bfd/stabs.c

   1 /* Stabs in sections linking support.
   2    Copyright 1996, 1997, 1998, 1999, 2000, 2001
   3    Free Software Foundation, Inc.
   4    Written by Ian Lance Taylor, Cygnus Support.
   5
   6 This file is part of BFD, the Binary File Descriptor library.
   7
   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 2 of the License, or
  11 (at your option) any later version.
  12
  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.
  17
  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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  21
  22 /* This file contains support for linking stabs in sections, as used
  23    on COFF and ELF.  */
  24
  25 #include "bfd.h"
  26 #include "sysdep.h"
  27 #include "libbfd.h"
  28 #include "aout/stab_gnu.h"
  29 #include "safe-ctype.h"
  30
  31 /* Stabs entries use a 12 byte format:
  32      4 byte string table index
  33      1 byte stab type
  34      1 byte stab other field
  35      2 byte stab desc field
  36      4 byte stab value
  37    FIXME: This will have to change for a 64 bit object format.
  38
  39    The stabs symbols are divided into compilation units.  For the
  40    first entry in each unit, the type of 0, the value is the length of
  41    the string table for this unit, and the desc field is the number of
  42    stabs symbols for this unit.  */
  43
  44 #define STRDXOFF (0)
  45 #define TYPEOFF (4)
  46 #define OTHEROFF (5)
  47 #define DESCOFF (6)
  48 #define VALOFF (8)
  49 #define STABSIZE (12)
  50
  51 /* A hash table used for header files with N_BINCL entries.  */
  52
  53 struct stab_link_includes_table
  54 {
  55   struct bfd_hash_table root;
  56 };
  57
  58 /* A linked list of totals that we have found for a particular header
  59    file.  */
  60
  61 struct stab_link_includes_totals
  62 {
  63   struct stab_link_includes_totals *next;
  64   bfd_vma total;
  65 };
  66
  67 /* An entry in the header file hash table.  */
  68
  69 struct stab_link_includes_entry
  70 {
  71   struct bfd_hash_entry root;
  72   /* List of totals we have found for this file.  */
  73   struct stab_link_includes_totals *totals;
  74 };
  75
  76 /* Look up an entry in an the header file hash table.  */
  77
  78 #define stab_link_includes_lookup(table, string, create, copy) \
  79   ((struct stab_link_includes_entry *) \
  80    bfd_hash_lookup (&(table)->root, (string), (create), (copy)))
  81
  82 /* This structure is used to hold a list of N_BINCL symbols, some of
  83    which might be converted into N_EXCL symbols.  */
  84
  85 struct stab_excl_list
  86 {
  87   /* The next symbol to convert.  */
  88   struct stab_excl_list *next;
  89   /* The offset to this symbol in the section contents.  */
  90   bfd_size_type offset;
  91   /* The value to use for the symbol.  */
  92   bfd_vma val;
  93   /* The type of this symbol (N_BINCL or N_EXCL).  */
  94   int type;
  95 };
  96
  97 /* This structure is stored with each .stab section.  */
  98
  99 struct stab_section_info
 100 {
 101   /* This is a linked list of N_BINCL symbols which should be
 102      converted into N_EXCL symbols.  */
 103   struct stab_excl_list *excls;
 104
 105   /* This is used to map input stab offsets within their sections
 106      to output stab offsets, to take into account stabs that have
 107      been deleted.  If it is NULL, the output offsets are the same
 108      as the input offsets, because no stabs have been deleted from
 109      this section.  Otherwise the i'th entry is the number of
 110      bytes of stabs that have been deleted prior to the i'th
 111      stab.  */
 112   bfd_size_type *cumulative_skips;
 113
 114   /* This is an array of string indices.  For each stab symbol, we
 115      store the string index here.  If a stab symbol should not be
 116      included in the final output, the string index is -1.  */
 117   bfd_size_type stridxs[1];
 118 };
 119
 120 /* This structure is used to keep track of stabs in sections
 121    information while linking.  */
 122
 123 struct stab_info
 124 {
 125   /* A hash table used to hold stabs strings.  */
 126   struct bfd_strtab_hash *strings;
 127   /* The header file hash table.  */
 128   struct stab_link_includes_table includes;
 129   /* The first .stabstr section.  */
 130   asection *stabstr;
 131 };
 132
 133 static struct bfd_hash_entry *stab_link_includes_newfunc
 134   PARAMS ((struct bfd_hash_entry *, struct bfd_hash_table *, const char *));
 135 \f
 136 /* The function to create a new entry in the header file hash table.  */
 137
 138 static struct bfd_hash_entry *
 139 stab_link_includes_newfunc (entry, table, string)
 140      struct bfd_hash_entry *entry;
 141      struct bfd_hash_table *table;
 142      const char *string;
 143 {
 144   struct stab_link_includes_entry *ret =
 145     (struct stab_link_includes_entry *) entry;
 146
 147   /* Allocate the structure if it has not already been allocated by a
 148      subclass.  */
 149   if (ret == (struct stab_link_includes_entry *) NULL)
 150     ret = ((struct stab_link_includes_entry *)
 151            bfd_hash_allocate (table,
 152                               sizeof (struct stab_link_includes_entry)));
 153   if (ret == (struct stab_link_includes_entry *) NULL)
 154     return (struct bfd_hash_entry *) ret;
 155
 156   /* Call the allocation method of the superclass.  */
 157   ret = ((struct stab_link_includes_entry *)
 158          bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string));
 159   if (ret)
 160     {
 161       /* Set local fields.  */
 162       ret->totals = NULL;
 163     }
 164
 165   return (struct bfd_hash_entry *) ret;
 166 }
 167 \f
 168 /* This function is called for each input file from the add_symbols
 169    pass of the linker.  */
 170
 171 boolean
 172 _bfd_link_section_stabs (abfd, psinfo, stabsec, stabstrsec, psecinfo)
 173      bfd *abfd;
 174      PTR *psinfo;
 175      asection *stabsec;
 176      asection *stabstrsec;
 177      PTR *psecinfo;
 178 {
 179   boolean first;
 180   struct stab_info *sinfo;
 181   bfd_size_type count, amt;
 182   struct stab_section_info *secinfo;
 183   bfd_byte *stabbuf = NULL;
 184   bfd_byte *stabstrbuf = NULL;
 185   bfd_byte *sym, *symend;
 186   bfd_size_type stroff, next_stroff, skip;
 187   bfd_size_type *pstridx;
 188
 189   if (stabsec->_raw_size == 0
 190       || stabstrsec->_raw_size == 0)
 191     {
 192       /* This file does not contain stabs debugging information.  */
 193       return true;
 194     }
 195
 196   if (stabsec->_raw_size % STABSIZE != 0)
 197     {
 198       /* Something is wrong with the format of these stab symbols.
 199          Don't try to optimize them.  */
 200       return true;
 201     }
 202
 203   if ((stabstrsec->flags & SEC_RELOC) != 0)
 204     {
 205       /* We shouldn't see relocations in the strings, and we aren't
 206          prepared to handle them.  */
 207       return true;
 208     }
 209
 210   if ((stabsec->output_section != NULL
 211        && bfd_is_abs_section (stabsec->output_section))
 212       || (stabstrsec->output_section != NULL
 213           && bfd_is_abs_section (stabstrsec->output_section)))
 214     {
 215       /* At least one of the sections is being discarded from the
 216          link, so we should just ignore them.  */
 217       return true;
 218     }
 219
 220   first = false;
 221
 222   if (*psinfo == NULL)
 223     {
 224       /* Initialize the stabs information we need to keep track of.  */
 225       first = true;
 226       amt = sizeof (struct stab_info);
 227       *psinfo = (PTR) bfd_alloc (abfd, amt);
 228       if (*psinfo == NULL)
 229         goto error_return;
 230       sinfo = (struct stab_info *) *psinfo;
 231       sinfo->strings = _bfd_stringtab_init ();
 232       if (sinfo->strings == NULL)
 233         goto error_return;
 234       /* Make sure the first byte is zero.  */
 235       (void) _bfd_stringtab_add (sinfo->strings, "", true, true);
 236       if (! bfd_hash_table_init_n (&sinfo->includes.root,
 237                                    stab_link_includes_newfunc,
 238                                    251))
 239         goto error_return;
 240       sinfo->stabstr = bfd_make_section_anyway (abfd, ".stabstr");
 241       sinfo->stabstr->flags |= SEC_HAS_CONTENTS | SEC_READONLY | SEC_DEBUGGING;
 242     }
 243
 244   sinfo = (struct stab_info *) *psinfo;
 245
 246   /* Initialize the information we are going to store for this .stab
 247      section.  */
 248
 249   count = stabsec->_raw_size / STABSIZE;
 250
 251   amt = sizeof (struct stab_section_info);
 252   amt += (count - 1) * sizeof (bfd_size_type);
 253   *psecinfo = bfd_alloc (abfd, amt);
 254   if (*psecinfo == NULL)
 255     goto error_return;
 256
 257   secinfo = (struct stab_section_info *) *psecinfo;
 258   secinfo->excls = NULL;
 259   secinfo->cumulative_skips = NULL;
 260   memset (secinfo->stridxs, 0, (size_t) count * sizeof (bfd_size_type));
 261
 262   /* Read the stabs information from abfd.  */
 263
 264   stabbuf = (bfd_byte *) bfd_malloc (stabsec->_raw_size);
 265   stabstrbuf = (bfd_byte *) bfd_malloc (stabstrsec->_raw_size);
 266   if (stabbuf == NULL || stabstrbuf == NULL)
 267     goto error_return;
 268
 269   if (! bfd_get_section_contents (abfd, stabsec, stabbuf, (bfd_vma) 0,
 270                                   stabsec->_raw_size)
 271       || ! bfd_get_section_contents (abfd, stabstrsec, stabstrbuf, (bfd_vma) 0,
 272                                      stabstrsec->_raw_size))
 273     goto error_return;
 274
 275   /* Look through the stabs symbols, work out the new string indices,
 276      and identify N_BINCL symbols which can be eliminated.  */
 277
 278   stroff = 0;
 279   next_stroff = 0;
 280   skip = 0;
 281
 282   symend = stabbuf + stabsec->_raw_size;
 283   for (sym = stabbuf, pstridx = secinfo->stridxs;
 284        sym < symend;
 285        sym += STABSIZE, ++pstridx)
 286     {
 287       int type;
 288       const char *string;
 289
 290       if (*pstridx != 0)
 291         {
 292           /* This symbol has already been handled by an N_BINCL pass.  */
 293           continue;
 294         }
 295
 296       type = sym[TYPEOFF];
 297
 298       if (type == 0)
 299         {
 300           /* Special type 0 stabs indicate the offset to the next
 301              string table.  We only copy the very first one.  */
 302           stroff = next_stroff;
 303           next_stroff += bfd_get_32 (abfd, sym + 8);
 304           if (! first)
 305             {
 306               *pstridx = (bfd_size_type) -1;
 307               ++skip;
 308               continue;
 309             }
 310           first = false;
 311         }
 312
 313       /* Store the string in the hash table, and record the index.  */
 314       string = ((char *) stabstrbuf
 315                 + stroff
 316                 + bfd_get_32 (abfd, sym + STRDXOFF));
 317       *pstridx = _bfd_stringtab_add (sinfo->strings, string, true, true);
 318
 319       /* An N_BINCL symbol indicates the start of the stabs entries
 320          for a header file.  We need to scan ahead to the next N_EINCL
 321          symbol, ignoring nesting, adding up all the characters in the
 322          symbol names, not including the file numbers in types (the
 323          first number after an open parenthesis).  */
 324       if (type == N_BINCL)
 325         {
 326           bfd_vma val;
 327           int nest;
 328           bfd_byte *incl_sym;
 329           struct stab_link_includes_entry *incl_entry;
 330           struct stab_link_includes_totals *t;
 331           struct stab_excl_list *ne;
 332
 333           val = 0;
 334           nest = 0;
 335           for (incl_sym = sym + STABSIZE;
 336                incl_sym < symend;
 337                incl_sym += STABSIZE)
 338             {
 339               int incl_type;
 340
 341               incl_type = incl_sym[TYPEOFF];
 342               if (incl_type == 0)
 343                 break;
 344               else if (incl_type == N_EINCL)
 345                 {
 346                   if (nest == 0)
 347                     break;
 348                   --nest;
 349                 }
 350               else if (incl_type == N_BINCL)
 351                 ++nest;
 352               else if (nest == 0)
 353                 {
 354                   const char *str;
 355
 356                   str = ((char *) stabstrbuf
 357                          + stroff
 358                          + bfd_get_32 (abfd, incl_sym + STRDXOFF));
 359                   for (; *str != '\0'; str++)
 360                     {
 361                       val += *str;
 362                       if (*str == '(')
 363                         {
 364                           /* Skip the file number.  */
 365                           ++str;
 366                           while (ISDIGIT (*str))
 367                             ++str;
 368                           --str;
 369                         }
 370                     }
 371                 }
 372             }
 373
 374           /* If we have already included a header file with the same
 375              value, then replaced this one with an N_EXCL symbol.  */
 376           incl_entry = stab_link_includes_lookup (&sinfo->includes, string,
 377                                                   true, true);
 378           if (incl_entry == NULL)
 379             goto error_return;
 380
 381           for (t = incl_entry->totals; t != NULL; t = t->next)
 382             if (t->total == val)
 383               break;
 384
 385           /* Record this symbol, so that we can set the value
 386              correctly.  */
 387           amt = sizeof *ne;
 388           ne = (struct stab_excl_list *) bfd_alloc (abfd, amt);
 389           if (ne == NULL)
 390             goto error_return;
 391           ne->offset = sym - stabbuf;
 392           ne->val = val;
 393           ne->type = N_BINCL;
 394           ne->next = secinfo->excls;
 395           secinfo->excls = ne;
 396
 397           if (t == NULL)
 398             {
 399               /* This is the first time we have seen this header file
 400                  with this set of stabs strings.  */
 401               t = ((struct stab_link_includes_totals *)
 402                    bfd_hash_allocate (&sinfo->includes.root, sizeof *t));
 403               if (t == NULL)
 404                 goto error_return;
 405               t->total = val;
 406               t->next = incl_entry->totals;
 407               incl_entry->totals = t;
 408             }
 409           else
 410             {
 411               bfd_size_type *incl_pstridx;
 412
 413               /* We have seen this header file before.  Tell the final
 414                  pass to change the type to N_EXCL.  */
 415               ne->type = N_EXCL;
 416
 417               /* Mark the skipped symbols.  */
 418
 419               nest = 0;
 420               for (incl_sym = sym + STABSIZE, incl_pstridx = pstridx + 1;
 421                    incl_sym < symend;
 422                    incl_sym += STABSIZE, ++incl_pstridx)
 423                 {
 424                   int incl_type;
 425
 426                   incl_type = incl_sym[TYPEOFF];
 427
 428                   if (incl_type == N_EINCL)
 429                     {
 430                       if (nest == 0)
 431                         {
 432                           *incl_pstridx = (bfd_size_type) -1;
 433                           ++skip;
 434                           break;
 435                         }
 436                       --nest;
 437                     }
 438                   else if (incl_type == N_BINCL)
 439                     ++nest;
 440                   else if (nest == 0)
 441                     {
 442                       *incl_pstridx = (bfd_size_type) -1;
 443                       ++skip;
 444                     }
 445                 }
 446             }
 447         }
 448     }
 449
 450   free (stabbuf);
 451   stabbuf = NULL;
 452   free (stabstrbuf);
 453   stabstrbuf = NULL;
 454
 455   /* We need to set the section sizes such that the linker will
 456      compute the output section sizes correctly.  We set the .stab
 457      size to not include the entries we don't want.  We set
 458      SEC_EXCLUDE for the .stabstr section, so that it will be dropped
 459      from the link.  We record the size of the strtab in the first
 460      .stabstr section we saw, and make sure we don't set SEC_EXCLUDE
 461      for that section.  */
 462   stabsec->_cooked_size = (count - skip) * STABSIZE;
 463   if (stabsec->_cooked_size == 0)
 464     stabsec->flags |= SEC_EXCLUDE;
 465   stabstrsec->flags |= SEC_EXCLUDE;
 466   sinfo->stabstr->_cooked_size = _bfd_stringtab_size (sinfo->strings);
 467
 468   /* Calculate the `cumulative_skips' array now that stabs have been
 469      deleted for this section.  */
 470
 471   if (skip != 0)
 472     {
 473       bfd_size_type i, offset;
 474       bfd_size_type *pskips;
 475
 476       amt = count * sizeof (bfd_size_type);
 477       secinfo->cumulative_skips = (bfd_size_type *) bfd_alloc (abfd, amt);
 478       if (secinfo->cumulative_skips == NULL)
 479         goto error_return;
 480
 481       pskips = secinfo->cumulative_skips;
 482       pstridx = secinfo->stridxs;
 483       offset = 0;
 484
 485       for (i = 0; i < count; i++, pskips++, pstridx++)
 486         {
 487           *pskips = offset;
 488           if (*pstridx == (bfd_size_type) -1)
 489             offset += STABSIZE;
 490         }
 491
 492       BFD_ASSERT (offset != 0);
 493     }
 494
 495   return true;
 496
 497  error_return:
 498   if (stabbuf != NULL)
 499     free (stabbuf);
 500   if (stabstrbuf != NULL)
 501     free (stabstrbuf);
 502   return false;
 503 }
 504
 505 /* Write out the stab section.  This is called with the relocated
 506    contents.  */
 507
 508 boolean
 509 _bfd_write_section_stabs (output_bfd, psinfo, stabsec, psecinfo, contents)
 510      bfd *output_bfd;
 511      PTR *psinfo;
 512      asection *stabsec;
 513      PTR *psecinfo;
 514      bfd_byte *contents;
 515 {
 516   struct stab_info *sinfo;
 517   struct stab_section_info *secinfo;
 518   struct stab_excl_list *e;
 519   bfd_byte *sym, *tosym, *symend;
 520   bfd_size_type *pstridx;
 521
 522   sinfo = (struct stab_info *) *psinfo;
 523   secinfo = (struct stab_section_info *) *psecinfo;
 524
 525   if (secinfo == NULL)
 526     return bfd_set_section_contents (output_bfd, stabsec->output_section,
 527                                      contents,
 528                                      (file_ptr) stabsec->output_offset,
 529                                      stabsec->_raw_size);
 530
 531   /* Handle each N_BINCL entry.  */
 532   for (e = secinfo->excls; e != NULL; e = e->next)
 533     {
 534       bfd_byte *excl_sym;
 535
 536       BFD_ASSERT (e->offset < stabsec->_raw_size);
 537       excl_sym = contents + e->offset;
 538       bfd_put_32 (output_bfd, e->val, excl_sym + VALOFF);
 539       excl_sym[TYPEOFF] = e->type;
 540     }
 541
 542   /* Copy over all the stabs symbols, omitting the ones we don't want,
 543      and correcting the string indices for those we do want.  */
 544   tosym = contents;
 545   symend = contents + stabsec->_raw_size;
 546   for (sym = contents, pstridx = secinfo->stridxs;
 547        sym < symend;
 548        sym += STABSIZE, ++pstridx)
 549     {
 550       if (*pstridx != (bfd_size_type) -1)
 551         {
 552           if (tosym != sym)
 553             memcpy (tosym, sym, STABSIZE);
 554           bfd_put_32 (output_bfd, *pstridx, tosym + STRDXOFF);
 555
 556           if (sym[TYPEOFF] == 0)
 557             {
 558               /* This is the header symbol for the stabs section.  We
 559                  don't really need one, since we have merged all the
 560                  input stabs sections into one, but we generate one
 561                  for the benefit of readers which expect to see one.  */
 562               BFD_ASSERT (sym == contents);
 563               bfd_put_32 (output_bfd, _bfd_stringtab_size (sinfo->strings),
 564                           tosym + VALOFF);
 565               bfd_put_16 (output_bfd,
 566                           stabsec->output_section->_raw_size / STABSIZE - 1,
 567                           tosym + DESCOFF);
 568             }
 569
 570           tosym += STABSIZE;
 571         }
 572     }
 573
 574   BFD_ASSERT ((bfd_size_type) (tosym - contents) == stabsec->_cooked_size);
 575
 576   return bfd_set_section_contents (output_bfd, stabsec->output_section,
 577                                    contents, (file_ptr) stabsec->output_offset,
 578                                    stabsec->_cooked_size);
 579 }
 580
 581 /* Write out the .stabstr section.  */
 582
 583 boolean
 584 _bfd_write_stab_strings (output_bfd, psinfo)
 585      bfd *output_bfd;
 586      PTR *psinfo;
 587 {
 588   struct stab_info *sinfo;
 589
 590   sinfo = (struct stab_info *) *psinfo;
 591
 592   if (sinfo == NULL)
 593     return true;
 594
 595   if (bfd_is_abs_section (sinfo->stabstr->output_section))
 596     {
 597       /* The section was discarded from the link.  */
 598       return true;
 599     }
 600
 601   BFD_ASSERT ((sinfo->stabstr->output_offset
 602                + _bfd_stringtab_size (sinfo->strings))
 603               <= sinfo->stabstr->output_section->_raw_size);
 604
 605   if (bfd_seek (output_bfd,
 606                 (file_ptr) (sinfo->stabstr->output_section->filepos
 607                             + sinfo->stabstr->output_offset),
 608                 SEEK_SET) != 0)
 609     return false;
 610
 611   if (! _bfd_stringtab_emit (output_bfd, sinfo->strings))
 612     return false;
 613
 614   /* We no longer need the stabs information.  */
 615   _bfd_stringtab_free (sinfo->strings);
 616   bfd_hash_table_free (&sinfo->includes.root);
 617
 618   return true;
 619 }
 620
 621 /* Adjust an address in the .stab section.  Given OFFSET within
 622    STABSEC, this returns the new offset in the adjusted stab section,
 623    or -1 if the address refers to a stab which has been removed.  */
 624
 625 bfd_vma
 626 _bfd_stab_section_offset (output_bfd, psinfo, stabsec, psecinfo, offset)
 627      bfd *output_bfd ATTRIBUTE_UNUSED;
 628      PTR *psinfo ATTRIBUTE_UNUSED;
 629      asection *stabsec;
 630      PTR *psecinfo;
 631      bfd_vma offset;
 632 {
 633   struct stab_section_info *secinfo;
 634
 635   secinfo = (struct stab_section_info *) *psecinfo;
 636
 637   if (secinfo == NULL)
 638     return offset;
 639
 640   if (offset >= stabsec->_raw_size)
 641     return offset - (stabsec->_cooked_size - stabsec->_raw_size);
 642
 643   if (secinfo->cumulative_skips)
 644     {
 645       bfd_vma i;
 646
 647       i = offset / STABSIZE;
 648
 649       if (secinfo->stridxs [i] == (bfd_size_type) -1)
 650         return (bfd_vma) -1;
 651
 652       return offset - secinfo->cumulative_skips [i];
 653     }
 654
 655   return offset;
 656 }