/* Copyright (C) 2002-2018 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper , 2002. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifndef NEED_SEPARATE_REGISTER_STACK /* Most architectures have exactly one stack pointer. Some have more. */ # define STACK_VARIABLES void *stackaddr = NULL /* How to pass the values to the 'create_thread' function. */ # define STACK_VARIABLES_ARGS stackaddr /* How to declare function which gets there parameters. */ # define STACK_VARIABLES_PARMS void *stackaddr /* How to declare allocate_stack. */ # define ALLOCATE_STACK_PARMS void **stack /* This is how the function is called. We do it this way to allow other variants of the function to have more parameters. */ # define ALLOCATE_STACK(attr, pd) allocate_stack (attr, pd, &stackaddr) #else /* We need two stacks. The kernel will place them but we have to tell the kernel about the size of the reserved address space. */ # define STACK_VARIABLES void *stackaddr = NULL; size_t stacksize = 0 /* How to pass the values to the 'create_thread' function. */ # define STACK_VARIABLES_ARGS stackaddr, stacksize /* How to declare function which gets there parameters. */ # define STACK_VARIABLES_PARMS void *stackaddr, size_t stacksize /* How to declare allocate_stack. */ # define ALLOCATE_STACK_PARMS void **stack, size_t *stacksize /* This is how the function is called. We do it this way to allow other variants of the function to have more parameters. */ # define ALLOCATE_STACK(attr, pd) \ allocate_stack (attr, pd, &stackaddr, &stacksize) #endif /* Default alignment of stack. */ #ifndef STACK_ALIGN # define STACK_ALIGN __alignof__ (long double) #endif /* Default value for minimal stack size after allocating thread descriptor and guard. */ #ifndef MINIMAL_REST_STACK # define MINIMAL_REST_STACK 4096 #endif /* Newer kernels have the MAP_STACK flag to indicate a mapping is used for a stack. Use it when possible. */ #ifndef MAP_STACK # define MAP_STACK 0 #endif /* This yields the pointer that TLS support code calls the thread pointer. */ #if TLS_TCB_AT_TP # define TLS_TPADJ(pd) (pd) #elif TLS_DTV_AT_TP # define TLS_TPADJ(pd) ((struct pthread *)((char *) (pd) + TLS_PRE_TCB_SIZE)) #endif /* Cache handling for not-yet free stacks. */ /* Maximum size in kB of cache. */ static size_t stack_cache_maxsize = 40 * 1024 * 1024; /* 40MiBi by default. */ static size_t stack_cache_actsize; /* Mutex protecting this variable. */ static int stack_cache_lock = LLL_LOCK_INITIALIZER; /* List of queued stack frames. */ static LIST_HEAD (stack_cache); /* List of the stacks in use. */ static LIST_HEAD (stack_used); /* We need to record what list operations we are going to do so that, in case of an asynchronous interruption due to a fork() call, we can correct for the work. */ static uintptr_t in_flight_stack; /* List of the threads with user provided stacks in use. No need to initialize this, since it's done in __pthread_initialize_minimal. */ list_t __stack_user __attribute__ ((nocommon)); hidden_data_def (__stack_user) /* Check whether the stack is still used or not. */ #define FREE_P(descr) ((descr)->tid <= 0) static void stack_list_del (list_t *elem) { in_flight_stack = (uintptr_t) elem; atomic_write_barrier (); list_del (elem); atomic_write_barrier (); in_flight_stack = 0; } static void stack_list_add (list_t *elem, list_t *list) { in_flight_stack = (uintptr_t) elem | 1; atomic_write_barrier (); list_add (elem, list); atomic_write_barrier (); in_flight_stack = 0; } /* We create a double linked list of all cache entries. Double linked because this allows removing entries from the end. */ /* Get a stack frame from the cache. We have to match by size since some blocks might be too small or far too large. */ static struct pthread * get_cached_stack (size_t *sizep, void **memp) { size_t size = *sizep; struct pthread *result = NULL; list_t *entry; lll_lock (stack_cache_lock, LLL_PRIVATE); /* Search the cache for a matching entry. We search for the smallest stack which has at least the required size. Note that in normal situations the size of all allocated stacks is the same. As the very least there are only a few different sizes. Therefore this loop will exit early most of the time with an exact match. */ list_for_each (entry, &stack_cache) { struct pthread *curr; curr = list_entry (entry, struct pthread, list); if (FREE_P (curr) && curr->stackblock_size >= size) { if (curr->stackblock_size == size) { result = curr; break; } if (result == NULL || result->stackblock_size > curr->stackblock_size) result = curr; } } if (__builtin_expect (result == NULL, 0) /* Make sure the size difference is not too excessive. In that case we do not use the block. */ || __builtin_expect (result->stackblock_size > 4 * size, 0)) { /* Release the lock. */ lll_unlock (stack_cache_lock, LLL_PRIVATE); return NULL; } /* Don't allow setxid until cloned. */ result->setxid_futex = -1; /* Dequeue the entry. */ stack_list_del (&result->list); /* And add to the list of stacks in use. */ stack_list_add (&result->list, &stack_used); /* And decrease the cache size. */ stack_cache_actsize -= result->stackblock_size; /* Release the lock early. */ lll_unlock (stack_cache_lock, LLL_PRIVATE); /* Report size and location of the stack to the caller. */ *sizep = result->stackblock_size; *memp = result->stackblock; /* Cancellation handling is back to the default. */ result->cancelhandling = 0; result->cleanup = NULL; /* No pending event. */ result->nextevent = NULL; /* Clear the DTV. */ dtv_t *dtv = GET_DTV (TLS_TPADJ (result)); _dl_clear_dtv (dtv); /* Re-initialize the TLS. */ _dl_allocate_tls_init (TLS_TPADJ (result)); return result; } /* Free stacks until cache size is lower than LIMIT. */ void __free_stacks (size_t limit) { /* We reduce the size of the cache. Remove the last entries until the size is below the limit. */ list_t *entry; list_t *prev; /* Search from the end of the list. */ list_for_each_prev_safe (entry, prev, &stack_cache) { struct pthread *curr; curr = list_entry (entry, struct pthread, list); if (FREE_P (curr)) { /* Unlink the block. */ stack_list_del (entry); /* Account for the freed memory. */ stack_cache_actsize -= curr->stackblock_size; /* Free the memory associated with the ELF TLS. */ _dl_deallocate_tls (TLS_TPADJ (curr), false); /* Remove this block. This should never fail. If it does something is really wrong. */ if (munmap (curr->stackblock, curr->stackblock_size) != 0) abort (); /* Maybe we have freed enough. */ if (stack_cache_actsize <= limit) break; } } } /* Add a stack frame which is not used anymore to the stack. Must be called with the cache lock held. */ static inline void __attribute ((always_inline)) queue_stack (struct pthread *stack) { /* We unconditionally add the stack to the list. The memory may still be in use but it will not be reused until the kernel marks the stack as not used anymore. */ stack_list_add (&stack->list, &stack_cache); stack_cache_actsize += stack->stackblock_size; if (__glibc_unlikely (stack_cache_actsize > stack_cache_maxsize)) __free_stacks (stack_cache_maxsize); } static int change_stack_perm (struct pthread *pd #ifdef NEED_SEPARATE_REGISTER_STACK , size_t pagemask #endif ) { #ifdef NEED_SEPARATE_REGISTER_STACK void *stack = (pd->stackblock + (((((pd->stackblock_size - pd->guardsize) / 2) & pagemask) + pd->guardsize) & pagemask)); size_t len = pd->stackblock + pd->stackblock_size - stack; #elif _STACK_GROWS_DOWN void *stack = pd->stackblock + pd->guardsize; size_t len = pd->stackblock_size - pd->guardsize; #elif _STACK_GROWS_UP void *stack = pd->stackblock; size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock; #else # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP" #endif if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0) return errno; return 0; } /* Return the guard page position on allocated stack. */ static inline char * __attribute ((always_inline)) guard_position (void *mem, size_t size, size_t guardsize, struct pthread *pd, size_t pagesize_m1) { #ifdef NEED_SEPARATE_REGISTER_STACK return mem + (((size - guardsize) / 2) & ~pagesize_m1); #elif _STACK_GROWS_DOWN return mem; #elif _STACK_GROWS_UP return (char *) (((uintptr_t) pd - guardsize) & ~pagesize_m1); #endif } /* Based on stack allocated with PROT_NONE, setup the required portions with 'prot' flags based on the guard page position. */ static inline int setup_stack_prot (char *mem, size_t size, char *guard, size_t guardsize, const int prot) { char *guardend = guard + guardsize; #if _STACK_GROWS_DOWN && !defined(NEED_SEPARATE_REGISTER_STACK) /* As defined at guard_position, for architectures with downward stack the guard page is always at start of the allocated area. */ if (__mprotect (guardend, size - guardsize, prot) != 0) return errno; #else size_t mprots1 = (uintptr_t) guard - (uintptr_t) mem; if (__mprotect (mem, mprots1, prot) != 0) return errno; size_t mprots2 = ((uintptr_t) mem + size) - (uintptr_t) guardend; if (__mprotect (guardend, mprots2, prot) != 0) return errno; #endif return 0; } /* Mark the memory of the stack as usable to the kernel. It frees everything except for the space used for the TCB itself. */ static inline void __always_inline advise_stack_range (void *mem, size_t size, uintptr_t pd, size_t guardsize) { uintptr_t sp = (uintptr_t) CURRENT_STACK_FRAME; size_t pagesize_m1 = __getpagesize () - 1; #if _STACK_GROWS_DOWN && !defined(NEED_SEPARATE_REGISTER_STACK) size_t freesize = (sp - (uintptr_t) mem) & ~pagesize_m1; assert (freesize < size); if (freesize > PTHREAD_STACK_MIN) __madvise (mem, freesize - PTHREAD_STACK_MIN, MADV_DONTNEED); #else /* Page aligned start of memory to free (higher than or equal to current sp plus the minimum stack size). */ uintptr_t freeblock = (sp + PTHREAD_STACK_MIN + pagesize_m1) & ~pagesize_m1; uintptr_t free_end = (pd - guardsize) & ~pagesize_m1; if (free_end > freeblock) { size_t freesize = free_end - freeblock; assert (freesize < size); __madvise ((void*) freeblock, freesize, MADV_DONTNEED); } #endif } /* Returns a usable stack for a new thread either by allocating a new stack or reusing a cached stack of sufficient size. ATTR must be non-NULL and point to a valid pthread_attr. PDP must be non-NULL. */ static int allocate_stack (const struct pthread_attr *attr, struct pthread **pdp, ALLOCATE_STACK_PARMS) { struct pthread *pd; size_t size; size_t pagesize_m1 = __getpagesize () - 1; assert (powerof2 (pagesize_m1 + 1)); assert (TCB_ALIGNMENT >= STACK_ALIGN); /* Get the stack size from the attribute if it is set. Otherwise we use the default we determined at start time. */ if (attr->stacksize != 0) size = attr->stacksize; else { lll_lock (__default_pthread_attr_lock, LLL_PRIVATE); size = __default_pthread_attr.stacksize; lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE); } /* Get memory for the stack. */ if (__glibc_unlikely (attr->flags & ATTR_FLAG_STACKADDR)) { uintptr_t adj; char *stackaddr = (char *) attr->stackaddr; /* Assume the same layout as the _STACK_GROWS_DOWN case, with struct pthread at the top of the stack block. Later we adjust the guard location and stack address to match the _STACK_GROWS_UP case. */ if (_STACK_GROWS_UP) stackaddr += attr->stacksize; /* If the user also specified the size of the stack make sure it is large enough. */ if (attr->stacksize != 0 && attr->stacksize < (__static_tls_size + MINIMAL_REST_STACK)) return EINVAL; /* Adjust stack size for alignment of the TLS block. */ #if TLS_TCB_AT_TP adj = ((uintptr_t) stackaddr - TLS_TCB_SIZE) & __static_tls_align_m1; assert (size > adj + TLS_TCB_SIZE); #elif TLS_DTV_AT_TP adj = ((uintptr_t) stackaddr - __static_tls_size) & __static_tls_align_m1; assert (size > adj); #endif /* The user provided some memory. Let's hope it matches the size... We do not allocate guard pages if the user provided the stack. It is the user's responsibility to do this if it is wanted. */ #if TLS_TCB_AT_TP pd = (struct pthread *) ((uintptr_t) stackaddr - TLS_TCB_SIZE - adj); #elif TLS_DTV_AT_TP pd = (struct pthread *) (((uintptr_t) stackaddr - __static_tls_size - adj) - TLS_PRE_TCB_SIZE); #endif /* The user provided stack memory needs to be cleared. */ memset (pd, '\0', sizeof (struct pthread)); /* The first TSD block is included in the TCB. */ pd->specific[0] = pd->specific_1stblock; /* Remember the stack-related values. */ pd->stackblock = (char *) stackaddr - size; pd->stackblock_size = size; /* This is a user-provided stack. It will not be queued in the stack cache nor will the memory (except the TLS memory) be freed. */ pd->user_stack = true; /* This is at least the second thread. */ pd->header.multiple_threads = 1; #ifndef TLS_MULTIPLE_THREADS_IN_TCB __pthread_multiple_threads = *__libc_multiple_threads_ptr = 1; #endif #ifndef __ASSUME_PRIVATE_FUTEX /* The thread must know when private futexes are supported. */ pd->header.private_futex = THREAD_GETMEM (THREAD_SELF, header.private_futex); #endif #ifdef NEED_DL_SYSINFO SETUP_THREAD_SYSINFO (pd); #endif /* Don't allow setxid until cloned. */ pd->setxid_futex = -1; /* Allocate the DTV for this thread. */ if (_dl_allocate_tls (TLS_TPADJ (pd)) == NULL) { /* Something went wrong. */ assert (errno == ENOMEM); return errno; } /* Prepare to modify global data. */ lll_lock (stack_cache_lock, LLL_PRIVATE); /* And add to the list of stacks in use. */ list_add (&pd->list, &__stack_user); lll_unlock (stack_cache_lock, LLL_PRIVATE); } else { /* Allocate some anonymous memory. If possible use the cache. */ size_t guardsize; size_t reqsize; void *mem; const int prot = (PROT_READ | PROT_WRITE | ((GL(dl_stack_flags) & PF_X) ? PROT_EXEC : 0)); /* Adjust the stack size for alignment. */ size &= ~__static_tls_align_m1; assert (size != 0); /* Make sure the size of the stack is enough for the guard and eventually the thread descriptor. */ guardsize = (attr->guardsize + pagesize_m1) & ~pagesize_m1; if (guardsize < attr->guardsize || size + guardsize < guardsize) /* Arithmetic overflow. */ return EINVAL; size += guardsize; if (__builtin_expect (size < ((guardsize + __static_tls_size + MINIMAL_REST_STACK + pagesize_m1) & ~pagesize_m1), 0)) /* The stack is too small (or the guard too large). */ return EINVAL; /* Try to get a stack from the cache. */ reqsize = size; pd = get_cached_stack (&size, &mem); if (pd == NULL) { /* To avoid aliasing effects on a larger scale than pages we adjust the allocated stack size if necessary. This way allocations directly following each other will not have aliasing problems. */ #if MULTI_PAGE_ALIASING != 0 if ((size % MULTI_PAGE_ALIASING) == 0) size += pagesize_m1 + 1; #endif /* If a guard page is required, avoid committing memory by first allocate with PROT_NONE and then reserve with required permission excluding the guard page. */ mem = mmap (NULL, size, (guardsize == 0) ? prot : PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0); if (__glibc_unlikely (mem == MAP_FAILED)) return errno; /* SIZE is guaranteed to be greater than zero. So we can never get a null pointer back from mmap. */ assert (mem != NULL); /* Place the thread descriptor at the end of the stack. */ #if TLS_TCB_AT_TP pd = (struct pthread *) ((char *) mem + size) - 1; #elif TLS_DTV_AT_TP pd = (struct pthread *) ((((uintptr_t) mem + size - __static_tls_size) & ~__static_tls_align_m1) - TLS_PRE_TCB_SIZE); #endif /* Now mprotect the required region excluding the guard area. */ if (__glibc_likely (guardsize > 0)) { char *guard = guard_position (mem, size, guardsize, pd, pagesize_m1); if (setup_stack_prot (mem, size, guard, guardsize, prot) != 0) { munmap (mem, size); return errno; } } /* Remember the stack-related values. */ pd->stackblock = mem; pd->stackblock_size = size; /* Update guardsize for newly allocated guardsize to avoid an mprotect in guard resize below. */ pd->guardsize = guardsize; /* We allocated the first block thread-specific data array. This address will not change for the lifetime of this descriptor. */ pd->specific[0] = pd->specific_1stblock; /* This is at least the second thread. */ pd->header.multiple_threads = 1; #ifndef TLS_MULTIPLE_THREADS_IN_TCB __pthread_multiple_threads = *__libc_multiple_threads_ptr = 1; #endif #ifndef __ASSUME_PRIVATE_FUTEX /* The thread must know when private futexes are supported. */ pd->header.private_futex = THREAD_GETMEM (THREAD_SELF, header.private_futex); #endif #ifdef NEED_DL_SYSINFO SETUP_THREAD_SYSINFO (pd); #endif /* Don't allow setxid until cloned. */ pd->setxid_futex = -1; /* Allocate the DTV for this thread. */ if (_dl_allocate_tls (TLS_TPADJ (pd)) == NULL) { /* Something went wrong. */ assert (errno == ENOMEM); /* Free the stack memory we just allocated. */ (void) munmap (mem, size); return errno; } /* Prepare to modify global data. */ lll_lock (stack_cache_lock, LLL_PRIVATE); /* And add to the list of stacks in use. */ stack_list_add (&pd->list, &stack_used); lll_unlock (stack_cache_lock, LLL_PRIVATE); /* There might have been a race. Another thread might have caused the stacks to get exec permission while this new stack was prepared. Detect if this was possible and change the permission if necessary. */ if (__builtin_expect ((GL(dl_stack_flags) & PF_X) != 0 && (prot & PROT_EXEC) == 0, 0)) { int err = change_stack_perm (pd #ifdef NEED_SEPARATE_REGISTER_STACK , ~pagesize_m1 #endif ); if (err != 0) { /* Free the stack memory we just allocated. */ (void) __munmap (mem, size); return err; } } /* Note that all of the stack and the thread descriptor is zeroed. This means we do not have to initialize fields with initial value zero. This is specifically true for the 'tid' field which is always set back to zero once the stack is not used anymore and for the 'guardsize' field which will be read next. */ } /* Create or resize the guard area if necessary. */ if (__glibc_unlikely (guardsize > pd->guardsize)) { char *guard = guard_position (mem, size, guardsize, pd, pagesize_m1); if (__mprotect (guard, guardsize, PROT_NONE) != 0) { mprot_error: lll_lock (stack_cache_lock, LLL_PRIVATE); /* Remove the thread from the list. */ stack_list_del (&pd->list); lll_unlock (stack_cache_lock, LLL_PRIVATE); /* Get rid of the TLS block we allocated. */ _dl_deallocate_tls (TLS_TPADJ (pd), false); /* Free the stack memory regardless of whether the size of the cache is over the limit or not. If this piece of memory caused problems we better do not use it anymore. Uh, and we ignore possible errors. There is nothing we could do. */ (void) __munmap (mem, size); return errno; } pd->guardsize = guardsize; } else if (__builtin_expect (pd->guardsize - guardsize > size - reqsize, 0)) { /* The old guard area is too large. */ #ifdef NEED_SEPARATE_REGISTER_STACK char *guard = mem + (((size - guardsize) / 2) & ~pagesize_m1); char *oldguard = mem + (((size - pd->guardsize) / 2) & ~pagesize_m1); if (oldguard < guard && __mprotect (oldguard, guard - oldguard, prot) != 0) goto mprot_error; if (__mprotect (guard + guardsize, oldguard + pd->guardsize - guard - guardsize, prot) != 0) goto mprot_error; #elif _STACK_GROWS_DOWN if (__mprotect ((char *) mem + guardsize, pd->guardsize - guardsize, prot) != 0) goto mprot_error; #elif _STACK_GROWS_UP char *new_guard = (char *)(((uintptr_t) pd - guardsize) & ~pagesize_m1); char *old_guard = (char *)(((uintptr_t) pd - pd->guardsize) & ~pagesize_m1); /* The guard size difference might be > 0, but once rounded to the nearest page the size difference might be zero. */ if (new_guard > old_guard && mprotect (old_guard, new_guard - old_guard, prot) != 0) goto mprot_error; #endif pd->guardsize = guardsize; } /* The pthread_getattr_np() calls need to get passed the size requested in the attribute, regardless of how large the actually used guardsize is. */ pd->reported_guardsize = guardsize; } /* Initialize the lock. We have to do this unconditionally since the stillborn thread could be canceled while the lock is taken. */ pd->lock = LLL_LOCK_INITIALIZER; /* The robust mutex lists also need to be initialized unconditionally because the cleanup for the previous stack owner might have happened in the kernel. */ pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock) - offsetof (pthread_mutex_t, __data.__list.__next)); pd->robust_head.list_op_pending = NULL; #if __PTHREAD_MUTEX_HAVE_PREV pd->robust_prev = &pd->robust_head; #endif pd->robust_head.list = &pd->robust_head; /* We place the thread descriptor at the end of the stack. */ *pdp = pd; #if _STACK_GROWS_DOWN void *stacktop; # if TLS_TCB_AT_TP /* The stack begins before the TCB and the static TLS block. */ stacktop = ((char *) (pd + 1) - __static_tls_size); # elif TLS_DTV_AT_TP stacktop = (char *) (pd - 1); # endif # ifdef NEED_SEPARATE_REGISTER_STACK *stack = pd->stackblock; *stacksize = stacktop - *stack; # else *stack = stacktop; # endif #else *stack = pd->stackblock; #endif return 0; } void __deallocate_stack (struct pthread *pd) { lll_lock (stack_cache_lock, LLL_PRIVATE); /* Remove the thread from the list of threads with user defined stacks. */ stack_list_del (&pd->list); /* Not much to do. Just free the mmap()ed memory. Note that we do not reset the 'used' flag in the 'tid' field. This is done by the kernel. If no thread has been created yet this field is still zero. */ if (__glibc_likely (! pd->user_stack)) (void) queue_stack (pd); else /* Free the memory associated with the ELF TLS. */ _dl_deallocate_tls (TLS_TPADJ (pd), false); lll_unlock (stack_cache_lock, LLL_PRIVATE); } int __make_stacks_executable (void **stack_endp) { /* First the main thread's stack. */ int err = _dl_make_stack_executable (stack_endp); if (err != 0) return err; #ifdef NEED_SEPARATE_REGISTER_STACK const size_t pagemask = ~(__getpagesize () - 1); #endif lll_lock (stack_cache_lock, LLL_PRIVATE); list_t *runp; list_for_each (runp, &stack_used) { err = change_stack_perm (list_entry (runp, struct pthread, list) #ifdef NEED_SEPARATE_REGISTER_STACK , pagemask #endif ); if (err != 0) break; } /* Also change the permission for the currently unused stacks. This might be wasted time but better spend it here than adding a check in the fast path. */ if (err == 0) list_for_each (runp, &stack_cache) { err = change_stack_perm (list_entry (runp, struct pthread, list) #ifdef NEED_SEPARATE_REGISTER_STACK , pagemask #endif ); if (err != 0) break; } lll_unlock (stack_cache_lock, LLL_PRIVATE); return err; } /* In case of a fork() call the memory allocation in the child will be the same but only one thread is running. All stacks except that of the one running thread are not used anymore. We have to recycle them. */ void __reclaim_stacks (void) { struct pthread *self = (struct pthread *) THREAD_SELF; /* No locking necessary. The caller is the only stack in use. But we have to be aware that we might have interrupted a list operation. */ if (in_flight_stack != 0) { bool add_p = in_flight_stack & 1; list_t *elem = (list_t *) (in_flight_stack & ~(uintptr_t) 1); if (add_p) { /* We always add at the beginning of the list. So in this case we only need to check the beginning of these lists to see if the pointers at the head of the list are inconsistent. */ list_t *l = NULL; if (stack_used.next->prev != &stack_used) l = &stack_used; else if (stack_cache.next->prev != &stack_cache) l = &stack_cache; if (l != NULL) { assert (l->next->prev == elem); elem->next = l->next; elem->prev = l; l->next = elem; } } else { /* We can simply always replay the delete operation. */ elem->next->prev = elem->prev; elem->prev->next = elem->next; } } /* Mark all stacks except the still running one as free. */ list_t *runp; list_for_each (runp, &stack_used) { struct pthread *curp = list_entry (runp, struct pthread, list); if (curp != self) { /* This marks the stack as free. */ curp->tid = 0; /* Account for the size of the stack. */ stack_cache_actsize += curp->stackblock_size; if (curp->specific_used) { /* Clear the thread-specific data. */ memset (curp->specific_1stblock, '\0', sizeof (curp->specific_1stblock)); curp->specific_used = false; for (size_t cnt = 1; cnt < PTHREAD_KEY_1STLEVEL_SIZE; ++cnt) if (curp->specific[cnt] != NULL) { memset (curp->specific[cnt], '\0', sizeof (curp->specific_1stblock)); /* We have allocated the block which we do not free here so re-set the bit. */ curp->specific_used = true; } } } } /* Add the stack of all running threads to the cache. */ list_splice (&stack_used, &stack_cache); /* Remove the entry for the current thread to from the cache list and add it to the list of running threads. Which of the two lists is decided by the user_stack flag. */ stack_list_del (&self->list); /* Re-initialize the lists for all the threads. */ INIT_LIST_HEAD (&stack_used); INIT_LIST_HEAD (&__stack_user); if (__glibc_unlikely (THREAD_GETMEM (self, user_stack))) list_add (&self->list, &__stack_user); else list_add (&self->list, &stack_used); /* There is one thread running. */ __nptl_nthreads = 1; in_flight_stack = 0; /* Initialize locks. */ stack_cache_lock = LLL_LOCK_INITIALIZER; __default_pthread_attr_lock = LLL_LOCK_INITIALIZER; } #if HP_TIMING_AVAIL # undef __find_thread_by_id /* Find a thread given the thread ID. */ attribute_hidden struct pthread * __find_thread_by_id (pid_t tid) { struct pthread *result = NULL; lll_lock (stack_cache_lock, LLL_PRIVATE); /* Iterate over the list with system-allocated threads first. */ list_t *runp; list_for_each (runp, &stack_used) { struct pthread *curp; curp = list_entry (runp, struct pthread, list); if (curp->tid == tid) { result = curp; goto out; } } /* Now the list with threads using user-allocated stacks. */ list_for_each (runp, &__stack_user) { struct pthread *curp; curp = list_entry (runp, struct pthread, list); if (curp->tid == tid) { result = curp; goto out; } } out: lll_unlock (stack_cache_lock, LLL_PRIVATE); return result; } #endif #ifdef SIGSETXID static void setxid_mark_thread (struct xid_command *cmdp, struct pthread *t) { int ch; /* Wait until this thread is cloned. */ if (t->setxid_futex == -1 && ! atomic_compare_and_exchange_bool_acq (&t->setxid_futex, -2, -1)) do futex_wait_simple (&t->setxid_futex, -2, FUTEX_PRIVATE); while (t->setxid_futex == -2); /* Don't let the thread exit before the setxid handler runs. */ t->setxid_futex = 0; do { ch = t->cancelhandling; /* If the thread is exiting right now, ignore it. */ if ((ch & EXITING_BITMASK) != 0) { /* Release the futex if there is no other setxid in progress. */ if ((ch & SETXID_BITMASK) == 0) { t->setxid_futex = 1; futex_wake (&t->setxid_futex, 1, FUTEX_PRIVATE); } return; } } while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling, ch | SETXID_BITMASK, ch)); } static void setxid_unmark_thread (struct xid_command *cmdp, struct pthread *t) { int ch; do { ch = t->cancelhandling; if ((ch & SETXID_BITMASK) == 0) return; } while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling, ch & ~SETXID_BITMASK, ch)); /* Release the futex just in case. */ t->setxid_futex = 1; futex_wake (&t->setxid_futex, 1, FUTEX_PRIVATE); } static int setxid_signal_thread (struct xid_command *cmdp, struct pthread *t) { if ((t->cancelhandling & SETXID_BITMASK) == 0) return 0; int val; pid_t pid = __getpid (); INTERNAL_SYSCALL_DECL (err); val = INTERNAL_SYSCALL_CALL (tgkill, err, pid, t->tid, SIGSETXID); /* If this failed, it must have had not started yet or else exited. */ if (!INTERNAL_SYSCALL_ERROR_P (val, err)) { atomic_increment (&cmdp->cntr); return 1; } else return 0; } /* Check for consistency across set*id system call results. The abort should not happen as long as all privileges changes happen through the glibc wrappers. ERROR must be 0 (no error) or an errno code. */ void attribute_hidden __nptl_setxid_error (struct xid_command *cmdp, int error) { do { int olderror = cmdp->error; if (olderror == error) break; if (olderror != -1) { /* Mismatch between current and previous results. Save the error value to memory so that is not clobbered by the abort function and preserved in coredumps. */ volatile int xid_err __attribute__((unused)) = error; abort (); } } while (atomic_compare_and_exchange_bool_acq (&cmdp->error, error, -1)); } int attribute_hidden __nptl_setxid (struct xid_command *cmdp) { int signalled; int result; lll_lock (stack_cache_lock, LLL_PRIVATE); __xidcmd = cmdp; cmdp->cntr = 0; cmdp->error = -1; struct pthread *self = THREAD_SELF; /* Iterate over the list with system-allocated threads first. */ list_t *runp; list_for_each (runp, &stack_used) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self) continue; setxid_mark_thread (cmdp, t); } /* Now the list with threads using user-allocated stacks. */ list_for_each (runp, &__stack_user) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self) continue; setxid_mark_thread (cmdp, t); } /* Iterate until we don't succeed in signalling anyone. That means we have gotten all running threads, and their children will be automatically correct once started. */ do { signalled = 0; list_for_each (runp, &stack_used) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self) continue; signalled += setxid_signal_thread (cmdp, t); } list_for_each (runp, &__stack_user) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self) continue; signalled += setxid_signal_thread (cmdp, t); } int cur = cmdp->cntr; while (cur != 0) { futex_wait_simple ((unsigned int *) &cmdp->cntr, cur, FUTEX_PRIVATE); cur = cmdp->cntr; } } while (signalled != 0); /* Clean up flags, so that no thread blocks during exit waiting for a signal which will never come. */ list_for_each (runp, &stack_used) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self) continue; setxid_unmark_thread (cmdp, t); } list_for_each (runp, &__stack_user) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self) continue; setxid_unmark_thread (cmdp, t); } /* This must be last, otherwise the current thread might not have permissions to send SIGSETXID syscall to the other threads. */ INTERNAL_SYSCALL_DECL (err); result = INTERNAL_SYSCALL_NCS (cmdp->syscall_no, err, 3, cmdp->id[0], cmdp->id[1], cmdp->id[2]); int error = 0; if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err))) { error = INTERNAL_SYSCALL_ERRNO (result, err); __set_errno (error); result = -1; } __nptl_setxid_error (cmdp, error); lll_unlock (stack_cache_lock, LLL_PRIVATE); return result; } #endif /* SIGSETXID. */ static inline void __attribute__((always_inline)) init_one_static_tls (struct pthread *curp, struct link_map *map) { dtv_t *dtv = GET_DTV (TLS_TPADJ (curp)); # if TLS_TCB_AT_TP void *dest = (char *) curp - map->l_tls_offset; # elif TLS_DTV_AT_TP void *dest = (char *) curp + map->l_tls_offset + TLS_PRE_TCB_SIZE; # else # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined" # endif /* Initialize the memory. */ memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size), '\0', map->l_tls_blocksize - map->l_tls_initimage_size); /* Pairs against the read barrier in tls_get_attr_tail, guaranteeing any thread waiting for an update to pointer.val sees the initimage write. */ atomic_write_barrier (); dtv[map->l_tls_modid].pointer.val = dest; } void attribute_hidden __pthread_init_static_tls (struct link_map *map) { lll_lock (stack_cache_lock, LLL_PRIVATE); /* Iterate over the list with system-allocated threads first. */ list_t *runp; list_for_each (runp, &stack_used) init_one_static_tls (list_entry (runp, struct pthread, list), map); /* Now the list with threads using user-allocated stacks. */ list_for_each (runp, &__stack_user) init_one_static_tls (list_entry (runp, struct pthread, list), map); lll_unlock (stack_cache_lock, LLL_PRIVATE); } void attribute_hidden __wait_lookup_done (void) { lll_lock (stack_cache_lock, LLL_PRIVATE); struct pthread *self = THREAD_SELF; /* Iterate over the list with system-allocated threads first. */ list_t *runp; list_for_each (runp, &stack_used) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED) continue; int *const gscope_flagp = &t->header.gscope_flag; /* We have to wait until this thread is done with the global scope. First tell the thread that we are waiting and possibly have to be woken. */ if (atomic_compare_and_exchange_bool_acq (gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, THREAD_GSCOPE_FLAG_USED)) continue; do futex_wait_simple ((unsigned int *) gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE); while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT); } /* Now the list with threads using user-allocated stacks. */ list_for_each (runp, &__stack_user) { struct pthread *t = list_entry (runp, struct pthread, list); if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED) continue; int *const gscope_flagp = &t->header.gscope_flag; /* We have to wait until this thread is done with the global scope. First tell the thread that we are waiting and possibly have to be woken. */ if (atomic_compare_and_exchange_bool_acq (gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, THREAD_GSCOPE_FLAG_USED)) continue; do futex_wait_simple ((unsigned int *) gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE); while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT); } lll_unlock (stack_cache_lock, LLL_PRIVATE); }