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7458026b | 1 | /* Library support for -fsplit-stack. */ |
457186f6 | 2 | /* Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc. |
7458026b ILT |
3 | Contributed by Ian Lance Taylor <iant@google.com>. |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it under | |
8 | the terms of the GNU General Public License as published by the Free | |
9 | Software Foundation; either version 3, or (at your option) any later | |
10 | version. | |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | for more details. | |
16 | ||
17 | Under Section 7 of GPL version 3, you are granted additional | |
18 | permissions described in the GCC Runtime Library Exception, version | |
19 | 3.1, as published by the Free Software Foundation. | |
20 | ||
21 | You should have received a copy of the GNU General Public License and | |
22 | a copy of the GCC Runtime Library Exception along with this program; | |
23 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
24 | <http://www.gnu.org/licenses/>. */ | |
25 | ||
26 | #include "tconfig.h" | |
27 | #include "tsystem.h" | |
28 | #include "coretypes.h" | |
29 | #include "tm.h" | |
30 | ||
31 | /* If inhibit_libc is defined, we can not compile this file. The | |
32 | effect is that people will not be able to use -fsplit-stack. That | |
33 | is much better than failing the build particularly since people | |
34 | will want to define inhibit_libc while building a compiler which | |
35 | can build glibc. */ | |
36 | ||
37 | #ifndef inhibit_libc | |
38 | ||
39 | #include <assert.h> | |
40 | #include <errno.h> | |
41 | #include <signal.h> | |
42 | #include <stdlib.h> | |
43 | #include <unistd.h> | |
44 | #include <sys/mman.h> | |
45 | #include <sys/uio.h> | |
46 | ||
47 | #include "generic-morestack.h" | |
48 | ||
49 | /* This file contains subroutines that are used by code compiled with | |
50 | -fsplit-stack. */ | |
51 | ||
52 | /* Declare functions to avoid warnings--there is no header file for | |
53 | these internal functions. We give most of these functions the | |
54 | flatten attribute in order to minimize their stack usage--here we | |
55 | must minimize stack usage even at the cost of code size, and in | |
56 | general inlining everything will do that. */ | |
57 | ||
58 | extern void | |
59 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
60 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
61 | ||
62 | extern void * | |
63 | __generic_morestack (size_t *frame_size, void *old_stack, size_t param_size) | |
64 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
65 | ||
66 | extern void * | |
67 | __generic_releasestack (size_t *pavailable) | |
68 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
69 | ||
70 | extern void | |
71 | __morestack_block_signals (void) | |
72 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
73 | ||
74 | extern void | |
75 | __morestack_unblock_signals (void) | |
76 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
77 | ||
78 | extern size_t | |
79 | __generic_findstack (void *stack) | |
80 | __attribute__ ((no_split_stack, flatten, visibility ("hidden"))); | |
81 | ||
82 | extern void | |
83 | __morestack_load_mmap (void) | |
84 | __attribute__ ((no_split_stack, visibility ("hidden"))); | |
85 | ||
86 | extern void * | |
87 | __morestack_allocate_stack_space (size_t size) | |
88 | __attribute__ ((visibility ("hidden"))); | |
89 | ||
90 | /* This is a function which -fsplit-stack code can call to get a list | |
91 | of the stacks. Since it is not called only by the compiler, it is | |
92 | not hidden. */ | |
93 | ||
94 | extern void * | |
95 | __splitstack_find (void *, void *, size_t *, void **, void **, void **) | |
96 | __attribute__ ((visibility ("default"))); | |
97 | ||
98 | /* When we allocate a stack segment we put this header at the | |
99 | start. */ | |
100 | ||
101 | struct stack_segment | |
102 | { | |
103 | /* The previous stack segment--when a function running on this stack | |
104 | segment returns, it will run on the previous one. */ | |
105 | struct stack_segment *prev; | |
106 | /* The next stack segment, if it has been allocated--when a function | |
107 | is running on this stack segment, the next one is not being | |
108 | used. */ | |
109 | struct stack_segment *next; | |
110 | /* The total size of this stack segment. */ | |
111 | size_t size; | |
112 | /* The stack address when this stack was created. This is used when | |
113 | popping the stack. */ | |
114 | void *old_stack; | |
115 | /* A list of memory blocks allocated by dynamic stack | |
116 | allocation. */ | |
117 | struct dynamic_allocation_blocks *dynamic_allocation; | |
118 | /* A list of dynamic memory blocks no longer needed. */ | |
119 | struct dynamic_allocation_blocks *free_dynamic_allocation; | |
120 | /* An extra pointer in case we need some more information some | |
121 | day. */ | |
122 | void *extra; | |
123 | }; | |
124 | ||
125 | /* This structure holds the (approximate) initial stack pointer and | |
126 | size for the system supplied stack for a thread. This is set when | |
127 | the thread is created. We also store a sigset_t here to hold the | |
128 | signal mask while splitting the stack, since we don't want to store | |
129 | that on the stack. */ | |
130 | ||
131 | struct initial_sp | |
132 | { | |
133 | /* The initial stack pointer. */ | |
134 | void *sp; | |
135 | /* The stack length. */ | |
136 | size_t len; | |
137 | /* A signal mask, put here so that the thread can use it without | |
138 | needing stack space. */ | |
139 | sigset_t mask; | |
140 | /* Some extra space for later extensibility. */ | |
141 | void *extra[5]; | |
142 | }; | |
143 | ||
144 | /* A list of memory blocks allocated by dynamic stack allocation. | |
145 | This is used for code that calls alloca or uses variably sized | |
146 | arrays. */ | |
147 | ||
148 | struct dynamic_allocation_blocks | |
149 | { | |
150 | /* The next block in the list. */ | |
151 | struct dynamic_allocation_blocks *next; | |
152 | /* The size of the allocated memory. */ | |
153 | size_t size; | |
154 | /* The allocated memory. */ | |
155 | void *block; | |
156 | }; | |
157 | ||
158 | /* These thread local global variables must be shared by all split | |
159 | stack code across shared library boundaries. Therefore, they have | |
160 | default visibility. They have extensibility fields if needed for | |
161 | new versions. If more radical changes are needed, new code can be | |
162 | written using new variable names, while still using the existing | |
163 | variables in a backward compatible manner. Symbol versioning is | |
164 | also used, although, since these variables are only referenced by | |
165 | code in this file and generic-morestack-thread.c, it is likely that | |
166 | simply using new names will suffice. */ | |
167 | ||
168 | /* The first stack segment allocated for this thread. */ | |
169 | ||
170 | __thread struct stack_segment *__morestack_segments | |
171 | __attribute__ ((visibility ("default"))); | |
172 | ||
173 | /* The stack segment that we think we are currently using. This will | |
174 | be correct in normal usage, but will be incorrect if an exception | |
175 | unwinds into a different stack segment or if longjmp jumps to a | |
176 | different stack segment. */ | |
177 | ||
178 | __thread struct stack_segment *__morestack_current_segment | |
179 | __attribute__ ((visibility ("default"))); | |
180 | ||
181 | /* The initial stack pointer and size for this thread. */ | |
182 | ||
183 | __thread struct initial_sp __morestack_initial_sp | |
184 | __attribute__ ((visibility ("default"))); | |
185 | ||
186 | /* A static signal mask, to avoid taking up stack space. */ | |
187 | ||
188 | static sigset_t __morestack_fullmask; | |
189 | ||
190 | /* Convert an integer to a decimal string without using much stack | |
191 | space. Return a pointer to the part of the buffer to use. We this | |
192 | instead of sprintf because sprintf will require too much stack | |
193 | space. */ | |
194 | ||
195 | static char * | |
196 | print_int (int val, char *buf, int buflen, size_t *print_len) | |
197 | { | |
198 | int is_negative; | |
199 | int i; | |
200 | unsigned int uval; | |
201 | ||
202 | uval = (unsigned int) val; | |
203 | if (val >= 0) | |
204 | is_negative = 0; | |
205 | else | |
206 | { | |
207 | is_negative = 1; | |
208 | uval = - uval; | |
209 | } | |
210 | ||
211 | i = buflen; | |
212 | do | |
213 | { | |
214 | --i; | |
215 | buf[i] = '0' + (uval % 10); | |
216 | uval /= 10; | |
217 | } | |
218 | while (uval != 0 && i > 0); | |
219 | ||
220 | if (is_negative) | |
221 | { | |
222 | if (i > 0) | |
223 | --i; | |
224 | buf[i] = '-'; | |
225 | } | |
226 | ||
227 | *print_len = buflen - i; | |
228 | return buf + i; | |
229 | } | |
230 | ||
231 | /* Print the string MSG/LEN, the errno number ERR, and a newline on | |
232 | stderr. Then crash. */ | |
233 | ||
234 | void | |
235 | __morestack_fail (const char *, size_t, int) __attribute__ ((noreturn)); | |
236 | ||
237 | void | |
238 | __morestack_fail (const char *msg, size_t len, int err) | |
239 | { | |
240 | char buf[24]; | |
241 | static const char nl[] = "\n"; | |
242 | struct iovec iov[3]; | |
243 | union { char *p; const char *cp; } const_cast; | |
244 | ||
245 | const_cast.cp = msg; | |
246 | iov[0].iov_base = const_cast.p; | |
247 | iov[0].iov_len = len; | |
248 | /* We can't call strerror, because it may try to translate the error | |
249 | message, and that would use too much stack space. */ | |
250 | iov[1].iov_base = print_int (err, buf, sizeof buf, &iov[1].iov_len); | |
251 | const_cast.cp = &nl[0]; | |
252 | iov[2].iov_base = const_cast.p; | |
253 | iov[2].iov_len = sizeof nl - 1; | |
254 | /* FIXME: On systems without writev we need to issue three write | |
255 | calls, or punt on printing errno. For now this is irrelevant | |
256 | since stack splitting only works on GNU/Linux anyhow. */ | |
257 | writev (2, iov, 3); | |
258 | abort (); | |
259 | } | |
260 | ||
261 | /* Allocate a new stack segment. FRAME_SIZE is the required frame | |
262 | size. */ | |
263 | ||
264 | static struct stack_segment * | |
265 | allocate_segment (size_t frame_size) | |
266 | { | |
267 | static unsigned int static_pagesize; | |
268 | static int use_guard_page; | |
269 | unsigned int pagesize; | |
270 | unsigned int overhead; | |
271 | unsigned int allocate; | |
272 | void *space; | |
273 | struct stack_segment *pss; | |
274 | ||
275 | pagesize = static_pagesize; | |
276 | if (pagesize == 0) | |
277 | { | |
278 | unsigned int p; | |
279 | ||
280 | pagesize = getpagesize (); | |
281 | ||
282 | #ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 | |
283 | p = __sync_val_compare_and_swap (&static_pagesize, 0, pagesize); | |
284 | #else | |
285 | /* Just hope this assignment is atomic. */ | |
286 | static_pagesize = pagesize; | |
287 | p = 0; | |
288 | #endif | |
289 | ||
290 | use_guard_page = getenv ("SPLIT_STACK_GUARD") != 0; | |
291 | ||
292 | /* FIXME: I'm not sure this assert should be in the released | |
293 | code. */ | |
294 | assert (p == 0 || p == pagesize); | |
295 | } | |
296 | ||
297 | overhead = sizeof (struct stack_segment); | |
298 | ||
299 | allocate = pagesize; | |
300 | if (allocate < MINSIGSTKSZ) | |
301 | allocate = ((MINSIGSTKSZ + overhead + pagesize - 1) | |
302 | & ~ (pagesize - 1)); | |
303 | if (allocate < frame_size) | |
304 | allocate = ((frame_size + overhead + pagesize - 1) | |
305 | & ~ (pagesize - 1)); | |
306 | ||
307 | if (use_guard_page) | |
308 | allocate += pagesize; | |
309 | ||
310 | /* FIXME: If this binary requires an executable stack, then we need | |
311 | to set PROT_EXEC. Unfortunately figuring that out is complicated | |
312 | and target dependent. We would need to use dl_iterate_phdr to | |
313 | see if there is any object which does not have a PT_GNU_STACK | |
314 | phdr, though only for architectures which use that mechanism. */ | |
315 | space = mmap (NULL, allocate, PROT_READ | PROT_WRITE, | |
316 | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); | |
317 | if (space == MAP_FAILED) | |
318 | { | |
319 | static const char msg[] = | |
320 | "unable to allocate additional stack space: errno "; | |
321 | __morestack_fail (msg, sizeof msg - 1, errno); | |
322 | } | |
323 | ||
324 | if (use_guard_page) | |
325 | { | |
326 | void *guard; | |
327 | ||
328 | #ifdef STACK_GROWS_DOWNWARD | |
329 | guard = space; | |
330 | space = (char *) space + pagesize; | |
331 | #else | |
332 | guard = space + allocate - pagesize; | |
333 | #endif | |
334 | ||
335 | mprotect (guard, pagesize, PROT_NONE); | |
336 | allocate -= pagesize; | |
337 | } | |
338 | ||
339 | pss = (struct stack_segment *) space; | |
340 | ||
341 | pss->prev = __morestack_current_segment; | |
342 | pss->next = NULL; | |
343 | pss->size = allocate - overhead; | |
344 | pss->dynamic_allocation = NULL; | |
345 | pss->free_dynamic_allocation = NULL; | |
346 | pss->extra = NULL; | |
347 | ||
348 | if (__morestack_current_segment != NULL) | |
349 | __morestack_current_segment->next = pss; | |
350 | else | |
351 | __morestack_segments = pss; | |
352 | ||
353 | return pss; | |
354 | } | |
355 | ||
356 | /* Free a list of dynamic blocks. */ | |
357 | ||
358 | static void | |
359 | free_dynamic_blocks (struct dynamic_allocation_blocks *p) | |
360 | { | |
361 | while (p != NULL) | |
362 | { | |
363 | struct dynamic_allocation_blocks *next; | |
364 | ||
365 | next = p->next; | |
366 | free (p->block); | |
367 | free (p); | |
368 | p = next; | |
369 | } | |
370 | } | |
371 | ||
372 | /* Merge two lists of dynamic blocks. */ | |
373 | ||
374 | static struct dynamic_allocation_blocks * | |
375 | merge_dynamic_blocks (struct dynamic_allocation_blocks *a, | |
376 | struct dynamic_allocation_blocks *b) | |
377 | { | |
378 | struct dynamic_allocation_blocks **pp; | |
379 | ||
380 | if (a == NULL) | |
381 | return b; | |
382 | if (b == NULL) | |
383 | return a; | |
384 | for (pp = &a->next; *pp != NULL; pp = &(*pp)->next) | |
385 | ; | |
386 | *pp = b; | |
387 | return a; | |
388 | } | |
389 | ||
390 | /* Release stack segments. If FREE_DYNAMIC is non-zero, we also free | |
391 | any dynamic blocks. Otherwise we return them. */ | |
392 | ||
393 | struct dynamic_allocation_blocks * | |
394 | __morestack_release_segments (struct stack_segment **pp, int free_dynamic) | |
395 | { | |
396 | struct dynamic_allocation_blocks *ret; | |
397 | struct stack_segment *pss; | |
398 | ||
399 | ret = NULL; | |
400 | pss = *pp; | |
401 | while (pss != NULL) | |
402 | { | |
403 | struct stack_segment *next; | |
404 | unsigned int allocate; | |
405 | ||
406 | next = pss->next; | |
407 | ||
408 | if (pss->dynamic_allocation != NULL | |
409 | || pss->free_dynamic_allocation != NULL) | |
410 | { | |
411 | if (free_dynamic) | |
412 | { | |
413 | free_dynamic_blocks (pss->dynamic_allocation); | |
414 | free_dynamic_blocks (pss->free_dynamic_allocation); | |
415 | } | |
416 | else | |
417 | { | |
418 | ret = merge_dynamic_blocks (pss->dynamic_allocation, ret); | |
419 | ret = merge_dynamic_blocks (pss->free_dynamic_allocation, ret); | |
420 | } | |
421 | } | |
422 | ||
423 | allocate = pss->size + sizeof (struct stack_segment); | |
424 | if (munmap (pss, allocate) < 0) | |
425 | { | |
426 | static const char msg[] = "munmap of stack space failed: errno "; | |
427 | __morestack_fail (msg, sizeof msg - 1, errno); | |
428 | } | |
429 | ||
430 | pss = next; | |
431 | } | |
432 | *pp = NULL; | |
433 | ||
434 | return ret; | |
435 | } | |
436 | ||
437 | /* This function is called by a processor specific function to set the | |
438 | initial stack pointer for a thread. The operating system will | |
439 | always create a stack for a thread. Here we record a stack pointer | |
440 | near the base of that stack. The size argument lets the processor | |
441 | specific code estimate how much stack space is available on this | |
442 | initial stack. */ | |
443 | ||
444 | void | |
445 | __generic_morestack_set_initial_sp (void *sp, size_t len) | |
446 | { | |
447 | /* The stack pointer most likely starts on a page boundary. Adjust | |
448 | to the nearest 512 byte boundary. It's not essential that we be | |
449 | precise here; getting it wrong will just leave some stack space | |
450 | unused. */ | |
451 | #ifdef STACK_GROWS_DOWNWARD | |
452 | sp = (void *) ((((__UINTPTR_TYPE__) sp + 511U) / 512U) * 512U); | |
453 | #else | |
454 | sp = (void *) ((((__UINTPTR_TYPE__) sp - 511U) / 512U) * 512U); | |
455 | #endif | |
456 | ||
457 | __morestack_initial_sp.sp = sp; | |
458 | __morestack_initial_sp.len = len; | |
459 | sigemptyset (&__morestack_initial_sp.mask); | |
460 | ||
461 | sigfillset (&__morestack_fullmask); | |
462 | #ifdef __linux__ | |
463 | /* On Linux, the first two real time signals are used by the NPTL | |
464 | threading library. By taking them out of the set of signals, we | |
465 | avoiding copying the signal mask in pthread_sigmask. More | |
466 | importantly, pthread_sigmask uses less stack space on x86_64. */ | |
467 | sigdelset (&__morestack_fullmask, __SIGRTMIN); | |
468 | sigdelset (&__morestack_fullmask, __SIGRTMIN + 1); | |
469 | #endif | |
470 | } | |
471 | ||
472 | /* This function is called by a processor specific function which is | |
473 | run in the prologue when more stack is needed. The processor | |
474 | specific function handles the details of saving registers and | |
475 | frobbing the actual stack pointer. This function is responsible | |
476 | for allocating a new stack segment and for copying a parameter | |
477 | block from the old stack to the new one. On function entry | |
478 | *PFRAME_SIZE is the size of the required stack frame--the returned | |
479 | stack must be at least this large. On function exit *PFRAME_SIZE | |
480 | is the amount of space remaining on the allocated stack. OLD_STACK | |
481 | points at the parameters the old stack (really the current one | |
482 | while this function is running). OLD_STACK is saved so that it can | |
483 | be returned by a later call to __generic_releasestack. PARAM_SIZE | |
484 | is the size in bytes of parameters to copy to the new stack. This | |
485 | function returns a pointer to the new stack segment, pointing to | |
486 | the memory after the parameters have been copied. The returned | |
487 | value minus the returned *PFRAME_SIZE (or plus if the stack grows | |
488 | upward) is the first address on the stack which should not be used. | |
489 | ||
490 | This function is running on the old stack and has only a limited | |
491 | amount of stack space available. */ | |
492 | ||
493 | void * | |
494 | __generic_morestack (size_t *pframe_size, void *old_stack, size_t param_size) | |
495 | { | |
496 | size_t frame_size = *pframe_size; | |
497 | struct stack_segment *current; | |
498 | struct stack_segment **pp; | |
499 | struct dynamic_allocation_blocks *dynamic; | |
500 | char *from; | |
501 | char *to; | |
502 | void *ret; | |
503 | size_t i; | |
504 | ||
505 | current = __morestack_current_segment; | |
506 | ||
507 | pp = current != NULL ? ¤t->next : &__morestack_segments; | |
508 | if (*pp != NULL && (*pp)->size < frame_size) | |
509 | dynamic = __morestack_release_segments (pp, 0); | |
510 | else | |
511 | dynamic = NULL; | |
512 | current = *pp; | |
513 | ||
514 | if (current == NULL) | |
91a639a1 | 515 | current = allocate_segment (frame_size + param_size); |
7458026b ILT |
516 | |
517 | current->old_stack = old_stack; | |
518 | ||
519 | __morestack_current_segment = current; | |
520 | ||
521 | if (dynamic != NULL) | |
522 | { | |
523 | /* Move the free blocks onto our list. We don't want to call | |
524 | free here, as we are short on stack space. */ | |
525 | current->free_dynamic_allocation = | |
526 | merge_dynamic_blocks (dynamic, current->free_dynamic_allocation); | |
527 | } | |
528 | ||
529 | *pframe_size = current->size - param_size; | |
530 | ||
531 | #ifdef STACK_GROWS_DOWNWARD | |
532 | { | |
533 | char *bottom = (char *) (current + 1) + current->size; | |
534 | to = bottom - param_size; | |
535 | ret = bottom - param_size; | |
536 | } | |
537 | #else | |
538 | to = current + 1; | |
539 | ret = (char *) (current + 1) + param_size; | |
540 | #endif | |
541 | ||
542 | /* We don't call memcpy to avoid worrying about the dynamic linker | |
543 | trying to resolve it. */ | |
544 | from = (char *) old_stack; | |
545 | for (i = 0; i < param_size; i++) | |
546 | *to++ = *from++; | |
547 | ||
548 | return ret; | |
549 | } | |
550 | ||
551 | /* This function is called by a processor specific function when it is | |
552 | ready to release a stack segment. We don't actually release the | |
553 | stack segment, we just move back to the previous one. The current | |
554 | stack segment will still be available if we need it in | |
555 | __generic_morestack. This returns a pointer to the new stack | |
556 | segment to use, which is the one saved by a previous call to | |
557 | __generic_morestack. The processor specific function is then | |
558 | responsible for actually updating the stack pointer. This sets | |
559 | *PAVAILABLE to the amount of stack space now available. */ | |
560 | ||
561 | void * | |
562 | __generic_releasestack (size_t *pavailable) | |
563 | { | |
564 | struct stack_segment *current; | |
565 | void *old_stack; | |
566 | ||
567 | current = __morestack_current_segment; | |
568 | old_stack = current->old_stack; | |
569 | current = current->prev; | |
570 | __morestack_current_segment = current; | |
571 | ||
572 | if (current != NULL) | |
573 | { | |
574 | #ifdef STACK_GROWS_DOWNWARD | |
575 | *pavailable = (char *) old_stack - (char *) (current + 1); | |
576 | #else | |
577 | *pavailable = (char *) (current + 1) + current->size - (char *) old_stack; | |
578 | #endif | |
579 | } | |
580 | else | |
581 | { | |
582 | size_t used; | |
583 | ||
584 | /* We have popped back to the original stack. */ | |
585 | #ifdef STACK_GROWS_DOWNWARD | |
586 | if ((char *) old_stack >= (char *) __morestack_initial_sp.sp) | |
587 | used = 0; | |
588 | else | |
589 | used = (char *) __morestack_initial_sp.sp - (char *) old_stack; | |
590 | #else | |
591 | if ((char *) old_stack <= (char *) __morestack_initial_sp.sp) | |
592 | used = 0; | |
593 | else | |
594 | used = (char *) old_stack - (char *) __morestack_initial_sp.sp; | |
595 | #endif | |
596 | ||
597 | if (used > __morestack_initial_sp.len) | |
598 | *pavailable = 0; | |
599 | else | |
600 | *pavailable = __morestack_initial_sp.len - used; | |
601 | } | |
602 | ||
603 | return old_stack; | |
604 | } | |
605 | ||
606 | /* Block signals while splitting the stack. This avoids trouble if we | |
607 | try to invoke a signal handler which itself wants to split the | |
608 | stack. */ | |
609 | ||
610 | extern int pthread_sigmask (int, const sigset_t *, sigset_t *) | |
611 | __attribute__ ((weak)); | |
612 | ||
613 | void | |
614 | __morestack_block_signals (void) | |
615 | { | |
616 | if (pthread_sigmask) | |
617 | pthread_sigmask (SIG_BLOCK, &__morestack_fullmask, | |
618 | &__morestack_initial_sp.mask); | |
619 | else | |
620 | sigprocmask (SIG_BLOCK, &__morestack_fullmask, | |
621 | &__morestack_initial_sp.mask); | |
622 | } | |
623 | ||
624 | /* Unblock signals while splitting the stack. */ | |
625 | ||
626 | void | |
627 | __morestack_unblock_signals (void) | |
628 | { | |
629 | if (pthread_sigmask) | |
630 | pthread_sigmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); | |
631 | else | |
632 | sigprocmask (SIG_SETMASK, &__morestack_initial_sp.mask, NULL); | |
633 | } | |
634 | ||
635 | /* This function is called to allocate dynamic stack space, for alloca | |
636 | or a variably sized array. This is a regular function with | |
637 | sufficient stack space, so we just use malloc to allocate the | |
638 | space. We attach the allocated blocks to the current stack | |
639 | segment, so that they will eventually be reused or freed. */ | |
640 | ||
641 | void * | |
642 | __morestack_allocate_stack_space (size_t size) | |
643 | { | |
644 | struct stack_segment *seg, *current; | |
645 | struct dynamic_allocation_blocks *p; | |
646 | ||
647 | /* We have to block signals to avoid getting confused if we get | |
648 | interrupted by a signal whose handler itself uses alloca or a | |
649 | variably sized array. */ | |
650 | __morestack_block_signals (); | |
651 | ||
652 | /* Since we don't want to call free while we are low on stack space, | |
653 | we may have a list of already allocated blocks waiting to be | |
654 | freed. Release them all, unless we find one that is large | |
655 | enough. We don't look at every block to see if one is large | |
656 | enough, just the first one, because we aren't trying to build a | |
657 | memory allocator here, we're just trying to speed up common | |
658 | cases. */ | |
659 | ||
660 | current = __morestack_current_segment; | |
661 | p = NULL; | |
662 | for (seg = __morestack_segments; seg != NULL; seg = seg->next) | |
663 | { | |
664 | p = seg->free_dynamic_allocation; | |
665 | if (p != NULL) | |
666 | { | |
667 | if (p->size >= size) | |
668 | { | |
669 | seg->free_dynamic_allocation = p->next; | |
670 | break; | |
671 | } | |
672 | ||
673 | free_dynamic_blocks (p); | |
674 | seg->free_dynamic_allocation = NULL; | |
675 | p = NULL; | |
676 | } | |
677 | } | |
678 | ||
679 | if (p == NULL) | |
680 | { | |
681 | /* We need to allocate additional memory. */ | |
682 | p = malloc (sizeof (*p)); | |
683 | if (p == NULL) | |
684 | abort (); | |
685 | p->size = size; | |
686 | p->block = malloc (size); | |
687 | if (p->block == NULL) | |
688 | abort (); | |
689 | } | |
690 | ||
691 | /* If we are still on the initial stack, then we have a space leak. | |
692 | FIXME. */ | |
693 | if (current != NULL) | |
694 | { | |
695 | p->next = current->dynamic_allocation; | |
696 | current->dynamic_allocation = p; | |
697 | } | |
698 | ||
699 | __morestack_unblock_signals (); | |
700 | ||
701 | return p->block; | |
702 | } | |
703 | ||
704 | /* Find the stack segment for STACK and return the amount of space | |
705 | available. This is used when unwinding the stack because of an | |
706 | exception, in order to reset the stack guard correctly. */ | |
707 | ||
708 | size_t | |
709 | __generic_findstack (void *stack) | |
710 | { | |
711 | struct stack_segment *pss; | |
712 | size_t used; | |
713 | ||
714 | for (pss = __morestack_current_segment; pss != NULL; pss = pss->prev) | |
715 | { | |
716 | if ((char *) pss < (char *) stack | |
717 | && (char *) pss + pss->size > (char *) stack) | |
718 | { | |
719 | __morestack_current_segment = pss; | |
720 | #ifdef STACK_GROWS_DOWNWARD | |
721 | return (char *) stack - (char *) (pss + 1); | |
722 | #else | |
723 | return (char *) (pss + 1) + pss->size - (char *) stack; | |
724 | #endif | |
725 | } | |
726 | } | |
727 | ||
728 | /* We have popped back to the original stack. */ | |
729 | #ifdef STACK_GROWS_DOWNWARD | |
730 | if ((char *) stack >= (char *) __morestack_initial_sp.sp) | |
731 | used = 0; | |
732 | else | |
733 | used = (char *) __morestack_initial_sp.sp - (char *) stack; | |
734 | #else | |
735 | if ((char *) stack <= (char *) __morestack_initial_sp.sp) | |
736 | used = 0; | |
737 | else | |
738 | used = (char *) stack - (char *) __morestack_initial_sp.sp; | |
739 | #endif | |
740 | ||
741 | if (used > __morestack_initial_sp.len) | |
742 | return 0; | |
743 | else | |
744 | return __morestack_initial_sp.len - used; | |
745 | } | |
746 | ||
747 | /* This function is called at program startup time to make sure that | |
748 | mmap, munmap, and getpagesize are resolved if linking dynamically. | |
749 | We want to resolve them while we have enough stack for them, rather | |
750 | than calling into the dynamic linker while low on stack space. */ | |
751 | ||
752 | void | |
753 | __morestack_load_mmap (void) | |
754 | { | |
755 | /* Call with bogus values to run faster. We don't care if the call | |
756 | fails. Pass __MORESTACK_CURRENT_SEGMENT to make sure that any | |
757 | TLS accessor function is resolved. */ | |
758 | mmap (__morestack_current_segment, 0, PROT_READ, MAP_ANONYMOUS, -1, 0); | |
759 | mprotect (NULL, 0, 0); | |
760 | munmap (0, getpagesize ()); | |
761 | } | |
762 | ||
763 | /* This function may be used to iterate over the stack segments. | |
764 | This can be called like this. | |
765 | void *next_segment = NULL; | |
766 | void *next_sp = NULL; | |
767 | void *initial_sp = NULL; | |
768 | void *stack; | |
769 | size_t stack_size; | |
770 | while ((stack = __splitstack_find (next_segment, next_sp, &stack_size, | |
771 | &next_segment, &next_sp, | |
772 | &initial_sp)) != NULL) | |
773 | { | |
774 | // Stack segment starts at stack and is stack_size bytes long. | |
775 | } | |
776 | ||
777 | There is no way to iterate over the stack segments of a different | |
778 | thread. However, what is permitted is for one thread to call this | |
779 | with the first two values NULL, to pass next_segment, next_sp, and | |
780 | initial_sp to a different thread, and then to suspend one way or | |
781 | another. A different thread may run the subsequent | |
782 | __morestack_find iterations. Of course, this will only work if the | |
783 | first thread is suspended during the __morestack_find iterations. | |
784 | If not, the second thread will be looking at the stack while it is | |
785 | changing, and anything could happen. | |
786 | ||
787 | FIXME: This should be declared in some header file, but where? */ | |
788 | ||
789 | void * | |
790 | __splitstack_find (void *segment_arg, void *sp, size_t *len, | |
791 | void **next_segment, void **next_sp, | |
792 | void **initial_sp) | |
793 | { | |
794 | struct stack_segment *segment; | |
795 | void *ret; | |
796 | char *nsp; | |
797 | ||
798 | if (segment_arg == (void *) 1) | |
799 | { | |
800 | char *isp = (char *) *initial_sp; | |
801 | ||
802 | *next_segment = (void *) 2; | |
803 | *next_sp = NULL; | |
804 | #ifdef STACK_GROWS_DOWNWARD | |
805 | if ((char *) sp >= isp) | |
806 | return NULL; | |
807 | *len = (char *) isp - (char *) sp; | |
808 | return sp; | |
809 | #else | |
810 | if ((char *) sp <= (char *) isp) | |
811 | return NULL; | |
812 | *len = (char *) sp - (char *) isp; | |
813 | return (void *) isp; | |
814 | #endif | |
815 | } | |
816 | else if (segment_arg == (void *) 2) | |
817 | return NULL; | |
818 | else if (segment_arg != NULL) | |
819 | segment = (struct stack_segment *) segment_arg; | |
820 | else | |
821 | { | |
822 | *initial_sp = __morestack_initial_sp.sp; | |
823 | segment = __morestack_current_segment; | |
824 | sp = (void *) &segment; | |
825 | while (1) | |
826 | { | |
827 | if (segment == NULL) | |
828 | return __splitstack_find ((void *) 1, sp, len, next_segment, | |
829 | next_sp, initial_sp); | |
830 | if ((char *) sp >= (char *) (segment + 1) | |
831 | && (char *) sp <= (char *) (segment + 1) + segment->size) | |
832 | break; | |
833 | segment = segment->prev; | |
834 | } | |
835 | } | |
836 | ||
837 | if (segment->prev == NULL) | |
838 | *next_segment = (void *) 1; | |
839 | else | |
840 | *next_segment = segment->prev; | |
841 | ||
842 | /* The old_stack value is the address of the function parameters of | |
843 | the function which called __morestack. So if f1 called f2 which | |
844 | called __morestack, the stack looks like this: | |
845 | ||
846 | parameters <- old_stack | |
847 | return in f1 | |
848 | return in f2 | |
457186f6 | 849 | registers pushed by __morestack |
7458026b | 850 | |
457186f6 ILT |
851 | The registers pushed by __morestack may not be visible on any |
852 | other stack, if we are being called by a signal handler | |
853 | immediately after the call to __morestack_unblock_signals. We | |
854 | want to adjust our return value to include those registers. This | |
855 | is target dependent. */ | |
7458026b ILT |
856 | |
857 | nsp = (char *) segment->old_stack; | |
457186f6 ILT |
858 | |
859 | #if defined (__x86_64__) | |
860 | nsp -= 12 * sizeof (void *); | |
861 | #elif defined (__i386__) | |
862 | nsp -= 6 * sizeof (void *); | |
7458026b | 863 | #else |
457186f6 | 864 | #error "unrecognized target" |
7458026b | 865 | #endif |
457186f6 | 866 | |
7458026b ILT |
867 | *next_sp = (void *) nsp; |
868 | ||
869 | #ifdef STACK_GROWS_DOWNWARD | |
870 | *len = (char *) (segment + 1) + segment->size - (char *) sp; | |
871 | ret = (void *) sp; | |
872 | #else | |
873 | *len = (char *) sp - (char *) (segment + 1); | |
874 | ret = (void *) (segment + 1); | |
875 | #endif | |
876 | ||
877 | return ret; | |
878 | } | |
879 | ||
880 | #endif /* !defined (inhibit_libc) */ |