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>
42 /* We use this macro to refer to ELF types independent of the native wordsize.
43 `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
44 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
46 /* All references to the value of l_info[DT_PLTGOT],
47 l_info[DT_STRTAB], l_info[DT_SYMTAB], l_info[DT_RELA],
48 l_info[DT_REL], l_info[DT_JMPREL], and l_info[VERSYMIDX (DT_VERSYM)]
49 have to be accessed via the D_PTR macro. The macro is needed since for
50 most architectures the entry is already relocated - but for some not
51 and we need to relocate at access time. */
52 #ifdef DL_RO_DYN_SECTION
53 # define D_PTR(map,i) (map->i->d_un.d_ptr + map->l_addr)
55 # define D_PTR(map,i) map->i->d_un.d_ptr
58 /* On some platforms more information than just the address of the symbol
59 is needed from the lookup functions. In this case we return the whole
61 #ifdef DL_LOOKUP_RETURNS_MAP
62 typedef struct link_map *lookup_t;
63 # define LOOKUP_VALUE(map) map
64 # define LOOKUP_VALUE_ADDRESS(map) (map ? map->l_addr : 0)
66 typedef ElfW(Addr) lookup_t;
67 # define LOOKUP_VALUE(map) map->l_addr
68 # define LOOKUP_VALUE_ADDRESS(address) address
71 /* on some architectures a pointer to a function is not just a pointer
72 to the actual code of the function but rather an architecture
73 specific descriptor. */
74 #ifndef ELF_FUNCTION_PTR_IS_SPECIAL
75 # define DL_SYMBOL_ADDRESS(map, ref) \
76 (void *) (LOOKUP_VALUE_ADDRESS (map) + ref->st_value)
77 # define DL_LOOKUP_ADDRESS(addr) ((ElfW(Addr)) (addr))
78 # define DL_DT_INIT_ADDRESS(map, start) (start)
79 # define DL_DT_FINI_ADDRESS(map, start) (start)
82 /* Unmap a loaded object, called by _dl_close (). */
83 #ifndef DL_UNMAP_IS_SPECIAL
84 # define DL_UNMAP(map) \
85 __munmap ((void *) (map)->l_map_start, \
86 (map)->l_map_end - (map)->l_map_start)
89 /* By default we do not need special support to initialize DSOs loaded
90 by statically linked binaries. */
91 #ifndef DL_STATIC_INIT
92 # define DL_STATIC_INIT(map)
95 /* Reloc type classes as returned by elf_machine_type_class().
96 ELF_RTYPE_CLASS_PLT means this reloc should not be satisfied by
97 some PLT symbol, ELF_RTYPE_CLASS_COPY means this reloc should not be
98 satisfied by any symbol in the executable. */
99 #define ELF_RTYPE_CLASS_PLT 1
100 #define ELF_RTYPE_CLASS_COPY 2
102 /* ELF uses the PF_x macros to specify the segment permissions, mmap
103 uses PROT_xxx. In most cases the three macros have the values 1, 2,
104 and 3 but not in a matching order. The following macros allows
105 converting from the PF_x values to PROT_xxx values. */
107 ((PROT_READ << (PF_R * 4)) \
108 | (PROT_WRITE << (PF_W * 4)) \
109 | (PROT_EXEC << (PF_X * 4)) \
110 | ((PROT_READ | PROT_WRITE) << ((PF_R | PF_W) * 4)) \
111 | ((PROT_READ | PROT_EXEC) << ((PF_R | PF_X) * 4)) \
112 | ((PROT_WRITE | PROT_EXEC) << (PF_W | PF_X) * 4) \
113 | ((PROT_READ | PROT_WRITE | PROT_EXEC) << ((PF_R | PF_W | PF_X) * 4)))
116 /* For the version handling we need an array with only names and their
118 struct r_found_version
124 const char *filename;
127 /* We want to cache information about the searches for shared objects. */
129 enum r_dir_status { unknown, nonexisting, existing };
131 struct r_search_path_elem
133 /* This link is only used in the `all_dirs' member of `r_search_path'. */
134 struct r_search_path_elem *next;
136 /* Strings saying where the definition came from. */
140 /* Basename for this search path element. The string must end with
141 a slash character. */
145 enum r_dir_status status[0];
155 /* A data structure for a simple single linked list of strings. */
158 const char *name; /* Name requested (before search). */
159 struct libname_list *next; /* Link to next name for this object. */
160 int dont_free; /* Flag whether this element should be freed
161 if the object is not entirely unloaded. */
165 /* Test whether given NAME matches any of the names of the given object. */
167 __attribute__ ((unused))
168 _dl_name_match_p (const char *__name, struct link_map *__map)
170 int __found = strcmp (__name, __map->l_name) == 0;
171 struct libname_list *__runp = __map->l_libname;
173 while (! __found && __runp != NULL)
174 if (strcmp (__name, __runp->name) == 0)
177 __runp = __runp->next;
182 /* Function used as argument for `_dl_receive_error' function. The
183 arguments are the error code, error string, and the objname the
184 error occurred in. */
185 typedef void (*receiver_fct) (int, const char *, const char *);
187 /* Internal functions of the run-time dynamic linker.
188 These can be accessed if you link again the dynamic linker
189 as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
190 but are not normally of interest to user programs.
192 The `-ldl' library functions in <dlfcn.h> provide a simple
193 user interface to run-time dynamic linking. */
197 # define EXTERN extern
198 # define GL(name) _##name
201 # define GL(name) _rtld_global._##name
205 /* Don't change the order of the following elements. 'dl_loaded'
206 must remain the first element. Forever. */
208 /* And a pointer to the map for the main map. */
209 EXTERN struct link_map *_dl_loaded;
210 /* Number of object in the _dl_loaded list. */
211 EXTERN unsigned int _dl_nloaded;
212 /* Array representing global scope. */
213 EXTERN struct r_scope_elem *_dl_global_scope[2];
214 /* Direct pointer to the searchlist of the main object. */
215 EXTERN struct r_scope_elem *_dl_main_searchlist;
216 /* Copy of the content of `_dl_main_searchlist'. */
217 EXTERN struct r_scope_elem _dl_initial_searchlist;
218 /* This is zero at program start to signal that the global scope map is
219 allocated by rtld. Later it keeps the size of the map. It might be
220 reset if in _dl_close if the last global object is removed. */
221 EXTERN size_t _dl_global_scope_alloc;
223 /* If nonzero the appropriate debug information is printed. */
224 EXTERN int _dl_debug_mask;
225 #define DL_DEBUG_LIBS (1 << 0)
226 #define DL_DEBUG_IMPCALLS (1 << 1)
227 #define DL_DEBUG_BINDINGS (1 << 2)
228 #define DL_DEBUG_SYMBOLS (1 << 3)
229 #define DL_DEBUG_VERSIONS (1 << 4)
230 #define DL_DEBUG_RELOC (1 << 5)
231 #define DL_DEBUG_FILES (1 << 6)
232 #define DL_DEBUG_STATISTICS (1 << 7)
233 /* This one is used only internally. */
234 #define DL_DEBUG_HELP (1 << 8)
235 #define DL_DEBUG_PRELINK (1 << 9)
237 /* Cached value of `getpagesize ()'. */
238 EXTERN size_t _dl_pagesize;
240 /* During the program run we must not modify the global data of
241 loaded shared object simultanously in two threads. Therefore we
242 protect `_dl_open' and `_dl_close' in dl-close.c.
244 This must be a recursive lock since the initializer function of
245 the loaded object might as well require a call to this function.
246 At this time it is not anymore a problem to modify the tables. */
247 __libc_lock_define_recursive (EXTERN, _dl_load_lock)
250 EXTERN unsigned int _dl_osversion;
252 EXTERN const char *_dl_platform;
253 EXTERN size_t _dl_platformlen;
256 /* File descriptor referring to the zero-fill device. */
257 EXTERN int _dl_zerofd;
260 /* CLK_TCK as reported by the kernel. */
261 EXTERN int _dl_clktck;
263 /* If nonzero print warnings messages. */
264 EXTERN int _dl_verbose;
266 /* Do we do lazy relocations? */
269 /* Nonzero if runtime lookups should not update the .got/.plt. */
270 EXTERN int _dl_bind_not;
272 /* Nonzero if references should be treated as weak during runtime
274 EXTERN int _dl_dynamic_weak;
276 /* Default floating-point control word. */
277 EXTERN fpu_control_t _dl_fpu_control;
279 /* The object to be initialized first. */
280 EXTERN struct link_map *_dl_initfirst;
283 /* Start time on CPU clock. */
284 EXTERN hp_timing_t _dl_cpuclock_offset;
286 /* Overhead of a high-precision timing measurement. */
287 EXTERN hp_timing_t _dl_hp_timing_overhead;
291 /* Offset of the TLS block for ld.so from the thread-pointer. */
292 EXTERN size_t _rtld_tlsoffset;
295 /* Name of the shared object to be profiled (if any). */
296 EXTERN const char *_dl_profile;
297 /* Map of shared object to be profiled. */
298 EXTERN struct link_map *_dl_profile_map;
299 /* Filename of the output file. */
300 EXTERN const char *_dl_profile_output;
301 /* Map of shared object to be prelink traced. */
302 EXTERN struct link_map *_dl_trace_prelink_map;
303 /* Name of the object we want to trace the prelinking. */
304 EXTERN const char *_dl_trace_prelink;
306 /* Expected cache ID. */
307 EXTERN int _dl_correct_cache_id;
309 /* Counters for the number of relocations performed. */
310 EXTERN unsigned long int _dl_num_relocations;
311 EXTERN unsigned long int _dl_num_cache_relocations;
313 /* Mask for hardware capabilities that are available. */
314 EXTERN unsigned long int _dl_hwcap;
316 /* Mask for important hardware capabilities we honour. */
317 EXTERN unsigned long int _dl_hwcap_mask;
319 /* Names of shared object for which the RPATH should be ignored. */
320 EXTERN const char *_dl_inhibit_rpath;
322 /* Location of the binary. */
323 EXTERN const char *_dl_origin_path;
325 /* List of search directories. */
326 EXTERN struct r_search_path_elem *_dl_all_dirs;
327 EXTERN struct r_search_path_elem *_dl_init_all_dirs;
329 /* File descriptor to write debug messages to. */
330 EXTERN int _dl_debug_fd;
332 /* Get architecture specific definitions. */
333 #define PROCINFO_DECL
334 #include <dl-procinfo.c>
336 /* Structure describing the dynamic linker itself. */
337 EXTERN struct link_map _dl_rtld_map;
340 extern struct rtld_global _rtld_global;
344 /* Parameters passed to the dynamic linker. */
346 extern char **_dl_argv;
348 /* The array with message we print as a last resort. */
349 extern const char _dl_out_of_memory[];
352 /* OS-dependent function to open the zero-fill device. */
353 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
356 /* Write message on the debug file descriptor. The parameters are
357 interpreted as for a `printf' call. All the lines start with a
358 tag showing the PID. */
359 extern void _dl_debug_printf (const char *fmt, ...)
360 __attribute__ ((__format__ (__printf__, 1, 2)));
361 extern void _dl_debug_printf_internal (const char *fmt, ...)
362 __attribute__ ((__format__ (__printf__, 1, 2)));
364 /* Write message on the debug file descriptor. The parameters are
365 interpreted as for a `printf' call. All the lines buf the first
366 start with a tag showing the PID. */
367 extern void _dl_debug_printf_c (const char *fmt, ...)
368 __attribute__ ((__format__ (__printf__, 1, 2)));
371 /* Write a message on the specified descriptor FD. The parameters are
372 interpreted as for a `printf' call. */
373 extern void _dl_dprintf (int fd, const char *fmt, ...)
374 __attribute__ ((__format__ (__printf__, 2, 3)));
376 /* Write a message on the specified descriptor standard output. The
377 parameters are interpreted as for a `printf' call. */
378 #define _dl_printf(fmt, args...) \
379 _dl_dprintf (STDOUT_FILENO, fmt, ##args)
381 /* Write a message on the specified descriptor standard error. The
382 parameters are interpreted as for a `printf' call. */
383 #define _dl_error_printf(fmt, args...) \
384 _dl_dprintf (STDERR_FILENO, fmt, ##args)
386 /* Write a message on the specified descriptor standard error and exit
387 the program. The parameters are interpreted as for a `printf' call. */
388 #define _dl_fatal_printf(fmt, args...) \
391 _dl_dprintf (STDERR_FILENO, fmt, ##args); \
397 /* This function is called by all the internal dynamic linker functions
398 when they encounter an error. ERRCODE is either an `errno' code or
399 zero; OBJECT is the name of the problematical shared object, or null if
400 it is a general problem; ERRSTRING is a string describing the specific
402 extern void _dl_signal_error (int errcode, const char *object,
403 const char *occurred, const char *errstring)
405 __attribute__ ((__noreturn__));
406 extern void _dl_signal_error_internal (int errcode, const char *object,
407 const char *occurred,
408 const char *errstring)
410 __attribute__ ((__noreturn__));
412 /* Like _dl_signal_error, but may return when called in the context of
413 _dl_receive_error. */
414 extern void _dl_signal_cerror (int errcode, const char *object,
415 const char *occation, const char *errstring)
418 /* Call OPERATE, receiving errors from `dl_signal_cerror'. Unlike
419 `_dl_catch_error' the operation is resumed after the OPERATE
421 ARGS is passed as argument to OPERATE. */
422 extern void _dl_receive_error (receiver_fct fct, void (*operate) (void *),
427 /* Open the shared object NAME and map in its segments.
428 LOADER's DT_RPATH is used in searching for NAME.
429 If the object is already opened, returns its existing map.
430 For preloaded shared objects PRELOADED is set to a non-zero
431 value to allow additional security checks. */
432 extern struct link_map *_dl_map_object (struct link_map *loader,
433 const char *name, int preloaded,
434 int type, int trace_mode, int mode)
436 extern struct link_map *_dl_map_object_internal (struct link_map *loader,
439 int type, int trace_mode,
443 /* Call _dl_map_object on the dependencies of MAP, and set up
444 MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
445 loaded objects that will be inserted into MAP->l_searchlist after MAP
446 but before its dependencies. */
447 extern void _dl_map_object_deps (struct link_map *map,
448 struct link_map **preloads,
449 unsigned int npreloads, int trace_mode)
451 extern void _dl_map_object_deps_internal (struct link_map *map,
452 struct link_map **preloads,
453 unsigned int npreloads,
457 /* Cache the locations of MAP's hash table. */
458 extern void _dl_setup_hash (struct link_map *map) internal_function;
461 /* Search loaded objects' symbol tables for a definition of the symbol
462 referred to by UNDEF. *SYM is the symbol table entry containing the
463 reference; it is replaced with the defining symbol, and the base load
464 address of the defining object is returned. SYMBOL_SCOPE is a
465 null-terminated list of object scopes to search; each object's
466 l_searchlist (i.e. the segment of the dependency tree starting at that
467 object) is searched in turn. REFERENCE_NAME should name the object
468 containing the reference; it is used in error messages.
469 TYPE_CLASS describes the type of symbol we are looking for. */
470 extern lookup_t _dl_lookup_symbol (const char *undef,
471 struct link_map *undef_map,
472 const ElfW(Sym) **sym,
473 struct r_scope_elem *symbol_scope[],
474 int type_class, int explicit)
476 extern lookup_t _dl_lookup_symbol_internal (const char *undef,
477 struct link_map *undef_map,
478 const ElfW(Sym) **sym,
479 struct r_scope_elem *symbol_scope[],
480 int type_class, int explicit)
483 /* Lookup versioned symbol. */
484 extern lookup_t _dl_lookup_versioned_symbol (const char *undef,
485 struct link_map *undef_map,
486 const ElfW(Sym) **sym,
487 struct r_scope_elem *symbol_scope[],
488 const struct r_found_version *version,
489 int type_class, int explicit)
491 extern lookup_t _dl_lookup_versioned_symbol_internal (const char *undef,
492 struct link_map *undef_map,
493 const ElfW(Sym) **sym,
494 struct r_scope_elem *symbol_scope[],
495 const struct r_found_version *version,
500 /* For handling RTLD_NEXT we must be able to skip shared objects. */
501 extern lookup_t _dl_lookup_symbol_skip (const char *undef,
502 struct link_map *undef_map,
503 const ElfW(Sym) **sym,
504 struct r_scope_elem *symbol_scope[],
505 struct link_map *skip_this)
508 /* For handling RTLD_NEXT with versioned symbols we must be able to
509 skip shared objects. */
510 extern lookup_t _dl_lookup_versioned_symbol_skip (const char *undef,
511 struct link_map *undef_map,
512 const ElfW(Sym) **sym,
513 struct r_scope_elem *symbol_scope[],
514 const struct r_found_version *version,
515 struct link_map *skip_this)
518 /* Look up symbol NAME in MAP's scope and return its run-time address. */
519 extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name)
522 /* Allocate a `struct link_map' for a new object being loaded,
523 and enter it into the _dl_main_map list. */
524 extern struct link_map *_dl_new_object (char *realname, const char *libname,
525 int type, struct link_map *loader)
528 /* Relocate the given object (if it hasn't already been).
529 SCOPE is passed to _dl_lookup_symbol in symbol lookups.
530 If LAZY is nonzero, don't relocate its PLT. */
531 extern void _dl_relocate_object (struct link_map *map,
532 struct r_scope_elem *scope[],
533 int lazy, int consider_profiling);
534 extern void _dl_relocate_object_internal (struct link_map *map,
535 struct r_scope_elem *scope[],
536 int lazy, int consider_profiling);
538 /* Call _dl_signal_error with a message about an unhandled reloc type.
539 TYPE is the result of ELFW(R_TYPE) (r_info), i.e. an R_<CPU>_* value.
540 PLT is nonzero if this was a PLT reloc; it just affects the message. */
541 extern void _dl_reloc_bad_type (struct link_map *map,
542 unsigned int type, int plt)
543 internal_function __attribute__ ((__noreturn__));
545 /* Resolve conflicts if prelinking. */
546 extern void _dl_resolve_conflicts (struct link_map *l,
547 ElfW(Rela) *conflict,
548 ElfW(Rela) *conflictend);
550 /* Check the version dependencies of all objects available through
551 MAP. If VERBOSE print some more diagnostics. */
552 extern int _dl_check_all_versions (struct link_map *map, int verbose,
556 /* Check the version dependencies for MAP. If VERBOSE print some more
558 extern int _dl_check_map_versions (struct link_map *map, int verbose,
562 /* Initialize the object in SCOPE by calling the constructors with
563 ARGC, ARGV, and ENV as the parameters. */
564 extern void _dl_init (struct link_map *main_map, int argc, char **argv,
565 char **env) internal_function;
567 /* Call the finalizer functions of all shared objects whose
568 initializer functions have completed. */
569 extern void _dl_fini (void) internal_function;
571 /* The dynamic linker calls this function before and having changing
572 any shared object mappings. The `r_state' member of `struct r_debug'
573 says what change is taking place. This function's address is
574 the value of the `r_brk' member. */
575 extern void _dl_debug_state (void);
576 extern void _dl_debug_state_internal (void);
578 /* Initialize `struct r_debug' if it has not already been done. The
579 argument is the run-time load address of the dynamic linker, to be put
580 in the `r_ldbase' member. Returns the address of the structure. */
581 extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase)
584 /* Initialize the basic data structure for the search paths. */
585 extern void _dl_init_paths (const char *library_path) internal_function;
587 /* Gather the information needed to install the profiling tables and start
589 extern void _dl_start_profile (struct link_map *map, const char *output_dir)
591 extern void _dl_start_profile_internal (struct link_map *map,
592 const char *output_dir)
595 /* The actual functions used to keep book on the calls. */
596 extern void _dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc);
598 /* This function is simply a wrapper around the _dl_mcount function
599 which does not require a FROMPC parameter since this is the
601 extern void _dl_mcount_wrapper (void *selfpc);
603 /* Show the members of the auxiliary array passed up from the kernel. */
604 extern void _dl_show_auxv (void) internal_function;
606 /* Return all environment variables starting with `LD_', one after the
608 extern char *_dl_next_ld_env_entry (char ***position) internal_function;
610 /* Return an array with the names of the important hardware capabilities. */
611 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
614 size_t *max_capstrlen)
617 /* Look up NAME in ld.so.cache and return the file name stored there,
618 or null if none is found. */
619 extern const char *_dl_load_cache_lookup (const char *name)
622 /* If the system does not support MAP_COPY we cannot leave the file open
623 all the time since this would create problems when the file is replaced.
624 Therefore we provide this function to close the file and open it again
626 extern void _dl_unload_cache (void);
627 extern void _dl_unload_cache_internal (void);
629 /* System-dependent function to read a file's whole contents in the
630 most convenient manner available. *SIZEP gets the size of the
631 file. On error MAP_FAILED is returned. */
632 extern void *_dl_sysdep_read_whole_file (const char *file, size_t *sizep,
636 /* System-specific function to do initial startup for the dynamic linker.
637 After this, file access calls and getenv must work. This is responsible
638 for setting __libc_enable_secure if we need to be secure (e.g. setuid),
639 and for setting _dl_argc and _dl_argv, and then calling _dl_main. */
640 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
641 void (*dl_main) (const ElfW(Phdr) *phdr,
643 ElfW(Addr) *user_entry));
645 extern void _dl_sysdep_start_cleanup (void)
651 #endif /* ldsodefs.h */