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7458026b | 1 | /* Library support for -fsplit-stack. */ |
ac1dca3c | 2 | /* Copyright (C) 2009-2014 Free Software Foundation, Inc. |
7458026b ILT |
3 | Contributed by Ian Lance Taylor <iant@google.com>. |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it under | |
8 | the terms of the GNU General Public License as published by the Free | |
9 | Software Foundation; either version 3, or (at your option) any later | |
10 | version. | |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | for more details. | |
16 | ||
17 | Under Section 7 of GPL version 3, you are granted additional | |
18 | permissions described in the GCC Runtime Library Exception, version | |
19 | 3.1, as published by the Free Software Foundation. | |
20 | ||
21 | You should have received a copy of the GNU General Public License and | |
22 | a copy of the GCC Runtime Library Exception along with this program; | |
23 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
24 | <http://www.gnu.org/licenses/>. */ | |
25 | ||
26 | #include "tconfig.h" | |
27 | #include "tsystem.h" | |
28 | #include "coretypes.h" | |
29 | #include "tm.h" | |
852b75ed | 30 | #include "libgcc_tm.h" |
7458026b ILT |
31 | |
32 | /* If inhibit_libc is defined, we can not compile this file. The | |
33 | effect is that people will not be able to use -fsplit-stack. That | |
34 | is much better than failing the build particularly since people | |
35 | will want to define inhibit_libc while building a compiler which | |
36 | can build glibc. */ | |
37 | ||
38 | #ifndef inhibit_libc | |
39 | ||
40 | #include <assert.h> | |
41 | #include <errno.h> | |
42 | #include <signal.h> | |
43 | #include <stdlib.h> | |
e14304ef | 44 | #include <string.h> |
7458026b ILT |
45 | #include <unistd.h> |
46 | #include <sys/mman.h> | |
47 | #include <sys/uio.h> | |
48 | ||
49 | #include "generic-morestack.h" | |
50 | ||
e14304ef ILT |
51 | typedef unsigned uintptr_type __attribute__ ((mode (pointer))); |
52 | ||
7458026b ILT |
53 | /* This file contains subroutines that are used by code compiled with |
54 | -fsplit-stack. */ | |
55 | ||
56 | /* Declare functions to avoid warnings--there is no header file for | |
57 | these internal functions. We give most of these functions the | |
58 | flatten attribute in order to minimize their stack usage--here we | |
59 | must minimize stack usage even at the cost of code size, and in | |
60 | general inlining everything will do that. */ | |
61 | ||
62 | extern void | |
63 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
64 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
65 | ||
66 | extern void * | |
67 | __generic_morestack (size_t *frame_size, void *old_stack, size_t param_size) | |
68 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
69 | ||
70 | extern void * | |
71 | __generic_releasestack (size_t *pavailable) | |
72 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
73 | ||
74 | extern void | |
75 | __morestack_block_signals (void) | |
76 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
77 | ||
78 | extern void | |
79 | __morestack_unblock_signals (void) | |
80 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
81 | ||
82 | extern size_t | |
83 | __generic_findstack (void *stack) | |
84 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
85 | ||
86 | extern void | |
87 | __morestack_load_mmap (void) | |
88 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
89 | ||
90 | extern void * | |
91 | __morestack_allocate_stack_space (size_t size) | |
92 | __attribute__ ((visibility ("hidden"))); | |
93 | ||
e14304ef ILT |
94 | /* These are functions which -fsplit-stack code can call. These are |
95 | not called by the compiler, and are not hidden. FIXME: These | |
96 | should be in some header file somewhere, somehow. */ | |
7458026b ILT |
97 | |
98 | extern void * | |
99 | __splitstack_find (void *, void *, size_t *, void **, void **, void **) | |
100 | __attribute__ ((visibility ("default"))); | |
101 | ||
e14304ef ILT |
102 | extern void |
103 | __splitstack_block_signals (int *, int *) | |
104 | __attribute__ ((visibility ("default"))); | |
105 | ||
106 | extern void | |
107 | __splitstack_getcontext (void *context[10]) | |
108 | __attribute__ ((no_split_stack, visibility ("default"))); | |
109 | ||
110 | extern void | |
111 | __splitstack_setcontext (void *context[10]) | |
112 | __attribute__ ((no_split_stack, visibility ("default"))); | |
113 | ||
114 | extern void * | |
115 | __splitstack_makecontext (size_t, void *context[10], size_t *) | |
116 | __attribute__ ((visibility ("default"))); | |
117 | ||
a01207c4 ILT |
118 | extern void * |
119 | __splitstack_resetcontext (void *context[10], size_t *) | |
120 | __attribute__ ((visibility ("default"))); | |
121 | ||
122 | extern void | |
123 | __splitstack_releasecontext (void *context[10]) | |
124 | __attribute__ ((visibility ("default"))); | |
125 | ||
e14304ef ILT |
126 | extern void |
127 | __splitstack_block_signals_context (void *context[10], int *, int *) | |
128 | __attribute__ ((visibility ("default"))); | |
129 | ||
130 | extern void * | |
131 | __splitstack_find_context (void *context[10], size_t *, void **, void **, | |
132 | void **) | |
133 | __attribute__ ((visibility ("default"))); | |
134 | ||
135 | /* These functions must be defined by the processor specific code. */ | |
136 | ||
137 | extern void *__morestack_get_guard (void) | |
138 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
139 | ||
140 | extern void __morestack_set_guard (void *) | |
141 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
142 | ||
143 | extern void *__morestack_make_guard (void *, size_t) | |
144 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
145 | ||
7458026b ILT |
146 | /* When we allocate a stack segment we put this header at the |
147 | start. */ | |
148 | ||
149 | struct stack_segment | |
150 | { | |
151 | /* The previous stack segment--when a function running on this stack | |
152 | segment returns, it will run on the previous one. */ | |
153 | struct stack_segment *prev; | |
154 | /* The next stack segment, if it has been allocated--when a function | |
155 | is running on this stack segment, the next one is not being | |
156 | used. */ | |
157 | struct stack_segment *next; | |
158 | /* The total size of this stack segment. */ | |
159 | size_t size; | |
160 | /* The stack address when this stack was created. This is used when | |
161 | popping the stack. */ | |
162 | void *old_stack; | |
163 | /* A list of memory blocks allocated by dynamic stack | |
164 | allocation. */ | |
165 | struct dynamic_allocation_blocks *dynamic_allocation; | |
166 | /* A list of dynamic memory blocks no longer needed. */ | |
167 | struct dynamic_allocation_blocks *free_dynamic_allocation; | |
168 | /* An extra pointer in case we need some more information some | |
169 | day. */ | |
170 | void *extra; | |
171 | }; | |
172 | ||
173 | /* This structure holds the (approximate) initial stack pointer and | |
174 | size for the system supplied stack for a thread. This is set when | |
175 | the thread is created. We also store a sigset_t here to hold the | |
176 | signal mask while splitting the stack, since we don't want to store | |
177 | that on the stack. */ | |
178 | ||
179 | struct initial_sp | |
180 | { | |
181 | /* The initial stack pointer. */ | |
182 | void *sp; | |
183 | /* The stack length. */ | |
184 | size_t len; | |
185 | /* A signal mask, put here so that the thread can use it without | |
186 | needing stack space. */ | |
187 | sigset_t mask; | |
e14304ef ILT |
188 | /* Non-zero if we should not block signals. This is a reversed flag |
189 | so that the default zero value is the safe value. The type is | |
190 | uintptr_type because it replaced one of the void * pointers in | |
191 | extra. */ | |
192 | uintptr_type dont_block_signals; | |
7458026b | 193 | /* Some extra space for later extensibility. */ |
e14304ef | 194 | void *extra[4]; |
7458026b ILT |
195 | }; |
196 | ||
197 | /* A list of memory blocks allocated by dynamic stack allocation. | |
198 | This is used for code that calls alloca or uses variably sized | |
199 | arrays. */ | |
200 | ||
201 | struct dynamic_allocation_blocks | |
202 | { | |
203 | /* The next block in the list. */ | |
204 | struct dynamic_allocation_blocks *next; | |
205 | /* The size of the allocated memory. */ | |
206 | size_t size; | |
207 | /* The allocated memory. */ | |
208 | void *block; | |
209 | }; | |
210 | ||
211 | /* These thread local global variables must be shared by all split | |
212 | stack code across shared library boundaries. Therefore, they have | |
213 | default visibility. They have extensibility fields if needed for | |
214 | new versions. If more radical changes are needed, new code can be | |
215 | written using new variable names, while still using the existing | |
216 | variables in a backward compatible manner. Symbol versioning is | |
217 | also used, although, since these variables are only referenced by | |
218 | code in this file and generic-morestack-thread.c, it is likely that | |
219 | simply using new names will suffice. */ | |
220 | ||
221 | /* The first stack segment allocated for this thread. */ | |
222 | ||
223 | __thread struct stack_segment *__morestack_segments | |
224 | __attribute__ ((visibility ("default"))); | |
225 | ||
226 | /* The stack segment that we think we are currently using. This will | |
227 | be correct in normal usage, but will be incorrect if an exception | |
228 | unwinds into a different stack segment or if longjmp jumps to a | |
229 | different stack segment. */ | |
230 | ||
231 | __thread struct stack_segment *__morestack_current_segment | |
232 | __attribute__ ((visibility ("default"))); | |
233 | ||
234 | /* The initial stack pointer and size for this thread. */ | |
235 | ||
236 | __thread struct initial_sp __morestack_initial_sp | |
237 | __attribute__ ((visibility ("default"))); | |
238 | ||
239 | /* A static signal mask, to avoid taking up stack space. */ | |
240 | ||
241 | static sigset_t __morestack_fullmask; | |
242 | ||
243 | /* Convert an integer to a decimal string without using much stack | |
244 | space. Return a pointer to the part of the buffer to use. We this | |
245 | instead of sprintf because sprintf will require too much stack | |
246 | space. */ | |
247 | ||
248 | static char * | |
249 | print_int (int val, char *buf, int buflen, size_t *print_len) | |
250 | { | |
251 | int is_negative; | |
252 | int i; | |
253 | unsigned int uval; | |
254 | ||
255 | uval = (unsigned int) val; | |
256 | if (val >= 0) | |
257 | is_negative = 0; | |
258 | else | |
259 | { | |
260 | is_negative = 1; | |
261 | uval = - uval; | |
262 | } | |
263 | ||
264 | i = buflen; | |
265 | do | |
266 | { | |
267 | --i; | |
268 | buf[i] = '0' + (uval % 10); | |
269 | uval /= 10; | |
270 | } | |
271 | while (uval != 0 && i > 0); | |
272 | ||
273 | if (is_negative) | |
274 | { | |
275 | if (i > 0) | |
276 | --i; | |
277 | buf[i] = '-'; | |
278 | } | |
279 | ||
280 | *print_len = buflen - i; | |
281 | return buf + i; | |
282 | } | |
283 | ||
284 | /* Print the string MSG/LEN, the errno number ERR, and a newline on | |
285 | stderr. Then crash. */ | |
286 | ||
287 | void | |
288 | __morestack_fail (const char *, size_t, int) __attribute__ ((noreturn)); | |
289 | ||
290 | void | |
291 | __morestack_fail (const char *msg, size_t len, int err) | |
292 | { | |
293 | char buf[24]; | |
294 | static const char nl[] = "\n"; | |
295 | struct iovec iov[3]; | |
296 | union { char *p; const char *cp; } const_cast; | |
297 | ||
298 | const_cast.cp = msg; | |
299 | iov[0].iov_base = const_cast.p; | |
300 | iov[0].iov_len = len; | |
301 | /* We can't call strerror, because it may try to translate the error | |
302 | message, and that would use too much stack space. */ | |
303 | iov[1].iov_base = print_int (err, buf, sizeof buf, &iov[1].iov_len); | |
304 | const_cast.cp = &nl[0]; | |
305 | iov[2].iov_base = const_cast.p; | |
306 | iov[2].iov_len = sizeof nl - 1; | |
307 | /* FIXME: On systems without writev we need to issue three write | |
308 | calls, or punt on printing errno. For now this is irrelevant | |
309 | since stack splitting only works on GNU/Linux anyhow. */ | |
310 | writev (2, iov, 3); | |
311 | abort (); | |
312 | } | |
313 | ||
314 | /* Allocate a new stack segment. FRAME_SIZE is the required frame | |
315 | size. */ | |
316 | ||
317 | static struct stack_segment * | |
318 | allocate_segment (size_t frame_size) | |
319 | { | |
320 | static unsigned int static_pagesize; | |
321 | static int use_guard_page; | |
322 | unsigned int pagesize; | |
323 | unsigned int overhead; | |
324 | unsigned int allocate; | |
325 | void *space; | |
326 | struct stack_segment *pss; | |
327 | ||
328 | pagesize = static_pagesize; | |
329 | if (pagesize == 0) | |
330 | { | |
331 | unsigned int p; | |
332 | ||
333 | pagesize = getpagesize (); | |
334 | ||
335 | #ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 | |
336 | p = __sync_val_compare_and_swap (&static_pagesize, 0, pagesize); | |
337 | #else | |
338 | /* Just hope this assignment is atomic. */ | |
339 | static_pagesize = pagesize; | |
340 | p = 0; | |
341 | #endif | |
342 | ||
343 | use_guard_page = getenv ("SPLIT_STACK_GUARD") != 0; | |
344 | ||
345 | /* FIXME: I'm not sure this assert should be in the released | |
346 | code. */ | |
347 | assert (p == 0 || p == pagesize); | |
348 | } | |
349 | ||
350 | overhead = sizeof (struct stack_segment); | |
351 | ||
352 | allocate = pagesize; | |
353 | if (allocate < MINSIGSTKSZ) | |
354 | allocate = ((MINSIGSTKSZ + overhead + pagesize - 1) | |
355 | & ~ (pagesize - 1)); | |
356 | if (allocate < frame_size) | |
357 | allocate = ((frame_size + overhead + pagesize - 1) | |
358 | & ~ (pagesize - 1)); | |
359 | ||
360 | if (use_guard_page) | |
361 | allocate += pagesize; | |
362 | ||
363 | /* FIXME: If this binary requires an executable stack, then we need | |
364 | to set PROT_EXEC. Unfortunately figuring that out is complicated | |
365 | and target dependent. We would need to use dl_iterate_phdr to | |
366 | see if there is any object which does not have a PT_GNU_STACK | |
367 | phdr, though only for architectures which use that mechanism. */ | |
368 | space = mmap (NULL, allocate, PROT_READ | PROT_WRITE, | |
369 | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); | |
370 | if (space == MAP_FAILED) | |
371 | { | |
372 | static const char msg[] = | |
373 | "unable to allocate additional stack space: errno "; | |
374 | __morestack_fail (msg, sizeof msg - 1, errno); | |
375 | } | |
376 | ||
377 | if (use_guard_page) | |
378 | { | |
379 | void *guard; | |
380 | ||
53d68b9f | 381 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
382 | guard = space; |
383 | space = (char *) space + pagesize; | |
384 | #else | |
385 | guard = space + allocate - pagesize; | |
386 | #endif | |
387 | ||
388 | mprotect (guard, pagesize, PROT_NONE); | |
389 | allocate -= pagesize; | |
390 | } | |
391 | ||
392 | pss = (struct stack_segment *) space; | |
393 | ||
e14304ef | 394 | pss->prev = NULL; |
7458026b ILT |
395 | pss->next = NULL; |
396 | pss->size = allocate - overhead; | |
397 | pss->dynamic_allocation = NULL; | |
398 | pss->free_dynamic_allocation = NULL; | |
399 | pss->extra = NULL; | |
400 | ||
7458026b ILT |
401 | return pss; |
402 | } | |
403 | ||
404 | /* Free a list of dynamic blocks. */ | |
405 | ||
406 | static void | |
407 | free_dynamic_blocks (struct dynamic_allocation_blocks *p) | |
408 | { | |
409 | while (p != NULL) | |
410 | { | |
411 | struct dynamic_allocation_blocks *next; | |
412 | ||
413 | next = p->next; | |
414 | free (p->block); | |
415 | free (p); | |
416 | p = next; | |
417 | } | |
418 | } | |
419 | ||
420 | /* Merge two lists of dynamic blocks. */ | |
421 | ||
422 | static struct dynamic_allocation_blocks * | |
423 | merge_dynamic_blocks (struct dynamic_allocation_blocks *a, | |
424 | struct dynamic_allocation_blocks *b) | |
425 | { | |
426 | struct dynamic_allocation_blocks **pp; | |
427 | ||
428 | if (a == NULL) | |
429 | return b; | |
430 | if (b == NULL) | |
431 | return a; | |
432 | for (pp = &a->next; *pp != NULL; pp = &(*pp)->next) | |
433 | ; | |
434 | *pp = b; | |
435 | return a; | |
436 | } | |
437 | ||
438 | /* Release stack segments. If FREE_DYNAMIC is non-zero, we also free | |
439 | any dynamic blocks. Otherwise we return them. */ | |
440 | ||
441 | struct dynamic_allocation_blocks * | |
442 | __morestack_release_segments (struct stack_segment **pp, int free_dynamic) | |
443 | { | |
444 | struct dynamic_allocation_blocks *ret; | |
445 | struct stack_segment *pss; | |
446 | ||
447 | ret = NULL; | |
448 | pss = *pp; | |
449 | while (pss != NULL) | |
450 | { | |
451 | struct stack_segment *next; | |
452 | unsigned int allocate; | |
453 | ||
454 | next = pss->next; | |
455 | ||
456 | if (pss->dynamic_allocation != NULL | |
457 | || pss->free_dynamic_allocation != NULL) | |
458 | { | |
459 | if (free_dynamic) | |
460 | { | |
461 | free_dynamic_blocks (pss->dynamic_allocation); | |
462 | free_dynamic_blocks (pss->free_dynamic_allocation); | |
463 | } | |
464 | else | |
465 | { | |
466 | ret = merge_dynamic_blocks (pss->dynamic_allocation, ret); | |
467 | ret = merge_dynamic_blocks (pss->free_dynamic_allocation, ret); | |
468 | } | |
469 | } | |
470 | ||
471 | allocate = pss->size + sizeof (struct stack_segment); | |
472 | if (munmap (pss, allocate) < 0) | |
473 | { | |
474 | static const char msg[] = "munmap of stack space failed: errno "; | |
475 | __morestack_fail (msg, sizeof msg - 1, errno); | |
476 | } | |
477 | ||
478 | pss = next; | |
479 | } | |
480 | *pp = NULL; | |
481 | ||
482 | return ret; | |
483 | } | |
484 | ||
485 | /* This function is called by a processor specific function to set the | |
486 | initial stack pointer for a thread. The operating system will | |
487 | always create a stack for a thread. Here we record a stack pointer | |
488 | near the base of that stack. The size argument lets the processor | |
489 | specific code estimate how much stack space is available on this | |
490 | initial stack. */ | |
491 | ||
492 | void | |
493 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
494 | { | |
495 | /* The stack pointer most likely starts on a page boundary. Adjust | |
496 | to the nearest 512 byte boundary. It's not essential that we be | |
497 | precise here; getting it wrong will just leave some stack space | |
498 | unused. */ | |
53d68b9f | 499 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
500 | sp = (void *) ((((__UINTPTR_TYPE__) sp + 511U) / 512U) * 512U); |
501 | #else | |
502 | sp = (void *) ((((__UINTPTR_TYPE__) sp - 511U) / 512U) * 512U); | |
503 | #endif | |
504 | ||
505 | __morestack_initial_sp.sp = sp; | |
506 | __morestack_initial_sp.len = len; | |
507 | sigemptyset (&__morestack_initial_sp.mask); | |
508 | ||
509 | sigfillset (&__morestack_fullmask); | |
d80c632e | 510 | #if defined(__GLIBC__) && defined(__linux__) |
a13780a6 | 511 | /* In glibc, the first two real time signals are used by the NPTL |
7458026b ILT |
512 | threading library. By taking them out of the set of signals, we |
513 | avoiding copying the signal mask in pthread_sigmask. More | |
514 | importantly, pthread_sigmask uses less stack space on x86_64. */ | |
515 | sigdelset (&__morestack_fullmask, __SIGRTMIN); | |
516 | sigdelset (&__morestack_fullmask, __SIGRTMIN + 1); | |
517 | #endif | |
518 | } | |
519 | ||
520 | /* This function is called by a processor specific function which is | |
521 | run in the prologue when more stack is needed. The processor | |
522 | specific function handles the details of saving registers and | |
523 | frobbing the actual stack pointer. This function is responsible | |
524 | for allocating a new stack segment and for copying a parameter | |
525 | block from the old stack to the new one. On function entry | |
526 | *PFRAME_SIZE is the size of the required stack frame--the returned | |
527 | stack must be at least this large. On function exit *PFRAME_SIZE | |
528 | is the amount of space remaining on the allocated stack. OLD_STACK | |
529 | points at the parameters the old stack (really the current one | |
530 | while this function is running). OLD_STACK is saved so that it can | |
531 | be returned by a later call to __generic_releasestack. PARAM_SIZE | |
532 | is the size in bytes of parameters to copy to the new stack. This | |
533 | function returns a pointer to the new stack segment, pointing to | |
534 | the memory after the parameters have been copied. The returned | |
535 | value minus the returned *PFRAME_SIZE (or plus if the stack grows | |
536 | upward) is the first address on the stack which should not be used. | |
537 | ||
538 | This function is running on the old stack and has only a limited | |
539 | amount of stack space available. */ | |
540 | ||
541 | void * | |
542 | __generic_morestack (size_t *pframe_size, void *old_stack, size_t param_size) | |
543 | { | |
544 | size_t frame_size = *pframe_size; | |
545 | struct stack_segment *current; | |
546 | struct stack_segment **pp; | |
547 | struct dynamic_allocation_blocks *dynamic; | |
548 | char *from; | |
549 | char *to; | |
550 | void *ret; | |
551 | size_t i; | |
e808687a | 552 | size_t aligned; |
7458026b ILT |
553 | |
554 | current = __morestack_current_segment; | |
555 | ||
556 | pp = current != NULL ? ¤t->next : &__morestack_segments; | |
557 | if (*pp != NULL && (*pp)->size < frame_size) | |
558 | dynamic = __morestack_release_segments (pp, 0); | |
559 | else | |
560 | dynamic = NULL; | |
561 | current = *pp; | |
562 | ||
563 | if (current == NULL) | |
e14304ef ILT |
564 | { |
565 | current = allocate_segment (frame_size + param_size); | |
566 | current->prev = __morestack_current_segment; | |
567 | *pp = current; | |
568 | } | |
7458026b ILT |
569 | |
570 | current->old_stack = old_stack; | |
571 | ||
572 | __morestack_current_segment = current; | |
573 | ||
574 | if (dynamic != NULL) | |
575 | { | |
576 | /* Move the free blocks onto our list. We don't want to call | |
577 | free here, as we are short on stack space. */ | |
578 | current->free_dynamic_allocation = | |
579 | merge_dynamic_blocks (dynamic, current->free_dynamic_allocation); | |
580 | } | |
581 | ||
582 | *pframe_size = current->size - param_size; | |
583 | ||
e808687a ILT |
584 | /* Align the returned stack to a 32-byte boundary. */ |
585 | aligned = (param_size + 31) & ~ (size_t) 31; | |
586 | ||
53d68b9f | 587 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
588 | { |
589 | char *bottom = (char *) (current + 1) + current->size; | |
e808687a ILT |
590 | to = bottom - aligned; |
591 | ret = bottom - aligned; | |
7458026b ILT |
592 | } |
593 | #else | |
594 | to = current + 1; | |
e808687a ILT |
595 | to += aligned - param_size; |
596 | ret = (char *) (current + 1) + aligned; | |
7458026b ILT |
597 | #endif |
598 | ||
599 | /* We don't call memcpy to avoid worrying about the dynamic linker | |
600 | trying to resolve it. */ | |
601 | from = (char *) old_stack; | |
602 | for (i = 0; i < param_size; i++) | |
603 | *to++ = *from++; | |
604 | ||
605 | return ret; | |
606 | } | |
607 | ||
608 | /* This function is called by a processor specific function when it is | |
609 | ready to release a stack segment. We don't actually release the | |
610 | stack segment, we just move back to the previous one. The current | |
611 | stack segment will still be available if we need it in | |
612 | __generic_morestack. This returns a pointer to the new stack | |
613 | segment to use, which is the one saved by a previous call to | |
614 | __generic_morestack. The processor specific function is then | |
615 | responsible for actually updating the stack pointer. This sets | |
616 | *PAVAILABLE to the amount of stack space now available. */ | |
617 | ||
618 | void * | |
619 | __generic_releasestack (size_t *pavailable) | |
620 | { | |
621 | struct stack_segment *current; | |
622 | void *old_stack; | |
623 | ||
624 | current = __morestack_current_segment; | |
625 | old_stack = current->old_stack; | |
626 | current = current->prev; | |
627 | __morestack_current_segment = current; | |
628 | ||
629 | if (current != NULL) | |
630 | { | |
53d68b9f | 631 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
632 | *pavailable = (char *) old_stack - (char *) (current + 1); |
633 | #else | |
634 | *pavailable = (char *) (current + 1) + current->size - (char *) old_stack; | |
635 | #endif | |
636 | } | |
637 | else | |
638 | { | |
639 | size_t used; | |
640 | ||
641 | /* We have popped back to the original stack. */ | |
53d68b9f | 642 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
643 | if ((char *) old_stack >= (char *) __morestack_initial_sp.sp) |
644 | used = 0; | |
645 | else | |
646 | used = (char *) __morestack_initial_sp.sp - (char *) old_stack; | |
647 | #else | |
648 | if ((char *) old_stack <= (char *) __morestack_initial_sp.sp) | |
649 | used = 0; | |
650 | else | |
651 | used = (char *) old_stack - (char *) __morestack_initial_sp.sp; | |
652 | #endif | |
653 | ||
654 | if (used > __morestack_initial_sp.len) | |
655 | *pavailable = 0; | |
656 | else | |
657 | *pavailable = __morestack_initial_sp.len - used; | |
658 | } | |
659 | ||
660 | return old_stack; | |
661 | } | |
662 | ||
663 | /* Block signals while splitting the stack. This avoids trouble if we | |
664 | try to invoke a signal handler which itself wants to split the | |
665 | stack. */ | |
666 | ||
667 | extern int pthread_sigmask (int, const sigset_t *, sigset_t *) | |
668 | __attribute__ ((weak)); | |
669 | ||
670 | void | |
671 | __morestack_block_signals (void) | |
672 | { | |
e14304ef ILT |
673 | if (__morestack_initial_sp.dont_block_signals) |
674 | ; | |
675 | else if (pthread_sigmask) | |
7458026b ILT |
676 | pthread_sigmask (SIG_BLOCK, &__morestack_fullmask, |
677 | &__morestack_initial_sp.mask); | |
678 | else | |
679 | sigprocmask (SIG_BLOCK, &__morestack_fullmask, | |
680 | &__morestack_initial_sp.mask); | |
681 | } | |
682 | ||
683 | /* Unblock signals while splitting the stack. */ | |
684 | ||
685 | void | |
686 | __morestack_unblock_signals (void) | |
687 | { | |
e14304ef ILT |
688 | if (__morestack_initial_sp.dont_block_signals) |
689 | ; | |
690 | else if (pthread_sigmask) | |
7458026b ILT |
691 | pthread_sigmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); |
692 | else | |
693 | sigprocmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); | |
694 | } | |
695 | ||
696 | /* This function is called to allocate dynamic stack space, for alloca | |
697 | or a variably sized array. This is a regular function with | |
698 | sufficient stack space, so we just use malloc to allocate the | |
699 | space. We attach the allocated blocks to the current stack | |
700 | segment, so that they will eventually be reused or freed. */ | |
701 | ||
702 | void * | |
703 | __morestack_allocate_stack_space (size_t size) | |
704 | { | |
705 | struct stack_segment *seg, *current; | |
706 | struct dynamic_allocation_blocks *p; | |
707 | ||
708 | /* We have to block signals to avoid getting confused if we get | |
709 | interrupted by a signal whose handler itself uses alloca or a | |
710 | variably sized array. */ | |
711 | __morestack_block_signals (); | |
712 | ||
713 | /* Since we don't want to call free while we are low on stack space, | |
714 | we may have a list of already allocated blocks waiting to be | |
715 | freed. Release them all, unless we find one that is large | |
716 | enough. We don't look at every block to see if one is large | |
717 | enough, just the first one, because we aren't trying to build a | |
718 | memory allocator here, we're just trying to speed up common | |
719 | cases. */ | |
720 | ||
721 | current = __morestack_current_segment; | |
722 | p = NULL; | |
723 | for (seg = __morestack_segments; seg != NULL; seg = seg->next) | |
724 | { | |
725 | p = seg->free_dynamic_allocation; | |
726 | if (p != NULL) | |
727 | { | |
728 | if (p->size >= size) | |
729 | { | |
730 | seg->free_dynamic_allocation = p->next; | |
731 | break; | |
732 | } | |
733 | ||
734 | free_dynamic_blocks (p); | |
735 | seg->free_dynamic_allocation = NULL; | |
736 | p = NULL; | |
737 | } | |
738 | } | |
739 | ||
740 | if (p == NULL) | |
741 | { | |
742 | /* We need to allocate additional memory. */ | |
743 | p = malloc (sizeof (*p)); | |
744 | if (p == NULL) | |
745 | abort (); | |
746 | p->size = size; | |
747 | p->block = malloc (size); | |
748 | if (p->block == NULL) | |
749 | abort (); | |
750 | } | |
751 | ||
752 | /* If we are still on the initial stack, then we have a space leak. | |
753 | FIXME. */ | |
754 | if (current != NULL) | |
755 | { | |
756 | p->next = current->dynamic_allocation; | |
757 | current->dynamic_allocation = p; | |
758 | } | |
759 | ||
760 | __morestack_unblock_signals (); | |
761 | ||
762 | return p->block; | |
763 | } | |
764 | ||
765 | /* Find the stack segment for STACK and return the amount of space | |
766 | available. This is used when unwinding the stack because of an | |
767 | exception, in order to reset the stack guard correctly. */ | |
768 | ||
769 | size_t | |
770 | __generic_findstack (void *stack) | |
771 | { | |
772 | struct stack_segment *pss; | |
773 | size_t used; | |
774 | ||
775 | for (pss = __morestack_current_segment; pss != NULL; pss = pss->prev) | |
776 | { | |
777 | if ((char *) pss < (char *) stack | |
778 | && (char *) pss + pss->size > (char *) stack) | |
779 | { | |
780 | __morestack_current_segment = pss; | |
53d68b9f | 781 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
782 | return (char *) stack - (char *) (pss + 1); |
783 | #else | |
784 | return (char *) (pss + 1) + pss->size - (char *) stack; | |
785 | #endif | |
786 | } | |
787 | } | |
788 | ||
789 | /* We have popped back to the original stack. */ | |
e14304ef ILT |
790 | |
791 | if (__morestack_initial_sp.sp == NULL) | |
792 | return 0; | |
793 | ||
53d68b9f | 794 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
795 | if ((char *) stack >= (char *) __morestack_initial_sp.sp) |
796 | used = 0; | |
797 | else | |
798 | used = (char *) __morestack_initial_sp.sp - (char *) stack; | |
799 | #else | |
800 | if ((char *) stack <= (char *) __morestack_initial_sp.sp) | |
801 | used = 0; | |
802 | else | |
803 | used = (char *) stack - (char *) __morestack_initial_sp.sp; | |
804 | #endif | |
805 | ||
806 | if (used > __morestack_initial_sp.len) | |
807 | return 0; | |
808 | else | |
809 | return __morestack_initial_sp.len - used; | |
810 | } | |
811 | ||
812 | /* This function is called at program startup time to make sure that | |
813 | mmap, munmap, and getpagesize are resolved if linking dynamically. | |
814 | We want to resolve them while we have enough stack for them, rather | |
815 | than calling into the dynamic linker while low on stack space. */ | |
816 | ||
817 | void | |
818 | __morestack_load_mmap (void) | |
819 | { | |
820 | /* Call with bogus values to run faster. We don't care if the call | |
821 | fails. Pass __MORESTACK_CURRENT_SEGMENT to make sure that any | |
822 | TLS accessor function is resolved. */ | |
823 | mmap (__morestack_current_segment, 0, PROT_READ, MAP_ANONYMOUS, -1, 0); | |
824 | mprotect (NULL, 0, 0); | |
825 | munmap (0, getpagesize ()); | |
826 | } | |
827 | ||
828 | /* This function may be used to iterate over the stack segments. | |
829 | This can be called like this. | |
830 | void *next_segment = NULL; | |
831 | void *next_sp = NULL; | |
832 | void *initial_sp = NULL; | |
833 | void *stack; | |
834 | size_t stack_size; | |
835 | while ((stack = __splitstack_find (next_segment, next_sp, &stack_size, | |
836 | &next_segment, &next_sp, | |
837 | &initial_sp)) != NULL) | |
838 | { | |
839 | // Stack segment starts at stack and is stack_size bytes long. | |
840 | } | |
841 | ||
842 | There is no way to iterate over the stack segments of a different | |
843 | thread. However, what is permitted is for one thread to call this | |
844 | with the first two values NULL, to pass next_segment, next_sp, and | |
845 | initial_sp to a different thread, and then to suspend one way or | |
846 | another. A different thread may run the subsequent | |
847 | __morestack_find iterations. Of course, this will only work if the | |
848 | first thread is suspended during the __morestack_find iterations. | |
849 | If not, the second thread will be looking at the stack while it is | |
850 | changing, and anything could happen. | |
851 | ||
852 | FIXME: This should be declared in some header file, but where? */ | |
853 | ||
854 | void * | |
855 | __splitstack_find (void *segment_arg, void *sp, size_t *len, | |
856 | void **next_segment, void **next_sp, | |
857 | void **initial_sp) | |
858 | { | |
859 | struct stack_segment *segment; | |
860 | void *ret; | |
861 | char *nsp; | |
862 | ||
e14304ef | 863 | if (segment_arg == (void *) (uintptr_type) 1) |
7458026b ILT |
864 | { |
865 | char *isp = (char *) *initial_sp; | |
866 | ||
e14304ef ILT |
867 | if (isp == NULL) |
868 | return NULL; | |
869 | ||
870 | *next_segment = (void *) (uintptr_type) 2; | |
7458026b | 871 | *next_sp = NULL; |
53d68b9f | 872 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
873 | if ((char *) sp >= isp) |
874 | return NULL; | |
875 | *len = (char *) isp - (char *) sp; | |
876 | return sp; | |
877 | #else | |
878 | if ((char *) sp <= (char *) isp) | |
879 | return NULL; | |
880 | *len = (char *) sp - (char *) isp; | |
881 | return (void *) isp; | |
882 | #endif | |
883 | } | |
e14304ef | 884 | else if (segment_arg == (void *) (uintptr_type) 2) |
7458026b ILT |
885 | return NULL; |
886 | else if (segment_arg != NULL) | |
887 | segment = (struct stack_segment *) segment_arg; | |
888 | else | |
889 | { | |
890 | *initial_sp = __morestack_initial_sp.sp; | |
891 | segment = __morestack_current_segment; | |
892 | sp = (void *) &segment; | |
893 | while (1) | |
894 | { | |
895 | if (segment == NULL) | |
e14304ef ILT |
896 | return __splitstack_find ((void *) (uintptr_type) 1, sp, len, |
897 | next_segment, next_sp, initial_sp); | |
7458026b ILT |
898 | if ((char *) sp >= (char *) (segment + 1) |
899 | && (char *) sp <= (char *) (segment + 1) + segment->size) | |
900 | break; | |
901 | segment = segment->prev; | |
902 | } | |
903 | } | |
904 | ||
905 | if (segment->prev == NULL) | |
e14304ef | 906 | *next_segment = (void *) (uintptr_type) 1; |
7458026b ILT |
907 | else |
908 | *next_segment = segment->prev; | |
909 | ||
910 | /* The old_stack value is the address of the function parameters of | |
911 | the function which called __morestack. So if f1 called f2 which | |
912 | called __morestack, the stack looks like this: | |
913 | ||
914 | parameters <- old_stack | |
915 | return in f1 | |
916 | return in f2 | |
457186f6 | 917 | registers pushed by __morestack |
7458026b | 918 | |
457186f6 ILT |
919 | The registers pushed by __morestack may not be visible on any |
920 | other stack, if we are being called by a signal handler | |
921 | immediately after the call to __morestack_unblock_signals. We | |
922 | want to adjust our return value to include those registers. This | |
923 | is target dependent. */ | |
7458026b ILT |
924 | |
925 | nsp = (char *) segment->old_stack; | |
457186f6 | 926 | |
a01207c4 ILT |
927 | if (nsp == NULL) |
928 | { | |
929 | /* We've reached the top of the stack. */ | |
930 | *next_segment = (void *) (uintptr_type) 2; | |
931 | } | |
932 | else | |
933 | { | |
457186f6 | 934 | #if defined (__x86_64__) |
a01207c4 | 935 | nsp -= 12 * sizeof (void *); |
457186f6 | 936 | #elif defined (__i386__) |
a01207c4 | 937 | nsp -= 6 * sizeof (void *); |
7458026b | 938 | #else |
457186f6 | 939 | #error "unrecognized target" |
7458026b | 940 | #endif |
457186f6 | 941 | |
a01207c4 ILT |
942 | *next_sp = (void *) nsp; |
943 | } | |
7458026b | 944 | |
53d68b9f | 945 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
7458026b ILT |
946 | *len = (char *) (segment + 1) + segment->size - (char *) sp; |
947 | ret = (void *) sp; | |
948 | #else | |
949 | *len = (char *) sp - (char *) (segment + 1); | |
950 | ret = (void *) (segment + 1); | |
951 | #endif | |
952 | ||
953 | return ret; | |
954 | } | |
955 | ||
e14304ef ILT |
956 | /* Tell the split stack code whether it has to block signals while |
957 | manipulating the stack. This is for programs in which some threads | |
958 | block all signals. If a thread already blocks signals, there is no | |
959 | need for the split stack code to block them as well. If NEW is not | |
960 | NULL, then if *NEW is non-zero signals will be blocked while | |
961 | splitting the stack, otherwise they will not. If OLD is not NULL, | |
962 | *OLD will be set to the old value. */ | |
963 | ||
964 | void | |
965 | __splitstack_block_signals (int *new, int *old) | |
966 | { | |
967 | if (old != NULL) | |
968 | *old = __morestack_initial_sp.dont_block_signals ? 0 : 1; | |
969 | if (new != NULL) | |
970 | __morestack_initial_sp.dont_block_signals = *new ? 0 : 1; | |
971 | } | |
972 | ||
973 | /* The offsets into the arrays used by __splitstack_getcontext and | |
974 | __splitstack_setcontext. */ | |
975 | ||
976 | enum __splitstack_context_offsets | |
977 | { | |
978 | MORESTACK_SEGMENTS = 0, | |
979 | CURRENT_SEGMENT = 1, | |
980 | CURRENT_STACK = 2, | |
981 | STACK_GUARD = 3, | |
982 | INITIAL_SP = 4, | |
983 | INITIAL_SP_LEN = 5, | |
984 | BLOCK_SIGNALS = 6, | |
985 | ||
986 | NUMBER_OFFSETS = 10 | |
987 | }; | |
988 | ||
989 | /* Get the current split stack context. This may be used for | |
990 | coroutine switching, similar to getcontext. The argument should | |
991 | have at least 10 void *pointers for extensibility, although we | |
992 | don't currently use all of them. This would normally be called | |
993 | immediately before a call to getcontext or swapcontext or | |
994 | setjmp. */ | |
995 | ||
996 | void | |
997 | __splitstack_getcontext (void *context[NUMBER_OFFSETS]) | |
998 | { | |
999 | memset (context, 0, NUMBER_OFFSETS * sizeof (void *)); | |
1000 | context[MORESTACK_SEGMENTS] = (void *) __morestack_segments; | |
1001 | context[CURRENT_SEGMENT] = (void *) __morestack_current_segment; | |
1002 | context[CURRENT_STACK] = (void *) &context; | |
1003 | context[STACK_GUARD] = __morestack_get_guard (); | |
1004 | context[INITIAL_SP] = (void *) __morestack_initial_sp.sp; | |
1005 | context[INITIAL_SP_LEN] = (void *) (uintptr_type) __morestack_initial_sp.len; | |
1006 | context[BLOCK_SIGNALS] = (void *) __morestack_initial_sp.dont_block_signals; | |
1007 | } | |
1008 | ||
1009 | /* Set the current split stack context. The argument should be a | |
1010 | context previously passed to __splitstack_getcontext. This would | |
1011 | normally be called immediately after a call to getcontext or | |
1012 | swapcontext or setjmp if something jumped to it. */ | |
1013 | ||
1014 | void | |
1015 | __splitstack_setcontext (void *context[NUMBER_OFFSETS]) | |
1016 | { | |
1017 | __morestack_segments = (struct stack_segment *) context[MORESTACK_SEGMENTS]; | |
1018 | __morestack_current_segment = | |
1019 | (struct stack_segment *) context[CURRENT_SEGMENT]; | |
1020 | __morestack_set_guard (context[STACK_GUARD]); | |
1021 | __morestack_initial_sp.sp = context[INITIAL_SP]; | |
1022 | __morestack_initial_sp.len = (size_t) context[INITIAL_SP_LEN]; | |
1023 | __morestack_initial_sp.dont_block_signals = | |
1024 | (uintptr_type) context[BLOCK_SIGNALS]; | |
1025 | } | |
1026 | ||
1027 | /* Create a new split stack context. This will allocate a new stack | |
1028 | segment which may be used by a coroutine. STACK_SIZE is the | |
1029 | minimum size of the new stack. The caller is responsible for | |
1030 | actually setting the stack pointer. This would normally be called | |
1031 | before a call to makecontext, and the returned stack pointer and | |
1032 | size would be used to set the uc_stack field. A function called | |
1033 | via makecontext on a stack created by __splitstack_makecontext may | |
1034 | not return. Note that the returned pointer points to the lowest | |
1035 | address in the stack space, and thus may not be the value to which | |
1036 | to set the stack pointer. */ | |
1037 | ||
1038 | void * | |
1039 | __splitstack_makecontext (size_t stack_size, void *context[NUMBER_OFFSETS], | |
1040 | size_t *size) | |
1041 | { | |
1042 | struct stack_segment *segment; | |
1043 | void *initial_sp; | |
1044 | ||
1045 | memset (context, 0, NUMBER_OFFSETS * sizeof (void *)); | |
1046 | segment = allocate_segment (stack_size); | |
1047 | context[MORESTACK_SEGMENTS] = segment; | |
1048 | context[CURRENT_SEGMENT] = segment; | |
53d68b9f | 1049 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
e14304ef ILT |
1050 | initial_sp = (void *) ((char *) (segment + 1) + segment->size); |
1051 | #else | |
1052 | initial_sp = (void *) (segment + 1); | |
1053 | #endif | |
1054 | context[STACK_GUARD] = __morestack_make_guard (initial_sp, segment->size); | |
1055 | context[INITIAL_SP] = NULL; | |
1056 | context[INITIAL_SP_LEN] = 0; | |
1057 | *size = segment->size; | |
1058 | return (void *) (segment + 1); | |
1059 | } | |
1060 | ||
a01207c4 ILT |
1061 | /* Given an existing split stack context, reset it back to the start |
1062 | of the stack. Return the stack pointer and size, appropriate for | |
1063 | use with makecontext. This may be used if a coroutine exits, in | |
1064 | order to reuse the stack segments for a new coroutine. */ | |
1065 | ||
1066 | void * | |
1067 | __splitstack_resetcontext (void *context[10], size_t *size) | |
1068 | { | |
1069 | struct stack_segment *segment; | |
1070 | void *initial_sp; | |
1071 | size_t initial_size; | |
1072 | void *ret; | |
1073 | ||
1074 | /* Reset the context assuming that MORESTACK_SEGMENTS, INITIAL_SP | |
1075 | and INITIAL_SP_LEN are correct. */ | |
1076 | ||
1077 | segment = context[MORESTACK_SEGMENTS]; | |
1078 | context[CURRENT_SEGMENT] = segment; | |
1079 | context[CURRENT_STACK] = NULL; | |
1080 | if (segment == NULL) | |
1081 | { | |
1082 | initial_sp = context[INITIAL_SP]; | |
1083 | initial_size = (uintptr_type) context[INITIAL_SP_LEN]; | |
1084 | ret = initial_sp; | |
53d68b9f | 1085 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
a01207c4 ILT |
1086 | ret = (void *) ((char *) ret - initial_size); |
1087 | #endif | |
1088 | } | |
1089 | else | |
1090 | { | |
53d68b9f | 1091 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
a01207c4 ILT |
1092 | initial_sp = (void *) ((char *) (segment + 1) + segment->size); |
1093 | #else | |
1094 | initial_sp = (void *) (segment + 1); | |
1095 | #endif | |
1096 | initial_size = segment->size; | |
1097 | ret = (void *) (segment + 1); | |
1098 | } | |
1099 | context[STACK_GUARD] = __morestack_make_guard (initial_sp, initial_size); | |
1100 | context[BLOCK_SIGNALS] = NULL; | |
1101 | *size = initial_size; | |
1102 | return ret; | |
1103 | } | |
1104 | ||
1105 | /* Release all the memory associated with a splitstack context. This | |
1106 | may be used if a coroutine exits and the associated stack should be | |
1107 | freed. */ | |
1108 | ||
1109 | void | |
1110 | __splitstack_releasecontext (void *context[10]) | |
1111 | { | |
e9e053eb ILT |
1112 | __morestack_release_segments (((struct stack_segment **) |
1113 | &context[MORESTACK_SEGMENTS]), | |
1114 | 1); | |
a01207c4 ILT |
1115 | } |
1116 | ||
e14304ef ILT |
1117 | /* Like __splitstack_block_signals, but operating on CONTEXT, rather |
1118 | than on the current state. */ | |
1119 | ||
1120 | void | |
1121 | __splitstack_block_signals_context (void *context[NUMBER_OFFSETS], int *new, | |
1122 | int *old) | |
1123 | { | |
1124 | if (old != NULL) | |
1125 | *old = ((uintptr_type) context[BLOCK_SIGNALS]) != 0 ? 0 : 1; | |
1126 | if (new != NULL) | |
1127 | context[BLOCK_SIGNALS] = (void *) (uintptr_type) (*new ? 0 : 1); | |
1128 | } | |
1129 | ||
1130 | /* Find the stack segments associated with a split stack context. | |
1131 | This will return the address of the first stack segment and set | |
1132 | *STACK_SIZE to its size. It will set next_segment, next_sp, and | |
1133 | initial_sp which may be passed to __splitstack_find to find the | |
1134 | remaining segments. */ | |
1135 | ||
1136 | void * | |
1137 | __splitstack_find_context (void *context[NUMBER_OFFSETS], size_t *stack_size, | |
1138 | void **next_segment, void **next_sp, | |
1139 | void **initial_sp) | |
1140 | { | |
1141 | void *sp; | |
1142 | struct stack_segment *segment; | |
1143 | ||
1144 | *initial_sp = context[INITIAL_SP]; | |
1145 | ||
1146 | sp = context[CURRENT_STACK]; | |
1147 | if (sp == NULL) | |
1148 | { | |
1149 | /* Most likely this context was created but was never used. The | |
1150 | value 2 is a code used by __splitstack_find to mean that we | |
1151 | have reached the end of the list of stacks. */ | |
1152 | *next_segment = (void *) (uintptr_type) 2; | |
1153 | *next_sp = NULL; | |
1154 | *initial_sp = NULL; | |
1155 | return NULL; | |
1156 | } | |
1157 | ||
1158 | segment = context[CURRENT_SEGMENT]; | |
1159 | if (segment == NULL) | |
1160 | { | |
1161 | /* Most likely this context was saved by a thread which was not | |
1162 | created using __splistack_makecontext and which has never | |
1163 | split the stack. The value 1 is a code used by | |
1164 | __splitstack_find to look at the initial stack. */ | |
1165 | segment = (struct stack_segment *) (uintptr_type) 1; | |
1166 | } | |
1167 | ||
1168 | return __splitstack_find (segment, sp, stack_size, next_segment, next_sp, | |
1169 | initial_sp); | |
1170 | } | |
1171 | ||
7458026b | 1172 | #endif /* !defined (inhibit_libc) */ |