path: root/lib/genalloc.c

/*
 * 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.
 *
 * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
 *
 * 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_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;
		pool->name = 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.