1 /* Generic symbol-table support for the BFD library.
2 Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
3 Written by Cygnus Support.
5 This file is part of BFD, the Binary File Descriptor library.
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. */
25 BFD tries to maintain as much symbol information as it can when
26 it moves information from file to file. BFD passes information
27 to applications though the <<asymbol>> structure. When the
28 application requests the symbol table, BFD reads the table in
29 the native form and translates parts of it into the internal
30 format. To maintain more than the information passed to
31 applications, some targets keep some information ``behind the
32 scenes'' in a structure only the particular back end knows
33 about. For example, the coff back end keeps the original
34 symbol table structure as well as the canonical structure when
35 a BFD is read in. On output, the coff back end can reconstruct
36 the output symbol table so that no information is lost, even
37 information unique to coff which BFD doesn't know or
38 understand. If a coff symbol table were read, but were written
39 through an a.out back end, all the coff specific information
40 would be lost. The symbol table of a BFD
41 is not necessarily read in until a canonicalize request is
42 made. Then the BFD back end fills in a table provided by the
43 application with pointers to the canonical information. To
44 output symbols, the application provides BFD with a table of
45 pointers to pointers to <<asymbol>>s. This allows applications
46 like the linker to output a symbol as it was read, since the ``behind
47 the scenes'' information will be still available.
52 @* symbol handling functions::
56 Reading Symbols, Writing Symbols, Symbols, Symbols
60 There are two stages to reading a symbol table from a BFD:
61 allocating storage, and the actual reading process. This is an
62 excerpt from an application which reads the symbol table:
64 | unsigned int storage_needed;
65 | asymbol **symbol_table;
66 | unsigned int number_of_symbols;
69 | storage_needed = get_symtab_upper_bound (abfd);
71 | if (storage_needed == 0) {
74 | symbol_table = (asymbol **) bfd_xmalloc (storage_needed);
77 | bfd_canonicalize_symtab (abfd, symbol_table);
79 | for (i = 0; i < number_of_symbols; i++) {
80 | process_symbol (symbol_table[i]);
83 All storage for the symbols themselves is in an obstack
84 connected to the BFD; it is freed when the BFD is closed.
88 Writing Symbols, typedef asymbol, Reading Symbols, Symbols
92 Writing of a symbol table is automatic when a BFD open for
93 writing is closed. The application attaches a vector of
94 pointers to pointers to symbols to the BFD being written, and
95 fills in the symbol count. The close and cleanup code reads
96 through the table provided and performs all the necessary
97 operations. The BFD output code must always be provided with an
98 ``owned'' symbol: one which has come from another BFD, or one
99 which has been created using <<bfd_make_empty_symbol>>. Here is an
100 example showing the creation of a symbol table with only one element:
109 | abfd = bfd_openw("foo","a.out-sunos-big");
110 | bfd_set_format(abfd, bfd_object);
111 | new = bfd_make_empty_symbol(abfd);
112 | new->name = "dummy_symbol";
113 | new->section = bfd_make_section_old_way(abfd, ".text");
114 | new->flags = BSF_GLOBAL;
115 | new->value = 0x12345;
118 | ptrs[1] = (asymbol *)0;
120 | bfd_set_symtab(abfd, ptrs, 1);
126 | 00012345 A dummy_symbol
128 Many formats cannot represent arbitary symbol information; for
129 instance, the <<a.out>> object format does not allow an
130 arbitary number of sections. A symbol pointing to a section
131 which is not one of <<.text>>, <<.data>> or <<.bss>> cannot
141 typedef asymbol, symbol handling functions, Writing Symbols, Symbols
148 An <<asymbol>> has the form:
156 .typedef struct symbol_cache_entry
158 . {* A pointer to the BFD which owns the symbol. This information
159 . is necessary so that a back end can work out what additional
160 . information (invisible to the application writer) is carried
163 . This field is *almost* redundant, since you can use section->owner
164 . instead, except that some symbols point to the global sections
165 . bfd_{abs,com,und}_section. This could be fixed by making
166 . these globals be per-bfd (or per-target-flavor). FIXME. *}
168 . struct _bfd *the_bfd; {* Use bfd_asymbol_bfd(sym) to access this field. *}
170 . {* The text of the symbol. The name is left alone, and not copied; the
171 . application may not alter it. *}
174 . {* The value of the symbol. This really should be a union of a
175 . numeric value with a pointer, since some flags indicate that
176 . a pointer to another symbol is stored here. *}
179 . {* Attributes of a symbol: *}
181 .#define BSF_NO_FLAGS 0x00
183 . {* The symbol has local scope; <<static>> in <<C>>. The value
184 . is the offset into the section of the data. *}
185 .#define BSF_LOCAL 0x01
187 . {* The symbol has global scope; initialized data in <<C>>. The
188 . value is the offset into the section of the data. *}
189 .#define BSF_GLOBAL 0x02
191 . {* The symbol has global scope and is exported. The value is
192 . the offset into the section of the data. *}
193 .#define BSF_EXPORT BSF_GLOBAL {* no real difference *}
195 . {* A normal C symbol would be one of:
196 . <<BSF_LOCAL>>, <<BSF_FORT_COMM>>, <<BSF_UNDEFINED>> or
199 . {* The symbol is a debugging record. The value has an arbitary
201 .#define BSF_DEBUGGING 0x08
203 . {* The symbol denotes a function entry point. Used in ELF,
204 . perhaps others someday. *}
205 .#define BSF_FUNCTION 0x10
207 . {* Used by the linker. *}
208 .#define BSF_KEEP 0x20
209 .#define BSF_KEEP_G 0x40
211 . {* A weak global symbol, overridable without warnings by
212 . a regular global symbol of the same name. *}
213 .#define BSF_WEAK 0x80
215 . {* This symbol was created to point to a section, e.g. ELF's
216 . STT_SECTION symbols. *}
217 .#define BSF_SECTION_SYM 0x100
219 . {* The symbol used to be a common symbol, but now it is
221 .#define BSF_OLD_COMMON 0x200
223 . {* The default value for common data. *}
224 .#define BFD_FORT_COMM_DEFAULT_VALUE 0
226 . {* In some files the type of a symbol sometimes alters its
227 . location in an output file - ie in coff a <<ISFCN>> symbol
228 . which is also <<C_EXT>> symbol appears where it was
229 . declared and not at the end of a section. This bit is set
230 . by the target BFD part to convey this information. *}
232 .#define BSF_NOT_AT_END 0x400
234 . {* Signal that the symbol is the label of constructor section. *}
235 .#define BSF_CONSTRUCTOR 0x800
237 . {* Signal that the symbol is a warning symbol. If the symbol
238 . is a warning symbol, then the value field (I know this is
239 . tacky) will point to the asymbol which when referenced will
240 . cause the warning. *}
241 .#define BSF_WARNING 0x1000
243 . {* Signal that the symbol is indirect. The value of the symbol
244 . is a pointer to an undefined asymbol which contains the
245 . name to use instead. *}
246 .#define BSF_INDIRECT 0x2000
248 . {* BSF_FILE marks symbols that contain a file name. This is used
249 . for ELF STT_FILE symbols. *}
250 .#define BSF_FILE 0x4000
254 . {* A pointer to the section to which this symbol is
255 . relative. This will always be non NULL, there are special
256 . sections for undefined and absolute symbols *}
257 . struct sec *section;
259 . {* Back end special data. This is being phased out in favour
260 . of making this a union. *}
270 #include "aout/stab_gnu.h"
275 symbol handling functions, , typedef asymbol, Symbols
277 Symbol handling functions
282 get_symtab_upper_bound
285 Return the number of bytes required to store a vector of pointers
286 to <<asymbols>> for all the symbols in the BFD @var{abfd},
287 including a terminal NULL pointer. If there are no symbols in
288 the BFD, then return 0.
290 .#define get_symtab_upper_bound(abfd) \
291 . BFD_SEND (abfd, _get_symtab_upper_bound, (abfd))
297 bfd_canonicalize_symtab
300 Read the symbols from the BFD @var{abfd}, and fills in
301 the vector @var{location} with pointers to the symbols and
303 Return the actual number of symbol pointers, not
307 .#define bfd_canonicalize_symtab(abfd, location) \
308 . BFD_SEND (abfd, _bfd_canonicalize_symtab,\
319 boolean bfd_set_symtab (bfd *abfd, asymbol **location, unsigned int count);
322 Arrange that when the output BFD @var{abfd} is closed,
323 the table @var{location} of @var{count} pointers to symbols
328 bfd_set_symtab (abfd
, location
, symcount
)
331 unsigned int symcount
;
333 if ((abfd
->format
!= bfd_object
) || (bfd_read_p (abfd
))) {
334 bfd_error
= invalid_operation
;
338 bfd_get_outsymbols (abfd
) = location
;
339 bfd_get_symcount (abfd
) = symcount
;
345 bfd_print_symbol_vandf
348 void bfd_print_symbol_vandf(PTR file, asymbol *symbol);
351 Print the value and flags of the @var{symbol} supplied to the
355 DEFUN(bfd_print_symbol_vandf
,(file
, symbol
),
359 flagword type
= symbol
->flags
;
360 if (symbol
->section
!= (asection
*)NULL
)
362 fprintf_vma(file
, symbol
->value
+symbol
->section
->vma
);
366 fprintf_vma(file
, symbol
->value
);
368 fprintf(file
," %c%c%c%c%c%c%c",
369 (type
& BSF_LOCAL
) ? 'l':' ',
370 (type
& BSF_GLOBAL
) ? 'g' : ' ',
371 (type
& BSF_WEAK
) ? 'w' : ' ',
372 (type
& BSF_CONSTRUCTOR
) ? 'C' : ' ',
373 (type
& BSF_WARNING
) ? 'W' : ' ',
374 (type
& BSF_INDIRECT
) ? 'I' : ' ',
375 (type
& BSF_DEBUGGING
) ? 'd' :' ');
382 bfd_make_empty_symbol
385 Create a new <<asymbol>> structure for the BFD @var{abfd}
386 and return a pointer to it.
388 This routine is necessary because each back end has private
389 information surrounding the <<asymbol>>. Building your own
390 <<asymbol>> and pointing to it will not create the private
391 information, and will cause problems later on.
393 .#define bfd_make_empty_symbol(abfd) \
394 . BFD_SEND (abfd, _bfd_make_empty_symbol, (abfd))
399 bfd_make_debug_symbol
402 Create a new <<asymbol>> structure for the BFD @var{abfd},
403 to be used as a debugging symbol. Further details of its use have
404 yet to be worked out.
406 .#define bfd_make_debug_symbol(abfd,ptr,size) \
407 . BFD_SEND (abfd, _bfd_make_debug_symbol, (abfd, ptr, size))
410 struct section_to_type
416 /* Map section names to POSIX/BSD single-character symbol types.
417 This table is probably incomplete. It is sorted for convenience of
418 adding entries. Since it is so short, a linear search is used. */
419 static CONST
struct section_to_type stt
[] = {
423 {".sbss", 's'}, /* Small BSS (uninitialized data) */
424 {".scommon", 'c'}, /* Small common */
425 {".sdata", 'g'}, /* Small initialized data */
430 /* Return the single-character symbol type corresponding to
431 section S, or '?' for an unknown COFF section. */
434 coff_section_type (s
)
437 CONST
struct section_to_type
*t
;
439 for (t
= &stt
[0]; t
->section
; t
++)
440 if (!strcmp (s
, t
->section
))
446 #define islower(c) ((c) >= 'a' && (c) <= 'z')
449 #define toupper(c) (islower(c) ? ((c) & ~0x20) : (c))
457 Return a character corresponding to the symbol
458 class of @var{symbol}, or '?' for an unknown class.
461 int bfd_decode_symclass(asymbol *symbol);
464 DEFUN(bfd_decode_symclass
,(symbol
),
469 if (bfd_is_com_section (symbol
->section
))
471 if (symbol
->section
== &bfd_und_section
)
473 if (symbol
->section
== &bfd_ind_section
)
475 if (!(symbol
->flags
& (BSF_GLOBAL
|BSF_LOCAL
)))
478 if (symbol
->section
== &bfd_abs_section
)
480 else if (symbol
->section
)
481 c
= coff_section_type (symbol
->section
->name
);
484 if (symbol
->flags
& BSF_GLOBAL
)
488 /* We don't have to handle these cases just yet, but we will soon:
503 Fill in the basic info about symbol that nm needs.
504 Additional info may be added by the back-ends after
505 calling this function.
508 void bfd_symbol_info(asymbol *symbol, symbol_info *ret);
512 DEFUN(bfd_symbol_info
,(symbol
, ret
),
516 ret
->type
= bfd_decode_symclass (symbol
);
517 if (ret
->type
!= 'U')
518 ret
->value
= symbol
->value
+symbol
->section
->vma
;
521 ret
->name
= symbol
->name
;
525 bfd_symbol_is_absolute()
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