src/src/store.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2015 */
   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 /* keep config.h before memcheck.h, for NVALGRIND */
  43 #include "config.h"
  44
  45 #include "memcheck.h"
  46
  47
  48 /* We need to know how to align blocks of data for general use. I'm not sure
  49 how to get an alignment factor in general. In the current world, a value of 8
  50 is probably right, and this is sizeof(double) on some systems and sizeof(void
  51 *) on others, so take the larger of those. Since everything in this expression
  52 is a constant, the compiler should optimize it to a simple constant wherever it
  53 appears (I checked that gcc does do this). */
  54
  55 #define alignment \
  56   ((sizeof(void *) > sizeof(double))? sizeof(void *) : sizeof(double))
  57
  58 /* Size of block to get from malloc to carve up into smaller ones. This
  59 must be a multiple of the alignment. We assume that 8192 is going to be
  60 suitably aligned. */
  61
  62 #define STORE_BLOCK_SIZE 8192
  63
  64 /* store_reset() will not free the following block if the last used block has
  65 less than this much left in it. */
  66
  67 #define STOREPOOL_MIN_SIZE 256
  68
  69 /* Structure describing the beginning of each big block. */
  70
  71 typedef struct storeblock {
  72   struct storeblock *next;
  73   size_t length;
  74 } storeblock;
  75
  76 /* Just in case we find ourselves on a system where the structure above has a
  77 length that is not a multiple of the alignment, set up a macro for the padded
  78 length. */
  79
  80 #define ALIGNED_SIZEOF_STOREBLOCK \
  81   (((sizeof(storeblock) + alignment - 1) / alignment) * alignment)
  82
  83 /* Variables holding data for the local pools of store. The current pool number
  84 is held in store_pool, which is global so that it can be changed from outside.
  85 Setting the initial length values to -1 forces a malloc for the first call,
  86 even if the length is zero (which is used for getting a point to reset to). */
  87
  88 int store_pool = POOL_PERM;
  89
  90 static storeblock *chainbase[3] = { NULL, NULL, NULL };
  91 static storeblock *current_block[3] = { NULL, NULL, NULL };
  92 static void *next_yield[3] = { NULL, NULL, NULL };
  93 static int yield_length[3] = { -1, -1, -1 };
  94
  95 /* pool_malloc holds the amount of memory used by the store pools; this goes up
  96 and down as store is reset or released. nonpool_malloc is the total got by
  97 malloc from other calls; this doesn't go down because it is just freed by
  98 pointer. */
  99
 100 static int pool_malloc = 0;
 101 static int nonpool_malloc = 0;
 102
 103 /* This variable is set by store_get() to its yield, and by store_reset() to
 104 NULL. This enables string_cat() to optimize its store handling for very long
 105 strings. That's why the variable is global. */
 106
 107 void *store_last_get[3] = { NULL, NULL, NULL };
 108
 109
 110
 111 /*************************************************
 112 *       Get a block from the current pool        *
 113 *************************************************/
 114
 115 /* Running out of store is a total disaster. This function is called via the
 116 macro store_get(). It passes back a block of store within the current big
 117 block, getting a new one if necessary. The address is saved in
 118 store_last_was_get.
 119
 120 Arguments:
 121   size        amount wanted
 122   filename    source file from which called
 123   linenumber  line number in source file.
 124
 125 Returns:      pointer to store (panic on malloc failure)
 126 */
 127
 128 void *
 129 store_get_3(int size, const char *filename, int linenumber)
 130 {
 131 /* Round up the size to a multiple of the alignment. Although this looks a
 132 messy statement, because "alignment" is a constant expression, the compiler can
 133 do a reasonable job of optimizing, especially if the value of "alignment" is a
 134 power of two. I checked this with -O2, and gcc did very well, compiling it to 4
 135 instructions on a Sparc (alignment = 8). */
 136
 137 if (size % alignment != 0) size += alignment - (size % alignment);
 138
 139 /* If there isn't room in the current block, get a new one. The minimum
 140 size is STORE_BLOCK_SIZE, and we would expect this to be the norm, since
 141 these functions are mostly called for small amounts of store. */
 142
 143 if (size > yield_length[store_pool])
 144   {
 145   int length = (size <= STORE_BLOCK_SIZE)? STORE_BLOCK_SIZE : size;
 146   int mlength = length + ALIGNED_SIZEOF_STOREBLOCK;
 147   storeblock *newblock = NULL;
 148
 149   /* Sometimes store_reset() may leave a block for us; check if we can use it */
 150
 151   if (current_block[store_pool] != NULL &&
 152       current_block[store_pool]->next != NULL)
 153     {
 154     newblock = current_block[store_pool]->next;
 155     if (newblock->length < length)
 156       {
 157       /* Give up on this block, because it's too small */
 158       store_free(newblock);
 159       newblock = NULL;
 160       }
 161     }
 162
 163   /* If there was no free block, get a new one */
 164
 165   if (newblock == NULL)
 166     {
 167     pool_malloc += mlength;           /* Used in pools */
 168     nonpool_malloc -= mlength;        /* Exclude from overall total */
 169     newblock = store_malloc(mlength);
 170     newblock->next = NULL;
 171     newblock->length = length;
 172     if (chainbase[store_pool] == NULL) chainbase[store_pool] = newblock;
 173       else current_block[store_pool]->next = newblock;
 174     }
 175
 176   current_block[store_pool] = newblock;
 177   yield_length[store_pool] = newblock->length;
 178   next_yield[store_pool] =
 179     (void *)((char *)current_block[store_pool] + ALIGNED_SIZEOF_STOREBLOCK);
 180   (void) VALGRIND_MAKE_MEM_NOACCESS(next_yield[store_pool], yield_length[store_pool]);
 181   }
 182
 183 /* There's (now) enough room in the current block; the yield is the next
 184 pointer. */
 185
 186 store_last_get[store_pool] = next_yield[store_pool];
 187
 188 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 189 giving warnings. */
 190
 191 #ifdef COMPILE_UTILITY
 192 filename = filename;
 193 linenumber = linenumber;
 194 #else
 195 DEBUG(D_memory)
 196   {
 197   if (running_in_test_harness)
 198     debug_printf("---%d Get %5d\n", store_pool, size);
 199   else
 200     debug_printf("---%d Get %6p %5d %-14s %4d\n", store_pool,
 201       store_last_get[store_pool], size, filename, linenumber);
 202   }
 203 #endif  /* COMPILE_UTILITY */
 204
 205 (void) VALGRIND_MAKE_MEM_UNDEFINED(store_last_get[store_pool], size);
 206 /* Update next pointer and number of bytes left in the current block. */
 207
 208 next_yield[store_pool] = (void *)((char *)next_yield[store_pool] + size);
 209 yield_length[store_pool] -= size;
 210
 211 return store_last_get[store_pool];
 212 }
 213
 214
 215
 216 /*************************************************
 217 *       Get a block from the PERM pool           *
 218 *************************************************/
 219
 220 /* This is just a convenience function, useful when just a single block is to
 221 be obtained.
 222
 223 Arguments:
 224   size        amount wanted
 225   filename    source file from which called
 226   linenumber  line number in source file.
 227
 228 Returns:      pointer to store (panic on malloc failure)
 229 */
 230
 231 void *
 232 store_get_perm_3(int size, const char *filename, int linenumber)
 233 {
 234 void *yield;
 235 int old_pool = store_pool;
 236 store_pool = POOL_PERM;
 237 yield = store_get_3(size, filename, linenumber);
 238 store_pool = old_pool;
 239 return yield;
 240 }
 241
 242
 243
 244 /*************************************************
 245 *      Extend a block if it is at the top        *
 246 *************************************************/
 247
 248 /* While reading strings of unknown length, it is often the case that the
 249 string is being read into the block at the top of the stack. If it needs to be
 250 extended, it is more efficient just to extend the top block rather than
 251 allocate a new block and then have to copy the data. This function is provided
 252 for the use of string_cat(), but of course can be used elsewhere too.
 253
 254 Arguments:
 255   ptr        pointer to store block
 256   oldsize    current size of the block, as requested by user
 257   newsize    new size required
 258   filename   source file from which called
 259   linenumber line number in source file
 260
 261 Returns:     TRUE if the block is at the top of the stack and has been
 262              extended; FALSE if it isn't at the top of the stack, or cannot
 263              be extended
 264 */
 265
 266 BOOL
 267 store_extend_3(void *ptr, int oldsize, int newsize, const char *filename,
 268   int linenumber)
 269 {
 270 int inc = newsize - oldsize;
 271 int rounded_oldsize = oldsize;
 272
 273 if (rounded_oldsize % alignment != 0)
 274   rounded_oldsize += alignment - (rounded_oldsize % alignment);
 275
 276 if ((char *)ptr + rounded_oldsize != (char *)(next_yield[store_pool]) ||
 277     inc > yield_length[store_pool] + rounded_oldsize - oldsize)
 278   return FALSE;
 279
 280 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 281 giving warnings. */
 282
 283 #ifdef COMPILE_UTILITY
 284 filename = filename;
 285 linenumber = linenumber;
 286 #else
 287 DEBUG(D_memory)
 288   {
 289   if (running_in_test_harness)
 290     debug_printf("---%d Ext %5d\n", store_pool, newsize);
 291   else
 292     debug_printf("---%d Ext %6p %5d %-14s %4d\n", store_pool, ptr, newsize,
 293       filename, linenumber);
 294   }
 295 #endif  /* COMPILE_UTILITY */
 296
 297 if (newsize % alignment != 0) newsize += alignment - (newsize % alignment);
 298 next_yield[store_pool] = (char *)ptr + newsize;
 299 yield_length[store_pool] -= newsize - rounded_oldsize;
 300 (void) VALGRIND_MAKE_MEM_UNDEFINED(ptr + oldsize, inc);
 301 return TRUE;
 302 }
 303
 304
 305
 306
 307 /*************************************************
 308 *    Back up to a previous point on the stack    *
 309 *************************************************/
 310
 311 /* This function resets the next pointer, freeing any subsequent whole blocks
 312 that are now unused. Normally it is given a pointer that was the yield of a
 313 call to store_get, and is therefore aligned, but it may be given an offset
 314 after such a pointer in order to release the end of a block and anything that
 315 follows.
 316
 317 Arguments:
 318   ptr         place to back up to
 319   filename    source file from which called
 320   linenumber  line number in source file
 321
 322 Returns:      nothing
 323 */
 324
 325 void
 326 store_reset_3(void *ptr, const char *filename, int linenumber)
 327 {
 328 storeblock *bb;
 329 storeblock *b = current_block[store_pool];
 330 char *bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
 331 int newlength;
 332
 333 /* Last store operation was not a get */
 334
 335 store_last_get[store_pool] = NULL;
 336
 337 /* See if the place is in the current block - as it often will be. Otherwise,
 338 search for the block in which it lies. */
 339
 340 if ((char *)ptr < bc || (char *)ptr > bc + b->length)
 341   {
 342   for (b = chainbase[store_pool]; b != NULL; b = b->next)
 343     {
 344     bc = (char *)b + ALIGNED_SIZEOF_STOREBLOCK;
 345     if ((char *)ptr >= bc && (char *)ptr <= bc + b->length) break;
 346     }
 347   if (b == NULL)
 348     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "internal error: store_reset(%p) "
 349       "failed: pool=%d %-14s %4d", ptr, store_pool, filename, linenumber);
 350   }
 351
 352 /* Back up, rounding to the alignment if necessary. When testing, flatten
 353 the released memory. */
 354
 355 newlength = bc + b->length - (char *)ptr;
 356 #ifndef COMPILE_UTILITY
 357 if (running_in_test_harness) memset(ptr, 0xF0, newlength);
 358 #endif
 359 (void) VALGRIND_MAKE_MEM_NOACCESS(ptr, newlength);
 360 yield_length[store_pool] = newlength - (newlength % alignment);
 361 next_yield[store_pool] = (char *)ptr + (newlength % alignment);
 362 current_block[store_pool] = b;
 363
 364 /* Free any subsequent block. Do NOT free the first successor, if our
 365 current block has less than 256 bytes left. This should prevent us from
 366 flapping memory. However, keep this block only when it has the default size. */
 367
 368 if (yield_length[store_pool] < STOREPOOL_MIN_SIZE &&
 369     b->next != NULL &&
 370     b->next->length == STORE_BLOCK_SIZE)
 371   {
 372   b = b->next;
 373   (void) VALGRIND_MAKE_MEM_NOACCESS((char *)b + ALIGNED_SIZEOF_STOREBLOCK,
 374                 b->length - ALIGNED_SIZEOF_STOREBLOCK);
 375   }
 376
 377 bb = b->next;
 378 b->next = NULL;
 379
 380 while (bb != NULL)
 381   {
 382   b = bb;
 383   bb = bb->next;
 384   pool_malloc -= b->length + ALIGNED_SIZEOF_STOREBLOCK;
 385   store_free_3(b, filename, linenumber);
 386   }
 387
 388 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 389 giving warnings. */
 390
 391 #ifdef COMPILE_UTILITY
 392 filename = filename;
 393 linenumber = linenumber;
 394 #else
 395 DEBUG(D_memory)
 396   {
 397   if (running_in_test_harness)
 398     debug_printf("---%d Rst    ** %d\n", store_pool, pool_malloc);
 399   else
 400     debug_printf("---%d Rst %6p    ** %-14s %4d %d\n", store_pool, ptr,
 401       filename, linenumber, pool_malloc);
 402   }
 403 #endif  /* COMPILE_UTILITY */
 404 }
 405
 406
 407
 408
 409
 410 /************************************************
 411 *             Release store                     *
 412 ************************************************/
 413
 414 /* This function is specifically provided for use when reading very
 415 long strings, e.g. header lines. When the string gets longer than a
 416 complete block, it gets copied to a new block. It is helpful to free
 417 the old block iff the previous copy of the string is at its start,
 418 and therefore the only thing in it. Otherwise, for very long strings,
 419 dead store can pile up somewhat disastrously. This function checks that
 420 the pointer it is given is the first thing in a block, and if so,
 421 releases that block.
 422
 423 Arguments:
 424   block       block of store to consider
 425   filename    source file from which called
 426   linenumber  line number in source file
 427
 428 Returns:      nothing
 429 */
 430
 431 void
 432 store_release_3(void *block, const char *filename, int linenumber)
 433 {
 434 storeblock *b;
 435
 436 /* It will never be the first block, so no need to check that. */
 437
 438 for (b = chainbase[store_pool]; b != NULL; b = b->next)
 439   {
 440   storeblock *bb = b->next;
 441   if (bb != NULL && (char *)block == (char *)bb + ALIGNED_SIZEOF_STOREBLOCK)
 442     {
 443     b->next = bb->next;
 444     pool_malloc -= bb->length + ALIGNED_SIZEOF_STOREBLOCK;
 445
 446     /* Cut out the debugging stuff for utilities, but stop picky compilers
 447     from giving warnings. */
 448
 449     #ifdef COMPILE_UTILITY
 450     filename = filename;
 451     linenumber = linenumber;
 452     #else
 453     DEBUG(D_memory)
 454       {
 455       if (running_in_test_harness)
 456         debug_printf("-Release       %d\n", pool_malloc);
 457       else
 458         debug_printf("-Release %6p %-20s %4d %d\n", (void *)bb, filename,
 459           linenumber, pool_malloc);
 460       }
 461     if (running_in_test_harness)
 462       memset(bb, 0xF0, bb->length+ALIGNED_SIZEOF_STOREBLOCK);
 463     #endif  /* COMPILE_UTILITY */
 464
 465     free(bb);
 466     return;
 467     }
 468   }
 469 }
 470
 471
 472
 473
 474 /*************************************************
 475 *                Malloc store                    *
 476 *************************************************/
 477
 478 /* Running out of store is a total disaster for exim. Some malloc functions
 479 do not run happily on very small sizes, nor do they document this fact. This
 480 function is called via the macro store_malloc().
 481
 482 Arguments:
 483   size        amount of store wanted
 484   filename    source file from which called
 485   linenumber  line number in source file
 486
 487 Returns:      pointer to gotten store (panic on failure)
 488 */
 489
 490 void *
 491 store_malloc_3(int size, const char *filename, int linenumber)
 492 {
 493 void *yield;
 494
 495 if (size < 16) size = 16;
 496 yield = malloc((size_t)size);
 497
 498 if (yield == NULL)
 499   log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to malloc %d bytes of memory: "
 500     "called from line %d of %s", size, linenumber, filename);
 501
 502 nonpool_malloc += size;
 503
 504 /* Cut out the debugging stuff for utilities, but stop picky compilers from
 505 giving warnings. */
 506
 507 #ifdef COMPILE_UTILITY
 508 filename = filename;
 509 linenumber = linenumber;
 510 #else
 511
 512 /* If running in test harness, spend time making sure all the new store
 513 is not filled with zeros so as to catch problems. */
 514
 515 if (running_in_test_harness)
 516   {
 517   memset(yield, 0xF0, (size_t)size);
 518   DEBUG(D_memory) debug_printf("--Malloc %5d %d %d\n", size, pool_malloc,
 519     nonpool_malloc);
 520   }
 521 else
 522   {
 523   DEBUG(D_memory) debug_printf("--Malloc %6p %5d %-14s %4d %d %d\n", yield,
 524     size, filename, linenumber, pool_malloc, nonpool_malloc);
 525   }
 526 #endif  /* COMPILE_UTILITY */
 527
 528 return yield;
 529 }
 530
 531
 532 /************************************************
 533 *             Free store                        *
 534 ************************************************/
 535
 536 /* This function is called by the macro store_free().
 537
 538 Arguments:
 539   block       block of store to free
 540   filename    source file from which called
 541   linenumber  line number in source file
 542
 543 Returns:      nothing
 544 */
 545
 546 void
 547 store_free_3(void *block, const char *filename, int linenumber)
 548 {
 549 #ifdef COMPILE_UTILITY
 550 filename = filename;
 551 linenumber = linenumber;
 552 #else
 553 DEBUG(D_memory)
 554   {
 555   if (running_in_test_harness)
 556     debug_printf("----Free\n");
 557   else
 558     debug_printf("----Free %6p %-20s %4d\n", block, filename, linenumber);
 559   }
 560 #endif  /* COMPILE_UTILITY */
 561 free(block);
 562 }
 563
 564 /* End of store.c */