1 /* Run-time dynamic linker data structures for loaded ELF shared objects.
2 Copyright (C) 1995, 1996, 1997, 1998 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. */
34 /* We use this macro to refer to ELF types independent of the native wordsize.
35 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
36 #define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type)
37 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
38 #define _ElfW(e,w,t) _ElfW_1 (e, w, _##t)
39 #define _ElfW_1(e,w,t) e##w##t
41 #include <bits/elfclass.h> /* Defines __ELF_NATIVE_CLASS. */
43 /* Rendezvous structure used by the run-time dynamic linker to communicate
44 details of shared object loading to the debugger. If the executable's
45 dynamic section has a DT_DEBUG element, the run-time linker sets that
46 element's value to the address where this structure can be found. */
50 int r_version; /* Version number for this protocol. */
52 struct link_map *r_map; /* Head of the chain of loaded objects. */
54 /* This is the address of a function internal to the run-time linker,
55 that will always be called when the linker begins to map in a
56 library or unmap it, and again when the mapping change is complete.
57 The debugger can set a breakpoint at this address if it wants to
58 notice shared object mapping changes. */
62 /* This state value describes the mapping change taking place when
63 the `r_brk' address is called. */
64 RT_CONSISTENT, /* Mapping change is complete. */
65 RT_ADD, /* Beginning to add a new object. */
66 RT_DELETE /* Beginning to remove an object mapping. */
69 ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */
72 /* This is the instance of that structure used by the dynamic linker. */
73 extern struct r_debug _r_debug;
75 /* This symbol refers to the "dynamic structure" in the `.dynamic' section
76 of whatever module refers to `_DYNAMIC'. So, to find its own
77 `struct r_debug', a program could do:
78 for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL)
79 if (dyn->d_tag == DT_DEBUG) r_debug = (struct r_debug) dyn->d_un.d_ptr;
82 extern ElfW(Dyn) _DYNAMIC[];
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
104 enum r_dir_status dirstatus;
106 size_t machdirnamelen;
107 enum r_dir_status machdirstatus;
109 /* Strings saying where the definition came from. */
113 /* This link is only used in the `all_dirs' member of `r_search_path'. */
114 struct r_search_path_elem *next;
118 /* A data structure for a simple single linked list of strings. */
121 const char *name; /* Name requested (before search). */
122 struct libname_list *next; /* Link to next name for this object. */
126 /* Structure describing a loaded shared object. The `l_next' and `l_prev'
127 members form a chain of all the shared objects loaded at startup.
129 These data structures exist in space used by the run-time dynamic linker;
130 modifying them may have disastrous results. */
134 /* These first few members are part of the protocol with the debugger.
135 This is the same format used in SVR4. */
137 ElfW(Addr) l_addr; /* Base address shared object is loaded at. */
138 char *l_name; /* Absolute file name object was found in. */
139 ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */
140 struct link_map *l_next, *l_prev; /* Chain of loaded objects. */
142 /* All following members are internal to the dynamic linker.
143 They may change without notice. */
145 struct libname_list *l_libname;
146 /* Indexed pointers to dynamic section.
147 [0,DT_NUM) are indexed by the processor-independent tags.
148 [DT_NUM,DT_NUM+DT_PROCNUM) are indexed by the tag minus DT_LOPROC.
149 [DT_NUM+DT_PROCNUM,DT_NUM+DT_PROCNUM+DT_EXTRANUM) are indexed
150 by DT_EXTRATAGIDX(tagvalue) and
151 [DT_NUM+DT_PROCNUM+DT_VERSIONTAGNUM,
152 DT_NUM+DT_PROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM)
153 are indexed by DT_EXTRATAGIDX(tagvalue) (see <elf.h>). */
155 ElfW(Dyn) *l_info[DT_NUM + DT_PROCNUM + DT_VERSIONTAGNUM + DT_EXTRANUM];
156 const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */
157 ElfW(Addr) l_entry; /* Entry point location. */
158 ElfW(Half) l_phnum; /* Number of program header entries. */
160 /* Array of DT_NEEDED dependencies and their dependencies, in
161 dependency order for symbol lookup. This is null before the
162 dependencies have been loaded. */
163 struct link_map **l_searchlist;
164 unsigned int l_nsearchlist;
166 /* We keep another list in which we keep duplicates. This is
167 needed in _dl_lookup_symbol_skip to implemented RTLD_NEXT. */
168 struct link_map **l_dupsearchlist;
169 unsigned int l_ndupsearchlist;
171 /* Dependent object that first caused this object to be loaded. */
172 struct link_map *l_loader;
174 /* Symbol hash table. */
175 ElfW(Symndx) l_nbuckets;
176 const ElfW(Symndx) *l_buckets, *l_chain;
178 unsigned int l_opencount; /* Reference count for dlopen/dlclose. */
179 enum /* Where this object came from. */
181 lt_executable, /* The main executable program. */
182 lt_library, /* Library needed by main executable. */
183 lt_loaded /* Extra run-time loaded shared object. */
185 unsigned int l_relocated:1; /* Nonzero if object's relocations done. */
186 unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */
187 unsigned int l_init_running:1; /* Nonzero while DT_INIT function runs. */
188 unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */
189 unsigned int l_reserved:2; /* Reserved for internal use. */
191 /* Array with version names. */
192 unsigned int l_nversions;
193 struct r_found_version *l_versions;
195 /* Collected information about own RPATH directories. */
196 struct r_search_path_elem **l_rpath_dirs;
198 /* Collected results of relocation while profiling. */
199 ElfW(Addr) *l_reloc_result;
203 /* Test whether given NAME matches any of the names of the given object. */
205 __attribute__ ((unused))
206 _dl_name_match_p (const char *__name, struct link_map *__map)
208 int __found = strcmp (__name, __map->l_name) == 0;
209 struct libname_list *__runp = __map->l_libname;
211 while (! __found && __runp != NULL)
212 if (strcmp (__name, __runp->name) == 0)
215 __runp = __runp->next;
220 /* Function used as argument for `_dl_receive_error' function. The
221 arguments are the error code, error string, and the objname the
222 error occurred in. */
223 typedef void (*receiver_fct) (int, const char *, const char *);
225 /* Internal functions of the run-time dynamic linker.
226 These can be accessed if you link again the dynamic linker
227 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
228 but are not normally of interest to user programs.
230 The `-ldl' library functions in <dlfcn.h> provide a simple
231 user interface to run-time dynamic linking. */
234 /* Parameters passed to the dynamic linker. */
235 extern char **_dl_argv;
237 /* Cached value of `getpagesize ()'. */
238 extern size_t _dl_pagesize;
240 /* File descriptor referring to the zero-fill device. */
241 extern int _dl_zerofd;
243 /* Name of the shared object to be profiled (if any). */
244 extern const char *_dl_profile;
245 /* Map of shared object to be profiled. */
246 extern struct link_map *_dl_profile_map;
248 /* If nonzero the appropriate debug information is printed. */
249 extern int _dl_debug_libs;
250 extern int _dl_debug_impcalls;
252 /* File deccriptor to write debug messages to. */
253 extern int _dl_debug_fd;
255 /* OS-dependent function to open the zero-fill device. */
256 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
258 /* OS-dependent function to write a message on the specified
259 descriptor FD. All arguments are `const char *'; args until a null
260 pointer are concatenated to form the message to print. */
261 extern void _dl_sysdep_output (int fd, const char *string, ...);
263 /* OS-dependent function to write a debug message on the specified
264 descriptor for this. All arguments are `const char *'; args until
265 a null pointer are concatenated to form the message to print. */
266 #define _dl_debug_message(string, args...) \
267 _dl_sysdep_output (_dl_debug_fd, string, ##args)
269 /* OS-dependent function to write a message on the standard output.
270 All arguments are `const char *'; args until a null pointer
271 are concatenated to form the message to print. */
272 #define _dl_sysdep_message(string, args...) \
273 _dl_sysdep_output (STDOUT_FILENO, string, ##args)
275 /* OS-dependent function to write a message on the standard error.
276 All arguments are `const char *'; args until a null pointer
277 are concatenated to form the message to print. */
278 #define _dl_sysdep_error(string, args...) \
279 _dl_sysdep_output (STDERR_FILENO, string, ##args)
281 /* OS-dependent function to give a fatal error message and exit
282 when the dynamic linker fails before the program is fully linked.
283 All arguments are `const char *'; args until a null pointer
284 are concatenated to form the message to print. */
285 #define _dl_sysdep_fatal(string, args...) \
288 _dl_sysdep_output (STDERR_FILENO, string, ##args); \
293 /* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch).
294 This tells the dynamic linker to ignore environment variables. */
295 extern int _dl_secure;
297 /* This function is called by all the internal dynamic linker functions
298 when they encounter an error. ERRCODE is either an `errno' code or
299 zero; OBJECT is the name of the problematical shared object, or null if
300 it is a general problem; ERRSTRING is a string describing the specific
302 extern void _dl_signal_error (int errcode,
304 const char *errstring);
306 /* Call OPERATE, catching errors from `dl_signal_error'. If there is no
307 error, *ERRSTRING is set to null. If there is an error, *ERRSTRING and
308 *OBJECT are set to the strings passed to _dl_signal_error, and the error
309 code passed is the return value. ERRSTRING if nonzero points to a
310 malloc'ed string which the caller has to free after use.
311 ARGS is passed as argument to OPERATE. */
312 extern int _dl_catch_error (char **errstring,
314 void (*operate) (void *),
317 /* Call OPERATE, receiving errors from `dl_signal_error'. Unlike
318 `_dl_catch_error' the operation is resumed after the OPERATE
320 ARGS is passed as argument to OPERATE. */
321 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
325 /* Helper function for <dlfcn.h> functions. Runs the OPERATE function via
326 _dl_catch_error. Returns zero for success, nonzero for failure; and
327 arranges for `dlerror' to return the error details.
328 ARGS is passed as argument to OPERATE. */
329 extern int _dlerror_run (void (*operate) (void *), void *args);
332 /* Open the shared object NAME and map in its segments.
333 LOADER's DT_RPATH is used in searching for NAME.
334 If the object is already opened, returns its existing map.
335 For preloaded shared objects PRELOADED is set to a non-zero
336 value to allow additional security checks. */
337 extern struct link_map *_dl_map_object (struct link_map *loader,
338 const char *name, int preloaded,
339 int type, int trace_mode);
341 /* Call _dl_map_object on the dependencies of MAP, and set up
342 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
343 loaded objects that will be inserted into MAP->l_searchlist after MAP
344 but before its dependencies. */
345 extern void _dl_map_object_deps (struct link_map *map,
346 struct link_map **preloads,
347 unsigned int npreloads, int trace_mode);
349 /* Cache the locations of MAP's hash table. */
350 extern void _dl_setup_hash (struct link_map *map);
353 /* Open the shared object NAME, relocate it, and run its initializer if it
354 hasn't already been run. MODE is as for `dlopen' (see <dlfcn.h>). If
355 the object is already opened, returns its existing map. */
356 extern struct link_map *_dl_open (const char *name, int mode);
358 /* Close an object previously opened by _dl_open. */
359 extern void _dl_close (struct link_map *map);
362 /* Search loaded objects' symbol tables for a definition of the symbol
363 referred to by UNDEF. *SYM is the symbol table entry containing the
364 reference; it is replaced with the defining symbol, and the base load
365 address of the defining object is returned. SYMBOL_SCOPE is a
366 null-terminated list of object scopes to search; each object's
367 l_searchlist (i.e. the segment of the dependency tree starting at that
368 object) is searched in turn. REFERENCE_NAME should name the object
369 containing the reference; it is used in error messages.
370 RELOC_TYPE is a machine-dependent reloc type, which is passed to
371 the `elf_machine_lookup_*_p' macros in dl-machine.h to affect which
372 symbols can be chosen. */
373 extern ElfW(Addr) _dl_lookup_symbol (const char *undef,
374 const ElfW(Sym) **sym,
375 struct link_map *symbol_scope[],
376 const char *reference_name,
379 /* Lookup versioned symbol. */
380 extern ElfW(Addr) _dl_lookup_versioned_symbol (const char *undef,
381 const ElfW(Sym) **sym,
382 struct link_map *symbol_scope[],
383 const char *reference_name,
384 const struct r_found_version *version,
387 /* For handling RTLD_NEXT we must be able to skip shared objects. */
388 extern ElfW(Addr) _dl_lookup_symbol_skip (const char *undef,
389 const ElfW(Sym) **sym,
390 struct link_map *symbol_scope[],
391 const char *reference_name,
392 struct link_map *skip_this);
394 /* For handling RTLD_NEXT with versioned symbols we must be able to
395 skip shared objects. */
396 extern ElfW(Addr) _dl_lookup_versioned_symbol_skip (const char *undef,
397 const ElfW(Sym) **sym,
398 struct link_map *symbol_scope[],
399 const char *reference_name,
400 const struct r_found_version *version,
401 struct link_map *skip_this);
403 /* Locate shared object containing the given address. */
404 extern int _dl_addr (const void *address, Dl_info *info);
406 /* Look up symbol NAME in MAP's scope and return its run-time address. */
407 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name);
410 /* Structure describing the dynamic linker itself. */
411 extern struct link_map _dl_rtld_map;
413 /* The list of objects currently loaded is the third element of the
414 `_dl_default_scope' array, and the fourth element is always null.
415 This leaves two slots before it that are used when resolving
416 DT_SYMBOLIC objects' references one after it for normal references
418 #define _dl_loaded (_dl_default_scope[2])
419 extern struct link_map *_dl_default_scope[5];
421 /* Null-terminated list of objects in the dynamic `global scope'. The
422 list starts at [2]; i.e. &_dl_global_scope[2] is the argument
423 passed to _dl_lookup_symbol to search the global scope. To search
424 a specific object and its dependencies in preference to the global
425 scope, fill in the [1] slot and pass its address; for two specific
426 object scopes, fill [0] and [1]. The list is double-terminated; to
427 search the global scope and then a specific object and its
428 dependencies, set *_dl_global_scope_end. This variable initially
429 points to _dl_default_scope, and _dl_loaded is always kept in [2]
430 of this list. A new list is malloc'd when new objects are loaded
432 extern struct link_map **_dl_global_scope, **_dl_global_scope_end;
433 extern size_t _dl_global_scope_alloc; /* Number of slots malloc'd. */
435 /* Hack _dl_global_scope[0] and [1] as necessary, and return a pointer into
436 _dl_global_scope that should be passed to _dl_lookup_symbol for symbol
437 references made in the object MAP's relocations. */
438 extern struct link_map **_dl_object_relocation_scope (struct link_map *map);
441 /* Allocate a `struct link_map' for a new object being loaded,
442 and enter it into the _dl_loaded list. */
443 extern struct link_map *_dl_new_object (char *realname, const char *libname,
446 /* Relocate the given object (if it hasn't already been).
447 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
448 If LAZY is nonzero, don't relocate its PLT. */
449 extern void _dl_relocate_object (struct link_map *map,
450 struct link_map *scope[],
453 /* Check the version dependencies of all objects available through
454 MAP. If VERBOSE print some more diagnostics. */
455 extern int _dl_check_all_versions (struct link_map *map, int verbose);
457 /* Check the version dependencies for MAP. If VERBOSE print some more
459 extern int _dl_check_map_versions (struct link_map *map, int verbose);
461 /* Return the address of the next initializer function for MAP or one of
462 its dependencies that has not yet been run. When there are no more
463 initializers to be run, this returns zero. The functions are returned
464 in the order they should be called. */
465 extern ElfW(Addr) _dl_init_next (struct link_map *map);
467 /* Call the finalizer functions of all shared objects whose
468 initializer functions have completed. */
469 extern void _dl_fini (void);
471 /* The dynamic linker calls this function before and having changing
472 any shared object mappings. The `r_state' member of `struct r_debug'
473 says what change is taking place. This function's address is
474 the value of the `r_brk' member. */
475 extern void _dl_debug_state (void);
477 /* Initialize `struct r_debug' if it has not already been done. The
478 argument is the run-time load address of the dynamic linker, to be put
479 in the `r_ldbase' member. Returns the address of the structure. */
480 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase);
482 /* Initialize the basic data structure for the search paths. */
483 extern void _dl_init_paths (const char *library_path);
485 /* Gather the information needed to install the profiling tables and start
487 extern void _dl_start_profile (struct link_map *map, const char *output_dir);
489 /* The actual functions used to keep book on the calls. */
490 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
493 /* Show the members of the auxiliary array passed up from the kernel. */
494 extern void _dl_show_auxv (void);
496 /* Return all environment variables starting with `LD_', one after the
498 extern char *_dl_next_ld_env_entry (char ***position);