include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2018 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   /* Symbol will be converted from absolute to section-relative.  Set for
 119      symbols defined by a script from "dot" (also SEGMENT_START or ORIGIN)
 120      outside of an output section statement.  */
 121   unsigned int rel_from_abs : 1;
 122
 123   /* A union of information depending upon the type.  */
 124   union
 125     {
 126       /* Nothing is kept for bfd_hash_new.  */
 127       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 128       struct
 129         {
 130           /* Undefined and common symbols are kept in a linked list through
 131              this field.  This field is present in all of the union element
 132              so that we don't need to remove entries from the list when we
 133              change their type.  Removing entries would either require the
 134              list to be doubly linked, which would waste more memory, or
 135              require a traversal.  When an undefined or common symbol is
 136              created, it should be added to this list, the head of which is in
 137              the link hash table itself.  As symbols are defined, they need
 138              not be removed from the list; anything which reads the list must
 139              doublecheck the symbol type.
 140
 141              Weak symbols are not kept on this list.
 142
 143              Defined and defweak symbols use this field as a reference marker.
 144              If the field is not NULL, or this structure is the tail of the
 145              undefined symbol list, the symbol has been referenced.  If the
 146              symbol is undefined and becomes defined, this field will
 147              automatically be non-NULL since the symbol will have been on the
 148              undefined symbol list.  */
 149           struct bfd_link_hash_entry *next;
 150           /* BFD symbol was found in.  */
 151           bfd *abfd;
 152         } undef;
 153       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 154       struct
 155         {
 156           struct bfd_link_hash_entry *next;
 157           /* Symbol section.  */
 158           asection *section;
 159           /* Symbol value.  */
 160           bfd_vma value;
 161         } def;
 162       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 163       struct
 164         {
 165           struct bfd_link_hash_entry *next;
 166           /* Real symbol.  */
 167           struct bfd_link_hash_entry *link;
 168           /* Warning message (bfd_link_hash_warning only).  */
 169           const char *warning;
 170         } i;
 171       /* bfd_link_hash_common.  */
 172       struct
 173         {
 174           struct bfd_link_hash_entry *next;
 175           /* The linker needs to know three things about common
 176              symbols: the size, the alignment, and the section in
 177              which the symbol should be placed.  We store the size
 178              here, and we allocate a small structure to hold the
 179              section and the alignment.  The alignment is stored as a
 180              power of two.  We don't store all the information
 181              directly because we don't want to increase the size of
 182              the union; this structure is a major space user in the
 183              linker.  */
 184           struct bfd_link_hash_common_entry *p;
 185           /* Common symbol size.  */
 186           bfd_size_type size;
 187         } c;
 188     } u;
 189 };
 190
 191 /* This is the link hash table.  It is a derived class of
 192    bfd_hash_table.  */
 193
 194 struct bfd_link_hash_table
 195 {
 196   /* The hash table itself.  */
 197   struct bfd_hash_table table;
 198   /* A linked list of undefined and common symbols, linked through the
 199      next field in the bfd_link_hash_entry structure.  */
 200   struct bfd_link_hash_entry *undefs;
 201   /* Entries are added to the tail of the undefs list.  */
 202   struct bfd_link_hash_entry *undefs_tail;
 203   /* Function to free the hash table on closing BFD.  */
 204   void (*hash_table_free) (bfd *);
 205   /* The type of the link hash table.  */
 206   enum bfd_link_hash_table_type type;
 207 };
 208
 209 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 210    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 211    the real symbol.  */
 212 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 213   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 214    bfd_boolean copy, bfd_boolean follow);
 215
 216 /* Look up an entry in the main linker hash table if the symbol might
 217    be wrapped.  This should only be used for references to an
 218    undefined symbol, not for definitions of a symbol.  */
 219
 220 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 221   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 222    bfd_boolean, bfd_boolean);
 223
 224 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 225    and the remainder is found in wrap_hash, return the real symbol.  */
 226
 227 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 228   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 229
 230 /* Traverse a link hash table.  */
 231 extern void bfd_link_hash_traverse
 232   (struct bfd_link_hash_table *,
 233     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 234     void *);
 235
 236 /* Add an entry to the undefs list.  */
 237 extern void bfd_link_add_undef
 238   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 239
 240 /* Remove symbols from the undefs list that don't belong there.  */
 241 extern void bfd_link_repair_undef_list
 242   (struct bfd_link_hash_table *table);
 243
 244 /* Read symbols and cache symbol pointer array in outsymbols.  */
 245 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 246
 247 /* Check the relocs in the BFD.  Called after all the input
 248    files have been loaded, and garbage collection has tagged
 249    any unneeded sections.  */
 250 extern bfd_boolean bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 251
 252 struct bfd_sym_chain
 253 {
 254   struct bfd_sym_chain *next;
 255   const char *name;
 256 };
 257 \f
 258 /* How to handle unresolved symbols.
 259    There are four possibilities which are enumerated below:  */
 260 enum report_method
 261 {
 262   /* This is the initial value when then link_info structure is created.
 263      It allows the various stages of the linker to determine whether they
 264      allowed to set the value.  */
 265   RM_NOT_YET_SET = 0,
 266   RM_IGNORE,
 267   RM_GENERATE_WARNING,
 268   RM_GENERATE_ERROR
 269 };
 270
 271 typedef enum {with_flags, without_flags} flag_type;
 272
 273 /* A section flag list.  */
 274 struct flag_info_list
 275 {
 276   flag_type with;
 277   const char *name;
 278   bfd_boolean valid;
 279   struct flag_info_list *next;
 280 };
 281
 282 /* Section flag info.  */
 283 struct flag_info
 284 {
 285   flagword only_with_flags;
 286   flagword not_with_flags;
 287   struct flag_info_list *flag_list;
 288   bfd_boolean flags_initialized;
 289 };
 290
 291 struct bfd_elf_dynamic_list;
 292 struct bfd_elf_version_tree;
 293
 294 /* Types of output.  */
 295
 296 enum output_type
 297 {
 298   type_pde,
 299   type_pie,
 300   type_relocatable,
 301   type_dll,
 302 };
 303
 304 #define bfd_link_pde(info)         ((info)->type == type_pde)
 305 #define bfd_link_dll(info)         ((info)->type == type_dll)
 306 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 307 #define bfd_link_pie(info)         ((info)->type == type_pie)
 308 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 309 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 310
 311 /* This structure holds all the information needed to communicate
 312    between BFD and the linker when doing a link.  */
 313
 314 struct bfd_link_info
 315 {
 316   /* Output type.  */
 317   ENUM_BITFIELD (output_type) type : 2;
 318
 319   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 320   unsigned int symbolic: 1;
 321
 322   /* TRUE if executable should not contain copy relocs.
 323      Setting this true may result in a non-sharable text segment.  */
 324   unsigned int nocopyreloc: 1;
 325
 326   /* TRUE if BFD should export all symbols in the dynamic symbol table
 327      of an executable, rather than only those used.  */
 328   unsigned int export_dynamic: 1;
 329
 330   /* TRUE if a default symbol version should be created and used for
 331      exported symbols.  */
 332   unsigned int create_default_symver: 1;
 333
 334   /* TRUE if unreferenced sections should be removed.  */
 335   unsigned int gc_sections: 1;
 336
 337   /* TRUE if exported symbols should be kept during section gc.  */
 338   unsigned int gc_keep_exported: 1;
 339
 340   /* TRUE if every symbol should be reported back via the notice
 341      callback.  */
 342   unsigned int notice_all: 1;
 343
 344   /* TRUE if the LTO plugin is active.  */
 345   unsigned int lto_plugin_active: 1;
 346
 347   /* TRUE if global symbols in discarded sections should be stripped.  */
 348   unsigned int strip_discarded: 1;
 349
 350   /* TRUE if all data symbols should be dynamic.  */
 351   unsigned int dynamic_data: 1;
 352
 353   /* TRUE if section groups should be resolved.  */
 354   unsigned int resolve_section_groups: 1;
 355
 356   /* Which symbols to strip.  */
 357   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 358
 359   /* Which local symbols to discard.  */
 360   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 361
 362   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 363   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 364
 365   /* Criteria for skipping symbols when determining
 366      whether to include an object from an archive. */
 367   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 368
 369   /* What to do with unresolved symbols in an object file.
 370      When producing executables the default is GENERATE_ERROR.
 371      When producing shared libraries the default is IGNORE.  The
 372      assumption with shared libraries is that the reference will be
 373      resolved at load/execution time.  */
 374   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 375
 376   /* What to do with unresolved symbols in a shared library.
 377      The same defaults apply.  */
 378   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 379
 380   /* TRUE if shared objects should be linked directly, not shared.  */
 381   unsigned int static_link: 1;
 382
 383   /* TRUE if symbols should be retained in memory, FALSE if they
 384      should be freed and reread.  */
 385   unsigned int keep_memory: 1;
 386
 387   /* TRUE if BFD should generate relocation information in the final
 388      executable.  */
 389   unsigned int emitrelocations: 1;
 390
 391   /* TRUE if PT_GNU_RELRO segment should be created.  */
 392   unsigned int relro: 1;
 393
 394   /* TRUE if separate code segment should be created.  */
 395   unsigned int separate_code: 1;
 396
 397   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 398      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 399   unsigned int eh_frame_hdr_type: 2;
 400
 401   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 402   unsigned int warn_shared_textrel: 1;
 403
 404   /* TRUE if we should error when adding a DT_TEXTREL.  */
 405   unsigned int error_textrel: 1;
 406
 407   /* TRUE if .hash section should be created.  */
 408   unsigned int emit_hash: 1;
 409
 410   /* TRUE if .gnu.hash section should be created.  */
 411   unsigned int emit_gnu_hash: 1;
 412
 413   /* If TRUE reduce memory overheads, at the expense of speed. This will
 414      cause map file generation to use an O(N^2) algorithm and disable
 415      caching ELF symbol buffer.  */
 416   unsigned int reduce_memory_overheads: 1;
 417
 418   /* TRUE if the output file should be in a traditional format.  This
 419      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 420      on the output file, but may be checked when reading the input
 421      files.  */
 422   unsigned int traditional_format: 1;
 423
 424   /* TRUE if non-PLT relocs should be merged into one reloc section
 425      and sorted so that relocs against the same symbol come together.  */
 426   unsigned int combreloc: 1;
 427
 428   /* TRUE if a default symbol version should be created and used for
 429      imported symbols.  */
 430   unsigned int default_imported_symver: 1;
 431
 432   /* TRUE if the new ELF dynamic tags are enabled. */
 433   unsigned int new_dtags: 1;
 434
 435   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 436      linker created sections, TRUE if it should be omitted.  */
 437   unsigned int no_ld_generated_unwind_info: 1;
 438
 439   /* TRUE if BFD should generate a "task linked" object file,
 440      similar to relocatable but also with globals converted to
 441      statics.  */
 442   unsigned int task_link: 1;
 443
 444   /* TRUE if ok to have multiple definition.  */
 445   unsigned int allow_multiple_definition: 1;
 446
 447   /* TRUE if ok to have prohibit multiple definition of absolute symbols.  */
 448   unsigned int prohibit_multiple_definition_absolute: 1;
 449
 450   /* TRUE if ok to have version with no definition.  */
 451   unsigned int allow_undefined_version: 1;
 452
 453   /* TRUE if some symbols have to be dynamic, controlled by
 454      --dynamic-list command line options.  */
 455   unsigned int dynamic: 1;
 456
 457   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 458      flags.  */
 459   unsigned int execstack: 1;
 460
 461   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 462      flags.  */
 463   unsigned int noexecstack: 1;
 464
 465   /* TRUE if we want to produced optimized output files.  This might
 466      need much more time and therefore must be explicitly selected.  */
 467   unsigned int optimize: 1;
 468
 469   /* TRUE if user should be informed of removed unreferenced sections.  */
 470   unsigned int print_gc_sections: 1;
 471
 472   /* TRUE if we should warn alternate ELF machine code.  */
 473   unsigned int warn_alternate_em: 1;
 474
 475   /* TRUE if the linker script contained an explicit PHDRS command.  */
 476   unsigned int user_phdrs: 1;
 477
 478   /* TRUE if we should check relocations after all input files have
 479      been opened.  */
 480   unsigned int check_relocs_after_open_input: 1;
 481
 482   /* TRUE if BND prefix in PLT entries is always generated.  */
 483   unsigned int bndplt: 1;
 484
 485   /* TRUE if IBT-enabled PLT entries should be generated.  */
 486   unsigned int ibtplt: 1;
 487
 488   /* TRUE if GNU_PROPERTY_X86_FEATURE_1_IBT should be generated.  */
 489   unsigned int ibt: 1;
 490
 491   /* TRUE if GNU_PROPERTY_X86_FEATURE_1_SHSTK should be generated.  */
 492   unsigned int shstk: 1;
 493
 494   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 495   unsigned int nointerp: 1;
 496
 497   /* TRUE if we shouldn't check relocation overflow.  */
 498   unsigned int no_reloc_overflow_check: 1;
 499
 500   /* TRUE if generate a 1-byte NOP as suffix for x86 call instruction.  */
 501   unsigned int call_nop_as_suffix : 1;
 502
 503   /* TRUE if common symbols should be treated as undefined.  */
 504   unsigned int inhibit_common_definition : 1;
 505
 506   /* The 1-byte NOP for x86 call instruction.  */
 507   char call_nop_byte;
 508
 509   /* Char that may appear as the first char of a symbol, but should be
 510      skipped (like symbol_leading_char) when looking up symbols in
 511      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 512   char wrap_char;
 513
 514   /* Separator between archive and filename in linker script filespecs.  */
 515   char path_separator;
 516
 517   /* Compress DWARF debug sections.  */
 518   enum compressed_debug_section_type compress_debug;
 519
 520   /* Default stack size.  Zero means default (often zero itself), -1
 521      means explicitly zero-sized.  */
 522   bfd_signed_vma stacksize;
 523
 524   /* Enable or disable target specific optimizations.
 525
 526      Not all targets have optimizations to enable.
 527
 528      Normally these optimizations are disabled by default but some targets
 529      prefer to enable them by default.  So this field is a tri-state variable.
 530      The values are:
 531
 532      zero: Enable the optimizations (either from --relax being specified on
 533        the command line or the backend's before_allocation emulation function.
 534
 535      positive: The user has requested that these optimizations be disabled.
 536        (Via the --no-relax command line option).
 537
 538      negative: The optimizations are disabled.  (Set when initializing the
 539        args_type structure in ldmain.c:main.  */
 540   signed int disable_target_specific_optimizations;
 541
 542   /* Function callbacks.  */
 543   const struct bfd_link_callbacks *callbacks;
 544
 545   /* Hash table handled by BFD.  */
 546   struct bfd_link_hash_table *hash;
 547
 548   /* Hash table of symbols to keep.  This is NULL unless strip is
 549      strip_some.  */
 550   struct bfd_hash_table *keep_hash;
 551
 552   /* Hash table of symbols to report back via the notice callback.  If
 553      this is NULL, and notice_all is FALSE, then no symbols are
 554      reported back.  */
 555   struct bfd_hash_table *notice_hash;
 556
 557   /* Hash table of symbols which are being wrapped (the --wrap linker
 558      option).  If this is NULL, no symbols are being wrapped.  */
 559   struct bfd_hash_table *wrap_hash;
 560
 561   /* Hash table of symbols which may be left unresolved during
 562      a link.  If this is NULL, no symbols can be left unresolved.  */
 563   struct bfd_hash_table *ignore_hash;
 564
 565   /* The output BFD.  */
 566   bfd *output_bfd;
 567
 568   /* The import library generated.  */
 569   bfd *out_implib_bfd;
 570
 571   /* The list of input BFD's involved in the link.  These are chained
 572      together via the link.next field.  */
 573   bfd *input_bfds;
 574   bfd **input_bfds_tail;
 575
 576   /* If a symbol should be created for each input BFD, this is section
 577      where those symbols should be placed.  It must be a section in
 578      the output BFD.  It may be NULL, in which case no such symbols
 579      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 580      linker command language.  */
 581   asection *create_object_symbols_section;
 582
 583   /* List of global symbol names that are starting points for marking
 584      sections against garbage collection.  */
 585   struct bfd_sym_chain *gc_sym_list;
 586
 587   /* If a base output file is wanted, then this points to it */
 588   void *base_file;
 589
 590   /* The function to call when the executable or shared object is
 591      loaded.  */
 592   const char *init_function;
 593
 594   /* The function to call when the executable or shared object is
 595      unloaded.  */
 596   const char *fini_function;
 597
 598   /* Number of relaxation passes.  Usually only one relaxation pass
 599      is needed.  But a backend can have as many relaxation passes as
 600      necessary.  During bfd_relax_section call, it is set to the
 601      current pass, starting from 0.  */
 602   int relax_pass;
 603
 604   /* Number of relaxation trips.  This number is incremented every
 605      time the relaxation pass is restarted due to a previous
 606      relaxation returning true in *AGAIN.  */
 607   int relax_trip;
 608
 609   /* > 0 to treat protected data defined in the shared library as
 610      reference external.  0 to treat it as internal.  -1 to let
 611      backend to decide.  */
 612   int extern_protected_data;
 613
 614   /* 1 to make undefined weak symbols dynamic when building a dynamic
 615      object.  0 to resolve undefined weak symbols to zero.  -1 to let
 616      the backend decide.  */
 617   int dynamic_undefined_weak;
 618
 619   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 620      should be generated/linked against.  Set to 1 if this feature
 621      is explicitly requested by the user, -1 if enabled by default.  */
 622   int pei386_auto_import;
 623
 624   /* Non-zero if runtime relocs for DATA items with non-zero addends
 625      in pei386 DLLs should be generated.  Set to 1 if this feature
 626      is explicitly requested by the user, -1 if enabled by default.  */
 627   int pei386_runtime_pseudo_reloc;
 628
 629   /* How many spare .dynamic DT_NULL entries should be added?  */
 630   unsigned int spare_dynamic_tags;
 631
 632   /* May be used to set DT_FLAGS for ELF. */
 633   bfd_vma flags;
 634
 635   /* May be used to set DT_FLAGS_1 for ELF. */
 636   bfd_vma flags_1;
 637
 638   /* Start and end of RELRO region.  */
 639   bfd_vma relro_start, relro_end;
 640
 641   /* List of symbols should be dynamic.  */
 642   struct bfd_elf_dynamic_list *dynamic_list;
 643
 644   /* The version information.  */
 645   struct bfd_elf_version_tree *version_info;
 646 };
 647
 648 /* This structures holds a set of callback functions.  These are called
 649    by the BFD linker routines.  */
 650
 651 struct bfd_link_callbacks
 652 {
 653   /* A function which is called when an object is added from an
 654      archive.  ABFD is the archive element being added.  NAME is the
 655      name of the symbol which caused the archive element to be pulled
 656      in.  This function may set *SUBSBFD to point to an alternative
 657      BFD from which symbols should in fact be added in place of the
 658      original BFD's symbols.  Returns TRUE if the object should be
 659      added, FALSE if it should be skipped.  */
 660   bfd_boolean (*add_archive_element)
 661     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 662   /* A function which is called when a symbol is found with multiple
 663      definitions.  H is the symbol which is defined multiple times.
 664      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 665      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 666   void (*multiple_definition)
 667     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 668      bfd *nbfd, asection *nsec, bfd_vma nval);
 669   /* A function which is called when a common symbol is defined
 670      multiple times.  H is the symbol appearing multiple times.
 671      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 672      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 673      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 674      is the size of the new symbol.  */
 675   void (*multiple_common)
 676     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 677      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 678   /* A function which is called to add a symbol to a set.  ENTRY is
 679      the link hash table entry for the set itself (e.g.,
 680      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 681      the set when generating a relocatable file, and is also used to
 682      get the size of the entry when generating an executable file.
 683      ABFD, SEC and VALUE identify the value to add to the set.  */
 684   void (*add_to_set)
 685     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 686      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 687   /* A function which is called when the name of a g++ constructor or
 688      destructor is found.  This is only called by some object file
 689      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 690      destructor.  This will use BFD_RELOC_CTOR when generating a
 691      relocatable file.  NAME is the name of the symbol found.  ABFD,
 692      SECTION and VALUE are the value of the symbol.  */
 693   void (*constructor)
 694     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 695      bfd *abfd, asection *sec, bfd_vma value);
 696   /* A function which is called to issue a linker warning.  For
 697      example, this is called when there is a reference to a warning
 698      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 699      of the symbol which triggered the warning; it may be NULL if
 700      there is none.  ABFD, SECTION and ADDRESS identify the location
 701      which trigerred the warning; either ABFD or SECTION or both may
 702      be NULL if the location is not known.  */
 703   void (*warning)
 704     (struct bfd_link_info *, const char *warning, const char *symbol,
 705      bfd *abfd, asection *section, bfd_vma address);
 706   /* A function which is called when a relocation is attempted against
 707      an undefined symbol.  NAME is the symbol which is undefined.
 708      ABFD, SECTION and ADDRESS identify the location from which the
 709      reference is made. IS_FATAL indicates whether an undefined symbol is
 710      a fatal error or not. In some cases SECTION may be NULL.  */
 711   void (*undefined_symbol)
 712     (struct bfd_link_info *, const char *name, bfd *abfd,
 713      asection *section, bfd_vma address, bfd_boolean is_fatal);
 714   /* A function which is called when a reloc overflow occurs. ENTRY is
 715      the link hash table entry for the symbol the reloc is against.
 716      NAME is the name of the local symbol or section the reloc is
 717      against, RELOC_NAME is the name of the relocation, and ADDEND is
 718      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 719      location at which the overflow occurs; if this is the result of a
 720      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 721      ABFD will be NULL.  */
 722   void (*reloc_overflow)
 723     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 724      const char *name, const char *reloc_name, bfd_vma addend,
 725      bfd *abfd, asection *section, bfd_vma address);
 726   /* A function which is called when a dangerous reloc is performed.
 727      MESSAGE is an appropriate message.
 728      ABFD, SECTION and ADDRESS identify the location at which the
 729      problem occurred; if this is the result of a
 730      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 731      ABFD will be NULL.  */
 732   void (*reloc_dangerous)
 733     (struct bfd_link_info *, const char *message,
 734      bfd *abfd, asection *section, bfd_vma address);
 735   /* A function which is called when a reloc is found to be attached
 736      to a symbol which is not being written out.  NAME is the name of
 737      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 738      the reloc; if this is the result of a
 739      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 740      ABFD will be NULL.  */
 741   void (*unattached_reloc)
 742     (struct bfd_link_info *, const char *name,
 743      bfd *abfd, asection *section, bfd_vma address);
 744   /* A function which is called when a symbol in notice_hash is
 745      defined or referenced.  H is the symbol, INH the indirect symbol
 746      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 747      the symbol.  If SECTION is bfd_und_section, this is a reference.
 748      FLAGS are the symbol BSF_* flags.  */
 749   bfd_boolean (*notice)
 750     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 751      struct bfd_link_hash_entry *inh,
 752      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 753   /* Error or warning link info message.  */
 754   void (*einfo)
 755     (const char *fmt, ...);
 756   /* General link info message.  */
 757   void (*info)
 758     (const char *fmt, ...);
 759   /* Message to be printed in linker map file.  */
 760   void (*minfo)
 761     (const char *fmt, ...);
 762   /* This callback provides a chance for users of the BFD library to
 763      override its decision about whether to place two adjacent sections
 764      into the same segment.  */
 765   bfd_boolean (*override_segment_assignment)
 766     (struct bfd_link_info *, bfd * abfd,
 767      asection * current_section, asection * previous_section,
 768      bfd_boolean new_segment);
 769 };
 770 \f
 771 /* The linker builds link_order structures which tell the code how to
 772    include input data in the output file.  */
 773
 774 /* These are the types of link_order structures.  */
 775
 776 enum bfd_link_order_type
 777 {
 778   bfd_undefined_link_order,     /* Undefined.  */
 779   bfd_indirect_link_order,      /* Built from a section.  */
 780   bfd_data_link_order,          /* Set to explicit data.  */
 781   bfd_section_reloc_link_order, /* Relocate against a section.  */
 782   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 783 };
 784
 785 /* This is the link_order structure itself.  These form a chain
 786    attached to the output section whose contents they are describing.  */
 787
 788 struct bfd_link_order
 789 {
 790   /* Next link_order in chain.  */
 791   struct bfd_link_order *next;
 792   /* Type of link_order.  */
 793   enum bfd_link_order_type type;
 794   /* Offset within output section.  */
 795   bfd_vma offset;
 796   /* Size within output section.  */
 797   bfd_size_type size;
 798   /* Type specific information.  */
 799   union
 800     {
 801       struct
 802         {
 803           /* Section to include.  If this is used, then
 804              section->output_section must be the section the
 805              link_order is attached to, section->output_offset must
 806              equal the link_order offset field, and section->size
 807              must equal the link_order size field.  Maybe these
 808              restrictions should be relaxed someday.  */
 809           asection *section;
 810         } indirect;
 811       struct
 812         {
 813           /* Size of contents, or zero when contents should be filled by
 814              the architecture-dependent fill function.
 815              A non-zero value allows filling of the output section
 816              with an arbitrary repeated pattern.  */
 817           unsigned int size;
 818           /* Data to put into file.  */
 819           bfd_byte *contents;
 820         } data;
 821       struct
 822         {
 823           /* Description of reloc to generate.  Used for
 824              bfd_section_reloc_link_order and
 825              bfd_symbol_reloc_link_order.  */
 826           struct bfd_link_order_reloc *p;
 827         } reloc;
 828     } u;
 829 };
 830
 831 /* A linker order of type bfd_section_reloc_link_order or
 832    bfd_symbol_reloc_link_order means to create a reloc against a
 833    section or symbol, respectively.  This is used to implement -Ur to
 834    generate relocs for the constructor tables.  The
 835    bfd_link_order_reloc structure describes the reloc that BFD should
 836    create.  It is similar to a arelent, but I didn't use arelent
 837    because the linker does not know anything about most symbols, and
 838    any asymbol structure it creates will be partially meaningless.
 839    This information could logically be in the bfd_link_order struct,
 840    but I didn't want to waste the space since these types of relocs
 841    are relatively rare.  */
 842
 843 struct bfd_link_order_reloc
 844 {
 845   /* Reloc type.  */
 846   bfd_reloc_code_real_type reloc;
 847
 848   union
 849     {
 850       /* For type bfd_section_reloc_link_order, this is the section
 851          the reloc should be against.  This must be a section in the
 852          output BFD, not any of the input BFDs.  */
 853       asection *section;
 854       /* For type bfd_symbol_reloc_link_order, this is the name of the
 855          symbol the reloc should be against.  */
 856       const char *name;
 857     } u;
 858
 859   /* Addend to use.  The object file should contain zero.  The BFD
 860      backend is responsible for filling in the contents of the object
 861      file correctly.  For some object file formats (e.g., COFF) the
 862      addend must be stored into in the object file, and for some
 863      (e.g., SPARC a.out) it is kept in the reloc.  */
 864   bfd_vma addend;
 865 };
 866
 867 /* Allocate a new link_order for a section.  */
 868 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 869
 870 /* These structures are used to describe version information for the
 871    ELF linker.  These structures could be manipulated entirely inside
 872    BFD, but it would be a pain.  Instead, the regular linker sets up
 873    these structures, and then passes them into BFD.  */
 874
 875 /* Glob pattern for a version.  */
 876
 877 struct bfd_elf_version_expr
 878 {
 879   /* Next glob pattern for this version.  */
 880   struct bfd_elf_version_expr *next;
 881   /* Glob pattern.  */
 882   const char *pattern;
 883   /* Set if pattern is not a glob.  */
 884   unsigned int literal : 1;
 885   /* Defined by ".symver".  */
 886   unsigned int symver : 1;
 887   /* Defined by version script.  */
 888   unsigned int script : 1;
 889   /* Pattern type.  */
 890 #define BFD_ELF_VERSION_C_TYPE          1
 891 #define BFD_ELF_VERSION_CXX_TYPE        2
 892 #define BFD_ELF_VERSION_JAVA_TYPE       4
 893   unsigned int mask : 3;
 894 };
 895
 896 struct bfd_elf_version_expr_head
 897 {
 898   /* List of all patterns, both wildcards and non-wildcards.  */
 899   struct bfd_elf_version_expr *list;
 900   /* Hash table for non-wildcards.  */
 901   void *htab;
 902   /* Remaining patterns.  */
 903   struct bfd_elf_version_expr *remaining;
 904   /* What kind of pattern types are present in list (bitmask).  */
 905   unsigned int mask;
 906 };
 907
 908 /* Version dependencies.  */
 909
 910 struct bfd_elf_version_deps
 911 {
 912   /* Next dependency for this version.  */
 913   struct bfd_elf_version_deps *next;
 914   /* The version which this version depends upon.  */
 915   struct bfd_elf_version_tree *version_needed;
 916 };
 917
 918 /* A node in the version tree.  */
 919
 920 struct bfd_elf_version_tree
 921 {
 922   /* Next version.  */
 923   struct bfd_elf_version_tree *next;
 924   /* Name of this version.  */
 925   const char *name;
 926   /* Version number.  */
 927   unsigned int vernum;
 928   /* Regular expressions for global symbols in this version.  */
 929   struct bfd_elf_version_expr_head globals;
 930   /* Regular expressions for local symbols in this version.  */
 931   struct bfd_elf_version_expr_head locals;
 932   /* List of versions which this version depends upon.  */
 933   struct bfd_elf_version_deps *deps;
 934   /* Index of the version name.  This is used within BFD.  */
 935   unsigned int name_indx;
 936   /* Whether this version tree was used.  This is used within BFD.  */
 937   int used;
 938   /* Matching hook.  */
 939   struct bfd_elf_version_expr *(*match)
 940     (struct bfd_elf_version_expr_head *head,
 941      struct bfd_elf_version_expr *prev, const char *sym);
 942 };
 943
 944 struct bfd_elf_dynamic_list
 945 {
 946   struct bfd_elf_version_expr_head head;
 947   struct bfd_elf_version_expr *(*match)
 948     (struct bfd_elf_version_expr_head *head,
 949      struct bfd_elf_version_expr *prev, const char *sym);
 950 };
 951
 952 #endif