lib/libthread_xu/thread/thr_stack.c

   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: src/lib/libpthread/thread/thr_stack.c,v 1.9 2004/10/06 08:11:07 davidxu Exp $
  28  * $DragonFly: src/lib/libthread_xu/thread/thr_stack.c,v 1.4 2006/04/06 13:03:09 davidxu Exp $
  29  */
  30 #include <sys/types.h>
  31 #include <sys/mman.h>
  32 #include <sys/queue.h>
  33
  34 #include <machine/tls.h>
  35
  36 #include <stdlib.h>
  37 #include <pthread.h>
  38 #include "thr_private.h"
  39
  40 /* Spare thread stack. */
  41 struct stack {
  42         LIST_ENTRY(stack)       qe;             /* Stack queue linkage. */
  43         size_t                  stacksize;      /* Stack size (rounded up). */
  44         size_t                  guardsize;      /* Guard size. */
  45         void                    *stackaddr;     /* Stack address. */
  46 };
  47
  48 /*
  49  * Default sized (stack and guard) spare stack queue.  Stacks are cached
  50  * to avoid additional complexity managing mmap()ed stack regions.  Spare
  51  * stacks are used in LIFO order to increase cache locality.
  52  */
  53 static LIST_HEAD(, stack)       dstackq = LIST_HEAD_INITIALIZER(dstackq);
  54
  55 /*
  56  * Miscellaneous sized (non-default stack and/or guard) spare stack queue.
  57  * Stacks are cached to avoid additional complexity managing mmap()ed
  58  * stack regions.  This list is unordered, since ordering on both stack
  59  * size and guard size would be more trouble than it's worth.  Stacks are
  60  * allocated from this cache on a first size match basis.
  61  */
  62 static LIST_HEAD(, stack)       mstackq = LIST_HEAD_INITIALIZER(mstackq);
  63
  64 /**
  65  * Base address of the last stack allocated (including its red zone, if
  66  * there is one).  Stacks are allocated contiguously, starting beyond the
  67  * top of the main stack.  When a new stack is created, a red zone is
  68  * typically created (actually, the red zone is mapped with PROT_NONE) above
  69  * the top of the stack, such that the stack will not be able to grow all
  70  * the way to the bottom of the next stack.  This isn't fool-proof.  It is
  71  * possible for a stack to grow by a large amount, such that it grows into
  72  * the next stack, and as long as the memory within the red zone is never
  73  * accessed, nothing will prevent one thread stack from trouncing all over
  74  * the next.
  75  *
  76  * low memory
  77  *     . . . . . . . . . . . . . . . . . .
  78  *    |                                   |
  79  *    |             stack 3               | start of 3rd thread stack
  80  *    +-----------------------------------+
  81  *    |                                   |
  82  *    |       Red Zone (guard page)       | red zone for 2nd thread
  83  *    |                                   |
  84  *    +-----------------------------------+
  85  *    |  stack 2 - _thr_stack_default     | top of 2nd thread stack
  86  *    |                                   |
  87  *    |                                   |
  88  *    |                                   |
  89  *    |                                   |
  90  *    |             stack 2               |
  91  *    +-----------------------------------+ <-- start of 2nd thread stack
  92  *    |                                   |
  93  *    |       Red Zone                    | red zone for 1st thread
  94  *    |                                   |
  95  *    +-----------------------------------+
  96  *    |  stack 1 - _thr_stack_default     | top of 1st thread stack
  97  *    |                                   |
  98  *    |                                   |
  99  *    |                                   |
 100  *    |                                   |
 101  *    |             stack 1               |
 102  *    +-----------------------------------+ <-- start of 1st thread stack
 103  *    |                                   |   (initial value of last_stack)
 104  *    |       Red Zone                    |
 105  *    |                                   | red zone for main thread
 106  *    +-----------------------------------+
 107  *    | USRSTACK - _thr_stack_initial     | top of main thread stack
 108  *    |                                   | ^
 109  *    |                                   | |
 110  *    |                                   | |
 111  *    |                                   | | stack growth
 112  *    |                                   |
 113  *    +-----------------------------------+ <-- start of main thread stack
 114  *                                              (USRSTACK)
 115  * high memory
 116  *
 117  */
 118 static char *last_stack = NULL;
 119
 120 /*
 121  * Round size up to the nearest multiple of
 122  * _thr_page_size.
 123  */
 124 static inline size_t
 125 round_up(size_t size)
 126 {
 127         if (size % _thr_page_size != 0)
 128                 size = ((size / _thr_page_size) + 1) *
 129                     _thr_page_size;
 130         return size;
 131 }
 132
 133 int
 134 _thr_stack_alloc(struct pthread_attr *attr)
 135 {
 136         struct pthread *curthread = tls_get_curthread();
 137         struct stack *spare_stack;
 138         size_t stacksize;
 139         size_t guardsize;
 140         char *stackaddr;
 141
 142         /*
 143          * Round up stack size to nearest multiple of _thr_page_size so
 144          * that mmap() * will work.  If the stack size is not an even
 145          * multiple, we end up initializing things such that there is
 146          * unused space above the beginning of the stack, so the stack
 147          * sits snugly against its guard.
 148          */
 149         stacksize = round_up(attr->stacksize_attr);
 150         guardsize = round_up(attr->guardsize_attr);
 151
 152         attr->stackaddr_attr = NULL;
 153         attr->flags &= ~THR_STACK_USER;
 154
 155         /*
 156          * Use the garbage collector lock for synchronization of the
 157          * spare stack lists and allocations from usrstack.
 158          */
 159         THREAD_LIST_LOCK(curthread);
 160         /*
 161          * If the stack and guard sizes are default, try to allocate a stack
 162          * from the default-size stack cache:
 163          */
 164         if ((stacksize == THR_STACK_DEFAULT) &&
 165             (guardsize == _thr_guard_default)) {
 166                 if ((spare_stack = LIST_FIRST(&dstackq)) != NULL) {
 167                         /* Use the spare stack. */
 168                         LIST_REMOVE(spare_stack, qe);
 169                         attr->stackaddr_attr = spare_stack->stackaddr;
 170                 }
 171         }
 172         /*
 173          * The user specified a non-default stack and/or guard size, so try to
 174          * allocate a stack from the non-default size stack cache, using the
 175          * rounded up stack size (stack_size) in the search:
 176          */
 177         else {
 178                 LIST_FOREACH(spare_stack, &mstackq, qe) {
 179                         if (spare_stack->stacksize == stacksize &&
 180                             spare_stack->guardsize == guardsize) {
 181                                 LIST_REMOVE(spare_stack, qe);
 182                                 attr->stackaddr_attr = spare_stack->stackaddr;
 183                                 break;
 184                         }
 185                 }
 186         }
 187         if (attr->stackaddr_attr != NULL) {
 188                 /* A cached stack was found.  Release the lock. */
 189                 THREAD_LIST_UNLOCK(curthread);
 190         }
 191         else {
 192                 /* Allocate a stack from usrstack. */
 193                 if (last_stack == NULL) {
 194                         last_stack = _usrstack - _thr_stack_initial -
 195                                      _thr_guard_default;
 196                 }
 197
 198                 /* Allocate a new stack. */
 199                 stackaddr = last_stack - stacksize - guardsize;
 200
 201                 /*
 202                  * Even if stack allocation fails, we don't want to try to
 203                  * use this location again, so unconditionally decrement
 204                  * last_stack.  Under normal operating conditions, the most
 205                  * likely reason for an mmap() error is a stack overflow of
 206                  * the adjacent thread stack.
 207                  */
 208                 last_stack -= (stacksize + guardsize);
 209
 210                 /* Release the lock before mmap'ing it. */
 211                 THREAD_LIST_UNLOCK(curthread);
 212
 213                 /*
 214                  * Map the stack and guard page together then split the
 215                  * guard page from allocated space.
 216                  *
 217                  * NOTE: MAP_STACK mappings are grow-down and the
 218                  * initial mapping does not actually extend to the guard
 219                  * area, so creating the guard requires doing a fixed
 220                  * anonymous mmap of the guard area.
 221                  */
 222                 stackaddr = mmap(stackaddr, stacksize + guardsize,
 223                                  PROT_READ | PROT_WRITE, MAP_STACK, -1, 0);
 224                 if (stackaddr != MAP_FAILED && guardsize) {
 225                         if (mmap(stackaddr, guardsize, 0,
 226                                  MAP_ANON | MAP_FIXED, -1, 0) == MAP_FAILED) {
 227                                 munmap(stackaddr, stacksize + guardsize);
 228                                 stackaddr = MAP_FAILED;
 229                         } else {
 230                                 stackaddr += guardsize;
 231                         }
 232                 }
 233                 if (stackaddr == MAP_FAILED)
 234                         stackaddr = NULL;
 235                 attr->stackaddr_attr = stackaddr;
 236         }
 237         if (attr->stackaddr_attr != NULL)
 238                 return (0);
 239         else
 240                 return (-1);
 241 }
 242
 243 /* This function must be called with _thread_list_lock held. */
 244 void
 245 _thr_stack_free(struct pthread_attr *attr)
 246 {
 247         struct stack *spare_stack;
 248
 249         if ((attr != NULL) && ((attr->flags & THR_STACK_USER) == 0)
 250             && (attr->stackaddr_attr != NULL)) {
 251                 spare_stack = (struct stack *)((char *)attr->stackaddr_attr +
 252                         attr->stacksize_attr - sizeof(struct stack));
 253                 spare_stack->stacksize = round_up(attr->stacksize_attr);
 254                 spare_stack->guardsize = round_up(attr->guardsize_attr);
 255                 spare_stack->stackaddr = attr->stackaddr_attr;
 256
 257                 if (spare_stack->stacksize == THR_STACK_DEFAULT &&
 258                     spare_stack->guardsize == _thr_guard_default) {
 259                         /* Default stack/guard size. */
 260                         LIST_INSERT_HEAD(&dstackq, spare_stack, qe);
 261                 } else {
 262                         /* Non-default stack/guard size. */
 263                         LIST_INSERT_HEAD(&mstackq, spare_stack, qe);
 264                 }
 265                 attr->stackaddr_attr = NULL;
 266         }
 267 }