1 /* bfdlink.h -- header file for BFD link routines
2 Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000
3 Free Software Foundation, Inc.
4 Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
6 This file is part of BFD, the Binary File Descriptor library.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
25 /* Which symbols to strip during a link. */
28 strip_none, /* Don't strip any symbols. */
29 strip_debugger, /* Strip debugging symbols. */
30 strip_some, /* keep_hash is the list of symbols to keep. */
31 strip_all /* Strip all symbols. */
34 /* Which local symbols to discard during a link. This is irrelevant
35 if strip_all is used. */
38 discard_none, /* Don't discard any locals. */
39 discard_l, /* Discard local temporary symbols. */
40 discard_all /* Discard all locals. */
43 /* These are the possible types of an entry in the BFD link hash
46 enum bfd_link_hash_type
48 bfd_link_hash_new, /* Symbol is new. */
49 bfd_link_hash_undefined, /* Symbol seen before, but undefined. */
50 bfd_link_hash_undefweak, /* Symbol is weak and undefined. */
51 bfd_link_hash_defined, /* Symbol is defined. */
52 bfd_link_hash_defweak, /* Symbol is weak and defined. */
53 bfd_link_hash_common, /* Symbol is common. */
54 bfd_link_hash_indirect, /* Symbol is an indirect link. */
55 bfd_link_hash_warning /* Like indirect, but warn if referenced. */
58 /* The linking routines use a hash table which uses this structure for
61 struct bfd_link_hash_entry
63 /* Base hash table entry structure. */
64 struct bfd_hash_entry root;
65 /* Type of this entry. */
66 enum bfd_link_hash_type type;
68 /* Undefined and common symbols are kept in a linked list through
69 this field. This field is not in the union because that would
70 force us to remove entries from the list when we changed their
71 type, which would force the list to be doubly linked, which would
72 waste more memory. When an undefined or common symbol is
73 created, it should be added to this list, the head of which is in
74 the link hash table itself. As symbols are defined, they need
75 not be removed from the list; anything which reads the list must
76 doublecheck the symbol type.
78 Weak symbols are not kept on this list.
80 Defined and defweak symbols use this field as a reference marker.
81 If the field is not NULL, or this structure is the tail of the
82 undefined symbol list, the symbol has been referenced. If the
83 symbol is undefined and becomes defined, this field will
84 automatically be non-NULL since the symbol will have been on the
85 undefined symbol list. */
86 struct bfd_link_hash_entry *next;
87 /* A union of information depending upon the type. */
90 /* Nothing is kept for bfd_hash_new. */
91 /* bfd_link_hash_undefined, bfd_link_hash_undefweak. */
94 bfd *abfd; /* BFD symbol was found in. */
96 /* bfd_link_hash_defined, bfd_link_hash_defweak. */
99 bfd_vma value; /* Symbol value. */
100 asection *section; /* Symbol section. */
102 /* bfd_link_hash_indirect, bfd_link_hash_warning. */
105 struct bfd_link_hash_entry *link; /* Real symbol. */
106 const char *warning; /* Warning (bfd_link_hash_warning only). */
108 /* bfd_link_hash_common. */
111 /* The linker needs to know three things about common
112 symbols: the size, the alignment, and the section in
113 which the symbol should be placed. We store the size
114 here, and we allocate a small structure to hold the
115 section and the alignment. The alignment is stored as a
116 power of two. We don't store all the information
117 directly because we don't want to increase the size of
118 the union; this structure is a major space user in the
120 bfd_size_type size; /* Common symbol size. */
121 struct bfd_link_hash_common_entry
123 unsigned int alignment_power; /* Alignment. */
124 asection *section; /* Symbol section. */
130 /* This is the link hash table. It is a derived class of
133 struct bfd_link_hash_table
135 /* The hash table itself. */
136 struct bfd_hash_table table;
137 /* The back end which created this hash table. This indicates the
138 type of the entries in the hash table, which is sometimes
139 important information when linking object files of different
141 const bfd_target *creator;
142 /* A linked list of undefined and common symbols, linked through the
143 next field in the bfd_link_hash_entry structure. */
144 struct bfd_link_hash_entry *undefs;
145 /* Entries are added to the tail of the undefs list. */
146 struct bfd_link_hash_entry *undefs_tail;
149 /* Look up an entry in a link hash table. If FOLLOW is true, this
150 follows bfd_link_hash_indirect and bfd_link_hash_warning links to
152 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
153 PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
154 boolean copy, boolean follow));
156 /* Look up an entry in the main linker hash table if the symbol might
157 be wrapped. This should only be used for references to an
158 undefined symbol, not for definitions of a symbol. */
160 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
161 PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
164 /* Traverse a link hash table. */
165 extern void bfd_link_hash_traverse
166 PARAMS ((struct bfd_link_hash_table *,
167 boolean (*) (struct bfd_link_hash_entry *, PTR),
170 /* Add an entry to the undefs list. */
171 extern void bfd_link_add_undef
172 PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
174 /* This structure holds all the information needed to communicate
175 between BFD and the linker when doing a link. */
179 /* Function callbacks. */
180 const struct bfd_link_callbacks *callbacks;
181 /* true if BFD should generate a relocateable object file. */
182 boolean relocateable;
183 /* true if BFD should generate relocation information in the final executable. */
184 boolean emitrelocations;
185 /* true if BFD should generate a "task linked" object file,
186 similar to relocatable but also with globals converted to statics. */
188 /* true if BFD should generate a shared object. */
190 /* true if BFD should pre-bind symbols in a shared object. */
192 /* true if shared objects should be linked directly, not shared. */
194 /* true if the output file should be in a traditional format. This
195 is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
196 on the output file, but may be checked when reading the input
198 boolean traditional_format;
199 /* true if we want to produced optimized output files. This might
200 need much more time and therefore must be explicitly selected. */
202 /* true if BFD should generate errors for undefined symbols
203 even if generating a shared object. */
204 boolean no_undefined;
205 /* true if BFD should allow undefined symbols in shared objects even
206 when no_undefined is set to disallow undefined symbols. The net
207 result will be that undefined symbols in regular objects will
208 still trigger an error, but undefined symbols in shared objects
209 will be ignored. The implementation of no_undefined makes the
210 assumption that the runtime linker will choke on undefined
211 symbols. However there is at least one system (BeOS) where
212 undefined symbols in shared libraries is normal since the kernel
213 patches them at load time to select which function is most
214 appropriate for the current architecture. I.E. dynamically
215 select an appropriate memset function. Apparently it is also
216 normal for HPPA shared libraries to have undefined symbols. */
217 boolean allow_shlib_undefined;
218 /* Which symbols to strip. */
219 enum bfd_link_strip strip;
220 /* Which local symbols to discard. */
221 enum bfd_link_discard discard;
222 /* true if symbols should be retained in memory, false if they
223 should be freed and reread. */
225 /* The list of input BFD's involved in the link. These are chained
226 together via the link_next field. */
228 /* If a symbol should be created for each input BFD, this is section
229 where those symbols should be placed. It must be a section in
230 the output BFD. It may be NULL, in which case no such symbols
231 will be created. This is to support CREATE_OBJECT_SYMBOLS in the
232 linker command language. */
233 asection *create_object_symbols_section;
234 /* Hash table handled by BFD. */
235 struct bfd_link_hash_table *hash;
236 /* Hash table of symbols to keep. This is NULL unless strip is
238 struct bfd_hash_table *keep_hash;
239 /* true if every symbol should be reported back via the notice
242 /* Hash table of symbols to report back via the notice callback. If
243 this is NULL, and notice_all is false, then no symbols are
245 struct bfd_hash_table *notice_hash;
246 /* Hash table of symbols which are being wrapped (the --wrap linker
247 option). If this is NULL, no symbols are being wrapped. */
248 struct bfd_hash_table *wrap_hash;
249 /* If a base output file is wanted, then this points to it */
252 /* If non-zero, specifies that branches which are problematic for the
253 MPC860 C0 (or earlier) should be checked for and modified. It gives the
254 number of bytes that should be checked at the end of each text page. */
257 /* The function to call when the executable or shared object is
259 const char *init_function;
260 /* The function to call when the executable or shared object is
262 const char *fini_function;
264 /* true if the new ELF dynamic tags are enabled. */
267 /* May be used to set DT_FLAGS for ELF. */
270 /* May be used to set DT_FLAGS_1 for ELF. */
274 /* This structures holds a set of callback functions. These are
275 called by the BFD linker routines. The first argument to each
276 callback function is the bfd_link_info structure being used. Each
277 function returns a boolean value. If the function returns false,
278 then the BFD function which called it will return with a failure
281 struct bfd_link_callbacks
283 /* A function which is called when an object is added from an
284 archive. ABFD is the archive element being added. NAME is the
285 name of the symbol which caused the archive element to be pulled
287 boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
290 /* A function which is called when a symbol is found with multiple
291 definitions. NAME is the symbol which is defined multiple times.
292 OBFD is the old BFD, OSEC is the old section, OVAL is the old
293 value, NBFD is the new BFD, NSEC is the new section, and NVAL is
294 the new value. OBFD may be NULL. OSEC and NSEC may be
295 bfd_com_section or bfd_ind_section. */
296 boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
304 /* A function which is called when a common symbol is defined
305 multiple times. NAME is the symbol appearing multiple times.
306 OBFD is the BFD of the existing symbol; it may be NULL if this is
307 not known. OTYPE is the type of the existing symbol, which may
308 be bfd_link_hash_defined, bfd_link_hash_defweak,
309 bfd_link_hash_common, or bfd_link_hash_indirect. If OTYPE is
310 bfd_link_hash_common, OSIZE is the size of the existing symbol.
311 NBFD is the BFD of the new symbol. NTYPE is the type of the new
312 symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
313 bfd_link_hash_indirect. If NTYPE is bfd_link_hash_common, NSIZE
314 is the size of the new symbol. */
315 boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
318 enum bfd_link_hash_type otype,
321 enum bfd_link_hash_type ntype,
323 /* A function which is called to add a symbol to a set. ENTRY is
324 the link hash table entry for the set itself (e.g.,
325 __CTOR_LIST__). RELOC is the relocation to use for an entry in
326 the set when generating a relocateable file, and is also used to
327 get the size of the entry when generating an executable file.
328 ABFD, SEC and VALUE identify the value to add to the set. */
329 boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
330 struct bfd_link_hash_entry *entry,
331 bfd_reloc_code_real_type reloc,
332 bfd *abfd, asection *sec, bfd_vma value));
333 /* A function which is called when the name of a g++ constructor or
334 destructor is found. This is only called by some object file
335 formats. CONSTRUCTOR is true for a constructor, false for a
336 destructor. This will use BFD_RELOC_CTOR when generating a
337 relocateable file. NAME is the name of the symbol found. ABFD,
338 SECTION and VALUE are the value of the symbol. */
339 boolean (*constructor) PARAMS ((struct bfd_link_info *,
341 const char *name, bfd *abfd, asection *sec,
343 /* A function which is called to issue a linker warning. For
344 example, this is called when there is a reference to a warning
345 symbol. WARNING is the warning to be issued. SYMBOL is the name
346 of the symbol which triggered the warning; it may be NULL if
347 there is none. ABFD, SECTION and ADDRESS identify the location
348 which trigerred the warning; either ABFD or SECTION or both may
349 be NULL if the location is not known. */
350 boolean (*warning) PARAMS ((struct bfd_link_info *,
351 const char *warning, const char *symbol,
352 bfd *abfd, asection *section,
354 /* A function which is called when a relocation is attempted against
355 an undefined symbol. NAME is the symbol which is undefined.
356 ABFD, SECTION and ADDRESS identify the location from which the
357 reference is made. FATAL indicates whether an undefined symbol is
358 a fatal error or not. In some cases SECTION may be NULL. */
359 boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
360 const char *name, bfd *abfd,
364 /* A function which is called when a reloc overflow occurs. NAME is
365 the name of the symbol or section the reloc is against,
366 RELOC_NAME is the name of the relocation, and ADDEND is any
367 addend that is used. ABFD, SECTION and ADDRESS identify the
368 location at which the overflow occurs; if this is the result of a
369 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
370 ABFD will be NULL. */
371 boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
373 const char *reloc_name, bfd_vma addend,
374 bfd *abfd, asection *section,
376 /* A function which is called when a dangerous reloc is performed.
377 The canonical example is an a29k IHCONST reloc which does not
378 follow an IHIHALF reloc. MESSAGE is an appropriate message.
379 ABFD, SECTION and ADDRESS identify the location at which the
380 problem occurred; if this is the result of a
381 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
382 ABFD will be NULL. */
383 boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
385 bfd *abfd, asection *section,
387 /* A function which is called when a reloc is found to be attached
388 to a symbol which is not being written out. NAME is the name of
389 the symbol. ABFD, SECTION and ADDRESS identify the location of
390 the reloc; if this is the result of a
391 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
392 ABFD will be NULL. */
393 boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
395 bfd *abfd, asection *section,
397 /* A function which is called when a symbol in notice_hash is
398 defined or referenced. NAME is the symbol. ABFD, SECTION and
399 ADDRESS are the value of the symbol. If SECTION is
400 bfd_und_section, this is a reference. */
401 boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
402 bfd *abfd, asection *section, bfd_vma address));
405 /* The linker builds link_order structures which tell the code how to
406 include input data in the output file. */
408 /* These are the types of link_order structures. */
410 enum bfd_link_order_type
412 bfd_undefined_link_order, /* Undefined. */
413 bfd_indirect_link_order, /* Built from a section. */
414 bfd_fill_link_order, /* Fill with a 16 bit constant. */
415 bfd_data_link_order, /* Set to explicit data. */
416 bfd_section_reloc_link_order, /* Relocate against a section. */
417 bfd_symbol_reloc_link_order /* Relocate against a symbol. */
420 /* This is the link_order structure itself. These form a chain
421 attached to the section whose contents they are describing. */
423 struct bfd_link_order
425 /* Next link_order in chain. */
426 struct bfd_link_order *next;
427 /* Type of link_order. */
428 enum bfd_link_order_type type;
429 /* Offset within output section. */
431 /* Size within output section. */
433 /* Type specific information. */
438 /* Section to include. If this is used, then
439 section->output_section must be the section the
440 link_order is attached to, section->output_offset must
441 equal the link_order offset field, and section->_raw_size
442 must equal the link_order size field. Maybe these
443 restrictions should be relaxed someday. */
448 /* Value to fill with. */
453 /* Data to put into file. The size field gives the number
454 of bytes which this field points to. */
459 /* Description of reloc to generate. Used for
460 bfd_section_reloc_link_order and
461 bfd_symbol_reloc_link_order. */
462 struct bfd_link_order_reloc *p;
467 /* A linker order of type bfd_section_reloc_link_order or
468 bfd_symbol_reloc_link_order means to create a reloc against a
469 section or symbol, respectively. This is used to implement -Ur to
470 generate relocs for the constructor tables. The
471 bfd_link_order_reloc structure describes the reloc that BFD should
472 create. It is similar to a arelent, but I didn't use arelent
473 because the linker does not know anything about most symbols, and
474 any asymbol structure it creates will be partially meaningless.
475 This information could logically be in the bfd_link_order struct,
476 but I didn't want to waste the space since these types of relocs
477 are relatively rare. */
479 struct bfd_link_order_reloc
482 bfd_reloc_code_real_type reloc;
486 /* For type bfd_section_reloc_link_order, this is the section
487 the reloc should be against. This must be a section in the
488 output BFD, not any of the input BFDs. */
490 /* For type bfd_symbol_reloc_link_order, this is the name of the
491 symbol the reloc should be against. */
495 /* Addend to use. The object file should contain zero. The BFD
496 backend is responsible for filling in the contents of the object
497 file correctly. For some object file formats (e.g., COFF) the
498 addend must be stored into in the object file, and for some
499 (e.g., SPARC a.out) it is kept in the reloc. */
503 /* Allocate a new link_order for a section. */
504 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
506 /* These structures are used to describe version information for the
507 ELF linker. These structures could be manipulated entirely inside
508 BFD, but it would be a pain. Instead, the regular linker sets up
509 these structures, and then passes them into BFD. */
511 /* Regular expressions for a version. */
513 struct bfd_elf_version_expr
515 /* Next regular expression for this version. */
516 struct bfd_elf_version_expr *next;
517 /* Regular expression. */
519 /* Matching function. */
520 int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
523 /* Version dependencies. */
525 struct bfd_elf_version_deps
527 /* Next dependency for this version. */
528 struct bfd_elf_version_deps *next;
529 /* The version which this version depends upon. */
530 struct bfd_elf_version_tree *version_needed;
533 /* A node in the version tree. */
535 struct bfd_elf_version_tree
538 struct bfd_elf_version_tree *next;
539 /* Name of this version. */
541 /* Version number. */
543 /* Regular expressions for global symbols in this version. */
544 struct bfd_elf_version_expr *globals;
545 /* Regular expressions for local symbols in this version. */
546 struct bfd_elf_version_expr *locals;
547 /* List of versions which this version depends upon. */
548 struct bfd_elf_version_deps *deps;
549 /* Index of the version name. This is used within BFD. */
550 unsigned int name_indx;
551 /* Whether this version tree was used. This is used within BFD. */