src/src/store.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2009 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* Exim gets and frees all its store through these functions. In the original
   9 implementation there was a lot of mallocing and freeing of small bits of store.
  10 The philosophy has now changed to a scheme which includes the concept of
  11 "stacking pools" of store. For the short-lived processes, there isn't any real
  12 need to do any garbage collection, but the stack concept allows quick resetting
  13 in places where this seems sensible.
  14
  15 Obviously the long-running processes (the daemon, the queue runner, and eximon)
  16 must take care not to eat store.
  17
  18 The following different types of store are recognized:
  19
  20 . Long-lived, large blocks: This is implemented by retaining the original
  21   malloc/free functions, and it used for permanent working buffers and for
  22   getting blocks to cut up for the other types.
  23
  24 . Long-lived, small blocks: This is used for blocks that have to survive until
  25   the process exits. It is implemented as a stacking pool (POOL_PERM). This is
  26   functionally the same as store_malloc(), except that the store can't be
  27   freed, but I expect it to be more efficient for handling small blocks.
  28
  29 . Short-lived, short blocks: Most of the dynamic store falls into this
  30   category. It is implemented as a stacking pool (POOL_MAIN) which is reset
  31   after accepting a message when multiple messages are received by a single
  32   process. Resetting happens at some other times as well, usually fairly
  33   locally after some specific processing that needs working store.
  34
  35 . There is a separate pool (POOL_SEARCH) that is used only for lookup storage.
  36   This means it can be freed when search_tidyup() is called to close down all
  37   the lookup caching.
  38 */
  39
  40
  41 #include "exim.h"
  42 #include "memcheck.h"
  43
  44
  45 /* We need to know how to align blocks of data for general use. I'm not sure
  46 how to get an alignment factor in general. In the current world, a value of 8
  47 is probably right, and this is sizeof(double) on some systems and sizeof(void
  48 *) on others, so take the larger of those. Since everything in this expression
  49 is a constant, the compiler should optimize it to a simple constant wherever it
  50 appears (I checked that gcc does do this). */
  51
  52 #define alignment \
  53   ((sizeof(void *) > sizeof(double))? sizeof(void *) : sizeof(double))
  54
  55 /* Size of block to get from malloc to carve up into smaller ones. This
  56 must be a multiple of the alignment. We assume that 8192 is going to be
  57 suitably aligned. */
  58
  59 #define STORE_BLOCK_SIZE 8192
  60
  61 /* store_reset() will not free the following block if the last used block has
  62 less than this much left in it. */
  63
  64 #define STOREPOOL_MIN_SIZE 256
  65
  66 /* Structure describing the beginning of each big block. */
  67
  68 typedef struct storeblock {
  69   struct storeblock *next;
  70   size_t length;
  71 } storeblock;
  72
  73 /* Just in case we find ourselves on a system where the structure above has a
  74 length that is not a multiple of the alignment, set up a macro for the padded
  75 length. */
  76
  77 #define ALIGNED_SIZEOF_STOREBLOCK \
  78   (((sizeof(storeblock) + alignment - 1) / alignment) * alignment)
  79
  80 /* Variables holding data for the local pools of store. The current pool number
  81 is held in store_pool, which is global so that it can be changed from outside.
  82 Setting the initial length values to -1 forces a malloc for the first call,
  83 even if the length is zero (which is used for getting a point to reset to). */
  84
  85 int store_pool = POOL_PERM;
  86
  87 static storeblock *chainbase[3] = { NULL, NULL, NULL };
  88 static storeblock *current_block[3] = { NULL, NULL, NULL };
  89 static void *next_yield[3] = { NULL, NULL, NULL };
  90 static int yield_length[3] = { -1, -1, -1 };
  91
  92 /* pool_malloc holds the amount of memory used by the store pools; this goes up
  93 and down as store is reset or released. nonpool_malloc is the total got by
  94 malloc from other calls; this doesn't go down because it is just freed by
  95 pointer. */
  96
  97 static int pool_malloc = 0;
  98 static int nonpool_malloc = 0;
  99
 100 /* This variable is set by store_get() to its yield, and by store_reset() to
 101 NULL. This enables string_cat() to optimize its store handling for very long
 102 strings. That's why the variable is global. */
 103
 104 void *store_last_get[3] = { NULL, NULL, NULL };
 105
 106
 107
 108 /*************************************************
 109 *       Get a block from the current pool        *
 110 *************************************************/
 111
 112 /* Running out of store is a total disaster. This function is called via the
 113 macro store_get(). It passes back a block of store within the current big
 114 block, getting a new one if necessary. The address is saved in
 115 store_last_was_get.
 116
 117 Arguments:
 118   size        amount wanted
 119   filename    source file from which called
 120   linenumber  line number in source file.
 121
 122 Returns:      pointer to store (panic on malloc failure)
 123 */
 124
 125 void *
 126 store_get_3(int size, const char *filename, int linenumber)
 127 {
 128 /* Round up the size to a multiple of the alignment. Although this looks a
 129 messy statement, because "alignment" is a constant expression, the compiler can
 130 do a reasonable job of optimizing, especially if the value of "alignment" is a
 131 power of two. I checked this with -O2, and gcc did very well, compiling it to 4
 132 instructions on a Sparc (alignment = 8). */
 133
 134 if (size % alignment != 0) size += alignment - (size % alignment);
 135
 136 /* If there isn't room in the current block, get a new one. The minimum
 137 size is STORE_BLOCK_SIZE, and we would expect this to be the norm, since
 138 these functions are mostly called for small amounts of store. */
 139
 140 if (size > yield_length[store_pool])
 141   {
 142   int length = (size <= STORE_BLOCK_SIZE)? STORE_BLOCK_SIZE : size;
 143   int mlength = length + ALIGNED_SIZEOF_STOREBLOCK;
 144   storeblock *newblock = NULL;
 145
 146   /* Sometimes store_reset() may leave a block for us; check if we can use it */
 147
 148   if (current_block[store_pool] != NULL &&
 149       current_block[store_pool]->next != NULL)
 150     {
 151     newblock = current_block[store_pool]->next;
 152     if (newblock->length < length)
 153       {
 154       /* Give up on this block, because it's too small */
 155       store_free(newblock);
 156       newblock = NULL;
 157       }
 158     }
 159
 160   /* If there was no free block, get a new one */
 161
 162   if (newblock == NULL)
 163     {
 164     pool_malloc += mlength;           /* Used in pools */
 165     nonpool_malloc -= mlength;        /* Exclude from overall total */
 166     newblock = store_malloc(mlength);
 167     newblock->next = NULL;
 168     newblock->length = length;
 169     if (chainbase[store_pool] == NULL) chainbase[store_pool] = newblock;
 170       else current_block[store_pool]->next = newblock;
 171     }
 172
 173   current_block[store_pool] = newblock;
 174   yield_length[store_pool] = newblock->length;
 175   next_yield[store_pool] =
 176     (void *)((char *)current_block[store_pool] + ALIGNED_SIZEOF_STOREBLOCK);
 177   VALGRIND_MAKE_MEM_NOACCESS(next_yield[store_pool], yield_length[store_pool]);
 178   }
 179
 180 /* There's (now) enough room in the current block; the yield is the next
 181 pointer. */
 182
 183 store_last_get[store_pool] = next_yield[store_pool];
 184
 185 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 186 giving warnings. */
 187
 188 #ifdef COMPILE_UTILITY
 189 filename = filename;
 190 linenumber = linenumber;
 191 #else
 192 DEBUG(D_memory)
 193   {
 194   if (running_in_test_harness)
 195     debug_printf("---%d Get %5d\n", store_pool, size);
 196   else
 197     debug_printf("---%d Get %6p %5d %-14s %4d\n", store_pool,
 198       store_last_get[store_pool], size, filename, linenumber);
 199   }
 200 #endif  /* COMPILE_UTILITY */
 201
 202 VALGRIND_MAKE_MEM_UNDEFINED(store_last_get[store_pool], size);
 203 /* Update next pointer and number of bytes left in the current block. */
 204
 205 next_yield[store_pool] = (void *)((char *)next_yield[store_pool] + size);
 206 yield_length[store_pool] -= size;
 207
 208 return store_last_get[store_pool];
 209 }
 210
 211
 212
 213 /*************************************************
 214 *       Get a block from the PERM pool           *
 215 *************************************************/
 216
 217 /* This is just a convenience function, useful when just a single block is to
 218 be obtained.
 219
 220 Arguments:
 221   size        amount wanted
 222   filename    source file from which called
 223   linenumber  line number in source file.
 224
 225 Returns:      pointer to store (panic on malloc failure)
 226 */
 227
 228 void *
 229 store_get_perm_3(int size, const char *filename, int linenumber)
 230 {
 231 void *yield;
 232 int old_pool = store_pool;
 233 store_pool = POOL_PERM;
 234 yield = store_get_3(size, filename, linenumber);
 235 store_pool = old_pool;
 236 return yield;
 237 }
 238
 239
 240
 241 /*************************************************
 242 *      Extend a block if it is at the top        *
 243 *************************************************/
 244
 245 /* While reading strings of unknown length, it is often the case that the
 246 string is being read into the block at the top of the stack. If it needs to be
 247 extended, it is more efficient just to extend the top block rather than
 248 allocate a new block and then have to copy the data. This function is provided
 249 for the use of string_cat(), but of course can be used elsewhere too.
 250
 251 Arguments:
 252   ptr        pointer to store block
 253   oldsize    current size of the block, as requested by user
 254   newsize    new size required
 255   filename   source file from which called
 256   linenumber line number in source file
 257
 258 Returns:     TRUE if the block is at the top of the stack and has been
 259              extended; FALSE if it isn't at the top of the stack, or cannot
 260              be extended
 261 */
 262
 263 BOOL
 264 store_extend_3(void *ptr, int oldsize, int newsize, const char *filename,
 265   int linenumber)
 266 {
 267 int inc = newsize - oldsize;
 268 int rounded_oldsize = oldsize;
 269
 270 if (rounded_oldsize % alignment != 0)
 271   rounded_oldsize += alignment - (rounded_oldsize % alignment);
 272
 273 if ((char *)ptr + rounded_oldsize != (char *)(next_yield[store_pool]) ||
 274     inc > yield_length[store_pool] + rounded_oldsize - oldsize)
 275   return FALSE;
 276
 277 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 278 giving warnings. */
 279
 280 #ifdef COMPILE_UTILITY
 281 filename = filename;
 282 linenumber = linenumber;
 283 #else
 284 DEBUG(D_memory)
 285   {
 286   if (running_in_test_harness)
 287     debug_printf("---%d Ext %5d\n", store_pool, newsize);
 288   else
 289     debug_printf("---%d Ext %6p %5d %-14s %4d\n", store_pool, ptr, newsize,
 290       filename, linenumber);
 291   }
 292 #endif  /* COMPILE_UTILITY */
 293
 294 if (newsize % alignment != 0) newsize += alignment - (newsize % alignment);
 295 next_yield[store_pool] = (char *)ptr + newsize;
 296 yield_length[store_pool] -= newsize - rounded_oldsize;
 297 VALGRIND_MAKE_MEM_UNDEFINED(ptr + oldsize, inc);
 298 return TRUE;
 299 }
 300
 301
 302
 303
 304 /*************************************************
 305 *    Back up to a previous point on the stack    *
 306 *************************************************/
 307
 308 /* This function resets the next pointer, freeing any subsequent whole blocks
 309 that are now unused. Normally it is given a pointer that was the yield of a
 310 call to store_get, and is therefore aligned, but it may be given an offset
 311 after such a pointer in order to release the end of a block and anything that
 312 follows.
 313
 314 Arguments:
 315   ptr         place to back up to
 316   filename    source file from which called
 317   linenumber  line number in source file
 318
 319 Returns:      nothing
 320 */
 321
 322 void
 323 store_reset_3(void *ptr, const char *filename, int linenumber)
 324 {
 325 storeblock *bb;
 326 storeblock *b = current_block[store_pool];
 327 char *bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
 328 int newlength;
 329
 330 /* Last store operation was not a get */
 331
 332 store_last_get[store_pool] = NULL;
 333
 334 /* See if the place is in the current block - as it often will be. Otherwise,
 335 search for the block in which it lies. */
 336
 337 if ((char *)ptr < bc || (char *)ptr > bc + b->length)
 338   {
 339   for (b = chainbase[store_pool]; b != NULL; b = b->next)
 340     {
 341     bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
 342     if ((char *)ptr >= bc && (char *)ptr <= bc + b->length) break;
 343     }
 344   if (b == NULL)
 345     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "internal error: store_reset(%d) "
 346       "failed: pool=%d %-14s %4d", ptr, store_pool, filename, linenumber);
 347   }
 348
 349 /* Back up, rounding to the alignment if necessary. When testing, flatten
 350 the released memory. */
 351
 352 newlength = bc + b->length - (char *)ptr;
 353 #ifndef COMPILE_UTILITY
 354 if (running_in_test_harness) memset(ptr, 0xF0, newlength);
 355 #endif
 356 VALGRIND_MAKE_MEM_NOACCESS(ptr, newlength);
 357 yield_length[store_pool] = newlength - (newlength % alignment);
 358 next_yield[store_pool] = (char *)ptr + (newlength % alignment);
 359 current_block[store_pool] = b;
 360
 361 /* Free any subsequent block. Do NOT free the first successor, if our
 362 current block has less than 256 bytes left. This should prevent us from
 363 flapping memory. However, keep this block only when it has the default size. */
 364
 365 if (yield_length[store_pool] < STOREPOOL_MIN_SIZE &&
 366     b->next != NULL &&
 367     b->next->length == STORE_BLOCK_SIZE)
 368   {
 369   b = b->next;
 370   VALGRIND_MAKE_MEM_NOACCESS((char *)b + ALIGNED_SIZEOF_STOREBLOCK, b->length - ALIGNED_SIZEOF_STOREBLOCK);
 371   }
 372
 373 bb = b->next;
 374 b->next = NULL;
 375
 376 while (bb != NULL)
 377   {
 378   b = bb;
 379   bb = bb->next;
 380   pool_malloc -= b->length + ALIGNED_SIZEOF_STOREBLOCK;
 381   store_free_3(b, filename, linenumber);
 382   }
 383
 384 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 385 giving warnings. */
 386
 387 #ifdef COMPILE_UTILITY
 388 filename = filename;
 389 linenumber = linenumber;
 390 #else
 391 DEBUG(D_memory)
 392   {
 393   if (running_in_test_harness)
 394     debug_printf("---%d Rst    ** %d\n", store_pool, pool_malloc);
 395   else
 396     debug_printf("---%d Rst %6p    ** %-14s %4d %d\n", store_pool, ptr,
 397       filename, linenumber, pool_malloc);
 398   }
 399 #endif  /* COMPILE_UTILITY */
 400 }
 401
 402
 403
 404
 405
 406 /************************************************
 407 *             Release store                     *
 408 ************************************************/
 409
 410 /* This function is specifically provided for use when reading very
 411 long strings, e.g. header lines. When the string gets longer than a
 412 complete block, it gets copied to a new block. It is helpful to free
 413 the old block iff the previous copy of the string is at its start,
 414 and therefore the only thing in it. Otherwise, for very long strings,
 415 dead store can pile up somewhat disastrously. This function checks that
 416 the pointer it is given is the first thing in a block, and if so,
 417 releases that block.
 418
 419 Arguments:
 420   block       block of store to consider
 421   filename    source file from which called
 422   linenumber  line number in source file
 423
 424 Returns:      nothing
 425 */
 426
 427 void
 428 store_release_3(void *block, const char *filename, int linenumber)
 429 {
 430 storeblock *b;
 431
 432 /* It will never be the first block, so no need to check that. */
 433
 434 for (b = chainbase[store_pool]; b != NULL; b = b->next)
 435   {
 436   storeblock *bb = b->next;
 437   if (bb != NULL && (char *)block == (char *)bb + ALIGNED_SIZEOF_STOREBLOCK)
 438     {
 439     b->next = bb->next;
 440     pool_malloc -= bb->length + ALIGNED_SIZEOF_STOREBLOCK;
 441
 442     /* Cut out the debugging stuff for utilities, but stop picky compilers
 443     from giving warnings. */
 444
 445     #ifdef COMPILE_UTILITY
 446     filename = filename;
 447     linenumber = linenumber;
 448     #else
 449     DEBUG(D_memory)
 450       {
 451       if (running_in_test_harness)
 452         debug_printf("-Release       %d\n", pool_malloc);
 453       else
 454         debug_printf("-Release %6p %-20s %4d %d\n", (void *)bb, filename,
 455           linenumber, pool_malloc);
 456       }
 457     if (running_in_test_harness)
 458       memset(bb, 0xF0, bb->length+ALIGNED_SIZEOF_STOREBLOCK);
 459     #endif  /* COMPILE_UTILITY */
 460
 461     free(bb);
 462     return;
 463     }
 464   }
 465 }
 466
 467
 468
 469
 470 /*************************************************
 471 *                Malloc store                    *
 472 *************************************************/
 473
 474 /* Running out of store is a total disaster for exim. Some malloc functions
 475 do not run happily on very small sizes, nor do they document this fact. This
 476 function is called via the macro store_malloc().
 477
 478 Arguments:
 479   size        amount of store wanted
 480   filename    source file from which called
 481   linenumber  line number in source file
 482
 483 Returns:      pointer to gotten store (panic on failure)
 484 */
 485
 486 void *
 487 store_malloc_3(int size, const char *filename, int linenumber)
 488 {
 489 void *yield;
 490
 491 if (size < 16) size = 16;
 492 yield = malloc((size_t)size);
 493
 494 if (yield == NULL)
 495   log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to malloc %d bytes of memory: "
 496     "called from line %d of %s", size, linenumber, filename);
 497
 498 nonpool_malloc += size;
 499
 500 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 501 giving warnings. */
 502
 503 #ifdef COMPILE_UTILITY
 504 filename = filename;
 505 linenumber = linenumber;
 506 #else
 507
 508 /* If running in test harness, spend time making sure all the new store
 509 is not filled with zeros so as to catch problems. */
 510
 511 if (running_in_test_harness)
 512   {
 513   memset(yield, 0xF0, (size_t)size);
 514   DEBUG(D_memory) debug_printf("--Malloc %5d %d %d\n", size, pool_malloc,
 515     nonpool_malloc);
 516   }
 517 else
 518   {
 519   DEBUG(D_memory) debug_printf("--Malloc %6p %5d %-14s %4d %d %d\n", yield,
 520     size, filename, linenumber, pool_malloc, nonpool_malloc);
 521   }
 522 #endif  /* COMPILE_UTILITY */
 523
 524 return yield;
 525 }
 526
 527
 528 /************************************************
 529 *             Free store                        *
 530 ************************************************/
 531
 532 /* This function is called by the macro store_free().
 533
 534 Arguments:
 535   block       block of store to free
 536   filename    source file from which called
 537   linenumber  line number in source file
 538
 539 Returns:      nothing
 540 */
 541
 542 void
 543 store_free_3(void *block, const char *filename, int linenumber)
 544 {
 545 #ifdef COMPILE_UTILITY
 546 filename = filename;
 547 linenumber = linenumber;
 548 #else
 549 DEBUG(D_memory)
 550   {
 551   if (running_in_test_harness)
 552     debug_printf("----Free\n");
 553   else
 554     debug_printf("----Free %6p %-20s %4d\n", block, filename, linenumber);
 555   }
 556 #endif  /* COMPILE_UTILITY */
 557 free(block);
 558 }
 559
 560 /* End of store.c */