linux/lib/genalloc.c at master · bufferoverflow/linux · GitHub

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* Basic general purpose allocator for managing special purpose

* memory, for example, memory that is not managed by the regular

* kmalloc/kfree interface. Uses for this includes on-device special

* memory, uncached memory etc.

* It is safe to use the allocator in NMI handlers and other special

* unblockable contexts that could otherwise deadlock on locks. This

* is implemented by using atomic operations and retries on any

* conflicts. The disadvantage is that there may be livelocks in

* extreme cases. For better scalability, one allocator can be used

* for each CPU.

* The lockless operation only works if there is enough memory

* available. If new memory is added to the pool a lock has to be

* still taken. So any user relying on locklessness has to ensure

* that sufficient memory is preallocated.

* The basic atomic operation of this allocator is cmpxchg on long.

* On architectures that don't have NMI-safe cmpxchg implementation,

* the allocator can NOT be used in NMI handler. So code uses the

* allocator in NMI handler should depend on

* CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.

* This source code is licensed under the GNU General Public License,

* Version 2. See the file COPYING for more details.

#include <linux/slab.h>

#include <linux/export.h>

#include <linux/bitmap.h>

#include <linux/rculist.h>

#include <linux/interrupt.h>

#include <linux/genalloc.h>

#include <linux/of_address.h>

#include <linux/of_device.h>

static inline size_t chunk_size(const struct gen_pool_chunk *chunk)

{

return chunk->end_addr - chunk->start_addr + 1;

}

static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)

{

unsigned long val, nval;

nval = *addr;

do {

val = nval;

if (val & mask_to_set)

return -EBUSY;

cpu_relax();

} while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);

return 0;

}

static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)

{

unsigned long val, nval;

nval = *addr;

do {

val = nval;

if ((val & mask_to_clear) != mask_to_clear)

return -EBUSY;

cpu_relax();

} while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);

return 0;

}

* bitmap_set_ll - set the specified number of bits at the specified position

* @map: pointer to a bitmap

* @start: a bit position in @map

* @nr: number of bits to set

* Set @nr bits start from @start in @map lock-lessly. Several users

* can set/clear the same bitmap simultaneously without lock. If two

* users set the same bit, one user will return remain bits, otherwise

* return 0.

static int bitmap_set_ll(unsigned long *map, int start, int nr)

{

unsigned long *p = map + BIT_WORD(start);

const int size = start + nr;

int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);

unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

while (nr - bits_to_set >= 0) {

if (set_bits_ll(p, mask_to_set))

return nr;

nr -= bits_to_set;

bits_to_set = BITS_PER_LONG;

mask_to_set = ~0UL;

p++;

}

if (nr) {

mask_to_set &= BITMAP_LAST_WORD_MASK(size);

if (set_bits_ll(p, mask_to_set))

return nr;

}

return 0;

}

* bitmap_clear_ll - clear the specified number of bits at the specified position

* @map: pointer to a bitmap

* @start: a bit position in @map

* @nr: number of bits to set

* Clear @nr bits start from @start in @map lock-lessly. Several users

* can set/clear the same bitmap simultaneously without lock. If two

* users clear the same bit, one user will return remain bits,

* otherwise return 0.

static int bitmap_clear_ll(unsigned long *map, int start, int nr)

{

unsigned long *p = map + BIT_WORD(start);

const int size = start + nr;

int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);

unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

while (nr - bits_to_clear >= 0) {

if (clear_bits_ll(p, mask_to_clear))

return nr;

nr -= bits_to_clear;

bits_to_clear = BITS_PER_LONG;

mask_to_clear = ~0UL;

p++;

}

if (nr) {

mask_to_clear &= BITMAP_LAST_WORD_MASK(size);

if (clear_bits_ll(p, mask_to_clear))

return nr;

}

return 0;

}

/**

* gen_pool_create - create a new special memory pool

* @min_alloc_order: log base 2 of number of bytes each bitmap bit represents

* @nid: node id of the node the pool structure should be allocated on, or -1

* Create a new special memory pool that can be used to manage special purpose

* memory not managed by the regular kmalloc/kfree interface.

struct gen_pool *gen_pool_create(int min_alloc_order, int nid)

{

struct gen_pool *pool;

pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);

if (pool != NULL) {

spin_lock_init(&pool->lock);

INIT_LIST_HEAD(&pool->chunks);

pool->min_alloc_order = min_alloc_order;

pool->algo = gen_pool_first_fit;

pool->data = NULL;

}

return pool;

}

EXPORT_SYMBOL(gen_pool_create);

/**

* gen_pool_add_virt - add a new chunk of special memory to the pool

* @pool: pool to add new memory chunk to

* @virt: virtual starting address of memory chunk to add to pool

* @phys: physical starting address of memory chunk to add to pool

* @size: size in bytes of the memory chunk to add to pool

* @nid: node id of the node the chunk structure and bitmap should be

* allocated on, or -1

* Add a new chunk of special memory to the specified pool.

* Returns 0 on success or a -ve errno on failure.

int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,

size_t size, int nid)

{

struct gen_pool_chunk *chunk;

int nbits = size >> pool->min_alloc_order;

int nbytes = sizeof(struct gen_pool_chunk) +

BITS_TO_LONGS(nbits) * sizeof(long);

chunk = kzalloc_node(nbytes, GFP_KERNEL, nid);

if (unlikely(chunk == NULL))

return -ENOMEM;

chunk->phys_addr = phys;

chunk->start_addr = virt;

chunk->end_addr = virt + size - 1;

atomic_set(&chunk->avail, size);

spin_lock(&pool->lock);

list_add_rcu(&chunk->next_chunk, &pool->chunks);

spin_unlock(&pool->lock);

return 0;

}

EXPORT_SYMBOL(gen_pool_add_virt);

/**

* gen_pool_virt_to_phys - return the physical address of memory

* @pool: pool to allocate from

* @addr: starting address of memory

* Returns the physical address on success, or -1 on error.

phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)

{

struct gen_pool_chunk *chunk;

phys_addr_t paddr = -1;

rcu_read_lock();

list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {

if (addr >= chunk->start_addr && addr <= chunk->end_addr) {

paddr = chunk->phys_addr + (addr - chunk->start_addr);

break;

}

rcu_read_unlock();

return paddr;

}

EXPORT_SYMBOL(gen_pool_virt_to_phys);

/**

* gen_pool_destroy - destroy a special memory pool

* @pool: pool to destroy

* Destroy the specified special memory pool. Verifies that there are no

* outstanding allocations.

void gen_pool_destroy(struct gen_pool *pool)

{

struct list_head *_chunk, *_next_chunk;

struct gen_pool_chunk *chunk;

int order = pool->min_alloc_order;

int bit, end_bit;

list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {

chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);

list_del(&chunk->next_chunk);

end_bit = chunk_size(chunk) >> order;

bit = find_next_bit(chunk->bits, end_bit, 0);

BUG_ON(bit < end_bit);

kfree(chunk);

}

kfree(pool);

return;

}

EXPORT_SYMBOL(gen_pool_destroy);

/**

* gen_pool_alloc - allocate special memory from the pool

* @pool: pool to allocate from

* @size: number of bytes to allocate from the pool

* Allocate the requested number of bytes from the specified pool.

* Uses the pool allocation function (with first-fit algorithm by default).

* Can not be used in NMI handler on architectures without

* NMI-safe cmpxchg implementation.

unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)

{

struct gen_pool_chunk *chunk;

unsigned long addr = 0;

int order = pool->min_alloc_order;

int nbits, start_bit = 0, end_bit, remain;

#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

BUG_ON(in_nmi());

#endif

if (size == 0)

return 0;

nbits = (size + (1UL << order) - 1) >> order;

rcu_read_lock();

list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {

if (size > atomic_read(&chunk->avail))

continue;

end_bit = chunk_size(chunk) >> order;

retry:

start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,

pool->data);

if (start_bit >= end_bit)

continue;

remain = bitmap_set_ll(chunk->bits, start_bit, nbits);

if (remain) {

remain = bitmap_clear_ll(chunk->bits, start_bit,

nbits - remain);

BUG_ON(remain);

goto retry;

}

addr = chunk->start_addr + ((unsigned long)start_bit << order);

size = nbits << order;

atomic_sub(size, &chunk->avail);

break;

}

rcu_read_unlock();

return addr;

}

EXPORT_SYMBOL(gen_pool_alloc);

/**

* gen_pool_dma_alloc - allocate special memory from the pool for DMA usage

* @pool: pool to allocate from

* @size: number of bytes to allocate from the pool

* @dma: dma-view physical address

* Allocate the requested number of bytes from the specified pool.

* Uses the pool allocation function (with first-fit algorithm by default).

* Can not be used in NMI handler on architectures without

* NMI-safe cmpxchg implementation.

void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size, dma_addr_t *dma)

{

unsigned long vaddr;

if (!pool)

return NULL;

vaddr = gen_pool_alloc(pool, size);

if (!vaddr)

return NULL;

*dma = gen_pool_virt_to_phys(pool, vaddr);

return (void *)vaddr;

}

EXPORT_SYMBOL(gen_pool_dma_alloc);

/**

* gen_pool_free - free allocated special memory back to the pool

* @pool: pool to free to

* @addr: starting address of memory to free back to pool

* @size: size in bytes of memory to free

* Free previously allocated special memory back to the specified

* pool. Can not be used in NMI handler on architectures without

* NMI-safe cmpxchg implementation.

void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)

{

struct gen_pool_chunk *chunk;

int order = pool->min_alloc_order;

int start_bit, nbits, remain;

#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

BUG_ON(in_nmi());

#endif

nbits = (size + (1UL << order) - 1) >> order;

rcu_read_lock();

list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {

if (addr >= chunk->start_addr && addr <= chunk->end_addr) {

BUG_ON(addr + size - 1 > chunk->end_addr);

start_bit = (addr - chunk->start_addr) >> order;

remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);

BUG_ON(remain);

size = nbits << order;

atomic_add(size, &chunk->avail);

rcu_read_unlock();

return;

}

rcu_read_unlock();

BUG();

}

EXPORT_SYMBOL(gen_pool_free);

/**

* gen_pool_for_each_chunk - call func for every chunk of generic memory pool

* @pool: the generic memory pool

* @func: func to call

* @data: additional data used by @func

* Call @func for every chunk of generic memory pool. The @func is

* called with rcu_read_lock held.

void gen_pool_for_each_chunk(struct gen_pool *pool,

void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),

void *data)

{

struct gen_pool_chunk *chunk;

rcu_read_lock();

list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)

func(pool, chunk, data);

rcu_read_unlock();

}

EXPORT_SYMBOL(gen_pool_for_each_chunk);

/**

* gen_pool_avail - get available free space of the pool

* @pool: pool to get available free space

* Return available free space of the specified pool.

size_t gen_pool_avail(struct gen_pool *pool)

{

struct gen_pool_chunk *chunk;

size_t avail = 0;

rcu_read_lock();

list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)

avail += atomic_read(&chunk->avail);

rcu_read_unlock();

return avail;

}

EXPORT_SYMBOL_GPL(gen_pool_avail);

/**

* gen_pool_size - get size in bytes of memory managed by the pool

* @pool: pool to get size

* Return size in bytes of memory managed by the pool.

size_t gen_pool_size(struct gen_pool *pool)

{

struct gen_pool_chunk *chunk;

size_t size = 0;

rcu_read_lock();

list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)

size += chunk_size(chunk);

rcu_read_unlock();

return size;

}

EXPORT_SYMBOL_GPL(gen_pool_size);

/**

* gen_pool_set_algo - set the allocation algorithm

* @pool: pool to change allocation algorithm

* @algo: custom algorithm function

* @data: additional data used by @algo

* Call @algo for each memory allocation in the pool.

* If @algo is NULL use gen_pool_first_fit as default

* memory allocation function.

void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo, void *data)

{

rcu_read_lock();

pool->algo = algo;

if (!pool->algo)

pool->algo = gen_pool_first_fit;

pool->data = data;

rcu_read_unlock();

}

EXPORT_SYMBOL(gen_pool_set_algo);

/**

* gen_pool_first_fit - find the first available region

* of memory matching the size requirement (no alignment constraint)

* @map: The address to base the search on

* @size: The bitmap size in bits

* @start: The bitnumber to start searching at

* @nr: The number of zeroed bits we're looking for

* @data: additional data - unused

unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,

unsigned long start, unsigned int nr, void *data)

{

return bitmap_find_next_zero_area(map, size, start, nr, 0);

}

EXPORT_SYMBOL(gen_pool_first_fit);

/**

* gen_pool_best_fit - find the best fitting region of memory

* macthing the size requirement (no alignment constraint)

* @map: The address to base the search on

* @size: The bitmap size in bits

* @start: The bitnumber to start searching at

* @nr: The number of zeroed bits we're looking for

* @data: additional data - unused

* Iterate over the bitmap to find the smallest free region

* which we can allocate the memory.

unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,

unsigned long start, unsigned int nr, void *data)

{

unsigned long start_bit = size;

unsigned long len = size + 1;

unsigned long index;

index = bitmap_find_next_zero_area(map, size, start, nr, 0);

while (index < size) {

int next_bit = find_next_bit(map, size, index + nr);

if ((next_bit - index) < len) {

len = next_bit - index;

start_bit = index;

if (len == nr)

return start_bit;

}

index = bitmap_find_next_zero_area(map, size,

next_bit + 1, nr, 0);

}

return start_bit;

}

EXPORT_SYMBOL(gen_pool_best_fit);

static void devm_gen_pool_release(struct device *dev, void *res)

{

gen_pool_destroy(*(struct gen_pool **)res);

}

/**

* devm_gen_pool_create - managed gen_pool_create

* @dev: device that provides the gen_pool

* @min_alloc_order: log base 2 of number of bytes each bitmap bit represents

* @nid: node id of the node the pool structure should be allocated on, or -1

* Create a new special memory pool that can be used to manage special purpose

* memory not managed by the regular kmalloc/kfree interface. The pool will be

* automatically destroyed by the device management code.

struct gen_pool *devm_gen_pool_create(struct device *dev, int min_alloc_order,

int nid)

{

struct gen_pool **ptr, *pool;

ptr = devres_alloc(devm_gen_pool_release, sizeof(*ptr), GFP_KERNEL);

pool = gen_pool_create(min_alloc_order, nid);

if (pool) {

*ptr = pool;

devres_add(dev, ptr);

} else {

devres_free(ptr);

}

return pool;

}

/**

* dev_get_gen_pool - Obtain the gen_pool (if any) for a device

* @dev: device to retrieve the gen_pool from

* Returns the gen_pool for the device if one is present, or NULL.

struct gen_pool *dev_get_gen_pool(struct device *dev)

{

struct gen_pool **p = devres_find(dev, devm_gen_pool_release, NULL,

NULL);

if (!p)

return NULL;

return *p;

}

EXPORT_SYMBOL_GPL(dev_get_gen_pool);

#ifdef CONFIG_OF

/**

* of_get_named_gen_pool - find a pool by phandle property

* @np: device node

* @propname: property name containing phandle(s)

* @index: index into the phandle array

* Returns the pool that contains the chunk starting at the physical

* address of the device tree node pointed at by the phandle property,

* or NULL if not found.

struct gen_pool *of_get_named_gen_pool(struct device_node *np,

const char *propname, int index)

{

struct platform_device *pdev;

struct device_node *np_pool;

np_pool = of_parse_phandle(np, propname, index);

if (!np_pool)

return NULL;

pdev = of_find_device_by_node(np_pool);

if (!pdev)

return NULL;

return dev_get_gen_pool(&pdev->dev);

}

EXPORT_SYMBOL_GPL(of_get_named_gen_pool);

#endif /* CONFIG_OF */

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