include/bfdlink.h

   1 /* bfdlink.h -- header file for BFD link routines
   2    Copyright 1993 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 locals with a certain prefix.  */
  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 /* Traverse a link hash table.  */
 156 extern void bfd_link_hash_traverse
 157   PARAMS ((struct bfd_link_hash_table *,
 158            boolean (*) (struct bfd_link_hash_entry *, PTR),
 159            PTR));
 160
 161 /* Add an entry to the undefs list.  */
 162 extern void bfd_link_add_undef
 163   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 164 \f
 165 /* This structure holds all the information needed to communicate
 166    between BFD and the linker when doing a link.  */
 167
 168 struct bfd_link_info
 169 {
 170   /* Function callbacks.  */
 171   const struct bfd_link_callbacks *callbacks;
 172   /* true if BFD should generate a relocateable object file.  */
 173   boolean relocateable;
 174   /* true if BFD should generate a shared object.  */
 175   boolean shared;
 176   /* true if BFD should pre-bind symbols in a shared object.  */
 177   boolean symbolic;
 178   /* true if shared objects should be linked directly, not shared.  */
 179   boolean static_link;
 180   /* Which symbols to strip.  */
 181   enum bfd_link_strip strip;
 182   /* Which local symbols to discard.  */
 183   enum bfd_link_discard discard;
 184   /* The local symbol prefix to discard if using discard_l.  */
 185   unsigned int lprefix_len;
 186   const char *lprefix;
 187   /* true if symbols should be retained in memory, false if they
 188      should be freed and reread.  */
 189   boolean keep_memory;
 190   /* The list of input BFD's involved in the link.  These are chained
 191      together via the link_next field.  */
 192   bfd *input_bfds;
 193   /* If a symbol should be created for each input BFD, this is section
 194      where those symbols should be placed.  It must be a section in
 195      the output BFD.  It may be NULL, in which case no such symbols
 196      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 197      linker command language.  */
 198   asection *create_object_symbols_section;
 199   /* Hash table handled by BFD.  */
 200   struct bfd_link_hash_table *hash;
 201   /* Hash table of symbols to keep.  This is NULL unless strip is
 202      strip_some.  */
 203   struct bfd_hash_table *keep_hash;
 204   /* Hash table of symbols to report back via notice_callback.  If
 205      this is NULL no symbols are reported back.  */
 206   struct bfd_hash_table *notice_hash;
 207
 208   /* If a base output file is wanted, then this points to it */
 209   PTR base_file;
 210 };
 211
 212 /* This structures holds a set of callback functions.  These are
 213    called by the BFD linker routines.  The first argument to each
 214    callback function is the bfd_link_info structure being used.  Each
 215    function returns a boolean value.  If the function returns false,
 216    then the BFD function which called it will return with a failure
 217    indication.  */
 218
 219 struct bfd_link_callbacks
 220 {
 221   /* A function which is called when an object is added from an
 222      archive.  ABFD is the archive element being added.  NAME is the
 223      name of the symbol which caused the archive element to be pulled
 224      in.  */
 225   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 226                                           bfd *abfd,
 227                                           const char *name));
 228   /* A function which is called when a symbol is found with multiple
 229      definitions.  NAME is the symbol which is defined multiple times.
 230      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 231      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 232      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 233      bfd_com_section or bfd_ind_section.  */
 234   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 235                                           const char *name,
 236                                           bfd *obfd,
 237                                           asection *osec,
 238                                           bfd_vma oval,
 239                                           bfd *nbfd,
 240                                           asection *nsec,
 241                                           bfd_vma nval));
 242   /* A function which is called when a common symbol is defined
 243      multiple times.  NAME is the symbol appearing multiple times.
 244      OBFD is the BFD of the existing symbol; it may be NULL if this is
 245      not known.  OTYPE is the type of the existing symbol, which may
 246      be bfd_link_hash_defined, bfd_link_hash_defweak,
 247      bfd_link_hash_common, or bfd_link_hash_indirect.  If OTYPE is
 248      bfd_link_hash_common, OSIZE is the size of the existing symbol.
 249      NBFD is the BFD of the new symbol.  NTYPE is the type of the new
 250      symbol, one of bfd_link_hash_defined, bfd_link_hash_common, or
 251      bfd_link_hash_indirect.  If NTYPE is bfd_link_hash_common, NSIZE
 252      is the size of the new symbol.  */
 253   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 254                                       const char *name,
 255                                       bfd *obfd,
 256                                       enum bfd_link_hash_type otype,
 257                                       bfd_vma osize,
 258                                       bfd *nbfd,
 259                                       enum bfd_link_hash_type ntype,
 260                                       bfd_vma nsize));
 261   /* A function which is called to add a symbol to a set.  ENTRY is
 262      the link hash table entry for the set itself (e.g.,
 263      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 264      the set when generating a relocateable file, and is also used to
 265      get the size of the entry when generating an executable file.
 266      ABFD, SEC and VALUE identify the value to add to the set.  */
 267   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 268                                  struct bfd_link_hash_entry *entry,
 269                                  bfd_reloc_code_real_type reloc,
 270                                  bfd *abfd, asection *sec, bfd_vma value));
 271   /* A function which is called when the name of a g++ constructor or
 272      destructor is found.  This is only called by some object file
 273      formats.  CONSTRUCTOR is true for a constructor, false for a
 274      destructor.  This will use BFD_RELOC_CTOR when generating a
 275      relocateable file.  NAME is the name of the symbol found.  ABFD,
 276      SECTION and VALUE are the value of the symbol.  */
 277   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 278                                   boolean constructor,
 279                                   const char *name, bfd *abfd, asection *sec,
 280                                   bfd_vma value));
 281   /* A function which is called to issue a linker warning.  For
 282      example, this is called when there is a reference to a warning
 283      symbol.  WARNING is the warning to be issued.  SYMBOL is the name
 284      of the symbol which triggered the warning; it may be NULL if
 285      there is none.  ABFD, SECTION and ADDRESS identify the location
 286      which trigerred the warning; either ABFD or SECTION or both may
 287      be NULL if the location is not known.  */
 288   boolean (*warning) PARAMS ((struct bfd_link_info *,
 289                               const char *warning, const char *symbol,
 290                               bfd *abfd, asection *section,
 291                               bfd_vma address));
 292   /* A function which is called when a relocation is attempted against
 293      an undefined symbol.  NAME is the symbol which is undefined.
 294      ABFD, SECTION and ADDRESS identify the location from which the
 295      reference is made.  In some cases SECTION may be NULL.  */
 296   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 297                                        const char *name, bfd *abfd,
 298                                        asection *section, bfd_vma address));
 299   /* A function which is called when a reloc overflow occurs.  NAME is
 300      the name of the symbol or section the reloc is against,
 301      RELOC_NAME is the name of the relocation, and ADDEND is any
 302      addend that is used.  ABFD, SECTION and ADDRESS identify the
 303      location at which the overflow occurs; if this is the result of a
 304      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 305      ABFD will be NULL.  */
 306   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 307                                      const char *name,
 308                                      const char *reloc_name, bfd_vma addend,
 309                                      bfd *abfd, asection *section,
 310                                      bfd_vma address));
 311   /* A function which is called when a dangerous reloc is performed.
 312      The canonical example is an a29k IHCONST reloc which does not
 313      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 314      ABFD, SECTION and ADDRESS identify the location at which the
 315      problem occurred; if this is the result of a
 316      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 317      ABFD will be NULL.  */
 318   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 319                                       const char *message,
 320                                       bfd *abfd, asection *section,
 321                                       bfd_vma address));
 322   /* A function which is called when a reloc is found to be attached
 323      to a symbol which is not being written out.  NAME is the name of
 324      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 325      the reloc; if this is the result of a
 326      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 327      ABFD will be NULL.  */
 328   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 329                                        const char *name,
 330                                        bfd *abfd, asection *section,
 331                                        bfd_vma address));
 332   /* A function which is called when a symbol in notice_hash is
 333      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 334      ADDRESS are the value of the symbol.  If SECTION is
 335      bfd_und_section, this is a reference.  */
 336   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 337                              bfd *abfd, asection *section, bfd_vma address));
 338 };
 339 \f
 340 /* The linker builds link_order structures which tell the code how to
 341    include input data in the output file.  */
 342
 343 /* These are the types of link_order structures.  */
 344
 345 enum bfd_link_order_type
 346 {
 347   bfd_undefined_link_order,     /* Undefined.  */
 348   bfd_indirect_link_order,      /* Built from a section.  */
 349   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 350   bfd_data_link_order,          /* Set to explicit data.  */
 351   bfd_section_reloc_link_order, /* Relocate against a section.  */
 352   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 353 };
 354
 355 /* This is the link_order structure itself.  These form a chain
 356    attached to the section whose contents they are describing.  */
 357
 358 struct bfd_link_order
 359 {
 360   /* Next link_order in chain.  */
 361   struct bfd_link_order *next;
 362   /* Type of link_order.  */
 363   enum bfd_link_order_type type;
 364   /* Offset within output section.  */
 365   bfd_vma offset;
 366   /* Size within output section.  */
 367   bfd_size_type size;
 368   /* Type specific information.  */
 369   union
 370     {
 371       struct
 372         {
 373           /* Section to include.  If this is used, then
 374              section->output_section must be the section the
 375              link_order is attached to, section->output_offset must
 376              equal the link_order offset field, and section->_raw_size
 377              must equal the link_order size field.  Maybe these
 378              restrictions should be relaxed someday.  */
 379           asection *section;
 380         } indirect;
 381       struct
 382         {
 383           /* Value to fill with.  */
 384           unsigned int value;
 385         } fill;
 386       struct
 387         {
 388           /* Data to put into file.  The size field gives the number
 389              of bytes which this field points to.  */
 390           bfd_byte *contents;
 391         } data;
 392       struct
 393         {
 394           /* Description of reloc to generate.  Used for
 395              bfd_section_reloc_link_order and
 396              bfd_symbol_reloc_link_order.  */
 397           struct bfd_link_order_reloc *p;
 398         } reloc;
 399     } u;
 400 };
 401
 402 /* A linker order of type bfd_section_reloc_link_order or
 403    bfd_symbol_reloc_link_order means to create a reloc against a
 404    section or symbol, respectively.  This is used to implement -Ur to
 405    generate relocs for the constructor tables.  The
 406    bfd_link_order_reloc structure describes the reloc that BFD should
 407    create.  It is similar to a arelent, but I didn't use arelent
 408    because the linker does not know anything about most symbols, and
 409    any asymbol structure it creates will be partially meaningless.
 410    This information could logically be in the bfd_link_order struct,
 411    but I didn't want to waste the space since these types of relocs
 412    are relatively rare.  */
 413
 414 struct bfd_link_order_reloc
 415 {
 416   /* Reloc type.  */
 417   bfd_reloc_code_real_type reloc;
 418
 419   union
 420     {
 421       /* For type bfd_section_reloc_link_order, this is the section
 422          the reloc should be against.  This must be a section in the
 423          output BFD, not any of the input BFDs.  */
 424       asection *section;
 425       /* For type bfd_symbol_reloc_link_order, this is the name of the
 426          symbol the reloc should be against.  */
 427       const char *name;
 428     } u;
 429
 430   /* Addend to use.  The object file should contain zero.  The BFD
 431      backend is responsible for filling in the contents of the object
 432      file correctly.  For some object file formats (e.g., COFF) the
 433      addend must be stored into in the object file, and for some
 434      (e.g., SPARC a.out) it is kept in the reloc.  */
 435   bfd_vma addend;
 436 };
 437
 438 /* Allocate a new link_order for a section.  */
 439 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 440
 441 #endif