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