include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2014 Free Software Foundation, Inc.
   3    Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   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 3 of the License, or
  10    (at your option) any later version.
  11
  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.
  16
  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., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 #ifndef BFDLINK_H
  23 #define BFDLINK_H
  24
  25 /* Which symbols to strip during a link.  */
  26 enum bfd_link_strip
  27 {
  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.  */
  32 };
  33
  34 /* Which local symbols to discard during a link.  This is irrelevant
  35    if strip_all is used.  */
  36 enum bfd_link_discard
  37 {
  38   discard_sec_merge,    /* Discard local temporary symbols in SEC_MERGE
  39                            sections.  */
  40   discard_none,         /* Don't discard any locals.  */
  41   discard_l,            /* Discard local temporary symbols.  */
  42   discard_all           /* Discard all locals.  */
  43 };
  44
  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
  49   {
  50     bfd_link_generic_hash_table,
  51     bfd_link_elf_hash_table
  52   };
  53 \f
  54 /* These are the possible types of an entry in the BFD link hash
  55    table.  */
  56
  57 enum bfd_link_hash_type
  58 {
  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.  */
  67 };
  68
  69 enum bfd_link_common_skip_ar_symbols
  70 {
  71   bfd_link_common_skip_none,
  72   bfd_link_common_skip_text,
  73   bfd_link_common_skip_data,
  74   bfd_link_common_skip_all
  75 };
  76
  77 struct bfd_link_hash_common_entry
  78   {
  79     unsigned int alignment_power;       /* Alignment.  */
  80     asection *section;          /* Symbol section.  */
  81   };
  82
  83 /* The linking routines use a hash table which uses this structure for
  84    its elements.  */
  85
  86 struct bfd_link_hash_entry
  87 {
  88   /* Base hash table entry structure.  */
  89   struct bfd_hash_entry root;
  90
  91   /* Type of this entry.  */
  92   ENUM_BITFIELD (bfd_link_hash_type) type : 8;
  93
  94   unsigned int non_ir_ref : 1;
  95
  96   /* A union of information depending upon the type.  */
  97   union
  98     {
  99       /* Nothing is kept for bfd_hash_new.  */
 100       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 101       struct
 102         {
 103           /* Undefined and common symbols are kept in a linked list through
 104              this field.  This field is present in all of the union element
 105              so that we don't need to remove entries from the list when we
 106              change their type.  Removing entries would either require the
 107              list to be doubly linked, which would waste more memory, or
 108              require a traversal.  When an undefined or common symbol is
 109              created, it should be added to this list, the head of which is in
 110              the link hash table itself.  As symbols are defined, they need
 111              not be removed from the list; anything which reads the list must
 112              doublecheck the symbol type.
 113
 114              Weak symbols are not kept on this list.
 115
 116              Defined and defweak symbols use this field as a reference marker.
 117              If the field is not NULL, or this structure is the tail of the
 118              undefined symbol list, the symbol has been referenced.  If the
 119              symbol is undefined and becomes defined, this field will
 120              automatically be non-NULL since the symbol will have been on the
 121              undefined symbol list.  */
 122           struct bfd_link_hash_entry *next;
 123           bfd *abfd;            /* BFD symbol was found in.  */
 124         } undef;
 125       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 126       struct
 127         {
 128           struct bfd_link_hash_entry *next;
 129           asection *section;    /* Symbol section.  */
 130           bfd_vma value;        /* Symbol value.  */
 131         } def;
 132       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 133       struct
 134         {
 135           struct bfd_link_hash_entry *next;
 136           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 137           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 138         } i;
 139       /* bfd_link_hash_common.  */
 140       struct
 141         {
 142           struct bfd_link_hash_entry *next;
 143           /* The linker needs to know three things about common
 144              symbols: the size, the alignment, and the section in
 145              which the symbol should be placed.  We store the size
 146              here, and we allocate a small structure to hold the
 147              section and the alignment.  The alignment is stored as a
 148              power of two.  We don't store all the information
 149              directly because we don't want to increase the size of
 150              the union; this structure is a major space user in the
 151              linker.  */
 152           struct bfd_link_hash_common_entry *p;
 153           bfd_size_type size;   /* Common symbol size.  */
 154         } c;
 155     } u;
 156 };
 157
 158 /* This is the link hash table.  It is a derived class of
 159    bfd_hash_table.  */
 160
 161 struct bfd_link_hash_table
 162 {
 163   /* The hash table itself.  */
 164   struct bfd_hash_table table;
 165   /* A linked list of undefined and common symbols, linked through the
 166      next field in the bfd_link_hash_entry structure.  */
 167   struct bfd_link_hash_entry *undefs;
 168   /* Entries are added to the tail of the undefs list.  */
 169   struct bfd_link_hash_entry *undefs_tail;
 170   /* Function to free the hash table on closing BFD.  */
 171   void (*hash_table_free) (bfd *);
 172   /* The type of the link hash table.  */
 173   enum bfd_link_hash_table_type type;
 174 };
 175
 176 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 177    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 178    the real symbol.  */
 179 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 180   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 181    bfd_boolean copy, bfd_boolean follow);
 182
 183 /* Look up an entry in the main linker hash table if the symbol might
 184    be wrapped.  This should only be used for references to an
 185    undefined symbol, not for definitions of a symbol.  */
 186
 187 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 188   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 189    bfd_boolean, bfd_boolean);
 190
 191 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 192    and the remainder is found in wrap_hash, return the real symbol.  */
 193
 194 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 195   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 196
 197 /* Traverse a link hash table.  */
 198 extern void bfd_link_hash_traverse
 199   (struct bfd_link_hash_table *,
 200     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 201     void *);
 202
 203 /* Add an entry to the undefs list.  */
 204 extern void bfd_link_add_undef
 205   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 206
 207 /* Remove symbols from the undefs list that don't belong there.  */
 208 extern void bfd_link_repair_undef_list
 209   (struct bfd_link_hash_table *table);
 210
 211 /* Read symbols and cache symbol pointer array in outsymbols.  */
 212 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 213
 214 struct bfd_sym_chain
 215 {
 216   struct bfd_sym_chain *next;
 217   const char *name;
 218 };
 219 \f
 220 /* How to handle unresolved symbols.
 221    There are four possibilities which are enumerated below:  */
 222 enum report_method
 223 {
 224   /* This is the initial value when then link_info structure is created.
 225      It allows the various stages of the linker to determine whether they
 226      allowed to set the value.  */
 227   RM_NOT_YET_SET = 0,
 228   RM_IGNORE,
 229   RM_GENERATE_WARNING,
 230   RM_GENERATE_ERROR
 231 };
 232
 233 typedef enum {with_flags, without_flags} flag_type;
 234
 235 /* A section flag list.  */
 236 struct flag_info_list
 237 {
 238   flag_type with;
 239   const char *name;
 240   bfd_boolean valid;
 241   struct flag_info_list *next;
 242 };
 243
 244 /* Section flag info.  */
 245 struct flag_info
 246 {
 247   flagword only_with_flags;
 248   flagword not_with_flags;
 249   struct flag_info_list *flag_list;
 250   bfd_boolean flags_initialized;
 251 };
 252
 253 struct bfd_elf_dynamic_list;
 254 struct bfd_elf_version_tree;
 255
 256 /* This structure holds all the information needed to communicate
 257    between BFD and the linker when doing a link.  */
 258
 259 struct bfd_link_info
 260 {
 261   /* TRUE if BFD should generate a shared object (or a pie).  */
 262   unsigned int shared: 1;
 263
 264   /* TRUE if generating an executable, position independent or not.  */
 265   unsigned int executable : 1;
 266
 267   /* TRUE if generating a position independent executable.  */
 268   unsigned int pie: 1;
 269
 270   /* TRUE if BFD should generate a relocatable object file.  */
 271   unsigned int relocatable: 1;
 272
 273   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 274   unsigned int symbolic: 1;
 275
 276   /* TRUE if executable should not contain copy relocs.
 277      Setting this true may result in a non-sharable text segment.  */
 278   unsigned int nocopyreloc: 1;
 279
 280   /* TRUE if BFD should export all symbols in the dynamic symbol table
 281      of an executable, rather than only those used.  */
 282   unsigned int export_dynamic: 1;
 283
 284   /* TRUE if a default symbol version should be created and used for
 285      exported symbols.  */
 286   unsigned int create_default_symver: 1;
 287
 288   /* TRUE if unreferenced sections should be removed.  */
 289   unsigned int gc_sections: 1;
 290
 291   /* TRUE if every symbol should be reported back via the notice
 292      callback.  */
 293   unsigned int notice_all: 1;
 294
 295   /* TRUE if the LTO plugin is active.  */
 296   unsigned int lto_plugin_active: 1;
 297
 298   /* TRUE if we are loading LTO outputs.  */
 299   unsigned int loading_lto_outputs: 1;
 300
 301   /* TRUE if global symbols in discarded sections should be stripped.  */
 302   unsigned int strip_discarded: 1;
 303
 304   /* TRUE if all data symbols should be dynamic.  */
 305   unsigned int dynamic_data: 1;
 306
 307   /* Which symbols to strip.  */
 308   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 309
 310   /* Which local symbols to discard.  */
 311   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 312
 313   /* Criteria for skipping symbols when determining
 314      whether to include an object from an archive. */
 315   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 316
 317   /* What to do with unresolved symbols in an object file.
 318      When producing executables the default is GENERATE_ERROR.
 319      When producing shared libraries the default is IGNORE.  The
 320      assumption with shared libraries is that the reference will be
 321      resolved at load/execution time.  */
 322   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 323
 324   /* What to do with unresolved symbols in a shared library.
 325      The same defaults apply.  */
 326   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 327
 328   /* TRUE if shared objects should be linked directly, not shared.  */
 329   unsigned int static_link: 1;
 330
 331   /* TRUE if symbols should be retained in memory, FALSE if they
 332      should be freed and reread.  */
 333   unsigned int keep_memory: 1;
 334
 335   /* TRUE if BFD should generate relocation information in the final
 336      executable.  */
 337   unsigned int emitrelocations: 1;
 338
 339   /* TRUE if PT_GNU_RELRO segment should be created.  */
 340   unsigned int relro: 1;
 341
 342   /* TRUE if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 343      should be created.  */
 344   unsigned int eh_frame_hdr: 1;
 345
 346   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 347   unsigned int warn_shared_textrel: 1;
 348
 349   /* TRUE if we should error when adding a DT_TEXTREL.  */
 350   unsigned int error_textrel: 1;
 351
 352   /* TRUE if .hash section should be created.  */
 353   unsigned int emit_hash: 1;
 354
 355   /* TRUE if .gnu.hash section should be created.  */
 356   unsigned int emit_gnu_hash: 1;
 357
 358   /* If TRUE reduce memory overheads, at the expense of speed. This will
 359      cause map file generation to use an O(N^2) algorithm and disable
 360      caching ELF symbol buffer.  */
 361   unsigned int reduce_memory_overheads: 1;
 362
 363   /* TRUE if the output file should be in a traditional format.  This
 364      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 365      on the output file, but may be checked when reading the input
 366      files.  */
 367   unsigned int traditional_format: 1;
 368
 369   /* TRUE if non-PLT relocs should be merged into one reloc section
 370      and sorted so that relocs against the same symbol come together.  */
 371   unsigned int combreloc: 1;
 372
 373   /* TRUE if a default symbol version should be created and used for
 374      imported symbols.  */
 375   unsigned int default_imported_symver: 1;
 376
 377   /* TRUE if the new ELF dynamic tags are enabled. */
 378   unsigned int new_dtags: 1;
 379
 380   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 381      linker created sections, TRUE if it should be omitted.  */
 382   unsigned int no_ld_generated_unwind_info: 1;
 383
 384   /* TRUE if BFD should generate a "task linked" object file,
 385      similar to relocatable but also with globals converted to
 386      statics.  */
 387   unsigned int task_link: 1;
 388
 389   /* TRUE if ok to have multiple definition.  */
 390   unsigned int allow_multiple_definition: 1;
 391
 392   /* TRUE if ok to have version with no definition.  */
 393   unsigned int allow_undefined_version: 1;
 394
 395   /* TRUE if some symbols have to be dynamic, controlled by
 396      --dynamic-list command line options.  */
 397   unsigned int dynamic: 1;
 398
 399   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 400      flags.  */
 401   unsigned int execstack: 1;
 402
 403   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 404      flags.  */
 405   unsigned int noexecstack: 1;
 406
 407   /* TRUE if we want to produced optimized output files.  This might
 408      need much more time and therefore must be explicitly selected.  */
 409   unsigned int optimize: 1;
 410
 411   /* TRUE if user should be informed of removed unreferenced sections.  */
 412   unsigned int print_gc_sections: 1;
 413
 414   /* TRUE if we should warn alternate ELF machine code.  */
 415   unsigned int warn_alternate_em: 1;
 416
 417   /* TRUE if the linker script contained an explicit PHDRS command.  */
 418   unsigned int user_phdrs: 1;
 419
 420   /* TRUE if BND prefix in PLT entries is always generated.  */
 421   unsigned int bndplt: 1;
 422
 423   /* Char that may appear as the first char of a symbol, but should be
 424      skipped (like symbol_leading_char) when looking up symbols in
 425      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 426   char wrap_char;
 427
 428   /* Separator between archive and filename in linker script filespecs.  */
 429   char path_separator;
 430
 431   /* Default stack size.  Zero means default (often zero itself), -1
 432      means explicitly zero-sized.  */
 433   bfd_signed_vma stacksize;
 434
 435   /* Enable or disable target specific optimizations.
 436
 437      Not all targets have optimizations to enable.
 438
 439      Normally these optimizations are disabled by default but some targets
 440      prefer to enable them by default.  So this field is a tri-state variable.
 441      The values are:
 442
 443      zero: Enable the optimizations (either from --relax being specified on
 444        the command line or the backend's before_allocation emulation function.
 445
 446      positive: The user has requested that these optimizations be disabled.
 447        (Via the --no-relax command line option).
 448
 449      negative: The optimizations are disabled.  (Set when initializing the
 450        args_type structure in ldmain.c:main.  */
 451   signed int disable_target_specific_optimizations;
 452
 453   /* Function callbacks.  */
 454   const struct bfd_link_callbacks *callbacks;
 455
 456   /* Hash table handled by BFD.  */
 457   struct bfd_link_hash_table *hash;
 458
 459   /* Hash table of symbols to keep.  This is NULL unless strip is
 460      strip_some.  */
 461   struct bfd_hash_table *keep_hash;
 462
 463   /* Hash table of symbols to report back via the notice callback.  If
 464      this is NULL, and notice_all is FALSE, then no symbols are
 465      reported back.  */
 466   struct bfd_hash_table *notice_hash;
 467
 468   /* Hash table of symbols which are being wrapped (the --wrap linker
 469      option).  If this is NULL, no symbols are being wrapped.  */
 470   struct bfd_hash_table *wrap_hash;
 471
 472   /* Hash table of symbols which may be left unresolved during
 473      a link.  If this is NULL, no symbols can be left unresolved.  */
 474   struct bfd_hash_table *ignore_hash;
 475
 476   /* The output BFD.  */
 477   bfd *output_bfd;
 478
 479   /* The list of input BFD's involved in the link.  These are chained
 480      together via the link.next field.  */
 481   bfd *input_bfds;
 482   bfd **input_bfds_tail;
 483
 484   /* If a symbol should be created for each input BFD, this is section
 485      where those symbols should be placed.  It must be a section in
 486      the output BFD.  It may be NULL, in which case no such symbols
 487      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 488      linker command language.  */
 489   asection *create_object_symbols_section;
 490
 491   /* List of global symbol names that are starting points for marking
 492      sections against garbage collection.  */
 493   struct bfd_sym_chain *gc_sym_list;
 494
 495   /* If a base output file is wanted, then this points to it */
 496   void *base_file;
 497
 498   /* The function to call when the executable or shared object is
 499      loaded.  */
 500   const char *init_function;
 501
 502   /* The function to call when the executable or shared object is
 503      unloaded.  */
 504   const char *fini_function;
 505
 506   /* Number of relaxation passes.  Usually only one relaxation pass
 507      is needed.  But a backend can have as many relaxation passes as
 508      necessary.  During bfd_relax_section call, it is set to the
 509      current pass, starting from 0.  */
 510   int relax_pass;
 511
 512   /* Number of relaxation trips.  This number is incremented every
 513      time the relaxation pass is restarted due to a previous
 514      relaxation returning true in *AGAIN.  */
 515   int relax_trip;
 516
 517   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 518      should be generated/linked against.  Set to 1 if this feature
 519      is explicitly requested by the user, -1 if enabled by default.  */
 520   int pei386_auto_import;
 521
 522   /* Non-zero if runtime relocs for DATA items with non-zero addends
 523      in pei386 DLLs should be generated.  Set to 1 if this feature
 524      is explicitly requested by the user, -1 if enabled by default.  */
 525   int pei386_runtime_pseudo_reloc;
 526
 527   /* How many spare .dynamic DT_NULL entries should be added?  */
 528   unsigned int spare_dynamic_tags;
 529
 530   /* May be used to set DT_FLAGS for ELF. */
 531   bfd_vma flags;
 532
 533   /* May be used to set DT_FLAGS_1 for ELF. */
 534   bfd_vma flags_1;
 535
 536   /* Start and end of RELRO region.  */
 537   bfd_vma relro_start, relro_end;
 538
 539   /* List of symbols should be dynamic.  */
 540   struct bfd_elf_dynamic_list *dynamic_list;
 541
 542   /* The version information.  */
 543   struct bfd_elf_version_tree *version_info;
 544 };
 545
 546 /* This structures holds a set of callback functions.  These are called
 547    by the BFD linker routines.  Except for the info functions, the first
 548    argument to each callback function is the bfd_link_info structure
 549    being used and each function returns a boolean value.  If the
 550    function returns FALSE, then the BFD function which called it should
 551    return with a failure indication.  */
 552
 553 struct bfd_link_callbacks
 554 {
 555   /* A function which is called when an object is added from an
 556      archive.  ABFD is the archive element being added.  NAME is the
 557      name of the symbol which caused the archive element to be pulled
 558      in.  This function may set *SUBSBFD to point to an alternative
 559      BFD from which symbols should in fact be added in place of the
 560      original BFD's symbols.  */
 561   bfd_boolean (*add_archive_element)
 562     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 563   /* A function which is called when a symbol is found with multiple
 564      definitions.  H is the symbol which is defined multiple times.
 565      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 566      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 567   bfd_boolean (*multiple_definition)
 568     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 569      bfd *nbfd, asection *nsec, bfd_vma nval);
 570   /* A function which is called when a common symbol is defined
 571      multiple times.  H is the symbol appearing multiple times.
 572      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 573      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 574      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 575      is the size of the new symbol.  */
 576   bfd_boolean (*multiple_common)
 577     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 578      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 579   /* A function which is called to add a symbol to a set.  ENTRY is
 580      the link hash table entry for the set itself (e.g.,
 581      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 582      the set when generating a relocatable file, and is also used to
 583      get the size of the entry when generating an executable file.
 584      ABFD, SEC and VALUE identify the value to add to the set.  */
 585   bfd_boolean (*add_to_set)
 586     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 587      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 588   /* A function which is called when the name of a g++ constructor or
 589      destructor is found.  This is only called by some object file
 590      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 591      destructor.  This will use BFD_RELOC_CTOR when generating a
 592      relocatable file.  NAME is the name of the symbol found.  ABFD,
 593      SECTION and VALUE are the value of the symbol.  */
 594   bfd_boolean (*constructor)
 595     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 596      bfd *abfd, asection *sec, bfd_vma value);
 597   /* A function which is called to issue a linker warning.  For
 598      example, this is called when there is a reference to a warning
 599      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 600      of the symbol which triggered the warning; it may be NULL if
 601      there is none.  ABFD, SECTION and ADDRESS identify the location
 602      which trigerred the warning; either ABFD or SECTION or both may
 603      be NULL if the location is not known.  */
 604   bfd_boolean (*warning)
 605     (struct bfd_link_info *, const char *warning, const char *symbol,
 606      bfd *abfd, asection *section, bfd_vma address);
 607   /* A function which is called when a relocation is attempted against
 608      an undefined symbol.  NAME is the symbol which is undefined.
 609      ABFD, SECTION and ADDRESS identify the location from which the
 610      reference is made. IS_FATAL indicates whether an undefined symbol is
 611      a fatal error or not. In some cases SECTION may be NULL.  */
 612   bfd_boolean (*undefined_symbol)
 613     (struct bfd_link_info *, const char *name, bfd *abfd,
 614      asection *section, bfd_vma address, bfd_boolean is_fatal);
 615   /* A function which is called when a reloc overflow occurs. ENTRY is
 616      the link hash table entry for the symbol the reloc is against.
 617      NAME is the name of the local symbol or section the reloc is
 618      against, RELOC_NAME is the name of the relocation, and ADDEND is
 619      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 620      location at which the overflow occurs; if this is the result of a
 621      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 622      ABFD will be NULL.  */
 623   bfd_boolean (*reloc_overflow)
 624     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 625      const char *name, const char *reloc_name, bfd_vma addend,
 626      bfd *abfd, asection *section, bfd_vma address);
 627   /* A function which is called when a dangerous reloc is performed.
 628      MESSAGE is an appropriate message.
 629      ABFD, SECTION and ADDRESS identify the location at which the
 630      problem occurred; if this is the result of a
 631      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 632      ABFD will be NULL.  */
 633   bfd_boolean (*reloc_dangerous)
 634     (struct bfd_link_info *, const char *message,
 635      bfd *abfd, asection *section, bfd_vma address);
 636   /* A function which is called when a reloc is found to be attached
 637      to a symbol which is not being written out.  NAME is the name of
 638      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 639      the reloc; if this is the result of a
 640      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 641      ABFD will be NULL.  */
 642   bfd_boolean (*unattached_reloc)
 643     (struct bfd_link_info *, const char *name,
 644      bfd *abfd, asection *section, bfd_vma address);
 645   /* A function which is called when a symbol in notice_hash is
 646      defined or referenced.  H is the symbol, INH the indirect symbol
 647      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 648      the symbol.  If SECTION is bfd_und_section, this is a reference.
 649      FLAGS are the symbol BSF_* flags.  */
 650   bfd_boolean (*notice)
 651     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 652      struct bfd_link_hash_entry *inh,
 653      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 654   /* Error or warning link info message.  */
 655   void (*einfo)
 656     (const char *fmt, ...);
 657   /* General link info message.  */
 658   void (*info)
 659     (const char *fmt, ...);
 660   /* Message to be printed in linker map file.  */
 661   void (*minfo)
 662     (const char *fmt, ...);
 663   /* This callback provides a chance for users of the BFD library to
 664      override its decision about whether to place two adjacent sections
 665      into the same segment.  */
 666   bfd_boolean (*override_segment_assignment)
 667     (struct bfd_link_info *, bfd * abfd,
 668      asection * current_section, asection * previous_section,
 669      bfd_boolean new_segment);
 670 };
 671 \f
 672 /* The linker builds link_order structures which tell the code how to
 673    include input data in the output file.  */
 674
 675 /* These are the types of link_order structures.  */
 676
 677 enum bfd_link_order_type
 678 {
 679   bfd_undefined_link_order,     /* Undefined.  */
 680   bfd_indirect_link_order,      /* Built from a section.  */
 681   bfd_data_link_order,          /* Set to explicit data.  */
 682   bfd_section_reloc_link_order, /* Relocate against a section.  */
 683   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 684 };
 685
 686 /* This is the link_order structure itself.  These form a chain
 687    attached to the output section whose contents they are describing.  */
 688
 689 struct bfd_link_order
 690 {
 691   /* Next link_order in chain.  */
 692   struct bfd_link_order *next;
 693   /* Type of link_order.  */
 694   enum bfd_link_order_type type;
 695   /* Offset within output section.  */
 696   bfd_vma offset;
 697   /* Size within output section.  */
 698   bfd_size_type size;
 699   /* Type specific information.  */
 700   union
 701     {
 702       struct
 703         {
 704           /* Section to include.  If this is used, then
 705              section->output_section must be the section the
 706              link_order is attached to, section->output_offset must
 707              equal the link_order offset field, and section->size
 708              must equal the link_order size field.  Maybe these
 709              restrictions should be relaxed someday.  */
 710           asection *section;
 711         } indirect;
 712       struct
 713         {
 714           /* Size of contents, or zero when contents should be filled by
 715              the architecture-dependent fill function.
 716              A non-zero value allows filling of the output section
 717              with an arbitrary repeated pattern.  */
 718           unsigned int size;
 719           /* Data to put into file.  */
 720           bfd_byte *contents;
 721         } data;
 722       struct
 723         {
 724           /* Description of reloc to generate.  Used for
 725              bfd_section_reloc_link_order and
 726              bfd_symbol_reloc_link_order.  */
 727           struct bfd_link_order_reloc *p;
 728         } reloc;
 729     } u;
 730 };
 731
 732 /* A linker order of type bfd_section_reloc_link_order or
 733    bfd_symbol_reloc_link_order means to create a reloc against a
 734    section or symbol, respectively.  This is used to implement -Ur to
 735    generate relocs for the constructor tables.  The
 736    bfd_link_order_reloc structure describes the reloc that BFD should
 737    create.  It is similar to a arelent, but I didn't use arelent
 738    because the linker does not know anything about most symbols, and
 739    any asymbol structure it creates will be partially meaningless.
 740    This information could logically be in the bfd_link_order struct,
 741    but I didn't want to waste the space since these types of relocs
 742    are relatively rare.  */
 743
 744 struct bfd_link_order_reloc
 745 {
 746   /* Reloc type.  */
 747   bfd_reloc_code_real_type reloc;
 748
 749   union
 750     {
 751       /* For type bfd_section_reloc_link_order, this is the section
 752          the reloc should be against.  This must be a section in the
 753          output BFD, not any of the input BFDs.  */
 754       asection *section;
 755       /* For type bfd_symbol_reloc_link_order, this is the name of the
 756          symbol the reloc should be against.  */
 757       const char *name;
 758     } u;
 759
 760   /* Addend to use.  The object file should contain zero.  The BFD
 761      backend is responsible for filling in the contents of the object
 762      file correctly.  For some object file formats (e.g., COFF) the
 763      addend must be stored into in the object file, and for some
 764      (e.g., SPARC a.out) it is kept in the reloc.  */
 765   bfd_vma addend;
 766 };
 767
 768 /* Allocate a new link_order for a section.  */
 769 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 770
 771 /* These structures are used to describe version information for the
 772    ELF linker.  These structures could be manipulated entirely inside
 773    BFD, but it would be a pain.  Instead, the regular linker sets up
 774    these structures, and then passes them into BFD.  */
 775
 776 /* Glob pattern for a version.  */
 777
 778 struct bfd_elf_version_expr
 779 {
 780   /* Next glob pattern for this version.  */
 781   struct bfd_elf_version_expr *next;
 782   /* Glob pattern.  */
 783   const char *pattern;
 784   /* Set if pattern is not a glob.  */
 785   unsigned int literal : 1;
 786   /* Defined by ".symver".  */
 787   unsigned int symver : 1;
 788   /* Defined by version script.  */
 789   unsigned int script : 1;
 790   /* Pattern type.  */
 791 #define BFD_ELF_VERSION_C_TYPE          1
 792 #define BFD_ELF_VERSION_CXX_TYPE        2
 793 #define BFD_ELF_VERSION_JAVA_TYPE       4
 794   unsigned int mask : 3;
 795 };
 796
 797 struct bfd_elf_version_expr_head
 798 {
 799   /* List of all patterns, both wildcards and non-wildcards.  */
 800   struct bfd_elf_version_expr *list;
 801   /* Hash table for non-wildcards.  */
 802   void *htab;
 803   /* Remaining patterns.  */
 804   struct bfd_elf_version_expr *remaining;
 805   /* What kind of pattern types are present in list (bitmask).  */
 806   unsigned int mask;
 807 };
 808
 809 /* Version dependencies.  */
 810
 811 struct bfd_elf_version_deps
 812 {
 813   /* Next dependency for this version.  */
 814   struct bfd_elf_version_deps *next;
 815   /* The version which this version depends upon.  */
 816   struct bfd_elf_version_tree *version_needed;
 817 };
 818
 819 /* A node in the version tree.  */
 820
 821 struct bfd_elf_version_tree
 822 {
 823   /* Next version.  */
 824   struct bfd_elf_version_tree *next;
 825   /* Name of this version.  */
 826   const char *name;
 827   /* Version number.  */
 828   unsigned int vernum;
 829   /* Regular expressions for global symbols in this version.  */
 830   struct bfd_elf_version_expr_head globals;
 831   /* Regular expressions for local symbols in this version.  */
 832   struct bfd_elf_version_expr_head locals;
 833   /* List of versions which this version depends upon.  */
 834   struct bfd_elf_version_deps *deps;
 835   /* Index of the version name.  This is used within BFD.  */
 836   unsigned int name_indx;
 837   /* Whether this version tree was used.  This is used within BFD.  */
 838   int used;
 839   /* Matching hook.  */
 840   struct bfd_elf_version_expr *(*match)
 841     (struct bfd_elf_version_expr_head *head,
 842      struct bfd_elf_version_expr *prev, const char *sym);
 843 };
 844
 845 struct bfd_elf_dynamic_list
 846 {
 847   struct bfd_elf_version_expr_head head;
 848   struct bfd_elf_version_expr *(*match)
 849     (struct bfd_elf_version_expr_head *head,
 850      struct bfd_elf_version_expr *prev, const char *sym);
 851 };
 852
 853 #endif