1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2001 Daniel Eischen <deischen@freebsd.org> 5 * Copyright (c) 2000-2001 Jason Evans <jasone@freebsd.org> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 #include <sys/param.h> 31 #include <sys/auxv.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 return (roundup2(size, _thr_page_size)); 130 } 131 132 void 133 _thr_stack_fix_protection(struct pthread *thrd) 134 { 135 136 mprotect((char *)thrd->attr.stackaddr_attr + 137 round_up(thrd->attr.guardsize_attr), 138 round_up(thrd->attr.stacksize_attr), 139 _rtld_get_stack_prot()); 140 } 141 142 static void 143 singlethread_map_stacks_exec(void) 144 { 145 char *usrstack; 146 size_t stacksz; 147 148 if (!__thr_get_main_stack_base(&usrstack) || 149 !__thr_get_main_stack_lim(&stacksz)) 150 return; 151 mprotect(usrstack - stacksz, stacksz, _rtld_get_stack_prot()); 152 } 153 154 void 155 __thr_map_stacks_exec(void) 156 { 157 struct pthread *curthread, *thrd; 158 struct stack *st; 159 160 if (!_thr_is_inited()) { 161 singlethread_map_stacks_exec(); 162 return; 163 } 164 curthread = _get_curthread(); 165 THREAD_LIST_RDLOCK(curthread); 166 LIST_FOREACH(st, &mstackq, qe) 167 mprotect((char *)st->stackaddr + st->guardsize, st->stacksize, 168 _rtld_get_stack_prot()); 169 LIST_FOREACH(st, &dstackq, qe) 170 mprotect((char *)st->stackaddr + st->guardsize, st->stacksize, 171 _rtld_get_stack_prot()); 172 TAILQ_FOREACH(thrd, &_thread_gc_list, gcle) 173 _thr_stack_fix_protection(thrd); 174 TAILQ_FOREACH(thrd, &_thread_list, tle) 175 _thr_stack_fix_protection(thrd); 176 THREAD_LIST_UNLOCK(curthread); 177 } 178 179 int 180 _thr_stack_alloc(struct pthread_attr *attr) 181 { 182 struct pthread *curthread = _get_curthread(); 183 struct stack *spare_stack; 184 size_t stacksize; 185 size_t guardsize; 186 char *stackaddr; 187 188 /* 189 * Round up stack size to nearest multiple of _thr_page_size so 190 * that mmap() * will work. If the stack size is not an even 191 * multiple, we end up initializing things such that there is 192 * unused space above the beginning of the stack, so the stack 193 * sits snugly against its guard. 194 */ 195 stacksize = round_up(attr->stacksize_attr); 196 guardsize = round_up(attr->guardsize_attr); 197 198 attr->stackaddr_attr = NULL; 199 attr->flags &= ~THR_STACK_USER; 200 201 /* 202 * Use the garbage collector lock for synchronization of the 203 * spare stack lists and allocations from usrstack. 204 */ 205 THREAD_LIST_WRLOCK(curthread); 206 /* 207 * If the stack and guard sizes are default, try to allocate a stack 208 * from the default-size stack cache: 209 */ 210 if ((stacksize == THR_STACK_DEFAULT) && 211 (guardsize == _thr_guard_default)) { 212 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) { 213 /* Use the spare stack. */ 214 LIST_REMOVE(spare_stack, qe); 215 attr->stackaddr_attr = spare_stack->stackaddr; 216 } 217 } 218 /* 219 * The user specified a non-default stack and/or guard size, so try to 220 * allocate a stack from the non-default size stack cache, using the 221 * rounded up stack size (stack_size) in the search: 222 */ 223 else { 224 LIST_FOREACH(spare_stack, &mstackq, qe) { 225 if (spare_stack->stacksize == stacksize && 226 spare_stack->guardsize == guardsize) { 227 LIST_REMOVE(spare_stack, qe); 228 attr->stackaddr_attr = spare_stack->stackaddr; 229 break; 230 } 231 } 232 } 233 if (attr->stackaddr_attr != NULL) { 234 /* A cached stack was found. Release the lock. */ 235 THREAD_LIST_UNLOCK(curthread); 236 } 237 else { 238 /* 239 * Allocate a stack from or below usrstack, depending 240 * on the LIBPTHREAD_BIGSTACK_MAIN env variable. 241 */ 242 if (last_stack == NULL) 243 last_stack = _usrstack - _thr_stack_initial - 244 _thr_guard_default; 245 246 /* Allocate a new stack. */ 247 stackaddr = last_stack - stacksize - guardsize; 248 249 /* 250 * Even if stack allocation fails, we don't want to try to 251 * use this location again, so unconditionally decrement 252 * last_stack. Under normal operating conditions, the most 253 * likely reason for an mmap() error is a stack overflow of 254 * the adjacent thread stack. 255 */ 256 last_stack -= (stacksize + guardsize); 257 258 /* Release the lock before mmap'ing it. */ 259 THREAD_LIST_UNLOCK(curthread); 260 261 /* Map the stack and guard page together, and split guard 262 page from allocated space: */ 263 if ((stackaddr = mmap(stackaddr, stacksize + guardsize, 264 _rtld_get_stack_prot(), MAP_STACK, 265 -1, 0)) != MAP_FAILED && 266 (guardsize == 0 || 267 mprotect(stackaddr, guardsize, PROT_NONE) == 0)) { 268 stackaddr += guardsize; 269 } else { 270 if (stackaddr != MAP_FAILED) 271 munmap(stackaddr, stacksize + guardsize); 272 stackaddr = NULL; 273 } 274 attr->stackaddr_attr = stackaddr; 275 } 276 if (attr->stackaddr_attr != NULL) 277 return (0); 278 else 279 return (-1); 280 } 281 282 /* This function must be called with _thread_list_lock held. */ 283 void 284 _thr_stack_free(struct pthread_attr *attr) 285 { 286 struct stack *spare_stack; 287 288 if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0) 289 && (attr->stackaddr_attr != NULL)) { 290 spare_stack = (struct stack *) 291 ((char *)attr->stackaddr_attr + 292 attr->stacksize_attr - sizeof(struct stack)); 293 spare_stack->stacksize = round_up(attr->stacksize_attr); 294 spare_stack->guardsize = round_up(attr->guardsize_attr); 295 spare_stack->stackaddr = attr->stackaddr_attr; 296 297 if (spare_stack->stacksize == THR_STACK_DEFAULT && 298 spare_stack->guardsize == _thr_guard_default) { 299 /* Default stack/guard size. */ 300 LIST_INSERT_HEAD(&dstackq, spare_stack, qe); 301 } else { 302 /* Non-default stack/guard size. */ 303 LIST_INSERT_HEAD(&mstackq, spare_stack, qe); 304 } 305 attr->stackaddr_attr = NULL; 306 } 307 } 308