1 /* 2 * Copyright (c) 2001 Daniel Eischen <deischen@freebsd.org> 3 * Copyright (c) 2000-2001 Jason Evans <jasone@freebsd.org> 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 * $FreeBSD$ 28 */ 29 30 #include <sys/types.h> 31 #include <sys/mman.h> 32 #include <sys/queue.h> 33 #include <stdlib.h> 34 #include <pthread.h> 35 36 #include "thr_private.h" 37 38 /* Spare thread stack. */ 39 struct stack { 40 LIST_ENTRY(stack) qe; /* Stack queue linkage. */ 41 size_t stacksize; /* Stack size (rounded up). */ 42 size_t guardsize; /* Guard size. */ 43 void *stackaddr; /* Stack address. */ 44 }; 45 46 /* 47 * Default sized (stack and guard) spare stack queue. Stacks are cached 48 * to avoid additional complexity managing mmap()ed stack regions. Spare 49 * stacks are used in LIFO order to increase cache locality. 50 */ 51 static LIST_HEAD(, stack) dstackq = LIST_HEAD_INITIALIZER(dstackq); 52 53 /* 54 * Miscellaneous sized (non-default stack and/or guard) spare stack queue. 55 * Stacks are cached to avoid additional complexity managing mmap()ed 56 * stack regions. This list is unordered, since ordering on both stack 57 * size and guard size would be more trouble than it's worth. Stacks are 58 * allocated from this cache on a first size match basis. 59 */ 60 static LIST_HEAD(, stack) mstackq = LIST_HEAD_INITIALIZER(mstackq); 61 62 /** 63 * Base address of the last stack allocated (including its red zone, if 64 * there is one). Stacks are allocated contiguously, starting beyond the 65 * top of the main stack. When a new stack is created, a red zone is 66 * typically created (actually, the red zone is mapped with PROT_NONE) above 67 * the top of the stack, such that the stack will not be able to grow all 68 * the way to the bottom of the next stack. This isn't fool-proof. It is 69 * possible for a stack to grow by a large amount, such that it grows into 70 * the next stack, and as long as the memory within the red zone is never 71 * accessed, nothing will prevent one thread stack from trouncing all over 72 * the next. 73 * 74 * low memory 75 * . . . . . . . . . . . . . . . . . . 76 * | | 77 * | stack 3 | start of 3rd thread stack 78 * +-----------------------------------+ 79 * | | 80 * | Red Zone (guard page) | red zone for 2nd thread 81 * | | 82 * +-----------------------------------+ 83 * | stack 2 - _thr_stack_default | top of 2nd thread stack 84 * | | 85 * | | 86 * | | 87 * | | 88 * | stack 2 | 89 * +-----------------------------------+ <-- start of 2nd thread stack 90 * | | 91 * | Red Zone | red zone for 1st thread 92 * | | 93 * +-----------------------------------+ 94 * | stack 1 - _thr_stack_default | top of 1st thread stack 95 * | | 96 * | | 97 * | | 98 * | | 99 * | stack 1 | 100 * +-----------------------------------+ <-- start of 1st thread stack 101 * | | (initial value of last_stack) 102 * | Red Zone | 103 * | | red zone for main thread 104 * +-----------------------------------+ 105 * | USRSTACK - _thr_stack_initial | top of main thread stack 106 * | | ^ 107 * | | | 108 * | | | 109 * | | | stack growth 110 * | | 111 * +-----------------------------------+ <-- start of main thread stack 112 * (USRSTACK) 113 * high memory 114 * 115 */ 116 static char *last_stack = NULL; 117 118 /* 119 * Round size up to the nearest multiple of 120 * _thr_page_size. 121 */ 122 static inline size_t 123 round_up(size_t size) 124 { 125 if (size % _thr_page_size != 0) 126 size = ((size / _thr_page_size) + 1) * 127 _thr_page_size; 128 return size; 129 } 130 131 int 132 _thr_stack_alloc(struct pthread_attr *attr) 133 { 134 struct pthread *curthread = _get_curthread(); 135 struct stack *spare_stack; 136 size_t stacksize; 137 size_t guardsize; 138 char *stackaddr; 139 140 /* 141 * Round up stack size to nearest multiple of _thr_page_size so 142 * that mmap() * will work. If the stack size is not an even 143 * multiple, we end up initializing things such that there is 144 * unused space above the beginning of the stack, so the stack 145 * sits snugly against its guard. 146 */ 147 stacksize = round_up(attr->stacksize_attr); 148 guardsize = round_up(attr->guardsize_attr); 149 150 attr->stackaddr_attr = NULL; 151 attr->flags &= ~THR_STACK_USER; 152 153 /* 154 * Use the garbage collector lock for synchronization of the 155 * spare stack lists and allocations from usrstack. 156 */ 157 THREAD_LIST_WRLOCK(curthread); 158 /* 159 * If the stack and guard sizes are default, try to allocate a stack 160 * from the default-size stack cache: 161 */ 162 if ((stacksize == THR_STACK_DEFAULT) && 163 (guardsize == _thr_guard_default)) { 164 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) { 165 /* Use the spare stack. */ 166 LIST_REMOVE(spare_stack, qe); 167 attr->stackaddr_attr = spare_stack->stackaddr; 168 } 169 } 170 /* 171 * The user specified a non-default stack and/or guard size, so try to 172 * allocate a stack from the non-default size stack cache, using the 173 * rounded up stack size (stack_size) in the search: 174 */ 175 else { 176 LIST_FOREACH(spare_stack, &mstackq, qe) { 177 if (spare_stack->stacksize == stacksize && 178 spare_stack->guardsize == guardsize) { 179 LIST_REMOVE(spare_stack, qe); 180 attr->stackaddr_attr = spare_stack->stackaddr; 181 break; 182 } 183 } 184 } 185 if (attr->stackaddr_attr != NULL) { 186 /* A cached stack was found. Release the lock. */ 187 THREAD_LIST_UNLOCK(curthread); 188 } 189 else { 190 /* Allocate a stack from usrstack. */ 191 if (last_stack == NULL) 192 last_stack = _usrstack - _thr_stack_initial - 193 _thr_guard_default; 194 195 /* Allocate a new stack. */ 196 stackaddr = last_stack - stacksize - guardsize; 197 198 /* 199 * Even if stack allocation fails, we don't want to try to 200 * use this location again, so unconditionally decrement 201 * last_stack. Under normal operating conditions, the most 202 * likely reason for an mmap() error is a stack overflow of 203 * the adjacent thread stack. 204 */ 205 last_stack -= (stacksize + guardsize); 206 207 /* Release the lock before mmap'ing it. */ 208 THREAD_LIST_UNLOCK(curthread); 209 210 /* Map the stack and guard page together, and split guard 211 page from allocated space: */ 212 if ((stackaddr = mmap(stackaddr, stacksize+guardsize, 213 PROT_READ | PROT_WRITE, MAP_STACK, 214 -1, 0)) != MAP_FAILED && 215 (guardsize == 0 || 216 mprotect(stackaddr, guardsize, PROT_NONE) == 0)) { 217 stackaddr += guardsize; 218 } else { 219 if (stackaddr != MAP_FAILED) 220 munmap(stackaddr, stacksize + guardsize); 221 stackaddr = NULL; 222 } 223 attr->stackaddr_attr = stackaddr; 224 } 225 if (attr->stackaddr_attr != NULL) 226 return (0); 227 else 228 return (-1); 229 } 230 231 /* This function must be called with _thread_list_lock held. */ 232 void 233 _thr_stack_free(struct pthread_attr *attr) 234 { 235 struct stack *spare_stack; 236 237 if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0) 238 && (attr->stackaddr_attr != NULL)) { 239 spare_stack = (struct stack *) 240 ((char *)attr->stackaddr_attr + 241 attr->stacksize_attr - sizeof(struct stack)); 242 spare_stack->stacksize = round_up(attr->stacksize_attr); 243 spare_stack->guardsize = round_up(attr->guardsize_attr); 244 spare_stack->stackaddr = attr->stackaddr_attr; 245 246 if (spare_stack->stacksize == THR_STACK_DEFAULT && 247 spare_stack->guardsize == _thr_guard_default) { 248 /* Default stack/guard size. */ 249 LIST_INSERT_HEAD(&dstackq, spare_stack, qe); 250 } else { 251 /* Non-default stack/guard size. */ 252 LIST_INSERT_HEAD(&mstackq, spare_stack, qe); 253 } 254 attr->stackaddr_attr = NULL; 255 } 256 } 257