include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright (C) 1993-2016 Free Software Foundation, Inc.
   3    Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 #ifndef BFDLINK_H
  23 #define BFDLINK_H
  24
  25 /* Which symbols to strip during a link.  */
  26 enum bfd_link_strip
  27 {
  28   strip_none,           /* Don't strip any symbols.  */
  29   strip_debugger,       /* Strip debugging symbols.  */
  30   strip_some,           /* keep_hash is the list of symbols to keep.  */
  31   strip_all             /* Strip all symbols.  */
  32 };
  33
  34 /* Which local symbols to discard during a link.  This is irrelevant
  35    if strip_all is used.  */
  36 enum bfd_link_discard
  37 {
  38   discard_sec_merge,    /* Discard local temporary symbols in SEC_MERGE
  39                            sections.  */
  40   discard_none,         /* Don't discard any locals.  */
  41   discard_l,            /* Discard local temporary symbols.  */
  42   discard_all           /* Discard all locals.  */
  43 };
  44
  45 /* Whether to generate ELF common symbols with the STT_COMMON type
  46    during a relocatable link.  */
  47 enum bfd_link_elf_stt_common
  48 {
  49   unchanged,
  50   elf_stt_common,
  51   no_elf_stt_common
  52 };
  53
  54 /* Describes the type of hash table entry structure being used.
  55    Different hash table structure have different fields and so
  56    support different linking features.  */
  57 enum bfd_link_hash_table_type
  58   {
  59     bfd_link_generic_hash_table,
  60     bfd_link_elf_hash_table
  61   };
  62 \f
  63 /* These are the possible types of an entry in the BFD link hash
  64    table.  */
  65
  66 enum bfd_link_hash_type
  67 {
  68   bfd_link_hash_new,            /* Symbol is new.  */
  69   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  70   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  71   bfd_link_hash_defined,        /* Symbol is defined.  */
  72   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  73   bfd_link_hash_common,         /* Symbol is common.  */
  74   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  75   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  76 };
  77
  78 enum bfd_link_common_skip_ar_symbols
  79 {
  80   bfd_link_common_skip_none,
  81   bfd_link_common_skip_text,
  82   bfd_link_common_skip_data,
  83   bfd_link_common_skip_all
  84 };
  85
  86 struct bfd_link_hash_common_entry
  87   {
  88     unsigned int alignment_power;       /* Alignment.  */
  89     asection *section;          /* Symbol section.  */
  90   };
  91
  92 /* The linking routines use a hash table which uses this structure for
  93    its elements.  */
  94
  95 struct bfd_link_hash_entry
  96 {
  97   /* Base hash table entry structure.  */
  98   struct bfd_hash_entry root;
  99
 100   /* Type of this entry.  */
 101   ENUM_BITFIELD (bfd_link_hash_type) type : 8;
 102
 103   /* Symbol is referenced in a normal object file, as distict from a LTO
 104      IR object file.  */
 105   unsigned int non_ir_ref : 1;
 106
 107   /* Symbol is a built-in define.  These will be overridden by PROVIDE
 108      in a linker script.  */
 109   unsigned int linker_def : 1;
 110
 111   /* Symbol defined in a linker script.  */
 112   unsigned int ldscript_def : 1;
 113
 114   /* A union of information depending upon the type.  */
 115   union
 116     {
 117       /* Nothing is kept for bfd_hash_new.  */
 118       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
 119       struct
 120         {
 121           /* Undefined and common symbols are kept in a linked list through
 122              this field.  This field is present in all of the union element
 123              so that we don't need to remove entries from the list when we
 124              change their type.  Removing entries would either require the
 125              list to be doubly linked, which would waste more memory, or
 126              require a traversal.  When an undefined or common symbol is
 127              created, it should be added to this list, the head of which is in
 128              the link hash table itself.  As symbols are defined, they need
 129              not be removed from the list; anything which reads the list must
 130              doublecheck the symbol type.
 131
 132              Weak symbols are not kept on this list.
 133
 134              Defined and defweak symbols use this field as a reference marker.
 135              If the field is not NULL, or this structure is the tail of the
 136              undefined symbol list, the symbol has been referenced.  If the
 137              symbol is undefined and becomes defined, this field will
 138              automatically be non-NULL since the symbol will have been on the
 139              undefined symbol list.  */
 140           struct bfd_link_hash_entry *next;
 141           /* BFD symbol was found in.  */
 142           bfd *abfd;
 143           /* For __start_<name> and __stop_<name> symbols, the first
 144              input section matching the name.  */
 145           asection *section;
 146         } undef;
 147       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
 148       struct
 149         {
 150           struct bfd_link_hash_entry *next;
 151           /* Symbol section.  */
 152           asection *section;
 153           /* Symbol value.  */
 154           bfd_vma value;
 155         } def;
 156       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 157       struct
 158         {
 159           struct bfd_link_hash_entry *next;
 160           /* Real symbol.  */
 161           struct bfd_link_hash_entry *link;
 162           /* Warning message (bfd_link_hash_warning only).  */
 163           const char *warning;
 164         } i;
 165       /* bfd_link_hash_common.  */
 166       struct
 167         {
 168           struct bfd_link_hash_entry *next;
 169           /* The linker needs to know three things about common
 170              symbols: the size, the alignment, and the section in
 171              which the symbol should be placed.  We store the size
 172              here, and we allocate a small structure to hold the
 173              section and the alignment.  The alignment is stored as a
 174              power of two.  We don't store all the information
 175              directly because we don't want to increase the size of
 176              the union; this structure is a major space user in the
 177              linker.  */
 178           struct bfd_link_hash_common_entry *p;
 179           /* Common symbol size.  */
 180           bfd_size_type size;
 181         } c;
 182     } u;
 183 };
 184
 185 /* This is the link hash table.  It is a derived class of
 186    bfd_hash_table.  */
 187
 188 struct bfd_link_hash_table
 189 {
 190   /* The hash table itself.  */
 191   struct bfd_hash_table table;
 192   /* A linked list of undefined and common symbols, linked through the
 193      next field in the bfd_link_hash_entry structure.  */
 194   struct bfd_link_hash_entry *undefs;
 195   /* Entries are added to the tail of the undefs list.  */
 196   struct bfd_link_hash_entry *undefs_tail;
 197   /* Function to free the hash table on closing BFD.  */
 198   void (*hash_table_free) (bfd *);
 199   /* The type of the link hash table.  */
 200   enum bfd_link_hash_table_type type;
 201 };
 202
 203 /* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
 204    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 205    the real symbol.  */
 206 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 207   (struct bfd_link_hash_table *, const char *, bfd_boolean create,
 208    bfd_boolean copy, bfd_boolean follow);
 209
 210 /* Look up an entry in the main linker hash table if the symbol might
 211    be wrapped.  This should only be used for references to an
 212    undefined symbol, not for definitions of a symbol.  */
 213
 214 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 215   (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
 216    bfd_boolean, bfd_boolean);
 217
 218 /* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"
 219    and the remainder is found in wrap_hash, return the real symbol.  */
 220
 221 extern struct bfd_link_hash_entry *unwrap_hash_lookup
 222   (struct bfd_link_info *, bfd *, struct bfd_link_hash_entry *);
 223
 224 /* Traverse a link hash table.  */
 225 extern void bfd_link_hash_traverse
 226   (struct bfd_link_hash_table *,
 227     bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
 228     void *);
 229
 230 /* Add an entry to the undefs list.  */
 231 extern void bfd_link_add_undef
 232   (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);
 233
 234 /* Remove symbols from the undefs list that don't belong there.  */
 235 extern void bfd_link_repair_undef_list
 236   (struct bfd_link_hash_table *table);
 237
 238 /* Read symbols and cache symbol pointer array in outsymbols.  */
 239 extern bfd_boolean bfd_generic_link_read_symbols (bfd *);
 240
 241 /* Check the relocs in the BFD.  Called after all the input
 242    files have been loaded, and garbage collection has tagged
 243    any unneeded sections.  */
 244 extern bfd_boolean bfd_link_check_relocs (bfd *,struct bfd_link_info *);
 245
 246 struct bfd_sym_chain
 247 {
 248   struct bfd_sym_chain *next;
 249   const char *name;
 250 };
 251 \f
 252 /* How to handle unresolved symbols.
 253    There are four possibilities which are enumerated below:  */
 254 enum report_method
 255 {
 256   /* This is the initial value when then link_info structure is created.
 257      It allows the various stages of the linker to determine whether they
 258      allowed to set the value.  */
 259   RM_NOT_YET_SET = 0,
 260   RM_IGNORE,
 261   RM_GENERATE_WARNING,
 262   RM_GENERATE_ERROR
 263 };
 264
 265 typedef enum {with_flags, without_flags} flag_type;
 266
 267 /* A section flag list.  */
 268 struct flag_info_list
 269 {
 270   flag_type with;
 271   const char *name;
 272   bfd_boolean valid;
 273   struct flag_info_list *next;
 274 };
 275
 276 /* Section flag info.  */
 277 struct flag_info
 278 {
 279   flagword only_with_flags;
 280   flagword not_with_flags;
 281   struct flag_info_list *flag_list;
 282   bfd_boolean flags_initialized;
 283 };
 284
 285 struct bfd_elf_dynamic_list;
 286 struct bfd_elf_version_tree;
 287
 288 /* Types of output.  */
 289
 290 enum output_type
 291 {
 292   type_pde,
 293   type_pie,
 294   type_relocatable,
 295   type_dll,
 296 };
 297
 298 #define bfd_link_pde(info)         ((info)->type == type_pde)
 299 #define bfd_link_dll(info)         ((info)->type == type_dll)
 300 #define bfd_link_relocatable(info) ((info)->type == type_relocatable)
 301 #define bfd_link_pie(info)         ((info)->type == type_pie)
 302 #define bfd_link_executable(info)  (bfd_link_pde (info) || bfd_link_pie (info))
 303 #define bfd_link_pic(info)         (bfd_link_dll (info) || bfd_link_pie (info))
 304
 305 /* This structure holds all the information needed to communicate
 306    between BFD and the linker when doing a link.  */
 307
 308 struct bfd_link_info
 309 {
 310   /* Output type.  */
 311   ENUM_BITFIELD (output_type) type : 2;
 312
 313   /* TRUE if BFD should pre-bind symbols in a shared object.  */
 314   unsigned int symbolic: 1;
 315
 316   /* TRUE if executable should not contain copy relocs.
 317      Setting this true may result in a non-sharable text segment.  */
 318   unsigned int nocopyreloc: 1;
 319
 320   /* TRUE if BFD should export all symbols in the dynamic symbol table
 321      of an executable, rather than only those used.  */
 322   unsigned int export_dynamic: 1;
 323
 324   /* TRUE if a default symbol version should be created and used for
 325      exported symbols.  */
 326   unsigned int create_default_symver: 1;
 327
 328   /* TRUE if unreferenced sections should be removed.  */
 329   unsigned int gc_sections: 1;
 330
 331   /* TRUE if every symbol should be reported back via the notice
 332      callback.  */
 333   unsigned int notice_all: 1;
 334
 335   /* TRUE if the LTO plugin is active.  */
 336   unsigned int lto_plugin_active: 1;
 337
 338   /* TRUE if global symbols in discarded sections should be stripped.  */
 339   unsigned int strip_discarded: 1;
 340
 341   /* TRUE if all data symbols should be dynamic.  */
 342   unsigned int dynamic_data: 1;
 343
 344   /* Which symbols to strip.  */
 345   ENUM_BITFIELD (bfd_link_strip) strip : 2;
 346
 347   /* Which local symbols to discard.  */
 348   ENUM_BITFIELD (bfd_link_discard) discard : 2;
 349
 350   /* Whether to generate ELF common symbols with the STT_COMMON type.  */
 351   ENUM_BITFIELD (bfd_link_elf_stt_common) elf_stt_common : 2;
 352
 353   /* Criteria for skipping symbols when determining
 354      whether to include an object from an archive. */
 355   ENUM_BITFIELD (bfd_link_common_skip_ar_symbols) common_skip_ar_symbols : 2;
 356
 357   /* What to do with unresolved symbols in an object file.
 358      When producing executables the default is GENERATE_ERROR.
 359      When producing shared libraries the default is IGNORE.  The
 360      assumption with shared libraries is that the reference will be
 361      resolved at load/execution time.  */
 362   ENUM_BITFIELD (report_method) unresolved_syms_in_objects : 2;
 363
 364   /* What to do with unresolved symbols in a shared library.
 365      The same defaults apply.  */
 366   ENUM_BITFIELD (report_method) unresolved_syms_in_shared_libs : 2;
 367
 368   /* TRUE if shared objects should be linked directly, not shared.  */
 369   unsigned int static_link: 1;
 370
 371   /* TRUE if symbols should be retained in memory, FALSE if they
 372      should be freed and reread.  */
 373   unsigned int keep_memory: 1;
 374
 375   /* TRUE if BFD should generate relocation information in the final
 376      executable.  */
 377   unsigned int emitrelocations: 1;
 378
 379   /* TRUE if PT_GNU_RELRO segment should be created.  */
 380   unsigned int relro: 1;
 381
 382   /* Nonzero if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
 383      should be created.  1 for DWARF2 tables, 2 for compact tables.  */
 384   unsigned int eh_frame_hdr_type: 2;
 385
 386   /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
 387   unsigned int warn_shared_textrel: 1;
 388
 389   /* TRUE if we should error when adding a DT_TEXTREL.  */
 390   unsigned int error_textrel: 1;
 391
 392   /* TRUE if .hash section should be created.  */
 393   unsigned int emit_hash: 1;
 394
 395   /* TRUE if .gnu.hash section should be created.  */
 396   unsigned int emit_gnu_hash: 1;
 397
 398   /* If TRUE reduce memory overheads, at the expense of speed. This will
 399      cause map file generation to use an O(N^2) algorithm and disable
 400      caching ELF symbol buffer.  */
 401   unsigned int reduce_memory_overheads: 1;
 402
 403   /* TRUE if the output file should be in a traditional format.  This
 404      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 405      on the output file, but may be checked when reading the input
 406      files.  */
 407   unsigned int traditional_format: 1;
 408
 409   /* TRUE if non-PLT relocs should be merged into one reloc section
 410      and sorted so that relocs against the same symbol come together.  */
 411   unsigned int combreloc: 1;
 412
 413   /* TRUE if a default symbol version should be created and used for
 414      imported symbols.  */
 415   unsigned int default_imported_symver: 1;
 416
 417   /* TRUE if the new ELF dynamic tags are enabled. */
 418   unsigned int new_dtags: 1;
 419
 420   /* FALSE if .eh_frame unwind info should be generated for PLT and other
 421      linker created sections, TRUE if it should be omitted.  */
 422   unsigned int no_ld_generated_unwind_info: 1;
 423
 424   /* TRUE if BFD should generate a "task linked" object file,
 425      similar to relocatable but also with globals converted to
 426      statics.  */
 427   unsigned int task_link: 1;
 428
 429   /* TRUE if ok to have multiple definition.  */
 430   unsigned int allow_multiple_definition: 1;
 431
 432   /* TRUE if ok to have version with no definition.  */
 433   unsigned int allow_undefined_version: 1;
 434
 435   /* TRUE if some symbols have to be dynamic, controlled by
 436      --dynamic-list command line options.  */
 437   unsigned int dynamic: 1;
 438
 439   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
 440      flags.  */
 441   unsigned int execstack: 1;
 442
 443   /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
 444      flags.  */
 445   unsigned int noexecstack: 1;
 446
 447   /* TRUE if we want to produced optimized output files.  This might
 448      need much more time and therefore must be explicitly selected.  */
 449   unsigned int optimize: 1;
 450
 451   /* TRUE if user should be informed of removed unreferenced sections.  */
 452   unsigned int print_gc_sections: 1;
 453
 454   /* TRUE if we should warn alternate ELF machine code.  */
 455   unsigned int warn_alternate_em: 1;
 456
 457   /* TRUE if the linker script contained an explicit PHDRS command.  */
 458   unsigned int user_phdrs: 1;
 459
 460   /* TRUE if we should check relocations after all input files have
 461      been opened.  */
 462   unsigned int check_relocs_after_open_input: 1;
 463
 464   /* TRUE if BND prefix in PLT entries is always generated.  */
 465   unsigned int bndplt: 1;
 466
 467   /* TRUE if generation of .interp/PT_INTERP should be suppressed.  */
 468   unsigned int nointerp: 1;
 469
 470   /* TRUE if we shouldn't check relocation overflow.  */
 471   unsigned int no_reloc_overflow_check: 1;
 472
 473   /* TRUE if generate a 1-byte NOP as suffix for x86 call instruction.  */
 474   unsigned int call_nop_as_suffix : 1;
 475
 476   /* The 1-byte NOP for x86 call instruction.  */
 477   char call_nop_byte;
 478
 479   /* Char that may appear as the first char of a symbol, but should be
 480      skipped (like symbol_leading_char) when looking up symbols in
 481      wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
 482   char wrap_char;
 483
 484   /* Separator between archive and filename in linker script filespecs.  */
 485   char path_separator;
 486
 487   /* Compress DWARF debug sections.  */
 488   enum compressed_debug_section_type compress_debug;
 489
 490   /* Default stack size.  Zero means default (often zero itself), -1
 491      means explicitly zero-sized.  */
 492   bfd_signed_vma stacksize;
 493
 494   /* Enable or disable target specific optimizations.
 495
 496      Not all targets have optimizations to enable.
 497
 498      Normally these optimizations are disabled by default but some targets
 499      prefer to enable them by default.  So this field is a tri-state variable.
 500      The values are:
 501
 502      zero: Enable the optimizations (either from --relax being specified on
 503        the command line or the backend's before_allocation emulation function.
 504
 505      positive: The user has requested that these optimizations be disabled.
 506        (Via the --no-relax command line option).
 507
 508      negative: The optimizations are disabled.  (Set when initializing the
 509        args_type structure in ldmain.c:main.  */
 510   signed int disable_target_specific_optimizations;
 511
 512   /* Function callbacks.  */
 513   const struct bfd_link_callbacks *callbacks;
 514
 515   /* Hash table handled by BFD.  */
 516   struct bfd_link_hash_table *hash;
 517
 518   /* Hash table of symbols to keep.  This is NULL unless strip is
 519      strip_some.  */
 520   struct bfd_hash_table *keep_hash;
 521
 522   /* Hash table of symbols to report back via the notice callback.  If
 523      this is NULL, and notice_all is FALSE, then no symbols are
 524      reported back.  */
 525   struct bfd_hash_table *notice_hash;
 526
 527   /* Hash table of symbols which are being wrapped (the --wrap linker
 528      option).  If this is NULL, no symbols are being wrapped.  */
 529   struct bfd_hash_table *wrap_hash;
 530
 531   /* Hash table of symbols which may be left unresolved during
 532      a link.  If this is NULL, no symbols can be left unresolved.  */
 533   struct bfd_hash_table *ignore_hash;
 534
 535   /* The output BFD.  */
 536   bfd *output_bfd;
 537
 538   /* The import library generated.  */
 539   bfd *out_implib_bfd;
 540
 541   /* The list of input BFD's involved in the link.  These are chained
 542      together via the link.next field.  */
 543   bfd *input_bfds;
 544   bfd **input_bfds_tail;
 545
 546   /* If a symbol should be created for each input BFD, this is section
 547      where those symbols should be placed.  It must be a section in
 548      the output BFD.  It may be NULL, in which case no such symbols
 549      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 550      linker command language.  */
 551   asection *create_object_symbols_section;
 552
 553   /* List of global symbol names that are starting points for marking
 554      sections against garbage collection.  */
 555   struct bfd_sym_chain *gc_sym_list;
 556
 557   /* If a base output file is wanted, then this points to it */
 558   void *base_file;
 559
 560   /* The function to call when the executable or shared object is
 561      loaded.  */
 562   const char *init_function;
 563
 564   /* The function to call when the executable or shared object is
 565      unloaded.  */
 566   const char *fini_function;
 567
 568   /* Number of relaxation passes.  Usually only one relaxation pass
 569      is needed.  But a backend can have as many relaxation passes as
 570      necessary.  During bfd_relax_section call, it is set to the
 571      current pass, starting from 0.  */
 572   int relax_pass;
 573
 574   /* Number of relaxation trips.  This number is incremented every
 575      time the relaxation pass is restarted due to a previous
 576      relaxation returning true in *AGAIN.  */
 577   int relax_trip;
 578
 579   /* > 0 to treat protected data defined in the shared library as
 580      reference external.  0 to treat it as internal.  -1 to let
 581      backend to decide.  */
 582   int extern_protected_data;
 583
 584   /* > 0 to treat undefined weak symbol in the executable as dynamic,
 585      requiring dynamic relocation.  */
 586   int dynamic_undefined_weak;
 587
 588   /* Non-zero if auto-import thunks for DATA items in pei386 DLLs
 589      should be generated/linked against.  Set to 1 if this feature
 590      is explicitly requested by the user, -1 if enabled by default.  */
 591   int pei386_auto_import;
 592
 593   /* Non-zero if runtime relocs for DATA items with non-zero addends
 594      in pei386 DLLs should be generated.  Set to 1 if this feature
 595      is explicitly requested by the user, -1 if enabled by default.  */
 596   int pei386_runtime_pseudo_reloc;
 597
 598   /* How many spare .dynamic DT_NULL entries should be added?  */
 599   unsigned int spare_dynamic_tags;
 600
 601   /* May be used to set DT_FLAGS for ELF. */
 602   bfd_vma flags;
 603
 604   /* May be used to set DT_FLAGS_1 for ELF. */
 605   bfd_vma flags_1;
 606
 607   /* Start and end of RELRO region.  */
 608   bfd_vma relro_start, relro_end;
 609
 610   /* List of symbols should be dynamic.  */
 611   struct bfd_elf_dynamic_list *dynamic_list;
 612
 613   /* The version information.  */
 614   struct bfd_elf_version_tree *version_info;
 615 };
 616
 617 /* This structures holds a set of callback functions.  These are called
 618    by the BFD linker routines.  */
 619
 620 struct bfd_link_callbacks
 621 {
 622   /* A function which is called when an object is added from an
 623      archive.  ABFD is the archive element being added.  NAME is the
 624      name of the symbol which caused the archive element to be pulled
 625      in.  This function may set *SUBSBFD to point to an alternative
 626      BFD from which symbols should in fact be added in place of the
 627      original BFD's symbols.  Returns TRUE if the object should be
 628      added, FALSE if it should be skipped.  */
 629   bfd_boolean (*add_archive_element)
 630     (struct bfd_link_info *, bfd *abfd, const char *name, bfd **subsbfd);
 631   /* A function which is called when a symbol is found with multiple
 632      definitions.  H is the symbol which is defined multiple times.
 633      NBFD is the new BFD, NSEC is the new section, and NVAL is the new
 634      value.  NSEC may be bfd_com_section or bfd_ind_section.  */
 635   void (*multiple_definition)
 636     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 637      bfd *nbfd, asection *nsec, bfd_vma nval);
 638   /* A function which is called when a common symbol is defined
 639      multiple times.  H is the symbol appearing multiple times.
 640      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 641      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 642      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 643      is the size of the new symbol.  */
 644   void (*multiple_common)
 645     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 646      bfd *nbfd, enum bfd_link_hash_type ntype, bfd_vma nsize);
 647   /* A function which is called to add a symbol to a set.  ENTRY is
 648      the link hash table entry for the set itself (e.g.,
 649      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 650      the set when generating a relocatable file, and is also used to
 651      get the size of the entry when generating an executable file.
 652      ABFD, SEC and VALUE identify the value to add to the set.  */
 653   void (*add_to_set)
 654     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 655      bfd_reloc_code_real_type reloc, bfd *abfd, asection *sec, bfd_vma value);
 656   /* A function which is called when the name of a g++ constructor or
 657      destructor is found.  This is only called by some object file
 658      formats.  CONSTRUCTOR is TRUE for a constructor, FALSE for a
 659      destructor.  This will use BFD_RELOC_CTOR when generating a
 660      relocatable file.  NAME is the name of the symbol found.  ABFD,
 661      SECTION and VALUE are the value of the symbol.  */
 662   void (*constructor)
 663     (struct bfd_link_info *, bfd_boolean constructor, const char *name,
 664      bfd *abfd, asection *sec, bfd_vma value);
 665   /* A function which is called to issue a linker warning.  For
 666      example, this is called when there is a reference to a warning
 667      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 668      of the symbol which triggered the warning; it may be NULL if
 669      there is none.  ABFD, SECTION and ADDRESS identify the location
 670      which trigerred the warning; either ABFD or SECTION or both may
 671      be NULL if the location is not known.  */
 672   void (*warning)
 673     (struct bfd_link_info *, const char *warning, const char *symbol,
 674      bfd *abfd, asection *section, bfd_vma address);
 675   /* A function which is called when a relocation is attempted against
 676      an undefined symbol.  NAME is the symbol which is undefined.
 677      ABFD, SECTION and ADDRESS identify the location from which the
 678      reference is made. IS_FATAL indicates whether an undefined symbol is
 679      a fatal error or not. In some cases SECTION may be NULL.  */
 680   void (*undefined_symbol)
 681     (struct bfd_link_info *, const char *name, bfd *abfd,
 682      asection *section, bfd_vma address, bfd_boolean is_fatal);
 683   /* A function which is called when a reloc overflow occurs. ENTRY is
 684      the link hash table entry for the symbol the reloc is against.
 685      NAME is the name of the local symbol or section the reloc is
 686      against, RELOC_NAME is the name of the relocation, and ADDEND is
 687      any addend that is used.  ABFD, SECTION and ADDRESS identify the
 688      location at which the overflow occurs; if this is the result of a
 689      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 690      ABFD will be NULL.  */
 691   void (*reloc_overflow)
 692     (struct bfd_link_info *, struct bfd_link_hash_entry *entry,
 693      const char *name, const char *reloc_name, bfd_vma addend,
 694      bfd *abfd, asection *section, bfd_vma address);
 695   /* A function which is called when a dangerous reloc is performed.
 696      MESSAGE is an appropriate message.
 697      ABFD, SECTION and ADDRESS identify the location at which the
 698      problem occurred; if this is the result of a
 699      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 700      ABFD will be NULL.  */
 701   void (*reloc_dangerous)
 702     (struct bfd_link_info *, const char *message,
 703      bfd *abfd, asection *section, bfd_vma address);
 704   /* A function which is called when a reloc is found to be attached
 705      to a symbol which is not being written out.  NAME is the name of
 706      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 707      the reloc; if this is the result of a
 708      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 709      ABFD will be NULL.  */
 710   void (*unattached_reloc)
 711     (struct bfd_link_info *, const char *name,
 712      bfd *abfd, asection *section, bfd_vma address);
 713   /* A function which is called when a symbol in notice_hash is
 714      defined or referenced.  H is the symbol, INH the indirect symbol
 715      if applicable.  ABFD, SECTION and ADDRESS are the (new) value of
 716      the symbol.  If SECTION is bfd_und_section, this is a reference.
 717      FLAGS are the symbol BSF_* flags.  */
 718   bfd_boolean (*notice)
 719     (struct bfd_link_info *, struct bfd_link_hash_entry *h,
 720      struct bfd_link_hash_entry *inh,
 721      bfd *abfd, asection *section, bfd_vma address, flagword flags);
 722   /* Error or warning link info message.  */
 723   void (*einfo)
 724     (const char *fmt, ...);
 725   /* General link info message.  */
 726   void (*info)
 727     (const char *fmt, ...);
 728   /* Message to be printed in linker map file.  */
 729   void (*minfo)
 730     (const char *fmt, ...);
 731   /* This callback provides a chance for users of the BFD library to
 732      override its decision about whether to place two adjacent sections
 733      into the same segment.  */
 734   bfd_boolean (*override_segment_assignment)
 735     (struct bfd_link_info *, bfd * abfd,
 736      asection * current_section, asection * previous_section,
 737      bfd_boolean new_segment);
 738 };
 739 \f
 740 /* The linker builds link_order structures which tell the code how to
 741    include input data in the output file.  */
 742
 743 /* These are the types of link_order structures.  */
 744
 745 enum bfd_link_order_type
 746 {
 747   bfd_undefined_link_order,     /* Undefined.  */
 748   bfd_indirect_link_order,      /* Built from a section.  */
 749   bfd_data_link_order,          /* Set to explicit data.  */
 750   bfd_section_reloc_link_order, /* Relocate against a section.  */
 751   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 752 };
 753
 754 /* This is the link_order structure itself.  These form a chain
 755    attached to the output section whose contents they are describing.  */
 756
 757 struct bfd_link_order
 758 {
 759   /* Next link_order in chain.  */
 760   struct bfd_link_order *next;
 761   /* Type of link_order.  */
 762   enum bfd_link_order_type type;
 763   /* Offset within output section.  */
 764   bfd_vma offset;
 765   /* Size within output section.  */
 766   bfd_size_type size;
 767   /* Type specific information.  */
 768   union
 769     {
 770       struct
 771         {
 772           /* Section to include.  If this is used, then
 773              section->output_section must be the section the
 774              link_order is attached to, section->output_offset must
 775              equal the link_order offset field, and section->size
 776              must equal the link_order size field.  Maybe these
 777              restrictions should be relaxed someday.  */
 778           asection *section;
 779         } indirect;
 780       struct
 781         {
 782           /* Size of contents, or zero when contents should be filled by
 783              the architecture-dependent fill function.
 784              A non-zero value allows filling of the output section
 785              with an arbitrary repeated pattern.  */
 786           unsigned int size;
 787           /* Data to put into file.  */
 788           bfd_byte *contents;
 789         } data;
 790       struct
 791         {
 792           /* Description of reloc to generate.  Used for
 793              bfd_section_reloc_link_order and
 794              bfd_symbol_reloc_link_order.  */
 795           struct bfd_link_order_reloc *p;
 796         } reloc;
 797     } u;
 798 };
 799
 800 /* A linker order of type bfd_section_reloc_link_order or
 801    bfd_symbol_reloc_link_order means to create a reloc against a
 802    section or symbol, respectively.  This is used to implement -Ur to
 803    generate relocs for the constructor tables.  The
 804    bfd_link_order_reloc structure describes the reloc that BFD should
 805    create.  It is similar to a arelent, but I didn't use arelent
 806    because the linker does not know anything about most symbols, and
 807    any asymbol structure it creates will be partially meaningless.
 808    This information could logically be in the bfd_link_order struct,
 809    but I didn't want to waste the space since these types of relocs
 810    are relatively rare.  */
 811
 812 struct bfd_link_order_reloc
 813 {
 814   /* Reloc type.  */
 815   bfd_reloc_code_real_type reloc;
 816
 817   union
 818     {
 819       /* For type bfd_section_reloc_link_order, this is the section
 820          the reloc should be against.  This must be a section in the
 821          output BFD, not any of the input BFDs.  */
 822       asection *section;
 823       /* For type bfd_symbol_reloc_link_order, this is the name of the
 824          symbol the reloc should be against.  */
 825       const char *name;
 826     } u;
 827
 828   /* Addend to use.  The object file should contain zero.  The BFD
 829      backend is responsible for filling in the contents of the object
 830      file correctly.  For some object file formats (e.g., COFF) the
 831      addend must be stored into in the object file, and for some
 832      (e.g., SPARC a.out) it is kept in the reloc.  */
 833   bfd_vma addend;
 834 };
 835
 836 /* Allocate a new link_order for a section.  */
 837 extern struct bfd_link_order *bfd_new_link_order (bfd *, asection *);
 838
 839 /* These structures are used to describe version information for the
 840    ELF linker.  These structures could be manipulated entirely inside
 841    BFD, but it would be a pain.  Instead, the regular linker sets up
 842    these structures, and then passes them into BFD.  */
 843
 844 /* Glob pattern for a version.  */
 845
 846 struct bfd_elf_version_expr
 847 {
 848   /* Next glob pattern for this version.  */
 849   struct bfd_elf_version_expr *next;
 850   /* Glob pattern.  */
 851   const char *pattern;
 852   /* Set if pattern is not a glob.  */
 853   unsigned int literal : 1;
 854   /* Defined by ".symver".  */
 855   unsigned int symver : 1;
 856   /* Defined by version script.  */
 857   unsigned int script : 1;
 858   /* Pattern type.  */
 859 #define BFD_ELF_VERSION_C_TYPE          1
 860 #define BFD_ELF_VERSION_CXX_TYPE        2
 861 #define BFD_ELF_VERSION_JAVA_TYPE       4
 862   unsigned int mask : 3;
 863 };
 864
 865 struct bfd_elf_version_expr_head
 866 {
 867   /* List of all patterns, both wildcards and non-wildcards.  */
 868   struct bfd_elf_version_expr *list;
 869   /* Hash table for non-wildcards.  */
 870   void *htab;
 871   /* Remaining patterns.  */
 872   struct bfd_elf_version_expr *remaining;
 873   /* What kind of pattern types are present in list (bitmask).  */
 874   unsigned int mask;
 875 };
 876
 877 /* Version dependencies.  */
 878
 879 struct bfd_elf_version_deps
 880 {
 881   /* Next dependency for this version.  */
 882   struct bfd_elf_version_deps *next;
 883   /* The version which this version depends upon.  */
 884   struct bfd_elf_version_tree *version_needed;
 885 };
 886
 887 /* A node in the version tree.  */
 888
 889 struct bfd_elf_version_tree
 890 {
 891   /* Next version.  */
 892   struct bfd_elf_version_tree *next;
 893   /* Name of this version.  */
 894   const char *name;
 895   /* Version number.  */
 896   unsigned int vernum;
 897   /* Regular expressions for global symbols in this version.  */
 898   struct bfd_elf_version_expr_head globals;
 899   /* Regular expressions for local symbols in this version.  */
 900   struct bfd_elf_version_expr_head locals;
 901   /* List of versions which this version depends upon.  */
 902   struct bfd_elf_version_deps *deps;
 903   /* Index of the version name.  This is used within BFD.  */
 904   unsigned int name_indx;
 905   /* Whether this version tree was used.  This is used within BFD.  */
 906   int used;
 907   /* Matching hook.  */
 908   struct bfd_elf_version_expr *(*match)
 909     (struct bfd_elf_version_expr_head *head,
 910      struct bfd_elf_version_expr *prev, const char *sym);
 911 };
 912
 913 struct bfd_elf_dynamic_list
 914 {
 915   struct bfd_elf_version_expr_head head;
 916   struct bfd_elf_version_expr *(*match)
 917     (struct bfd_elf_version_expr_head *head,
 918      struct bfd_elf_version_expr *prev, const char *sym);
 919 };
 920
 921 #endif