1 /* Run-time dynamic linker data structures for loaded ELF shared objects.
2 Copyright (C) 1995-1999, 2000, 2001 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
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 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
33 #include <dl-lookupcfg.h>
34 #include <bits/libc-lock.h>
38 /* We use this macro to refer to ELF types independent of the native wordsize.
39 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
40 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
42 /* All references to the value of l_info[DT_PLTGOT],
43 l_info[DT_STRTAB], l_info[DT_SYMTAB], l_info[DT_RELA],
44 l_info[DT_REL], l_info[DT_JMPREL], and l_info[VERSYMIDX (DT_VERSYM)]
45 have to be accessed via the D_PTR macro. The macro is needed since for
46 most architectures the entry is already relocated - but for some not
47 and we need to relocate at access time. */
48 #ifdef DL_RO_DYN_SECTION
49 # define D_PTR(map,i) (map->i->d_un.d_ptr + map->l_addr)
51 # define D_PTR(map,i) map->i->d_un.d_ptr
54 /* On some platforms more information than just the address of the symbol
55 is needed from the lookup functions. In this case we return the whole
57 #ifdef DL_LOOKUP_RETURNS_MAP
58 typedef struct link_map *lookup_t;
59 # define LOOKUP_VALUE(map) map
60 # define LOOKUP_VALUE_ADDRESS(map) (map ? map->l_addr : 0)
62 typedef ElfW(Addr) lookup_t;
63 # define LOOKUP_VALUE(map) map->l_addr
64 # define LOOKUP_VALUE_ADDRESS(address) address
67 /* on some architectures a pointer to a function is not just a pointer
68 to the actual code of the function but rather an architecture
69 specific descriptor. */
70 #ifndef ELF_FUNCTION_PTR_IS_SPECIAL
71 # define DL_SYMBOL_ADDRESS(map, ref) \
72 (void *) (LOOKUP_VALUE_ADDRESS (map) + ref->st_value)
73 # define DL_LOOKUP_ADDRESS(addr) ((ElfW(Addr)) (addr))
74 # define DL_DT_INIT_ADDRESS(map, start) (start)
75 # define DL_DT_FINI_ADDRESS(map, start) (start)
78 /* Unmap a loaded object, called by _dl_close (). */
79 #ifndef DL_UNMAP_IS_SPECIAL
80 # define DL_UNMAP(map) \
81 __munmap ((void *) (map)->l_map_start, \
82 (map)->l_map_end - (map)->l_map_start)
85 /* By default we do not need special support to initialize DSOs loaded
86 by statically linked binaries. */
87 #ifndef DL_STATIC_INIT
88 # define DL_STATIC_INIT(map)
91 /* Reloc type classes as returned by elf_machine_type_class().
92 ELF_RTYPE_CLASS_PLT means this reloc should not be satisfied by
93 some PLT symbol, ELF_RTYPE_CLASS_COPY means this reloc should not be
94 satisfied by any symbol in the executable. */
95 #define ELF_RTYPE_CLASS_PLT 1
96 #define ELF_RTYPE_CLASS_COPY 2
98 /* For the version handling we need an array with only names and their
100 struct r_found_version
106 const char *filename;
109 /* We want to cache information about the searches for shared objects. */
111 enum r_dir_status { unknown, nonexisting, existing };
113 struct r_search_path_elem
115 /* This link is only used in the `all_dirs' member of `r_search_path'. */
116 struct r_search_path_elem *next;
118 /* Strings saying where the definition came from. */
122 /* Basename for this search path element. The string must end with
123 a slash character. */
127 enum r_dir_status status[0];
137 /* A data structure for a simple single linked list of strings. */
140 const char *name; /* Name requested (before search). */
141 struct libname_list *next; /* Link to next name for this object. */
142 int dont_free; /* Flag whether this element should be freed
143 if the object is not entirely unloaded. */
147 /* Test whether given NAME matches any of the names of the given object. */
149 __attribute__ ((unused))
150 _dl_name_match_p (const char *__name, struct link_map *__map)
152 int __found = strcmp (__name, __map->l_name) == 0;
153 struct libname_list *__runp = __map->l_libname;
155 while (! __found && __runp != NULL)
156 if (strcmp (__name, __runp->name) == 0)
159 __runp = __runp->next;
164 /* Function used as argument for `_dl_receive_error' function. The
165 arguments are the error code, error string, and the objname the
166 error occurred in. */
167 typedef void (*receiver_fct) (int, const char *, const char *);
169 /* Internal functions of the run-time dynamic linker.
170 These can be accessed if you link again the dynamic linker
171 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
172 but are not normally of interest to user programs.
174 The `-ldl' library functions in <dlfcn.h> provide a simple
175 user interface to run-time dynamic linking. */
178 /* Parameters passed to the dynamic linker. */
179 extern char **_dl_argv;
181 /* Cached value of `getpagesize ()'. */
182 extern size_t _dl_pagesize;
185 extern unsigned int _dl_osversion;
187 /* File descriptor referring to the zero-fill device. */
188 extern int _dl_zerofd;
190 /* Name of the shared object to be profiled (if any). */
191 extern const char *_dl_profile;
192 /* Map of shared object to be profiled. */
193 extern struct link_map *_dl_profile_map;
194 /* Filename of the output file. */
195 extern const char *_dl_profile_output;
197 /* If nonzero the appropriate debug information is printed. */
198 extern int _dl_debug_mask;
199 #define DL_DEBUG_LIBS (1 << 0)
200 #define DL_DEBUG_IMPCALLS (1 << 1)
201 #define DL_DEBUG_BINDINGS (1 << 2)
202 #define DL_DEBUG_SYMBOLS (1 << 3)
203 #define DL_DEBUG_VERSIONS (1 << 4)
204 #define DL_DEBUG_RELOC (1 << 5)
205 #define DL_DEBUG_FILES (1 << 6)
206 #define DL_DEBUG_STATISTICS (1 << 7)
207 /* This one is used only internally. */
208 #define DL_DEBUG_HELP (1 << 8)
210 /* Expect cache ID. */
211 extern int _dl_correct_cache_id;
213 /* Mask for hardware capabilities that are available. */
214 extern unsigned long int _dl_hwcap;
216 /* Mask for important hardware capabilities we honour. */
217 extern unsigned long int _dl_hwcap_mask;
219 /* File descriptor to write debug messages to. */
220 extern int _dl_debug_fd;
222 /* Names of shared object for which the RPATH should be ignored. */
223 extern const char *_dl_inhibit_rpath;
225 /* Nonzero if references should be treated as weak during runtime linking. */
226 extern int _dl_dynamic_weak;
228 /* The array with message we print as a last resort. */
229 extern const char _dl_out_of_memory[];
231 /* Nonzero if runtime lookups should not update the .got/.plt. */
232 extern int _dl_bind_not;
234 /* List of search directories. */
235 extern struct r_search_path_elem *_dl_all_dirs;
236 extern struct r_search_path_elem *_dl_init_all_dirs;
238 /* OS-dependent function to open the zero-fill device. */
239 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
242 /* During the program run we must not modify the global data of
243 loaded shared object simultanously in two threads. Therefore we
244 protect `_dl_open' and `_dl_close' in dl-close.c.
246 This must be a recursive lock since the initializer function of
247 the loaded object might as well require a call to this function.
248 At this time it is not anymore a problem to modify the tables. */
249 __libc_lock_define_recursive (extern, _dl_load_lock)
252 /* Write message on the debug file descriptor. The parameters are
253 interpreted as for a `printf' call. All the lines start with a
254 tag showing the PID. */
255 extern void _dl_debug_printf (const char *fmt, ...)
256 __attribute__ ((__format__ (__printf__, 1, 2)));
258 /* Write message on the debug file descriptor. The parameters are
259 interpreted as for a `printf' call. All the lines buf the first
260 start with a tag showing the PID. */
261 extern void _dl_debug_printf_c (const char *fmt, ...)
262 __attribute__ ((__format__ (__printf__, 1, 2)));
265 /* Write a message on the specified descriptor FD. The parameters are
266 interpreted as for a `printf' call. */
267 extern void _dl_dprintf (int fd, const char *fmt, ...)
268 __attribute__ ((__format__ (__printf__, 2, 3)));
270 /* Write a message on the specified descriptor standard output. The
271 parameters are interpreted as for a `printf' call. */
272 #define _dl_printf(fmt, args...) \
273 _dl_dprintf (STDOUT_FILENO, fmt, ##args)
275 /* Write a message on the specified descriptor standard error. The
276 parameters are interpreted as for a `printf' call. */
277 #define _dl_error_printf(fmt, args...) \
278 _dl_dprintf (STDERR_FILENO, fmt, ##args)
280 /* Write a message on the specified descriptor standard error and exit
281 the program. The parameters are interpreted as for a `printf' call. */
282 #define _dl_fatal_printf(fmt, args...) \
285 _dl_dprintf (STDERR_FILENO, fmt, ##args); \
291 /* This function is called by all the internal dynamic linker functions
292 when they encounter an error. ERRCODE is either an `errno' code or
293 zero; OBJECT is the name of the problematical shared object, or null if
294 it is a general problem; ERRSTRING is a string describing the specific
296 extern void _dl_signal_error (int errcode, const char *object,
297 const char *occurred, const char *errstring)
299 __attribute__ ((__noreturn__));
301 /* Like _dl_signal_error, but may return when called in the context of
302 _dl_receive_error. */
303 extern void _dl_signal_cerror (int errcode, const char *object,
304 const char *occation, const char *errstring)
307 /* Call OPERATE, receiving errors from `dl_signal_cerror'. Unlike
308 `_dl_catch_error' the operation is resumed after the OPERATE
310 ARGS is passed as argument to OPERATE. */
311 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
316 /* Open the shared object NAME and map in its segments.
317 LOADER's DT_RPATH is used in searching for NAME.
318 If the object is already opened, returns its existing map.
319 For preloaded shared objects PRELOADED is set to a non-zero
320 value to allow additional security checks. */
321 extern struct link_map *_dl_map_object (struct link_map *loader,
322 const char *name, int preloaded,
323 int type, int trace_mode, int mode)
326 /* Call _dl_map_object on the dependencies of MAP, and set up
327 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
328 loaded objects that will be inserted into MAP->l_searchlist after MAP
329 but before its dependencies. */
330 extern void _dl_map_object_deps (struct link_map *map,
331 struct link_map **preloads,
332 unsigned int npreloads, int trace_mode)
335 /* Cache the locations of MAP's hash table. */
336 extern void _dl_setup_hash (struct link_map *map) internal_function;
339 /* Search loaded objects' symbol tables for a definition of the symbol
340 referred to by UNDEF. *SYM is the symbol table entry containing the
341 reference; it is replaced with the defining symbol, and the base load
342 address of the defining object is returned. SYMBOL_SCOPE is a
343 null-terminated list of object scopes to search; each object's
344 l_searchlist (i.e. the segment of the dependency tree starting at that
345 object) is searched in turn. REFERENCE_NAME should name the object
346 containing the reference; it is used in error messages.
347 TYPE_CLASS describes the type of symbol we are looking for. */
348 extern lookup_t _dl_lookup_symbol (const char *undef,
349 struct link_map *undef_map,
350 const ElfW(Sym) **sym,
351 struct r_scope_elem *symbol_scope[],
352 int type_class, int explicit)
355 /* Lookup versioned symbol. */
356 extern lookup_t _dl_lookup_versioned_symbol (const char *undef,
357 struct link_map *undef_map,
358 const ElfW(Sym) **sym,
359 struct r_scope_elem *symbol_scope[],
360 const struct r_found_version *version,
361 int type_class, int explicit)
364 /* For handling RTLD_NEXT we must be able to skip shared objects. */
365 extern lookup_t _dl_lookup_symbol_skip (const char *undef,
366 struct link_map *undef_map,
367 const ElfW(Sym) **sym,
368 struct r_scope_elem *symbol_scope[],
369 struct link_map *skip_this)
372 /* For handling RTLD_NEXT with versioned symbols we must be able to
373 skip shared objects. */
374 extern lookup_t _dl_lookup_versioned_symbol_skip (const char *undef,
375 struct link_map *undef_map,
376 const ElfW(Sym) **sym,
377 struct r_scope_elem *symbol_scope[],
378 const struct r_found_version *version,
379 struct link_map *skip_this)
382 /* Look up symbol NAME in MAP's scope and return its run-time address. */
383 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
387 /* Structure describing the dynamic linker itself. */
388 extern struct link_map _dl_rtld_map;
389 /* And a pointer to the map for the main map. */
390 extern struct link_map *_dl_loaded;
391 /* Number of object in the _dl_loaded list. */
392 extern unsigned int _dl_nloaded;
393 /* Array representing global scope. */
394 extern struct r_scope_elem *_dl_global_scope[2];
395 /* Direct pointer to the searchlist of the main object. */
396 extern struct r_scope_elem *_dl_main_searchlist;
397 /* Copy of the content of `_dl_main_searchlist'. */
398 extern struct r_scope_elem _dl_initial_searchlist;
399 /* This is zero at program start to signal that the global scope map is
400 allocated by rtld. Later it keeps the size of the map. It might be
401 reset if in _dl_close if the last global object is removed. */
402 extern size_t _dl_global_scope_alloc;
404 /* Allocate a `struct link_map' for a new object being loaded,
405 and enter it into the _dl_main_map list. */
406 extern struct link_map *_dl_new_object (char *realname, const char *libname,
407 int type, struct link_map *loader)
410 /* Relocate the given object (if it hasn't already been).
411 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
412 If LAZY is nonzero, don't relocate its PLT. */
413 extern void _dl_relocate_object (struct link_map *map,
414 struct r_scope_elem *scope[],
415 int lazy, int consider_profiling);
417 /* Call _dl_signal_error with a message about an unhandled reloc type.
418 TYPE is the result of ELFW(R_TYPE) (r_info), i.e. an R_<CPU>_* value.
419 PLT is nonzero if this was a PLT reloc; it just affects the message. */
420 extern void _dl_reloc_bad_type (struct link_map *map,
421 unsigned int type, int plt)
422 internal_function __attribute__ ((__noreturn__));
424 /* Check the version dependencies of all objects available through
425 MAP. If VERBOSE print some more diagnostics. */
426 extern int _dl_check_all_versions (struct link_map *map, int verbose,
430 /* Check the version dependencies for MAP. If VERBOSE print some more
432 extern int _dl_check_map_versions (struct link_map *map, int verbose,
436 /* Initialize the object in SCOPE by calling the constructors with
437 ARGC, ARGV, and ENV as the parameters. */
438 extern void _dl_init (struct link_map *main_map, int argc, char **argv,
439 char **env) internal_function;
441 /* Call the finalizer functions of all shared objects whose
442 initializer functions have completed. */
443 extern void _dl_fini (void) internal_function;
445 /* The dynamic linker calls this function before and having changing
446 any shared object mappings. The `r_state' member of `struct r_debug'
447 says what change is taking place. This function's address is
448 the value of the `r_brk' member. */
449 extern void _dl_debug_state (void);
451 /* Initialize `struct r_debug' if it has not already been done. The
452 argument is the run-time load address of the dynamic linker, to be put
453 in the `r_ldbase' member. Returns the address of the structure. */
454 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
457 /* Initialize the basic data structure for the search paths. */
458 extern void _dl_init_paths (const char *library_path) internal_function;
460 /* Gather the information needed to install the profiling tables and start
462 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
465 /* The actual functions used to keep book on the calls. */
466 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
468 /* This function is simply a wrapper around the _dl_mcount function
469 which does not require a FROMPC parameter since this is the
471 extern void _dl_mcount_wrapper (void *selfpc);
473 /* Show the members of the auxiliary array passed up from the kernel. */
474 extern void _dl_show_auxv (void) internal_function;
476 /* Return all environment variables starting with `LD_', one after the
478 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
480 /* Return an array with the names of the important hardware capabilities. */
481 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
484 size_t *max_capstrlen)
487 /* Look up NAME in ld.so.cache and return the file name stored there,
488 or null if none is found. */
489 extern const char *_dl_load_cache_lookup (const char *name)
492 /* If the system does not support MAP_COPY we cannot leave the file open
493 all the time since this would create problems when the file is replaced.
494 Therefore we provide this function to close the file and open it again
496 extern void _dl_unload_cache (void);
498 /* System-dependent function to read a file's whole contents
499 in the most convenient manner available. */
500 extern void *_dl_sysdep_read_whole_file (const char *file, size_t *sizep,
504 /* System-specific function to do initial startup for the dynamic linker.
505 After this, file access calls and getenv must work. This is responsible
506 for setting __libc_enable_secure if we need to be secure (e.g. setuid),
507 and for setting _dl_argc and _dl_argv, and then calling _dl_main. */
508 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
509 void (*dl_main) (const ElfW(Phdr) *phdr,
511 ElfW(Addr) *user_entry));
513 extern void _dl_sysdep_start_cleanup (void)
519 #endif /* ldsodefs.h */