gdb/elfread.c

   1 /* Read ELF (Executable and Linking Format) object files for GDB.
   2    Copyright 1991, 1992 Free Software Foundation, Inc.
   3    Written by Fred Fish at Cygnus Support.
   4
   5 This file is part of GDB.
   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., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  20
  21 #include "defs.h"
  22 #include "bfd.h"
  23 #include <time.h> /* For time_t in libbfd.h.  */
  24 #include "libbfd.h"             /* For bfd_elf_find_section */
  25 #include "libelf.h"
  26 #include "symtab.h"
  27 #include "symfile.h"
  28 #include "objfiles.h"
  29 #include "buildsym.h"
  30 #include "stabsread.h"
  31 #include "gdb-stabs.h"
  32 #include "complaints.h"
  33 #include <string.h>
  34 #include "demangle.h"
  35
  36 /* The struct elfinfo is available only during ELF symbol table and
  37    psymtab reading.  It is destroyed at the complation of psymtab-reading.
  38    It's local to elf_symfile_read.  */
  39
  40 struct elfinfo {
  41   file_ptr dboffset;            /* Offset to dwarf debug section */
  42   unsigned int dbsize;          /* Size of dwarf debug section */
  43   file_ptr lnoffset;            /* Offset to dwarf line number section */
  44   unsigned int lnsize;          /* Size of dwarf line number section */
  45   asection *stabsect;           /* Section pointer for .stab section */
  46   asection *stabindexsect;      /* Section pointer for .stab.index section */
  47 };
  48
  49 /* Various things we might complain about... */
  50
  51 struct complaint section_info_complaint =
  52   {"elf/stab section information %s without a preceding file symbol", 0, 0};
  53
  54 struct complaint section_info_dup_complaint =
  55   {"duplicated elf/stab section information for %s", 0, 0};
  56
  57 struct complaint stab_info_mismatch_complaint =
  58   {"elf/stab section information missing for %s", 0, 0};
  59
  60 struct complaint stab_info_questionable_complaint =
  61   {"elf/stab section information questionable for %s", 0, 0};
  62
  63 static void
  64 elf_symfile_init PARAMS ((struct objfile *));
  65
  66 static void
  67 elf_new_init PARAMS ((struct objfile *));
  68
  69 static void
  70 elf_symfile_read PARAMS ((struct objfile *, struct section_offsets *, int));
  71
  72 static void
  73 elf_symfile_finish PARAMS ((struct objfile *));
  74
  75 static void
  76 elf_symtab_read PARAMS ((bfd *,  CORE_ADDR, struct objfile *));
  77
  78 static void
  79 free_elfinfo PARAMS ((PTR));
  80
  81 static struct section_offsets *
  82 elf_symfile_offsets PARAMS ((struct objfile *, CORE_ADDR));
  83
  84 static void
  85 record_minimal_symbol_and_info PARAMS ((char *, CORE_ADDR,
  86                                         enum minimal_symbol_type, char *,
  87                                         struct objfile *));
  88
  89 static void
  90 elf_locate_sections PARAMS ((bfd *, asection *, PTR));
  91
  92 /* We are called once per section from elf_symfile_read.  We
  93    need to examine each section we are passed, check to see
  94    if it is something we are interested in processing, and
  95    if so, stash away some access information for the section.
  96
  97    For now we recognize the dwarf debug information sections and
  98    line number sections from matching their section names.  The
  99    ELF definition is no real help here since it has no direct
 100    knowledge of DWARF (by design, so any debugging format can be
 101    used).
 102
 103    We also recognize the ".stab" sections used by the Sun compilers
 104    released with Solaris 2.
 105
 106    FIXME:  The section names should not be hardwired strings. */
 107
 108 static void
 109 elf_locate_sections (ignore_abfd, sectp, eip)
 110      bfd *ignore_abfd;
 111      asection *sectp;
 112      PTR eip;
 113 {
 114   register struct elfinfo *ei;
 115
 116   ei = (struct elfinfo *) eip;
 117   if (STREQ (sectp -> name, ".debug"))
 118     {
 119       ei -> dboffset = sectp -> filepos;
 120       ei -> dbsize = bfd_get_section_size_before_reloc (sectp);
 121     }
 122   else if (STREQ (sectp -> name, ".line"))
 123     {
 124       ei -> lnoffset = sectp -> filepos;
 125       ei -> lnsize = bfd_get_section_size_before_reloc (sectp);
 126     }
 127   else if (STREQ (sectp -> name, ".stab"))
 128     {
 129       ei -> stabsect = sectp;
 130     }
 131   else if (STREQ (sectp -> name, ".stab.index"))
 132     {
 133       ei -> stabindexsect = sectp;
 134     }
 135 }
 136
 137 #if 0   /* Currently unused */
 138
 139 char *
 140 elf_interpreter (abfd)
 141      bfd *abfd;
 142 {
 143   sec_ptr interp_sec;
 144   unsigned size;
 145   char *interp = NULL;
 146
 147   interp_sec = bfd_get_section_by_name (abfd, ".interp");
 148   if (interp_sec)
 149     {
 150       size = bfd_section_size (abfd, interp_sec);
 151       interp = alloca (size);
 152       if (bfd_get_section_contents (abfd, interp_sec, interp, (file_ptr)0,
 153                                     size))
 154         {
 155           interp = savestring (interp, size - 1);
 156         }
 157       else
 158         {
 159           interp = NULL;
 160         }
 161     }
 162   return (interp);
 163 }
 164
 165 #endif
 166
 167 static void
 168 record_minimal_symbol_and_info (name, address, ms_type, info, objfile)
 169      char *name;
 170      CORE_ADDR address;
 171      enum minimal_symbol_type ms_type;
 172      char *info;                /* FIXME, is this really char *? */
 173      struct objfile *objfile;
 174 {
 175   name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
 176   prim_record_minimal_symbol_and_info (name, address, ms_type, info, -1);
 177 }
 178
 179 /*
 180
 181 LOCAL FUNCTION
 182
 183         elf_symtab_read -- read the symbol table of an ELF file
 184
 185 SYNOPSIS
 186
 187         void elf_symtab_read (bfd *abfd, CORE_ADDR addr,
 188                               struct objfile *objfile)
 189
 190 DESCRIPTION
 191
 192         Given an open bfd, a base address to relocate symbols to, and a
 193         flag that specifies whether or not this bfd is for an executable
 194         or not (may be shared library for example), add all the global
 195         function and data symbols to the minimal symbol table.
 196
 197         In stabs-in-ELF, as implemented by Sun, there are some local symbols
 198         defined in the ELF symbol table, which can be used to locate
 199         the beginnings of sections from each ".o" file that was linked to
 200         form the executable objfile.  We gather any such info and record it
 201         in data structures hung off the objfile's private data.
 202
 203 */
 204
 205 static void
 206 elf_symtab_read (abfd, addr, objfile)
 207      bfd *abfd;
 208      CORE_ADDR addr;
 209      struct objfile *objfile;
 210 {
 211   unsigned int storage_needed;
 212   asymbol *sym;
 213   asymbol **symbol_table;
 214   unsigned int number_of_symbols;
 215   unsigned int i;
 216   int index;
 217   struct cleanup *back_to;
 218   CORE_ADDR symaddr;
 219   enum minimal_symbol_type ms_type;
 220   /* If sectinfo is nonNULL, it contains section info that should end up
 221      filed in the objfile.  */
 222   struct stab_section_info *sectinfo = NULL;
 223   /* If filesym is nonzero, it points to a file symbol, but we haven't
 224      seen any section info for it yet.  */
 225   asymbol *filesym = 0;
 226   struct dbx_symfile_info *dbx = (struct dbx_symfile_info *)
 227                                  objfile->sym_private;
 228   unsigned long size;
 229
 230   storage_needed = get_symtab_upper_bound (abfd);
 231   if (storage_needed > 0)
 232     {
 233       symbol_table = (asymbol **) xmalloc (storage_needed);
 234       back_to = make_cleanup (free, symbol_table);
 235       number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
 236       for (i = 0; i < number_of_symbols; i++)
 237         {
 238           sym = symbol_table[i];
 239           if (sym -> name == NULL || *sym -> name == '\0')
 240             {
 241               /* Skip names that don't exist (shouldn't happen), or names
 242                  that are null strings (may happen). */
 243               continue;
 244             }
 245           if (sym -> flags & BSF_FILE)
 246             {
 247               /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
 248                  Chain any old one onto the objfile; remember new sym.  */
 249               if (sectinfo != NULL)
 250                 {
 251                   sectinfo -> next = dbx -> stab_section_info;
 252                   dbx -> stab_section_info = sectinfo;
 253                   sectinfo = NULL;
 254                 }
 255               filesym = sym;
 256             }
 257           else if (sym -> flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK))
 258             {
 259               /* Select global/local/weak symbols.  Note that bfd puts abs
 260                  symbols in their own section, so all symbols we are
 261                  interested in will have a section. */
 262               /* Bfd symbols are section relative. */
 263               symaddr = sym -> value + sym -> section -> vma;
 264               /* Relocate all non-absolute symbols by base address.  */
 265               if (sym -> section != &bfd_abs_section)
 266                 {
 267                   symaddr += addr;
 268                 }
 269               /* For non-absolute symbols, use the type of the section
 270                  they are relative to, to intuit text/data.  Bfd provides
 271                  no way of figuring this out for absolute symbols. */
 272               if (sym -> section == &bfd_abs_section)
 273                 {
 274                   ms_type = mst_abs;
 275                 }
 276               else if (sym -> section -> flags & SEC_CODE)
 277                 {
 278                   if (sym -> flags & BSF_GLOBAL)
 279                     {
 280                       ms_type = mst_text;
 281                     }
 282                   else if (sym->name[0] == '.' && sym->name[1] == 'L')
 283                     /* Looks like a compiler-generated label.  Skip it.
 284                        The assembler should be skipping these (to keep
 285                        executables small), but apparently with gcc on the
 286                        delta m88k SVR4, it loses.  So to have us check too
 287                        should be harmless (but I encourage people to fix this
 288                        in the assembler instead of adding checks here).  */
 289                     continue;
 290                   else
 291                     {
 292                       ms_type = mst_file_text;
 293                     }
 294                 }
 295               else if (sym -> section -> flags & SEC_DATA)
 296                 {
 297                   if (sym -> flags & BSF_GLOBAL)
 298                     {
 299                       if (sym -> section -> flags & SEC_HAS_CONTENTS)
 300                         {
 301                           ms_type = mst_data;
 302                         }
 303                       else
 304                         {
 305                           ms_type = mst_bss;
 306                         }
 307                     }
 308                   else if (sym -> flags & BSF_LOCAL)
 309                     {
 310                       /* Named Local variable in a Data section.  Check its
 311                          name for stabs-in-elf.  The STREQ macro checks the
 312                          first character inline, so we only actually do a
 313                          strcmp function call on names that start with 'B'
 314                          or 'D' */
 315                       index = SECT_OFF_MAX;
 316                       if (STREQ ("Bbss.bss", sym -> name))
 317                         {
 318                           index = SECT_OFF_BSS;
 319                         }
 320                       else if (STREQ ("Ddata.data", sym -> name))
 321                         {
 322                           index = SECT_OFF_DATA;
 323                         }
 324                       else if (STREQ ("Drodata.rodata", sym -> name))
 325                         {
 326                           index = SECT_OFF_RODATA;
 327                         }
 328                       if (index != SECT_OFF_MAX)
 329                         {
 330                           /* Found a special local symbol.  Allocate a
 331                              sectinfo, if needed, and fill it in.  */
 332                           if (sectinfo == NULL)
 333                             {
 334                               sectinfo = (struct stab_section_info *)
 335                                 xmmalloc (objfile -> md, sizeof (*sectinfo));
 336                               memset ((PTR) sectinfo, 0, sizeof (*sectinfo));
 337                               if (filesym == NULL)
 338                                 {
 339                                   complain (&section_info_complaint,
 340                                             sym -> name);
 341                                 }
 342                               else
 343                                 {
 344                                   sectinfo -> filename =
 345                                     (char *) filesym -> name;
 346                                 }
 347                             }
 348                           if (sectinfo -> sections[index] != 0)
 349                             {
 350                               complain (&section_info_dup_complaint,
 351                                         sectinfo -> filename);
 352                             }
 353                           /* Bfd symbols are section relative. */
 354                           symaddr = sym -> value + sym -> section -> vma;
 355                           /* Relocate non-absolute symbols by base address.  */
 356                           if (sym -> section != &bfd_abs_section)
 357                             {
 358                               symaddr += addr;
 359                             }
 360                           sectinfo -> sections[index] = symaddr;
 361                           /* The special local symbols don't go in the
 362                              minimal symbol table, so ignore this one. */
 363                           continue;
 364                         }
 365                       /* Not a special stabs-in-elf symbol, do regular
 366                          symbol processing. */
 367                       if (sym -> section -> flags & SEC_HAS_CONTENTS)
 368                         {
 369                           ms_type = mst_file_data;
 370                         }
 371                       else
 372                         {
 373                           ms_type = mst_file_bss;
 374                         }
 375                     }
 376                   else
 377                     {
 378                       ms_type = mst_unknown;
 379                     }
 380                 }
 381               else
 382                 {
 383                   /* FIXME:  Solaris2 shared libraries include lots of
 384                      odd "absolute" and "undefined" symbols, that play
 385                      hob with actions like finding what function the PC
 386                      is in.  Ignore them if they aren't text, data, or bss.  */
 387                   /* ms_type = mst_unknown; */
 388                   continue;             /* Skip this symbol. */
 389                 }
 390               /* Pass symbol size field in via BFD.  FIXME!!!  */
 391               size = ((elf_symbol_type *) sym) -> internal_elf_sym.st_size;
 392               record_minimal_symbol_and_info ((char *) sym -> name, symaddr,
 393                                               ms_type, (PTR) size, objfile);
 394             }
 395         }
 396       do_cleanups (back_to);
 397     }
 398 }
 399
 400 /* Scan and build partial symbols for a symbol file.
 401    We have been initialized by a call to elf_symfile_init, which
 402    currently does nothing.
 403
 404    SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
 405    in each section.  We simplify it down to a single offset for all
 406    symbols.  FIXME.
 407
 408    MAINLINE is true if we are reading the main symbol
 409    table (as opposed to a shared lib or dynamically loaded file).
 410
 411    This function only does the minimum work necessary for letting the
 412    user "name" things symbolically; it does not read the entire symtab.
 413    Instead, it reads the external and static symbols and puts them in partial
 414    symbol tables.  When more extensive information is requested of a
 415    file, the corresponding partial symbol table is mutated into a full
 416    fledged symbol table by going back and reading the symbols
 417    for real.
 418
 419    We look for sections with specific names, to tell us what debug
 420    format to look for:  FIXME!!!
 421
 422    dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
 423    elfstab_build_psymtabs() handles STABS symbols.
 424
 425    Note that ELF files have a "minimal" symbol table, which looks a lot
 426    like a COFF symbol table, but has only the minimal information necessary
 427    for linking.  We process this also, and use the information to
 428    build gdb's minimal symbol table.  This gives us some minimal debugging
 429    capability even for files compiled without -g.  */
 430
 431 static void
 432 elf_symfile_read (objfile, section_offsets, mainline)
 433      struct objfile *objfile;
 434      struct section_offsets *section_offsets;
 435      int mainline;
 436 {
 437   bfd *abfd = objfile->obfd;
 438   struct elfinfo ei;
 439   struct cleanup *back_to;
 440   CORE_ADDR offset;
 441
 442   init_minimal_symbol_collection ();
 443   back_to = make_cleanup (discard_minimal_symbols, 0);
 444
 445   memset ((char *) &ei, 0, sizeof (ei));
 446
 447   /* Allocate struct to keep track of the symfile */
 448   objfile->sym_private = (PTR)
 449     xmmalloc (objfile -> md, sizeof (struct dbx_symfile_info));
 450   memset ((char *) objfile->sym_private, 0, sizeof (struct dbx_symfile_info));
 451   make_cleanup (free_elfinfo, (PTR) objfile);
 452
 453   /* Process the normal ELF symbol table first.  This may write some
 454      chain of info into the dbx_symfile_info in objfile->sym_private,
 455      which can later be used by elfstab_offset_sections.  */
 456
 457   /* FIXME, should take a section_offsets param, not just an offset.  */
 458   offset = ANOFFSET (section_offsets, 0);
 459   elf_symtab_read (abfd, offset, objfile);
 460
 461   /* Now process debugging information, which is contained in
 462      special ELF sections.  We first have to find them... */
 463
 464   bfd_map_over_sections (abfd, elf_locate_sections, (PTR) &ei);
 465   if (ei.dboffset && ei.lnoffset)
 466     {
 467       /* DWARF sections */
 468       dwarf_build_psymtabs (objfile,
 469                             section_offsets, mainline,
 470                             ei.dboffset, ei.dbsize,
 471                             ei.lnoffset, ei.lnsize);
 472     }
 473   if (ei.stabsect)
 474     {
 475       /* STABS sections */
 476
 477       /* FIXME:  Sun didn't really know how to implement this well.
 478          They made .stab sections that don't point to the .stabstr
 479          section with the sh_link field.  BFD doesn't make string table
 480          sections visible to the caller.  So we have to search the
 481          ELF section table, not the BFD section table, for the string
 482          table.  */
 483       struct elf32_internal_shdr *elf_sect;
 484
 485       elf_sect = bfd_elf_find_section (abfd, ".stabstr");
 486       if (elf_sect)
 487         elfstab_build_psymtabs (objfile,
 488           section_offsets,
 489           mainline,
 490           ei.stabsect->filepos,                         /* .stab offset */
 491           bfd_get_section_size_before_reloc (ei.stabsect),/* .stab size */
 492           (file_ptr) elf_sect->sh_offset,               /* .stabstr offset */
 493           elf_sect->sh_size);                           /* .stabstr size */
 494     }
 495
 496   if (!have_partial_symbols ())
 497     {
 498       wrap_here ("");
 499       printf_filtered ("(no debugging symbols found)...");
 500       wrap_here ("");
 501     }
 502
 503   /* Install any minimal symbols that have been collected as the current
 504      minimal symbols for this objfile. */
 505
 506   install_minimal_symbols (objfile);
 507
 508   do_cleanups (back_to);
 509 }
 510
 511 /* This cleans up the objfile's sym_private pointer, and the chain of
 512    stab_section_info's, that might be dangling from it.  */
 513
 514 static void
 515 free_elfinfo (objp)
 516      PTR objp;
 517 {
 518   struct objfile *objfile = (struct objfile *)objp;
 519   struct dbx_symfile_info *dbxinfo = (struct dbx_symfile_info *)
 520                                      objfile->sym_private;
 521   struct stab_section_info *ssi, *nssi;
 522
 523   ssi = dbxinfo->stab_section_info;
 524   while (ssi)
 525     {
 526       nssi = ssi->next;
 527       mfree (objfile->md, ssi);
 528       ssi = nssi;
 529     }
 530
 531   dbxinfo->stab_section_info = 0;       /* Just say No mo info about this.  */
 532 }
 533
 534
 535 /* Initialize anything that needs initializing when a completely new symbol
 536    file is specified (not just adding some symbols from another file, e.g. a
 537    shared library).
 538
 539    We reinitialize buildsym, since we may be reading stabs from an ELF file.  */
 540
 541 static void
 542 elf_new_init (ignore)
 543      struct objfile *ignore;
 544 {
 545   stabsread_new_init ();
 546   buildsym_new_init ();
 547 }
 548
 549 /* Perform any local cleanups required when we are done with a particular
 550    objfile.  I.E, we are in the process of discarding all symbol information
 551    for an objfile, freeing up all memory held for it, and unlinking the
 552    objfile struct from the global list of known objfiles. */
 553
 554 static void
 555 elf_symfile_finish (objfile)
 556      struct objfile *objfile;
 557 {
 558   if (objfile -> sym_private != NULL)
 559     {
 560       mfree (objfile -> md, objfile -> sym_private);
 561     }
 562 }
 563
 564 /* ELF specific initialization routine for reading symbols.
 565
 566    It is passed a pointer to a struct sym_fns which contains, among other
 567    things, the BFD for the file whose symbols are being read, and a slot for
 568    a pointer to "private data" which we can fill with goodies.
 569
 570    For now at least, we have nothing in particular to do, so this function is
 571    just a stub. */
 572
 573 static void
 574 elf_symfile_init (ignore)
 575      struct objfile *ignore;
 576 {
 577 }
 578
 579 /* ELF specific parsing routine for section offsets.
 580
 581    Plain and simple for now.  */
 582
 583 static
 584 struct section_offsets *
 585 elf_symfile_offsets (objfile, addr)
 586      struct objfile *objfile;
 587      CORE_ADDR addr;
 588 {
 589   struct section_offsets *section_offsets;
 590   int i;
 591
 592   section_offsets = (struct section_offsets *)
 593     obstack_alloc (&objfile -> psymbol_obstack,
 594                    sizeof (struct section_offsets) +
 595                           sizeof (section_offsets->offsets) * (SECT_OFF_MAX-1));
 596
 597   for (i = 0; i < SECT_OFF_MAX; i++)
 598     ANOFFSET (section_offsets, i) = addr;
 599
 600   return section_offsets;
 601 }
 602 \f
 603 /* When handling an ELF file that contains Sun STABS debug info,
 604    some of the debug info is relative to the particular chunk of the
 605    section that was generated in its individual .o file.  E.g.
 606    offsets to static variables are relative to the start of the data
 607    segment *for that module before linking*.  This information is
 608    painfully squirreled away in the ELF symbol table as local symbols
 609    with wierd names.  Go get 'em when needed.  */
 610
 611 void
 612 elfstab_offset_sections (objfile, pst)
 613      struct objfile *objfile;
 614      struct partial_symtab *pst;
 615 {
 616   char *filename = pst->filename;
 617   struct dbx_symfile_info *dbx = (struct dbx_symfile_info *)
 618                                  objfile->sym_private;
 619   struct stab_section_info *maybe = dbx->stab_section_info;
 620   struct stab_section_info *questionable = 0;
 621   int i;
 622   char *p;
 623
 624   /* The ELF symbol info doesn't include path names, so strip the path
 625      (if any) from the psymtab filename.  */
 626   while (0 != (p = strchr (filename, '/')))
 627     filename = p+1;
 628
 629   /* FIXME:  This linear search could speed up significantly
 630      if it was chained in the right order to match how we search it,
 631      and if we unchained when we found a match. */
 632   for (; maybe; maybe = maybe->next)
 633     {
 634       if (filename[0] == maybe->filename[0]
 635           && STREQ (filename, maybe->filename))
 636         {
 637           /* We found a match.  But there might be several source files
 638              (from different directories) with the same name.  */
 639           if (0 == maybe->found)
 640             break;
 641           questionable = maybe;         /* Might use it later.  */
 642         }
 643     }
 644
 645   if (maybe == 0 && questionable != 0)
 646     {
 647       complain (&stab_info_questionable_complaint, filename);
 648       maybe = questionable;
 649     }
 650
 651   if (maybe)
 652     {
 653       /* Found it!  Allocate a new psymtab struct, and fill it in.  */
 654       maybe->found++;
 655       pst->section_offsets = (struct section_offsets *)
 656         obstack_alloc (&objfile -> psymbol_obstack,
 657                        sizeof (struct section_offsets) +
 658                sizeof (pst->section_offsets->offsets) * (SECT_OFF_MAX-1));
 659
 660       for (i = 0; i < SECT_OFF_MAX; i++)
 661         ANOFFSET (pst->section_offsets, i) = maybe->sections[i];
 662       return;
 663     }
 664
 665   /* We were unable to find any offsets for this file.  Complain.  */
 666   if (dbx->stab_section_info)           /* If there *is* any info, */
 667     complain (&stab_info_mismatch_complaint, filename);
 668 }
 669 \f
 670 /*  Register that we are able to handle ELF object file formats and DWARF
 671     debugging formats.
 672
 673     Unlike other object file formats, where the debugging information format
 674     is implied by the object file format, the ELF object file format and the
 675     DWARF debugging information format are two distinct, and potentially
 676     separate entities.  I.E. it is perfectly possible to have ELF objects
 677     with debugging formats other than DWARF.  And it is conceivable that the
 678     DWARF debugging format might be used with another object file format,
 679     like COFF, by simply using COFF's custom section feature.
 680
 681     GDB, and to a lesser extent BFD, should support the notion of separate
 682     object file formats and debugging information formats.  For now, we just
 683     use "elf" in the same sense as "a.out" or "coff", to imply both the ELF
 684     object file format and the DWARF debugging format. */
 685
 686 static struct sym_fns elf_sym_fns =
 687 {
 688   "elf",                /* sym_name: name or name prefix of BFD target type */
 689   3,                    /* sym_namelen: number of significant sym_name chars */
 690   elf_new_init,         /* sym_new_init: init anything gbl to entire symtab */
 691   elf_symfile_init,     /* sym_init: read initial info, setup for sym_read() */
 692   elf_symfile_read,     /* sym_read: read a symbol file into symtab */
 693   elf_symfile_finish,   /* sym_finish: finished with file, cleanup */
 694   elf_symfile_offsets,  /* sym_offsets:  Translate ext. to int. relocation */
 695   NULL                  /* next: pointer to next struct sym_fns */
 696 };
 697
 698 void
 699 _initialize_elfread ()
 700 {
 701   add_symtab_fns (&elf_sym_fns);
 702 }