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 ************************************************************************/
36 #include "elf/common.h"
37 #include "elf/external.h"
38 #include "elf/internal.h"
40 #include "libbfd.h" /* For bfd_elf_find_section */
45 #include "gdb-stabs.h"
46 #include "complaints.h"
49 #define STREQ(a,b) (strcmp((a),(b))==0)
51 /* The struct elfinfo is available only during ELF symbol table and
52 psymtab reading. It is destroyed at the complation of psymtab-reading.
53 It's local to elf_symfile_read. */
56 file_ptr dboffset; /* Offset to dwarf debug section */
57 unsigned int dbsize; /* Size of dwarf debug section */
58 file_ptr lnoffset; /* Offset to dwarf line number section */
59 unsigned int lnsize; /* Size of dwarf line number section */
60 asection *stabsect; /* Section pointer for .stab section */
61 asection *stabindexsect; /* Section pointer for .stab.index section */
64 /* Various things we might complain about... */
66 struct complaint section_info_complaint =
67 {"elf/stab section information %s without a preceding file symbol", 0, 0};
69 struct complaint section_info_dup_complaint =
70 {"duplicated elf/stab section information for %s", 0, 0};
72 struct complaint stab_info_mismatch_complaint =
73 {"elf/stab section information missing for %s", 0, 0};
75 struct complaint stab_info_questionable_complaint =
76 {"elf/stab section information questionable for %s", 0, 0};
79 elf_symfile_init PARAMS ((struct objfile *));
82 elf_new_init PARAMS ((struct objfile *));
85 elf_symfile_read PARAMS ((struct objfile *, struct section_offsets *, int));
88 elf_symfile_finish PARAMS ((struct objfile *));
91 elf_symtab_read PARAMS ((bfd *, CORE_ADDR, struct objfile *));
94 free_elfinfo PARAMS ((PTR));
96 static struct section_offsets *
97 elf_symfile_offsets PARAMS ((struct objfile *, CORE_ADDR));
101 record_minimal_symbol PARAMS ((char *, CORE_ADDR, enum minimal_symbol_type,
106 record_minimal_symbol_and_info PARAMS ((char *, CORE_ADDR,
107 enum minimal_symbol_type, char *,
111 elf_locate_sections PARAMS ((bfd *, asection *, PTR));
113 /* We are called once per section from elf_symfile_read. We
114 need to examine each section we are passed, check to see
115 if it is something we are interested in processing, and
116 if so, stash away some access information for the section.
118 For now we recognize the dwarf debug information sections and
119 line number sections from matching their section names. The
120 ELF definition is no real help here since it has no direct
121 knowledge of DWARF (by design, so any debugging format can be
124 We also recognize the ".stab" sections used by the Sun compilers
125 released with Solaris 2.
127 FIXME: The section names should not be hardwired strings. */
130 elf_locate_sections (ignore_abfd, sectp, eip)
135 register struct elfinfo *ei;
137 ei = (struct elfinfo *) eip;
138 if (STREQ (sectp -> name, ".debug"))
140 ei -> dboffset = sectp -> filepos;
141 ei -> dbsize = bfd_get_section_size_before_reloc (sectp);
143 else if (STREQ (sectp -> name, ".line"))
145 ei -> lnoffset = sectp -> filepos;
146 ei -> lnsize = bfd_get_section_size_before_reloc (sectp);
148 else if (STREQ (sectp -> name, ".stab"))
150 ei -> stabsect = sectp;
152 else if (STREQ (sectp -> name, ".stab.index"))
154 ei -> stabindexsect = sectp;
158 #if 0 /* Currently unused */
161 elf_interpreter (abfd)
168 interp_sec = bfd_get_section_by_name (abfd, ".interp");
171 size = bfd_section_size (abfd, interp_sec);
172 interp = alloca (size);
173 if (bfd_get_section_contents (abfd, interp_sec, interp, (file_ptr)0,
176 interp = savestring (interp, size - 1);
192 record_minimal_symbol -- add entry to minimal symbol table
196 static void record_minimal_symbol (char *name, CORE_ADDR address)
200 Given a pointer to the name of a symbol that should be added to the
201 minimal symbol table and the address associated with that symbol, records
202 this information for later use in building the minimal symbol table.
206 #if 0 /* FIXME: Unused */
209 record_minimal_symbol (name, address, ms_type, objfile)
212 enum minimal_symbol_type ms_type;
213 struct objfile *objfile;
215 name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
216 prim_record_minimal_symbol (name, address, ms_type);
222 record_minimal_symbol_and_info (name, address, ms_type, info, objfile)
225 enum minimal_symbol_type ms_type;
226 char *info; /* FIXME, is this really char *? */
227 struct objfile *objfile;
229 name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
230 prim_record_minimal_symbol_and_info (name, address, ms_type, info);
237 elf_symtab_read -- read the symbol table of an ELF file
241 void elf_symtab_read (bfd *abfd, CORE_ADDR addr,
242 struct objfile *objfile)
246 Given an open bfd, a base address to relocate symbols to, and a
247 flag that specifies whether or not this bfd is for an executable
248 or not (may be shared library for example), add all the global
249 function and data symbols to the minimal symbol table.
251 In stabs-in-ELF, as implemented by Sun, there are some local symbols
252 defined in the ELF symbol table, which can be used to locate
253 the beginnings of sections from each ".o" file that was linked to
254 form the executable objfile. We gather any such info and record it
255 in data structures hung off the objfile's private data.
260 elf_symtab_read (abfd, addr, objfile)
263 struct objfile *objfile;
265 unsigned int storage_needed;
267 asymbol **symbol_table;
268 unsigned int number_of_symbols;
271 struct cleanup *back_to;
273 enum minimal_symbol_type ms_type;
274 /* If sectinfo is nonzero, it contains section info that should end up
275 filed in the objfile. */
276 struct stab_section_info *sectinfo = 0;
277 /* If filesym is nonzero, it points to a file symbol, but we haven't
278 seen any section info for it yet. */
279 asymbol *filesym = 0;
280 struct dbx_symfile_info *dbx = (struct dbx_symfile_info *)
281 objfile->sym_private;
283 storage_needed = get_symtab_upper_bound (abfd);
285 if (storage_needed > 0)
287 symbol_table = (asymbol **) xmalloc (storage_needed);
288 back_to = make_cleanup (free, symbol_table);
289 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
291 for (i = 0; i < number_of_symbols; i++)
293 sym = symbol_table[i];
294 /* Select global/weak symbols that are defined in a specific section.
295 Note that bfd now puts abs symbols in their own section, so
296 all symbols we are interested in will have a section. */
297 if ((sym -> flags & (BSF_GLOBAL | BSF_WEAK))
298 && (sym -> section != NULL))
300 symaddr = sym -> value;
301 /* Relocate all non-absolute symbols by base address. */
302 if (sym -> section != &bfd_abs_section)
305 /* For non-absolute symbols, use the type of the section
306 they are relative to, to intuit text/data. Bfd provides
307 no way of figuring this out for absolute symbols. */
308 if (sym -> section -> flags & SEC_CODE)
312 else if (sym -> section -> flags & SEC_DATA)
318 /* FIXME: Solaris2 shared libraries include lots of
319 odd "absolute" and "undefined" symbols, that play
320 hob with actions like finding what function the PC
321 is in. Ignore them if they aren't text or data. */
322 /* ms_type = mst_unknown; */
323 continue; /* Skip this symbol. */
325 /* Pass symbol size field in via BFD. FIXME!!! */
326 record_minimal_symbol_and_info ((char *) sym -> name,
327 symaddr, ms_type, sym->udata, objfile);
330 /* See if this is a debugging symbol that helps Solaris
331 stabs-in-elf debugging. */
333 else if (sym->flags & BSF_FILE)
335 /* Chain any old one onto the objfile; remember new sym. */
338 sectinfo->next = dbx->stab_section_info;
339 dbx->stab_section_info = sectinfo;
344 else if ((sym->flags & BSF_LOCAL) &&
346 (sym->section->flags & SEC_DATA) &&
349 /* Named Local variable in a Data section. Check its name. */
351 switch (sym->name[1])
354 if (!strcmp ("Bbss.bss", sym->name))
355 index = SECT_OFF_BSS;
358 if (!strcmp ("Ddata.data", sym->name))
359 index = SECT_OFF_DATA;
362 if (!strcmp ("Drodata.rodata", sym->name))
363 index = SECT_OFF_RODATA;
368 /* We have some new info. Allocate a sectinfo, if
369 needed, and fill it in. */
372 sectinfo = (struct stab_section_info *)
373 xmmalloc (objfile -> md,
375 memset ((PTR) sectinfo, 0, sizeof (*sectinfo));
377 complain (§ion_info_complaint, sym->name);
379 sectinfo->filename = (char *)filesym->name;
381 if (sectinfo->sections[index])
382 complain (§ion_info_dup_complaint, sectinfo->filename);
384 symaddr = sym -> value;
385 /* Relocate all non-absolute symbols by base address. */
386 if (sym -> section != &bfd_abs_section)
388 sectinfo->sections[index] = symaddr;
392 do_cleanups (back_to);
396 /* Scan and build partial symbols for a symbol file.
397 We have been initialized by a call to elf_symfile_init, which
398 currently does nothing.
400 SECTION_OFFSETS is a set of offsets to apply to relocate the symbols
401 in each section. We simplify it down to a single offset for all
404 MAINLINE is true if we are reading the main symbol
405 table (as opposed to a shared lib or dynamically loaded file).
407 This function only does the minimum work necessary for letting the
408 user "name" things symbolically; it does not read the entire symtab.
409 Instead, it reads the external and static symbols and puts them in partial
410 symbol tables. When more extensive information is requested of a
411 file, the corresponding partial symbol table is mutated into a full
412 fledged symbol table by going back and reading the symbols
415 We look for sections with specific names, to tell us what debug
416 format to look for: FIXME!!!
418 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
419 elfstab_build_psymtabs() handles STABS symbols.
421 Note that ELF files have a "minimal" symbol table, which looks a lot
422 like a COFF symbol table, but has only the minimal information necessary
423 for linking. We process this also, and use the information to
424 build gdb's minimal symbol table. This gives us some minimal debugging
425 capability even for files compiled without -g. */
428 elf_symfile_read (objfile, section_offsets, mainline)
429 struct objfile *objfile;
430 struct section_offsets *section_offsets;
433 bfd *abfd = objfile->obfd;
435 struct dbx_symfile_info *dbx;
436 struct cleanup *back_to;
440 init_minimal_symbol_collection ();
441 back_to = make_cleanup (discard_minimal_symbols, 0);
443 memset ((char *) &ei, 0, sizeof (ei));
445 /* Allocate struct to keep track of the symfile */
446 objfile->sym_private = (PTR)
447 xmmalloc (objfile -> md, sizeof (struct dbx_symfile_info));
448 memset ((char *) objfile->sym_private, 0, sizeof (struct dbx_symfile_info));
449 make_cleanup (free_elfinfo, (PTR) objfile);
451 /* Process the normal ELF symbol table first. This may write some
452 chain of info into the dbx_symfile_info in objfile->sym_private,
453 which can later be used by elfstab_offset_sections. */
455 /* FIXME, should take a section_offsets param, not just an offset. */
456 offset = ANOFFSET (section_offsets, 0);
457 elf_symtab_read (abfd, offset, objfile);
459 /* Now process debugging information, which is contained in
460 special ELF sections. We first have to find them... */
462 bfd_map_over_sections (abfd, elf_locate_sections, (PTR) &ei);
463 if (ei.dboffset && ei.lnoffset)
466 dwarf_build_psymtabs (objfile,
467 section_offsets, mainline,
468 ei.dboffset, ei.dbsize,
469 ei.lnoffset, ei.lnsize);
475 /* FIXME: Sun didn't really know how to implement this well.
476 They made .stab sections that don't point to the .stabstr
477 section with the sh_link field. BFD doesn't make string table
478 sections visible to the caller. So we have to search the
479 ELF section table, not the BFD section table, for the string
481 struct elf_internal_shdr *elf_sect;
483 elf_sect = bfd_elf_find_section (abfd, ".stabstr");
485 elfstab_build_psymtabs (objfile,
488 ei.stabsect->filepos, /* .stab offset */
489 bfd_get_section_size_before_reloc (ei.stabsect),/* .stab size */
490 (file_ptr) elf_sect->sh_offset, /* .stabstr offset */
491 elf_sect->sh_size); /* .stabstr size */
494 if (!have_partial_symbols ())
497 printf_filtered ("(no debugging symbols found)...");
501 /* Install any minimal symbols that have been collected as the current
502 minimal symbols for this objfile. */
504 install_minimal_symbols (objfile);
506 do_cleanups (back_to);
509 /* This cleans up the objfile's sym_private pointer, and the chain of
510 stab_section_info's, that might be dangling from it. */
516 struct objfile *objfile = (struct objfile *)objp;
517 struct dbx_symfile_info *dbxinfo = (struct dbx_symfile_info *)
518 objfile->sym_private;
519 struct stab_section_info *ssi, *nssi;
521 ssi = dbxinfo->stab_section_info;
525 mfree (objfile->md, ssi);
529 dbxinfo->stab_section_info = 0; /* Just say No mo info about this. */
533 /* Initialize anything that needs initializing when a completely new symbol
534 file is specified (not just adding some symbols from another file, e.g. a
537 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
540 elf_new_init (ignore)
541 struct objfile *ignore;
543 stabsread_new_init ();
544 buildsym_new_init ();
547 /* Perform any local cleanups required when we are done with a particular
548 objfile. I.E, we are in the process of discarding all symbol information
549 for an objfile, freeing up all memory held for it, and unlinking the
550 objfile struct from the global list of known objfiles. */
553 elf_symfile_finish (objfile)
554 struct objfile *objfile;
556 if (objfile -> sym_private != NULL)
558 mfree (objfile -> md, objfile -> sym_private);
562 /* ELF specific initialization routine for reading symbols.
564 It is passed a pointer to a struct sym_fns which contains, among other
565 things, the BFD for the file whose symbols are being read, and a slot for
566 a pointer to "private data" which we can fill with goodies.
568 For now at least, we have nothing in particular to do, so this function is
572 elf_symfile_init (ignore)
573 struct objfile *ignore;
577 /* ELF specific parsing routine for section offsets.
579 Plain and simple for now. */
582 struct section_offsets *
583 elf_symfile_offsets (objfile, addr)
584 struct objfile *objfile;
587 struct section_offsets *section_offsets;
590 section_offsets = (struct section_offsets *)
591 obstack_alloc (&objfile -> psymbol_obstack,
592 sizeof (struct section_offsets) +
593 sizeof (section_offsets->offsets) * (SECT_OFF_MAX-1));
595 for (i = 0; i < SECT_OFF_MAX; i++)
596 ANOFFSET (section_offsets, i) = addr;
598 return section_offsets;
601 /* When handling an ELF file that contains Sun STABS debug info,
602 some of the debug info is relative to the particular chunk of the
603 section that was generated in its individual .o file. E.g.
604 offsets to static variables are relative to the start of the data
605 segment *for that module before linking*. This information is
606 painfully squirreled away in the ELF symbol table as local symbols
607 with wierd names. Go get 'em when needed. */
610 elfstab_offset_sections (objfile, pst)
611 struct objfile *objfile;
612 struct partial_symtab *pst;
614 char *filename = pst->filename;
615 struct dbx_symfile_info *dbx = (struct dbx_symfile_info *)
616 objfile->sym_private;
617 struct stab_section_info *maybe = dbx->stab_section_info;
618 struct stab_section_info *questionable = 0;
622 /* The ELF symbol info doesn't include path names, so strip the path
623 (if any) from the psymtab filename. */
624 while (0 != (p = strchr (filename, '/')))
627 /* FIXME: This linear search could speed up significantly
628 if it was chained in the right order to match how we search it,
629 and if we unchained when we found a match. */
630 for (; maybe; maybe = maybe->next)
632 if (filename[0] == maybe->filename[0]
633 && !strcmp (filename, maybe->filename))
635 /* We found a match. But there might be several source files
636 (from different directories) with the same name. */
637 if (0 == maybe->found)
639 questionable = maybe; /* Might use it later. */
643 if (maybe == 0 && questionable != 0)
645 complain (&stab_info_questionable_complaint, filename);
646 maybe = questionable;
651 /* Found it! Allocate a new psymtab struct, and fill it in. */
653 pst->section_offsets = (struct section_offsets *)
654 obstack_alloc (&objfile -> psymbol_obstack,
655 sizeof (struct section_offsets) +
656 sizeof (pst->section_offsets->offsets) * (SECT_OFF_MAX-1));
658 for (i = 0; i < SECT_OFF_MAX; i++)
659 ANOFFSET (pst->section_offsets, i) = maybe->sections[i];
663 /* We were unable to find any offsets for this file. Complain. */
664 if (dbx->stab_section_info) /* If there *is* any info, */
665 complain (&stab_info_mismatch_complaint, filename);
668 /* Register that we are able to handle ELF object file formats and DWARF
671 Unlike other object file formats, where the debugging information format
672 is implied by the object file format, the ELF object file format and the
673 DWARF debugging information format are two distinct, and potentially
674 separate entities. I.E. it is perfectly possible to have ELF objects
675 with debugging formats other than DWARF. And it is conceivable that the
676 DWARF debugging format might be used with another object file format,
677 like COFF, by simply using COFF's custom section feature.
679 GDB, and to a lesser extent BFD, should support the notion of separate
680 object file formats and debugging information formats. For now, we just
681 use "elf" in the same sense as "a.out" or "coff", to imply both the ELF
682 object file format and the DWARF debugging format. */
684 static struct sym_fns elf_sym_fns =
686 "elf", /* sym_name: name or name prefix of BFD target type */
687 3, /* sym_namelen: number of significant sym_name chars */
688 elf_new_init, /* sym_new_init: init anything gbl to entire symtab */
689 elf_symfile_init, /* sym_init: read initial info, setup for sym_read() */
690 elf_symfile_read, /* sym_read: read a symbol file into symtab */
691 elf_symfile_finish, /* sym_finish: finished with file, cleanup */
692 elf_symfile_offsets, /* sym_offsets: Translate ext. to int. relocation */
693 NULL /* next: pointer to next struct sym_fns */
697 _initialize_elfread ()
699 add_symtab_fns (&elf_sym_fns);