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 (sectp);
88 else if (strcmp (sectp->name, ".line") == 0)
90 ei->lnoffset = sectp->filepos;
91 ei->lnsize = bfd_get_section_size (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,
128 long number_of_symbols, asymbol **symbol_table)
132 Given an objfile, a symbol table, and a flag indicating whether the
133 symbol table contains dynamic symbols, add all the global function
134 and data symbols to the minimal symbol table.
136 In stabs-in-ELF, as implemented by Sun, there are some local symbols
137 defined in the ELF symbol table, which can be used to locate
138 the beginnings of sections from each ".o" file that was linked to
139 form the executable objfile. We gather any such info and record it
140 in data structures hung off the objfile's private data.
145 elf_symtab_read (struct objfile *objfile, int dynamic,
146 long number_of_symbols, asymbol **symbol_table)
153 enum minimal_symbol_type ms_type;
154 /* If sectinfo is nonNULL, it contains section info that should end up
155 filed in the objfile. */
156 struct stab_section_info *sectinfo = NULL;
157 /* If filesym is nonzero, it points to a file symbol, but we haven't
158 seen any section info for it yet. */
159 asymbol *filesym = 0;
160 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
161 /* Name of filesym, as saved on the objfile_obstack. */
162 char *filesymname = obsavestring ("", 0, &objfile->objfile_obstack);
164 struct dbx_symfile_info *dbx = objfile->sym_stab_info;
165 int stripped = (bfd_get_symcount (objfile->obfd) == 0);
169 for (i = 0; i < number_of_symbols; i++)
171 sym = symbol_table[i];
172 if (sym->name == NULL || *sym->name == '\0')
174 /* Skip names that don't exist (shouldn't happen), or names
175 that are null strings (may happen). */
179 offset = ANOFFSET (objfile->section_offsets, sym->section->index);
181 && sym->section == &bfd_und_section
182 && (sym->flags & BSF_FUNCTION))
184 struct minimal_symbol *msym;
186 /* Symbol is a reference to a function defined in
188 If its value is non zero then it is usually the address
189 of the corresponding entry in the procedure linkage table,
190 plus the desired section offset.
191 If its value is zero then the dynamic linker has to resolve
192 the symbol. We are unable to find any meaningful address
193 for this symbol in the executable file, so we skip it. */
194 symaddr = sym->value;
198 msym = record_minimal_symbol
199 ((char *) sym->name, symaddr,
200 mst_solib_trampoline, sym->section, objfile);
201 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
203 msym->filename = filesymname;
208 /* If it is a nonstripped executable, do not enter dynamic
209 symbols, as the dynamic symbol table is usually a subset
210 of the main symbol table. */
211 if (dynamic && !stripped)
213 if (sym->flags & BSF_FILE)
215 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
216 Chain any old one onto the objfile; remember new sym. */
217 if (sectinfo != NULL)
219 sectinfo->next = dbx->stab_section_info;
220 dbx->stab_section_info = sectinfo;
224 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
226 obsavestring ((char *) filesym->name, strlen (filesym->name),
227 &objfile->objfile_obstack);
230 else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK))
232 struct minimal_symbol *msym;
234 /* Select global/local/weak symbols. Note that bfd puts abs
235 symbols in their own section, so all symbols we are
236 interested in will have a section. */
237 /* Bfd symbols are section relative. */
238 symaddr = sym->value + sym->section->vma;
239 /* Relocate all non-absolute symbols by the section offset. */
240 if (sym->section != &bfd_abs_section)
244 /* For non-absolute symbols, use the type of the section
245 they are relative to, to intuit text/data. Bfd provides
246 no way of figuring this out for absolute symbols. */
247 if (sym->section == &bfd_abs_section)
249 /* This is a hack to get the minimal symbol type
250 right for Irix 5, which has absolute addresses
251 with special section indices for dynamic symbols. */
252 unsigned short shndx =
253 ((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
263 case SHN_MIPS_ACOMMON:
270 /* If it is an Irix dynamic symbol, skip section name
271 symbols, relocate all others by section offset. */
272 if (ms_type != mst_abs)
274 if (sym->name[0] == '.')
279 else if (sym->section->flags & SEC_CODE)
281 if (sym->flags & BSF_GLOBAL)
285 else if ((sym->name[0] == '.' && sym->name[1] == 'L')
286 || ((sym->flags & BSF_LOCAL)
287 && sym->name[0] == '$'
288 && sym->name[1] == 'L'))
289 /* Looks like a compiler-generated label. Skip
290 it. The assembler should be skipping these (to
291 keep executables small), but apparently with
292 gcc on the (deleted) delta m88k SVR4, it loses.
293 So to have us check too should be harmless (but
294 I encourage people to fix this in the assembler
295 instead of adding checks here). */
299 ms_type = mst_file_text;
302 else if (sym->section->flags & SEC_ALLOC)
304 if (sym->flags & (BSF_GLOBAL | BSF_WEAK))
306 if (sym->section->flags & SEC_LOAD)
315 else if (sym->flags & BSF_LOCAL)
317 /* Named Local variable in a Data section.
318 Check its name for stabs-in-elf. */
319 int special_local_sect;
320 if (strcmp ("Bbss.bss", sym->name) == 0)
321 special_local_sect = SECT_OFF_BSS (objfile);
322 else if (strcmp ("Ddata.data", sym->name) == 0)
323 special_local_sect = SECT_OFF_DATA (objfile);
324 else if (strcmp ("Drodata.rodata", sym->name) == 0)
325 special_local_sect = SECT_OFF_RODATA (objfile);
327 special_local_sect = -1;
328 if (special_local_sect >= 0)
330 /* Found a special local symbol. Allocate a
331 sectinfo, if needed, and fill it in. */
332 if (sectinfo == NULL)
338 = max (SECT_OFF_BSS (objfile),
339 max (SECT_OFF_DATA (objfile),
340 SECT_OFF_RODATA (objfile)));
342 /* max_index is the largest index we'll
343 use into this array, so we must
344 allocate max_index+1 elements for it.
345 However, 'struct stab_section_info'
346 already includes one element, so we
347 need to allocate max_index aadditional
349 size = (sizeof (struct stab_section_info)
350 + (sizeof (CORE_ADDR)
352 sectinfo = (struct stab_section_info *)
353 xmmalloc (objfile->md, size);
354 memset (sectinfo, 0, size);
355 sectinfo->num_sections = max_index;
358 complaint (&symfile_complaints,
359 "elf/stab section information %s without a preceding file symbol",
365 (char *) filesym->name;
368 if (sectinfo->sections[special_local_sect] != 0)
369 complaint (&symfile_complaints,
370 "duplicated elf/stab section information for %s",
372 /* BFD symbols are section relative. */
373 symaddr = sym->value + sym->section->vma;
374 /* Relocate non-absolute symbols by the
376 if (sym->section != &bfd_abs_section)
378 sectinfo->sections[special_local_sect] = symaddr;
379 /* The special local symbols don't go in the
380 minimal symbol table, so ignore this one. */
383 /* Not a special stabs-in-elf symbol, do regular
384 symbol processing. */
385 if (sym->section->flags & SEC_LOAD)
387 ms_type = mst_file_data;
391 ms_type = mst_file_bss;
396 ms_type = mst_unknown;
401 /* FIXME: Solaris2 shared libraries include lots of
402 odd "absolute" and "undefined" symbols, that play
403 hob with actions like finding what function the PC
404 is in. Ignore them if they aren't text, data, or bss. */
405 /* ms_type = mst_unknown; */
406 continue; /* Skip this symbol. */
408 msym = record_minimal_symbol
409 ((char *) sym->name, symaddr,
410 ms_type, sym->section, objfile);
413 /* Pass symbol size field in via BFD. FIXME!!! */
414 unsigned long size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
415 MSYMBOL_SIZE(msym) = size;
417 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
419 msym->filename = filesymname;
421 ELF_MAKE_MSYMBOL_SPECIAL (sym, msym);
427 /* Scan and build partial symbols for a symbol file.
428 We have been initialized by a call to elf_symfile_init, which
429 currently does nothing.
431 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
432 in each section. We simplify it down to a single offset for all
435 MAINLINE is true if we are reading the main symbol
436 table (as opposed to a shared lib or dynamically loaded file).
438 This function only does the minimum work necessary for letting the
439 user "name" things symbolically; it does not read the entire symtab.
440 Instead, it reads the external and static symbols and puts them in partial
441 symbol tables. When more extensive information is requested of a
442 file, the corresponding partial symbol table is mutated into a full
443 fledged symbol table by going back and reading the symbols
446 We look for sections with specific names, to tell us what debug
447 format to look for: FIXME!!!
449 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
450 elfstab_build_psymtabs() handles STABS symbols;
451 mdebug_build_psymtabs() handles ECOFF debugging information.
453 Note that ELF files have a "minimal" symbol table, which looks a lot
454 like a COFF symbol table, but has only the minimal information necessary
455 for linking. We process this also, and use the information to
456 build gdb's minimal symbol table. This gives us some minimal debugging
457 capability even for files compiled without -g. */
460 elf_symfile_read (struct objfile *objfile, int mainline)
462 bfd *abfd = objfile->obfd;
464 struct cleanup *back_to;
466 long symcount = 0, dynsymcount = 0, synthcount, storage_needed;
467 asymbol **symbol_table = NULL, **dyn_symbol_table = NULL;
470 init_minimal_symbol_collection ();
471 back_to = make_cleanup_discard_minimal_symbols ();
473 memset ((char *) &ei, 0, sizeof (ei));
475 /* Allocate struct to keep track of the symfile */
476 objfile->sym_stab_info = (struct dbx_symfile_info *)
477 xmmalloc (objfile->md, sizeof (struct dbx_symfile_info));
478 memset ((char *) objfile->sym_stab_info, 0, sizeof (struct dbx_symfile_info));
479 make_cleanup (free_elfinfo, (void *) objfile);
481 /* Process the normal ELF symbol table first. This may write some
482 chain of info into the dbx_symfile_info in objfile->sym_stab_info,
483 which can later be used by elfstab_offset_sections. */
485 storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
486 if (storage_needed < 0)
487 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
488 bfd_errmsg (bfd_get_error ()));
490 if (storage_needed > 0)
492 symbol_table = (asymbol **) xmalloc (storage_needed);
493 make_cleanup (xfree, symbol_table);
494 symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
497 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
498 bfd_errmsg (bfd_get_error ()));
500 elf_symtab_read (objfile, 0, symcount, symbol_table);
503 /* Add the dynamic symbols. */
505 storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
507 if (storage_needed > 0)
509 dyn_symbol_table = (asymbol **) xmalloc (storage_needed);
510 make_cleanup (xfree, dyn_symbol_table);
511 dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,
515 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
516 bfd_errmsg (bfd_get_error ()));
518 elf_symtab_read (objfile, 1, dynsymcount, dyn_symbol_table);
521 /* Add synthetic symbols - for instance, names for any PLT entries. */
523 synthcount = bfd_get_synthetic_symtab (abfd, symcount, symbol_table,
524 dynsymcount, dyn_symbol_table,
528 asymbol **synth_symbol_table;
531 make_cleanup (xfree, synthsyms);
532 synth_symbol_table = xmalloc (sizeof (asymbol *) * synthcount);
533 for (i = 0; i < synthcount; i++)
535 synth_symbol_table[i] = synthsyms + i;
536 /* Synthetic symbols are not, strictly speaking, either local
537 or global. But we can treat them as global symbols, since
538 they are effectively dynamic symbols. */
539 synth_symbol_table[i]->flags |= BSF_GLOBAL;
541 make_cleanup (xfree, synth_symbol_table);
542 elf_symtab_read (objfile, 0, synthcount, synth_symbol_table);
545 /* Install any minimal symbols that have been collected as the current
546 minimal symbols for this objfile. The debug readers below this point
547 should not generate new minimal symbols; if they do it's their
548 responsibility to install them. "mdebug" appears to be the only one
549 which will do this. */
551 install_minimal_symbols (objfile);
552 do_cleanups (back_to);
554 /* Now process debugging information, which is contained in
555 special ELF sections. */
557 /* If we are reinitializing, or if we have never loaded syms yet,
558 set table to empty. MAINLINE is cleared so that *_read_psymtab
559 functions do not all also re-initialize the psymbol table. */
562 init_psymbol_list (objfile, 0);
566 /* We first have to find them... */
567 bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);
569 /* ELF debugging information is inserted into the psymtab in the
570 order of least informative first - most informative last. Since
571 the psymtab table is searched `most recent insertion first' this
572 increases the probability that more detailed debug information
573 for a section is found.
575 For instance, an object file might contain both .mdebug (XCOFF)
576 and .debug_info (DWARF2) sections then .mdebug is inserted first
577 (searched last) and DWARF2 is inserted last (searched first). If
578 we don't do this then the XCOFF info is found first - for code in
579 an included file XCOFF info is useless. */
583 const struct ecoff_debug_swap *swap;
585 /* .mdebug section, presumably holding ECOFF debugging
587 swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
589 elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
595 /* Stab sections have an associated string table that looks like
596 a separate section. */
597 str_sect = bfd_get_section_by_name (abfd, ".stabstr");
599 /* FIXME should probably warn about a stab section without a stabstr. */
601 elfstab_build_psymtabs (objfile,
605 bfd_section_size (abfd, str_sect));
607 if (dwarf2_has_info (abfd))
609 /* DWARF 2 sections */
610 dwarf2_build_psymtabs (objfile, mainline);
612 else if (ei.dboffset && ei.lnoffset)
615 dwarf_build_psymtabs (objfile,
617 ei.dboffset, ei.dbsize,
618 ei.lnoffset, ei.lnsize);
621 /* FIXME: kettenis/20030504: This still needs to be integrated with
622 dwarf2read.c in a better way. */
623 dwarf2_build_frame_info (objfile);
626 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
627 stab_section_info's, that might be dangling from it. */
630 free_elfinfo (void *objp)
632 struct objfile *objfile = (struct objfile *) objp;
633 struct dbx_symfile_info *dbxinfo = objfile->sym_stab_info;
634 struct stab_section_info *ssi, *nssi;
636 ssi = dbxinfo->stab_section_info;
640 xmfree (objfile->md, ssi);
644 dbxinfo->stab_section_info = 0; /* Just say No mo info about this. */
648 /* Initialize anything that needs initializing when a completely new symbol
649 file is specified (not just adding some symbols from another file, e.g. a
652 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
655 elf_new_init (struct objfile *ignore)
657 stabsread_new_init ();
658 buildsym_new_init ();
661 /* Perform any local cleanups required when we are done with a particular
662 objfile. I.E, we are in the process of discarding all symbol information
663 for an objfile, freeing up all memory held for it, and unlinking the
664 objfile struct from the global list of known objfiles. */
667 elf_symfile_finish (struct objfile *objfile)
669 if (objfile->sym_stab_info != NULL)
671 xmfree (objfile->md, objfile->sym_stab_info);
675 /* ELF specific initialization routine for reading symbols.
677 It is passed a pointer to a struct sym_fns which contains, among other
678 things, the BFD for the file whose symbols are being read, and a slot for
679 a pointer to "private data" which we can fill with goodies.
681 For now at least, we have nothing in particular to do, so this function is
685 elf_symfile_init (struct objfile *objfile)
687 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
688 find this causes a significant slowdown in gdb then we could
689 set it in the debug symbol readers only when necessary. */
690 objfile->flags |= OBJF_REORDERED;
693 /* When handling an ELF file that contains Sun STABS debug info,
694 some of the debug info is relative to the particular chunk of the
695 section that was generated in its individual .o file. E.g.
696 offsets to static variables are relative to the start of the data
697 segment *for that module before linking*. This information is
698 painfully squirreled away in the ELF symbol table as local symbols
699 with wierd names. Go get 'em when needed. */
702 elfstab_offset_sections (struct objfile *objfile, struct partial_symtab *pst)
704 char *filename = pst->filename;
705 struct dbx_symfile_info *dbx = objfile->sym_stab_info;
706 struct stab_section_info *maybe = dbx->stab_section_info;
707 struct stab_section_info *questionable = 0;
711 /* The ELF symbol info doesn't include path names, so strip the path
712 (if any) from the psymtab filename. */
713 while (0 != (p = strchr (filename, '/')))
716 /* FIXME: This linear search could speed up significantly
717 if it was chained in the right order to match how we search it,
718 and if we unchained when we found a match. */
719 for (; maybe; maybe = maybe->next)
721 if (filename[0] == maybe->filename[0]
722 && strcmp (filename, maybe->filename) == 0)
724 /* We found a match. But there might be several source files
725 (from different directories) with the same name. */
726 if (0 == maybe->found)
728 questionable = maybe; /* Might use it later. */
732 if (maybe == 0 && questionable != 0)
734 complaint (&symfile_complaints,
735 "elf/stab section information questionable for %s", filename);
736 maybe = questionable;
741 /* Found it! Allocate a new psymtab struct, and fill it in. */
743 pst->section_offsets = (struct section_offsets *)
744 obstack_alloc (&objfile->objfile_obstack,
745 SIZEOF_N_SECTION_OFFSETS (objfile->num_sections));
746 for (i = 0; i < maybe->num_sections; i++)
747 (pst->section_offsets)->offsets[i] = maybe->sections[i];
751 /* We were unable to find any offsets for this file. Complain. */
752 if (dbx->stab_section_info) /* If there *is* any info, */
753 complaint (&symfile_complaints,
754 "elf/stab section information missing for %s", filename);
757 /* Register that we are able to handle ELF object file formats. */
759 static struct sym_fns elf_sym_fns =
761 bfd_target_elf_flavour,
762 elf_new_init, /* sym_new_init: init anything gbl to entire symtab */
763 elf_symfile_init, /* sym_init: read initial info, setup for sym_read() */
764 elf_symfile_read, /* sym_read: read a symbol file into symtab */
765 elf_symfile_finish, /* sym_finish: finished with file, cleanup */
766 default_symfile_offsets, /* sym_offsets: Translate ext. to int. relocation */
767 NULL /* next: pointer to next struct sym_fns */
771 _initialize_elfread (void)
773 add_symtab_fns (&elf_sym_fns);