/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 2001 Daniel Eischen <deischen@freebsd.org> * Copyright (c) 2000-2001 Jason Evans <jasone@freebsd.org> * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/param.h> #include <sys/auxv.h> #include <sys/mman.h> #include <sys/queue.h> #include <sys/resource.h> #include <sys/sysctl.h> #include <stdlib.h> #include <pthread.h> #include <link.h> #include "thr_private.h" /* Spare thread stack. */ struct stack { LIST_ENTRY(stack) qe; /* Stack queue linkage. */ size_t stacksize; /* Stack size (rounded up). */ size_t guardsize; /* Guard size. */ void *stackaddr; /* Stack address. */ }; /* * Default sized (stack and guard) spare stack queue. Stacks are cached * to avoid additional complexity managing mmap()ed stack regions. Spare * stacks are used in LIFO order to increase cache locality. */ static LIST_HEAD(, stack) dstackq = LIST_HEAD_INITIALIZER(dstackq); /* * Miscellaneous sized (non-default stack and/or guard) spare stack queue. * Stacks are cached to avoid additional complexity managing mmap()ed * stack regions. This list is unordered, since ordering on both stack * size and guard size would be more trouble than it's worth. Stacks are * allocated from this cache on a first size match basis. */ static LIST_HEAD(, stack) mstackq = LIST_HEAD_INITIALIZER(mstackq); /** * Base address of the last stack allocated (including its red zone, if * there is one). Stacks are allocated contiguously, starting beyond the * top of the main stack. When a new stack is created, a red zone is * typically created (actually, the red zone is mapped with PROT_NONE) above * the top of the stack, such that the stack will not be able to grow all * the way to the bottom of the next stack. This isn't fool-proof. It is * possible for a stack to grow by a large amount, such that it grows into * the next stack, and as long as the memory within the red zone is never * accessed, nothing will prevent one thread stack from trouncing all over * the next. * * low memory * . . . . . . . . . . . . . . . . . . * | | * | stack 3 | start of 3rd thread stack * +-----------------------------------+ * | | * | Red Zone (guard page) | red zone for 2nd thread * | | * +-----------------------------------+ * | stack 2 - _thr_stack_default | top of 2nd thread stack * | | * | | * | | * | | * | stack 2 | * +-----------------------------------+ <-- start of 2nd thread stack * | | * | Red Zone | red zone for 1st thread * | | * +-----------------------------------+ * | stack 1 - _thr_stack_default | top of 1st thread stack * | | * | | * | | * | | * | stack 1 | * +-----------------------------------+ <-- start of 1st thread stack * | | (initial value of last_stack) * | Red Zone | * | | red zone for main thread * +-----------------------------------+ * | USRSTACK - _thr_stack_initial | top of main thread stack * | | ^ * | | | * | | | * | | | stack growth * | | * +-----------------------------------+ <-- start of main thread stack * (USRSTACK) * high memory * */ static char *last_stack = NULL; /* * Round size up to the nearest multiple of * _thr_page_size. */ static inline size_t round_up(size_t size) { return (roundup2(size, _thr_page_size)); } void _thr_stack_fix_protection(struct pthread *thrd) { mprotect((char *)thrd->attr.stackaddr_attr + round_up(thrd->attr.guardsize_attr), round_up(thrd->attr.stacksize_attr), _rtld_get_stack_prot()); } static void singlethread_map_stacks_exec(void) { char *usrstack; size_t stacksz; if (!__thr_get_main_stack_base(&usrstack) || !__thr_get_main_stack_lim(&stacksz)) return; mprotect(usrstack - stacksz, stacksz, _rtld_get_stack_prot()); } void __thr_map_stacks_exec(void) { struct pthread *curthread, *thrd; struct stack *st; if (!_thr_is_inited()) { singlethread_map_stacks_exec(); return; } curthread = _get_curthread(); THREAD_LIST_RDLOCK(curthread); LIST_FOREACH(st, &mstackq, qe) mprotect((char *)st->stackaddr + st->guardsize, st->stacksize, _rtld_get_stack_prot()); LIST_FOREACH(st, &dstackq, qe) mprotect((char *)st->stackaddr + st->guardsize, st->stacksize, _rtld_get_stack_prot()); TAILQ_FOREACH(thrd, &_thread_gc_list, gcle) _thr_stack_fix_protection(thrd); TAILQ_FOREACH(thrd, &_thread_list, tle) _thr_stack_fix_protection(thrd); THREAD_LIST_UNLOCK(curthread); } int _thr_stack_alloc(struct pthread_attr *attr) { struct pthread *curthread = _get_curthread(); struct stack *spare_stack; size_t stacksize; size_t guardsize; char *stackaddr; /* * Round up stack size to nearest multiple of _thr_page_size so * that mmap() * will work. If the stack size is not an even * multiple, we end up initializing things such that there is * unused space above the beginning of the stack, so the stack * sits snugly against its guard. */ stacksize = round_up(attr->stacksize_attr); guardsize = round_up(attr->guardsize_attr); attr->stackaddr_attr = NULL; attr->flags &= ~THR_STACK_USER; /* * Use the garbage collector lock for synchronization of the * spare stack lists and allocations from usrstack. */ THREAD_LIST_WRLOCK(curthread); /* * If the stack and guard sizes are default, try to allocate a stack * from the default-size stack cache: */ if ((stacksize == THR_STACK_DEFAULT) && (guardsize == _thr_guard_default)) { if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) { /* Use the spare stack. */ LIST_REMOVE(spare_stack, qe); attr->stackaddr_attr = spare_stack->stackaddr; } } /* * The user specified a non-default stack and/or guard size, so try to * allocate a stack from the non-default size stack cache, using the * rounded up stack size (stack_size) in the search: */ else { LIST_FOREACH(spare_stack, &mstackq, qe) { if (spare_stack->stacksize == stacksize && spare_stack->guardsize == guardsize) { LIST_REMOVE(spare_stack, qe); attr->stackaddr_attr = spare_stack->stackaddr; break; } } } if (attr->stackaddr_attr != NULL) { /* A cached stack was found. Release the lock. */ THREAD_LIST_UNLOCK(curthread); } else { /* * Allocate a stack from or below usrstack, depending * on the LIBPTHREAD_BIGSTACK_MAIN env variable. */ if (last_stack == NULL) last_stack = _usrstack - _thr_stack_initial - _thr_guard_default; /* Allocate a new stack. */ stackaddr = last_stack - stacksize - guardsize; /* * Even if stack allocation fails, we don't want to try to * use this location again, so unconditionally decrement * last_stack. Under normal operating conditions, the most * likely reason for an mmap() error is a stack overflow of * the adjacent thread stack. */ last_stack -= (stacksize + guardsize); /* Release the lock before mmap'ing it. */ THREAD_LIST_UNLOCK(curthread); /* Map the stack and guard page together, and split guard page from allocated space: */ if ((stackaddr = mmap(stackaddr, stacksize + guardsize, _rtld_get_stack_prot(), MAP_STACK, -1, 0)) != MAP_FAILED && (guardsize == 0 || mprotect(stackaddr, guardsize, PROT_NONE) == 0)) { stackaddr += guardsize; } else { if (stackaddr != MAP_FAILED) munmap(stackaddr, stacksize + guardsize); stackaddr = NULL; } attr->stackaddr_attr = stackaddr; } if (attr->stackaddr_attr != NULL) return (0); else return (-1); } /* This function must be called with _thread_list_lock held. */ void _thr_stack_free(struct pthread_attr *attr) { struct stack *spare_stack; if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0) && (attr->stackaddr_attr != NULL)) { spare_stack = (struct stack *) ((char *)attr->stackaddr_attr + attr->stacksize_attr - sizeof(struct stack)); spare_stack->stacksize = round_up(attr->stacksize_attr); spare_stack->guardsize = round_up(attr->guardsize_attr); spare_stack->stackaddr = attr->stackaddr_attr; if (spare_stack->stacksize == THR_STACK_DEFAULT && spare_stack->guardsize == _thr_guard_default) { /* Default stack/guard size. */ LIST_INSERT_HEAD(&dstackq, spare_stack, qe); } else { /* Non-default stack/guard size. */ LIST_INSERT_HEAD(&mstackq, spare_stack, qe); } attr->stackaddr_attr = NULL; } }
