include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2020 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 *, bfd_boolean create,
 220    bfd_boolean copy, bfd_boolean 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 *, bfd_boolean,
 228    bfd_boolean, bfd_boolean);
 229
 230 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 231    and the remainder is found in wrap_hash, return the real symbol.  */
 232
 233 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 234   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 235
 236 /* Traverse a link hash table.  */
 237 extern void bfd_link_hash_traverse
 238   (struct bfd_link_hash_table *,
 239     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 240     void *);
 241
 242 /* Add an entry to the undefs list.  */
 243 extern void bfd_link_add_undef
 244   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 245
 246 /* Remove symbols from the undefs list that don't belong there.  */
 247 extern void bfd_link_repair_undef_list
 248   (struct bfd_link_hash_table *table);
 249
 250 /* Read symbols and cache symbol pointer array in outsymbols.  */
 251 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 252
 253 /* Check the relocs in the BFD.  Called after all the input
 254    files have been loaded, and garbage collection has tagged
 255    any unneeded sections.  */
 256 extern bfd_boolean bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 257
 258 struct bfd_sym_chain
 259 {
 260   struct bfd_sym_chain *next;
 261   const char *name;
 262 };
 263 \f
 264 /* How to handle unresolved symbols.
 265    There are four possibilities which are enumerated below:  */
 266 enum report_method
 267 {
 268   /* This is the initial value when then link_info structure is created.
 269      It allows the various stages of the linker to determine whether they
 270      allowed to set the value.  */
 271   RM_NOT_YET_SET = 0,
 272   RM_IGNORE,
 273   RM_GENERATE_WARNING,
 274   RM_GENERATE_ERROR
 275 };
 276
 277 typedef enum {with_flags, without_flags} flag_type;
 278
 279 /* A section flag list.  */
 280 struct flag_info_list
 281 {
 282   flag_type with;
 283   const char *name;
 284   bfd_boolean valid;
 285   struct flag_info_list *next;
 286 };
 287
 288 /* Section flag info.  */
 289 struct flag_info
 290 {
 291   flagword only_with_flags;
 292   flagword not_with_flags;
 293   struct flag_info_list *flag_list;
 294   bfd_boolean flags_initialized;
 295 };
 296
 297 struct bfd_elf_dynamic_list;
 298 struct bfd_elf_version_tree;
 299
 300 /* Types of output.  */
 301
 302 enum output_type
 303 {
 304   type_pde,
 305   type_pie,
 306   type_relocatable,
 307   type_dll,
 308 };
 309
 310 #define bfd_link_pde(info)         ((info)->type == type_pde)
 311 #define bfd_link_dll(info)         ((info)->type == type_dll)
 312 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 313 #define bfd_link_pie(info)         ((info)->type == type_pie)
 314 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 315 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 316
 317 /* This structure holds all the information needed to communicate
 318    between BFD and the linker when doing a link.  */
 319
 320 struct bfd_link_info
 321 {
 322   /* Output type.  */
 323   ENUM_BITFIELD (output_type) type : 2;
 324
 325   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 326   unsigned int symbolic: 1;
 327
 328   /* TRUE if executable should not contain copy relocs.
 329      Setting this true may result in a non-sharable text segment.  */
 330   unsigned int nocopyreloc: 1;
 331
 332   /* TRUE if BFD should export all symbols in the dynamic symbol table
 333      of an executable, rather than only those used.  */
 334   unsigned int export_dynamic: 1;
 335
 336   /* TRUE if a default symbol version should be created and used for
 337      exported symbols.  */
 338   unsigned int create_default_symver: 1;
 339
 340   /* TRUE if unreferenced sections should be removed.  */
 341   unsigned int gc_sections: 1;
 342
 343   /* TRUE if exported symbols should be kept during section gc.  */
 344   unsigned int gc_keep_exported: 1;
 345
 346   /* TRUE if every symbol should be reported back via the notice
 347      callback.  */
 348   unsigned int notice_all: 1;
 349
 350   /* TRUE if the LTO plugin is active.  */
 351   unsigned int lto_plugin_active: 1;
 352
 353   /* TRUE if global symbols in discarded sections should be stripped.  */
 354   unsigned int strip_discarded: 1;
 355
 356   /* TRUE if all data symbols should be dynamic.  */
 357   unsigned int dynamic_data: 1;
 358
 359   /* TRUE if section groups should be resolved.  */
 360   unsigned int resolve_section_groups: 1;
 361
 362   /* Set if output file is big-endian, or if that is unknown, from
 363      the command line or first input file endianness.  */
 364   unsigned int big_endian : 1;
 365
 366   /* Which symbols to strip.  */
 367   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 368
 369   /* Which local symbols to discard.  */
 370   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 371
 372   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 373   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 374
 375   /* Criteria for skipping symbols when determining
 376      whether to include an object from an archive. */
 377   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 378
 379   /* What to do with unresolved symbols in an object file.
 380      When producing executables the default is GENERATE_ERROR.
 381      When producing shared libraries the default is IGNORE.  The
 382      assumption with shared libraries is that the reference will be
 383      resolved at load/execution time.  */
 384   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 385
 386   /* What to do with unresolved symbols in a shared library.
 387      The same defaults apply.  */
 388   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 389
 390   /* TRUE if shared objects should be linked directly, not shared.  */
 391   unsigned int static_link: 1;
 392
 393   /* TRUE if symbols should be retained in memory, FALSE if they
 394      should be freed and reread.  */
 395   unsigned int keep_memory: 1;
 396
 397   /* TRUE if BFD should generate relocation information in the final
 398      executable.  */
 399   unsigned int emitrelocations: 1;
 400
 401   /* TRUE if PT_GNU_RELRO segment should be created.  */
 402   unsigned int relro: 1;
 403
 404   /* TRUE if separate code segment should be created.  */
 405   unsigned int separate_code: 1;
 406
 407   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 408      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 409   unsigned int eh_frame_hdr_type: 2;
 410
 411   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 412   unsigned int warn_shared_textrel: 1;
 413
 414   /* TRUE if we should error when adding a DT_TEXTREL.  */
 415   unsigned int error_textrel: 1;
 416
 417   /* TRUE if .hash section should be created.  */
 418   unsigned int emit_hash: 1;
 419
 420   /* TRUE if .gnu.hash section should be created.  */
 421   unsigned int emit_gnu_hash: 1;
 422
 423   /* If TRUE reduce memory overheads, at the expense of speed. This will
 424      cause map file generation to use an O(N^2) algorithm and disable
 425      caching ELF symbol buffer.  */
 426   unsigned int reduce_memory_overheads: 1;
 427
 428   /* TRUE if the output file should be in a traditional format.  This
 429      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 430      on the output file, but may be checked when reading the input
 431      files.  */
 432   unsigned int traditional_format: 1;
 433
 434   /* TRUE if non-PLT relocs should be merged into one reloc section
 435      and sorted so that relocs against the same symbol come together.  */
 436   unsigned int combreloc: 1;
 437
 438   /* TRUE if a default symbol version should be created and used for
 439      imported symbols.  */
 440   unsigned int default_imported_symver: 1;
 441
 442   /* TRUE if the new ELF dynamic tags are enabled. */
 443   unsigned int new_dtags: 1;
 444
 445   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 446      linker created sections, TRUE if it should be omitted.  */
 447   unsigned int no_ld_generated_unwind_info: 1;
 448
 449   /* TRUE if BFD should generate a "task linked" object file,
 450      similar to relocatable but also with globals converted to
 451      statics.  */
 452   unsigned int task_link: 1;
 453
 454   /* TRUE if ok to have multiple definition.  */
 455   unsigned int allow_multiple_definition: 1;
 456
 457   /* TRUE if ok to have prohibit multiple definition of absolute symbols.  */
 458   unsigned int prohibit_multiple_definition_absolute: 1;
 459
 460   /* TRUE if ok to have version with no definition.  */
 461   unsigned int allow_undefined_version: 1;
 462
 463   /* TRUE if some symbols have to be dynamic, controlled by
 464      --dynamic-list command line options.  */
 465   unsigned int dynamic: 1;
 466
 467   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 468      flags.  */
 469   unsigned int execstack: 1;
 470
 471   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 472      flags.  */
 473   unsigned int noexecstack: 1;
 474
 475   /* TRUE if we want to produced optimized output files.  This might
 476      need much more time and therefore must be explicitly selected.  */
 477   unsigned int optimize: 1;
 478
 479   /* TRUE if user should be informed of removed unreferenced sections.  */
 480   unsigned int print_gc_sections: 1;
 481
 482   /* TRUE if we should warn alternate ELF machine code.  */
 483   unsigned int warn_alternate_em: 1;
 484
 485   /* TRUE if the linker script contained an explicit PHDRS command.  */
 486   unsigned int user_phdrs: 1;
 487
 488   /* TRUE if program headers ought to be loaded.  */
 489   unsigned int load_phdrs: 1;
 490
 491   /* TRUE if we should check relocations after all input files have
 492      been opened.  */
 493   unsigned int check_relocs_after_open_input: 1;
 494
 495   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 496   unsigned int nointerp: 1;
 497
 498   /* TRUE if common symbols should be treated as undefined.  */
 499   unsigned int inhibit_common_definition : 1;
 500
 501   /* TRUE if "-Map map" is passed to linker.  */
 502   unsigned int has_map_file : 1;
 503
 504   /* TRUE if "--enable-non-contiguous-regions" is passed to the
 505      linker.  */
 506   unsigned int non_contiguous_regions : 1;
 507
 508   /* TRUE if "--enable-non-contiguous-regions-warnings" is passed to
 509      the linker.  */
 510   unsigned int non_contiguous_regions_warnings : 1;
 511
 512   /* Char that may appear as the first char of a symbol, but should be
 513      skipped (like symbol_leading_char) when looking up symbols in
 514      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 515   char wrap_char;
 516
 517   /* Separator between archive and filename in linker script filespecs.  */
 518   char path_separator;
 519
 520   /* Compress DWARF debug sections.  */
 521   enum compressed_debug_section_type compress_debug;
 522
 523   /* Default stack size.  Zero means default (often zero itself), -1
 524      means explicitly zero-sized.  */
 525   bfd_signed_vma stacksize;
 526
 527   /* Enable or disable target specific optimizations.
 528
 529      Not all targets have optimizations to enable.
 530
 531      Normally these optimizations are disabled by default but some targets
 532      prefer to enable them by default.  So this field is a tri-state variable.
 533      The values are:
 534
 535      zero: Enable the optimizations (either from --relax being specified on
 536        the command line or the backend's before_allocation emulation function.
 537
 538      positive: The user has requested that these optimizations be disabled.
 539        (Via the --no-relax command line option).
 540
 541      negative: The optimizations are disabled.  (Set when initializing the
 542        args_type structure in ldmain.c:main.  */
 543   signed int disable_target_specific_optimizations;
 544
 545   /* Function callbacks.  */
 546   const struct bfd_link_callbacks *callbacks;
 547
 548   /* Hash table handled by BFD.  */
 549   struct bfd_link_hash_table *hash;
 550
 551   /* Hash table of symbols to keep.  This is NULL unless strip is
 552      strip_some.  */
 553   struct bfd_hash_table *keep_hash;
 554
 555   /* Hash table of symbols to report back via the notice callback.  If
 556      this is NULL, and notice_all is FALSE, then no symbols are
 557      reported back.  */
 558   struct bfd_hash_table *notice_hash;
 559
 560   /* Hash table of symbols which are being wrapped (the --wrap linker
 561      option).  If this is NULL, no symbols are being wrapped.  */
 562   struct bfd_hash_table *wrap_hash;
 563
 564   /* Hash table of symbols which may be left unresolved during
 565      a link.  If this is NULL, no symbols can be left unresolved.  */
 566   struct bfd_hash_table *ignore_hash;
 567
 568   /* The output BFD.  */
 569   bfd *output_bfd;
 570
 571   /* The import library generated.  */
 572   bfd *out_implib_bfd;
 573
 574   /* The list of input BFD's involved in the link.  These are chained
 575      together via the link.next field.  */
 576   bfd *input_bfds;
 577   bfd **input_bfds_tail;
 578
 579   /* If a symbol should be created for each input BFD, this is section
 580      where those symbols should be placed.  It must be a section in
 581      the output BFD.  It may be NULL, in which case no such symbols
 582      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 583      linker command language.  */
 584   asection *create_object_symbols_section;
 585
 586   /* List of global symbol names that are starting points for marking
 587      sections against garbage collection.  */
 588   struct bfd_sym_chain *gc_sym_list;
 589
 590   /* If a base output file is wanted, then this points to it */
 591   void *base_file;
 592
 593   /* The function to call when the executable or shared object is
 594      loaded.  */
 595   const char *init_function;
 596
 597   /* The function to call when the executable or shared object is
 598      unloaded.  */
 599   const char *fini_function;
 600
 601   /* Number of relaxation passes.  Usually only one relaxation pass
 602      is needed.  But a backend can have as many relaxation passes as
 603      necessary.  During bfd_relax_section call, it is set to the
 604      current pass, starting from 0.  */
 605   int relax_pass;
 606
 607   /* Number of relaxation trips.  This number is incremented every
 608      time the relaxation pass is restarted due to a previous
 609      relaxation returning true in *AGAIN.  */
 610   int relax_trip;
 611
 612   /* > 0 to treat protected data defined in the shared library as
 613      reference external.  0 to treat it as internal.  -1 to let
 614      backend to decide.  */
 615   int extern_protected_data;
 616
 617   /* 1 to make undefined weak symbols dynamic when building a dynamic
 618      object.  0 to resolve undefined weak symbols to zero.  -1 to let
 619      the backend decide.  */
 620   int dynamic_undefined_weak;
 621
 622   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 623      should be generated/linked against.  Set to 1 if this feature
 624      is explicitly requested by the user, -1 if enabled by default.  */
 625   int pei386_auto_import;
 626
 627   /* Non-zero if runtime relocs for DATA items with non-zero addends
 628      in pei386 DLLs should be generated.  Set to 1 if this feature
 629      is explicitly requested by the user, -1 if enabled by default.  */
 630   int pei386_runtime_pseudo_reloc;
 631
 632   /* How many spare .dynamic DT_NULL entries should be added?  */
 633   unsigned int spare_dynamic_tags;
 634
 635   /* May be used to set DT_FLAGS for ELF. */
 636   bfd_vma flags;
 637
 638   /* May be used to set DT_FLAGS_1 for ELF. */
 639   bfd_vma flags_1;
 640
 641   /* Start and end of RELRO region.  */
 642   bfd_vma relro_start, relro_end;
 643
 644   /* List of symbols should be dynamic.  */
 645   struct bfd_elf_dynamic_list *dynamic_list;
 646
 647   /* The version information.  */
 648   struct bfd_elf_version_tree *version_info;
 649 };
 650
 651 /* Some forward-definitions used by some callbacks.  */
 652
 653 struct elf_strtab_hash;
 654 struct elf_sym_strtab;
 655
 656 /* This structures holds a set of callback functions.  These are called
 657    by the BFD linker routines.  */
 658
 659 struct bfd_link_callbacks
 660 {
 661   /* A function which is called when an object is added from an
 662      archive.  ABFD is the archive element being added.  NAME is the
 663      name of the symbol which caused the archive element to be pulled
 664      in.  This function may set *SUBSBFD to point to an alternative
 665      BFD from which symbols should in fact be added in place of the
 666      original BFD's symbols.  Returns TRUE if the object should be
 667      added, FALSE if it should be skipped.  */
 668   bfd_boolean (*add_archive_element)
 669     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 670   /* A function which is called when a symbol is found with multiple
 671      definitions.  H is the symbol which is defined multiple times.
 672      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 673      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 674   void (*multiple_definition)
 675     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 676      bfd *nbfd, asection *nsec, bfd_vma nval);
 677   /* A function which is called when a common symbol is defined
 678      multiple times.  H is the symbol appearing multiple times.
 679      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 680      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 681      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 682      is the size of the new symbol.  */
 683   void (*multiple_common)
 684     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 685      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 686   /* A function which is called to add a symbol to a set.  ENTRY is
 687      the link hash table entry for the set itself (e.g.,
 688      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 689      the set when generating a relocatable file, and is also used to
 690      get the size of the entry when generating an executable file.
 691      ABFD, SEC and VALUE identify the value to add to the set.  */
 692   void (*add_to_set)
 693     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 694      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 695   /* A function which is called when the name of a g++ constructor or
 696      destructor is found.  This is only called by some object file
 697      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 698      destructor.  This will use BFD_RELOC_CTOR when generating a
 699      relocatable file.  NAME is the name of the symbol found.  ABFD,
 700      SECTION and VALUE are the value of the symbol.  */
 701   void (*constructor)
 702     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 703      bfd *abfd, asection *sec, bfd_vma value);
 704   /* A function which is called to issue a linker warning.  For
 705      example, this is called when there is a reference to a warning
 706      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 707      of the symbol which triggered the warning; it may be NULL if
 708      there is none.  ABFD, SECTION and ADDRESS identify the location
 709      which trigerred the warning; either ABFD or SECTION or both may
 710      be NULL if the location is not known.  */
 711   void (*warning)
 712     (struct bfd_link_info *, const char *warning, const char *symbol,
 713      bfd *abfd, asection *section, bfd_vma address);
 714   /* A function which is called when a relocation is attempted against
 715      an undefined symbol.  NAME is the symbol which is undefined.
 716      ABFD, SECTION and ADDRESS identify the location from which the
 717      reference is made. IS_FATAL indicates whether an undefined symbol is
 718      a fatal error or not. In some cases SECTION may be NULL.  */
 719   void (*undefined_symbol)
 720     (struct bfd_link_info *, const char *name, bfd *abfd,
 721      asection *section, bfd_vma address, bfd_boolean is_fatal);
 722   /* A function which is called when a reloc overflow occurs. ENTRY is
 723      the link hash table entry for the symbol the reloc is against.
 724      NAME is the name of the local symbol or section the reloc is
 725      against, RELOC_NAME is the name of the relocation, and ADDEND is
 726      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 727      location at which the overflow occurs; if this is the result of a
 728      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 729      ABFD will be NULL.  */
 730   void (*reloc_overflow)
 731     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 732      const char *name, const char *reloc_name, bfd_vma addend,
 733      bfd *abfd, asection *section, bfd_vma address);
 734   /* A function which is called when a dangerous reloc is performed.
 735      MESSAGE is an appropriate message.
 736      ABFD, SECTION and ADDRESS identify the location at which the
 737      problem occurred; if this is the result of a
 738      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 739      ABFD will be NULL.  */
 740   void (*reloc_dangerous)
 741     (struct bfd_link_info *, const char *message,
 742      bfd *abfd, asection *section, bfd_vma address);
 743   /* A function which is called when a reloc is found to be attached
 744      to a symbol which is not being written out.  NAME is the name of
 745      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 746      the reloc; if this is the result of a
 747      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 748      ABFD will be NULL.  */
 749   void (*unattached_reloc)
 750     (struct bfd_link_info *, const char *name,
 751      bfd *abfd, asection *section, bfd_vma address);
 752   /* A function which is called when a symbol in notice_hash is
 753      defined or referenced.  H is the symbol, INH the indirect symbol
 754      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 755      the symbol.  If SECTION is bfd_und_section, this is a reference.
 756      FLAGS are the symbol BSF_* flags.  */
 757   bfd_boolean (*notice)
 758     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 759      struct bfd_link_hash_entry *inh,
 760      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 761   /* Error or warning link info message.  */
 762   void (*einfo)
 763     (const char *fmt, ...);
 764   /* General link info message.  */
 765   void (*info)
 766     (const char *fmt, ...);
 767   /* Message to be printed in linker map file.  */
 768   void (*minfo)
 769     (const char *fmt, ...);
 770   /* This callback provides a chance for users of the BFD library to
 771      override its decision about whether to place two adjacent sections
 772      into the same segment.  */
 773   bfd_boolean (*override_segment_assignment)
 774     (struct bfd_link_info *, bfd * abfd,
 775      asection * current_section, asection * previous_section,
 776      bfd_boolean new_segment);
 777   /* This callback provides a chance for callers of the BFD to examine the
 778      ELF string table and symbol table once they are complete and indexes and
 779      offsets assigned.  */
 780   void (*examine_strtab)
 781     (struct elf_sym_strtab *syms, bfd_size_type symcount,
 782      struct elf_strtab_hash *symstrtab);
 783   /* This callback should emit the CTF section into a non-loadable section in
 784      the output BFD named .ctf or a name beginning with ".ctf.".  */
 785   void (*emit_ctf)
 786     (void);
 787 };
 788 \f
 789 /* The linker builds link_order structures which tell the code how to
 790    include input data in the output file.  */
 791
 792 /* These are the types of link_order structures.  */
 793
 794 enum bfd_link_order_type
 795 {
 796   bfd_undefined_link_order,     /* Undefined.  */
 797   bfd_indirect_link_order,      /* Built from a section.  */
 798   bfd_data_link_order,          /* Set to explicit data.  */
 799   bfd_section_reloc_link_order, /* Relocate against a section.  */
 800   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 801 };
 802
 803 /* This is the link_order structure itself.  These form a chain
 804    attached to the output section whose contents they are describing.  */
 805
 806 struct bfd_link_order
 807 {
 808   /* Next link_order in chain.  */
 809   struct bfd_link_order *next;
 810   /* Type of link_order.  */
 811   enum bfd_link_order_type type;
 812   /* Offset within output section in bytes.  */
 813   bfd_vma offset;
 814   /* Size within output section in octets.  */
 815   bfd_size_type size;
 816   /* Type specific information.  */
 817   union
 818     {
 819       struct
 820         {
 821           /* Section to include.  If this is used, then
 822              section->output_section must be the section the
 823              link_order is attached to, section->output_offset must
 824              equal the link_order offset field, and section->size
 825              must equal the link_order size field.  Maybe these
 826              restrictions should be relaxed someday.  */
 827           asection *section;
 828         } indirect;
 829       struct
 830         {
 831           /* Size of contents, or zero when contents should be filled by
 832              the architecture-dependent fill function.
 833              A non-zero value allows filling of the output section
 834              with an arbitrary repeated pattern.  */
 835           unsigned int size;
 836           /* Data to put into file.  */
 837           bfd_byte *contents;
 838         } data;
 839       struct
 840         {
 841           /* Description of reloc to generate.  Used for
 842              bfd_section_reloc_link_order and
 843              bfd_symbol_reloc_link_order.  */
 844           struct bfd_link_order_reloc *p;
 845         } reloc;
 846     } u;
 847 };
 848
 849 /* A linker order of type bfd_section_reloc_link_order or
 850    bfd_symbol_reloc_link_order means to create a reloc against a
 851    section or symbol, respectively.  This is used to implement -Ur to
 852    generate relocs for the constructor tables.  The
 853    bfd_link_order_reloc structure describes the reloc that BFD should
 854    create.  It is similar to a arelent, but I didn't use arelent
 855    because the linker does not know anything about most symbols, and
 856    any asymbol structure it creates will be partially meaningless.
 857    This information could logically be in the bfd_link_order struct,
 858    but I didn't want to waste the space since these types of relocs
 859    are relatively rare.  */
 860
 861 struct bfd_link_order_reloc
 862 {
 863   /* Reloc type.  */
 864   bfd_reloc_code_real_type reloc;
 865
 866   union
 867     {
 868       /* For type bfd_section_reloc_link_order, this is the section
 869          the reloc should be against.  This must be a section in the
 870          output BFD, not any of the input BFDs.  */
 871       asection *section;
 872       /* For type bfd_symbol_reloc_link_order, this is the name of the
 873          symbol the reloc should be against.  */
 874       const char *name;
 875     } u;
 876
 877   /* Addend to use.  The object file should contain zero.  The BFD
 878      backend is responsible for filling in the contents of the object
 879      file correctly.  For some object file formats (e.g., COFF) the
 880      addend must be stored into in the object file, and for some
 881      (e.g., SPARC a.out) it is kept in the reloc.  */
 882   bfd_vma addend;
 883 };
 884
 885 /* Allocate a new link_order for a section.  */
 886 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 887
 888 struct bfd_section_already_linked;
 889
 890 extern bfd_boolean bfd_section_already_linked_table_init (void);
 891 extern void bfd_section_already_linked_table_free (void);
 892 extern bfd_boolean _bfd_handle_already_linked
 893   (struct bfd_section *, struct bfd_section_already_linked *,
 894    struct bfd_link_info *);
 895
 896 extern struct bfd_section *_bfd_nearby_section
 897   (bfd *, struct bfd_section *, bfd_vma);
 898
 899 extern void _bfd_fix_excluded_sec_syms
 900   (bfd *, struct bfd_link_info *);
 901
 902 /* These structures are used to describe version information for the
 903    ELF linker.  These structures could be manipulated entirely inside
 904    BFD, but it would be a pain.  Instead, the regular linker sets up
 905    these structures, and then passes them into BFD.  */
 906
 907 /* Glob pattern for a version.  */
 908
 909 struct bfd_elf_version_expr
 910 {
 911   /* Next glob pattern for this version.  */
 912   struct bfd_elf_version_expr *next;
 913   /* Glob pattern.  */
 914   const char *pattern;
 915   /* Set if pattern is not a glob.  */
 916   unsigned int literal : 1;
 917   /* Defined by ".symver".  */
 918   unsigned int symver : 1;
 919   /* Defined by version script.  */
 920   unsigned int script : 1;
 921   /* Pattern type.  */
 922 #define BFD_ELF_VERSION_C_TYPE          1
 923 #define BFD_ELF_VERSION_CXX_TYPE        2
 924 #define BFD_ELF_VERSION_JAVA_TYPE       4
 925   unsigned int mask : 3;
 926 };
 927
 928 struct bfd_elf_version_expr_head
 929 {
 930   /* List of all patterns, both wildcards and non-wildcards.  */
 931   struct bfd_elf_version_expr *list;
 932   /* Hash table for non-wildcards.  */
 933   void *htab;
 934   /* Remaining patterns.  */
 935   struct bfd_elf_version_expr *remaining;
 936   /* What kind of pattern types are present in list (bitmask).  */
 937   unsigned int mask;
 938 };
 939
 940 /* Version dependencies.  */
 941
 942 struct bfd_elf_version_deps
 943 {
 944   /* Next dependency for this version.  */
 945   struct bfd_elf_version_deps *next;
 946   /* The version which this version depends upon.  */
 947   struct bfd_elf_version_tree *version_needed;
 948 };
 949
 950 /* A node in the version tree.  */
 951
 952 struct bfd_elf_version_tree
 953 {
 954   /* Next version.  */
 955   struct bfd_elf_version_tree *next;
 956   /* Name of this version.  */
 957   const char *name;
 958   /* Version number.  */
 959   unsigned int vernum;
 960   /* Regular expressions for global symbols in this version.  */
 961   struct bfd_elf_version_expr_head globals;
 962   /* Regular expressions for local symbols in this version.  */
 963   struct bfd_elf_version_expr_head locals;
 964   /* List of versions which this version depends upon.  */
 965   struct bfd_elf_version_deps *deps;
 966   /* Index of the version name.  This is used within BFD.  */
 967   unsigned int name_indx;
 968   /* Whether this version tree was used.  This is used within BFD.  */
 969   int used;
 970   /* Matching hook.  */
 971   struct bfd_elf_version_expr *(*match)
 972     (struct bfd_elf_version_expr_head *head,
 973      struct bfd_elf_version_expr *prev, const char *sym);
 974 };
 975
 976 struct bfd_elf_dynamic_list
 977 {
 978   struct bfd_elf_version_expr_head head;
 979   struct bfd_elf_version_expr *(*match)
 980     (struct bfd_elf_version_expr_head *head,
 981      struct bfd_elf_version_expr *prev, const char *sym);
 982 };
 983
 984 #endif