1 /* bfdlink.h -- header file for BFD link routines
2 Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2002
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_sec_merge, /* Discard local temporary symbols in SEC_MERGE
40 discard_none, /* Don't discard any locals. */
41 discard_l, /* Discard local temporary symbols. */
42 discard_all /* Discard all locals. */
45 /* Describes the type of hash table entry structure being used.
46 Different hash table structure have different fields and so
47 support different linking features. */
48 enum bfd_link_hash_table_type
50 bfd_link_generic_hash_table,
51 bfd_link_elf_hash_table
54 /* These are the possible types of an entry in the BFD link hash
57 enum bfd_link_hash_type
59 bfd_link_hash_new, /* Symbol is new. */
60 bfd_link_hash_undefined, /* Symbol seen before, but undefined. */
61 bfd_link_hash_undefweak, /* Symbol is weak and undefined. */
62 bfd_link_hash_defined, /* Symbol is defined. */
63 bfd_link_hash_defweak, /* Symbol is weak and defined. */
64 bfd_link_hash_common, /* Symbol is common. */
65 bfd_link_hash_indirect, /* Symbol is an indirect link. */
66 bfd_link_hash_warning /* Like indirect, but warn if referenced. */
69 enum bfd_link_common_skip_ar_aymbols
71 bfd_link_common_skip_none,
72 bfd_link_common_skip_text,
73 bfd_link_common_skip_data,
74 bfd_link_common_skip_all
77 /* The linking routines use a hash table which uses this structure for
80 struct bfd_link_hash_entry
82 /* Base hash table entry structure. */
83 struct bfd_hash_entry root;
84 /* Type of this entry. */
85 enum bfd_link_hash_type type;
87 /* Undefined and common symbols are kept in a linked list through
88 this field. This field is not in the union because that would
89 force us to remove entries from the list when we changed their
90 type, which would force the list to be doubly linked, which would
91 waste more memory. When an undefined or common symbol is
92 created, it should be added to this list, the head of which is in
93 the link hash table itself. As symbols are defined, they need
94 not be removed from the list; anything which reads the list must
95 doublecheck the symbol type.
97 Weak symbols are not kept on this list.
99 Defined and defweak symbols use this field as a reference marker.
100 If the field is not NULL, or this structure is the tail of the
101 undefined symbol list, the symbol has been referenced. If the
102 symbol is undefined and becomes defined, this field will
103 automatically be non-NULL since the symbol will have been on the
104 undefined symbol list. */
105 struct bfd_link_hash_entry *next;
106 /* A union of information depending upon the type. */
109 /* Nothing is kept for bfd_hash_new. */
110 /* bfd_link_hash_undefined, bfd_link_hash_undefweak. */
113 bfd *abfd; /* BFD symbol was found in. */
115 /* bfd_link_hash_defined, bfd_link_hash_defweak. */
118 bfd_vma value; /* Symbol value. */
119 asection *section; /* Symbol section. */
121 /* bfd_link_hash_indirect, bfd_link_hash_warning. */
124 struct bfd_link_hash_entry *link; /* Real symbol. */
125 const char *warning; /* Warning (bfd_link_hash_warning only). */
127 /* bfd_link_hash_common. */
130 /* The linker needs to know three things about common
131 symbols: the size, the alignment, and the section in
132 which the symbol should be placed. We store the size
133 here, and we allocate a small structure to hold the
134 section and the alignment. The alignment is stored as a
135 power of two. We don't store all the information
136 directly because we don't want to increase the size of
137 the union; this structure is a major space user in the
139 bfd_size_type size; /* Common symbol size. */
140 struct bfd_link_hash_common_entry
142 unsigned int alignment_power; /* Alignment. */
143 asection *section; /* Symbol section. */
149 /* This is the link hash table. It is a derived class of
152 struct bfd_link_hash_table
154 /* The hash table itself. */
155 struct bfd_hash_table table;
156 /* The back end which created this hash table. This indicates the
157 type of the entries in the hash table, which is sometimes
158 important information when linking object files of different
160 const bfd_target *creator;
161 /* A linked list of undefined and common symbols, linked through the
162 next field in the bfd_link_hash_entry structure. */
163 struct bfd_link_hash_entry *undefs;
164 /* Entries are added to the tail of the undefs list. */
165 struct bfd_link_hash_entry *undefs_tail;
166 /* The type of the ink hash table. */
167 enum bfd_link_hash_table_type type;
170 /* Look up an entry in a link hash table. If FOLLOW is true, this
171 follows bfd_link_hash_indirect and bfd_link_hash_warning links to
173 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
174 PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
175 boolean copy, boolean follow));
177 /* Look up an entry in the main linker hash table if the symbol might
178 be wrapped. This should only be used for references to an
179 undefined symbol, not for definitions of a symbol. */
181 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
182 PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
185 /* Traverse a link hash table. */
186 extern void bfd_link_hash_traverse
187 PARAMS ((struct bfd_link_hash_table *,
188 boolean (*) (struct bfd_link_hash_entry *, PTR),
191 /* Add an entry to the undefs list. */
192 extern void bfd_link_add_undef
193 PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
197 struct bfd_sym_chain *next;
201 /* This structure holds all the information needed to communicate
202 between BFD and the linker when doing a link. */
206 /* Function callbacks. */
207 const struct bfd_link_callbacks *callbacks;
209 /* true if BFD should generate a relocateable object file. */
210 boolean relocateable;
212 /* true if BFD should generate relocation information in the final
214 boolean emitrelocations;
216 /* true if BFD should generate a "task linked" object file,
217 similar to relocatable but also with globals converted to
221 /* true if BFD should generate a shared object. */
224 /* true if BFD should pre-bind symbols in a shared object. */
227 /* true if BFD should export all symbols in the dynamic symbol table
228 of an executable, rather than only those used. */
229 boolean export_dynamic;
231 /* true if shared objects should be linked directly, not shared. */
234 /* true if the output file should be in a traditional format. This
235 is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
236 on the output file, but may be checked when reading the input
238 boolean traditional_format;
240 /* true if we want to produced optimized output files. This might
241 need much more time and therefore must be explicitly selected. */
244 /* true if BFD should generate errors for undefined symbols
245 even if generating a shared object. */
246 boolean no_undefined;
248 /* true if BFD should allow undefined symbols in shared objects even
249 when no_undefined is set to disallow undefined symbols. The net
250 result will be that undefined symbols in regular objects will
251 still trigger an error, but undefined symbols in shared objects
252 will be ignored. The implementation of no_undefined makes the
253 assumption that the runtime linker will choke on undefined
254 symbols. However there is at least one system (BeOS) where
255 undefined symbols in shared libraries is normal since the kernel
256 patches them at load time to select which function is most
257 appropriate for the current architecture. I.E. dynamically
258 select an appropriate memset function. Apparently it is also
259 normal for HPPA shared libraries to have undefined symbols. */
260 boolean allow_shlib_undefined;
262 /* true if ok to have multiple definition. */
263 boolean allow_multiple_definition;
265 /* Which symbols to strip. */
266 enum bfd_link_strip strip;
268 /* Which local symbols to discard. */
269 enum bfd_link_discard discard;
271 /* true if symbols should be retained in memory, false if they
272 should be freed and reread. */
275 /* The list of input BFD's involved in the link. These are chained
276 together via the link_next field. */
279 /* If a symbol should be created for each input BFD, this is section
280 where those symbols should be placed. It must be a section in
281 the output BFD. It may be NULL, in which case no such symbols
282 will be created. This is to support CREATE_OBJECT_SYMBOLS in the
283 linker command language. */
284 asection *create_object_symbols_section;
286 /* List of global symbol names that are starting points for marking
287 sections against garbage collection. */
288 struct bfd_sym_chain *gc_sym_list;
290 /* Hash table handled by BFD. */
291 struct bfd_link_hash_table *hash;
293 /* Hash table of symbols to keep. This is NULL unless strip is
295 struct bfd_hash_table *keep_hash;
297 /* true if every symbol should be reported back via the notice
301 /* Hash table of symbols to report back via the notice callback. If
302 this is NULL, and notice_all is false, then no symbols are
304 struct bfd_hash_table *notice_hash;
306 /* Hash table of symbols which are being wrapped (the --wrap linker
307 option). If this is NULL, no symbols are being wrapped. */
308 struct bfd_hash_table *wrap_hash;
310 /* If a base output file is wanted, then this points to it */
313 /* If non-zero, specifies that branches which are problematic for the
314 MPC860 C0 (or earlier) should be checked for and modified. It gives the
315 number of bytes that should be checked at the end of each text page. */
318 /* The function to call when the executable or shared object is
320 const char *init_function;
322 /* The function to call when the executable or shared object is
324 const char *fini_function;
326 /* true if the new ELF dynamic tags are enabled. */
329 /* May be used to set DT_FLAGS for ELF. */
332 /* May be used to set DT_FLAGS_1 for ELF. */
335 /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
336 should be generated/linked against. Set to 1 if this feature
337 is explicitly requested by the user, -1 if enabled by default. */
338 int pei386_auto_import;
340 /* True if non-PLT relocs should be merged into one reloc section
341 and sorted so that relocs against the same symbol come together. */
344 /* True if executable should not contain copy relocs.
345 Setting this true may result in a non-sharable text segment. */
348 /* True if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
349 should be created. */
350 boolean eh_frame_hdr;
352 /* How many spare .dynamic DT_NULL entries should be added? */
353 unsigned int spare_dynamic_tags;
355 /* Criteria for skipping symbols when detemining
356 whether to include an object from an archive. */
357 enum bfd_link_common_skip_ar_aymbols common_skip_ar_aymbols;
360 /* This structures holds a set of callback functions. These are
361 called by the BFD linker routines. The first argument to each
362 callback function is the bfd_link_info structure being used. Each
363 function returns a boolean value. If the function returns false,
364 then the BFD function which called it will return with a failure
367 struct bfd_link_callbacks
369 /* A function which is called when an object is added from an
370 archive. ABFD is the archive element being added. NAME is the
371 name of the symbol which caused the archive element to be pulled
373 boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
376 /* A function which is called when a symbol is found with multiple
377 definitions. NAME is the symbol which is defined multiple times.
378 OBFD is the old BFD, OSEC is the old section, OVAL is the old
379 value, NBFD is the new BFD, NSEC is the new section, and NVAL is
380 the new value. OBFD may be NULL. OSEC and NSEC may be
381 bfd_com_section or bfd_ind_section. */
382 boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
390 /* A function which is called when a common symbol is defined
391 multiple times. NAME is the symbol appearing multiple times.
392 OBFD is the BFD of the existing symbol; it may be NULL if this is
393 not known. OTYPE is the type of the existing symbol, which may
394 be bfd_link_hash_defined, bfd_link_hash_defweak,
395 bfd_link_hash_common, or bfd_link_hash_indirect. If OTYPE is
396 bfd_link_hash_common, OSIZE is the size of the existing symbol.
397 NBFD is the BFD of the new symbol. NTYPE is the type of the new
398 symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
399 bfd_link_hash_indirect. If NTYPE is bfd_link_hash_common, NSIZE
400 is the size of the new symbol. */
401 boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
404 enum bfd_link_hash_type otype,
407 enum bfd_link_hash_type ntype,
409 /* A function which is called to add a symbol to a set. ENTRY is
410 the link hash table entry for the set itself (e.g.,
411 __CTOR_LIST__). RELOC is the relocation to use for an entry in
412 the set when generating a relocateable file, and is also used to
413 get the size of the entry when generating an executable file.
414 ABFD, SEC and VALUE identify the value to add to the set. */
415 boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
416 struct bfd_link_hash_entry *entry,
417 bfd_reloc_code_real_type reloc,
418 bfd *abfd, asection *sec, bfd_vma value));
419 /* A function which is called when the name of a g++ constructor or
420 destructor is found. This is only called by some object file
421 formats. CONSTRUCTOR is true for a constructor, false for a
422 destructor. This will use BFD_RELOC_CTOR when generating a
423 relocateable file. NAME is the name of the symbol found. ABFD,
424 SECTION and VALUE are the value of the symbol. */
425 boolean (*constructor) PARAMS ((struct bfd_link_info *,
427 const char *name, bfd *abfd, asection *sec,
429 /* A function which is called to issue a linker warning. For
430 example, this is called when there is a reference to a warning
431 symbol. WARNING is the warning to be issued. SYMBOL is the name
432 of the symbol which triggered the warning; it may be NULL if
433 there is none. ABFD, SECTION and ADDRESS identify the location
434 which trigerred the warning; either ABFD or SECTION or both may
435 be NULL if the location is not known. */
436 boolean (*warning) PARAMS ((struct bfd_link_info *,
437 const char *warning, const char *symbol,
438 bfd *abfd, asection *section,
440 /* A function which is called when a relocation is attempted against
441 an undefined symbol. NAME is the symbol which is undefined.
442 ABFD, SECTION and ADDRESS identify the location from which the
443 reference is made. FATAL indicates whether an undefined symbol is
444 a fatal error or not. In some cases SECTION may be NULL. */
445 boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
446 const char *name, bfd *abfd,
450 /* A function which is called when a reloc overflow occurs. NAME is
451 the name of the symbol or section the reloc is against,
452 RELOC_NAME is the name of the relocation, and ADDEND is any
453 addend that is used. ABFD, SECTION and ADDRESS identify the
454 location at which the overflow occurs; if this is the result of a
455 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
456 ABFD will be NULL. */
457 boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
459 const char *reloc_name, bfd_vma addend,
460 bfd *abfd, asection *section,
462 /* A function which is called when a dangerous reloc is performed.
463 The canonical example is an a29k IHCONST reloc which does not
464 follow an IHIHALF reloc. MESSAGE is an appropriate message.
465 ABFD, SECTION and ADDRESS identify the location at which the
466 problem occurred; if this is the result of a
467 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
468 ABFD will be NULL. */
469 boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
471 bfd *abfd, asection *section,
473 /* A function which is called when a reloc is found to be attached
474 to a symbol which is not being written out. NAME is the name of
475 the symbol. ABFD, SECTION and ADDRESS identify the location of
476 the reloc; if this is the result of a
477 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
478 ABFD will be NULL. */
479 boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
481 bfd *abfd, asection *section,
483 /* A function which is called when a symbol in notice_hash is
484 defined or referenced. NAME is the symbol. ABFD, SECTION and
485 ADDRESS are the value of the symbol. If SECTION is
486 bfd_und_section, this is a reference. */
487 boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
488 bfd *abfd, asection *section, bfd_vma address));
491 /* The linker builds link_order structures which tell the code how to
492 include input data in the output file. */
494 /* These are the types of link_order structures. */
496 enum bfd_link_order_type
498 bfd_undefined_link_order, /* Undefined. */
499 bfd_indirect_link_order, /* Built from a section. */
500 bfd_data_link_order, /* Set to explicit data. */
501 bfd_section_reloc_link_order, /* Relocate against a section. */
502 bfd_symbol_reloc_link_order /* Relocate against a symbol. */
505 /* This is the link_order structure itself. These form a chain
506 attached to the section whose contents they are describing. */
508 struct bfd_link_order
510 /* Next link_order in chain. */
511 struct bfd_link_order *next;
512 /* Type of link_order. */
513 enum bfd_link_order_type type;
514 /* Offset within output section. */
516 /* Size within output section. */
518 /* Type specific information. */
523 /* Section to include. If this is used, then
524 section->output_section must be the section the
525 link_order is attached to, section->output_offset must
526 equal the link_order offset field, and section->_raw_size
527 must equal the link_order size field. Maybe these
528 restrictions should be relaxed someday. */
533 /* Size of contents, or zero when contents size == size
534 within output section.
535 A non-zero value allows filling of the output section
536 with an arbitrary repeated pattern. */
538 /* Data to put into file. */
543 /* Description of reloc to generate. Used for
544 bfd_section_reloc_link_order and
545 bfd_symbol_reloc_link_order. */
546 struct bfd_link_order_reloc *p;
551 /* A linker order of type bfd_section_reloc_link_order or
552 bfd_symbol_reloc_link_order means to create a reloc against a
553 section or symbol, respectively. This is used to implement -Ur to
554 generate relocs for the constructor tables. The
555 bfd_link_order_reloc structure describes the reloc that BFD should
556 create. It is similar to a arelent, but I didn't use arelent
557 because the linker does not know anything about most symbols, and
558 any asymbol structure it creates will be partially meaningless.
559 This information could logically be in the bfd_link_order struct,
560 but I didn't want to waste the space since these types of relocs
561 are relatively rare. */
563 struct bfd_link_order_reloc
566 bfd_reloc_code_real_type reloc;
570 /* For type bfd_section_reloc_link_order, this is the section
571 the reloc should be against. This must be a section in the
572 output BFD, not any of the input BFDs. */
574 /* For type bfd_symbol_reloc_link_order, this is the name of the
575 symbol the reloc should be against. */
579 /* Addend to use. The object file should contain zero. The BFD
580 backend is responsible for filling in the contents of the object
581 file correctly. For some object file formats (e.g., COFF) the
582 addend must be stored into in the object file, and for some
583 (e.g., SPARC a.out) it is kept in the reloc. */
587 /* Allocate a new link_order for a section. */
588 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
590 /* These structures are used to describe version information for the
591 ELF linker. These structures could be manipulated entirely inside
592 BFD, but it would be a pain. Instead, the regular linker sets up
593 these structures, and then passes them into BFD. */
595 /* Regular expressions for a version. */
597 struct bfd_elf_version_expr
599 /* Next regular expression for this version. */
600 struct bfd_elf_version_expr *next;
601 /* Regular expression. */
603 /* Matching function. */
604 int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
607 /* Version dependencies. */
609 struct bfd_elf_version_deps
611 /* Next dependency for this version. */
612 struct bfd_elf_version_deps *next;
613 /* The version which this version depends upon. */
614 struct bfd_elf_version_tree *version_needed;
617 /* A node in the version tree. */
619 struct bfd_elf_version_tree
622 struct bfd_elf_version_tree *next;
623 /* Name of this version. */
625 /* Version number. */
627 /* Regular expressions for global symbols in this version. */
628 struct bfd_elf_version_expr *globals;
629 /* Regular expressions for local symbols in this version. */
630 struct bfd_elf_version_expr *locals;
631 /* List of versions which this version depends upon. */
632 struct bfd_elf_version_deps *deps;
633 /* Index of the version name. This is used within BFD. */
634 unsigned int name_indx;
635 /* Whether this version tree was used. This is used within BFD. */