include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000
   3    Free Software Foundation, Inc.
   4    Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support.
   5
   6 This file is part of BFD, the Binary File Descriptor library.
   7
   8 This program is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2 of the License, or
  11 (at your option) any later version.
  12
  13 This program is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with this program; if not, write to the Free Software
  20 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 \f
  45 /* These are the possible types of an entry in the BFD link hash
  46    table.  */
  47
  48 enum bfd_link_hash_type
  49 {
  50   bfd_link_hash_new,            /* Symbol is new.  */
  51   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  52   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  53   bfd_link_hash_defined,        /* Symbol is defined.  */
  54   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  55   bfd_link_hash_common,         /* Symbol is common.  */
  56   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  57   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  58 };
  59
  60 /* The linking routines use a hash table which uses this structure for
  61    its elements.  */
  62
  63 struct bfd_link_hash_entry
  64 {
  65   /* Base hash table entry structure.  */
  66   struct bfd_hash_entry root;
  67   /* Type of this entry.  */
  68   enum bfd_link_hash_type type;
  69
  70   /* Undefined and common symbols are kept in a linked list through
  71      this field.  This field is not in the union because that would
  72      force us to remove entries from the list when we changed their
  73      type, which would force the list to be doubly linked, which would
  74      waste more memory.  When an undefined or common symbol is
  75      created, it should be added to this list, the head of which is in
  76      the link hash table itself.  As symbols are defined, they need
  77      not be removed from the list; anything which reads the list must
  78      doublecheck the symbol type.
  79
  80      Weak symbols are not kept on this list.
  81
  82      Defined and defweak symbols use this field as a reference marker.
  83      If the field is not NULL, or this structure is the tail of the
  84      undefined symbol list, the symbol has been referenced.  If the
  85      symbol is undefined and becomes defined, this field will
  86      automatically be non-NULL since the symbol will have been on the
  87      undefined symbol list.  */
  88   struct bfd_link_hash_entry *next;
  89   /* A union of information depending upon the type.  */
  90   union
  91     {
  92       /* Nothing is kept for bfd_hash_new.  */
  93       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
  94       struct
  95         {
  96           bfd *abfd;            /* BFD symbol was found in.  */
  97         } undef;
  98       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
  99       struct
 100         {
 101           bfd_vma value;        /* Symbol value.  */
 102           asection *section;    /* Symbol section.  */
 103         } def;
 104       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 105       struct
 106         {
 107           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 108           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 109         } i;
 110       /* bfd_link_hash_common.  */
 111       struct
 112         {
 113           /* The linker needs to know three things about common
 114              symbols: the size, the alignment, and the section in
 115              which the symbol should be placed.  We store the size
 116              here, and we allocate a small structure to hold the
 117              section and the alignment.  The alignment is stored as a
 118              power of two.  We don't store all the information
 119              directly because we don't want to increase the size of
 120              the union; this structure is a major space user in the
 121              linker.  */
 122           bfd_size_type size;   /* Common symbol size.  */
 123           struct bfd_link_hash_common_entry
 124             {
 125               unsigned int alignment_power;     /* Alignment.  */
 126               asection *section;                /* Symbol section.  */
 127             } *p;
 128         } c;
 129     } u;
 130 };
 131
 132 /* This is the link hash table.  It is a derived class of
 133    bfd_hash_table.  */
 134
 135 struct bfd_link_hash_table
 136 {
 137   /* The hash table itself.  */
 138   struct bfd_hash_table table;
 139   /* The back end which created this hash table.  This indicates the
 140      type of the entries in the hash table, which is sometimes
 141      important information when linking object files of different
 142      types together.  */
 143   const bfd_target *creator;
 144   /* A linked list of undefined and common symbols, linked through the
 145      next field in the bfd_link_hash_entry structure.  */
 146   struct bfd_link_hash_entry *undefs;
 147   /* Entries are added to the tail of the undefs list.  */
 148   struct bfd_link_hash_entry *undefs_tail;
 149 };
 150
 151 /* Look up an entry in a link hash table.  If FOLLOW is true, this
 152    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 153    the real symbol.  */
 154 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 155   PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
 156            boolean copy, boolean follow));
 157
 158 /* Look up an entry in the main linker hash table if the symbol might
 159    be wrapped.  This should only be used for references to an
 160    undefined symbol, not for definitions of a symbol.  */
 161
 162 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 163   PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
 164            boolean));
 165
 166 /* Traverse a link hash table.  */
 167 extern void bfd_link_hash_traverse
 168   PARAMS ((struct bfd_link_hash_table *,
 169            boolean (*) (struct bfd_link_hash_entry *, PTR),
 170            PTR));
 171
 172 /* Add an entry to the undefs list.  */
 173 extern void bfd_link_add_undef
 174   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 175 \f
 176 /* This structure holds all the information needed to communicate
 177    between BFD and the linker when doing a link.  */
 178
 179 struct bfd_link_info
 180 {
 181   /* Function callbacks.  */
 182   const struct bfd_link_callbacks *callbacks;
 183   /* true if BFD should generate a relocateable object file.  */
 184   boolean relocateable;
 185   /* true if BFD should generate relocation information in the final executable.  */
 186   boolean emitrelocations;
 187   /* true if BFD should generate a "task linked" object file,
 188      similar to relocatable but also with globals converted to statics. */
 189   boolean task_link;
 190   /* true if BFD should generate a shared object.  */
 191   boolean shared;
 192   /* true if BFD should pre-bind symbols in a shared object.  */
 193   boolean symbolic;
 194   /* true if BFD should export all symbols in the dynamic symbol table
 195      of an executable, rather than only those used.  */
 196   boolean export_dynamic;
 197   /* true if shared objects should be linked directly, not shared.  */
 198   boolean static_link;
 199   /* true if the output file should be in a traditional format.  This
 200      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 201      on the output file, but may be checked when reading the input
 202      files.  */
 203   boolean traditional_format;
 204   /* true if we want to produced optimized output files.  This might
 205      need much more time and therefore must be explicitly selected.  */
 206   boolean optimize;
 207   /* true if BFD should generate errors for undefined symbols
 208      even if generating a shared object.  */
 209   boolean no_undefined;
 210   /* true if BFD should allow undefined symbols in shared objects even
 211      when no_undefined is set to disallow undefined symbols.  The net
 212      result will be that undefined symbols in regular objects will
 213      still trigger an error, but undefined symbols in shared objects
 214      will be ignored.  The implementation of no_undefined makes the
 215      assumption that the runtime linker will choke on undefined
 216      symbols.  However there is at least one system (BeOS) where
 217      undefined symbols in shared libraries is normal since the kernel
 218      patches them at load time to select which function is most
 219      appropriate for the current architecture.  I.E. dynamically
 220      select an appropriate memset function.  Apparently it is also
 221      normal for HPPA shared libraries to have undefined symbols.  */
 222   boolean allow_shlib_undefined;
 223   /* Which symbols to strip.  */
 224   enum bfd_link_strip strip;
 225   /* Which local symbols to discard.  */
 226   enum bfd_link_discard discard;
 227   /* true if symbols should be retained in memory, false if they
 228      should be freed and reread.  */
 229   boolean keep_memory;
 230   /* The list of input BFD's involved in the link.  These are chained
 231      together via the link_next field.  */
 232   bfd *input_bfds;
 233   /* If a symbol should be created for each input BFD, this is section
 234      where those symbols should be placed.  It must be a section in
 235      the output BFD.  It may be NULL, in which case no such symbols
 236      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 237      linker command language.  */
 238   asection *create_object_symbols_section;
 239   /* Hash table handled by BFD.  */
 240   struct bfd_link_hash_table *hash;
 241   /* Hash table of symbols to keep.  This is NULL unless strip is
 242      strip_some.  */
 243   struct bfd_hash_table *keep_hash;
 244   /* true if every symbol should be reported back via the notice
 245      callback.  */
 246   boolean notice_all;
 247   /* Hash table of symbols to report back via the notice callback.  If
 248      this is NULL, and notice_all is false, then no symbols are
 249      reported back.  */
 250   struct bfd_hash_table *notice_hash;
 251   /* Hash table of symbols which are being wrapped (the --wrap linker
 252      option).  If this is NULL, no symbols are being wrapped.  */
 253   struct bfd_hash_table *wrap_hash;
 254   /* If a base output file is wanted, then this points to it */
 255   PTR base_file;
 256
 257   /* If non-zero, specifies that branches which are problematic for the
 258   MPC860 C0 (or earlier) should be checked for and modified.  It gives the
 259   number of bytes that should be checked at the end of each text page. */
 260   int mpc860c0;
 261
 262   /* The function to call when the executable or shared object is
 263      loaded.  */
 264   const char *init_function;
 265   /* The function to call when the executable or shared object is
 266      unloaded.  */
 267   const char *fini_function;
 268
 269   /* true if the new ELF dynamic tags are enabled. */
 270   boolean new_dtags;
 271
 272   /* May be used to set DT_FLAGS for ELF. */
 273   bfd_vma flags;
 274
 275   /* May be used to set DT_FLAGS_1 for ELF. */
 276   bfd_vma flags_1;
 277
 278   /* true if auto-import thunks for DATA items in pei386 DLLs
 279      should be generated/linked against.  */
 280   boolean pei386_auto_import;
 281 };
 282
 283 /* This structures holds a set of callback functions.  These are
 284    called by the BFD linker routines.  The first argument to each
 285    callback function is the bfd_link_info structure being used.  Each
 286    function returns a boolean value.  If the function returns false,
 287    then the BFD function which called it will return with a failure
 288    indication.  */
 289
 290 struct bfd_link_callbacks
 291 {
 292   /* A function which is called when an object is added from an
 293      archive.  ABFD is the archive element being added.  NAME is the
 294      name of the symbol which caused the archive element to be pulled
 295      in.  */
 296   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 297                                           bfd *abfd,
 298                                           const char *name));
 299   /* A function which is called when a symbol is found with multiple
 300      definitions.  NAME is the symbol which is defined multiple times.
 301      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 302      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 303      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 304      bfd_com_section or bfd_ind_section.  */
 305   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 306                                           const char *name,
 307                                           bfd *obfd,
 308                                           asection *osec,
 309                                           bfd_vma oval,
 310                                           bfd *nbfd,
 311                                           asection *nsec,
 312                                           bfd_vma nval));
 313   /* A function which is called when a common symbol is defined
 314      multiple times.  NAME is the symbol appearing multiple times.
 315      OBFD is the BFD of the existing symbol; it may be NULL if this is
 316      not known.  OTYPE is the type of the existing symbol, which may
 317      be bfd_link_hash_defined, bfd_link_hash_defweak,
 318      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 319      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 320      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 321      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 322      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 323      is the size of the new symbol.  */
 324   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 325                                       const char *name,
 326                                       bfd *obfd,
 327                                       enum bfd_link_hash_type otype,
 328                                       bfd_vma osize,
 329                                       bfd *nbfd,
 330                                       enum bfd_link_hash_type ntype,
 331                                       bfd_vma nsize));
 332   /* A function which is called to add a symbol to a set.  ENTRY is
 333      the link hash table entry for the set itself (e.g.,
 334      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 335      the set when generating a relocateable file, and is also used to
 336      get the size of the entry when generating an executable file.
 337      ABFD, SEC and VALUE identify the value to add to the set.  */
 338   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 339                                  struct bfd_link_hash_entry *entry,
 340                                  bfd_reloc_code_real_type reloc,
 341                                  bfd *abfd, asection *sec, bfd_vma value));
 342   /* A function which is called when the name of a g++ constructor or
 343      destructor is found.  This is only called by some object file
 344      formats.  CONSTRUCTOR is true for a constructor, false for a
 345      destructor.  This will use BFD_RELOC_CTOR when generating a
 346      relocateable file.  NAME is the name of the symbol found.  ABFD,
 347      SECTION and VALUE are the value of the symbol.  */
 348   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 349                                   boolean constructor,
 350                                   const char *name, bfd *abfd, asection *sec,
 351                                   bfd_vma value));
 352   /* A function which is called to issue a linker warning.  For
 353      example, this is called when there is a reference to a warning
 354      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 355      of the symbol which triggered the warning; it may be NULL if
 356      there is none.  ABFD, SECTION and ADDRESS identify the location
 357      which trigerred the warning; either ABFD or SECTION or both may
 358      be NULL if the location is not known.  */
 359   boolean (*warning) PARAMS ((struct bfd_link_info *,
 360                               const char *warning, const char *symbol,
 361                               bfd *abfd, asection *section,
 362                               bfd_vma address));
 363   /* A function which is called when a relocation is attempted against
 364      an undefined symbol.  NAME is the symbol which is undefined.
 365      ABFD, SECTION and ADDRESS identify the location from which the
 366      reference is made. FATAL indicates whether an undefined symbol is
 367      a fatal error or not. In some cases SECTION may be NULL.  */
 368   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 369                                        const char *name, bfd *abfd,
 370                                        asection *section,
 371                                        bfd_vma address,
 372                                        boolean fatal));
 373   /* A function which is called when a reloc overflow occurs.  NAME is
 374      the name of the symbol or section the reloc is against,
 375      RELOC_NAME is the name of the relocation, and ADDEND is any
 376      addend that is used.  ABFD, SECTION and ADDRESS identify the
 377      location at which the overflow occurs; if this is the result of a
 378      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 379      ABFD will be NULL.  */
 380   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 381                                      const char *name,
 382                                      const char *reloc_name, bfd_vma addend,
 383                                      bfd *abfd, asection *section,
 384                                      bfd_vma address));
 385   /* A function which is called when a dangerous reloc is performed.
 386      The canonical example is an a29k IHCONST reloc which does not
 387      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 388      ABFD, SECTION and ADDRESS identify the location at which the
 389      problem occurred; if this is the result of a
 390      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 391      ABFD will be NULL.  */
 392   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 393                                       const char *message,
 394                                       bfd *abfd, asection *section,
 395                                       bfd_vma address));
 396   /* A function which is called when a reloc is found to be attached
 397      to a symbol which is not being written out.  NAME is the name of
 398      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 399      the reloc; if this is the result of a
 400      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 401      ABFD will be NULL.  */
 402   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 403                                        const char *name,
 404                                        bfd *abfd, asection *section,
 405                                        bfd_vma address));
 406   /* A function which is called when a symbol in notice_hash is
 407      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 408      ADDRESS are the value of the symbol.  If SECTION is
 409      bfd_und_section, this is a reference.  */
 410   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 411                              bfd *abfd, asection *section, bfd_vma address));
 412 };
 413 \f
 414 /* The linker builds link_order structures which tell the code how to
 415    include input data in the output file.  */
 416
 417 /* These are the types of link_order structures.  */
 418
 419 enum bfd_link_order_type
 420 {
 421   bfd_undefined_link_order,     /* Undefined.  */
 422   bfd_indirect_link_order,      /* Built from a section.  */
 423   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 424   bfd_data_link_order,          /* Set to explicit data.  */
 425   bfd_section_reloc_link_order, /* Relocate against a section.  */
 426   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 427 };
 428
 429 /* This is the link_order structure itself.  These form a chain
 430    attached to the section whose contents they are describing.  */
 431
 432 struct bfd_link_order
 433 {
 434   /* Next link_order in chain.  */
 435   struct bfd_link_order *next;
 436   /* Type of link_order.  */
 437   enum bfd_link_order_type type;
 438   /* Offset within output section.  */
 439   bfd_vma offset;
 440   /* Size within output section.  */
 441   bfd_size_type size;
 442   /* Type specific information.  */
 443   union
 444     {
 445       struct
 446         {
 447           /* Section to include.  If this is used, then
 448              section->output_section must be the section the
 449              link_order is attached to, section->output_offset must
 450              equal the link_order offset field, and section->_raw_size
 451              must equal the link_order size field.  Maybe these
 452              restrictions should be relaxed someday.  */
 453           asection *section;
 454         } indirect;
 455       struct
 456         {
 457           /* Value to fill with.  */
 458           unsigned int value;
 459         } fill;
 460       struct
 461         {
 462           /* Data to put into file.  The size field gives the number
 463              of bytes which this field points to.  */
 464           bfd_byte *contents;
 465         } data;
 466       struct
 467         {
 468           /* Description of reloc to generate.  Used for
 469              bfd_section_reloc_link_order and
 470              bfd_symbol_reloc_link_order.  */
 471           struct bfd_link_order_reloc *p;
 472         } reloc;
 473     } u;
 474 };
 475
 476 /* A linker order of type bfd_section_reloc_link_order or
 477    bfd_symbol_reloc_link_order means to create a reloc against a
 478    section or symbol, respectively.  This is used to implement -Ur to
 479    generate relocs for the constructor tables.  The
 480    bfd_link_order_reloc structure describes the reloc that BFD should
 481    create.  It is similar to a arelent, but I didn't use arelent
 482    because the linker does not know anything about most symbols, and
 483    any asymbol structure it creates will be partially meaningless.
 484    This information could logically be in the bfd_link_order struct,
 485    but I didn't want to waste the space since these types of relocs
 486    are relatively rare.  */
 487
 488 struct bfd_link_order_reloc
 489 {
 490   /* Reloc type.  */
 491   bfd_reloc_code_real_type reloc;
 492
 493   union
 494     {
 495       /* For type bfd_section_reloc_link_order, this is the section
 496          the reloc should be against.  This must be a section in the
 497          output BFD, not any of the input BFDs.  */
 498       asection *section;
 499       /* For type bfd_symbol_reloc_link_order, this is the name of the
 500          symbol the reloc should be against.  */
 501       const char *name;
 502     } u;
 503
 504   /* Addend to use.  The object file should contain zero.  The BFD
 505      backend is responsible for filling in the contents of the object
 506      file correctly.  For some object file formats (e.g., COFF) the
 507      addend must be stored into in the object file, and for some
 508      (e.g., SPARC a.out) it is kept in the reloc.  */
 509   bfd_vma addend;
 510 };
 511
 512 /* Allocate a new link_order for a section.  */
 513 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 514
 515 /* These structures are used to describe version information for the
 516    ELF linker.  These structures could be manipulated entirely inside
 517    BFD, but it would be a pain.  Instead, the regular linker sets up
 518    these structures, and then passes them into BFD.  */
 519
 520 /* Regular expressions for a version.  */
 521
 522 struct bfd_elf_version_expr
 523 {
 524   /* Next regular expression for this version.  */
 525   struct bfd_elf_version_expr *next;
 526   /* Regular expression.  */
 527   const char *pattern;
 528   /* Matching function.  */
 529   int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
 530 };
 531
 532 /* Version dependencies.  */
 533
 534 struct bfd_elf_version_deps
 535 {
 536   /* Next dependency for this version.  */
 537   struct bfd_elf_version_deps *next;
 538   /* The version which this version depends upon.  */
 539   struct bfd_elf_version_tree *version_needed;
 540 };
 541
 542 /* A node in the version tree.  */
 543
 544 struct bfd_elf_version_tree
 545 {
 546   /* Next version.  */
 547   struct bfd_elf_version_tree *next;
 548   /* Name of this version.  */
 549   const char *name;
 550   /* Version number.  */
 551   unsigned int vernum;
 552   /* Regular expressions for global symbols in this version.  */
 553   struct bfd_elf_version_expr *globals;
 554   /* Regular expressions for local symbols in this version.  */
 555   struct bfd_elf_version_expr *locals;
 556   /* List of versions which this version depends upon.  */
 557   struct bfd_elf_version_deps *deps;
 558   /* Index of the version name.  This is used within BFD.  */
 559   unsigned int name_indx;
 560   /* Whether this version tree was used.  This is used within BFD.  */
 561   int used;
 562 };
 563
 564 #endif