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 | long storage_needed;
65 | asymbol **symbol_table;
66 | long number_of_symbols;
69 | storage_needed = bfd_get_symtab_upper_bound (abfd);
71 | if (storage_needed < 0)
74 | if (storage_needed == 0) {
77 | symbol_table = (asymbol **) xmalloc (storage_needed);
80 | bfd_canonicalize_symtab (abfd, symbol_table);
82 | if (number_of_symbols < 0)
85 | for (i = 0; i < number_of_symbols; i++) {
86 | process_symbol (symbol_table[i]);
89 All storage for the symbols themselves is in an obstack
90 connected to the BFD; it is freed when the BFD is closed.
94 Writing Symbols, typedef asymbol, Reading Symbols, Symbols
98 Writing of a symbol table is automatic when a BFD open for
99 writing is closed. The application attaches a vector of
100 pointers to pointers to symbols to the BFD being written, and
101 fills in the symbol count. The close and cleanup code reads
102 through the table provided and performs all the necessary
103 operations. The BFD output code must always be provided with an
104 ``owned'' symbol: one which has come from another BFD, or one
105 which has been created using <<bfd_make_empty_symbol>>. Here is an
106 example showing the creation of a symbol table with only one element:
115 | abfd = bfd_openw("foo","a.out-sunos-big");
116 | bfd_set_format(abfd, bfd_object);
117 | new = bfd_make_empty_symbol(abfd);
118 | new->name = "dummy_symbol";
119 | new->section = bfd_make_section_old_way(abfd, ".text");
120 | new->flags = BSF_GLOBAL;
121 | new->value = 0x12345;
124 | ptrs[1] = (asymbol *)0;
126 | bfd_set_symtab(abfd, ptrs, 1);
132 | 00012345 A dummy_symbol
134 Many formats cannot represent arbitary symbol information; for
135 instance, the <<a.out>> object format does not allow an
136 arbitary number of sections. A symbol pointing to a section
137 which is not one of <<.text>>, <<.data>> or <<.bss>> cannot
147 typedef asymbol, symbol handling functions, Writing Symbols, Symbols
154 An <<asymbol>> has the form:
162 .typedef struct symbol_cache_entry
164 . {* A pointer to the BFD which owns the symbol. This information
165 . is necessary so that a back end can work out what additional
166 . information (invisible to the application writer) is carried
169 . This field is *almost* redundant, since you can use section->owner
170 . instead, except that some symbols point to the global sections
171 . bfd_{abs,com,und}_section. This could be fixed by making
172 . these globals be per-bfd (or per-target-flavor). FIXME. *}
174 . struct _bfd *the_bfd; {* Use bfd_asymbol_bfd(sym) to access this field. *}
176 . {* The text of the symbol. The name is left alone, and not copied; the
177 . application may not alter it. *}
180 . {* The value of the symbol. This really should be a union of a
181 . numeric value with a pointer, since some flags indicate that
182 . a pointer to another symbol is stored here. *}
185 . {* Attributes of a symbol: *}
187 .#define BSF_NO_FLAGS 0x00
189 . {* The symbol has local scope; <<static>> in <<C>>. The value
190 . is the offset into the section of the data. *}
191 .#define BSF_LOCAL 0x01
193 . {* The symbol has global scope; initialized data in <<C>>. The
194 . value is the offset into the section of the data. *}
195 .#define BSF_GLOBAL 0x02
197 . {* The symbol has global scope and is exported. The value is
198 . the offset into the section of the data. *}
199 .#define BSF_EXPORT BSF_GLOBAL {* no real difference *}
201 . {* A normal C symbol would be one of:
202 . <<BSF_LOCAL>>, <<BSF_FORT_COMM>>, <<BSF_UNDEFINED>> or
205 . {* The symbol is a debugging record. The value has an arbitary
207 .#define BSF_DEBUGGING 0x08
209 . {* The symbol denotes a function entry point. Used in ELF,
210 . perhaps others someday. *}
211 .#define BSF_FUNCTION 0x10
213 . {* Used by the linker. *}
214 .#define BSF_KEEP 0x20
215 .#define BSF_KEEP_G 0x40
217 . {* A weak global symbol, overridable without warnings by
218 . a regular global symbol of the same name. *}
219 .#define BSF_WEAK 0x80
221 . {* This symbol was created to point to a section, e.g. ELF's
222 . STT_SECTION symbols. *}
223 .#define BSF_SECTION_SYM 0x100
225 . {* The symbol used to be a common symbol, but now it is
227 .#define BSF_OLD_COMMON 0x200
229 . {* The default value for common data. *}
230 .#define BFD_FORT_COMM_DEFAULT_VALUE 0
232 . {* In some files the type of a symbol sometimes alters its
233 . location in an output file - ie in coff a <<ISFCN>> symbol
234 . which is also <<C_EXT>> symbol appears where it was
235 . declared and not at the end of a section. This bit is set
236 . by the target BFD part to convey this information. *}
238 .#define BSF_NOT_AT_END 0x400
240 . {* Signal that the symbol is the label of constructor section. *}
241 .#define BSF_CONSTRUCTOR 0x800
243 . {* Signal that the symbol is a warning symbol. If the symbol
244 . is a warning symbol, then the value field (I know this is
245 . tacky) will point to the asymbol which when referenced will
246 . cause the warning. *}
247 .#define BSF_WARNING 0x1000
249 . {* Signal that the symbol is indirect. The value of the symbol
250 . is a pointer to an undefined asymbol which contains the
251 . name to use instead. *}
252 .#define BSF_INDIRECT 0x2000
254 . {* BSF_FILE marks symbols that contain a file name. This is used
255 . for ELF STT_FILE symbols. *}
256 .#define BSF_FILE 0x4000
258 . {* Symbol is from dynamic linking information. *}
259 .#define BSF_DYNAMIC 0x8000
263 . {* A pointer to the section to which this symbol is
264 . relative. This will always be non NULL, there are special
265 . sections for undefined and absolute symbols. *}
266 . struct sec *section;
268 . {* Back end special data. *}
282 #include "aout/stab_gnu.h"
287 symbol handling functions, , typedef asymbol, Symbols
289 Symbol handling functions
294 bfd_get_symtab_upper_bound
297 Return the number of bytes required to store a vector of pointers
298 to <<asymbols>> for all the symbols in the BFD @var{abfd},
299 including a terminal NULL pointer. If there are no symbols in
300 the BFD, then return 0. If an error occurs, return -1.
302 .#define bfd_get_symtab_upper_bound(abfd) \
303 . BFD_SEND (abfd, _bfd_get_symtab_upper_bound, (abfd))
312 boolean bfd_is_local_label(bfd *abfd, asymbol *sym);
315 Return true if the given symbol @var{sym} in the BFD @var{abfd} is
316 a compiler generated local label, else return false.
317 .#define bfd_is_local_label(abfd, sym) \
318 . BFD_SEND (abfd, _bfd_is_local_label,(abfd, sym))
323 bfd_canonicalize_symtab
326 Read the symbols from the BFD @var{abfd}, and fills in
327 the vector @var{location} with pointers to the symbols and
329 Return the actual number of symbol pointers, not
333 .#define bfd_canonicalize_symtab(abfd, location) \
334 . BFD_SEND (abfd, _bfd_canonicalize_symtab,\
345 boolean bfd_set_symtab (bfd *abfd, asymbol **location, unsigned int count);
348 Arrange that when the output BFD @var{abfd} is closed,
349 the table @var{location} of @var{count} pointers to symbols
354 bfd_set_symtab (abfd
, location
, symcount
)
357 unsigned int symcount
;
359 if ((abfd
->format
!= bfd_object
) || (bfd_read_p (abfd
)))
361 bfd_set_error (bfd_error_invalid_operation
);
365 bfd_get_outsymbols (abfd
) = location
;
366 bfd_get_symcount (abfd
) = symcount
;
372 bfd_print_symbol_vandf
375 void bfd_print_symbol_vandf(PTR file, asymbol *symbol);
378 Print the value and flags of the @var{symbol} supplied to the
382 bfd_print_symbol_vandf (arg
, symbol
)
386 FILE *file
= (FILE *) arg
;
387 flagword type
= symbol
->flags
;
388 if (symbol
->section
!= (asection
*) NULL
)
390 fprintf_vma (file
, symbol
->value
+ symbol
->section
->vma
);
394 fprintf_vma (file
, symbol
->value
);
397 /* This presumes that a symbol can not be both BSF_DEBUGGING and
398 BSF_DYNAMIC, nor both BSF_FUNCTION and BSF_FILE. */
399 fprintf (file
, " %c%c%c%c%c%c%c",
401 ? (type
& BSF_GLOBAL
) ? '!' : 'l'
402 : (type
& BSF_GLOBAL
) ? 'g' : ' '),
403 (type
& BSF_WEAK
) ? 'w' : ' ',
404 (type
& BSF_CONSTRUCTOR
) ? 'C' : ' ',
405 (type
& BSF_WARNING
) ? 'W' : ' ',
406 (type
& BSF_INDIRECT
) ? 'I' : ' ',
407 (type
& BSF_DEBUGGING
) ? 'd' : (type
& BSF_DYNAMIC
) ? 'D' : ' ',
408 (type
& BSF_FUNCTION
) ? 'F' : (type
& BSF_FILE
) ? 'f' : ' ');
414 bfd_make_empty_symbol
417 Create a new <<asymbol>> structure for the BFD @var{abfd}
418 and return a pointer to it.
420 This routine is necessary because each back end has private
421 information surrounding the <<asymbol>>. Building your own
422 <<asymbol>> and pointing to it will not create the private
423 information, and will cause problems later on.
425 .#define bfd_make_empty_symbol(abfd) \
426 . BFD_SEND (abfd, _bfd_make_empty_symbol, (abfd))
431 bfd_make_debug_symbol
434 Create a new <<asymbol>> structure for the BFD @var{abfd},
435 to be used as a debugging symbol. Further details of its use have
436 yet to be worked out.
438 .#define bfd_make_debug_symbol(abfd,ptr,size) \
439 . BFD_SEND (abfd, _bfd_make_debug_symbol, (abfd, ptr, size))
442 struct section_to_type
448 /* Map section names to POSIX/BSD single-character symbol types.
449 This table is probably incomplete. It is sorted for convenience of
450 adding entries. Since it is so short, a linear search is used. */
451 static CONST
struct section_to_type stt
[] =
456 {".rdata", 'r'}, /* Read only data. */
457 {".rodata", 'r'}, /* Read only data. */
458 {".sbss", 's'}, /* Small BSS (uninitialized data). */
459 {".scommon", 'c'}, /* Small common. */
460 {".sdata", 'g'}, /* Small initialized data. */
465 /* Return the single-character symbol type corresponding to
466 section S, or '?' for an unknown COFF section.
468 Check for any leading string which matches, so .text5 returns
469 't' as well as .text */
472 coff_section_type (s
)
475 CONST
struct section_to_type
*t
;
477 for (t
= &stt
[0]; t
->section
; t
++)
478 if (!strncmp (s
, t
->section
, strlen (t
->section
)))
485 #define islower(c) ((c) >= 'a' && (c) <= 'z')
488 #define toupper(c) (islower(c) ? ((c) & ~0x20) : (c))
496 Return a character corresponding to the symbol
497 class of @var{symbol}, or '?' for an unknown class.
500 int bfd_decode_symclass(asymbol *symbol);
503 bfd_decode_symclass (symbol
)
508 if (bfd_is_com_section (symbol
->section
))
510 if (bfd_is_und_section (symbol
->section
))
512 if (bfd_is_ind_section (symbol
->section
))
514 if (symbol
->flags
& BSF_WEAK
)
516 if (!(symbol
->flags
& (BSF_GLOBAL
| BSF_LOCAL
)))
519 if (bfd_is_abs_section (symbol
->section
))
521 else if (symbol
->section
)
522 c
= coff_section_type (symbol
->section
->name
);
525 if (symbol
->flags
& BSF_GLOBAL
)
529 /* We don't have to handle these cases just yet, but we will soon:
544 Fill in the basic info about symbol that nm needs.
545 Additional info may be added by the back-ends after
546 calling this function.
549 void bfd_symbol_info(asymbol *symbol, symbol_info *ret);
553 bfd_symbol_info (symbol
, ret
)
557 ret
->type
= bfd_decode_symclass (symbol
);
558 if (ret
->type
!= 'U')
559 ret
->value
= symbol
->value
+ symbol
->section
->vma
;
562 ret
->name
= symbol
->name
;
566 bfd_symbol_is_absolute ()
573 bfd_copy_private_symbol_data
576 boolean bfd_copy_private_symbol_data(bfd *ibfd, asymbol *isym, bfd *obfd, asymbol *osym);
579 Copy private symbol information from @var{isym} in the BFD
580 @var{ibfd} to the symbol @var{osym} in the BFD @var{obfd}.
581 Return <<true>> on success, <<false>> on error. Possible error
584 o <<bfd_error_no_memory>> -
585 Not enough memory exists to create private data for @var{osec}.
587 .#define bfd_copy_private_symbol_data(ibfd, isymbol, obfd, osymbol) \
588 . BFD_SEND (ibfd, _bfd_copy_private_symbol_data, \
589 . (ibfd, isymbol, obfd, osymbol))