1 // target-reloc.h -- target specific relocation support -*- C++ -*-
3 // Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
23 #ifndef GOLD_TARGET_RELOC_H
24 #define GOLD_TARGET_RELOC_H
29 #include "reloc-types.h"
34 // This function implements the generic part of reloc scanning. The
35 // template parameter Scan must be a class type which provides two
36 // functions: local() and global(). Those functions implement the
37 // machine specific part of scanning. We do it this way to
38 // avoidmaking a function call for each relocation, and to avoid
39 // repeating the generic code for each target.
41 template<int size, bool big_endian, typename Target_type, int sh_type,
45 const General_options& options,
49 Sized_relobj<size, big_endian>* object,
50 unsigned int data_shndx,
51 const unsigned char* prelocs,
53 Output_section* output_section,
54 bool needs_special_offset_handling,
56 const unsigned char* plocal_syms)
58 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
59 const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
60 const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
63 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
65 Reltype reloc(prelocs);
67 if (needs_special_offset_handling
68 && !output_section->is_input_address_mapped(object, data_shndx,
69 reloc.get_r_offset()))
72 typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
73 unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
74 unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
76 if (r_sym < local_count)
78 gold_assert(plocal_syms != NULL);
79 typename elfcpp::Sym<size, big_endian> lsym(plocal_syms
81 unsigned int shndx = lsym.get_st_shndx();
83 shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
85 && shndx != elfcpp::SHN_UNDEF
86 && !object->is_section_included(shndx))
88 // RELOC is a relocation against a local symbol in a
89 // section we are discarding. We can ignore this
90 // relocation. It will eventually become a reloc
91 // against the value zero.
93 // FIXME: We should issue a warning if this is an
94 // allocated section; is this the best place to do it?
96 // FIXME: The old GNU linker would in some cases look
97 // for the linkonce section which caused this section to
98 // be discarded, and, if the other section was the same
99 // size, change the reloc to refer to the other section.
100 // That seems risky and weird to me, and I don't know of
101 // any case where it is actually required.
106 scan.local(options, symtab, layout, target, object, data_shndx,
107 output_section, reloc, r_type, lsym);
111 Symbol* gsym = object->global_symbol(r_sym);
112 gold_assert(gsym != NULL);
113 if (gsym->is_forwarder())
114 gsym = symtab->resolve_forwards(gsym);
116 scan.global(options, symtab, layout, target, object, data_shndx,
117 output_section, reloc, r_type, gsym);
122 // Behavior for relocations to discarded comdat sections.
126 CB_UNDETERMINED, // Not yet determined -- need to look at section name.
127 CB_PRETEND, // Attempt to map to the corresponding kept section.
128 CB_IGNORE, // Ignore the relocation.
129 CB_WARNING // Print a warning.
132 // Decide what the linker should do for relocations that refer to discarded
133 // comdat sections. This decision is based on the name of the section being
136 inline Comdat_behavior
137 get_comdat_behavior(const char* name)
139 if (Layout::is_debug_info_section(name))
141 if (strcmp(name, ".eh_frame") == 0
142 || strcmp(name, ".gcc_except_table") == 0)
147 // This function implements the generic part of relocation processing.
148 // The template parameter Relocate must be a class type which provides
149 // a single function, relocate(), which implements the machine
150 // specific part of a relocation.
152 // SIZE is the ELF size: 32 or 64. BIG_ENDIAN is the endianness of
153 // the data. SH_TYPE is the section type: SHT_REL or SHT_RELA.
154 // RELOCATE implements operator() to do a relocation.
156 // PRELOCS points to the relocation data. RELOC_COUNT is the number
157 // of relocs. OUTPUT_SECTION is the output section.
158 // NEEDS_SPECIAL_OFFSET_HANDLING is true if input offsets need to be
159 // mapped to output offsets.
161 // VIEW is the section data, VIEW_ADDRESS is its memory address, and
162 // VIEW_SIZE is the size. These refer to the input section, unless
163 // NEEDS_SPECIAL_OFFSET_HANDLING is true, in which case they refer to
164 // the output section.
166 template<int size, bool big_endian, typename Target_type, int sh_type,
170 const Relocate_info<size, big_endian>* relinfo,
172 const unsigned char* prelocs,
174 Output_section* output_section,
175 bool needs_special_offset_handling,
177 typename elfcpp::Elf_types<size>::Elf_Addr view_address,
178 section_size_type view_size)
180 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
181 const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
184 Sized_relobj<size, big_endian>* object = relinfo->object;
185 unsigned int local_count = object->local_symbol_count();
187 Comdat_behavior comdat_behavior = CB_UNDETERMINED;
189 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
191 Reltype reloc(prelocs);
193 section_offset_type offset =
194 convert_to_section_size_type(reloc.get_r_offset());
196 if (needs_special_offset_handling)
198 offset = output_section->output_offset(relinfo->object,
205 typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
206 unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
207 unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
209 const Sized_symbol<size>* sym;
211 Symbol_value<size> symval;
212 const Symbol_value<size> *psymval;
213 if (r_sym < local_count)
216 psymval = object->local_symbol(r_sym);
218 // If the local symbol belongs to a section we are discarding,
219 // and that section is a debug section, try to find the
220 // corresponding kept section and map this symbol to its
221 // counterpart in the kept section.
223 unsigned int shndx = psymval->input_shndx(&is_ordinary);
225 && shndx != elfcpp::SHN_UNDEF
226 && !object->is_section_included(shndx))
228 if (comdat_behavior == CB_UNDETERMINED)
230 std::string name = object->section_name(relinfo->data_shndx);
231 comdat_behavior = get_comdat_behavior(name.c_str());
233 if (comdat_behavior == CB_PRETEND)
236 typename elfcpp::Elf_types<size>::Elf_Addr value =
237 object->map_to_kept_section(shndx, &found);
239 symval.set_output_value(value + psymval->input_value());
241 symval.set_output_value(0);
245 if (comdat_behavior == CB_WARNING)
246 gold_warning_at_location(relinfo, i, offset,
247 _("Relocation refers to discarded "
249 symval.set_output_value(0);
251 symval.set_no_output_symtab_entry();
257 const Symbol* gsym = object->global_symbol(r_sym);
258 gold_assert(gsym != NULL);
259 if (gsym->is_forwarder())
260 gsym = relinfo->symtab->resolve_forwards(gsym);
262 sym = static_cast<const Sized_symbol<size>*>(gsym);
263 if (sym->has_symtab_index())
264 symval.set_output_symtab_index(sym->symtab_index());
266 symval.set_no_output_symtab_entry();
267 symval.set_output_value(sym->value());
271 if (!relocate.relocate(relinfo, target, i, reloc, r_type, sym, psymval,
272 view + offset, view_address + offset, view_size))
275 if (offset < 0 || static_cast<section_size_type>(offset) >= view_size)
277 gold_error_at_location(relinfo, i, offset,
278 _("reloc has bad offset %zu"),
279 static_cast<size_t>(offset));
284 && sym->is_undefined()
285 && sym->binding() != elfcpp::STB_WEAK
286 && !target->is_defined_by_abi(sym)
287 && (!parameters->options().shared() // -shared
288 || parameters->options().defs())) // -z defs
289 gold_undefined_symbol(sym, relinfo, i, offset);
291 if (sym != NULL && sym->has_warning())
292 relinfo->symtab->issue_warning(sym, relinfo, i, offset);
296 // This class may be used as a typical class for the
297 // Scan_relocatable_reloc parameter to scan_relocatable_relocs. The
298 // template parameter Classify_reloc must be a class type which
299 // provides a function get_size_for_reloc which returns the number of
300 // bytes to which a reloc applies. This class is intended to capture
301 // the most typical target behaviour, while still permitting targets
302 // to define their own independent class for Scan_relocatable_reloc.
304 template<int sh_type, typename Classify_reloc>
305 class Default_scan_relocatable_relocs
308 // Return the strategy to use for a local symbol which is not a
309 // section symbol, given the relocation type.
310 inline Relocatable_relocs::Reloc_strategy
311 local_non_section_strategy(unsigned int, Relobj*)
312 { return Relocatable_relocs::RELOC_COPY; }
314 // Return the strategy to use for a local symbol which is a section
315 // symbol, given the relocation type.
316 inline Relocatable_relocs::Reloc_strategy
317 local_section_strategy(unsigned int r_type, Relobj* object)
319 if (sh_type == elfcpp::SHT_RELA)
320 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA;
323 Classify_reloc classify;
324 switch (classify.get_size_for_reloc(r_type, object))
327 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0;
329 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1;
331 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2;
333 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4;
335 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8;
342 // Return the strategy to use for a global symbol, given the
343 // relocation type, the object, and the symbol index.
344 inline Relocatable_relocs::Reloc_strategy
345 global_strategy(unsigned int, Relobj*, unsigned int)
346 { return Relocatable_relocs::RELOC_COPY; }
349 // Scan relocs during a relocatable link. This is a default
350 // definition which should work for most targets.
351 // Scan_relocatable_reloc must name a class type which provides three
352 // functions which return a Relocatable_relocs::Reloc_strategy code:
353 // global_strategy, local_non_section_strategy, and
354 // local_section_strategy. Most targets should be able to use
355 // Default_scan_relocatable_relocs as this class.
357 template<int size, bool big_endian, int sh_type,
358 typename Scan_relocatable_reloc>
360 scan_relocatable_relocs(
361 const General_options&,
364 Sized_relobj<size, big_endian>* object,
365 unsigned int data_shndx,
366 const unsigned char* prelocs,
368 Output_section* output_section,
369 bool needs_special_offset_handling,
370 size_t local_symbol_count,
371 const unsigned char* plocal_syms,
372 Relocatable_relocs* rr)
374 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
375 const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
376 const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
377 Scan_relocatable_reloc scan;
379 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
381 Reltype reloc(prelocs);
383 Relocatable_relocs::Reloc_strategy strategy;
385 if (needs_special_offset_handling
386 && !output_section->is_input_address_mapped(object, data_shndx,
387 reloc.get_r_offset()))
388 strategy = Relocatable_relocs::RELOC_DISCARD;
391 typename elfcpp::Elf_types<size>::Elf_WXword r_info =
393 const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
394 const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
396 if (r_sym >= local_symbol_count)
397 strategy = scan.global_strategy(r_type, object, r_sym);
400 gold_assert(plocal_syms != NULL);
401 typename elfcpp::Sym<size, big_endian> lsym(plocal_syms
403 unsigned int shndx = lsym.get_st_shndx();
405 shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
407 && shndx != elfcpp::SHN_UNDEF
408 && !object->is_section_included(shndx))
410 // RELOC is a relocation against a local symbol
411 // defined in a section we are discarding. Discard
412 // the reloc. FIXME: Should we issue a warning?
413 strategy = Relocatable_relocs::RELOC_DISCARD;
415 else if (lsym.get_st_type() != elfcpp::STT_SECTION)
416 strategy = scan.local_non_section_strategy(r_type, object);
419 strategy = scan.local_section_strategy(r_type, object);
420 if (strategy != Relocatable_relocs::RELOC_DISCARD)
421 object->output_section(shndx)->set_needs_symtab_index();
426 rr->set_next_reloc_strategy(strategy);
430 // Relocate relocs during a relocatable link. This is a default
431 // definition which should work for most targets.
433 template<int size, bool big_endian, int sh_type>
435 relocate_for_relocatable(
436 const Relocate_info<size, big_endian>* relinfo,
437 const unsigned char* prelocs,
439 Output_section* output_section,
440 typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section,
441 const Relocatable_relocs* rr,
443 typename elfcpp::Elf_types<size>::Elf_Addr view_address,
445 unsigned char* reloc_view,
446 section_size_type reloc_view_size)
448 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
449 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
450 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc_write
452 const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
454 Sized_relobj<size, big_endian>* const object = relinfo->object;
455 const unsigned int local_count = object->local_symbol_count();
457 unsigned char* pwrite = reloc_view;
459 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
461 Relocatable_relocs::Reloc_strategy strategy = rr->strategy(i);
462 if (strategy == Relocatable_relocs::RELOC_DISCARD)
465 Reltype reloc(prelocs);
466 Reltype_write reloc_write(pwrite);
468 typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
469 const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
470 const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
472 // Get the new symbol index.
474 unsigned int new_symndx;
475 if (r_sym < local_count)
479 case Relocatable_relocs::RELOC_COPY:
480 new_symndx = object->symtab_index(r_sym);
481 gold_assert(new_symndx != -1U);
484 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
485 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
486 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
487 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
488 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
489 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
491 // We are adjusting a section symbol. We need to find
492 // the symbol table index of the section symbol for
493 // the output section corresponding to input section
494 // in which this symbol is defined.
495 gold_assert(r_sym < local_count);
498 object->local_symbol_input_shndx(r_sym, &is_ordinary);
499 gold_assert(is_ordinary);
500 Output_section* os = object->output_section(shndx);
501 gold_assert(os != NULL);
502 gold_assert(os->needs_symtab_index());
503 new_symndx = os->symtab_index();
513 const Symbol* gsym = object->global_symbol(r_sym);
514 gold_assert(gsym != NULL);
515 if (gsym->is_forwarder())
516 gsym = relinfo->symtab->resolve_forwards(gsym);
518 gold_assert(gsym->has_symtab_index());
519 new_symndx = gsym->symtab_index();
522 // Get the new offset--the location in the output section where
523 // this relocation should be applied.
525 Address offset = reloc.get_r_offset();
527 if (offset_in_output_section != -1U)
528 new_offset = offset + offset_in_output_section;
531 section_offset_type sot_offset =
532 convert_types<section_offset_type, Address>(offset);
533 section_offset_type new_sot_offset =
534 output_section->output_offset(object, relinfo->data_shndx,
536 gold_assert(new_sot_offset != -1);
537 new_offset = new_sot_offset;
540 // In an object file, r_offset is an offset within the section.
541 // In an executable or dynamic object, generated by
542 // --emit-relocs, r_offset is an absolute address.
543 if (!parameters->options().relocatable())
545 new_offset += view_address;
546 if (offset_in_output_section != -1U)
547 new_offset -= offset_in_output_section;
550 reloc_write.put_r_offset(new_offset);
551 reloc_write.put_r_info(elfcpp::elf_r_info<size>(new_symndx, r_type));
553 // Handle the reloc addend based on the strategy.
555 if (strategy == Relocatable_relocs::RELOC_COPY)
557 if (sh_type == elfcpp::SHT_RELA)
558 Reloc_types<sh_type, size, big_endian>::
559 copy_reloc_addend(&reloc_write,
564 // The relocation uses a section symbol in the input file.
565 // We are adjusting it to use a section symbol in the output
566 // file. The input section symbol refers to some address in
567 // the input section. We need the relocation in the output
568 // file to refer to that same address. This adjustment to
569 // the addend is the same calculation we use for a simple
570 // absolute relocation for the input section symbol.
572 const Symbol_value<size>* psymval = object->local_symbol(r_sym);
574 unsigned char* padd = view + offset;
577 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
579 typename elfcpp::Elf_types<size>::Elf_Swxword addend;
580 addend = Reloc_types<sh_type, size, big_endian>::
581 get_reloc_addend(&reloc);
582 addend = psymval->value(object, addend);
583 Reloc_types<sh_type, size, big_endian>::
584 set_reloc_addend(&reloc_write, addend);
588 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
591 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
592 Relocate_functions<size, big_endian>::rel8(padd, object,
596 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
597 Relocate_functions<size, big_endian>::rel16(padd, object,
601 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
602 Relocate_functions<size, big_endian>::rel32(padd, object,
606 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
607 Relocate_functions<size, big_endian>::rel64(padd, object,
616 pwrite += reloc_size;
619 gold_assert(static_cast<section_size_type>(pwrite - reloc_view)
623 } // End namespace gold.
625 #endif // !defined(GOLD_TARGET_RELOC_H)