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 */
46 #define STREQ(a,b) (strcmp((a),(b))==0)
49 unsigned int dboffset; /* Offset to dwarf debug section */
50 unsigned int dbsize; /* Size of dwarf debug section */
51 unsigned int lnoffset; /* Offset to dwarf line number section */
52 unsigned int lnsize; /* Size of dwarf line number section */
53 asection *stabsect; /* Section pointer for .stab section */
54 asection *stabindexsect; /* Section pointer for .stab.index section */
58 elf_symfile_init PARAMS ((struct objfile *));
61 elf_new_init PARAMS ((struct objfile *));
64 elf_symfile_read PARAMS ((struct objfile *, CORE_ADDR, int));
67 elf_symfile_finish PARAMS ((struct objfile *));
70 elf_symtab_read PARAMS ((bfd *, CORE_ADDR, struct objfile *));
74 record_minimal_symbol PARAMS ((char *, CORE_ADDR, enum minimal_symbol_type,
79 record_minimal_symbol_and_info PARAMS ((char *, CORE_ADDR,
80 enum minimal_symbol_type, char *,
84 elf_locate_sections PARAMS ((bfd *, asection *, PTR));
86 /* We are called once per section from elf_symfile_read. We
87 need to examine each section we are passed, check to see
88 if it is something we are interested in processing, and
89 if so, stash away some access information for the section.
91 For now we recognize the dwarf debug information sections and
92 line number sections from matching their section names. The
93 ELF definition is no real help here since it has no direct
94 knowledge of DWARF (by design, so any debugging format can be
97 We also recognize the ".stab" sections used by the Sun compilers
98 released with Solaris 2.
100 FIXME: The section names should not be hardwired strings. */
103 elf_locate_sections (ignore_abfd, sectp, eip)
108 register struct elfinfo *ei;
110 ei = (struct elfinfo *) eip;
111 if (STREQ (sectp -> name, ".debug"))
113 ei -> dboffset = sectp -> filepos;
114 ei -> dbsize = bfd_get_section_size_before_reloc (sectp);
116 else if (STREQ (sectp -> name, ".line"))
118 ei -> lnoffset = sectp -> filepos;
119 ei -> lnsize = bfd_get_section_size_before_reloc (sectp);
121 else if (STREQ (sectp -> name, ".stab"))
123 ei -> stabsect = sectp;
125 else if (STREQ (sectp -> name, ".stab.index"))
127 ei -> stabindexsect = sectp;
131 #if 0 /* Currently unused */
134 elf_interpreter (abfd)
141 interp_sec = bfd_get_section_by_name (abfd, ".interp");
144 size = bfd_section_size (abfd, interp_sec);
145 interp = alloca (size);
146 if (bfd_get_section_contents (abfd, interp_sec, interp, (file_ptr)0,
149 interp = savestring (interp, size - 1);
165 record_minimal_symbol -- add entry to minimal symbol table
169 static void record_minimal_symbol (char *name, CORE_ADDR address)
173 Given a pointer to the name of a symbol that should be added to the
174 minimal symbol table and the address associated with that symbol, records
175 this information for later use in building the minimal symbol table.
179 #if 0 /* FIXME: Unused */
182 record_minimal_symbol (name, address, ms_type, objfile)
185 enum minimal_symbol_type ms_type;
186 struct objfile *objfile;
188 name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
189 prim_record_minimal_symbol (name, address, ms_type);
195 record_minimal_symbol_and_info (name, address, ms_type, info, objfile)
198 enum minimal_symbol_type ms_type;
199 char *info; /* FIXME, is this really char *? */
200 struct objfile *objfile;
202 name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
203 prim_record_minimal_symbol_and_info (name, address, ms_type, info);
210 elf_symtab_read -- read the symbol table of an ELF file
214 void elf_symtab_read (bfd *abfd, CORE_ADDR addr,
215 struct objfile *objfile)
219 Given an open bfd, a base address to relocate symbols to, and a
220 flag that specifies whether or not this bfd is for an executable
221 or not (may be shared library for example), add all the global
222 function and data symbols to the minimal symbol table.
227 elf_symtab_read (abfd, addr, objfile)
230 struct objfile *objfile;
232 unsigned int storage_needed;
234 asymbol **symbol_table;
235 unsigned int number_of_symbols;
237 struct cleanup *back_to;
239 enum minimal_symbol_type ms_type;
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++;
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)
264 /* For non-absolute symbols, use the type of the section
265 they are relative to, to intuit text/data. Bfd provides
266 no way of figuring this out for absolute symbols. */
267 if (sym -> section -> flags & SEC_CODE)
271 else if (sym -> section -> flags & SEC_DATA)
277 /* FIXME: Solaris2 shared libraries include lots of
278 odd "absolute" and "undefined" symbols, that play
279 hob with actions like finding what function the PC
280 is in. Ignore them if they aren't text or data. */
281 /* ms_type = mst_unknown; */
282 continue; /* Skip this symbol. */
284 /* Pass symbol size field in via BFD. FIXME!!! */
285 record_minimal_symbol_and_info ((char *) sym -> name,
286 symaddr, ms_type, sym->udata, objfile);
289 do_cleanups (back_to);
293 /* Scan and build partial symbols for a symbol file.
294 We have been initialized by a call to elf_symfile_init, which
295 currently does nothing.
297 ADDR is the address relative to which the symbols in it are (e.g.
298 the base address of the text segment).
300 MAINLINE is true if we are reading the main symbol
301 table (as opposed to a shared lib or dynamically loaded file).
303 This function only does the minimum work necessary for letting the
304 user "name" things symbolically; it does not read the entire symtab.
305 Instead, it reads the external and static symbols and puts them in partial
306 symbol tables. When more extensive information is requested of a
307 file, the corresponding partial symbol table is mutated into a full
308 fledged symbol table by going back and reading the symbols
311 We look for sections with specific names, to tell us what debug
312 format to look for: FIXME!!!
314 dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
315 elfstab_build_psymtabs() handles STABS symbols.
317 Note that ELF files have a "minimal" symbol table, which looks a lot
318 like a COFF symbol table, but has only the minimal information necessary
319 for linking. We process this also, and use the information to
320 build gdb's minimal symbol table. This gives us some minimal debugging
321 capability even for files compiled without -g. */
324 elf_symfile_read (objfile, addr, mainline)
325 struct objfile *objfile;
329 bfd *abfd = objfile->obfd;
331 struct cleanup *back_to;
335 init_minimal_symbol_collection ();
336 back_to = make_cleanup (discard_minimal_symbols, 0);
338 /* Compute the amount to relocate all symbols by. The value passed in
339 as ADDR is typically either the actual address of the text section,
340 or a user specified address. By subtracting off the actual address
341 of the text section, we can compute the relocation amount. */
343 text_sect = bfd_get_section_by_name (objfile -> obfd, ".text");
344 offset = addr - bfd_section_vma (objfile -> obfd, text_sect);
346 /* Process the normal ELF symbol table first. */
348 elf_symtab_read (abfd, offset, objfile);
350 /* Now process debugging information, which is contained in
351 special ELF sections. We first have to find them... */
353 memset ((char *) &ei, 0, sizeof (ei));
354 bfd_map_over_sections (abfd, elf_locate_sections, (PTR) &ei);
355 if (ei.dboffset && ei.lnoffset)
358 dwarf_build_psymtabs (fileno ((FILE *)(abfd -> iostream)),
359 bfd_get_filename (abfd),
361 ei.dboffset, ei.dbsize,
362 ei.lnoffset, ei.lnsize, objfile);
368 /* FIXME: Sun didn't really know how to implement this well.
369 They made .stab sections that don't point to the .stabstr
370 section with the sh_link field. BFD doesn't make string table
371 sections visible to the caller. So we have to search the
372 ELF section table, not the BFD section table, for the string
374 struct elf_internal_shdr *elf_sect;
376 elf_sect = bfd_elf_find_section (abfd, ".stabstr");
378 elfstab_build_psymtabs (objfile,
379 addr, /* We really pass the text seg addr, not the offset, here. */
381 ei.stabsect->filepos, /* .stab offset */
382 bfd_get_section_size_before_reloc (ei.stabsect),/* .stab size */
383 elf_sect->sh_offset, /* .stabstr offset */
384 elf_sect->sh_size); /* .stabstr size */
387 if (!have_partial_symbols ())
390 printf_filtered ("(no debugging symbols found)...");
394 /* Install any minimal symbols that have been collected as the current
395 minimal symbols for this objfile. */
397 install_minimal_symbols (objfile);
399 do_cleanups (back_to);
402 /* Initialize anything that needs initializing when a completely new symbol
403 file is specified (not just adding some symbols from another file, e.g. a
406 We reinitialize buildsym, since we may be reading stabs from an ELF file. */
409 elf_new_init (ignore)
410 struct objfile *ignore;
412 buildsym_new_init ();
415 /* Perform any local cleanups required when we are done with a particular
416 objfile. I.E, we are in the process of discarding all symbol information
417 for an objfile, freeing up all memory held for it, and unlinking the
418 objfile struct from the global list of known objfiles. */
421 elf_symfile_finish (objfile)
422 struct objfile *objfile;
424 if (objfile -> sym_private != NULL)
426 mfree (objfile -> md, objfile -> sym_private);
430 /* ELF specific initialization routine for reading symbols.
432 It is passed a pointer to a struct sym_fns which contains, among other
433 things, the BFD for the file whose symbols are being read, and a slot for
434 a pointer to "private data" which we can fill with goodies.
436 For now at least, we have nothing in particular to do, so this function is
440 elf_symfile_init (ignore)
441 struct objfile *ignore;
446 /* Register that we are able to handle ELF object file formats and DWARF
449 Unlike other object file formats, where the debugging information format
450 is implied by the object file format, the ELF object file format and the
451 DWARF debugging information format are two distinct, and potentially
452 separate entities. I.E. it is perfectly possible to have ELF objects
453 with debugging formats other than DWARF. And it is conceivable that the
454 DWARF debugging format might be used with another object file format,
455 like COFF, by simply using COFF's custom section feature.
457 GDB, and to a lesser extent BFD, should support the notion of separate
458 object file formats and debugging information formats. For now, we just
459 use "elf" in the same sense as "a.out" or "coff", to imply both the ELF
460 object file format and the DWARF debugging format. */
462 static struct sym_fns elf_sym_fns =
464 "elf", /* sym_name: name or name prefix of BFD target type */
465 3, /* sym_namelen: number of significant sym_name chars */
466 elf_new_init, /* sym_new_init: init anything gbl to entire symtab */
467 elf_symfile_init, /* sym_init: read initial info, setup for sym_read() */
468 elf_symfile_read, /* sym_read: read a symbol file into symtab */
469 elf_symfile_finish, /* sym_finish: finished with file, cleanup */
470 NULL /* next: pointer to next struct sym_fns */
474 _initialize_elfread ()
476 add_symtab_fns (&elf_sym_fns);