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[binutils.git] / gold / target-reloc.h
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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
26 #include "elfcpp.h"
27 #include "symtab.h"
28 #include "reloc.h"
29 #include "reloc-types.h"
31 namespace gold
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,
42 typename Scan>
43 inline void
44 scan_relocs(
45 const General_options& options,
46 Symbol_table* symtab,
47 Layout* layout,
48 Target_type* target,
49 Sized_relobj<size, big_endian>* object,
50 unsigned int data_shndx,
51 const unsigned char* prelocs,
52 size_t reloc_count,
53 Output_section* output_section,
54 bool needs_special_offset_handling,
55 size_t local_count,
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;
61 Scan scan;
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()))
70 continue;
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
80 + r_sym * sym_size);
81 unsigned int shndx = lsym.get_st_shndx();
82 bool is_ordinary;
83 shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
84 if (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?
95 //
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.
103 continue;
106 scan.local(options, symtab, layout, target, object, data_shndx,
107 output_section, reloc, r_type, lsym);
109 else
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.
124 enum Comdat_behavior
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
134 // relocated.
136 inline Comdat_behavior
137 get_comdat_behavior(const char* name)
139 if (Layout::is_debug_info_section(name))
140 return CB_PRETEND;
141 if (strcmp(name, ".eh_frame") == 0
142 || strcmp(name, ".gcc_except_table") == 0)
143 return CB_IGNORE;
144 return CB_WARNING;
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,
167 typename Relocate>
168 inline void
169 relocate_section(
170 const Relocate_info<size, big_endian>* relinfo,
171 Target_type* target,
172 const unsigned char* prelocs,
173 size_t reloc_count,
174 Output_section* output_section,
175 bool needs_special_offset_handling,
176 unsigned char* view,
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;
182 Relocate relocate;
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,
199 relinfo->data_shndx,
200 offset);
201 if (offset == -1)
202 continue;
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)
215 sym = NULL;
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.
222 bool is_ordinary;
223 unsigned int shndx = psymval->input_shndx(&is_ordinary);
224 if (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)
235 bool found;
236 typename elfcpp::Elf_types<size>::Elf_Addr value =
237 object->map_to_kept_section(shndx, &found);
238 if (found)
239 symval.set_output_value(value + psymval->input_value());
240 else
241 symval.set_output_value(0);
243 else
245 if (comdat_behavior == CB_WARNING)
246 gold_warning_at_location(relinfo, i, offset,
247 _("Relocation refers to discarded "
248 "comdat section"));
249 symval.set_output_value(0);
251 symval.set_no_output_symtab_entry();
252 psymval = &symval;
255 else
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());
265 else
266 symval.set_no_output_symtab_entry();
267 symval.set_output_value(sym->value());
268 psymval = &symval;
271 if (!relocate.relocate(relinfo, target, i, reloc, r_type, sym, psymval,
272 view + offset, view_address + offset, view_size))
273 continue;
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));
280 continue;
283 if (sym != NULL
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
307 public:
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 r_type, Relobj*, unsigned int r_sym)
313 // We assume that relocation type 0 is NONE. Targets which are
314 // different must override.
315 if (r_type == 0 && r_sym == 0)
316 return Relocatable_relocs::RELOC_DISCARD;
317 return Relocatable_relocs::RELOC_COPY;
320 // Return the strategy to use for a local symbol which is a section
321 // symbol, given the relocation type.
322 inline Relocatable_relocs::Reloc_strategy
323 local_section_strategy(unsigned int r_type, Relobj* object)
325 if (sh_type == elfcpp::SHT_RELA)
326 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA;
327 else
329 Classify_reloc classify;
330 switch (classify.get_size_for_reloc(r_type, object))
332 case 0:
333 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0;
334 case 1:
335 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1;
336 case 2:
337 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2;
338 case 4:
339 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4;
340 case 8:
341 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8;
342 default:
343 gold_unreachable();
348 // Return the strategy to use for a global symbol, given the
349 // relocation type, the object, and the symbol index.
350 inline Relocatable_relocs::Reloc_strategy
351 global_strategy(unsigned int, Relobj*, unsigned int)
352 { return Relocatable_relocs::RELOC_COPY; }
355 // Scan relocs during a relocatable link. This is a default
356 // definition which should work for most targets.
357 // Scan_relocatable_reloc must name a class type which provides three
358 // functions which return a Relocatable_relocs::Reloc_strategy code:
359 // global_strategy, local_non_section_strategy, and
360 // local_section_strategy. Most targets should be able to use
361 // Default_scan_relocatable_relocs as this class.
363 template<int size, bool big_endian, int sh_type,
364 typename Scan_relocatable_reloc>
365 void
366 scan_relocatable_relocs(
367 const General_options&,
368 Symbol_table*,
369 Layout*,
370 Sized_relobj<size, big_endian>* object,
371 unsigned int data_shndx,
372 const unsigned char* prelocs,
373 size_t reloc_count,
374 Output_section* output_section,
375 bool needs_special_offset_handling,
376 size_t local_symbol_count,
377 const unsigned char* plocal_syms,
378 Relocatable_relocs* rr)
380 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
381 const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
382 const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
383 Scan_relocatable_reloc scan;
385 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
387 Reltype reloc(prelocs);
389 Relocatable_relocs::Reloc_strategy strategy;
391 if (needs_special_offset_handling
392 && !output_section->is_input_address_mapped(object, data_shndx,
393 reloc.get_r_offset()))
394 strategy = Relocatable_relocs::RELOC_DISCARD;
395 else
397 typename elfcpp::Elf_types<size>::Elf_WXword r_info =
398 reloc.get_r_info();
399 const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
400 const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
402 if (r_sym >= local_symbol_count)
403 strategy = scan.global_strategy(r_type, object, r_sym);
404 else
406 gold_assert(plocal_syms != NULL);
407 typename elfcpp::Sym<size, big_endian> lsym(plocal_syms
408 + r_sym * sym_size);
409 unsigned int shndx = lsym.get_st_shndx();
410 bool is_ordinary;
411 shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
412 if (is_ordinary
413 && shndx != elfcpp::SHN_UNDEF
414 && !object->is_section_included(shndx))
416 // RELOC is a relocation against a local symbol
417 // defined in a section we are discarding. Discard
418 // the reloc. FIXME: Should we issue a warning?
419 strategy = Relocatable_relocs::RELOC_DISCARD;
421 else if (lsym.get_st_type() != elfcpp::STT_SECTION)
422 strategy = scan.local_non_section_strategy(r_type, object,
423 r_sym);
424 else
426 strategy = scan.local_section_strategy(r_type, object);
427 if (strategy != Relocatable_relocs::RELOC_DISCARD)
428 object->output_section(shndx)->set_needs_symtab_index();
433 rr->set_next_reloc_strategy(strategy);
437 // Relocate relocs during a relocatable link. This is a default
438 // definition which should work for most targets.
440 template<int size, bool big_endian, int sh_type>
441 void
442 relocate_for_relocatable(
443 const Relocate_info<size, big_endian>* relinfo,
444 const unsigned char* prelocs,
445 size_t reloc_count,
446 Output_section* output_section,
447 typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section,
448 const Relocatable_relocs* rr,
449 unsigned char* view,
450 typename elfcpp::Elf_types<size>::Elf_Addr view_address,
451 section_size_type,
452 unsigned char* reloc_view,
453 section_size_type reloc_view_size)
455 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
456 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
457 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc_write
458 Reltype_write;
459 const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
460 const Address invalid_address = static_cast<Address>(0) - 1;
462 Sized_relobj<size, big_endian>* const object = relinfo->object;
463 const unsigned int local_count = object->local_symbol_count();
465 unsigned char* pwrite = reloc_view;
467 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
469 Relocatable_relocs::Reloc_strategy strategy = rr->strategy(i);
470 if (strategy == Relocatable_relocs::RELOC_DISCARD)
471 continue;
473 Reltype reloc(prelocs);
474 Reltype_write reloc_write(pwrite);
476 typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
477 const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
478 const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
480 // Get the new symbol index.
482 unsigned int new_symndx;
483 if (r_sym < local_count)
485 switch (strategy)
487 case Relocatable_relocs::RELOC_COPY:
488 new_symndx = object->symtab_index(r_sym);
489 gold_assert(new_symndx != -1U);
490 break;
492 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
493 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
494 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
495 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
496 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
497 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
499 // We are adjusting a section symbol. We need to find
500 // the symbol table index of the section symbol for
501 // the output section corresponding to input section
502 // in which this symbol is defined.
503 gold_assert(r_sym < local_count);
504 bool is_ordinary;
505 unsigned int shndx =
506 object->local_symbol_input_shndx(r_sym, &is_ordinary);
507 gold_assert(is_ordinary);
508 Output_section* os = object->output_section(shndx);
509 gold_assert(os != NULL);
510 gold_assert(os->needs_symtab_index());
511 new_symndx = os->symtab_index();
513 break;
515 default:
516 gold_unreachable();
519 else
521 const Symbol* gsym = object->global_symbol(r_sym);
522 gold_assert(gsym != NULL);
523 if (gsym->is_forwarder())
524 gsym = relinfo->symtab->resolve_forwards(gsym);
526 gold_assert(gsym->has_symtab_index());
527 new_symndx = gsym->symtab_index();
530 // Get the new offset--the location in the output section where
531 // this relocation should be applied.
533 Address offset = reloc.get_r_offset();
534 Address new_offset;
535 if (offset_in_output_section != invalid_address)
536 new_offset = offset + offset_in_output_section;
537 else
539 section_offset_type sot_offset =
540 convert_types<section_offset_type, Address>(offset);
541 section_offset_type new_sot_offset =
542 output_section->output_offset(object, relinfo->data_shndx,
543 sot_offset);
544 gold_assert(new_sot_offset != -1);
545 new_offset = new_sot_offset;
548 // In an object file, r_offset is an offset within the section.
549 // In an executable or dynamic object, generated by
550 // --emit-relocs, r_offset is an absolute address.
551 if (!parameters->options().relocatable())
553 new_offset += view_address;
554 if (offset_in_output_section != invalid_address)
555 new_offset -= offset_in_output_section;
558 reloc_write.put_r_offset(new_offset);
559 reloc_write.put_r_info(elfcpp::elf_r_info<size>(new_symndx, r_type));
561 // Handle the reloc addend based on the strategy.
563 if (strategy == Relocatable_relocs::RELOC_COPY)
565 if (sh_type == elfcpp::SHT_RELA)
566 Reloc_types<sh_type, size, big_endian>::
567 copy_reloc_addend(&reloc_write,
568 &reloc);
570 else
572 // The relocation uses a section symbol in the input file.
573 // We are adjusting it to use a section symbol in the output
574 // file. The input section symbol refers to some address in
575 // the input section. We need the relocation in the output
576 // file to refer to that same address. This adjustment to
577 // the addend is the same calculation we use for a simple
578 // absolute relocation for the input section symbol.
580 const Symbol_value<size>* psymval = object->local_symbol(r_sym);
582 unsigned char* padd = view + offset;
583 switch (strategy)
585 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
587 typename elfcpp::Elf_types<size>::Elf_Swxword addend;
588 addend = Reloc_types<sh_type, size, big_endian>::
589 get_reloc_addend(&reloc);
590 addend = psymval->value(object, addend);
591 Reloc_types<sh_type, size, big_endian>::
592 set_reloc_addend(&reloc_write, addend);
594 break;
596 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
597 break;
599 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
600 Relocate_functions<size, big_endian>::rel8(padd, object,
601 psymval);
602 break;
604 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
605 Relocate_functions<size, big_endian>::rel16(padd, object,
606 psymval);
607 break;
609 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
610 Relocate_functions<size, big_endian>::rel32(padd, object,
611 psymval);
612 break;
614 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
615 Relocate_functions<size, big_endian>::rel64(padd, object,
616 psymval);
617 break;
619 default:
620 gold_unreachable();
624 pwrite += reloc_size;
627 gold_assert(static_cast<section_size_type>(pwrite - reloc_view)
628 == reloc_view_size);
631 } // End namespace gold.
633 #endif // !defined(GOLD_TARGET_RELOC_H)