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, 2004 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)
82 ei = (struct elfinfo *) eip;
83 if (strcmp (sectp->name, ".debug") == 0)
85 ei->dboffset = sectp->filepos;
86 ei->dbsize = bfd_get_section_size_before_reloc (sectp);
88 else if (strcmp (sectp->name, ".line") == 0)
90 ei->lnoffset = sectp->filepos;
91 ei->lnsize = bfd_get_section_size_before_reloc (sectp);
93 else if (strcmp (sectp->name, ".stab") == 0)
97 else if (strcmp (sectp->name, ".stab.index") == 0)
99 ei->stabindexsect = sectp;
101 else if (strcmp (sectp->name, ".mdebug") == 0)
103 ei->mdebugsect = sectp;
107 static struct minimal_symbol *
108 record_minimal_symbol (char *name, CORE_ADDR address,
109 enum minimal_symbol_type ms_type,
110 asection *bfd_section, struct objfile *objfile)
112 if (ms_type == mst_text || ms_type == mst_file_text)
113 address = SMASH_TEXT_ADDRESS (address);
115 return prim_record_minimal_symbol_and_info
116 (name, address, ms_type, NULL, bfd_section->index, bfd_section, objfile);
123 elf_symtab_read -- read the symbol table of an ELF file
127 void elf_symtab_read (struct objfile *objfile, int dynamic)
131 Given an objfile and a flag that specifies whether or not the objfile
132 is for an executable or not (may be shared library for example), add
133 all the global function and data symbols to the minimal symbol table.
135 In stabs-in-ELF, as implemented by Sun, there are some local symbols
136 defined in the ELF symbol table, which can be used to locate
137 the beginnings of sections from each ".o" file that was linked to
138 form the executable objfile. We gather any such info and record it
139 in data structures hung off the objfile's private data.
144 elf_symtab_read (struct objfile *objfile, int dynamic)
148 asymbol **symbol_table;
149 long number_of_symbols;
151 struct cleanup *back_to;
154 enum minimal_symbol_type ms_type;
155 /* If sectinfo is nonNULL, it contains section info that should end up
156 filed in the objfile. */
157 struct stab_section_info *sectinfo = NULL;
158 /* If filesym is nonzero, it points to a file symbol, but we haven't
159 seen any section info for it yet. */
160 asymbol *filesym = 0;
161 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
162 /* Name of filesym, as saved on the objfile_obstack. */
163 char *filesymname = obsavestring ("", 0, &objfile->objfile_obstack);
165 struct dbx_symfile_info *dbx = objfile->sym_stab_info;
166 int stripped = (bfd_get_symcount (objfile->obfd) == 0);
170 storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
172 /* Nothing to be done if there is no dynamic symtab. */
173 if (storage_needed < 0)
178 storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
179 if (storage_needed < 0)
180 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile->obfd),
181 bfd_errmsg (bfd_get_error ()));
183 if (storage_needed > 0)
185 symbol_table = (asymbol **) xmalloc (storage_needed);
186 back_to = make_cleanup (xfree, symbol_table);
188 number_of_symbols = bfd_canonicalize_dynamic_symtab (objfile->obfd,
191 number_of_symbols = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
192 if (number_of_symbols < 0)
193 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile->obfd),
194 bfd_errmsg (bfd_get_error ()));
196 for (i = 0; i < number_of_symbols; i++)
198 sym = symbol_table[i];
199 if (sym->name == NULL || *sym->name == '\0')
201 /* Skip names that don't exist (shouldn't happen), or names
202 that are null strings (may happen). */
206 offset = ANOFFSET (objfile->section_offsets, sym->section->index);
208 && sym->section == &bfd_und_section
209 && (sym->flags & BSF_FUNCTION))
211 struct minimal_symbol *msym;
213 /* Symbol is a reference to a function defined in
215 If its value is non zero then it is usually the address
216 of the corresponding entry in the procedure linkage table,
217 plus the desired section offset.
218 If its value is zero then the dynamic linker has to resolve
219 the symbol. We are unable to find any meaningful address
220 for this symbol in the executable file, so we skip it. */
221 symaddr = sym->value;
225 msym = record_minimal_symbol
226 ((char *) sym->name, symaddr,
227 mst_solib_trampoline, sym->section, objfile);
228 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
230 msym->filename = filesymname;
235 /* If it is a nonstripped executable, do not enter dynamic
236 symbols, as the dynamic symbol table is usually a subset
237 of the main symbol table. */
238 if (dynamic && !stripped)
240 if (sym->flags & BSF_FILE)
242 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
243 Chain any old one onto the objfile; remember new sym. */
244 if (sectinfo != NULL)
246 sectinfo->next = dbx->stab_section_info;
247 dbx->stab_section_info = sectinfo;
251 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
253 obsavestring ((char *) filesym->name, strlen (filesym->name),
254 &objfile->objfile_obstack);
257 else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK))
259 struct minimal_symbol *msym;
261 /* Select global/local/weak symbols. Note that bfd puts abs
262 symbols in their own section, so all symbols we are
263 interested in will have a section. */
264 /* Bfd symbols are section relative. */
265 symaddr = sym->value + sym->section->vma;
266 /* Relocate all non-absolute symbols by the section offset. */
267 if (sym->section != &bfd_abs_section)
271 /* For non-absolute symbols, use the type of the section
272 they are relative to, to intuit text/data. Bfd provides
273 no way of figuring this out for absolute symbols. */
274 if (sym->section == &bfd_abs_section)
276 /* This is a hack to get the minimal symbol type
277 right for Irix 5, which has absolute addresses
278 with special section indices for dynamic symbols. */
279 unsigned short shndx =
280 ((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
290 case SHN_MIPS_ACOMMON:
297 /* If it is an Irix dynamic symbol, skip section name
298 symbols, relocate all others by section offset. */
299 if (ms_type != mst_abs)
301 if (sym->name[0] == '.')
306 else if (sym->section->flags & SEC_CODE)
308 if (sym->flags & BSF_GLOBAL)
312 else if ((sym->name[0] == '.' && sym->name[1] == 'L')
313 || ((sym->flags & BSF_LOCAL)
314 && sym->name[0] == '$'
315 && sym->name[1] == 'L'))
316 /* Looks like a compiler-generated label. Skip
317 it. The assembler should be skipping these (to
318 keep executables small), but apparently with
319 gcc on the (deleted) delta m88k SVR4, it loses.
320 So to have us check too should be harmless (but
321 I encourage people to fix this in the assembler
322 instead of adding checks here). */
326 ms_type = mst_file_text;
329 else if (sym->section->flags & SEC_ALLOC)
331 if (sym->flags & (BSF_GLOBAL | BSF_WEAK))
333 if (sym->section->flags & SEC_LOAD)
342 else if (sym->flags & BSF_LOCAL)
344 /* Named Local variable in a Data section.
345 Check its name for stabs-in-elf. */
346 int special_local_sect;
347 if (strcmp ("Bbss.bss", sym->name) == 0)
348 special_local_sect = SECT_OFF_BSS (objfile);
349 else if (strcmp ("Ddata.data", sym->name) == 0)
350 special_local_sect = SECT_OFF_DATA (objfile);
351 else if (strcmp ("Drodata.rodata", sym->name) == 0)
352 special_local_sect = SECT_OFF_RODATA (objfile);
354 special_local_sect = -1;
355 if (special_local_sect >= 0)
357 /* Found a special local symbol. Allocate a
358 sectinfo, if needed, and fill it in. */
359 if (sectinfo == NULL)
365 = max (SECT_OFF_BSS (objfile),
366 max (SECT_OFF_DATA (objfile),
367 SECT_OFF_RODATA (objfile)));
369 /* max_index is the largest index we'll
370 use into this array, so we must
371 allocate max_index+1 elements for it.
372 However, 'struct stab_section_info'
373 already includes one element, so we
374 need to allocate max_index aadditional
376 size = (sizeof (struct stab_section_info)
377 + (sizeof (CORE_ADDR)
379 sectinfo = (struct stab_section_info *)
380 xmmalloc (objfile->md, size);
381 memset (sectinfo, 0, size);
382 sectinfo->num_sections = max_index;
385 complaint (&symfile_complaints,
386 "elf/stab section information %s without a preceding file symbol",
392 (char *) filesym->name;
395 if (sectinfo->sections[special_local_sect] != 0)
396 complaint (&symfile_complaints,
397 "duplicated elf/stab section information for %s",
399 /* BFD symbols are section relative. */
400 symaddr = sym->value + sym->section->vma;
401 /* Relocate non-absolute symbols by the
403 if (sym->section != &bfd_abs_section)
405 sectinfo->sections[special_local_sect] = symaddr;
406 /* The special local symbols don't go in the
407 minimal symbol table, so ignore this one. */
410 /* Not a special stabs-in-elf symbol, do regular
411 symbol processing. */
412 if (sym->section->flags & SEC_LOAD)
414 ms_type = mst_file_data;
418 ms_type = mst_file_bss;
423 ms_type = mst_unknown;
428 /* FIXME: Solaris2 shared libraries include lots of
429 odd "absolute" and "undefined" symbols, that play
430 hob with actions like finding what function the PC
431 is in. Ignore them if they aren't text, data, or bss. */
432 /* ms_type = mst_unknown; */
433 continue; /* Skip this symbol. */
435 msym = record_minimal_symbol
436 ((char *) sym->name, symaddr,
437 ms_type, sym->section, objfile);
440 /* Pass symbol size field in via BFD. FIXME!!! */
441 unsigned long size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
442 MSYMBOL_SIZE(msym) = size;
444 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
446 msym->filename = filesymname;
448 ELF_MAKE_MSYMBOL_SPECIAL (sym, msym);
451 do_cleanups (back_to);
455 /* Scan and build partial symbols for a symbol file.
456 We have been initialized by a call to elf_symfile_init, which
457 currently does nothing.
459 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
460 in each section. We simplify it down to a single offset for all
463 MAINLINE is true if we are reading the main symbol
464 table (as opposed to a shared lib or dynamically loaded file).
466 This function only does the minimum work necessary for letting the
467 user "name" things symbolically; it does not read the entire symtab.
468 Instead, it reads the external and static symbols and puts them in partial
469 symbol tables. When more extensive information is requested of a
470 file, the corresponding partial symbol table is mutated into a full
471 fledged symbol table by going back and reading the symbols
474 We look for sections with specific names, to tell us what debug
475 format to look for: FIXME!!!
477 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
478 elfstab_build_psymtabs() handles STABS symbols;
479 mdebug_build_psymtabs() handles ECOFF debugging information.
481 Note that ELF files have a "minimal" symbol table, which looks a lot
482 like a COFF symbol table, but has only the minimal information necessary
483 for linking. We process this also, and use the information to
484 build gdb's minimal symbol table. This gives us some minimal debugging
485 capability even for files compiled without -g. */
488 elf_symfile_read (struct objfile *objfile, int mainline)
490 bfd *abfd = objfile->obfd;
492 struct cleanup *back_to;
495 init_minimal_symbol_collection ();
496 back_to = make_cleanup_discard_minimal_symbols ();
498 memset ((char *) &ei, 0, sizeof (ei));
500 /* Allocate struct to keep track of the symfile */
501 objfile->sym_stab_info = (struct dbx_symfile_info *)
502 xmmalloc (objfile->md, sizeof (struct dbx_symfile_info));
503 memset ((char *) objfile->sym_stab_info, 0, sizeof (struct dbx_symfile_info));
504 make_cleanup (free_elfinfo, (void *) objfile);
506 /* Process the normal ELF symbol table first. This may write some
507 chain of info into the dbx_symfile_info in objfile->sym_stab_info,
508 which can later be used by elfstab_offset_sections. */
510 elf_symtab_read (objfile, 0);
512 /* Add the dynamic symbols. */
514 elf_symtab_read (objfile, 1);
516 /* Install any minimal symbols that have been collected as the current
517 minimal symbols for this objfile. The debug readers below this point
518 should not generate new minimal symbols; if they do it's their
519 responsibility to install them. "mdebug" appears to be the only one
520 which will do this. */
522 install_minimal_symbols (objfile);
523 do_cleanups (back_to);
525 /* Now process debugging information, which is contained in
526 special ELF sections. */
528 /* If we are reinitializing, or if we have never loaded syms yet,
529 set table to empty. MAINLINE is cleared so that *_read_psymtab
530 functions do not all also re-initialize the psymbol table. */
533 init_psymbol_list (objfile, 0);
537 /* We first have to find them... */
538 bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);
540 /* ELF debugging information is inserted into the psymtab in the
541 order of least informative first - most informative last. Since
542 the psymtab table is searched `most recent insertion first' this
543 increases the probability that more detailed debug information
544 for a section is found.
546 For instance, an object file might contain both .mdebug (XCOFF)
547 and .debug_info (DWARF2) sections then .mdebug is inserted first
548 (searched last) and DWARF2 is inserted last (searched first). If
549 we don't do this then the XCOFF info is found first - for code in
550 an included file XCOFF info is useless. */
554 const struct ecoff_debug_swap *swap;
556 /* .mdebug section, presumably holding ECOFF debugging
558 swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
560 elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
566 /* Stab sections have an associated string table that looks like
567 a separate section. */
568 str_sect = bfd_get_section_by_name (abfd, ".stabstr");
570 /* FIXME should probably warn about a stab section without a stabstr. */
572 elfstab_build_psymtabs (objfile,
576 bfd_section_size (abfd, str_sect));
578 if (dwarf2_has_info (abfd))
580 /* DWARF 2 sections */
581 dwarf2_build_psymtabs (objfile, mainline);
583 else if (ei.dboffset && ei.lnoffset)
586 dwarf_build_psymtabs (objfile,
588 ei.dboffset, ei.dbsize,
589 ei.lnoffset, ei.lnsize);
592 /* FIXME: kettenis/20030504: This still needs to be integrated with
593 dwarf2read.c in a better way. */
594 dwarf2_build_frame_info (objfile);
597 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
598 stab_section_info's, that might be dangling from it. */
601 free_elfinfo (void *objp)
603 struct objfile *objfile = (struct objfile *) objp;
604 struct dbx_symfile_info *dbxinfo = objfile->sym_stab_info;
605 struct stab_section_info *ssi, *nssi;
607 ssi = dbxinfo->stab_section_info;
611 xmfree (objfile->md, ssi);
615 dbxinfo->stab_section_info = 0; /* Just say No mo info about this. */
619 /* Initialize anything that needs initializing when a completely new symbol
620 file is specified (not just adding some symbols from another file, e.g. a
623 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
626 elf_new_init (struct objfile *ignore)
628 stabsread_new_init ();
629 buildsym_new_init ();
632 /* Perform any local cleanups required when we are done with a particular
633 objfile. I.E, we are in the process of discarding all symbol information
634 for an objfile, freeing up all memory held for it, and unlinking the
635 objfile struct from the global list of known objfiles. */
638 elf_symfile_finish (struct objfile *objfile)
640 if (objfile->sym_stab_info != NULL)
642 xmfree (objfile->md, objfile->sym_stab_info);
646 /* ELF specific initialization routine for reading symbols.
648 It is passed a pointer to a struct sym_fns which contains, among other
649 things, the BFD for the file whose symbols are being read, and a slot for
650 a pointer to "private data" which we can fill with goodies.
652 For now at least, we have nothing in particular to do, so this function is
656 elf_symfile_init (struct objfile *objfile)
658 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
659 find this causes a significant slowdown in gdb then we could
660 set it in the debug symbol readers only when necessary. */
661 objfile->flags |= OBJF_REORDERED;
664 /* When handling an ELF file that contains Sun STABS debug info,
665 some of the debug info is relative to the particular chunk of the
666 section that was generated in its individual .o file. E.g.
667 offsets to static variables are relative to the start of the data
668 segment *for that module before linking*. This information is
669 painfully squirreled away in the ELF symbol table as local symbols
670 with wierd names. Go get 'em when needed. */
673 elfstab_offset_sections (struct objfile *objfile, struct partial_symtab *pst)
675 char *filename = pst->filename;
676 struct dbx_symfile_info *dbx = objfile->sym_stab_info;
677 struct stab_section_info *maybe = dbx->stab_section_info;
678 struct stab_section_info *questionable = 0;
682 /* The ELF symbol info doesn't include path names, so strip the path
683 (if any) from the psymtab filename. */
684 while (0 != (p = strchr (filename, '/')))
687 /* FIXME: This linear search could speed up significantly
688 if it was chained in the right order to match how we search it,
689 and if we unchained when we found a match. */
690 for (; maybe; maybe = maybe->next)
692 if (filename[0] == maybe->filename[0]
693 && strcmp (filename, maybe->filename) == 0)
695 /* We found a match. But there might be several source files
696 (from different directories) with the same name. */
697 if (0 == maybe->found)
699 questionable = maybe; /* Might use it later. */
703 if (maybe == 0 && questionable != 0)
705 complaint (&symfile_complaints,
706 "elf/stab section information questionable for %s", filename);
707 maybe = questionable;
712 /* Found it! Allocate a new psymtab struct, and fill it in. */
714 pst->section_offsets = (struct section_offsets *)
715 obstack_alloc (&objfile->objfile_obstack,
716 SIZEOF_N_SECTION_OFFSETS (objfile->num_sections));
717 for (i = 0; i < maybe->num_sections; i++)
718 (pst->section_offsets)->offsets[i] = maybe->sections[i];
722 /* We were unable to find any offsets for this file. Complain. */
723 if (dbx->stab_section_info) /* If there *is* any info, */
724 complaint (&symfile_complaints,
725 "elf/stab section information missing for %s", filename);
728 /* Register that we are able to handle ELF object file formats. */
730 static struct sym_fns elf_sym_fns =
732 bfd_target_elf_flavour,
733 elf_new_init, /* sym_new_init: init anything gbl to entire symtab */
734 elf_symfile_init, /* sym_init: read initial info, setup for sym_read() */
735 elf_symfile_read, /* sym_read: read a symbol file into symtab */
736 elf_symfile_finish, /* sym_finish: finished with file, cleanup */
737 default_symfile_offsets, /* sym_offsets: Translate ext. to int. relocation */
738 NULL /* next: pointer to next struct sym_fns */
742 _initialize_elfread (void)
744 add_symtab_fns (&elf_sym_fns);