1 /* __cxa_atexit backwards-compatibility support for Darwin.
2 Copyright (C) 2006-2023 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 Under Section 7 of GPL version 3, you are granted additional
17 permissions described in the GCC Runtime Library Exception, version
18 3.1, as published by the Free Software Foundation.
19
20 You should have received a copy of the GNU General Public License and
21 a copy of the GCC Runtime Library Exception along with this program;
22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 <http://www.gnu.org/licenses/>. */
24
25 /* Don't do anything if we are compiling for a kext multilib. */
26 #ifdef __PIC__
27
28 #include "tconfig.h"
29 #include "tsystem.h"
30
31 #include <dlfcn.h>
32 #include <stdbool.h>
33 #include <stdlib.h>
34 #include <string.h>
35
36 /* This file works around two different problems.
37
38 The first problem is that there is no __cxa_atexit on Mac OS versions
39 before 10.4. It fixes this by providing a complete atexit and
40 __cxa_atexit emulation called from the regular atexit.
41
42 The second problem is that on all shipping versions of Mac OS,
43 __cxa_finalize and exit() don't work right: they don't run routines
44 that were registered while other atexit routines are running. This
45 is worked around by wrapping each atexit/__cxa_atexit routine with
46 our own routine which ensures that any __cxa_atexit calls while it
47 is running are honoured.
48
49 There are still problems which this does not solve. Before 10.4,
50 shared objects linked with previous compilers won't have their
51 atexit calls properly interleaved with code compiled with newer
52 compilers. Also, atexit routines registered from shared objects
53 linked with previous compilers won't get the bug fix. */
54
55 typedef int (*cxa_atexit_p)(void (*func) (void*), void* arg, const void* dso);
56 typedef void (*cxa_finalize_p)(const void *dso);
57 typedef int (*atexit_p)(void (*func)(void));
58
59 /* These are from "keymgr.h". */
60 extern void *_keymgr_get_and_lock_processwide_ptr (unsigned key);
61 extern int _keymgr_get_and_lock_processwide_ptr_2 (unsigned, void **);
62 extern int _keymgr_set_and_unlock_processwide_ptr (unsigned key, void *ptr);
63
64 extern void *__keymgr_global[];
65 typedef struct _Sinfo_Node {
66 unsigned int size ; /*size of this node*/
67 unsigned short major_version ; /*API major version.*/
68 unsigned short minor_version ; /*API minor version.*/
69 } _Tinfo_Node ;
70
71 #ifdef __ppc__
72 #define CHECK_KEYMGR_ERROR(e) \
73 (((_Tinfo_Node *)__keymgr_global[2])->major_version >= 4 ? (e) : 0)
74 #else
75 #define CHECK_KEYMGR_ERROR(e) (e)
76 #endif
77
78 /* Our globals are stored under this keymgr index. */
79 #define KEYMGR_ATEXIT_LIST 14
80
81 /* The different kinds of callback routines. */
82 typedef void (*atexit_callback)(void);
83 typedef void (*cxa_atexit_callback)(void *);
84
85 /* This structure holds a routine to call. There may be extra fields
86 at the end of the structure that this code doesn't know about. */
87 struct one_atexit_routine
88 {
89 union {
90 atexit_callback ac;
91 cxa_atexit_callback cac;
92 } callback;
93 /* has_arg is 0/2/4 if 'ac' is live, 1/3/5 if 'cac' is live.
94 Higher numbers indicate a later version of the structure that this
95 code doesn't understand and will ignore. */
96 int has_arg;
97 void * arg;
98 };
99
100 struct atexit_routine_list
101 {
102 struct atexit_routine_list * next;
103 struct one_atexit_routine r;
104 };
105
106 /* The various possibilities for status of atexit(). */
107 enum atexit_status {
108 atexit_status_unknown = 0,
109 atexit_status_missing = 1,
110 atexit_status_broken = 2,
111 atexit_status_working = 16
112 };
113
114 struct keymgr_atexit_list
115 {
116 /* Version of this list. This code knows only about version 0.
117 If the version is higher than 0, this code may add new atexit routines
118 but should not attempt to run the list. */
119 short version;
120 /* 1 if an atexit routine is currently being run by this code, 0
121 otherwise. */
122 char running_routines;
123 /* Holds a value from 'enum atexit_status'. */
124 unsigned char atexit_status;
125 /* The list of atexit and cxa_atexit routines registered. If
126 atexit_status_missing it contains all routines registered while
127 linked with this code. If atexit_status_broken it contains all
128 routines registered during cxa_finalize while linked with this
129 code. */
130 struct atexit_routine_list *l;
131 /* &__cxa_atexit; set if atexit_status >= atexit_status_broken. */
132 cxa_atexit_p cxa_atexit_f;
133 /* &__cxa_finalize; set if atexit_status >= atexit_status_broken. */
134 cxa_finalize_p cxa_finalize_f;
135 /* &atexit; set if atexit_status >= atexit_status_working
136 or atexit_status == atexit_status_missing. */
137 atexit_p atexit_f;
138 };
139
140 /* Return 0 if __cxa_atexit has the bug it has in Mac OS 10.4: it
141 fails to call routines registered while an atexit routine is
142 running. Return 1 if it works properly, and -1 if an error occurred. */
143
144 struct atexit_data
145 {
146 int result;
147 cxa_atexit_p cxa_atexit;
148 };
149
150 static void cxa_atexit_check_2 (void *arg)
151 {
152 ((struct atexit_data *)arg)->result = 1;
153 }
154
155 static void cxa_atexit_check_1 (void *arg)
156 {
157 struct atexit_data * aed = arg;
158 if (aed->cxa_atexit (cxa_atexit_check_2, arg, arg) != 0)
159 aed->result = -1;
160 }
161
162 static int
163 check_cxa_atexit (cxa_atexit_p cxa_atexit, cxa_finalize_p cxa_finalize)
164 {
165 struct atexit_data aed = { 0, cxa_atexit };
166
167 /* We re-use &aed as the 'dso' parameter, since it's a unique address. */
168 if (cxa_atexit (cxa_atexit_check_1, &aed, &aed) != 0)
169 return -1;
170 cxa_finalize (&aed);
171 if (aed.result == 0)
172 {
173 /* Call __cxa_finalize again to make sure that cxa_atexit_check_2
174 is removed from the list before AED goes out of scope. */
175 cxa_finalize (&aed);
176 aed.result = 0;
177 }
178 return aed.result;
179 }
180
181 #ifdef __ppc__
182 /* This comes from Csu. It works only before 10.4. The prototype has
183 been altered a bit to avoid casting. */
184 extern int _dyld_func_lookup(const char *dyld_func_name,
185 void *address) __attribute__((visibility("hidden")));
186
187 static void our_atexit (void);
188
189 /* We're running on 10.3.9. Find the address of the system atexit()
190 function. So easy to say, so hard to do. */
191 static atexit_p
192 find_atexit_10_3 (void)
193 {
194 unsigned int (*dyld_image_count_fn)(void);
195 const char *(*dyld_get_image_name_fn)(unsigned int image_index);
196 const void *(*dyld_get_image_header_fn)(unsigned int image_index);
197 const void *(*NSLookupSymbolInImage_fn)(const void *image,
198 const char *symbolName,
199 unsigned int options);
200 void *(*NSAddressOfSymbol_fn)(const void *symbol);
201 unsigned i, count;
202
203 /* Find some dyld functions. */
204 _dyld_func_lookup("__dyld_image_count", &dyld_image_count_fn);
205 _dyld_func_lookup("__dyld_get_image_name", &dyld_get_image_name_fn);
206 _dyld_func_lookup("__dyld_get_image_header", &dyld_get_image_header_fn);
207 _dyld_func_lookup("__dyld_NSLookupSymbolInImage", &NSLookupSymbolInImage_fn);
208 _dyld_func_lookup("__dyld_NSAddressOfSymbol", &NSAddressOfSymbol_fn);
209
210 /* If any of these don't exist, that's an error. */
211 if (! dyld_image_count_fn || ! dyld_get_image_name_fn
212 || ! dyld_get_image_header_fn || ! NSLookupSymbolInImage_fn
213 || ! NSAddressOfSymbol_fn)
214 return NULL;
215
216 count = dyld_image_count_fn ();
217 for (i = 0; i < count; i++)
218 {
219 const char * path = dyld_get_image_name_fn (i);
220 const void * image;
221 const void * symbol;
222
223 if (strcmp (path, "/usr/lib/libSystem.B.dylib") != 0)
224 continue;
225 image = dyld_get_image_header_fn (i);
226 if (! image)
227 return NULL;
228 /* '4' is NSLOOKUPSYMBOLINIMAGE_OPTION_RETURN_ON_ERROR. */
229 symbol = NSLookupSymbolInImage_fn (image, "_atexit", 4);
230 if (! symbol)
231 return NULL;
232 return NSAddressOfSymbol_fn (symbol);
233 }
234 return NULL;
235 }
236 #endif
237
238 /* Create (if necessary), find, lock, fill in, and return our globals.
239 Return NULL on error, in which case the globals will not be locked.
240 The caller should call keymgr_set_and_unlock. */
241 static struct keymgr_atexit_list *
242 get_globals (void)
243 {
244 struct keymgr_atexit_list * r;
245
246 #ifdef __ppc__
247 /* 10.3.9 doesn't have _keymgr_get_and_lock_processwide_ptr_2 so the
248 PPC side can't use it. On 10.4 this just means the error gets
249 reported a little later when
250 _keymgr_set_and_unlock_processwide_ptr finds that the key was
251 never locked. */
252 r = _keymgr_get_and_lock_processwide_ptr (KEYMGR_ATEXIT_LIST);
253 #else
254 void * rr;
255 if (_keymgr_get_and_lock_processwide_ptr_2 (KEYMGR_ATEXIT_LIST, &rr))
256 return NULL;
257 r = rr;
258 #endif
259
260 if (r == NULL)
261 {
262 r = calloc (sizeof (struct keymgr_atexit_list), 1);
263 if (! r)
264 return NULL;
265 }
266
267 if (r->atexit_status == atexit_status_unknown)
268 {
269 void *handle;
270
271 handle = dlopen ("/usr/lib/libSystem.B.dylib", RTLD_NOLOAD);
272 if (!handle)
273 {
274 #ifdef __ppc__
275 r->atexit_status = atexit_status_missing;
276 r->atexit_f = find_atexit_10_3 ();
277 if (! r->atexit_f)
278 goto error;
279 if (r->atexit_f (our_atexit))
280 goto error;
281 #else
282 goto error;
283 #endif
284 }
285 else
286 {
287 int chk_result;
288
289 r->cxa_atexit_f = (cxa_atexit_p)dlsym (handle, "__cxa_atexit");
290 r->cxa_finalize_f = (cxa_finalize_p)dlsym (handle, "__cxa_finalize");
291 if (! r->cxa_atexit_f || ! r->cxa_finalize_f)
292 goto error;
293
294 chk_result = check_cxa_atexit (r->cxa_atexit_f, r->cxa_finalize_f);
295 if (chk_result == -1)
296 goto error;
297 else if (chk_result == 0)
298 r->atexit_status = atexit_status_broken;
299 else
300 {
301 r->atexit_f = (atexit_p)dlsym (handle, "atexit");
302 if (! r->atexit_f)
303 goto error;
304 r->atexit_status = atexit_status_working;
305 }
306 }
307 }
308
309 return r;
310
311 error:
312 _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, r);
313 return NULL;
314 }
315
316 /* Add TO_ADD to ATEXIT_LIST. ATEXIT_LIST may be NULL but is
317 always the result of calling _keymgr_get_and_lock_processwide_ptr and
318 so KEYMGR_ATEXIT_LIST is known to be locked; this routine is responsible
319 for unlocking it. */
320
321 static int
322 add_routine (struct keymgr_atexit_list * g,
323 const struct one_atexit_routine * to_add)
324 {
325 struct atexit_routine_list * s
326 = malloc (sizeof (struct atexit_routine_list));
327 int result;
328
329 if (!s)
330 {
331 _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
332 return -1;
333 }
334 s->r = *to_add;
335 s->next = g->l;
336 g->l = s;
337 result = _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
338 return CHECK_KEYMGR_ERROR (result) == 0 ? 0 : -1;
339 }
340
341 /* This runs the routines in G->L up to STOP. */
342 static struct keymgr_atexit_list *
343 run_routines (struct keymgr_atexit_list *g,
344 struct atexit_routine_list *stop)
345 {
346 for (;;)
347 {
348 struct atexit_routine_list * cur = g->l;
349 if (! cur || cur == stop)
350 break;
351 g->l = cur->next;
352 _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
353
354 switch (cur->r.has_arg) {
355 case 0: case 2: case 4:
356 cur->r.callback.ac ();
357 break;
358 case 1: case 3: case 5:
359 cur->r.callback.cac (cur->r.arg);
360 break;
361 default:
362 /* Don't understand, so don't call it. */
363 break;
364 }
365 free (cur);
366
367 g = _keymgr_get_and_lock_processwide_ptr (KEYMGR_ATEXIT_LIST);
368 if (! g)
369 break;
370 }
371 return g;
372 }
373
374 /* Call the routine described by ROUTINE_PARAM and then call any
375 routines added to KEYMGR_ATEXIT_LIST while that routine was
376 running, all with in_cxa_finalize set. */
377
378 static void
379 cxa_atexit_wrapper (void* routine_param)
380 {
381 struct one_atexit_routine * routine = routine_param;
382 struct keymgr_atexit_list *g;
383 struct atexit_routine_list * base = NULL;
384 char prev_running = 0;
385
386 g = _keymgr_get_and_lock_processwide_ptr (KEYMGR_ATEXIT_LIST);
387 if (g)
388 {
389 prev_running = g->running_routines;
390 g->running_routines = 1;
391 base = g->l;
392 _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
393 }
394
395 if (routine->has_arg)
396 routine->callback.cac (routine->arg);
397 else
398 routine->callback.ac ();
399
400 if (g)
401 g = _keymgr_get_and_lock_processwide_ptr (KEYMGR_ATEXIT_LIST);
402 if (g)
403 g = run_routines (g, base);
404 if (g)
405 {
406 g->running_routines = prev_running;
407 _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
408 }
409 }
410
411 #ifdef __ppc__
412 /* This code is used while running on 10.3.9, when __cxa_atexit doesn't
413 exist in the system library. 10.3.9 only supported regular PowerPC,
414 so this code isn't necessary on x86 or ppc64. */
415
416 /* This routine is called from the system atexit(); it runs everything
417 registered on the KEYMGR_ATEXIT_LIST. */
418
419 static void
420 our_atexit (void)
421 {
422 struct keymgr_atexit_list *g;
423 char prev_running;
424
425 g = _keymgr_get_and_lock_processwide_ptr (KEYMGR_ATEXIT_LIST);
426 if (! g || g->version != 0 || g->atexit_status != atexit_status_missing)
427 return;
428
429 prev_running = g->running_routines;
430 g->running_routines = 1;
431 g = run_routines (g, NULL);
432 if (! g)
433 return;
434 g->running_routines = prev_running;
435 _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
436 }
437 #endif
438
439 /* This is our wrapper around atexit and __cxa_atexit. It will return
440 nonzero if an error occurs, and otherwise:
441 - if in_cxa_finalize is set, or running on 10.3.9, add R to
442 KEYMGR_ATEXIT_LIST; or
443 - call the system __cxa_atexit to add cxa_atexit_wrapper with an argument
444 that indicates how cxa_atexit_wrapper should call R. */
445
446 static int
447 atexit_common (const struct one_atexit_routine *r, const void *dso)
448 {
449 struct keymgr_atexit_list *g = get_globals ();
450
451 if (! g)
452 return -1;
453
454 if (g->running_routines || g->atexit_status == atexit_status_missing)
455 return add_routine (g, r);
456
457 if (g->atexit_status >= atexit_status_working)
458 {
459 int result;
460 if (r->has_arg)
461 {
462 cxa_atexit_p cxa_atexit = g->cxa_atexit_f;
463 result = _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST,
464 g);
465 if (CHECK_KEYMGR_ERROR (result))
466 return -1;
467 return cxa_atexit (r->callback.cac, r->arg, dso);
468 }
469 else
470 {
471 atexit_p atexit_f = g->atexit_f;
472 result = _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST,
473 g);
474 if (CHECK_KEYMGR_ERROR (result))
475 return -1;
476 return atexit_f (r->callback.ac);
477 }
478 }
479 else
480 {
481 cxa_atexit_p cxa_atexit = g->cxa_atexit_f;
482 struct one_atexit_routine *alloced;
483 int result;
484
485 result = _keymgr_set_and_unlock_processwide_ptr (KEYMGR_ATEXIT_LIST, g);
486 if (CHECK_KEYMGR_ERROR (result))
487 return -1;
488
489 alloced = malloc (sizeof (struct one_atexit_routine));
490 if (! alloced)
491 return -1;
492 *alloced = *r;
493 return cxa_atexit (cxa_atexit_wrapper, alloced, dso);
494 }
495 }
496
497 /* These are the actual replacement routines; they just funnel into
498 atexit_common. */
499
500 int __cxa_atexit (cxa_atexit_callback func, void* arg,
501 const void* dso) __attribute__((visibility("hidden")));
502
503 int
504 __cxa_atexit (cxa_atexit_callback func, void* arg, const void* dso)
505 {
506 struct one_atexit_routine r;
507 r.callback.cac = func;
508 r.has_arg = 1;
509 r.arg = arg;
510 return atexit_common (&r, dso);
511 }
512
513 int atexit (atexit_callback func) __attribute__((visibility("hidden")));
514
515 /* Use __dso_handle to allow even bundles that call atexit() to be unloaded
516 on 10.4. */
517 extern void __dso_handle;
518
519 int
520 atexit (atexit_callback func)
521 {
522 struct one_atexit_routine r;
523 r.callback.ac = func;
524 r.has_arg = 0;
525 return atexit_common (&r, &__dso_handle);
526 }
527
528 #endif /* __PIC__ */