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 relocation information in the final executable.  */
 183   boolean emitrelocations;
 184   /* true if BFD should generate a "task linked" object file,
 185      similar to relocatable but also with globals converted to statics. */
 186   boolean task_link;
 187   /* true if BFD should generate a shared object.  */
 188   boolean shared;
 189   /* true if BFD should pre-bind symbols in a shared object.  */
 190   boolean symbolic;
 191   /* true if shared objects should be linked directly, not shared.  */
 192   boolean static_link;
 193   /* true if the output file should be in a traditional format.  This
 194      is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
 195      on the output file, but may be checked when reading the input
 196      files.  */
 197   boolean traditional_format;
 198   /* true if we want to produced optimized output files.  This might
 199      need much more time and therefore must be explicitly selected.  */
 200   boolean optimize;
 201   /* true if BFD should generate errors for undefined symbols
 202      even if generating a shared object.  */
 203   boolean no_undefined;
 204   /* Which symbols to strip.  */
 205   enum bfd_link_strip strip;
 206   /* Which local symbols to discard.  */
 207   enum bfd_link_discard discard;
 208   /* true if symbols should be retained in memory, false if they
 209      should be freed and reread.  */
 210   boolean keep_memory;
 211   /* The list of input BFD's involved in the link.  These are chained
 212      together via the link_next field.  */
 213   bfd *input_bfds;
 214   /* If a symbol should be created for each input BFD, this is section
 215      where those symbols should be placed.  It must be a section in
 216      the output BFD.  It may be NULL, in which case no such symbols
 217      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 218      linker command language.  */
 219   asection *create_object_symbols_section;
 220   /* Hash table handled by BFD.  */
 221   struct bfd_link_hash_table *hash;
 222   /* Hash table of symbols to keep.  This is NULL unless strip is
 223      strip_some.  */
 224   struct bfd_hash_table *keep_hash;
 225   /* true if every symbol should be reported back via the notice
 226      callback.  */
 227   boolean notice_all;
 228   /* Hash table of symbols to report back via the notice callback.  If
 229      this is NULL, and notice_all is false, then no symbols are
 230      reported back.  */
 231   struct bfd_hash_table *notice_hash;
 232   /* Hash table of symbols which are being wrapped (the --wrap linker
 233      option).  If this is NULL, no symbols are being wrapped.  */
 234   struct bfd_hash_table *wrap_hash;
 235   /* If a base output file is wanted, then this points to it */
 236   PTR base_file;
 237
 238   /* If non-zero, specifies that branches which are problematic for the
 239   MPC860 C0 (or earlier) should be checked for and modified.  It gives the
 240   number of bytes that should be checked at the end of each text page. */
 241   int mpc860c0;
 242
 243   /* The function to call when the executable or shared object is
 244      loaded.  */
 245   const char *init_function;
 246   /* The function to call when the executable or shared object is
 247      unloaded.  */
 248   const char *fini_function;
 249
 250   /* May be used to set DT_FLAGS for ELF. */
 251   bfd_vma flags;
 252
 253   /* May be used to set DT_FLAGS_1 for ELF. */
 254   bfd_vma flags_1;
 255 };
 256
 257 /* This structures holds a set of callback functions.  These are
 258    called by the BFD linker routines.  The first argument to each
 259    callback function is the bfd_link_info structure being used.  Each
 260    function returns a boolean value.  If the function returns false,
 261    then the BFD function which called it will return with a failure
 262    indication.  */
 263
 264 struct bfd_link_callbacks
 265 {
 266   /* A function which is called when an object is added from an
 267      archive.  ABFD is the archive element being added.  NAME is the
 268      name of the symbol which caused the archive element to be pulled
 269      in.  */
 270   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 271                                           bfd *abfd,
 272                                           const char *name));
 273   /* A function which is called when a symbol is found with multiple
 274      definitions.  NAME is the symbol which is defined multiple times.
 275      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 276      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 277      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 278      bfd_com_section or bfd_ind_section.  */
 279   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 280                                           const char *name,
 281                                           bfd *obfd,
 282                                           asection *osec,
 283                                           bfd_vma oval,
 284                                           bfd *nbfd,
 285                                           asection *nsec,
 286                                           bfd_vma nval));
 287   /* A function which is called when a common symbol is defined
 288      multiple times.  NAME is the symbol appearing multiple times.
 289      OBFD is the BFD of the existing symbol; it may be NULL if this is
 290      not known.  OTYPE is the type of the existing symbol, which may
 291      be bfd_link_hash_defined, bfd_link_hash_defweak,
 292      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 293      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 294      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 295      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 296      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 297      is the size of the new symbol.  */
 298   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 299                                       const char *name,
 300                                       bfd *obfd,
 301                                       enum bfd_link_hash_type otype,
 302                                       bfd_vma osize,
 303                                       bfd *nbfd,
 304                                       enum bfd_link_hash_type ntype,
 305                                       bfd_vma nsize));
 306   /* A function which is called to add a symbol to a set.  ENTRY is
 307      the link hash table entry for the set itself (e.g.,
 308      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 309      the set when generating a relocateable file, and is also used to
 310      get the size of the entry when generating an executable file.
 311      ABFD, SEC and VALUE identify the value to add to the set.  */
 312   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 313                                  struct bfd_link_hash_entry *entry,
 314                                  bfd_reloc_code_real_type reloc,
 315                                  bfd *abfd, asection *sec, bfd_vma value));
 316   /* A function which is called when the name of a g++ constructor or
 317      destructor is found.  This is only called by some object file
 318      formats.  CONSTRUCTOR is true for a constructor, false for a
 319      destructor.  This will use BFD_RELOC_CTOR when generating a
 320      relocateable file.  NAME is the name of the symbol found.  ABFD,
 321      SECTION and VALUE are the value of the symbol.  */
 322   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 323                                   boolean constructor,
 324                                   const char *name, bfd *abfd, asection *sec,
 325                                   bfd_vma value));
 326   /* A function which is called to issue a linker warning.  For
 327      example, this is called when there is a reference to a warning
 328      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 329      of the symbol which triggered the warning; it may be NULL if
 330      there is none.  ABFD, SECTION and ADDRESS identify the location
 331      which trigerred the warning; either ABFD or SECTION or both may
 332      be NULL if the location is not known.  */
 333   boolean (*warning) PARAMS ((struct bfd_link_info *,
 334                               const char *warning, const char *symbol,
 335                               bfd *abfd, asection *section,
 336                               bfd_vma address));
 337   /* A function which is called when a relocation is attempted against
 338      an undefined symbol.  NAME is the symbol which is undefined.
 339      ABFD, SECTION and ADDRESS identify the location from which the
 340      reference is made. FATAL indicates whether an undefined symbol is
 341      a fatal error or not. In some cases SECTION may be NULL.  */
 342   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 343                                        const char *name, bfd *abfd,
 344                                        asection *section,
 345                                        bfd_vma address,
 346                                        boolean fatal));
 347   /* A function which is called when a reloc overflow occurs.  NAME is
 348      the name of the symbol or section the reloc is against,
 349      RELOC_NAME is the name of the relocation, and ADDEND is any
 350      addend that is used.  ABFD, SECTION and ADDRESS identify the
 351      location at which the overflow occurs; if this is the result of a
 352      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 353      ABFD will be NULL.  */
 354   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 355                                      const char *name,
 356                                      const char *reloc_name, bfd_vma addend,
 357                                      bfd *abfd, asection *section,
 358                                      bfd_vma address));
 359   /* A function which is called when a dangerous reloc is performed.
 360      The canonical example is an a29k IHCONST reloc which does not
 361      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 362      ABFD, SECTION and ADDRESS identify the location at which the
 363      problem occurred; if this is the result of a
 364      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 365      ABFD will be NULL.  */
 366   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 367                                       const char *message,
 368                                       bfd *abfd, asection *section,
 369                                       bfd_vma address));
 370   /* A function which is called when a reloc is found to be attached
 371      to a symbol which is not being written out.  NAME is the name of
 372      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 373      the reloc; if this is the result of a
 374      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 375      ABFD will be NULL.  */
 376   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 377                                        const char *name,
 378                                        bfd *abfd, asection *section,
 379                                        bfd_vma address));
 380   /* A function which is called when a symbol in notice_hash is
 381      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 382      ADDRESS are the value of the symbol.  If SECTION is
 383      bfd_und_section, this is a reference.  */
 384   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 385                              bfd *abfd, asection *section, bfd_vma address));
 386 };
 387 \f
 388 /* The linker builds link_order structures which tell the code how to
 389    include input data in the output file.  */
 390
 391 /* These are the types of link_order structures.  */
 392
 393 enum bfd_link_order_type
 394 {
 395   bfd_undefined_link_order,     /* Undefined.  */
 396   bfd_indirect_link_order,      /* Built from a section.  */
 397   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 398   bfd_data_link_order,          /* Set to explicit data.  */
 399   bfd_section_reloc_link_order, /* Relocate against a section.  */
 400   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 401 };
 402
 403 /* This is the link_order structure itself.  These form a chain
 404    attached to the section whose contents they are describing.  */
 405
 406 struct bfd_link_order
 407 {
 408   /* Next link_order in chain.  */
 409   struct bfd_link_order *next;
 410   /* Type of link_order.  */
 411   enum bfd_link_order_type type;
 412   /* Offset within output section.  */
 413   bfd_vma offset;
 414   /* Size within output section.  */
 415   bfd_size_type size;
 416   /* Type specific information.  */
 417   union
 418     {
 419       struct
 420         {
 421           /* Section to include.  If this is used, then
 422              section->output_section must be the section the
 423              link_order is attached to, section->output_offset must
 424              equal the link_order offset field, and section->_raw_size
 425              must equal the link_order size field.  Maybe these
 426              restrictions should be relaxed someday.  */
 427           asection *section;
 428         } indirect;
 429       struct
 430         {
 431           /* Value to fill with.  */
 432           unsigned int value;
 433         } fill;
 434       struct
 435         {
 436           /* Data to put into file.  The size field gives the number
 437              of bytes which this field points to.  */
 438           bfd_byte *contents;
 439         } data;
 440       struct
 441         {
 442           /* Description of reloc to generate.  Used for
 443              bfd_section_reloc_link_order and
 444              bfd_symbol_reloc_link_order.  */
 445           struct bfd_link_order_reloc *p;
 446         } reloc;
 447     } u;
 448 };
 449
 450 /* A linker order of type bfd_section_reloc_link_order or
 451    bfd_symbol_reloc_link_order means to create a reloc against a
 452    section or symbol, respectively.  This is used to implement -Ur to
 453    generate relocs for the constructor tables.  The
 454    bfd_link_order_reloc structure describes the reloc that BFD should
 455    create.  It is similar to a arelent, but I didn't use arelent
 456    because the linker does not know anything about most symbols, and
 457    any asymbol structure it creates will be partially meaningless.
 458    This information could logically be in the bfd_link_order struct,
 459    but I didn't want to waste the space since these types of relocs
 460    are relatively rare.  */
 461
 462 struct bfd_link_order_reloc
 463 {
 464   /* Reloc type.  */
 465   bfd_reloc_code_real_type reloc;
 466
 467   union
 468     {
 469       /* For type bfd_section_reloc_link_order, this is the section
 470          the reloc should be against.  This must be a section in the
 471          output BFD, not any of the input BFDs.  */
 472       asection *section;
 473       /* For type bfd_symbol_reloc_link_order, this is the name of the
 474          symbol the reloc should be against.  */
 475       const char *name;
 476     } u;
 477
 478   /* Addend to use.  The object file should contain zero.  The BFD
 479      backend is responsible for filling in the contents of the object
 480      file correctly.  For some object file formats (e.g., COFF) the
 481      addend must be stored into in the object file, and for some
 482      (e.g., SPARC a.out) it is kept in the reloc.  */
 483   bfd_vma addend;
 484 };
 485
 486 /* Allocate a new link_order for a section.  */
 487 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 488
 489 /* These structures are used to describe version information for the
 490    ELF linker.  These structures could be manipulated entirely inside
 491    BFD, but it would be a pain.  Instead, the regular linker sets up
 492    these structures, and then passes them into BFD.  */
 493
 494 /* Regular expressions for a version.  */
 495
 496 struct bfd_elf_version_expr
 497 {
 498   /* Next regular expression for this version.  */
 499   struct bfd_elf_version_expr *next;
 500   /* Regular expression.  */
 501   const char *pattern;
 502   /* Matching function.  */
 503   int (*match) PARAMS((struct bfd_elf_version_expr *, const char *));
 504 };
 505
 506 /* Version dependencies.  */
 507
 508 struct bfd_elf_version_deps
 509 {
 510   /* Next dependency for this version.  */
 511   struct bfd_elf_version_deps *next;
 512   /* The version which this version depends upon.  */
 513   struct bfd_elf_version_tree *version_needed;
 514 };
 515
 516 /* A node in the version tree.  */
 517
 518 struct bfd_elf_version_tree
 519 {
 520   /* Next version.  */
 521   struct bfd_elf_version_tree *next;
 522   /* Name of this version.  */
 523   const char *name;
 524   /* Version number.  */
 525   unsigned int vernum;
 526   /* Regular expressions for global symbols in this version.  */
 527   struct bfd_elf_version_expr *globals;
 528   /* Regular expressions for local symbols in this version.  */
 529   struct bfd_elf_version_expr *locals;
 530   /* List of versions which this version depends upon.  */
 531   struct bfd_elf_version_deps *deps;
 532   /* Index of the version name.  This is used within BFD.  */
 533   unsigned int name_indx;
 534   /* Whether this version tree was used.  This is used within BFD.  */
 535   int used;
 536 };
 537
 538 #endif