1 /* Read ELF (Executable and Linking Format) object files for GDB.
2 Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
4 Free Software Foundation, Inc.
5 Written by Fred Fish at Cygnus Support.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
26 #include "gdb_string.h"
33 #include "stabsread.h"
34 #include "gdb-stabs.h"
35 #include "complaints.h"
38 extern void _initialize_elfread (void);
40 /* The struct elfinfo is available only during ELF symbol table and
41 psymtab reading. It is destroyed at the completion of psymtab-reading.
42 It's local to elf_symfile_read. */
46 file_ptr dboffset
; /* Offset to dwarf debug section */
47 unsigned int dbsize
; /* Size of dwarf debug section */
48 file_ptr lnoffset
; /* Offset to dwarf line number section */
49 unsigned int lnsize
; /* Size of dwarf line number section */
50 asection
*stabsect
; /* Section pointer for .stab section */
51 asection
*stabindexsect
; /* Section pointer for .stab.index section */
52 asection
*mdebugsect
; /* Section pointer for .mdebug section */
55 /* Various things we might complain about... */
57 struct complaint section_info_complaint
=
58 {"elf/stab section information %s without a preceding file symbol", 0, 0};
60 struct complaint section_info_dup_complaint
=
61 {"duplicated elf/stab section information for %s", 0, 0};
63 struct complaint stab_info_mismatch_complaint
=
64 {"elf/stab section information missing for %s", 0, 0};
66 struct complaint stab_info_questionable_complaint
=
67 {"elf/stab section information questionable for %s", 0, 0};
69 static void elf_symfile_init (struct objfile
*);
71 static void elf_new_init (struct objfile
*);
73 static void elf_symfile_read (struct objfile
*, int);
75 static void elf_symfile_finish (struct objfile
*);
77 static void elf_symtab_read (struct objfile
*, int);
79 static void free_elfinfo (PTR
);
81 static struct minimal_symbol
*record_minimal_symbol_and_info (char *,
91 static void elf_locate_sections (bfd
*, asection
*, PTR
);
93 /* We are called once per section from elf_symfile_read. We
94 need to examine each section we are passed, check to see
95 if it is something we are interested in processing, and
96 if so, stash away some access information for the section.
98 For now we recognize the dwarf debug information sections and
99 line number sections from matching their section names. The
100 ELF definition is no real help here since it has no direct
101 knowledge of DWARF (by design, so any debugging format can be
104 We also recognize the ".stab" sections used by the Sun compilers
105 released with Solaris 2.
107 FIXME: The section names should not be hardwired strings (what
108 should they be? I don't think most object file formats have enough
109 section flags to specify what kind of debug section it is
113 elf_locate_sections (bfd
*ignore_abfd
, asection
*sectp
, PTR eip
)
115 register struct elfinfo
*ei
;
117 ei
= (struct elfinfo
*) eip
;
118 if (STREQ (sectp
->name
, ".debug"))
120 ei
->dboffset
= sectp
->filepos
;
121 ei
->dbsize
= bfd_get_section_size_before_reloc (sectp
);
123 else if (STREQ (sectp
->name
, ".line"))
125 ei
->lnoffset
= sectp
->filepos
;
126 ei
->lnsize
= bfd_get_section_size_before_reloc (sectp
);
128 else if (STREQ (sectp
->name
, ".stab"))
130 ei
->stabsect
= sectp
;
132 else if (STREQ (sectp
->name
, ".stab.index"))
134 ei
->stabindexsect
= sectp
;
136 else if (STREQ (sectp
->name
, ".mdebug"))
138 ei
->mdebugsect
= sectp
;
142 #if 0 /* Currently unused */
145 elf_interpreter (bfd
*abfd
)
151 interp_sec
= bfd_get_section_by_name (abfd
, ".interp");
154 size
= bfd_section_size (abfd
, interp_sec
);
155 interp
= alloca (size
);
156 if (bfd_get_section_contents (abfd
, interp_sec
, interp
, (file_ptr
) 0,
159 interp
= savestring (interp
, size
- 1);
171 static struct minimal_symbol
*
172 record_minimal_symbol_and_info (char *name
, CORE_ADDR address
,
173 enum minimal_symbol_type ms_type
, char *info
, /* FIXME, is this really char *? */
174 asection
*bfd_section
, struct objfile
*objfile
)
176 if (ms_type
== mst_text
|| ms_type
== mst_file_text
)
177 address
= SMASH_TEXT_ADDRESS (address
);
179 return prim_record_minimal_symbol_and_info
180 (name
, address
, ms_type
, info
, bfd_section
->index
, bfd_section
, objfile
);
187 elf_symtab_read -- read the symbol table of an ELF file
191 void elf_symtab_read (struct objfile *objfile, int dynamic)
195 Given an objfile and a flag that specifies whether or not the objfile
196 is for an executable or not (may be shared library for example), add
197 all the global function and data symbols to the minimal symbol table.
199 In stabs-in-ELF, as implemented by Sun, there are some local symbols
200 defined in the ELF symbol table, which can be used to locate
201 the beginnings of sections from each ".o" file that was linked to
202 form the executable objfile. We gather any such info and record it
203 in data structures hung off the objfile's private data.
208 elf_symtab_read (struct objfile
*objfile
, int dynamic
)
212 asymbol
**symbol_table
;
213 long number_of_symbols
;
216 struct cleanup
*back_to
;
219 enum minimal_symbol_type ms_type
;
220 /* If sectinfo is nonNULL, it contains section info that should end up
221 filed in the objfile. */
222 struct stab_section_info
*sectinfo
= NULL
;
223 /* If filesym is nonzero, it points to a file symbol, but we haven't
224 seen any section info for it yet. */
225 asymbol
*filesym
= 0;
226 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
227 /* Name of filesym, as saved on the symbol_obstack. */
228 char *filesymname
= obsavestring ("", 0, &objfile
->symbol_obstack
);
230 struct dbx_symfile_info
*dbx
= objfile
->sym_stab_info
;
232 int stripped
= (bfd_get_symcount (objfile
->obfd
) == 0);
236 storage_needed
= bfd_get_dynamic_symtab_upper_bound (objfile
->obfd
);
238 /* Nothing to be done if there is no dynamic symtab. */
239 if (storage_needed
< 0)
244 storage_needed
= bfd_get_symtab_upper_bound (objfile
->obfd
);
245 if (storage_needed
< 0)
246 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile
->obfd
),
247 bfd_errmsg (bfd_get_error ()));
249 if (storage_needed
> 0)
251 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
252 back_to
= make_cleanup (xfree
, symbol_table
);
254 number_of_symbols
= bfd_canonicalize_dynamic_symtab (objfile
->obfd
,
257 number_of_symbols
= bfd_canonicalize_symtab (objfile
->obfd
, symbol_table
);
258 if (number_of_symbols
< 0)
259 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile
->obfd
),
260 bfd_errmsg (bfd_get_error ()));
262 for (i
= 0; i
< number_of_symbols
; i
++)
264 sym
= symbol_table
[i
];
265 if (sym
->name
== NULL
|| *sym
->name
== '\0')
267 /* Skip names that don't exist (shouldn't happen), or names
268 that are null strings (may happen). */
272 offset
= ANOFFSET (objfile
->section_offsets
, sym
->section
->index
);
274 && sym
->section
== &bfd_und_section
275 && (sym
->flags
& BSF_FUNCTION
))
277 struct minimal_symbol
*msym
;
279 /* Symbol is a reference to a function defined in
281 If its value is non zero then it is usually the address
282 of the corresponding entry in the procedure linkage table,
283 plus the desired section offset.
284 If its value is zero then the dynamic linker has to resolve
285 the symbol. We are unable to find any meaningful address
286 for this symbol in the executable file, so we skip it. */
287 symaddr
= sym
->value
;
291 msym
= record_minimal_symbol_and_info
292 ((char *) sym
->name
, symaddr
,
293 mst_solib_trampoline
, NULL
, sym
->section
, objfile
);
294 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
296 msym
->filename
= filesymname
;
301 /* If it is a nonstripped executable, do not enter dynamic
302 symbols, as the dynamic symbol table is usually a subset
303 of the main symbol table. */
304 if (dynamic
&& !stripped
)
306 if (sym
->flags
& BSF_FILE
)
308 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
309 Chain any old one onto the objfile; remember new sym. */
310 if (sectinfo
!= NULL
)
312 sectinfo
->next
= dbx
->stab_section_info
;
313 dbx
->stab_section_info
= sectinfo
;
317 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
319 obsavestring ((char *) filesym
->name
, strlen (filesym
->name
),
320 &objfile
->symbol_obstack
);
323 else if (sym
->flags
& (BSF_GLOBAL
| BSF_LOCAL
| BSF_WEAK
))
325 struct minimal_symbol
*msym
;
327 /* Select global/local/weak symbols. Note that bfd puts abs
328 symbols in their own section, so all symbols we are
329 interested in will have a section. */
330 /* Bfd symbols are section relative. */
331 symaddr
= sym
->value
+ sym
->section
->vma
;
332 /* Relocate all non-absolute symbols by the section offset. */
333 if (sym
->section
!= &bfd_abs_section
)
337 /* For non-absolute symbols, use the type of the section
338 they are relative to, to intuit text/data. Bfd provides
339 no way of figuring this out for absolute symbols. */
340 if (sym
->section
== &bfd_abs_section
)
342 /* This is a hack to get the minimal symbol type
343 right for Irix 5, which has absolute addresses
344 with special section indices for dynamic symbols. */
345 unsigned short shndx
=
346 ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_shndx
;
356 case SHN_MIPS_ACOMMON
:
363 /* If it is an Irix dynamic symbol, skip section name
364 symbols, relocate all others by section offset. */
365 if (ms_type
!= mst_abs
)
367 if (sym
->name
[0] == '.')
372 else if (sym
->section
->flags
& SEC_CODE
)
374 if (sym
->flags
& BSF_GLOBAL
)
378 else if ((sym
->name
[0] == '.' && sym
->name
[1] == 'L')
379 || ((sym
->flags
& BSF_LOCAL
)
380 && sym
->name
[0] == '$'
381 && sym
->name
[1] == 'L'))
382 /* Looks like a compiler-generated label. Skip it.
383 The assembler should be skipping these (to keep
384 executables small), but apparently with gcc on the
385 delta m88k SVR4, it loses. So to have us check too
386 should be harmless (but I encourage people to fix this
387 in the assembler instead of adding checks here). */
390 else if (sym
->name
[0] == '.' && sym
->name
[1] == '.')
392 /* Looks like a Harris compiler generated label for the
393 purpose of marking instructions that are relevant to
394 DWARF dies. The assembler can't get rid of these
395 because they are relocatable addresses that the
396 linker needs to resolve. */
402 ms_type
= mst_file_text
;
405 else if (sym
->section
->flags
& SEC_ALLOC
)
407 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
))
409 if (sym
->section
->flags
& SEC_LOAD
)
418 else if (sym
->flags
& BSF_LOCAL
)
420 /* Named Local variable in a Data section. Check its
421 name for stabs-in-elf. The STREQ macro checks the
422 first character inline, so we only actually do a
423 strcmp function call on names that start with 'B'
425 index
= SECT_OFF_MAX
;
426 if (STREQ ("Bbss.bss", sym
->name
))
428 index
= SECT_OFF_BSS (objfile
);
430 else if (STREQ ("Ddata.data", sym
->name
))
432 index
= SECT_OFF_DATA (objfile
);
434 else if (STREQ ("Drodata.rodata", sym
->name
))
436 index
= SECT_OFF_RODATA (objfile
);
438 if (index
!= SECT_OFF_MAX
)
440 /* Found a special local symbol. Allocate a
441 sectinfo, if needed, and fill it in. */
442 if (sectinfo
== NULL
)
444 sectinfo
= (struct stab_section_info
*)
445 xmmalloc (objfile
->md
, sizeof (*sectinfo
));
446 memset ((PTR
) sectinfo
, 0, sizeof (*sectinfo
));
449 complain (§ion_info_complaint
,
455 (char *) filesym
->name
;
460 if (sectinfo
->sections
[index
] != 0)
462 complain (§ion_info_dup_complaint
,
467 internal_error (__FILE__
, __LINE__
,
468 "Section index uninitialized.");
469 /* Bfd symbols are section relative. */
470 symaddr
= sym
->value
+ sym
->section
->vma
;
471 /* Relocate non-absolute symbols by the section offset. */
472 if (sym
->section
!= &bfd_abs_section
)
477 sectinfo
->sections
[index
] = symaddr
;
479 internal_error (__FILE__
, __LINE__
,
480 "Section index uninitialized.");
481 /* The special local symbols don't go in the
482 minimal symbol table, so ignore this one. */
485 /* Not a special stabs-in-elf symbol, do regular
486 symbol processing. */
487 if (sym
->section
->flags
& SEC_LOAD
)
489 ms_type
= mst_file_data
;
493 ms_type
= mst_file_bss
;
498 ms_type
= mst_unknown
;
503 /* FIXME: Solaris2 shared libraries include lots of
504 odd "absolute" and "undefined" symbols, that play
505 hob with actions like finding what function the PC
506 is in. Ignore them if they aren't text, data, or bss. */
507 /* ms_type = mst_unknown; */
508 continue; /* Skip this symbol. */
510 /* Pass symbol size field in via BFD. FIXME!!! */
511 size
= ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_size
;
512 msym
= record_minimal_symbol_and_info
513 ((char *) sym
->name
, symaddr
,
514 ms_type
, (PTR
) size
, sym
->section
, objfile
);
515 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
517 msym
->filename
= filesymname
;
519 #ifdef ELF_MAKE_MSYMBOL_SPECIAL
520 ELF_MAKE_MSYMBOL_SPECIAL (sym
, msym
);
524 do_cleanups (back_to
);
528 /* Scan and build partial symbols for a symbol file.
529 We have been initialized by a call to elf_symfile_init, which
530 currently does nothing.
532 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
533 in each section. We simplify it down to a single offset for all
536 MAINLINE is true if we are reading the main symbol
537 table (as opposed to a shared lib or dynamically loaded file).
539 This function only does the minimum work necessary for letting the
540 user "name" things symbolically; it does not read the entire symtab.
541 Instead, it reads the external and static symbols and puts them in partial
542 symbol tables. When more extensive information is requested of a
543 file, the corresponding partial symbol table is mutated into a full
544 fledged symbol table by going back and reading the symbols
547 We look for sections with specific names, to tell us what debug
548 format to look for: FIXME!!!
550 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
551 elfstab_build_psymtabs() handles STABS symbols;
552 mdebug_build_psymtabs() handles ECOFF debugging information.
554 Note that ELF files have a "minimal" symbol table, which looks a lot
555 like a COFF symbol table, but has only the minimal information necessary
556 for linking. We process this also, and use the information to
557 build gdb's minimal symbol table. This gives us some minimal debugging
558 capability even for files compiled without -g. */
561 elf_symfile_read (struct objfile
*objfile
, int mainline
)
563 bfd
*abfd
= objfile
->obfd
;
565 struct cleanup
*back_to
;
568 init_minimal_symbol_collection ();
569 back_to
= make_cleanup_discard_minimal_symbols ();
571 memset ((char *) &ei
, 0, sizeof (ei
));
573 /* Allocate struct to keep track of the symfile */
574 objfile
->sym_stab_info
= (struct dbx_symfile_info
*)
575 xmmalloc (objfile
->md
, sizeof (struct dbx_symfile_info
));
576 memset ((char *) objfile
->sym_stab_info
, 0, sizeof (struct dbx_symfile_info
));
577 make_cleanup (free_elfinfo
, (PTR
) objfile
);
579 /* Process the normal ELF symbol table first. This may write some
580 chain of info into the dbx_symfile_info in objfile->sym_stab_info,
581 which can later be used by elfstab_offset_sections. */
583 elf_symtab_read (objfile
, 0);
585 /* Add the dynamic symbols. */
587 elf_symtab_read (objfile
, 1);
589 /* Now process debugging information, which is contained in
590 special ELF sections. */
592 /* If we are reinitializing, or if we have never loaded syms yet,
593 set table to empty. MAINLINE is cleared so that *_read_psymtab
594 functions do not all also re-initialize the psymbol table. */
597 init_psymbol_list (objfile
, 0);
601 /* We first have to find them... */
602 bfd_map_over_sections (abfd
, elf_locate_sections
, (PTR
) & ei
);
604 /* ELF debugging information is inserted into the psymtab in the
605 order of least informative first - most informative last. Since
606 the psymtab table is searched `most recent insertion first' this
607 increases the probability that more detailed debug information
608 for a section is found.
610 For instance, an object file might contain both .mdebug (XCOFF)
611 and .debug_info (DWARF2) sections then .mdebug is inserted first
612 (searched last) and DWARF2 is inserted last (searched first). If
613 we don't do this then the XCOFF info is found first - for code in
614 an included file XCOFF info is useless. */
618 const struct ecoff_debug_swap
*swap
;
620 /* .mdebug section, presumably holding ECOFF debugging
622 swap
= get_elf_backend_data (abfd
)->elf_backend_ecoff_debug_swap
;
624 elfmdebug_build_psymtabs (objfile
, swap
, ei
.mdebugsect
);
630 /* Stab sections have an associated string table that looks like
631 a separate section. */
632 str_sect
= bfd_get_section_by_name (abfd
, ".stabstr");
634 /* FIXME should probably warn about a stab section without a stabstr. */
636 elfstab_build_psymtabs (objfile
,
638 ei
.stabsect
->filepos
,
639 bfd_section_size (abfd
, ei
.stabsect
),
641 bfd_section_size (abfd
, str_sect
));
643 if (dwarf2_has_info (abfd
))
645 /* DWARF 2 sections */
646 dwarf2_build_psymtabs (objfile
, mainline
);
648 else if (ei
.dboffset
&& ei
.lnoffset
)
651 dwarf_build_psymtabs (objfile
,
653 ei
.dboffset
, ei
.dbsize
,
654 ei
.lnoffset
, ei
.lnsize
);
657 if (DWARF2_BUILD_FRAME_INFO_P ())
658 DWARF2_BUILD_FRAME_INFO(objfile
);
660 /* Install any minimal symbols that have been collected as the current
661 minimal symbols for this objfile. */
663 install_minimal_symbols (objfile
);
665 do_cleanups (back_to
);
668 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
669 stab_section_info's, that might be dangling from it. */
672 free_elfinfo (PTR objp
)
674 struct objfile
*objfile
= (struct objfile
*) objp
;
675 struct dbx_symfile_info
*dbxinfo
= objfile
->sym_stab_info
;
676 struct stab_section_info
*ssi
, *nssi
;
678 ssi
= dbxinfo
->stab_section_info
;
682 xmfree (objfile
->md
, ssi
);
686 dbxinfo
->stab_section_info
= 0; /* Just say No mo info about this. */
690 /* Initialize anything that needs initializing when a completely new symbol
691 file is specified (not just adding some symbols from another file, e.g. a
694 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
697 elf_new_init (struct objfile
*ignore
)
699 stabsread_new_init ();
700 buildsym_new_init ();
703 /* Perform any local cleanups required when we are done with a particular
704 objfile. I.E, we are in the process of discarding all symbol information
705 for an objfile, freeing up all memory held for it, and unlinking the
706 objfile struct from the global list of known objfiles. */
709 elf_symfile_finish (struct objfile
*objfile
)
711 if (objfile
->sym_stab_info
!= NULL
)
713 xmfree (objfile
->md
, objfile
->sym_stab_info
);
717 /* ELF specific initialization routine for reading symbols.
719 It is passed a pointer to a struct sym_fns which contains, among other
720 things, the BFD for the file whose symbols are being read, and a slot for
721 a pointer to "private data" which we can fill with goodies.
723 For now at least, we have nothing in particular to do, so this function is
727 elf_symfile_init (struct objfile
*objfile
)
729 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
730 find this causes a significant slowdown in gdb then we could
731 set it in the debug symbol readers only when necessary. */
732 objfile
->flags
|= OBJF_REORDERED
;
735 /* When handling an ELF file that contains Sun STABS debug info,
736 some of the debug info is relative to the particular chunk of the
737 section that was generated in its individual .o file. E.g.
738 offsets to static variables are relative to the start of the data
739 segment *for that module before linking*. This information is
740 painfully squirreled away in the ELF symbol table as local symbols
741 with wierd names. Go get 'em when needed. */
744 elfstab_offset_sections (struct objfile
*objfile
, struct partial_symtab
*pst
)
746 char *filename
= pst
->filename
;
747 struct dbx_symfile_info
*dbx
= objfile
->sym_stab_info
;
748 struct stab_section_info
*maybe
= dbx
->stab_section_info
;
749 struct stab_section_info
*questionable
= 0;
753 /* The ELF symbol info doesn't include path names, so strip the path
754 (if any) from the psymtab filename. */
755 while (0 != (p
= strchr (filename
, '/')))
758 /* FIXME: This linear search could speed up significantly
759 if it was chained in the right order to match how we search it,
760 and if we unchained when we found a match. */
761 for (; maybe
; maybe
= maybe
->next
)
763 if (filename
[0] == maybe
->filename
[0]
764 && STREQ (filename
, maybe
->filename
))
766 /* We found a match. But there might be several source files
767 (from different directories) with the same name. */
768 if (0 == maybe
->found
)
770 questionable
= maybe
; /* Might use it later. */
774 if (maybe
== 0 && questionable
!= 0)
776 complain (&stab_info_questionable_complaint
, filename
);
777 maybe
= questionable
;
782 /* Found it! Allocate a new psymtab struct, and fill it in. */
784 pst
->section_offsets
= (struct section_offsets
*)
785 obstack_alloc (&objfile
->psymbol_obstack
, SIZEOF_SECTION_OFFSETS
);
786 for (i
= 0; i
< SECT_OFF_MAX
; i
++)
787 (pst
->section_offsets
)->offsets
[i
] = maybe
->sections
[i
];
791 /* We were unable to find any offsets for this file. Complain. */
792 if (dbx
->stab_section_info
) /* If there *is* any info, */
793 complain (&stab_info_mismatch_complaint
, filename
);
796 /* Register that we are able to handle ELF object file formats. */
798 static struct sym_fns elf_sym_fns
=
800 bfd_target_elf_flavour
,
801 elf_new_init
, /* sym_new_init: init anything gbl to entire symtab */
802 elf_symfile_init
, /* sym_init: read initial info, setup for sym_read() */
803 elf_symfile_read
, /* sym_read: read a symbol file into symtab */
804 elf_symfile_finish
, /* sym_finish: finished with file, cleanup */
805 default_symfile_offsets
, /* sym_offsets: Translate ext. to int. relocation */
806 NULL
/* next: pointer to next struct sym_fns */
810 _initialize_elfread (void)
812 add_symtab_fns (&elf_sym_fns
);