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