/*
* static int split_block
*
* DESCRIPTION:
*
* When freeing space in a multi-block chunk we have to create new
* blocks out of the upper areas being freed.
*
* RETURNS:
*
* Success - MPOOL_ERROR_NONE
*
* Failure - Mpool error code
*
* ARGUMENTS:
*
* mp_p <-> Pointer to the memory pool.
*
* free_addr -> Address that we are freeing.
*
* size -> Size of the space that we are taking from address.
*/
static int split_block(mpool_t * mp_p, void *free_addr,
const unsigned long size)
{
mpool_block_t *block_p, *new_block_p;
int ret, page_n;
void *end_p;
/*
* 1st we find the block pointer from our free addr. At this point
* the pointer must be the 1st one in the block if it is spans
* multiple blocks.
*/
block_p = (mpool_block_t *) ((char *)free_addr - sizeof(mpool_block_t));
if (block_p->mb_magic != BLOCK_MAGIC
|| block_p->mb_magic2 != BLOCK_MAGIC) {
return MPOOL_ERROR_POOL_OVER;
}
page_n = PAGES_IN_SIZE(mp_p, size);
/* we are creating a new block structure for the 2nd ... */
new_block_p = (mpool_block_t *) ((char *)block_p +
SIZE_OF_PAGES(mp_p, page_n));
new_block_p->mb_magic = BLOCK_MAGIC;
/* New bounds is 1st block bounds. The 1st block's is reset below. */
new_block_p->mb_bounds_p = block_p->mb_bounds_p;
/* Continue the linked list. The 1st block will point to us below. */
new_block_p->mb_next_p = block_p->mb_next_p;
new_block_p->mb_magic2 = BLOCK_MAGIC;
/* bounds for the 1st block are reset to the 1st page only */
block_p->mb_bounds_p = (char *)new_block_p;
/* the next block pointer for the 1st block is now the new one */
block_p->mb_next_p = new_block_p;
/* only free the space in the 1st block if it is only 1 block in size */
if (page_n == 1) {
/* now free the rest of the 1st block block */
end_p = (char *)free_addr + size;
ret = free_pointer(mp_p, end_p,
(char *)block_p->mb_bounds_p -
(char *)end_p);
if (ret != MPOOL_ERROR_NONE) {
return ret;
}
}
/* now free the rest of the block */
ret = free_pointer(mp_p, FIRST_ADDR_IN_BLOCK(new_block_p),
MEMORY_IN_BLOCK(new_block_p));
if (ret != MPOOL_ERROR_NONE) {
return ret;
}
return MPOOL_ERROR_NONE;
}
/*
* mpool_t *mpool_open
*
* DESCRIPTION:
*
* Open/allocate a new memory pool.
*
* RETURNS:
*
* Success - Pool pointer which must be passed to mpool_close to
* deallocate.
*
* Failure - NULL
*
* ARGUMENTS:
*
* flags -> Flags to set attributes of the memory pool. See the top
* of mpool.h.
*
* page_size -> Set the internal memory page-size. This must be a
* multiple of the getpagesize() value. Set to 0 for the default.
*
* start_addr -> Starting address to try and allocate memory pools.
* This is ignored if the MPOOL_FLAG_USE_SBRK is enabled.
*
* error_p <- Pointer to integer which, if not NULL, will be set with
* a mpool error code.
*/
mpool_t *mpool_open(const unsigned int flags, const unsigned int page_size,
void *start_addr, int *error_p)
{
mpool_block_t *block_p;
int page_n, ret;
mpool_t mp, *mp_p;
void *free_addr;
if (! enabled_b) {
startup();
}
/* zero our temp struct */
memset(&mp, 0, sizeof(mp));
mp.mp_magic = MPOOL_MAGIC;
mp.mp_flags = flags;
mp.mp_alloc_c = 0;
mp.mp_user_alloc = 0;
mp.mp_max_alloc = 0;
mp.mp_page_c = 0;
/* mp.mp_page_size set below */
/* mp.mp_blocks_bit_n set below */
/* mp.mp_fd set below */
/* mp.mp_top set below */
/* mp.mp_addr set below */
mp.mp_log_func = NULL;
mp.mp_min_p = NULL;
mp.mp_bounds_p = NULL;
mp.mp_first_p = NULL;
mp.mp_last_p = NULL;
mp.mp_magic2 = MPOOL_MAGIC;
/* get and sanity check our page size */
if (page_size > 0) {
mp.mp_page_size = page_size;
if (mp.mp_page_size % getpagesize() != 0) {
SET_POINTER(error_p, MPOOL_ERROR_ARG_INVALID);
return NULL;
}
}
else {
mp.mp_page_size = getpagesize() * DEFAULT_PAGE_MULT;
if (mp.mp_page_size % 1024 != 0) {
SET_POINTER(error_p, MPOOL_ERROR_PAGE_SIZE);
return NULL;
}
}
if (BIT_IS_SET(flags, MPOOL_FLAG_USE_SBRK)) {
mp.mp_fd = -1;
mp.mp_addr = NULL;
mp.mp_top = 0;
}
else {
/* open dev-zero for our mmaping */
mp.mp_fd = open("/dev/zero", O_RDWR, 0);
if (mp.mp_fd < 0) {
SET_POINTER(error_p, MPOOL_ERROR_OPEN_ZERO);
return NULL;
}
mp.mp_addr = start_addr;
/* we start at the front of the file */
mp.mp_top = 0;
}
/*
* Find out how many pages we need for our mpool structure.
*
* NOTE: this adds possibly unneeded space for mpool_block_t which
* may not be in this block.
*/
page_n = PAGES_IN_SIZE(&mp, sizeof(mpool_t));
/* now allocate us space for the actual struct */
mp_p = alloc_pages(&mp, page_n, error_p);
if (mp_p == NULL) {
if (mp.mp_fd >= 0) {
(void)close(mp.mp_fd);
mp.mp_fd = -1;
}
return NULL;
}
/*
* NOTE: we do not normally free the rest of the block here because
* we want to lesson the chance of an allocation overwriting the
* main structure.
*/
if (BIT_IS_SET(flags, MPOOL_FLAG_HEAVY_PACKING)) {
/* we add a block header to the front of the block */
block_p = (mpool_block_t *)mp_p;
/* init the block header */
block_p->mb_magic = BLOCK_MAGIC;
block_p->mb_bounds_p = (char *)block_p + SIZE_OF_PAGES(&mp, page_n);
block_p->mb_next_p = NULL;
block_p->mb_magic2 = BLOCK_MAGIC;
/* the mpool pointer is then the 2nd thing in the block */
mp_p = FIRST_ADDR_IN_BLOCK(block_p);
free_addr = (char *)mp_p + sizeof(mpool_t);
/* free the rest of the block */
ret = free_pointer(&mp, free_addr,
(char *)block_p->mb_bounds_p - (char *)free_addr);
if (ret != MPOOL_ERROR_NONE) {
if (mp.mp_fd >= 0) {
(void)close(mp.mp_fd);
mp.mp_fd = -1;
}
/* NOTE: after this line mp_p will be invalid */
(void)free_pages(block_p, SIZE_OF_PAGES(&mp, page_n),
BIT_IS_SET(flags, MPOOL_FLAG_USE_SBRK));
SET_POINTER(error_p, ret);
return NULL;
}
/*
* NOTE: if we are HEAVY_PACKING then the 1st block with the mpool
* header is not on the block linked list.
*/
/* now copy our tmp structure into our new memory area */
memcpy(mp_p, &mp, sizeof(mpool_t));
/* we setup min/max to our current address which is as good as any */
mp_p->mp_min_p = block_p;
mp_p->mp_bounds_p = block_p->mb_bounds_p;
}
else {
/* now copy our tmp structure into our new memory area */
memcpy(mp_p, &mp, sizeof(mpool_t));
/* we setup min/max to our current address which is as good as any */
mp_p->mp_min_p = mp_p;
mp_p->mp_bounds_p = (char *)mp_p + SIZE_OF_PAGES(mp_p, page_n);
}
SET_POINTER(error_p, MPOOL_ERROR_NONE);
return mp_p;
}
/*
* static void *get_space
*
* DESCRIPTION:
*
* Moved a pointer into our free lists.
*
* RETURNS:
*
* Success - New address that we can use.
*
* Failure - NULL
*
* ARGUMENTS:
*
* mp_p <-> Pointer to the memory pool.
*
* byte_size -> Size of the address space that we need.
*
* error_p <- Pointer to integer which, if not NULL, will be set with
* a mpool error code.
*/
static void *get_space(mpool_t *mp_p, const unsigned long byte_size,
int *error_p)
{
mpool_block_t *block_p;
mpool_free_t free_pnt;
int ret;
unsigned long size;
unsigned int bit_c, page_n, left;
void *free_addr = NULL, *free_end;
size = byte_size;
while ((size & (sizeof(void *) - 1)) > 0) {
size++;
}
/*
* First we check the free lists looking for something with enough
* pages. Maybe we should only look X bits higher in the list.
*
* XXX: this is where we'd do the best fit. We'd look for the
* closest match. We then could put the rest of the allocation that
* we did not use in a lower free list. Have a define which states
* how deep in the free list to go to find the closest match.
*/
for (bit_c = size_to_bits(size); bit_c <= MAX_BITS; bit_c++) {
if (mp_p->mp_free[bit_c] != NULL) {
free_addr = mp_p->mp_free[bit_c];
break;
}
}
/*
* If we haven't allocated any blocks or if the last block doesn't
* have enough memory then we need a new block.
*/
if (bit_c > MAX_BITS) {
/* we need to allocate more space */
page_n = PAGES_IN_SIZE(mp_p, size);
/* now we try and get the pages we need/want */
block_p = alloc_pages(mp_p, page_n, error_p);
if (block_p == NULL) {
/* error_p set in alloc_pages */
return NULL;
}
/* init the block header */
block_p->mb_magic = BLOCK_MAGIC;
block_p->mb_bounds_p = (char *)block_p + SIZE_OF_PAGES(mp_p, page_n);
block_p->mb_next_p = mp_p->mp_first_p;
block_p->mb_magic2 = BLOCK_MAGIC;
/*
* We insert it into the front of the queue. We could add it to
* the end but there is not much use.
*/
mp_p->mp_first_p = block_p;
if (mp_p->mp_last_p == NULL) {
mp_p->mp_last_p = block_p;
}
free_addr = FIRST_ADDR_IN_BLOCK(block_p);
#ifdef DEBUG
(void)printf("had to allocate space for %lx of %lu bytes\n",
(long)free_addr, size);
#endif
free_end = (char *)free_addr + size;
left = (char *)block_p->mb_bounds_p - (char *)free_end;
}
else {
if (bit_c < min_bit_free_next) {
mp_p->mp_free[bit_c] = NULL;
/* calculate the number of left over bytes */
left = bits_to_size(bit_c) - size;
}
else if (bit_c < min_bit_free_next) {
/* grab the next pointer from the freed address into our list */
memcpy(mp_p->mp_free + bit_c, free_addr, sizeof(void *));
/* calculate the number of left over bytes */
left = bits_to_size(bit_c) - size;
}
else {
/* grab the free structure from the address */
memcpy(&free_pnt, free_addr, sizeof(free_pnt));
mp_p->mp_free[bit_c] = free_pnt.mf_next_p;
/* are we are splitting up a multiblock chunk into fewer blocks? */
if (PAGES_IN_SIZE(mp_p, free_pnt.mf_size) > PAGES_IN_SIZE(mp_p, size)) {
ret = split_block(mp_p, free_addr, size);
if (ret != MPOOL_ERROR_NONE) {
SET_POINTER(error_p, ret);
return NULL;
}
/* left over memory was taken care of in split_block */
left = 0;
}
else {
/* calculate the number of left over bytes */
left = free_pnt.mf_size - size;
}
}
#ifdef DEBUG
(void)printf("found a free block at %lx of %lu bytes\n",
(long)free_addr, left + size);
#endif
free_end = (char *)free_addr + size;
}
/*
* If we have memory left over then we free it so someone else can
* use it. We do not free the space if we just allocated a
* multi-block chunk because we need to have every allocation easily
* find the start of the block. Every user address % page-size
* should take us to the start of the block.
*/
if (left > 0 && size <= MAX_BLOCK_USER_MEMORY(mp_p)) {
/* free the rest of the block */
ret = free_pointer(mp_p, free_end, left);
if (ret != MPOOL_ERROR_NONE) {
SET_POINTER(error_p, ret);
return NULL;
}
}
/* update our bounds */
if (free_addr > mp_p->mp_bounds_p) {
mp_p->mp_bounds_p = free_addr;
}
else if (free_addr < mp_p->mp_min_p) {
mp_p->mp_min_p = free_addr;
}
return free_addr;
}
/*
* static void free_pointer
*
* DESCRIPTION:
*
* Moved a pointer into our free lists.
*
* RETURNS:
*
* Success - MPOOL_ERROR_NONE
*
* Failure - Mpool error code
*
* ARGUMENTS:
*
* mp_p <-> Pointer to the memory pool.
*
* addr <-> Address where to write the magic. We may write a next
* pointer to it.
*
* size -> Size of the address space.
*/
static int free_pointer(mpool_t *mp_p, void *addr,
const unsigned long size)
{
unsigned int bit_n;
unsigned long real_size;
mpool_free_t free_pnt;
#ifdef DEBUG
(void)printf("freeing a block at %lx of %lu bytes\n", (long)addr, size);
#endif
if (size == 0) {
return MPOOL_ERROR_NONE;
}
/*
* if the user size is larger then can fit in an entire block then
* we change the size
*/
if (size > MAX_BLOCK_USER_MEMORY(mp_p)) {
real_size = SIZE_OF_PAGES(mp_p, PAGES_IN_SIZE(mp_p, size)) -
sizeof(mpool_block_t);
}
else {
real_size = size;
}
/*
* We use a specific free bits calculation here because if we are
* freeing 10 bytes then we will be putting it into the 8-byte free
* list and not the 16 byte list. size_to_bits(10) will return 4
* instead of 3.
*/
bit_n = size_to_free_bits(real_size);
/*
* Minimal error checking. We could go all the way through the
* list however this might be prohibitive.
*/
if (mp_p->mp_free[bit_n] == addr) {
return MPOOL_ERROR_IS_FREE;
}
/* add the freed pointer to the free list */
if (bit_n < min_bit_free_next) {
/*
* Yes we know this will lose 99% of the allocations but what else
* can we do? No space for a next pointer.
*/
if (mp_p->mp_free[bit_n] == NULL) {
mp_p->mp_free[bit_n] = addr;
}
}
else if (bit_n < min_bit_free_size) {
/* we copy, not assign, to maintain the free list */
memcpy(addr, mp_p->mp_free + bit_n, sizeof(void *));
mp_p->mp_free[bit_n] = addr;
}
else {
/* setup our free list structure */
free_pnt.mf_next_p = mp_p->mp_free[bit_n];
free_pnt.mf_size = real_size;
/* we copy the structure in since we don't know about alignment */
memcpy(addr, &free_pnt, sizeof(free_pnt));
mp_p->mp_free[bit_n] = addr;
}
return MPOOL_ERROR_NONE;
}
