atexit.c 9.5 KB

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  1. /* Copyright (C) 1995,1996 Robert de Bath <rdebath@cix.compulink.co.uk>
  2. * This file is part of the Linux-8086 C library and is distributed
  3. * under the GNU Library General Public License.
  4. */
  5. /*
  6. * Dec 2000 Manuel Novoa III
  7. *
  8. * Made atexit handling conform to standards... i.e. no args.
  9. * Removed on_exit since it did not match gnu libc definition.
  10. * Combined atexit and __do_exit into one object file.
  11. *
  12. * Feb 2001 Manuel Novoa III
  13. *
  14. * Reworked file after addition of __uClibc_main.
  15. * Changed name of __do_exit to atexit_handler.
  16. * Changed name of __cleanup to __uClibc_cleanup.
  17. * Moved declaration of __uClibc_cleanup to __uClibc_main
  18. * where it is initialized with (possibly weak alias)
  19. * _stdio_term.
  20. *
  21. * Jul 2001 Steve Thayer
  22. *
  23. * Added an on_exit implementation (that now matches gnu libc definition.)
  24. * Pulled atexit_handler out of the atexit object since it is now required by
  25. * on_exit as well. Renamed it to __exit_handler.
  26. * Fixed a problem where exit functions stop getting called if one of
  27. * them calls exit().
  28. * As a side effect of these changes, abort() no longer calls the exit
  29. * functions (it now matches the gnu libc definition).
  30. *
  31. * August 2002 Erik Andersen
  32. * Added locking so atexit and friends can be thread safe
  33. *
  34. * August 2005 Stephen Warren
  35. * Added __cxa_atexit and __cxa_finalize support
  36. *
  37. */
  38. #define _GNU_SOURCE
  39. #include <features.h>
  40. #include <unistd.h>
  41. #include <stdlib.h>
  42. #include <errno.h>
  43. #include <atomic.h>
  44. libc_hidden_proto(exit)
  45. libc_hidden_proto(_exit)
  46. #ifdef __UCLIBC_HAS_THREADS__
  47. # include <pthread.h>
  48. extern pthread_mutex_t mylock;
  49. #endif
  50. #define LOCK __pthread_mutex_lock(&mylock)
  51. #define UNLOCK __pthread_mutex_unlock(&mylock)
  52. typedef void (*aefuncp) (void); /* atexit function pointer */
  53. typedef void (*oefuncp) (int, void *); /* on_exit function pointer */
  54. typedef void (*cxaefuncp) (void *); /* __cxa_atexit function pointer */
  55. typedef enum {
  56. ef_free,
  57. ef_in_use,
  58. ef_on_exit,
  59. ef_cxa_atexit
  60. } ef_type; /* exit function types */
  61. /* this is in the L_exit object */
  62. extern void (*__exit_cleanup) (int) attribute_hidden;
  63. /* these are in the L___do_exit object */
  64. extern int __exit_slots attribute_hidden;
  65. extern int __exit_count attribute_hidden;
  66. extern void __exit_handler(int) attribute_hidden;
  67. struct exit_function {
  68. /*
  69. * 'type' should be of type of the 'enum ef_type' above but since we
  70. * need this element in an atomic operation we have to use 'long int'.
  71. */
  72. long int type; /* enum ef_type */
  73. union {
  74. struct {
  75. oefuncp func;
  76. void *arg;
  77. } on_exit;
  78. struct {
  79. cxaefuncp func;
  80. void *arg;
  81. void* dso_handle;
  82. } cxa_atexit;
  83. } funcs;
  84. };
  85. #ifdef __UCLIBC_DYNAMIC_ATEXIT__
  86. extern struct exit_function *__exit_function_table attribute_hidden;
  87. #else
  88. extern struct exit_function __exit_function_table[__UCLIBC_MAX_ATEXIT] attribute_hidden;
  89. #endif
  90. extern struct exit_function *__new_exitfn (void) attribute_hidden;
  91. /* this is in the L___cxa_atexit object */
  92. extern int __cxa_atexit (cxaefuncp, void *arg, void *dso_handle);
  93. /* remove old_atexit after 0.9.29 */
  94. #if defined(L_atexit) || defined(L_old_atexit)
  95. extern void *__dso_handle __attribute__ ((__weak__));
  96. /*
  97. * register a function to be called at normal program termination
  98. * (the registered function takes no arguments)
  99. */
  100. #ifdef L_atexit
  101. int attribute_hidden atexit(aefuncp func)
  102. #else
  103. int old_atexit(aefuncp func)
  104. #endif
  105. {
  106. /*
  107. * glibc casts aefuncp to cxaefuncp.
  108. * This seems dodgy, but I guess callling a function with more
  109. * parameters than it needs will work everywhere?
  110. */
  111. return __cxa_atexit((cxaefuncp)func, NULL,
  112. &__dso_handle == NULL ? NULL : __dso_handle);
  113. }
  114. #ifndef L_atexit
  115. weak_alias(old_atexit,atexit)
  116. #endif
  117. #endif
  118. #ifdef L_on_exit
  119. /*
  120. * register a function to be called at normal program termination
  121. * the registered function takes two arguments:
  122. * status - the exit status that was passed to the exit() function
  123. * arg - generic argument
  124. */
  125. int on_exit(oefuncp func, void *arg)
  126. {
  127. struct exit_function *efp;
  128. if (func == NULL) {
  129. return 0;
  130. }
  131. efp = __new_exitfn();
  132. if (efp == NULL) {
  133. return -1;
  134. }
  135. efp->funcs.on_exit.func = func;
  136. efp->funcs.on_exit.arg = arg;
  137. /* assign last for thread safety, since we're now unlocked */
  138. efp->type = ef_on_exit;
  139. return 0;
  140. }
  141. #endif
  142. #ifdef L___cxa_atexit
  143. extern int __cxa_atexit (cxaefuncp func, void *arg, void *dso_handle)
  144. {
  145. struct exit_function *efp;
  146. if (func == NULL) {
  147. return 0;
  148. }
  149. efp = __new_exitfn();
  150. if (efp == NULL) {
  151. return -1;
  152. }
  153. efp->funcs.cxa_atexit.func = func;
  154. efp->funcs.cxa_atexit.arg = arg;
  155. efp->funcs.cxa_atexit.dso_handle = dso_handle;
  156. /* assign last for thread safety, since we're now unlocked */
  157. efp->type = ef_cxa_atexit;
  158. return 0;
  159. }
  160. #endif
  161. #ifdef L___cxa_finalize
  162. /*
  163. * If D is non-NULL, call all functions registered with `__cxa_atexit'
  164. * with the same dso handle. Otherwise, if D is NULL, call all of the
  165. * registered handlers.
  166. */
  167. void __cxa_finalize (void *dso_handle)
  168. {
  169. struct exit_function *efp;
  170. int exit_count_snapshot = __exit_count;
  171. /* In reverse order */
  172. while (exit_count_snapshot) {
  173. efp = &__exit_function_table[--exit_count_snapshot];
  174. /*
  175. * We check dso_handle match before we verify the type of the union entry.
  176. * However, the atomic_exchange will validate that we were really "allowed"
  177. * to read dso_handle...
  178. */
  179. if ((dso_handle == NULL || dso_handle == efp->funcs.cxa_atexit.dso_handle)
  180. /* We don't want to run this cleanup more than once. */
  181. && !atomic_compare_and_exchange_bool_acq(&efp->type, ef_free, ef_cxa_atexit)
  182. ) {
  183. /* glibc passes status (0) too, but that's not in the prototype */
  184. (*efp->funcs.cxa_atexit.func)(efp->funcs.cxa_atexit.arg);
  185. }
  186. }
  187. #if 0 /* haven't looked into this yet... */
  188. /*
  189. * Remove the registered fork handlers. We do not have to
  190. * unregister anything if the program is going to terminate anyway.
  191. */
  192. #ifdef UNREGISTER_ATFORK
  193. if (d != NULL) {
  194. UNREGISTER_ATFORK (d);
  195. }
  196. #endif
  197. #endif
  198. }
  199. #endif
  200. #ifdef L___exit_handler
  201. int __exit_count = 0; /* Number of registered exit functions */
  202. #ifdef __UCLIBC_DYNAMIC_ATEXIT__
  203. struct exit_function *__exit_function_table = NULL;
  204. int __exit_slots = 0; /* Size of __exit_function_table */
  205. #else
  206. struct exit_function __exit_function_table[__UCLIBC_MAX_ATEXIT];
  207. #endif
  208. /*
  209. * Find and return a new exit_function pointer, for atexit,
  210. * onexit and __cxa_atexit to initialize
  211. */
  212. struct exit_function attribute_hidden *__new_exitfn(void)
  213. {
  214. struct exit_function *efp;
  215. LOCK;
  216. #ifdef __UCLIBC_DYNAMIC_ATEXIT__
  217. /* If we are out of function table slots, make some more */
  218. if (__exit_slots < __exit_count+1) {
  219. efp=realloc(__exit_function_table,
  220. (__exit_slots+20)*sizeof(struct exit_function));
  221. if (efp == NULL) {
  222. UNLOCK;
  223. __set_errno(ENOMEM);
  224. return 0;
  225. }
  226. __exit_function_table = efp;
  227. __exit_slots += 20;
  228. }
  229. #else
  230. if (__exit_count >= __UCLIBC_MAX_ATEXIT) {
  231. UNLOCK;
  232. __set_errno(ENOMEM);
  233. return 0;
  234. }
  235. #endif
  236. __exit_cleanup = __exit_handler; /* enable cleanup */
  237. efp = &__exit_function_table[__exit_count++];
  238. efp->type = ef_in_use;
  239. UNLOCK;
  240. return efp;
  241. }
  242. /*
  243. * Handle the work of executing the registered exit functions
  244. * This is called while we are locked, so no additional locking
  245. * is needed...
  246. */
  247. void __exit_handler(int status)
  248. {
  249. struct exit_function *efp;
  250. /* In reverse order */
  251. while ( __exit_count ) {
  252. efp = &__exit_function_table[--__exit_count];
  253. switch (efp->type) {
  254. case ef_on_exit:
  255. if (efp->funcs.on_exit.func) {
  256. (efp->funcs.on_exit.func) (status, efp->funcs.on_exit.arg);
  257. }
  258. break;
  259. case ef_cxa_atexit:
  260. if (efp->funcs.cxa_atexit.func) {
  261. /* glibc passes status too, but that's not in the prototype */
  262. (efp->funcs.cxa_atexit.func) (efp->funcs.cxa_atexit.arg);
  263. }
  264. break;
  265. }
  266. }
  267. #ifdef __UCLIBC_DYNAMIC_ATEXIT__
  268. /* Free up memory used by the __exit_function_table structure */
  269. if (__exit_function_table)
  270. free(__exit_function_table);
  271. #endif
  272. }
  273. #endif
  274. #ifdef L_exit
  275. extern void weak_function _stdio_term(void) attribute_hidden;
  276. attribute_hidden void (*__exit_cleanup) (int) = 0;
  277. #ifdef __UCLIBC_HAS_THREADS__
  278. pthread_mutex_t mylock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  279. #endif
  280. #ifdef __UCLIBC_CTOR_DTOR__
  281. extern void (*__app_fini)(void);
  282. #endif
  283. extern void (*__rtld_fini)(void);
  284. /*
  285. * Normal program termination
  286. */
  287. void exit(int rv)
  288. {
  289. /* Perform exit-specific cleanup (atexit and on_exit) */
  290. LOCK;
  291. if (__exit_cleanup) {
  292. __exit_cleanup(rv);
  293. }
  294. UNLOCK;
  295. #ifdef __UCLIBC_CTOR_DTOR__
  296. if (__app_fini != NULL)
  297. (__app_fini)();
  298. #endif
  299. if (__rtld_fini != NULL)
  300. (__rtld_fini)();
  301. /* If we are using stdio, try to shut it down. At the very least,
  302. * this will attempt to commit all buffered writes. It may also
  303. * unbuffer all writable files, or close them outright.
  304. * Check the stdio routines for details. */
  305. if (_stdio_term)
  306. _stdio_term();
  307. _exit(rv);
  308. }
  309. libc_hidden_def(exit)
  310. #endif