include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
   3    2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   4    Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
   5
   6    This file is part of BFD, the Binary File Descriptor library.
   7
   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 3 of the License, or
  11    (at your option) any later version.
  12
  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.
  17
  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., 51 Franklin Street - Fifth Floor, Boston,
  21    MA 02110-1301, USA.  */
  22
  23 #ifndef BFDLINK_H
  24 #define BFDLINK_H
  25
  26 /* Which symbols to strip during a link.  */
  27 enum bfd_link_strip
  28 {
  29   strip_none,           /* Don't strip any symbols.  */
  30   strip_debugger,       /* Strip debugging symbols.  */
  31   strip_some,           /* keep_hash is the list of symbols to keep.  */
  32   strip_all             /* Strip all symbols.  */
  33 };
  34
  35 /* Which local symbols to discard during a link.  This is irrelevant
  36    if strip_all is used.  */
  37 enum bfd_link_discard
  38 {
  39   discard_sec_merge,    /* Discard local temporary symbols in SEC_MERGE
  40                            sections.  */
  41   discard_none,         /* Don't discard any locals.  */
  42   discard_l,            /* Discard local temporary symbols.  */
  43   discard_all           /* Discard all locals.  */
  44 };
  45
  46 /* Describes the type of hash table entry structure being used.
  47    Different hash table structure have different fields and so
  48    support different linking features.  */
  49 enum bfd_link_hash_table_type
  50   {
  51     bfd_link_generic_hash_table,
  52     bfd_link_elf_hash_table
  53   };
  54 \f
  55 /* These are the possible types of an entry in the BFD link hash
  56    table.  */
  57
  58 enum bfd_link_hash_type
  59 {
  60   bfd_link_hash_new,            /* Symbol is new.  */
  61   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  62   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  63   bfd_link_hash_defined,        /* Symbol is defined.  */
  64   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  65   bfd_link_hash_common,         /* Symbol is common.  */
  66   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  67   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  68 };
  69
  70 enum bfd_link_common_skip_ar_aymbols
  71 {
  72   bfd_link_common_skip_none,
  73   bfd_link_common_skip_text,
  74   bfd_link_common_skip_data,
  75   bfd_link_common_skip_all
  76 };
  77
  78 /* The linking routines use a hash table which uses this structure for
  79    its elements.  */
  80
  81 struct bfd_link_hash_entry
  82 {
  83   /* Base hash table entry structure.  */
  84   struct bfd_hash_entry root;
  85
  86   /* Type of this entry.  */
  87   enum bfd_link_hash_type type;
  88
  89   /* A union of information depending upon the type.  */
  90   union
  91     {
  92       /* Nothing is kept for bfd_hash_new.  */
  93       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
  94       struct
  95         {
  96           /* Undefined and common symbols are kept in a linked list through
  97              this field.  This field is present in all of the union element
  98              so that we don't need to remove entries from the list when we
  99              change their type.  Removing entries would either require the
 100              list to be doubly linked, which would waste more memory, or
 101              require a traversal.  When an undefined or common symbol is
 102              created, it should be added to this list, the head of which is in
 103              the link hash table itself.  As symbols are defined, they need
 104              not be removed from the list; anything which reads the list must
 105              doublecheck the symbol type.
 106
 107              Weak symbols are not kept on this list.
 108
 109              Defined and defweak symbols use this field as a reference marker.
 110              If the field is not NULL, or this structure is the tail of the
 111              undefined symbol list, the symbol has been referenced.  If the
 112              symbol is undefined and becomes defined, this field will
 113              automatically be non-NULL since the symbol will have been on the
 114              undefined symbol list.  */
 115           struct bfd_link_hash_entry *next;
 116           bfd *abfd;            /* BFD symbol was found in.  */
 117           bfd *weak;            /* BFD weak symbol was found in.  */
 118         } undef;
 119       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 120       struct
 121         {
 122           struct bfd_link_hash_entry *next;
 123           asection *section;    /* Symbol section.  */
 124           bfd_vma value;        /* Symbol value.  */
 125         } def;
 126       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 127       struct
 128         {
 129           struct bfd_link_hash_entry *next;
 130           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 131           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 132         } i;
 133       /* bfd_link_hash_common.  */
 134       struct
 135         {
 136           struct bfd_link_hash_entry *next;
 137           /* The linker needs to know three things about common
 138              symbols: the size, the alignment, and the section in
 139              which the symbol should be placed.  We store the size
 140              here, and we allocate a small structure to hold the
 141              section and the alignment.  The alignment is stored as a
 142              power of two.  We don't store all the information
 143              directly because we don't want to increase the size of
 144              the union; this structure is a major space user in the
 145              linker.  */
 146           struct bfd_link_hash_common_entry
 147             {
 148               unsigned int alignment_power;     /* Alignment.  */
 149               asection *section;                /* Symbol section.  */
 150             } *p;
 151           bfd_size_type size;   /* Common symbol size.  */
 152         } c;
 153     } u;
 154 };
 155
 156 /* This is the link hash table.  It is a derived class of
 157    bfd_hash_table.  */
 158
 159 struct bfd_link_hash_table
 160 {
 161   /* The hash table itself.  */
 162   struct bfd_hash_table table;
 163   /* A linked list of undefined and common symbols, linked through the
 164      next field in the bfd_link_hash_entry structure.  */
 165   struct bfd_link_hash_entry *undefs;
 166   /* Entries are added to the tail of the undefs list.  */
 167   struct bfd_link_hash_entry *undefs_tail;
 168   /* The type of the link hash table.  */
 169   enum bfd_link_hash_table_type type;
 170 };
 171
 172 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 173    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 174    the real symbol.  */
 175 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 176   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 177    bfd_boolean copy, bfd_boolean follow);
 178
 179 /* Look up an entry in the main linker hash table if the symbol might
 180    be wrapped.  This should only be used for references to an
 181    undefined symbol, not for definitions of a symbol.  */
 182
 183 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 184   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 185    bfd_boolean, bfd_boolean);
 186
 187 /* Traverse a link hash table.  */
 188 extern void bfd_link_hash_traverse
 189   (struct bfd_link_hash_table *,
 190     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 191     void *);
 192
 193 /* Add an entry to the undefs list.  */
 194 extern void bfd_link_add_undef
 195   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 196
 197 /* Remove symbols from the undefs list that don't belong there.  */
 198 extern void bfd_link_repair_undef_list
 199   (struct bfd_link_hash_table *table);
 200
 201 struct bfd_sym_chain
 202 {
 203   struct bfd_sym_chain *next;
 204   const char *name;
 205 };
 206 \f
 207 /* How to handle unresolved symbols.
 208    There are four possibilities which are enumerated below:  */
 209 enum report_method
 210 {
 211   /* This is the initial value when then link_info structure is created.
 212      It allows the various stages of the linker to determine whether they
 213      allowed to set the value.  */
 214   RM_NOT_YET_SET = 0,
 215   RM_IGNORE,
 216   RM_GENERATE_WARNING,
 217   RM_GENERATE_ERROR
 218 };
 219
 220 struct bfd_elf_dynamic_list;
 221
 222 /* This structure holds all the information needed to communicate
 223    between BFD and the linker when doing a link.  */
 224
 225 struct bfd_link_info
 226 {
 227   /* TRUE if BFD should generate a relocatable object file.  */
 228   unsigned int relocatable: 1;
 229
 230   /* TRUE if BFD should generate relocation information in the final
 231      executable.  */
 232   unsigned int emitrelocations: 1;
 233
 234   /* TRUE if BFD should generate a "task linked" object file,
 235      similar to relocatable but also with globals converted to
 236      statics.  */
 237   unsigned int task_link: 1;
 238
 239   /* TRUE if BFD should generate a shared object.  */
 240   unsigned int shared: 1;
 241
 242   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 243   unsigned int symbolic: 1;
 244
 245   /* TRUE if BFD should export all symbols in the dynamic symbol table
 246      of an executable, rather than only those used.  */
 247   unsigned int export_dynamic: 1;
 248
 249   /* TRUE if shared objects should be linked directly, not shared.  */
 250   unsigned int static_link: 1;
 251
 252   /* TRUE if the output file should be in a traditional format.  This
 253      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 254      on the output file, but may be checked when reading the input
 255      files.  */
 256   unsigned int traditional_format: 1;
 257
 258   /* TRUE if we want to produced optimized output files.  This might
 259      need much more time and therefore must be explicitly selected.  */
 260   unsigned int optimize: 1;
 261
 262   /* TRUE if ok to have multiple definition.  */
 263   unsigned int allow_multiple_definition: 1;
 264
 265   /* TRUE if ok to have version with no definition.  */
 266   unsigned int allow_undefined_version: 1;
 267
 268   /* TRUE if a default symbol version should be created and used for
 269      exported symbols.  */
 270   unsigned int create_default_symver: 1;
 271
 272   /* TRUE if a default symbol version should be created and used for
 273      imported symbols.  */
 274   unsigned int default_imported_symver: 1;
 275
 276   /* TRUE if symbols should be retained in memory, FALSE if they
 277      should be freed and reread.  */
 278   unsigned int keep_memory: 1;
 279
 280   /* TRUE if every symbol should be reported back via the notice
 281      callback.  */
 282   unsigned int notice_all: 1;
 283
 284   /* TRUE if executable should not contain copy relocs.
 285      Setting this true may result in a non-sharable text segment.  */
 286   unsigned int nocopyreloc: 1;
 287
 288   /* TRUE if the new ELF dynamic tags are enabled. */
 289   unsigned int new_dtags: 1;
 290
 291   /* TRUE if non-PLT relocs should be merged into one reloc section
 292      and sorted so that relocs against the same symbol come together.  */
 293   unsigned int combreloc: 1;
 294
 295   /* TRUE if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 296      should be created.  */
 297   unsigned int eh_frame_hdr: 1;
 298
 299   /* TRUE if global symbols in discarded sections should be stripped.  */
 300   unsigned int strip_discarded: 1;
 301
 302   /* TRUE if generating a position independent executable.  */
 303   unsigned int pie: 1;
 304
 305   /* TRUE if generating an executable, position independent or not.  */
 306   unsigned int executable : 1;
 307
 308   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 309      flags.  */
 310   unsigned int execstack: 1;
 311
 312   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 313      flags.  */
 314   unsigned int noexecstack: 1;
 315
 316   /* TRUE if PT_GNU_RELRO segment should be created.  */
 317   unsigned int relro: 1;
 318
 319   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 320   unsigned int warn_shared_textrel: 1;
 321
 322   /* TRUE if unreferenced sections should be removed.  */
 323   unsigned int gc_sections: 1;
 324
 325   /* TRUE if user shoudl be informed of removed unreferenced sections.  */
 326   unsigned int print_gc_sections: 1;
 327
 328   /* TRUE if .hash section should be created.  */
 329   unsigned int emit_hash: 1;
 330
 331   /* TRUE if .gnu.hash section should be created.  */
 332   unsigned int emit_gnu_hash: 1;
 333
 334   /* If TRUE reduce memory overheads, at the expense of speed. This will
 335      cause map file generation to use an O(N^2) algorithm and disable
 336      caching ELF symbol buffer.  */
 337   unsigned int reduce_memory_overheads: 1;
 338
 339   /* TRUE if all data symbols should be dynamic.  */
 340    unsigned int dynamic_data: 1;
 341
 342   /* TRUE if some symbols have to be dynamic, controlled by
 343      --dynamic-list command line options.  */
 344   unsigned int dynamic: 1;
 345
 346   /* Non-NULL if .note.gnu.build-id section should be created.  */
 347   char *emit_note_gnu_build_id;
 348
 349   /* What to do with unresolved symbols in an object file.
 350      When producing executables the default is GENERATE_ERROR.
 351      When producing shared libraries the default is IGNORE.  The
 352      assumption with shared libraries is that the reference will be
 353      resolved at load/execution time.  */
 354   enum report_method unresolved_syms_in_objects;
 355
 356   /* What to do with unresolved symbols in a shared library.
 357      The same defaults apply.  */
 358   enum report_method unresolved_syms_in_shared_libs;
 359
 360   /* Which symbols to strip.  */
 361   enum bfd_link_strip strip;
 362
 363   /* Which local symbols to discard.  */
 364   enum bfd_link_discard discard;
 365
 366   /* Criteria for skipping symbols when detemining
 367      whether to include an object from an archive. */
 368   enum bfd_link_common_skip_ar_aymbols common_skip_ar_aymbols;
 369
 370   /* Char that may appear as the first char of a symbol, but should be
 371      skipped (like symbol_leading_char) when looking up symbols in
 372      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 373   char wrap_char;
 374
 375   /* Function callbacks.  */
 376   const struct bfd_link_callbacks *callbacks;
 377
 378   /* Hash table handled by BFD.  */
 379   struct bfd_link_hash_table *hash;
 380
 381   /* Hash table of symbols to keep.  This is NULL unless strip is
 382      strip_some.  */
 383   struct bfd_hash_table *keep_hash;
 384
 385   /* Hash table of symbols to report back via the notice callback.  If
 386      this is NULL, and notice_all is FALSE, then no symbols are
 387      reported back.  */
 388   struct bfd_hash_table *notice_hash;
 389
 390   /* Hash table of symbols which are being wrapped (the --wrap linker
 391      option).  If this is NULL, no symbols are being wrapped.  */
 392   struct bfd_hash_table *wrap_hash;
 393
 394   /* The output BFD.  */
 395   bfd *output_bfd;
 396
 397   /* The list of input BFD's involved in the link.  These are chained
 398      together via the link_next field.  */
 399   bfd *input_bfds;
 400   bfd **input_bfds_tail;
 401
 402   /* If a symbol should be created for each input BFD, this is section
 403      where those symbols should be placed.  It must be a section in
 404      the output BFD.  It may be NULL, in which case no such symbols
 405      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 406      linker command language.  */
 407   asection *create_object_symbols_section;
 408
 409   /* List of global symbol names that are starting points for marking
 410      sections against garbage collection.  */
 411   struct bfd_sym_chain *gc_sym_list;
 412
 413   /* If a base output file is wanted, then this points to it */
 414   void *base_file;
 415
 416   /* The function to call when the executable or shared object is
 417      loaded.  */
 418   const char *init_function;
 419
 420   /* The function to call when the executable or shared object is
 421      unloaded.  */
 422   const char *fini_function;
 423
 424   /* Number of relaxation passes.  Usually only one relaxation pass
 425      is needed.  But a backend can have as many relaxation passes as
 426      necessary.  During bfd_relax_section call, it is set to the
 427      current pass, starting from 0.  */
 428   int relax_pass;
 429
 430   /* Number of relaxation trips.  This number is incremented every
 431      time the relaxation pass is restarted due to a previous
 432      relaxation returning true in *AGAIN.  */
 433   int relax_trip;
 434
 435   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 436      should be generated/linked against.  Set to 1 if this feature
 437      is explicitly requested by the user, -1 if enabled by default.  */
 438   int pei386_auto_import;
 439
 440   /* Non-zero if runtime relocs for DATA items with non-zero addends
 441      in pei386 DLLs should be generated.  Set to 1 if this feature
 442      is explicitly requested by the user, -1 if enabled by default.  */
 443   int pei386_runtime_pseudo_reloc;
 444
 445   /* How many spare .dynamic DT_NULL entries should be added?  */
 446   unsigned int spare_dynamic_tags;
 447
 448   /* May be used to set DT_FLAGS for ELF. */
 449   bfd_vma flags;
 450
 451   /* May be used to set DT_FLAGS_1 for ELF. */
 452   bfd_vma flags_1;
 453
 454   /* Start and end of RELRO region.  */
 455   bfd_vma relro_start, relro_end;
 456
 457   /* List of symbols should be dynamic.  */
 458   struct bfd_elf_dynamic_list *dynamic_list;
 459 };
 460
 461 /* This structures holds a set of callback functions.  These are called
 462    by the BFD linker routines.  Except for the info functions, the first
 463    argument to each callback function is the bfd_link_info structure
 464    being used and each function returns a boolean value.  If the
 465    function returns FALSE, then the BFD function which called it should
 466    return with a failure indication.  */
 467
 468 struct bfd_link_callbacks
 469 {
 470   /* A function which is called when an object is added from an
 471      archive.  ABFD is the archive element being added.  NAME is the
 472      name of the symbol which caused the archive element to be pulled
 473      in.  */
 474   bfd_boolean (*add_archive_element)
 475     (struct bfd_link_info *, bfd *abfd, const char *name);
 476   /* A function which is called when a symbol is found with multiple
 477      definitions.  NAME is the symbol which is defined multiple times.
 478      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 479      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 480      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 481      bfd_com_section or bfd_ind_section.  */
 482   bfd_boolean (*multiple_definition)
 483     (struct bfd_link_info *, const char *name,
 484      bfd *obfd, asection *osec, bfd_vma oval,
 485      bfd *nbfd, asection *nsec, bfd_vma nval);
 486   /* A function which is called when a common symbol is defined
 487      multiple times.  NAME is the symbol appearing multiple times.
 488      OBFD is the BFD of the existing symbol; it may be NULL if this is
 489      not known.  OTYPE is the type of the existing symbol, which may
 490      be bfd_link_hash_defined, bfd_link_hash_defweak,
 491      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 492      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 493      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 494      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 495      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 496      is the size of the new symbol.  */
 497   bfd_boolean (*multiple_common)
 498     (struct bfd_link_info *, const char *name,
 499      bfd *obfd, enum bfd_link_hash_type otype, bfd_vma osize,
 500      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 501   /* A function which is called to add a symbol to a set.  ENTRY is
 502      the link hash table entry for the set itself (e.g.,
 503      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 504      the set when generating a relocatable file, and is also used to
 505      get the size of the entry when generating an executable file.
 506      ABFD, SEC and VALUE identify the value to add to the set.  */
 507   bfd_boolean (*add_to_set)
 508     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 509      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 510   /* A function which is called when the name of a g++ constructor or
 511      destructor is found.  This is only called by some object file
 512      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 513      destructor.  This will use BFD_RELOC_CTOR when generating a
 514      relocatable file.  NAME is the name of the symbol found.  ABFD,
 515      SECTION and VALUE are the value of the symbol.  */
 516   bfd_boolean (*constructor)
 517     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 518      bfd *abfd, asection *sec, bfd_vma value);
 519   /* A function which is called to issue a linker warning.  For
 520      example, this is called when there is a reference to a warning
 521      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 522      of the symbol which triggered the warning; it may be NULL if
 523      there is none.  ABFD, SECTION and ADDRESS identify the location
 524      which trigerred the warning; either ABFD or SECTION or both may
 525      be NULL if the location is not known.  */
 526   bfd_boolean (*warning)
 527     (struct bfd_link_info *, const char *warning, const char *symbol,
 528      bfd *abfd, asection *section, bfd_vma address);
 529   /* A function which is called when a relocation is attempted against
 530      an undefined symbol.  NAME is the symbol which is undefined.
 531      ABFD, SECTION and ADDRESS identify the location from which the
 532      reference is made. FATAL indicates whether an undefined symbol is
 533      a fatal error or not. In some cases SECTION may be NULL.  */
 534   bfd_boolean (*undefined_symbol)
 535     (struct bfd_link_info *, const char *name, bfd *abfd,
 536      asection *section, bfd_vma address, bfd_boolean fatal);
 537   /* A function which is called when a reloc overflow occurs. ENTRY is
 538      the link hash table entry for the symbol the reloc is against.
 539      NAME is the name of the local symbol or section the reloc is
 540      against, RELOC_NAME is the name of the relocation, and ADDEND is
 541      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 542      location at which the overflow occurs; if this is the result of a
 543      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 544      ABFD will be NULL.  */
 545   bfd_boolean (*reloc_overflow)
 546     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 547      const char *name, const char *reloc_name, bfd_vma addend,
 548      bfd *abfd, asection *section, bfd_vma address);
 549   /* A function which is called when a dangerous reloc is performed.
 550      MESSAGE is an appropriate message.
 551      ABFD, SECTION and ADDRESS identify the location at which the
 552      problem occurred; if this is the result of a
 553      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 554      ABFD will be NULL.  */
 555   bfd_boolean (*reloc_dangerous)
 556     (struct bfd_link_info *, const char *message,
 557      bfd *abfd, asection *section, bfd_vma address);
 558   /* A function which is called when a reloc is found to be attached
 559      to a symbol which is not being written out.  NAME is the name of
 560      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 561      the reloc; if this is the result of a
 562      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 563      ABFD will be NULL.  */
 564   bfd_boolean (*unattached_reloc)
 565     (struct bfd_link_info *, const char *name,
 566      bfd *abfd, asection *section, bfd_vma address);
 567   /* A function which is called when a symbol in notice_hash is
 568      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 569      ADDRESS are the value of the symbol.  If SECTION is
 570      bfd_und_section, this is a reference.  */
 571   bfd_boolean (*notice)
 572     (struct bfd_link_info *, const char *name,
 573      bfd *abfd, asection *section, bfd_vma address);
 574   /* Error or warning link info message.  */
 575   void (*einfo)
 576     (const char *fmt, ...);
 577   /* General link info message.  */
 578   void (*info)
 579     (const char *fmt, ...);
 580   /* Message to be printed in linker map file.  */
 581   void (*minfo)
 582     (const char *fmt, ...);
 583   /* This callback provides a chance for users of the BFD library to
 584      override its decision about whether to place two adjacent sections
 585      into the same segment.  */
 586   bfd_boolean (*override_segment_assignment)
 587     (struct bfd_link_info *, bfd * abfd,
 588      asection * current_section, asection * previous_section,
 589      bfd_boolean new_segment);
 590 };
 591 \f
 592 /* The linker builds link_order structures which tell the code how to
 593    include input data in the output file.  */
 594
 595 /* These are the types of link_order structures.  */
 596
 597 enum bfd_link_order_type
 598 {
 599   bfd_undefined_link_order,     /* Undefined.  */
 600   bfd_indirect_link_order,      /* Built from a section.  */
 601   bfd_data_link_order,          /* Set to explicit data.  */
 602   bfd_section_reloc_link_order, /* Relocate against a section.  */
 603   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 604 };
 605
 606 /* This is the link_order structure itself.  These form a chain
 607    attached to the output section whose contents they are describing.  */
 608
 609 struct bfd_link_order
 610 {
 611   /* Next link_order in chain.  */
 612   struct bfd_link_order *next;
 613   /* Type of link_order.  */
 614   enum bfd_link_order_type type;
 615   /* Offset within output section.  */
 616   bfd_vma offset;
 617   /* Size within output section.  */
 618   bfd_size_type size;
 619   /* Type specific information.  */
 620   union
 621     {
 622       struct
 623         {
 624           /* Section to include.  If this is used, then
 625              section->output_section must be the section the
 626              link_order is attached to, section->output_offset must
 627              equal the link_order offset field, and section->size
 628              must equal the link_order size field.  Maybe these
 629              restrictions should be relaxed someday.  */
 630           asection *section;
 631         } indirect;
 632       struct
 633         {
 634           /* Size of contents, or zero when contents size == size
 635              within output section.
 636              A non-zero value allows filling of the output section
 637              with an arbitrary repeated pattern.  */
 638           unsigned int size;
 639           /* Data to put into file.  */
 640           bfd_byte *contents;
 641         } data;
 642       struct
 643         {
 644           /* Description of reloc to generate.  Used for
 645              bfd_section_reloc_link_order and
 646              bfd_symbol_reloc_link_order.  */
 647           struct bfd_link_order_reloc *p;
 648         } reloc;
 649     } u;
 650 };
 651
 652 /* A linker order of type bfd_section_reloc_link_order or
 653    bfd_symbol_reloc_link_order means to create a reloc against a
 654    section or symbol, respectively.  This is used to implement -Ur to
 655    generate relocs for the constructor tables.  The
 656    bfd_link_order_reloc structure describes the reloc that BFD should
 657    create.  It is similar to a arelent, but I didn't use arelent
 658    because the linker does not know anything about most symbols, and
 659    any asymbol structure it creates will be partially meaningless.
 660    This information could logically be in the bfd_link_order struct,
 661    but I didn't want to waste the space since these types of relocs
 662    are relatively rare.  */
 663
 664 struct bfd_link_order_reloc
 665 {
 666   /* Reloc type.  */
 667   bfd_reloc_code_real_type reloc;
 668
 669   union
 670     {
 671       /* For type bfd_section_reloc_link_order, this is the section
 672          the reloc should be against.  This must be a section in the
 673          output BFD, not any of the input BFDs.  */
 674       asection *section;
 675       /* For type bfd_symbol_reloc_link_order, this is the name of the
 676          symbol the reloc should be against.  */
 677       const char *name;
 678     } u;
 679
 680   /* Addend to use.  The object file should contain zero.  The BFD
 681      backend is responsible for filling in the contents of the object
 682      file correctly.  For some object file formats (e.g., COFF) the
 683      addend must be stored into in the object file, and for some
 684      (e.g., SPARC a.out) it is kept in the reloc.  */
 685   bfd_vma addend;
 686 };
 687
 688 /* Allocate a new link_order for a section.  */
 689 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 690
 691 /* These structures are used to describe version information for the
 692    ELF linker.  These structures could be manipulated entirely inside
 693    BFD, but it would be a pain.  Instead, the regular linker sets up
 694    these structures, and then passes them into BFD.  */
 695
 696 /* Glob pattern for a version.  */
 697
 698 struct bfd_elf_version_expr
 699 {
 700   /* Next glob pattern for this version.  */
 701   struct bfd_elf_version_expr *next;
 702   /* Glob pattern.  */
 703   const char *pattern;
 704   /* NULL for a glob pattern, otherwise a straight symbol.  */
 705   const char *symbol;
 706   /* Defined by ".symver".  */
 707   unsigned int symver : 1;
 708   /* Defined by version script.  */
 709   unsigned int script : 1;
 710   /* Pattern type.  */
 711 #define BFD_ELF_VERSION_C_TYPE          1
 712 #define BFD_ELF_VERSION_CXX_TYPE        2
 713 #define BFD_ELF_VERSION_JAVA_TYPE       4
 714   unsigned int mask : 3;
 715 };
 716
 717 struct bfd_elf_version_expr_head
 718 {
 719   /* List of all patterns, both wildcards and non-wildcards.  */
 720   struct bfd_elf_version_expr *list;
 721   /* Hash table for non-wildcards.  */
 722   void *htab;
 723   /* Remaining patterns.  */
 724   struct bfd_elf_version_expr *remaining;
 725   /* What kind of pattern types are present in list (bitmask).  */
 726   unsigned int mask;
 727 };
 728
 729 /* Version dependencies.  */
 730
 731 struct bfd_elf_version_deps
 732 {
 733   /* Next dependency for this version.  */
 734   struct bfd_elf_version_deps *next;
 735   /* The version which this version depends upon.  */
 736   struct bfd_elf_version_tree *version_needed;
 737 };
 738
 739 /* A node in the version tree.  */
 740
 741 struct bfd_elf_version_tree
 742 {
 743   /* Next version.  */
 744   struct bfd_elf_version_tree *next;
 745   /* Name of this version.  */
 746   const char *name;
 747   /* Version number.  */
 748   unsigned int vernum;
 749   /* Regular expressions for global symbols in this version.  */
 750   struct bfd_elf_version_expr_head globals;
 751   /* Regular expressions for local symbols in this version.  */
 752   struct bfd_elf_version_expr_head locals;
 753   /* List of versions which this version depends upon.  */
 754   struct bfd_elf_version_deps *deps;
 755   /* Index of the version name.  This is used within BFD.  */
 756   unsigned int name_indx;
 757   /* Whether this version tree was used.  This is used within BFD.  */
 758   int used;
 759   /* Matching hook.  */
 760   struct bfd_elf_version_expr *(*match)
 761     (struct bfd_elf_version_expr_head *head,
 762      struct bfd_elf_version_expr *prev, const char *sym);
 763 };
 764
 765 struct bfd_elf_dynamic_list
 766 {
 767   struct bfd_elf_version_expr_head head;
 768   struct bfd_elf_version_expr *(*match)
 769     (struct bfd_elf_version_expr_head *head,
 770      struct bfd_elf_version_expr *prev, const char *sym);
 771 };
 772
 773 #endif