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., 675 Mass Ave, Cambridge, MA 02139, 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_weak,           /* Symbol is weak and undefined.  */
  50   bfd_link_hash_defined,        /* Symbol is defined.  */
  51   bfd_link_hash_common,         /* Symbol is common.  */
  52   bfd_link_hash_indirect,       /* Symbol is an indirect link.  */
  53   bfd_link_hash_warning         /* Like indirect, but warn if referenced.  */
  54 };
  55
  56 /* The linking routines use a hash table which uses this structure for
  57    its elements.  */
  58
  59 struct bfd_link_hash_entry
  60 {
  61   /* Base hash table entry structure.  */
  62   struct bfd_hash_entry root;
  63   /* Type of this entry.  */
  64   enum bfd_link_hash_type type;
  65   /* Undefined and common entries are kept in a linked list through
  66      this field.  This field is not in the union because that would
  67      force us to remove entries from the list when we changed their
  68      type, which would force the list to be doubly linked, which would
  69      waste more memory.  When an undefined or common symbol is
  70      created, it should be added to this list, the head of which is in
  71      the link hash table itself.  As symbols are defined, they need
  72      not be removed from the list; anything which reads the list must
  73      doublecheck the symbol type.  Weak symbols are not kept on this
  74      list.  */
  75   struct bfd_link_hash_entry *next;
  76   /* A union of information depending upon the type.  */
  77   union
  78     {
  79       /* Nothing is kept for bfd_hash_new.  */
  80       /* bfd_link_hash_undefined, bfd_link_hash_weak.  */
  81       struct
  82         {
  83           bfd *abfd;            /* BFD symbol was found in.  */
  84         } undef;
  85       /* bfd_link_hash_defined.  */
  86       struct
  87         {
  88           bfd_vma value;        /* Symbol value.  */
  89           asection *section;    /* Symbol section.  */
  90         } def;
  91       /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
  92       struct
  93         {
  94           struct bfd_link_hash_entry *link;     /* Real symbol.  */
  95           const char *warning;  /* Warning (bfd_link_hash_warning only).  */
  96         } i;
  97       /* bfd_link_hash_common.  */
  98       struct
  99         {
 100           bfd_vma size;         /* Common symbol size.  */
 101           asection *section;    /* Symbol section.  */
 102         } c;
 103     } u;
 104 };
 105
 106 /* This is the link hash table.  It is a derived class of
 107    bfd_hash_table.  */
 108
 109 struct bfd_link_hash_table
 110 {
 111   /* The hash table itself.  */
 112   struct bfd_hash_table table;
 113   /* The back end which created this hash table.  This indicates the
 114      type of the entries in the hash table, which is sometimes
 115      important information when linking object files of different
 116      types together.  */
 117   bfd_target *creator;
 118   /* A linked list of undefined and common symbols, linked through the
 119      next field in the bfd_link_hash_entry structure.  */
 120   struct bfd_link_hash_entry *undefs;
 121   /* Entries are added to the tail of the undefs list.  */
 122   struct bfd_link_hash_entry *undefs_tail;
 123 };
 124
 125 /* Look up an entry in a link hash table.  If FOLLOW is true, this
 126    follows bfd_link_hash_indirect and bfd_link_hash_warning links to
 127    the real symbol.  */
 128 extern struct bfd_link_hash_entry *bfd_link_hash_lookup
 129   PARAMS ((struct bfd_link_hash_table *, const char *, boolean create,
 130            boolean copy, boolean follow));
 131
 132 /* Traverse a link hash table.  */
 133 extern void bfd_link_hash_traverse
 134   PARAMS ((struct bfd_link_hash_table *,
 135            boolean (*) (struct bfd_link_hash_entry *, PTR),
 136            PTR));
 137
 138 /* Add an entry to the undefs list.  */
 139 extern void bfd_link_add_undef
 140   PARAMS ((struct bfd_link_hash_table *, struct bfd_link_hash_entry *));
 141 \f
 142 /* This structure holds all the information needed to communicate
 143    between BFD and the linker when doing a link.  */
 144
 145 struct bfd_link_info
 146 {
 147   /* Function callbacks.  */
 148   const struct bfd_link_callbacks *callbacks;
 149   /* true if BFD should generate a relocateable object file.  */
 150   boolean relocateable;
 151   /* Which symbols to strip.  */
 152   enum bfd_link_strip strip;
 153   /* Which local symbols to discard.  */
 154   enum bfd_link_discard discard;
 155   /* The local symbol prefix to discard if using discard_l.  */
 156   unsigned int lprefix_len;
 157   const char *lprefix;
 158   /* true if symbols should be retained in memory, false if they
 159      should be freed and reread.  */
 160   boolean keep_memory;
 161   /* The list of input BFD's involved in the link.  These are chained
 162      together via the link_next field.  */
 163   bfd *input_bfds;
 164   /* If a symbol should be created for each input BFD, this is section
 165      where those symbols should be placed.  It must be a section in
 166      the output BFD.  It may be NULL, in which case no such symbols
 167      will be created.  This is to support CREATE_OBJECT_SYMBOLS in the
 168      linker command language.  */
 169   asection *create_object_symbols_section;
 170   /* Hash table handled by BFD.  */
 171   struct bfd_link_hash_table *hash;
 172   /* Hash table of symbols to keep.  This is NULL unless strip is
 173      strip_some.  */
 174   struct bfd_hash_table *keep_hash;
 175   /* Hash table of symbols to report back via notice_callback.  If
 176      this is NULL no symbols are reported back.  */
 177   struct bfd_hash_table *notice_hash;
 178 };
 179
 180 /* This structures holds a set of callback functions.  These are
 181    called by the BFD linker routines.  The first argument to each
 182    callback function is the bfd_link_info structure being used.  Each
 183    function returns a boolean value.  If the function returns false,
 184    then the BFD function which called it will return with a failure
 185    indication.  */
 186
 187 struct bfd_link_callbacks
 188 {
 189   /* A function which is called when an object is added from an
 190      archive.  ABFD is the archive element being added.  NAME is the
 191      name of the symbol which caused the archive element to be pulled
 192      in.  */
 193   boolean (*add_archive_element) PARAMS ((struct bfd_link_info *,
 194                                           bfd *abfd,
 195                                           const char *name));
 196   /* A function which is called when a symbol is found with multiple
 197      definitions.  NAME is the symbol which is defined multiple times.
 198      OBFD is the old BFD, OSEC is the old section, OVAL is the old
 199      value, NBFD is the new BFD, NSEC is the new section, and NVAL is
 200      the new value.  OBFD may be NULL.  OSEC and NSEC may be
 201      bfd_com_section or bfd_ind_section.  */
 202   boolean (*multiple_definition) PARAMS ((struct bfd_link_info *,
 203                                           const char *name,
 204                                           bfd *obfd,
 205                                           asection *osec,
 206                                           bfd_vma oval,
 207                                           bfd *nbfd,
 208                                           asection *nsec,
 209                                           bfd_vma nval));
 210   /* A function which is called when a common symbol is defined
 211      multiple times.  NAME is the symbol appearing multiple times.
 212      OBFD is the BFD of the existing symbol.  OTYPE is the type of the
 213      existing symbol, either bfd_link_hash_defined or
 214      bfd_link_hash_common.  If OTYPE is bfd_link_hash_common, OSIZE is
 215      the size of the existing symbol.  NBFD is the BFD of the new
 216      symbol.  NTYPE is the type of the new symbol, either
 217      bfd_link_hash_defined or bfd_link_hash_common.  If NTYPE is
 218      bfd_link_hash_common, NSIZE is the size of the new symbol.  */
 219   boolean (*multiple_common) PARAMS ((struct bfd_link_info *,
 220                                       const char *name,
 221                                       bfd *obfd,
 222                                       enum bfd_link_hash_type otype,
 223                                       bfd_vma osize,
 224                                       bfd *nbfd,
 225                                       enum bfd_link_hash_type ntype,
 226                                       bfd_vma nsize));
 227   /* A function which is called to add a symbol to a set.  ENTRY is
 228      the link hash table entry for the set itself (e.g.,
 229      __CTOR_LIST__).  RELOC is the relocation to use for an entry in
 230      the set when generating a relocateable file, and is also used to
 231      get the size of the entry when generating an executable file.
 232      ABFD, SEC and VALUE identify the value to add to the set.  */
 233   boolean (*add_to_set) PARAMS ((struct bfd_link_info *,
 234                                  struct bfd_link_hash_entry *entry,
 235                                  bfd_reloc_code_real_type reloc,
 236                                  bfd *abfd, asection *sec, bfd_vma value));
 237   /* A function which is called when the name of a g++ constructor or
 238      destructor is found.  This is only called by some object file
 239      formats.  CONSTRUCTOR is true for a constructor, false for a
 240      destructor.  This will use BFD_RELOC_CTOR when generating a
 241      relocateable file.  NAME is the name of the symbol found.  ABFD,
 242      SECTION and VALUE are the value of the symbol.  */
 243   boolean (*constructor) PARAMS ((struct bfd_link_info *,
 244                                   boolean constructor,
 245                                   const char *name, bfd *abfd, asection *sec,
 246                                   bfd_vma value));
 247   /* A function which is called when there is a reference to a warning
 248      symbol.  WARNING is the warning to be issued.  */
 249   boolean (*warning) PARAMS ((struct bfd_link_info *,
 250                               const char *warning));
 251   /* A function which is called when a relocation is attempted against
 252      an undefined symbol.  NAME is the symbol which is undefined.
 253      ABFD, SECTION and ADDRESS identify the location from which the
 254      reference is made.  */
 255   boolean (*undefined_symbol) PARAMS ((struct bfd_link_info *,
 256                                        const char *name, bfd *abfd,
 257                                        asection *section, bfd_vma address));
 258   /* A function which is called when a reloc overflow occurs.  NAME is
 259      the name of the symbol or section the reloc is against,
 260      RELOC_NAME is the name of the relocation, and ADDEND is any
 261      addend that is used.  ABFD, SECTION and ADDRESS identify the
 262      location at which the overflow occurs; if this is the result of a
 263      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 264      ABFD will be NULL.  */
 265   boolean (*reloc_overflow) PARAMS ((struct bfd_link_info *,
 266                                      const char *name,
 267                                      const char *reloc_name, bfd_vma addend,
 268                                      bfd *abfd, asection *section,
 269                                      bfd_vma address));
 270   /* A function which is called when a dangerous reloc is performed.
 271      The canonical example is an a29k IHCONST reloc which does not
 272      follow an IHIHALF reloc.  MESSAGE is an appropriate message.
 273      ABFD, SECTION and ADDRESS identify the location at which the
 274      problem occurred; if this is the result of a
 275      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 276      ABFD will be NULL.  */
 277   boolean (*reloc_dangerous) PARAMS ((struct bfd_link_info *,
 278                                       const char *message,
 279                                       bfd *abfd, asection *section,
 280                                       bfd_vma address));
 281   /* A function which is called when a reloc is found to be attached
 282      to a symbol which is not being written out.  NAME is the name of
 283      the symbol.  ABFD, SECTION and ADDRESS identify the location of
 284      the reloc; if this is the result of a
 285      bfd_section_reloc_link_order or bfd_symbol_reloc_link_order, then
 286      ABFD will be NULL.  */
 287   boolean (*unattached_reloc) PARAMS ((struct bfd_link_info *,
 288                                        const char *name,
 289                                        bfd *abfd, asection *section,
 290                                        bfd_vma address));
 291   /* A function which is called when a symbol in notice_hash is
 292      defined or referenced.  NAME is the symbol.  ABFD, SECTION and
 293      ADDRESS are the value of the symbol.  If SECTION is
 294      bfd_und_section, this is a reference.  */
 295   boolean (*notice) PARAMS ((struct bfd_link_info *, const char *name,
 296                              bfd *abfd, asection *section, bfd_vma address));
 297 };
 298 \f
 299 /* The linker builds link_order structures which tell the code how to
 300    include input data in the output file.  */
 301
 302 /* These are the types of link_order structures.  */
 303
 304 enum bfd_link_order_type
 305 {
 306   bfd_undefined_link_order,     /* Undefined.  */
 307   bfd_indirect_link_order,      /* Built from a section.  */
 308   bfd_fill_link_order,          /* Fill with a 16 bit constant.  */
 309   bfd_data_link_order,          /* Set to explicit data.  */
 310   bfd_section_reloc_link_order, /* Relocate against a section.  */
 311   bfd_symbol_reloc_link_order   /* Relocate against a symbol.  */
 312 };
 313
 314 /* This is the link_order structure itself.  These form a chain
 315    attached to the section whose contents they are describing.  */
 316
 317 struct bfd_link_order
 318 {
 319   /* Next link_order in chain.  */
 320   struct bfd_link_order *next;
 321   /* Type of link_order.  */
 322   enum bfd_link_order_type type;
 323   /* Offset within output section.  */
 324   bfd_vma offset;
 325   /* Size within output section.  */
 326   bfd_size_type size;
 327   /* Type specific information.  */
 328   union
 329     {
 330       struct
 331         {
 332           /* Section to include.  If this is used, then
 333              section->output_section must be the section the
 334              link_order is attached to, section->output_offset must
 335              equal the link_order offset field, and section->_raw_size
 336              must equal the link_order size field.  Maybe these
 337              restrictions should be relaxed someday.  */
 338           asection *section;
 339         } indirect;
 340       struct
 341         {
 342           /* Value to fill with.  */
 343           unsigned int value;
 344         } fill;
 345       struct
 346         {
 347           /* Data to put into file.  The size field gives the number
 348              of bytes which this field points to.  */
 349           bfd_byte *contents;
 350         } data;
 351       struct
 352         {
 353           /* Description of reloc to generate.  Used for
 354              bfd_section_reloc_link_order and
 355              bfd_symbol_reloc_link_order.  */
 356           struct bfd_link_order_reloc *p;
 357         } reloc;
 358     } u;
 359 };
 360
 361 /* A linker order of type bfd_section_reloc_link_order or
 362    bfd_symbol_reloc_link_order means to create a reloc against a
 363    section or symbol, respectively.  This is used to implement -Ur to
 364    generate relocs for the constructor tables.  The
 365    bfd_link_order_reloc structure describes the reloc that BFD should
 366    create.  It is similar to a arelent, but I didn't use arelent
 367    because the linker does not know anything about most symbols, and
 368    any asymbol structure it creates will be partially meaningless.
 369    This information could logically be in the bfd_link_order struct,
 370    but I didn't want to waste the space since these types of relocs
 371    are relatively rare.  */
 372
 373 struct bfd_link_order_reloc
 374 {
 375   /* Reloc type.  */
 376   bfd_reloc_code_real_type reloc;
 377
 378   union
 379     {
 380       /* For type bfd_section_reloc_link_order, this is the section
 381          the reloc should be against.  This must be a section in the
 382          output BFD, not any of the input BFDs.  */
 383       asection *section;
 384       /* For type bfd_symbol_reloc_link_order, this is the name of the
 385          symbol the reloc should be against.  */
 386       const char *name;
 387     } u;
 388
 389   /* Addend to use.  The object file should contain zero.  The BFD
 390      backend is responsible for filling in the contents of the object
 391      file correctly.  For some object file formats (e.g., COFF) the
 392      addend must be stored into in the object file, and for some
 393      (e.g., SPARC a.out) it is kept in the reloc.  */
 394   bfd_vma addend;
 395 };
 396
 397 /* Allocate a new link_order for a section.  */
 398 extern struct bfd_link_order *bfd_new_link_order PARAMS ((bfd *, asection *));
 399
 400 #endif