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)
74 /* For the version handling we need an array with only names and their
76 struct r_found_version
85 /* We want to cache information about the searches for shared objects. */
87 enum r_dir_status { unknown, nonexisting, existing };
89 struct r_search_path_elem
91 /* This link is only used in the `all_dirs' member of `r_search_path'. */
92 struct r_search_path_elem *next;
94 /* Strings saying where the definition came from. */
98 /* Basename for this search path element. The string must end with
103 enum r_dir_status status[0];
113 /* A data structure for a simple single linked list of strings. */
116 const char *name; /* Name requested (before search). */
117 struct libname_list *next; /* Link to next name for this object. */
118 int dont_free; /* Flag whether this element should be freed
119 if the object is not entirely unloaded. */
123 /* Test whether given NAME matches any of the names of the given object. */
125 __attribute__ ((unused))
126 _dl_name_match_p (const char *__name, struct link_map *__map)
128 int __found = strcmp (__name, __map->l_name) == 0;
129 struct libname_list *__runp = __map->l_libname;
131 while (! __found && __runp != NULL)
132 if (strcmp (__name, __runp->name) == 0)
135 __runp = __runp->next;
140 /* Function used as argument for `_dl_receive_error' function. The
141 arguments are the error code, error string, and the objname the
142 error occurred in. */
143 typedef void (*receiver_fct) (int, const char *, const char *);
145 /* Internal functions of the run-time dynamic linker.
146 These can be accessed if you link again the dynamic linker
147 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
148 but are not normally of interest to user programs.
150 The `-ldl' library functions in <dlfcn.h> provide a simple
151 user interface to run-time dynamic linking. */
154 /* Parameters passed to the dynamic linker. */
155 extern char **_dl_argv;
157 /* Cached value of `getpagesize ()'. */
158 extern size_t _dl_pagesize;
160 /* File descriptor referring to the zero-fill device. */
161 extern int _dl_zerofd;
163 /* Name of the shared object to be profiled (if any). */
164 extern const char *_dl_profile;
165 /* Map of shared object to be profiled. */
166 extern struct link_map *_dl_profile_map;
167 /* Filename of the output file. */
168 extern const char *_dl_profile_output;
170 /* If nonzero the appropriate debug information is printed. */
171 extern int _dl_debug_libs;
172 extern int _dl_debug_impcalls;
173 extern int _dl_debug_bindings;
174 extern int _dl_debug_symbols;
175 extern int _dl_debug_versions;
176 extern int _dl_debug_reloc;
177 extern int _dl_debug_files;
179 /* Expect cache ID. */
180 extern int _dl_correct_cache_id;
182 /* Mask for hardware capabilities that are available. */
183 extern unsigned long int _dl_hwcap;
185 /* Mask for important hardware capabilities we honour. */
186 extern unsigned long int _dl_hwcap_mask;
188 /* File descriptor to write debug messages to. */
189 extern int _dl_debug_fd;
191 /* Names of shared object for which the RPATH should be ignored. */
192 extern const char *_dl_inhibit_rpath;
194 /* Nonzero if references should be treated as weak during runtime linking. */
195 extern int _dl_dynamic_weak;
197 /* The array with message we print as a last resort. */
198 extern const char _dl_out_of_memory[];
200 /* Nonzero if runtime lookups should not update the .got/.plt. */
201 extern int _dl_bind_not;
203 /* OS-dependent function to open the zero-fill device. */
204 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
206 /* OS-dependent function to write a message on the specified
207 descriptor FD. All arguments are `const char *'; args until a null
208 pointer are concatenated to form the message to print. */
209 extern void _dl_sysdep_output (int fd, const char *string, ...);
211 /* OS-dependent function to write a debug message on the specified
212 descriptor for this. All arguments are `const char *'; args until
213 a null pointer are concatenated to form the message to print. If
214 NEW_LINE is nonzero it is assumed that the message starts on a new
216 extern void _dl_debug_message (int new_line, const char *string, ...);
218 /* OS-dependent function to write a message on the standard output.
219 All arguments are `const char *'; args until a null pointer
220 are concatenated to form the message to print. */
221 #define _dl_sysdep_message(string, args...) \
222 _dl_sysdep_output (STDOUT_FILENO, string, ##args)
224 /* OS-dependent function to write a message on the standard error.
225 All arguments are `const char *'; args until a null pointer
226 are concatenated to form the message to print. */
227 #define _dl_sysdep_error(string, args...) \
228 _dl_sysdep_output (STDERR_FILENO, string, ##args)
230 /* OS-dependent function to give a fatal error message and exit
231 when the dynamic linker fails before the program is fully linked.
232 All arguments are `const char *'; args until a null pointer
233 are concatenated to form the message to print. */
234 #define _dl_sysdep_fatal(string, args...) \
237 _dl_sysdep_output (STDERR_FILENO, string, ##args); \
242 /* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch).
243 This tells the dynamic linker to ignore environment variables. */
244 extern int _dl_secure;
246 /* This function is called by all the internal dynamic linker functions
247 when they encounter an error. ERRCODE is either an `errno' code or
248 zero; OBJECT is the name of the problematical shared object, or null if
249 it is a general problem; ERRSTRING is a string describing the specific
251 extern void _dl_signal_error (int errcode, const char *object,
252 const char *errstring)
254 __attribute__ ((__noreturn__));
256 /* Like _dl_signal_error, but may return when called in the context of
257 _dl_receive_error. */
258 extern void _dl_signal_cerror (int errcode,
260 const char *errstring)
263 /* Call OPERATE, receiving errors from `dl_signal_cerror'. Unlike
264 `_dl_catch_error' the operation is resumed after the OPERATE
266 ARGS is passed as argument to OPERATE. */
267 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
272 /* Open the shared object NAME and map in its segments.
273 LOADER's DT_RPATH is used in searching for NAME.
274 If the object is already opened, returns its existing map.
275 For preloaded shared objects PRELOADED is set to a non-zero
276 value to allow additional security checks. */
277 extern struct link_map *_dl_map_object (struct link_map *loader,
278 const char *name, int preloaded,
279 int type, int trace_mode, int mode)
282 /* Call _dl_map_object on the dependencies of MAP, and set up
283 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
284 loaded objects that will be inserted into MAP->l_searchlist after MAP
285 but before its dependencies. */
286 extern void _dl_map_object_deps (struct link_map *map,
287 struct link_map **preloads,
288 unsigned int npreloads, int trace_mode)
291 /* Cache the locations of MAP's hash table. */
292 extern void _dl_setup_hash (struct link_map *map) internal_function;
295 /* Search loaded objects' symbol tables for a definition of the symbol
296 referred to by UNDEF. *SYM is the symbol table entry containing the
297 reference; it is replaced with the defining symbol, and the base load
298 address of the defining object is returned. SYMBOL_SCOPE is a
299 null-terminated list of object scopes to search; each object's
300 l_searchlist (i.e. the segment of the dependency tree starting at that
301 object) is searched in turn. REFERENCE_NAME should name the object
302 containing the reference; it is used in error messages.
303 RELOC_TYPE is a machine-dependent reloc type, which is passed to
304 the `elf_machine_lookup_*_p' macros in dl-machine.h to affect which
305 symbols can be chosen. */
306 extern lookup_t _dl_lookup_symbol (const char *undef,
307 struct link_map *undef_map,
308 const ElfW(Sym) **sym,
309 struct r_scope_elem *symbol_scope[],
313 /* Lookup versioned symbol. */
314 extern lookup_t _dl_lookup_versioned_symbol (const char *undef,
315 struct link_map *undef_map,
316 const ElfW(Sym) **sym,
317 struct r_scope_elem *symbol_scope[],
318 const struct r_found_version *version,
322 /* For handling RTLD_NEXT we must be able to skip shared objects. */
323 extern lookup_t _dl_lookup_symbol_skip (const char *undef,
324 struct link_map *undef_map,
325 const ElfW(Sym) **sym,
326 struct r_scope_elem *symbol_scope[],
327 struct link_map *skip_this)
330 /* For handling RTLD_NEXT with versioned symbols we must be able to
331 skip shared objects. */
332 extern lookup_t _dl_lookup_versioned_symbol_skip (const char *undef,
333 struct link_map *undef_map,
334 const ElfW(Sym) **sym,
335 struct r_scope_elem *symbol_scope[],
336 const struct r_found_version *version,
337 struct link_map *skip_this)
340 /* Look up symbol NAME in MAP's scope and return its run-time address. */
341 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
345 /* Structure describing the dynamic linker itself. */
346 extern struct link_map _dl_rtld_map;
347 /* And a pointer to the map for the main map. */
348 extern struct link_map *_dl_loaded;
349 /* Number of object in the _dl_loaded list. */
350 extern unsigned int _dl_nloaded;
351 /* Array representing global scope. */
352 extern struct r_scope_elem *_dl_global_scope[2];
353 /* Direct pointer to the searchlist of the main object. */
354 extern struct r_scope_elem *_dl_main_searchlist;
355 /* Copy of the content of `_dl_main_searchlist'. */
356 extern struct r_scope_elem _dl_initial_searchlist;
357 /* This is zero at program start to signal that the global scope map is
358 allocated by rtld. Later it keeps the size of the map. It might be
359 reset if in _dl_close if the last global object is removed. */
360 extern size_t _dl_global_scope_alloc;
362 /* Allocate a `struct link_map' for a new object being loaded,
363 and enter it into the _dl_main_map list. */
364 extern struct link_map *_dl_new_object (char *realname, const char *libname,
365 int type, struct link_map *loader)
368 /* Relocate the given object (if it hasn't already been).
369 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
370 If LAZY is nonzero, don't relocate its PLT. */
371 extern void _dl_relocate_object (struct link_map *map,
372 struct r_scope_elem *scope[],
373 int lazy, int consider_profiling);
375 /* Call _dl_signal_error with a message about an unhandled reloc type.
376 TYPE is the result of ELFW(R_TYPE) (r_info), i.e. an R_<CPU>_* value.
377 PLT is nonzero if this was a PLT reloc; it just affects the message. */
378 extern void _dl_reloc_bad_type (struct link_map *map,
379 uint_fast8_t type, int plt)
382 /* Check the version dependencies of all objects available through
383 MAP. If VERBOSE print some more diagnostics. */
384 extern int _dl_check_all_versions (struct link_map *map, int verbose,
388 /* Check the version dependencies for MAP. If VERBOSE print some more
390 extern int _dl_check_map_versions (struct link_map *map, int verbose,
394 /* Initialize the object in SCOPE by calling the constructors with
395 ARGC, ARGV, and ENV as the parameters. */
396 extern void _dl_init (struct link_map *main_map, int argc, char **argv,
397 char **env) internal_function;
399 /* Call the finalizer functions of all shared objects whose
400 initializer functions have completed. */
401 extern void _dl_fini (void) internal_function;
403 /* The dynamic linker calls this function before and having changing
404 any shared object mappings. The `r_state' member of `struct r_debug'
405 says what change is taking place. This function's address is
406 the value of the `r_brk' member. */
407 extern void _dl_debug_state (void);
409 /* Initialize `struct r_debug' if it has not already been done. The
410 argument is the run-time load address of the dynamic linker, to be put
411 in the `r_ldbase' member. Returns the address of the structure. */
412 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
415 /* Initialize the basic data structure for the search paths. */
416 extern void _dl_init_paths (const char *library_path) internal_function;
418 /* Gather the information needed to install the profiling tables and start
420 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
423 /* The actual functions used to keep book on the calls. */
424 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
426 /* This function is simply a wrapper around the _dl_mcount function
427 which does not require a FROMPC parameter since this is the
429 extern void _dl_mcount_wrapper (void *selfpc);
431 /* Show the members of the auxiliary array passed up from the kernel. */
432 extern void _dl_show_auxv (void) internal_function;
434 /* Return all environment variables starting with `LD_', one after the
436 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
438 /* Return an array with the names of the important hardware capabilities. */
439 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
442 size_t *max_capstrlen)
447 #endif /* ldsodefs.h */