CRC32 checksum
  /// validation.  Directories must be separated by the ':' character.
  /// The search order depends on if each path is absolute or relative
  /// as described by that comment.
  ///
  /// In any case, let's format the debuginfo search path here for
  /// elfutils consumption.
  void
  initialize_debug_info_root_paths()
  {
    vector<string> root_paths = debug_info_root_paths;

    for (auto path : debug_info_root_paths)
      if (tools_utils::string_begins_with(path, "/"))
    {
      // For absolute root directories, let's add all the
      // sub-directories of these directories that contain a
      // (debug info) file.  This can be helpful to help elfutils
      // find alternate debuginfo files when the altdebuginfolink
      // is itself an absolute file path that is contained under
      // the root directory.  This what we see in PR30329 and its
      // associated regression test in test-abidiff-exit.cc
      vector<string> additional_subdirs;
      tools_utils::get_file_path_dirs_under_dir(path, additional_subdirs);
      for (auto& subdir : additional_subdirs)
        root_paths.push_back(subdir);
    }

    for (auto path : root_paths)
      {
    if (formated_di_root_paths.empty())
      formated_di_root_paths = "-";
    if (!path.empty())
      formated_di_root_paths += path + ":";
      }
    raw_formated_di_root_paths =
      const_cast<char*>(formated_di_root_paths.c_str());
  }

  /// Setup the necessary plumbing to open the ELF file and find all
  /// the associated split debug info files.
  ///
  /// This function also setup the various handles on the opened ELF
  /// file and whatnot.
  void
  crack_open_elf_file()
  {
    // Initialize the callback functions used by elfutils.
    initialize_debug_info_root_paths();
    elf_helpers::initialize_dwfl_callbacks(offline_callbacks,
                       formated_di_root_paths.empty()
                       ? nullptr
                       : &raw_formated_di_root_paths);

    // Create a handle to the DWARF Front End Library that we'll need.
    dwfl_handle = elf_helpers::create_new_dwfl_handle(offline_callbacks);

    const string& elf_path = rdr.corpus_path();
    // Get the set of addresses that make up the ELF file we are
    // looking at.
    elf_module =
      dwfl_report_offline(dwfl_handle.get(),
              basename(const_cast<char*>(elf_path.c_str())),
              elf_path.c_str(), -1);
    dwfl_report_end(dwfl_handle.get(), 0, 0);
    ABG_ASSERT(elf_module);

    // Finally, get and handle at the representation of the ELF file
    // we've just cracked open.
    GElf_Addr bias = 0;
    elf_handle = dwfl_module_getelf(elf_module, &bias);
    ABG_ASSERT(elf_handle);
  }

  /// Clear the resources related to the alternate DWARF data.
  void
  clear_alt_dwarf_debug_info_data()
  {
    if (alt_dwarf_fd)
      {
        if (alt_dwarf_handle)
          {
            dwarf_end(alt_dwarf_handle);
            alt_dwarf_handle = nullptr;
          }
        close(alt_dwarf_fd);
        alt_dwarf_fd = 0;
      }
    alt_dwarf_path.clear();
  }

  /// Locate the DWARF debug info in the ELF file.
  ///
  /// This also knows how to locate split debug info.
  void
  locate_dwarf_debug_info()
  {
    ABG_ASSERT(dwfl_handle);

    if (dwarf_handle)
      return;

    Dwarf_Addr bias = 0;
    dwarf_handle = dwfl_module_getdwarf(elf_module, &bias);
    alt_dwarf_handle = dwarf_getalt(dwarf_handle);
    find_alt_dwarf_debug_info_link(elf_module, alt_dwarf_path);
  }

  /// Clear the resources related to the alternate CTF data.
  void
  clear_alt_ctf_debug_info_data()
  {
    if (alt_ctf_fd)
      {
    close(alt_ctf_fd);
    alt_ctf_fd = 0;
      }
    if (alt_ctf_handle)
      {
    elf_end(alt_ctf_handle);
    alt_ctf_handle = nullptr;
      }
  }

  /// Locate the CTF "alternate" debug information associated with the
  /// current ELF file ( and split out somewhere else).
  ///
  /// This is a sub-routine of @ref locate_ctf_debug_info().
  void
  locate_alt_ctf_debug_info()
  {
    if (alt_ctf_section)
      return;

    Elf_Scn *section =
      elf_helpers::find_section(elf_handle,
                ".gnu_debuglink",
                SHT_PROGBITS);

    std::string name;
    Elf_Data *data;
    if (section
    && (data = elf_getdata(section, nullptr))
    && data->d_size != 0)
      name = (char *) data->d_buf;

    if (!name.empty())
      for (const auto& path : rdr.debug_info_root_paths())
    {
      std::string file_path;
      if (!tools_utils::find_file_under_dir(path, name, file_path))
        continue;

      if ((alt_ctf_fd = open(file_path.c_str(), O_RDONLY)) == -1)
        continue;

      if ((alt_ctf_handle = elf_begin(alt_ctf_fd,
                      ELF_C_READ,
                      nullptr)) == nullptr)
        continue;

      // unlikely .ctf was designed to be present in stripped file
      alt_ctf_section =
        elf_helpers::find_section(alt_ctf_handle, ".ctf", SHT_PROGBITS);

      if (alt_ctf_section)
        break;
    }
  }

  /// Locate the CTF debug information associated with the current ELF
  /// file.  It also locates the CTF debug information that is split
  /// out in a separate file.
  void
  locate_ctf_debug_info()
  {
    ABG_ASSERT(elf_handle);

    ctf_section = elf_helpers::find_section_by_name(elf_handle, ".ctf");
    if (ctf_section == nullptr)
      {
    locate_alt_ctf_debug_info();
    ctf_section = alt_ctf_section;
      }
  }
}; //end reader::priv

/// The constructor of the @ref elf::reader type.
///
/// @param elf_path the path to the ELF file to read from.
///
/// @param debug_info_root a vector of directory paths to look into
/// for split debug information files.
///
/// @param env the environment which the reader operates in.
reader::reader(const string&        elf_path,
           const vector<string>&    debug_info_roots,
           ir::environment& env)
  : fe_iface(elf_path, env),
    priv_(new priv(*this, elf_path, debug_info_roots))
{
  priv_->crack_open_elf_file();
  priv_->locate_dwarf_debug_info();
  priv_->locate_ctf_debug_info();
}

/// The destructor of the @ref elf::reader type.
reader::~reader()
{delete priv_;}

/// Re-initialize the resources used by the current @ref elf::reader
/// type.
///
/// This lets the reader in a state where it's ready to read from
/// another ELF file.
///
/// @param elf_path the new ELF path to read from.
///
/// @param debug_info_roots a vector of directory paths to look into
/// for split debug information files.
void
reader::initialize(const std::string&       elf_path,
           const vector<string>&    debug_info_roots)
{
  fe_iface::initialize(elf_path);
  corpus_path(elf_path);
  priv_->initialize(debug_info_roots);
  priv_->crack_open_elf_file();
  priv_->locate_dwarf_debug_info();
  priv_->locate_ctf_debug_info();
}

/// Re-initialize the resources used by the current @ref elf::reader
/// type.
///
/// This lets the reader in a state where it's ready to read from
/// another ELF file.
///
/// @param elf_path the new ELF path to read from.
void
reader::initialize(const std::string&   elf_path)
{
  vector<string> v;
  initialize(elf_path, v);
}

/// Getter of the vector of directory paths to look into for split
/// debug information files.
///
/// @return the vector of directory paths to look into for split
/// debug information files.
const vector<string>&
reader::debug_info_root_paths() const
{return priv_->debug_info_root_paths;}

/// Getter of the functions used by the DWARF Front End library of
/// elfutils to locate DWARF debug information.
///
/// @return the functions used by the DWARF Front End library of
const Dwfl_Callbacks&
reader::dwfl_offline_callbacks() const
{return priv_->offline_callbacks;}

/// Getter of the functions used by the DWARF Front End library of
/// elfutils to locate DWARF debug information.
///
/// @return the functions used by the DWARF Front End library of
Dwfl_Callbacks&
reader::dwfl_offline_callbacks()
{return priv_->offline_callbacks;}

/// Getter of the handle used to access ELF information from the
/// current ELF file.
///
/// @return the handle used to access ELF information from the current
/// ELF file.
Elf*
reader::elf_handle() const
{return priv_->elf_handle;}

/// Getter of the handle used to access DWARF information from the
/// current ELF file.
///
/// @return the handle used to access DWARF information from the
/// current ELF file.
const Dwarf*
reader::dwarf_debug_info() const
{return priv_->dwarf_handle;}

/// Test if the binary has DWARF debug info.
///
/// @return true iff the binary has DWARF debug info.
bool
reader::has_dwarf_debug_info() const
{return ((priv_->dwarf_handle != nullptr)
      || (priv_->alt_dwarf_handle != nullptr));}

/// Test if the binary has CTF debug info.
///
/// @return true iff the binary has CTF debug info.
bool
reader::has_ctf_debug_info() const
{return (priv_->ctf_section != nullptr);}

/// Test if the binary has BTF debug info.
///
/// @return true iff the binary has BTF debug info
bool
reader::has_btf_debug_info() const
{return (priv_->btf_section != nullptr);}

/// Getter of the handle use to access DWARF information from the
/// alternate split DWARF information.
///
/// In other words, this accesses the factorized DWARF information
/// that has been constructed by the DWZ tool to de-duplicate DWARF
/// information on disk.
///
/// @return the handle use to access DWARF information from the
/// alternate split DWARF information.
const Dwarf*
reader::alternate_dwarf_debug_info() const
{return priv_->alt_dwarf_handle;}


/// Getter of the path to the alternate split DWARF information file,
/// on disk.  In othe words, this returns the path to the factorized
/// DWARF information used by the current ELF file, created by the
/// 'DWZ' tool.
///
/// @return the path to the alternate split DWARF information file,
/// on disk.
const string&
reader::alternate_dwarf_debug_info_path() const
{return priv_->alt_dwarf_path;}

/// Check if the underlying elf file refers to an alternate debug info
/// file associated to it.
///
/// Note that "alternate debug info sections" is a GNU extension as
/// of DWARF4 and is described at
/// http://www.dwarfstd.org/ShowIssue.php?issue=120604.1.
///
/// @param alt_di the path to the alternate debug info file.  This is
/// set iff the function returns true.
///
/// @return true if the ELF file refers to an alternate debug info
/// file.
bool
reader::refers_to_alt_debug_info(string& alt_di_path) const
{
  if (!alternate_dwarf_debug_info_path().empty())
    {
      alt_di_path = alternate_dwarf_debug_info_path();
      return true;
    }
  return false;
}

/// Find and return a pointer to the ELF symbol table
/// section.
///
/// @return a pointer to the ELF symbol table section.
const Elf_Scn*
reader::find_symbol_table_section() const
{
  if (!priv_->symtab_section)
      priv_->symtab_section =
    elf_helpers::find_symbol_table_section(elf_handle());
    return priv_->symtab_section;
}

/// Clear the pointer to the ELF symbol table section.
void
reader::reset_symbol_table_section()
{priv_->symtab_section = nullptr;}

/// Find and return a pointer to the the CTF section.
///
/// @return a pointer to the the CTF section.
const Elf_Scn*
reader::find_ctf_section() const
{
  if (priv_->ctf_section == nullptr)
    priv_->locate_ctf_debug_info();

  if (priv_->ctf_section)
    return priv_->ctf_section;

  return priv_->alt_ctf_section;
}

/// Find and return a pointer to the alternate CTF section of the
/// current ELF file.
///
/// @return a pointer to the alternate CTF section of the current ELF
/// file.
const Elf_Scn*
reader::find_alternate_ctf_section() const
{
  if (priv_->alt_ctf_section == nullptr)
    priv_->locate_alt_ctf_debug_info();

  return priv_->alt_ctf_section;
}

/// Find and return a pointer to the BTF section of the current ELF
/// file.
///
/// @return a pointer to the BTF section of the current ELF file.
const Elf_Scn*
reader::find_btf_section() const
{
  if (priv_->btf_section == nullptr)
    priv_->btf_section =
      elf_helpers::find_section(priv_->elf_handle,
                ".BTF", SHT_PROGBITS);
  return priv_->btf_section;
}

/// Get the value of the DT_NEEDED property of the current ELF file.
///
/// @return the value of the DT_NEEDED property.
const vector<string>&
reader::dt_needed()const
{return priv_->dt_needed;}


/// Get the value of the 'ARCHITECTURE' property of the current ELF file.
///
/// @return the value of the 'ARCHITECTURE' property of the current
/// ELF file.
const string&
reader::elf_architecture() const
{return priv_->elf_architecture;}

/// Getter of an abstract representation of the symbol table of the
/// underlying ELF file.
///
/// Note that the symbol table is loaded lazily, upon the first
/// invocation of this member function.
///
/// @returnt the symbol table.
symtab_reader::symtab_sptr&
reader::symtab() const
{
  ABG_ASSERT(elf_handle());

  if (!priv_->symt)
    priv_->symt = symtab_reader::symtab::load
      (elf_handle(), options().env,
       [&](const elf_symbol_sptr& symbol)
       {
     // This closure determines if a given symbol is suppressed by
     // taking into accont symbol aliases.  Basically, a symbol is
     // suppressed if all its aliases are suppressed.
     if (!symbol)
       return false;
     if (!suppr::is_elf_symbol_suppressed(*this, symbol))
       return false;
     for (elf_symbol_sptr a = symbol->get_next_alias();
          a && a.get() != symbol->get_main_symbol().get();
          a = a->get_next_alias())
       {
         if (!suppr::is_elf_symbol_suppressed(*this, a))
           return false;
       }
     return true;
       }
       );

  if (!priv_->symt)
    std::cerr << "Symbol table of '" << corpus_path()
          << "' could not be loaded\n";
  return priv_->symt;
}

/// Test if a given function symbol has been exported.
///
/// @param symbol_address the address of the symbol we are looking
/// for.  Note that this address must be a relative offset from the
/// beginning of the .text section, just like the kind of addresses
/// that are present in the .symtab section.
///
/// @return the elf symbol if found, or nil otherwise.
elf_symbol_sptr
reader::function_symbol_is_exported(GElf_Addr symbol_address) const
{

  elf_symbol_sptr symbol =
    symtab()->function_symbol_is_exported(symbol_address);
  if (!symbol)
    return symbol;

  address_set_sptr set;
  bool looking_at_linux_kernel_binary =
    load_in_linux_kernel_mode() && elf_helpers::is_linux_kernel(elf_handle());

  if (looking_at_linux_kernel_binary)
    {
    if (symbol->is_in_ksymtab())
      return symbol;
    return elf_symbol_sptr();
    }

  return symbol;
}

/// Test if a given variable symbol has been exported.
///
/// @param symbol_address the address of the symbol we are looking
/// for.  Note that this address must be a relative offset from the
/// beginning of the .text section, just like the kind of addresses
/// that are present in the .symtab section.
///
/// @return the elf symbol if found, or nil otherwise.
elf_symbol_sptr
reader::variable_symbol_is_exported(GElf_Addr symbol_address) const
{
  elf_symbol_sptr symbol =
    symtab()->variable_symbol_is_exported(symbol_address);
  if (!symbol)
    return symbol;

  address_set_sptr set;
  bool looking_at_linux_kernel_binary =
    load_in_linux_kernel_mode() && elf_helpers::is_linux_kernel(elf_handle());

  if (looking_at_linux_kernel_binary)
    {
    if (symbol->is_in_ksymtab())
      return symbol;
    return elf_symbol_sptr();
    }

  return symbol;
}

/// Test if a given function symbol has been exported.
///
/// @param name the name of the symbol we are looking for.
///
/// @return the elf symbol if found, or nil otherwise.
elf_symbol_sptr
reader::function_symbol_is_exported(const string& name) const
{
  const elf_symbol_sptr s = symtab()->function_symbol_is_exported(name);
  if (s && s->is_function() && s->is_public())
    {
      bool looking_at_linux_kernel_binary =
    (load_in_linux_kernel_mode()
     && elf_helpers::is_linux_kernel(elf_handle()));

      if (looking_at_linux_kernel_binary)
    {
      if (s->is_in_ksymtab())
        return s;
    }
      else
    return s;
    }
  return elf_symbol_sptr();
}

/// Test if a given variable symbol has been exported.
///
/// @param name the name of the symbol we are looking
/// for.
///
/// @return the elf symbol if found, or nil otherwise.
elf_symbol_sptr
reader::variable_symbol_is_exported(const string& name) const
{
  const elf_symbol_sptr s  = symtab()->variable_symbol_is_exported(name);
  if (s && s->is_variable() && s->is_public())
    {
      bool looking_at_linux_kernel_binary =
    (load_in_linux_kernel_mode()
     && elf_helpers::is_linux_kernel(elf_handle()));

      if (looking_at_linux_kernel_binary)
    {
      if (s->is_in_ksymtab())
        return s;
    }
      else
    return s;
    }
  return elf_symbol_sptr();
}

/// Test if a name is the name of an undefined function symbol.
///
/// @param name the symbol name to consider.
///
/// @return the undefined function symbol or nil if none was found.
elf_symbol_sptr
reader::function_symbol_is_undefined(const string& name) const
{return symtab()->function_symbol_is_undefined(name);}

/// Test if a name is the name of an undefined variable symbol.
///
/// @param name the symbol name to consider.
///
/// @return the undefined variable symbol or nil if none was found.
elf_symbol_sptr
reader::variable_symbol_is_undefined(const string& name) const
{return symtab()->variable_symbol_is_undefined(name);}

/// Load the DT_NEEDED and DT_SONAME elf TAGS.
void
reader::load_dt_soname_and_needed()
{
  elf_helpers::lookup_data_tag_from_dynamic_segment(elf_handle(),
                            DT_NEEDED,
                            priv_->dt_needed);

  vector<string> dt_tag_data;
  elf_helpers::lookup_data_tag_from_dynamic_segment(elf_handle(),
                            DT_SONAME,
                            dt_tag_data);
  if (!dt_tag_data.empty())
    dt_soname(dt_tag_data[0]);
}

/// Read the string representing the architecture of the current ELF
/// file.
void
reader::load_elf_architecture()
{
  if (!elf_handle())
    return;

  GElf_Ehdr eh_mem;
  GElf_Ehdr* elf_header = gelf_getehdr(elf_handle(), &eh_mem);

  priv_->elf_architecture =
    elf_helpers::e_machine_to_string(elf_header->e_machine);
}

/// Load various ELF data.
///
/// This function loads ELF data that are not symbol maps or debug
/// info.  That is, things like various tags, elf architecture and
/// so on.
void
reader::load_elf_properties()
{
  // Note that we don't load the symbol table as it's loaded lazily,
  // on demand.

  load_dt_soname_and_needed();
  load_elf_architecture();
}

/// Read the ELF information associated to the current ELF file and
/// construct an ABI representation from it.
///
/// Note that this reader doesn't know how to interpret any debug
/// information so the resulting ABI corpus won't have any type
/// information.  Rather, it will only have ELF symbol representation.
///
/// To have type information, consider using readers that know how to
/// interpret the symbolic type information comprised in DWARF, CTF or
/// other symbolic debug information format, like the @ref or
/// abigail::dwarf_reader::reader, @ref abigail::ctf_reader::reader
/// readers.
///
/// @return the resulting ABI corpus.
ir::corpus_sptr
reader::read_corpus(status& status)
{
  status = STATUS_UNKNOWN;

  corpus::origin origin = corpus()->get_origin();
  origin |= corpus::ELF_ORIGIN;
  if (is_linux_kernel(elf_handle()))
    origin |= corpus::LINUX_KERNEL_BINARY_ORIGIN;
  corpus()->set_origin(origin);

  load_elf_properties(); // DT_SONAME, DT_NEEDED, architecture
  corpus()->set_soname(dt_soname());
  corpus()->set_needed(dt_needed());
  corpus()->set_architecture_name(elf_architecture());

  // See if we could find symbol tables.
  if (!symtab())
    {
      status |= STATUS_NO_SYMBOLS_FOUND | STATUS_OK;
      // We found no ELF symbol, so we can't handle the binary.  Note
      // that we could have found a symbol table with no defined &
      // exported ELF symbols in it.  Both cases are handled as an
      // empty corpus.
      return corpus();
    }

  // Set symbols information to the corpus.
  corpus()->set_symtab(symtab());

  // If we couldn't load debug info from the elf path, then say it.
  if ((origin & abigail::ir::corpus::DWARF_ORIGIN)
        && !has_dwarf_debug_info())
    status |= STATUS_DEBUG_INFO_NOT_FOUND;
  else if ((origin & abigail::ir::corpus::CTF_ORIGIN)
             && !has_ctf_debug_info())
    status |= STATUS_DEBUG_INFO_NOT_FOUND;

  status |= STATUS_OK;
  return corpus();
}

/// Get the SONAME property of a designated ELF file.
///
/// @param path the path to the ELF file to consider.
///
/// @param soname output parameter.  This is set to the SONAME of the
/// file located at @p path, iff this function return true.
///
/// @return true iff the SONAME property was found in the ELF file
/// located at @p path and set into the argument of the parameter @p
/// soname.
bool
get_soname_of_elf_file(const string& path, string &soname)
{return elf_helpers::get_soname_of_elf_file(path, soname);}

/// Convert the type of ELF file into @ref elf_type.
///
/// @param elf the elf handle to use for the query.
///
/// @return the @ref elf_type for a given elf type.
static elf::elf_type
elf_file_type(Elf* elf)
{
  GElf_Ehdr ehdr_mem;
  GElf_Ehdr *header = gelf_getehdr (elf, &ehdr_mem);
  vector<string> dt_debug_data;

  switch (header->e_type)
    {
    case ET_DYN:
      if (lookup_data_tag_from_dynamic_segment(elf, DT_DEBUG, dt_debug_data))
    return elf::ELF_TYPE_PI_EXEC;
      else
    return elf::ELF_TYPE_DSO;
    case ET_EXEC:
      return elf::ELF_TYPE_EXEC;
    case ET_REL:
      return elf::ELF_TYPE_RELOCATABLE;
    default:
      return elf::ELF_TYPE_UNKNOWN;
    }
}

/// Get the type of a given elf type.
///
/// @param path the absolute path to the ELF file to analyzed.
///
/// @param type the kind of the ELF file designated by @p path.
///
/// @param out parameter.  Is set to the type of ELF file of @p path.
/// This parameter is set iff the function returns true.
///
/// @return true iff the file could be opened and analyzed.
bool
get_type_of_elf_file(const string& path, elf::elf_type& type)
{
  int fd = open(path.c_str(), O_RDONLY);
  if (fd == -1)
    return false;

  elf_version (EV_CURRENT);
  // Note that the dwelf_elf_begin function supports decompressing the
  // content of the input file, which is pretty cool.
  Elf *elf = dwelf_elf_begin(fd);
  type = elf_file_type(elf);
  elf_end(elf);
  close(fd);

  return true;
}

}// end namespace elf
} // end namespace abigail