1 /* Run-time dynamic linker data structures for loaded ELF shared objects.
2 Copyright (C) 1995-1999, 2000, 2001, 2002 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
32 #include <fpu_control.h>
35 #include <dl-lookupcfg.h>
36 #include <bits/libc-lock.h>
37 #include <hp-timing.h>
41 /* We use this macro to refer to ELF types independent of the native wordsize.
42 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
43 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
45 /* All references to the value of l_info[DT_PLTGOT],
46 l_info[DT_STRTAB], l_info[DT_SYMTAB], l_info[DT_RELA],
47 l_info[DT_REL], l_info[DT_JMPREL], and l_info[VERSYMIDX (DT_VERSYM)]
48 have to be accessed via the D_PTR macro. The macro is needed since for
49 most architectures the entry is already relocated - but for some not
50 and we need to relocate at access time. */
51 #ifdef DL_RO_DYN_SECTION
52 # define D_PTR(map,i) (map->i->d_un.d_ptr + map->l_addr)
54 # define D_PTR(map,i) map->i->d_un.d_ptr
57 /* On some platforms more information than just the address of the symbol
58 is needed from the lookup functions. In this case we return the whole
60 #ifdef DL_LOOKUP_RETURNS_MAP
61 typedef struct link_map *lookup_t;
62 # define LOOKUP_VALUE(map) map
63 # define LOOKUP_VALUE_ADDRESS(map) (map ? map->l_addr : 0)
65 typedef ElfW(Addr) lookup_t;
66 # define LOOKUP_VALUE(map) map->l_addr
67 # define LOOKUP_VALUE_ADDRESS(address) address
70 /* on some architectures a pointer to a function is not just a pointer
71 to the actual code of the function but rather an architecture
72 specific descriptor. */
73 #ifndef ELF_FUNCTION_PTR_IS_SPECIAL
74 # define DL_SYMBOL_ADDRESS(map, ref) \
75 (void *) (LOOKUP_VALUE_ADDRESS (map) + ref->st_value)
76 # define DL_LOOKUP_ADDRESS(addr) ((ElfW(Addr)) (addr))
77 # define DL_DT_INIT_ADDRESS(map, start) (start)
78 # define DL_DT_FINI_ADDRESS(map, start) (start)
81 /* Unmap a loaded object, called by _dl_close (). */
82 #ifndef DL_UNMAP_IS_SPECIAL
83 # define DL_UNMAP(map) \
84 __munmap ((void *) (map)->l_map_start, \
85 (map)->l_map_end - (map)->l_map_start)
88 /* By default we do not need special support to initialize DSOs loaded
89 by statically linked binaries. */
90 #ifndef DL_STATIC_INIT
91 # define DL_STATIC_INIT(map)
94 /* Reloc type classes as returned by elf_machine_type_class().
95 ELF_RTYPE_CLASS_PLT means this reloc should not be satisfied by
96 some PLT symbol, ELF_RTYPE_CLASS_COPY means this reloc should not be
97 satisfied by any symbol in the executable. */
98 #define ELF_RTYPE_CLASS_PLT 1
99 #define ELF_RTYPE_CLASS_COPY 2
101 /* ELF uses the PF_x macros to specify the segment permissions, mmap
102 uses PROT_xxx. In most cases the three macros have the values 1, 2,
103 and 3 but not in a matching order. The following macros allows
104 converting from the PF_x values to PROT_xxx values. */
106 ((PROT_READ << (PF_R * 4)) \
107 | (PROT_WRITE << (PF_W * 4)) \
108 | (PROT_EXEC << (PF_X * 4)) \
109 | ((PROT_READ | PROT_WRITE) << ((PF_R | PF_W) * 4)) \
110 | ((PROT_READ | PROT_EXEC) << ((PF_R | PF_X) * 4)) \
111 | ((PROT_WRITE | PROT_EXEC) << (PF_W | PF_X) * 4) \
112 | ((PROT_READ | PROT_WRITE | PROT_EXEC) << ((PF_R | PF_W | PF_X) * 4)))
115 /* For the version handling we need an array with only names and their
117 struct r_found_version
123 const char *filename;
126 /* We want to cache information about the searches for shared objects. */
128 enum r_dir_status { unknown, nonexisting, existing };
130 struct r_search_path_elem
132 /* This link is only used in the `all_dirs' member of `r_search_path'. */
133 struct r_search_path_elem *next;
135 /* Strings saying where the definition came from. */
139 /* Basename for this search path element. The string must end with
140 a slash character. */
144 enum r_dir_status status[0];
154 /* A data structure for a simple single linked list of strings. */
157 const char *name; /* Name requested (before search). */
158 struct libname_list *next; /* Link to next name for this object. */
159 int dont_free; /* Flag whether this element should be freed
160 if the object is not entirely unloaded. */
164 /* Test whether given NAME matches any of the names of the given object. */
166 __attribute__ ((unused))
167 _dl_name_match_p (const char *__name, struct link_map *__map)
169 int __found = strcmp (__name, __map->l_name) == 0;
170 struct libname_list *__runp = __map->l_libname;
172 while (! __found && __runp != NULL)
173 if (strcmp (__name, __runp->name) == 0)
176 __runp = __runp->next;
181 /* Function used as argument for `_dl_receive_error' function. The
182 arguments are the error code, error string, and the objname the
183 error occurred in. */
184 typedef void (*receiver_fct) (int, const char *, const char *);
186 /* Internal functions of the run-time dynamic linker.
187 These can be accessed if you link again the dynamic linker
188 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
189 but are not normally of interest to user programs.
191 The `-ldl' library functions in <dlfcn.h> provide a simple
192 user interface to run-time dynamic linking. */
196 # define EXTERN extern
197 # define GL(name) _##name
200 # define GL(name) _rtld_global._##name
204 /* Don't change the order of the following elements. 'dl_loaded'
205 must remain the first element. Forever. */
207 /* And a pointer to the map for the main map. */
208 EXTERN struct link_map *_dl_loaded;
209 /* Number of object in the _dl_loaded list. */
210 EXTERN unsigned int _dl_nloaded;
211 /* Array representing global scope. */
212 EXTERN struct r_scope_elem *_dl_global_scope[2];
213 /* Direct pointer to the searchlist of the main object. */
214 EXTERN struct r_scope_elem *_dl_main_searchlist;
215 /* Copy of the content of `_dl_main_searchlist'. */
216 EXTERN struct r_scope_elem _dl_initial_searchlist;
217 /* This is zero at program start to signal that the global scope map is
218 allocated by rtld. Later it keeps the size of the map. It might be
219 reset if in _dl_close if the last global object is removed. */
220 EXTERN size_t _dl_global_scope_alloc;
222 /* If nonzero the appropriate debug information is printed. */
223 EXTERN int _dl_debug_mask;
224 #define DL_DEBUG_LIBS (1 << 0)
225 #define DL_DEBUG_IMPCALLS (1 << 1)
226 #define DL_DEBUG_BINDINGS (1 << 2)
227 #define DL_DEBUG_SYMBOLS (1 << 3)
228 #define DL_DEBUG_VERSIONS (1 << 4)
229 #define DL_DEBUG_RELOC (1 << 5)
230 #define DL_DEBUG_FILES (1 << 6)
231 #define DL_DEBUG_STATISTICS (1 << 7)
232 /* This one is used only internally. */
233 #define DL_DEBUG_HELP (1 << 8)
234 #define DL_DEBUG_PRELINK (1 << 9)
236 /* Cached value of `getpagesize ()'. */
237 EXTERN size_t _dl_pagesize;
239 /* During the program run we must not modify the global data of
240 loaded shared object simultanously in two threads. Therefore we
241 protect `_dl_open' and `_dl_close' in dl-close.c.
243 This must be a recursive lock since the initializer function of
244 the loaded object might as well require a call to this function.
245 At this time it is not anymore a problem to modify the tables. */
246 __libc_lock_define_recursive (EXTERN, _dl_load_lock)
249 EXTERN unsigned int _dl_osversion;
251 EXTERN const char *_dl_platform;
252 EXTERN size_t _dl_platformlen;
255 /* File descriptor referring to the zero-fill device. */
256 EXTERN int _dl_zerofd;
259 /* CLK_TCK as reported by the kernel. */
260 EXTERN int _dl_clktck;
262 /* If nonzero print warnings messages. */
263 EXTERN int _dl_verbose;
265 /* Do we do lazy relocations? */
268 /* Nonzero if runtime lookups should not update the .got/.plt. */
269 EXTERN int _dl_bind_not;
271 /* Nonzero if references should be treated as weak during runtime
273 EXTERN int _dl_dynamic_weak;
275 /* Default floating-point control word. */
276 EXTERN fpu_control_t _dl_fpu_control;
278 /* The object to be initialized first. */
279 EXTERN struct link_map *_dl_initfirst;
282 /* Start time on CPU clock. */
283 EXTERN hp_timing_t _dl_cpuclock_offset;
285 /* Overhead of a high-precision timing measurement. */
286 EXTERN hp_timing_t _dl_hp_timing_overhead;
289 /* Name of the shared object to be profiled (if any). */
290 EXTERN const char *_dl_profile;
291 /* Map of shared object to be profiled. */
292 EXTERN struct link_map *_dl_profile_map;
293 /* Filename of the output file. */
294 EXTERN const char *_dl_profile_output;
295 /* Map of shared object to be prelink traced. */
296 EXTERN struct link_map *_dl_trace_prelink_map;
297 /* Name of the object we want to trace the prelinking. */
298 EXTERN const char *_dl_trace_prelink;
300 /* Expected cache ID. */
301 EXTERN int _dl_correct_cache_id;
303 /* Counters for the number of relocations performed. */
304 EXTERN unsigned long int _dl_num_relocations;
305 EXTERN unsigned long int _dl_num_cache_relocations;
307 /* Mask for hardware capabilities that are available. */
308 EXTERN unsigned long int _dl_hwcap;
310 /* Mask for important hardware capabilities we honour. */
311 EXTERN unsigned long int _dl_hwcap_mask;
313 /* Names of shared object for which the RPATH should be ignored. */
314 EXTERN const char *_dl_inhibit_rpath;
316 /* Location of the binary. */
317 EXTERN const char *_dl_origin_path;
319 /* List of search directories. */
320 EXTERN struct r_search_path_elem *_dl_all_dirs;
321 EXTERN struct r_search_path_elem *_dl_init_all_dirs;
323 /* File descriptor to write debug messages to. */
324 EXTERN int _dl_debug_fd;
326 /* Get architecture specific definitions. */
327 #define PROCINFO_DECL
328 #include <dl-procinfo.c>
330 /* Structure describing the dynamic linker itself. */
331 EXTERN struct link_map _dl_rtld_map;
334 extern struct rtld_global _rtld_global;
338 /* Parameters passed to the dynamic linker. */
340 extern char **_dl_argv;
342 /* The array with message we print as a last resort. */
343 extern const char _dl_out_of_memory[];
346 /* OS-dependent function to open the zero-fill device. */
347 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
350 /* During the program run we must not modify the global data of
351 loaded shared object simultanously in two threads. Therefore we
352 protect `_dl_open' and `_dl_close' in dl-close.c.
354 This must be a recursive lock since the initializer function of
355 the loaded object might as well require a call to this function.
356 At this time it is not anymore a problem to modify the tables. */
357 __libc_lock_define_recursive (extern, _dl_load_lock)
360 /* Write message on the debug file descriptor. The parameters are
361 interpreted as for a `printf' call. All the lines start with a
362 tag showing the PID. */
363 extern void _dl_debug_printf (const char *fmt, ...)
364 __attribute__ ((__format__ (__printf__, 1, 2)));
366 /* Write message on the debug file descriptor. The parameters are
367 interpreted as for a `printf' call. All the lines buf the first
368 start with a tag showing the PID. */
369 extern void _dl_debug_printf_c (const char *fmt, ...)
370 __attribute__ ((__format__ (__printf__, 1, 2)));
373 /* Write a message on the specified descriptor FD. The parameters are
374 interpreted as for a `printf' call. */
375 extern void _dl_dprintf (int fd, const char *fmt, ...)
376 __attribute__ ((__format__ (__printf__, 2, 3)));
378 /* Write a message on the specified descriptor standard output. The
379 parameters are interpreted as for a `printf' call. */
380 #define _dl_printf(fmt, args...) \
381 _dl_dprintf (STDOUT_FILENO, fmt, ##args)
383 /* Write a message on the specified descriptor standard error. The
384 parameters are interpreted as for a `printf' call. */
385 #define _dl_error_printf(fmt, args...) \
386 _dl_dprintf (STDERR_FILENO, fmt, ##args)
388 /* Write a message on the specified descriptor standard error and exit
389 the program. The parameters are interpreted as for a `printf' call. */
390 #define _dl_fatal_printf(fmt, args...) \
393 _dl_dprintf (STDERR_FILENO, fmt, ##args); \
399 /* This function is called by all the internal dynamic linker functions
400 when they encounter an error. ERRCODE is either an `errno' code or
401 zero; OBJECT is the name of the problematical shared object, or null if
402 it is a general problem; ERRSTRING is a string describing the specific
404 extern void _dl_signal_error (int errcode, const char *object,
405 const char *occurred, const char *errstring)
407 __attribute__ ((__noreturn__));
409 /* Like _dl_signal_error, but may return when called in the context of
410 _dl_receive_error. */
411 extern void _dl_signal_cerror (int errcode, const char *object,
412 const char *occation, const char *errstring)
415 /* Call OPERATE, receiving errors from `dl_signal_cerror'. Unlike
416 `_dl_catch_error' the operation is resumed after the OPERATE
418 ARGS is passed as argument to OPERATE. */
419 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
424 /* Open the shared object NAME and map in its segments.
425 LOADER's DT_RPATH is used in searching for NAME.
426 If the object is already opened, returns its existing map.
427 For preloaded shared objects PRELOADED is set to a non-zero
428 value to allow additional security checks. */
429 extern struct link_map *_dl_map_object (struct link_map *loader,
430 const char *name, int preloaded,
431 int type, int trace_mode, int mode)
434 /* Call _dl_map_object on the dependencies of MAP, and set up
435 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
436 loaded objects that will be inserted into MAP->l_searchlist after MAP
437 but before its dependencies. */
438 extern void _dl_map_object_deps (struct link_map *map,
439 struct link_map **preloads,
440 unsigned int npreloads, int trace_mode)
443 /* Cache the locations of MAP's hash table. */
444 extern void _dl_setup_hash (struct link_map *map) internal_function;
447 /* Search loaded objects' symbol tables for a definition of the symbol
448 referred to by UNDEF. *SYM is the symbol table entry containing the
449 reference; it is replaced with the defining symbol, and the base load
450 address of the defining object is returned. SYMBOL_SCOPE is a
451 null-terminated list of object scopes to search; each object's
452 l_searchlist (i.e. the segment of the dependency tree starting at that
453 object) is searched in turn. REFERENCE_NAME should name the object
454 containing the reference; it is used in error messages.
455 TYPE_CLASS describes the type of symbol we are looking for. */
456 extern lookup_t _dl_lookup_symbol (const char *undef,
457 struct link_map *undef_map,
458 const ElfW(Sym) **sym,
459 struct r_scope_elem *symbol_scope[],
460 int type_class, int explicit)
463 /* Lookup versioned symbol. */
464 extern lookup_t _dl_lookup_versioned_symbol (const char *undef,
465 struct link_map *undef_map,
466 const ElfW(Sym) **sym,
467 struct r_scope_elem *symbol_scope[],
468 const struct r_found_version *version,
469 int type_class, int explicit)
472 /* For handling RTLD_NEXT we must be able to skip shared objects. */
473 extern lookup_t _dl_lookup_symbol_skip (const char *undef,
474 struct link_map *undef_map,
475 const ElfW(Sym) **sym,
476 struct r_scope_elem *symbol_scope[],
477 struct link_map *skip_this)
480 /* For handling RTLD_NEXT with versioned symbols we must be able to
481 skip shared objects. */
482 extern lookup_t _dl_lookup_versioned_symbol_skip (const char *undef,
483 struct link_map *undef_map,
484 const ElfW(Sym) **sym,
485 struct r_scope_elem *symbol_scope[],
486 const struct r_found_version *version,
487 struct link_map *skip_this)
490 /* Look up symbol NAME in MAP's scope and return its run-time address. */
491 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
494 /* Allocate a `struct link_map' for a new object being loaded,
495 and enter it into the _dl_main_map list. */
496 extern struct link_map *_dl_new_object (char *realname, const char *libname,
497 int type, struct link_map *loader)
500 /* Relocate the given object (if it hasn't already been).
501 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
502 If LAZY is nonzero, don't relocate its PLT. */
503 extern void _dl_relocate_object (struct link_map *map,
504 struct r_scope_elem *scope[],
505 int lazy, int consider_profiling);
507 /* Call _dl_signal_error with a message about an unhandled reloc type.
508 TYPE is the result of ELFW(R_TYPE) (r_info), i.e. an R_<CPU>_* value.
509 PLT is nonzero if this was a PLT reloc; it just affects the message. */
510 extern void _dl_reloc_bad_type (struct link_map *map,
511 unsigned int type, int plt)
512 internal_function __attribute__ ((__noreturn__));
514 /* Resolve conflicts if prelinking. */
515 extern void _dl_resolve_conflicts (struct link_map *l,
516 ElfW(Rela) *conflict,
517 ElfW(Rela) *conflictend);
519 /* Check the version dependencies of all objects available through
520 MAP. If VERBOSE print some more diagnostics. */
521 extern int _dl_check_all_versions (struct link_map *map, int verbose,
525 /* Check the version dependencies for MAP. If VERBOSE print some more
527 extern int _dl_check_map_versions (struct link_map *map, int verbose,
531 /* Initialize the object in SCOPE by calling the constructors with
532 ARGC, ARGV, and ENV as the parameters. */
533 extern void _dl_init (struct link_map *main_map, int argc, char **argv,
534 char **env) internal_function;
536 /* Call the finalizer functions of all shared objects whose
537 initializer functions have completed. */
538 extern void _dl_fini (void) internal_function;
540 /* The dynamic linker calls this function before and having changing
541 any shared object mappings. The `r_state' member of `struct r_debug'
542 says what change is taking place. This function's address is
543 the value of the `r_brk' member. */
544 extern void _dl_debug_state (void);
546 /* Initialize `struct r_debug' if it has not already been done. The
547 argument is the run-time load address of the dynamic linker, to be put
548 in the `r_ldbase' member. Returns the address of the structure. */
549 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
552 /* Initialize the basic data structure for the search paths. */
553 extern void _dl_init_paths (const char *library_path) internal_function;
555 /* Gather the information needed to install the profiling tables and start
557 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
560 /* The actual functions used to keep book on the calls. */
561 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
563 /* This function is simply a wrapper around the _dl_mcount function
564 which does not require a FROMPC parameter since this is the
566 extern void _dl_mcount_wrapper (void *selfpc);
568 /* Show the members of the auxiliary array passed up from the kernel. */
569 extern void _dl_show_auxv (void) internal_function;
571 /* Return all environment variables starting with `LD_', one after the
573 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
575 /* Return an array with the names of the important hardware capabilities. */
576 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
579 size_t *max_capstrlen)
582 /* Look up NAME in ld.so.cache and return the file name stored there,
583 or null if none is found. */
584 extern const char *_dl_load_cache_lookup (const char *name)
587 /* If the system does not support MAP_COPY we cannot leave the file open
588 all the time since this would create problems when the file is replaced.
589 Therefore we provide this function to close the file and open it again
591 extern void _dl_unload_cache (void);
593 /* System-dependent function to read a file's whole contents in the
594 most convenient manner available. *SIZEP gets the size of the
595 file. On error MAP_FAILED is returned. */
596 extern void *_dl_sysdep_read_whole_file (const char *file, size_t *sizep,
600 /* System-specific function to do initial startup for the dynamic linker.
601 After this, file access calls and getenv must work. This is responsible
602 for setting __libc_enable_secure if we need to be secure (e.g. setuid),
603 and for setting _dl_argc and _dl_argv, and then calling _dl_main. */
604 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
605 void (*dl_main) (const ElfW(Phdr) *phdr,
607 ElfW(Addr) *user_entry));
609 extern void _dl_sysdep_start_cleanup (void)
615 #endif /* ldsodefs.h */