elf/ldsodefs.h

   1 /* Run-time dynamic linker data structures for loaded ELF shared objects.
   2    Copyright (C) 1995, 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #ifndef _LDSODEFS_H
  21 #define _LDSODEFS_H     1
  22
  23 #include <features.h>
  24
  25 #define __need_size_t
  26 #define __need_NULL
  27 #include <stddef.h>
  28
  29 #include <elf.h>
  30 #include <dlfcn.h>
  31 #include <link.h>
  32
  33 __BEGIN_DECLS
  34
  35 /* We use this macro to refer to ELF types independent of the native wordsize.
  36    `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
  37 #define ELFW(type)      _ElfW (ELF, __ELF_NATIVE_CLASS, type)
  38
  39 /* For the version handling we need an array with only names and their
  40    hash values.  */
  41 struct r_found_version
  42   {
  43     const char *name;
  44     ElfW(Word) hash;
  45
  46     int hidden;
  47     const char *filename;
  48   };
  49
  50 /* We want to cache information about the searches for shared objects.  */
  51
  52 enum r_dir_status { unknown, nonexisting, existing };
  53
  54 struct r_search_path_elem
  55   {
  56     /* This link is only used in the `all_dirs' member of `r_search_path'.  */
  57     struct r_search_path_elem *next;
  58
  59     /* Strings saying where the definition came from.  */
  60     const char *what;
  61     const char *where;
  62
  63     /* Basename for this search path element.  The string must end with
  64        a slash character.  */
  65     const char *dirname;
  66     size_t dirnamelen;
  67
  68     enum r_dir_status status[0];
  69   };
  70
  71 struct r_strlenpair
  72   {
  73     const char *str;
  74     size_t len;
  75   };
  76
  77
  78 /* A data structure for a simple single linked list of strings.  */
  79 struct libname_list
  80   {
  81     const char *name;           /* Name requested (before search).  */
  82     struct libname_list *next;  /* Link to next name for this object.  */
  83   };
  84
  85
  86 /* Test whether given NAME matches any of the names of the given object.  */
  87 static __inline int
  88 __attribute__ ((unused))
  89 _dl_name_match_p (const char *__name, struct link_map *__map)
  90 {
  91   int __found = strcmp (__name, __map->l_name) == 0;
  92   struct libname_list *__runp = __map->l_libname;
  93
  94   while (! __found && __runp != NULL)
  95     if (strcmp (__name, __runp->name) == 0)
  96       __found = 1;
  97     else
  98       __runp = __runp->next;
  99
 100   return __found;
 101 }
 102
 103 /* Function used as argument for `_dl_receive_error' function.  The
 104    arguments are the error code, error string, and the objname the
 105    error occurred in.  */
 106 typedef void (*receiver_fct) (int, const char *, const char *);
 107 \f
 108 /* Internal functions of the run-time dynamic linker.
 109    These can be accessed if you link again the dynamic linker
 110    as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
 111    but are not normally of interest to user programs.
 112
 113    The `-ldl' library functions in <dlfcn.h> provide a simple
 114    user interface to run-time dynamic linking.  */
 115
 116
 117 /* Parameters passed to the dynamic linker.  */
 118 extern char **_dl_argv;
 119
 120 /* Cached value of `getpagesize ()'.  */
 121 extern size_t _dl_pagesize;
 122
 123 /* File descriptor referring to the zero-fill device.  */
 124 extern int _dl_zerofd;
 125
 126 /* Name of the shared object to be profiled (if any).  */
 127 extern const char *_dl_profile;
 128 /* Map of shared object to be profiled.  */
 129 extern struct link_map *_dl_profile_map;
 130 /* Filename of the output file.  */
 131 extern const char *_dl_profile_output;
 132
 133 /* If nonzero the appropriate debug information is printed.  */
 134 extern int _dl_debug_libs;
 135 extern int _dl_debug_impcalls;
 136 extern int _dl_debug_bindings;
 137 extern int _dl_debug_symbols;
 138 extern int _dl_debug_versions;
 139 extern int _dl_debug_reloc;
 140 extern int _dl_debug_files;
 141
 142 /* Expect cache ID.  */
 143 extern int _dl_correct_cache_id;
 144
 145 /* Mask for hardware capabilities that are available.  */
 146 extern unsigned long int _dl_hwcap;
 147
 148 /* Mask for important hardware capabilities we honour. */
 149 extern unsigned long int _dl_hwcap_mask;
 150
 151 /* File descriptor to write debug messages to.  */
 152 extern int _dl_debug_fd;
 153
 154 /* Names of shared object for which the RPATH should be ignored.  */
 155 extern const char *_dl_inhibit_rpath;
 156
 157 /* OS-dependent function to open the zero-fill device.  */
 158 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
 159
 160 /* OS-dependent function to write a message on the specified
 161    descriptor FD.  All arguments are `const char *'; args until a null
 162    pointer are concatenated to form the message to print.  */
 163 extern void _dl_sysdep_output (int fd, const char *string, ...);
 164
 165 /* OS-dependent function to write a debug message on the specified
 166    descriptor for this.  All arguments are `const char *'; args until
 167    a null pointer are concatenated to form the message to print.  If
 168    NEW_LINE is nonzero it is assumed that the message starts on a new
 169    line.  */
 170 extern void _dl_debug_message (int new_line, const char *string, ...);
 171
 172 /* OS-dependent function to write a message on the standard output.
 173    All arguments are `const char *'; args until a null pointer
 174    are concatenated to form the message to print.  */
 175 #define _dl_sysdep_message(string, args...) \
 176   _dl_sysdep_output (STDOUT_FILENO, string, ##args)
 177
 178 /* OS-dependent function to write a message on the standard error.
 179    All arguments are `const char *'; args until a null pointer
 180    are concatenated to form the message to print.  */
 181 #define _dl_sysdep_error(string, args...) \
 182   _dl_sysdep_output (STDERR_FILENO, string, ##args)
 183
 184 /* OS-dependent function to give a fatal error message and exit
 185    when the dynamic linker fails before the program is fully linked.
 186    All arguments are `const char *'; args until a null pointer
 187    are concatenated to form the message to print.  */
 188 #define _dl_sysdep_fatal(string, args...) \
 189   do                                                                          \
 190     {                                                                         \
 191       _dl_sysdep_output (STDERR_FILENO, string, ##args);                      \
 192       _exit (127);                                                            \
 193     }                                                                         \
 194   while (1)
 195
 196 /* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch).
 197    This tells the dynamic linker to ignore environment variables.  */
 198 extern int _dl_secure;
 199
 200 /* This function is called by all the internal dynamic linker functions
 201    when they encounter an error.  ERRCODE is either an `errno' code or
 202    zero; OBJECT is the name of the problematical shared object, or null if
 203    it is a general problem; ERRSTRING is a string describing the specific
 204    problem.  */
 205 extern void _dl_signal_error (int errcode,
 206                               const char *object,
 207                               const char *errstring)
 208      internal_function
 209      __attribute__ ((__noreturn__));
 210
 211 /* Like _dl_signal_error, but may return when called in the context of
 212    _dl_receive_error.  */
 213 extern void _dl_signal_cerror (int errcode,
 214                                const char *object,
 215                                const char *errstring)
 216      internal_function;
 217
 218 /* Call OPERATE, catching errors from `dl_signal_error'.  If there is no
 219    error, *ERRSTRING is set to null.  If there is an error, *ERRSTRING is
 220    set to a string constructed from the strings passed to _dl_signal_error,
 221    and the error code passed is the return value.  ERRSTRING if nonzero
 222    points to a malloc'ed string which the caller has to free after use.
 223    ARGS is passed as argument to OPERATE.  */
 224 extern int _dl_catch_error (char **errstring,
 225                             void (*operate) (void *),
 226                             void *args)
 227      internal_function;
 228
 229 /* Call OPERATE, receiving errors from `dl_signal_cerror'.  Unlike
 230    `_dl_catch_error' the operation is resumed after the OPERATE
 231    function returns.
 232    ARGS is passed as argument to OPERATE.  */
 233 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
 234                                void *args)
 235      internal_function;
 236
 237
 238 /* Helper function for <dlfcn.h> functions.  Runs the OPERATE function via
 239    _dl_catch_error.  Returns zero for success, nonzero for failure; and
 240    arranges for `dlerror' to return the error details.
 241    ARGS is passed as argument to OPERATE.  */
 242 extern int _dlerror_run (void (*operate) (void *), void *args)
 243      internal_function;
 244
 245
 246 /* Open the shared object NAME and map in its segments.
 247    LOADER's DT_RPATH is used in searching for NAME.
 248    If the object is already opened, returns its existing map.
 249    For preloaded shared objects PRELOADED is set to a non-zero
 250    value to allow additional security checks.  */
 251 extern struct link_map *_dl_map_object (struct link_map *loader,
 252                                         const char *name, int preloaded,
 253                                         int type, int trace_mode)
 254      internal_function;
 255
 256 /* Call _dl_map_object on the dependencies of MAP, and set up
 257    MAP->l_searchlist.  PRELOADS points to a vector of NPRELOADS previously
 258    loaded objects that will be inserted into MAP->l_searchlist after MAP
 259    but before its dependencies.  */
 260 extern unsigned int _dl_map_object_deps (struct link_map *map,
 261                                          struct link_map **preloads,
 262                                          unsigned int npreloads,
 263                                          int trace_mode, int global_scope)
 264      internal_function;
 265
 266 /* Cache the locations of MAP's hash table.  */
 267 extern void _dl_setup_hash (struct link_map *map) internal_function;
 268
 269
 270 /* Open the shared object NAME, relocate it, and run its initializer if it
 271    hasn't already been run.  MODE is as for `dlopen' (see <dlfcn.h>).  If
 272    the object is already opened, returns its existing map.  */
 273 extern struct link_map *_dl_open (const char *name, int mode)
 274      internal_function;
 275
 276 /* Close an object previously opened by _dl_open.  */
 277 extern void _dl_close (struct link_map *map)
 278      internal_function;
 279
 280
 281 /* Search loaded objects' symbol tables for a definition of the symbol
 282    referred to by UNDEF.  *SYM is the symbol table entry containing the
 283    reference; it is replaced with the defining symbol, and the base load
 284    address of the defining object is returned.  SYMBOL_SCOPE is a
 285    null-terminated list of object scopes to search; each object's
 286    l_searchlist (i.e. the segment of the dependency tree starting at that
 287    object) is searched in turn.  REFERENCE_NAME should name the object
 288    containing the reference; it is used in error messages.
 289    RELOC_TYPE is a machine-dependent reloc type, which is passed to
 290    the `elf_machine_lookup_*_p' macros in dl-machine.h to affect which
 291    symbols can be chosen.  */
 292 extern ElfW(Addr) _dl_lookup_symbol (const char *undef,
 293                                      const ElfW(Sym) **sym,
 294                                      struct r_scope_elem *symbol_scope[],
 295                                      const char *reference_name,
 296                                      int reloc_type)
 297      internal_function;
 298
 299 /* Lookup versioned symbol.  */
 300 extern ElfW(Addr) _dl_lookup_versioned_symbol (const char *undef,
 301                                                const ElfW(Sym) **sym,
 302                                                struct r_scope_elem *symbol_scope[],
 303                                                const char *reference_name,
 304                                                const struct r_found_version *version,
 305                                                int reloc_type)
 306      internal_function;
 307
 308 /* For handling RTLD_NEXT we must be able to skip shared objects.  */
 309 extern ElfW(Addr) _dl_lookup_symbol_skip (const char *undef,
 310                                           const ElfW(Sym) **sym,
 311                                           struct r_scope_elem *symbol_scope[],
 312                                           const char *reference_name,
 313                                           struct link_map *skip_this)
 314      internal_function;
 315
 316 /* For handling RTLD_NEXT with versioned symbols we must be able to
 317    skip shared objects.  */
 318 extern ElfW(Addr) _dl_lookup_versioned_symbol_skip (const char *undef,
 319                                                     const ElfW(Sym) **sym,
 320                                                     struct r_scope_elem *symbol_scope[],
 321                                                     const char *reference_name,
 322                                                     const struct r_found_version *version,
 323                                                     struct link_map *skip_this)
 324      internal_function;
 325
 326 /* Locate shared object containing the given address.  */
 327 extern int _dl_addr (const void *address, Dl_info *info)
 328      internal_function;
 329
 330 /* Look up symbol NAME in MAP's scope and return its run-time address.  */
 331 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
 332      internal_function;
 333
 334
 335 /* Structure describing the dynamic linker itself.  */
 336 extern struct link_map _dl_rtld_map;
 337 /* And a pointer to the map for the main map.  */
 338 extern struct link_map *_dl_loaded;
 339 /* Array representing global scope.  */
 340 extern struct r_scope_elem *_dl_global_scope[2];
 341 /* Direct pointer to the searchlist of the main object.  */
 342 extern struct r_scope_elem *_dl_main_searchlist;
 343 /* Copy of the content of `_dl_main_searchlist'.  */
 344 extern struct r_scope_elem _dl_initial_searchlist;
 345 /* This is zero at program start to signal that the global scope map is
 346    allocated by rtld.  Later it keeps the size of the map.  It might be
 347    reset if in _dl_close if the last global object is removed.  */
 348 extern size_t _dl_global_scope_alloc;
 349
 350 /* Allocate a `struct link_map' for a new object being loaded,
 351    and enter it into the _dl_main_map list.  */
 352 extern struct link_map *_dl_new_object (char *realname, const char *libname,
 353                                         int type, struct link_map *loader)
 354      internal_function;
 355
 356 /* Relocate the given object (if it hasn't already been).
 357    SCOPE is passed to _dl_lookup_symbol in symbol lookups.
 358    If LAZY is nonzero, don't relocate its PLT.  */
 359 extern void _dl_relocate_object (struct link_map *map,
 360                                  struct r_scope_elem *scope[],
 361                                  int lazy, int consider_profiling);
 362
 363 /* Check the version dependencies of all objects available through
 364    MAP.  If VERBOSE print some more diagnostics.  */
 365 extern int _dl_check_all_versions (struct link_map *map, int verbose)
 366      internal_function;
 367
 368 /* Check the version dependencies for MAP.  If VERBOSE print some more
 369    diagnostics.  */
 370 extern int _dl_check_map_versions (struct link_map *map, int verbose)
 371      internal_function;
 372
 373 /* Return the address of the next initializer function for SCOPE or one of
 374    its dependencies that has not yet been run.  When there are no more
 375    initializers to be run, this returns zero.  The functions are returned
 376    in the order they should be called.  */
 377 extern ElfW(Addr) _dl_init_next (struct r_scope_elem *scope) internal_function;
 378
 379 /* Call the finalizer functions of all shared objects whose
 380    initializer functions have completed.  */
 381 extern void _dl_fini (void) internal_function;
 382
 383 /* The dynamic linker calls this function before and having changing
 384    any shared object mappings.  The `r_state' member of `struct r_debug'
 385    says what change is taking place.  This function's address is
 386    the value of the `r_brk' member.  */
 387 extern void _dl_debug_state (void);
 388
 389 /* Initialize `struct r_debug' if it has not already been done.  The
 390    argument is the run-time load address of the dynamic linker, to be put
 391    in the `r_ldbase' member.  Returns the address of the structure.  */
 392 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
 393      internal_function;
 394
 395 /* Initialize the basic data structure for the search paths.  */
 396 extern void _dl_init_paths (const char *library_path) internal_function;
 397
 398 /* Gather the information needed to install the profiling tables and start
 399    the timers.  */
 400 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
 401      internal_function;
 402
 403 /* The actual functions used to keep book on the calls.  */
 404 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
 405
 406 /* This function is simply a wrapper around the _dl_mcount function
 407    which does not require a FROMPC parameter since this is the
 408    calling function.  */
 409 extern void _dl_mcount_wrapper (ElfW(Addr) selfpc);
 410
 411
 412 /* Show the members of the auxiliary array passed up from the kernel.  */
 413 extern void _dl_show_auxv (void) internal_function;
 414
 415 /* Return all environment variables starting with `LD_', one after the
 416    other.  */
 417 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
 418
 419 /* Return an array with the names of the important hardware capabilities.  */
 420 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
 421                                                         size_t paltform_len,
 422                                                         size_t *sz,
 423                                                         size_t *max_capstrlen)
 424      internal_function;
 425
 426
 427 /* When we do profiling we have the problem that uses of `dlopen'ed
 428    objects don't use the PLT but instead use a pointer to the function.
 429    We still want to have profiling data and in these cases we must do
 430    the work of calling `_dl_mcount' ourself.  The following macros
 431    helps do it.  */
 432 #define _CALL_DL_FCT(fctp, args) \
 433   ({ if (_dl_profile_map != NULL)                                             \
 434        _dl_mcount_wrapper ((ElfW(Addr)) fctp);                                \
 435      (*fctp) args;                                                            \
 436   })
 437
 438 __END_DECLS
 439
 440 #endif /* ldsodefs.h */