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[thirdparty/binutils-gdb.git] / bfd / elflink.c
1 /* ELF linking support for BFD.
2 Copyright 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
3 Free Software Foundation, Inc.
4
5 This file is part of BFD, the Binary File Descriptor library.
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
20
21 #include "bfd.h"
22 #include "sysdep.h"
23 #include "bfdlink.h"
24 #include "libbfd.h"
25 #define ARCH_SIZE 0
26 #include "elf-bfd.h"
27
28 bfd_boolean
29 _bfd_elf_create_got_section (abfd, info)
30 bfd *abfd;
31 struct bfd_link_info *info;
32 {
33 flagword flags;
34 register asection *s;
35 struct elf_link_hash_entry *h;
36 struct bfd_link_hash_entry *bh;
37 struct elf_backend_data *bed = get_elf_backend_data (abfd);
38 int ptralign;
39
40 /* This function may be called more than once. */
41 if (bfd_get_section_by_name (abfd, ".got") != NULL)
42 return TRUE;
43
44 switch (bed->s->arch_size)
45 {
46 case 32:
47 ptralign = 2;
48 break;
49
50 case 64:
51 ptralign = 3;
52 break;
53
54 default:
55 bfd_set_error (bfd_error_bad_value);
56 return FALSE;
57 }
58
59 flags = (SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY
60 | SEC_LINKER_CREATED);
61
62 s = bfd_make_section (abfd, ".got");
63 if (s == NULL
64 || !bfd_set_section_flags (abfd, s, flags)
65 || !bfd_set_section_alignment (abfd, s, ptralign))
66 return FALSE;
67
68 if (bed->want_got_plt)
69 {
70 s = bfd_make_section (abfd, ".got.plt");
71 if (s == NULL
72 || !bfd_set_section_flags (abfd, s, flags)
73 || !bfd_set_section_alignment (abfd, s, ptralign))
74 return FALSE;
75 }
76
77 if (bed->want_got_sym)
78 {
79 /* Define the symbol _GLOBAL_OFFSET_TABLE_ at the start of the .got
80 (or .got.plt) section. We don't do this in the linker script
81 because we don't want to define the symbol if we are not creating
82 a global offset table. */
83 bh = NULL;
84 if (!(_bfd_generic_link_add_one_symbol
85 (info, abfd, "_GLOBAL_OFFSET_TABLE_", BSF_GLOBAL, s,
86 bed->got_symbol_offset, (const char *) NULL, FALSE,
87 bed->collect, &bh)))
88 return FALSE;
89 h = (struct elf_link_hash_entry *) bh;
90 h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_REGULAR;
91 h->type = STT_OBJECT;
92
93 if (info->shared
94 && ! _bfd_elf_link_record_dynamic_symbol (info, h))
95 return FALSE;
96
97 elf_hash_table (info)->hgot = h;
98 }
99
100 /* The first bit of the global offset table is the header. */
101 s->_raw_size += bed->got_header_size + bed->got_symbol_offset;
102
103 return TRUE;
104 }
105 \f
106 /* Create dynamic sections when linking against a dynamic object. */
107
108 bfd_boolean
109 _bfd_elf_create_dynamic_sections (abfd, info)
110 bfd *abfd;
111 struct bfd_link_info *info;
112 {
113 flagword flags, pltflags;
114 register asection *s;
115 struct elf_backend_data *bed = get_elf_backend_data (abfd);
116 int ptralign;
117
118 switch (bed->s->arch_size)
119 {
120 case 32:
121 ptralign = 2;
122 break;
123
124 case 64:
125 ptralign = 3;
126 break;
127
128 default:
129 bfd_set_error (bfd_error_bad_value);
130 return FALSE;
131 }
132
133 /* We need to create .plt, .rel[a].plt, .got, .got.plt, .dynbss, and
134 .rel[a].bss sections. */
135
136 flags = (SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY
137 | SEC_LINKER_CREATED);
138
139 pltflags = flags;
140 pltflags |= SEC_CODE;
141 if (bed->plt_not_loaded)
142 pltflags &= ~ (SEC_CODE | SEC_LOAD | SEC_HAS_CONTENTS);
143 if (bed->plt_readonly)
144 pltflags |= SEC_READONLY;
145
146 s = bfd_make_section (abfd, ".plt");
147 if (s == NULL
148 || ! bfd_set_section_flags (abfd, s, pltflags)
149 || ! bfd_set_section_alignment (abfd, s, bed->plt_alignment))
150 return FALSE;
151
152 if (bed->want_plt_sym)
153 {
154 /* Define the symbol _PROCEDURE_LINKAGE_TABLE_ at the start of the
155 .plt section. */
156 struct elf_link_hash_entry *h;
157 struct bfd_link_hash_entry *bh = NULL;
158
159 if (! (_bfd_generic_link_add_one_symbol
160 (info, abfd, "_PROCEDURE_LINKAGE_TABLE_", BSF_GLOBAL, s,
161 (bfd_vma) 0, (const char *) NULL, FALSE,
162 get_elf_backend_data (abfd)->collect, &bh)))
163 return FALSE;
164 h = (struct elf_link_hash_entry *) bh;
165 h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_REGULAR;
166 h->type = STT_OBJECT;
167
168 if (info->shared
169 && ! _bfd_elf_link_record_dynamic_symbol (info, h))
170 return FALSE;
171 }
172
173 s = bfd_make_section (abfd,
174 bed->default_use_rela_p ? ".rela.plt" : ".rel.plt");
175 if (s == NULL
176 || ! bfd_set_section_flags (abfd, s, flags | SEC_READONLY)
177 || ! bfd_set_section_alignment (abfd, s, ptralign))
178 return FALSE;
179
180 if (! _bfd_elf_create_got_section (abfd, info))
181 return FALSE;
182
183 if (bed->want_dynbss)
184 {
185 /* The .dynbss section is a place to put symbols which are defined
186 by dynamic objects, are referenced by regular objects, and are
187 not functions. We must allocate space for them in the process
188 image and use a R_*_COPY reloc to tell the dynamic linker to
189 initialize them at run time. The linker script puts the .dynbss
190 section into the .bss section of the final image. */
191 s = bfd_make_section (abfd, ".dynbss");
192 if (s == NULL
193 || ! bfd_set_section_flags (abfd, s, SEC_ALLOC))
194 return FALSE;
195
196 /* The .rel[a].bss section holds copy relocs. This section is not
197 normally needed. We need to create it here, though, so that the
198 linker will map it to an output section. We can't just create it
199 only if we need it, because we will not know whether we need it
200 until we have seen all the input files, and the first time the
201 main linker code calls BFD after examining all the input files
202 (size_dynamic_sections) the input sections have already been
203 mapped to the output sections. If the section turns out not to
204 be needed, we can discard it later. We will never need this
205 section when generating a shared object, since they do not use
206 copy relocs. */
207 if (! info->shared)
208 {
209 s = bfd_make_section (abfd,
210 (bed->default_use_rela_p
211 ? ".rela.bss" : ".rel.bss"));
212 if (s == NULL
213 || ! bfd_set_section_flags (abfd, s, flags | SEC_READONLY)
214 || ! bfd_set_section_alignment (abfd, s, ptralign))
215 return FALSE;
216 }
217 }
218
219 return TRUE;
220 }
221 \f
222 /* Record a new dynamic symbol. We record the dynamic symbols as we
223 read the input files, since we need to have a list of all of them
224 before we can determine the final sizes of the output sections.
225 Note that we may actually call this function even though we are not
226 going to output any dynamic symbols; in some cases we know that a
227 symbol should be in the dynamic symbol table, but only if there is
228 one. */
229
230 bfd_boolean
231 _bfd_elf_link_record_dynamic_symbol (info, h)
232 struct bfd_link_info *info;
233 struct elf_link_hash_entry *h;
234 {
235 if (h->dynindx == -1)
236 {
237 struct elf_strtab_hash *dynstr;
238 char *p, *alc;
239 const char *name;
240 bfd_boolean copy;
241 bfd_size_type indx;
242
243 /* XXX: The ABI draft says the linker must turn hidden and
244 internal symbols into STB_LOCAL symbols when producing the
245 DSO. However, if ld.so honors st_other in the dynamic table,
246 this would not be necessary. */
247 switch (ELF_ST_VISIBILITY (h->other))
248 {
249 case STV_INTERNAL:
250 case STV_HIDDEN:
251 if (h->root.type != bfd_link_hash_undefined
252 && h->root.type != bfd_link_hash_undefweak)
253 {
254 h->elf_link_hash_flags |= ELF_LINK_FORCED_LOCAL;
255 return TRUE;
256 }
257
258 default:
259 break;
260 }
261
262 h->dynindx = elf_hash_table (info)->dynsymcount;
263 ++elf_hash_table (info)->dynsymcount;
264
265 dynstr = elf_hash_table (info)->dynstr;
266 if (dynstr == NULL)
267 {
268 /* Create a strtab to hold the dynamic symbol names. */
269 elf_hash_table (info)->dynstr = dynstr = _bfd_elf_strtab_init ();
270 if (dynstr == NULL)
271 return FALSE;
272 }
273
274 /* We don't put any version information in the dynamic string
275 table. */
276 name = h->root.root.string;
277 p = strchr (name, ELF_VER_CHR);
278 if (p == NULL)
279 {
280 alc = NULL;
281 copy = FALSE;
282 }
283 else
284 {
285 size_t len = p - name + 1;
286
287 alc = bfd_malloc ((bfd_size_type) len);
288 if (alc == NULL)
289 return FALSE;
290 memcpy (alc, name, len - 1);
291 alc[len - 1] = '\0';
292 name = alc;
293 copy = TRUE;
294 }
295
296 indx = _bfd_elf_strtab_add (dynstr, name, copy);
297
298 if (alc != NULL)
299 free (alc);
300
301 if (indx == (bfd_size_type) -1)
302 return FALSE;
303 h->dynstr_index = indx;
304 }
305
306 return TRUE;
307 }
308
309 /* Record a new local dynamic symbol. Returns 0 on failure, 1 on
310 success, and 2 on a failure caused by attempting to record a symbol
311 in a discarded section, eg. a discarded link-once section symbol. */
312
313 int
314 elf_link_record_local_dynamic_symbol (info, input_bfd, input_indx)
315 struct bfd_link_info *info;
316 bfd *input_bfd;
317 long input_indx;
318 {
319 bfd_size_type amt;
320 struct elf_link_local_dynamic_entry *entry;
321 struct elf_link_hash_table *eht;
322 struct elf_strtab_hash *dynstr;
323 unsigned long dynstr_index;
324 char *name;
325 Elf_External_Sym_Shndx eshndx;
326 char esym[sizeof (Elf64_External_Sym)];
327
328 if (! is_elf_hash_table (info))
329 return 0;
330
331 /* See if the entry exists already. */
332 for (entry = elf_hash_table (info)->dynlocal; entry ; entry = entry->next)
333 if (entry->input_bfd == input_bfd && entry->input_indx == input_indx)
334 return 1;
335
336 amt = sizeof (*entry);
337 entry = (struct elf_link_local_dynamic_entry *) bfd_alloc (input_bfd, amt);
338 if (entry == NULL)
339 return 0;
340
341 /* Go find the symbol, so that we can find it's name. */
342 if (!bfd_elf_get_elf_syms (input_bfd, &elf_tdata (input_bfd)->symtab_hdr,
343 (size_t) 1, (size_t) input_indx,
344 &entry->isym, esym, &eshndx))
345 {
346 bfd_release (input_bfd, entry);
347 return 0;
348 }
349
350 if (entry->isym.st_shndx != SHN_UNDEF
351 && (entry->isym.st_shndx < SHN_LORESERVE
352 || entry->isym.st_shndx > SHN_HIRESERVE))
353 {
354 asection *s;
355
356 s = bfd_section_from_elf_index (input_bfd, entry->isym.st_shndx);
357 if (s == NULL || bfd_is_abs_section (s->output_section))
358 {
359 /* We can still bfd_release here as nothing has done another
360 bfd_alloc. We can't do this later in this function. */
361 bfd_release (input_bfd, entry);
362 return 2;
363 }
364 }
365
366 name = (bfd_elf_string_from_elf_section
367 (input_bfd, elf_tdata (input_bfd)->symtab_hdr.sh_link,
368 entry->isym.st_name));
369
370 dynstr = elf_hash_table (info)->dynstr;
371 if (dynstr == NULL)
372 {
373 /* Create a strtab to hold the dynamic symbol names. */
374 elf_hash_table (info)->dynstr = dynstr = _bfd_elf_strtab_init ();
375 if (dynstr == NULL)
376 return 0;
377 }
378
379 dynstr_index = _bfd_elf_strtab_add (dynstr, name, FALSE);
380 if (dynstr_index == (unsigned long) -1)
381 return 0;
382 entry->isym.st_name = dynstr_index;
383
384 eht = elf_hash_table (info);
385
386 entry->next = eht->dynlocal;
387 eht->dynlocal = entry;
388 entry->input_bfd = input_bfd;
389 entry->input_indx = input_indx;
390 eht->dynsymcount++;
391
392 /* Whatever binding the symbol had before, it's now local. */
393 entry->isym.st_info
394 = ELF_ST_INFO (STB_LOCAL, ELF_ST_TYPE (entry->isym.st_info));
395
396 /* The dynindx will be set at the end of size_dynamic_sections. */
397
398 return 1;
399 }
400
401 /* Return the dynindex of a local dynamic symbol. */
402
403 long
404 _bfd_elf_link_lookup_local_dynindx (info, input_bfd, input_indx)
405 struct bfd_link_info *info;
406 bfd *input_bfd;
407 long input_indx;
408 {
409 struct elf_link_local_dynamic_entry *e;
410
411 for (e = elf_hash_table (info)->dynlocal; e ; e = e->next)
412 if (e->input_bfd == input_bfd && e->input_indx == input_indx)
413 return e->dynindx;
414 return -1;
415 }
416
417 /* This function is used to renumber the dynamic symbols, if some of
418 them are removed because they are marked as local. This is called
419 via elf_link_hash_traverse. */
420
421 static bfd_boolean elf_link_renumber_hash_table_dynsyms
422 PARAMS ((struct elf_link_hash_entry *, PTR));
423
424 static bfd_boolean
425 elf_link_renumber_hash_table_dynsyms (h, data)
426 struct elf_link_hash_entry *h;
427 PTR data;
428 {
429 size_t *count = (size_t *) data;
430
431 if (h->root.type == bfd_link_hash_warning)
432 h = (struct elf_link_hash_entry *) h->root.u.i.link;
433
434 if (h->dynindx != -1)
435 h->dynindx = ++(*count);
436
437 return TRUE;
438 }
439
440 /* Assign dynsym indices. In a shared library we generate a section
441 symbol for each output section, which come first. Next come all of
442 the back-end allocated local dynamic syms, followed by the rest of
443 the global symbols. */
444
445 unsigned long
446 _bfd_elf_link_renumber_dynsyms (output_bfd, info)
447 bfd *output_bfd;
448 struct bfd_link_info *info;
449 {
450 unsigned long dynsymcount = 0;
451
452 if (info->shared)
453 {
454 asection *p;
455 for (p = output_bfd->sections; p ; p = p->next)
456 if ((p->flags & SEC_EXCLUDE) == 0)
457 elf_section_data (p)->dynindx = ++dynsymcount;
458 }
459
460 if (elf_hash_table (info)->dynlocal)
461 {
462 struct elf_link_local_dynamic_entry *p;
463 for (p = elf_hash_table (info)->dynlocal; p ; p = p->next)
464 p->dynindx = ++dynsymcount;
465 }
466
467 elf_link_hash_traverse (elf_hash_table (info),
468 elf_link_renumber_hash_table_dynsyms,
469 &dynsymcount);
470
471 /* There is an unused NULL entry at the head of the table which
472 we must account for in our count. Unless there weren't any
473 symbols, which means we'll have no table at all. */
474 if (dynsymcount != 0)
475 ++dynsymcount;
476
477 return elf_hash_table (info)->dynsymcount = dynsymcount;
478 }
479 \f
480 /* Create a special linker section, or return a pointer to a linker
481 section already created */
482
483 elf_linker_section_t *
484 _bfd_elf_create_linker_section (abfd, info, which, defaults)
485 bfd *abfd;
486 struct bfd_link_info *info;
487 enum elf_linker_section_enum which;
488 elf_linker_section_t *defaults;
489 {
490 bfd *dynobj = elf_hash_table (info)->dynobj;
491 elf_linker_section_t *lsect;
492
493 /* Record the first bfd section that needs the special section */
494 if (!dynobj)
495 dynobj = elf_hash_table (info)->dynobj = abfd;
496
497 /* If this is the first time, create the section */
498 lsect = elf_linker_section (dynobj, which);
499 if (!lsect)
500 {
501 asection *s;
502 bfd_size_type amt = sizeof (elf_linker_section_t);
503
504 lsect = (elf_linker_section_t *) bfd_alloc (dynobj, amt);
505
506 *lsect = *defaults;
507 elf_linker_section (dynobj, which) = lsect;
508 lsect->which = which;
509 lsect->hole_written_p = FALSE;
510
511 /* See if the sections already exist */
512 lsect->section = s = bfd_get_section_by_name (dynobj, lsect->name);
513 if (!s || (s->flags & defaults->flags) != defaults->flags)
514 {
515 lsect->section = s = bfd_make_section_anyway (dynobj, lsect->name);
516
517 if (s == NULL)
518 return (elf_linker_section_t *)0;
519
520 bfd_set_section_flags (dynobj, s, defaults->flags);
521 bfd_set_section_alignment (dynobj, s, lsect->alignment);
522 }
523 else if (bfd_get_section_alignment (dynobj, s) < lsect->alignment)
524 bfd_set_section_alignment (dynobj, s, lsect->alignment);
525
526 s->_raw_size = align_power (s->_raw_size, lsect->alignment);
527
528 /* Is there a hole we have to provide? If so check whether the segment is
529 too big already */
530 if (lsect->hole_size)
531 {
532 lsect->hole_offset = s->_raw_size;
533 s->_raw_size += lsect->hole_size;
534 if (lsect->hole_offset > lsect->max_hole_offset)
535 {
536 (*_bfd_error_handler) (_("%s: Section %s is too large to add hole of %ld bytes"),
537 bfd_get_filename (abfd),
538 lsect->name,
539 (long) lsect->hole_size);
540
541 bfd_set_error (bfd_error_bad_value);
542 return (elf_linker_section_t *)0;
543 }
544 }
545
546 #ifdef DEBUG
547 fprintf (stderr, "Creating section %s, current size = %ld\n",
548 lsect->name, (long)s->_raw_size);
549 #endif
550
551 if (lsect->sym_name)
552 {
553 struct elf_link_hash_entry *h;
554 struct bfd_link_hash_entry *bh;
555
556 #ifdef DEBUG
557 fprintf (stderr, "Adding %s to section %s\n",
558 lsect->sym_name,
559 lsect->name);
560 #endif
561 bh = bfd_link_hash_lookup (info->hash, lsect->sym_name,
562 FALSE, FALSE, FALSE);
563
564 if ((bh == NULL || bh->type == bfd_link_hash_undefined)
565 && !(_bfd_generic_link_add_one_symbol
566 (info, abfd, lsect->sym_name, BSF_GLOBAL, s,
567 (lsect->hole_size
568 ? s->_raw_size - lsect->hole_size + lsect->sym_offset
569 : lsect->sym_offset),
570 (const char *) NULL, FALSE,
571 get_elf_backend_data (abfd)->collect, &bh)))
572 return (elf_linker_section_t *) 0;
573 h = (struct elf_link_hash_entry *) bh;
574
575 if ((defaults->which != LINKER_SECTION_SDATA)
576 && (defaults->which != LINKER_SECTION_SDATA2))
577 h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_DYNAMIC;
578
579 h->type = STT_OBJECT;
580 lsect->sym_hash = h;
581
582 if (info->shared
583 && ! _bfd_elf_link_record_dynamic_symbol (info, h))
584 return (elf_linker_section_t *) 0;
585 }
586 }
587
588 #if 0
589 /* This does not make sense. The sections which may exist in the
590 object file have nothing to do with the sections we want to
591 create. */
592
593 /* Find the related sections if they have been created */
594 if (lsect->bss_name && !lsect->bss_section)
595 lsect->bss_section = bfd_get_section_by_name (dynobj, lsect->bss_name);
596
597 if (lsect->rel_name && !lsect->rel_section)
598 lsect->rel_section = bfd_get_section_by_name (dynobj, lsect->rel_name);
599 #endif
600
601 return lsect;
602 }
603 \f
604 /* Find a linker generated pointer with a given addend and type. */
605
606 elf_linker_section_pointers_t *
607 _bfd_elf_find_pointer_linker_section (linker_pointers, addend, which)
608 elf_linker_section_pointers_t *linker_pointers;
609 bfd_vma addend;
610 elf_linker_section_enum_t which;
611 {
612 for ( ; linker_pointers != NULL; linker_pointers = linker_pointers->next)
613 {
614 if (which == linker_pointers->which && addend == linker_pointers->addend)
615 return linker_pointers;
616 }
617
618 return (elf_linker_section_pointers_t *)0;
619 }
620 \f
621 /* Make the .rela section corresponding to the generated linker section. */
622
623 bfd_boolean
624 _bfd_elf_make_linker_section_rela (dynobj, lsect, alignment)
625 bfd *dynobj;
626 elf_linker_section_t *lsect;
627 int alignment;
628 {
629 if (lsect->rel_section)
630 return TRUE;
631
632 lsect->rel_section = bfd_get_section_by_name (dynobj, lsect->rel_name);
633 if (lsect->rel_section == NULL)
634 {
635 lsect->rel_section = bfd_make_section (dynobj, lsect->rel_name);
636 if (lsect->rel_section == NULL
637 || ! bfd_set_section_flags (dynobj,
638 lsect->rel_section,
639 (SEC_ALLOC
640 | SEC_LOAD
641 | SEC_HAS_CONTENTS
642 | SEC_IN_MEMORY
643 | SEC_LINKER_CREATED
644 | SEC_READONLY))
645 || ! bfd_set_section_alignment (dynobj, lsect->rel_section, alignment))
646 return FALSE;
647 }
648
649 return TRUE;
650 }