1 /* Read ELF (Executable and Linking Format) object files for GDB.
3 Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
4 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
6 Written by Fred Fish at Cygnus Support.
8 This file is part of GDB.
10 This program is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 2 of the License, or
13 (at your option) any later version.
15 This program is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with this program; if not, write to the Free Software
22 Foundation, Inc., 59 Temple Place - Suite 330,
23 Boston, MA 02111-1307, USA. */
27 #include "gdb_string.h"
34 #include "stabsread.h"
35 #include "gdb-stabs.h"
36 #include "complaints.h"
39 extern void _initialize_elfread (void);
41 /* The struct elfinfo is available only during ELF symbol table and
42 psymtab reading. It is destroyed at the completion of psymtab-reading.
43 It's local to elf_symfile_read. */
47 file_ptr dboffset; /* Offset to dwarf debug section */
48 unsigned int dbsize; /* Size of dwarf debug section */
49 file_ptr lnoffset; /* Offset to dwarf line number section */
50 unsigned int lnsize; /* Size of dwarf line number section */
51 asection *stabsect; /* Section pointer for .stab section */
52 asection *stabindexsect; /* Section pointer for .stab.index section */
53 asection *mdebugsect; /* Section pointer for .mdebug section */
56 static void free_elfinfo (void *);
58 /* We are called once per section from elf_symfile_read. We
59 need to examine each section we are passed, check to see
60 if it is something we are interested in processing, and
61 if so, stash away some access information for the section.
63 For now we recognize the dwarf debug information sections and
64 line number sections from matching their section names. The
65 ELF definition is no real help here since it has no direct
66 knowledge of DWARF (by design, so any debugging format can be
69 We also recognize the ".stab" sections used by the Sun compilers
70 released with Solaris 2.
72 FIXME: The section names should not be hardwired strings (what
73 should they be? I don't think most object file formats have enough
74 section flags to specify what kind of debug section it is
78 elf_locate_sections (bfd *ignore_abfd, asection *sectp, void *eip)
80 register struct elfinfo *ei;
82 ei = (struct elfinfo *) eip;
83 if (STREQ (sectp->name, ".debug"))
85 ei->dboffset = sectp->filepos;
86 ei->dbsize = bfd_get_section_size_before_reloc (sectp);
88 else if (STREQ (sectp->name, ".line"))
90 ei->lnoffset = sectp->filepos;
91 ei->lnsize = bfd_get_section_size_before_reloc (sectp);
93 else if (STREQ (sectp->name, ".stab"))
97 else if (STREQ (sectp->name, ".stab.index"))
99 ei->stabindexsect = sectp;
101 else if (STREQ (sectp->name, ".mdebug"))
103 ei->mdebugsect = sectp;
107 #if 0 /* Currently unused */
110 elf_interpreter (bfd *abfd)
116 interp_sec = bfd_get_section_by_name (abfd, ".interp");
119 size = bfd_section_size (abfd, interp_sec);
120 interp = alloca (size);
121 if (bfd_get_section_contents (abfd, interp_sec, interp, (file_ptr) 0,
124 interp = savestring (interp, size - 1);
136 static struct minimal_symbol *
137 record_minimal_symbol_and_info (char *name, CORE_ADDR address,
138 enum minimal_symbol_type ms_type, char *info, /* FIXME, is this really char *? */
139 asection *bfd_section, struct objfile *objfile)
141 if (ms_type == mst_text || ms_type == mst_file_text)
142 address = SMASH_TEXT_ADDRESS (address);
144 return prim_record_minimal_symbol_and_info
145 (name, address, ms_type, info, bfd_section->index, bfd_section, objfile);
152 elf_symtab_read -- read the symbol table of an ELF file
156 void elf_symtab_read (struct objfile *objfile, int dynamic)
160 Given an objfile and a flag that specifies whether or not the objfile
161 is for an executable or not (may be shared library for example), add
162 all the global function and data symbols to the minimal symbol table.
164 In stabs-in-ELF, as implemented by Sun, there are some local symbols
165 defined in the ELF symbol table, which can be used to locate
166 the beginnings of sections from each ".o" file that was linked to
167 form the executable objfile. We gather any such info and record it
168 in data structures hung off the objfile's private data.
173 elf_symtab_read (struct objfile *objfile, int dynamic)
177 asymbol **symbol_table;
178 long number_of_symbols;
181 struct cleanup *back_to;
184 enum minimal_symbol_type ms_type;
185 /* If sectinfo is nonNULL, it contains section info that should end up
186 filed in the objfile. */
187 struct stab_section_info *sectinfo = NULL;
188 /* If filesym is nonzero, it points to a file symbol, but we haven't
189 seen any section info for it yet. */
190 asymbol *filesym = 0;
191 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
192 /* Name of filesym, as saved on the symbol_obstack. */
193 char *filesymname = obsavestring ("", 0, &objfile->symbol_obstack);
195 struct dbx_symfile_info *dbx = objfile->sym_stab_info;
197 int stripped = (bfd_get_symcount (objfile->obfd) == 0);
201 storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
203 /* Nothing to be done if there is no dynamic symtab. */
204 if (storage_needed < 0)
209 storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
210 if (storage_needed < 0)
211 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile->obfd),
212 bfd_errmsg (bfd_get_error ()));
214 if (storage_needed > 0)
216 symbol_table = (asymbol **) xmalloc (storage_needed);
217 back_to = make_cleanup (xfree, symbol_table);
219 number_of_symbols = bfd_canonicalize_dynamic_symtab (objfile->obfd,
222 number_of_symbols = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
223 if (number_of_symbols < 0)
224 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile->obfd),
225 bfd_errmsg (bfd_get_error ()));
227 for (i = 0; i < number_of_symbols; i++)
229 sym = symbol_table[i];
230 if (sym->name == NULL || *sym->name == '\0')
232 /* Skip names that don't exist (shouldn't happen), or names
233 that are null strings (may happen). */
237 offset = ANOFFSET (objfile->section_offsets, sym->section->index);
239 && sym->section == &bfd_und_section
240 && (sym->flags & BSF_FUNCTION))
242 struct minimal_symbol *msym;
244 /* Symbol is a reference to a function defined in
246 If its value is non zero then it is usually the address
247 of the corresponding entry in the procedure linkage table,
248 plus the desired section offset.
249 If its value is zero then the dynamic linker has to resolve
250 the symbol. We are unable to find any meaningful address
251 for this symbol in the executable file, so we skip it. */
252 symaddr = sym->value;
256 msym = record_minimal_symbol_and_info
257 ((char *) sym->name, symaddr,
258 mst_solib_trampoline, NULL, sym->section, objfile);
259 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
261 msym->filename = filesymname;
266 /* If it is a nonstripped executable, do not enter dynamic
267 symbols, as the dynamic symbol table is usually a subset
268 of the main symbol table. */
269 if (dynamic && !stripped)
271 if (sym->flags & BSF_FILE)
273 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
274 Chain any old one onto the objfile; remember new sym. */
275 if (sectinfo != NULL)
277 sectinfo->next = dbx->stab_section_info;
278 dbx->stab_section_info = sectinfo;
282 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
284 obsavestring ((char *) filesym->name, strlen (filesym->name),
285 &objfile->symbol_obstack);
288 else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK))
290 struct minimal_symbol *msym;
292 /* Select global/local/weak symbols. Note that bfd puts abs
293 symbols in their own section, so all symbols we are
294 interested in will have a section. */
295 /* Bfd symbols are section relative. */
296 symaddr = sym->value + sym->section->vma;
297 /* Relocate all non-absolute symbols by the section offset. */
298 if (sym->section != &bfd_abs_section)
302 /* For non-absolute symbols, use the type of the section
303 they are relative to, to intuit text/data. Bfd provides
304 no way of figuring this out for absolute symbols. */
305 if (sym->section == &bfd_abs_section)
307 /* This is a hack to get the minimal symbol type
308 right for Irix 5, which has absolute addresses
309 with special section indices for dynamic symbols. */
310 unsigned short shndx =
311 ((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
321 case SHN_MIPS_ACOMMON:
328 /* If it is an Irix dynamic symbol, skip section name
329 symbols, relocate all others by section offset. */
330 if (ms_type != mst_abs)
332 if (sym->name[0] == '.')
337 else if (sym->section->flags & SEC_CODE)
339 if (sym->flags & BSF_GLOBAL)
343 else if ((sym->name[0] == '.' && sym->name[1] == 'L')
344 || ((sym->flags & BSF_LOCAL)
345 && sym->name[0] == '$'
346 && sym->name[1] == 'L'))
347 /* Looks like a compiler-generated label. Skip
348 it. The assembler should be skipping these (to
349 keep executables small), but apparently with
350 gcc on the (deleted) delta m88k SVR4, it loses.
351 So to have us check too should be harmless (but
352 I encourage people to fix this in the assembler
353 instead of adding checks here). */
357 ms_type = mst_file_text;
360 else if (sym->section->flags & SEC_ALLOC)
362 if (sym->flags & (BSF_GLOBAL | BSF_WEAK))
364 if (sym->section->flags & SEC_LOAD)
373 else if (sym->flags & BSF_LOCAL)
375 int special_local_sym_p = 0;
376 /* Named Local variable in a Data section. Check its
377 name for stabs-in-elf. The STREQ macro checks the
378 first character inline, so we only actually do a
379 strcmp function call on names that start with 'B'
381 if (STREQ ("Bbss.bss", sym->name))
383 index = SECT_OFF_BSS (objfile);
384 special_local_sym_p = 1;
386 else if (STREQ ("Ddata.data", sym->name))
388 index = SECT_OFF_DATA (objfile);
389 special_local_sym_p = 1;
391 else if (STREQ ("Drodata.rodata", sym->name))
393 index = SECT_OFF_RODATA (objfile);
394 special_local_sym_p = 1;
396 if (special_local_sym_p)
398 /* Found a special local symbol. Allocate a
399 sectinfo, if needed, and fill it in. */
400 if (sectinfo == NULL)
406 = max (SECT_OFF_BSS (objfile),
407 max (SECT_OFF_DATA (objfile),
408 SECT_OFF_RODATA (objfile)));
409 size = (sizeof (struct stab_section_info)
410 + (sizeof (CORE_ADDR)
412 sectinfo = (struct stab_section_info *)
413 xmmalloc (objfile->md, size);
414 memset (sectinfo, 0, size);
415 sectinfo->num_sections = max_index;
418 complaint (&symfile_complaints,
419 "elf/stab section information %s without a preceding file symbol",
425 (char *) filesym->name;
430 if (sectinfo->sections[index] != 0)
432 complaint (&symfile_complaints,
433 "duplicated elf/stab section information for %s",
438 internal_error (__FILE__, __LINE__,
439 "Section index uninitialized.");
440 /* Bfd symbols are section relative. */
441 symaddr = sym->value + sym->section->vma;
442 /* Relocate non-absolute symbols by the section offset. */
443 if (sym->section != &bfd_abs_section)
448 sectinfo->sections[index] = symaddr;
450 internal_error (__FILE__, __LINE__,
451 "Section index uninitialized.");
452 /* The special local symbols don't go in the
453 minimal symbol table, so ignore this one. */
456 /* Not a special stabs-in-elf symbol, do regular
457 symbol processing. */
458 if (sym->section->flags & SEC_LOAD)
460 ms_type = mst_file_data;
464 ms_type = mst_file_bss;
469 ms_type = mst_unknown;
474 /* FIXME: Solaris2 shared libraries include lots of
475 odd "absolute" and "undefined" symbols, that play
476 hob with actions like finding what function the PC
477 is in. Ignore them if they aren't text, data, or bss. */
478 /* ms_type = mst_unknown; */
479 continue; /* Skip this symbol. */
481 /* Pass symbol size field in via BFD. FIXME!!! */
482 size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
483 msym = record_minimal_symbol_and_info
484 ((char *) sym->name, symaddr,
485 ms_type, (void *) size, sym->section, objfile);
486 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
488 msym->filename = filesymname;
490 ELF_MAKE_MSYMBOL_SPECIAL (sym, msym);
493 do_cleanups (back_to);
497 /* Scan and build partial symbols for a symbol file.
498 We have been initialized by a call to elf_symfile_init, which
499 currently does nothing.
501 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
502 in each section. We simplify it down to a single offset for all
505 MAINLINE is true if we are reading the main symbol
506 table (as opposed to a shared lib or dynamically loaded file).
508 This function only does the minimum work necessary for letting the
509 user "name" things symbolically; it does not read the entire symtab.
510 Instead, it reads the external and static symbols and puts them in partial
511 symbol tables. When more extensive information is requested of a
512 file, the corresponding partial symbol table is mutated into a full
513 fledged symbol table by going back and reading the symbols
516 We look for sections with specific names, to tell us what debug
517 format to look for: FIXME!!!
519 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
520 elfstab_build_psymtabs() handles STABS symbols;
521 mdebug_build_psymtabs() handles ECOFF debugging information.
523 Note that ELF files have a "minimal" symbol table, which looks a lot
524 like a COFF symbol table, but has only the minimal information necessary
525 for linking. We process this also, and use the information to
526 build gdb's minimal symbol table. This gives us some minimal debugging
527 capability even for files compiled without -g. */
530 elf_symfile_read (struct objfile *objfile, int mainline)
532 bfd *abfd = objfile->obfd;
534 struct cleanup *back_to;
537 init_minimal_symbol_collection ();
538 back_to = make_cleanup_discard_minimal_symbols ();
540 memset ((char *) &ei, 0, sizeof (ei));
542 /* Allocate struct to keep track of the symfile */
543 objfile->sym_stab_info = (struct dbx_symfile_info *)
544 xmmalloc (objfile->md, sizeof (struct dbx_symfile_info));
545 memset ((char *) objfile->sym_stab_info, 0, sizeof (struct dbx_symfile_info));
546 make_cleanup (free_elfinfo, (void *) objfile);
548 /* Process the normal ELF symbol table first. This may write some
549 chain of info into the dbx_symfile_info in objfile->sym_stab_info,
550 which can later be used by elfstab_offset_sections. */
552 elf_symtab_read (objfile, 0);
554 /* Add the dynamic symbols. */
556 elf_symtab_read (objfile, 1);
558 /* Install any minimal symbols that have been collected as the current
559 minimal symbols for this objfile. The debug readers below this point
560 should not generate new minimal symbols; if they do it's their
561 responsibility to install them. "mdebug" appears to be the only one
562 which will do this. */
564 install_minimal_symbols (objfile);
565 do_cleanups (back_to);
567 /* Now process debugging information, which is contained in
568 special ELF sections. */
570 /* If we are reinitializing, or if we have never loaded syms yet,
571 set table to empty. MAINLINE is cleared so that *_read_psymtab
572 functions do not all also re-initialize the psymbol table. */
575 init_psymbol_list (objfile, 0);
579 /* We first have to find them... */
580 bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);
582 /* ELF debugging information is inserted into the psymtab in the
583 order of least informative first - most informative last. Since
584 the psymtab table is searched `most recent insertion first' this
585 increases the probability that more detailed debug information
586 for a section is found.
588 For instance, an object file might contain both .mdebug (XCOFF)
589 and .debug_info (DWARF2) sections then .mdebug is inserted first
590 (searched last) and DWARF2 is inserted last (searched first). If
591 we don't do this then the XCOFF info is found first - for code in
592 an included file XCOFF info is useless. */
596 const struct ecoff_debug_swap *swap;
598 /* .mdebug section, presumably holding ECOFF debugging
600 swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
602 elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
608 /* Stab sections have an associated string table that looks like
609 a separate section. */
610 str_sect = bfd_get_section_by_name (abfd, ".stabstr");
612 /* FIXME should probably warn about a stab section without a stabstr. */
614 elfstab_build_psymtabs (objfile,
618 bfd_section_size (abfd, str_sect));
620 if (dwarf2_has_info (abfd))
622 /* DWARF 2 sections */
623 dwarf2_build_psymtabs (objfile, mainline);
625 else if (ei.dboffset && ei.lnoffset)
628 dwarf_build_psymtabs (objfile,
630 ei.dboffset, ei.dbsize,
631 ei.lnoffset, ei.lnsize);
634 if (DWARF2_BUILD_FRAME_INFO_P ())
635 DWARF2_BUILD_FRAME_INFO(objfile);
638 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
639 stab_section_info's, that might be dangling from it. */
642 free_elfinfo (void *objp)
644 struct objfile *objfile = (struct objfile *) objp;
645 struct dbx_symfile_info *dbxinfo = objfile->sym_stab_info;
646 struct stab_section_info *ssi, *nssi;
648 ssi = dbxinfo->stab_section_info;
652 xmfree (objfile->md, ssi);
656 dbxinfo->stab_section_info = 0; /* Just say No mo info about this. */
660 /* Initialize anything that needs initializing when a completely new symbol
661 file is specified (not just adding some symbols from another file, e.g. a
664 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
667 elf_new_init (struct objfile *ignore)
669 stabsread_new_init ();
670 buildsym_new_init ();
673 /* Perform any local cleanups required when we are done with a particular
674 objfile. I.E, we are in the process of discarding all symbol information
675 for an objfile, freeing up all memory held for it, and unlinking the
676 objfile struct from the global list of known objfiles. */
679 elf_symfile_finish (struct objfile *objfile)
681 if (objfile->sym_stab_info != NULL)
683 xmfree (objfile->md, objfile->sym_stab_info);
687 /* ELF specific initialization routine for reading symbols.
689 It is passed a pointer to a struct sym_fns which contains, among other
690 things, the BFD for the file whose symbols are being read, and a slot for
691 a pointer to "private data" which we can fill with goodies.
693 For now at least, we have nothing in particular to do, so this function is
697 elf_symfile_init (struct objfile *objfile)
699 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
700 find this causes a significant slowdown in gdb then we could
701 set it in the debug symbol readers only when necessary. */
702 objfile->flags |= OBJF_REORDERED;
705 /* When handling an ELF file that contains Sun STABS debug info,
706 some of the debug info is relative to the particular chunk of the
707 section that was generated in its individual .o file. E.g.
708 offsets to static variables are relative to the start of the data
709 segment *for that module before linking*. This information is
710 painfully squirreled away in the ELF symbol table as local symbols
711 with wierd names. Go get 'em when needed. */
714 elfstab_offset_sections (struct objfile *objfile, struct partial_symtab *pst)
716 char *filename = pst->filename;
717 struct dbx_symfile_info *dbx = objfile->sym_stab_info;
718 struct stab_section_info *maybe = dbx->stab_section_info;
719 struct stab_section_info *questionable = 0;
723 /* The ELF symbol info doesn't include path names, so strip the path
724 (if any) from the psymtab filename. */
725 while (0 != (p = strchr (filename, '/')))
728 /* FIXME: This linear search could speed up significantly
729 if it was chained in the right order to match how we search it,
730 and if we unchained when we found a match. */
731 for (; maybe; maybe = maybe->next)
733 if (filename[0] == maybe->filename[0]
734 && STREQ (filename, maybe->filename))
736 /* We found a match. But there might be several source files
737 (from different directories) with the same name. */
738 if (0 == maybe->found)
740 questionable = maybe; /* Might use it later. */
744 if (maybe == 0 && questionable != 0)
746 complaint (&symfile_complaints,
747 "elf/stab section information questionable for %s", filename);
748 maybe = questionable;
753 /* Found it! Allocate a new psymtab struct, and fill it in. */
755 pst->section_offsets = (struct section_offsets *)
756 obstack_alloc (&objfile->psymbol_obstack,
757 SIZEOF_N_SECTION_OFFSETS (objfile->num_sections));
758 for (i = 0; i < maybe->num_sections; i++)
759 (pst->section_offsets)->offsets[i] = maybe->sections[i];
763 /* We were unable to find any offsets for this file. Complain. */
764 if (dbx->stab_section_info) /* If there *is* any info, */
765 complaint (&symfile_complaints,
766 "elf/stab section information missing for %s", filename);
769 /* Register that we are able to handle ELF object file formats. */
771 static struct sym_fns elf_sym_fns =
773 bfd_target_elf_flavour,
774 elf_new_init, /* sym_new_init: init anything gbl to entire symtab */
775 elf_symfile_init, /* sym_init: read initial info, setup for sym_read() */
776 elf_symfile_read, /* sym_read: read a symbol file into symtab */
777 elf_symfile_finish, /* sym_finish: finished with file, cleanup */
778 default_symfile_offsets, /* sym_offsets: Translate ext. to int. relocation */
779 NULL /* next: pointer to next struct sym_fns */
783 _initialize_elfread (void)
785 add_symtab_fns (&elf_sym_fns);