include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2017 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 regular object file,
 104      as distinct from a LTO IR object file.  */
 105   unsigned int non_ir_ref_regular : 1;
 106
 107   /* Symbol is referenced in a normal dynamic object file,
 108      as distinct from a LTO IR object file.  */
 109   unsigned int non_ir_ref_dynamic : 1;
 110
 111   /* Symbol is a built-in define.  These will be overridden by PROVIDE
 112      in a linker script.  */
 113   unsigned int linker_def : 1;
 114
 115   /* Symbol defined in a linker script.  */
 116   unsigned int ldscript_def : 1;
 117
 118   /* A union of information depending upon the type.  */
 119   union
 120     {
 121       /* Nothing is kept for bfd_hash_new.  */
 122       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 123       struct
 124         {
 125           /* Undefined and common symbols are kept in a linked list through
 126              this field.  This field is present in all of the union element
 127              so that we don't need to remove entries from the list when we
 128              change their type.  Removing entries would either require the
 129              list to be doubly linked, which would waste more memory, or
 130              require a traversal.  When an undefined or common symbol is
 131              created, it should be added to this list, the head of which is in
 132              the link hash table itself.  As symbols are defined, they need
 133              not be removed from the list; anything which reads the list must
 134              doublecheck the symbol type.
 135
 136              Weak symbols are not kept on this list.
 137
 138              Defined and defweak symbols use this field as a reference marker.
 139              If the field is not NULL, or this structure is the tail of the
 140              undefined symbol list, the symbol has been referenced.  If the
 141              symbol is undefined and becomes defined, this field will
 142              automatically be non-NULL since the symbol will have been on the
 143              undefined symbol list.  */
 144           struct bfd_link_hash_entry *next;
 145           /* BFD symbol was found in.  */
 146           bfd *abfd;
 147           /* For __start_<name> and __stop_<name> symbols, the first
 148              input section matching the name.  */
 149           asection *section;
 150         } undef;
 151       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 152       struct
 153         {
 154           struct bfd_link_hash_entry *next;
 155           /* Symbol section.  */
 156           asection *section;
 157           /* Symbol value.  */
 158           bfd_vma value;
 159         } def;
 160       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 161       struct
 162         {
 163           struct bfd_link_hash_entry *next;
 164           /* Real symbol.  */
 165           struct bfd_link_hash_entry *link;
 166           /* Warning message (bfd_link_hash_warning only).  */
 167           const char *warning;
 168         } i;
 169       /* bfd_link_hash_common.  */
 170       struct
 171         {
 172           struct bfd_link_hash_entry *next;
 173           /* The linker needs to know three things about common
 174              symbols: the size, the alignment, and the section in
 175              which the symbol should be placed.  We store the size
 176              here, and we allocate a small structure to hold the
 177              section and the alignment.  The alignment is stored as a
 178              power of two.  We don't store all the information
 179              directly because we don't want to increase the size of
 180              the union; this structure is a major space user in the
 181              linker.  */
 182           struct bfd_link_hash_common_entry *p;
 183           /* Common symbol size.  */
 184           bfd_size_type size;
 185         } c;
 186     } u;
 187 };
 188
 189 /* This is the link hash table.  It is a derived class of
 190    bfd_hash_table.  */
 191
 192 struct bfd_link_hash_table
 193 {
 194   /* The hash table itself.  */
 195   struct bfd_hash_table table;
 196   /* A linked list of undefined and common symbols, linked through the
 197      next field in the bfd_link_hash_entry structure.  */
 198   struct bfd_link_hash_entry *undefs;
 199   /* Entries are added to the tail of the undefs list.  */
 200   struct bfd_link_hash_entry *undefs_tail;
 201   /* Function to free the hash table on closing BFD.  */
 202   void (*hash_table_free) (bfd *);
 203   /* The type of the link hash table.  */
 204   enum bfd_link_hash_table_type type;
 205 };
 206
 207 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 208    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 209    the real symbol.  */
 210 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 211   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 212    bfd_boolean copy, bfd_boolean follow);
 213
 214 /* Look up an entry in the main linker hash table if the symbol might
 215    be wrapped.  This should only be used for references to an
 216    undefined symbol, not for definitions of a symbol.  */
 217
 218 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 219   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 220    bfd_boolean, bfd_boolean);
 221
 222 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 223    and the remainder is found in wrap_hash, return the real symbol.  */
 224
 225 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 226   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 227
 228 /* Traverse a link hash table.  */
 229 extern void bfd_link_hash_traverse
 230   (struct bfd_link_hash_table *,
 231     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 232     void *);
 233
 234 /* Add an entry to the undefs list.  */
 235 extern void bfd_link_add_undef
 236   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 237
 238 /* Remove symbols from the undefs list that don't belong there.  */
 239 extern void bfd_link_repair_undef_list
 240   (struct bfd_link_hash_table *table);
 241
 242 /* Read symbols and cache symbol pointer array in outsymbols.  */
 243 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 244
 245 /* Check the relocs in the BFD.  Called after all the input
 246    files have been loaded, and garbage collection has tagged
 247    any unneeded sections.  */
 248 extern bfd_boolean bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 249
 250 struct bfd_sym_chain
 251 {
 252   struct bfd_sym_chain *next;
 253   const char *name;
 254 };
 255 \f
 256 /* How to handle unresolved symbols.
 257    There are four possibilities which are enumerated below:  */
 258 enum report_method
 259 {
 260   /* This is the initial value when then link_info structure is created.
 261      It allows the various stages of the linker to determine whether they
 262      allowed to set the value.  */
 263   RM_NOT_YET_SET = 0,
 264   RM_IGNORE,
 265   RM_GENERATE_WARNING,
 266   RM_GENERATE_ERROR
 267 };
 268
 269 typedef enum {with_flags, without_flags} flag_type;
 270
 271 /* A section flag list.  */
 272 struct flag_info_list
 273 {
 274   flag_type with;
 275   const char *name;
 276   bfd_boolean valid;
 277   struct flag_info_list *next;
 278 };
 279
 280 /* Section flag info.  */
 281 struct flag_info
 282 {
 283   flagword only_with_flags;
 284   flagword not_with_flags;
 285   struct flag_info_list *flag_list;
 286   bfd_boolean flags_initialized;
 287 };
 288
 289 struct bfd_elf_dynamic_list;
 290 struct bfd_elf_version_tree;
 291
 292 /* Types of output.  */
 293
 294 enum output_type
 295 {
 296   type_pde,
 297   type_pie,
 298   type_relocatable,
 299   type_dll,
 300 };
 301
 302 #define bfd_link_pde(info)         ((info)->type == type_pde)
 303 #define bfd_link_dll(info)         ((info)->type == type_dll)
 304 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 305 #define bfd_link_pie(info)         ((info)->type == type_pie)
 306 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 307 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 308
 309 /* This structure holds all the information needed to communicate
 310    between BFD and the linker when doing a link.  */
 311
 312 struct bfd_link_info
 313 {
 314   /* Output type.  */
 315   ENUM_BITFIELD (output_type) type : 2;
 316
 317   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 318   unsigned int symbolic: 1;
 319
 320   /* TRUE if executable should not contain copy relocs.
 321      Setting this true may result in a non-sharable text segment.  */
 322   unsigned int nocopyreloc: 1;
 323
 324   /* TRUE if BFD should export all symbols in the dynamic symbol table
 325      of an executable, rather than only those used.  */
 326   unsigned int export_dynamic: 1;
 327
 328   /* TRUE if a default symbol version should be created and used for
 329      exported symbols.  */
 330   unsigned int create_default_symver: 1;
 331
 332   /* TRUE if unreferenced sections should be removed.  */
 333   unsigned int gc_sections: 1;
 334
 335   /* TRUE if exported symbols should be kept during section gc.  */
 336   unsigned int gc_keep_exported: 1;
 337
 338   /* TRUE if every symbol should be reported back via the notice
 339      callback.  */
 340   unsigned int notice_all: 1;
 341
 342   /* TRUE if the LTO plugin is active.  */
 343   unsigned int lto_plugin_active: 1;
 344
 345   /* TRUE if global symbols in discarded sections should be stripped.  */
 346   unsigned int strip_discarded: 1;
 347
 348   /* TRUE if all data symbols should be dynamic.  */
 349   unsigned int dynamic_data: 1;
 350
 351   /* Which symbols to strip.  */
 352   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 353
 354   /* Which local symbols to discard.  */
 355   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 356
 357   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 358   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 359
 360   /* Criteria for skipping symbols when determining
 361      whether to include an object from an archive. */
 362   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 363
 364   /* What to do with unresolved symbols in an object file.
 365      When producing executables the default is GENERATE_ERROR.
 366      When producing shared libraries the default is IGNORE.  The
 367      assumption with shared libraries is that the reference will be
 368      resolved at load/execution time.  */
 369   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 370
 371   /* What to do with unresolved symbols in a shared library.
 372      The same defaults apply.  */
 373   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 374
 375   /* TRUE if shared objects should be linked directly, not shared.  */
 376   unsigned int static_link: 1;
 377
 378   /* TRUE if symbols should be retained in memory, FALSE if they
 379      should be freed and reread.  */
 380   unsigned int keep_memory: 1;
 381
 382   /* TRUE if BFD should generate relocation information in the final
 383      executable.  */
 384   unsigned int emitrelocations: 1;
 385
 386   /* TRUE if PT_GNU_RELRO segment should be created.  */
 387   unsigned int relro: 1;
 388
 389   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 390      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 391   unsigned int eh_frame_hdr_type: 2;
 392
 393   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 394   unsigned int warn_shared_textrel: 1;
 395
 396   /* TRUE if we should error when adding a DT_TEXTREL.  */
 397   unsigned int error_textrel: 1;
 398
 399   /* TRUE if .hash section should be created.  */
 400   unsigned int emit_hash: 1;
 401
 402   /* TRUE if .gnu.hash section should be created.  */
 403   unsigned int emit_gnu_hash: 1;
 404
 405   /* If TRUE reduce memory overheads, at the expense of speed. This will
 406      cause map file generation to use an O(N^2) algorithm and disable
 407      caching ELF symbol buffer.  */
 408   unsigned int reduce_memory_overheads: 1;
 409
 410   /* TRUE if the output file should be in a traditional format.  This
 411      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 412      on the output file, but may be checked when reading the input
 413      files.  */
 414   unsigned int traditional_format: 1;
 415
 416   /* TRUE if non-PLT relocs should be merged into one reloc section
 417      and sorted so that relocs against the same symbol come together.  */
 418   unsigned int combreloc: 1;
 419
 420   /* TRUE if a default symbol version should be created and used for
 421      imported symbols.  */
 422   unsigned int default_imported_symver: 1;
 423
 424   /* TRUE if the new ELF dynamic tags are enabled. */
 425   unsigned int new_dtags: 1;
 426
 427   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 428      linker created sections, TRUE if it should be omitted.  */
 429   unsigned int no_ld_generated_unwind_info: 1;
 430
 431   /* TRUE if BFD should generate a "task linked" object file,
 432      similar to relocatable but also with globals converted to
 433      statics.  */
 434   unsigned int task_link: 1;
 435
 436   /* TRUE if ok to have multiple definition.  */
 437   unsigned int allow_multiple_definition: 1;
 438
 439   /* TRUE if ok to have version with no definition.  */
 440   unsigned int allow_undefined_version: 1;
 441
 442   /* TRUE if some symbols have to be dynamic, controlled by
 443      --dynamic-list command line options.  */
 444   unsigned int dynamic: 1;
 445
 446   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 447      flags.  */
 448   unsigned int execstack: 1;
 449
 450   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 451      flags.  */
 452   unsigned int noexecstack: 1;
 453
 454   /* TRUE if we want to produced optimized output files.  This might
 455      need much more time and therefore must be explicitly selected.  */
 456   unsigned int optimize: 1;
 457
 458   /* TRUE if user should be informed of removed unreferenced sections.  */
 459   unsigned int print_gc_sections: 1;
 460
 461   /* TRUE if we should warn alternate ELF machine code.  */
 462   unsigned int warn_alternate_em: 1;
 463
 464   /* TRUE if the linker script contained an explicit PHDRS command.  */
 465   unsigned int user_phdrs: 1;
 466
 467   /* TRUE if we should check relocations after all input files have
 468      been opened.  */
 469   unsigned int check_relocs_after_open_input: 1;
 470
 471   /* TRUE if BND prefix in PLT entries is always generated.  */
 472   unsigned int bndplt: 1;
 473
 474   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 475   unsigned int nointerp: 1;
 476
 477   /* TRUE if we shouldn't check relocation overflow.  */
 478   unsigned int no_reloc_overflow_check: 1;
 479
 480   /* TRUE if generate a 1-byte NOP as suffix for x86 call instruction.  */
 481   unsigned int call_nop_as_suffix : 1;
 482
 483   /* The 1-byte NOP for x86 call instruction.  */
 484   char call_nop_byte;
 485
 486   /* Char that may appear as the first char of a symbol, but should be
 487      skipped (like symbol_leading_char) when looking up symbols in
 488      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 489   char wrap_char;
 490
 491   /* Separator between archive and filename in linker script filespecs.  */
 492   char path_separator;
 493
 494   /* Compress DWARF debug sections.  */
 495   enum compressed_debug_section_type compress_debug;
 496
 497   /* Default stack size.  Zero means default (often zero itself), -1
 498      means explicitly zero-sized.  */
 499   bfd_signed_vma stacksize;
 500
 501   /* Enable or disable target specific optimizations.
 502
 503      Not all targets have optimizations to enable.
 504
 505      Normally these optimizations are disabled by default but some targets
 506      prefer to enable them by default.  So this field is a tri-state variable.
 507      The values are:
 508
 509      zero: Enable the optimizations (either from --relax being specified on
 510        the command line or the backend's before_allocation emulation function.
 511
 512      positive: The user has requested that these optimizations be disabled.
 513        (Via the --no-relax command line option).
 514
 515      negative: The optimizations are disabled.  (Set when initializing the
 516        args_type structure in ldmain.c:main.  */
 517   signed int disable_target_specific_optimizations;
 518
 519   /* Function callbacks.  */
 520   const struct bfd_link_callbacks *callbacks;
 521
 522   /* Hash table handled by BFD.  */
 523   struct bfd_link_hash_table *hash;
 524
 525   /* Hash table of symbols to keep.  This is NULL unless strip is
 526      strip_some.  */
 527   struct bfd_hash_table *keep_hash;
 528
 529   /* Hash table of symbols to report back via the notice callback.  If
 530      this is NULL, and notice_all is FALSE, then no symbols are
 531      reported back.  */
 532   struct bfd_hash_table *notice_hash;
 533
 534   /* Hash table of symbols which are being wrapped (the --wrap linker
 535      option).  If this is NULL, no symbols are being wrapped.  */
 536   struct bfd_hash_table *wrap_hash;
 537
 538   /* Hash table of symbols which may be left unresolved during
 539      a link.  If this is NULL, no symbols can be left unresolved.  */
 540   struct bfd_hash_table *ignore_hash;
 541
 542   /* The output BFD.  */
 543   bfd *output_bfd;
 544
 545   /* The import library generated.  */
 546   bfd *out_implib_bfd;
 547
 548   /* The list of input BFD's involved in the link.  These are chained
 549      together via the link.next field.  */
 550   bfd *input_bfds;
 551   bfd **input_bfds_tail;
 552
 553   /* If a symbol should be created for each input BFD, this is section
 554      where those symbols should be placed.  It must be a section in
 555      the output BFD.  It may be NULL, in which case no such symbols
 556      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 557      linker command language.  */
 558   asection *create_object_symbols_section;
 559
 560   /* List of global symbol names that are starting points for marking
 561      sections against garbage collection.  */
 562   struct bfd_sym_chain *gc_sym_list;
 563
 564   /* If a base output file is wanted, then this points to it */
 565   void *base_file;
 566
 567   /* The function to call when the executable or shared object is
 568      loaded.  */
 569   const char *init_function;
 570
 571   /* The function to call when the executable or shared object is
 572      unloaded.  */
 573   const char *fini_function;
 574
 575   /* Number of relaxation passes.  Usually only one relaxation pass
 576      is needed.  But a backend can have as many relaxation passes as
 577      necessary.  During bfd_relax_section call, it is set to the
 578      current pass, starting from 0.  */
 579   int relax_pass;
 580
 581   /* Number of relaxation trips.  This number is incremented every
 582      time the relaxation pass is restarted due to a previous
 583      relaxation returning true in *AGAIN.  */
 584   int relax_trip;
 585
 586   /* > 0 to treat protected data defined in the shared library as
 587      reference external.  0 to treat it as internal.  -1 to let
 588      backend to decide.  */
 589   int extern_protected_data;
 590
 591   /* 1 to make undefined weak symbols dynamic when building a dynamic
 592      object.  0 to resolve undefined weak symbols to zero.  -1 to let
 593      the backend decide.  */
 594   int dynamic_undefined_weak;
 595
 596   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 597      should be generated/linked against.  Set to 1 if this feature
 598      is explicitly requested by the user, -1 if enabled by default.  */
 599   int pei386_auto_import;
 600
 601   /* Non-zero if runtime relocs for DATA items with non-zero addends
 602      in pei386 DLLs should be generated.  Set to 1 if this feature
 603      is explicitly requested by the user, -1 if enabled by default.  */
 604   int pei386_runtime_pseudo_reloc;
 605
 606   /* How many spare .dynamic DT_NULL entries should be added?  */
 607   unsigned int spare_dynamic_tags;
 608
 609   /* May be used to set DT_FLAGS for ELF. */
 610   bfd_vma flags;
 611
 612   /* May be used to set DT_FLAGS_1 for ELF. */
 613   bfd_vma flags_1;
 614
 615   /* Start and end of RELRO region.  */
 616   bfd_vma relro_start, relro_end;
 617
 618   /* List of symbols should be dynamic.  */
 619   struct bfd_elf_dynamic_list *dynamic_list;
 620
 621   /* The version information.  */
 622   struct bfd_elf_version_tree *version_info;
 623 };
 624
 625 /* This structures holds a set of callback functions.  These are called
 626    by the BFD linker routines.  */
 627
 628 struct bfd_link_callbacks
 629 {
 630   /* A function which is called when an object is added from an
 631      archive.  ABFD is the archive element being added.  NAME is the
 632      name of the symbol which caused the archive element to be pulled
 633      in.  This function may set *SUBSBFD to point to an alternative
 634      BFD from which symbols should in fact be added in place of the
 635      original BFD's symbols.  Returns TRUE if the object should be
 636      added, FALSE if it should be skipped.  */
 637   bfd_boolean (*add_archive_element)
 638     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 639   /* A function which is called when a symbol is found with multiple
 640      definitions.  H is the symbol which is defined multiple times.
 641      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 642      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 643   void (*multiple_definition)
 644     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 645      bfd *nbfd, asection *nsec, bfd_vma nval);
 646   /* A function which is called when a common symbol is defined
 647      multiple times.  H is the symbol appearing multiple times.
 648      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 649      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 650      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 651      is the size of the new symbol.  */
 652   void (*multiple_common)
 653     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 654      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 655   /* A function which is called to add a symbol to a set.  ENTRY is
 656      the link hash table entry for the set itself (e.g.,
 657      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 658      the set when generating a relocatable file, and is also used to
 659      get the size of the entry when generating an executable file.
 660      ABFD, SEC and VALUE identify the value to add to the set.  */
 661   void (*add_to_set)
 662     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 663      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 664   /* A function which is called when the name of a g++ constructor or
 665      destructor is found.  This is only called by some object file
 666      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 667      destructor.  This will use BFD_RELOC_CTOR when generating a
 668      relocatable file.  NAME is the name of the symbol found.  ABFD,
 669      SECTION and VALUE are the value of the symbol.  */
 670   void (*constructor)
 671     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 672      bfd *abfd, asection *sec, bfd_vma value);
 673   /* A function which is called to issue a linker warning.  For
 674      example, this is called when there is a reference to a warning
 675      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 676      of the symbol which triggered the warning; it may be NULL if
 677      there is none.  ABFD, SECTION and ADDRESS identify the location
 678      which trigerred the warning; either ABFD or SECTION or both may
 679      be NULL if the location is not known.  */
 680   void (*warning)
 681     (struct bfd_link_info *, const char *warning, const char *symbol,
 682      bfd *abfd, asection *section, bfd_vma address);
 683   /* A function which is called when a relocation is attempted against
 684      an undefined symbol.  NAME is the symbol which is undefined.
 685      ABFD, SECTION and ADDRESS identify the location from which the
 686      reference is made. IS_FATAL indicates whether an undefined symbol is
 687      a fatal error or not. In some cases SECTION may be NULL.  */
 688   void (*undefined_symbol)
 689     (struct bfd_link_info *, const char *name, bfd *abfd,
 690      asection *section, bfd_vma address, bfd_boolean is_fatal);
 691   /* A function which is called when a reloc overflow occurs. ENTRY is
 692      the link hash table entry for the symbol the reloc is against.
 693      NAME is the name of the local symbol or section the reloc is
 694      against, RELOC_NAME is the name of the relocation, and ADDEND is
 695      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 696      location at which the overflow occurs; if this is the result of a
 697      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 698      ABFD will be NULL.  */
 699   void (*reloc_overflow)
 700     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 701      const char *name, const char *reloc_name, bfd_vma addend,
 702      bfd *abfd, asection *section, bfd_vma address);
 703   /* A function which is called when a dangerous reloc is performed.
 704      MESSAGE is an appropriate message.
 705      ABFD, SECTION and ADDRESS identify the location at which the
 706      problem occurred; if this is the result of a
 707      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 708      ABFD will be NULL.  */
 709   void (*reloc_dangerous)
 710     (struct bfd_link_info *, const char *message,
 711      bfd *abfd, asection *section, bfd_vma address);
 712   /* A function which is called when a reloc is found to be attached
 713      to a symbol which is not being written out.  NAME is the name of
 714      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 715      the reloc; if this is the result of a
 716      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 717      ABFD will be NULL.  */
 718   void (*unattached_reloc)
 719     (struct bfd_link_info *, const char *name,
 720      bfd *abfd, asection *section, bfd_vma address);
 721   /* A function which is called when a symbol in notice_hash is
 722      defined or referenced.  H is the symbol, INH the indirect symbol
 723      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 724      the symbol.  If SECTION is bfd_und_section, this is a reference.
 725      FLAGS are the symbol BSF_* flags.  */
 726   bfd_boolean (*notice)
 727     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 728      struct bfd_link_hash_entry *inh,
 729      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 730   /* Error or warning link info message.  */
 731   void (*einfo)
 732     (const char *fmt, ...);
 733   /* General link info message.  */
 734   void (*info)
 735     (const char *fmt, ...);
 736   /* Message to be printed in linker map file.  */
 737   void (*minfo)
 738     (const char *fmt, ...);
 739   /* This callback provides a chance for users of the BFD library to
 740      override its decision about whether to place two adjacent sections
 741      into the same segment.  */
 742   bfd_boolean (*override_segment_assignment)
 743     (struct bfd_link_info *, bfd * abfd,
 744      asection * current_section, asection * previous_section,
 745      bfd_boolean new_segment);
 746 };
 747 \f
 748 /* The linker builds link_order structures which tell the code how to
 749    include input data in the output file.  */
 750
 751 /* These are the types of link_order structures.  */
 752
 753 enum bfd_link_order_type
 754 {
 755   bfd_undefined_link_order,     /* Undefined.  */
 756   bfd_indirect_link_order,      /* Built from a section.  */
 757   bfd_data_link_order,          /* Set to explicit data.  */
 758   bfd_section_reloc_link_order, /* Relocate against a section.  */
 759   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 760 };
 761
 762 /* This is the link_order structure itself.  These form a chain
 763    attached to the output section whose contents they are describing.  */
 764
 765 struct bfd_link_order
 766 {
 767   /* Next link_order in chain.  */
 768   struct bfd_link_order *next;
 769   /* Type of link_order.  */
 770   enum bfd_link_order_type type;
 771   /* Offset within output section.  */
 772   bfd_vma offset;
 773   /* Size within output section.  */
 774   bfd_size_type size;
 775   /* Type specific information.  */
 776   union
 777     {
 778       struct
 779         {
 780           /* Section to include.  If this is used, then
 781              section->output_section must be the section the
 782              link_order is attached to, section->output_offset must
 783              equal the link_order offset field, and section->size
 784              must equal the link_order size field.  Maybe these
 785              restrictions should be relaxed someday.  */
 786           asection *section;
 787         } indirect;
 788       struct
 789         {
 790           /* Size of contents, or zero when contents should be filled by
 791              the architecture-dependent fill function.
 792              A non-zero value allows filling of the output section
 793              with an arbitrary repeated pattern.  */
 794           unsigned int size;
 795           /* Data to put into file.  */
 796           bfd_byte *contents;
 797         } data;
 798       struct
 799         {
 800           /* Description of reloc to generate.  Used for
 801              bfd_section_reloc_link_order and
 802              bfd_symbol_reloc_link_order.  */
 803           struct bfd_link_order_reloc *p;
 804         } reloc;
 805     } u;
 806 };
 807
 808 /* A linker order of type bfd_section_reloc_link_order or
 809    bfd_symbol_reloc_link_order means to create a reloc against a
 810    section or symbol, respectively.  This is used to implement -Ur to
 811    generate relocs for the constructor tables.  The
 812    bfd_link_order_reloc structure describes the reloc that BFD should
 813    create.  It is similar to a arelent, but I didn't use arelent
 814    because the linker does not know anything about most symbols, and
 815    any asymbol structure it creates will be partially meaningless.
 816    This information could logically be in the bfd_link_order struct,
 817    but I didn't want to waste the space since these types of relocs
 818    are relatively rare.  */
 819
 820 struct bfd_link_order_reloc
 821 {
 822   /* Reloc type.  */
 823   bfd_reloc_code_real_type reloc;
 824
 825   union
 826     {
 827       /* For type bfd_section_reloc_link_order, this is the section
 828          the reloc should be against.  This must be a section in the
 829          output BFD, not any of the input BFDs.  */
 830       asection *section;
 831       /* For type bfd_symbol_reloc_link_order, this is the name of the
 832          symbol the reloc should be against.  */
 833       const char *name;
 834     } u;
 835
 836   /* Addend to use.  The object file should contain zero.  The BFD
 837      backend is responsible for filling in the contents of the object
 838      file correctly.  For some object file formats (e.g., COFF) the
 839      addend must be stored into in the object file, and for some
 840      (e.g., SPARC a.out) it is kept in the reloc.  */
 841   bfd_vma addend;
 842 };
 843
 844 /* Allocate a new link_order for a section.  */
 845 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 846
 847 /* These structures are used to describe version information for the
 848    ELF linker.  These structures could be manipulated entirely inside
 849    BFD, but it would be a pain.  Instead, the regular linker sets up
 850    these structures, and then passes them into BFD.  */
 851
 852 /* Glob pattern for a version.  */
 853
 854 struct bfd_elf_version_expr
 855 {
 856   /* Next glob pattern for this version.  */
 857   struct bfd_elf_version_expr *next;
 858   /* Glob pattern.  */
 859   const char *pattern;
 860   /* Set if pattern is not a glob.  */
 861   unsigned int literal : 1;
 862   /* Defined by ".symver".  */
 863   unsigned int symver : 1;
 864   /* Defined by version script.  */
 865   unsigned int script : 1;
 866   /* Pattern type.  */
 867 #define BFD_ELF_VERSION_C_TYPE          1
 868 #define BFD_ELF_VERSION_CXX_TYPE        2
 869 #define BFD_ELF_VERSION_JAVA_TYPE       4
 870   unsigned int mask : 3;
 871 };
 872
 873 struct bfd_elf_version_expr_head
 874 {
 875   /* List of all patterns, both wildcards and non-wildcards.  */
 876   struct bfd_elf_version_expr *list;
 877   /* Hash table for non-wildcards.  */
 878   void *htab;
 879   /* Remaining patterns.  */
 880   struct bfd_elf_version_expr *remaining;
 881   /* What kind of pattern types are present in list (bitmask).  */
 882   unsigned int mask;
 883 };
 884
 885 /* Version dependencies.  */
 886
 887 struct bfd_elf_version_deps
 888 {
 889   /* Next dependency for this version.  */
 890   struct bfd_elf_version_deps *next;
 891   /* The version which this version depends upon.  */
 892   struct bfd_elf_version_tree *version_needed;
 893 };
 894
 895 /* A node in the version tree.  */
 896
 897 struct bfd_elf_version_tree
 898 {
 899   /* Next version.  */
 900   struct bfd_elf_version_tree *next;
 901   /* Name of this version.  */
 902   const char *name;
 903   /* Version number.  */
 904   unsigned int vernum;
 905   /* Regular expressions for global symbols in this version.  */
 906   struct bfd_elf_version_expr_head globals;
 907   /* Regular expressions for local symbols in this version.  */
 908   struct bfd_elf_version_expr_head locals;
 909   /* List of versions which this version depends upon.  */
 910   struct bfd_elf_version_deps *deps;
 911   /* Index of the version name.  This is used within BFD.  */
 912   unsigned int name_indx;
 913   /* Whether this version tree was used.  This is used within BFD.  */
 914   int used;
 915   /* Matching hook.  */
 916   struct bfd_elf_version_expr *(*match)
 917     (struct bfd_elf_version_expr_head *head,
 918      struct bfd_elf_version_expr *prev, const char *sym);
 919 };
 920
 921 struct bfd_elf_dynamic_list
 922 {
 923   struct bfd_elf_version_expr_head head;
 924   struct bfd_elf_version_expr *(*match)
 925     (struct bfd_elf_version_expr_head *head,
 926      struct bfd_elf_version_expr *prev, const char *sym);
 927 };
 928
 929 #endif