1 /* Read ELF (Executable and Linking Format) object files for GDB.
2 Copyright 1991, 1992 Free Software Foundation, Inc.
3 Written by Fred Fish at Cygnus Support.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
21 /************************************************************************
25 * This file is still under construction. When it is complete, this *
26 * notice will be removed. Until then, direct any questions or changes *
27 * to Fred Fish at Cygnus Support (fnf@cygnus.com) *
29 * FIXME Still needs support for shared libraries. *
30 * FIXME Still needs support for core files. *
31 * FIXME The ".debug" and ".line" section names are hardwired. *
33 ************************************************************************/
37 #include "libbfd.h" /* For bfd_elf_find_section */
43 #include "gdb-stabs.h"
44 #include "complaints.h"
48 /* The struct elfinfo is available only during ELF symbol table and
49 psymtab reading. It is destroyed at the complation of psymtab-reading.
50 It's local to elf_symfile_read. */
53 file_ptr dboffset
; /* Offset to dwarf debug section */
54 unsigned int dbsize
; /* Size of dwarf debug section */
55 file_ptr lnoffset
; /* Offset to dwarf line number section */
56 unsigned int lnsize
; /* Size of dwarf line number section */
57 asection
*stabsect
; /* Section pointer for .stab section */
58 asection
*stabindexsect
; /* Section pointer for .stab.index section */
61 /* Various things we might complain about... */
63 struct complaint section_info_complaint
=
64 {"elf/stab section information %s without a preceding file symbol", 0, 0};
66 struct complaint section_info_dup_complaint
=
67 {"duplicated elf/stab section information for %s", 0, 0};
69 struct complaint stab_info_mismatch_complaint
=
70 {"elf/stab section information missing for %s", 0, 0};
72 struct complaint stab_info_questionable_complaint
=
73 {"elf/stab section information questionable for %s", 0, 0};
76 elf_symfile_init
PARAMS ((struct objfile
*));
79 elf_new_init
PARAMS ((struct objfile
*));
82 elf_symfile_read
PARAMS ((struct objfile
*, struct section_offsets
*, int));
85 elf_symfile_finish
PARAMS ((struct objfile
*));
88 elf_symtab_read
PARAMS ((bfd
*, CORE_ADDR
, struct objfile
*));
91 free_elfinfo
PARAMS ((PTR
));
93 static struct section_offsets
*
94 elf_symfile_offsets
PARAMS ((struct objfile
*, CORE_ADDR
));
97 record_minimal_symbol_and_info
PARAMS ((char *, CORE_ADDR
,
98 enum minimal_symbol_type
, char *,
102 elf_locate_sections
PARAMS ((bfd
*, asection
*, PTR
));
104 /* We are called once per section from elf_symfile_read. We
105 need to examine each section we are passed, check to see
106 if it is something we are interested in processing, and
107 if so, stash away some access information for the section.
109 For now we recognize the dwarf debug information sections and
110 line number sections from matching their section names. The
111 ELF definition is no real help here since it has no direct
112 knowledge of DWARF (by design, so any debugging format can be
115 We also recognize the ".stab" sections used by the Sun compilers
116 released with Solaris 2.
118 FIXME: The section names should not be hardwired strings. */
121 elf_locate_sections (ignore_abfd
, sectp
, eip
)
126 register struct elfinfo
*ei
;
128 ei
= (struct elfinfo
*) eip
;
129 if (STREQ (sectp
-> name
, ".debug"))
131 ei
-> dboffset
= sectp
-> filepos
;
132 ei
-> dbsize
= bfd_get_section_size_before_reloc (sectp
);
134 else if (STREQ (sectp
-> name
, ".line"))
136 ei
-> lnoffset
= sectp
-> filepos
;
137 ei
-> lnsize
= bfd_get_section_size_before_reloc (sectp
);
139 else if (STREQ (sectp
-> name
, ".stab"))
141 ei
-> stabsect
= sectp
;
143 else if (STREQ (sectp
-> name
, ".stab.index"))
145 ei
-> stabindexsect
= sectp
;
149 #if 0 /* Currently unused */
152 elf_interpreter (abfd
)
159 interp_sec
= bfd_get_section_by_name (abfd
, ".interp");
162 size
= bfd_section_size (abfd
, interp_sec
);
163 interp
= alloca (size
);
164 if (bfd_get_section_contents (abfd
, interp_sec
, interp
, (file_ptr
)0,
167 interp
= savestring (interp
, size
- 1);
180 record_minimal_symbol_and_info (name
, address
, ms_type
, info
, objfile
)
183 enum minimal_symbol_type ms_type
;
184 char *info
; /* FIXME, is this really char *? */
185 struct objfile
*objfile
;
187 name
= obsavestring (name
, strlen (name
), &objfile
-> symbol_obstack
);
188 prim_record_minimal_symbol_and_info (name
, address
, ms_type
, info
, -1);
195 elf_symtab_read -- read the symbol table of an ELF file
199 void elf_symtab_read (bfd *abfd, CORE_ADDR addr,
200 struct objfile *objfile)
204 Given an open bfd, a base address to relocate symbols to, and a
205 flag that specifies whether or not this bfd is for an executable
206 or not (may be shared library for example), add all the global
207 function and data symbols to the minimal symbol table.
209 In stabs-in-ELF, as implemented by Sun, there are some local symbols
210 defined in the ELF symbol table, which can be used to locate
211 the beginnings of sections from each ".o" file that was linked to
212 form the executable objfile. We gather any such info and record it
213 in data structures hung off the objfile's private data.
218 elf_symtab_read (abfd
, addr
, objfile
)
221 struct objfile
*objfile
;
223 unsigned int storage_needed
;
225 asymbol
**symbol_table
;
226 unsigned int number_of_symbols
;
229 struct cleanup
*back_to
;
231 enum minimal_symbol_type ms_type
;
232 /* If sectinfo is nonzero, it contains section info that should end up
233 filed in the objfile. */
234 struct stab_section_info
*sectinfo
= 0;
235 /* If filesym is nonzero, it points to a file symbol, but we haven't
236 seen any section info for it yet. */
237 asymbol
*filesym
= 0;
238 struct dbx_symfile_info
*dbx
= (struct dbx_symfile_info
*)
239 objfile
->sym_private
;
241 storage_needed
= get_symtab_upper_bound (abfd
);
243 if (storage_needed
> 0)
245 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
246 back_to
= make_cleanup (free
, symbol_table
);
247 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
249 for (i
= 0; i
< number_of_symbols
; i
++)
251 sym
= symbol_table
[i
];
252 /* Select global/weak symbols that are defined in a specific section.
253 Note that bfd now puts abs symbols in their own section, so
254 all symbols we are interested in will have a section. */
255 if ((sym
-> flags
& (BSF_GLOBAL
| BSF_WEAK
))
256 && (sym
-> section
!= NULL
))
258 symaddr
= sym
-> value
;
259 /* Relocate all non-absolute symbols by base address. */
260 if (sym
-> section
!= &bfd_abs_section
)
263 /* For non-absolute symbols, use the type of the section
264 they are relative to, to intuit text/data. Bfd provides
265 no way of figuring this out for absolute symbols. */
266 if (sym
-> section
-> flags
& SEC_CODE
)
270 else if (sym
-> section
-> flags
& SEC_DATA
)
276 /* FIXME: Solaris2 shared libraries include lots of
277 odd "absolute" and "undefined" symbols, that play
278 hob with actions like finding what function the PC
279 is in. Ignore them if they aren't text or data. */
280 /* ms_type = mst_unknown; */
281 continue; /* Skip this symbol. */
283 /* Pass symbol size field in via BFD. FIXME!!! */
285 elf32_symbol_type
*esym
= (elf32_symbol_type
*) sym
;
286 unsigned long size
= esym
->internal_elf_sym
.st_size
;
287 record_minimal_symbol_and_info ((char *) sym
-> name
, symaddr
,
288 ms_type
, (PTR
) size
, objfile
);
292 /* See if this is a debugging symbol that helps Solaris
293 stabs-in-elf debugging. */
295 else if (sym
->flags
& BSF_FILE
)
297 /* Chain any old one onto the objfile; remember new sym. */
300 sectinfo
->next
= dbx
->stab_section_info
;
301 dbx
->stab_section_info
= sectinfo
;
306 else if ((sym
->flags
& BSF_LOCAL
) &&
308 (sym
->section
->flags
& SEC_DATA
) &&
311 /* Named Local variable in a Data section. Check its name. */
313 switch (sym
->name
[1])
316 if (STREQ ("Bbss.bss", sym
->name
))
317 index
= SECT_OFF_BSS
;
320 if (STREQ ("Ddata.data", sym
->name
))
321 index
= SECT_OFF_DATA
;
324 if (STREQ ("Drodata.rodata", sym
->name
))
325 index
= SECT_OFF_RODATA
;
330 /* We have some new info. Allocate a sectinfo, if
331 needed, and fill it in. */
334 sectinfo
= (struct stab_section_info
*)
335 xmmalloc (objfile
-> md
,
337 memset ((PTR
) sectinfo
, 0, sizeof (*sectinfo
));
339 complain (§ion_info_complaint
, sym
->name
);
341 sectinfo
->filename
= (char *)filesym
->name
;
343 if (sectinfo
->sections
[index
])
344 complain (§ion_info_dup_complaint
, sectinfo
->filename
);
346 symaddr
= sym
-> value
;
347 /* Relocate all non-absolute symbols by base address. */
348 if (sym
-> section
!= &bfd_abs_section
)
350 sectinfo
->sections
[index
] = symaddr
;
354 do_cleanups (back_to
);
358 /* Scan and build partial symbols for a symbol file.
359 We have been initialized by a call to elf_symfile_init, which
360 currently does nothing.
362 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
363 in each section. We simplify it down to a single offset for all
366 MAINLINE is true if we are reading the main symbol
367 table (as opposed to a shared lib or dynamically loaded file).
369 This function only does the minimum work necessary for letting the
370 user "name" things symbolically; it does not read the entire symtab.
371 Instead, it reads the external and static symbols and puts them in partial
372 symbol tables. When more extensive information is requested of a
373 file, the corresponding partial symbol table is mutated into a full
374 fledged symbol table by going back and reading the symbols
377 We look for sections with specific names, to tell us what debug
378 format to look for: FIXME!!!
380 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
381 elfstab_build_psymtabs() handles STABS symbols.
383 Note that ELF files have a "minimal" symbol table, which looks a lot
384 like a COFF symbol table, but has only the minimal information necessary
385 for linking. We process this also, and use the information to
386 build gdb's minimal symbol table. This gives us some minimal debugging
387 capability even for files compiled without -g. */
390 elf_symfile_read (objfile
, section_offsets
, mainline
)
391 struct objfile
*objfile
;
392 struct section_offsets
*section_offsets
;
395 bfd
*abfd
= objfile
->obfd
;
397 struct cleanup
*back_to
;
400 init_minimal_symbol_collection ();
401 back_to
= make_cleanup (discard_minimal_symbols
, 0);
403 memset ((char *) &ei
, 0, sizeof (ei
));
405 /* Allocate struct to keep track of the symfile */
406 objfile
->sym_private
= (PTR
)
407 xmmalloc (objfile
-> md
, sizeof (struct dbx_symfile_info
));
408 memset ((char *) objfile
->sym_private
, 0, sizeof (struct dbx_symfile_info
));
409 make_cleanup (free_elfinfo
, (PTR
) objfile
);
411 /* Process the normal ELF symbol table first. This may write some
412 chain of info into the dbx_symfile_info in objfile->sym_private,
413 which can later be used by elfstab_offset_sections. */
415 /* FIXME, should take a section_offsets param, not just an offset. */
416 offset
= ANOFFSET (section_offsets
, 0);
417 elf_symtab_read (abfd
, offset
, objfile
);
419 /* Now process debugging information, which is contained in
420 special ELF sections. We first have to find them... */
422 bfd_map_over_sections (abfd
, elf_locate_sections
, (PTR
) &ei
);
423 if (ei
.dboffset
&& ei
.lnoffset
)
426 dwarf_build_psymtabs (objfile
,
427 section_offsets
, mainline
,
428 ei
.dboffset
, ei
.dbsize
,
429 ei
.lnoffset
, ei
.lnsize
);
435 /* FIXME: Sun didn't really know how to implement this well.
436 They made .stab sections that don't point to the .stabstr
437 section with the sh_link field. BFD doesn't make string table
438 sections visible to the caller. So we have to search the
439 ELF section table, not the BFD section table, for the string
441 struct elf32_internal_shdr
*elf_sect
;
443 elf_sect
= bfd_elf32_find_section (abfd
, ".stabstr");
445 elfstab_build_psymtabs (objfile
,
448 ei
.stabsect
->filepos
, /* .stab offset */
449 bfd_get_section_size_before_reloc (ei
.stabsect
),/* .stab size */
450 (file_ptr
) elf_sect
->sh_offset
, /* .stabstr offset */
451 elf_sect
->sh_size
); /* .stabstr size */
454 if (!have_partial_symbols ())
457 printf_filtered ("(no debugging symbols found)...");
461 /* Install any minimal symbols that have been collected as the current
462 minimal symbols for this objfile. */
464 install_minimal_symbols (objfile
);
466 do_cleanups (back_to
);
469 /* This cleans up the objfile's sym_private pointer, and the chain of
470 stab_section_info's, that might be dangling from it. */
476 struct objfile
*objfile
= (struct objfile
*)objp
;
477 struct dbx_symfile_info
*dbxinfo
= (struct dbx_symfile_info
*)
478 objfile
->sym_private
;
479 struct stab_section_info
*ssi
, *nssi
;
481 ssi
= dbxinfo
->stab_section_info
;
485 mfree (objfile
->md
, ssi
);
489 dbxinfo
->stab_section_info
= 0; /* Just say No mo info about this. */
493 /* Initialize anything that needs initializing when a completely new symbol
494 file is specified (not just adding some symbols from another file, e.g. a
497 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
500 elf_new_init (ignore
)
501 struct objfile
*ignore
;
503 stabsread_new_init ();
504 buildsym_new_init ();
507 /* Perform any local cleanups required when we are done with a particular
508 objfile. I.E, we are in the process of discarding all symbol information
509 for an objfile, freeing up all memory held for it, and unlinking the
510 objfile struct from the global list of known objfiles. */
513 elf_symfile_finish (objfile
)
514 struct objfile
*objfile
;
516 if (objfile
-> sym_private
!= NULL
)
518 mfree (objfile
-> md
, objfile
-> sym_private
);
522 /* ELF specific initialization routine for reading symbols.
524 It is passed a pointer to a struct sym_fns which contains, among other
525 things, the BFD for the file whose symbols are being read, and a slot for
526 a pointer to "private data" which we can fill with goodies.
528 For now at least, we have nothing in particular to do, so this function is
532 elf_symfile_init (ignore
)
533 struct objfile
*ignore
;
537 /* ELF specific parsing routine for section offsets.
539 Plain and simple for now. */
542 struct section_offsets
*
543 elf_symfile_offsets (objfile
, addr
)
544 struct objfile
*objfile
;
547 struct section_offsets
*section_offsets
;
550 section_offsets
= (struct section_offsets
*)
551 obstack_alloc (&objfile
-> psymbol_obstack
,
552 sizeof (struct section_offsets
) +
553 sizeof (section_offsets
->offsets
) * (SECT_OFF_MAX
-1));
555 for (i
= 0; i
< SECT_OFF_MAX
; i
++)
556 ANOFFSET (section_offsets
, i
) = addr
;
558 return section_offsets
;
561 /* When handling an ELF file that contains Sun STABS debug info,
562 some of the debug info is relative to the particular chunk of the
563 section that was generated in its individual .o file. E.g.
564 offsets to static variables are relative to the start of the data
565 segment *for that module before linking*. This information is
566 painfully squirreled away in the ELF symbol table as local symbols
567 with wierd names. Go get 'em when needed. */
570 elfstab_offset_sections (objfile
, pst
)
571 struct objfile
*objfile
;
572 struct partial_symtab
*pst
;
574 char *filename
= pst
->filename
;
575 struct dbx_symfile_info
*dbx
= (struct dbx_symfile_info
*)
576 objfile
->sym_private
;
577 struct stab_section_info
*maybe
= dbx
->stab_section_info
;
578 struct stab_section_info
*questionable
= 0;
582 /* The ELF symbol info doesn't include path names, so strip the path
583 (if any) from the psymtab filename. */
584 while (0 != (p
= strchr (filename
, '/')))
587 /* FIXME: This linear search could speed up significantly
588 if it was chained in the right order to match how we search it,
589 and if we unchained when we found a match. */
590 for (; maybe
; maybe
= maybe
->next
)
592 if (filename
[0] == maybe
->filename
[0]
593 && STREQ (filename
, maybe
->filename
))
595 /* We found a match. But there might be several source files
596 (from different directories) with the same name. */
597 if (0 == maybe
->found
)
599 questionable
= maybe
; /* Might use it later. */
603 if (maybe
== 0 && questionable
!= 0)
605 complain (&stab_info_questionable_complaint
, filename
);
606 maybe
= questionable
;
611 /* Found it! Allocate a new psymtab struct, and fill it in. */
613 pst
->section_offsets
= (struct section_offsets
*)
614 obstack_alloc (&objfile
-> psymbol_obstack
,
615 sizeof (struct section_offsets
) +
616 sizeof (pst
->section_offsets
->offsets
) * (SECT_OFF_MAX
-1));
618 for (i
= 0; i
< SECT_OFF_MAX
; i
++)
619 ANOFFSET (pst
->section_offsets
, i
) = maybe
->sections
[i
];
623 /* We were unable to find any offsets for this file. Complain. */
624 if (dbx
->stab_section_info
) /* If there *is* any info, */
625 complain (&stab_info_mismatch_complaint
, filename
);
628 /* Register that we are able to handle ELF object file formats and DWARF
631 Unlike other object file formats, where the debugging information format
632 is implied by the object file format, the ELF object file format and the
633 DWARF debugging information format are two distinct, and potentially
634 separate entities. I.E. it is perfectly possible to have ELF objects
635 with debugging formats other than DWARF. And it is conceivable that the
636 DWARF debugging format might be used with another object file format,
637 like COFF, by simply using COFF's custom section feature.
639 GDB, and to a lesser extent BFD, should support the notion of separate
640 object file formats and debugging information formats. For now, we just
641 use "elf" in the same sense as "a.out" or "coff", to imply both the ELF
642 object file format and the DWARF debugging format. */
644 static struct sym_fns elf_sym_fns
=
646 "elf", /* sym_name: name or name prefix of BFD target type */
647 3, /* sym_namelen: number of significant sym_name chars */
648 elf_new_init
, /* sym_new_init: init anything gbl to entire symtab */
649 elf_symfile_init
, /* sym_init: read initial info, setup for sym_read() */
650 elf_symfile_read
, /* sym_read: read a symbol file into symtab */
651 elf_symfile_finish
, /* sym_finish: finished with file, cleanup */
652 elf_symfile_offsets
, /* sym_offsets: Translate ext. to int. relocation */
653 NULL
/* next: pointer to next struct sym_fns */
657 _initialize_elfread ()
659 add_symtab_fns (&elf_sym_fns
);