/************************************************* * Exim - an Internet mail transport agent * *************************************************/ /* Copyright (c) University of Cambridge 1995 - 2018 */ /* See the file NOTICE for conditions of use and distribution. */ /* Exim gets and frees all its store through these functions. In the original implementation there was a lot of mallocing and freeing of small bits of store. The philosophy has now changed to a scheme which includes the concept of "stacking pools" of store. For the short-lived processes, there isn't any real need to do any garbage collection, but the stack concept allows quick resetting in places where this seems sensible. Obviously the long-running processes (the daemon, the queue runner, and eximon) must take care not to eat store. The following different types of store are recognized: . Long-lived, large blocks: This is implemented by retaining the original malloc/free functions, and it used for permanent working buffers and for getting blocks to cut up for the other types. . Long-lived, small blocks: This is used for blocks that have to survive until the process exits. It is implemented as a stacking pool (POOL_PERM). This is functionally the same as store_malloc(), except that the store can't be freed, but I expect it to be more efficient for handling small blocks. . Short-lived, short blocks: Most of the dynamic store falls into this category. It is implemented as a stacking pool (POOL_MAIN) which is reset after accepting a message when multiple messages are received by a single process. Resetting happens at some other times as well, usually fairly locally after some specific processing that needs working store. . There is a separate pool (POOL_SEARCH) that is used only for lookup storage. This means it can be freed when search_tidyup() is called to close down all the lookup caching. */ #include "exim.h" /* keep config.h before memcheck.h, for NVALGRIND */ #include "config.h" #include "memcheck.h" /* We need to know how to align blocks of data for general use. I'm not sure how to get an alignment factor in general. In the current world, a value of 8 is probably right, and this is sizeof(double) on some systems and sizeof(void *) on others, so take the larger of those. Since everything in this expression is a constant, the compiler should optimize it to a simple constant wherever it appears (I checked that gcc does do this). */ #define alignment \ ((sizeof(void *) > sizeof(double))? sizeof(void *) : sizeof(double)) /* Size of block to get from malloc to carve up into smaller ones. This must be a multiple of the alignment. We assume that 8192 is going to be suitably aligned. */ #define STORE_BLOCK_SIZE 8192 /* store_reset() will not free the following block if the last used block has less than this much left in it. */ #define STOREPOOL_MIN_SIZE 256 /* Structure describing the beginning of each big block. */ typedef struct storeblock { struct storeblock *next; size_t length; } storeblock; /* Just in case we find ourselves on a system where the structure above has a length that is not a multiple of the alignment, set up a macro for the padded length. */ #define ALIGNED_SIZEOF_STOREBLOCK \ (((sizeof(storeblock) + alignment - 1) / alignment) * alignment) /* Variables holding data for the local pools of store. The current pool number is held in store_pool, which is global so that it can be changed from outside. Setting the initial length values to -1 forces a malloc for the first call, even if the length is zero (which is used for getting a point to reset to). */ int store_pool = POOL_PERM; static storeblock *chainbase[3] = { NULL, NULL, NULL }; static storeblock *current_block[3] = { NULL, NULL, NULL }; static void *next_yield[3] = { NULL, NULL, NULL }; static int yield_length[3] = { -1, -1, -1 }; /* pool_malloc holds the amount of memory used by the store pools; this goes up and down as store is reset or released. nonpool_malloc is the total got by malloc from other calls; this doesn't go down because it is just freed by pointer. */ static int pool_malloc = 0; static int nonpool_malloc = 0; /* This variable is set by store_get() to its yield, and by store_reset() to NULL. This enables string_cat() to optimize its store handling for very long strings. That's why the variable is global. */ void *store_last_get[3] = { NULL, NULL, NULL }; /************************************************* * Get a block from the current pool * *************************************************/ /* Running out of store is a total disaster. This function is called via the macro store_get(). It passes back a block of store within the current big block, getting a new one if necessary. The address is saved in store_last_was_get. Arguments: size amount wanted filename source file from which called linenumber line number in source file. Returns: pointer to store (panic on malloc failure) */ void * store_get_3(int size, const char *filename, int linenumber) { /* Round up the size to a multiple of the alignment. Although this looks a messy statement, because "alignment" is a constant expression, the compiler can do a reasonable job of optimizing, especially if the value of "alignment" is a power of two. I checked this with -O2, and gcc did very well, compiling it to 4 instructions on a Sparc (alignment = 8). */ if (size % alignment != 0) size += alignment - (size % alignment); /* If there isn't room in the current block, get a new one. The minimum size is STORE_BLOCK_SIZE, and we would expect this to be the norm, since these functions are mostly called for small amounts of store. */ if (size > yield_length[store_pool]) { int length = (size <= STORE_BLOCK_SIZE)? STORE_BLOCK_SIZE : size; int mlength = length + ALIGNED_SIZEOF_STOREBLOCK; storeblock * newblock = NULL; /* Sometimes store_reset() may leave a block for us; check if we can use it */ if ( (newblock = current_block[store_pool]) && (newblock = newblock->next) && newblock->length < length ) { /* Give up on this block, because it's too small */ store_free(newblock); newblock = NULL; } /* If there was no free block, get a new one */ if (!newblock) { pool_malloc += mlength; /* Used in pools */ nonpool_malloc -= mlength; /* Exclude from overall total */ newblock = store_malloc(mlength); newblock->next = NULL; newblock->length = length; if (!chainbase[store_pool]) chainbase[store_pool] = newblock; else current_block[store_pool]->next = newblock; } current_block[store_pool] = newblock; yield_length[store_pool] = newblock->length; next_yield[store_pool] = (void *)(CS current_block[store_pool] + ALIGNED_SIZEOF_STOREBLOCK); (void) VALGRIND_MAKE_MEM_NOACCESS(next_yield[store_pool], yield_length[store_pool]); } /* There's (now) enough room in the current block; the yield is the next pointer. */ store_last_get[store_pool] = next_yield[store_pool]; /* Cut out the debugging stuff for utilities, but stop picky compilers from giving warnings. */ #ifdef COMPILE_UTILITY filename = filename; linenumber = linenumber; #else DEBUG(D_memory) { if (f.running_in_test_harness) debug_printf("---%d Get %5d\n", store_pool, size); else debug_printf("---%d Get %6p %5d %-14s %4d\n", store_pool, store_last_get[store_pool], size, filename, linenumber); } #endif /* COMPILE_UTILITY */ (void) VALGRIND_MAKE_MEM_UNDEFINED(store_last_get[store_pool], size); /* Update next pointer and number of bytes left in the current block. */ next_yield[store_pool] = (void *)(CS next_yield[store_pool] + size); yield_length[store_pool] -= size; return store_last_get[store_pool]; } /************************************************* * Get a block from the PERM pool * *************************************************/ /* This is just a convenience function, useful when just a single block is to be obtained. Arguments: size amount wanted filename source file from which called linenumber line number in source file. Returns: pointer to store (panic on malloc failure) */ void * store_get_perm_3(int size, const char *filename, int linenumber) { void *yield; int old_pool = store_pool; store_pool = POOL_PERM; yield = store_get_3(size, filename, linenumber); store_pool = old_pool; return yield; } /************************************************* * Extend a block if it is at the top * *************************************************/ /* While reading strings of unknown length, it is often the case that the string is being read into the block at the top of the stack. If it needs to be extended, it is more efficient just to extend the top block rather than allocate a new block and then have to copy the data. This function is provided for the use of string_cat(), but of course can be used elsewhere too. Arguments: ptr pointer to store block oldsize current size of the block, as requested by user newsize new size required filename source file from which called linenumber line number in source file Returns: TRUE if the block is at the top of the stack and has been extended; FALSE if it isn't at the top of the stack, or cannot be extended */ BOOL store_extend_3(void *ptr, int oldsize, int newsize, const char *filename, int linenumber) { int inc = newsize - oldsize; int rounded_oldsize = oldsize; if (rounded_oldsize % alignment != 0) rounded_oldsize += alignment - (rounded_oldsize % alignment); if (CS ptr + rounded_oldsize != CS (next_yield[store_pool]) || inc > yield_length[store_pool] + rounded_oldsize - oldsize) return FALSE; /* Cut out the debugging stuff for utilities, but stop picky compilers from giving warnings. */ #ifdef COMPILE_UTILITY filename = filename; linenumber = linenumber; #else DEBUG(D_memory) { if (f.running_in_test_harness) debug_printf("---%d Ext %5d\n", store_pool, newsize); else debug_printf("---%d Ext %6p %5d %-14s %4d\n", store_pool, ptr, newsize, filename, linenumber); } #endif /* COMPILE_UTILITY */ if (newsize % alignment != 0) newsize += alignment - (newsize % alignment); next_yield[store_pool] = CS ptr + newsize; yield_length[store_pool] -= newsize - rounded_oldsize; (void) VALGRIND_MAKE_MEM_UNDEFINED(ptr + oldsize, inc); return TRUE; } /************************************************* * Back up to a previous point on the stack * *************************************************/ /* This function resets the next pointer, freeing any subsequent whole blocks that are now unused. Normally it is given a pointer that was the yield of a call to store_get, and is therefore aligned, but it may be given an offset after such a pointer in order to release the end of a block and anything that follows. Arguments: ptr place to back up to filename source file from which called linenumber line number in source file Returns: nothing */ void store_reset_3(void *ptr, const char *filename, int linenumber) { storeblock * bb; storeblock * b = current_block[store_pool]; char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK; int newlength; /* Last store operation was not a get */ store_last_get[store_pool] = NULL; /* See if the place is in the current block - as it often will be. Otherwise, search for the block in which it lies. */ if (CS ptr < bc || CS ptr > bc + b->length) { for (b = chainbase[store_pool]; b; b = b->next) { bc = CS b + ALIGNED_SIZEOF_STOREBLOCK; if (CS ptr >= bc && CS ptr <= bc + b->length) break; } if (!b) log_write(0, LOG_MAIN|LOG_PANIC_DIE, "internal error: store_reset(%p) " "failed: pool=%d %-14s %4d", ptr, store_pool, filename, linenumber); } /* Back up, rounding to the alignment if necessary. When testing, flatten the released memory. */ newlength = bc + b->length - CS ptr; #ifndef COMPILE_UTILITY if (debug_store) { assert_no_variables(ptr, newlength, filename, linenumber); if (f.running_in_test_harness) { (void) VALGRIND_MAKE_MEM_DEFINED(ptr, newlength); memset(ptr, 0xF0, newlength); } } #endif (void) VALGRIND_MAKE_MEM_NOACCESS(ptr, newlength); yield_length[store_pool] = newlength - (newlength % alignment); next_yield[store_pool] = CS ptr + (newlength % alignment); current_block[store_pool] = b; /* Free any subsequent block. Do NOT free the first successor, if our current block has less than 256 bytes left. This should prevent us from flapping memory. However, keep this block only when it has the default size. */ if (yield_length[store_pool] < STOREPOOL_MIN_SIZE && b->next && b->next->length == STORE_BLOCK_SIZE) { b = b->next; #ifndef COMPILE_UTILITY if (debug_store) assert_no_variables(b, b->length + ALIGNED_SIZEOF_STOREBLOCK, filename, linenumber); #endif (void) VALGRIND_MAKE_MEM_NOACCESS(CS b + ALIGNED_SIZEOF_STOREBLOCK, b->length - ALIGNED_SIZEOF_STOREBLOCK); } bb = b->next; b->next = NULL; while ((b = bb)) { #ifndef COMPILE_UTILITY if (debug_store) assert_no_variables(b, b->length + ALIGNED_SIZEOF_STOREBLOCK, filename, linenumber); #endif bb = bb->next; pool_malloc -= b->length + ALIGNED_SIZEOF_STOREBLOCK; store_free_3(b, filename, linenumber); } /* Cut out the debugging stuff for utilities, but stop picky compilers from giving warnings. */ #ifdef COMPILE_UTILITY filename = filename; linenumber = linenumber; #else DEBUG(D_memory) { if (f.running_in_test_harness) debug_printf("---%d Rst ** %d\n", store_pool, pool_malloc); else debug_printf("---%d Rst %6p ** %-14s %4d %d\n", store_pool, ptr, filename, linenumber, pool_malloc); } #endif /* COMPILE_UTILITY */ } /************************************************ * Release store * ************************************************/ /* This function checks that the pointer it is given is the first thing in a block, and if so, releases that block. Arguments: block block of store to consider filename source file from which called linenumber line number in source file Returns: nothing */ static void store_release_3(void * block, const char * filename, int linenumber) { /* It will never be the first block, so no need to check that. */ for (storeblock * b = chainbase[store_pool]; b; b = b->next) { storeblock * bb = b->next; if (bb && CS block == CS bb + ALIGNED_SIZEOF_STOREBLOCK) { b->next = bb->next; pool_malloc -= bb->length + ALIGNED_SIZEOF_STOREBLOCK; /* Cut out the debugging stuff for utilities, but stop picky compilers from giving warnings. */ #ifdef COMPILE_UTILITY filename = filename; linenumber = linenumber; #else DEBUG(D_memory) if (f.running_in_test_harness) debug_printf("-Release %d\n", pool_malloc); else debug_printf("-Release %6p %-20s %4d %d\n", (void *)bb, filename, linenumber, pool_malloc); if (f.running_in_test_harness) memset(bb, 0xF0, bb->length+ALIGNED_SIZEOF_STOREBLOCK); #endif /* COMPILE_UTILITY */ free(bb); return; } } } /************************************************ * Move store * ************************************************/ /* Allocate a new block big enough to expend to the given size and copy the current data into it. Free the old one if possible. This function is specifically provided for use when reading very long strings, e.g. header lines. When the string gets longer than a complete block, it gets copied to a new block. It is helpful to free the old block iff the previous copy of the string is at its start, and therefore the only thing in it. Otherwise, for very long strings, dead store can pile up somewhat disastrously. This function checks that the pointer it is given is the first thing in a block, and that nothing has been allocated since. If so, releases that block. Arguments: block newsize len Returns: new location of data */ void * store_newblock_3(void * block, int newsize, int len, const char * filename, int linenumber) { BOOL release_ok = store_last_get[store_pool] == block; uschar * newtext = store_get(newsize); memcpy(newtext, block, len); if (release_ok) store_release_3(block, filename, linenumber); return (void *)newtext; } /************************************************* * Malloc store * *************************************************/ /* Running out of store is a total disaster for exim. Some malloc functions do not run happily on very small sizes, nor do they document this fact. This function is called via the macro store_malloc(). Arguments: size amount of store wanted filename source file from which called linenumber line number in source file Returns: pointer to gotten store (panic on failure) */ void * store_malloc_3(int size, const char *filename, int linenumber) { void *yield; if (size < 16) size = 16; if (!(yield = malloc((size_t)size))) log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to malloc %d bytes of memory: " "called from line %d of %s", size, linenumber, filename); nonpool_malloc += size; /* Cut out the debugging stuff for utilities, but stop picky compilers from giving warnings. */ #ifdef COMPILE_UTILITY filename = filename; linenumber = linenumber; #else /* If running in test harness, spend time making sure all the new store is not filled with zeros so as to catch problems. */ if (f.running_in_test_harness) { memset(yield, 0xF0, (size_t)size); DEBUG(D_memory) debug_printf("--Malloc %5d %d %d\n", size, pool_malloc, nonpool_malloc); } else { DEBUG(D_memory) debug_printf("--Malloc %6p %5d %-14s %4d %d %d\n", yield, size, filename, linenumber, pool_malloc, nonpool_malloc); } #endif /* COMPILE_UTILITY */ return yield; } /************************************************ * Free store * ************************************************/ /* This function is called by the macro store_free(). Arguments: block block of store to free filename source file from which called linenumber line number in source file Returns: nothing */ void store_free_3(void *block, const char *filename, int linenumber) { #ifdef COMPILE_UTILITY filename = filename; linenumber = linenumber; #else DEBUG(D_memory) { if (f.running_in_test_harness) debug_printf("----Free\n"); else debug_printf("----Free %6p %-20s %4d\n", block, filename, linenumber); } #endif /* COMPILE_UTILITY */ free(block); } /* End of store.c */