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 // This function implements the generic part of relocation processing.
123 // The template parameter Relocate must be a class type which provides
124 // a single function, relocate(), which implements the machine
125 // specific part of a relocation.
127 // SIZE is the ELF size: 32 or 64. BIG_ENDIAN is the endianness of
128 // the data. SH_TYPE is the section type: SHT_REL or SHT_RELA.
129 // RELOCATE implements operator() to do a relocation.
131 // PRELOCS points to the relocation data. RELOC_COUNT is the number
132 // of relocs. OUTPUT_SECTION is the output section.
133 // NEEDS_SPECIAL_OFFSET_HANDLING is true if input offsets need to be
134 // mapped to output offsets.
136 // VIEW is the section data, VIEW_ADDRESS is its memory address, and
137 // VIEW_SIZE is the size. These refer to the input section, unless
138 // NEEDS_SPECIAL_OFFSET_HANDLING is true, in which case they refer to
139 // the output section.
141 template<int size
, bool big_endian
, typename Target_type
, int sh_type
,
145 const Relocate_info
<size
, big_endian
>* relinfo
,
147 const unsigned char* prelocs
,
149 Output_section
* output_section
,
150 bool needs_special_offset_handling
,
152 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
153 section_size_type view_size
)
155 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
156 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
159 Sized_relobj
<size
, big_endian
>* object
= relinfo
->object
;
160 unsigned int local_count
= object
->local_symbol_count();
162 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
164 Reltype
reloc(prelocs
);
166 section_offset_type offset
=
167 convert_to_section_size_type(reloc
.get_r_offset());
169 if (needs_special_offset_handling
)
171 offset
= output_section
->output_offset(relinfo
->object
,
178 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
= reloc
.get_r_info();
179 unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
180 unsigned int r_type
= elfcpp::elf_r_type
<size
>(r_info
);
182 const Sized_symbol
<size
>* sym
;
184 Symbol_value
<size
> symval
;
185 const Symbol_value
<size
> *psymval
;
186 if (r_sym
< local_count
)
189 psymval
= object
->local_symbol(r_sym
);
193 const Symbol
* gsym
= object
->global_symbol(r_sym
);
194 gold_assert(gsym
!= NULL
);
195 if (gsym
->is_forwarder())
196 gsym
= relinfo
->symtab
->resolve_forwards(gsym
);
198 sym
= static_cast<const Sized_symbol
<size
>*>(gsym
);
199 if (sym
->has_symtab_index())
200 symval
.set_output_symtab_index(sym
->symtab_index());
202 symval
.set_no_output_symtab_entry();
203 symval
.set_output_value(sym
->value());
207 if (!relocate
.relocate(relinfo
, target
, i
, reloc
, r_type
, sym
, psymval
,
208 view
+ offset
, view_address
+ offset
, view_size
))
211 if (offset
< 0 || static_cast<section_size_type
>(offset
) >= view_size
)
213 gold_error_at_location(relinfo
, i
, offset
,
214 _("reloc has bad offset %zu"),
215 static_cast<size_t>(offset
));
220 && sym
->is_undefined()
221 && sym
->binding() != elfcpp::STB_WEAK
222 && (!parameters
->options().shared() // -shared
223 || parameters
->options().defs())) // -z defs
224 gold_undefined_symbol(sym
, relinfo
, i
, offset
);
226 if (sym
!= NULL
&& sym
->has_warning())
227 relinfo
->symtab
->issue_warning(sym
, relinfo
, i
, offset
);
231 // This class may be used as a typical class for the
232 // Scan_relocatable_reloc parameter to scan_relocatable_relocs. The
233 // template parameter Classify_reloc must be a class type which
234 // provides a function get_size_for_reloc which returns the number of
235 // bytes to which a reloc applies. This class is intended to capture
236 // the most typical target behaviour, while still permitting targets
237 // to define their own independent class for Scan_relocatable_reloc.
239 template<int sh_type
, typename Classify_reloc
>
240 class Default_scan_relocatable_relocs
243 // Return the strategy to use for a local symbol which is not a
244 // section symbol, given the relocation type.
245 inline Relocatable_relocs::Reloc_strategy
246 local_non_section_strategy(unsigned int, Relobj
*)
247 { return Relocatable_relocs::RELOC_COPY
; }
249 // Return the strategy to use for a local symbol which is a section
250 // symbol, given the relocation type.
251 inline Relocatable_relocs::Reloc_strategy
252 local_section_strategy(unsigned int r_type
, Relobj
* object
)
254 if (sh_type
== elfcpp::SHT_RELA
)
255 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA
;
258 Classify_reloc classify
;
259 switch (classify
.get_size_for_reloc(r_type
, object
))
262 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0
;
264 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1
;
266 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2
;
268 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4
;
270 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8
;
277 // Return the strategy to use for a global symbol, given the
278 // relocation type, the object, and the symbol index.
279 inline Relocatable_relocs::Reloc_strategy
280 global_strategy(unsigned int, Relobj
*, unsigned int)
281 { return Relocatable_relocs::RELOC_COPY
; }
284 // Scan relocs during a relocatable link. This is a default
285 // definition which should work for most targets.
286 // Scan_relocatable_reloc must name a class type which provides three
287 // functions which return a Relocatable_relocs::Reloc_strategy code:
288 // global_strategy, local_non_section_strategy, and
289 // local_section_strategy. Most targets should be able to use
290 // Default_scan_relocatable_relocs as this class.
292 template<int size
, bool big_endian
, int sh_type
,
293 typename Scan_relocatable_reloc
>
295 scan_relocatable_relocs(
296 const General_options
&,
299 Sized_relobj
<size
, big_endian
>* object
,
300 unsigned int data_shndx
,
301 const unsigned char* prelocs
,
303 Output_section
* output_section
,
304 bool needs_special_offset_handling
,
305 size_t local_symbol_count
,
306 const unsigned char* plocal_syms
,
307 Relocatable_relocs
* rr
)
309 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
310 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
311 const int sym_size
= elfcpp::Elf_sizes
<size
>::sym_size
;
312 Scan_relocatable_reloc scan
;
314 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
316 Reltype
reloc(prelocs
);
318 Relocatable_relocs::Reloc_strategy strategy
;
320 if (needs_special_offset_handling
321 && !output_section
->is_input_address_mapped(object
, data_shndx
,
322 reloc
.get_r_offset()))
323 strategy
= Relocatable_relocs::RELOC_DISCARD
;
326 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
=
328 const unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
329 const unsigned int r_type
= elfcpp::elf_r_type
<size
>(r_info
);
331 if (r_sym
>= local_symbol_count
)
332 strategy
= scan
.global_strategy(r_type
, object
, r_sym
);
335 gold_assert(plocal_syms
!= NULL
);
336 typename
elfcpp::Sym
<size
, big_endian
> lsym(plocal_syms
338 unsigned int shndx
= lsym
.get_st_shndx();
340 shndx
= object
->adjust_sym_shndx(r_sym
, shndx
, &is_ordinary
);
342 && shndx
!= elfcpp::SHN_UNDEF
343 && !object
->is_section_included(shndx
))
345 // RELOC is a relocation against a local symbol
346 // defined in a section we are discarding. Discard
347 // the reloc. FIXME: Should we issue a warning?
348 strategy
= Relocatable_relocs::RELOC_DISCARD
;
350 else if (lsym
.get_st_type() != elfcpp::STT_SECTION
)
351 strategy
= scan
.local_non_section_strategy(r_type
, object
);
354 strategy
= scan
.local_section_strategy(r_type
, object
);
355 if (strategy
!= Relocatable_relocs::RELOC_DISCARD
)
357 section_offset_type dummy
;
358 Output_section
* os
= object
->output_section(shndx
,
360 os
->set_needs_symtab_index();
366 rr
->set_next_reloc_strategy(strategy
);
370 // Relocate relocs during a relocatable link. This is a default
371 // definition which should work for most targets.
373 template<int size
, bool big_endian
, int sh_type
>
375 relocate_for_relocatable(
376 const Relocate_info
<size
, big_endian
>* relinfo
,
377 const unsigned char* prelocs
,
379 Output_section
* output_section
,
380 off_t offset_in_output_section
,
381 const Relocatable_relocs
* rr
,
383 typename
elfcpp::Elf_types
<size
>::Elf_Addr view_address
,
385 unsigned char* reloc_view
,
386 section_size_type reloc_view_size
)
388 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
389 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc_write
391 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
393 Sized_relobj
<size
, big_endian
>* const object
= relinfo
->object
;
394 const unsigned int local_count
= object
->local_symbol_count();
396 unsigned char* pwrite
= reloc_view
;
398 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
400 Relocatable_relocs::Reloc_strategy strategy
= rr
->strategy(i
);
401 if (strategy
== Relocatable_relocs::RELOC_DISCARD
)
404 Reltype
reloc(prelocs
);
405 Reltype_write
reloc_write(pwrite
);
407 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
= reloc
.get_r_info();
408 const unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
409 const unsigned int r_type
= elfcpp::elf_r_type
<size
>(r_info
);
411 // Get the new symbol index.
413 unsigned int new_symndx
;
414 if (r_sym
< local_count
)
418 case Relocatable_relocs::RELOC_COPY
:
419 new_symndx
= object
->symtab_index(r_sym
);
420 gold_assert(new_symndx
!= -1U);
423 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA
:
424 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0
:
425 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1
:
426 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2
:
427 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4
:
428 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8
:
430 // We are adjusting a section symbol. We need to find
431 // the symbol table index of the section symbol for
432 // the output section corresponding to input section
433 // in which this symbol is defined.
434 gold_assert(r_sym
< local_count
);
437 object
->local_symbol_input_shndx(r_sym
, &is_ordinary
);
438 gold_assert(is_ordinary
);
439 section_offset_type dummy
;
440 Output_section
* os
= object
->output_section(shndx
, &dummy
);
441 gold_assert(os
!= NULL
);
442 gold_assert(os
->needs_symtab_index());
443 new_symndx
= os
->symtab_index();
453 const Symbol
* gsym
= object
->global_symbol(r_sym
);
454 gold_assert(gsym
!= NULL
);
455 if (gsym
->is_forwarder())
456 gsym
= relinfo
->symtab
->resolve_forwards(gsym
);
458 gold_assert(gsym
->has_symtab_index());
459 new_symndx
= gsym
->symtab_index();
462 // Get the new offset--the location in the output section where
463 // this relocation should be applied.
465 off_t offset
= reloc
.get_r_offset();
467 if (offset_in_output_section
!= -1)
468 new_offset
= offset
+ offset_in_output_section
;
471 new_offset
= output_section
->output_offset(object
,
474 gold_assert(new_offset
!= -1);
477 // In an object file, r_offset is an offset within the section.
478 // In an executable or dynamic object, generated by
479 // --emit-relocs, r_offset is an absolute address.
480 if (!parameters
->options().relocatable())
481 new_offset
+= view_address
;
483 reloc_write
.put_r_offset(new_offset
);
484 reloc_write
.put_r_info(elfcpp::elf_r_info
<size
>(new_symndx
, r_type
));
486 // Handle the reloc addend based on the strategy.
488 if (strategy
== Relocatable_relocs::RELOC_COPY
)
490 if (sh_type
== elfcpp::SHT_RELA
)
491 Reloc_types
<sh_type
, size
, big_endian
>::
492 copy_reloc_addend(&reloc_write
,
497 // The relocation uses a section symbol in the input file.
498 // We are adjusting it to use a section symbol in the output
499 // file. The input section symbol refers to some address in
500 // the input section. We need the relocation in the output
501 // file to refer to that same address. This adjustment to
502 // the addend is the same calculation we use for a simple
503 // absolute relocation for the input section symbol.
505 const Symbol_value
<size
>* psymval
= object
->local_symbol(r_sym
);
507 unsigned char* padd
= view
+ offset
;
510 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA
:
512 typename
elfcpp::Elf_types
<size
>::Elf_Swxword addend
;
513 addend
= Reloc_types
<sh_type
, size
, big_endian
>::
514 get_reloc_addend(&reloc
);
515 addend
= psymval
->value(object
, addend
);
516 Reloc_types
<sh_type
, size
, big_endian
>::
517 set_reloc_addend(&reloc_write
, addend
);
521 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0
:
524 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1
:
525 Relocate_functions
<size
, big_endian
>::rel8(padd
, object
,
529 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2
:
530 Relocate_functions
<size
, big_endian
>::rel16(padd
, object
,
534 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4
:
535 Relocate_functions
<size
, big_endian
>::rel32(padd
, object
,
539 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8
:
540 Relocate_functions
<size
, big_endian
>::rel64(padd
, object
,
549 pwrite
+= reloc_size
;
552 gold_assert(static_cast<section_size_type
>(pwrite
- reloc_view
)
556 } // End namespace gold.
558 #endif // !defined(GOLD_TARGET_RELOC_H)