// copy-relocs.h -- handle COPY relocations for gold -*- C++ -*- // Copyright (C) 2006-2016 Free Software Foundation, Inc. // Written by Ian Lance Taylor . // This file is part of gold. // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3 of the License, or // (at your option) any later version. // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, // MA 02110-1301, USA. #ifndef GOLD_COPY_RELOCS_H #define GOLD_COPY_RELOCS_H #include "elfcpp.h" #include "reloc-types.h" #include "output.h" namespace gold { // This class is used to manage COPY relocations. We try to avoid // them when possible. A COPY relocation may be required when an // executable refers to a variable defined in a shared library. COPY // relocations are problematic because they tie the executable to the // exact size of the variable in the shared library. We can avoid // them if all the references to the variable are in a writeable // section. In that case we can simply use dynamic relocations. // However, when scanning relocs, we don't know when we see the // relocation whether we will be forced to use a COPY relocation or // not. So we have to save the relocation during the reloc scanning, // and then emit it as a dynamic relocation if necessary. This class // implements that. It is used by the target specific code. // The template parameter SH_TYPE is the type of the reloc section to // be used for COPY relocs: elfcpp::SHT_REL or elfcpp::SHT_RELA. template class Copy_relocs { private: typedef typename Reloc_types::Reloc Reloc; public: Copy_relocs(unsigned int copy_reloc_type) : entries_(), copy_reloc_type_(copy_reloc_type), dynbss_(NULL), dynrelro_(NULL) { } // This is called while scanning relocs if we see a relocation // against a symbol which may force us to generate a COPY reloc. // SYM is the symbol. OBJECT is the object whose relocs we are // scanning. The relocation is being applied to section SHNDX in // OBJECT. OUTPUT_SECTION is the output section where section SHNDX // will wind up. REL is the reloc itself. The Output_data_reloc // section is where the dynamic relocs are put. void copy_reloc(Symbol_table*, Layout*, Sized_symbol* sym, Sized_relobj_file* object, unsigned int shndx, Output_section* output_section, unsigned int r_type, typename elfcpp::Elf_types::Elf_Addr r_offset, typename elfcpp::Elf_types::Elf_Swxword r_addend, Output_data_reloc*); // Return whether there are any saved relocations. bool any_saved_relocs() const { return !this->entries_.empty(); } // Emit any saved relocations which turn out to be needed. This is // called after all the relocs have been scanned. void emit(Output_data_reloc*); // Emit a COPY reloc. void emit_copy_reloc(Symbol_table*, Sized_symbol*, Output_data*, off_t, Output_data_reloc*); protected: typedef typename elfcpp::Elf_types::Elf_Addr Address; typedef typename elfcpp::Elf_types::Elf_Addr Addend; // This POD class holds the relocations we are saving. We will emit // these relocations if it turns out that the symbol does not // require a COPY relocation. struct Copy_reloc_entry { Copy_reloc_entry(Symbol* sym, unsigned int reloc_type, Sized_relobj_file* relobj, unsigned int shndx, Output_section* output_section, Address address, Addend addend) : sym_(sym), reloc_type_(reloc_type), relobj_(relobj), shndx_(shndx), output_section_(output_section), address_(address), addend_(addend) { } Symbol* sym_; unsigned int reloc_type_; Sized_relobj_file* relobj_; unsigned int shndx_; Output_section* output_section_; Address address_; Addend addend_; }; // Make a new COPY reloc and emit it. void make_copy_reloc(Symbol_table*, Layout*, Sized_symbol*, Sized_relobj_file* object, Output_data_reloc*); // A list of relocs to be saved. typedef std::vector Copy_reloc_entries; // The list of relocs we are saving. Copy_reloc_entries entries_; private: // Return whether we need a COPY reloc. bool need_copy_reloc(Sized_symbol* gsym, Sized_relobj_file* object, unsigned int shndx) const; // Save a reloc against SYM for possible emission later. void save(Symbol*, Sized_relobj_file*, unsigned int shndx, Output_section*, unsigned int r_type, typename elfcpp::Elf_types::Elf_Addr r_offset, typename elfcpp::Elf_types::Elf_Swxword r_addend); // The target specific relocation type of the COPY relocation. const unsigned int copy_reloc_type_; // The dynamic BSS data which goes into the .bss section. This is // where writable variables which require COPY relocations are placed. Output_data_space* dynbss_; // The dynamic read-only data, which goes into the .data.rel.ro section. // This is where read-only variables which require COPY relocations are // placed. Output_data_space* dynrelro_; }; } // End namespace gold. #endif // !defined(GOLD_COPY_RELOCS_H)