include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2016 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 /* Whether to generate ELF common symbols with the STT_COMMON type
  46    during a relocatable link.  */
  47 enum bfd_link_elf_stt_common
  48 {
  49   unchanged,
  50   elf_stt_common,
  51   no_elf_stt_common
  52 };
  53
  54 /* Describes the type of hash table entry structure being used.
  55    Different hash table structure have different fields and so
  56    support different linking features.  */
  57 enum bfd_link_hash_table_type
  58   {
  59     bfd_link_generic_hash_table,
  60     bfd_link_elf_hash_table
  61   };
  62 \f
  63 /* These are the possible types of an entry in the BFD link hash
  64    table.  */
  65
  66 enum bfd_link_hash_type
  67 {
  68   bfd_link_hash_new,            /* Symbol is new.  */
  69   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  70   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  71   bfd_link_hash_defined,        /* Symbol is defined.  */
  72   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  73   bfd_link_hash_common,         /* Symbol is common.  */
  74   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  75   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  76 };
  77
  78 enum bfd_link_common_skip_ar_symbols
  79 {
  80   bfd_link_common_skip_none,
  81   bfd_link_common_skip_text,
  82   bfd_link_common_skip_data,
  83   bfd_link_common_skip_all
  84 };
  85
  86 struct bfd_link_hash_common_entry
  87   {
  88     unsigned int alignment_power;       /* Alignment.  */
  89     asection *section;          /* Symbol section.  */
  90   };
  91
  92 /* The linking routines use a hash table which uses this structure for
  93    its elements.  */
  94
  95 struct bfd_link_hash_entry
  96 {
  97   /* Base hash table entry structure.  */
  98   struct bfd_hash_entry root;
  99
 100   /* Type of this entry.  */
 101   ENUM_BITFIELD (bfd_link_hash_type) type : 8;
 102
 103   /* Symbol is referenced in a normal object file, as distict from a LTO
 104      IR object file.  */
 105   unsigned int non_ir_ref : 1;
 106
 107   /* Symbol is a built-in define.  These will be overridden by PROVIDE
 108      in a linker script.  */
 109   unsigned int linker_def : 1;
 110
 111   /* A union of information depending upon the type.  */
 112   union
 113     {
 114       /* Nothing is kept for bfd_hash_new.  */
 115       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 116       struct
 117         {
 118           /* Undefined and common symbols are kept in a linked list through
 119              this field.  This field is present in all of the union element
 120              so that we don't need to remove entries from the list when we
 121              change their type.  Removing entries would either require the
 122              list to be doubly linked, which would waste more memory, or
 123              require a traversal.  When an undefined or common symbol is
 124              created, it should be added to this list, the head of which is in
 125              the link hash table itself.  As symbols are defined, they need
 126              not be removed from the list; anything which reads the list must
 127              doublecheck the symbol type.
 128
 129              Weak symbols are not kept on this list.
 130
 131              Defined and defweak symbols use this field as a reference marker.
 132              If the field is not NULL, or this structure is the tail of the
 133              undefined symbol list, the symbol has been referenced.  If the
 134              symbol is undefined and becomes defined, this field will
 135              automatically be non-NULL since the symbol will have been on the
 136              undefined symbol list.  */
 137           struct bfd_link_hash_entry *next;
 138           bfd *abfd;            /* BFD symbol was found in.  */
 139         } undef;
 140       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 141       struct
 142         {
 143           struct bfd_link_hash_entry *next;
 144           asection *section;    /* Symbol section.  */
 145           bfd_vma value;        /* Symbol value.  */
 146         } def;
 147       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 148       struct
 149         {
 150           struct bfd_link_hash_entry *next;
 151           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 152           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 153         } i;
 154       /* bfd_link_hash_common.  */
 155       struct
 156         {
 157           struct bfd_link_hash_entry *next;
 158           /* The linker needs to know three things about common
 159              symbols: the size, the alignment, and the section in
 160              which the symbol should be placed.  We store the size
 161              here, and we allocate a small structure to hold the
 162              section and the alignment.  The alignment is stored as a
 163              power of two.  We don't store all the information
 164              directly because we don't want to increase the size of
 165              the union; this structure is a major space user in the
 166              linker.  */
 167           struct bfd_link_hash_common_entry *p;
 168           bfd_size_type size;   /* Common symbol size.  */
 169         } c;
 170     } u;
 171 };
 172
 173 /* This is the link hash table.  It is a derived class of
 174    bfd_hash_table.  */
 175
 176 struct bfd_link_hash_table
 177 {
 178   /* The hash table itself.  */
 179   struct bfd_hash_table table;
 180   /* A linked list of undefined and common symbols, linked through the
 181      next field in the bfd_link_hash_entry structure.  */
 182   struct bfd_link_hash_entry *undefs;
 183   /* Entries are added to the tail of the undefs list.  */
 184   struct bfd_link_hash_entry *undefs_tail;
 185   /* Function to free the hash table on closing BFD.  */
 186   void (*hash_table_free) (bfd *);
 187   /* The type of the link hash table.  */
 188   enum bfd_link_hash_table_type type;
 189 };
 190
 191 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 192    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 193    the real symbol.  */
 194 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 195   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 196    bfd_boolean copy, bfd_boolean follow);
 197
 198 /* Look up an entry in the main linker hash table if the symbol might
 199    be wrapped.  This should only be used for references to an
 200    undefined symbol, not for definitions of a symbol.  */
 201
 202 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 203   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 204    bfd_boolean, bfd_boolean);
 205
 206 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 207    and the remainder is found in wrap_hash, return the real symbol.  */
 208
 209 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 210   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 211
 212 /* Traverse a link hash table.  */
 213 extern void bfd_link_hash_traverse
 214   (struct bfd_link_hash_table *,
 215     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 216     void *);
 217
 218 /* Add an entry to the undefs list.  */
 219 extern void bfd_link_add_undef
 220   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 221
 222 /* Remove symbols from the undefs list that don't belong there.  */
 223 extern void bfd_link_repair_undef_list
 224   (struct bfd_link_hash_table *table);
 225
 226 /* Read symbols and cache symbol pointer array in outsymbols.  */
 227 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 228
 229 /* Check the relocs in the BFD.  Called after all the input
 230    files have been loaded, and garbage collection has tagged
 231    any unneeded sections.  */
 232 extern bfd_boolean bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 233
 234 struct bfd_sym_chain
 235 {
 236   struct bfd_sym_chain *next;
 237   const char *name;
 238 };
 239 \f
 240 /* How to handle unresolved symbols.
 241    There are four possibilities which are enumerated below:  */
 242 enum report_method
 243 {
 244   /* This is the initial value when then link_info structure is created.
 245      It allows the various stages of the linker to determine whether they
 246      allowed to set the value.  */
 247   RM_NOT_YET_SET = 0,
 248   RM_IGNORE,
 249   RM_GENERATE_WARNING,
 250   RM_GENERATE_ERROR
 251 };
 252
 253 typedef enum {with_flags, without_flags} flag_type;
 254
 255 /* A section flag list.  */
 256 struct flag_info_list
 257 {
 258   flag_type with;
 259   const char *name;
 260   bfd_boolean valid;
 261   struct flag_info_list *next;
 262 };
 263
 264 /* Section flag info.  */
 265 struct flag_info
 266 {
 267   flagword only_with_flags;
 268   flagword not_with_flags;
 269   struct flag_info_list *flag_list;
 270   bfd_boolean flags_initialized;
 271 };
 272
 273 struct bfd_elf_dynamic_list;
 274 struct bfd_elf_version_tree;
 275
 276 /* Types of output.  */
 277
 278 enum output_type
 279 {
 280   type_pde,
 281   type_pie,
 282   type_relocatable,
 283   type_dll,
 284 };
 285
 286 #define bfd_link_pde(info)         ((info)->type == type_pde)
 287 #define bfd_link_dll(info)         ((info)->type == type_dll)
 288 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 289 #define bfd_link_pie(info)         ((info)->type == type_pie)
 290 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 291 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 292
 293 /* This structure holds all the information needed to communicate
 294    between BFD and the linker when doing a link.  */
 295
 296 struct bfd_link_info
 297 {
 298   /* Output type.  */
 299   ENUM_BITFIELD (output_type) type : 2;
 300
 301   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 302   unsigned int symbolic: 1;
 303
 304   /* TRUE if executable should not contain copy relocs.
 305      Setting this true may result in a non-sharable text segment.  */
 306   unsigned int nocopyreloc: 1;
 307
 308   /* TRUE if BFD should export all symbols in the dynamic symbol table
 309      of an executable, rather than only those used.  */
 310   unsigned int export_dynamic: 1;
 311
 312   /* TRUE if a default symbol version should be created and used for
 313      exported symbols.  */
 314   unsigned int create_default_symver: 1;
 315
 316   /* TRUE if unreferenced sections should be removed.  */
 317   unsigned int gc_sections: 1;
 318
 319   /* TRUE if every symbol should be reported back via the notice
 320      callback.  */
 321   unsigned int notice_all: 1;
 322
 323   /* TRUE if the LTO plugin is active.  */
 324   unsigned int lto_plugin_active: 1;
 325
 326   /* TRUE if global symbols in discarded sections should be stripped.  */
 327   unsigned int strip_discarded: 1;
 328
 329   /* TRUE if all data symbols should be dynamic.  */
 330   unsigned int dynamic_data: 1;
 331
 332   /* Which symbols to strip.  */
 333   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 334
 335   /* Which local symbols to discard.  */
 336   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 337
 338   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 339   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 340
 341   /* Criteria for skipping symbols when determining
 342      whether to include an object from an archive. */
 343   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 344
 345   /* What to do with unresolved symbols in an object file.
 346      When producing executables the default is GENERATE_ERROR.
 347      When producing shared libraries the default is IGNORE.  The
 348      assumption with shared libraries is that the reference will be
 349      resolved at load/execution time.  */
 350   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 351
 352   /* What to do with unresolved symbols in a shared library.
 353      The same defaults apply.  */
 354   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 355
 356   /* TRUE if shared objects should be linked directly, not shared.  */
 357   unsigned int static_link: 1;
 358
 359   /* TRUE if symbols should be retained in memory, FALSE if they
 360      should be freed and reread.  */
 361   unsigned int keep_memory: 1;
 362
 363   /* TRUE if BFD should generate relocation information in the final
 364      executable.  */
 365   unsigned int emitrelocations: 1;
 366
 367   /* TRUE if PT_GNU_RELRO segment should be created.  */
 368   unsigned int relro: 1;
 369
 370   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 371      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 372   unsigned int eh_frame_hdr_type: 2;
 373
 374   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 375   unsigned int warn_shared_textrel: 1;
 376
 377   /* TRUE if we should error when adding a DT_TEXTREL.  */
 378   unsigned int error_textrel: 1;
 379
 380   /* TRUE if .hash section should be created.  */
 381   unsigned int emit_hash: 1;
 382
 383   /* TRUE if .gnu.hash section should be created.  */
 384   unsigned int emit_gnu_hash: 1;
 385
 386   /* If TRUE reduce memory overheads, at the expense of speed. This will
 387      cause map file generation to use an O(N^2) algorithm and disable
 388      caching ELF symbol buffer.  */
 389   unsigned int reduce_memory_overheads: 1;
 390
 391   /* TRUE if the output file should be in a traditional format.  This
 392      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 393      on the output file, but may be checked when reading the input
 394      files.  */
 395   unsigned int traditional_format: 1;
 396
 397   /* TRUE if non-PLT relocs should be merged into one reloc section
 398      and sorted so that relocs against the same symbol come together.  */
 399   unsigned int combreloc: 1;
 400
 401   /* TRUE if a default symbol version should be created and used for
 402      imported symbols.  */
 403   unsigned int default_imported_symver: 1;
 404
 405   /* TRUE if the new ELF dynamic tags are enabled. */
 406   unsigned int new_dtags: 1;
 407
 408   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 409      linker created sections, TRUE if it should be omitted.  */
 410   unsigned int no_ld_generated_unwind_info: 1;
 411
 412   /* TRUE if BFD should generate a "task linked" object file,
 413      similar to relocatable but also with globals converted to
 414      statics.  */
 415   unsigned int task_link: 1;
 416
 417   /* TRUE if ok to have multiple definition.  */
 418   unsigned int allow_multiple_definition: 1;
 419
 420   /* TRUE if ok to have version with no definition.  */
 421   unsigned int allow_undefined_version: 1;
 422
 423   /* TRUE if some symbols have to be dynamic, controlled by
 424      --dynamic-list command line options.  */
 425   unsigned int dynamic: 1;
 426
 427   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 428      flags.  */
 429   unsigned int execstack: 1;
 430
 431   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 432      flags.  */
 433   unsigned int noexecstack: 1;
 434
 435   /* TRUE if we want to produced optimized output files.  This might
 436      need much more time and therefore must be explicitly selected.  */
 437   unsigned int optimize: 1;
 438
 439   /* TRUE if user should be informed of removed unreferenced sections.  */
 440   unsigned int print_gc_sections: 1;
 441
 442   /* TRUE if we should warn alternate ELF machine code.  */
 443   unsigned int warn_alternate_em: 1;
 444
 445   /* TRUE if the linker script contained an explicit PHDRS command.  */
 446   unsigned int user_phdrs: 1;
 447
 448   /* TRUE if we should check relocations after all input files have
 449      been opened.  */
 450   unsigned int check_relocs_after_open_input: 1;
 451
 452   /* TRUE if BND prefix in PLT entries is always generated.  */
 453   unsigned int bndplt: 1;
 454
 455   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 456   unsigned int nointerp: 1;
 457
 458   /* TRUE if we shouldn't check relocation overflow.  */
 459   unsigned int no_reloc_overflow_check: 1;
 460
 461   /* TRUE if generate a 1-byte NOP as suffix for x86 call instruction.  */
 462   unsigned int call_nop_as_suffix : 1;
 463
 464   /* The 1-byte NOP for x86 call instruction.  */
 465   char call_nop_byte;
 466
 467   /* Char that may appear as the first char of a symbol, but should be
 468      skipped (like symbol_leading_char) when looking up symbols in
 469      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 470   char wrap_char;
 471
 472   /* Separator between archive and filename in linker script filespecs.  */
 473   char path_separator;
 474
 475   /* Compress DWARF debug sections.  */
 476   enum compressed_debug_section_type compress_debug;
 477
 478   /* Default stack size.  Zero means default (often zero itself), -1
 479      means explicitly zero-sized.  */
 480   bfd_signed_vma stacksize;
 481
 482   /* Enable or disable target specific optimizations.
 483
 484      Not all targets have optimizations to enable.
 485
 486      Normally these optimizations are disabled by default but some targets
 487      prefer to enable them by default.  So this field is a tri-state variable.
 488      The values are:
 489
 490      zero: Enable the optimizations (either from --relax being specified on
 491        the command line or the backend's before_allocation emulation function.
 492
 493      positive: The user has requested that these optimizations be disabled.
 494        (Via the --no-relax command line option).
 495
 496      negative: The optimizations are disabled.  (Set when initializing the
 497        args_type structure in ldmain.c:main.  */
 498   signed int disable_target_specific_optimizations;
 499
 500   /* Function callbacks.  */
 501   const struct bfd_link_callbacks *callbacks;
 502
 503   /* Hash table handled by BFD.  */
 504   struct bfd_link_hash_table *hash;
 505
 506   /* Hash table of symbols to keep.  This is NULL unless strip is
 507      strip_some.  */
 508   struct bfd_hash_table *keep_hash;
 509
 510   /* Hash table of symbols to report back via the notice callback.  If
 511      this is NULL, and notice_all is FALSE, then no symbols are
 512      reported back.  */
 513   struct bfd_hash_table *notice_hash;
 514
 515   /* Hash table of symbols which are being wrapped (the --wrap linker
 516      option).  If this is NULL, no symbols are being wrapped.  */
 517   struct bfd_hash_table *wrap_hash;
 518
 519   /* Hash table of symbols which may be left unresolved during
 520      a link.  If this is NULL, no symbols can be left unresolved.  */
 521   struct bfd_hash_table *ignore_hash;
 522
 523   /* The output BFD.  */
 524   bfd *output_bfd;
 525
 526   /* The list of input BFD's involved in the link.  These are chained
 527      together via the link.next field.  */
 528   bfd *input_bfds;
 529   bfd **input_bfds_tail;
 530
 531   /* If a symbol should be created for each input BFD, this is section
 532      where those symbols should be placed.  It must be a section in
 533      the output BFD.  It may be NULL, in which case no such symbols
 534      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 535      linker command language.  */
 536   asection *create_object_symbols_section;
 537
 538   /* List of global symbol names that are starting points for marking
 539      sections against garbage collection.  */
 540   struct bfd_sym_chain *gc_sym_list;
 541
 542   /* If a base output file is wanted, then this points to it */
 543   void *base_file;
 544
 545   /* The function to call when the executable or shared object is
 546      loaded.  */
 547   const char *init_function;
 548
 549   /* The function to call when the executable or shared object is
 550      unloaded.  */
 551   const char *fini_function;
 552
 553   /* Number of relaxation passes.  Usually only one relaxation pass
 554      is needed.  But a backend can have as many relaxation passes as
 555      necessary.  During bfd_relax_section call, it is set to the
 556      current pass, starting from 0.  */
 557   int relax_pass;
 558
 559   /* Number of relaxation trips.  This number is incremented every
 560      time the relaxation pass is restarted due to a previous
 561      relaxation returning true in *AGAIN.  */
 562   int relax_trip;
 563
 564   /* > 0 to treat protected data defined in the shared library as
 565      reference external.  0 to treat it as internal.  -1 to let
 566      backend to decide.  */
 567   int extern_protected_data;
 568
 569   /* > 0 to treat undefined weak symbol in the executable as dynamic,
 570      requiring dynamic relocation.  */
 571   int dynamic_undefined_weak;
 572
 573   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 574      should be generated/linked against.  Set to 1 if this feature
 575      is explicitly requested by the user, -1 if enabled by default.  */
 576   int pei386_auto_import;
 577
 578   /* Non-zero if runtime relocs for DATA items with non-zero addends
 579      in pei386 DLLs should be generated.  Set to 1 if this feature
 580      is explicitly requested by the user, -1 if enabled by default.  */
 581   int pei386_runtime_pseudo_reloc;
 582
 583   /* How many spare .dynamic DT_NULL entries should be added?  */
 584   unsigned int spare_dynamic_tags;
 585
 586   /* May be used to set DT_FLAGS for ELF. */
 587   bfd_vma flags;
 588
 589   /* May be used to set DT_FLAGS_1 for ELF. */
 590   bfd_vma flags_1;
 591
 592   /* Start and end of RELRO region.  */
 593   bfd_vma relro_start, relro_end;
 594
 595   /* List of symbols should be dynamic.  */
 596   struct bfd_elf_dynamic_list *dynamic_list;
 597
 598   /* The version information.  */
 599   struct bfd_elf_version_tree *version_info;
 600 };
 601
 602 /* This structures holds a set of callback functions.  These are called
 603    by the BFD linker routines.  Except for the info functions, the first
 604    argument to each callback function is the bfd_link_info structure
 605    being used and each function returns a boolean value.  If the
 606    function returns FALSE, then the BFD function which called it should
 607    return with a failure indication.  */
 608
 609 struct bfd_link_callbacks
 610 {
 611   /* A function which is called when an object is added from an
 612      archive.  ABFD is the archive element being added.  NAME is the
 613      name of the symbol which caused the archive element to be pulled
 614      in.  This function may set *SUBSBFD to point to an alternative
 615      BFD from which symbols should in fact be added in place of the
 616      original BFD's symbols.  */
 617   bfd_boolean (*add_archive_element)
 618     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 619   /* A function which is called when a symbol is found with multiple
 620      definitions.  H is the symbol which is defined multiple times.
 621      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 622      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 623   bfd_boolean (*multiple_definition)
 624     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 625      bfd *nbfd, asection *nsec, bfd_vma nval);
 626   /* A function which is called when a common symbol is defined
 627      multiple times.  H is the symbol appearing multiple times.
 628      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 629      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 630      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 631      is the size of the new symbol.  */
 632   bfd_boolean (*multiple_common)
 633     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 634      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 635   /* A function which is called to add a symbol to a set.  ENTRY is
 636      the link hash table entry for the set itself (e.g.,
 637      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 638      the set when generating a relocatable file, and is also used to
 639      get the size of the entry when generating an executable file.
 640      ABFD, SEC and VALUE identify the value to add to the set.  */
 641   bfd_boolean (*add_to_set)
 642     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 643      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 644   /* A function which is called when the name of a g++ constructor or
 645      destructor is found.  This is only called by some object file
 646      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 647      destructor.  This will use BFD_RELOC_CTOR when generating a
 648      relocatable file.  NAME is the name of the symbol found.  ABFD,
 649      SECTION and VALUE are the value of the symbol.  */
 650   bfd_boolean (*constructor)
 651     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 652      bfd *abfd, asection *sec, bfd_vma value);
 653   /* A function which is called to issue a linker warning.  For
 654      example, this is called when there is a reference to a warning
 655      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 656      of the symbol which triggered the warning; it may be NULL if
 657      there is none.  ABFD, SECTION and ADDRESS identify the location
 658      which trigerred the warning; either ABFD or SECTION or both may
 659      be NULL if the location is not known.  */
 660   bfd_boolean (*warning)
 661     (struct bfd_link_info *, const char *warning, const char *symbol,
 662      bfd *abfd, asection *section, bfd_vma address);
 663   /* A function which is called when a relocation is attempted against
 664      an undefined symbol.  NAME is the symbol which is undefined.
 665      ABFD, SECTION and ADDRESS identify the location from which the
 666      reference is made. IS_FATAL indicates whether an undefined symbol is
 667      a fatal error or not. In some cases SECTION may be NULL.  */
 668   bfd_boolean (*undefined_symbol)
 669     (struct bfd_link_info *, const char *name, bfd *abfd,
 670      asection *section, bfd_vma address, bfd_boolean is_fatal);
 671   /* A function which is called when a reloc overflow occurs. ENTRY is
 672      the link hash table entry for the symbol the reloc is against.
 673      NAME is the name of the local symbol or section the reloc is
 674      against, RELOC_NAME is the name of the relocation, and ADDEND is
 675      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 676      location at which the overflow occurs; if this is the result of a
 677      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 678      ABFD will be NULL.  */
 679   bfd_boolean (*reloc_overflow)
 680     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 681      const char *name, const char *reloc_name, bfd_vma addend,
 682      bfd *abfd, asection *section, bfd_vma address);
 683   /* A function which is called when a dangerous reloc is performed.
 684      MESSAGE is an appropriate message.
 685      ABFD, SECTION and ADDRESS identify the location at which the
 686      problem occurred; if this is the result of a
 687      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 688      ABFD will be NULL.  */
 689   bfd_boolean (*reloc_dangerous)
 690     (struct bfd_link_info *, const char *message,
 691      bfd *abfd, asection *section, bfd_vma address);
 692   /* A function which is called when a reloc is found to be attached
 693      to a symbol which is not being written out.  NAME is the name of
 694      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 695      the reloc; if this is the result of a
 696      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 697      ABFD will be NULL.  */
 698   bfd_boolean (*unattached_reloc)
 699     (struct bfd_link_info *, const char *name,
 700      bfd *abfd, asection *section, bfd_vma address);
 701   /* A function which is called when a symbol in notice_hash is
 702      defined or referenced.  H is the symbol, INH the indirect symbol
 703      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 704      the symbol.  If SECTION is bfd_und_section, this is a reference.
 705      FLAGS are the symbol BSF_* flags.  */
 706   bfd_boolean (*notice)
 707     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 708      struct bfd_link_hash_entry *inh,
 709      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 710   /* Error or warning link info message.  */
 711   void (*einfo)
 712     (const char *fmt, ...);
 713   /* General link info message.  */
 714   void (*info)
 715     (const char *fmt, ...);
 716   /* Message to be printed in linker map file.  */
 717   void (*minfo)
 718     (const char *fmt, ...);
 719   /* This callback provides a chance for users of the BFD library to
 720      override its decision about whether to place two adjacent sections
 721      into the same segment.  */
 722   bfd_boolean (*override_segment_assignment)
 723     (struct bfd_link_info *, bfd * abfd,
 724      asection * current_section, asection * previous_section,
 725      bfd_boolean new_segment);
 726 };
 727 \f
 728 /* The linker builds link_order structures which tell the code how to
 729    include input data in the output file.  */
 730
 731 /* These are the types of link_order structures.  */
 732
 733 enum bfd_link_order_type
 734 {
 735   bfd_undefined_link_order,     /* Undefined.  */
 736   bfd_indirect_link_order,      /* Built from a section.  */
 737   bfd_data_link_order,          /* Set to explicit data.  */
 738   bfd_section_reloc_link_order, /* Relocate against a section.  */
 739   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 740 };
 741
 742 /* This is the link_order structure itself.  These form a chain
 743    attached to the output section whose contents they are describing.  */
 744
 745 struct bfd_link_order
 746 {
 747   /* Next link_order in chain.  */
 748   struct bfd_link_order *next;
 749   /* Type of link_order.  */
 750   enum bfd_link_order_type type;
 751   /* Offset within output section.  */
 752   bfd_vma offset;
 753   /* Size within output section.  */
 754   bfd_size_type size;
 755   /* Type specific information.  */
 756   union
 757     {
 758       struct
 759         {
 760           /* Section to include.  If this is used, then
 761              section->output_section must be the section the
 762              link_order is attached to, section->output_offset must
 763              equal the link_order offset field, and section->size
 764              must equal the link_order size field.  Maybe these
 765              restrictions should be relaxed someday.  */
 766           asection *section;
 767         } indirect;
 768       struct
 769         {
 770           /* Size of contents, or zero when contents should be filled by
 771              the architecture-dependent fill function.
 772              A non-zero value allows filling of the output section
 773              with an arbitrary repeated pattern.  */
 774           unsigned int size;
 775           /* Data to put into file.  */
 776           bfd_byte *contents;
 777         } data;
 778       struct
 779         {
 780           /* Description of reloc to generate.  Used for
 781              bfd_section_reloc_link_order and
 782              bfd_symbol_reloc_link_order.  */
 783           struct bfd_link_order_reloc *p;
 784         } reloc;
 785     } u;
 786 };
 787
 788 /* A linker order of type bfd_section_reloc_link_order or
 789    bfd_symbol_reloc_link_order means to create a reloc against a
 790    section or symbol, respectively.  This is used to implement -Ur to
 791    generate relocs for the constructor tables.  The
 792    bfd_link_order_reloc structure describes the reloc that BFD should
 793    create.  It is similar to a arelent, but I didn't use arelent
 794    because the linker does not know anything about most symbols, and
 795    any asymbol structure it creates will be partially meaningless.
 796    This information could logically be in the bfd_link_order struct,
 797    but I didn't want to waste the space since these types of relocs
 798    are relatively rare.  */
 799
 800 struct bfd_link_order_reloc
 801 {
 802   /* Reloc type.  */
 803   bfd_reloc_code_real_type reloc;
 804
 805   union
 806     {
 807       /* For type bfd_section_reloc_link_order, this is the section
 808          the reloc should be against.  This must be a section in the
 809          output BFD, not any of the input BFDs.  */
 810       asection *section;
 811       /* For type bfd_symbol_reloc_link_order, this is the name of the
 812          symbol the reloc should be against.  */
 813       const char *name;
 814     } u;
 815
 816   /* Addend to use.  The object file should contain zero.  The BFD
 817      backend is responsible for filling in the contents of the object
 818      file correctly.  For some object file formats (e.g., COFF) the
 819      addend must be stored into in the object file, and for some
 820      (e.g., SPARC a.out) it is kept in the reloc.  */
 821   bfd_vma addend;
 822 };
 823
 824 /* Allocate a new link_order for a section.  */
 825 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 826
 827 /* These structures are used to describe version information for the
 828    ELF linker.  These structures could be manipulated entirely inside
 829    BFD, but it would be a pain.  Instead, the regular linker sets up
 830    these structures, and then passes them into BFD.  */
 831
 832 /* Glob pattern for a version.  */
 833
 834 struct bfd_elf_version_expr
 835 {
 836   /* Next glob pattern for this version.  */
 837   struct bfd_elf_version_expr *next;
 838   /* Glob pattern.  */
 839   const char *pattern;
 840   /* Set if pattern is not a glob.  */
 841   unsigned int literal : 1;
 842   /* Defined by ".symver".  */
 843   unsigned int symver : 1;
 844   /* Defined by version script.  */
 845   unsigned int script : 1;
 846   /* Pattern type.  */
 847 #define BFD_ELF_VERSION_C_TYPE          1
 848 #define BFD_ELF_VERSION_CXX_TYPE        2
 849 #define BFD_ELF_VERSION_JAVA_TYPE       4
 850   unsigned int mask : 3;
 851 };
 852
 853 struct bfd_elf_version_expr_head
 854 {
 855   /* List of all patterns, both wildcards and non-wildcards.  */
 856   struct bfd_elf_version_expr *list;
 857   /* Hash table for non-wildcards.  */
 858   void *htab;
 859   /* Remaining patterns.  */
 860   struct bfd_elf_version_expr *remaining;
 861   /* What kind of pattern types are present in list (bitmask).  */
 862   unsigned int mask;
 863 };
 864
 865 /* Version dependencies.  */
 866
 867 struct bfd_elf_version_deps
 868 {
 869   /* Next dependency for this version.  */
 870   struct bfd_elf_version_deps *next;
 871   /* The version which this version depends upon.  */
 872   struct bfd_elf_version_tree *version_needed;
 873 };
 874
 875 /* A node in the version tree.  */
 876
 877 struct bfd_elf_version_tree
 878 {
 879   /* Next version.  */
 880   struct bfd_elf_version_tree *next;
 881   /* Name of this version.  */
 882   const char *name;
 883   /* Version number.  */
 884   unsigned int vernum;
 885   /* Regular expressions for global symbols in this version.  */
 886   struct bfd_elf_version_expr_head globals;
 887   /* Regular expressions for local symbols in this version.  */
 888   struct bfd_elf_version_expr_head locals;
 889   /* List of versions which this version depends upon.  */
 890   struct bfd_elf_version_deps *deps;
 891   /* Index of the version name.  This is used within BFD.  */
 892   unsigned int name_indx;
 893   /* Whether this version tree was used.  This is used within BFD.  */
 894   int used;
 895   /* Matching hook.  */
 896   struct bfd_elf_version_expr *(*match)
 897     (struct bfd_elf_version_expr_head *head,
 898      struct bfd_elf_version_expr *prev, const char *sym);
 899 };
 900
 901 struct bfd_elf_dynamic_list
 902 {
 903   struct bfd_elf_version_expr_head head;
 904   struct bfd_elf_version_expr *(*match)
 905     (struct bfd_elf_version_expr_head *head,
 906      struct bfd_elf_version_expr *prev, const char *sym);
 907 };
 908
 909 #endif