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 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_before_reloc (sectp
);
88 else if (strcmp (sectp
->name
, ".line") == 0)
90 ei
->lnoffset
= sectp
->filepos
;
91 ei
->lnsize
= bfd_get_section_size_before_reloc (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)
131 Given an objfile and a flag that specifies whether or not the objfile
132 is for an executable or not (may be shared library for example), add
133 all the global function and data symbols to the minimal symbol table.
135 In stabs-in-ELF, as implemented by Sun, there are some local symbols
136 defined in the ELF symbol table, which can be used to locate
137 the beginnings of sections from each ".o" file that was linked to
138 form the executable objfile. We gather any such info and record it
139 in data structures hung off the objfile's private data.
144 elf_symtab_read (struct objfile
*objfile
, int dynamic
)
148 asymbol
**symbol_table
;
149 long number_of_symbols
;
151 struct cleanup
*back_to
;
154 enum minimal_symbol_type ms_type
;
155 /* If sectinfo is nonNULL, it contains section info that should end up
156 filed in the objfile. */
157 struct stab_section_info
*sectinfo
= NULL
;
158 /* If filesym is nonzero, it points to a file symbol, but we haven't
159 seen any section info for it yet. */
160 asymbol
*filesym
= 0;
161 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
162 /* Name of filesym, as saved on the symbol_obstack. */
163 char *filesymname
= obsavestring ("", 0, &objfile
->symbol_obstack
);
165 struct dbx_symfile_info
*dbx
= objfile
->sym_stab_info
;
166 int stripped
= (bfd_get_symcount (objfile
->obfd
) == 0);
170 storage_needed
= bfd_get_dynamic_symtab_upper_bound (objfile
->obfd
);
172 /* Nothing to be done if there is no dynamic symtab. */
173 if (storage_needed
< 0)
178 storage_needed
= bfd_get_symtab_upper_bound (objfile
->obfd
);
179 if (storage_needed
< 0)
180 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile
->obfd
),
181 bfd_errmsg (bfd_get_error ()));
183 if (storage_needed
> 0)
185 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
186 back_to
= make_cleanup (xfree
, symbol_table
);
188 number_of_symbols
= bfd_canonicalize_dynamic_symtab (objfile
->obfd
,
191 number_of_symbols
= bfd_canonicalize_symtab (objfile
->obfd
, symbol_table
);
192 if (number_of_symbols
< 0)
193 error ("Can't read symbols from %s: %s", bfd_get_filename (objfile
->obfd
),
194 bfd_errmsg (bfd_get_error ()));
196 for (i
= 0; i
< number_of_symbols
; i
++)
198 sym
= symbol_table
[i
];
199 if (sym
->name
== NULL
|| *sym
->name
== '\0')
201 /* Skip names that don't exist (shouldn't happen), or names
202 that are null strings (may happen). */
206 offset
= ANOFFSET (objfile
->section_offsets
, sym
->section
->index
);
208 && sym
->section
== &bfd_und_section
209 && (sym
->flags
& BSF_FUNCTION
))
211 struct minimal_symbol
*msym
;
213 /* Symbol is a reference to a function defined in
215 If its value is non zero then it is usually the address
216 of the corresponding entry in the procedure linkage table,
217 plus the desired section offset.
218 If its value is zero then the dynamic linker has to resolve
219 the symbol. We are unable to find any meaningful address
220 for this symbol in the executable file, so we skip it. */
221 symaddr
= sym
->value
;
225 msym
= record_minimal_symbol
226 ((char *) sym
->name
, symaddr
,
227 mst_solib_trampoline
, sym
->section
, objfile
);
228 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
230 msym
->filename
= filesymname
;
235 /* If it is a nonstripped executable, do not enter dynamic
236 symbols, as the dynamic symbol table is usually a subset
237 of the main symbol table. */
238 if (dynamic
&& !stripped
)
240 if (sym
->flags
& BSF_FILE
)
242 /* STT_FILE debugging symbol that helps stabs-in-elf debugging.
243 Chain any old one onto the objfile; remember new sym. */
244 if (sectinfo
!= NULL
)
246 sectinfo
->next
= dbx
->stab_section_info
;
247 dbx
->stab_section_info
= sectinfo
;
251 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
253 obsavestring ((char *) filesym
->name
, strlen (filesym
->name
),
254 &objfile
->symbol_obstack
);
257 else if (sym
->flags
& (BSF_GLOBAL
| BSF_LOCAL
| BSF_WEAK
))
259 struct minimal_symbol
*msym
;
261 /* Select global/local/weak symbols. Note that bfd puts abs
262 symbols in their own section, so all symbols we are
263 interested in will have a section. */
264 /* Bfd symbols are section relative. */
265 symaddr
= sym
->value
+ sym
->section
->vma
;
266 /* Relocate all non-absolute symbols by the section offset. */
267 if (sym
->section
!= &bfd_abs_section
)
271 /* For non-absolute symbols, use the type of the section
272 they are relative to, to intuit text/data. Bfd provides
273 no way of figuring this out for absolute symbols. */
274 if (sym
->section
== &bfd_abs_section
)
276 /* This is a hack to get the minimal symbol type
277 right for Irix 5, which has absolute addresses
278 with special section indices for dynamic symbols. */
279 unsigned short shndx
=
280 ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_shndx
;
290 case SHN_MIPS_ACOMMON
:
297 /* If it is an Irix dynamic symbol, skip section name
298 symbols, relocate all others by section offset. */
299 if (ms_type
!= mst_abs
)
301 if (sym
->name
[0] == '.')
306 else if (sym
->section
->flags
& SEC_CODE
)
308 if (sym
->flags
& BSF_GLOBAL
)
312 else if ((sym
->name
[0] == '.' && sym
->name
[1] == 'L')
313 || ((sym
->flags
& BSF_LOCAL
)
314 && sym
->name
[0] == '$'
315 && sym
->name
[1] == 'L'))
316 /* Looks like a compiler-generated label. Skip
317 it. The assembler should be skipping these (to
318 keep executables small), but apparently with
319 gcc on the (deleted) delta m88k SVR4, it loses.
320 So to have us check too should be harmless (but
321 I encourage people to fix this in the assembler
322 instead of adding checks here). */
326 ms_type
= mst_file_text
;
329 else if (sym
->section
->flags
& SEC_ALLOC
)
331 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
))
333 if (sym
->section
->flags
& SEC_LOAD
)
342 else if (sym
->flags
& BSF_LOCAL
)
344 /* Named Local variable in a Data section.
345 Check its name for stabs-in-elf. The STREQ
346 macro checks the first character inline, so
347 we only actually do a strcmp function call on
348 names that start with 'B' or 'D'. */
349 int special_local_sect
;
350 if (strcmp ("Bbss.bss", sym
->name
) == 0)
351 special_local_sect
= SECT_OFF_BSS (objfile
);
352 else if (strcmp ("Ddata.data", sym
->name
) == 0)
353 special_local_sect
= SECT_OFF_DATA (objfile
);
354 else if (strcmp ("Drodata.rodata", sym
->name
) == 0)
355 special_local_sect
= SECT_OFF_RODATA (objfile
);
357 special_local_sect
= -1;
358 if (special_local_sect
>= 0)
360 /* Found a special local symbol. Allocate a
361 sectinfo, if needed, and fill it in. */
362 if (sectinfo
== NULL
)
368 = max (SECT_OFF_BSS (objfile
),
369 max (SECT_OFF_DATA (objfile
),
370 SECT_OFF_RODATA (objfile
)));
372 /* max_index is the largest index we'll
373 use into this array, so we must
374 allocate max_index+1 elements for it.
375 However, 'struct stab_section_info'
376 already includes one element, so we
377 need to allocate max_index aadditional
379 size
= (sizeof (struct stab_section_info
)
380 + (sizeof (CORE_ADDR
)
382 sectinfo
= (struct stab_section_info
*)
383 xmmalloc (objfile
->md
, size
);
384 memset (sectinfo
, 0, size
);
385 sectinfo
->num_sections
= max_index
;
388 complaint (&symfile_complaints
,
389 "elf/stab section information %s without a preceding file symbol",
395 (char *) filesym
->name
;
398 if (sectinfo
->sections
[special_local_sect
] != 0)
399 complaint (&symfile_complaints
,
400 "duplicated elf/stab section information for %s",
402 /* BFD symbols are section relative. */
403 symaddr
= sym
->value
+ sym
->section
->vma
;
404 /* Relocate non-absolute symbols by the
406 if (sym
->section
!= &bfd_abs_section
)
408 sectinfo
->sections
[special_local_sect
] = symaddr
;
409 /* The special local symbols don't go in the
410 minimal symbol table, so ignore this one. */
413 /* Not a special stabs-in-elf symbol, do regular
414 symbol processing. */
415 if (sym
->section
->flags
& SEC_LOAD
)
417 ms_type
= mst_file_data
;
421 ms_type
= mst_file_bss
;
426 ms_type
= mst_unknown
;
431 /* FIXME: Solaris2 shared libraries include lots of
432 odd "absolute" and "undefined" symbols, that play
433 hob with actions like finding what function the PC
434 is in. Ignore them if they aren't text, data, or bss. */
435 /* ms_type = mst_unknown; */
436 continue; /* Skip this symbol. */
438 msym
= record_minimal_symbol
439 ((char *) sym
->name
, symaddr
,
440 ms_type
, sym
->section
, objfile
);
443 /* Pass symbol size field in via BFD. FIXME!!! */
444 unsigned long size
= ((elf_symbol_type
*) sym
)->internal_elf_sym
.st_size
;
445 MSYMBOL_SIZE(msym
) = size
;
447 #ifdef SOFUN_ADDRESS_MAYBE_MISSING
449 msym
->filename
= filesymname
;
451 ELF_MAKE_MSYMBOL_SPECIAL (sym
, msym
);
454 do_cleanups (back_to
);
458 /* Scan and build partial symbols for a symbol file.
459 We have been initialized by a call to elf_symfile_init, which
460 currently does nothing.
462 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
463 in each section. We simplify it down to a single offset for all
466 MAINLINE is true if we are reading the main symbol
467 table (as opposed to a shared lib or dynamically loaded file).
469 This function only does the minimum work necessary for letting the
470 user "name" things symbolically; it does not read the entire symtab.
471 Instead, it reads the external and static symbols and puts them in partial
472 symbol tables. When more extensive information is requested of a
473 file, the corresponding partial symbol table is mutated into a full
474 fledged symbol table by going back and reading the symbols
477 We look for sections with specific names, to tell us what debug
478 format to look for: FIXME!!!
480 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
481 elfstab_build_psymtabs() handles STABS symbols;
482 mdebug_build_psymtabs() handles ECOFF debugging information.
484 Note that ELF files have a "minimal" symbol table, which looks a lot
485 like a COFF symbol table, but has only the minimal information necessary
486 for linking. We process this also, and use the information to
487 build gdb's minimal symbol table. This gives us some minimal debugging
488 capability even for files compiled without -g. */
491 elf_symfile_read (struct objfile
*objfile
, int mainline
)
493 bfd
*abfd
= objfile
->obfd
;
495 struct cleanup
*back_to
;
498 init_minimal_symbol_collection ();
499 back_to
= make_cleanup_discard_minimal_symbols ();
501 memset ((char *) &ei
, 0, sizeof (ei
));
503 /* Allocate struct to keep track of the symfile */
504 objfile
->sym_stab_info
= (struct dbx_symfile_info
*)
505 xmmalloc (objfile
->md
, sizeof (struct dbx_symfile_info
));
506 memset ((char *) objfile
->sym_stab_info
, 0, sizeof (struct dbx_symfile_info
));
507 make_cleanup (free_elfinfo
, (void *) objfile
);
509 /* Process the normal ELF symbol table first. This may write some
510 chain of info into the dbx_symfile_info in objfile->sym_stab_info,
511 which can later be used by elfstab_offset_sections. */
513 elf_symtab_read (objfile
, 0);
515 /* Add the dynamic symbols. */
517 elf_symtab_read (objfile
, 1);
519 /* Install any minimal symbols that have been collected as the current
520 minimal symbols for this objfile. The debug readers below this point
521 should not generate new minimal symbols; if they do it's their
522 responsibility to install them. "mdebug" appears to be the only one
523 which will do this. */
525 install_minimal_symbols (objfile
);
526 do_cleanups (back_to
);
528 /* Now process debugging information, which is contained in
529 special ELF sections. */
531 /* If we are reinitializing, or if we have never loaded syms yet,
532 set table to empty. MAINLINE is cleared so that *_read_psymtab
533 functions do not all also re-initialize the psymbol table. */
536 init_psymbol_list (objfile
, 0);
540 /* We first have to find them... */
541 bfd_map_over_sections (abfd
, elf_locate_sections
, (void *) & ei
);
543 /* ELF debugging information is inserted into the psymtab in the
544 order of least informative first - most informative last. Since
545 the psymtab table is searched `most recent insertion first' this
546 increases the probability that more detailed debug information
547 for a section is found.
549 For instance, an object file might contain both .mdebug (XCOFF)
550 and .debug_info (DWARF2) sections then .mdebug is inserted first
551 (searched last) and DWARF2 is inserted last (searched first). If
552 we don't do this then the XCOFF info is found first - for code in
553 an included file XCOFF info is useless. */
557 const struct ecoff_debug_swap
*swap
;
559 /* .mdebug section, presumably holding ECOFF debugging
561 swap
= get_elf_backend_data (abfd
)->elf_backend_ecoff_debug_swap
;
563 elfmdebug_build_psymtabs (objfile
, swap
, ei
.mdebugsect
);
569 /* Stab sections have an associated string table that looks like
570 a separate section. */
571 str_sect
= bfd_get_section_by_name (abfd
, ".stabstr");
573 /* FIXME should probably warn about a stab section without a stabstr. */
575 elfstab_build_psymtabs (objfile
,
579 bfd_section_size (abfd
, str_sect
));
581 if (dwarf2_has_info (abfd
))
583 /* DWARF 2 sections */
584 dwarf2_build_psymtabs (objfile
, mainline
);
586 else if (ei
.dboffset
&& ei
.lnoffset
)
589 dwarf_build_psymtabs (objfile
,
591 ei
.dboffset
, ei
.dbsize
,
592 ei
.lnoffset
, ei
.lnsize
);
595 /* FIXME: kettenis/20030504: This still needs to be integrated with
596 dwarf2read.c in a better way. */
597 dwarf2_build_frame_info (objfile
);
600 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
601 stab_section_info's, that might be dangling from it. */
604 free_elfinfo (void *objp
)
606 struct objfile
*objfile
= (struct objfile
*) objp
;
607 struct dbx_symfile_info
*dbxinfo
= objfile
->sym_stab_info
;
608 struct stab_section_info
*ssi
, *nssi
;
610 ssi
= dbxinfo
->stab_section_info
;
614 xmfree (objfile
->md
, ssi
);
618 dbxinfo
->stab_section_info
= 0; /* Just say No mo info about this. */
622 /* Initialize anything that needs initializing when a completely new symbol
623 file is specified (not just adding some symbols from another file, e.g. a
626 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
629 elf_new_init (struct objfile
*ignore
)
631 stabsread_new_init ();
632 buildsym_new_init ();
635 /* Perform any local cleanups required when we are done with a particular
636 objfile. I.E, we are in the process of discarding all symbol information
637 for an objfile, freeing up all memory held for it, and unlinking the
638 objfile struct from the global list of known objfiles. */
641 elf_symfile_finish (struct objfile
*objfile
)
643 if (objfile
->sym_stab_info
!= NULL
)
645 xmfree (objfile
->md
, objfile
->sym_stab_info
);
649 /* ELF specific initialization routine for reading symbols.
651 It is passed a pointer to a struct sym_fns which contains, among other
652 things, the BFD for the file whose symbols are being read, and a slot for
653 a pointer to "private data" which we can fill with goodies.
655 For now at least, we have nothing in particular to do, so this function is
659 elf_symfile_init (struct objfile
*objfile
)
661 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
662 find this causes a significant slowdown in gdb then we could
663 set it in the debug symbol readers only when necessary. */
664 objfile
->flags
|= OBJF_REORDERED
;
667 /* When handling an ELF file that contains Sun STABS debug info,
668 some of the debug info is relative to the particular chunk of the
669 section that was generated in its individual .o file. E.g.
670 offsets to static variables are relative to the start of the data
671 segment *for that module before linking*. This information is
672 painfully squirreled away in the ELF symbol table as local symbols
673 with wierd names. Go get 'em when needed. */
676 elfstab_offset_sections (struct objfile
*objfile
, struct partial_symtab
*pst
)
678 char *filename
= pst
->filename
;
679 struct dbx_symfile_info
*dbx
= objfile
->sym_stab_info
;
680 struct stab_section_info
*maybe
= dbx
->stab_section_info
;
681 struct stab_section_info
*questionable
= 0;
685 /* The ELF symbol info doesn't include path names, so strip the path
686 (if any) from the psymtab filename. */
687 while (0 != (p
= strchr (filename
, '/')))
690 /* FIXME: This linear search could speed up significantly
691 if it was chained in the right order to match how we search it,
692 and if we unchained when we found a match. */
693 for (; maybe
; maybe
= maybe
->next
)
695 if (filename
[0] == maybe
->filename
[0]
696 && strcmp (filename
, maybe
->filename
) == 0)
698 /* We found a match. But there might be several source files
699 (from different directories) with the same name. */
700 if (0 == maybe
->found
)
702 questionable
= maybe
; /* Might use it later. */
706 if (maybe
== 0 && questionable
!= 0)
708 complaint (&symfile_complaints
,
709 "elf/stab section information questionable for %s", filename
);
710 maybe
= questionable
;
715 /* Found it! Allocate a new psymtab struct, and fill it in. */
717 pst
->section_offsets
= (struct section_offsets
*)
718 obstack_alloc (&objfile
->psymbol_obstack
,
719 SIZEOF_N_SECTION_OFFSETS (objfile
->num_sections
));
720 for (i
= 0; i
< maybe
->num_sections
; i
++)
721 (pst
->section_offsets
)->offsets
[i
] = maybe
->sections
[i
];
725 /* We were unable to find any offsets for this file. Complain. */
726 if (dbx
->stab_section_info
) /* If there *is* any info, */
727 complaint (&symfile_complaints
,
728 "elf/stab section information missing for %s", filename
);
731 /* Register that we are able to handle ELF object file formats. */
733 static struct sym_fns elf_sym_fns
=
735 bfd_target_elf_flavour
,
736 elf_new_init
, /* sym_new_init: init anything gbl to entire symtab */
737 elf_symfile_init
, /* sym_init: read initial info, setup for sym_read() */
738 elf_symfile_read
, /* sym_read: read a symbol file into symtab */
739 elf_symfile_finish
, /* sym_finish: finished with file, cleanup */
740 default_symfile_offsets
, /* sym_offsets: Translate ext. to int. relocation */
741 NULL
/* next: pointer to next struct sym_fns */
745 _initialize_elfread (void)
747 add_symtab_fns (&elf_sym_fns
);