1 /* Run-time dynamic linker data structures for loaded ELF shared objects.
2 Copyright (C) 1995-1999, 2000 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 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.
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.
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. */
33 #include <dl-lookupcfg.h>
37 /* We use this macro to refer to ELF types independent of the native wordsize.
38 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
39 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
41 /* All references to the value of l_info[DT_PLTGOT],
42 l_info[DT_STRTAB], l_info[DT_SYMTAB], l_info[DT_RELA],
43 l_info[DT_REL], l_info[DT_JMPREL], and l_info[VERSYMIDX (DT_VERSYM)]
44 have to be accessed via the D_PTR macro. The macro is needed since for
45 most architectures the entry is already relocated - but for some not
46 and we need to relocate at access time. */
47 #ifdef DL_RO_DYN_SECTION
48 # define D_PTR(map,i) (map->i->d_un.d_ptr + map->l_addr)
50 # define D_PTR(map,i) map->i->d_un.d_ptr
53 /* On some platforms more information than just the address of the symbol
54 is needed from the lookup functions. In this case we return the whole
56 #ifdef DL_LOOKUP_RETURNS_MAP
57 typedef struct link_map *lookup_t;
58 # define LOOKUP_VALUE(map) map
59 # define LOOKUP_VALUE_ADDRESS(map) (map ? map->l_addr : 0)
61 typedef ElfW(Addr) lookup_t;
62 # define LOOKUP_VALUE(map) map->l_addr
63 # define LOOKUP_VALUE_ADDRESS(address) address
66 /* on some architectures a pointer to a function is not just a pointer
67 to the actual code of the function but rather an architecture
68 specific descriptor. */
69 #ifndef ELF_FUNCTION_PTR_IS_SPECIAL
70 # define DL_SYMBOL_ADDRESS(map, ref) \
71 (void *) (LOOKUP_VALUE_ADDRESS (map) + ref->st_value)
72 # define DL_LOOKUP_ADDRESS(addr) ((ElfW(Addr)) (addr))
73 # define DL_DT_INIT_ADDRESS(map, start) (start)
74 # define DL_DT_FINI_ADDRESS(map, start) (start)
77 /* Unmap a loaded object, called by _dl_close (). */
78 #ifndef DL_UNMAP_IS_SPECIAL
79 # define DL_UNMAP(map) \
80 __munmap ((void *) (map)->l_map_start, \
81 (map)->l_map_end - (map)->l_map_start)
84 /* For the version handling we need an array with only names and their
86 struct r_found_version
95 /* We want to cache information about the searches for shared objects. */
97 enum r_dir_status { unknown, nonexisting, existing };
99 struct r_search_path_elem
101 /* This link is only used in the `all_dirs' member of `r_search_path'. */
102 struct r_search_path_elem *next;
104 /* Strings saying where the definition came from. */
108 /* Basename for this search path element. The string must end with
109 a slash character. */
113 enum r_dir_status status[0];
123 /* A data structure for a simple single linked list of strings. */
126 const char *name; /* Name requested (before search). */
127 struct libname_list *next; /* Link to next name for this object. */
128 int dont_free; /* Flag whether this element should be freed
129 if the object is not entirely unloaded. */
133 /* Test whether given NAME matches any of the names of the given object. */
135 __attribute__ ((unused))
136 _dl_name_match_p (const char *__name, struct link_map *__map)
138 int __found = strcmp (__name, __map->l_name) == 0;
139 struct libname_list *__runp = __map->l_libname;
141 while (! __found && __runp != NULL)
142 if (strcmp (__name, __runp->name) == 0)
145 __runp = __runp->next;
150 /* Function used as argument for `_dl_receive_error' function. The
151 arguments are the error code, error string, and the objname the
152 error occurred in. */
153 typedef void (*receiver_fct) (int, const char *, const char *);
155 /* Internal functions of the run-time dynamic linker.
156 These can be accessed if you link again the dynamic linker
157 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
158 but are not normally of interest to user programs.
160 The `-ldl' library functions in <dlfcn.h> provide a simple
161 user interface to run-time dynamic linking. */
164 /* Parameters passed to the dynamic linker. */
165 extern char **_dl_argv;
167 /* Cached value of `getpagesize ()'. */
168 extern size_t _dl_pagesize;
170 /* File descriptor referring to the zero-fill device. */
171 extern int _dl_zerofd;
173 /* Name of the shared object to be profiled (if any). */
174 extern const char *_dl_profile;
175 /* Map of shared object to be profiled. */
176 extern struct link_map *_dl_profile_map;
177 /* Filename of the output file. */
178 extern const char *_dl_profile_output;
180 /* If nonzero the appropriate debug information is printed. */
181 extern int _dl_debug_libs;
182 extern int _dl_debug_impcalls;
183 extern int _dl_debug_bindings;
184 extern int _dl_debug_symbols;
185 extern int _dl_debug_versions;
186 extern int _dl_debug_reloc;
187 extern int _dl_debug_files;
189 /* Expect cache ID. */
190 extern int _dl_correct_cache_id;
192 /* Mask for hardware capabilities that are available. */
193 extern unsigned long int _dl_hwcap;
195 /* Mask for important hardware capabilities we honour. */
196 extern unsigned long int _dl_hwcap_mask;
198 /* File descriptor to write debug messages to. */
199 extern int _dl_debug_fd;
201 /* Names of shared object for which the RPATH should be ignored. */
202 extern const char *_dl_inhibit_rpath;
204 /* Nonzero if references should be treated as weak during runtime linking. */
205 extern int _dl_dynamic_weak;
207 /* The array with message we print as a last resort. */
208 extern const char _dl_out_of_memory[];
210 /* Nonzero if runtime lookups should not update the .got/.plt. */
211 extern int _dl_bind_not;
213 /* List of search directories. */
214 extern struct r_search_path_elem *_dl_all_dirs;
215 extern struct r_search_path_elem *_dl_init_all_dirs;
217 /* OS-dependent function to open the zero-fill device. */
218 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
220 /* OS-dependent function to write a message on the specified
221 descriptor FD. All arguments are `const char *'; args until a null
222 pointer are concatenated to form the message to print. */
223 extern void _dl_sysdep_output (int fd, const char *string, ...);
225 /* OS-dependent function to write a debug message on the specified
226 descriptor for this. All arguments are `const char *'; args until
227 a null pointer are concatenated to form the message to print. If
228 NEW_LINE is nonzero it is assumed that the message starts on a new
230 extern void _dl_debug_message (int new_line, const char *string, ...);
232 /* OS-dependent function to write a message on the standard output.
233 All arguments are `const char *'; args until a null pointer
234 are concatenated to form the message to print. */
235 #define _dl_sysdep_message(string, args...) \
236 _dl_sysdep_output (STDOUT_FILENO, string, ##args)
238 /* OS-dependent function to write a message on the standard error.
239 All arguments are `const char *'; args until a null pointer
240 are concatenated to form the message to print. */
241 #define _dl_sysdep_error(string, args...) \
242 _dl_sysdep_output (STDERR_FILENO, string, ##args)
244 /* OS-dependent function to give a fatal error message and exit
245 when the dynamic linker fails before the program is fully linked.
246 All arguments are `const char *'; args until a null pointer
247 are concatenated to form the message to print. */
248 #define _dl_sysdep_fatal(string, args...) \
251 _dl_sysdep_output (STDERR_FILENO, string, ##args); \
256 /* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch).
257 This tells the dynamic linker to ignore environment variables. */
258 extern int _dl_secure;
260 /* This function is called by all the internal dynamic linker functions
261 when they encounter an error. ERRCODE is either an `errno' code or
262 zero; OBJECT is the name of the problematical shared object, or null if
263 it is a general problem; ERRSTRING is a string describing the specific
265 extern void _dl_signal_error (int errcode, const char *object,
266 const char *errstring)
268 __attribute__ ((__noreturn__));
270 /* Like _dl_signal_error, but may return when called in the context of
271 _dl_receive_error. */
272 extern void _dl_signal_cerror (int errcode,
274 const char *errstring)
277 /* Call OPERATE, receiving errors from `dl_signal_cerror'. Unlike
278 `_dl_catch_error' the operation is resumed after the OPERATE
280 ARGS is passed as argument to OPERATE. */
281 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
286 /* Open the shared object NAME and map in its segments.
287 LOADER's DT_RPATH is used in searching for NAME.
288 If the object is already opened, returns its existing map.
289 For preloaded shared objects PRELOADED is set to a non-zero
290 value to allow additional security checks. */
291 extern struct link_map *_dl_map_object (struct link_map *loader,
292 const char *name, int preloaded,
293 int type, int trace_mode, int mode)
296 /* Call _dl_map_object on the dependencies of MAP, and set up
297 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
298 loaded objects that will be inserted into MAP->l_searchlist after MAP
299 but before its dependencies. */
300 extern void _dl_map_object_deps (struct link_map *map,
301 struct link_map **preloads,
302 unsigned int npreloads, int trace_mode)
305 /* Cache the locations of MAP's hash table. */
306 extern void _dl_setup_hash (struct link_map *map) internal_function;
309 /* Search loaded objects' symbol tables for a definition of the symbol
310 referred to by UNDEF. *SYM is the symbol table entry containing the
311 reference; it is replaced with the defining symbol, and the base load
312 address of the defining object is returned. SYMBOL_SCOPE is a
313 null-terminated list of object scopes to search; each object's
314 l_searchlist (i.e. the segment of the dependency tree starting at that
315 object) is searched in turn. REFERENCE_NAME should name the object
316 containing the reference; it is used in error messages.
317 RELOC_TYPE is a machine-dependent reloc type, which is passed to
318 the `elf_machine_lookup_*_p' macros in dl-machine.h to affect which
319 symbols can be chosen. */
320 extern lookup_t _dl_lookup_symbol (const char *undef,
321 struct link_map *undef_map,
322 const ElfW(Sym) **sym,
323 struct r_scope_elem *symbol_scope[],
324 int reloc_type, int explicit)
327 /* Lookup versioned symbol. */
328 extern lookup_t _dl_lookup_versioned_symbol (const char *undef,
329 struct link_map *undef_map,
330 const ElfW(Sym) **sym,
331 struct r_scope_elem *symbol_scope[],
332 const struct r_found_version *version,
333 int reloc_type, int explicit)
336 /* For handling RTLD_NEXT we must be able to skip shared objects. */
337 extern lookup_t _dl_lookup_symbol_skip (const char *undef,
338 struct link_map *undef_map,
339 const ElfW(Sym) **sym,
340 struct r_scope_elem *symbol_scope[],
341 struct link_map *skip_this)
344 /* For handling RTLD_NEXT with versioned symbols we must be able to
345 skip shared objects. */
346 extern lookup_t _dl_lookup_versioned_symbol_skip (const char *undef,
347 struct link_map *undef_map,
348 const ElfW(Sym) **sym,
349 struct r_scope_elem *symbol_scope[],
350 const struct r_found_version *version,
351 struct link_map *skip_this)
354 /* Look up symbol NAME in MAP's scope and return its run-time address. */
355 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
359 /* Structure describing the dynamic linker itself. */
360 extern struct link_map _dl_rtld_map;
361 /* And a pointer to the map for the main map. */
362 extern struct link_map *_dl_loaded;
363 /* Number of object in the _dl_loaded list. */
364 extern unsigned int _dl_nloaded;
365 /* Array representing global scope. */
366 extern struct r_scope_elem *_dl_global_scope[2];
367 /* Direct pointer to the searchlist of the main object. */
368 extern struct r_scope_elem *_dl_main_searchlist;
369 /* Copy of the content of `_dl_main_searchlist'. */
370 extern struct r_scope_elem _dl_initial_searchlist;
371 /* This is zero at program start to signal that the global scope map is
372 allocated by rtld. Later it keeps the size of the map. It might be
373 reset if in _dl_close if the last global object is removed. */
374 extern size_t _dl_global_scope_alloc;
376 /* Allocate a `struct link_map' for a new object being loaded,
377 and enter it into the _dl_main_map list. */
378 extern struct link_map *_dl_new_object (char *realname, const char *libname,
379 int type, struct link_map *loader)
382 /* Relocate the given object (if it hasn't already been).
383 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
384 If LAZY is nonzero, don't relocate its PLT. */
385 extern void _dl_relocate_object (struct link_map *map,
386 struct r_scope_elem *scope[],
387 int lazy, int consider_profiling);
389 /* Call _dl_signal_error with a message about an unhandled reloc type.
390 TYPE is the result of ELFW(R_TYPE) (r_info), i.e. an R_<CPU>_* value.
391 PLT is nonzero if this was a PLT reloc; it just affects the message. */
392 extern void _dl_reloc_bad_type (struct link_map *map,
393 uint_fast8_t type, int plt)
395 __attribute__ ((__noreturn__));
397 /* Check the version dependencies of all objects available through
398 MAP. If VERBOSE print some more diagnostics. */
399 extern int _dl_check_all_versions (struct link_map *map, int verbose,
403 /* Check the version dependencies for MAP. If VERBOSE print some more
405 extern int _dl_check_map_versions (struct link_map *map, int verbose,
409 /* Initialize the object in SCOPE by calling the constructors with
410 ARGC, ARGV, and ENV as the parameters. */
411 extern void _dl_init (struct link_map *main_map, int argc, char **argv,
412 char **env) internal_function;
414 /* Call the finalizer functions of all shared objects whose
415 initializer functions have completed. */
416 extern void _dl_fini (void) internal_function;
418 /* The dynamic linker calls this function before and having changing
419 any shared object mappings. The `r_state' member of `struct r_debug'
420 says what change is taking place. This function's address is
421 the value of the `r_brk' member. */
422 extern void _dl_debug_state (void);
424 /* Initialize `struct r_debug' if it has not already been done. The
425 argument is the run-time load address of the dynamic linker, to be put
426 in the `r_ldbase' member. Returns the address of the structure. */
427 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
430 /* Initialize the basic data structure for the search paths. */
431 extern void _dl_init_paths (const char *library_path) internal_function;
433 /* Gather the information needed to install the profiling tables and start
435 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
438 /* The actual functions used to keep book on the calls. */
439 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
441 /* This function is simply a wrapper around the _dl_mcount function
442 which does not require a FROMPC parameter since this is the
444 extern void _dl_mcount_wrapper (void *selfpc);
446 /* Show the members of the auxiliary array passed up from the kernel. */
447 extern void _dl_show_auxv (void) internal_function;
449 /* Return all environment variables starting with `LD_', one after the
451 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
453 /* Return an array with the names of the important hardware capabilities. */
454 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
457 size_t *max_capstrlen)
460 /* Look up NAME in ld.so.cache and return the file name stored there,
461 or null if none is found. */
462 extern const char *_dl_load_cache_lookup (const char *name)
465 /* If the system does not support MAP_COPY we cannot leave the file open
466 all the time since this would create problems when the file is replaced.
467 Therefore we provide this function to close the file and open it again
469 extern void _dl_unload_cache (void);
471 /* System-dependent function to read a file's whole contents
472 in the most convenient manner available. */
473 extern void *_dl_sysdep_read_whole_file (const char *file, size_t *sizep,
477 /* System-specific function to do initial startup for the dynamic linker.
478 After this, file access calls and getenv must work. This is responsible
479 for setting __libc_enable_secure if we need to be secure (e.g. setuid),
480 and for setting _dl_argc and _dl_argv, and then calling _dl_main. */
481 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
482 void (*dl_main) (const ElfW(Phdr) *phdr,
484 ElfW(Addr) *user_entry));
486 extern void _dl_sysdep_start_cleanup (void)
492 #endif /* ldsodefs.h */