| // target-reloc.h -- target specific relocation support -*- C++ -*- |
| |
| // Copyright 2006, 2007, 2008 Free Software Foundation, Inc. |
| // Written by Ian Lance Taylor <iant@google.com>. |
| |
| // 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_TARGET_RELOC_H |
| #define GOLD_TARGET_RELOC_H |
| |
| #include "elfcpp.h" |
| #include "symtab.h" |
| #include "reloc.h" |
| #include "reloc-types.h" |
| |
| namespace gold |
| { |
| |
| // This function implements the generic part of reloc scanning. The |
| // template parameter Scan must be a class type which provides two |
| // functions: local() and global(). Those functions implement the |
| // machine specific part of scanning. We do it this way to |
| // avoidmaking a function call for each relocation, and to avoid |
| // repeating the generic code for each target. |
| |
| template<int size, bool big_endian, typename Target_type, int sh_type, |
| typename Scan> |
| inline void |
| scan_relocs( |
| const General_options& options, |
| Symbol_table* symtab, |
| Layout* layout, |
| Target_type* target, |
| Sized_relobj<size, big_endian>* object, |
| unsigned int data_shndx, |
| const unsigned char* prelocs, |
| size_t reloc_count, |
| Output_section* output_section, |
| bool needs_special_offset_handling, |
| size_t local_count, |
| const unsigned char* plocal_syms) |
| { |
| typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype; |
| const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size; |
| const int sym_size = elfcpp::Elf_sizes<size>::sym_size; |
| Scan scan; |
| |
| for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) |
| { |
| Reltype reloc(prelocs); |
| |
| if (needs_special_offset_handling |
| && !output_section->is_input_address_mapped(object, data_shndx, |
| reloc.get_r_offset())) |
| continue; |
| |
| typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info(); |
| unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info); |
| unsigned int r_type = elfcpp::elf_r_type<size>(r_info); |
| |
| if (r_sym < local_count) |
| { |
| gold_assert(plocal_syms != NULL); |
| typename elfcpp::Sym<size, big_endian> lsym(plocal_syms |
| + r_sym * sym_size); |
| unsigned int shndx = lsym.get_st_shndx(); |
| bool is_ordinary; |
| shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary); |
| if (is_ordinary |
| && shndx != elfcpp::SHN_UNDEF |
| && !object->is_section_included(shndx)) |
| { |
| // RELOC is a relocation against a local symbol in a |
| // section we are discarding. We can ignore this |
| // relocation. It will eventually become a reloc |
| // against the value zero. |
| // |
| // FIXME: We should issue a warning if this is an |
| // allocated section; is this the best place to do it? |
| // |
| // FIXME: The old GNU linker would in some cases look |
| // for the linkonce section which caused this section to |
| // be discarded, and, if the other section was the same |
| // size, change the reloc to refer to the other section. |
| // That seems risky and weird to me, and I don't know of |
| // any case where it is actually required. |
| |
| continue; |
| } |
| |
| scan.local(options, symtab, layout, target, object, data_shndx, |
| output_section, reloc, r_type, lsym); |
| } |
| else |
| { |
| Symbol* gsym = object->global_symbol(r_sym); |
| gold_assert(gsym != NULL); |
| if (gsym->is_forwarder()) |
| gsym = symtab->resolve_forwards(gsym); |
| |
| scan.global(options, symtab, layout, target, object, data_shndx, |
| output_section, reloc, r_type, gsym); |
| } |
| } |
| } |
| |
| // Behavior for relocations to discarded comdat sections. |
| |
| enum Comdat_behavior |
| { |
| CB_UNDETERMINED, // Not yet determined -- need to look at section name. |
| CB_PRETEND, // Attempt to map to the corresponding kept section. |
| CB_IGNORE, // Ignore the relocation. |
| CB_WARNING // Print a warning. |
| }; |
| |
| // Decide what the linker should do for relocations that refer to discarded |
| // comdat sections. This decision is based on the name of the section being |
| // relocated. |
| |
| inline Comdat_behavior |
| get_comdat_behavior(const char* name) |
| { |
| if (Layout::is_debug_info_section(name)) |
| return CB_PRETEND; |
| if (strcmp(name, ".eh_frame") == 0 |
| || strcmp(name, ".gcc_except_table") == 0) |
| return CB_IGNORE; |
| return CB_WARNING; |
| } |
| |
| // This function implements the generic part of relocation processing. |
| // The template parameter Relocate must be a class type which provides |
| // a single function, relocate(), which implements the machine |
| // specific part of a relocation. |
| |
| // SIZE is the ELF size: 32 or 64. BIG_ENDIAN is the endianness of |
| // the data. SH_TYPE is the section type: SHT_REL or SHT_RELA. |
| // RELOCATE implements operator() to do a relocation. |
| |
| // PRELOCS points to the relocation data. RELOC_COUNT is the number |
| // of relocs. OUTPUT_SECTION is the output section. |
| // NEEDS_SPECIAL_OFFSET_HANDLING is true if input offsets need to be |
| // mapped to output offsets. |
| |
| // VIEW is the section data, VIEW_ADDRESS is its memory address, and |
| // VIEW_SIZE is the size. These refer to the input section, unless |
| // NEEDS_SPECIAL_OFFSET_HANDLING is true, in which case they refer to |
| // the output section. |
| |
| template<int size, bool big_endian, typename Target_type, int sh_type, |
| typename Relocate> |
| inline void |
| relocate_section( |
| const Relocate_info<size, big_endian>* relinfo, |
| Target_type* target, |
| const unsigned char* prelocs, |
| size_t reloc_count, |
| Output_section* output_section, |
| bool needs_special_offset_handling, |
| unsigned char* view, |
| typename elfcpp::Elf_types<size>::Elf_Addr view_address, |
| section_size_type view_size) |
| { |
| typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype; |
| const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size; |
| Relocate relocate; |
| |
| Sized_relobj<size, big_endian>* object = relinfo->object; |
| unsigned int local_count = object->local_symbol_count(); |
| |
| Comdat_behavior comdat_behavior = CB_UNDETERMINED; |
| |
| for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) |
| { |
| Reltype reloc(prelocs); |
| |
| section_offset_type offset = |
| convert_to_section_size_type(reloc.get_r_offset()); |
| |
| if (needs_special_offset_handling) |
| { |
| offset = output_section->output_offset(relinfo->object, |
| relinfo->data_shndx, |
| offset); |
| if (offset == -1) |
| continue; |
| } |
| |
| typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info(); |
| unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info); |
| unsigned int r_type = elfcpp::elf_r_type<size>(r_info); |
| |
| const Sized_symbol<size>* sym; |
| |
| Symbol_value<size> symval; |
| const Symbol_value<size> *psymval; |
| if (r_sym < local_count) |
| { |
| sym = NULL; |
| psymval = object->local_symbol(r_sym); |
| |
| // If the local symbol belongs to a section we are discarding, |
| // and that section is a debug section, try to find the |
| // corresponding kept section and map this symbol to its |
| // counterpart in the kept section. |
| bool is_ordinary; |
| unsigned int shndx = psymval->input_shndx(&is_ordinary); |
| if (is_ordinary |
| && shndx != elfcpp::SHN_UNDEF |
| && !object->is_section_included(shndx)) |
| { |
| if (comdat_behavior == CB_UNDETERMINED) |
| { |
| std::string name = object->section_name(relinfo->data_shndx); |
| comdat_behavior = get_comdat_behavior(name.c_str()); |
| } |
| if (comdat_behavior == CB_PRETEND) |
| { |
| bool found; |
| typename elfcpp::Elf_types<size>::Elf_Addr value = |
| object->map_to_kept_section(shndx, &found); |
| if (found) |
| symval.set_output_value(value + psymval->input_value()); |
| else |
| symval.set_output_value(0); |
| } |
| else |
| { |
| if (comdat_behavior == CB_WARNING) |
| gold_warning_at_location(relinfo, i, offset, |
| _("Relocation refers to discarded " |
| "comdat section")); |
| symval.set_output_value(0); |
| } |
| symval.set_no_output_symtab_entry(); |
| psymval = &symval; |
| } |
| } |
| else |
| { |
| const Symbol* gsym = object->global_symbol(r_sym); |
| gold_assert(gsym != NULL); |
| if (gsym->is_forwarder()) |
| gsym = relinfo->symtab->resolve_forwards(gsym); |
| |
| sym = static_cast<const Sized_symbol<size>*>(gsym); |
| if (sym->has_symtab_index()) |
| symval.set_output_symtab_index(sym->symtab_index()); |
| else |
| symval.set_no_output_symtab_entry(); |
| symval.set_output_value(sym->value()); |
| psymval = &symval; |
| } |
| |
| if (!relocate.relocate(relinfo, target, i, reloc, r_type, sym, psymval, |
| view + offset, view_address + offset, view_size)) |
| continue; |
| |
| if (offset < 0 || static_cast<section_size_type>(offset) >= view_size) |
| { |
| gold_error_at_location(relinfo, i, offset, |
| _("reloc has bad offset %zu"), |
| static_cast<size_t>(offset)); |
| continue; |
| } |
| |
| if (sym != NULL |
| && sym->is_undefined() |
| && sym->binding() != elfcpp::STB_WEAK |
| && !target->is_defined_by_abi(sym) |
| && (!parameters->options().shared() // -shared |
| || parameters->options().defs())) // -z defs |
| gold_undefined_symbol(sym, relinfo, i, offset); |
| |
| if (sym != NULL && sym->has_warning()) |
| relinfo->symtab->issue_warning(sym, relinfo, i, offset); |
| } |
| } |
| |
| // This class may be used as a typical class for the |
| // Scan_relocatable_reloc parameter to scan_relocatable_relocs. The |
| // template parameter Classify_reloc must be a class type which |
| // provides a function get_size_for_reloc which returns the number of |
| // bytes to which a reloc applies. This class is intended to capture |
| // the most typical target behaviour, while still permitting targets |
| // to define their own independent class for Scan_relocatable_reloc. |
| |
| template<int sh_type, typename Classify_reloc> |
| class Default_scan_relocatable_relocs |
| { |
| public: |
| // Return the strategy to use for a local symbol which is not a |
| // section symbol, given the relocation type. |
| inline Relocatable_relocs::Reloc_strategy |
| local_non_section_strategy(unsigned int, Relobj*) |
| { return Relocatable_relocs::RELOC_COPY; } |
| |
| // Return the strategy to use for a local symbol which is a section |
| // symbol, given the relocation type. |
| inline Relocatable_relocs::Reloc_strategy |
| local_section_strategy(unsigned int r_type, Relobj* object) |
| { |
| if (sh_type == elfcpp::SHT_RELA) |
| return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA; |
| else |
| { |
| Classify_reloc classify; |
| switch (classify.get_size_for_reloc(r_type, object)) |
| { |
| case 0: |
| return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0; |
| case 1: |
| return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1; |
| case 2: |
| return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2; |
| case 4: |
| return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4; |
| case 8: |
| return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8; |
| default: |
| gold_unreachable(); |
| } |
| } |
| } |
| |
| // Return the strategy to use for a global symbol, given the |
| // relocation type, the object, and the symbol index. |
| inline Relocatable_relocs::Reloc_strategy |
| global_strategy(unsigned int, Relobj*, unsigned int) |
| { return Relocatable_relocs::RELOC_COPY; } |
| }; |
| |
| // Scan relocs during a relocatable link. This is a default |
| // definition which should work for most targets. |
| // Scan_relocatable_reloc must name a class type which provides three |
| // functions which return a Relocatable_relocs::Reloc_strategy code: |
| // global_strategy, local_non_section_strategy, and |
| // local_section_strategy. Most targets should be able to use |
| // Default_scan_relocatable_relocs as this class. |
| |
| template<int size, bool big_endian, int sh_type, |
| typename Scan_relocatable_reloc> |
| void |
| scan_relocatable_relocs( |
| const General_options&, |
| Symbol_table*, |
| Layout*, |
| Sized_relobj<size, big_endian>* object, |
| unsigned int data_shndx, |
| const unsigned char* prelocs, |
| size_t reloc_count, |
| Output_section* output_section, |
| bool needs_special_offset_handling, |
| size_t local_symbol_count, |
| const unsigned char* plocal_syms, |
| Relocatable_relocs* rr) |
| { |
| typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype; |
| const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size; |
| const int sym_size = elfcpp::Elf_sizes<size>::sym_size; |
| Scan_relocatable_reloc scan; |
| |
| for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) |
| { |
| Reltype reloc(prelocs); |
| |
| Relocatable_relocs::Reloc_strategy strategy; |
| |
| if (needs_special_offset_handling |
| && !output_section->is_input_address_mapped(object, data_shndx, |
| reloc.get_r_offset())) |
| strategy = Relocatable_relocs::RELOC_DISCARD; |
| else |
| { |
| typename elfcpp::Elf_types<size>::Elf_WXword r_info = |
| reloc.get_r_info(); |
| const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info); |
| const unsigned int r_type = elfcpp::elf_r_type<size>(r_info); |
| |
| if (r_sym >= local_symbol_count) |
| strategy = scan.global_strategy(r_type, object, r_sym); |
| else |
| { |
| gold_assert(plocal_syms != NULL); |
| typename elfcpp::Sym<size, big_endian> lsym(plocal_syms |
| + r_sym * sym_size); |
| unsigned int shndx = lsym.get_st_shndx(); |
| bool is_ordinary; |
| shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary); |
| if (is_ordinary |
| && shndx != elfcpp::SHN_UNDEF |
| && !object->is_section_included(shndx)) |
| { |
| // RELOC is a relocation against a local symbol |
| // defined in a section we are discarding. Discard |
| // the reloc. FIXME: Should we issue a warning? |
| strategy = Relocatable_relocs::RELOC_DISCARD; |
| } |
| else if (lsym.get_st_type() != elfcpp::STT_SECTION) |
| strategy = scan.local_non_section_strategy(r_type, object); |
| else |
| { |
| strategy = scan.local_section_strategy(r_type, object); |
| if (strategy != Relocatable_relocs::RELOC_DISCARD) |
| object->output_section(shndx)->set_needs_symtab_index(); |
| } |
| } |
| } |
| |
| rr->set_next_reloc_strategy(strategy); |
| } |
| } |
| |
| // Relocate relocs during a relocatable link. This is a default |
| // definition which should work for most targets. |
| |
| template<int size, bool big_endian, int sh_type> |
| void |
| relocate_for_relocatable( |
| const Relocate_info<size, big_endian>* relinfo, |
| const unsigned char* prelocs, |
| size_t reloc_count, |
| Output_section* output_section, |
| typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section, |
| const Relocatable_relocs* rr, |
| unsigned char* view, |
| typename elfcpp::Elf_types<size>::Elf_Addr view_address, |
| section_size_type, |
| unsigned char* reloc_view, |
| section_size_type reloc_view_size) |
| { |
| typedef typename elfcpp::Elf_types<size>::Elf_Addr Address; |
| typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype; |
| typedef typename Reloc_types<sh_type, size, big_endian>::Reloc_write |
| Reltype_write; |
| const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size; |
| const Address invalid_address = static_cast<Address>(0) - 1; |
| |
| Sized_relobj<size, big_endian>* const object = relinfo->object; |
| const unsigned int local_count = object->local_symbol_count(); |
| |
| unsigned char* pwrite = reloc_view; |
| |
| for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) |
| { |
| Relocatable_relocs::Reloc_strategy strategy = rr->strategy(i); |
| if (strategy == Relocatable_relocs::RELOC_DISCARD) |
| continue; |
| |
| Reltype reloc(prelocs); |
| Reltype_write reloc_write(pwrite); |
| |
| typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info(); |
| const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info); |
| const unsigned int r_type = elfcpp::elf_r_type<size>(r_info); |
| |
| // Get the new symbol index. |
| |
| unsigned int new_symndx; |
| if (r_sym < local_count) |
| { |
| switch (strategy) |
| { |
| case Relocatable_relocs::RELOC_COPY: |
| new_symndx = object->symtab_index(r_sym); |
| gold_assert(new_symndx != -1U); |
| break; |
| |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA: |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0: |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1: |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2: |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4: |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8: |
| { |
| // We are adjusting a section symbol. We need to find |
| // the symbol table index of the section symbol for |
| // the output section corresponding to input section |
| // in which this symbol is defined. |
| gold_assert(r_sym < local_count); |
| bool is_ordinary; |
| unsigned int shndx = |
| object->local_symbol_input_shndx(r_sym, &is_ordinary); |
| gold_assert(is_ordinary); |
| Output_section* os = object->output_section(shndx); |
| gold_assert(os != NULL); |
| gold_assert(os->needs_symtab_index()); |
| new_symndx = os->symtab_index(); |
| } |
| break; |
| |
| default: |
| gold_unreachable(); |
| } |
| } |
| else |
| { |
| const Symbol* gsym = object->global_symbol(r_sym); |
| gold_assert(gsym != NULL); |
| if (gsym->is_forwarder()) |
| gsym = relinfo->symtab->resolve_forwards(gsym); |
| |
| gold_assert(gsym->has_symtab_index()); |
| new_symndx = gsym->symtab_index(); |
| } |
| |
| // Get the new offset--the location in the output section where |
| // this relocation should be applied. |
| |
| Address offset = reloc.get_r_offset(); |
| Address new_offset; |
| if (offset_in_output_section != invalid_address) |
| new_offset = offset + offset_in_output_section; |
| else |
| { |
| section_offset_type sot_offset = |
| convert_types<section_offset_type, Address>(offset); |
| section_offset_type new_sot_offset = |
| output_section->output_offset(object, relinfo->data_shndx, |
| sot_offset); |
| gold_assert(new_sot_offset != -1); |
| new_offset = new_sot_offset; |
| } |
| |
| // In an object file, r_offset is an offset within the section. |
| // In an executable or dynamic object, generated by |
| // --emit-relocs, r_offset is an absolute address. |
| if (!parameters->options().relocatable()) |
| { |
| new_offset += view_address; |
| if (offset_in_output_section != invalid_address) |
| new_offset -= offset_in_output_section; |
| } |
| |
| reloc_write.put_r_offset(new_offset); |
| reloc_write.put_r_info(elfcpp::elf_r_info<size>(new_symndx, r_type)); |
| |
| // Handle the reloc addend based on the strategy. |
| |
| if (strategy == Relocatable_relocs::RELOC_COPY) |
| { |
| if (sh_type == elfcpp::SHT_RELA) |
| Reloc_types<sh_type, size, big_endian>:: |
| copy_reloc_addend(&reloc_write, |
| &reloc); |
| } |
| else |
| { |
| // The relocation uses a section symbol in the input file. |
| // We are adjusting it to use a section symbol in the output |
| // file. The input section symbol refers to some address in |
| // the input section. We need the relocation in the output |
| // file to refer to that same address. This adjustment to |
| // the addend is the same calculation we use for a simple |
| // absolute relocation for the input section symbol. |
| |
| const Symbol_value<size>* psymval = object->local_symbol(r_sym); |
| |
| unsigned char* padd = view + offset; |
| switch (strategy) |
| { |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA: |
| { |
| typename elfcpp::Elf_types<size>::Elf_Swxword addend; |
| addend = Reloc_types<sh_type, size, big_endian>:: |
| get_reloc_addend(&reloc); |
| addend = psymval->value(object, addend); |
| Reloc_types<sh_type, size, big_endian>:: |
| set_reloc_addend(&reloc_write, addend); |
| } |
| break; |
| |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0: |
| break; |
| |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1: |
| Relocate_functions<size, big_endian>::rel8(padd, object, |
| psymval); |
| break; |
| |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2: |
| Relocate_functions<size, big_endian>::rel16(padd, object, |
| psymval); |
| break; |
| |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4: |
| Relocate_functions<size, big_endian>::rel32(padd, object, |
| psymval); |
| break; |
| |
| case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8: |
| Relocate_functions<size, big_endian>::rel64(padd, object, |
| psymval); |
| break; |
| |
| default: |
| gold_unreachable(); |
| } |
| } |
| |
| pwrite += reloc_size; |
| } |
| |
| gold_assert(static_cast<section_size_type>(pwrite - reloc_view) |
| == reloc_view_size); |
| } |
| |
| } // End namespace gold. |
| |
| #endif // !defined(GOLD_TARGET_RELOC_H) |