1 // SPDX-License-Identifier: BSD-2-Clause 2 /* 3 * Copyright (c) 2014, STMicroelectronics International N.V. 4 * Copyright (c) 2018, Linaro Limited 5 */ 6 7 8 #include <assert.h> 9 #include <compiler.h> 10 #include <malloc.h> 11 #include <mempool.h> 12 #include <util.h> 13 14 #if defined(__KERNEL__) 15 #include <kernel/mutex.h> 16 #include <kernel/panic.h> 17 #include <kernel/thread.h> 18 #include <kernel/refcount.h> 19 #endif 20 21 /* 22 * Allocation of temporary memory buffers which are used in a stack like 23 * fashion. One exmaple is when a Big Number is needed for a temporary 24 * variable in a Big Number computation: Big Number operations (add,...), 25 * crypto algorithms (rsa, ecc,,...). 26 * 27 * The allocation algorithm takes memory buffers from a pool, 28 * characterized by (cf. struct mempool): 29 * - the total size (in bytes) of the pool 30 * - the offset of the last item allocated in the pool (struct 31 * mempool_item). This offset is -1 is nothing is allocated yet. 32 * 33 * Each item consists of (struct mempool_item) 34 * - the size of the item 35 * - the offsets, in the pool, of the previous and next items 36 * 37 * The allocation allocates an item for a given size. 38 * The allocation is performed in the pool after the last 39 * allocated items. This means: 40 * - the heap is never used. 41 * - there is no assumption on the size of the allocated memory buffers. Only 42 * the size of the pool will limit the allocation. 43 * - a constant time allocation and free as there is no list scan 44 * - but a potentially fragmented memory as the allocation does not take into 45 * account "holes" in the pool (allocation is performed after the last 46 * allocated variable). Indeed, this interface is supposed to be used 47 * with stack like allocations to avoid this issue. This means that 48 * allocated items: 49 * - should have a short life cycle 50 * - if an item A is allocated before another item B, then A should be 51 * released after B. 52 * So the potential fragmentation is mitigated. 53 */ 54 55 #define POOL_ALIGN __alignof__(long) 56 57 struct mempool { 58 size_t size; /* size of the memory pool, in bytes */ 59 ssize_t last_offset; /* offset to the last one */ 60 vaddr_t data; 61 #if defined(__KERNEL__) 62 void (*release_mem)(void *ptr, size_t size); 63 struct mutex mu; 64 struct condvar cv; 65 struct refcount refc; 66 int owner; 67 #endif 68 }; 69 70 static void get_pool(struct mempool *pool __maybe_unused) 71 { 72 #if defined(__KERNEL__) 73 if (refcount_inc(&pool->refc)) { 74 if (pool->owner == thread_get_id()) 75 return; 76 refcount_dec(&pool->refc); 77 } 78 79 mutex_lock(&pool->mu); 80 81 /* Wait until the pool is available */ 82 while (pool->owner != THREAD_ID_INVALID) 83 condvar_wait(&pool->cv, &pool->mu); 84 85 pool->owner = thread_get_id(); 86 refcount_set(&pool->refc, 1); 87 88 mutex_unlock(&pool->mu); 89 #endif 90 } 91 92 static void put_pool(struct mempool *pool __maybe_unused) 93 { 94 #if defined(__KERNEL__) 95 assert(pool->owner == thread_get_id()); 96 97 if (refcount_dec(&pool->refc)) { 98 mutex_lock(&pool->mu); 99 100 pool->owner = THREAD_ID_INVALID; 101 condvar_signal(&pool->cv); 102 103 /* As the refcount is 0 there should be no items left */ 104 if (pool->last_offset >= 0) 105 panic(); 106 if (pool->release_mem) 107 pool->release_mem((void *)pool->data, pool->size); 108 109 mutex_unlock(&pool->mu); 110 } 111 #endif 112 } 113 114 struct mempool * 115 mempool_alloc_pool(void *data, size_t size, 116 void (*release_mem)(void *ptr, size_t size) __maybe_unused) 117 { 118 struct mempool *pool = calloc(1, sizeof(*pool)); 119 120 COMPILE_TIME_ASSERT(POOL_ALIGN >= __alignof__(struct mempool_item)); 121 assert(!((vaddr_t)data & (POOL_ALIGN - 1))); 122 123 if (pool) { 124 pool->size = size; 125 pool->data = (vaddr_t)data; 126 pool->last_offset = -1; 127 #if defined(__KERNEL__) 128 pool->release_mem = release_mem; 129 mutex_init(&pool->mu); 130 condvar_init(&pool->cv); 131 pool->owner = THREAD_ID_INVALID; 132 #endif 133 } 134 135 return pool; 136 } 137 138 void *mempool_alloc(struct mempool *pool, size_t size) 139 { 140 size_t offset; 141 struct mempool_item *new_item; 142 struct mempool_item *last_item = NULL; 143 144 get_pool(pool); 145 146 if (pool->last_offset < 0) { 147 offset = 0; 148 } else { 149 last_item = (struct mempool_item *)(pool->data + 150 pool->last_offset); 151 offset = pool->last_offset + last_item->size; 152 153 offset = ROUNDUP(offset, POOL_ALIGN); 154 if (offset > pool->size) 155 goto error; 156 } 157 158 size = sizeof(struct mempool_item) + size; 159 size = ROUNDUP(size, POOL_ALIGN); 160 if (offset + size > pool->size) 161 goto error; 162 163 new_item = (struct mempool_item *)(pool->data + offset); 164 new_item->size = size; 165 new_item->prev_item_offset = pool->last_offset; 166 if (last_item) 167 last_item->next_item_offset = offset; 168 new_item->next_item_offset = -1; 169 pool->last_offset = offset; 170 171 return new_item + 1; 172 173 error: 174 EMSG("Failed to allocate %zu bytes, please tune the pool size", size); 175 put_pool(pool); 176 return NULL; 177 } 178 179 void mempool_free(struct mempool *pool, void *ptr) 180 { 181 struct mempool_item *item; 182 struct mempool_item *prev_item; 183 struct mempool_item *next_item; 184 ssize_t last_offset = -1; 185 186 if (!ptr) 187 return; 188 189 item = (struct mempool_item *)((vaddr_t)ptr - 190 sizeof(struct mempool_item)); 191 if (item->prev_item_offset >= 0) { 192 prev_item = (struct mempool_item *)(pool->data + 193 item->prev_item_offset); 194 prev_item->next_item_offset = item->next_item_offset; 195 last_offset = item->prev_item_offset; 196 } 197 198 if (item->next_item_offset >= 0) { 199 next_item = (struct mempool_item *)(pool->data + 200 item->next_item_offset); 201 next_item->prev_item_offset = item->prev_item_offset; 202 last_offset = pool->last_offset; 203 } 204 205 pool->last_offset = last_offset; 206 put_pool(pool); 207 } 208