/* Copyright 2017 R. Thomas
 * Copyright 2017 Quarkslab
 *
 * 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.
 */
#ifndef LIEF_ELF_PARSER_H_
#define LIEF_ELF_PARSER_H_

#include <vector>
#include <string>
#include <memory>
#include <fstream>
#include <iterator>
#include <iostream>
#include <algorithm>
#include <stdexcept>
#include <functional>

#include "LIEF/visibility.h"
#include "LIEF/exception.hpp"
#include "LIEF/BinaryStream/VectorStream.hpp"

#include "LIEF/Abstract/Parser.hpp"

#include "LIEF/ELF/Binary.hpp"
#include "LIEF/ELF/Structures.hpp"
#include "LIEF/ELF/DynamicEntryArray.hpp"
#include "LIEF/ELF/DynamicEntryRpath.hpp"
#include "LIEF/ELF/DynamicEntryRunPath.hpp"
#include "LIEF/ELF/GnuHash.hpp"

namespace LIEF {

namespace OAT {
class Parser;
}
namespace ELF {


//! @brief Class which parse an ELF file and transform into a ELF::Binary
class LIEF_API Parser : public LIEF::Parser {
  friend class OAT::Parser;
  public:

    static constexpr uint32_t NB_MAX_SYMBOLS         = 1000000;
    static constexpr uint32_t DELTA_NB_SYMBOLS       = 3000;
    static constexpr uint32_t NB_MAX_BUCKETS         = NB_MAX_SYMBOLS;
    static constexpr uint32_t NB_MAX_CHAINS          = 1000000;
    static constexpr uint32_t NB_MAX_SECTION         = 10000;
    static constexpr uint32_t NB_MAX_SEGMENTS        = 10000;
    static constexpr uint32_t NB_MAX_RELOCATIONS     = 3000000;
    static constexpr uint32_t NB_MAX_DYNAMIC_ENTRIES = 1000;
    static constexpr uint32_t NB_MAX_MASKWORD        = 512;
    static constexpr uint32_t MAX_NOTE_DESCRIPTION   = 1_MB;
    static constexpr uint32_t MAX_SECTION_SIZE       = 100_MB;
    static constexpr uint32_t MAX_SEGMENT_SIZE       = MAX_SECTION_SIZE;


    //! @brief Parse an ELF file an return a LIEF::ELF::Binary object
    //!
    //! For weird binaries (e.g. sectionless) you can choose which method use to count dynamic symbols
    //!
    //! @param[in] file Path to the ELF binary
    //! @param[in] count_mtd Method used to count dynamic symbols. Default: LIEF::ELF::DYNSYM_COUNT_METHODS::COUNT_AUTO
    //! @Return LIEF::ELF::Binary
    static std::unique_ptr<Binary> parse(const std::string& file, DYNSYM_COUNT_METHODS count_mtd = DYNSYM_COUNT_METHODS::COUNT_AUTO);

    //! @brief Parse the given raw data as an ELF binary and return a LIEF::ELF::Binary object
    //!
    //! For weird binaries (e.g. sectionless) you can choose which method use to count dynamic symbols
    //!
    //! @param[in] data Raw ELF
    //! @param[in] name Binary name (optional)
    //! @param[in] count_mtd Method used to count dynamic symbols. Default: LIEF::ELF::DYNSYM_COUNT_METHODS::COUNT_AUTO
    //! @Return LIEF::ELF::Binary
    static std::unique_ptr<Binary> parse(const std::vector<uint8_t>& data, const std::string& name = "", DYNSYM_COUNT_METHODS count_mtd = DYNSYM_COUNT_METHODS::COUNT_AUTO);

    Parser& operator=(const Parser& copy) = delete;
    Parser(const Parser& copy)            = delete;

  private:
    Parser(void);
    Parser(const std::string& file, DYNSYM_COUNT_METHODS count_mtd = DYNSYM_COUNT_METHODS::COUNT_AUTO, Binary* output = nullptr);
    Parser(const std::vector<uint8_t>& data, const std::string& name, DYNSYM_COUNT_METHODS count_mtd = DYNSYM_COUNT_METHODS::COUNT_AUTO, Binary* output = nullptr);
    ~Parser(void);

    void init(const std::string& name = "");

    bool should_swap(void) const;

    // map, dynamic_symbol.version <----> symbol_version
    // symbol_version comes from symbol_version table
    void link_symbol_version(void);

    template<typename ELF_T>
    void parse_binary(void);

    template<typename ELF_T>
    bool parse_header(void);

    //! @brief Parse binary's Section
    //!
    //! Parse sections by using the ``e_shoff`` field as offset
    template<typename ELF_T>
    void parse_sections(void);

    //! @brief Parse binary's segments
    //!
    //! Parse segment by using the ``e_phoff`` field as offset
    template<typename ELF_T>
    void parse_segments(void);

    //! @brief Return offset of the dynamic string table
    uint64_t get_dynamic_string_table(void) const;

    uint64_t get_dynamic_string_table_from_segments(void) const;

    uint64_t get_dynamic_string_table_from_sections(void) const;

    //! @brief Return the number of dynamic symbols using the given method
    template<typename ELF_T>
    uint32_t get_numberof_dynamic_symbols(DYNSYM_COUNT_METHODS mtd) const;

    //! @brief Count based on hash table (reliable)
    template<typename ELF_T>
    uint32_t nb_dynsym_hash(void) const;

    //! @brief Count based on SYSV hash table
    template<typename ELF_T>
    uint32_t nb_dynsym_sysv_hash(void) const;

    //! @brief Count based on GNU hash table
    template<typename ELF_T>
    uint32_t nb_dynsym_gnu_hash(void) const;

    //! @brief Count based on sections (not very reliable)
    template<typename ELF_T>
    uint32_t nb_dynsym_section(void) const;

    //! @brief Count based on PLT/GOT relocations (very reliable but not accurate)
    template<typename ELF_T>
    uint32_t nb_dynsym_relocations(void) const;

    template<typename ELF_T>
    void parse_dynamic_entries(uint64_t offset, uint64_t size);

    template<typename ELF_T>
    void parse_dynamic_symbols(uint64_t offset);

    //! @brief Parse static Symbol
    //!
    //! Parser find Symbols offset by using the file offset attribute of the
    //! ELF_SECTION_TYPES::SHT_SYMTAB Section.
    //!
    //! The number of symbols is taken from the `information` attribute in the section header.
    //!
    //! The section containing symbols name is found with the `link` attribute.
    template<typename ELF_T>
    void parse_static_symbols(uint64_t offset, uint32_t nbSymbols, const Section* string_section);

    //! @brief Parse Dynamic relocations
    //!
    //! It use DT_REL/DT_RELA dynamic entries to parse it
    template<typename ELF_T, typename REL_T>
    void parse_dynamic_relocations(uint64_t relocations_offset, uint64_t size);

    //! @brief Parse `.plt.got`/`got` relocations
    //!
    //! For:
    //! * ELF32 it uses **DT_JMPREL** and **DT_PLTRELSZ**
    //! * ELF64 it uses **DT_PLTREL** and **DT_PLTRELSZ**
    template<typename ELF_T, typename REL_T>
    void parse_pltgot_relocations(uint64_t offset, uint64_t size);


    //! @brief Parse relocations using LIEF::ELF::Section.
    //!
    //! Parser::parse_dynamic_relocations and Parser::parse_pltgot_relocations
    //! use parse relocations by using LIEF::ELF::Segment. This method parse relocations
    //! that are not reachable through segments (For example Object file).
    template<typename ELF_T, typename REL_T>
    void parse_section_relocations(Section const& section);

    //! @brief Parse SymbolVersionRequirement
    //!
    //! We use the virtual address stored in the
    //! DYNAMIC_TAGS::DT_VERNEED entry to get the offset.
    //! and DYNAMIC_TAGS::DT_VERNEEDNUM to get the number of entries
    template<typename ELF_T>
    void parse_symbol_version_requirement(uint64_t offset, uint32_t nb_entries);


    //! @brief Parse SymbolVersionDefinition.
    //!
    //! We use the virtual address stored in
    //! the DYNAMIC_TAGS::DT_VERDEF DT_VERDEF entry to get the offset.
    //! DYNAMIC_TAGS::DT_VERDEFNUM gives the number of entries
    template<typename ELF_T>
    void parse_symbol_version_definition(uint64_t offset, uint32_t nb_entries);


    //! @brief Parse @link SymbolVersion Symbol version @endlink.
    //!
    //! We use the virtual address stored in the
    //! DYNAMIC_TAGS::DT_VERSYM entry to parse it.
    //!
    //! @see http://dev.gentoo.org/~solar/elf/symbol-versioning
    void parse_symbol_version(uint64_t symbol_version_offset);

    //! @brief Parse Symbols's GNU hash
    //!
    //! @see https://blogs.oracle.com/ali/entry/gnu_hash_elf_sections
    template<typename ELF_T>
    void parse_symbol_gnu_hash(uint64_t offset);

    //! @brief Parse Note (.gnu.note)
    void parse_notes(uint64_t offset, uint64_t size);

    //! @brief Parse Symbols's SYSV hash
    void parse_symbol_sysv_hash(uint64_t offset);

    void parse_overlay(void);

    template<typename ELF_T, typename REL_T>
    uint32_t max_relocation_index(uint64_t relocations_offset, uint64_t size) const;

    std::unique_ptr<VectorStream> stream_;
    Binary*                       binary_;
    ELF_CLASS                     type_;
    DYNSYM_COUNT_METHODS          count_mtd_;
};




} // namespace ELF
} // namespace LIEF
#endif
