1 // resolve.cc -- symbol resolution for gold
3 // Copyright 2006, 2007 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.
33 // Symbol methods used in this file.
35 // Override the fields in Symbol.
37 template<int size
, bool big_endian
>
39 Symbol::override_base(const elfcpp::Sym
<size
, big_endian
>& sym
,
40 Object
* object
, const char* version
)
42 gold_assert(this->source_
== FROM_OBJECT
);
43 this->u_
.from_object
.object
= object
;
44 if (version
!= NULL
&& this->version() != version
)
46 gold_assert(this->version() == NULL
);
47 this->version_
= version
;
49 // FIXME: Handle SHN_XINDEX.
50 this->u_
.from_object
.shndx
= sym
.get_st_shndx();
51 this->type_
= sym
.get_st_type();
52 this->binding_
= sym
.get_st_bind();
53 this->visibility_
= sym
.get_st_visibility();
54 this->nonvis_
= sym
.get_st_nonvis();
55 if (object
->is_dynamic())
61 // Override the fields in Sized_symbol.
64 template<bool big_endian
>
66 Sized_symbol
<size
>::override(const elfcpp::Sym
<size
, big_endian
>& sym
,
67 Object
* object
, const char* version
)
69 this->override_base(sym
, object
, version
);
70 this->value_
= sym
.get_st_value();
71 this->symsize_
= sym
.get_st_size();
74 // The resolve functions build a little code for each symbol.
75 // Bit 0: 0 for global, 1 for weak.
76 // Bit 1: 0 for regular object, 1 for shared object
77 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
78 // This gives us values from 0 to 11.
80 static const int global_or_weak_shift
= 0;
81 static const unsigned int global_flag
= 0 << global_or_weak_shift
;
82 static const unsigned int weak_flag
= 1 << global_or_weak_shift
;
84 static const int regular_or_dynamic_shift
= 1;
85 static const unsigned int regular_flag
= 0 << regular_or_dynamic_shift
;
86 static const unsigned int dynamic_flag
= 1 << regular_or_dynamic_shift
;
88 static const int def_undef_or_common_shift
= 2;
89 static const unsigned int def_flag
= 0 << def_undef_or_common_shift
;
90 static const unsigned int undef_flag
= 1 << def_undef_or_common_shift
;
91 static const unsigned int common_flag
= 2 << def_undef_or_common_shift
;
93 // Resolve a symbol. This is called the second and subsequent times
94 // we see a symbol. TO is the pre-existing symbol. SYM is the new
95 // symbol, seen in OBJECT. VERSION of the version of SYM.
97 template<int size
, bool big_endian
>
99 Symbol_table::resolve(Sized_symbol
<size
>* to
,
100 const elfcpp::Sym
<size
, big_endian
>& sym
,
101 Object
* object
, const char* version
)
103 if (object
->target()->has_resolve())
105 Sized_target
<size
, big_endian
>* sized_target
;
106 sized_target
= object
->sized_target
107 SELECT_SIZE_ENDIAN_NAME(size
, big_endian
) (
108 SELECT_SIZE_ENDIAN_ONLY(size
, big_endian
));
109 sized_target
->resolve(to
, sym
, object
, version
);
113 if (!object
->is_dynamic())
115 // Record that we've seen this symbol in a regular object.
120 // Record that we've seen this symbol in a dynamic object.
124 unsigned int frombits
;
125 switch (sym
.get_st_bind())
127 case elfcpp::STB_GLOBAL
:
128 frombits
= global_flag
;
131 case elfcpp::STB_WEAK
:
132 frombits
= weak_flag
;
135 case elfcpp::STB_LOCAL
:
136 gold_error(_("%s: invalid STB_LOCAL symbol %s in external symbols"),
137 object
->name().c_str(), to
->name());
138 frombits
= global_flag
;
142 gold_error(_("%s: unsupported symbol binding %d for symbol %s"),
143 object
->name().c_str(),
144 static_cast<int>(sym
.get_st_bind()), to
->name());
145 frombits
= global_flag
;
149 if (!object
->is_dynamic())
150 frombits
|= regular_flag
;
152 frombits
|= dynamic_flag
;
154 switch (sym
.get_st_shndx())
156 case elfcpp::SHN_UNDEF
:
157 frombits
|= undef_flag
;
160 case elfcpp::SHN_COMMON
:
161 frombits
|= common_flag
;
165 if (sym
.get_st_type() == elfcpp::STT_COMMON
)
166 frombits
|= common_flag
;
168 frombits
|= def_flag
;
172 bool adjust_common_sizes
;
173 if (Symbol_table::should_override(to
, frombits
, &adjust_common_sizes
))
175 typename Sized_symbol
<size
>::Size_type tosize
= to
->symsize();
177 to
->override(sym
, object
, version
);
179 if (adjust_common_sizes
&& tosize
> to
->symsize())
180 to
->set_symsize(tosize
);
184 if (adjust_common_sizes
&& sym
.get_st_size() > to
->symsize())
185 to
->set_symsize(sym
.get_st_size());
189 // Handle the core of symbol resolution. This is called with the
190 // existing symbol, TO, and a bitflag describing the new symbol. This
191 // returns true if we should override the existing symbol with the new
192 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to
193 // true if we should set the symbol size to the maximum of the TO and
194 // FROM sizes. It handles error conditions.
197 Symbol_table::should_override(const Symbol
* to
, unsigned int frombits
,
198 bool* adjust_common_sizes
)
200 *adjust_common_sizes
= false;
203 switch (to
->binding())
205 case elfcpp::STB_GLOBAL
:
206 tobits
= global_flag
;
209 case elfcpp::STB_WEAK
:
213 case elfcpp::STB_LOCAL
:
214 // We should only see externally visible symbols in the symbol
219 // Any target which wants to handle STB_LOOS, etc., needs to
220 // define a resolve method.
224 if (to
->source() == Symbol::FROM_OBJECT
225 && to
->object()->is_dynamic())
226 tobits
|= dynamic_flag
;
228 tobits
|= regular_flag
;
232 case elfcpp::SHN_UNDEF
:
233 tobits
|= undef_flag
;
236 case elfcpp::SHN_COMMON
:
237 tobits
|= common_flag
;
241 if (to
->type() == elfcpp::STT_COMMON
)
242 tobits
|= common_flag
;
248 // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
250 // We use a giant switch table for symbol resolution. This code is
251 // unwieldy, but: 1) it is efficient; 2) we definitely handle all
252 // cases; 3) it is easy to change the handling of a particular case.
253 // The alternative would be a series of conditionals, but it is easy
254 // to get the ordering wrong. This could also be done as a table,
255 // but that is no easier to understand than this large switch
258 // These are the values generated by the bit codes.
261 DEF
= global_flag
| regular_flag
| def_flag
,
262 WEAK_DEF
= weak_flag
| regular_flag
| def_flag
,
263 DYN_DEF
= global_flag
| dynamic_flag
| def_flag
,
264 DYN_WEAK_DEF
= weak_flag
| dynamic_flag
| def_flag
,
265 UNDEF
= global_flag
| regular_flag
| undef_flag
,
266 WEAK_UNDEF
= weak_flag
| regular_flag
| undef_flag
,
267 DYN_UNDEF
= global_flag
| dynamic_flag
| undef_flag
,
268 DYN_WEAK_UNDEF
= weak_flag
| dynamic_flag
| undef_flag
,
269 COMMON
= global_flag
| regular_flag
| common_flag
,
270 WEAK_COMMON
= weak_flag
| regular_flag
| common_flag
,
271 DYN_COMMON
= global_flag
| dynamic_flag
| common_flag
,
272 DYN_WEAK_COMMON
= weak_flag
| dynamic_flag
| common_flag
275 switch (tobits
* 16 + frombits
)
278 // Two definitions of the same symbol.
279 // FIXME: Report locations.
280 gold_error(_("multiple definition of %s"), to
->name());
283 case WEAK_DEF
* 16 + DEF
:
284 // We've seen a weak definition, and now we see a strong
285 // definition. In the original SVR4 linker, this was treated as
286 // a multiple definition error. In the Solaris linker and the
287 // GNU linker, a weak definition followed by a regular
288 // definition causes the weak definition to be overridden. We
289 // are currently compatible with the GNU linker. In the future
290 // we should add a target specific option to change this.
294 case DYN_DEF
* 16 + DEF
:
295 case DYN_WEAK_DEF
* 16 + DEF
:
296 // We've seen a definition in a dynamic object, and now we see a
297 // definition in a regular object. The definition in the
298 // regular object overrides the definition in the dynamic
302 case UNDEF
* 16 + DEF
:
303 case WEAK_UNDEF
* 16 + DEF
:
304 case DYN_UNDEF
* 16 + DEF
:
305 case DYN_WEAK_UNDEF
* 16 + DEF
:
306 // We've seen an undefined reference, and now we see a
307 // definition. We use the definition.
310 case COMMON
* 16 + DEF
:
311 case WEAK_COMMON
* 16 + DEF
:
312 case DYN_COMMON
* 16 + DEF
:
313 case DYN_WEAK_COMMON
* 16 + DEF
:
314 // We've seen a common symbol and now we see a definition. The
315 // definition overrides. FIXME: We should optionally issue, version a
319 case DEF
* 16 + WEAK_DEF
:
320 case WEAK_DEF
* 16 + WEAK_DEF
:
321 // We've seen a definition and now we see a weak definition. We
322 // ignore the new weak definition.
325 case DYN_DEF
* 16 + WEAK_DEF
:
326 case DYN_WEAK_DEF
* 16 + WEAK_DEF
:
327 // We've seen a dynamic definition and now we see a regular weak
328 // definition. The regular weak definition overrides.
331 case UNDEF
* 16 + WEAK_DEF
:
332 case WEAK_UNDEF
* 16 + WEAK_DEF
:
333 case DYN_UNDEF
* 16 + WEAK_DEF
:
334 case DYN_WEAK_UNDEF
* 16 + WEAK_DEF
:
335 // A weak definition of a currently undefined symbol.
338 case COMMON
* 16 + WEAK_DEF
:
339 case WEAK_COMMON
* 16 + WEAK_DEF
:
340 // A weak definition does not override a common definition.
343 case DYN_COMMON
* 16 + WEAK_DEF
:
344 case DYN_WEAK_COMMON
* 16 + WEAK_DEF
:
345 // A weak definition does override a definition in a dynamic
346 // object. FIXME: We should optionally issue a warning.
349 case DEF
* 16 + DYN_DEF
:
350 case WEAK_DEF
* 16 + DYN_DEF
:
351 case DYN_DEF
* 16 + DYN_DEF
:
352 case DYN_WEAK_DEF
* 16 + DYN_DEF
:
353 // Ignore a dynamic definition if we already have a definition.
356 case UNDEF
* 16 + DYN_DEF
:
357 case WEAK_UNDEF
* 16 + DYN_DEF
:
358 case DYN_UNDEF
* 16 + DYN_DEF
:
359 case DYN_WEAK_UNDEF
* 16 + DYN_DEF
:
360 // Use a dynamic definition if we have a reference.
363 case COMMON
* 16 + DYN_DEF
:
364 case WEAK_COMMON
* 16 + DYN_DEF
:
365 case DYN_COMMON
* 16 + DYN_DEF
:
366 case DYN_WEAK_COMMON
* 16 + DYN_DEF
:
367 // Ignore a dynamic definition if we already have a common
371 case DEF
* 16 + DYN_WEAK_DEF
:
372 case WEAK_DEF
* 16 + DYN_WEAK_DEF
:
373 case DYN_DEF
* 16 + DYN_WEAK_DEF
:
374 case DYN_WEAK_DEF
* 16 + DYN_WEAK_DEF
:
375 // Ignore a weak dynamic definition if we already have a
379 case UNDEF
* 16 + DYN_WEAK_DEF
:
380 case WEAK_UNDEF
* 16 + DYN_WEAK_DEF
:
381 case DYN_UNDEF
* 16 + DYN_WEAK_DEF
:
382 case DYN_WEAK_UNDEF
* 16 + DYN_WEAK_DEF
:
383 // Use a weak dynamic definition if we have a reference.
386 case COMMON
* 16 + DYN_WEAK_DEF
:
387 case WEAK_COMMON
* 16 + DYN_WEAK_DEF
:
388 case DYN_COMMON
* 16 + DYN_WEAK_DEF
:
389 case DYN_WEAK_COMMON
* 16 + DYN_WEAK_DEF
:
390 // Ignore a weak dynamic definition if we already have a common
394 case DEF
* 16 + UNDEF
:
395 case WEAK_DEF
* 16 + UNDEF
:
396 case DYN_DEF
* 16 + UNDEF
:
397 case DYN_WEAK_DEF
* 16 + UNDEF
:
398 case UNDEF
* 16 + UNDEF
:
399 // A new undefined reference tells us nothing.
402 case WEAK_UNDEF
* 16 + UNDEF
:
403 case DYN_UNDEF
* 16 + UNDEF
:
404 case DYN_WEAK_UNDEF
* 16 + UNDEF
:
405 // A strong undef overrides a dynamic or weak undef.
408 case COMMON
* 16 + UNDEF
:
409 case WEAK_COMMON
* 16 + UNDEF
:
410 case DYN_COMMON
* 16 + UNDEF
:
411 case DYN_WEAK_COMMON
* 16 + UNDEF
:
412 // A new undefined reference tells us nothing.
415 case DEF
* 16 + WEAK_UNDEF
:
416 case WEAK_DEF
* 16 + WEAK_UNDEF
:
417 case DYN_DEF
* 16 + WEAK_UNDEF
:
418 case DYN_WEAK_DEF
* 16 + WEAK_UNDEF
:
419 case UNDEF
* 16 + WEAK_UNDEF
:
420 case WEAK_UNDEF
* 16 + WEAK_UNDEF
:
421 case DYN_UNDEF
* 16 + WEAK_UNDEF
:
422 case DYN_WEAK_UNDEF
* 16 + WEAK_UNDEF
:
423 case COMMON
* 16 + WEAK_UNDEF
:
424 case WEAK_COMMON
* 16 + WEAK_UNDEF
:
425 case DYN_COMMON
* 16 + WEAK_UNDEF
:
426 case DYN_WEAK_COMMON
* 16 + WEAK_UNDEF
:
427 // A new weak undefined reference tells us nothing.
430 case DEF
* 16 + DYN_UNDEF
:
431 case WEAK_DEF
* 16 + DYN_UNDEF
:
432 case DYN_DEF
* 16 + DYN_UNDEF
:
433 case DYN_WEAK_DEF
* 16 + DYN_UNDEF
:
434 case UNDEF
* 16 + DYN_UNDEF
:
435 case WEAK_UNDEF
* 16 + DYN_UNDEF
:
436 case DYN_UNDEF
* 16 + DYN_UNDEF
:
437 case DYN_WEAK_UNDEF
* 16 + DYN_UNDEF
:
438 case COMMON
* 16 + DYN_UNDEF
:
439 case WEAK_COMMON
* 16 + DYN_UNDEF
:
440 case DYN_COMMON
* 16 + DYN_UNDEF
:
441 case DYN_WEAK_COMMON
* 16 + DYN_UNDEF
:
442 // A new dynamic undefined reference tells us nothing.
445 case DEF
* 16 + DYN_WEAK_UNDEF
:
446 case WEAK_DEF
* 16 + DYN_WEAK_UNDEF
:
447 case DYN_DEF
* 16 + DYN_WEAK_UNDEF
:
448 case DYN_WEAK_DEF
* 16 + DYN_WEAK_UNDEF
:
449 case UNDEF
* 16 + DYN_WEAK_UNDEF
:
450 case WEAK_UNDEF
* 16 + DYN_WEAK_UNDEF
:
451 case DYN_UNDEF
* 16 + DYN_WEAK_UNDEF
:
452 case DYN_WEAK_UNDEF
* 16 + DYN_WEAK_UNDEF
:
453 case COMMON
* 16 + DYN_WEAK_UNDEF
:
454 case WEAK_COMMON
* 16 + DYN_WEAK_UNDEF
:
455 case DYN_COMMON
* 16 + DYN_WEAK_UNDEF
:
456 case DYN_WEAK_COMMON
* 16 + DYN_WEAK_UNDEF
:
457 // A new weak dynamic undefined reference tells us nothing.
460 case DEF
* 16 + COMMON
:
461 // A common symbol does not override a definition.
464 case WEAK_DEF
* 16 + COMMON
:
465 case DYN_DEF
* 16 + COMMON
:
466 case DYN_WEAK_DEF
* 16 + COMMON
:
467 // A common symbol does override a weak definition or a dynamic
471 case UNDEF
* 16 + COMMON
:
472 case WEAK_UNDEF
* 16 + COMMON
:
473 case DYN_UNDEF
* 16 + COMMON
:
474 case DYN_WEAK_UNDEF
* 16 + COMMON
:
475 // A common symbol is a definition for a reference.
478 case COMMON
* 16 + COMMON
:
479 // Set the size to the maximum.
480 *adjust_common_sizes
= true;
483 case WEAK_COMMON
* 16 + COMMON
:
484 // I'm not sure just what a weak common symbol means, but
485 // presumably it can be overridden by a regular common symbol.
488 case DYN_COMMON
* 16 + COMMON
:
489 case DYN_WEAK_COMMON
* 16 + COMMON
:
490 // Use the real common symbol, but adjust the size if necessary.
491 *adjust_common_sizes
= true;
494 case DEF
* 16 + WEAK_COMMON
:
495 case WEAK_DEF
* 16 + WEAK_COMMON
:
496 case DYN_DEF
* 16 + WEAK_COMMON
:
497 case DYN_WEAK_DEF
* 16 + WEAK_COMMON
:
498 // Whatever a weak common symbol is, it won't override a
502 case UNDEF
* 16 + WEAK_COMMON
:
503 case WEAK_UNDEF
* 16 + WEAK_COMMON
:
504 case DYN_UNDEF
* 16 + WEAK_COMMON
:
505 case DYN_WEAK_UNDEF
* 16 + WEAK_COMMON
:
506 // A weak common symbol is better than an undefined symbol.
509 case COMMON
* 16 + WEAK_COMMON
:
510 case WEAK_COMMON
* 16 + WEAK_COMMON
:
511 case DYN_COMMON
* 16 + WEAK_COMMON
:
512 case DYN_WEAK_COMMON
* 16 + WEAK_COMMON
:
513 // Ignore a weak common symbol in the presence of a real common
517 case DEF
* 16 + DYN_COMMON
:
518 case WEAK_DEF
* 16 + DYN_COMMON
:
519 case DYN_DEF
* 16 + DYN_COMMON
:
520 case DYN_WEAK_DEF
* 16 + DYN_COMMON
:
521 // Ignore a dynamic common symbol in the presence of a
525 case UNDEF
* 16 + DYN_COMMON
:
526 case WEAK_UNDEF
* 16 + DYN_COMMON
:
527 case DYN_UNDEF
* 16 + DYN_COMMON
:
528 case DYN_WEAK_UNDEF
* 16 + DYN_COMMON
:
529 // A dynamic common symbol is a definition of sorts.
532 case COMMON
* 16 + DYN_COMMON
:
533 case WEAK_COMMON
* 16 + DYN_COMMON
:
534 case DYN_COMMON
* 16 + DYN_COMMON
:
535 case DYN_WEAK_COMMON
* 16 + DYN_COMMON
:
536 // Set the size to the maximum.
537 *adjust_common_sizes
= true;
540 case DEF
* 16 + DYN_WEAK_COMMON
:
541 case WEAK_DEF
* 16 + DYN_WEAK_COMMON
:
542 case DYN_DEF
* 16 + DYN_WEAK_COMMON
:
543 case DYN_WEAK_DEF
* 16 + DYN_WEAK_COMMON
:
544 // A common symbol is ignored in the face of a definition.
547 case UNDEF
* 16 + DYN_WEAK_COMMON
:
548 case WEAK_UNDEF
* 16 + DYN_WEAK_COMMON
:
549 case DYN_UNDEF
* 16 + DYN_WEAK_COMMON
:
550 case DYN_WEAK_UNDEF
* 16 + DYN_WEAK_COMMON
:
551 // I guess a weak common symbol is better than a definition.
554 case COMMON
* 16 + DYN_WEAK_COMMON
:
555 case WEAK_COMMON
* 16 + DYN_WEAK_COMMON
:
556 case DYN_COMMON
* 16 + DYN_WEAK_COMMON
:
557 case DYN_WEAK_COMMON
* 16 + DYN_WEAK_COMMON
:
558 // Set the size to the maximum.
559 *adjust_common_sizes
= true;
567 // A special case of should_override which is only called for a strong
568 // defined symbol from a regular object file. This is used when
569 // defining special symbols.
572 Symbol_table::should_override_with_special(const Symbol
* to
)
574 bool adjust_common_sizes
;
575 unsigned int frombits
= global_flag
| regular_flag
| def_flag
;
576 bool ret
= Symbol_table::should_override(to
, frombits
, &adjust_common_sizes
);
577 gold_assert(!adjust_common_sizes
);
581 // Override symbol base with a special symbol.
584 Symbol::override_base_with_special(const Symbol
* from
)
586 this->source_
= from
->source_
;
587 switch (from
->source_
)
590 this->u_
.from_object
= from
->u_
.from_object
;
593 this->u_
.in_output_data
= from
->u_
.in_output_data
;
595 case IN_OUTPUT_SEGMENT
:
596 this->u_
.in_output_segment
= from
->u_
.in_output_segment
;
605 if (from
->version_
!= NULL
&& this->version_
!= from
->version_
)
607 gold_assert(this->version_
== NULL
);
608 this->version_
= from
->version_
;
611 this->type_
= from
->type_
;
612 this->binding_
= from
->binding_
;
613 this->visibility_
= from
->visibility_
;
614 this->nonvis_
= from
->nonvis_
;
616 // Special symbols are always considered to be regular symbols.
617 this->in_reg_
= true;
620 // Override a symbol with a special symbol.
624 Sized_symbol
<size
>::override_with_special(const Sized_symbol
<size
>* from
)
626 this->override_base_with_special(from
);
627 this->value_
= from
->value_
;
628 this->symsize_
= from
->symsize_
;
631 // Instantiate the templates we need. We could use the configure
632 // script to restrict this to only the ones needed for implemented
635 #ifdef HAVE_TARGET_32_LITTLE
638 Symbol_table::resolve
<32, false>(
639 Sized_symbol
<32>* to
,
640 const elfcpp::Sym
<32, false>& sym
,
642 const char* version
);
645 #ifdef HAVE_TARGET_32_BIG
648 Symbol_table::resolve
<32, true>(
649 Sized_symbol
<32>* to
,
650 const elfcpp::Sym
<32, true>& sym
,
652 const char* version
);
655 #ifdef HAVE_TARGET_64_LITTLE
658 Symbol_table::resolve
<64, false>(
659 Sized_symbol
<64>* to
,
660 const elfcpp::Sym
<64, false>& sym
,
662 const char* version
);
665 #ifdef HAVE_TARGET_64_BIG
668 Symbol_table::resolve
<64, true>(
669 Sized_symbol
<64>* to
,
670 const elfcpp::Sym
<64, true>& sym
,
672 const char* version
);
675 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
678 Sized_symbol
<32>::override_with_special(const Sized_symbol
<32>*);
681 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
684 Sized_symbol
<64>::override_with_special(const Sized_symbol
<64>*);
687 } // End namespace gold.