1 // target-reloc.h -- target specific relocation support -*- C++ -*-
3 // Copyright 2006, 2007, 2008, 2009, 2010 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
30 #include "reloc-types.h"
35 // This function implements the generic part of reloc scanning. The
36 // template parameter Scan must be a class type which provides two
37 // functions: local() and global(). Those functions implement the
38 // machine specific part of scanning. We do it this way to
39 // avoidmaking a function call for each relocation, and to avoid
40 // repeating the generic code for each target.
42 template<int size
, bool big_endian
, typename Target_type
, int sh_type
,
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(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(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 // RELOC_SYMBOL_CHANGES is used for -fsplit-stack support. If it is
167 // not NULL, it is a vector indexed by relocation index. If that
168 // entry is not NULL, it points to a global symbol which used as the
169 // symbol for the relocation, ignoring the symbol index in the
172 template<int size
, bool big_endian
, typename Target_type
, int sh_type
,
176 const Relocate_info
<size
, big_endian
>* relinfo
,
178 const unsigned char* prelocs
,
180 Output_section
* output_section
,
181 bool needs_special_offset_handling
,
183 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
184 section_size_type view_size
,
185 const Reloc_symbol_changes
* reloc_symbol_changes
)
187 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
188 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
191 Sized_relobj
<size
, big_endian
>* object
= relinfo
->object
;
192 unsigned int local_count
= object
->local_symbol_count();
194 Comdat_behavior comdat_behavior
= CB_UNDETERMINED
;
196 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
198 Reltype
reloc(prelocs
);
200 section_offset_type offset
=
201 convert_to_section_size_type(reloc
.get_r_offset());
203 if (needs_special_offset_handling
)
205 offset
= output_section
->output_offset(relinfo
->object
,
212 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
= reloc
.get_r_info();
213 unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
214 unsigned int r_type
= elfcpp::elf_r_type
<size
>(r_info
);
216 const Sized_symbol
<size
>* sym
;
218 Symbol_value
<size
> symval
;
219 const Symbol_value
<size
> *psymval
;
220 bool is_defined_in_discarded_section
;
222 if (r_sym
< local_count
223 && (reloc_symbol_changes
== NULL
224 || (*reloc_symbol_changes
)[i
] == NULL
))
227 psymval
= object
->local_symbol(r_sym
);
229 // If the local symbol belongs to a section we are discarding,
230 // and that section is a debug section, try to find the
231 // corresponding kept section and map this symbol to its
232 // counterpart in the kept section. The symbol must not
233 // correspond to a section we are folding.
235 shndx
= psymval
->input_shndx(&is_ordinary
);
236 is_defined_in_discarded_section
=
238 && shndx
!= elfcpp::SHN_UNDEF
239 && !object
->is_section_included(shndx
)
240 && !relinfo
->symtab
->is_section_folded(object
, shndx
));
245 if (reloc_symbol_changes
!= NULL
246 && (*reloc_symbol_changes
)[i
] != NULL
)
247 gsym
= (*reloc_symbol_changes
)[i
];
250 gsym
= object
->global_symbol(r_sym
);
251 gold_assert(gsym
!= NULL
);
252 if (gsym
->is_forwarder())
253 gsym
= relinfo
->symtab
->resolve_forwards(gsym
);
256 sym
= static_cast<const Sized_symbol
<size
>*>(gsym
);
257 if (sym
->has_symtab_index())
258 symval
.set_output_symtab_index(sym
->symtab_index());
260 symval
.set_no_output_symtab_entry();
261 symval
.set_output_value(sym
->value());
264 is_defined_in_discarded_section
=
265 (gsym
->is_defined_in_discarded_section()
266 && gsym
->is_undefined());
270 Symbol_value
<size
> symval2
;
271 if (is_defined_in_discarded_section
)
273 if (comdat_behavior
== CB_UNDETERMINED
)
275 std::string name
= object
->section_name(relinfo
->data_shndx
);
276 comdat_behavior
= get_comdat_behavior(name
.c_str());
278 if (comdat_behavior
== CB_PRETEND
)
280 // FIXME: This case does not work for global symbols.
281 // We have no place to store the original section index.
282 // Fortunately this does not matter for comdat sections,
283 // only for sections explicitly discarded by a linker
286 typename
elfcpp::Elf_types
<size
>::Elf_Addr value
=
287 object
->map_to_kept_section(shndx
, &found
);
289 symval2
.set_output_value(value
+ psymval
->input_value());
291 symval2
.set_output_value(0);
295 if (comdat_behavior
== CB_WARNING
)
296 gold_warning_at_location(relinfo
, i
, offset
,
297 _("relocation refers to discarded "
299 symval2
.set_output_value(0);
301 symval2
.set_no_output_symtab_entry();
305 if (!relocate
.relocate(relinfo
, target
, output_section
, i
, reloc
,
306 r_type
, sym
, psymval
, view
+ offset
,
307 view_address
+ offset
, view_size
))
310 if (offset
< 0 || static_cast<section_size_type
>(offset
) >= view_size
)
312 gold_error_at_location(relinfo
, i
, offset
,
313 _("reloc has bad offset %zu"),
314 static_cast<size_t>(offset
));
319 && sym
->is_undefined()
320 && sym
->binding() != elfcpp::STB_WEAK
321 && !is_defined_in_discarded_section
322 && !target
->is_defined_by_abi(sym
)
323 && (!parameters
->options().shared() // -shared
324 || parameters
->options().defs())) // -z defs
325 gold_undefined_symbol_at_location(sym
, relinfo
, i
, offset
);
327 if (sym
!= NULL
&& sym
->has_warning())
328 relinfo
->symtab
->issue_warning(sym
, relinfo
, i
, offset
);
332 // This class may be used as a typical class for the
333 // Scan_relocatable_reloc parameter to scan_relocatable_relocs. The
334 // template parameter Classify_reloc must be a class type which
335 // provides a function get_size_for_reloc which returns the number of
336 // bytes to which a reloc applies. This class is intended to capture
337 // the most typical target behaviour, while still permitting targets
338 // to define their own independent class for Scan_relocatable_reloc.
340 template<int sh_type
, typename Classify_reloc
>
341 class Default_scan_relocatable_relocs
344 // Return the strategy to use for a local symbol which is not a
345 // section symbol, given the relocation type.
346 inline Relocatable_relocs::Reloc_strategy
347 local_non_section_strategy(unsigned int r_type
, Relobj
*, unsigned int r_sym
)
349 // We assume that relocation type 0 is NONE. Targets which are
350 // different must override.
351 if (r_type
== 0 && r_sym
== 0)
352 return Relocatable_relocs::RELOC_DISCARD
;
353 return Relocatable_relocs::RELOC_COPY
;
356 // Return the strategy to use for a local symbol which is a section
357 // symbol, given the relocation type.
358 inline Relocatable_relocs::Reloc_strategy
359 local_section_strategy(unsigned int r_type
, Relobj
* object
)
361 if (sh_type
== elfcpp::SHT_RELA
)
362 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA
;
365 Classify_reloc classify
;
366 switch (classify
.get_size_for_reloc(r_type
, object
))
369 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0
;
371 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1
;
373 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2
;
375 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4
;
377 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8
;
384 // Return the strategy to use for a global symbol, given the
385 // relocation type, the object, and the symbol index.
386 inline Relocatable_relocs::Reloc_strategy
387 global_strategy(unsigned int, Relobj
*, unsigned int)
388 { return Relocatable_relocs::RELOC_COPY
; }
391 // Scan relocs during a relocatable link. This is a default
392 // definition which should work for most targets.
393 // Scan_relocatable_reloc must name a class type which provides three
394 // functions which return a Relocatable_relocs::Reloc_strategy code:
395 // global_strategy, local_non_section_strategy, and
396 // local_section_strategy. Most targets should be able to use
397 // Default_scan_relocatable_relocs as this class.
399 template<int size
, bool big_endian
, int sh_type
,
400 typename Scan_relocatable_reloc
>
402 scan_relocatable_relocs(
405 Sized_relobj
<size
, big_endian
>* object
,
406 unsigned int data_shndx
,
407 const unsigned char* prelocs
,
409 Output_section
* output_section
,
410 bool needs_special_offset_handling
,
411 size_t local_symbol_count
,
412 const unsigned char* plocal_syms
,
413 Relocatable_relocs
* rr
)
415 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
416 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
417 const int sym_size
= elfcpp::Elf_sizes
<size
>::sym_size
;
418 Scan_relocatable_reloc scan
;
420 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
422 Reltype
reloc(prelocs
);
424 Relocatable_relocs::Reloc_strategy strategy
;
426 if (needs_special_offset_handling
427 && !output_section
->is_input_address_mapped(object
, data_shndx
,
428 reloc
.get_r_offset()))
429 strategy
= Relocatable_relocs::RELOC_DISCARD
;
432 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
=
434 const unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
435 const unsigned int r_type
= elfcpp::elf_r_type
<size
>(r_info
);
437 if (r_sym
>= local_symbol_count
)
438 strategy
= scan
.global_strategy(r_type
, object
, r_sym
);
441 gold_assert(plocal_syms
!= NULL
);
442 typename
elfcpp::Sym
<size
, big_endian
> lsym(plocal_syms
444 unsigned int shndx
= lsym
.get_st_shndx();
446 shndx
= object
->adjust_sym_shndx(r_sym
, shndx
, &is_ordinary
);
448 && shndx
!= elfcpp::SHN_UNDEF
449 && !object
->is_section_included(shndx
))
451 // RELOC is a relocation against a local symbol
452 // defined in a section we are discarding. Discard
453 // the reloc. FIXME: Should we issue a warning?
454 strategy
= Relocatable_relocs::RELOC_DISCARD
;
456 else if (lsym
.get_st_type() != elfcpp::STT_SECTION
)
457 strategy
= scan
.local_non_section_strategy(r_type
, object
,
461 strategy
= scan
.local_section_strategy(r_type
, object
);
462 if (strategy
!= Relocatable_relocs::RELOC_DISCARD
)
463 object
->output_section(shndx
)->set_needs_symtab_index();
468 rr
->set_next_reloc_strategy(strategy
);
472 // Relocate relocs during a relocatable link. This is a default
473 // definition which should work for most targets.
475 template<int size
, bool big_endian
, int sh_type
>
477 relocate_for_relocatable(
478 const Relocate_info
<size
, big_endian
>* relinfo
,
479 const unsigned char* prelocs
,
481 Output_section
* output_section
,
482 typename
elfcpp::Elf_types
<size
>::Elf_Addr offset_in_output_section
,
483 const Relocatable_relocs
* rr
,
485 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
487 unsigned char* reloc_view
,
488 section_size_type reloc_view_size
)
490 typedef typename
elfcpp::Elf_types
<size
>::Elf_Addr Address
;
491 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
492 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc_write
494 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
495 const Address invalid_address
= static_cast<Address
>(0) - 1;
497 Sized_relobj
<size
, big_endian
>* const object
= relinfo
->object
;
498 const unsigned int local_count
= object
->local_symbol_count();
500 unsigned char* pwrite
= reloc_view
;
502 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
504 Relocatable_relocs::Reloc_strategy strategy
= rr
->strategy(i
);
505 if (strategy
== Relocatable_relocs::RELOC_DISCARD
)
508 Reltype
reloc(prelocs
);
509 Reltype_write
reloc_write(pwrite
);
511 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
= reloc
.get_r_info();
512 const unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
513 const unsigned int r_type
= elfcpp::elf_r_type
<size
>(r_info
);
515 // Get the new symbol index.
517 unsigned int new_symndx
;
518 if (r_sym
< local_count
)
522 case Relocatable_relocs::RELOC_COPY
:
527 new_symndx
= object
->symtab_index(r_sym
);
528 gold_assert(new_symndx
!= -1U);
532 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA
:
533 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0
:
534 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1
:
535 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2
:
536 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4
:
537 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8
:
539 // We are adjusting a section symbol. We need to find
540 // the symbol table index of the section symbol for
541 // the output section corresponding to input section
542 // in which this symbol is defined.
543 gold_assert(r_sym
< local_count
);
546 object
->local_symbol_input_shndx(r_sym
, &is_ordinary
);
547 gold_assert(is_ordinary
);
548 Output_section
* os
= object
->output_section(shndx
);
549 gold_assert(os
!= NULL
);
550 gold_assert(os
->needs_symtab_index());
551 new_symndx
= os
->symtab_index();
561 const Symbol
* gsym
= object
->global_symbol(r_sym
);
562 gold_assert(gsym
!= NULL
);
563 if (gsym
->is_forwarder())
564 gsym
= relinfo
->symtab
->resolve_forwards(gsym
);
566 gold_assert(gsym
->has_symtab_index());
567 new_symndx
= gsym
->symtab_index();
570 // Get the new offset--the location in the output section where
571 // this relocation should be applied.
573 Address offset
= reloc
.get_r_offset();
575 if (offset_in_output_section
!= invalid_address
)
576 new_offset
= offset
+ offset_in_output_section
;
579 section_offset_type sot_offset
=
580 convert_types
<section_offset_type
, Address
>(offset
);
581 section_offset_type new_sot_offset
=
582 output_section
->output_offset(object
, relinfo
->data_shndx
,
584 gold_assert(new_sot_offset
!= -1);
585 new_offset
= new_sot_offset
;
588 // In an object file, r_offset is an offset within the section.
589 // In an executable or dynamic object, generated by
590 // --emit-relocs, r_offset is an absolute address.
591 if (!parameters
->options().relocatable())
593 new_offset
+= view_address
;
594 if (offset_in_output_section
!= invalid_address
)
595 new_offset
-= offset_in_output_section
;
598 reloc_write
.put_r_offset(new_offset
);
599 reloc_write
.put_r_info(elfcpp::elf_r_info
<size
>(new_symndx
, r_type
));
601 // Handle the reloc addend based on the strategy.
603 if (strategy
== Relocatable_relocs::RELOC_COPY
)
605 if (sh_type
== elfcpp::SHT_RELA
)
606 Reloc_types
<sh_type
, size
, big_endian
>::
607 copy_reloc_addend(&reloc_write
,
612 // The relocation uses a section symbol in the input file.
613 // We are adjusting it to use a section symbol in the output
614 // file. The input section symbol refers to some address in
615 // the input section. We need the relocation in the output
616 // file to refer to that same address. This adjustment to
617 // the addend is the same calculation we use for a simple
618 // absolute relocation for the input section symbol.
620 const Symbol_value
<size
>* psymval
= object
->local_symbol(r_sym
);
622 unsigned char* padd
= view
+ offset
;
625 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA
:
627 typename
elfcpp::Elf_types
<size
>::Elf_Swxword addend
;
628 addend
= Reloc_types
<sh_type
, size
, big_endian
>::
629 get_reloc_addend(&reloc
);
630 addend
= psymval
->value(object
, addend
);
631 Reloc_types
<sh_type
, size
, big_endian
>::
632 set_reloc_addend(&reloc_write
, addend
);
636 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0
:
639 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1
:
640 Relocate_functions
<size
, big_endian
>::rel8(padd
, object
,
644 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2
:
645 Relocate_functions
<size
, big_endian
>::rel16(padd
, object
,
649 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4
:
650 Relocate_functions
<size
, big_endian
>::rel32(padd
, object
,
654 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8
:
655 Relocate_functions
<size
, big_endian
>::rel64(padd
, object
,
664 pwrite
+= reloc_size
;
667 gold_assert(static_cast<section_size_type
>(pwrite
- reloc_view
)
671 } // End namespace gold.
673 #endif // !defined(GOLD_TARGET_RELOC_H)