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1 | /* Library support for -fsplit-stack. */ | |
2 | /* Copyright (C) 2009-2024 Free Software Foundation, Inc. | |
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 | #pragma GCC optimize ("no-isolate-erroneous-paths-dereference") | |
27 | ||
28 | /* powerpc 32-bit not supported. */ | |
29 | #if !defined __powerpc__ || defined __powerpc64__ | |
30 | ||
31 | #include "tconfig.h" | |
32 | #include "tsystem.h" | |
33 | #include "coretypes.h" | |
34 | #include "tm.h" | |
35 | #include "libgcc_tm.h" | |
36 | ||
37 | /* If inhibit_libc is defined, we cannot compile this file. The | |
38 | effect is that people will not be able to use -fsplit-stack. That | |
39 | is much better than failing the build particularly since people | |
40 | will want to define inhibit_libc while building a compiler which | |
41 | can build glibc. */ | |
42 | ||
43 | #ifndef inhibit_libc | |
44 | ||
45 | #include <assert.h> | |
46 | #include <errno.h> | |
47 | #include <signal.h> | |
48 | #include <stdlib.h> | |
49 | #include <string.h> | |
50 | #include <unistd.h> | |
51 | #include <sys/mman.h> | |
52 | #include <sys/uio.h> | |
53 | ||
54 | #include "generic-morestack.h" | |
55 | ||
56 | /* Some systems use LD_PRELOAD or similar tricks to add hooks to | |
57 | mmap/munmap. That breaks this code, because when we call mmap | |
58 | there is enough stack space for the system call but there is not, | |
59 | in general, enough stack space to run a hook. Try to avoid the | |
60 | problem by calling syscall directly. We only do this on GNU/Linux | |
61 | for now, but it should be easy to add support for more systems with | |
62 | testing. */ | |
63 | ||
64 | #if defined(__gnu_linux__) | |
65 | ||
66 | #include <sys/syscall.h> | |
67 | ||
68 | #if defined(SYS_mmap) || defined(SYS_mmap2) | |
69 | ||
70 | #ifdef SYS_mmap2 | |
71 | #define MORESTACK_MMAP SYS_mmap2 | |
72 | #define MORESTACK_ADJUST_OFFSET(x) ((x) / 4096ULL) | |
73 | #else | |
74 | #define MORESTACK_MMAP SYS_mmap | |
75 | #define MORESTACK_ADJUST_OFFSET(x) (x) | |
76 | #endif | |
77 | ||
78 | static void * | |
79 | morestack_mmap (void *addr, size_t length, int prot, int flags, int fd, | |
80 | off_t offset) | |
81 | { | |
82 | offset = MORESTACK_ADJUST_OFFSET (offset); | |
83 | ||
84 | #ifdef __s390__ | |
85 | long args[6] = { (long) addr, (long) length, (long) prot, (long) flags, | |
86 | (long) fd, (long) offset }; | |
87 | return (void *) syscall (MORESTACK_MMAP, args); | |
88 | #else | |
89 | return (void *) syscall (MORESTACK_MMAP, addr, length, prot, flags, fd, | |
90 | offset); | |
91 | #endif | |
92 | } | |
93 | ||
94 | #define mmap morestack_mmap | |
95 | ||
96 | #endif /* defined(SYS_MMAP) || defined(SYS_mmap2) */ | |
97 | ||
98 | #if defined(SYS_munmap) | |
99 | ||
100 | static int | |
101 | morestack_munmap (void * addr, size_t length) | |
102 | { | |
103 | return (int) syscall (SYS_munmap, addr, length); | |
104 | } | |
105 | ||
106 | #define munmap morestack_munmap | |
107 | ||
108 | #endif /* defined(SYS_munmap) */ | |
109 | ||
110 | #endif /* defined(__gnu_linux__) */ | |
111 | ||
112 | typedef unsigned uintptr_type __attribute__ ((mode (pointer))); | |
113 | ||
114 | /* This file contains subroutines that are used by code compiled with | |
115 | -fsplit-stack. */ | |
116 | ||
117 | /* Declare functions to avoid warnings--there is no header file for | |
118 | these internal functions. We give most of these functions the | |
119 | flatten attribute in order to minimize their stack usage--here we | |
120 | must minimize stack usage even at the cost of code size, and in | |
121 | general inlining everything will do that. */ | |
122 | ||
123 | extern void | |
124 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
125 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
126 | ||
127 | extern void * | |
128 | __generic_morestack (size_t *frame_size, void *old_stack, size_t param_size) | |
129 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
130 | ||
131 | extern void * | |
132 | __generic_releasestack (size_t *pavailable) | |
133 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
134 | ||
135 | extern void | |
136 | __morestack_block_signals (void) | |
137 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
138 | ||
139 | extern void | |
140 | __morestack_unblock_signals (void) | |
141 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
142 | ||
143 | extern size_t | |
144 | __generic_findstack (void *stack) | |
145 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
146 | ||
147 | extern void | |
148 | __morestack_load_mmap (void) | |
149 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
150 | ||
151 | extern void * | |
152 | __morestack_allocate_stack_space (size_t size) | |
153 | __attribute__ ((visibility ("hidden"))); | |
154 | ||
155 | /* These are functions which -fsplit-stack code can call. These are | |
156 | not called by the compiler, and are not hidden. FIXME: These | |
157 | should be in some header file somewhere, somehow. */ | |
158 | ||
159 | extern void * | |
160 | __splitstack_find (void *, void *, size_t *, void **, void **, void **) | |
161 | __attribute__ ((visibility ("default"))); | |
162 | ||
163 | extern void | |
164 | __splitstack_block_signals (int *, int *) | |
165 | __attribute__ ((visibility ("default"))); | |
166 | ||
167 | extern void | |
168 | __splitstack_getcontext (void *context[10]) | |
169 | __attribute__ ((no_split_stack, visibility ("default"))); | |
170 | ||
171 | extern void | |
172 | __splitstack_setcontext (void *context[10]) | |
173 | __attribute__ ((no_split_stack, visibility ("default"))); | |
174 | ||
175 | extern void * | |
176 | __splitstack_makecontext (size_t, void *context[10], size_t *) | |
177 | __attribute__ ((visibility ("default"))); | |
178 | ||
179 | extern void * | |
180 | __splitstack_resetcontext (void *context[10], size_t *) | |
181 | __attribute__ ((visibility ("default"))); | |
182 | ||
183 | extern void | |
184 | __splitstack_releasecontext (void *context[10]) | |
185 | __attribute__ ((visibility ("default"))); | |
186 | ||
187 | extern void | |
188 | __splitstack_block_signals_context (void *context[10], int *, int *) | |
189 | __attribute__ ((visibility ("default"))); | |
190 | ||
191 | extern void * | |
192 | __splitstack_find_context (void *context[10], size_t *, void **, void **, | |
193 | void **) | |
194 | __attribute__ ((visibility ("default"))); | |
195 | ||
196 | /* These functions must be defined by the processor specific code. */ | |
197 | ||
198 | extern void *__morestack_get_guard (void) | |
199 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
200 | ||
201 | extern void __morestack_set_guard (void *) | |
202 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
203 | ||
204 | extern void *__morestack_make_guard (void *, size_t) | |
205 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
206 | ||
207 | /* When we allocate a stack segment we put this header at the | |
208 | start. */ | |
209 | ||
210 | struct stack_segment | |
211 | { | |
212 | /* The previous stack segment--when a function running on this stack | |
213 | segment returns, it will run on the previous one. */ | |
214 | struct stack_segment *prev; | |
215 | /* The next stack segment, if it has been allocated--when a function | |
216 | is running on this stack segment, the next one is not being | |
217 | used. */ | |
218 | struct stack_segment *next; | |
219 | /* The total size of this stack segment. */ | |
220 | size_t size; | |
221 | /* The stack address when this stack was created. This is used when | |
222 | popping the stack. */ | |
223 | void *old_stack; | |
224 | /* A list of memory blocks allocated by dynamic stack | |
225 | allocation. */ | |
226 | struct dynamic_allocation_blocks *dynamic_allocation; | |
227 | /* A list of dynamic memory blocks no longer needed. */ | |
228 | struct dynamic_allocation_blocks *free_dynamic_allocation; | |
229 | /* An extra pointer in case we need some more information some | |
230 | day. */ | |
231 | void *extra; | |
232 | }; | |
233 | ||
234 | /* This structure holds the (approximate) initial stack pointer and | |
235 | size for the system supplied stack for a thread. This is set when | |
236 | the thread is created. We also store a sigset_t here to hold the | |
237 | signal mask while splitting the stack, since we don't want to store | |
238 | that on the stack. */ | |
239 | ||
240 | struct initial_sp | |
241 | { | |
242 | /* The initial stack pointer. */ | |
243 | void *sp; | |
244 | /* The stack length. */ | |
245 | size_t len; | |
246 | /* A signal mask, put here so that the thread can use it without | |
247 | needing stack space. */ | |
248 | sigset_t mask; | |
249 | /* Non-zero if we should not block signals. This is a reversed flag | |
250 | so that the default zero value is the safe value. The type is | |
251 | uintptr_type because it replaced one of the void * pointers in | |
252 | extra. */ | |
253 | uintptr_type dont_block_signals; | |
254 | /* Some extra space for later extensibility. */ | |
255 | void *extra[4]; | |
256 | }; | |
257 | ||
258 | /* A list of memory blocks allocated by dynamic stack allocation. | |
259 | This is used for code that calls alloca or uses variably sized | |
260 | arrays. */ | |
261 | ||
262 | struct dynamic_allocation_blocks | |
263 | { | |
264 | /* The next block in the list. */ | |
265 | struct dynamic_allocation_blocks *next; | |
266 | /* The size of the allocated memory. */ | |
267 | size_t size; | |
268 | /* The allocated memory. */ | |
269 | void *block; | |
270 | }; | |
271 | ||
272 | /* These thread local global variables must be shared by all split | |
273 | stack code across shared library boundaries. Therefore, they have | |
274 | default visibility. They have extensibility fields if needed for | |
275 | new versions. If more radical changes are needed, new code can be | |
276 | written using new variable names, while still using the existing | |
277 | variables in a backward compatible manner. Symbol versioning is | |
278 | also used, although, since these variables are only referenced by | |
279 | code in this file and generic-morestack-thread.c, it is likely that | |
280 | simply using new names will suffice. */ | |
281 | ||
282 | /* The first stack segment allocated for this thread. */ | |
283 | ||
284 | __thread struct stack_segment *__morestack_segments | |
285 | __attribute__ ((visibility ("default"))); | |
286 | ||
287 | /* The stack segment that we think we are currently using. This will | |
288 | be correct in normal usage, but will be incorrect if an exception | |
289 | unwinds into a different stack segment or if longjmp jumps to a | |
290 | different stack segment. */ | |
291 | ||
292 | __thread struct stack_segment *__morestack_current_segment | |
293 | __attribute__ ((visibility ("default"))); | |
294 | ||
295 | /* The initial stack pointer and size for this thread. */ | |
296 | ||
297 | __thread struct initial_sp __morestack_initial_sp | |
298 | __attribute__ ((visibility ("default"))); | |
299 | ||
300 | /* A static signal mask, to avoid taking up stack space. */ | |
301 | ||
302 | static sigset_t __morestack_fullmask; | |
303 | ||
304 | /* Page size, as returned from getpagesize(). Set on startup. */ | |
305 | static unsigned int static_pagesize; | |
306 | ||
307 | /* Set on startup to non-zero value if SPLIT_STACK_GUARD env var is set. */ | |
308 | static int use_guard_page; | |
309 | ||
310 | /* Convert an integer to a decimal string without using much stack | |
311 | space. Return a pointer to the part of the buffer to use. We this | |
312 | instead of sprintf because sprintf will require too much stack | |
313 | space. */ | |
314 | ||
315 | static char * | |
316 | print_int (int val, char *buf, int buflen, size_t *print_len) | |
317 | { | |
318 | int is_negative; | |
319 | int i; | |
320 | unsigned int uval; | |
321 | ||
322 | uval = (unsigned int) val; | |
323 | if (val >= 0) | |
324 | is_negative = 0; | |
325 | else | |
326 | { | |
327 | is_negative = 1; | |
328 | uval = - uval; | |
329 | } | |
330 | ||
331 | i = buflen; | |
332 | do | |
333 | { | |
334 | --i; | |
335 | buf[i] = '0' + (uval % 10); | |
336 | uval /= 10; | |
337 | } | |
338 | while (uval != 0 && i > 0); | |
339 | ||
340 | if (is_negative) | |
341 | { | |
342 | if (i > 0) | |
343 | --i; | |
344 | buf[i] = '-'; | |
345 | } | |
346 | ||
347 | *print_len = buflen - i; | |
348 | return buf + i; | |
349 | } | |
350 | ||
351 | /* Print the string MSG/LEN, the errno number ERR, and a newline on | |
352 | stderr. Then crash. */ | |
353 | ||
354 | void | |
355 | __morestack_fail (const char *, size_t, int) __attribute__ ((noreturn)); | |
356 | ||
357 | void | |
358 | __morestack_fail (const char *msg, size_t len, int err) | |
359 | { | |
360 | char buf[24]; | |
361 | static const char nl[] = "\n"; | |
362 | struct iovec iov[3]; | |
363 | union { char *p; const char *cp; } const_cast; | |
364 | ||
365 | const_cast.cp = msg; | |
366 | iov[0].iov_base = const_cast.p; | |
367 | iov[0].iov_len = len; | |
368 | /* We can't call strerror, because it may try to translate the error | |
369 | message, and that would use too much stack space. */ | |
370 | iov[1].iov_base = print_int (err, buf, sizeof buf, &iov[1].iov_len); | |
371 | const_cast.cp = &nl[0]; | |
372 | iov[2].iov_base = const_cast.p; | |
373 | iov[2].iov_len = sizeof nl - 1; | |
374 | /* FIXME: On systems without writev we need to issue three write | |
375 | calls, or punt on printing errno. For now this is irrelevant | |
376 | since stack splitting only works on GNU/Linux anyhow. */ | |
377 | writev (2, iov, 3); | |
378 | abort (); | |
379 | } | |
380 | ||
381 | /* Allocate a new stack segment. FRAME_SIZE is the required frame | |
382 | size. */ | |
383 | ||
384 | static struct stack_segment * | |
385 | allocate_segment (size_t frame_size) | |
386 | { | |
387 | unsigned int pagesize; | |
388 | unsigned int overhead; | |
389 | unsigned int allocate; | |
390 | void *space; | |
391 | struct stack_segment *pss; | |
392 | ||
393 | pagesize = static_pagesize; | |
394 | overhead = sizeof (struct stack_segment); | |
395 | ||
396 | allocate = pagesize; | |
397 | if (allocate < MINSIGSTKSZ) | |
398 | allocate = ((MINSIGSTKSZ + overhead + pagesize - 1) | |
399 | & ~ (pagesize - 1)); | |
400 | if (allocate < frame_size) | |
401 | allocate = ((frame_size + overhead + pagesize - 1) | |
402 | & ~ (pagesize - 1)); | |
403 | ||
404 | if (use_guard_page) | |
405 | allocate += pagesize; | |
406 | ||
407 | /* FIXME: If this binary requires an executable stack, then we need | |
408 | to set PROT_EXEC. Unfortunately figuring that out is complicated | |
409 | and target dependent. We would need to use dl_iterate_phdr to | |
410 | see if there is any object which does not have a PT_GNU_STACK | |
411 | phdr, though only for architectures which use that mechanism. */ | |
412 | space = mmap (NULL, allocate, PROT_READ | PROT_WRITE, | |
413 | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); | |
414 | if (space == MAP_FAILED) | |
415 | { | |
416 | static const char msg[] = | |
417 | "unable to allocate additional stack space: errno "; | |
418 | __morestack_fail (msg, sizeof msg - 1, errno); | |
419 | } | |
420 | ||
421 | if (use_guard_page) | |
422 | { | |
423 | void *guard; | |
424 | ||
425 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
426 | guard = space; | |
427 | space = (char *) space + pagesize; | |
428 | #else | |
429 | guard = space + allocate - pagesize; | |
430 | #endif | |
431 | ||
432 | mprotect (guard, pagesize, PROT_NONE); | |
433 | allocate -= pagesize; | |
434 | } | |
435 | ||
436 | pss = (struct stack_segment *) space; | |
437 | ||
438 | pss->prev = NULL; | |
439 | pss->next = NULL; | |
440 | pss->size = allocate - overhead; | |
441 | pss->dynamic_allocation = NULL; | |
442 | pss->free_dynamic_allocation = NULL; | |
443 | pss->extra = NULL; | |
444 | ||
445 | return pss; | |
446 | } | |
447 | ||
448 | /* Free a list of dynamic blocks. */ | |
449 | ||
450 | static void | |
451 | free_dynamic_blocks (struct dynamic_allocation_blocks *p) | |
452 | { | |
453 | while (p != NULL) | |
454 | { | |
455 | struct dynamic_allocation_blocks *next; | |
456 | ||
457 | next = p->next; | |
458 | free (p->block); | |
459 | free (p); | |
460 | p = next; | |
461 | } | |
462 | } | |
463 | ||
464 | /* Merge two lists of dynamic blocks. */ | |
465 | ||
466 | static struct dynamic_allocation_blocks * | |
467 | merge_dynamic_blocks (struct dynamic_allocation_blocks *a, | |
468 | struct dynamic_allocation_blocks *b) | |
469 | { | |
470 | struct dynamic_allocation_blocks **pp; | |
471 | ||
472 | if (a == NULL) | |
473 | return b; | |
474 | if (b == NULL) | |
475 | return a; | |
476 | for (pp = &a->next; *pp != NULL; pp = &(*pp)->next) | |
477 | ; | |
478 | *pp = b; | |
479 | return a; | |
480 | } | |
481 | ||
482 | /* Release stack segments. If FREE_DYNAMIC is non-zero, we also free | |
483 | any dynamic blocks. Otherwise we return them. */ | |
484 | ||
485 | struct dynamic_allocation_blocks * | |
486 | __morestack_release_segments (struct stack_segment **pp, int free_dynamic) | |
487 | { | |
488 | struct dynamic_allocation_blocks *ret; | |
489 | struct stack_segment *pss; | |
490 | ||
491 | ret = NULL; | |
492 | pss = *pp; | |
493 | while (pss != NULL) | |
494 | { | |
495 | struct stack_segment *next; | |
496 | unsigned int allocate; | |
497 | ||
498 | next = pss->next; | |
499 | ||
500 | if (pss->dynamic_allocation != NULL | |
501 | || pss->free_dynamic_allocation != NULL) | |
502 | { | |
503 | if (free_dynamic) | |
504 | { | |
505 | free_dynamic_blocks (pss->dynamic_allocation); | |
506 | free_dynamic_blocks (pss->free_dynamic_allocation); | |
507 | } | |
508 | else | |
509 | { | |
510 | ret = merge_dynamic_blocks (pss->dynamic_allocation, ret); | |
511 | ret = merge_dynamic_blocks (pss->free_dynamic_allocation, ret); | |
512 | } | |
513 | } | |
514 | ||
515 | allocate = pss->size + sizeof (struct stack_segment); | |
516 | if (munmap (pss, allocate) < 0) | |
517 | { | |
518 | static const char msg[] = "munmap of stack space failed: errno "; | |
519 | __morestack_fail (msg, sizeof msg - 1, errno); | |
520 | } | |
521 | ||
522 | pss = next; | |
523 | } | |
524 | *pp = NULL; | |
525 | ||
526 | return ret; | |
527 | } | |
528 | ||
529 | /* This function is called by a processor specific function to set the | |
530 | initial stack pointer for a thread. The operating system will | |
531 | always create a stack for a thread. Here we record a stack pointer | |
532 | near the base of that stack. The size argument lets the processor | |
533 | specific code estimate how much stack space is available on this | |
534 | initial stack. */ | |
535 | ||
536 | void | |
537 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
538 | { | |
539 | /* The stack pointer most likely starts on a page boundary. Adjust | |
540 | to the nearest 512 byte boundary. It's not essential that we be | |
541 | precise here; getting it wrong will just leave some stack space | |
542 | unused. */ | |
543 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
544 | sp = (void *) ((((__UINTPTR_TYPE__) sp + 511U) / 512U) * 512U); | |
545 | #else | |
546 | sp = (void *) ((((__UINTPTR_TYPE__) sp - 511U) / 512U) * 512U); | |
547 | #endif | |
548 | ||
549 | __morestack_initial_sp.sp = sp; | |
550 | __morestack_initial_sp.len = len; | |
551 | sigemptyset (&__morestack_initial_sp.mask); | |
552 | ||
553 | sigfillset (&__morestack_fullmask); | |
554 | #if defined(__GLIBC__) && defined(__linux__) | |
555 | /* In glibc, the first two real time signals are used by the NPTL | |
556 | threading library. By taking them out of the set of signals, we | |
557 | avoiding copying the signal mask in pthread_sigmask. More | |
558 | importantly, pthread_sigmask uses less stack space on x86_64. */ | |
559 | sigdelset (&__morestack_fullmask, __SIGRTMIN); | |
560 | sigdelset (&__morestack_fullmask, __SIGRTMIN + 1); | |
561 | #endif | |
562 | } | |
563 | ||
564 | /* This function is called by a processor specific function which is | |
565 | run in the prologue when more stack is needed. The processor | |
566 | specific function handles the details of saving registers and | |
567 | frobbing the actual stack pointer. This function is responsible | |
568 | for allocating a new stack segment and for copying a parameter | |
569 | block from the old stack to the new one. On function entry | |
570 | *PFRAME_SIZE is the size of the required stack frame--the returned | |
571 | stack must be at least this large. On function exit *PFRAME_SIZE | |
572 | is the amount of space remaining on the allocated stack. OLD_STACK | |
573 | points at the parameters the old stack (really the current one | |
574 | while this function is running). OLD_STACK is saved so that it can | |
575 | be returned by a later call to __generic_releasestack. PARAM_SIZE | |
576 | is the size in bytes of parameters to copy to the new stack. This | |
577 | function returns a pointer to the new stack segment, pointing to | |
578 | the memory after the parameters have been copied. The returned | |
579 | value minus the returned *PFRAME_SIZE (or plus if the stack grows | |
580 | upward) is the first address on the stack which should not be used. | |
581 | ||
582 | This function is running on the old stack and has only a limited | |
583 | amount of stack space available. */ | |
584 | ||
585 | void * | |
586 | __generic_morestack (size_t *pframe_size, void *old_stack, size_t param_size) | |
587 | { | |
588 | size_t frame_size = *pframe_size; | |
589 | struct stack_segment *current; | |
590 | struct stack_segment **pp; | |
591 | struct dynamic_allocation_blocks *dynamic; | |
592 | char *from; | |
593 | char *to; | |
594 | void *ret; | |
595 | size_t i; | |
596 | size_t aligned; | |
597 | ||
598 | current = __morestack_current_segment; | |
599 | ||
600 | pp = current != NULL ? ¤t->next : &__morestack_segments; | |
601 | if (*pp != NULL && (*pp)->size < frame_size) | |
602 | dynamic = __morestack_release_segments (pp, 0); | |
603 | else | |
604 | dynamic = NULL; | |
605 | current = *pp; | |
606 | ||
607 | if (current == NULL) | |
608 | { | |
609 | current = allocate_segment (frame_size + param_size); | |
610 | current->prev = __morestack_current_segment; | |
611 | *pp = current; | |
612 | } | |
613 | ||
614 | current->old_stack = old_stack; | |
615 | ||
616 | __morestack_current_segment = current; | |
617 | ||
618 | if (dynamic != NULL) | |
619 | { | |
620 | /* Move the free blocks onto our list. We don't want to call | |
621 | free here, as we are short on stack space. */ | |
622 | current->free_dynamic_allocation = | |
623 | merge_dynamic_blocks (dynamic, current->free_dynamic_allocation); | |
624 | } | |
625 | ||
626 | *pframe_size = current->size - param_size; | |
627 | ||
628 | /* Align the returned stack to a 32-byte boundary. */ | |
629 | aligned = (param_size + 31) & ~ (size_t) 31; | |
630 | ||
631 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
632 | { | |
633 | char *bottom = (char *) (current + 1) + current->size; | |
634 | to = bottom - aligned; | |
635 | ret = bottom - aligned; | |
636 | } | |
637 | #else | |
638 | to = current + 1; | |
639 | to += aligned - param_size; | |
640 | ret = (char *) (current + 1) + aligned; | |
641 | #endif | |
642 | ||
643 | /* We don't call memcpy to avoid worrying about the dynamic linker | |
644 | trying to resolve it. */ | |
645 | from = (char *) old_stack; | |
646 | for (i = 0; i < param_size; i++) | |
647 | *to++ = *from++; | |
648 | ||
649 | return ret; | |
650 | } | |
651 | ||
652 | /* This function is called by a processor specific function when it is | |
653 | ready to release a stack segment. We don't actually release the | |
654 | stack segment, we just move back to the previous one. The current | |
655 | stack segment will still be available if we need it in | |
656 | __generic_morestack. This returns a pointer to the new stack | |
657 | segment to use, which is the one saved by a previous call to | |
658 | __generic_morestack. The processor specific function is then | |
659 | responsible for actually updating the stack pointer. This sets | |
660 | *PAVAILABLE to the amount of stack space now available. */ | |
661 | ||
662 | void * | |
663 | __generic_releasestack (size_t *pavailable) | |
664 | { | |
665 | struct stack_segment *current; | |
666 | void *old_stack; | |
667 | ||
668 | current = __morestack_current_segment; | |
669 | old_stack = current->old_stack; | |
670 | current = current->prev; | |
671 | __morestack_current_segment = current; | |
672 | ||
673 | if (current != NULL) | |
674 | { | |
675 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
676 | *pavailable = (char *) old_stack - (char *) (current + 1); | |
677 | #else | |
678 | *pavailable = (char *) (current + 1) + current->size - (char *) old_stack; | |
679 | #endif | |
680 | } | |
681 | else | |
682 | { | |
683 | size_t used; | |
684 | ||
685 | /* We have popped back to the original stack. */ | |
686 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
687 | if ((char *) old_stack >= (char *) __morestack_initial_sp.sp) | |
688 | used = 0; | |
689 | else | |
690 | used = (char *) __morestack_initial_sp.sp - (char *) old_stack; | |
691 | #else | |
692 | if ((char *) old_stack <= (char *) __morestack_initial_sp.sp) | |
693 | used = 0; | |
694 | else | |
695 | used = (char *) old_stack - (char *) __morestack_initial_sp.sp; | |
696 | #endif | |
697 | ||
698 | if (used > __morestack_initial_sp.len) | |
699 | *pavailable = 0; | |
700 | else | |
701 | *pavailable = __morestack_initial_sp.len - used; | |
702 | } | |
703 | ||
704 | return old_stack; | |
705 | } | |
706 | ||
707 | /* Block signals while splitting the stack. This avoids trouble if we | |
708 | try to invoke a signal handler which itself wants to split the | |
709 | stack. */ | |
710 | ||
711 | extern int pthread_sigmask (int, const sigset_t *, sigset_t *) | |
712 | __attribute__ ((weak)); | |
713 | ||
714 | void | |
715 | __morestack_block_signals (void) | |
716 | { | |
717 | if (__morestack_initial_sp.dont_block_signals) | |
718 | ; | |
719 | else if (pthread_sigmask) | |
720 | pthread_sigmask (SIG_BLOCK, &__morestack_fullmask, | |
721 | &__morestack_initial_sp.mask); | |
722 | else | |
723 | sigprocmask (SIG_BLOCK, &__morestack_fullmask, | |
724 | &__morestack_initial_sp.mask); | |
725 | } | |
726 | ||
727 | /* Unblock signals while splitting the stack. */ | |
728 | ||
729 | void | |
730 | __morestack_unblock_signals (void) | |
731 | { | |
732 | if (__morestack_initial_sp.dont_block_signals) | |
733 | ; | |
734 | else if (pthread_sigmask) | |
735 | pthread_sigmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); | |
736 | else | |
737 | sigprocmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); | |
738 | } | |
739 | ||
740 | /* This function is called to allocate dynamic stack space, for alloca | |
741 | or a variably sized array. This is a regular function with | |
742 | sufficient stack space, so we just use malloc to allocate the | |
743 | space. We attach the allocated blocks to the current stack | |
744 | segment, so that they will eventually be reused or freed. */ | |
745 | ||
746 | void * | |
747 | __morestack_allocate_stack_space (size_t size) | |
748 | { | |
749 | struct stack_segment *seg, *current; | |
750 | struct dynamic_allocation_blocks *p; | |
751 | ||
752 | /* We have to block signals to avoid getting confused if we get | |
753 | interrupted by a signal whose handler itself uses alloca or a | |
754 | variably sized array. */ | |
755 | __morestack_block_signals (); | |
756 | ||
757 | /* Since we don't want to call free while we are low on stack space, | |
758 | we may have a list of already allocated blocks waiting to be | |
759 | freed. Release them all, unless we find one that is large | |
760 | enough. We don't look at every block to see if one is large | |
761 | enough, just the first one, because we aren't trying to build a | |
762 | memory allocator here, we're just trying to speed up common | |
763 | cases. */ | |
764 | ||
765 | current = __morestack_current_segment; | |
766 | p = NULL; | |
767 | for (seg = __morestack_segments; seg != NULL; seg = seg->next) | |
768 | { | |
769 | p = seg->free_dynamic_allocation; | |
770 | if (p != NULL) | |
771 | { | |
772 | if (p->size >= size) | |
773 | { | |
774 | seg->free_dynamic_allocation = p->next; | |
775 | break; | |
776 | } | |
777 | ||
778 | free_dynamic_blocks (p); | |
779 | seg->free_dynamic_allocation = NULL; | |
780 | p = NULL; | |
781 | } | |
782 | } | |
783 | ||
784 | if (p == NULL) | |
785 | { | |
786 | /* We need to allocate additional memory. */ | |
787 | p = malloc (sizeof (*p)); | |
788 | if (p == NULL) | |
789 | abort (); | |
790 | p->size = size; | |
791 | p->block = malloc (size); | |
792 | if (p->block == NULL) | |
793 | abort (); | |
794 | } | |
795 | ||
796 | /* If we are still on the initial stack, then we have a space leak. | |
797 | FIXME. */ | |
798 | if (current != NULL) | |
799 | { | |
800 | p->next = current->dynamic_allocation; | |
801 | current->dynamic_allocation = p; | |
802 | } | |
803 | ||
804 | __morestack_unblock_signals (); | |
805 | ||
806 | return p->block; | |
807 | } | |
808 | ||
809 | /* Find the stack segment for STACK and return the amount of space | |
810 | available. This is used when unwinding the stack because of an | |
811 | exception, in order to reset the stack guard correctly. */ | |
812 | ||
813 | size_t | |
814 | __generic_findstack (void *stack) | |
815 | { | |
816 | struct stack_segment *pss; | |
817 | size_t used; | |
818 | ||
819 | for (pss = __morestack_current_segment; pss != NULL; pss = pss->prev) | |
820 | { | |
821 | if ((char *) pss < (char *) stack | |
822 | && (char *) pss + pss->size > (char *) stack) | |
823 | { | |
824 | __morestack_current_segment = pss; | |
825 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
826 | return (char *) stack - (char *) (pss + 1); | |
827 | #else | |
828 | return (char *) (pss + 1) + pss->size - (char *) stack; | |
829 | #endif | |
830 | } | |
831 | } | |
832 | ||
833 | /* We have popped back to the original stack. */ | |
834 | ||
835 | if (__morestack_initial_sp.sp == NULL) | |
836 | return 0; | |
837 | ||
838 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
839 | if ((char *) stack >= (char *) __morestack_initial_sp.sp) | |
840 | used = 0; | |
841 | else | |
842 | used = (char *) __morestack_initial_sp.sp - (char *) stack; | |
843 | #else | |
844 | if ((char *) stack <= (char *) __morestack_initial_sp.sp) | |
845 | used = 0; | |
846 | else | |
847 | used = (char *) stack - (char *) __morestack_initial_sp.sp; | |
848 | #endif | |
849 | ||
850 | if (used > __morestack_initial_sp.len) | |
851 | return 0; | |
852 | else | |
853 | return __morestack_initial_sp.len - used; | |
854 | } | |
855 | ||
856 | /* This function is called at program startup time to make sure that | |
857 | mmap, munmap, and getpagesize are resolved if linking dynamically. | |
858 | We want to resolve them while we have enough stack for them, rather | |
859 | than calling into the dynamic linker while low on stack space. | |
860 | Similarly, invoke getenv here to check for split-stack related control | |
861 | variables, since doing do as part of the __morestack path can result | |
862 | in unwanted use of SSE/AVX registers (see GCC PR 86213). */ | |
863 | ||
864 | void | |
865 | __morestack_load_mmap (void) | |
866 | { | |
867 | /* Call with bogus values to run faster. We don't care if the call | |
868 | fails. Pass __MORESTACK_CURRENT_SEGMENT to make sure that any | |
869 | TLS accessor function is resolved. */ | |
870 | mmap (__morestack_current_segment, 0, PROT_READ, MAP_ANONYMOUS, -1, 0); | |
871 | mprotect (NULL, 0, 0); | |
872 | munmap (0, static_pagesize); | |
873 | ||
874 | /* Initialize these values here, so as to avoid dynamic linker | |
875 | activity as part of a __morestack call. */ | |
876 | static_pagesize = getpagesize(); | |
877 | use_guard_page = getenv ("SPLIT_STACK_GUARD") != 0; | |
878 | } | |
879 | ||
880 | /* This function may be used to iterate over the stack segments. | |
881 | This can be called like this. | |
882 | void *next_segment = NULL; | |
883 | void *next_sp = NULL; | |
884 | void *initial_sp = NULL; | |
885 | void *stack; | |
886 | size_t stack_size; | |
887 | while ((stack = __splitstack_find (next_segment, next_sp, &stack_size, | |
888 | &next_segment, &next_sp, | |
889 | &initial_sp)) != NULL) | |
890 | { | |
891 | // Stack segment starts at stack and is stack_size bytes long. | |
892 | } | |
893 | ||
894 | There is no way to iterate over the stack segments of a different | |
895 | thread. However, what is permitted is for one thread to call this | |
896 | with the first two values NULL, to pass next_segment, next_sp, and | |
897 | initial_sp to a different thread, and then to suspend one way or | |
898 | another. A different thread may run the subsequent | |
899 | __morestack_find iterations. Of course, this will only work if the | |
900 | first thread is suspended during the __morestack_find iterations. | |
901 | If not, the second thread will be looking at the stack while it is | |
902 | changing, and anything could happen. | |
903 | ||
904 | FIXME: This should be declared in some header file, but where? */ | |
905 | ||
906 | void * | |
907 | __splitstack_find (void *segment_arg, void *sp, size_t *len, | |
908 | void **next_segment, void **next_sp, | |
909 | void **initial_sp) | |
910 | { | |
911 | struct stack_segment *segment; | |
912 | void *ret; | |
913 | char *nsp; | |
914 | ||
915 | if (segment_arg == (void *) (uintptr_type) 1) | |
916 | { | |
917 | char *isp = (char *) *initial_sp; | |
918 | ||
919 | if (isp == NULL) | |
920 | return NULL; | |
921 | ||
922 | *next_segment = (void *) (uintptr_type) 2; | |
923 | *next_sp = NULL; | |
924 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
925 | if ((char *) sp >= isp) | |
926 | return NULL; | |
927 | *len = (char *) isp - (char *) sp; | |
928 | return sp; | |
929 | #else | |
930 | if ((char *) sp <= (char *) isp) | |
931 | return NULL; | |
932 | *len = (char *) sp - (char *) isp; | |
933 | return (void *) isp; | |
934 | #endif | |
935 | } | |
936 | else if (segment_arg == (void *) (uintptr_type) 2) | |
937 | return NULL; | |
938 | else if (segment_arg != NULL) | |
939 | segment = (struct stack_segment *) segment_arg; | |
940 | else | |
941 | { | |
942 | *initial_sp = __morestack_initial_sp.sp; | |
943 | segment = __morestack_current_segment; | |
944 | sp = (void *) &segment; | |
945 | while (1) | |
946 | { | |
947 | if (segment == NULL) | |
948 | return __splitstack_find ((void *) (uintptr_type) 1, sp, len, | |
949 | next_segment, next_sp, initial_sp); | |
950 | if ((char *) sp >= (char *) (segment + 1) | |
951 | && (char *) sp <= (char *) (segment + 1) + segment->size) | |
952 | break; | |
953 | segment = segment->prev; | |
954 | } | |
955 | } | |
956 | ||
957 | if (segment->prev == NULL) | |
958 | *next_segment = (void *) (uintptr_type) 1; | |
959 | else | |
960 | *next_segment = segment->prev; | |
961 | ||
962 | /* The old_stack value is the address of the function parameters of | |
963 | the function which called __morestack. So if f1 called f2 which | |
964 | called __morestack, the stack looks like this: | |
965 | ||
966 | parameters <- old_stack | |
967 | return in f1 | |
968 | return in f2 | |
969 | registers pushed by __morestack | |
970 | ||
971 | The registers pushed by __morestack may not be visible on any | |
972 | other stack, if we are being called by a signal handler | |
973 | immediately after the call to __morestack_unblock_signals. We | |
974 | want to adjust our return value to include those registers. This | |
975 | is target dependent. */ | |
976 | ||
977 | nsp = (char *) segment->old_stack; | |
978 | ||
979 | if (nsp == NULL) | |
980 | { | |
981 | /* We've reached the top of the stack. */ | |
982 | *next_segment = (void *) (uintptr_type) 2; | |
983 | } | |
984 | else | |
985 | { | |
986 | #if defined (__x86_64__) | |
987 | nsp -= 12 * sizeof (void *); | |
988 | #elif defined (__i386__) | |
989 | nsp -= 6 * sizeof (void *); | |
990 | #elif defined __powerpc64__ | |
991 | #elif defined __s390x__ | |
992 | nsp -= 2 * 160; | |
993 | #elif defined __s390__ | |
994 | nsp -= 2 * 96; | |
995 | #else | |
996 | #error "unrecognized target" | |
997 | #endif | |
998 | ||
999 | *next_sp = (void *) nsp; | |
1000 | } | |
1001 | ||
1002 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
1003 | *len = (char *) (segment + 1) + segment->size - (char *) sp; | |
1004 | ret = (void *) sp; | |
1005 | #else | |
1006 | *len = (char *) sp - (char *) (segment + 1); | |
1007 | ret = (void *) (segment + 1); | |
1008 | #endif | |
1009 | ||
1010 | return ret; | |
1011 | } | |
1012 | ||
1013 | /* Tell the split stack code whether it has to block signals while | |
1014 | manipulating the stack. This is for programs in which some threads | |
1015 | block all signals. If a thread already blocks signals, there is no | |
1016 | need for the split stack code to block them as well. If NEW is not | |
1017 | NULL, then if *NEW is non-zero signals will be blocked while | |
1018 | splitting the stack, otherwise they will not. If OLD is not NULL, | |
1019 | *OLD will be set to the old value. */ | |
1020 | ||
1021 | void | |
1022 | __splitstack_block_signals (int *new, int *old) | |
1023 | { | |
1024 | if (old != NULL) | |
1025 | *old = __morestack_initial_sp.dont_block_signals ? 0 : 1; | |
1026 | if (new != NULL) | |
1027 | __morestack_initial_sp.dont_block_signals = *new ? 0 : 1; | |
1028 | } | |
1029 | ||
1030 | /* The offsets into the arrays used by __splitstack_getcontext and | |
1031 | __splitstack_setcontext. */ | |
1032 | ||
1033 | enum __splitstack_context_offsets | |
1034 | { | |
1035 | MORESTACK_SEGMENTS = 0, | |
1036 | CURRENT_SEGMENT = 1, | |
1037 | CURRENT_STACK = 2, | |
1038 | STACK_GUARD = 3, | |
1039 | INITIAL_SP = 4, | |
1040 | INITIAL_SP_LEN = 5, | |
1041 | BLOCK_SIGNALS = 6, | |
1042 | ||
1043 | NUMBER_OFFSETS = 10 | |
1044 | }; | |
1045 | ||
1046 | /* Get the current split stack context. This may be used for | |
1047 | coroutine switching, similar to getcontext. The argument should | |
1048 | have at least 10 void *pointers for extensibility, although we | |
1049 | don't currently use all of them. This would normally be called | |
1050 | immediately before a call to getcontext or swapcontext or | |
1051 | setjmp. */ | |
1052 | ||
1053 | void | |
1054 | __splitstack_getcontext (void *context[NUMBER_OFFSETS]) | |
1055 | { | |
1056 | memset (context, 0, NUMBER_OFFSETS * sizeof (void *)); | |
1057 | context[MORESTACK_SEGMENTS] = (void *) __morestack_segments; | |
1058 | context[CURRENT_SEGMENT] = (void *) __morestack_current_segment; | |
1059 | context[CURRENT_STACK] = (void *) &context; | |
1060 | context[STACK_GUARD] = __morestack_get_guard (); | |
1061 | context[INITIAL_SP] = (void *) __morestack_initial_sp.sp; | |
1062 | context[INITIAL_SP_LEN] = (void *) (uintptr_type) __morestack_initial_sp.len; | |
1063 | context[BLOCK_SIGNALS] = (void *) __morestack_initial_sp.dont_block_signals; | |
1064 | } | |
1065 | ||
1066 | /* Set the current split stack context. The argument should be a | |
1067 | context previously passed to __splitstack_getcontext. This would | |
1068 | normally be called immediately after a call to getcontext or | |
1069 | swapcontext or setjmp if something jumped to it. */ | |
1070 | ||
1071 | void | |
1072 | __splitstack_setcontext (void *context[NUMBER_OFFSETS]) | |
1073 | { | |
1074 | __morestack_segments = (struct stack_segment *) context[MORESTACK_SEGMENTS]; | |
1075 | __morestack_current_segment = | |
1076 | (struct stack_segment *) context[CURRENT_SEGMENT]; | |
1077 | __morestack_set_guard (context[STACK_GUARD]); | |
1078 | __morestack_initial_sp.sp = context[INITIAL_SP]; | |
1079 | __morestack_initial_sp.len = (size_t) context[INITIAL_SP_LEN]; | |
1080 | __morestack_initial_sp.dont_block_signals = | |
1081 | (uintptr_type) context[BLOCK_SIGNALS]; | |
1082 | } | |
1083 | ||
1084 | /* Create a new split stack context. This will allocate a new stack | |
1085 | segment which may be used by a coroutine. STACK_SIZE is the | |
1086 | minimum size of the new stack. The caller is responsible for | |
1087 | actually setting the stack pointer. This would normally be called | |
1088 | before a call to makecontext, and the returned stack pointer and | |
1089 | size would be used to set the uc_stack field. A function called | |
1090 | via makecontext on a stack created by __splitstack_makecontext may | |
1091 | not return. Note that the returned pointer points to the lowest | |
1092 | address in the stack space, and thus may not be the value to which | |
1093 | to set the stack pointer. */ | |
1094 | ||
1095 | void * | |
1096 | __splitstack_makecontext (size_t stack_size, void *context[NUMBER_OFFSETS], | |
1097 | size_t *size) | |
1098 | { | |
1099 | struct stack_segment *segment; | |
1100 | void *initial_sp; | |
1101 | ||
1102 | memset (context, 0, NUMBER_OFFSETS * sizeof (void *)); | |
1103 | segment = allocate_segment (stack_size); | |
1104 | context[MORESTACK_SEGMENTS] = segment; | |
1105 | context[CURRENT_SEGMENT] = segment; | |
1106 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
1107 | initial_sp = (void *) ((char *) (segment + 1) + segment->size); | |
1108 | #else | |
1109 | initial_sp = (void *) (segment + 1); | |
1110 | #endif | |
1111 | context[STACK_GUARD] = __morestack_make_guard (initial_sp, segment->size); | |
1112 | context[INITIAL_SP] = NULL; | |
1113 | context[INITIAL_SP_LEN] = 0; | |
1114 | *size = segment->size; | |
1115 | return (void *) (segment + 1); | |
1116 | } | |
1117 | ||
1118 | /* Given an existing split stack context, reset it back to the start | |
1119 | of the stack. Return the stack pointer and size, appropriate for | |
1120 | use with makecontext. This may be used if a coroutine exits, in | |
1121 | order to reuse the stack segments for a new coroutine. */ | |
1122 | ||
1123 | void * | |
1124 | __splitstack_resetcontext (void *context[10], size_t *size) | |
1125 | { | |
1126 | struct stack_segment *segment; | |
1127 | void *initial_sp; | |
1128 | size_t initial_size; | |
1129 | void *ret; | |
1130 | ||
1131 | /* Reset the context assuming that MORESTACK_SEGMENTS, INITIAL_SP | |
1132 | and INITIAL_SP_LEN are correct. */ | |
1133 | ||
1134 | segment = context[MORESTACK_SEGMENTS]; | |
1135 | context[CURRENT_SEGMENT] = segment; | |
1136 | context[CURRENT_STACK] = NULL; | |
1137 | if (segment == NULL) | |
1138 | { | |
1139 | initial_sp = context[INITIAL_SP]; | |
1140 | initial_size = (uintptr_type) context[INITIAL_SP_LEN]; | |
1141 | ret = initial_sp; | |
1142 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
1143 | ret = (void *) ((char *) ret - initial_size); | |
1144 | #endif | |
1145 | } | |
1146 | else | |
1147 | { | |
1148 | #ifdef __LIBGCC_STACK_GROWS_DOWNWARD__ | |
1149 | initial_sp = (void *) ((char *) (segment + 1) + segment->size); | |
1150 | #else | |
1151 | initial_sp = (void *) (segment + 1); | |
1152 | #endif | |
1153 | initial_size = segment->size; | |
1154 | ret = (void *) (segment + 1); | |
1155 | } | |
1156 | context[STACK_GUARD] = __morestack_make_guard (initial_sp, initial_size); | |
1157 | context[BLOCK_SIGNALS] = NULL; | |
1158 | *size = initial_size; | |
1159 | return ret; | |
1160 | } | |
1161 | ||
1162 | /* Release all the memory associated with a splitstack context. This | |
1163 | may be used if a coroutine exits and the associated stack should be | |
1164 | freed. */ | |
1165 | ||
1166 | void | |
1167 | __splitstack_releasecontext (void *context[10]) | |
1168 | { | |
1169 | __morestack_release_segments (((struct stack_segment **) | |
1170 | &context[MORESTACK_SEGMENTS]), | |
1171 | 1); | |
1172 | } | |
1173 | ||
1174 | /* Like __splitstack_block_signals, but operating on CONTEXT, rather | |
1175 | than on the current state. */ | |
1176 | ||
1177 | void | |
1178 | __splitstack_block_signals_context (void *context[NUMBER_OFFSETS], int *new, | |
1179 | int *old) | |
1180 | { | |
1181 | if (old != NULL) | |
1182 | *old = ((uintptr_type) context[BLOCK_SIGNALS]) != 0 ? 0 : 1; | |
1183 | if (new != NULL) | |
1184 | context[BLOCK_SIGNALS] = (void *) (uintptr_type) (*new ? 0 : 1); | |
1185 | } | |
1186 | ||
1187 | /* Find the stack segments associated with a split stack context. | |
1188 | This will return the address of the first stack segment and set | |
1189 | *STACK_SIZE to its size. It will set next_segment, next_sp, and | |
1190 | initial_sp which may be passed to __splitstack_find to find the | |
1191 | remaining segments. */ | |
1192 | ||
1193 | void * | |
1194 | __splitstack_find_context (void *context[NUMBER_OFFSETS], size_t *stack_size, | |
1195 | void **next_segment, void **next_sp, | |
1196 | void **initial_sp) | |
1197 | { | |
1198 | void *sp; | |
1199 | struct stack_segment *segment; | |
1200 | ||
1201 | *initial_sp = context[INITIAL_SP]; | |
1202 | ||
1203 | sp = context[CURRENT_STACK]; | |
1204 | if (sp == NULL) | |
1205 | { | |
1206 | /* Most likely this context was created but was never used. The | |
1207 | value 2 is a code used by __splitstack_find to mean that we | |
1208 | have reached the end of the list of stacks. */ | |
1209 | *next_segment = (void *) (uintptr_type) 2; | |
1210 | *next_sp = NULL; | |
1211 | *initial_sp = NULL; | |
1212 | return NULL; | |
1213 | } | |
1214 | ||
1215 | segment = context[CURRENT_SEGMENT]; | |
1216 | if (segment == NULL) | |
1217 | { | |
1218 | /* Most likely this context was saved by a thread which was not | |
1219 | created using __splistack_makecontext and which has never | |
1220 | split the stack. The value 1 is a code used by | |
1221 | __splitstack_find to look at the initial stack. */ | |
1222 | segment = (struct stack_segment *) (uintptr_type) 1; | |
1223 | } | |
1224 | ||
1225 | return __splitstack_find (segment, sp, stack_size, next_segment, next_sp, | |
1226 | initial_sp); | |
1227 | } | |
1228 | ||
1229 | #endif /* !defined (inhibit_libc) */ | |
1230 | #endif /* not powerpc 32-bit */ |