1 /* bfdlink.h -- header file for BFD link routines
2 Copyright 1993 Free Software Foundation, Inc.
3 Written by Steve Chamberlain and Ian Lance Taylor, 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. */
24 /* Which symbols to strip during a link. */
27 strip_none
, /* Don't strip any symbols. */
28 strip_debugger
, /* Strip debugging symbols. */
29 strip_some
, /* keep_hash is the list of symbols to keep. */
30 strip_all
/* Strip all symbols. */
33 /* Which local symbols to discard during a link. This is irrelevant
34 if strip_all is used. */
37 discard_none
, /* Don't discard any locals. */
38 discard_l
, /* Discard locals with a certain prefix. */
39 discard_all
/* Discard all locals. */
42 /* These are the possible types of an entry in the BFD link hash
45 enum bfd_link_hash_type
47 bfd_link_hash_new
, /* Symbol is new. */
48 bfd_link_hash_undefined
, /* Symbol seen before, but undefined. */
49 bfd_link_hash_undefweak
, /* Symbol is weak and undefined. */
50 bfd_link_hash_defined
, /* Symbol is defined. */
51 bfd_link_hash_defweak
, /* Symbol is weak and defined. */
52 bfd_link_hash_common
, /* Symbol is common. */
53 bfd_link_hash_indirect
, /* Symbol is an indirect link. */
54 bfd_link_hash_warning
/* Like indirect, but warn if referenced. */
57 /* The linking routines use a hash table which uses this structure for
60 struct bfd_link_hash_entry
62 /* Base hash table entry structure. */
63 struct bfd_hash_entry root
;
64 /* Type of this entry. */
65 enum bfd_link_hash_type type
;
67 /* Undefined and common symbols are kept in a linked list through
68 this field. This field is not in the union because that would
69 force us to remove entries from the list when we changed their
70 type, which would force the list to be doubly linked, which would
71 waste more memory. When an undefined or common symbol is
72 created, it should be added to this list, the head of which is in
73 the link hash table itself. As symbols are defined, they need
74 not be removed from the list; anything which reads the list must
75 doublecheck the symbol type.
77 Weak symbols are not kept on this list.
79 Defined and defweak symbols use this field as a reference marker.
80 If the field is not NULL, or this structure is the tail of the
81 undefined symbol list, the symbol has been referenced. If the
82 symbol is undefined and becomes defined, this field will
83 automatically be non-NULL since the symbol will have been on the
84 undefined symbol list. */
85 struct bfd_link_hash_entry
*next
;
86 /* A union of information depending upon the type. */
89 /* Nothing is kept for bfd_hash_new. */
90 /* bfd_link_hash_undefined, bfd_link_hash_undefweak. */
93 bfd
*abfd
; /* BFD symbol was found in. */
95 /* bfd_link_hash_defined, bfd_link_hash_defweak. */
98 bfd_vma value
; /* Symbol value. */
99 asection
*section
; /* Symbol section. */
101 /* bfd_link_hash_indirect, bfd_link_hash_warning. */
104 struct bfd_link_hash_entry
*link
; /* Real symbol. */
105 const char *warning
; /* Warning (bfd_link_hash_warning only). */
107 /* bfd_link_hash_common. */
110 /* The linker needs to know three things about common
111 symbols: the size, the alignment, and the section in
112 which the symbol should be placed. On the assumption
113 that a single common symbol will not take up incredible
114 amounts of memory, we pack the size and the alignment
115 into the space of a single integer. The alignment is
116 stored as a power of two. */
117 unsigned int alignment_power
: 6; /* Alignment. */
118 unsigned int size
: 26; /* Common symbol size. */
119 asection
*section
; /* Symbol section. */
124 /* This is the link hash table. It is a derived class of
127 struct bfd_link_hash_table
129 /* The hash table itself. */
130 struct bfd_hash_table table
;
131 /* The back end which created this hash table. This indicates the
132 type of the entries in the hash table, which is sometimes
133 important information when linking object files of different
135 const bfd_target
*creator
;
136 /* A linked list of undefined and common symbols, linked through the
137 next field in the bfd_link_hash_entry structure. */
138 struct bfd_link_hash_entry
*undefs
;
139 /* Entries are added to the tail of the undefs list. */
140 struct bfd_link_hash_entry
*undefs_tail
;
143 /* Look up an entry in a link hash table. If FOLLOW is true, this
144 follows bfd_link_hash_indirect and bfd_link_hash_warning links to
146 extern struct bfd_link_hash_entry
*bfd_link_hash_lookup
147 PARAMS ((struct bfd_link_hash_table
*, const char *, boolean create
,
148 boolean copy
, boolean follow
));
150 /* Traverse a link hash table. */
151 extern void bfd_link_hash_traverse
152 PARAMS ((struct bfd_link_hash_table
*,
153 boolean (*) (struct bfd_link_hash_entry
*, PTR
),
156 /* Add an entry to the undefs list. */
157 extern void bfd_link_add_undef
158 PARAMS ((struct bfd_link_hash_table
*, struct bfd_link_hash_entry
*));
160 /* This structure holds all the information needed to communicate
161 between BFD and the linker when doing a link. */
165 /* Function callbacks. */
166 const struct bfd_link_callbacks
*callbacks
;
167 /* true if BFD should generate a relocateable object file. */
168 boolean relocateable
;
169 /* true if BFD should generate a shared object. */
171 /* Which symbols to strip. */
172 enum bfd_link_strip strip
;
173 /* Which local symbols to discard. */
174 enum bfd_link_discard discard
;
175 /* The local symbol prefix to discard if using discard_l. */
176 unsigned int lprefix_len
;
178 /* true if symbols should be retained in memory, false if they
179 should be freed and reread. */
181 /* The list of input BFD's involved in the link. These are chained
182 together via the link_next field. */
184 /* If a symbol should be created for each input BFD, this is section
185 where those symbols should be placed. It must be a section in
186 the output BFD. It may be NULL, in which case no such symbols
187 will be created. This is to support CREATE_OBJECT_SYMBOLS in the
188 linker command language. */
189 asection
*create_object_symbols_section
;
190 /* Hash table handled by BFD. */
191 struct bfd_link_hash_table
*hash
;
192 /* Hash table of symbols to keep. This is NULL unless strip is
194 struct bfd_hash_table
*keep_hash
;
195 /* Hash table of symbols to report back via notice_callback. If
196 this is NULL no symbols are reported back. */
197 struct bfd_hash_table
*notice_hash
;
200 /* This structures holds a set of callback functions. These are
201 called by the BFD linker routines. The first argument to each
202 callback function is the bfd_link_info structure being used. Each
203 function returns a boolean value. If the function returns false,
204 then the BFD function which called it will return with a failure
207 struct bfd_link_callbacks
209 /* A function which is called when an object is added from an
210 archive. ABFD is the archive element being added. NAME is the
211 name of the symbol which caused the archive element to be pulled
213 boolean (*add_archive_element
) PARAMS ((struct bfd_link_info
*,
216 /* A function which is called when a symbol is found with multiple
217 definitions. NAME is the symbol which is defined multiple times.
218 OBFD is the old BFD, OSEC is the old section, OVAL is the old
219 value, NBFD is the new BFD, NSEC is the new section, and NVAL is
220 the new value. OBFD may be NULL. OSEC and NSEC may be
221 bfd_com_section or bfd_ind_section. */
222 boolean (*multiple_definition
) PARAMS ((struct bfd_link_info
*,
230 /* A function which is called when a common symbol is defined
231 multiple times. NAME is the symbol appearing multiple times.
232 OBFD is the BFD of the existing symbol; it may be NULL if this is
233 not known. OTYPE is the type of the existing symbol, which may
234 be bfd_link_hash_defined, bfd_link_hash_defweak,
235 bfd_link_hash_common, or bfd_link_hash_indirect. If OTYPE is
236 bfd_link_hash_common, OSIZE is the size of the existing symbol.
237 NBFD is the BFD of the new symbol. NTYPE is the type of the new
238 symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
239 bfd_link_hash_indirect. If NTYPE is bfd_link_hash_common, NSIZE
240 is the size of the new symbol. */
241 boolean (*multiple_common
) PARAMS ((struct bfd_link_info
*,
244 enum bfd_link_hash_type otype
,
247 enum bfd_link_hash_type ntype
,
249 /* A function which is called to add a symbol to a set. ENTRY is
250 the link hash table entry for the set itself (e.g.,
251 __CTOR_LIST__). RELOC is the relocation to use for an entry in
252 the set when generating a relocateable file, and is also used to
253 get the size of the entry when generating an executable file.
254 ABFD, SEC and VALUE identify the value to add to the set. */
255 boolean (*add_to_set
) PARAMS ((struct bfd_link_info
*,
256 struct bfd_link_hash_entry
*entry
,
257 bfd_reloc_code_real_type reloc
,
258 bfd
*abfd
, asection
*sec
, bfd_vma value
));
259 /* A function which is called when the name of a g++ constructor or
260 destructor is found. This is only called by some object file
261 formats. CONSTRUCTOR is true for a constructor, false for a
262 destructor. This will use BFD_RELOC_CTOR when generating a
263 relocateable file. NAME is the name of the symbol found. ABFD,
264 SECTION and VALUE are the value of the symbol. */
265 boolean (*constructor
) PARAMS ((struct bfd_link_info
*,
267 const char *name
, bfd
*abfd
, asection
*sec
,
269 /* A function which is called when there is a reference to a warning
270 symbol. WARNING is the warning to be issued. */
271 boolean (*warning
) PARAMS ((struct bfd_link_info
*,
272 const char *warning
));
273 /* A function which is called when a relocation is attempted against
274 an undefined symbol. NAME is the symbol which is undefined.
275 ABFD, SECTION and ADDRESS identify the location from which the
276 reference is made. In some cases SECTION may be NULL. */
277 boolean (*undefined_symbol
) PARAMS ((struct bfd_link_info
*,
278 const char *name
, bfd
*abfd
,
279 asection
*section
, bfd_vma address
));
280 /* A function which is called when a reloc overflow occurs. NAME is
281 the name of the symbol or section the reloc is against,
282 RELOC_NAME is the name of the relocation, and ADDEND is any
283 addend that is used. ABFD, SECTION and ADDRESS identify the
284 location at which the overflow occurs; if this is the result of a
285 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
286 ABFD will be NULL. */
287 boolean (*reloc_overflow
) PARAMS ((struct bfd_link_info
*,
289 const char *reloc_name
, bfd_vma addend
,
290 bfd
*abfd
, asection
*section
,
292 /* A function which is called when a dangerous reloc is performed.
293 The canonical example is an a29k IHCONST reloc which does not
294 follow an IHIHALF reloc. MESSAGE is an appropriate message.
295 ABFD, SECTION and ADDRESS identify the location at which the
296 problem occurred; if this is the result of a
297 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
298 ABFD will be NULL. */
299 boolean (*reloc_dangerous
) PARAMS ((struct bfd_link_info
*,
301 bfd
*abfd
, asection
*section
,
303 /* A function which is called when a reloc is found to be attached
304 to a symbol which is not being written out. NAME is the name of
305 the symbol. ABFD, SECTION and ADDRESS identify the location of
306 the reloc; if this is the result of a
307 bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
308 ABFD will be NULL. */
309 boolean (*unattached_reloc
) PARAMS ((struct bfd_link_info
*,
311 bfd
*abfd
, asection
*section
,
313 /* A function which is called when a symbol in notice_hash is
314 defined or referenced. NAME is the symbol. ABFD, SECTION and
315 ADDRESS are the value of the symbol. If SECTION is
316 bfd_und_section, this is a reference. */
317 boolean (*notice
) PARAMS ((struct bfd_link_info
*, const char *name
,
318 bfd
*abfd
, asection
*section
, bfd_vma address
));
321 /* The linker builds link_order structures which tell the code how to
322 include input data in the output file. */
324 /* These are the types of link_order structures. */
326 enum bfd_link_order_type
328 bfd_undefined_link_order
, /* Undefined. */
329 bfd_indirect_link_order
, /* Built from a section. */
330 bfd_fill_link_order
, /* Fill with a 16 bit constant. */
331 bfd_data_link_order
, /* Set to explicit data. */
332 bfd_section_reloc_link_order
, /* Relocate against a section. */
333 bfd_symbol_reloc_link_order
/* Relocate against a symbol. */
336 /* This is the link_order structure itself. These form a chain
337 attached to the section whose contents they are describing. */
339 struct bfd_link_order
341 /* Next link_order in chain. */
342 struct bfd_link_order
*next
;
343 /* Type of link_order. */
344 enum bfd_link_order_type type
;
345 /* Offset within output section. */
347 /* Size within output section. */
349 /* Type specific information. */
354 /* Section to include. If this is used, then
355 section->output_section must be the section the
356 link_order is attached to, section->output_offset must
357 equal the link_order offset field, and section->_raw_size
358 must equal the link_order size field. Maybe these
359 restrictions should be relaxed someday. */
364 /* Value to fill with. */
369 /* Data to put into file. The size field gives the number
370 of bytes which this field points to. */
375 /* Description of reloc to generate. Used for
376 bfd_section_reloc_link_order and
377 bfd_symbol_reloc_link_order. */
378 struct bfd_link_order_reloc
*p
;
383 /* A linker order of type bfd_section_reloc_link_order or
384 bfd_symbol_reloc_link_order means to create a reloc against a
385 section or symbol, respectively. This is used to implement -Ur to
386 generate relocs for the constructor tables. The
387 bfd_link_order_reloc structure describes the reloc that BFD should
388 create. It is similar to a arelent, but I didn't use arelent
389 because the linker does not know anything about most symbols, and
390 any asymbol structure it creates will be partially meaningless.
391 This information could logically be in the bfd_link_order struct,
392 but I didn't want to waste the space since these types of relocs
393 are relatively rare. */
395 struct bfd_link_order_reloc
398 bfd_reloc_code_real_type reloc
;
402 /* For type bfd_section_reloc_link_order, this is the section
403 the reloc should be against. This must be a section in the
404 output BFD, not any of the input BFDs. */
406 /* For type bfd_symbol_reloc_link_order, this is the name of the
407 symbol the reloc should be against. */
411 /* Addend to use. The object file should contain zero. The BFD
412 backend is responsible for filling in the contents of the object
413 file correctly. For some object file formats (e.g., COFF) the
414 addend must be stored into in the object file, and for some
415 (e.g., SPARC a.out) it is kept in the reloc. */
419 /* Allocate a new link_order for a section. */
420 extern struct bfd_link_order
*bfd_new_link_order
PARAMS ((bfd
*, asection
*));