include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2021 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 enum notice_asneeded_action {
  46   notice_as_needed,
  47   notice_not_needed,
  48   notice_needed
  49 };
  50
  51 /* Whether to generate ELF common symbols with the STT_COMMON type
  52    during a relocatable link.  */
  53 enum bfd_link_elf_stt_common
  54 {
  55   unchanged,
  56   elf_stt_common,
  57   no_elf_stt_common
  58 };
  59
  60 /* Describes the type of hash table entry structure being used.
  61    Different hash table structure have different fields and so
  62    support different linking features.  */
  63 enum bfd_link_hash_table_type
  64   {
  65     bfd_link_generic_hash_table,
  66     bfd_link_elf_hash_table
  67   };
  68 \f
  69 /* These are the possible types of an entry in the BFD link hash
  70    table.  */
  71
  72 enum bfd_link_hash_type
  73 {
  74   bfd_link_hash_new,            /* Symbol is new.  */
  75   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  76   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  77   bfd_link_hash_defined,        /* Symbol is defined.  */
  78   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  79   bfd_link_hash_common,         /* Symbol is common.  */
  80   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  81   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  82 };
  83
  84 enum bfd_link_common_skip_ar_symbols
  85 {
  86   bfd_link_common_skip_none,
  87   bfd_link_common_skip_text,
  88   bfd_link_common_skip_data,
  89   bfd_link_common_skip_all
  90 };
  91
  92 struct bfd_link_hash_common_entry
  93   {
  94     unsigned int alignment_power;       /* Alignment.  */
  95     asection *section;          /* Symbol section.  */
  96   };
  97
  98 /* The linking routines use a hash table which uses this structure for
  99    its elements.  */
 100
 101 struct bfd_link_hash_entry
 102 {
 103   /* Base hash table entry structure.  */
 104   struct bfd_hash_entry root;
 105
 106   /* Type of this entry.  */
 107   ENUM_BITFIELD (bfd_link_hash_type) type : 8;
 108
 109   /* Symbol is referenced in a normal regular object file,
 110      as distinct from a LTO IR object file.  */
 111   unsigned int non_ir_ref_regular : 1;
 112
 113   /* Symbol is referenced in a normal dynamic object file,
 114      as distinct from a LTO IR object file.  */
 115   unsigned int non_ir_ref_dynamic : 1;
 116
 117   /* Symbol is a built-in define.  These will be overridden by PROVIDE
 118      in a linker script.  */
 119   unsigned int linker_def : 1;
 120
 121   /* Symbol defined in a linker script.  */
 122   unsigned int ldscript_def : 1;
 123
 124   /* Symbol will be converted from absolute to section-relative.  Set for
 125      symbols defined by a script from "dot" (also SEGMENT_START or ORIGIN)
 126      outside of an output section statement.  */
 127   unsigned int rel_from_abs : 1;
 128
 129   /* A union of information depending upon the type.  */
 130   union
 131     {
 132       /* Nothing is kept for bfd_hash_new.  */
 133       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 134       struct
 135         {
 136           /* Undefined and common symbols are kept in a linked list through
 137              this field.  This field is present in all of the union element
 138              so that we don't need to remove entries from the list when we
 139              change their type.  Removing entries would either require the
 140              list to be doubly linked, which would waste more memory, or
 141              require a traversal.  When an undefined or common symbol is
 142              created, it should be added to this list, the head of which is in
 143              the link hash table itself.  As symbols are defined, they need
 144              not be removed from the list; anything which reads the list must
 145              doublecheck the symbol type.
 146
 147              Weak symbols are not kept on this list.
 148
 149              Defined and defweak symbols use this field as a reference marker.
 150              If the field is not NULL, or this structure is the tail of the
 151              undefined symbol list, the symbol has been referenced.  If the
 152              symbol is undefined and becomes defined, this field will
 153              automatically be non-NULL since the symbol will have been on the
 154              undefined symbol list.  */
 155           struct bfd_link_hash_entry *next;
 156           /* BFD symbol was found in.  */
 157           bfd *abfd;
 158         } undef;
 159       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 160       struct
 161         {
 162           struct bfd_link_hash_entry *next;
 163           /* Symbol section.  */
 164           asection *section;
 165           /* Symbol value.  */
 166           bfd_vma value;
 167         } def;
 168       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 169       struct
 170         {
 171           struct bfd_link_hash_entry *next;
 172           /* Real symbol.  */
 173           struct bfd_link_hash_entry *link;
 174           /* Warning message (bfd_link_hash_warning only).  */
 175           const char *warning;
 176         } i;
 177       /* bfd_link_hash_common.  */
 178       struct
 179         {
 180           struct bfd_link_hash_entry *next;
 181           /* The linker needs to know three things about common
 182              symbols: the size, the alignment, and the section in
 183              which the symbol should be placed.  We store the size
 184              here, and we allocate a small structure to hold the
 185              section and the alignment.  The alignment is stored as a
 186              power of two.  We don't store all the information
 187              directly because we don't want to increase the size of
 188              the union; this structure is a major space user in the
 189              linker.  */
 190           struct bfd_link_hash_common_entry *p;
 191           /* Common symbol size.  */
 192           bfd_size_type size;
 193         } c;
 194     } u;
 195 };
 196
 197 /* This is the link hash table.  It is a derived class of
 198    bfd_hash_table.  */
 199
 200 struct bfd_link_hash_table
 201 {
 202   /* The hash table itself.  */
 203   struct bfd_hash_table table;
 204   /* A linked list of undefined and common symbols, linked through the
 205      next field in the bfd_link_hash_entry structure.  */
 206   struct bfd_link_hash_entry *undefs;
 207   /* Entries are added to the tail of the undefs list.  */
 208   struct bfd_link_hash_entry *undefs_tail;
 209   /* Function to free the hash table on closing BFD.  */
 210   void (*hash_table_free) (bfd *);
 211   /* The type of the link hash table.  */
 212   enum bfd_link_hash_table_type type;
 213 };
 214
 215 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 216    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 217    the real symbol.  */
 218 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 219   (struct bfd_link_hash_table *, const char *, bool create,
 220    bool copy, bool follow);
 221
 222 /* Look up an entry in the main linker hash table if the symbol might
 223    be wrapped.  This should only be used for references to an
 224    undefined symbol, not for definitions of a symbol.  */
 225
 226 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 227   (bfd *, struct bfd_link_info *, const char *, bool, bool, bool);
 228
 229 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 230    and the remainder is found in wrap_hash, return the real symbol.  */
 231
 232 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 233   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 234
 235 /* Traverse a link hash table.  */
 236 extern void bfd_link_hash_traverse
 237   (struct bfd_link_hash_table *,
 238     bool (*) (struct bfd_link_hash_entry *, void *),
 239     void *);
 240
 241 /* Add an entry to the undefs list.  */
 242 extern void bfd_link_add_undef
 243   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 244
 245 /* Remove symbols from the undefs list that don't belong there.  */
 246 extern void bfd_link_repair_undef_list
 247   (struct bfd_link_hash_table *table);
 248
 249 /* Read symbols and cache symbol pointer array in outsymbols.  */
 250 extern bool bfd_generic_link_read_symbols (bfd *);
 251
 252 /* Check the relocs in the BFD.  Called after all the input
 253    files have been loaded, and garbage collection has tagged
 254    any unneeded sections.  */
 255 extern bool bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 256
 257 struct bfd_sym_chain
 258 {
 259   struct bfd_sym_chain *next;
 260   const char *name;
 261 };
 262 \f
 263 /* How to handle unresolved symbols.
 264    There are four possibilities which are enumerated below:  */
 265 enum report_method
 266 {
 267   /* This is the initial value when then link_info structure is created.
 268      It allows the various stages of the linker to determine whether they
 269      allowed to set the value.  */
 270   RM_NOT_YET_SET = 0,
 271   RM_IGNORE,
 272   RM_DIAGNOSE,
 273 };
 274
 275 /* How to handle DT_TEXTREL.  */
 276
 277 enum textrel_check_method
 278 {
 279   textrel_check_none,
 280   textrel_check_warning,
 281   textrel_check_error
 282 };
 283
 284 #define bfd_link_textrel_check(info) \
 285   (info->textrel_check != textrel_check_none)
 286
 287 typedef enum {with_flags, without_flags} flag_type;
 288
 289 /* A section flag list.  */
 290 struct flag_info_list
 291 {
 292   flag_type with;
 293   const char *name;
 294   bool valid;
 295   struct flag_info_list *next;
 296 };
 297
 298 /* Section flag info.  */
 299 struct flag_info
 300 {
 301   flagword only_with_flags;
 302   flagword not_with_flags;
 303   struct flag_info_list *flag_list;
 304   bool flags_initialized;
 305 };
 306
 307 struct bfd_elf_dynamic_list;
 308 struct bfd_elf_version_tree;
 309
 310 /* Types of output.  */
 311
 312 enum output_type
 313 {
 314   type_pde,
 315   type_pie,
 316   type_relocatable,
 317   type_dll,
 318 };
 319
 320 #define bfd_link_pde(info)         ((info)->type == type_pde)
 321 #define bfd_link_dll(info)         ((info)->type == type_dll)
 322 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 323 #define bfd_link_pie(info)         ((info)->type == type_pie)
 324 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 325 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 326
 327 /* This structure holds all the information needed to communicate
 328    between BFD and the linker when doing a link.  */
 329
 330 struct bfd_link_info
 331 {
 332   /* Output type.  */
 333   ENUM_BITFIELD (output_type) type : 2;
 334
 335   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 336   unsigned int symbolic: 1;
 337
 338   /* TRUE if executable should not contain copy relocs.
 339      Setting this true may result in a non-sharable text segment.  */
 340   unsigned int nocopyreloc: 1;
 341
 342   /* TRUE if BFD should export all symbols in the dynamic symbol table
 343      of an executable, rather than only those used.  */
 344   unsigned int export_dynamic: 1;
 345
 346   /* TRUE if a default symbol version should be created and used for
 347      exported symbols.  */
 348   unsigned int create_default_symver: 1;
 349
 350   /* TRUE if unreferenced sections should be removed.  */
 351   unsigned int gc_sections: 1;
 352
 353   /* TRUE if exported symbols should be kept during section gc.  */
 354   unsigned int gc_keep_exported: 1;
 355
 356   /* TRUE if every symbol should be reported back via the notice
 357      callback.  */
 358   unsigned int notice_all: 1;
 359
 360   /* TRUE if the LTO plugin is active.  */
 361   unsigned int lto_plugin_active: 1;
 362
 363   /* TRUE if all LTO IR symbols have been read.  */
 364   unsigned int lto_all_symbols_read : 1;
 365
 366   /* TRUE if global symbols in discarded sections should be stripped.  */
 367   unsigned int strip_discarded: 1;
 368
 369   /* TRUE if all data symbols should be dynamic.  */
 370   unsigned int dynamic_data: 1;
 371
 372   /* TRUE if section groups should be resolved.  */
 373   unsigned int resolve_section_groups: 1;
 374
 375   /* Set if output file is big-endian, or if that is unknown, from
 376      the command line or first input file endianness.  */
 377   unsigned int big_endian : 1;
 378
 379   /* Which symbols to strip.  */
 380   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 381
 382   /* Which local symbols to discard.  */
 383   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 384
 385   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 386   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 387
 388   /* Criteria for skipping symbols when determining
 389      whether to include an object from an archive.  */
 390   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 391
 392   /* What to do with unresolved symbols in an object file.
 393      When producing executables the default is GENERATE_ERROR.
 394      When producing shared libraries the default is IGNORE.  The
 395      assumption with shared libraries is that the reference will be
 396      resolved at load/execution time.  */
 397   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 398
 399   /* What to do with unresolved symbols in a shared library.
 400      The same defaults apply.  */
 401   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 402
 403   /* TRUE if unresolved symbols are to be warned, rather than errored.  */
 404   unsigned int warn_unresolved_syms: 1;
 405
 406   /* TRUE if shared objects should be linked directly, not shared.  */
 407   unsigned int static_link: 1;
 408
 409   /* TRUE if symbols should be retained in memory, FALSE if they
 410      should be freed and reread.  */
 411   unsigned int keep_memory: 1;
 412
 413   /* TRUE if BFD should generate relocation information in the final
 414      executable.  */
 415   unsigned int emitrelocations: 1;
 416
 417   /* TRUE if PT_GNU_RELRO segment should be created.  */
 418   unsigned int relro: 1;
 419
 420   /* TRUE if separate code segment should be created.  */
 421   unsigned int separate_code: 1;
 422
 423   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 424      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 425   unsigned int eh_frame_hdr_type: 2;
 426
 427   /* What to do with DT_TEXTREL in output.  */
 428   ENUM_BITFIELD (textrel_check_method) textrel_check: 2;
 429
 430   /* TRUE if .hash section should be created.  */
 431   unsigned int emit_hash: 1;
 432
 433   /* TRUE if .gnu.hash section should be created.  */
 434   unsigned int emit_gnu_hash: 1;
 435
 436   /* If TRUE reduce memory overheads, at the expense of speed. This will
 437      cause map file generation to use an O(N^2) algorithm and disable
 438      caching ELF symbol buffer.  */
 439   unsigned int reduce_memory_overheads: 1;
 440
 441   /* TRUE if the output file should be in a traditional format.  This
 442      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 443      on the output file, but may be checked when reading the input
 444      files.  */
 445   unsigned int traditional_format: 1;
 446
 447   /* TRUE if non-PLT relocs should be merged into one reloc section
 448      and sorted so that relocs against the same symbol come together.  */
 449   unsigned int combreloc: 1;
 450
 451   /* TRUE if a default symbol version should be created and used for
 452      imported symbols.  */
 453   unsigned int default_imported_symver: 1;
 454
 455   /* TRUE if the new ELF dynamic tags are enabled. */
 456   unsigned int new_dtags: 1;
 457
 458   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 459      linker created sections, TRUE if it should be omitted.  */
 460   unsigned int no_ld_generated_unwind_info: 1;
 461
 462   /* TRUE if BFD should generate a "task linked" object file,
 463      similar to relocatable but also with globals converted to
 464      statics.  */
 465   unsigned int task_link: 1;
 466
 467   /* TRUE if ok to have multiple definitions, without warning.  */
 468   unsigned int allow_multiple_definition: 1;
 469
 470   /* TRUE if multiple definition of absolute symbols (eg. from -R) should
 471      be reported.  */
 472   unsigned int prohibit_multiple_definition_absolute: 1;
 473
 474   /* TRUE if multiple definitions should only warn.  */
 475   unsigned int warn_multiple_definition: 1;
 476
 477   /* TRUE if ok to have version with no definition.  */
 478   unsigned int allow_undefined_version: 1;
 479
 480   /* TRUE if some symbols have to be dynamic, controlled by
 481      --dynamic-list command line options.  */
 482   unsigned int dynamic: 1;
 483
 484   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 485      flags.  */
 486   unsigned int execstack: 1;
 487
 488   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 489      flags.  */
 490   unsigned int noexecstack: 1;
 491
 492   /* TRUE if we want to produced optimized output files.  This might
 493      need much more time and therefore must be explicitly selected.  */
 494   unsigned int optimize: 1;
 495
 496   /* TRUE if user should be informed of removed unreferenced sections.  */
 497   unsigned int print_gc_sections: 1;
 498
 499   /* TRUE if we should warn alternate ELF machine code.  */
 500   unsigned int warn_alternate_em: 1;
 501
 502   /* TRUE if the linker script contained an explicit PHDRS command.  */
 503   unsigned int user_phdrs: 1;
 504
 505   /* TRUE if program headers ought to be loaded.  */
 506   unsigned int load_phdrs: 1;
 507
 508   /* TRUE if we should check relocations after all input files have
 509      been opened.  */
 510   unsigned int check_relocs_after_open_input: 1;
 511
 512   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 513   unsigned int nointerp: 1;
 514
 515   /* TRUE if common symbols should be treated as undefined.  */
 516   unsigned int inhibit_common_definition : 1;
 517
 518   /* TRUE if "-Map map" is passed to linker.  */
 519   unsigned int has_map_file : 1;
 520
 521   /* TRUE if "--enable-non-contiguous-regions" is passed to the
 522      linker.  */
 523   unsigned int non_contiguous_regions : 1;
 524
 525   /* TRUE if "--enable-non-contiguous-regions-warnings" is passed to
 526      the linker.  */
 527   unsigned int non_contiguous_regions_warnings : 1;
 528
 529   /* TRUE if all symbol names should be unique.  */
 530   unsigned int unique_symbol : 1;
 531
 532   /* Char that may appear as the first char of a symbol, but should be
 533      skipped (like symbol_leading_char) when looking up symbols in
 534      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 535   char wrap_char;
 536
 537   /* Separator between archive and filename in linker script filespecs.  */
 538   char path_separator;
 539
 540   /* Compress DWARF debug sections.  */
 541   enum compressed_debug_section_type compress_debug;
 542
 543   /* Default stack size.  Zero means default (often zero itself), -1
 544      means explicitly zero-sized.  */
 545   bfd_signed_vma stacksize;
 546
 547   /* Enable or disable target specific optimizations.
 548
 549      Not all targets have optimizations to enable.
 550
 551      Normally these optimizations are disabled by default but some targets
 552      prefer to enable them by default.  So this field is a tri-state variable.
 553      The values are:
 554
 555      zero: Enable the optimizations (either from --relax being specified on
 556        the command line or the backend's before_allocation emulation function.
 557
 558      positive: The user has requested that these optimizations be disabled.
 559        (Via the --no-relax command line option).
 560
 561      negative: The optimizations are disabled.  (Set when initializing the
 562        args_type structure in ldmain.c:main.  */
 563   signed int disable_target_specific_optimizations;
 564
 565   /* Function callbacks.  */
 566   const struct bfd_link_callbacks *callbacks;
 567
 568   /* Hash table handled by BFD.  */
 569   struct bfd_link_hash_table *hash;
 570
 571   /* Hash table of symbols to keep.  This is NULL unless strip is
 572      strip_some.  */
 573   struct bfd_hash_table *keep_hash;
 574
 575   /* Hash table of symbols to report back via the notice callback.  If
 576      this is NULL, and notice_all is FALSE, then no symbols are
 577      reported back.  */
 578   struct bfd_hash_table *notice_hash;
 579
 580   /* Hash table of symbols which are being wrapped (the --wrap linker
 581      option).  If this is NULL, no symbols are being wrapped.  */
 582   struct bfd_hash_table *wrap_hash;
 583
 584   /* Hash table of symbols which may be left unresolved during
 585      a link.  If this is NULL, no symbols can be left unresolved.  */
 586   struct bfd_hash_table *ignore_hash;
 587
 588   /* The output BFD.  */
 589   bfd *output_bfd;
 590
 591   /* The import library generated.  */
 592   bfd *out_implib_bfd;
 593
 594   /* The list of input BFD's involved in the link.  These are chained
 595      together via the link.next field.  */
 596   bfd *input_bfds;
 597   bfd **input_bfds_tail;
 598
 599   /* If a symbol should be created for each input BFD, this is section
 600      where those symbols should be placed.  It must be a section in
 601      the output BFD.  It may be NULL, in which case no such symbols
 602      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 603      linker command language.  */
 604   asection *create_object_symbols_section;
 605
 606   /* List of global symbol names that are starting points for marking
 607      sections against garbage collection.  */
 608   struct bfd_sym_chain *gc_sym_list;
 609
 610   /* If a base output file is wanted, then this points to it */
 611   void *base_file;
 612
 613   /* The function to call when the executable or shared object is
 614      loaded.  */
 615   const char *init_function;
 616
 617   /* The function to call when the executable or shared object is
 618      unloaded.  */
 619   const char *fini_function;
 620
 621   /* Number of relaxation passes.  Usually only one relaxation pass
 622      is needed.  But a backend can have as many relaxation passes as
 623      necessary.  During bfd_relax_section call, it is set to the
 624      current pass, starting from 0.  */
 625   int relax_pass;
 626
 627   /* Number of relaxation trips.  This number is incremented every
 628      time the relaxation pass is restarted due to a previous
 629      relaxation returning true in *AGAIN.  */
 630   int relax_trip;
 631
 632   /* > 0 to treat protected data defined in the shared library as
 633      reference external.  0 to treat it as internal.  -1 to let
 634      backend to decide.  */
 635   int extern_protected_data;
 636
 637   /* 1 to make undefined weak symbols dynamic when building a dynamic
 638      object.  0 to resolve undefined weak symbols to zero.  -1 to let
 639      the backend decide.  */
 640   int dynamic_undefined_weak;
 641
 642   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 643      should be generated/linked against.  Set to 1 if this feature
 644      is explicitly requested by the user, -1 if enabled by default.  */
 645   int pei386_auto_import;
 646
 647   /* Non-zero if runtime relocs for DATA items with non-zero addends
 648      in pei386 DLLs should be generated.  Set to 1 if this feature
 649      is explicitly requested by the user, -1 if enabled by default.  */
 650   int pei386_runtime_pseudo_reloc;
 651
 652   /* How many spare .dynamic DT_NULL entries should be added?  */
 653   unsigned int spare_dynamic_tags;
 654
 655   /* May be used to set DT_FLAGS for ELF. */
 656   bfd_vma flags;
 657
 658   /* May be used to set DT_FLAGS_1 for ELF. */
 659   bfd_vma flags_1;
 660
 661   /* May be used to set DT_GNU_FLAGS_1 for ELF. */
 662   bfd_vma gnu_flags_1;
 663
 664   /* TRUE if references to __start_/__stop_ synthesized symbols do not
 665      specially retain C identifier named sections.  */
 666   int start_stop_gc;
 667
 668   /* May be used to set ELF visibility for __start_* / __stop_.  */
 669   unsigned int start_stop_visibility;
 670
 671   /* The maximum page size for ELF.  */
 672   bfd_vma maxpagesize;
 673
 674   /* The common page size for ELF.  */
 675   bfd_vma commonpagesize;
 676
 677   /* Start and end of RELRO region.  */
 678   bfd_vma relro_start, relro_end;
 679
 680   /* List of symbols should be dynamic.  */
 681   struct bfd_elf_dynamic_list *dynamic_list;
 682
 683   /* The version information.  */
 684   struct bfd_elf_version_tree *version_info;
 685 };
 686
 687 /* Some forward-definitions used by some callbacks.  */
 688
 689 struct elf_strtab_hash;
 690 struct elf_internal_sym;
 691
 692 /* This structures holds a set of callback functions.  These are called
 693    by the BFD linker routines.  */
 694
 695 struct bfd_link_callbacks
 696 {
 697   /* A function which is called when an object is added from an
 698      archive.  ABFD is the archive element being added.  NAME is the
 699      name of the symbol which caused the archive element to be pulled
 700      in.  This function may set *SUBSBFD to point to an alternative
 701      BFD from which symbols should in fact be added in place of the
 702      original BFD's symbols.  Returns TRUE if the object should be
 703      added, FALSE if it should be skipped.  */
 704   bool (*add_archive_element)
 705     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 706   /* A function which is called when a symbol is found with multiple
 707      definitions.  H is the symbol which is defined multiple times.
 708      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 709      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 710   void (*multiple_definition)
 711     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 712      bfd *nbfd, asection *nsec, bfd_vma nval);
 713   /* A function which is called when a common symbol is defined
 714      multiple times.  H is the symbol appearing multiple times.
 715      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 716      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 717      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 718      is the size of the new symbol.  */
 719   void (*multiple_common)
 720     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 721      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 722   /* A function which is called to add a symbol to a set.  ENTRY is
 723      the link hash table entry for the set itself (e.g.,
 724      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 725      the set when generating a relocatable file, and is also used to
 726      get the size of the entry when generating an executable file.
 727      ABFD, SEC and VALUE identify the value to add to the set.  */
 728   void (*add_to_set)
 729     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 730      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 731   /* A function which is called when the name of a g++ constructor or
 732      destructor is found.  This is only called by some object file
 733      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 734      destructor.  This will use BFD_RELOC_CTOR when generating a
 735      relocatable file.  NAME is the name of the symbol found.  ABFD,
 736      SECTION and VALUE are the value of the symbol.  */
 737   void (*constructor)
 738     (struct bfd_link_info *, bool constructor, const char *name,
 739      bfd *abfd, asection *sec, bfd_vma value);
 740   /* A function which is called to issue a linker warning.  For
 741      example, this is called when there is a reference to a warning
 742      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 743      of the symbol which triggered the warning; it may be NULL if
 744      there is none.  ABFD, SECTION and ADDRESS identify the location
 745      which trigerred the warning; either ABFD or SECTION or both may
 746      be NULL if the location is not known.  */
 747   void (*warning)
 748     (struct bfd_link_info *, const char *warning, const char *symbol,
 749      bfd *abfd, asection *section, bfd_vma address);
 750   /* A function which is called when a relocation is attempted against
 751      an undefined symbol.  NAME is the symbol which is undefined.
 752      ABFD, SECTION and ADDRESS identify the location from which the
 753      reference is made. IS_FATAL indicates whether an undefined symbol is
 754      a fatal error or not. In some cases SECTION may be NULL.  */
 755   void (*undefined_symbol)
 756     (struct bfd_link_info *, const char *name, bfd *abfd,
 757      asection *section, bfd_vma address, bool is_fatal);
 758   /* A function which is called when a reloc overflow occurs. ENTRY is
 759      the link hash table entry for the symbol the reloc is against.
 760      NAME is the name of the local symbol or section the reloc is
 761      against, RELOC_NAME is the name of the relocation, and ADDEND is
 762      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 763      location at which the overflow occurs; if this is the result of a
 764      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 765      ABFD will be NULL.  */
 766   void (*reloc_overflow)
 767     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 768      const char *name, const char *reloc_name, bfd_vma addend,
 769      bfd *abfd, asection *section, bfd_vma address);
 770   /* A function which is called when a dangerous reloc is performed.
 771      MESSAGE is an appropriate message.
 772      ABFD, SECTION and ADDRESS identify the location at which the
 773      problem occurred; if this is the result of a
 774      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 775      ABFD will be NULL.  */
 776   void (*reloc_dangerous)
 777     (struct bfd_link_info *, const char *message,
 778      bfd *abfd, asection *section, bfd_vma address);
 779   /* A function which is called when a reloc is found to be attached
 780      to a symbol which is not being written out.  NAME is the name of
 781      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 782      the reloc; if this is the result of a
 783      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 784      ABFD will be NULL.  */
 785   void (*unattached_reloc)
 786     (struct bfd_link_info *, const char *name,
 787      bfd *abfd, asection *section, bfd_vma address);
 788   /* A function which is called when a symbol in notice_hash is
 789      defined or referenced.  H is the symbol, INH the indirect symbol
 790      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 791      the symbol.  If SECTION is bfd_und_section, this is a reference.
 792      FLAGS are the symbol BSF_* flags.  */
 793   bool (*notice)
 794     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 795      struct bfd_link_hash_entry *inh,
 796      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 797   /* Error or warning link info message.  */
 798   void (*einfo)
 799     (const char *fmt, ...);
 800   /* General link info message.  */
 801   void (*info)
 802     (const char *fmt, ...);
 803   /* Message to be printed in linker map file.  */
 804   void (*minfo)
 805     (const char *fmt, ...);
 806   /* This callback provides a chance for users of the BFD library to
 807      override its decision about whether to place two adjacent sections
 808      into the same segment.  */
 809   bool (*override_segment_assignment)
 810     (struct bfd_link_info *, bfd * abfd,
 811      asection * current_section, asection * previous_section,
 812      bool new_segment);
 813   /* This callback provides a chance for callers of the BFD to examine the
 814      ELF (dynamic) string table once it is complete.  */
 815   void (*examine_strtab)
 816     (struct elf_strtab_hash *symstrtab);
 817   /* This callback is called just before a symbol is swapped out, so that the
 818      CTF machinery can look up symbols during construction.  The name is
 819      already an external strtab offset at this point.  */
 820   void (*ctf_new_symbol)
 821     (int symidx, struct elf_internal_sym *sym);
 822   /* Likewise, for dynamic symbols.  */
 823   void (*ctf_new_dynsym)
 824     (int symidx, struct elf_internal_sym *sym);
 825   /* This callback should emit the CTF section into a non-loadable section in
 826      the output BFD named .ctf or a name beginning with ".ctf.".  */
 827   void (*emit_ctf)
 828     (void);
 829 };
 830 \f
 831 /* The linker builds link_order structures which tell the code how to
 832    include input data in the output file.  */
 833
 834 /* These are the types of link_order structures.  */
 835
 836 enum bfd_link_order_type
 837 {
 838   bfd_undefined_link_order,     /* Undefined.  */
 839   bfd_indirect_link_order,      /* Built from a section.  */
 840   bfd_data_link_order,          /* Set to explicit data.  */
 841   bfd_section_reloc_link_order, /* Relocate against a section.  */
 842   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 843 };
 844
 845 /* This is the link_order structure itself.  These form a chain
 846    attached to the output section whose contents they are describing.  */
 847
 848 struct bfd_link_order
 849 {
 850   /* Next link_order in chain.  */
 851   struct bfd_link_order *next;
 852   /* Type of link_order.  */
 853   enum bfd_link_order_type type;
 854   /* Offset within output section in bytes.  */
 855   bfd_vma offset;
 856   /* Size within output section in octets.  */
 857   bfd_size_type size;
 858   /* Type specific information.  */
 859   union
 860     {
 861       struct
 862         {
 863           /* Section to include.  If this is used, then
 864              section->output_section must be the section the
 865              link_order is attached to, section->output_offset must
 866              equal the link_order offset field, and section->size
 867              must equal the link_order size field.  Maybe these
 868              restrictions should be relaxed someday.  */
 869           asection *section;
 870         } indirect;
 871       struct
 872         {
 873           /* Size of contents, or zero when contents should be filled by
 874              the architecture-dependent fill function.
 875              A non-zero value allows filling of the output section
 876              with an arbitrary repeated pattern.  */
 877           unsigned int size;
 878           /* Data to put into file.  */
 879           bfd_byte *contents;
 880         } data;
 881       struct
 882         {
 883           /* Description of reloc to generate.  Used for
 884              bfd_section_reloc_link_order and
 885              bfd_symbol_reloc_link_order.  */
 886           struct bfd_link_order_reloc *p;
 887         } reloc;
 888     } u;
 889 };
 890
 891 /* A linker order of type bfd_section_reloc_link_order or
 892    bfd_symbol_reloc_link_order means to create a reloc against a
 893    section or symbol, respectively.  This is used to implement -Ur to
 894    generate relocs for the constructor tables.  The
 895    bfd_link_order_reloc structure describes the reloc that BFD should
 896    create.  It is similar to a arelent, but I didn't use arelent
 897    because the linker does not know anything about most symbols, and
 898    any asymbol structure it creates will be partially meaningless.
 899    This information could logically be in the bfd_link_order struct,
 900    but I didn't want to waste the space since these types of relocs
 901    are relatively rare.  */
 902
 903 struct bfd_link_order_reloc
 904 {
 905   /* Reloc type.  */
 906   bfd_reloc_code_real_type reloc;
 907
 908   union
 909     {
 910       /* For type bfd_section_reloc_link_order, this is the section
 911          the reloc should be against.  This must be a section in the
 912          output BFD, not any of the input BFDs.  */
 913       asection *section;
 914       /* For type bfd_symbol_reloc_link_order, this is the name of the
 915          symbol the reloc should be against.  */
 916       const char *name;
 917     } u;
 918
 919   /* Addend to use.  The object file should contain zero.  The BFD
 920      backend is responsible for filling in the contents of the object
 921      file correctly.  For some object file formats (e.g., COFF) the
 922      addend must be stored into in the object file, and for some
 923      (e.g., SPARC a.out) it is kept in the reloc.  */
 924   bfd_vma addend;
 925 };
 926
 927 /* Allocate a new link_order for a section.  */
 928 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 929
 930 struct bfd_section_already_linked;
 931
 932 extern bool bfd_section_already_linked_table_init (void);
 933 extern void bfd_section_already_linked_table_free (void);
 934 extern bool _bfd_handle_already_linked
 935   (struct bfd_section *, struct bfd_section_already_linked *,
 936    struct bfd_link_info *);
 937
 938 extern struct bfd_section *_bfd_nearby_section
 939   (bfd *, struct bfd_section *, bfd_vma);
 940
 941 extern void _bfd_fix_excluded_sec_syms
 942   (bfd *, struct bfd_link_info *);
 943
 944 /* These structures are used to describe version information for the
 945    ELF linker.  These structures could be manipulated entirely inside
 946    BFD, but it would be a pain.  Instead, the regular linker sets up
 947    these structures, and then passes them into BFD.  */
 948
 949 /* Glob pattern for a version.  */
 950
 951 struct bfd_elf_version_expr
 952 {
 953   /* Next glob pattern for this version.  */
 954   struct bfd_elf_version_expr *next;
 955   /* Glob pattern.  */
 956   const char *pattern;
 957   /* Set if pattern is not a glob.  */
 958   unsigned int literal : 1;
 959   /* Defined by ".symver".  */
 960   unsigned int symver : 1;
 961   /* Defined by version script.  */
 962   unsigned int script : 1;
 963   /* Pattern type.  */
 964 #define BFD_ELF_VERSION_C_TYPE          1
 965 #define BFD_ELF_VERSION_CXX_TYPE        2
 966 #define BFD_ELF_VERSION_JAVA_TYPE       4
 967   unsigned int mask : 3;
 968 };
 969
 970 struct bfd_elf_version_expr_head
 971 {
 972   /* List of all patterns, both wildcards and non-wildcards.  */
 973   struct bfd_elf_version_expr *list;
 974   /* Hash table for non-wildcards.  */
 975   void *htab;
 976   /* Remaining patterns.  */
 977   struct bfd_elf_version_expr *remaining;
 978   /* What kind of pattern types are present in list (bitmask).  */
 979   unsigned int mask;
 980 };
 981
 982 /* Version dependencies.  */
 983
 984 struct bfd_elf_version_deps
 985 {
 986   /* Next dependency for this version.  */
 987   struct bfd_elf_version_deps *next;
 988   /* The version which this version depends upon.  */
 989   struct bfd_elf_version_tree *version_needed;
 990 };
 991
 992 /* A node in the version tree.  */
 993
 994 struct bfd_elf_version_tree
 995 {
 996   /* Next version.  */
 997   struct bfd_elf_version_tree *next;
 998   /* Name of this version.  */
 999   const char *name;
1000   /* Version number.  */
1001   unsigned int vernum;
1002   /* Regular expressions for global symbols in this version.  */
1003   struct bfd_elf_version_expr_head globals;
1004   /* Regular expressions for local symbols in this version.  */
1005   struct bfd_elf_version_expr_head locals;
1006   /* List of versions which this version depends upon.  */
1007   struct bfd_elf_version_deps *deps;
1008   /* Index of the version name.  This is used within BFD.  */
1009   unsigned int name_indx;
1010   /* Whether this version tree was used.  This is used within BFD.  */
1011   int used;
1012   /* Matching hook.  */
1013   struct bfd_elf_version_expr *(*match)
1014     (struct bfd_elf_version_expr_head *head,
1015      struct bfd_elf_version_expr *prev, const char *sym);
1016 };
1017
1018 struct bfd_elf_dynamic_list
1019 {
1020   struct bfd_elf_version_expr_head head;
1021   struct bfd_elf_version_expr *(*match)
1022     (struct bfd_elf_version_expr_head *head,
1023      struct bfd_elf_version_expr *prev, const char *sym);
1024 };
1025
1026 #endif