include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2015 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   /* Symbol is referenced in a normal object file, as distict from a LTO
  95      IR object file.  */
  96   unsigned int non_ir_ref : 1;
  97
  98   /* Symbol is a built-in define.  These will be overridden by PROVIDE
  99      in a linker script.  */
 100   unsigned int linker_def : 1;
 101
 102   /* A union of information depending upon the type.  */
 103   union
 104     {
 105       /* Nothing is kept for bfd_hash_new.  */
 106       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 107       struct
 108         {
 109           /* Undefined and common symbols are kept in a linked list through
 110              this field.  This field is present in all of the union element
 111              so that we don't need to remove entries from the list when we
 112              change their type.  Removing entries would either require the
 113              list to be doubly linked, which would waste more memory, or
 114              require a traversal.  When an undefined or common symbol is
 115              created, it should be added to this list, the head of which is in
 116              the link hash table itself.  As symbols are defined, they need
 117              not be removed from the list; anything which reads the list must
 118              doublecheck the symbol type.
 119
 120              Weak symbols are not kept on this list.
 121
 122              Defined and defweak symbols use this field as a reference marker.
 123              If the field is not NULL, or this structure is the tail of the
 124              undefined symbol list, the symbol has been referenced.  If the
 125              symbol is undefined and becomes defined, this field will
 126              automatically be non-NULL since the symbol will have been on the
 127              undefined symbol list.  */
 128           struct bfd_link_hash_entry *next;
 129           bfd *abfd;            /* BFD symbol was found in.  */
 130         } undef;
 131       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 132       struct
 133         {
 134           struct bfd_link_hash_entry *next;
 135           asection *section;    /* Symbol section.  */
 136           bfd_vma value;        /* Symbol value.  */
 137         } def;
 138       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 139       struct
 140         {
 141           struct bfd_link_hash_entry *next;
 142           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 143           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 144         } i;
 145       /* bfd_link_hash_common.  */
 146       struct
 147         {
 148           struct bfd_link_hash_entry *next;
 149           /* The linker needs to know three things about common
 150              symbols: the size, the alignment, and the section in
 151              which the symbol should be placed.  We store the size
 152              here, and we allocate a small structure to hold the
 153              section and the alignment.  The alignment is stored as a
 154              power of two.  We don't store all the information
 155              directly because we don't want to increase the size of
 156              the union; this structure is a major space user in the
 157              linker.  */
 158           struct bfd_link_hash_common_entry *p;
 159           bfd_size_type size;   /* Common symbol size.  */
 160         } c;
 161     } u;
 162 };
 163
 164 /* This is the link hash table.  It is a derived class of
 165    bfd_hash_table.  */
 166
 167 struct bfd_link_hash_table
 168 {
 169   /* The hash table itself.  */
 170   struct bfd_hash_table table;
 171   /* A linked list of undefined and common symbols, linked through the
 172      next field in the bfd_link_hash_entry structure.  */
 173   struct bfd_link_hash_entry *undefs;
 174   /* Entries are added to the tail of the undefs list.  */
 175   struct bfd_link_hash_entry *undefs_tail;
 176   /* Function to free the hash table on closing BFD.  */
 177   void (*hash_table_free) (bfd *);
 178   /* The type of the link hash table.  */
 179   enum bfd_link_hash_table_type type;
 180 };
 181
 182 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 183    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 184    the real symbol.  */
 185 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 186   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 187    bfd_boolean copy, bfd_boolean follow);
 188
 189 /* Look up an entry in the main linker hash table if the symbol might
 190    be wrapped.  This should only be used for references to an
 191    undefined symbol, not for definitions of a symbol.  */
 192
 193 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 194   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 195    bfd_boolean, bfd_boolean);
 196
 197 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 198    and the remainder is found in wrap_hash, return the real symbol.  */
 199
 200 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 201   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 202
 203 /* Traverse a link hash table.  */
 204 extern void bfd_link_hash_traverse
 205   (struct bfd_link_hash_table *,
 206     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 207     void *);
 208
 209 /* Add an entry to the undefs list.  */
 210 extern void bfd_link_add_undef
 211   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 212
 213 /* Remove symbols from the undefs list that don't belong there.  */
 214 extern void bfd_link_repair_undef_list
 215   (struct bfd_link_hash_table *table);
 216
 217 /* Read symbols and cache symbol pointer array in outsymbols.  */
 218 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 219
 220 struct bfd_sym_chain
 221 {
 222   struct bfd_sym_chain *next;
 223   const char *name;
 224 };
 225 \f
 226 /* How to handle unresolved symbols.
 227    There are four possibilities which are enumerated below:  */
 228 enum report_method
 229 {
 230   /* This is the initial value when then link_info structure is created.
 231      It allows the various stages of the linker to determine whether they
 232      allowed to set the value.  */
 233   RM_NOT_YET_SET = 0,
 234   RM_IGNORE,
 235   RM_GENERATE_WARNING,
 236   RM_GENERATE_ERROR
 237 };
 238
 239 typedef enum {with_flags, without_flags} flag_type;
 240
 241 /* A section flag list.  */
 242 struct flag_info_list
 243 {
 244   flag_type with;
 245   const char *name;
 246   bfd_boolean valid;
 247   struct flag_info_list *next;
 248 };
 249
 250 /* Section flag info.  */
 251 struct flag_info
 252 {
 253   flagword only_with_flags;
 254   flagword not_with_flags;
 255   struct flag_info_list *flag_list;
 256   bfd_boolean flags_initialized;
 257 };
 258
 259 struct bfd_elf_dynamic_list;
 260 struct bfd_elf_version_tree;
 261
 262 /* Types of output.  */
 263
 264 enum output_type
 265 {
 266   type_pde,
 267   type_pie,
 268   type_relocatable,
 269   type_dll,
 270 };
 271
 272 #define bfd_link_pde(info)         ((info)->type == type_pde)
 273 #define bfd_link_dll(info)         ((info)->type == type_dll)
 274 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 275 #define bfd_link_pie(info)         ((info)->type == type_pie)
 276 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 277 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 278
 279 /* This structure holds all the information needed to communicate
 280    between BFD and the linker when doing a link.  */
 281
 282 struct bfd_link_info
 283 {
 284   /* Output type.  */
 285   ENUM_BITFIELD (output_type) type : 2;
 286
 287   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 288   unsigned int symbolic: 1;
 289
 290   /* TRUE if executable should not contain copy relocs.
 291      Setting this true may result in a non-sharable text segment.  */
 292   unsigned int nocopyreloc: 1;
 293
 294   /* TRUE if BFD should export all symbols in the dynamic symbol table
 295      of an executable, rather than only those used.  */
 296   unsigned int export_dynamic: 1;
 297
 298   /* TRUE if a default symbol version should be created and used for
 299      exported symbols.  */
 300   unsigned int create_default_symver: 1;
 301
 302   /* TRUE if unreferenced sections should be removed.  */
 303   unsigned int gc_sections: 1;
 304
 305   /* TRUE if every symbol should be reported back via the notice
 306      callback.  */
 307   unsigned int notice_all: 1;
 308
 309   /* TRUE if the LTO plugin is active.  */
 310   unsigned int lto_plugin_active: 1;
 311
 312   /* TRUE if global symbols in discarded sections should be stripped.  */
 313   unsigned int strip_discarded: 1;
 314
 315   /* TRUE if all data symbols should be dynamic.  */
 316   unsigned int dynamic_data: 1;
 317
 318   /* Which symbols to strip.  */
 319   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 320
 321   /* Which local symbols to discard.  */
 322   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 323
 324   /* Criteria for skipping symbols when determining
 325      whether to include an object from an archive. */
 326   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 327
 328   /* What to do with unresolved symbols in an object file.
 329      When producing executables the default is GENERATE_ERROR.
 330      When producing shared libraries the default is IGNORE.  The
 331      assumption with shared libraries is that the reference will be
 332      resolved at load/execution time.  */
 333   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 334
 335   /* What to do with unresolved symbols in a shared library.
 336      The same defaults apply.  */
 337   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 338
 339   /* TRUE if shared objects should be linked directly, not shared.  */
 340   unsigned int static_link: 1;
 341
 342   /* TRUE if symbols should be retained in memory, FALSE if they
 343      should be freed and reread.  */
 344   unsigned int keep_memory: 1;
 345
 346   /* TRUE if BFD should generate relocation information in the final
 347      executable.  */
 348   unsigned int emitrelocations: 1;
 349
 350   /* TRUE if PT_GNU_RELRO segment should be created.  */
 351   unsigned int relro: 1;
 352
 353   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 354      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 355   unsigned int eh_frame_hdr_type: 2;
 356
 357   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 358   unsigned int warn_shared_textrel: 1;
 359
 360   /* TRUE if we should error when adding a DT_TEXTREL.  */
 361   unsigned int error_textrel: 1;
 362
 363   /* TRUE if .hash section should be created.  */
 364   unsigned int emit_hash: 1;
 365
 366   /* TRUE if .gnu.hash section should be created.  */
 367   unsigned int emit_gnu_hash: 1;
 368
 369   /* If TRUE reduce memory overheads, at the expense of speed. This will
 370      cause map file generation to use an O(N^2) algorithm and disable
 371      caching ELF symbol buffer.  */
 372   unsigned int reduce_memory_overheads: 1;
 373
 374   /* TRUE if the output file should be in a traditional format.  This
 375      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 376      on the output file, but may be checked when reading the input
 377      files.  */
 378   unsigned int traditional_format: 1;
 379
 380   /* TRUE if non-PLT relocs should be merged into one reloc section
 381      and sorted so that relocs against the same symbol come together.  */
 382   unsigned int combreloc: 1;
 383
 384   /* TRUE if a default symbol version should be created and used for
 385      imported symbols.  */
 386   unsigned int default_imported_symver: 1;
 387
 388   /* TRUE if the new ELF dynamic tags are enabled. */
 389   unsigned int new_dtags: 1;
 390
 391   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 392      linker created sections, TRUE if it should be omitted.  */
 393   unsigned int no_ld_generated_unwind_info: 1;
 394
 395   /* TRUE if BFD should generate a "task linked" object file,
 396      similar to relocatable but also with globals converted to
 397      statics.  */
 398   unsigned int task_link: 1;
 399
 400   /* TRUE if ok to have multiple definition.  */
 401   unsigned int allow_multiple_definition: 1;
 402
 403   /* TRUE if ok to have version with no definition.  */
 404   unsigned int allow_undefined_version: 1;
 405
 406   /* TRUE if some symbols have to be dynamic, controlled by
 407      --dynamic-list command line options.  */
 408   unsigned int dynamic: 1;
 409
 410   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 411      flags.  */
 412   unsigned int execstack: 1;
 413
 414   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 415      flags.  */
 416   unsigned int noexecstack: 1;
 417
 418   /* TRUE if we want to produced optimized output files.  This might
 419      need much more time and therefore must be explicitly selected.  */
 420   unsigned int optimize: 1;
 421
 422   /* TRUE if user should be informed of removed unreferenced sections.  */
 423   unsigned int print_gc_sections: 1;
 424
 425   /* TRUE if we should warn alternate ELF machine code.  */
 426   unsigned int warn_alternate_em: 1;
 427
 428   /* TRUE if the linker script contained an explicit PHDRS command.  */
 429   unsigned int user_phdrs: 1;
 430
 431   /* TRUE if BND prefix in PLT entries is always generated.  */
 432   unsigned int bndplt: 1;
 433
 434   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 435   unsigned int nointerp: 1;
 436
 437   /* Char that may appear as the first char of a symbol, but should be
 438      skipped (like symbol_leading_char) when looking up symbols in
 439      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 440   char wrap_char;
 441
 442   /* Separator between archive and filename in linker script filespecs.  */
 443   char path_separator;
 444
 445   /* Compress DWARF debug sections.  */
 446   enum compressed_debug_section_type compress_debug;
 447
 448   /* Default stack size.  Zero means default (often zero itself), -1
 449      means explicitly zero-sized.  */
 450   bfd_signed_vma stacksize;
 451
 452   /* Enable or disable target specific optimizations.
 453
 454      Not all targets have optimizations to enable.
 455
 456      Normally these optimizations are disabled by default but some targets
 457      prefer to enable them by default.  So this field is a tri-state variable.
 458      The values are:
 459
 460      zero: Enable the optimizations (either from --relax being specified on
 461        the command line or the backend's before_allocation emulation function.
 462
 463      positive: The user has requested that these optimizations be disabled.
 464        (Via the --no-relax command line option).
 465
 466      negative: The optimizations are disabled.  (Set when initializing the
 467        args_type structure in ldmain.c:main.  */
 468   signed int disable_target_specific_optimizations;
 469
 470   /* Function callbacks.  */
 471   const struct bfd_link_callbacks *callbacks;
 472
 473   /* Hash table handled by BFD.  */
 474   struct bfd_link_hash_table *hash;
 475
 476   /* Hash table of symbols to keep.  This is NULL unless strip is
 477      strip_some.  */
 478   struct bfd_hash_table *keep_hash;
 479
 480   /* Hash table of symbols to report back via the notice callback.  If
 481      this is NULL, and notice_all is FALSE, then no symbols are
 482      reported back.  */
 483   struct bfd_hash_table *notice_hash;
 484
 485   /* Hash table of symbols which are being wrapped (the --wrap linker
 486      option).  If this is NULL, no symbols are being wrapped.  */
 487   struct bfd_hash_table *wrap_hash;
 488
 489   /* Hash table of symbols which may be left unresolved during
 490      a link.  If this is NULL, no symbols can be left unresolved.  */
 491   struct bfd_hash_table *ignore_hash;
 492
 493   /* The output BFD.  */
 494   bfd *output_bfd;
 495
 496   /* The list of input BFD's involved in the link.  These are chained
 497      together via the link.next field.  */
 498   bfd *input_bfds;
 499   bfd **input_bfds_tail;
 500
 501   /* If a symbol should be created for each input BFD, this is section
 502      where those symbols should be placed.  It must be a section in
 503      the output BFD.  It may be NULL, in which case no such symbols
 504      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 505      linker command language.  */
 506   asection *create_object_symbols_section;
 507
 508   /* List of global symbol names that are starting points for marking
 509      sections against garbage collection.  */
 510   struct bfd_sym_chain *gc_sym_list;
 511
 512   /* If a base output file is wanted, then this points to it */
 513   void *base_file;
 514
 515   /* The function to call when the executable or shared object is
 516      loaded.  */
 517   const char *init_function;
 518
 519   /* The function to call when the executable or shared object is
 520      unloaded.  */
 521   const char *fini_function;
 522
 523   /* Number of relaxation passes.  Usually only one relaxation pass
 524      is needed.  But a backend can have as many relaxation passes as
 525      necessary.  During bfd_relax_section call, it is set to the
 526      current pass, starting from 0.  */
 527   int relax_pass;
 528
 529   /* Number of relaxation trips.  This number is incremented every
 530      time the relaxation pass is restarted due to a previous
 531      relaxation returning true in *AGAIN.  */
 532   int relax_trip;
 533
 534   /* > 0 to treat protected data defined in the shared library as
 535      reference external.  0 to treat it as internal.  -1 to let
 536      backend to decide.  */
 537   int extern_protected_data;
 538
 539   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 540      should be generated/linked against.  Set to 1 if this feature
 541      is explicitly requested by the user, -1 if enabled by default.  */
 542   int pei386_auto_import;
 543
 544   /* Non-zero if runtime relocs for DATA items with non-zero addends
 545      in pei386 DLLs should be generated.  Set to 1 if this feature
 546      is explicitly requested by the user, -1 if enabled by default.  */
 547   int pei386_runtime_pseudo_reloc;
 548
 549   /* How many spare .dynamic DT_NULL entries should be added?  */
 550   unsigned int spare_dynamic_tags;
 551
 552   /* May be used to set DT_FLAGS for ELF. */
 553   bfd_vma flags;
 554
 555   /* May be used to set DT_FLAGS_1 for ELF. */
 556   bfd_vma flags_1;
 557
 558   /* Start and end of RELRO region.  */
 559   bfd_vma relro_start, relro_end;
 560
 561   /* List of symbols should be dynamic.  */
 562   struct bfd_elf_dynamic_list *dynamic_list;
 563
 564   /* The version information.  */
 565   struct bfd_elf_version_tree *version_info;
 566 };
 567
 568 /* This structures holds a set of callback functions.  These are called
 569    by the BFD linker routines.  Except for the info functions, the first
 570    argument to each callback function is the bfd_link_info structure
 571    being used and each function returns a boolean value.  If the
 572    function returns FALSE, then the BFD function which called it should
 573    return with a failure indication.  */
 574
 575 struct bfd_link_callbacks
 576 {
 577   /* A function which is called when an object is added from an
 578      archive.  ABFD is the archive element being added.  NAME is the
 579      name of the symbol which caused the archive element to be pulled
 580      in.  This function may set *SUBSBFD to point to an alternative
 581      BFD from which symbols should in fact be added in place of the
 582      original BFD's symbols.  */
 583   bfd_boolean (*add_archive_element)
 584     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 585   /* A function which is called when a symbol is found with multiple
 586      definitions.  H is the symbol which is defined multiple times.
 587      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 588      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 589   bfd_boolean (*multiple_definition)
 590     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 591      bfd *nbfd, asection *nsec, bfd_vma nval);
 592   /* A function which is called when a common symbol is defined
 593      multiple times.  H is the symbol appearing multiple times.
 594      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 595      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 596      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 597      is the size of the new symbol.  */
 598   bfd_boolean (*multiple_common)
 599     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 600      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 601   /* A function which is called to add a symbol to a set.  ENTRY is
 602      the link hash table entry for the set itself (e.g.,
 603      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 604      the set when generating a relocatable file, and is also used to
 605      get the size of the entry when generating an executable file.
 606      ABFD, SEC and VALUE identify the value to add to the set.  */
 607   bfd_boolean (*add_to_set)
 608     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 609      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 610   /* A function which is called when the name of a g++ constructor or
 611      destructor is found.  This is only called by some object file
 612      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 613      destructor.  This will use BFD_RELOC_CTOR when generating a
 614      relocatable file.  NAME is the name of the symbol found.  ABFD,
 615      SECTION and VALUE are the value of the symbol.  */
 616   bfd_boolean (*constructor)
 617     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 618      bfd *abfd, asection *sec, bfd_vma value);
 619   /* A function which is called to issue a linker warning.  For
 620      example, this is called when there is a reference to a warning
 621      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 622      of the symbol which triggered the warning; it may be NULL if
 623      there is none.  ABFD, SECTION and ADDRESS identify the location
 624      which trigerred the warning; either ABFD or SECTION or both may
 625      be NULL if the location is not known.  */
 626   bfd_boolean (*warning)
 627     (struct bfd_link_info *, const char *warning, const char *symbol,
 628      bfd *abfd, asection *section, bfd_vma address);
 629   /* A function which is called when a relocation is attempted against
 630      an undefined symbol.  NAME is the symbol which is undefined.
 631      ABFD, SECTION and ADDRESS identify the location from which the
 632      reference is made. IS_FATAL indicates whether an undefined symbol is
 633      a fatal error or not. In some cases SECTION may be NULL.  */
 634   bfd_boolean (*undefined_symbol)
 635     (struct bfd_link_info *, const char *name, bfd *abfd,
 636      asection *section, bfd_vma address, bfd_boolean is_fatal);
 637   /* A function which is called when a reloc overflow occurs. ENTRY is
 638      the link hash table entry for the symbol the reloc is against.
 639      NAME is the name of the local symbol or section the reloc is
 640      against, RELOC_NAME is the name of the relocation, and ADDEND is
 641      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 642      location at which the overflow occurs; if this is the result of a
 643      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 644      ABFD will be NULL.  */
 645   bfd_boolean (*reloc_overflow)
 646     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 647      const char *name, const char *reloc_name, bfd_vma addend,
 648      bfd *abfd, asection *section, bfd_vma address);
 649   /* A function which is called when a dangerous reloc is performed.
 650      MESSAGE is an appropriate message.
 651      ABFD, SECTION and ADDRESS identify the location at which the
 652      problem occurred; if this is the result of a
 653      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 654      ABFD will be NULL.  */
 655   bfd_boolean (*reloc_dangerous)
 656     (struct bfd_link_info *, const char *message,
 657      bfd *abfd, asection *section, bfd_vma address);
 658   /* A function which is called when a reloc is found to be attached
 659      to a symbol which is not being written out.  NAME is the name of
 660      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 661      the reloc; if this is the result of a
 662      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 663      ABFD will be NULL.  */
 664   bfd_boolean (*unattached_reloc)
 665     (struct bfd_link_info *, const char *name,
 666      bfd *abfd, asection *section, bfd_vma address);
 667   /* A function which is called when a symbol in notice_hash is
 668      defined or referenced.  H is the symbol, INH the indirect symbol
 669      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 670      the symbol.  If SECTION is bfd_und_section, this is a reference.
 671      FLAGS are the symbol BSF_* flags.  */
 672   bfd_boolean (*notice)
 673     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 674      struct bfd_link_hash_entry *inh,
 675      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 676   /* Error or warning link info message.  */
 677   void (*einfo)
 678     (const char *fmt, ...);
 679   /* General link info message.  */
 680   void (*info)
 681     (const char *fmt, ...);
 682   /* Message to be printed in linker map file.  */
 683   void (*minfo)
 684     (const char *fmt, ...);
 685   /* This callback provides a chance for users of the BFD library to
 686      override its decision about whether to place two adjacent sections
 687      into the same segment.  */
 688   bfd_boolean (*override_segment_assignment)
 689     (struct bfd_link_info *, bfd * abfd,
 690      asection * current_section, asection * previous_section,
 691      bfd_boolean new_segment);
 692 };
 693 \f
 694 /* The linker builds link_order structures which tell the code how to
 695    include input data in the output file.  */
 696
 697 /* These are the types of link_order structures.  */
 698
 699 enum bfd_link_order_type
 700 {
 701   bfd_undefined_link_order,     /* Undefined.  */
 702   bfd_indirect_link_order,      /* Built from a section.  */
 703   bfd_data_link_order,          /* Set to explicit data.  */
 704   bfd_section_reloc_link_order, /* Relocate against a section.  */
 705   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 706 };
 707
 708 /* This is the link_order structure itself.  These form a chain
 709    attached to the output section whose contents they are describing.  */
 710
 711 struct bfd_link_order
 712 {
 713   /* Next link_order in chain.  */
 714   struct bfd_link_order *next;
 715   /* Type of link_order.  */
 716   enum bfd_link_order_type type;
 717   /* Offset within output section.  */
 718   bfd_vma offset;
 719   /* Size within output section.  */
 720   bfd_size_type size;
 721   /* Type specific information.  */
 722   union
 723     {
 724       struct
 725         {
 726           /* Section to include.  If this is used, then
 727              section->output_section must be the section the
 728              link_order is attached to, section->output_offset must
 729              equal the link_order offset field, and section->size
 730              must equal the link_order size field.  Maybe these
 731              restrictions should be relaxed someday.  */
 732           asection *section;
 733         } indirect;
 734       struct
 735         {
 736           /* Size of contents, or zero when contents should be filled by
 737              the architecture-dependent fill function.
 738              A non-zero value allows filling of the output section
 739              with an arbitrary repeated pattern.  */
 740           unsigned int size;
 741           /* Data to put into file.  */
 742           bfd_byte *contents;
 743         } data;
 744       struct
 745         {
 746           /* Description of reloc to generate.  Used for
 747              bfd_section_reloc_link_order and
 748              bfd_symbol_reloc_link_order.  */
 749           struct bfd_link_order_reloc *p;
 750         } reloc;
 751     } u;
 752 };
 753
 754 /* A linker order of type bfd_section_reloc_link_order or
 755    bfd_symbol_reloc_link_order means to create a reloc against a
 756    section or symbol, respectively.  This is used to implement -Ur to
 757    generate relocs for the constructor tables.  The
 758    bfd_link_order_reloc structure describes the reloc that BFD should
 759    create.  It is similar to a arelent, but I didn't use arelent
 760    because the linker does not know anything about most symbols, and
 761    any asymbol structure it creates will be partially meaningless.
 762    This information could logically be in the bfd_link_order struct,
 763    but I didn't want to waste the space since these types of relocs
 764    are relatively rare.  */
 765
 766 struct bfd_link_order_reloc
 767 {
 768   /* Reloc type.  */
 769   bfd_reloc_code_real_type reloc;
 770
 771   union
 772     {
 773       /* For type bfd_section_reloc_link_order, this is the section
 774          the reloc should be against.  This must be a section in the
 775          output BFD, not any of the input BFDs.  */
 776       asection *section;
 777       /* For type bfd_symbol_reloc_link_order, this is the name of the
 778          symbol the reloc should be against.  */
 779       const char *name;
 780     } u;
 781
 782   /* Addend to use.  The object file should contain zero.  The BFD
 783      backend is responsible for filling in the contents of the object
 784      file correctly.  For some object file formats (e.g., COFF) the
 785      addend must be stored into in the object file, and for some
 786      (e.g., SPARC a.out) it is kept in the reloc.  */
 787   bfd_vma addend;
 788 };
 789
 790 /* Allocate a new link_order for a section.  */
 791 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 792
 793 /* These structures are used to describe version information for the
 794    ELF linker.  These structures could be manipulated entirely inside
 795    BFD, but it would be a pain.  Instead, the regular linker sets up
 796    these structures, and then passes them into BFD.  */
 797
 798 /* Glob pattern for a version.  */
 799
 800 struct bfd_elf_version_expr
 801 {
 802   /* Next glob pattern for this version.  */
 803   struct bfd_elf_version_expr *next;
 804   /* Glob pattern.  */
 805   const char *pattern;
 806   /* Set if pattern is not a glob.  */
 807   unsigned int literal : 1;
 808   /* Defined by ".symver".  */
 809   unsigned int symver : 1;
 810   /* Defined by version script.  */
 811   unsigned int script : 1;
 812   /* Pattern type.  */
 813 #define BFD_ELF_VERSION_C_TYPE          1
 814 #define BFD_ELF_VERSION_CXX_TYPE        2
 815 #define BFD_ELF_VERSION_JAVA_TYPE       4
 816   unsigned int mask : 3;
 817 };
 818
 819 struct bfd_elf_version_expr_head
 820 {
 821   /* List of all patterns, both wildcards and non-wildcards.  */
 822   struct bfd_elf_version_expr *list;
 823   /* Hash table for non-wildcards.  */
 824   void *htab;
 825   /* Remaining patterns.  */
 826   struct bfd_elf_version_expr *remaining;
 827   /* What kind of pattern types are present in list (bitmask).  */
 828   unsigned int mask;
 829 };
 830
 831 /* Version dependencies.  */
 832
 833 struct bfd_elf_version_deps
 834 {
 835   /* Next dependency for this version.  */
 836   struct bfd_elf_version_deps *next;
 837   /* The version which this version depends upon.  */
 838   struct bfd_elf_version_tree *version_needed;
 839 };
 840
 841 /* A node in the version tree.  */
 842
 843 struct bfd_elf_version_tree
 844 {
 845   /* Next version.  */
 846   struct bfd_elf_version_tree *next;
 847   /* Name of this version.  */
 848   const char *name;
 849   /* Version number.  */
 850   unsigned int vernum;
 851   /* Regular expressions for global symbols in this version.  */
 852   struct bfd_elf_version_expr_head globals;
 853   /* Regular expressions for local symbols in this version.  */
 854   struct bfd_elf_version_expr_head locals;
 855   /* List of versions which this version depends upon.  */
 856   struct bfd_elf_version_deps *deps;
 857   /* Index of the version name.  This is used within BFD.  */
 858   unsigned int name_indx;
 859   /* Whether this version tree was used.  This is used within BFD.  */
 860   int used;
 861   /* Matching hook.  */
 862   struct bfd_elf_version_expr *(*match)
 863     (struct bfd_elf_version_expr_head *head,
 864      struct bfd_elf_version_expr *prev, const char *sym);
 865 };
 866
 867 struct bfd_elf_dynamic_list
 868 {
 869   struct bfd_elf_version_expr_head head;
 870   struct bfd_elf_version_expr *(*match)
 871     (struct bfd_elf_version_expr_head *head,
 872      struct bfd_elf_version_expr *prev, const char *sym);
 873 };
 874
 875 #endif