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 28 #include <sys/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include <sys/types.h> 32 #include <sys/mman.h> 33 #include <sys/queue.h> 34 #include <sys/resource.h> 35 #include <sys/sysctl.h> 36 #include <stdlib.h> 37 #include <pthread.h> 38 #include <link.h> 39 40 #include "thr_private.h" 41 42 /* Spare thread stack. */ 43 struct stack { 44 LIST_ENTRY(stack) qe; /* Stack queue linkage. */ 45 size_t stacksize; /* Stack size (rounded up). */ 46 size_t guardsize; /* Guard size. */ 47 void *stackaddr; /* Stack address. */ 48 }; 49 50 /* 51 * Default sized (stack and guard) spare stack queue. Stacks are cached 52 * to avoid additional complexity managing mmap()ed stack regions. Spare 53 * stacks are used in LIFO order to increase cache locality. 54 */ 55 static LIST_HEAD(, stack) dstackq = LIST_HEAD_INITIALIZER(dstackq); 56 57 /* 58 * Miscellaneous sized (non-default stack and/or guard) spare stack queue. 59 * Stacks are cached to avoid additional complexity managing mmap()ed 60 * stack regions. This list is unordered, since ordering on both stack 61 * size and guard size would be more trouble than it's worth. Stacks are 62 * allocated from this cache on a first size match basis. 63 */ 64 static LIST_HEAD(, stack) mstackq = LIST_HEAD_INITIALIZER(mstackq); 65 66 /** 67 * Base address of the last stack allocated (including its red zone, if 68 * there is one). Stacks are allocated contiguously, starting beyond the 69 * top of the main stack. When a new stack is created, a red zone is 70 * typically created (actually, the red zone is mapped with PROT_NONE) above 71 * the top of the stack, such that the stack will not be able to grow all 72 * the way to the bottom of the next stack. This isn't fool-proof. It is 73 * possible for a stack to grow by a large amount, such that it grows into 74 * the next stack, and as long as the memory within the red zone is never 75 * accessed, nothing will prevent one thread stack from trouncing all over 76 * the next. 77 * 78 * low memory 79 * . . . . . . . . . . . . . . . . . . 80 * | | 81 * | stack 3 | start of 3rd thread stack 82 * +-----------------------------------+ 83 * | | 84 * | Red Zone (guard page) | red zone for 2nd thread 85 * | | 86 * +-----------------------------------+ 87 * | stack 2 - _thr_stack_default | top of 2nd thread stack 88 * | | 89 * | | 90 * | | 91 * | | 92 * | stack 2 | 93 * +-----------------------------------+ <-- start of 2nd thread stack 94 * | | 95 * | Red Zone | red zone for 1st thread 96 * | | 97 * +-----------------------------------+ 98 * | stack 1 - _thr_stack_default | top of 1st thread stack 99 * | | 100 * | | 101 * | | 102 * | | 103 * | stack 1 | 104 * +-----------------------------------+ <-- start of 1st thread stack 105 * | | (initial value of last_stack) 106 * | Red Zone | 107 * | | red zone for main thread 108 * +-----------------------------------+ 109 * | USRSTACK - _thr_stack_initial | top of main thread stack 110 * | | ^ 111 * | | | 112 * | | | 113 * | | | stack growth 114 * | | 115 * +-----------------------------------+ <-- start of main thread stack 116 * (USRSTACK) 117 * high memory 118 * 119 */ 120 static char *last_stack = NULL; 121 122 /* 123 * Round size up to the nearest multiple of 124 * _thr_page_size. 125 */ 126 static inline size_t 127 round_up(size_t size) 128 { 129 if (size % _thr_page_size != 0) 130 size = ((size / _thr_page_size) + 1) * 131 _thr_page_size; 132 return size; 133 } 134 135 void 136 _thr_stack_fix_protection(struct pthread *thrd) 137 { 138 139 mprotect((char *)thrd->attr.stackaddr_attr + 140 round_up(thrd->attr.guardsize_attr), 141 round_up(thrd->attr.stacksize_attr), 142 _rtld_get_stack_prot()); 143 } 144 145 static void 146 singlethread_map_stacks_exec(void) 147 { 148 int mib[2]; 149 struct rlimit rlim; 150 u_long usrstack; 151 size_t len; 152 153 mib[0] = CTL_KERN; 154 mib[1] = KERN_USRSTACK; 155 len = sizeof(usrstack); 156 if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), &usrstack, &len, NULL, 0) 157 == -1) 158 return; 159 if (getrlimit(RLIMIT_STACK, &rlim) == -1) 160 return; 161 mprotect((void *)(uintptr_t)(usrstack - rlim.rlim_cur), 162 rlim.rlim_cur, _rtld_get_stack_prot()); 163 } 164 165 void 166 __thr_map_stacks_exec(void) 167 { 168 struct pthread *curthread, *thrd; 169 struct stack *st; 170 171 if (!_thr_is_inited()) { 172 singlethread_map_stacks_exec(); 173 return; 174 } 175 curthread = _get_curthread(); 176 THREAD_LIST_RDLOCK(curthread); 177 LIST_FOREACH(st, &mstackq, qe) 178 mprotect((char *)st->stackaddr + st->guardsize, st->stacksize, 179 _rtld_get_stack_prot()); 180 LIST_FOREACH(st, &dstackq, qe) 181 mprotect((char *)st->stackaddr + st->guardsize, st->stacksize, 182 _rtld_get_stack_prot()); 183 TAILQ_FOREACH(thrd, &_thread_gc_list, gcle) 184 _thr_stack_fix_protection(thrd); 185 TAILQ_FOREACH(thrd, &_thread_list, tle) 186 _thr_stack_fix_protection(thrd); 187 THREAD_LIST_UNLOCK(curthread); 188 } 189 190 int 191 _thr_stack_alloc(struct pthread_attr *attr) 192 { 193 struct pthread *curthread = _get_curthread(); 194 struct stack *spare_stack; 195 size_t stacksize; 196 size_t guardsize; 197 char *stackaddr; 198 199 /* 200 * Round up stack size to nearest multiple of _thr_page_size so 201 * that mmap() * will work. If the stack size is not an even 202 * multiple, we end up initializing things such that there is 203 * unused space above the beginning of the stack, so the stack 204 * sits snugly against its guard. 205 */ 206 stacksize = round_up(attr->stacksize_attr); 207 guardsize = round_up(attr->guardsize_attr); 208 209 attr->stackaddr_attr = NULL; 210 attr->flags &= ~THR_STACK_USER; 211 212 /* 213 * Use the garbage collector lock for synchronization of the 214 * spare stack lists and allocations from usrstack. 215 */ 216 THREAD_LIST_WRLOCK(curthread); 217 /* 218 * If the stack and guard sizes are default, try to allocate a stack 219 * from the default-size stack cache: 220 */ 221 if ((stacksize == THR_STACK_DEFAULT) && 222 (guardsize == _thr_guard_default)) { 223 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) { 224 /* Use the spare stack. */ 225 LIST_REMOVE(spare_stack, qe); 226 attr->stackaddr_attr = spare_stack->stackaddr; 227 } 228 } 229 /* 230 * The user specified a non-default stack and/or guard size, so try to 231 * allocate a stack from the non-default size stack cache, using the 232 * rounded up stack size (stack_size) in the search: 233 */ 234 else { 235 LIST_FOREACH(spare_stack, &mstackq, qe) { 236 if (spare_stack->stacksize == stacksize && 237 spare_stack->guardsize == guardsize) { 238 LIST_REMOVE(spare_stack, qe); 239 attr->stackaddr_attr = spare_stack->stackaddr; 240 break; 241 } 242 } 243 } 244 if (attr->stackaddr_attr != NULL) { 245 /* A cached stack was found. Release the lock. */ 246 THREAD_LIST_UNLOCK(curthread); 247 } 248 else { 249 /* 250 * Allocate a stack from or below usrstack, depending 251 * on the LIBPTHREAD_BIGSTACK_MAIN env variable. 252 */ 253 if (last_stack == NULL) 254 last_stack = _usrstack - _thr_stack_initial - 255 _thr_guard_default; 256 257 /* Allocate a new stack. */ 258 stackaddr = last_stack - stacksize - guardsize; 259 260 /* 261 * Even if stack allocation fails, we don't want to try to 262 * use this location again, so unconditionally decrement 263 * last_stack. Under normal operating conditions, the most 264 * likely reason for an mmap() error is a stack overflow of 265 * the adjacent thread stack. 266 */ 267 last_stack -= (stacksize + guardsize); 268 269 /* Release the lock before mmap'ing it. */ 270 THREAD_LIST_UNLOCK(curthread); 271 272 /* Map the stack and guard page together, and split guard 273 page from allocated space: */ 274 if ((stackaddr = mmap(stackaddr, stacksize + guardsize, 275 _rtld_get_stack_prot(), MAP_STACK, 276 -1, 0)) != MAP_FAILED && 277 (guardsize == 0 || 278 mprotect(stackaddr, guardsize, PROT_NONE) == 0)) { 279 stackaddr += guardsize; 280 } else { 281 if (stackaddr != MAP_FAILED) 282 munmap(stackaddr, stacksize + guardsize); 283 stackaddr = NULL; 284 } 285 attr->stackaddr_attr = stackaddr; 286 } 287 if (attr->stackaddr_attr != NULL) 288 return (0); 289 else 290 return (-1); 291 } 292 293 /* This function must be called with _thread_list_lock held. */ 294 void 295 _thr_stack_free(struct pthread_attr *attr) 296 { 297 struct stack *spare_stack; 298 299 if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0) 300 && (attr->stackaddr_attr != NULL)) { 301 spare_stack = (struct stack *) 302 ((char *)attr->stackaddr_attr + 303 attr->stacksize_attr - sizeof(struct stack)); 304 spare_stack->stacksize = round_up(attr->stacksize_attr); 305 spare_stack->guardsize = round_up(attr->guardsize_attr); 306 spare_stack->stackaddr = attr->stackaddr_attr; 307 308 if (spare_stack->stacksize == THR_STACK_DEFAULT && 309 spare_stack->guardsize == _thr_guard_default) { 310 /* Default stack/guard size. */ 311 LIST_INSERT_HEAD(&dstackq, spare_stack, qe); 312 } else { 313 /* Non-default stack/guard size. */ 314 LIST_INSERT_HEAD(&mstackq, spare_stack, qe); 315 } 316 attr->stackaddr_attr = NULL; 317 } 318 } 319