1 /* Read ELF (Executable and Linking Format) object files for GDB.
2 Copyright (C) 1991 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@cygint) *
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. *
32 * FIXME Still needs support ELF symbol tables (as distinct *
33 * from DWARF support). Can use them to build the misc *
34 * function vector at least. This is fairly trivial once *
35 * bfd is extended to handle ELF symbol tables. *
37 ************************************************************************/
42 #include "elf/common.h"
43 #include "elf/external.h"
44 #include "elf/internal.h"
50 extern int EXFUN (strcmp, (CONST char *a, CONST char *b));
51 extern int EXFUN (dwarf_build_psymtabs,
52 (int desc, char *filename, CORE_ADDR addr, int mainline,
53 unsigned int dbfoff, unsigned int dbsize, unsigned int lnoffset,
54 unsigned int lnsize, struct objfile *objfile));
56 #define STREQ(a,b) (strcmp((a),(b))==0)
59 unsigned int dboffset; /* Offset to dwarf debug section */
60 unsigned int dbsize; /* Size of dwarf debug section */
61 unsigned int lnoffset; /* Offset to dwarf line number section */
62 unsigned int lnsize; /* Size of dwarf line number section */
65 /* We are called once per section from elf_symfile_read. We
66 need to examine each section we are passed, check to see
67 if it is something we are interested in processing, and
68 if so, stash away some access information for the section.
70 For now we recognize the dwarf debug information sections and
71 line number sections from matching their section names. The
72 ELF definition is no real help here since it has no direct
73 knowledge of DWARF (by design, so any debugging format can be
76 FIXME: The section names should not be hardwired strings. */
79 DEFUN(elf_locate_sections, (abfd, sectp, ei),
84 if (STREQ (sectp -> name, ".debug"))
86 ei -> dboffset = sectp -> filepos;
87 ei -> dbsize = sectp -> size;
89 else if (STREQ (sectp -> name, ".line"))
91 ei -> lnoffset = sectp -> filepos;
92 ei -> lnsize = sectp -> size;
97 DEFUN(elf_interpreter, (abfd),
104 interp_sec = bfd_get_section_by_name (abfd, ".interp");
107 size = bfd_section_size (abfd, interp_sec);
108 interp = alloca (size);
109 if (bfd_get_section_contents (abfd, interp_sec, interp, (file_ptr)0,
112 interp = savestring (interp, size - 1);
126 record_misc_function -- add entry to miscellaneous function vector
130 static void record_misc_function (char *name, CORE_ADDR address)
134 Given a pointer to the name of a symbol that should be added to the
135 miscellaneous function vector, and the address associated with that
136 symbol, records this information for later use in building the
137 miscellaneous function vector.
141 FIXME: For now we just use mf_unknown as the type. This should be
146 DEFUN(record_misc_function, (name, address, mf_type),
147 char *name AND CORE_ADDR address AND enum misc_function_type mf_type)
149 prim_record_misc_function (obsavestring (name, strlen (name)), address,
157 elf_symtab_read -- read the symbol table of an ELF file
161 void elf_symtab_read (bfd *abfd, CORE_ADDR addr, int mainline)
165 Given an open bfd, a base address to relocate symbols to, and a
166 flag that specifies whether or not this bfd is for an executable
167 or not (may be shared library for example), add all the global
168 function and data symbols to the miscellaneous function vector.
173 DEFUN (elf_symtab_read, (abfd, addr, mainline),
178 unsigned int storage_needed;
180 asymbol **symbol_table;
181 unsigned int number_of_symbols;
183 struct cleanup *back_to;
185 enum misc_function_type mf_type;
187 storage_needed = get_symtab_upper_bound (abfd);
189 if (storage_needed > 0)
191 symbol_table = (asymbol **) bfd_xmalloc (storage_needed);
192 back_to = make_cleanup (free, symbol_table);
193 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
195 for (i = 0; i < number_of_symbols; i++)
197 sym = *symbol_table++;
198 /* Select global symbols that are defined in a specific section
200 if (sym -> flags & BSF_GLOBAL
201 && ((sym -> section != NULL) || (sym -> flags & BSF_ABSOLUTE)))
203 symaddr = sym -> value;
206 /* Relocate all symbols by base address */
209 /* For non-absolute symbols, use the type of the section
210 they are relative to, to intuit text/data. Bfd provides
211 no way of figuring this out for absolute symbols. */
212 if (sym -> section && (sym -> section -> flags & SEC_CODE))
216 else if (sym -> section && (sym -> section -> flags & SEC_DATA))
222 mf_type = mf_unknown;
224 record_misc_function ((char *) sym -> name, symaddr, mf_type);
227 do_cleanups (back_to);
231 /* Scan and build partial symbols for a symbol file.
232 We have been initialized by a call to elf_symfile_init, which
233 currently does nothing.
235 ADDR is the address relative to which the symbols in it are (e.g.
236 the base address of the text segment).
238 MAINLINE is true if we are reading the main symbol
239 table (as opposed to a shared lib or dynamically loaded file).
241 This function only does the minimum work necessary for letting the
242 user "name" things symbolically; it does not read the entire symtab.
243 Instead, it reads the external and static symbols and puts them in partial
244 symbol tables. When more extensive information is requested of a
245 file, the corresponding partial symbol table is mutated into a full
246 fledged symbol table by going back and reading the symbols
247 for real. The function dwarf_psymtab_to_symtab() is the function that
248 does this for DWARF symbols.
250 Note that ELF files have a "minimal" symbol table, which looks a lot
251 like a COFF symbol table, but has only the minimal information necessary
252 for linking. We process this also, and just use the information to
253 add to the misc function vector. This gives us some minimal debugging
254 capability even for files compiled without -g.
258 DEFUN(elf_symfile_read, (sf, addr, mainline),
259 struct sym_fns *sf AND
263 bfd *abfd = sf->objfile->obfd;
265 struct cleanup *back_to;
267 init_misc_bunches ();
268 back_to = make_cleanup (discard_misc_bunches, 0);
270 /* Process the normal ELF symbol table first. */
272 elf_symtab_read (abfd, addr, mainline);
274 /* Now process the DWARF debugging information, which is contained in
275 special ELF sections. We first have to find them... */
277 (void) memset ((char *) &ei, 0, sizeof (ei));
278 bfd_map_over_sections (abfd, elf_locate_sections, &ei);
279 if (ei.dboffset && ei.lnoffset)
281 dwarf_build_psymtabs (fileno ((FILE *)(abfd -> iostream)),
282 bfd_get_filename (abfd),
284 ei.dboffset, ei.dbsize,
285 ei.lnoffset, ei.lnsize, sf->objfile);
288 if (!partial_symtab_list)
291 printf_filtered ("(no debugging symbols found)...");
295 /* Go over the miscellaneous functions and install them in the
296 miscellaneous function vector. */
298 condense_misc_bunches (!mainline);
299 do_cleanups (back_to);
302 /* Initialize anything that needs initializing when a completely new symbol
303 file is specified (not just adding some symbols from another file, e.g. a
306 For now at least, we have nothing in particular to do, so this function is
310 DEFUN_VOID (elf_new_init)
314 /* ELF specific initialization routine for reading symbols.
316 It is passed a pointer to a struct sym_fns which contains, among other
317 things, the BFD for the file whose symbols are being read, and a slot for
318 a pointer to "private data" which we can fill with goodies.
320 For now at least, we have nothing in particular to do, so this function is
324 DEFUN(elf_symfile_init, (sf),
330 /* Register that we are able to handle ELF object file formats and DWARF
333 Unlike other object file formats, where the debugging information format
334 is implied by the object file format, the ELF object file format and the
335 DWARF debugging information format are two distinct, and potentially
336 separate entities. I.E. it is perfectly possible to have ELF objects
337 with debugging formats other than DWARF. And it is conceivable that the
338 DWARF debugging format might be used with another object file format,
339 like COFF, by simply using COFF's custom section feature.
341 GDB, and to a lesser extent BFD, should support the notion of separate
342 object file formats and debugging information formats. For now, we just
343 use "elf" in the same sense as "a.out" or "coff", to imply both the ELF
344 object file format and the DWARF debugging format. */
346 static struct sym_fns elf_sym_fns = {
347 "elf", /* sym_name: name or name prefix of BFD target type */
348 3, /* sym_namelen: number of significant sym_name chars */
349 elf_new_init, /* sym_new_init: init anything gbl to entire symtab */
350 elf_symfile_init, /* sym_init: read initial info, setup for sym_read() */
351 elf_symfile_read, /* sym_read: read a symbol file into symtab */
352 NULL, /* sym_bfd: accessor for symbol file being read */
353 NULL, /* sym_private: sym_init & sym_read shared info */
354 NULL /* next: pointer to next struct sym_fns */
358 DEFUN_VOID (_initialize_elfread)
360 add_symtab_fns (&elf_sym_fns);