1 /* Read ELF (Executable and Linking Format) object files for GDB.
3 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
4 2001, 2002, 2003, 2004, 2005, 2006, 2007 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., 51 Franklin Street, Fifth Floor,
23 Boston, MA 02110-1301, 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 asection
*stabsect
; /* Section pointer for .stab section */
48 asection
*stabindexsect
; /* Section pointer for .stab.index section */
49 asection
*mdebugsect
; /* Section pointer for .mdebug section */
52 static void free_elfinfo (void *);
54 /* We are called once per section from elf_symfile_read. We
55 need to examine each section we are passed, check to see
56 if it is something we are interested in processing, and
57 if so, stash away some access information for the section.
59 For now we recognize the dwarf debug information sections and
60 line number sections from matching their section names. The
61 ELF definition is no real help here since it has no direct
62 knowledge of DWARF (by design, so any debugging format can be
65 We also recognize the ".stab" sections used by the Sun compilers
66 released with Solaris 2.
68 FIXME: The section names should not be hardwired strings (what
69 should they be? I don't think most object file formats have enough
70 section flags to specify what kind of debug section it is
74 elf_locate_sections (bfd
*ignore_abfd
, asection
*sectp
, void *eip
)
78 ei
= (struct elfinfo
*) eip
;
79 if (strcmp (sectp
->name
, ".stab") == 0)
83 else if (strcmp (sectp
->name
, ".stab.index") == 0)
85 ei
->stabindexsect
= sectp
;
87 else if (strcmp (sectp
->name
, ".mdebug") == 0)
89 ei
->mdebugsect
= sectp
;
93 static struct minimal_symbol
*
94 record_minimal_symbol (char *name
, CORE_ADDR address
,
95 enum minimal_symbol_type ms_type
,
96 asection
*bfd_section
, struct objfile
*objfile
)
98 if (ms_type
== mst_text
|| ms_type
== mst_file_text
)
99 address
= SMASH_TEXT_ADDRESS (address
);
101 return prim_record_minimal_symbol_and_info
102 (name
, address
, ms_type
, NULL
, bfd_section
->index
, bfd_section
, objfile
);
109 elf_symtab_read -- read the symbol table of an ELF file
113 void elf_symtab_read (struct objfile *objfile, int dynamic,
114 long number_of_symbols, asymbol **symbol_table)
118 Given an objfile, a symbol table, and a flag indicating whether the
119 symbol table contains dynamic symbols, add all the global function
120 and data symbols to the minimal symbol table.
122 In stabs-in-ELF, as implemented by Sun, there are some local symbols
123 defined in the ELF symbol table, which can be used to locate
124 the beginnings of sections from each ".o" file that was linked to
125 form the executable objfile. We gather any such info and record it
126 in data structures hung off the objfile's private data.
131 elf_symtab_read (struct objfile
*objfile
, int dynamic
,
132 long number_of_symbols
, asymbol
**symbol_table
)
139 enum minimal_symbol_type ms_type
;
140 /* If sectinfo is nonNULL, it contains section info that should end up
141 filed in the objfile. */
142 struct stab_section_info
*sectinfo
= NULL
;
143 /* If filesym is nonzero, it points to a file symbol, but we haven't
144 seen any section info for it yet. */
145 asymbol
*filesym
= 0;
146 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
147 /* Name of filesym, as saved on the objfile_obstack. */
148 char *filesymname
= obsavestring ("", 0, &objfile
->objfile_obstack
);
150 struct dbx_symfile_info
*dbx
= objfile
->deprecated_sym_stab_info
;
151 int stripped
= (bfd_get_symcount (objfile
->obfd
) == 0);
153 for (i
= 0; i
< number_of_symbols
; i
++)
155 sym
= symbol_table
[i
];
156 if (sym
->name
== NULL
|| *sym
->name
== '\0')
158 /* Skip names that don't exist (shouldn't happen), or names
159 that are null strings (may happen). */
163 /* Skip "special" symbols, e.g. ARM mapping symbols. These are
164 symbols which do not correspond to objects in the symbol table,
165 but have some other target-specific meaning. */
166 if (bfd_is_target_special_symbol (objfile
->obfd
, sym
))
169 offset
= ANOFFSET (objfile
->section_offsets
, sym
->section
->index
);
171 && sym
->section
== &bfd_und_section
172 && (sym
->flags
& BSF_FUNCTION
))
174 struct minimal_symbol
*msym
;
176 /* Symbol is a reference to a function defined in
178 If its value is non zero then it is usually the address
179 of the corresponding entry in the procedure linkage table,
180 plus the desired section offset.
181 If its value is zero then the dynamic linker has to resolve
182 the symbol. We are unable to find any meaningful address
183 for this symbol in the executable file, so we skip it. */
184 symaddr
= sym
->value
;
188 msym
= record_minimal_symbol
189 ((char *) sym
->name
, symaddr
,
190 mst_solib_trampoline
, sym
->section
, objfile
);
191 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
193 msym
->filename
= filesymname
;
198 /* If it is a nonstripped executable, do not enter dynamic
199 symbols, as the dynamic symbol table is usually a subset
200 of the main symbol table. */
201 if (dynamic
&& !stripped
)
203 if (sym
->flags
& BSF_FILE
)
205 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
206 Chain any old one onto the objfile; remember new sym. */
207 if (sectinfo
!= NULL
)
209 sectinfo
->next
= dbx
->stab_section_info
;
210 dbx
->stab_section_info
= sectinfo
;
214 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
216 obsavestring ((char *) filesym
->name
, strlen (filesym
->name
),
217 &objfile
->objfile_obstack
);
220 else if (sym
->flags
& BSF_SECTION_SYM
)
222 else if (sym
->flags
& (BSF_GLOBAL
| BSF_LOCAL
| BSF_WEAK
))
224 struct minimal_symbol
*msym
;
226 /* Select global/local/weak symbols. Note that bfd puts abs
227 symbols in their own section, so all symbols we are
228 interested in will have a section. */
229 /* Bfd symbols are section relative. */
230 symaddr
= sym
->value
+ sym
->section
->vma
;
231 /* Relocate all non-absolute symbols by the section offset. */
232 if (sym
->section
!= &bfd_abs_section
)
236 /* For non-absolute symbols, use the type of the section
237 they are relative to, to intuit text/data. Bfd provides
238 no way of figuring this out for absolute symbols. */
239 if (sym
->section
== &bfd_abs_section
)
241 /* This is a hack to get the minimal symbol type
242 right for Irix 5, which has absolute addresses
243 with special section indices for dynamic symbols. */
244 unsigned short shndx
=
245 ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_shndx
;
255 case SHN_MIPS_ACOMMON
:
262 /* If it is an Irix dynamic symbol, skip section name
263 symbols, relocate all others by section offset. */
264 if (ms_type
!= mst_abs
)
266 if (sym
->name
[0] == '.')
271 else if (sym
->section
->flags
& SEC_CODE
)
273 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
))
277 else if ((sym
->name
[0] == '.' && sym
->name
[1] == 'L')
278 || ((sym
->flags
& BSF_LOCAL
)
279 && sym
->name
[0] == '$'
280 && sym
->name
[1] == 'L'))
281 /* Looks like a compiler-generated label. Skip
282 it. The assembler should be skipping these (to
283 keep executables small), but apparently with
284 gcc on the (deleted) delta m88k SVR4, it loses.
285 So to have us check too should be harmless (but
286 I encourage people to fix this in the assembler
287 instead of adding checks here). */
291 ms_type
= mst_file_text
;
294 else if (sym
->section
->flags
& SEC_ALLOC
)
296 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
))
298 if (sym
->section
->flags
& SEC_LOAD
)
307 else if (sym
->flags
& BSF_LOCAL
)
309 /* Named Local variable in a Data section.
310 Check its name for stabs-in-elf. */
311 int special_local_sect
;
312 if (strcmp ("Bbss.bss", sym
->name
) == 0)
313 special_local_sect
= SECT_OFF_BSS (objfile
);
314 else if (strcmp ("Ddata.data", sym
->name
) == 0)
315 special_local_sect
= SECT_OFF_DATA (objfile
);
316 else if (strcmp ("Drodata.rodata", sym
->name
) == 0)
317 special_local_sect
= SECT_OFF_RODATA (objfile
);
319 special_local_sect
= -1;
320 if (special_local_sect
>= 0)
322 /* Found a special local symbol. Allocate a
323 sectinfo, if needed, and fill it in. */
324 if (sectinfo
== NULL
)
330 = max (SECT_OFF_BSS (objfile
),
331 max (SECT_OFF_DATA (objfile
),
332 SECT_OFF_RODATA (objfile
)));
334 /* max_index is the largest index we'll
335 use into this array, so we must
336 allocate max_index+1 elements for it.
337 However, 'struct stab_section_info'
338 already includes one element, so we
339 need to allocate max_index aadditional
341 size
= (sizeof (struct stab_section_info
)
342 + (sizeof (CORE_ADDR
)
344 sectinfo
= (struct stab_section_info
*)
346 memset (sectinfo
, 0, size
);
347 sectinfo
->num_sections
= max_index
;
350 complaint (&symfile_complaints
,
351 _("elf/stab section information %s without a preceding file symbol"),
357 (char *) filesym
->name
;
360 if (sectinfo
->sections
[special_local_sect
] != 0)
361 complaint (&symfile_complaints
,
362 _("duplicated elf/stab section information for %s"),
364 /* BFD symbols are section relative. */
365 symaddr
= sym
->value
+ sym
->section
->vma
;
366 /* Relocate non-absolute symbols by the
368 if (sym
->section
!= &bfd_abs_section
)
370 sectinfo
->sections
[special_local_sect
] = symaddr
;
371 /* The special local symbols don't go in the
372 minimal symbol table, so ignore this one. */
375 /* Not a special stabs-in-elf symbol, do regular
376 symbol processing. */
377 if (sym
->section
->flags
& SEC_LOAD
)
379 ms_type
= mst_file_data
;
383 ms_type
= mst_file_bss
;
388 ms_type
= mst_unknown
;
393 /* FIXME: Solaris2 shared libraries include lots of
394 odd "absolute" and "undefined" symbols, that play
395 hob with actions like finding what function the PC
396 is in. Ignore them if they aren't text, data, or bss. */
397 /* ms_type = mst_unknown; */
398 continue; /* Skip this symbol. */
400 msym
= record_minimal_symbol
401 ((char *) sym
->name
, symaddr
,
402 ms_type
, sym
->section
, objfile
);
405 /* Pass symbol size field in via BFD. FIXME!!! */
406 unsigned long size
= ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_size
;
407 MSYMBOL_SIZE(msym
) = size
;
409 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
411 msym
->filename
= filesymname
;
413 gdbarch_elf_make_msymbol_special (current_gdbarch
, sym
, msym
);
418 /* Scan and build partial symbols for a symbol file.
419 We have been initialized by a call to elf_symfile_init, which
420 currently does nothing.
422 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
423 in each section. We simplify it down to a single offset for all
426 MAINLINE is true if we are reading the main symbol
427 table (as opposed to a shared lib or dynamically loaded file).
429 This function only does the minimum work necessary for letting the
430 user "name" things symbolically; it does not read the entire symtab.
431 Instead, it reads the external and static symbols and puts them in partial
432 symbol tables. When more extensive information is requested of a
433 file, the corresponding partial symbol table is mutated into a full
434 fledged symbol table by going back and reading the symbols
437 We look for sections with specific names, to tell us what debug
438 format to look for: FIXME!!!
440 elfstab_build_psymtabs() handles STABS symbols;
441 mdebug_build_psymtabs() handles ECOFF debugging information.
443 Note that ELF files have a "minimal" symbol table, which looks a lot
444 like a COFF symbol table, but has only the minimal information necessary
445 for linking. We process this also, and use the information to
446 build gdb's minimal symbol table. This gives us some minimal debugging
447 capability even for files compiled without -g. */
450 elf_symfile_read (struct objfile
*objfile
, int mainline
)
452 bfd
*abfd
= objfile
->obfd
;
454 struct cleanup
*back_to
;
456 long symcount
= 0, dynsymcount
= 0, synthcount
, storage_needed
;
457 asymbol
**symbol_table
= NULL
, **dyn_symbol_table
= NULL
;
460 init_minimal_symbol_collection ();
461 back_to
= make_cleanup_discard_minimal_symbols ();
463 memset ((char *) &ei
, 0, sizeof (ei
));
465 /* Allocate struct to keep track of the symfile */
466 objfile
->deprecated_sym_stab_info
= (struct dbx_symfile_info
*)
467 xmalloc (sizeof (struct dbx_symfile_info
));
468 memset ((char *) objfile
->deprecated_sym_stab_info
, 0, sizeof (struct dbx_symfile_info
));
469 make_cleanup (free_elfinfo
, (void *) objfile
);
471 /* Process the normal ELF symbol table first. This may write some
472 chain of info into the dbx_symfile_info in objfile->deprecated_sym_stab_info,
473 which can later be used by elfstab_offset_sections. */
475 storage_needed
= bfd_get_symtab_upper_bound (objfile
->obfd
);
476 if (storage_needed
< 0)
477 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile
->obfd
),
478 bfd_errmsg (bfd_get_error ()));
480 if (storage_needed
> 0)
482 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
483 make_cleanup (xfree
, symbol_table
);
484 symcount
= bfd_canonicalize_symtab (objfile
->obfd
, symbol_table
);
487 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile
->obfd
),
488 bfd_errmsg (bfd_get_error ()));
490 elf_symtab_read (objfile
, 0, symcount
, symbol_table
);
493 /* Add the dynamic symbols. */
495 storage_needed
= bfd_get_dynamic_symtab_upper_bound (objfile
->obfd
);
497 if (storage_needed
> 0)
499 dyn_symbol_table
= (asymbol
**) xmalloc (storage_needed
);
500 make_cleanup (xfree
, dyn_symbol_table
);
501 dynsymcount
= bfd_canonicalize_dynamic_symtab (objfile
->obfd
,
505 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile
->obfd
),
506 bfd_errmsg (bfd_get_error ()));
508 elf_symtab_read (objfile
, 1, dynsymcount
, dyn_symbol_table
);
511 /* Add synthetic symbols - for instance, names for any PLT entries. */
513 synthcount
= bfd_get_synthetic_symtab (abfd
, symcount
, symbol_table
,
514 dynsymcount
, dyn_symbol_table
,
518 asymbol
**synth_symbol_table
;
521 make_cleanup (xfree
, synthsyms
);
522 synth_symbol_table
= xmalloc (sizeof (asymbol
*) * synthcount
);
523 for (i
= 0; i
< synthcount
; i
++)
524 synth_symbol_table
[i
] = synthsyms
+ i
;
525 make_cleanup (xfree
, synth_symbol_table
);
526 elf_symtab_read (objfile
, 0, synthcount
, synth_symbol_table
);
529 /* Install any minimal symbols that have been collected as the current
530 minimal symbols for this objfile. The debug readers below this point
531 should not generate new minimal symbols; if they do it's their
532 responsibility to install them. "mdebug" appears to be the only one
533 which will do this. */
535 install_minimal_symbols (objfile
);
536 do_cleanups (back_to
);
538 /* Now process debugging information, which is contained in
539 special ELF sections. */
541 /* If we are reinitializing, or if we have never loaded syms yet,
542 set table to empty. MAINLINE is cleared so that *_read_psymtab
543 functions do not all also re-initialize the psymbol table. */
546 init_psymbol_list (objfile
, 0);
550 /* We first have to find them... */
551 bfd_map_over_sections (abfd
, elf_locate_sections
, (void *) & ei
);
553 /* ELF debugging information is inserted into the psymtab in the
554 order of least informative first - most informative last. Since
555 the psymtab table is searched `most recent insertion first' this
556 increases the probability that more detailed debug information
557 for a section is found.
559 For instance, an object file might contain both .mdebug (XCOFF)
560 and .debug_info (DWARF2) sections then .mdebug is inserted first
561 (searched last) and DWARF2 is inserted last (searched first). If
562 we don't do this then the XCOFF info is found first - for code in
563 an included file XCOFF info is useless. */
567 const struct ecoff_debug_swap
*swap
;
569 /* .mdebug section, presumably holding ECOFF debugging
571 swap
= get_elf_backend_data (abfd
)->elf_backend_ecoff_debug_swap
;
573 elfmdebug_build_psymtabs (objfile
, swap
, ei
.mdebugsect
);
579 /* Stab sections have an associated string table that looks like
580 a separate section. */
581 str_sect
= bfd_get_section_by_name (abfd
, ".stabstr");
583 /* FIXME should probably warn about a stab section without a stabstr. */
585 elfstab_build_psymtabs (objfile
,
589 bfd_section_size (abfd
, str_sect
));
591 if (dwarf2_has_info (objfile
))
593 /* DWARF 2 sections */
594 dwarf2_build_psymtabs (objfile
, mainline
);
597 /* FIXME: kettenis/20030504: This still needs to be integrated with
598 dwarf2read.c in a better way. */
599 dwarf2_build_frame_info (objfile
);
602 /* This cleans up the objfile's deprecated_sym_stab_info pointer, and
603 the chain of stab_section_info's, that might be dangling from
607 free_elfinfo (void *objp
)
609 struct objfile
*objfile
= (struct objfile
*) objp
;
610 struct dbx_symfile_info
*dbxinfo
= objfile
->deprecated_sym_stab_info
;
611 struct stab_section_info
*ssi
, *nssi
;
613 ssi
= dbxinfo
->stab_section_info
;
621 dbxinfo
->stab_section_info
= 0; /* Just say No mo info about this. */
625 /* Initialize anything that needs initializing when a completely new symbol
626 file is specified (not just adding some symbols from another file, e.g. a
629 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
632 elf_new_init (struct objfile
*ignore
)
634 stabsread_new_init ();
635 buildsym_new_init ();
638 /* Perform any local cleanups required when we are done with a particular
639 objfile. I.E, we are in the process of discarding all symbol information
640 for an objfile, freeing up all memory held for it, and unlinking the
641 objfile struct from the global list of known objfiles. */
644 elf_symfile_finish (struct objfile
*objfile
)
646 if (objfile
->deprecated_sym_stab_info
!= NULL
)
648 xfree (objfile
->deprecated_sym_stab_info
);
652 /* ELF specific initialization routine for reading symbols.
654 It is passed a pointer to a struct sym_fns which contains, among other
655 things, the BFD for the file whose symbols are being read, and a slot for
656 a pointer to "private data" which we can fill with goodies.
658 For now at least, we have nothing in particular to do, so this function is
662 elf_symfile_init (struct objfile
*objfile
)
664 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
665 find this causes a significant slowdown in gdb then we could
666 set it in the debug symbol readers only when necessary. */
667 objfile
->flags
|= OBJF_REORDERED
;
670 /* When handling an ELF file that contains Sun STABS debug info,
671 some of the debug info is relative to the particular chunk of the
672 section that was generated in its individual .o file. E.g.
673 offsets to static variables are relative to the start of the data
674 segment *for that module before linking*. This information is
675 painfully squirreled away in the ELF symbol table as local symbols
676 with wierd names. Go get 'em when needed. */
679 elfstab_offset_sections (struct objfile
*objfile
, struct partial_symtab
*pst
)
681 char *filename
= pst
->filename
;
682 struct dbx_symfile_info
*dbx
= objfile
->deprecated_sym_stab_info
;
683 struct stab_section_info
*maybe
= dbx
->stab_section_info
;
684 struct stab_section_info
*questionable
= 0;
688 /* The ELF symbol info doesn't include path names, so strip the path
689 (if any) from the psymtab filename. */
690 while (0 != (p
= strchr (filename
, '/')))
693 /* FIXME: This linear search could speed up significantly
694 if it was chained in the right order to match how we search it,
695 and if we unchained when we found a match. */
696 for (; maybe
; maybe
= maybe
->next
)
698 if (filename
[0] == maybe
->filename
[0]
699 && strcmp (filename
, maybe
->filename
) == 0)
701 /* We found a match. But there might be several source files
702 (from different directories) with the same name. */
703 if (0 == maybe
->found
)
705 questionable
= maybe
; /* Might use it later. */
709 if (maybe
== 0 && questionable
!= 0)
711 complaint (&symfile_complaints
,
712 _("elf/stab section information questionable for %s"), filename
);
713 maybe
= questionable
;
718 /* Found it! Allocate a new psymtab struct, and fill it in. */
720 pst
->section_offsets
= (struct section_offsets
*)
721 obstack_alloc (&objfile
->objfile_obstack
,
722 SIZEOF_N_SECTION_OFFSETS (objfile
->num_sections
));
723 for (i
= 0; i
< maybe
->num_sections
; i
++)
724 (pst
->section_offsets
)->offsets
[i
] = maybe
->sections
[i
];
728 /* We were unable to find any offsets for this file. Complain. */
729 if (dbx
->stab_section_info
) /* If there *is* any info, */
730 complaint (&symfile_complaints
,
731 _("elf/stab section information missing for %s"), filename
);
734 /* Register that we are able to handle ELF object file formats. */
736 static struct sym_fns elf_sym_fns
=
738 bfd_target_elf_flavour
,
739 elf_new_init
, /* sym_new_init: init anything gbl to entire symtab */
740 elf_symfile_init
, /* sym_init: read initial info, setup for sym_read() */
741 elf_symfile_read
, /* sym_read: read a symbol file into symtab */
742 elf_symfile_finish
, /* sym_finish: finished with file, cleanup */
743 default_symfile_offsets
, /* sym_offsets: Translate ext. to int. relocation */
744 NULL
/* next: pointer to next struct sym_fns */
748 _initialize_elfread (void)
750 add_symtab_fns (&elf_sym_fns
);