1 /* Copyright (C) 2002-2017 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
26 #include <sys/param.h>
27 #include <dl-sysdep.h>
31 #include <lowlevellock.h>
32 #include <futex-internal.h>
33 #include <kernel-features.h>
34 #include <stack-aliasing.h>
37 #ifndef NEED_SEPARATE_REGISTER_STACK
39 /* Most architectures have exactly one stack pointer. Some have more. */
40 # define STACK_VARIABLES void *stackaddr = NULL
42 /* How to pass the values to the 'create_thread' function. */
43 # define STACK_VARIABLES_ARGS stackaddr
45 /* How to declare function which gets there parameters. */
46 # define STACK_VARIABLES_PARMS void *stackaddr
48 /* How to declare allocate_stack. */
49 # define ALLOCATE_STACK_PARMS void **stack
51 /* This is how the function is called. We do it this way to allow
52 other variants of the function to have more parameters. */
53 # define ALLOCATE_STACK(attr, pd) allocate_stack (attr, pd, &stackaddr)
57 /* We need two stacks. The kernel will place them but we have to tell
58 the kernel about the size of the reserved address space. */
59 # define STACK_VARIABLES void *stackaddr = NULL; size_t stacksize = 0
61 /* How to pass the values to the 'create_thread' function. */
62 # define STACK_VARIABLES_ARGS stackaddr, stacksize
64 /* How to declare function which gets there parameters. */
65 # define STACK_VARIABLES_PARMS void *stackaddr, size_t stacksize
67 /* How to declare allocate_stack. */
68 # define ALLOCATE_STACK_PARMS void **stack, size_t *stacksize
70 /* This is how the function is called. We do it this way to allow
71 other variants of the function to have more parameters. */
72 # define ALLOCATE_STACK(attr, pd) \
73 allocate_stack (attr, pd, &stackaddr, &stacksize)
78 /* Default alignment of stack. */
80 # define STACK_ALIGN __alignof__ (long double)
83 /* Default value for minimal stack size after allocating thread
84 descriptor and guard. */
85 #ifndef MINIMAL_REST_STACK
86 # define MINIMAL_REST_STACK 4096
90 /* Newer kernels have the MAP_STACK flag to indicate a mapping is used for
91 a stack. Use it when possible. */
96 /* This yields the pointer that TLS support code calls the thread pointer. */
98 # define TLS_TPADJ(pd) (pd)
100 # define TLS_TPADJ(pd) ((struct pthread *)((char *) (pd) + TLS_PRE_TCB_SIZE))
103 /* Cache handling for not-yet free stacks. */
105 /* Maximum size in kB of cache. */
106 static size_t stack_cache_maxsize
= 40 * 1024 * 1024; /* 40MiBi by default. */
107 static size_t stack_cache_actsize
;
109 /* Mutex protecting this variable. */
110 static int stack_cache_lock
= LLL_LOCK_INITIALIZER
;
112 /* List of queued stack frames. */
113 static LIST_HEAD (stack_cache
);
115 /* List of the stacks in use. */
116 static LIST_HEAD (stack_used
);
118 /* We need to record what list operations we are going to do so that,
119 in case of an asynchronous interruption due to a fork() call, we
120 can correct for the work. */
121 static uintptr_t in_flight_stack
;
123 /* List of the threads with user provided stacks in use. No need to
124 initialize this, since it's done in __pthread_initialize_minimal. */
125 list_t __stack_user
__attribute__ ((nocommon
));
126 hidden_data_def (__stack_user
)
129 /* Check whether the stack is still used or not. */
130 #define FREE_P(descr) ((descr)->tid <= 0)
134 stack_list_del (list_t
*elem
)
136 in_flight_stack
= (uintptr_t) elem
;
138 atomic_write_barrier ();
142 atomic_write_barrier ();
149 stack_list_add (list_t
*elem
, list_t
*list
)
151 in_flight_stack
= (uintptr_t) elem
| 1;
153 atomic_write_barrier ();
155 list_add (elem
, list
);
157 atomic_write_barrier ();
163 /* We create a double linked list of all cache entries. Double linked
164 because this allows removing entries from the end. */
167 /* Get a stack frame from the cache. We have to match by size since
168 some blocks might be too small or far too large. */
169 static struct pthread
*
170 get_cached_stack (size_t *sizep
, void **memp
)
172 size_t size
= *sizep
;
173 struct pthread
*result
= NULL
;
176 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
178 /* Search the cache for a matching entry. We search for the
179 smallest stack which has at least the required size. Note that
180 in normal situations the size of all allocated stacks is the
181 same. As the very least there are only a few different sizes.
182 Therefore this loop will exit early most of the time with an
184 list_for_each (entry
, &stack_cache
)
186 struct pthread
*curr
;
188 curr
= list_entry (entry
, struct pthread
, list
);
189 if (FREE_P (curr
) && curr
->stackblock_size
>= size
)
191 if (curr
->stackblock_size
== size
)
198 || result
->stackblock_size
> curr
->stackblock_size
)
203 if (__builtin_expect (result
== NULL
, 0)
204 /* Make sure the size difference is not too excessive. In that
205 case we do not use the block. */
206 || __builtin_expect (result
->stackblock_size
> 4 * size
, 0))
208 /* Release the lock. */
209 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
214 /* Don't allow setxid until cloned. */
215 result
->setxid_futex
= -1;
217 /* Dequeue the entry. */
218 stack_list_del (&result
->list
);
220 /* And add to the list of stacks in use. */
221 stack_list_add (&result
->list
, &stack_used
);
223 /* And decrease the cache size. */
224 stack_cache_actsize
-= result
->stackblock_size
;
226 /* Release the lock early. */
227 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
229 /* Report size and location of the stack to the caller. */
230 *sizep
= result
->stackblock_size
;
231 *memp
= result
->stackblock
;
233 /* Cancellation handling is back to the default. */
234 result
->cancelhandling
= 0;
235 result
->cleanup
= NULL
;
237 /* No pending event. */
238 result
->nextevent
= NULL
;
241 dtv_t
*dtv
= GET_DTV (TLS_TPADJ (result
));
242 for (size_t cnt
= 0; cnt
< dtv
[-1].counter
; ++cnt
)
243 free (dtv
[1 + cnt
].pointer
.to_free
);
244 memset (dtv
, '\0', (dtv
[-1].counter
+ 1) * sizeof (dtv_t
));
246 /* Re-initialize the TLS. */
247 _dl_allocate_tls_init (TLS_TPADJ (result
));
253 /* Free stacks until cache size is lower than LIMIT. */
255 __free_stacks (size_t limit
)
257 /* We reduce the size of the cache. Remove the last entries until
258 the size is below the limit. */
262 /* Search from the end of the list. */
263 list_for_each_prev_safe (entry
, prev
, &stack_cache
)
265 struct pthread
*curr
;
267 curr
= list_entry (entry
, struct pthread
, list
);
270 /* Unlink the block. */
271 stack_list_del (entry
);
273 /* Account for the freed memory. */
274 stack_cache_actsize
-= curr
->stackblock_size
;
276 /* Free the memory associated with the ELF TLS. */
277 _dl_deallocate_tls (TLS_TPADJ (curr
), false);
279 /* Remove this block. This should never fail. If it does
280 something is really wrong. */
281 if (__munmap (curr
->stackblock
, curr
->stackblock_size
) != 0)
284 /* Maybe we have freed enough. */
285 if (stack_cache_actsize
<= limit
)
292 /* Add a stack frame which is not used anymore to the stack. Must be
293 called with the cache lock held. */
295 __attribute ((always_inline
))
296 queue_stack (struct pthread
*stack
)
298 /* We unconditionally add the stack to the list. The memory may
299 still be in use but it will not be reused until the kernel marks
300 the stack as not used anymore. */
301 stack_list_add (&stack
->list
, &stack_cache
);
303 stack_cache_actsize
+= stack
->stackblock_size
;
304 if (__glibc_unlikely (stack_cache_actsize
> stack_cache_maxsize
))
305 __free_stacks (stack_cache_maxsize
);
310 change_stack_perm (struct pthread
*pd
311 #ifdef NEED_SEPARATE_REGISTER_STACK
316 #ifdef NEED_SEPARATE_REGISTER_STACK
317 void *stack
= (pd
->stackblock
318 + (((((pd
->stackblock_size
- pd
->guardsize
) / 2)
319 & pagemask
) + pd
->guardsize
) & pagemask
));
320 size_t len
= pd
->stackblock
+ pd
->stackblock_size
- stack
;
321 #elif _STACK_GROWS_DOWN
322 void *stack
= pd
->stackblock
+ pd
->guardsize
;
323 size_t len
= pd
->stackblock_size
- pd
->guardsize
;
324 #elif _STACK_GROWS_UP
325 void *stack
= pd
->stackblock
;
326 size_t len
= (uintptr_t) pd
- pd
->guardsize
- (uintptr_t) pd
->stackblock
;
328 # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
330 if (__mprotect (stack
, len
, PROT_READ
| PROT_WRITE
| PROT_EXEC
) != 0)
336 /* Return the guard page position on allocated stack. */
338 __attribute ((always_inline
))
339 guard_position (void *mem
, size_t size
, size_t guardsize
, struct pthread
*pd
,
342 #ifdef NEED_SEPARATE_REGISTER_STACK
343 return mem
+ (((size
- guardsize
) / 2) & ~pagesize_m1
);
344 #elif _STACK_GROWS_DOWN
346 #elif _STACK_GROWS_UP
347 return (char *) (((uintptr_t) pd
- guardsize
) & ~pagesize_m1
);
351 /* Based on stack allocated with PROT_NONE, setup the required portions with
352 'prot' flags based on the guard page position. */
354 setup_stack_prot (char *mem
, size_t size
, char *guard
, size_t guardsize
,
357 char *guardend
= guard
+ guardsize
;
358 #if _STACK_GROWS_DOWN && !defined(NEED_SEPARATE_REGISTER_STACK)
359 /* As defined at guard_position, for architectures with downward stack
360 the guard page is always at start of the allocated area. */
361 if (__mprotect (guardend
, size
- guardsize
, prot
) != 0)
364 size_t mprots1
= (uintptr_t) guard
- (uintptr_t) mem
;
365 if (__mprotect (mem
, mprots1
, prot
) != 0)
367 size_t mprots2
= ((uintptr_t) mem
+ size
) - (uintptr_t) guardend
;
368 if (__mprotect (guardend
, mprots2
, prot
) != 0)
374 /* Mark the memory of the stack as usable to the kernel. It frees everything
375 except for the space used for the TCB itself. */
378 advise_stack_range (void *mem
, size_t size
, uintptr_t pd
, size_t guardsize
)
380 uintptr_t sp
= (uintptr_t) CURRENT_STACK_FRAME
;
381 size_t pagesize_m1
= __getpagesize () - 1;
382 #if _STACK_GROWS_DOWN && !defined(NEED_SEPARATE_REGISTER_STACK)
383 size_t freesize
= (sp
- (uintptr_t) mem
) & ~pagesize_m1
;
384 assert (freesize
< size
);
385 if (freesize
> PTHREAD_STACK_MIN
)
386 __madvise (mem
, freesize
- PTHREAD_STACK_MIN
, MADV_DONTNEED
);
388 /* Page aligned start of memory to free (higher than or equal
389 to current sp plus the minimum stack size). */
390 uintptr_t freeblock
= (sp
+ PTHREAD_STACK_MIN
+ pagesize_m1
) & ~pagesize_m1
;
391 uintptr_t free_end
= (pd
- guardsize
) & ~pagesize_m1
;
392 if (free_end
> freeblock
)
394 size_t freesize
= free_end
- freeblock
;
395 assert (freesize
< size
);
396 __madvise ((void*) freeblock
, freesize
, MADV_DONTNEED
);
401 /* Returns a usable stack for a new thread either by allocating a
402 new stack or reusing a cached stack of sufficient size.
403 ATTR must be non-NULL and point to a valid pthread_attr.
404 PDP must be non-NULL. */
406 allocate_stack (const struct pthread_attr
*attr
, struct pthread
**pdp
,
407 ALLOCATE_STACK_PARMS
)
411 size_t pagesize_m1
= __getpagesize () - 1;
413 assert (powerof2 (pagesize_m1
+ 1));
414 assert (TCB_ALIGNMENT
>= STACK_ALIGN
);
416 /* Get the stack size from the attribute if it is set. Otherwise we
417 use the default we determined at start time. */
418 if (attr
->stacksize
!= 0)
419 size
= attr
->stacksize
;
422 lll_lock (__default_pthread_attr_lock
, LLL_PRIVATE
);
423 size
= __default_pthread_attr
.stacksize
;
424 lll_unlock (__default_pthread_attr_lock
, LLL_PRIVATE
);
427 /* Get memory for the stack. */
428 if (__glibc_unlikely (attr
->flags
& ATTR_FLAG_STACKADDR
))
431 char *stackaddr
= (char *) attr
->stackaddr
;
433 /* Assume the same layout as the _STACK_GROWS_DOWN case, with struct
434 pthread at the top of the stack block. Later we adjust the guard
435 location and stack address to match the _STACK_GROWS_UP case. */
437 stackaddr
+= attr
->stacksize
;
439 /* If the user also specified the size of the stack make sure it
441 if (attr
->stacksize
!= 0
442 && attr
->stacksize
< (__static_tls_size
+ MINIMAL_REST_STACK
))
445 /* Adjust stack size for alignment of the TLS block. */
447 adj
= ((uintptr_t) stackaddr
- TLS_TCB_SIZE
)
448 & __static_tls_align_m1
;
449 assert (size
> adj
+ TLS_TCB_SIZE
);
451 adj
= ((uintptr_t) stackaddr
- __static_tls_size
)
452 & __static_tls_align_m1
;
456 /* The user provided some memory. Let's hope it matches the
457 size... We do not allocate guard pages if the user provided
458 the stack. It is the user's responsibility to do this if it
461 pd
= (struct pthread
*) ((uintptr_t) stackaddr
462 - TLS_TCB_SIZE
- adj
);
464 pd
= (struct pthread
*) (((uintptr_t) stackaddr
465 - __static_tls_size
- adj
)
469 /* The user provided stack memory needs to be cleared. */
470 memset (pd
, '\0', sizeof (struct pthread
));
472 /* The first TSD block is included in the TCB. */
473 pd
->specific
[0] = pd
->specific_1stblock
;
475 /* Remember the stack-related values. */
476 pd
->stackblock
= (char *) stackaddr
- size
;
477 pd
->stackblock_size
= size
;
479 /* This is a user-provided stack. It will not be queued in the
480 stack cache nor will the memory (except the TLS memory) be freed. */
481 pd
->user_stack
= true;
483 /* This is at least the second thread. */
484 pd
->header
.multiple_threads
= 1;
485 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
486 __pthread_multiple_threads
= *__libc_multiple_threads_ptr
= 1;
489 #ifndef __ASSUME_PRIVATE_FUTEX
490 /* The thread must know when private futexes are supported. */
491 pd
->header
.private_futex
= THREAD_GETMEM (THREAD_SELF
,
492 header
.private_futex
);
495 #ifdef NEED_DL_SYSINFO
496 SETUP_THREAD_SYSINFO (pd
);
499 /* Don't allow setxid until cloned. */
500 pd
->setxid_futex
= -1;
502 /* Allocate the DTV for this thread. */
503 if (_dl_allocate_tls (TLS_TPADJ (pd
)) == NULL
)
505 /* Something went wrong. */
506 assert (errno
== ENOMEM
);
511 /* Prepare to modify global data. */
512 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
514 /* And add to the list of stacks in use. */
515 list_add (&pd
->list
, &__stack_user
);
517 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
521 /* Allocate some anonymous memory. If possible use the cache. */
525 const int prot
= (PROT_READ
| PROT_WRITE
526 | ((GL(dl_stack_flags
) & PF_X
) ? PROT_EXEC
: 0));
528 /* Adjust the stack size for alignment. */
529 size
&= ~__static_tls_align_m1
;
532 /* Make sure the size of the stack is enough for the guard and
533 eventually the thread descriptor. */
534 guardsize
= (attr
->guardsize
+ pagesize_m1
) & ~pagesize_m1
;
535 if (__builtin_expect (size
< ((guardsize
+ __static_tls_size
536 + MINIMAL_REST_STACK
+ pagesize_m1
)
539 /* The stack is too small (or the guard too large). */
542 /* Try to get a stack from the cache. */
544 pd
= get_cached_stack (&size
, &mem
);
547 /* To avoid aliasing effects on a larger scale than pages we
548 adjust the allocated stack size if necessary. This way
549 allocations directly following each other will not have
550 aliasing problems. */
551 #if MULTI_PAGE_ALIASING != 0
552 if ((size
% MULTI_PAGE_ALIASING
) == 0)
553 size
+= pagesize_m1
+ 1;
556 /* If a guard page is required, avoid committing memory by first
557 allocate with PROT_NONE and then reserve with required permission
558 excluding the guard page. */
559 mem
= __mmap (NULL
, size
, (guardsize
== 0) ? prot
: PROT_NONE
,
560 MAP_PRIVATE
| MAP_ANONYMOUS
| MAP_STACK
, -1, 0);
562 if (__glibc_unlikely (mem
== MAP_FAILED
))
565 /* SIZE is guaranteed to be greater than zero.
566 So we can never get a null pointer back from mmap. */
567 assert (mem
!= NULL
);
569 /* Place the thread descriptor at the end of the stack. */
571 pd
= (struct pthread
*) ((char *) mem
+ size
) - 1;
573 pd
= (struct pthread
*) ((((uintptr_t) mem
+ size
575 & ~__static_tls_align_m1
)
579 /* Now mprotect the required region excluding the guard area. */
580 if (__glibc_likely (guardsize
> 0))
582 char *guard
= guard_position (mem
, size
, guardsize
, pd
,
584 if (setup_stack_prot (mem
, size
, guard
, guardsize
, prot
) != 0)
586 __munmap (mem
, size
);
591 /* Remember the stack-related values. */
592 pd
->stackblock
= mem
;
593 pd
->stackblock_size
= size
;
594 /* Update guardsize for newly allocated guardsize to avoid
595 an mprotect in guard resize below. */
596 pd
->guardsize
= guardsize
;
598 /* We allocated the first block thread-specific data array.
599 This address will not change for the lifetime of this
601 pd
->specific
[0] = pd
->specific_1stblock
;
603 /* This is at least the second thread. */
604 pd
->header
.multiple_threads
= 1;
605 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
606 __pthread_multiple_threads
= *__libc_multiple_threads_ptr
= 1;
609 #ifndef __ASSUME_PRIVATE_FUTEX
610 /* The thread must know when private futexes are supported. */
611 pd
->header
.private_futex
= THREAD_GETMEM (THREAD_SELF
,
612 header
.private_futex
);
615 #ifdef NEED_DL_SYSINFO
616 SETUP_THREAD_SYSINFO (pd
);
619 /* Don't allow setxid until cloned. */
620 pd
->setxid_futex
= -1;
622 /* Allocate the DTV for this thread. */
623 if (_dl_allocate_tls (TLS_TPADJ (pd
)) == NULL
)
625 /* Something went wrong. */
626 assert (errno
== ENOMEM
);
628 /* Free the stack memory we just allocated. */
629 (void) __munmap (mem
, size
);
635 /* Prepare to modify global data. */
636 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
638 /* And add to the list of stacks in use. */
639 stack_list_add (&pd
->list
, &stack_used
);
641 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
644 /* There might have been a race. Another thread might have
645 caused the stacks to get exec permission while this new
646 stack was prepared. Detect if this was possible and
647 change the permission if necessary. */
648 if (__builtin_expect ((GL(dl_stack_flags
) & PF_X
) != 0
649 && (prot
& PROT_EXEC
) == 0, 0))
651 int err
= change_stack_perm (pd
652 #ifdef NEED_SEPARATE_REGISTER_STACK
658 /* Free the stack memory we just allocated. */
659 (void) __munmap (mem
, size
);
666 /* Note that all of the stack and the thread descriptor is
667 zeroed. This means we do not have to initialize fields
668 with initial value zero. This is specifically true for
669 the 'tid' field which is always set back to zero once the
670 stack is not used anymore and for the 'guardsize' field
671 which will be read next. */
674 /* Create or resize the guard area if necessary. */
675 if (__glibc_unlikely (guardsize
> pd
->guardsize
))
677 char *guard
= guard_position (mem
, size
, guardsize
, pd
,
679 if (__mprotect (guard
, guardsize
, PROT_NONE
) != 0)
682 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
684 /* Remove the thread from the list. */
685 stack_list_del (&pd
->list
);
687 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
689 /* Get rid of the TLS block we allocated. */
690 _dl_deallocate_tls (TLS_TPADJ (pd
), false);
692 /* Free the stack memory regardless of whether the size
693 of the cache is over the limit or not. If this piece
694 of memory caused problems we better do not use it
695 anymore. Uh, and we ignore possible errors. There
696 is nothing we could do. */
697 (void) __munmap (mem
, size
);
702 pd
->guardsize
= guardsize
;
704 else if (__builtin_expect (pd
->guardsize
- guardsize
> size
- reqsize
,
707 /* The old guard area is too large. */
709 #ifdef NEED_SEPARATE_REGISTER_STACK
710 char *guard
= mem
+ (((size
- guardsize
) / 2) & ~pagesize_m1
);
711 char *oldguard
= mem
+ (((size
- pd
->guardsize
) / 2) & ~pagesize_m1
);
714 && __mprotect (oldguard
, guard
- oldguard
, prot
) != 0)
717 if (__mprotect (guard
+ guardsize
,
718 oldguard
+ pd
->guardsize
- guard
- guardsize
,
721 #elif _STACK_GROWS_DOWN
722 if (__mprotect ((char *) mem
+ guardsize
, pd
->guardsize
- guardsize
,
725 #elif _STACK_GROWS_UP
726 char *new_guard
= (char *)(((uintptr_t) pd
- guardsize
)
728 char *old_guard
= (char *)(((uintptr_t) pd
- pd
->guardsize
)
730 /* The guard size difference might be > 0, but once rounded
731 to the nearest page the size difference might be zero. */
732 if (new_guard
> old_guard
733 && mprotect (old_guard
, new_guard
- old_guard
, prot
) != 0)
737 pd
->guardsize
= guardsize
;
739 /* The pthread_getattr_np() calls need to get passed the size
740 requested in the attribute, regardless of how large the
741 actually used guardsize is. */
742 pd
->reported_guardsize
= guardsize
;
745 /* Initialize the lock. We have to do this unconditionally since the
746 stillborn thread could be canceled while the lock is taken. */
747 pd
->lock
= LLL_LOCK_INITIALIZER
;
749 /* The robust mutex lists also need to be initialized
750 unconditionally because the cleanup for the previous stack owner
751 might have happened in the kernel. */
752 pd
->robust_head
.futex_offset
= (offsetof (pthread_mutex_t
, __data
.__lock
)
753 - offsetof (pthread_mutex_t
,
754 __data
.__list
.__next
));
755 pd
->robust_head
.list_op_pending
= NULL
;
756 #if __PTHREAD_MUTEX_HAVE_PREV
757 pd
->robust_prev
= &pd
->robust_head
;
759 pd
->robust_head
.list
= &pd
->robust_head
;
761 /* We place the thread descriptor at the end of the stack. */
764 #if _STACK_GROWS_DOWN
768 /* The stack begins before the TCB and the static TLS block. */
769 stacktop
= ((char *) (pd
+ 1) - __static_tls_size
);
771 stacktop
= (char *) (pd
- 1);
774 # ifdef NEED_SEPARATE_REGISTER_STACK
775 *stack
= pd
->stackblock
;
776 *stacksize
= stacktop
- *stack
;
781 *stack
= pd
->stackblock
;
789 __deallocate_stack (struct pthread
*pd
)
791 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
793 /* Remove the thread from the list of threads with user defined
795 stack_list_del (&pd
->list
);
797 /* Not much to do. Just free the mmap()ed memory. Note that we do
798 not reset the 'used' flag in the 'tid' field. This is done by
799 the kernel. If no thread has been created yet this field is
801 if (__glibc_likely (! pd
->user_stack
))
802 (void) queue_stack (pd
);
804 /* Free the memory associated with the ELF TLS. */
805 _dl_deallocate_tls (TLS_TPADJ (pd
), false);
807 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
812 __make_stacks_executable (void **stack_endp
)
814 /* First the main thread's stack. */
815 int err
= _dl_make_stack_executable (stack_endp
);
819 #ifdef NEED_SEPARATE_REGISTER_STACK
820 const size_t pagemask
= ~(__getpagesize () - 1);
823 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
826 list_for_each (runp
, &stack_used
)
828 err
= change_stack_perm (list_entry (runp
, struct pthread
, list
)
829 #ifdef NEED_SEPARATE_REGISTER_STACK
837 /* Also change the permission for the currently unused stacks. This
838 might be wasted time but better spend it here than adding a check
841 list_for_each (runp
, &stack_cache
)
843 err
= change_stack_perm (list_entry (runp
, struct pthread
, list
)
844 #ifdef NEED_SEPARATE_REGISTER_STACK
852 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
858 /* In case of a fork() call the memory allocation in the child will be
859 the same but only one thread is running. All stacks except that of
860 the one running thread are not used anymore. We have to recycle
863 __reclaim_stacks (void)
865 struct pthread
*self
= (struct pthread
*) THREAD_SELF
;
867 /* No locking necessary. The caller is the only stack in use. But
868 we have to be aware that we might have interrupted a list
871 if (in_flight_stack
!= 0)
873 bool add_p
= in_flight_stack
& 1;
874 list_t
*elem
= (list_t
*) (in_flight_stack
& ~(uintptr_t) 1);
878 /* We always add at the beginning of the list. So in this case we
879 only need to check the beginning of these lists to see if the
880 pointers at the head of the list are inconsistent. */
883 if (stack_used
.next
->prev
!= &stack_used
)
885 else if (stack_cache
.next
->prev
!= &stack_cache
)
890 assert (l
->next
->prev
== elem
);
891 elem
->next
= l
->next
;
898 /* We can simply always replay the delete operation. */
899 elem
->next
->prev
= elem
->prev
;
900 elem
->prev
->next
= elem
->next
;
904 /* Mark all stacks except the still running one as free. */
906 list_for_each (runp
, &stack_used
)
908 struct pthread
*curp
= list_entry (runp
, struct pthread
, list
);
911 /* This marks the stack as free. */
914 /* Account for the size of the stack. */
915 stack_cache_actsize
+= curp
->stackblock_size
;
917 if (curp
->specific_used
)
919 /* Clear the thread-specific data. */
920 memset (curp
->specific_1stblock
, '\0',
921 sizeof (curp
->specific_1stblock
));
923 curp
->specific_used
= false;
925 for (size_t cnt
= 1; cnt
< PTHREAD_KEY_1STLEVEL_SIZE
; ++cnt
)
926 if (curp
->specific
[cnt
] != NULL
)
928 memset (curp
->specific
[cnt
], '\0',
929 sizeof (curp
->specific_1stblock
));
931 /* We have allocated the block which we do not
932 free here so re-set the bit. */
933 curp
->specific_used
= true;
939 /* Add the stack of all running threads to the cache. */
940 list_splice (&stack_used
, &stack_cache
);
942 /* Remove the entry for the current thread to from the cache list
943 and add it to the list of running threads. Which of the two
944 lists is decided by the user_stack flag. */
945 stack_list_del (&self
->list
);
947 /* Re-initialize the lists for all the threads. */
948 INIT_LIST_HEAD (&stack_used
);
949 INIT_LIST_HEAD (&__stack_user
);
951 if (__glibc_unlikely (THREAD_GETMEM (self
, user_stack
)))
952 list_add (&self
->list
, &__stack_user
);
954 list_add (&self
->list
, &stack_used
);
956 /* There is one thread running. */
961 /* Initialize locks. */
962 stack_cache_lock
= LLL_LOCK_INITIALIZER
;
963 __default_pthread_attr_lock
= LLL_LOCK_INITIALIZER
;
968 # undef __find_thread_by_id
969 /* Find a thread given the thread ID. */
972 __find_thread_by_id (pid_t tid
)
974 struct pthread
*result
= NULL
;
976 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
978 /* Iterate over the list with system-allocated threads first. */
980 list_for_each (runp
, &stack_used
)
982 struct pthread
*curp
;
984 curp
= list_entry (runp
, struct pthread
, list
);
986 if (curp
->tid
== tid
)
993 /* Now the list with threads using user-allocated stacks. */
994 list_for_each (runp
, &__stack_user
)
996 struct pthread
*curp
;
998 curp
= list_entry (runp
, struct pthread
, list
);
1000 if (curp
->tid
== tid
)
1008 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
1017 setxid_mark_thread (struct xid_command
*cmdp
, struct pthread
*t
)
1021 /* Wait until this thread is cloned. */
1022 if (t
->setxid_futex
== -1
1023 && ! atomic_compare_and_exchange_bool_acq (&t
->setxid_futex
, -2, -1))
1025 futex_wait_simple (&t
->setxid_futex
, -2, FUTEX_PRIVATE
);
1026 while (t
->setxid_futex
== -2);
1028 /* Don't let the thread exit before the setxid handler runs. */
1029 t
->setxid_futex
= 0;
1033 ch
= t
->cancelhandling
;
1035 /* If the thread is exiting right now, ignore it. */
1036 if ((ch
& EXITING_BITMASK
) != 0)
1038 /* Release the futex if there is no other setxid in
1040 if ((ch
& SETXID_BITMASK
) == 0)
1042 t
->setxid_futex
= 1;
1043 futex_wake (&t
->setxid_futex
, 1, FUTEX_PRIVATE
);
1048 while (atomic_compare_and_exchange_bool_acq (&t
->cancelhandling
,
1049 ch
| SETXID_BITMASK
, ch
));
1054 setxid_unmark_thread (struct xid_command
*cmdp
, struct pthread
*t
)
1060 ch
= t
->cancelhandling
;
1061 if ((ch
& SETXID_BITMASK
) == 0)
1064 while (atomic_compare_and_exchange_bool_acq (&t
->cancelhandling
,
1065 ch
& ~SETXID_BITMASK
, ch
));
1067 /* Release the futex just in case. */
1068 t
->setxid_futex
= 1;
1069 futex_wake (&t
->setxid_futex
, 1, FUTEX_PRIVATE
);
1074 setxid_signal_thread (struct xid_command
*cmdp
, struct pthread
*t
)
1076 if ((t
->cancelhandling
& SETXID_BITMASK
) == 0)
1080 pid_t pid
= __getpid ();
1081 INTERNAL_SYSCALL_DECL (err
);
1082 val
= INTERNAL_SYSCALL_CALL (tgkill
, err
, pid
, t
->tid
, SIGSETXID
);
1084 /* If this failed, it must have had not started yet or else exited. */
1085 if (!INTERNAL_SYSCALL_ERROR_P (val
, err
))
1087 atomic_increment (&cmdp
->cntr
);
1094 /* Check for consistency across set*id system call results. The abort
1095 should not happen as long as all privileges changes happen through
1096 the glibc wrappers. ERROR must be 0 (no error) or an errno
1100 __nptl_setxid_error (struct xid_command
*cmdp
, int error
)
1104 int olderror
= cmdp
->error
;
1105 if (olderror
== error
)
1109 /* Mismatch between current and previous results. Save the
1110 error value to memory so that is not clobbered by the
1111 abort function and preserved in coredumps. */
1112 volatile int xid_err
__attribute__((unused
)) = error
;
1116 while (atomic_compare_and_exchange_bool_acq (&cmdp
->error
, error
, -1));
1121 __nptl_setxid (struct xid_command
*cmdp
)
1125 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
1131 struct pthread
*self
= THREAD_SELF
;
1133 /* Iterate over the list with system-allocated threads first. */
1135 list_for_each (runp
, &stack_used
)
1137 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1141 setxid_mark_thread (cmdp
, t
);
1144 /* Now the list with threads using user-allocated stacks. */
1145 list_for_each (runp
, &__stack_user
)
1147 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1151 setxid_mark_thread (cmdp
, t
);
1154 /* Iterate until we don't succeed in signalling anyone. That means
1155 we have gotten all running threads, and their children will be
1156 automatically correct once started. */
1161 list_for_each (runp
, &stack_used
)
1163 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1167 signalled
+= setxid_signal_thread (cmdp
, t
);
1170 list_for_each (runp
, &__stack_user
)
1172 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1176 signalled
+= setxid_signal_thread (cmdp
, t
);
1179 int cur
= cmdp
->cntr
;
1182 futex_wait_simple ((unsigned int *) &cmdp
->cntr
, cur
,
1187 while (signalled
!= 0);
1189 /* Clean up flags, so that no thread blocks during exit waiting
1190 for a signal which will never come. */
1191 list_for_each (runp
, &stack_used
)
1193 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1197 setxid_unmark_thread (cmdp
, t
);
1200 list_for_each (runp
, &__stack_user
)
1202 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1206 setxid_unmark_thread (cmdp
, t
);
1209 /* This must be last, otherwise the current thread might not have
1210 permissions to send SIGSETXID syscall to the other threads. */
1211 INTERNAL_SYSCALL_DECL (err
);
1212 result
= INTERNAL_SYSCALL_NCS (cmdp
->syscall_no
, err
, 3,
1213 cmdp
->id
[0], cmdp
->id
[1], cmdp
->id
[2]);
1215 if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result
, err
)))
1217 error
= INTERNAL_SYSCALL_ERRNO (result
, err
);
1218 __set_errno (error
);
1221 __nptl_setxid_error (cmdp
, error
);
1223 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
1226 #endif /* SIGSETXID. */
1229 static inline void __attribute__((always_inline
))
1230 init_one_static_tls (struct pthread
*curp
, struct link_map
*map
)
1233 void *dest
= (char *) curp
- map
->l_tls_offset
;
1234 # elif TLS_DTV_AT_TP
1235 void *dest
= (char *) curp
+ map
->l_tls_offset
+ TLS_PRE_TCB_SIZE
;
1237 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
1240 /* Initialize the memory. */
1241 memset (__mempcpy (dest
, map
->l_tls_initimage
, map
->l_tls_initimage_size
),
1242 '\0', map
->l_tls_blocksize
- map
->l_tls_initimage_size
);
1247 __pthread_init_static_tls (struct link_map
*map
)
1249 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
1251 /* Iterate over the list with system-allocated threads first. */
1253 list_for_each (runp
, &stack_used
)
1254 init_one_static_tls (list_entry (runp
, struct pthread
, list
), map
);
1256 /* Now the list with threads using user-allocated stacks. */
1257 list_for_each (runp
, &__stack_user
)
1258 init_one_static_tls (list_entry (runp
, struct pthread
, list
), map
);
1260 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);
1266 __wait_lookup_done (void)
1268 lll_lock (stack_cache_lock
, LLL_PRIVATE
);
1270 struct pthread
*self
= THREAD_SELF
;
1272 /* Iterate over the list with system-allocated threads first. */
1274 list_for_each (runp
, &stack_used
)
1276 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1277 if (t
== self
|| t
->header
.gscope_flag
== THREAD_GSCOPE_FLAG_UNUSED
)
1280 int *const gscope_flagp
= &t
->header
.gscope_flag
;
1282 /* We have to wait until this thread is done with the global
1283 scope. First tell the thread that we are waiting and
1284 possibly have to be woken. */
1285 if (atomic_compare_and_exchange_bool_acq (gscope_flagp
,
1286 THREAD_GSCOPE_FLAG_WAIT
,
1287 THREAD_GSCOPE_FLAG_USED
))
1291 futex_wait_simple ((unsigned int *) gscope_flagp
,
1292 THREAD_GSCOPE_FLAG_WAIT
, FUTEX_PRIVATE
);
1293 while (*gscope_flagp
== THREAD_GSCOPE_FLAG_WAIT
);
1296 /* Now the list with threads using user-allocated stacks. */
1297 list_for_each (runp
, &__stack_user
)
1299 struct pthread
*t
= list_entry (runp
, struct pthread
, list
);
1300 if (t
== self
|| t
->header
.gscope_flag
== THREAD_GSCOPE_FLAG_UNUSED
)
1303 int *const gscope_flagp
= &t
->header
.gscope_flag
;
1305 /* We have to wait until this thread is done with the global
1306 scope. First tell the thread that we are waiting and
1307 possibly have to be woken. */
1308 if (atomic_compare_and_exchange_bool_acq (gscope_flagp
,
1309 THREAD_GSCOPE_FLAG_WAIT
,
1310 THREAD_GSCOPE_FLAG_USED
))
1314 futex_wait_simple ((unsigned int *) gscope_flagp
,
1315 THREAD_GSCOPE_FLAG_WAIT
, FUTEX_PRIVATE
);
1316 while (*gscope_flagp
== THREAD_GSCOPE_FLAG_WAIT
);
1319 lll_unlock (stack_cache_lock
, LLL_PRIVATE
);