EnvironmentLoader/source/elfio/elfio_symbols.hpp

/*
Copyright (C) 2001-present by Serge Lamikhov-Center

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#ifndef ELFIO_SYMBOLS_HPP
#define ELFIO_SYMBOLS_HPP

namespace ELFIO {

//------------------------------------------------------------------------------
template <class S> class symbol_section_accessor_template
{
  public:
    //------------------------------------------------------------------------------
    explicit symbol_section_accessor_template( const elfio& elf_file,
                                               S*           symbol_section )
        : elf_file( elf_file ), symbol_section( symbol_section )
    {
        find_hash_section();
    }

    //------------------------------------------------------------------------------
    Elf_Xword get_symbols_num() const
    {
        Elf_Xword nRet = 0;

        size_t minimum_symbol_size;
        switch ( elf_file.get_class() ) {
        case ELFCLASS32:
            minimum_symbol_size = sizeof( Elf32_Sym );
            break;
        case ELFCLASS64:
            minimum_symbol_size = sizeof( Elf64_Sym );
            break;
        default:
            return nRet;
        }

        if ( symbol_section->get_entry_size() >= minimum_symbol_size ) {
            nRet =
                symbol_section->get_size() / symbol_section->get_entry_size();
        }

        return nRet;
    }

    //------------------------------------------------------------------------------
    bool get_symbol( Elf_Xword      index,
                     std::string&   name,
                     Elf64_Addr&    value,
                     Elf_Xword&     size,
                     unsigned char& bind,
                     unsigned char& type,
                     Elf_Half&      section_index,
                     unsigned char& other ) const
    {
        bool ret = false;

        if ( elf_file.get_class() == ELFCLASS32 ) {
            ret = generic_get_symbol<Elf32_Sym>( index, name, value, size, bind,
                                                 type, section_index, other );
        }
        else {
            ret = generic_get_symbol<Elf64_Sym>( index, name, value, size, bind,
                                                 type, section_index, other );
        }

        return ret;
    }

    //------------------------------------------------------------------------------
    bool get_symbol( const std::string& name,
                     Elf64_Addr&        value,
                     Elf_Xword&         size,
                     unsigned char&     bind,
                     unsigned char&     type,
                     Elf_Half&          section_index,
                     unsigned char&     other ) const
    {
        bool ret = false;

        if ( 0 != get_hash_table_index() ) {
            if ( hash_section->get_type() == SHT_HASH ) {
                ret = hash_lookup( name, value, size, bind, type, section_index,
                                   other );
            }
            if ( hash_section->get_type() == SHT_GNU_HASH ||
                 hash_section->get_type() == DT_GNU_HASH ) {
                if ( elf_file.get_class() == ELFCLASS32 ) {
                    ret = gnu_hash_lookup<uint32_t>(
                        name, value, size, bind, type, section_index, other );
                }
                else {
                    ret = gnu_hash_lookup<uint64_t>(
                        name, value, size, bind, type, section_index, other );
                }
            }
        }

        if ( !ret ) {
            for ( Elf_Xword i = 0; !ret && i < get_symbols_num(); i++ ) {
                std::string symbol_name;
                if ( get_symbol( i, symbol_name, value, size, bind, type,
                                 section_index, other ) ) {
                    if ( symbol_name == name ) {
                        ret = true;
                    }
                }
            }
        }

        return ret;
    }

    //------------------------------------------------------------------------------
    bool get_symbol( const Elf64_Addr& value,
                     std::string&      name,
                     Elf_Xword&        size,
                     unsigned char&    bind,
                     unsigned char&    type,
                     Elf_Half&         section_index,
                     unsigned char&    other ) const
    {

        const endianess_convertor& convertor = elf_file.get_convertor();

        Elf_Xword  idx   = 0;
        bool       match = false;
        Elf64_Addr v     = 0;

        if ( elf_file.get_class() == ELFCLASS32 ) {
            match = generic_search_symbols<Elf32_Sym>(
                [&]( const Elf32_Sym* sym ) {
                    return convertor( sym->st_value ) == value;
                },
                idx );
        }
        else {
            match = generic_search_symbols<Elf64_Sym>(
                [&]( const Elf64_Sym* sym ) {
                    return convertor( sym->st_value ) == value;
                },
                idx );
        }

        if ( match ) {
            return get_symbol( idx, name, v, size, bind, type, section_index,
                               other );
        }

        return false;
    }

    //------------------------------------------------------------------------------
    Elf_Word add_symbol( Elf_Word      name,
                         Elf64_Addr    value,
                         Elf_Xword     size,
                         unsigned char info,
                         unsigned char other,
                         Elf_Half      shndx )
    {
        Elf_Word nRet;

        if ( symbol_section->get_size() == 0 ) {
            if ( elf_file.get_class() == ELFCLASS32 ) {
                nRet = generic_add_symbol<Elf32_Sym>( 0, 0, 0, 0, 0, 0 );
            }
            else {
                nRet = generic_add_symbol<Elf64_Sym>( 0, 0, 0, 0, 0, 0 );
            }
        }

        if ( elf_file.get_class() == ELFCLASS32 ) {
            nRet = generic_add_symbol<Elf32_Sym>( name, value, size, info,
                                                  other, shndx );
        }
        else {
            nRet = generic_add_symbol<Elf64_Sym>( name, value, size, info,
                                                  other, shndx );
        }

        return nRet;
    }

    //------------------------------------------------------------------------------
    Elf_Word add_symbol( Elf_Word      name,
                         Elf64_Addr    value,
                         Elf_Xword     size,
                         unsigned char bind,
                         unsigned char type,
                         unsigned char other,
                         Elf_Half      shndx )
    {
        return add_symbol( name, value, size, ELF_ST_INFO( bind, type ), other,
                           shndx );
    }

    //------------------------------------------------------------------------------
    Elf_Word add_symbol( string_section_accessor& pStrWriter,
                         const char*              str,
                         Elf64_Addr               value,
                         Elf_Xword                size,
                         unsigned char            info,
                         unsigned char            other,
                         Elf_Half                 shndx )
    {
        Elf_Word index = pStrWriter.add_string( str );
        return add_symbol( index, value, size, info, other, shndx );
    }

    //------------------------------------------------------------------------------
    Elf_Word add_symbol( string_section_accessor& pStrWriter,
                         const char*              str,
                         Elf64_Addr               value,
                         Elf_Xword                size,
                         unsigned char            bind,
                         unsigned char            type,
                         unsigned char            other,
                         Elf_Half                 shndx )
    {
        return add_symbol( pStrWriter, str, value, size,
                           ELF_ST_INFO( bind, type ), other, shndx );
    }

    //------------------------------------------------------------------------------
    Elf_Xword arrange_local_symbols(
        std::function<void( Elf_Xword first, Elf_Xword second )> func =
            nullptr )
    {
        Elf_Xword nRet = 0;

        if ( elf_file.get_class() == ELFCLASS32 ) {
            nRet = generic_arrange_local_symbols<Elf32_Sym>( func );
        }
        else {
            nRet = generic_arrange_local_symbols<Elf64_Sym>( func );
        }

        return nRet;
    }

    //------------------------------------------------------------------------------
  private:
    //------------------------------------------------------------------------------
    void find_hash_section()
    {
        Elf_Half nSecNo = elf_file.sections.size();
        for ( Elf_Half i = 0; i < nSecNo; ++i ) {
            const section* sec = elf_file.sections[i];
            if ( sec->get_link() == symbol_section->get_index() &&
                 ( sec->get_type() == SHT_HASH ||
                   sec->get_type() == SHT_GNU_HASH ||
                   sec->get_type() == DT_GNU_HASH ) ) {
                hash_section       = sec;
                hash_section_index = i;
                break;
            }
        }
    }

    //------------------------------------------------------------------------------
    Elf_Half get_string_table_index() const
    {
        return (Elf_Half)symbol_section->get_link();
    }

    //------------------------------------------------------------------------------
    Elf_Half get_hash_table_index() const { return hash_section_index; }

    //------------------------------------------------------------------------------
    bool hash_lookup( const std::string& name,
                      Elf64_Addr&        value,
                      Elf_Xword&         size,
                      unsigned char&     bind,
                      unsigned char&     type,
                      Elf_Half&          section_index,
                      unsigned char&     other ) const
    {
        bool                       ret       = false;
        const endianess_convertor& convertor = elf_file.get_convertor();

        Elf_Word nbucket = *(const Elf_Word*)hash_section->get_data();
        nbucket          = convertor( nbucket );
        Elf_Word nchain =
            *(const Elf_Word*)( hash_section->get_data() + sizeof( Elf_Word ) );
        nchain       = convertor( nchain );
        Elf_Word val = elf_hash( (const unsigned char*)name.c_str() );
        Elf_Word y =
            *(const Elf_Word*)( hash_section->get_data() +
                                ( 2 + val % nbucket ) * sizeof( Elf_Word ) );
        y = convertor( y );
        std::string str;
        get_symbol( y, str, value, size, bind, type, section_index, other );
        while ( str != name && STN_UNDEF != y && y < nchain ) {
            y = *(const Elf_Word*)( hash_section->get_data() +
                                    ( 2 + nbucket + y ) * sizeof( Elf_Word ) );
            y = convertor( y );
            get_symbol( y, str, value, size, bind, type, section_index, other );
        }

        if ( str == name ) {
            ret = true;
        }

        return ret;
    }

    //------------------------------------------------------------------------------
    template <class T>
    bool gnu_hash_lookup( const std::string& name,
                          Elf64_Addr&        value,
                          Elf_Xword&         size,
                          unsigned char&     bind,
                          unsigned char&     type,
                          Elf_Half&          section_index,
                          unsigned char&     other ) const
    {
        bool                       ret       = false;
        const endianess_convertor& convertor = elf_file.get_convertor();

        uint32_t nbuckets    = *( (uint32_t*)hash_section->get_data() + 0 );
        uint32_t symoffset   = *( (uint32_t*)hash_section->get_data() + 1 );
        uint32_t bloom_size  = *( (uint32_t*)hash_section->get_data() + 2 );
        uint32_t bloom_shift = *( (uint32_t*)hash_section->get_data() + 3 );
        nbuckets             = convertor( nbuckets );
        symoffset            = convertor( symoffset );
        bloom_size           = convertor( bloom_size );
        bloom_shift          = convertor( bloom_shift );

        T* bloom_filter =
            (T*)( hash_section->get_data() + 4 * sizeof( uint32_t ) );

        uint32_t hash = elf_gnu_hash( (const unsigned char*)name.c_str() );
        uint32_t bloom_index = ( hash / ( 8 * sizeof( T ) ) ) % bloom_size;
        T        bloom_bits =
            ( (T)1 << ( hash % ( 8 * sizeof( T ) ) ) ) |
            ( (T)1 << ( ( hash >> bloom_shift ) % ( 8 * sizeof( T ) ) ) );

        if ( ( convertor( bloom_filter[bloom_index] ) & bloom_bits ) !=
             bloom_bits )
            return ret;

        uint32_t bucket = hash % nbuckets;
        auto*    buckets =
            (uint32_t*)( hash_section->get_data() + 4 * sizeof( uint32_t ) +
                         bloom_size * sizeof( T ) );
        auto* chains =
            (uint32_t*)( hash_section->get_data() + 4 * sizeof( uint32_t ) +
                         bloom_size * sizeof( T ) +
                         nbuckets * sizeof( uint32_t ) );

        if ( convertor( buckets[bucket] ) >= symoffset ) {
            uint32_t    chain_index = convertor( buckets[bucket] ) - symoffset;
            uint32_t    chain_hash  = convertor( chains[chain_index] );
            std::string symname;

            while ( true ) {
                if ( ( chain_hash >> 1 ) == ( hash >> 1 ) &&
                     get_symbol( chain_index + symoffset, symname, value, size,
                                 bind, type, section_index, other ) &&
                     name == symname ) {
                    ret = true;
                    break;
                }

                if ( chain_hash & 1 )
                    break;
                chain_hash = convertor( chains[++chain_index] );
            }
        }

        return ret;
    }

    //------------------------------------------------------------------------------
    template <class T> const T* generic_get_symbol_ptr( Elf_Xword index ) const
    {
        if ( 0 != symbol_section->get_data() && index < get_symbols_num() ) {
            const T* pSym = reinterpret_cast<const T*>(
                symbol_section->get_data() +
                index * symbol_section->get_entry_size() );

            return pSym;
        }

        return nullptr;
    }

    //------------------------------------------------------------------------------
    template <class T>
    bool generic_search_symbols( std::function<bool( const T* )> match,
                                 Elf_Xword&                      idx ) const
    {
        for ( Elf_Xword i = 0; i < get_symbols_num(); i++ ) {
            const T* symPtr = generic_get_symbol_ptr<T>( i );

            if ( symPtr == nullptr )
                return false;

            if ( match( symPtr ) ) {
                idx = i;
                return true;
            }
        }

        return false;
    }

    //------------------------------------------------------------------------------
    template <class T>
    bool generic_get_symbol( Elf_Xword      index,
                             std::string&   name,
                             Elf64_Addr&    value,
                             Elf_Xword&     size,
                             unsigned char& bind,
                             unsigned char& type,
                             Elf_Half&      section_index,
                             unsigned char& other ) const
    {
        bool ret = false;

        if ( nullptr != symbol_section->get_data() &&
             index < get_symbols_num() ) {
            const T* pSym = reinterpret_cast<const T*>(
                symbol_section->get_data() +
                index * symbol_section->get_entry_size() );

            const endianess_convertor& convertor = elf_file.get_convertor();

            section* string_section =
                elf_file.sections[get_string_table_index()];
            string_section_accessor str_reader( string_section );
            const char*             pStr =
                str_reader.get_string( convertor( pSym->st_name ) );
            if ( nullptr != pStr ) {
                name = pStr;
            }
            value         = convertor( pSym->st_value );
            size          = convertor( pSym->st_size );
            bind          = ELF_ST_BIND( pSym->st_info );
            type          = ELF_ST_TYPE( pSym->st_info );
            section_index = convertor( pSym->st_shndx );
            other         = pSym->st_other;

            ret = true;
        }

        return ret;
    }

    //------------------------------------------------------------------------------
    template <class T>
    Elf_Word generic_add_symbol( Elf_Word      name,
                                 Elf64_Addr    value,
                                 Elf_Xword     size,
                                 unsigned char info,
                                 unsigned char other,
                                 Elf_Half      shndx )
    {
        const endianess_convertor& convertor = elf_file.get_convertor();

        T entry;
        entry.st_name  = convertor( name );
        entry.st_value = decltype( entry.st_value )( value );
        entry.st_value = convertor( entry.st_value );
        entry.st_size  = decltype( entry.st_size )( size );
        entry.st_size  = convertor( entry.st_size );
        entry.st_info  = convertor( info );
        entry.st_other = convertor( other );
        entry.st_shndx = convertor( shndx );

        symbol_section->append_data( reinterpret_cast<char*>( &entry ),
                                     sizeof( entry ) );

        Elf_Word nRet =
            Elf_Word( symbol_section->get_size() / sizeof( entry ) - 1 );

        return nRet;
    }

    //------------------------------------------------------------------------------
    template <class T>
    Elf_Xword generic_arrange_local_symbols(
        std::function<void( Elf_Xword first, Elf_Xword second )> func )
    {
        const endianess_convertor& convertor = elf_file.get_convertor();

        Elf_Word first_not_local =
            1; // Skip the first entry. It is always NOTYPE
        Elf_Xword current = 0;
        Elf_Xword count   = get_symbols_num();

        while ( true ) {
            T* p1 = nullptr;
            T* p2 = nullptr;

            while ( first_not_local < count ) {
                p1 = const_cast<T*>(
                    generic_get_symbol_ptr<T>( first_not_local ) );
                if ( ELF_ST_BIND( convertor( p1->st_info ) ) != STB_LOCAL )
                    break;
                ++first_not_local;
            }

            current = first_not_local + 1;
            while ( current < count ) {
                p2 = const_cast<T*>( generic_get_symbol_ptr<T>( current ) );
                if ( ELF_ST_BIND( convertor( p2->st_info ) ) == STB_LOCAL )
                    break;
                ++current;
            }

            if ( first_not_local < count && current < count ) {
                if ( func )
                    func( first_not_local, current );

                std::swap( *p1, *p2 );
            }
            else {
                // Update 'info' field of the section
                symbol_section->set_info( first_not_local );
                break;
            }
        }

        return first_not_local;
    }

    //------------------------------------------------------------------------------
  private:
    const elfio&   elf_file;
    S*             symbol_section;
    Elf_Half       hash_section_index{ 0 };
    const section* hash_section{ nullptr };
};

using symbol_section_accessor = symbol_section_accessor_template<section>;
using const_symbol_section_accessor =
    symbol_section_accessor_template<const section>;

} // namespace ELFIO

#endif // ELFIO_SYMBOLS_HPP