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 /* For the version handling we need an array with only names and their
93 struct r_found_version
102 /* We want to cache information about the searches for shared objects. */
104 enum r_dir_status { unknown, nonexisting, existing };
106 struct r_search_path_elem
108 /* This link is only used in the `all_dirs' member of `r_search_path'. */
109 struct r_search_path_elem *next;
111 /* Strings saying where the definition came from. */
115 /* Basename for this search path element. The string must end with
116 a slash character. */
120 enum r_dir_status status[0];
130 /* A data structure for a simple single linked list of strings. */
133 const char *name; /* Name requested (before search). */
134 struct libname_list *next; /* Link to next name for this object. */
135 int dont_free; /* Flag whether this element should be freed
136 if the object is not entirely unloaded. */
140 /* Test whether given NAME matches any of the names of the given object. */
142 __attribute__ ((unused))
143 _dl_name_match_p (const char *__name, struct link_map *__map)
145 int __found = strcmp (__name, __map->l_name) == 0;
146 struct libname_list *__runp = __map->l_libname;
148 while (! __found && __runp != NULL)
149 if (strcmp (__name, __runp->name) == 0)
152 __runp = __runp->next;
157 /* Function used as argument for `_dl_receive_error' function. The
158 arguments are the error code, error string, and the objname the
159 error occurred in. */
160 typedef void (*receiver_fct) (int, const char *, const char *);
162 /* Internal functions of the run-time dynamic linker.
163 These can be accessed if you link again the dynamic linker
164 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
165 but are not normally of interest to user programs.
167 The `-ldl' library functions in <dlfcn.h> provide a simple
168 user interface to run-time dynamic linking. */
171 /* Parameters passed to the dynamic linker. */
172 extern char **_dl_argv;
174 /* Cached value of `getpagesize ()'. */
175 extern size_t _dl_pagesize;
178 extern unsigned int _dl_osversion;
180 /* File descriptor referring to the zero-fill device. */
181 extern int _dl_zerofd;
183 /* Name of the shared object to be profiled (if any). */
184 extern const char *_dl_profile;
185 /* Map of shared object to be profiled. */
186 extern struct link_map *_dl_profile_map;
187 /* Filename of the output file. */
188 extern const char *_dl_profile_output;
190 /* If nonzero the appropriate debug information is printed. */
191 extern int _dl_debug_mask;
192 #define DL_DEBUG_LIBS (1 << 0)
193 #define DL_DEBUG_IMPCALLS (1 << 1)
194 #define DL_DEBUG_BINDINGS (1 << 2)
195 #define DL_DEBUG_SYMBOLS (1 << 3)
196 #define DL_DEBUG_VERSIONS (1 << 4)
197 #define DL_DEBUG_RELOC (1 << 5)
198 #define DL_DEBUG_FILES (1 << 6)
199 #define DL_DEBUG_STATISTICS (1 << 7)
201 /* Expect cache ID. */
202 extern int _dl_correct_cache_id;
204 /* Mask for hardware capabilities that are available. */
205 extern unsigned long int _dl_hwcap;
207 /* Mask for important hardware capabilities we honour. */
208 extern unsigned long int _dl_hwcap_mask;
210 /* File descriptor to write debug messages to. */
211 extern int _dl_debug_fd;
213 /* Names of shared object for which the RPATH should be ignored. */
214 extern const char *_dl_inhibit_rpath;
216 /* Nonzero if references should be treated as weak during runtime linking. */
217 extern int _dl_dynamic_weak;
219 /* The array with message we print as a last resort. */
220 extern const char _dl_out_of_memory[];
222 /* Nonzero if runtime lookups should not update the .got/.plt. */
223 extern int _dl_bind_not;
225 /* List of search directories. */
226 extern struct r_search_path_elem *_dl_all_dirs;
227 extern struct r_search_path_elem *_dl_init_all_dirs;
229 /* OS-dependent function to open the zero-fill device. */
230 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
233 /* During the program run we must not modify the global data of
234 loaded shared object simultanously in two threads. Therefore we
235 protect `_dl_open' and `_dl_close' in dl-close.c.
237 This must be a recursive lock since the initializer function of
238 the loaded object might as well require a call to this function.
239 At this time it is not anymore a problem to modify the tables. */
240 __libc_lock_define_recursive (extern, _dl_load_lock)
243 /* Write message on the debug file descriptor. The parameters are
244 interpreted as for a `printf' call. All the lines start with a
245 tag showing the PID. */
246 extern void _dl_debug_printf (const char *fmt, ...)
247 __attribute__ ((__format__ (__printf__, 1, 2)));
249 /* Write message on the debug file descriptor. The parameters are
250 interpreted as for a `printf' call. All the lines buf the first
251 start with a tag showing the PID. */
252 extern void _dl_debug_printf_c (const char *fmt, ...)
253 __attribute__ ((__format__ (__printf__, 1, 2)));
256 /* Write a message on the specified descriptor FD. The parameters are
257 interpreted as for a `printf' call. */
258 extern void _dl_dprintf (int fd, const char *fmt, ...)
259 __attribute__ ((__format__ (__printf__, 2, 3)));
261 /* Write a message on the specified descriptor standard output. The
262 parameters are interpreted as for a `printf' call. */
263 #define _dl_printf(fmt, args...) \
264 _dl_dprintf (STDOUT_FILENO, fmt, ##args)
266 /* Write a message on the specified descriptor standard error. The
267 parameters are interpreted as for a `printf' call. */
268 #define _dl_error_printf(fmt, args...) \
269 _dl_dprintf (STDERR_FILENO, fmt, ##args)
271 /* Write a message on the specified descriptor standard error and exit
272 the program. The parameters are interpreted as for a `printf' call. */
273 #define _dl_fatal_printf(fmt, args...) \
276 _dl_dprintf (STDERR_FILENO, fmt, ##args); \
282 /* This function is called by all the internal dynamic linker functions
283 when they encounter an error. ERRCODE is either an `errno' code or
284 zero; OBJECT is the name of the problematical shared object, or null if
285 it is a general problem; ERRSTRING is a string describing the specific
287 extern void _dl_signal_error (int errcode, const char *object,
288 const char *errstring)
290 __attribute__ ((__noreturn__));
292 /* Like _dl_signal_error, but may return when called in the context of
293 _dl_receive_error. */
294 extern void _dl_signal_cerror (int errcode,
296 const char *errstring)
299 /* Call OPERATE, receiving errors from `dl_signal_cerror'. Unlike
300 `_dl_catch_error' the operation is resumed after the OPERATE
302 ARGS is passed as argument to OPERATE. */
303 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
308 /* Open the shared object NAME and map in its segments.
309 LOADER's DT_RPATH is used in searching for NAME.
310 If the object is already opened, returns its existing map.
311 For preloaded shared objects PRELOADED is set to a non-zero
312 value to allow additional security checks. */
313 extern struct link_map *_dl_map_object (struct link_map *loader,
314 const char *name, int preloaded,
315 int type, int trace_mode, int mode)
318 /* Call _dl_map_object on the dependencies of MAP, and set up
319 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
320 loaded objects that will be inserted into MAP->l_searchlist after MAP
321 but before its dependencies. */
322 extern void _dl_map_object_deps (struct link_map *map,
323 struct link_map **preloads,
324 unsigned int npreloads, int trace_mode)
327 /* Cache the locations of MAP's hash table. */
328 extern void _dl_setup_hash (struct link_map *map) internal_function;
331 /* Search loaded objects' symbol tables for a definition of the symbol
332 referred to by UNDEF. *SYM is the symbol table entry containing the
333 reference; it is replaced with the defining symbol, and the base load
334 address of the defining object is returned. SYMBOL_SCOPE is a
335 null-terminated list of object scopes to search; each object's
336 l_searchlist (i.e. the segment of the dependency tree starting at that
337 object) is searched in turn. REFERENCE_NAME should name the object
338 containing the reference; it is used in error messages.
339 RELOC_TYPE is a machine-dependent reloc type, which is passed to
340 the `elf_machine_lookup_*_p' macros in dl-machine.h to affect which
341 symbols can be chosen. */
342 extern lookup_t _dl_lookup_symbol (const char *undef,
343 struct link_map *undef_map,
344 const ElfW(Sym) **sym,
345 struct r_scope_elem *symbol_scope[],
346 int reloc_type, int explicit)
349 /* Lookup versioned symbol. */
350 extern lookup_t _dl_lookup_versioned_symbol (const char *undef,
351 struct link_map *undef_map,
352 const ElfW(Sym) **sym,
353 struct r_scope_elem *symbol_scope[],
354 const struct r_found_version *version,
355 int reloc_type, int explicit)
358 /* For handling RTLD_NEXT we must be able to skip shared objects. */
359 extern lookup_t _dl_lookup_symbol_skip (const char *undef,
360 struct link_map *undef_map,
361 const ElfW(Sym) **sym,
362 struct r_scope_elem *symbol_scope[],
363 struct link_map *skip_this)
366 /* For handling RTLD_NEXT with versioned symbols we must be able to
367 skip shared objects. */
368 extern lookup_t _dl_lookup_versioned_symbol_skip (const char *undef,
369 struct link_map *undef_map,
370 const ElfW(Sym) **sym,
371 struct r_scope_elem *symbol_scope[],
372 const struct r_found_version *version,
373 struct link_map *skip_this)
376 /* Look up symbol NAME in MAP's scope and return its run-time address. */
377 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
381 /* Structure describing the dynamic linker itself. */
382 extern struct link_map _dl_rtld_map;
383 /* And a pointer to the map for the main map. */
384 extern struct link_map *_dl_loaded;
385 /* Number of object in the _dl_loaded list. */
386 extern unsigned int _dl_nloaded;
387 /* Array representing global scope. */
388 extern struct r_scope_elem *_dl_global_scope[2];
389 /* Direct pointer to the searchlist of the main object. */
390 extern struct r_scope_elem *_dl_main_searchlist;
391 /* Copy of the content of `_dl_main_searchlist'. */
392 extern struct r_scope_elem _dl_initial_searchlist;
393 /* This is zero at program start to signal that the global scope map is
394 allocated by rtld. Later it keeps the size of the map. It might be
395 reset if in _dl_close if the last global object is removed. */
396 extern size_t _dl_global_scope_alloc;
398 /* Allocate a `struct link_map' for a new object being loaded,
399 and enter it into the _dl_main_map list. */
400 extern struct link_map *_dl_new_object (char *realname, const char *libname,
401 int type, struct link_map *loader)
404 /* Relocate the given object (if it hasn't already been).
405 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
406 If LAZY is nonzero, don't relocate its PLT. */
407 extern void _dl_relocate_object (struct link_map *map,
408 struct r_scope_elem *scope[],
409 int lazy, int consider_profiling);
411 /* Call _dl_signal_error with a message about an unhandled reloc type.
412 TYPE is the result of ELFW(R_TYPE) (r_info), i.e. an R_<CPU>_* value.
413 PLT is nonzero if this was a PLT reloc; it just affects the message. */
414 extern void _dl_reloc_bad_type (struct link_map *map,
415 uint_fast8_t type, int plt)
417 __attribute__ ((__noreturn__));
419 /* Check the version dependencies of all objects available through
420 MAP. If VERBOSE print some more diagnostics. */
421 extern int _dl_check_all_versions (struct link_map *map, int verbose,
425 /* Check the version dependencies for MAP. If VERBOSE print some more
427 extern int _dl_check_map_versions (struct link_map *map, int verbose,
431 /* Initialize the object in SCOPE by calling the constructors with
432 ARGC, ARGV, and ENV as the parameters. */
433 extern void _dl_init (struct link_map *main_map, int argc, char **argv,
434 char **env) internal_function;
436 /* Call the finalizer functions of all shared objects whose
437 initializer functions have completed. */
438 extern void _dl_fini (void) internal_function;
440 /* The dynamic linker calls this function before and having changing
441 any shared object mappings. The `r_state' member of `struct r_debug'
442 says what change is taking place. This function's address is
443 the value of the `r_brk' member. */
444 extern void _dl_debug_state (void);
446 /* Initialize `struct r_debug' if it has not already been done. The
447 argument is the run-time load address of the dynamic linker, to be put
448 in the `r_ldbase' member. Returns the address of the structure. */
449 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
452 /* Initialize the basic data structure for the search paths. */
453 extern void _dl_init_paths (const char *library_path) internal_function;
455 /* Gather the information needed to install the profiling tables and start
457 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
460 /* The actual functions used to keep book on the calls. */
461 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
463 /* This function is simply a wrapper around the _dl_mcount function
464 which does not require a FROMPC parameter since this is the
466 extern void _dl_mcount_wrapper (void *selfpc);
468 /* Show the members of the auxiliary array passed up from the kernel. */
469 extern void _dl_show_auxv (void) internal_function;
471 /* Return all environment variables starting with `LD_', one after the
473 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
475 /* Return an array with the names of the important hardware capabilities. */
476 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
479 size_t *max_capstrlen)
482 /* Look up NAME in ld.so.cache and return the file name stored there,
483 or null if none is found. */
484 extern const char *_dl_load_cache_lookup (const char *name)
487 /* If the system does not support MAP_COPY we cannot leave the file open
488 all the time since this would create problems when the file is replaced.
489 Therefore we provide this function to close the file and open it again
491 extern void _dl_unload_cache (void);
493 /* System-dependent function to read a file's whole contents
494 in the most convenient manner available. */
495 extern void *_dl_sysdep_read_whole_file (const char *file, size_t *sizep,
499 /* System-specific function to do initial startup for the dynamic linker.
500 After this, file access calls and getenv must work. This is responsible
501 for setting __libc_enable_secure if we need to be secure (e.g. setuid),
502 and for setting _dl_argc and _dl_argv, and then calling _dl_main. */
503 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
504 void (*dl_main) (const ElfW(Phdr) *phdr,
506 ElfW(Addr) *user_entry));
508 extern void _dl_sysdep_start_cleanup (void)
514 #endif /* ldsodefs.h */