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