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, 2005 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
->deprecated_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_SECTION_SYM
)
232 else if (sym
->flags
& (BSF_GLOBAL
| BSF_LOCAL
| BSF_WEAK
))
234 struct minimal_symbol
*msym
;
236 /* Select global/local/weak symbols. Note that bfd puts abs
237 symbols in their own section, so all symbols we are
238 interested in will have a section. */
239 /* Bfd symbols are section relative. */
240 symaddr
= sym
->value
+ sym
->section
->vma
;
241 /* Relocate all non-absolute symbols by the section offset. */
242 if (sym
->section
!= &bfd_abs_section
)
246 /* For non-absolute symbols, use the type of the section
247 they are relative to, to intuit text/data. Bfd provides
248 no way of figuring this out for absolute symbols. */
249 if (sym
->section
== &bfd_abs_section
)
251 /* This is a hack to get the minimal symbol type
252 right for Irix 5, which has absolute addresses
253 with special section indices for dynamic symbols. */
254 unsigned short shndx
=
255 ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_shndx
;
265 case SHN_MIPS_ACOMMON
:
272 /* If it is an Irix dynamic symbol, skip section name
273 symbols, relocate all others by section offset. */
274 if (ms_type
!= mst_abs
)
276 if (sym
->name
[0] == '.')
281 else if (sym
->section
->flags
& SEC_CODE
)
283 if (sym
->flags
& BSF_GLOBAL
)
287 else if ((sym
->name
[0] == '.' && sym
->name
[1] == 'L')
288 || ((sym
->flags
& BSF_LOCAL
)
289 && sym
->name
[0] == '$'
290 && sym
->name
[1] == 'L'))
291 /* Looks like a compiler-generated label. Skip
292 it. The assembler should be skipping these (to
293 keep executables small), but apparently with
294 gcc on the (deleted) delta m88k SVR4, it loses.
295 So to have us check too should be harmless (but
296 I encourage people to fix this in the assembler
297 instead of adding checks here). */
301 ms_type
= mst_file_text
;
304 else if (sym
->section
->flags
& SEC_ALLOC
)
306 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
))
308 if (sym
->section
->flags
& SEC_LOAD
)
317 else if (sym
->flags
& BSF_LOCAL
)
319 /* Named Local variable in a Data section.
320 Check its name for stabs-in-elf. */
321 int special_local_sect
;
322 if (strcmp ("Bbss.bss", sym
->name
) == 0)
323 special_local_sect
= SECT_OFF_BSS (objfile
);
324 else if (strcmp ("Ddata.data", sym
->name
) == 0)
325 special_local_sect
= SECT_OFF_DATA (objfile
);
326 else if (strcmp ("Drodata.rodata", sym
->name
) == 0)
327 special_local_sect
= SECT_OFF_RODATA (objfile
);
329 special_local_sect
= -1;
330 if (special_local_sect
>= 0)
332 /* Found a special local symbol. Allocate a
333 sectinfo, if needed, and fill it in. */
334 if (sectinfo
== NULL
)
340 = max (SECT_OFF_BSS (objfile
),
341 max (SECT_OFF_DATA (objfile
),
342 SECT_OFF_RODATA (objfile
)));
344 /* max_index is the largest index we'll
345 use into this array, so we must
346 allocate max_index+1 elements for it.
347 However, 'struct stab_section_info'
348 already includes one element, so we
349 need to allocate max_index aadditional
351 size
= (sizeof (struct stab_section_info
)
352 + (sizeof (CORE_ADDR
)
354 sectinfo
= (struct stab_section_info
*)
356 memset (sectinfo
, 0, size
);
357 sectinfo
->num_sections
= max_index
;
360 complaint (&symfile_complaints
,
361 _("elf/stab section information %s without a preceding file symbol"),
367 (char *) filesym
->name
;
370 if (sectinfo
->sections
[special_local_sect
] != 0)
371 complaint (&symfile_complaints
,
372 _("duplicated elf/stab section information for %s"),
374 /* BFD symbols are section relative. */
375 symaddr
= sym
->value
+ sym
->section
->vma
;
376 /* Relocate non-absolute symbols by the
378 if (sym
->section
!= &bfd_abs_section
)
380 sectinfo
->sections
[special_local_sect
] = symaddr
;
381 /* The special local symbols don't go in the
382 minimal symbol table, so ignore this one. */
385 /* Not a special stabs-in-elf symbol, do regular
386 symbol processing. */
387 if (sym
->section
->flags
& SEC_LOAD
)
389 ms_type
= mst_file_data
;
393 ms_type
= mst_file_bss
;
398 ms_type
= mst_unknown
;
403 /* FIXME: Solaris2 shared libraries include lots of
404 odd "absolute" and "undefined" symbols, that play
405 hob with actions like finding what function the PC
406 is in. Ignore them if they aren't text, data, or bss. */
407 /* ms_type = mst_unknown; */
408 continue; /* Skip this symbol. */
410 msym
= record_minimal_symbol
411 ((char *) sym
->name
, symaddr
,
412 ms_type
, sym
->section
, objfile
);
415 /* Pass symbol size field in via BFD. FIXME!!! */
416 unsigned long size
= ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_size
;
417 MSYMBOL_SIZE(msym
) = size
;
419 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
421 msym
->filename
= filesymname
;
423 ELF_MAKE_MSYMBOL_SPECIAL (sym
, msym
);
429 /* Scan and build partial symbols for a symbol file.
430 We have been initialized by a call to elf_symfile_init, which
431 currently does nothing.
433 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
434 in each section. We simplify it down to a single offset for all
437 MAINLINE is true if we are reading the main symbol
438 table (as opposed to a shared lib or dynamically loaded file).
440 This function only does the minimum work necessary for letting the
441 user "name" things symbolically; it does not read the entire symtab.
442 Instead, it reads the external and static symbols and puts them in partial
443 symbol tables. When more extensive information is requested of a
444 file, the corresponding partial symbol table is mutated into a full
445 fledged symbol table by going back and reading the symbols
448 We look for sections with specific names, to tell us what debug
449 format to look for: FIXME!!!
451 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
452 elfstab_build_psymtabs() handles STABS symbols;
453 mdebug_build_psymtabs() handles ECOFF debugging information.
455 Note that ELF files have a "minimal" symbol table, which looks a lot
456 like a COFF symbol table, but has only the minimal information necessary
457 for linking. We process this also, and use the information to
458 build gdb's minimal symbol table. This gives us some minimal debugging
459 capability even for files compiled without -g. */
462 elf_symfile_read (struct objfile
*objfile
, int mainline
)
464 bfd
*abfd
= objfile
->obfd
;
466 struct cleanup
*back_to
;
468 long symcount
= 0, dynsymcount
= 0, synthcount
, storage_needed
;
469 asymbol
**symbol_table
= NULL
, **dyn_symbol_table
= NULL
;
472 init_minimal_symbol_collection ();
473 back_to
= make_cleanup_discard_minimal_symbols ();
475 memset ((char *) &ei
, 0, sizeof (ei
));
477 /* Allocate struct to keep track of the symfile */
478 objfile
->deprecated_sym_stab_info
= (struct dbx_symfile_info
*)
479 xmalloc (sizeof (struct dbx_symfile_info
));
480 memset ((char *) objfile
->deprecated_sym_stab_info
, 0, sizeof (struct dbx_symfile_info
));
481 make_cleanup (free_elfinfo
, (void *) objfile
);
483 /* Process the normal ELF symbol table first. This may write some
484 chain of info into the dbx_symfile_info in objfile->deprecated_sym_stab_info,
485 which can later be used by elfstab_offset_sections. */
487 storage_needed
= bfd_get_symtab_upper_bound (objfile
->obfd
);
488 if (storage_needed
< 0)
489 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile
->obfd
),
490 bfd_errmsg (bfd_get_error ()));
492 if (storage_needed
> 0)
494 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
495 make_cleanup (xfree
, symbol_table
);
496 symcount
= bfd_canonicalize_symtab (objfile
->obfd
, symbol_table
);
499 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile
->obfd
),
500 bfd_errmsg (bfd_get_error ()));
502 elf_symtab_read (objfile
, 0, symcount
, symbol_table
);
505 /* Add the dynamic symbols. */
507 storage_needed
= bfd_get_dynamic_symtab_upper_bound (objfile
->obfd
);
509 if (storage_needed
> 0)
511 dyn_symbol_table
= (asymbol
**) xmalloc (storage_needed
);
512 make_cleanup (xfree
, dyn_symbol_table
);
513 dynsymcount
= bfd_canonicalize_dynamic_symtab (objfile
->obfd
,
517 error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile
->obfd
),
518 bfd_errmsg (bfd_get_error ()));
520 elf_symtab_read (objfile
, 1, dynsymcount
, dyn_symbol_table
);
523 /* Add synthetic symbols - for instance, names for any PLT entries. */
525 synthcount
= bfd_get_synthetic_symtab (abfd
, symcount
, symbol_table
,
526 dynsymcount
, dyn_symbol_table
,
530 asymbol
**synth_symbol_table
;
533 make_cleanup (xfree
, synthsyms
);
534 synth_symbol_table
= xmalloc (sizeof (asymbol
*) * synthcount
);
535 for (i
= 0; i
< synthcount
; i
++)
537 synth_symbol_table
[i
] = synthsyms
+ i
;
538 /* Synthetic symbols are not, strictly speaking, either local
539 or global. But we can treat them as global symbols, since
540 they are effectively dynamic symbols. */
541 synth_symbol_table
[i
]->flags
|= BSF_GLOBAL
;
543 make_cleanup (xfree
, synth_symbol_table
);
544 elf_symtab_read (objfile
, 0, synthcount
, synth_symbol_table
);
547 /* Install any minimal symbols that have been collected as the current
548 minimal symbols for this objfile. The debug readers below this point
549 should not generate new minimal symbols; if they do it's their
550 responsibility to install them. "mdebug" appears to be the only one
551 which will do this. */
553 install_minimal_symbols (objfile
);
554 do_cleanups (back_to
);
556 /* Now process debugging information, which is contained in
557 special ELF sections. */
559 /* If we are reinitializing, or if we have never loaded syms yet,
560 set table to empty. MAINLINE is cleared so that *_read_psymtab
561 functions do not all also re-initialize the psymbol table. */
564 init_psymbol_list (objfile
, 0);
568 /* We first have to find them... */
569 bfd_map_over_sections (abfd
, elf_locate_sections
, (void *) & ei
);
571 /* ELF debugging information is inserted into the psymtab in the
572 order of least informative first - most informative last. Since
573 the psymtab table is searched `most recent insertion first' this
574 increases the probability that more detailed debug information
575 for a section is found.
577 For instance, an object file might contain both .mdebug (XCOFF)
578 and .debug_info (DWARF2) sections then .mdebug is inserted first
579 (searched last) and DWARF2 is inserted last (searched first). If
580 we don't do this then the XCOFF info is found first - for code in
581 an included file XCOFF info is useless. */
585 const struct ecoff_debug_swap
*swap
;
587 /* .mdebug section, presumably holding ECOFF debugging
589 swap
= get_elf_backend_data (abfd
)->elf_backend_ecoff_debug_swap
;
591 elfmdebug_build_psymtabs (objfile
, swap
, ei
.mdebugsect
);
597 /* Stab sections have an associated string table that looks like
598 a separate section. */
599 str_sect
= bfd_get_section_by_name (abfd
, ".stabstr");
601 /* FIXME should probably warn about a stab section without a stabstr. */
603 elfstab_build_psymtabs (objfile
,
607 bfd_section_size (abfd
, str_sect
));
609 if (dwarf2_has_info (objfile
))
611 /* DWARF 2 sections */
612 dwarf2_build_psymtabs (objfile
, mainline
);
614 else if (ei
.dboffset
&& ei
.lnoffset
)
617 dwarf_build_psymtabs (objfile
,
619 ei
.dboffset
, ei
.dbsize
,
620 ei
.lnoffset
, ei
.lnsize
);
623 /* FIXME: kettenis/20030504: This still needs to be integrated with
624 dwarf2read.c in a better way. */
625 dwarf2_build_frame_info (objfile
);
628 /* This cleans up the objfile's deprecated_sym_stab_info pointer, and
629 the chain of stab_section_info's, that might be dangling from
633 free_elfinfo (void *objp
)
635 struct objfile
*objfile
= (struct objfile
*) objp
;
636 struct dbx_symfile_info
*dbxinfo
= objfile
->deprecated_sym_stab_info
;
637 struct stab_section_info
*ssi
, *nssi
;
639 ssi
= dbxinfo
->stab_section_info
;
647 dbxinfo
->stab_section_info
= 0; /* Just say No mo info about this. */
651 /* Initialize anything that needs initializing when a completely new symbol
652 file is specified (not just adding some symbols from another file, e.g. a
655 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
658 elf_new_init (struct objfile
*ignore
)
660 stabsread_new_init ();
661 buildsym_new_init ();
664 /* Perform any local cleanups required when we are done with a particular
665 objfile. I.E, we are in the process of discarding all symbol information
666 for an objfile, freeing up all memory held for it, and unlinking the
667 objfile struct from the global list of known objfiles. */
670 elf_symfile_finish (struct objfile
*objfile
)
672 if (objfile
->deprecated_sym_stab_info
!= NULL
)
674 xfree (objfile
->deprecated_sym_stab_info
);
678 /* ELF specific initialization routine for reading symbols.
680 It is passed a pointer to a struct sym_fns which contains, among other
681 things, the BFD for the file whose symbols are being read, and a slot for
682 a pointer to "private data" which we can fill with goodies.
684 For now at least, we have nothing in particular to do, so this function is
688 elf_symfile_init (struct objfile
*objfile
)
690 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
691 find this causes a significant slowdown in gdb then we could
692 set it in the debug symbol readers only when necessary. */
693 objfile
->flags
|= OBJF_REORDERED
;
696 /* When handling an ELF file that contains Sun STABS debug info,
697 some of the debug info is relative to the particular chunk of the
698 section that was generated in its individual .o file. E.g.
699 offsets to static variables are relative to the start of the data
700 segment *for that module before linking*. This information is
701 painfully squirreled away in the ELF symbol table as local symbols
702 with wierd names. Go get 'em when needed. */
705 elfstab_offset_sections (struct objfile
*objfile
, struct partial_symtab
*pst
)
707 char *filename
= pst
->filename
;
708 struct dbx_symfile_info
*dbx
= objfile
->deprecated_sym_stab_info
;
709 struct stab_section_info
*maybe
= dbx
->stab_section_info
;
710 struct stab_section_info
*questionable
= 0;
714 /* The ELF symbol info doesn't include path names, so strip the path
715 (if any) from the psymtab filename. */
716 while (0 != (p
= strchr (filename
, '/')))
719 /* FIXME: This linear search could speed up significantly
720 if it was chained in the right order to match how we search it,
721 and if we unchained when we found a match. */
722 for (; maybe
; maybe
= maybe
->next
)
724 if (filename
[0] == maybe
->filename
[0]
725 && strcmp (filename
, maybe
->filename
) == 0)
727 /* We found a match. But there might be several source files
728 (from different directories) with the same name. */
729 if (0 == maybe
->found
)
731 questionable
= maybe
; /* Might use it later. */
735 if (maybe
== 0 && questionable
!= 0)
737 complaint (&symfile_complaints
,
738 _("elf/stab section information questionable for %s"), filename
);
739 maybe
= questionable
;
744 /* Found it! Allocate a new psymtab struct, and fill it in. */
746 pst
->section_offsets
= (struct section_offsets
*)
747 obstack_alloc (&objfile
->objfile_obstack
,
748 SIZEOF_N_SECTION_OFFSETS (objfile
->num_sections
));
749 for (i
= 0; i
< maybe
->num_sections
; i
++)
750 (pst
->section_offsets
)->offsets
[i
] = maybe
->sections
[i
];
754 /* We were unable to find any offsets for this file. Complain. */
755 if (dbx
->stab_section_info
) /* If there *is* any info, */
756 complaint (&symfile_complaints
,
757 _("elf/stab section information missing for %s"), filename
);
760 /* Register that we are able to handle ELF object file formats. */
762 static struct sym_fns elf_sym_fns
=
764 bfd_target_elf_flavour
,
765 elf_new_init
, /* sym_new_init: init anything gbl to entire symtab */
766 elf_symfile_init
, /* sym_init: read initial info, setup for sym_read() */
767 elf_symfile_read
, /* sym_read: read a symbol file into symtab */
768 elf_symfile_finish
, /* sym_finish: finished with file, cleanup */
769 default_symfile_offsets
, /* sym_offsets: Translate ext. to int. relocation */
770 NULL
/* next: pointer to next struct sym_fns */
774 _initialize_elfread (void)
776 add_symtab_fns (&elf_sym_fns
);