include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993, 94, 95, 96, 97, 1999 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 2 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 #ifndef BFDLINK_H
  22 #define BFDLINK_H
  23
  24 /* Which symbols to strip during a link.  */
  25 enum bfd_link_strip
  26 {
  27   strip_none,           /* Don't strip any symbols.  */
  28   strip_debugger,       /* Strip debugging symbols.  */
  29   strip_some,           /* keep_hash is the list of symbols to keep.  */
  30   strip_all             /* Strip all symbols.  */
  31 };
  32
  33 /* Which local symbols to discard during a link.  This is irrelevant
  34    if strip_all is used.  */
  35 enum bfd_link_discard
  36 {
  37   discard_none,         /* Don't discard any locals.  */
  38   discard_l,            /* Discard local temporary symbols.  */
  39   discard_all           /* Discard all locals.  */
  40 };
  41 \f
  42 /* These are the possible types of an entry in the BFD link hash
  43    table.  */
  44
  45 enum bfd_link_hash_type
  46 {
  47   bfd_link_hash_new,            /* Symbol is new.  */
  48   bfd_link_hash_undefined,      /* Symbol seen before, but undefined.  */
  49   bfd_link_hash_undefweak,      /* Symbol is weak and undefined.  */
  50   bfd_link_hash_defined,        /* Symbol is defined.  */
  51   bfd_link_hash_defweak,        /* Symbol is weak and defined.  */
  52   bfd_link_hash_common,         /* Symbol is common.  */
  53   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  54   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  55 };
  56
  57 /* The linking routines use a hash table which uses this structure for
  58    its elements.  */
  59
  60 struct bfd_link_hash_entry
  61 {
  62   /* Base hash table entry structure.  */
  63   struct bfd_hash_entry root;
  64   /* Type of this entry.  */
  65   enum bfd_link_hash_type type;
  66
  67   /* Undefined and common symbols are kept in a linked list through
  68      this field.  This field is not in the union because that would
  69      force us to remove entries from the list when we changed their
  70      type, which would force the list to be doubly linked, which would
  71      waste more memory.  When an undefined or common symbol is
  72      created, it should be added to this list, the head of which is in
  73      the link hash table itself.  As symbols are defined, they need
  74      not be removed from the list; anything which reads the list must
  75      doublecheck the symbol type.
  76
  77      Weak symbols are not kept on this list.
  78
  79      Defined and defweak symbols use this field as a reference marker.
  80      If the field is not NULL, or this structure is the tail of the
  81      undefined symbol list, the symbol has been referenced.  If the
  82      symbol is undefined and becomes defined, this field will
  83      automatically be non-NULL since the symbol will have been on the
  84      undefined symbol list.  */
  85   struct bfd_link_hash_entry *next;
  86   /* A union of information depending upon the type.  */
  87   union
  88     {
  89       /* Nothing is kept for bfd_hash_new.  */
  90       /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
  91       struct
  92         {
  93           bfd *abfd;            /* BFD symbol was found in.  */
  94         } undef;
  95       /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
  96       struct
  97         {
  98           bfd_vma value;        /* Symbol value.  */
  99           asection *section;    /* Symbol section.  */
 100         } def;
 101       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
 102       struct
 103         {
 104           struct bfd_link_hash_entry *link;     /* Real symbol.  */
 105           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
 106         } i;
 107       /* bfd_link_hash_common.  */
 108       struct
 109         {
 110           /* The linker needs to know three things about common
 111              symbols: the size, the alignment, and the section in
 112              which the symbol should be placed.  We store the size
 113              here, and we allocate a small structure to hold the
 114              section and the alignment.  The alignment is stored as a
 115              power of two.  We don't store all the information
 116              directly because we don't want to increase the size of
 117              the union; this structure is a major space user in the
 118              linker.  */
 119           bfd_size_type size;   /* Common symbol size.  */
 120           struct bfd_link_hash_common_entry
 121             {
 122               unsigned int alignment_power;     /* Alignment.  */
 123               asection *section;                /* Symbol section.  */
 124             } *p;
 125         } c;
 126     } u;
 127 };
 128
 129 /* This is the link hash table.  It is a derived class of
 130    bfd_hash_table.  */
 131
 132 struct bfd_link_hash_table
 133 {
 134   /* The hash table itself.  */
 135   struct bfd_hash_table table;
 136   /* The back end which created this hash table.  This indicates the
 137      type of the entries in the hash table, which is sometimes
 138      important information when linking object files of different
 139      types together.  */
 140   const bfd_target *creator;
 141   /* A linked list of undefined and common symbols, linked through the
 142      next field in the bfd_link_hash_entry structure.  */
 143   struct bfd_link_hash_entry *undefs;
 144   /* Entries are added to the tail of the undefs list.  */
 145   struct bfd_link_hash_entry *undefs_tail;
 146 };
 147
 148 /* Look up an entry in a link hash table.  If FOLLOW is true, this
 149    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 150    the real symbol.  */
 151 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 152   PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
 153            boolean copy, boolean follow));
 154
 155 /* Look up an entry in the main linker hash table if the symbol might
 156    be wrapped.  This should only be used for references to an
 157    undefined symbol, not for definitions of a symbol.  */
 158
 159 extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
 160   PARAMS ((bfd *, struct bfd_link_info *, const char *, boolean, boolean,
 161            boolean));
 162
 163 /* Traverse a link hash table.  */
 164 extern void bfd_link_hash_traverse
 165   PARAMS ((struct bfd_link_hash_table *,
 166            boolean (*) (struct bfd_link_hash_entry *, PTR),
 167            PTR));
 168
 169 /* Add an entry to the undefs list.  */
 170 extern void bfd_link_add_undef
 171   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 172 \f
 173 /* This structure holds all the information needed to communicate
 174    between BFD and the linker when doing a link.  */
 175
 176 struct bfd_link_info
 177 {
 178   /* Function callbacks.  */
 179   const struct bfd_link_callbacks *callbacks;
 180   /* true if BFD should generate a relocateable object file.  */
 181   boolean relocateable;
 182   /* true if BFD should generate a "task linked" object file,
 183      similar to relocatable but also with globals converted to statics. */
 184   boolean task_link;
 185   /* true if BFD should generate a shared object.  */
 186   boolean shared;
 187   /* true if BFD should pre-bind symbols in a shared object.  */
 188   boolean symbolic;
 189   /* true if shared objects should be linked directly, not shared.  */
 190   boolean static_link;
 191   /* true if the output file should be in a traditional format.  This
 192      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 193      on the output file, but may be checked when reading the input
 194      files.  */
 195   boolean traditional_format;
 196   /* true if we want to produced optimized output files.  This might
 197      need much more time and therefore must be explicitly selected.  */
 198   boolean optimize;
 199   /* true if BFD should generate errors for undefined symbols
 200      even if generating a shared object.  */
 201   boolean no_undefined;
 202   /* Which symbols to strip.  */
 203   enum bfd_link_strip strip;
 204   /* Which local symbols to discard.  */
 205   enum bfd_link_discard discard;
 206   /* true if symbols should be retained in memory, false if they
 207      should be freed and reread.  */
 208   boolean keep_memory;
 209   /* The list of input BFD's involved in the link.  These are chained
 210      together via the link_next field.  */
 211   bfd *input_bfds;
 212   /* If a symbol should be created for each input BFD, this is section
 213      where those symbols should be placed.  It must be a section in
 214      the output BFD.  It may be NULL, in which case no such symbols
 215      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 216      linker command language.  */
 217   asection *create_object_symbols_section;
 218   /* Hash table handled by BFD.  */
 219   struct bfd_link_hash_table *hash;
 220   /* Hash table of symbols to keep.  This is NULL unless strip is
 221      strip_some.  */
 222   struct bfd_hash_table *keep_hash;
 223   /* true if every symbol should be reported back via the notice
 224      callback.  */
 225   boolean notice_all;
 226   /* Hash table of symbols to report back via the notice callback.  If
 227      this is NULL, and notice_all is false, then no symbols are
 228      reported back.  */
 229   struct bfd_hash_table *notice_hash;
 230   /* Hash table of symbols which are being wrapped (the --wrap linker
 231      option).  If this is NULL, no symbols are being wrapped.  */
 232   struct bfd_hash_table *wrap_hash;
 233   /* If a base output file is wanted, then this points to it */
 234   PTR base_file;
 235
 236   /* If non-zero, specifies that branches which are problematic for the
 237   MPC860 C0 (or earlier) should be checked for and modified.  It gives the
 238   number of bytes that should be checked at the end of each text page. */
 239   int mpc860c0;
 240
 241   /* The function to call when the executable or shared object is
 242      loaded.  */
 243   const char *init_function;
 244   /* The function to call when the executable or shared object is
 245      unloaded.  */
 246   const char *fini_function;
 247 };
 248
 249 /* This structures holds a set of callback functions.  These are
 250    called by the BFD linker routines.  The first argument to each
 251    callback function is the bfd_link_info structure being used.  Each
 252    function returns a boolean value.  If the function returns false,
 253    then the BFD function which called it will return with a failure
 254    indication.  */
 255
 256 struct bfd_link_callbacks
 257 {
 258   /* A function which is called when an object is added from an
 259      archive.  ABFD is the archive element being added.  NAME is the
 260      name of the symbol which caused the archive element to be pulled
 261      in.  */
 262   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 263                                           bfd *abfd,
 264                                           const char *name));
 265   /* A function which is called when a symbol is found with multiple
 266      definitions.  NAME is the symbol which is defined multiple times.
 267      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 268      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 269      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 270      bfd_com_section or bfd_ind_section.  */
 271   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 272                                           const char *name,
 273                                           bfd *obfd,
 274                                           asection *osec,
 275                                           bfd_vma oval,
 276                                           bfd *nbfd,
 277                                           asection *nsec,
 278                                           bfd_vma nval));
 279   /* A function which is called when a common symbol is defined
 280      multiple times.  NAME is the symbol appearing multiple times.
 281      OBFD is the BFD of the existing symbol; it may be NULL if this is
 282      not known.  OTYPE is the type of the existing symbol, which may
 283      be bfd_link_hash_defined, bfd_link_hash_defweak,
 284      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 285      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 286      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 287      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 288      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 289      is the size of the new symbol.  */
 290   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 291                                       const char *name,
 292                                       bfd *obfd,
 293                                       enum bfd_link_hash_type otype,
 294                                       bfd_vma osize,
 295                                       bfd *nbfd,
 296                                       enum bfd_link_hash_type ntype,
 297                                       bfd_vma nsize));
 298   /* A function which is called to add a symbol to a set.  ENTRY is
 299      the link hash table entry for the set itself (e.g.,
 300      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 301      the set when generating a relocateable file, and is also used to
 302      get the size of the entry when generating an executable file.
 303      ABFD, SEC and VALUE identify the value to add to the set.  */
 304   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 305                                  struct bfd_link_hash_entry *entry,
 306                                  bfd_reloc_code_real_type reloc,
 307                                  bfd *abfd, asection *sec, bfd_vma value));
 308   /* A function which is called when the name of a g++ constructor or
 309      destructor is found.  This is only called by some object file
 310      formats.  CONSTRUCTOR is true for a constructor, false for a
 311      destructor.  This will use BFD_RELOC_CTOR when generating a
 312      relocateable file.  NAME is the name of the symbol found.  ABFD,
 313      SECTION and VALUE are the value of the symbol.  */
 314   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 315                                   boolean constructor,
 316                                   const char *name, bfd *abfd, asection *sec,
 317                                   bfd_vma value));
 318   /* A function which is called to issue a linker warning.  For
 319      example, this is called when there is a reference to a warning
 320      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 321      of the symbol which triggered the warning; it may be NULL if
 322      there is none.  ABFD, SECTION and ADDRESS identify the location
 323      which trigerred the warning; either ABFD or SECTION or both may
 324      be NULL if the location is not known.  */
 325   boolean (*warning) PARAMS ((struct bfd_link_info *,
 326                               const char *warning, const char *symbol,
 327                               bfd *abfd, asection *section,
 328                               bfd_vma address));
 329   /* A function which is called when a relocation is attempted against
 330      an undefined symbol.  NAME is the symbol which is undefined.
 331      ABFD, SECTION and ADDRESS identify the location from which the
 332      reference is made.  In some cases SECTION may be NULL.  */
 333   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 334                                        const char *name, bfd *abfd,
 335                                        asection *section, bfd_vma address));
 336   /* A function which is called when a reloc overflow occurs.  NAME is
 337      the name of the symbol or section the reloc is against,
 338      RELOC_NAME is the name of the relocation, and ADDEND is any
 339      addend that is used.  ABFD, SECTION and ADDRESS identify the
 340      location at which the overflow occurs; if this is the result of a
 341      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 342      ABFD will be NULL.  */
 343   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 344                                      const char *name,
 345                                      const char *reloc_name, bfd_vma addend,
 346                                      bfd *abfd, asection *section,
 347                                      bfd_vma address));
 348   /* A function which is called when a dangerous reloc is performed.
 349      The canonical example is an a29k IHCONST reloc which does not
 350      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 351      ABFD, SECTION and ADDRESS identify the location at which the
 352      problem occurred; if this is the result of a
 353      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 354      ABFD will be NULL.  */
 355   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 356                                       const char *message,
 357                                       bfd *abfd, asection *section,
 358                                       bfd_vma address));
 359   /* A function which is called when a reloc is found to be attached
 360      to a symbol which is not being written out.  NAME is the name of
 361      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 362      the reloc; if this is the result of a
 363      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 364      ABFD will be NULL.  */
 365   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 366                                        const char *name,
 367                                        bfd *abfd, asection *section,
 368                                        bfd_vma address));
 369   /* A function which is called when a symbol in notice_hash is
 370      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 371      ADDRESS are the value of the symbol.  If SECTION is
 372      bfd_und_section, this is a reference.  */
 373   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 374                              bfd *abfd, asection *section, bfd_vma address));
 375 };
 376 \f
 377 /* The linker builds link_order structures which tell the code how to
 378    include input data in the output file.  */
 379
 380 /* These are the types of link_order structures.  */
 381
 382 enum bfd_link_order_type
 383 {
 384   bfd_undefined_link_order,     /* Undefined.  */
 385   bfd_indirect_link_order,      /* Built from a section.  */
 386   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 387   bfd_data_link_order,          /* Set to explicit data.  */
 388   bfd_section_reloc_link_order, /* Relocate against a section.  */
 389   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 390 };
 391
 392 /* This is the link_order structure itself.  These form a chain
 393    attached to the section whose contents they are describing.  */
 394
 395 struct bfd_link_order
 396 {
 397   /* Next link_order in chain.  */
 398   struct bfd_link_order *next;
 399   /* Type of link_order.  */
 400   enum bfd_link_order_type type;
 401   /* Offset within output section.  */
 402   bfd_vma offset;
 403   /* Size within output section.  */
 404   bfd_size_type size;
 405   /* Type specific information.  */
 406   union
 407     {
 408       struct
 409         {
 410           /* Section to include.  If this is used, then
 411              section->output_section must be the section the
 412              link_order is attached to, section->output_offset must
 413              equal the link_order offset field, and section->_raw_size
 414              must equal the link_order size field.  Maybe these
 415              restrictions should be relaxed someday.  */
 416           asection *section;
 417         } indirect;
 418       struct
 419         {
 420           /* Value to fill with.  */
 421           unsigned int value;
 422         } fill;
 423       struct
 424         {
 425           /* Data to put into file.  The size field gives the number
 426              of bytes which this field points to.  */
 427           bfd_byte *contents;
 428         } data;
 429       struct
 430         {
 431           /* Description of reloc to generate.  Used for
 432              bfd_section_reloc_link_order and
 433              bfd_symbol_reloc_link_order.  */
 434           struct bfd_link_order_reloc *p;
 435         } reloc;
 436     } u;
 437 };
 438
 439 /* A linker order of type bfd_section_reloc_link_order or
 440    bfd_symbol_reloc_link_order means to create a reloc against a
 441    section or symbol, respectively.  This is used to implement -Ur to
 442    generate relocs for the constructor tables.  The
 443    bfd_link_order_reloc structure describes the reloc that BFD should
 444    create.  It is similar to a arelent, but I didn't use arelent
 445    because the linker does not know anything about most symbols, and
 446    any asymbol structure it creates will be partially meaningless.
 447    This information could logically be in the bfd_link_order struct,
 448    but I didn't want to waste the space since these types of relocs
 449    are relatively rare.  */
 450
 451 struct bfd_link_order_reloc
 452 {
 453   /* Reloc type.  */
 454   bfd_reloc_code_real_type reloc;
 455
 456   union
 457     {
 458       /* For type bfd_section_reloc_link_order, this is the section
 459          the reloc should be against.  This must be a section in the
 460          output BFD, not any of the input BFDs.  */
 461       asection *section;
 462       /* For type bfd_symbol_reloc_link_order, this is the name of the
 463          symbol the reloc should be against.  */
 464       const char *name;
 465     } u;
 466
 467   /* Addend to use.  The object file should contain zero.  The BFD
 468      backend is responsible for filling in the contents of the object
 469      file correctly.  For some object file formats (e.g., COFF) the
 470      addend must be stored into in the object file, and for some
 471      (e.g., SPARC a.out) it is kept in the reloc.  */
 472   bfd_vma addend;
 473 };
 474
 475 /* Allocate a new link_order for a section.  */
 476 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 477
 478 /* These structures are used to describe version information for the
 479    ELF linker.  These structures could be manipulated entirely inside
 480    BFD, but it would be a pain.  Instead, the regular linker sets up
 481    these structures, and then passes them into BFD.  */
 482
 483 /* Regular expressions for a version.  */
 484
 485 struct bfd_elf_version_expr
 486 {
 487   /* Next regular expression for this version.  */
 488   struct bfd_elf_version_expr *next;
 489   /* Regular expression.  */
 490   const char *pattern;
 491   /* Matching function.  */
 492   int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
 493 };
 494
 495 /* Version dependencies.  */
 496
 497 struct bfd_elf_version_deps
 498 {
 499   /* Next dependency for this version.  */
 500   struct bfd_elf_version_deps *next;
 501   /* The version which this version depends upon.  */
 502   struct bfd_elf_version_tree *version_needed;
 503 };
 504
 505 /* A node in the version tree.  */
 506
 507 struct bfd_elf_version_tree
 508 {
 509   /* Next version.  */
 510   struct bfd_elf_version_tree *next;
 511   /* Name of this version.  */
 512   const char *name;
 513   /* Version number.  */
 514   unsigned int vernum;
 515   /* Regular expressions for global symbols in this version.  */
 516   struct bfd_elf_version_expr *globals;
 517   /* Regular expressions for local symbols in this version.  */
 518   struct bfd_elf_version_expr *locals;
 519   /* List of versions which this version depends upon.  */
 520   struct bfd_elf_version_deps *deps;
 521   /* Index of the version name.  This is used within BFD.  */
 522   unsigned int name_indx;
 523   /* Whether this version tree was used.  This is used within BFD.  */
 524   int used;
 525 };
 526
 527 #endif