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[binutils-gdb.git] / bfd / stabs.c
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1 /* Stabs in sections linking support.
2 Copyright (C) 1996-2022 Free Software Foundation, Inc.
3 Written by Ian Lance Taylor, Cygnus Support.
5 This file is part of BFD, the Binary File Descriptor library.
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 3 of the License, or
10 (at your option) any later version.
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.
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., 51 Franklin Street - Fifth Floor, Boston,
20 MA 02110-1301, USA. */
23 /* This file contains support for linking stabs in sections, as used
24 on COFF and ELF. */
26 #include "sysdep.h"
27 #include "bfd.h"
28 #include "libbfd.h"
29 #include "aout/stab_gnu.h"
30 #include "safe-ctype.h"
32 /* Stabs entries use a 12 byte format:
33 4 byte string table index
34 1 byte stab type
35 1 byte stab other field
36 2 byte stab desc field
37 4 byte stab value
38 FIXME: This will have to change for a 64 bit object format.
40 The stabs symbols are divided into compilation units. For the
41 first entry in each unit, the type of 0, the value is the length of
42 the string table for this unit, and the desc field is the number of
43 stabs symbols for this unit. */
45 #define STRDXOFF 0
46 #define TYPEOFF 4
47 #define OTHEROFF 5
48 #define DESCOFF 6
49 #define VALOFF 8
50 #define STABSIZE 12
52 /* A linked list of totals that we have found for a particular header
53 file. A total is a unique identifier for a particular BINCL...EINCL
54 sequence of STABs that can be used to identify duplicate sequences.
55 It consists of three fields, 'sum_chars' which is the sum of all the
56 STABS characters; 'num_chars' which is the number of these charactes
57 and 'symb' which is a buffer of all the symbols in the sequence. This
58 buffer is only checked as a last resort. */
60 struct stab_link_includes_totals
62 struct stab_link_includes_totals *next;
63 bfd_vma sum_chars; /* Accumulated sum of STABS characters. */
64 bfd_vma num_chars; /* Number of STABS characters. */
65 const char* symb; /* The STABS characters themselves. */
68 /* An entry in the header file hash table. */
70 struct stab_link_includes_entry
72 struct bfd_hash_entry root;
73 /* List of totals we have found for this file. */
74 struct stab_link_includes_totals *totals;
77 /* This structure is used to hold a list of N_BINCL symbols, some of
78 which might be converted into N_EXCL symbols. */
80 struct stab_excl_list
82 /* The next symbol to convert. */
83 struct stab_excl_list *next;
84 /* The offset to this symbol in the section contents. */
85 bfd_size_type offset;
86 /* The value to use for the symbol. */
87 bfd_vma val;
88 /* The type of this symbol (N_BINCL or N_EXCL). */
89 int type;
92 /* This structure is stored with each .stab section. */
94 struct stab_section_info
96 /* This is a linked list of N_BINCL symbols which should be
97 converted into N_EXCL symbols. */
98 struct stab_excl_list *excls;
100 /* This is used to map input stab offsets within their sections
101 to output stab offsets, to take into account stabs that have
102 been deleted. If it is NULL, the output offsets are the same
103 as the input offsets, because no stabs have been deleted from
104 this section. Otherwise the i'th entry is the number of
105 bytes of stabs that have been deleted prior to the i'th
106 stab. */
107 bfd_size_type *cumulative_skips;
109 /* This is an array of string indices. For each stab symbol, we
110 store the string index here. If a stab symbol should not be
111 included in the final output, the string index is -1. */
112 bfd_size_type stridxs[1];
116 /* The function to create a new entry in the header file hash table. */
118 static struct bfd_hash_entry *
119 stab_link_includes_newfunc (struct bfd_hash_entry *entry,
120 struct bfd_hash_table *table,
121 const char *string)
123 struct stab_link_includes_entry *ret =
124 (struct stab_link_includes_entry *) entry;
126 /* Allocate the structure if it has not already been allocated by a
127 subclass. */
128 if (ret == NULL)
129 ret = (struct stab_link_includes_entry *)
130 bfd_hash_allocate (table, sizeof (struct stab_link_includes_entry));
131 if (ret == NULL)
132 return NULL;
134 /* Call the allocation method of the superclass. */
135 ret = ((struct stab_link_includes_entry *)
136 bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string));
137 if (ret)
138 /* Set local fields. */
139 ret->totals = NULL;
141 return (struct bfd_hash_entry *) ret;
144 /* This function is called for each input file from the add_symbols
145 pass of the linker. */
147 bool
148 _bfd_link_section_stabs (bfd *abfd,
149 struct stab_info *sinfo,
150 asection *stabsec,
151 asection *stabstrsec,
152 void * *psecinfo,
153 bfd_size_type *pstring_offset)
155 bool first;
156 bfd_size_type count, amt;
157 struct stab_section_info *secinfo;
158 bfd_byte *stabbuf = NULL;
159 bfd_byte *stabstrbuf = NULL;
160 bfd_byte *sym, *symend;
161 bfd_size_type stroff, next_stroff, skip;
162 bfd_size_type *pstridx;
164 if (stabsec->size == 0
165 || stabstrsec->size == 0)
166 /* This file does not contain stabs debugging information. */
167 return true;
169 if (stabsec->size % STABSIZE != 0)
170 /* Something is wrong with the format of these stab symbols.
171 Don't try to optimize them. */
172 return true;
174 if ((stabstrsec->flags & SEC_RELOC) != 0)
175 /* We shouldn't see relocations in the strings, and we aren't
176 prepared to handle them. */
177 return true;
179 if (bfd_is_abs_section (stabsec->output_section)
180 || bfd_is_abs_section (stabstrsec->output_section))
181 /* At least one of the sections is being discarded from the
182 link, so we should just ignore them. */
183 return true;
185 first = false;
187 if (sinfo->stabstr == NULL)
189 flagword flags;
191 /* Initialize the stabs information we need to keep track of. */
192 first = true;
193 sinfo->strings = _bfd_stringtab_init ();
194 if (sinfo->strings == NULL)
195 goto error_return;
196 /* Make sure the first byte is zero. */
197 (void) _bfd_stringtab_add (sinfo->strings, "", true, true);
198 if (! bfd_hash_table_init (&sinfo->includes,
199 stab_link_includes_newfunc,
200 sizeof (struct stab_link_includes_entry)))
201 goto error_return;
202 flags = (SEC_HAS_CONTENTS | SEC_READONLY | SEC_DEBUGGING
203 | SEC_LINKER_CREATED);
204 sinfo->stabstr = bfd_make_section_anyway_with_flags (abfd, ".stabstr",
205 flags);
206 if (sinfo->stabstr == NULL)
207 goto error_return;
210 /* Initialize the information we are going to store for this .stab
211 section. */
212 count = stabsec->size / STABSIZE;
214 amt = sizeof (struct stab_section_info);
215 amt += (count - 1) * sizeof (bfd_size_type);
216 *psecinfo = bfd_alloc (abfd, amt);
217 if (*psecinfo == NULL)
218 goto error_return;
220 secinfo = (struct stab_section_info *) *psecinfo;
221 secinfo->excls = NULL;
222 stabsec->rawsize = stabsec->size;
223 secinfo->cumulative_skips = NULL;
224 memset (secinfo->stridxs, 0, (size_t) count * sizeof (bfd_size_type));
226 /* Read the stabs information from abfd. */
227 if (!bfd_malloc_and_get_section (abfd, stabsec, &stabbuf)
228 || !bfd_malloc_and_get_section (abfd, stabstrsec, &stabstrbuf))
229 goto error_return;
231 /* Look through the stabs symbols, work out the new string indices,
232 and identify N_BINCL symbols which can be eliminated. */
233 stroff = 0;
234 /* The stabs sections can be split when
235 -split-by-reloc/-split-by-file is used. We must keep track of
236 each stab section's place in the single concatenated string
237 table. */
238 next_stroff = pstring_offset ? *pstring_offset : 0;
239 skip = 0;
241 symend = stabbuf + stabsec->size;
242 for (sym = stabbuf, pstridx = secinfo->stridxs;
243 sym < symend;
244 sym += STABSIZE, ++pstridx)
246 bfd_size_type symstroff;
247 int type;
248 const char *string;
250 if (*pstridx != 0)
251 /* This symbol has already been handled by an N_BINCL pass. */
252 continue;
254 type = sym[TYPEOFF];
256 if (type == 0)
258 /* Special type 0 stabs indicate the offset to the next
259 string table. We only copy the very first one. */
260 stroff = next_stroff;
261 next_stroff += bfd_get_32 (abfd, sym + 8);
262 if (pstring_offset)
263 *pstring_offset = next_stroff;
264 if (! first)
266 *pstridx = (bfd_size_type) -1;
267 ++skip;
268 continue;
270 first = false;
273 /* Store the string in the hash table, and record the index. */
274 symstroff = stroff + bfd_get_32 (abfd, sym + STRDXOFF);
275 if (symstroff >= stabstrsec->size)
277 _bfd_error_handler
278 /* xgettext:c-format */
279 (_("%pB(%pA+%#lx): stabs entry has invalid string index"),
280 abfd, stabsec, (long) (sym - stabbuf));
281 bfd_set_error (bfd_error_bad_value);
282 goto error_return;
284 string = (char *) stabstrbuf + symstroff;
285 *pstridx = _bfd_stringtab_add (sinfo->strings, string, true, true);
287 /* An N_BINCL symbol indicates the start of the stabs entries
288 for a header file. We need to scan ahead to the next N_EINCL
289 symbol, ignoring nesting, adding up all the characters in the
290 symbol names, not including the file numbers in types (the
291 first number after an open parenthesis). */
292 if (type == (int) N_BINCL)
294 bfd_vma sum_chars;
295 bfd_vma num_chars;
296 bfd_vma buf_len = 0;
297 char * symb;
298 char * symb_rover;
299 int nest;
300 bfd_byte * incl_sym;
301 struct stab_link_includes_entry * incl_entry;
302 struct stab_link_includes_totals * t;
303 struct stab_excl_list * ne;
305 symb = symb_rover = NULL;
306 sum_chars = num_chars = 0;
307 nest = 0;
309 for (incl_sym = sym + STABSIZE;
310 incl_sym < symend;
311 incl_sym += STABSIZE)
313 int incl_type;
315 incl_type = incl_sym[TYPEOFF];
316 if (incl_type == 0)
317 break;
318 else if (incl_type == (int) N_EXCL)
319 continue;
320 else if (incl_type == (int) N_EINCL)
322 if (nest == 0)
323 break;
324 --nest;
326 else if (incl_type == (int) N_BINCL)
327 ++nest;
328 else if (nest == 0)
330 const char *str;
332 str = ((char *) stabstrbuf
333 + stroff
334 + bfd_get_32 (abfd, incl_sym + STRDXOFF));
335 for (; *str != '\0'; str++)
337 if (num_chars >= buf_len)
339 buf_len += 32 * 1024;
340 symb = (char *) bfd_realloc_or_free (symb, buf_len);
341 if (symb == NULL)
342 goto error_return;
343 symb_rover = symb + num_chars;
345 * symb_rover ++ = * str;
346 sum_chars += *str;
347 num_chars ++;
348 if (*str == '(')
350 /* Skip the file number. */
351 ++str;
352 while (ISDIGIT (*str))
353 ++str;
354 --str;
360 BFD_ASSERT (num_chars == (bfd_vma) (symb_rover - symb));
362 /* If we have already included a header file with the same
363 value, then replaced this one with an N_EXCL symbol. */
364 incl_entry = (struct stab_link_includes_entry * )
365 bfd_hash_lookup (&sinfo->includes, string, true, true);
366 if (incl_entry == NULL)
367 goto error_return;
369 for (t = incl_entry->totals; t != NULL; t = t->next)
370 if (t->sum_chars == sum_chars
371 && t->num_chars == num_chars
372 && memcmp (t->symb, symb, num_chars) == 0)
373 break;
375 /* Record this symbol, so that we can set the value
376 correctly. */
377 amt = sizeof *ne;
378 ne = (struct stab_excl_list *) bfd_alloc (abfd, amt);
379 if (ne == NULL)
380 goto error_return;
381 ne->offset = sym - stabbuf;
382 ne->val = sum_chars;
383 ne->type = (int) N_BINCL;
384 ne->next = secinfo->excls;
385 secinfo->excls = ne;
387 if (t == NULL)
389 /* This is the first time we have seen this header file
390 with this set of stabs strings. */
391 t = (struct stab_link_includes_totals *)
392 bfd_hash_allocate (&sinfo->includes, sizeof *t);
393 if (t == NULL)
394 goto error_return;
395 t->sum_chars = sum_chars;
396 t->num_chars = num_chars;
397 /* Trim data down. */
398 t->symb = symb = (char *) bfd_realloc_or_free (symb, num_chars);
399 t->next = incl_entry->totals;
400 incl_entry->totals = t;
402 else
404 bfd_size_type *incl_pstridx;
406 /* We have seen this header file before. Tell the final
407 pass to change the type to N_EXCL. */
408 ne->type = (int) N_EXCL;
410 /* Free off superfluous symbols. */
411 free (symb);
413 /* Mark the skipped symbols. */
415 nest = 0;
416 for (incl_sym = sym + STABSIZE, incl_pstridx = pstridx + 1;
417 incl_sym < symend;
418 incl_sym += STABSIZE, ++incl_pstridx)
420 int incl_type;
422 incl_type = incl_sym[TYPEOFF];
424 if (incl_type == (int) N_EINCL)
426 if (nest == 0)
428 *incl_pstridx = (bfd_size_type) -1;
429 ++skip;
430 break;
432 --nest;
434 else if (incl_type == (int) N_BINCL)
435 ++nest;
436 else if (incl_type == (int) N_EXCL)
437 /* Keep existing exclusion marks. */
438 continue;
439 else if (nest == 0)
441 *incl_pstridx = (bfd_size_type) -1;
442 ++skip;
449 free (stabbuf);
450 stabbuf = NULL;
451 free (stabstrbuf);
452 stabstrbuf = NULL;
454 /* We need to set the section sizes such that the linker will
455 compute the output section sizes correctly. We set the .stab
456 size to not include the entries we don't want. We set
457 SEC_EXCLUDE for the .stabstr section, so that it will be dropped
458 from the link. We record the size of the strtab in the first
459 .stabstr section we saw, and make sure we don't set SEC_EXCLUDE
460 for that section. */
461 stabsec->size = (count - skip) * STABSIZE;
462 if (stabsec->size == 0)
463 stabsec->flags |= SEC_EXCLUDE | SEC_KEEP;
464 stabstrsec->flags |= SEC_EXCLUDE | SEC_KEEP;
465 sinfo->stabstr->size = _bfd_stringtab_size (sinfo->strings);
467 /* Calculate the `cumulative_skips' array now that stabs have been
468 deleted for this section. */
470 if (skip != 0)
472 bfd_size_type i, offset;
473 bfd_size_type *pskips;
475 amt = count * sizeof (bfd_size_type);
476 secinfo->cumulative_skips = (bfd_size_type *) bfd_alloc (abfd, amt);
477 if (secinfo->cumulative_skips == NULL)
478 goto error_return;
480 pskips = secinfo->cumulative_skips;
481 pstridx = secinfo->stridxs;
482 offset = 0;
484 for (i = 0; i < count; i++, pskips++, pstridx++)
486 *pskips = offset;
487 if (*pstridx == (bfd_size_type) -1)
488 offset += STABSIZE;
491 BFD_ASSERT (offset != 0);
494 return true;
496 error_return:
497 free (stabbuf);
498 free (stabstrbuf);
499 return false;
502 /* This function is called for each input file before the stab
503 section is relocated. It discards stab entries for discarded
504 functions and variables. The function returns TRUE iff
505 any entries have been deleted.
508 bool
509 _bfd_discard_section_stabs (bfd *abfd,
510 asection *stabsec,
511 void * psecinfo,
512 bool (*reloc_symbol_deleted_p) (bfd_vma, void *),
513 void * cookie)
515 bfd_size_type count, amt;
516 struct stab_section_info *secinfo;
517 bfd_byte *stabbuf = NULL;
518 bfd_byte *sym, *symend;
519 bfd_size_type skip;
520 bfd_size_type *pstridx;
521 int deleting;
523 if (stabsec->size == 0)
524 /* This file does not contain stabs debugging information. */
525 return false;
527 if (stabsec->size % STABSIZE != 0)
528 /* Something is wrong with the format of these stab symbols.
529 Don't try to optimize them. */
530 return false;
532 if ((stabsec->output_section != NULL
533 && bfd_is_abs_section (stabsec->output_section)))
534 /* At least one of the sections is being discarded from the
535 link, so we should just ignore them. */
536 return false;
538 /* We should have initialized our data in _bfd_link_section_stabs.
539 If there was some bizarre error reading the string sections, though,
540 we might not have. Bail rather than asserting. */
541 if (psecinfo == NULL)
542 return false;
544 count = stabsec->rawsize / STABSIZE;
545 secinfo = (struct stab_section_info *) psecinfo;
547 /* Read the stabs information from abfd. */
548 if (!bfd_malloc_and_get_section (abfd, stabsec, &stabbuf))
549 goto error_return;
551 /* Look through the stabs symbols and discard any information for
552 discarded functions. */
553 skip = 0;
554 deleting = -1;
556 symend = stabbuf + stabsec->rawsize;
557 for (sym = stabbuf, pstridx = secinfo->stridxs;
558 sym < symend;
559 sym += STABSIZE, ++pstridx)
561 int type;
563 if (*pstridx == (bfd_size_type) -1)
564 /* This stab was deleted in a previous pass. */
565 continue;
567 type = sym[TYPEOFF];
569 if (type == (int) N_FUN)
571 int strx = bfd_get_32 (abfd, sym + STRDXOFF);
573 if (strx == 0)
575 if (deleting)
577 skip++;
578 *pstridx = -1;
580 deleting = -1;
581 continue;
583 deleting = 0;
584 if ((*reloc_symbol_deleted_p) (sym + VALOFF - stabbuf, cookie))
585 deleting = 1;
588 if (deleting == 1)
590 *pstridx = -1;
591 skip++;
593 else if (deleting == -1)
595 /* Outside of a function. Check for deleted variables. */
596 if (type == (int) N_STSYM || type == (int) N_LCSYM)
597 if ((*reloc_symbol_deleted_p) (sym + VALOFF - stabbuf, cookie))
599 *pstridx = -1;
600 skip ++;
602 /* We should also check for N_GSYM entries which reference a
603 deleted global, but those are less harmful to debuggers
604 and would require parsing the stab strings. */
608 free (stabbuf);
609 stabbuf = NULL;
611 /* Shrink the stabsec as needed. */
612 stabsec->size -= skip * STABSIZE;
613 if (stabsec->size == 0)
614 stabsec->flags |= SEC_EXCLUDE | SEC_KEEP;
616 /* Recalculate the `cumulative_skips' array now that stabs have been
617 deleted for this section. */
619 if (skip != 0)
621 bfd_size_type i, offset;
622 bfd_size_type *pskips;
624 if (secinfo->cumulative_skips == NULL)
626 amt = count * sizeof (bfd_size_type);
627 secinfo->cumulative_skips = (bfd_size_type *) bfd_alloc (abfd, amt);
628 if (secinfo->cumulative_skips == NULL)
629 goto error_return;
632 pskips = secinfo->cumulative_skips;
633 pstridx = secinfo->stridxs;
634 offset = 0;
636 for (i = 0; i < count; i++, pskips++, pstridx++)
638 *pskips = offset;
639 if (*pstridx == (bfd_size_type) -1)
640 offset += STABSIZE;
643 BFD_ASSERT (offset != 0);
646 return skip > 0;
648 error_return:
649 free (stabbuf);
650 return false;
653 /* Write out the stab section. This is called with the relocated
654 contents. */
656 bool
657 _bfd_write_section_stabs (bfd *output_bfd,
658 struct stab_info *sinfo,
659 asection *stabsec,
660 void * *psecinfo,
661 bfd_byte *contents)
663 struct stab_section_info *secinfo;
664 struct stab_excl_list *e;
665 bfd_byte *sym, *tosym, *symend;
666 bfd_size_type *pstridx;
668 secinfo = (struct stab_section_info *) *psecinfo;
670 if (secinfo == NULL)
671 return bfd_set_section_contents (output_bfd, stabsec->output_section,
672 contents, stabsec->output_offset,
673 stabsec->size);
675 /* Handle each N_BINCL entry. */
676 for (e = secinfo->excls; e != NULL; e = e->next)
678 bfd_byte *excl_sym;
680 BFD_ASSERT (e->offset < stabsec->rawsize);
681 excl_sym = contents + e->offset;
682 bfd_put_32 (output_bfd, e->val, excl_sym + VALOFF);
683 excl_sym[TYPEOFF] = e->type;
686 /* Copy over all the stabs symbols, omitting the ones we don't want,
687 and correcting the string indices for those we do want. */
688 tosym = contents;
689 symend = contents + stabsec->rawsize;
690 for (sym = contents, pstridx = secinfo->stridxs;
691 sym < symend;
692 sym += STABSIZE, ++pstridx)
694 if (*pstridx != (bfd_size_type) -1)
696 if (tosym != sym)
697 memcpy (tosym, sym, STABSIZE);
698 bfd_put_32 (output_bfd, *pstridx, tosym + STRDXOFF);
700 if (sym[TYPEOFF] == 0)
702 /* This is the header symbol for the stabs section. We
703 don't really need one, since we have merged all the
704 input stabs sections into one, but we generate one
705 for the benefit of readers which expect to see one. */
706 BFD_ASSERT (sym == contents);
707 bfd_put_32 (output_bfd, _bfd_stringtab_size (sinfo->strings),
708 tosym + VALOFF);
709 bfd_put_16 (output_bfd,
710 stabsec->output_section->size / STABSIZE - 1,
711 tosym + DESCOFF);
714 tosym += STABSIZE;
718 BFD_ASSERT ((bfd_size_type) (tosym - contents) == stabsec->size);
720 return bfd_set_section_contents (output_bfd, stabsec->output_section,
721 contents, (file_ptr) stabsec->output_offset,
722 stabsec->size);
725 /* Write out the .stabstr section. */
727 bool
728 _bfd_write_stab_strings (bfd *output_bfd, struct stab_info *sinfo)
730 if (bfd_is_abs_section (sinfo->stabstr->output_section))
731 /* The section was discarded from the link. */
732 return true;
734 BFD_ASSERT ((sinfo->stabstr->output_offset
735 + _bfd_stringtab_size (sinfo->strings))
736 <= sinfo->stabstr->output_section->size);
738 if (bfd_seek (output_bfd,
739 (file_ptr) (sinfo->stabstr->output_section->filepos
740 + sinfo->stabstr->output_offset),
741 SEEK_SET) != 0)
742 return false;
744 if (! _bfd_stringtab_emit (output_bfd, sinfo->strings))
745 return false;
747 /* We no longer need the stabs information. */
748 _bfd_stringtab_free (sinfo->strings);
749 bfd_hash_table_free (&sinfo->includes);
751 return true;
754 /* Adjust an address in the .stab section. Given OFFSET within
755 STABSEC, this returns the new offset in the adjusted stab section,
756 or -1 if the address refers to a stab which has been removed. */
758 bfd_vma
759 _bfd_stab_section_offset (asection *stabsec,
760 void * psecinfo,
761 bfd_vma offset)
763 struct stab_section_info *secinfo;
765 secinfo = (struct stab_section_info *) psecinfo;
767 if (secinfo == NULL)
768 return offset;
770 if (offset >= stabsec->rawsize)
771 return offset - stabsec->rawsize + stabsec->size;
773 if (secinfo->cumulative_skips)
775 bfd_vma i;
777 i = offset / STABSIZE;
779 if (secinfo->stridxs [i] == (bfd_size_type) -1)
780 return (bfd_vma) -1;
782 return offset - secinfo->cumulative_skips [i];
785 return offset;