1 /* mmap.c -- Memory allocation with mmap. 2 Copyright (C) 2012-2013 Free Software Foundation, Inc. 3 Written by Ian Lance Taylor, Google. 4 5 Redistribution and use in source and binary forms, with or without 6 modification, are permitted provided that the following conditions are 7 met: 8 9 (1) Redistributions of source code must retain the above copyright 10 notice, this list of conditions and the following disclaimer. 11 12 (2) Redistributions in binary form must reproduce the above copyright 13 notice, this list of conditions and the following disclaimer in 14 the documentation and/or other materials provided with the 15 distribution. 16 17 (3) The name of the author may not be used to 18 endorse or promote products derived from this software without 19 specific prior written permission. 20 21 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 23 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 24 DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 25 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 26 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 27 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 29 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 30 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 31 POSSIBILITY OF SUCH DAMAGE. */ 32 33 #include "config.h" 34 35 #include <errno.h> 36 #include <string.h> 37 #include <stdlib.h> 38 #include <unistd.h> 39 #include <sys/types.h> 40 #include <sys/mman.h> 41 42 #include "backtrace.h" 43 #include "internal.h" 44 45 /* Memory allocation on systems that provide anonymous mmap. This 46 permits the backtrace functions to be invoked from a signal 47 handler, assuming that mmap is async-signal safe. */ 48 49 #ifndef MAP_ANONYMOUS 50 #define MAP_ANONYMOUS MAP_ANON 51 #endif 52 53 /* A list of free memory blocks. */ 54 55 struct backtrace_freelist_struct 56 { 57 /* Next on list. */ 58 struct backtrace_freelist_struct *next; 59 /* Size of this block, including this structure. */ 60 size_t size; 61 }; 62 63 /* Free memory allocated by backtrace_alloc. */ 64 65 static void 66 backtrace_free_locked (struct backtrace_state *state, void *addr, size_t size) 67 { 68 /* Just leak small blocks. We don't have to be perfect. */ 69 if (size >= sizeof (struct backtrace_freelist_struct)) 70 { 71 struct backtrace_freelist_struct *p; 72 73 p = (struct backtrace_freelist_struct *) addr; 74 p->next = state->freelist; 75 p->size = size; 76 state->freelist = p; 77 } 78 } 79 80 /* Allocate memory like malloc. */ 81 82 void * 83 backtrace_alloc (struct backtrace_state *state, 84 size_t size, backtrace_error_callback error_callback, 85 void *data) 86 { 87 void *ret; 88 int locked; 89 struct backtrace_freelist_struct **pp; 90 size_t pagesize; 91 size_t asksize; 92 void *page; 93 94 ret = NULL; 95 96 /* If we can acquire the lock, then see if there is space on the 97 free list. If we can't acquire the lock, drop straight into 98 using mmap. __sync_lock_test_and_set returns the old state of 99 the lock, so we have acquired it if it returns 0. */ 100 101 if (!state->threaded) 102 locked = 1; 103 else 104 locked = __sync_lock_test_and_set (&state->lock_alloc, 1) == 0; 105 106 if (locked) 107 { 108 for (pp = &state->freelist; *pp != NULL; pp = &(*pp)->next) 109 { 110 if ((*pp)->size >= size) 111 { 112 struct backtrace_freelist_struct *p; 113 114 p = *pp; 115 *pp = p->next; 116 117 /* Round for alignment; we assume that no type we care about 118 is more than 8 bytes. */ 119 size = (size + 7) & ~ (size_t) 7; 120 if (size < p->size) 121 backtrace_free_locked (state, (char *) p + size, 122 p->size - size); 123 124 ret = (void *) p; 125 126 break; 127 } 128 } 129 130 if (state->threaded) 131 __sync_lock_release (&state->lock_alloc); 132 } 133 134 if (ret == NULL) 135 { 136 /* Allocate a new page. */ 137 138 pagesize = getpagesize (); 139 asksize = (size + pagesize - 1) & ~ (pagesize - 1); 140 page = mmap (NULL, asksize, PROT_READ | PROT_WRITE, 141 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); 142 if (page == NULL) 143 error_callback (data, "mmap", errno); 144 else 145 { 146 size = (size + 7) & ~ (size_t) 7; 147 if (size < asksize) 148 backtrace_free (state, (char *) page + size, asksize - size, 149 error_callback, data); 150 151 ret = page; 152 } 153 } 154 155 return ret; 156 } 157 158 /* Free memory allocated by backtrace_alloc. */ 159 160 void 161 backtrace_free (struct backtrace_state *state, void *addr, size_t size, 162 backtrace_error_callback error_callback ATTRIBUTE_UNUSED, 163 void *data ATTRIBUTE_UNUSED) 164 { 165 int locked; 166 167 /* If we can acquire the lock, add the new space to the free list. 168 If we can't acquire the lock, just leak the memory. 169 __sync_lock_test_and_set returns the old state of the lock, so we 170 have acquired it if it returns 0. */ 171 172 if (!state->threaded) 173 locked = 1; 174 else 175 locked = __sync_lock_test_and_set (&state->lock_alloc, 1) == 0; 176 177 if (locked) 178 { 179 backtrace_free_locked (state, addr, size); 180 181 if (state->threaded) 182 __sync_lock_release (&state->lock_alloc); 183 } 184 } 185 186 /* Grow VEC by SIZE bytes. */ 187 188 void * 189 backtrace_vector_grow (struct backtrace_state *state,size_t size, 190 backtrace_error_callback error_callback, 191 void *data, struct backtrace_vector *vec) 192 { 193 void *ret; 194 195 if (size > vec->alc) 196 { 197 size_t pagesize; 198 size_t alc; 199 void *base; 200 201 pagesize = getpagesize (); 202 alc = vec->size + size; 203 if (vec->size == 0) 204 alc = 16 * size; 205 else if (alc < pagesize) 206 { 207 alc *= 2; 208 if (alc > pagesize) 209 alc = pagesize; 210 } 211 else 212 alc = (alc + pagesize - 1) & ~ (pagesize - 1); 213 base = backtrace_alloc (state, alc, error_callback, data); 214 if (base == NULL) 215 return NULL; 216 if (vec->base != NULL) 217 { 218 memcpy (base, vec->base, vec->size); 219 backtrace_free (state, vec->base, vec->alc, error_callback, data); 220 } 221 vec->base = base; 222 vec->alc = alc - vec->size; 223 } 224 225 ret = (char *) vec->base + vec->size; 226 vec->size += size; 227 vec->alc -= size; 228 return ret; 229 } 230 231 /* Finish the current allocation on VEC. */ 232 233 void * 234 backtrace_vector_finish ( 235 struct backtrace_state *state ATTRIBUTE_UNUSED, 236 struct backtrace_vector *vec, 237 backtrace_error_callback error_callback ATTRIBUTE_UNUSED, 238 void *data ATTRIBUTE_UNUSED) 239 { 240 void *ret; 241 242 ret = vec->base; 243 vec->base = (char *) vec->base + vec->size; 244 vec->size = 0; 245 return ret; 246 } 247 248 /* Release any extra space allocated for VEC. */ 249 250 int 251 backtrace_vector_release (struct backtrace_state *state, 252 struct backtrace_vector *vec, 253 backtrace_error_callback error_callback, 254 void *data) 255 { 256 size_t size; 257 size_t alc; 258 size_t aligned; 259 260 /* Make sure that the block that we free is aligned on an 8-byte 261 boundary. */ 262 size = vec->size; 263 alc = vec->alc; 264 aligned = (size + 7) & ~ (size_t) 7; 265 alc -= aligned - size; 266 267 backtrace_free (state, (char *) vec->base + aligned, alc, 268 error_callback, data); 269 vec->alc = 0; 270 return 1; 271 } 272