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// SPDX-License-Identifier: BSD-2-Clause
/*
* Copyright (c) 2014, STMicroelectronics International N.V.
* Copyright (c) 2018, Linaro Limited
*/
#include <assert.h>
#include <compiler.h>
#include <malloc.h>
#include <mempool.h>
#include <util.h>
#if defined(__KERNEL__)
#include <kernel/mutex.h>
#include <kernel/panic.h>
#include <kernel/thread.h>
#include <kernel/refcount.h>
#endif
/*
* Allocation of temporary memory buffers which are used in a stack like
* fashion. One exmaple is when a Big Number is needed for a temporary
* variable in a Big Number computation: Big Number operations (add,...),
* crypto algorithms (rsa, ecc,,...).
*
* The allocation algorithm takes memory buffers from a pool,
* characterized by (cf. struct mempool):
* - the total size (in bytes) of the pool
* - the offset of the last item allocated in the pool (struct
* mempool_item). This offset is -1 is nothing is allocated yet.
*
* Each item consists of (struct mempool_item)
* - the size of the item
* - the offsets, in the pool, of the previous and next items
*
* The allocation allocates an item for a given size.
* The allocation is performed in the pool after the last
* allocated items. This means:
* - the heap is never used.
* - there is no assumption on the size of the allocated memory buffers. Only
* the size of the pool will limit the allocation.
* - a constant time allocation and free as there is no list scan
* - but a potentially fragmented memory as the allocation does not take into
* account "holes" in the pool (allocation is performed after the last
* allocated variable). Indeed, this interface is supposed to be used
* with stack like allocations to avoid this issue. This means that
* allocated items:
* - should have a short life cycle
* - if an item A is allocated before another item B, then A should be
* released after B.
* So the potential fragmentation is mitigated.
*/
#define POOL_ALIGN __alignof__(long)
struct mempool {
size_t size; /* size of the memory pool, in bytes */
ssize_t last_offset; /* offset to the last one */
vaddr_t data;
#if defined(__KERNEL__)
void (*release_mem)(void *ptr, size_t size);
struct mutex mu;
struct condvar cv;
struct refcount refc;
int owner;
#endif
};
static void get_pool(struct mempool *pool __maybe_unused)
{
#if defined(__KERNEL__)
if (refcount_inc(&pool->refc)) {
if (pool->owner == thread_get_id())
return;
refcount_dec(&pool->refc);
}
mutex_lock(&pool->mu);
/* Wait until the pool is available */
while (pool->owner != THREAD_ID_INVALID)
condvar_wait(&pool->cv, &pool->mu);
pool->owner = thread_get_id();
refcount_set(&pool->refc, 1);
mutex_unlock(&pool->mu);
#endif
}
static void put_pool(struct mempool *pool __maybe_unused)
{
#if defined(__KERNEL__)
assert(pool->owner == thread_get_id());
if (refcount_dec(&pool->refc)) {
mutex_lock(&pool->mu);
pool->owner = THREAD_ID_INVALID;
condvar_signal(&pool->cv);
/* As the refcount is 0 there should be no items left */
if (pool->last_offset >= 0)
panic();
if (pool->release_mem)
pool->release_mem((void *)pool->data, pool->size);
mutex_unlock(&pool->mu);
}
#endif
}
struct mempool *
mempool_alloc_pool(void *data, size_t size,
void (*release_mem)(void *ptr, size_t size) __maybe_unused)
{
struct mempool *pool = calloc(1, sizeof(*pool));
COMPILE_TIME_ASSERT(POOL_ALIGN >= __alignof__(struct mempool_item));
assert(!((vaddr_t)data & (POOL_ALIGN - 1)));
if (pool) {
pool->size = size;
pool->data = (vaddr_t)data;
pool->last_offset = -1;
#if defined(__KERNEL__)
pool->release_mem = release_mem;
mutex_init(&pool->mu);
condvar_init(&pool->cv);
pool->owner = THREAD_ID_INVALID;
#endif
}
return pool;
}
void *mempool_alloc(struct mempool *pool, size_t size)
{
size_t offset;
struct mempool_item *new_item;
struct mempool_item *last_item = NULL;
get_pool(pool);
if (pool->last_offset < 0) {
offset = 0;
} else {
last_item = (struct mempool_item *)(pool->data +
pool->last_offset);
offset = pool->last_offset + last_item->size;
offset = ROUNDUP(offset, POOL_ALIGN);
if (offset > pool->size)
goto error;
}
size = sizeof(struct mempool_item) + size;
size = ROUNDUP(size, POOL_ALIGN);
if (offset + size > pool->size)
goto error;
new_item = (struct mempool_item *)(pool->data + offset);
new_item->size = size;
new_item->prev_item_offset = pool->last_offset;
if (last_item)
last_item->next_item_offset = offset;
new_item->next_item_offset = -1;
pool->last_offset = offset;
return new_item + 1;
error:
EMSG("Failed to allocate %zu bytes, please tune the pool size", size);
put_pool(pool);
return NULL;
}
void mempool_free(struct mempool *pool, void *ptr)
{
struct mempool_item *item;
struct mempool_item *prev_item;
struct mempool_item *next_item;
ssize_t last_offset = -1;
if (!ptr)
return;
item = (struct mempool_item *)((vaddr_t)ptr -
sizeof(struct mempool_item));
if (item->prev_item_offset >= 0) {
prev_item = (struct mempool_item *)(pool->data +
item->prev_item_offset);
prev_item->next_item_offset = item->next_item_offset;
last_offset = item->prev_item_offset;
}
if (item->next_item_offset >= 0) {
next_item = (struct mempool_item *)(pool->data +
item->next_item_offset);
next_item->prev_item_offset = item->prev_item_offset;
last_offset = pool->last_offset;
}
pool->last_offset = last_offset;
put_pool(pool);
}
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