]>
Commit | Line | Data |
---|---|---|
48b14f50 | 1 | /* Library support for -fsplit-stack. */ |
fbd26352 | 2 | /* Copyright (C) 2009-2019 Free Software Foundation, Inc. |
48b14f50 | 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 | ||
ec3f28c9 | 26 | /* powerpc 32-bit not supported. */ |
27 | #if !defined __powerpc__ || defined __powerpc64__ | |
28 | ||
48b14f50 | 29 | #include "tconfig.h" |
30 | #include "tsystem.h" | |
31 | #include "coretypes.h" | |
32 | #include "tm.h" | |
022a2799 | 33 | #include "libgcc_tm.h" |
48b14f50 | 34 | |
f4d3c071 | 35 | /* If inhibit_libc is defined, we cannot compile this file. The |
48b14f50 | 36 | effect is that people will not be able to use -fsplit-stack. That |
37 | is much better than failing the build particularly since people | |
38 | will want to define inhibit_libc while building a compiler which | |
39 | can build glibc. */ | |
40 | ||
41 | #ifndef inhibit_libc | |
42 | ||
43 | #include <assert.h> | |
44 | #include <errno.h> | |
45 | #include <signal.h> | |
46 | #include <stdlib.h> | |
23371076 | 47 | #include <string.h> |
48b14f50 | 48 | #include <unistd.h> |
49 | #include <sys/mman.h> | |
50 | #include <sys/uio.h> | |
51 | ||
52 | #include "generic-morestack.h" | |
53 | ||
23371076 | 54 | typedef unsigned uintptr_type __attribute__ ((mode (pointer))); |
55 | ||
48b14f50 | 56 | /* This file contains subroutines that are used by code compiled with |
57 | -fsplit-stack. */ | |
58 | ||
59 | /* Declare functions to avoid warnings--there is no header file for | |
60 | these internal functions. We give most of these functions the | |
61 | flatten attribute in order to minimize their stack usage--here we | |
62 | must minimize stack usage even at the cost of code size, and in | |
63 | general inlining everything will do that. */ | |
64 | ||
65 | extern void | |
66 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
67 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
68 | ||
69 | extern void * | |
70 | __generic_morestack (size_t *frame_size, void *old_stack, size_t param_size) | |
71 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
72 | ||
73 | extern void * | |
74 | __generic_releasestack (size_t *pavailable) | |
75 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
76 | ||
77 | extern void | |
78 | __morestack_block_signals (void) | |
79 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
80 | ||
81 | extern void | |
82 | __morestack_unblock_signals (void) | |
83 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
84 | ||
85 | extern size_t | |
86 | __generic_findstack (void *stack) | |
87 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
88 | ||
89 | extern void | |
90 | __morestack_load_mmap (void) | |
91 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
92 | ||
93 | extern void * | |
94 | __morestack_allocate_stack_space (size_t size) | |
95 | __attribute__ ((visibility ("hidden"))); | |
96 | ||
23371076 | 97 | /* These are functions which -fsplit-stack code can call. These are |
98 | not called by the compiler, and are not hidden. FIXME: These | |
99 | should be in some header file somewhere, somehow. */ | |
48b14f50 | 100 | |
101 | extern void * | |
102 | __splitstack_find (void *, void *, size_t *, void **, void **, void **) | |
103 | __attribute__ ((visibility ("default"))); | |
104 | ||
23371076 | 105 | extern void |
106 | __splitstack_block_signals (int *, int *) | |
107 | __attribute__ ((visibility ("default"))); | |
108 | ||
109 | extern void | |
110 | __splitstack_getcontext (void *context[10]) | |
111 | __attribute__ ((no_split_stack, visibility ("default"))); | |
112 | ||
113 | extern void | |
114 | __splitstack_setcontext (void *context[10]) | |
115 | __attribute__ ((no_split_stack, visibility ("default"))); | |
116 | ||
117 | extern void * | |
118 | __splitstack_makecontext (size_t, void *context[10], size_t *) | |
119 | __attribute__ ((visibility ("default"))); | |
120 | ||
bda4944f | 121 | extern void * |
122 | __splitstack_resetcontext (void *context[10], size_t *) | |
123 | __attribute__ ((visibility ("default"))); | |
124 | ||
125 | extern void | |
126 | __splitstack_releasecontext (void *context[10]) | |
127 | __attribute__ ((visibility ("default"))); | |
128 | ||
23371076 | 129 | extern void |
130 | __splitstack_block_signals_context (void *context[10], int *, int *) | |
131 | __attribute__ ((visibility ("default"))); | |
132 | ||
133 | extern void * | |
134 | __splitstack_find_context (void *context[10], size_t *, void **, void **, | |
135 | void **) | |
136 | __attribute__ ((visibility ("default"))); | |
137 | ||
138 | /* These functions must be defined by the processor specific code. */ | |
139 | ||
140 | extern void *__morestack_get_guard (void) | |
141 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
142 | ||
143 | extern void __morestack_set_guard (void *) | |
144 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
145 | ||
146 | extern void *__morestack_make_guard (void *, size_t) | |
147 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
148 | ||
48b14f50 | 149 | /* When we allocate a stack segment we put this header at the |
150 | start. */ | |
151 | ||
152 | struct stack_segment | |
153 | { | |
154 | /* The previous stack segment--when a function running on this stack | |
155 | segment returns, it will run on the previous one. */ | |
156 | struct stack_segment *prev; | |
157 | /* The next stack segment, if it has been allocated--when a function | |
158 | is running on this stack segment, the next one is not being | |
159 | used. */ | |
160 | struct stack_segment *next; | |
161 | /* The total size of this stack segment. */ | |
162 | size_t size; | |
163 | /* The stack address when this stack was created. This is used when | |
164 | popping the stack. */ | |
165 | void *old_stack; | |
166 | /* A list of memory blocks allocated by dynamic stack | |
167 | allocation. */ | |
168 | struct dynamic_allocation_blocks *dynamic_allocation; | |
169 | /* A list of dynamic memory blocks no longer needed. */ | |
170 | struct dynamic_allocation_blocks *free_dynamic_allocation; | |
171 | /* An extra pointer in case we need some more information some | |
172 | day. */ | |
173 | void *extra; | |
174 | }; | |
175 | ||
176 | /* This structure holds the (approximate) initial stack pointer and | |
177 | size for the system supplied stack for a thread. This is set when | |
178 | the thread is created. We also store a sigset_t here to hold the | |
179 | signal mask while splitting the stack, since we don't want to store | |
180 | that on the stack. */ | |
181 | ||
182 | struct initial_sp | |
183 | { | |
184 | /* The initial stack pointer. */ | |
185 | void *sp; | |
186 | /* The stack length. */ | |
187 | size_t len; | |
188 | /* A signal mask, put here so that the thread can use it without | |
189 | needing stack space. */ | |
190 | sigset_t mask; | |
23371076 | 191 | /* Non-zero if we should not block signals. This is a reversed flag |
192 | so that the default zero value is the safe value. The type is | |
193 | uintptr_type because it replaced one of the void * pointers in | |
194 | extra. */ | |
195 | uintptr_type dont_block_signals; | |
48b14f50 | 196 | /* Some extra space for later extensibility. */ |
23371076 | 197 | void *extra[4]; |
48b14f50 | 198 | }; |
199 | ||
200 | /* A list of memory blocks allocated by dynamic stack allocation. | |
201 | This is used for code that calls alloca or uses variably sized | |
202 | arrays. */ | |
203 | ||
204 | struct dynamic_allocation_blocks | |
205 | { | |
206 | /* The next block in the list. */ | |
207 | struct dynamic_allocation_blocks *next; | |
208 | /* The size of the allocated memory. */ | |
209 | size_t size; | |
210 | /* The allocated memory. */ | |
211 | void *block; | |
212 | }; | |
213 | ||
214 | /* These thread local global variables must be shared by all split | |
215 | stack code across shared library boundaries. Therefore, they have | |
216 | default visibility. They have extensibility fields if needed for | |
217 | new versions. If more radical changes are needed, new code can be | |
218 | written using new variable names, while still using the existing | |
219 | variables in a backward compatible manner. Symbol versioning is | |
220 | also used, although, since these variables are only referenced by | |
221 | code in this file and generic-morestack-thread.c, it is likely that | |
222 | simply using new names will suffice. */ | |
223 | ||
224 | /* The first stack segment allocated for this thread. */ | |
225 | ||
226 | __thread struct stack_segment *__morestack_segments | |
227 | __attribute__ ((visibility ("default"))); | |
228 | ||
229 | /* The stack segment that we think we are currently using. This will | |
230 | be correct in normal usage, but will be incorrect if an exception | |
231 | unwinds into a different stack segment or if longjmp jumps to a | |
232 | different stack segment. */ | |
233 | ||
234 | __thread struct stack_segment *__morestack_current_segment | |
235 | __attribute__ ((visibility ("default"))); | |
236 | ||
237 | /* The initial stack pointer and size for this thread. */ | |
238 | ||
239 | __thread struct initial_sp __morestack_initial_sp | |
240 | __attribute__ ((visibility ("default"))); | |
241 | ||
242 | /* A static signal mask, to avoid taking up stack space. */ | |
243 | ||
244 | static sigset_t __morestack_fullmask; | |
245 | ||
a9ee5a85 | 246 | /* Page size, as returned from getpagesize(). Set on startup. */ |
247 | static unsigned int static_pagesize; | |
248 | ||
249 | /* Set on startup to non-zero value if SPLIT_STACK_GUARD env var is set. */ | |
250 | static int use_guard_page; | |
251 | ||
48b14f50 | 252 | /* Convert an integer to a decimal string without using much stack |
253 | space. Return a pointer to the part of the buffer to use. We this | |
254 | instead of sprintf because sprintf will require too much stack | |
255 | space. */ | |
256 | ||
257 | static char * | |
258 | print_int (int val, char *buf, int buflen, size_t *print_len) | |
259 | { | |
260 | int is_negative; | |
261 | int i; | |
262 | unsigned int uval; | |
263 | ||
264 | uval = (unsigned int) val; | |
265 | if (val >= 0) | |
266 | is_negative = 0; | |
267 | else | |
268 | { | |
269 | is_negative = 1; | |
270 | uval = - uval; | |
271 | } | |
272 | ||
273 | i = buflen; | |
274 | do | |
275 | { | |
276 | --i; | |
277 | buf[i] = '0' + (uval % 10); | |
278 | uval /= 10; | |
279 | } | |
280 | while (uval != 0 && i > 0); | |
281 | ||
282 | if (is_negative) | |
283 | { | |
284 | if (i > 0) | |
285 | --i; | |
286 | buf[i] = '-'; | |
287 | } | |
288 | ||
289 | *print_len = buflen - i; | |
290 | return buf + i; | |
291 | } | |
292 | ||
293 | /* Print the string MSG/LEN, the errno number ERR, and a newline on | |
294 | stderr. Then crash. */ | |
295 | ||
296 | void | |
297 | __morestack_fail (const char *, size_t, int) __attribute__ ((noreturn)); | |
298 | ||
299 | void | |
300 | __morestack_fail (const char *msg, size_t len, int err) | |
301 | { | |
302 | char buf[24]; | |
303 | static const char nl[] = "\n"; | |
304 | struct iovec iov[3]; | |
305 | union { char *p; const char *cp; } const_cast; | |
306 | ||
307 | const_cast.cp = msg; | |
308 | iov[0].iov_base = const_cast.p; | |
309 | iov[0].iov_len = len; | |
310 | /* We can't call strerror, because it may try to translate the error | |
311 | message, and that would use too much stack space. */ | |
312 | iov[1].iov_base = print_int (err, buf, sizeof buf, &iov[1].iov_len); | |
313 | const_cast.cp = &nl[0]; | |
314 | iov[2].iov_base = const_cast.p; | |
315 | iov[2].iov_len = sizeof nl - 1; | |
316 | /* FIXME: On systems without writev we need to issue three write | |
317 | calls, or punt on printing errno. For now this is irrelevant | |
318 | since stack splitting only works on GNU/Linux anyhow. */ | |
319 | writev (2, iov, 3); | |
320 | abort (); | |
321 | } | |
322 | ||
323 | /* Allocate a new stack segment. FRAME_SIZE is the required frame | |
324 | size. */ | |
325 | ||
326 | static struct stack_segment * | |
327 | allocate_segment (size_t frame_size) | |
328 | { | |
48b14f50 | 329 | unsigned int pagesize; |
330 | unsigned int overhead; | |
331 | unsigned int allocate; | |
332 | void *space; | |
333 | struct stack_segment *pss; | |
334 | ||
335 | pagesize = static_pagesize; | |
48b14f50 | 336 | overhead = sizeof (struct stack_segment); |
337 | ||
338 | allocate = pagesize; | |
339 | if (allocate < MINSIGSTKSZ) | |
340 | allocate = ((MINSIGSTKSZ + overhead + pagesize - 1) | |
341 | & ~ (pagesize - 1)); | |
342 | if (allocate < frame_size) | |
343 | allocate = ((frame_size + overhead + pagesize - 1) | |
344 | & ~ (pagesize - 1)); | |
345 | ||
346 | if (use_guard_page) | |
347 | allocate += pagesize; | |
348 | ||
349 | /* FIXME: If this binary requires an executable stack, then we need | |
350 | to set PROT_EXEC. Unfortunately figuring that out is complicated | |
351 | and target dependent. We would need to use dl_iterate_phdr to | |
352 | see if there is any object which does not have a PT_GNU_STACK | |
353 | phdr, though only for architectures which use that mechanism. */ | |
354 | space = mmap (NULL, allocate, PROT_READ | PROT_WRITE, | |
355 | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); | |
356 | if (space == MAP_FAILED) | |
357 | { | |
358 | static const char msg[] = | |
359 | "unable to allocate additional stack space: errno "; | |
360 | __morestack_fail (msg, sizeof msg - 1, errno); | |
361 | } | |
362 | ||
363 | if (use_guard_page) | |
364 | { | |
365 | void *guard; | |
366 | ||
325b8c3c | 367 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 368 | guard = space; |
369 | space = (char *) space + pagesize; | |
370 | #else | |
371 | guard = space + allocate - pagesize; | |
372 | #endif | |
373 | ||
374 | mprotect (guard, pagesize, PROT_NONE); | |
375 | allocate -= pagesize; | |
376 | } | |
377 | ||
378 | pss = (struct stack_segment *) space; | |
379 | ||
23371076 | 380 | pss->prev = NULL; |
48b14f50 | 381 | pss->next = NULL; |
382 | pss->size = allocate - overhead; | |
383 | pss->dynamic_allocation = NULL; | |
384 | pss->free_dynamic_allocation = NULL; | |
385 | pss->extra = NULL; | |
386 | ||
48b14f50 | 387 | return pss; |
388 | } | |
389 | ||
390 | /* Free a list of dynamic blocks. */ | |
391 | ||
392 | static void | |
393 | free_dynamic_blocks (struct dynamic_allocation_blocks *p) | |
394 | { | |
395 | while (p != NULL) | |
396 | { | |
397 | struct dynamic_allocation_blocks *next; | |
398 | ||
399 | next = p->next; | |
400 | free (p->block); | |
401 | free (p); | |
402 | p = next; | |
403 | } | |
404 | } | |
405 | ||
406 | /* Merge two lists of dynamic blocks. */ | |
407 | ||
408 | static struct dynamic_allocation_blocks * | |
409 | merge_dynamic_blocks (struct dynamic_allocation_blocks *a, | |
410 | struct dynamic_allocation_blocks *b) | |
411 | { | |
412 | struct dynamic_allocation_blocks **pp; | |
413 | ||
414 | if (a == NULL) | |
415 | return b; | |
416 | if (b == NULL) | |
417 | return a; | |
418 | for (pp = &a->next; *pp != NULL; pp = &(*pp)->next) | |
419 | ; | |
420 | *pp = b; | |
421 | return a; | |
422 | } | |
423 | ||
424 | /* Release stack segments. If FREE_DYNAMIC is non-zero, we also free | |
425 | any dynamic blocks. Otherwise we return them. */ | |
426 | ||
427 | struct dynamic_allocation_blocks * | |
428 | __morestack_release_segments (struct stack_segment **pp, int free_dynamic) | |
429 | { | |
430 | struct dynamic_allocation_blocks *ret; | |
431 | struct stack_segment *pss; | |
432 | ||
433 | ret = NULL; | |
434 | pss = *pp; | |
435 | while (pss != NULL) | |
436 | { | |
437 | struct stack_segment *next; | |
438 | unsigned int allocate; | |
439 | ||
440 | next = pss->next; | |
441 | ||
442 | if (pss->dynamic_allocation != NULL | |
443 | || pss->free_dynamic_allocation != NULL) | |
444 | { | |
445 | if (free_dynamic) | |
446 | { | |
447 | free_dynamic_blocks (pss->dynamic_allocation); | |
448 | free_dynamic_blocks (pss->free_dynamic_allocation); | |
449 | } | |
450 | else | |
451 | { | |
452 | ret = merge_dynamic_blocks (pss->dynamic_allocation, ret); | |
453 | ret = merge_dynamic_blocks (pss->free_dynamic_allocation, ret); | |
454 | } | |
455 | } | |
456 | ||
457 | allocate = pss->size + sizeof (struct stack_segment); | |
458 | if (munmap (pss, allocate) < 0) | |
459 | { | |
460 | static const char msg[] = "munmap of stack space failed: errno "; | |
461 | __morestack_fail (msg, sizeof msg - 1, errno); | |
462 | } | |
463 | ||
464 | pss = next; | |
465 | } | |
466 | *pp = NULL; | |
467 | ||
468 | return ret; | |
469 | } | |
470 | ||
471 | /* This function is called by a processor specific function to set the | |
472 | initial stack pointer for a thread. The operating system will | |
473 | always create a stack for a thread. Here we record a stack pointer | |
474 | near the base of that stack. The size argument lets the processor | |
475 | specific code estimate how much stack space is available on this | |
476 | initial stack. */ | |
477 | ||
478 | void | |
479 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
480 | { | |
481 | /* The stack pointer most likely starts on a page boundary. Adjust | |
482 | to the nearest 512 byte boundary. It's not essential that we be | |
483 | precise here; getting it wrong will just leave some stack space | |
484 | unused. */ | |
325b8c3c | 485 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 486 | sp = (void *) ((((__UINTPTR_TYPE__) sp + 511U) / 512U) * 512U); |
487 | #else | |
488 | sp = (void *) ((((__UINTPTR_TYPE__) sp - 511U) / 512U) * 512U); | |
489 | #endif | |
490 | ||
491 | __morestack_initial_sp.sp = sp; | |
492 | __morestack_initial_sp.len = len; | |
493 | sigemptyset (&__morestack_initial_sp.mask); | |
494 | ||
495 | sigfillset (&__morestack_fullmask); | |
8d2259c8 | 496 | #if defined(__GLIBC__) && defined(__linux__) |
3efc00f6 | 497 | /* In glibc, the first two real time signals are used by the NPTL |
48b14f50 | 498 | threading library. By taking them out of the set of signals, we |
499 | avoiding copying the signal mask in pthread_sigmask. More | |
500 | importantly, pthread_sigmask uses less stack space on x86_64. */ | |
501 | sigdelset (&__morestack_fullmask, __SIGRTMIN); | |
502 | sigdelset (&__morestack_fullmask, __SIGRTMIN + 1); | |
503 | #endif | |
504 | } | |
505 | ||
506 | /* This function is called by a processor specific function which is | |
507 | run in the prologue when more stack is needed. The processor | |
508 | specific function handles the details of saving registers and | |
509 | frobbing the actual stack pointer. This function is responsible | |
510 | for allocating a new stack segment and for copying a parameter | |
511 | block from the old stack to the new one. On function entry | |
512 | *PFRAME_SIZE is the size of the required stack frame--the returned | |
513 | stack must be at least this large. On function exit *PFRAME_SIZE | |
514 | is the amount of space remaining on the allocated stack. OLD_STACK | |
515 | points at the parameters the old stack (really the current one | |
516 | while this function is running). OLD_STACK is saved so that it can | |
517 | be returned by a later call to __generic_releasestack. PARAM_SIZE | |
518 | is the size in bytes of parameters to copy to the new stack. This | |
519 | function returns a pointer to the new stack segment, pointing to | |
520 | the memory after the parameters have been copied. The returned | |
521 | value minus the returned *PFRAME_SIZE (or plus if the stack grows | |
522 | upward) is the first address on the stack which should not be used. | |
523 | ||
524 | This function is running on the old stack and has only a limited | |
525 | amount of stack space available. */ | |
526 | ||
527 | void * | |
528 | __generic_morestack (size_t *pframe_size, void *old_stack, size_t param_size) | |
529 | { | |
530 | size_t frame_size = *pframe_size; | |
531 | struct stack_segment *current; | |
532 | struct stack_segment **pp; | |
533 | struct dynamic_allocation_blocks *dynamic; | |
534 | char *from; | |
535 | char *to; | |
536 | void *ret; | |
537 | size_t i; | |
20f6e7a3 | 538 | size_t aligned; |
48b14f50 | 539 | |
540 | current = __morestack_current_segment; | |
541 | ||
542 | pp = current != NULL ? ¤t->next : &__morestack_segments; | |
543 | if (*pp != NULL && (*pp)->size < frame_size) | |
544 | dynamic = __morestack_release_segments (pp, 0); | |
545 | else | |
546 | dynamic = NULL; | |
547 | current = *pp; | |
548 | ||
549 | if (current == NULL) | |
23371076 | 550 | { |
551 | current = allocate_segment (frame_size + param_size); | |
552 | current->prev = __morestack_current_segment; | |
553 | *pp = current; | |
554 | } | |
48b14f50 | 555 | |
556 | current->old_stack = old_stack; | |
557 | ||
558 | __morestack_current_segment = current; | |
559 | ||
560 | if (dynamic != NULL) | |
561 | { | |
562 | /* Move the free blocks onto our list. We don't want to call | |
563 | free here, as we are short on stack space. */ | |
564 | current->free_dynamic_allocation = | |
565 | merge_dynamic_blocks (dynamic, current->free_dynamic_allocation); | |
566 | } | |
567 | ||
568 | *pframe_size = current->size - param_size; | |
569 | ||
20f6e7a3 | 570 | /* Align the returned stack to a 32-byte boundary. */ |
571 | aligned = (param_size + 31) & ~ (size_t) 31; | |
572 | ||
325b8c3c | 573 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 574 | { |
575 | char *bottom = (char *) (current + 1) + current->size; | |
20f6e7a3 | 576 | to = bottom - aligned; |
577 | ret = bottom - aligned; | |
48b14f50 | 578 | } |
579 | #else | |
580 | to = current + 1; | |
20f6e7a3 | 581 | to += aligned - param_size; |
582 | ret = (char *) (current + 1) + aligned; | |
48b14f50 | 583 | #endif |
584 | ||
585 | /* We don't call memcpy to avoid worrying about the dynamic linker | |
586 | trying to resolve it. */ | |
587 | from = (char *) old_stack; | |
588 | for (i = 0; i < param_size; i++) | |
589 | *to++ = *from++; | |
590 | ||
591 | return ret; | |
592 | } | |
593 | ||
594 | /* This function is called by a processor specific function when it is | |
595 | ready to release a stack segment. We don't actually release the | |
596 | stack segment, we just move back to the previous one. The current | |
597 | stack segment will still be available if we need it in | |
598 | __generic_morestack. This returns a pointer to the new stack | |
599 | segment to use, which is the one saved by a previous call to | |
600 | __generic_morestack. The processor specific function is then | |
601 | responsible for actually updating the stack pointer. This sets | |
602 | *PAVAILABLE to the amount of stack space now available. */ | |
603 | ||
604 | void * | |
605 | __generic_releasestack (size_t *pavailable) | |
606 | { | |
607 | struct stack_segment *current; | |
608 | void *old_stack; | |
609 | ||
610 | current = __morestack_current_segment; | |
611 | old_stack = current->old_stack; | |
612 | current = current->prev; | |
613 | __morestack_current_segment = current; | |
614 | ||
615 | if (current != NULL) | |
616 | { | |
325b8c3c | 617 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 618 | *pavailable = (char *) old_stack - (char *) (current + 1); |
619 | #else | |
620 | *pavailable = (char *) (current + 1) + current->size - (char *) old_stack; | |
621 | #endif | |
622 | } | |
623 | else | |
624 | { | |
625 | size_t used; | |
626 | ||
627 | /* We have popped back to the original stack. */ | |
325b8c3c | 628 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 629 | if ((char *) old_stack >= (char *) __morestack_initial_sp.sp) |
630 | used = 0; | |
631 | else | |
632 | used = (char *) __morestack_initial_sp.sp - (char *) old_stack; | |
633 | #else | |
634 | if ((char *) old_stack <= (char *) __morestack_initial_sp.sp) | |
635 | used = 0; | |
636 | else | |
637 | used = (char *) old_stack - (char *) __morestack_initial_sp.sp; | |
638 | #endif | |
639 | ||
640 | if (used > __morestack_initial_sp.len) | |
641 | *pavailable = 0; | |
642 | else | |
643 | *pavailable = __morestack_initial_sp.len - used; | |
644 | } | |
645 | ||
646 | return old_stack; | |
647 | } | |
648 | ||
649 | /* Block signals while splitting the stack. This avoids trouble if we | |
650 | try to invoke a signal handler which itself wants to split the | |
651 | stack. */ | |
652 | ||
653 | extern int pthread_sigmask (int, const sigset_t *, sigset_t *) | |
654 | __attribute__ ((weak)); | |
655 | ||
656 | void | |
657 | __morestack_block_signals (void) | |
658 | { | |
23371076 | 659 | if (__morestack_initial_sp.dont_block_signals) |
660 | ; | |
661 | else if (pthread_sigmask) | |
48b14f50 | 662 | pthread_sigmask (SIG_BLOCK, &__morestack_fullmask, |
663 | &__morestack_initial_sp.mask); | |
664 | else | |
665 | sigprocmask (SIG_BLOCK, &__morestack_fullmask, | |
666 | &__morestack_initial_sp.mask); | |
667 | } | |
668 | ||
669 | /* Unblock signals while splitting the stack. */ | |
670 | ||
671 | void | |
672 | __morestack_unblock_signals (void) | |
673 | { | |
23371076 | 674 | if (__morestack_initial_sp.dont_block_signals) |
675 | ; | |
676 | else if (pthread_sigmask) | |
48b14f50 | 677 | pthread_sigmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); |
678 | else | |
679 | sigprocmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); | |
680 | } | |
681 | ||
682 | /* This function is called to allocate dynamic stack space, for alloca | |
683 | or a variably sized array. This is a regular function with | |
684 | sufficient stack space, so we just use malloc to allocate the | |
685 | space. We attach the allocated blocks to the current stack | |
686 | segment, so that they will eventually be reused or freed. */ | |
687 | ||
688 | void * | |
689 | __morestack_allocate_stack_space (size_t size) | |
690 | { | |
691 | struct stack_segment *seg, *current; | |
692 | struct dynamic_allocation_blocks *p; | |
693 | ||
694 | /* We have to block signals to avoid getting confused if we get | |
695 | interrupted by a signal whose handler itself uses alloca or a | |
696 | variably sized array. */ | |
697 | __morestack_block_signals (); | |
698 | ||
699 | /* Since we don't want to call free while we are low on stack space, | |
700 | we may have a list of already allocated blocks waiting to be | |
701 | freed. Release them all, unless we find one that is large | |
702 | enough. We don't look at every block to see if one is large | |
703 | enough, just the first one, because we aren't trying to build a | |
704 | memory allocator here, we're just trying to speed up common | |
705 | cases. */ | |
706 | ||
707 | current = __morestack_current_segment; | |
708 | p = NULL; | |
709 | for (seg = __morestack_segments; seg != NULL; seg = seg->next) | |
710 | { | |
711 | p = seg->free_dynamic_allocation; | |
712 | if (p != NULL) | |
713 | { | |
714 | if (p->size >= size) | |
715 | { | |
716 | seg->free_dynamic_allocation = p->next; | |
717 | break; | |
718 | } | |
719 | ||
720 | free_dynamic_blocks (p); | |
721 | seg->free_dynamic_allocation = NULL; | |
722 | p = NULL; | |
723 | } | |
724 | } | |
725 | ||
726 | if (p == NULL) | |
727 | { | |
728 | /* We need to allocate additional memory. */ | |
729 | p = malloc (sizeof (*p)); | |
730 | if (p == NULL) | |
731 | abort (); | |
732 | p->size = size; | |
733 | p->block = malloc (size); | |
734 | if (p->block == NULL) | |
735 | abort (); | |
736 | } | |
737 | ||
738 | /* If we are still on the initial stack, then we have a space leak. | |
739 | FIXME. */ | |
740 | if (current != NULL) | |
741 | { | |
742 | p->next = current->dynamic_allocation; | |
743 | current->dynamic_allocation = p; | |
744 | } | |
745 | ||
746 | __morestack_unblock_signals (); | |
747 | ||
748 | return p->block; | |
749 | } | |
750 | ||
751 | /* Find the stack segment for STACK and return the amount of space | |
752 | available. This is used when unwinding the stack because of an | |
753 | exception, in order to reset the stack guard correctly. */ | |
754 | ||
755 | size_t | |
756 | __generic_findstack (void *stack) | |
757 | { | |
758 | struct stack_segment *pss; | |
759 | size_t used; | |
760 | ||
761 | for (pss = __morestack_current_segment; pss != NULL; pss = pss->prev) | |
762 | { | |
763 | if ((char *) pss < (char *) stack | |
764 | && (char *) pss + pss->size > (char *) stack) | |
765 | { | |
766 | __morestack_current_segment = pss; | |
325b8c3c | 767 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 768 | return (char *) stack - (char *) (pss + 1); |
769 | #else | |
770 | return (char *) (pss + 1) + pss->size - (char *) stack; | |
771 | #endif | |
772 | } | |
773 | } | |
774 | ||
775 | /* We have popped back to the original stack. */ | |
23371076 | 776 | |
777 | if (__morestack_initial_sp.sp == NULL) | |
778 | return 0; | |
779 | ||
325b8c3c | 780 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 781 | if ((char *) stack >= (char *) __morestack_initial_sp.sp) |
782 | used = 0; | |
783 | else | |
784 | used = (char *) __morestack_initial_sp.sp - (char *) stack; | |
785 | #else | |
786 | if ((char *) stack <= (char *) __morestack_initial_sp.sp) | |
787 | used = 0; | |
788 | else | |
789 | used = (char *) stack - (char *) __morestack_initial_sp.sp; | |
790 | #endif | |
791 | ||
792 | if (used > __morestack_initial_sp.len) | |
793 | return 0; | |
794 | else | |
795 | return __morestack_initial_sp.len - used; | |
796 | } | |
797 | ||
798 | /* This function is called at program startup time to make sure that | |
799 | mmap, munmap, and getpagesize are resolved if linking dynamically. | |
800 | We want to resolve them while we have enough stack for them, rather | |
a9ee5a85 | 801 | than calling into the dynamic linker while low on stack space. |
802 | Similarly, invoke getenv here to check for split-stack related control | |
803 | variables, since doing do as part of the __morestack path can result | |
804 | in unwanted use of SSE/AVX registers (see GCC PR 86213). */ | |
48b14f50 | 805 | |
806 | void | |
807 | __morestack_load_mmap (void) | |
808 | { | |
809 | /* Call with bogus values to run faster. We don't care if the call | |
810 | fails. Pass __MORESTACK_CURRENT_SEGMENT to make sure that any | |
811 | TLS accessor function is resolved. */ | |
812 | mmap (__morestack_current_segment, 0, PROT_READ, MAP_ANONYMOUS, -1, 0); | |
813 | mprotect (NULL, 0, 0); | |
a9ee5a85 | 814 | munmap (0, static_pagesize); |
815 | ||
816 | /* Initialize these values here, so as to avoid dynamic linker | |
817 | activity as part of a __morestack call. */ | |
818 | static_pagesize = getpagesize(); | |
819 | use_guard_page = getenv ("SPLIT_STACK_GUARD") != 0; | |
48b14f50 | 820 | } |
821 | ||
822 | /* This function may be used to iterate over the stack segments. | |
823 | This can be called like this. | |
824 | void *next_segment = NULL; | |
825 | void *next_sp = NULL; | |
826 | void *initial_sp = NULL; | |
827 | void *stack; | |
828 | size_t stack_size; | |
829 | while ((stack = __splitstack_find (next_segment, next_sp, &stack_size, | |
830 | &next_segment, &next_sp, | |
831 | &initial_sp)) != NULL) | |
832 | { | |
833 | // Stack segment starts at stack and is stack_size bytes long. | |
834 | } | |
835 | ||
836 | There is no way to iterate over the stack segments of a different | |
837 | thread. However, what is permitted is for one thread to call this | |
838 | with the first two values NULL, to pass next_segment, next_sp, and | |
839 | initial_sp to a different thread, and then to suspend one way or | |
840 | another. A different thread may run the subsequent | |
841 | __morestack_find iterations. Of course, this will only work if the | |
842 | first thread is suspended during the __morestack_find iterations. | |
843 | If not, the second thread will be looking at the stack while it is | |
844 | changing, and anything could happen. | |
845 | ||
846 | FIXME: This should be declared in some header file, but where? */ | |
847 | ||
848 | void * | |
849 | __splitstack_find (void *segment_arg, void *sp, size_t *len, | |
850 | void **next_segment, void **next_sp, | |
851 | void **initial_sp) | |
852 | { | |
853 | struct stack_segment *segment; | |
854 | void *ret; | |
855 | char *nsp; | |
856 | ||
23371076 | 857 | if (segment_arg == (void *) (uintptr_type) 1) |
48b14f50 | 858 | { |
859 | char *isp = (char *) *initial_sp; | |
860 | ||
23371076 | 861 | if (isp == NULL) |
862 | return NULL; | |
863 | ||
864 | *next_segment = (void *) (uintptr_type) 2; | |
48b14f50 | 865 | *next_sp = NULL; |
325b8c3c | 866 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 867 | if ((char *) sp >= isp) |
868 | return NULL; | |
869 | *len = (char *) isp - (char *) sp; | |
870 | return sp; | |
871 | #else | |
872 | if ((char *) sp <= (char *) isp) | |
873 | return NULL; | |
874 | *len = (char *) sp - (char *) isp; | |
875 | return (void *) isp; | |
876 | #endif | |
877 | } | |
23371076 | 878 | else if (segment_arg == (void *) (uintptr_type) 2) |
48b14f50 | 879 | return NULL; |
880 | else if (segment_arg != NULL) | |
881 | segment = (struct stack_segment *) segment_arg; | |
882 | else | |
883 | { | |
884 | *initial_sp = __morestack_initial_sp.sp; | |
885 | segment = __morestack_current_segment; | |
886 | sp = (void *) &segment; | |
887 | while (1) | |
888 | { | |
889 | if (segment == NULL) | |
23371076 | 890 | return __splitstack_find ((void *) (uintptr_type) 1, sp, len, |
891 | next_segment, next_sp, initial_sp); | |
48b14f50 | 892 | if ((char *) sp >= (char *) (segment + 1) |
893 | && (char *) sp <= (char *) (segment + 1) + segment->size) | |
894 | break; | |
895 | segment = segment->prev; | |
896 | } | |
897 | } | |
898 | ||
899 | if (segment->prev == NULL) | |
23371076 | 900 | *next_segment = (void *) (uintptr_type) 1; |
48b14f50 | 901 | else |
902 | *next_segment = segment->prev; | |
903 | ||
904 | /* The old_stack value is the address of the function parameters of | |
905 | the function which called __morestack. So if f1 called f2 which | |
906 | called __morestack, the stack looks like this: | |
907 | ||
908 | parameters <- old_stack | |
909 | return in f1 | |
910 | return in f2 | |
82c96609 | 911 | registers pushed by __morestack |
48b14f50 | 912 | |
82c96609 | 913 | The registers pushed by __morestack may not be visible on any |
914 | other stack, if we are being called by a signal handler | |
915 | immediately after the call to __morestack_unblock_signals. We | |
916 | want to adjust our return value to include those registers. This | |
917 | is target dependent. */ | |
48b14f50 | 918 | |
919 | nsp = (char *) segment->old_stack; | |
82c96609 | 920 | |
bda4944f | 921 | if (nsp == NULL) |
922 | { | |
923 | /* We've reached the top of the stack. */ | |
924 | *next_segment = (void *) (uintptr_type) 2; | |
925 | } | |
926 | else | |
927 | { | |
82c96609 | 928 | #if defined (__x86_64__) |
bda4944f | 929 | nsp -= 12 * sizeof (void *); |
82c96609 | 930 | #elif defined (__i386__) |
bda4944f | 931 | nsp -= 6 * sizeof (void *); |
ec3f28c9 | 932 | #elif defined __powerpc64__ |
c6d481f7 | 933 | #elif defined __s390x__ |
934 | nsp -= 2 * 160; | |
935 | #elif defined __s390__ | |
936 | nsp -= 2 * 96; | |
48b14f50 | 937 | #else |
82c96609 | 938 | #error "unrecognized target" |
48b14f50 | 939 | #endif |
82c96609 | 940 | |
bda4944f | 941 | *next_sp = (void *) nsp; |
942 | } | |
48b14f50 | 943 | |
325b8c3c | 944 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
48b14f50 | 945 | *len = (char *) (segment + 1) + segment->size - (char *) sp; |
946 | ret = (void *) sp; | |
947 | #else | |
948 | *len = (char *) sp - (char *) (segment + 1); | |
949 | ret = (void *) (segment + 1); | |
950 | #endif | |
951 | ||
952 | return ret; | |
953 | } | |
954 | ||
23371076 | 955 | /* Tell the split stack code whether it has to block signals while |
956 | manipulating the stack. This is for programs in which some threads | |
957 | block all signals. If a thread already blocks signals, there is no | |
958 | need for the split stack code to block them as well. If NEW is not | |
959 | NULL, then if *NEW is non-zero signals will be blocked while | |
960 | splitting the stack, otherwise they will not. If OLD is not NULL, | |
961 | *OLD will be set to the old value. */ | |
962 | ||
963 | void | |
964 | __splitstack_block_signals (int *new, int *old) | |
965 | { | |
966 | if (old != NULL) | |
967 | *old = __morestack_initial_sp.dont_block_signals ? 0 : 1; | |
968 | if (new != NULL) | |
969 | __morestack_initial_sp.dont_block_signals = *new ? 0 : 1; | |
970 | } | |
971 | ||
972 | /* The offsets into the arrays used by __splitstack_getcontext and | |
973 | __splitstack_setcontext. */ | |
974 | ||
975 | enum __splitstack_context_offsets | |
976 | { | |
977 | MORESTACK_SEGMENTS = 0, | |
978 | CURRENT_SEGMENT = 1, | |
979 | CURRENT_STACK = 2, | |
980 | STACK_GUARD = 3, | |
981 | INITIAL_SP = 4, | |
982 | INITIAL_SP_LEN = 5, | |
983 | BLOCK_SIGNALS = 6, | |
984 | ||
985 | NUMBER_OFFSETS = 10 | |
986 | }; | |
987 | ||
988 | /* Get the current split stack context. This may be used for | |
989 | coroutine switching, similar to getcontext. The argument should | |
990 | have at least 10 void *pointers for extensibility, although we | |
991 | don't currently use all of them. This would normally be called | |
992 | immediately before a call to getcontext or swapcontext or | |
993 | setjmp. */ | |
994 | ||
995 | void | |
996 | __splitstack_getcontext (void *context[NUMBER_OFFSETS]) | |
997 | { | |
998 | memset (context, 0, NUMBER_OFFSETS * sizeof (void *)); | |
999 | context[MORESTACK_SEGMENTS] = (void *) __morestack_segments; | |
1000 | context[CURRENT_SEGMENT] = (void *) __morestack_current_segment; | |
1001 | context[CURRENT_STACK] = (void *) &context; | |
1002 | context[STACK_GUARD] = __morestack_get_guard (); | |
1003 | context[INITIAL_SP] = (void *) __morestack_initial_sp.sp; | |
1004 | context[INITIAL_SP_LEN] = (void *) (uintptr_type) __morestack_initial_sp.len; | |
1005 | context[BLOCK_SIGNALS] = (void *) __morestack_initial_sp.dont_block_signals; | |
1006 | } | |
1007 | ||
1008 | /* Set the current split stack context. The argument should be a | |
1009 | context previously passed to __splitstack_getcontext. This would | |
1010 | normally be called immediately after a call to getcontext or | |
1011 | swapcontext or setjmp if something jumped to it. */ | |
1012 | ||
1013 | void | |
1014 | __splitstack_setcontext (void *context[NUMBER_OFFSETS]) | |
1015 | { | |
1016 | __morestack_segments = (struct stack_segment *) context[MORESTACK_SEGMENTS]; | |
1017 | __morestack_current_segment = | |
1018 | (struct stack_segment *) context[CURRENT_SEGMENT]; | |
1019 | __morestack_set_guard (context[STACK_GUARD]); | |
1020 | __morestack_initial_sp.sp = context[INITIAL_SP]; | |
1021 | __morestack_initial_sp.len = (size_t) context[INITIAL_SP_LEN]; | |
1022 | __morestack_initial_sp.dont_block_signals = | |
1023 | (uintptr_type) context[BLOCK_SIGNALS]; | |
1024 | } | |
1025 | ||
1026 | /* Create a new split stack context. This will allocate a new stack | |
1027 | segment which may be used by a coroutine. STACK_SIZE is the | |
1028 | minimum size of the new stack. The caller is responsible for | |
1029 | actually setting the stack pointer. This would normally be called | |
1030 | before a call to makecontext, and the returned stack pointer and | |
1031 | size would be used to set the uc_stack field. A function called | |
1032 | via makecontext on a stack created by __splitstack_makecontext may | |
1033 | not return. Note that the returned pointer points to the lowest | |
1034 | address in the stack space, and thus may not be the value to which | |
1035 | to set the stack pointer. */ | |
1036 | ||
1037 | void * | |
1038 | __splitstack_makecontext (size_t stack_size, void *context[NUMBER_OFFSETS], | |
1039 | size_t *size) | |
1040 | { | |
1041 | struct stack_segment *segment; | |
1042 | void *initial_sp; | |
1043 | ||
1044 | memset (context, 0, NUMBER_OFFSETS * sizeof (void *)); | |
1045 | segment = allocate_segment (stack_size); | |
1046 | context[MORESTACK_SEGMENTS] = segment; | |
1047 | context[CURRENT_SEGMENT] = segment; | |
325b8c3c | 1048 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
23371076 | 1049 | initial_sp = (void *) ((char *) (segment + 1) + segment->size); |
1050 | #else | |
1051 | initial_sp = (void *) (segment + 1); | |
1052 | #endif | |
1053 | context[STACK_GUARD] = __morestack_make_guard (initial_sp, segment->size); | |
1054 | context[INITIAL_SP] = NULL; | |
1055 | context[INITIAL_SP_LEN] = 0; | |
1056 | *size = segment->size; | |
1057 | return (void *) (segment + 1); | |
1058 | } | |
1059 | ||
bda4944f | 1060 | /* Given an existing split stack context, reset it back to the start |
1061 | of the stack. Return the stack pointer and size, appropriate for | |
1062 | use with makecontext. This may be used if a coroutine exits, in | |
1063 | order to reuse the stack segments for a new coroutine. */ | |
1064 | ||
1065 | void * | |
1066 | __splitstack_resetcontext (void *context[10], size_t *size) | |
1067 | { | |
1068 | struct stack_segment *segment; | |
1069 | void *initial_sp; | |
1070 | size_t initial_size; | |
1071 | void *ret; | |
1072 | ||
1073 | /* Reset the context assuming that MORESTACK_SEGMENTS, INITIAL_SP | |
1074 | and INITIAL_SP_LEN are correct. */ | |
1075 | ||
1076 | segment = context[MORESTACK_SEGMENTS]; | |
1077 | context[CURRENT_SEGMENT] = segment; | |
1078 | context[CURRENT_STACK] = NULL; | |
1079 | if (segment == NULL) | |
1080 | { | |
1081 | initial_sp = context[INITIAL_SP]; | |
1082 | initial_size = (uintptr_type) context[INITIAL_SP_LEN]; | |
1083 | ret = initial_sp; | |
325b8c3c | 1084 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
bda4944f | 1085 | ret = (void *) ((char *) ret - initial_size); |
1086 | #endif | |
1087 | } | |
1088 | else | |
1089 | { | |
325b8c3c | 1090 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ |
bda4944f | 1091 | initial_sp = (void *) ((char *) (segment + 1) + segment->size); |
1092 | #else | |
1093 | initial_sp = (void *) (segment + 1); | |
1094 | #endif | |
1095 | initial_size = segment->size; | |
1096 | ret = (void *) (segment + 1); | |
1097 | } | |
1098 | context[STACK_GUARD] = __morestack_make_guard (initial_sp, initial_size); | |
1099 | context[BLOCK_SIGNALS] = NULL; | |
1100 | *size = initial_size; | |
1101 | return ret; | |
1102 | } | |
1103 | ||
1104 | /* Release all the memory associated with a splitstack context. This | |
1105 | may be used if a coroutine exits and the associated stack should be | |
1106 | freed. */ | |
1107 | ||
1108 | void | |
1109 | __splitstack_releasecontext (void *context[10]) | |
1110 | { | |
154b49cd | 1111 | __morestack_release_segments (((struct stack_segment **) |
1112 | &context[MORESTACK_SEGMENTS]), | |
1113 | 1); | |
bda4944f | 1114 | } |
1115 | ||
23371076 | 1116 | /* Like __splitstack_block_signals, but operating on CONTEXT, rather |
1117 | than on the current state. */ | |
1118 | ||
1119 | void | |
1120 | __splitstack_block_signals_context (void *context[NUMBER_OFFSETS], int *new, | |
1121 | int *old) | |
1122 | { | |
1123 | if (old != NULL) | |
1124 | *old = ((uintptr_type) context[BLOCK_SIGNALS]) != 0 ? 0 : 1; | |
1125 | if (new != NULL) | |
1126 | context[BLOCK_SIGNALS] = (void *) (uintptr_type) (*new ? 0 : 1); | |
1127 | } | |
1128 | ||
1129 | /* Find the stack segments associated with a split stack context. | |
1130 | This will return the address of the first stack segment and set | |
1131 | *STACK_SIZE to its size. It will set next_segment, next_sp, and | |
1132 | initial_sp which may be passed to __splitstack_find to find the | |
1133 | remaining segments. */ | |
1134 | ||
1135 | void * | |
1136 | __splitstack_find_context (void *context[NUMBER_OFFSETS], size_t *stack_size, | |
1137 | void **next_segment, void **next_sp, | |
1138 | void **initial_sp) | |
1139 | { | |
1140 | void *sp; | |
1141 | struct stack_segment *segment; | |
1142 | ||
1143 | *initial_sp = context[INITIAL_SP]; | |
1144 | ||
1145 | sp = context[CURRENT_STACK]; | |
1146 | if (sp == NULL) | |
1147 | { | |
1148 | /* Most likely this context was created but was never used. The | |
1149 | value 2 is a code used by __splitstack_find to mean that we | |
1150 | have reached the end of the list of stacks. */ | |
1151 | *next_segment = (void *) (uintptr_type) 2; | |
1152 | *next_sp = NULL; | |
1153 | *initial_sp = NULL; | |
1154 | return NULL; | |
1155 | } | |
1156 | ||
1157 | segment = context[CURRENT_SEGMENT]; | |
1158 | if (segment == NULL) | |
1159 | { | |
1160 | /* Most likely this context was saved by a thread which was not | |
1161 | created using __splistack_makecontext and which has never | |
1162 | split the stack. The value 1 is a code used by | |
1163 | __splitstack_find to look at the initial stack. */ | |
1164 | segment = (struct stack_segment *) (uintptr_type) 1; | |
1165 | } | |
1166 | ||
1167 | return __splitstack_find (segment, sp, stack_size, next_segment, next_sp, | |
1168 | initial_sp); | |
1169 | } | |
1170 | ||
48b14f50 | 1171 | #endif /* !defined (inhibit_libc) */ |
ec3f28c9 | 1172 | #endif /* not powerpc 32-bit */ |