1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
|
// resolve.cc -- symbol resolution for gold
#include "gold.h"
#include "elfcpp.h"
#include "target.h"
#include "object.h"
#include "symtab.h"
namespace gold
{
// Symbol methods used in this file.
// Override the fields in Symbol.
template<int size, bool big_endian>
void
Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
Object* object, const char* version)
{
gold_assert(this->source_ == FROM_OBJECT);
this->u_.from_object.object = object;
if (version != NULL && this->version() != version)
{
gold_assert(this->version() == NULL);
this->version_ = version;
}
// FIXME: Handle SHN_XINDEX.
this->u_.from_object.shndx = sym.get_st_shndx();
this->type_ = sym.get_st_type();
this->binding_ = sym.get_st_bind();
this->visibility_ = sym.get_st_visibility();
this->nonvis_ = sym.get_st_nonvis();
if (object->is_dynamic())
this->in_dyn_ = true;
else
this->in_reg_ = true;
}
// Override the fields in Sized_symbol.
template<int size>
template<bool big_endian>
void
Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
Object* object, const char* version)
{
this->override_base(sym, object, version);
this->value_ = sym.get_st_value();
this->symsize_ = sym.get_st_size();
}
// Resolve a symbol. This is called the second and subsequent times
// we see a symbol. TO is the pre-existing symbol. SYM is the new
// symbol, seen in OBJECT. VERSION of the version of SYM.
template<int size, bool big_endian>
void
Symbol_table::resolve(Sized_symbol<size>* to,
const elfcpp::Sym<size, big_endian>& sym,
Object* object, const char* version)
{
if (object->target()->has_resolve())
{
Sized_target<size, big_endian>* sized_target;
sized_target = object->sized_target
SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
sized_target->resolve(to, sym, object, version);
return;
}
// Build a little code for each symbol.
// Bit 0: 0 for global, 1 for weak.
// Bit 1: 0 for regular object, 1 for shared object
// Bits 2-3: 0 for normal, 1 for undefined, 2 for common
// This gives us values from 0 to 11:
enum
{
DEF = 0,
WEAK_DEF = 1,
DYN_DEF = 2,
DYN_WEAK_DEF = 3,
UNDEF = 4,
WEAK_UNDEF = 5,
DYN_UNDEF = 6,
DYN_WEAK_UNDEF = 7,
COMMON = 8,
WEAK_COMMON = 9,
DYN_COMMON = 10,
DYN_WEAK_COMMON = 11
};
int tobits;
switch (to->binding())
{
case elfcpp::STB_GLOBAL:
tobits = 0;
break;
case elfcpp::STB_WEAK:
tobits = 1;
break;
case elfcpp::STB_LOCAL:
// We should only see externally visible symbols in the symbol
// table.
gold_unreachable();
default:
// Any target which wants to handle STB_LOOS, etc., needs to
// define a resolve method.
gold_unreachable();
}
if (to->source() == Symbol::FROM_OBJECT
&& to->object()->is_dynamic())
tobits |= (1 << 1);
switch (to->shndx())
{
case elfcpp::SHN_UNDEF:
tobits |= (1 << 2);
break;
case elfcpp::SHN_COMMON:
tobits |= (2 << 2);
break;
default:
if (to->type() == elfcpp::STT_COMMON)
tobits |= (2 << 2);
break;
}
int frombits;
switch (sym.get_st_bind())
{
case elfcpp::STB_GLOBAL:
frombits = 0;
break;
case elfcpp::STB_WEAK:
frombits = 1;
break;
case elfcpp::STB_LOCAL:
fprintf(stderr,
_("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
program_name, object->name().c_str(), to->name());
gold_exit(false);
default:
fprintf(stderr,
_("%s: %s: unsupported symbol binding %d for symbol %s\n"),
program_name, object->name().c_str(),
static_cast<int>(sym.get_st_bind()), to->name());
gold_exit(false);
}
if (!object->is_dynamic())
{
// Record that we've seen this symbol in a regular object.
to->set_in_reg();
}
else
{
frombits |= (1 << 1);
// Record that we've seen this symbol in a dynamic object.
to->set_in_dyn();
}
switch (sym.get_st_shndx())
{
case elfcpp::SHN_UNDEF:
frombits |= (1 << 2);
break;
case elfcpp::SHN_COMMON:
frombits |= (2 << 2);
break;
default:
if (sym.get_st_type() == elfcpp::STT_COMMON)
frombits |= (2 << 2);
break;
}
if ((tobits & (1 << 1)) != (frombits & (1 << 1)))
{
// This symbol is seen in both a dynamic object and a regular
// object. That means that we need the symbol to go into the
// dynamic symbol table, so that the dynamic linker can use the
// regular symbol to override or define the dynamic symbol.
to->set_needs_dynsym_entry();
}
// FIXME: Warn if either but not both of TO and SYM are STT_TLS.
// We use a giant switch table for symbol resolution. This code is
// unwieldy, but: 1) it is efficient; 2) we definitely handle all
// cases; 3) it is easy to change the handling of a particular case.
// The alternative would be a series of conditionals, but it is easy
// to get the ordering wrong. This could also be done as a table,
// but that is no easier to understand than this large switch
// statement.
switch (tobits * 16 + frombits)
{
case DEF * 16 + DEF:
// Two definitions of the same symbol.
fprintf(stderr, "%s: %s: multiple definition of %s\n",
program_name, object->name().c_str(), to->name());
// FIXME: Report locations. Record that we have seen an error.
return;
case WEAK_DEF * 16 + DEF:
// We've seen a weak definition, and now we see a strong
// definition. In the original SVR4 linker, this was treated as
// a multiple definition error. In the Solaris linker and the
// GNU linker, a weak definition followed by a regular
// definition causes the weak definition to be overridden. We
// are currently compatible with the GNU linker. In the future
// we should add a target specific option to change this.
// FIXME.
to->override(sym, object, version);
return;
case DYN_DEF * 16 + DEF:
case DYN_WEAK_DEF * 16 + DEF:
// We've seen a definition in a dynamic object, and now we see a
// definition in a regular object. The definition in the
// regular object overrides the definition in the dynamic
// object.
to->override(sym, object, version);
return;
case UNDEF * 16 + DEF:
case WEAK_UNDEF * 16 + DEF:
case DYN_UNDEF * 16 + DEF:
case DYN_WEAK_UNDEF * 16 + DEF:
// We've seen an undefined reference, and now we see a
// definition. We use the definition.
to->override(sym, object, version);
return;
case COMMON * 16 + DEF:
case WEAK_COMMON * 16 + DEF:
case DYN_COMMON * 16 + DEF:
case DYN_WEAK_COMMON * 16 + DEF:
// We've seen a common symbol and now we see a definition. The
// definition overrides. FIXME: We should optionally issue, version a
// warning.
to->override(sym, object, version);
return;
case DEF * 16 + WEAK_DEF:
case WEAK_DEF * 16 + WEAK_DEF:
// We've seen a definition and now we see a weak definition. We
// ignore the new weak definition.
return;
case DYN_DEF * 16 + WEAK_DEF:
case DYN_WEAK_DEF * 16 + WEAK_DEF:
// We've seen a dynamic definition and now we see a regular weak
// definition. The regular weak definition overrides.
to->override(sym, object, version);
return;
case UNDEF * 16 + WEAK_DEF:
case WEAK_UNDEF * 16 + WEAK_DEF:
case DYN_UNDEF * 16 + WEAK_DEF:
case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
// A weak definition of a currently undefined symbol.
to->override(sym, object, version);
return;
case COMMON * 16 + WEAK_DEF:
case WEAK_COMMON * 16 + WEAK_DEF:
// A weak definition does not override a common definition.
return;
case DYN_COMMON * 16 + WEAK_DEF:
case DYN_WEAK_COMMON * 16 + WEAK_DEF:
// A weak definition does override a definition in a dynamic
// object. FIXME: We should optionally issue a warning.
to->override(sym, object, version);
return;
case DEF * 16 + DYN_DEF:
case WEAK_DEF * 16 + DYN_DEF:
case DYN_DEF * 16 + DYN_DEF:
case DYN_WEAK_DEF * 16 + DYN_DEF:
// Ignore a dynamic definition if we already have a definition.
return;
case UNDEF * 16 + DYN_DEF:
case WEAK_UNDEF * 16 + DYN_DEF:
case DYN_UNDEF * 16 + DYN_DEF:
case DYN_WEAK_UNDEF * 16 + DYN_DEF:
// Use a dynamic definition if we have a reference.
to->override(sym, object, version);
return;
case COMMON * 16 + DYN_DEF:
case WEAK_COMMON * 16 + DYN_DEF:
case DYN_COMMON * 16 + DYN_DEF:
case DYN_WEAK_COMMON * 16 + DYN_DEF:
// Ignore a dynamic definition if we already have a common
// definition.
return;
case DEF * 16 + DYN_WEAK_DEF:
case WEAK_DEF * 16 + DYN_WEAK_DEF:
case DYN_DEF * 16 + DYN_WEAK_DEF:
case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
// Ignore a weak dynamic definition if we already have a
// definition.
return;
case UNDEF * 16 + DYN_WEAK_DEF:
case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
case DYN_UNDEF * 16 + DYN_WEAK_DEF:
case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
// Use a weak dynamic definition if we have a reference.
to->override(sym, object, version);
return;
case COMMON * 16 + DYN_WEAK_DEF:
case WEAK_COMMON * 16 + DYN_WEAK_DEF:
case DYN_COMMON * 16 + DYN_WEAK_DEF:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
// Ignore a weak dynamic definition if we already have a common
// definition.
return;
case DEF * 16 + UNDEF:
case WEAK_DEF * 16 + UNDEF:
case DYN_DEF * 16 + UNDEF:
case DYN_WEAK_DEF * 16 + UNDEF:
case UNDEF * 16 + UNDEF:
// A new undefined reference tells us nothing.
return;
case WEAK_UNDEF * 16 + UNDEF:
case DYN_UNDEF * 16 + UNDEF:
case DYN_WEAK_UNDEF * 16 + UNDEF:
// A strong undef overrides a dynamic or weak undef.
to->override(sym, object, version);
return;
case COMMON * 16 + UNDEF:
case WEAK_COMMON * 16 + UNDEF:
case DYN_COMMON * 16 + UNDEF:
case DYN_WEAK_COMMON * 16 + UNDEF:
// A new undefined reference tells us nothing.
return;
case DEF * 16 + WEAK_UNDEF:
case WEAK_DEF * 16 + WEAK_UNDEF:
case DYN_DEF * 16 + WEAK_UNDEF:
case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
case UNDEF * 16 + WEAK_UNDEF:
case WEAK_UNDEF * 16 + WEAK_UNDEF:
case DYN_UNDEF * 16 + WEAK_UNDEF:
case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
case COMMON * 16 + WEAK_UNDEF:
case WEAK_COMMON * 16 + WEAK_UNDEF:
case DYN_COMMON * 16 + WEAK_UNDEF:
case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
// A new weak undefined reference tells us nothing.
return;
case DEF * 16 + DYN_UNDEF:
case WEAK_DEF * 16 + DYN_UNDEF:
case DYN_DEF * 16 + DYN_UNDEF:
case DYN_WEAK_DEF * 16 + DYN_UNDEF:
case UNDEF * 16 + DYN_UNDEF:
case WEAK_UNDEF * 16 + DYN_UNDEF:
case DYN_UNDEF * 16 + DYN_UNDEF:
case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
case COMMON * 16 + DYN_UNDEF:
case WEAK_COMMON * 16 + DYN_UNDEF:
case DYN_COMMON * 16 + DYN_UNDEF:
case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
// A new dynamic undefined reference tells us nothing.
return;
case DEF * 16 + DYN_WEAK_UNDEF:
case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
case DYN_DEF * 16 + DYN_WEAK_UNDEF:
case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
case UNDEF * 16 + DYN_WEAK_UNDEF:
case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
case COMMON * 16 + DYN_WEAK_UNDEF:
case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
// A new weak dynamic undefined reference tells us nothing.
return;
case DEF * 16 + COMMON:
// A common symbol does not override a definition.
return;
case WEAK_DEF * 16 + COMMON:
case DYN_DEF * 16 + COMMON:
case DYN_WEAK_DEF * 16 + COMMON:
// A common symbol does override a weak definition or a dynamic
// definition.
to->override(sym, object, version);
return;
case UNDEF * 16 + COMMON:
case WEAK_UNDEF * 16 + COMMON:
case DYN_UNDEF * 16 + COMMON:
case DYN_WEAK_UNDEF * 16 + COMMON:
// A common symbol is a definition for a reference.
to->override(sym, object, version);
return;
case COMMON * 16 + COMMON:
// Set the size to the maximum.
if (sym.get_st_size() > to->symsize())
to->set_symsize(sym.get_st_size());
return;
case WEAK_COMMON * 16 + COMMON:
// I'm not sure just what a weak common symbol means, but
// presumably it can be overridden by a regular common symbol.
to->override(sym, object, version);
return;
case DYN_COMMON * 16 + COMMON:
case DYN_WEAK_COMMON * 16 + COMMON:
{
// Use the real common symbol, but adjust the size if necessary.
typename Sized_symbol<size>::Size_type symsize = to->symsize();
to->override(sym, object, version);
if (to->symsize() < symsize)
to->set_symsize(symsize);
}
return;
case DEF * 16 + WEAK_COMMON:
case WEAK_DEF * 16 + WEAK_COMMON:
case DYN_DEF * 16 + WEAK_COMMON:
case DYN_WEAK_DEF * 16 + WEAK_COMMON:
// Whatever a weak common symbol is, it won't override a
// definition.
return;
case UNDEF * 16 + WEAK_COMMON:
case WEAK_UNDEF * 16 + WEAK_COMMON:
case DYN_UNDEF * 16 + WEAK_COMMON:
case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
// A weak common symbol is better than an undefined symbol.
to->override(sym, object, version);
return;
case COMMON * 16 + WEAK_COMMON:
case WEAK_COMMON * 16 + WEAK_COMMON:
case DYN_COMMON * 16 + WEAK_COMMON:
case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
// Ignore a weak common symbol in the presence of a real common
// symbol.
return;
case DEF * 16 + DYN_COMMON:
case WEAK_DEF * 16 + DYN_COMMON:
case DYN_DEF * 16 + DYN_COMMON:
case DYN_WEAK_DEF * 16 + DYN_COMMON:
// Ignore a dynamic common symbol in the presence of a
// definition.
return;
case UNDEF * 16 + DYN_COMMON:
case WEAK_UNDEF * 16 + DYN_COMMON:
case DYN_UNDEF * 16 + DYN_COMMON:
case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
// A dynamic common symbol is a definition of sorts.
to->override(sym, object, version);
return;
case COMMON * 16 + DYN_COMMON:
case WEAK_COMMON * 16 + DYN_COMMON:
case DYN_COMMON * 16 + DYN_COMMON:
case DYN_WEAK_COMMON * 16 + DYN_COMMON:
// Set the size to the maximum.
if (sym.get_st_size() > to->symsize())
to->set_symsize(sym.get_st_size());
return;
case DEF * 16 + DYN_WEAK_COMMON:
case WEAK_DEF * 16 + DYN_WEAK_COMMON:
case DYN_DEF * 16 + DYN_WEAK_COMMON:
case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
// A common symbol is ignored in the face of a definition.
return;
case UNDEF * 16 + DYN_WEAK_COMMON:
case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
// I guess a weak common symbol is better than a definition.
to->override(sym, object, version);
return;
case COMMON * 16 + DYN_WEAK_COMMON:
case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
case DYN_COMMON * 16 + DYN_WEAK_COMMON:
case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
// Set the size to the maximum.
if (sym.get_st_size() > to->symsize())
to->set_symsize(sym.get_st_size());
return;
default:
gold_unreachable();
}
}
// Instantiate the templates we need. We could use the configure
// script to restrict this to only the ones needed for implemented
// targets.
template
void
Symbol_table::resolve<32, true>(
Sized_symbol<32>* to,
const elfcpp::Sym<32, true>& sym,
Object* object,
const char* version);
template
void
Symbol_table::resolve<32, false>(
Sized_symbol<32>* to,
const elfcpp::Sym<32, false>& sym,
Object* object,
const char* version);
template
void
Symbol_table::resolve<64, true>(
Sized_symbol<64>* to,
const elfcpp::Sym<64, true>& sym,
Object* object,
const char* version);
template
void
Symbol_table::resolve<64, false>(
Sized_symbol<64>* to,
const elfcpp::Sym<64, false>& sym,
Object* object,
const char* version);
} // End namespace gold.
|