1 /* Read ELF (Executable and Linking Format) object files for GDB.
2 Copyright 1991, 92, 93, 94, 95, 96, 1998, 2001
3 Free Software Foundation, Inc.
4 Written by Fred Fish at Cygnus Support.
6 This file is part of GDB.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
25 #include "gdb_string.h"
32 #include "stabsread.h"
33 #include "gdb-stabs.h"
34 #include "complaints.h"
37 extern void _initialize_elfread (void);
39 /* The struct elfinfo is available only during ELF symbol table and
40 psymtab reading. It is destroyed at the completion of psymtab-reading.
41 It's local to elf_symfile_read. */
45 file_ptr dboffset
; /* Offset to dwarf debug section */
46 unsigned int dbsize
; /* Size of dwarf debug section */
47 file_ptr lnoffset
; /* Offset to dwarf line number section */
48 unsigned int lnsize
; /* Size of dwarf line number section */
49 asection
*stabsect
; /* Section pointer for .stab section */
50 asection
*stabindexsect
; /* Section pointer for .stab.index section */
51 asection
*mdebugsect
; /* Section pointer for .mdebug section */
54 /* Various things we might complain about... */
56 struct complaint section_info_complaint
=
57 {"elf/stab section information %s without a preceding file symbol", 0, 0};
59 struct complaint section_info_dup_complaint
=
60 {"duplicated elf/stab section information for %s", 0, 0};
62 struct complaint stab_info_mismatch_complaint
=
63 {"elf/stab section information missing for %s", 0, 0};
65 struct complaint stab_info_questionable_complaint
=
66 {"elf/stab section information questionable for %s", 0, 0};
68 static void elf_symfile_init (struct objfile
*);
70 static void elf_new_init (struct objfile
*);
72 static void elf_symfile_read (struct objfile
*, int);
74 static void elf_symfile_finish (struct objfile
*);
76 static void elf_symtab_read (struct objfile
*, int);
78 static void free_elfinfo (void *);
80 static struct minimal_symbol
*record_minimal_symbol_and_info (char *,
90 static void elf_locate_sections (bfd
*, asection
*, void *);
92 /* We are called once per section from elf_symfile_read. We
93 need to examine each section we are passed, check to see
94 if it is something we are interested in processing, and
95 if so, stash away some access information for the section.
97 For now we recognize the dwarf debug information sections and
98 line number sections from matching their section names. The
99 ELF definition is no real help here since it has no direct
100 knowledge of DWARF (by design, so any debugging format can be
103 We also recognize the ".stab" sections used by the Sun compilers
104 released with Solaris 2.
106 FIXME: The section names should not be hardwired strings (what
107 should they be? I don't think most object file formats have enough
108 section flags to specify what kind of debug section it is
112 elf_locate_sections (bfd
*ignore_abfd
, asection
*sectp
, PTR eip
)
114 register struct elfinfo
*ei
;
116 ei
= (struct elfinfo
*) eip
;
117 if (STREQ (sectp
->name
, ".debug"))
119 ei
->dboffset
= sectp
->filepos
;
120 ei
->dbsize
= bfd_get_section_size_before_reloc (sectp
);
122 else if (STREQ (sectp
->name
, ".line"))
124 ei
->lnoffset
= sectp
->filepos
;
125 ei
->lnsize
= bfd_get_section_size_before_reloc (sectp
);
127 else if (STREQ (sectp
->name
, ".stab"))
129 ei
->stabsect
= sectp
;
131 else if (STREQ (sectp
->name
, ".stab.index"))
133 ei
->stabindexsect
= sectp
;
135 else if (STREQ (sectp
->name
, ".mdebug"))
137 ei
->mdebugsect
= sectp
;
141 #if 0 /* Currently unused */
144 elf_interpreter (bfd
*abfd
)
150 interp_sec
= bfd_get_section_by_name (abfd
, ".interp");
153 size
= bfd_section_size (abfd
, interp_sec
);
154 interp
= alloca (size
);
155 if (bfd_get_section_contents (abfd
, interp_sec
, interp
, (file_ptr
) 0,
158 interp
= savestring (interp
, size
- 1);
170 static struct minimal_symbol
*
171 record_minimal_symbol_and_info (char *name
, CORE_ADDR address
,
172 enum minimal_symbol_type ms_type
, char *info
, /* FIXME, is this really char *? */
173 asection
*bfd_section
, struct objfile
*objfile
)
175 #ifdef SMASH_TEXT_ADDRESS
176 if (ms_type
== mst_text
|| ms_type
== mst_file_text
)
177 SMASH_TEXT_ADDRESS (address
);
180 return prim_record_minimal_symbol_and_info
181 (name
, address
, ms_type
, info
, bfd_section
->index
, bfd_section
, objfile
);
188 elf_symtab_read -- read the symbol table of an ELF file
192 void elf_symtab_read (struct objfile *objfile, int dynamic)
196 Given an objfile and a flag that specifies whether or not the objfile
197 is for an executable or not (may be shared library for example), add
198 all the global function and data symbols to the minimal symbol table.
200 In stabs-in-ELF, as implemented by Sun, there are some local symbols
201 defined in the ELF symbol table, which can be used to locate
202 the beginnings of sections from each ".o" file that was linked to
203 form the executable objfile. We gather any such info and record it
204 in data structures hung off the objfile's private data.
209 elf_symtab_read (struct objfile
*objfile
, int dynamic
)
213 asymbol
**symbol_table
;
214 long number_of_symbols
;
217 struct cleanup
*back_to
;
220 enum minimal_symbol_type ms_type
;
221 /* If sectinfo is nonNULL, it contains section info that should end up
222 filed in the objfile. */
223 struct stab_section_info
*sectinfo
= NULL
;
224 /* If filesym is nonzero, it points to a file symbol, but we haven't
225 seen any section info for it yet. */
226 asymbol
*filesym
= 0;
227 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
228 /* Name of filesym, as saved on the symbol_obstack. */
229 char *filesymname
= obsavestring ("", 0, &objfile
->symbol_obstack
);
231 struct dbx_symfile_info
*dbx
= objfile
->sym_stab_info
;
233 int stripped
= (bfd_get_symcount (objfile
->obfd
) == 0);
237 storage_needed
= bfd_get_dynamic_symtab_upper_bound (objfile
->obfd
);
239 /* Nothing to be done if there is no dynamic symtab. */
240 if (storage_needed
< 0)
245 storage_needed
= bfd_get_symtab_upper_bound (objfile
->obfd
);
246 if (storage_needed
< 0)
247 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile
->obfd
),
248 bfd_errmsg (bfd_get_error ()));
250 if (storage_needed
> 0)
252 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
253 back_to
= make_cleanup (xfree
, symbol_table
);
255 number_of_symbols
= bfd_canonicalize_dynamic_symtab (objfile
->obfd
,
258 number_of_symbols
= bfd_canonicalize_symtab (objfile
->obfd
, symbol_table
);
259 if (number_of_symbols
< 0)
260 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile
->obfd
),
261 bfd_errmsg (bfd_get_error ()));
263 for (i
= 0; i
< number_of_symbols
; i
++)
265 sym
= symbol_table
[i
];
266 if (sym
->name
== NULL
|| *sym
->name
== '\0')
268 /* Skip names that don't exist (shouldn't happen), or names
269 that are null strings (may happen). */
273 offset
= ANOFFSET (objfile
->section_offsets
, sym
->section
->index
);
275 && sym
->section
== &bfd_und_section
276 && (sym
->flags
& BSF_FUNCTION
))
278 struct minimal_symbol
*msym
;
280 /* Symbol is a reference to a function defined in
282 If its value is non zero then it is usually the address
283 of the corresponding entry in the procedure linkage table,
284 plus the desired section offset.
285 If its value is zero then the dynamic linker has to resolve
286 the symbol. We are unable to find any meaningful address
287 for this symbol in the executable file, so we skip it. */
288 symaddr
= sym
->value
;
292 msym
= record_minimal_symbol_and_info
293 ((char *) sym
->name
, symaddr
,
294 mst_solib_trampoline
, NULL
, sym
->section
, objfile
);
295 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
297 msym
->filename
= filesymname
;
302 /* If it is a nonstripped executable, do not enter dynamic
303 symbols, as the dynamic symbol table is usually a subset
304 of the main symbol table. */
305 if (dynamic
&& !stripped
)
307 if (sym
->flags
& BSF_FILE
)
309 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
310 Chain any old one onto the objfile; remember new sym. */
311 if (sectinfo
!= NULL
)
313 sectinfo
->next
= dbx
->stab_section_info
;
314 dbx
->stab_section_info
= sectinfo
;
318 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
320 obsavestring ((char *) filesym
->name
, strlen (filesym
->name
),
321 &objfile
->symbol_obstack
);
324 else if (sym
->flags
& (BSF_GLOBAL
| BSF_LOCAL
| BSF_WEAK
))
326 struct minimal_symbol
*msym
;
328 /* Select global/local/weak symbols. Note that bfd puts abs
329 symbols in their own section, so all symbols we are
330 interested in will have a section. */
331 /* Bfd symbols are section relative. */
332 symaddr
= sym
->value
+ sym
->section
->vma
;
333 /* Relocate all non-absolute symbols by the section offset. */
334 if (sym
->section
!= &bfd_abs_section
)
338 /* For non-absolute symbols, use the type of the section
339 they are relative to, to intuit text/data. Bfd provides
340 no way of figuring this out for absolute symbols. */
341 if (sym
->section
== &bfd_abs_section
)
343 /* This is a hack to get the minimal symbol type
344 right for Irix 5, which has absolute addresses
345 with special section indices for dynamic symbols. */
346 unsigned short shndx
=
347 ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_shndx
;
357 case SHN_MIPS_ACOMMON
:
364 /* If it is an Irix dynamic symbol, skip section name
365 symbols, relocate all others by section offset. */
366 if (ms_type
!= mst_abs
)
368 if (sym
->name
[0] == '.')
373 else if (sym
->section
->flags
& SEC_CODE
)
375 if (sym
->flags
& BSF_GLOBAL
)
379 else if ((sym
->name
[0] == '.' && sym
->name
[1] == 'L')
380 || ((sym
->flags
& BSF_LOCAL
)
381 && sym
->name
[0] == '$'
382 && sym
->name
[1] == 'L'))
383 /* Looks like a compiler-generated label. Skip it.
384 The assembler should be skipping these (to keep
385 executables small), but apparently with gcc on the
386 delta m88k SVR4, it loses. So to have us check too
387 should be harmless (but I encourage people to fix this
388 in the assembler instead of adding checks here). */
391 else if (sym
->name
[0] == '.' && sym
->name
[1] == '.')
393 /* Looks like a Harris compiler generated label for the
394 purpose of marking instructions that are relevant to
395 DWARF dies. The assembler can't get rid of these
396 because they are relocatable addresses that the
397 linker needs to resolve. */
403 ms_type
= mst_file_text
;
406 else if (sym
->section
->flags
& SEC_ALLOC
)
408 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
))
410 if (sym
->section
->flags
& SEC_LOAD
)
419 else if (sym
->flags
& BSF_LOCAL
)
421 /* Named Local variable in a Data section. Check its
422 name for stabs-in-elf. The STREQ macro checks the
423 first character inline, so we only actually do a
424 strcmp function call on names that start with 'B'
426 index
= SECT_OFF_MAX
;
427 if (STREQ ("Bbss.bss", sym
->name
))
429 index
= SECT_OFF_BSS (objfile
);
431 else if (STREQ ("Ddata.data", sym
->name
))
433 index
= SECT_OFF_DATA (objfile
);
435 else if (STREQ ("Drodata.rodata", sym
->name
))
437 index
= SECT_OFF_RODATA (objfile
);
439 if (index
!= SECT_OFF_MAX
)
441 /* Found a special local symbol. Allocate a
442 sectinfo, if needed, and fill it in. */
443 if (sectinfo
== NULL
)
445 sectinfo
= (struct stab_section_info
*)
446 xmmalloc (objfile
->md
, sizeof (*sectinfo
));
447 memset ((PTR
) sectinfo
, 0, sizeof (*sectinfo
));
450 complain (§ion_info_complaint
,
456 (char *) filesym
->name
;
461 if (sectinfo
->sections
[index
] != 0)
463 complain (§ion_info_dup_complaint
,
468 internal_error (__FILE__
, __LINE__
,
469 "Section index uninitialized.");
470 /* Bfd symbols are section relative. */
471 symaddr
= sym
->value
+ sym
->section
->vma
;
472 /* Relocate non-absolute symbols by the section offset. */
473 if (sym
->section
!= &bfd_abs_section
)
478 sectinfo
->sections
[index
] = symaddr
;
480 internal_error (__FILE__
, __LINE__
,
481 "Section index uninitialized.");
482 /* The special local symbols don't go in the
483 minimal symbol table, so ignore this one. */
486 /* Not a special stabs-in-elf symbol, do regular
487 symbol processing. */
488 if (sym
->section
->flags
& SEC_LOAD
)
490 ms_type
= mst_file_data
;
494 ms_type
= mst_file_bss
;
499 ms_type
= mst_unknown
;
504 /* FIXME: Solaris2 shared libraries include lots of
505 odd "absolute" and "undefined" symbols, that play
506 hob with actions like finding what function the PC
507 is in. Ignore them if they aren't text, data, or bss. */
508 /* ms_type = mst_unknown; */
509 continue; /* Skip this symbol. */
511 /* Pass symbol size field in via BFD. FIXME!!! */
512 size
= ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_size
;
513 msym
= record_minimal_symbol_and_info
514 ((char *) sym
->name
, symaddr
,
515 ms_type
, (PTR
) size
, sym
->section
, objfile
);
516 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
518 msym
->filename
= filesymname
;
520 #ifdef ELF_MAKE_MSYMBOL_SPECIAL
521 ELF_MAKE_MSYMBOL_SPECIAL (sym
, msym
);
525 do_cleanups (back_to
);
529 /* Scan and build partial symbols for a symbol file.
530 We have been initialized by a call to elf_symfile_init, which
531 currently does nothing.
533 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
534 in each section. We simplify it down to a single offset for all
537 MAINLINE is true if we are reading the main symbol
538 table (as opposed to a shared lib or dynamically loaded file).
540 This function only does the minimum work necessary for letting the
541 user "name" things symbolically; it does not read the entire symtab.
542 Instead, it reads the external and static symbols and puts them in partial
543 symbol tables. When more extensive information is requested of a
544 file, the corresponding partial symbol table is mutated into a full
545 fledged symbol table by going back and reading the symbols
548 We look for sections with specific names, to tell us what debug
549 format to look for: FIXME!!!
551 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
552 elfstab_build_psymtabs() handles STABS symbols;
553 mdebug_build_psymtabs() handles ECOFF debugging information.
555 Note that ELF files have a "minimal" symbol table, which looks a lot
556 like a COFF symbol table, but has only the minimal information necessary
557 for linking. We process this also, and use the information to
558 build gdb's minimal symbol table. This gives us some minimal debugging
559 capability even for files compiled without -g. */
562 elf_symfile_read (struct objfile
*objfile
, int mainline
)
564 bfd
*abfd
= objfile
->obfd
;
566 struct cleanup
*back_to
;
569 init_minimal_symbol_collection ();
570 back_to
= make_cleanup_discard_minimal_symbols ();
572 memset ((char *) &ei
, 0, sizeof (ei
));
574 /* Allocate struct to keep track of the symfile */
575 objfile
->sym_stab_info
= (struct dbx_symfile_info
*)
576 xmmalloc (objfile
->md
, sizeof (struct dbx_symfile_info
));
577 memset ((char *) objfile
->sym_stab_info
, 0, sizeof (struct dbx_symfile_info
));
578 make_cleanup (free_elfinfo
, (PTR
) objfile
);
580 /* Process the normal ELF symbol table first. This may write some
581 chain of info into the dbx_symfile_info in objfile->sym_stab_info,
582 which can later be used by elfstab_offset_sections. */
584 elf_symtab_read (objfile
, 0);
586 /* Add the dynamic symbols. */
588 elf_symtab_read (objfile
, 1);
590 /* Now process debugging information, which is contained in
591 special ELF sections. */
593 /* If we are reinitializing, or if we have never loaded syms yet,
594 set table to empty. MAINLINE is cleared so that *_read_psymtab
595 functions do not all also re-initialize the psymbol table. */
598 init_psymbol_list (objfile
, 0);
602 /* We first have to find them... */
603 bfd_map_over_sections (abfd
, elf_locate_sections
, (PTR
) & ei
);
605 /* ELF debugging information is inserted into the psymtab in the
606 order of least informative first - most informative last. Since
607 the psymtab table is searched `most recent insertion first' this
608 increases the probability that more detailed debug information
609 for a section is found.
611 For instance, an object file might contain both .mdebug (XCOFF)
612 and .debug_info (DWARF2) sections then .mdebug is inserted first
613 (searched last) and DWARF2 is inserted last (searched first). If
614 we don't do this then the XCOFF info is found first - for code in
615 an included file XCOFF info is useless. */
619 const struct ecoff_debug_swap
*swap
;
621 /* .mdebug section, presumably holding ECOFF debugging
623 swap
= get_elf_backend_data (abfd
)->elf_backend_ecoff_debug_swap
;
625 elfmdebug_build_psymtabs (objfile
, swap
, ei
.mdebugsect
);
631 /* Stab sections have an associated string table that looks like
632 a separate section. */
633 str_sect
= bfd_get_section_by_name (abfd
, ".stabstr");
635 /* FIXME should probably warn about a stab section without a stabstr. */
637 elfstab_build_psymtabs (objfile
,
639 ei
.stabsect
->filepos
,
640 bfd_section_size (abfd
, ei
.stabsect
),
642 bfd_section_size (abfd
, str_sect
));
644 if (dwarf2_has_info (abfd
))
646 /* DWARF 2 sections */
647 dwarf2_build_psymtabs (objfile
, mainline
);
649 else if (ei
.dboffset
&& ei
.lnoffset
)
652 dwarf_build_psymtabs (objfile
,
654 ei
.dboffset
, ei
.dbsize
,
655 ei
.lnoffset
, ei
.lnsize
);
658 /* Install any minimal symbols that have been collected as the current
659 minimal symbols for this objfile. */
661 install_minimal_symbols (objfile
);
663 do_cleanups (back_to
);
666 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
667 stab_section_info's, that might be dangling from it. */
670 free_elfinfo (PTR objp
)
672 struct objfile
*objfile
= (struct objfile
*) objp
;
673 struct dbx_symfile_info
*dbxinfo
= objfile
->sym_stab_info
;
674 struct stab_section_info
*ssi
, *nssi
;
676 ssi
= dbxinfo
->stab_section_info
;
680 mfree (objfile
->md
, ssi
);
684 dbxinfo
->stab_section_info
= 0; /* Just say No mo info about this. */
688 /* Initialize anything that needs initializing when a completely new symbol
689 file is specified (not just adding some symbols from another file, e.g. a
692 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
695 elf_new_init (struct objfile
*ignore
)
697 stabsread_new_init ();
698 buildsym_new_init ();
701 /* Perform any local cleanups required when we are done with a particular
702 objfile. I.E, we are in the process of discarding all symbol information
703 for an objfile, freeing up all memory held for it, and unlinking the
704 objfile struct from the global list of known objfiles. */
707 elf_symfile_finish (struct objfile
*objfile
)
709 if (objfile
->sym_stab_info
!= NULL
)
711 mfree (objfile
->md
, objfile
->sym_stab_info
);
715 /* ELF specific initialization routine for reading symbols.
717 It is passed a pointer to a struct sym_fns which contains, among other
718 things, the BFD for the file whose symbols are being read, and a slot for
719 a pointer to "private data" which we can fill with goodies.
721 For now at least, we have nothing in particular to do, so this function is
725 elf_symfile_init (struct objfile
*objfile
)
727 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
728 find this causes a significant slowdown in gdb then we could
729 set it in the debug symbol readers only when necessary. */
730 objfile
->flags
|= OBJF_REORDERED
;
733 /* When handling an ELF file that contains Sun STABS debug info,
734 some of the debug info is relative to the particular chunk of the
735 section that was generated in its individual .o file. E.g.
736 offsets to static variables are relative to the start of the data
737 segment *for that module before linking*. This information is
738 painfully squirreled away in the ELF symbol table as local symbols
739 with wierd names. Go get 'em when needed. */
742 elfstab_offset_sections (struct objfile
*objfile
, struct partial_symtab
*pst
)
744 char *filename
= pst
->filename
;
745 struct dbx_symfile_info
*dbx
= objfile
->sym_stab_info
;
746 struct stab_section_info
*maybe
= dbx
->stab_section_info
;
747 struct stab_section_info
*questionable
= 0;
751 /* The ELF symbol info doesn't include path names, so strip the path
752 (if any) from the psymtab filename. */
753 while (0 != (p
= strchr (filename
, '/')))
756 /* FIXME: This linear search could speed up significantly
757 if it was chained in the right order to match how we search it,
758 and if we unchained when we found a match. */
759 for (; maybe
; maybe
= maybe
->next
)
761 if (filename
[0] == maybe
->filename
[0]
762 && STREQ (filename
, maybe
->filename
))
764 /* We found a match. But there might be several source files
765 (from different directories) with the same name. */
766 if (0 == maybe
->found
)
768 questionable
= maybe
; /* Might use it later. */
772 if (maybe
== 0 && questionable
!= 0)
774 complain (&stab_info_questionable_complaint
, filename
);
775 maybe
= questionable
;
780 /* Found it! Allocate a new psymtab struct, and fill it in. */
782 pst
->section_offsets
= (struct section_offsets
*)
783 obstack_alloc (&objfile
->psymbol_obstack
, SIZEOF_SECTION_OFFSETS
);
784 for (i
= 0; i
< SECT_OFF_MAX
; i
++)
785 (pst
->section_offsets
)->offsets
[i
] = maybe
->sections
[i
];
789 /* We were unable to find any offsets for this file. Complain. */
790 if (dbx
->stab_section_info
) /* If there *is* any info, */
791 complain (&stab_info_mismatch_complaint
, filename
);
794 /* Register that we are able to handle ELF object file formats. */
796 static struct sym_fns elf_sym_fns
=
798 bfd_target_elf_flavour
,
799 elf_new_init
, /* sym_new_init: init anything gbl to entire symtab */
800 elf_symfile_init
, /* sym_init: read initial info, setup for sym_read() */
801 elf_symfile_read
, /* sym_read: read a symbol file into symtab */
802 elf_symfile_finish
, /* sym_finish: finished with file, cleanup */
803 default_symfile_offsets
, /* sym_offsets: Translate ext. to int. relocation */
804 NULL
/* next: pointer to next struct sym_fns */
808 _initialize_elfread (void)
810 add_symtab_fns (&elf_sym_fns
);