1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * queue_stack_maps.c: BPF queue and stack maps 4 * 5 * Copyright (c) 2018 Politecnico di Torino 6 */ 7 #include <linux/bpf.h> 8 #include <linux/list.h> 9 #include <linux/slab.h> 10 #include "percpu_freelist.h" 11 12 #define QUEUE_STACK_CREATE_FLAG_MASK \ 13 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY) 14 15 16 struct bpf_queue_stack { 17 struct bpf_map map; 18 raw_spinlock_t lock; 19 u32 head, tail; 20 u32 size; /* max_entries + 1 */ 21 22 char elements[0] __aligned(8); 23 }; 24 25 static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map) 26 { 27 return container_of(map, struct bpf_queue_stack, map); 28 } 29 30 static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs) 31 { 32 return qs->head == qs->tail; 33 } 34 35 static bool queue_stack_map_is_full(struct bpf_queue_stack *qs) 36 { 37 u32 head = qs->head + 1; 38 39 if (unlikely(head >= qs->size)) 40 head = 0; 41 42 return head == qs->tail; 43 } 44 45 /* Called from syscall */ 46 static int queue_stack_map_alloc_check(union bpf_attr *attr) 47 { 48 /* check sanity of attributes */ 49 if (attr->max_entries == 0 || attr->key_size != 0 || 50 attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK) 51 return -EINVAL; 52 53 if (attr->value_size > KMALLOC_MAX_SIZE) 54 /* if value_size is bigger, the user space won't be able to 55 * access the elements. 56 */ 57 return -E2BIG; 58 59 return 0; 60 } 61 62 static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr) 63 { 64 int ret, numa_node = bpf_map_attr_numa_node(attr); 65 struct bpf_queue_stack *qs; 66 u32 size, value_size; 67 u64 queue_size, cost; 68 69 size = attr->max_entries + 1; 70 value_size = attr->value_size; 71 72 queue_size = sizeof(*qs) + (u64) value_size * size; 73 74 cost = queue_size; 75 if (cost >= U32_MAX - PAGE_SIZE) 76 return ERR_PTR(-E2BIG); 77 78 cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; 79 80 ret = bpf_map_precharge_memlock(cost); 81 if (ret < 0) 82 return ERR_PTR(ret); 83 84 qs = bpf_map_area_alloc(queue_size, numa_node); 85 if (!qs) 86 return ERR_PTR(-ENOMEM); 87 88 memset(qs, 0, sizeof(*qs)); 89 90 bpf_map_init_from_attr(&qs->map, attr); 91 92 qs->map.pages = cost; 93 qs->size = size; 94 95 raw_spin_lock_init(&qs->lock); 96 97 return &qs->map; 98 } 99 100 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ 101 static void queue_stack_map_free(struct bpf_map *map) 102 { 103 struct bpf_queue_stack *qs = bpf_queue_stack(map); 104 105 /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0, 106 * so the programs (can be more than one that used this map) were 107 * disconnected from events. Wait for outstanding critical sections in 108 * these programs to complete 109 */ 110 synchronize_rcu(); 111 112 bpf_map_area_free(qs); 113 } 114 115 static int __queue_map_get(struct bpf_map *map, void *value, bool delete) 116 { 117 struct bpf_queue_stack *qs = bpf_queue_stack(map); 118 unsigned long flags; 119 int err = 0; 120 void *ptr; 121 122 raw_spin_lock_irqsave(&qs->lock, flags); 123 124 if (queue_stack_map_is_empty(qs)) { 125 err = -ENOENT; 126 goto out; 127 } 128 129 ptr = &qs->elements[qs->tail * qs->map.value_size]; 130 memcpy(value, ptr, qs->map.value_size); 131 132 if (delete) { 133 if (unlikely(++qs->tail >= qs->size)) 134 qs->tail = 0; 135 } 136 137 out: 138 raw_spin_unlock_irqrestore(&qs->lock, flags); 139 return err; 140 } 141 142 143 static int __stack_map_get(struct bpf_map *map, void *value, bool delete) 144 { 145 struct bpf_queue_stack *qs = bpf_queue_stack(map); 146 unsigned long flags; 147 int err = 0; 148 void *ptr; 149 u32 index; 150 151 raw_spin_lock_irqsave(&qs->lock, flags); 152 153 if (queue_stack_map_is_empty(qs)) { 154 err = -ENOENT; 155 goto out; 156 } 157 158 index = qs->head - 1; 159 if (unlikely(index >= qs->size)) 160 index = qs->size - 1; 161 162 ptr = &qs->elements[index * qs->map.value_size]; 163 memcpy(value, ptr, qs->map.value_size); 164 165 if (delete) 166 qs->head = index; 167 168 out: 169 raw_spin_unlock_irqrestore(&qs->lock, flags); 170 return err; 171 } 172 173 /* Called from syscall or from eBPF program */ 174 static int queue_map_peek_elem(struct bpf_map *map, void *value) 175 { 176 return __queue_map_get(map, value, false); 177 } 178 179 /* Called from syscall or from eBPF program */ 180 static int stack_map_peek_elem(struct bpf_map *map, void *value) 181 { 182 return __stack_map_get(map, value, false); 183 } 184 185 /* Called from syscall or from eBPF program */ 186 static int queue_map_pop_elem(struct bpf_map *map, void *value) 187 { 188 return __queue_map_get(map, value, true); 189 } 190 191 /* Called from syscall or from eBPF program */ 192 static int stack_map_pop_elem(struct bpf_map *map, void *value) 193 { 194 return __stack_map_get(map, value, true); 195 } 196 197 /* Called from syscall or from eBPF program */ 198 static int queue_stack_map_push_elem(struct bpf_map *map, void *value, 199 u64 flags) 200 { 201 struct bpf_queue_stack *qs = bpf_queue_stack(map); 202 unsigned long irq_flags; 203 int err = 0; 204 void *dst; 205 206 /* BPF_EXIST is used to force making room for a new element in case the 207 * map is full 208 */ 209 bool replace = (flags & BPF_EXIST); 210 211 /* Check supported flags for queue and stack maps */ 212 if (flags & BPF_NOEXIST || flags > BPF_EXIST) 213 return -EINVAL; 214 215 raw_spin_lock_irqsave(&qs->lock, irq_flags); 216 217 if (queue_stack_map_is_full(qs)) { 218 if (!replace) { 219 err = -E2BIG; 220 goto out; 221 } 222 /* advance tail pointer to overwrite oldest element */ 223 if (unlikely(++qs->tail >= qs->size)) 224 qs->tail = 0; 225 } 226 227 dst = &qs->elements[qs->head * qs->map.value_size]; 228 memcpy(dst, value, qs->map.value_size); 229 230 if (unlikely(++qs->head >= qs->size)) 231 qs->head = 0; 232 233 out: 234 raw_spin_unlock_irqrestore(&qs->lock, irq_flags); 235 return err; 236 } 237 238 /* Called from syscall or from eBPF program */ 239 static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key) 240 { 241 return NULL; 242 } 243 244 /* Called from syscall or from eBPF program */ 245 static int queue_stack_map_update_elem(struct bpf_map *map, void *key, 246 void *value, u64 flags) 247 { 248 return -EINVAL; 249 } 250 251 /* Called from syscall or from eBPF program */ 252 static int queue_stack_map_delete_elem(struct bpf_map *map, void *key) 253 { 254 return -EINVAL; 255 } 256 257 /* Called from syscall */ 258 static int queue_stack_map_get_next_key(struct bpf_map *map, void *key, 259 void *next_key) 260 { 261 return -EINVAL; 262 } 263 264 const struct bpf_map_ops queue_map_ops = { 265 .map_alloc_check = queue_stack_map_alloc_check, 266 .map_alloc = queue_stack_map_alloc, 267 .map_free = queue_stack_map_free, 268 .map_lookup_elem = queue_stack_map_lookup_elem, 269 .map_update_elem = queue_stack_map_update_elem, 270 .map_delete_elem = queue_stack_map_delete_elem, 271 .map_push_elem = queue_stack_map_push_elem, 272 .map_pop_elem = queue_map_pop_elem, 273 .map_peek_elem = queue_map_peek_elem, 274 .map_get_next_key = queue_stack_map_get_next_key, 275 }; 276 277 const struct bpf_map_ops stack_map_ops = { 278 .map_alloc_check = queue_stack_map_alloc_check, 279 .map_alloc = queue_stack_map_alloc, 280 .map_free = queue_stack_map_free, 281 .map_lookup_elem = queue_stack_map_lookup_elem, 282 .map_update_elem = queue_stack_map_update_elem, 283 .map_delete_elem = queue_stack_map_delete_elem, 284 .map_push_elem = queue_stack_map_push_elem, 285 .map_pop_elem = stack_map_pop_elem, 286 .map_peek_elem = stack_map_peek_elem, 287 .map_get_next_key = queue_stack_map_get_next_key, 288 }; 289